The SALORA 1G CHASSIS is awesome even in the CRT SOCKET.
It has in it the degauss circuit which is absolutely unique.
Normally we can see a classic PTC resistor which has some negative aspects.
Here we don't have any PTC but an one shot active oscillator circuit.
When the set is powered up even from STBY a capacitor will be loaded at high voltage. At a prefixed point, the energy stored in, discharged via a special THYRISTOR OSCILLATOR CIRCUIT directly in the degauss coil fitted around the tube.
The frequency of oscillations is higher than the normal mains frequency and has higly more efficiency than a normal PTC Technology type.
When the energy is completely discharged the one shot time is over and the tube is surently degaussed and the set runs normally.
To restart a degauss session you have to shut down the set even only from remote.
This degauss circuit is very powerful since I've tested with highly magnetized tubes and it works surprisingly even in desperate circumstances.
Another advantage is that this circuit doesn't eat energy during running the set like a normal PTC. (no heaters around the chassis, and no energy loss)
SALORA 1G6H CHASSIS 1G Resonant degaussing apparatus:
First and second capacitors are charged prior to a degaussing interval. A
first switch couples the first capacitor to a degaussing coil to
initiate the degaussing interval. The first capacitor and the degaussing
coil form a resonant circuit that resonates to generate a decaying
degaussing current. During a predetermined portion of each cycle of the
degaussing current, a second switch couples a precharged second
capacitor in parallel with the first capacitor to form a charge transfer
arrangement that transfers charge from the second to the first
capacitor for replenishing energy losses in the first capacitor. The
charge transfer arrangement increases the duration of the time it takes
to the amplitude of the degaussing current to decay and, hence, the
length of the degaussing interval.
1. A resonant degaussing circuit of a television apparatus, comprising: a degaussing coil;
a first switch;
a first capacitance that is precharged prior to a degaussing interval, said first capacitance being coupled to said degaussing coil by said first switch to form with said degaussing coil a resonant circuit that generates a plurality of cycles of a degaussing current in said degaussing coil, during said degaussing interval;
a second capacitance that is precharged prior to at least one of said plurality of cycles of said degaussing current; and
a second switch for coupling said second capacitance to said first capacitance during a predetermined portion of said at least one cycle of said degaussing current to couple charge from said second capacitance to said resonant circuit during said degaussing interval.
2. An apparatus according to claim 1 further comprising, means responsive to said degaussing current for generating a control signal that is coupled to a control terminal of said second switch during said predetermined portion of said cycle that causes said second switch to be conductive during said portion.
3. An apparatus according to claim 2 wherein said control signal generating means comprises a current sensing transformer coupled in a current path of said degaussing current that generates a pulse when said degaussing current changes polarity having a duration that is substantially shorter than that of said cycle of said degaussing current.
4. An apparatus according to claim 1 wherein said second switch is conductive at least once during each cycle of said plurality cycles of said degaussing current.
5. An apparatus according to claim 1 wherein said second switch couples said second capacitance in parallel with said first capacitance to transfer charge from said second to said first capacitance when said second switch is conductive.
6. A circuit according to claim 1 wherein said second capacitance is coupled to said resonant circuit during said predetermined portion that is substantially shorter than that of said degaussing cycle such that the resonant frequency of said resonant circuit is substantially unaffected by said second capacitance.
7. An apparatus according to claim 1 wherein said second capacitance reduces a rate by which an amplitude of degaussing current diminishes.
8. A resonant degaussing circuit of a television apparatus, comprising: a degaussing coil;
a first switch;
a first capacitance that is precharged prior to a degaussing interval, said first capacitance being coupled to said degaussing coil by said first switch to form with said degaussing coil a resonant circuit that generates, in accordance with a charge that is stored therein, a plurality of cycles of a degaussing current in said degaussing coil during said degaussing interval; and
means responsive to said degaussing current for generating a pulse of current that is coupled to said first capacitance during a portion of at least one cycle of said plurality of cycles that augments said charge that is stored in said first capacitance.
9. A resonant degaussing circuit according to claim 8 wherein said pulse of current generating means comprises a current transformer that is coupled in a path of said degaussing current that generates a pulse during said portion, a second switch that is responsive to said pulse and a second capacitance that is coupled to said first capacitor by said second switch when said pulse occurs.
10. A circuit according to claim 9 wherein said current transformer has a primary winding that conducts at least a substantial portion of said degaussing current.
a first switch;
a first capacitance that is precharged prior to a degaussing interval, said first capacitance being coupled to said degaussing coil by said first switch to form with said degaussing coil a resonant circuit that generates a plurality of cycles of a degaussing current in said degaussing coil, during said degaussing interval;
a second capacitance that is precharged prior to at least one of said plurality of cycles of said degaussing current; and
a second switch for coupling said second capacitance to said first capacitance during a predetermined portion of said at least one cycle of said degaussing current to couple charge from said second capacitance to said resonant circuit during said degaussing interval.
2. An apparatus according to claim 1 further comprising, means responsive to said degaussing current for generating a control signal that is coupled to a control terminal of said second switch during said predetermined portion of said cycle that causes said second switch to be conductive during said portion.
3. An apparatus according to claim 2 wherein said control signal generating means comprises a current sensing transformer coupled in a current path of said degaussing current that generates a pulse when said degaussing current changes polarity having a duration that is substantially shorter than that of said cycle of said degaussing current.
4. An apparatus according to claim 1 wherein said second switch is conductive at least once during each cycle of said plurality cycles of said degaussing current.
5. An apparatus according to claim 1 wherein said second switch couples said second capacitance in parallel with said first capacitance to transfer charge from said second to said first capacitance when said second switch is conductive.
6. A circuit according to claim 1 wherein said second capacitance is coupled to said resonant circuit during said predetermined portion that is substantially shorter than that of said degaussing cycle such that the resonant frequency of said resonant circuit is substantially unaffected by said second capacitance.
7. An apparatus according to claim 1 wherein said second capacitance reduces a rate by which an amplitude of degaussing current diminishes.
8. A resonant degaussing circuit of a television apparatus, comprising: a degaussing coil;
a first switch;
a first capacitance that is precharged prior to a degaussing interval, said first capacitance being coupled to said degaussing coil by said first switch to form with said degaussing coil a resonant circuit that generates, in accordance with a charge that is stored therein, a plurality of cycles of a degaussing current in said degaussing coil during said degaussing interval; and
means responsive to said degaussing current for generating a pulse of current that is coupled to said first capacitance during a portion of at least one cycle of said plurality of cycles that augments said charge that is stored in said first capacitance.
9. A resonant degaussing circuit according to claim 8 wherein said pulse of current generating means comprises a current transformer that is coupled in a path of said degaussing current that generates a pulse during said portion, a second switch that is responsive to said pulse and a second capacitance that is coupled to said first capacitor by said second switch when said pulse occurs.
10. A circuit according to claim 9 wherein said current transformer has a primary winding that conducts at least a substantial portion of said degaussing current.
Description:
This invention relates to degaussing circuits for video display equipment.
Color
cathode ray tubes require periodic degaussing or demagnetization to
counteract the effects of the earth's magnetic field or of
electromagnetic fields produced by nearby electrical devices, such as
motors or appliances. These fields may magnetize metallic portions of
the cathode ray tube, such as the shadow mask, causing a degradation of
the color purity of the tube. Video display apparatus, such as
television receivers and computer or video display monitors, usually
incorporate a degaussing circuit which is operative when the apparatus
is energized to produce an alternating current field that decays toward
zero in order to demagnetize the metallic components in the vicinity of
the tube and of the tube itself.
A common type of degaussing circuit that includes a degaussing coil is powered from the AC line supply, which in the United States has a frequency of 60 Hz. This type of degaussing circuit ordinarily utilizes a positive temperature coefficient resistor, or thermistor, or other temperature sensitive component, which increases in resistance as it heats due to degaussing current flow. This causes the alternating degaussing current to decay in a manner that provides demagnetization of the cathode ray tube metallic components.
Another type of degaussing circuit utilizes a resonant or ring-down degaussing circuit. The resonant degaussing circuit operates by causing a capacitor connected in parallel with the degaussing coil to resonate with the coil in an oscillating manner. The finite Q of the resonant circuit causes the degaussing current to decay in the manner shown in FIG. 5b, for example, to effect demagnetization of the display apparatus metallic parts. The resonant frequency of the degaussing circuit may be of the order of 2 kHz, so that degaussing is completed in less than 5 milliseconds.
Because of the finite Q of the resonant circuit, the duration of a degaussing interval such as interval TDGI of FIG. 5b is limited by the parameters of the resonant circuit. In some degaussing circuit applications, it may be desirable to lengthen the duration of the degaussing interval beyond that obtained from the conventional degaussing resonant circuit in a way that does not have an adverse impact on the cost of, for example, the degaussing coil.
In accordance with an aspect of the invention, a resonant degaussing circuit of a television apparatus includes a degaussing coil, a first switch, and a first capacitance that is precharged prior to a degaussing interval. The first capacitance is coupled to the degaussing coil by said first switch to form with the degaussing coil a resonant circuit that generates a plurality of cycles of a degaussing current in the degaussing coil, during the degaussing interval. A second capacitance is precharged prior to at least one of the plurality of cycles of the degaussing current. A second switch couples the second capacitance to the first capacitance during a predetermined portion of the one cycle of degaussing current to couple charge from the second capacitance to the resonant circuit, during the degaussing interval.
In accordance with another aspect of the invention, a first capacitor is precharged prior to a degaussing interval. A first switch couples the first capacitor to a degaussing coil at a beginning time of the degaussing interval. The first capacitor and the degaussing coil form a resonant circuit that resonates and that generates an AC degaussing current in the degaussing coil. The amplitude of the degaussing current decays during the degaussing interval. During a predetermined portion of a given cycle of the degaussing current, a second switch couples to the first capacitor a second capacitor that is precharged to form a charge transfer arrangement that transfers charge from the second to the first capacitor for augmenting the charge in the first capacitor. In this way, the length of the degaussing interval increases relative to that of a conventional resonant degaussing circuit.
In accordance with yet another aspect of the invention, the second capacitor is coupled to the first capacitor during each cycle of the degaussing current when the degaussing current is close to zero; thereby, disturbance in the degaussing current is reduced.
In accordance with a further aspect of the invention, the switching operation of the second switch is synchronized to the degaussing current using a current sensing transformer in a current path of the degaussing current.
FIG. 1 illustrates a resonant degaussing circuit that includes a charge transfer arrangement, embodying some aspects of the invention, that utilizes a current sensing transformer;
FIG. 2 illustrates an example of waveforms of the current and voltage in a degaussing coil of the circuit of FIG. 1;
FIG. 3 illustrates a waveform of pulses generated by the current sensing transformer of FIG. 1;
FIG. 4 illustrates the way the current sensing transformer of FIG. 1 is constructed;
FIG. 5a illustrates the waveform of the degaussing current of the circuit of FIG. 1 when the charge transfer arrangement is included; and
FIG. 5b illustrates, for comparison purpose, the waveform of the degaussing current of the circuit of FIG. 1 when the charge transfer arrangement is disconnected.
FIG. 1 illustrates a resonant degaussing circuitDG.
200 that includes a charge pump or transfer arrangement 100, embodying
some aspects of the invention. Degaussing circuit 200 includes a
capacitor C1 that is precharged prior to a degaussing interval, in a
polarity shown, from a DC-to-DC converter 51 that generates a DC voltage
V1. Voltage V1 is coupled to capacitor C1 through a large resistor R1
and through a DC current path that is formed in a degaussing coil L
A switch SCR1, that includes a combination of thyristor and a diode forming an ITR, couples, in a well known manner, capacitor C1 across degaussing coil LDG, at a beginning time of a degaussing interval. An example of the way a switch such as switch SCR1 operates is described in U.S. Pat. No. 4,489,253 entitled AUTOMATIC DEGAUSSING CIRCUIT WITH SWITCH MODE POWER SUPPLY in the name of T. J. Godawski.
Switch SCR1 of FIG. 1 is turned on for a duration of, for example, 5 milliseconds by a pulse that is generated by a one-shot flip-flop 52 and that is coupled through a transistor Q1 to the gate of switch SCR1. The maximum current that can flow through resistor R1 is lower than the holding current of switch SCR1. Therefore, after the end of the degaussing interval, switch SCR1 becomes nonconductive that allows capacitor C1 to recharge via resistor R1 that provides the initial conditions for the next degaussing interval. The pulse that turns on switch SCR1 may be generated, in a well known manner, by manually activating a switch such as a switch S1 of FIG. 1 and/or, automatically, each time power is applied to the degaussing circuit.
Charge transfer arrangement 100 of FIG. 1 includes a capacitor C2 that is precharged prior to, for example, degaussing interval TDG2 of FIG. 5a in a polarity shown in FIG. 1 from a voltage V2 produced by converter 51. Voltage V2 may be, for example, equal to voltage V1. Voltage V2 is coupled to capacitor C2 through a resistor R2 and through the current path that is formed by degaussing coil LDG.
In carrying out an aspect of the invention, a current transformer TF having a primary winding N1, that is formed by, for example, a single winding loop around a ferrite core that is constructed in a manner shown in FIG. 4, is coupled in the current path of degaussing current iDG of FIG. 1. Transformer TF generates a positive pulse V' in a secondary winding N2 of FIG. 3 in a positive polarity, as shown in FIG. 1. Pulse V' is generated each time, in a given cycle, when current iDG of FIG. 2 DG across coil LDG of FIG. 1 is at its maximum negative level and current iDG at a maximum rate of change such as at times T, 2T, 3T etc. of FIGS. 2 and 3.
changes from a positive to a negative polarity. Thus, pulse V' of FIG. 3 is generated when voltage V
Pulse V' is coupled through a pulse shaping and drive arrangement that includes transistors Q2 and Q3 to the base electrode of a transistor switch Q4 to turn on transistor switch Q4 during, for example, a short duration each degaussing cycle DCY of FIG. 2 when voltage VDG is at the maximum negative level. Capacitor C2 of FIG. 1 is precharged prior to, for example, the initiation of the degaussing interval. Capacitor C2 may be precharged, provided the value of resistor R2 is sufficiently small, even during each degaussing cycle DCY of the degaussing interval of FIG. 2 that precedes the current degaussing cycle of current iDG of FIG. 1.
When pulse V' occurs, transistor switch Q4 couples capacitor C2 in parallel with capacitor C1. Consequently, capacitor C2 transfers a charge to capacitor C1 that augments to that already stored in capacitor C1. Therefore, advantageously, by periodically augmenting the charge in capacitor C1 from that stored in capacitor C2, the corresponding duration of degaussing interval TDG2 of FIG. 5a that can be obtained for given circuit parameters is longer than if arrangement 100 was not used.
Degaussing interval TDG1
is shown in FIG. 5b depicts a situation that occurs when transistor
switch Q4 of FIG. 1 is removed from the circuit, for explanation
purposes. It can be seen that interval TDGl of FIG. 5b is shorter than degaussing interval TDG2 of FIG. 5a. Interval TDG2
occurs when transistor switch Q4 is included in arrangement 100 of FIG.
1, embodying the invention, that renders arrangement 100 fully
operative.
It should be understood that the charge transfer DG cycle that occurs when degaussing current iDG is zero and when the rate of change of voltage VDG is minimal. Because the coupling of capacitor C2 to the resonant circuit occurs when current iDG is small, the disturbance to degaussing current iDG of FIG. 1 is, advantageously, small. Furthermore, because the duration in which capacitor C2 is coupled to the resonant circuit is short, the resonant frequency remains, advantageously, substantially unaffected.
from capacitor C2 to capacitor C1 may be designed to occur, during, for example, a relatively short duration, every half period T of FIG. 2 of current i
It should be understood that circuit 200 parameters such as, for example, the polarity and levels of voltages V1 and V2, respectively, the value of resistor R2, and the width of pulse V' may be tailored to fit the particular requirements.
Color
cathode ray tubes require periodic degaussing or demagnetization to
counteract the effects of the earth's magnetic field or of
electromagnetic fields produced by nearby electrical devices, such as
motors or appliances. These fields may magnetize metallic portions of
the cathode ray tube, such as the shadow mask, causing a degradation of
the color purity of the tube. Video display apparatus, such as
television receivers and computer or video display monitors, usually
incorporate a degaussing circuit which is operative when the apparatus
is energized to produce an alternating current field that decays toward
zero in order to demagnetize the metallic components in the vicinity of
the tube and of the tube itself. A common type of degaussing circuit that includes a degaussing coil is powered from the AC line supply, which in the United States has a frequency of 60 Hz. This type of degaussing circuit ordinarily utilizes a positive temperature coefficient resistor, or thermistor, or other temperature sensitive component, which increases in resistance as it heats due to degaussing current flow. This causes the alternating degaussing current to decay in a manner that provides demagnetization of the cathode ray tube metallic components.
Another type of degaussing circuit utilizes a resonant or ring-down degaussing circuit. The resonant degaussing circuit operates by causing a capacitor connected in parallel with the degaussing coil to resonate with the coil in an oscillating manner. The finite Q of the resonant circuit causes the degaussing current to decay in the manner shown in FIG. 5b, for example, to effect demagnetization of the display apparatus metallic parts. The resonant frequency of the degaussing circuit may be of the order of 2 kHz, so that degaussing is completed in less than 5 milliseconds.
Because of the finite Q of the resonant circuit, the duration of a degaussing interval such as interval TDGI of FIG. 5b is limited by the parameters of the resonant circuit. In some degaussing circuit applications, it may be desirable to lengthen the duration of the degaussing interval beyond that obtained from the conventional degaussing resonant circuit in a way that does not have an adverse impact on the cost of, for example, the degaussing coil.
In accordance with an aspect of the invention, a resonant degaussing circuit of a television apparatus includes a degaussing coil, a first switch, and a first capacitance that is precharged prior to a degaussing interval. The first capacitance is coupled to the degaussing coil by said first switch to form with the degaussing coil a resonant circuit that generates a plurality of cycles of a degaussing current in the degaussing coil, during the degaussing interval. A second capacitance is precharged prior to at least one of the plurality of cycles of the degaussing current. A second switch couples the second capacitance to the first capacitance during a predetermined portion of the one cycle of degaussing current to couple charge from the second capacitance to the resonant circuit, during the degaussing interval.
In accordance with another aspect of the invention, a first capacitor is precharged prior to a degaussing interval. A first switch couples the first capacitor to a degaussing coil at a beginning time of the degaussing interval. The first capacitor and the degaussing coil form a resonant circuit that resonates and that generates an AC degaussing current in the degaussing coil. The amplitude of the degaussing current decays during the degaussing interval. During a predetermined portion of a given cycle of the degaussing current, a second switch couples to the first capacitor a second capacitor that is precharged to form a charge transfer arrangement that transfers charge from the second to the first capacitor for augmenting the charge in the first capacitor. In this way, the length of the degaussing interval increases relative to that of a conventional resonant degaussing circuit.
In accordance with yet another aspect of the invention, the second capacitor is coupled to the first capacitor during each cycle of the degaussing current when the degaussing current is close to zero; thereby, disturbance in the degaussing current is reduced.
In accordance with a further aspect of the invention, the switching operation of the second switch is synchronized to the degaussing current using a current sensing transformer in a current path of the degaussing current.
FIG. 1 illustrates a resonant degaussing circuit that includes a charge transfer arrangement, embodying some aspects of the invention, that utilizes a current sensing transformer;
FIG. 2 illustrates an example of waveforms of the current and voltage in a degaussing coil of the circuit of FIG. 1;
FIG. 3 illustrates a waveform of pulses generated by the current sensing transformer of FIG. 1;
FIG. 4 illustrates the way the current sensing transformer of FIG. 1 is constructed;
FIG. 5a illustrates the waveform of the degaussing current of the circuit of FIG. 1 when the charge transfer arrangement is included; and
FIG. 5b illustrates, for comparison purpose, the waveform of the degaussing current of the circuit of FIG. 1 when the charge transfer arrangement is disconnected.
FIG. 1 illustrates a resonant degaussing circuitDG.
A switch SCR1, that includes a combination of thyristor and a diode forming an ITR, couples, in a well known manner, capacitor C1 across degaussing coil LDG, at a beginning time of a degaussing interval. An example of the way a switch such as switch SCR1 operates is described in U.S. Pat. No. 4,489,253 entitled AUTOMATIC DEGAUSSING CIRCUIT WITH SWITCH MODE POWER SUPPLY in the name of T. J. Godawski.
Switch SCR1 of FIG. 1 is turned on for a duration of, for example, 5 milliseconds by a pulse that is generated by a one-shot flip-flop 52 and that is coupled through a transistor Q1 to the gate of switch SCR1. The maximum current that can flow through resistor R1 is lower than the holding current of switch SCR1. Therefore, after the end of the degaussing interval, switch SCR1 becomes nonconductive that allows capacitor C1 to recharge via resistor R1 that provides the initial conditions for the next degaussing interval. The pulse that turns on switch SCR1 may be generated, in a well known manner, by manually activating a switch such as a switch S1 of FIG. 1 and/or, automatically, each time power is applied to the degaussing circuit.
Charge transfer arrangement 100 of FIG. 1 includes a capacitor C2 that is precharged prior to, for example, degaussing interval TDG2 of FIG. 5a in a polarity shown in FIG. 1 from a voltage V2 produced by converter 51. Voltage V2 may be, for example, equal to voltage V1. Voltage V2 is coupled to capacitor C2 through a resistor R2 and through the current path that is formed by degaussing coil LDG.
In carrying out an aspect of the invention, a current transformer TF having a primary winding N1, that is formed by, for example, a single winding loop around a ferrite core that is constructed in a manner shown in FIG. 4, is coupled in the current path of degaussing current iDG of FIG. 1. Transformer TF generates a positive pulse V' in a secondary winding N2 of FIG. 3 in a positive polarity, as shown in FIG. 1. Pulse V' is generated each time, in a given cycle, when current iDG of FIG. 2 DG across coil LDG of FIG. 1 is at its maximum negative level and current iDG at a maximum rate of change such as at times T, 2T, 3T etc. of FIGS. 2 and 3.
Pulse V' is coupled through a pulse shaping and drive arrangement that includes transistors Q2 and Q3 to the base electrode of a transistor switch Q4 to turn on transistor switch Q4 during, for example, a short duration each degaussing cycle DCY of FIG. 2 when voltage VDG is at the maximum negative level. Capacitor C2 of FIG. 1 is precharged prior to, for example, the initiation of the degaussing interval. Capacitor C2 may be precharged, provided the value of resistor R2 is sufficiently small, even during each degaussing cycle DCY of the degaussing interval of FIG. 2 that precedes the current degaussing cycle of current iDG of FIG. 1.
When pulse V' occurs, transistor switch Q4 couples capacitor C2 in parallel with capacitor C1. Consequently, capacitor C2 transfers a charge to capacitor C1 that augments to that already stored in capacitor C1. Therefore, advantageously, by periodically augmenting the charge in capacitor C1 from that stored in capacitor C2, the corresponding duration of degaussing interval TDG2 of FIG. 5a that can be obtained for given circuit parameters is longer than if arrangement 100 was not used.
Degaussing interval TDG1
is shown in FIG. 5b depicts a situation that occurs when transistor
switch Q4 of FIG. 1 is removed from the circuit, for explanation
purposes. It can be seen that interval TDGl of FIG. 5b is shorter than degaussing interval TDG2 of FIG. 5a. Interval TDG2
occurs when transistor switch Q4 is included in arrangement 100 of FIG.
1, embodying the invention, that renders arrangement 100 fully
operative. It should be understood that the charge transfer DG cycle that occurs when degaussing current iDG is zero and when the rate of change of voltage VDG is minimal. Because the coupling of capacitor C2 to the resonant circuit occurs when current iDG is small, the disturbance to degaussing current iDG of FIG. 1 is, advantageously, small. Furthermore, because the duration in which capacitor C2 is coupled to the resonant circuit is short, the resonant frequency remains, advantageously, substantially unaffected.
from capacitor C2 to capacitor C1 may be designed to occur, during, for example, a relatively short duration, every half period T of FIG. 2 of current i
It should be understood that circuit 200 parameters such as, for example, the polarity and levels of voltages V1 and V2, respectively, the value of resistor R2, and the width of pulse V' may be tailored to fit the particular requirements.
CRT TUBE HITACHI 560EGB22-TC01. Self-converging deflection yoke:
A deflection yoke for use with a picture tube of a television receiver. A vertical deflection coil of the deflection coil has a larger winding angle on an electron gun side thereof than on a screen side thereof. A magnetic material piece is disposed inside the vertical deflection coil so that a vertical deflection magnetic field is formed into a strong barrel magnetic field on the electron gun side. As a result, a raster scanned on a faceplate of the picture tube is free from misconvergence and pincushion distortion. A core of the deflection yoke has sawtooth-shaped end surfaces, or auxiliary rings having sawtooth-shaped end surfaces are disposed on the end surfaces of the core. As a result, a wire of the vertical deflection coil is prevented from slipping on the end surfaces of the core although the wire of the vertical deflection coil is wound at a large winding angle on the electron gun side.
1. A deflection yoke for a television receiver comprising:
a horn-shaped core having a larger opening and a smaller opening; a horizontal deflection coil disposed inside said core;
a vertical deflection coil wound on said core so as to produce a pincushion shape magnetic field at said larger opening and a barrel shape magnetic field at said smaller opening with a winding angle of said vertical deflection coil at said smaller opening of said core being larger than a winding angle at said larger opening; and
a magnetic material piece disposed inside said vertical deflection coil at a position, on said vertical deflection coil, close to said smaller opening.
2. A deflection yoke according to claim 1, wherein said magnetic material piece is bonded to said vertical deflection coil.
3. A deflection yoke according to claim 1, wherein said magnetic material piece is attached to a separator.
4. A deflection yoke according to claim 1, wherein said magnetic material piece is an iron plate.
5. A deflection yoke according to one of claims 1, 2, 3 or 4 wherein said magnetic material piece is disposed at a position separated from said larger opening by 1/2-3/4 of a distance between said larger opening and said smaller opening.
6. A deflection yoke according to one of claims 1, 2, 3 or 4, wherein the width of said magnetic material piece is equal to 1/5-1/2 of the distance from said larger opening to said smaller opening of said core and the length of said magnetic material piece is chosen such that an angle looking into said magnetic material piece from the center of said deflection yoke is equal to 30°-70°.
7. A deflection yoke according to claim 1, wherein auxiliary rings, each having end surfaces formed into sawtooth shape, are attached to end surfaces of said core at said larger opening and said smaller opening to prevent a wire of said coil from slipping, said vertical deflection coil being wound on the sawtooth portions of said auxiliary rings.
8. A deflection yoke according to claim 1, wherein end surfaces of said larger opening and said smaller opening of said core are notched in sawtooth shape to prevent a wire of said coil from slipping, said vertical deflection coil being wound on the sawtooth portions of said end surfaces.
9. A deflection yoke according to claims 2 or 3, wherein said magnetic material piece is rectangularly shaped.
10. A deflection yoke according to claims 7 or 8, wherein said sawtooth shape includes small areas about which said wire of said coil is wound, each of said small areas defining a plane which is normal to said wire of said coil, whereby the tensile force acting on said wire is normal to said plane so as to prevent slipping of said wire.
Description:
FIELD OF THE INVENTION
The pres
ent invention
relates to a deflection yoke for a color television receiver, and more
particularly to a deflection yoke capable of reducing a pincushion
distortion of a raster scanned on a faceplate of a picture tube.
In a conventional television receiver, a raster scanned on the faceplate of the picture tube includes much distortion and nonconvergence. In a self-converging deflection yoke for a color picture tube having inline electron guns, convergence is compensated by forming a magnetic field generated by a horizontal deflection coil into a pincushion field and forming a magnetic field generated by a vertical deflection coil into a barrel field, as is well known in the art. Accordingly, as for the pincushion deflection distortion (hereinafter referred to simply as pincushion distortion) at the left and right edge of a screen of a color television receiver, in addition to an inherent pincushion distortion due to a radius of curvature of the picture tube, a further pincushion distortion is added by the fact that the vertical deflection magnetic field is formed into an intensified barrel field in order to compensate for the convergence, resulting in the movement of electron beam normal to magnetic line of force created by the vertical deflection coil. A pincushion distortion compensation circuit is, therefore, usually provided to compensate for such pincushion distortion at the left and right edge of the screen. In order to simultaneously compensate for the convergence and the pincushion distortion by a deflection coil only, without using the pincushion distortion compensation circuit, it is necessary to form that portion of the vertical deflection magnetic field which faces the screen into a pincushion shape to compensate for the pincushion distortion, and at the same time to form that portion of the vertical deflection magnetic field which faces the electron guns into a barrel shape which is intensified enough to balance out the pincushion magnetic field on the screen side, to compensate for the convergence.
FIG. 1 shows a perspective view of a deflection yoke. A major section of the deflection yoke 1 includes a saddle-shaped horizontal deflection coil 2, a toroidal vertical deflection coil 3, a core 4 and a separator 5.
FIGS. 2A and 2B show the vertical deflection coil 3 which forms a pincushion magnetic field on the screen side and an intensified barrel magnetic field on the electron gun side. FIG. 2A is a perspective view and FIG. 2B is a front view. A feature of the vertical deflection coil 3 resides in that a winding angle φ2 of a coil 6, wound on the core 4, at a larger opening 4a located on the screen side is smaller than a winding angle φ1 at a smaller opening 4b located on the electron gun side. A drawback of this vertical deflection coil 3 resides in that a wire 7 is apt to slip on the surface of the core 4 and hence it is difficult to attain proper winding angles φ1 and φ2 because the wire 7 of the coil 6 wound at positions having larger winding angles φ1 and φ2 is wound obliquely to the core 4.
In the vertical deflection coil used for a picture tube having a large pincushion distortion such as a wide deflection angle picture tube, e.g. 90° deflection picture tube, the winding angle φ1 of more than 150° and the winding angle φ2 of approximately 80° are required. Therefore, the wire 7 wound at the position of the winding angle φ1 is especially apt to slip. It is, therefore, necessary to form the magnetic field on the electron gun side into an intensified barrel field without increasing the winding angle φ1 at the opening 4b located on the electron gun side to over 150°.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a deflection yoke having means for producing an intensified barrel magnetic field without
materially increasing a winding angle at a smaller opening.
It is another object of the present invention to provide a deflection yoke in which a wire wound at a large winding angle position does not slip on a surface of a core.
The deflection yoke in accordance with the present invention comprises a vertical deflection coil having a smaller winding angle at a larger opening than a winding angle at a smaller opening, and a magnetic material piece disposed inside the vertical deflection coil. The deflection yoke of the present invention further includes a core having its end surfaces deformed or auxiliary ring for locking the wire. The deformed end surfaces of the core or the auxiliary ring are notched in sawtooth shape to prevent the wire of the vertical deflection coil from slipping.
When the magnetic material piece is disposed inside the vertical deflection coil, the shape of the vertical deflection magnetic field changes. Since the lines of magnetic force around the magnetic material piece pass in the body of the magnetic material piece or attracted thereto, the barrel magnetic field is further enhanced. Where the barrel magnetic field is enhanced, the pincushion magnetic field may be formed on the screen side. Accordingly, the pincushion distortion can be relieved.
If the end of the end surface of the core is normal to the wire of the vertical deflection coil, a force acting on the wire is normal to the end of the end surface and the slip of the wire on the end surface is prevented. The core of the deflection yoke of the present invention has its end surfaces notched in the sawtooth shape and the ends of the notched end surfaces are arranged to be normal to the wire of the vertical deflection coil, or the auxiliary ring having sawtooth-notched end surfaces is disposed over the end surfaces of the core. Consequently, the wire wound at the large winding angle position is prevented from slipping on the surface of the core.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a prior art deflection yoke.
FIG. 2A is a perspective view of a vertical deflection coil of the prior art.
FIG. 2B is a front view of the vertical deflection coil shown in FIG. 2A.
FIG. 3 is a front view of a deflection yoke of the present invention.
FIG. 4 is a sectional view of the deflection yoke of the present invention.
FIG. 5 shows a distribution graph of lines of magnetic force of a barrel magnetic field.
FIG. 6 shows a graph illustrating shapes of a pincushion magnetic field and a barrel magnetic field.
FIG. 7 is a side elevational view of a vertical deflection coil having an auxiliary ring of sawtooth shape.
FIG. 8 is a side elevational view of a vertical deflection coil wound on a core having its end surfaces deformed into sawtooth shape.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The preferred embodiments of the present invention will now be explained. Referring to FIG. 3, a deflection yoke 20 of the present invention includes a magnetic material piece 8 of iron or permaloy plate of rectangular or pedestal shape disposed inside a coil 6 of a vertical deflection coil 3. The magnetic material piece 8 is attached by bond or the like at a position closer to a smaller opening 4b in an inside of the coil 6, being separated from a larger opening 4a by 1/2-3/4 of a full distance between both openings. The width l1 of the magnetic material piece 8 is approximately 1/5-1/2 of the distance from the larger opening 4a of the vertical deflection coil to the smaller opening 4b. The length of the magnetic material piece 8 is chosen such that an angle φ3 looking into the magnetic material piece 8 from a center 0 is approximately 30°-70° C. By this magnetic material piece 8, the magnetic field on the side of the smaller opening 4b is formed into an intensified barrel field. In FIG. 3, a separator 5 is not shown. FIG. 4 shows a side sectional view of the deflection yoke 20 of the present invention, which clearly shows that the magnetic material piece 8 is attached to the vertical deflection coil 3 on the side of the smaller opening 4b. The magnetic material piece 8 may be attached to a horn-shaped portion 5b of the separator 5 instead of the vertical deflection coil 3, at a position close to a smaller opening 5a of the separator 5. In this case, a similarly intensified barrel field to that produced when it is attached to the vertical deflection coil 3 can be formed.
FIG. 5 shows a distribution graph of the lines of magnetic flux in the barrel magnetic field formed by the magnetic material piece 8, as looked from the larger opening side. The lines of magnetic force shown by dotted lines show lines of magnetic flux in the absence of the magnetic material piece 8 and the solid lines of magnetic flux show lines of magnetic flux in the presence of the magnetic material piece 8. Since the dotted lines of magnetic flux are altered to the solid lines of magnetic flux, the barrel magnetic field is enhanced.
FIG. 6 shows shapes of the pincushion magnetic field and the barrel magnetic field, in which an abscissa represents a center axis z of the deflection yoke 20 shown in FIG. 4. A strength B of the vertical magnetic field in the deflection yoke is generally expressed by: B=Bo +B2 y2
where Bo is a strength of the magnetic field at any point on the z-axis and represents a strength of magnetic field in x-axis direction normal to the plane of drawing. A strength of magnetic field at a position displaced in y-axis direction from that point on the z-axis which assumes the magnetic field strength Bo is given by the magnetic field strength B. B2 is a constant. An ordinate in FIG. 6 represents B2 /Bo. If B2 /Bo >0, the pincushion magnetic field is formed, if B2 /Bo =0, a uniform magnetic field is formed, and if B2 /Bo >0, the barrel magnetic field is formed. In FIG. 6, a solid line 16 shows a shape of the magnetic field in the presence of the magnetic material piece 8, and a broken line shows a shape of the magnetic field in the absence of the magnetic material piece 8. The z-axis of FIG. 6 corresponds to the z-axis shown in FIG. 4. It is seen from FIG. 6 that when the magnetic material piece 8 is attached, the barrel magnetic field is enhanced on the smaller opening side. As a result, the winding angle φ1 may be in the order of 150° and need not be more than 150°.
Referring to FIG. 7, in the deflection yoke 20 of the present invention, there are provided auxiliary rings 11a and 11b on end surfaces 4c and 4d of the core 4 to prevent the wire 7 of the vertical deflection coil 3 from slipping on the end surfaces 4c and 4d of the core 4. When the wire 7 intersects a center line 18 with an angle θ3, end surfaces of the auxiliary rings 11a and 11b are divided into small areas 12 and 13 in sawtooth shape with the small areas 12 and 13 intersecting a plane normal to the center line at angles of θ4 and θ5, respectively. When the angles θ4 and θ5 are equal to the angle θ3, tensile force acting on the wire 7 is normal to the small areas 12 and 13 and hence the wire 7 does not slip.
In FIG. 8, the wire 7 of the vertical deflection coil 3 is wound on a core 24 having its end surfaces 4c and 4d deformed into sawtooth shape. The end surfaces 4c and 4d of the core 24 have small areas 14 and 15 formed in sawtooth shape, like in the case of the auxiliary rings 11a and 11b shown in FIG. 7. The wire 7 wound on the end surfaces 4c and 4d is prevented from slipping by the small areas 14 and 15 by the same reason described above in connection with the auxiliary rings of FIG. 7.
In the deflection yoke, the overall magnetic field spreading from the smaller opening on the electron gun side to the larger opening on the screen side influences the convergence, but the pincushion distortion is largely influenced by the magnetic field on the larger opening side. This is because the distance between the electron beam and the deflection coil when the electron beam is deflected is shorter on the larger opening side than on the electron gun side, and the electron beam on the larger opening side of the deflection coil travels through curved ends of the lines of magnetic flux so that the magnetic field on the larger opening side largely influences the pincushion distortion. It
is seen from the above that the magnetic field distribution necessary
to simultaneously compensate for both the nonconvergence and the
pincushion distortion at the left and right edge of the screen only by
the deflection yoke, is the vertical deflection magnetic field which
forms the pincushion magnetic field on the larger opening side and the
barrel magnetic field on the smaller opening side. Thus, the deflection
yoke of the present invention can simultaneously compensate for both the
misconvergence and the pincushion distortion at the left and right
edges of the screen.
As described hereinabove, in accordance with the deflection yoke of the present invention, in order to form different shapes of magnetic field on the larger opening side and the smaller opening side, that is, in order to form the pincushion magnetic field on the larger opening side and form the barrel magnetic field on the smaller opening side, the winding angle of the vertical deflection coil at the larger opening is changed from that at the smaller opening, that is, the winding angle of the vertical deflection coil at the smaller opening is made larger than that at the larger opening. Furthermore, the magnetic material piece is disposed inside the vertical deflection coil to enhance the barrel magnetic field. As a result, the deflection yoke of the present invention can compensate for both the misconvergence and the pincushion distortion at the left and right edges of the screen.
Furthermore, the deflection yoke of the present invention includes a core having its end surfaces formed in sawtooth shape or auxiliary rings having sawtooth-shaped end surfaces. Accordingly, the wire of the vertical deflection coil is prevented from slipping on the end surfaces of the core although the wire of the vertical deflection coil is wound at the smaller opening with a large winding angle.
The pres
ent invention
relates to a deflection yoke for a color television receiver, and more
particularly to a deflection yoke capable of reducing a pincushion
distortion of a raster scanned on a faceplate of a picture tube. In a conventional television receiver, a raster scanned on the faceplate of the picture tube includes much distortion and nonconvergence. In a self-converging deflection yoke for a color picture tube having inline electron guns, convergence is compensated by forming a magnetic field generated by a horizontal deflection coil into a pincushion field and forming a magnetic field generated by a vertical deflection coil into a barrel field, as is well known in the art. Accordingly, as for the pincushion deflection distortion (hereinafter referred to simply as pincushion distortion) at the left and right edge of a screen of a color television receiver, in addition to an inherent pincushion distortion due to a radius of curvature of the picture tube, a further pincushion distortion is added by the fact that the vertical deflection magnetic field is formed into an intensified barrel field in order to compensate for the convergence, resulting in the movement of electron beam normal to magnetic line of force created by the vertical deflection coil. A pincushion distortion compensation circuit is, therefore, usually provided to compensate for such pincushion distortion at the left and right edge of the screen. In order to simultaneously compensate for the convergence and the pincushion distortion by a deflection coil only, without using the pincushion distortion compensation circuit, it is necessary to form that portion of the vertical deflection magnetic field which faces the screen into a pincushion shape to compensate for the pincushion distortion, and at the same time to form that portion of the vertical deflection magnetic field which faces the electron guns into a barrel shape which is intensified enough to balance out the pincushion magnetic field on the screen side, to compensate for the convergence.
FIG. 1 shows a perspective view of a deflection yoke. A major section of the deflection yoke 1 includes a saddle-shaped horizontal deflection coil 2, a toroidal vertical deflection coil 3, a core 4 and a separator 5.
FIGS. 2A and 2B show the vertical deflection coil 3 which forms a pincushion magnetic field on the screen side and an intensified barrel magnetic field on the electron gun side. FIG. 2A is a perspective view and FIG. 2B is a front view. A feature of the vertical deflection coil 3 resides in that a winding angle φ2 of a coil 6, wound on the core 4, at a larger opening 4a located on the screen side is smaller than a winding angle φ1 at a smaller opening 4b located on the electron gun side. A drawback of this vertical deflection coil 3 resides in that a wire 7 is apt to slip on the surface of the core 4 and hence it is difficult to attain proper winding angles φ1 and φ2 because the wire 7 of the coil 6 wound at positions having larger winding angles φ1 and φ2 is wound obliquely to the core 4.
In the vertical deflection coil used for a picture tube having a large pincushion distortion such as a wide deflection angle picture tube, e.g. 90° deflection picture tube, the winding angle φ1 of more than 150° and the winding angle φ2 of approximately 80° are required. Therefore, the wire 7 wound at the position of the winding angle φ1 is especially apt to slip. It is, therefore, necessary to form the magnetic field on the electron gun side into an intensified barrel field without increasing the winding angle φ1 at the opening 4b located on the electron gun side to over 150°.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a deflection yoke havi
ng means for producing an intensified barrel magnetic field without
materially increasing a winding angle at a smaller opening. It is another object of the present invention to provide a deflection yoke in which a wire wound at a large winding angle position does not slip on a surface of a core.
The deflection yoke in accordance with the present invention comprises a vertical deflection coil having a smaller winding angle at a larger opening than a winding angle at a smaller opening, and a magnetic material piece disposed inside the vertical deflection coil. The deflection yoke of the present invention further includes a core having its end surfaces deformed or auxiliary ring for locking the wire. The deformed end surfaces of the core or the auxiliary ring are notched in sawtooth shape to prevent the wire of the vertical deflection coil from slipping.
When the magnetic material piece is disposed inside the vertical deflection coil, the shape of the vertical deflection magnetic field changes. Since the lines of magnetic force around the magnetic material piece pass in the body of the magnetic material piece or attracted thereto, the barrel magnetic field is further enhanced. Where the barrel magnetic field is enhanced, the pincushion magnetic field may be formed on the screen side. Accordingly, the pincushion distortion can be relieved.
If the end of the end surface of the core is normal to the wire of the vertical deflection coil, a force acting on the wire is normal to the end of the end surface and the slip of the wire on the end surface is prevented. The core of the deflection yoke of the present invention has its end surfaces notched in the sawtooth shape and the ends of the notched end surfaces are arranged to be normal to the wire of the vertical deflection coil, or the auxiliary ring having sawtooth-notched end surfaces is disposed over the end surfaces of the core. Consequently, the wire wound at the large winding angle position is prevented from slipping on the surface of the core.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a prior art deflection yoke.
FIG. 2A is a perspective view of a vertical deflection coil of the prior art.
FIG. 2B is a front view of the vertical deflection coil shown in FIG. 2A.
FIG. 3 is a front view of a deflection yoke of the present invention.
FIG. 4 is a sectional view of the deflection yoke of the present invention.
FIG. 5 shows a distribution graph of lines of magnetic force of a barrel magnetic field.
FIG. 6 shows a graph illustrating shapes of a pincushion magnetic field and a barrel magnetic field.
FIG. 7 is a side elevational view of a vertical deflection coil having an auxiliary ring of sawtooth shape.
FIG. 8 is a side elevational view of a vertical deflection coil wound on a core having its end surfaces deformed into sawtooth shape.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The preferred embodiments of the present invention will now be explained. Referring to FIG. 3, a deflection yoke 20 of the present invention includes a magnetic material piece 8 of iron or permaloy plate of rectangular or pedestal shape disposed inside a coil 6 of a vertical deflection coil 3. The magnetic material piece 8 is attached by bond or the like at a position closer to a smaller opening 4b in an inside of the coil 6, being separated from a larger opening 4a by 1/2-3/4 of a full distance between both openings. The width l1 of the magnetic material piece 8 is approximately 1/5-1/2 of the distance from the larger opening 4a of the vertical deflection coil to the smaller opening 4b. The length of the magnetic material piece 8 is chosen such that an angle φ3 looking into the magnetic material piece 8 from a center 0 is approximately 30°-70° C. By this magnetic material piece 8, the magnetic field on the side of the smaller opening 4b is formed into an intensified barrel field. In FIG. 3, a separator 5 is not shown. FIG. 4 shows a side sectional view of the deflection yoke 20 of the present invention, which clearly shows that the magnetic material piece 8 is attached to the vertical deflection coil 3 on the side of the smaller opening 4b. The magnetic material piece 8 may be attached to a horn-shaped portion 5b of the separator 5 instead of the vertical deflection coil 3, at a position close to a smaller opening 5a of the separator 5. In this case, a similarly intensified barrel field to that produced when it is attached to the vertical deflection coil 3 can be formed.
FIG. 5 shows a distribution graph of the lines of magnetic flux in the barrel magnetic field formed by the magnetic material piece 8, as looked from the larger opening side. The lines of magnetic force shown by dotted lines show lines of magnetic flux in the absence of the magnetic material piece 8 and the solid lines of magnetic flux show lines of magnetic flux in the presence of the magnetic material piece 8. Since the dotted lines of magnetic flux are altered to the solid lines of magnetic flux, the barrel magnetic field is enhanced.
FIG. 6 shows shapes of the pincushion magnetic field and the barrel magnetic field, in which an abscissa represents a center axis z of the deflection yoke 20 shown in FIG. 4. A strength B of the vertical magnetic field in the deflection yoke is generally expressed by: B=Bo +B2 y2
where Bo is a strength of the magnetic field at any point on the z-axis and represents a strength of magnetic field in x-axis direction normal to the plane of drawing. A strength of magnetic field at a position displaced in y-axis direction from that point on the z-axis which assumes the magnetic field strength Bo is given by the magnetic field strength B. B2 is a constant. An ordinate in FIG. 6 represents B2 /Bo. If B2 /Bo >0, the pincushion magnetic field is formed, if B2 /Bo =0, a uniform magnetic field is formed, and if B2 /Bo >0, the barrel magnetic field is formed. In FIG. 6, a solid line 16 shows a shape of the magnetic field in the presence of the magnetic material piece 8, and a broken line shows a shape of the magnetic field in the absence of the magnetic material piece 8. The z-axis of FIG. 6 corresponds to the z-axis shown in FIG. 4. It is seen from FIG. 6 that when the magnetic material piece 8 is attached, the barrel magnetic field is enhanced on the smaller opening side. As a result, the winding angle φ1 may be in the order of 150° and need not be more than 150°.
Referring to FIG. 7, in the deflection yoke 20 of the present invention, there are provided auxiliary rings 11a and 11b on end surfaces 4c and 4d of the core 4 to prevent the wire 7 of the vertical deflection coil 3 from slipping on the end surfaces 4c and 4d of the core 4. When the wire 7 intersects a center line 18 with an angle θ3, end surfaces of the auxiliary rings 11a and 11b are divided into small areas 12 and 13 in sawtooth shape with the small areas 12 and 13 intersecting a plane normal to the center line at angles of θ4 and θ5, respectively. When the angles θ4 and θ5 are equal to the angle θ3, tensile force acting on the wire 7 is normal to the small areas 12 and 13 and hence the wire 7 does not slip.
In FIG. 8, the wire 7 of the vertical deflection coil 3 is wound on a core 24 having its end surfaces 4c and 4d deformed into sawtooth shape. The end surfaces 4c and 4d of the core 24 have small areas 14 and 15 formed in sawtooth shape, like in the case of the auxiliary rings 11a and 11b shown in FIG. 7. The wire 7 wound on the end surfaces 4c and 4d is prevented from slipping by the small areas 14 and 15 by the same reason described above in connection with the auxiliary rings of FIG. 7.
In the deflection yoke, the overall magnetic field spreading from the smaller opening on the electron gun side to the larger opening on the screen side influences the convergence, but the pincushion distortion is largely influenced by the magnetic field on the larger opening side. This is because the distance between the electron beam and the deflection coil when the electron beam is deflected is shorter on the larger opening side than on the electron gun side, and the electron beam on the larger opening side of the deflection coil travels through curved ends of the lines of magnetic flux so that the magnetic field on the larger opening side largely influences the pin
cushion distortion. It
is seen from the above that the magnetic field distribution necessary
to simultaneously compensate for both the nonconvergence and the
pincushion distortion at the left and right edge of the screen only by
the deflection yoke, is the vertical deflection magnetic field which
forms the pincushion magnetic field on the larger opening side and the
barrel magnetic field on the smaller opening side. Thus, the deflection
yoke of the present invention can simultaneously compensate for both the
misconvergence and the pincushion distortion at the left and right
edges of the screen. As described hereinabove, in accordance with the deflection yoke of the present invention, in order to form different shapes of magnetic field on the larger opening side and the smaller opening side, that is, in order to form the pincushion magnetic field on the larger opening side and form the barrel magnetic field on the smaller opening side, the winding angle of the vertical deflection coil at the larger opening is changed from that at the smaller opening, that is, the winding angle of the vertical deflection coil at the smaller opening is made larger than that at the larger opening. Furthermore, the magnetic material piece is disposed inside the vertical deflection coil to enhance the barrel magnetic field. As a result, the deflection yoke of the present invention can compensate for both the misconvergence and the pincushion distortion at the left and right edges of the screen.
Furthermore, the deflection yoke of the present invention includes a core having its end surfaces formed in sawtooth shape or auxiliary rings having sawtooth-shaped end surfaces. Accordingly, the wire of the vertical deflection coil is prevented from slipping on the end surfaces of the core although the wire of the vertical deflection coil is wound at the smaller opening with a large winding angle.
CRT TUBE HITACHI 560EGB22-TC01. Black matrix color picture tube:
A black matrix color picture tube has a phosphor layer and black matrix layer formed on the inner surface of the faceplate. A layer of glass having a low softening point is provided between the phosphor layer and the inner surface of the faceplate and between the black matrix layer and the inner surface of the faceplate. The softening point of the glass is below the temperature at which the tube is subjected during a frit baking step employed in the fabrication of the tube. For example, a borophosphate glass is used as the layer of glass having a low softening point.
1. A black matrix color picture tube having a phosphor layer and a black matrix layer on an inner surface of a faceplate, comprising said tube having a layer of glass between the inner surface of said faceplate and said phosphor layer and between the inner surface of said faceplate and said black matrix layer, wherein said glass of said layer is a borophosphate glass including 30-70 mol % of P2 O5 and 2-10 mol % of B2 O3, and further includes alkaline earth metal and alkaline metal oxide as remaining components.
2. A black matrix color picture tube having a phosphor layer and a black matrix layer on an inner surface of a faceplate, comprising said tube having a layer of glass between the inner surface of said faceplate and said phosphor layer and between the inner surface of said faceplate and said black matrix layer, wherein said glass of said layer is a borophosphate glass with a composition including 35-50 mol % of P2 O5, 3-7 mol % of B2 O3, 5-15 mol % of MgO, 5-15 mol % of CaO, 5-25 mol % of Li2 O, 5-25 mol % of Na2 O, 0-10 mol % of BaO, 0-10 mol % of K2 O, and 0.01-1 mol % of CeO2.
3. A frit baked black matrix color picture tube, comprising said tube having a faceplate with an inner surface, and a phosphor layer and a black matrix layer on the inner surface of the faceplate, said tube having a layer of glass between the inner surface of said faceplate and said black matrix layer, wherein the glass of said layer has a softening point lower than a predetermined frit baking temperature and wherein said glass comprises a borophosphate glass including 30-70 mol % of P2 O5 and 2-10 mol % of B2 O3, and further includes alkaline earth metal and alkaline metal oxide as remaining components.
4. A frit baked black matrix color picture tube, comprising said tube having a faceplate with an inner surface, and a phosphor layer and a black matrix layer on the inner surface of the faceplate, said tube having a layer of glass between the inner surface of said faceplate and said black matrix layer, wherein the glass of said layer has a softening point lower than a predetermined frit baking temperature and wherein said glass comprises borophosphate glass with a composition including 35-50 mol % of P2 O5, 3-7 mol % of B2 O3, 5-15 mol % of MgO, 5-15 mol % of CaO, 5-25 mol % of Li2 O, 5-25 mol % of Na2 O, 0-10 mol % of BaO, 0-10 mol % of K2 O, and 0.01-1 mol % of CeO2.
Description:
BACKGROUND OF THE INVENTION
This invention relates to a black matrix color picture tube and a method for its fabrication and particularly to a high-contrast black matrix color picture tube and a method for its fabrication.
The phosphor screen of a so-called black matrix color picture tube has on its faceplate the formation of a nonluminous, light-absorptive powder layer (black matrix) for partly covering the phosphor layer so that the phosphor layer appears through aperture sections (matrix holes).
Among the two major methods of forming such a phosphor screen, one is the wet process, which is typically as follows. On the inner surface of the faceplate, a photoresist is applied to form a film, and portions of the photoresist film where phosphor will be laid are hardened. After the development process, carbon suspension is applied to it to form a carbon application film and, thereafter, a removal agent is poured onto it to remove the hardened photoresist together with the overlaying carbon layer so that matrix holes are formed. Next, the photoresist slurry including phosphor is applied to form a film and the application film at positions where the phosphor will be laid is hardened. Following the development process, a phosphor layer is formed in the matrix holes. For making a phosphor layer of three colors, i.e., red, green and blue, the above process is repeated for each type of phosphor. Finally, the baking process is conducted to eliminate organic substances.
The
second is the dry process which was developed by some of the inventors
of the present invention (see JP-B-57-20651 which corresponds to
JP-A-53-126861). This method typically includes the processes of forming
an application film including aromatic diazonium salt, which exhibits
adhesion or tackiness by being exposed to light, on the faceplate, and
exposing it to the light radiation so that phosphor is deposited in the
irradiated portions. For making a phosphor layer of three colors, the
light irradiation and following processes are repeated three times.
Next, the entire application film is exposed to light and carbon is
deposited in portions other than the phosphor layer so that a black
matrix is formed. Finally, a fixing process using a polymer aqueous
solution, etc. is conducted so that these layers are made insoluble in
water. In case of a striped phosphor pattern, it is also possible to
form a black matrix layer before forming the phosphor layer.
In the formation of a phosphor screen by any of the above methods, there is created a gap partly between the phosphor layer and black matrix layer and the faceplate. When the light is incident from the outside (from the viewer's side), part of the light is reflected on the outer surface of the faceplate, and, because of the presence of the gap, part of the light is further reflected on the inner surface. The inner surface reflection, which depends on the refractivity of the faceplate, is over as much as 3-5% of the incident light. Therefore, suppression of the inner surface reflection is desired.
A method of reducing the inner surface reflection has been proposed, in which a material having virtually the same refractivity as the faceplate material, e.g., water glass, is filled in the gap between the faceplate and the black matrix layer. See, for example, JP-A-57-115749. This conventional technique, however, has a problem in that the water glass filled in the black matrix layer penetrates into the phosphor layer, causing a decrease in the light intensity of the phosphor.
Sticking of water glass to the phosphor surface by capillary action is unavoidable, and conceivably electron rays emitted by phosphor are retarded by the water glass, resulting in a decreasing intensity of the phosphor. Water glass does not much exist in the portion of the phosphor layer, but instead bubbles rest there and the inner surface reflection cannot be prevented completely in this portion. It is also undesirable to use water glass because of the mismatch of refractivity between water glass and the glass of the faceplate.
SUMMARY OF THE INVENTION
An object of this invention is to provide a black matrix color picture tube and a method of fabricating the same, which reduces the reflection on the inner surface of the faceplate without sacrificing the intensity of the phosphor.
According to one aspect of the present invention, in a black matrix color picture tube having a phosphor layer and a black matrix layer on the inner surface of a faceplate, a layer of glass of a low softening point is formed between the inner surface of the faceplate and the black matrix layer, so that the black matrix layer optically contacts the faceplate.
According to another aspect of the present invention, in a black matrix color picture tube having a phosphor layer and a black matrix layer on the inner surface of the faceplate, a layer of glass of a low softening point is formed between the inner surface of the faceplate and the phosphor layer and between the inner surface of the faceplate and the black matrix layer, so that the black matrix layer and the phosphor layer optically contact the faceplate. In consequence, the reflectivity of the faceplate is lowered, and a high-contrast picture tube is realized.
In the fabricating method according to one embodiment of the invention, formation of a phosphor screen includes a step of forming a glass layer having a low softening point on the inner surface of faceplate, a step of forming a black matrix layer and phosphor layer on the glass layer, and a step of softening the glass layer by heating.
In the case of forming a glass layer of a low softening point only between the black matrix layer and the faceplate based on this invention, the following method is preferably followed. The method is characterized by the formation of a phosphor screen including a step of applying a film of photoresist on the inner surface of a faceplate a step of forming a desired film pattern by exposing the applied film to light using a shadow mask followed by development, a step of forming a glass layer of low softening point on the faceplate and the applied film pattern, a step of forming a black matrix layer on the glass layer, a step of removing the applied film pattern together with the glass layer and black matrix layer formed on it using a removal agent, a step of softening the glass layer by heating, and a step of forming a phosphor layer on the portion of the applied film where the pattern has been removed.
In any of the above methods, if phosphor layers of three different colors are to be formed, the step of phosphor layer formation is conducted three times for the three types of phosphor. The methods may be based either on the wet process or dry process.
In the former method, the wet process and dry process may be employed for forming the black matrix layer and phosphor layer respectively, or both layers may be formed by either the wet process or the dry process.
The low softening point glass is preferably one having a softening point in the range of 200°-450° C., or more preferably in the range of 200°-430° C. Namely, the softening temperature is chosen to be below the frit baking temperature which is slightly above 450° C. in the fabrication of color picture tubes. The low softening point glass needs to be nonaqueous or aqua-resistive.
An example of low softening point glass is borophosphate glass (see Glass Technology, Vol. 17, No. 2, pp. 66-71). A preferable composition of glass used for this invention includes 30-70 mol % of P2 O5, 2-10 mol % of B2 O3, with an alkaline earth metal and alkaline metal oxide as the remaining components, for example. Too much or too little of the P2 O5 results in a crystallization of the glass, and too much P2 O5 further deteriorates the phosphors. Inclusion of MgO and/or, CaO is favorable for preventing the blackening of the phosphor. However, too much MgO or CaO tends to raise the softening point, although resistivity against water is improved. In order to prevent the discoloring of glass attributable to the electron rays, it is preferable for the glass composition to include 0.01-1 mol % of CeO2.
The following is an example of a composition of a low softening glass that is preferably used in practicing this invention.
P2 O5 --35-50 mol %, B2 O3 --3-7 mol %,
MgO--5-15 mol %, CaO--5-15 mol %,
Li2 O--5-25 mol %, Na2 O--5-25 mol %,
BaO--0-10 mol %, K2 O--0-10 mol %,
CeO2 --0.01-1 mol %
Glass of the above composition has a refractivity in the range of 1.50-1.55. To eliminate the inner surface reflection of the faceplate almost completely, it is especially desirable to use glass with a refractivity in the range of 1.52-1.54.
Use of glass including heavy metal such as Pb and Bi is unfavorable, since these heavy metals deteriorate the phosphors.
Low softening point glass in the form of a powder is more desirable, particularly glass powder with an average particle diameter ranging 0.5-20 μm is desirable.
The thickness of the glass layer is required to such an extent of flattening the roughness at the bottom of the phosphor layer and black matrix layer, and the presence of sole glass layer up to 0.1-60 μm is allowed.
The glass layer is softened by being heated, and it fills the space between the phosphor layer and black matrix layer. If the materials of the glass layer and faceplate have equal refractivity, the inner surface reflection of the face plate is eliminated. Practically, the condition is met unless the refractivities of both parts are greatly different. Generally, low softening point glass has similar refractivity to that of a faceplate material, except for special glass, and therefore the inner surface reflection of the faceplate can virtually be nullified. This point will further be described with reference to the, drawings
FIG. 2 shows a schematic partial cross-section of a faceplate used in a conventional color picture tube. Most of the light 1 is incident to the interior, although part of it is reflected on the surface of the faceplate 3. If there is a space between the faceplate 3 and phosphor layer 5 or black matrix layer 4, part of the incident light 1 is reflected on the inner surface of faceplate 3 to produce reflected light, indicated by light rays 2 and 2'. However, if the space is filled with low softening point glass 6 as shown in FIG. 1, which shows a partial schematic cross-section of a faceplate of the inventive color picture tube, reflection does not occur on the inner surface of the faceplate 3, and all of the incident light 1 is absorbed by the black matrix layer 4. Since the glass layer and phosphor layer have virtually equal refractivities, the surface of the phosphor layer 5 merely allows a little dispersion and does not reflect the light.
Since the glass layer does not melt at the above-mentioned processing temperature, it does not cover the phosphor layer, and the intensity of the phosphor does not fall.
Next, the formation of a black matrix film by employment of the dry process will be described. This work is done by a sequential process including a step of applying a light-sensitive material, which exhibits adhesion or tackiness by being exposed to light, on the surface of a substrate so as to form a thin layer, a step of exposing the thin layer in its portions of a figure pattern to light so that the exposed portions develop tackiness, and a step of sticking a nonluminous powder, thereby forming a pattern of nonluminous powder. The nonluminous powder pattern forming method is characterized by mixing the nonluminous powder with a low softening point glass powder and sticking the mixture to the exposed portions. The nonluminous powder pattern forming method further includes a subsequent step of developing the light-sensitive material to form a pattern of thin film, a step of forming a nonluminous powder layer on the light-sensitive thin film, and a step of removing the light-sensitive film together with the nonluminous powder layer on it, thereby forming the mixture of the nonluminous powder and low softening point glass powder on the pattern of the light-sensitive thin film.
In the dry process, the formation of the nonluminous powder pattern may be either before or after the formation of the phosphor pattern. However, in the case of a dot pattern of phosphor, the phosphor pattern is preferably formed first for the expedient of forming the exposure pattern. In the case of a striped pattern of phosphor, the patterns may be formed in an arbritrary order. In the wet process, the nonluminous powder pattern is formed first in general.
The mixing ratio of nonluminous powder and
glass powder is preferably such that the nonluminous powder is 0.1-7
weight % of the mixture, and is more preferably 0.3-4 weight %. A lesser
amount of nonluminous powder below 0.1 weight % spoils the effect of
forming a black matrix and allows for the easy formation of pin holes.
An excess amount of the powder above 7 weight % spoils the effect of the
reduction of the inner surface reflection as shown in Table 1, which
shows the results of measurements of reflection attained by varying the
quantity of carbon black in the same condition as in FIG. 1, as will be
explained later. The inner surface reflectivity represents the value of
5° regular reflection for a 550 nm wavelength.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a partial schematic cross-sectional diagram showing the inventive color picture tube faceplate.
FIG. 2 is a partial schematic cross-sectional diagram showing the conventional color picture tube faceplate.
FIGS. 3 and 4 are diagrams of reflectivity used to explain the present invention.
FIG. 5 is a spectral diagram of 5° regular reflection on the nonluminous powder layer resulting from the inventive method and conventional method.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
EMBODIMENT 1
The following materials were metered, mixed in an agate mortar, heated gradually from room temperature in a crucible, and baked at 800° C. for one hour in air. Borophosphate glass was yielded with the composition (mol %) of: 45P2 O5.5B2 O3.11MgO. 11CaO.9Li2 O.19Na2 O. The softening point was 400° C. (Generally, the measurement of the softening point involves an error of around ±10° C.). The glass was powdered.
Phosphoric acid (85% H3 PO4)--51.88 g, Boron oxide (B2 O3)--1.83 g, Basic magnesium carbonate ((MgCO3)4.Mg(OH)2.5H2 O)--5.46 g, Calcium carbonate (CaCO3)--5.69 g, Lithium carbonate (LiCO3)--3.27 g, Sodium carbonate (Na2 CO3)--9.99 g.
On the inner surface of the faceplate, the aqueous solution including 1% polyvinyl alcohol, 2% diethylene glycol and 2% diglycerol was applied by rotatary application to a thickness of about 1 μm. The applied surface was dusted with the glass powder so that a glass powder layer was formed. The faceplate was heated gradually from room temperature to 450° C. for 30 minutes, and a borophosphate glass layer with a thickness of about 10 um was formed. Photoresist was applied to the faceplate to form a film, and the light was irradiated through a shadow mask to positions where phosphor dots of three types (R, G, B) would be formed. Through, the development process, hardened photoresist dots were formed. Colloidal black carbon suspension was applied to the inner surface of the faceplate, and it was dryed. By pouring a removal agent to remove the hardened photoresist dots together with carbon on them, matrix holes were formed.
Through the application, light exposure and development using the photoresist phosphor slurry for the three types of phosphors sequentially, as in the conventional method, phosphor layers were formed.
The above process was followed by aluminizing, frit baking, and mounting of electron guns to complete a color picture tube. The glass layer was softened in the process of frit baking.
For the comparison purposes, a conventional color picture tube, in which the borophosphate glass layer was absent and the rest of the tube was constructed according to the inventive method, was fabricated. FIG. 3 shows the result of measurement of 5° regular reflection on the red, green and blue phosphor layers of both picture tubes. Indicated by 31, 32 and 33 are reflectivities of the conventional blue, red and green phosphor screen, while 34, 35 and 36 indicate the counterparts of this invention. As will be appreciated from the figure, the inventive phosphor screen has almost no reflectivity on all phosphor layers in a wide range of wavelength. FIG. 4 shows the reflectivity on the black matrix layer. Also in this case, the inventive color picture tube has almost no reflectivity on the black matrix layer. The light release factor of phosphor was 108-112% greater than that of the conventional one.
EMBODIMENT 2
The following materials were used to obtain borophosphate glass of 40P2 O5.5B2 O3.12MgO.12CaO.10Li2 O. 21Na2 O. The process was identical to Embodiment 1. The glass has a softening point of 410° C. The measurement result was virtually identical to Embodiment 1.
Phosphoric acid (85% H3 PO4)--46.12 g,
Boron oxide (B2 O3)--1.83 g, Basic magnesium carbonate ((MgCO3)4.Mg(OH)2.5H2 O)--6.01 g,
Calsium carbonate (CaCO3)--6.26 g,
Lithium carbonate (LiCO3)--3.59 g,
Sodium carbonate (Na2 CO3)--10.99 g.
EMBODIMENT 3
The same process as Embodiment 1 was conducted, except that borophosphate glass was used. The measurement result was virtually identical to Embodiment 1.
EMBODIMENT 4
Light-sensitive polymer compound was applied by rotation on the inner surface of the faceplate. Using a super high pressure mercury lamp as a light source, positions where phosphor dots of red, green and blue would be put were exposed to the light through a shadow mask. After development in water, 3-color dots made of light-hardened resist were obtained. After the panel had been dried, an adhesive of the following composition was applied thinly and evenly.
Composition of adhesive:
Zinc chloride--3%; Polyvinyl alcohol--0.15%; Water--rest
Subsequently, powder of borophosphate glass was dusted to form a powder layer. After exposure to ammonia vapor, the plate was washed in water, and a fixed layer of borophosphate glass was formed. Colloidal liquid of black carbon was applied over the layer, and it was dried. After the light-hardened photoresist dots had been processed using a removal agent, the dots and borophosphate glass and carbon on it were removed using a hot water spray, and black matrix holes were obtained. Next, by completing the conventional application, exposure, development and dry processes for each of the 3-color phosphors sequentially, phosphor films were formed. Finally, aluminizing, frit baking and mounting of electron guns were conducted following the conventional method, and a black matrix color picture tube was completed.
EMBODIMENT 5
The glass produced in Embodiment 1 was powdered and mixed with black carbon in the following proportion, and the following mixture was obtained.
Glass of low softening point--25 g;
Carbon black--1 g
EMBODIMENT 6
A film of the following composition was applied as a light-sensitive material on a glass substrate.
Zinc chloride double salt of N,N-dimethylaniline-p-diazonium chloride--95 weight %; Polyvinyl alcohol--5 weight %
Using a super high pressure mercury lamp, the film was exposed to the ultraviolet rays through a mask, and the exposed portions developed stickiness.
The black powder produced in Embodiment 5 was dusted and developed in air blow. The black powder sticked in the stickiness portion, and a pattern of nonluminous powder layer was formed. Following the process in ammonia vapor and then washing in water, the powder layer was fixed, and it was baked at 430° C. for 30 minutes. A pattern of a nonluminous powder layer, with the inner surface reflectivity being lowered, was obtained.
It was tried to expose an application film of light-sensitive material to a pattern of ultraviolet rays in advance and, following the deposition of phosphor on the exposed portions, the entire surface was exposed, which was followed by dusting of the black powder produced in Embodiment 5, development, ammonia process, washing in water, and baking at 430° C. for 30 minutes, as in the same manner as Embodiment 5, and as a result the intensity of the phosphor was not spoiled at all and the inner surface reflectivity was lowered.
FIG. 5 shows the reduction of inner surface reflectivity. In the figure, indicated by (a) is the spectrum of 5° regular reflectivity on the nonluminous powder layer produced by the conventional method (wet process), and (b) is the result accomplished by the present invention. The measurement of reflectivity was conducted by making the light incident at 5° to normal on the surface. The reflectivity of the glass surface was subtracted from the measurement result. The same result as when the film produced by the inventive method in close contact with the substrate was reached, and the inner surface reflectivity was nullified at any wavelength.
This invention relates to a black matrix color picture tube and a method for its fabrication and particularly to a high-contrast black matrix color picture tube and a method for its fabrication.
The phosphor screen of a so-called black matrix color picture tube has on its faceplate the formation of a nonluminous, light-absorptive powder layer (black matrix) for partly covering the phosphor layer so that the phosphor layer appears through aperture sections (matrix holes).
Among the two major methods of forming such a phosphor screen, one is the wet process, which is typically as follows. On the inner surface of the faceplate, a photoresist is applied to form a film, and portions of the photoresist film where phosphor will be laid are hardened. After the development process, carbon suspension is applied to it to form a carbon application film and, thereafter, a removal agent is poured onto it to remove the hardened photoresist together with the overlaying carbon layer so that matrix holes are formed. Next, the photoresist slurry including phosphor is applied to form a film and the application film at positions where the phosphor will be laid is hardened. Following the development process, a phosphor layer is formed in the matrix holes. For making a phosphor layer of three colors, i.e., red, green and blue, the above process is repeated for each type of phosphor. Finally, the baking process is conducted to eliminate organic substances.
The
second is the dry process which was developed by some of the inventors
of the present invention (see JP-B-57-20651 which corresponds to
JP-A-53-126861). This method typically includes the processes of forming
an application film including aromatic diazonium salt, which exhibits
adhesion or tackiness by being exposed to light, on the faceplate, and
exposing it to the light radiation so that phosphor is deposited in the
irradiated portions. For making a phosphor layer of three colors, the
light irradiation and following processes are repeated three times.
Next, the entire application film is exposed to light and carbon is
deposited in portions other than the phosphor layer so that a black
matrix is formed. Finally, a fixing process using a polymer aqueous
solution, etc. is conducted so that these layers are made insoluble in
water. In case of a striped phosphor pattern, it is also possible to
form a black matrix layer before forming the phosphor layer. In the formation of a phosphor screen by any of the above methods, there is created a gap partly between the phosphor layer and black matrix layer and the faceplate. When the light is incident from the outside (from the viewer's side), part of the light is reflected on the outer surface of the faceplate, and, because of the presence of the gap, part of the light is further reflected on the inner surface. The inner surface reflection, which depends on the refractivity of the faceplate, is over as much as 3-5% of the incident light. Therefore, suppression of the inner surface reflection is desired.
A method of reducing the inner surface reflection has been proposed, in which a material having virtually the same refractivity as the faceplate material, e.g., water glass, is filled in the gap between the faceplate and the black matrix layer. See, for example, JP-A-57-115749. This conventional technique, however, has a problem in that the water glass filled in the black matrix layer penetrates into the phosphor layer, causing a decrease in the light intensity of the phosphor.
Sticking of water glass to the phosphor surface by capillary action is unavoidable, and conceivably electron rays emitted by phosphor are retarded by the water glass, resulting in a decreasing intensity of the phosphor. Water glass does not much exist in the portion of the phosphor layer, but instead bubbles rest there and the inner surface reflection cannot be prevented completely in this portion. It is also undesirable to use water glass because of the mismatch of refractivity between water glass and the glass of the faceplate.
SUMMARY OF THE INVENTION
An object of this invention is to provide a black matrix color picture tube and a method of fabricating the same, which reduces the reflection on the inner surface of the faceplate without sacrificing the intensity of the phosphor.
According to one aspect of the present invention, in a black matrix color picture tube having a phosphor layer and a black matrix layer on the inner surface of a faceplate, a layer of glass of a low softening point is formed between the inner surface of the faceplate and the black matrix layer, so that the black matrix layer optically contacts the faceplate.
According to another aspect of the present invention, in a black matrix color picture tube having a phosphor layer and a black matrix layer on the inner surface of the faceplate, a layer of glass of a low softening point is formed between the inner surface of the faceplate and the phosphor layer and between the inner surface of the faceplate and the black matrix layer, so that the black matrix layer and the phosphor layer optically contact the faceplate. In consequence, the reflectivity of the faceplate is lowered, and a high-contrast picture tube is realized.
In the fabricating method according to one embodiment of the invention, formation of a phosphor screen includes a step of forming a glass layer having a low softening point on the inner surface of faceplate, a step of forming a black matrix layer and phosphor layer on the glass layer, and a step of softening the glass layer by heating.
In the case of forming a glass layer of a low softening point only between the black matrix layer and the faceplate based on this invention, the following method is preferably followed. The method is characterized by the formation of a phosphor screen including a step of applying a film of photoresist on the inner surface of a faceplate a step of forming a desired film pattern by exposing the applied film to light using a shadow mask followed by development, a step of forming a glass layer of low softening point on the faceplate and the applied film pattern, a step of forming a black matrix layer on the glass layer, a step of removing the applied film pattern together with the glass layer and black matrix layer formed on it using a removal agent, a step of softening the glass layer by heating, and a step of forming a phosphor layer on the portion of the applied film where the pattern has been removed.
In any of the above methods, if phosphor layers of three different colors are to be formed, the step of phosphor layer formation is conducted three times for the three types of phosphor. The methods may be based either on the wet process or dry process.
In the former method, the wet process and dry process may be employed for forming the black matrix layer and phosphor layer respectively, or both layers may be formed by either the wet process or the dry process.
The low softening point glass is preferably one having a softening point in the range of 200°-450° C., or more preferably in the range of 200°-430° C. Namely, the softening temperature is chosen to be below the frit baking temperature which is slightly above 450° C. in the fabrication of color picture tubes. The low softening point glass needs to be nonaqueous or aqua-resistive.
An example of low softening point glass is borophosphate glass (see Glass Technology, Vol. 17, No. 2, pp. 66-71). A preferable composition of glass used for this invention includes 30-70 mol % of P2 O5, 2-10 mol % of B2 O3, with an alkaline earth metal and alkaline metal oxide as the remaining components, for example. Too much or too little of the P2 O5 results in a crystallization of the glass, and too much P2 O5 further deteriorates the phosphors. Inclusion of MgO and/or, CaO is favorable for preventing the blackening of the phosphor. However, too much MgO or CaO tends to raise the softening point, although resistivity against water is improved. In order to prevent the discoloring of glass attributable to the electron rays, it is preferable for the glass composition to include 0.01-1 mol % of CeO2.
The following is an example of a composition of a low softening glass that is preferably used in practicing this invention.
P2 O5 --35-50 mol %, B2 O3 --3-7 mol %,
MgO--5-15 mol %, CaO--5-15 mol %,
Li2 O--5-25 mol %, Na2 O--5-25 mol %,
BaO--0-10 mol %, K2 O--0-10 mol %,
CeO2 --0.01-1 mol %
Glass of the above composition has a refractivity in the range of 1.50-1.55. To eliminate the inner surface reflection of the faceplate almost completely, it is especially desirable to use glass with a refractivity in the range of 1.52-1.54.
Use of glass including heavy metal such as Pb and Bi is unfavorable, since these heavy metals deteriorate the phosphors.
Low softening point glass in the form of a powder is more desirable, particularly glass powder with an average particle diameter ranging 0.5-20 μm is desirable.
The thickness of the glass layer is required to such an extent of flattening the roughness at the bottom of the phosphor layer and black matrix layer, and the presence of sole glass layer up to 0.1-60 μm is allowed.
The glass layer is softened by being heated, and it fills the space between the phosphor layer and black matrix layer. If the materials of the glass layer and faceplate have equal refractivity, the inner surface reflection of the face plate is eliminated. Practically, the condition is met unless the refractivities of both parts are greatly different. Generally, low softening point glass has similar refractivity to that of a faceplate material, except for special glass, and therefore the inner surface reflection of the faceplate can virtually be nullified. This point will further be described with reference to the, drawings
FIG. 2 shows a schematic partial cross-section of a faceplate used in a conventional color picture tube. Most of the light 1 is incident to the interior, although part of it is reflected on the surface of the faceplate 3. If there is a space between the faceplate 3 and phosphor layer 5 or black matrix layer 4, part of the incident light 1 is reflected on the inner surface of faceplate 3 to produce reflected light, indicated by light rays 2 and 2'. However, if the space is filled with low softening point glass 6 as shown in FIG. 1, which shows a partial schematic cross-section of a faceplate of the inventive color picture tube, reflection does not occur on the inner surface of the faceplate 3, and all of the incident light 1 is absorbed by the black matrix layer 4. Since the glass layer and phosphor layer have virtually equal refractivities, the surface of the phosphor layer 5 merely allows a little dispersion and does not reflect the light.
Since the glass layer does not melt at the above-mentioned processing temperature, it does not cover the phosphor layer, and the intensity of the phosphor does not fall.
Next, the formation of a black matrix film by employment of the dry process will be described. This work is done by a sequential process including a step of applying a light-sensitive material, which exhibits adhesion or tackiness by being exposed to light, on the surface of a substrate so as to form a thin layer, a step of exposing the thin layer in its portions of a figure pattern to light so that the exposed portions develop tackiness, and a step of sticking a nonluminous powder, thereby forming a pattern of nonluminous powder. The nonluminous powder pattern forming method is characterized by mixing the nonluminous powder with a low softening point glass powder and sticking the mixture to the exposed portions. The nonluminous powder pattern forming method further includes a subsequent step of developing the light-sensitive material to form a pattern of thin film, a step of forming a nonluminous powder layer on the light-sensitive thin film, and a step of removing the light-sensitive film together with the nonluminous powder layer on it, thereby forming the mixture of the nonluminous powder and low softening point glass powder on the pattern of the light-sensitive thin film.
In the dry process, the formation of the nonluminous powder pattern may be either before or after the formation of the phosphor pattern. However, in the case of a dot pattern of phosphor, the phosphor pattern is preferably formed first for the expedient of forming the exposure pattern. In the case of a striped pattern of phosphor, the patterns may be formed in an arbritrary order. In the wet process, the nonluminous powder pattern is formed first in general.
| TABLE 1 |
| ______________________________________ |
| Quantity of carbon Inner surface black (weight %) reflectivity (%) |
| ______________________________________ |
0.1 1 0.3 0 0.5 0 0.8 0 1.0 0 1.6 0 4.0 0 4.7 0 5.5 1 7.0 2 10.0 4 17.0 4 |
| ______________________________________ |
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a partial schematic cross-sectional diagram showing the inventive color picture tube faceplate.
FIG. 2 is a partial schematic cross-sectional diagram showing the conventional color picture tube faceplate.
FIGS. 3 and 4 are diagrams of reflectivity used to explain the present invention.
FIG. 5 is a spectral diagram of 5° regular reflection on the nonluminous powder layer resulting from the inventive method and conventional method.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
EMBODIMENT 1
The following materials were metered, mixed in an agate mortar, heated gradually from room temperature in a crucible, and baked at 800° C. for one hour in air. Borophosphate glass was yielded with the composition (mol %) of: 45P2 O5.5B2 O3.11MgO. 11CaO.9Li2 O.19Na2 O. The softening point was 400° C. (Generally, the measurement of the softening point involves an error of around ±10° C.). The glass was powdered.
Phosphoric acid (85% H3 PO4)--51.88 g, Boron oxide (B2 O3)--1.83 g, Basic magnesium carbonate ((MgCO3)4.Mg(OH)2.5H2 O)--5.46 g, Calcium carbonate (CaCO3)--5.69 g, Lithium carbonate (LiCO3)--3.27 g, Sodium carbonate (Na2 CO3)--9.99 g.
On the inner surface of the faceplate, the aqueous solution including 1% polyvinyl alcohol, 2% diethylene glycol and 2% diglycerol was applied by rotatary application to a thickness of about 1 μm. The applied surface was dusted with the glass powder so that a glass powder layer was formed. The faceplate was heated gradually from room temperature to 450° C. for 30 minutes, and a borophosphate glass layer with a thickness of about 10 um was formed. Photoresist was applied to the faceplate to form a film, and the light was irradiated through a shadow mask to positions where phosphor dots of three types (R, G, B) would be formed. Through, the development process, hardened photoresist dots were formed. Colloidal black carbon suspension was applied to the inner surface of the faceplate, and it was dryed. By pouring a removal agent to remove the hardened photoresist dots together with carbon on them, matrix holes were formed.
Through the application, light exposure and development using the photoresist phosphor slurry for the three types of phosphors sequentially, as in the conventional method, phosphor layers were formed.
The above process was followed by aluminizing, frit baking, and mounting of electron guns to complete a color picture tube. The glass layer was softened in the process of frit baking.
For the comparison purposes, a conventional color picture tube, in which the borophosphate glass layer was absent and the rest of the tube was constructed according to the inventive method, was fabricated. FIG. 3 shows the result of measurement of 5° regular reflection on the red, green and blue phosphor layers of both picture tubes. Indicated by 31, 32 and 33 are reflectivities of the conventional blue, red and green phosphor screen, while 34, 35 and 36 indicate the counterparts of this invention. As will be appreciated from the figure, the inventive phosphor screen has almost no reflectivity on all phosphor layers in a wide range of wavelength. FIG. 4 shows the reflectivity on the black matrix layer. Also in this case, the inventive color picture tube has almost no reflectivity on the black matrix layer. The light release factor of phosphor was 108-112% greater than that of the conventional one.
EMBODIMENT 2
The following materials were used to obtain borophosphate glass of 40P2 O5.5B2 O3.12MgO.12CaO.10Li2 O. 21Na2 O. The process was identical to Embodiment 1. The glass has a softening point of 410° C. The measurement result was virtually identical to Embodiment 1.
Phosphoric acid (85% H3 PO4)--46.12 g,
Boron oxide (B2 O3)--1.83 g, Basic magnesium carbonate ((MgCO3)4.Mg(OH)2.5H2 O)--6.01 g,
Calsium carbonate (CaCO3)--6.26 g,
Lithium carbonate (LiCO3)--3.59 g,
Sodium carbonate (Na2 CO3)--10.99 g.
EMBODIMENT 3
The same process as Embodiment 1 was conducted, except that borophosphate glass was used. The measurement result was virtually identical to Embodiment 1.
| TABLE 2 |
| __________________________________________________________________________ |
| Composition No. (mol %) 1 2 3 4 5 6 7 8 9 10 11 12 |
| __________________________________________________________________________ |
P2 O5 35 40 45 50 45 45 45 45 45 45 50 55 B2 O3 5 5 5 5 5 5 5 5 5 5 3.6 5 MgO 13.5 12.5 12 9 9 12.5 9 11.2 7 5 -- 9 CaO 13.5 12.5 12 9 9 12.5 9 11.2 7 5 -- 9 BaO -- -- -- -- 9 4.7 -- -- -- -- -- -- Li2 O 10.5 15 9 7 10 10 7 8.8 20.8 20 20 7 Na2 O 22.5 14.7 16.7 20 12.7 10 10 18.8 15 19.75 10 15 K2 O -- -- -- -- -- -- 9.7 -- -- -- 16.4 -- CeO2 -- 0.3 0.3 -- 0.3 0.3 0.3 -- 0.2 0.25 -- -- Softening point 410 410 420 410 400 420 410 400 360 320 280 370 (°C.) |
| __________________________________________________________________________ |
EMBODIMENT 4
Light-sensitive polymer compound was applied by rotation on the inner surface of the faceplate. Using a super high pressure mercury lamp as a light source, positions where phosphor dots of red, green and blue would be put were exposed to the light through a shadow mask. After development in water, 3-color dots made of light-hardened resist were obtained. After the panel had been dried, an adhesive of the following composition was applied thinly and evenly.
Composition of adhesive:
Zinc chloride--3%; Polyvinyl alcohol--0.15%; Water--rest
Subsequently, powder of borophosphate glass was dusted to form a powder layer. After exposure to ammonia vapor, the plate was washed in water, and a fixed layer of borophosphate glass was formed. Colloidal liquid of black carbon was applied over the layer, and it was dried. After the light-hardened photoresist dots had been processed using a removal agent, the dots and borophosphate glass and carbon on it were removed using a hot water spray, and black matrix holes were obtained. Next, by completing the conventional application, exposure, development and dry processes for each of the 3-color phosphors sequentially, phosphor films were formed. Finally, aluminizing, frit baking and mounting of electron guns were conducted following the conventional method, and a black matrix color picture tube was completed.
EMBODIMENT 5
The glass produced in Embodiment 1 was powdered and mixed with black carbon in the following proportion, and the following mixture was obtained.
Glass of low softening point--25 g;
Carbon black--1 g
EMBODIMENT 6
A film of the following composition was applied as a light-sensitive material on a glass substrate.
Zinc chloride double salt of N,N-dimethylaniline-p-diazonium chloride--95 weight %; Polyvinyl alcohol--5 weight %
Using a super high pressure mercury lamp, the film was exposed to the ultraviolet rays through a mask, and the exposed portions developed stickiness.
The black powder produced in Embodiment 5 was dusted and developed in air blow. The black powder sticked in the stickiness portion, and a pattern of nonluminous powder layer was formed. Following the process in ammonia vapor and then washing in water, the powder layer was fixed, and it was baked at 430° C. for 30 minutes. A pattern of a nonluminous powder layer, with the inner surface reflectivity being lowered, was obtained.
It was tried to expose an application film of light-sensitive material to a pattern of ultraviolet rays in advance and, following the deposition of phosphor on the exposed portions, the entire surface was exposed, which was followed by dusting of the black powder produced in Embodiment 5, development, ammonia process, washing in water, and baking at 430° C. for 30 minutes, as in the same manner as Embodiment 5, and as a result the intensity of the phosphor was not spoiled at all and the inner surface reflectivity was lowered.
FIG. 5 shows the reduction of inner surface reflectivity. In the figure, indicated by (a) is the spectrum of 5° regular reflectivity on the nonluminous powder layer produced by the conventional method (wet process), and (b) is the result accomplished by the present invention. The measurement of reflectivity was conducted by making the light incident at 5° to normal on the surface. The reflectivity of the glass surface was subtracted from the measurement result. The same result as when the film produced by the inventive method in close contact with the substrate was reached, and the inner surface reflectivity was nullified at any wavelength.
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