JP3135460B2 - Aging method of cathode ray tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aging method for improving emission characteristics of a cathode ray tube such as a projection tube or a color picture tube, particularly a cathode ray tube incorporating an impregnated cathode.

[0002]

2. Description of the Related Art Impregnated cathodes are used in cathode ray tubes such as projection tubes and color picture tubes. The impregnated cathode is made of BaO, Ca on a porous tungsten cathode substrate.
It is impregnated with an emitter material such as O and Al ₂ O ₃ . When the cathode substrate is heated by the heater, Ba reduced by tungsten is diffused to the surface of the cathode substrate, and O
A Ba monoatomic layer is generated in s-Ru or the like, and thermoelectrons are emitted.

[0003] Such an impregnated cathode has a higher electric conductivity than an oxide cathode, and can increase a cathode current (also a cathode load) per unit area. For this reason, projection tubes that require high brightness and high resolution,
Impregnated cathodes are used in large color picture tubes or high definition display tubes.

Although the impregnated cathode has the advantages described above, the Ba monoatomic layer on the cathode surface is destroyed by the ion bombardment due to the residual gas in the tube.
The emission of thermoelectrons is reduced. Most of the gas remaining in the cathode ray tube after the getter flash and load aging steps is an inert gas that is not adsorbed by the getter. Thermions emitted from the cathode collide with the inert gas, and a portion of the inert gas ionized by cations is accelerated by the electric field and collides with the cathode, so that the Ba monoatomic layer on the cathode surface is destroyed. You.

[0005] Among the inert gases remaining in the tube, Ar gas is particularly large in mass, so that the impact force applied to the cathode is large. Ba on the cathode surface is successively supplied from within the layer by thermal diffusion, but if the pressure of Ar gas is large,
Since the breaking rate of the Ba monoatomic layer increases, the formation of the Ba monoatomic layer required for emission of thermoelectrons is inhibited. Generally, the pressure of Ar gas that does not reduce the amount of emitted thermoelectrons is 2 ×
10 ⁻⁴ Pa or less.

Therefore, after activating the cathode in the load aging step, the inert gas in the tube is reduced by applying a raster aging method. In the raster aging method, almost the same potential as in the normal operation of the cathode ray tube is applied to each electrode of the electron gun, and the entire area of the phosphor screen is scanned with an electron beam to obtain a white raster (no signal image).
Is projected. At this time, if further activation of the cathode is required, the heater voltage is set slightly higher than its rated value. Taking a projection tube as an example, 6.3 V for the heater, 250 to 0 V for the cathode, 0 V for the control electrode, and 50 V for the acceleration electrode
0-700V, 6-8kV for focusing electrode , 30 for anode
A voltage of about kV is applied.

When the raster aging process is set, the inert gas in the tube collides with the electron beam emitted from the cathode to be ionized, and is buried in an electrode or the like lower than the anode by the action of an electric field. Can be increased.

[0008]

However, since the ionization efficiency by the raster aging method is low, the degree of vacuum in the tube cannot be sufficiently increased unless the aging treatment is performed for a long time. The reason for the low efficiency of ionization to cationize the inert gas is that the anode voltage is too high . In addition, the input power to the phosphor screen of the cathode ray tube is limited, and the current that can flow is also limited.

As described above, the inert gas that has collided with the thermoelectrons is ionized into cations and accelerated toward the cathode by the action of the electric field. Then, since a part thereof collides with the cathode to destroy the Ba monoatomic layer, in the raster aging method, the cathode is continuously subjected to ion bombardment in the process of reducing the inert gas.

An object of the present invention is to provide an improved aging method capable of efficiently reducing an inert gas remaining in a tube while protecting a cathode from ion bombardment.

[0011]

According to the present invention, in order to achieve the above-mentioned object, it is necessary to emit thermoelectrons from the cathode to the acceleration electrode through the control electrode while applying a high negative voltage to the anode. A method for aging a cathode ray tube is provided.

Further, a heating current is supplied to the heater, a positive bias voltage is applied to the cathode based on the control electrode potential, a positive voltage is applied to at least one of the accelerating electrode and the focusing electrode, and
Further, there is provided a method of aging a cathode ray tube, wherein a negative high voltage is applied to each of the anodes.

[0013]

According to the present invention, since the heating current is supplied to the heater to activate the cathode and emit thermionic electrons from the cathode to the accelerating electrode side, there is no floating between the cathode and the accelerating electrode or the focusing electrode. The active gas is ionized into cations by electron impact. On the other hand, since a negative high voltage is applied to the anode, the positively charged cations are accelerated by the negative potential of the anode and buried in the glass or the anode on the inner wall of the tube without colliding with the cathode.
That is, since the inert gas remaining in the tube can be reduced without impacting the cathode surface with the ionized cations, the emission characteristics can be improved without requiring a long time.

[0014]

Next, an embodiment of the present invention will be described with reference to the drawings.

A cathode ray tube 1 shown in FIG. 1 is a projection tube incorporating a BPF (bipotential focus) type electron gun.
It is connected to the power supply circuit for aging. The electron gun includes an impregnated cathode 3 heated by a heater 2.
, A control electrode 4, an acceleration electrode 5, a focusing electrode 6, and an anode 7, and a conductive film 8 connected to the anode 7.
Have reached the phosphor screen 9. Reference numeral 10 denotes an anode terminal.

The heater 2 is connected to a heating power supply 11, and the acceleration electrode 5 and the focusing electrode 6 are connected to a positive electrode of a DC power supply 12. The anode terminal 10 is connected to the negative electrode of the high-voltage DC power supply 13 and
The negative electrode 2 and the positive electrode of the high-voltage DC power supply 13 are grounded. The control electrode 4 is grounded and the cathode 3
Are grounded via a self-biasing resistor 14. In this example, the accelerating electrode 5 and the focusing electrode 6 are connected to a common DC power supply 12, but each is connected to a separate power supply and a positive voltage higher than that for the accelerating electrode 5 is applied to the focusing electrode 6. This can increase the electron beam trajectory. Although the resistor 14 is set to a value that does not exceed the limit of the cathode load, the cathode 3 can be connected to a dedicated DC power supply.

With such a circuit configuration, the thermoelectrons radiated from the cathode 3 collide with the inert gas floating in the tube and ionize the inert gas into cations.
The gas molecules having a positive charge due to the ionization are accelerated toward the phosphor screen 9 by the negative high potential of the anode 7 and are embedded in the glass on the inner wall of the tube or a solid such as the anode 7. That is, the degree of vacuum in the tube can be increased while protecting the cathode 3.

The negative high voltage applied to the anode 7 must be set to a value that does not cause the gas embedded in the solid to be re-emitted due to environmental changes such as temperature changes. According to an experiment, in the case of the projection tube used in this example, when the anode voltage was set to -10 kV , a good degree of vacuum in the tube could be maintained without being affected by environmental changes. In order to improve the efficiency of reducing gas in the pipe,
The larger the number of times of ionization at which the electron beam collides with the inert gas, the better. Therefore, the voltage applied to the accelerating electrode 5 and the focusing electrode 6 is determined by considering the cathode load, the impact ionization efficiency, the cathode current, and the electron beam orbit. Set to maximize the product of lengths. According to an experiment, in the case of the projection tube used in this example, the best gas reduction effect was obtained when the voltage applied to the acceleration electrode 5 and the focusing electrode 6 was set to 700V. The voltage applied to the accelerating electrode 5 and the focusing electrode 6 depends on the design of the electron gun.
It is desirable to adjust in the range of 00V.

By the aging to which the present invention is applied, the effect of reducing the gas in the pipe having the characteristic shown by the curve a in FIG. 2 is obtained. Curve b shows the characteristic of reducing gas in a pipe obtained by conventional raster aging. As can be seen, when the aging method according to the present invention is applied, the pressure of the Ar gas remaining in the pipe is reduced to 2 × 10 ⁻⁴ Pa in 1/5 of the processing time as compared with the case where the conventional raster aging is applied. Can be reduced.

The cathode ray tube used in the above embodiment is BP
Although the projection tube has a built-in F-type electron gun, other types of electron guns, such as a DPF (discelerate prefocus) type, a UPF (unipotential focus) type, and an OMF (outer magnetic focus) type, etc. The aging method of the present invention can be applied to a cathode ray tube having a built-in electron gun. Further, the present invention can be applied to aging of a color picture tube incorporating an in-line type or delta type electron gun. Further, the voltage applied to each of the anode, the acceleration electrode and the focusing electrode may be a pulsating voltage.

The aging method of the present invention is applied after the getter flash step, but is also effective after the load aging step or after the spot knocking step. Further, the aging method of the present invention can be applied as a means for reproducing a cathode ray tube having poor emission.

[0022]

As described above, according to the aging method for a cathode ray tube of the present invention, since a negative high voltage is applied to the anode, the concentration of inert gas remaining in the tube can be reduced while preventing ion bombardment on the cathode. Can be lowered in time,
Emission characteristics can be significantly improved.

Also, unlike conventional raster aging, since the electron beam does not reach the phosphor screen, there is an advantage that the electron beam does not need to be deflected and the processing equipment can be simplified.

[Brief description of the drawings]

FIG. 1 is an electrical connection diagram of a cathode ray tube aging method according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a relationship between an aging treatment time and an Ar gas pressure in a pipe.

[Explanation of symbols]

 Reference Signs List 1 cathode ray tube 2 heater 3 cathode 4 control electrode 5 acceleration electrode 6 focusing electrode 7 anode

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-64-71036 (JP, A) JP-A-64-77834 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01J 9/44

Claims (2)

(57) [Claims] 1. A method of aging a cathode ray tube, wherein a thermoelectron is emitted from a cathode to a side of an acceleration electrode through a control electrode while applying a high negative voltage to an anode. 2. A heating current is supplied to the heater, a positive bias voltage is applied to the cathode with reference to the control electrode potential, a positive voltage is applied to at least one of the accelerating electrode and the focusing electrode, and a negative high voltage is applied to the anode. Aging method for a cathode ray tube, wherein