JPS6252422B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a color cathode ray tube, and particularly to a conductive graphite coating (hereinafter referred to as graphite coating) coated on the inner wall surface of the tube. Normally, the graphite coating formed on the inner wall surface of the funnel part of a color cathode ray tube has the function of accelerating the electron beam by applying a high voltage, and collecting secondary electrons generated from electrodes such as a shadow mask. It performs various important functions such as preventing deterioration of color purity and supplying high voltage to the electron gun structure, and is required to have no adverse effect on the vacuum inside the tube such as gas release and adsorption ability. There is. On the other hand, this graphite film containing graphite as a main component is formed on the inner wall surface of the funnel portion of the pulp by the following method. That is, after cleaning the inner wall surface of the funnel part constituting the color cathode ray tube using a cleaning agent such as hydrogen fluoride and drying, a predetermined portion of the inner wall surface is coated with a binder such as potassium silicate, sodium silicate, or lithium silicate in graphite. After applying a graphite paint prepared by adding a certain proportion of silicate, such as the following, using a brush coating method or a spray method, heat treatment is performed to form a graphite coating. The color cathode ray tube formed in this way has an anode button buried in the center of the funnel that contacts this graphite coating and supplies a high voltage, and a high voltage connected to the final electrode of the electron gun structure in the neck. A receiving valve spacer contact is disposed in contact with the graphite coating, and a high voltage is supplied from an external high voltage generating circuit to the electrode of the electron gun via the anode button, the graphite coating, and the valve spacer contact. However, the graphite coating has a valve spacer contact that is part of the electron gun structure and receives high voltage, and is placed in contact with the neck portion of the graphite coating.
During operation, a large current from sparks generated by foreign objects inside the pipe was flowing through the relevant part. Therefore, attempts to reduce the incidence of such sparks include, for example, applying an impact to the bulb to remove dust from the bulb before sealing the electron gun assembly in the funnel. Various methods have been used to treat the problem, such as re-cleaning the neck area, or forming a strong graphite film to prevent the contact area from being scraped.
It was difficult to reliably eliminate spark generation. On the other hand, such a spark is generated from the high voltage generation circuit to the electron gun circuit via the anode button, graphite coating and valve spacer contact.
A large current of 1000A (Eb = 30KV) flows, damaging the valve spacer contact and the graphite film in contact with it, significantly reducing the current supplied to the electron gun circuit, and also damaging the electron gun circuit connected to the electron gun structure. was causing damage. In addition, the specific resistance of the graphite coating in such a structure is about 0.15 Ω-cm, and the resistance value is about less than about 1 KΩ. An attempt has been made to eliminate these defects by applying a high-resistance graphite film containing Fe ₂ O ₃ , graphite, and water glass as the main components to the inner wall of the funnel to give it a high resistance value. Methods have been proposed to reduce the large current generated. However, this Fe ₂ O ₃ -based graphite coating is a TiO ₂ -based graphite coating (mainly composed of TiO ₂ , graphite, and water glass).
Compared to TiO2-based graphite coatings, the gas release properties are inferior to those of _TiO2- based graphite coatings, which may result in poor vacuum, poor emission, etc. This can be countered by increasing the amount of getters scattered, but this is not advantageous because it increases cost. Also,
Fe ₂ O ₃ -based graphite coatings have a larger specific gravity difference between graphite and Fe ₂ O ₃ than TiO ₂ -based graphite coatings, so the stability of the material slurry tends to be somewhat inferior. This leads to an increase in management man-hours at the time,
It's still not advantageous. Furthermore, the strength of the graphite coating is
Fe ₂ O ₃ -based graphite coatings and TiO ₂ -based graphite coatings are equivalent, or Fe ₂ O ₃ -based graphite coatings are more or less advantageous, but in terms of practical strength, TiO ₂ -based graphite coatings are sufficient and there are no problems at all. do not have. Therefore, if the two are comprehensively compared, the TiO ₂ -based graphite coating is superior. Therefore, it is an object of the present invention to reduce the occurrence of sparks, and even if sparks occur, damage to the valve spacer contact and the graphite coating in contact with it, and prevent the electron gun from being damaged. An object of the present invention is to provide a color cathode ray tube whose circuits are prevented from being damaged. In order to achieve this object, the color cathode ray tube according to the present invention has a funnel cone and a graphite coating material mainly composed of graphite, titanium dioxide, and water glass and having a specific resistance of 10 ⁰ to ^{10 5} Ω-cm. 5KΩ between the valve spacer contact connected to the anode button and the electron gun electrode.
It has a resistance value of ~5MΩ. The color cathode ray tube according to the present invention will be described in detail below with reference to the drawings. FIG. 1 is a sectional view of essential parts showing an embodiment of a color cathode ray tube according to the present invention. In the same figure, 1
2 is a panel portion, 2 is a funnel portion, 2a is a funnel cone portion, 2b is a funnel neck portion, 3 is a shadow mask disposed on the inner surface side of the panel portion 1,
4 is a cone internal graphite coating formed on the inner wall surface of the funnel cone portion 2a; 5 is a TiO ₂ -based high-resistance graphite coating according to the present invention formed on the inner wall surface of the funnel cone portion 2a; 6 Reference numeral 1 indicates a graphite coating inside the neck portion formed on the inner wall surface of the funnel neck portion 2b, 7 indicates an anode button for supplying high voltage from the outside to the graphite coating 4 on the interior of the cone portion, 8 indicates the electron gun structure, and 9 indicates graphite coating inside the neck portion. a valve spacer contact which forms part of the electron gun assembly 8 by bringing its contact piece into contact with the coating 6 and receives high voltage;
10 is a getter provided at the tip of the electron gun assembly 8, and 11 is a getter shield for shielding the getter 10 from scattering in the direction of the electron gun assembly 8. Example 1 First, TiO ₂ -based graphite whose main components are graphite = 11, TiO ₂ = 100, and water glass = 30 in weight ratio was placed in the funnel cone portion 2a of a 20-inch 90° deflection color cathode ray tube shown in Fig. 1. Funnel neck part 2b on the inner wall surface of
A high resistance graphite coating 5 was formed by applying the coating in the vicinity. With this configuration, a high resistance value of about 400KΩ can be obtained between the anode button 7 and the valve spacer contact 9 of the electron gun assembly 8 in a vacuum, and the current at the time of sparking is reduced to about 1/30 of the conventional one. I was able to do that. In this case, the getter 10 is attached to the tip of the electron gun assembly 8, and the getter 10 is attached to the tip of the electron gun assembly 8.
However, the cone interior graphite coating 4 was not applied to the portion where the support of the getter 10 contacts the inner wall of the funnel cone portion 2a. Further, a getter shield 11 is attached to the getter 10 to prevent the material of the getter 10 from directly flying onto the high-resistance graphite coating 5 except for adhesion due to wrapping or the like. Embodiment 2 FIG. 2 is a sectional view of a main part showing another embodiment of the color cathode ray tube according to the present invention, and since the same symbols as in FIG. 1 represent the same elements, a description thereof will be omitted. In the same figure, first, graphite = 12, TiO ₂ =
100, water glass = 30 is applied as a main component on the inner wall surface of the funnel cone portion _2a , near the funnel neck portion 2b and between the anode button 7,
A high resistance graphite coating 12 was deposited. With this configuration, the spark current between the anode button 7 and the valve spacer contact 9 in a vacuum can be reduced to about 1/15. In this case, the getter 10 was a frittable getter manufactured by SAES Getter Co., Ltd., attached to the frame of the shadow mask 3, and the getter was scattered mainly in the direction of the phosphorescent surface. In the above embodiment, the case where the high-resistance graphite coatings 5 and 12 are deposited in a ring shape on the inner wall surface of the funnel cone portion 2a has been described, but the present invention is not limited to this. Instead, if a resistance value of 5KΩ to 5MΩ is obtained between the anode button 7 and the valve spacer contact 9 by forming it independently on a part of other graphite coatings, for example, in a band shape, the same effect as described above can be obtained. It will be done. In addition, in the above embodiment, the position and scattering direction of the getter 10 are determined so as to prevent the getter 10 from directly flying onto the high-resistance graphite coatings 5 and 12 and deteriorating the resistance value, excluding adhesion due to wrapping etc. Must. In addition, if this is difficult, a getter shield 1 is provided to prevent the getter material from scattering in the direction of the high-resistance graphite coatings 5 and 12 and deteriorating the resistance value.
1 structure. In addition, in the above-mentioned embodiment, the high-resistance graphite coatings 5, 1
Although it has been explained that the getter material does not fly directly onto the surface of the material 2, it is difficult to avoid adhesion by wrapping around the material, and there is no problem as long as it is discontinuous. In the above, the specific resistance is
10 ⁰ to 10 ⁵ Ω-cm, and the resistance value was set to 5KΩ to 5MΩ. However, if the specific resistance and resistance value are out of this range, the spark current will become large, the spot-knocking work will be difficult, and there will be problems due to poor continuity. There are problems such as valve cracks, and there are also problems with focus stability due to changes in dark current, and these values are based on sparks during operation,
It is decided based on the balance with spotting during manufacturing. To explain this in more detail, Table 1 shows the results of trial production using 19'' and 20'' color cathode ray tubes with different resistivities, resistance values, etc.

[Table] As is clear from Table 1, when the resistivity and resistance value are smaller than 1Ω-cm and 5KΩ, respectively, such as samples A and B, the spark current is large;
This will cause damage to the external circuit. Conversely, in samples K and L, which have large specific resistance and resistance values, the spark current itself is small, but when the resistance becomes high, the amount of insulating material in the coating increases, and it is evenly distributed with graphite, which is a conductor. The problem arises that the resistance value is not distributed, and the resistance value fluctuates widely, making it difficult to perform the desired spot-knocking work.The current value fluctuates greatly with each spark, making it impossible to maintain stability, and furthermore, valve cracking occurs. The problem arises. On the other hand, in Samples C to J, the spark current value was also small, and desired spot spotting could be performed. As explained above, according to the color cathode ray tube according to the present invention, when a spark is generated for some reason at the contact portion between the electron gun structure and the graphite coating, the current that flows can be reduced, for example, compared to the conventional structure.
This means that it can be made extremely small, such as 1/30 or 1/15, which prevents damage to the graphite coating and the valve spacer contact of the electron gun assembly that comes into contact with it, and furthermore, reduces the size of the circuit connected to the electron gun assembly. This provides an extremely excellent effect of preventing damage to color cathode ray tubes and greatly improving reliability, quality, etc. of color cathode ray tubes.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part showing one embodiment of a color cathode ray tube according to the present invention, and FIG. 2 is a sectional view of a main part showing another embodiment of a color cathode ray tube according to the invention. 1...Panel part, 2...Funnel part, 2a...
...Funnel cone part, 2b...Funnel neck part, 3...Panel part, 4...Graphite coating inside the cone part, 5...High resistance graphite coating, 6...Graphite coating inside the neck part, 7...Anode button, 8...Electron gun structure, 9...Valve spacer contact, 10
...Getter, 11...Getter Shield, 12
...High resistance graphite coating.

Claims (1)

[Claims] 1. In a color cathode ray tube having a conductive graphite coating formed on the inner wall surface of the funnel, at least a portion of the conductive graphite coating existing between the points where the anode button and the electron gun structure contact the conductive graphite coating is It is made of a graphite coating material whose main components are graphite, titanium dioxide, and water glass and has a specific resistance of 10 ⁰ to ^{10 5} Ω-cm to provide a resistance value of 5 KΩ to 5 MΩ between the anode button and the electron gun structure. Features a color cathode ray tube.