JPH0414737A - Cathode ray tube - Google Patents

Abstract

PURPOSE:To maintain a good high vacuum condition inside a tube and offer a long-life cathode ray tube by forming an inside film containing activated carbon and alumina sol on the surface of material inside the tube except for a fluorescent face. CONSTITUTION:To prevent oxidation and burning of inside material in a frit sealing process, alumina sol is used as binder for the inside material containing activated carbon. The alumina sol is formed by, in general, dispersing fine alumina powder in water using acid stabilizer such as HCl, H2CO3, CH3COOH. For the alumina sol, alumina solid is preferably added so as to be within 0.1-10 pts.wt. to 1 pts.wt. activated carbon. As the alumina sol is used instead of water glass used in the past as binder which is added to the inside material, the decrease of activated carbon firing temperature due to alkaline metal in the water glass is prevented. As a result, there is no possibility of oxidation and burning of the inside material even when heated in a frit sealing process.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to cathode ray tubes, and particularly to improvements in the conductive coating that is the interior material of the tube body.

[Summary of the invention]

The present invention provides a method of forming an interior film containing alumina sol and activated carbon as a conductive film used as an interior material of a cathode ray tube body, or by forming an alumina sol film on an interior film using activated carbon and water glass. This aims to stabilize the getter effect and extend the life of the cathode.

[Traditional technique (nete)]

Generally, the tube body of a cathode ray tube includes a panel having a phosphor screen formed on the inner surface, a funnel body coupled to the panel and having a conductive coating on the inner surface, and a funnel body coupled to the funnel body.
It consists of a neck that houses the electron gun. In this specification, the funnel body and neck will be collectively referred to as a funnel.

These panels and funnels are fused together (frit-sealed) via a solder glass called a frit after going through a predetermined manufacturing process or assembly process, respectively.

In this frit sealing step, heating is performed at approximately 440° C. to crystallize the frit. An electron gun, etc. is built into the cathode ray tube body constructed in this way, and is exhausted.

Cathode ray tubes are manufactured through various processes such as getter flash and knocking.

By the way, various gases are released into the tube during operation of the cathode ray tube, which causes a decrease in the degree of vacuum within the tube and shortens the life of the cathode ray tube. These gases are
For example, the electron beam may be emitted from the vicinity of the heater due to the heat of the heater constituting the electron gun, or the electron beam emitted from the electron gun may collide with the electrode single color selection mechanism, conductive coating, etc. that are internal members of the tube body. released. The emitted gas is ionized by the accelerated electron beam and collides with the cathode surface of the electron gun, or is adsorbed on the cathode surface as it cools when the cathode ray tube stops operating. When such collisions and adsorption occur on the cathode surface, the electron emitting material layer is poisoned and the emission characteristics (T!
single-child release ability) deteriorates. For example, CO or CO inside the tube.
When t is emitted, they react with the Ba-BaO system, which is the electron emitting material layer of the electron gun, resulting in consumption of free Ba and B
Change of aO to BaC01 causes carburization (adsorption of W released carbon) and inhibits electron emission. Therefore, in order to adsorb unnecessary gases and maintain a high vacuum state inside the tube body, generally, getters such as Ba and C are used inside the cathode ray tube tube body.
a, a metal such as Mg is provided in bulk or thin film form.

On the other hand, a conductive film is coated on the inner wall of the tube, particularly on the inner wall of the funnel, for the purpose of stabilizing the internal potential. The above-mentioned conductive film is usually formed by suspending graphite in water glass, applying an interior paint made by adding a surfactant or the like as necessary, and drying.

Since the conductive film formed in this way has a black color, it has a heat dissipation effect and absorbs the light emitted from the phosphor screen towards the funnel side, while blocking external light and maintaining a high contrast ratio. have an effect.

Furthermore, it also has the effect of supplementing the function of the gainer by adsorbing unnecessary gases.

As described above, in a cathode ray tube, it is important to adsorb unnecessary gases and maintain a high vacuum state inside the tube in order to extend the life of the tube, and several techniques have been proposed for this purpose. One example is a method of applying an organic ammonium silicate aqueous solution such as a 5in2-choline aqueous solution to the inside of the tube.

Also, although the purpose is slightly different from that of a cathode ray tube,
Publication No. 136747 discloses a technique for improving the brightness and preventing deterioration of phosphors by providing an adsorption layer mainly composed of graphite or carbon on the inner wall of a fluorescent display tube and adsorbing gas inside the tube. has been done.

[Problem to be solved by the invention]

However, it is currently not possible to obtain a satisfactory effect depending on the conventionally proposed techniques.For example, in the method of applying an organic ammonium silicate aqueous solution,
A practically sufficient getter effect is not obtained. In addition, in the technique disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 57-136747, a paint in which fine particles of graphite or carbon with an average particle size of 0.1 to 100 μm are dispersed in water glass is applied to the inner wall of a fluorescent display tube. After that, it is fired at around 500"C to form a porous adsorption layer, but the gas adsorption ability has not actually improved that much, so it is not very effective even when applied as an interior material for cathode ray tubes. cannot be expected.

SUMMARY OF THE INVENTION The present invention has been proposed in view of the conventional situation, and an object of the present invention is to provide a cathode ray tube that maintains a high vacuum state inside the tube body and has a long life.

(Means for Solving the Problems) As a result of conducting studies to achieve the above-mentioned object, the present inventors have determined that activated carbon, which has a sufficiently high oxidation temperature, can be used instead of conventional graphite as a constituent material of the conductive film. The present inventors have discovered that a remarkable getter effect can be stably obtained by using this method, and have completed the present invention.

That is, the cathode ray tube according to the first invention of the present application is characterized in that the interior film containing activated carbon and alumina sol is small (both are formed on the surface of the inner member of the tube excluding the phosphor screen).

Further, in the cathode ray tube according to the second invention of the present application, an inner film containing activated carbon and water glass is formed on at least the surface of the inner member of the tube excluding the phosphor screen, and an alumina sol film is formed on the inner film. It is characterized by becoming.

Activated carbon is used in the present invention because its specific surface area is extremely large compared to that of graphite (approximately less than 100 ryf/g), and excellent gas absorption ability can be expected. In fact, if we leave sufficiently degassed activated carbon and graphite in the air at room temperature for one day and examine the weight change due to the adsorption of water vapor, co, etc., we find that the weight increase for graphite is only 4 to 5%. On the other hand, preliminary experiments have confirmed that activated carbon increases the weight by about 30%. Practically, it is desirable that activated carbon has a specific surface area of about 100 to 3000 m/g.

However, activated carbon is more susceptible to oxidation than graphite due to its crystal structure. Furthermore, it has been known that the ignition temperature of activated carbon is lowered by the inclusion of alkali metals. In the field of manufacturing cathode ray tubes, the ignition temperature of activated carbon in the atmosphere is 3.3% because the alkali metals in the water glass used as a binder when preparing interior paints promote this phenomenon.
The temperature will drop to around 30°C. However, in the frit sealing process in the actual manufacture of cathode ray tubes, oxygen is consumed for crystallization of the frit and combustion of the phosphor screen.
The oxygen concentration inside the tube is lower than in the atmosphere, and the ignition temperature of the activated carbon interior material has risen to about 400 to 460°C. However, even with this, it is impossible to always prevent oxidation in the frit sealing process performed at around 440° C., and this may be a cause of lowering the yield of cathode ray tubes. In other words, if the activated carbon interior material is burnt out, the conductive film becomes transparent in the burnt area, degrading the light-shielding effect, and the inner wall of the funnel becomes charged due to the deterioration of conductivity, making it impossible to accurately deflect the electron beam. This is because various inconveniences occur.

Therefore, in the first invention of the present application, alumina sol is used as a binder for the interior material containing activated carbon in order to prevent the interior material from being oxidized and burned away during the frit sealing process. Alumina sol is generally made of fine alumina powder MC1,
It is dispersed in water using an acid stabilizer such as HtCOs or CH3COOH. Alumina sol is
Alumina solid content is 0.1 to 10 per part by weight of activated carbon
It is preferable that the amount is added within the range of parts by weight.

If the solid content of alumina is less than 0.1 part by weight, the adhesion to the internal members of the tube will be insufficient. Conversely, if it is more than 10 parts by weight, the conductivity of the inner membrane formed will decrease and it will become nearly transparent. , the heat dissipation effect, light shielding properties, etc. will be reduced.

Moreover, in the second invention of the present application, an alumina sol film is formed on the interior crotch containing activated carbon and water glass.

This alumina sol film has a thickness of several μm, which is sufficient for practical use; if it is too thick, it will impair the getter effect of the interior material, and
There are holes that cause cracks in the membrane.

When forming an alumina sol film, a solution prepared by diluting alumina sol with pure water or the like may be spin-coded or sprayed.

Note that the alumina sol film has been conventionally formed as an oxidation-preventing film on the carbon stripes of the phosphor screen, and even if it exists inside the cathode ray tube tube, it does not have any adverse effect on the operating characteristics of the cathode ray tube in practice.

[Effect]

In the present invention, activated carbon, which has a large specific surface area, is used instead of graphite, which is conventionally used as the interior material of cathode ray tubes, so that the degree of vacuum inside the cathode ray tube deteriorates due to its gas absorption ability. This makes it possible to prevent this and extend the service life.

Further, in the first invention of the present application, alumina sol is used as a binder added to the interior material instead of water glass, which is conventionally used, so that a decrease in the ignition temperature of activated carbon due to the alkali metal in the water glass is prevented. Ru. Therefore,
Since there is no spread that would cause oxidation and burnout of the interior material even when subjected to heating in the frit sealing process, the yield in manufacturing cathode ray tubes can be improved.

Furthermore, in the second invention of the present application, since an alumina sol film is formed on the inner film containing activated carbon and water glass, contact of activated carbon with oxidizing gases such as oxygen and carbon monoxide is suppressed. Therefore, in the frit sealing process, the activated carbon is less likely to be oxidized, so there is no risk that the interior material will be oxidized and burned out.

Therefore, the yield in manufacturing cathode ray tubes can be improved.

〔Example〕

Hereinafter, preferred embodiments of the present invention will be described based on experimental results.

After drying, it was heated in an electric furnace. At this time, the temperature was increased in 10°C increments, and after holding each set temperature for 30 minutes, the preparations were taken out and the presence or absence of oxidation burnout was determined.

For comparison with this example, the oxidation temperature was similarly determined for activated carbon powder alone and interior paint containing activated carbon using water glass as a binder.

The results are shown in Table 1.

Table 1 JL [Tsu 1 First, as a preliminary experiment, the oxidation temperature of the interior film in the atmosphere was confirmed.

That is, 1 part by weight of activated carbon having a specific surface area of 1000 n'r/g was dispersed in 3 parts by weight of pure water, and 8 parts by weight of alumina sol (alumina solid content 10% by weight) were added and mixed to prepare an interior paint.

Next, apply this interior paint on the preparation and dry. From Table 1, when alumina sol is used as a binder,
It was confirmed that the oxidation temperature was significantly improved compared to the conventional case of using water glass. Therefore, in the frit sealing process of actual cathode ray tube manufacturing, there is no risk of oxidation and burnout of the interior material containing activated carbon, so that the yield in cathode ray tube manufacturing can be improved.

On the other hand, when the film properties of the interior membrane obtained using alumina sol were investigated, it was found that the hardness, electrical conductivity, and adhesive strength were on the same level as conventional interior membranes.

Therefore, an interior paint using alumina sol as a binder as described above was applied to the inner wall of the funnel, and an 80°
Dry with C to remove water by evaporation to a thickness of 1 to 200 μm.
After forming the inner membrane, the normal frit sealing process,
A cathode ray tube was created through the electron gun assembly process, exhaust process, etc.

First, 1 part by weight of activated carbon having a specific surface area of 1000 nf/H was dispersed in 2 parts by weight of pure water, and 2 parts by weight of water glass was added to this dispersion and mixed to prepare an interior paint.

Apply this interior paint to the inner wall of the funnel, approximately 50 to 6
It was dried at 0°C to form an interior film with a thickness of 10 to 30 μm. Then, an alumina sol aqueous solution prepared by diluting alumina sol 2 to 3 times with pure water was thinly applied onto the interior film using a spin cord to form an alumina sol film.

In this way, when the alumina sol film was formed on the interior film, the oxidation temperature was 450°C. Therefore, it was found that by forming an alumina sol film on the interior crotch, the oxidation temperature was significantly improved compared to the 330°C oxidation temperature of the interior film using water glass. By forming an alumina sol film on the interior film, the alumina sol film functions as an oxidation-preventing film for the interior film, preventing the activated carbon contained in the interior film from coming into contact with oxidizing gases such as oxygen and carbon monoxide. suppress. For this reason, the activated carbon becomes less likely to be oxidized, so it is thought that the oxidation temperature is significantly improved. Therefore, even after the frit sealing process in the actual manufacture of cathode ray tubes, there is no risk that the inner membrane will be oxidized and burnt out, and an improvement in the manufacturing yield of cathode ray tubes can be expected.

Therefore, a cathode ray tube was actually fabricated using the funnel described above through the usual frit sealing process, electron gun assembly process, exhaust process, etc.

Here, the results of an emission life test conducted at a predetermined operating current density on the cathode ray tubes fabricated in Example 1 and Example 2 above, and a conventional cathode ray tube using graphite prepared for comparison, are summarized in the first section. As shown in the figure. In the figure, the vertical axis represents the residual emission rate (%) after a predetermined time has elapsed when the initial emission before the start of the test is taken as 100%, the horizontal axis represents the elapsed time (arbitrary scale), and the solid line represents the internal addition of alumina sol. The cathode ray tube of Example 1 using an interior film containing activated carbon, the dashed line shows the cathode ray tube of Example 2 in which an alumina sol film was formed on the interior film containing water glass and activated carbon, and the broken line shows the results of a conventional cathode ray tube. are shown respectively. From this figure, it can be seen that the cathode ray tube of Example 1 has an emission life that is more than twice that of the conventional cathode ray tube, and that the cathode ray tube of Example 2 has an emission life that is nearly twice that of the conventional cathode ray tube. It became clear. This is due to the getter effect of the inner membrane.
This is because the life of the cathode has been extended.

In this example, an inner film containing activated carbon was formed on the inner wall of the funnel, but in light of the purpose of adsorbing unnecessary gas inside the tube, the inner film does not cover the inside of the cathode ray tube, at least except on the phosphor screen. For example, it may be formed on the surface of any internal member of the tube as long as it does not affect the operating characteristics.
It is also possible to form it on the surface of the magnetic shield plate.

(Effects of the Invention) As is clear from the above explanation, in the cathode ray tube of the present invention, the activated carbon constituting the conductive film is particularly effective in adsorbing and removing unnecessary gas within the tube. Deterioration of the cathode is prevented and a longer service life is achieved.Moreover, in the cathode ray tube of the present invention, alumina sol is used as a binder for the interior material, and an alumina sol film that functions as an oxidation prevention film is formed on the interior film. As a result, the oxidation temperature of the interior material increases.Therefore, there is no risk of the interior material being oxidized and burnt out even after the frit sealing process, improving the manufacturing yield of cathode ray tubes.

Further, the cathode ray tube of the present invention can be manufactured by simply changing the composition of the conventional interior paint and without changing the existing manufacturing process, and is therefore excellent in productivity and economy.

[Brief explanation of the drawing]

FIG. 1 is a characteristic diagram showing the emission life of one example of the cathode ray tube of the present invention and another example in comparison with that of a conventional cathode ray tube using graphite. Figure 1

Claims (2)

[Claims] (1) A cathode ray tube characterized in that an internal film containing activated carbon and alumina sol is formed on at least the surface of the internal members of the tube excluding the phosphor screen. (2) A cathode ray tube characterized in that an inner film containing activated carbon and water glass is formed on at least the surface of an internal member of the tube excluding the phosphor screen, and an alumina sol film is formed on the inner film.