KR100204172B1 - Coating material for inner coat of cathode-ray tube - Google Patents

Abstract

The present invention relates to paints forming conductive inner coatings. The paint of the present invention contains graphite particles, filler particles, an aqueous medium, a dispersant and water glass. The filler particles have a core and a membrane covering the core. The core consists of metal oxides or metal carbides, the membrane consists of alumina and silica, and the weight ratio of alumina to membrane is in the range of 20 to 60% by weight. If the core is iron oxide, the filler particles used have a membrane of at least 4% by weight and the membrane contains 20 to 90% by weight of alumina and silica.

Description

Cathode ray tube paint

The present invention relates to paints applied to the inner surface of a cathode ray tube, in particular filler particles and graphite particles, which are dispersed in a medium containing water-glass.

Cathode ray tubes have funnel glass, and the inner surface of the funnel glass is covered with a conductive film. Such conductive films can be formed by applying a paint containing conductive particles to the inner surface of the funnel glass, then drying the paint and heating it in air.

The paints described above are formed, for example, by dispersing and suspending conductive graphite particles and filler particles of metal oxides or metal carbides in an aqueous medium containing water glass and a dispersant to which the paint adheres. Metal oxides and metal carbides are used to adjust the electrical resistance of the film to an appropriate value, and such compounds include, for example, iron oxide, titanium oxide, silicon carbide, and the like.

There is also another type of paint used for other types of cathode ray tubes. Although these paints contain graphite, they do not contain metal oxides or metal carbides. When this type of paint is applied to the funnel glass, a rather large amount of sparking current flows due to the low resistance of the film. Therefore, it is a common method to use the coating material containing graphite particle and metal oxide particle for a cathode ray tube.

In the conductive film made of the paint described above, graphite provides conductivity to the film and serves to reduce the electrical resistance of the film. Metal oxide particles added as fillers, on the other hand, act to increase the electrical resistance of water glass adhesives as well as films. Therefore, the mixing amount of the raw material is appropriately determined in consideration of the electrical resistance of the adhesive of the film and the coating.

As a method of applying paint to the inner surface of the funnel glass of the cathode ray tube, a spraying or brushing method is commonly used. However, the use of flow-coating methods has recently increased in line with the need to improve the manufacturing process of cathode ray tubes. In order to use the flow-coating method, it is necessary to reduce the viscosity of the paint so that the paint flows smoothly in the funnel glass of the cathode ray tube. Specifically, the viscosity of paints suitable for conventional spraying and brushing use ranges from 100 to 200 mPa · s. On the other hand, the viscosity of the flow-coating method is about 10 mPa · s, which is a very low value. Therefore, even if a paint having a reduced viscosity is obtained by changing the composition ratio of a conventional paint, it is difficult to keep the metal oxide particles suspended in the paint for a long time. This can be easily seen from the Stokes' equation for the natural sedimentation of particles. In addition, considering the preservation conditions of the paint, which can be easily changed, the dispersibility of the usual paint is not yet satisfactory.

As mentioned above, it is very important for the coating of cathode ray tubes that the metal oxide particles can be dispersed in the paint and suspended for a long time in the paint, thereby extending the service life for the time that can be used in the flow-coating system.

The inventors of the present invention have conducted various studies on improving the dispersion stability of the particles in the paint and extending the life of the paint when the flow-coating process is used for the funnel glass. Japanese Patent Publication No. 63-45428 filed on September 9, 1988, filed by the applicant of the present invention, describes a cathode ray tube paint. Paints are prepared by preparing composition particles in which all particles are negatively charged and suspending the composition particles in water containing a binder and a dispersant. Compositional particles are prepared using graphite powder, metal oxide particles, and negatively charged surface treatment agents. The paints of the aforementioned patent publications have improved dispersibility and dispersion stability. However, this level of improvement in dispersibility and dispersion stability is not yet sufficient for use in flow-coating systems, in particular when used at high temperatures.

In addition, the flow-coating system has a problem in efficiently recovering and recycling the conventional paints described above. In detail, in the flow-coating system, the excess paint flows on the inner surface of the funnel glass, so that the excess paint flowing in the funnel glass has to be recovered and stirred to make the recovered paint uniform. However, when the particles of the paint are not durable, the particles in the paint are destroyed during the stirring treatment.

In addition, the conductive film obtained from the paint must be firmly adhered to the funnel glass so as not to be detrimental to the properties of the cathode ray tube.

Thus, there is a need for new paints that can be used in flow-coating systems with significant improvements in dispersion stability.

An object of the present invention is to provide a novel paint for cathode ray tubes. That is, an object of the present invention is to provide a paint containing metal oxide or metal carbide particles, graphite particles and water glass, the paint of the present invention is remarkable dispersion stability at high temperature, can be preserved for a long time, and easily processed can do.

It is another object of the present invention to provide a conductive inner coating that is strongly adhered to the funnel glass.

In order to achieve the above object, the paint for cathode ray tubes according to the present invention is graphite particles; Filler particles, wherein each filler particle comprises a core and a film covering the core, the core comprises a component selected from the group consisting of metal oxides and metal carbides, the film comprises alumina and silica, and alumina in the film Content is within 20 to 60% by weight); An aqueous medium in which graphite particles and filler particles are dispersed; Dispersion effective amounts of dispersants; And water glass which gives adhesion to the paint.

Another paint is graphite particles; Filler particles, wherein each filler particle comprises a core and a membrane covering the core, the core comprises iron oxide, the membrane comprises alumina and silica, and the content of the membrane in the filler particles is at least 4% by weight, The content of alumina in the film is within 20 to 90% by weight); An aqueous medium in which graphite particles and filler particles are dispersed; Dispersion effective amounts of dispersants; And water glass which gives adhesion to the paint.

The conductive inner coating of the cathode ray tube of the present invention comprises 2 to 40% by weight of graphite particles; 40 to 80% by weight of filler particles, wherein each filler particle comprises a core and a membrane covering the core, the core comprises a component selected from the group consisting of metal oxides and metal carbides, the membrane comprising alumina and silica The content of alumina in the film is within the range of 20 to 60% by weight); And 20 to 40% by weight of water glass.

Another conductive inner coating of the cathode ray tube comprises 2-40% by weight of graphite particles; 40 to 80% by weight of filler particles, wherein each filler particle comprises a core and a membrane covering the core, the core comprises iron oxide, the membrane comprises alumina and silica, and the content of the membrane in the filler particles is 4% by weight Above, and the content of alumina in the film is within the range of 20 to 90% by weight); And 20 to 40% by weight of water glass.

The coating material for the inner coating of the cathode ray tube according to the present invention described above is not sensitive to changes in the storage environment, so that it can be stored for a long time and the treatment of the paint is easy. In addition, the paint can be easily produced in a simple and economical process without complicated operations such as the spray drying method.

The features and advantages of the paints of the present invention as compared to the conventional paints described above will be more clearly understood in the following description.

It is known that metal oxides such as titanium oxide and iron oxide are generally used as pigments. However, metal oxides do not have high dispersibility in water. This is not advantageous for the production of aqueous paints in which metal oxide pigments are dispersed. Therefore, studies have been conducted to improve the dispersibility of the pigments, and as a result, the above-mentioned dispersibility defects may cause the surface of the metal oxide pigment to have a silica (SiO ₂ ) film or an alumina (Al ₂ O ₃ ) film, or two components thereof. It has been discovered that the metal oxide pigment can be supplemented by appropriately dispersing and suspending the metal oxide pigment in water (Manabu KIYONO, Titanium Oxide-Physical Properties and Application Technique, p29-30). In aqueous dispersions of coated metal oxide pigments, the silica film serves to make the metal oxide pigments have hydrophilic properties. Alumina films, on the other hand, serve to improve the hydrophobic properties and environmental resistance of the pigments. Similar pigments are described in Japanese Patent Application Laid-Open No. 53-33228, which are titanium dioxide pigments coated with silica and alumina. Such pigments are prepared by coating titanium oxide particles with a continuous film of high density amorphous silica and then adhering alumina to its surface.

As can be seen from the above description, silica and alumina are useful for improving the properties of an aqueous dispersion of metal oxide particles. However, it is known that both silica and alumina are soluble in alkaline water, meaning that aggregation and sedimentation in alkaline water can occur with slight changes in environmental conditions. In other words, since the coating liquid for cathode ray tube contains water glass and is therefore alkaline, a metal oxide particle having a film of silica or alumina, or both, is used to prepare a stable and long-life coating liquid for cathode ray tube. It is very uncertain whether this is possible or impossible.

Under the conditions described above, the present invention has realized a cathode ray tube paint, which is an alkaline aqueous dispersion containing water glass and a filler particle having a metal oxide core as filler and a coating film made of silica and alumina, and having a temperature change and transport. And stable to treatment and long-lived, and the dispersed particles did not aggregate or settle. Dispersion stability and long life of the paint are achieved by controlling the content of the alumina component in the film, and the film consisting of a mixture of alumina and silica on the filler particles, to a predetermined range.

The paint according to the invention is described in detail below.

The paints of the present invention comprise graphite particles, filler particles, dispersants, and aqueous media containing waterglass or silicate anions. For the filler particles, core particles coated with alumina / silica membranes are used.

Fillers are used to control the conductivity of films made from paints applied to the funnel glass of cathode ray tubes. Thus, the core material of the filler particles is not limited to metal oxides, and metal carbide particles may also be used. The alumina / silica film not only improves the dispersion stability of the metal carbide filler but also serves to improve the dispersion stability of the metal oxide pigment.

As the core material of the filler, the metal oxide may be selected from titanium oxide, iron oxide, zinc oxide, chromium oxide, nickel oxide, manganese oxide, cobalt oxide, and the like. Silicon carbide or the like may be used as the metal carbide. Of these, titanium dioxide and ferric oxide are preferred. The preferred diameter size of the core of the filler particles, taking into account the easy treatment of the core material and the stability of the coated filler particles, is within the range of 0.1 to 3 μm.

The core particles described above are coated with a film made of a mixture containing alumina and silica.

The silica component of the membrane acts to impart hydrophilicity to the filler particles, and to impart hydrophilicity to the pigment described above as well. However, the alumina component of the present invention serves to inhibit the silica component from being dissolved in the medium containing the water glass. Therefore, the content of the alumina component in the film should be in the range of 20 to 60% by weight, preferably 30 to 50% by weight. The film preferably consists essentially of alumina and silica, but unavoidable impurities and components may be acceptable as long as it is not detrimental to the features of the present invention. The reason for controlling the alumina content in the film is as follows.

If the content of the alumina component exceeds 60% by weight, the low surface charge of the alumina component may increase the aggregation and sedimentation of the filler particles. Thus, the alumina component of the membrane is controlled to less than 60% by weight. However, even when the content of the alumina component is less than 20% by weight and the content of the silica is more than 80% by weight, the aggregation and sedimentation of the filler particles is increased, in particular, the environment in which the paint is allowed to stand for a considerable time and the paint is preserved. Aggregation and sedimentation of the filler particles is increased when the temperature of is changed. This is due to the difference in solubility between the silica component and the alumina component associated with each other. More particularly, the solubility of the silica component into the water glass is very large compared to the solubility of the alumina component. Therefore, when the amount of the silica component in the film is excessively large, a part of the silica component in the film is dissolved into the water glass contained in the aqueous medium, and the effect of increasing the concentration of the silicate ion micelle is partially raised in the aqueous medium. . Since these ion-micell-rich portions are unstable in terms of concentration balance in the medium, the silica ions adhere to the surface of the filler particles in the form of silica. Thus, when such dissolution and adhesion cycles are repeated, the filler particles tend to mix easily with each other. As a result, aggregation and sedimentation of the filler particles occurs. Therefore, it is difficult to improve the dispersion stability of the filler particles and to extend the shelf life of the paint.

Here, even if an appropriate amount of alumina component is contained in the membrane, if the alkaline substance contained in the medium is not water glass but a metal hydroxide such as sodium hydroxide or potassium hydroxide, the effect of inhibiting the dissolution of the silica component can be expected. It should be noted that there is no.

Filler particles with a membrane as described above can be prepared using a general method of surface treating metal oxide pigments. In particular, the core material, ie the metal oxide particles or the metal carbide particles, is poured into an aqueous solution of aluminum salts and silicon salts (or aluminates and silicates) and dispersed uniformly. Alkaline or acid is then added to the mixture to neutralize to produce hydrated aluminum oxide and hydrated silicon oxide, and the core particles are separated from the solution and coated. Hydrated aluminum oxide and hydrated silicon oxide are separated from the neutralized liquid, washed and dried to obtain filler particles coated with a membrane of alumina and silica. The composition ratio of the film covering the core particles can be adjusted by adjusting the amounts of aluminum salts and silicon salts contained in the aqueous solution before the neutralization step.

Suitable amounts of membranes for filler particles generally correspond to the amounts in which the membrane covers the entire surface of the core particles with a thickness of about 0.001 to 0.5 μm, generally about 4 to 20% by weight.

The paints of the present invention can be readily prepared by dispersing filler particles, graphite powder, dispersants and binders having the alumina / silica membranes described above in an aqueous medium.

The particle size of the graphite powder is preferably 0.1 to 10 mu m. Moreover, the range of the suitable amount of graphite powder in paint is 0.2-20 weight%.

As the dispersant, various materials generally used as dispersants such as, for example, sodium carboxymethylcellulose (CMC), sodium naphthalenesulfonate, sodium lignin sulfonate, and the like can be used in a conventional manner. Preferably, the content of dispersant in the paint is about 0.1 to 3% by weight.

The paint of the present invention essentially comprises water glass as a binder. However, this does not mean that other conventional binder materials are not used and, of course, many binder materials may be used. In the paint of the present invention, the water glass is preferably contained in a proportion of 2 to 20% by weight of the paint.

The dispersion medium of the paint, ie water, is used in an amount of 50 to 90% by weight of the paint.

The above ingredients are mixed and thoroughly stirred to disperse the particles in an aqueous medium. If necessary, the dispersion is further treated with a ball mill or the like to improve the dispersion of the particles in the aqueous medium. As a result of the above, the paint of the present invention is obtained. The paint is coated on the inner surface of the cathode ray tube funnel glass by a flow-coating method to form an inner coating film.

In general, dispersions of metal oxide particles with conventional membranes may not be able to withstand long term mechanical treatments such as stirring and conveying. In detail, when a conventional dispersion is stirred for a long time, the film covering the metal oxide particles is destroyed and the charge on the particle surface is changed, thereby increasing the aggregation of the particles due to the attractive force due to the changed charge. However, in the case of the paint of the present invention, the aggregation of the particles described above is significantly reduced, so that the paint can be used even after a long mechanical treatment.

As mentioned above, membranes composed of 20 to 60% by weight of alumina components and balanced silica are generally effective for improving the dispersion stability of core particles in a medium containing water glass.

The paint of the present invention described above may be suitably applied to funnel glass by a flow-coating method. The applied paint is then dried and calcined to form a conductive film. When a paint having a preferred composition as described above is used, the film formed on the glass may contain 2 to 40% by weight graphite particles, 40 to 80% by weight filler particles, 1 to 6% by weight dispersant and 20 to 40% by weight. Contains water glass.

In addition to the aspects of the invention described above, the inventors of the present invention have further studied the paints to find paints in which other features may be improved. This feature relates to the particular case where iron oxide is used as the core material of filler particles dispersed in the paint. A second aspect of the paint of the present invention relating to this feature is described below.

The surface charge of the iron oxide particles is a positive charge. Thus, when iron oxide is used as the core material of the filler particles, the core of the filler particles is positively charged. However, a film composed of alumina and silica acts to change the charge on the particle surface to negative charge. Thus, the coated filler particles are negatively charged. On the other hand, graphite particles dispersed in the paint also have a negative charge on their surface. Since repulsive force is formed between particles having the same charge, graphite particles and iron oxide particles coated with a film of alumina and silica repel each other and remain dispersed by repulsive force.

In this regard, if the amount of the film in the filler particles is less than 4% by weight, the core of the filler particles is not preferably coated with the membrane, so that some core material is exposed to the outside and the positively charged iron oxide attracts the graphite particles. Pulled. As a result, the aggregation of the dispersed particles increases. Therefore, the ratio of the film to the total filler particles is 4% by weight or more.

Here, in the case of filler particles in which at least 4% by weight of the alumina / silica film covers the iron oxide core, the suitable alumina content ratio in the film is increased to 90% by weight or less. On the other hand, when iron oxide is used as the core material, an alumina / silica film containing up to 90% by weight of alumina can be suitably used as the film of the filler particles.

However, when the amount of the film exceeds 20% by weight, the film becomes the majority of the filler particles, and the conductive film formed of the paint does not adhere strongly to the funnel glass of the cathode ray tube. This is because the alumina and silica membranes are softer than the iron oxide cores, and the excess alumina and silica membranes remove the rigidity of the conductive film obtained from the filler particles and the paint, resulting in poor adhesion of the film. Since rigidity is an essential function of the filler, the excess film tends to make the metal oxide or iron oxide mixed with the coating material for cathode ray tubes insignificant. In addition, when the film exceeds 20% by weight, the dispersion stability of the paint is no longer improved. Therefore, it is economically disadvantageous in terms of cost and time in preparing the filler particles.

As described above, the filler particles of the paint of the second aspect comprise an iron oxide core and a membrane of alumina and silica, and the ratio of the membrane to the coated filler particles is 4 to 20% by weight, preferably 10 to 15% by weight. The alumina content of the alumina / silica membrane is 20 to 90% by weight, preferably 40 to 80% by weight and most preferably 45 to 60% by weight.

The paint of the second aspect comprises graphite particles, a dispersant, an aqueous medium containing water glass or silicate anions and the filler particles described above, and can be prepared in the same manner as in the first aspect described above. The composition ratio of the paint of the second aspect may be similar to that of the first aspect described above.

The coating of the second aspect is formed not only into a strong coating film by coating the dispersion paint on the funnel glass, but also improves the dispersion stability of the dispersion paint.

Although the characteristic example of the coating material of this invention is described below, this does not intend to limit this invention.

EXAMPLE

[Sample 1]

The following raw materials for the paint were poured into a container and sufficiently stirred with a stirrer to prepare a suspension. Subsequently, the suspension was treated with a ball mill to prepare a fine dispersion, to obtain a paint of sample # 1.

Raw material

Conductive material: 3.0 parts by weight of graphite powder ground to a particle size of 0.05 to 0.1 ㎛

Filler material: 18.0 parts by weight of powder 1 shown in Table 1

Dispersant: 0.3 parts by weight of sodium carboxymethylcellulose

Binder: Sodium Silicate 8.7 parts by weight

Medium: 70.0 parts by weight of water

The dispersion stability of the paint of the first sample was measured as follows.

First, some of the paint was poured into a 100 ml volume tube with a screw, tightly sealed with a lid, and left for 3 weeks at a temperature of 50 ° C. Subsequently, the depth of the paint and the thickness of the precipitate precipitated from the paint at the bottom of the tube were measured. Using the measured values, the sedimentation rate (ST ratio) at high temperature was calculated by the following equation.

Next, some other paint was stirred for 6 hours using a stirrer operated at a rotational speed of 400 rpm. After stirring, the paint was poured into a screwed tube and sealed. The tube was left at room temperature for 10 minutes. Subsequently, the depth of the paint and the thickness (or height) of the precipitate precipitated from the paint at the bottom of the tube were measured. Using the measured value, the sedimentation ratio (SM ratio) by stirring treatment was calculated by the above formula.

The ST ratio and SM ratio are shown in Table 2, which can be used to evaluate the dispersion stability of the paint.

[Samples 2-8 and 10-15]

For each sample, the second to eighth and the first and second samples were prepared using the preparation method of the first sample except that each of the powders 2 to 8 and 10 to 15 specified in Table 1 was used as the respective filling material. Paints of samples 10 to 15 were obtained.

Dispersion stability was evaluated by measuring the ST ratio and SM ratio for each paint. The results are shown in Table 2.

[Sample 9]

Sample No. 1 except that the composition powder composed of graphite, titanium oxide and silicon oxide, described in Japanese Patent Publication No. 63-45428, was used as a filler, and no conductive material was added because the composition powder contained graphite. The coating material of the 9th sample was obtained using the manufacturing method of the following.

Dispersion stability was evaluated by similarly measuring the ST ratio and SM ratio to the paint. The results are shown in Table 2.

*) The ratio in the particles means the weight ratio of the membrane to the weight of the particles, and the alumina content means the weight ratio of the alumina component to the weight of the coating or the weight ratio of the alumina component to the total weight of the alumina component and the silica component. do.

When the paint is allowed to stand at a high temperature for a long time, the dispersion conditions of the dispersed particles change accordingly. The viscosity of the paint also drops. As a result, the dispersed particles easily settle out of the coating liquid. Thus, dispersion stability at high temperatures is very important for prolonging the period of time during which the paint can be used and preserved without being involved in changes in the environment. Dispersion stability at high temperature can be seen from the sedimentation rate (ST ratio) at high temperature.

In addition, as described above, dispersion stability under mechanical treatment is also important. This property can be seen from the sedimentation rate by mechanical treatment.

As is evident from the results shown in Table 2, the occurrence of sedimentation was significantly changed depending on the composition of the membrane, ie the alumina content of the membrane. In particular, when the alumina content of the film covering the titanium oxide core is less than 20% by weight (sample 1) or exceeds 60% by weight (sample 7), the sediment increases in an amount related to the ST ratio and SM ratio. It was. Similar changes can be seen in the results of sample 10, where the core material coated with the membrane is iron oxide, and the precipitate increased when the alumina component of the membrane was less than 20% by weight. In addition, the ST ratio and SM ratio were particularly markedly reduced when the content of alumina was in the range of 30 to 50% by weight. In contrast, large amounts of sediment settled in the conventional paint of each of Samples 8, 9 and 15.

As a result, both dispersion stability at high temperature and dispersion stability under mechanical treatment are significantly improved when the alumina content of the alumina / silica membrane is controlled in the range of 20 to 60% by weight, preferably 30 to 50% by weight. Able to know. Thus, paints in which membranes meeting the compositional requirements described above are used can be suitably used to coat cathode ray tubes with a flow-coating system, and the paint can be efficiently recycled through a mechanical treatment to homogenize the recovered paint. .

[Samples 16-31]

In each of these cases, paints of samples 16 through 31 were obtained using the preparation method of sample 1 except that each of the powders 16 to 31 specified in Table 3 was used as the respective filler.

The ST ratio and SM ratio for the paints were measured similarly to assess the dispersion stability of each of samples 16-31. The results are shown in Table 4.

In addition, according to the flow-coating method, another portion of the paint of each of samples 16-31 was poured into a clean glass plate that was 150 mm × 100 mm × 1 mm in dimension and supported at an inclination of 60 °. The paint flowed down to the glass plate to coat the glass plate. After the excess paint flowed completely out of the glass plate, the paint on the glass plate was dried at a temperature of about 100 ° C. and further calcined at a temperature of 400 ° C. to form a conductive film. One piece of adhesive tape was applied to the resulting conductive film and then peeled off. It was observed whether the adhesive tape peeled off the conductive film from the glass plate. The results are shown in Table 4.

The above observation as to whether the conductive film is peeled off is useful for evaluating the adhesion of the film formed from the paint.

*) The ratio in the particles means the weight ratio of the membrane to the weight of the particles, and the alumina content means the weight ratio of the alumina component to the weight of the coating or the weight ratio of the alumina component to the total weight of the alumina component and the silica component. do.

Each paint of Samples 16-31 contains filler particles wherein the core material is iron oxide.

As shown in Table 4, in each of the paints of samples 16 and 17, a large amount of sediment subsided from the paint, and peeling of the film formed from the paint was observed on the adhesive tape. Poor adhesion of the film is believed to be increased by the low dispersibility of the paint due to the lack or insufficiency of the alumina / silica membrane such as not completely covering the core particles.

In addition, when the ratio of the amount of alumina / silica membrane to the amount of the total filler particles was about 4% by weight, the sedimentation rate was about 10% by weight for the membrane containing 19.5% by weight of alumina (sample 18). However, for membranes containing 39.7% by weight of alumina the dispersion stability was markedly improved and the sedimentation was reduced (sample 19). Such variation in dispersion stability can be seen in paints in which the amount of membrane in the filler particles is in the range of about 10 to 20% by weight (samples 21 to 30). In particular, when the alumina content of the membrane of the filler particles was within 40 to 80% by weight, there was almost no sedimentation of the paint even after the paint was left standing or stirred for 3 weeks at a temperature of 50 ° C.

Even when the paint contained filler particles in which the amount of the membrane exceeded 20% by weight, dispersion stability was maintained and the amount of sedimentation was small. However, the adhesion of the conductive film formed from the paint was lowered. This is presumably because the excess membrane reduces the hardness of the filler particles and the film containing the filler particles may not adhere well.

As a result of the above, when the ratio of the amount of the alumina / silica membrane to the total amount of the filler particles is at least about 4% by weight, and when the alumina content of the alumina / silica membrane is within the range of about 20 to 90% by weight, the graphite particles and the filler It will be appreciated that the particles are well dispersed in the medium, which significantly improves the dispersion stability of the paint. In addition, the conductive film that is excellently adhered to the glass can be obtained by adjusting the ratio of the film to 20% by weight or less. The proportion of the membrane is within the range of 10 to 15% by weight, and the alumina content of the membrane is preferably within the range of 40 to 80% by weight, most preferably 45 to 60% by weight. A paint that meets these requirements significantly improves the dispersion stability of the cathode ray tube paint, allowing the paint to be stable at high temperatures and withstand mechanical processing. In addition, the conductive film formed from the paint has sufficient durability.

It is to be understood that the invention is not limited to the embodiments described above but may be varied within the scope of the invention as indicated in the claims.

Claims (9)

0.2 to 20 wt% graphite particles; Filler particles each comprising a core and a film covering the core, wherein the core described above comprises a component selected from metal oxides and metal carbides, the membrane described above comprises alumina and silica, and the alumina content in the film is from 20 to 60% by weight. 4 to 40% by weight of filler particles within the range; 50 to 90% by weight of an aqueous medium in which the graphite particles and the filler particles are dispersed; 0.1 to 3% by weight of dispersant; And 2 to 20% by weight of water glass giving adhesion to the paint. The method of claim 1, wherein the metal oxide comprises titanium oxide, iron oxide, chromium oxide, nickel oxide, manganese oxide and cobalt oxide; A paint in which the metal carbide comprises silicon carbide. The paint according to claim 1, wherein the core component comprises titanium oxide or iron oxide. 2. The paint of claim 1, wherein the membrane comprises 30-50% by weight of alumina and balance silica. The paint of claim 1 wherein the dispersant comprises carboxymethylcellulose. 2. The paint of claim 1 wherein the aqueous medium is water. The paint according to claim 1, wherein the content of the membrane in the filler particles is within the range of 4 to 20% by weight. The paint according to claim 1, wherein the particle size of the graphite particles is 0.1 to 10 mu m, and the particle size of the filler particles is 0.1 to 3 mu m. Graphite particles 2 to 40% by weight; Filler particles each comprising a core and a film covering the core, wherein the core described above comprises a component selected from metal oxides and metal carbides, the membrane described above comprises alumina and silica, and the alumina content in the film is from 20 to 60% by weight. 40 to 80% by weight of filler particles within the range; And a conductive inner coating of the cathode ray tube containing 20 to 40% by weight of water glass.