JPS6123231B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to fluorescent film printing compositions, particularly to fluorescent film printing compositions for cathode ray tubes. Conventionally, known methods for forming a fluorescent film on the face plate of a cathode ray tube include a slurry coating exposure method, a sedimentation method, a dusting method, and an electrodeposition coating method. Slurry coating exposure method and sedimentation method have been put into practical use. However, both the slurry coating exposure method and the sedimentation method have drawbacks such as complicated steps, high equipment costs, and large loss of phosphor. In particular, the slurry coating exposure method, which is more widely used than the sedimentation method, has had problems such as a reduction in luminance of the fluorescent film obtained due to chromium contained in the photosensitizer used. Further, the above-mentioned fluorescent film forming methods other than the slurry coating exposure method and the sedimentation method have many practical problems such as a high defect rate. Recently, printing has been used as a method for forming phosphor films in cathode ray tubes, replacing the currently practical slurry coating exposure method and sedimentation method, because the process is simple, equipment costs are low, and phosphor loss is significantly reduced. The law began to be considered. In this printing method, a fluorescent film having a metal back layer is formed on the face plate as follows. First, a composition having an appropriate viscosity is prepared by dispersing the phosphor in an appropriate dispersion medium. Next, this composition is applied onto a face plate by a printing coating method such as a screen printing method or a gravure offset printing method, and dried to form a dry coating film, and then a metal backing such as aluminum is applied to the surface of this dry coating film. The layers are formed in a conventional manner. Thereafter, the face plate on which the dried coating film having the metal back layer has been formed is fired, and the dispersion medium in the dried coating film is removed by thermal decomposition, and the dried coating film is transformed into a fluorescent material consisting essentially only of phosphors. Make it a membrane. Currently, in the above printing method, a resin solution in which an appropriate resin is dissolved in an appropriate solvent is used as the dispersion medium, and a suitable viscosity can be obtained by dispersing a phosphor in this resin solution. A composition for fluorescent film printing has been prepared. As the resin, for example, a resin such as a cellulose resin that is easily thermally decomposed and dispersed as gas during the above-mentioned firing process is used. However, fluorescent film printing compositions prepared by dispersing a phosphor in a resin solution have the following drawbacks. First of all, a fluorescent film printing composition formed by dispersing a phosphor in a resin solution has poor printability. That is, when this composition is applied by printing, the edge portions of the coating film are difficult to cut and sag easily occurs at the edge portions. Such poor printability becomes a serious problem when a fluorescent film consisting of a repeating pattern such as stripes or dots is formed. The printability of a composition for fluorescent film printing is related to the thixotropy of the composition, and in order for the composition to exhibit good printability, it is necessary that the composition has appropriate thixotropy. It is thought that
Fluorescent film printing compositions in which a phosphor is dispersed in a resin solution generally have low thixotropy because the resin solution, which is a dispersion medium for the phosphor, does not have thixotropy. This seems to be the reason for its poor printability. Note that the printability of the fluorescent film printing composition obtained by dispersing a fluorescent material in this resin solution can be improved by adding a thixotropic agent such as finely powdered silica to the composition. Addition of such a thixotropic agent is not preferable because the thixotropic agent remains in the resulting fluorescent film and causes a decrease in luminance of the fluorescent film. In addition, in a fluorescent film printing composition in which a phosphor is dispersed in a resin solution, the resin used is easily dissolved, and a composition having a viscosity suitable for printing and coating can be easily obtained. As such, a solvent with a relatively low boiling point is generally used as a solvent for a resin solution. For this reason, fluorescent film printing compositions prepared by dispersing a phosphor in a resin solution generally have a drawback of low compositional stability (viscosity stability).
That is, the amount of the solvent, which is a component of the composition, tends to decrease over time due to volatilization or the like, and therefore the viscosity of the composition tends to increase over time. Such low compositional stability (viscosity stability) is caused by, for example, when printing and coating a large number of fluorescent films continuously using a large amount of composition, the state of the coating film changes as the number of printing increases. This gradually worsens, causing problems such as blurring of the coating film and the resulting poor fluorescent film. The above-mentioned compositional instability (viscosity instability) that fluorescent film printing compositions made by dispersing fluorophores in a resin solution generally have can be solved by adding and replenishing the composition with an appropriate solvent, or by increasing the boiling point. It can be improved to some extent by using a relatively expensive solvent. However, as long as a resin solution is used as a dispersion medium for a phosphor, such compositional instability always becomes a problem, although the degree varies depending on the type of solvent used. Furthermore, the coating film obtained by printing and coating a fluorescent film printing composition on a face plate (printed coating film) has a smooth surface, which impairs the smoothness of the metal back layer provided on the surface. In addition, when the printed coating film is fired to become a fluorescent film, it must not cause defects such as swelling or cracks in the metal back layer. It is very difficult to obtain a printed coating film that satisfies the above two points at the same time using a fluorescent film printing composition in which a photon is dispersed.
Generally, in order to satisfy one, one must sacrifice the other to some extent. The reason is as follows. The surface smoothness of the printed coating depends on the amount of resin solution to phosphor in the fluorescent film printing composition;
The larger the amount of resin solution, the better the smoothness. Therefore, in order to improve smoothness by increasing the amount of resin solution, it is necessary to use a large amount of resin in order to maintain the appropriate viscosity of the composition. For example, in a fluorescent film printing composition that uses a cellulose resin solution as a dispersion medium, the amount of resin is generally greater than 15% by volume of the amount of phosphor in order to give the printed film good smoothness. If the amount of resin is less than 15% by volume, the printed coating film cannot have good smoothness. On the other hand, the occurrence of defects such as blisters and cracks in the metal back layer when baking a printed coating film to form a fluorescent film depends on the amount of resin contained in the printed coating film, that is, the amount of resin contained in the fluorescent film printing composition. Depends on the amount of resin involved. In other words, the greater the amount of resin contained in the composition, the greater the amount of gas generated by thermal decomposition of the resin, which makes the metal back layer more likely to swell and cause defects such as cracks. This reduces the amount of gas generated by thermal decomposition of the resin, making it difficult for defects to occur in the metal back layer (note that most of the solvent contained in the composition is removed when the printed coating is dried before the metal back layer is formed). (There is almost no residue left in the printed coating upon firing). For example, in a fluorescent film printing composition that uses a cellulose resin solution as a dispersion medium, the amount of resin is generally reduced to the amount of phosphor in order to prevent defects from forming in the metal back layer during baking of the printed film.
It needs to be 15% by volume or less, preferably 10% by volume or less. Therefore, in a fluorescent film printing composition using a cellulose resin solution as a dispersion medium, if the resin amount is more than 15% by volume in order to give the printed coating film good smoothness, the metal back layer will form during firing. Defects begin to appear. As mentioned above, in a fluorescent film printing composition formed by dispersing a phosphor in a resin solution, the resin contained in the composition is generally required to obtain a printed coating film with good surface smoothness. The amount of resin in the composition for fluorescent film printing must be reduced in order to prevent defects from forming in the metal back layer during firing. For this reason, some fluorescent film printing compositions, which are made by dispersing fluorescent materials in a resin solution, have a smooth surface and at the same time prevent the metal back layer from blistering or creating defects such as cracks during firing. It is very difficult to obtain a printed coating. for example,
As mentioned above, it is impossible to obtain a printed coating film that satisfies the above two points at the same time using a fluorescent film printing composition using a cellulose resin solution as a dispersion medium. As explained above, fluorescent film printing compositions made by dispersing phosphors in resin solutions, which are being considered for application to existing printing methods, have poor printability and compositional stability (viscosity stability). ), and furthermore, it is difficult to provide a printed coating film that has a smooth surface and does not cause defects in the metal back layer during firing, and these drawbacks hinder the practical application of printing methods. This has become a major obstacle. Therefore, the present invention has good printability, high composition stability (viscosity stability), and a smooth surface that does not cause defects such as swelling and cracks in the metal back layer during firing. It is an object of the present invention to provide a fluorescent film printing composition capable of providing a printed coating film. In order to achieve the above object, the present inventor has conducted various studies on dispersion media for fluorescent film printing compositions. As a result, cellulose resin, octyl alcohol, diethylene glycol monobutyl ether acetate, diethien glycol monoethyl ether acetate, diethylbenzene,
A transparent liquid obtained by mixing at least one of diphenylethane, trimethylpentadiol monoisobutyrate, and tetralin is used as a dispersion medium, and an appropriate amount of the phosphor is dispersed in this dispersion medium. The composition for fluorescent film printing having a viscosity within a specific range obtained by the method has good printability, high composition stability (viscosity stability),
They also discovered that it is possible to provide a printed coating film that has a smooth surface and does not cause defects in the metal back layer during firing, leading to the completion of the present invention. The fluorescent film printing composition of the present invention is a fluorescent film printing composition comprising a phosphor dispersed in a dispersion medium, in which the dispersion medium is a cellulose-based composition containing 1 to 15% by volume of the phosphor. a resin and one or more compounds selected from the organic compound group consisting of octyl alcohol, diethylene glycol monobutyl ether acetate, diethien glycol monoethyl ether acetate, diethylbenzene, diphenylethane, trimethylpentadiol monoisobutyrate, and tetralin. It is a transparent liquid obtained by mixing, and the viscosity of the fluorescent film printing composition is 20,000 to 150,000 cps at 25°C and 5 rpm when measured with a cone plate rotational viscometer. Features. The present invention will be explained in detail below. The composition for fluorescent film printing of the present invention is prepared as follows. First, a cellulose resin and one or two compounds selected from the group of organic compounds consisting of octyl alcohol, diethylene glycol monobutyl ether acetate, diethien glycol monoethyl ether acetate, diethylbenzene, diphenylethane, trimethylpentadiol monoisobutyrate, and tetralin. By mixing the above components, a dispersion medium for the fluorescent film printing composition of the present invention is prepared. The cellulosic resin is used in an amount of 1 to 15% by volume, preferably 1 to 10% by volume of the phosphor to be subsequently dispersed in the dispersion medium. The upper limit for the amount of resin is 15% by volume because if the amount of resin exceeds 15% by volume, the composition will swell on the metal back layer during firing, resulting in a printed coating that will cause defects such as cracks. This is because it becomes.
On the other hand, the lower limit of the resin amount is set to 1% by volume because if the resin amount is less than 1% by volume, the composition will give a printed coating film with poor surface smoothness. Cellulose resin is usually commercially available as a powder, and it is preferable to use this powdered cellulose resin. On the other hand, the organic compound is used so that the viscosity of the resulting fluorescent film printing composition is 20,000 to 150,000 cps, preferably 30,000 to 80,000 cps at 25°C and 5 rpm when measured with a cone-plate rotational viscometer. used in large quantities. If the viscosity of the resulting fluorescent film printing composition is within the above range, it will be impossible to print and coat the composition. Mixing of the two is carried out using a conventional mixer such as a ball mill. Mixing is continued until solid cellulose resin and turbidity are no longer observed in the mixed system and the entire mixed system becomes a transparent liquid. The time required for the mixed system to become a transparent liquid varies depending on the type and shape of the cellulose resin used, the type of organic compound used, the amount of the mixed system, the type of mixer used, etc., but usually When a commercially available powdered cellulose resin is used, the heating time is generally several tens to several hundreds of hours. The transparent liquid thus obtained is used as a dispersion medium for the phosphor. The solubility of cellulose resin in each of the above organic compounds is extremely low. Considering this point, it seems that in the transparent liquid obtained as described above, the cellulose resin is not dissolved in the organic compound, but is mainly dispersed in the organic compound as colloidal particles. It can be done. That is, the transparent liquid obtained as described above is considered to be a sol of cellulose resin colloid particles using the above organic compound as a dispersion medium. The cellulosic resin used to prepare the transparent liquid (dispersion medium) is preferably at least one of nitrocellulose, acetylcellulose, cellulose acetate propionate, cellulose acetate butyrate, and ethylcellulose. In addition, a transparent liquid is prepared using at least one of nitrocellulose and ethylcellulose as a cellulose-based resin and at least one of diethylbenzene, diphenylethane, and trimethylpentanediol monoisobutyrate as an organic compound, and this is dispersed. Particularly good results are obtained when using as a medium. Next, a fluorescent film printing composition of the present invention is prepared by adding a phosphor to the transparent liquid obtained as described above and dispersing the phosphor in the liquid. Dispersion of the phosphor into the transparent liquid is carried out by mixing the transparent liquid to which the phosphor has been added using a mixer such as a ball mill or mixer mill. The phosphor to be dispersed in the transparent liquid is appropriately selected depending on the use of the fluorescent film produced from the obtained fluorescent film printing composition. This phosphor may be a single phosphor, a mixture of two or more types of phosphors, or even a coating or the like. Good too. Although the composition for fluorescent film printing of the present invention is prepared as described above, the composition for fluorescent film printing of the present invention may further contain an amount that does not adversely affect the various properties of the composition. Additives such as antioxidants and preservatives may be added, and an appropriate amount of an organic compound (diluent) other than the above-mentioned organic compounds for adjusting viscosity may be added. The composition for fluorescent film printing of the present invention exhibits good printability, and when printed and coated on a face plate, the edge portions of the printed coating film are easily cut, and the edge portions are less likely to sag. The reason why the fluorescent film printing composition of the present invention exhibits good printability is considered to be because the composition has appropriate thixotropic properties. That is, as mentioned above, the transparent liquid that is the dispersion medium of the fluorescent film printing composition of the present invention is considered to be a sol of cellulose resin colloidal particles using the above-mentioned organic compound as the dispersion medium.
This is believed to be because, unlike a resin solution, this transparent liquid has thixotropic properties, which makes the thixotropic properties of the entire composition appropriate. Further, the fluorescent film printing composition of the present invention has high compositional stability (viscosity stability). This is because the organic compound constituting the transparent liquid that is the dispersion medium of the fluorescent film printing composition of the present invention has a high boiling point (approximately 180°C).
This is because it has the above). Therefore, by using the fluorescent film printing composition of the present invention, a large number of fluorescent films can be printed and coated continuously without changing (degrading) the state of the coating film. Furthermore, the fluorescent film printing composition of the present invention exhibits excellent surface smoothness even though the amount of cellulose resin contained in the composition is 15% by volume or less based on the amount of phosphor. Give a membrane. Therefore, by using the fluorescent film printing composition of the present invention, it is possible to obtain a printed film that has a smooth surface and does not cause defects such as swelling and cracks in the metal back layer during firing. It can be formed on the face plate. The table below shows compositions for fluorescent film printing of the present invention (No. 1 to
The printability and compositional stability of 4) and the smoothness of the printed coating film of fluorescent film printing compositions (Nos. 5 to 7) using cellulose resin solution as a dispersion medium and the smoothness of the printed coating film. This is shown in comparison to the smoothness of the printed coating. In both compositions, ethyl cellulose with an ethoxyl group content of 47.5 to 49.5% and a ZnS:Ag phosphor are used as the cellulose resin and the phosphor, respectively, to prevent defects from forming in the metal back layer during firing. The amount of ethylcellulose is 5% by volume of the ZnS:Ag phosphor. Also, both compositions are 70,000 yen.
cps viscosity (at 25℃ using a cone-plate rotational viscometer, the rotational speed was 5 rpm).
). Printability, composition stability and smoothness were each evaluated as follows. Printability: Checked for sag on the edges of the printed coating. That is, when the composition was applied by printing to a thickness of 30 μm, the protrusion from the edge portion was investigated. 〇…20μ or less, △…21 to 50μ, ×…51μ or more. Composition stability...The composition was applied 1000 times and 1000
The state of the coating film for the first time was compared with the state of the film for the first time. 〇...no change, △...slight change but passed, ×...fade due to blurring, etc. Smoothness: The difference in unevenness of the coating film surface was investigated when the composition was printed and applied to a thickness of 30 μm. 〇…3μ or less, ×…5μ or more.

[Table] As is clear from the above table, the fluorescent film printing composition of the present invention exhibits better printability than the fluorescent film printing composition using a cellulose resin solution as a dispersion medium. Further, the composition for fluorescent film printing of the present invention exhibits high compositional stability (viscosity stability). Further, the composition for fluorescent film printing of the present invention provides a printed coating film having good surface smoothness even when the amount of resin is 15% by volume or less. As explained above, the present invention has good printability and
In addition, it has high compositional stability (viscosity stability), and at the same time has a smooth surface and can provide a printed coating that does not swell or cause defects such as cracks on the metal back layer during firing. The present invention provides a composition for film printing, which significantly improves the practicality of the printing method. Next, the present invention will be explained with reference to Examples. Example 1 ZnS:Ag phosphor 40 parts by volume Ethylene cellulose powder (ethoxyl group content 47.5-49.5%) 3 parts by volume 2,2,4 trimethylpentadiol 1,3 monoisobutyrate 57 parts by volume The above ethylcellulose powder and the above 2,2,4 trimethylpentadiol 1,3 monoisobutyrate were mixed using a ball mill for 100 hours to obtain a transparent liquid. Next, the above ZnS:Ag phosphor was added to the obtained transparent liquid, and the transparent liquid and phosphor were mixed using a ball mill to disperse the phosphor in the transparent liquid.
In this way, a pasty fluorescent film printing composition was obtained. This composition was measured with a cone-plate rotational viscometer at 25°C and 5 rpm at 80,000 cps.
It had a viscosity of Next, the composition obtained as described above was applied to a thickness of 30 μm on a face plate by screen printing, and after drying, protrusion of the edge portion of the dried coating film was examined. There is little protrusion of the edge part.
It was less than 20μ. Next, an aluminum metal back layer was formed on the dried coating film by a conventional method, and then baking was performed by a conventional method to obtain a fluorescent film having a metal back layer. The surface of the metal back layer was smooth and had a mirror surface. Moreover, no defects such as bulges or cracks were observed in the metal backing layer. Separately from the above, the composition was continuously applied 1000 times by a screen printing method, and the state of the coating film after the first application was compared with the state of the coating film after the 1000th application. No change was observed in the condition of the coating film. Example 2 ZnS: Cu, Al phosphor 42 parts by volume Ethyl cellulose powder (ethoxyl group content 47.5-49.5%) 2 parts by volume Diphenylethane 47 parts by volume Diethylene glycol monobutyl ether 9 parts by volume The above ethylene cellulose powder, the above diphenylethane and diethylene glycol monobutyl ether and were mixed for 100 hours using a ball mill to obtain a transparent liquid. Then add the above to the resulting transparent liquid.
ZnS:Cu, Al phosphors were added, and the transparent liquid and phosphor were mixed using a ball mill to disperse the phosphor in the transparent liquid. In this way, a pasty fluorescent film printing composition was obtained. This composition was measured at 25℃ using a cone-plate rotational viscometer.
It had a viscosity of 60,000 cps at 5 rpm. Next, the composition obtained as described above was applied to a thickness of 30 μm on a face plate by screen printing, and after drying, protrusion of the edge portion of the dried coating film was examined. There is little protrusion of the edge part.
It was less than 20μ. Next, an aluminum metal back layer was formed on the dried coating film by a conventional method, and then baking was performed by a conventional method to obtain a fluorescent film having a metal back layer. The surface of the metal back layer was smooth and had a mirror surface. Moreover, no defects such as bulges or cracks were observed in the metal backing layer. Separately from the above, the composition was continuously applied 1000 times by screen printing, and the state of the coating film after the 1st and 1000th application was compared. No change was observed in the condition of the coating film. Example 3 Y ₂ O ₂ S: Eu phosphor 35 parts by volume Ethyl cellulose powder (ethoxyl group content 45.0-46.5%) 1.5 parts by volume Nitrocellulose powder 0.5 parts by volume Diethylene glycol monobutyl ether acetate 63 parts by volume The above ethyl cellulose powder and nitrocellulose powder Using a ball mill, cellulose powder and the above diethylene glycol monobutyl ether acetate were mixed to 100%
Mixed for an hour to obtain a clear liquid. Next, the above Y ₂ O ₂ S:Eu phosphor was added to the obtained transparent liquid, and the transparent liquid and phosphor were mixed using a ball mill to disperse the phosphor in the transparent liquid. In this way, a pasty fluorescent film printing composition was obtained. This composition had a viscosity of 70,000 cps at 25° C. and 5 rpm, as measured by a cone-plate rotational viscometer. Next, the composition obtained as described above was applied to a thickness of 30 μm on a face plate by screen printing, and after drying, protrusion of the edge portion of the dried coating film was examined. There is little protrusion of the edge part.
It was less than 20μ. Next, an aluminum metal back layer was formed on the dried coating film by a conventional method, and then baking was performed by a conventional method to obtain a fluorescent film having a metal back layer. The surface of the metal back layer was smooth and had a mirror surface. Moreover, no defects such as bulges or cracks were observed in the metal backing layer. Separately from the above, the composition was continuously applied 1000 times by screen printing, and the state of the coating film after the 1st and 1000th application was compared. No change was observed in the condition of the coating film.

Claims (1)

[Scope of Claims] 1. A fluorescent film printing composition comprising a phosphor dispersed in a dispersion medium, wherein the dispersion medium contains one of the phosphors.
-15% by volume of cellulose resin and one or more compounds selected from the group of organic compounds consisting of octyl alcohol, diethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate, diethylbenzene, diphenylethane, trimethylpentadiol monoisobutyrate, and tetralin. It is a transparent liquid obtained by mixing two or more types, and the viscosity of the composition for fluorescent film printing is 20,000 to 150,000 at 25°C and 5 rpm when measured with a cone plate rotational viscometer. A fluorescent film printing composition characterized by being cps. 2 The amount of the above cellulose resin is 1 to 10% by volume
The composition for fluorescent film printing according to claim 1, characterized in that: 3. The fluorescent film printing composition according to claim 1 or 2, wherein the viscosity is 30,000 to 80,000 cps. 4 The cellulose resin mentioned above is nitrocellulose,
Fluorescent film printing according to claim 1, 2 or 3, which is at least one of acetyl cellulose, cellulose acetate propionate, cellulose acetate butyrate and ethyl cellulose. Composition. 5. Claims 1 to 5, wherein the cellulose resin is at least one of nitrocellulose and ethylcellulose, and the organic compound group consists of diethylbenzene, diphenylethane, and trimethylpentadiol monoisoptylate. The composition for fluorescent film printing according to any one of item 4.