JPH0142459B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for forming a phosphor surface of a color picture tube by a so-called slurry method, and in particular to the composition of a phosphor suspension. Conventionally, the following method has generally been used to form a fluorescent surface of a color picture tube using a shadow mask method. That is, first, a photosensitive phosphor suspension is applied to the inner surface of the face plate panel and dried using a heater or the like. Next, this is irradiated with ultraviolet rays through a shadow mask to render the exposed areas insoluble in water. Thereafter, the unexposed areas are removed by hot water spray or the like and developed to obtain a dot or stripe-shaped phosphor pattern. This kind of operation is done in green, blue,
By repeating this process for each of the three red color phosphors, a desired color picture tube phosphor surface can be formed. Here, the photosensitive phosphor suspension is usually a suspension consisting of phosphor powder, polyvinyl alcohol, ammonium dichromate, water, etc., and is called a slurry. The conventional method of forming a fluorescent surface of a color picture tube using the method requires a very large amount of energy. For example, it is necessary to heat the panel to 40-45°C when pouring slurry for coating, and further heating is necessary to dry the coating. In addition, in order to sufficiently develop and remove the coating film in areas that have not been irradiated with ultraviolet rays, it is necessary to heat the hot water used as developing water to about 40 to 45°C.
In other words, if the heating temperature is lowered by reducing the heater power used for heating, the phosphor dots or stripes may peel off during development, resulting in defects such as
Poor color mixing, in which the phosphor penetrates into the phosphor film of another color, and poor filling properties, in which pinholes or cracks occur in the phosphor film, occur. Therefore, it has been technically extremely difficult to save energy consumption. The present invention has been made in view of the above circumstances, and its purpose is to save energy consumption by lowering the panel temperature and developing water temperature in the process of forming a fluorescent surface. In order to achieve this purpose, the method for forming a color picture tube fluorescent surface according to the present invention uses polyvinyl alcohol for slurry with an average degree of polymerization.
2700 or higher, and the viscosity of a 4% aqueous solution is 50 centipoise or higher at 20°C. That is, conventional polyvinyl alcohol for slurry has a saponification degree of about 88 mol% and an average polymerization degree of 1700 to
2400, a 4% aqueous solution of approximately 20 to 44 centipoise, was used, and it was generally believed that those with an average degree of polymerization exceeding 2400 could not be used because they had poor solubility in water and caused poor color mixing. However, as a result of a detailed study of the effects of various conditions in the manufacturing process on the quality of the coating film, we found that the average degree of polymerization is 2700 or more and the viscosity of a 4% aqueous solution is 50 centipoise or more at 20°C. In some cases, the panel temperature during slurry injection, etc. may be set to 25 to 30℃.
It has been found that a good fluorescent surface can be formed when the developing water temperature is lowered to about 20 to 35°C. In addition, we similarly investigated highly polymerized products of modified polyvinyl alcohol with increased solubility in water by introducing carbonyl groups, amide groups, amino groups, nitrile groups, etc., and good results were obtained with these. I couldn't get it. The reason why a good fluorescent surface could be obtained in a low-temperature process using polyvinyl alcohol with an average degree of polymerization of 2700 or more is considered as follows. That is, in general, as the panel temperature decreases, the binding force of the polyvinyl alcohol in the phosphor film between the phosphors and between the phosphors and the inner surface of the panel decreases; however, the degree of polymerization of the polyvinyl alcohol increases. Therefore, it was possible to compensate for this decrease in binding strength. On the other hand, the occurrence of thermal fog caused by increasing the degree of polymerization can be prevented by performing the treatment at a low temperature. In addition, the viscosity of the slurry is preferably about 25 centipoise in order to obtain good coating properties, but by setting the degree of polymerization of polyvinyl alcohol to 2700, the polyvinyl alcohol concentration to meet the above conditions has been reduced from the conventional 2.5 wt%. We were able to reduce it from 2.0wt%. As a result, the slurry dries quickly after application, eliminates the pinholes and cracks that conventionally occur due to delayed drying and agglomeration of the phosphors, and makes it possible to obtain a dense film. In addition, by reducing the amount of polyvinyl alcohol and speeding up the drying of the coating film, it is possible to reduce the stickiness of the polyvinyl alcohol in the previously formed phosphor dots or stripes. The phosphor applied later no longer adheres and causes color mixture. Furthermore, the occurrence of color mixing due to a decrease in solubility in water, which has conventionally made it difficult to increase the degree of polymerization of polyvinyl alcohol, can be solved by reducing the amount of polyvinyl alcohol in the slurry and lowering the panel temperature as described above. This is effectively compensated for by reducing the degree of solidification of the coating film before development. Specific examples will be described below. First, green, blue, and red phosphor slurries having the compositions shown in the table below are prepared.

[Table] Here, polyvinyl alcohol has a saponification degree of 88
%, average degree of polymerization 3500, 4% aqueous solution viscosity 70 at 20℃
Use centipoise. The temperature is then about 30° C., the panel is rotated at 15 rpm with the inner surface facing upward, and the green phosphor slurry described above is injected to coat the entire inner surface with the slurry. Next, in order to make the film thickness uniform, the rotation speed of the panel was increased to 150 rpm, and then the inner surface of the panel was turned horizontally and dried using a heater. Next, after irradiating it with ultraviolet light from an ultra-high pressure mercury lamp for about 30 seconds through a shadow mask, it was developed by spraying with 25°C water to obtain green phosphor stripes. Furthermore, the same process was repeated for the blue and red phosphors to obtain blue and red phosphor stripes, respectively. The thus obtained phosphorescent surface was of good quality, with no stripe drop or color mixture. In addition, the degree of polymerization of polyvinyl alcohol has increased, resulting in high sensitivity, making it possible to increase the degree of polymerization that was previously possible.
Compared to using polyvinyl alcohol of about 2000, the UV irradiation time could be halved. In addition, polyvinyl alcohol has an average degree of polymerization.
2700 or more, and the viscosity of the 4% aqueous solution should be 50 centipoise or more at 20℃, but 3000-5000 and 60 centipoise, respectively.
Particularly desirable results are obtained with ~100 centipoise. In addition, the saponification degree of polyvinyl alcohol is 86~
The content is preferably about 90 mol% from the viewpoint of water solubility. As explained above, according to the method for forming a color picture tube fluorescent surface according to the present invention, polyvinyl alcohol for slurry having an average degree of polymerization of 2,700 or more and a 4% aqueous solution having a viscosity of 50 centipoise or more is used. The panel temperature and developing water temperature have been reduced from the conventional 40 to 45 degrees Celsius and 40 to 50 degrees Celsius to 25 to 35 degrees Celsius.
It is possible to form a good fluorescent surface free from poor fall-off, poor color mixing, poor filling properties, etc., and to shorten the exposure time. As a result, it has the excellent effect of being able to significantly save energy consumption such as electricity and petroleum.

Claims (1)

[Claims] 1. A step of applying a photosensitive phosphor suspension containing a phosphor and polyvinyl alcohol to the inner surface of the panel, a step of drying the coating film, and exposing and developing the dried coating film. and forming a phosphor pattern at a predetermined position on the inner surface of the panel, wherein the polyvinyl alcohol has an average degree of polymerization.
2700 or more, and the viscosity of its 4% aqueous solution is 20
A method for forming a fluorescent surface of a color picture tube characterized by having a luminance of 50 centipoise or more at °C. 2 Polyvinyl alcohol has an average degree of polymerization of 3000
~5000, and the viscosity of its 4% aqueous solution is 20℃
2. A method for forming a fluorescent surface of a color picture tube according to claim 1, wherein the luminance is 60 to 100 centipoise.