JPS6312344B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a fluorescent surface on a metal back of a cathode ray tube, and more particularly to a method for forming a resin film as a base for applying a metal back.

In general, the fluorescent surface of a cathode ray tube is coated with a specified phosphor on the inner surface of the face plate, and then a metal with good electron transparency, such as aluminum, is vapor-deposited on the back surface, and the back is covered with a thin metal film, which is called a metal backing process. is being done. Usually, a high voltage of several tens of kilovolts is applied to the fluorescent surface of a cathode ray tube, and the electron beam is pressurized by this high voltage and collides with the fluorescent surface, causing the phosphor to emit light. The phosphor surface, which has not conventionally been used in the metal back, exhibits a charge map phenomenon in which charges accumulate on the surface of the phosphor, resulting in acceleration effects,
There were many problems with poor brightness and contrast.
However, an innovative method called the metal bag was developed and all of the aforementioned problems were solved. In other words, the metal film (aluminum) formed by vapor deposition on the back surface of the phosphor keeps the surface of the phosphor conductive, and reflects the light beam directed toward the back surface by the specular effect of the vapor-deposited film, directing it toward the viewing side. can be made. Furthermore, it has the effect of protecting the phosphor from collisions with ion particles. The production of conventional metal back fluorescent surfaces will be explained.

After the color picture tube glass panel is cleaned,
A light-absorbing material, such as graphite, is applied to the non-emissive area of the phosphor by applying a photographic method to form a pattern of the light-absorbing layer. Next, an organic photosensitizer,
For example, the steps of suspending the phosphor in a solution containing polyvinyl alcohol and ammonium dichromate, coating, exposing, and developing the phosphor are repeated for each color of phosphor to correspond to the non-patterned positions of the light-absorbing layer. In the designated position, green, which is the three primary colors,
Complete the blue and red phosphor deposition. In the case of other glass bulbs that are mainly monochrome, after cleaning, place the phosphor in an aqueous solution containing, for example, potassium silicate (Wako Pure Chemical's Wako Seal) as a binder and barium acetate as a charge neutralizer. Suspend and inject into a glass bulb. Once the phosphor has settled on the face surface, the supernatant liquid is removed and the phosphor is dried and fixed, generally forming a smooth and uniform phosphor surface over the entire surface.

Following the phosphor deposition process as described above, a process commonly referred to as filming is performed as a preparation for the next aluminum vapor deposition process. The purpose of this filming step is to obtain a smooth surface as a base for aluminum vapor deposition.

In other words, if aluminum is vapor-deposited directly onto a phosphor surface that has been completely coated with a phosphor, the aluminum vapor will directly adhere to the highly uneven surface of the phosphor, and will not form a continuous evaporated film. Neither conductivity nor mirror effect can be obtained. Therefore, it is preferable that aluminum vapor deposition is not performed directly on the phosphor surface, but after a thin organic film is formed on the back surface of the phosphor. Filming is the process of forming such a thin organic film, and there are two main types of filming methods: emulsion-type filming, which is usually used for the glass panels of color picture tubes, and film-based methods, which are used for the glass panels of other cathode ray tubes. There are two solvent-based filming methods used for valves.

FIG. 1a is an explanatory diagram of the construction state of the emulsion method. The glass panel 21 that has been coated with the phosphor is first preheated to about 40°C, and then an acrylic emulsion, for example, a lacquer liquid 31 whose main component is B-74 manufactured by Nippon Acrylic Co., is applied to the glass panel by rotating it through a nozzle 32. 21. Next, remove the excess lacquer solution 31 from the glass panel 21 by rotating it at high speed (approx.
150 rpm), then add Lutzker solution 3.
1 is heated and dried to form a smooth coating 33 of polymethacrylate resin as the main component. That is, the emulsion particles in the lacquer solution 31 are melted and integrated during the heating and drying process to form a continuous film (US Pat. No. 3,067,055). FIG. 1b is an explanatory diagram of the construction state of the solvent-based film. The glass bulb 26 that has been coated with the fluorescent surface is turned with the fluorescent surface facing upward, and while rotating the glass bulb 26,
First, a spray 34 for wetting the fluorescent surface with water, called rewetting, is performed using a spray nozzle 35 as shown in FIG. 1B. Next, a lacquer solution prepared by dissolving, for example, isobutyl methacrylate resin in a solvent such as toluene or ethyl acetate is passed through another nozzle 3.
6, and by the rewetting, an extremely thin organic continuous film 37 is formed on top of a thin water film. Next, drying is performed to obtain a solidified organic film that adheres to the surface of the phosphor.

In general, the latter solvent type produces a smoother film;
The vapor-deposited film for the metal back described below can provide a brighter fluorescent surface of good quality, but the latter solvent-based filming method is technically more difficult.

Next, the glass panel 21 that has been filmed is placed in a vacuum chamber, and the vacuum is drawn to approximately 10 ^-4 Torr using a vacuum pump and a diffusion pump. Once a predetermined degree of vacuum is reached, a heater in the vacuum chamber, such as a tungsten coil, is heated by passing an electric current through it. A predetermined amount of aluminum metal pieces previously placed in the heater is melted and evaporated by the heating to form a vapor deposited film on the lacquer film on the fluorescent surface. The fluorescent surface of glass bulbs 26 is also metal-backed in the same way, and the vapor-deposited film is usually 2000 ml.
The thickness is controlled to ~4000Å. After completing the metal backing, the phosphor surface is sent to a baking step in which the organic components used in the phosphor deposition and filming steps are blown away by thermal decomposition.
As mentioned above, in this baking process, if the filming method is not appropriate, the deposited film will blister or peel, resulting in a defective product. Therefore, the filming process requires sufficient control and advanced technology.

The conventional metal bag method described above has the following problems depending on the filming method. In other words, in the case of a solvent-based method, even if the brightness is good, there are restrictions due to the use of organic solvents in the implementation stage, and there are also time and material restrictions in the process of removing the coating from unnecessary parts. There were some technical difficulties. On the other hand, in the case of an emulsion type, there are relatively few technical restrictions compared to a solvent type, but the quality and brightness of the product are unsatisfactory. In the past, various studies and experiments have been conducted on filming methods to overcome these drawbacks.
It can be said that no fully satisfactory method has yet been established.

The present invention has been made to solve the above-mentioned conventional drawbacks and provides a novel filming method. The inventor investigated and experimented with a new filming method that combines the advantages of the solvent-based and emulsion-based methods described above, and finally found that the average particle size of the emulsion was 0.01 to 0.06 microns instead of the conventional one with an average particle size of 0.1 micron. It has been found that good results can be obtained by using ultrafine particles and applying a spray method, which is common for solvent-type products, and a pouring method, which is common to emulsion-type products, to form a film.

The feature of the emulsion having a small average particle size is that it retains its shape on the treated surface, that is, the shape of the treated surface does not change much even after a film is formed on the treated surface. On the other hand, the coating itself is very dense and has a highly smooth surface.

One of the conditions necessary to increase the brightness of the fluorescent surface is the smoothness of the latter coating, and it is important to form a smooth coating that does not cause blistering or peeling. This can be said to be contradictory to the explanation of the conventional method described above. However, in the case of the present invention, both can be achieved due to the above-mentioned characteristics due to the small size of the emulsion particles.

Furthermore, the filming method according to the present invention includes:
It has secondary effects due to the emulsion of ultra-fine particles. That is, the aqueous emulsion is easy to handle and requires less material. For example, the volume of emulsion required to form one layer of film decreases with the particle size ratio, and if the particle size is 1/10, the volume of emulsion required is 1/10, which reduces the inconvenience caused by gas generated during decomposition. It is something. Hereinafter, embodiments will be described in detail with reference to the drawings.

FIG. 2 shows a first embodiment of the invention, in which a fine phosphor 50
The fluorescent surface of a 3-inch glass bulb 26 coated with (average particle size: about 3μ) is shown, and after heating to about 60°C, ultrafine particle emulsion (US Patent 3740367 or ROHMandHAAS Acrysol WS-68) is sprayed. The ultrafine particle emulsion coating 51 is formed by spraying the ultrafine particle emulsion film 51. After that, metal backing was carried out in the conventional manner, and the ultrafine particle emulsion coating 51 was decomposed and removed by baking. As a result, no blistering or peeling of the metal film occurred, and the brightness of the fluorescent surface was almost the same as that of conventional solvent-based coatings. Also, technical problems have been reduced by half.

FIG. 3 shows a second embodiment, showing the fluorescent surface of a glass panel 21 for a color picture tube on which a relatively large phosphor 40 (average particle size: about 5 to 12 .mu.m) is coated. First, a base film 33 is formed by conventional emulsion type filming. That is, emulsion with a large particle size (product name B- manufactured by Nippon Acrylic Co., Ltd.)
Pour 8% solution of 74) on it and dry it. Next, an ultrafine particle emulsion (same as above) is poured and dried to form an ultrafine particle emulsion coating 51. After that, metal backing was carried out in the conventional manner, and the base film 33 and ultrafine emulsion film 51 were removed by baking. There was no blistering or peeling of the metal film, and the brightness of the fluorescent surface was lower than that of the conventional single emulsion film. This is a 10% improvement compared to the mining method.

Although the above embodiments have been described for a monochrome 3-inch tube and a general color picture tube, it goes without saying that the present invention can be similarly used in an effective manner for various other cathode ray tubes. In addition, the emulsion composition for direct spraying, overcoating, etc., the method of drying the fluorescent surface, etc. should be optimally selected depending on the shape and characteristics of the fluorescent surface.

As described above, according to the method of forming a metal back fluorescent surface using this filming method, it is possible to directly or relatively For fluorescent surfaces made of large particle phosphors, by forming a base coat and then filming with ultrafine particle emulsion, we can improve the brightness of the fluorescent surface, which was a drawback of the conventional method. As a result, it is possible to eliminate blistering and peeling during the baking process, which can improve product quality and process yield, overcome technical difficulties in manufacturing, and further reduce the total amount of materials used. If you do this, you can get very good results, such as the secondary benefit of being able to use less.

[Brief explanation of the drawing]

FIG. 1a is an explanatory diagram of the construction state of the emulsion method, and FIG. 1b is an explanatory diagram of the construction state of the solvent type filming. FIGS. 2 and 3 are sectional views showing a filming state according to an embodiment of the present invention. In the figure, 21 is a glass panel, 26 is a glass bulb, 33 is a film (emulsion), 37 is a film (solvent type), 40 is a phosphor, and 51 is an ultrafine particle emulsion film. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. A first step of coating a fluorescent surface with an aqueous emulsion of a water-insoluble film-forming resin and drying it to form a resin film, and a second step of depositing a metal vapor deposition film on the resin film. and a third step of decomposing and removing the resin coating by baking, wherein the water-soluble emulsion has an average grain size.
A method for forming a metal back fluorescent surface, comprising a water-insoluble film-forming resin of 0.01 to 0.06 microns. 2. After heating the fluorescent surface of the aqueous emulsion,
2. A method for forming a metal back fluorescent surface according to claim 1, wherein said fluorescent surface is applied by spraying. 3. The method of forming a metal back fluorescent surface according to claim 1, wherein the water-soluble emulsion is poured onto the fluorescent surface after wetting the fluorescent surface. 4. The method for forming a metal back fluorescent surface according to any one of claims 1 to 3, wherein the fluorescent surface is coated with emulsion particles having an average particle size of 0.1 micron or more. .