JPS6310858B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a metal back film for a color cathode ray tube.

FIG. 1 is a diagram for explaining the metal back process, which is one process of manufacturing color cathode ray tubes. As shown in FIG. 1, a phosphor layer 2 is formed on the inner surface of a glass panel 1 forming the face plate of a color cathode ray tube, and an organic intermediate film 3 is formed on the phosphor layer 2. A smooth vapor-deposited thin film of aluminum, ie, a metal back film 4, is formed on the surface of the film 3 by vacuum evaporation. This process is called the metal back process.
The metal back film 4 extracts as much of the light emitted from the phosphor layer 2 as possible to the viewer during operation of the color cathode ray tube, and at the same time plays the role of a light reflecting surface to increase the luminance of the color cathode ray tube.
It also has the function of preventing ion burnout of the phosphor. Specifically, the phosphor layer 2 and the organic intermediate film 3
The glass panel 1 on which is formed is transferred to a metal bag machine 5
The vapor deposition tank 7 is placed on a panel support stand 6 and evacuated using a vacuum pump 8 until the inside of the vapor deposition tank 7 reaches a high vacuum state.
Inside the vapor deposition tank 7, a helical coil heater 10 made of a tungsten W wire charged with an aluminum rod 11 as an evaporation source is fixed to the heater support electrode 9 so as to be located on the center line Cl of the glass panel 1. When the inside of the vapor deposition tank 7 reaches a specified degree of vacuum, a constant voltage is applied to both ends of the helical coil heater 10 through the heater support electrode 9 by a power supply device 12 provided outside the vapor deposition tank 7 . Since the helical coil heater 10 is a good resistance heating element, the aluminum rod 11 charged inside the helical coil heater 10 is heated, melted, and evaporated by the heat generated by the helical coil heater 10, and is formed on the inner surface of the glass panel 1. A vapor-deposited aluminum film, that is, a metal back film 4, is formed on the organic intermediate film 3. When the formation of the metal back film 4 is completed, the supply of voltage from the power supply device 12 is stopped and the vapor deposition tank 7 is leaked to return the inside of the vapor deposition tank 7 to atmospheric pressure, and then the glass panel 1 on which the metal back process has been completed is removed. Remove it from the metal bag machine 5. A new aluminum rod is charged to the helical coil heater 10, the next glass panel is set, and aluminum is deposited one after another in the same manner as described above.

The helical coil heater 10 is used repeatedly until it breaks. The conventional helical coil heater 10 has a structure as schematically shown in FIG.
The number of lifetimes varied depending on usage conditions such as the amount of charge of the aluminum rod 11, but on average it was 10 to 20 times of vapor deposition. Increasing this service life is important in terms of improving the workability and economic efficiency of the metal bag process. Therefore, in order to improve the service life of the heater, we conducted various studies and found that if a conical basket-shaped heater 13 as shown in FIG. It was found that it could withstand an average of 30 to 40 deposition cycles. This is because in the conical basket-shaped heater 13 shown in Fig. 3, the curvature of the tungsten W wire is relatively large and there is little mechanical distortion, and in the conventional helical coil-shaped heater 10, the thermal change is small. When the situation worsens, it becomes difficult to charge the aluminum rod 11, making it unusable.However, since the conical basket-shaped heater 13 has a large opening, the problem is that even if it is slightly deformed by heat, the aluminum rod 11 cannot be charged. It depends on things that don't happen.

In this way, the conical basket-shaped heater 13 as shown in FIG. 3 is used in place of the conventional helical coil-shaped heater 10 as shown in FIG. Although this greatly improves the service life of the heater as described above and greatly improves the workability and economic efficiency of the metal backing process, the following major problems arise in terms of the characteristics of the metal backing film 4. Figure 4 shows a conventional helical coil heater 10.
When the metal backing process is performed by charging the same amount of aluminum rods 11 to the conical basket-shaped heater 13 for the purpose of increasing the number of service life mentioned above, the metal backing film 4 is formed from the center to the periphery of the glass panel 1. This figure shows a comparison of the film thickness distribution for both directions. Line a in FIG. 4 shows the film thickness distribution of the metal back film 4 formed by the conventional helical coil heater 10, and line b shows the film thickness distribution by the conical basket heater 13 described above. When the conical basket-shaped heater 13 is used, there is a large difference in film thickness between the central part and the peripheral part of the glass panel 1, but this is due to the shape of the heater. That is, when depositing aluminum, evaporation begins after the aluminum rod 11 melts once and wets the entire surface of the heater made of tungsten W wire, so the film thickness distribution is likely to be influenced by the shape of the heater. be.

On the other hand, the performance of the metal back film is determined by the light reflection efficiency of the film and the electron beam transmittance during operation of the completed color cathode ray tube, and there is an optimum film thickness value. Therefore, it is not preferable that the thickness of the metal back film differs drastically at each position on the glass panel 1, as shown by line b in FIG.
When the center part of the glass panel 1 is adjusted to the optimum film thickness value, the film thickness at the periphery becomes extremely thinner than the optimum film thickness value, resulting in poor light reflection efficiency and lower brightness at the periphery when the completed color cathode ray tube is in operation. I don't like it because it gets droopy. On the other hand, if the optimum film thickness is set at the periphery of the glass panel 1, the film thickness at the center becomes extremely thicker than the optimum film thickness, resulting in poor electron beam penetration during operation of the completed color cathode ray tube. This is not desirable because the brightness of the area decreases. Furthermore, if the film thickness becomes extremely thick, problems such as the metal back film 4 becoming loose or peeling off during the thermal decomposition process of the organic interlayer film 3 after forming the metal back film 4 tend to occur, which is extremely undesirable. do not have. For these reasons, it is ideal to form a metal back film with a constant film thickness from the center to the periphery of the glass panel 1, that is, with an optimum film thickness value, as shown by line c in FIG. 4.

As mentioned above, this invention arises inevitably when a conical basket-shaped heater is used in place of a conventional helical coil-shaped heater in order to improve the service life of the heater used in the metal bag process of color cathode ray tubes. This method was developed to improve the problem of film thickness distribution of metal back films such as the above, and it is possible to obtain a metal back film with a uniform deposition film thickness distribution even when using a conical basket-shaped heater, which is advantageous in terms of durability. The object of the present invention is to provide a method for forming a metal back film for a color cathode ray tube.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 5 is a diagram for explaining the method of forming a metal back film according to the present invention. A conical basket-shaped heater 13 is installed as an evaporation source for the purpose of increasing the number of service life.
A mesh structure plate 14 is disposed between the conical basket-shaped heater 13 and the glass panel 1. This mesh structure plate 14
As shown in FIG. 6 with the central part A and the peripheral part B enlarged, openings 15 are arranged in a metal plate at a constant pitch P, and the size of the openings 15 is determined by the size of the mesh structure plate 14. It is provided so that it gradually increases from the center to the periphery, and therefore,
As shown by line l in FIG.
The aperture ratio is from the central aperture ratio T _C to the peripheral aperture ratio T _E
It is gradually increasing up to. The mesh structure plate 14 is arranged so that the center line Cl of the glass panel 1 substantially passes through its center point.

The metal back film 4 is formed by vacuum evaporation using the conical basket-shaped heater 13 as an evaporation source to improve the number of lifetimes, using the same method as the conventional method shown in FIG. 1 and described above except for the above-mentioned configuration. Then, by appropriately selecting the line l of the aperture ratio distribution of the mesh structure plate 14, the film thickness distribution of the metal back film 4 is corrected, and the line c is shown in FIG.
As shown in FIG. 1, a metal back film 4 having a uniform thickness distribution from the center to the periphery of the glass panel 1 can be obtained.

Two technical problems arose during the practical application of the method for forming a metal back film as described above. One of them is that as the number of times of vapor deposition increases, an aluminum vapor deposition film is deposited on the surface of the mesh structure plate 14, and the aperture ratio distribution thereof gradually changes.
Another problem is that the shadow of the mesh structure plate 14 is formed as a pattern on the metal back film 4. In order to solve these problems, the structure and position of the mesh structure plate 14,
As a result of various experiments regarding the size of the evaporation source, we found that the minimum diameter of the side of the evaporation source facing the glass panel 1 was dmm, the arrangement pitch of the openings of the mesh structure plate 14 was Pmm, and the evaporation source and the glass panel were The ratio of the distance L between the inner surface of the glass panel 1 and the distance l between the evaporation source and the mesh structure plate 14 is l/L, and the aperture ratio of the mesh structure plate 14 corresponding to the center and periphery of the glass panel 1 is respectively Assuming T _C % and T _E %, if these values are selected within the following ranges, one mesh structure plate 14 will be Even if evaporation is performed 30 to 100 times during continuous use, the aperture ratio distribution will change due to the deposition of the aluminum evaporation film on the surface of the mesh structure plate 14.
That is, the change in the film thickness distribution of the metal back film 4 can be suppressed within the permissible limit, and the problem of the shadow of the mesh structure plate 14 being formed as a pattern on the metal back film 4 can also be avoided.

0.7≦P≦4.0, 20≦T _C ≦60, T _E ≧75, d≧5, 0.2≦l/L≦0.7 The above explanation is for vapor deposition when the conical basket heater 13 is used as the evaporation source. Although the correction of the film thickness distribution of the metal bag film 4 has been described above, the present invention is not limited to those using a conical basket heater as an evaporation source, but can be widely applied to evaporation sources of various shapes.

As explained above, according to the method for forming a metal back film of the present invention, even if an evaporation source with poor deposition film thickness distribution, such as a conical basket heater, is used, a metal back film having a uniform deposition film thickness distribution can be formed. This has the effect of making it possible to take advantage of significant advantages such as increasing the service life of the evaporation source, and greatly contributing to improving the workability and economic efficiency of the metal backing process for color cathode ray tubes.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view for explaining an example of a conventional metal bag process, Figure 2 is a front view of a helical coil heater, Figure 3 is a front view of a conical basket heater, and Figure 4 is a metal bag film. 5 is a sectional view for explaining the metal backing process according to an embodiment of the present invention, FIG. 6 is a schematic plan view showing the structure of a mesh structure plate, and FIG. 7 is a diagram showing the mesh structure. It is a figure showing the aperture ratio distribution of the aperture of a board. 1... Glass panel, 2... Phosphor layer, 3...
Organic interlayer film, 4... Metal back film, 5... Metal back machine, 6... Panel support stand, 7... Vapor deposition tank, 8... Vacuum pump, 9... Heater support electrode,
DESCRIPTION OF SYMBOLS 10... Helical coil heater, 11... Aluminum rod, 12... Power supply device, 13... Conical basket shaped heater, 14... Mesh structure plate, 15... Opening. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. An evaporation source is placed on the center line of a glass panel on which a phosphor layer and an organic interlayer film are formed,
A mesh structure plate in which the aperture ratio gradually increases from the center toward the periphery is arranged between this evaporation source and the glass panel, and the aperture arrangement pitch of this mesh structure plate is set to Pmm, and the mesh structure corresponding to the center and periphery of the glass panel is The aperture ratio of the structural plate is T _C % and
T _E %, the minimum diameter of the side of the evaporation source facing the glass panel is dmm, and the ratio of the distance L between the evaporation source and the inner surface of the glass panel to the distance l between the evaporation source and the mesh structure plate is When l/L, P, T _C , T _E ,
The respective values of d and l/L are 0.7≦P<4.0, 20
A method for forming a metal back film for a color cathode ray tube, characterized in that vacuum deposition is performed in the following ranges: ≦T _C ≦60, T _E ≧75, d≧5, 0.2≦l/L≦0.7. 2. A method for forming a metal back film for a color cathode ray tube according to claim 1, characterized in that a conical basket-shaped heater is used as an evaporation source.