JPS6311738B2 - - 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 serves as a light reflecting surface to extract as much light as possible from the phosphor layer 2 to the viewer when the color cathode ray tube is in operation, and to increase the luminance of the color cathode ray tube. It also has the function of preventing ion burn.
Specifically, the glass panel 1 on which the phosphor layer 2 and organic interlayer film 3 have been formed is placed on the panel support stand 6 of the metal bag machine 5, and the inside of the vapor deposition tank 7 is brought into a high vacuum state using the vacuum pump 8. exhaust to. Inside the vapor deposition tank 7, an aluminum rod 11 is installed as an evaporation source.
A coiled heater 10 made of a charged tungsten W wire is fixed to the heater support electrode 9 so as to be positioned on the center line l 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 coiled heater 10 through the heater support electrode 9 by a power supply device 12 provided outside the vapor deposition tank 7 . Since the coiled heater 10 is a good resistance heating element, the aluminum rod 11 charged inside the coiled heater 10 is heated, melted, and evaporated by the heat generated by the coiled heater 10, and is formed on the inner surface of the glass panel 1. A vapor-deposited aluminum film, ie, 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 from the metal bag machine. A new aluminum rod is charged to the coiled heater 10, the next glass panel is set, and aluminum is deposited one after another in the same manner as described above. Note that the coiled heater 10
is used repeatedly until it becomes unusable due to disconnection or severe thermal deformation.

Normally, the inner surface of the glass panel 1 is a spherical arc surface with a large radius of curvature. The radius of curvature is chosen to be quite small. Line b in FIG. 2 shows the film thickness distribution of the metal back film 4 formed as described above from the center of the glass panel 1 toward the periphery. The performance of metal back membrane is
There is an optimum film thickness value determined by the light reflection efficiency of this film and the electron beam transmittance during operation of the completed color cathode ray tube. Therefore, it is undesirable that the thickness of the metal back film differs at each position on the glass panel 1, and in a case like line b in FIG. This is undesirable because the peripheral area becomes thinner than the maximum film thickness value, the light reflection efficiency deteriorates, and the brightness of the peripheral area decreases when the completed color cathode ray tube is operated. Conversely, if the peripheral part of the glass panel 1 is adjusted to the optimum film thickness value, the film thickness will be thicker than the optimum value in the center part, which will deteriorate the transmission of electron beams when the completed color cathode ray tube is operated, and the brightness of the central part will be reduced. This is not desirable because it lowers the value. Furthermore, if the film thickness becomes extremely thick, the metal back film 4 tends to float or peel off during the thermal decomposition step of the organic intermediate film 3 after the metal back film 4 is formed. I really don't like it. For these reasons, it is ideal to form the metal back film 4 with a constant film thickness from the center to the periphery of the glass panel 1, that is, with an optimum film thickness, as shown by line a in FIG. 2. To do this, theoretically, the distance d between the coiled heater 10 and the glass panel 1 should be increased to the radius of curvature of the inner surface of the glass panel 1. Since the radius is very large, if the distance d is made equal to the inner surface of the glass panel 1 and the radius of curvature, the volume of the vapor deposition tank 7 will become very large, and a large amount of power will be required to exhaust the vapor deposition tank 7. This results in poor economic efficiency. Furthermore, such a difference in thickness between the metal back film 4 at the center and the periphery of the glass panel 1 becomes more significant as the size of the glass panel 1 increases.

Therefore, as a method for eliminating the above-mentioned difference in film thickness of the metal back film, it has been proposed to install a plurality of evaporation sources as shown in FIG. 3. As the number of vapor deposition sources increases, the thickness distribution of the deposited metal back film 4 becomes more uniform, and it becomes possible to obtain a film thickness distribution close to line a in FIG. 2, but according to this method, Coiled heater 1
It is necessary to increase the number of heaters, which is not only economically disadvantageous, but also reduces the number of installed coil heaters.
Since the number of aluminum rods 11 is large, extra work is required when charging the aluminum rods 11, and a problem arises in the workability of the metal bag process.

This invention was made in order to eliminate the above-mentioned drawbacks, and it provides a metal back for color cathode ray tubes, which makes it possible to obtain a metal back film having a uniform deposition film thickness distribution without causing any problems in terms of economy and workability. The present invention aims to provide a method for forming a film.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 4 is a diagram for explaining the method of forming a metal back film according to the present invention. As shown in FIG. 4, a coiled heater 10 made of a charged aluminum rod 11 is arranged approximately on the center line l of the glass panel 1, and in particular, a mesh structure is provided between the coiled heater 10 and the glass panel 1. That is, a mosaic-like shield 13 is provided. This mesh-structured shielding body 13 has mesh-structured openings 14 made of metal plates, as shown in FIG. is provided so as to gradually increase from the center to the periphery of the shielding body 13, as shown by line c in FIG. Further, this shielding body 13 is arranged so that the center line l of the glass panel 1 substantially passes through its center point. In addition,
The center points of the aluminum rod 11 and the shield 13 are arranged approximately on the center line l of the glass panel 1.

If the metal back film 4 is formed by vacuum evaporation in the same manner as the conventional method shown in FIG. A metal back film 4 having a uniform thickness distribution from the center to the periphery of the glass panel 1 as shown by line a in FIG. 2 can be obtained. In this case, there is a possibility that a shadow of the mesh-structured shielding body 13 may be formed as a pattern on the metal back film 4, but this depends on the size of the mesh-structured pattern of the shielding body 13, the installation position of this shielding body 13, and the shape of the coil. Heater 1
This can be solved by appropriately selecting the area as the evaporation source. Further, the shielding body 13 has an aluminum evaporated film deposited on its surface, and can be repeatedly used for a considerable number of metal backing processes.

As explained above, according to the method for forming a metal back film of the present invention, a metal back film with a uniform thickness distribution can be formed without increasing the volume of the vapor deposition tank or increasing the number of evaporation sources. Since it can be formed on the organic interlayer film on the inner surface of a glass panel of any size, it is possible to form a metal back film with high performance while increasing the economic efficiency and rationality of the metal back process. The effect is that color cathode ray tubes can be manufactured at a lower cost.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view for explaining an example of a conventional metal back process, FIG. 2 is a view showing the film thickness distribution of a metal back film, and FIG. 3 is a cross-sectional view for explaining another example of a metal back process. FIG. 4 is a cross-sectional view for explaining the metal bag process according to an embodiment of the present invention, FIG. 5 is a schematic plan view showing the structure of the shield, and FIG. 6 is a diagram showing the aperture ratio distribution of the shield. DESCRIPTION OF SYMBOLS 1... Glass panel, 2... Phosphor layer, 3... Organic interlayer, 4... Metal back film, 5... Metal back machine, 6... Panel support stand, 7... Vapor deposition tank, 8... Vacuum pump, 9... Heater support electrode, 10 ... Coiled heater, 11 ... Aluminum rod, 12 ... Power supply device, 1
3... Shielding body, 14... 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 the glass panel on which the phosphor layer and organic interlayer film are formed, and
Vacuum evaporation is carried out by arranging a shielding member having a mesh structure in which the aperture ratio gradually increases from the center toward the periphery, with its center point located on the center line of the glass panel, and between the evaporation source and the glass panel. A method for forming a metal back film for a color cathode ray tube.