JPS6139698B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a light-reflecting metal thin film on the fluorescent surface of a color picture tube having a metal back structure.

The phosphor surface of a normal color picture tube is a phosphor film attached to the inner surface of a glass face plate (panel) that forms part of the tube body of the picture tube. A so-called metal back structure in which a light-reflecting metal thin film is formed to effectively extract the light to the front of the color picture tube is common.

This metal back fluorescent surface has the advantage of increasing the brightness of the color picture tube and preventing the phenomenon of ion burnout, and its manufacturing process will be described with reference to FIG.

In FIG. 1, 1 is a glass face plate, 2 is a fluorescent film coated on the inner surface of this plate 1, and 3 is a film mainly composed of an organic substance for smoothing the surface of this fluorescent film 2. The intermediate film 4 made of a commercial lacquer material is an aluminum thin film, and the fluorescent film 2 is formed by coating the inner surface of the plate 1 to a uniform thickness and drying it. Further, the aluminum thin film 4 is formed by depositing aluminum on the intermediate film 3 in a vacuum, and then the intermediate film 3 is removed by baking treatment.

Conventionally, in order to form an aluminum thin film by vapor deposition, as shown in FIG. 2, a glass face plate 1 with an intermediate film 3 formed thereon is formed into one or more basket-shaped pieces using three or four stranded tungsten wires. vacuum envelope 6 having an evaporation source 5 of
A method is used in which aluminum is vapor-deposited on the intermediate film 3 in a vacuum of 10 ⁻⁴ torr while supporting the intermediate film 3 at a predetermined position within the intermediate film 3 .

The thickness of the aluminum thin film formed by such means varies depending on the position of the glass face plate 1, and the ratio of the film thickness between the central part and the peripheral part of the plate 1 is 1:0.5 to 1. This level of deposition film thickness distribution is within a range that is sufficiently satisfactory in terms of the performance of the color picture tube, but since a coil made of tungsten wire is used as the evaporation source 5, there is a drawback that the service life is short.

In order to eliminate this drawback, a method was devised to use a resistance heating element instead of the tungsten wire coil.
It is put into practical use. A resistive heating element whose main component is boron nitride is generally used, but it is difficult to form this type of resistor into a basket shape similar to a tungsten wire coil during molding. For this reason, the heating resistor has a so-called boat-like structure in which a recess 10a is formed on the upper surface of the rectangular parallelepiped resistor 10, as shown in FIG.
Note that there is also a flat surface without the recess 10a.

Even when using this boat-shaped resistance heater evaporation source whose main component is boron nitride (hereinafter abbreviated as boron nitride heater), the evaporation effect of the aluminum thin film is the same as when the tungsten wire coil is used as the evaporation source. However, the deposited film thickness distribution is different. An example of the distribution of the deposited film thickness in this case is as shown by the curve (a) in FIG. 4, where the film thickness ratio between the central part (origin 0) and the peripheral part becomes large. However, one boron nitride heating element having the structure shown in FIG. 3 was used as the evaporation source, and the distance from the glass face plate, which was the object to be evaporated, was approximately 350 mm.

Generally, when using an aluminum thin film as a light-reflective metal vapor deposition film, the aluminum film thickness required for a color picture tube is 1500 Å to 2000 Å or more, but when aluminum is vapor deposited using a boron nitride heating element as an evaporation source, In order to obtain the minimum aluminum film thickness of 1500 Å to 2000 Å required for color picture tubes at the periphery of the glass face plate, the maximum aluminum film thickness within the glass face plate is more than 4 times that of the periphery, which is more than necessary. Parts arise.

Such non-uniformity in the film thickness distribution of the aluminum vapor deposited film can be corrected to some extent by installing a plurality of boron nitride heating elements, for example four or more, but it is still insufficient to achieve the desired aluminum film thickness distribution. The equipment becomes very complex and expensive. Further, from the viewpoint of vacuum maintenance, it is not preferable to complicate the internal structure.

For the above reasons, the current situation is to focus on simplifying the equipment by using only one or two boron nitride heating elements, and to ignore the uneven distribution of aluminum film thickness.However, as mentioned above, it is necessary to When the aluminum film becomes thicker than this, the energy of electrons decreases in the aluminum film, and the brightness of the color picture tube decreases. This significantly reduces the effective use of the luminescence of the phosphor by the aluminum film, that is, the effect of increasing the brightness of the color picture tube.

This invention was made in view of the above points,
The present invention aims to provide a method for producing a deposited film that can deposit a metal thin film with a uniform thickness distribution.

The present invention will be described in detail below with reference to the accompanying drawings. However, the same parts as in FIGS. 2 and 3 are given the same reference numerals.

In FIG. 5, 1 is a glass face plate, 2 is a fluorescent film, 3 is an intermediate film, 4 is an aluminum thin film, 6 is a vacuum envelope, 10 is a boron nitride heating element,
7 is an automatic aluminum wire inserter, 8 is an aluminum wire, and 9 is a shield. A fluorescent substance is applied to the inner surface of the glass face plate 1, and this is dried to form a fluorescent film 2. The process of forming the intermediate film 3 is well known and is the same as the conventional process.

The boron nitride heating element 10 is installed at a predetermined position at the bottom of the envelope 6, and a shield is placed above the central part at a required height. This shield 9
In this example, a stainless steel disc with a diameter of 200 mm is used, and the size of the plate 1, which is the object to be deposited, is placed between the plate 1 and the heating element 10, which are arranged at an interval of 350 mm, on the side closer to the heating element 10. This is determined by considering the distance between the plate 1 and the heating element 10, etc.

Thus, the aluminum thin film 4 is placed on the intermediate film 3 of the glass face plate 1 which has undergone the previous processing step.
To form this, the inside of the envelope 6 is evacuated using an evacuation device such as a vacuum pump (not shown), and the aluminum wire 8, which is the vapor deposition material, is inserted into the recess (the vapor deposition material mounting portion) 10a of the heating body 10 using the automatic inserter 7. Insert
Also, a current is passed through the heating body 10 to generate heat. The aluminum wire 8 evaporates and scatters upward due to the temperature rise caused by the heat generated by the heating body 10. This evaporation forms an aluminum thin film 4 on the intermediate film 3.
In this case, more aluminum is scattered above the central part of the heating element 10 (see curve a in FIG. 4), but since the shield 9 is placed in the central part, about 3/4 of the aluminum scattered in this part is prevented from reaching the intermediate film 3. As a result, as shown by line b in FIG. 4, a deposited film with a substantially uniform thickness distribution is formed on the intermediate film 3, which is the minimum thickness necessary for a color picture tube and has a uniform thickness. Ru.

In the above embodiment, one boron nitride heating element is used, but a plurality of boron nitride heating elements may be used. However, as described above, it is desirable to have a small number of devices in order to avoid complication of the device. In addition, the shielding object 9 is not limited to a circular plate, but may also be a rectangular flat plate, a rectangular parallelepiped, a spherical body, etc., and by appropriately selecting its size and distance from the surface to be deposited, the distribution of the deposited film thickness can be controlled appropriately. can do.

As described above, according to the present invention, a metal vapor deposited film can be uniformly coated with a simple means of arranging a shield at a position close to the heating element between the boron nitride heating element and the glass face plate installation position. Moreover, it can be formed to the minimum thickness required for color picture tubes, and can greatly contribute to the production of high-brightness color picture tubes with a high metal back effect. Further, there is an advantage that vacuum maintenance becomes easier.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view for explaining the manufacturing process of the fluorescent surface part of a color picture tube, Fig. 2 is a schematic configuration diagram of an example of a conventional vapor deposition apparatus, and Fig. 3 is a sectional view for explaining the manufacturing process of the fluorescent surface part of a color picture tube. FIG. 4 is a curve diagram showing the film thickness distribution of an aluminum vapor-deposited film, and FIG. 5 is a configuration diagram showing an embodiment of the present invention. 1... Glass face plate, 2... Fluorescent film, 3... Intermediate film, 4... Aluminum thin film, 6
... Vacuum envelope, 7 ... Aluminum wire automatic inserter, 8 ... Aluminum wire, 9 ... Shielding object, 10
...Boron nitride heating element, 10a... recess. Note that the same reference numerals in the figures indicate the same parts.

Claims (1)

[Claims] 1. A vapor deposition film production method in which a light-reflecting metal thin film is vacuum vapor-deposited on the intermediate film of the fluorescent surface portion of a color picture tube using a rectangular rod-shaped resistance heating body having a flat or concave vapor deposition material placement portion as an evaporation source. A method for producing a vapor deposited film for a color picture tube, characterized in that a metal vapor deposition film is formed on an intermediate film while removing a part of the metal that evaporates and scatters directly above the center of a resistance heating element.