JPS63211536A - Method for forming inner conductive film of cathode-ray tube - Google Patents

Abstract

PURPOSE:To make a film hard to be peeled off and reduce the gas emission by coating a conductive paint made of a suspension of conductive grains added with a binder on the inner face of a bulb, drying it at a low speed, coating the conductive paint again on the dried film, and drying it at a high speed. CONSTITUTION:A conductive paint made of an aqueous suspension containing about 5-13wt.% of a binder made of potassium silicate as converted to 23-25wt.% silica of graphite fine grains as conductive grains is coated with a brush, the coated film is dried for 5-7 min. by the hot air of 38-42 deg.C blasted with a flow quantity of 15-20(l)/min. to form a film with a thickness of about 2mum. Then, the conductive paint is coated again by the same method on the dried film, and the coated film is dried quickly by the hot air of 70-80 deg.C blasted with a flow quantity of 60-70(l)/min. Then, this film is baked for tens of min. in the air atmosphere of 400-450 deg.C to form an inner conductive film.

Description

DETAILED DESCRIPTION OF THE INVENTION OBJECTS OF THE INVENTION Field of Industrial Application This invention relates to a method for forming an internal electrocardial coating on the inner surface of a cathode ray tube bulb.

(Prior Art) Cathode ray tubes that display images on a fluorescent screen using electron beams emitted from an electron gun include color picture tubes and monochrome picture tubes. Furthermore, by application, there are monitor tubes installed in aircraft and vehicles, display tubes that display characters and figures, and projection tubes that enlarge and project images displayed on a fluorescent screen onto a screen.

All of these cathode ray tubes have a fourth structure as their basic structure.
The faceplate (or panel) (
1) and a funnel-shaped funnel (2);
A fluorescent screen (4) is disposed on the inner surface, and an electron gun (6) consisting of a plurality of electrodes is disposed within the neck (5) of the funnel (2). In order to display an image on the fluorescent screen (4) using the electron beam emitted from the electron gun (6), a predetermined voltage is applied to each electrode of the electron gun (6). The voltage is applied to the cathode, which is the source of the electron beam,
and a low voltage electrode adjacent to this cathode that controls the electrons generated from the cathode is supplied from the stem pin (7) at the end of the neck (5) and is used to fluoresce the electron beam emitted from this electron gun (6). The high voltage electrode (8) for focusing on the surface (4) is connected to the funnel (2) from the anode terminal (9) provided on the side of the funnel (2).
The internal conductive coating (10) is attached to the internal conductive coating (10) formed on the inner surface and the high voltage electrode (8).
Valve spacer (11) made of an elastic member that presses against
). Normally, this valve spacer (1
A plurality of electrodes 1) are attached to the circumferential surface of the electrode (8) at equal intervals.

Note that the internal conductive coating (10) is an anode terminal (9).
An electric field for accelerating the electron beam emitted from the electron gun (6) is formed in the bulb (3) by the anode voltage applied from the electron gun (6). In addition, in Fig. 4, (12) is.

In order to prevent the phosphor screen (4) from deteriorating due to high-energy electron beams, a metal back layer is formed on the back surface of the phosphor screen (4). It is connected to the.

By the way, the internal conductive coating (10) is attached to the bulb (3).
) After cleaning the inner surface with hydrofluoric acid and drying it,
Usually, a conductive paint made of so-called DAG, which is an aqueous suspension of graphite particles added with a binder such as sodium silicate or potassium silicate, is applied by spraying or using a sponge or brush, and after drying, It is formed by baking in an air atmosphere at about 400-450°C.

However, the internal conductive coating (10
), especially the valve spacer (11
) may peel off at the contact area. This peeled internal conductive coating may adhere to the high voltage application part of the electron gun (6), causing discharges such as sparks during operation of the cathode ray tube, or may adhere to the phosphor screen (4). This causes problems such as degrading the image quality.

One way to solve this problem is to increase the amount of binder added to the conductive paint. However, if the amount of binder such as sodium silicate or potassium silicate is increased,
), which causes the problem of shortening the life of the cathode ray tube.

(Problems to be Solved by the Invention) As mentioned above, cathode ray tubes with an internal conductive coating formed by applying conductive paint to the inner surface of the bulb are susceptible to vibrations and shocks applied during transportation or operation. It is easy to peel off at the contact part with the valve spacer attached to the electrode of the electron gun, and the peeled internal conductive coating adheres to the high voltage application part of the electron gun, causing discharge inside the tube during operation of the cathode ray tube. In addition, there are problems such as adhesion to the phosphor screen and deteriorating the image quality. In order to solve this problem, increasing the amount of binder added in the conductive paint increases the amount of gas released from the internal conductive coating, resulting in a shortened lifespan of the cathode ray tube.

This invention was made to solve the above problems, and aims to form an internal conductive coating of a cathode ray tube that is difficult to peel off and that releases less gas.

[Structure of the invention]

(Means for solving the problem) In a method of forming an internal conductive coating on the inner surface of a cathode ray tube bulb, first, a conductive paint consisting of a suspension of conductive particles to which a binder is added is applied to the inner surface of the bulb. After coating and drying at low speed, the conductive paint was applied on the film formed by this slow drying and dried at high speed to form an internal conductive film.

(Function) As described above, a conductive paint made of a suspension of conductive particles to which a binder has been added is applied to the inner surface of the bulb, and after this is dried at low speed, the conductive paint is applied again on the dried film. death,
When this is dried at high speed to form an internal conductive coating, a layer with a large amount of binder can be formed on the interface with the valve and on the surface of the internal conductive coating, which increases the adhesion to the inner surface of the valve and the valve spacer. The internal conductive coating can be resistant to contact with

(Example) The present invention will be described below based on an example of a projection tube.

First, a bulb with a fluorescent screen formed on the inner surface of the face plate is attached to a conductive paint applicator, and then heated for 60 to 1100 r.
This is rotated at a rotation speed of about p. Then, 23 to 22 graphite fine particles were added as conductive particles to this rotating valve.
A conductive paint made of an aqueous suspension containing about 5 to 13 νt% of a binder made of potassium silicate in terms of silica (Sin2) is applied with a brush, and the coating film is coated with a brush.
It is dried for 5 to 7 minutes using warm air at 38 to 42° C. blown at a flow rate of 5 to 20 Q/min to form a film with a thickness of about 2 μm. Thereafter, the above conductive paint is overlaid on the dried film by the same method, and the coated film is coated with a coating film of 60-70%
Rapid drying is performed by hot air of 70 to 80°C blown at a flow rate of Q/min. Thereafter, this film is baked in an air atmosphere at 400 to 450° C. for several tens of minutes to form an internal conductive film.

The distribution of binder in the internal conductive coating formed by this method is shown in FIG. 1 by curve (a). In this figure, the horizontal axis shows the film thickness, and the vertical axis shows the amount of binder remaining in the film, converted to silica, as a relative value (percentage). Further, in this figure, a point with a film thickness of 0% represents the surface of the internal conductive film, and a point with a film thickness of 100% represents the interface with the inner surface of the bulb.

By the way, according to the inventor's experiments, when a conductive paint consisting of an aqueous suspension of fine graphite particles to which a binder has been added is applied to a non-water-absorbing substrate made of glass or the like and then quickly dried, the conductive paint is formed. Regardless of the application method or drying method, the binder migrates along the surface of the coating, as shown by curve (b) in Figure 2, and as a result, the strength of the coating increases at the surface, but at the interface with the substrate. In fact, it has been found that the binder is reduced and the adhesion to the substrate is reduced.

In addition, the above conductive paint was similarly applied to a non-water absorbing substrate,
When this is dried at a low speed, the binder moves to the interface with the substrate, increasing the adhesion to the substrate, as shown by curve (c) in Figure 3, but as the surface becomes looser, the binder decreases. It was found that the strength of the coating decreased.

The method for forming the internal conductive film in the above-mentioned Example was carried out based on this experimental result, and as shown in curve (a), the interface with the bulb and the surface of the film were bonded together. This indicates that the inner conductive coating has a large amount of agent and has a high adhesion to the bulb and a high surface strength.

Table 1 shows that an internal conductive coating was formed on the inner surface of a projection tube bulb by the above method, an electron gun was attached, a valve spacer attached to the electron gun was pressed against the internal conductive coating, and this was tested. This shows the peeling of the contact area with the valve spacer when the face plate is set on a rubber ring attached to a stand and a 600G impact is applied repeatedly to the face plate using a wooden hammer, in comparison with a conventional internal conductive coating. It is something. As shown in the results of this forced breakdown test, the conventional internal conductive coating was 0.52% after 50 repeated impacts.
However, the test product did not peel off even after 100 repeated impacts, and only slightly peeled off after 150 repeated impacts, indicating that it was significantly strengthened compared to conventional internal conductive coatings. I know that there is.

Table 1 Furthermore, no deterioration in withstand voltage characteristics was observed in the actually manufactured projection tubes. Further, in a life test, there was no particular deterioration in characteristics, and it was shown that the internal conductive coating was stable with little gas release.

Although an example of a projection tube has been described above, it goes without saying that the method for forming an internal conductive coating of the present invention can also be applied to other cathode ray tubes in which a coating of conductive paint is formed on at least a portion of the bulb. Nor.

〔Effect of the invention〕

In the method of forming an internal conductive coating on the inner surface of a cathode ray tube bulb, first, a conductive paint consisting of a suspension of conductive particles to which a binder has been added is applied to the inner surface of the bulb, and then dried at low speed. When a conductive paint is applied again on the film formed by this slow drying and dried at high speed to form an internal conductive film, a layer with a large amount of binder is formed at the interface with the bulb and on the surface of the internal conductive film. can do. Therefore, even without increasing the amount of binder added, it is possible to create an internal conductive coating that is resistant to peeling due to adhesion to the valve or contact with other pipe internal materials, and is effective in improving voltage resistance and service life. A stable cathode ray tube can be easily manufactured.

[Brief explanation of the drawing]

Fig. 1 shows the distribution of the binder in the internal conductive film formed by the method of the present invention, Fig. 2 shows the distribution of the binder in the internal conductive film formed by slow drying, and Fig. 3 4 is a diagram showing the distribution of the binder in the internal conductive film formed by high-speed drying, and FIG. 4 is a diagram showing the structure of the cathode ray tube.

Claims (1)

[Claims] An internal conductive coating for a cathode ray tube, in which a conductive paint consisting of a suspension of conductive particles to which a binder is added is applied to the inner surface of a bulb of the cathode ray tube and dried to form an internal conductive coating. The forming method is characterized in that the conductive paint is applied to the inner surface of the valve and dried at low speed, and then the conductive paint is applied on the film formed by this slow drying and dried at high speed to form an internal conductive film. A method of forming an internal conductive coating for a cathode ray tube.