JPH0644448B2 - Method for forming conductive film of cathode ray tube - Google Patents

Description

The present invention relates to a method for forming a conductive film of a cathode ray tube such as a color television picture tube, and more particularly to a conductive film on the inner surface of a neck portion used as a resistance film for suppressing discharge current. The present invention relates to a method for forming a film.

[Outline of Invention]

The present invention is a method of forming a conductive film over a predetermined length on the inner surface of a neck portion for suppressing a discharge current during internal discharge of a cathode ray tube, in which a coating means having a length corresponding to the predetermined length is moved in the tube axis direction. It is possible to form a uniform conductive film that can surely suppress the discharge current by rotating and applying the conductive film paint without rotating.

[Conventional technology]

In the cathode ray tube, internal discharge during operation, for example, discharge between the high voltage electrode of the electron gun and a low potential electrode adjacent thereto causes a large current to flow, causing a failure of the set circuit part,
Problems such as cathode damage, screen noise, discharge noise, and malfunction of peripheral devices occur. In order to avoid this, when an internal discharge occurs, it is necessary to constantly suppress the discharge current to a small value (for example, 100 A or less). As a method of suppressing the discharge current, for example, a method of suppressing the discharge current at the time of internal discharge by utilizing the resistance of the internal conductive film in the portion extending from the funnel portion to the neck portion is known.

Figure 10 shows an example. In the figure, (1) indicates an electron gun arranged in the neck portion (2a) of the tubular body (2). The electron gun (1) has, for example, three cathodes K _R , K _G and K corresponding to red, green and blue.
_In common with _B , the first grid G ₁ , the second grid G ₂ ,
Third grid G ₃ , fourth grid G ₄ and fifth grid G
Unipoten type with ₅ arranged in sequence, 5th grid G ₅
Convergence means (3) is arranged in the subsequent stage.
Convergence means (3) are inner deflection electrode plates facing each other
(3a) and (3b) and the outer deflection electrode plates (3c) and (3
d) and. The inner deflection electrode plates (3a) and (3b) are the fifth
It is connected to the grid G ₅ and is supplied with an anode voltage HV, and the outer deflection electrode plates (3c) and (3d) are supplied with a convergence voltage CV lower than the anode voltage HV.

On the other hand, although the internal conductive film (4) is formed by adhering from the funnel portion (2b) of the tubular body (2) to the neck portion (2a), the funnel portion (from the part of the neck portion (2a) ( The internal conductive film (4a) extending over a part of 2b) is used as a resistance film for suppressing discharge current.

The anode voltage HV and the convergence voltage CV are supplied by a coaxial cable (6) from an anode button (not shown). That is, the central conductor (7) of the coaxial cable (6) is connected to the outer deflection plate (3c) to give a convergence voltage CV, and the C-shaped metal leaf spring (9) is connected to the outer conductor (8). ) Contacts the inner conductive film (4) and the fifth grid G ₅
The conductive contact 10 is elastically brought into contact with the end of the inner conductive film 4 at the neck, and the anode voltage HV is applied. Therefore, if the internal discharge occurs, anode button (high pressure feed end) -G ₃ or G ₅ -G ₂ or G ₄ - terminal pin (1
1) -Even if a large current flows in the current path of the circuit part, the current is suppressed to a small value by the resistance of the internal conductive film (4a).

Conventionally, the coating of the internal conductive film (4a) extending from the neck portion (2a) to the funnel portion (2b) is performed by applying the coating means to the operating rod (21) which is vertically moved and rotated as shown in FIG. (23) is rotatably attached and the coating means (23) is applied through the paint supply hose (24).
Brush or sponge (sponge in this example) for impregnating (22)
First, the coating means (23) impregnated with the conductive film paint is used to apply the conductive film paint to the neck part (2a).
After moving (lowering) to a predetermined position on the inner surface of (Fig. 11A), the tube body (2) and the coating means (23) are relatively rotated (Fig. 11B), and then the coating is performed. The means (23) was rotated and raised (FIGS. 11C and 11D), and was applied from the neck portion (2a) to a part of the funnel portion (2b).

Japanese Patent Application No. 56-134881 proposes a method of forming an internal conductive film (4a) by applying the same coating method twice and at different pitches.

[Problems to be solved by the invention]

However, it was difficult to form a uniform internal conductive film (4a) by the above-mentioned conventional coating method, because the coating thickness varies from 5 to 50 μm. That is, with the sliding contact movement of the coating means (23) with a sponge or a brush, the flow of the paint (25) becomes as shown in FIG. 12, and as a result, as shown in FIG. 13, the pitch overlapping portion (26). In this case, the film thickness becomes large and so-called uneven coating occurs. Further, when the coated surface between the pitches is seen, fine grooves (27) called sponge and brush are formed in the conductive film (4a) as shown in FIGS. 14 and 15. This is caused by the difference in contact pressure with the inner surface of the neck portion (2a). With such uneven coating and uneven internal conductive film (4a) with fine grooves,
When a large current flows in the direction traversing the irregularities or the narrow grooves, the irregularities cause discharge to generate a creeping discharge, and as a result, the function as a resistance film deteriorates, and the discharge current cannot be sufficiently controlled.

Although the internal conductive film is formed by the flow coating method, one end portion of the neck portion side needs to be regulated by a means such as washing with water, which complicates the manufacturing process.

In view of the above points, the present invention provides a method for forming a conductive film of a cathode ray tube capable of forming a uniform internal conductive film capable of reliably suppressing discharge current due to internal discharge.

[Means for solving problems]

The present invention provides a coating means (31) having a length corresponding to a predetermined length D of, for example, 20 mm or more of the tubular body neck portion (2a) and impregnating the coating means (31) with a conductive film paint. The main inner conductive film (4) for controlling the discharge current is provided over the length D on the inner surface of the neck (2a) by rotating relative to the neck (2a) without moving in the axial direction.
a ₁ ) is formed by coating. Further, the same coating means (31) is rotationally moved relative to each other to form an internal conductive film (4a ₂ ) on the inner surface of the funnel portion side, which is continuous with the internal conductive film (4a ₁ ) of the neck portion. In this case, the length D of the main internal conductive film (4a ₁ ) for suppressing the discharge current formed on the inner surface of the neck portion is, for example, the neck portion (2a).
In the tube axis direction, corresponds to the length between the portion in contact with the conductive contact (10) extending from the high voltage electrode G ₅ of the electron gun (1) and the portion near the boundary with the funnel portion (2b). The number of times of application can be appropriately selected such as one application and two applications.

As the paint impregnated body used for the coating means (31), for example, a sponge (32), a sponge having a shape in which the center of the sponge surface on the side in contact with the inner surface of the neck portion is recessed from both ends is used.

In this sponge (32), the central groove (33) is designed so that the sponge surface does not directly contact the inner surface of the neck part, and the projections at both ends (32a) (32b) prevent the escape of paint and the neck part. This is for controlling the contact pressure on the inner surface.

[Action]

Using a coating means of length D, the conductive film (4a ₁ ) is applied to the inner surface of the neck portion (2a) over the length D by rotating without moving in the tube axis direction.
Since the coating film is formed by coating, the formed conductive film (4a ₁ ) does not have coating unevenness as in the conventional case. Further, since the center of the sponge surface of the coating means (31) does not directly contact the inner surface of the neck portion, a fine groove is unlikely to occur. Therefore, the unevenness and the fine grooves on the film surface are improved, and an extremely uniform conductive film having a variation in film thickness of 10 to 20 μm can be obtained.

Particularly, in the present invention, the discharge current can be reliably controlled only by the resistance of the internal conductive film (4a ₁ ) on the inner surface of the neck portion.

〔Example〕

 Examples of the present invention will be described below.

In the present invention, a coating means (31) integrally having a paint impregnated body such as a sponge (32) as shown in FIG. 1 is used. As this sponge (32), for example, as shown in FIGS. 4A, 4B, and 4C, a concave groove in which the center is recessed leaving both ends (32a) and (32b) on the sponge surface on the side in contact with the inner surface of the neck portion.
It has a shape having (33), and its total length D is the same as the length D of the inner conductive film (4a ₁ ) formed on the inner surface of the neck portion (2a) shown in FIG. 3 in the tube axis direction. To configure. Length D
Is the fifth grid G ₅ of the electron gun (1) at the neck.
It corresponds to the distance from the contact portion of the conductive contact (10) extending further to the portion near the boundary with the funnel portion (2b). In this example, the length D is 40 mm. The sponge (32) shown in FIG. 4A is a U-shaped sponge in which concave grooves (33) having the same depth in the length direction are formed. The sponge (32) shown in FIG. 4B is a sponge having the same depth in the length direction but having a concave groove (33) inclined to one side in the width direction orthogonal to this. In addition,
The sponge of FIG. 4B is slid in the direction of the arrow during application.
The sponge (32) of FIG. 4C is a sponge having a concave groove (33) formed on a cylindrical surface.

The coating means (31) is attached to the tip of the operating rod (34) of the coating machine. The operating rod (34) is connected to a drive source and is configured to be vertically movable, horizontally movable, and rotationally driven. A coating material supply hose (35) is connected to the coating means (31), and a conductive film coating material such as carbon coating material is supplied to the sponge (32) of the coating means (31) through this (see FIG. 1). A metering pump is used to impregnate the sponge (32) with the carbon paint.

Thus, in this example, first, as shown in FIG. 1A, the sponge (32) of the coating means (31) has a carbon coating material (No. 1 to No. 4) having suitable characteristics shown in the following table. ) Is impregnated in an appropriate amount, and then the coating means (31) is relatively moved to a predetermined position in the neck portion (2a). Then, the application means (31) is relatively moved at that position without moving in the tube axis direction, and the neck portion (2
a) A carbon film (4a ₁ ) having a predetermined length D is formed on the inner surface by coating.
The state of the surface of the sponge (32) and the inner surface of the neck portion at the time of this application are as shown in FIG. That is, in the concave groove (33) at the center of the sponge (32), the sponge surface does not directly contact the inner surface of the neck portion (2a), and the escape of carbon paint is prevented by the protruding portions of both ends (32a) (32b). At the same time, the contact pressure on the inner surface of the neck is controlled and the carbon film is uniform in the center (4a ₁ )
Is formed.

Next, as shown in FIG. 1B, the coating means (31) is moved away from the inner surface of the neck portion and then moved to the funnel portion (2b) side,
As shown in FIG. C, the coating means (31) is again brought into contact with the inner surface of the tube so as to overlap with the upper end of the carbon film (4a ₁ ) (that is, the end near the boundary with the funnel portion).

Next, as shown in FIG. 1C, the coating means (31) is slidably moved while relatively rotating to form a carbon film (4a ₂ ) on a predetermined portion of the inner surface of the funnel portion (2b). As a result, as shown in FIG. 6, an internal carbon film (4a) continuous from a part of the neck part (2a) to a part of the funnel part (2b) is formed. In this case, the carbon film (4a ₁ ) extending over the predetermined length D of the neck part (2a) has a sheet resistance of 750Ω / □ at each part.
A uniform film is formed that does not exceed the above. This carbon film
(4a ₁ ) functions as the main resistance film for suppressing the discharge current.

Thus, FIG. 8 shows the experimental results of the control rates of the respective discharge currents when the internal conductive film extending from the neck portion to the funnel portion is formed by the conventional coating method and the coating method of the present invention as the above example. Looking at the state of the internal conductive film in the neck portion at this time, the conventional one had coating unevenness as shown in FIG. 7A, but the one of the present invention as shown in FIG. 7B. It was a uniform film with no coating unevenness.

In FIG. 8, the discharge current in the case of the method of the present invention is represented by
, The control rate is shown by ●, the discharge current in the conventional method is shown by Δ, and the control rate is shown by ▲. Here, the discharge current is an average value, and the control rate means that the flowing discharge current is 100A.
We say the following probabilities.

From this experimental result, when the conductive film for suppressing the discharge current is formed by the coating method of the present invention, the discharge current can be suppressed to 100 A or less even at a high voltage of 25 KV or higher (corresponding to the anode voltage of the cathode ray tube). You can

Incidentally, FIG. 2 shows another example of the coating method of the present invention. In this example, as shown in FIG. 2A, first, the coating means (31) is brought into contact with the inner surface of the funnel portion (2b), and then relatively rotationally slidingly moved to move the carbon film (2b) to the funnel portion (2b). 4a ₂ ) is applied and formed, and when it is continuously moved to a predetermined position in the coating means (31) or the neck portion (2a), the coating means (31) is not moved in the axial direction of the pipe and is relatively moved at that position. The neck (2
a) Form a uniform carbon film (4a ₁ ) on the inner surface. Next, after the coating is finished, the coating means (31) is moved away from the inner surface of the neck portion (2a) and stopped at a predetermined position as shown in FIGS. 2B and 2C. Internal conductive film formed by the coating method of FIG.
Also in (4a), similar results to the above example were obtained.

In the above example, the present invention is applied to the cathode ray tube that supplies the convergence voltage CV by the coaxial cable, but the present invention also incorporates a dividing resistor plate (41) as shown in FIG. 9, and thereby supplies the convergence voltage CV. It can also be applied to a cathode ray tube adapted to do so. In FIGS. 9A and 9B, parts corresponding to those in FIG. 10 are denoted by the same reference numerals and redundant description is omitted, but (41) indicates a dividing resistance plate, which is an insulating substrate (42) such as ceramics. A resistance path (43) is printed on one surface, and terminals t ₁ , t ₂ and t ₃ are formed at both ends of the resistance path (43) and a predetermined intermediate portion, respectively. Reference numeral (44) is a protective film that is applied as necessary. This Split Resistor Plate (41)
Is located on the side of the first grid G ₁ ~ fifth grid G _5, the terminal t ₂ is the terminal pins of the earth potential (11a), the terminal t ₁ is respectively connected to the fifth grid G ₅ of the anode voltage,
The intermediate terminal t ₃ is connected to the outer deflection electrode plates (3c), (3d) of the convergence means (3), which gives a convergence voltage.

〔The invention's effect〕

According to the conductive film forming method of the present invention described above, it is possible to easily form a uniform conductive film for suppressing the discharge current over the predetermined length D of the inner surface of the neck portion without uneven coating. Therefore, the discharge current due to the internal discharge of the cathode ray tube can be surely suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1A to 1D are process drawings showing an example of a conductive film forming method according to the present invention, and FIGS. 2A to 2C are processes showing another example of a conductive film forming method of the present invention. FIGS. 3 and 4 are sectional views of the main part of the cathode ray tube showing the coating range according to the method of the present invention, and FIGS. 4A, B and C are perspective views showing examples of the coating material impregnated body of the coating means applied to the present invention. FIG. 5 is a cross-sectional view showing the state of the paint impregnated body and the inner surface of the neck portion at the time of coating in the present invention, FIG. 6 is a cross-sectional view of the internal conductive film formed by coating by the method of the present invention, FIG. B is a sectional view comparing the states of the conductive films formed by the conventional method and the method of the present invention, and FIG. 8 is a discharge current and its control when the conductive films formed by the conventional method and the present invention are used. FIG. 9A is a sectional view of a main part of a cathode ray tube to which the method of the present invention is applied, and FIG. FIG. 10 is a plan view of a resistance plate, FIG. 10 is a cross-sectional view of a cathode ray tube used for explaining the present invention, and FIGS. 11A to 11D are process diagrams of a conventional conductive film forming method.
12 and 13 are cross-sectional views for explaining coating unevenness of the conductive film, and FIGS. 14 and 15 are cross-sectional views for explaining fine grooves of the conductive film, respectively. (1) is an electron gun, (2) is a tube, (2a) is a neck part, (2b) is a funnel part, (4) is an internal conductive film, (4a) is a conductive film for suppressing discharge current, (31 ) Is a coating means, and (32) is a paint impregnated body (for example, sponge).

Claims (1)

[Claims] 1. A conductive film for suppressing a discharge current is formed on the inner surface of the neck by rotating a coating means having a length corresponding to a predetermined length of the neck of the tubular body without moving in the tube axis direction. And a method of forming a conductive film of a cathode ray tube.