JPS6323615B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a projection cathode ray tube constituting an enlarged projection type television image projection image source.
In particular, we aim to improve the performance of the cathode ray tube itself by improving its optical precision, to reduce manufacturing processes and parts by rationally simplifying the structure, and to prevent leakage from outside air, shortening its life and deteriorating its performance. The purpose of this is to comprehensively reduce the need for adjustment and reduce the cost of TV projection equipment by preventing such problems. A typical conventional example of this type of projection cathode ray tube is disclosed in Japanese Patent Application Laid-open No. 52232/1983. In such a conventional example, before sealing the vacuum container, the target and the concave mirror are each placed at the center of the electron beam or the latter at the optical center of the image to be imaged on the target surface with a high degree of precision. Not only must the anode lead be supported and fixed with a container, but it is also essential to improve optical accuracy by suspending the anode lead inside the container, and it is also necessary to eliminate the need for adjustment of the device after completion.
This had become a bottleneck in reducing processes and parts. As one such improvement, a structure in which a metal such as aluminum is vapor-deposited on the inner surface of the funnel portion, which has a curvature similar to that of a concave mirror, and the vapor-deposited surface is made into a Schmitt mirror (i.e., equivalent to the aforementioned concave mirror) has already been proposed. This was proposed by the same applicant as the present case (Japanese Patent Application Laid-open No. 53-21523). However, even in such a case, the optical accuracy is largely dependent on the accuracy with which the target surface is fixed in the vacuum container, and it cannot be said that the optical accuracy has been sufficiently improved. In view of this, the face plate 20 with the target surface 21 formed on the central metal deposition surface is made of convex glass of equal thickness, as shown in FIG. 1 and FIG. 2, respectively. The open end surface 25 of the cylindrical body 24 following the funnel portion 23 is arranged so that the center of curvature coincides with the center of curvature O of the inner surface 22 of the funnel portion 22 to form a so-called spherical seat. , 25 are ground and polished so that they have the same curvature as the face plate 20, and the face plate 20 is held in contact with the open end surface in its normal direction, and then sealed with welded glass or the like. can also be considered. With such a configuration, even if the face plate 20 is slightly shifted and comes into contact with the open end surface of the cylindrical body 24, the concave mirror 22 formed by the face plate 20, the target surface, and the inner surface of the funnel will still be able to hold the spherical seat. Since both centers of curvature are still at point O, the accuracy of the optical system is not affected. A lead wire 27 connects the anode 28 and the anode terminal 29 and is suspended in the vacuum container with some margin. However, in such an example, variations in the thickness of the fused glass, that is, the thickness of the bonding layer between the face plate and the open end surface, affect optical accuracy and cause a decrease in manufacturing yield. Even when welding the part 23 or sealing between the funnel part 23 and the cylindrical body, it is essential to pay close attention to the welding thickness, which not only becomes a bottleneck in process-saving, but also a second problem. As shown in the figure, since the external pressure is applied in the normal direction of the face plate 20, the resultant force P' of the atmospheric pressure W and the compressive stress P of the cylindrical body 24 acts as a shearing force on the welded part F of the flint glass. , shear strength of fused glass (320Kg/cm ² )
Coupled with the fact that the compressive strength is only about 1/4 of the compressive strength (1270Kg/cm ² ), this causes cracks to occur in the welded part, leading to vacuum leaks in the cathode ray tube, and therefore shortening the life of the tube. In extreme cases, it can cause implosion. The present invention has been made in view of the drawbacks of the conventional example. The details of the projection cathode ray tube of the present invention will be explained below with reference to FIGS. 3 to 6 showing one embodiment. The main components of the present invention are a rigid metal casing 30 formed by integrally molding or sealing a funnel portion and a cylindrical body, a hollow spherical face plate 40 having an equal thickness, and a central portion of the face plate. A target block 50 provided in the section, and a sealing means 6 for the face plate 40 and the cylindrical body 34 are provided.
0, the neck tube 70 , and the rigid metal casing 30 are provided with a stem 80 that performs fixed sealing with high precision. The funnel portion 31 forming the rigid metal casing 30 is formed into a magnifying reflecting mirror 32 by giving the inner surface a concave reflective shape and polishing it to a mirror surface, or by vapor depositing Cr or Al. The cylindrical body 34 following the funnel portion doubles as an anode lead as will be described later, and is configured to supply high pressure from an appropriate location, so a high pressure supply lead wire (not shown) covering the anode cap is wired with wax Except for the parts to be covered, insulating coating is made of a material with good insulation resistance such as tetrafluoroethylene (Teflon), silicone rubber, or 1-2 polybutadiene. The face plate 40 is made of lead glass or soda glass, and has a hollow spherical shape (inner diameter r,
However, the center is placed on the deflection center of the electron beam, that is, on the tube axis of the network tube 70. ), and its center is placed at X-X' (on the tube axis). Particularly with reference to FIGS. 3 and 5, the target block 50 is a convex lens-shaped block made of sealing metal, Al, etc., and has a radius R1 centered on the X-X' axis. A target forming surface (anode electrode) is formed on the spherical surface of the target, and a target surface 51 coated with a hardly saturable fluorescent material is formed thereon. Three or more fixed-sized protrusions 53 , 54 are arranged radially at equiangular intervals and equidistant positions from the center of the lower surface 52 of the target block 50, and the protrusions are brought into direct contact with the face plate surface. While avoiding variations due to molten glass when bonding the plate with flint glass or the like, one of the protrusions 54 is directly conductively connected to the lead end 42 formed of the metal layer 41 deposited on the inner surface of the face plate. (See Figure 5) The above-mentioned rigid metal housing 30 and face plate 40
It is necessary that the temperature coefficients are substantially the same, and that even if it expands due to the ambient temperature and the temperature generated from the inside, it does not particularly affect the sealed portion. The face plate 40 and the rigid metal casing 30
The sealing means for sealing and fixing the flange ring has a cross section as shown in FIG.
It is divided into a ring 630 which is welded to two. As shown in FIG. 5B, the flange ring 610 is formed by an annular portion 611 that welds the flange ring to the rigid metal casing and is bent outward from the annular portion into a U-shape. It is composed of a bulging portion 612 and a flexible elastic piece 613 extending from a U-shaped lower wing tip. The upper part of the elastic piece is spaced a little from the ends 33, 33 of the cylindrical body 34 (△
l) and is fixed to absorb or avoid thermal expansion and contraction due to self-heating of the cathode ray tube or ambient temperature during operation. Furthermore, at least three protrusions 614, 614, . That is, the face plate 40 and the protrusions 614, 614, . . . directly contact each other without intervening the welded glass, and serve for positioning. Said ring belt 63
0, three or more inward protrusions 631, 631 are provided at equal angular intervals by a method such as press molding, and the position of the face plate 40 in the width (or surface) direction is determined, and the face plate 40 is fixed at that position. The plate 40 is configured to be sealed to the cylindrical body 34 . When welding the above-mentioned sealing means 60 and flint glass 40 , the former is subjected to an oxide film treatment in a wet hydrogen furnace in advance to facilitate sealing and increase reliability. In addition, the projections 614, 614, . . . can be polished in advance with a spherical seat centered at point O' before sealing, so that the precision between the projections and the face plate 40 can be increased. With such a configuration, the atmospheric pressure W is applied to the cylindrical body 34
Balance is maintained between the stress P of the face plate 40 and the component force P' in the tangential direction of the face plate 40 .
The component force of the atmospheric pressure W at the center of 0 becomes the component force P'' that tries to flatten the face plate 40 ,
At the point of action of each force, it cancels out with P′. Therefore,
The shear force acting on fused glass (fritted glass), which has a shear strength that is much weaker than its compressive strength, can be greatly reduced, preventing the occurrence of cracks, etc., and reducing tube life deterioration and explosions due to vacuum leaks. Avoid shrinkage etc. In order to improve the connection accuracy between the neck tube 70 and the funnel portion 31 of the rigid metal housing 30 , the stem 80
Use. This stem 80 has Cr: 42% by weight,
A rigid metal body made of a so-called 42-6 alloy containing Ni: 6% by weight and Fe (remainder) can be used, and basically the bottom outer surface 81 is formed to have the same curvature as the outer surface of the funnel 31. It has a double cylindrical shape at the bottom, and on the inner surface of the cylindrical part 82 of one of the two inner and outer cylindrical parts 82 and 83 (the inner one in the embodiment), at least three places are arranged at equal intervals (120° intervals). It has a structure in which protrusions 84 and 85 for positioning the neck tube 70 are integrally provided. If welded or brazed in a fixed state as shown in FIG . Accurately cut network tube 7
The inner diameter end 71 of the open end of the stem 80 is connected to the bottom 81 of the stem 80.
The neck tube 70 can be fixed to the funnel portion 31 with a predetermined accuracy by holding the neck tube 70 in contact with the funnel portion 31 and oxidizing it in a wet hydrogen furnace and then fixing it with a sealing glass such as frit glass. In addition, instead of forming the target block with a sealing metal or Al, such a metal is vapor-deposited on glass that is integrally molded with the face plate.
A target surface may be formed thereon. Since the present invention has the above-described configuration, it not only simplifies the structure of the projection cathode ray tube, but also
Since the shearing force acting between the cylindrical body and the face plate can be greatly reduced, reliability can be expected to be greatly improved.

[Brief explanation of the drawing]

Figures 1 and 2 show conventional examples.
The figure is a longitudinal sectional view, and FIG. 2 is a longitudinal sectional view of the main part. 3 to 6 relate to the projection cathode ray tube of the present invention, FIG. 3 is an exploded view of a main part, FIG. 4 is an exploded perspective view, FIG. 5A is a vertical sectional view of a main part, and FIG. FIG. 6 is an enlarged side view of the main part and a partially cutaway perspective view. 30 ...Rigid metal housing, 31...Funnel portion, 34...Cylindrical body, 40...Face plate, 50 ...Target block, 51...Target surface.

Claims (1)

[Claims] 1. A neck tube is joined to the outer surface of the funnel portion of a rigid metal body in which a funnel portion having a magnifying reflection mirror formed on the inner surface and a cylindrical portion are integrally provided, and an outer A face plate made of convex glass of equal thickness and having a center of curvature that coincides with the center of curvature of the reflecting mirror is placed at the center of the inner surface facing the reflecting mirror, is sealed by a sealing means. A vacuum container is formed by the neck tube, the rigid metal body, and the face plate, the temperature coefficients of the rigid metal body and the face plate are made substantially the same, and the sealing means is provided with at least one part that abuts the inner surface of the face plate. It consists of a metal collar ring having a flexible elastic piece having three protrusions and a metal ring band having at least three protrusions that abuts the peripheral end surface of the face plate, and the flexible elastic piece has a cylindrical shape. A cathode ray tube for projection, which is arranged at a certain distance from the open end of the tube.