JPS6240346Y2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field of the Invention The present invention relates to a color picture tube, and particularly to the structure of its shadow mask.

Technical background and problems of the invention Shadow mask type color picture tubes are generally used. That is, an electron gun that emits a plurality of electron beams, for example, three, is disposed within the neck portion at one end of the envelope, and an electron gun corresponding to the electron beam is provided on the inner surface of the panel portion at the other end of the envelope via the funnel portion. A phosphor screen made of a large number of phosphor groups that emit red, green, and blue light is provided, and a shadow mask having a large number of apertures is disposed close to and opposite to this phosphor screen. In a color picture tube with such a structure, the three electron beams are concentrated on one of the many holes in the shadow mask, are dispersed again, and are emitted correctly onto the corresponding phosphors on the phosphor screen to produce a color image. It is being reproduced. FIG. 1 shows the vicinity of the shadow mask of such a color picture tube, in which a main body of the shadow mask 2 is disposed close to and opposite to the inner surface of a panel 1 having a phosphor screen (not shown), and the skirt of the shadow mask 2 A part of the portion 2-2a is supported and fixed to the mask frame 3a by welding or the like, and the mask frame 3a is formed with an L-shaped cross section to ensure its mechanical strength, and is attached to the panel via a support holder (not shown). Locked to the side wall.

By the way, the aperture ratio of Shadow Mask 2 is approximately
Since it is less than 30%, thermal expansion occurs due to the impact of electron beams during operation. However, the effective part 2-1a is provided with a large number of holes, and the skirt part 2-2 is bent and extends in the peripheral direction of the effective part.
Since the mechanical strength is different from that of the effective part 2-1a, the effective part 2-1a is deformed into a dome shape in the direction of the tube axis Z, that is, in the direction of the arrow A, as indicated by the dotted line 2-1b due to thermal expansion. Therefore, the electron beam does not strike a predetermined phosphor, resulting in so-called mislanding. That is,
The beam spot of the electron beam 4 passing through the aperture near the center of the effective part 2-1a shifts from 6a to 6b, resulting in mislanding. Similarly, the beam spot of the electron beam 5 passing through the aperture near the effective portion also causes mislanding from 7a to 7b. However, this value is smaller near the center of the effective area. Therefore, since the amount of mislanding differs between the center and the periphery of the effective part of the shadow mask, adjustments using deflection coils, magnets, etc. must be made as a compromise between the two, and since there is no margin for mislanding, the color purity of the screen may be affected. deteriorates easily.

In order to solve these drawbacks, for example, Jitsukaiaki
48-76857 proposes reducing the strength of the skirt portion 2-2a as shown in FIG. According to this proposal, the shadow mask 2 due to thermal expansion has a skirt portion 2 as shown by the dotted line 2-1c.
-2c also falls in the outer X-axis direction, that is, in the direction of arrow B. That is, the thermal expansion of the effective part 2-1c is released to the skirt part 2-2c to reduce the displacement from 2-1a to 2-1c near the center of the effective part, thereby preventing mislanding.
That is, the deviations 6a to 6c of the beam spots are smaller than those in FIG. 1. However, if the strength of the skirt part is simply reduced, the direction of displacement near the effective part will be different from that in Fig. 1, and will be in the direction of falling toward the skirt part 2-2c, so mislanding will also occur in the same direction as the beam spot. It shifts from 7a to 7c, and this value is a value that imposes a considerable sacrifice because of the emphasis on mislanding near the center of the effective area. In addition, the mislandings near the center and the periphery are in opposite directions, and in the end the mislanding between the center and the periphery of the screen is just a compromise, just like the one in FIG. 1, which is adjusted at a compromise.

Therefore, Japanese Patent Application Laid-Open No. 48-12935 and Utility Model Application No.
48-76857 proposes what is shown in FIG. 3. That is, the effective part 11 and the skirt part 13 are connected to form an angle ψ, and the value of the angle ψ is ψ=tan ^-1 (E-F/E・tanθ) where θ is the deflection angle of the electron beam E : Thermal expansion coefficient of the shadow mask F: Thermal expansion coefficient of the mask frame (E>
F) in order to make the direction of thermal deformation around the effective part coincide with the direction of electron beam irradiation. When this function is actually calculated, it is approximately ψ≒θ, which is about 40 to 45 degrees for a 90-degree deflection tube and about 50 to 55 degrees for a 110-degree deflection tube. However, in such a structure, the effective part 1
1. Since the entire shadow mask consisting of the part 12 having an angle ψ around the effective part and the skirt part 13 is made of the same plate thickness, no matter what condition the angle ψ is set, the thermal expansion of the effective part will be the same as before. Therefore, the skirt portion still falls in the direction of arrow B in FIG. That is, it is not possible to expect an effect of matching the direction of thermal deformation around the effective part with the direction of electron beam irradiation, and there is no difference from the conventional method simply by changing the shape of the shadow mask. This means that even if grooves are provided at the connection points of the effective portion 11, the angle ψ portion 12, and the skirt portion 13, the direction in which the skirt portion falls is the same. That is, the strength of the portion 12 having the angle ψ is the same as the strength of the skirt portion 13, and stress acts on the tip portion relative to the length of the skirt portion 13, and the portion 12 having the angle ψ moves in the direction of arrow B in FIG. This is extremely insufficient as a solution to thermal expansion displacement.

Purpose of the invention The present invention has been made in view of the above points, and its purpose is to prevent mislanding due to thermal expansion of the shadow mask.

Summary of the invention This invention connects the effective part and skirt part of a shadow mask via an intermediate connection part, makes the strength of the intermediate connection sufficiently weaker than that of the effective part and the skirt part, and
The angle γ of the intermediate connection with respect to the plane orthogonal to the tube axis is greater than the angle α of the connection of the shadow mask surface with respect to the plane orthogonal to the tube axis, and the angle β of the orthogonal line with the electron beam irradiation angle with respect to the plane orthogonal to the tube axis. By making the size smaller, the direction of thermal displacement of the effective portion is made to coincide with the direction of electron beam irradiation, thereby preventing mislanding and preventing deterioration of color purity.

Embodiment of the invention Hereinafter, one embodiment of the invention will be described in detail with reference to FIGS. 4 to 6. The present invention is the same as a conventional color picture tube except for the shadow mask, so a description of the structure will be omitted and only the essential parts will be explained.

FIG. 4 shows the main parts of the shadow mask applied to the present invention, and the arrangement and assembly method of the shadow mask 8 body and mask frame 3a are the same as those in FIG. 1. In Figure 4, shadow mask 8
is an intermediate connecting portion 8-3 that connects the skirt portion 8-2a and the periphery of the effective portion 8-1a having a large number of openings;
a, the intermediate connecting portion 8-3a has a predetermined angle γ with respect to the tube axis Z direction, and its mechanical strength is sufficiently smaller than that of the effective portion 8-1a and the skirt portion 8-2a. It is formed.

The direction of displacement and effect of the shadow mask shown in FIG. 4 due to thermal processes will be explained with reference to FIG. 5.

Regarding mislanding, if the thermal displacement direction of the effective part of the shadow mask is made to match the electron beam irradiation direction of each part of the effective part as much as possible, mislanding will be reduced. direction arrow B
It is sufficient to approximate the elongation in the direction of arrow D in FIG. 3, that is, in the irradiation direction of the electron beam 5. As a result, the effect near the center of the effective part in Fig. 2 is maintained, and the displacement near the periphery of the effective part approximates the electron beam irradiation direction, so that the displacement of the shadow mask, that is, 8
- Displacement of central electron beam spot due to 1a to 8-1b and 8-3a to 8-3b 9a to 9
Mislanding-N due to b causes the surrounding electron beam spot 10a to maintain the effect shown in Fig. 2.
Most of the mislandings will be eliminated. When this is applied to a 20-inch, 110-degree deflection tube, the equation of the tangent to the shadow mask curvature Rm at a certain distance r from the center c of the shadow mask is: (x-x ¹ ) (x ₂ −x ₁ ) +(z−z ¹ )(z ₂ −z ₁ )=Rm ² …(1), and the angle α is α=tan ⁻¹ x ₂ −x ₁ /z ₂ −z ₁ ...(2). Roughly calculating this using actual values, at deflection angle θ = 55 degrees, r = 240 mm, Rm = 900R,
From equation (2), α≒12.8 degrees.

Here, the intermediate connection part of the shadow mask shown in FIG. 4 is made thinner than the effective part 8-1a and the skirt part 8-2a, for example, as shown in FIG. Effective mechanical strength part 8
-1a and the skirt portion 8-2a.

With such a configuration, if the value of the angle γ of the intermediate connection portion is larger than the angle α of the tangent at that position, a stress in the direction of arrow D will be applied rather than a stress that would tilt the skirt portion. The maximum directional limit of the value of this angle γ can be considered as the angle until the maximum stress in the direction of arrow D is generated; if the angle is too large, the stress in the D direction becomes small and the thermal expansion of the effective part becomes a shadow mask. It only extends towards the periphery. Therefore, if this angle is perpendicular to the electron beam irradiation direction, that is, if it is smaller than the angle β formed by the -' line, the stress in the direction of arrow D will be generated to the maximum. Here, the angle β formed by the -' line is β = 90 - θ, and the angle γ formed by the intermediate connection is α < γ < β = 90 - θ (3). good.

If we calculate equation (3) using the same approximate numerical values, we get 12.8 degrees < γ < 35 degrees is obtained.

The point to note here is that the collapse strength of the intermediate connection part in the direction around the effective part must be sufficiently smaller than that of the skirt part, and the purpose can be achieved by satisfying the following configuration and strength relationships. be done.

Although FIG. 6 shows an example in which the plate thickness of the intermediate connection part is reduced, the present invention is not limited to this, and may be applied to other structures as long as the strength of the intermediate connection part is weakened, for example, by changing the material. Needless to say, it's a good thing.

Effects of the Device As described above, according to the present invention, mislanding can be effectively suppressed throughout the center and peripheral areas of the shadow mask, and by giving a predetermined angle to the intermediate connection part, the inner wall of the shadow mask can be effectively suppressed. Since the incident electron beam can be scattered outside the effective area, deterioration of color purity can be prevented.

[Brief explanation of the drawing]

1 to 3 are schematic diagrams for explaining the structure and operation of the conventional color picture tube in the vicinity of the shadow mask, and FIGS. 4 to 6 are schematic diagrams for explaining the structure and operation of the color picture tube of the present invention in the vicinity of the shadow mask. It is a schematic diagram for explanation. 3a...Mask frame, 4, 5...Electron beam, 8...Shadow mask, 8-1a...Effective part, 8-2a...Skirt part, 8-3a...Intermediate connection part.

Claims (1)

[Claims for Utility Model Registration] An electron gun disposed within a neck portion at one end of the envelope, and an electron gun disposed on the inner surface of a panel portion at the other end of the envelope from the neck portion through a funnel portion. In a color picture tube that includes a phosphor screen and a shadow mask that is disposed close to and opposite to the phosphor screen and has a large number of apertures, the shadow mask has an effective part that has a large number of apertures, and a periphery of the effective part. It consists of an intermediate connecting part extending in the direction and a skirt part extending from the intermediate connecting part, the strength of the intermediate connecting part is weaker than the effective part and the skirt part, and the intermediate connecting part is perpendicular to the pipe axis. The angle γ with respect to the plane is between the angle α with respect to the plane where the connection of the shadow mask plane is perpendicular to the tube axis and the angle β with respect to the plane with which the orthogonal line of the electron beam irradiation angle is perpendicular to the tube axis, such that α<γ<β. A color picture tube characterized by satisfying relationships.