JP2680021B2 - Shadow mask type color cathode ray tube - Google Patents

Description

The present invention relates to a shadow mask type color cathode ray tube,
In particular, it relates to an aspherical panel for reducing doming.

[Conventional technology]

As shown in FIG. 3, the shear mask type color picture tube has a glass envelope 4 including a rectangular panel 1, a tubular neck portion 2 and a funnel portion 3 connecting the two.
The panel 1 includes a face plate 1a for display and an outer peripheral flange or side wall 1b sealed to the funnel portion 3 with a low melting point glass 5. A three-color phosphor screen 6 is formed inside the face plate 1a.

A shadow mask 7 is attached to the inside of the panel 1 at a predetermined distance from the screen 6, and an electron gun 8 is attached to the inside of the neck portion 2.
Are arranged and arranged in an in-line type or a delta type, and the three electron beams 9 generated therefrom are guided to the screen 6 through the shadow mask 7. An external magnetic deflection yoke 10 is provided on the outer side in the vicinity of the joint between the neck portion 2 and the funnel portion 3. Using this yoke 10, horizontal and vertical magnetic fluxes are applied to the three beams 9 to make them horizontal. Direction, that is, the long axis XX, and vertical direction, that is, the short axis YY
By scanning in the direction, a rectangular raster is formed on the screen 6.

By the way, conventionally, the surface shape of the panel 1 is usually spherical or cylindrical. In order to make this closer to a planar shape, while maintaining the strength of the envelope 4, in the case of a shadow mask type color picture tube, a local color shift occurs due to thermal expansion of the shadow mask 7 due to the impact of the electron beam 9. The doming phenomenon becomes a problem. This doming phenomenon occurs when a certain part of the shadow mask becomes hotter than the other parts, a spherical phenomenon occurs, and as the hole position of the shadow mask moves, the relative position of the electron beam and the phosphor changes, resulting in local color shift. Is what is observed.

This doming phenomenon will be described in more detail. When a spherical panel is used, the inner surface shape of the panel is also substantially spherical, and the curved shape of the sheer mask attached inside is also substantially spherical along the inner surface shape of the panel. As the surface shape of the panel becomes closer to a flat surface, the curved surface shape of the shear mask also becomes closer to a flat surface, and the deviation between the normal direction and the electron beam direction becomes large. That is, the angle of incidence of the electron beam on the shadow mask increases. As the temperature of the shadow mask rises due to the impact of the electron beam, the shadow mask expands thermally, and the hole position of the shadow mask moves almost in the normal direction, so that the electron beam passing through the same shadow mask hole position moves. The trajectory will change with the thermal expansion of the shadow mask and will be observed as a local color shift.

4 to 6 are explanatory views for explaining the doming phenomenon in an easy-to-understand manner. The amount of change in the relative position between the electron beam and the phosphor due to doming is calculated by the following equation.

Here, d is the amount of change in the hole position of the shed mask due to thermal expansion of the shed mask, α is the incident angle of the electron beam with respect to the shed mask, and p _r and q _r are the deflection centers of the beam trajectories and the distance between the shed mask and the shed mask's fluorescent surface, respectively. Represents

When the curved surface shape of the shadow mask is a single spherical surface and the radius of curvature is R, the above α is calculated by the following equation.

Here, Po represents the distance between the deflection center of the beam trajectory on the tube axis and the shadow mask.

Taking a 21-inch 90 ° color picture tube as an example, in a conventional color picture tube, R is about 840 mm, and Po and Pr are Po28, respectively.
It is 1.5mm, Pr306.7mm (point 150mm from the center on the long axis), and becomes α {18.8}.

If this is flattened and the radius of curvature R is doubled to 1680 mm, then Po = 281.5 mm and Pr = 313.1 mm, so α = 23.5 °.

Therefore, when the panel is flattened (doubled in the radius of curvature), the doming amount is calculated to be about 1.3 times, according to the equation (1). This is a value obtained by assuming that the amount of change in the hole position of the shadow mask is constant. According to the results of computer analysis by the finite element method, when the radius of curvature is doubled, the doming amount is more than doubled. This is almost the same as the measurement data of the sphere.

As described above, in the shadow mask type color picture tube, there is a limit in flattening the surface shape of the panel due to the doming phenomenon. That is, it is effective to reduce the radius of curvature of the shear mask in order to improve the doming phenomenon, but this is in the opposite direction to the planarization of the panel.

Conventionally, the one disclosed in Japanese Patent Application Laid-Open No. 59-163738 has been known as one that achieves both flatness of the panel and improvement of the doming phenomenon. This makes the short axis a quadratic function,
Moreover, the curvature of the minor axis is made larger than the curvature of the major axis in the central portion.

[Problems to be solved by the invention]

In the above conventional example, there is an undesirable problem in the following points,
It is an obstacle to practical application. According to the curved surface design, reflection of external light on the panel surface becomes a problem. When the area where the second derivative of the curvature along the diagonal line is negative becomes large, the strength and thermal deformation of the shadow mask become problems. Since the shape of the boundary of the effective surface is related to the doming phenomenon, it is difficult to optimize the doming.

Therefore, as a solution to this problem, a component that changes quarticly to the inner and outer surface curvatures on the major axis of the panel is added, and the ratio of the secondary component at the effective surface edge on the major axis is set to 0.
A panel with a range of 3 to 0.6 is being applied for as a patent application No. 62-63796.

As a result, it was possible to make the panel look flat and to reduce local color shift due to the doming phenomenon.

As a result of conducting a trial experiment on such a panel, when a quaternary component is added to the panel curvature, there occurs a problem that the reflection (reflection image) on the outer surface of the panel is quarticly distorted.

An object of the present invention is to reduce the distortion of a reflected image in a panel that adds a quaternary component to the panel curvature.

[Means for solving the problem]

The above-mentioned object is achieved by forming the effective surface on the major axis so that the proportion of the secondary component is larger on the outer surface than on the inner surface.

[Action]

When there are many secondary components, on the contrary, there are few quaternary components. When the quaternary component is reduced, the distortion of the reflected image is reduced. By the way, in the reflection image of the panel, the method of the outer surface reflection is more conspicuous than the method of the inner surface reflection. Therefore, by making the quaternary component added to the outer surface curvature smaller than the quaternary component added to the inner surface curvature, the distortion of the reflected image is reduced.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. Considering the rotational symmetry, the curvature shape of panel 1
When approximated by the combination of the quadratic equation and the quadratic equation, the panel curvature Z
Is represented by the following equation.

Z = A ₁ X ² ＋ A ₂ X ⁴ ＋ A ₃ Y ² ＋ A ₄ Y ⁴ ＋ A ₅ X ² Y ² ＋ A ₆ X ⁴ Y ² ＋ A ₇ X ² Y ⁴ ＋ A ₈ X ⁴ Y ⁴ That is, long axis (X axis) The curved surface shape Z _X is Y in the above equation
By setting = 0, the curved surface shape on the short axis (Y axis)
Z _Y is represented by the following equations by setting X = 0 in the above equation.

Z _X = A ₁ X ² + A ₂ X ⁴ Z _Y = A ₃ Y ² + A ₄ Y ⁴ Now, the X coordinate of the effective surface end on the major axis of the panel effective surface 1c shown in FIG. 2 is X ₁ , on the minor axis. If the Y coordinate of the effective surface edge is Y ₂ ,
The proportions P _X and P _Y of the secondary components in X ₁ and Y ₂ are expressed by the following equations.

Therefore, when the constants A ₁ and A ₂ satisfy 0.3 ≦ P _X ≦ 0.6, and the constant A satisfying 0.95 ≦ P _Y ≦ 1.0.
The optimum shape of the panel can be obtained at ₃ and A ₄ .

 The above is disclosed in Japanese Patent Application No. 62-63796.

As is clear from the above, P _X contains many quaternary components, and P _Y has almost no quaternary components. As described above, since P _X contains many quartic components, the most distortion of the reflected image appears on the long axis.

Therefore, as shown in FIG.
0.6 P _X of the inner surface curvature 11 of the effective surface of the P _X of the outer surface curvature 12 0.7
As a result, the distortion of the reflected image was reduced. this is,
Since the external reflection is more conspicuous in the reflection image of the panel than the internal reflection, the quaternary component added to the external curvature 12 is the internal curvature 11
It is mitigated by making it smaller than the quaternary component added to.

The above embodiment is merely an example, and the distortion of the reflected image can be reduced by forming the secondary component so that the proportion of the secondary component is larger on the outer surface than on the inner surface.

〔The invention's effect〕

According to the present invention, the distortion of the reflected image is reduced in the panel in which the fourth-order component is added to the panel curvature.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view on a panel long axis (X axis) showing an embodiment of the present invention, FIG. 2 is a front view of a panel effective surface when the panel is viewed from the front, and FIG. 3 is a shear mask type color CRT. A sectional view, FIG. 4 is an explanatory view for explaining the doming phenomenon,
FIG. 5 is an enlarged view of part A of FIG. 4, and FIG. 6 is an explanatory view on the screen surface of FIG. 1 ... panel, 11 ... inner surface curvature, 12 ... outer surface curvature.

Claims (2)

(57) [Claims] Claim: What is claimed is: 1. When the shape of the outer surface of the face plate panel is expressed by a three-dimensional space formula with the major axis being the X axis, the minor axis being the Y axis, and the tube axis being the Z axis, the major axis and the minor axis are Curvature shape of Z _X ,
Z _Y respectively ^{_{Z X = A 1 X 2 +}} A 2 X 4, Z Y = A 3 Y 2 + A 4 Y 4 ( however,
A ₁ , A ₂ , A ₃ , and A ₄ are constants, and the ratio of the secondary component at the X coordinate (X = X ₁ ) of the effective screen edge on the long axis is calculated.
P _X = A ₁ X ² / (A ₁ X ² + A ₂ X ⁴ ), P _Y = A ₃ Y ^{2 is the} ratio of the secondary component at the Y coordinate (Y = Y ₂ ) of the effective screen edge on the short axis.
If / (A ₃ Y ² + A ₄ Y ⁴ ), the ratio P _X of the secondary component at the effective screen edge on the major axis is the ratio P _X of the secondary component at the effective screen edge on the minor axis. Smaller than _Y ,
A shadow mask type color cathode ray tube characterized in that the P _X is formed to be larger on the outer surface than on the inner surface of the face plate panel. 2. The difference between the inner surface and the outer surface of the face plate panel in the ratio P _X of the secondary component at the effective screen edge on the long axis is 0.1 or more. The shadow mask type color cathode ray tube according to item 1.