JPS59173247A - Cathode ray tube - Google Patents

Abstract

PURPOSE:To simplify the structure of a cathode ray tube and to attain to stabilize image quality by enhancing the attachment preciseness of a shadow mask, by using a thin plate comprising a permanent elastic alloy as the shadow mask. CONSTITUTION:A shadow mask 11 comprising a thin plate made of a permanent elastic alloy is fixed while receiving tension force in the longitudinal direction thereof. By this method, the structure of a cathode ray tube 10 becomes simple and the shadow mask 11 is attached with high accuracy. In addition, the shadow mask becomes perfectly flat and generates no dimensional variation caused by temp. change and imparts stable image quality.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to a cathode ray tube using a mask.

[Technical background of the invention and its problems]

Conventionally, a so-called shadow mask tube using a shadow mask has been widely used as a cathode ray tube. As is well known, a shadow mask tube is constructed by providing a shadow mask having a large number of electron beam passage holes between three electron guns and a three-color phosphor surface. This shadow mask has the function of shaping an electron beam emitted from an electron gun and aiming at a specific electron beam passage hole, and projecting the beam onto a three-color fluorescent surface with an accurate beam pattern.

By the way, about 80 inches of the electron beam is absorbed by the shadow mask. As a result, the surface temperature of the shadow mask during operation may reach 80 to 90°C.

For this reason, there is a problem in that the shadow mask thermally expands, causing a shift in the relative positional relationship between the electron beam passage hole and the three-color fluorescent surface, resulting in a decrease in color purity. Conventionally, this problem has been dealt with by using bimetal to support the shadow mask. That is, FIG. 1 and FIG. 2(a),
As shown in (b), the shadow mask tube has a structure in which a shadow mask 1 is supported via a mounting plate 2 by a bimetal 3 whose central portion is bent. The bimetal 3 is fixed to a plate 5 fixed to the inner side wall of the tube 4. With this configuration, when the temperature is high, as shown in FIG. 2(b), the plate spring 5 is pressed by the thermal expansion of the shadow mask 1, and the bent portion of the bimetal 3 is extended, so that the shadow Mask 1 moves in the normal direction.

This movement is in the direction in which each electron beam passage hole 6 formed in the shadow mask 1 moves in the electron beam traveling direction. Therefore, image quality deterioration due to an increase in the temperature of the shadow mask 1 does not occur.

However, a cathode ray tube having such a structure is not only complicated in structure, but also requires a considerable amount of man-hours for forming the curved surface of the shadow mask, mounting it, etc. Moreover, it has been difficult to ensure high accuracy in the mounting position.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a cathode ray tube which has an extremely simple structure, can easily ensure high mounting accuracy of a shadow mask, and can always obtain good image quality.

[Summary of the invention]

The present invention is characterized in that the shadow mask is held such that a constant stress is applied to the shadow mask made of a thin plate of a constant modulus alloy at room temperature (20° C.).

In other words, even if a material with an extremely low coefficient of linear expansion is selected for the shadow mask material, there is a limit to suppressing dimensional fluctuations due to thermal expansion to zero as long as the operating conditions have a wide temperature range. be. Therefore, in the present invention, the dimensional variation due to the thermal expansion is completely canceled out by the strain variation due to the variation in stress acting on the material. This suppresses dimensional fluctuations due to temperature to almost zero.

In other words, now consider that stress σ is acting uniformly in the longitudinal direction of the shadow mask plate.

When 20° C. is the standard, the longitudinal dimension variation ε of the shadow mask at the temperature T can be expressed as follows. Here, Δt is the amount of dimensional variation, t is the longitudinal length of the shadow mask, α is the linear expansion coefficient at temperature T of the shadow mask material, and To=
20° C., E is the elastic modulus at temperature T. Tsumashi,
The first term on the right side of equation (1) is the dimensional variation due to thermal expansion,
The second term is the strain due to stress σ. wife,! p, (
In order to keep ε constant in equation x), the first term on the right side, which is an increase in dimension due to a temperature increase, should be equal to the second term, which is a decrease in strain due to a decrease in stress. However, in general iron and alloys, both α and E have temperature dependence, so for all temperatures within a certain temperature range, ε
It was impossible to keep constant. Therefore, in the present invention, we focused on a constant modulus alloy. The constant modulus alloys mainly include the Fe-Ni Erimba type alloys shown in Tables 1 and 2.
It is shown in Table 3. It is a general term for Co-Fe-based Erimba type alloys and the like. This constant-modulus alloy has two major features: (1) the rate of change in the coefficient of thermal expansion with temperature is small; and (2) the rate of change in the coefficient of elasticity with temperature is almost zero. Therefore, if equation (1) is considered only for constant modulus alloys, the first term on the right side of equation (1), which is the increase in size due to the temperature increase, and the second term, which is the decrease in strain due to the decrease in stress, are both linear changes.

In other words, if the above increases and decreases are made the same (
1) ε in the equation is constant. Therefore, if the normal operating temperature of the shadow mask is 20 to 90°C, the dimensional variation ε1 in the first term on the right side of equation (1) is εT (T=20')=
O... River... River... River (2) εT (T=9
0°)=70α ・・・・・・・・・・・・・・・
...(3). Therefore, the amount of distortion ε1 in the second term on the right side of equation (1) is also ε, (T=20°)=70α...
・・・・・・・・・(4)εP(T=90°)=0
・・・・・・・・・・・・・・・・・・(5)

Thus, the stress σ at T=20°C.

is σo=70α・E・・・・・・・・・
・・・・・・・・・(6)

In other words, it is good to apply tension in the longitudinal direction of the shadow mask so that the dimensional variation due to thermal expansion considered at normal operating temperatures is given as distortion at the lowest temperature.

〔Effect of the invention〕

According to the present invention, the glossy mask is fixed by an extremely simple method of applying tension in the longitudinal direction of the shadow mask. Therefore, the structure of the cathode ray tube becomes simple.

Furthermore, in connection with this, high mounting accuracy of the shadow mask can be ensured. Furthermore, since the shadow mask can be made completely flat, it is possible to provide the entire flat cathode hi tube. On the other hand, since there is almost no dimensional variation due to temperature changes in the shadow mass, it is possible to provide a cathode ray tube with stable image quality.

[Embodiments of the invention]

The present invention will be explained in detail below. In this example, the present invention was applied to a 14-inch color television picture tube using a shadow mask made of super elinvar listed in Table 1.

In the case of Super Nirimper, the thermal expansion coefficient α-7,5X10-6
It is. Now, the longitudinal length of the shadow mask 4 = 300
mm, the dimensional variation Δt due to thermal expansion between T = 20-'90°C is based on equation (3), where Δ is near 0.
α・l20.158C]. Therefore, after attaching a shadow mask to the tube, at 20℃, 0.158
Tension is applied to the shadow mask so that a strain of m+n occurs. Such an installation is possible as the structure of a color television picture tube, for example, as shown in FIGS. 3 to 5.
The one shown in the figure can be considered. In Figures 3 to 5,
The color television picture tube 10 has a structure in which both short sides of a shadow mask 11 are supported by support means 12. The support means 12 includes a mounting base 14 fixed to the inner side wall of the tube 13 at three locations at the top, middle and bottom, and the shadow mask 1.
1, and a bolt 16 that connects both the mounting base 14 and the support frame 15.

The support frame 15 has a shape in which a single slit is provided in the longitudinal direction of a tubular body having a rectangular cross section. The shadow mask 11 is supported by the support frame 15 by housing both short sides thereof, which are press-molded into a hook shape, inside the tube through the slits in the support frame 15.

In the color television picture tube configured in this way, the amount of distortion described above can be applied to the shadow mask 11 by appropriately adjusting the degree of tightening of the bolts 16.

By the way, the stress σO that acts on the Nyadou mask due to the aforementioned 0.158+++m strain is σo from equation (4).
= 70 α・E =70X7.5X10X18000=9.45[
Yu/m]. This is the maximum valley stress of the class Elinvar, 127
Since the value is sufficiently lower than kg/wn2, plastic deformation will not occur.

According to this embodiment described above, there is no change in dimension in the longitudinal direction due to temperature rise of the shadow mask. Therefore, it is possible to fully exhibit the effects described above. Needless to say, this can be similarly applied to other cathode ray tubes.

Note that in this embodiment, a description of the dimensional variation in the vertical direction of the shadow mask is omitted, but if the idea of the present invention is developed, it is possible to similarly suppress the dimensional variation in the four directions of the top, bottom, left, and right.

Furthermore, the shadow mask support means 12 described above is not particularly limited to this type. That is, various modifications can be considered as long as the structure allows the shadow mask to be fixed and attached at a constant length.

knee

[Brief explanation of drawings]

Figure 1 is a schematic cross-sectional view showing the structure of a conventional cathode ray tube.
FIG. 2(a) is a detailed cross-sectional view of part A when the shadow mask in FIG. 1 is at a low temperature, FIG. 2(b) is a cross-sectional view when the shadow mask is at a high temperature, and FIG. A partially cutaway perspective view of a color television picture tube according to an embodiment, FIG. 4 is a schematic sectional view of the same as seen from direction B in FIG. 3, and FIG. 5 shows a detailed view of part 0 in FIG. 4. FIG. 1.11...Shadow mask, 2...Mounting plate, 3.
...bimetal, 4.13...pipe, 5...plate spring,
6...Electron beam passing hole, No.0...Color television picture tube, 12...Supporting means, 14...Mounting base, 15.
...Support frame, 16...bolts.

Claims (1)

[Claims] A cathode ray tube characterized by using a constant elastic alloy as a shadow mask.