JPS61185851A - Cathode-ray tube - Google Patents

Abstract

PURPOSE:To maintain the brightness ratio at the circumference and in the center at same level with that of clear glass even when a dark tint glass having low transmission factor is employed thus to fully satisfy the demand of uniform brightness, in a cathode-ray tube employing low transmission factor glass having different thickness in the center and at the circumference, by specifying the relation between the light absorption factor and the concentration of said panel and the relation between the light absorption factor and the concentration of a panel having higher transmission factor. CONSTITUTION:In a cathode-ray tube employing low transmission factor glass panel having different thickness in the center and at the circumference, the light absorption factor (epsilon1) and the concentration (c1) of said panel and the light transmission factor (epsilon0) and the concentration (c0) of a panel having higher transmission factor are selected to satisfy the formula. Even when employing a dark tint glass in place of a clear glass, the gradient of the transmission factor is approximately same with that of clear glass thereby variation of the transmission factor due to the thickness of panel is low.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a cathode ray tube used in displays for computer terminal devices and the like.

[Conventional Technique #i] Figure 2 is a top view of a cathode ray tube to which the present invention can be applied. In the figure, (1) is a CRT, (2) is a panel section, and is provided with a fluorescent screen (3), and a shadow mask (4) is provided opposite to this fluorescent screen (3).
), a funnel part (5) and a neck part (6) are connected to form a glass vacuum container. An electron gun (not shown) is housed in the neck portion (6).

Incidentally, recently, CRT devices have been frequently used as displays for computer terminal devices. CRTs used for such purposes are CRTs for general television receivers.
Because the usage is different from that, the required specifications are different. For example, in a CRT for a television receiver, brightness and focus are the most important characteristics, but in a CRT for a display, focus, misconvergence, screen distortion, etc. are important characteristics. Also,
In particular, in the case of television receivers, most viewers only see the center of the fluorescent screen;
In the case of a display CRT, since the displayed content is fixed, strict conditions are required regarding misconvergence, focus, and brightness uniformity throughout the screen.

FIG. 3 shows a square fluorescent screen (3), and in designing such a fluorescent screen (3), a design method called gradation is usually used. Fourth
The figure explains this gradation, and the vertical axis shows the brightness ratio.The center part C of the fluorescent screen (3) is set as 100%, and the peripheral part e usually has a brightness of about 80%. Designed.

Such a design can be said to follow the design flow of CRTs for television receivers. That is, in the case of a television receiver, as mentioned above, viewers mostly look at the center of the fluorescent screen (3), and
In the case of a shadow mask type CRT, considering the deformation of the shadow mask and the influence of the earth's magnetism on the electron beam, the error (the electron beam is on the screen with respect to the center of the phosphor dot) is larger at the periphery of the fluorescent screen (3). (This error is called a landing error) is large, so it is necessary to provide a larger margin for the 1st periphery.As shown in Figure 4, the brightness is lower than that for the center. We needed a design that would be dark. This also applies to CRTs for displays.
Therefore, gradation as shown in FIG. 4 is necessary in the design of the CRT.

However, from the viewpoint of display applications, it is not only the central part of the screen (3) that is viewed as described above, but rather the performance of the peripheral part becomes more important. Under such a background, 70% sin is often the absolute requirement for the brightness ratio (peripheral brightness/center brightness).
On the other hand, empirically, in order to satisfy this 70% sin, the standard value of the gradation needs to be about 85% when manufacturing variations in CRTs are considered.

However, the following new problem occurred regarding the brightness ratio. In other words, a design like the one above can be applied to a glass panel (
2) is valid if a glass with a transmittance of about 86% called clear glass is used, but in order to improve the contrast, for example, a panel with a transmittance of about 46% called dark tint is used. In some cases, the above transmittance ratio decreases by approximately 10%, that is, by 70% for CRTs using clear glass fabric panels.
ff1in can be guaranteed, but the guaranteed brightness ratio for CRTs changed to dark tint fabric panels is 6.
It becomes 0% sin.

This phenomenon has been theoretically elucidated and can be explained as follows.

FIG. 5 shows a partially enlarged view of the glass panel (2), and the outer surface is R with respect to the glass panel thickness To at the center.
PE, also inner surface (surface coated with fluorescent screen)
is shaped such that the radius of curvature is RPI. 1
Specific dimensions for 4 and 20 inch CRTs are, for example, as follows.

l 4” 20” RP I (mm) 551.0 792.
25RP E (mus) 575.0 819.7
-74L8 (Note) T o' (mm) 10.
0 10.92 (Note 1) If we take the example of a glass panel (2
), and if we consider a periphery where r = 150 mm, for example, the wall thickness TE at this periphery (here, considered in the direction of the tube axis, that is, the center axis of the panel) is the wall thickness at the center, To = 10 0 mm, "rE=tt" is about the same as a partial layer, and the thickness around the periphery is about 11% thicker.

By the way, in Fig. 5, if the intensity of light when light with intensity Io passes through glass with absorption coefficient (, thickness d, and material concentration C) and exits outside, then the relationship between ■ and Io is The following relational expression holds true between them.

log(I/Io)=e*c*d...-■The above equation is L
This is known as the ambert-Beer law. Figure 6 is an example of a characteristic diagram of CRT panel glass showing the relationship between I/Io, that is, transmittance, and glass thickness d. This shows that the formula holds true. In this figure, the two wooden lines indicate the characteristics of two types of panel glass with different fabrics, FT-28C is the characteristic of clear glass, and FT-28T is the characteristic of dark tint glass. Note that these clear glasses and dark tint glasses differ only in transmittance and have the same other properties such as thermal expansion coefficient and density.

Now, based on Figure 6, if we consider the degree of change in the transmittance ratio between the center and the periphery of the screen for each case of clear glass and dark tint glass, we get the following.

Panel thickness (II■) 10 11 Clear (
%) 88.0 85.5 Dark taint (%) 47.0 43.3 Therefore, considering that in an actual panel, the wall thickness is approximately lθ% thicker at the periphery than at the center, the transmittance ratio at the periphery/center is , 85.5788.0 = 99.4% for clear glass, 43.3747. for dark tint glass. O=
92.1%, and this result agrees with the actual measurement value.

[Problems to be Solved by the Invention] As explained above, when the designs of the shadow mask and the fluorescent screen are the same, the brightness ratio is 70%ll1n in the case of clear glass.

The brightness ratio of dark tint glass has to be 60% in, which is about 0% less than that.

Therefore, even if the contrast is improved by using dark tint glass with low transmittance as the panel glass, a problem arises in that the peripheral/center brightness ratio is worse than in the case of clear glass.

The present invention has been made to eliminate such problems, and an object of the present invention is to provide a cathode ray tube with an improved peripheral/center brightness ratio when dark tint glass with low transmittance is used.

[Means for solving the problem] ε·C on the right side of the equation represents the slope of the straight line in FIG. Therefore, it can be seen that when dark tint glass with low transmittance is used, if the slope is brought closer to the slope of the characteristic of clear glass by some means, the brightness ratio of 1 periphery/center can be improved.

The present invention has been made from this point of view, and is a cathode ray tube using a panel made of glass with different wall thicknesses at the center and the periphery and low transmittance, the absorption coefficient εl and It is characterized in that the concentration cl, the extinction coefficient ε0 of a panel with higher transmittance than this panel, and the concentration CO are selected to have a relationship of ε1·C (0·co . . .■).

[Function] In this invention, even when dark tint glass is used instead of clear glass, the slope of the transmittance characteristic is almost the same as in the case of clear glass due to equation (2), so the panel thickness / The center brightness ratio can be improved.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram for explaining the transmittance characteristics of the cathode ray tube according to the present invention, and in FIG. 0, which corresponds to FIG. 6, PT-28C is similar to that shown in FIG. Characteristics of clear glass, FT-28S represents characteristics of glass using conventional materials, and 5-P-P represents characteristics of glass according to the embodiment of the present invention. In addition, here C
The size of the RT is 14 inches, and the external dimensions of the panels are all under the same design conditions. The external shape cannot be changed because
This is to standardize the monitor bezel (window frame).

Now, in Figure 1, the slope of 5-P-P is FT-2
It should be noted that the slope was chosen to be approximately similar to the 8G slope. i.e. 5-p-p and FT-28
The formula ■ holds true with C. In this way, 5-P-
In order to change the characteristic of P, that is, ε1·cl, to bring it closer to εOφCO of FT-28C, the extinction coefficient can be changed by changing the trace components in the material of the panel glass.

Now, based on FIG. 1, the transmittance for each glass material is calculated as follows.

Panel thickness (m) 10 11 Tll
/Tl0PT-28G (%) 88 85
．． 5 99.4S-P-P (X) 57
55 98.5PT-289(X)
58 55.5 95.7 Here, in the conventional glass panel FT-285, there is a transmittance difference of 99.4 - 95.7 = 3.7 (%) compared to the case of clear glass FT-28C. On the other hand, in the glass panel 5-P-P according to the embodiment of the present invention, the transmittance difference is reduced to 99.4-96.5 = 2.9 (%) compared to the case of clear glass PT-28C. I understand that.

In addition, since the trace components in the material of the panel glass are changed, the color of the panel when the fluorescent screen is not emitting light must be a slightly darker color than usual. However, in general, in display devices for monitors, For example, it is common practice to place a bluish glass plate or resin plate on the front of a CRT, so this difference in color is minor compared to that of a television receiver. It is.

Note that the present invention is not limited to the above-mentioned embodiments; for example, by introducing a concept similar to the above in a case where another glass panel is provided on the front of a normal CRT, the brightness ratio between the periphery and the center can be improved. It is also possible to adjust the relationship.

Furthermore, although the above description takes a color CRT as an example, the present invention can also be applied to a monochrome CRT.

Further, in the above embodiment, improvements were made to bring the luminance ratio between the periphery and the center closer to that of clear glass, but the present invention can also be applied to the case where the luminance ratio between the periphery and the center is intentionally changed as necessary.

[Effects of the Invention] As described above, according to the present invention, even when using clear glass with low transmittance, the peripheral/center luminance ratio can be maintained in the same relationship as when clear glass is used. Therefore, it is possible to provide a cathode ray tube that can fully satisfy the requirement for brightness uniformity.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the transmittance characteristics of a glass panel according to an embodiment of the present invention in comparison with other glass panels, and FIG. 2 is a partially cutaway sectional view showing the structure of a cathode ray tube to which the present invention can be applied. Figure 3 is a diagram showing a square fluorescent screen, Figure 4
The figure is a diagram explaining gradation, FIG. 5 is a partially enlarged view of a glass panel, and FIG. 6 is a diagram showing transmittance characteristics of clear glass in comparison with dark tint glass. (1)...Cathode ray tube, (2)...Glass panel, C
... central part, e... peripheral part, 5-P-P... transmittance characteristic curve. show.

Claims (1)

[Claims] (1) A cathode ray tube that uses a panel made of glass with a low transmittance and whose wall thickness is different between the central part and the peripheral part,
A cathode ray tube characterized in that the extinction coefficient ε1 and concentration c1 of the panel and the extinction coefficient ε0 and concentration C0 of a panel having a higher transmittance than this panel are selected to have a relationship of ε1・c1≒ε0・c0. .