JPS61185852A - Cathode-ray tube - Google Patents

Abstract

PURPOSE:To maintain the luminance ratio at the circumference and in the center constant irrespectively of the transmission factor of panel thus to fully satisfy the demand of uniform luminance by arranging a front panel in front of a glass panel then making said front panel thin at the portion corresponding with the thick section of glass panel while making thick at the portion corresponding with the thin section of glass panel. CONSTITUTION:In a cathode-ray tube employing such glass panel as having different thickness in the center and at the circumference, the glass panel is provided with a front panel which is thin at the portion corresponding with the thick section of glass panel but thick at the portion corresponding with the thin section of the glass panel. Since the differential thickness in the center and at the circumference of glass panel is corrected by the front panel, deterioration of luminance conventionally occurring at the circumferential section is cancelled to provide same transmission factor in the center and at the circumference. Consequently, the luminance ratio will never deteriorate even when employing a dark tint glass in place of a clear glass.

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.

[Jukyo's branch book] Figure 5 is a partially cutaway cross-sectional view showing the schematic structure of a general cathode ray tube (hereinafter referred to as CRT).
) is a CRT, (2) is a panel part, a fluorescent screen (3) is provided on the inner surface of the panel part (2), and a shadow mask (4) is arranged opposite to this fluorescent screen (3). has been done. The panel part (2) has a funnel part (5
) and the neck portion (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. 6 shows a square fluorescent screen (3), and in designing such a fluorescent screen (3), a design method called gradation is usually used. 7th
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, the viewer mostly looks 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). Since the error in the position of landing is large (this error is called landing error), it is necessary to provide a larger margin for the periphery, so as shown in Figure 7, 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. 7 is necessary in the design of 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/central brightness).
On the other hand, empirically, in order to satisfy this 70% 1n, the standard value of the gradation needs to be about 85% when manufacturing variations of 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.
We can guarantee a win, but for CRTs that have been changed to panels made of dark tint fabric, the guaranteed brightness ratio is 60%.
It becomes sin.

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

FIG. 8 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.

14”2-0” RPI (wear ■) 551.0? 92.25
R P E (am) 575.0 819.7-74
9.6 (Note 1) T o (mpeng) 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 ms, 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 = lO , Omm, TE is approximately 11.1 mm, and the peripheral wall thickness is approximately 11% thicker.

By the way, in Figure 8, if the intensity of light when light with an intensity of Io passes through glass with an absorption coefficient of 6, a thickness of d, and a fabric concentration of C and exits to the outside is represented by , then ■ and 0 are obtained. The following relational expression holds true between .

log (I/Io) = ε・C fist d...■The above formula is La
This is known as the Bert-Beer law. Figure 9 is a characteristic diagram of CRT panel glass showing the relationship between I/I O, that is, transmittance, and glass plate thickness d.
This is an example and 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-28G is the characteristic of clear glass, and PT-28T is the characteristic of dark tint glass. Note that these clear glass and dark tint glass differ only in transmittance, and other characteristics such as thermal expansion coefficient and density are the same.

Now, based on FIG. 9, 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 indigo glass, it becomes linear.

Panel thickness (mm) l Ol 1 clear (%)
88.0 85.5 Dark Taint (
%) 47.0 43.3 Therefore, considering that in an actual panel, the wall thickness is approximately 10% thicker at the periphery than at the center, the transmittance ratio at the periphery/center is 85.5788 in the case of clear glass. .0 = 99.4%, 43.3/47.0 = 92 for dark tint glass
．． 1%, and this result agrees with the actual measurement value.

[Problem to be Solved by the Invention 1] As explained above, when the designs of the shadow mask and fluorescent screen are the same, the luminance ratio of dark tint glass is 70% sin compared to the luminance ratio of 70% sin for clear glass. The ratio has to be 60% win, 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 Problems] The present invention provides a front panel disposed in front of a glass panel, and this front panel has a thinner wall thickness at a portion corresponding to a thicker wall portion of the glass panel. The glass panel is characterized by having a thicker wall thickness at a portion corresponding to a thinner wall portion of the glass panel.

[Function] In this invention, the front panel corrects the difference in wall thickness between the center and the periphery of the glass panel, thereby canceling out the decrease in brightness that conventionally occurred in the periphery, and reducing the brightness in the center as well. Since the peripheral area also has a similar transmittance, even if dark tint glass is used instead of clear glass, the brightness ratio will not deteriorate.

[Embodiment] Prior to a detailed description of the present invention, a front reinforced CRT, which is the background thereof, will be described with reference to FIG. In FIG. 3, a front panel (21) is provided on the curved surface of an ordinary CRT (1). This crystal surface par), +17r
') I) I 10 ka) - 9 Resin such as epoxy (22
) to the glass panel (2).

FIG. 4 is an enlarged view of the glass panel portion in FIG. 3. Considering the case of a 14-inch CRT, the wall thickness t of the front panel (21) is 3 mm, and the radius of curvature RI of its inner surface is
and the radius of curvature RIT of the outer surface are equal, RI=RII=6
It is 00. The material of the front panel (21) may be clear glass with a transmittance of about 85% or a transmittance of about 7.
This includes gray glass, which accounts for about 3%.

On the other hand, the resin (22) is made of resin that has approximately the same refractive index as glass in order to prevent diffused reflection of light, and from the viewpoint of ease of manufacture, the resin layer is usually made to have approximately the same thickness. For example, the thickness is about 5 mm.

The above is an outline of the front reinforced CRT. When the radius of curvature RI of the inner surface and the radius of curvature RII of the outer surface are equal as described above, the front panel (21 ) has not contributed in any way.

FIG. 1 is a partially cutaway cross-sectional view of a front reinforced CRT according to an embodiment of the present invention.
Although the resin (22) and the resin (22) are the same as those shown in FIG. 3, the front panel (21) differs from that shown in FIG. 3 in the following points.

That is, in FIG. 2, the radius of curvature of the inner surface of the front panel (21) is RI = 575°0, the radius of curvature of the outer surface is RII = 551.0, the thickness of the central portion is 4 mm,
The wall thickness at the periphery is 2.9ffi■. The front panel (2) is made of dark tint fabric with a transmittance of 46%, which is approximately the same as the glass panel (2).

Therefore, in the glass panel (2), the wall thickness at the periphery is about 1 mm thicker than at the center, as in the past, but on the contrary, for the front panel (21), the wall thickness at the periphery is thicker than at the center. Because the thickness is about 1 m thinner, the reduction in brightness of about 10% that occurs in the peripheral area when conventional dark tint glass fabric is used is offset by providing the front panel (21), /The brightness ratio in the center can be maintained almost the same as in the case of clear glass.

In the above description, a color CRT was taken as an example, but the present invention can also be applied to a monochrome CRT.

Furthermore, in the above embodiment, the resin (22) was interposed between the front panel (21) and the glass panel (2), but the front panel (21) was simply placed in front of the glass panel (2). Needless to say, it is possible.

Furthermore, in addition to improving the peripheral/center brightness ratio, the present invention can also be applied to cases where it is necessary to intentionally increase the peripheral brightness.

[Effects of the Invention] As described above, according to the present invention, even if the transmittance of the panel changes, the side/center brightness ratio can be kept constant, so the requirement for brightness uniformity can be satisfactorily met. This has the effect of providing a satisfactory cathode ray tube.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway cross-sectional view showing an embodiment of a cathode ray tube according to the present invention, FIG. 2 is an enlarged view of the glass panel portion in FIG. 1, and FIG. 3 is a partially cutaway view showing a general front reinforced CRT. 4 is an enlarged view of the glass panel in FIG. 3; FIG. 5 is a partially cutaway sectional view showing the structure of a conventional cathode ray tube; FIG. 6 is a diagram showing a square fluorescent screen; 7
The figure is a diagram explaining gradation, Figure 8 is a partially enlarged view of the glass panel in a conventional shade 8i-ray tube, and Figure 9 is a diagram showing the transmittance characteristics of clear glass in comparison with dark tint glass. . (1)...Cathode ray tube, (2)...Glass panel, (
21)...Front panel. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (2)

[Claims] (1) A cathode ray tube using a glass panel with different wall thicknesses in the center and periphery, in which a front panel is arranged in front of the glass panel, and this front panel is the thicker part of the glass panel. A cathode ray tube characterized in that a portion corresponding to the glass panel has a thinner wall thickness, and a portion corresponding to the thinner wall portion of the glass panel has a thicker wall thickness. (2) A cathode ray tube according to claim 1, wherein the glass panel and the front panel are made of a material having substantially the same transmittance.