JPS61185850A - Cathode-ray tube - Google Patents

Abstract

PURPOSE:To improve the brightness ratio at the circumference and in the center when employing a dark tint glass having low transmission factor by differentiating the curvature of outer face in the center of a glass panel from that of the outer face at the circumference. CONSTITUTION:The curvature RPI of the inner face of panel 2 is same in the center and at the circumference while the curvature RPE at the circumference of the outer face of panel 2 is same with conventional one. The curvature RQE in the center of the outer face of panel 2 is different from conventional one where the curvatures RQE and RPE are continued smoothly to be rotary symmetrical against the central shaft of panel. Consequently, the thickness T in the center of the outer face of panel 2 is thicker when compared with conventional one. When employing a dark tint glass, the brightness will drop by about 10% at the circumference but since the thickness in the center is increased by about 10%, the brightness will drop by about 10% in the center. Consequently, droppage of brightness at the circumference is cancelled to maintain the brightness ratio at the circumference and in the center at same level with that of clear glass.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Applications g7] The present invention relates to a cathode ray tube used in displays for computer terminal devices and the like.

[Prior Art] FIG. 3 is a partially cutaway sectional view showing the schematic structure of a general cathode ray tube (hereinafter referred to as CRT). In the figure, (1
) 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 provided opposite to this light screen (3).
) are provided. A funnel part (5) and a neck part (6) are connected to the panel part (2) 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 focus, brightness uniformity, etc. in order to avoid misconvergence to every corner of the screen.

Figure 4 shows a rectangular fluorescent screen (3). In the design of such a fluorescent screen (3), an F-stage, usually called a gradation, is used. Figure 5 explains this gradation, and the vertical axis shows the brightness ratio, and the central part C of the fluorescent screen (3)
is 100%, the peripheral area e is usually designed to have a brightness of about 80%.

Such a design can be said to be based on the IA omission in the design of CRTs for television receivers. In other words, in the case of a secondary receiver, the viewing direction is usually to look at the center of the condensing screen (3), as mentioned above;
And, in the case of shadow mask type CRT, modification of Nyadou mask and IT! ! Effect of air on electron beam+
Considering 2!1 magnification, the error at the periphery of the phosphor screen (3) (this is the error in the position where the electron r-beam reaches the screen, which is tilted towards the center of the phosphor dot); Because of the large landing error (landing error), it was necessary to give more margin to the periphery, so it was necessary to design the brightness to be darker than the center, as shown in Figure 5. This means that C for display
The same is true for RT, and therefore, a gradation as shown in FIG. 5 is necessary due to the popularity 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 this background.

70%1Ilin as brightness ratio (peripheral brightness/center brightness)
is often an absolute requirement. On the other hand, empirically, in order to satisfy this 70%ff1in, 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.

Approximately 86% of the glass panels (2) are called clear glass.
However, in order to improve the contrast, if a panel with a transmittance of about 46% called Dark Tin i is used, - the above transmission = <1 ratio or around 11%. In other words, for a CRT using a panel made of clear glass fabric, a 1:1F ratio of 70% can be maintained, but for a CRT changed to a panel made of dark tint fabric, the guaranteed value of the 11 degree ratio is 60% ton. I end up.

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

Figure 6 shows a partially enlarged view of the glass panel (2), and the outer surface is RPE and the inner surface (the surface coated with the fluorescent screen) is RPI for the glass panel thickness 1 zo To at the center. It has a shape with a radius of curvature.

Specific dimensions for 14 and 2C inch CRTs are, for example, as follows.

14 ” 20 ” RP I (mm) 551.0? 92.25R
P E (mm) 575.0 819.7-749
．． 8 (, h 1 ) T o (mm) IQ, 0
10.92 (total 1) If we take the example of a 14 inch or less rotationally symmetrical shape with two radiuses or a smoothly connected tube axis as the center, 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 TE=11.110DI for .0mm
The wall thickness around the periphery is about 11% thicker.

By the way, in Fig. 6, if r is the intensity of light when light with intensity Io passes through glass with extinction coefficient ε, thickness d, and fabric concentration C, then the relationship between ■ and Io is The following relational expression holds true between them.

log(I/Io)=e−c−d−−−·−i+The above equation is known as Lambsr t−Beer’s law. FIG. 7 is an example of a characteristic diagram of a CRT panel glass showing the relationship between I/r o, that is, transmittance, and the glass plate thickness d, and shows that the formula (2) holds true. In this figure, the two wooden lines represent the characteristics of two types of panel glass with different fabrics.
28C is a clear glass, and FT-28T is a 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.

Based on FIG. 1, if we consider the degree of change in the transmittance ratio between the center and the periphery of the NuClean for each case of clear glass and turquoise glass, we will find the following.

Pennel thickness Ji (m+a) 10 11 clear (%) 136.0 115.5 Guk chi ind (%) 47,0 43.3 Therefore, in the panel near χ, the wall thickness is approximately 10% thicker at the periphery than at the center. Considering, the peripheral/center transmittance ratio is 85.5/813.0= for clear glass.
9!3.4%, 43.4% in case of dark tint glass.
3/47. O=92.1%, and this result agrees with the actual measurement value.

[Problem to be solved by the invention] As explained below, when the shadow mask and light screen have the same design, dark tint has a brightness ratio of 70% win for clear glass. The brightness ratio of glass has no choice but 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 transmission +g for 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 is characterized in that the radius of curvature of the outer surface of the central portion of the glass panel is different from the radius of curvature of the outer surface of the peripheral portion.

[Function] In this invention, since the curvature of the outer surface of the central part is different, the brightness of the central part decreases, and the decrease in brightness that conventionally occurs in the peripheral part is offset, and the central part and the peripheral part are the same. Therefore, even if dark tint glass is used instead of clear glass, the brightness ratio will not deteriorate.

[Example] Embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows a partially enlarged view of a glass panel in Embodiment 8 of the cathode ray tube of the present invention.

In the figure, the radius of curvature RPI of the inner surface of panel (2) is
Like the conventional one shown in FIG. 6, the central part and the peripheral part are equal, and the radius of curvature RPE at the peripheral part of the outer surface of the panel (2) is also the same as in FIG. On the other hand, the panel (
2) The curve at the center of the outer surface - ← radius is RQE, which is different from the conventional one, and this radius of curvature RQE and radius of curvature RP
E are smoothly connected and are rotationally symmetrical about the panel center axis. As a result, panel (2)
The wall thickness T at the center of the outer surface of is T=11.0III1
1! te, fl, o compared to the conventional wall thickness to=10.0 mm
ml+! (〈becoming.

In other words, when dark tint glass fabric is used, the brightness decreases by about 10% at the periphery, but in this example, the thickness at the center is about 10% thicker than before. , the brightness also decreases by about 10% in the center. As a result, the decrease in brightness at the periphery is offset, and the brightness ratio at the periphery/center can be maintained almost the same as in the case of clear glass.

Further, even if the radius of curvature is partially different as shown in L, there is no problem when incorporating the CRT into a device. That is, as shown in Fig. 2, a window frame [21] called a bezel is usually installed in a television receiver or a monitor device so as to be almost in contact with the outer periphery of the glass panel (2). Since the shape of the panel (2) has the same radius of curvature as the conventional one as described above, no problem arises.

By the way, the dimension d where the bezel (21) goes inward from the outside diameter of the CRT is the distance from the center of the panel (2) to the CRT.
It almost never exceeds the dimension to the circumferential wall of T.

Although color CRT was taken as an example in the explanation 1-1, the present invention can also be applied to monochrome CRT.

[Effects of the Invention] As described below, according to the present invention, the transmission of the panel (
Since the peripheral/center brightness ratio can be kept constant even if i changes, it is possible to provide a cathode ray tube that can better satisfy the requirement for brightness uniformity.

[Brief explanation of the drawing]

1st [4 is a partial enlargement of the crow panel in the embodiment of the cathode ray tube of this invention): A, Fig. 2 is a diagram for explaining the dimensional relationship between the crow spring IL and the hazel, and No. 314 is a general cathode ray tube. FIG. 4 is a partially cutaway sectional view showing the structure of the tube, and FIG. 4 is a diagram showing a square fluorescent screen. Figure 5 is a diagram explaining gradation, Figure 6 is a partially enlarged view of a glass panel in a conventional cathode ray tube, and Figure 71 is a diagram explaining gradation.
A is a diagram showing the transmittance characteristics of clear glass in comparison with that of Gokuko Indian Glass. (2)...Crow panel, RPE, RQE...Radius of curvature. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] (1) A cathode ray tube characterized by using a glass panel in which the radius of curvature of the outer surface of the central portion is different from the radius of curvature of the outer surface of the peripheral portion.