JPS58218731A - Color cathode-ray tube - Google Patents

Abstract

PURPOSE:To obtain a cathode-ray tube suitable for data display and easy to see by making brightness distribution on a picture screen to be uniform up to the peripheral part without showing any especially high brightness in the central part. CONSTITUTION:When exposing a phosphor film, an optical fiber for regulating the illumination distribution is made to have a transmission factor of such characteristics wherein a peripheral transmission factor is higher than the transmission factor of the former filter while the distribution of the opening factor of a shadow mask is so made that the peripheral opening factor is raised. Thereby, the uniform brightness distribution up to the peripheral part is obtainable thus a color cathode-ray tube easy to see and suitable for data display can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the distribution of the size of the phosphor area (fluorescent dot diameter or phosphor "stripe width") of a shadow mask type color cathode ray tube.

In general, the distribution of the size of the phosphor area of a shadow mask type color cathode ray tube is determined based on the balance between the luminous efficiency of the screen surface and the sinding tolerance.

When an electron beam passes through a shadow mask and hits the screen surface, a part of the periphery of a typical screen is greatly influenced by the earth's magnetism and is easily affected by errors in the manufacturing process. Therefore, conventionally, the size of the phosphor area at the periphery of the #J surface was reduced, and the luminance at the periphery was reduced to an extent that was not visually noticeable compared to the center of the 61 screen. A method was used to increase the number of locations. This method is extremely effective and has been widely used in television picture tubes. Next, the reason why the Landink tolerance increases due to such a reduction in the light emitting area will be explained.

FIGS. 1 and 2 show the relationship between the electron beam area and the phosphor area of in-line color cathode ray tubes having two different screen structures.

In other words, Figure 1 shows the electron beam 1) 4.1G that has passed through the round hole shadow mask, IB is the phosphor drum) 1r, Ig*
Figure 2 shows a state in which 4J, 2 (3, zB are phosphor stripes 2r, 2g) are excited by the electron beam 2 that has passed through a rectangular slit type shadow mask.
, shows a state in which 2bt is excited. In addition, in all the examples shown here, the parts other than the phosphor are covered with black material,
This paper demonstrated the so-called negative guard band type screen. In the case of Figure 1, the three-color phosphor drum l'
By reducing the diameters of lrsIg and 1b, when the three color electron beams 1B, IQ, and IB move, a phenomenon in which the color purity decreases, in which colors other than the phosphor dots of the corresponding colors are excited, that is, It is possible to increase tolerance for printing other colors. Such a reduction in the diameter of the phosphor dots can be achieved by reducing the amount of exposure during the exposure process during the production of the phosphor screen, thereby reducing the brightness but increasing the landing latitude.

The distribution of the phosphor emission area ratio and the luminance distribution on the screen in this case are shown in FIGS. 3 and 4, respectively.

However, for a cathode ray tube used for a cheetah display such as a character 0 graphic display, it is said that it is easier to see if the brightness is as uniform as possible within the display area, and it will not cause fatigue even when used for a long time. Apart from the resolution, it is also unsuitable for conventional television cathode ray tubes.

For the reasons mentioned above, it is necessary to improve peripheral brightness t'' for cathode ray tubes for data displays.
There are two deterioration factors. In other words, in order to ensure sufficient mechanical strength of a cathode ray tube, the glass panel at the periphery of the screen must be made thicker, so the light transmittance is lower than that at the center of the screen, and the phosphor film is thicker on the screen. The problem is that the light emitting efficiency decreases because it tends to become thinner in the peripheral area.

The present invention has been made to improve such drawbacks, and provides a color cathode ray tube in which the light emitting area ratio is increased in the periphery, contrary to the conventional distribution of the light emitting area ratio. An example of the area ratio distribution is shown, and FIG. 6 shows its luminance distribution.

There are two methods for obtaining such a luminance distribution. That is, as shown in FIG. 7, the optical filter for adjusting the illuminance distribution during fluorescent M exposure has transmittance characteristic 7-b, which has higher transmittance in the peripheral area than the transmittance characteristic 7-a of the conventional filter. The other is to make the aperture ratio distribution of the shadow mask 8b, which has a higher aperture ratio at the periphery than the conventional 83 distribution, as shown in Figure 8. . The distribution of the apertures of the shadow mask corresponds to the distribution of the size of the phosphor area through which exposure takes place, and corresponds to the size of the electron beam area shown in FIGS. 1 and 2.

In actual design, whether to enlarge the phosphor area at the periphery by using the transmittance distribution of the exposure filter, by the aperture ratio distribution of the shadow mask, or by appropriately combining both methods. O is determined based on the balance between the tolerance for other colors and the tolerance for missing landing, which is a phenomenon in which the electron beam cannot excite all of the relevant phosphors. By making the luminance distribution on the screen as shown in Fig. 5,
As shown in the figure, although the central portion does not exhibit particularly high brightness, it exhibits a uniform brightness distribution to the peripheral portion, providing an easy-to-read color cathode ray tube suitable for data display.

[Brief explanation of the drawing]

Is Figure 1 a nine-person shadow mask? A plan view showing the relationship between the electron beam area and the phosphor dot area of the dot-type screen structure used, and Figure 2 shows the relationship between the electron beam area and the stripe phosphor area of the stripe screen structure using a rectangular slit-type shadow mask. Plan views shown, Figures 3 and 4
The figure shows the size distribution of the phosphor light emitting area and its brightness distribution in a conventional shadow mask type color cathode ray tube. FIG. 3 is a diagram showing the distribution of brightness and its brightness distribution. FIG. 7 is a diagram showing the transmittance distribution of a conventional exposure filter and the transmittance distribution of an exposure filter according to the present invention, and FIG. 8 is a diagram showing the aperture weight of a conventional shadow mask and the aperture ratio distribution of a shadow mask according to the present invention. show. 7th eye 8th eye 1 out of 1 power y giant 1

Claims (1)

[Claims] 1. A color cathode ray tube of a shadow mask type, characterized in that the distribution of the luminescent area ratio of the phosphor to the phosphor screen increases as it approaches the outermost periphery of the screen.