JPH0589800A - Green luminous projection type cathode-ray tube - Google Patents

Abstract

PURPOSE:To provide a green luminous projection type CRT capable of reducing browning of face plate glass while having a fluorescent screen causing little deterioration in brightness. CONSTITUTION:A fluorescent screen of an inside face of a face plate 4 is composed of a first fluophor layer 3 consisting of LaOCl:Tb fluophor in the shape of a flat plate angular grain and a fluophor layer 2 consisting of a Y2SiO5:Tb fluophor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to green light emission used in a projection television apparatus for reproducing a color image by enlarging and projecting an image displayed on the phosphor screen of each monochromatic cathode ray tube emitting green light on a large screen. Regarding a cathode ray tube.

[0002]

2. Description of the Related Art A projection television apparatus for displaying a color image on a screen is provided with monochromatic cathode ray tubes which emit red, blue and green light, and the image displayed on the fluorescent surface of these cathode ray tubes is displayed on the cathode ray tube. It has a structure for reproducing a color image by enlarging and projecting it by an optical lens arranged on the front surface of the. In order to brighten the image on the screen, it is necessary to apply 10 times or more electron beam energy to the fluorescent surface of the projection cathode ray tube as compared with a normal direct-viewing cathode ray tube. Conventionally, as a green phosphor of a projection cathode ray tube, Zn ₂ SiO ₄ : Mn has been used.
Phosphors, Gd ₂ O ₂ S: Tb phosphors, Y ₂ SiO ₅ : Tb phosphors or LaOCl: Tb phosphors are known.
The Zn ₂ SiO ₄ : Mn phosphor has a drawback that it causes so-called burning, which causes deterioration of the phosphor screen under a high electron beam current. Also, G
Although the d ₂ O ₂ S: Tb phosphor has a high luminous efficiency, it has a large so-called temperature quenching, in which the luminous efficiency decreases as the temperature rises. In addition, the Y ₂ SiO ₅ : Tb phosphor has excellent luminance saturation characteristics from a low current region to a high current region of the electron beam current, but the luminous efficiency in the low current region is higher than that of the Gd ₂ O ₂ S: Tb phosphor. There is a problem of being low. Furthermore, it is known that the LaOCl: Tb phosphor is inferior to the Y ₂ SiO ₅ : Tb phosphor in brightness saturation characteristics in a high current region. Then, Japanese Patent Laid-Open No. 1-215884
As described in Japanese Patent Publication No. JP-A-2003-242, by mixing a LaOCl: Tb phosphor and a Y ₂ SiO ₅ : Tb phosphor to form a phosphor screen, the emission brightness is high from a low current region to a high current region, and It is known that the cathode ray tube has excellent brightness saturation characteristics in the current region.

[0003]

However, in the recent projection type television apparatus, the electron beam current for forming an image on the fluorescent screen of the cathode ray tube is greatly increased in order to increase the brightness of the screen on the screen. Tends to be larger. Therefore, there is a problem of deterioration in brightness in which the brightness of the phosphor screen decreases with time due to long-term use. The factors of deterioration in luminance are roughly classified into decrease of luminous efficiency of phosphor, reabsorption of light emission due to coloring of phosphor, and coloring of face plate glass, so-called browning. Among them, it is said that the ratio of browning caused by direct incidence of the excited electron beam on the face plate glass is about half, and improvement thereof has been desired. Further, in order to reduce the browning of the glass, it was not possible to obtain a sufficient effect by using the mixed phosphor as in the above-mentioned known example.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a green light emitting projection type cathode ray tube having a phosphor screen which can reduce the browning of the face plate glass and has less deterioration in brightness.

[0005]

A green light emission projection type cathode ray tube of the present invention is a face plate, and LaOCl having a tabular prismatic particle shape provided on an inner surface of the face plate:
A first phosphor layer made of Tb phosphor and a second phosphor layer made of Y ₂ SiO ₅ : Tb phosphor provided on the first phosphor layer are provided.

[0006]

OPERATION For example, in the publication {Procedures for the 199th Annual Meeting of the Phosphors Society of Japan (1984)}, LaOCl: Tb phosphor has a tabular prism shape or a tabular round particle shape, and when a phosphor screen is formed, the brightness is reduced. It has been shown that the tabular prismatic particles are superior in terms of temperature characteristics, afterglow time, and the like.
We paid attention to the particle shape of the phosphor, and found that by covering the inner surface of the face plate with the phosphor of tabular particles, the electron beam could be prevented from directly entering the face glass and browning could be reduced. That is, in the present invention, the first surface is composed of a LaOCl: Tb phosphor having a tabular prismatic particle shape on the inner surface of the face plate.
Phosphor layer, on which Y ₂ SiO ₅ excellent in luminance saturation characteristics:
By providing a second phosphor layer made of Tb phosphor to form a phosphor screen, the excitation electron beam is prevented from entering the face plate, the brightness of the glass is less browning, and the brightness is excellent. The fluorescent screen has high emission brightness up to the basin and excellent brightness saturation characteristics.

[0007]

【Example】

Example 1 Glass bulb for a 1.7-inch projection cathode ray tube, 400 cc of pure water, 1.8 wt% aqueous barium acetate solution 15
cc was injected, and flat plate-shaped LaOCl: Tb was injected into this.
A mixed solution of 100 cc of pure water in which 735 mg of the phosphor is suspended and 10 cc of 25 wt% water glass is injected. After standing for about 30 minutes, the supernatant is gently drained and dried at room temperature. After sufficiently drying, Y ₂ SiO ₅ : Tb phosphor was applied on the phosphor layer by precipitation under the same conditions. Filming was applied to this phosphor screen, and an aluminum reflective film was formed thereon by vacuum vapor deposition.
After performing a panel baking process and mounting an electron gun, it was evacuated to obtain a 7-inch cathode ray tube. FIG. 1 is a structural diagram of a part of a fluorescent screen of a cathode ray tube according to an embodiment of the present invention. In the figure, 4 is a face plate, 3 is a first phosphor layer, 2 is a second phosphor layer, and 1 is an aluminum pack. Using this cathode ray tube, anode voltage 30kV, raster size 120m
The brightness was measured by changing the anode current to m × 90 mm. Luminance measurement was performed in a 2 ° field of view, and the measurement area was a region of about 2 cm ² at the center of the raster. FIG. 2 shows the luminance (cd / m ² ) according to the anode current (μA) comparing the present invention with the conventional example.
FIG. 6 is a luminance saturation characteristic diagram showing a change, in which a shows the luminance characteristic of the embodiment of the present invention. Furthermore, in the cathode ray tube of the above embodiment, the anode voltage is 30 kV and the raster size is 120.
mm × 90 mm, the anode current was set to 350 μA, and the luminance was measured at regular intervals after the driving was started. Figure 3
Is a luminance life characteristic diagram showing a change in relative luminance according to an elapsed time (hr) comparing the present invention with a conventional example, and a in the figure is a luminance life characteristic of the embodiment of the present invention.

Comparative Example. LaOCl: Tb phosphor or Y
_A cathode ray tube was prepared by using ₂ SiO ₅ : Tb phosphor alone and a mixed phosphor obtained by mixing the above two kinds of phosphors at a weight ratio of 1: 1 under the same conditions as the phosphor screen thickness of the above-mentioned embodiment. The same brightness saturation characteristics and brightness life characteristics as in the example were measured. Curves b, c and d in FIGS. 2 and 3 are LaOCl: Tb phosphor or Y ₂ SiO ₅ : Tb, respectively.
The characteristics of a cathode ray tube in which a phosphor screen is formed by a phosphor alone or a mixed phosphor of the above two types are shown.

As can be seen from FIG. 2, the cathode ray tube of the embodiment of the present invention having the curve a has higher brightness from the low current region to the high current region and the brightness saturation characteristic as compared with the comparative example of the curves b, c and d. It also has an excellent fluorescent screen. Further, as can be seen from FIG. 3, the cathode ray tube having the phosphor screen of the embodiment of the present invention having the curve a has the luminance of 2,000 hours after the lapse of the brightness as compared with the comparative examples of the curves b, c and d. The phosphor screen has a small decrease and improved brightness deterioration. further,
The cathode ray tube subjected to the 2,000-hour life test was disassembled to take out the Fiesplate glass, and the light transmittance of the portion where the browning occurred was measured by the raster display. For the measurement, the light transmittance in the uncolored part is 100%,
It was calculated as a relative value. Table 1 shows the transmittance of each cathode ray tube for the light of wavelength 543 nm of the Fies plate glass.

[0010]

[Table 1]

From this table, it can be seen that the cathode ray tube of the embodiment of the present invention has less browning of the glass due to the coating of the phosphor of tabular prismatic particles on the first layer.

In the embodiment, the precipitation method is used as the fluorescent screen forming method, but the fluorescent screen may be formed by another forming method such as a silk screen printing method.

[0013]

As described above, the present invention comprises a face plate and a LaOCl: Tb phosphor in the form of a tabular prism provided on the inner surface of the face plate.
Y ₂ SiO ₅ provided on the phosphor layer and the first phosphor layer:
By using the one provided with the second phosphor layer made of Tb phosphor, the browning of the face plate glass can be reduced, and the green light emitting projection type cathode ray tube having the phosphor screen with less luminance deterioration can be obtained.

[Brief description of drawings]

FIG. 1 is a structural diagram of a part of a phosphor screen of a cathode ray tube according to an embodiment of the present invention.

FIG. 2 is a luminance saturation characteristic diagram comparing the present invention with a conventional example.

FIG. 3 is a luminance life characteristic diagram comparing the present invention with a conventional example.

[Explanation of symbols]

 2 2nd fluorescent substance layer 3 1st fluorescent substance 4 Face plate

Claims (1)

[Claims] 1. A face plate, and LaOCl in the form of tabular prism particles provided on the inner surface of the face plate:
A green-light-emitting projection cathode ray tube comprising a first phosphor layer made of a Tb phosphor and a second phosphor layer made of a Y ₂ SiO ₅ : Tb phosphor provided on the first phosphor layer.