JPH06192656A - Rare earth oxysulfide phosphor and image display tube using same - Google Patents

Abstract

PURPOSE:To provide a 3mum or smaller particulate phosphor having high luminance and a highly elaborate cathode-ray tube using the same. CONSTITUTION:The phosphor is represented by the general formula: (Ln1-x-yInxLn'y)2O2S (wherein Ln is at least one element selected from among y, Gd, La and Lu; Ln' is at least one element selected from among Eu, Tb, Sm, Tm, Er and Pr; and x and y are rare-earth oxysulfide phosphor in the ranges: 0.005<=x<=0.07 and 0.0001<=y<=0.2, respectively) and the CR tube is produced by using the same.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rare earth oxysulfide phosphor and an image display tube using the same.

[0002]

2. Description of the Related Art Rare earth oxysulfide phosphors such as Y ₂ O ₂
S: Eu is a red phosphor for a color cathode ray tube, Gd ₂ O ₂ :
Tb is widely used as a green phosphor for projection tubes.
This type of phosphor is prepared by dissolving Ln ₂ O ₃ and Ln ′ ₂ O ₃ which are rare earth oxide raw materials in a mineral acid and then adding oxalic acid (HOOC).
-COOH) to coprecipitate as oxalate,
There is known a method in which this is decomposed by heating to produce a Ln ₂ O ₃ · Ln ′ ₂ O ₃ mixed crystal, and a sulphating agent and a fluxing agent are added and fired. The firing temperature is about 900 to 1250 ° C., and the flux plays the role of promoting the above reaction and promoting the growth of particles.

The particle size of the phosphor may be changed depending on its application, but conventionally, the above has been dealt with by changing the firing temperature and the kind and addition amount of the flux.

[0004]

In recent years, the definition of image display tubes such as cathode ray tubes and fluorescent display tubes has become higher and higher, and it is necessary to apply phosphor particles to the cathode ray tube in a dot pattern or a thin stripe pattern smaller than before. It came out. When a small dot pattern or a thin stripe pattern is formed using a conventional phosphor, the space between the particles becomes large because the phosphor particles are large, and the film filling degree of the picture element (dot pattern, stripe) decreases. In addition, the unevenness of the edge becomes large and the shape becomes poor. These are major obstacles in promoting high-definition high definition.

Particularly, in an ultra-high-definition cathode ray tube, it is necessary to use a phosphor having an average particle diameter of 3 μm or less, but in the prior art, a phosphor having an average particle diameter of about 4 μm can be obtained by forced pulverization, classification or the like. It was the limit. Conventionally, additives for obtaining a phosphor having a relatively large particle size have been known (Japanese Patent Publication No. 51-35555 and Japanese Patent Publication No. 54-461).
82, Japanese Patent Publication No. 57-192484). However, no additive is known for obtaining small particle sizes,
If you try to obtain a phosphor with a relatively small particle size by changing the firing temperature, etc., the crystal growth is insufficient compared to ordinary phosphors, resulting in low brightness and dispersibility as a powder property. However, it was not possible to form a dense and high-luminance phosphor film for the above purpose.

Small particles (2 μm order) are used in applications such as print coating and viewfinder applications.
However, as mentioned above, a manufacturing method that satisfies this has not yet been established, and brightness reduction due to forced crushing, classification, etc., low yield, and unavoidable use of small particle phosphors Was. It is known that rare earth oxysulfides are added with various elements in a trace amount or a small amount for various purposes. In particular, regarding indium (In), it is proposed that by adding an extremely small amount of indium of 200 ppm or less to europium-activated yttrium oxysulfide, it is possible to impart high luminance and excellent current luminance saturation characteristics to this phosphor. It has been known.

Therefore, the present invention is intended to solve the above problems and to provide a rare earth oxysulfide phosphor having a small particle size of 3 μm or less and having high brightness.

[0008]

The present invention is based on the general formula (Ln
_1-xy In _x Ln ' _y ) ₂ O ₂ S, and Ln is
At least one element selected from Y, Gd, La, and Lu, and Ln ′ is Eu, Tb, Sm, Tm, E
It is at least one element selected from r and Pr, and x and y are 0.005 ≦ x ≦ 0.07 and 0.00
The rare earth oxysulfide phosphor having a range of 01 ≦ y ≦ 0.2, and the rare earth oxysulfide described above, which contains Eu or Tb as a main activator and has an average particle diameter of 3 μm or less. An image display tube characterized by containing a fluorescent substance in a fluorescent film.

[0009]

[Function] When a rare earth oxysulfide phosphor is manufactured by mixing a rare earth oxide with a sulfidizing agent and a flux, and heating and synthesizing the same, the particle growth of the phosphor is affected by the sulfiding agent, the flux, and the firing temperature. The particle size was controlled mainly by selecting the kind and amount of the flux and the firing temperature. However, although these methods can control the particle size of more than 4 μm, it was not possible to obtain a phosphor having a small particle size of 4 μm or less.

Therefore, the present inventors have changed the conventional way of controlling the grain size and added In in a small amount to the oxysulfide crystal matrix such as Y, Gd, La, and Lu to grow grains during crystal formation. It has been found that there is an effect of suppressing. That is, according to the present invention, it is possible to produce a small rare earth oxysulfide phosphor having a particle diameter of 3 μm or less, which has been impossible in the past, by adding 0.5 to 7 atomic% of In to the composition of the rare earth oxysulfide phosphor. Found.

In particular, in order to stably maintain the average particle size of the rare earth oxysulfide phosphor at 3 μm or less, it is preferable that the x value in the above general formula be in the range of 0.8 to 5 atom%. If In is added in excess of this upper limit, fine particles having a single particle size of 3 μm or less may be obtained, but due to insufficient crystal growth or the like, re-aggregation occurs and substantial agglomerates are formed. Since the average particle diameter above is 4 μm or more,
Due to its quality, it could not be applied to high definition cathode ray tubes. It has been confirmed that the above In substitution is effective in controlling the particle size of the host crystal, and is almost unaffected by the type of activator, and the above effect is exhibited.

As the raw material, indium compounds such as indium sulfate, indium sulfide, indium nitrate, indium chloride, indium bromide and indium iodide can be used instead of indium oxide.
In addition, the addition of indium oxide causes a slight change in color tone as compared with the conventional non-added phosphor, but it can be sufficiently adjusted by controlling the amount of the activator, and there is no practical problem. The present invention can be applied to image display tubes such as high definition cathode ray tubes.

[0013]

Examples (Examples 1 to 7, Comparative Example 1) Y ₂ O ₃ : 10.0 g, E
u ₂ O ₃ : 0.592 g, In ₂ O ₃ : 0.168 g,
A compound consisting of Li ₂ CO ₃ : 3.84 g and S: 5.00 g was mixed well and put in an alumina crucible at 1100 ° C.
It was baked for 1 hour. The fired product obtained is thawed in water and washed repeatedly, and the residual alkali content is further neutralized with an acid, followed by sieving with a fine mesh, dehydration filtration and drying at 120 ° C for 12 hours to obtain a powder. It was

The obtained powder has the formula (Y _0.948 In _0.014
It was a red-emitting phosphor represented by Eu _0.038 ) ₂ O ₂ S (Example 1). Further, for comparison, In ₂ O ₃ was _removed from the above raw material structure and the same conditions (Y _0.962
A red light emitting phosphor of Eu _0.038 ) ₂ O ₂ S (Comparative Example 1) was obtained. Further, the phosphors shown in Table 1 below were obtained by the same manufacturing method by changing the type and mixing amount of each element (Examples 2 to 7).

(Examples 2 to 7) The results of measuring the particle size of these phosphors with a Coulter counter particle size analyzer are shown in Table 1.
Shown in.

[0016]

[Table 1]

The characteristics of these phosphors are compared with each other as shown in Table 1. In particular, when the phosphors are applied to a cathode ray tube having a high definition pattern and the coating characteristics are examined, the phosphors of Examples 1 to 7 are the same as those of Comparative Example 1. Since the particle size was smaller than that of the phosphor, a dense phosphor film could be formed.

[0018]

EFFECTS OF THE INVENTION The present invention makes it possible to provide a rare-earth oxysulfide phosphor having a small particle size of 3 μm or less by adopting the above-mentioned constitution, which is suitable for a video display tube such as a high-definition Braun tube. It facilitated the formation of the fluorescent film.

Front Page Continuation (72) Inventor Yasuo Oguri 1060 Narita, Odawara, Kanagawa Kasei Optonix Co., Ltd. Odawara Plant

Claims (2)

[Claims] 1. A general formula (Ln _1-xy In _x Ln ' _y ) ₂
It is represented by O ₂ S, Ln is at least one element selected from Y, Gd, La and Lu, and Ln ′ is E
at least one element selected from u, Tb, Sm, Tm, Er and Pr, and x and y are 0.005 ≦ x
A rare earth oxysulfide phosphor characterized by having a range of ≦ 0.07 and 0.0001 ≦ y ≦ 0.2. 2. A video display tube containing a rare earth oxysulfide phosphor according to claim 1, which contains Eu or Tb as a main activator and has an average particle diameter of 3 μm or less. .