JPS628469B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a green-emitting phosphor used in a green-emitting phosphor film of a cathode ray tube including a color picture tube, particularly a green-emitting phosphor that provides high brightness and high contrast characteristics. .

The green-emitting phosphor film of the color picture tube contains ZnS/
Green-emitting phosphors based on zinc sulfide such as Cu, ZnCdS/Cu, ZnS/Cu, Au, and Al are used. These phosphors have the advantage of emitting high-intensity light under electron beam excitation and providing a bright screen;
It also has the disadvantage of causing brightness saturation.
Here, the brightness saturation phenomenon means that when a zinc sulfide phosphor is excited to emit light by an electron beam, in a region where the current density of the electron beam is low, there is a linear increase in brightness corresponding to an increase in current density; This means that when the density becomes higher than a certain value, the brightness hardly changes even if the current density increases. Therefore, as for the overall screen of a color cathode ray tube, a white screen that requires high current density excitation may not have the desired brightness, and as a result of weakening green, only a white screen with a lower color temperature than the desired color temperature may be obtained. The problem is that it is not available.

In order to improve these drawbacks, we discovered that it would be advantageous to add a rare earth oxysulfide green-emitting phosphor that hardly shows current saturation phenomenon to the zinc sulfide-based green-emitting phosphor, and we have already filed a patent application No. 54-11735. , special request 1977-
118770, patent application 1987-118771, and further patent application 1982-129160
The following applications have been submitted. Both applications employ a rare earth oxysulfide phosphor and a zinc sulfide phosphor in the form of a mixed film or a double film. The saturation phenomenon is compensated for by the rare earth oxysulfides, providing an overall high-brightness, high-contrast screen.

Although each of these applications has great effects as a product, they also have drawbacks in manufacturing, such as the complicated coating process during fluorescent film formation, poor product stability, and difficulty in quality control. I have it. In other words, in the case of a double film, the coating process is doubled and complicated, and in the case of a mixed film, the two types of fluorescein are separated between each fluorescent film, or between each part of the same fluorescent film. This causes variations in the composition of the mixture, making quality control difficult.

The present invention eliminates these drawbacks and provides a green-emitting phosphor with further improved characteristics. That is, this phosphor consists of (1) a core and a skin layer, and the core is either a green-emitting phosphor whose matrix is a rare earth oxysulfide or a green-emitting phosphor whose main body is zinc sulfide; (2) In item (1) above, the green light-emitting phosphor based on rare earth oxysulfide is at least one of Tb and Dy. is the activator, the matrix is Ln and Y,
The composition consists of Ln ₂ O ₂ S containing at least one selected from La, Gd, and Lu, or (3) the host green luminescence mainly composed of zinc sulfide in item (1) above. The phosphor is ZnS/Cu, ZnCdS/Cu, ZnS/
It is made of one of Cu, Au, and Al.

In the green-emitting phosphor of the present invention, each phosphor particle has a two-layer structure consisting of a skin layer and a core, and each layer is made of a rare earth oxysulfide phosphor and a zinc sulfide phosphor. formed on one side and on the other.
This eliminates the need to mix phosphors during the coating process, and since each particle has high brightness and high contrast, the resulting phosphor film has a uniform effect in all parts. It will have the following. Such effects can be obtained by any combination of rare earth oxysulfide phosphor and zinc sulfide phosphor.

Below, the core is Y ₂ O ₂ S/Tb, Dy, and the epidermis is
This invention will be explained in more detail regarding a green-emitting phosphor made of ZnS/Cu. First, the structure of a phosphor particle is shown in FIG. The diagram assumes that the phosphor is a sphere,
This is a simplified cross-sectional view taken along a plane passing through the center, showing that the core 11 is made of Y ₂ O ₂ S/Tb and Dy particles, and the precipitated skin layer 12 is made of ZnS/Cu. In order to form such phosphor particles, first, fine particles of Y ₂ O ₂ S/Tb, Dy having a size of about 1 to 5 μm are produced by a conventional firing method or other method. Next, this Y ₂ O ₂ S/Tb, Dy
The particles are placed in a solution containing Zn ^{2+ and} H ₂ S gas is passed through the solution with sufficient stirring to precipitate ZnS around Y ₂ O ₂ S/Tb and Dy as cores. Cu ²⁺ as an activator and a suitable flux are added to the two-layer particles, and the particles are fired in a weakly reducing atmosphere containing S. In this way, the bilayered phosphor particles shown in FIG. 1 are obtained. In this example, the ratio of the thickness of the core and epidermal layers can be varied arbitrarily. The core Y ₂ O ₂ S/Tb, Dy can be obtained by changing the firing temperature, firing time, and amount of flux during production, and the desired particle size can be obtained by changing the firing temperature, firing time, and amount of flux during production.
ZnS/Cu can be made to have any desired thickness by changing the amount of Zn dissolved in the solution or by controlling the degree of reaction with H ₂ S. In addition, during firing to introduce Cu ²⁺ into ZnS, Y ₂ O ₂ S/
Heat is also applied to Tb and Dy phosphor particles, but at a temperature of just under 1000℃ required for introducing Cu ²⁺ , Tb and Dy are converted to Y ₂ O ₂ S.
Considering both the ionic radius and ionic charge, it is natural that they remain stably in the ZnS crystal lattice and are not introduced into the ZnS crystal lattice. Also, around Y ₂ O ₂ S
Since ZnS protects it and the firing atmosphere is weakly reducing and contains S, Y ₂ O ₂ S decomposes.
Oxidation to Y ₂ O ₃ does not occur.

Next, FIG. 2 shows the current characteristics of a green-emitting phosphor formed using the two-layer particles of the example shown in FIG. 1 and a green-emitting phosphor film made of the comparative example single-layer particles of ZnS/Cu. In the figure, the vertical axis shows the luminance of the fluorescent film as a relative value, and the horizontal axis shows the current density of the 25 kV electron beam used to excite the fluorescent film. Curve 13 represents the current characteristics of the fluorescent film made of the single-layer particles of the comparative example, and curve 14 represents the current characteristics of the fluorescent film made of the two-layer particles of the example shown in FIG. As is clear from the figure, the phosphor film of the green-emitting phosphor of the present invention has a lower current density of 0.2 μA/cm ² than the phosphor film of the comparative example phosphor. -5
%, but it is almost the same at 0.5 μA/cm ² and +12% in the high current density region of 3 μA/cm ²
This results in a bright, high-brightness, and high-contrast screen. Such an effect can also be obtained by the mixed film or double film according to the previously proposed application, and the characteristics are almost the same as the fluorescent film according to this example, but when forming the fluorescent film, Y ₂ O ₂ The process of mixing S/Tb, Dy and ZnS/Cu can be omitted, and it is also excellent in that the effect can be uniformly obtained over the entire fluorescent film.

Such an effect is caused by Y ₂ O ₂ S/Tb, Dy and ZnS/
Not only the combination of Cu, but also Ln with Y, La, Gd,
Rare earth oxysulfide phosphor with any Lu, e.g.
Either Ln ₂ O ₂ S/Tb or Ln ₂ O ₂ S/Tb, Dy phosphor, or ZnS/Cu, ZnCdS/ as zinc sulfide phosphor.
Any of Cu, ZnS/Cu, Au, and Al phosphors may be combined, or a rare earth oxysulfide phosphor may be used for the skin layer and a zinc sulfide phosphor for the core.

Other embodiments will be described below.

Example 1 Using a conventional method, ZnCdS/Cu containing 0.02% by weight of Cu metal as a Cu activator and 5.1% by weight of a Tb activator and 0.3% by weight of a Dy activator with an average particle size of 0.8μ was prepared.
Obtain Y ₂ O ₂ S/Tb, Dy. ZnCdS/Cu100g and
After weighing and collecting at a ratio of Y ₂ O ₂ S/Tb and 10 g of Dy, both are thoroughly mixed in an aqueous solution. Next, "Primal" (trade name) manufactured by Nippon Acrylic Co., Ltd., as an acrylic emulsion resin, was added to this slurry in an amount equivalent to 0.05 g in terms of solid content, and the mixture was thoroughly stirred. next
Add an appropriate amount of H ₂ SO ₄ to adjust the pH of the slurry to about 3.0, and continue stirring for more than 1 hour. After this stirring is completed, the solid content is removed by decantation, thoroughly washed with deionized water, filtered,
Dry to form a finished product.

In this way, a green light-emitting phosphor is obtained in which the surfaces of ZnCdS/Cu particles with an average particle size of 6 μm are coated with Y ₂ O ₂ S/Tb and Dy fine particles to an average thickness of 0.9 μm. FIG. 3 is a schematic diagram showing the structure of this fluorescent particle, in which the core 15 is made of ZnCdS/Cu, and the skin layer 16 is made of Y ₂ O ₂ S/Tb and Dy. Also the fourth
The figure shows the current characteristics of a phosphor film using the two-layer particle green-emitting phosphor of this example in comparison with a phosphor film using a comparative single-layer particle of ZnCdS/Cu. However, the curve 17 relates to the comparative example, and the curve 18 relates to the current characteristic curve of this example. As can be seen from the figure, in the low current density region of 0.2 μA/cm ² , the green light-emitting film of the phosphor of this example is about -1% darker than the phosphor of the comparative example, but about 0.4 It is equivalent at μA/cm ² , and at about 3 μA/cm ^{2 ,} it is possible to obtain a screen that is approximately +7% brighter, with high brightness and high contrast. Such an effect can also be obtained by using a mixed film or a double film in which the two types of phosphors used in this example have the same composition, but it is easier to achieve uniform characteristics over the entire screen. This method is superior in that a green-emitting fluorescent film can be obtained.

Example 2 Gd ₂ O ₂ S/Tb particles activated with 2.5 wt % Tb and having an average particle size of about 5 μm are formed by a conventional method. this
Disperse 50 g of Gd ₂ O ₂ S/Tb in water and stir well. Separately, prepare a hydrochloric acid solution in which 50 g of ZnO is dissolved. A hydrochloric acid solution of ZnO is added to the previously prepared Gd ₂ O ₂ S/Tb slurry and stirred thoroughly. Next, while stirring is continued, hydrogen sulfide gas is introduced into the liquid to precipitate zinc sulfide on the surface of the Gd ₂ O ₂ S/Tb. When the precipitation reaction of zinc sulfide is completed, the precipitated particles are thoroughly washed to remove excess Cl ^-
remove. To this precipitated product, 0.039 g of copper sulfate, 0.031 g of chloroauric acid, 0.139 g of aluminum nitrate, and an appropriate flux were added, and the mixture was heated to 1000°C.
Calcinate for 100 minutes in a weakly cyclic atmosphere.

In this way, Gd ₂ O ₂ S/Tb is used as the core and ZnS/
A green-emitting phosphor having a skin layer of Cu, Au, and Al with an average thickness of 3.7 μm is obtained. The current characteristics of a phosphor film using the phosphor of this example are shown in curve 20 in FIG. Curve 19 shows the current characteristics of a fluorescent film made of comparative single-layer particles of ZnS/Cu, Au, and Al. As can be seen from the figure, the green-emitting phosphor film of this Example phosphor is approximately 0.2μA/
In the low current range of cm ² , -2% compared to conventional technology, 0.4μ
Equivalent at A/cm ² , + at high current density region of 3 μA/cm ²
It exhibits high brightness and high contrast characteristics of 8%. Further, as in the previous example, there is no particular problem in forming the fluorescent film, and the film has uniform characteristics over the entire surface.

Example 3 Activated with 6.0 wt% Tb with an average particle size of about 1.0μ
Y ₂ O ₂ S/Tb, 0.02 wt% Cu, 0.03 wt%
ZnS/Cu, Au, and Al activated with Au and 0.03% by weight of Al and having an average particle size of about 7 μm are obtained by a normal firing method. Next, using the same method as in Example 1, both of these phosphors were made to emit green light with a core of ZnS/Cu, Au, Al, and a skin layer of Y ₂ O ₂ S/Tb with a thickness of approximately 0.8μ. Create a phosphor. At this time, the composition of both phosphors is as follows:
ZnS/Cu, Au, Al 100g, Y ₂ O ₂ S/Tb 7g
Weigh it so that

The current characteristics of the phosphor film of the green-emitting phosphor obtained as described above are shown as a curve 21 in FIG. Curve 19 represents the curve of a film related to a conventional ZnS/Cu, Au, Al phosphor. As can be seen from the figure, the fluorescent film according to this invention is 0.2μ
-0.5% compared to conventional technology in the low current density region of A/ ^cm2
Furthermore, it was possible to obtain a high-brightness, high-contrast screen with approximately the same current density of 0.3 μA/cm ² and +5% in a high current density region of 3 μA/cm ² . Further, there are no particular problems in forming the fluorescent film, and a screen having uniform film characteristics over the entire surface of the fluorescent film can be obtained.

Example 4 By ordinary firing method, Tb
La ₂ O ₂ S/Tb with an activator concentration of 2.0% by weight is obtained. Next, 70g of this was weighed, 30g of ZnO was added, and a green-emitting phosphor of ZnS/Cu with a core of La ₂ O ₂ S/Tb and a skin layer of approximately 2 μm in thickness was prepared in the same manner as in Example 2. Manufacture. At this time, the activator concentration in ZnS/Cu is assumed to be 0.02% by weight of Cu.

The current characteristics of the phosphor film formed using the green-emitting phosphor of this example obtained as described above are shown in curve 22 in Figure 2.
Shown below. As already mentioned, curve 13 represents the characteristics of the ZnS/Cu film alone. The green-emitting phosphor film of the phosphor of the present invention has a luminance of 0.2μA/
It exhibits -3% brightness at cm ² , approximately the same brightness at 0.6 μA/cm ² , and +9% brightness at 3 μA/cm ² . It is possible to obtain a screen with high brightness and high contrast. Even in this example, no particular problem occurs in obtaining the fluorescent film, and a screen having a uniform effect over the entire screen can be obtained.

The green-emitting phosphor of the present invention has the advantage of simplifying the coating process during the formation of a fluorescent film, facilitating easy and reliable management of the phosphor slurry, and making it possible to obtain a uniform fluorescent film.

[Brief explanation of the drawing]

1 and 3 are schematic cross-sectional views of the green-emitting phosphor of the present invention, FIG. 2 is the current saturation characteristics of the film bodies related to the conventional green-emitting phosphor and the green-emitting phosphor of the present invention, and FIG. 4 and FIG. FIG. 5 is a current saturation characteristic curve diagram of each film body related to the conventional green light-emitting phosphor and the present invention. In each figure, 11... core made of Y ₂ O ₂ S/Tb, Dy, 12... skin layer made of ZnS/Cu, 13...
Comparative Example Current saturation curve of film body related to ZnS/Cu single phosphor, 14...Current saturation curve of film body related to green emitting phosphor of Example, 15... Core made of ZnCdS/Cu, 16 ... Skin layer consisting of Y ₂ O ₂ S / Tb, Dy fine particles, 17 ... Comparative example Current saturation curve of film body related to ZnCdS / Cu single phosphor, 18 ... Example 1
Current saturation curve of a membrane related to a green-emitting phosphor, 1
9...Current saturation curve of film body related to comparative example ZnS/Cu, Au, Al single phosphor, 20...Current saturation curve of film body related to green emitting phosphor of Example 2, 21...
Current saturation curve of the film body related to the green-emitting phosphor of Example 3, 22...Current saturation curve of the film body related to the green-emitting phosphor of Example 4.

Claims (1)

[Scope of Claims] 1. Either a green-emitting phosphor consisting of a core and a skin layer and having a rare earth oxysulfide as a matrix or a green-emitting phosphor having a matrix mainly of zinc sulfide as a core. A green-emitting phosphor, characterized in that one of the two is an epidermal layer. 2 A green light-emitting phosphor containing rare earth oxysulfide as a matrix uses at least one of Tb or Dy as an activator, and the matrix contains Ln as at least one selected from Y, La, Gd, and Lu. The green-emitting phosphor according to claim 1, characterized in that it has a composition of Ln ₂ O ₂ S. 3 The parent green-emitting phosphor mainly consists of zinc sulfide.
The green-emitting phosphor according to claim 1, which is any one of ZnS/Cu, ZnCdS/Cu, ZnS/Cu, Au, and Al.