JPH0430996B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) The present invention relates to a blue-emitting zinc sulfide phosphor with long afterglow.

(Prior Art) It is desired to use high-resolution cathode ray tubes for computer terminal display devices, display devices for aircraft control systems, etc. that display detailed characters and figures. It is known that one effective way to improve the resolution of cathode ray tubes is to make the scanning speed of the fluorescent film by electron beams two to three times slower than that of cathode ray tubes for ordinary display devices. There are 10 phosphors that make up the phosphor film of a cathode ray tube.
% afterglow time (emission brightness after excitation stops is 10% of excitation)
It is necessary that the time required for the temperature to decrease to 100% is several tens to hundreds of times longer than that of the phosphor that constitutes the fluorescent film of a typical cathode ray tube for display devices.

Among such long afterglow phosphors, blue-emitting phosphors are disclosed in Japanese Patent Application Laid-open No. 120521/1983 and Japanese Patent Application Laid-Open No. 58-120521.
Publication No. 115024, Japanese Patent Application Publication No. 1983-129083, Publication No. 129083, Japanese Patent Publication No.
No. 58-79814, JP-A No. 58-83084, and JP-A No. 58-83085 disclose that the ZnS:Ag phosphor used in the blue phosphor for ordinary color receiver tubes is used as a matrix, and gallium or It is described that a suitable amount of indium is introduced and, if necessary, copper, a halogen, aluminum, etc. are added as a co-activator. Some of these phosphors have also been put into practical use as blue-emitting phosphors with long afterglow properties that can be used in the above-mentioned high-resolution cathode ray tubes.

(Problems to be Solved by the Invention) However, the long-afterglow blue-emitting phosphor has a drawback in that its brightness current saturation characteristics are considerably worse than other ordinary phosphors. In other words, color cathode ray tubes use a combination of three colors, red, green, and blue, and white-emitting monochromatic cathode ray tubes use a mixture of phosphors from the three colors mentioned above. . In these cathode ray tubes, it is necessary to change the magnitude of the excitation current in order to adjust the brightness of the screen, but since the current saturation characteristics of the three color phosphors are different, it is difficult to adjust the brightness level of the screen. A problem arises in that the color tone changes. Therefore, in a cathode ray tube that uses the above-mentioned long-afterglow blue-emitting phosphor as one of the three color phosphors, when the screen is dark, the color tone of the screen becomes bluish-white, and as it becomes brighter, the color tone of the screen becomes bluish-white. There was a problem that the color tone changed from white to yellow. Furthermore, in the above-mentioned high-resolution cathode ray tube, the diameter of the electron beam emitted from the electron gun is smaller than that of a normal cathode ray tube in order to improve the resolution, and the excitation current density is also used at a high level, so the current saturation characteristic of brightness is Because of the increased emphasis, the color tone changes on the screen become even more significant, and this is one of the reasons that is hindering the spread of high-resolution cathode ray tubes.

An object of the present invention is to provide a long afterglow blue emitting phosphor with low brightness current saturation, particularly a long afterglow blue emitting zinc sulfide phosphor suitable for use in high resolution cathode ray tubes. do.

(Means for Solving the Problems) In order to achieve the above object, the present inventors have developed ZnS:Ag, which is widely used as a blue-emitting phosphor.
We conducted various experiments to make the phosphor into a phosphor with long afterglow properties, and found that by using a composite compound made by reacting ZnS and an appropriate amount of Sc ₂ O ₃ as the base material, we were able to improve the conventional phosphor.
The inventors have discovered that it is possible to obtain a blue-emitting phosphor that has a significantly longer afterglow time of 10% than that of a ZnS:Ag,X phosphor and has less current saturation of brightness, leading to the present invention.

That is, the long afterglow blue-emitting zinc sulfide phosphor of the present invention has the general formula ZnS x Sc ₂ O ₃ : Ag _y , X _z (where X is composed of fluorine, chlorine, bromine, iodine, and aluminum). At least one element selected from the group, x, y and z are each 1×10 ^-5 ≦x≦8×10 ^-2 , 4.5×10 ^-6 ≦y≦9×
10 ^-4 , 0≦z≦5.5×10 ^-4 ).

The blue-emitting zinc sulfide phosphor of the present invention has almost the same 10% afterglow time as the conventional long-afterglow blue phosphor co-activated with gallium or indium, and has less current saturation of brightness. This is preferable.

Note that the "10% afterglow time" used in this specification is a value when the current density of the stimulating electron beam is 1 μA/cm ² .

(Function) Figure 1 shows ZnS, one of the phosphors of the present invention.
0.003Sc ₂ O ₃ : Shows the afterglow characteristics of Ag and C. The vertical axis represents relative luminance, and the horizontal axis represents time. As is clear from Figure 1, the 10% afterglow time is approximately 42 msec, and although it is not shown in the figure, it is almost the same as the conventional blue-emitting long afterglow phosphor co-activated with gallium or indium. shows afterglow characteristics.

Figure 2 shows the molar ratio x of scandium oxide to zinc sulfide in the matrix of the phosphor of the present invention and 10
It is a graph showing the relationship with % afterglow time, and the activation amounts y and z of silver and chlorine are 9 × 10 -5 and 9 × 10 ^-5 , respectively.
This shows the relationship in ZnS·xSc ₂ O ₃ :Ag, C which is 2.7×10 ⁻⁶ .

As is clear from Figure 2, x is 10 ^-5 ~ 8×
The phosphor of the present invention in the range of 10 ^-2 has an afterglow time of approximately
The time is 35 msec, which is sufficiently practical. x
When is larger than 10 ^-2 , the afterglow time becomes short, which is not preferable. The preferred range of x in the phosphor of the present invention is 5 x 10 ^-5 to 1.2 x 10 ^-2 .

FIG. 3 shows the relationship between brightness and current density. The vertical axis represents the relative luminance when the brightness of a normal short afterglow ZnS:Ag phosphor is taken as 100%, and the horizontal axis represents the current density (μA/cm ² ). Third
As is clear from the figure, ZnS・0.005Sc ₂ O ₃ :Ag, which is one of the phosphors of the present invention shown by curve A in the figure,
C is one of the above conventional phosphors shown by curve B.
It can be seen that compared to ZnS:Ag, Ga, and C, it has high brightness and low current saturation characteristics. This current saturation characteristic is expressed as a brightness ratio at 0.5 μA/cm ² and 3 μA/cm ² for ZnS・0.005Sc ₂ O ₃ , one of the phosphors of the present invention, shown by curve A in the figure: While Ag,C is about 95%, the conventional phosphor mentioned above has only 1%.
It can be seen that ZnS:Ag, Ga, and C are about 67%, and the current saturation characteristics are also small. However, scandium is not scandium oxide,
When introduced in the form of an aqueous salt such as scandium chloride or scandium nitrate, it becomes a phosphor with large current saturation characteristics that is almost the same as the conventional blue-emitting long afterglow phosphor co-activated with gallium or indium.
The general formula of the phosphor of the present invention is ZnS・xSc ₂ O ₃ :Ag _y , X _z
It was confirmed that this is different from the blue-emitting long afterglow phosphor represented by .

(Example) The method for manufacturing the phosphor of the present invention will be described below. For example, the following compounds are used as raw materials for producing the phosphor of the present invention.

Zinc sulfide fine particle powder Scandium oxide Silver compounds such as silver nitrate, silver sulfide, silver halide, etc. Alkali metals (Na, K, Li, Rb and Cs)
and alkaline earth metals (Ca, Mg, Sr, Zn,
Cd and Ba) fluoride, chloride, bromide,
At least one compound selected from the group consisting of iodide and aluminum compounds such as aluminum nitrate, aluminum sulfate, aluminum oxide, aluminum halide, etc. It is used within the quantitative ratio range shown in the general formula of the phosphor. Most of the halogen in the coactivation raw material is lost during firing, and only a small portion remains in the resulting phosphor. Therefore, the alkali metal or alkaline earth metal halide used as the raw material for the halogen is used in an amount that contains several tens to hundreds of times as much halogen as the desired halogen activation amount, depending on the firing temperature, etc. . This excess alkali metal or alkaline earth metal halide also acts as a flux. The necessary amounts of the four phosphor raw materials mentioned above are weighed and thoroughly mixed using a ball mill or the like. Note that this mixing may be carried out in a wet manner by adding the activator as a solution. in this case,
Allow the mixture to dry thoroughly.

Next, the obtained phosphor raw material mixture is filled into a heat-resistant container such as a quartz crucible and fired. The firing temperature is
Temperatures in the range 800-1050°C are suitable. 1050℃
If the zinc sulfide phosphor is fired at a temperature exceeding this temperature, the crystal type of the zinc sulfide phosphor becomes hexagonal, the emission color becomes shorter in wavelength, and the emission brightness also decreases, which is not preferable.
The firing time varies depending on the firing temperature used and the amount of the phosphor raw material mixture, but is suitably 0.5 to 7 hours. After firing, the obtained fired product is washed with water, dried, and sieved to obtain the phosphor of the present invention.

Example 1 Zinc sulfide ZnS 2000g, silver nitrate AgNO ₃ 0.32g, scandium oxide Sc ₂ O ₃ 10.55g, sodium chloride
After thoroughly mixing 10 g of NaC and 10 g of magnesium chloride MgC ₂ using a ball mill or the like, appropriate amounts of sulfur and carbon were added and the mixture was filled into a quartz crucible.
After covering the quartz crucible, the crucible was placed in an electric furnace and fired at a temperature of 950°C for 3 hours. After firing, take out the fired product from the crucible, wash it with water,
Dry and sieve.

In this way, one of the phosphors of the present invention
ZnS・0.0037Sc ₂ O ₃ :Ag0.00009, C0.000006 was obtained. This phosphor emits blue light under electron beam excitation, and its emission brightness is approximately 70% of the brightness of a normal short afterglow ZnS:Ag phosphor as 100%, and the 10% afterglow time is approximately It was 45% msec. Current saturation characteristics
Expressed as the brightness ratio between 0.5 μA/cm ² and 3 μA/cm ² ,
It was 94%. This is because the brightness, 10% afterglow time, and current saturation characteristics of ZnS:Ag, Ga, and C, which are one of the conventional phosphors mentioned above, are 35%, 50 msec, and 67%, respectively.
%, it has excellent brightness and current saturation characteristics.

Example 2 One of the phosphors of the present invention, ZnS・0.03Sc ₂ O ₃ :Ag0.00009, C0.000006, was prepared in the same manner as in Example 1 except that 85.55 g of scandium oxide was used.
I got it. This phosphor emits blue light under electron beam excitation, and its emission brightness is similar to that of ZnS:Ag with a short afterglow.
The brightness of the phosphor is approximately 65% and 10%.
The afterglow time was approximately 38% msec. The current saturation characteristic was approximately 85% when expressed as a brightness ratio between 0.5 μA/cm ² and 3 μA/cm ² .

Example 3 Zinc sulfide ZnS 2000g, silver nitrate AgNO ₃ 3.22g, scandium oxide Sc ₂ O ₃ 2.155g, sodium chloride
After 10 g of NaC and 10 g of magnesium chloride MgC ₂ were thoroughly mixed using a ball mill or the like, appropriate amounts of sulfur and carbon were added and the mixture was filled into a quartz crucible. After covering the quartz crucible, the crucible was placed in an electric furnace and fired at a temperature of 950°C for 3 hours. After firing, the resulting fired product was taken out of the crucible, washed with water, dried, and sieved. In this way, one of the phosphors of the present invention, ZnS.
0.00076Sc ₂ O ₃ :Ag0.00009, C0.000006 was obtained.
This phosphor emits blue light under electron beam excitation, and its emission brightness is approximately 76% of the brightness of a normal short-afterglow ZnS:Ag phosphor as 100%, and the 10% afterglow time is approximately It was 45%msec. Current saturation characteristics
Expressed as the brightness ratio between 0.5 μA/cm ² and 3 μA/cm ² , it is approximately
It was 96%.

[Effects of the Invention] As explained above, the zinc sulfide phosphor of the present invention has the following properties:
It has high luminance, low current saturation, and has excellent characteristics as a long afterglow blue-emitting phosphor.

[Brief explanation of drawings]

Figure 1 shows ZnS, one of the phosphors of the present invention.
0.03Sc ₂ O ₃ : Graph showing afterglow characteristics of Ag, C,
Figure 2 shows the molar ratio x and 10% of scandium oxide to zinc sulfide in the matrix in the phosphor of the present invention.
A graph showing the relationship between luminance and afterglow time, and FIG. 3 is a graph showing the relationship between brightness and current density.

Claims (1)

[Claims] 1 General formula ZnS xSc ₂ O ₃ :Ag _Y ,X _z (where X is at least one element selected from the group consisting of fluorine, chlorine, bromine, iodine and aluminum) , x, y and z are respectively 1×10 ^-5 ≦x≦8×10 ^-2 , 4.5×10 ^-6 ≦y≦9×
10 ^-4 , 0≦z≦5.5×10 ^-4 ). 2. The phosphor according to claim 1, wherein x in the general formula is 5×10 ⁻⁵ ≦x≦1.2×10 ⁻² .