JPS62225584A - Zinc sulfide fluorescent substance - Google Patents

Abstract

NEW MATERIAL:A compound expressed by the formula (X is F, Cl, Br, I or Al; 1X10<-5=x<=8X10<-2>; 4.5X10<-6=y<=9X10<-4>; 0<=z<=5.5X10<-4>). EXAMPLE:ZnS.0.0037Sc2O3: Ag0.00009, Cl0.000006. USE:A constituent material, useful for fluorescent films in cathode-ray tubes of high resolution and having high emission brightness and small current saturation as well as improved characteristics as a long afterglow blue light emitting fluorescent substance. PREPARATION:For example, fine zinc sulfide particulate powder is blended with scandium oxide, a silver compound and alkali (earth) metal halide or aluminum compound and the resultant blend is normally fired at 800-1,050 deg.C for 0.5-7hr.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to long afterglow blue emitting zinc sulfide phosphors.

(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 an effective method for improving 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 ordinary cathode ray tubes for display devices. The phosphor that makes up the phosphor film of a high-resolution cathode ray tube has a 10% afterglow time (after excitation, the stop luminance is 10% of the excitation level).
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 constituting the fluorescent film of the cathode ray tube used in the display device.

Among such long afterglow phosphors, blue-emitting phosphors are disclosed in Japanese Patent Application Laid-open No. 58-120521 and Japanese Patent Application Laid-open No. 58-11.
No. 5024, JP 58-129083, JP 58-79814 ¥3, JP 58-83
ZnS used in the blue phosphor for ordinary color receiver tubes in Japanese Patent Application Laid-open No. 084 and 'Japanese Patent Application Laid-open No. 58-83085:
A (Jl light material as a base material, an appropriate amount of cypress or indium is introduced, and if necessary, halogen, aluminum, etc. are added as copper or 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, in color cathode ray tubes, red,
A combination of three colors, green and blue, is used, and a self-luminous monochromatic cathode ray tube uses a mixture of the three phosphors. In these cathode ray tubes, it is necessary to change the amplitude 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, the color tone can be adjusted by changing the brightness level of the screen. The problem arises that the Therefore, in a cathode ray tube that uses the long-afterglow blue-emitting phosphor described above as one of the three color phosphors, when the screen is dark, the color tone of the screen is bluish-white, and as it becomes brighter, it becomes white. I often had the problem that the color tone changed from yellow to yellow. In order to improve the resolution, the diameter of the electron beam emitted from the electron gun is smaller than that of a normal cathode ray tube, and the excitation current density is also used at a high level, which reduces the current saturation of brightness. As the characteristics are further emphasized, the color tone changes on the screen become more pronounced, and this is one of the reasons that hinders 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 a ZnS:A (II phosphor), which is widely used as a blue phosphor, as a long-afterglow phosphor. We conducted various experiments to find out that ZnS
By using a composite compound made by reacting with 5C203 and an appropriate amount of 5C203 as a base material, the afterglow time is significantly longer by 10% than the conventional ZnS:A(II, The inventors discovered that it is possible to obtain a blue-emitting phosphor, leading to the present invention.

That is, the long afterglow blue-emitting zinc sulfide phosphor of the present invention has the general formula % (where X is at least one element selected from the group consisting of fluorine, chlorine, bromine, iodine, and aluminum). , and X, Y and 2 are each lX10-5≦x≦
8×10-2, 4.5×10-6≦y≦9×10-4,
0≦z≦5.5×10−′).

The blue-emitting zinc sulfide phosphor of the present invention has approximately the same 10% afterglow time as the conventional long-afterglow blue phosphor co-activated with gallium cum or indium, and the current saturation of brightness. It is preferable that the amount of water is small.

Note that the "10% afterglow time" used in this specification refers to the current density of the stimulating electron beam of 1 μA/c! This is the value when .

(Function) FIG. 1 shows ZnS・0.00, which is one of the phosphors of the present invention.
3SC203: Shows the afterglow characteristics of A(J, CJl. 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 m5,
Although not shown in the figure, it exhibits almost the same afterglow characteristics as the conventional blue-emitting long-afterglow phosphor co-activated with gallium or indium.

FIG. 2 is a graph showing the relationship between the molar ratio of scandi oxide "cum" to zinc sulfide in the matrix of the phosphor of the present invention and the 10% afterglow time, and the activation of silver and chlorine ff
1v, z are 9X10-' and 2,7X 10 respectively
-6 Zn5-xSC203:AIJ.

This shows the relationship at 0°C.

As is clear from Figure 2, X is 10-5 to 8X10-
The phosphor of the present invention in the range of 2 has an afterglow time of about 35 m5.
ec, and is ``-9 practical. × is 10-
If it is larger than 2, the afterglow intercostal space will conversely become shorter, which is not preferable. The preferred range of x in the phosphor of the present invention is 5X10-
5 to 1.2 x 10-''.

FIG. 3 shows the relationship between brightness and current density. The vertical axis represents the relative luminance when the brightness of the normal short afterglow ZnS:A () phosphor is taken as 100%, and the horizontal axis represents the current density (μA/cf). From Figure 3. As is clear, one of the phosphors of the present invention, ZnS. :
It can be seen that compared to Ag, Ga, and Cfl, it has high brightness and low current saturation characteristics. This current saturation characteristic is 0.5μA
/cJ and 3μA/cnf, the brightness ratio is:
Zn, which is one of the phosphors of the present invention, is shown by curve A in the figure.
S・0.005SC203: A(1, Ca is about 95%
In contrast, ZN, one of the conventional phosphors mentioned above,
It can be seen that s:△(], Ga, and Ca are about 67%, and the current saturation characteristics are also small. However, if scandium is introduced in the form of a water-soluble salt such as scandium chloride or scandium nitrate instead of scandium oxide, the above The phosphor of the present invention has a large current saturation characteristic that is almost the same as the conventional blue-emitting long afterglow phosphor co-activated with gallium or indium.
It was confirmed that it is different from the blue-emitting long afterglow phosphor represented by 03:A(+,,X2).

(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, Ni, Li, Rb, and C
S) and alkaline earth metals (Ca, M(], Sr
, Zn, Cd and Ba) fluorides, chlorides,
At least one compound selected from the group consisting of bromide, iodide, and aluminum compounds such as aluminum nitrate, aluminum sulfate, aluminum oxide, and aluminum halide. The amount used is within the quantitative ratio range shown in the above general formula of the phosphor of the present invention. Most of the halogen in the co-activation raw material (2) 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 and the like. This excess alkali metal or alkaline earth metal halide also acts as a flux. The necessary amount of the above-mentioned four phosphor raw materials is 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 activators (1) and (2) as a solution. In this case, the mixture is thoroughly dried.

Next, the obtained phosphor raw material mixture is filled into a heat-resistant container such as a quartz crucible and fired. Firing temperature is 800-105
Temperatures in the range 0'C are suitable. If the zinc sulfide phosphor is fired at a temperature exceeding 1050° C., 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 M of the phosphor raw material mixture, but is 0.5 to 7
The time is appropriate.

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 zn 32000(], silver nitrate AgNChO
, 32C1, scandium oxide 3c 20310.55
After sufficiently mixing 2210 g of sodium chloride, Na Clog , and magnesium chloride Ma using a ball mill or the like, sulfur and carbon were appropriately added, and the mixture was filled into a quartz crucible. After the quartz crucible was covered, the crucible was placed in an electric furnace and fired at a temperature of 950''C for 3 hours.The fired product obtained after firing was taken out of the crucible, washed with water, dried, and sieved.

In this way, one of the phosphors of the present invention, ZnS-
0,00373c 203: A(1□, 0000g
.

Cβ0.000006 was obtained. This phosphor emits blue light under electron beam excitation, and its emission brightness is comparable to the normal short afterglow Z
The brightness of the nS:Aql light body was about 70%, and the 10% afterglow time was about 45711S. The current saturation characteristic is 0.5μA/c! When expressed as a luminance ratio at 3 μA/cJ, it was 94%. This is based on the brightness of ZnS:Ag, Ga, Cβ, which is made from one of the conventional phosphors mentioned above.
10% afterglow time and current saturation characteristics are 35% and 50% respectively
ns, 67%, but has excellent brightness and current saturation characteristics.

Example 2 One of the phosphors of the present invention, Z
n S 110.03 SC203: Ao □
,0000g.

C10,00006 was obtained. This phosphor emits blue light under electron beam excitation, and its emission brightness is higher than that of ordinary Zn with a short afterglow.
S: A () The luminance of the phosphor was 100%, which was about 65%, and the 10% afterglow time was about 3813.The current saturation characteristics were compared at 0.5 μA/c and 3 μA/c. The brightness ratio was 85%.

Example 3 Zinc sulfide Zn 32000 (1, silver nitrate A!J NO3
3,22g, scandium oxide 3C2Q3 2,155
g, Sodium chloride NaCβ10 (1), Magnesium chloride M (JCβ210 (L) were thoroughly mixed using a ball mill, etc., and appropriate amounts of sulfur and carbon were added and filled into a quartz crucible. After the quartz crucible was covered, the crucible was was placed in an electric furnace and fired at a temperature of 950°C for 3 hours.The fired product obtained after firing was taken out from the crucible, washed with water, dried, and sieved. Zn S-0,0O076Sc 2, one of the light bodies
(h: Ao □, 000g.

CJ20.00006 was obtained. This phosphor emits blue light under electron beam excitation, and the luminance of this luminescence is higher than that of normal short afterglow Z.
The brightness of the nS:Ag phosphor was about 76%, taking it as 100%, and the 10% afterglow time was about 45 m5. The current saturation characteristic was 96% when expressed as a brightness ratio between 0.5 μA/cJ and 3 μA/cf.

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

[Brief explanation of drawings]

Figure 1 shows ZnS 0.03 which is one of the phosphors of the present invention.
3c 203 :A(], A graph showing the afterglow characteristics of Cβ, FIG. 2 shows the relationship between the molar ratio x of scandium oxide to zinc sulfide in the matrix and the 10% afterglow time in the phosphor of the present invention. The graph shown in Fig. 3 is a graph showing the relationship between luminance and current density. Applicant: Toshiba Corporation Patent attorney: Satoshi Suyama - Fig. 1: Scandium Mol kLX

Claims (2)

[Claims] (1) General formula ZnS x Sc_2O_3:Ag_y, 10＾−＾5≦x≦8
×10^-^2, 4.5×10^-^6≦y≦9×10
^-^4, 0≦z≦5.5×10^-^4)
A zinc sulfide phosphor comprising a compound represented by: (2) The phosphor according to claim 1, wherein x in the general formula is 5×10^-^5≦x≦1.2×10^-^2.