JPS5943074B2 - luminescent material - Google Patents

Description

[Detailed Description of the Invention] The present invention is a novel luminescent material for slow electron beam excitation that emits red light, more specifically, it is made by mixing an appropriate amount of an indium oxide conductive material and a silver-activated phosphor. This invention relates to a luminescent material for slow electron beam excitation.

Conventionally, a self-activated zinc oxide phosphor (Z
nO■Zn) is known.

This phosphor emits green light when excited with a slow electron beam,
It is used as a phosphor for fluorescent display tubes in calculators, various measuring instruments, etc. In fact, in the laboratory, Y
202S■EU, ZnS■Ag, etc. are known to have been given conductivity with In2o3, but they have not been put to practical use in display tubes because the conductivity is insufficient.

As a result, the uses of fluorescent display tubes that only emit green light are limited, and in order to expand the use of display tubes, there has been a strong demand for the development of light-emitting materials that emit bright light other than green.

In order to meet the above-mentioned needs, the inventors of the present invention imparted electrical conductivity to the phosphor itself in the process of conducting various research aimed at obtaining a luminescent material that emits light in a color other than green through slow electron beam excitation. We found that it is necessary to prevent electron charging on the surface of phosphor particles in slow electron beam excitation.

Based on these facts, an appropriate amount of silver-coated active phosphor (Zn, --xCdx)S■Ag (0.6≦X≦0.9), which does not emit light by slow electron beam excitation, was added. Indium oxide (In) doped with tin.

03) It has been discovered that when a mixture of a certain range of conductive materials is excited with a slow electron beam, it emits high-intensity red light.

Although tin-doped indium oxide-based conductive material is an oxide, tin acts as a donor and free carriers are 10
21 (177!-3), and the specific resistance is as low as 10-4 to 10-2 Ω.It is effective for lowering the threshold voltage of light emission by slow electron beam excitation. That is, The apparent conductivity of a powder-filled layer like a normal fluorescent display tube is σ and the apparent permittivity is εa, and there is q in this conductor layer.

Suppose that the charges (X, Y, Z) are spatially distributed,
This is the point (X, Y, Z) at time t, q(X, Y,
z, t). In the process of charge relaxation, as in the case of a continuous medium, if it is assumed that the equation of continuity of current, Boatzson's equation, and Ohm's law hold true, then solutions to (1) to (3) can be obtained.

However, l is the current density and E is the vector that generates the electric field. τ is the relaxation time. In the case of a self-activated zinc oxide phosphor (ZnO:Zn) that emits light by slow electron beam excitation, or a europium-activated tin oxide phosphor, the value of τ is approximately 3 seconds and 5 seconds, respectively. Estimated. Therefore, for example, if the dielectric constant of a powder-filled layer made of a mixture of europium-activated yttrium oxide phosphor and tin-doped indium oxide is 17.1, the electrical conductivity is 3.4.
If it is made to be about v/Crn, the relaxation time will be about 5 seconds and the threshold voltage for light emission will be several volts, like zinc oxide phosphors and tin oxide phosphors. The first tin-doped indium oxide conductive material that meets these requirements is
The layer resistance value shown in the figure is 10Ω or less, that is, SnO2/
A range of 0.8% to 10% by weight of N2O3 was obtained. Conventionally, zinc oxide (ZnO) alone or undoped indium oxide (In2O3) has been used in some cases to impart conductivity to phosphors, but compared to the above-mentioned indium oxide-based conductive materials, , both have a specific resistance of 3
~4 orders of magnitude larger. Therefore, using an indium oxide-based conductive material provides more sufficient conductivity to the phosphor than using zinc oxide or undoped indium oxide.
Light emission starts from a lower excitation voltage, which is consistent with the purpose of the present invention. Even when indium oxide, which is a component of the luminescent material according to the present invention, is doped with germanium, lead, or silicon in addition to tin, the specific resistance similarly decreases, and an effective low-speed electron beam-excited luminescent material can be formed. To create these conductive materials, indium oxide powder is combined with tin, germanium,
Add a solution of at least one salt of lead or silicon in an amount corresponding to the amount added, make a slurry, and evaporate to dryness.
It may be fired at a temperature of 0.000°C to 1300°C. In addition, silver-activated phosphor (Znl), which is the other component of the luminescent material,
-XCdx)S:Ag is produced as follows. The ratio of zinc sulfide (ZnS) raw powder and cadmium sulfide (CdS) raw powder to x mol of CdS raw powder so that ZnS raw powder is (1-x) mol (however, 06≦X≦0.9) The raw mixed sulfide powder obtained by mixing is immersed in an aqueous solution of silver ions, for example, an aqueous solution of silver nitrate (AgNO3) to form a slurry, and the resulting powder is evaporated to dryness and pulverized at 900 to 1200°C in a reducing atmosphere.
It is obtained by baking for several hours.

The amount of activator Ag is 10-5 to 10-29 relative to the base material (Znl-XCdx)Sly.

Note that as the value of x becomes less than 0.6, yellow to green light is emitted, and as the value of x becomes greater than 0.9, the light becomes infrared, so it cannot be a component of the luminescent composition of the present invention. do not have.

In the above phosphor production, an alkali metal halide,
It is desirable to add a fluxing agent such as an alkaline earth metal halide and then perform the firing.

The above phosphor emits bright red light under high-speed electron beam excitation at an accelerating voltage of several KV or higher;
It hardly emits light under slow electron beam excitation of about V.

The present invention provides a luminescent material that emits bright red light even at an accelerating voltage of several tens or less by sufficiently mixing the above-mentioned phosphor and an indium oxide-based conductive material doped with tin in a mortar, ball mill, etc. There is a particular thing.

For example, the luminescent material powder obtained in the present invention is set on the luminescent surface 5 in the low-speed electron beam excitation device 1 as shown in FIG.
By irradiating the light-emitting surface 5 with an electron beam from the cathode 2 through the grid 4, sufficiently bright light can be emitted under the low-speed electron beam.

In the description of the embodiments of the present invention, tin-doped indium oxide (In2O3:S) is used as an indium oxide-based conductive material.
n) is selected, but the results are almost the same no matter which indium oxide-based conductive material used in the present invention is used or which combination is used.

Next, embodiments of the present invention will be described.

Example 1 Ag activation amount is 10-29/9 (ZnO.2CdO
．． 8) After thoroughly mixing a mixed powder of S:Ag phosphor and tin-doped indium oxide in a weight ratio of 1:1 in a mortar, it was heated with a low-speed electron beam in the apparatus shown in Figure 2. When excited, it emitted bright red light.

When mixed powders with various mixing weight ratios are excited with a slow electron beam at an accelerating voltage of 20 V, bright light is emitted at mixing weight ratios of 14/1 to 1/14, as shown in FIG.

In particular, the brightness is high from 4/1 to 1/4. In addition, the emission spectrum when excited by a slow electron beam is as shown in Figure 4, and the emission brightness characteristics with respect to acceleration voltage are as shown in the solid line in Figure 5. Light emission started at a considerably lower voltage than that using the method using the method, and sufficient brightness for practical use was obtained at an accelerating voltage of several tens of volts. Even when other indium oxide-based conductive materials were used in place of the tin-doped indium oxide used above, the same results as described above were obtained.

As is clear from the above examples, in the luminescent material obtained by the present invention, the mixing weight ratio of the phosphor and the indium oxide conductive material, that is, the value of the phosphor/conductive material is 1.
If it is smaller than /14, the amount of phosphor is small and the light emission will be very weak, while if it is larger than 14/1, the amount of conductive material is small and the phosphor will not be sufficiently conductive, resulting in a slow electron beam. Upon excitation, the fluorescent surface becomes charged and no longer emits light. Therefore, the mixing weight ratio of the phosphor and the conductive material is 14
/1 to 1/14, preferably 4
/1 to 1/4. As mentioned above, silver-activated phosphor (Zn, ?XCdx) S:Ag (however, 0.6≦x≦0.
9) and indium oxide-based conductive materials exhibit a luminance that can be used practically when excited with slow electron beams, and the only green-emitting phosphor (ZnO:Zn) that has been used as a phosphor for excitation with slow electron beams has been used in the past. This luminescent material enables color display by low-speed electron beam excitation, and the industrial value of the present invention is great.

[Brief explanation of drawings]

FIG. 1 is a graph showing the layer resistance of a disk formed by pressure molding of tin-doped indium oxide powder versus the ratio of stannic oxide to indium oxide. Figure 2 is a cross-sectional view showing a low-speed electron beam excitation device, where 1 is a vacuum chamber, 2 is a cathode, 3 is irradiated electrons, 4 is a grid, and 5
6 is a light emitting surface material, 6 is an anode, and 7 is an insulating substrate. Figure 3 is a diagram showing the change in luminescence intensity with respect to the mixing weight ratio of the (ZnO.2CdO.8)S:Ag phosphor and In2O3:Sn in the present invention, and Figure 4 is the emission spectrum of the luminescent material of the present invention. FIG. 5 is a diagram showing emission brightness characteristics with respect to excitation voltage, where the solid line is for the present invention and the dotted line is for the conventional one.

Claims (1)

[Claims] 1 The composition formula is expressed as Zn_1_-_xCd_xS:Ag (0.6≦x≦0.9), and the activation amount of silver is
10^-^5 to 5 for n_1_-_xCd_xS1g
x10^-^2g of phosphor and a tin-doped indium oxide-based conductive material (In_2O_3:XSnO_
2, but 0.008<x≦0.1) and 14:1 to 1:
A luminescent material characterized by being mixed at a weight ratio of 14 to 14.