JPS5943073B2 - 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, a material made by mixing an appropriate amount of a stannic oxide-based conductive material and a europium-activated phosphor. This invention relates to a light-emitting device for excitation of slow electron beams in which a phosphor is given conductivity.

Conventionally, the self-activated zinc oxide phosphor (
ZnOZn) 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 recent years, many phosphors using transition metal ions, rare earth element ions, etc. as activators have been developed.

It has long been known that when these metal ions in various solids or liquids are irradiated with electron beams, ultraviolet rays, near-infrared light, etc., they exhibit bright line-like emission spectra that are unique to each metal ion. In particular, it has attracted attention and research as a laser material. Among these studies, for example, YAG:Nd
While lasers were put into practical use, it was also discovered that cerium, europium, erbium, etc. can emit light with high efficiency when contained in various matrixes, and since then, phosphors using rare earth element ions as activators have become popular. was studied. As a result, many products have been put into practical use, among which yttrium oxide activated with europium, yttrium oxysulfide, and yttrium panadate are particularly important, and are used as red components in color televisions, high-pressure mercury lamps, etc. These phosphors are excited by high-speed electron beams of several KV or more, ultraviolet rays, etc.
Emits high brightness.

However, it cannot be used as a phosphor for fluorescent display tubes because it hardly emits light under low-speed electron beam excitation of several IOV or less. As a result, the uses of fluorescent display tubes that emit green light due to the self-activated zinc oxide phosphor described above are limited.
In order to expand the use of display tubes, there has been a strong demand for the development of luminescent materials that emit bright light other than green. Therefore, in the laboratory, Y2O2 is a phosphor that emits colors other than green, such as red, yellow, and blue when excited by slow electron beams.
S:EU, ZnS:Ag, etc. have been developed that have been made conductive with In2O3, but the reality is that they have not been put to practical use in display tubes because the conductivity is insufficient. be.

In order to meet the above-mentioned needs, the present inventors conducted various research aimed at obtaining a luminescent material that emits light in a color other than green by low-speed electron beam excitation. It was found that it is necessary to prevent electron charging on the surface of the phosphor particles in low-speed electron beam excitation.

Based on these facts, we developed a europium-activated acidic weak yttrium lanthanum gadolinium phosphor [(Y1-x-YLaxGdy)203:E
u, provided that O≦x≦1, 0≦y≦1, x+y≦1), europium activated yttrium lanthanum gadolinium oxysulfide phosphor [(Y1-x-YLaxGdy) 202S: EU
, provided that O≦X≦1, 0≦y≦1, x+y≦1], and europium-activated yttrium lanthanum gadolinium vanadate phosphor (Y1-x-YLaxGdyVO4'E
u, provided that O≦X≦1, 0≦y≦1, x+y≦1), and a mixture of indium oxide (In2O3) conductive material doped with an appropriate amount of tin within a certain range. It was found that when excited with a slow electron beam, it emits high-intensity red light.

Although tin-doped indium oxide conductive material is an oxide, tin acts as a donor and the free carrier becomes 102
It increases until it reaches about 1cm-3, and its resistivity becomes 10-
4~1 [2Ω? Therefore, it is effective for lowering the threshold voltage of light emission due to slow electron beam excitation. That is, let the apparent conductivity of a powder-filled layer like a normal fluorescent display tube be σa1, and the apparent permittivity be εa, and Q in this conductor layer.
Suppose that a charge O(X, Y, Z) is spatially distributed, and at time t it becomes q(X, Y, Z) at a point (X, Y, Z).
, Z, t).

In the process of charge relaxation, as in the case of a continuous medium, assuming that the equation of current continuity r/n holds true, solutions to (1) to (3) can be obtained.

However, t 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 (ZuO:Zu) 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/CTrL, the relaxation time will be about 5 seconds and the threshold voltage for light emission will be several volts, similar to zinc oxide phosphors and tin oxide phosphors. The tin-doped indium oxide conductive material that meets these requirements has a layer resistance value of 10Ω or less, as shown in Figure 1, that is, SnO/
The weight percent of In2O3 is 0.80! ) to 10%. Conventionally, zinc oxide (ZnO) or undoped indium oxide has been used for the purpose of imparting conductivity to a phosphor, but compared to the above-mentioned indium oxide-based conductive materials, both have low specific resistance. is about 3 to 4 orders of magnitude larger. Therefore, when using an indium oxide-based conductive material such as zinc oxide or undoped indium oxide, electrical conductivity is more fully imparted to the phosphor, and light emission starts from a lower excitation voltage, which is advantageous in the present invention. is suitable for the purpose of Even if indium oxide, which is a component of the luminescent material according to the present invention, is doped with germanium, lead, or silane in addition to tin, the resistivity similarly decreases, and it constitutes an effective slow electron beam-excited luminescent material. sell. To create these conductive materials, a solution of at least one salt of tin, germanium, lead, or silicon is added to indium oxide powder in an amount corresponding to the amount added, and the mixture is evaporated to dryness. It may be fired in air at 100°C to 1300°C. In addition, Y, -x-YLaxG, which is the other component of the luminescent material,
dyVO4:Eu is generally produced by a force method as described below. However, in any phosphor, O≦X≦1,
0≦y≦1, x+y≦1. (Y1-x-YLax
Gdy)203:Eu fluorophore is Y2O3(1-x-y)
Mol, La2O3x mole, Gd2O3y mole and a predetermined amount of EU2O3 are dissolved in nitric acid, and an oxalic acid solution is added thereto to obtain a coprecipitated rare earth oxalate.

Next, this coprecipitated powder is thermally decomposed in air to obtain a mixed powder of rare earth compounds. Boron oxide (
B2O3), sodium carbonate (Na2CO3), etc. in air at 1000°C or higher, preferably 13000°C.
The desired (Y
1-x-YLaxGdy)203:Eu phosphor is obtained.

The amount of europium oxide (EU2O3) as an activator is 10-2 to 1.5 x 10-19, preferably 5 x
It is 10-2 to 6×10-29. Also, (Y1-x-
YLaxGdy)202S:Eu fluorophore is the above (Y1
-XyLaxGdy) f) 3: Add the same rare earth oxide mixed powder as when obtaining the Eu phosphor in a hydrogen sulfide (H2S) atmosphere, or add 20 to 40% by weight of sulfur (S) to the mixed powder.
and 20 to 40% by weight of sodium carbonate, mixed, and calcined in air at 12,000C to 1,500C for several hours. The amount of europium oxide activator is 10-2 to 1.5 x 10-19, preferably 5 x
It is 10-2 to 6×10-29.

The Y1-x-YLaxGdyVO4:Eu phosphor is prepared by adding a predetermined amount of vanadium pentoxide ( V2O5), mixed, and calcined in air at 1000°C to 1100°C for several hours. The amount of activator europium oxide is the base Y1-
10-2 to 10 for x-YLaxGdyVO4l9
5×10−19, preferably 7×10−2 to 8×
It is 10-29. On their own, the above-mentioned phosphors emit bright red light under high-speed electron beam excitation with an accelerating voltage of several kilovolts or more, but they hardly emit light under slow electron beam excitation with an accelerating voltage of several tens of kilovolts or more. do not have.

The present invention provides a luminescent material that emits bright red light even at an accelerating voltage of several tens of volts or less by thoroughly mixing at least one of the above-mentioned phosphors and an indium oxide conductive material in a mortar, ball mill, etc. be. The luminescent material powder obtained by the present invention is set on the luminescent surface 5 in a low-speed electron beam excitation device as shown in FIG.
By irradiating the light-emitting surface 5 with an electron beam from the electron beam 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), but the results are almost the same even if an indium oxide-based conductive material doped with something other than tin is used.

Next, embodiments of the present invention will be described. Example 1 Y2O3:Eu with Eu activation amount of 5 x 10-2g/9
The weight ratio of (x-y-0) and In2O3:Sn is l:1
After thoroughly mixing the powder mixture in a mortar, it emitted bright red light when excited with a slow electron beam in the apparatus shown in FIG.

Similarly, when mixed powders with various mixed weight ratios are excited with a slow electron beam at an accelerating voltage of 20 V, bright light is emitted at mixed weight ratios of 14/1 to 1/14, as shown in FIG. 3A.

In particular, the brightness is high from 4/1 to 1/4. Yztrium (
La2O3 where 7) was replaced with lanthanum (La) and gadolinium (Gd): EU (x = 1, y = 0), Gd2O
3: Eu (x=0, y=1) or any other X
, y (however, O≦x≦1, 0≦y≦1, x+y<1) (Y1-X-YLaXG(1y) 203:Similar results were obtained for mixed powder with In2O3:Sn using Eu. was gotten.

For example, in this example, Y2O3:EU/IU2O3:Snl
When the /1 mixed powder is excited with a slow electron beam, the emission vector is as shown in Figure 4A, and the emission brightness characteristics with respect to the accelerating voltage are as shown in the solid line in Figure 5, which is indicated by the dotted line. Light emission begins at a much lower voltage than with zinc oxide or undoped indium oxide as the conductive material;
At an excitation voltage of several tens of volts, sufficient brightness for practical use was obtained.

The above (Y1-x-YLaxGdy)203:Eu (
Y, -XyLaxGdy)202S:Eu or Y1-
Similar results were obtained when replacing x-YLaxGdyVO4:Eu, and FIGS. 3B and C show Y2O2S:
EUYVO4: The luminance changes depending on the weight ratio of EU and N2O3:Sn, and Fig. 4 B and C show Y2O2S:
This is an emission spectrum of a luminescent material consisting of EU, YVO4:EU, and In2O3:Sn. N2 used above
Even when other indium oxide-based conductive materials were used in place of O3:Sll, the same results as described above were obtained.

Example 2 Y2O3:EU with Eu activation amount of 5 x 10-29/9
and Y2O2S:EU (51n203:Sn) in a weight ratio of 1:1:2 and the powder was thoroughly mixed in a mortar. When the same experiment as in Example 1 was carried out, the same results as in Figs. 3 and 5 were obtained. was gotten.

The results of this example were similar to those of mixed powders of other combinations of phosphors and other indium oxide-based conductive materials. As is clear from the above examples, in the luminescent material obtained by the present invention, the weight ratio of the phosphor and the indium oxide-based conductive material, that is, the value of the phosphor/conductive material, is lower than 1/14. If it is smaller than 14/1, the amount of phosphor is small and the emission will be very weak. On the other hand, if it is larger than 14/1, there is not enough conductive material and the phosphor is not sufficiently conductive and cannot be used with slow electron beam excitation. Electrostatic charging occurs on the fluorescent surface and it no longer emits light. Therefore, the mixing weight ratio of the fluorescent material and the conductive material must be 14/1 to 1/14, preferably 4/1 to 1/4. As mentioned above, europium-activated (Y1-x-YLaxGdy)2
03:Eu, (Y1-x-YLaxGdy)202S:
At least one of Eu and Y1-x-YLaxGdyVO4:Eu and an indium oxide-based conductive material in a ratio of 14/1
The luminescent material of the present invention, mixed at a weight ratio of ~1/14, exhibits a luminance that can be used practically by low-speed electron beam excitation, and is the only green-emitting phosphor (ZnO:
Whereas Zn) was used, it emits red light and
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 the drawing]

FIG. 1 is a graph showing the layer resistance of a lunar plate made of pressure-molded tin-doped indium oxide powder versus the ratio of stannic oxide to indium oxide.

Claims (1)

[Claims] 1 Europium activated yttrium lanthanum gadolinium oxide phosphor [(Y_1-x-yLaxGdy)_2O_
3: Eu, but 0≦x≦1, 0≦y≦1, x+y≦1]
, europium-activated yttrium lanthanum gadolinium oxysulfide phosphor [(Y_1-x-yLaxGby)_2O_
2:S:Eu, however, 0≦x≦1, 0≦y≦1, x+y≦
1] and europium-activated yttrium lanthanum panadate gadolinium phosphor (Y_1-x-yLaxGd
yVO_4: Eu, however, 0≦x≦1, 0≦y≦1, x+
y≦1) and an indium oxide conductive material doped with tin (In_2O_3 xSnO_2
, but 0.008≦x≦0.1) and 14:1 to 1:1
A luminescent material characterized by being mixed at a weight ratio of 4 to 4.