JP3942766B2 - Phosphor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a phosphor whose conductivity is increased by reduction treatment.
[0002]
[Prior art]
The so-called low-energy electron beam phosphor used at an acceleration voltage of 1 kV or less is required to have a low resistance of the phosphor itself. Currently, a so-called sulfide phosphor such as ZnS: Ag is known as a material that satisfies such conditions.
[0003]
[Problems to be solved by the invention]
However, sulfide phosphors have problems in terms of reliability, such as being decomposed and scattered by electron beam irradiation, causing deterioration of the cathode in the device, and thus reducing the lifetime of the device.
[0004]
In order to solve such a problem, a material having a composition that is difficult to be decomposed by an electron beam is required, but most of such a material is often an insulator. There is also a proposal to reduce the resistance of the phosphor film by adding a conductive material such as InO ₂ to the insulating phosphor. However, in this method, the reactive current due to the conductive material is increased, and the heat generated due to this increases the reliability.
[0005]
If the resistance value of the high-resistance phosphor can be lowered by some method, it can be used for a low-speed electron beam.
[0006]
As a high-resistance phosphor used at an acceleration voltage of 5 kV or more, a Y ₂ O ₃ : Eu phosphor that emits red light with high efficiency has been used as a phosphor such as a cathode ray tube or a projection tube. Are known. However, this phosphor has a high resistance itself, and in a region of a low-speed electron beam of 1 kV or less, charge-up occurs and does not show sufficient light emission.
[0007]
Therefore, such a high-resistance phosphor cannot be used at all in a normal fluorescent light emitting tube having a driving voltage of several tens of volts at most, and in a field emission light emitting device (FED) having a driving anode voltage of about 400 to 1 kV. However, it is difficult to obtain sufficient light emission.
[0008]
The present invention provides a phosphor having high resistance that has been conventionally used at a high acceleration voltage, imparting conductivity to the phosphor without impairing the luminous efficiency of the phosphor itself, and reducing its resistance by a simple method. It is aimed.
[0009]
[Means for Solving the Problems]
The phosphor described in claim 1 is a phosphor annealed in a reducing atmosphere, and is an A ₂ O _{3 -X} : Eu phosphor used in an FED or a fluorescent display tube (where A is Y or It is a rare earth element made of Gd, 1 × 10 ⁻⁶ <X <5 × 10 ⁻⁴ ) .
[0012]
【Example】
(1) Example 1
4 kg of raw material (Y _0.965 Eu _0.035 ) ₂ O ₃ and 4.0 kg of NaCl as a flux are weighed and mixed thoroughly. This is filled in a crucible and baked at 1400 ° C. for 6 hours. The sample thus obtained is put into pure water, stirred and decanted, and the flux is washed with water. Then, after dehydrating and drying at 110 ° C., it is passed through a sieve to obtain a Y ₂ O ₃ : Eu phosphor. A part of this sample is separately provided as a comparative phosphor.
[0013]
400 g of the above Y ₂ O ₃ : Eu phosphor is filled in a crucible and annealed by changing the reduction amount in a carbon reducing atmosphere at a temperature of 900 to 1300 ° C. and in a range of 1 to 4 hours. object through a sieve after cooling of Y ₂ O _3-X: obtaining Eu phosphor (reduced phosphor).
[0014]
The comparative phosphor and the reduced phosphor were mounted on anodes of different fluorescent display tubes, and the light emission states were compared. That is, each phosphor is made into a paste using a vehicle containing an ethyl cellulose binder, applied to the ITO electrode on the anode substrate by screen printing, and baked in the atmosphere at 500 ° C. to remove the binder, and the phosphor-coated anode substrate Was made. Using this anode substrate, a filament, a grid and the like were mounted, and the container part was further sealed to produce a fluorescent display tube.
[0015]
FIG. 1 shows the relative relationship between the oxygen defect amount and the luminance expressed by the ratio of oxygen and yttrium measured by using mass spectrometry such as SIMS when the anode voltage is 400V. FIG. 2 similarly shows the relationship with the light emission start voltage. FIG. 3 shows the relationship between the amount of oxygen defects and the luminance maintenance rate in the life test.
[0016]
In FIG. 2, the fact that the light emission starting voltage decreases as the oxygen defect amount increases means that the charge-up on the phosphor surface is eliminated at a low voltage, that is, the phosphor resistance value decreases. It shows that.
[0017]
From the above results, it has been found that the reduction treatment has an effect on the initial and life characteristics. On the other hand, if the intensity of reduction is too strong, oxygen defects inhibit light emission. Therefore, the value of X is optimally in the range of 1 × 10 ⁻⁶ to 5 × 10 ⁻⁴ .
[0018]
In this embodiment, the phosphor is reduced in a carbon reducing atmosphere. However, as the carbon reducing atmosphere, carbon powder may be directly mixed with the phosphor, or a double crucible may be used.
[0019]
(2) Example 2
The (Y _0.955 Eu _0.035 Sm _0.01 ) ₂ O ₃ phosphor was also evaluated by changing the reduction intensity. As a result, the light emission start voltage was lowered as in Example 1, the initial light emission efficiency when the oxygen defect amount X = 1 × 10 ⁻⁵ was 130%, and the lifetime characteristics were improved about 10 times.
[0020]
In Examples 1 and 2 described above, the concentration of the luminescent center is particularly good in the range of 0.1 mol% / Y to 10 mol% / Y, and the concentration of the coactivator is in the range of 0 mol% / Y to 5 mol% / Y. Results were obtained.
[0021]
(3) Example 3
A phosphor obtained by adding a substance similar to that described above to Gd ₂ O ₃ as the phosphor matrix was also tested in the same manner as in Examples 1 and 2. As a result, the same effect as in Examples 1 and 2 was obtained.
[0022]
(4) Example 4
In addition, experiments were conducted in many combinations with other rare earth elements and other various additive substances. As a result, in general, A ₂ O _{3 -X} : Re phosphor (where A is a rare earth element, Re is selected from Eu, Tb, Er, Tm, Dy, Ho, Nd, Pr, Sm, Ce) The same effect due to the improvement in conductivity was almost the same as in Example 1-3.
[0023]
In the embodiment described above, the phosphor is reduced in a carbon reducing atmosphere. However, the reduction may be performed in a hydrogen atmosphere. In particular, when the phosphor applied to the FED is reduced in a hydrogen atmosphere, the hydrogen stored in the phosphor is released in the envelope after mounting, improving the electron emission performance of the emitter, etc. The effect of improving the atmosphere is obtained.
[0024]
【The invention's effect】
According to the phosphor of the present invention, the conductivity is improved by reduction, and it is possible to cope with a low anode voltage that cannot be used conventionally. For example, the phosphor of the present invention can be sufficiently used for an FED having an anode voltage of about 1 kV, and can be used for a fluorescent display tube having an anode voltage of several tens of volts by adding a conductive material such as In. be able to.
[Brief description of the drawings]
FIG. 1 is a graph showing a relationship between an oxygen defect amount and luminance expressed as a ratio of oxygen and yttrium at an anode voltage of 400 V in Example 1 as a relative value.
2 is a graph showing a relative value of the relationship between the amount of oxygen defects expressed as a ratio of oxygen and yttrium and the light emission start voltage under the same driving conditions as in FIG. 1 in Example 1. FIG.
3 is a diagram showing the relationship between the amount of oxygen defects and the luminance maintenance rate in a life test under the same driving conditions as in FIG. 1 in Example 1. FIG.

Claims (1)

A phosphor that has been annealed in a reducing atmosphere and is used for FED or fluorescent display tube, A ₂ O _3-x : Eu phosphor (where A is a rare earth element consisting of Y or Gd , 1 × 10 ⁻⁶ <X <5 × 10 ⁻⁴ ).

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