JPH10212476A - Phosphor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a phosphor designed to reproduce more colors than desired ones without causing deterioration in display quality of a fluorescent display tube by sticking tungsten oxide (WO3 ) to a phosphor and mixing a pigment therewith. SOLUTION: This phosphor is obtained by sticking (B) WO3 to (A) a phosphor emitting light by the collision of electrons and mixing (C) a pigment therewith. For example, ZnO:Zn phosphor is cited as the component A and, e.g. pigment particles comprising TiO2 -ZnO-CoO-NiO are cited as the component C. The particle diameter of the components B and C is preferably smaller than that of the ZnO:Zn phosphor. Since the component C is an insulating material, the charge-up is readily caused when used as the phosphor to prevent the emission of the ZnO:Zn. Thereby, indium oxide is preferably added to the component C to suppress the charge-up.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phosphor used for a fluorescent display tube.

[0002]

2. Description of the Related Art Phosphors used in fluorescent display tubes are usually called low-speed electron-beam-excited light-emitting phosphors and have a wavelength of 100 eV.
It is a phosphor that can obtain practical luminance with a moderate acceleration voltage. Unlike high voltage excitation of a cathode ray tube or the like, the penetration depth of an electron beam is said to be several nm at most. Therefore, since the fluorescent display tube has a low electron beam transmission capability, a metal back process such as a cathode ray tube cannot be used. For this reason, the resistance of the phosphor material matrix is reduced, or the apparent resistance is reduced by mixing a conductive material to prevent charging due to excitation in a region where the secondary electron emission ability is 1 or less, and to generate excitation light. The starting voltage is reduced.

The requirements for the phosphor material for a fluorescent display tube as described above include the following. Low resistance. Light emission start voltage is low. High luminous efficiency at low acceleration voltage and no luminance saturation. In particular, there should be few defects on the surface of the phosphor particles, stable emission state by slow electron excitation, and no decomposition or the like. Be stable against heat treatment in the fluorescent display tube manufacturing process. Do not emit substances that may adversely affect the oxide filament during excitation light emission.

[0004] In recent years, with the expanding use of fluorescent display tubes, demands for multicolor display have increased. In the early days of flat-type fluorescent display tubes, as a phosphor that can obtain practically sufficient luminance with a low-speed electron beam with an operating voltage of about 10 to 50 V,
There was no other than green-emitting ZnO: Zn. But I
Since the development of the technology for reducing the resistance using a conductive material such as n ₂ O ₃ , multicolor light emission using a sulfide phosphor or the like has been made possible to some extent. For example, blue-emitting ZnS: Cl
+ In ₂ O ₃ and yellow-green ZnS: Cu, Al + In ₂ O ₃ .

[0005]

However, although multi-color light emission has been possible to some extent in the past, it has not been possible to completely reproduce a desired color. For multicolor light emission, a sulfide phosphor is used. When the phosphor is irradiated with electrons, sulfur is scattered from the sulfide. The scattering of the sulfur deteriorates the cathode and reduces the electron emission function of the cathode. As described above, when the electron emission function of the cathode is reduced, the brightness is reduced, and uneven interference of electrons is generated with respect to the potential distribution around the anode, and as a result, the display quality is significantly reduced. This will shorten the life of the tube.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made to solve the above-mentioned problems, and an object of the present invention is to make it possible to reproduce more colors than desired without deteriorating the display quality of a fluorescent display tube. With the goal.

[0007]

The phosphor of the present invention is a mixture of a phosphor which emits light upon collision with electrons and WO ₃ attached to the phosphor at a predetermined ratio, at a predetermined ratio. And a pigment. By configuring the phosphor in this way, if a predetermined amount of pigment of a desired color is mixed, the phosphor has a luminescent color defined by the pigment.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. Embodiment 1 In Embodiment 1, a phosphor is constituted by a ZnO: Zn phosphor to which 1.0 wt% of tungsten oxide (WO ₃ ) is attached and a pigment. First, a pigment is added so that a more diverse color can be developed. The added pigment particles selectively reflect, transmit and absorb the light emitted from ZnO: Zn, and function as a kind of optical filter. Therefore, a desired emission color can be obtained by selecting and adding an appropriate pigment. In addition, since the filter function is exhibited also for external light, the contrast can be improved.

For example, TiO ₂ -ZnO-CoO-N
Pigment particles composed of iO and having a particle diameter of about 1.1 μm
By adding to Zn, a green emission color can be obtained as shown by a white circle in FIG. In addition, TiO ₂
By adding pigment particles composed of —Sb ₂ O ₃ —Cr ₂ O _{3 having} a particle size of about 0.8 μm to ZnO: Zn, a yellow emission color can be obtained as shown by a white circle in (b). . Further, by adding pigment particles made of CoO—Al ₂ O _{3 having} a particle size of about 1.2 μm to ZnO: Zn, a light-blue (bluish) emission color can be obtained as shown by a white circle in (c). it can. Then, by adding pigment particles of Fe ₂ O _{3 having} a particle size of about 1 μm to ZnO: Zn, a red emission color can be obtained as shown by a white circle in (d). In addition, the black circles indicate a color-developed state in which no pigment is added.

Incidentally, it is preferable that the particle size of the pigment to be added is appropriately small. In order for the light from ZnO: Zn to be effectively reflected and absorbed by the pigment particles, ZnO: Z
It is better to cover the ZnO: Zn particles with particles smaller than n so as not to completely cover them. For example, the particle size of the pigment to be added is preferably 5 μm or less. Further, the amount of the pigment to be added is preferably set to about 30% by weight or less. When an amount exceeding this amount is added, a decrease in luminance is caused and unevenness of light emission becomes remarkable. Also,
If the amount of the pigment is too small, the effect of changing the luminescent color is lost. Therefore, the amount of the additive that can most effectively balance the luminance and the filter effect is appropriately 1 to 25% by weight.

Incidentally, the phosphor is used in an evacuated environment such as a fluorescent display tube, and is heated by irradiation with an electron beam or the like. Therefore, when a pigment is added to obtain a desired emission color, a small amount of gas is released from the pigment. When the gas is released in this manner, the gas is adsorbed on the ZnO: Zn surface, which causes a deterioration in initial luminance, change with time, high-temperature storage characteristics, and the like. Therefore, Zn
By attaching tungsten oxide to O: Zn, it is possible to improve the initial luminance, the high-temperature storage characteristics, and the luminance stability of the phosphor. The reason we can improve is Z
This is because when the tungsten oxide is attached to the surface of nO: Zn, the surface of the phosphor is immobilized and a decrease in the light emission rate due to gas adsorption can be prevented.

Here, the relationship between the particle size and the amount of tungsten oxide added is the same as in the case of the pigment described above.
It can be considered as a relationship between the contact ratio with Zn and the covering ratio. That is, the effect of tungsten oxide is Zn
O: When considered to be exerted by contact with Zn,
The smaller the particle size, the better. The average particle size of ZnO: Zn is 2 to 9 μm, among which the commonly used particle size is 3 to 5 μm. When the particle diameter of tungsten oxide is small, the specific surface area is increased in terms of weight%, and when the same amount is added as in the case where the particle diameter is large, ZnO: Z
n coverage = contact rate increases.

Therefore, the optimum amount of addition differs depending on the particle size. As a matter of course, when the contact ratio is increased, the coverage increases, and when the coverage is too large, the luminous efficiency is reduced. Here, as a method of adding the tungsten oxide with a reduced particle size, for example, ammonium paratungstate may be coated on ZnO: Zn and fired at a high temperature (APT coating). Ammonium paratungstate decomposes at a temperature of 300 to 400 ° C. to form fine particle tungsten oxide.

FIG. 2 is an explanatory diagram showing the effect of improving the initial luminance with respect to the added amount of tungsten oxide. FIG. 2 (a)
Indicates a case where the phosphor is manufactured by the APT coat,
(B) shows a case where a phosphor is formed by mixing tungsten oxide 0.7 μm powder, and (c) shows a case where a phosphor is formed by mixing tungsten oxide 3 μm powder. As is apparent from FIG.
The highest initial luminance is obtained when about 0.03 wt% of tungsten oxide is added by the T coat.
Further, when a phosphor is formed by mixing a 3 μm powder of tungsten oxide, if the amount of addition exceeds 5 wt%, the obtained brightness falls below 100%. For this reason,
The addition amount of tungsten oxide which exerts an effect on the improvement in brightness is in the range of 0.03 to 5 wt%.

FIG. 3 is an explanatory diagram showing a change in luminance due to high temperature storage. 3A shows a case where a phosphor is manufactured by APT coating, FIG. 3B shows a case where a phosphor is formed by mixing a 0.7 μm powder of tungsten oxide, and FIG. 3 shows a case in which a phosphor is formed by mixing 3 μm powder. As shown in FIG. 3, when the phosphor is manufactured by the APT coating, the high-temperature storage characteristics are good even if the amount of the phosphor added is small. Therefore, it is better for the addition of tungsten oxide to have a smaller particle size.

Embodiment 2 Hereinafter, a second embodiment of the present invention will be described.
In the second embodiment, indium oxide (In ₂ O ₃ ) is added to a phosphor composed of a ZnO: Zn phosphor to which tungsten oxide (WO ₃ ) is attached and a pigment. By adding a pigment, a wider variety of colors can be developed. However, since the pigment is an insulator, it is easy to charge up when used as a phosphor, thereby inhibiting the emission of ZnO: Zn. For this purpose, indium oxide is added to the pigment particles. This is because charge-up can be suppressed by adding indium oxide to the pigment.

Since ZnO: Zn is conductive, the route for taking charge of the pigment is pigment → ZnO: Zn → anode. By adding indium oxide to this, besides, a path for releasing charge, such as a pigment → indium oxide → anode, can be increased. For example, if the pigment ratio is 15
%, Indium oxide may be added in a maximum range of 5%. Since this indium oxide does not emit light even when irradiated with electrons, if it is added in excess of 5%, the light emission of ZnO: Zn will be inhibited. Therefore, it is better not to add more than 5%. .

In particular, when the phosphor layer is formed in an area larger than the anode and there is a portion of the phosphor layer which protrudes larger than the anode, the protruding portion may not emit light unless indium oxide is added. . In the protruding portion, the above-mentioned phenomenon occurs because there is no anode for releasing the charge in the lower layer, and the pigment is added so that the lateral conductivity of the phosphor layer is reduced. In such a case, by adding indium oxide, a path for releasing the charge can be formed in the lateral direction, and the protruding portion can be made to emit light. Since indium oxide itself is light yellow, the pigment particles made of CoO—Al ₂ O ₃ described above are coated with Zn.
When a blue light emission color is obtained by adding to O: Zn, a color improving effect can also be obtained. This is probably because indium oxide itself has spectral characteristics different from those of the pigment, and thus has a synergistic effect when combined with the pigment.

[0019]

As described above, according to the present invention, a phosphor mixed at a predetermined ratio with a phosphor which emits light upon collision with electrons, WO ₃ adhered to the phosphor at a predetermined ratio, and the like. And made up of By configuring the phosphor in this way, if a predetermined amount of pigment of a desired color is mixed, the phosphor has a luminescent color defined by the pigment. As a result, according to the present invention, various luminescent colors can be obtained without using a phosphor containing sulfur or the like, so that if this is used for a fluorescent display tube, the display quality of the fluorescent display tube does not deteriorate. Thus, the effect of reproducing more colors than desired can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a color improvement effect by chromaticity.

FIG. 2 is an explanatory diagram showing an effect of improving initial luminance with respect to an added amount of tungsten oxide.

FIG. 3 is an explanatory diagram showing a change in luminance due to high temperature storage.

Claims (5)

[Claims] 1. A phosphor which emits light upon collision with electrons, WO ₃ attached to the phosphor at a predetermined ratio, and a pigment mixed at a predetermined ratio. Phosphor. 2. The phosphor according to claim 1, wherein In ₂ O ₃ is attached to the pigment at a predetermined ratio. 3. The phosphor according to claim 1, wherein the pigment is Ti, Zn, Co, Ni, Sb, Cr, A
A phosphor characterized by containing any one of oxides of 1, Zr, V, Sn, and Fe. 4. The phosphor according to claim 1, wherein the average particle diameter of the pigment and WO ₃ is smaller than the average particle diameter of the ZnO: Zn phosphor. . 5. The phosphor according to claim 1, wherein the average particle diameter of the In ₂ O ₃ is smaller than the average particle diameter of the ZnO: Zn phosphor.