JP2967559B2 - Phosphor and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method of forming a diamond thin film layer on a phosphor particle surface by a microwave plasma method and utilizing the excellent thermal conductivity, light transmission characteristics and chemical stability of diamond. The present invention relates to a novel phosphor having improved temperature quenching, improved chemical stability and lifetime, and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, a microwave plasma method has attracted attention as a method for stably synthesizing film diamond on a substrate surface. In this microwave plasma method, for example, as shown in JP-A-58-110494, a mixed gas of hydrogen and methane permeated through microwave plasma is introduced onto a substrate surface heated to 300 ° C. to 1300 ° C. Then, diamond can be deposited on the substrate surface by thermal decomposition of hydrocarbons.

[0003]

However, in the above-mentioned microwave plasma method, diamond is deposited on the surface of a substrate such as molybdenum or a silicon wafer. For example, Japanese Patent Application Laid-Open No. Sho 59-133731.
Japanese Patent Application Laid-Open No. 63-270394 and Japanese Patent Application Laid-Open No. Sho 63-270394 have proposed methods of forming a fluidized bed and depositing diamond on the powder surface. The apparatus is complicated and is not suitable for continuous processing in the case of mass production. Also, fluidization of fine particles of several μm like phosphor particles is extremely difficult, and development of a new method for depositing diamond on the surface of powder particles of several μm is desired.

[0004] On the other hand, in the case of phosphors, despite the recent demand for higher luminance of the light-emitting surface in accordance with higher definition and larger screens of televisions and displays, a higher load on the excited electron beam has been desired. The high current causes problems such as luminance saturation characteristics, temperature characteristics, and life of the phosphor particles on the phosphor screen, and the improvement of the brightness of the phosphor screen is stagnant. In particular, in a projection tube having a high current and voltage for exciting the phosphor, it is remarkably desired to improve the luminance saturation characteristics, the temperature characteristics, and the life of the phosphor.

Accordingly, an object of the present invention is to provide a novel phosphor having improved temperature quenching, chemical stability and lifetime by utilizing the excellent thermal conductivity, light transmission characteristics and chemical stability of diamond. And a method for manufacturing the same.

[0006]

In order to form a high-quality diamond thin film layer on the surface of a phosphor particle by a microwave plasma method, the present inventors have first adapted to a phosphor particle of several μm, and We developed a new device that can continuously operate powder particles, which is useful in practice, and succeeded in forming a diamond thin film layer of a desired thickness on the surface of phosphor particles.

That is, the phosphor of the present invention is characterized in that it has a diamond thin film layer deposited by a microwave plasma method on the surface of the phosphor particles.

Further, according to the method for producing a phosphor of the present invention, a microwave plasma is generated in a part of a rotary reaction vessel which is hermetically shut off from the outside air and the inside of which is maintained at a reduced pressure, and the microwave plasma is generated in the microwave plasma generation region. At the same time as introducing the hydrogen-methane mixed gas, the phosphor particles are continuously supplied to the microwave plasma generation region by the rotation and gradient of the rotary reaction vessel,
Thereby, a diamond thin film layer is formed on the phosphor particle surface.

[0009]

[Function] By forming a uniform diamond thin film layer on the phosphor particle surface by microwave plasma method,
The excellent thermal conductivity, light transmission properties and chemical stability of diamond can be used to improve temperature quenching, chemical stability and lifetime. This is itemized below. In particular, by coating a diamond thin film layer on a phosphor used when the temperature rise of the phosphor film is large, for example, a phosphor for a projection tube, heat dissipation can be achieved and luminance degradation due to temperature quenching can be improved. Due to the uniform diamond thin film layer, there is no ion burning and no change in the composition of the particle surface.
No color center is formed due to diffusion of impurities from the outside. Conventionally, it is possible to improve a phosphor which is remarkably deteriorated by hydrolysis, for example, an alkaline earth metal salt phosphor, a lanthanum sulfide phosphor and the like. Since the surface of the phosphor is the same type of diamond thin film layer, the coating properties can be made uniform even if the base composition of the phosphor is different. Since the phosphor surface is a uniform diamond thin film layer, adhesion to the glass surface to be coated can be achieved.

Further, according to the method for producing a phosphor of the present invention,
A diamond thin film layer of a desired thickness can be easily and industrially continuously formed on a phosphor particle surface, and a phosphor having improved temperature quenching, chemical stability and life can be obtained. it can.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to the description of the embodiments, a diamond coating apparatus newly developed by the present inventors in carrying out the present invention will be described. I do.

FIG. 1 is a schematic sectional view of a diamond coating apparatus capable of coating a desired diamond thin film layer on the surface of a powder particle. This apparatus has a tubular rotary reaction vessel 4 rotatably supported at both ends by a suitable roller means 2 on a base and capable of holding an arbitrary inclination angle.

One end (the left side in FIG. 1) of the rotary reaction vessel 4 on the inclined upper side is airtightly connected to a screw feeder 8 for supplying powder through a rotor joint 6. One end of the screw feeder 8 is air-tightly connected to a source gas source 10 containing at least a methane-hydrogen mixed gas through a source gas supply port for depositing diamond. A powder supply device 12 is provided at the upper part of the device, and the powder supply device 12 is connected to a back pressure gas source 14 of hydrogen gas through a back pressure gas port.

On the other hand, at one end (right side in FIG. 1) of the rotary reaction vessel 4 on the inclined lower side, a collector 18 for collecting powder is airtightly provided via a rotor joint 16. A powder collection unit 20 is provided below the collection unit 18. A gas transport pipe 22 is connected to an upper portion of the collector 18, and the gas transport pipe 22 is connected to another transport pipe 26 via a bag filter 24. Depending on the particle size of the powder, that is, in the case of fine powder, the powder is collected at the lower part of the bag filter 24.

The rotary reactor 4 is installed so as to pass through a microwave cavity 28, and the microwave cavity 28 is connected to a microwave oscillator 32 through a waveguide 30. On the other side of the waveguide 30 facing the microwave oscillator 32 with the rotary reactor 4 interposed therebetween, a plunger 34 for reflecting microwaves is arranged. During operation, the microwave from the microwave oscillator 32 passes through the rotary reaction vessel 4 in the center of the rotary reactor 4, and the microwave plasma reaction region 3
6 are formed.

Referring to FIG. 2, it is apparent that powder particles are stably supplied to the inside of the rotary reactor 4, and that the diamond particles Stirring blade 3 to precipitate
8 are formed, and the powder is stably supplied in a gradually dispersed state along the inclined direction in the rotary reactor 4 with the rotation of the rotary reactor 4.

Next, the operation of the thus configured diamond coating apparatus will be described.

First, the transport pipe 26, the bag filter 24, the transport pipe 22, and the collector 18 are moved by a vacuum pump (not shown).
, The pressure inside the rotary reaction vessel 4, the waveguide 30 and the screw feeder 8 is reduced to a predetermined pressure. At the same time, the source gas is supplied from the source gas source 10 into the rotary reaction vessel 4 and the waveguide 30 via the screw feeder. At the same time, the microwave oscillator 32 operates, and the microwave plasma is generated by the waveguide 30 and the plunger 34. Is opening 26
, And is introduced into the rotary reaction vessel 4 to generate an excited state hydrocarbon, an excited state or an atomic state hydrogen from the raw material gas, thereby forming a microwave plasma reaction region 36.

On the other hand, the powder particles are supplied into the rotary reaction vessel 4 via the powder feeder 12 and the screw feeder 8, and the powder supplied into the rotary reaction vessel 4 The fluidity is increased by the supply of the gas, and the gas is gradually supplied to the microwave plasma reaction region 26 by the stirring blade 38. The particles are heated to a predetermined temperature by the action of microwaves and plasma.

The microwave plasma reaction region 36
The hydrogen and hydrocarbons excited in the step are transported to generate a plurality of types of hydrocarbon radicals, which become elementary, and coat the powder surface in the microwave plasma reaction region with the diamond thin film layer. Thereafter, the inside of the rotary reaction container 4 is gradually moved by the rotation of the rotary reaction container 4 again, and the powder is collected in the powder collection unit 20. On the other hand, the remaining fine particles and the gas component are introduced into the bag filter 24 via the transport pipe 22, the remaining fine particles are separated at the lower part of the bag filter 24, and the gas component is passed through the transport pipe 26 and a vacuum pump (not shown). Exhausted.

Hereinafter, the conditions for depositing diamond in the microwave plasma reaction region 26 will be described, particularly when applied to phosphor particles of several μm to tens of μm.
Total gas supply amount 100 sccm. The gas supply amount from the source gas source 10 is 50 sccm. Gas supply rate from back pressure gas source 14 50 sccm.

The gas component of the source gas source 10 includes methane
As an additive gas to the hydrogen mixed gas, water vapor and hydrogen sulfide gas may be mixed to prevent a change in the base composition of the phosphor due to melting with the plasma and precipitate high-quality diamond. The gas from the source 14 is hydrogen gas, and the gas mixture ratio is as follows, taking this hydrogen gas into consideration. CH4 concentration (CH4 / H2 ratio) 1-10%. Preferably, it is 0.1 to 1.0%. H2O concentration (H2O / CH4 ratio) O-500%. Preferably, 30 to 100%. H2S concentration (H2S / CH4 ratio) O to 500%. Preferably, 50 to 150%.

The pressure, processing temperature and processing time in the microwave plasma reaction region 36 are as follows. Pressure 10-100 torr. Preferably 20 to 40 torr. Processing temperature 90-900 ° C. Preferably, 300-500 ° C. Processing time 0.2-20 hours (hrs). Preferably, 0.5-5 hours (hrs).

The microwave output is 2.45 gigahertz (Ghz) and 50 to 500 W.
100-300W.

The thickness of the diamond thin film layer formed on the phosphor particle surface can be freely adjusted by changing the residence time in the microwave plasma reaction region 36, the processing time, the gas concentration or the gas component.

In the case of this diamond coating apparatus, the residence time τ (time) of the phosphor particles in the plasma is given by the following equation. τ = 0.0004θL / ΔnD where θ is the powder angle of repose (degrees) and L is the total plasma length (m
m) and Δ are the gradients of the rotating reaction vessel, n is the number of rotations (rpm) of the rotating reaction vessel, and D is the diameter (mm) of the rotating reaction vessel.

Embodiment 1 Hereinafter, a specific embodiment will be described.

The rotary reaction vessel 4 made of quartz having an inner diameter of 40 mm was set at a gradient of 1/400, and the number of rotation was 10 rpm. The plasma wave oscillator 32 generated a microwave of 2.45 GHz. The powder feeder 12 has an average particle 4
μm Y2O2S: Eu phosphor particles were filled. By preparing the back pressure gas source 14 and the source gas source 10, the composition of the source gas in the microwave plasma reaction region 36 is changed to 0.5% methane (hydrogen ratio), 20% steam (methane ratio), and hydrogen sulfide. 20% (methane ratio), treatment temperature is 500 ° C,
Pressure 20 torr, microwave power 300
W, and under these conditions, the residence time determined from the above equation was 0.7 hours.

As a result of depositing diamond on the phosphor surface, a diamond thin film layer of about 0.01 μm was formed. As confirmed by an electron micrograph, as shown in FIG. 3, the surface of the phosphor particles 40 was almost uniformly coated with the diamond thin film layer 42. Further, by performing Raman analysis on the diamond thin film layer 42, it was confirmed that the diamond thin film layer 42 was high quality diamond.

When a phosphor film for a cathode ray tube was prepared using the obtained phosphor particles, that is, the diamond-coated Y2O2S: Eu phosphor particles, the Y2O2S: Eu phosphor particles of the present example were subjected to a gas phase reaction. Since the surface of each particle was uniformly coated with diamond, the adhesion between the glass plate to be coated and the phosphor particles was extremely uniform, and the dispersibility as coating characteristics was excellent.

When the characteristics of the fluorescent film were examined, it was found that the heat dissipating property was extremely good as compared with the conventional Y2O2S: Eu phosphor particles not coated with diamond, and that the temperature rise of the fluorescent film due to the irradiation of the electron beam. Since the phosphor is extremely low, deterioration of the phosphor due to temperature quenching can be suppressed. As shown in FIG. 4, as the temperature of the phosphor film rises, in the phosphor film using the conventional Y2O2S: Eu phosphor particles that do not coat diamond, as shown by the wavy line in FIG. On the other hand, Y
In the phosphor film using the 2O2S: Eu phosphor particles, as shown by the solid line in FIG. 4, the brightness was reduced only by about 5%, which was extremely improved. In addition, in terms of life, there was no ion burning and no change in the composition of the particle surface.

Next, the film thickness of the diamond thin film layer 42 is variously set by changing the gradient and the number of revolutions of the rotary reaction vessel 4 of the diamond coating apparatus, and the obtained phosphor particles are used to form the diamond thin film. The relationship between the layer thickness and the relative luminance of the fluorescent film at 50 ° C. was examined. The result is shown in FIG.

In FIG. 5, the luminance of a phosphor film using phosphor particles not coated with diamond is set to 100%. As is clear from FIG. 5, the thickness of the diamond thin film layer is 0.1 μm in terms of emission luminance as well as the heat dissipation characteristics of the fluorescent film.
The following is preferable from the viewpoint of light emission luminance. Preferably, it is 0.01 μm.

(Examples 2 and 3) As a phosphor, a ZnS: Ag, Al phosphor having an average particle diameter of 4.2 μm and a Y3Al5O12: Tb phosphor having an average particle diameter of 4.5 μm were each 0.01 μm in thickness. Of the diamond thin film layer 42 was coated.

In any case, the adhesion between the glass and the phosphor particles can be remarkably improved, and the heat dissipation of the phosphor film is excellent. In particular, there was no formation of a color center due to diffusion of impurities from the outside, and the product was excellent.

[0036]

As described above, according to the present invention,
By forming a diamond thin film layer on the phosphor particle surface by microwave plasma method, it is possible to take advantage of diamond's excellent thermal conductivity, light transmission characteristics and chemical stability, temperature quenching, chemical stability In addition, according to the production method of the present invention, a diamond thin film layer can be provided on a phosphor particle surface by a microwave plasma method in a simple and industrially continuous manner. Can be formed.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a diamond coating apparatus according to the present invention in a partial cross section.

FIG. 2 is an enlarged sectional view showing a section taken along line A in FIG.

FIG. 3 is a schematic sectional view showing a diamond-coated phosphor according to one embodiment of the present invention.

FIG. 4 is a graph showing a relationship between a film temperature and a relative luminance in a phosphor film coated with the phosphor of FIG. 3;

FIG. 5 is a graph showing the relationship between the thickness of the diamond thin film layer and the relative luminance according to one embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 4 rotating reaction vessel 10 raw material gas source 12 phosphor raw material 14 back pressure gas source 18 collector 24 bag filter 28 microwave cavity 30 waveguide 32 microwave oscillator 36 microwave plasma reaction region 40 phosphor 42 diamond thin film layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C09K 11/84 CPD C09K 11/84 CPD

Claims (2)

(57) [Claims] 1. A phosphor characterized in that it has a diamond thin film layer deposited on a phosphor particle surface by a microwave plasma method. 2. A microwave plasma is generated in a part of a rotary reaction vessel which is airtightly shielded from the outside air and the inside of which is maintained at a reduced pressure, and a hydrogen-methane mixed gas is introduced into the microwave plasma generation region at the same time. A method for producing a phosphor, comprising continuously supplying phosphor particles to a microwave plasma generation region by rotation and gradient of the rotary reaction vessel, thereby forming a diamond thin film layer on the surface of the phosphor particles. .