JPH0593188A - Production of infrared-visible ray conversion phosphor - Google Patents

Abstract

PURPOSE:To produce the title phosphor within a shorter production time while preventing its properties from being deteriorated by oxidation caused by the oxygen get mixed in the sintering atmosphere due to careless handling in its production. CONSTITUTION:The title process comprises the steps of: mixing a powdery alkaline earth metal chalcogenide phosphor A containing at least one element selected from among europium, cerium, manganese and copper with a powdery alkaline earth metal chalcogenide phosphor B containing at least one element selected from among samarium, bismuth and lead, and fusing the phosphor A powder with the phosphor B powder together by heating the resulting mixture under pressure. Thus, the title phosphor which can be produced within a shorter production time and does not deteriorate so much in its properties in a sintering process can be provided by mixing the phosphor containing the principal activator with the phosphor containing the subsidiary activator and heating the resulting mixture under pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an infrared-visible conversion phosphor, and more particularly to a method for manufacturing an infrared-visible conversion phosphor which shortens the manufacturing time and causes less quality deterioration in the sintering process.

[0002]

2. Description of the Related Art Many infrared-visible conversion phosphors for converting infrared light into visible light are known so far. Among them, writing light energy can be stored and read by irradiation with infrared light. Infrared stimulated phosphors have been attracting attention in recent years as optical rewriting memory materials and optical information processing materials. The infrared stimulable phosphor is a phosphor that emits light in the visible range when stimulated with infrared light after being excited with short-wavelength light, X-rays, radiation, or the like in advance, such as a semiconductor laser or a YAG laser. It is widely used for detecting infrared light. A phosphor obtained by adding europium (Eu) and samarium (Sm) or cerium (Ce) and samarium (Sm) to calcium sulfide (CaS) or strontium sulfide (SrS) is known as a phosphor with high infrared-visible conversion efficiency. ing.

Before describing the technical background of the present infrared-visible conversion phosphor and its manufacturing method, the operating principle of the infrared-stimulated phosphor will be described.

FIGS. 1a and 1b are diagrams showing a band model of CaS: Eu: Sm, which is one of infrared stimulable phosphors. The present phosphor operates by the following two processes, an excitation process (FIG. 1a) and a light emission process (FIG. 1b).

Excitation process (FIG. 1a) (1) Upon irradiation with excitation light (blue-green) 1, Eu ²⁺ is ionized and electrons 2 are emitted on the conduction band to become Eu ³⁺ .

(2) The electrons excited on the conduction band are Sm ³⁺
Are captured by Sm ²⁺ .

Emission process (FIG. 1b) (3) Electrons trapped in Sm ³⁺ by stimulation of infrared light 3 are excited on the conduction band and Sm ²⁺ becomes Sm ³⁺ .

(4) Electrons excited on the conduction band are Eu ³⁺
Eu ³⁺ is captured by and becomes Eu ²⁺ . At this time, Eu ²⁺ transits to the ground state by the emission transition and emits the light 4. The emission at this time is called infrared stimulated emission (red).

That is, infrared stimulated emission is generated by passing through the above steps (1) to (4). As is clear from the above, recording is written during excitation, and recording is read during stimulation.

As can be seen from this operating principle, the Eu element determines the wavelength characteristics relating to excitation light and infrared stimulated emission, and S
The m element determines the wavelength characteristic for infrared stimulation. The element that controls the wavelength characteristics of excitation light and infrared stimulated emission is called a main activator, and the element that controls the wavelength characteristics of infrared stimulation is called a sub-activator.

As can be seen from the operating characteristics, the infrared stimulable phosphor is an energy storage type phosphor, and by utilizing this property, it can be used as a memory material. Further, it has wavelength selectivity that the operating wavelength can be changed to some extent by selecting the type of activator added to the phosphor and the matrix material.

[0012]

However, the conventional manufacturing method, that is, the sintered phosphor in which the main activator and the sub-activator are added and mixed in the phosphor matrix is not sufficient in both memory characteristics and wavelength selectivity. However, after writing information, afterglow is involved, so that it takes about several seconds to write the next information, which is disadvantageous in that high-speed information writing cannot be performed.

Therefore, the inventors of the present invention invented a phosphor and a method for manufacturing the same that solve the above problems, and have a wide operating wavelength selection range, high memory characteristics and high infrared-visible conversion efficiency, and high-speed writing of optical information. We realized a readable infrared-visible conversion phosphor and its manufacturing method, and as a result of manufacturing and examining the phosphor a number of times by that manufacturing method, the phosphor manufacturing method previously invented, that is, alkaline earth metal chalcogenide Is used as a phosphor host material, and at least one element selected from europium, cerium, manganese, and copper and at least one element selected from samarium, bismuth, and lead is added. In the method for producing an infrared-visible conversion phosphor by mixing powdered phosphor B added with and then heating and sintering it to fuse phosphor A powder particles and phosphor B powder particles, The disadvantage that the sintering process after mixing the body A and the phosphor B takes time, and the phosphor is oxidized by oxygen mixed in the sintering atmosphere gas due to careless handling in the manufacturing process, and the characteristics are deteriorated. It turns out that there are cases.

[0014]

The present invention has been made in view of the above problems, and is selected from europium, cerium, manganese, and copper using an alkaline earth metal chalcogenide as a phosphor host material. A step of mixing the powdered phosphor A added with at least one element and the powdered phosphor B added with at least one element selected from samarium, bismuth and lead, and heating the mixture under pressure Then, the method includes the step of fusing the phosphor A powder particles and the phosphor B powder particles to form an infrared-visible conversion phosphor.

That is, after mixing both the phosphors, the phosphor particles are fused by heating under pressure to solve the above problems, shorten the manufacturing time, and reduce the quality in the sintering process. It is possible to obtain a method of producing an infrared-visible conversion phosphor having a small amount.

According to the method for producing an infrared-visible conversion phosphor of the present invention, a powder of an alkali metal chalcogenide matrix to which at least one element selected from europium, cerium, manganese, and copper is added as described above. A phosphor-like phosphor A and a powdery phosphor B of an alkali metal chalcogenide matrix to which at least one element selected from samarium, bismuth and lead is added,
This mixing ratio is not fundamentally limited in the present invention, and can be variously changed depending on the characteristics of the manufactured phosphor.

On the other hand, the average particle size of the powdered phosphors A and B is
It is preferably 1 μm or less. This is because when it exceeds 1 μm, the interaction between the phosphors A and B becomes difficult to occur.

[Function] Usually, when a phosphor is sintered, the phosphor is placed in a sintering furnace and a gas mixed with an inert gas such as Ar gas or an antioxidant gas such as hydrogen sulfide is flowed in the furnace. 1
It is heated and sintered at a high temperature of 000 ° C. or higher for several hours. At this time, if gas replacement in the furnace is insufficient or if the purity of the atmosphere gas is poor, oxygen is mixed into the atmosphere gas, and the phosphor is oxidized during heating and sintering, causing characteristic deterioration.

Therefore, according to the method of the present invention, since the phosphor powder is mixed and then heated while being pressurized, excess air is exhausted at the time of pressurization, and no atmospheric gas is required at the time of heating, so that the atmosphere The phosphor can be formed without being affected by the purity of the gas. For this reason, there is no cause of deterioration of phosphor characteristics such as phosphor oxidation caused by careless handling, so that a high quality phosphor with good yield can be manufactured. Also,
The pressurization accelerates the solid-phase reaction between the phosphor particles, which shortens the heating time and shortens the manufacturing time.

Due to the above-mentioned effects, by using the method for producing an infrared-visible conversion phosphor of the present invention, it is possible to shorten the production time and to provide a method for producing a phosphor in which the quality is less deteriorated in the sintering step. ..

[0020]

EXAMPLES The method for producing the infrared-visible conversion phosphor of the present invention will be described below in detail based on specific examples.

[0021]

Example 1 An example in which calcium sulfide (CaS) is used as a phosphor matrix material and europium (Eu) is selected as the element A and samarium (Sm) is selected as the element B will be described in detail.

In manufacturing the above phosphor, first,
CaS phosphor containing 500 ppm of europium oxide (Eu ₂ O ₃ ) and samarium oxide (Sm ₂ O ₃ ) 150 p
A pm-doped CaS phosphor is manufactured. These phosphors are sufficiently pulverized by a ball mill until the average particle diameter becomes 1 μm or less, and then both phosphors are mixed. This mixed powder is placed in a pressing jig and pressed at a pressure of 10 t / cm ^{2 to} 10
Hold at 00 ° C for 20 minutes. After that, the phosphor was taken out from the pressing jig and pulverized into a powder having an average particle size of about 50 μm by allowing the temperature to reach room temperature. The phosphor thus obtained is placed in a scanning electron microscope, and the fluorescence emitted from the phosphor by electron beam irradiation is inspected while scanning the electron beam so that the concentration distribution of europium and the concentration distribution of samarium differ from each other. Was confirmed to be added to.

When the phosphor was manufactured a number of times by this method and the variation in its characteristics was examined, the variation was 1% or less.
In the chemical analysis, no sign of oxidation was observed, indicating that the phosphor manufactured by the manufacturing method of the present invention has good reproducibility of characteristics. Furthermore, although it took 1 hour or more to sinter the phosphor in the conventional method, it became clear that this method only requires 20 minutes and is effective in shortening the manufacturing time.

[0024]

Example 2 Strontium selenide (SrSe) added with cerium (Ce) as the element A and calcium sulfide (Ca added with samarium (Sm) as the element B)
An example of manufacturing a phosphor body including S) will be described in detail.

In manufacturing the above phosphor, first,
S added with 1500 ppm of cerium oxide (CeO ₂ ).
150p of rSe phosphor and samarium oxide (Sm ₂ O ₃ )
A pm-doped CaS phosphor is manufactured. These phosphors are sufficiently pulverized by a jet mill until the average particle diameter becomes 1 μm or less, and then both phosphors are mixed. This mixed powder is placed in a press jig and pressed with a pressure of 10 t / cm ²
Hold at 000 ° C for 20 minutes. After that, the phosphor was taken out from the pressing jig and pulverized into a powder having an average particle size of about 50 μm by allowing the temperature to reach room temperature. The phosphor thus obtained is placed in a scanning electron microscope, and the fluorescence emitted from the phosphor by electron beam irradiation is inspected while scanning the electron beam so that the concentration distribution of europium and the concentration distribution of samarium differ from each other. Was confirmed to be added to.

When the phosphor was manufactured a number of times by this method and the variation in its characteristics was examined, the variation was 1% or less.
In the chemical analysis, no sign of oxidation was observed, indicating that the phosphor manufactured by the manufacturing method of the present invention has good reproducibility of characteristics. Furthermore, although it took 1 hour or more to sinter the phosphor in the conventional method, it became clear that this method only requires 20 minutes and is effective in shortening the manufacturing time.

[0027]

Example 3 Calcium sulfide (CaS) phosphor fine powder to which europium (Eu) was added as element A, and element B
A detailed description will be given of an example in which calcium sulfide (CaS) phosphor fine powder to which samarium (Sm) has been added is mixed and then heated while being pressurized.

In manufacturing the above phosphor, first,
Calcium carbonate, europium oxide, sodium carbonate, and sulfur were mixed so that the Eu concentration in CaS after burning the phosphor would be 500 ppm, and the mixture was filled in an alumina crucible, covered with a lid, and placed in an electric furnace at 1000 ° C. Heat for 1 hour.
The unreacted raw material is removed by crushing the sintered body thus obtained and washing with water. After that, when washed with ethanol and dried, CaS: E having an average particle size of 100 nm or less
u phosphor fine particles are obtained. Calcium carbonate, samarium oxide, sodium carbonate, and sulfur were mixed so that the Sm concentration in CaS after sintering the phosphor would be 100 ppm, and the mixture was filled in an alumina crucible, covered with a lid, and placed in an electric furnace.
Heat at 00 ° C. for 1 hour. The sintered body thus obtained is crushed and washed with water to remove unreacted raw materials.
After that, when washed with ethanol and dried, an average particle size of 10
CaS: Sm phosphor fine particles having a particle size of 0 nm or less are obtained.

The CaS: Eu phosphor fine particles obtained by the above method and the CaS: Sm phosphor fine particles were mixed and then placed in a pressing jig and pressurized at a pressure of 10 t / cm ^{2 to} 1000
Hold at 20 ° C for 20 minutes. After that, the phosphor is taken out from the pressing jig and ground until the temperature reaches room temperature, and the average particle size is 5
The powder was about 0 μm. The phosphor thus obtained is placed in a scanning electron microscope, and the fluorescence emitted from the phosphor by electron beam irradiation is inspected while scanning the electron beam so that the concentration distribution of europium and the concentration distribution of samarium differ from each other. Was confirmed to be added to.

When the phosphor was manufactured a number of times by this method and the variation in its characteristics was examined, the variation was 1% or less.
In the chemical analysis, no sign of oxidation was observed, indicating that the phosphor manufactured by the manufacturing method of the present invention has good reproducibility of characteristics. Furthermore, although it took 1 hour or more to sinter the phosphor in the conventional method, it became clear that this method only requires 20 minutes and is effective in shortening the manufacturing time.

[0031]

As described above, the method for producing the infrared-visible conversion phosphor is the method for producing the infrared-visible conversion phosphor having the constitution of the present invention, that is, the phosphor to which the main activator is added. A method for manufacturing an infrared-visible conversion phosphor with less quality deterioration in the sintering process by shortening the manufacturing time by a manufacturing method in which a phosphor with a sub-activator added is mixed and then heated under pressure is manufactured. We were able to.

[Brief description of drawings]

FIG. 1a is a diagram showing the operating principle of an infrared stimulable phosphor.

FIG. 1b is a diagram showing the operating principle of an infrared stimulable phosphor.

Claims (1)

[Claims] 1. A powdered phosphor A containing an alkaline earth metal chalcogenide as a phosphor base material and at least one element selected from europium, cerium, manganese and copper, and samarium, bismuth and lead. Powdered phosphor B to which at least one element selected from the above is added
And a step of heating the mixture while pressurizing the mixture to fuse the phosphor A powder particles and the phosphor B powder particles to each other.