JP2001019948A - Production of barium fluoride halide fluorescent material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for the production of a barium fluoride halide fluorescent material effective for preventing the contamination of a baking furnace in baking to stably obtain a fluorescent material having excellent luminescent characteristics, reducing the maintenance load of the baking furnace and improving the flexibility of the control of the luminescent characteristics of the obtained fluorescent material. SOLUTION: The process for the production of a barium fluoride halide fluorescent material at least comprises a raw material mixing step to prepare a mixture of raw materials of the fluorescent material by mixing the raw materials and a baking step to bake the raw material mixture to produce a barium fluoride halide fluorescent material expressed by a specific structural formula. A prebaking process to bake the fluorescent raw material mixture for 0.1-10 hrs at 200-900 deg.C and a temperature lower than the baking temperature of the baking step is placed between the raw material mixing step and the baking step.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a barium fluorohalide-based phosphor which can be used as a stimulable phosphor in a radiation image conversion panel or the like.

[0002]

2. Description of the Related Art A radiation image recording / reproducing method using a stimulable phosphor is known as an alternative to the conventional radiographic method. This method uses a radiation image conversion panel (a stimulable phosphor sheet) containing a stimulable phosphor, and transmits radiation transmitted through a subject or emitted from a subject to the stimulable phosphor of the panel. By absorbing the stimulable phosphor with electromagnetic waves (excitation light) such as visible light and infrared light in a time series manner, the radiation energy stored in the stimulable phosphor is absorbed by the body. The fluorescent light is emitted (stimulated emission light), the fluorescent light is read photoelectrically to obtain an electric signal, and a radiation image of a subject or a subject is reproduced as a visible image based on the obtained electric signal. . After the reading, the panel is prepared for the next photographing after the remaining image is erased. That is, the radiation image conversion panel can be used repeatedly.

According to the above-described radiographic image recording / reproducing method, a radiation having a much smaller amount of exposure and a richer amount of information than a conventional radiographic method using a combination of a radiographic film and an intensifying screen. There is an advantage that an image can be obtained. Furthermore, while the conventional radiographic method consumes radiographic film for each shot, the radiographic image recording / reproducing method uses a radiographic image conversion panel repeatedly, which leads to resource conservation and economic efficiency. Is also advantageous.

A stimulable phosphor is a phosphor that emits stimulable light when irradiated with radiation and then with excitation light. However, in practice, the stimulable phosphor has a wavelength of 400 to 900 nm due to the excitation light. Phosphors that exhibit stimulated emission in the 500 nm wavelength range are commonly used. Examples of stimulable phosphors conventionally used in radiation image conversion panels include barium fluorohalide-based phosphors.

[0005] Barium fluoride halide-based phosphors are generally produced by the following method. First, a phosphor material mixture is uniformly mixed in a dry state (dry method) or a slurry state in which the phosphor materials are uniformly mixed, and then dried (wet method) to prepare a phosphor material mixture. Do.

Next, usually, the obtained phosphor raw material mixture is calcined at a temperature close to the melting point of the base crystal (BaFX or the like) in a neutral or weakly oxidizing atmosphere at about atmospheric pressure for several hours ( Firing step). If desired, the fired product once obtained may be refired. In the firing step, the host crystal of the phosphor grows, and at the same time, the activator element (E
u) is diffused, and halogen centers such as F ^{+, which} are sources of photostimulated centers, are also generated. Therefore, the firing step is an important step that affects the emission characteristics of the phosphor. After firing, the obtained phosphor is subjected to washing, classification, and the like, as necessary.

The firing furnace used in the firing step generally includes a furnace core tube made of a ceramic material such as quartz and alumina, and a heat source disposed outside the furnace core tube. A firing vessel capable of containing the mixture is provided so as to be able to be taken in and out of the furnace core tube. Further, a gas introduction / exhaust pipe for adjusting a firing atmosphere inside the furnace core tube is connected to the furnace core tube. At the time of firing, the phosphor raw material mixture is accommodated in the firing vessel, charged into the furnace core tube, and fired by the heat from the heat source while adjusting the firing atmosphere inside the furnace core tube by a gas introduction / exhaust pipe. The inside of the furnace is heated to a high temperature, and the phosphor raw material mixture is fired.

However, when firing is performed in a firing furnace, various components such as activators and additives contained in the phosphor raw material mixture may be scattered and contaminate the furnace core tube and the gas introduction / exhaust tube. Due to these contaminations, problems such as unstable pressure conditions in the furnace core tube and incorporation of contaminants into the fired product may occur, and the emission characteristics of the obtained phosphor may deteriorate. In order to solve such a problem, it is necessary to periodically clean the furnace core pipe and the gas introduction / exhaust pipe, which imposes a heavy load on maintenance work. In addition, in the conventional method, since the synthesis (mixing of crystals) of the phosphor crystals from the phosphor raw material mixture and the diffusion of the activator in the crystals are performed at one time, the emission characteristics of the obtained phosphor are controlled. Is difficult.

[0009]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to prevent contamination in a firing furnace at the time of firing, to stably obtain a phosphor having excellent light emission characteristics, and to carry out maintenance work for the firing furnace. An object of the present invention is to provide a method for producing a barium fluoride halide-based phosphor that can also reduce the load. It is another object of the present invention to provide a method for producing a barium fluorohalide-based phosphor, which can more freely control the emission characteristics of the obtained phosphor.

[0010]

The above object is achieved by the present invention described below. That is, the present invention provides: <1> at least a raw material mixing step of mixing a fluorescent raw material to prepare a fluorescent raw material mixture, and baking the fluorescent raw material mixture to obtain the following composition formula (I): (Ba _{1-a) ^{, M II a) FX · bM}} I · cM III · dA: xLn formula (I) wherein, M ^II _a is, Sr, Ca, at least one alkaline earth metal selected from the group consisting of Mg Stands for M
^I represents at least one alkali metal compound selected from the group consisting of Li, Na, K, Rb and Cs;
M ^III is Al, Ga, In, Tl, Sc, Y, Cd,
It represents a compound of at least one trivalent metal selected from the group consisting of Lu (excluding Al ₂ O ₃ ). X is C
represents at least one halogen selected from the group consisting of l, Br and I. Ln is Ce, Pr, Sm, Eu,
It represents at least one rare earth element selected from the group consisting of Gd, Tb, Dy, Ho, Nd, Er, Tm, and Yb. A represents at least one metal oxide selected from the group consisting of Al ₂ O ₃ , SiO ₂ and ZrO ₂ . a,
b, c, d, x are respectively 0 ≦ a ≦ 0.3, 0 ≦ b ≦
2, 0 ≦ c ≦ 2, 0 ≦ d ≦ 0.5, and 0 <x ≦ 0.2. A sintering step of producing a barium fluorinated halogen-based phosphor represented by: and a method of producing a barium fluorinated halide-based phosphor, comprising, between the raw material mixing step and the sintering step, In the range of 200 to 900 ° C., and
At a temperature lower than the temperature at the time of firing in the firing step,
A method for producing a barium fluorohalide-based phosphor, comprising a preliminary firing step of previously firing the phosphor raw material mixture for 0.1 to 10 hours.

<2> The halogen fluoride according to <1>, wherein a difference between a temperature at the time of the preliminary firing in the preliminary firing step and a temperature at the time of the preliminary firing step is 20 ° C. or more. This is a method for producing a barium fluoride-based phosphor.

<3> The method according to <1> or <2>, wherein the firing temperature in the firing step is in the range of 600 to 1000 ° C. It is.

<4> The pre-firing step is a step of pre-firing the phosphor raw material mixture by putting a firing container accommodating the phosphor raw material mixture into a pre-firing space. It consists of a main body and a lid,
Further, the opening edge of the container body and the outer periphery of the lid portion are in contact with each other in a surface, so that the opening of the container body is closed, and the phosphor raw material mixture is supplied to the firing container. After the container is housed, the edge of the opening of the container body and the periphery of the lid are sealed by rubbing each other, and this is put into the pre-baking space. <1.
> The method for producing a barium fluorohalide-based phosphor according to any one of <3>.

<5> Each of the surfaces of the container main body and the outer peripheral edge of the lid, which is in contact with the edge of the opening, is No. <4> The method for producing a barium fluorohalide-based phosphor according to <4>, wherein the surface is polished with at least 150 abrasives.

<6> Both surfaces of the opening edge of the container main body and the periphery of the lid are in contact with each other via a sealant, so that the container main body and the lid are in contact with each other. Is a method for producing a barium fluoride halide-based phosphor according to <4>, wherein the phosphor is sealed.

<7> The method for producing a barium fluorohalide-based phosphor according to <6>, wherein the sealant is a substance that can be solidified at a temperature during the preliminary firing in the preliminary firing step. It is.

<8> The method for producing a barium fluorohalide-based phosphor according to <6>, wherein the sealant is a substance that can be melted at a temperature during the preliminary firing in the preliminary firing step. It is.

<9> A second firing container having the same configuration as that of any one of <4> to <8> and slightly larger than the second firing container is prepared, and the phosphor is prepared. After storing the firing container described in any one of <4> to <8> that stores the raw material mixture in the second firing container, the opening edge of the container body of the second firing container and The method according to any one of <4> to <8>, wherein the second firing vessel is sealed by rubbing the periphery of the outer periphery of a lid of the second firing vessel, and is then charged into the temporary firing space. This is a method for producing a barium fluorohalide-based phosphor.

<10> Carbon black powder is interposed between the firing container described in any one of <4> to <8> that contains the phosphor raw material mixture and the second firing container. <9> is a method for producing a barium fluorohalide-based phosphor described in <9>.

<11> The barium fluoride halide system according to any one of <1> to <10>, wherein the calcination in the calcination step is performed in a continuous furnace capable of continuously calcination. This is a method for producing a phosphor.

In the present invention, the calcination in the calcination step
It may be referred to as “final firing”. Preliminary firing prior to) allows the roles of the two to be shared, greatly reducing the emission characteristics of the resulting phosphor due to contamination of the firing furnace during main firing, and greatly reducing the maintenance work load of the firing furnace. further,
The light emission characteristics of the obtained phosphor can be controlled more freely.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
First, a barium fluorohalide-based phosphor obtained by the method for producing a phosphor of the present invention will be described.

The barium fluoride halide-based phosphor produced according to the present invention is represented by the following composition formula (I). After firing, the phosphor having the composition represented by the following composition formula (I) is obtained. The phosphor raw material mixture is obtained by mixing the phosphor raw materials so as to be manufactured, and the mixture is fired by the phosphor manufacturing method of the present invention.

[0024] ^{_{(Ba 1-a, M II}} a) FX · bM I · cM III · dA: xLn formula (I) wherein, M ^II _a is selected from the group consisting Sr, Ca, and Mg Represents at least one alkaline earth metal,
^I represents at least one alkali metal compound selected from the group consisting of Li, Na, K, Rb and Cs;
M ^III is Al, Ga, In, Tl, Sc, Y, Cd,
It represents a compound of at least one trivalent metal selected from the group consisting of Lu (excluding Al ₂ O ₃ ). X is C
represents at least one halogen selected from the group consisting of l, Br and I. Ln is Ce, Pr, Sm, Eu,
It represents at least one rare earth element selected from the group consisting of Gd, Tb, Dy, Ho, Nd, Er, Tm, and Yb. A represents at least one metal oxide selected from the group consisting of Al ₂ O ₃ , SiO ₂ and ZrO ₂ . a,
b, c, d, x are respectively 0 ≦ a ≦ 0.3, 0 ≦ b ≦
2, 0 ≦ c ≦ 2, 0 ≦ d ≦ 0.5, and 0 <x ≦ 0.2. ]

A general process for producing a barium fluorohalide-based phosphor is a raw powder synthesizing step of synthesizing a raw powder as a phosphor raw material, and a raw material mixing step of mixing the phosphor raw material to obtain a phosphor raw material mixture. And a firing step of firing the phosphor raw material mixture. The method further includes a cooling step of cooling the fired material as required, a treatment / drying step of washing and drying, and a sieving step. However, there are many phosphor raw materials available on the market, and if these are used, the raw powder synthesis step is omitted. The method for producing a phosphor of the present invention is characterized in that a pre-firing step of pre-firing the phosphor raw material mixture is provided between the raw material mixing step and the firing step. Hereinafter, each step will be described separately.

[Phosphor Material] The phosphor material is not particularly limited, and may be obtained by any known method. Examples of the phosphor material include the following materials (1) to (5). (1) BaF ₂ , BaCl ₂ , BaBr ₂ , BaI ₂ , Ba
At least one barium halide selected from the group consisting of FBr, BaFI and BaFCl. (2) CaF ₂ , CaCl ₂ , CaBr ₂ , CaI ₂ , Sr
F ₂ , SrCl ₂ , SrBr ₂ , SrI ₂ , MgF ₂ , Mg
At least one alkaline earth metal halide selected from the group consisting of Cl ₂ , MgBr ₂ and MgI ₂ . (3) CsCl, CsBr, CsI, NaCl, NaB
r, NaI, KCl, KBr, KI, RbCl, RbB
r, RbI, RbF, CsF, NaF, KF, LiF,
At least one alkali metal halide selected from the group consisting of LiCl, LiBr and LiI. (4) At least one metal oxide selected from the group consisting of Al ₂ O ₃ , SiO ₂ and ZrO ₂ . (5) Rare earth element compounds such as halides, oxides, nitrates and sulfates (Ce, Pr, Sm, Eu, Gd, Tb,
At least one compound selected from the group consisting of Dy, Pr, Ho, Nd, Er, Tm, and Yb). If desired
In addition, ammonium halide (NH ₄ X ′,
X ′ represents F, Cl, Br or I. ) May be used as the flux.

[Raw Material Mixing Step] In preparing the phosphor raw material mixture, a desired raw material is arbitrarily selected from each of the raw materials (1) to (5), and a composition corresponding to the composition formula (I) is prepared. A stoichiometric basis weight and a mixture are prepared so as to obtain a ratio to prepare a phosphor raw material mixture.

The method of preparing the phosphor material mixture can be appropriately selected from known mixing methods. For example, the phosphor material mixture is prepared by the following methods (i) to (iv). May be. (I) A preparation method in which the phosphor raw materials (1) to (5) are weighed and simply mixed. (Ii) The phosphor raw materials (1) to (4) are weighed and mixed,
After heating this mixture at a temperature above 100 ° C. for several hours,
A preparation method in which the phosphor material (5) is mixed with the obtained heat-treated product. (Iii) A preparation method in which the phosphor raw materials (1) to (5) are mixed, and the mixture is heated at a temperature of 100 ° C. or higher for several hours. (Iv) The phosphor materials (1) to (4) are mixed in the form of a suspension, and the suspension is heated, preferably 50 to 20.
A preparation method in which the phosphor material (5) is mixed with the obtained dried material after drying under reduced pressure, vacuum drying, spray drying and the like at 0 ° C.

As a modification of the above-mentioned preparation method (iv),
The phosphor raw materials (1) to (5) are mixed in a suspension state, and the suspension is dried. The preparation method (iv-2) includes the phosphor raw materials (1) and (5). Heating the suspension,
Preferably after heating to 50 to 200 ° C. or after drying under reduced pressure, vacuum drying, spray drying and the like under the heating,
In the preparation method (iv-3) of adding and mixing the phosphor raw materials (2) to (4) to the obtained mixture, or when preparing by performing firing twice or more, the phosphor raw material (1) And (2) are mixed in a suspension state, and the phosphor raw material (3) is mixed.
After adding (4) after the first firing, the suspension is dried under heating, preferably at 50 to 200 ° C. by vacuum drying, vacuum drying, spray drying, or the like. A preparation method (iv-4) of mixing the phosphor raw material (5) can also be preferably mentioned.

Further, a tetrahedral rare earth-activated alkaline earth metal fluorohalide-based stimulant having a controlled particle shape and particle aspect ratio described in JP-A-7-233369 and JP-A-10-195431 is disclosed. Method for producing luminescent phosphor, ie, method for preparing phosphor mixture (i)
In addition to (iv-4), various conditions such as a preparation method (v) using a means capable of imparting a shearing force when mixing phosphor materials, addition of each phosphor material, and timing of mixing are also defined. It can also be prepared by the preparation method (vi) using a controllable means.

The mixing apparatus used for the mixing in the preparation methods (v) and (vi) can be appropriately selected from known mixing apparatuses, and examples thereof include various mixers, V-type blenders, ball mills, and the like. Rod mills and the like can be mentioned.

In the production of the phosphor represented by the composition formula (I), the following various additives may be added for the purpose of further improving the stimulated emission, erasing performance and the like. For example, B described in JP-A-57-23673, As described in JP-A-57-23675, a tetrafluoroboric acid compound described in JP-A-59-27980, No. 47289, hexafluoro compounds, transition metals such as V, Cr, Mn, Fe, Co, Ni, etc. described in JP-A-59-56480;
Or BeX " ₂ described in JP-A-59-75200.
(Where X ″ represents at least one halogen atom selected from the group consisting of F, Cl, Br and I).

When the above-mentioned additive component is added, the additive component is added when the phosphor raw materials are weighed and mixed or before firing,
Mixed.

[Preliminary Firing Step] In the present invention, the phosphor raw material mixture obtained in the above raw material mixing step is subjected to a preliminary firing step. The pre-baking step is a step of pre-baking the phosphor raw material mixture in a temperature range of 200 to 900 ° C. and lower than the firing temperature in the baking step for 0.1 to 10 hours. The sintering in the general sintering step is responsible for all the functions of imparting photostimulated luminescence properties to the resulting phosphor, such as synthesis of the phosphor crystals (mixing of crystals) at high temperatures and diffusion of the activator in the crystals. On the other hand, one of the objects of the preliminary firing in the present invention is to synthesize (crystallize) phosphor crystals at a temperature lower than the temperature at the time of the firing.

By assigning the role to the preliminary firing in this way, the role of the main firing in the subsequent firing step is reduced, and the emission characteristics of the obtained phosphor can be more freely controlled. In addition, since the preliminary firing does not have a function of imparting the photostimulated luminescent property to the phosphor, it does not require strict atmosphere control unlike the main firing, and therefore requires firing in a firing furnace such as a so-called atmosphere furnace. Because of this, it can be performed in a furnace having a simple structure. Since various components contained in the phosphor raw material mixture to be scattered are scattered in advance by the calcination, the sintering hardly scatters in the subsequent sintering and hardly pollutes the sintering furnace in the sintering. Suppression of the contamination of the firing furnace, which requires strict atmosphere control, leads to stabilization of the emission characteristics of the obtained phosphor and reduction of the maintenance work load. From the viewpoint of preventing contamination, the raw materials to be fired in the temporary firing are not necessarily a raw material mixture, and the individual raw materials before mixing may be temporarily fired individually, the temporarily fired raw materials may be mixed, and the final firing may be performed. .

The temperature during the preliminary firing is 200 to 900
The temperature is in the range of ° C. and lower than the temperature at the time of firing in the firing step. Here, the temperature lower than the temperature at the time of firing in the firing step is a temperature at which the phosphor crystals obtained from the phosphor raw material mixture cannot provide stimulated emission characteristics, and the composition of the phosphor raw material mixture Although it depends on the pre-baking time and the like, the difference between the pre-baking temperature and the main baking temperature is preferably 20 ° C. or more,
More preferably 50 ° C or higher, further preferably 100 ° C
That is all.

As a specific temperature during the preliminary firing, 200
It is indispensable that the temperature is in the range of -900 ° C, preferably in the range of 300-700 ° C, and more preferably in the range of 500-6.
It is in the range of 00 ° C. If the temperature is lower than 200 ° C., the scattering of various components of the phosphor raw material is insufficient, so that the contamination of the firing furnace in the main firing is not reduced. If the temperature exceeds 900 ° C., the brightness to be strictly controlled in the main firing is required. Since there is a possibility that pre-firing may be performed even to the effect of imparting the luminescent characteristics, it is not preferable for each.

It is essential that the time for the preliminary firing is in the range of 0.1 to 10 hours, but it is preferably in the range of 0.5 to 10 hours.
The range is 5 hours, more preferably 1 to 3 hours. If the time is less than 0.1 hour, the effect of scattering the various components of the phosphor raw material and synthesizing (crystallizing) the phosphor crystal is not sufficient. Worsens.

As described above, the preliminary firing does not have a function of imparting the photostimulated luminescent property to the phosphor, so that the firing atmosphere does not need to be strictly controlled, and therefore, the firing can be performed at a target temperature. Any furnace may be used as long as it is provided, and examples thereof include a muffle furnace, a rotary kiln, and an atmosphere furnace. In order to clarify the role sharing with the main firing and sufficiently achieve the effects of the present invention, it is preferable to perform the preliminary firing in a furnace different from the main firing. In particular, it is preferable to use a continuous furnace (so-called tunnel furnace) that can be continuously fired from the viewpoint of phosphor productivity.

The calcination is performed by putting a calcination vessel containing the phosphor raw material mixture into a calcination space such as a tunnel furnace. At this time, as the firing container, a quartz boat or the like generally used for firing may be used, but it is composed of a container main body and a lid portion, and the opening edge of the container main body and the periphery of the lid portion are around, It is preferable to adopt a structure in which the opening of the container main body is closed by contacting with the surface, and the structure is such that the surfaces are sealed by sliding the surfaces together. By using the firing container having such a structure, the firing can be performed while appropriately blocking the outside air and maintaining the firing atmosphere in the firing container.

FIG. 1 is a schematic sectional view of a firing vessel 10 having such a structure. In FIG. 1, a firing container 10 includes a container body 2 and a lid 4. The container body 2 has a columnar shape with an open upper part and a closed lower part.
It has a disk shape with approximately the same diameter as. The container body 2 accommodates the phosphor raw material mixture 12. The opening edge 6 of the container body 2 is flat, and the outer periphery 8 of the lid 4 is also flat. Here, the periphery 8 of the lid 4 refers to a portion that comes into contact with the opening edge 6 of the container main body 2 when the lid 4 is placed on the container main body 2. The opening edge 6 and the outer periphery 8 are brought into close contact with each other by being rubbed together, so that the container body 2 and the lid 4 are sealed.

However, the term “sealing” as used herein refers to a state in which the edge of the opening is in close contact with the periphery of the outer periphery, and is different from a state in which there is no invasion or outflow of gas inside and outside the container. . For example, when the inside of the container is pressurized during firing, the lid is lifted and the atmosphere flows out, and when the inside of the container is depressurized, the outside atmosphere enters.

By using such a baking container 10 for preliminary baking, baking can be performed while keeping the baking atmosphere in the baking container while appropriately blocking the outside air.

Both planes of the opening edge 6 and the outer periphery 8 are No. No. 150 or more, preferably no. 300 or more N
o. The surface is preferably polished with an abrasive of 500 or less. If the surface is polished with such a finely polished abrasive, the sealing of the opening edge 6 and the outer periphery 8 is improved, and the degree of shielding of outside air is improved. In addition,
The “No.” of the abrasive here means “No.” in a so-called sandpaper.

It is preferable that the respective surfaces of both the opening edge 6 and the outer periphery 8 come into contact with each other via a sealing agent, so that the container body and the lid are sealed. The sealing property is further improved by interposing the sealing agent. As such a sealant, there are two kinds of substances, that is, a substance that can be solidified at the temperature at the time of preliminary firing, and a substance that can be melted at the temperature at the time of preliminary firing.

Examples of the substance which can be solidified at the temperature during the preliminary firing include kaolin, bentonite, Kibushi clay and Gairome clay. It is preferable in terms of hermeticity to use a substance that can be solidified at the temperature during pre-baking as a sealant.

On the other hand, substances that can be melted at the temperature during the preliminary firing include phosphor raw materials, pyrex glass, lead glass, MnSO ₄ , K ₂ Mg ₂ (SO ₄ ) ₃ , Na ₂ S, and K ₂
S, MgI ₂ , LiI, Na ₃ VO ₄ , Ba (NO ₃ ) ₂ ,
NaBr and CsBr and the like. When used as a material sealing agent that can be melted at the temperature during pre-firing,
It is preferable in terms of hermeticity.

The size of the container main body 2 varies depending on the amount of firing, and it is preferable that approximately 20 to 90% of the inner space of the container becomes the phosphor material when the phosphor material is charged. . Examples of the shape of the container include a cube, a rectangular parallelepiped, and a columnar shape, and any shape can be used as long as the above-mentioned condition can be satisfied.

The material of the firing vessel 10 is alumina,
Quartz, SiC, SiN, carbon, platinum and the like can be mentioned.

As the firing vessel used for the preliminary firing, it is preferable that the firing vessel 10 described above has a double structure. More specifically, as shown in FIG. 2, the double structure has the same configuration as the above-described firing container 10, and a second firing container 20 which is slightly larger than that is prepared.
2 is a structure in which the entirety of the firing container 10 that houses the firing container 2 is stored in the firing container 20. “Slightly larger than firing container 10” means that there is no problem as long as it is large enough to accommodate firing container 10.

The structure of the firing container 20 is the same as that of the firing container 10 except for the size. By thus forming the firing container in a double structure, airtightness is further improved, so that the air is completely shielded from outside air, and firing can be performed while maintaining the atmosphere in the firing container. Further, from the viewpoint of airtightness, a triple structure in which a firing container having a double structure is housed in a firing container which is one size larger may be used. However, if the structure is too multiplex, the structure becomes complicated and time is required for preparation and handling. However, the obtained effect is not changed.

It is preferable that a powdery carbon black 14 is charged between the firing container 10 and the second firing container 20. , The remaining oxygen can be reduced. The amount of the powdered carbon black 14 to be charged may be an amount that remains after the calcination is completed.

The preliminary firing is performed as described above. It is not necessary to grind the phosphor raw material mixture after calcination, but it is desirable to easily loosen it in a mortar or the like in view of the phosphor particle size and the uniformity of the phosphor raw material.

[Firing Step] The phosphor raw material mixture that has undergone the preliminary firing step is a quartz boat, an alumina crucible, a quartz crucible,
This is filled in a heat-resistant container such as a furnace core tube, and then put into a furnace core of an electric furnace to perform main firing. In the present invention, the firing is preferably performed at a temperature in the range of 600 to 1000 ° C, more preferably 700 to 850 ° C. If the temperature of the main firing is less than 600 ° C., the diffusion of the activator element in the host crystal and the generation of F ^{+ serving} as a source of the photostimulated center may be insufficient. May melt.

The firing time during the main firing varies depending on the filling amount of the phosphor raw material mixture, the firing temperature or the temperature at which the phosphor material is taken out of the furnace, and is generally 0.5 to 6 hours, preferably 1 to 3 hours. Is more preferred. If the firing time during the main firing is less than 0.5 hour, the diffusion of the activator element in the host crystal and the generation of F ⁺ as a source of the photostimulated center may be insufficient. Even if the main baking is performed beyond that, there is little change in the properties of the phosphor further, which may reduce the productivity.

The atmosphere in the furnace tube at the time of the main firing is preferably an atmosphere using a neutral or slightly oxidizing atmosphere gas. Examples of the neutral atmosphere gas include an inert gas such as He, Ne, Ar, and N ₂ . The slightly oxidizing atmosphere gas is 100 to 100000 ppm in a neutral gas per unit volume,
Refers to a weakly oxidizing atmosphere gas preferably containing 150 to 50,000 ppm of oxygen, for example, He, Ne, A
A weakly oxidizing atmosphere gas containing the above concentration of oxygen in an inert gas such as r or N ₂ may be used.

The amount of oxygen introduced is preferably 0.1 to 200 ml, more preferably 0.2 to 100 ml, at room temperature, per 1 liter of the firing partial volume of the furnace. When the oxygen introduction amount is less than 0.1 ml, the effect of improving the erasing performance of the stimulable phosphor may not be sufficiently obtained. When the oxygen introduction amount exceeds 200 ml, the stimulable luminescence amount may be significantly reduced. There is.

As a method for introducing oxygen into the neutral gas,
It is not particularly limited and can be appropriately selected from known introduction methods. Among them, once the inside of the furnace core tube is evacuated to a state close to a vacuum, a predetermined amount of oxygen is introduced, and the inside of the furnace is weakly oxidizing. It is preferable to perform firing as an atmosphere. The required amount of oxygen can be accurately introduced, and the influence of other gases can be minimized.

That is, 1 kg of the phosphor raw material mixture to be fully fired
By specifying the amount of oxygen introduced per unit volume of the fired part of the furnace and one liter of the fired part, the amount of the phosphor necessary for improving the erasing performance of the stimulable phosphor in the firing step of the phosphor raw material mixture is determined. Oxygen can be introduced. Also,
By replacing the gas in the furnace core tube with a gas containing a predetermined amount of oxygen, the amount of oxygen in the furnace core tube can be introduced so as to be changed stepwise or continuously.

For example, a desired amount of oxygen can be introduced by the following operation. First, after the phosphor raw material mixture is put into the firing furnace that has reached the firing temperature, vacuum evacuation is immediately performed for several minutes to remove air in the furnace core tube. In this case, the degree of vacuum can be calcined in a state close to a vacuum state, but is preferably 0.1 torr or less from the viewpoint of making the amount of oxygen in the atmosphere accurate.

Next, a predetermined amount of oxygen is supplied into the furnace core tube,
Fill to desired pressure. As described above, the amount of oxygen introduced is preferably 0.1 to 200 ml with respect to the partial volume of calcination of the furnace core tube, as described above. The amount of oxygen introduced is measured at room temperature. After accurately introducing a predetermined amount of oxygen into the furnace core tube, the neutral gas is further charged into the furnace core tube, and the pressure in the furnace is set to about 760 torr (1 atm), that is,
The atmosphere can be set to be near the atmospheric pressure, and the atmosphere can be a weakly oxidizing atmosphere.

When adjusting the inside of the furnace tube to a weakly oxidizing atmosphere,
Instead of oxygen, oxygen may be introduced using, for example, a gas containing oxygen such as air or an inert gas. As the introduction amount of the gas containing oxygen such as the air, it is generally preferable to introduce a gas amount necessary for obtaining the same oxygen amount as in the case of introducing oxygen. 0.5 to 1000 ml is more preferable for 1 L, and 5 to 500 ml.
ml is most preferred.

The introduction of oxygen into the furnace core tube does not necessarily have to be performed after evacuation to a vacuum state, but only a small amount of oxygen is introduced into the furnace core tube under an atmospheric pressure (1 atm) neutral gas or a weakly oxidizing atmosphere. May be introduced, or the oxygen-containing gas such as air may be introduced into the furnace while increasing the amount of oxygen in the furnace core tube. By performing the main baking as described above, a powdery stimulable phosphor can be obtained.

Further, as a process after firing the phosphor raw material mixture at a constant temperature in the firing step as described above, it is preferable to provide a step of gradually cooling before moving to a cooling step described later. The slow cooling may be performed immediately after the phosphor raw material mixture is fired, but is preferably performed after a certain period of time while removing and replacing the atmosphere while maintaining a constant temperature.

In the slow cooling, the temperature is controlled by a gentle temperature gradient from the start until a predetermined temperature is reached, and the temperature is lowered. In particular, slow cooling is effective in improving the light emission characteristics of the stimulable phosphor.
It is preferable to perform the process at a temperature lowering rate of 2 to 5 ° C./min until the temperature at the end of the firing becomes lower by 20 to 200 ° C.

[Cooling Step] The cooling in the cooling step may be either a method of lowering the temperature by standing or a method of forcibly lowering the temperature while controlling the temperature using a cooler. However, from the viewpoint of shortening the cooling time and stably producing a stimulable phosphor having sufficient characteristics, a method of cooling at a desired temperature is preferable.

[Other Steps] In addition, the stimulable phosphor after firing may be provided with various general steps such as a treatment / drying step for performing washing and drying and a sieving step, if necessary. Can also.

[0068]

EXAMPLES Example 1 1) Raw Material Mixing Step In order to synthesize a stimulable phosphor precursor of europium-activated barium fluorobromide, a BaBr ₂ aqueous solution (2.5 mol / mol) was used.
L) 1200 mL, EuBr ₃ aqueous solution (0.2 mol /
L) 40 mL, 0.85 g of CaBr ₂ .2H ₂ O, and 1760 mL of water were placed in a 4000 mL reactor. The reaction mother liquor (BaBr ₂ concentration was 1.
(0 mol / L) was kept at 60 ° C., and the reaction mother liquor was stirred by rotating a screw stirring blade having a diameter of 60 mm at 500 rpm. Ammonium fluoride aqueous solution (10 mol / m
L) 150 mL of water and 150 mL of water are mixed, and 300 mL of the mixed solution is poured into the reaction mother liquor kept under stirring at a rate of 5 mL / min using a roller pump to form a precipitate. Was. After completion of the injection, the mixture was kept warm and stirred for 2 hours to mature the precipitate.

Next, the precipitate was separated by filtration and washed with 2 L of methanol. Next, the washed precipitate was taken out,
For about 4 hours to obtain about 330 g of europium-activated barium fluorobromide crystals. Observation of the obtained crystals with a scanning electron microscope revealed that most of the crystals were tetrahedral crystals.

Next, when the crystals were measured with a light diffraction type particle size distribution analyzer (LA-500, manufactured by Horiba, Ltd.), it was confirmed that the average crystal size was 5.0 μm. For the above BaFBr crystal 1000 g,
In order to prevent a change in particle shape due to sintering during firing and a change in particle size distribution due to inter-particle fusion, 212 wt. The mixture was sufficiently stirred with a mixer to uniformly adhere the ultrafine alumina powder to the crystal surface.

2) Preliminary Firing Step 1000 g of the obtained phosphor raw material mixture was placed in the firing vessel 10 shown in FIG. Further, as shown in FIG. 2, between the firing container 10 and the firing container 20, 100 g of carbon black powder was spread, and the lid of the firing container 20 was adhered. The outline of the firing container 10 and the firing container 20 is as follows.

(Firing container 10) Material: Quartz (both container body 2 and lid 4) Size: 25cm × 25cm, height 10cm ・ Opening edge 6 and outer periphery 8 Processing: N
o. Polished with 400 abrasives

(Sintering container 20) Material: quartz (both container body 2 and lid 4) Size: 30cm in height x 30cm in width, 15cm in height Processing: N
o. Polished with 400 abrasives

The firing vessel having a double structure containing the phosphor raw material mixture was put into a muffle furnace, and was preliminarily fired at 400 ° C. for 2 hours. The phosphor raw material mixture after the calcination was easily loosened in a mortar.

3) Firing Step The preliminarily fired phosphor raw material mixture was spread over a quartz boat and main firing was performed. That is, after 100 g of the phosphor material mixture after calcination is filled in a quartz boat, the volume in the furnace is reduced to 1 g.
Put into a 0 L evacuable core, immediately start evacuation, and reduce the degree of vacuum in the core to about 0.1 torr in 10 minutes.
r. Next, after introducing 50 ml of air into the furnace, nitrogen gas was charged until the inside of the furnace reached atmospheric pressure (760 torr), thereby forming a weakly oxidizing atmosphere. Firing was performed at 850 ° C. for 2 hours in a weakly oxidizing atmosphere.

3) Cooling Step After firing, vacuum evacuation was started. After one minute, the furnace core tube was taken out of the electric furnace while vacuum evacuation was performed, air-cooled with a simple fan for 30 minutes, and the fired product was taken out of the furnace core tube. Crushed in a mortar.
Thus, the composition (Ba _0.995 Ca _0.005 ) FBr _0.85
A europium-activated barium fluorohalide-based phosphor of I _0.15 : 0.005Eu ²⁺ was obtained.

Example 2 A europium-activated barium fluorohalide-based phosphor was obtained in the same manner as in Example 1 except that the calcination temperature in the calcination step was 500 ° C.

Example 3 A europium-activated barium fluorinated halogenated phosphor was obtained in the same manner as in Example 1 except that the calcination temperature in the calcination step was 600 ° C.

Example 4 A europium-activated barium fluorinated halogenated phosphor was obtained in the same manner as in Example 1 except that the calcination temperature in the calcination step was 700 ° C.

Example 5 In the raw material mixing step and the calcining step, 1000 g of BaFBr and 212 g of BaFI were used.
Are individually calcined at 500 ° C., and the calcined B
1 wt% of ultrafine particles of alumina were added to 1000 g of aFBr and 212 g of BaFI, and the mixture was sufficiently stirred with a mixer.
A europium-activated barium fluorohalide-based phosphor was obtained in the same manner as in Example 1 except that ultrafine particles of alumina were uniformly attached to the crystal surface.

[Comparative Example 1] In the same manner as in Example 1 except that the phosphor raw material mixture was immediately spread over a quartz boat and subjected to the firing step without performing the preliminary firing step. Thus, a europium-activated barium fluorobromide-based phosphor was obtained.

[Evaluation of Phosphor] Each of the phosphors obtained in the above Examples and Comparative Examples was subjected to the following evaluation tests. The results are shown in Table 1 below.

(1) Sensitivity Each of the phosphors obtained in the above Examples and Comparative Examples was applied at 80 kV.
Of 100 mR was irradiated with 4.3 J / m ² of light having a wavelength of 660 nm by a semiconductor laser, and the amount of stimulated emission emitted from the phosphor was measured, and this was defined as sensitivity.

(2) Erasure value Each of the phosphors for which the above sensitivity was measured was subjected to an erasing operation of 500,000 lux · sec with each white phosphor using a white fluorescent lamp, and then a light having a wavelength of 660 nm was applied by a semiconductor laser to 4.3 J. / M ² and measure the amount of stimulated emission emitted from the phosphor,
This was defined as the erase level value. The erasure value was obtained by the following formula. Erase value = erase level value / sensitivity

(3) Dirt in the Furnace The dirt in the furnace was visually evaluated for the state of deposits in the furnace after the completion of the main firing.

[0086]

[Table 1]

As shown in Table 1 above, the properties of the phosphor obtained by performing the calcination can be improved. Further, from the results of Examples 1 to 5 and Comparative Example 1, when the phosphor raw material mixture was preliminarily baked, the scattering of the raw material was small in the initial stage of the main firing, but when the preliminary firing was not performed, the main firing was not performed. It is considered that the scattering of the raw material occurs at an early stage, which adheres to the inside of the baking furnace and the piping, becomes dirty, and causes a reduction in the efficiency of evacuation. Therefore, if pre-baking is performed,
It is possible to reduce the maintenance work of the firing furnace and to improve the stability by repeated use.

[0088]

According to the method for producing a barium fluoride halide phosphor of the present invention, contamination in a firing furnace during firing can be prevented, and a phosphor excellent in emission characteristics can be stably obtained. In addition, the load on the maintenance work of the firing furnace can be reduced. Further, according to the method for producing a barium fluorohalide-based phosphor of the present invention, the emission characteristics of the obtained phosphor can be controlled more freely.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing an example of a firing container preferably applied during preliminary firing in the present invention.

FIG. 2 is a schematic cross-sectional view showing an example of a firing container having a double structure which is preferably applied at the time of preliminary firing in the present invention.

[Explanation of symbols]

 2 Container body 4 Lid 6 Opening edge 8 Outer periphery 10 Firing container 12 Phosphor raw material mixture 14 Carbon black 20 Firing container

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C09K 11/61 CPR C09K 11/61 CPR 11/62 CPN 11/62 CPN 11/64 CPM 11/64 CPM 11 / 67 CPQ 11/67 CPQ 11/85 CPF 11/85 CPF 11/86 11/86 F term (reference) 4G076 AA02 AA04 AA05 AA06 AA07 AA08 AA18 AA24 AB02 AB04 BA11 BA38 BA40 BB02 BC08 DA15 4H001 CA08 CF02 XA03 XA09 XA11 XA XA13 XA19 XA20 XA21 XA31 XA37 XA38 XA39 XA49 XA55 XA56 XA64 XA71 XA81 YA58 YA59 YA60 YA62 YA63 YA64 YA65 YA66 YA67 YA68 YA69 YA70

Claims (11)

[Claims] At least a raw material mixing step of mixing a fluorescent raw material to prepare a fluorescent raw material mixture, and sintering the fluorescent raw material mixture to obtain the following composition formula (I): (Ba _1-a , M ^{II _{a) FX · bM I · cM}} III · dA: xLn formula (I) wherein, M ^II _a represents Sr, Ca, at least one alkaline earth metal selected from the group consisting of Mg, M
^I represents at least one alkali metal compound selected from the group consisting of Li, Na, K, Rb and Cs;
M ^III is Al, Ga, In, Tl, Sc, Y, Cd,
It represents a compound of at least one trivalent metal selected from the group consisting of Lu (excluding Al ₂ O ₃ ). X is C
represents at least one halogen selected from the group consisting of l, Br and I. Ln is Ce, Pr, Sm, Eu,
It represents at least one rare earth element selected from the group consisting of Gd, Tb, Dy, Ho, Nd, Er, Tm, and Yb. A represents at least one metal oxide selected from the group consisting of Al ₂ O ₃ , SiO ₂ and ZrO ₂ . a,
b, c, d, x are respectively 0 ≦ a ≦ 0.3, 0 ≦ b ≦
2, 0 ≦ c ≦ 2, 0 ≦ d ≦ 0.5, and 0 <x ≦ 0.2. A sintering step of producing a barium fluorinated halogen-based phosphor represented by: and a method of producing a barium fluorinated halide-based phosphor, comprising, between the raw material mixing step and the sintering step, In the range of 200 to 900 ° C., and
At a temperature lower than the temperature at the time of firing in the firing step,
A method for producing a barium fluorohalide-based phosphor, comprising a preliminary firing step of temporarily firing the phosphor raw material mixture for 0.1 to 10 hours. 2. The difference between the temperature at the time of the preliminary firing in the preliminary firing step and the temperature at the time of the preliminary firing in the firing step is 20.
The method for producing a barium fluoride halide-based phosphor according to claim 1, wherein the temperature is not lower than ℃. 3. The firing temperature in the firing step is as follows:
The method for producing a barium fluorohalide-based phosphor according to claim 1 or 2, wherein the temperature is in the range of 600 to 1000 ° C. 4. The pre-firing step is a step of pre-firing the phosphor raw material mixture by putting a firing container containing the phosphor raw material mixture into a pre-firing space, wherein the firing container is a container main body. And a lid, wherein the edge of the opening of the container main body and the periphery of the outer periphery of the lid are in contact with each other on a surface, whereby the opening of the container main body is closed, and After storing the body raw material mixture in the firing container, the opening edge of the container body and the periphery of the lid are sealed by rubbing each other, and this is put into the temporary firing space. The method for producing a barium fluorohalide-based phosphor according to any one of claims 1 to 3. 5. A surface in which both the edge of the opening of the container body and the periphery of the lid are in contact with each other.
o. 5. The method according to claim 4, wherein the surface is polished with at least 150 abrasives. 6. An opening edge of the container main body and respective surfaces that come into contact with both the periphery of the lid and the periphery of the lid come into contact with each other via a sealant, so that the container main body and the lid are in contact with each other. The method for producing a barium fluoride halide-based phosphor according to claim 4, wherein the phosphor is sealed. 7. The method for producing a barium fluoride halide-based phosphor according to claim 6, wherein the sealant is a substance that can be solidified at a temperature during the preliminary firing in the preliminary firing step. 8. The method for producing a barium fluoride halide-based phosphor according to claim 6, wherein the sealant is a substance that can be melted at a temperature during the preliminary firing in the preliminary firing step. 9. A second firing container having the same configuration as the firing container described in any one of claims 4 to 8 and one size larger than the second firing container, and preparing the phosphor raw material mixture. 9. After accommodating the accommodated sintering container according to any one of claims 4 to 8 in the second sintering container, an opening edge of a container body of the second sintering container and the second sintering container. The barium fluoride halogenated fluorescent material according to any one of claims 4 to 8, wherein the container is hermetically sealed by rubbing with the periphery of a lid portion of the container, and is charged into the pre-baking space. How to make the body. 10. A carbon black powder is charged between the firing container according to any one of claims 4 to 8 containing the phosphor raw material mixture and the second firing container. The method for producing a barium fluorohalide-based phosphor according to claim 9, wherein: 11. The barium fluoride halide-based phosphor according to claim 1, wherein the pre-firing in the pre-firing step is performed in a continuous furnace capable of continuously firing. Production method.