JP2004170405A - Method of manufacturing radiological image converting panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a radiological image converting panel for imparting a radiological image having high durability, high sensitivity and high image quality. <P>SOLUTION: This method of manufacturing the radiological image converting panel, includes a process for forming a stimulable europium activating halogenated cesium type phosphor layer by depositing a substance generated by heating an evaporation source including a europium activating halogenated cesium type phosphor or its raw material on a base board under a decompressing condition, and is composed of the base board and the stimulable europium activating halogenated cesium type phosphor layer formed on the base board, and is characterized in that the deposition is performed under a condition of satisfying a prescribed relational expression in the mole ratio of europium/cesium in the europium activating halogenated cesium type phosphor layer formed on the base board and a base board temperature in deposition. <P>COPYRIGHT: (C)2004,JPO

Description

  The present invention relates to a method for manufacturing a radiation image conversion panel used in a radiation image recording / reproducing method using a stimulable phosphor.

  When irradiated with radiation such as X-rays, it absorbs and accumulates part of the radiation energy, and then emits light according to the accumulated radiation energy when irradiated with electromagnetic waves (excitation light) such as visible light and infrared rays. Using a stimulable phosphor having properties (such as a stimulable phosphor exhibiting stimulating luminescence), the specimen is transmitted through the sheet-shaped radiation image conversion panel containing the stimulable phosphor or the subject. The radiation image information of the subject is once accumulated and recorded by irradiating the radiation emitted from the laser beam, and then the panel is scanned with excitation light such as laser light and emitted sequentially as emitted light, and this emitted light is read photoelectrically. Thus, a radiation image recording / reproducing method comprising obtaining an image signal has been widely put into practical use. After the reading of the panel is completed, the remaining radiation energy is erased, and then the panel is prepared and used repeatedly for the next imaging.

  A radiation image conversion panel (also referred to as an accumulative phosphor sheet) used in a radiation image recording / reproducing method includes a support and a phosphor layer provided thereon as a basic structure. However, a support is not necessarily required when the phosphor layer is self-supporting. In addition, a protective layer is usually provided on the upper surface of the phosphor layer (the surface not facing the support) to protect the phosphor layer from chemical alteration or physical impact.

  The phosphor layer is composed of a stimulable phosphor and a binder containing and supporting the phosphor in a dispersed state, and only aggregates of the stimulable phosphor without a binder formed by vapor deposition or sintering. And those in which a polymer substance is impregnated in the gaps between the aggregates of the stimulable phosphor are known.

  As another method of recording and reproducing the radiation image, a radiation image containing at least a storage phosphor (energy storage phosphor) by separating the radiation absorption function and the energy storage function of a conventional storage phosphor. A radiation image forming method using a combination of a conversion panel and a phosphor screen containing a phosphor (radiation absorbing phosphor) that absorbs radiation and emits light in the ultraviolet to visible region has been proposed (Patent Document 1). . In this method, radiation that has passed through the subject is first converted into light in the ultraviolet or visible region by the screen or panel radiation absorbing phosphor, and then the radiation image information is transmitted to the energy storage phosphor of the panel. As an accumulation record. Next, the panel is scanned with excitation light to emit emitted light, and the emitted light is read photoelectrically to obtain an image signal. Such a radiation image conversion panel and a fluorescent screen are also included in the present invention.

  The radiographic image recording / reproducing method (and the radiographic image forming method) is a method having a number of excellent advantages as described above. However, the radiographic image conversion panel used in this method is as sensitive as possible. In addition, it is desired to provide an image with good image quality (sharpness, graininess, etc.).

  For the purpose of improving sensitivity and image quality, a method for manufacturing a radiation image conversion panel comprising forming a phosphor layer by a vapor deposition method has been proposed. Vapor deposition methods include vapor deposition and sputtering. In the vapor deposition method, an evaporation source made of a phosphor or a raw material thereof is heated by a resistance heater (resistance heating) or heated by electron beam irradiation (electron beam irradiation) to evaporate and scatter the evaporation source, such as a glass plate. By depositing the evaporated material on the surface of the substrate, a phosphor layer composed of phosphor columnar crystals is formed.

  The phosphor layer formed by the vapor deposition method does not contain a binder and is composed only of the phosphor, and there are voids (cracks) between the columnar crystals of the phosphor. For this reason, it is possible to increase the entrance efficiency of the excitation light and the extraction efficiency of the emitted light, so that the sensitivity is high, and scattering of the excitation light in the plane direction can be prevented, so that a high sharpness image can be provided. .

Conventionally, when forming a phosphor layer by a vapor deposition method such as vapor deposition, it is known that the substrate may be heated in order to improve the shape of the columnar crystals of the phosphor. Patent Document 2 discloses that the temperature of the substrate is lowered with time when the photostimulable phosphor layer is formed by a vapor deposition method. Patent Document 3 discloses that the temperature of a plurality of regions of the substrate is heated to a predetermined temperature by controlling the heating means, and the predetermined temperature is preferably in the range of 150 to 350 ° C. Has been. However, the photostimulable phosphors specifically described are RbBr: Tl and BaFBr: Eu ²⁺ phosphors. Further, the relationship between the substrate temperature and the activator concentration is not mentioned.

JP 2001-255610 A Japanese Patent No. 3070940 Japanese Patent Laid-Open No. 10-62599

  The inventor has studied in detail the formation of a phosphor layer made of a europium-activated cesium halide (CsX: Eu, X is a halogen) -based stimulable phosphor by a vapor deposition method. As a result, in the vapor deposition of the europium activated cesium halide phosphor, a divalent to trivalent Eu activator is introduced into the phosphor matrix compound (CsX) which is a monovalent metal compound. The columnar crystal structure of the phosphor tends to be disturbed due to the difference in valence and melting point, and the concentration of activator (europium / cesium gram atomic ratio) greatly contributes to the columnar crystal structure of the deposited phosphor. I found out. As a result of further research, it has been found that the shape of the columnar crystals formed correlates with a specific relationship between the concentration of the activator Eu and the heating temperature of the substrate. Further, the inventors have found that the amount of stimulated light emission and the adhesion between the phosphor layer and the substrate correlate with a specific relationship between the activator concentration and the substrate temperature. As a result of further research, columnar crystallinity can be improved by setting the activator concentration and the substrate temperature in a relationship satisfying a specific range during vapor deposition, and the amount of stimulated luminescence and It has been found that the adhesion to the substrate can be improved, and the present invention has been achieved.

  Accordingly, it is an object of the present invention to provide a method for manufacturing a radiation image conversion panel that provides a high-quality radiation image with high durability and high sensitivity.

The present invention relates to a stimulable europium-activated cesium halide fluorescent material by depositing on a substrate a substance generated by heating an europium-activated cesium halide fluorescent material or an evaporation source containing the raw material under reduced pressure conditions. In a method for producing a radiation image conversion panel comprising a substrate and a photostimulable europium-activated cesium halide phosphor layer formed on the substrate, including the step of forming a body layer, the vapor deposition is performed on the substrate. The europium / cesium molar ratio (or gram atomic ratio) in the europium-activated cesium halide phosphor layer formed on the substrate and the substrate temperature during deposition satisfy all of the following relational expressions (1) to (3): In the manufacturing method of the radiation image conversion panel, which is performed under satisfying conditions:

Relational expression (1): T ≧ 867.24 ^{× 0.4537}
Relational expression (2): T ≧ 0.0985x ^-1.0587
Relational expression (3): T ≦ 1485.4x ² −760.75x + 297.37

[Wherein T represents the substrate temperature (° C.) during deposition, and x represents the molar ratio of europium / cesium in the europium-activated cesium halide phosphor layer].

  If the production method of the present invention is used, the columnar crystal structure is good, the stimulated light emission amount is high, and the substrate (by combining the activator concentration and the substrate temperature during vapor deposition within a specific range, and the substrate ( A photostimulable phosphor layer having excellent adhesion to the support) can be formed. Therefore, it is possible to obtain a radiation image conversion panel that has high durability and high sensitivity and gives a high-quality radiation image.

  When the production method of the present invention is performed using heating by electron beam irradiation, it is preferable to perform the deposition at a high vacuum of 1 Pa or less, particularly at a high vacuum of 0.1 Pa or less.

On the other hand, when the production method of the present invention is performed using resistance heating, it is preferable to perform deposition at a vacuum degree in the range of 0.1 Pa to 5 Pa, and deposition at a vacuum degree in the range of 0.1 Pa to 2 Pa. It is particularly preferable to carry out. In the case of performing vapor deposition by the resistance heating method in such a range, the vapor deposition is performed with the molar ratio of europium / cesium in the europium-activated cesium halide phosphor layer formed on the substrate and the substrate temperature during vapor deposition. Are preferably performed under conditions that satisfy all of the following relational expressions (4) to (7).

Relational expression (4): T ≦ 175.14x ^−0.0682
Relational expression (5): T ≧ 0.028x- ^1.3048
Relational expression (6): T ≧ −63745x ² −3581.4x + 304.61
Relational expression (7): T ≦ 23.844Ln (x) +265.01

[T and x have the same meaning as T and x in claim 1, respectively. ]

  The substrate preferably has a fine uneven pattern on the surface, and the pitch of the uneven pattern is preferably 15 μm or less.

  As the evaporation source, it is preferable to perform multi-source vapor deposition using an evaporation source containing at least cesium halide which is a matrix component of the stimulable phosphor and an evaporation source containing a europium compound which is an activator component. Moreover, it is preferable to first form a vapor deposition film made of a photostimulable phosphor base material on the substrate, and then laminate the vapor deposition film made of the phosphor on the vapor deposition film.

  The europium activated cesium halide photostimulable phosphor according to the present invention preferably has the following basic composition formula (I), and in the basic composition formula (I), X is preferably Br.

CsX · aM ^II X ′ ₂ · bM ^III X ″ ₃ : zEu (I)

[Wherein M ^II represents at least one alkaline earth metal or divalent metal selected from the group consisting of Be, Mg, Ca, Sr, Ba, Ni, Cu, Zn and Cd; M ^III represents Sc, Y, At least one rare earth element or trivalent metal selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Al, Ga and In X, X ′ and X ″ each represent at least one halogen selected from the group consisting of F, Cl, Br and I; and a, b and z are each 0 ≦ a <0.5, Represents a numerical value in the range of 0 ≦ b <0.5, 5 × 10 ⁻⁴ ≦ z ≦ 7 × 10 ⁻² ]

  Below, the manufacturing method of the radiation image conversion panel of this invention is described in detail taking the case where a fluorescent substance layer is formed by the electron beam vapor deposition method which is a kind of vapor deposition method as an example.

  The substrate for forming the vapor deposition film usually serves also as a support for the radiation image conversion panel, and can be arbitrarily selected from known materials as a support for the conventional radiation image conversion panel. A quartz glass sheet, a sapphire glass sheet; a metal sheet made of aluminum, iron, tin, chromium or the like; a resin sheet made of aramid or the like. In a known radiation image conversion panel, in order to improve the sensitivity or image quality (sharpness, graininess) of the panel, a light reflecting layer made of a light reflecting material such as titanium dioxide, or a light absorbing material such as carbon black It is known to provide a light absorption layer made of or the like. These various layers can also be provided on the substrate used in the present invention, and the configuration thereof can be arbitrarily selected according to the desired purpose and application of the radiation image conversion panel.

  Further, for the purpose of enhancing the columnar crystallinity of the deposited film, the surface of the substrate on which the deposited film is formed (an auxiliary layer such as an undercoat layer (adhesion-imparting layer), a light reflecting layer or a light absorbing layer on the surface of the substrate) May be provided on the surface of these auxiliary layers) may have a fine uneven pattern. The pitch of the concavo-convex pattern is generally 15 μm or less, and preferably in the range of 1 to 10 μm. Since the uneven pattern on the substrate surface functions as a growth base point when the columnar crystal of the phosphor grows, a deposited film with better columnar crystallinity can be obtained. If the pattern pitch is larger than 15 μm, the uneven pattern does not function sufficiently.

  As the phosphor, a europium activated cesium halide photostimulable phosphor represented by the basic composition formula (I) is used. X in the basic composition formula (I) preferably contains at least Br. Further, in the basic composition formula (I), if necessary, a metal oxide such as aluminum oxide, silicon dioxide, zirconium oxide or the like may be added in an amount of 0.5 mol or less with respect to 1 mol of CsX. Good.

  In the case of forming a phosphor layer by multi-source deposition (co-evaporation), first, at least two of an evaporation source comprising a compound of a matrix component of the stimulable phosphor and an activator component are included. Prepare an evaporation source. Multi-source deposition can control the deposition rate when the vapor pressures of the matrix component and the activator component of the phosphor are greatly different as in the europium activated cesium halide photostimulable phosphor. preferable. Each evaporation source may be composed of only a phosphor base material compound and an activator component, or may be a mixture with additive components, depending on the desired phosphor composition. . Further, the number of evaporation sources is not limited to two, and for example, three or more evaporation sources may be added by separately adding evaporation sources composed of additive components.

  The matrix component compound of the phosphor may be cesium halide itself constituting the matrix, or may be a mixture of two or more raw materials that can react to form cesium halide. The activator component is generally a compound containing an activator europium, for example, europium halide or europium oxide.

The molar ratio of the Eu ²⁺ compound in the europium compound is preferably 70% or more. In general, Eu compounds contain a mixture of Eu ²⁺ and Eu ^3+, but the desired stimulating luminescence (or even instantaneous luminescence) is a phosphor using Eu ²⁺ as an activator. Because it is emitted from. Eu compound EuX _m (X is halogen as defined above), preferably in particular EuBr _m, in which case, m is preferably a number within a range of 2.0 ≦ m ≦ 2.3 . m is preferably 2.0, but oxygen tends to be mixed if it is close to 2.0. Therefore, in practice, the state where m is around 2.2 and the ratio of X is relatively high is stable. However, EuBr _{2 from} which contained oxygen has been removed by a melting treatment in a Br gas atmosphere may be used.

The evaporation source preferably has a water content of 0.5% by weight or less. In particular, when the phosphor matrix component and the activator component serving as the evaporation source are hygroscopic, such as CsX and EuX _m , it is possible to suppress the water content to such a low value from the viewpoint of preventing bumping. is important. The dehydration of the evaporation source is performed by heating each of the above phosphor components in a temperature range of 100 to 300 ° C. under reduced pressure, or in an atmosphere not containing water such as a nitrogen atmosphere at a temperature equal to or higher than the melting point of the component. It can be carried out by heating and melting for several tens of minutes to several hours.

The relative density of the evaporation source is preferably 80% or more and 98% or less, more preferably 90% or more and 96% or less. Here, the relative density means the ratio of the actual density of the evaporation source to the density specific to the phosphor or its raw material. For example, relative density of 80% or more means CsBr ≧ 3.5 g / cm ³ and EuBr ₂ ≧ 4.4 g / cm ³ . If the evaporation source is in a powder state with a low relative density, there will be inconveniences such as powder scattering during vapor deposition, or the film thickness of the vapor deposition film will be non-uniform without evaporating uniformly from the surface of the evaporation source. Or Therefore, it is desirable that the density of the evaporation source is high to some extent in order to realize stable vapor deposition. In order to obtain the above relative density, generally, the powder is pressure-molded at a pressure of 20 MPa or more, or heated and melted at a temperature of the melting point or more to form a tablet (tablet). However, the evaporation source is not necessarily in the form of a tablet.

  Further, the evaporation source, particularly the evaporation source including the host component of the phosphor has a content of alkali metal impurities (that is, alkali metals other than the constituent elements of the phosphor) of 10 ppm or less, and alkaline earth metal impurities (that is, The content of the alkaline earth metal other than the constituent elements of the phosphor is desirably 1 ppm or less. Such an evaporation source can be prepared by using a raw material having a low impurity content such as an alkali metal or an alkaline earth metal. As a result, it is possible to form a vapor-deposited film with less contamination of impurities, and the vapor-deposited film thus formed increases the amount of light emitted.

The evaporation source and the substrate are placed in a vapor deposition apparatus, and the inside of the apparatus is evacuated to a high vacuum level of 1 Pa or less. The degree of vacuum is preferably 0.1 Pa or less, more preferably about 1 × 10 ⁻⁵ to 1 × 10 ⁻² Pa. In the electron beam evaporation method, the evaporation rate can be easily controlled as described above, but an electron gun for generating an electron beam cannot be used at a vacuum level lower than 1 Pa even if it is an arc-free type. At this time, an inert gas such as Ar gas, Ne gas, or N ₂ gas may be introduced while maintaining the degree of vacuum at this level. Further, the moisture pressure in the atmosphere in the apparatus is preferably set to 7.0 × 10 ⁻³ Pa or less by using a cryopump, a combination of a diffusion pump and a cold trap or the like.

  In the case of vapor deposition, it is common to heat the substrate. The substrate is usually heated from the back side of the substrate using the radiant heat of the heater.

  The concentration (Eu / Cs, molar ratio) of the activator Eu with respect to Cs, which is the host constituent element of the phosphor in the photostimulable europium-activated cesium halide phosphor layer produced by the present inventors, and the substrate When the relationship with the heating temperature is within a specific range, it can be seen that a vapor-deposited film having a good columnar crystal shape, a large amount of photostimulated luminescence, and good adhesion to the substrate can be obtained. It was. That is, in the present invention, at the time of vapor deposition, the substrate is heated at a temperature T (° C.) that satisfies all of the relational expressions (1) to (3) with respect to the activator Eu concentration x.

FIG. 1 is a graph showing the relationship between the activator concentration x (Eu / Cs) and the substrate temperature T. In FIG. 1, curve 1 represents the equation T = 867.24 × ^0.4537 , curve 2 represents the equation T = 0.0985x ^−1.0587 , and curve 3 represents T = 1485.4x ² −760.75x + 297.37. Represents. In the present invention, the substrate temperature T is set with respect to the activator concentration x so as to be within a region (shaded portion) surrounded by these curves 1 to 3.

  The substrate temperature may be changed during vapor deposition within a range satisfying the above relational expression. In that case, it is preferable that the substrate temperature at the start of vapor deposition is higher than the substrate temperature at the end and the difference is less than 100 ° C. Alternatively, the temperature may be controlled by dividing the substrate in the horizontal direction so that the substrate temperature becomes a predetermined temperature, or radiation heating may be performed from both the front and back surfaces of the substrate.

As is clear from FIG. 1, in order to obtain a desired effect, the activator Eu is also used at a concentration in the hatched region, that is, in the range of about 5 × 10 ^{−4 to} 7 × 10 ⁻² . In the case of electron beam irradiation, the concentration of the activator is adjusted by suitably adjusting the emission current of each electron gun when each electron beam is generated from two electron guns and irradiated to each evaporation source. In the case of resistance heating, it can be adjusted by adjusting the amount of electrical energy supplied to each steaming source.

  In the electron beam irradiation, it is desirable to set the acceleration voltage of the electron beam to 1.5 kV or more and 5.0 kV or less. By the irradiation of the electron beam, the matrix component and activator component of the stimulable phosphor as an evaporation source are heated to evaporate and scatter, and react to form the phosphor and deposit on the substrate surface. The deposition rate of the phosphor, that is, the deposition rate is generally in the range of 0.1 to 1000 μm / min, and preferably in the range of 1 to 100 μm / min.

  Prior to forming a vapor deposition film made of a stimulable phosphor on the substrate, a vapor deposition film made only of the host compound of the phosphor may be formed. Thus, the phosphor columnar crystals can be grown in a one-to-one correspondence on the base compound columnar crystals having a good shape, and thus a vapor deposition film with even better columnar crystallinity can be obtained. In that case, it is preferable that the substrate temperature is in the range of 50 to 300 ° C. and is equal to or lower than the substrate temperature T at the time of phosphor deposition. Additives such as an activator in the vapor deposition film made of the phosphor diffuse into the vapor deposition film made of the phosphor base compound by heating the substrate and / or heat treatment after the vapor deposition. The boundaries are not always clear.

  Also, two or more phosphor layers can be formed by performing electron beam irradiation or resistance heating in a plurality of times. Alternatively, the phosphor layer may be heat-treated (annealed) after vapor deposition. The heat treatment is generally performed at a temperature in the range of 50 ° C. to 600 ° C. in an inert gas atmosphere (which may contain a small amount of oxygen gas or hydrogen gas) for 1 to 8 hours. Preferably, it is performed for 1 to 4 hours at a temperature in the range of 50 ° C. to 300 ° C.

  In the case of single vapor deposition (pseudo single vapor deposition), a single evaporation source is prepared that contains the phosphor matrix component compound and the activator component separately in a direction perpendicular to the evaporation flow (direction parallel to the substrate). It is preferable. Alternatively, single vapor deposition using a stimulable phosphor or a raw material mixture thereof as an evaporation source may be used. In that case, the evaporation source is prepared in advance so as to contain a desired concentration of activator. Alternatively, it is also possible to perform vapor deposition while supplying the matrix component of the phosphor to the evaporation source in consideration of the vapor pressure difference between the phosphor matrix component and the activator component.

  In this way, a layer in which the columnar crystals made of the photostimulable phosphor are grown in the thickness direction is obtained. The layer thickness of the phosphor layer is usually in the range of 50 to 1000 μm, preferably in the range of 200 μm to 700 mm.

  In the present invention, as described above, the vapor deposition method is not limited to the electron beam vapor deposition method, and other known methods such as a resistance heating method may be used. In addition, the substrate does not necessarily have to serve as a support for the radiation image conversion panel. After forming the phosphor layer, the phosphor layer is peeled off from the substrate and bonded to the prepared support using an adhesive or the like. A method of providing a phosphor layer on a support may be used. Alternatively, the support (substrate) may not be attached to the phosphor layer.

It is desirable to provide a protective layer on the surface of the phosphor layer in order to facilitate transportation and handling of the radiation image conversion panel and avoid characteristic changes. It is desirable that the protective layer be transparent so that it does not affect the incidence of excitation light and emission of emitted light, and the radiation image conversion panel is sufficiently protected from physical impacts and chemical effects given from the outside. It is desirable to be chemically stable, highly moisture-proof, and have high physical strength.
As the protective layer, a solution prepared by dissolving a transparent organic polymer substance such as cellulose derivative, polymethyl methacrylate, organic solvent-soluble fluorine-based resin in an appropriate solvent is applied on the phosphor layer. Formed, or separately formed a protective layer forming sheet such as an organic polymer film such as polyethylene terephthalate or a transparent glass plate, and provided with an appropriate adhesive on the surface of the phosphor layer, or inorganic A compound formed on the phosphor layer by vapor deposition or the like is used. In addition, in the protective layer, various additives such as light scattering fine particles such as magnesium oxide, zinc oxide, titanium dioxide and alumina, slipping agents such as perfluoroolefin resin powder and silicone resin powder, and crosslinking agents such as polyisocyanate. May be dispersed and contained. The thickness of the protective layer is generally in the range of about 0.1 to 20 μm when it is made of a polymer substance, and is in the range of 100 to 1000 μm when it is made of an inorganic compound such as glass.

  A fluororesin coating layer may be further provided on the surface of the protective layer in order to increase the stain resistance of the protective layer. The fluororesin coating layer can be formed by coating a fluororesin solution prepared by dissolving (or dispersing) a fluororesin in an organic solvent on the surface of the protective layer and drying. Although the fluororesin may be used alone, it is usually used as a mixture of a fluororesin and a resin having a high film forming property. In addition, an oligomer having a polysiloxane skeleton or an oligomer having a perfluoroalkyl group can be used in combination. The fluororesin coating layer can be filled with a fine particle filler in order to reduce interference unevenness and further improve the image quality of the radiation image. The thickness of the fluororesin coating layer is usually in the range of 0.5 μm to 20 μm. In forming the fluororesin coating layer, additive components such as a cross-linking agent, a hardener, and a yellowing inhibitor can be used. In particular, the addition of a crosslinking agent is advantageous for improving the durability of the fluororesin coating layer.

  Although the radiation image conversion panel of the present invention is obtained as described above, the configuration of the panel of the present invention may include various known variations. For example, for the purpose of improving the sharpness of the obtained image, at least one of the layers may be colored with a colorant that absorbs excitation light and does not absorb stimulated emission light.

[Example 1] Binary vapor-deposited phosphor layer (electron beam irradiation)
(1) Raw material As a raw material, cesium bromide (CsBr) having a purity of 4N or higher and europium bromide (EuBr _m , m = 2.2) having a purity of 3N or higher were used. As a result of analyzing trace elements in each raw material by ICP-MS method (inductively coupled plasma spectroscopy-mass spectrometry), alkali metals (Li, Na, K, Rb) other than Cs in CsBr are each 10 ppm or less. Yes, and other elements such as alkaline earth metals (Mg, Ca, Sr, Ba) were 2 ppm or less. Also, rare earth elements other than Eu in EuBr _m is at each 20ppm or less, other elements were 10ppm or less. Since these raw materials have high hygroscopicity, they were stored in a desiccator that maintained a dry atmosphere with a dew point of -20 ° C. or less, and were taken out immediately before use.

(2) Production of CsBr evaporation source 75 g of CsBr powder was placed in a zirconia powder molding die (inner diameter: 35 mm), and a powder mold press molding machine (table press TB-5 type, manufactured by NP System Co., Ltd.) Pressurization was performed at a pressure of 50 MPa to form a tablet (diameter: 35 mm, thickness: 20 mm). At this time, the pressure applied to the CsBr powder was about 40 MPa. Next, this tablet was vacuum dried at a temperature of 200 ° C. for 2 hours with a vacuum dryer. The density of the obtained tablet was 3.9 g / cm ³ and the water content was 0.3% by weight.

(3) Production of EuBr _m evaporation source 25 g of EuBr _m (m = 2.2) powder was placed in a zirconia powder molding die (inner diameter: 25 mm), and pressurized with a powder mold press molding machine at a pressure of 50 MPa. Molded into a tablet (diameter: 25 mm, thickness: 10 mm). The pressure applied to the EuBr _m powder was about 80 MPa. Next, this tablet was vacuum dried at a temperature of 200 ° C. for 2 hours with a vacuum dryer. The density of the obtained tablet was 5.1 g / cm ³ and the water content was 0.5% by weight.

(4) Formation of phosphor layer As a support, a glass substrate with minute projections patterned on one side in a regular array (diameter φ = 5 μm of each projection, height h = 5 μm, pitch d between projections d = 2 μm) ) Was prepared, and in this order, alkali cleaning, pure water cleaning, and IPA (isopropanol) cleaning were performed. The glass substrate was placed on a substrate holder in the vapor deposition apparatus so that the patterned surface was a vapor deposition surface. After placing in position in the apparatus of the above CsBr evaporation source and EuBr _m evaporation source was set to 1 × 10 ^-3 Pa vacuum degree by evacuating the apparatus (argon gas present). At this time, a combination of a rotary pump, a mechanical booster, and a turbo molecular pump was used as a vacuum exhaust device. Next, the glass substrate was heated to 200 ° C. (measurement temperature) with a sheathed heater located on the side opposite to the deposition surface of the substrate. An electron gun was used for each of the evaporation sources, and an electron beam with an acceleration voltage of 4.0 kV was irradiated and co-evaporated to deposit a CsBr: Eu photostimulable phosphor. At this time, the emission current of each electron gun was adjusted so that the Eu / Cs molar ratio in the photostimulable phosphor was 0.003 / 1, and deposition was performed at a rate of 4 μm / min. The water pressure in the vapor deposition atmosphere was 4 × 10 ⁻³ Pa.

  After vapor deposition, the inside of the apparatus was returned to atmospheric pressure, and the glass substrate having the vapor deposition film was taken out from the apparatus. This glass substrate was placed in a quartz boat, placed in the core of a tube furnace, and heat-treated at a temperature of 200 ° C. for 2 hours in a nitrogen gas atmosphere. Before and during the heat treatment, the inside of the furnace core was evacuated to about 10 Pa with a rotary pump to remove moisture adsorbed on the deposited film. The glass substrate was cooled under vacuum and removed from the furnace core when the temperature was sufficiently lowered. On the glass substrate, a phosphor layer (layer thickness: about 400 μm, area 30 mm × 30 mm) having a structure in which columnar crystals of the phosphor were densely planted substantially vertically was formed. Thus, the radiation image conversion panel which consists of a support body and a fluorescent substance layer was manufactured by co-evaporation.

  Furthermore, the emission current of the electron gun was changed so that the heating temperature of the glass substrate was changed between 30 to 350 ° C., and the Eu / Cs molar ratio was changed between 0.0003 / 1 to 0.03 / 1. A number of radiation image conversion panels were produced in the same manner as described above except that was adjusted.

[Performance evaluation 1 of radiation image conversion panel]
Each radiation image conversion panel was evaluated for columnarity, sensitivity, and adhesiveness.
(1) Columnarity After the phosphor layer of the radiation image conversion panel is cut in the thickness direction together with the support and coated with gold (thickness: 300 angstrom) by ion sputtering, a scanning electron microscope (JSM-5400 type, JEOL Ltd.) The surface and the cut surface of the phosphor layer were observed using a product manufactured by Co., Ltd., and the shape of the columnar crystal was evaluated based on the average value of the scores given by five people when the perfect score was 7 points. The practical level is 1.5 points or more.

(2) Sensitivity The radiation image conversion panel was housed in a cassette capable of shielding room light, and was irradiated with 26 J / m ² of X-rays. Next, after removing the panel from the cassette, the panel is excited with an LD laser beam (wavelength: 650 nm), and the stimulated emission light emitted from the conversion panel is detected by a photomultiplier, and the sensitivity ( (Relative value) was evaluated. The practical level is 100 or more.

(3) Adhesive After sticking an adhesive tape on the surface of the phosphor layer, the adhesive tape is peeled off and the presence or absence of peeling of the phosphor layer from the support (substrate) is observed. Evaluation was made based on the number of points. There are two or more practical levels.
The obtained results are collectively shown in Tables 1 to 3.

[Table 1]
Table 1 [Columnar]
───────────────────────────────
Substrate Eu / Cs mole ratio <br/> temperature ^{(℃) 3 × 10 -4 1} × 10 -3 3 × 10 -3 1 × 10 -2 3 × 10 -2
───────────────────────────────
30 1.8 1.6 1 1 1
50 4.4 2.6 1.6 1.2 1
100 5.6 5.2 3.4 1.6 1
150 6.2 5.8 4.6 3.4 1
200 6.6 6.6 6.4 4.6 1.6
250 6.8 6.6 6.6 5.4 2.6
300 6.8 6.8 6.8 6.4 2.8
350 7 6.8 6.8 6.4 4
───────────────────────────────

[Table 2]
Table 2 [Sensitivity]
───────────────────────────────
Substrate Eu / Cs molar ratio temperature (° C) 3 × 10 ^-4 1 × 10 ^-3 3 × 10 ^-3 1 × 10 ^-2 3 × 10 ^-2
───────────────────────────────
30 56 59 72 83 120
50 57 72 80 78 123
100 58 98 325 62 114
150 59 202 515 101 106
200 61 332 845 102 104
250 67 339 685 144 102
300 66 340 683 177 64
350 53 57 270 175 58
───────────────────────────────

[Table 3]
Table 3 [Adhesiveness]
───────────────────────────────
Substrate Eu / Cs molar ratio temperature (° C) 3 × 10 ^-4 1 × 10 ^-3 3 × 10 ^-3 1 × 10 ^-2 3 × 10 ^-2
───────────────────────────────
30 4 4 4 2 2
50 4 4 4 2 2
100 4 4 4 2 2
150 4 4 3 2 2
200 4 3 3 2 2
250 3 3 2 2 1
300 2 3 1 1 1
350 1 1 1 1 1
───────────────────────────────

[Example 2] Binary vapor-deposited phosphor layer (electron beam irradiation) having a phosphor matrix compound layer
(1) Raw material The raw material similar to Example 1 was used.
(2) Production of CsBr Evaporation Source A CsBr tablet was produced in the same manner as in Example 1.
(3) Production of EuBr _m evaporation source A tablet of EuBr _m (m = 2.2) was produced in the same manner as in Example 1.

(4) Formation of phosphor layer A flat synthetic quartz substrate subjected to alkali cleaning, pure water cleaning, and IPA cleaning in this order was prepared as a support, and placed on a substrate holder in a vapor deposition apparatus. The CsBr evaporation source and the EuBr _m evaporation source were arranged at predetermined positions in the apparatus, and then the apparatus was evacuated to a vacuum degree of 1 × 10 ⁻³ Pa. At this time, a combination of a rotary pump, a mechanical booster, and a turbo molecular pump was used as a vacuum exhaust device. Next, the quartz substrate is heated to 200 ° C. with a sheathed heater installed on the side opposite to the deposition surface of the substrate, and an electron beam with an acceleration voltage of 4.0 kV is irradiated to the CsBr evaporation source with an electron gun at 10 μm / min. The CsBr phosphor matrix was deposited at a rate of 5 minutes. Next, while maintaining the quartz substrate at 200 ° C., each evaporation source was irradiated with an electron beam with an acceleration voltage of 4.0 kV by an electron gun and co-evaporated to deposit a CsBr: Eu stimulable phosphor. At this time, the emission current of each electron gun was adjusted so that the Eu / Cs molar ratio in the photostimulable phosphor was 0.003 / 1, and deposition was performed at a rate of 4 μm / min. The water pressure in the vapor deposition atmosphere was 4 × 10 ⁻³ Pa.

  After the completion of vapor deposition, the quartz substrate having the vapor deposition film was subjected to heat treatment in the same manner as in Example 1. On the quartz substrate, a phosphor layer (layer thickness: about 400 μm, area 30 mm × 30 mm) having a structure in which the columnar crystals of the phosphor are densely grown in a substantially vertical direction was formed. Thus, the radiation image conversion panel which consists of a support body and a fluorescent substance layer was manufactured.

  Furthermore, the emission current of the electron gun was changed so that the heating temperature of the quartz substrate was changed between 30 to 350 ° C., and the Eu / Cs molar ratio was changed between 0.0003 / 1 to 0.03 / 1. A number of radiation image conversion panels were produced in the same manner as described above except that was adjusted.

[Performance evaluation 2 of radiation image conversion panel]
The columnar properties, sensitivity, and adhesiveness of each radiation image conversion panel were evaluated in the same manner as described above. The obtained results are collectively shown in Tables 4-6.

[Table 4]
Table 4 [Columnar]
───────────────────────────────
Substrate Eu / Cs molar ratio temperature (° C) 3 × 10 ^-4 1 × 10 ^-3 3 × 10 ^-3 1 × 10 ^-2 3 × 10 ^-2
───────────────────────────────
30 1.6 1.6 1.2 1.2 1 1
50 3.6 2.8 1.6 1.4 1
100 4.6 4 3.6 1.8 1
150 5.4 4.8 4.2 2.4 1.2
200 5.8 5.2 4.8 3 1.6
250 6.4 5.8 5.6 3.4 1.8
300 6.6 6 5.8 3.8 2.4
350 6.8 6.4 5.8 4 3.2
───────────────────────────────

[Table 5]
Table 5 [Sensitivity]
───────────────────────────────
Substrate Eu / Cs molar ratio temperature (° C) 3 × 10 ^-4 1 × 10 ^-3 3 × 10 ^-3 1 × 10 ^-2 3 × 10 ^-2
───────────────────────────────
30 52 60 60 60 54
50 53 62 65 61 56
100 54 95 125 92 61
150 55 185 194 168 92
200 57 249 492 205 139
250 56 170 201 151 102
300 54 73 80 70 64
350 53 62 68 56 52
───────────────────────────────

[Table 6]
Table 6 [Adhesiveness]
───────────────────────────────
Substrate Eu / Cs molar ratio temperature (° C) 3 × 10 ^-4 1 × 10 ^-3 3 × 10 ^-3 1 × 10 ^-2 3 × 10 ^-2
───────────────────────────────
30 4 3 3 3 3
50 4 3 3 3 2
100 4 3 3 3 2
150 4 3 3 2 2
200 4 3 3 2 2
250 4 3 2 2 1
300 2 2 1 1 1
350 1 1 1 1 1
───────────────────────────────

The evaluation results (columnarity, sensitivity, adhesiveness) obtained for Examples 1 and 2 were comprehensively judged, and final evaluation was performed according to the following criteria.
AA: Extremely good A: Good and suitable for practical use C: Poor and practically problematic The results are summarized in Table 7 and FIG.

[Table 7]
Table 7 (Comprehensive evaluation)
───────────────────────────────
Substrate Eu / Cs molar ratio temperature (° C) 3 × 10 ^-4 1 × 10 ^-3 3 × 10 ^-3 1 × 10 ^-2 3 × 10 ^-2
───────────────────────────────
30 C C C C C
50 C C C C C
100 C C A A C
150 C A AA A C
200 C AA AA A A
250 C A A A A
300 C C C C C
350 C C C C C
───────────────────────────────

  In Table 7, examples of combinations of Eu / Cs molar ratio (activator concentration) and substrate temperature that have reached a practically suitable level (A or higher) in the final evaluation are combinations included in the present invention. These combinations are combinations in the area surrounded by the curves 1 to 3 in FIG. In FIG. 1, curve 1 corresponds to relational expression (1) and is determined mainly from the evaluation result of columnarity, and curve 2 corresponds to relational expression (2) and mainly from the evaluation result of sensitivity. Curve 3 corresponds to the relational expression (3) and was mainly determined from the adhesive evaluation result.

  As is apparent from the results shown in Table 7 and FIG. 1, all of the columnarity, sensitivity, and adhesiveness are obtained by performing deposition at the activator concentration and the substrate temperature within the range defined by the relational expression of the present invention. A favorable radiation image conversion panel can be manufactured.

[Example 3] Binary vapor-deposited phosphor layer (resistance heating) having a phosphor host compound layer
(1) Raw material The raw material similar to Example 1 was used.
(2) Production of CsBr Evaporation Source A CsBr tablet was produced in the same manner as in Example 1.
(3) Preparation of EuBr _m evaporation source EuBr ₂ tablets were prepared by melting in Br gas.

(4) Formation of phosphor layer According to a known resistance heating method, each evaporation source is arranged on each heating tool of a resistance heater having a plurality of heating regions, and the degree of vacuum is set to 1 Pa (argon gas). A base compound layer (CsBr layer) and a CsBr: Eu photostimulable phosphor were deposited on a heated substrate in the same manner as in Example 2 except that the method of changing the electrical energy supplied to the heating tool was used. .

  After the completion of vapor deposition, the quartz substrate having the vapor deposition film was subjected to heat treatment in the same manner as in Example 1. On the quartz substrate, a phosphor layer (layer thickness: about 400 μm, area 30 mm × 30 mm) having a structure in which the columnar crystals of the phosphor are densely grown in a substantially vertical direction was formed. Thus, the radiation image conversion panel which consists of a support body and a fluorescent substance layer was manufactured.

  In the above vapor deposition operation, the heating conditions are changed so that the heating temperature of the quartz substrate is changed between 100 to 300 ° C. and the Eu / Cs molar ratio is changed between 0.0003 / 1 to 0.03 / 1. A number of radiation image conversion panels were manufactured by adjusting.

[Performance evaluation of radiation image conversion panel 3]
The columnar properties, sensitivity, and adhesiveness of each radiation image conversion panel were evaluated in the same manner as described above. The obtained results are collectively shown in Tables 8 to 10.

[Table 8]
Table 8 [Columnar]
───────────────────────────────
Substrate Eu / Cs molar ratio temperature (° C) 3 × 10 ^-4 1 × 10 ^-3 3 × 10 ^-3 1 × 10 ^-2 3 × 10 ^-2
───────────────────────────────
100 1.8 1.8 1.6 1 1
150 6.6 6 4.8 1.4 1
200 7 6.6 6.4 3.4 1.4
250 7 6 5.6 3.6 1.8
300 6.2 4.6 2.4 2 2
───────────────────────────────

[Table 9]
Table 9 [Sensitivity]
───────────────────────────────
Substrate Eu / Cs molar ratio temperature (° C) 3 × 10 ^-4 1 × 10 ^-3 3 × 10 ^-3 1 × 10 ^-2 3 × 10 ^-2
───────────────────────────────
100 32 93 475 364 103
150 43 640 1420 555 141
200 85 1980 2750 1120 183
250 73 2030 2630 1030 122
300 68 1010 970 900 70
───────────────────────────────

[Table 10]
Table 10 [Adhesiveness]
───────────────────────────────
Substrate Eu / Cs molar ratio temperature (° C) 3 × 10 ^-4 1 × 10 ^-3 3 × 10 ^-3 1 × 10 ^-2 3 × 10 ^-2
───────────────────────────────
100 4 4 4 3 2
150 4 4 4 3 2
200 4 4 4 3 1
250 1 1 3 2 1
300 1 1 1 1 1
───────────────────────────────

The evaluation results (columnarity, sensitivity, adhesiveness) obtained for Example 3 were comprehensively judged, and final evaluation was performed according to the following criteria.
AA: Extremely good A: Good and suitable for practical use C: Poor and problematic in practical use The results are summarized in Table 11.

[Table 11]
Table 11 (Comprehensive evaluation)
───────────────────────────────
Substrate Eu / Cs molar ratio temperature (° C) 3 × 10 ^-4 1 × 10 ^-3 3 × 10 ^-3 1 × 10 ^-2 3 × 10 ^-2
───────────────────────────────
100 C C A A C
150 C A AA A C
200 C AA AA A A
250 C AA A A A
300 C C C C C
───────────────────────────────

  In Table 11, examples of combinations of Eu / Cs molar ratio (activator concentration) and substrate temperature that have reached practically suitable levels (A and AA) in the final evaluation are included in the present invention. These combinations are combinations in the region surrounded by the curves 1 to 3 in FIG. In addition, examples of combinations of Eu / Cs molar ratio (activator concentration) and substrate temperature that have reached the AA level are included in the region defined by the relational expressions (4) to (7) described above. Are particularly preferred.

  As is clear from the results shown in Table 11, all the columnarity, sensitivity, and adhesiveness are good by performing vapor deposition at an activator concentration and substrate temperature within the range defined by the relational expression of the present invention. A radiation image conversion panel can be manufactured.

It is a graph which shows the range which satisfies each relational expression of activator density | concentration x (Eu / Cs molar ratio) according to this invention, and substrate temperature T.

Claims (12)

A europium-activated cesium halide phosphor or a material generated by heating an evaporation source containing the raw material under reduced pressure is deposited on a substrate to form a stimulable europium-activated cesium halide phosphor layer. In the method for manufacturing a radiation image conversion panel comprising a substrate and a photostimulable europium-activated cesium halide phosphor layer formed on the substrate, the vapor deposition is formed on the substrate. The molar ratio of europium / cesium in the europium-activated cesium halide phosphor layer and the substrate temperature during deposition satisfy the following relational expressions (1) to (3): Manufacturing method of radiation image conversion panel.

Relational expression (1): T ≧ 867.24 ^{× 0.4537}
Relational expression (2): T ≧ 0.0985x ^-1.0587
Relational expression (3): T ≦ 1485.4x ² −760.75x + 297.37

[Wherein T represents the substrate temperature (° C.) during vapor deposition, and x represents the molar ratio of europium / cesium in the europium-activated cesium halide phosphor layer. ]   The manufacturing method of the radiation image conversion panel of Claim 1 which vapor-deposits with a vacuum degree of 1 Pa or less.   The manufacturing method of the radiation image conversion panel of Claim 2 which vapor-deposits by the vacuum degree of 0.1 Pa or less.   The manufacturing method of the radiation image conversion panel of Claim 1 which vapor-deposits by the vacuum degree of the range of 0.1 Pa-5Pa.   The manufacturing method of the radiation image conversion panel of Claim 4 which vapor-deposits with the vacuum degree of the range of 0.1 Pa-2 Pa. In the above vapor deposition, the molar ratio of europium / cesium in the europium activated cesium halide phosphor layer formed on the substrate and the substrate temperature at the time of vapor deposition satisfy all the following relational expressions (4) to (7). 6. The method for producing a radiation image conversion panel according to claim 4, wherein the method is carried out under a satisfying condition.

Relational expression (4): T ≦ 175.14x ^−0.0682
Relational expression (5): T ≧ 0.028x- ^1.3048
Relational expression (6): T ≧ −63745x ² −3581.4x + 304.61
Relational expression (7): T ≦ 23.844Ln (x) +265.01

[T and x have the same meaning as T and x in claim 1, respectively. ]   The manufacturing method of the radiation image conversion panel of any one of Claims 1 thru | or 6 with which a board | substrate has a fine uneven | corrugated pattern on the surface.   The method for manufacturing a radiation image conversion panel according to claim 7, wherein the pitch of the minute uneven pattern is 15 μm or less.   The method for producing a radiation image conversion panel according to any one of claims 1 to 8, wherein multi-source vapor deposition is performed using an evaporation source containing cesium halide and an evaporation source containing a europium compound as the evaporation source.   10. The vapor deposition film made of cesium halide is formed on the substrate, and then the vapor deposition film made of europium-activated cesium halide phosphor is laminated on the vapor deposition film. The manufacturing method of the radiation image conversion panel of description. Europium-activated cesium halide photostimulable phosphor has the basic composition formula (I):

CsX · aM ^II X ′ ₂ · bM ^III X ″ ₃ : zEu (I)

[Wherein M ^II represents at least one alkaline earth metal or divalent metal selected from the group consisting of Be, Mg, Ca, Sr, Ba, Ni, Cu, Zn and Cd; M ^III represents Sc, Y, At least one rare earth element or trivalent metal selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Al, Ga and In X, X ′ and X ″ each represent at least one halogen selected from the group consisting of F, Cl, Br and I; and a, b and z are each 0 ≦ a <0.5, Represents a numerical value in the range of 0 ≦ b <0.5, 5 × 10 ⁻⁴ ≦ z ≦ 7 × 10 ⁻² ]
The method for manufacturing a radiation image conversion panel according to any one of claims 1 to 10, wherein the phosphor includes a phosphor. The method for producing a radiation image conversion panel according to claim 11, wherein X in the basic composition formula (I) is Br.

Images