JP2020097669A - Manufacturing method for scintillator - Google Patents

Abstract

To provide a technique advantageous for suppressing a bright burn effect and improving quality of a scintillator.SOLUTION: A manufacturing method for a scintillator includes: a process of preparing a material supply source containing a cesium iodide material and a copper material; and a vapor deposition process of using the material supply source to form a scintillator on a substrate. In the vapor deposition process, the cesium iodide material is melted in the material supply source and heated to a temperature lower than a melting point of the copper material, and copper iodide generated by a reaction of the copper material and the cesium iodide material is vaporized along with the melted cesium iodide material, so that a scintillator containing cesium iodide and copper is formed on the substrate.SELECTED DRAWING: Figure 1

Description

The present invention relates to a scintillator manufacturing method.

Some radiation imaging devices are configured to convert radiation into light with a scintillator and detect the light with a photoelectric conversion element. The characteristics of the scintillator may change depending on the irradiation of radiation, and such a phenomenon is also called “bright burn”. In Patent Document 1, in order to suppress bright burn, an atom that becomes a monovalent cation is added to a scintillator containing an alkali metal iodide as a base material and an activator for improving the luminous efficiency of the scintillator. It has been shown to further contain.

JP, 2016-88988, A

In Patent Document 1, a base material compound, an activator compound, and a compound containing an atom capable of forming a monovalent cation are housed in different vapor deposition sources and heated to form a scintillator on a support. Has been shown to do. Since the atoms that become monovalent cations are supplied from a vapor deposition source that is different from the scintillator base material compound, it becomes complicated to control the concentration added to the scintillator and the uniformity of concentration in the film thickness direction. there is a possibility.

An object of the present invention is to provide a technique that is advantageous for suppressing bright burn and improving scintillator quality.

In view of the above problems, the method of manufacturing a scintillator according to an embodiment of the present invention, a step of preparing a material supply source containing a cesium iodide raw material and a copper raw material, and forming the scintillator on the substrate using the material supply source In the vapor deposition step, the material supply source is formed by the reaction between the copper raw material and the cesium iodide raw material, in which the cesium iodide raw material is melted and heated to a temperature lower than the melting point of the copper raw material. The copper iodide thus formed is vaporized together with the dissolved cesium iodide raw material to form a scintillator containing cesium iodide and copper on the substrate.

By the above means, a technique advantageous in suppressing bright burn and improving the quality of the scintillator is provided.

The figure which shows the example of the apparatus which forms a scintillator. The figure which shows the method of adding copper to a scintillator. The figure which shows the example of the evaluation method of bright burn. The figure which shows the characteristic of the scintillator of a present Example and a comparative example.

Specific embodiments of the scintillator manufacturing method according to the present invention will be described below with reference to the accompanying drawings. In the following description and drawings, common reference numerals are given to common configurations across a plurality of drawings. Therefore, common configurations will be described with reference to a plurality of drawings, and description of configurations having common reference numerals will be appropriately omitted. The radiation in the present invention includes, in addition to α-rays, β-rays, γ-rays, etc., which are beams produced by particles (including photons) emitted by radiation decay, beams having similar or higher energy such as X-rays. It may include rays, particle rays, cosmic rays, and the like.

A method of manufacturing a scintillator according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing a configuration example of a vapor deposition device 100 for forming a scintillator according to an embodiment of the present invention. The vapor deposition device 100 supports evaporation parts 101a and 101b (for example, a crucible) in which a material supply source for forming a scintillator is stored and a substrate 107 on which a scintillator is formed in a chamber 109 capable of being evacuated. The support part 108 for is included. The support 108 may rotate the substrate 107 during vapor deposition, as shown in FIG.

The material supply source stored in the evaporation unit 101a includes an alkali halide raw material as a base material of the scintillator and a metal raw material added to the scintillator. In this embodiment, the cesium iodide raw material 102 is used as the alkali halide raw material. The alkali halide raw material is not limited to the cesium iodide raw material, and needle-shaped (columnar) crystals such as sodium iodide, potassium iodide, and cesium bromide can be formed as the alkali halide raw material. Other raw materials may be used. Further, in the present embodiment, copper (copper raw material 103) is used as the metal raw material. That is, in this embodiment, the material supply source includes the cesium iodide raw material 102 and the copper raw material 103. The metal raw material is not limited to copper, and gold, silver, platinum, palladium, rhodium, iridium, ruthenium, osmium, mercury, or the like may be used as the metal raw material.

An evaporating portion 101b, which is different from the evaporating portion 101a in which a material supply source including a cesium iodide raw material 102 and a copper raw material 103 is stored, stores an activator raw material that functions as a luminescence center and improves the luminous efficiency. It In other words, as shown in FIG. 1, in addition to the material supply source containing the cesium iodide raw material 102 and the copper raw material 103, another material supply source containing the activator raw material is prepared. In this embodiment, thallium iodide raw material 104 containing thallium is used as the activator raw material. The activator is not limited to thallium, and, for example, europium or indium may be used as the activator. In this case, europium iodide, indium iodide, or the like may be used as the activator raw material. When the base material of the scintillator is cesium bromide, thallium bromide, europium bromide, indium bromide or the like may be used. In the scintillator, thallium iodide is contained in an amount of about 0.1 to 5 mol% with respect to cesium iodide as a base material, whereby sufficient light emission can be obtained.

In the present embodiment, it has been described above that the copper raw material 103 is included in the material supply source stored in the evaporation unit 101a as the raw material of the additive added to the scintillator. The copper raw material 103 will be described. The copper raw material 103 can be, for example, granular, block-shaped, mesh-shaped, or wire-shaped copper. Further, the copper raw material 103 is filled in the evaporation portion 101a so that the surface area is constant during vapor deposition. That is, when the cesium iodide raw material is heated and melted for vapor deposition, the shape and material of the metal material are set so that the contact area between the dissolved cesium iodide raw material 102 and the copper raw material 103 is kept constant. , Respectively selected.

Next, a vapor deposition process for forming a scintillator on the substrate 107 will be described. FIGS. 2(a) to 2(d) explain the mechanism assumed when copper, more specifically, copper iodide, which is a metal halide, is added to the scintillator in the vapor deposition process. FIG.

First, as shown in FIG. 2A, the material supply source in the evaporation unit 101a is heated. At this time, the material supply source is heated to a temperature at which the cesium iodide raw material 102 is dissolved and which is lower than the melting point of the copper raw material 103. Specifically, the cesium iodide raw material 102 melts at 621° C. to form a melt. On the other hand, since the melting point of copper is 1085° C., which is higher than the melting point of cesium iodide, the copper raw material 103 exists in a solid state in the dissolved cesium iodide raw material 102.

Next, as shown in FIG. 2B, the reaction of the surface portion of the copper raw material 103 with the dissolved cesium iodide raw material 102 produces copper iodide 110. The melting point of the copper iodide 110 generated on the surface portion of the copper raw material 103 is 605° C., which is lower than the melting point of the cesium iodide raw material 102. Therefore, as shown in FIG. 2C, the copper iodide 110 is evaporated together with the dissolved cesium iodide raw material 102, and a scintillator containing cesium iodide and copper is formed on the substrate 107. Further, as shown in FIG. 2D, copper iodide 110 is newly generated on the surface of the copper raw material 103, and the state shown in FIG. 2B is restored. By repeating the cycle of FIGS. 2B to 2D, copper iodide is added to the scintillator having cesium iodide as a base material formed on the substrate 107 in constant amounts. ..

As for the concentration of copper added to the scintillator, the effect can be obtained at a very low concentration of about several tens of ppm as in Examples described later. That is, the amount of copper iodide generated on the surface of the copper raw material 103 is small. Further, in Examples described later, the weight change of the used copper raw material 103 before and after vapor deposition was below the measurement limit. Therefore, in the vapor deposition step of forming the scintillator on the substrate 107, the outer shape of the copper raw material 103 is considered to be substantially unchanged, and the contact area between the molten cesium iodide raw material 102 and the copper raw material 103 is kept constant. It is considered to be dripping.

In this vapor deposition step, in order to keep the contact area between the cesium iodide raw material 102 and the copper raw material 103 constant, the copper cesium raw material 103 is disposed in the molten cesium iodide raw material 102 so that the cesium iodide raw material 102 is distributed. And the amount and shape of the copper raw material 103 may be determined. In addition, in the vapor deposition step, the film formation of the scintillator may be started and ended by operating a shutter (not shown) provided between the substrate 107 and the evaporation unit 101a. In this case, the shutter may be closed to complete the film formation before the copper raw material 103 is exposed from the dissolved cesium iodide raw material 102. That is, in the vapor deposition step, the scintillator may be vapor deposited so that the copper raw material 103 included in the material supply source in the evaporation unit 101a is not exposed from the dissolved cesium iodide raw material 102.

In the present embodiment, since the contact area between the copper raw material 103 and the cesium iodide raw material 102 can be kept constant, the amount of copper iodide 110 generated and evaporated during vapor deposition can be kept constant. Become. Therefore, the concentration of copper contained in the formed scintillator becomes constant in the film thickness direction. That is, by using the method shown in the present embodiment, it is possible to add a metal having a desired uniform concentration in the film thickness direction of the scintillator.

Although an example will be described later, a vapor deposition experiment was performed by changing the surface area of the copper raw material 103 and the filling amount of the cesium iodide raw material 102. As a result, the value obtained by dividing the surface area [mm ² ] of the copper raw material 103 by the filling amount [g] of the cesium iodide raw material 102 is 3.4 or more, and the surface area of the copper raw material is 1200 mm ² or more, and the bright burn evaluation value is Was clearly reduced and the characteristics were significantly improved. The resolution characteristics and the brightness characteristics of the scintillator at this time were almost the same as those when copper was not added.

In the vapor deposition step, at the same time as the vapor deposition from the material supply source in the evaporation unit 101b, the thallium iodide raw material 104 as the activator raw material is vaporized from the material supply source in the evaporation unit 101b. As a result, thallium is added to the scintillator as an activator. Furthermore, after forming the scintillator in the vapor deposition step, a protective film such as parylene, a fluororesin, or a TEOS film may be formed so as to cover the scintillator. The protective film can be formed by using various coating methods such as a spray method, a coating method, and a CVD method.

Next, a method for evaluating bright burn in which the characteristics of the scintillator fluctuate according to the irradiation of radiation will be described with reference to FIGS. As shown in FIG. 3B, here, with respect to the radiation detection apparatus AP in which the scintillator 301 deposited on the substrate 107 is attached to the sensor substrate (sensor unit) 302 in which a plurality of photoelectric conversion elements are arranged, Brightburn is evaluated. The scintillator 301 receives radiation to generate light (scintillation light), and this light is detected by the sensor substrate 302. The radiation detection apparatus AP can detect radiation with such a configuration.

FIG. 3A shows a state in which the radiation shielding material 303 is arranged on the radiation detecting device AP. In FIG. 3A, a portion of the scintillator 301 not covered with the radiation shielding material 303 is shown as an “exposed portion 311”, and a portion covered with the radiation shielding material 303 is shown as a “covered portion 321”. When the radiation detection apparatus AP is irradiated with radiation in this state, the radiation is incident on the exposed portion 311 and the radiation is not incident on the covered portion 321. Here, after the irradiation of radiation, a difference (bright burn) in characteristics (sensitivity, conversion efficiency from radiation to light, etc.) may occur between the exposed portion 311 and the covered portion 321.

Brightburn is evaluated by measuring the brightness of the scintillator 301 when a comparatively large radiation intensity (dose) is irradiated and a so-called “baking” is performed and then a comparatively small radiation intensity is irradiated. Done in. In this specification, the Brightburn evaluation value BB(t) is
BB(t)≡{a(t)/b(t)}/{a(0)/b(0)}-1...(1)
here,
a(0): brightness value of exposed portion 311 before baking (per unit volume (the same applies below))
b(0): Luminance value of the coated portion 321 before baking a(t): Luminance value of the exposed portion 311 after the time t has elapsed after baking b(t): The luminance value of the covered portion 321 after the time t elapsed after baking It is represented by a brightness value.

In the equation (1), a(0)/b(0) represents the ratio of the brightness value between the exposed portion 311 and the coated portion 321 before baking. Here, the brightness distribution of the scintillator 301 is uniform between the exposed portion 311 and the covered portion 321,
a(0)/b(0)=1,
Shall hold.

In the state shown in FIG. 3A, the radiation shielding material 303 is installed and baked, and then the radiation shielding material 303 is removed. Next, in the state shown in FIG. 3B, the luminance values of the exposed portion 311 and the coated portion 321 after the time t has elapsed from the baking were measured to obtain a(t)/b(t).

Here, if the above-mentioned bright burn occurs,
a(t)/b(t)>1
Is established,
BB(t)>0
Becomes On the other hand, if bright burn is suppressed or reduced,
BB(t)≈0,
Becomes That is, it can be said that the smaller the evaluation value BB(t), the more suppressed or reduced the bright burn, and the better the quality of the scintillator 301.

When the bright burn evaluation value BB(t) is large, the signal obtained in a certain shooting may be superimposed on the signal obtained in a certain shooting. This may cause an afterimage or an artifact in an image obtained by shooting, and may cause deterioration in image quality. This can be remarkable when, for example, radiography is continuously performed (so-called continuous radiography is performed).

Here, when the target value of the bright burn evaluation value BB(t) is sufficiently smaller than the noise (noise component caused by dark current, so-called dark noise) in the photoelectric conversion element on the sensor substrate 302 (for example, , 1/10 or less), it can be said that the amount of change in the brightness value of the exposed portion 311 and the covering portion 321 after baking is buried in the noise and difficult to distinguish. Therefore, when the S/N ratio of the photoelectric conversion element on the sensor substrate 302 that is generally used is set to 30 dB (20×log ₁₀ (S/N)=30, that is, S/N≈33), bright A target value of the burn evaluation value BB(t) may be set to 0.3% or less.

Hereinafter, examples and comparative examples of this embodiment will be described. As for the resolution characteristics of the scintillator 301, MTF (Modulation Transfer Function) at a spatial frequency of 2 LP/mm (pieces/mm) based on the edge method was evaluated using a quality RQA5 conforming to international standards. The brightness characteristics of the scintillator 301 can be evaluated by a light receiving element such as CCD (charge coupled device) or CMOS (complementary metal oxide film semiconductor), or a photodetector such as a flat panel detector or a camera. In the present embodiment, the luminance characteristic is that the film formation surface of the scintillator 301 is brought into close contact with the CMOS photodetector via a FOP (Fiber Optic Plate), and radiation corresponding to the radiation quality RQA5 of the international standard is applied to the CMOS photodetector. It evaluated using the output value obtained by. The chemical composition of the scintillator 301 can be evaluated by, for example, fluorescent X-ray analysis or inductively coupled plasma analysis (ICP). The crystallinity of the scintillator 301 can be evaluated by, for example, X-ray diffraction analysis.

In the evaluation of bright burn, first, in the state of FIG. 3A (the state in which the radiation shielding material 303 is arranged), the radiation voltage is 80 kV and the dose is 2.9 mGy. Was irradiated (baked). After that, the radiation shielding material 303 is removed, and after each of 2.5 minutes, 10 minutes, and 30 minutes after baking, the tube voltage is 70 kV and the dose is 2 μGy. The scintillator 301 was irradiated with the radiation. Thereby, the evaluation values BB(2.5), BB(10), and BB(30) of Brightburn were obtained.

Here, first, a comparative example will be described.

Comparative Example 1
First, 340 g of the cesium iodide raw material 102 was prepared as a material supply source, and was filled in the evaporation unit 101a (made of tantalum, cylindrical type). Further, thallium iodide raw material 104 was prepared as a material supply source for the activator, and was filled in the evaporation unit 101b (made of tantalum, cylindrical type). These evaporation units 101a and 101b were arranged at predetermined positions in the chamber 109 of the vapor deposition device 100. In addition, the substrate 107 was placed at a predetermined position in the chamber 109 via the support portion 108. As the substrate 107, used was a silicon substrate on which an aluminum reflective layer having a thickness of 200 nm and silicon dioxide having a thickness of 100 nm were laminated.

After the evaporation parts 101a and 101b filled with the material supply source and the substrate 107 are arranged at predetermined positions in the chamber 109 of the vapor deposition apparatus 100, the chamber 109 of the vapor deposition apparatus 100 is evacuated to a pressure of 0.01 Pa or less. .. Then, a current is gradually passed through each of the evaporation units 101a and 101b to heat the material supply source, and when a preset temperature and output are reached, a shutter (not opened) provided between the substrate 107 and the evaporation units 101a and 101b. The formation (deposition) of the scintillator was started by opening (shown). At this time, the substrate temperature was 80° C. and the substrate rotation speed was 60 rpm. Film formation was performed while gradually raising the substrate temperature to 140° C., and the shutter was closed before the material supply sources (cesium iodide raw material 102 and thallium iodide raw material 104) were exhausted, and film formation was completed. After cooling the substrate 107 and the evaporation units 101a and 101b to room temperature, the substrate 107 was taken out.

The formed scintillator of Comparative Example 1 was observed with a scanning electron microscope to confirm the formation of needle crystal groups. The film thickness of the scintillator of Comparative Example 1 was 795 μm. From the ICP analysis, the thallium concentration of cesium in the scintillator of Comparative Example 1 was 0.57 mol %.

As the brightness characteristics, the output value obtained by the scintillator of Comparative Example 1 using the above-described evaluation method was set to 100, and comparison was made with each Example and Comparative Example described later. As the resolution, the MTF of the scintillator of Comparative Example 1 obtained by the above-mentioned edge method using a knife edge made of tungsten was set to 100, and comparison was made with each Example and Comparative Example described later.

Bright burn evaluation was performed by using the above-described evaluation method to obtain BB (2.5) which is an evaluation value of Bright burn obtained from the brightness data 2.5 minutes after the irradiation of the radiation obtained by the scintillator of Comparative Example 1. It was set to 100 and compared. In the scintillator of Comparative Example 1, the evaluation value BB(10) of bright burn after 10 minutes was 96, and the evaluation value BB(30) of bright burn after 30 minutes was 88.

Comparative example 2
First, a material supply source containing 352 g of a cesium iodide raw material 102 and a block-shaped copper raw material 103 of 2×5×40 [mm] was prepared, and the evaporation portion 101a (made of tantalum, cylindrical) was filled. In Comparative Example 2, the surface area of the copper raw material 103 is 580 mm ² , and the value obtained by dividing the surface area [mm ² ] of the copper raw material 103 by the filling amount [g] of the cesium iodide raw material 102 is 1.6. Further, thallium iodide raw material 104 was prepared as a material supply source for the activator, and was filled in the evaporation unit 101b (made of tantalum, cylindrical type). Further, a substrate 107 having the same configuration as that of Comparative Example 1 was prepared.

After the evaporation parts 101a and 101b filled with the material supply source and the substrate 107 are arranged at predetermined positions in the chamber 109 of the vapor deposition apparatus 100, the scintillator of the comparative example 2 is placed on the substrate 107 in the same procedure as the comparative example 1. It was formed (vapor deposition). During film formation of the scintillator of Comparative Example 2, the cesium iodide raw material 102 was melted and vapor-deposited in the evaporation section 101a at a temperature lower than the melting point of copper.

After forming the scintillator of Comparative Example 2, the formed scintillator of Comparative Example 2 was observed with a scanning electron microscope to confirm the formation of needle-shaped crystal groups. The film thickness of the scintillator of Comparative Example 2 was 830 μm. From the ICP analysis, the scintillator of Comparative Example 2 had a thallium concentration of 0.97 mol% relative to cesium and a copper concentration of 1.6 ppm (parts per million).

The brightness of the scintillator of Comparative Example 2 was 113 as compared with the scintillator of Comparative Example 1. The MTF of the scintillator of Comparative Example 2 was 113 as compared with the scintillator of Comparative Example 1.

The bright burn evaluation values of the scintillator of Comparative Example 2 were BB(2.5)=104, BB(10)=98, and BB(30)=79, respectively. Although 1.6 ppm of copper was added to the scintillator of Comparative Example 2, the effect of reducing the bright burn phenomenon was limited as compared with the scintillator of Comparative Example 1.

Next, examples will be described.

Example 1
First, a material supply source containing 350 g of the cesium iodide raw material 102 and 50 pieces of 2 mm square granular copper raw material 103 was prepared, and the evaporation part 101a (made of tantalum, cylindrical type) was filled. In Example 1, the surface area of the copper raw material 103 was 1200 mm ² , and the value obtained by dividing the surface area [mm ² ] of the copper raw material 103 by the filling amount [g] of the cesium iodide raw material 102 was 3.4. Further, thallium iodide raw material 104 was prepared as a material supply source for the activator, and was filled in the evaporation unit 101b (made of tantalum, cylindrical type). Further, a substrate 107 having the same configuration as in Comparative Examples 1 and 2 was prepared.

After the evaporation parts 101a and 101b filled with the material supply source and the substrate 107 are arranged at predetermined positions in the chamber 109 of the vapor deposition apparatus 100, the scintillator of Example 1 is placed on the substrate 107 in the same procedure as in Comparative Example 2. It was formed (vapor deposition). At the time of film formation of the scintillator of Example 1, as in Comparative Example 2, in the evaporation section 101a, the cesium iodide raw material 102 was melted at a temperature lower than the melting point of copper and vapor deposition was performed.

After forming the scintillator of Example 1, the formed scintillator of Example 1 was observed with a scanning electron microscope to confirm the formation of needle-shaped crystal groups. The film thickness of the scintillator of Example 1 was 860 μm. From the ICP analysis, the scintillator of Example 1 had a thallium concentration of 0.74 mol% relative to cesium and a copper concentration of 35 ppm.

The brightness of the scintillator of Example 1 was 110 as compared with the scintillator of Comparative Example 1. The MTF of the scintillator of Example 1 was 117 as compared with the scintillator of Comparative Example 1.

The bright burn evaluation values of the scintillator of Example 1 were BB(2.5)=40, BB(10)=39, and BB(30)=38, respectively.

In this example, the value obtained by dividing the surface area [mm ² ] of the copper raw material 103 by the filling amount [g] of the cesium iodide raw material 102 was 3.4, and the surface area of the copper raw material was 1200 mm ² to obtain bright. The burn evaluation value was clearly reduced. Further, it was found that the resolution and luminance characteristics of the scintillator of Example 1 were not deteriorated as compared with the scintillator of Comparative Example 1 to which copper was not added. That is, it was found that it is possible to reduce the bright burn phenomenon without impairing the resolution and the brightness characteristics.

Example 2
First, a material supply source including 359 g of the cesium iodide raw material 102 and 150 pieces of 2 mm square granular copper raw material 103 was prepared, and the evaporation portion 101 a (made of tantalum, cylindrical type) was filled. In Example 2, the surface area of the copper material 103 is 3600 mm ^2, the value obtained by dividing the filling amount [g] of the surface area [mm ^2] cesium iodide material 102 of copper material 103 is 10.0. Further, thallium iodide raw material 104 was prepared as a material supply source for the activator, and was filled in the evaporation unit 101b (made of tantalum, cylindrical type). Further, a substrate 107 having the same configuration as that of Example 1 and Comparative Examples 1 and 2 was prepared.

After the evaporation portions 101a and 101b filled with the material supply source and the substrate 107 are arranged at predetermined positions in the chamber 109 of the vapor deposition apparatus 100, the substrate 107 is formed on the substrate 107 in the same procedure as in Example 1 and Comparative Example 2. The scintillator of No. 2 was formed into a film. At the time of film formation of the scintillator of Example 2, as in Example 1 and Comparative Example 2, in the evaporation section 101a, the cesium iodide raw material 102 was melted at a temperature lower than the melting point of copper and vapor deposition was performed.

After forming the scintillator of Example 2, the formed scintillator of Example 2 was observed with a scanning electron microscope to confirm the formation of needle-shaped crystal groups. The film thickness of the scintillator of Example 2 was 890 μm. According to ICP analysis, the scintillator of Example 2 had a thallium concentration of 0.71 mol% relative to cesium and a copper concentration of 38 ppm.

The brightness of the scintillator of Example 2 was 96 as compared with the scintillator of Comparative Example 1. Further, the MTF of the scintillator of Example 2 was 111 as compared with the scintillator of Comparative Example 1.

Bright burn evaluation values of the scintillator of Example 2 were BB(2.5)=54, BB(10)=40, and BB(30)=36, respectively.

In this example, the value obtained by dividing the surface area [mm ² ] of the copper raw material 103 by the filling amount [g] of the cesium iodide raw material 102 was 10.0, and the surface area of the copper raw material was 3600 mm ² to obtain bright. The burn evaluation value was clearly reduced. Further, it was found that the resolution and luminance characteristics of the scintillator of Example 2 were not deteriorated as compared with the scintillator of Comparative Example 1 in which copper was not added. That is, it was found that it is possible to reduce the bright burn phenomenon without impairing the resolution and the brightness characteristics.

Example 3
First, a material supply source including 360 g of cesium iodide raw material 102 and 300 pieces of 2 mm square granular copper raw material 103 was prepared, and the evaporation portion 101 a (made of tantalum, cylindrical type) was filled. In Example 3, the surface area of the copper raw material 103 was 7200 mm ² , and the value obtained by dividing the surface area [mm ² ] of the copper raw material 103 by the filling amount [g] of the cesium iodide raw material 102 was 20.0. Further, thallium iodide raw material 104 was prepared as a material supply source for the activator, and was filled in the evaporation unit 101b (made of tantalum, cylindrical type). In addition, a substrate 107 having the same configuration as in Examples 1 and 2 and Comparative Examples 1 and 2 was prepared.

After arranging the evaporation units 101a and 101b and the substrate 107 at predetermined positions in the chamber 109 of the vapor deposition apparatus 100, the scintillator of Example 3 was formed on the substrate 107 in the same procedure as in Examples 1 and 2 and Comparative Example 2. Filmed At the time of film formation of the scintillator of Example 3, as in Examples 1 and 2 and Comparative Example 2, in the evaporation section 101a, the cesium iodide raw material 102 was melted at a temperature lower than the melting point of copper and vapor deposition was performed.

After forming the scintillator of Example 3, the formed scintillator of Example 3 was observed with a scanning electron microscope to confirm the formation of needle-shaped crystal groups. The film thickness of the scintillator of Example 3 was 880 μm. From the ICP analysis, the scintillator of Example 3 had a thallium concentration of 0.69 mol% relative to cesium and a copper concentration of 39 ppm.

The brightness of the scintillator of Example 3 was 97 as compared with that of the scintillator of Comparative Example 1. The MTF of the scintillator of Example 2 was 100 as compared with the scintillator of Comparative Example 1.

Bright burn evaluation values of the scintillator of Example 3 were BB(2.5)=37, BB(10)<10, and BB(30)<10, respectively.

In this example, the value obtained by dividing the surface area [mm ² ] of the copper raw material 103 by the filling amount [g] of the cesium iodide raw material 102 was 20.0, and the surface area of the copper raw material was 7200 mm ² , whereby bright was obtained. The burn evaluation value was clearly reduced. Further, it was found that the resolution and luminance characteristics of the scintillator of Example 3 were not deteriorated as compared with the scintillator of Comparative Example 1 to which copper was not added. That is, it was found that it is possible to reduce the bright burn phenomenon without impairing the resolution and the brightness characteristics.

The results of Examples 1 to 3 and Comparative Examples 1 and 2 are summarized in FIG. As shown in Examples 1 to 3, a value obtained by dividing the surface area [mm ² ] of the copper raw material 103 by the filling amount [g] of the cesium iodide raw material 102 is 3.4 or more, and the surface area of the copper raw material is 1200 mm. It was found that when it is ² or more, the bright burn evaluation value is clearly reduced.

Further, in this embodiment, as described above, the contact area between the copper raw material 103 and the cesium iodide raw material 102 can be kept constant, so that the amount of the copper iodide 110 generated and evaporated during the vapor deposition is constant. It is possible to keep it. That is, the concentration of copper contained in the scintillator can be made constant in the film thickness direction. At this time, it was found that by setting the concentration of copper contained in the scintillator to 35 ppm or more and 39 ppm or less, it is possible to reduce the bright burn phenomenon without impairing the resolution and the brightness characteristics.

By using the method of this embodiment and the method of this example, it is possible to manufacture a scintillator while stably supplying such a small amount of additive. Further, the concentration of the additive may depend on the contact area between the cesium iodide raw material 102 and the copper raw material 103 as described above. Therefore, the additive can be supplied at a constant concentration without changing the concentration of the additive during film formation, and segregation of the additive in the scintillator can be suppressed. That is, for example, as compared with the case where the cesium iodide raw material 102 and the copper raw material 103 are supplied from different material supply sources and the concentration added to the scintillator and the uniformity of the concentration in the film thickness direction are controlled, It becomes possible to easily add a small amount of the additive uniformly to the scintillator.

Although the embodiments according to the present invention have been described above, it goes without saying that the present invention is not limited to these embodiments, and the above-described embodiments may be appropriately modified and combined without departing from the gist of the present invention. It is possible. Therefore, the following claims are attached to open the scope of the present invention.

102: Cesium iodide raw material, 103: Copper raw material, 107: Substrate, 110: Copper iodide

Claims (10)

A method of manufacturing a scintillator,
Preparing a material supply source containing a cesium iodide raw material and a copper raw material;
A vapor deposition step of forming a scintillator on a substrate using the material supply source,
In the vapor deposition step,
The material supply source, the cesium iodide raw material is dissolved, and is heated to a temperature lower than the melting point of the copper raw material,
Copper iodide produced by the reaction between the copper raw material and the cesium iodide raw material is evaporated together with the dissolved cesium iodide raw material to form a scintillator containing cesium iodide and copper on the substrate. And a manufacturing method. The manufacturing method according to claim 1, wherein a contact area between the dissolved cesium iodide raw material and the copper raw material is kept constant in the vapor deposition step. The said copper raw material is distribute|arranged in the said dissolved cesium iodide raw material in the said vapor deposition process, The manufacturing method of Claim 1 or 2 characterized by the above-mentioned. The manufacturing method according to claim 3, wherein, in the vapor deposition step, the copper raw material is not exposed from the dissolved cesium iodide raw material. The value obtained by dividing the surface area [mm ² ] of the copper raw material by the filling amount [g] of the cesium iodide raw material is 3.4 or more, and any one of claims 1 to 4 is characterized. Manufacturing method. The surface area of the said copper raw material is 1200 mm< ² > or more, The manufacturing method in any one of Claim 1 thru|or 5 characterized by the above-mentioned. The manufacturing method according to claim 1, wherein the concentration of copper contained in the scintillator is constant in the film thickness direction. The manufacturing method according to any one of claims 1 to 7, wherein a concentration of copper contained in the scintillator is 35 ppm or more and 39 ppm or less. In addition to the material source, the method further includes the step of preparing another material source containing an activator raw material,
9. The manufacturing method according to claim 1, wherein in the vapor deposition step, the activator raw material is evaporated from the another material supply source to the scintillator. The manufacturing method according to claim 9, wherein the activator raw material contains thallium.

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