JP3913031B2 - X-ray photoelectric converter - Google Patents

Description

【００３９】
上記表１によると、ＳｉＯ₂を真空加熱蒸着で形成させてなるケイ素酸化物からなる下引層３が設けられている実施例１のＸ線光電変換器１０は、耐久性試験において２０Ｖ／μｍの電界を与えても放電破壊せず、連続使用にも耐え得ることがわかった。また、Ｓ／Ｎ比は４５００以上であり優れた特性を示すことがわかった。
【００４０】
一方、下引層を全く設けていない比較例１やシラン化合物からなる下地層を設けた比較例４では、耐久性試験においてそれぞれ１２Ｖ／μｍ、１５Ｖ／μｍで放電破壊を起こし、また、Ｓ／Ｎ比も非常に小さく、ノイズ電流が大きく実用に耐えないことがわかった。
【００４１】
また、ポリカーボネートからなる下引層を設けた比較例２及びＣｅＯ₂からなる下引層を設けた比較例３は、耐久性試験において１５Ｖ／μｍで放電破壊を起こし高電界の印加に弱いことがわかった。
【００４２】
尚、真空加熱蒸着法に変え、ＳｉＯ₂からなるターゲットを用いてスパッタリング法により下引層３を形成したところ、耐久性とＳ／Ｎ比が上記実施例１と同程度に優れたＸ線光電変換器１０が得られた。
【００４３】
【発明の効果】
以上の結果より、真空中でＳｉＯ₂にエネルギーを与えて飛翔させて形成させてなるケイ素酸化物からなる下引層が設けられている本発明のＸ線光電変換器は、高電界印加に対する耐久性が高く、Ｓ／Ｎ比の高い優れたＸ線光電変換器である。
【図面の簡単な説明】
【図１】本発明のＸ線光電変換器の製造に用いる真空加熱蒸着装置の一例を示す断面図
【図２】本発明のＸ線光電変換器の第一例を示す断面図
【図３】本発明のＸ線光電変換器の第二例を示す断面図
【図４】本発明のＸ線光電変換器の第三例を示す断面図
【図５】本発明のＸ線光電変換器の第四例を示す断面図
【図６】本発明のＸ線光電変換器の第五例を示す断面図
【図７】寿命試験及びＳ／Ｎ比を測定するための回路接続図
【符号の説明】
１……ガラス基板
２……電荷収集電極
３……下引層
４……Ｘ線光導電層
５……上部電極
６……電荷輸送層
７……保護層
８……上引層
１０、２０、３０、４０、５０……Ｘ線光電変換器[0001]
BACKGROUND OF THE INVENTION
The present invention relates to the technical field of an electric field application type X-ray photoelectric converter in which an undercoat layer is provided between an X-ray photoconductive layer and an electrode.
[0002]
[Prior art]
Technology for converting X-rays into electrical signals and digitizing the extracted charges has begun to be widely used in industrial and medical applications.
[0003]
The present inventors have studied an X-ray photoelectric converter in which an X-ray photoconductive layer is provided between parallel electrodes as an X-ray photoelectric converter for converting X-rays into electric signals and extracting them. The current value (noise) when an electric field is applied to the X-ray photoelectric converter is large, and the ratio of the current value (signal) to noise (S / N ratio) when the X-ray photoelectric converter applied with the electric field is irradiated with X-rays ) Has become smaller.
Moreover, when a high electric field was applied between the electrodes, the X-ray photoelectric converter caused discharge breakdown and was weak against external energy.
[0004]
[Problems to be solved by the invention]
An object of the present invention is to improve the S / N ratio and to show high durability against external energy for an electric field application type X-ray photoelectric converter.
[0005]
[Means for Solving the Problems]
The inventors of the present invention applied an undercoat layer formed by releasing SiO ₂ particles from a film-forming material containing SiO _{2 in} a vacuum atmosphere to the lower part of the X-ray photoconductive layer, that is, the charge collection electrode and the X-rays. It has been found that the above-mentioned problems can be solved by providing it between the photoconductive layer.
[0006]
The invention according to claim 1 made on the basis of such knowledge includes a substrate, a charge collecting electrode layer disposed on the substrate, an X-ray photoconductive layer disposed on the charge collecting electrode layer , and a gold thin film. And an upper electrode layer disposed on the X-ray photoconductive layer, and when X-rays are irradiated with a voltage applied between the charge collection electrode layer and the upper electrode layer , An X-ray photoelectric converter in which a latent image is formed in a line photoconductive layer , wherein an undercoat layer is disposed between the charge collection electrode layer and the X-ray photoconductive layer, The charge collecting electrode layer on the substrate is arranged by disposing the substrate and a film forming material mainly composed of SiO ₂ in a vacuum atmosphere and releasing SiO ₂ particles from the film forming material in the vacuum atmosphere. is deposited on the film thickness of the undercoat layer is in the 0.1μm or 100μm or less, wherein The line photoconductive layer is an amorphous selenium thin film, the X-ray photoconductive layer is formed on the undercoat layer, and on the surface of the X-ray photoconductive layer, the upper electrode layer, a charge transport layer, The X-ray photoelectric conversion device according to claim 2 , wherein any one of the overcoating layers formed at or below the crystal transition temperature of selenium is in close contact with each other. The SiO ₂ particles are X-ray photoelectric converters released into the vacuum atmosphere by a vacuum heating deposition method.
A third aspect of the present invention is the X-ray photoelectric converter according to the first aspect, wherein the SiO ₂ particles are released into the vacuum atmosphere by a sputtering method.
The invention according to claim 4 is a substrate, a charge collection electrode layer disposed on the substrate, an undercoat layer disposed on the charge collection electrode layer, and an X-ray disposed on the undercoat layer. A photoconductive layer, and an upper electrode layer made of a gold thin film and disposed on the X-ray photoconductive layer, with a voltage applied between the charge collection electrode layer and the upper electrode layer. An X-ray photoelectric converter manufacturing method for manufacturing an X-ray photoelectric converter in which a latent image is formed in the X-ray photoconductive layer when irradiated with rays, wherein the substrate on which the charge collection electrode layer is formed And a film-forming material containing SiO ₂ as a main component in a vacuum atmosphere, and SiO ₂ particles are released from the film-forming material in the vacuum atmosphere . An undercoat layer of 1 μm or more and 100 μm or less is formed, and an amorphous selenium film is formed on the undercoat layer. After forming the X-ray photoconductive layer, any one of the upper electrode layer, the charge transport layer, and the overcoat layer formed at a crystal transition temperature of selenium or lower is used as the X-ray photoconductive layer. It is the manufacturing method of the X-ray photoelectric converter which carries out close_contact | adherence formation on the surface of this.
[0007]
The present invention is configured as described above, and the film forming material used for forming the undercoat layer contains SiO ₂ as a main component and does not contain a solvent. Therefore, the undercoat layer of the present invention is a dense SiO ₂ film, and impurities such as a solvent do not remain unlike a SiO ₂ thin film formed by spin coating or the like.
An additive can be added to the film forming material. For example, if a colorant is added as an additive, the undercoat layer can be colored.
[0008]
In the present invention, the SiO ₂ particles are directly emitted from the film forming material, and the SiO ₂ particles are deposited on the charge collecting electrode. Therefore, it is not necessary to polymerize the film forming material as in the case of using the silane compound as the film forming material and polymerizing the silane compound to form the SiO ₂ film, and the reaction by-product is formed during the film forming. Therefore, the quality of the obtained SiO ₂ film is excellent.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the electric field application type X-ray photoelectric converter of the present invention are shown below, but are not limited thereto.
[0010]
The code | symbol 11 of FIG. 1 has shown an example of the vacuum heating vapor deposition apparatus used for manufacture of an X-ray photoelectric converter. The vacuum heating vapor deposition apparatus 11 has a vacuum chamber 12, and a container 15 such as a crucible or a boat is disposed on the bottom wall side in the vacuum chamber 12. A vacuum exhaust system 14 is installed outside the vacuum chamber 12.
[0011]
In order to manufacture an X-ray photoelectric converter using this vacuum heating vapor deposition apparatus 11, first, the vacuum exhaust system 14 is activated, the vacuum chamber 12 is evacuated, and the vacuum chamber 12 has a predetermined degree of vacuum. A vacuum atmosphere is formed.
[0012]
Next, while maintaining the vacuum atmosphere, the substrate 1 made of glass having the charge collecting electrode 2 formed on one side is carried into the vacuum chamber 12, and the surface on which the charge collecting electrode 2 is formed faces downward. The glass substrate 1 is disposed above the container 15.
[0013]
A film forming material 17 made of silicon dioxide (SiO ₂ ) powder is previously stored in the container 15, and the container 15 is heated by energizing a heating means (not shown) provided in the container 15. The film forming material 17 is heated to evaporate the film forming material 17, and the SiO ₂ particles are released as vapor in a vacuum atmosphere.
When the SiO ₂ particles released in the vacuum atmosphere reach the surface of the charge collection electrode 2, an undercoat layer made of a thin film of silicon oxide (SiO ₂ ) is formed on the surface of the charge collection electrode 2 (vacuum heating deposition method). .
[0014]
After carrying the substrate 1 with the undercoat layer formed into another vacuum heating vapor deposition apparatus and forming selenium thin film on the surface of the undercoat layer 3 using selenium as a film forming material, Further, when the substrate 1 is carried into another vacuum heating vapor deposition apparatus and the upper electrode 5 made of a gold thin film is formed on the surface of the X-ray photoconductive layer using gold as a film forming material, the X-ray photoelectric converter of the present invention is obtained. It is done. Reference numeral 10 in FIG. 2 indicates an X-ray photoelectric converter in which the upper electrode 5 is formed.
[0015]
Although the case where the X-ray photoconductive layer 4 is formed on the surface of the undercoat layer 3 has been described above, the present invention is not limited to this. For example, the X-ray photoelectric converter 20 shown in FIG. In addition, the charge transport layer 6 may be provided on the undercoat layer 3. Moreover, the charge transport layer 6 can also be provided between the X-ray photoconductive layer 4 and the upper electrode 5 like the X-ray photoelectric converter 30 shown in FIG. Furthermore, you may provide the protective layer 7 on the upper electrode 5, like the X-ray photoelectric converter 40 shown in FIG. Furthermore, an overcoat layer 8 may be provided between the X-ray photoconductive layer 4 and the upper electrode 5 as in the X-ray photoelectric converter 50 shown in FIG.
[0016]
Although not particularly illustrated, the charge transport layer 6, the protective layer 7, and the overcoat layer 8 can be provided in the same X-ray photoelectric converter.
The undercoat layer 3 of the present invention is formed by applying energy such as heat, electron beam, and ion collision to the SiO ₂ film forming material in a vacuum atmosphere as in the above-described vacuum heating deposition method. It is formed by releasing SiO ₂ particles.
[0017]
As a specific method for forming the undercoat layer 3, in addition to the vacuum heating vapor deposition method, an inert gas such as Ar gas is introduced into the vacuum atmosphere in which the substrate 1 is disposed, and the inert layer is inactive in the vacuum atmosphere. A sputtering method can be used in which a gas plasma is generated to sputter a target (film forming material) made of SiO ₂ to form a film.
[0018]
The undercoat layer 3 may be transparent or colored. The thickness of the undercoat layer 3 is not particularly limited, but is preferably 0.1 μm or more and 100 μm or less. Further, the undercoat layer 3 made of silicon oxide obtained by the above method has a high electric resistance, and may be in an amorphous state or a crystalline state.
[0019]
As the charge collecting electrode 2 of the present invention, gold, aluminum, ITO (indium / tin oxide), or the like can be used. The electrode 2 may be uniformly formed so as to cover the X-ray irradiation region, or may be formed in a matrix shape or a stripe shape. Alternatively, a TFT (thin film transistor) in which a transistor is provided between the glass substrate 1 and the charge collecting electrode 2 may be used.
[0020]
For the X-ray photoconductive layer 4 of the present invention, a material that electrically converts X-rays is used. As this material, inorganic materials such as selenium, a selenium tellurium compound, a selenium arsenic compound, cadmium sulfide, zinc oxide, and amorphous silicon can be used, and selenium or a selenium compound is preferable.
[0021]
The X-ray photoconductive layer 4 can be formed by vacuum heating vapor deposition, sputtering, CVD, or the like, depending on the material used. The film thickness of the formed X-ray photoconductive layer 4 also varies depending on the material used, but is formed to be about 50 μm or more and 2000 μm or less.
[0022]
As the upper electrode 5 of the present invention, gold, aluminum, ITO or the like can be used. The film formation method of the upper electrode 5 is not limited to the vacuum heating vapor deposition method, and can be formed by various methods such as a sputtering method.
[0023]
The charge transport layer 6 that can be used in the present invention has an effect of further reducing noise. As a material for the charge transport layer 6, inorganic materials such as antimony trisulfide and zinc cadmium telluride can be used. An organic material exhibiting charge mobility can also be used.
[0024]
As the protective layer 7 and the overcoat layer 8 that can be used in the present invention, an organic or inorganic high resistance film can be used. When selenium is used as the X-ray photoconductive layer 4, it can be formed at a temperature below the crystal transition temperature of selenium.
[0025]
Further, the position of X-ray irradiation is not particularly limited, and as a result, X-rays may be irradiated to the upper electrode 5 as long as the X-rays reach the X-ray photoconductive layer 4. The glass substrate 1 may be irradiated.
[0026]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to a following example, unless the summary is exceeded.
[0027]
<Example 1>
A glass substrate 1 having an ITO matrix formed as a charge collecting electrode 2 is prepared and installed in a vacuum heating vapor deposition apparatus 11. The container 15 of the vacuum heating vapor deposition apparatus 11 is sprinkled with SiO ₂ as the film forming material 17 to be in a vacuum state, the container sprinkled with SiO ₂ is heated to 1800 ° C., and the surface of the charge collecting electrode 2 has a thickness of 1 μm. The drawing layer 3 was formed.
[0028]
Next, selenium is used as a film forming material, and a selenium layer (X-ray photoconductive layer) 4 having a film thickness of 500 μm is formed on the undercoat layer 3 by a vacuum heating vapor deposition method. A gold thin film (upper electrode) 5 having a film thickness of 0.1 μm was formed on the X-ray photoconductive layer 4 by a heat evaporation method, and the X-ray photoelectric converter 10 of Example 1 was produced.
[0029]
<Comparative Example 1>
In Example 1, the selenium layer having a thickness of 500 μm and the gold thin film having a thickness of 0.1 μm are formed on the charge collecting electrode without forming the undercoat layer, and the X-ray of Comparative Example 1 having no undercoat layer is formed. A photoelectric converter was produced.
[0030]
<Comparative example 2>
100 parts by volume of polycarbonate was added to 100 parts by volume of chloroform as a solvent, and polycarbonate was dissolved while stirring to obtain a coating solution for forming an undercoat layer. Next, the coating solution for forming the undercoat layer is applied on a charge collecting electrode in which ITO is matrix-formed on a glass substrate, and this is heated at 100 ° C. for 5 hours to evaporate chloroform, and a transparent film having a thickness of 1 μm is obtained. An undercoat layer made of a polycarbonate thin film was formed. Further, an X-ray photoconductive layer and an upper electrode were formed on the undercoat layer in the same manner as in Example 1 to produce an X-ray photoelectric converter of Comparative Example 2.
[0031]
<Comparative Example 3>
A subbing layer made of CeO ₂ was formed on the charge collection electrode under the same conditions as in Example 1 except that CeO ₂ was used as the film forming material instead of SiO ₂ used in Example 1 and then the subbing was performed. An X-ray photoconductive layer and an upper electrode were formed on the layer under the same conditions as in Example 1 to prepare an X-ray photoelectric converter of Comparative Example 3.
[0032]
<Comparative example 4>
100 parts by volume of polymethyl methacrylate (PMMA) was dissolved in 100 parts by volume of tetrahydrofuran with good stirring. 30 parts by volume of β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, which is a silane coupling agent, was added thereto and mixed well to prepare a coating solution for forming an undercoat layer. Next, the coating solution for forming the undercoat layer was applied to the charge collecting electrode in which ITO was matrix-formed on the glass substrate, and this was heated at 100 ° C. for 5 hours to form a transparent undercoat layer having a thickness of 1 μm. . In this reaction, a condensation polymerization reaction due to hydrolysis of the silane coupling agent does not occur, and the undercoat layer is mainly composed of β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, not SiO ₂ .
[0033]
Further, an X-ray photoconductive layer and an upper electrode were formed on the undercoat layer under the same conditions as in Example 1 to produce an X-ray photoelectric converter of Comparative Example 4.
In addition, the X-ray photoelectric converter produced by the said Example 1 and Comparative Examples 2-4 has the same structure as the X-ray photoelectric converter 10 shown in FIG.
[0034]
<Evaluation>
Evaluation items for the X-ray photoelectric converters produced in Examples and Comparative Examples 1 to 4 are shown below.
[0035]
(1) Durability test The X-ray photoelectric converter 10 is connected to a circuit as shown in FIG. 7, and the X-ray radiation device 61 irradiates the surface of the upper electrode 5 with X-rays 65, and 1V / The applied voltage was raised at μm / hour, and the electric field value at which the discharge was broken was measured to make a durability test. The X-ray irradiation conditions at this time are an X-ray tube voltage of 120 kV and a dose of 18 R / min.
[0036]
(2) Current when the S / N ratio X-ray photoelectric converter 10 is connected in a circuit as shown in FIG. 7 and the electric field is 10 V / μm and left for 10 minutes in the dark without being irradiated with X-rays. The value was the noise current value N, and the current value when X-rays were irradiated at 18 R / min was the signal current value S. The ratio (S / N ratio) between the obtained signal current value S and noise current value N was calculated.
[0037]
The evaluation results of the tests (1) and (2) are shown in Table 1 below.
[0038]
[Table 1]

[0039]
According to Table 1 above, the X-ray photoelectric converter 10 of Example 1 provided with the undercoat layer 3 made of silicon oxide formed by vacuum heating vapor deposition of SiO ₂ is 20 V / μm in the durability test. It was found that even when an electric field of about 10 mm was applied, the discharge was not broken and it could withstand continuous use. Moreover, it was found that the S / N ratio was 4500 or more, indicating excellent characteristics.
[0040]
On the other hand, in Comparative Example 1 in which no undercoat layer was provided and in Comparative Example 4 in which a base layer made of a silane compound was provided, discharge breakdown was caused at 12 V / μm and 15 V / μm, respectively, in the durability test. It was found that the N ratio was very small and the noise current was large and could not be put into practical use.
[0041]
Further, Comparative Example 2 provided with a subbing layer made of polycarbonate and Comparative Example 3 provided with a subbing layer made of CeO ₂ are susceptible to discharge breakdown at 15 V / μm in a durability test and are vulnerable to application of a high electric field. all right.
[0042]
In addition, when the undercoat layer 3 was formed by sputtering using a target made of SiO ₂ instead of the vacuum heating vapor deposition method, the X-ray photoelectric conversion was excellent in durability and S / N ratio to the same extent as in Example 1 above. A transducer 10 was obtained.
[0043]
【The invention's effect】
From the above results, the X-ray photoelectric converter of the present invention provided with an undercoat layer made of silicon oxide formed by applying energy to SiO ₂ in a vacuum and flying is durable against high electric field application. This is an excellent X-ray photoelectric converter having high properties and a high S / N ratio.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an example of a vacuum heating vapor deposition apparatus used for manufacturing the X-ray photoelectric converter of the present invention. FIG. 2 is a cross-sectional view showing a first example of the X-ray photoelectric converter of the present invention. FIG. 4 is a cross-sectional view showing a second example of the X-ray photoelectric converter of the present invention. FIG. 4 is a cross-sectional view showing a third example of the X-ray photoelectric converter of the present invention. FIG. 6 is a sectional view showing a fifth example of the X-ray photoelectric converter of the present invention. FIG. 7 is a circuit connection diagram for measuring the life test and S / N ratio.
DESCRIPTION OF SYMBOLS 1 ... Glass substrate 2 ... Charge collection electrode 3 ... Undercoat layer 4 ... X-ray photoconductive layer 5 ... Upper electrode 6 ... Charge transport layer 7 ... Protective layer 8 ... Overcoat layers 10, 20 , 30, 40, 50 ... X-ray photoelectric converter

Claims (4)

A substrate,
A charge collection electrode layer disposed on the substrate;
An X-ray photoconductive layer disposed on the charge collection electrode layer ;
An upper electrode layer made of a gold thin film and disposed on the X-ray photoconductive layer;
An X-ray photoelectric converter in which a latent image is formed in the X-ray photoconductive layer when irradiated with X-rays while a voltage is applied between the charge collection electrode layer and the upper electrode layer ,
An undercoat layer is disposed between the charge collection electrode layer and the X-ray photoconductive layer,
The undercoat layer is formed on the substrate by disposing the substrate and a film forming material mainly composed of SiO ₂ in a vacuum atmosphere and releasing SiO ₂ particles from the film forming material in the vacuum atmosphere. Deposited on the charge collection electrode layer ;
The thickness of the undercoat layer is 0.1 μm or more and 100 μm or less,
The X-ray photoconductive layer is an amorphous selenium thin film, and the X-ray photoconductive layer is formed on the undercoat layer;
X-rays in which any one of the upper electrode layer, the charge transport layer, and the overcoat layer formed below the crystal transition temperature of selenium is in close contact with the surface of the X-ray photoconductive layer Photoelectric converter. The X-ray photoelectric converter according to claim 1, wherein the SiO ₂ particles are released into the vacuum atmosphere by a vacuum heating vapor deposition method. The X-ray photoelectric converter according to claim 1, wherein the SiO ₂ particles are released into the vacuum atmosphere by a sputtering method. A substrate,
  A charge collection electrode layer disposed on the substrate;
  An undercoat layer disposed on the charge collection electrode layer;
  An X-ray photoconductive layer disposed on the undercoat layer;
  An upper electrode layer made of a gold thin film and disposed on the X-ray photoconductive layer;
  X-rays for producing an X-ray photoelectric converter in which a latent image is formed in the X-ray photoconductive layer when X-rays are irradiated with a voltage applied between the charge collection electrode layer and the upper electrode layer A method of manufacturing a photoelectric converter,
  The substrate on which the charge collecting electrode layer is formed; and SiO. ₂ And a film-forming material containing as a main component in a vacuum atmosphere, and from the film-forming material in the vacuum atmosphere SiO 2 ₂ By releasing particles, a subbing layer having a thickness of 0.1 μm or more and 100 μm or less is formed on the charge collection electrode layer,
  After forming the X-ray photoconductive layer made of an amorphous selenium film on the undercoat layer,
An X-ray photoelectric converter in which any one of the upper electrode layer, the charge transport layer, and an overcoat layer formed at a temperature lower than the crystal transition temperature of selenium is formed in close contact with the surface of the X-ray photoconductive layer. Production method.

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