JP2011021223A - Vapor deposition apparatus and thin film deposition method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vapor deposition apparatus in which a thin film, which does not possess film defects to be generated by sudden boiling or re-evaporation, can be deposited when a phosphor of a radiation image transformation panel is deposited by a vapor deposition method and to provide a method for depositing the phosphor of the radiation image transformation panel by using the vapor deposition apparatus. <P>SOLUTION: A crucible 2 of the vapor deposition apparatus 1 has a cover 3 which has a projecting part projecting into the internal space of the crucible 2, on the side wall face 8 of whose projecting part a boring 34 to be communicated with the inside of the crucible 2 is arranged and which can be removed from the crucible 2. The boring 34 is arranged in such a position that a raw material in the crucible 2 can not be viewed directly through the boring 34 from any place on a vapor deposition plane. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a vapor deposition apparatus and a phosphor film forming method for a radiation image conversion panel using the vapor deposition apparatus.

  Conventionally, radiographic images such as X-ray images have been widely used for diagnosis of medical conditions in the medical field. In particular, radiographic images using intensifying screen-film systems have been developed as an imaging system that combines high reliability and excellent cost performance as a result of high sensitivity and high image quality in the long history. Used in the medical field.

  However, these pieces of image information are so-called analog image information, and free image processing and instantaneous electric transmission cannot be performed like the digital image information that has been developed in recent years.

  In recent years, digital radiographic image detection apparatuses represented by computed radiography (CR), flat panel type radiation detectors (FPD) and the like have appeared. In these, since a digital radiographic image is directly obtained and an image can be directly displayed on an image display device such as a cathode tube or a liquid crystal panel, image formation on a photographic film is not necessarily required. As a result, these digital X-ray image detection devices reduce the need for image formation by the silver halide photography method, and greatly improve the convenience of diagnosis work in hospitals and clinics.

  By the way, in recent years, as a radiation image conversion method using a high-luminance, high-sensitivity, high-sharp stimulable phosphor, CR is a stimulator in which Eu is activated based on an alkali halide such as cesium bromide (CsBr). A radiation image conversion panel using a fluorescent material has been proposed. In particular, by using Eu as an activator, X-ray conversion efficiency, which has been impossible in the past, can be improved. Similarly, FPD has proposed a radiation image conversion panel using a phosphor in which Tl is activated based on an alkali halide such as cesium iodide (CsI).

  Further, in the analysis of diagnostic images, a radiation image conversion panel with higher sharpness is required, and as a means for improving the sharpness, for example, the shape itself of the photostimulable phosphor to be formed is controlled and sensitivity and Attempts have been made to improve sharpness.

  As one of these attempts, for example, a radiographic image having a photostimulable phosphor layer in which elongated columnar crystals having a certain inclination with respect to the normal direction of the support are formed on the support by vapor deposition. A conversion panel has been proposed (see, for example, Patent Document 1).

  However, in the vapor phase volume method (evaporation method), bumping (splash) occurs when the powder raw material in the crucible changes from a solid to a liquid or after it changes to a liquid. The bumping becomes an image defect, which greatly reduces the yield of the radiation image conversion panel.

  As means for solving this problem, a method is disclosed in which a nozzle is attached to the opening of the crucible so that bumping does not directly adhere to the substrate (see, for example, Patent Documents 2 and 3).

  Further, as a method for eliminating image defects due to bumping, a method is disclosed in which a material bumped directly using two covers is prevented from adhering to a substrate (see, for example, Patent Document 4).

JP-A-2-58000 JP-A-8-269696 JP-A-8-274090 JP 2009-108408 A

  As in the techniques disclosed in Patent Documents 2 and 3, when a cylindrical object such as a nozzle is attached on the opening of the crucible, the temperature of the part becomes lower than that of the crucible, and the composition of the deposited film changes. Will provoke. Further, if the nozzle portion is to be heated separately, an extra heating device is required, which becomes a great obstacle when it is inserted into an existing device.

  In addition, as in the technique disclosed in Patent Document 4, when two covers are stacked, the above that has passed through the inner cover adheres to the outer cover, and a material pool is generated. By re-evaporating the raw material reservoir, the raw material may adhere to the substrate and cause image defects.

  The present invention relates to a vapor deposition apparatus capable of producing a thin film free from film defects due to bumping or re-evaporation when forming a phosphor of a radiation image conversion panel by vapor deposition, and uses the film deposition method. An object of the present invention is to provide a method for forming a phosphor film for a radiation image conversion panel.

  The above object is achieved by the invention described below.

1. Crucible,
A convex part in the inner direction of the crucible, provided with a perforation communicating with the inside of the crucible on the side wall surface of the convex part, and a lid removable on the crucible;
Heating means for heating the crucible;
Have
A vapor deposition apparatus capable of mounting, at a predetermined position, a substrate on which a raw material inside the crucible evaporated by heating by the heating means is formed on the vapor deposition surface through the perforations,
The vapor deposition apparatus, wherein the perforation is disposed at a position where the raw material inside the crucible cannot be directly seen from any place on the vapor deposition surface.

  2. 2. The vapor deposition apparatus as set forth in claim 1, wherein the convex portion has a shape spreading in an inner direction of the crucible.

  3. 3. The vapor deposition apparatus according to 1 or 2 above, wherein a difference in coefficient of thermal expansion between the material of the lid 3 and the material of the crucible is within 50% based on one coefficient of thermal expansion.

  4). The material of the lid and the crucible is a metal having a melting point of 900 ° C. or higher and 3600 ° C. or lower, or a ceramic having a thermal conductivity of 10 W / (m · K) or higher and 400 W / (m · K) or lower. 4. The vapor deposition apparatus according to any one of 1 to 3, wherein:

5. 5. The vapor deposition according to any one of 1 to 4 above, which is used for forming a film of a phosphor of a radiation image conversion panel based on an alkali halide represented by the following general formula (1): apparatus.
General formula (1)
M ¹ X · aM ² X ′ ₂ · bM ³ X ″ ₃ : eA
[Wherein, M ¹ represents at least one alkali metal selected from Li, Na, K, Rb and Cs, and M ² is selected from the group consisting of Li, Na, K, Rb and Cs other than M ^1. M ³ represents at least one alkali metal, and M ³ represents at least one selected from Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. Represents a valent metal, X, X ′ and X ″ represent at least one halogen selected from F, Cl, Br and I, and A represents Eu, Tb, In, Ce, Tm, Dy, Pr, Ho, Represents at least one rare earth element selected from Nd, Yb, Er, Gd, Lu, Sm, Y, and Tl, and a, b, and e are 0 ≦ a <0.5, 0 ≦ b <0.5, Represents a numerical value in the range of 0 <e ≦ 0.2.]
6). 6. A method of forming a phosphor film for a radiation image conversion panel, wherein the film is manufactured using the vapor deposition apparatus according to any one of 1 to 5 above.

  A vapor deposition apparatus capable of producing a thin film free from film defects due to bumping or re-evaporation when a phosphor of a radiation image conversion panel is formed by vapor deposition, and radiation image conversion using the film formation method A method of forming a phosphor film for a panel can be provided.

2 is a cross-sectional view of the main part of the vapor deposition apparatus 1. FIG. It is sectional drawing of the vapor deposition apparatus 1 of the principal part in case the side wall surface 32 is formed perpendicularly to the flange part 31. FIG. It is sectional drawing showing an example of the principal part of the vapor deposition apparatus of a comparison. It is sectional drawing showing an example of the principal part of the vapor deposition apparatus of a comparison.

  Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to the embodiments described below. In addition, the structure which attached | subjected the same code | symbol in each figure shows that it is the same structure, The description is abbreviate | omitted.

  FIG. 1 is a cross-sectional view of a main part of a vapor deposition apparatus 1 according to the present embodiment.

  The vapor deposition apparatus 1 of the present invention includes a crucible 2, a lid 3 that can be removed from the crucible 2, and a heating means 7 that heats the crucible 2.

  The lid 3 has a shape having a convex portion, and includes a flange portion 31, a side wall surface 32, and a bottom surface 33. The bottom surface 33 is directed toward the inside of the crucible 2 with respect to the flange portion 31.

  The side wall surface 32 has a shape that expands from the flange portion 31 toward the bottom surface 33 in the inner direction of the crucible. In FIG. 1, the angle θ formed between the perpendicular of the flange portion 31 and the side wall surface 32 is preferably 0 ° <θ <90 °, more preferably 0 ° <θ <85 °, and particularly preferably. 0 degrees <θ <80 degrees.

  The side wall surface 32 is formed with perforations 34 that communicate with the side wall surface 32.

  The lid 3 can be removed from the crucible 2, and the lid 3 is opened to fill the crucible 2 with the raw material to be deposited. Since the lid 3 having the perforations 34 is removable, it is easy to fill the evaporation material and to clean the crucible 2.

  The vacuum device 9 is configured so that a substrate 5 which is a deposition target on which raw materials are deposited by vapor deposition can be mounted.

  The difference in the coefficient of thermal expansion between the material of the lid 3 and the material of the crucible 2 is preferably within 50% based on one coefficient of thermal expansion. When the difference in coefficient of thermal expansion is large when the crucible 2 or the lid 3 is heated, a gap is generated between the crucible 2 and the lid 3, and the raw material jumps into the vacuum apparatus 9 from a place other than the perforations 34, and the vapor deposition target In some cases, the characteristics of the radiation image conversion panel deteriorate. However, if the difference in thermal expansion coefficient between the material of the lid 3 and the material of the crucible 2 is set within 50% based on one thermal expansion coefficient, such a problem does not occur.

  The vapor deposition device 1 and the substrate 5 are arranged at predetermined positions in the vacuum device 9. The substrate 5 to be deposited is attached to a predetermined substrate holder 10.

  As described above, the lid 3 having the perforations 34 has a structure having a convex portion in the crucible 2 inside, and has the perforations 34 communicating with the inside of the crucible 2 on the side wall surface 8 of the convex portion. The raw material in the crucible 2 cannot be directly seen from any place on the surface. That is, in FIG. 1, the straight line 13 drawn in the direction of the perforation 34 from the end of the substrate 5 does not allow the upper surface 12 of the raw material in the crucible 2 to be seen.

  On the other hand, as shown in FIG. 2, when the side wall surface 32 is formed perpendicular to the flange portion 31, the straight line 13 drawn from the end portion of the substrate 5 through the perforation 34 is inside the crucible 2. Will reach the upper surface 12 of the raw material. FIG. 2 is a cross-sectional view of the main part of the vapor deposition apparatus 1 when the side wall surface 32 is formed perpendicular to the flange portion 31.

  In this way, the side wall surface 32 has a shape that expands from the flange portion 31 toward the bottom surface 33 in the inner direction of the crucible, so that bumping particles flying linearly by bumping from inside the crucible 2 are transferred from the crucible to the substrate. There is no collision.

  Therefore, it is possible to form a thin film without film defects due to adhesion of bumping particles.

  In the vapor deposition apparatus 1 of the present invention, it is preferable that the lid 3 and the crucible 2 are provided with a protrusion for fixing, so that the lid 3 and the crucible 2 can be fixed with a metal wire 15 or the like (see FIG. 1). Even if the internal pressure in the crucible 2 is increased by fixing with the metal wire 15, the lid 3 does not come off.

  In the vapor deposition apparatus 1 of the present invention, the material of the lid 3 and the crucible 2 is a metal having a melting point of 900 ° C. or higher and 3600 ° C. or lower, preferably 1400 ° C. or higher and 3500 ° C. or lower, more preferably 2000 ° C. or higher and 3100 ° C. or lower. Is preferred. Examples of such metals include gold, silver, cobalt, tungsten, zirconium, tantalum, titanium, iron, copper, niobium, nickel, neodymium, platinum, molybdenum, manganese, and stainless steel. In the above, when the melting point is in the above range, effects of high durability, stability of the deposition rate, and high uniformity of the film thickness can be obtained.

  Alternatively, in the vapor deposition apparatus 1 of the present invention, the material of the lid 3 and the crucible 2 has a thermal conductivity of 10 W / (m · K) to 400 W / (m · K), preferably 50 W / (m · K). A ceramic of 350 W / (m · K) or less, more preferably 80 W / (m · K) or more and 300 W / (m · K) or less is also preferable. Examples of such ceramics include aluminum nitride, silicon carbide, alumina, boron nitride, and carbon.

  In the above, when the thermal conductivity is in the above range, the crucible 2 is uniformly heated, and the effects of stability of the deposition rate and high in-plane uniformity of the film thickness / activator can be exhibited.

The metal wire used for fixing the lid 3 and the crucible 2 is preferably a metal having a melting point of 900 ° C. or higher and 3600 ° C. or lower, preferably 1400 ° C. or higher and 3500 ° C. or lower, more preferably 2000 ° C. or higher and 3100 ° C. or lower. Examples thereof include gold, silver, cobalt, tungsten, zirconium, tantalum, titanium, iron, copper, niobium, nickel, neodymium, platinum, molybdenum, manganese, and stainless steel, and the diameter is preferably 0.2 to 1.0 mm. In the above, since the melting point is in the above range, the wire is not loosened or cut during the vapor deposition, so that the effect of vapor deposition rate stability can be obtained.
(Phosphor deposition method)
The crucible 2 is set in a Knudsen cell (indirect heating evaporation source, hereinafter referred to as K cell) in the vacuum device 9, and the substrate 5 to be deposited is set and then evacuated.

  The vapor deposition apparatus 1 can be heated by a method in which an electric current is directly applied to the crucible 2 for resistance heating, a method in which the crucible is indirectly heated by a surrounding heater, a method in which the crucible and the evaporation material are heated by high frequency induction heating, and the like.

  As the substrate 5, a flat metal substrate 5 is used. For example, aluminum or magnesium alloy can be used, but resin or ceramic may be used. Further, a reflective layer or a protective layer may be provided on the substrate 5.

The inside of the vacuum device 9 is preferably evacuated to about 1.0 × 10 ⁻³ Pa, and then introduced with a gas such as Ar gas, oxygen gas, nitrogen gas, etc., and has a gas of about 5.0 × 10 ⁻² Pa. The pressure is appropriately adjusted by adjusting the degree of vacuum. After the substrate 5 is rotated and the substrate 5 is preferably heated to 60 to 250 ° C., the crucible 2 is heated. During the initial melting, the shutter is opened on the crucible 2 and the shutter is opened when the temperature reaches a predetermined temperature (preferably 700 to 900 ° C.), and the phosphor material (for example, CsBr: Eu, CsI: Tl, etc.) is applied to the substrate 5. Is vapor-deposited. When the film thickness reaches a desired predetermined thickness (100 to 1000 μm (preferably 500 μm)), the vapor deposition is finished, and after cooling, the substrate 5 on which the phosphor is formed on the substrate 5 is taken out. Further, if necessary, a protective layer for physically or chemically protecting the phosphor layer may be provided on the surface of the photostimulable phosphor layer opposite to the support. The protective layer may be formed by directly applying a coating solution for the protective layer to the surface of the phosphor layer, or a protective layer separately formed in advance may be adhered to the phosphor layer.

  The protective film can be formed using various materials. For example, a polyparaxylylene film is formed by a CVD method. That is, a polyparaxylylene film can be formed on the entire surface of the substrate 5 on which the phosphor has been formed to provide a protective film.

  Moreover, a polymer protective film can also be provided as a protective film of another aspect.

  The thickness of the polymer protective film is preferably 12 μm or more and 100 μm or less, more preferably 20 μm or more, taking into consideration the formation of voids, the protection of the phosphor layer, sharpness, moisture resistance, workability, etc. 60 μm or less is preferable. Further, the haze ratio is preferably 3% or more and 40% or less, more preferably 3% or more and 10% or less in consideration of sharpness, radiation image unevenness, manufacturing stability, workability, and the like. A haze rate shows the value measured by Nippon Denshoku Industries Co., Ltd. NDH 5000W.

  The required haze ratio is appropriately selected from commercially available polymer films and can be easily obtained. Thus, the radiation image conversion panel of the present invention in which the phosphor is formed on the substrate 5 is obtained.

Examples of the phosphor of the radiation image conversion panel that is suitably formed and manufactured using the vapor deposition apparatus 1 of the present invention include CsBr: Eu, CsI: Tl, and the like. The phosphor of the radiation image conversion panel based on the alkali halide represented is preferable.
General formula (1)
M ¹ X · aM ² X ′ ₂ · bM ³ X ″ ₃ : eA
[Wherein, M ¹ represents at least one alkali metal selected from Li, Na, K, Rb and Cs, and M ² is selected from the group consisting of Li, Na, K, Rb and Cs other than M ^1. M ³ represents at least one alkali metal, and M ³ represents at least one selected from Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. Represents a valent metal, X, X ′ and X ″ represent at least one halogen selected from F, Cl, Br and I, and A represents Eu, Tb, In, Ce, Tm, Dy, Pr, Ho, Represents at least one rare earth element selected from Nd, Yb, Er, Gd, Lu, Sm, Y, and Tl, and a, b, and e are 0 ≦ a <0.5, 0 ≦ b <0.5, Represents a numerical value in the range of 0 <e ≦ 0.2.]

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, this invention is not limited to these.

The vapor deposition apparatus 1 of the present invention uses the vapor deposition apparatus shown in FIG. As a comparative vapor deposition apparatus, the vapor deposition apparatus shown in FIGS. 3 and 4 is used.
<< Production of Radiation Image Conversion Panel P1 of the Present Invention >>
Using the vapor deposition apparatus 1 of the present invention shown in FIG. 1, the aluminum nitride crucible 2 of the vapor deposition apparatus 1 is filled with 400 g of CsBr: Eu, and an aluminum nitride lid having a perforation 34 on the side (removable). A lid having a perforated hole 34) was fixed to the crucible 2 with a metal wire 15 (metal: tantalum, melting point: 3017 ° C.).

  The crucible 2 is set in the K cell in the vacuum device 9 and a 500 mm square substrate (type: polyimide resin sheet) is set and then evacuated.

  The vapor deposition apparatus 1 uses a K cell.

After evacuating the vacuum apparatus to 1.0 × 10 ⁻³ Pa, Ar is introduced and the degree of vacuum is adjusted to 5.0 × 10 ⁻² Pa. After the substrate 5 is rotated and the substrate 5 is heated to 100 ° C., the crucible 2 is heated. During the initial melting, the shutter is opened on the crucible 2 and the shutter is opened when the temperature reaches a predetermined temperature (800 ° C.), and CsBr: Eu is deposited on the substrate 5. When the film thickness reached 150 μm, the vapor deposition was terminated, the substrate 5 on which the phosphor was formed on the substrate 5 was cooled and taken out, and the radiation image conversion panel P1 of the present invention in which the phosphor was formed on the substrate 5 was produced. .
<< Production of Radiation Image Conversion Panel P4 of the Present Invention >>
Except for using the phosphor material CsI: Tl, the radiation image conversion panel P4 of the present invention in which the phosphor is formed on the substrate 5 in the same manner as in the case of “<< Preparation of the radiation image conversion panel P1 of the present invention >>”. Were prepared.
<< Production of Comparative Radiation Image Conversion Panels P2 and P3 >>
Instead of using each of the vapor deposition apparatuses 1 of the present invention shown in FIG. 1, the comparative vapor deposition apparatus 20 shown in FIG. 3 (using a lid 16 having perforations 14 on the upper surface) and the comparative vapor deposition apparatus 30 shown in FIG. In the present invention, a phosphor is formed on the substrate 5 in the same manner as in the above-described << Preparation of Radiation Image Conversion Panel P1 of the Present Invention >> except that each of the crucibles 2 is used. The radiation image conversion panels P2 and P3 were prepared.
<< Production of Comparative Radiation Image Conversion Panels P5 and P6 >>
Except for using the phosphor material CsI: Tl, the radiographic image conversion of the present invention in which the phosphor is formed on the substrate 5 in the same manner as in the case of “<< Preparation of the radiographic image conversion panels P2 and P3 of the present invention >>” above. Panels P5 and P6 were produced respectively.
"Evaluation methods"
The surface of the produced radiation image conversion panel was observed with a microscope (magnification: 100 times), and the number of protrusions of 50 μm or more in 500 mm □ was examined. The results are shown in Table 1.

  The films made of the crucible 2 with the lid having the perforations 14 in front of the comparative examples P2 and P5 have 10 and 8 protrusions of 50 μm or more, respectively. The films made of the crucible 2 without a cover of Comparative Examples P3 and P6 had 97 and 52 protrusions of 50 μm or more, respectively, but 0 when using the lids A and B having the perforations 34 on the side surfaces. Met.

  From Table 1, it can be seen that in the case of the present invention, a thin film free from bump defects due to bumping can be formed when the thin film is produced by vapor deposition.

  As described above, the lid 3 of the crucible 2 of the vapor deposition apparatus is provided with the perforations 34 having a convex portion in the inner direction of the crucible 2 and communicating with the inside of the crucible 2 on the side wall surface 8 of the convex portion. 3 is disposed, and the perforations 34 are arranged at positions where the raw material inside the crucible 2 cannot be directly seen from any position on the vapor deposition surface through the perforations 34, thereby forming a thin film free from film defects due to adhesion of bumping particles. Can be membrane. Accordingly, a vapor deposition apparatus capable of producing a thin film free from film defects due to bumping or re-evaporation when forming a phosphor of the radiation image conversion panel by vapor deposition, and radiation using the film deposition method A phosphor film forming method for an image conversion panel can be provided.

DESCRIPTION OF SYMBOLS 1, 20, 30 Deposition apparatus 2 Crucible 3, 16 Lid 5 Substrate 8 Side wall surface 9 Vacuum apparatus 10 Substrate holder 14, 34 Perforation 15 Metal wire 31 Flange part 32 Side wall surface 33 Bottom surface

Claims (6)

Crucible,
A convex part in the inner direction of the crucible, provided with a perforation communicating with the inside of the crucible on the side wall surface of the convex part, and a lid removable on the crucible;
Heating means for heating the crucible;
Have
A vapor deposition apparatus capable of mounting, at a predetermined position, a substrate on which a raw material inside the crucible evaporated by heating by the heating means is formed on the vapor deposition surface through the perforations,
The vapor deposition apparatus, wherein the perforation is disposed at a position where the raw material inside the crucible cannot be directly seen from any place on the vapor deposition surface.   The vapor deposition apparatus according to claim 1, wherein the convex portion has a shape spreading in an inner direction of the crucible.   The vapor deposition apparatus according to claim 1 or 2, wherein a difference in thermal expansion coefficient between the material of the lid 3 and the material of the crucible is within 50% based on one thermal expansion coefficient.   The material of the lid and the crucible is a metal having a melting point of 900 ° C. or higher and 3600 ° C. or lower, or a ceramic having a thermal conductivity of 10 W / (m · K) or higher and 400 W / (m · K) or lower. The vapor deposition apparatus according to any one of claims 1 to 3. 5. The method according to claim 1, wherein the phosphor is used to form a phosphor of a radiation image conversion panel based on an alkali halide represented by the following general formula (1). Vapor deposition equipment.
General formula (1)
M ¹ X · aM ² X ′ ₂ · bM ³ X ″ ₃ : eA
[Wherein, M ¹ represents at least one alkali metal selected from Li, Na, K, Rb and Cs, and M ² is selected from the group consisting of Li, Na, K, Rb and Cs other than M ^1. M ³ represents at least one alkali metal, and M ³ represents at least one selected from Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. Represents a valent metal, X, X ′ and X ″ represent at least one halogen selected from F, Cl, Br and I, and A represents Eu, Tb, In, Ce, Tm, Dy, Pr, Ho, Represents at least one rare earth element selected from Nd, Yb, Er, Gd, Lu, Sm, Y, and Tl, and a, b, and e are 0 ≦ a <0.5, 0 ≦ b <0.5, Represents a numerical value in the range of 0 <e ≦ 0.2.]   6. A method of forming a phosphor film for a radiation image conversion panel, wherein the phosphor film is manufactured using the vapor deposition apparatus according to claim 1.

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