JPH0631902B2 - Radiation image conversion panel manufacturing method - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to a method of manufacturing a radiation image conversion panel using a stimulable phosphor, and more particularly to a method of manufacturing a radiation image conversion panel that gives a radiation image with high sharpness.

2. Description of the Related Art Radiation images such as X-ray images are often used for disease diagnosis. In order to obtain this X-ray image, X-rays that have passed through the subject are irradiated onto the phosphor layer (fluorescent screen), thereby generating visible light, and when this visible light is taken in a normal photograph, the same silver salt is used. A so-called radiograph, which is developed by irradiating a film using a film, is used. However, in recent years, a method for directly taking out an image from the phosphor layer has been devised without using a film coated with silver salt. As this method, the radiation that has passed through the subject is absorbed by the phosphor, and then the phosphor is excited by, for example, light or thermal energy so that the radiation energy accumulated by the absorption by the phosphor is emitted as fluorescence. , There is a method of detecting this fluorescence and imaging. Specifically, for example, U.S. Pat. No. 3,859,527 and JP-A-55-12144.
Japanese Patent No. 3187242 discloses a radiation image conversion method using a stimulable phosphor and using visible light or infrared light as stimulated excitation light. This method uses a radiation image conversion panel in which a stimulable phosphor layer is formed on a support, and the radiation that has passed through the subject is applied to the stimulable phosphor layer of this radiation image conversion panel to apply the radiation to each part of the subject. The latent energy is formed by accumulating the radiation energy corresponding to the radiation transmittance, and then the radiation energy accumulated in each part is radiated as stimulated emission by scanning this stimulable phosphor layer with stimulating excitation light. Then, the optical signal depending on the intensity of the light is photoelectrically converted, for example, and an image is obtained by the image reproducing device. This final image may be reproduced as a hard copy or may be reproduced on a CRT. Now, the radiation image conversion panel having the stimulable phosphor layer used in this radiation image conversion method has the same radiation absorption rate and light conversion rate (including both) as in the case of the radiographic method using the above-mentioned fluorescent screen. Not to mention that "radiation sensitivity" is high, it is required that the image has good graininess and high sharpness. However, in general, a radiation image conversion panel having a stimulable phosphor layer coats a support or a protective layer with a dispersion containing a particle-shaped stimulable phosphor having a particle size of about 1 to 30 μm and an organic binder.・ Because it is produced by a manufacturing method in which drying is performed, the packing density of the stimulable phosphor is low (filling rate 50%), and the stimulability is as shown in Fig. 4 (a) in order to increase radiation sensitivity sufficiently It was necessary to increase the thickness of the phosphor layer. As is clear from the figure, the layer thickness of the stimulable phosphor layer is 200 μm.
In this case, the deposition amount of the stimulable phosphor is 50 mg / cm ² , and the radiation sensitivity increases linearly up to 450 μm until the layer thickness reaches 350 μm.
Saturates above m. Incidentally, the radiation sensitivity is saturated, when the stimulable phosphor layer becomes too thick, the stimulated luminescence generated inside the stimulable phosphor layer due to scattering between the stimulable phosphor particles is emitted to the outside. This is because it will not come out. On the other hand, the sharpness of the image in the radiation image conversion method tends to be higher as the layer thickness of the stimulable phosphor layer of the radiation image conversion panel is thinner, as shown in FIG. 4 (b). In order to improve the property, it was necessary to reduce the thickness of the stimulable phosphor layer. Further, since the graininess of the image in the radiation image conversion method is determined by the spatial fluctuation of the radiation quantum number (quantum mottle) or the structural disorder of the stimulable phosphor layer of the radiation image conversion panel (structure mottle), etc. , When the thickness of the stimulable phosphor layer becomes thin, the number of radiation quantum absorbed in the stimulable phosphor layer decreases and the quantum mottle increases, or structural disorder becomes apparent and the structural mottle increases. As a result, image deterioration occurs. Therefore, in order to improve the graininess of the image, the stimulable phosphor layer needs to be thick. That is, as described above, in the conventional radiation image conversion panel, the sensitivity to radiation, the graininess of the image, and the sharpness of the image show completely opposite tendencies to the stimulable phosphor layer and the layer thickness. Radiation image conversion panels have been made at the trade-off of radiation sensitivity and some degree of graininess and sharpness. By the way, it is well known that the sharpness of the image in the conventional radiographic method is determined by the spread of the instantaneous light emission (light emission at the time of radiation irradiation) of the phosphor in the phosphor screen. The sharpness of the image in the radiation image conversion method using the stimulable phosphor is not determined by the spread of the stimulated emission of the stimulable phosphor in the radiation image conversion panel, that is, as in radiography. It is not determined by the spread of the emission of the phosphor, but depends on the spread of the stimulated excitation light in the panel. Because, in this radiation image conversion method, since radiation image information accumulated in the radiation image conversion panel is taken out in time series, stimulated emission by stimulated excitation light irradiated at a certain time (ti) is desirable. Is recorded as the output from a certain pixel (xi, yi) on the panel that was all illuminated and was irradiated with stimulated excitation light at that time, but if the stimulated excitation light spreads in the panel due to scattering, etc. , Illuminated pixel
If the stimulable phosphor existing outside (xi, yi) is also excited, the output from a region wider than that pixel will be recorded as the output from the pixel (xi, yi). Is. Therefore, stimulated emission by the stimulated excitation light irradiated at a certain time (ti), from the pixel (xi, yi) on the panel that was actually irradiated with the stimulated excitation light at that time (ti) If only the luminescence is emitted, the sharpness of the obtained image will not be affected regardless of the extent of the luminescence. Under such circumstances, some methods for improving the sharpness of radiographic images have been devised. For example, JP-A-55-14644
No. 7, a method of mixing a white powder in the stimulable phosphor layer of the radiation image conversion panel, the radiation image conversion panel described in JP-A-55-163500, the stimulable excitation light wavelength of the stimulable phosphor For example, there is a method of coloring so that the average reflectance in the region is smaller than the average reflectance in the stimulated emission wavelength region of the stimulable phosphor. However, these methods are not preferable methods because the sensitivity inevitably decreases remarkably when the sharpness is improved. On the other hand, the applicant of the present invention has already proposed in Japanese Patent Application No. 59-196365 a novel radiation image conversion panel and a method for producing the same which have improved the conventional defects in the radiation image conversion panel using the stimulable phosphor as described above. As a result, a radiation image conversion panel in which the stimulable phosphor layer does not contain a binder and a method for manufacturing the same have been proposed. According to this, since the stimulable phosphor layer of the radiation image conversion panel does not contain a binder, the filling rate of the stimulable phosphor is significantly improved and the transparency of the stimulable phosphor layer is improved. The sensitivity of the radiation image conversion panel to radiation and the graininess of the image are improved, and at the same time, the sharpness of the image is improved. Further, the present applicant proposes in Japanese Patent Application No. 59-266912 to 266916 a radiation image conversion panel having a stimulable phosphor layer having a fine columnar block structure and a method for producing the same. According to this, the stimulated excitation light reaches the bottom of the columnar block without being scattered to the outside of the columnar block while repeating reflection in the columnar block due to the light guiding effect of the fine columnar block structure. Sharpness can be further increased. However, in the method for producing a radiation image conversion panel of the above-mentioned Japanese Patent Application No. 59-266912 to 266916, the layer to be the base of the fine columnar block, that is, the fine concavo-convex pattern on the surface of the support or the fine tile-shaped plate is separated from each other. However, the manufacturing process is complicated because it includes a process of manufacturing such a structure or a combination of a fine tile-shaped plate and a fine wire net for partitioning them. Further, it is difficult to reduce the structure of the base layer to a certain extent or more, and the sharpness of the image is limited.

[Object of the Invention]

The present invention relates to the above-mentioned proposed method for producing a radiation image conversion panel using a stimulable phosphor, and further improves the method. The object of the present invention is to improve sensitivity to radiation and high sharpness. An object of the present invention is to provide a method of manufacturing a radiation image conversion panel that gives an image. Another object of the present invention is to provide a method for manufacturing a radiation image conversion panel which improves the graininess and provides an image with high sharpness. Still another object of the present invention is to provide a simple manufacturing method capable of inexpensively and stably manufacturing a radiation image conversion panel (hereinafter referred to as a conversion panel).

[Constitution of the invention]

The object of the present invention is a method for producing a radiation image conversion panel having at least one stimulable phosphor layer on a support, wherein the stimulable phosphor layer is vapor-deposited in a gas atmosphere to form voids. A conversion panel comprising a step of forming a phosphor layer having, and a step of heating the stimulable phosphor layer to expand a part of the voids in a thickness direction of the stimulable phosphor layer. It is achieved by the manufacturing method of. Next, the present invention will be specifically described. FIG. 2 shows a schematic view of an example of a vapor deposition apparatus used for forming a stimulable phosphor layer in the conversion panel manufacturing method of the present invention (hereinafter sometimes simply referred to as a panel manufacturing method). The vapor deposition apparatus shown in FIG. 2 has a vacuum chamber 20, a vacuum chamber substrate 21, and an exhaust port 22 and a main valve 23 provided in a part thereof. Inside the vacuum chamber 20, there is a boat or crucible 24 for heating the evaporation source, and the stimulable phosphor 25 is filled in the boat or crucible. Boat or crucible 24
There is a support 26 of the conversion panel above the open end of the phosphor, and the stimulable phosphor 25 is vapor-deposited on the surface of this support to form a stimulable phosphor layer. A heater 27 for heating the support is provided above the support 26, and a probe 28 for controlling the film thickness is provided in parallel with the support. A pipe 29 for introducing an inert gas through the vacuum chamber substrate 21 and a vacuum gauge 211 are attached, and a variable leak valve 210 capable of controlling a small amount of gas inflow is attached to the gas introduction pipe 29. The vapor deposition apparatus used in the panel manufacturing method of the present invention is not limited to that shown in FIG. 2, and any vapor deposition apparatus capable of vapor-depositing a stimulable phosphor on an object to be vapor-deposited in an inert gas atmosphere. It may be one. Now, the panel manufacturing method of the present invention performed using the apparatus shown in FIG. 2 will be described as a specific example. In the method, first, the support is placed in the vapor deposition apparatus, and then the apparatus is evacuated to 10 ^-6 ~
The degree of vacuum is about 10 ^-7 Torr. Next, after heating to 300 to 500 ° C. by the support heating heater 27 to clean the surface of the support, the temperature of the support is set to 100 to 2
The temperature is set to about 00 ° C, the variable leak valve 210 is opened, and an inert gas such as Ar, He, or N ₂ is introduced, and the pressure is 10 ^-3 to 10 ^-4.
Use a vacuum as low as Torr. Ar is a preferable atmosphere gas. Next, the boat or crucible 24 is energized, and the stimulable phosphor 25 in the boat or crucible, for example, the rubidium bromide phosphor with thallium as the activator, is evaporated by the resistance heating method.
Then, the stimulable phosphor is crystallized at the same time as being deposited on the support 26, and columnar crystals are formed in the vertical direction from the support surface. However, in the vapor deposition process, a crystal plane in which crystal growth is promoted and a plane in which atmospheric gas is partially adsorbed and crystal growth is suppressed occur. The surface on which crystal growth is promoted grows in the direction in which vaporized molecules or atoms attach. The surface on which crystal growth is suppressed forms a large number of minute cavities or voids in the deposited layer. The shape of the cavity is often an elongated shape extending in a direction substantially perpendicular to the support surface. In this way, a stimulable phosphor layer having a large number of fine cavities is formed by vapor deposition on the support. At this time, the growth rate of the stimulable phosphor layer deposited while adsorbing the atmospheric gas is 10 ² to 10 ⁷ Å / min, preferably 10 ³
It is ~ 10 ⁶ Å / min. When the panel having the stimulable phosphor layer thus created is taken out into the atmosphere and heat-treated at a temperature of about 300 to 400 ° C., a part of the cavities in the stimulable phosphor layer are supported. It extends in the direction perpendicular to the body surface and develops along the boundary surface between the columnar crystals to form voids or cracks (however, some remain as voids). In this way, the columnar crystals are in the form of several bundles, each of which is partitioned by the voids or cracks to form optically independent columnar blocks, and the stimulation of the fine columnar block structure having many fine cavities is performed. Fluorescent phosphor layer is formed. In the above example, the case where the heat treatment is performed in the air has been described, but the same structure can be obtained by omitting the heat treatment and applying the baking in the exhaust gas to the step of forming the columnar block structure. Also, the heater for heating the support is heated to a high temperature,
C. to 400.degree. C. may be set so that the columnar block structure formation similar to the case of the heat treatment is promoted at the same time as vapor deposition. In the vapor deposition process, an electron beam method may be used instead of the resistance heating method. Further, in the vapor deposition step, it is also possible to perform co-deposition using a plurality of resistance heaters or electron beams, co-evaporation of the stimulable phosphor raw material using a plurality of resistance heaters or electron beams, It is also possible to form the stimulable phosphor layer at the same time as synthesizing the target stimulable phosphor on the support. After completion of the vapor deposition step and the heat treatment step, a conversion panel is manufactured by optionally providing a protective layer on the exposed surface of the stimulable phosphor layer on the support, if necessary. In addition, after forming the stimulable phosphor layer on the protective layer, a procedure of providing a support may be adopted. FIG. 1 shows an example of a conversion panel manufactured by the panel manufacturing method of the present invention as a cross-sectional view in the thickness direction. In the figure, reference numeral 10 shows the form of the conversion panel according to the present invention. 11 is a support, 12 is a stimulable phosphor layer having a fine columnar block structure extending in a direction substantially perpendicular to the support surface,
a represents each fine columnar block, and 12b represents fine voids or cracks separating the 12a. Further, in the fine columnar block, there is an elongated cavity 12c extending in a direction substantially perpendicular to the support surface. The average diameter of the fine columnar blocks 12a is preferably 1 to 400 μm, and the gaps 12b between the fine columnar blocks may be any intervals as long as the fine columnar blocks 12a are optically independent of each other, but on average Is preferably 0 to 20 μm. The space between the cavities 12c is preferably 100 μm or less, more preferably 40 μm or less. A protective layer 13 is preferably provided on the stimulable phosphor layer 12. If necessary, an adhesive layer may be provided between the support 11 and the stimulable phosphor layer 12 to improve the adhesiveness between the layers, or stimulable excitation light and / or luminescent An exhaustive reflection layer or absorption layer may be provided. The stimulable phosphor in the panel manufacturing method of the present invention, after being irradiated with the first light or high-energy radiation,
Phosphors that exhibit stimulated emission corresponding to the dose of the first light or high-energy radiation by photo-, thermal-, mechanical-, chemical-, or electrical-stimulation (stimulation excitation).
From a practical point of view, it is preferably a phosphor that exhibits stimulated emission by stimulated excitation light of 500 nm or more. Examples of the photostimulable phosphor used in the panel of the present invention include JP-A-48-80487.
BaSO ₄ : Ax (where A is at least one of Dy, Tb and Tm, and x is 0.001 ≦ x <1 mol%
Is. ), The phosphor described in JP-A-48-80488
MgSO ₄ : Ax (where A is either Ho or Dy, and 0.001 ≦ x ≦ 1 mol%),
SrSO ₄ : Ax (provided that A
Is at least one of Dy, Tb and Tm, and x is 0.001 ≦
x <1 mol%. ), Na ₂ SO ₄ , CaSO ₄ and BaSO ₄ described in JP-A-51-29889.
Etc. to which at least one of Mn, Dy and Tb is added, BeO, LiF, MgSO ₄ described in JP-A-52-30487
And phosphors such as CaF _2, Li ₂ B ₄ O ₇ described in JP-A-53-39277: Cu, phosphors such as Ag, Li ₂ O described in JP-A-54-47883・ (B ₂ O ₂ ) x: Cu (where x is 2 <x ≦ 3),
And phosphors such as Li ₂ O · (B ₂ O ₂ ) x: Cu, Ag (where x is 2 <x ≦ 3), SrS: C described in US Pat. No. 3,859,527.
e, Sm, SrS; Eu, Sm, La ₂ O ₂ S: Eu, Sm and (Zn, Cd) S: Mn,
Examples include phosphors represented by X (where X is halogen). Further, ZnS: Cu described in JP-A-55-12142,
Pb phosphor, general formula BaO ・ xAl ₂ O ₃ : Eu (however 0.8 ≦ x ≦ 1
0) barium aluminate phosphor represented by the general formula and M ^II O.xSiO ₂ : A (where M ^II is Mg, Ca, Sr, Zn, Cd or Ba).
And A is at least one of Ce, Tb, Eu, Tm, Pb, Tl, Bi and Mn, and x is 0.5 ≦ x <2.5. ) Alkaline earth metal silicate-based phosphors represented by Also, the general formula is (Ba _1-xy Mg _x Ca _y ) FX: eEu ²⁺ (where X is at least one of Br and Cl, and x, y
And e are 0 <x + y ≦ 0.6, xy ≠ 0 and 10 ⁺⁶ ≦ e ≦, respectively.
It is a number that satisfies the condition of 5 × 10 ⁺² . ) The phosphor represented by The general formula is LnOX: xA (where Ln is at least one of La, Y, Gd and Lu, and X is Cl.
And / or Br, A is Ce and / or Tb, and x is 0 <x <
Represents a number that satisfies 0.1. ), A phosphor represented by
The general formula described in 5-12145 is (Ba _1-x M ^II _x ) FX: yA (where M ^II is at least one of Mg, Ca, Sr, Zn and Cd).
X is at least one of Cl, Br and I, A
Is at least one of Eu, Tb, Ce, Tm, Dy, Pr, Ho, Nd, Yb and Er, and x and y are numbers satisfying conditions 0 ≦ x ≦ 0.6 and 0 ≦ y ≦ 0.2. . ), A phosphor represented by
-84389 has the general formula BaFX: xCe, yA (where X is at least one of Cl, Br and I, A is In,
It is at least one of Tl, Gd, Sm, and Zr, and x and y are 0 <x ≦ 2 × 10 ⁻¹ and 0 <y ≦ 5 × 10 ₋₂ , respectively. ), The general formula described in JP-A-55-160078 is M ^II FXxA: yLn (where M ^II is at least Mg, Ca, Ba, Sr, Zn and Cd). Type 1, A is BeO, MgO, CaO, SrO, BaO, ZnO, Al ₂ O ₃ , Y ₂ O ₃ , La
₂ O ₃ , In ₂ O ₃ , SiO ₂ , TiO ₂ , ZrO ₂ , GeO ₂ , SnO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ and
At least one of ThO ₂ and Ln is Eu, Tb, Ce, Tm, Dy, Pr,
At least one of Ho, Nd, Yb, Er, Sm and Gd,
X is at least one of Cl, Br and I, and x and y are numbers satisfying the conditions of 5 × 10 ⁻⁵ ≦ x ≦ 0.5 and 0 <y ≦ 0.2, respectively. ) Rare earth element activation 2
Valuate metal fluorohalide phosphor, with general formula ZnS: A, (Z
n, Cd) S: A, CdS: A, ZnS: A, X and CdS: A,
A phosphor represented by X (wherein A is Cu, Ag, Au or Mn and X is halogen), a general formula [I] or [II] described in JP-A-57-148285. , General formula [I] xM ₃ (PO ₄ ) ₂ · NX ₂ : yA General formula [II] M ₃ (PO ₄ ) ₂ : yA (In the formula, M and N are Mg, Ca, Sr, Ba, Zn respectively. And at least one of Cd, X is at least one of F, Cl, Br, and I, A is Eu, Tb, Ce, Tm, Dy, Pr, Ho, Nd, Er, Sb, Tl, Mn.
And at least one of Sn. Further, x and y are numbers satisfying the conditions of 0 <x ≦ 6 and 0 ≦ y ≦ 1. )
A phosphor represented by the general formula [III] or [IV] general formula [III] nReX ₃ · mAX ′ ₂ : xEu general formula [IV] nReX ₃ · mAX ′ ₂ : xEu, ySm (wherein Re is At least one of La, Gd, Y and Lu, A is an alkaline earth metal, at least one of Ba, Sr and Ca, and X and X ′ are at least one of F, Cl and Br. , X and y are 1 × 10 ⁻⁴ <x <3 × 10 ⁻¹ , 1 × 10 ⁻⁴ <
It is a number satisfying the condition of y <1 × 10 ⁻¹ , and n / m is 1 ×
The condition of 10 ^-3 <n / m <7 × 10 ^{-1 is} satisfied. Phosphor represented by), and the general formula ^{M I X · aM II X '} · bM III X ": cA ( provided that at least one alkali metal M ^I of Li, Na, K, selected from Rb and Cs And M ^II is Be, Mg, Ca, Sr, Ba, Z
It is at least one divalent metal selected from n, Cd, Cu and Ni. M ^III is Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, D
It is at least one trivalent metal selected from y, Ho, Er, Tm, Yb, Lu, Al, Ga, and In. X, X'and X "are at least one halogen selected from F, Cl, Br and I. A is Eu, Tb, Ce, Tm, Dy, P
It is at least one metal selected from r, Ho, Nd, Yb, Er, Gd, Lu, Sm, Y, Tl, Na, Ag, Cu and Mg. Also, a is a numerical value in the range of 0 ≦ a <0.5, and b is 0 ≦ b <
It is a numerical value in the range of 0.5, and c is a numerical value in the range of 0 <c ≦ 0.2. ) Alkali halide phosphors represented by). Alkali halide phosphors are particularly preferable and preferred for vapor deposition. However, the stimulable phosphor used in the panel manufacturing method of the present invention is not limited to the above-mentioned phosphor, and a phosphor showing stimulated fluorescence when irradiated with stimulated excitation light after being irradiated with radiation. Any phosphor may be used as long as it is a phosphor. The panel manufacturing method of the present invention may include a step of forming a stimulable phosphor layer group composed of one or more stimulable phosphor layers containing at least one kind of the stimulable phosphor. Good. The stimulable phosphor contained in each stimulable phosphor layer may be the same or different. In the panel manufacturing method of the present invention, various polymeric materials, glass, metals and the like are used as the support.
In particular, a material that can be processed into a flexible sheet or web as an information recording material is suitable, and from this point, for example, a cellulose acetate film, a polyester film, a polyethylene terephthalate film,
A plastic film such as a polyamide film, a polyimide film, a triacetate film or a polycarbonate film, a metal sheet of aluminum, iron, copper, chromium or the like or a metal sheet having a coating layer of the metal oxide is preferable. The layer thickness of these supports varies depending on the material of the support used, etc., but is generally 80 μm to 1000 μm, and more preferably 80 μm to 500 μm from the viewpoint of handling. In the panel manufacturing method of the present invention, a protective layer for physically or chemically protecting the stimulable phosphor layer group is generally provided on the surface on which the stimulable phosphor layer is exposed. preferable. This protective layer may be formed by directly coating the protective layer coating solution on the stimulable phosphor layer, or by forming a protective layer separately formed in advance on the stimulable phosphor layer. Good. Materials for the protective layer include cellulose acetate, nitrocellulose, polymethylmethacrylate, polyvinyl butyral, polyvinyl formal, polycarbonate, polyester, polyethylene terephthalate, polyethylene, polypropylene, polyvinylidene chloride, nylon, polytetrafluoroethylene, polytrifluoride. Materials for the protective layer such as ethylene chloride, tetrafluoroethylene-hexafluoropropylene copolymer, vinylidene chloride-vinyl chloride copolymer, vinylidene chloride and acrylonitrile copolymer are used. In addition, this protective layer is formed by vacuum deposition, sputtering, etc.
It may be formed by stacking inorganic materials such as SiC, SiO ₂ , SiN, and Al ₂ O ₃ . Since the conversion panel obtained by the panel manufacturing method of the present invention as described above does not contain a binder in the stimulable phosphor layer, the amount (filling rate) of the stimulable phosphor is the same as that of the conventional stimulable phosphor. It is about twice as thick as the stimulable phosphor layer coated with the body, and the radiation absorption rate per unit thickness of the stimulable phosphor layer is improved, and not only the sensitivity to radiation is high, but also the image graininess is improved. improves. Furthermore, the stimulable phosphor layer formed by the vapor deposition method is excellent in transparency, has high transparency to stimulated excitation light and stimulated emission, and is thicker than the stimulable phosphor layer formed by a conventional coating method. It is possible and more sensitive to radiation. FIG. 3 (a) shows an example of the relationship between the radiation sensitivity and the stimulable phosphor layer corresponding to the stimulable phosphor layer of the conversion panel according to the panel manufacturing method of the present invention. An example of the sharpness of a panel having a stimulable phosphor layer having a fine columnar block structure obtained by the panel manufacturing method of the present invention is shown by a characteristic curve 31 in FIG. 3 (b). According to the panel manufacturing method of the present invention, Japanese Patent Application No. 59-266912-2
A finer structure than the fine columnar block structure described in No. 66916 is formed, and the obtained panel has, for example, a special structure because the stimulated excitation light is repeatedly reflected inside by the inner surface of the columnar block and the cavity surface due to the light induction effect. As is clear from comparison with 32 in FIG. 3 (b), which shows the characteristics of the tile-shaped structure shown in Japanese Patent Application No. 59-266914, the sharpness of the image is improved and the photostimulable phosphor layer is formed. It is possible to further improve the sharpness as the thickness increases. The characteristic of the conversion panel manufactured by the conventional manufacturing method in which the stimulable phosphor particles are dispersed and applied to the binder is shown in FIG. 3 (b) at 33. This clearly shows that the sharpness of the image is excellent. Also, the panel manufacturing method of the present invention is described in Japanese Patent Application No. 59-266912-2.
Since it does not require the step of manufacturing the base layer of the fine columnar block structure, that is, the fine concavo-convex pattern on the surface of the support, the fine tile-like plate structure, or the combination of the fine tile-like plate and the fine wire net described in 66915. The process is simplified as compared with the conventional panel manufacturing method.

【Example】

Next, the present invention will be described with reference to examples. Example 1. An aluminum plate having a thickness of 0.5 mm was placed in the vapor depositor as a support. Next, put the alkali halide stimulable phosphor RbBr: 0.004Tl in a molybdenum boat for resistance heating, set it on the electrode for resistance heating, and then evacuate the inside of the evaporator to 1 ×.
The degree of vacuum was 10 ⁻⁷ Torr. Then, the support is heated to 300-500 ° C by a heater for cleaning the support to clean the surface of the support, and then the support is set at 100 ° C and argon gas is introduced to maintain the support at about 1 × 10 ^-4 Torr. did. Next, a molybdenum boat was energized and RbBr: 0.004 Tl was evaporated by a resistance heating method to prepare a conversion panel raw material having a stimulable phosphor layer having a thickness of about 250 μm. The raw material of the conversion panel was taken out into the atmosphere and heat-treated at 350 ° C. for 30 minutes to obtain a conversion panel A by the panel manufacturing method of the present invention. The conversion panel A thus obtained according to the panel manufacturing method of the present invention was irradiated with 10 mR of X-ray having a tube voltage of 80 KVp,
Photodetector (photomultiplier tube) for photostimulated luminescence emitted from photostimulable phosphor layer after photostimulation by semiconductor laser light (780 nm)
Photoelectric conversion was carried out, and this signal was reproduced as an image by an image reproducing device and recorded on a silver salt film. The sensitivity of the conversion panel A to X-rays was examined from the signal intensity, and the modulation transfer function (MTF) and graininess of the image were examined from the obtained image. In Table 1, the sensitivity to X-rays is shown in 100 relative values for panel A of the present invention. Also, the modulation transfer function (MTF)
Is the value when the spatial frequency is 2 cycles / mm. Example 2. In Example 1, the argon pressure during vapor deposition was set to 5 × 10 ⁻⁴ Torr.
Further, by performing the same operation as in Example 1 except that the temperature of the support during vapor deposition was set to 350 ° C. and the heat treatment after the vapor deposition was completed, the conversion panel B according to the panel manufacturing method of the present invention was obtained. Got The conversion panel B thus obtained according to the panel manufacturing method of the present invention was evaluated in the same manner as in Example 1, and the results are also shown in Table 1. Comparative Example 1. 8 parts by weight of stimulable phosphor RbBr: 0.004 Tl and 1 part by weight of polyvinyl butyral resin were mixed and dispersed with 5 parts by weight of a solvent (cyclohexanone) to prepare a coating liquid for the stimulable phosphor layer. Next, this coating solution was uniformly applied on a black polyethylene terephthalate film as a support having a thickness of 300 μm placed horizontally, and naturally dried to form a stimulable phosphor layer having a thickness of 250 μm. The comparative conversion panel P thus obtained is the same as in Example 1.
Evaluation is carried out in the same manner as above, and the results are also shown in Table 1. Comparative example 2. A 0.5 mm thick aluminum plate was anodized, sealed, and heat-treated by the method described in Japanese Patent Application No. 59-266914 to obtain a tile-like plate having a surface structure such that the tile plates were spread over each other and separated by fine gaps. The thus prepared support was placed in a vapor depositor. Next, put the alkali halide stimulable phosphor RbBr: 0.004Tl in a molybdenum boat for resistance heating, set it on the electrode for resistance heating, and then evacuate the inside of the vaporizer to 1 × 10 ^-7 Torr.
And the degree of vacuum. Then, the support was heated to 300 to 500 ° C. by a support heating heater to clean the surface of the support, and then the support was set to 100 ° C. and the degree of vacuum was set to 2 × 10 ⁻⁶ Torr. Next, energize the molybdenum boat and apply RbB by resistance heating.
r: 0.004 Tl was evaporated and vacuum-deposited to a thickness of about 250 μm to obtain a comparative conversion panel Q. The comparative conversion panel Q thus obtained is the same as in Example 1.
Evaluation is carried out in the same manner as above, and the results are also shown in Table 1. As is clear from Table 1, the conversion panels A and B produced by the manufacturing method of the present invention were about twice as high in X-ray sensitivity as the comparison conversion panel P and had excellent image graininess. This is because the conversion panel according to the production method of the present invention does not contain a binder in the stimulable phosphor layer, the filling rate of the stimulable phosphor is higher than that of the comparative conversion panel, and the absorption rate of X-rays is high. Because it is good. In addition, the conversion panels A and B produced by the manufacturing method of the present invention were superior to the comparative conversion panel P in terms of sharpness in spite of higher X-ray sensitivity. According to the manufacturing method of the present invention, this is because the stimulable phosphor layer of the conversion panel has a fine columnar block structure and fine voids. This is because scattering in the body layer is reduced. Further, the conversion panels A and B produced by the manufacturing method of the present invention were excellent in sharpness as compared with the comparative conversion panel Q although the X-ray sensitivity and the graininess were equivalent. In the manufacturing method of the present invention, the conversion panels A and B have a finer structure than the fine columnar block structure of the comparative conversion panel Q because they are vapor-deposited and heat-treated in an argon atmosphere, This is because the induction effect is more excellent.

【The invention's effect】

As described above, according to the present invention, since the stimulable phosphor layer has a fine columnar block structure and fine voids, the scattering of stimulable excitation light in the stimulable phosphor layer is significantly reduced. As a result, the sharpness of the image can be improved. Further, according to the present invention, since the decrease in the sharpness of the image due to the increase of the stimulable phosphor layer is small, the radiation sensitivity can be increased without decreasing the sharpness of the image by increasing the size of the stimulable phosphor layer. It is possible to improve. Further, according to the present invention, since the deterioration of the sharpness of the image due to the increase of the stimulable phosphor layer is small, by increasing the thickness of the stimulable phosphor layer, the image sharpness can be reduced without decreasing the sharpness of the image. It is possible to improve the graininess. Further, according to the present invention, the radiation image conversion panel of the present invention can be manufactured inexpensively and stably. The present invention is extremely effective and industrially useful.

[Brief description of drawings]

FIG. 1 is a sectional view showing a part of an example of a conversion panel according to the manufacturing method of the present invention. FIG. 2 is a schematic diagram showing an example of a vapor deposition apparatus used in the present invention. FIG. 3 (a) is a diagram showing the stimulable phosphor layer thickness and deposition amount and the sensitivity to radiation in an example of a conversion panel prepared according to the present invention, and FIG. 3 (b) is a spatial frequency and a modulation transfer function (MTF). ) Is a diagram showing a relationship with FIG. FIG. 4 (a) is a diagram showing the stimulable phosphor layer and the adhesion amount and the sensitivity to radiation in the conventional conversion panel, and (b) is the stimulable phosphor layer thickness in the conventional conversion panel and It is a figure which shows an adhesion amount and a modulation transfer function (MTF) in case a spatial frequency is 2 cycles / mm. 10 ... Conversion panel, 11 ... Support 12 ... Photostimulable phosphor layer, 13 ... Protective layer 20 ... Vacuum tank, 21 ... Vacuum tank substrate 22 ... Exhaust port, 23 ... Main valve 24 ... Boat or crucible 25 ... Photostimulation Fluorescent substance, 26 ... Support 27 ... Support heating heater 28 ... Thickness control probe 29 ... Gas inlet tube 210 ... Variable leak valve 211 ... Vacuum gauge 31 ... Characteristic curve of conversion panel by the manufacturing method of the present invention 32 ... Characteristic curve of conversion panel having fine columnar block structure 33 ... Characteristic curve of conventional conversion panel

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-62-39800 (JP, A) JP-A-59-126299 (JP, A)

Claims (1)

[Claims] 1. A method for producing a radiation image conversion panel having at least one photostimulable phosphor layer on a support, wherein the photostimulable phosphor layer is vapor-deposited in an inert gas atmosphere to form voids. Radiation image conversion comprising a step of forming a phosphor layer and a step of heating the stimulable phosphor layer to expand a part of the voids in a thickness direction of the stimulable phosphor layer. Panel manufacturing method.