JPH0727079B2 - Radiation image information reader - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to a radiation image information reading device using a stimulable phosphor, and more particularly to a radiation image information reading device capable of giving a radiation image with high sharpness.

[Prior 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 this visible light is used in the same way as when taking a normal photograph. A so-called radiograph in which a film using salt is irradiated and developed is used. However, in recent years, a method of directly taking out an image from the phosphor layer without using a film coated with silver salt has been devised. 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. A latent image is formed by accumulating the radiation energy corresponding to the radiation transmittance, and thereafter, the stimulable phosphor layer is scanned with stimulable excitation light to radiate the accumulated radiation energy of each part to generate a latent image. The light is converted into light, and an image is obtained by an optical signal depending on the intensity of the light.
This final image may be played back as a hard copy or 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. -Since it is produced by drying, the packing density of the stimulable phosphor is low (filling rate 50%), and the stimulable phosphor layer is required to have sufficiently high radiation sensitivity as shown in Fig. 6 (a). It was necessary to increase the layer thickness of. 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.
It saturates above. It should be noted that the radiation sensitivity is saturated because when the stimulable phosphor layer becomes too thick, the stimulable phosphor layer scatters among the stimulable phosphor particles, resulting in a bright inside the stimulable phosphor layer. This is because exhaust emission does not come out to the outside. 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 smaller, as shown in FIG. 6 (b). It was necessary to reduce the thickness of the stimulable phosphor layer in order to improve. 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, the image quality is degraded. 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 and the graininess of the image, and the sharpness of the image show the opposite tendency to the layer thickness of the stimulable phosphor layer. The radiation image conversion panel has been made at the expense of some sensitivity to radiation, 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. In this radiation image conversion method, since the radiation image information accumulated in the radiation image conversion panel is taken out in time series, it is desirable that the stimulated emission due to the stimulated excitation light irradiated at a certain time (ti). 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 due to scattering etc. in the panel , If the stimulable phosphor existing outside the irradiation pixel (xi, yi) is also excited, the output from the pixel (xi, yi) above is recorded as the output from a wider area than that pixel. This is because it will end up. Therefore, the stimulated emission by the stimulated excitation light irradiated at a certain time (ti) is emitted 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 wavelength region of the stimulable phosphor And the like so that the average reflectance in the above 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, on the other hand, the Applicant has already reported in Japanese Patent Application No. 59-196365 that a radiation image conversion panel using a stimulable phosphor as described above has been improved as a new radiation image conversion panel to improve the conventional defects. A radiation image conversion panel in which the luminescent phosphor layer does not contain a binder is 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 remarkably improved and the stimulable excitation light in the stimulable phosphor layer is increased. Also, since the directivity of stimulated emission 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 also improved. However, in the radiation image conversion method, the sensitivity,
The demand for image quality with excellent sharpness without impairing graininess is becoming more severe.

[Object of the Invention]

It is an object of the present invention to provide a radiation image information reading apparatus capable of obtaining an image with high sensitivity to radiation, good graininess, and high sharpness by further improving the proposed radiation image conversion panel. To provide.

[Constitution of the invention]

The object of the present invention is to provide a radiation image conversion panel for recording radiation image information, comprising a stimulable phosphor layer formed by vapor deposition on a support, and the stimulable phosphor layer. Light source means for irradiating a laser beam for irradiating, and detecting the stimulated emission light generated by irradiating the photostimulable phosphor with the laser light, a signal based on the amount of the stimulated emission light In a radiation image information reading device having a photoelectric converter for outputting, and configured to obtain image information based on the output of the photoelectric converter, the stimulable phosphor layer is the surface of the support. And a block structure of crystallographically discontinuous fine columnar crystals based on a concavo-convex pattern in which rectangular concavities and convexities are alternately arranged, and the light source means is provided from one side with respect to the radiation image conversion panel. By said stimulable fluorescence It can be achieved by the radiation image information reading apparatus being characterized in that configured to perform irradiation and detection of the stimulated light by the photoelectric converter of the laser light to the layer. Next, the present invention will be specifically described. FIG. 1 (a) is a sectional view of a radiation image conversion panel according to the present invention (hereinafter sometimes simply referred to as a panel when the meaning is clear). FIG. 3B is a sectional view in the thickness direction of the support having an uneven pattern when the stimulable phosphor layer having the fine columnar block structure is not provided yet. The distribution pattern on the support may be arbitrary. FIG. 2 shows (a) and (b) as examples of the distribution pattern.
And (c). The same symbols in FIGS. 1 and 2 are functionally synonymous with each other. In FIG. 1, 10 is a panel, 11ij is a convex portion of the support, and (11ij) is a concave portion thereof. 12 is a support.
Reference numeral 13ij denotes each fine columnar block of the stimulable phosphor which succeeds the convex portion 11ij as it is, and (13ij) denotes each fine columnar block which inherits the concave portion (11ij). By the above 13ij and (13ij), the stimulable phosphor layer 13 having the fine columnar block structure according to the present invention is formed. The average diameter of the convex portion 11ij and the concave portion (11ij) is 10 to 400μ.
m is preferable, and 15-100 μm is more preferable. The thickness of the stimulable phosphor layer 13 varies depending on the sensitivity of the panel to radiation, the type of stimulable phosphor, etc., but is 10 to 1000.
The thickness is preferably in the range of μm, and more preferably in the range of 20 to 800 μm. Further, if necessary, an adhesive layer for assisting adhesion of the stimulable phosphor layer, or a reflection layer or absorption layer for stimulated excitation light and / or stimulated emission may be provided on the uneven surface of the support. . Since the stimulable phosphor layer 13 is deposited while sequentially growing crystals while maintaining the concavo-convex structure on the surface of the support during the deposition of the stimulable phosphor, the fine columnar blocks (13ij) grown on the recesses (11ij) are formed. ) And the fine columnar block 13ij grown on the convex portion 11ij are crystallographically discontinuous, and the columnar block (13ij) and the columnar block 13ij are optically independent from each other. Therefore, when photostimulable excitation light enters the photostimulable phosphor layer having fine columnar block structures optically independent of each other from the fine columnar crystal cross section on the surface of the layer, the excitation light is photoinduced to the fine columnar block structure. Due to the effect, while repeatedly reflecting on the inner surface of the columnar block, the light reaches the bottom of the columnar block without being scattered to the outside, and is absorbed or reflected and again emerges in the columnar direction of the columnar block while being reflected again on the inner surface of the columnar block. Therefore, the sharpness of the image due to stimulated emission is significantly increased while increasing the chances of stimulated excitation. Note that, in the present invention, as shown in FIG. 3, the panel has a structure in which the stimulable phosphor layer 13 is deposited and then the stimulable phosphor layer is polished so that the convex portions 11ij on the surface of the support are exposed. May be. In the radiation image conversion panel according to the present invention, the stimulable phosphor means that the first light or high-energy radiation is irradiated, and then the first light or high-energy radiation is irradiated by optical stimulation (stimulation excitation). It refers to a phosphor showing stimulated emission corresponding to the amount, but is preferably 50 from a practical point of view.
It is a phosphor showing stimulated emission by stimulated excitation light of 0 nm or more. Examples of the photostimulable phosphor used in the radiation image conversion panel according to the present invention include BaSO ₄ : Ax (where A is at least one of Dy, Tb and Tm) described in JP-A-48-80487. And x is 0.001 ≦ x <1 mol%), MgS described in JP-A-48-80488.
O ₄ : Ax (where A is either Ho or Dy, 0.0
01 ≦ x <1 mol%)
No. 80489 discloses a phosphor represented by SrSO ₄ : Ax (where A is at least one of Dy, Tb and Tm and x is 0.001 ≦ x <1 mol%). In Na ₂ SO ₄ , CaSO ₄ and BaSO ₄ etc. described in Japanese Patent Publication No. 51-29889, Mn, Dy and
Phosphor to which at least one of Tb is added
BeO, LiF, MgSO ₄ and CaF _{2 and the} like described in 0487, Li ₂ B ₄ O ₇ : Cu, A described in JP-A-53-39277
g and other phosphors, Li ₂ O. described in JP-A-54-47883
(B ₂ O ₂ ) x: Cu (where x is 2 <x ≦ 3), and Li ₂ O · (B ₂ O ₂ ).
Phosphor such as x: Cu, Ag (where x is 2 <x ≦ 3), US patent
SrS: Ce, Sm, SrS; Eu, Sm, L described in No. 3,859,527
a ₂ O ₂ S: Eu, Sm and (Zn, Cd) S: Mn, X (where X is halogen)
The fluorescent substance represented by In addition, JP-A-55-12142
ZnS: Cu, Pb phosphor, whose general formula is BaOxA
l ₂ O ₃ : Eu (provided that 0.8 ≦ x ≦ 10) and a barium aluminate phosphor represented by the general formula M ^II O · xSiO ₂ : A (where M ^II is M
g, Ca, Sr, Zn, Cd or Ba, and A is Ce, Tb, Eu, Tm, Pb, Tl, Bi
And at least one of Mn, and x is 0.5 ≦ x ≦ 2.5
Is. ) Alkaline earth metal silicate-based phosphors represented by. 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 ≦, respectively.
It is a number that satisfies the condition of e ≦ 5 × 10 ^-2 . ) Alkaline earth fluorohalide phosphor represented by JP-A-55-12144
The general formula described in No. 1 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 −xM ^II x) FX: yA (where M ^II is at least one of Mg, Ca, Sr, Zn and Cd, and X is Cl, Br. And at least one of I, A is Eu,
At least one of Tb, Ce, Tm, Dy, Pr, Ho, Nd, Yb and Er
On the other hand, x and y represent numbers satisfying the conditions of 0 ≦ x ≦ 0.6 and 0 ≦ y ≦ 0.2. ), The phosphor represented by JP-A-55-84
The general formula described in No. 389 is BaFx: xCe, yA (however, X
Is at least one of Cl, Br and I, A is In, Tl, Gd,
It is at least one of 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 FX xA: 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
Valuable metal fluorohalide phosphor, general formula ZnS: A, CdS:
A, (Zn, Cd) S: A, ZnS: A, X and CdS: A, X (where A is Cu, A
g, Au, or Mn, and X is halogen. ), A general formula [I] or [II] described in JP-A-57-148285, a 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 at least one of Mg, Ca, Sr, Ba, Zn, and Cd, respectively, and X is at least one of F, Cl, Br, and I. One, A represents at least one of Eu, Tb, Ce, Tm, Dy, Pr, Ho, Nd, Er, Sb, Tl, Mn and Sn, and x and y are 0.
It is a number that satisfies the condition of <x ≦ 6, 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 (where Re Represents at least one of La, Gd, Y and Lu, A represents an alkaline earth metal, at least one of Ba, Sr and Ca, and X and X ′ represent at least one of F, Cl and Br. Also,
x and y are 1 × 10 ⁻⁴ <x <3 × 10 ⁻¹ , 1 × 10 ⁻⁴ <y <
It is a number that satisfies the condition 1 × 10 ^-1 , and n / m is 1 × 10 ^-3 <n
The condition of / m <7 × 10 ^{-1 is} satisfied. ) Phosphor represented by
And the general formula ^{M I X · aM II X '} 2 · bM III X "3: cA ( where, M ^I is at least one alkali metal selected Li, Na, K, Rb, and from Cs, 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, Dy, H
It is at least one trivalent metal selected from o, 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, T
It is at least one metal selected from b, Ce, Tm, Dy, Pr, 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 <y ≦ 0.2. ) Alkali halide phosphors represented by). In particular, the alkali halide phosphor is preferable because it facilitates the formation of a stimulable phosphor layer by a method such as vacuum deposition and sputtering. However, the stimulable phosphor used in the radiation image conversion panel according to the present invention is not limited to the above-described phosphor, and it exhibits stimulated emission when irradiated with stimulated excitation light after irradiation with radiation. Any phosphor may be used as long as it is a phosphor. The radiation image conversion panel according to the present invention may be a stimulable phosphor layer group composed of one or more stimulable phosphor layers containing at least one kind of the stimulable phosphor described above. The stimulable phosphor contained in each stimulable phosphor layer may be the same or different. In the radiation image conversion panel according to the present invention, various types of polymer materials, glass, metals, etc. are used as the support, and those which can be processed into a flexible sheet or web for handling, especially as an information recording material. From this point of view, for example, cellulose acetate film, polyester film, polyethylene terephthalate film, polyamide film, polyimide film, triacetate film, plastic film such as polycarbonate film, aluminum, iron, copper,
A metal sheet such as chromium 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 radiation image conversion panel according to the present invention, a protective layer for physically or chemically protecting the stimulable phosphor layer is generally provided on the surface on which the stimulable phosphor layer is exposed. Is preferred. 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,
Usual protective layer materials such as polyvinyl butyral, polyvinyl formal, polycarbonate, polyester, polyethylene terephthalate, polyethylene, vinylidene chloride and nylon are used. In addition, this protective layer is formed by vacuum deposition, sputtering, etc.
SiC, SiO ₂ , SiN, Al ₂ O ₃ or the like may be formed by laminating inorganic materials. Generally, the thickness of these protective layers is preferably about 0.1 μm to 100 μm. Next, a method of manufacturing the panel according to the present invention will be described. In FIG. 1, the manufacturing process proceeds in the order of (b) → (a) in FIG. Step (b): Support having fine concave-convex pattern A base pattern composed of concave portions (11ij) and convex portions 11ij on the surface of the support 12 is formed by an embossing method of embossing the support itself, light, heat, chemicals, etc. It can be prepared by a printing method or a photo-etching method in which an ink made of a resin which is fixed and hardened on a support is used as a material, and is dried and cured by printing by a gravure method or a silk method. In the photo-etching method, for example, when a photosensitive resin plate is used, first, a mask having an island-shaped pattern that is opaque to light is formed on the surface of, for example, a nylon photosensitive resin (Printite; manufactured by Toyobo Co., Ltd.). Closely contact and irradiate with ultraviolet rays containing a wavelength in the photosensitive wavelength range of 250 to 400 nm. After exposure, the photosensitive resin is developed. In the case of the above-mentioned photosensitive resin, the unexposed portion is washed away by this development,
The exposed portion remains convex. Step (a): stimulable phosphor layer 13 As a method for forming the stimulable phosphor layer having a fine columnar block structure, a vapor deposition method is the most preferable in terms of reliability and sensitivity of the columnar block formation. preferable. There is a vacuum evaporation method as the first method of the vapor deposition method. In this method, first, the support is placed in the vapor deposition apparatus and then the apparatus is evacuated to a vacuum degree of about 10 ⁻⁶ Torr. Then, at least one of the stimulable phosphors is heated and evaporated by a method such as a resistance heating method or an electron beam method to deposit the stimulable phosphor on the surface of the support to a desired thickness. As a result, a stimulable phosphor layer containing no binder is formed, but it is also possible to form the stimulable phosphor layer in a plurality of times in the vapor deposition step. Further, in the vapor deposition step, co-evaporation can be performed using a plurality of resistance heaters or electron beams. After completion of the vapor deposition, a protective layer is preferably provided on the side of the stimulable phosphor layer opposite to the side of the support, if necessary, to produce the radiation image conversion panel according to the present invention. Incidentally, after forming the stimulable phosphor layer on the protective layer, a procedure of providing a support may be adopted. In the vacuum deposition method, the stimulable phosphor material is co-evaporated using a plurality of resistance heaters or electron beams to synthesize the desired stimulable phosphor on the support and at the same time stimulable. It is also possible to form a phosphor layer. Further, in the vacuum vapor deposition method, the object to be vapor-deposited (support or protective layer) may be cooled or heated during vapor deposition, if necessary. In addition, the stimulable phosphor layer may be heat-treated after completion of vapor deposition. The second method is a sputtering method. In this method, as in the vapor deposition method, after the support is placed in the sputtering apparatus, the inside of the apparatus is once evacuated to a vacuum degree of about 10 ^-6 Torr, and then an inert gas such as Ar or Ne is used as a gas for sputtering. The gas is introduced into the sputtering apparatus to a gas pressure of about 10 ^-3 Torr. Next, the stimulable phosphor is deposited on the surface of the support to a desired thickness by sputtering using the stimulable phosphor as a target. In the sputtering step, it is possible to form the stimulable phosphor layer in a plurality of times in the same manner as in the vacuum deposition method, and it is also possible to simultaneously use a plurality of targets made of different stimulable phosphors. Alternatively, it is also possible to sequentially sputter the target to form a stimulable phosphor layer. After the completion of sputtering, if necessary, a protective layer is preferably provided on the side of the stimulable phosphor layer opposite to the side of the support, as in the vacuum deposition method, to produce the radiation image conversion panel of the present invention. Incidentally, after forming the stimulable phosphor layer on the protective layer, a procedure of providing a support may be adopted. In the sputtering method, a plurality of stimulable phosphor raw materials are used as targets, and these are simultaneously or sequentially sputtered to synthesize a target stimulable phosphor on a support and at the same time a stimulable phosphor layer. Can also be formed. In the sputtering method, if necessary
Reactive sputtering may be performed by introducing a gas such as O ₂ or H ₂ . Further, in the sputtering method, the material to be vapor-deposited (support or protective layer) may be cooled or heated during the sputtering, if necessary. Further, the stimulable phosphor layer may be heat-treated after completion of sputtering. The third method is the CVD method. In this method, a target stimulable phosphor or an organometallic compound containing a raw material for a stimulable phosphor is decomposed by energy such as heat or high-frequency power to give a binder containing no binder on the support. A fluorescent phosphor layer is obtained. FIG. 4 (a) shows the relationship between the stimulable phosphor layer thickness of the radiation image conversion panel according to the present invention obtained by the vapor deposition method and the amount of the stimulable phosphor attached corresponding to the layer thickness and the radiation sensitivity. Represents an example. Since the stimulable phosphor layer by the vapor deposition method according to the present invention does not contain a binder, the amount of the stimulable phosphor attached (filling rate) is the same as that obtained by coating a conventional stimulable phosphor. It is about twice as thick as the stimulable phosphor layer, 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 graininess of the image is improved. Furthermore, the stimulable phosphor layer produced by the vapor deposition method has excellent directivity for stimulated excitation light and stimulated emission, has high transmittance for stimulated excitation light and stimulated emission, and is bright by conventional coating methods. It is possible to make the layer thickness thicker than that of the exhaustive phosphor layer, resulting in higher sensitivity to radiation. An example of the sharpness of the panel according to the present invention having the stimulable phosphor layer having the fine columnar block structure obtained as described above is shown in FIG. 4 (b). In the panel according to the present invention, due to the light guiding effect of the fine columnar block structure, the stimulated excitation light is repeatedly reflected on the inner surface of the columnar block and is rarely scattered outside the columnar block. As is clear from comparison with (b), it is possible to improve the sharpness of the image and reduce the decrease in the sharpness due to the increase in the layer thickness of the stimulable phosphor. The radiation image conversion panel according to the present invention provides excellent sharpness, graininess and sensitivity when used in the radiation image conversion method schematically shown in FIG. That is, in FIG. 5, 51 is a radiation generator, 52 is a subject, 53 is a radiation image conversion panel according to the present invention, 54 is a stimulated excitation laser light source, and 55 is stimulated emission emitted from the radiation image conversion panel. Photoelectric conversion device for detecting, 56 is a device for reproducing the signal detected by 55 as an image, 57 is a device for displaying the reproduced image, 58 is for separating stimulated excitation light and stimulated emission, and stimulated It is a filter that transmits only light emission. It should be noted that after 55, it is not limited to the above as long as it can reproduce the optical information from 53 as an image in some form. As shown in FIG. 5, the radiation from the radiation generator 51 passes through the subject 52 and the radiation image conversion panel according to the present invention.
Incident on 53. The incident radiation is absorbed by the stimulable phosphor layer of the radiation image conversion panel 43, the energy is accumulated, and an accumulated image of a radiation transmission image is formed. Next, this accumulated image is stimulated by emitting stimulated excitation light from the stimulated excitation light source 54 from the cross section of fine columnar crystals on the surface of the stimulable phosphor layer to excite it as stimulated emission. The radiation image conversion panel 53 according to the present invention, since the stimulable phosphor layer has a fine columnar block structure, during the scanning with the stimulable excitation light, the stimulable excitation light is a stimulable phosphor. Diffusion in the layers is suppressed. Since the intensity of the stimulated emission emitted is proportional to the amount of accumulated radiation energy, this optical signal is photoelectrically converted by the photoelectric conversion device 55 such as a photomultiplier tube, and reproduced as an image by the image reproduction device 56. By displaying with the display device 57, the radiation transmission image of the subject can be observed.

【Example】

Next, the present invention will be specifically described with reference to examples. Example 1 A photoresist resin was applied to an aluminum plate having a thickness of 500 μm, and pattern exposure and development were performed to form a fine concavo-convex pattern as shown in FIG. 2 (a) on the surface of the aluminum plate to obtain a support. The size of the fine concavo-convex pattern was 80 μm × 80 μm and the thickness was 40 μm. Next, this support was placed in a vapor deposition machine, and an alkali halide stimulable phosphor (0.
9RbBr.0.1CsF: 0.01Tl) was put in and set on the electrode for resistance heating, and then the vaporizer was evacuated to a vacuum degree of 2 × 10 ⁻⁶ Torr. Next, an electric current is applied to the tungsten boat to evaporate the alkali halide stimulable phosphor by a resistance heating method and deposit the stimulable phosphor layer on the support until the layer thickness becomes 300 μm. A radiation image conversion panel A according to the above was obtained. The thus obtained radiation image conversion panel A according to the present invention was irradiated with 10 mR of X-ray having a tube voltage of 80 kVp, and then He-Ne laser light (633 nm) was applied to the stimulable phosphor layer surface to form a cross section of fine columnar crystals. From the photostimulable phosphor layer and photo-electrically converted by the photodetector (photomultiplier),
This signal was reproduced as an image by an image reproducing device and recorded on a silver salt film. The sensitivity of the radiation image 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 as a relative value with the radiation image conversion panel A according to the present invention as 100.
The modulation transfer function (MTF) is a value when the spatial frequency is 2 cycles / mm, and the granularity is (good, normal, bad).
Are each indicated by (○, Δ, ×). Example 2 Nylon-based photosensitive resin was applied to a 500 μm thick aluminum plate.
It was applied to a thickness of 30 μm, subjected to pattern exposure and development to form a fine concavo-convex pattern as shown in FIG. 2 (b) on the surface of the aluminum plate, and used as a support. The size of the concave and convex portions of the fine concavo-convex pattern is 110 μm × 110 μm, and the width of the convex portion is 20 μm.
Met. Next, a stimulable phosphor layer was provided on this support in the same manner as in Example 1, and then the upper surface of the stimulable phosphor layer was polished to expose a convex portion on the surface of the support to obtain the present invention. The radiation image conversion panel B was obtained. The radiation image conversion panel B according to the present invention thus obtained was evaluated in the same manner as in Example 1, and the results are also shown in Table 1. Example 3 The present invention is carried out in the same manner as in Example 1 except that a 300 μm thick black polyethylene terephthalate film surface is embossed by the embossing method to form a fine concavo-convex pattern as the support in Example 1. Radiation image conversion panel C was obtained. The radiation image conversion panel C according to the present invention thus obtained was evaluated in the same manner as in Example 1, and the results are also shown in Table 1. Comparative Example 1 Alkali halide stimulable phosphor (0.9RbBr / 0.1CsF: 0.01
Tl) 8 parts by weight, polyvinyl butyral resin 1 part by weight and solvent (cyclohexanone) 5 parts by weight were mixed and dispersed to prepare a coating liquid for the stimulable phosphor layer. Next, this coating solution was uniformly applied on a black polyerythrylene terephthalate film as a support having a thickness of 300 μm and horizontally dried to form a stimulable phosphor layer having a thickness of 300 μm. The comparative radiation image conversion panel P thus obtained
Is evaluated in the same manner as in Example 1, and the results are also shown in Table 1. Comparative Example 2 A comparative radiation image conversion panel Q was obtained in the same manner as in Comparative Example 1 except that the thickness of the stimulable phosphor layer in Comparative Example 1 was changed to 130 μm. Comparative radiation image conversion panel Q obtained in this way
Is evaluated in the same manner as in Example 1, and the results are also shown in Table 1. As is clear from Table 1, the radiation image conversion panels A to C according to the present invention have X-ray sensitivities of about 10% or less as compared with the comparative radiation image conversion panels P and Q each having a corresponding stimulable phosphor layer thickness. It was twice as high and the image graininess was excellent. This is because the radiation image conversion panel according to 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 panel, and the X-ray absorption rate is good. This is because. Further, the radiation image conversion panels A to C according to the present invention have higher X-ray sensitivity than the comparative radiation image conversion panels P and Q each having a corresponding stimulable phosphor layer thickness, but have sharpness. It was also excellent in terms. This is because the radiation image conversion panel according to the present invention has a columnar block structure in which the stimulable phosphor layer is subdivided by the fine concavo-convex pattern on the surface of the support, so that the stimulable excitation in the stimulable phosphor layer is performed. This is because the scattering of He-Ne laser, which is light, is controlled and reduced.

【The invention's effect】

As described above, according to the present invention, since the stimulable phosphor layer has a fine columnar block structure, the scattering of the stimulable excitation light in the stimulable phosphor layer is significantly reduced, resulting in an image. The sharpness of can be improved. Further, according to the present invention, since the stimulated excitation light is repeatedly reflected on the inner surface of the columnar block to increase the stimulated excitation (use of light) efficiency, it is possible to improve the radiation sensitivity and the graininess of the image. is there. Further, according to the present invention, since the sharpness of the image is not significantly reduced due to the increase in the stimulable phosphor layer thickness, increasing the stimulable phosphor layer thickness allows the radiation without decreasing the sharpness of the image. It is possible to improve the sensitivity. Further, according to the present invention, since the deterioration of the sharpness of the image due to the increase of the stimulable phosphor layer thickness is small, by increasing the thickness of the stimulable phosphor layer, the image sharpness is not deteriorated without decreasing the image sharpness. It is possible to improve the graininess of the. Further, the effects of improving the sharpness of the image, improving the radiation sensitivity, and improving the graininess of the image according to the present invention, which have been described so far, become particularly significant when the stimulating excitation light is laser light. Further, the radiation image conversion panel according to 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 a support surface during a manufacturing process and a radiation image conversion panel according to the present invention. FIG. 2 is a plan view showing an example of the concavo-convex pattern on the support surface. Third
The figure shows an example of a radiation image conversion panel according to the present invention. FIG. 4 (a) is a diagram showing the stimulable phosphor layer thickness and the amount of attachment and the sensitivity to radiation in the radiation image conversion panel according to an example of the present invention, and FIG. 4 (b) is the radiation in the radiation image conversion panel. Modulation Transfer Function (M
FIG. FIG. 5 is a schematic diagram of a radiation image conversion method used in the present invention. FIG. 6 (a) is a diagram showing the stimulable phosphor layer thickness and deposition amount and radiation sensitivity in a radiation image conversion panel according to a conventional radiation image conversion method, and FIG. 6 (b) is the conventional radiation image. It is a figure which shows the stimulable fluorescent substance layer thickness and the amount of attachment, and the modulation transfer function (MTF) in case the spatial frequency is 2 cycles / mm in the radiation image conversion panel concerning the conversion method. 10 …… Panel 11ij …… Convex part (11ij) …… Concave part 12 …… Support 13 …… Stimulable phosphor layer 13ij …… Fine column block (13ij) …… Fine column block

 ─────────────────────────────────────────────────── --Continued from the front page Judgment panel for referees Nobuo Takahashi Judge Judge Akira Shiozaki Judge Naoki Kono (56) References JP-A-52-70784 (JP, A) JP-A-57-7049 (JP, A) ) JP-A-59-202100 (JP, A)

Claims (1)

[Claims] 1. A radiation image conversion panel for recording radiation image information, comprising a photostimulable phosphor layer formed by vapor deposition on a support, and irradiation of the photostimulable phosphor layer. A light source means for emitting a laser beam for detecting the photostimulated luminescent light generated by irradiating the photostimulable phosphor with the laser light, and outputs a signal based on the amount of the photostimulated luminescent light. A radiation image information reading apparatus having a photoelectric converter and configured to obtain image information based on the output of the photoelectric converter, wherein the stimulable phosphor layer is provided on the surface of the support. Based on the concavo-convex pattern in which the formed rectangular concavities and convexities are alternately arranged,
Irradiation of laser light to the stimulable phosphor layer by the light source means from one side with respect to the radiation image conversion panel, and photoelectric conversion, as well as including a block structure of crystallographically discontinuous fine columnar crystals. A radiation image information reading device, characterized in that it is configured to detect the stimulated emission light by a container.