JPH0631901B2 - Radiation image conversion panel - Google Patents

Description

TECHNICAL FIELD The present invention relates to a radiation image conversion panel using a stimulable phosphor, and more particularly to a radiation image conversion panel that gives a radiation image with high sharpness. It is a thing.

(Background of the Invention) 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.

A radiation image conversion panel having a stimulable phosphor layer used in this radiation image conversion method has a radiation absorption rate and a light conversion rate (including both of them, as in the case of the radiographic method using the above-described fluorescent screen). Radiation sensitivity ")
Needless to say, the image has good graininess and high sharpness.

However, in general, a radiation image conversion panel having a stimulable phosphor layer applies a dispersion containing a granular stimulable phosphor having a particle size of about 1 to 30 μm and an organic binder onto a support or a protective layer, Since it is produced by drying, the packing density of the stimulable phosphor is low (filling rate 50%), and it was necessary to increase the layer thickness of the stimulable phosphor layer in order to sufficiently increase the radiation sensitivity ( Sixth
(A)).

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. It was necessary to thin the fluorescent phosphor layer (Fig. 6).
(b)).

Further, the graininess of the image in the radiation image conversion method is determined by the spatial fluctuation of the radiation quantum number (quantum mottle), the structural disorder of the stimulable phosphor layer of the radiation image conversion panel (structural mottle), or the like. Therefore, as the layer thickness of the stimulable phosphor layer becomes thinner, the number of radiation quantum absorbed in the stimulable phosphor layer decreases and the quantum mottle increases, or structural disorder becomes apparent and the structure 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 panels have been made at the trade-off between radiation sensitivity and some degree of graininess and sharpness.

By the way, it is well known that the sharpness of an 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 fluorescent screen. The sharpness of the image in the radiation image conversion method using a fluorescent substance 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, Rather than being determined by the spread of
It is determined depending on the spread of 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 a pixel on the panel that is fully illuminated and is irradiated with stimulated excitation light at that time.
It is recorded as the output from (xi, yi), but if the stimulated excitation light spreads in the panel due to scattering, etc., the irradiation pixel (xi, yi
This is because if the stimulable phosphor existing outside i) is also excited, the output from a region wider than the pixel (xi, yi) is recorded as the output from the pixel (xi, yi). 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 these circumstances, some methods have been devised to improve the sharpness of radiographic images. 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, Japanese Patent Application Laid-Open No. 59-60300 discloses a radiographic image reading apparatus using a radiographic image conversion panel made of a transparent film composed only of a stimulable phosphor material.
The radiation image conversion panel used in the apparatus is different from the stimulable phosphor layer in which a stimulable phosphor is dispersed in a binder, and the stimulable phosphor layer is composed of only a stimulable phosphor material. It is said that the phosphor layer becomes a transparent film, scattering of stimulated excitation light is reduced, and image sharpness is improved. However, since the stimulable phosphor layer of the panel is transparent, the stimulable excitation light incident on the phosphor layer is, as shown in FIG. 7, an interface between the stimulable phosphor layer 71 and the support or Since it repeatedly diffuses at the interface of the panel constituent layers such as the interface between the photostimulable phosphor layer 71 and the protective layer to cause halation, improvement in image sharpness could not be expected so much.

(Object of the invention) The present invention has been made in view of the above-mentioned drawbacks and reciprocity between characteristics in a radiation image conversion panel using a stimulable phosphor, and the object of the present invention is to have a sensitivity to radiation. An object of the present invention is to provide a radiation image conversion panel that improves and provides an image with high sharpness.

It is another object of the present invention to provide a radiation image conversion panel which improves the graininess and gives an image with high sharpness.

(Structure of the Invention) As a result of intensive studies on the formation of a stimulable phosphor layer by a vapor deposition method, the present inventors have conducted fine crystallization of the stimulable phosphor layer to form the stimulable phosphor layer. The present invention has been completed by finding that the opaque film exhibits high sharpness as compared with a conventional radiation image conversion panel having a transparent photostimulable phosphor layer.

That is, the object of the present invention is a radiation image conversion panel having at least one stimulable phosphor layer on a support, wherein the stimulable phosphor layer is a vapor-deposited stimulable phosphor. And a layer which is opaque to stimulated excitation light.

In the present invention, opaque to stimulated excitation light refers to the case where the parallel light transmittance of the stimulable phosphor layer for light in the stimulated excitation light wavelength region is 60% or less, preferably the parallel light It means the case where the transmittance is 45% or less, more preferably the case where the parallel light transmittance is 30% or less.

The parallel light transmittance referred to in the present invention is used to represent the transmittance of a substance having strong diffusivity, and is expressed by the following equation.

(Where T is the parallel light transmittance in percent, Io
Is the parallel irradiation light intensity incident on the sample, and I is the transmitted light intensity of the component parallel to the irradiation light of the light transmitted through the sample. ) Also, the parallel light transmittance is measured by the apparatus outlined in FIG.

In the figure, 51 is a halogen lamp, 52 is a condenser lens, 53 is an aperture, 54 is a prism, and 58 is an irradiation lens, and 51 to 58 form an irradiation optical system. Further, 60 is a condenser lens, 63 is a prism, 65 is an aperture, 66 is a mirror, 67 is a bandpass filter, and 68 is a photomultiplier tube, which form a photometric optical system.
Further, 55 is a beam splitter, 56 is a lens, 57 is a shutter, and 69 is a mirror, and these form an illumination optical system of the sample 59. Further, 61 is a beam splitter, and 62 is a finder screen, which form a finder.

The white light from the halogen lamp 51 is collimated by the condenser lens 52, the irradiation field is limited by the aperture 53, and the sample 59 is irradiated by the irradiation lens. The light transmitted through the sample 59 is collected by the condenser lens 60 and passed through the aperture 65 to become parallel transmitted light having only a component parallel to the irradiation light. The parallel transmitted light then passes through a bandpass filter 67 that transmits only light in the target wavelength range, and then enters the photomultiplier tube to obtain the parallel transmitted light intensity I. The parallel irradiation light intensity Io can be measured by removing the sample 59. The parallel light transmittance T is obtained from Io and I. The apertures 53 and 65 are interlocked with the aperture setting dial 64, but the size of the aperture is preferably about 500 μm × 500 μm.

In the present invention, the vapor deposition method generally means Physical Vapor D
eposition (PVD) and Chemical Vapor Deposition
It is a film forming technique called (CVD) and includes, for example, a vapor deposition method, a sputtering method, an ion plating method and the like.

As an embodiment of the method for producing a radiation image conversion panel of the present invention, it is preferable to use a vapor deposition method or a sputtering method when forming the stimulable phosphor layer.

Further, when a vapor deposition method or a sputtering method is applied, penetration of the stimulable phosphor into the support containing layer of the panel, the subbing layer thereof, or the layer containing the binder of the protective layer, or any one of the above The binder of the undercoat layer or the protective layer penetrates into the stimulable phosphor layer formed by the method, but a mixed layer of the stimulable phosphor and the binder for the above reason is practically used. It will be simply described below as negligible, that is, the mixed layer is not generated by any of the above methods.

Hereinafter, the present invention will be described in detail.

In the radiation image conversion panel of the present invention, the stimulable phosphor means a stimulus (luminance) such as optical, thermal, mechanical, chemical or electrical after the first irradiation of light or high energy radiation. Excitation excitation) refers to a phosphor that exhibits stimulated emission corresponding to the dose of the first light or high-energy radiation, but from a practical point of view, preferably fluorescence that exhibits stimulated emission by stimulated excitation light of 500 nm or more. It is the body. Examples of the stimulable phosphor used in the radiation image conversion panel of the present invention include BaSO ₄ : Ax (where A is at least one of Dy, Tb and Tm) described in JP-A-48-80487. Yes, x is
0.001 ≦ x <1 mol%. ) Phosphor represented by
MgSO ₄ : Ax described in JP-A-48-80488 (where A is Ho or D
Either of y and 0.001 ≦ x ≦ 1 mol%. ), SrSO ₄ : Ax described in JP-A-48-80489 (wherein A is at least one of Dy, Tb and Tm, and x is 0.001 ≦ x <1 mol% is there.)
, A phosphor obtained by adding at least one of Mn, Dy and Tb to Na ₂ SO ₄ , CaSO ₄ and BaSO ₄ described in JP-A-51-29889, Phosphors such as BeO, LiF, MgSO ₄ and CaF ₂ described in JP-A-52-30487, Li ₂ B ₄ O ₇ : Cu, Ag fluorescence described in JP-A-53-39277 Body, Li ₂ O. (B ₂ O ₂ ) x described in JP-A-54-47883:
Cu (however, x is 2 <x ≦ 3), and Li ₂ O · (B ₂ O ₂ ) x: Cu, Ag
(Where x is 2 <x ≦ 3) or the like, US Pat. No. 3,859,52
SrS: Ce, Sm, SrS: Eu, Sm, La ₂ O ₂ S: E described in No. 7
Examples include phosphors represented by u, Sm and (Zn, Cd) S: Mn, X (where X is a halogen). In addition, JP-A-55-12142
ZnS: Cu, Pb phosphor described in No. 6, general formula BaO.xA
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 (provided that M ^II
Is Mg, Ca, Sr, Zn, Cd or Ba, and A is Ce, Tb, Eu, Tm, Pb, Tl,
At least one of 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 ≦, respectively
It is a number that satisfies the condition of e ≦ 5 × 10 ^-2 . ) Alkaline earth fluorohalide phosphor represented by JP-A-55-121
The general formula described in No. 44 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. ), The general formula described in JP-A-55-12145 is (Ba _1-x M ^II _x ) FX: yA (where M ^II is Mg, Ca, Sr, Zn or Cd). At least one of
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 the conditions 0 ≦ x ≦ 0.6 and 0 ≦ y ≦ 0.2 . ), The general formula described in JP-A-55-84389 has the formula BaFX: xCe, yA
(However, X is at least one of Cl, Br and I, A
Is at least one of In, Tl, Gd, Sm and Zr, and x
And y are 0 <x ≦ 2 × 10 ⁻¹ and 0 <y ≦ 5 × 10, respectively.
^-2 . ), A phosphor represented by the formula: M ^II FX xA: yLn (where M ^II is at least one of Mg, Ca, Ba, Sr, Zn and Cd). Species, 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. ) A rare earth element-activated divalent metal fluorohalide phosphor having a general formula of ZnS: A, C
dS: A, (Zn, Cd) S: A, ZnS: A, X and CdS: A, X
(Wherein A is Cu, Ag, Au or Mn and X is a halogen), and one of the following general formula xM ₃ (PO ₄ ) described in JP-A-57-148285. ) ₂・ NX ₂ : yA M ₃ (PO ₄ ) ₂・ yA (In the formula, M and N are at least one of Mg, Ca, Sr, Ba, Zn and Cd, and X is F, Cl, Br and At least one of I, A is Eu, Tb, Ce, Tm, Dy, Pr, Ho, Nd, Yb, Er, Sb, Tl,
Represents at least one of Mn and Sn. Further, x and y are numbers satisfying the conditions of 0 <x ≦ 6 and 0 ≦ y ≦ 1. ), A phosphor represented by any of the following general formulas nReX ₃ · mAX ′ ₂ : xEu nReX ₃ · mAX ′ ₂ : xEu, ySm (wherein Re is at least one of La, Gd, Y and Lu, A represents an alkaline earth metal, at least one of Ba, Sr and Ca, X and X'represent at least one of F, Cl and Br, and 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 × 10.
^{The condition of -3} <n / m <7 × 10 ^{-1 is} satisfied. Phosphor represented by), and the following general formula ^{M I X · aM II X '} 2 · bM III X "3: cA ( where, M ^I is Li, Na, K, at least one selected from Rb and Cs Alkali metal, 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 F, Cl, Br
And at least one halogen selected from I.
A is Eu, Tb, Ce, Tm, Dy, Pr, Ho, Nd, Yb, Er, Gd, Lu, Sm, Y, T
It is at least one metal selected from l, Na, Ag, Cu and Mg.

Also, a is a numerical value in the range of 0 ≦ a <0.5, and b is 0 ≦ a <0.5.
The value is in the range of b <05, and the value of c is in the range of 0 <c ≦ 02. ) Alkali halide phosphors represented by). In particular, an alkali halide phosphor is preferable because it facilitates formation of a stimulable phosphor layer by a method such as vapor deposition and sputtering.

However, the stimulable phosphor used in the radiation image conversion panel of the present invention is not limited to the above-mentioned phosphor,
Any phosphor may be used as long as it exhibits stimulated emission when it is irradiated with radiation and then stimulated by excitation light.

The stimulable phosphor layer is made into a stimulable phosphor layer which is opaque to the stimulable excitation light by finely crystallizing it on a support and vapor-depositing it, or by an addition means. An image conversion panel is created.

When the stimulable phosphor layer of the radiation image storage panel of the present invention has the fine crystals, fine columnar crystals have a layer thickness of the stimulable phosphor as shown in the electron micrograph of FIG. 1 (a). It is preferable to have a structure that develops in the direction.

In this case, as shown in the schematic diagram (b), the photostimulation effect of each of the fine columnar crystals a ₁ , a ₂ , a ₃ , ... Light emission 12 proceeds in the layer thickness direction while repeating total reflection. As a result, the stimulable excitation light 11 incident on the radiation image conversion panel is the stimulable phosphor layer.
It reaches the deep part of the phosphor layer 13 without causing diffusion by halation in 13 and excites the stimulable phosphor, so that the sensitivity and the graininess to the radiation of the radiation image conversion panel are improved and at the same time the image Sharpness is also improved. Further, since the stimulated emission 12 generated in the deep portion of the stimulable phosphor layer 13 of the radiation image conversion panel also reaches the surface of the phosphor layer 13 without being scattered and diffused, sensitivity to radiation and granularity Is improved.

When the stimulable phosphor layer of the present invention has the structure, the stimulable phosphor layer is microscopically transparent to stimulable excitation light due to the light-inducing effect of columnar crystals of the stimulable phosphor. However, since it is an aggregate of fine columnar crystals macroscopically, it becomes opaque due to diffuse reflection of stimulated excitation light on the surface of the fine columnar crystal grains.

However, the stimulable phosphor layer of the radiation image conversion panel of the present invention has only to be opaque and does not necessarily have to have a fine columnar crystal structure.

The radiation image conversion panel of 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.

Next, a method for manufacturing the radiation image conversion panel of the present invention, in which the stimulable phosphor layer is opaque to stimulable excitation light, will be described.

The first method is a vapor deposition method. In this 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 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 that is opaque to the stimulable excitation light 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 vapor deposition, a radiation image conversion panel of the present invention is manufactured by providing a protective layer on the side of the stimulable phosphor layer opposite to the support side, if necessary. In addition, after forming the stimulable phosphor layer on the protective layer, a procedure of providing a support may be adopted.

In the vapor deposition method, the stimulable phosphor material is co-evaporated by using a plurality of resistance heaters or electron beams to synthesize the target stimulable phosphor on the support and at the same time stimulate the stimulable phosphor. It is also possible to form a fluorescent layer.

Further, in the 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. In the vapor deposition method, if necessary, O
Reactive vapor deposition may be performed by introducing a gas such as ₂ , H ₂ or the like.

The second method is a sputtering method. In the method, as in the vapor deposition method, after the support is placed in the sputtering apparatus, 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. Introduce gas into the sputtering system to reach 10 ^-3 To
The gas pressure should be about rr.

Next, by using the stimulable phosphor as a target, sputtering is performed to deposit a stimulable phosphor layer on the surface of the support to a desired thickness.

In the sputtering step, it is possible to form the stimulable phosphor layer by dividing it into a plurality of times in the same manner as the vapor deposition method, and by using a plurality of targets each made of different stimulable phosphors, It is also possible to simultaneously or sequentially sputter the target to form a stimulable phosphor layer.

After the completion of sputtering, the radiation image conversion panel of the present invention is manufactured by providing a protective layer on the side of the stimulable phosphor layer opposite to the support side, if necessary, as in the vapor deposition method. After forming the stimulable phosphor layer on the protective layer,
You may take the procedure of providing a support body.

In the sputtering method, a plurality of stimulable phosphor raw materials are used as targets, and they are simultaneously or sequentially sputtered to synthesize a target stimulable phosphor on a support and at the same time stimulable phosphor. It is also possible to form a body layer. Further, in the above-mentioned sputtering method, if necessary, a gas such as O ₂ or H ₂ may be introduced to carry out reactive sputtering.

Furthermore, in the above-mentioned sputtering method, the material to be vapor-deposited (support or protective layer) may be cooled or heated during sputtering, if necessary. Further, the stimulable phosphor layer may be heat-treated after the completion of sputtering.

The third method is the CVD method. A fourth method is an ion plating method.

In the manufacturing method of the present invention, the deposition rate of the stimulable phosphor layer is preferably 0.2 μm / min to 300 μm / min.
When the deposition rate is less than 0.2 μm / min, not only the stimulable phosphor layer tends to be transparent, but also the productivity of the radiation image conversion panel of the present invention is low, which is not preferable.

Further, when the deposition rate exceeds 300 μm / min, it is difficult to control the deposition rate, which is not preferable.

The layer thickness of the stimulable phosphor layer of the radiation image conversion panel of the present invention varies depending on the sensitivity of the intended radiation image conversion panel to radiation, the type of stimulable phosphor, and the like, but is 30 μm to
It is preferably selected from the range of 1000 μm, 50 μm to 80
More preferably, it is selected from the range of 0 μm. When the thickness of the stimulable phosphor layer is less than 30 μm, the radiation absorptivity is extremely reduced, the radiation sensitivity is deteriorated, the graininess of the image is deteriorated, and the stimulable phosphor becomes transparent. Easy,
This is not preferable because the lateral spread of the stimulable excitation light in the stimulable phosphor layer remarkably increases and the sharpness of the image tends to deteriorate.

When the stimulable phosphor layer of the radiation image conversion panel of the present invention has fine columnar crystals, the size of the fine columnar crystals is such that the column diameter is 1 μm to 300 μm, preferably 1 μm to 1
It is selected from the range of 50 μm. If the fine columnar crystals are too thin, the scattering property of the stimulable phosphor layer is enhanced, the stimulable excitation light is diffused, and the sharpness of the image of the radiation image conversion panel is deteriorated, which is not preferable. Further, if the fine columnar crystals are too thick, the stimulable phosphor layer is likely to be transparent, increasing the lateral spread of the stimulable excitation light in the stimulable phosphor layer,
Image sharpness is also deteriorated, which is also not preferable.

In order to make the stimulable phosphor layer opaque to the stimulable excitation light in the present invention, the phosphor layer becomes an aggregate of fine crystals during vapor deposition of the stimulable phosphor as described above. In this way, the stimulable phosphor layer may be colored with a dye, a pigment or the like that absorbs light in the wavelength region of the stimulating excitation light.
Further, an absorption layer that absorbs light in the wavelength region of the stimulable excitation light may be provided on the surface of the stimulable phosphor layer opposite to the incident side of the stimulable excitation light.

Further, the above methods may be used in combination.

FIG. 2 (a) shows the relationship between the stimulable phosphor layer thickness and the amount of the stimulable phosphor deposited corresponding to the layer thickness and the sensitivity to radiation in one example of the radiation image conversion panel of the present invention, Fig. 2
(b) shows the relationship between the stimulable phosphor layer thickness of the radiation image conversion panel of the present invention and the sharpness of the image obtained by the radiation image conversion panel.

The vapor deposition type photostimulable phosphor layer in which a phosphor is deposited like the radiation image conversion panel of the present invention is a dispersion type radiation image conversion panel in which a conventional phosphor is suspended and dispersed in a binder. As apparent from the comparison with a binder, since the binder does not contain a stimulable phosphor, the adhering amount (filling rate) of the stimulable phosphor layer is about twice that of the conventional radiation image conversion panel. The radiation absorptivity is improved, the radiation sensitivity is higher than that of the conventional radiation image conversion panel, and the graininess of the image is improved.

Further, like the stimulable phosphor layer of the radiation image conversion panel of the present invention, fine crystals of the stimulable phosphor are developed in the layer thickness direction of the stimulable phosphor layer, and the light-inducing effect of the layer Thus, when the directivity of stimulated excitation light and stimulated emission is excellent, it is possible to make the layer thickness thicker than the conventional dispersion type radiation image conversion panel.

Furthermore, since the vapor deposition type stimulable phosphor layer of the radiation image conversion panel of the present invention is opaque as described above, the lateral spread of the stimulable excitation light in the stimulable phosphor layer is And the sharpness of the image is significantly improved.

As the support used in the radiation image conversion panel of the present invention, various polymer materials, glass, metal and the like are used, and cellulose acetate film, polyester film, polyethylene terephthalate film, polyamide film, polyimide film, triacetate film, polycarbonate film, etc. Plastic film, metal sheet such as aluminum, iron, copper, chrome,
Alternatively, a metal sheet having a coating layer of the metal oxide is preferable.

The surface of these supports may be a smooth surface, may be a matte surface for the purpose of improving the adhesiveness with the stimulable phosphor layer, and may be provided with a reflection layer or an absorption layer. Further, the surface of the support may be an uneven surface 31 as shown in FIG. 3 (a), or may be a structure in which tile-shaped plates 33 separated from each other are spread as shown in FIG. 3 (b). In the case of FIG. 3 (a), the stimulable phosphor layer is subdivided by the uneven surface 31 as shown in the sectional view of FIG. 3 (c), so that the sharpness of the image is further improved.
In the case of FIG. 3 (b), the stimulable phosphor layer is deposited while maintaining the contour of the tile plate 33 of the support, and as a result, the stimulable phosphor layer is formed as shown in FIG. ) Crack 3 as shown in the cross section
Since the columnar blocks 35 of the stimulable phosphor are separated by 6, the sharpness of the image is further improved.

Further, these supports may be provided with an undercoat layer on the surface on which the stimulable phosphor layer is provided for the purpose of improving the adhesiveness with the stimulable phosphor layer. Further, the layer thickness of these supports varies depending on the material of the support used, etc., but is generally 80 μm
2000 μm, more preferably 80 from the viewpoint of handling
It is μm to 1000 μm.

In the radiation image conversion panel of 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. Good. This protective layer may be formed by directly coating the protective layer coating solution on the stimulable phosphor layer, or a protective layer separately formed in advance may be adhered onto the stimulable phosphor layer. . As a material for the protective layer, a usual protective layer material such as cellulose acetate, nitrocellulose, polymethylmethacrylate, polyvinyl butyral, polyvinyl formal, polycarbonate, polyester, polyethylene terephthalate, polyethylene, vinylidene chloride, nylon is used. Further, this protective layer may be formed by laminating inorganic substances such as SiC, SiO ₂ , SiN, and Al ₂ O ₃ by vapor deposition or sputtering. Generally, the thickness of these protective layers is preferably about 0.1 μm to 100 μm.

The radiation image conversion panel of 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. 4, 41 is a radiation generator, 42 is a subject, 43 is a radiation image conversion panel of the present invention, 44 is a stimulated excitation light source, and 45 is stimulated emission emitted from the radiation image conversion panel. Photoelectric conversion device, 46 is a device for reproducing the signal detected by 45 as an image, 47 is a device for displaying the reproduced image, 48 is a separation of stimulated excitation light and stimulated emission, only stimulated emission It is a filter that transmits. It should be noted that after 45, it is sufficient if the optical information from 43 can be reproduced as an image in some form, and is not limited to the above.

As shown in FIG. 4, the radiation from the radiation generator 41 passes through the subject 42 and the radiation image conversion panel 43 of the present invention.
Incident on. 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 excited by stimulated excitation light from the stimulated excitation light source 44 and emitted as stimulated emission. The radiation image conversion panel 43 is
Since the stimulable phosphor layer is opaque to the stimulable excitation light, the directivity of the stimulable excitation light in the stimulable phosphor layer is high, and the stimulable phosphor is stimulated during scanning by the stimulable excitation light. Diffusion of excitation light in the stimulable phosphor layer is suppressed.

Since the intensity of stimulated emission emitted is proportional to the amount of accumulated radiation energy, this optical signal is photoelectrically converted by the photoelectric conversion device 45 such as a photomultiplier tube, and reproduced as an image by the image reproduction device 46. By displaying with the image display device 47, a radiation transmission image of the subject can be observed.

(Example) Next, the present invention will be described with reference to an example.

Example 1 As a support, a chemically strengthened glass having a thickness of 500 μm was placed in an evaporator, and the support was heated to 150 ° C. Next, put an alkali halide stimulable phosphor (RbBr: 0.0006Tl) in a water-cooled copper crucible for electron beam vapor deposition, set it in a predetermined position, and then evacuate the vaporizer to obtain 2 × 10 ^-6 Torr. The degree of vacuum was set.

Next, an electric current is applied to the electron beam gun, and the alkali halide stimulable phosphor is heated and evaporated by the electron beam method to form the stimulable phosphor layer on the chemically strengthened glass.
The radiation image conversion panel A of the present invention was obtained by depositing to a thickness of 300 μm. The vapor deposition rate was 5 μm / min.

The thus obtained radiation image conversion panel A of the present invention was irradiated with 10 mR of X-ray with a tube voltage of 80 KVp, and then stimulated by He-Ne laser light (633 nm) to be radiated from the stimulable phosphor layer. The stimulated emission thus generated was photoelectrically converted by a photodetector (photomultiplier tube), and 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 of the present invention as 100. The modulation transfer function (MTF) has a spatial frequency of 2 cycles / m.
It is a value at the time of m, and granularity (good, normal, bad) is shown by (○, Δ, ×), respectively.

Further, the parallel light transmittance of the stimulable phosphor layer of the radiation image conversion panel A of the present invention was measured by an apparatus (drum scan densitometer model 2605 manufactured by Abe Design Co., Ltd.) shown in FIG. 5, and is also shown in Table 1. To do. The wavelength of the light used was 630 nm.

Example 2 As a support, a chemically strengthened glass having a thickness of 500 μm was placed in a high frequency sputtering apparatus, and the support was heated to 200 ° C. Next, an alkali halide stimulable phosphor (0.95RbBr.0.05CsF: 0.001Tl) was placed as a sputtering target in the sputtering apparatus, and then the vacuum was evacuated to 1 × 10 ^-6 Torr. Sputtering was performed while introducing Ar gas as a sputtering gas, and the photostimulable phosphor layer was deposited on the chemically strengthened glass until the layer thickness became 300 μm, to obtain a radiation image conversion panel B of the present invention. The sputtering rate was 4 μm / min.

The radiation image conversion panel B of 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 In Example 1, instead of using chemically strengthened glass as the support, the surface was oxidized by an anodic oxidation method to 500 μm.
Using a support having a structure in which a thick aluminum sheet is subjected to sealing treatment, heat treatment at 200 ° C. or more is applied thereto to generate a large number of cracks in the aluminum oxide layer, and tile-shaped plates separated by the cracks are spread. A radiation image conversion panel C of the present invention was obtained in the same manner as in Example 1 except for the above.

The radiation image conversion panel C of 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 8 parts by weight of an alkali halide stimulable phosphor (RbBr: 0.0006Tl) 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 stimulable phosphor layer. The coating liquid was adjusted. Next, this coating solution was uniformly applied on a chemically strengthened glass as a support having a thickness of 300 μm placed horizontally, and naturally 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.

As is clear from Table 1, the radiation image conversion panels A to C of the present invention have X-ray sensitivities about two times higher than those of the comparative radiation image conversion panel P having the corresponding stimulable phosphor layer thickness. Moreover, the graininess of the image was excellent. This is because the radiation image conversion panel of the present invention is manufactured by a vapor deposition method, so that the filling rate of the stimulable phosphor in the stimulable phosphor layer is higher than that of a comparative panel manufactured by coating. This is because the absorption rate of is good.

Further, the radiation image conversion panels A to C of the present invention are also superior in sharpness in comparison with the comparative radiation image conversion panel P having the corresponding stimulable phosphor layer thickness, although they have higher X-ray sensitivity. It was

This also has a structure of fine columnar crystal stimulable phosphor layer of the radiation image conversion panel of the present invention, because the directivity of the stimulated excitation light is high, the luminescence of He-Ne laser which is the stimulated excitation light. This is because scattering in the exhaustive phosphor layer is reduced.

Particularly, in the radiation image conversion panel C of the present invention, the support is devised so that cracks in the support also cause cracks in the stimulable phosphor layer, thereby subdividing the stimulable phosphor layer. As a result, it becomes possible to further suppress and reduce the scattering of the stimulable excitation light in the stimulable phosphor layer, and as a result, the sharpness of the image is further improved.

Example 4 A radiation image conversion panel D of the present invention was obtained in the same manner as in Example 2 except that the thickness of the stimulable phosphor layer was changed to 60 μm.

The radiation image conversion panel D of the present invention thus obtained was evaluated in the same manner as in Example 1, and the results are shown in Table 2.

Example 5 A radiation image conversion panel E of the present invention was obtained in the same manner as in Example 4 except that the heating temperature of the support was 350 ° C. and the sputtering rate was 0.8 μm / min. .

The radiation image conversion panel E of the present invention thus obtained was evaluated in the same manner as in Example 1, and the results are also shown in Table 2.

Example 6 Example 4 was repeated except that the heating temperature of the support was 350 ° C. and the sputtering rate was 20 μm / min.
A radiation image conversion panel F of the present invention was obtained in the same manner as in.

The radiation image conversion panel F of the present invention thus obtained was evaluated in the same manner as in Example 1, and the results are also shown in Table 2.

Comparative Example 2 Comparative transparent sensitization in the same manner as in Example 5 except that the thickness of the stimulable phosphor layer was 20 μm and the sputtering rate was 0.05 μm / min. A radiation image conversion panel Q having a fluorescent layer was obtained.

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 2.

As is clear from Table 2, as compared with the radiation image conversion panel D of the present invention, the comparative panel Q was inferior in image sharpness although the stimulable phosphor layer thickness was thin. This is because the stimulable phosphor layer of the comparative panel Q is transparent, so that the lateral spread of the stimulable excitation light becomes large.

Further, in the comparative panel Q, when the sputtering rate is increased, the transparency of the stimulable phosphor layer is lost, so that high-speed sputtering cannot be performed and the productivity is remarkably poor.

The radiation image conversion panels D, E, and F of the present invention tended to have lower sharpness as the parallel light transmittance improved.

Example 6 A radiation image conversion panel G of the present invention was prepared in the same manner as in Example 1 except that an alkaline earth fluorohalide phosphor (BaFBr: 0.002Eu) was used as the stimulable phosphor.
Got

The radiation image conversion panel G of the present invention thus obtained was evaluated in the same manner as in Example 1, and the results are shown in Table 3.

(Effect of the invention) As described above, according to the present invention, the radiation image conversion panel of the present invention is a stimulable phosphor layer in which a stimulable phosphor is vapor-deposited, and the layer is bright. Since it is opaque to the stimulated excitation light, the lateral spread of the stimulated excitation light in the stimulable phosphor layer is suppressed, and deterioration of the sharpness of the image due to the spread of the stimulated excitation light can be prevented. .

Further, when the stimulable phosphor layer of the present invention has a fine columnar crystal structure as a result of vapor deposition, the directivity of stimulated excitation light and stimulated emission in the stimulable phosphor layer is improved. Since the stimulated emission from the inside of the stimulable phosphor layer can be detected, the sensitivity is improved, and at the same time, the scattering of the stimulated excitation light is reduced and the sharpness of the image is improved.

Further, according to the present invention, since the binder is not contained in the stimulable phosphor layer, the filling rate of the stimulable phosphor is improved, the sensitivity to radiation is improved, and at the same time the quantum mottle and the stimulus due to radiation are Since the structural mottle of the fluorescent phosphor layer is reduced, the graininess of the image is improved.

The present invention is extremely effective and industrially useful.

[Brief description of drawings]

FIG. 1 (a) is an electron micrograph of a cross section of the crystal structure of the stimulable phosphor layer of the present invention, and FIG. 1 (b) is an explanatory view of the light induction effect in the phosphor layer. FIG. 2 shows the relationship between the layer thickness (adhesion amount) of the stimulable phosphor and the relative sensitivity (FIG. (A)) and MTF (FIG. (B)) in one example of the radiation image conversion panel of the present invention. Indicates. Incidentally, FIGS. 6 (a) and 6 (b) show a conventional dispersion type stimulable phosphor layer as shown in FIGS.
The characteristics corresponding to (b) are shown. FIG. 3 is a schematic cross-sectional view of the surface of the support according to the present invention on which the stimulable phosphor is deposited (FIGS. (A) and (b)) and the state after deposition. FIG. 4 is a schematic diagram of a radiation image conversion method using the radiation image conversion panel of the present invention. FIG. 5 is a schematic diagram of an apparatus used for measuring parallel light transmittance according to the present invention. FIG. 7 is a sectional view showing halation in a radiation image conversion panel having a transparent stimulable phosphor layer. 11 ... stimulated excitation light, 12 ... stimulated emission, 13 ... stimulable phosphor layer, 31 and 32 ... support, 33 ... tile plate 34 and 35 ... stimulable phosphor layer , 36 ... crack, 41 ... radiation generator, 42 ... subject, 43 ... panel 44 ... stimulated excitation light source, 48 ... filter.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Fumio Shimada 1 Sakura-cho, Hino-shi, Tokyo Konishi Roku Photo Industrial Co., Ltd. Examiner Taji Tamura (56) References JP 62-105097 (JP, A)

Claims (1)

[Claims] 1. A radiation image conversion panel having at least one stimulable phosphor layer on a support, wherein the stimulable phosphor layer is a layer in which a stimulable phosphor is vapor-deposited, Moreover, the radiation image conversion panel, wherein the layer is opaque to stimulated excitation light.