JP2514321B2 - 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 specifically, a radiation image having a high practical level in both sharpness and sensitivity. The present invention relates to a radiation image conversion panel that provides

(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 radiated to the phosphor layer (fluorescent screen),
Thus, so-called radiography is used in which visible light is generated and the visible light is applied to a film using a silver salt to develop it in the same manner as when taking a normal picture.
However, in recent years, a method has been devised in which an image is directly taken out from the phosphor layer without using a film coated with a silver salt.

In 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 phosphor is absorbed. There is a method of emitting light as light and detecting the fluorescence to form an image. Specifically, for example, U.S. Pat. No. 3,859,527 and JP-A-55-12144.
JP-A No. 1994-187 discloses a radiation image conversion method using a stimulable fluorescent substance and using visible light or infrared rays as stimulable excitation light. This method uses a radiation image conversion panel in which a stimulable phosphor layer is formed on a support. The latent energy is formed by accumulating the radiation energy corresponding to the radiation transmittance of each part, and then the radiation energy accumulated in each part is emitted by scanning the photostimulable phosphor layer with photostimulation excitation light. This is converted into light, and an image is obtained by an optical signal depending on the intensity of this light.
This final image may be played back as a hard copy or on a CRT.

Now, the 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 (both of which are the same as those in the radiographic method using the above-mentioned fluorescent screen). Including "radiation sensitivity"
Not to mention that it is high, it is required that the image has good graininess and high sharpness.

However, since a radiation image conversion panel having a photostimulable phosphor layer is generally prepared by coating and drying a dispersion containing a photostimulable phosphor and an organic binder on a support or a protective layer. , Packing density of photostimulable phosphor is low (filling rate 50%),
In order to make radiation sensitivity sufficiently high, it was necessary to increase the layer thickness of the stimulable phosphor layer.

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 reduce the thickness of the exhaustive phosphor layer.

The granularity 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). Therefore, as the layer thickness of the photostimulable phosphor layer becomes thinner, the number of radiation quantum absorbed by the photostimulable phosphor layer decreases and the quantum mottle increases, or structural disorder becomes manifest and The image quality is deteriorated due to increased mottle. 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 the opposite tendency to the layer thickness of the stimulable phosphor layer. The radiation image conversion panel has been made with some degree of mutual sacrifice between sensitivity to radiation and graininess and sharpness.

That is, in the conventional radiation image conversion panel, the scattering of the photostimulable excitation light by the photostimulable phosphor particles, because the diffusion is large, the sharpness of the image sharply decreases with the increase of the photostimulable phosphor layer thickness,
Although there are some points that both sensitivity and sharpness are bad, it is difficult to find good points.

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 irradiation) of the phosphor in the fluorescent 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, in radiography. As described above, 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. Because it will be done. 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 have been attempted for improving the above-mentioned drawbacks of the radiation image conversion panel having the photostimulable phosphor layer formed by dispersing the photostimulable phosphor in the binder. .

For example, JP-A-56-12600 discloses a method of providing a white pigment reflective layer on one surface of a stimulable phosphor layer formed by dispersing a stimulable phosphor in a binder. . According to this method
A layer of the stimulable phosphor layer by converting the stimulable phosphor layer of the portion entering from the surface of the stimulable excitation light incident side of the stimulable phosphor layer into a white pigment light reflecting layer. It is said that the thickness can be made thinner, and by this, the spread of the photostimulable excitation light in the photostimulable phosphor layer can be suppressed, and a radiation image with high sharpness can be obtained.

However, in this method, a part of the stimulable phosphor layer obtained by dispersing a stimulable phosphor which is a kind of white pigment in a binder, a white pigment is dispersed in the binder. It was simply replaced with a white pigment light reflecting layer. Therefore, this method has the effect of suppressing the spread (scattering) of the photostimulable excitation light in the layer, which can reduce the thickness of the photostimulable phosphor layer, but the white pigment light reflection while scattering in the layer. The photostimulable excitation light that has reached the layer is diffusely reflected on the surface of the white pigment light-reflecting layer, or scattered inside the white pigment light-reflecting layer and reflected to the side of the photostimulable phosphor layer, and then inside the photostimulable phosphor layer. The image sharpness is not improved so much because it scatters again and excites the stimulable phosphor over a wide range.

Further, JP-A-56-11393 discloses a method of providing a metal light-reflecting layer instead of the white pigment light-reflecting layer disclosed in JP-A-56-12600. According to this method, by changing the photostimulable phosphor layer in the portion entering from the photostimulable excitation light incident side surface of the photostimulable phosphor layer into the metal light reflection layer, the photostimulable phosphor layer is formed. The layer thickness of the photoconductor layer can be made thinner, which makes it possible to suppress the spread of the photostimulable excitation light in the photostimulable phosphor layer, resulting in a highly sharp radiation image. Is.

However, this method can well control the spread (scattering) of photostimulable excitation light in the layer, which can reduce the thickness of the photostimulable phosphor layer, but reaches the metal light reflection layer while scattering in the layer. Since the stimulated excitation light has almost no directivity, it is reflected in accordance with the incident angle of the stimulated excitation light with respect to the metal reflection layer, returns to the side of the stimulable phosphor layer, and is scattered again. The sharpness of the image is not significantly improved because it excites the stimulable phosphor over a wide range.

As described above, the reciprocity between the sensitivity to radiation and the sharpness of the image in the conventional radiation image conversion panel has hardly been improved, and the improvement has been strongly desired.

(Object of the Invention) The present invention has been made in view of the above-mentioned drawbacks in a radiation image conversion panel using a stimulable phosphor,
An object of the present invention is to provide a radiation image conversion panel that gives a sharper image than conventional radiation image conversion panels when comparing radiation image conversion panels having the same radiation sensitivity.

Another object of the present invention is to provide a radiation image conversion panel having higher sensitivity to radiation than conventional radiation image conversion panels when comparing radiation image conversion panels having the same sharpness.

(Structure of the Invention) As described above, the sharpness of the image of the radiation image conversion panel is governed by the scattering of the stimulable excitation light in the stimulable phosphor layer.

According to the research conducted by the present inventors, in order to improve the sharpness of an image without lowering the sensitivity to radiation, the directivity of stimulated excitation light and / or stimulated emission in the stimulable phosphor layer. It has been found that it is significantly effective to combine both of the improvement of the above-mentioned values and the provision of a light-reflecting layer to reduce the thickness of the photostimulable phosphor layer.

Based on the above findings, an object of the present invention is to have a stimulable phosphor layer, and a light reflecting layer having a smooth surface provided on the side opposite to the stimulable excitation light incident side of the stimulable phosphor layer. The stimulable phosphor layer is achieved by a radiation image conversion panel comprising columnar crystals of the stimulable phosphor extending in the layer thickness direction of the light reflection layer.

Further, the radiation image conversion panel is colored on the incident side of photostimulable excitation light than the light reflection layer, and the average reflectance for light in the photostimulable excitation light wavelength region after passing through the photostimulable phosphor layer. May be smaller than the average reflectance for light in the synonymous stimulated emission wavelength region.

Further, as a layer structure, it is practically preferable that the support, the light reflection layer, and the stimulable phosphor layer are laminated in this order.

The light-reflecting layer preferably has an average reflectance of 50% or more with respect to light in each wavelength region of stimulated excitation light and / or stimulated emission, and has a smooth surface interface where the refractive index is optically changed. A layer having, for example, a metal surface or a ceramic surface is used.

 Next, the present invention will be described in detail.

In the present invention, the stimulable phosphor layer is provided with a phosphor phase having a morphology in which columnar crystals are arranged, and a portion having a non-uniform refractive index in the layer thickness direction of the layer, for example, a crack interface, In order to provide a directivity of stimulated excitation light or stimulated emission in the layer thickness direction by providing a gap or the like, it is generally achieved by forming a stimulable phosphor by a vapor deposition method.

FIG. 1 (a) is a cross section of a photostimulable phosphor layer composed of fine columnar crystals formed by joining by vapor deposition, which is one of vapor deposition methods, and having gaps and cracks in the layer thickness direction. 2B is an electron micrograph showing the directivity of light in the layer, that is, the light-inducing effect of the layer.

In the same figure (b), each fine columnar crystal a ₁ , a ₂ ,
The photoexcitation effect of a ₃ ...
Alternatively, the stimulated emission 12 proceeds in the layer thickness direction while repeating total reflection. As a result, the photostimulable excitation light 11 that has entered the radiation image conversion panel is not scattered and diffused in the photostimulable phosphor layer 13, and the directivity is improved. Similarly, the directivity of the stimulated emission 12 is also improved.

As the vapor deposition method of the stimulable phosphor, a vapor deposition method, a sputtering method, an ion plating method and the like can be used.

In the vapor deposition method as the first method, first, the support is placed in the vapor deposition apparatus, and then the interior of 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 phosphors to a desired thickness on the surface of the support.

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 vapor deposition, a radiation image conversion panel of the present invention is manufactured by providing a protective layer on the side of the photostimulable phosphor layer opposite to the support side, if necessary. Incidentally, after forming the stimulable fluorescent substance layer on the protective layer, a procedure of providing a support may be adopted.

In the vapor deposition method, the photostimulable phosphor material is co-evaporated using a plurality of resistance heaters or electron beams to simultaneously synthesize the desired photostimulable phosphor on the support. It is also possible to form a stimulable phosphor 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. Further, the photostimulable phosphor layer may be heat-treated after completion of vapor deposition. In the vapor deposition method, if necessary, O ₂ ,
Reactive vapor deposition may be performed by introducing a gas such as H ₂ .

In the sputtering method as the second method, similarly to the vapor deposition method, after the support is placed in the sputtering apparatus, the inside of the apparatus is temporarily evacuated to a vacuum degree of about 10 ^-6 Torr, and then the sputtering gas is used. As such, an inert gas such as Ar or Ne is introduced into the sputtering apparatus to a gas pressure of about 10 ⁻³ Torr.

Next, a stimulable phosphor layer 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 also possible to form the stimulable phosphor layer in a plurality of times in the same manner as the vapor deposition method,
It is also possible to form a stimulable phosphor layer by simultaneously or sequentially sputtering a plurality of targets made of different stimulable phosphors.

After the completion of sputtering, the radiation image conversion panel of the present invention is manufactured by providing a protective layer on the side opposite to the support side of the stimulable phosphor layer, 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 photostimulable phosphor raw materials are used as targets, and these are simultaneously or sequentially sputtered to synthesize the desired photostimulable phosphor on the support and at the same time the photostimulable phosphor. It is also possible to form an optical layer. In the sputtering method, reactive sputtering may be performed by introducing a gas such as O ₂ or H ₂ as necessary.

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. In addition, 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.

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 the stimulable phosphor, and the like, but is 30 μm.
Is preferably selected from the range of up to 1000 μm, and 40 μm
More preferably, it is selected from the range of 800 μm.

When the layer thickness of the stimulable phosphor layer is less than 30 μm, the radiation absorption rate is extremely lowered, the radiation sensitivity is deteriorated, the graininess of the image is deteriorated, and the stimulable phosphor layer is also deteriorated. Is likely to be transparent, the lateral spread of the stimulable excitation light in the stimulable phosphor layer is significantly increased, and the sharpness of the image tends to be deteriorated, which is not preferable.

In the production of the radiation image conversion panel of the present invention, the deposition rate of the stimulable phosphor layer is 0.05 μm / min to 300 μm /
It is preferably minutes. When the deposition rate is less than 0.05 μm / min, the productivity of the radiation image conversion panel of the present invention is low, which is not preferable. When the deposition rate exceeds 300 μm / min, it is difficult to control the deposition rate, which is not preferable.

The light-reflecting layer according to the present invention is provided on the surface of the stimulable phosphor layer opposite to the surface on the incident side of the stimulable excitation light.

The light-reflecting layer may be provided directly on the surface of the photostimulable phosphor layer, or may be provided via an undercoat layer for enhancing the adhesiveness between the light-reflecting layer and the photostimulable phosphor layer. May be.

The light reflecting layer can be applied to the present invention as long as it has a different optical density (different refractive index) at the interface and a smooth surface, but is practically a metal smooth surface or a ceramic smooth surface such as glass. Is.

The metal smooth surface may be formed by a vapor deposition method, a sputtering method, an ion plating method, a plating method, or a light reflection layer may be formed on the surface of the support or the photostimulable phosphor layer, or a metal foil may be laminated. Good.

The vapor deposition method such as the vapor deposition method of the metal is particularly preferable because the light reflecting layer can be easily formed and the layer can be formed regardless of the shape of the unevenness of the surface of the support or the like.

The metals used are aluminum, silver, chrome,
Examples thereof include nickel, platinum, rhodium, tin and the like.

When a ceramic or metal sheet is used for the light-reflecting layer, the light-reflecting layer may also serve as a support, and the photostimulable phosphor may be vapor-deposited on the light-reflecting surface side. Good.

The thickness of the light-reflecting layer according to the present invention is generally preferably 0.01 to 50 μm, and has an average reflectance of 50% or more and 70% or more with respect to stimulated excitation light and / or light in the stimulated emission wavelength region. preferable.

 The reflectance is determined by an integrating sphere type spectrophotometer.

In the radiation image conversion panel of the present invention, for the purpose of further improving the sharpness of the obtained image, the radiation image conversion panel may be colored on the incident side of the stimulated excitation light rather than the light reflection layer.

In the present invention, the coloring applied on the incident side of the photostimulable excitation light with respect to the light reflection layer of the radiation image conversion panel may be all over the photostimulable phosphor layer or the surface layer of the photostimulable phosphor layer. Portion, a layer portion adjacent to the light reflection layer, any one of an undercoat layer, a protective layer, or two or more of these, or a layer surface or a colored layer between the layer and the light reflection layer. However, it is particularly preferable that the colored layer is provided between the photoreflective layer and the stimulable phosphor layer. The colorant used for the coloring is a colorant that absorbs at least a part of the stimulable excitation light for stimulating the stimulable phosphor to emit light, and is particularly applied to the stimulable phosphor. Depending on the type, it is preferable that the radiation image conversion panel have a light absorption property such that the average reflectance for light in the stimulated emission wavelength region is smaller than the average reflectance for light in the stimulated emission wavelength region.

From the point of image sharpness, the colorant has a large absorptance for light in the wavelength region of the stimulable excitation light of the stimulable phosphor (small average reflectance for light in the wavelength region of the radiation image conversion panel). From the standpoint of sensitivity, it is better that the photostimulable phosphor has a smaller absorption rate for light in the stimulated emission wavelength region (higher average reflectance for light in the wavelength region of the radiation image conversion panel). . More specifically, the average reflectance for light in the stimulated emission wavelength region of the radiation image conversion panel colored with a coloring agent is the average reflectance for light in the same wavelength region of an equivalent uncolored radiation image conversion panel. 20% or more is preferable, and the average reflectance of the radiation image conversion panel colored with the colorant with respect to the light in the wavelength region of the stimulated excitation light is the same as that of the uncolored equivalent radiation image conversion panel. It is preferable that the average reflectance is less than 95%.

The colorant may be either an organic or inorganic colorant, but a blue to green colorant is useful in terms of hue.

As an organic colorant, Zapon Fast Blue 3G
(Made by Hoechst), Estrol Brill Blue N-3RL
(Sumitomo Chemical), D & C Blue No.1 (National Aniline), Spirit Blue (Hodogaya Chemical), Oil Blue No.603 (Orient), Kiton Blue A (Ciba Geigy), Aizenka Tiron Blue GLH ( Hodogaya Chemical), Lake Blue AFH (Kyowa Sangyo), Primocyanin 6GX (Inabata Sangyo), Pril Acid Green 6BH (Hodogaya Chemical), Cyanine Blue BNRS (Toyo Ink),
Lionol Blue SL (manufactured by Toyo Ink) or the like is used.

Also, color index No.24411,23160,74180,742
00,22800,23150,23155,24401,14880,15050,15706,1570
7,17941,74220,13425,13361,13420,11836,74140,74380,
Other examples include organic metal complex salt colorants such as 74350 and 74460.

Inorganic colorants include ultramarine blue, cobalt blue,
Examples include cerulean blue, chromium oxide, and TiO ₂ —ZnO—CoO—NiO based pigments.

In the radiation image conversion panel of the present invention, the photostimulable phosphor means a stimulus (photostimulation) such as optical, thermal, mechanical, chemical or electrical after the first irradiation of light or high energy radiation. Excitation), it means a phosphor that shows stimulated emission corresponding to the irradiation dose of the first light or high-energy radiation, but from a practical point of view, it is preferably a fluorescent substance that shows stimulated emission by stimulated excitation light of 500 nm or more. It is a light body. Examples of the photostimulable phosphor used in the radiation image conversion panel of the present invention include:
For example, BaSO ₄ : Ax described in JP-A-48-80487 (where A is at least one of Dy, Tb and Tm, and x is
0.001 ≦ x <1 mol%. ) Phosphor represented by
MgSO ₄ : Ax described in JP-A-48-80488 (where A is Ho or Dy
Whichever of the above, 0.001 ≦ x ≦ 1 mol%)
A fluorescent substance represented by the formula: SrSO ₄ : Ax described in JP-A-48-80489 (wherein A is at least 1 of Dy, Tb and Tm)
And x is 0.001 ≦ x <1 mol%. ), Which are described in JP-A-51-29889
Fluorescent substance obtained by adding at least one of Mn, Dy and Tb to Na ₂ SO ₄ , CaSO _4, BaSO _4, etc., BeO, LiF, MgSO ₄ and CaF ₂ described in JP-A-52-30487. Fluorescent substance such as JP-A-53-
Fluorescent materials such as Li ₂ B ₄ O ₇ : Cu, Ag described in 39277, Li ₂ O. (B ₂ O ₂ ) _x : Cu (however, described in JP-A-54-47883) x is 2 <x ≦ 3), and a fluorescent substance such as Li ₂ O · (B ₂ O ₂ ) _x : Cu, Ay (where x is 2 <X ≦ 3), which is described in US Pat. No. 3,859,527. Fluorescent substances represented by SrS: Ce, Sm, SrS: Eu, Sm, La ₂ O ₂ S: Eu, Sm and (Zn, Cd) S: Mn, X (where X is a halogen) are mentioned. Further, ZnS is described in JP-A-55-12142: Cu, Pb fluorescers, general formula BaO · xAl ₂ O _3: Eu
(Provided that 0.8 ≦ x ≦ 10), and a barium aluminate phosphor having the general formula of M _II O · xSiO ₂ : A (where M ^II is Mg, Ca,
Sr, Zn, Cd or Ba, where A is Ce, Tb, Eu, Tm, Pb, Tl, Bi and Mn
At least one of them, and x is 0.5 ≦ x <2.5. ) Alkaline earth metal silicate-based phosphors represented by. Further, the general formula is (Ba _1-xy Mg _x Ca _y ) FX: eEu ²⁺ (where X is at least one of Br and Cl, 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 C
l and / or Br, A is Ce and / or Tb, x is 0 <x
Represents a number that satisfies <0.1. ) Fluorescent material,
The general formula described in JP-A-55-12145 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 0 ≦ x ≦ 0.6 and 0 ≦ y ≦ 0.2. Represent. ), The general formula described in JP-A-55-84389 is 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,
x and y are 0 <x ≦ 2 × 10 ⁻¹ and 0 <y ≦ 5 ×, respectively.
10 ^-2 . The 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
_At least one of ₂ O ₅ , Ta ₂ O ₅ and ThO ₂ , Ln is Eu, T
b, Ce, Tm, Dy, Pr, Ho, Nd, Yb, Er, Sm, and Gd, and X is at least one of Cl, Br, and I, and x and y ^Are 5 × 10 ⁺⁵ ≦ x ≦ 0.5 and 0 respectively
It is a number that satisfies the condition of <y ≦ 0.2. ) A rare earth element-activated divalent metal fluorohalide phosphor having a general formula of ZnS: A, CdS: A, (Zn, Cd) S: A, ZnS: A, X and CdS: A, X
(Wherein A is Cu, Ag, Au, or Mn, and X is halogen), a phosphor represented by the general formula xM ₃ (PO) described in JP-A-57-148285. ₄ ) 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 formula nReX ₃ · mAX ′ ₂ : xEu 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, Ca, X
And X'represents at least one of F, Cl and Br.
Further, x and y are 1 × 10 ⁻⁴ <x <3 × 10 ⁻¹ , 1 × 10 ^−4.
<Y <1 × 10 ^-1 is a number satisfying the condition, and n / m is 1 × 1
The condition of 0 ^-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 at least one is of Li, Na, K, selected from Rb and Cs Is an alkali metal, 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, Dy, H
at least one selected from o, Er, Tm, Yb, Lu, Al, Ga and In
Species of trivalent metal. 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.

A is a numerical value in the range of 0 ≦ a <0.5, and b is 0
It is a numerical value in the range of ≦ b <0.5, and c is a numerical value in the range of 0 <c ≦ 0.2. ) 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, and stimulates luminescence when irradiated with stimulable excitation light after irradiation with radiation. Any fluorescent substance may be used as long as it is the fluorescent substance shown.

The radiation image conversion panel of the present invention may be a photostimulable phosphor layer group composed of one or more photostimulable phosphor layers containing at least one kind of the photostimulable phosphor. Good.
The photostimulable phosphors contained in each photostimulable phosphor layer may be the same or different.

In the radiation image conversion panel of the present invention, when the light-reflecting layer or the stimulable phosphor layer has no self-supporting ability, a support for supporting the light-reflecting layer and the stimulable phosphor layer. The body is provided. As the support, various polymer materials, glass,
Metals and the like are used, cellulose acetate film, polyester film, polyethylene terephthalate film, polyamide film, polyimide film, triacetate film, plastic film such as polycarbonate film, aluminum sheet, iron sheet,
A metal sheet such as a copper sheet or a metal sheet having a coating layer of the metal oxide is preferable.

The surface of these supports may be a smooth surface, or may be a matte surface for the purpose of improving the adhesiveness with the photostimulable phosphor layer. Further, the surface of the support may be an uneven surface 21 as shown in FIG. 2 (a), or may be a structure in which tile-shaped plates 23 separated from each other are spread as shown in FIG. 2 (b). In the case of FIG. 2 (a), the photostimulable phosphor layer is subdivided by the uneven surface 21 as shown in the sectional view of FIG. 2 (c), so that the sharpness of the image is further improved. In the case of FIG. 2 (b), the photostimulable phosphor layer is deposited while maintaining the contour of the tile plate 23 of the support, and as a result, the photostimulable phosphor layer is formed as shown in FIG. As shown in the sectional view of (d), since the columnar block 25 of photostimulable phosphor is isolated by the crack 26, 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 or the light reflection layer is provided for the purpose of improving the adhesiveness with the stimulable phosphor layer or the light reflection layer. . The film thickness of these supports varies depending on the material of the support used and the like, but is generally 80 μm to 2000 μm, and more preferably 80 μm to 1000 μm from the viewpoint of handling.

In the radiation image conversion panel of the present invention, generally, on the surface opposite to the surface of the photostimulable phosphor layer on which the light reflection layer is provided, a photostimulable phosphor layer is physically or chemically formed. A protective layer for protective protection may be provided. This protective layer may be formed by directly applying a coating solution for protective layer onto the stimulable phosphor layer, or by attaching a separately formed protective layer onto the stimulable phosphor layer. May be. 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. In addition, this protective layer is formed by vapor deposition, sputtering, etc.
It may be formed by stacking inorganic materials such as SiC, SiO ₂ , SiN, and Al ₂ O ₃ . The layer thickness of these protective layers is generally 0.1 μm to 100 μm.
About μm is preferable.

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. 3, 31 is a radiation generator, 32 is a subject, 33 is a radiation image conversion panel of the present invention, 34 is a stimulated excitation light source, and 35 is stimulated emission emitted from the radiation image conversion panel. The photoelectric conversion device, 36 is a device for reproducing the signal detected in 35 as an image, 37 is a device for displaying the reproduced image, 38 is for separating stimulated excitation light and stimulated emission, only stimulated emission It is a filter that transmits. It should be noted that, after 35, any light information from 33 can be reproduced as an image in some form,
It is not limited to the above.

As shown in FIG. 3, the radiation from the radiation generator 31 passes through the subject 32 and the radiation image conversion panel of the present invention.
It is incident on 33. The incident radiation is absorbed by the stimulable phosphor layer of the radiation image conversion panel 33, 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 34 and emitted as stimulated emission. The radiation image conversion panel 33 of the present invention does not contain a binder in the photostimulable phosphor layer and has high directivity of the photostimulable phosphor layer, so that the photostimulable excitation light beam is scanned. In addition, diffusion of stimulated excitation light in the stimulable phosphor layer 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 35 such as a photomultiplier tube, and reproduced as an image by the image reproduction device 36. By displaying with the image display device 37, the radiation transmission image of the subject can be observed.

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

Example 1 1 μm as a reflective layer on chemically strengthened glass (thickness 400 μm)
Silver was vapor deposited to a thickness of m.

Next, the support on which the light reflecting layer was formed was placed in a vapor deposition device. Then, the alkali halide stimulable phosphor (RbBr: 0.0006Tl) was put in a water-cooled crucible and pressed to form a crucible shape.

The vaporizer was subsequently evacuated to a vacuum of 5 × 10 ^-6 Torr. Next, while keeping the support heated at 150 ° C., power was supplied to the EB gun to evaporate the photostimulable phosphor. In order to obtain the target photostimulable phosphor layer, the deposition rate was detected by a film thickness monitor, and the deposition rate was controlled to be 5 μm / min. The electron beam scanned the surface of the photostimulable phosphor of the crucible in a raster pattern.

When the layer thickness of the photostimulable phosphor layer reached 200 μm, vapor deposition was terminated to obtain a radiation image conversion panel of the present invention composed of a support, a light reflection layer and a photostimulable phosphor layer.

Furthermore, by changing the layer thickness of the photostimulable phosphor layer in the range of 100 to 400 μm, various radiation image conversion panels A composed of a support, a light reflection layer and a photostimulable phosphor layer can be obtained. Manufactured.

The radiation image conversion panel A of the present invention was evaluated by the radiation sensitivity test and the image sharpness test described below, and the result is shown as a curve A in Table 5.

(1) Radiation sensitivity test After irradiating a radiation image conversion panel with X-rays at a tube voltage of 80 KVp for 10 mR, the He-Ne laser beam (633 nm) was used to excite it, and the photostimulable phosphor layer emitted it. The emitted light was photoelectrically converted by a photodetector (photomultiplier tube), and the sensitivity of the radiation image conversion panel to X-rays was examined from the magnitude of this signal.

Incidentally, the sensitivity to X-rays is shown as a relative value with the radiation image conversion panel A of the present invention having a stimulable phosphor layer thickness of 200 μm as 100.

(2) Image sharpness test 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 excited by He-Ne laser light (633 nm). Photostimulated luminescence emitted from the photostimulable phosphor layer is photoelectrically converted by a photodetector (photomultiplier tube), and this signal is reproduced as an image by an image reproducing device, and the obtained image is modulated. The transfer function (MTF) was investigated.

The modulation transfer function (MTF) is a value when the spatial frequency is 2 cycles / mm.

(Example 2) Instead of using the support provided with the light reflection layer in Example 1, a polished chemically strengthened glass (thickness: 400 µm) having a sufficiently polished surface and a polished surface serving as a reflection surface was used. Various radiation image conversion panels B of the present invention having a stimulable phosphor layer were manufactured in the same manner as in Example 1 except for the above.

The radiation image conversion panel B of the present invention was evaluated for radiation sensitivity and image sharpness in the same manner as in Example 1, and the result is shown as a curve B in FIG.

(Example 3) In the same manner as in Example 1, except that an aluminum plate (thickness: 400 μm) having a reflecting surface of a clear surface from which dirt was washed was used instead of using the support provided with the light reflecting layer. In the same manner as in Example 1, various radiation image conversion panels C of the present invention in which a stimulable phosphor layer was formed on an aluminum plate were manufactured.

The radiation image conversion panel C of the present invention was evaluated for radiation sensitivity and image sharpness in the same manner as in Example 1, and the result is shown as a curve C in FIG.

Comparative Example 1 In Example 3, an aluminum plate having an oxide film with an average reflectance of 40% with respect to stimulated excitation light and stimulated emission (thickness 40
Various comparative radiation image conversion panels P composed of an aluminum plate and a stimulable phosphor layer were produced in the same manner as in Example 3 except that the stimulable phosphor layer was directly vapor-deposited on the aluminum plate. .

The comparative radiation image conversion panel P was evaluated for radiation sensitivity and image sharpness in the same manner as in Examples 1 to 3, and the result is shown as a curve P in FIG.

Comparative Example 2 An alkali halide stimulable phosphor (RbBr: 0.0006T) was formed on the aluminum support having the oxide film used in Comparative Example 1.
Methyl ethyl ketone was added to the mixture of the particles of 1) and the linear polyester resin, and nitrocellulose having a nitrification degree of 11.5% was further added to prepare a dispersion liquid containing phosphor particles in a dispersed state. Next, tricresyl phosphate, n-butanol, and methyl ethyl ketone were added to this dispersion, and the mixture was thoroughly stirred and mixed using a propeller mixer to uniformly disperse the phosphor particles, thereby forming a binder and a phosphor. A coating solution having a mixing ratio of 1:20 (weight ratio) and a viscosity of 25 to 35 PS (25 ° C) was prepared.

This coating solution is applied on the support by the same operation as above, and then dried to obtain a layer thickness of about 200 μm.
m photostimulable phosphor layer was formed.

In this way, the layer thickness of the photostimulable phosphor layer is 100 to 400 μm.
Various comparative radiation image conversion panels Q composed of a support and a stimulable phosphor layer were produced by varying in the range of m.

The comparative radiation image conversion panel Q evaluated radiation sensitivity and image sharpness in the same manner as in Examples 1 to 3, and the result is shown as a curve Q in FIG.

Comparative Example 3 A comparative example having various phosphor layer thicknesses composed of an aluminum plate and a photostimulable phosphor layer in the same manner as in Comparative Example 2 except that the aluminum plate support used in Example 1 was used. The radiation image image conversion panel R was manufactured.

The comparative radiation image conversion panel R is the same as Examples 1 to 3.
The radiation sensitivity and the sharpness of the image were evaluated in the same manner as in, and the result is shown as a curve R in FIG.

As is clear from FIG. 4, the radiation image conversion panels A, B and C of the present invention have the same image sharpness as long as they have the same radiation sensitivity as compared with the conventional radiation image conversion panels P and Q. If the image sharpness is the same, the radiation sensitivity is high.

(Effects of the Invention) As described above, the photostimulable phosphor layer is formed by using fine columnar crystals extending in the thickness direction of the light reflection layer and collected in the form of frost columns, and providing the light reflection layer at the layer interface of the layer. It was possible to improve both reciprocal sensitivity and sharpness.

[Brief description of drawings]

FIG. 1 is an explanatory view of a stimulable phosphor layer of the present invention, and FIG. 1 (a) is an electron micrograph of a cross-section of a layer composed of fine crystals formed by a vapor phase deposition method. (B) is a schematic cross-sectional view showing the light directivity of the layer. FIGS. 2 (a) and 2 (b) show examples of the shape of the layer surface on which the stimulable phosphor of the support according to the present invention is deposited, and FIGS. 2 (c) and (d) show the shape of the layer surface. The cross section at the time of forming an exhaustive fluorescent substance layer is shown. FIG. 3 is a schematic diagram of the image conversion method of the present invention used in the present invention. FIG. 4 is a diagram showing the relationship between relative sensitivity and image sharpness in the radiation image conversion panels A, B and C of the present invention and the comparative radiation image conversion panels P and Q. 21 and 22 …… Support 23 …… Tile plate 24 and 25 …… Photostimulable phosphor layer 27 …… Light reflecting layer 26 …… Crack 31 …… Radiation generator 32 …… Subject 33 …… Radiation image Conversion panel 34 …… Stimulated excitation light source 38 …… Filter

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Fumio Shimada, 1 Sakura-cho, Hino City Konishi Roku Photo Industry Co., Ltd. 56-11393 (JP, A) JP 51-131264 (JP, A) JP 54-120576 (JP, A) JP 57-7051 (JP, A)

Claims (1)

(57) [Claims] 1. A photostimulable phosphor layer comprising: a photostimulable phosphor layer; and a smooth light-reflecting layer provided on the side of the photostimulable phosphor layer opposite to the photostimulable excitation light incident side. The radiation image conversion panel, wherein the body layer is formed by arranging columnar crystals of a stimulable phosphor extending in the layer thickness direction of the light reflection layer.