JP2514322B2 - 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 of high practical level in terms of both sharpness and sensitivity. The present invention relates to a radiation image conversion panel.

(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 applied 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 for directly taking out an image from the phosphor layer without using a film coated with a silver salt.

As this method, the radiation that has passed through the subject is absorbed by the phosphor, and then the phosphor is excited by, for example, light or thermal energy so that the radiation energy accumulated by the absorption of 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-55-1214.
No. 4 discloses a radiation image conversion method using a stimulable phosphor and using visible light or infrared light as stimulated excitation light. This method uses a radiation image conversion panel in which a stimulable phosphor layer is formed on a support, and the radiation that has passed through the subject is applied to the stimulable phosphor layer of this radiation image conversion panel to apply the radiation to each part of the subject. A latent image is formed by accumulating the radiation energy corresponding to the radiation transmittance, and thereafter, the stimulable phosphor layer is scanned with stimulable excitation light to radiate the accumulated radiation energy of each part to generate a latent image. The light is converted into light and an image is obtained by an optical signal depending on the intensity of the light. This final image may be played back as a hard copy or on a CRT.

Now, the radiation image conversion panel having the stimulable phosphor layer used in this radiation image conversion method has the same radiation absorption rate and light conversion rate (including both) as in the case of the radiographic method using the above-mentioned fluorescent screen. The "radiation sensitivity" is high), and the image has good graininess.
Moreover, high sharpness is required.

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 ratio 50%), and it was necessary to increase the layer thickness of the stimulable phosphor layer in order to sufficiently increase the radiation sensitivity.

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, and in order to improve the sharpness, It was necessary to reduce the thickness of the stimulable phosphor layer.

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.

That is, in the conventional radiation image conversion panel, the sharpness of the image sharply decreases with an increase in the thickness of the stimulable phosphor layer due to the large scattering and diffusion of the stimulable excitation light by the stimulable phosphor particles,
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 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, Of the stimulated excitation light within the panel. Because 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 stimulated by the stimulated excitation light irradiated at a certain time (ti). Is preferably 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 is scattered in the panel, etc. When the photostimulable phosphor existing outside the irradiation pixel (xi, yi) is also excited, the output from the pixel (xi, yi) above is output from a region wider than that pixel. It will be recorded. 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 these circumstances, some attempts have been made to improve the above-mentioned drawbacks of the radiation image conversion panel having the stimulable phosphor layer obtained by dispersing the stimulable phosphor in the binder.

For example, JP-A-56-11393 discloses a method in which a metal light reflection layer is provided at the interface of one side of a stimulable phosphor layer in which a stimulable phosphor is dispersed in a binder. According to this method, the stimulable phosphor layer is formed by changing the portion of the stimulable phosphor layer entering the inside from the stimulable excitation light incident side interface of the stimulable phosphor layer to the metal light reflection layer. It is possible to make the layer thickness thinner, and thereby to suppress the spread of the stimulated excitation light in the stimulable phosphor layer, so that a radiation image with high sharpness can be obtained.

However, although this method can suppress the spread (scattering) of the stimulable excitation light in the layer by the thinned thickness of the stimulable phosphor layer, it reaches the metal light reflection layer while scattering in the layer. Since the stimulated excitation light has almost no directivity, it is reflected according to the angle of incidence of the stimulated excitation light with respect to the metal reflection layer, returns to the stimulable phosphor layer side, and repeats scattering again to stimulate the stimulable light. Since the phosphor is excited over a wide range, the sharpness of the image is not significantly improved.

Further, JP-A-56-12600 discloses a stimulable phosphor obtained by dispersing a stimulable phosphor in a binder instead of the metal light-reflecting layer disclosed in JP-A-56-11393. A method of providing a white pigment light reflecting layer on one side of the layer is shown. According to this method, the stimulable phosphor is converted into a white pigment light-reflecting layer by changing the portion of the stimulable phosphor layer that is inside the stimulable excitation light incident side surface of the stimulable phosphor layer. It is said that the layer thickness can be made thinner, which makes it possible to suppress the spread of stimulated excitation light in the stimulable phosphor layer, and a radiation image with high sharpness can be obtained. .

However, also 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 is formed by dispersing a white pigment in the binder. Only the white pigment light reflecting layer was replaced. Therefore, this method has an 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-reflecting layer while scattering in the layer. The photostimulable excitation light that has reached 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 stimulable phosphor layer side, and scattered again in the stimulable phosphor layer. Since the stimulable phosphor is excited over a wide range, the sharpness of the image is not improved so much.

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, and an object of the present invention is a radiation image conversion panel having the same radiation sensitivity. The purpose of the present invention is to provide a radiation image conversion panel that provides an image with higher sharpness than the conventional radiation image conversion panel.

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 dominated by the scattering of the stimulating 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 reducing the sensitivity to radiation,
A combination of improving the directivity of stimulated excitation light and / or stimulated emission within the stimulable phosphor layer and providing a light scattering layer to reduce the thickness of the stimulable phosphor layer are combined. Proved to be remarkably effective.

Based on the above findings, the object of the present invention is to provide a photostimulable phosphor layer and a non-smooth light scattering layer provided on the side opposite to the photostimulable excitation light incident side of the photostimulable phosphor layer. The photostimulable phosphor layer has a columnar crystal of a photostimulable phosphor that extends in the layer thickness direction of the light scattering layer and is arranged in the radiation image conversion panel.

Further, the radiation image conversion panel is colored on the incident side of the photostimulable excitation light than the light scattering layer, the average reflectance for light in the photostimulable excitation light wavelength region transmitted through the photostimulable phosphor layer. It may be smaller than the average reflectance for light in the synonymous stimulated emission wavelength region.

Further, it is practically preferable that the layers are laminated in the order of support-light scattering layer-stimulable phosphor layer.

The light-scattering layer preferably has an average reflectance of 50% or more with respect to light in the stimulated excitation light wavelength region and / or light in the stimulated emission wavelength region. For example, a pigment layer having fine particles and a layer having a rough surface at the interface are used.

 Next, the present invention will be described in detail.

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

FIG. 1 (a) shows a cross section of a stimulable 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. An electron micrograph is shown, and FIG. 2B schematically shows the directivity of light in the layer, that is, the light guide effect of the layer.

In the same figure (b), each fine columnar crystal a ¹ , a ² ,
Due to the photo-induced effect of a ₃ ……, stimulated excitation light is generated at the crystal interface.
11 or stimulated emission 12 proceeds in the layer thickness direction while repeating total reflection. As a result, the photostimulable excitation light 11 incident on the radiation image conversion panel does not scatter and diffuse 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, or 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 phosphor on the surface of the support to a desired thickness.

As a result, a stimulable phosphor layer containing no binder is formed, but it is 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. Incidentally, 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 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, 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 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 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 these are simultaneously or sequentially sputtered to synthesize a target stimulable phosphor on a support and at the same time a stimulable phosphor layer. Can also be formed. In the sputtering method, 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. 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.

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, etc.
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 reduced, the radiation sensitivity is deteriorated, the granularity of the image is deteriorated, and the stimulable phosphor layer becomes transparent. This is not preferred because it tends to occur easily, the lateral spread of the stimulable excitation light in the stimulable phosphor layer significantly increases, and the sharpness of the image tends to deteriorate.

Further, 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-scattering layer according to the present invention is provided on the surface of the stimulable phosphor layer opposite to the surface on which the stimulable excitation light is incident.

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

As the light scattering layer, a layer having an interface or a layer capable of scattering light, such as a pigment layer, a porous metal layer, a grainy metal layer, a ceramic layer, a glass slide layer or an opal glass layer is used.

The light-scattering layer other than the pigment layer may also be used as a support, and the stimulable phosphor may be vapor-deposited on the light-scattering surface side. When a support is used separately, it may be attached before vapor deposition. Alternatively, the procedure may be such that the light scattering layer is attached to the support after vapor deposition.

When the light scattering layer is used as a pigment layer, the vapor deposition method may be used for the pigment capable of vapor deposition, or a pigment coating material suspended in a binder may be applied.

As the pigment, those having high reflectance for both stimulated excitation light and stimulated emission are preferable, and from this viewpoint, white pigments are particularly preferable.

Examples of the preferred white pigment include TiO ₂ (anatase type, rutile type), MgO, 2PbCO ₃ .PB (OH) ₂ , BaSO ₄ , Al ₂
O ₃ , M ^II FX (provided that M ^II is at least one of Ba, Sr and Ca and X is at least one of Cl and Br), CaCO ₃ , ZnO, Sb ₂ O ₃ , SiO ₂ , ZrO ₂ , Nb ₂ O ₅ , lithopone (BaSO ₄ + ZnS), magnesium silicate, basic lead silicate sulfate, basic lead phosphate, aluminum silicate and the like. Since these white pigments have a strong hiding power and a large refractive index, they easily scatter light by reflecting or refracting light, thereby significantly improving the sensitivity of the obtained radiation image conversion panel.

Divalent eurobium activated alkaline earth metal fluoride halide phosphor, rare earth element activated rare earth oxyhalide phosphor, thallium activated alkali halide phosphor etc. as stimulable phosphor for radiation image conversion panel. When using a stimulable phosphor that also emits light in the near-ultraviolet region, M ^II FX, anatase-type TiO ₂ among the white pigments is particularly preferable because the reflection spectrum extends to the near-ultraviolet region. , MgO, 2PbCO ₃ · Pb (OH) ₂ , BaSO ₄ and Al ₂
O ₃ is preferred.

When used as a pigment coating, the average particle size of the pigment is
The thickness is preferably 0.05 to 50 μm, more preferably 0.1 to 10 μm.

A polymer material having film-forming properties is used as the binder used in the paint, and various resins such as nitrocellulose, vinyl chloride-vinyl acetate copolymer, and polyurethane can be used. A practical weight ratio of the binder to the pigment is about 0.05 to 0.5.

The thickness of the light-scattering layer according to the present invention is generally preferably 2 to 100 μm, and it is preferable that the light-scattering layer 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. .

 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 scattering layer.

In the present invention, the coloring applied to the incident side of the photostimulable excitation light than the light scattering layer of the radiation image conversion panel is over the entire layer of the photostimulable phosphor layer, or the surface layer portion of the layer, It is applied to any one of a layer portion adjacent to the light scattering layer, an undercoat layer, a protective layer, or two or more of these. Alternatively, a coloring layer is provided on the surface of the layer or between the layer and the light scattering 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 the kind of the stimulable phosphor that is particularly applied. Accordingly, the radiation image conversion panel preferably has 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 viewpoint of image sharpness, the colorant has a large absorptivity for light in the wavelength region of stimulable excitation light of the stimulable phosphor (small average reflectance for light in the wavelength region of the radiation image conversion panel). From the viewpoint of sensitivity, it is preferable that the stimulable phosphor has a small absorptance with respect to light in the stimulable emission wavelength region (a large average reflectance with respect to 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.
In addition, color index No. 24411, 23160, 74180, 74
200, 22800, 23150, 23155, 24401, 14880, 15050, 157
06, 15707, 17941, 74220, 13425, 13361, 13420, 1183
Other examples include organic metal complex salt colorants such as 6,74140,74380,74350,74460.

Examples of the inorganic colorant include ultramarine blue, cobalt blue, cerulean blue, chromium oxide, and TiO ₂ —ZnO—CoO—NiO type pigment.

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 photostimulable 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 0.0
01 ≦ x <1 mol%. ), A phosphor represented by MgSO ₄ : Ax (where A is either Ho or Dy and 0.001 ≦ x ≦ 1 mol%) described in JP-A-48-80488. Described in JP-A-48-80489
SrSO ₄ : Ax (where A is at least one of Dy, Tb and Tm, and x is 0.001 ≦ x <1 mol%), JP-A-51-29889 Na listed in
₂ SO ₄ , CaSO _4, BaSO _4, etc., containing at least one of Mn, Dy and Tb, a phosphor such as BeO, LiF, MgSO ₄ and CaF ₂ described in JP-A-52-30487. Phosphor, JP-A-53-39
277, phosphors such as Li ₂ B ₄ O ₇ : Cu, Ag, Li ₂ O. (B ₂ O ₂ ) _x : Cu (where x Is 2 <x ≦ 3), and Li ₂ O · (B ₂ O ₂ ) _x : Cu, Ay (where x is
Is a phosphor such as 2 <x ≦ 3), SrS: Ce, Sm, SrS: Eu, Sm, La ₂ O ₂ S: Eu, Sm and (Zn, Cd) S: described in US Pat. No. 3,859,527. Examples include phosphors represented by Mn, X (where X is halogen). Further, a ZnS: Cu, Pb phosphor described in JP-A-55-12142, a barium aluminate phosphor represented by a general formula of BaO.xAl ₂ O ₃ : Eu (however 0.8 ≦ x ≦ 10), And the general formula is M ^II O ・ xSiO ₂ : A (where M ^II is Mg, Ca, Sr, Z
n, Cd or Ba, A is at least one of Ce, Tb, Eu, Tm, Pb, Tl, Bi and Mn, and x is 0.5 ≦ x <2.5. )
An alkaline earth metal silicate-based phosphor 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
Represents a number that satisfies <x <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 these, 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 . ), A phosphor represented by JP-A-55-160078
The general formula described in No. is M ^II FX xA: yLn (where M ^II is at least one of Mg, Ca, Ba, Sr, Zn and Cd, 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 at least one of Gd, and X is at least one of Cl, Br and I.
X and y are numbers that satisfy 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, CdS: A, (Zn, Cd) S: A, ZnS: A, X and CdS:
Phosphors represented by A and X (where A is Cu, Ag, Au or Mn and X is halogen), any one of the following general formulas xM ₃ described in JP-A-57-148285. (PO ₄ ) ₂・ NX ₂ : yA M ₃ (PO ₄ ) ₂ ) ・ yA (wherein M and N are at least one of Mg, Ca, Sr, Ba, Zn and Cd, X is F, At least one of Cl, Br and 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 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, 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. And the like. 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 fluorescence that exhibits stimulated emission when irradiated with stimulated excitation light after irradiation with radiation. Any phosphor may be used as long as it is a body.

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

In the radiation image conversion panel of the present invention, when the light scattering layer or the stimulable phosphor layer has no self-supporting ability, a support for supporting the light scattering layer and the stimulable phosphor layer is used. It 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 to the photostimulable phosphor layer or the light scattering 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 stimulable phosphor layer is second.
As shown in the sectional view of FIG. 7C, the sharpness of the image is further improved because it is subdivided by the uneven surface 21. In the case of FIG. 2B, the stimulable phosphor layer is a tile-shaped plate with a support.
As a result, the photostimulable phosphor layer is cracked as shown in the cross-sectional view of FIG.
The sharpness of the image is further improved because it is composed of the columnar block 25 of the stimulable phosphor that is isolated by.

Further, these supports may be provided with an undercoat layer on the surface on which the stimulable phosphor layer or the optical confusion layer is provided for the purpose of improving the adhesiveness to the stimulable phosphor layer or the optical confusion layer. The layer 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, a stimulable phosphor layer is physically or chemically provided on the surface opposite to the surface on which the optical confusion layer of the stimulable phosphor layer is provided. A protective layer for protection may be provided. This protective layer may be formed by directly coating the protective layer coating solution on the stimulable phosphor layer, or by forming a protective layer separately formed in advance on the stimulable phosphor layer. Good. 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 1 μm.
It is preferably about 00 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. 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 photostimulable 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 stimulable phosphor layer, and therefore has high directivity of the stimulable phosphor layer, and therefore, when scanning by the stimulable excitation light, 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 Toluene and ethanol were added to a mixture of barium fluorobromide (BaFBr) particles and polyurethane, and the mixture was thoroughly stirred and mixed using a homogenizer to uniformly disperse the barium fluorobromide particles, and to form a mixture. Mixing ratio of adhesive and barium fluorobromide is 1:10 (weight ratio) and viscosity is 25 ~ 35PS (25 ℃)
Was prepared.

Next, a chemically strengthened glass (support, thickness: 400 μm) was placed horizontally, and the coating solution was uniformly applied thereon by using a doctor blade. After coating, the support with the coating film is placed in a dryer, and the temperature inside the dryer is adjusted.
The coating film was dried by gradually increasing the temperature from 25 ° C to 100 ° C. In this way, a light scattering layer having a layer thickness of about 30 μm was formed on the support.

Next, the support having the light-scattering layer formed thereon was placed in an evaporator. Then, the alkali halide stimulable phosphor (RbBr: 0.0006Tl) was put into 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 heating the support at 150 ° C., power was supplied to the EB gun to evaporate the stimulable phosphor. In order to obtain the target stimulable phosphor layer, the vapor deposition rate was detected by a film thickness monitor, and the vapor deposition rate was controlled to be 5 μm / min. The electron beam scanned the surface of the stimulable phosphor of the crucible in a raster pattern.

When the layer thickness of the stimulable 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 scattering layer, and a stimulable phosphor layer.

Further, by changing the layer thickness of the stimulable phosphor layer in the range of 100 to 400 μm, various radiation image conversion panels A composed of a support, a light scattering layer, and a stimulable phosphor layer were 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 4.

(1) Radiation sensitivity test After irradiating a radiation image conversion panel with X-rays at a tube voltage of 80 KVp for 10 mR, it is stimulated by He-Ne laser light (633 nm) and stimulated by the stimulable phosphor layer. Was photoelectrically converted by a photodetector (photomultiplier), and the sensitivity of the radiation image conversion panel to X-rays was examined based on the magnitude of this signal.

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-rays at a tube voltage of 80 KVp, and then stimulated by He-Ne laser light (633 nm) to stimulate it. Photostimulated luminescence emitted from the stimulable phosphor layer is photoelectrically converted by a photodetector (photomultiplier tube), this signal is reproduced as an image by an image reproducing device, and the image obtained is modulated and transmitted. I examined the function (MTF).

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

Example 2 Example 2 was repeated except that a polyethylene terephthalate filter (thickness: 300 μm) in which a powdery white pigment was kneaded was used in place of the support provided by coating the light scattering layer in Example 1. Various radiation image conversion panels B of the present invention composed of white PET and a stimulable phosphor layer were manufactured in the same manner as in 1.

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 Example 3 is the same as Example 1 except that an aluminum plate (thickness: 400 μm) was used as the light-scattering layer, instead of using the support coated with the light-scattering layer, the surface was grained. 1
Various radiation image conversion panels C of the present invention composed of a grained aluminum plate and a stimulable phosphor layer in the same manner as
Was 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 1, various chemical compositions including a chemically reinforced glass and a stimulable phosphor layer were prepared in the same manner as in Example 1 except that the stimulable phosphor layer was directly deposited on the chemically strengthened glass. A comparative radiation image conversion panel P was manufactured.

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

Comparative Example 2 Toluene and ethanol were added to a mixture of barium fluorobromide (BaFBr) particles and polyurethane, and the mixture was thoroughly stirred and mixed using a homogenizer to uniformly disperse the barium fluorobromide particles. Mixing ratio of adhesive, barium fluorobromide and pigment is 1:10 (weight ratio), and viscosity is 25 ~ 35PS
(25 ° C.) was prepared.

Next, a chemically strengthened glass (support, thickness: 250 μm) was placed horizontally, and the coating solution was uniformly applied thereon by using a doctor blade. After coating, the support with the coating film is placed in a dryer, and the temperature inside the dryer is adjusted.
The coating film was dried by gradually increasing the temperature from 25 ° C to 100 ° C. Thus, a light scattering layer having a layer thickness of about 30 μm was formed on the support.

Next, alkali halide stimulable phosphor (RbBr: 0.0006T
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 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 liquid 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 light-scattering layer by the same procedure as above, and then dried to obtain a layer thickness of about 200 μm.
To form a stimulable phosphor layer.

In this way, a comparative radiation image conversion panel composed of the support, the light scattering layer and the stimulable phosphor layer was produced.

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

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

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

Comparative Example 3 In Comparative Example 2, the chemical reinforced glass and the stimulable phosphor layer were used in the same manner as in Comparative Example 2 except that the stimulable phosphor coating liquid was directly applied onto the chemically strengthened glass. Comparative radiographic image conversion panels R were produced with different phosphor layer thicknesses.

The comparative radiation image conversion panel R evaluated radiation sensitivity and image sharpness in the same manner as in Example 1, and the result is shown as a curve P in FIG.

(Effect of the invention) As described above, the stimulable phosphor layer is formed by using fine columnar crystals that extend in the layer thickness direction of the light scattering layer and are gathered in a frost column shape, and provide the light scattering layer at the layer interface of the layer. It was possible to improve both the reciprocal sensitivity and sharpness.

[Brief description of drawings]

FIG. 1 is an explanatory view of a stimulable phosphor layer of the present invention. 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 when the luminescent phosphor layer is formed is shown. FIG. 3 is a schematic diagram of a radiation image conversion method 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 scattering 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. 56-12600 (JP, A) JP 59-162498 (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, and a non-smooth light-scattering layer provided on the side of the photostimulable phosphor layer opposite to the photostimulable excitation light incident side. The phosphor layer is formed by arranging columnar crystals of a stimulable phosphor extending in the layer thickness direction of the light scattering layer.