JPH0664195B2 - Radiation image conversion panel having a phosphor layer shielded between crack interfaces - 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 conversion panel which gives a radiation image with high sharpness, and The present invention relates to a manufacturing method thereof.

[Prior art]

Radiation images such as X-ray images are often used for disease diagnosis. In order to obtain this X-ray image, X-rays that have passed through the subject are irradiated onto the phosphor layer (fluorescent screen), thereby generating visible light, and this visible light is used in the same way as when taking a normal photograph. The so-called radiography in which a film using salt is irradiated to develop the film is used. However, in recent years, a method of directly taking out an image from the phosphor layer without using a film coated with silver salt has been devised.

As this method, the radiation that has passed through the subject is absorbed by the phosphor, and then the phosphor is excited by, for example, light or thermal energy so that the radiation energy accumulated by the absorption by the phosphor is emitted as fluorescence. , There is a method of detecting this fluorescence and imaging. Specifically, for example, U.S. Pat. No. 3,859,527 and JP-A-55-12144.
Japanese Patent No. 3187242 discloses a radiation image conversion method using a stimulable phosphor and using visible light or infrared light as stimulated excitation light. This method uses a radiation image conversion panel in which a stimulable phosphor layer is formed on a support, and the radiation that has passed through the subject is applied to the stimulable phosphor layer of this radiation image conversion panel to apply the radiation to each part of the subject. The latent energy is formed by accumulating the radiation energy corresponding to the radiation transmittance, and thereafter, the radiation energy accumulated in each part is emitted by scanning the stimulable phosphor layer with stimulable excitation light. To light,
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, also in the radiation image conversion panel having the stimulable phosphor layer used in this radiation image conversion method, the radiation sensitivity is high and the image graininess is good as in the radiographic method using the above-mentioned fluorescent screen, Also, it is required that the sharpness of the image is high. However, in the radiation image conversion panel and the fluorescent screen, the high radiation sensitivity of the radiation image conversion panel means that the radiation energy has a high efficiency of absorbing and accumulating so that the radiation energy can be stimulated and emitted later by the excitation light. The high radiation sensitivity of the fluorescent screen means that the efficiency of converting the radiation energy into light is high, and the absorption of radiation energy reduces the amount of conversion into light immediately. There are different natural laws.

Regarding the radiation sensitivity of the radiation image conversion panel, the radiation image conversion panel having the conventional stimulable phosphor layer has a particle size of 1 to 1.
The packing density of the stimulable phosphor is low because it is prepared by coating and drying a dispersion containing a particle-shaped stimulable phosphor of about 30 μm and an organic binder on a support or a protective layer ( Filling rate
50%), it was necessary to increase the thickness of the stimulable phosphor layer as shown in FIG. 5 (a) in order to sufficiently increase the radiation sensitivity.

As is clear from the figure, the layer thickness of the stimulable phosphor layer is 200 μm.
In this case, the deposition amount of the stimulable phosphor is 50 mg / cm ² , and the radiation sensitivity increases linearly up to 450 μm until the layer thickness reaches 350 μm.
Saturates above m. Incidentally, the radiation sensitivity is saturated, because when the stimulable phosphor layer becomes too thick, the scattering of the stimulable phosphor layer among the stimulable phosphor particles results in This is because the stimulated emission does not come out to the outside.

On the other hand, as shown in FIG. 5 (b), the sharpness of the image obtained by 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. In order to improve the property, it was necessary to reduce the thickness of the stimulable phosphor layer.

Further, since the graininess of the image in the radiation image conversion method is determined by the spatial fluctuation of the radiation quantum number (quantum mottle) or the structural disorder of the stimulable phosphor layer of the radiation image conversion panel (structure mottle), etc. , When the thickness of the stimulable phosphor layer becomes thin, the number of radiation quantum absorbed in the stimulable phosphor layer decreases and the quantum mottle increases, or structural disorder becomes apparent and the structural mottle increases. As a result, the image quality is degraded. Therefore, in order to improve the graininess of the image, the stimulable phosphor layer needs to be thick.

That is, as described above, in the conventional radiation image conversion panel, the sensitivity to radiation and the graininess of the image, and the sharpness of the image show the opposite tendency to the layer thickness of the stimulable phosphor layer. The radiation image conversion panel has been made at the expense of some sensitivity to radiation, graininess and sharpness. Regarding the difference between the fluorescent screen and the radiation image conversion panel described above, it is well known that the sharpness of the image in radiography is determined by the spread of the instantaneous light emission (light emission upon irradiation) of the phosphor in the fluorescent screen. In contrast, the sharpness of the image in the radiation image conversion method using the stimulable phosphor described above is determined by the spread of the stimulated emission of the stimulable phosphor in the radiation image conversion panel. There is also the difference that it is not determined by the spread of the emission of the phosphor, ie, as in radiography, but rather by the spread of the stimulated excitation light within the panel. This difference is that in the radiation image conversion method, since the radiation image information accumulated in the radiation image conversion panel is taken out in time series, the stimulated emission due to the stimulated excitation light irradiated at a certain time (ti) does not occur. It is recorded as the output from a certain pixel (xi, yi) on the panel that was desirably illuminated and stimulated by excitation light at that time, but if the stimulated excitation light is scattered in the panel, etc. If the stimulable phosphor existing outside the radiated pixel (xi, yi) is also excited, the output from a pixel wider than that pixel will be recorded as the output from the pixel (xi, yi) above. Because it is done. Therefore, a certain time (ti)
If the stimulated emission by the stimulated excitation light irradiated to the, only the light emission from the pixel (xi, yi) on the panel that was actually irradiated with the stimulated excitation light at that time (ti), Whatever spread the luminescence has, it does not affect the sharpness of the resulting image.

Under these circumstances, some methods have been devised to improve the sharpness of radiographic images. For example, JP-A-55-1464
A method of mixing white powder in the stimulable phosphor layer of the radiation image conversion panel described in No. 47, the radiation image conversion panel described in JP-A-55-163500 is a stimulable excitation wavelength region of the stimulable phosphor. And the like so that the average reflectance in the above is smaller than the average reflectance in the stimulated emission wavelength region of the stimulable phosphor. However, these methods are not preferable methods because the sensitivity inevitably decreases remarkably when the sharpness is improved.

On the other hand, the applicant of the present invention has already proposed in Japanese Patent Application No. 59-196365 a new radiation image conversion panel which is a novel radiation image conversion panel that improves on the conventional defects in the radiation image conversion panel using the stimulable phosphor as described above. A radiation image conversion panel in which the luminescent phosphor layer does not contain a binder is proposed. According to this, since the stimulable phosphor layer of the radiation image conversion panel does not contain a binder, the filling rate of the stimulable phosphor is significantly improved and the directivity of stimulated excitation light and stimulated emission is improved. Therefore, the radiation sensitivity of the radiation image conversion panel and the graininess of the image are improved, and at the same time, the sharpness of the image is improved.

However, in the radiation image conversion method, the sensitivity,
The demand for image quality with excellent sharpness without impairing graininess is becoming more severe.

[Object of the Invention]

The present invention relates to the above proposed radiation image conversion panel using a stimulable phosphor, which is to further improve it.
It is an object of the present invention to provide a radiation image conversion panel which has improved sensitivity to radiation and provides an image with high sharpness.

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

[Structure of Invention]

The above-mentioned object of the present invention has a stimulable phosphor layer for storing radiation image information on a support, and when the stimulable excitation light is incident from the upper surface side to the stimulable phosphor layer, it is brightened. In the radiation image conversion panel which emits the radiation image information stored in the stimulable phosphor layer to the upper surface side as stimulated emission, the stimulable phosphor layer is deposited by a vapor deposition method. A radiation image characterized by comprising a crack formed in a net shape on the upper surface side and cut in the layer thickness direction, and the crack is filled with a substance having a high light reflectance or a high light absorption rate. Accomplished by a conversion panel.

Next, the present invention will be specifically described.

FIG. 1 (a) is a sectional view in the thickness direction of an example of the radiation image conversion panel of the present invention (hereinafter sometimes simply referred to as a panel when the meaning is clear).

In the figure, reference numeral 10 shows the form of the panel of the present invention. Reference numeral 11 is a support, and 12 is a stimulable phosphor layer provided on the support, which is a stimulable phosphor layer formed by a vapor deposition method. If necessary, an adhesive layer may be provided between the support 11 and the stimulable phosphor layer 12 to improve the adhesiveness between the layers, or stimulated excitation light and / or stimulated emission. You may provide the reflective layer or the absorption layer. Further, 14 is a protective layer which is preferably provided.

Fine cracks 13 are provided in the stimulable phosphor layer 12, and the cracks 13 are filled with a substance having high light reflectance or high light absorption, which is a feature of the panel of the present invention.

The crack in the stimulable phosphor layer in the present invention is specifically a general term for fine cracks, grooves, depressions, crevasses and the like provided along a plane parallel to the crystal grain boundaries of the stimulable phosphor. is doing.
The morphology of the cracks is, for example, in a stimulable phosphor layer having a juxtaposed structure of fine columnar blocks of stimulable phosphor extending in a direction substantially perpendicular to the support 11 as shown in FIG. 1 (a). It may be a crevasse that partitions each of the fine columnar blocks. The juxtaposed structure of the columnar blocks may have any pattern. 2 (a), (b) and (c) show examples of the pattern as plan views of the stimulable phosphor layer.
In FIG. 2, 21 is a stimulable phosphor layer, 22 is the fine columnar block, and 23 is the crevasse.

Further, the panel of the present invention may have a structure having a crack 13 which is inserted from the surface side of the stimulable phosphor layer 12 as shown in FIG. 1 (b).

The thickness of the stimulable phosphor layer of the panel of the present invention varies depending on the sensitivity of the panel to radiation, the type of the stimulable phosphor, etc., but is preferably in the range of 10 to 800 μm, and 50 to 500 μm.
The range of m is more preferable.

In the panel of the present invention, the width of the crack 13 is preferably about 1 to 20 μm, and the distance between adjacent cracks is preferably about 1 to 400 μm.

In the panel of the present invention, as a material having a high light reflectance used as a filling material for cracks in the stimulable phosphor layer, for example, aluminum, magnesium, silver, indium and other metals are used, and a high light absorptivity As the substance, for example, carbon, chromium oxide, nickel oxide, iron oxide or the like is used.

In the panel of the present invention, lateral diffusion of the stimulable excitation light incident on the stimulable phosphor layer is almost completely prevented by the substance having the high light reflectance or the high light absorption rate. Repeats reflection at the interface of the crack, and reaches the surface of the support without being dissipated outside the section surrounded by the crack. Therefore, the sharpness of the image due to stimulated emission can be significantly increased.

In the radiation image conversion panel of the present invention, the stimulable phosphor means a stimulus such as an optical, a thermal, a mechanical, a chemical, or an electrical stimulus (stimulation excitation) after being irradiated with the first light or high-energy radiation. ), The 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 a phosphor that exhibits stimulated emission by stimulated excitation light of 500 nm or more. is there. Examples of the stimulable phosphor used in the radiation image conversion panel of the present invention include BaSO ₄ : Ax (where A is at least one of Dy, Tb and Tm) described in JP-A-48-80487. Yes, x is
0.001 ≦ x <1 mol%. ) Phosphor represented by
MgSO ₄ : Ax described in JP-A-48-80488 (where A is Ho or
Phosphor represented by any one of Dy, where x is 0.001 ≦ x ≦ 1 mol%, SrSO ₄ : Ax described in JP-A-48-80489 (where A is Dy, Tb and Tm) Which is at least one of the above, and x is 0.001 ≦ x <1 mol%.), Na ₂ SO ₄ , CaSO ₄ and Na ₂ SO ₄ and CaSO ₄ described in JP-A-51-29889. BaSO ₄ etc. with Mn, Dy and Tb
A phosphor to which at least one of them is added, Japanese Patent Application Laid-Open No. 52-30
BeO, LiF, MgSO _4, CaF _{2 and} other phosphors described in JP-A No. 487, Li ₂ B ₄ O ₇ : Cu, A described in JP-A-53-39277.
g and other phosphors, Li ₂ O described in JP-A-54-47883
・ (B ₂ O ₂ ) x: Cu (where x is 2 <x ≦ 3), and Li ₂ O ・ (B ₂ O
₂ ) x: Cu, Ag (where x is 2 <x ≦ 3) and other phosphors, SrS: Ce, Sm, SrS: Eu, S described in US Pat. No. 3,859,527
Examples include phosphors represented by m, La ₂ O ₂ S: Eu, Sm and (Zn, Cd) S: Mn, X (where X is a halogen). In addition, JP-A-55
No. 12142, a znS: Cu, Pb phosphor, a barium aluminate phosphor represented by the general formula of BaO.xA ₂ O ₃ : Eu (however 0.8 ≦ x ≦ 10), and a general formula of M ^II O ・ xS
iO ₂ : A (where M ^II is Mg, Ca, Sr, Zn, Cd or Ba, and A is C
It is at least one of e, Tb, Eu, Tm, Pb, T, Bi and Mn, and x is 0.5 ≦ x <2.5. ) Alkaline earth metal silicate-based phosphors represented by Also, the general formula is (Ba ₁ -x-yMgxCay) FX: eEu ²⁺ (where X is at least one of Br and C, and x,
y and e are 0 <x + y ≦ 0.6, xy ≠ 0 and 10 ⁻⁶ ≦, respectively
It is a number that satisfies the condition of e ≦ 5 × 10 ^-2 . ) Alkaline earth fluorohalide phosphor, represented by JP-A-55-12
The general formula described in No. 144 is LnOX: xA (where Ln is at least one of La, Y, Gd and Lu, and X is C
And / or Br, A is Ce and / or Tb, and x is 0 <x
Represents a number that satisfies <0.1. ) Phosphor represented by
The general formula described in JP-A-55-12145 is (Ba ₁ -xM ^II x) FX: yA (where M ^II is at least one of Mg, Ca, Sr, Zn and Cd is X Is at least one of C, 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 0 ≦ x. ≦ 0.6 and 0 ≦ y ≦
Represents a number that satisfies the condition 0.2. ), The general formula described in JP-A-55-84389 is BaF
X: xCe, yA (where X is at least one of C, Br and I, A is at least one of In, T, Gd, Sm and Zr, and x and y are each 0 <x ≦ 2 × 10 ⁻¹ and 0 <y ≦ 5 × 10 ⁻² ), the general formula described in JP-A No. 55-160078 is M ^II FX · xA: yLn (however, M ^II is at least one of Mg, Ca, Ba, Sr, Zn and Cd, A is BeO, MgO, CaO, SrO, BaO, ZnO, A ₂ O ₃ , Y ₂ O ₃ ,
_{La 2 O 3, In 2 O} 3, SiO 2, TiO 2, ZrO 2, GeO 2, SnO 2, Nb 2 O 5, Ta 2 O 5,
And at least one of ThO ₂ , Ln is Eu, Tb, Ce, Tm, D
at least one of y, Pr, Ho, Nd, Yb, Er, Sm and Gd, X is at least one of C, Br and I, and x and y are each 5 × 10 ^{− 5} ≤ x ≤ 0.5 and 0 <y
It is a number that satisfies the condition of ≦ 0.2. ) A rare earth element-activated divalent metal fluorohalide phosphor, represented by the general formula
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 ₄ ) described in JP-A-57-148285. ) ₂・ NX ₂ : yA M ₃ (PO ₄ ) ₂ : yA (In the formula, M and N are at least one of Mg, Ca, Sr, Ba, Zn and Cd, and X is F, C, Br and At least one of I, A is Eu, Tb, Ce, Tm, Dy, Pr, Ho, Nd, Yb, Er, Sb, T
, Mn and Sn represent at least one kind. Also, x
And y are numbers satisfying the conditions of 0 <x ≦ 6 and 0 ≦ y ≦ 1. ), A phosphor represented by any of the following general formulas nReX ₃ · mA ▲ X ^′ ₂ ▼: xEu nReX ₃ · mA ▲ X ^′ ₂ ▼: xEu, ySm (where Re is La, Gd, Y, Lu) At least one of them, A is an alkaline earth metal, at least one of Ba, Sr, and Ca, X and X ′ are at least one of F, C, and Br, and x and y are 1 ×. 10 ^-4 <x <3 x 10 ^-1 , 1 x 10 ^-4 <
It is a number satisfying the condition of y <1 × 10 ⁻¹ , and n / m is 1 ×
The condition of 10 ^-3 <n / m <7 × 10 ^{-1 is} satisfied. Phosphor represented by), and the following general formula ^{M I X · aM II ▲ X} '2 ▼ · bM III ▲ X "2 ▼: cA ( where, M ^I is selected Li, Na, K, from Rb and Cs At least one 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,
It is at least one trivalent metal selected from Ho, Er, Tm, Yb, Lu, A, Ga and In. X, X'and X "are at least one halogen selected from F, C, Br and I. A is
Eu, Tb, Ce, Tm, Dy, Pr, Ho, Nd, Yb, Er, Gd, Lu, Sm, Y, T, Na, A
It is at least one metal selected from g, Cu and Mg.

Also, a is a numerical value in the range of 0 ≦ a <0.5, and b is 0 ≦ a <0.5.
The value is in the range of b <0.5, and the value of c is in the range of 0 <c ≦ 0.2. ) Alkali halide phosphors represented by). Alkali halide phosphors are especially
A stimulable phosphor layer can be easily formed by a method such as sputtering, which is preferable.

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

The radiation image conversion panel of the present invention may have 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, various polymeric materials, glass, metals and the like are used as the support. In particular, a material that can be processed into a flexible sheet or web for handling as an information recording material is preferable, and from this point, for example, a cellulose acetate film,
A plastic film such as a polyester film, a polyethylene terephthalate film, a polyamide film, a polyimide film, a triacetate film and a polycarbonate film, a metal sheet of aluminum, iron, copper, chromium or the like or a metal sheet having a coating layer of the metal oxide is preferable.

The layer thickness of these supports varies depending on the material of the support used, etc., but is generally 80 μm to 1000 μm, and more preferably 80 μm to 500 μm from the viewpoint of handling.

In the radiation image conversion panel of the present invention, a protective layer for physically or chemically protecting the stimulable phosphor layer group is generally provided on the surface on which the stimulable phosphor layer is exposed. Is preferred. This protective layer may be formed by directly coating the protective layer coating solution on the stimulable phosphor layer, or by forming a protective layer separately formed in advance on the stimulable phosphor layer. Good. Alternatively, a method may be used in which a support is adhered after providing a stimulable phosphor layer on a separately formed protective layer. Materials for the protective layer include cellulose acetate, nitrocellulose, polymethylmethacrylate, polyvinyl butyral, polyvinyl formal, polycarbonate, polyester, polyethylene terephthalate, polyethylene, polypropylene, polyvinylidene chloride, nylon, polytetrafluoroethylene, and polytrifluoride. Materials for the protective layer such as ethylene chloride, tetrafluoroethylene-hexafluoropropylene copolymer, vinylidene chloride-vinyl chloride copolymer and vinylidene chloride-acrylonitrile copolymer are used.

In addition, this protective layer is formed by vacuum vapor deposition, sputtering, etc.
It may be formed by stacking inorganic materials such as SiC, SiO ₂ , SiN, and Al ₂ O ₃ .

Next, the vapor phase deposition method of the stimulable phosphor layer will be described.

The first method is a vacuum vapor deposition method. In this method, first, the support is placed in the vapor deposition apparatus and then the apparatus is evacuated to a vacuum degree of about 10 ⁻⁶ Torr.

Then, at least one of the stimulable phosphors is heated and evaporated by a method such as a resistance heating method or an electron beam method to deposit the stimulable phosphor on the surface of the support to a desired thickness.

As a result, a stimulable phosphor layer containing no binder is formed, but it is also possible to form the stimulable phosphor layer in a plurality of times in the vapor deposition step. Further, in the vapor deposition step, co-evaporation can be performed using a plurality of resistance heaters or electron beams.

After complete formation of the stimulable phosphor layer that has also been filled in the cracks, preferably a protective layer is provided on the side opposite to the support side of the stimulable phosphor layer, if necessary, for the radiation image conversion of the present invention. The panel is manufactured.

Incidentally, after forming the stimulable phosphor layer on the protective layer, the support may be provided.

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

Further, in the vacuum vapor deposition method, the object to be vapor-deposited (support or protective layer) may be cooled or heated during vapor deposition, if necessary. In addition, the stimulable phosphor layer may be heat-treated after completion of vapor deposition.

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

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

In the sputtering step, it is possible to form the stimulable phosphor layer in a plurality of times in the same manner as in the vacuum deposition method, and it is also possible to simultaneously use a plurality of targets made of different stimulable phosphors. Alternatively, it is also possible to sequentially sputter the target to form a stimulable phosphor layer.

Also in the case of using the sputtering method, similarly to the case of the vacuum deposition method, preferably a protective layer is provided on the side opposite to the support side of the stimulable phosphor layer, if necessary, to provide a radiation image conversion panel of the present invention. Manufactured. Incidentally, after forming the stimulable phosphor layer on the protective layer, a procedure of providing a support may be adopted.

In the sputtering method, a plurality of stimulable phosphor raw materials are used as targets and are simultaneously or sequentially sputtered to synthesize a target stimulable phosphor on a support and at the same time a stimulable phosphor layer is formed. It is also possible to form. In the sputtering method, if necessary, O
Reactive sputtering may be performed by introducing a gas such as ₂ , H ₂ or the like.

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

The third method is the CVD method. In this method, a target stimulable phosphor or an organometallic compound containing a raw material for a stimulable phosphor is decomposed by energy such as heat or high-frequency power to give a binder containing no binder on the support. A fluorescent phosphor layer is obtained.

As a method for forming a crack in the stimulable phosphor layer of the panel of the present invention, for example, the method described in Japanese Patent Application Nos. 59-266912 to 266916 can be used. That is, on a support having a surface structure such as a large number of micro tile-shaped plates separated from each other by a minute gap and spread, or on a support having a surface structure in which each of the micro tile-shaped plates is surrounded and divided by a fine wire net. The stimulable phosphor may be vapor-deposited to form a structure as shown in FIG. 1 (a). The stimulable phosphor layer thus provided may be further shock-treated to develop cracks.

Moreover, as described in Japanese Patent Application No. 60-180704, a crack is generated by applying a heat shock to the stimulable phosphor layer formed by the vapor deposition method, and the crack is generated as shown in FIG. 1 (b). It is also possible to obtain the structure shown.

Furthermore, as described in Japanese Patent Application No. 60-250530,
After forming a stimulable phosphor layer having cavities by vapor deposition in an atmosphere, heat treatment may be performed to grow the cavities to form cracks.

Next, a method of filling the crack formed in the stimulable phosphor layer with a substance having high light reflectance or high light absorption will be described.

As mentioned above, the width of the crack is preferably 1 to 20 μm.
Since the material is in the order of magnitude, when the substance to be filled is ultrafine particles having a particle size of several hundred mμ or less, this can be directly embedded in the crack. When the substance to be filled is a metal having a relatively low melting point, the temperature may be raised to the melting point of the metal and the cracks may be filled by utilizing the fluidity of the melt. In addition to the above method, a substance to be filled is dissolved or dispersed in an appropriate solvent or dispersion medium to prepare a solution or dispersion having an appropriate viscosity, and the solution or dispersion is permeated into the crack. After that, a method of depositing the filler by evaporating the solvent or denaturing by heating may be used.

FIG. 3 (a) is an example of the relationship between the photostimulable phosphor layer of the radiation image conversion panel of the present invention obtained by the vapor deposition method and the amount of the photostimulable phosphor deposited corresponding to the layer thickness and the radiation sensitivity. Is represented.

Since the stimulable phosphor layer by the vapor deposition method according to the present invention does not contain a binder, the amount of the stimulable phosphor attached (filling rate) is the same as that obtained by coating a conventional stimulable phosphor. It is about twice as thick as the stimulable phosphor layer, and the radiation absorptivity per unit thickness of the stimulable phosphor layer is improved and the sensitivity to radiation is high, and the graininess of the image is improved.

Furthermore, the stimulable phosphor layer produced by the vapor deposition method has high directivity for stimulated excitation light and stimulated emission, and the layer thickness can be made larger than that of the stimulable phosphor layer produced by the conventional coating method. , Becomes more sensitive to radiation.

An example of the sharpness of the panel of the present invention having a stimulable phosphor layer having a high light reflectance or high light absorption filler in the crack obtained as described above is shown by 31 in FIG. 3 (b). Show.

The panel of the present invention is more excellent in its light-inducing effect than the fine columnar block structure having no filling described in Japanese Patent Application No. 59-266912 to 266916, and the transverse direction of stimulated excitation light in the lateral direction. Since diffusion is prevented, for example, the characteristics of a panel having a columnar block structure that inherits the tile-like structure specified in Japanese Patent Application No. 59-266914 and having no filling in cracks are shown in FIG. As is clear from comparison with 32 of (b), it is possible to improve the sharpness of the image and further improve the sharpness with an increase in the layer thickness of the stimulable phosphor.

The characteristics of a conventional panel obtained by dispersing and coating stimulable phosphor particles on a binder are shown in 33 of FIG. 3 (b). This clearly shows that the sharpness of the image is excellent.

The radiation image conversion panel of the present invention provides excellent sharpness and graininess when used in the radiation image conversion method shown schematically in FIG. That is, in FIG. 4, 41 is a radiation generator, 42 is a subject, 43 is a radiation image conversion panel of the present invention, 44 is a stimulated excitation light source, and 45 is stimulated emission emitted from the radiation image conversion panel. A photoelectric conversion device, 46 is a device for reproducing the signal detected at 45 as an image 47 is a device for displaying the reproduced image, 48 is for separating stimulated excitation light and stimulated emission, only stimulated emission It is a filter that allows light to pass through. It should be noted that after 45, it is not limited to the above as long as the optical information from 43 can be reproduced as an image in some form.

As shown in FIG. 4, the radiation from the radiation generator 41 enters the radiation image conversion panel 43 of the present invention through the subject 42. The incident radiation is absorbed by the photostimulable phosphor layer of the panel 43, the energy is accumulated, and an accumulated image of a radiation transmission image is formed. Next, this accumulated image is excited by stimulated excitation light from the stimulated excitation light source 44 and emitted as stimulated emission. The radiation image conversion panel 43 of the present invention is excellent in the light induction effect of the stimulated excitation light, and during the scanning by the stimulated excitation light, the stimulated excitation light diffuses 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 45 such as a photomultiplier tube and reproduced as an image by the image reproduction device 46. By displaying with the display device 47, a radiation transmission image of the subject can be observed.

〔Example〕

 Next, the present invention will be described with reference to examples.

EXAMPLE A surface such as an aluminum plate having a thickness of 0.5 mm was anodized, sealed, and heat-treated by the method described in Japanese Patent Application No. 59-266914 so that the tile-shaped plates were separated from each other by fine gaps and spread. The structured support was placed in the vaporizer.

Next, the alkali halide stimulable phosphor RbBr: 0.0002T was placed in a molybdenum boat for resistance heating, set on the resistance heating electrode, and then the vaporizer was evacuated to 1 × 10 ^-7 To.
The vacuum degree was rr. Next, the support was heated to 300 to 500 ° C. by a support heating heater to wash the surface of the support, and then the support was set to 100 ° C. and the degree of vacuum was set to 2 × 10 ⁻⁶ Torr. Next, energize the molybdenum boat, evaporate RbBr: 0.0002T by a resistance heating method, and vacuum deposit to a thickness of about 250 μm to form a stimulable phosphor layer having a fine columnar block structure, which is taken out into the atmosphere. It was

Next, the melted indium is permeated into the cracks separating the fine columnar blocks of the stimulable phosphor layer and cooled to room temperature to obtain the radiation image conversion panel A of the present invention in which the indium is bound in the cracks. It was

A tube voltage of 80 KV was applied to the panel A of the present invention thus obtained.
After irradiating 10 mR of X-ray of p, it is stimulated by exciting with a semiconductor laser beam (780 nm), and the stimulated emission emitted from the stimulable phosphor layer is photoelectrically converted by a photodetector (photomultiplier tube). This signal was reproduced as an image by an image reproducing device and recorded on a silver salt film. From the magnitude of the signal, the sensitivity of the radiation image conversion panel A to X-rays was examined, and from the obtained image,
The modulation transfer function (MTF) and graininess of the image were investigated and are shown in Table 1.

In Table 1, the sensitivity to X-rays is shown as a relative value with the radiation image conversion panel A of the present invention as 100. The modulation transfer function (MTF) is a value when the spatial frequency is 2 cycles / mm.

Comparative Example A comparative radiation image conversion panel B was obtained in the same manner as in the Example, except that the work of filling the cracks of the stimulable phosphor layer with indium was omitted.

Comparative panel B was evaluated in the same manner as in Example, and the results are also shown in Table 1.

As is clear from Table 1, the panel A of the present invention had a slightly higher X-ray sensitivity than the comparative panel B, but the sharpness was remarkably excellent although the graininess was equivalent. this is,
The panel A of the present invention has cracks in the stimulable phosphor layer, and the cracks are filled with indium which is a high light reflectance material. This is because the light guiding effect is higher.

〔The invention's effect〕

As described above, according to the present invention, the stimulable phosphor layer has a crack, and the crack is filled with a substance having a high light reflectance or a high light absorptivity. The scattering in the fluorescent layer is significantly reduced, and as a result, the sharpness of the image can be improved.

Further, according to the present invention, since the sharpness of the image is not significantly reduced due to the increase in the stimulable phosphor layer thickness, increasing the stimulable phosphor layer thickness allows the radiation without decreasing the sharpness of the image. It is possible to improve the sensitivity.

Further, according to the present invention, since the deterioration of the sharpness of the image due to the increase of the stimulable phosphor layer thickness is small, by increasing the thickness of the stimulable phosphor layer, the image sharpness is not deteriorated without decreasing the image sharpness. It is possible to improve the graininess of the.

Further, according to the present invention, the radiation image conversion panel of the present invention can be manufactured inexpensively and stably.

The present invention is extremely effective and industrially useful.

[Brief description of drawings]

FIG. 1 (a) is a sectional view showing a part of a radiation image conversion panel of an example of the present invention. FIG. 1 (b) is a sectional view showing a part of a radiation image conversion panel of another example of the present invention. 2 (a), (b) and (c) are examples of plan views showing a part of the radiation image conversion panel of the present invention. FIG. 3 (a) is a diagram showing the stimulable phosphor layer thickness and deposition amount and radiation sensitivity of the radiation image conversion panel of one example of the present invention, and FIG. 3 (b) is a spatial frequency and modulation transfer function (MTF). ) Is a diagram showing a relationship with FIG. FIG. 4 is a schematic diagram of a radiation image conversion device in which the panel of the present invention is used. FIG. 5 (a) is a diagram showing the stimulable phosphor layer thickness and deposition amount and radiation sensitivity in a conventional radiation image conversion panel, and FIG. 5 (b) is a stimulability in the conventional radiation image conversion panel. It is a figure which shows a phosphor layer thickness and a modulation transfer function (MTF) in case spatial frequency is 2 cycles / mm. 11 …… Support 12 …… Photostimulable phosphor layer 13 …… Crack 14 …… Protective layer 21 …… Photostimulable phosphor layer 22 …… Fine column block 23 …… Crack 31 …… Radiation image of the present invention Characteristics of conversion panel 32 …… Characteristics of radiation image conversion panel having fine columnar block structure 33 …… Characteristics of conventional radiation image conversion panel 41 …… Radiation generator 42 …… Subject 43 …… Radiation image conversion panel 44 …… Photostimulated excitation light source 45 …… Photoelectric conversion device 46 …… Image playback device 47 …… Image display device 48 …… Filter

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Fumio Shimada 1 Sakura-cho, Hino-shi, Tokyo Konishi Roku Photo Industrial Co., Ltd. Judge Tamura (56) Reference JP-A-59-202100 (JP, A) Special Kai 59-60300 (JP, A) JP 57-7051 (JP, A) JP 54-120576 (JP, A) JP 51-131264 (JP, A) Actual 48-56971 JP, U)

Claims (1)

[Claims] 1. A photostimulable phosphor layer for storing radiation image information on a support, and photostimulable fluorescent light when photostimulable excitation light is incident on the photostimulable phosphor layer from the upper surface side. In the radiation image conversion panel which emits the radiation image information stored in the body layer as the stimulated emission to the upper surface side, the stimulable phosphor layer is formed by deposition of the stimulable phosphor by a vapor deposition method. hand,
A radiation image conversion panel comprising a net-like crack on the upper surface side that is cut in the layer thickness direction, and the crack is filled with a substance having a high light reflectance or a high light absorption rate.