JPH0689329B2 - Radiation image conversion method and radiation image conversion panel applied to the method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a radiation image conversion method and a radiation image conversion panel used in the method, and more specifically, a radiation image conversion method using a stimulable phosphor and The present invention relates to a radiation image conversion panel used in the method.

(Background of the Invention) Conventionally, a so-called radiographic method, which uses a silver salt to obtain a radiographic image, has been used, but a method of imaging a radiographic image without using the silver salt has been desired.

As an alternative to the radiographic method described above, the phosphor that absorbs the radiation that has passed through the subject is absorbed, and then the phosphor is excited with a certain energy to reduce the radiation energy accumulated in the phosphor. A method has been considered in which it is emitted as stimulated emission, and this stimulated emission is detected to form an image. As a specific method, a method of using a thermostimulable phosphor as a phosphor and converting a radiation image by using thermal energy as photostimulation excitation energy has been proposed (UK Patent 1,46
2,769 and JP-A-51-29889). This conversion method uses a radiation image conversion panel in which a thermostimulable phosphor layer is formed on a support, and the thermostimulable phosphor layer of this panel absorbs the radiation transmitted through the subject to reduce the intensity of the radiation. The radiation energy corresponding to the above is accumulated, and then the accumulated radiation energy is extracted as a light signal by heating the thermostimulable phosphor layer, and an image is obtained by the intensity of this light. However, since this method heats the accumulated radiation energy when converting it into a signal of light, it is absolutely necessary that the panel has heat resistance and is not deformed or deteriorated by heat. There are major restrictions on the materials of the exhaustive fluorescent layer and the support. As described above, the radiation image conversion method using the thermal stimulable phosphor as the phosphor and the thermal energy as the stimulating excitation energy has a great difficulty in application. on the other hand,
Using a panel having a photostimulable phosphor layer formed on a support,
Radiation image conversion methods using one or both of visible light and infrared light as stimulated excitation energy are also known (US Pat. No. 3,859,527). This method does not require heating when converting the stored radiation energy into a light signal as in the above method, and therefore, the panel does not need to have heat resistance. I can say.

Conventionally, as the thermostimulable phosphor among the phosphors used in the radiation image conversion method, LiF: Mg, BaSo ₄ : Mn, CaF ₂ : Dy
Are known, and as a photostimulable phosphor, KCl:
Tl, BaFX: Fu system (X: Cl, Br, described in JP-A-59-75200)
I) Fluorescent materials are known.

By the way, when the radiation image conversion method is used for X-ray image conversion for the purpose of medical diagnosis, it is desirable that the method has high sensitivity as much as possible in order to reduce a patient's exposure dose. It is desirable that the stimulable phosphor heat and photostimulable phosphor to be emitted have as high a luminance as possible due to excitation by stimulus.

Further, in the above method, in order to improve the operation efficiency as a system, it is necessary to increase the reading speed of the radiation image, and therefore the stimulable phosphor used in the method is a stimulable luminescent material for stimulated stimulating light. It is desirable that the response speed is fast.

Further, in the above method, the radiation image conversion panel is generally used repeatedly after erasing the afterimage caused by the previous use, but the remaining line erasing time of the radiation image conversion panel is short in order to improve the operation efficiency of the system. It is desirable that the stimulable phosphor used in the method has a high afterimage erasing speed.

However, the stimulable phosphor is not sufficiently satisfactory in all of the stimulated emission luminance, the response speed of the stimulated emission and the afterimage erasing speed, and improvements thereof are desired.

Further, in the above method, it is desirable that the reader for reading the radiation image is small, low-priced, and simple.
For that purpose, it is indispensable to use a semiconductor laser as a photostimulable excitation light source rather than a gas laser such as Ar ⁺ laser or He-Ne laser. Therefore, the photostimulable phosphor used in the method is a semiconductor laser. It is desirable to have a stimulated excitation spectrum adapted to the oscillation wavelength of 750 nm or more.

However, the stimulable phosphor exhibits almost no stimulated emission with respect to the oscillation wavelength of the semiconductor laser, and it is desired to extend the wavelength of the stimulated excitation spectrum.

(Object of the Invention) The present invention makes a photostimulable phosphor absorb the radiation transmitted through a subject, and then the photostimulable phosphor is converted into visible light and / or
Alternatively, by exciting with an electromagnetic wave in the infrared range, the radiation energy accumulated in the stimulable phosphor is released as stimulated emission, and in the radiation image conversion method for detecting this stimulated emission, higher brightness is obtained. An object of the present invention is to provide a highly sensitive radiation image conversion method using a stimulable phosphor that exhibits stimulated emission.

Another object of the present invention is to provide a high-speed readable radiation image conversion method using a stimulable phosphor having a fast response speed of stimulated emission to stimulated excitation light.

It is another object of the present invention to provide a radiation image conversion method using a stimulable phosphor having a high afterimage erasing speed during repeated use and having a short afterimage erasing time.

A further object of the present invention is to provide a radiation image conversion method in which a semiconductor laser can be used as a stimulated excitation light source using a stimulable phosphor having a stimulated excitation spectrum expanded to the near infrared region.

It is another object of the present invention to provide a radiation image conversion panel that satisfies the above object.

(Structure of the Invention) The present inventors have conducted various studies on stimulable phosphors that exhibit high-intensity stimulated emission in accordance with the object of the present invention and have a stimulated excitation spectrum expanded to the near infrared region. The photostimulable phosphor containing the alkali halide phosphor represented by the following general formula (I) absorbs the radiation transmitted through the subject or emitted from the subject, and thereafter, the phosphor is converted into visible light. And a radiation image conversion method which is characterized by detecting the stimulated luminescence by exciting the radiant energy accumulated in the phosphor by exciting it with an electromagnetic wave selected from infrared rays, and radiating the stimulated luminescence. The filling radiographic image conversion panel achieves the objects of the invention.

General formula ^{(I) M I X · aM} II ▲ X '2 ▼: bTl However, M ^I is at least one alkali metal selected Na, K, from Rb and Cs.

M ^II is at least one divalent metal selected from Zn, Cd, Cu and Ni.

X and X'are at least 1 selected from F, Cl, Br and I
Seed halogen. Further, a is a numerical value in the range of 0 <a ≦ 4.0, and b is a numerical value in the range of 0 <b ≦ 0.2.

That is, the photostimulable phosphor of the composition according to the present invention shows a higher intensity of photostimulable luminescence than the conventionally known photostimulable phosphor when excited by electromagnetic waves in the visible to infrared region, and in the near infrared region. In particular, a highly sensitive radiation image conversion method can be obtained practically.

The radiation image conversion method of the present invention is carried out in a form using a radiation image conversion panel containing the stimulable phosphor of the general formula (I).

The radiation image conversion panel basically comprises a support and at least one photostimulable phosphor layer provided on one or both sides of the support. Further, generally, a protective layer for chemically or physically protecting the stimulable phosphor layer is provided on the surface of the stimulable phosphor layer opposite to the support. That is, the radiation image conversion method of the present invention is a radiation image conversion consisting essentially of a support and at least one photostimulable phosphor containing the photostimulable phosphor provided on the support. In a panel, at least one layer of the photostimulable phosphor layer contains a photostimulable phosphor represented by the general formula (I). It

The photostimulable phosphor of the general formula (I) absorbs radiation such as X-rays and then emits light in the visible or infrared region, preferably 50
When it is irradiated with light in the wavelength region of 0 to 900 nm (stimulated excitation light), it exhibits stimulated emission. Therefore, the irradiation line transmitted through the subject or emitted from the subject is absorbed by the photostimulable phosphor contained in the photostimulable phosphor layer of the radiation image conversion panel in proportion to the radiation dose, A subject or a radiation image of the subject is formed on the radiation image conversion panel as a latent image in which radiation energy is accumulated. This latent image is 50
By exciting with stimulated excitation light in the wavelength region of 0 nm or more, stimulated emission is shown in proportion to the accumulated radiation energy, and by photoelectrically reading this stimulated emission, the latent image with accumulated radiation energy is visible. It becomes possible to image.

The present invention will be described in detail below.

FIG. 1 shows the response characteristics of the photostimulable phosphor represented by the general formula (I) used in the radiation image conversion method of the present invention to the photostimulable excitation light used in the conventional method. Shown in comparison to the body.

In FIG. 1, (a) shows the response characteristics of the stimulable phosphor used in the radiation image conversion method of the present invention to the stimulated excitation light, and (b) and (c) show the luminescence used in the conventional method. It is the response characteristics of the exhaustive fluorescent materials BaFBr: Eu and BaFCl: Eu. The broken line shows the state of stimulated excitation light whose intensity changes into a rectangular shape.

As is clear from FIG. 1, the photostimulable phosphor used in the radiation image conversion method of the present invention has a remarkably excellent response characteristic to photostimulation excitation light, and the read speed of the radiation image can be changed to that of the conventional method. It is possible to speed up by comparison.

FIG. 2 compares the residual line erasing characteristics of the photostimulable phosphor represented by the general formula (I) used in the radiation image conversion method of the present invention with those of the photostimulable phosphor used in the conventional method. Indicate.

In FIG. 2, (d) shows that after irradiating a certain amount of radiation to the photostimulable phosphor used in the radiation image conversion method of the present invention,
The decay characteristic of the stored energy when the stored energy is erased by the light of a tungsten lamp was obtained by exciting the semiconductor laser (780 nm) to detect the stimulated emission luminance, and (e) is the stimulated excitation. Attenuation characteristics of accumulated energy when measured in the same manner as described above except that a He-Ne laser (633 nm) is used instead of a semiconductor laser as a light source. (F) and (g) are used in the conventional method. It is the decay characteristic of the stored energy when the He—Ne laser (633 nm) is used as the photostimulable excitation light source for the photostimulable phosphors BaFBr: Eu and BaFCl: Eu in the same manner as described above.

As is clear from FIG. 2, the stimulable phosphor used in the radiation image conversion method of the present invention has accumulated energy (afterimage).
Since the decay speed is high, it is possible to shorten the afterimage erasing time as compared with the conventional method.

FIG. 3 shows an outline of an embodiment example in which the stimulable phosphor represented by the general formula (I) is used in the form of a radiation image conversion panel in the radiation image conversion method of the present invention.

In FIG. 3, 11 is a radiation generator, 12 is a subject, and 13 is a radiation image having a visible or infrared photostimulable phosphor layer containing the photostimulable phosphor represented by the general formula (I). Conversion panel, 14 is a stimulated excitation light source for emitting the radiation latent image of the radiation image conversion panel 13 as stimulated emission, 15 is a photoelectric conversion device for detecting the stimulated emission emitted from the radiation image conversion panel 13, 16 Is a device for reproducing the photoelectric conversion signal detected by the photoelectric conversion device 15 as an image, 17 is a device for displaying the reproduced image, 18 is a device for cutting the reflected light from the light source 14, and emitted from the radiation image conversion panel 13. It is a filter for transmitting only the light. Although FIG. 3 shows an example of obtaining a radiation transmission image of a subject, the radiation generator 11 is not particularly required when the subject 12 itself emits radiation. Further, the photoelectric conversion device 15 and the subsequent devices may be any device that can reproduce the optical information from the radiation image conversion panel 13 as an image in some form, and are not limited to the above. As shown in FIG. 3, when the subject 12 is arranged between the radiation generator 11 and the radiation image conversion panel 13 and is irradiated with the radiation, the radiation is transmitted according to the change in the radiation transmittance of each part of the subject 12, and the transmission thereof is performed. An image (that is, an image of the intensity of radiation) is incident on the radiation image conversion panel 13. This incident transmission image is absorbed by the photostimulable phosphor layer of the radiation image conversion panel 13, whereby a number of electrons and / or holes proportional to the amount of radiation absorbed in the photostimulable phosphor layer. Is generated, and this is accumulated in the trap level of the photostimulable phosphor. That is, a latent image is formed by accumulating the energy of the radiation transmission image. Next, this latent image is excited by light energy to become visible. That is, a light source 14 that emits light in the visible or infrared region irradiates the photostimulable phosphor layer to expel the electrons and / or holes accumulated at the trap level,
The accumulated energy is emitted as stimulated emission.
The intensity of the emitted stimulated emission is proportional to the number of accumulated electrons and / or holes, that is, the intensity of the radiation energy absorbed in the stimulable phosphor layer of the radiation image conversion panel 13, This optical signal is converted into an electric signal by a photoelectric conversion device 15 such as a photomultiplier tube, reproduced by an image processing device 16 as an image, and displayed by the image display device 17. It is more effective if the image processing device 16 uses not only an electric signal to be reproduced as an image signal but also a so-called image processing, image calculation, image storage and storage.

When excited by light energy in the method of the present invention,
It is necessary to separate the reflected light of the photostimulable excitation light from the photostimulated luminescence emitted from the photostimulable phosphor layer, and a photoelectric converter that receives the light emitted from the photostimulable phosphor layer. Is generally 600n
The photostimulable luminescence emitted from the photostimulable phosphor layer preferably has a spectral distribution in the short wavelength region as much as possible, because the sensitivity to light energy of a short wavelength of m or less is high. The emission wavelength range of the stimulable phosphor used in the method according to the present invention is 300 to 500 nm, while the excitation wavelength range of the stimulable phosphor is 500 to 900 nm, which simultaneously satisfy the above conditions.

That is, the stimulable phosphors used in the present invention both show emission having a main peak at 500 nm or less, because it is easy to separate from the stimulable excitation light and well coincides with the spectral sensitivity of the light receiver, As a result of efficient light reception, the sensitivity of the image receiving system can be increased.

As the stimulated excitation light source 14 used in the method of the present invention, a light source containing the stimulated excitation wavelength of the stimulable phosphor used in the radiation image conversion panel 13 is used. In particular, when a laser beam is used, the optical system becomes simple, and the intensity of stimulated excitation light can be increased, so that the stimulated emission efficiency can be increased and more preferable results can be obtained. As a laser, He
-Ne laser, He-Cd laser, Ar ion laser, Kr ion laser, N ₂ laser, YAG laser and its second harmonic, ruby laser, semiconductor laser, various dye lasers, metal vapor lasers such as copper vapor laser, etc. There is. Normally, a continuous wave laser such as a He-Ne laser or an Ar ion laser is desirable, but a pulsed laser can be used if the scanning time of one pixel on the panel is synchronized with the pulse. Further, in the case of the method of separating by utilizing the delay of light emission shown in JP-A-59-22046 without using the filter 18, it is preferable to use a pulse oscillation laser rather than modulation using a continuous oscillation laser. preferable.

Among the various laser light sources described above, the semiconductor laser is particularly preferable because it is small and inexpensive, and a modulator is unnecessary.

Since the filter 18 transmits the stimulated emission emitted from the radiation image conversion panel 13 and cuts the stimulated excitation light, this is the luminescence of the stimulable phosphor contained in the radiation image conversion panel 13. It is determined by a combination of the exhaust emission wavelength and the wavelength of the stimulated excitation light source 14.

For example, the stimulated excitation wavelength is 500 to 900 nm and the stimulated emission wavelength is 30.
In the case of a practically preferable combination such as 0 to 500 nm,
As the filter, for example, Toshiba Corporation C-39, C-40, V-40, V
-42, V-44, Corning 7-54, 7-59, Spectrofilm BG-1, BG-3, BG-25, BG-37, BG-38, etc. Can be used. or,
When the interference filter is used, a filter having arbitrary characteristics can be selected and used to some extent.

The photoelectric conversion device 15 may be a photoelectric tube, a photomultiplier tube, a photodiode, a phototransistor, a solar cell, a photoconductive element, or any other device capable of converting a change in the amount of light into a change in an electric signal.

Next, the radiation image conversion panel used in the radiation image conversion method of the present invention will be described.

As described above, the radiation image conversion panel comprises a support and at least one stimulable phosphor layer containing the stimulable phosphor represented by the general formula (I) provided on the support. Composed of.

Since the photostimulable phosphor represented by the general formula (I) has high photostimulated luminescence brightness, M ^I in the general formula (I) is at least one alkali selected from Na, K, Rb and Cs. A metal is preferable, and at least one alkali metal selected from Rb and Cs is particularly preferable. As X ', at least one halogen selected from F, Cl and Br is preferable. The value a representing the content of M ^II ▲ X ^′ ₂ ▼ and the value b representing the content of the activating metal Tl were 0 <a.
It is preferably selected from the range of ≦ 4.0 and 0 <b ≦ 0.2. When the value of a is a> 4.0, the stimulated emission luminance sharply decreases, which is not particularly preferable.

Stimulable phosphor according to the present invention ^{M I X · aM II ▲ X} '2 ▼: bTl
Is manufactured, for example, by the manufacturing method described below.

First, as the stimulable phosphor raw material, I) NaF, NaCl, NaBr, NaI, KF, KCl, KBr, KI, RbF, RbCl, RbB
one or more of r, RbI, CsF, CsCl, CsBr, CsI, II) ZnF ₂ , ZnCl ₂ , ZnBr ₂ , ZnI ₂ , CdF ₂ , CdCl ₂ , CdBr ₂ , CdI ₂ ,
One or more of CuF ₂ , CuCl ₂ , CuBr ₂ , CuI, NiF ₂ , NiCl ₂ , NiBr ₂ , and NiI ₂ , and III) Tl compound group activator raw material is used.

Stoichiometric formula M represented by ^{(I) I X · aM II} ▲ X '2 ▼: In bTl, 0 <a ≦ 4 good preferably 0 <a <1.0, 0 < b ≦ 0.2 preferably 10 ^The raw materials for the stimulable phosphor of the above I) to III) are weighed so that a mixed composition of ^-6 <b <0.1 is obtained, and sufficiently mixed using a mortar, a ball mill, a mixer mill and the like.

Next, the obtained mixture of stimulable phosphor raw materials is filled in a heat-resistant container such as a quartz crucible or an alumina crucible and baked in an electric furnace. A firing temperature of 500 to 1000 ° C is suitable.
The firing time varies depending on the filling amount of the raw material mixture, the firing temperature, etc., but is generally 0.5 to 6 hours. The firing atmosphere includes a nitrogen gas atmosphere containing a small amount of hydrogen gas, a weak reducing atmosphere such as a carbon dioxide gas atmosphere containing a small amount of carbon monoxide, a neutral atmosphere such as a nitrogen gas atmosphere or an argon gas atmosphere, or a small amount of oxygen gas. A weakly oxidizing atmosphere is preferred. After firing once under the above firing conditions, the fired product is taken out of the electric furnace and crushed, and then the fired product powder is charged again in a heat resistant container and placed in an electric furnace, and refired under the same firing conditions as above. By performing the above, the emission brightness of the fluorescent substance can be further increased. Further, when cooling the fired product to room temperature from the firing temperature, the desired stimulable phosphor can be obtained by taking out the fired product from the electric furnace and allowing it to cool in the air. It may be cooled in a weak reducing atmosphere or a neutral atmosphere. Further, by moving the fired product from the heating unit to the cooling unit in the electric furnace and quenching it in a weak reducing atmosphere, a neutral atmosphere or a weak oxidizing atmosphere, the stimulable phosphor obtained is stimulated. It is possible to further increase the light emission brightness.

The photostimulable phosphor obtained by calcination is crushed and then treated by various operations generally used in phosphor production such as washing, drying and sieving to treat the photostimulable phosphor. Get the body.

The average particle size of the stimulable phosphor used in the radiation image conversion panel 13 of the present invention is usually in the range of 0.1 to 100 μm in consideration of the sensitivity and granularity of the radiation image conversion panel 13. It is selected appropriately. More preferably, those having an average particle diameter of 1 to 30 μm are used.

In the radiation image conversion panel 13 of the present invention, generally, the photostimulable phosphor of the present invention is dispersed in a suitable binder and applied to a support. Examples of the binder include proteins such as gelatin, polysaccharides such as dextran or gum arabic, polyvinyl butyral, polyvinyl acetate, nitrocellulose, ethyl cellulose,
Binders usually used for layer formation are used, such as vinylidene chloride-vinyl chloride copolymer, polymethylmethacrylate, vinyl chloride-vinyl acetate copolymer, polyurethane, cellulose acetate butyrate, polyvinyl alcohol and the like.

Generally, the binder is 0.01 parts by weight relative to 1 part by weight of the photostimulable phosphor.
Used in the range of up to 1 part by weight. However, in terms of the sensitivity and sharpness of the obtained radiation image conversion panel 13, it is preferable that the amount of the binder is small, and in view of the ease of application, the range of 0.03 to 0.2 parts by weight is more preferable.

Next, as an example of a method of manufacturing the radiation image conversion panel 13, a method of applying a phosphor coating solution will be described below.

First, the pulverized photostimulable phosphor powder, a binder and a solvent are mixed and sufficiently kneaded to prepare a coating liquid in which the photostimulable phosphor is uniformly dispersed.

The solvent, methanol, ethanol, n-propanol, lower alcohols such as n-butanol, methylene chloride, chlorine-containing hydrocarbons such as ethylene chloride, acetone, methyl ethyl ketone, ketones such as methyl isobutyl ketone, methyl acetate, Examples thereof include lower esters such as ethyl acetate and butyl acetate, and ethers such as dioxane, ethylene glycol monomethyl ether and ethylene glycol monoethyl ether. These solvents may be mixed and used.

Further, various useful agents such as a dispersant for complementing the dispersibility of the photostimulable phosphor in the coating liquid or a plasticizer for ensuring the retention of the phosphor particles in the binder after coating and drying. The additive may be added.

Examples of the dispersant include phthalic acid, stearic acid, caproic acid, and lipophilic surfactants.

Examples of the plasticizer include triphenyl phosphate, tricresyl phosphate, diphenyl phosphate, and other phosphoric acid esters, diethyl phthalate, dimethoxyethyl phthalate, and other phthalic acid esters, ethyl phthalyl glycolate, butyl phthalacryl butyl glycolate, and the like. Examples thereof include polyethylene glycol-aliphatic dibasic acid polyesters such as triethylene glycol-adipic acid polyester and diethylene glycol-succinic acid polyester.

The coating solution prepared as described above is uniformly coated on the support by a commonly used coating method such as a roll coater method or a blade doctor method to form a stimulable phosphor layer.

As the support used in the present invention, various synthetic resin sheets (for example, sheets of cellulose acetate, polyester, polyethylene terephthalate, polyamide, polyimide, triacetate, polycarbonate, etc.), various metal sheets (for example, sheets of aluminum, aluminum alloy, etc.), various Examples thereof include paper sheets (for example, sheets such as baryta paper, resin-coated paper and pigment paper).

The dry thickness of the photostimulable phosphor layer varies depending on the purpose of use of the radiation image conversion panel, the type of the photostimulable phosphor, the mixing ratio of the binder and the photostimulable phosphor, and the like. Generally, 10 μm to 1000 μm is suitable, preferably 80 μm
m to 600 μm.

In order to enhance the sharpness of the image formed on the radiation image conversion panel 13, white powder is dispersed in the photostimulable phosphor layer as described in, for example, JP-A-55-146447. Alternatively, as described in JP-A-55-163500, a stimulable phosphor may be prepared by dispersing a colorant capable of absorbing stimulable excitation light in the stimulable phosphor layer. It may be appropriately colored in order to enhance the sharpness of the image of the layer and to absorb the stimulated excitation light. Furthermore, this radiation image conversion panel
JP-A-56-1139 for the purpose of improving the sharpness and sensitivity of 13
As disclosed in No. 3, a light reflecting layer may be provided between the support and the stimulable phosphor layer.

Further, the photostimulable phosphor layer according to the present invention may be formed by a vapor deposition method.

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 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 synthesize the desired photostimulable phosphor on the support and simultaneously stimulate the photostimulable phosphor. It is also possible to form a fluorescent layer.

Further, in the vapor deposition method, the vapor deposition target (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
Reactive vapor deposition may be performed by introducing a gas such as O ₂ or H ₂ .

In the sputtering method as the second method, as in the vapor deposition method, after the support is set in the sputtering apparatus, the inside of the apparatus is temporarily evacuated to a vacuum degree of about 10 ^-6 Torr, and then Ar is used as a gas for sputtering. Then, an inert gas such as 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 process, various applied treatments can be used as in the vapor deposition method.

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

The deposition rate of the stimulable phosphor layer in the vapor deposition is preferably 0.05 μm / min to 300 μm / min. 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. In addition, the deposition rate
When it exceeds 300 μm / min, it is difficult to control the deposition rate, which is not preferable.

The radiation image conversion panel of the present invention, the vacuum deposition method described above,
When obtained by a sputtering method or the like, since no binder is present, the packing density of the photostimulable phosphor can be increased, and a radiation image conversion panel that is preferable in terms of sensitivity and resolution can be obtained.

In the radiation image conversion panel of the present invention, generally, on the surface opposite to the surface on which the support of the stimulable phosphor layer is provided, a stimulable phosphor layer is physically or chemically A protective layer may be provided for protection. This protective layer is
It may be formed by directly coating the protective layer coating solution on the photostimulable phosphor layer, or a separately formed protective layer may be adhered onto the photostimulable phosphor layer. Alternatively, a procedure of forming a stimulable phosphor layer on a separately formed protective layer may be performed. Materials for the protective layer include cellulose acetate, nitrocellulose, polymethylmethacrylate, polyvinyl butyral, polyvinyl formal, polycarbonate, polyester, polyethylene terephthalate, polyethylene, polyvinylidene chloride, nylon, polytetrafluoroethylene, polytrifluoroethylene chloride. Ordinary protective layer materials such as ethylene tetrafluoride-hexafluoropropylene copolymer, vinylidene chloride-vinyl chloride copolymer, vinylidene chloride-acrylonitrile copolymer and the like are used. In addition, this protective layer is made of SiC, Si
It may be formed by stacking inorganic substances such as O ₂ , SiN, and Al ₂ O ₃ . The thickness of these protective layers is generally 0.1 μm to 100 μm.
A degree is preferable.

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

Example 1 Each stimulable phosphor raw material was weighed as shown in the following (1) to (19) and then thoroughly mixed using a ball mill.
A mixture of different photostimulable phosphor raw materials was prepared.

Next, each of the above 19 kinds of stimulable phosphor raw material mixture was packed in a quartz boat and placed in an electric furnace for firing. Firing 10
Nitrogen gas containing a volume% of oxygen gas was flowed at a flow rate of 500 cc / min for 2 hours at 650 ° C., and then cooled to room temperature.

After crushing the obtained fired product using a ball mill, 150
The particles were sieved with a mesh sieve to make the particle diameter uniform, and each photostimulable phosphor was obtained.

Next, a radiation image conversion panel of the present invention was manufactured using the above-mentioned 19-type photostimulable phosphor. Each radiation image conversion panel was manufactured as follows.

First, 8 parts by weight of the photostimulable phosphor are dispersed in a solvent in which 1 part by weight of polyvinyl butyral (binder) is mixed with an equal amount of acetone and ethyl acetate, and this is placed horizontally. A polyethylene terephthalate film (support) ) A radiation image conversion panel of the present invention having a film layer thickness of about 300 μm was prepared by uniformly coating the above with a wire bar and naturally drying.

These 19 types of radiation image conversion panels according to the present invention were applied to a tube voltage of 80 KVp and a tube current of 100 m at a distance of 100 cm from the X-ray tube focus.
After irradiating the X-ray of A for 0.1 seconds, this was excited with a semiconductor laser beam (780 nm, 10 mW), and the emission due to the photostimulation emitted from the photostimulable phosphor layer was measured with a photodetector. The results are shown in Table 1.

Comparative Example 1 Example BaF ₂ stimulable phosphor raw material in 1 175.4G (1 _{mol), BaBr 2 · 2H 2 O333.3g} (1 mol) and Eu ₂ O ₃ 0.352 g
A photostimulable phosphor BaFBr: 0.001Eu was obtained in the same manner as in Example 1 except that the amount was (0.001 mol). Using this stimulable phosphor, a comparative radiation image conversion panel was prepared in the same manner as in Example 1, and the stimulated emission luminance was measured using a semiconductor laser (780 nm, 10 mW). The results are also shown in Table 1.

Comparative Example 2 Instead of using the semiconductor laser in Comparative Example 1, He-Ne
The stimulated emission luminance was measured in the same manner as in Comparative Example 1 except that a laser (633 nm, 10 mW) was used. The results are also shown in Table 1.

From Table 1, the stimulated emission luminance of the radiation image conversion panel of the present invention produced using the stimulable phosphors of Samples (1) to (19) according to the present invention is shown in Comparative Example 1, Significantly higher than the stimulated emission brightness measured under the same conditions of the comparative radiographic image conversion panel made with the conventional photostimulable phosphor BaFBr: Eu, and therefore the invention using the radiographic image conversion panel of the invention. The radiation image conversion method of 1 was higher in sensitivity than the conventional radiation image conversion method using the comparative radiation image conversion panel.

By the way, the conventional photostimulable phosphor Ba taken up in Comparative Example 1 was used.
FBr: Eu has a peak wavelength of the stimulated excitation spectrum around 600 nm, and the He-Ne laser light (633n
m) is said to be particularly preferable (JP-A-55-15025).
etc). Therefore, regarding the comparative radiation image conversion panel manufactured using BaFBr: Eu, in the measurement method of the stimulated emission luminance, the semiconductor laser (780 nm) was replaced by the He-Ne laser (63
3 nm), and otherwise measured under the same conditions as Comparative Example 2
As shown in Table 1 above, the comparative radiation image conversion panel had lower stimulated emission luminance than any of the radiation image conversion panels of the present invention. Therefore, the radiation image conversion method of the present invention using the radiation image conversion panel of the present invention, since the semiconductor laser can be used as a stimulated excitation light source, He-Ne
Compared with the conventional radiation image conversion method using a laser, it can be downsized and has high sensitivity.

Example 2 Photostimulable phosphors (1), (2) prepared in Example 1,
After the radiation image conversion panel of the present invention using (4), (6), (10), (15), (18) and (19) was irradiated with X-rays as in Example 1, the intensity was rectangular. A He-Ne laser as an excitation light that changes in shape was irradiated for 10 μsec, and the change in luminance of photostimulated luminescence emitted from the photostimulable phosphor layer was measured by a photodetector. The time required for the change in luminance of stimulated emission to change from 10% to 90% was determined as the response speed of the stimulable phosphor to the stimulated excitation light and is shown in Table 2.

Comparative Example 3 The response speed was obtained in the same manner as in Example 2 except that the comparative radiation image conversion panel prepared in Comparative Example 1 was used instead of the radiation image conversion panel of the present invention.

The results are shown in Table 2.

From Table 2, the photostimulable phosphor according to the present invention has a response speed which is about 3 times or more faster than that of the comparative photostimulable phosphor, and the radiation image conversion using the photostimulable phosphor according to the present invention. It is possible to increase the read speed of the radiographic image in the method by a factor of 3 or more than when using a comparative photostimulable phosphor.

Example 3 The radiation image conversion panel of the present invention used in Example 2 was irradiated with X-rays in the same manner as in Example 1, and then the stored energy was erased with a halogen lamp of 10,000 lux for 10 seconds. Next, this was stimulated with a semiconductor laser (780 nm, 10 mW) to measure the stimulated emission luminance emitted from the stimulable phosphor layer with a photodetector. The measurement results are shown in Table 3 with the stimulated emission luminance before erasing by the halogen lamp as 1.

Example 4 The stimulated emission luminance was measured in the same manner as in Example 3 except that a He-Ne laser (533 nm, 10 mW) was used instead of the semiconductor laser. As in Example 3, the measurement results are shown in Table 3 with the stimulated emission luminance before erasing by the halogen lamp being 1.

Comparative Example 4 The stimulated emission luminance was measured in the same manner as in Example 4 except that the comparative radiation image conversion panel prepared in Comparative Example 1 was used instead of the radiation image conversion panel of the present invention. . As in Example 4, the measurement results are shown in Table 3 with the stimulated emission luminance before erasing by the halogen lamp as 1.

From Table 3, the photostimulable phosphor according to the present invention has an erase speed of accumulated energy (afterimage) of about 10 as compared with the comparative photostimulable phosphor.
00 times or more faster, it is possible to reduce the afterimage erasing time in the radiation image conversion method using the stimulable phosphor according to the present invention to 1/1000 or less than when using the comparative stimulable phosphor. is there.

(Effects of the Invention) As described above, since the stimulable phosphor according to the present invention has high sensitivity to radiation, when the radiation image conversion method of the present invention is used for X-ray diagnosis or the like, X-rays of a subject are detected. It is possible to reduce the exposure dose.

Further, the photostimulable phosphor according to the present invention has a high response speed to photostimulable excitation light and a high erase speed of accumulated energy (afterglow). Therefore, the radiographic image reading speed in the radiographic image conversion method of the present invention is increased, and afterimage It is possible to improve the operation efficiency of the system by shortening the erase time.

Furthermore, since the stimulated excitation spectrum of the stimulable phosphor according to the present invention is extended to the oscillation wavelength region of the semiconductor laser, it is possible to perform the stimulated excitation by the semiconductor laser and downsize the radiation image reading device. It is possible to reduce the price and simplify it.

[Brief description of drawings]

FIG. 1 is a diagram showing the response characteristics of a stimulable phosphor. FIG. 2 is a diagram showing the afterimage erasing characteristics of the stimulable phosphor. FIG. 3 is an explanatory diagram showing an outline of an example of an embodiment of the method of the present invention. 11 …… Radiation generator 12 …… Subject 13 …… Radiation image conversion panel 14 …… Stimulated excitation light source 15 …… Photoelectric converter 18 …… Filter

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Fumio Shimada 1 Sakura-cho, Hino-shi, Tokyo Konishi Roku Photo Co., Ltd. Hideji Sasaki Examiner

Claims (10)

[Claims] 1. Radiation transmitted through or emitted from a subject is absorbed by at least one of the stimulable phosphors represented by the following general formula (I), and then this stimulable phosphor is used. A radiation image conversion method, characterized in that it is excited by an electromagnetic wave selected from visible light and infrared light to emit radiation energy accumulated in a stimulable phosphor as stimulated emission, and the stimulated emission is detected. . General formula ^{(I) M I X · aM} II X '2: bTl [ However, ^{M I} is at least one alkali metal selected Na, K, from Rb and Cs. M ^II is Zn, Cd, Cu and Ni
It is at least one divalent metal selected from X and X'are at least one halogen selected from F, Cl, Br and I. Further, a is a numerical value in the range of 0a ≦ 4.0, and b is a numerical value in the range of 0 <b ≦ 0.2. ] 2. A in the general formula (I) is 0a ≦ 1.
The radiation image conversion method according to claim 1, wherein the radiation image conversion method is 0. 3. M ^I in the general formula (I) is Rb and Cs.
The radiation image conversion method according to claim 1 or 2, wherein the method is at least one kind of alkali metal selected from the group consisting of: 4. The radiation image conversion method according to claim 1, wherein X in the general formula (I) is at least one kind of halogen selected from Br and I. 5. The radiation image conversion method according to claim 1, wherein the electromagnetic wave is laser light. 6. The radiation image conversion method according to claim 1, wherein the laser light is a semiconductor laser. 7. A radiation image conversion panel comprising a support and at least one photostimulable phosphor layer provided on the support, wherein at least one of the phosphor layers has the following general formula (I): A radiation image conversion panel comprising a phosphor represented by: General formula ^{(I) M I X · aM} II X '2: bTl [ However, ^{M I} is at least one alkali metal selected Na, K, from Rb and Cs. M ^II is Zn, Cd, Cu and Ni
It is at least one divalent metal selected from X and X'are at least one halogen selected from F, Cl, Br and I. Further, a is a numerical value in the range of 0a ≦ 4.0, and b is a numerical value in the range of 0 <b ≦ 0.2. ] 8. A in the general formula (I) is 0a ≦ 1.
The radiation image conversion panel according to claim 7, wherein the radiation image conversion panel is 0. 9. M ^I in the formula (I) is Rb and Cs
9. The radiation image conversion panel according to claim 7, which is at least one kind of alkali metal selected from the group consisting of: 10. X in the general formula (I) is Br or I.
The radiation image conversion panel according to claim 7, wherein the radiation image conversion panel is at least one kind of halogen selected from the group consisting of: