JPH02289680A - Radiation image transformation panel - Google Patents

Abstract

PURPOSE:To obtain the subject panel, composed of a specific rare earth element oxyhalide fluorescent substance activated with cerium, a fluorescent substance layer containing the above-mentioned fluorescent substance and a protective film capable of absorbing specified light, having high sensitivity and hardly causing fogging with ultraviolet rays and visible rays within a blue color region. CONSTITUTION:The objective panel composed of (A) a fluorescent substance layer containing (i) a rare earth element oxyhalide fluorescent substance, expressed by the formula (Ln is rare earth element consisting of Y, La, Gd and/or Lu; X is Cl, Br or I; x is 0-0.2), having the ratio X/Ln of 0.500<X/Ln<=0.998 and the maximum wavelength (lambda) of excitation spectrum of accelerated phosphorescence of 550-700nm, activated with cerium and capable of exhibiting light emission of accelerated phosphorescence within the wavelength region of 350-450nm and (ii) a fluorescent substance capable of emitting light at >=450nm excited with light within the wavelength region of 350-450nm and (B) a protective film, composed of a material capable of absorbing light at <=350nm together with light at 350-450nm and placed on the component (A).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a radiation image conversion panel used in a radiation image conversion method using a stimulable phosphor.

[Technical Background of the Invention and Prior Art] As an alternative to conventional radiography, there is a radiation image conversion method using a stimulable phosphor as described in, for example, Japanese Unexamined Patent Publication No. 55-12145. Are known.

This method uses a radiation image conversion panel (also referred to as a stimulable phosphor sheet) containing a photostimulable phosphor, and uses the radiation transmitted through or emitted from the subject to convert the radiation into the stimulable phosphor of the panel. The stimulable phosphor is absorbed by the phosphor, and then exposed to electromagnetic waves (excitation light) such as visible light and infrared rays.
By excitation in a time series with
This fluorescence is photoelectrically read to obtain an electrical signal, and based on the obtained electrical signal, a radiation image of the subject or subject is reproduced as a visible image.

On the other hand, after the reading is completed, the remaining image is erased from the panel, and then the panel is prepared for the next photographing. That is, the radiation image conversion panel is used repeatedly.

According to this radiation image conversion method, it is possible to obtain a radiation image with a rich amount of information with a much lower exposure dose compared to the conventional radiography method that uses a combination of a radiographic film and an intensifying screen. It has the advantage of being possible. Furthermore, in contrast to conventional radiography, which consumes radiographic film for each imaging session, this radiographic image conversion method uses the radiographic image conversion panel repeatedly, which is advantageous in terms of resource conservation and economic efficiency. It is.

The radiation image conversion panel used in the radiation image conversion method is
The basic structure consists of a support and a stimulable phosphor layer provided on the surface of the support, but if the phosphor layer is self-supporting, the support is not necessarily required.

The stimulable phosphor layer is generally known to be composed of a stimulable phosphor and a binder that contains and supports the stimulable phosphor in a dispersed form. It is also known to be formed solely from aggregates of stimulable phosphor without containing a binder. In addition, the applicant has already filed a patent application for a radiation image conversion panel having a stimulable phosphor layer in which the gaps between aggregates of stimulable phosphor are impregnated with a polymeric substance (Japanese Patent Application Laid-Open No. 1983-1992-1). 26260
(See Publication No. 0). In any of these phosphor layers, the stimulable phosphor has the property of exhibiting stimulated luminescence when irradiated with excitation light after absorbing radiation such as X-rays. The radiation emitted from the specimen is absorbed by the stimulable phosphor layer of the radiation image conversion panel in proportion to the radiation dose, and a radiation image of the subject or subject is formed on the panel as an image of accumulated radiation energy. . This accumulated image can be emitted as stimulated luminescence light by irradiating the above excitation light, and this stimulated luminescence light is read photoelectrically and converted into an electrical signal. Based on the obtained electrical signal, radiation energy is generated. It becomes possible to reproduce the accumulated image as a visible image.

When a stimulable phosphor layer is provided on a support, a protective film is generally provided on the surface of the stimulable phosphor layer opposite to the support (the surface not facing the support). This protective film protects the phosphor layer from chemical alteration or physical impact.

The protective film can be formed by dissolving an organic polymer material such as a cellulose derivative or polymethyl methacrylate in an appropriate solvent and coating it on the phosphor layer, or a film made of polyethylene terephthalate or the like. A protective film-forming sheet such as an organic polymer film or a transparent glass plate is formed separately and placed on the phosphor layer via an adhesive layer, or an inorganic compound is formed on the phosphor layer by vapor deposition. Film-coated products are known.

When a radiation image conversion panel made of stimulable phosphor is used for radiography such as X-ray photography for the purpose of medical diagnosis, it can reduce the exposure dose to the human body or facilitate electrical processing later. Due to the need for ease of use, it is desirable that the sensitivity of the panel be as high as possible. Therefore, it is desirable that the stimulable phosphor used in the radiation image storage panel has high luminance at the point where the stimulable phosphor originates.

As a stimulable phosphor used in radiation image conversion panels,
The following formula (I): LnOX:xCe (I) (wherein Ln is at least one rare earth element selected from the group consisting of Y, La, Gd and Lu; X is from the group consisting of CIt, Br and I) A rare earth oxyhalide phosphor activated with cerium is known (Japanese Patent Publication No. 59-44339 (see publication).

This cerium-activated rare earth oxyhalide phosphor is
Cerium is activated in a host crystal having a PbFCJE type crystal structure called LnOX, which is composed of rare earth element Ln, oxygen 0, and halogen X as shown in formula (I), but the above formula (I) The notation LnOX in , indicates that the rare earth element Ln, oxygen 0, and halogen This does not indicate that it is contained in the phosphor.

Among the cerium-activated rare earth oxyhalide phosphors represented by (I) above, especially the Ln and the X
The ratio X/L n is the atomic ratio, 0.500<X/
Ln≦0.998, and the maximum wavelength λ of the photostimulated excitation spectrum is 550 nm<λ<700 nm, and 35
The cerium-activated rare earth oxyhalide phosphor that exhibits stimulated luminescence in the wavelength range from 0 nm to 450 nm has the maximum wavelength of the stimulated excitation vector on the long wavelength side, and is suitable for use as a stimulated excitation light source. -Since the oscillation wavelength matches the oscillation wavelength of Ne lasers and semiconductor lasers, it is possible to sufficiently absorb the excitation light emitted from these lasers, and it was found that the stimulated luminescence brightness is also high, reflecting or even more than that. It was done. Based on this knowledge, the applicant has proposed the above-mentioned phosphor and a radiation image conversion method using the above-mentioned phosphor,
A patent application was filed for the radiation image conversion panel on the same day as this case (
(See the specification of Japanese Patent Application No. 11).

The cerium-activated rare earth oxyhalide phosphor described in the above-mentioned Japanese Patent Application No. 11 has a high stimulated luminance, and a radiation image conversion panel using it also has high sensitivity. Since this phosphor tends to accumulate energy of ultraviolet rays or visible light in the blue region, a radiation image conversion panel using this phosphor is likely to be fogged by ultraviolet rays or visible light in the blue region. for example,
GdOCJ! : Ce (However, Cl/Gd=0.
900) A radiation image conversion panel using a phosphor is significantly fogged by light having a wavelength of 450 nm or less, as shown in FIG.

Therefore, the handling of radiation image conversion panels using the above-mentioned phosphors is limited to external light (including ultraviolet rays or visible light in the blue region).
They require special attention to sunlight (sunlight or indoor light such as fluorescent lights), and are often bothersome.

Furthermore, after reading the radiation image conversion panel, the remaining radiation image is erased by irradiation with erasing light such as fluorescent lamp light, but at this time, if the erasing light contains ultraviolet rays or visible light in the blue region. While the residual radiation image is erased, the energy of the ultraviolet rays of the erasing light or visible light in the blue region is accumulated in the stimulable phosphor, and as a result,
Fog will occur in the next radiographic image taken. Therefore, it is necessary to select a light source for erasing light that does not contain ultraviolet rays or visible light in the blue region as much as possible, and therefore only a limited number of light sources can be used.

In order to prevent fogging caused by ultraviolet rays during erasing, the applicant has already filed an application for an apparatus for erasing residual radiation images on a radiation image conversion panel, which irradiates the panel with erasing light through an ultraviolet removal filter (Unexamined Japanese Patent Publication No. (See Publication No. 63-97939).

However, even if such a special erasing device is used for erasing, the panel after erasing must still be handled in a light-shielded state until the next photographing.

Further, in the erasing device as described above, the ultraviolet ray removal filter removes even the effective erasing light to some extent, so that the erasing ability is inferior to that of a normal erasing device. Therefore, in order to perform sufficient erasing using the above-described erasing device, a stronger erasing light source than in the normal case is required, leading to an increase in the size of the device and the power consumption.

The applicant has proposed a radiation image conversion panel characterized in that a protective film, an adhesive layer, or a phosphor layer contains an ultraviolet absorber for the purpose of preventing fogging caused by ultraviolet rays contained in external light. (See the specification of Japanese Patent Application No. 63-298593.) However, in such a radiation image conversion panel, the above-mentioned cerium-activated rare earth oxyhalide phosphor is used as a stimulable phosphor. In this case, a part of the stimulated luminescence is absorbed by the ultraviolet absorber, resulting in a significant decrease in sensitivity.

[Summary of the Invention] The present invention contains a cerium-activated rare earth oxyhalide phosphor with high stimulated luminance in the phosphor layer, has high sensitivity, and is less likely to cause capriulation due to ultraviolet light and visible light in the blue region. The object of the present invention is to provide a radiation image conversion panel.

The above-mentioned object is the following formula (I) LnOX:xCe...(I) (however, Ln
is at least one rare earth element selected from the group consisting of Y, La%Gd and Lu; X is at least one halogen selected from the group consisting of CIL, Br and I; and X is 0<x≦0 .2), and the ratio of the Ln to the X is X/L.
n is the atomic ratio, 0.500<X/Ln≦0.998, and the maximum wavelength λ of the photostimulated excitation spectrum is 550n
m<λ<700 nm, and a cerium-activated rare earth oxyhalide phosphor exhibiting stimulated luminescence in a wavelength range of 350 nm to 450 nm;
A phosphor layer including a phosphor that is excited by light in a wavelength range of less than 0 nm and emits light in a wavelength range of 450 nm or more, and a phosphor layer disposed thereon with light in a wavelength range of 350 nm or less and a wavelength of 350 nm or more and 450 nm or less. This can be achieved by a radiation image conversion panel characterized in that it is comprised of a protective film made of a material that also absorbs light in the area.

Note that the above-mentioned phosphor that is excited by light in the wavelength range of 350 nm or more and less than 450 nm and emits light in the wavelength range of 450 nm or more has at least a part of its excitation spectrum
It is sufficient that the excitation spectrum has a substantial intensity in the wavelength region of 50 nm or more and less than 450 nm, and the entire excitation spectrum does not necessarily have to be within this region.

In the radiation image conversion panel of the present invention, the protective film is made of a material that absorbs light in the wavelength region of 350 nm or more and 450 nm or less as well as the wavelength region of 350 nm or less.
Ultraviolet rays and visible light in the blue region included in external light or erasing light are absorbed by this protective film and do not reach the phosphor layer.

Therefore, the stimulable phosphor in the phosphor layer does not accumulate energy of ultraviolet rays or visible light in the blue region, and fogging caused by ultraviolet rays or visible light in the blue region can be prevented.

Here, if the radiation image conversion panel using the stimulable phosphor is simply provided with the above-mentioned protective film, the stimulable phosphor will exhibit stimulated luminescence (emission wavelength: 350 nm to 4.0 nm).
Since most of the radiation (50 nm) is absorbed by the protective film, the stimulated luminescence is not emitted outside the panel, and the sensitivity of the panel is significantly reduced.Therefore, in the radiation image storage panel of the present invention, Not only fluorescent phosphors <350nm
Excited by light in the wavelength range of 450nm or more
This problem was solved by also using a phosphor (wavelength shifter) that emits light of m or more.

That is, the phosphor layer of the radiation image conversion panel of the present invention is
In addition to the cerium-activated rare earth oxyhalide phosphor, which is a stimulable phosphor, it also contains a phosphor (wavelength shifter) that is excited by light in a wavelength range of 350 nm or more and less than 450 nm and emits light with a wavelength of 450 nm or more. Therefore, the stimulable excitation light emitted by the stimulable phosphor by irradiation with the stimulable excitation light excites the above phosphor (wavelength shifter), and the excited phosphor (wavelength shifter) has a wavelength of 450 nm. It emits more light. For example, the stimulable phosphor GdOCJ exhibits a stimulable emission spectrum as shown in FIG. :Ce
(CIL/Gd=0.900) and a wavelength shifter that shows the emission and excitation spectra shown in Figure 2, it is possible to use a wavelength shifter that shows the emission and excitation spectra as shown in Figure 2. The wavelength shifter can convert stimulated luminescence into luminescence with a longer wavelength (and therefore not absorbed by the protective film).

Therefore, by irradiation with photostimulating excitation light, as a result, 450
Since emitted light of nm or more is emitted to the outside of the panel without being absorbed by the protective film, the sensitivity of the panel does not decrease.

Furthermore, the radiation image conversion panel of the present invention uses a cerium-activated rare earth oxyhalide phosphor whose maximum wavelength λ of the photostimulated excitation spectrum is 550 nm < λ < 700 nm as the photostimulable phosphor. Excitation light having a wavelength that is not absorbed by the protective film can be fully utilized.

Preferred embodiments of the present invention are listed below. (I) A radiation image storage panel, wherein the protective film is made of a material that absorbs 90% or more of light of 450 nm or less.

(2) Note 6H The amount of the phosphor that is excited by light with a wavelength of 350 nm to 450 nm and emits light of 450 nm or more is 10 - 6 to 10 w of the above stimulable phosphor in terms of weight ratio.
A radiation image conversion panel characterized in that: t%.

(3) A radiation image conversion panel characterized in that the ratio X/Ln between Doki Ln and the above-mentioned X is 0.700≦X/Ln≦0.995 in terms of atomic ratio.

(4) The ratio X/Ln of the above Ln and the above X is an atomic ratio, and o. A radiation image conversion panel characterized in that aoo≦X/Ln≦0.990.

[Configuration of the Invention] The radiation image conversion panel of the present invention will be described in detail below.

First, the phosphor layer of the radiation image conversion panel of the present invention is composed of the following formula (I): LnOX: xCe - (I) (wherein Ln is at least one selected from the group consisting of Y, La, Gd, and Lu) is a rare earth element; X is CJ2
, Br and I; and X is a numerical value in the range of O<x≦0.2), and the ratio of the Ln to the X
/Ln is the atomic ratio, 0.500<X/Ln≦0.
998, the maximum wavelength λ of the stimulated excitation spectrum is 550 nm<λ<7oonm, and the cerium-activated rare earth oxyhalide phosphor exhibits stimulated luminescence in the wavelength range from 350 nm to 450 nm.

This phosphor can be manufactured, for example, by the manufacturing method described below.

First, as phosphor raw materials, 1) Y203, La2o3, Gd203 S and L
At least one rare earth element oxide selected from the group consisting of It may also be a variable rare earth element compound) 2) Cl! , Br, and 1); and 3) at least one cerium compound (cerium halide, cerium oxide, cerium nitrate, cerium sulfate, etc.).

Examples of the halogen donor in 2) above include ammonium halide (NH4X), hydrogen halide (HX) in an aqueous solution or gaseous state, and rare earth element halides (LnXs). X is Cλ, Br or !, and Ln is Y%La, Gd or Lu). In addition, when the above-mentioned rare earth element halide is used as a halogen donor, this halogen donor not only donates the halogen that constitutes the matrix of the obtained phosphor, but also donates one of the rare earth elements that also constitutes the matrix of the phosphor. Donate part or even all of it.

When manufacturing the above-mentioned stimulable phosphor, the relative amounts of rare earth oxide and halogen donor in the phosphor raw material (preparation ratio)
By adjusting the firing atmosphere, the ratio of rare earth element Ln and halogen X in the obtained phosphor is controlled. Therefore, it is preferable to use ammonium halide as the halogen donor since it is easy to control the relative amounts of the rare earth oxide and the halogen donor.

Hereinafter, a case where ammonium halide is used as a halogen donor will be explained as an example.

First, a phosphor raw material mixture is prepared using appropriate amounts of the above phosphor raw materials 1) to 3).

The cerium compound of 3) is used in a stoichiometric amount corresponding to formula (I) above. That is, rare earth oxide L of 1)
Cerium is mixed in an amount of X mole to n, O, 0.5 mole (rare earth element Lnl mole).

For mixing, use various mixers, V-type blenders, ball mills,
A conventional mixer such as a rod mill is used.

Next, the phosphor raw material mixture thus obtained is filled into a heat-resistant container such as a quartz boat, an alumina crucible, or a quartz crucible, and fired in an electric furnace.

Note that, prior to firing, the phosphor raw material mixture may be heat-treated at a temperature lower than the firing temperature to form LnOx crystals.

The firing temperature is suitably 500 to 1500°C, preferably 700 to 1400°C. The firing time varies depending on the amount of the phosphor raw material mixture or its heat-treated product filled into the heat-resistant container and the firing temperature, but generally it is 0.
．． A suitable time is 5 to 20 hours, preferably 1 to 3 hours.

As the firing atmosphere, a weakly reducing atmosphere such as a nitrogen gas atmosphere containing a small amount of hydrogen gas or a carbon dioxide atmosphere containing carbon monoxide; or a neutral atmosphere such as a nitrogen gas atmosphere or an argon gas atmosphere is used. When a cerium compound in which the valence of cerium is tetravalent is used as the cerium compound in 3 above, firing is performed in the weakly reducing atmosphere described above, and the tetravalent cerium is reduced to trivalent cerium. Ru.

In addition, after firing once under the above firing conditions, the fired product is taken out of the electric furnace, left to cool, and then pulverized.Then, the fired product powder is again filled into a heat-resistant container and placed in the electric furnace again. Firing may also be performed. As the firing atmosphere for re-firing, a weakly reducing atmosphere or a neutral atmosphere can be used in the same manner as described above.

The ratio of the rare earth element Ln and the halogen X in the obtained phosphor is determined by the relative amount of the rare earth oxide and the halogen donor in the phosphor raw material in the preparation of the phosphor raw material mixture (preparation ratio).
The temperature can be controlled by adjusting the firing atmosphere.

That is, in this example, rare earth oxide Ln. 0. By adjusting the mixing ratio of ammonium halide and ammonium halide NH4X and the firing atmosphere, the ratio X/Ln of rare earth element Ln and halogen
Adjust so that <X/Ln≦0.998. This ratio X/Ln is preferably set to 0.995 or less in terms of atomic ratio, since the resulting phosphor has a high stimulated luminance, and as a result, a radiation image conversion panel with high sensitivity can be manufactured. More preferably, it is 0.990 or less. Also, for the same reason, this ratio
It is preferable that n is 0.700 or more in atomic ratio, and o
．． It is more preferable to set it to aoo or more.

Generally, the fired product obtained through the firing process is pulverized to obtain a powdered phosphor. Note that the obtained powdered phosphor may be further subjected to various general operations in the production of phosphors, such as washing, drying, and sieving, as necessary. As described above, the following formula (■): LnOX : xCe (provided that at least one rare earth element selected from the group consisting of l, nldY, La%Gd and Lu;
X is CI. , Br, and I; and X is 0<x≦0.
．． 2), and the ratio X/Ln of the Ln and the X is an atomic ratio, and 0.500<X
/Ln≦0.998, and the maximum wavelength λ of the stimulated excitation spectrum is 550 nm<λ<700 nm, and the phosphor exhibiting stimulated luminescence in the wavelength range from 350 nm to 450 nm can be obtained.

The phosphor layer of the radiation image conversion panel of the present invention includes not only the above-mentioned stimulable phosphor but also a phosphor that emits light of 450 nm or more when excited by light with a wavelength of 350 nm to 450 nm (
It also contains a wavelength shifter.

Examples of this phosphor (wavelength shifter) include rhodamine B, rhodamine 6G, fluorescein, and coumarin dyes. More specifically, FZ-5012 manufactured by Shinroihi ■, Kayaset manufactured by Nippon Kayaku ■
Yellow SF-G, Nippon Kayaku Ka
yaset FlavineF N, General. Examples include 117-15-1 manufactured by Zlectric, 117-1 5-2 manufactured by General Electric, and Maxilon Brill-Flavine manufactured by Ciba-Geigy.

The stimulable phosphor layer of the radiation image storage panel of the present invention is not only composed of a stimulable phosphor and a binder that contains and supports the stimulable phosphor in a dispersed state, but also contains a stimulable phosphor layer without a binder. It may be composed only of aggregates of stimulable phosphors, or it may be one in which the gaps between aggregates of stimulable phosphors are impregnated with a polymeric substance.

Since the wavelength shifter is an organic or organometallic complex phosphor as described above, it is generally contained in the phosphor layer in a state mixed with a binder or a polymeric substance. Therefore, in such a case, the phosphor layer must necessarily consist of a stimulable phosphor and a binder that contains and supports the stimulable phosphor in a dispersed form, or a polymer layer must be formed between the aggregates of the stimulable phosphor. This results in a phosphor layer impregnated with a substance.

However, even in the case of a phosphor layer made of aggregates of stimulable phosphors that do not contain a binder or polymeric substance, the phosphor layer is immersed in a solution containing a wavelength shifter, or this solution is mixed with the stimulable phosphor. If the solvent is evaporated after coating,
Since the wavelength shifter is retained in the phosphor layer while being attached to the aggregate of the stimulable phosphor, the wavelength shifter can be included.

The radiation image conversion panel of the present invention will be manufactured by taking as an example the case where the phosphor layer is composed of a stimulable phosphor and a binder containing and supporting the stimulable phosphor in a dispersed form and is provided on a support. Explain how to do this.

The phosphor layer can be formed on the support, for example, by the following method.

First, the above-mentioned stimulable phosphor, binder, and wavelength shifter are added to a suitable solvent, and the mixture is thoroughly mixed to produce a phosphor in which the stimulable phosphor and wavelength shifter are uniformly dispersed in the binder solution. Prepare a coating solution for layer formation.

The amount of the wavelength shifter varies depending on the type of wavelength shifter, the stimulated emission wavelength of the stimulable phosphor, the transmittance of the protective film, etc., but 10 wt% from to-' of the stimulable phosphor is appropriate. .

Examples of binders for the phosphor layer include proteins such as gelatin,
Polysaccharides such as dextran, or natural polymeric substances such as gum arabic; Binders typified by synthetic polymeric substances such as vinyl acetate copolymer, polyurethane, cellulose acetate butyrate, polyvinyl alcohol, linear polyester, etc. can be mentioned. Particularly preferred among such binders are nitrocellulose, linear polyester,
These are polyalkyl (meth)acrylates, polyurethanes, mixtures of nitrocellulose and linear polyesters, and mixtures of nitrocellulose and polyalkyl (meth)acrylates.

Examples of the solvent for preparing the coating solution include lower alcohols such as methanol, ethanol, n-probanol, and n-butanol; chlorine-containing hydrocarbons such as methylene chloride and ethylene chloride; acetone, methyl ethyl ketone, and methyl isobutyl ketone. Ketones; esters of lower fatty acids and lower alcohols such as methyl acetate, ethyl acetate, and butyl acetate; ethers such as dioxane, ethylene glycol monoethyl ether, and ethylene glycol monomethyl ether; and mixtures thereof.

The mixing ratio of the binder and the stimulable phosphor in the above coating solution varies depending on the characteristics of the intended radiation image conversion panel, the type of phosphor, etc., but in general, the mixing ratio of the binder and the stimulable phosphor is as follows: It is selected from the range of 1:1 to 1:100 (weight ratio), and particularly preferably selected from the range of 1:8 to 1:40 (weight ratio).

The coating solution for forming a phosphor layer includes a dispersant to improve the dispersibility of the phosphor in the coating solution, and a bonding agent between the binder and the phosphor in the phosphor layer after formation. Various additives such as plasticizers to improve strength may be mixed. Examples of dispersants used for such purposes include phthalic acid, stearic acid, cabroic acid, lipophilic surfactants, and the like. Examples of plasticizers include phosphate esters such as triphenyl phosphate, tricresyl phosphate, and diphenyl phosphate; phthalate esters such as diethyl phthalate and dimethoxyethyl phthalate; ethyl phthalylethyl glycolate, butylphthalyl glycolate. Glycolic acid esters such as butyl; and polyesters of polyethylene glycol and aliphatic dibasic acids, such as polyesters of triethylene glycol and adivic acid and polyesters of diethylene glycol and succinic acid.

The coating solution for forming a phosphor layer containing the phosphor, binder, and wavelength shifter prepared as described above is then uniformly applied to the surface of the support to form a coating film.

This coating operation can be carried out using conventional coating means such as a doctor blade, roll coater, knife coater, etc.

The support can be arbitrarily selected from materials known as supports for conventional radiation image storage panels. Examples of such materials include films of plastic substances such as cellulose acetate, polyester, polyethylene terephthalate, polyamide, polyimide, triacetate, polycarbonate, metal sheets such as aluminum foil, aluminum alloy foil, regular paper, baryta paper, resins, etc. Examples include coated paper, pigment paper containing pigments such as titanium dioxide, paper sized with polyvinyl alcohol, and plates or sheets of ceramics such as alumina, zirconia, magnesia, and titania.

In known radiation image conversion panels, a phosphor layer is provided in order to strengthen the bond between the support and the phosphor layer, or to improve the sensitivity or image quality (sharpness, granularity) of the radiation image conversion panel. A polymeric substance such as gelatin is coated on the surface of the support on the side to be coated to form an adhesion imparting layer, or a light reflective layer made of a light reflective material such as titanium dioxide, or a light absorbing material such as carbon plaque. It is known to provide a light absorption layer or the like.

The support used in the present invention can also be provided with these various layers, and their configurations can be arbitrarily selected depending on the purpose, use, etc. of the desired radiation image storage panel.

Furthermore, as described in JP-A-58-200200, in order to improve the sharpness of the obtained image, the surface of the support on the phosphor layer side (the surface of the support on the phosphor layer side) When an adhesion-imparting layer, a light-reflecting layer, a light-absorbing layer, etc. are provided, minute irregularities may be formed on the surface (meaning the surface thereof).

After the coating film is formed on the support as described above, it is dried to complete the formation of the stimulable phosphor layer on the support. The thickness of the phosphor layer varies depending on the characteristics of the intended radiation image conversion panel, the type of phosphor, the mixing ratio of the binder and the phosphor, and is usually 20 μm to 1 mm. However, the thickness of this layer is preferably 50 to 500 μm.

In addition, the stimulable phosphor layer does not necessarily need to be formed by directly applying a coating solution onto the support as described above, but can be formed by separately applying it onto a sheet such as a glass plate, metal plate, or plastic sheet. After a phosphor layer is formed by applying a liquid and drying, the phosphor layer may be pressed onto a support, or the support and the phosphor layer may be bonded together using an adhesive.

Next, the protective film of the radiation image storage panel of the present invention will be described.

The protective film of the radiation image storage panel of the present invention is made of a material that absorbs not only light in the wavelength region of 350 nm or less, but also light in the wavelength region of 350 nm or more and 450 nm or less. This material preferably absorbs 90% or more of light in a wavelength range of 450 nm or less.

The protective film of the radiation image conversion panel of the present invention can be formed by, for example, adhering optical glass or a plastic sheet used in an ultraviolet removal filter having the above-mentioned optical properties onto the phosphor layer via an adhesive layer. It can be provided in

Alternatively, in a solution of an organic polymer substance such as a cellulose derivative, polymethyl methacrylate, or polyurethane resin,
A protective film can also be formed by applying a coating liquid for forming a protective film containing an ultraviolet absorber to the surface of the phosphor layer.

Ultraviolet absorbers are substances that have a strong absorption band in the ultraviolet region.
Even if it absorbs ultraviolet rays, it does not exhibit phenomena such as photolysis, photosensitization, fluorescence, or phosphorescence, but converts the energy of ultraviolet rays into harmless energy and releases it to the outside. At this time,
Since the UV absorber itself does not change in any way,
There is no negative impact on the surroundings, and the ultraviolet absorber itself is not consumed. As the ultraviolet absorber, salicylic acid esters, benzophenone derivatives, penzotriazole derivatives, hydroxybenzoate derivatives, cyanoacrylate derivatives, etc. are used.

Specific examples include the following substances.

Phenyl salicylate, 2-hydroxyphenyl penzotriazole, 2-(2゜-hydroxy-5゜methylphenyl)penzotriazole, 2- (2'-hydroxy-3'-t-butyl-5''- methylphenyl)
-5-chloropenzotriazole, 2- (2' -
Hydroxy-3゜5゜-di-t-butylphenyl)penzotriazole, 2-(2"-hydroxy-5゜1t-
octylphenyl) penzotriazole, 2-(2゜-hydroxy-3゜,5゜-di-t-amylphenyl》penzotriazole, 2-hydroxy penzophenone,
2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2,2゛-
Dihydroxy-4-methoxybenzophenone, pt-
Butyl phenyl salicylate, 2,4°-dihydroxy penzophenone, benzophenone complex (Viosorb 180-^ manufactured by Kyodo Yakuhin ■), 2,4-di-t-butyl phenyl 3°. 5゜-dibutyl-4゜-hydroxy penzoate, ethyl-2-cyano 3
,3゛-diphenyl acrylate, 2-{2゜-hydroxy-3゜-(3''4''5'',6''-tetrahydrophthalmidomethyl)-5゜-methylphenyl}-benzotriazole, { 2.2°-thiobis(4-t-octylphenylate)-n-butylamine nickel, dimethyl-P-methoxy penzylidine malonate. In addition to organic polymeric substances such as cellulose derivatives, polymethyl methacrylate, and polyurethane resin, a crosslinking agent for crosslinking these materials may be added to this coating solution for forming a protective film.

Coating onto the surface of the phosphor layer can be carried out in the same manner as in the case of the phosphor layer described above. Of course, the coating solution for forming the protective film and the coating solution for forming the phosphor layer may be coated simultaneously by a multi-layer coating method using a dual hopper coater or the like (Japanese Unexamined Patent Publication No. 61-61100 and (See Japanese Patent Application Laid-Open No. 61-80100).

After the coating liquid for forming a protective film is applied to the surface of the phosphor layer as described above, it is heated and dried to form a film to form a protective film.

The thickness of the protective film is generally 2 to 25 μm, whether it is provided by adhesion or by coating.

In addition, for the purpose of improving the sharpness of the obtained image, at least one of the above layers constituting the radiation image conversion panel of the present invention is colored so that it absorbs excitation light and does not absorb stimulated luminescence light. It may be colored by an agent. (Refer to Japanese Patent Publication No. 59-23400).

Examples and comparative examples of the present invention are described below. However, the present invention is not limited to this example.

[Example 1] A photostimulable phosphor (GdOCIL: 10-'Ce) (Cl/G
d=0.900) 600g: 300mg of a wavelength shifter (FZ-5012 manufactured by Shinroihi) that exhibits the emission spectrum and excitation spectrum as shown in Figure 2 (ratio to photostimulable phosphor, 0.05wt%); Polyurethane resin(
Crisbon NT-50) manufactured by Dainippon Ink■16. ag:
Nitrocellulose (RS-120 manufactured by Daicel Chemical Industries, Ltd.)
) 3.0g: was added to a mixed solvent of methyl ethyl ketone and toluene (I:1) and dispersed with a propeller mixer, so that the mixing ratio of the binder and the stimulable phosphor was 1=30 (weight ratio) and the viscosity was 25. A coating solution for forming a phosphor layer of ~30 PS (25° C.) was prepared, coated, and dried to form a phosphor layer.

Next, use an ultraviolet removal filter (SC-42: 420n
A radiation image conversion panel of the present invention was manufactured by adhering a thin film having a thickness of 10 μm and having an optical characteristic of 50% transmittance at 100 m to the surface of the phosphor layer.

[Comparative Example 1] Radiation treatment was carried out in the same manner as in Example 1, except that a wavelength shifter was not added to the coating solution for forming a phosphor layer and a transparent polyethylene terephthalate film was used as a protective film. An image conversion panel was manufactured.

Regarding the radiation image conversion panel of Comparative Example 1, 350n
The degree of fog caused by ultraviolet rays was measured by irradiating light with a wavelength of m to 450 nm to accumulate energy, and then exciting it with light of 633 nm and observing stimulated luminescence. 3rd result
Shown in the figure. In FIG. 3, the horizontal axis represents the wavelength of accumulated light, and the vertical axis represents the fog level. From Figure 3, 450n
It can be seen that fogging can be significantly prevented by removing wavelengths of m or less.

Turnip 1 The panel of Example 1 and the panel of Comparative Example 1 were compared in terms of the degree of capri caused by ultraviolet rays.

Both panels were previously irradiated with high-pressure sodium lamp light through an ultraviolet removal filter to completely eliminate fog. Next, place both panels indoors under fluorescent light for 10 minutes.
After being left for 10 minutes under irradiation with a light intensity of 0.00 lux, the sample was excited with a He-Ne laser (633 nm) and the amount of stimulated luminescence due to fog caused by the ultraviolet component of the fluorescent lamp was measured.

The results are shown in Table 1.

Table 1 Example 1 Comparative Example 1 Relative stimulated luminescence amount 0.01 100 As is clear from these results, the radiation image conversion panel of the present invention has
It can be seen that this is a radiation image conversion panel that is less prone to fogging caused by ultraviolet rays.

[Brief explanation of the drawing]

Figure 1 shows GdOCIL: Ce (CJ!/Gd=0.
900). FIG. 2 shows the emission and excitation spectra of the wavelength shifter. FIG. 3 is a diagram showing the degree of fog caused by ultraviolet rays in a conventional radiation image conversion panel. Patent applicant: Fuji Photo Film Co., Ltd. Representative: Yasuo Yanagawa, patent attorney Figure I Figure Wavelength/nm Figure -. ″: fλ continuation 117 iE”iM (self-e) 1. Case description 1989 Patent Application No. 143645 2. Title of the invention: Radiation image conversion panel 3. Person making the amendment Relationship with Matter 11G Patent applicant name (5
20) Fuji Photo Film Co., Ltd. 4. A (P Company address: 8th floor, Miyya Yotsuya Building, 2-14 Yotsuya, Shinjuku-ku, Tokyo. ``Detailed explanation of the invention'' section of the specification. 6. Contents of amendment

Claims (1)

[Claims] 1. The following formula (I) LnOX:xCe...(I) (wherein Ln is at least one rare earth element selected from the group consisting of Y, La, Gd and Lu; X is selected from the group consisting of Cl, Br and I and x is a numerical value in the range of 0<x≦0.2), and the ratio X/Ln of the Ln and the X is an atomic ratio of 0.500< X/Ln≦0.9
98, and the maximum wavelength λ of the photostimulated excitation spectrum is 5
50nm<λ<700nm, and from 350nm to 45
A cerium-activated rare earth oxyhalide phosphor that exhibits stimulated luminescence in a wavelength region of 0 nm and a wavelength region of 350 nm or more, 450 nm
a phosphor layer including a phosphor that is excited by light in a wavelength range of less than m and emits light in a wavelength range of 450 nm or more, and a phosphor layer disposed thereon with light in a wavelength range of 350 nm or less and a wavelength of 350 nm or more and 450 nm or less A radiation image conversion panel comprising a protective film made of a material that also absorbs light in a region.