JP2010014666A - Radiological image conversion panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radiological image conversion panel that has a coating type phosphor layer, prevents bubble swelling of the phosphor layer, and provides a high-quality radiological image. <P>SOLUTION: The phosphor layer does not contain a component causing a polymerization reaction of a binder, a protective film contains inorganic particles, and the content of the inorganic particles is set 8 to 18 wt.% to the solid component other than the inorganic particles. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a radiation image conversion panel such as a so-called IP (Imaging Plate) or a scintillator panel, and more specifically, it is possible to obtain a high-quality radiation image by suppressing the generation of bubble swelling of a phosphor layer that causes deterioration of image quality. The present invention relates to a radiation image conversion panel.

  There are known phosphors that exhibit a response according to the received radiation energy when irradiated with radiation (X-rays, α-rays, β-rays, γ-rays, electron beams, ultraviolet rays, etc.). It is used for purposes.

  As an example, when irradiated with radiation, a part of this radiation energy is accumulated, and when irradiated with excitation light such as visible light after that, stimulated light emission corresponding to the accumulated energy is exhibited. It is called a phosphor (accumulating phosphor) and is used for various applications such as medical applications.

A radiation image information recording / reproducing system using a radiation image conversion panel (so-called IP (Imaging Plate)) having the photostimulable phosphor layer is known. For example, an FCR (Fuji Computed Radiography) manufactured by Fujifilm Corporation is known. ) Etc.
In this system, a radiation image of a subject is recorded on a conversion panel (stimulable phosphor layer) by irradiating X-rays or the like through a subject such as a human body (taking a radiation image). After recording, the conversion panel is scanned two-dimensionally with excitation light to generate stimulated emission, and this stimulated emission light is photoelectrically read to obtain an image signal, and an image reproduced based on this image signal is A radiation image of the subject is output to a display device such as a CRT or a recording material such as a photographic photosensitive material.

In addition, as in the case of IP, there is also known a phosphor that emits (fluoresces) visible light by incident radiation, instead of accumulating and recording radiation images and obtaining a radiation image by stimulating light emitted by excitation light irradiation. ing. Radiation image conversion panels (so-called scintillator panels) having a phosphor layer made of this phosphor are also used for various applications such as medical applications.
In a system using a scintillator panel, radiation that has passed through the subject is incident on the scintillator panel to convert the radiation carrying the subject image into visible light, and this visible light is converted into electric charges by a photoelectric conversion element such as a photodiode. Then, this electric charge is sequentially read out by a TFT (Thin Film Transistor) or the like to obtain an electric signal, and this electric signal is output as a radiographic image of the subject as before.

  As an example, the phosphor layer in a radiation image conversion panel such as an IP or a scintillator panel is prepared by preparing a coating liquid in which phosphor particles and a binder (binder) are dispersed in a solvent. It is formed by coating and curing on a panel-like support made of metal.

Further, a protective film is formed on the phosphor layer thus formed to prevent the phosphor layer from being stained or damaged.
Examples of the method for forming the protective film include a method in which an adhesive is applied to a transparent resin film such as polyethylene terephthalate (PET), and the protective film (protective film) is adhered onto the phosphor layer. As another protective film, a coating solution prepared by dissolving a transparent resin such as cellulose derivative or polymethyl methacrylate in a suitable solvent is prepared, and this coating solution is applied to the surface of the phosphor layer and dried (cured). ) Is also known.

By the way, in order to obtain a radiation image with high sharpness, it is effective to make the protective film as thin as possible. On the other hand, in order to exhibit a sufficient function as a protective film, a certain degree of thickening is indispensable.
In the case of a protective film made by sticking a resin film, an adhesive layer is also required in addition to the resin film, so it is inevitably thick in order to exhibit a sufficient function as a protective film. Therefore, it is difficult to prevent deterioration in image quality due to thickening.
On the other hand, in the protective film formed by preparing a coating solution in which the resin is dissolved and coating / curing on the phosphor layer, as a method for preventing image quality deterioration accompanying thickening (coating solution thick film coating), There is known a method in which fine particles are added / dispersed in a coating solution for forming a protective film, and the fine particles are dispersed in the protective film.

For example, in Patent Document 1, in a radiation image conversion panel having a stimulable phosphor layer and a protective film, the light scattering length of the protective film at the main emission wavelength of the stimulated light emission is in the range of 5 to 80 μm. It is disclosed that a high-quality radiation image is obtained. Here, in Patent Document 1, as a method of forming such a protective film, a coating liquid prepared by dissolving a resin component in a solvent and dispersing light scattering fine particles is prepared. It is disclosed that a protective film having the light scattering length is formed by applying and curing to a phosphor layer.
In Patent Document 2, the protective film includes a resin and particles having a Mohs hardness of 9 or more and an average particle diameter of 0.1 to 1 μm, and the protective film has a weight of 50 to 200 with respect to the resin. A radiation image conversion panel that is excellent in antifouling property, scratch resistance and durability and can maintain good image quality is disclosed.

JP 11-281975 A JP 2002-6961 A

  By the way, as described above, the phosphor layer of the radiation image conversion panel is prepared by preparing a coating solution in which a binder and phosphor particles are dissolved / dispersed in a solvent, and applying and curing the coating solution on a substrate. It is formed. Here, as also shown in Patent Document 2, a curing agent (crosslinking agent) for polymerizing a binder and improving the strength of the phosphor layer is added to this coating solution. There are many cases.

On the other hand, in order to obtain a high-quality image with a high light emission amount, it is preferable to increase the thickness of the phosphor layer, reduce the amount of binder added, and not use a curing agent.
However, as described above, when a coating solution containing a resin and particles serving as a protective film is applied to a phosphor layer formed from a coating solution that does not contain a curing agent, the solvent component in the coating solution soaks into the phosphor layer. Therefore, when the coating solution is cured, foaming (hereinafter referred to as blister) occurs in the phosphor layer.

When such a blister is generated in the phosphor layer, light emission generated in the phosphor layer is deflected by the blister and unevenness is generated in the obtained radiation image.
Further, when there is a step of applying pressure to the phosphor layer in the subsequent manufacturing process, a phenomenon such as a fault displacement of the phosphor layer occurs when the pressure is applied. Similarly, in the tomographic part, the light emission generated in the phosphor layer is deflected, and the radiation image is uneven.

  An object of the present invention is to solve the above-mentioned problems of the prior art, a phosphor layer in which phosphor particles are dispersed in a binder, and particles for improving image quality dispersed in a resin. In a radiation image conversion panel having a protective film formed directly on the phosphor layer, the image quality improvement effect by dispersing particles in the protective film, and the phosphor layer has a binder curing agent. Insufficient penetration of the solvent component in the coating solution in which resin and particles are dissolved / dispersed in a solvent to form a protective film, while ensuring sufficient image quality improvement effect An object of the present invention is to provide a radiation image conversion panel that can suppress the deterioration of the image quality of a radiation image due to blistering (bubble expansion) of a phosphor layer.

  In order to achieve the object, the radiation image conversion panel of the present invention is a radiation image conversion panel having a phosphor layer and a protective film formed on the phosphor layer, the phosphor layer comprising , Having phosphor particles and a binder and not containing a component that causes a polymerization reaction of the binder, and further, the protective film contains inorganic particles, and the protective film contains inorganic particles. Provided is a radiation image conversion panel, wherein the weight ratio of the inorganic particles is 8 to 18% by weight with respect to the solid content other than the particles.

In such a radiation image conversion panel of the present invention, the inorganic particles are preferably alumina particles, or the inorganic particles are preferably silica particles.
The resin forming the protective film is preferably a fluororesin, and the protective film is preferably formed by being directly applied to the phosphor layer, and further, the phosphor layer The amount of the binder in is preferably 1/30 or less by weight with respect to the phosphor particles.

  The invention having the above-described structure includes a phosphor layer formed using a coating solution obtained by dissolving / dispersing a binder and phosphor particles in a solvent, and a coating solution obtained by dissolving / dispersing resin and particles in a solvent. In the radiation image conversion panel having a protective film formed by applying and curing the phosphor layer, the phosphor layer does not contain a component for polymerizing the binder, and the particles added to the protective film are inorganic particles. And content of this inorganic particle shall be 8-18 weight% with respect to solid content other than the inorganic particle which forms a protective film.

As will be described in detail later, the particles added to the protective film in order to improve the image quality such as sharpness are inorganic particles, and the content of the inorganic particles in the protective film is 8 to 18 with respect to the other solid content. By setting the weight%, even if the phosphor layer does not contain a curing agent, even if a coating solution for forming a protective film is applied to the phosphor layer, the solvent component in the coating solution to the phosphor layer Soaking can be suppressed.
Therefore, according to the present invention, the image quality improvement effect due to the dispersion of the particles in the protective film and the image quality improvement effect due to the fact that the phosphor layer does not have the binder curing agent are sufficiently secured and protected. A high-quality radiographic image can be obtained by preventing deterioration in radiographic image quality caused by blistering (bubble blistering) of the phosphor layer due to penetration of the solvent component into the phosphor layer in the coating liquid forming the film. Can be realized.

  Hereinafter, the radiation image conversion panel of the present invention will be described in detail with reference to preferred embodiments shown in the accompanying drawings.

In FIG. 1, the conceptual diagram of an example of the radiation image conversion panel of this invention is shown.
A radiation image conversion panel 10 (hereinafter referred to as a conversion panel 10) shown in FIG. 1 basically includes a substrate 12, a phosphor layer 14, and a protective film 16.

  The conversion panel 10 of the present invention has a layer made of a stimulable phosphor (stimulable phosphor layer), captures a radiation image by accumulating (recording) the radiation transmitted through the subject, and generates excitation light. It may be a so-called IP (Imaging Plate) that emits photostimulated luminescence according to the radiation image taken by the incidence of light, or has a layer (scintillator layer) made of a phosphor that emits visible light by the incidence of radiation. A so-called scintillator panel may be used in which the radiation transmitted through the subject is incident on the scintillator layer and the visible light emitted from the scintillator layer is read photoelectrically.

In the conversion panel 10 of the present invention, the substrate 12 is not particularly limited, and various types used as a substrate for a known radiation image conversion panel, such as a resin (plastic) plate, a resin film, a glass plate, and a metal plate, All are available.
The substrate 12 may have a layer that exhibits various functions such as a reflective layer, a protective film for preventing corrosion, and a smoothing layer on the surface.

The phosphor layer 14 is a layer in which phosphor particles are dispersed in a binder (binder).
In the present invention, the phosphor layer 14 is prepared by preparing a coating solution in which a binder is dissolved in a solvent and phosphor particles are dispersed, and this coating solution is applied to the surface of the substrate 12. It is formed by drying the liquid. That is, the conversion panel 10 of the present invention is a so-called coating type conversion panel.
Further, the phosphor layer 14 of the present invention does not contain a component (curing agent / crosslinking agent) that causes a polymerization reaction to occur in the binder (resin component serving as the binder) that forms the phosphor layer 14. Therefore, the component for polymerizing the binder is not added to the coating liquid for forming the phosphor layer 14.

  As described above, the conversion panel 10 of the present invention may be an IP using a photostimulable phosphor or a scintillator panel using a phosphor that emits visible light upon incidence of radiation. That is, the phosphor layer may be either a stimulable phosphor particle or a normal phosphor particle.

  There is no particular limitation on the photostimulable phosphor used in the conversion panel 10 of the present invention, and various known photostimulable phosphors can be used.

As the stimulable phosphor used in the phosphor layer, a general formula disclosed in JP-A No. 61-72087;
M ^I X • aM ^II X ′ ₂ • bM ^III X ″ ₃ : cA
An alkali halide photostimulable phosphor represented by the formula is preferably used.
(In the above formula, M ^I is at least one selected from the group consisting of Li, Na, K, Rb and Cs, and M ^II is Be, Mg, Ca, Sr, Ba, Zn, Cd, Cu and at least one trivalent metal selected from the group consisting of Ni, M ^III is, Sc, Y, La, Ce , Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, At least one trivalent metal selected from the group consisting of Tm, Yb, Lu, Al, Ga and In, and X, X ′ and X ″ are selected from the group consisting of F, Cl, Br and I A is from Eu, Tb, Ce, Tm, Dy, Pr, Ho, Nd, Yb, Er, Gd, Lu, Sm, Y, Tl, Na, Ag, Cu, Bi, and Mg. At least one selected from the group consisting of . Also, a 0 ≦ a <0.5, a 0 ≦ b <0.5, it is 0 <c ≦ 0.2.)

  In addition, U.S. Pat. No. 3,859,527, JP-A-55-12142, 55-12143, 55-12144, 55-12145, 55-160078, 56-116777, 57-23673, 57-23675, 58-69281, 58-206678, 59-27980, 59-38278, 59-47289, 59- No. 56479, 59-56480, 59-75200, 60-84381, 60-101173, 62-25189, JP-A-2-229882, etc. Exhaustive phosphors can also be suitably used.

Of the above-mentioned stimulable phosphor, divalent europium activated alkaline earth metal fluoride halide phosphor (e.g., BaFBr _0.85 I _0.15: Eu and BaFI: Eu), europium activated alkali metal halide phosphor (For example, CsBr: Eu), iodine-containing divalent europium-activated alkaline earth metal halide phosphor, iodine-containing rare earth element-activated rare earth oxyhalide phosphor, and iodine-containing bismuth-activated alkali metal Halide-based phosphors can be preferably used because they exhibit high-luminance photostimulated luminescence.

Moreover, there is no limitation in particular also in the fluorescent substance used for the conversion panel 10 of this invention, Various well-known fluorescent substances can be utilized.
Among them, the following general formula is preferable in that good light emission characteristics (fluorescence characteristics) can be obtained.
M ^I X · aM ^II X ′ ₂ · bM ^III X ″ ₃ : zA
An alkali metal halide phosphor represented by the formula is preferably exemplified.
(In the above formula, M ^I represents at least one alkali metal selected from the group consisting of Li, Na, K, Rb and Cs, and M ^II represents Be, Mg, Ca, Sr, Ba, Ni, Cu, Zn. And at least one alkaline earth metal or divalent metal selected from the group consisting of Cd, and M ^III is Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, It represents at least one rare earth element or trivalent metal selected from the group consisting of Ho, Er, Tm, Yb, Lu, Al, Ga and In. X, X ′ and X ″ are F, Cl, Represents at least one halogen selected from the group consisting of Br and I, and A represents Y, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Na, Mg, Cu, Ag Represents at least one rare earth element or metal selected from the group consisting of Tl, Bi, and a, b and z are 0 ≦ a <0.5, 0 ≦ b <0.5 and 0 <z, respectively. <Represents a numerical value within the range of 1.0.)
In particular, it is preferred that Cs is contained as M ^{I in the} general formula, ^I is preferably contained as X, T1 or Na is preferably contained as A, and z is 1 × 10 ^-4 ≦ z ≦ 0.1 is preferable. Among these, alkali metal halide phosphors represented by the formula CsI: Tl are preferably used.

In addition, the following general formula:
M ₂ O ₂ S: A
The rare earth oxysulfide-based phosphor represented by the formula is preferably used.
(In the above formula, M is at least one element selected from the group consisting of Y, La, Gd, and Lu, O is oxygen, S is sulfur, and A is at least one selected from the group consisting of Tb and Eu. Element)

  The diameter of the phosphor particles is not particularly limited and may be the same as that of a normal coating type conversion panel, and may be appropriately determined according to the type of the phosphor to be used. preferable.

The binder for forming the phosphor layer 14 is not particularly limited, and the binder used for forming the phosphor layer (stimulable phosphor layer / scintillator layer) in the coating type conversion panel 10. But all are available.
Examples include proteins such as gelatin, polysaccharides such as dextran, and various natural resins (natural polymer materials) such as gum arabic; polyvinyl butyral, polyvinyl acetate, nitrocellulose, ethyl cellulose, vinylidene chloride / vinyl chloride copolymer, poly Examples include various synthetic resins (synthetic polymer materials (polymers)) such as alkyl (meth) acrylate, vinyl chloride / vinyl acetate copolymer, polyurethane (urethane prepolymer), cellulose acetate butyrate, polyvinyl alcohol, and linear polyester. .
In particular, nitrocellulose, linear polyester, polyalkyl (meth) acrylate, polyurethane, a mixture of nitrocellulose and linear polyester, and a mixture of nitrocellulose and polyalkyl (meth) acrylate are preferably exemplified.
As described above, in the conversion panel 10 of the present invention, the phosphor layer 14 does not contain a substance (curing agent / crosslinking agent) that polymerizes these binders.

In the conversion panel 10 of the present invention, the mixing ratio of the binder and the phosphor particles in the phosphor layer 14 is not particularly limited, but the binder is 1/30 or less of the phosphor particles by weight. preferable.
By setting the mixing ratio of the binder to the phosphor particles within the above range, the radiation absorption and emission efficiency are increased by increasing the packing ratio of the phosphor, and the image is scattered by the light scattering caused by the binder polymer. This is preferable in that an effect such as blur reduction can be obtained and a high-quality image can be obtained.

  In the conversion panel 10 of the present invention, the layer thickness of the phosphor layer 14 is not particularly limited, and depends on the characteristics of the target conversion panel, the type of phosphor used, the mixing ratio of the binder and the phosphor, and the like. However, the thickness is not limited to the stimulable phosphor layer and the scintillator layer, and is preferably 250 μm or more.

In general, when the phosphor layer 14 is thicker, a high-quality radiation image can be obtained, and the conversion panel 10 having excellent performance can be obtained by setting the thickness of the phosphor layer 14 to 250 μm or more. Can be manufactured stably. On the other hand, the thicker the phosphor layer 14 is, the more easily the solvent component of the coating solution for forming the protective film 16 described later penetrates into the phosphor layer 14, and in particular, the coating is applied at a layer thickness of 250 μm or more. The soaking of the solvent component of the liquid becomes remarkable, and the image quality deterioration due to the blister of the phosphor layer 14 becomes remarkable.
That is, in the conversion panel 10 of the present invention, by setting the thickness of the phosphor layer 14 to 250 μm or more, the effect of improving the image quality due to the thickening of the phosphor layer 14 and the suppression of blistering in the thick phosphor layer 14 are achieved. The conversion panel 10 that can obtain a high-quality radiation image can be more stably obtained.
In addition, the thickness of the phosphor layer is not limited to the stimulable phosphor layer and the scintillator layer, and is more preferably 250 to 500 μm, in particular, 270 to 700, in that the above effect can be expressed more suitably. 350 μm is preferable.

In the conversion panel 10 of the present invention, the protective film 16 is directly formed on the phosphor layer 14 by applying a coating solution.
The protective film 16 is for preventing the phosphor layer 14 from being soiled or damaged, and has a resin and inorganic particles (inorganic particles) dispersed in the resin (protective film 16). The content of the inorganic particles is 8 to 18% by weight with respect to the solid content of the protective film 16 other than the inorganic particles (hereinafter simply referred to as “8 to 18 relative to the other solid content”). Also referred to as “% by weight”). Further, as described above, the phosphor layer 14 does not include a component (curing agent / crosslinking agent) that polymerizes the binder that forms the phosphor layer 14.
The conversion panel 10 of the present invention has such a configuration, thereby obtaining an image quality improvement effect due to particles dispersed in the protective film 16 and an image quality improvement effect due to the fact that the phosphor layer 14 does not contain a curing agent. This realizes a radiation image conversion panel that can prevent deterioration of the image quality of the radiation image due to blistering (bubble expansion) of the body layer 14 and obtain a high-quality radiation image.

As described above, in the coating type conversion panel, it is advantageous that the protective film is thin in terms of image quality of the obtained radiation image. On the other hand, in order to function sufficiently as a protective film, a certain degree of thickness is secured. There is a need to.
On the other hand, as shown in Patent Documents 1 and 2, by dispersing particles having photorepellent properties in the protective layer, the sharpness of the image can be improved, and the image quality of the radiation image is improved. be able to.

The phosphor layer of the coating type conversion sheet usually contains a curing agent for polymerizing the binder to improve the strength. However, it is advantageous not to contain a curing agent in terms of the image quality of the radiation image.
Here, the protective film is formed by preparing a coating solution obtained by dissolving a resin component or the like in a solvent and dispersing particles, and applying the coating solution to the phosphor layer and curing it. . However, when such a coating solution is applied to a phosphor layer formed without using a curing agent, the solvent component of the coating solution penetrates (impregnates) the phosphor layer, and the coating solution is cured. In addition, blisters are generated inside the phosphor layer. Such blisters cause image quality degradation such as unevenness in the radiation image.

In contrast, the conversion sheet 10 of the present invention is obtained when the coating liquid is applied to the phosphor layer 14 by dispersing 8 to 18% by weight of inorganic particles in the protective film 16 with respect to the other solid content. The penetration of the solvent component of the coating solution into the phosphor layer 14 can be greatly suppressed, that is, the formation of blisters inside the phosphor layer 14 can be prevented.
Therefore, according to the present invention, the phosphor can sufficiently exhibit the image quality improvement effect due to the protective film 16 containing particles and the image quality improvement effect due to the phosphor layer 14 having no curing agent. It is possible to prevent deterioration of the image quality of the radiation image due to the blister of the layer 14 and obtain a high-quality radiation image.

The reason why the penetration of the solvent component in the coating liquid into the phosphor layer 14 can be suppressed by dispersing 8 to 18% by weight of inorganic particles in the protective film 16 with respect to the other solid content is not clear.
According to the inventor's investigation and estimation, the inorganic particles are dispersed in the protective film 16 by the above-mentioned amount, so that the inorganic particles retain the solvent component in which the surrounding resin is dissolved, and the sand has absorbed water. As described above, it is considered that the inorganic particles suck the solvent component in the coating liquid, and as a result, the penetration of the solvent component in the coating liquid to be the protective film 16 into the phosphor layer 14 can be significantly suppressed.
In addition, even if the particles are organic particles (organic particles), it is not possible to obtain such an effect of suppressing the penetration of the solvent component in the coating liquid into the phosphor layer 14. This is also the inventor's guess, but the organic particles cannot retain the surrounding solvent components due to the smoothness and lubricity of the surface, and thus can obtain the effect of inorganic particles. This is thought to be because it is impossible.

As described above, in the protective film 16, the amount of inorganic particles is 8 to 18% by weight with respect to the solid content of the protective film 16 other than the inorganic particles.
If the amount of the inorganic particles is less than 8%, the effect of adding the inorganic particles cannot be sufficiently obtained, that is, the effect of suppressing the penetration of the solvent component in the coating liquid into the phosphor layer 14 cannot be obtained sufficiently. In addition, the effect of adding particles cannot be sufficiently obtained in terms of image quality.
On the other hand, if the amount of the inorganic particles exceeds 18% by weight, the effect of suppressing the penetration of the solvent component in the coating solution into the phosphor layer 14 cannot be obtained sufficiently. The reason for this is not clear, but according to the study and estimation by the present inventor, when the amount of inorganic particles exceeds 18% by weight, there are too many inorganic particles and the inorganic particles aggregate. As a result, it becomes the same state as the addition of inorganic particles is small, and it is considered that the effect of suppressing the penetration of the solvent component in the coating liquid cannot be obtained.

In the present invention, the amount of the inorganic particles is preferably 10 to 15% by weight with respect to the other solid content forming the protective film 16.
By setting the amount of the inorganic particles in the above range, it is preferable in that the effect of suppressing the penetration of the solvent component in the coating solution to the phosphor layer 14 can be more suitably obtained.

In the present invention, the weight ratio between the inorganic particles and the other solid content in the protective film 16 is the weight of the inorganic particles to be added in the coating solution for forming the protective film 16 and the addition in the manufacturing process. What is necessary is just to obtain | require the weight of solid content of components other than the inorganic particle to do, and to obtain | require the weight ratio of an inorganic particle and other solid content.
On the other hand, in the manufactured conversion panel 10, first, the protective film 16 is peeled off from the conversion panel 10, and the weight (weight A) of the protective film 16 is measured. Next, the protective film 16 is burned, and the solid content remaining after burning is regarded as inorganic particles, and the weight (weight B) is measured. Then, the weight ratio between the inorganic particles and the solid content of other components may be determined by the formula “weight B / (weight A−weight B)”.

In the conversion panel 10 of the present invention, the inorganic particles are not particularly limited, and particles of various inorganic materials can be used. Alumina (aluminum oxide), silica (silicon oxide), magnesium oxide, zinc oxide, sulfide Preferred examples include particles of zinc, titanium oxide, niobium oxide, barium sulfide, lead carbonate, silicon oxide and the like.
Among these, alumina and silica particles are particularly preferably used. By using alumina particles or silica particles as inorganic particles, suitable solvent retention ability can be expressed by surface activity due to the high specific surface area of alumina or silica particles. It is preferable in that it can be performed.
In addition, multiple types of inorganic particles may be used in combination.

In the present invention, the particle diameter of the inorganic particles is not particularly limited, but the average diameter is preferably 5 to 1000 nm, particularly preferably 400 to 600 nm.
By setting the particle diameter of the inorganic particles in the above range, aggregation can be suitably suppressed and the inorganic particles can be more suitably dispersed. Therefore, the surface area becomes sufficiently large, and a higher effect of adding inorganic particles is obtained. It is preferable in that it can be used.

In the conversion panel 10 of the present invention, the resin forming the protective film 16 is not particularly limited, and various resins (natural / synthetic polymer materials) used for the protective layer in the coating type conversion panel can be used. Is possible.
As an example, fluorine resin, polyurethane, polyacryl, cellulose derivative, polymethyl methacrylate, polyester, and epoxy resin are preferably exemplified. A plurality of these resins may be used in combination.
Of these, fluororesins are particularly preferred in terms of contamination resistance, scratch resistance, durability, and the like. The fluorine-based resin is a polymer of an olefin (fluoroolefin) containing fluorine or a copolymer containing an olefin containing fluorine as a copolymer component. Examples thereof include polytetrafluoroethylene and polychlorotrifluoroethylene. Polyvinyl fluoride, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, fluoroolefin-vinyl ether copolymer and the like are preferably exemplified.

In the conversion panel of the present invention, the thickness of the protective film 16 is not particularly limited and may be appropriately set according to the resin or inorganic particles used, but is preferably 1 to 5 μm.
By setting the thickness of the protective film 16 within the above range, it has sufficient performance as a protective film in terms of scratch resistance and durability, and can realize a high-quality image while suppressing blurring of emitted light. This is preferable.
In addition to the resin and inorganic particles, various additives such as a surfactant may be added to the protective film 16.

The conversion panel 10 of the present invention may be basically manufactured in the same manner as a known coating-type radiation image conversion panel. Hereinafter, an example of the manufacturing method of the conversion panel 10 of this invention is demonstrated.
First, a binder as described above is dissolved in a solvent, and a predetermined amount of phosphor particles are added and stirred / dispersed to prepare a coating liquid (paint) for forming the phosphor layer 14. In the present invention, since the binder in the phosphor layer 14 is preferably 1/30 or less of the phosphor particles by weight, the amount of the binder component is 1/30 or less of the phosphor particles. It is preferable to prepare a coating solution so that

  The solvent is not particularly limited, and various solvents that can dissolve the solvent may be used depending on the binder to be used. Commonly used solvents include: lower alcohols such as methanol, ethanol, n-propanol and n-butanol; chlorine atom-containing hydrocarbons such as methylene chloride and ethylene chloride; cyclic hydrocarbons such as cyclopentane and cyclohexane; toluene, xylene and the like Aromatic solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, etc .; esters such as methyl acetate, ethyl acetate, butyl acetate; ethers such as dioxane, ethylene glycol monoethyl ether, ethylene glycol monomethyl ether; mixed solvents thereof, etc. Is exemplified.

In addition, the coating solution may be provided with a dispersant for improving the dispersibility of the phosphor particles and a plastic for improving the binding force between the phosphor particles and the binder in the phosphor layer 14 as necessary. Various additives such as an agent may be added.
Examples of the dispersant include phthalic acid, stearic acid, caproic acid, lipophilic surfactant and the like. Examples of the plasticizer include phosphoric acid esters such as triphenyl phosphate, tricresyl phosphate, and diphenyl phosphate; phthalic acid esters such as diethyl phthalate and dimethoethyl phthalate: ethyl phthalyl ethyl glycolate, butyl phthalyl butyl glycolate Examples thereof include polyesters of triethylene glycol and adipic acid, polyesters of polyethylene glycol and aliphatic dibasic acid such as polyesters of diethylene glycol and succinic acid, and the like.

Here, in the change panel 10 of the present invention, the phosphor layer 14 does not include a component (curing agent) that polymerizes the binder.
Therefore, the coating liquid for forming the phosphor layer 14 is prepared without adding a component for polymerizing the binder. For example, when the binder is polyurethane (urethane prepolymer), the coating solution is prepared without adding a compound that causes a polymerization reaction of the urethane compound, such as an isocyanate compound.

The coating liquid prepared in this manner is applied to the substrate 12 so as to have the desired thickness of the phosphor layer 14 and dried to form the phosphor layer 14.
There are no particular limitations on the method of applying the coating solution, and any known coating method such as a doctor blade, a roll coater, or a knife coater can be used. Needless to say, drying may be performed by heating or the like as necessary.

The phosphor layer 14 is not necessarily limited to being formed by directly applying the coating liquid to the substrate 12 as described above. For example, separately, after applying a coating liquid on a sheet-like temporary support such as a glass plate, a metal plate, and a plastic sheet and drying to form a phosphor layer, the phosphor layer is pressed onto the substrate 12, Alternatively, a method of transferring the phosphor layer from the temporary support to the substrate 12 by using an adhesive and forming the phosphor layer 14 on the substrate 12 may be used.
Further, if necessary, a layer that exhibits various functions, such as a conductive layer and a light reflection layer, may be formed prior to or after the formation of the phosphor layer 14.

When the phosphor layer 14 is formed, a heat compression process is performed using a heating roller pair, a calendar machine, or the like as necessary.
The conditions for heat compression may be appropriately set according to the formed phosphor layer 14.

On the other hand, a resin as described above is dissolved in a solvent, and a predetermined amount of inorganic particles are added and stirred / dispersed to prepare a coating solution for forming the protective film 16.
Here, in this invention, since content of the inorganic particle in the protective film 16 is 8 to 18 weight% with respect to other solid content, this coating liquid has the weight of an inorganic particle other than an inorganic particle. It is prepared so as to be in the range of 8 to 18% by weight with respect to the weight of the solid content.

The solvent may be any of various solvents that can be dissolved in accordance with the resin to be used, and examples thereof are the same as the coating liquid for the phosphor layer 14.
When a fluororesin is used as the resin for forming the protective film 16, the fluororesin is generally insoluble in an organic solvent, but a copolymer containing a fluoroolefin as a copolymer component is particularly copolymerized. Some structural units (that is, other than fluoroolefins) can be suitably used because they are soluble in common organic solvents. An example of such a copolymer is a fluoroolefin-vinyl ether copolymer. In addition, since polytetrafluoroethylene and its modified products are soluble in an appropriate fluorine-based organic solvent such as a perfluoro solvent, the coating is applied in the same manner as the copolymer containing the fluoroolefin as a copolymer component. Thus, a resin composition layer containing a fluorine-based resin can be formed.

Further, as in the case of the coating solution for the phosphor layer 14, the above-described dispersant and plasticizer may be added as necessary. In addition, a known silicone oil, wax, reactive silicon, or the like may be added to the coating liquid for forming the protective film 16 in order to improve the antifouling property of the protective film.
Furthermore, you may add to the coating liquid for forming the protective layer 16 the component (hardening agent / crosslinking agent) which polymerizes resin (component) which forms the protective layer 16 as needed.

The protective film 16 is formed by applying the coating solution thus prepared to the phosphor layer 14 so as to have the desired thickness of the protective film 16 and drying (curing) it. Here, since this coating liquid contains 8 to 18% by weight of inorganic particles with respect to the other solid content, it was applied even if the phosphor layer 14 did not contain a curing agent as described above. The solvent component of the coating liquid does not soak into the phosphor layer 14, and blisters are not generated in the phosphor layer 14 due to the drying of the coating liquid.
The coating method for the coating solution may be performed in the same manner as for the phosphor layer 14. Similarly, the coating solution may be dried by heating as necessary.

  Although the radiation image conversion panel of the present invention has been described in detail above, the present invention is not limited to the above-described examples, and various changes and improvements may be made without departing from the scope of the present invention. Of course.

  Hereinafter, the present invention will be described in more detail with reference to specific examples of the method for producing a radiation image conversion panel of the present invention.

[Example 1]
(1) Formation stimulable phosphor particles of the phosphor layer, the average particle size is _{7μm BaF (Br 0.85 I 0.15)} : the Eu ²⁺ particles 1400 g, an average particle diameter of 2μm BaF (Br _0.85 I _0.15) : 600 g of Eu ²⁺ particles, 46.7 g of polyurethane elastomer (Pandex T-5265HM [solid], manufactured by Dainippon Ink & Chemicals, Inc.) as a binder, epoxy resin (jER # 1001 [j] Solid], oiled shell epoxy)) was prepared.
These materials were added to a mixed solvent of 380 g of methyl ethyl ketone (MEK) and 163 g of butyl acetate, and stirred using a propeller mixer to prepare a coating solution for forming the phosphor layer 14.

As a temporary support, a PET film coated with a silicone release agent was prepared.
The surface of the temporary support is coated with a coating solution for forming the phosphor layer 14 prepared previously using a doctor blade, dried, and then peeled off from the temporary support to obtain a thickness of 405 μm. A phosphor layer 14 was formed.

(2) Formation of conductive layer SnO ₂ (Sb doped) needle-shaped fine particles (major axis: 0.2-2 μm, minor axis: 0.01-0.02 μm, FS-10P, manufactured by Ishihara Sangyo Co., Ltd.) MEK dispersion (solid content: 30% by weight) of 500 g, resin: 60 g of saturated polyester resin (Byron 300, manufactured by Toyobo Co., Ltd.), curing agent: polyisocyanate (Takenate D140N [solid content: 75%], Mitsui Takeda Chemical 6.6 g) were prepared.

The above materials were added to MEK and mixed and dispersed to prepare a coating solution having a viscosity of 0.02 to 0.05 Pa · s.
This coating solution was applied to the surface of a polyethylene terephthalate (PET) sheet (support, thickness 188 μm, haze: about 27, Lumirror S-10, manufactured by Toray Industries, Inc.) using a doctor blade, dried, and conductive. A layer (layer thickness: 2 μm) was formed.

(3) Formation of light reflecting layer As a light reflecting substance, 500 g of high-purity alumina fine particles (average particle size: 0.4 μm, UA-5105, manufactured by Showa Denko KK) are used, and a soft acrylic resin (Chris Coat P) is used as a binder. -1018GS [20% toluene solution], Dainippon Ink & Chemicals, Inc.) 112 g, as a colorant, ultramarine (SM-03S, Daiichi Kasei Kogyo Co., Ltd.) 2.5 g, as a coupling agent 5 g of γ-aminopropyltriethoxysilane (KBE903, manufactured by Shin-Etsu Chemical Co., Ltd.) were prepared.

The above materials were added to a mixed solvent of MEK and butyl acetate, mixed and dispersed to prepare a coating solution having a viscosity of 2 to 3 Pa · s.
The coating liquid was applied to the surface of the conductive layer using a doctor blade and dried to form a light reflecting layer (layer thickness: about 70 μm), thereby preparing a substrate 12. The reflectance of the light reflection layer at the emission peak wavelength (400 nm) of the phosphor particles was 98%.

Next, using a calender machine, heat fusion of the phosphor layer 14 and the substrate 12 is performed under the conditions of an upper roll temperature of 45 ° C., a lower roll temperature of 45 ° C., a pressure of 48 kg / cm ² , and a feed rate of 0.3 m / min. -A compression process was performed.

(4) Formation of Protective Film 6.1 g of alumina particles (average particle size 0.5 μm) as inorganic particles, and fluororesin (fluoroolefin-vinyl ether copolymer) as resin (Lumiflon LF200 [60% xylene solution] 85.2 g, manufactured by Asahi Glass Co., Ltd., 23.1 g of polyisocyanate (Takenate D140N [solid content 75%], manufactured by Mitsui Takeda Chemical Co., Ltd.) as a crosslinking agent, and dibutyltin dilaurate (KS1260, manufactured by Kyodo Yakuhin Co., Ltd.) as a catalyst. ) Was prepared in an amount of 0.35 g.
These materials were added to a mixed solvent of 100 g of MEK and 120 g of cyclohexane, and stirred using a propeller mixer to prepare a coating solution for forming the protective film 16. That is, in this example, the amount of inorganic particles in the protective film 16 is 9% by weight with respect to the resin (6.1 / (85.2 × 0.6 + 23.1 × 0.75 + 0.35)).

  Next, a coating solution for forming the prepared protective film 16 is applied on the phosphor layer 14 using a doctor blade and dried to form a protective film 16 having a thickness of 3 μm. Panel 10 was produced.

[Example 2]
A conversion panel 10 was produced in exactly the same manner as in Example 1 except that the amount of alumina particles added was 9.1 g in the preparation of the coating solution for forming the protective film 16.
That is, in this example, the amount of inorganic particles in the protective film 16 is 13% by weight with respect to the resin.

[Example 3]
A conversion panel 10 was produced in exactly the same manner as in Example 1 except that in the preparation of the coating solution for forming the protective film 16, the amount of alumina particles added was 12.1 g.
That is, in this example, the amount of inorganic particles in the protective film 16 is 18% by weight with respect to the resin.

[Comparative Example 1]
In the preparation of the coating liquid for forming the phosphor layer 14, an isocyanate compound (Coronate XH, manufactured by Nippon Polyurethane Industry Co., Ltd.) is further added as a binder curing agent, and the protective film 16 is formed. A conversion panel was prepared in exactly the same manner as in Example 3 except that melamine resin particles (Eposter S6, manufactured by Nippon Shokubai Co., Ltd.) were used in place of the alumina particles in preparation of the liquid.
That is, in this example, the amount of organic particles in the protective film is 18% by weight with respect to the resin.

[Comparative Example 2]
In the preparation of the coating solution for forming the protective film 16, a conversion panel was produced in the same manner as in Example 3 except that melamine resin particles (Epester S6, manufactured by Nippon Shokubai Co., Ltd.) were used instead of alumina particles. did.
That is, in this example, the amount of organic particles in the protective film is 18% by weight with respect to the resin.

[Comparative Example 3]
A conversion panel 10 was produced in the same manner as in Example 1 except that the amount of alumina particles added was 3 g in the preparation of the coating liquid for forming the protective film 16.
That is, in this example, the amount of inorganic particles in the protective film 16 is 4% by weight with respect to the resin.

[Comparative Example 4]
A conversion panel 10 was produced in exactly the same manner as in Example 1 except that the amount of alumina particles added in the preparation of the coating solution for forming the protective film 16 was changed to 18.2 g.
That is, in this example, the amount of inorganic particles in the protective film 16 is 26% by weight with respect to the resin.

[Example 4]
The conversion panel 10 was produced in the same manner as in Example 1 except that silica particles (AEROSIL R104, manufactured by Nippon Aerosil Co., Ltd.) were used instead of alumina particles in the preparation of the coating liquid for forming the protective film 16. did.
That is, in this example, the amount of inorganic particles in the protective film is 9% by weight with respect to the resin.

[Comparative Example 5]
A protective film (laminate film) in which a polyester resin (thickness: 1.5 μm) was applied as an adhesive to a PET film having a thickness of 6 μm was prepared.
After forming the phosphor layer 14, this protective film was adhered to the surface of the phosphor layer 14 to form a protective film 16 (no protective film 16 by coating), and was exactly the same as in Example 1. Thus, the conversion panel 10 was produced.

Each conversion panel 10 obtained was inspected as follows.
[Presence / absence of blister NG section]
For each conversion panel 10 obtained, whether there is an image quality degradation portion due to blisters generated in the phosphor layer 14 by visual inspection of the surface with visible light and image inspection by X-ray irradiation (blisters). The presence or absence of NG part) was confirmed.

[Image quality evaluation (DQE)]
About each obtained conversion panel 10, DQE (Detective Quantum Efficency: detection quantum efficiency) in 1mR-1cy was measured based on IEC specification (IEC62220-1). The measurement of DQE was performed avoiding the blister generation part.
In addition, evaluation of DQE was performed by setting DQC in Comparative Example 2 to 100.
The above results are shown in the following table together with the characteristics of each conversion panel 10.

上記表に示されるように、保護膜１６に所定量の無機粒子を含有する本発明の変換パネルは、いずれも、蛍光体層１４のブリスタに起因する画質劣化が無く、かつ、良好な画質を有している。
これに対し、比較例１は、蛍光体層に硬化剤を添加しているため、保護膜１６の粒子が有機粒子であっても、ブリスタに起因する画質劣化は無いが、硬化剤を使用しているため、画質が他の物よりも劣っている。また、比較例２は、保護膜１６の粒子が有機粒子であるために、蛍光体層１４にブリスタが発生し、これに起因する画質劣化が生じている。また、比較例３および比較例４は、保護膜１６に無機粒子を用いているが、量が多すぎる／少なすぎるために、蛍光体層１４にブリスタが発生し、これに起因する画質劣化が生じている。 さらに、保護膜１６として保護フィルムを用いた比較例５は、保護フィルムによる画質劣化が生じてしまっている。
以上の結果より、本発明の効果は明らかである。

As shown in the above table, none of the conversion panels of the present invention containing a predetermined amount of inorganic particles in the protective film 16 is free from image quality deterioration due to the blisters of the phosphor layer 14 and has good image quality. Have.
On the other hand, in Comparative Example 1, since a curing agent is added to the phosphor layer, even if the particles of the protective film 16 are organic particles, there is no deterioration in image quality due to blistering, but the curing agent is used. Therefore, the image quality is inferior to other things. Further, in Comparative Example 2, since the particles of the protective film 16 are organic particles, blisters are generated in the phosphor layer 14 and image quality deterioration due to this occurs. Moreover, although the comparative example 3 and the comparative example 4 use the inorganic particle for the protective film 16, since the amount is too much / too little, a blister is generated in the phosphor layer 14, and the image quality deterioration due to this occurs. Has occurred. Furthermore, in Comparative Example 5 using a protective film as the protective film 16, image quality deterioration due to the protective film has occurred.
From the above results, the effects of the present invention are clear.

It is a schematic diagram of an example of the radiation image conversion panel of this invention.

Explanation of symbols

10 (Radiation image) conversion panel 12 Substrate 14 Phosphor layer 16 Protective film

Claims (6)

A radiation image conversion panel having a phosphor layer and a protective film formed on the phosphor layer,
The phosphor layer has phosphor particles and a binder and does not contain a component that causes a polymerization reaction of the binder, and further, the protective film contains inorganic particles, and A radiation image conversion panel, wherein the weight ratio of the inorganic particles is 8 to 18% by weight with respect to the solid content of the protective film other than the inorganic particles.   The radiation image conversion panel according to claim 1, wherein the inorganic particles are alumina particles.   The radiation image conversion panel according to claim 1, wherein the inorganic particles are silica particles.   The radiation image conversion panel according to claim 1, wherein the resin forming the protective film is a fluororesin.   The radiation image conversion panel according to claim 1, wherein the protective film is formed by being directly applied to a phosphor layer.   The radiation image conversion panel according to any one of claims 1 to 5, wherein the amount of the binder in the phosphor layer is 1/30 or less by weight with respect to the phosphor particles.

Images