JPH077114B2 - Phosphor panel for X-ray sensitization having heating and drying means - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to an intensifying screen for direct radiography of a medical X-ray photograph or a fluorescent screen for indirect radiography.

BACKGROUND OF THE INVENTION

Intensifying screens (generally called intensifying screens) for direct photography and fluorescent screens (generally called fluorescent screens) for indirect photography are
A phosphor that emits fluorescence by X-rays is coated on a support that does not interfere with X-ray photography, and the formed phosphor layer is covered with a protective layer. The intensifying screen is held in close contact with a photographic light-sensitive material (X-ray film) having a silver halide light-sensitive layer coated on the surface of a support, and emits light when irradiated with X-rays. The sensitivity to X-rays is indirectly improved. The fluorescent plate converts an X-ray image into a visible image, which can be photographed by an indirect photographing camera or a photographing tube. Since the fluorescent screens such as the intensifying screen and the fluorescent plate are generally in the form of a panel, they will be collectively referred to as X in the following description.
A liner-sensitized phosphor panel is referred to as a phosphor panel or simply a panel for brevity. The phosphor used for the intensifying screen is generally used when the X-ray film for direct photography has a regular color sensitivity.
Phosphor mainly composed of calcium tungstate having a fluorescence spectrum of 4000 to 5000Å Europium activated barium sulfate phosphor etc. is used, and if the X-ray film for direct photography is orthomatic, terbium is an activator. The cadmium oxysulfide-based phosphor having a peak near 5400Å is used. Further, since the photosensitivity of the X-ray film for indirect photography is orthomatic, a cadmium zinc sulfide-based one having silver having an emission spectrum of 5400 to 5500Å as an activator is used as the fluorescent plate. By the way, the above-mentioned phosphor has good absorption efficiency of X-ray energy, good emission effect, emits a fluorescence spectrum that efficiently covers the photosensitive spectrum of the photographic light-sensitive material, has no afterglow, and provides sharpness of an image. It is required not to interfere with the shooting operation. Here, rare-earth phosphors such as LaOBr: Tb, BaFBr: Eu, Ba
Alkaline earth phosphors such as FCl: Eu have high X-ray absorption efficiency and emission efficiency and are suitable in the emission spectrum region, and are preferable as X-ray sensitization phosphors. Also CsI: Na, CaI: Tl, RbB
Alkali halide phosphors such as r: Tl have the above-mentioned performance and can easily form a phosphor layer by a vapor deposition method such as vapor deposition, so the phosphor packing density in the phosphor layer is close to 100%, and the binder This is preferable because the sensitivity, the graininess and the sharpness of the image are remarkably improved as compared with the phosphor layer coated with the phosphor coating in which the phosphor particles are suspended and dispersed in the solution. Further, it is strongly required that the phosphor panel can be used repeatedly (durability). That is, the phosphor panel can be repeatedly used for a long time or many times without deteriorating the image quality of the obtained X-ray image. It is desired to have the ability to withstand the use of For that purpose, the phosphor layer in the phosphor panel must be sufficiently protected from external physical or chemical stimuli. However, the phosphors are generally hygroscopic, and the rare earth, alkaline earth or alkali halide phosphors are particularly hygroscopic. When the phosphor layer absorbs water, the alkaline earth-based phosphor (for example, BaFBr: Eu) is decomposed and the sensitivity to X-ray is lowered. In addition, the sensitivity of X-rays of alkali halide phosphors (such as CsI: Na) changes due to moisture absorption and dehumidification, which makes the imaging conditions unstable and the X
Since the quality of the line image is deteriorated, it is desired to protect the phosphor layer from containing water. In the conventional phosphor panel, in order to deal with the above-mentioned problems, a method has been adopted in which a phosphor having a low hygroscopic property is selected at the sacrifice of characteristics and a phosphor layer surface is covered with a protective layer as needed. This protective layer is formed, for example, as described in JP-A-59-42500, by directly applying a protective layer coating solution on the phosphor layer, or by forming a separately formed protective layer in advance. It is formed by a method of adhering on the body layer. However, if the protective layer is made thicker to reduce the water permeability, the sharpness of the image will be deteriorated, so it is necessary to make it thinner, and it is not possible to completely prevent the moisture transmission. It was possible. Therefore, the alkaline earth metal-based phosphors such as BaFBr: Eu, the alkali metal-based phosphors such as CsI: Na or the LaOBr: Tl phosphors or the like, which have remarkable hygroscopicity, have characteristics due to moisture absorption. Although these phosphors deteriorate due to their excellent properties such as X-ray absorption efficiency and emission efficiency, it has been difficult to use them as X-ray sensitizing phosphors. In order to improve the durability of the phosphor panel, further improvement is particularly desired in terms of moisture resistance and moisture-proof means, but most of the moisture-proof properties other than the method for reducing the moisture permeability of the protective layer. The current situation is that it has not been examined.

[Object of the Invention]

The present invention has been made in view of the above-mentioned current situation in the phosphor panel, and an object of the present invention is to maintain the dryness of the phosphor layer and to use the phosphor in a good state for a long period of time. To provide a panel.

[Constitution of the invention]

The above-mentioned object of the present invention is to incorporate a heating and drying means into a phosphor panel for X-ray photosensitization using a phosphor that emits fluorescence upon irradiation with X-rays. Achieved by As a mode of the present invention, the heating and drying means may be incorporated and incorporated in the constituent layer of the phosphor panel and the support, or a layer composed of a heating element may be separately provided. Next, the present invention will be specifically described. A phosphor panel using a phosphor that emits fluorescence upon irradiation with X-rays is generally a phosphor layer (hereinafter abbreviated as a fluorescent layer) on a support and various constituent layers (for example, a protective layer) for complementing the function of the fluorescent layer. , A filter layer or an adhesive layer). FIG. 1 illustrates various aspects of the phosphor panel of the present invention. In FIG. 1 (a), 1 is a support, 2H is a heat-generating fluorescent layer in which a drying / drying heating element (hereinafter abbreviated as a heating element) is incorporated, and 3 is a protective layer. An example is shown in which the protective layer covers the peripheral side surface of the fluorescent layer. In the same figure (b), on the back surface of the support 1 for the fluorescent layer 2, a heating layer H1 made of a heating element is provided on the support 1.
The heating layer H2 composed of a heating element is provided on the same side of the support as the fluorescent layer 2 and in contact with the support in FIG. It covers the surface. In FIG. 1D, 1H is a heat generating support in which a heat generating element is contained and incorporated in the support. In (e) of the figure, H3 is a supporting heating element in which the heating element itself also serves as a support, and the protective layer 3 covers and covers the entire surface including the back surface of the fluorescent layer 2 and the supporting heating element H3. The same figure (f) shows the heating layer H4
Is provided in contact with the upper surface of the fluorescent layer 2, and the fluorescent layer 2 is sandwiched between the heat generating layers H2 and H4 in FIG. FIG. 3H is an example having a heat generation protection layer 3H in which a heating element is contained and incorporated. The panel of the present invention is not limited to the above example, but when the layer formed of the heating element or the layer containing the heating element is located between the fluorescent layer and the photographic light-sensitive material, the panel is heated. Is a substance transparent to fluorescence. It is preferable to use a thin electroconductive fine powder such as carbon black or metal fine powder for the layer containing the heating element or incorporated therein or the heating support. In addition, the heating layer consisting of a heating element is applied with a thin film by vapor deposition or sputtering of a metal oxide or metal with a low electrical resistance such as transparent indium oxide, or by coating with a paint that disperses and suspends carbon black, fine metal powder, etc. Membranes are used. Further, a carbon fiber sheet or the like is used for the supporting heating element in which the heating element itself also serves as a supporting body. The heating temperature range for panel drying or moisture protection is 40 ~
The temperature is 150 ° C., preferably 40 to 80 ° C. Within this temperature range, the use of non-heat resistant materials (such as polyethylene terephthalate) for the support and the protective layer is allowed. On the other hand, if the heating temperature is too high, the sensitivity of the fluorescent layer is reduced during X-ray irradiation, the amount of afterglow is increased, and the photographic light-sensitive material is subject to thermal fog, which is not preferable. The heating may be performed at any time during X-ray irradiation and / or non-irradiation during which an X-ray image is provided. The time required for drying is 80 ° C even with a panel whose relative sensitivity is reduced by 30% due to moisture content.
It can recover to almost 100% in 0 to 2.0 hours. The adhesive layer-free fluorescent layer formed by vapor deposition has a better drying efficiency (sensitivity recovery speed). Further, measures such as increasing the heating temperature during non-irradiation rather than during irradiation to enhance the drying effect may be taken, or heating may be stopped during irradiation. It may be dried sequentially after each use, or it may be subjected to batch dehumidification when not in use, such as at night, or after long-term storage to the extent that the phosphor does not decompose and is unable to recover its function. Good. When the heating element is incorporated in the panel as in the above-mentioned embodiment,
The heating element may have any pattern as long as it forms a current circuit and has a form capable of exerting a sufficient heating effect on the entire surface of the panel and a form avoiding any troubles related to the arrangement. An example thereof is shown in FIG. The figure (a) is an example in which a uniform thin layer circuit is formed on the heating element, the figure (b) is a comb type, and the figure (c) is an example of a bent single line type circuit. In FIG. 2, P is an electrode and H is a heating element. Next, the panel drying temperature control can be easily performed by combining a temperature detector such as a thermocouple with a temperature controller and a heater power source. FIG. 3 shows a block diagram of one example thereof. Also, a heating / drying device may be separately used in combination. Next, an example of the dehumidification efficiency of the panel of the present invention is shown in FIG.
The structure of the panel has the specifications shown in FIG. 1 (c), and CsI: Na phosphor is used as the phosphor. Further, FIG. 5 shows the relationship between the water content of the fluorescent layer of the panel (mg water / exhaust layer 9) and the fluorescence emission intensity. As is apparent from the figure, heating of the fluorescent layer dehumidifies and protects the layer, ensuring the durability of the panel. As the support used in the panel of the present invention, various polymer materials, glass, wool, cotton, paper, metal and the like are used, or a combination thereof may be used. It may be one that can be processed into a flexible sheet or web for handling as an information recording material, and in this respect, for example, cellulose acetate film, polyester film, polyethylene terephthalate film, polyamide film, polyimide film, triacetate film, polycarbonate film, etc. Plastic films are preferred. The layer thickness of these supports varies depending on the material of the support used and the like, but is generally 80 μm to 1000 μm, and more preferably 150 μm to 500 μm from the viewpoint of handling. The surface of these supports may be a smooth surface, may be a matte surface for the purpose of improving the adhesiveness to the fluorescent layer, and may be provided with an undercoat layer. Examples of the phosphor used in the phosphor panel of the present invention include Y ₂
O ₂ S: Tb, Gd ₂ O ₂ S: Tb, La ₂ O ₂ S: Tb, (Y, Gd) ₂ O ₂ S: Tb,
(Y, Gd) ₂ O ₂ S: Tb, Tm, Y ₂ O ₂ S: Eu, Gd ₂ O ₂ S: Eu, (Y, Gd) ₂
O ₂ S: Eu, Y ₂ O ₃ : Eu, Gd ₂ O ₃ : Eu, (Y, Gd) ₂ O ₃ : Eu, YVO ₄ : E
u, YPO ₄ : Tb, GdPO ₄ : Tb, LaPO ₄ : Tb, YPO ₄ : Eu, LaOBr: T
b, LaOBr: Tb, Tm, LaOCl: Tb, LaOCl: Tb, Tm, GdOBr: Tb, G
dOCl: Tb, CaWO ₄ , CaWO: Pb, MgWO ₄ , BaSO ₄ : Pb, BaSO ₄ : Eu
²⁺ , (Ba, Sr) SO ₄ : Eu ²⁺ , Ba ₃ (PO ₄ ) ₂ : Eu ²⁺ , (Ba, Sr)
₃ (PO ₄ ) ₂ : Eu ²⁺ , BaFCl: Eu ²⁺ , BaFBr: Eu ²⁺ , BaFCl: Eu
²⁺ , Tb, BaFBr: Eu ²⁺ , Tb, BaF ₂ , BaCl ₂ , KCl: Eu ₂ ⁺ , BaF ₂ , Ba
Cl ₂ ,, BaSO ₄ , KCl: Eu ²⁺ , (Ba, Mg) F ₂ , BaCl ₂ , KCl: Eu ²⁺ , Cs
I: Na, CsI: Tl, RbBr: Tl, RbBr, CsBr: Tl, NaI, ZnS: Ag,
(Zn, Cd) S: Ag, ZnS: Cu, ZnS: Cu, Al, (Zn, Cd) S: Cu,
Examples of X-ray phosphors include (Zn, Cd) S: Cu, Al, (Zn, Cd) S: Au, Al, and HfP ₂ O ₇ : Cu. However, the phosphor used in the panel of the present invention is not limited to the above-mentioned phosphor, and may be any phosphor as long as it emits light upon irradiation with X-rays. Among the above phosphors, a phosphor that is particularly sensitive to moisture is LaOBr: Tb:
System phosphors, alkaline earth metal system phosphors, and alkali metal system phosphors, and when the present invention is applied to these phosphors, the effect is particularly large. The panel of the present invention may have a phosphor layer group consisting of one or more phosphor layers containing at least one kind of the above-mentioned phosphor. The phosphors contained in each phosphor layer may be the same or different. The phosphor layer is formed on the support as a layered structure containing no binder by using a phosphor such as a vapor deposition method or a sputtering method as described in JP-A-61-73100. Alternatively, the phosphor may be dispersed in an appropriate binder to prepare a coating solution, and the coating solution may be coated on a support to form the coating solution. At this time, the average particle size of the phosphor particles is 0.
It is 1 to 100 μm, preferably 0.5 to 30 μm. When a binder is used in the panel of the present invention, for example, a protein such as gelatin, a polysaccharide such as dextran or gum arabic, polyvinyl butyrate, polyvinyl acetate, nitrocellulose, ethyl cellulose, vinylidene chloride-vinyl chloride copolymer, Binders usually used for layer constitution such as polymethylmethacrylate, vinyl chloride-vinyl acetate copolymer, polyurethane, cellulose acetate butyrate and polyvinyl alcohol are used. However, regarding the panel of the present invention, the above-mentioned Japanese Patent Laid-Open No.
As proposed in No. 61-73100, it is preferable that the fluorescent layer has a structure containing no binder. Examples of the method for forming the fluorescent layer containing no binder include the following methods. The first method is a vapor deposition method. In this method, first, the support is placed in the vapor deposition apparatus, and then the apparatus is evacuated.
-Set the vacuum to about ^-6 Torr. Next, at least one of the phosphors is heated and evaporated by a method such as a resistance heating method or an electron beam method to deposit the phosphor to a desired thickness on the surface of the support. As a result, a fluorescent layer containing no binder is formed,
It is also possible to form the fluorescent layer in a plurality of times in the deposition process. Further, in the vapor deposition step, co-evaporation can be performed using a plurality of resistance heaters or electron beams. In the vapor deposition method, the phosphor material is co-deposited using a plurality of resistance heaters or electron beams,
It is also possible to synthesize the desired phosphor on the support and simultaneously form the phosphor layer. Further, in the vapor deposition method, the vapor deposition target may be cooled or heated during vapor deposition, if necessary. Further, the fluorescent layer may be heat-treated after completion of vapor deposition. The second method is a sputtering method. In this method, as in the vapor deposition method, after the support is placed in the sputtering apparatus, the inside of the apparatus is once evacuated to a vacuum degree of about 10 ^-6 Torr, and then an inert gas such as Ar or Ne is used as a gas for sputtering. The gas is introduced into the sputtering apparatus to a gas pressure of about 10 ^-3 Torr. Next, by using the phosphor as a target and performing sputtering, the phosphor is deposited on the surface of the support to a desired thickness, and a phosphor layer can be formed in the same manner as in the vapor deposition method. The third method is the CVD method. In this method, an organometallic compound containing a target phosphor or a phosphor raw material is decomposed by heat or energy such as high frequency power to obtain a binder-free phosphor layer on a support. The fourth method is the spraying method. In this method, a phosphor powder is sprayed on the binder layer to obtain a binder-free phosphor layer on the support. The layer thickness of the phosphor layer of the panel of the present invention varies depending on the sensitivity of the target panel to X-rays, the type of phosphor, etc.,
When the binder is not contained, it is preferably selected from the range of 60 μm to 1000 μm, more preferably from 100 μm to 800 μm, and when the binder is contained, 100 μm to 1000 μm.
It is preferable to be selected from the range of m, more preferably from 100 μm to 500 μm. In the present invention, it is preferable to provide the protective layer as described above. Examples of the material for the protective layer include cellulose derivatives such as cellulose acetate, nitrocellulose, and ethyl cellulose, or polymethyl methacrylate, polyvinyl butyral, polyvinyl formal, polycarbonate, polyvinyl acetate, polyacrylonitriletrilonitrile, polymethylallyl alcohol, polymethyl vinyl. Ketone, cellulose diacetate, cellulose triacetate, polyvinyl alcohol, polyacrylic acid, polymethacrylic acid, polyglycine, polyacrylamide, polyvinylpyrrolidone, polyvinylamine, polyethylene terephthalate, polyethylene, polyvinylidene chloride, polyvinyl chloride, polyamide (nylon), Polytetrafluoride ethylene, polytrifluoride-ethylene chloride, polypropylene,
Examples thereof include tetrafluoroethylene-hexafluoropropylene copolymer, polyvinyl isobutyl ether, polystyrene and the like. Further, as described in JP-A-61-176900, a coating solution containing at least one of a radiation-curable resin and a thermosetting resin is applied to the surface on which a protective layer is to be placed, The coating liquid may be cured by irradiating with radiation such as ultraviolet rays or electron beams and / or heating by using an apparatus as shown in No. 61-176900. The radiation curable resin may be a compound having an unsaturated double bond or a composition containing the same, and such a compound is preferably a prepolymer and / or an oligomer having two or more unsaturated double bonds. Further, a monomer having an unsaturated double bond (vinyl monomer) can be contained therein as a reactive diluent. The layer thickness of the protective layer formed as described above is 0.5 μm.
˜1000 μm, more preferably 1 μm to 50 μm. In addition, SiO ₂ , SiC, SiN, Al ₂ O ₃
Inorganic substance layers such as may be formed by a vacuum deposition method, a sputtering method, or the like. The inorganic material layer has a thickness of 0.1 μm to 1
About 0 μm is preferable. The panel of the present invention may be manufactured by providing a fluorescent layer on a support and then forming a protective layer on the fluorescent layer, or by manufacturing a protective layer formed on the fluorescent layer on the fluorescent layer. You may. Alternatively, after forming the fluorescent layer on the protective layer, a procedure for providing the support may be adopted. The protective layer preferably has no harmful absorption in the fluorescence spectrum region.

EXAMPLES Next, the present invention will be described with reference to examples. Example 1 As a support, a chemically strengthened glass having a thickness of 500 μm was placed in an evaporator. Next, put an alkali halide phosphor (CsI: 0.003Na) in a tungsten boat for resistance heating. , Set it to the resistance heating electrode, then evacuate the vaporizer to 2 x 10
^-6 Torr vacuum level. Next, an electric current was applied to the tungsten boat to evaporate the alkali halide phosphor by a resistance heating method and deposit the phosphor layer on the chemically strengthened glass until the layer thickness of the phosphor layer became 300 μm. Next, after taking this panel out into the air, a conductive film sheet (10 Ω / □, manufactured by Micro Engineering Laboratory Co., Ltd.) was prepared by depositing ITO on a polyimide film on the surface of the chemically strengthened glass where the stimulating layer was not provided. And a 20 μm thick transparent polyethylene terephthalate sheet on the surface of the fluorescent layer,
A panel A of the present invention having the structure shown in FIG. 1 (b) was obtained. Attach the electrodes and the temperature control circuit as shown in Fig. 3 to this panel A, and heat the fluorescent layer to 80 ℃, 30 ℃, relative humidity 70%.
The curve a in FIG. 6 shows the result of measuring the change in sensitivity with time by leaving it in a constant temperature chamber. Example 2 The sensitivity change with time was measured in the same manner as in Example 1 except that the heating of the fluorescent layer was 140 ° C., and the curve b in FIG. 6 was obtained. Example 3 In Example 1, a transparent conductive film (ITO, 10 Ω / □) was vapor-deposited on the side where a fluorescent layer was previously provided as a support 500 μ
A panel B of the present invention was obtained in the same manner as in Example 1 except that m-thick chemically strengthened glass was used. On the transparent conductive film, a SiO film (2000
Å) is provided. Next, the change in sensitivity with time of this panel B was measured in the same manner as in Example 1, and is shown as curve C in FIG. Comparative Example 1 The phosphor layer of panel A prepared in Example 1 was heated without heating.
The curve p in FIG. 6 shows the result of measuring the change in sensitivity with time after leaving it in a thermostatic chamber at a relative temperature of 70% at 70%. As shown in FIG. 6, the panel of the present invention prevents deterioration of sensitivity due to moisture absorption by heating the fluorescent layer and guarantees durability. Example 4 Alkali halide phosphor (0.9RbBr / 0.1CsI: 0.0001 / T
I) 8 parts by weight, 1 part by weight of polyvinyl butyral resin and 5 parts by weight of a solvent (cyclohexanone) were mixed and dispersed to prepare a coating solution for a fluorescent layer. Next, this coating solution was uniformly applied onto a 500 μm-thick chemically strengthened glass support placed horizontally, and naturally dried to form a 300 μm-thick photostimulation layer. The panel thus obtained was adhered to the surface of the chemically strengthened glass on which the fluorescent layer was not provided with the same conductive sheet as in Example 1, and to the surface of the fluorescent layer was adhered a transparent polyethylene terephthalate sheet having a thickness of 20 μm. The panel C of the present invention was obtained. After the panel A of Example 1 and the panel C of this example were left in a temperature-controlled room at 30 ° C. and a relative humidity of 80% for a sufficiently long period of time, they were taken out to a temperature-controlled room at a temperature of 30 ° C. and a relative humidity of 60%. Install a temperature control circuit like this, and heat the fluorescent layer to 80 ℃
The state of sensitivity recovery of was investigated. The results are shown in FIG. 8 as curve d (panel A) and curve e (panel C). Comparative Example 2 As in Example 4, the panel A of Example 1 was subjected to relative humidity at 30 ° C.
After leaving it in an 80% thermostatic chamber for a long time, the relative humidity at 30 ℃
It was taken out into a 60% thermostatic chamber, and the state of sensitivity recovery of the panel A was examined without heating the fluorescent layer. The result is shown in FIG.
Show as. It can be seen from FIG. 7 that the panel of the present invention recovers the sensitivity by heating the photosensitive layer even if the sensitivity is once lowered due to moisture absorption. In addition, since panel A of the panel of the present invention does not contain a binder in the fluorescent layer, the recovery of sensitivity is fast.

【The invention's effect】

As described above, the panel of the present invention having a built-in heating mechanism (1) is heated to prevent moisture from being adsorbed on the phosphor and prevent a decrease in sensitivity to radiation. (2) By heating, the water adsorbed on the phosphor is released, and the deterioration performance of the phosphor due to water adsorption is restored. (3) By heating, the trap level that causes long-life afterglow is reduced and S / N is improved. Etc., and the durability of the panel is improved.

[Brief description of drawings]

FIG. 1 is a sectional view of an example of the aspect of the panel of the present invention. Second
FIG. 3 is a diagram showing a circuit pattern of a heating element, and FIG. 3 is a block diagram of temperature control. FIG. 4 is a diagram showing the dehumidification efficiency of the panel fluorescent layer.
The figure shows the relationship between the water content of the fluorescent layer and the sensitivity. FIG. 6 shows the temperature effect on moisture proof, and FIG. 7 is a graph showing the sensitivity recovery behavior by heating. 1 ... Support, 2 ... Fluorescent layer, 3 ... Protective layer, 1H ... Exothermic support, 2H ... Exothermic fluorescent layer, 3H ... Exothermic protective layer, H1, H2 and H4 ... Exothermic layer, H3 …… Supporting heating element.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References Japanese Patent Publication 6-31910 (JP, B2)

Claims (1)

[Claims] 1. A phosphor panel for X-ray photosensitization, wherein a heating and drying means is incorporated into a phosphor panel for X-ray photosensitization using a phosphor that emits fluorescence upon irradiation with X-rays.