JPH11305000A - Radiation image conversion screen and manufacturing method thereof - Google Patents

Abstract

(57) Abstract: An object of the present invention is to provide an image conversion screen which is durable, in particular, does not peel off a support or a protective film from an edge portion due to repeated use, and a method for manufacturing the same. SOLUTION: In a radiation image conversion screen basically having a phosphor layer and at least one of a protective film and / or a support made of plastic, at least a part of an edge portion of the radiation image conversion screen is, for example, The protective film and / or the support are sealed with the same plastic by means such as heat melting.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation image conversion screen for converting a radiation image into visible light, such as an intensifying screen, a fluorescent plate, and an imaging plate, and a method of manufacturing the same. More specifically, the present invention relates to a radiation image conversion screen having excellent durability especially at an edge portion for repeated use, and a method of manufacturing the same.

[0002]

2. Description of the Related Art As is well known, a radiation image conversion screen (hereinafter simply referred to as an "image conversion screen") such as an intensifying screen, a fluorescent screen, an imaging plate or the like mainly converts an X-ray image of a subject into a visible image. It is used for medical diagnosis and nondestructive testing of substances.
These image conversion screens basically consist of a support such as paper or synthetic resin, and a phosphor layer provided on at least one side (possibly on both sides) of the support. Phosphors (for intensifying screens, fluorescent screens, etc.) that exhibit instantaneous emission of high brightness when excited by irradiated X-rays, or high-brightness stimuli when irradiated with visible or infrared light after X-ray irradiation X-ray phosphors such as stimulable phosphors (for imaging plates etc.) that emit light are dispersed in a binder. Further, the surface of the phosphor layer is protected by a transparent protective film such as cellulose acetate, cellulose acetate butyrate, or polyethylene terephthalate, if necessary.

Further, if necessary, the image conversion screen is usually made of a thermoplastic resin or a thermosetting resin which is different from the material forming the support or the protective film in order to prevent the protective film or the support from peeling off. In this case, sealing is performed by applying a resin such as an ultraviolet (UV) curable resin to the edge.

[0004]

However, as described above, if the resin that seals the edge of the image conversion screen is different from the material that forms the image conversion screen, its adhesiveness is insufficient, and the resin is repeatedly used. When a cleaning process such as wiping the image conversion screen surface with an organic solvent is performed, the sealing portion is dissolved or removed, or when heat curing or UV curing is performed, heat or UV is used to cure the resin. The image conversion screen performance may be adversely affected. Also, since the applied sealing resin swells on the surface, the X-ray film used in close contact with the image conversion screen is caught during the transportation of the film, which deteriorates the transportability, and intensifies screens for mammography, etc. In particular, in applications where it is necessary to obtain a good image up to the edge of the image (in mammography, one side of the image conversion screen is taken in close contact with the chest wall, In the image conversion screen used for the image conversion screen, which is used for imaging, the image at the edge of the image conversion screen which renders an image deteriorates the obtained image due to poor adhesion to the film at the edge. The negative effect often occurred.

Further, the image quality such as the sharpness and sensitivity of the image conversion screen is improved by reducing the amount of the binder resin used. However, the intensity of the phosphor layer is reduced, and the image conversion screen is reduced. In addition to the fact that the phosphor layer is easily dropped or the protective film is easily peeled off from the edge of the surface, in recent years, it has been used as a fluorescent plate for digital X-ray imaging by directly bonding the fluorescent plate to an optical sensor panel centered on amorphous silicon. However, in this case, stress is applied particularly at the edge of the bonding portion with the optical sensor, and the strength at the end of the phosphor plate is becoming more and more important. SUMMARY OF THE INVENTION It is an object of the present invention to provide an image conversion screen in which the durability of an edge portion is increased without lowering image quality such as sharpness and sensitivity.

[0006]

SUMMARY OF THE INVENTION The present inventors provide protection at the edges by sealing the edges with a protective film and / or support that is part of the image conversion screen. The film and the support are hardly peeled off, and the edges are no longer bulged, so that the images are unclear due to being caught by the X-ray film during use and poor adhesion to the X-ray film at the edges of the image conversion screen. The present inventors have found that an image conversion screen which does not cause troubles such as image formation can be obtained, and have reached the present invention.

(1) The present invention basically provides a phosphor layer, a protective film comprising at least one of plastics, and / or
Or a radiation image conversion screen having a support, wherein at least a part of the edge of the radiation image conversion screen is sealed with the same plastic as the protective film and / or the support. Screen, (2) Sealing by thermally melting at least a part of the edge of the radiation image conversion screen obtained by laminating a phosphor layer and a protective film and / or a support, at least one of which is made of plastic. (3) The method for producing a radiation image conversion screen according to (2), wherein the heat melting is performed by a laser beam.
(4) A phosphor layer and a protective film and / or a support, at least one of which is made of plastic, are laminated, and the surface is irradiated with laser light in a desired shape to cut the irradiated portion and cut the surface. And simultaneously performing heat melting of the radiation image conversion screen to seal an edge portion of the radiation image conversion screen.

Hereinafter, the present invention will be described in detail. As a method of manufacturing the image conversion screen of the present invention, first, a predetermined amount of the phosphor is mixed with a binder such as nitrified cotton,
Further, an organic solvent is added thereto to prepare a phosphor coating solution having an appropriate viscosity, and this coating solution is applied on a support by a knife coater, a roll coater, or the like, and dried to form a phosphor layer. In some cases, the steps of coating and drying are repeated to form a plurality of phosphor layers.

At this time, similarly to the conventional image conversion screen, if necessary, a light reflecting layer, a light absorbing layer, or a metal foil layer is provided on a support in advance, and the phosphor coating is formed thereon. The phosphor layer may be formed by applying and drying a liquid. The phosphor coating solution does not necessarily need to be formed by directly coating on the support. The phosphor coating solution is coated on a smooth substrate to form a phosphor layer in advance, and then pressed together with the substrate onto the support. After that, the phosphor layer may be peeled off from the substrate, or the phosphor layer may be peeled off from the substrate first and adhered to the support.

As the above-mentioned binder, besides nitrified cotton, cellulose acetate, ethyl cellulose, polyvinyl butyral,
Flocculent polyester, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, polyalkyl (meth) acrylate, polycarbonate, polyurethane, cellulose acetate butyrate, polyvinyl alcohol, gelatin,
There is no particular limitation as long as it is conventionally known as a binder for image conversion screens, such as polysaccharides such as dextrin and gum arabic.

The organic solvent used for preparing the phosphor coating solution includes, for example, ethanol, methyl ethyl ether, butyl acetate, ethyl acetate, ethyl ether, xylene and the like. In addition, a dispersant such as phthalic acid and stearic acid and a plasticizer such as triphenyl phosphate and diethyl phthalate are added to the phosphor coating solution as needed.

When the phosphor used as the phosphor layer of the image conversion screen of the present invention is used as an intensifying screen or a phosphor plate, Gd ₂ O ₂ S: Tb, Y
₂ O ₂ S: Tb, (Gd, Y) ₂ O ₂ S: Tb, La ₂
O ₂ S: Tb, (Gd, Y) ₂ O ₂ S: Tb: Tm, G
dTaO ₄ : Tb, Gd ₂ O ₃ .Ta ₂ O ₅ .B
₂ O ₃ : Tb, CaWO ₄ , BaSO ₄ : Pb, LaO
Br: Tm, LaOBr: Tb, HfO ₂ : Ti, Hf
P ₂ O ₇ : CU, CdWO ₄ , YTaO ₄ , YTa
O ₄ : Tm, YTaO ₄ : Nb, ZnS: Ag, BaF
Any phosphor, such as Cl: Eu, which exhibits highly efficient instantaneous emission upon X-ray excitation can be used.
On the other hand, when used as a phosphor layer of an imaging plate, BaFBr: Eu ²⁺ , BaFI: E
u ²⁺ , BaF (Br, I): Eu ²⁺ , ZnS: C
u, Pb, BaO.xAl ₂ O ₃ : Eu ²⁺ (however,
0.8 ≦ x ≦ 10), La ₂ O ₂ S: EU, Sm, Sr
S: Stimulable phosphors such as EU and Sm can be used.

Examples of the support include polyesters such as cellulose acetate, cellulose propionate, cellulose acetate butyrate, and polyethylene terephthalate; polystyrene;
Polymethyl methacrylate, polyamide, polyimide,
Film-shaped plastics such as vinyl chloride-vinyl acetate copolymer and polycarbonate, baryta paper, resin-coated paper, ordinary paper, and aluminum alloy are used. When the above-mentioned plastic film or paper is used as a support of the image conversion screen of the present invention, a light absorbing substance such as carbon black or a light reflecting substance such as titanium dioxide or calcium carbonate is kneaded into these. For example, these may be mixed in advance.

Next, although not essential, a protective film is further formed on the surface of the phosphor layer formed on the support as described above, if necessary. To form the protective film, cellulose acetate, nitrocellulose, a cellulose derivative such as cellulose acetate butyrate, or a plastic such as polyvinyl chloride is dissolved in a solvent to prepare a protective film coating solution having an appropriate viscosity. A protective film is formed by coating on the prepared phosphor layer and drying, or laminating a preformed protective film, for example, a transparent plastic film such as polyethylene terephthalate, polyvinylidene chloride, or polyamide, on the phosphor layer. You may let it.

In the image conversion screen of the present invention, a protective film and / or a support and a phosphor layer are laminated,
When both a protective film and a support are provided, a configuration in which a protective film is provided on one surface of the phosphor layer and a support is provided on the other surface is generally used. Does not require a support, in which case only a protective film may be provided on the surface of the phosphor layer. Further, a phosphor layer may be provided on both surfaces of the support, and a protective film may be provided on at least one of the surfaces as necessary. In some cases, only the support may be provided on one surface of the phosphor layer. The protective layer may not be provided. However, in the image conversion screen of the present invention, at least one of the support and the protective film is necessary, and the material for forming at least one of the support and the protective film can be melted by heat or the like. It is necessary to use a plastic material. Therefore, in the case of an image conversion screen in which the phosphor layer itself is used as a support and a self-supporting phosphor layer is used, a protective film made of plastic is formed, and if no protective film is provided, plastic is used. It is essential to provide a support as a material.

Next, the edge portion, which is the cut portion of the image conversion screen manufactured as described above, is locally melted by heat, so that the edge portion is sealed with the object to be melted. Thereby, the image conversion screen of the present invention is obtained.

As a method for thermally melting the edge portion, for example, there is the following method. The image conversion screen manufactured as described above is cut into a predetermined size by a press cutter, a cutting machine, or the like, and has a slightly smaller area than the cut image conversion screen. 1 at the edge
It is covered with a heat-resistant material such as a metal plate or a ceramic plate having a size and shape that is exposed to the outside by up to 2 mm, and the edge portion of the image conversion screen protruding from the heat-resistant material is made of city gas or propane gas. It passes through the upper part of the flame created by burning the thermal gas for a certain time. As a result, the plastic at the end of the image conversion screen constituting the protective film or the support is thermally melted, and the edge of the image conversion screen is fused by the melted plastic, which is cooled. By doing so, the edge is sealed. By irradiating a laser beam to the end (cut portion) of the image conversion screen cut into a predetermined size in the same manner as in the above method, the plastic forming the support or the protective film is thermally melted, and the melted plastic is formed. The edges are sealed with plastic. After laminating a protective film and / or a support on both surfaces of the phosphor layer, the image conversion screen is cut into a predetermined size by irradiating a laser beam to a desired shape and size (points to be cut). The plastic forming the support and / or the protective film in the vicinity of the cut edge is hot-melted, and the hot-melted plastic seals the edge including the cut portion. According to this method, the cutting of the image conversion screen and the sealing of the edge thereof can be performed at the same time, which is particularly preferable.

The edge of the image conversion screen to be sealed does not necessarily have to be the entire periphery. For example, if the image conversion screen is used for mammography, the edge of the image conversion screen contacts the chest wall of the subject at the time of photographing. However, it is preferable to seal only the portion which is highly necessary, but from the viewpoint of durability, it is preferable to seal the entire peripheral edge by the method of the present invention.

When the edge of the image conversion screen is sealed by using the laser beam as described above, the image conversion screen is mounted on a base plate for fixing the image conversion screen, and the image conversion screen is placed thereon. It is preferable to irradiate the laser beam from the laser beam.In that case, if the base plate used to fix the image conversion screen is cut in advance at the location where the laser beam hits, This is desirable because it can penetrate from the base plate to the image conversion screen without being directly reflected.

As the laser beam, any laser beam can be used as long as it can melt the plastic forming the protective film and / or the support of the image conversion screen. However, in terms of efficiency and operability, a carbon dioxide gas laser ( It is particularly preferred to use 10.6 μm). The laser may be of a continuous transmission type or a pulse transmission type. Also,
When the laser beam is irradiated, the laser beam not only melts the edge of the image conversion screen due to heat, but also partially gasifies and adheres around the edge of the image conversion screen, coloring it brown or black In order to prevent this, it is preferable to irradiate a laser beam while blowing a gas such as air or nitrogen gas at the time of laser beam irradiation, and to perform thermal melting.

[0021]

EXAMPLES Hereinafter, the present invention will be described in more detail by way of examples, taking the case of an intensifying screen as an example. However, the present invention is not limited to the following examples. It is needless to say that the present invention can be applied to the manufacture of other image conversion screens.

Example 1 The average particle size is 5 μm.
A phosphor coating solution was prepared by mixing 10 parts by weight of Gd ₂ O ₂ S: Tb phosphor, 1 part by weight of a vinyl chloride-vinyl acetate copolymer (binder) and ethyl acetate (organic solvent). This phosphor coating solution is kneaded with titanium dioxide to a thickness of 250 μm.
Was uniformly coated with a knife coater such that the coating weight of the phosphor after drying was 50 mg / cm ^2, and dried to form a phosphor layer. Next, a polyester-based adhesive was separately applied to a 6 μm-thick polyethylene terephthalate film to a thickness of 1.0 μm and dried to form a protective film. Next, the above-mentioned protective film separately produced was heat-laminated on the phosphor layer obtained as described above to obtain an intensifying screen [A]. The intensifying screen [A] thus obtained was cut into a predetermined size (252) by a metal blade cutter.
mm × 303 mm), and only the edge is passed through the upper part (outer flame) of the flame of the gas burner to melt the edge of the support made of polyethylene terephthalate resin and the edge of the protective film, thereby obtaining a phosphor. An intensifying screen (1) was obtained by covering the layers and sealing the edges.

Example 2 An intensifying screen [B] was produced in exactly the same manner as intensifying screen [A] of Example 1, and the edge was irradiated with a laser beam emitted under the following conditions. The intensifying screen (2) was obtained by melting the support and protective film made of polyethylene terephthalate resin in the portion, covering the phosphor layer edge of the intensifying screen [B], cooling and sealing. . The laser beam used to irradiate the edge of the intensifying screen [B] was output: 30 W, continuous transmission method, wavelength: 10.6 μm, beam diameter: 15 mm (beam diameter emitted from the laser transmitter). Beam diameter: 0.5 mm Scanning speed: 1500 mm / min

Example 3 An intensifying screen [C] was manufactured in exactly the same manner as intensifying screen [A] of Example 1, and was placed and fixed on a base plate with the protective film side up. Under the same scanning conditions as in Example 2 from the direction perpendicular to the surface of the intensifying screen [C] (252 m).
m × 303 mm) is irradiated with a laser beam to cut the irradiated surface, and at the same time, the support and the protective film on the cut surface made of polyethylene terephthalate resin are melted to cover the phosphor layer on the cut surface. The intensifying screen (3) was obtained by sealing the portion. At the time of laser light irradiation, compressed air was lightly blown to the laser irradiation surface, and the laser light was irradiated while replacing air near the melting surface.

The laser beam used to irradiate the intensifying screen [C] was the same as that used in Example 2 except that the scanning speed was 1200 mm / min. At this time, a groove was previously provided in a portion of the surface of the base plate on which the intensifying screen [C] was placed, where the laser light was irradiated, so that the reflection of the laser light from the base plate was eliminated.

COMPARATIVE EXAMPLE An edge burr solution for an intensifying screen was prepared from an ethyl acetate solution in which 10% of a vinyl chloride-vinyl acetate copolymer resin was dissolved. The edge burr was applied to the intensifying screen “A” obtained in Example 1 with a metal blade cutter at 252 × 303 m.
m and apply it to the edge of the intensifying screen cut with a brush.
After drying at room temperature for 1 hour, an intensifying screen (R) was obtained.

(Evaluation) The intensifying screens (1) to (3) and the intensifying screen (R) obtained as described above were fixed on a flat plate with the protective film side facing up. An adhesive tape having a length of 100 mm and a width of 50 mm (trade name: Nitto Danpro Tape No. 375) is provided at the center of one end of each intensifying screen.
A half length (50 mm) of the screen is stuck to one end of each intensifying screen so as to protrude from the end of the screen, and the intensifying screen is particularly adhered so that the edges of the intensifying screen are sufficiently adhered. The part stuck on the paper was rubbed with a finger from above the tape.

Next, the portion of the tape protruding from the edge of the intensifying screen was lifted and strongly pulled to peel off the adhesive tape from the intensifying screen. At this time, it was observed whether the protective film of the intensifying screen was peeled off from the end together with the tape. 1 is shown.

[0029]

[Table 1] As can be seen from Table 1, in the intensifying screen of the comparative example in which only the edge of the intensifying screen was coated with the resin, the protective film at the edge of the intensifying screen was easily peeled off. The intensifying screens of the examples in which the portions were sealed by heat melting showed that the protective film did not easily peel off at the edge portions, and had good durability.

[0030]

As described above, the end of the image conversion screen manufactured by the method of the present invention is sealed by the material itself constituting the support and / or the protective film of the image conversion screen. No peeling occurs at the protective film and / or at the edge of the support, so that an image conversion screen which is extremely superior in durability in repeated use to the conventional one can be obtained.

Claims (4)

[Claims] 1. A radiation image conversion screen having a phosphor layer and a protective film and / or a support, at least one of which is made of plastic, wherein at least a part of an edge portion of the radiation image conversion screen is the above-mentioned. A radiation image conversion screen, which is sealed with the same plastic as a protective film and / or a support. 2. Sealing by thermally melting at least a part of an edge of a radiation image conversion screen obtained by laminating a phosphor layer and a protective film and / or a support, at least one of which is made of plastic. A method for producing a radiation image conversion screen. 3. The method for producing a radiation image conversion screen according to claim 2, wherein the heat melting is performed by a laser beam. 4. A laminate of a phosphor layer and a protective film and / or a support, at least one of which is made of plastic,
A method for manufacturing a radiation image conversion screen, comprising irradiating a laser beam onto a surface of a desired shape and simultaneously cutting the irradiated portion and thermally melting the cut surface to seal an edge portion. .