JPS63313100A - Radiation image conversion screen - Google Patents

Abstract

PURPOSE:To obtain a high-sensitivity image conversion screen which has less X-ray absorption in the parts except phosphor layer by forming a base of a foamed white org. film internally contg. many air bubbles. CONSTITUTION:The base of the image conversion screen consisting of the base and the phosphor layer laminated on at least one face of the base and which base is formed by dispersing X-ray phosphors into a binder is formed of the foamed white org. film internally contg. the many air bubbles. Tungstenic acid phosphors, etc., such as CaWO4 and MgWO4, are used as the X-ray phosphor. Cellulose nitrate, cellulose acetate, etc., are used as the binder. The foamed white org. film formed by molding a resin such as cellulose acetate or cellulose propionate while foaming the same to form many gaps by the air bubbles therein is used as the base. The phosphor layer is formed on the base when a phosphor coating liquid prepd. by mixing the binder and the X-ray phosphor is coated on the base and is dried.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a highly sensitive radiation image screen (hereinafter referred to as "image conversion screen") in which X-ray absorption is reduced by improving the support. .

[Conventional technology]

The image conversion screen can be used as an intensifying screen, fluorescent screen, etc. It is used for the purpose of medical diagnosis and non-destructive testing of materials to convert M images into visible images.

These image conversion screens basically consist of a support such as paper or synthetic resin, and a phosphor layer laminated on at least one side of this support. And this phosphor layer is made of XiM phosphor dispersed in a binder. #
As the i-use phosphor, a phosphor that emits high-intensity instantaneous light when excited by X-rays is used.

Furthermore, the surface of the phosphor layer is protected by a transparent protective film made of cellulose acetate, cellulose acetate butyrate, polyethylene terephthalate, or the like, as required.

By the way, *2 conversion screens must have high sensitivity, provide images with good sharpness and graininess, have low x&1a yield in areas other than the phosphor layer, and have flexibility and mechanical Performance such as high mechanical strength is desired, and various improvements have been attempted for this purpose.

For example, in order to efficiently extract light emitted from the phosphor layer, one way to improve sensitivity is to provide a light-reflecting layer made of a white inorganic pigment such as titanium dioxide between the support and the phosphor layer. (Japanese Patent Application Laid-open No. 59-8782, etc.), using an organic tree manure film kneaded with white inorganic pigments such as titanium dioxide, magnesium oxide, and lithopone as a light-reflecting type support (Japanese Patent Application Laid-Open No. 59-8782) Public bulletin) etc. have been proposed.

However, when a light reflecting layer is provided, the manufacturing process is complicated, and there are also problems in that the flexibility of the resulting image conversion screen and the ability to pool with the phosphor layer are reduced.

In addition, an image conversion screen using a white inorganic pigment can improve sensitivity in that it can efficiently extract light from the phosphor layer, but on the other hand, there is a gap between the two image conversion screens. When XM films are held together and used as intensifying screens for X-ray photography, the white inorganic pigment in the front intensifying screen placed on the side of the X-starvation source causes X? 1
Due to the absorption of However, there is a disadvantage in that the sensitivity decreases significantly, and there is currently a need for improvement.

[Problem that the invention seeks to solve]

An object of the present invention is to provide an image conversion screen having a light-reflecting type support, which exhibits less X-ray absorption in areas other than the phosphor layer than before and has high sensitivity.

[Means and effects for solving the problem] The present invention has the following features:
An image conversion screen comprising a support and a phosphor layer laminated on at least one side of the support, and the phosphor layer has an Xll1iii phosphor dispersed in a binder, wherein the support is It is characterized by consisting of a foamed white organic film containing accidental air bubbles inside.

The present invention will be explained in more detail below.

The image conversion screen of the present invention is manufactured based on a method similar to that of conventional image conversion screens, except that a foamed white organic film containing accidental air bubbles therein is used as a support.

That is, basically, an X-ray phosphor and a binder are mixed, a solvent is added to prepare a phosphor coating solution of an appropriate viscosity, and this is coated onto a support and dried to coat the phosphor. form a layer.

As the X#M fluorophore used in the present invention, CaWO
4# Tungstate phosphor such as MgWO4, Y2
O2S: 'rb, Gd2O2S: 'rb
, L12028: Rare earth oxysulfide phosphor such as 'rb, La0Br: Tb, La0Br:
Tmv (La, Gd) OBr: Rare earth oxyhalodide phosphor such as Co, BaPO3: Eu
, BaF2・mBaCt2・nKct-qBi
SO4: Eu” (0.3≦m≦1.5, 0.
Alkaline earth metal fluorohalide phosphors such as 1≦n≦1.0゜0.1≦q≦1.0), ZnS2Ag,
(Zn, Cd) S: Sulfide-based phosphor such as Ag, YT
aO4: 'rb-(Y, Nb) Ta04:
Tb-YTaO4: Tm, GdTa04:
X, including rare earth tantalate phosphors such as Tb
Known phosphors that exhibit temporary luminescence with high brightness upon linear excitation can be mentioned.

In addition, the binders used in the present invention include conventional binders such as cellulose nitrate, cellulose acetate, ethyl cellulose, polyvinyl butyral, linear polyester, vinyl chloride-vinyl acetate copolymer, polycarnate, polyurethane, and polymethyl methacrylate. Known resins used in the phosphor layer of image conversion screens are listed, and these binders may be used alone or in combination of two or more.

Mix these binders with the X1iffl phosphor listed above, add dispersants such as phthalic acid and stearic acid, and plasticizers such as triphenyl phosphate and diethyl phthalate as necessary, and then add ethanol, methyl Add ethyl ether, butyl acetate, ethyl ether, xylene, acetone, etc. to adjust the viscosity and use it as a phosphor coating solution.

It is appropriate that the lid for the binder in the phosphor coating solution has a diameter of 3 to 20 mm for the X-ray phosphor to be mixed.

When the obtained phosphor coating liquid is applied onto a support described below and dried, a phosphor layer can be formed on the support. The coating amount of the above coating solution is generally approximately 20% after drying.
It is controlled to be ~200 m97cw'.

Supports used in the present invention include cellulose acetate,
Polyesters such as cellulose pionate, cellulose acetate butyrate, polyethylene terephthalate, polyamides,
Foaming of the resins listed above, such as polyimide, polyvinylidene chloride, polyethylene, polypropylene, polytetrafluoroethylene, polytrifluoroethylene, polystyrene, polymethyl methacrylate, vinyl chloride-vinyl acetate copolymer, polycarbonate, etc. While forming the stone, there are no accidental voids caused by air bubbles inside! l! A foamed white organic film is used.

From the viewpoint of chemical and physical durability (especially moisture resistance, flexibility, etc.) of the resulting image conversion screen, it is preferable to use a biaxially stretched 4-lyester film such as a polyethylene terephthalate film as the support. In addition, in terms of W&D (whiteness of the support) of the resulting image conversion screen, the size of the bubbles is from several microns to several tens of microns, and the proportion of the volume of the bubbles to the whole (porosity) is approximately 5 to 10. 60%, more preferably 3
It is more preferable to use a foamed white organic film containing air bubbles inside the film so that the concentration of air bubbles is 0 to 50%. Formation field will be formed. This protective film is made by dissolving resins such as cellulose acetate butyrate, cellulose acetate, polyvinyl butyral, vinyl chloride-vinyl acetate copolymer, polymethyl methacrylate, polyurethane, and polycarbonate in an excessively quiet bath, and then using the resulting wrinkle liquid. Either coat it on the previously formed phosphor layer and dry it, or apply a commercially available composite film such as polyethylene terephthalate, polymethyl methacrylate, polycarbonate, polystyrene, polyamide, etc. on the previously formed phosphor layer. It is formed by laminating, and the film thickness is preferably about 3 to 20 microns.

In addition, the protective film of the present invention is prepared by forming a protective film on a smooth substrate in advance, forming the phosphor Fa1 on top of the protective film, and then peeling off the protective film together with the protective film. It can also be manufactured by adhering a support to the substrate. Furthermore, the image conversion screen IJ of the present invention uses BaFBr: Eu,
BaFI: Eu”, ZnS: Cu, Pb
.

BaO-XAt205: Eu” (However, 0.8≦X
≦10).

La2O2S: Eu, Sm, SrS:
Storage type gj using stimulable phosphors such as Eu e Sm
! Also when used as a converter.

Compared to conventional storage type image converters in which white inorganic pigments are kneaded into organic film, X-ray absorption is lower, so when used for imaging by irradiating xlrM that has passed through the object 1c from the support side, the conventional It has high sensitivity compared to

〔Example〕

Next, the present invention will be explained in detail during the implementation session, but the present invention is not limited thereto.

Example I Ethyl acetate was added as a solvent to a mixture consisting of 100 parts of CaVK) 4 phosphor (Watabon standard, the same applies hereinafter) and 8 parts of vinyl chloride-vinyl chloride copolymer (binder), and the gel mill was used to fully dissolve the mixture. They were mixed to prepare a phosphor coating solution t=wp.

Next, a foamed white polyethylene terephthalate film having a thickness of 250μ and having accidental bubbles inside was prepared as a support, and the above phosphor coating liquid was applied onto it so that the amount of phosphor coating liquid after drying was 45 Tn9/cm''. A phosphor layer was formed by coating with a knife coater and drying to form a phosphor layer.

Further, on top of this phosphor j-, a protective film coating residue made of cellulose acetate thoroughly dissolved in acetone was spread with a cloth so that the film thickness after drying was approximately 10μ, and dried to form an image conversion screen CII e. Created.

On the other hand, for comparison, the above source conversion screen [■
] An image conversion screen [RI] was tabulated in the same manner.

For the image conversion screens CI) and [RII tabulated in this way, X-rays of different tube voltages were irradiated, and the photographic sensitivities of various image conversion screens under each X-ray irradiation condition and the various image conversion screens were used. When the X-ray absorption (expressed as At equivalent thickness) of the support was measured, the results shown in the table below were obtained, and the image conversion screen [
! ] had lower X-ray absorption and higher sensitivity than the conventional image conversion screen (RII), and was particularly sensitive to X-rays with low tube voltage (low-energy X-rays). .

*L: Hold the Regiera Tig's X @ film in the darkness of the two 'fr 91 conversion screens,
This was determined from the relative value of the degree of blackening of the Xs film obtained by irradiating it with X-rays at a predetermined tube voltage and developing it.

Book 2: Support and multiple aluminum plates of different thickness
By placing the X-ray film in close contact and irradiating X-rays from the side opposite to the X-ray film side, and comparing the degree of blackening of the X-ray film after development, it was found that an aluminum plate that gave the same degree of blackening as the support was It was determined by knowing the thickness.

Example 2 A compensation conversion screen [I[] was produced in the same manner as the image conversion screen CI of Example 1 except that Gd2O2S:Tb phosphor was used in place of the CaV104 phosphor.

On the other hand, for comparison, the same (Gd instead of CaWO4 phosphor)
2028: An image conversion screen (R11) was produced in the same manner as the image conversion screen (R1) of Example 1 except that Tb phosphor was used.

Regarding the image conversion screens (Il) and [RII] produced in this manner, each was performed in the same manner as in Example 1, except that orthomatic type X-ray film was used in place of Regi and Lartaig X-rays. Photographic sensitivity was determined.

As a result, the tube voltage d (80kV, 50kV and 2
8hvOX! The photographic sensitivity of the image conversion screen Cl) was compared with that of the conventional image conversion screen (Rn
] When the photographic sensitivity of
10 and 115, both of which were more sensitive than conventional ones, especially to X-rays with low tube voltage.

〔Effect of the invention〕

As is clear from the above, since the image conversion screen of the present invention uses as a support a centered white organic film whose whiteness is increased by allowing accidental air bubbles to meet inside the film,
Compared to conventional image conversion screens that use a light-reflecting organic film mixed with white inorganic pigment as a support, the X1 absorption of the support is significantly smaller, and there is no decrease in light reflection. When the image conversion screen of the present invention is used as a front intensifying screen, for example, when it is placed on the side of the T-ray source, it has a higher sensitivity than conventional image conversion screens, and it can be used as a front intensifying screen. This tube is extremely useful for low-pressure X-ray photography with a pressure of 50 kV or less.

Claims (1)

[Claims] A radiation image conversion screen consisting of a support and a phosphor layer laminated on at least one side of the support, the phosphor layer comprising an X-ray phosphor dispersed in a binder, wherein the support is A radiation image conversion screen characterized in that it consists of a foamed white organic film containing accidental air bubbles inside it.