JPS62137599A - Radiation intensifying screen - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a radiation intensifying screen;
More particularly, the present invention relates to a radiation intensifying screen for use in a cassette-less IM imaging system.

[Technical Background of the Invention] Radiation intensifying screens are
In order to improve the sensitivity of the imaging system, radiographic film (e.g., It is used by rolling it together so that it is in close contact with one or both sides of the film.

The basic structure of this radiation & a intensifying screen is a support and a phosphor layer provided on one side of the support. Note that the surface of this phosphor layer opposite to the support [
A transparent protective film made of a plastic film or the like is generally provided on the surface not facing the support to protect the phosphor layer from chemical deterioration or physical impact.

The phosphor layer is made of a binder containing and supporting phosphor particles in dispersed IE, and the phosphor particles have the property of emitting high-intensity light when excited by radiation such as X-rays. It is. Therefore, the phosphor emits high-intensity light depending on the amount of radiation that passes through the subject, and the radiographic film placed in contact with the surface of the phosphor layer of the radiation-sensitizing screen can detect this luminescence. Since it is also sensitized by light, sufficient sensitization of the radiation film can be achieved with a relatively small radiation dose. A radiation image of the subject is then formed on the radiation film.

The radiation intensifying screen having the above-mentioned basic structure is used in various ways, but in some cases, such as in high-speed imaging, where the intensifying screen and radiation film are used for continuous imaging without using a cassette (cassetteless). When used, it is desirable that the gap between the screen and the film be good.

For example, in an angiography device, x1
A pair of intensifying screens are fixed at the 1Iit imaging position, while a large number of radiation films stored in a magazine inside the device are automatically and continuously conveyed one by one and placed between the intensifying screens. Ru. After shooting, the used film is again stored in the magazine by the transport system, and at the same time, unused film is placed between the screens. In this way, continuous high-speed photographing can be performed. Therefore, in cassetteless photographing systems such as those used for high-speed photography, it is desired to improve the transportability of the film as much as possible to prevent transport failures.

In addition, as a conventional technique for reducing the friction between the radiation intensifying screen and the radiation film, the surface of the intensifying screen (in contact with the film) is It is known to provide minute irregularities on the side surface (Japanese Patent Publication No. 60-3).
4720 and West German Patent No. 2,835,780)
This is intended to prevent deterioration of the image quality of the film caused by friction with the screen or to improve the slippage of the film. Examples of the particulate solid material include organic fluorinated polymers, polystyrene, polyamide, etc. Solid particles (filler) having an average particle diameter of 5 Bm or more are exemplified.

[Summary of the Invention] An object of the present invention is to provide a radiation-sensitizing screen that can improve the gap between the radiation-sensitizing screen and the radiographic film.

Another object of the present invention is to provide a radiation intensifying screen that can improve the transportability of radiographic film without significantly reducing image quality.

Target 1 above is a radiation-sensitizing screen that has a support, a phosphor layer made of a supporting binder containing a phosphor in a dispersed state, and a protective film, in this order, in which the protective film contains hollow polymer fine particles for 10 to 10 minutes. This can be achieved by the radiation intensifying screen of the present invention, which is characterized in that the content is in the range of 70% by weight.

That is, 1. the present invention provides minute irregularities on the screen surface by dispersing and containing fine particles with a hollow structure made of a polymeric substance in the protective film of the radiation-sensitizing screen, thereby realizing a remarkable improvement in the slippage of the radiographic film. It is something to do.

According to the present invention, the surface of the protective film of the radiation intensifying screen (
That is, since minute irregularities are provided on the surface (the surface that contacts the radiographic film), the contact area with the radiographic film is reduced, and the smoothness between the screen and the film can be improved. As a result, in a cassetteless photographing system such as high-speed photographing, it is possible to improve film transportability and prevent transport failures.

In addition, in the present invention, the protective film having minute irregularities on the surface is obtained by preparing a coating solution by dispersing hollow polymer particles in a solution of a polymeric substance, and coating this coating solution on the phosphor layer and drying it. It can be formed by At this time, by using a solvent that can slightly dissolve or swell the polymer particles as a solvent in the coating solution, unevenness can be created on the surface of the protective film without forming a clear boundary between the polymer particles and the polymer substance. can be provided. As a result, compared to conventional intensifying screens containing solid particulate material in the outermost layer, scattering of emitted light from the phosphor at the interface between the particles and the binder in the protective film can be reduced, resulting in a benefit. There is almost no deterioration in the image quality such as the sharpness of the image.

Furthermore, since the polymer fine particles used in the present invention are hollow inside, they have a low specific gravity. Therefore, the polymer fine particles can be easily collected on the surface of the coating film for forming a protective film, and the surface of the protective film can be covered with a relatively small content. It is possible to form unevenness on the surface.

Particularly when hollow polymer fine particles having a particle diameter (outer diameter) of 1 gm or less are used.

Surface irregularities can be made almost constant. In addition, the thickness of the protective film can be reduced by 1.5 mm to the conventional protective film containing solid particulate material (
It is possible to make the layer thinner than the outermost layer (the outermost layer).

[Structure of the Invention] The radiation intensifying screen of the present invention having the preferable characteristics as described above can be manufactured, for example, by the method described below.

The support used in the present invention can be arbitrarily selected from various materials known as materials for producing radiation intensifying screens. Examples of such materials include films of plastic substances such as cellulose acetate, polyester, polyethylene terephthalate, polyamide, polyimide, triacetate, polycarbonate, metal sheets such as aluminum foil, aluminum alloy foil, regular paper, baryta paper, resin. Examples include coated paper, pigment paper containing pigments such as titanium dioxide, and paper sized with polyvinyl alcohol. However, in consideration of various properties as a radiation intensifying screen, a particularly preferred material for the support in the present invention is a plastic film. This plastic film may be kneaded with a light-absorbing substance such as carbon black, or may be kneaded with a light-reflecting substance such as titanium dioxide. The latter is a support suitable for radiation-sensitizing screens, the latter being a support suitable for radiation-sensitizing screens of the high-sensitivity type.

In known radiation-sensitizing screens, in order to strengthen the bond between the support and the phosphor layer, or to improve the sensitivity or image quality of the radiation-sensitizing screen, a layer is added to the surface of the support on the side where the phosphor layer is provided. It is possible to apply a polymeric substance such as gelatin to form an adhesion-imparting layer, or to provide a light-reflecting layer made of a light-reflecting substance such as titanium dioxide, or a light-absorbing layer made of a light-absorbing substance such as carbon black. It is being done. In addition, in radiation intensifying screens used in industrial radiography for the purpose of non-destructive testing of substances, lead foil or lead alloy foil is placed on the surface of the support on the side where the phosphor layer is provided for the purpose of removing scattered radiation. The support used in the present invention can also be provided with these various layers.

Furthermore, as described in JP-A-58-182599, in order to improve the sharpness, the surface of the support on which the phosphor layer is provided (adhesive properties are applied to the surface of the support on that side) When a layer, a light reflection layer, a light absorption layer, a metal foil, etc. are provided, minute irregularities may be provided on the surface thereof.

A phosphor layer is formed on this support.

The phosphor layer is a layer made of a binder containing and supporting phosphor particles in a dispersed state.

Various types of phosphors are already known. In the present invention, it is preferable to use phosphors in the near ultraviolet to visible region (
Examples of phosphors that emit light in the blue region, fJ color region, and red region include ditungstate-based phosphors (CaWO4, MgWOa,
, CaWo a: P b, etc.), Te/l/Hium IIa active rare upper oxysulfide phosphor [Y2O2S:Tb
, G d 202 S: T b , L a 202
S: T b, (Y, G d) 202 S
: Tb, (Y, Gd)202S:Tb, Tm, etc.]
, terbium-activated rare earth phosphate phosphor (YPOa:T
b, GdPO4:Tb, LaPO4:Tb, etc.), terbium-activated rare earth oxyhalide phosphor (LaO
B r :Tb, La0Br:Tb, Tm, La0C1
:Tb, La0C1: Tb, Tm, Gd0B r
:Tb, Gd0C:Tb, etc.), thulium-activated rare earth oxyhalide phosphors (LaO, Br:Tm, La
0Cu:Tm, etc.), barium sulfate-based phosphor [BaSO4
: Pb, BaSO4: Eu2°.

(Ba,Sr)SO4:Eu'' etc.], divalent europium activated alkaline earth metal phosphate phosphor [Ba3
(POa)2: Eu”, (Ha, Sr)*(P O
4) 2:Eu 2° etc.], divalent europium activated alkaline earth metal fluoride halide phosphor [BaFCJ
l 2 Eu”, BaFBr:Eu”,
BaFCI: Eu2°, Tb, B
aFBr:Eu”.

Tb, BaF2aBaC12sK(,l:Eu”,
BaF2*BaCJ12*xBaSO,*KCu:E
u ”, (Ba, Mg)F2 ・BaCAz e
) (C1:Eu” etc.), iodide-based phosphors (Csl:Na
, CsI:Tl, NaI, KI:Tu, etc.)
, sulfide-based phosphor [ZnS:Ag, (Zn,Cd)S:
Ag, (Zn, Cd)S:Cu, (Zn.

Cd)S: Cu, AJ1, etc.], hafnium phosphate phosphor (HfP207: Cu, etc.), europium-activated rare earth oxysulfide phosphor [Y2O2S: Eu, Gd
2O2S:Eu, La2O2S:Eu, (Y, Gd)2
025: Eu, etc.], europium-activated rare earth oxide phosphor [Y 20 z : Eu, G d 2o,
:Eu, La 20. :Eu,
(Y, Gd) 203: Eul, europium activated rare earth phosphate phosphor (Y P Oa: E
u, G d P Oa: E u, LaPO4:
Eu, etc.), europium-activated rare earth vanadate-based phosphor [YVO,: Eu, GdVo,: Eu, L
aVO,: Eu, (Y, Gd)VO2:Eul.

However, the phosphor used in the present invention is not limited to these, and any phosphor that emits light in the near-ultraviolet region or visible region when irradiated with radiation may be used.

Examples of binders for the phosphor layer include proteins such as gelatin,
Polysaccharides such as dextran, or natural polymeric substances such as gum arabic; and polyvinyl butyral, polyvinyl acetate, nitrocellulose, ethylcellulose, vinylidene chloride/vinyl chloride copolymer, polyalkyl (meth)acrylate, vinyl chloride/vinyl acetate Binders typified by synthetic polymeric materials such as copolymers, polyurethanes, cellulose acetate butyrate, polyvinyl alcohol, linear polyesters, etc., to name but a few. Particularly preferred among such binders are nitrocellulose, linear polyester,
These include polyargyl (meth)acrylate, a mixture of nitrocellulose and linear polyester, and a mixture of nitrocellulose and polyalkyl (meth)acrylate.

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

First, the above-mentioned phosphor and binder are added to a suitable solvent and thoroughly mixed to prepare a coating solution in which phosphor particles are uniformly dispersed in the binder solution.

Examples of solvents for preparing coating solutions include lower alcohols such as methanol, ethanol, n-propanol, and n-butanol; chlorine-containing hydrocarbons such as methylene chloride and ethylene chloride; aromatic hydrocarbons such as benzene and toluene. : Ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; Esters of lower fatty acids and lower alcohols such as methyl acetate, ethyl acetate, and butyl acetate; Ethers such as dioxane, ethylene glycol monoethyl ether, and ethylene glycol monoethyl ether; and, Mention may be made of mixtures thereof.

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

In addition, paint! Liquid No. 11 also contains a dispersant for improving the dispersibility of the phosphor particles in the coating liquid.

A dispersant used for such purposes, which may be mixed with various additives such as a plasticizer to improve the bonding strength between the binder and the phosphor particles in the phosphor layer after formation. Examples include phthalic acid, stearic acid, caproic acid, lipophilic surfactants, and the like. Examples of plasticizers include phosphate esters such as triphenyl phosphate, tricresyl phosphate, and diphenyl phosphate; phthalate esters such as diethyl phthalate and dimethoxyethyl phthalate; ethyl phthalyl ethyl glycolate, butyl phthalyl glycolate, etc. and polyesters of polyethylene glycol and aliphatic dibasic acids, such as polyesters of triethylene glycol and adipic acid and polyesters of diethylene glycol and succinic acid.

A coating film of the coating liquid is formed by uniformly applying the coating liquid containing the phosphor and binder prepared as described above onto the surface of the support. This coating operation can be carried out using conventional coating means such as a doctor blade, roll coater, knife coater, etc.

The formed coating film is then dried by gradually heating to complete the formation of the phosphor layer on the support. The thickness of the phosphor layer varies depending on the characteristics of the intended radiation intensifying screen, the type of phosphor, the mixing ratio of the binder and the phosphor, etc., but it is usually 20 ILm to 1 mm. However, the thickness of this layer is preferably 50 to 500 gm.
stomach.

Note that the phosphor layer does not necessarily have to be formed by directly applying a coating liquid onto the support as described above; for example, it is possible to form the phosphor layer by separately applying the coating liquid onto a sheet such as a glass plate, metal plate, or plastic sheet. After the phosphor layer is formed by drying, it may be pressed onto the support, or the support and the phosphor layer may be bonded together using an adhesive.

Next, a protective film is provided on the surface of the phosphor layer opposite to the side that contacts the support in order to physically and chemically protect the phosphor layer.

The protective film, which is a characteristic feature of the present invention, is a thin film of a polymeric material containing hollow polymer fine particles dispersed within a range of 10 to 70%.

The hollow polymer particles (polymer pigments) used in the present invention generally have an outer diameter of 0.2 to 1JLm.
and the small pore diameter (inner diameter) is in the range of 0.05 to 0.
These are fine particles in the range of 71 Lm. These hollow polymer fine particles have voids inside and have a low specific gravity, so when a coating film is formed using a coating liquid that disperses them, Al12
Polymer particles can be easily aggregated on the surface,
It is possible to uniformly provide minute irregularities on the surface of the J-retaining film with a relatively small content.

Specific examples of hollow polymer particles include styrenic polymer particles obtained by adding a suitable crosslinking agent to styrene and/or acrylic threads and bonding them into a spherical shell (core-e-shell polymerization); Examples include styrene acrylic copolymer fine particles.

These polymer fine particles have good heat resistance, and because they are crosslinked with a crosslinking agent, they have excellent mechanical strength (impact resistance) and weather resistance.

The protective film is prepared by adding the above-mentioned hollow polymer particles and a transparent polymer substance to a suitable solvent and mixing them thoroughly to prepare a coating solution in which the hollow polymer particles are uniformly dispersed in a solution of the polymer substance. After forming a coating film of the coating liquid by uniformly applying the liquid to the surface of the phosphor layer, the coating film can be formed on the phosphor layer by heating and drying the coating film.

Alternatively, a thin film containing dispersed hollow polymer particles is formed by separately applying a coating liquid onto a sheet such as a glass plate, metal plate, or plastic sheet and drying, and then this is applied to the surface of the phosphor layer using an adhesive. A protective film may be provided by bonding moxibustion.

Examples of transparent 1p1 polymeric substances include cellulose derivatives such as cellulose acetate and nitrocellulose; or polyurethane, polymethyl methacrylate, polyvinyl butyral, polyvinyl formal, polycarbonate, polyvinyl acetate, vinyl chloride/vinyl acetate copolymer, polyethylene terephthalate, Synthetic polymeric materials such as polyethylene, polyvinylidene chloride, and polyamide can be mentioned.

Further, the solvent is preferably one that can slightly dissolve or swell the hollow polymer fine particles. Examples of such solvents include ketones such as methyl ethyl ketone and methyl isobutyl ketone;
Examples include alkylbenzenes such as xylene and esters such as butyl acetate.

The hollow polymer fine particles are contained in the protective film within a range of 10 to 70% by weight. Further, the thickness of the protective film is preferably about 0.1 to 20 Bm.

Next, Examples and Comparative Examples of the present invention will be described.

However, these six examples do not limit the present invention.

[Example 1] Terbium activation-resistant gadolinium sulfide phosphor (Gd202
Methyl ethyl ketone was added to a mixture of particles of S:Tb) and 80 parts by weight of a linear polyester resin (Vylon Dew 500, manufactured by Toyobo ■), and 15 parts of 5% nitrocellulose (degree of nization 11) and incyanate ( After adding 5 parts by weight of Sumidur Door 5. manufactured by Sumitomo Bayer Urethane ■, the phosphor particles are uniformly dispersed by stirring and mixing thoroughly using a propeller mixer, and the mixing ratio of the binder and the phosphor is 1. :16 (weight ratio) and viscosity is 25-30P
A coating solution of S (25°C) was prepared.

Carbon black kneaded polyethylene terephthalate film placed horizontally on a glass plate (support, thickness: 2
The coating liquid was applied uniformly onto the sample (50 ILm) using a doctor blade. After coating, the support on which the coating film has been formed is placed in a dryer, and the temperature inside the dryer is lowered to 2.
The coating film was dried by gradually increasing the temperature from 5°C to 1OOoC.

In this way, a phosphor layer with a layer thickness of 150 gm was formed on the support.

Next, styrene/acrylic hollow polymer fine particles (VO
NCOAT PP-2000S, manufactured by Dainippon Ink Chemical ■), 1 part of polyurethane (Desmolac 4125, manufactured by Sumitomo Bayer Urethane ■), 1 part of 90ffi, and 710 parts by weight of nitrocellulose were thoroughly mixed to uniformly disperse hollow polymer particles. , the weight mixing ratio of binder and hollow polymer particles is 2:l (content of polymer particles: 33%)
A coating liquid having a viscosity of 7PS (at 25°C) was prepared.

This coating solution was applied onto the phosphor layer by the same operation as above, and then dried to form a protective film having a thickness of 8 lumens per layer.

In this way, a radiation-sensitizing screen was produced consisting of a support, a phosphor layer and a protective film containing hollow polymer particles.

[Comparative Example 1] A support, a phosphor layer, and a protective layer were prepared in the same manner as in Example 1 except that hollow polymer fine particles were not added to the coating solution for forming a protective film. A radiation intensifying screen constructed from a membrane was manufactured.

Next, using each of the obtained radiation-sensitizing screens, a radiographic film transportability test was conducted to evaluate the slippage between the screen and the film.

A pair of radiosensitized screens are attached to an angiography device (Si
emens-A OT (manufactured by Siemens) at the X-ray imaging position, and 30 sheets of commercially available radiographic film were automatically conveyed continuously between the screens. Then, it was observed whether or not film jamming (Illll broadcast) occurred.

As a result, in the known radiation intensifying screen (Comparative Example 1) which does not contain hollow polymer fine particles in the film 3IsIfl, jamming occurred in the film 1 during continuous transport and transport could not be carried out smoothly. - On the other hand, the radiation intensifying screen of the present invention containing hollow polymer fine particles was able to be conveyed smoothly to the end without any jamming of the film.

Claims (1)

[Scope of Claims] 1. A radiation intensifying screen comprising, in this order, a support, a phosphor layer made of a supporting binder containing a phosphor in a dispersed state, and a protective film, in which the protective film contains hollow polymer fine particles. A radiation intensifying screen characterized in that the content is in the range of 10 to 70% by weight. 2. The outer diameter of the hollow polymer fine particles is 0.2 to 1.
in the μm range, and the small pore diameter is 0.05 to 0.7 μm
The radiation intensifying screen according to claim 1, characterized in that the radiation intensifying screen is within the range of . 3. The radiation intensifying screen according to claim 1, wherein the hollow polymer fine particles are styrene-based and/or acrylic-based polymers.