JPS6140598A - Radiation sensitizing 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 invention] The present invention relates to radiation intensifying screens.

More particularly, the present invention relates to a radiation intensifying screen comprising, in this order, a support, a phosphor layer comprising a supporting binder containing dispersed phosphors, and a protective film.

[Technical Background of the Invention and Prior Art] Radiation intensifying screens are used in various fields such as medical radiography such as X-ray photography for the purpose of medical diagnosis, and industrial radiography for the purpose of non-destructive testing of materials. In radiography, in order to improve the sensitivity of the imaging system, it is used by stacking the radiographic film in close contact with one or both sides of the film. This radiation intensifying screen basically consists of a support and a phosphor layer provided on one side of the support. Note that a transparent protective film is generally provided on the surface of the phosphor layer opposite to the support (the surface not facing the support) to protect the phosphor layer from chemical deterioration or Protects from physical impact.

The phosphor layer is made of a binder that contains and supports phosphor particles in a dispersed state, and the phosphor particles have the property of emitting high-intensity light when excited by radiation such as X-rays. It is. Therefore, depending on the amount of radiation transmitted through the subject, the phosphor emits high-intensity light, and the radiographic film placed in contact with the surface of the phosphor layer of the radiation intensifying screen is Since sensitization is also caused by the emission of the phosphor, sufficient sensitization of the photographic film can be achieved with a relatively small dose of radiation.

Radiation sensitizing cloth with the basic structure as above
“With regard to lean, it is desirable to have high sensitivity and to provide images with good image quality (sharpness, graininess, etc.). Various improvements have been made.

In radiography using a radiation intensifying screen, the sharpness of the image is essentially determined by the spread of fluorescence in the radiation intensifying screen.

Therefore, although the sharpness of a radiation intensifying screen is generally improved by reducing the thickness of the phosphor layer, the sensitivity tends to decrease at the same time. In order to improve the sharpness without causing a decrease in sensitivity, the mixing ratio of binder and phosphor in the phosphor layer [binder/phosphor] should be reduced, and the phosphor layer of the intensifying screen should be It is desired that the phosphor layer is filled with phosphor at a high density.

On the other hand, radiation-sensitizing screens themselves hardly change in quality even when irradiated with radiation, so they can be used repeatedly over long periods of time. Even in such cases, it is necessary to have sufficient mechanical strength so that the support and the phosphor layer and the protective film and the phosphor layer do not separate.

However, the mixing ratio of the binder and the phosphor in the phosphor layer [
The bond strength of the phosphor layer to the support and the protective film tends to decrease as the amount of binder/phosphor becomes smaller, that is, as the phosphor layer becomes more filled with phosphor.

The applicant has proposed that the following general formula (I
By using a (meth)acrylic copolymer having repeating units represented by ), (II) and (IIF), it is possible to obtain a radiation-sensitizing screen that provides images of good quality and has improved mechanical strength. A patent application has already been filed for the invention (Japanese Patent Application No. 1414-1983).
No. 57).

(I) (■) (Machi) (However, R1, R3 and R5 are each hydrogen or an alkyl group: R2 is an alkyl group, a cycloalkyl group,
any of aryl, heterocyclic and aralkyl groups, and R4 is any of hydrogen and alkyl groups, and R25Ra; and x, y and 2 each represent a mole percentage; 5≦X≦99,
In other words, the above (meth)acrylic copolymer has a high affinity with phosphor particles, so it is suitable as a binder for radiation intensifying screens. By including this (meth)acrylic copolymer, it is possible to fill the binder with phosphor at a high density, making it possible to obtain high-sharp images without significantly reducing the sensitivity of the screen. . Also,
Even if the phosphor is packed in the phosphor layer at a high density, the binder and the phosphor particles separate during the drying process of the phosphor layer, causing a relatively large number of phosphor particles to aggregate on the support side, a so-called phenomenon. Since lifting of the binder is less likely to occur, the adhesion strength between the phosphor layer and the support can be increased. Since the (meth)acrylic copolymer is soft, it has excellent bending resistance, which can improve the mechanical strength of the screen against impact, bending, and the like. Furthermore, since the binding agent is less likely to lift up,
Compared to conventional radiation intensifying screens, the sharpness of the resulting image can be significantly improved even if the mixing ratio of binder and phosphor is the same.

However, in radiation-sensitizing screens containing the above-mentioned (meth)acrylic copolymer as a binder for the phosphor layer, when a protective film is provided on the phosphor layer, the adhesion strength between the phosphor layer and the protective film is sufficiently satisfactory. It's hard to say that it can be done.

In addition, if an acrylic resin other than the above, such as ordinary polyalkyl methacrylate, is used as a binder to improve the adhesion strength between the phosphor layer and the protective film, mechanical The phosphor layer tends to crack when stimulated.

On the other hand, from the viewpoint of flexibility and mechanical strength of radiation intensifying screens, it is known to use a polyester resin as a binder for the phosphor layer. However, acrylic resins and polyester resins generally have poor compatibility, and conventionally it has been almost impossible to use them together.

[Summary of the Invention] An object of the present invention is to provide a radiation-sensitizing screen that has both mechanical strength, particularly high adhesion strength of a phosphor layer to a protective film, and excellent bending resistance. be.

Another object of the present invention is to provide a radiation-sensitizing screen that has both the characteristics of providing high-sharp images in addition to the above-mentioned characteristics, and high adhesion strength of the phosphor layer to the support. That is.

The above object is to provide a radiation intensifying screen having a support, a phosphor layer consisting of a supporting binder containing a phosphor in a dispersed state, and a protective film in this order, in which the binder is a (meth)acrylic copolymer. Hydroxyl number is 20-7
5o-t mixture with linear polyester in the range of 0
This is achieved by a radiation intensifying screen characterized in that the linear polyester content in the mixture is 40% or less.

[Effects of the Invention] The present invention uses a mixture of a (meth)acrylic copolymer and a linear polyester having a hydroxyl value in the range of 20 to 70 as a binder for the phosphor layer of a radiation intensifying screen. This improves the mechanical strength of the intensifying screen, particularly the adhesion strength and bending resistance of the phosphor layer to the protective film. Furthermore, the radiation intensifying screen of the present invention provides improved image sharpness and improved adhesion strength of the phosphor layer to the support.

That is, the present inventor found that in a combination of an acrylic resin and a polyester resin, which are generally considered to have low compatibility, the polyester resin has a hydroxyl value of 20.
It has been found that by using linear polyesters in the range .about.70, mixtures of both can be used as binders. And, as mentioned above, radiation sensitization containing as a binder a mixture of (meth)acrylic copolymer which has excellent affinity with phosphor particles and a specific linear polyester which has excellent flexibility etc. The screen is
It was found that it provides images of good quality and exhibits high mechanical strength. In particular, the adhesion strength between the phosphor layer and the protective film is generally a peel strength of 90 g/cI11 or higher (90 g/cI11 or higher).
It is desirable to have a 0° peel strength, and according to the present invention, a radiation-sensitized screen with such high peel strength can be obtained.

In other words, compared to a radiation-sensitizing screen containing only a (meth)acrylic copolymer, the sharpness of the image is hardly reduced, and the bending resistance and phosphor layer support and protective film are improved. Mechanical strength such as adhesion strength can be significantly improved.

[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 in 1 below.

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

The binder, which is a characteristic feature of the invention, is a mixture of a (meth)acrylic copolymer and a linear polyester with a hydroxyl number in the range from 20 to 70.

Examples of the (meth)acrylic copolymer include (meth)acrylic copolymers having repeating units represented by the following general formulas (I), (n), and (III).

(I) (n) (III)
(However, R4, R3 and R5 are each water
I is an elementary or alkyl group; R2 is any one of an alkyl group, a cycloalkyl group, an aryl group, a heterocyclic group, and an aralkyl group, and R4 is any one of hydrogen and an alkyl group, And R2 lol R4;
and x, y and 2 each represent a mole percentage,
5≦X≦99.1≦y1z≦95, and x+y+z≧
In the above general formulas (I), (IF) and (IN), R1, R3 and R5 are each hydrogen or an alkyl group, such as methyl, ethyl, propyl, butyl, etc. Preferably, it is an alkyl group having 1 to 4 carbon atoms.

R2 is preferably an alkyl group having 1 to 20 carbon atoms such as methyl, ethyl, propyl, butyl, hexyl; 5 to 12 carbon atoms such as cyclopentyl, cyclohexyl
cycloalkyl groups having 7 to 20 carbon atoms; aryl groups such as phenyl; heterocyclic groups such as pyridyl; and aralkyl groups having 7 to 20 carbon atoms such as benzyl, phenylethyl, phenylpropyl, phenylbutyl, naphthylmethyl. It is one of the following.

R4 is hydrogen, or methyl when it is an alkyl group,
Preferred are alkyl groups having 1 to 6 carbon atoms such as ethyl, propyl, butyl, hexyl. However, R4 is not the same as R2.

From the viewpoints of affinity with phosphor particles and film hardness when forming a coating film, the preferred (meth)acrylic copolymer as the binder for the radiation intensifying screen of the present invention is X
, y and 2 are 50≦X≦95.5≦y+z≦50,
and a numerical value in the range of xy+z≧95. Also, X, y and 2 are 70≦X≦95, y=o, 5≦
The numerical value may be in the range of 2≦30 and x+y+z≧95. It is particularly preferable that x+y+z=100.

If x+y+z is less than 100, it means that the (meth)acrylic copolymer contains other repeating units, such as aliphatic alkylene, styrene, vinyl, etc. Mention may be made of derivatives, divalent groups derived from acrylamide.

Note that (meth)acrylic copolymers having repeating units represented by the above general formulas (I), (n), and (IN) may contain various monomers that can become the respective repeating units, namely, acrylic acid, acrylic acid, and acrylic acid. The monomers selected from acid esters, methacrylic acid, methacrylic esters, acrylonitrile, and methacrylate trile and, if desired, other monomers that can be copolymerized with these monomers are used as raw materials, and are copolymerized by known methods. It can be obtained by carrying out a polymerization reaction.

Further, the (meth)acrylic copolymer may be crosslinked with a crosslinking agent. Examples of the crosslinking agent include aliphatic or aromatic polyisocyanates.

The (meth)acrylic copolymer used in the present invention has the above general formulas (I), (II) and (+111).
The binder used in the present invention is not limited to those having a repeating unit represented by the formula, but any binder that has high compatibility with the linear polyester, which is one component of the binder used in the present invention, and has appropriate flexibility. It can be anything.

The linear polyester used in the present invention has a hydroxyl value (mgK OH/g) in the range of 20 to 70. Preferably, it is a linear saturated polyester having a molecular weight in the range of 3 x 103 to 10'.

In addition, the linear polyester is ethylene glycol, 1,
3-propanediol, ■, 4-butanediol, 1.
It is obtained by the polycondensation reaction of a dioxic compound such as 4-cyclohexane dimetatool with a dibasic acid such as succinic acid, glutaric acid, adipic acid, terephthalic acid, or isophthalic acid. By adjusting the ratio or reaction conditions, the hydroxyl value can be increased from 20 to
Linear saturated polyesters in the range of 70 can be obtained. Alternatively, it can be similarly obtained by polycondensation reaction of oxyacids such as glycolic acid, lactic acid, malic acid, tartaric acid, citric acid, salicylic acid, benzoic acid, gallic acid, mandelic acid, and tropic acid.

From the viewpoint of compatibility, the content (weight ratio) of the linear polyester in the mixture of the above (meth)acrylic copolymer and the linear polyester having a hydroxyl value in the range of 20 to 70 is 40% or less. Used in percentages. Preferably it is in the range of 10 to 40%.

In the phosphor layer, a mixture of a (meth)acrylic copolymer and a linear polyester with 60%
It is used by containing it in a range of 100% by weight. However, from the viewpoint of the dispersibility of the phosphor particles in the binder solution, the uniformity of coating, and the hardness of the resulting coating film, the binder for the phosphor layer should be 75 to 95% by weight of the ``:2 mixture.'' Preferably, the composition system contains the following components: and the remaining amounts are other binder components.

In the present invention, examples of binder components that can be used in combination with the mixture consisting of a (meth)acrylic copolymer and a linear polyester include polyesters other than the above (e.g.
Byron 530; manufactured by Toyobo ■), polyurethane (e.g., Desu Kol 400; Desmolac KL-5-2θ)
25; manufactured by Sumitomo Bayer Urethane ■), vinyl acetate resin (e.g., Denka ASRCL-13; manufactured by Denki Kagaku Kogyo ■), styrene resin (for example, Picolastic A-75)
, Elan Standard Sekiyu ■), polyisocyanates, cellulose derivatives, polyalkyl methacrylates (
For example, synthetic polymer materials such as Almatex (manufactured by Mitsui Toatsu Kagaku ■), cellulose resin, amine resin, melamine resin, etc. can be mentioned. Particularly preferred among such binder components are nitrocellulose and polyalkyl methacrylates.

Various types of phosphors for radiation sensitization are already known. Examples of phosphors preferably used in the present invention include the following substances.

Tungstate-based phosphors (CaWO4, MgWO4,
CaWO4:Pb, etc.), terbium-activated rare earth oxysulfide phosphor [Y2O2S:Tb, G d 202 S:
T b , L & 202 S: T b ,
(Y, G d ) 202 S: T b, (Y
, Gd) 202S:Tb, Tm, etc.], terbium-activated rare earth phosphate phosphors (YPO42Tb, GdPO4:T
b, LaPO4:Tb, etc.), terbium-activated rare earth oxyhalide phosphor (LaOBr:Tb, La0
Br:Tb, Tm, La0CJ1:Tb, La0Cu:
Tb, Tm, Gd0Br: Tb, Gd0Cl: Tb
etc.), thulium-activated rare earth oxyhalide-based phosphors (LaOBr:Tm, La0Cl:Tm, etc.), barium sulfate-based phosphors [BaSO4: Pb, BaSO4:
Eu2+, (Ba, Sr)SO4: Eu2'+, etc.]
, divalent noeurobium activated alkaline earth metal phosphate phosphor [Ba3(PO4)2: Eu2+, (Ba,5
r)3(PO4)2:Eu2+, etc.], divalent noeurohium-activated alkaline earth metal fluoride halide phosphor [B
aFCjl: Eu-1BaFBr: Eu2+, Ba
FCfL: Eu”, Tb, BaFB r: Eu2
+.

Tb, BaF2 life BaCl and 2 KCJL: Eu 2+, BaF2 eBac,
u2 ・xBaSO4*KCu :E u2+
, (Ba, Mg) F2*BaCfL 2*KC1
:Eu", etc.), iodide-based phosphors (Csl:Na, C8I
:T1. Na1. KI:Tu, etc.), sulfide-based phosphors [ZnS:Ag, (Zn, Cd)S:Ag, (Zn
, Cd) S:Cu, (Zn.

Cd) S: Cu, A pattern, etc.], phosphoric acid haffluorum-based phosphor (Hf P 20 y: Cu, etc.).

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

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 mixed thoroughly 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; acetone, methyl ethyl ketone, and methyl isobutyl ketone. Ketones such as; esters of lower fatty acids and lower alcohols such as methyl acetate, ethyl acetate, and butyl acetate; ethers such as dioxane, ethylene glycol 7-methyl ether, and ethylene glycol 7-methyl ether; and mixtures thereof. can.

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), preferably from the range of 1:8 to 1:50 (weight ratio).

The coating liquid also contains a dispersant to improve the dispersibility of the phosphor in the coating liquid, and a dispersant to improve the bonding force between the binder and the phosphor in the phosphor layer after formation. Examples of dispersants used for such purposes include phthalic acid, stearic acid, caproic acid, lipophilic surfactants, etc., which may be mixed with various additives such as plasticizers. can. 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.

The coating solution containing the phosphor and binder prepared as described above is then uniformly applied to the surface of the support to form a coating film of the coating solution.

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, and is usually 2071 m to 1 mm. However, the thickness of this layer is preferably 50 to 500 pm.

Note that the phosphor layer does not necessarily need 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.

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 its 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 former is a support suitable for a high sharpness type radiation intensifying screen, and the latter is a support suitable for a high sensitivity type radiation intensifying screen.

In known radiation-sensitizing screens, gelatin is added to the surface of the support on the side where the phosphor layer is provided, in order to strengthen the bond between the support and the phosphor layer, or to improve the sensitivity or image quality of the radiation-sensitized screen. Coating a polymeric substance such as to form an adhesion-imparting layer, or providing 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 blur 2. is also being carried out. In addition, in radiation intensifying screens used in industrial radiography for the purpose of non-destructive testing of substances, lead 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, etc.
Metal foils such as lead alloy foils and anchor chains are also provided. The support used in the present invention can also be provided with these various layers, and their configurations can be arbitrarily selected depending on the purpose, use, etc. of the desired radiation intensifying screen.

Furthermore, as described in JP-A-58-182599, in order to improve the sharpness of the obtained image, the surface of the support on the phosphor layer side (the surface of the support on the phosphor layer side) (If an adhesion-imparting layer, light-reflecting layer, light-absorbing layer, or metal foil is provided, this means the surface thereof)
may have minute irregularities formed uniformly.

In a typical radiation intensifying screen, a transparent protective film for physically and chemically protecting the phosphor layer is provided on the surface of the phosphor layer on the side opposite to the side in contact with the support. It is preferable to provide such a transparent protective film also in the radiation intensifying screen of the present invention.

The transparent protective film may be made of a transparent material such as a cellulose derivative such as cellulose acetate or nitrocellulose; or a synthetic polymer material such as polymethyl methacrylate, polyvinyl butyral, polyvinyl formal, polycarbonate, polyvinyl acetate, or vinyl chloride/vinyl acetate copolymer. It can be formed by coating the surface of the phosphor layer with a solution prepared by dissolving a polymeric substance in an appropriate solvent. Alternatively, it can also be formed by a method such as adhering a transparent thin film separately formed from polyethylene terephthalate, polyethylene, vinylidene chloride, polyamide, etc. to the surface of the phosphor layer using a suitable adhesive. The thickness of the transparent protective film formed in this way is approximately 3
It is desirable to set it to 20 pLm.

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

However, each of these aspects does not limit the invention. In each of the following, "parts" represent "parts by weight" unless otherwise specified.

[Example 1] Particles of calcium tungstate phosphor (CaW04), acrylic copolymer (Crisco, X=60,
y = 30 and z = 10) and linear saturated polyester (Vylon GK-130, manufactured by Toyobo ■; hydroxyl number = 3
0 to 60, molecular weight: 5 x 103 to 8 x 103), nitrocellulose (binder) and tricresyl phosphate (plasticizer), and after adding methyl ethyl ketone, thoroughly stir and mix using a propeller mixer. , the phosphor particles are uniformly dispersed, the mixing ratio of the binder and the phosphor is 1:20 (weight ratio), and the viscosity is 25 to 35 PS (
A coating solution was prepared at a temperature of 25°C.

[Reduced amount of evidence CaWO4 phosphor 500 parts Acrylic copolymer 13.8 parts Linear saturated polyester 8.8 parts Nitrocellulose
2.0 parts tricresyl phosphate
0.5 part methyl ethyl ketone
llO part (Content of linear saturated polyester in a mixture of acrylic copolymer and linear saturated polyester: 39%) Next, a carbon-mixed polyethylene terephthalate film (support, thickness: 2
The coating liquid was applied uniformly onto the sample (50 JLm) using a doctor blade. After coating, the support on which the coating film was formed was heated and dried for 10 minutes at a temperature of 90° C. and a wind speed of 1.0 m/sec.

In this way, a layer thickness of approximately 180 pm is applied to the support.
'A phosphor layer was formed.

Then, by placing a transparent film of polyethylene terephthalate (thickness = 12#1.m, coated with a polyester adhesive) on the second side of this phosphor layer with the adhesive layer side facing down, and adhering it. , forming a transparent protective film,
A radiation intensifying screen consisting of a support, a phosphor layer and a transparent protective film was produced.

[Example 2] Example 1 except that polymethyl methacrylate (binder; BR-107, manufactured by Mitsubishi Rayon ■) was added to the coating solution to make the coating solution have the following composition. 1
A radiation-sensitizing screen consisting of a support, a phosphor layer, and a transparent protective film was produced by carrying out a treatment similar to the method described above.

Margin coating below: CaWO4 phosphor 500 parts Acrylic copolymer 13.8 parts Linear saturated polyester 6.8 parts Polymethyl methacrylate 2.0 parts Nitrocellulose
2.0 parts tricresyl phosphate
0.5 parts methyl ethyl ketone 1
10 parts (Content of linear saturated polyester in mixture of acrylic copolymer and linear saturated polyester: 33%) [Comparative Example 1] In Example 1, polymethyl methacrylate was used instead of the linear saturated polyester in the coating solution. A radiation-sensitizing screen composed of a support, a phosphor layer and a transparent protective film was produced by carrying out the same treatment as in Example 1, except that the coating solution was added and the coating solution had the following composition. did.

Coating 1 modified Ca W Oa phosphor 500 parts Acrylic copolymer 13.8 parts Polymethyl methacrylate 8.8 parts Nitrocellulose 2.0 parts Tricresyl phosphate
0.5 part methyl ethyl ketone
95 parts [Comparative Example 2] In Comparative Example 1, a coating composition consisting of a support, a phosphor layer and a transparent protective film was prepared by performing the same treatment as in Example 1 except that the coating liquid had the following composition. A radiation intensifying screen was manufactured.

Coating 1 part CaWO4 phosphor 500 parts Acrylic copolymer 8.8 parts Polymethylmethacrylate 13.8 parts Nitrocellulose 2.0 parts Tricresyl phosphate
0.5 part methyl ethyl ketone
95 parts [Comparative Example 3] In Example 1, the same process as in Example 1 was carried out except that the coating liquid had the following composition. A radiation intensifying screen was manufactured.

Coating liquid 2JfL CaWOa phosphor 500 parts Acrylic copolymer 8.8 parts Linear saturated polyester 13, AS Nitrocellulose 2.0 parts Tricresyl phosphate
0.5 part methyl ethyl ketone
110 parts (Content of linear saturated polyester in the mixture of acrylic copolymer and linear saturated polyester: 61%) The obtained coating liquid has poor compatibility with the acrylic copolymer and linear saturated polyester, It was cloudy.

Each of the radiation intensifying screens produced as described above was evaluated by the bending resistance test described below, the adhesion strength test of the phosphor layer to the protective film and the support, and the image sharpness test.

(1) #Flexibility test A test piece made by cutting a radiation intensifying screen into a width of 100 mm was wrapped around a cylinder with a diameter in the range of 40 to 145 mm for a certain period of time, and the phosphor layer was visually observed to detect any cracks that occurred. evaluated.

(2) Adhesion strength test of phosphor layer to support A radiation intensifying screen was cut into a test piece having a width of 10 mm, and a cut was made at the interface between the phosphor layer and the support. Then, the adhesion strength of the phosphor layer to the support was measured by pulling apart the support portion of the test piece prepared in this manner and the phosphor layer and protective film portions. The measurement was performed using Tensilon (UTM-If-20 manufactured by Toyo Baldwin Co., Ltd.) by pulling both sections perpendicularly to each other at a pulling speed of 10 mm/min (900 peeling), and when the phosphor layer was peeled off by 40 mm, Acting force F (g/c
The adhesion strength was expressed by m).

(3) Adhesion strength test of phosphor layer to support A radiation intensifying screen was cut into a test piece having a width of 10 mm, and a cut was made at the interface between the phosphor layer and the protective film. Then, the adhesion strength of the phosphor layer to the protective film was measured by pulling apart the protective film portion of the test piece and the phosphor layer and support portion in the same manner as above.

(4) Image sharpness test A radiation intensifying screen and an X-ray photographic film are pressed together in a cassette, an X-ray photograph is taken using a resolution chart, and the modulation transfer function (MTF) of the completed X-ray photograph is determined.
was measured and expressed as a value of spatial frequency 2 cycles/mm.

The results obtained for each radiosensitizing screen are shown in Table 1.

From the results summarized in Table 1 below, it can be seen that the radiation intensifying screen according to the present invention (Examples 1 and 2) was
Compared to the radiation intensifying screen according to the No.-141457 application (Comparative Example 1), the adhesion strength between the phosphor layer and the protective film and between the phosphor layer and the support is high, and an image with sufficiently high sharpness can be obtained. Also, compared to the radiation intensifying screen (Comparative Example 2) according to the above-mentioned application, it has excellent bending resistance and high adhesion strength between the phosphor layer and the support.
It is also clear that the sharpness of the image is similarly high.

On the other hand, although the radiation intensifying screen of Comparative Example 3 has sufficiently high adhesion strength and bending resistance, the compatibility of the binder components is poor and the sharpness is poor due to the lifting of the binder due to phase separation of the binder components. It is somewhat lower.

Claims (1)

[Claims] 1. A radiation intensifying screen comprising a support, a phosphor layer comprising a supporting binder containing a phosphor in a dispersed state, and a protective film in this order, wherein the binder is (meth)acrylic. 60 to 100% by weight of a mixture of a polyester copolymer and a linear polyester having a hydroxyl value in the range of 20 to 70.
A radiation intensifying screen characterized in that the content of linear polyester in the mixture is 40% or less. 2. The above (meth)acrylic copolymer has the general formula (
I), (II) and (III): ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I)▲There are mathematical formulas, chemical formulas, tables, etc.▼(II)▲There are mathematical formulas, chemical formulas, tables, etc.▼(III) (However, R_1, R_3 and R_5 are each hydrogen or an alkyl group; R_2 is any one of an alkyl group, a cycloalkyl group, an aryl group, a heterocyclic group, and an aralkyl group, and R_4 is a hydrogen or an alkyl group. and R_2≠, R_4; and x, y and z each represent a molar percentage, 5≦x≦99, 1≦y+z≦95, and x+y
The radiation intensifying screen according to claim 1, characterized in that it has a repeating unit represented by: +z≧90. 3. The above linear polyester has a molecular weight of 3 x 10^3 ~
The radiation intensifying screen according to claim 1, characterized in that it is a linear saturated polyester having a molecular weight in the range of 10^4. 4. Any one of claims 1 to 3, wherein the binder contains a mixture of a (meth)acrylic copolymer and a linear polyester in a range of 75 to 95% by weight. Radiosensitizing screen as described in section. 5. The content of linear polyester in the above mixture is 1
The radiation intensifying screen according to any one of claims 1 to 3, characterized in that the radiation intensifying screen is in the range of 0 to 40%.