JPH04212100A - Radiation sensitizing screen - Google Patents

Abstract

PURPOSE:To obtain the title screen imparting an image enhanced in sharpness by constituting the screen of a support and the phosphor-containing resin layer wherein the compositional ratio of a binder and a phosphor is within a specific range provided on the support and specifying the void volume of the resin layer. CONSTITUTION:A radiation sensitizing screen is constituted of a support and the phosphor-containing resin layer wherein the compositional ratio of a binder and a phosphor is (1:1)-(1:25) (wt. ratio, 1:25 is not included provided on the support. The void volume of the phosphor-containing resin layer has a value 85% or less the void volume of a phosphor-containing resin layer having a compositional ratio formed by a usual coating method under atmospheric pressure. By this method, the density of the phosphor in the phosphor layer is enhanced and, as a result, the thickness of the phosphor layer is made thin to make it possible to enhance the sharpness of an image.

Description

[Detailed description of the invention]

0001

FIELD OF THE INVENTION This invention relates to radiation intensifying screens. More specifically, the present invention provides a method in which the composition ratio of the support, the binder provided on the support, and the phosphor is 1:1 to 1:25 (weight ratio, excluding 1:25). and a phosphor-containing resin layer of the present invention.

Radiation intensifying screens are used in radiography 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 order to improve the sensitivity of the film, it is used by superimposing it on one or both sides of a radiographic film such as an X-ray film. This radiation intensifying screen basically consists of a support and a phosphor-containing resin layer formed on one side of the support. Note that a transparent protective film is generally provided on the surface of this phosphor-containing resin layer opposite to the support (the surface not facing the support), and the phosphor layer is protected from chemicals. Protects from alteration or physical impact.

0003

2. Description of the Related Art A phosphor-containing resin layer is made of a binder containing and supporting phosphor particles in a dispersed state. The phosphor-containing resin layer is generally attached to the support using a coating method under normal pressure as described below. That is, a coating solution is prepared by mixing and dispersing phosphor particles and a binder in an appropriate solvent, and this coating solution is subjected to radiation sensitization under normal pressure using a coating means such as a doctor blade, roll coater, or knife coater. Either by directly coating the screen support and then removing the solvent from the coating film, or by applying the coating solution in advance on a temporary support such as a glass plate under normal pressure and then removing the solvent from the coating film. The phosphor-containing resin layer is attached to the support by forming a phosphor-containing resin thin film, peeling it from the temporary support, and bonding it to the support of the radiation intensifying screen. There is.

The phosphor particles in the phosphor-containing resin layer have the property of emitting high-intensity light when excited by radiation such as X-rays. 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-containing resin 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.

A radiation intensifying screen having the above-mentioned basic structure has high sensitivity and high image quality (
It is desired that an image with good sharpness, graininess, etc.) be provided. Among these, from the viewpoint of obtaining more accurate and detailed information about the subject, it is desired to develop a radiation intensifying screen that improves the sharpness of the obtained image even slightly.

It is an object of the present invention to provide a radiation intensifying screen which provides images with particularly improved sharpness.

In the present invention, the composition ratio of the support, the binder provided on the support, and the phosphor is 1:1 to 1:25 (
In the radiation intensifying screen, the porosity of the phosphor-containing resin layer is such that the porosity of the phosphor-containing resin layer is within the range of 1:25 (by weight ratio, but not including 1:25). A radiation intensifying screen characterized by having a porosity of 85% or less of the porosity of the phosphor-containing resin layer having the composition ratio formed by the coating method.

The radiation intensifying screen of the present invention has (1)
The composition ratio of the support, the binder and the phosphor formed on the support by a normal coating method under normal pressure is 1:1 to 1:25 (weight ratio, however, 1:25 is The porosity of the phosphor-containing resin layer is reduced to 85% or less of the porosity before the compression treatment by compressing a sheet substantially consisting of a phosphor-containing resin layer in the range of (not including). (2) The composition ratio of the binder and the phosphor is 1:1 to 1:25 (weight ratio, however, excluding 1:25) formed by a manufacturing method under normal pressure. By compressing the phosphor-containing resin layer within the range, the porosity of the phosphor-containing resin layer is set to 85% or less of the porosity before the compression treatment, and then the phosphor-containing resin layer is attached to the support. It can be advantageously manufactured by the manufacturing method.

Next, the present invention will be explained in detail. The present invention
The porosity of the phosphor-containing resin layer of a radiation intensifying screen in which the composition ratio of binder and phosphor is in the range of 1:1 to 1:25 (weight ratio, however, 1:25 is not included) is By reducing the porosity to a certain level or less than the porosity of the phosphor-containing resin layer of the composition ratio formed by the coating method under normal pressure, the sharpness of the radiation intensifying screen can be significantly improved, that is, radiation sensitization can be achieved. When the screen is used, the sharpness of images formed and recorded on radiographic film can be significantly improved.

That is, when forming a phosphor-containing resin layer (hereinafter simply referred to as phosphor layer) consisting of a phosphor and a binder on a support by a normal coating method under normal pressure, the phosphor layer Air tends to get mixed in, creating voids. This void is
It is particularly likely to occur around phosphor particles. Further, as the content of the phosphor in the binder increases, the phosphor particles become denser, and a large number of voids tend to occur between the phosphor particles.

By the way, when radiation such as X-rays that has passed through the subject enters the phosphor layer of the radiation intensifying screen,
The phosphor particles in the phosphor layer absorb radiation energy corresponding to the transmitted image, become excited, and instantaneously emit light in the visible to near ultraviolet region having a wavelength different from that of the radiation. The light emitted from the phosphor particles sensitizes the photographic film and contributes to image formation. Generally, as the amount of phosphor contained in the phosphor layer increases, the amount of light emitted increases, and therefore the sensitivity improves. On the other hand, sharpness depends on the thickness of the phosphor layer. In other words, the thicker the phosphor layer, the more the light emitted from the phosphor particles is diffused in the phosphor layer, and the more blurred the light image is recorded on the photographic film, the more the resulting image becomes Sharpness decreases. Therefore, by making the phosphor layer thinner, images with improved sharpness can be obtained.

According to the study conducted by the present inventor, the composition ratio of the binder and the phosphor is 1:1 to 1:25 (weight ratio, however, 1:2
5)), in which the porosity of the phosphor layer is reduced to the composition formed by a normal coating method under normal pressure. 85% of the porosity of the phosphor-containing resin layer
By making the density of the phosphor in the phosphor layer higher than that of the phosphor in the conventional radiation intensifying screen, the thickness of the phosphor layer can be reduced as a result, and the sharpness of the image can be improved. It was found that it was possible to significantly improve

[0013] Furthermore, the radiation intensifying screen of the present invention includes:
Since the phosphor layer has a higher density than that of the phosphor layer of a conventional radiation intensifying screen, for example, the phosphor layer of the radiation intensifying screen of the present invention has a higher density than that of the phosphor layer of a conventional radiation intensifying screen. If the layer thickness is the same as that of the phosphor layer of the present invention, the phosphor layer of the radiation intensifying screen of the present invention can contain more phosphor particles. , it is possible to improve sensitivity without reducing sharpness. That is, in comparing the same sharpness, the radiation intensifying screen of the present invention has higher sensitivity than the conventional radiation intensifying screen. Conversely, when comparing the same sensitivity, the radiation intensifying screen of the present invention has higher sharpness than the conventional radiation intensifying screen.

Furthermore, the radiation-sensitizing screen of the present invention has the same sensitivity and sharpness as conventional radiation-sensitizing screens by coloring the protective film or the phosphor layer. Good graininess.

The radiation sensitizing screen of the present invention having the preferable characteristics as described above can be manufactured, for example, by the method described below.

[0016] In the radiation intensifying screen of the present invention,
The phosphor-containing resin layer is basically a layer made of a binder that contains and supports phosphor particles in a dispersed state.

Various types of phosphor particles are already known. Examples of radiation-sensitizing phosphor particles preferably used in the present invention include particles made of the following substances.

[0018] Tungstate-based phosphor (CaWO4
, MgWO4, CaWO4:Pb, etc.), terbium-activated rare earth oxysulfide phosphor [Y2O2S:Tb,
Gd2O2S:Tb, La2O2S:Tb, (Y
,Gd)2O2S:Tb,(Y,Gd)2O2S
:Tb, Tm, etc.], terbium-activated rare earth phosphate phosphors (YPO4 :Tb, GdPO4 :Tb, LaPO
4:Tb, etc.), terbium-activated rare earth oxyhalide phosphor (LaOBr:Tb, LaOBr:Tb,
Tm, LaOCl:Tb, LaOCl:Tb, Tm, G
dOBr:Tb, GdOCl:Tb, etc.), thulium-activated rare earth oxyhalide phosphor (LaOBr:Tm, etc.)
, LaOCl:Tm, etc.), barium sulfate-based phosphor [Ba
SO4 :Pb, BaSO4 :Eu2+, (Ba,S
r) SO4 : Eu2+ etc.], divalent europium activated alkaline earth metal phosphate phosphor [Ba3 (PO4
)2 :Eu2+, (Ba,Sr)3 (PO4 )2
:Eu2+ etc.], divalent europium activated alkaline earth metal fluorohalide phosphor [BaFCl:Eu2+
, BaFBr:Eu2+, BaFCl:Eu2+,Tb
, BaFBr:Eu2+,Tb, BaF2・BaCl
2 ・KCl: Eu2+, BaF2 ・BaCl2 ・
xBaSO4 ・KCl:Eu2+, (Ba,Mg)F
2 ・BaCl2 ・KCl:Eu2+, etc.], iodide-based phosphors (CsI:Na, CsI:Tl, NaI, KI:
Tl, etc.), sulfide-based phosphors [ZnS:Ag, (Zn, C
d) S:Ag, (Zn,Cd)S:Cu, (Zn,Cd
) S: Cu, Al, etc.], hafnium phosphate phosphor (Hf
P2 O7 :Cu, etc.). However, the phosphor particles used in the present invention are not limited to these, and may be any phosphor particles that emit light in the visible to near ultraviolet region when irradiated with radiation.

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, polymethyl methacrylate, vinyl chloride/
Binders typified by synthetic polymeric materials such as vinyl acetate copolymers, polyurethanes, cellulose acetate butyrate, polyvinyl alcohol, linear polyesters, etc. may be mentioned. Particularly preferred among such binders are nitrocellulose, linear polyesters, and mixtures of nitrocellulose and linear polyesters.

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

First, phosphor particles and a 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 the coating solution 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; 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 monomethyl ether; and mixtures thereof.

The composition ratio of the binder and the radiation-sensitizing phosphor particles in the coating solution varies depending on the characteristics of the intended radiation-sensitizing screen, the type of phosphor particles, etc., but is 1:
1 to 1:25 (weight ratio, however, 1:25 is not included)
It is particularly preferable to select from the range of 1:8 to 1:22 (weight ratio).

[0024] The coating liquid also contains a dispersant for improving the dispersibility of the phosphor particles in the coating liquid, and
Various additives such as a plasticizer may be mixed in order to improve the bonding force between the binder and the phosphor particles in the phosphor layer after formation. Examples of dispersants used for such purposes 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.

The coating solution containing the phosphor particles and binder prepared as described above is then uniformly applied to the surface of the support to form a coating film. This coating operation can be carried out using conventional coating means such as a doctor blade, roll coater, knife coater, etc.

[0026] The formed coating film is then dried by gradual 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-sensitizing screen, the type of phosphor particles, the mixing ratio of the binder and the phosphor particles, and is usually 20 μm to 1 mm. However, this layer thickness is 50 to 500 μm.
It is preferable to set it to m.

Note that the phosphor-containing resin layer does not necessarily have to be formed by directly applying a coating liquid onto the support as described above; After forming a phosphor layer by applying a coating solution onto a temporary support and drying it, the support and phosphor layer are bonded together by pressing it onto the support or using an adhesive. May be joined.

Further, the phosphor-containing resin layer may be colored with a colorant for the purpose of improving the graininess of the resulting radiation intensifying screen.

The support used in the present invention can be arbitrarily selected from various materials known as materials for the production of 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, resins, etc. Examples include coated paper, pigment paper containing pigments such as titanium dioxide, and paper sized with polyvinyl alcohol. However, in consideration of the 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 sensitizing screen, and the latter is a support suitable for a high sensitivity type radiation sensitizing screen.

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, the support on the side on which the phosphor layer is provided is used. Applying a polymeric substance such as gelatin to the surface to create an adhesion layer,
Alternatively, 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 is also provided. In addition, in radiation-sensitizing screens used in industrial radiography for the purpose of non-destructive testing of substances, lead foil or lead alloy is used on the surface of the support on the side where the phosphor layer is provided for the purpose of removing scattered radiation. It is also practiced to provide metal foil such as foil or tin foil. The support used in the present invention can also be provided with these various layers.

Furthermore, 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 is coated with an adhesion imparting layer, a light reflection layer, a light absorption layer, Alternatively, if metal foil is provided, unevenness can be formed on the surface (meaning the surface thereof), and the configuration can be arbitrarily selected depending on the purpose and use of the desired radiation intensifying screen. can do.

The porosity of the phosphor-containing resin layer formed on the support as described above can be theoretically determined by the following equation (I).

(a+b)ρxρy
V-A (aρy + bρx) Vair /V=─
──────────────────────
---(I) V[(a+
b) ρx ρy − aρy ρair − bρx
ρair] (where, V: total volume of the phosphor layer Vair: air volume in the phosphor layer A: total weight of the phosphor ρx: density of the phosphor ρy: density of the binder ρair: density of the air a: phosphor weight b: weight of binder)

In formula (I), ρair is ~
0, the formula (I) can be approximately expressed by the following formula (II).

(a+b)ρxρy
V-A (aρy + bρx) Vair /V=─
────────────────────
---(II)
V[(a+b)ρx ρy] (However,
V, Vair, A, ρx, ρy, a, and
The definition of b is the same as in formula (I))

In the present invention, the porosity of the phosphor-containing resin layer was calculated using the above formula (II).

By way of example, the formation of a phosphor-containing resin layer on a support, consisting of a terbium-activated gadolinium oxysulfide phosphor and a mixture of linear polyester and nitrocellulose as a binder, can be carried out using the conventional techniques mentioned above. The coating method is carried out under pressure, and specifically, for example, as follows.

A mixture of linear polyester and nitrocellulose and terbium-activated gadolinium oxysulfide phosphor (G
d2 O2 S:Tb) particles at a composition ratio of 1:20 (
Mix thoroughly using a propeller mixer in methyl ethyl ketone so that the viscosity is 30 PS (25
℃)) Prepare a coating solution. After uniformly applying this coating liquid onto polyethylene terephthalate (support) using a doctor blade, place it in a dryer and lower the temperature inside the dryer to 2.
By gradually increasing the temperature from 5°C to 100°C and drying the coating film, a phosphor-containing resin layer is formed on the support.

The porosity of the thus formed phosphor-containing resin layer in which the composition ratio of binder and phosphor is 1:20 is 2.
It was 5.8%. Further, the porosity of a phosphor-containing resin layer with a composition ratio of binder and phosphor of 1:10, which was formed in the same manner as above except for changing the amounts of binder and phosphor used, was 10. It was 7%.

The above-mentioned phosphor-containing resin layer is a typical example of a phosphor layer formed by a normal coating method under normal pressure. However, the porosity of the obtained phosphor layer does not change significantly. Furthermore, in calculating the porosity using formula (II), the amount of additives added to the coating liquid is small and can be ignored. Furthermore, the porosity of the phosphor layer is not significantly affected by changes in coating conditions as long as it is within the range of commonly practiced coating operations.

Therefore, as is clear from the above formula (II), the biggest factor that changes the porosity of the phosphor-containing resin layer is the composition ratio of the binder and the phosphor [b from the definition of formula (II)]. :a, weight ratio]. As the ratio of the phosphor particles to the binder increases in the phosphor-containing resin layer, the average distance between the phosphor particles dispersed in the binder becomes shorter and voids are more likely to be formed therebetween. Therefore, the porosity of the phosphor-containing resin layer tends to increase as the amount of phosphor increases.

In the production of the radiation intensifying screen of the present invention, next, a portion of the air mixed in the phosphor layer is removed to reduce voids. This reduction in voids is achieved, for example, by compressing the phosphor layer.

The compression treatment of the phosphor layer is generally performed by 100 to 1
The heating is carried out at a pressure in the range of 500 kg/cm2 and at a temperature in the range from room temperature to around the melting point of the phosphor layer. Preferably, the compression time is in the range of 30 seconds to 5 minutes. The preferred pressure is 100 to 1000 kg/cm2, and the particularly preferred pressure is 300 to 700 kg/cm2.
It is. The preferred temperature is 50 to 120°C, although it varies depending on the binder used.

[0044] Examples of compression equipment used for the compression treatment of the present invention include commonly known equipment such as calender rolls and hot presses. For example, compression treatment using calender rolls is carried out by passing a sheet consisting of a support and a phosphor layer at a constant speed between rollers heated to a constant temperature. Further, the hot press compression treatment is performed by fixing the sheet between two metal plates heated to a certain temperature and then applying a certain pressure from both sides for a certain period of time. However, the compression device used in the present invention is not limited to these devices, and any device may be used as long as it can compress the sheet as described above while heating it.

[0045] For example, when compressing a phosphor-containing resin thin film formed on a temporary support, it is also possible to carry out the compression treatment before attaching the thin film to the support of the radiation intensifying screen. In that case, a thin phosphor-containing resin film alone or a composite sheet of a phosphor-containing resin thin film and a temporary support is compressed, and then the compressed phosphor-containing resin thin film is sensitized by radiation. Attached to the screen support.

[0046] In a normal radiation intensifying screen, a transparent protective film is provided on the surface of the phosphor layer on the side opposite to the side in contact with the support to physically and chemically protect the phosphor layer. It is provided. This kind of transparent protective film is
It is also preferable to install the radiation intensifying screen of the present invention.

The transparent protective film is made of, for example, cellulose acetate,
Dissolve transparent polymeric substances such as cellulose derivatives such as nitrocellulose; or synthetic polymeric substances such as polymethyl methacrylate, polyvinyl butyral, polyvinyl formal, polycarbonate, polyvinyl acetate, and vinyl chloride/vinyl acetate copolymers in an appropriate solvent. The phosphor layer can be formed by coating the surface of the phosphor layer with a solution prepared as described above. 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 thus formed is preferably about 3 to 20 μm.

The transparent protective film may be colored with a colorant for the purpose of improving the graininess of the resulting radiation intensifying screen.

The phosphor-containing resin layer of the radiation intensifying screen of the present invention manufactured by the method typified by the method described above (composition ratio of binder and phosphor is 1:1 to 1:1)
The porosity in the range of 1:25 (excluding 1:25) is 85% or less of the porosity of the phosphor-containing resin layer of the composition ratio formed by a normal coating method under normal pressure,
In addition, the porosity of the phosphor-containing resin layer obtained in this way (
absolute value) generally does not exceed 28%.

As described above, by reducing the porosity of the phosphor-containing resin layer in the radiation intensifying screen, the density of the phosphor in the phosphor layer increases, and therefore, when the amount of phosphor used is constant, the phosphor layer becomes thinner, and the sharpness of the resulting image is significantly improved.

Next, examples of the present invention and comparative examples will be described. However, these examples do not limit the invention.

[0052]

[Example] [Example 1] A mixture (binder) of linear polyester resin and nitrocellulose with a degree of nitrification of 11.5% and a terbium-activated gadolinium oxysulfide phosphor (Gd2O2S:Tb) for radiation sensitization. of particles at a weight composition ratio of 1:20, and after adding methyl ethyl ketone, stir and mix thoroughly using a propeller mixer to ensure that the phosphor particles are uniformly dispersed and that the viscosity is 30 PS (25 °C). A coating solution was prepared. Next, a polyethylene terephthalate sheet (support, thickness: 250
μm) was placed horizontally on a glass plate, and the coating solution was uniformly applied onto this support using a doctor blade. After coating, the support on which the coating film was formed was placed in a dryer, and the temperature inside the dryer was gradually raised from 25°C to 100°C to dry the coating film. In this way, a sheet consisting of a support and a fluorescent layer with a layer thickness of about 120 μm provided on the support was obtained.

Next, a sheet consisting of a support and a phosphor layer formed on one side of the support was compressed using a calender roll at a pressure of 620 kg/cm 2 and a temperature of 100°C.

[0054] Then, a transparent film of polyethylene terephthalate (thickness: 12
A transparent protective film is formed by placing and adhering the adhesive layer (with the adhesive layer facing down), which is composed of a support, a phosphor layer, and a transparent protective film. A radiation intensifying screen was manufactured.

[Example 2] A sheet identical to the sheet consisting of the support produced in Example 1 and the phosphor layer provided on the support was heated at a pressure of 520 kg/cm2 and at 1
A radiation intensifying screen consisting of a support, a phosphor layer, and a transparent protective film was manufactured by carrying out the same treatment as in Example 1 except that compression was carried out at a temperature of 00°C.

[Example 3] A sheet identical to the sheet consisting of the support produced in Example 1 and the phosphor layer provided on the support was heated at a pressure of 420 kg/cm2 and at 1
A radiation intensifying screen consisting of a support, a phosphor layer, and a transparent protective film was manufactured by carrying out the same treatment as in Example 1 except that compression was carried out at a temperature of 00°C.

[Example 4] A sheet identical to the sheet consisting of the support produced in Example 1 and the phosphor layer provided on the support was heated at a pressure of 620 kg/cm2 and at a pressure of 8 kg/cm2.
A radiation-sensitizing screen consisting of a support, a phosphor layer, and a transparent protective film was produced by carrying out the same treatment as in Example 1 except for compressing at a temperature of 0°C.

[Example 5] A sheet identical to the sheet consisting of the support produced in Example 1 and the phosphor layer provided on the support was heated at a pressure of 520 kg/cm2 and at a pressure of 8 kg/cm2.
A radiation-sensitizing screen consisting of a support, a phosphor layer, and a transparent protective film was produced by carrying out the same treatment as in Example 1 except for compressing at a temperature of 0°C.

[Example 6] A sheet identical to the sheet consisting of the support produced in Example 1 and the phosphor layer provided on this support was heated at a pressure of 420 kg/cm2 and at a pressure of 8 kg/cm2.
A radiation-sensitizing screen consisting of a support, a phosphor layer, and a transparent protective film was produced by carrying out the same treatment as in Example 1 except for compressing at a temperature of 0°C.

[Comparative Example 1] Same method as in Example 1 except that the same sheet consisting of the support produced in Example 1 and the phosphor layer provided on this support was not compressed. The support, phosphor layer,
A radiation-sensitizing screen consisting of a transparent protective film and a transparent protective film was manufactured.

Measured values of the volume and weight of the phosphor layer of each radiation intensifying screen produced as described above;
From the density of the phosphor used (7.5 g/cm3) and the density of the binder (1.258 g/cm3), (II
) The porosity of each phosphor-containing resin layer was calculated and determined using the following formula.

Table 1 shows the results obtained for each phosphor-containing resin layer.

[0063]

In addition, Example 1 produced as described above
The radiation intensifying screen of Comparative Example 1 was evaluated by the image sharpness test described below. That is, a radiation intensifying screen and an X-ray photographic film were pressed together in a cassette, an X-ray photograph was taken through a resolution chart, and the modulation transfer function (MTF) of the resulting X-ray photograph was measured.

The results obtained are summarized and shown in the form of a graph in the drawing.

In the drawings, A represents the relationship between the spatial frequency and MTF value in the radiation intensifying screen of Example 1, and B represents
represent the relationship between the spatial frequency and the MTF value in the radiation intensifying screen of Comparative Example 1, respectively.

Table 2 shows the results (MTF values at a spatial frequency of 2 cycles/mm) obtained for each radiation intensifying screen.

[0068]

[Example 7] Mixture of linear polyester resin and nitrocellulose with nitrification degree of 11.5% (binder)
and particles of terbium-activated gadolinium oxysulfide phosphor (Gd2O2S:Tb) for radiation sensitization were mixed at a weight composition ratio of 1:10, but the same treatment as in Example 1 was carried out. A radiation-sensitizing screen consisting of a support, a phosphor layer, and a transparent protective film was manufactured by the following method.

[Example 8] A sheet identical to the sheet consisting of the support produced in Example 7 and the phosphor layer provided on the support was heated at a pressure of 520 kg/cm2 and at 1
A radiation-sensitizing screen consisting of a support, a phosphor layer, and a transparent protective film was manufactured by performing the same treatment as in Example 7, except for compressing at a temperature of 00°C.

[Example 9] A sheet identical to the sheet consisting of the support produced in Example 7 and the phosphor layer provided on the support was heated at a pressure of 420 kg/cm2 and at 1
A radiation-sensitizing screen consisting of a support, a phosphor layer, and a transparent protective film was produced by performing the same treatment as in Example 7 except for compressing at a temperature of 00°C.

[Example 10] A sheet identical to the sheet made of the support produced in Example 7 and the phosphor layer provided on the support was heated at a pressure of 620 kg/cm2 and a temperature of 80°C. A radiation intensifying screen composed of a support, a phosphor layer, and a transparent protective film was manufactured by performing the same treatment as in Example 7 except for compression.

[Example 11] A sheet identical to the sheet consisting of the support produced in Example 7 and the phosphor layer provided on this support was heated at a pressure of 520 kg/cm2 and a temperature of 80°C. A radiation intensifying screen composed of a support, a phosphor layer, and a transparent protective film was manufactured by performing the same treatment as in Example 7 except for compression.

[Example 12] A sheet identical to the sheet consisting of the support produced in Example 7 and the phosphor layer provided on this support was heated at a pressure of 420 kg/cm2 and a temperature of 80°C. A radiation intensifying screen composed of a support, a phosphor layer, and a transparent protective film was manufactured by performing the same treatment as in Example 7 except for compression.

[Comparative Example 2] The same method as in Example 7 except that the same sheet as the sheet made of the support produced in Example 7 and the phosphor layer provided on this support was not compressed. The support, phosphor layer,
A radiation-sensitizing screen consisting of a transparent protective film and a transparent protective film was manufactured.

The porosity of the phosphor-containing resin layer of each of the radiation intensifying screens produced as described above was determined by calculation using the same method as described above.

Table 3 shows the results obtained for each phosphor-containing resin layer.

[0078]

In addition, Example 7 produced as described above
The radiation intensifying screen of Comparative Example 2 was evaluated by the image sharpness test described above.

For each radiation intensifying screen, the results obtained (MT at a spatial frequency of 2 cycles/mm
F value) are shown in Table 4.

[0081]

[Brief explanation of the drawing]

FIG. 1 is a graph of the modulation transfer function (MTF) of radiographs obtained using the radiation intensifying screens manufactured in Example 1 and Comparative Example 1. FIG.

Claims (2)

[Claims] Claim 1: Fluorescent material in which the composition ratio of a support, a binder provided on the support, and a phosphor is in the range of 1:1 to 1:25 (weight ratio, excluding 1:25). In the radiation intensifying screen, the porosity of the phosphor-containing resin layer is substantially composed of a phosphor-containing resin layer having the composition ratio formed by a normal coating method under normal pressure. A radiation intensifying screen characterized in that it has a value of 85% or less of the porosity of the layer. 2. The radiation intensifying screen according to claim 1, wherein the porosity of the phosphor-containing resin layer is reduced by subjecting the phosphor-containing resin layer to compression treatment.