JP2002098798A - Radiation intensifying screen, its manufacturing method, radiation receptor using it, and radiation testing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve both of sharpness and a mechanical property while maintaining high sensitivity of radiation intensifying screen and to provide a radiation testing device using the radiation intensifying screen and exhibiting good identifying ability to a small amount of radiation exposure. SOLUTION: This radiation intensifying screen is provided with a support 1, a phosphor layer 2 formed on the support 1, and a protective film 3 arranged on the phosphor layer 2. A refractive index of the protective film 3 ranges from 1.3 to 1.5 in measurement with a main luminous wavelength of the phosphor of the phosphor layer 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiographic intensifying screen used for X-ray photography and the like, a method for producing the same, a radiation receptor using the same, and a radiological examination apparatus.

[0002]

2. Description of the Related Art In X-ray photography used for medical diagnosis and industrial nondestructive inspection, a radiation film is usually used in combination with a radiographic intensifying screen in order to improve the sensitivity of an imaging system. . As a radiographic intensifying screen used for X-ray photography or the like, a phosphor intensifying layer and a relatively thin protective film for protecting the phosphor layer are sequentially formed on a support made of paper or plastic. In recent years, there has been an increasing demand for reduction of the radiation exposure of subjects in medical diagnosis and the like. For this reason, in direct X-ray photography, the radiation exposure of the subject is reduced by using a radiation film or a radiographic intensifying screen with high sensitivity. Here, the protective film of the radiation intensifying screen described above is an essential component for preventing physical and chemical deterioration of the phosphor layer generated when the radiation intensifying screen is repeatedly used. When the thickness is emphasized, the sensitivity of the obtained radiation image is reduced, and the sharpness is further reduced. On the other hand, when the thickness of the protective film is reduced, the function as the protective film is reduced. Therefore, many studies have been made to satisfy the conflicting characteristics of "improvement of the function of the protective film" and "suppression of decrease in sensitivity and sharpness". Up to now, γ-alumina particles, polymer particles, etc. have been added to the protective film to improve the slipperiness of the protective film surface, or the presence of a metal oxide or the like between the protective film and the phosphor layer has resulted in conductivity. Attempts have been made to provide, for example, Also, in JP-A-6-75097,
By using a coating film containing a fluorine-based resin soluble in an organic solvent and having a thickness of 5 μm or less as a protective film, a protective film excellent in stain resistance is provided.

[0003]

As described above, various protective films of radiographic intensifying screens which have been researched and developed so far have a physical and chemical protective function as a protective film, for example, a scratch-resistant material. It is produced as a result of considering functions such as resistance, stain resistance, and abrasion resistance, and suppressing reduction in sharpness of the obtained radiographic image, but the degree of improvement is not sufficient. Was. SUMMARY OF THE INVENTION The present invention has been made to address such a problem, and has made it possible to maintain all three characteristics of mechanical strength such as abrasion resistance, sharpness and sensitivity of a radiographic intensifying screen. It aims to provide an intensifying screen.

[0004]

According to the present invention, there is provided a radiographic intensifying screen according to the present invention, comprising: a support; a phosphor layer formed on the support; and a phosphor layer formed on the support. In the radiation intensifying screen comprising the provided protective film, the refractive index of the protective film obtained by measuring the main emission wavelength of the phosphor of the phosphor layer is in the range of 1.3 to 1.5. I have. Here, the refractive index of the protective film defined in the present invention is a value measured by spectroscopic ellipsometry.

[0005] In the radiographic intensifying screen of the present invention, the protective film is, for example, a resin film laminated on a phosphor layer as described in claim 3, and as described in claim 5, The protection film is particularly effective when it is made of a fluororesin. Further, as described in claim 6,
It is preferable that at least one of the phosphor layer, the protective film, and the support contains a fluorescent dye and / or a fluorescent pigment.

According to a seventh aspect of the present invention, there is provided a radiation receptor laminated on a radiation film and a surface of the radiation film on a subject side, comprising the above-described radiation intensifying screen of the present invention. An intensifying screen, a back intensifying screen which is laminated along a surface of the radiation film opposite to the surface on the subject side and is made of the above-described radiation intensifying screen of the present invention, and the front intensifying screen; A cassette accommodating a laminate of the radiation film and the back intensifying screen.

According to another aspect of the present invention, there is provided a radiation inspection apparatus including the radiation source and the radiation receptor according to the present invention, which is disposed to face the radiation source via a subject. Features.

In the present invention, the refractive index of the protective film of the radiation intensifying screen is adjusted in the range of 1.3 to 1.5. Therefore, X
Since the transmittance increases with respect to the angle of the light emitted from the phosphor excited by the line, it is considered that a captured image with higher sharpness than before can be obtained. That is, it is possible to minimize the loss when the light emitted from the phosphor passes through the protective film, and to more accurately deliver the signal from the subject to the surface of the protective layer.

[0009]

Embodiments of the present invention will be described below. FIG. 1 is a cross-sectional view showing a main structure of an embodiment of the radiation intensifying screen of the present invention. In FIG. 1, reference numeral 1 denotes a support made of a plastic film, a nonwoven fabric, or the like, and a phosphor layer 2 is formed on one surface of the support 1. On the phosphor layer 2, a protective film 3 made of a plastic film, a plastic coating film, or the like is provided. With these components, the radiation intensifying screen 4
For example, an intensifying screen for X-ray photography is configured. As the support, various supports used for known radiographic intensifying screens are appropriately used depending on the purpose. For example, a polymer film containing a white pigment such as titanium dioxide or a polymer film containing a black pigment such as carbon black is generally used. A phosphor layer can be directly provided on the upper surface of the support (the surface on the side where the phosphor layer is provided), but the phosphor layer is provided via an undercoat image (light reflection layer) into which a light reflecting material is introduced. Can also be provided. The light reflection layer is usually a layer formed from a polymer binder containing a white pigment such as titanium dioxide.

There is no particular limitation on the phosphor used for forming the phosphor layer of the radiation intensifying screen of the present invention.
O ₄ , YTaO ₄ , YTaO ₄ : Nb, LaOBr: T
m, BaSO ₄ : Pb, ZnS: Ag, BaSO ₄ : E
u, YTaO ₄ : Tm, BaFCl: Eu, BaF (B
r, I): Eu, Gd ₂ O ₂ S: Tb, Y ₂ O ₂ S: T
b, La ₂ O ₂ S: Tb, (Y, Gd) ₂ O ₂ S: T
b and known phosphors such as (Y, Gd) ₂ O ₂ S: Tb and Tm can be used alone or in combination.

In the radiation intensifying screen of the present invention, it is particularly preferable to use a terbium-activated rare earth oxychalcogenide-based phosphor represented by the following formula. M ₂ O ₂ X: Tb (where M is at least one element selected from the group consisting of yttrium, gadolinium and lutetium, and X is at least one element selected from the group consisting of sulfur, selenium and tellurium) Is.)

Examples of the terbium-activated rare earth oxysulfide phosphor preferably used in the radiographic intensifying screen of the present invention include Gd ₂ O ₂ S: Tb, Y ₂ O ₂ S: Tb, La ₂
Phosphors such as O ₂ S: Tb, (Y, Gd) ₂ O ₂ S: Tb, and (Y, Gd) ₂ O ₂ S: Tb, Tm can be given. Particularly preferably used in the radiation intensifying screen of the present invention is a phosphor represented by a composition formula of Gd ₂ O ₂ S: Tb.

The phosphor layer is prepared by dispersing the above phosphor in an organic solvent solution containing a binder resin to prepare a dispersion, and applying the dispersion directly to a support or an undercoat layer such as a light reflection layer. Through application and drying. Alternatively, the above dispersion is applied to a separately prepared temporary support, dried to form a phosphor sheet, the phosphor sheet is peeled off, and directly onto the support using an adhesive, or via an undercoat layer. It can also be attached.

As the binder used for preparing the phosphor coating solution, nitrated cotton, cellulose acetate, ethyl cellulose, polyvinyl butyral, flocculent polyester, polyvinyl acetate, vinylidene chloride-vinyl chloride copolymer, vinyl chloride-acetic acid copolymer, polyalkyl ( Examples thereof include those conventionally used such as (meth) acrylate, polycarbonate, polyurethane, cellulose acetate butyrate, and polyvinyl alcohol. Further, as the organic solvent, for example, ethanol, methyl ethyl ether,
Butyl acetate, ethyl acetate, ethyl ether, xylene and the like are used. In addition, if necessary,
Dispersants such as phthalic acid and stearic acid and plasticizers such as triphenyl phosphate and diethyl phthalate can be added.

The protective layer having a refractive index of 1.3 to 1.5, which is a characteristic component of the present invention and obtained by measuring the main emission wavelength of the phosphor of the phosphor layer, is a characteristic feature of the present invention. A film is formed. If the refractive index exceeds 1.5, the light emitted from the phosphor will pass through the protective film, causing a large loss, making it difficult to accurately deliver the signal from the subject to the surface of the protective layer, and improving the sharpness. In addition to the reduction, the sensitivity may be greatly reduced. On the other hand, when the refractive index is less than 1.3, the function as a protective film becomes insufficient. The more preferable refractive index of the protective film is in the range of 1.3 to 1.47, and more preferably 1.3.
A range of .about.1.45 is particularly preferred.

There are no particular restrictions on the resin material used to form the protective film, but cellulose derivatives such as cellulose acetate, nitrocellulose, cellulose acetate butyrate, fluororesins, polyvinyl chloride, polyvinyl acetate, and the like. A protective film coating solution having a suitable viscosity obtained by dissolving a resin such as vinyl chloride-vinyl acetate copolymer, polycarbonate, polyvinyl butyral, polymethyl methacrylate, polyvinyl formal, or polyurethane in a solvent is applied to the phosphor layer, and dried, or It can be formed by laminating a transparent resin film such as polyethylene terephthalate, polyethylene, polyvinylidene chloride, or polyamide on the phosphor layer.

As the protective film having the above-mentioned refractive index, a fluororesin film is preferable in the present invention. From the viewpoint of the mechanical strength of the intensifying screen, in the present invention, it is particularly preferable that the resin film is formed by laminating the resin film on the phosphor layer.

In the present invention, the thickness of the protective film is 2 to 10 μm
Is preferably within the range. If the thickness is less than 2 μm, the original function of the protective film such as abrasion resistance is reduced. On the other hand, when the thickness is greater than 10 μm, the sharpness becomes insufficient. The preferred thickness of the protective film is in the range of 3 to 9 μm.

In the present invention, it is preferable that at least one of the phosphor layer, the protective film and the support contains a fluorescent dye and / or a fluorescent pigment. This fluorescent dye,
The fluorescent pigment is appropriately selected according to the emission peak of the phosphor in the phosphor layer. From the emission spectrum of the Gd ₂ O ₂ S: Tb phosphor used in the present application, the fluorescent dye or fluorescent pigment to be contained has a light absorption peak in a wavelength region shorter than 500 nm and a wavelength region of 450 nm to 600 nm. Those having an emission peak therein are preferred. This makes it possible to adjust the emission wavelength of the phosphor and improve the sensitivity when combined with a photosensitive material.

The radiation intensifying screen 4 of the above-described embodiment is used for radiation photography such as X-ray photography, for example, as the radiation receptor 5 shown in FIG. In the radiation receptor 5 shown in FIG. 2, a radiation film 6 such as an X-ray film is sandwiched between two radiation intensifying screens 4 and housed in a cassette 7 in this state. Of the two radiation intensifying screens 4 described above, the radiation intensifying screen 4 arranged on the subject side is the front intensifying screen F, and the other radiation intensifying screen 4
Is a so-called back intensifying screen B, and its basic configuration is the same.

Such a radiation receptor 5 is used in a radiation inspection apparatus 8 as shown in FIG. The radiation inspection apparatus 8 shown in FIG. 3 is used by being inserted from a radiation source 9 and a side surface of an imaging table 11 opposed to the radiation source 9 via a subject 10 such as a subject. At this time, radiation receptor 5
Is inserted so that the front intensifying screen F is located on the subject 10 side.

The radiation receptor 5 constituted by using the radiation intensifying screen 4 of this embodiment and the radiation inspection apparatus 8 using the radiation receptor 5 have good discrimination ability even when the X-ray exposure to the subject is reduced. Can be obtained. That is, when used for medical X-ray imaging, it is possible to obtain a good diagnostic ability while reducing the amount of X-ray exposure to the subject. When used for industrial nondestructive inspection, etc., it is possible to improve the inspection accuracy while reducing the X-ray dose.

[0023]

EXAMPLES Next, specific examples of the radiation intensifying screen of the present invention and evaluation results thereof will be described. Example 1 (Sample Nos. 1 to 4) Gd ₂ O ₂ S: Tb phosphor powder 100 having an average particle diameter of 6 μm
3 parts by mass of polyvinyl butyral resin as a binder and an appropriate amount of butyl acetate as an organic solvent are mixed in parts by mass,
A phosphor coating solution was prepared. This phosphor coating solution was uniformly applied by a knife coater on a support made of a polyethylene terephthalate film having a thickness of 250 μm into which carbon black was kneaded, and dried to form a phosphor layer. A protective film made of a fluororesin film (AFLEX manufactured by Asahi Glass Co., Ltd.) having a thickness shown in Table 1 was laminated on the above-mentioned phosphor layer to prepare a target radiation intensifying screen. This radiation intensifying screen was subjected to the characteristic evaluation described later. The refractive index of the protective film is a value measured by spectroscopic ellipsometry of NPDM-1000 manufactured by Nikon Corporation at the main emission wavelength of the phosphor in the phosphor layer.

Example 2 (Samples Nos. 1 to 4) The procedure of Example 1 was repeated except that 0.2 parts by mass of a fluorescent dye (Shinloych Co., Ltd. FM-15) was added to the protective film of the phosphor of Example 1. Thus, a radiation intensifying screen was produced.

Comparative Example 1 For comparison with the present invention, a radiation intensifying screen was prepared in the same manner except that a polyethylene terephthalate laminate film having a refractive index of 1.80 was used as a protective film. Comparative Example 2 A fluororesin (Lumiflon manufactured by Asahi Glass Co., Ltd.) was used as the protective film.
A radiographic intensifying screen was prepared in the same manner except that a fluororesin coating film formed by directly applying an LF100) -containing organic solvent solution to the phosphor layer and drying was used.

Each radiation intensifying screen (sample
No. 1-4), the radiographic intensifying screens of Example 2 (Sample No. 5-
8) and the radiographic intensifying screens of Comparative Examples 1 and 2 were measured and evaluated for sensitivity and sharpness using an ortho-type film (manufactured by Konica Corporation, ES-G). The results are also shown in Table 1. The photographic performance of the radiation intensifying screen is
X through a water phantom with a thickness of 100 mm and a tube voltage of 120 kvp
The photographic sensitivity and sharpness when photographed with a line are shown. The photographic sensitivity is a relative value when the radiation intensifying screen of Comparative Example 1 is set to 100. For the sharpness, the MTF value at a spatial frequency of 2 lines / mm was obtained, and the MT of the radiographic intensifying screen of Comparative Example 1 at the spatial frequency was determined.
This is a relative value when the F value is 100. In addition, mechanical strength is measured by using X-ray film ES on a cassette equipped with a radiographic intensifying screen.
-G was inserted, the lid was opened and closed (intensifying screen and X-ray film were pressed) 10,000 times, and the surface of the radiographic intensifying screen was visually observed to estimate the number of insertable sheets.
During this operation, the X-ray film was replaced with a new one every 100 times.

[0027]

[Table 1]

As is clear from Table 1, each of the radiographic intensifying screens of Examples 1 and 2 has improved sharpness and mechanical properties as compared with the radiographic intensifying screens of Comparative Examples 1 and 2.

[0029]

As described above, according to the radiation intensifying screen of the present invention, both the sharpness and the mechanical properties can be improved while maintaining the sensitivity. The radiation receptor and the radiation inspection apparatus of the present invention using such a radiographic intensifying screen are particularly effective when increasing the sensitivity of an imaging system, and obtain good discrimination ability even in such a case. be able to.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of an embodiment of a radiographic intensifying screen of the present invention.

FIG. 2 is a sectional view showing a schematic structure of an embodiment of the radiation receptor of the present invention.

FIG. 3 is a diagram schematically showing a configuration of an embodiment of the radiation inspection apparatus of the present invention.

[Explanation of symbols]

 1． Support 2. Phosphor layer 3. Protective film 4. Radiation intensifying screen 5. Radiation receptor 6. Radiation film 7. Cassette 8． Radiation inspection equipment 9. Radiation source 10. Subject 11. Shooting stand

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Akihisa Saito 8th Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture F-term in the Toshiba Yokohama office (reference) 2G083 AA02 BB01 CC01 CC10 DD01 DD06 DD11 DD17 EE02 EE03 EE07 EE10 2H013 AC01 BA02 2H016 AA03

Claims (9)

[Claims] 1. A radiographic intensifying screen comprising a support, a phosphor layer formed on the support, and a protective film provided on the phosphor layer, wherein the phosphor of the phosphor layer is The refractive index of the protective film obtained by measuring at the main emission wavelength of 1.3 ~
A radiographic intensifying screen having a range of 1.5. 2. The radiation intensifying screen according to claim 1, wherein
A radiation intensifying screen, wherein the refractive index of the protective film is in the range of 1.3 to 1.47. 3. The radiation intensifying screen according to claim 1, wherein
A radiation intensifying screen, wherein the protective film is a resin film laminated on the phosphor layer. 4. The radiation intensifying screen according to claim 1,
A radiation intensifying screen, wherein the protective film has a thickness in a range of 2 to 10 μm. 5. The radiation intensifying screen according to claim 1, wherein
A radiation intensifying screen, wherein the protective film is a fluororesin. 6. The radiation intensifying screen according to claim 1, wherein
A radiographic intensifying screen, wherein at least one of the phosphor layer, the protective film, and the support contains a fluorescent dye and / or a fluorescent pigment. 7. A radiation film, a front intensifying screen comprising the radiation intensifying screen according to claim 1 laminated along a surface of the radiation film on a subject side, and a radiation intensifying screen on the subject side of the radiation film. A back intensifying screen laminated along the surface opposite to the surface and comprising the radiation intensifying screen of claim 1;
A radiation receptor, comprising: a cassette accommodating a laminate of the front intensifying screen, the radiation film, and the back intensifying screen. 8. A radiation inspection apparatus comprising: a radiation source; and a radiation receptor according to claim 7, which is disposed to face the radiation source with a subject interposed therebetween. 9. A method for producing a radiographic intensifying screen, comprising: a step of applying a phosphor coating solution to a support and drying to form a phosphor layer; and a step of forming a protective film on the phosphor layer. In the step of forming the protective film, the refractive index of the protective film obtained by measuring the main emission wavelength of the phosphor of the phosphor layer is 1.
A method for producing a radiographic intensifying screen, which is a laminating step of a film-like protective film having a range of 3 to 1.5.