JPH0570800B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a radiation image conversion sheet, and more particularly to a sensitivity-compensated radiation image conversion sheet.

[Conventional technology]

Radiation image conversion sheet (hereinafter referred to as conversion sheet)
is used in radiography in various fields, such as medical radiography such as direct X-ray photography, indirect radiography, and fluoroscopy for the purpose of medical diagnosis, and industrial radiography for the purpose of non-destructive testing of materials. In order to improve sensitivity, it is used in close contact with X-ray photographic film (hereinafter referred to as "film"), or it is used to convert X-rays into visible light and photograph the film through an optical system. Basically, it consists of a support such as paper or plastic and a phosphor layer provided on one side of the support. The phosphor layer is comprised of a phosphor that emits high-intensity light upon radiation excitation, dispersed in a binder resin. The surface of this phosphor layer (ie, the surface opposite to the support) is generally protected by a transparent protective layer made of cellulose acetate, cellulose acetate butyrate, polymethyl methacrylate, polyethylene terephthalate, or the like. Further, some conversion sheets have a light reflecting layer or a light absorbing layer between the support and the phosphor layer. When performing radiography, the conversion sheet and film are brought into close contact with each other with the transparent protective layer interposed between them so that the phosphor layer and the film face each other. Generally, the conversion sheet is placed closely on both sides of the film.
In this state, it is held in a frame called a cassette and photographed.

As mentioned above, a method in which a radiographic film having an emulsion layer made of a silver salt photosensitive material and a conversion sheet are combined in order to obtain a radiographic image as an image is called a radiographic method. In contrast, in recent years, due to problems such as the depletion of silver resources, a method of imaging radiographic images without using silver salts has become desirable.

One of the radiation image conversion methods that does not use silver salts is the use of photostimulable phosphors (phosphors that emit light when excited with electromagnetic waves selected from visible light and infrared rays after being irradiated with radiation; here, what does radiation mean? X-ray, α
refers to electromagnetic waves or particle beams such as rays, beta rays, gamma rays, high-energy neutron beams, electron beams, vacuum ultraviolet rays, and ultraviolet rays. ) (U.S. Pat. No. 3,859,527). In this method, the radiation that has passed through the object is absorbed by the stimulable phosphor of the panel, and then the panel is scanned with electromagnetic waves selected from visible light and infrared rays (hereinafter referred to as "excitation light") to produce a luminescent light. The radiation image accumulated in the exhaustible phosphor is taken out in time series as stimulated luminescence, and this is electrically processed to create an image.

By the way, recently, when diagnosing chest diseases such as lung cancer using chest X-rays, it is necessary to observe not only the lung field but also the thoracic vertebrae and the trachea and bronchi that overlap the heart in order to make an accurate diagnosis. is increasing. However, conventional general conversion sheets have uniform sensitivity over the entire surface, and when exposed to X-rays under the same conditions, the amount of fluorescence emitted from the phosphor layer is almost uniform over the entire surface, and the sensitivity of the film is also uniform over the entire surface. Because of this, when simple or cross-sectional imaging of the chest is performed with this type of imaging system, a single X-ray image will show the difference between the lung field and the trachea and bronchi that overlap with the thoracic vertebrae and heart. It is difficult to perform simultaneous observations. In other words, since the transmittance of X-rays to each organ in the thoracic region differs greatly, in an X-ray photograph, the thoracic vertebrae,
The degree of darkening increases in the order of the heart and lung areas, and the density range in the photograph covers a fairly wide range. Therefore, if images are taken under X-ray exposure conditions that provide an appropriate degree of photographic darkening for observation of the lung field, the darkening of these organs will occur due to X-ray absorption in the thoracic vertebrae and heart. Due to the insufficient strength, the trachea and bronchi superimposed on these organs cannot be seen, making it impossible to observe them. On the other hand, if images are taken under X-ray exposure conditions that provide an appropriate degree of photographic darkening for observation of the trachea and bronchi, the degree of photographic darkening of the lung field will be excessive, making observation impossible.

For this reason, conventionally, in order to obtain photographs with an appropriate degree of darkening for the lung field and the trachea, trachea, and bronchi, multiple photographs were taken under optimal X-ray exposure conditions for the lung field and the bronchi. Chest diseases have been diagnosed by observing chest X-rays by taking X-rays or by using bronchography using a contrast agent in combination. However, taking multiple X-rays is not preferable because it increases the patient's radiation exposure, and bronchography contrast X-rays cause pain to the patient, so it is not preferable to take simple X-rays. The problem is that it requires several times more time and expense.

In order to solve such problems, conversion sheets with partially different sensitivities, that is, sensitivity compensation conversion sheets, may be used. Conventionally, sensitivity compensation conversion sheets include those that compensate for sensitivity by partially changing the thickness of the phosphor layer, and those that compensate for sensitivity by partially changing the thickness of the phosphor layer, and those that compensate for sensitivity by partially changing the thickness of the phosphor layer. Types that compensate for sensitivity by providing a reflective layer to improve the sensitivity of that part, types that compensate for sensitivity by using phosphors with different luminance, or between the support and the phosphor layer. A type of device has been proposed in which a light absorbing layer made of a colorant having a body color such as black, blue, or red is provided partially on the surface of the photosensitive material, and the sensitivity is compensated for by lowering the sensitivity of that portion.

[Problem that the invention seeks to solve]

However, due to manufacturing technology issues with these types of sensitivity compensation conversion sheets, the boundary line between the high-sensitivity area and the low-sensitivity area tends to become clear, and in X-ray photographs taken using these sheets, there is a sharp increase in photographic sensitivity. A changing border line appears, which tends to have a negative impact on diagnosis. Further, it is not easy to manufacture these types of sensitivity compensation conversion sheets that meet desired specifications, and furthermore, it is not easy to manufacture a large number of homogeneous sheets in mass production.

Therefore, in order to solve these problems, Jikoaki
No. 55-10425 proposes a method in which a mount is used as a support and the sensitivity is changed by printing on the mount. However, even if the commonly used gradation (gradation blur density) method of printing is applied to the mount, the boundary between the area where printing is not performed and the area where printing has started is clearly visible on the mount. This was clinically inconvenient. For this reason, Japanese Patent Application Laid-open No. 161900/1983 proposes a method for eliminating the inconvenience caused by boundaries between areas having different sensitivities. However, this method can only compensate up to a sensitivity ratio of twice as high as the maximum, requires printing more than once, and has various problems with ink coloration, printing position, etc.

Therefore, in view of the above-mentioned prior art, the present invention has been made to
The purpose of this invention is to provide a sensitivity compensation conversion sheet that can easily obtain desired sensitivity compensation, and also to mass-produce a uniform sensitivity compensation conversion sheet.

[Means for solving problems]

That is, the first aspect of the present invention is to print a compensation pattern on a protective layer, and then apply thereon a coating liquid containing a phosphor and a solvent that dissolves the ink for printing the compensation pattern. Therefore, the light transmittance of a phosphor layer is obtained by dissolving the ink and forming a phosphor layer, and then forming a support layer on the phosphor layer. The present invention relates to a sensitivity compensation radiation image conversion sheet in which the compensation pattern is partially changed and the halftone dots of the compensation pattern printing and the boundary line between the printed portion and the unprinted portion are blurred.

Furthermore, a second aspect of the present invention is to print a compensation pattern on the support layer, and then apply thereon a coating liquid containing a phosphor and a solvent that dissolves the ink for printing the compensation pattern. Therefore, the light transmittance of the phosphor layer is obtained by dissolving the ink and forming a phosphor layer, and then forming a protective layer on the phosphor layer. The present invention relates to a sensitivity-compensated radiation image conversion sheet in which the halftone dots of compensation pattern printing and the boundary line between the printed portion and the unprinted portion are partially changed and blurred.

A third aspect of the present invention is to print a compensation pattern on the phosphor layer on the support layer, and then apply a coating thereon containing a solvent for dissolving the ink for printing the compensation pattern and a resin for the protective layer. Halftone dots for partially changing the light transmittance of the protective layer and printing a compensation pattern, characterized in that the ink is dissolved by applying a liquid and the protective layer is formed. The present invention also relates to a sensitivity-compensated radiation image conversion sheet in which the boundary line between a printed portion and an unprinted portion is blurred.

The present invention will be explained in detail below.

Any suitable material can be used as the "support" used in the present invention. For example, cellulose acetate as paper, polymer-coated paper such as polyethylene-coated paper, metal foil such as aluminum foil or foil-paper laminates, or various plastic films.
Cellulose propionate, cellulose acetate butyrate,
Examples include films and glass plates made of polystyrene, polymethyl methacrylate, vinyl chloride/acetate copolymer, polyethylene terephthalate, and the like.

The thickness of the support is approximately 300 to 400μ in the case of paper.
In the case of plastic films, the thickness is generally about 100 to 300μ, and the material and film thickness can be selected as appropriate depending on the application.

As the "phosphor" of the phosphor layer, phosphors used in general conversion sheets can be used as they are. For example, CaWO ₄ , BaSO ₄ :Pb, (Cd,Zn)S:Ag,
Examples include Gd ₂ O ₂ S:Tb and La ₂ O ₂ S:Tb. Examples of photostimulable phosphors used as one of the radiation image conversion methods that do not use silver salts include SrS:
Ce, Sm; SrS: Eu, Sm; (Ba, Mg, Ca)
Fcl: Examples include Eu. Also, these phosphors are preferably used as fine particles of about 1 to 30 microns.

The coating liquid for forming the phosphor layer is composed of the phosphor described above, a solvent, and a resin. Examples of the resin used here include cellulose nitrate, cellulose acetate, ethyl cellulose, polyvinyl butyral, vinyl chloride and vinyl acetate copolymer, polycarbonate, polymethyl methacrylate, and polyurethane polymer.

Further, in the first and second aspects of the present invention, the solvent dissolves the compensation pattern printing ink described later, and preferably has the following performance.

(a) It has appropriate dissolving power or diluting power for the resin that is a component of the ink, and has a desired evaporation rate.

(b) For the coloring agents (dyes, pigments) used in ink, crystal transition (change in hue, decrease in coloring power), aggregation (solvent shock, color separation,
Does not cause any negative effects such as sedimentation or decrease in coloring power.

Examples of such solvents include aliphatic hydrocarbons (mineral spirits, petroleum naphtha, etc.), aromatic hydrocarbons (toluene, xylene, etc.), alcohols (ethyl alcohol, isopropyl alcohol, butyl alcohol, etc.), and ketones. (acetone,
diisobutyl ketone, diethyl ketone, methyl ethyl ketone, etc.), esters (acetate, butyrate, etc.), ethers (isopropyl ether, ethyl ether, diethyl cellosolve, etc.)
etc. can be mentioned. As there is a general rule of thumb that "similar things dissolve well," it is preferable to select a solvent that has a solubility parameter value close to that of the respective resin.

The thickness of the phosphor layer formed using the above coating liquid for forming a phosphor layer is usually about 100 to 300 microns. The weight ratio of the phosphor to the resin (solid content) is preferably in the range of 2 to 20 parts by weight of the resin to 100 parts by weight of the phosphor.

Next, the "protective layer" may be formed using various commercially available plastic films as they are, or may be formed using various resin liquids.

Generally, 4 types of plastic films are used.
For example, transparent films of polycarbonate, polymethyl methacrylate, polyethylene terephthalate, etc. having a film thickness of ~12 μm can be used.

On the other hand, the resin liquid is a resin dissolved in a solvent. Examples of the resin used here include cellulose acetate butyrate, cellulose acetate, polyvinyl butyral, vinyl chloride and vinyl acetate copolymer, polymethyl methacrylate, and polyurethane. Further, the solvent is not particularly limited as long as it dissolves the above resin. However, the third aspect of the present invention
In this embodiment, the solvent dissolves the compensation pattern printing ink described later. Examples of such solvents include those used in coating solutions for forming phosphor layers.

The protective layer formed using the above resin liquid is about 3~
It is preferable to set it to 30μ.

Next, the "compensation pattern printing ink" used in the present invention can be used as long as it is soluble in the solvent constituting the coating liquid for forming the phosphor layer or the solvent constituting the resin liquid for forming the protective layer. can be used as is. Examples of resins used in such printing inks, which are particularly preferably evaporative drying inks, include natural resins such as rosin, shellac, copal, dammar, and gilsonite, and derivatives thereof such as hardened rosin, maleic acid resin, and fumaric acid resin. Acid resins, etc., and synthetic resins such as phenolic resins, xylene resins, ketone resins, petroleum resins, terpene resins, chlorinated rubber, alkyd resins, polyamide resins, acrylic resins, vinyl chloride resins, vinyl chloride/vinyl acetate copolymer resins, Examples of polyvinyl butyral, styrene resin, and cellulose derivatives include nitrocellulose, acetylcellulose, and cellulose acetate butyrate. In particular, in consideration of diffusion into the phosphor layer or the protective layer, it is preferable to use an ink using a resin of the same series as the resin constituting these layers.

As the colorant for the printing ink, any colorant that can be dissolved or dispersed in the ink vehicle, such as oil-soluble dyes, disperse dyes, organic pigments, and inorganic pigments, can be used. However, in order to obtain a large sensitivity ratio, for example, when CaWO ₄ is used as a phosphor, a yellow coloring agent with absorption near 420 μm is preferable.
When using Gd ₂ O ₂ S:Tb as a phosphor, it is preferable to use a red coloring agent that has absorption in the vicinity of 550 μm.

The "compensation pattern" in the present invention is not particularly limited, and any conventionally known pattern can be appropriately selected depending on the intended use.

Next, a method for manufacturing the radiation image conversion sheet of the present invention will be explained.

(1) First aspect of the present invention A compensation pattern is printed on a film for a protective layer using ink of an appropriate color, and then the ink is dried. Next, a predetermined amount of a coating liquid for forming a phosphor layer is applied thereon using a roll coater, knife coater, etc., and dried. At this time, the ink printed on the film for the protective layer is dissolved in the coating liquid for forming the phosphor layer and diffused into the coating liquid,
Finally, a layer is formed. As a result, a partially colored phosphor layer is formed with the periphery of the printed pattern blurred. Then, a support such as paper or plastic is laminated onto the thus dried and partially colored phosphor layer to obtain the radiation image conversion sheet of the present invention.

(2) Second aspect of the invention The compensation pattern is printed on a support such as paper or plastic, and then the ink is dried. Next, a coating liquid for forming a phosphor layer is applied thereon in the same manner as in (1) above, and dried. As a result, a partially colored phosphor layer is formed with a blurred edge around the printed pattern. Next, the radiation image conversion sheet of the present invention can be obtained by further providing a film for a protective layer on the phosphor layer.

(3) Third aspect of the present invention A coating solution for forming a phosphor layer is applied onto a support such as paper or plastic in the same manner as in (1) above, and dried.
Next, a compensation pattern is printed on this phosphor layer,
The ink is then allowed to dry. Furthermore, a resin solution for a protective layer is applied onto the pattern-printed phosphor layer using a coating solution such as a roll coater or a knife coater, and then dried. At this time, the ink printed on the phosphor layer is dissolved by a solvent that dissolves the compensation pattern printing ink contained in the resin liquid, and is diffused into the resin liquid to finally form a layer. . As a result, a partially colored protective layer is formed with the periphery of the printed pattern blurred, and the radiation image conversion sheet of the present invention can be obtained.

〔Example〕

The present invention will be further explained below with reference to Examples.

Example 1 On a protective film made of polyethylene terephthalate with a thickness of 9μ attached to a smooth support plate,
Length 30cm, width 8cm, inner 3cm with halftone dot size 60 lines,
I used a 300-mesh silk screen plate with a gradation of 100% to 0% to print the ink below. Next, the phosphor coating solution below was applied thereon using a knife coater, dried, and then peeled off from the support plate to form a phosphor sheet with a phosphor coating weight of 50 mg/cm ² . Further, this sheet was hot-press bonded onto a PET base having a thickness of 240 μm to obtain a sensitivity-compensated radiation image conversion sheet of the present invention, and an X-ray film density curve was determined (FIG. 1). The gradation part is a smooth curve, indicating that the halftone dots are blurred and flattened.

[Ink formulation]

Nitrified cotton 40g DOP 20g Cyclohexanone 200g Benzidine yellow 0.6g [Phosphor coating liquid formulation] CaWO ₄ 100g Nitrified cotton 7g DOP 3g Butyl acetate 90g Comparative example 1 An ink with the formulation below that does not dissolve in the phosphor coating liquid was used. A conversion sheet was obtained in the same manner as in Example 1, and an X-ray film density curve was determined (FIG. 2).
The gradation part has a zigzag shape, indicating that halftone dots also appear on the photograph.

[Ink formulation]

Acetate cotton 12g DOP 1g Acetone 87g Yellow pigment benzidine yellow 0.3g Example 2 On a PET 240 μ thick base, apply the phosphor coating solution below using a knife coater, dry it, and apply Example 1 on top of it. A silk screen plate similar to that used in was used to print the ink formulation below.

Next, a protective layer resin solution having the composition below was applied thereon using a knife coater and dried to obtain a conversion sheet of the present invention. The X-ray film density curve obtained for this sheet had a smooth gradation portion, similar to that shown in FIG.

[Ink formulation]

Acetate cotton 12g DOP 1g Acetone 87g Benzidine Yellow 0.3g [Fluorescent coating liquid combination] CaWO ₄ 300g Urethane resin Nitsuporan 5120 20g Coronate HL 2g Nippon Polyurethane Co., Ltd. MEK 70g [Protective film resin liquid] Acetate cotton 6g DOP 0.5g Acetone 94g Comparative Example 2 A conversion sheet was obtained in the same manner as in Example 2, except that the ink having the formulation below was used. The X-ray film density curve obtained for this sheet had a zigzag gradation portion similar to that shown in FIG.

[Ink formulation]

Urethane resin Nitsuporan 5120 50g Coronate HL 5g MEK 50g Benzidine Yellow 0.3g Example 3 The following compounded ink was printed in the same manner as in Example 1 on a PET 240μ thick base. A phosphor layer was then formed according to Example 1 using the phosphor coating solution below. Further, a resin liquid for a protective layer having the formulation below was applied thereon using a knife coater and dried to obtain a conversion sheet of the present invention. The X-ray film density curve obtained for this sheet had a smooth gradation portion, similar to that shown in FIG.

[Ink formulation]

Nitrified cotton 40g DOP 20g Butyl acetate 200g Benzidine Yellow 0.1g [Fluorescent coating liquid combination] CaWO ₄ 100g Nitrified cotton 7g DOP 3g Butyl acetate 90g [Protective layer resin liquid] Acetate cotton 12g DOP 1g Acetone 87g Comparative example 3 Lower A conversion sheet was obtained in the same manner as in Example 3, except that an ink having the following composition was used. The X-ray film density curve obtained for this sheet had a zigzag gradation portion similar to that shown in FIG.

[Ink formulation]

Urethane resin Nitsuporan 5120 50g Coronate HL 5g MEK 50g Benzidine Yellow 10g [Effects of the invention] The sensitivity compensation radiation image conversion sheet of the present invention has smooth changes in light transmittance in the gradation portion, and has a relatively wide sensitivity ratio. It is extremely effective for practical purposes.

[Brief explanation of drawings]

FIG. 1 shows the X-ray film density curve obtained for the radiation image conversion sheet of the present invention, and FIG. 2 shows the X-ray film density curve obtained for the radiation image conversion sheet other than the present invention.
This is a line film density curve.

Claims (1)

[Scope of Claims] 1. Printing a compensation pattern on a protective layer, and then applying thereon a coating solution containing a phosphor and a solvent that dissolves the ink for printing the compensation pattern. Partially reducing the light transmittance of the phosphor layer, characterized in that it is obtained by dissolving the phosphor layer and forming a phosphor layer, and then forming a support layer on the phosphor layer. A sensitivity-compensated radiation image conversion sheet in which the halftone dots of compensation pattern printing and the boundary line between a printed part and an unprinted part are blurred. 2. A compensation pattern is printed on the support layer, and then a coating solution containing a phosphor and a solvent that dissolves the ink for printing the compensation pattern is applied thereon to dissolve the ink and fluoresce it. A compensation pattern that partially changes the light transmittance of a phosphor layer and is obtained by forming a phosphor layer and then forming a protective layer on the phosphor layer. A sensitivity-compensated radiation image conversion sheet that blurs printed halftone dots and the border line between printed and unprinted areas. 3. A compensation pattern is printed on the phosphor layer on the support layer, and then a coating liquid containing a solvent for dissolving the ink for printing the compensation pattern and a resin for the protective layer is applied thereon to remove the ink. The light transmittance of the protective layer is partially changed, and the halftone dots of the compensation pattern printing and the boundary line between the printed part and the unprinted part are obtained by dissolving the protective layer and forming the protective layer. Sensitivity compensation radiation image conversion sheet for blurring.