JPH01263600A - Manufacture of radiation image conversion panel - Google Patents

Abstract

PURPOSE:To enable a composition of a sharply focused radiation image conversion without any deformation of a panel at its usage, by holding a temperature of a depositing layer base at a specific value and by forming a stimulative phosphorescent layer with a gaseous deposition method. CONSTITUTION:A crystallized glass carrier of around 1.0mm thick is placed in a vacuum evaporator as a depositing layer base and then an alkalihalide stimulative phosphorescence is put in a water cooled melting pot and is pressed so as to form the shape of the melting pot. After that, the vacuum evaporator is evacuated and the stimulative phosphorescence is vaporized with an EB gun, being supplied with power, while keeping the temperature of the base within + or -20 deg.C range of its operating temperature. When a radiation R is emitted from a radiation generator 41 through an object 42 into a radiation image conversion panel 43 obtained in this way, the radiation R is absorbed to the stimulated phosphorescent layer of the panel 43 to compose an accumulated image of transmissive image. Therewith, making the image stimulated with a stimulated light source of the layer 44, the photo-signal can be displayed 47 as an image through a photoelectric converter 45 and an image regenerator 46.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Field of Application) The present invention relates to a method for manufacturing a radiation image conversion panel having a stimulable phosphor layer, and more specifically to a method for manufacturing a radiation image conversion panel having a stimulable phosphor layer. The present invention relates to a method for manufacturing a radiation image conversion panel that provides a radiation image and has a stimulable phosphor layer that is less deformed due to warping or the like and has small sensitivity unevenness.

(Prior Art) Radiographic images such as XVJ images are often used for disease diagnosis.

In order to obtain this X-ray image, an xtllij image conversion method has been devised in which an image is directly extracted from a phosphor layer instead of a silver halide photosensitive material.

In this method, radiation (generally X-rays) transmitted through the object is absorbed by a phosphor, and then this phosphor is excited with light or thermal energy, so that the phosphor accumulates due to the absorption of the radiation. This method involves emitting radiation energy as fluorescence, detecting this fluorescence, and creating an image.

Specifically, for example, U.S. Patent No. 3,859,527 and Japanese Unexamined Patent Publication No. 12144/1987 disclose a radiation image conversion method using a stimulable phosphor and using visible light or infrared rays as stimulable excitation light. It is shown.

This method uses a radiation image conversion panel (hereinafter referred to as conversion panel) that has a photostimulable phosphor layer (hereinafter referred to as photostimulable layer). to accumulate radiation energy corresponding to the radiation transmittance of each part of the subject to form a latent image, and then scan this photostimulation layer with photostimulation excitation light to emit the accumulated radiation energy of each part. This is converted into light, and an image is obtained using an optical signal based on the intensity of this light.

This final image may be reproduced as a hard copy or on a CRT.

The conversion panel used in this radiation image conversion method stores radiation image information and then releases the stored energy by scanning the stimulated excitation light, so it is possible to store radiation images again within the scanning diameter, and it can be used repeatedly. It is possible.

When manufacturing such a conversion panel, on the substrate to be deposited,
A method of forming a stimulable layer by a vapor deposition method such as a vapor deposition method, a sputtering method, or a CVD method is used.

(Problems to be Solved by the Invention) However, when the photostimulated layer is formed on the substrate to be deposited by the above-mentioned method, in any case, the temperature at which the photostimulated layer is formed on the substrate to be deposited is Since the temperature is considerably higher than the normal operating temperature of the conversion panel, the difference in thermal expansion coefficient between the stimulable layer and the substrate on which it is deposited causes deformation such as warping during use, causing sensitivity unevenness. This sensitivity unevenness occurs because the distance between the light collection system of the radiation image conversion device and the conversion panel is not constant due to deformation of one conversion panel. Furthermore, the sharpness of the photostimulable layer formed at high temperatures also deteriorates, causing problems such as blurring of radiographic images.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for manufacturing a conversion panel having a stimulable layer that provides a radiographic image with high sharpness, less deformation such as warping, and less unevenness in sensitivity.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a method for manufacturing a radiation image conversion panel having a stimulable phosphor layer so that the variation on the substrate to be deposited is within ±20°C. The method is characterized in that the stimulable phosphor layer is formed on the substrate by a vapor deposition method.

The substrate to be deposited in the method of the present invention is a substrate on which a photostimulated layer is formed by a vapor deposition method.

A commonly used radiation image conversion panel generally has a stimulable phosphor layer on a support.

According to the method of the present invention, when manufacturing a conversion panel, a stimulable layer can be formed on the support by a vapor deposition method using the support as a substrate to be deposited.

Furthermore, if necessary, a protective layer for physically or chemically protecting the photostimulable layer may be provided on the side of the photostimulable layer opposite to the side on which the support is provided).

This protective layer may be formed by directly applying a coating solution for the protective layer onto the photostimulable layer, or by applying a separately formed protective layer in advance on the side opposite to the side where the support for the photostimulable layer is provided. Alternatively, the support may be provided after forming the stimulable layer by vapor deposition on a separately formed protective layer. In this case, the deposition substrate is the protective layer.

As mentioned above, the substrate to be deposited may be a support or a protective layer.

The stimulable phosphor used in the method of the present invention is a stimulable phosphor that is
A phosphor that exhibits stimulated luminescence corresponding to the amount of initial light or high-energy radiation irradiation when stimulated by mechanical, chemical, or electrical stimulation (photostimulation excitation), but is not practical. From this point of view, it is preferably a phosphor that exhibits stimulated luminescence by stimulated excitation light of 500 nm or more. Examples of such stimulable phosphors include BaSO4:Ax described in JP-A No. 48-80487, and JP-A No. 48-80.
5rSO,:Ax described in JP-A No. 489, L 12 B407 of JP-A-53-39277:
Cu, Ag, etc., Li of JP-A No. 54-47883
2O・(B202) x; Cu and Li20* (B
202) x:cu.

SrS:Ce of Ag et al., U.S. Pat. No. 3,859,527.
, Sm, SrS: Eu, Sm, La2O2S: Eu, S
Examples include phosphors represented by m and (Zn, Cd)S:Mn.

Furthermore, the ZnS:Cu, Pb phosphor described in JP-A-55-12142, general formula B aOx/M1
203: Barium aluminate phosphor represented by Eu and alkaline earth metal silicate phosphor represented by the general formula MHO-xSi02:A. In addition, alkaline earth fluorohalide phosphors having the general formula % described in JP-A-55-12143, general formula % described in JP-A-55-12144, %: A phosphor represented by the general formula % formula described in JP-A No. 55-12145 %: A phosphor represented by the general formula % formula % described in JP-A-55-84389 A phosphor represented by a rare earth element-activated divalent metal fluorohalide phosphor represented by the general formula % formula % described in JP-A-55-160.078: A phosphor represented by a rare earth element activated divalent metal fluorohalide, a general formula ZnS: A, CdS: A, (Zn
, Cd) S:A, S:A, ZnS:A, X and CdS:
A phosphor represented by A, Examples include phosphors represented by any of the following general formulas, and alkali halide phosphors represented by the following general formulas described in JP-A-61-72087: . In particular, alkali halide phosphors are preferred because they can easily form a stimulable layer by methods such as vapor deposition and sputtering.

However, the stimulable phosphor used in the conversion panel manufactured according to the present invention is not limited to the phosphor mentioned above, and can emit stimulated luminescence when irradiated with radiation and then irradiated with stimulable excitation light. Any phosphor may be used as long as it shows the phosphor.

The conversion panel manufactured according to the present invention may be a stimulable layer group consisting of one or more stimulable layers containing at least one kind of the above-mentioned stimulable phosphors. Furthermore, the stimulable phosphors contained in each stimulable layer may be the same or different.

The thickness of the stimulable layer of the conversion panel varies depending on the radiation sensitivity of the intended conversion panel, the type of stimulable phosphor, etc., but is in the range of 10 to 1000 μm, more preferably 20 μm to 100 μm. It is preferable to select from the range of I11 to 800 μs.

Supports used in the method of the present invention include various polymeric materials, glasses, ceramics, metals, and the like.

Examples of the polymer material 4 include films such as cellulose acetate film, polyester film, polyethylene terephthalate, polyamide, polyimide, triacetate, and polycarbonate. Examples of the metal include metal sheets or metal plates of aluminum, iron, copper, chromium, etc., or metal sheets or metal plates having a coating layer of the metal oxide. Examples of the glass include chemically strengthened glass, crystallized glass, quartz, and borosilicate glass. Examples of ceramics include sintered plates of alumina and zirconia.

In addition, the layer thickness of these supports varies depending on the material of the support used, etc., but for boat fishing it is 80 to 5000.
In terms of handling, more preferably 200 to 200 units.
It is 0μ.

The surfaces of these supports may be smooth or matte for the purpose of improving adhesion to the stimulable phosphor layer. Further, the surface of the support may be an uneven surface,
The surface structure may include individually arranged micro-iron plates.

Furthermore, on these supports, a subbing layer may be provided on the surface on which the photostimulable layer is provided for the purpose of improving adhesion with the photostimulable layer, and if necessary, a light reflecting layer, a light absorbing layer, etc. etc. may be provided.

Materials for the protective layer used in the method of the present invention include common protective layer materials such as cellulose acetate, nitrocellulose, polymethyl methacrylate, polyvinyl butyral, polyvinyl formal, polycarbonate, polyester, polyethylene terephthalate, polyethylene, vinylidene chloride, and nylon. Examples include plate glasses such as quartz, borosilicate glass, and chemically strengthened glass. The thickness of these protective layers is generally preferably about 1 g to 5 mm.

In the method of the present invention, a vapor deposition method is used to form a photostimulated layer, and in this specification, the vapor deposition method refers to a method of adsorbing components in a vapor phase to form a layer. Examples of the method include a vapor deposition method, a sputtering method, and a CVD method.

At that time, it is necessary that the difference between the temperature of the t<r laminated substrate (support body or protective layer) and the temperature when the conversion panel is used is within ±20°C, preferably within ±10”C, More preferably, it is within ±5°C. If the temperature of the substrate to be deposited is outside this range, the manufactured conversion panel may warp at the operating temperature due to the difference in thermal expansion coefficient between the substrate to be deposited and the stimulable layer. This is not preferable because it causes deformation of the stimulable phosphor, and also deteriorates the properties of the stimulable phosphor, causing blur in the radiation image.The operating temperature is usually around 40°C.

In the vapor deposition method, first, a substrate to be deposited is placed in a vapor deposition apparatus, and then the apparatus is evacuated to a degree of vacuum of about 10" Torr. Then, at least one of the stimulable phosphors is heated by resistance heating, The stimulable phosphor is deposited on the surface of the substrate to a desired thickness by heating and evaporating it using a method such as an electron beam method.

In the vapor deposition process, it is possible to form the stimulable layer in multiple steps, and it is also possible to co-evaporate using a plurality of resistance heaters or electron beams.

In addition, in the vapor deposition method, the stimulable phosphor raw materials are deposited together using a plurality of resistance heaters or an electron beam, and the target stimulable phosphor is synthesized on the substrate to be deposited, and the stimulable phosphor is simultaneously stimulable. It is also possible to form layers.

Next, a case using the sputtering method will be described.

In this method, similarly to the vapor deposition method, the substrate to be deposited is placed in a sputtering device, and then the inside of the device is once evacuated and heated at 10-6T.
The degree of vacuum is approximately 10 Torr, and then an inert gas such as Ar or Ne is introduced into the sputtering apparatus as a sputtering gas to obtain a gas pressure of approximately 10' Torr.

Next, the stimulable phosphor is deposited on the surface of the substrate to a desired thickness by sputtering using the stimulable phosphor as a target.

In the sputtering process, it is possible to form the stimulable layer in multiple steps as in the vapor deposition method, and also, by using multiple targets each made of a different stimulable phosphor,
It is also possible to form the stimulable layer by sputtering the targets simultaneously or sequentially.

In the Suba-Yu method, a plurality of stimulable phosphor raw materials are used as targets, and these are sputtered simultaneously or sequentially to synthesize the desired stimulable phosphor on the substrate to be deposited, and at the same time, the stimulable phosphor is sputtered. It is also possible to form layers. In addition, in the sputtering method, if necessary,
2, reactive sputtering may be performed by introducing a gas such as H2.

Furthermore, a case where the CVD method is used will be described.

In this method, a stimulable phosphor or an organometallic compound containing a stimulable phosphor raw material is decomposed using energy such as heat or high-frequency power to obtain a stimulable layer on a substrate to be deposited.

In the vapor phase deposition method, the substrate to be deposited is appropriately cooled (or heated) in order to maintain the temperature of the substrate to be deposited within ±20° C. from the temperature during use.

As a method for cooling the substrate to be deposited, for example, there is a method of cooling the substrate to be deposited by flowing cooling water through a jig that holds the substrate to be deposited. At this time, it is preferable to increase the contact area between the substrate to be deposited and the jig that holds it, since cooling can be performed more effectively. In addition, a separate cooling plate is provided at a position that does not interfere with the adsorption of vapor phase components to the substrate to be deposited, and by cooling the cooling plate, heat is removed from the substrate to be deposited and/or from other heat generation sources to the substrate to be deposited. It may also be a method to prevent heat from reaching the The means for cooling is not limited to using cooling water, and other cooling devices or Peltier devices may also be used.

As a method of heating the substrate to be deposited, for example, a halogen lamp, a resistance heater, or the like may be used.

Furthermore, it is preferable to use the cooling method and the heating method in combination because it allows for more accurate temperature control.

The conversion panel manufactured according to the present invention is used in the radiation image conversion method shown schematically in FIG.

That is, the radiation VAR from the radiation generating device 41 enters the conversion panel 43 through the subject 42.

This incident radiation is absorbed by the stimulable layer of the panel 43,
The energy is accumulated, and the MfI of the radiographic image! [
An image is formed.

Next, this accumulated image is excited with stimulated excitation light from the stimulated excitation light source 44 to emit stimulated luminescence.

Since the strength of the emitted stimulated luminescence is proportional to the amount of accumulated radiation energy, this optical signal is photoelectrically converted by a photoelectric conversion device 45 such as a photomultiplier tube, and an image reproduction device 46
By reproducing the image as an image and displaying it on the image display device 47, a radiographic image of the subject can be observed.

(Example) Next, the present invention will be explained by examples.

Example 1 1.0 mm thick crystallized glass support (400Il1mX
500IIlffi) was placed in a deposition device, and used as a substrate to be deposited. Next, an alkali halide stimulable phosphor (RbBr: 0.0006Tl) was placed in a water-cooled crucible and pressed to form a crucible shape.

Subsequently, the evacuator was evacuated, and the 0-order deposition substrate was maintained at 40°C to 45°C with a vacuum level of 5 x 104 Torr, and power was supplied to the EB gun to evaporate the stimulable phosphor. I let it happen. As a method for maintaining the temperature of the deposition target substrate, a method of cooling the deposition target substrate holding jig with cooling water and a method of heating it using a halogen lamp were used in combination.

In order to obtain the desired stimulable phosphor layer, the focusing speed was detected using a film thickness monitor, and the vapor deposition speed was 10' A/ff.
It was controlled to be 1 inch.

Further, the electron beam scanned the surface of the exhaustible phosphor in the crucible in a raster pattern.

The vapor deposition was terminated when the luminescent phosphor layer had a layer thickness of 300 mm, and a radiation image conversion panel A was obtained by the manufacturing method of the present invention.

The radiation image conversion panel thus obtained was subjected to a tube voltage of 80
After irradiating KVp X-rays for 10 mR, semiconductor laser light (
780++m), the stimulated luminescence emitted from the stimulable phosphor layer is photoelectrically converted by a photodetector (photomultiplier tube), and this signal is reproduced as an image by an image reproducing device. Recorded on film north. The operating temperature of the radiation image conversion panel at this time was 40°C±1°C.

The distribution of relative sensitivity and the sharpness according to the modulation transfer function were investigated from the obtained images and are shown in Table 1.

In Table 1, the distribution of relative sensitivity is 2048×204
The value obtained by dividing the standard deviation of the relative sensitivities of 8 pixels by the average value of the relative sensitivities is expressed as a percentage. The modulation transfer function shown in Table 1 (
MTF) has spatial frequencies of 1 (ip/++v+) and 2
(i p/+++m) c7).

Further, the warpage of the obtained conversion panel at a usage temperature of 40° C. was investigated and is shown in Table 1. The warpage in Table 1 is expressed as the average value of the four times the conversion panel is raised when placed on a flat plate with the stimulable layer facing up.

Examples 2 and 3.4 Conversion panel B,
I got C and D. Conversion panel B.

C and D were evaluated in the same manner as in Example 1 and are also listed in Table 1.

Comparative Examples 1 and 2.3 Conversion panels x and y were prepared in the same manner as in Example 1, except that the temperature of the substrate to be deposited in the deposition device was the temperature shown in the table below.
, got z. However, in Comparative Example 2, no special temperature control was performed, and in Comparative Example 3, only heating means were used. The conversion panels X, Y, and Z were evaluated in the same manner as in Example 1, and the results are also listed in Table 1.

Table 1 As shown in Table 1, all of the conversion panels manufactured by the method of the present invention, in which the temperature difference between the substrate to be deposited and the temperature during use was kept within ±20°C, had little warpage. The sensitivity unevenness associated with this is also small. It also has high sharpness and is sufficiently durable for practical use.

On the other hand, if the temperature of the substrate to be deposited is significantly different from the temperature during use, the warpage will be large, and accordingly, the sensitivity unevenness will also be large. Furthermore, since the temperature of the substrate to be deposited is high, the characteristics of the stimulable phosphor deteriorate, and the sharpness of the stimulable phosphor is low.

Example 5 A conversion panel P was obtained in the same manner as in Example 1 except that the support was borosilicate glass.

Example 6 A conversion panel Q was obtained in the same manner as in Example 1 except that the support was made of polyethylene terephthalate with a thickness of 0.5 mm.

Conversion panels P and Q were evaluated in the same manner as in Example 1, and the same results as conversion panel A were obtained.

[Effects of the Invention] Since the radiation image conversion panel manufactured according to the present invention is manufactured at a temperature close to the temperature during use, the panel does not undergo deformation such as warping during use, and furthermore, Since the properties of the fluorescent phosphor are good, sharp radiographic images can be provided, making it highly useful.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a radiation image conversion method using a radiation image conversion panel. 41...Radiation generating device 42...Subject 43...Radiation image conversion panel 44...Stimulating excitation light source 45...Photoelectric conversion device 46...Radiation image reproducing device 47...Radiation image display Device 48...filter first

Claims (1)

[Claims] In a method for manufacturing a radiation image conversion panel having a stimulable phosphor layer, the temperature of the substrate to be deposited is maintained within ±20°C from the temperature during use of the radiation image conversion panel, and the stimulable phosphor layer is A method for manufacturing a radiation image conversion panel, comprising forming an exhaustible phosphor layer on the substrate by a vapor deposition method.