JPH0718959B2 - Radiation image conversion panel manufacturing method - Google Patents

Description

The present invention relates to a method for producing a radiation image conversion panel using a stimulable phosphor.

[Background of the Invention]

Radiographic images such as X-ray images are often used for diagnosing diseases, etc., but in recent years, a method of directly extracting an image from a phosphor has been devised instead of radiography using a silver halide photosensitive material and a fluorescent screen. There is.

In this method, for example, the radiation that has passed through the subject is absorbed by the phosphor, and then the phosphor is excited by, for example, light or thermal energy, so that the radiation energy accumulated by the absorption by the phosphor is converted into fluorescence. This is a method of irradiating and detecting the fluorescence to form an image. Specifically, U.S. Pat. No. 3,859,527 and JP-A-55-12144 disclose a radiation image conversion method using a stimulable phosphor and using visible light or infrared light as stimulated excitation light. This method uses a radiation image conversion panel (hereinafter also referred to as "panel") in which a stimulable phosphor layer (hereinafter sometimes referred to as "fluorescence layer") is formed on a support. The radiation that has passed through the subject is applied to the fluorescent layer of this panel to accumulate the radiation energy corresponding to the radiation transmittance of each part of the subject to form a latent image, and then this fluorescent layer is stimulated with excitation light. By scanning, the accumulated radiation energy of each part is emitted and converted into light,
An image is obtained by a signal based on the intensity of this light.
This final image may be played back as a hard copy or on a CRT.

The panel having the fluorescent layer used in this radiation image conversion method has high radiation absorption rate and light conversion rate (both of which are referred to as "radiation sensitivity"), not to mention high image granularity, and High sharpness is required.

However, a panel having a fluorescent layer generally has a particle size of 1 to 30 μm.
The filling density of the stimulable phosphor is low (filling ratio 50%, since it is prepared by coating a support with a dispersion liquid containing about m of granular stimulable phosphor and an organic binder, and drying. ). Therefore, it is necessary to increase the thickness of the fluorescent layer in order to sufficiently increase the radiation sensitivity.

On the other hand, the sharpness of the image in the radiation image conversion method tends to be higher as the layer thickness of the fluorescent layer of the panel is thinner, and it is necessary to thin the fluorescent layer in order to improve the sharpness.

Further, since the graininess of the image in the radiation image conversion method is determined by the spatial fluctuation of the radiation quantum number (quantum mottle) or the structural disorder of the fluorescent layer of the panel (structural mottle), the layer thickness of the fluorescent layer is reduced. As the thickness becomes smaller, the number of radiation quantum absorbed by the fluorescent layer decreases and the quantum mottle increases, or structural disorder becomes apparent and the structural mottle increases, resulting in deterioration of image quality. Therefore, in order to improve the graininess of the image, the fluorescent layer needs to be thick.

That is, as described above, since the conventional panel exhibits fluorescence that is the opposite of the sensitivity to radiation and the graininess of the image and the sharpness of the image with respect to the layer thickness of the fluorescent layer, the panel is not sensitive to radiation. It has been created with a degree of mutual sacrifice between graininess and sharpness.

By the way, it is well known that the sharpness of an image in the conventional radiographic method is determined by the spread of the instantaneous light emission (light emission at the time of radiation irradiation) of the phosphor in the fluorescent screen. The sharpness of the image in the radiation image conversion method using a fluorescent substance is not determined by the spread of stimulated emission of the stimulable phosphor in the panel, but the spread of stimulated excitation light in the panel. Depends on.

Therefore, stimulated emission due to the stimulated excitation light irradiated at a certain time (ti) is emitted from the panel-shaped pixel (xi, yi) that was actually irradiated with the stimulated excitation light at that time (ti). If it is only, the sharpness of the obtained image will not be affected regardless of the extent of the emission.

From this point of view, some methods have been devised to improve the sharpness of radiographic images. For example, JP-A-55-146447
No. 55-163500, the average reflectance in the stimulable excitation wavelength region of the stimulable phosphor is the above stimulable fluorescence. For example, a method of coloring the body so as to make it smaller than the average reflectance in the stimulated emission wavelength region. However, these methods are not preferable methods because the sensitivity inevitably decreases remarkably when the sharpness is improved.

In view of the above-mentioned drawbacks and reciprocity between properties, JP-A-61-73100 proposes a panel in which a binder is removed from a fluorescent layer by a vapor deposition method such as vacuum deposition and a manufacturing method thereof. Has been done. According to this, since the fluorescent layer of the panel does not contain a binder, the filling rate of the fluorescent layer is significantly improved and the directivity of stimulated excitation light and stimulated emission in the fluorescent layer is improved, and the panel The sensitivity to radiation and the graininess of the image are improved, while the sharpness of the image is also improved.

Panels that do not contain the above binder are sputtered, CVD
It can be manufactured by various vapor deposition methods such as
It can be said that the vapor deposition method is the most preferable method in consideration of manufacturing cost and the like.

[Problems to be Solved by the Invention]

The photostimulable phosphor layer produced by such a vapor deposition method may be subjected to a heat treatment (annealing) as a post-treatment for the purpose of improving various characteristics such as sensitivity and sharpness. However, in the post-treatment, when the heat treatment (annealing) is performed by using the apparatus as shown in FIG. 6 which is generally performed, the radiation image conversion panel may be less sensitive to radiation. It turned out that there were some drawbacks.

Then, it is difficult to understand the cause of the decrease in the radiation sensitivity of the radiation image conversion panel.

However, as a result of earnestly investigating the cause, the following experimental facts were found. That is, when heat treatment (annealing) using a device as shown in FIG. 6 that is generally performed is performed, a plurality of stimulable phosphors in the fluorescent layer for a certain heat treatment (annealing) temperature are formed. Since substances have different vapor pressures, substances having higher vapor pressure preferentially evaporate. Therefore, the composition of the stimulable phosphor in the fluorescent layer after heat treatment (annealing) formed on the support does not match the composition in the fluorescent layer before heat treatment (annealing), and the concentration of the activator ( It has been found that the sensitivity of the radiation image conversion panel to radiation may decrease because the content rate varies from a predetermined concentration (content rate).

Incidentally, such development is a problem peculiar to a radiation image conversion panel having a stimulable phosphor layer.

For example, according to the research of the present inventors regarding the RbBr: Tl stimulable phosphor using Tl as an activator, the emission intensity of the phosphor is 5th.
Moment in the range Tl content of 10 ^-2 ~10 ⁰ mol% luminous intensity as shown in FIG. Note deep respect to its composition ratio as long as a general phosphor Tl content is constant is smoked constant width No need. However, the stimulated emission intensity of the radiation image conversion panel has a peak near 3 × 10 ^-2 mol% and greatly decreases before and after that.

Therefore, it has been found that control of the activator concentration in the heat treatment is particularly important in obtaining a radiation image conversion panel with high sensitivity in the production of a radiation image conversion panel utilizing stimulated emission.

Further, in that case, the activator component of the stimulable phosphor is placed directly in contact with the stimulable phosphor layer, and heat-treated to obtain the activator component of the stimulable phosphor layer. The activator concentration becomes high in the part which is in direct contact with it and in the vicinity thereof, and the activator concentration becomes low in the part which is not so that unevenness in the sensitivity distribution of the stimulable phosphor layer does not occur. , The activator component of the stimulable phosphor is arranged at a position apart from the stimulable phosphor layer.

[Object of the Invention]

An object of the present invention is to prevent a decrease in sensitivity of the radiation image conversion panel due to a change in the concentration (content rate) of the activator of the activatable stimulable phosphor during heat treatment. Another object is to increase the sensitivity of the radiation image conversion panel while preventing the occurrence of uneven sensitivity distribution of the stimulable phosphor layer.

[Structure and Action of Invention]

An object of the present invention is to form a stimulable phosphor layer containing an activating stimulable phosphor, heat it after forming it, and have radiation having a stimulable phosphor layer containing an activating stimulable phosphor. In the method for producing an image conversion panel, when heat-treating a stimulable phosphor layer containing an activating stimulable phosphor, the stimulable phosphor layer was separated from the stimulable phosphor layer in the same system. This is achieved by vaporizing the activator component of the activatable stimulable phosphor placed at the position.

Next, the present invention will be specifically described.

When the heat treatment (thermal sensitization treatment) is applied to the fluorescent layer made of a stimulable phosphor, a characteristic shape appears in the thermal sensitization curve.

FIG. 1 shows the thermal sensitization curve at each temperature of heat treatment. Curves a, b and c are RbBr: Tl at 200, 400 and 600 ℃.
2 is a thermal sensitization curve of the fluorescent layer consisting of

The thermal sensitization curve sharply raises the sensitization rate and sensitivity level with temperature, but there is a saturation point, and beyond that point, the sensitivity is monotonically desensitized.

This tendency is that the desensitization following the saturation point is small when the vapor pressure of the activator contained in the phosphor matrix is smaller than that in the stimulable phosphor matrix in the stimulable phosphor, although the desensitization is small. This is remarkable when the vapor pressures of the stimulable phosphor matrix and the activator are almost equal to each other or the vapor pressures of the activator are high.

That is, the sensitivity factor of the phosphor crystal is arranged by the thermal sensitization treatment to favorably increase the sensitivity, but at the same time, the activator escapes from the phosphor matrix, and at the saturation point the two antagonize each other.
After that, the desensitization effect due to the escape of the activator is predominant, and the desensitization will be exposed.

From this viewpoint, the thermal sensitization treatment temperature is set to 200, 400 and 600 ° C., and the atmosphere surrounding the phosphor is adjusted to adjust RbBr: T in the phosphor layer.
When the heat sensitization treatment was carried out while the composition of the stimulable phosphor was not changed, the desensitization phenomenon did not appear although it was toward the sensitization saturation as shown by the curves a ', b'and c'.

The present invention is based on the above findings.

Therefore, an aspect of the present invention is to amortize the escape loss of the activator during and / or after the heat sensitization treatment, and the atmosphere of the fluorescent layer in the heat sensitization treatment is based on the vapor pressure of the activator. Or a separately prepared film containing an activator may be brought into close contact with the fluorescent layer to diffuse the activator into the fluorescent layer by a diffusion method or an ion implantation method.

FIG. 2 (a) shows a schematic diagram of the diffusion type thermal sensitizer.

As shown in the figure, a radiation image conversion panel 21 having a stimulable phosphor layer containing an activating stimulable phosphor containing an activator.
Is installed in a heat treatment container 22 which is a container for heat treating the radiation image conversion panel 21. The substance powder 27 containing the activator component is placed in an evaporation container 26 which is a container for evaporating the substance powder 27. The substance powder 27 containing this activator component is, for example, RbBr: Tl phosphor, RbBr: TlBr, when the activatable stimulable phosphor of the radiation image conversion panel 21 is a phosphor composed of RbBr: Tl. It is a mixed powder or a TlBr mixed powder.

The heating heater 23, which is a heating means, is a radiation image conversion panel.
It is a means for heating 21. The heating heater 25, which is a heating means, is a means for heating the substance powder 27. The heat treatment container 22 and the evaporation container 26 are connected to each other via a gas amount adjusting valve 28.

First, the panel 21 to be sensitized is placed in the heat treatment container 22, and the substance powder 27 containing the activator is placed in the evaporation container 26.
Then, after heating each container to a predetermined temperature by the heating means 23, 25, the gas amount adjusting valve 28 is gradually opened to diffuse the activator gas into the heat treatment container 22. Here, the diffusion amount of the activator is determined by the heating temperature of the evaporator 26, the opening / closing amount of the temperature difference gas amount adjusting valve 28 between the heat treatment container 22 and the evaporation container 26, and the like.

Although the heat treatment (annealing) temperature T of the panel 21 varies depending on the type of the stimulable phosphor, it is preferably lower than the melting point Tm of the stimulable phosphor matrix, and more preferably 1 / 4Tm <T <Tm. preferable.

After the panel 21 is heat-treated, it is cooled to room temperature at a predetermined rate to complete the panel according to the present invention.

According to this apparatus, thermal sensitization of the phosphor crystal, compensation of the activator, and annealing for crystal disorder during vapor deposition are simultaneously performed.

FIG. 2B is a schematic view showing another example of the diffusion method thermal sensitizer. As shown in the figure, the radiation image conversion panel 21 having a stimulable phosphor layer containing an activating stimulable phosphor containing an activator is an atmosphere powder 29 which is a substance powder containing an activator component. Together with this, the radiation image conversion panel 21 is installed in a heat treatment container 30 which is a container for heat treatment. On this occasion,
Substantially sensitivity unevenness occurs, so as to be in direct contact with the stimulable phosphor layer of the radiation image conversion panel 21, by installing the atmosphere powder 29, which is a substance powder containing an activator component,
It is outside the scope of the present invention.

This apparatus is characterized in that the panel 21 to be sensitized and the substance powder (atmosphere powder 29) containing the activator coexist in the heat treatment container 30.

By using such atmosphere powder, the activator concentration in the panel can be easily adjusted and amortized.

The activator concentration of the atmosphere powder varies depending on the annealing conditions, but it is preferable that it is substantially equal to or higher than the activator concentration of the stimulable phosphor of the panel 21.

Further, the heat treatment temperature T of the panel 21 is preferably lower than the melting point Tm of the stimulable phosphor matrix as described above, and 1 / 4Tm <T <T
More preferably, it is in the range of m.

Next, FIG. 3 shows a structural example of an apparatus used in the ion implantation method. In the figure, a) In the ion source section 31, required activator ions are generated from the solid or gas such as chloride or hydride. b) The generated ions are extracted by the extraction electrode 32, and energy is selected and accelerated in the accelerating section according to the settings of the average projection range and the activator distribution. c) The mass spectrometric section 33 takes out ions having the required energy and mass, and d) the deflecting section 34 uniformly sweeps the ion beam in the χ-y direction, and e) the heating means attached to the sample chamber 35. The panel 36 that has been heat-treated (annealed) at 37 is uniformly irradiated. At this time, in order to avoid ion tunnel entry called channeling, it is important to incline the panel surface by about 7 to 8 ° with respect to the beam direction. The vacuum degree of the implanter is generally evacuated to about 1 × 10 ^-5 Torr in the ion source section and 10 ^-7 Torr in the sample section.

In the present invention, the fluorescent layer to be subjected to the thermal sensitization treatment including the activator compensation means is a fluorescent layer formed by a generally known vapor phase deposition method.

That is, the phosphor layer may be made of densely deposited phosphor non-crystal (amorphous), or may be in a form in which fine columnar crystals are vertically bundled in the layer thickness direction to form a layer in the shape of a scallop. . Alternatively, large and small crevasses running in the vertical and horizontal directions may be arranged on the surface of the layer formed by bundling the shell-shaped column. Further, the fluorescent matrix layer may have a shape in which voids are surrounded around each of the fine columnar crystals and are gathered in a frost column shape.

The crevasses or voids may disappear upward or downward in the layer thickness direction so that the fine columnar crystals are fused.

Further, a mixed fluorescent layer of each of the above-mentioned forms may be used.

Of the stimulable phosphors, the thermal stimulable phosphors are slow in response to excitation, and are practically useful as photostimulable phosphors because they are difficult to read in a time series.
Those that emit stimulated emission with stimulated excitation light of m or more are preferable.

As the photostimulable phosphor used in the panel of the present invention,
For example, the general formula described in JP-A-55-12143 is (Ba1 _- x _- yMgxCay) FX: eEu2 ⁺ (where X is at least one of Br and Cl,
x, y and e are 0 <x + y ≦ 0.6, xy ≠ 0 and
It is a number that satisfies the condition of 10 ⁻⁶ ≦ e ≦ 5 × 10 ^-2 . ) Alkaline earth fluorohalide phosphors represented by
The general formula described in No. 12144 is LnOX: xA (where Ln is at least one of La, Y, Gd and Lu, and X is C
l and / or Br, A is Ce and / or Tb, x
Represents a number satisfying 0 <x <0.1. Represented phosphor), the general formulas described in JP-A-employed stimulable phosphors are ^{_{(Ba 1 - xM II x)}} FX: yA ( where M ^II is, Mg, Ca, Sr, of Zn and Cd At least one of X, Cl is at least one of Cl, Br, and I,
A is at least one of Eu, Tb, Ce, Tm, Dy, Pr, Ho, Nd, Yb, and Er, and x and y are 0 ≦ x ≦ 0.6 and 0 ≦
It represents a number satisfying the condition y ≦ 0.2. ), A phosphor represented by the formula: BaFX: xCe, yA (where X is at least one of Cl, Br and I, A
Is at least one of In, Tl, Gd, Sm, and Zr, and x and y are 0 <x ≦ 2 × 10 ⁻¹ and 0 <, respectively.
y ≦ 5 × 10 ⁻² . ), A phosphor represented by
The general formula described in No. 160078 is M ^II FX xA: yLn (where M ^II is at least one of Mg, Ca, Ba, Sr, Zn, and Cd, A is BeO, MgO, CaO, SrO). , BaO, ZnO, Al ₂ O ₃ ,, Y ₂ O ₃ , La ₂
O ₃ , In ₂ O ₃ , SiO ₂ , TiO ₂ , ZrO ₂ , GeO ₂ , SnO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , and at least one of ThO ₂ , and Ln is Eu, Tb, Ce, Tm, Dy, Pr,
At least one of Ho, Nd, Yb, Er, Sm, and Gd, X is at least one of Cl, Br, and I, and x and y are 5 × 10 ⁻⁵ ≦ x ≦ 0.5, respectively. And 0
It is a number that satisfies the condition of <y ≦ 0.2. ) A divalent metal fluorohalide phosphor activated by a rare earth element represented by
59-38278, one of the following general formulas xM ₃ (PO ₄ ) ₂ · NX ₂ : yA M ₃ (PO ₄ ) ₂ · yA (In the formula, M and N are respectively Mg, Ca, Sr, Ba, Zn, and C
at least one of d, X is at least one of F, Cl, Br, and I, A is Eu, Tb, Ce, Tm, Dy, Pr, Ho, Nd, Yb, Er,
It represents at least one of Sb, Tl, Mn, and Sn. Further, x and y are numbers satisfying the conditions of 0 <x ≦ 6 and 0 ≦ y ≦ 1. ), A phosphor represented by the general formula nReX ₃ · mAX ₂ ′: xEu nReX ₃ · mAX ₂ ′: xEu, ySm (wherein Re is at least one of La, Gd, Y and Lu). , A is an alkaline earth metal, at least one of Ba, Sr, Ca, X
And X'represents at least one of F, Cl and Br. Further, x and y are 1 × 10 ⁻⁴ <x <3 × 10 ⁻¹ , 1 × 10 ^−4.
<Y <1 × 10 ^-1 is a number satisfying the condition, and n / m is 1 × 1
The condition of 0 ^-2 <n / m <7 × 10 ^{-1 is} satisfied. Phosphor represented by), and the following general formula _{^{M I X · aM II X 2}} '· bM III X 3 ": cA ( where, M ^I at least 1 to Li, Na, K, Rb, selected from Cs
Alkali metals of species, M ^II is Be, Mg, Ca, Sr, Ba, Zn, Cd,
It is at least one divalent metal selected from Cu and Ni.

M ^III is Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Td, Dy, Ho, Er, Tm,
It is at least one trivalent metal selected from Yb, Lu, Al, Ga, and In.

X, X'and X "are at least one halogen selected from F, Cl, Br and I.

A is Eu, Tb, Ce, Tm, Dy, Pr, Ho, Nd, Yb, Er, Gd, Lu, Sm, Y, Tl, N
It is at least one metal selected from a, Ag, Cu, and Mg. Also, a is a numerical value in the range of 0 ≦ a <0.5, and b
Is a numerical value in the range of 0 ≦ b <0.5, and c is a numerical value in the range of 0 <c ≦ 0.2. ) Alkali halide phosphors represented by). Alkali halide phosphors are particularly preferable because they facilitate the formation of a phosphor layer by a method such as vapor deposition and sputtering.

However, the stimulable phosphor used in the panel according to the present invention is not limited to the above-mentioned phosphor, and is a phosphor that exhibits stimulated emission when irradiated with stimulated excitation light after irradiation with radiation. Any phosphor may be used as long as it is used.

The panel according to the present invention may be a fluorescent layer group composed of one or two or more fluorescent layers containing at least one kind of the stimulable phosphor described above. The stimulable phosphors contained in each phosphor layer may be the same or different.

The layer thickness of the fluorescent layer of the panel according to the present invention varies depending on the sensitivity of the panel to radiation, the type of stimulable phosphor, and the like,
It is preferably selected from the range of 30 μm to 1000 μm, 60
It is more preferably selected from the range of μm to 600 μm.

Furthermore, since the fluorescent layer of the panel according to the present invention is excellent in the directivity of stimulated excitation light and stimulated emission as described above, scattering of the stimulated excitation light in the fluorescent layer is reduced, resulting in a sharp image. Significantly improved.

As the support used in the panel according to the present invention, various polymer materials, glass, metal, ceramics, etc. are used, and cellulose acetate film, polyester film, polyethylene terephthalate film, polyamide film, polyimide film, triacetate film, polycarbonate film, etc. The plastic film, a metal sheet of aluminum, iron, copper, chromium or the like, or a metal sheet having a coating layer of the metal oxide is preferable.

Further, these supports may be provided with an undercoat layer on the surface on which the fluorescent layer is provided for the purpose of improving the adhesiveness with the fluorescent layer. The layer thickness of these supports varies depending on the material of the support used, etc., but is generally 80 μm to 2000 μm,
From the viewpoint of handling, it is more preferably 80 μm to 1000 μm.

In the panel according to the present invention, a protective layer for physically or chemically protecting the fluorescent layer may be provided on the surface where the fluorescent layer is generally exposed. This protective layer may be formed by directly applying the protective layer application liquid onto the fluorescent layer, or by adhering a separately formed protective layer to the fluorescent layer. Cellulose acetate as the material of the protective layer,
Usual protective layer materials such as nitrocellulose, polymethylmethacrylate, polyvinyl butyral, polyvinyl formal, polycarbonate, polyester, polyethylene terephthalate, polyethylene, vinylidene chloride and nylon are used.

In addition, this protective layer is made of SiC,
It may be formed by stacking inorganic substances such as SiO ₂ , SiN, and Al ₂ O ₃ . The thickness of these protective layers is generally 0.1 μm to 100 μm.
A degree is preferable.

The panel according to the present invention provides excellent sharpness, graininess and sensitivity when used in the radiation image conversion method shown schematically in FIG. That is, in FIG. 4, 41 is a radiation generator, 42 is a subject, 43 is a panel according to the present invention, 44 is a stimulated excitation light source, 45 is a photoelectric conversion device for detecting stimulated emission emitted by the panel, 46 Is a device that reproduces the signal detected by 45 as an image, 47 is a device that displays the reproduced image, 48 separates stimulated excitation light and stimulated fluorescence,
It is a filter that transmits only stimulated fluorescence. After 45
The light information from 43 can be reproduced as an image in some form, and is not limited to the above.

As shown in FIG. 4, the radiation from the radiation generator 41 enters the panel 43 according to the present invention through the subject 42. The incident radiation is absorbed by the fluorescent layer of the panel 43, the energy is accumulated, and an accumulated image of a radiation transmission image is formed. Next, this accumulated image is excited by stimulated excitation light from the stimulated excitation light source 44 and emitted as stimulated emission. The panel 43 does not contain a binder in the fluorescent layer, and since the directivity of the stimulated excitation light of the fluorescent layer is high, during scanning with the stimulated excitation light, the stimulated excitation light is in the fluorescent layer. It suppresses the diffusion.

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

(Example) Next, the present invention will be described with reference to an example.

Example 1 Quartz glass having a thickness of 1000 μm was placed in a vapor depositor as a support. Next, put RbBr, which is the raw material of the desired alkali halide stimulable phosphor (RbBr: 0.0003Tl), into the molybdenum boat for resistance heating, and put it in the other tantalum boat.
TlBr was charged and set on the resistance heating electrode, and then the vaporizer was evacuated to a vacuum degree of 2 × 10 ⁻⁶ Torr. Next, RbBr and TlBr were evaporated by a resistance heating method by passing an electric current through each boat of molybdenum and tantalum. RbB by film thickness detector
A panel S was obtained by depositing RbBr; 0.0003Tl stimulable phosphor on the support while controlling the vapor deposition rates of r and TlBr to a thickness of 300 μm.

Next, the panel S was set in the heat treatment container of the diffusion type thermal sensitizer shown in FIG. 2 (a), and TlBr vapor in an amount so that the TlBr concentration was 0.0003 mol was fed into the panel S and heat treated at 600 ° C. for 1 hour. In this way, a panel A obtained by the manufacturing method of the present invention was obtained.

The tube voltage is applied to the panel A according to the present invention thus obtained.
After irradiating 10mR of 50KVp X-ray, semiconductor laser light (790n
The photostimulated luminescence emitted from the stimulable phosphor layer is photo-electrically converted by a photodetector (photomultiplier tube), and this signal is reproduced as an image by an image reproduction device. Recorded above. The sensitivity of panel A to X-rays was examined from the magnitude of the signal, and the results are shown in Table 1.

In Table 1, the sensitivities to X-rays are shown as relative values with panel A as 100 according to the invention.

(Example 2) The panel S obtained in Example 1 was placed in a heat treatment container of the apparatus shown in Fig. 2 (b), and around this, a mixed powder of the same composition as the intended composition of the fluorescent layer ( RbBr + 0.0003TlBr)
Was filled. Next, this container was heat-treated at 600 ° C. for 1 hour to obtain a panel B according to the manufacturing method of the present invention.
The panel B thus obtained was evaluated in the same manner as in Example 1 and the results are shown in Table 1.

(Example 3) A panel C according to the manufacturing method of the present invention was obtained in the same manner as in Example 2 except that the heat treatment conditions were 300 ° C and 3 hours. The panel C thus obtained was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Comparative Example (1) The panel S obtained in Example 1 was placed in a heat treatment container of the apparatus shown in FIG. 6 and heat-treated at 600 ° C. for 1 hour to obtain a comparative panel P. The comparative panel P thus obtained was evaluated in the same manner as in Example 1 and the results are shown in Table 1.

Comparative Example (2) A comparative panel Q was obtained in the same manner as in Comparative Example 1 except that the heat treatment conditions were 300 ° C. and 3 hours. The comparative panel Q thus obtained was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

As is clear from Table 1, the panels A, B, and C produced by the manufacturing method of the present invention have the same graininess and sharpness as those of the comparative panels P and Q, but the X-ray sensitivity is about 2-3 times higher. It became a thing.
This is because escape of the activator from the fluorescent layer during heat treatment was suppressed, and the thermal sensitizing effect was effectively utilized.
On the other hand, in the comparative panels P and Q, the activator escaped during the heat treatment, resulting in a marked decrease in X-ray sensitivity.

Further, the sensitizing effect by the heat treatment is clear by comparison with the unheated panel S.

(Effect of the Invention) According to the present invention, it is possible to prevent a decrease in sensitivity of a radiation image conversion panel due to a change in the concentration (content rate) of the activator of the activatable stimulable phosphor during heat treatment. In addition, occurrence of unevenness in the sensitivity distribution of the stimulable phosphor layer, as in the case where the activator component of the stimulable phosphor is placed in direct contact with the stimulable phosphor layer and subjected to heat treatment. Can also be prevented.

[Brief description of drawings]

FIG. 1 is a diagram showing a change in sensitivity with respect to heat treatment time. FIG. 2 is a schematic diagram showing an example of a diffusion-type thermal sensitizer used in the present invention, and FIG. 3 is a schematic diagram showing an example of an ion implantation device used in the present invention. FIG. 4 is an explanatory diagram of a radiation image conversion method using the panel according to the present invention. FIG. 5 is a graph showing the relationship between the emission intensity of the RbBr: Tl phosphor and the Tl content. FIG. 6 shows an example of a heat treatment apparatus used in a conventional heat treatment method. 21 …… Intensifying panel, 22,30,62 …… Heat treatment container 23,63 …… Heating heater, 24,64 …… Heat treatment furnace 25 …… Heating heater, 26 …… Evaporation container 27 …… Substance powder containing activator 28 …… Gas amount control valve, 29 …… Atmosphere powder 31 …… Ion source part, 32 …… Extraction / accelerating lens part 33 …… Material analysis part, 34 …… Deflecting part 35 …… Sample chamber, 36 ... Sensitization panel 37 ... Heating heater

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Fumio Shimada 1 Sakura-cho, Hino-shi, Tokyo Konishi Roku Photo Industrial Co., Ltd. Examiner Taji Tamura (56) Reference JP-A-59-36183 (JP, A) Special Kaisho 52-144386 (JP, A)

Claims (6)

[Claims] 1. A radiographic image having a stimulable phosphor layer containing an activating stimulable phosphor, which is formed by forming a stimulable phosphor layer containing an activating stimulable phosphor and then heat-treating. In the method for manufacturing a conversion panel, when heat-treating a stimulable phosphor layer containing an activating stimulable phosphor, a position separated from the stimulable phosphor layer in the same system as the stimulable phosphor layer A method for producing a radiation image conversion panel, characterized in that the activator component of the activatable stimulable phosphor installed in the above is vaporized. 2. The method for producing a radiation image conversion panel according to claim 1, wherein the stimulable phosphor layer is formed by a vapor deposition method. 3. The activating stimulable phosphor, wherein the vapor pressure of the activator of the activating stimulable phosphor is substantially equal to or larger than the vapor pressure of the stimulable phosphor matrix. It is a fluorescent substance, The manufacturing method of the radiation image conversion panel of Claim 1 or 2 characterized by the above-mentioned. 4. The radiation image conversion panel according to claim 1, 2 or 3, wherein the activatable stimulable phosphor has a peak of stimulated luminescence with respect to the content of the activator. Manufacturing method. 5. A method for vaporizing an activator component, wherein the activator phosphor is placed at a position apart from the photostimulable phosphor layer in the same system as the radiation image conversion panel. The method for producing a radiation image conversion panel according to claim 1, 2, 3 or 4, wherein the activator component is heated. 6. The vaporization of the activator component is performed by an ion source installed at a position apart from the stimulable phosphor layer in the same system as the radiation image conversion panel. 5. The method for producing a radiation image conversion panel according to claim 1, wherein the activator component ions of the fluorescent substance are generated.