JPH0631900B2 - Radiation image conversion panel manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a radiation image conversion panel using a stimulable phosphor, and more particularly to a method for producing a radiation image conversion panel having high sensitivity to radiation. It is a thing.

(Background of the Invention) Radiation images such as X-ray images are often used for disease diagnosis. In order to obtain this X-ray image, X-rays that have passed through the subject are irradiated onto the phosphor layer (fluorescent screen), thereby generating visible light, and this visible light is used in the same way as when taking a normal photograph. A so-called radiograph in which a film using salt is irradiated and developed is used. However, in recent years, a method of directly taking out an image from the phosphor layer without using a film coated with silver salt has been devised.

As this method, 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 emitted as fluorescence. , There is a method of detecting this fluorescence and imaging. Specifically, for example, U.S. Pat. No. 3,859,527 and JP-A-55-12144.
Japanese Patent No. 3187242 discloses 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 in which a stimulable phosphor layer is formed on a support, and the radiation that has passed through the subject is applied to the stimulable phosphor layer of this radiation image conversion panel to apply the radiation to each part of the subject. A latent image is formed by accumulating the radiation energy corresponding to the radiation transmittance, and thereafter, the stimulable phosphor layer is scanned with stimulable excitation light to radiate the accumulated radiation energy of each part to generate a latent image. The light is converted into light and an image is obtained by an optical signal depending on the intensity of the light.
This final image may be played back as a hard copy or on a CRT.

A radiation image conversion panel having a stimulable phosphor layer used in this radiation image conversion method has a radiation absorption rate and a light conversion rate (including both of them, as in the case of the radiographic method using the above-described fluorescent screen). Radiation sensitivity ")
Needless to say, the image has good graininess and high sharpness.

However, in general, a radiation image conversion panel having a stimulable phosphor layer applies a dispersion containing a granular stimulable phosphor having a particle size of about 1 to 30 μm and an organic binder onto a support or a protective layer, Since it is produced by drying, the packing density of the stimulable phosphor is low (filling ratio 50%), and it was necessary to increase the layer thickness of the stimulable phosphor 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 stimulable phosphor layer of the radiation image conversion panel is smaller. It was necessary to thin the luminescent phosphor layer.

Further, the graininess of the image in the radiation image conversion method is determined by the spatial fluctuation of the radiation quantum number (quantum mottle), the structural disorder of the stimulable phosphor layer of the radiation image conversion panel (structural malt), or the like. Therefore, as the layer thickness of the stimulable phosphor layer becomes thinner, the number of radiation quantum absorbed in the stimulable phosphor layer decreases and the quantum mottle increases, or structural disorder becomes apparent and the structure mottle increases. As a result, the image quality is degraded. Therefore, in order to improve the graininess of the image, the stimulable phosphor layer needs to be thick.

That is, as described above, in the conventional radiation image conversion panel, the sensitivity to radiation and the graininess of the image, and the sharpness of the image show the opposite tendency to the layer thickness of the stimulable phosphor layer. The radiation image conversion panels have been made at the trade-off between radiation sensitivity and some degree of 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 the stimulated emission of the stimulable phosphor in the radiation image conversion panel, that is, as in radiography, Rather than being determined by the spread of
It is determined depending on the spread of stimulated excitation light in the panel.
In this radiation image conversion method, since the radiation image information accumulated in the radiation image conversion panel is taken out in time series, it is desirable that the stimulated emission due to the stimulated excitation light irradiated at a certain time (ti). Is recorded as the output from a certain pixel (xi, yi) on the panel that was all illuminated and was irradiated with stimulated excitation light at that time, but if the stimulated excitation light spreads in the panel due to scattering, etc. , Irradiation pixel (x
If the stimulable phosphor existing outside (i, yi) is also excited, the output from a region wider than the pixel is recorded as the output from the pixel from (xi, yi) above. is there. Therefore, stimulated emission by the stimulated excitation light irradiated at a certain time (ti), from the pixel (xi, yi) on the panel that was actually irradiated with the stimulated excitation light at that time (ti) If only the luminescence is emitted, the sharpness of the obtained image will not be affected regardless of the extent of the luminescence.

Under these circumstances, some methods have been devised to improve the sharpness of radiographic images. For example, JP-A-55-14644
No. 7, a method of mixing a white powder in the stimulable phosphor layer of the radiation image conversion panel, the radiation image conversion panel described in JP-A-55-163500, the stimulable excitation light wavelength of the stimulable phosphor For example, there is a method of coloring so that the average reflectance in the region is smaller than the average reflectance in the stimulated emission wavelength region of the stimulable phosphor. 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, the present applicant has proposed a radiation image conversion panel containing no binder in the stimulable phosphor layer and a method for producing the same in Japanese Patent Application No. 59-196365. is suggesting. According to this, since the stimulable phosphor layer of the radiation image conversion panel does not contain a binder, the filling rate of the stimulable phosphor is significantly improved and the stimulable excitation light of the stimulable phosphor layer and The directivity of stimulated emission is improved, the sensitivity of the radiation image conversion panel to radiation and the graininess of the image are improved, and at the same time, the sharpness of the image is improved.

The radiation image conversion panel containing no binder can be manufactured by various vapor phase deposition methods such as a sputtering method, a CVD method, a vapor deposition method and an ion plating method. Method is the most preferred method.

However, when the stimulable phosphor layer is formed by the resistance heating method that is generally performed in the vapor deposition method, the vapor pressures of a plurality of substances constituting the stimulable phosphor for a certain crucible temperature are respectively different. In contrast, the higher the vapor pressure of the substance, the more preferentially it will evaporate. Therefore, the composition of the stimulable phosphor layer formed on the support does not match the composition of the stimulable phosphor charged in the crucible, and the sensitivity to radiation of the radiation image conversion panel is reduced. It became clear that there is.

That is, the method of vapor-depositing the stimulable phosphor brings about various advantages as described above, but when the layer of the stimulable phosphor is formed, the vaporization condition of the phosphor is neglected. Fall into a big trap.

For example, according to the present inventors' research on RbBr: Tl stimulable phosphor using Tl as an inactivating agent, the emission intensity of the phosphor is 9th.
Is Tl content as shown in FIG its composition ratio as 10 ^-2 ~10 ⁰ mol% of In the range instantaneous light emission intensity is constant and as long as common phosphor Tl content is Osamu' constant width You don't have to be very careful about it.

However, the stimulated emission that controls the death of the radiation image conversion panel according to the present invention has a peak at around 3 × 10 ^-2 mol%, and the intensity is greatly reduced before and after that.

Therefore, when vapor-depositing the stimulable phosphor by the vapor deposition method, the vapor pressures of the activator and the stimulable phosphor matrix are different, so that the evaporation source of the uniformly prepared stimulable phosphor is When the activator from the body is vapor-deposited on the panel support before or after the phosphor matrix and the activator concentration varies in the thickness direction in the stimulable phosphor layer and deviates from the optimum concentration, the activator is activated. The original purpose of imparting the activity of the agent eventually leads to the manifestation of poisoning by the activator. By the way, the vapor pressure of RbBr shows 1mmHg at 777 ℃ and TlB.
r is 10 mmHg at 522 ℃, and has a large difference in vapor pressure.

We have not paid any attention to this point, and we often look at examples of activatable stimulable phosphor layers that have poor performance despite overall optimum activator concentration.

On the other hand, the production of a transparent stimulable phosphor layer by the above-mentioned sputtering method is known from JP-A-59-60300.

The manufacturing method, by sequentially sputtering the stimulable phosphor from the surface, to form a stimulable phosphor layer, so the chemical composition of the stimulable phosphor before sputtering and the stimulability after vapor deposition There is an advantage that the chemical composition of the phosphor is approximately the same and the radiation sensitivity is improved.

However, the radiation image conversion panel having a transparent stimulable phosphor layer by the above-mentioned manufacturing method, since the stimulable phosphor layer is transparent as shown in FIG. 10, at the interface of the phosphor layer and other constituent layers. The reflection of the stimulated excitation light causes halation over a wide range, the stimulated excitation light is scattered, and the stimulable phosphor is stimulated to be excited, so that the sharpness of the image is significantly deteriorated.

Further, in order to form the transparent stimulable phosphor layer by the manufacturing method, it is necessary to grow the stimulable phosphor crystal to a large extent, and when the stimulable phosphor layer is formed at high speed, the phosphor layer is not transparent. Therefore, there is a drawback that the productivity of the radiation image conversion panel is extremely low, and improvement thereof has been desired.

(Object of the Invention) The present invention relates to the method for producing the proposed radiation image conversion panel using a stimulable phosphor, and the object of the present invention is to provide a radiation image conversion panel having high image sharpness and excellent resolution. It is to provide a manufacturing method.

Another object of the present invention is to provide a method for producing a radiation image conversion panel which has good graininess and sharpness of an image and which has the advantages of the vapor deposition method, and which is highly sensitive to radiation. Especially.

Still another object of the present invention is to provide a method of manufacturing a radiation image conversion panel having a high vapor deposition rate and high productivity.

(Structure of the Invention) As a result of intensive studies on the method for forming a stimulable phosphor layer by the present inventors, the inventors have found that the stimulable phosphor on the support is increased by increasing the sputtering rate of the stimulable phosphor. The present invention has been completed by finding that the body becomes finely crystallized and becomes opaque and exhibits high sharpness as compared with a conventional radiation image conversion panel having a transparent photostimulable phosphor layer.

That is, the object of the present invention is a method for producing a radiation image conversion panel in which at least one stimulable phosphor layer is formed by a sputtering method, and the deposition rate A of the stimulable phosphor layer is A ≧ 2 × 10 5. This is achieved by a method for manufacturing a radiation image conversion panel, which is characterized by being included in the range of ³ Å / min.

Further, according to an aspect of the present invention, the deposition rate A is 5 × 10 ³ Å
/ Min ≦ A ≦ 5 × 10 ⁵ Å / min is preferable.

In the present invention, it is preferable that the fine crystals have a fine columnar crystal structure arranged in the layer thickness direction of the stimulable phosphor layer because the sharpness of the image is improved.

In the present invention, the sputtering method uses a sputtering phenomenon in which, when accelerated particles (generally ions) collide with the surface of a solid, the atoms or molecules constituting the solid are knocked out into space by exchange of momentum, In this method, a target substance is evaporated and vapor-deposited on a predetermined conversion panel substrate (support).

The sputtering method referred to in the present invention includes all methods utilizing the above-mentioned sputtering phenomenon, but in order to efficiently sputter the stimulable phosphor which is generally an insulator, a high frequency is substantially used. The high frequency sputtering described above is preferable, and among the high frequency sputtering, magnetron sputtering is particularly preferable for the purpose of improving the deposition rate. Further, the sputtering method may be a reactive sputtering method, a chemical sputtering method, or the like,
Further, the sputtering method, the reactive sputtering method and the chemical sputtering method may be used in combination in a time series.

Further, as a sputtering method different from the above-mentioned sputtering method, there is an ion beam sputtering method.

The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic cross-sectional view of a high frequency sputtering device which is an example of the sputtering device used in the present invention.

In the figure, 1 is a bell jar (vacuum chamber), 2 is a high frequency power supply device, 11 is an impedance matching box, 3 is a shutter, 4 is a support for depositing a stimulable phosphor, 6
Is a target electrode that holds a stimulable phosphor (hereinafter also referred to as a target) 5 that is a sputtering material,
Reference numeral 7 is a counter electrode of a target electrode for holding the support 4, 8 is a sputtering gas inlet, and 9 is a shield plate for preventing discharge between the target electrode 6 and the bell jar 1. 10 is a film thickness monitor.

Further, 14 is a target 5 and a support 4 for plasma as necessary.
A magnet 13 confined between and is an ignition heater for supplying thermoelectrons at the start of sputtering if necessary.

In using the sputtering device in the present invention, the stimulable phosphor that is a sputtering material is first uniformly dissolved or formed into a plate shape by pressing or hot pressing to prepare a target 5, The target is adhered to the target electrode 6.

The target 5 does not necessarily have to be a stimulable phosphor having a composition to be deposited on a support, and may be a mixture of stimulable phosphor raw materials. The target composition may be produced by sputtering on a target or on a support or during flight to the support.

Since the target electrode 6 and the target 5 are violently hit by cations during sputtering to increase the temperature, it is preferable to flow cooling water on the back surface of the target electrode 6 to cool it. Further, since the counter electrode 7 and the support 4 are also heated by the collision of secondary electrons generated during sputtering, it is preferable to cool them if necessary.

First, the support 4 is placed on the counter electrode of the target electrode 6. The support 4 is heated to 50 to 350 ° C by a heater or the like.
It may be heated to.

The surface of the vapor-deposited substrate of the support 4 is formed by a series of Japanese Patent Application No. 59-266913.
No. 59 to 266916, the stimulable phosphor may be processed so as to be divided into fine columnar blocks.

Then, the main valve or the like (not shown) is operated to eliminate the gas inside the venger 1 to obtain a vacuum degree of about 10 ⁻⁴ to 10 ⁻⁷ Torr.

Next, after introducing an inert gas (eg, Ar, Ne, etc.) into the vacuum chamber from the sputtering gas inlet 8 to a vacuum degree of the order of 1 to 10 ^-2 Trr, a high frequency wave is applied between the target electrode 6 and the counter electrode 7. Supply power.

Discharge plasma is generated by the supply of the high frequency power, and the sputtering of the target 5 is started. Since the surface of the target is generally contaminated with oxidation, adsorbed gas, etc., pre-sputtering is performed with the shutter 3 closed, and after removing the contamination, the shutter 3 is opened to deposit the photostimulable phosphor on the support 4. It is preferable to start.

The sputtering proceeds while monitoring the deposition rate and the deposited film thickness by the film thickness monitor 10, and the sputtering is stopped when the film thickness reaches a predetermined value.

In the present invention, it is important that the deposition rate A of the stimulable phosphor is selected so that the stimulable phosphor layer formed on the support becomes finely crystallized and becomes opaque to the stimulable excitation light. is there. The deposition rate at which the stimulable phosphor layer becomes opaque varies depending on the temperature of the support, but a higher rate tends to cause opacity, and the deposition rate A must be A ≧ 2 × 10 ³ Å / min. And it is preferable that A ≧ 5 × 10 ³ Å / min. When the deposition rate A is less than 2 × 10 ³ Å / min, it takes too much time to manufacture the stimulable phosphor layer in addition to the reasons described above, which is not preferable. Further, if the deposition rate A exceeds 5 × 10 ⁵ Å / min, it is not preferable because it becomes difficult to control the sputtering rate or the sensitivity is lowered.

The support 4 may be sputtered (generally referred to as reverse sputtering) on the support before depositing the stimulable phosphor to obtain a clean surface.

Further, in the above-mentioned example of the device, the target was on the upper side and the support was on the lower side, but the present invention is not limited to this, and the target and the support may be placed so as to face each other. Further, reactive sputtering may be carried out by partially mixing a reactive gas with the sputtering gas, if necessary, in addition to the above-mentioned inert gas.

In the case of performing vapor phase deposition by sputtering a target as in the present invention, the layers in the stimulable phosphor layer are uniformly sputtered regardless of the type of stimulable phosphor and the presence or absence of an activator. There is no risk of bias in the composition in the thickness direction.

FIG. 2 shows a target electrode structure of a flat plate type high frequency magnetron sputtering apparatus.

The flat-plate high-frequency magnetron sputtering apparatus has the same basic structure as the above-described high-frequency sputtering apparatus except that the structure of the target electrode including the target is different.

In the figure, 5 is a target, 6a is an electrode plate (ball piece), and 6b is a magnet. The target electrode 6 is formed by the electrode plate 6a and the magnet 6b. The magnets 6b are provided between the target and the electrode plate so that a required number of magnetic poles are alternately arranged to form a toroidal tunnel-shaped magnetic field 20, and the discharge plasma is substantially confined to the periphery of the target, which increases target sputtering. The deposition rate on the support is increased, which is suitable for producing a large flat panel and has high productivity.

Further, FIG. 3 shows an example of another type of high frequency magnetron sputtering apparatus.

The example shown in the figure is a circular magnetron sputtering apparatus, and the characteristic of this apparatus is that the target and the counter electrode constitute one evaporation source, and high-frequency power is supplied between the two, toroidal magnetic field. A plasma ring is generated at the point where vapor deposition is performed on a support that is arranged electrically and mechanically independently. In the figure, 7 is a disk-shaped counter electrode, 5 is a target, and a ring-shaped counter electrode 7
Surrounds. An electrode plate (not shown) and a magnet 6b are arranged on the back surface of the target 5 to form the target electrode 6. As described above, the magnetic field 20 is generated by the magnet on the back surface of the target, and the plasma ring 21 is generated on the target by the electric field. The ions emitted from this ring sputter the target, and the highly-directed sputtering atoms are emitted.

In the figure, the same signals as those used in FIGS. 1 and 2 are functionally synonymous.

FIG. 4 shows an example of still another type of high frequency sputtering apparatus. This example is called a coaxial cylindrical electrode type magnetron sputtering device.

In this apparatus, a plurality of short magnets having the same magnetic poles are mounted facing each other in a cylinder composed of a target and a target electrode which are overlapped in a cylindrical shape, and FIG. 4 shows a cross section perpendicular to the cylinder axis. Ionization is large near the electrodes, and a large ionization current can be obtained even under low pressure gas.

The ion beam sputtering system is shown in FIG. 5 for reference. This device is not suitable for industrial production due to its low deposition rate, but it is important as a research tool and provided the basic data for the present invention.

In the radiation image conversion panel according to the present invention, the stimulable phosphor means a stimulus (photostimulation) such as optical, thermal, mechanical, chemical or electrical after first irradiation with light or high energy radiation. Excitation means a phosphor that exhibits stimulated emission corresponding to the initial irradiation dose of light or high-energy radiation. From a practical point of view, a phosphor that exhibits stimulated emission upon excitation of 500 nm or more is preferable. is there. Examples of the stimulable phosphor used in the radiation image conversion panel according to the present invention include BaSO ₄ ; Ax (where A is at least 1 of Ry, Tb and Tm) described in JP-A-48-80487.
And x is 0.001 ≦ x <1 mol%. ), MgS described in JP-A-48-80488
O ₄ : Ax (where A is either Ho or Dy, 0.
001 ≦ x ≦ 1 mol%, SrSO ₄ : Ax described in JP-A-48-80489 (wherein A is at least one of Dy, Tb and Tm, and x Is
0.001 ≦ x <1 mol%. ), Na ₂ S described in JP-A-51-29889
Phosphors obtained by adding at least one of Mn, Dy and Tb to O ₄ , CaSO _4, BaSO _4, etc., fluorescence of BeO, LiF, MgSO _4, CaF _2, etc. described in JP-A-52-30487 Body, JP-A-5
Phosphors such as Li ₂ B ₄ O ₇ : Cu, Ag described in JP-A-3-39277, and Li described in JP-A-54-47883.
₂ O ・ (B ₂ O ₂ ) x: Cu (where x is 2 <x ≦ 3), and Li ₂ O ・ (B ₂
O ₂ ) x: Cu, Ag (where x is 2 <x ≦ 3) and other phosphors, SrS: Ce, Sm, SrS: Eu, described in US Pat. No. 3,859,527.
Examples include phosphors represented by Sm, La ₂ O ₂ S: Eu, Sm and (Zn, Cd) S: Mn, X (where X is a halogen). Further, a ZnS: Cu, Pb phosphor described in JP-A-55-12142, which has a general formula of BaO.xAl ₂ O ₃ : Eu (however, 0.8 ≦ x ≦ 10)
The barium aluminate phosphor represented by
M ^II O · xSiO ₂ : A (where M ^II is Mg, Ca, Sr, Zn, Cd or Ba, and A is at least one of Ce, Tb, Eu, Tm, Pb, Tl, Bi and Mn)
Seed and x is 0.5 ≦ x <2.5. ) Alkaline earth metal silicate-based phosphors represented by Also, the general formula is (Ba _1-xy Mg _x Ca _y ) FX: eEu ²⁺ (where X is at least one of Br and Cl, and x,
y and e are 0 <x + y ≦ 0.6, xy ≠ 0 and 10 ≦, respectively.
It is a number that satisfies the condition of e ≦ 5 × 10. ) Alkaline earth fluorohalide phosphor, represented by JP-A-55-
No. 12144 has the general formula LnOX: xA (where Ln is at least one of La, Y, Gd and Lu, and X is Cl.
And / or Br, A is Ce and / or Tb, and x is 0 <x <
Represents a number that satisfies 0.1. ), The general formula described in JP-A-55-12145 is (Ba _1-x M ^II _x ) FX: yA (where M ^II is Mg, Ca, Sr, Zn and Cd). At least one
X is at least one of Cl, Br and I, A
Represents at least one of Eu, Tb, Ce, Tm, Dy, Pr, Ho, Nd, Yb and Er, and x and y represent numbers satisfying the conditions of 0 ≦ x ≦ 0.6 and ≦ y ≦ 0.2. ), A phosphor represented by
The general formula described in 5-84389 is 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 <y, respectively.
≦ 5 × 10 ₋₂ . ), A phosphor represented by
The general formula described in No. 5-160078 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 numbers satisfying the conditions of 5 × 10 ⁻⁵ ≦ x ≦ 0.5 and 0 <y ≦ 0.2, respectively. ) A rare earth element-activated divalent metal fluorohalide phosphor having a general formula of ZnS:
A, CdS: A, (Zn, Cd) S: A, ZnS: A, X and CdS:
Phosphors represented by A and X (where A is Cu, Ag, Au or Mn and X is halogen), JP-A-57-1482.
No. 85, one of the following general formulas xM ₃ (PO ₄ ) ₂ · NX ₂ : yA M ₃ (PO ₄ ) ₂ · yA (wherein M and N are Mg, Ca, Sr, Ba, and At least one of Zn and Cd, X at least one of F, Cl, Br and I, A is Eu, Tb, Ce, Tm, Dy, Pr, Ho, Nd, Yb, Er, Sb, Tl,
Represents at least one of 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, and Ca, X and X ′ are at least one of F, Cl, and Br, and x and y are 1 × 10 ⁻⁴ <x <. 3 x 10 ^-1 , 1 x 1
It is a number satisfying the condition of 0 ^-4 <y <1 × 10 ^-1 , and n / m
^{Satisfies the} condition 1 × 10 <n / m <7 × 10 ⁻¹ . )
Phosphor represented in the following general formula ^{M I X · aM II X '} 2 · bM III X "3: cA ( where, M ^I at least one alkali is that Li, Na, K, are selected from Rb and Co Is a metal, M ^II is Be, Mg, Ca, Sr, Ba,
It is at least one divalent metal selected from Zn, Cd, Cu and Ni. M ^III is Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, T
It is at least one trivalent metal selected from b, Dy, Ho, Er, Tm, 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, L
It is at least one metal selected from u, Sm, Y, Tl, Na, Ag, Cu and Mg.

Also, a is a numerical value in the range of 0 ≦ a <0.5, and b is 0 ≦ a <0.5.
The value is in the range of b <0.5, and the value of c is in the range of 0 <c ≦ 0.2. ) Alkali halide phosphors represented by). Alkali halide phosphors are particularly preferred because they facilitate formation of a stimulable phosphor layer by a sputtering method.

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

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

The layer thickness of the stimulable phosphor layer of the radiation image conversion panel according to the present invention varies depending on the sensitivity of the radiation image conversion panel to radiation, the type of stimulable phosphor, and the like, but is 30 μm to 10 μm.
It is preferably selected from the range of 00 μm, and 50 μm to
More preferably, it is selected from the range of 800 μm. When the layer thickness of the stimulable phosphor layer is less than 30 μm, the radiation absorptivity is extremely reduced, the radiation sensitivity is deteriorated, the granularity of the image is deteriorated, and the stimulable phosphor layer becomes transparent. This is not preferred because it tends to occur easily, the lateral spread of the stimulable excitation light in the stimulable phosphor layer significantly increases, and the sharpness of the image tends to deteriorate.

FIG. 6 shows the relationship between the radiation sensitivity and the layer thickness of the stimulable phosphor of the radiation image conversion panel according to the present invention, and the amount of the stimulable phosphor deposited corresponding to the layer thickness. Since the stimulable phosphor layer of the radiation image conversion panel according to the present invention does not contain a binder as in a dispersion type radiation image conversion panel in which a conventional phosphor is suspended and dispersed in a binder, it is bright. The adhering amount (filling rate) of the stimulable phosphor is about twice that of the conventional radiation image conversion panel, and the radiation absorption rate per unit thickness of the stimulable phosphor layer is improved, resulting in more radiation than the conventional radiation image conversion panel. On the other hand, not only high sensitivity but also graininess of the image is improved.

Further, the stimulable phosphor layer of the radiation image conversion panel according to the present invention does not contain a binder, and since the stimulable phosphor layer is finely crystallized, stimulating excitation light and stimulable It has excellent directivity of light emission, high transparency to stimulated excitation light and stimulated emission, and can have a larger layer thickness than the conventional dispersion type radiation image conversion panel.

Furthermore, since the stimulable phosphor layer of the radiation image conversion panel according to the present invention has excellent directivity as described above, scattering of the stimulable excitation light in the stimulable phosphor layer is reduced, and The sharpness of the image is remarkably improved as compared with the conventional vapor phase deposition type radiation image conversion panel having the dispersion type radiation image conversion panel and the transparent photostimulable phosphor layer.

As the support used in the radiation image conversion panel according to the present invention, various polymer materials, glass, metals and the like are used, and cellulose acetate film, polyester film, polyethylene terephthalate film, polyamide film, polyimide film, triacetate film, polycarbonate film. A plastic film such as the above, 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.

The surface of these supports may be a smooth surface, may be a matte surface for the purpose of improving the adhesion to the stimulable phosphor layer, and may be provided with a reflection layer or an absorption layer. Further, the surface of the support may be an uneven surface 41 as shown in FIG. 7 (a), or a tile-shaped plate 43 isolated as shown in FIG. 7 (b).
It may be a structure that is spread. In the case of FIG. 7 (a), the stimulable phosphor layer has an uneven surface 4 as shown in the sectional view of FIG. 7 (c).
Since it is subdivided by 1, the sharpness of the image is further improved. In the case of FIG. 7 (b), the stimulable phosphor layer is deposited while maintaining the contour of the tile plate 43 of the support, and as a result, the stimulable phosphor layer is formed as shown in FIG. As shown in the sectional view of), since the columnar block 45 of the stimulable phosphor is isolated by the crack 46, the sharpness of the image is further improved.

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

In the radiation image conversion panel according to the present invention, a protective layer for physically or chemically protecting the stimulable phosphor layer is generally provided on the surface on which the stimulable phosphor layer is exposed. It may be provided. This protective layer may be formed by directly coating the protective layer coating solution on the stimulable phosphor layer, or by forming a protective layer separately formed in advance on the stimulable phosphor layer. Good. 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. Further, this protective layer may be formed by laminating an inorganic substance such as SiC, SiO ₂ , SiN, Al ₂ O ₃ by a vapor deposition method, a sputtering method or the like. Generally, the thickness of these protective layers is preferably about 0.1 μm to 100 μm.

The radiation image conversion panel according to the present invention provides excellent sharpness, graininess and sensitivity when used in the radiation image conversion method schematically shown in FIG. That is, in FIG. 8, 51 is a radiation generator, 62 is a subject, 53 is a radiation image conversion panel according to the present invention, 54 is a stimulated excitation light source, and 55 is radiation stimulated by the radiation image conversion panel. A photoelectric conversion device for detecting light emission, a device 56 for reproducing the signal detected by 55 as an image, a device 57 for displaying the reproduced image, a device 58 for separating stimulated excitation light and stimulated emission light, It is a filter that transmits only exhausted light. 5
From 5 onward, the light information from 53 can be reproduced as an image in some form, and is not limited to the above.

As shown in FIG. 8, the radiation from the radiation generator 51 enters the radiation image conversion panel 53 according to the present invention through the subject 52. The incident radiation is absorbed by the stimulable phosphor layer of the radiation image conversion panel 53, 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 54 and emitted as stimulated emission. In the radiation image conversion panel 53, since the photostimulable phosphor layer is finely crystallized and the directivity of the photostimulable phosphor layer is enhanced, the directivity of the photostimulable phosphor layer and photostimulated light emission is increased. The diffusion of stimulated excitation light in the stimulable phosphor layer is suppressed.

Since the intensity of the stimulated luminescence emitted is proportional to the amount of accumulated radiation energy, this optical signal is photoelectrically converted by the photoelectric conversion device 55 such as a photomultiplier tube, and the image reproduction device 56.
By reproducing the image as an image and displaying it by the image display device 57, the radiation transmission image of the subject can be observed.

(Examples) Next, the present invention will be described by examples.

Example 1 As a support, a chemically strengthened glass having a thickness of 500 μm was placed in a vacuum chamber of a flat plate type high frequency sputtering apparatus. As the target, an RbBr: 0.0006Tl alkali halide stimulable phosphor processed into a flat plate by a press was used. Subsequently, the sputtering apparatus was evacuated to 5 × 10 ⁻⁶ Torr, and Ar was introduced as a sputtering gas to 4 × 10 ^−3.
The gas pressure was Torr.

Then, while holding the support at 200 ℃,
Sputtering was performed by supplying high frequency power of 3.56 MHz. In order to obtain the target stimulable phosphor layer, the sputtering rate was detected by a film thickness monitor, and the sputtering rate was controlled to be 2 × 10 ⁴ Å / min. When the layer thickness of the stimulable phosphor layer reached 200 μm, the sputtering was terminated to obtain a radiation image conversion panel A manufactured by the present invention.

The radiation image conversion panel A of the present invention thus obtained was irradiated with 10 mR of X-ray with a tube voltage of 80 KVp, and then stimulated by He-Ne laser light (633 nm) to radiate from the stimulable phosphor layer. The stimulated emission thus generated was photoelectrically converted by a photodetector (photomultiplier tube), and this signal was reproduced as an image by an image reproducing device and recorded on a silver salt film. From the size of the signal,
The sensitivity of the radiation image conversion panel A to X-rays was investigated, and the modulation transfer function (MTF) and graininess of the image were examined from the obtained image.

In Table 1, the sensitivity to X-rays is shown as a relative value with the radiation image conversion panel A of the present invention as 100. The modulation transfer function (MTF) is a value when the spatial frequency is 2 cycles / mm, and the granularity is (good, normal, bad).
Are each indicated by (○, Δ, ×).

Example 2 A radiation image conversion panel B according to the present invention was obtained in the same manner as in Example 1 except that the high frequency sputtering apparatus shown in FIG. 1 was used.

The radiation image conversion panel B according to the present invention thus obtained was evaluated in the same manner as in Example 1, and the results are also shown in Table 1.

Example 3 Example 3 except that an alkali halide stimulable phosphor raw material (a mixture of 1 mol of RbBr and 0.0006 mol of TlBr) was used instead of the alkali halide stimulable phosphor as a target in Example 3. A radiation image conversion panel C according to the present invention was obtained in the same manner as in 1.

The radiation image conversion panel C according to the present invention thus obtained was evaluated in the same manner as in Example 1, and the results are also shown in Table 1.

Comparative Example 1 8 parts by weight of an alkali halide stimulable phosphor (RbBr: 0.0006Tl) and 1 part by weight of polyvinyl butyral resin were mixed and dispersed with 5 parts by weight of a solvent (cyclohexanone) to form a stimulable phosphor layer. The coating liquid for the was prepared. Next, this coating liquid was uniformly applied on a chemically strengthened glass as a support having a thickness of 500 μm and horizontally dried to form a photostimulable phosphor layer having a thickness of 200 μm.

The comparative radiation image conversion panel P thus obtained was evaluated in the same manner as in Example 1, and the results are also shown in Table 1.

As is clear from Table 1, the radiation image conversion panels A to C according to the present invention had an X-ray sensitivity about twice higher than that of the comparison radiation image conversion panel P and excellent image graininess. This is because in the radiation image conversion panel according to the present invention, the stimulable phosphor layer is finely crystallized, and the directivity of stimulated excitation light and stimulated emission is high, and the filling rate of the stimulable phosphor is a comparative panel. This is because the X-ray absorption rate is higher than that of the conventional one.

Further, the radiation image conversion panels A to C according to the present invention were excellent in sharpness as compared with the radiation image conversion panel P for comparison, although the X-ray sensitivity was high. Also, the stimulable phosphor layer of the radiation image conversion panel according to the present invention has a structure of fine crystals, and since the directivity of the stimulable excitation light is high, the luminescence of He-Ne laser which is the stimulable excitation light. This is because scattering in the exhaustive phosphor layer is reduced.

Example 4 A radiation image conversion panel according to the present invention in the same manner as in Example 1 except that the sputtering rate was 8 × 10 ³ Å / min and the stimulable phosphor layer thickness was 50 μm. I got D.

The radiation image conversion panel D according to the present invention thus obtained was evaluated in the same manner as in Example 1, and the results are shown in Table 2.

Example 5 A radiation image conversion panel E according to the present invention was carried out in the same manner as in Example 1 except that the sputtering rate was 3 × 10 ³ Å / min and the stimulable phosphor layer was 50 μm.
Got

The radiation image conversion panel E according to the present invention thus obtained was evaluated in the same manner as in Example 1, and the results are also shown in Table 2.

Comparative Example 2 Comparative transparent stimulable fluorescence was carried out in the same manner as in Example 1 except that the sputtering rate was 5 × 10 ² Å / min and the stimulable phosphor layer thickness was 50 μm. A radiation image conversion panel Q having a body layer was obtained.

The comparative radiation image conversion panel Q thus obtained was evaluated in the same manner as in Example 1, and the results are also shown in Table 2.

As is clear from Table 2, the radiation image conversion panels D and E according to the present invention were superior in image sharpness to the comparison radiation image conversion panel Q. This is because in the radiation image conversion panel Q for comparison, the stimulable phosphor layer is transparent, the stimulable excitation light is widely spread in the lateral direction, and the sharpness is deteriorated.

Example 6 A radiation image conversion according to the present invention was performed in the same manner as in Example 1 except that BaFBr: 0.001Eu stimulable phosphor was used instead of the alkali halide stimulable phosphor as the target in Example 1. Panel F was obtained.

The radiation image conversion panel F according to the present invention thus obtained had a high sharpness and the MTF at 2 cycles / mm was 47%.

(Effects of the Invention) As a means for forming a vapor-phase deposited layer that faithfully copies the composition of a stimulable phosphor exhibiting design characteristics, a high frequency sputtering method for uniformly evaporating a stimulable phosphor of the composition from the surface Is adopted, the performance deviation between the design and the product is eliminated, the quality assurance is enhanced, and the production process is stable and reliable.

Further, according to the present invention, since the photostimulable phosphor layer is finely crystallized and opaque, lateral spread of the photostimulable excitation light is suppressed and the sharpness of the image is improved.

The present invention is extremely effective and industrially useful.

[Brief description of drawings]

FIG. 1 is a schematic view of a high frequency sputtering apparatus used in the present invention, and FIG. 2 shows a structure near a target cathode of a flat plate type high frequency magnetron sputtering apparatus. Third
FIG. 4 is a schematic view of a circular high-frequency magnetron sputtering apparatus, FIG. 4 is a schematic plan view of a coaxial same-cylinder high-frequency magnetron sputtering apparatus, and FIG. 5 is a schematic view of an ion beam sputtering apparatus. FIG. 6 is a characteristic diagram of the radiation image conversion panel obtained by the present invention. FIG. 7 shows an example of the ground surface of the support according to the present invention on the side where the stimulable phosphor is deposited and a cross section of the deposited layer. FIG. 8 is an explanatory diagram of radiation image conversion. FIG. 9 is a diagram showing the relationship between the concentration of the activator Tl in the stimulable phosphor and the emission intensity. Further, FIG. 10 is an explanatory diagram showing halation of photostimulation excitation light of a conversion panel having a transparent photostimulable phosphor layer. 1 ... Bell jar (vacuum chamber), 2 ... High frequency power source, 3 ... Shutter, 4 ... Support, 5 ... Target, 6 ... Target electrode, 7 ... Counter electrode, 8 ... Sputtering gas inlet port, 9 ... Shield plate, 10 ... Film thickness monitor, 11… matching box, 14… magnet, 20… magnetic field, 21… plasma ring.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Fumio Shimada No. 1 Sakura-cho, Hino-shi, Tokyo Konishi Roku Photo Co., Ltd. Judge Tamura

Claims (3)

[Claims] 1. A method for producing a radiation image conversion panel in which at least one stimulable phosphor layer is formed by a sputtering method, wherein the deposition rate A of the stimulable phosphor layer is A ≧ 2.
A method for manufacturing a radiation image conversion panel, characterized in that the radiation image conversion panel is contained in a range of × 10 ³ Å / min. 2. The deposition rate A is 5 × 10 ³ Å / min ≦ A ≦ 5
The method for producing a radiation image conversion panel according to claim 1, wherein the method is × 10 ⁵ Å / min. 3. The method of manufacturing a radiation image conversion panel according to claim 1, wherein the sputtering method is a high frequency sputtering method.