JPS62105097A - Manufacture of radiation picture conversion panel - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a radiation image conversion panel using a stimulable phosphor, and more particularly to a method for manufacturing a radiation image conversion panel that is highly sensitive to radiation. It is something.

(Background of the Invention) Radiographic images such as X-ray images are often used for disease diagnosis. In order to obtain this X-ray image, the X-rays that have passed through the subject are irradiated onto a phosphor layer (phosphor screen), thereby producing visible light, which is then irradiated with silver in the same way as when taking ordinary photographs. So-called radiography is used, which is made by exposing and developing a film using salt. However, in recent years, methods have been devised to directly extract images from the phosphor layer without using a film coated with silver salt.

In this method, the radiation transmitted through the object is absorbed by a phosphor, and then this phosphor is excited with light or thermal energy, so that the phosphor emits the radiation energy accumulated through the absorption as fluorescence. There is a method of detecting this fluorescence and creating an image. Specifically, for example, U.S. Pat.
No. 5-12144 discloses a radiation image conversion method using a stimulable phosphor and using visible light or infrared rays as stimulable excitation light. This method uses a radiation image conversion panel in which a stimulable phosphor layer is formed on a support, and radiation that has passed through the object is applied to the stimulable phosphor layer of this radiation image conversion panel to visualize various parts of the object. A latent image is formed by accumulating radiation energy corresponding to the radiation transmittance, and then this stimulable phosphor layer is scanned with stimulable excitation light to radiate the accumulated radiation energy in each part. An image is obtained by converting the light into light and using an optical signal based on the intensity of this light. This final image may be reproduced on a CRT or on a CRT.

The 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 (both of which are included below), as in the case of the radiography method using a fluorescent screen described above. (referred to as "radiation sensitivity")
It is required that the image quality be as high as 5K, and that the image should have good graininess and high sharpness.

However, in general, a radiation image conversion panel having a stimulable phosphor layer is prepared by coating a dispersion containing a granular stimulable phosphor with a particle size of about 1 to 30 μm and an organic binder on a support or a protective layer. Since it is created by drying, the packing density of the stimulable phosphor is ⇘ (filling rate 50%), and it was necessary to increase the thickness of the stimulable phosphor layer in order to obtain sufficiently high 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 becomes thinner.
In this case, it was necessary to make the stimulable phosphor layer thinner.

In addition, the graininess of the image in the radiation image conversion method is caused by local fluctuations in the number of radiation quanta (quantum mottles) or structural disturbances in the stimulable phosphor layer of the radiation image conversion panel.
As the thickness of the stimulable phosphor layer becomes thinner, the number of radiation quanta absorbed by the stimulable phosphor layer decreases, increasing the quantum mottle and causing structural disorder. becomes obvious and structural mottles increase, resulting in a decrease in image quality. Therefore, in order to improve the graininess of images, the stimulable phosphor layer needs to be thick.

That is, as mentioned above, in the conventional radiation image conversion panel, the sensitivity to radiation, the graininess of the image, and the sharpness of the image exhibit completely opposite tendencies with respect to the layer thickness of the stimulable phosphor layer. The radiation image conversion panels have been made with some trade-off between sensitivity to radiation, graininess, and sharpness.

By the way, it is well known that the sharpness of images in conventional radiography is determined by the spread of instantaneous light emission (light emission during radiation irradiation) of the phosphor in the fluorescent screen. The sharpness of images in radiation image conversion methods using stimulable phosphors is not determined by the spread of stimulated luminescence K of the stimulable phosphors in the radiation image conversion panel; Rather than being determined by the extent of the body's luminescence,
It depends on the spread of the stimulated excitation light within the panel.

This is because in this radiation image conversion method, the radiation image information stored in the radiation image conversion panel is retrieved in a time-series manner, so that the stimulated luminescence due to the stimulated excitation light irradiated at a certain time (ti) is Preferably, it is recorded as the output from every pixel (xi, yi) on the panel that is fully illuminated and irradiated with the stimulated excitation light at that time, but if the stimulated excitation light is scattered within the panel. It spreads due to
If the stimulable phosphor existing outside the irradiated pixel (xi, yi) is also excited, the output from the pixel (xi + yi) will be recorded as the output from a wider area than that pixel. This is because it will be put away. Therefore, for a certain time (
If the stimulated luminescence due to the stimulated excitation light irradiated at time (ti) is only the light emission from the pixel (xi + yi) on the panel that was truly irradiated with the stimulated excitation light at that time (ti). In other words, no matter how widespread the light emission is, it does not affect the sharpness of the image obtained.

Under these circumstances, several methods have been devised to improve the sharpness of radiographic images. For example, JP-A-55-1
Method of incorporating white powder into the stimulable phosphor layer of a radiation image conversion panel described in No. 46447, JP-A-55-163
A method of coloring the radiation image conversion panel described in No. 500 so that the average reflectance of the stimulable phosphor in the stimulated excitation wavelength region is smaller than the average reflectance of the stimulable phosphor in the stimulated emission wavelength region. etc. However, in these methods, improving sharpness inevitably leads to a significant decrease in sensitivity, and therefore cannot be said to be a preferable method.

In view of the above-mentioned drawbacks and incompatibility between characteristics, the applicant proposed in Japanese Patent Application No. 59-196365 a radiation image conversion panel that does not contain a binder in the stimulable phosphor layer and a method for manufacturing the same. 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 phosphor layer is stimulated by excitation light. The directivity of stimulated luminescence is improved, the sensitivity of the radiation image conversion panel to radiation and the granularity of the image are improved, and at the same time, the sharpness of the image is also improved.

The radiation image conversion panel that does not contain a binder can be manufactured by various vapor deposition methods such as sputtering method, CVD method, vapor deposition method, and ion blating method, but considering the manufacturing cost, sputtering method or vapor deposition method is The method can be said to be the most preferable method.

However, when a stimulable phosphor layer is formed by the resistance heating method that is commonly used in the vapor deposition method, the vapor pressures of the multiple substances constituting the stimulable phosphor for a certain crucible temperature are In contrast, substances with high vapor pressure evaporate preferentially. For this reason, the composition of the stimulable phosphor layer formed on the support does not match the composition of the stimulable phosphor charged in the crucible, resulting in a serious drawback of reducing the sensitivity of the radiation image conversion panel to radiation. One thing became clear.

That is, although the method of vapor phase deposition of a stimulable phosphor has many advantages as described above, when forming a layer of stimulable phosphor, the vaporization conditions of the phosphor must be changed. This causes a big problem.

For example, according to the research of the present inventors on RbBr: Tl stimulable phosphor using Tl as an activator, the emission intensity of the phosphor is as shown in Figure 8g9, when the Tl content is 10 to 1.
In the range of 0 mol %, the instantaneous emission intensity is constant, and as long as the Tl content is within a certain range, there is no need to pay close attention to the composition ratio as a general phosphor.

However, the fatal emission of the radiation image conversion panel according to the present invention has a peak near 3×10 mo1%, and the intensity increases (decreases) before and after that peak.

Therefore, when vapor-phase depositing the stimulable phosphor using the vapor deposition method, the vapor pressure of the activator and the stimulable phosphor matrix differ, so that the evaporation source of the activated stimulable phosphor can be uniformly prepared. If the activator is deposited on the panel support before or after the phosphor matrix, and the activator concentration differs in the thickness direction in the stimulable phosphor layer and deviates from the optimum concentration, activation will occur. The original purpose of the agent, which is to impart activity, ends up causing symptoms of toxicity due to the activator.

Incidentally, the vapor pressure of KRbBr is 11111 at 777cc.
1! Hg and TlBr is 110ml at 522℃
H and have large differences in vapor pressure.

There are no cases in which this point has been paid attention to, and we often see examples of activated stimulable phosphor layers with poor performance despite the overall optimal activator concentration.

On the other hand, the production of a transparent stimulable phosphor layer by the sputtering method is known from Japanese Patent Laid-Open No. 59-60300.

In the above manufacturing method, the stimulable phosphor layer is formed by sequentially sputtering the stimulable phosphor from the surface, so the chemical composition of the stimulable phosphor before sputtering and the stimulable phosphor after vapor deposition are different. This has the advantage that the chemical composition roughly matches that of the fluorescent phosphor and the radiation sensitivity is improved.

However, in the radiation image conversion panel having a transparent stimulable phosphor layer manufactured by the above manufacturing method, since the stimulable phosphor layer is transparent as shown in FIG. The reflection of the stimulable excitation light causes halation over a wide area, and the stimulable excitation light is scattered and stimulates the stimulable phosphor, resulting in a significant deterioration in the sharpness of the image.

In addition, in order to form a transparent stimulable phosphor layer by the above manufacturing method, it is necessary to grow the stimulable phosphor crystals to a large size, and if the stimulable phosphor layer is formed at a high speed, the phosphor layer will not be transparent. Therefore, 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 of manufacturing a radiation image conversion panel proposed above using a stimulable phosphor, and an object of the present invention is to produce a radiation image conversion panel with high image sharpness and excellent resolution. The purpose is to provide a manufacturing method.

Another object of the present invention is to provide a method for manufacturing a radiation image conversion panel that fully utilizes the advantages of vapor deposition, has good image granularity and sharpness, and is highly sensitive to radiation. It's about doing.

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

(Structure of the Invention) The present inventors have conducted intensive research on a method for forming a stimulable phosphor layer by the snok spooling method, and have found that by increasing the sputtering rate of the stimulable phosphor, The present inventors discovered that the stimulable phosphor crystallizes into fine crystals, becomes opaque, and exhibits higher sharpness than conventional radiation image conversion panels having a transparent stimulable phosphor layer, leading to the completion of the present invention.

That is, the object of the present invention is to produce a radiation image in which at least one stimulable phosphor layer is formed by a scattering method. This is achieved by a method for manufacturing a radiation image conversion panel characterized in that the radiation rate is within the range of ≧2×10 3 Å/min.

Furthermore, as an aspect of the present invention, the deposition rate A is 5×103
It is preferred that Å/min≦A≦5×10′ Å/min.

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

In the present invention, the sputtering method refers to accelerated particles (
When ions (generally ions) collide with a solid surface, the atoms or molecules that make up the solid are ejected into space through the exchange of momentum.The sputtering phenomenon is used to evaporate the target substance and attach it to a predetermined conversion panel substrate (support ) is a vapor phase deposition method.

The sputtering method referred to in the present invention includes all the methods that utilize the above-mentioned sno-(tsuttering) phenomenon, but in order to efficiently sputter the stimulable phosphor, which is generally an insulator, the sputtering method is essentially a high-frequency method. High-frequency sputtering using high-frequency sputtering is preferred, and magnetron sputtering is particularly preferred among high-frequency sputtering for the purpose of improving the deposition rate.The sputtering method may also be a reactive sputtering method, a chemical sputtering method, etc. The sputtering method and the chemical sputtering method may be used in combination in chronological order.

Furthermore, there is an ion beam sputtering method as a sputtering method different from the above sputtering method.

The present invention will be explained 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 a sputtering device used in the present invention.

In the figure, 1 is a Pelger (vacuum chamber), 2 is a high frequency power supply, 11 is an impedance matching box, and 3
4 is a shutter, 4 is a support on which the stimulable phosphor is deposited,
6 is a target electrode that holds the stimulable phosphor (hereinafter sometimes referred to as target) 5 which is a sputtering material; 7 is a counter electrode to the target electrode that holds the support 4; 8 is an introduction of sputtering gas The port 9 is a shield plate for preventing discharge between the target electrode 6 and the Pelger 1. 10 is a film thickness monitor.

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

In using the sputtering apparatus in the present invention, first, the stimulable phosphor which is the sputtering material is uniformly melted or formed into a plate shape by pressing or hot pressing to create the target 5. A target is bonded to the target electrode 6.

Further, 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 the target or on or while flying to the support.

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

First, the support 4 is placed on the target electrode 60 and the opposite electrode. Further, the support body 4 is heated to a temperature of 50 to 35
It may be heated to 0°C.

Incidentally, the surface of the vapor-deposited substrate of the support 4 is
As described in No. 6913 to No. 59-266916, the stimulable phosphor may be processed to be divided into fine columnar blocks.

Next, the main pulp etc. (not shown) are operated with () to remove the gas inside the Pel Jar 1 and create a degree of vacuum of about 10 to IQ Torr.

Then, inert gas (e.g. Ar, Ne, etc.) is placed in the vacuum chamber.
is introduced from the sputtering gas inlet 8 to 1 to 10
After establishing the vacuum level of the Torr stage, high frequency power is supplied between the target electrode 6 and the counter electrode 7.

A discharge plasma is generated by supplying the high frequency power, and sputtering of the target 5 is started.

The surface of the target is generally contaminated with oxidation, adsorbed gas, etc., so preliminary sputtering is performed with the shutter 3 closed, and after removing the dirt, the shutter 3 is opened and the support 4 is sputtered.
It is preferable to start depositing the stimulable phosphor on top.

Sputtering is performed while monitoring the deposition rate and the deposited film thickness using the film thickness monitor 10, and when a predetermined film thickness is reached, sputtering is stopped.

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 stimulable excitation light. be. The deposition rate at which the stimulable phosphor layer becomes opaque varies depending on the temperature of the support, but the higher the rate, the more likely it is to become opaque, and the deposition rate A needs to be A≧2×10”57 minutes. It is further preferable that A≧5×103 Å/min.If the deposition rate A is less than 2×103 Å/min, it is preferable because, in addition to the above reasons, it takes too much time to produce the stimulable phosphor layer. No. Also, if the deposition rate A is 5
If the X IQ exceeds 5 minutes/minute, it is not preferable because it becomes difficult to control the sputtering speed or the sensitivity decreases.

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

Further, in the above example of the apparatus, the target was located at the top and the support was located at the bottom, but the present invention is not limited to this, and it is sufficient that the target and the support are placed facing each other. Further, in addition to the above-mentioned inert gas, a part of a reactive gas may be mixed into the sputtering gas as required to perform reactive sputtering.

When performing vapor phase deposition by sputtering a target as in the present invention, sputtering is uniformly and sequentially performed regardless of the type of stimulable phosphor and the presence or absence of an activator. There is no risk of deviation in the composition in the thickness direction.

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

The flat plate type high frequency magnetron sputtering apparatus has the same basic structure as the above-described high frequency sputtering apparatus, except for the target electrode structure including the target.

In the figure, 5 is a target, 6a is an electrode plate (pole piece), and 6b is a magnet, and the target electrode 6 is formed by the electrode plate 6a and the magnet 6b. The required number of magnets 6b are provided between the target and the electrode plate so that the magnetic poles alternate to form a toroidal tunnel-like magnetic field, and since the discharge plasma is confined around the magnet, sputtering of the target is increased. The deposition rate on the support is increased, and it is suitable for making large flat panels 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 device, and the feature of this device is that the target and the opposing electrode constitute one evaporation source, and by supplying high-frequency power between them, a toroidal magnetic field is generated. The point is that a plasma ring is generated in the process, and the deposition is performed on supports that are electrically and mechanically independently arranged. In the figure, 7 is a disk-shaped counter electrode, 5 is a target, and the ring-shaped counter electrode 7
surrounding. An electrode plate (not shown) and a magnet 6b are arranged on the back surface of the target 5, and constitute the target electrode 6. As described above, a magnetic field is applied by the magnet on the back surface of the target, and a plasma ring 21 is generated on the target due to the electric field. Ions emitted from this ring sputter the target, and highly directional sputtering atoms are emitted.

In this figure, the same signals as those used in FIGS. 1 and 2 have functionally the same meaning.

FIG. 4 shows an example of yet another type of high frequency snow climbing device. A nuclear example is what is called a coaxial cylindrical electrode type magnetron sputtering device.

In this device, a plurality of short magnets with similar magnetic poles facing each other are loaded into a cylinder consisting of a cylindrical overlapping target and target electrode, and FIG. 4 shows a cross section perpendicular to the cylinder axis. Ionization is large near the electrode, and a large ionization current can be generated even under low pressure gas.

Further, FIG. 5 shows an ion beam sputter link device for reference. Although this device is not suitable for industrial production due to its slow deposition rate, it is important as a research tool and provided basic data for the present invention.

In the radiation image conversion panel according to the present invention, the photostimulable phosphor refers to a photostimulable phosphor that is stimulated by marshal, thermal, mechanical, chemical, or electrical stimulation (stimulable phosphor) after being irradiated with the first light or high-energy radiation. It refers to a phosphor that exhibits stimulated luminescence corresponding to the irradiation amount of initial light or high-energy radiation due to excitation (excitation), but from a practical standpoint, it is preferable to use a phosphor that exhibits stimulated luminescence upon stimulated excitation at a wavelength of 500 nm or more. It is a light body. The photostimulable phosphor used in the radiation image conversion panel according to the present invention is, for example, Ba5O, which is described in JP-A-48-80487: kx (where A is at least one of Dy, Tb, and Tm). species, and X is 0.001≦x
(1 mol%), JP-A No. 4
MgSO4 described in No. 8-80488: kx (However, A
is either HO or Dy, and 0.001≦
X ≦ 1 mol %), JP-A-48
=5rSO described in No. 80489.

: A phosphor represented by Ax (where A is at least one of Dy, Tb and Tm, and X is 0.001≦x<1 mol%), JP-A-51-29889
Na25O, CaSO4 and Ba described in No.
A phosphor in which at least one of Mn, Dy and Tb is added to SO4 etc., BeO, LiF, MgSO4 and (!aF,
phosphors such as Li□E described in JP-A-53-39277, phosphors such as 07:Ou, Ag, L120.
B20t)! :Ou (however, X is 2 (, r≦3), and Li2O・(B202) Z: au, Ag (however, X is 2
(x≦3) etc., U.S. Patent No. 3,859,527
SrS listed in the issue: Oe, Sm, Sr
S: mu, Sm, La20. S: Ku,
Examples include phosphors represented by Sm and (Zn, Cd)S:Mn, X (where X is halogen). In addition, ZnS described in JP-A No. 55-12142
:Ou, Pb phosphor, general formula is BaO・rA1203
: Barium aluminate phosphor represented by Eu (however, 08≦X≦10), and the general formula is M”O・rsi0
2: A (However, M is Mg, C!a, Sr,
Zn, cd or Ba and A is C! e, Tb,
It is at least one of Ku, Tm, Pb, Tl, Bi, and Mn, and X satisfies 05≦2<2,5.

Examples include alkaline earth metal silicate phosphors represented by the following. Also, the general formula is (Ea,, -yMg, Cay)
FX: ellcu2+ (where X is at least one of Br and (4, and !, 31 and θ are each O
(x + y≦0.6, xy〆O and 10≦e≦5×1
This is a number that satisfies the condition of 0. ) Alkaline earth fluorohalide phosphor represented by JP-A-55-12144
The general formula described in the issue is LnOX: xk (Ln is at least one of La, Y, Gd and Lu,
b, and X represents a number that satisfies o (x (0, 1).

), the general formula described in JP-A-55-12145 is (Ea, -, M 3:) FX : yA (Once M
(At least one of Ding, Mg, Ca, Sr, Zn and Cd, X is at least one of C1, Er and Ding, A is Ku, Tb, Cje,
Tm.

At least one of Dy, Pr, Ho, Nd, Yb and Er, X and y are ○≦X≦06 and 0≦
It represents a number that satisfies the condition y≦02. ] The general formula of the phosphor described in Special σa No. 55-84389 is BaFX: roe, yA (
X is at least one of Cjl, Br and ■, A is at least one of Tl, Gd, Sm and Zr, and X and y are each 0x≦2X
10-' and O< y≦5 X 10'. ) is a phosphor represented by n, i￥! The general formula described in 1987-160078 is M"FX-yA: yLn (where Mll is at least one of Mg, Oa, Ba, Sr, Zn and C (l, A is Beo, M
gO, (ao.

SrO, BaO, Zn('l, kl, 03.Y,
03. La, O,, engineering neo3゜Sin,, TiO
2,ZrO,,GeO2,5n(1,,Nb,O,,T
a.O.

and at least one of ThO□, Ln is Eu.

Tb, Ce, Tm, Dy, Pr, Ha, N
d, Yb, Kr.

is at least one of Sm and Gd, and X is (3
1, Br and I, and X and y are n5X, Lo≦X≦05 and 0kuy≦02, respectively.
This is a number that satisfies the condition. Rare earth 311 represented by ノ
Element-activated divalent metal fluorohalide phosphor, general formula Z
nS: A, OdS: A, (Zn, Cd)
S: A, ZnS: A, X and C! ds:A,X
(However, A is C!u, Ag, Au or Mn, and X is a halogen.) JP-A-57-1
Any of the following general formulas described in No. 48285 (where M and N are Mg, Ca, and Sr, respectively.

At least one of Ba, Zn and Cd, and X is F.

(At least one of 4', Br and ■, A is Ku
.

Tb, Ce, Tm, Dy, Pr, Ha, N
d, Yl)lEr.

Represents at least one of Sb, Te, Mn and Snf. In addition, X and y are numbers that satisfy the condition o (x≦6.0≦y≦). At least one of Od, Y, and Lu; A represents an alkaline earth metal; Ba, Sr, and at least one of (4); X and xl represent at least one of ?, (ll, and Br; X and y are lX10
'(,z:(3XIO',lXl0'<:y(IXlo
It is a number that satisfies the condition that n7m is 1×10 (n
Mn
are Be, Mg, Oa, Sr, Ba,
At least one divalent metal selected from Zn, Cd, Ou and N1. MIII is Sc, Y
, La, C! e, Pr, N(L.

Pm, Sm, mu, Gd, Tb, Dy, H
a, Er, Tm.

At least one divalent metal selected from Yb, Lu, Ke, Ga, and Ga. x, x' and xl
is F+ at least one selected from Cl, Br and ■
It is a type of halogen. A is mu, Tb, C! e,
Tm.

Dy, Pr, Ho, Nd, Yb, Er, G
d,, Lu, Sm.

At least one metal selected from Y, 're, Na, Ag, Cu, and Mg.

Also, a is a numerical value in the range of 0≦a (0,5, b is a numerical value in the range of 0≦b05, and C is a numerical value in the range of 0≦b<0.2
is a numerical value in the range of . ) and the like can be mentioned. In particular, alkali halide phosphors are preferred because they facilitate the formation of a stimulable phosphor layer by sputtering.

However, the photostimulable phosphor used in the radiation image conversion panel according to the present invention is not limited to the above-mentioned phosphor, and when irradiated with radiation and then irradiated with photostimulation excitation light, the photostimulable phosphor emits photostimulable light. Any phosphor may be used as long as it exhibits the following.

The radiation image conversion panel according to the present invention is a photostimulable phosphor layer group comprising one or more photostimulable phosphor layers containing at least one kind of the above-mentioned photostimulable phosphors. Good too. Furthermore, the stimulable phosphors contained in the stimulable phosphor layers t 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 is determined by the sensitivity of the radiation image conversion panel to radiation;
Although it varies depending on the Mll-exhaustive fluorescent phosphor, etc., it is 30 μm.
It is preferably selected from the range of ~1000 μm, and 50 μm.
More preferably, it is selected from the range of μm to 800 μm. If the thickness of the photostimulable phosphor layer is less than 30 μm, the radiation absorption rate will be extremely reduced and the radiation sensitivity will be poor.
Not only does the graininess of the image deteriorate, but the photostimulable phosphor layer tends to become transparent, and the horizontal spread of the photostimulable excitation light in the photostimulable phosphor layer increases significantly, reducing the sharpness of the image. is undesirable because it tends to deteriorate.

FIG. 6 shows the layer thickness of the photostimulable phosphor of the radiation image conversion panel according to the present invention and the relationship between the adhesion resistance of the photostimulable phosphor corresponding to the layer thickness and the radiation sensitivity. The stimulable phosphor layer of the radiation image conversion panel according to the present invention does not contain a binder unlike the conventional dispersed radiation image conversion panel in which a phosphor is suspended and dispersed in a binder. Therefore, the adhesion resistance 1 (filling rate) of the photostimulable phosphor is approximately twice that of the conventional radiation image conversion panel, and the radiation absorption rate per unit thickness of the photostimulable phosphor layer is improved. Not only is it more sensitive to radiation than an image conversion panel, but it also improves image graininess.

Furthermore, the photostimulable phosphor layer of the radiation image conversion panel according to the present invention does not contain a binder, and since the photostimulable phosphor layer is finely crystallized, it is possible to It has excellent directionality of stimulated luminescence, high transmittance of stimulated excitation light and stimulated luminescence, and can be made thicker than conventional dispersed radiation image conversion panels.

Furthermore, since the photostimulable phosphor layer of the radiation image conversion panel according to the present invention has excellent directivity as described above, scattering of the photostimulable excitation light in the photostimulable phosphor layer is reduced. , image sharpness is significantly improved over conventional dispersion type radiation image conversion panels and conventional vapor deposition type radiation image conversion panels having a transparent photostimulable phosphor layer.

Various polymeric materials, glass, metals, etc. are used as the support for the radiation image conversion panel according to the present invention, and examples include cellulose acetate film, polyester film, polyethylene terephthalate film, polyamide film, polyimide film, triacetate film, and polycarbonate film. Plastic films such as, metal sheets such as aluminum, iron, copper, chromium, etc., or metal sheets having a coating layer of the metal oxides are preferable.

The surface of these supports may be smooth, or may be matte for the purpose of improving adhesion to the stimulable phosphor layer, or may be provided with a reflective layer or an absorbing layer. Also,
The surface of the support may have an uneven surface 41 as shown in FIG. 7(a), or may have a structure in which spaced tile-like plates 43 are laid out as shown in FIG. 7(b). In the case of FIG. 7(a), the stimulable phosphor layer is subdivided by the uneven surface 41 as shown in the cross-sectional view of FIG. 7(C), so that the sharpness of the image is further improved. In the case of FIG. 7(b), the photostimulable phosphor layer is deposited while maintaining the outline of the tile-like plate 43 of the support, and as a result, the photostimulable phosphor layer is deposited as shown in FIG. As shown in the cross-sectional view of (d), the image is composed of columnar blocks 45 of photostimulable phosphor separated by cracks 46, so that the sharpness of the image is further improved.

Furthermore, these supports may be provided with a subbing layer on the surface on which the photostimulable phosphor layer is provided for the purpose of improving adhesion to the photostimulable phosphor layer. In addition, the layer thickness of these supports varies depending on the material of the support used, but generally 80 μm ~
The thickness is 2000 μm, and more preferably 80 μm to 100 μm from the viewpoint of handling.

In the radiation image conversion panel according to the present invention, protection for physically or chemically protecting the photostimulable phosphor layer is generally provided on the surface where the photostimulable phosphor layer is exposed. Layers may be provided. This protective layer may be formed by directly applying a protective layer coating solution onto the stimulable phosphor layer, or by adhering a separately formed protective layer onto the stimulable phosphor layer. It's okay. The material for the protective layer is cellulose acetate,
Common protective layer materials such as nitrocellulose, polymethyl methacrylate, polyvinyl butyral, polyvinyl formal, polycarbonate, polyester, polyethylene terephthalate, polyethylene, vinylidene chloride, nylon, etc. are used.

In addition, this protective layer is formed using SiC! by vapor deposition, sputtering, etc. , 310. , SiN, k1
20. It may also be formed by stacking inorganic substances such as. The thickness of these protective layers is generally 0.1 μm to 100 μm.
degree is preferred.

The radiographic image conversion panel according to the present invention provides excellent sharpness, graininess and sensitivity when used in the radiographic image conversion method shown schematically in FIG.

That is, in FIG. 8, 51 is a radiation generating device, and 62 is a radiation generating device.
is a subject, 53 is a radiation image conversion panel according to the present invention,
54 is a stimulated excitation light source; 55 is a photoelectric conversion device that detects stimulated luminescence emitted from the radiation image conversion panel; 56 is a device that reproduces the signal detected by 55 as an image; 57
58 is a device for displaying a reproduced image, and 58 is a filter that separates stimulated excitation light and stimulated luminescence and allows only stimulated luminescence to pass through. It should be noted that the elements after 55 are not limited to the above, as long as they can reproduce the optical information from 53 as an image in some form.

As shown in FIG. 8, radiation from a radiation generating device 51 enters a radiation image conversion panel 53 according to the present invention through a subject 52. This incident radiation is absorbed by the stimulable phosphor layer of the radiation image conversion panel 53, its energy is accumulated, and an accumulated radiation image is formed. Next, this stored M image is excited with stimulated excitation light from the stimulated excitation light source 54 to emit stimulated luminescence. In the radiation image conversion panel 53, the photostimulable phosphor layer is finely crystallized and the directivity of the stimulated excitation light and stimulated luminescence of the photostimulable phosphor layer becomes high, so that the scanning by the above-mentioned stimulated excitation light is improved. At the same time, diffusion of the photostimulable excitation light in the photostimulable phosphor layer is suppressed.

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 55 such as a photomultiplier tube, and an image reproduction device 56
By reproducing the image as an image and displaying it on the image display device 57, a radiographic image of the subject can be observed.

(Example) Next, the present invention will be explained using seven practical examples.

Example 1 A chemically strengthened glass having a thickness of 500 μm was placed as a support in a vacuum chamber of a flat plate type high frequency sputtering apparatus. As a target, a RbBr:O,0O06TJ alkaline rehalide stimulable phosphor processed into a flat plate shape by pressing was used. Subsequently, the sputtering device was
After exhausting to OTorr, Ar was introduced as a sputtering gas to obtain a gas pressure of 4×I OTorr.

Next, while heating and maintaining the support at 200°C, a
Sputtering was performed by supplying high frequency power of 3.56 MHz. In order to obtain the desired stimulable phosphor layer, the sputtering rate was detected using a film thickness monitor, and the sputtering rate was controlled to be 2×1 dA/min. Sputtering was terminated when the thickness of the stimulable phosphor layer reached 200 μm, and a radiation image conversion panel A was obtained by the manufacturing method of the present invention.

The thus obtained radiation image conversion panel A of the present invention was irradiated with X-rays at a tube voltage of 80 KVp for IQ mR, and then stimulated with He-No laser light (633 um) to produce photostimulable fluorescence. Stimulated luminescence emitted from the body layer was photoelectrically converted using a light director (photomultiplier tube), and this signal was reproduced as an image by an image reproducing device and recorded on a silver salt film. The sensitivity of the radiation image conversion panel A to X-rays was investigated based on the signal magnitude, and the modulation transfer function (MT?) and granularity of the image were investigated using the obtained images, as shown in Table 1G.

In Table 1, the sensitivity to X-rays is expressed as a relative value, with the radiation image conversion panel A of the present invention being taken as 100. In addition, the modulation transfer function (MTIF) is the value when the spatial frequency is 2 cycles/ms, and the graininess is (good, average, bad) (○, △).

It is indicated by X).

Example 2 A radiographic image conversion panel B according to the present invention was obtained in the same manner as in Example 1, except that the high-frequency wave and the tsuttering device shown in FIG. 1 were 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 listed in Table 1.

Example 3 In Example 1, instead of using an alkali halide stimulable phosphor as a target, alkali halide stimulable phosphor raw materials (RbBr 1 mol, TlBr 0.000
A radiation image conversion panel C according to the present invention was obtained in the same manner as in Example 1 except that 6 mol of the mixture was used.

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 listed in Table 1.

Comparative Example 1 Alkali halide stimulable phosphor (RbEr: 0.0
006Tl) and 1 part by weight of polyvinyl butyral resin were mixed and dispersed using 5 parts by weight of a solvent (cyclohexanone) to prepare a coating solution for a stimulable phosphor layer.

Next, this coating solution was uniformly applied onto a 500 μm thick chemically strengthened glass support placed horizontally and air dried to form a 200 μm thick stimulable phosphor layer.

The comparative radiation image conversion panel P obtained in this way was evaluated in the same manner as the example construction, and the results are also listed in Table 1.

Table 1 As clearly shown in Table 1, the radiation image conversion panels A to C according to the present invention have an X-ray sensitivity that is about twice as high as that of the comparative radiation image conversion panel P, and also have excellent image graininess. Ta. This is because in the radiation image conversion panel according to the present invention, the photostimulable phosphor layer is finely crystallized, and the directivity of stimulated excitation light and stimulated luminescence is high, and the filling rate of the photostimulable phosphor is comparatively high. This is because the absorption rate of high<xm is better than that of a panel.

Furthermore, the radiation image conversion panels A to C according to the present invention were superior in sharpness to the comparison radiation image conversion panel P despite having higher X-ray sensitivity. This is also because the photostimulable phosphor layer of the radiation image conversion panel according to the present invention has a fine crystal structure and the directivity of the photostimulated excitation light is high. This is because scattering in the stimulable phosphor layer is reduced.

Example 4 In Example 1, the sputtering rate was changed to 8 x 10'
A radiation image conversion panel D according to the present invention was obtained in the same manner as in Example 1 except that the stimulable phosphor layer thickness was 50 μm.

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 In Example 1, the sputtering rate was changed to 3×103
A radiation image conversion panel E according to the present invention was obtained in the same manner as in Example 1 except that the stimulable phosphor layer thickness was 50 μm.

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 listed in Table 2.

Comparative Example 2 In Example 1, the sputtering speed was changed to 5×10”
A comparative radiation image converting Nosenel Q having a transparent stimulable phosphor layer was obtained in the same manner as in Example 1 except that the stimulable phosphor layer thickness was 50 μm.

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

Table 2 As is clear from Table 2, the radiation image conversion panels D and E according to the present invention had poorer image sharpness than the comparative radiation image conversion panel Q. This is because the comparison radiation image conversion panel Q had a transparent photostimulable phosphor layer, and the photostimulable excitation light spread widely in the lateral direction, resulting in poor sharpness.

Example 6 Alkali halide catalyst I was used as the target in Example 1.
Instead of using an exhaustive fluorochrome, EaFBr: 0.0
A radiation image conversion panel 7 according to the present invention was obtained in the same manner as in Example 1 except that the OIH:u'N exhaustible band phosphor was used.

The radiation image conversion panel F according to the present invention obtained in this way has high sharpness and M'l at 2 cycles/mm.
'IF was 47%.

(Effect of the invention) As a means of forming a vapor phase deposited layer that faithfully copies the composition of the photostimulable phosphor that exhibits the designed characteristics, high frequency waves are used to uniformly evaporate the photostimulable phosphor having the composition from the surface. Adopting the sputtering method eliminates performance deviations between design and product, improves quality assurance, and provides a stable and reliable production process.

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

The present invention has extremely large effects and is industrially useful.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a high frequency wave sputtering apparatus used in the present invention, and FIG. 2 shows a structure near the target shadow i of the flat plate type high frequency magnetron sputtering apparatus. FIG. 3 is a schematic diagram of a circular high-frequency magnetron sputtering device, FIG. 4 is a schematic plan view of a coaxial, co-cylindrical high-frequency magnetron sputtering device, and FIG. 5 is a schematic diagram of an ion beam sputtering device. FIG. 6 is a characteristic diagram of the radiation image conversion panel obtained by the present invention. FIG. 7 shows an example of the base surface of the support according to the present invention on which 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 luminescence intensity. Further, FIG. 10 is a diagram showing the halation of stimulated excitation light in a conversion panel having a transparent photostimulable phosphor layer. l...Pelger (vacuum chamber), 2...High frequency power supply, 3...Shutter,
4...Support, 5...Target,
6...Target electrode, 7...Counter electrode, 8
... Sputtering gas inlet, 9... Shield plate, 10... Film thickness monitor, 11... Munching box, 14... Magnetic field, 2o... Magnetic field, 21... plasma ring. Applicant: Konishi Roku Photo Industry Co., Ltd. 21 Print h-ma 1' 59-Igm 30 H East Shinsun 31 ・ Ba Xun Sanshin 32 ・ Pei 75...-m Figure 8 9 T

Claims (3)

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