JPS6239800A - Radiation image 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]

[Industrial Application Field 1] The present invention relates to a radiation image conversion panel using a stimulable phosphor, and more specifically to a radiation image conversion panel that provides a radiation image with high fF sharpness and a method for manufacturing the same. be. 2. Description of the Related Art Radiographic images such as X-ray images are often used for disease diagnosis. In order to obtain this XR image, the X-rays that have passed through the subject are
-hl-1-n'74-4n, ~V, Lj4・I-Jyuμmr'' visible light is irradiated onto a film using silver salt in the same way as when taking ordinary photographs, and developed. Radiography is used.However, in recent years, a method has been devised in which images are taken directly from the phosphor layer without using a film coated with silver salt. The phosphor is absorbed by the body, and then the phosphor is excited by, for example, light or thermal energy, so that the phosphor emits the radiation energy accumulated by the absorption as fluorescence,
Therefore, there is a method to detect this fluorescence and create an image. Specifically, for example, U.S. Pat. . This method uses 111
This uses a radiation image conversion panel on which a stimulable phosphor layer is formed, and the radiation transmitted through the subject is applied to the stimulable phosphor layer of the radiation image conversion panel to calculate the radiation a of each part of the subject.
Radiation energy corresponding to the transmittance is applied Wvt to form a latent image, and then this stimulable phosphor layer is scanned with stimulable excitation light to radiate the radiation energy accumulated in each part and light it. An image is obtained from an optical signal based on the intensity of this light. This final image may be reproduced as a hard copy or on a CRT. Now, 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 (including both In addition to having high radiation sensitivity (hereinafter referred to as "radiation sensitivity"), images are required to have good graininess and high sharpness. However, in general, a radiation image conversion panel having a stimulable phosphor layer is produced by coating a dispersion containing a particulate stimulable phosphor with a particle size of about 1 to 30 μIII 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 low (filling rate 5096), and in order to obtain sufficiently high radiation sensitivity, the stimulable phosphor layer must be formed as shown in Figure 5 (, ). It was necessary to increase the layer thickness. As is clear from the figure, the layer thickness of the stimulable phosphor layer is 200 μm.
When m, the adhesion resistance of the stimulable phosphor is 50+ag/c+o
', and the radiation sensitivity increases linearly up to a layer thickness of 350 μm and saturates above 450 μm. Note that the radiation sensitivity is saturated because if the stimulable phosphor layer becomes too thick, This occurs because the stimulated luminescence inside the stimulable phosphor layer does not come out to the outside due to the SL of the stimulable phosphor layer between the stimulable phosphor particles. As shown in Figure 5(b), the image sharpness in the conversion method tends to be higher as the thickness of the stimulable phosphor layer of the radiation image conversion panel becomes thinner. In addition, the granularity of the image in the radiation image conversion method is due to radiation in quantum number positional fluctuation (1 to 7 tors) or the brightness of the radiation image conversion panel. This is determined by the structural disorder (structural mottle) of the stimulable phosphor layer, so as the layer thickness of the stimulable phosphor layer becomes thinner, the number of radiation quanta absorbed by the 11I stimulable phosphor layer decreases. As quantum mottles increase, structural disorder becomes apparent and structural mottles increase, resulting in a decrease in image quality.Therefore, in order to improve the graininess of images, the thickness of 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 tend to be completely opposite to the thickness of the stimulable phosphor layer. Therefore, the radiographic image conversion panels have been created by sacrificing sensitivity to radiation, graininess, and sharpness to a certain extent.By the way, the sharpness of images in conventional radiography is due to the moment of phosphor in the fluorescent screen. It is well known that the sharpness of the image in the radiation image conversion method using the stimulable phosphor is determined by the spread of light emission (light emission during radiation irradiation). It is not determined by the spread of the stimulable luminescence of the stimulable phosphor in the panel, i.e. it is not determined by the spread of the phosphor's luminescence as in radiography. This is determined depending on the spread within the panel.This is because in this radiation image conversion method, the radiation image information accumulated on the radiation image conversion panel is retrieved in chronological order.
It is desirable that all of the stimulated luminescence caused by the stimulated excitation light irradiated to the irradiated area is illuminated, and the stimulable luminescence is radiated at that time. - The excitation light is recorded as the output from a certain pixel (xi, yi) on the panel that was irradiated, but if the excitation light spreads within the panel due to scattering etc. If the outside stimulable phosphor is also excited, the above (xi
, yi), the output from an area wider than that pixel is recorded. Therefore, the brightness F irradiated at a certain time (ti)! , if the stimulated luminescence due to excitation is only the luminescence from the pixel (xi + yi) on the panel that was truly irradiated with the stimulated excitation light during that time (ti), then ``What kind of spread does that luminescence have?'' There is no effect on 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-55-14
Method of incorporating white powder into the stimulable phosphor layer of a radiation image conversion panel described in No. 6447, JP-A-55-1635
The radiation image conversion panel described in No. 00 is colored so that the average reflectance of the stimulable phosphor in the region where the stimulable excitation wave is distributed is smaller than the average reflectance at the stimulable emission wavelength of the stimulable phosphor. method etc. However, in these methods, improving the sharpness inevitably leads to a noticeable decrease in sensitivity, and therefore cannot be said to be a preferable method. On the other hand, the present applicant has already applied for vj application 59-1963.
As a new radiation image conversion panel that improves the conventional drawbacks of the radiation image conversion panel using the 141-stimulable phosphor as described in No. 65, the radiation image conversion panel does not contain a binder in the stimulable phosphor layer. We are proposing a panel. 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 transparency of the stimulable phosphor layer is improved. Therefore, the sensitivity to radiation of the radiation image conversion panel and the graininess of the image are improved, and at the same time, the sharpness of the image is also improved.However, in the radiation image conversion method, the sensitivity,
The demand for image quality with excellent sharpness without impairing graininess is becoming ever more stringent.

[Object of the Invention] The present invention relates to the above-mentioned proposed radiation image conversion panel using a stimulable phosphor, and further improves the same.
An object of the present invention is to provide a radiation image conversion panel that has improved sensitivity to radiation and provides images with high sharpness. Another object of the present invention is to provide a radiation image conversion spring that has improved graininess and provides images with high sharpness. Structure and operation of the invention 1 The object of the present invention is to provide a radiation/line image conversion panel having at least a stimulable phosphor layer on the supports T and R, in which a stimulable phosphor layer is provided. This is achieved by a radiation image conversion panel characterized in that fine voids are provided so that the porosity is 3 to 30%. Next, the present invention will be explained using a single shellfish. FIG. 1 is a sectional view in the thickness direction of a radiation image conversion panel (hereinafter sometimes simply referred to as a panel when the meaning is clear) of the present invention. In the figure, numeral 10 indicates the form of the panel of the present invention. 11 is a support, and 12 represents a stimulable phosphor layer formed on the support by vapor deposition. An adhesive layer may be provided between the support 11 and the stimulable phosphor layer 12 to improve adhesion between each layer, if necessary, or an adhesive layer may be provided between the support 11 and the stimulable phosphor layer 12. A reflective layer or an absorbing layer may also be provided. A large number of fine voids 13 are provided in the stimulable phosphor layer 12 . In order to prevent the lateral scattering of light, the voids 13 preferably have an elongated shape extending substantially perpendicularly to the surface of the support, and the spacing between the voids 13 is preferably 100 μm or less, more preferably 40 μm.
It is best to keep it under 100. Further, the voids 13 are provided so that the porosity of the stimulable phosphor layer 12 is 3 to 30%. More preferably, the porosity is 10 to 25%. This porosity is 3%
If it is less than 30%, the stimulable phosphor layer will gradually become denser, and sufficient freshness will be achieved. This increases the thickness of the stimulable phosphor layer, which in turn causes a decrease in sharpness. It is preferable to provide a protective layer 14 on top of the stimulable phosphor layer 12.Second. The figure shows another example of the panel of the present invention as a cross-sectional view in the thickness direction. 21 is a support, and 22 is a stimulable phosphor layer having a fine columnar block structure extending substantially perpendicular to the surface of the support. 22ij represents each fine columnar block structure, (22ij) is the crack between 22ij, 1
1 represents a gap in the form of a depression or the like. Furthermore, the fine columnar block structure has a porosity of 3% to 30%.
%, a large number of two minute gaps 23 are provided. The preferred shape of the void 23 is the same as that described in the explanation of FIG. Further, 24 is a protective layer that is preferably provided. In the panel of the present invention having the structure as shown in Fig. m2, the support 21 is a support having a large number of fine uneven patterns on its surface as described in Japanese Patent Application No. 59-2669]3, for example. You can also apply for the patent application No. 59-26691.
It may be a support having a surface structure in which a large number of micro tile-like plates are laid out and separated from each other by minute gaps as described in No. 4, or VF Application No. 5
9-266915, the support may have a fine wire network on its surface that surrounds and partitions a large number of micro tile-like plates, respectively. The average diameter of the fine columnar blocks 22ij is 1 shi 400
μm is preferable, and the gap between the fine columnar blocks (
22ij) may be any interval as long as the fine columnar blocks 22ij are optically independent from each other, but it is preferably 0 to 20 μm on average. When the stimulable excitation light is incident on the stimulable phosphor layer having the above-mentioned fine voids, the excitation light reaches the bottom surface of the stimulable phosphor layer while being repeatedly reflected internally on the surface of the voids. Therefore, the sharpness of images produced by stimulated luminescence can be significantly increased. In addition to the above-mentioned voids, a stimulable phosphor layer having a fine columnar block structure as shown in FIG. 2 also provides the above-mentioned effect, but is more effective. The thickness of the stimulable phosphor layer of the panel of the present invention is determined by the sensitivity of the panel to radiation and the f of the stimulable phosphor layer. It is preferably in the range of 0 to 800 μm, and more preferably in the range of 50 to 500 μm. In the radiation image conversion panel of the present invention, the stimulable phosphor refers to a stimulable phosphor that is stimulated by optical, thermal, mechanical, optical 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 dose of initial light or high-energy radiation (excitation), but from a practical standpoint, it is preferably stimulated by V$excitation of 500 nm or more. It is a phosphor that emits light. The exhaustible phosphor used in the radiation image conversion panel of the present invention is, for example, B aS O4:A x (where A is Dy) described in JP-A-48-80487.
At least one of 1Tb and T Tl+, and X
is 0.001≦x<1 mol%. ), MgSO described in JP-A-48-80488, :A
However, A is either Ho or Dy, r+,
o, oot≦X≦1 mol%);
SrS described in JP-A-48-80489
The phosphor represented by O=:A x (where A is at least one of DywTb and Tm, and x is 0.001≦x<1 mol%) is described in Japanese Patent Application Laid-Open No. 51-29889. The listed Na25O, Ca5O, and vBaS
A phosphor in which at least one of Mn, Dy, and Tb is added to O4, etc., B e Ov Li F v M g S O4 described in JP-A-52-30487.
and phosphors such as CaF2, JP-A-53-39277
Phosphors such as L i2B and 07:CuyAg described in JP-A-54-47883, L i20 ・(B 202)X:Cu (where X is 2<
×≦3), and L i20 ・(8202)X:Cu,
Phosphors such as Ag (where X is 2<x≦3), S rS :Ce described in U.S. Pat. No. 3°859.527,
S n+%S rS; Eu, Sm, L 11202S
:E uts vn and 1/(ZntCd)S:Mn,X
Examples include phosphors represented by (where X is halogen). Also, A1□O is described in JP-A-55-12142.
s: Barium aluminate phosphor represented by Eq (0.8≦X≦10) and whose general formula is M”O・X5iOz
:A (However, M!I is M g * Cat S r t
Z n * Cd or Ba and A is Ce, Tb, E
u, Tm, Pb, T 1. At least one of B i and Mn, and X satisfies 0.5≦X≦2.5. ) Alkaline earth metal silicate-based phosphors represented by: Also, the general formula is (Ba Mg Ca
) FX: eEu""-ni-y X
y (where X is at least one of Br and C1,
x, y and C are respectively 0<x+y≦0.6, xy≠0
and 10-6≦e≦5X10-2. ) can be mentioned. In addition, the general formula is L no X :xA (Ln is at least one of La, Y, Gd, and Lu,
b, and X represents a number satisfying O<x<0.1. ) is described in JP-A-55-12145 (B
n M ``x) F E u + T b r Ce
r T III + D y r P r. At least one of Ho, Nd, Yb and Er,
X and C/'y represent numbers satisfying the conditions of 0≦x≦0.6 and 0≦y≦0.2. ), a phosphor expressed by
The general formula described in No. 5-84389 is BaF
X:xCe. yA (However, X is at least one of CI, Br and ■, A is I n, T I, Gd, S+n and V Z r
and y are each O
<x≦2X10-' and O<y≦5X10-2. ), JP-A-55-1130078
The general formula described in the No.
At least if! of r r Z n and Cd! l,
A is B e O + M g O, Ca O + Sr○, B
a○, ZnO, Al2O2, Y 20 s r La
203°111203, S i02. Ti0z, Zr
O2, GeO2, Sn○2゜Nb20g, Ta205 and tF
is Eu, 1'b+Cc+T+n+Dy+Pr, IIo+
Nd. At least 61 types of Yl+, IE, r, S+o and Gd, X is at least one of CI, [3r and ■, and each of X and y is 5X10-5≦X
This is a number that satisfies the conditions of ≦0.5 and o<y≦0.2. ) Rare earth element-activated divalent metal fluorohalide phosphor with general formula ZnS:A, (Zn, Cd)S:A
, CdS:A, ZnS:A,X and CdS:A,X
(However, A is Cu+Ag+Au+ or Mn, and
is HaOden. ) Phosphor expressed by JP-A-57-
General formula CI) or CI described in No. 148285
[), General formula (1) XM 3 (P O4) 2 ・
N X 2:yA general formula (H) M3(PO,>
2.yA (where M and N are each M g HCa
I S r r I3 a + Z at least one kind among n and Cd, X is F, CI'. At least one of Br+ and A 1. tE 1
+, T I). Ce*T+n+Dy+Pr+Ho+Nd+Er+SI+
+T I + represents at least one of Mn and S n. Further, x and y are numbers that satisfy the condition 0<x≦6.0≦y≦1. ), a phosphor represented by the general formula (I[I
) or [■] General formula (III) nReX-・m
AX' 2: xEu general formula (III' 3 nRe
X*・IIIAX' z: xEu, ysm (in the formula, Re
is at least one of La, Gd, Y, and Lu, A is an alkaline earth metal, and at least one of Ba, Sr, and Ca.
The species, X and vx' represent at least one of F, CI and Br. Moreover, X and y are IX 10−→<x<
3 Xl0-', I Xl0-1'<y<1 x
io-' is a number that satisfies the condition, n/+n is I
The following condition is satisfied: 10-'<n/Im<7×10-'. ), and 1 general formula % formula %: (However, Mx is at least one kind of alkali metal selected from Li, Na, Rb, and Cs, and Ml is B
e v M g r Ca T S r , B a
r Z n + At least one divalent metal selected from Cd, Cu, and Ni. M” is Sc, Y, L
a, Ce, Pr, Nd, P+a, S+n, Eu, Gd,
Tb. At least one divalent metal selected from DytHo+Er, Tm+Yb, Lu+ALGa+, and In. 'v'V'RttV'' I-)
T':"/"I n +'Rjr
T! %/-: %I4' is at least one kind of halogen. A1. tEu. T btCe+T+a+Dy+Pr+Ho, Nd+Yb
tEr+Gd, Lu. s III+Y t'r' ltN atA g+c
It is at least one metal selected from u and M8. Also, al is a numerical value in the range of tO≦a<0.5, and b is O
A numerical value in the range of ≦b<0.5, and C is 0<c≦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 photostimulated phosphor layers by methods such as vacuum evaporation and sputtering. However, the stimulable phosphor included in the radiation image conversion panel of the present invention is not limited to the above-mentioned phosphor, and can emit stimulated luminescence when irradiated with radiation and then irradiated with stimulable excitation light. Any phosphor may be used as long as it shows the phosphor. The radiation image conversion panel of the present invention may have a stimulable phosphor layer group consisting of one or more stimulable phosphor layers containing at least -m of the above-mentioned stimulable phosphors. . Furthermore, the stimulable phosphors contained in each stimulable phosphor layer may be the same or different. In the radiation image conversion panel of the present invention, various polymeric materials, glass metals, etc. are used as the support. In particular, materials that can be processed into flexible sheets or webs are suitable for handling as information recording materials.
From this point of view, for example, plastic films such as cellulose acetate film, polyester film, polyethylene terephthalate film, polyamide film, polyimide film, triacetate film, and polycarbonate film, metal sheets such as aluminum, iron, copper, and chromium, or coatings of the metal oxides. Metal sheets with layers are preferred. The layer of these supports varies depending on the material of the support used, but generally has a thickness of 80μI11 to 1000μ, more preferably 80μ+ from the viewpoint of handling.
a-500 μm. In the radiation image conversion panel of the present invention, a protective layer for physically or chemically protecting the stimulable phosphor layer group is generally provided on the surface where the stimulable phosphor layer is exposed. is preferred. This protective layer may be formed by directly coating the protective layer coating liquid on the stimulable phosphor layer, or by adhering a separately formed protective layer on the stimulable phosphor layer. Good too. Materials for the protective layer include cellulose acetate, nitrocellulose, and polymethyl methacrylate. Polyvinyl butyral, polyvinyl formal, polycarbonate, polyester, polyethylene terephthalate, polyethylene, polypropylene 1. Polyvinylidene chloride, nylon, polytetra7-ethylene chloride, polytetra7-ethylene chloride, tetra7-ethylene propylene hexafluoride copolymer, vinylidene chloride-vinyl chloride copolymer,
A material for the protective layer such as vinylidene chloride-acrylonitrile copolymer is used. In addition, this protective layer can be formed by vacuum evaporation, sputtering, etc.
S iC, S io 2. It may also be formed by stacking inorganic materials such as SiN and A1203. Next, the vapor phase deposition method of the stimulable phosphor layer will be explained. The first method is a vapor deposition method in an inert gas atmosphere. In this method, the support is first placed in a vapor deposition apparatus, and then the inside of the apparatus is evacuated to a degree of vacuum of about 10-' Torr. Next, the heating temperature is 300 to 500° using a heater for heating the support.
After cleaning the surface of the support by heating it to C, the temperature of the support is set at 100 to 200C, preferably around 150C, and an inert gas is introduced to raise the pressure to I x 10-'Torr.
The degree of vacuum should be as low as possible. Examples of the inert gas include helium gas, nitrogen gas, argon gas, and argon gas is particularly preferred. Next, electricity is applied to the boat or crucible, and the stimulable phosphor, such as the rubinium bromide phosphor using thallium as an activator, in the boat or crucible is evaporated by a resistance heating method. Then, the stimulable phosphor is deposited on the support and at the same time crystals grow, forming columnar crystals in a direction perpendicular to the surface of the support. At this time, due to adsorption of atmospheric gas, the crystal planes where crystal growth is promoted and the planes where crystal growth is suppressed during the vapor deposition process are defined as 71-
Follow. ICI Z juice π to γ1'' of f, 7 becomes more pronounced as the Z pressure increases. The surface where crystal growth is promoted becomes increasingly r&shy; in the direction to which evaporated molecules or atoms attach. In this way, a stimulable phosphor layer is deposited on the support, and at this time, a large number of fine voids are formed in the stimulable phosphor layer, extending approximately perpendicularly to the surface of the support. be done. In the vapor deposition process, it is also possible to perform co-evaporation using a plurality of resistance heaters or electron beams. 7! After the deposition is completed, a protective layer is preferably provided on the side of the stimulable phosphor layer opposite to the support, if necessary, to produce the radiation image conversion panel of the present invention. Incidentally, after forming the Xl1lF phosphor layer on the protective layer, the support may be provided. In addition, in the vapor deposition method in an inert gas atmosphere, the stimulable phosphor raw material is codeposited using a plurality of resistance heaters or an electron beam, and the desired stimulable phosphor is synthesized on the support. It is also possible to form a stimulable phosphor layer at the same time. Furthermore, in the vacuum evaporation method, the stimulable phosphor layer may be heat-treated after the evaporation is completed. A second method is a sputtering method. In this method, as in the vapor deposition method, after the support is placed in a Svantai apparatus, the inside of the apparatus is once evacuated to a vacuum level of about 10-6 Torr, and then an inert gas such as Ar or He is used as a sputtering gas. Gas is introduced into the sputtering apparatus and the gas pressure is set to about 10-'Torr. In this case, Ar gas is particularly preferred. Next, the support is heated to 100 to 200°C, preferably around 150°C, and a stimulable phosphor, such as rubidium bromide with thallium as an inactivator, is sputtered as a tarded material in a direction substantially perpendicular to the surface of the support. It is possible to form a stimulable phosphor layer having a large number of fine voids extending over the entire length. In the sputtering process, it is possible to form the stimulable phosphor layer in multiple steps, similar to the vapor deposition method in an inert gas atmosphere, and it is also possible to form a stimulable phosphor layer in multiple stages, each consisting of a different stimulable phosphor layer. using, simultaneously or sequentially,
It is also possible to form a stimulable phosphor layer by sputtering the tarded material. After the sputtering is completed, a protective layer is preferably provided on the opposite side of the stimulable phosphor layer from the support side if necessary, as in the case of vapor deposition in an inert gas atmosphere. Manufactured. Note that a step may be taken in which the support is provided after forming the stimulable phosphor layer on the protective layer. In the above-mentioned sputtering method, a plurality of stimulable phosphor raw materials are used in a tarded manner and are sputtered/talled simultaneously or sequentially to synthesize the desired stimulable phosphor on a support and at the same time stimulable phosphor. It is also possible to form a phosphor layer. In addition, in the sputtering method, if necessary,
2. Reactive sputtering may be performed by introducing a gas such as T-12. Furthermore, in the sputtering method, the stimulable phosphor layer may be heat-treated after sputtering, if necessary. The CVD method is one such method. This method involves decomposing a target photostimulable phosphor or an organometallic compound containing a photostimulable phosphor raw material with energy such as heat or high-frequency power, thereby producing a photostimulable material on a support that does not contain a binder. Obtain a fluorescent phosphor layer. In addition, if the columnar block groove formation method described in Japanese Patent Application Nos. 59-266912 to 268916 is used in combination, a photostimulable structure having both a fine columnar block structure and fine voids as shown in FIG. A phosphor layer can be formed. ! @Figure 3 (,) shows the relationship between the stimulable phosphor layer of the radiation image conversion panel of the present invention obtained by vapor deposition method and the radiation sensitivity and the stimulable phosphor deposition amount corresponding to the layer thickness. represents an example. Since the stimulable phosphor layer produced by the vapor deposition method according to the present invention does not contain a binder, the adhesion resistance (filling rate) of the stimulable phosphor is lower than that of conventional stimulable phosphor. The amount of radiation absorption per unit thickness of the stimulable phosphor layer is about twice that of the stimulable phosphor layer, which not only improves the radiation absorption rate per unit thickness of the stimulable phosphor layer, resulting in high sensitivity to radiation, but also improves the graininess of the image. Furthermore, the stimulable phosphor layer produced by the vapor phase deposition method has excellent transparency, and has high permeability to stimulable excitation light and stimulable excitation light, and is superior to the conventional stimulable β phosphor layer formed in the form of a coating. It can be made thicker and more sensitive to radiation. An example of the sharpness of the panel of the present invention having a stimulable phosphor layer having fine voids obtained as described above is shown in FIG.
+3) is indicated by 31. The panel of the present invention is disclosed in Japanese Patent Application Nos. 59-2136912-26.
The structure of +1 is finer than the fine columnar pronk structure described in US Pat. As is clear from the comparison with 32 in Figure 3 (1), which shows the characteristics of the tile-like drawing designated in No. 2G6914, the sharpness of the image is improved and the layer of stimulable phosphor is It is possible to further improve sharpness as the thickness increases. 33 in FIG. 3 shows the characteristics of a conventional panel obtained by dispersing and coating stimulable phosphor particles in a binder. This clearly shows that the image sharpness is excellent. The radiographic image conversion panel of the present invention provides excellent sharpness, granularity and sensitivity when used in the radiographic image conversion method shown schematically in FIG. That is, in the f:rSJ diagram, 41 is a radiation generating device, 42 is a subject, 43 is a radiation image conversion panel of the present invention, 44 is a photostimulation excitation light source,
45 is a photoelectric conversion device that detects the stimulated luminescence emitted from the radiation image conversion panel; 46 is a device that reproduces the signal detected by 45 as an image; 47 is a device that displays the reproduced image; It is a filter that separates excitation light and stimulated luminescence and allows only stimulated luminescence to pass through. It should be noted that the elements after 45 may be of any type as long as they can reproduce the optical information from 43 as an image in some form, and are not limited to the above. As shown in FIG. 14, the radiation from the radiation generating device 41 enters the radiation image conversion panel 43 of the present invention through the subject 42. This incident radiation is absorbed by the stimulable phosphor layer of the panel 43, and its energy is accumulated to form an accumulated radiation transmission image. Next, this accumulated image is exposed to f! from the excitation light source 44 for 1ft. l[excited with excited light and emitted as stimulated luminescence. In the radiation image conversion panel 43 of the present invention, since the main layer containing the XIII stimulable fluorophore has f@ type voids, when the stimulable excitation light is scanned by the stimulable excitation light, the stimulable excitation light fluoresces the stimulable fluorescence. Diffusion within the body layers 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 45 such as a photomultiplier tube, and an image reproduction device 46
By reproducing the image as an image and displaying it on the image display device 47, a radiographic image of the subject can be observed. rExample] Next, the present invention will be described with reference to Examples. Example 1 An aluminum plate with a thickness of 0.5+n+n was used as a support and placed in a vapor deposition apparatus. Next, put RI)Br:o, o04T Q into a molybdenum crucible for resistance heating, set it on the electrode for resistance heating, then evacuate the evaporator and
The degree of vacuum was set at 0-' Torr. Next, the surface of the support was heated to 300 to 500°C using a heater for heating the support, and then the support was placed at 150°C, and fulgon gas was introduced to create a vacuum of about I x 10" Torr. Next, the stimulable phosphor RbB r:o,o04TQ was evaporated by a resistance heating method so that the layer thickness of the stimulable phosphor layer was approximately 250 mm.
A radiation image conversion panel A of the present invention having fine voids with a porosity of about 20% was obtained. The panel A of the present invention thus obtained had a tube voltage of 80
After irradiating K V p) This signal was reproduced as an image by an image reproducing device and recorded on a silver halide film.The sensitivity of the radiation image conversion panel A to X-rays was determined from the magnitude of the signal, and from the obtained image. , the modulation transfer function (M T F ) and graininess of the image were investigated and shown in Table 1. 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 set as 100. In addition, the modulation transfer function (MTF) is the value when the spatial frequency is 2 cycles/■.Example 2゜A 0.5 mm thick aluminum plate was used as the support.
%a a Solu 1 Naka Te 4'J 211. ? Between, I A
/dm2-1ffl Ml After forming an anodic oxide film layer on one side of the aluminum plate, it was heated in boiling water for about 1 hour.
A time-opening hole treatment was performed, and a heat treatment was further performed at 400° C. to produce a support having a surface structure in which tile-like plates were laid out separated by fine gaps. Next, the support was placed during vapor deposition, and RbBr r:o, o04T'l was vapor-deposited by the same vapor deposition method as in Example 1, so that the layer thickness of the stimulable phosphor layer was about 250 μlfi and the porosity was Panel B of the present invention was obtained, which had both a fine columnar block structure of approximately 20% and fine voids. Panel B of the present invention was evaluated in the same manner as in Example 1, and the results are also listed in Table 1. Comparative Example 1 Stimulable phosphor RbBr: 8 parts by weight of 0.004T, 1 part by weight of polyvinyl butyral resin, and 5 parts by weight of a solvent (cyclohexanone) were mixed and dispersed to form a coating solution for a stimulable phosphor layer. adjusted. Next, this coating liquid was placed horizontally for 30 minutes.
It was uniformly coated on a black polyethylene terephthalate film as a support with a thickness of 0μI11 and air-dried to form a t+lI exhaustible fluorescent phosphor layer with a thickness of 250μτ0. The comparative panel P thus obtained was evaluated in the same manner as in Example 1, and the results are also listed in Table P1&1. Table 1 As is clear from Table 1, the radiation image conversion panels A and B of the present invention are
The i-sensitivity was approximately twice as high, and the image graininess was excellent. This is because the radiation image conversion panel of the present invention does not contain a binder in the stimulable phosphor layer and has a higher absorption rate of stimulable phosphor than a comparative panel when the filling rate of the stimulable phosphor is high <xm. It is. Furthermore, the radiation image conversion panel A%B of the present invention was superior in sharpness to the comparative radiation image conversion panel P despite having higher X-ray sensitivity. Is this the stimulable phosphor layer of the radiation image conversion panel of the present invention? This is because, since it has a large number of Itm voids, scattering of the semiconductor laser, which is the stimulable excitation light, in the stimulable phosphor layer is reduced. Effects of the Invention As described above, according to the present invention, the stimulable phosphor layer has a large number of fine voids, so that the Asahiko II stimulable phosphor layer of stimulable rljJ luminescence is disrupted. As a result, the sharpness of the image can be improved. In addition, according to the present invention, the decrease in image sharpness due to an increase in the thickness of the stimulable phosphor layer is small. It is possible to improve sensitivity. In addition, according to the present invention, the decrease in image sharpness due to an increase in the thickness of the stimulable phosphor layer is small. It is possible to improve the graininess of. Further, according to the present invention, it is possible to stably manufacture the radiation image conversion panel of the present invention at low cost. The present invention has extremely great effects and is industrially useful.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a part of a radiation image conversion panel according to an example of the present invention. FIG. 2 is a sectional view showing a part of a radiation image conversion panel according to another example of the present invention. Third
Figure (a) is a diagram showing the amount of 1!11-exhaustive fluorescent fluorescence and radiation sensitivity in a radiation image conversion panel according to an example of the present invention, and (b) is a diagram showing spatial frequency and modulation transmission. 11 is a diagram showing the relationship with JWL (MTF). FIG. 4 is a schematic diagram of a radiation #I image conversion device in which the panel of the present invention is used. MS5 diagram (a) is a diagram showing the stimulable phosphor layer in the conventional radiation image conversion panel, its adhesion amount, and sensitivity to radiation, and (b) is a diagram showing the stimulable phosphor layer in the conventional radiation image conversion panel. FIG. 3 is a diagram showing the layer thickness and adhesion amount and the modulation transfer function (MTF) at a spatial frequency of 2 cycles/man. 11...Support 12...Stimulable phosphor layer 13...Void 14...Protective layer 21...Support 22. ... Stimulable phosphor layer 23 having one fine columnar block ... Void 24 ... Maintenance? A layer 31...Characteristics of the radiation image conversion panel of the present invention 32...Characteristics of the radiation image conversion panel having a fine columnar block structure 33...Conventional radiation image conversion Panel characteristics 4
1...Radiation generating device 42...Subject 43...Radiation image conversion panel 44...
・Photostimulation excitation light source 45...Photoelectric conversion device 46...Image reproduction device 47...Image display device 48...Filter applicant Konishiroku Photo Industry Co., Ltd. Company Figure 1 Figure 2 Figure 3 'RPAll 5LS ri: (Denmachi Shi'ry+rn) 4th
figure

Claims (1)

[Claims] A radiation image conversion panel having at least a stimulable phosphor layer on a support, characterized in that fine voids are provided in the stimulable phosphor layer so that the porosity is 3 to 30%. Radiographic image conversion panel.