JPH01269100A - Radiograph converting panel - Google Patents

Abstract

PURPOSE:To hold the characteristic of a stimulable phosphor layer which has been formed by a vapor accumulating method and to improve the durability by providing an insulating member which has decreased continuously film thickness of the peripheral edge part of the stimulable phosphor layer, or has decreased continuously thickness of the peripheral edge part. CONSTITUTION:As for a stimulable phosphor layer 12, film thickness of a peripheral edge part 12' decreases continuously, and a form of this decrease is, for instance, like a straight face inclination or a concave face inclination. As for a method for forming this peripheral edge part 12', for instance, the phosphor layer 12 is formed on a supporting body 11, and thereafter, brought to chamfering. Also, as a method for forming in a formed layer, a supporting body holder 13 is provided with a projecting piece 16 for controlling partially a vapor flow 15 from an evaporation source, on the lower side of a shelf part 14 for placing the peripheral edge of the supporting body 11, and in a part of a shadow of this projection piece 16, the vapor flow 15 which has turned in from an opening end 16' is accumulated. Accordingly, the accumulation quantity of an inner wall 16'' side becomes small against the opening end 16', and layer thickness decreases continuously. In such a way, while holding the characteristic of the stimulable phosphor layer which has been formed by a vapor accumulating method, the durability can be improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a radiation image conversion panel using a stimulable phosphor, and more specifically to a radiation image conversion panel that is highly durable and capable of providing high-quality radiation images. This relates to an image conversion panel.

[Conventional technology]

Radiographic images such as X-ray images are often used for disease diagnosis. In order to obtain this xNfA image, X-rays that have passed through the subject are irradiated onto a phosphor layer (phosphor screen) to generate visible light. A so-called radiographic photograph is used, which is a film made by irradiating and developing the film.

On the other hand, in recent years, a method has been devised to take out images directly from the phosphor layer without using a film coated with silver salt. In this method, the radiation transmitted through the subject is absorbed by a phosphor, and then this phosphor is excited with light or thermal energy, and the phosphor emits the radiation energy accumulated through the absorption as fluorescence. This is a method of detecting this fluorescence and creating an image.

Specifically, for example, U.S. Pat. No. 3,859,527 and Japanese Patent Application Laid-open No. 55-12144 disclose a radiation image conversion method using a stimulable phosphor and using visible light or infrared rays as stimulable excitation light. There is. These methods use 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 image each part of the object. A latent image (accumulated image) is created by accumulating radiation energy corresponding to the radiation transparency of
After that, by scanning this stimulable phosphor layer with stimulable excitation light, the radiation energy accumulated in each part is emitted and converted into light, and an image is created using optical signals depending on the strength of this light. It's something you get. This final image may be reproduced as a hard copy 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 (hereinafter, both are referred to as " It goes without saying that the image must have a high radiation sensitivity (referred to as "radiation sensitivity"), and the image must have good graininess and high sharpness.

However, in general, a radiation image conversion panel having a stimulable phosphor layer uses a dispersion containing a stimulable phosphor in particles with a particle size of about 1 μm to 30 μm and an organic binder as a support (or a protective layer). ), the packing density of the stimulable phosphor is low (filling rate 50%), and the layer thickness of the stimulable phosphor layer must be thick to achieve sufficiently high radiation sensitivity. I needed to.

On the other hand, in the radiation image conversion method, the image sharpness tends to be higher as the thickness of the stimulable phosphor layer of the radiation image conversion panel becomes thinner. , it was necessary to make the stimulable phosphor layer thinner.

Furthermore, the graininess of the image in the radiation image conversion method is determined by local fluctuations in the number of radiation quanta (quantum mottle) or structural disturbances in the stimulable phosphor layer of the radiation image conversion panel (structural mottle). Therefore, when the thickness of the stimulable phosphor layer becomes thinner, the number of radiation quanta absorbed by the stimulable phosphor layer decreases, resulting in an increase in quantum mottles, or structural disorder becomes apparent, resulting in an increase in structural mottles. This may cause 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 trends 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.

In view of the conflict between these characteristics, the present applicant proposed a radiation image conversion panel that does not contain a binder in the stimulable phosphor layer and a method for manufacturing the same in Japanese Patent Application No. 73100/1982. There is.

According to this, the stimulable phosphor layer of the radiation image conversion panel is formed using a method such as vapor deposition and does not contain a binder, so the filling rate of the stimulable phosphor layer is significantly improved. At the same time, the directivity of stimulated excitation light and stimulated luminescence in the stimulable phosphor layer is improved, and the sensitivity of the radiation image conversion panel to radiation and image granularity are improved, as well as image sharpness. will also be improved.

The radiation image conversion panel used here stores radiation image information and then releases the stored energy by scanning with excitation light, so it can store radiation images again after scanning and can be used repeatedly. Therefore, it is natural that the radiation image conversion panel is desired to have high quality images, but it is also required to have performance that can withstand long-term use.

For this purpose, the stimulable layer in the radiation image conversion panel needs to be sufficiently protected from external physical or chemical stimulation.

In order to solve the above problems in conventional radiation image conversion panels, a method has been adopted in which a protective layer is provided to cover the surface of the stimulable phosphor layer on the support of the radiation image conversion panel. This protective layer is, for example, disclosed in Japanese Patent Application Laid-Open No. 59-42500.
As described in the above issue, a protective layer coating solution is directly applied onto the stimulable phosphor layer, or a protective layer formed separately in advance is adhered onto the stimulable phosphor layer. It is formed by

Generally, a thin protective layer made of an organic polymer is used, and this thin protective layer has the advantage that it hardly reduces the sharpness of the radiation image conversion panel. The relationship between the sharpness of a radiation image conversion panel having a stimulable phosphor layer and the thickness of the protective layer is shown in Table 1 using MTFs (modulation transfer functions) of spatial frequencies of 14ip/Yu and 2Jp/Yu.

Table 1 As shown in the table above, the thicker the protective layer, the lower the sharpness.

The reason for this is that the reflected and scattered incident stimulable excitation light on the surface of the stimulable phosphor layer is reflected at the protective layer-air interface.
One example is that the light enters the stimulable phosphor layer again.

The thicker the gt layer, the farther the reflected and scattered light will reach.
Information about pixels other than the target pixel is mixed in.

In the general-type multilayer film system used for X-ray photography, l/! MTF for p/am is about 65%, '1ll
In the case of p/am, it is about 35%, so it is not preferable for the radiation image conversion panel to be inferior to the value of the intensifying screen-film system. Therefore, the thickness of the protective layer should be 10 μm.
m or less is desirable.

[Problem to be solved by the invention]

However, although the stimulable phosphor layer formed on the support by the vapor deposition method has many excellent features as mentioned above, the stimulable phosphor layer is Since the stimulable phosphor layer has a columnar structure extending in a substantially vertical direction, the peripheral edge of the stimulable phosphor layer is steep. Therefore, in the radiation image conversion panel obtained by the vapor deposition method, cracks are likely to occur at the peripheral edge of the protective layer, resulting in significantly accelerated deterioration. In addition, since the stimulable phosphor layer had no flexibility, it became brittle against stress, and in particular, the peripheral edge part became easily separated from the support.

This invention is intended to solve the above-mentioned problems, and while maintaining the excellent image quality characteristics of the stimulable phosphor layer formed by the vapor deposition method, it is possible to reduce the durability caused by the vapor deposition method. The object of the present invention is to provide a radiation image conversion panel that eliminates surface defects. Another object of the present invention is to provide a radiation image conversion panel in which the stimulable phosphor layer is not damaged due to peeling or the like.

Means for Solving Problem C] In order to achieve the above object, the present invention provides a radiation image conversion panel in which a stimulable phosphor layer is formed on a support by a vapor phase deposition method. The durability can be improved by continuously decreasing the thickness of the peripheral edge of the layer or by providing an edge member with a continuously decreasing thickness at the peripheral edge of the stimulable phosphor layer. It is composed of

Next, this invention will be specifically explained.

FIG. 1 is a sectional view showing a portion of the peripheral edge of the radiation image conversion panel (sometimes simply referred to as conversion panel) of the present invention in the thickness direction. In the figure, 11 is a support;
12 is a stimulable phosphor layer formed on the support 11.

This stimulable phosphor layer 12 has a peripheral edge 12' whose thickness is continuously decreased (gradually thinner/sloped toward the outside). This decreasing form can be seen in the face-sloping form as shown in Fig. 1 (a), the concave-sloping form as shown in Fig. 1 (b), the convex-sloping form as shown in Fig. 1 (C), and the wave surface as shown in Fig. 1 (d). It may be inclined.Of course, (a) to (dl) show typical examples of the reduction form of the peripheral edge portion 12', and the present invention is not limited to this.

The shape of the peripheral edge portion 12' may be formed in post-processing after the stimulable phosphor layer 12 is layered on the support 11, or may be formed during layering. Examples of the former post-processing include a chamfering method and a method of locally heating and melting the edges. As the heating method, heating using a gas laser is preferable. As the latter method, for example, there is a method using a support holder 13 shown in FIG. That is, this support holder 13 has a protrusion 16 on the underside of a shelf 14 on which the periphery of the support 11 is placed, which partially regulates the vapor flow (arrow) 15 from an evaporation source (not shown).
The steam flow 16 that has come around from the open end 16' is deposited in the shaded area of the protrusion 16. Therefore,
Back wall (outward side of support body) 16# with respect to open end 16'
Naturally, the amount of deposition on the sides decreases, and the layer thickness decreases continuously. In this case, the area around the stimulable phosphor layer 12 as shown in FIG. It becomes possible to form the portion 12'.

The rate of decrease of the peripheral edge portion 12' is not particularly limited, but from the perspective of the purpose of the present invention, it is better to have a gentle slope rather than an excessively steep slope. However, if the slope is too smooth, the effective area of the stimulable phosphor layer 12 for obtaining an image becomes narrow, which is undesirable.

From this, if the thickness of the stimulable phosphor is (1) and the range (length) where the thickness is reduced is (X), then x/l should be set as 0.1 to 100. It is preferable that 0.5
It is more preferable if it is 50.

In the above example, the area of the stimulable phosphor layer 12 is smaller than that of the support 11, but it goes without saying that the area may be the same.

Further, although the stimulable phosphor layer 12 is formed by a vapor deposition method, an adhesive may be added between the support 11 and the stimulable phosphor layer 12 to improve adhesion as necessary. A reflective layer or an absorbing layer for stimulated excitation light and/or stimulated luminescence may be provided. Methods for growing the stimulable phosphor using the vapor deposition method include vapor deposition, sputtering, and CVD. In the vapor deposition method, after the support is placed in a vapor deposition apparatus, the apparatus is evacuated to a vacuum level of about 10-' Torr, and then the stimulable phosphor is heated and evaporated using a resistance heating method, an electron beam method, etc. It is deposited on the surface of the support to a desired thickness, forming a stimulable phosphor layer that does not contain a binder. In the sputtering method, like the vapor deposition method, the support is placed in a sputtering device, and then the inside of the device is evacuated to a vacuum level of about 10-” Torr, and then an inert gas such as Ar or Ne is used as the sputtering gas. is introduced into a sputtering device to a gas pressure of about 10-' Torr, and the stimulable phosphor is deposited on the surface of the support by sputtering, using the stimulable phosphor as a target. Alternatively, it is a method of obtaining a binder-free stimulable phosphor layer on a support by decomposing an organometallic compound containing a stimulable phosphor raw material with energy such as heat or frequency electric power. .

FIG. 3 is a sectional view showing a radiation image conversion panel in which an edge member whose thickness is continuously reduced is provided at the peripheral edge of the stimulable phosphor layer. In the figure, 31 is a stimulable phosphor layer, 32
is a support body, and 33 is an edge member. As the edge member 33,
Even if after forming the stimulable phosphor layer 31 as shown in FIG. Even if an edge member 33 formed in advance using a radiation-curable resin or a glass material is fitted and fixed to the end of the stimulable phosphor layer 31 and the triangular part of the support body 32 as shown in the figure (false), Support 3 as shown in the same figure (C)
Even if the edge member 33 is formed by raising a part of 2,
As shown in FIG. 33 may be formed.

The above-mentioned "stimulable phosphor" refers to the first stimulable phosphor that is stimulated by a priori, thermal, mechanical, chemical, electrical, etc. (stimulable excitation) 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 light or high-energy radiation, and from a practical point of view, preferably 5
It is a phosphor that exhibits stimulated luminescence by stimulated excitation light of 00 nm or more.

As the stimulable phosphor used in the radiation image conversion panel of the present invention, for example, the phosphor represented by Ba5O, Ax described in JP-A No. 48-80487,
MgSO4 described in JP-A-48-80488: Phosphor represented by Ax, SrSO4 described in JP-A-48-80489: Phosphor represented by AX, JP-A-Sho 5
Na1SO, , C described in No. 1-29889
Phosphor containing at least one of Mn, Dy and Tb added to aSO4, Ba5O, etc., JP-A-52-30
Bear LiF+ Mg5 described in No. 487
Phosphors such as Oa and CaF, JP-A-53-39277
Li2B4O7:Cu, Ag phosphor described in JP-A-54-47883;
zO・(B*0t)x: Cu and LizO・(Bz
(h) x: phosphor such as Cu, Ag, 5rS=Cel described in US Pat.
S11, SrS: Eu, Sea, t, a, Oz
S: Eu, S11 and (Zn, Cd) S: M
Examples include phosphors represented by n and x. Also, JP-A-5
ZnS described in No. 5-12142:Cu,
Pb phosphor, the general formula is BaO.xAl□0. : Eu
A barium aluminate phosphor represented by the following formula and an alkaline earth metal silicate phosphor represented by the general formula MIO.xsioz :A are mentioned.

Furthermore, the general formula described in JP-A-55-12143 is (Ba+-x-yMg x Cay) FX:
Alkaline earth fluorohalide phosphor represented by "Eu", phosphor whose general formula is LnOX:xA described in JP-A-55-12144, JP-A-55-1
The general formula described in No. 2145 is (Ba+-xMI
x) FX i yA phosphor, the general formula described in JP-A-55-84389 is BaFX
: Phosphor expressed by xCe, yA, Japanese Patent Application Laid-open No. 1987-
The general formula described in No. 160078 is M"FX-
xA: Rare earth element activated divalent metal fluorohalide phosphor represented by yLn, general formula is ZnS: 8CdS
: A, (Zn, Cd)S : A, X and Cds;
A, X Te expressed phosphor, JP-A-59-38278
A phosphor represented by any of the following general formulas % formula % described in the No. 1987-155487, a phosphor represented by any of the following general formulas % formula % described in JP-A-59-155487 , an alkali halide phosphor represented by the following general formula % formula % described in JP-A-61-72087, and JP-A-61-72087.
General 2 M'X described in No. 228400: x
Examples include bismuth-activated alkali halide phosphor represented by Bi.

In particular, alkali halide phosphors are preferred because they facilitate the formation of a stimulable phosphor layer by methods such as vapor deposition and sputtering.

However, it is used in the radiation image conversion panel of this invention. The stimulable phosphor is not limited to the above-mentioned phosphors, but can be any phosphor that exhibits stimulated luminescence when irradiated with radiation and then irradiated with stimulable excitation light. good.

The layer thickness of the phosphor in the panel according to the present invention varies depending on the radiation sensitivity of the intended conversion panel, the type of stimulable phosphor, etc., but is selected from the range of 1 μm to 1000 μm, more preferably from 20 μm to 800 μm. is preferable.

The support is preferably a ceramic plate such as alumina, a glass plate such as chemically strengthened glass or crystallized glass, a metal plate such as aluminum, iron, copper, or chromium, or a metal plate having a coating layer of the metal oxide. However, it may also be a plastic film such as a polyester film, a polyethylene terephthalate film, or a polycarbonate film. The support is not limited to one layer, and may have a multilayer structure of two or more layers.

The layer thickness of these supports varies depending on the material of the support used, but is generally 80 μm to 3000 μm, and more preferably 80 μm from the viewpoint of handling.
~1000 μm. The surface of these supports may be a smooth surface, or may be a matte surface for the purpose of improving adhesion with the stimulable phosphor layer, or the surface of the support may be an uneven surface. It may also be a surface structure in which individual micro tile-like plates are closely arranged.

The vitreous material used as the protective layer 34 covering the stimulable phosphor layer 12 or the edge member 33 at the periphery of the stimulable phosphor layer 12 is selected from the following: Materials with excellent moisture resistance are preferred. Examples of glass materials that meet this requirement include oxide glass materials. That is, examples include silicate glass, phosphate glass, and borate glass, with silicate glass being particularly preferred. Specifically, quartz glass (SiOl), lead silicate glass (Pb
O・5iOt), lead borate glass (PbO-8!03・S
iO, zinc borate glass (ZnO・Bt03・5iO2
), aluminosilicate glass (A i gos Sta
g), alumino-lime silicate glass (CaO・AJ zo
s・Stow), calcium silicate glass (CaO
・Btus ・Stow), etc. In addition, the amount of CaO composition, Na
Addition of zO may be performed to lower the melting point. Moreover, the particle size of the glass powder is preferably 1-100 μm.

Furthermore, the peripheral portion 1 of the protective layer 34 or the stimulable phosphor layer 12
Examples of the organic polymer used as the edge member 33 of 2 include cellulose derivatives such as cellulose acetate, nitrocellulose, and ethylcellulose, or polymethyl methacrylate, polyvinyl butyral, polyvinyl formal, polycarbonate, polyvinyl acetate, polyacrylonitrile, and polymethyl. Allyl alcohol, polymethyl vinyl ketone, cellulose diacetate, cellulose triacetate, polyvinyl alcohol, polyacrylic acid,
Polymethacrylic acid, polyglycine, polyacrylamide, polyvinylpyrrolidone, polyvinylamine, polyethylene terephthalate, polyethylene, polyvinylidene chloride, polyvinyl chloride, polyamide (nylon), polytetrafluoroethylene, polytrifluoroethylene chloride, polypropylene, Examples include tetrafluoroethylene-hexafluoropropylene copolymer, polyvinyl isobutyl ether, and polystyrene.

Furthermore, the peripheral portion 1 of the protective layer 34 or the stimulable phosphor layer 12
The radiation-curable resin used as the edge member 33 of No. 2 may be any compound having an unsaturated double bond or a composition containing the same, and such a compound preferably has two or more unsaturated double bonds. These are prepolymers and/or oligomers, and can further contain a monomer (vinyl monomer) having an unsaturated double bond as a reactive diluent.

〔Example〕

Next, the present invention will be explained by examples.

◎Example (1) A crystallized glass support having a thickness of 1 fl is placed on a holder as shown in FIG. 2, and this is set in a vapor deposition apparatus.

Next, alkali halide stimulable phosphor (RbBr; 0.0O06Tl) was placed in a tungsten boat for resistance heating.
) and set it on the resistance heating electrode, the vapor deposition apparatus is evacuated to a vacuum degree of 2 x 10-'Torr.

Next, a current was applied to the tungsten boat to evaporate the stimulable phosphor by a resistance heating method, and a stimulable phosphor layer was deposited on the crystallized glass plate to a thickness of 300 μm.

As a result, a panel material in which the wall thickness of the peripheral portion gradually decreased in a wavy shape as shown in FIG. Panel A of the present application was manufactured by vacuum sealing and forming a protective layer using the method described in Japanese Patent No. 220492.

◎Example (2) A crystallized glass support with a thickness of one dragon was set in a vapor deposition apparatus,
Similarly to Example (1), an alkali halide stimulable phosphor (RbBr; 0
．． 0006T l) and set it on the resistance heating electrode, the evaporation apparatus was evacuated to a vacuum of 2 x 10-'Torr, a current was passed through the tungsten boat, and the stimulable phosphor was evaporated by the resistance heating method. A stimulable phosphor layer was deposited on the crystallized glass plate to a thickness of 300 μm.

Next, lead borate glass (Pb
O・B20.・SiO□) was installed and this part was heat-treated for 60ml at 600°C to form lead borate glass at the end of the stimulable phosphor layer and the triangular part of the support, as shown in Figure 3 (al). A protective layer was formed on this panel base material in the same manner as in Example (1) to obtain Panel B of the present invention.

In the panels A and B of the present invention obtained in this way, the thickness of the stimulable phosphor layer at the peripheral edge of the stimulable phosphor layer is continuously reduced, so that the stimulable phosphor layer is Unlike conventional panels that have steep edges, there will be no damage such as cracks on the edges of the protective layer or destruction of the phosphor layer, and the panel will not deteriorate over a long period of time. There was found.

〔Effect of the invention〕

As described above, the present invention provides a radiation image conversion panel in which a stimulable phosphor layer is formed on a support by a vapor deposition method, in which the thickness of the stimulable phosphor layer at the peripheral portion is continuously reduced. Moreover, since the stimulable phosphor layer is characterized by having an edge member whose thickness is continuously reduced at the periphery, the characteristics of the stimulable phosphor layer formed by the vapor deposition method are improved. This has the excellent effect of improving durability while retaining the same properties, and thus providing a panel that can be used for a long period of time.

[Brief explanation of the drawing]

1(a) to fdl are sectional views of a radiation image conversion panel of the present invention, FIG. 2 is a sectional view of a molding device, and FIG. 3 is a sectional view of another example of the present invention. 11, 22. 32-Support 12, 24. 31 - Stimulable phosphor layer 12' - Peripheral part 13 - Support holder 14 - Shelf part 15 - Vapor flow 16 - Projection Figure 1 Figure 2 Figure 3 (C) (b)

Claims (2)

[Claims] (1) A radiation image conversion panel in which a stimulable phosphor layer is formed on a support by a vapor deposition method, characterized in that the film thickness of the periphery of the stimulable phosphor layer is continuously reduced. A radiographic image conversion panel. (2) In a radiation image conversion panel in which a stimulable phosphor layer is formed on a support by a vapor deposition method, an edge member whose thickness is continuously reduced at the periphery of the stimulable phosphor layer. A radiation image conversion panel characterized by being provided with.