JP2004003939A - Phosphor screen without binder on support colored with pigment mixture - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To acquire a sharp and non-blurring image by high-speed recording. <P>SOLUTION: This stimulative phosphor screen without a binder includes a phosphor layer having a needle-shaped phosphor crystal on a support absorbing at least 30% of stimulating light and reflecting at least 60% of stimulated light. The support may be a PET support including a mixture of blue and white pigments. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
The present invention relates to binderless storage phosphor screens having acicular phosphors.
[0002]
BACKGROUND OF THE INVENTION A well-known use of storage phosphors is in the production of x-ray images. US-A 3,585,527 discloses a method for producing an X-ray image with a photostimulable phosphor contained in a panel. The panel is exposed to receive an X-ray beam modulated according to the pattern, so that the phosphor temporarily stores the energy contained in the X-ray radiation pattern. At some interval after exposure, a beam of visible or infrared light scans the panel and stimulates the emission of stored energy as light. The light is detected and sequentially converted to an electrical signal, which is processed to produce a visible image. For this purpose, the phosphor should store as much of the incident X-ray energy as possible and emit as little as possible of the stored energy until stimulated by the scanning beam. This is referred to as "digital radiography" or "computer radiography".
[0003]
The image quality produced by any radiographic system that uses a phosphor screen, and thus by a digital radiographic system, is highly dependent on the configuration of the phosphor screen. In general, the thinner the phosphor screen at a given amount of x-ray absorption, the better the image quality.
[0004]
This means that the lower the ratio of binder to phosphor of a phosphor screen, the better the image quality that can be achieved with that screen. Thus, optimal sharpness can be obtained when a screen without any binder is used. Such a screen can be manufactured, for example, by physical vapor deposition of a phosphor material on a substrate, which may be thermal vapor deposition, sputtering, e-beam evaporation, and the like. However, this manufacturing method cannot be used to manufacture high quality screens with all available phosphors. The above manufacturing method leads to the best results when phosphor crystals with high crystal symmetry and simple chemical composition are used.
[0005]
The use of alkali metal halide phosphors in storage screens or panels is well known in the field of storage phosphor radiation, and the high crystal symmetry of these phosphors gives structured and binderless screens. be able to.
[0006]
When binderless screens with alkali halide phosphors are produced, it is beneficial to deposit the phosphor crystals as some types of piles, needles, tiles, and the like. U.S. Pat. No. 4,769,549 discloses that the image quality of a binderless phosphor screen can be improved when the phosphor layer has a block structure formed by narrow columns.
[0007]
U.S. Pat. No. 5,055,681 discloses a storage phosphor screen containing an alkali halide phosphor in a pile-like structure. The image quality of such a screen still needs to be improved, and JP-A 06/230198 discloses that the surface of a screen having columnar phosphors is rough and that leveling of the surface can improve sharpness. U.S. Pat. No. 5,874,744 focuses on the reflectivity of phosphors used to produce storage phosphor screens having needle or columnar phosphors.
[0008]
EP-A-111 458 describes a binderless storage phosphor screen comprising an alkali metal storage phosphor, said screen having a (100) diffusion line having an intensity I ₁₀₀ and a (110) diffusion line having an intensity I ₁₁₀ and A storage phosphor screen is disclosed which exhibits an XRD spectrum such that I ₁₀₀ / I ₁₁₀ ≧ 1. Such a phosphor screen shows a good compromise between speed and sharpness.
[0009]
All of the screens disclosed in this prior art are capable of producing X-ray images with good quality, but better between images with high sharpness and low noise and the speed of the recording system (ie the lowest possible patient dose). There is still a need for a great compromise.
[0010]
OBJECTS AND SUMMARY OF THE INVENTION It is an object of the present invention to provide stimulable phosphorescence useful in X-ray recording systems having a very good compromise between images with high sharpness and low noise and the speed of the recording system (ie, the lowest possible patient dose). Is to provide a body screen.
[0011]
The above objective is accomplished by providing a stimulable phosphor screen having the features defined in claim 1. Features for preferred embodiments of the invention are disclosed in the dependent claims.
[0012]
Further advantages and embodiments of the present invention will become apparent from the following description.
[0013]
DETAILED DESCRIPTION OF THE INVENTION In the field of storage screen manufacture where the storage phosphor is dispersed in a binder, it is known to color the screen to improve sharpness. For example, US-A 4,394,581 and US-A 4,491,736 disclose such screens. US-A 4,618,778 also discloses adding a reflective layer between the support and the layer containing the phosphor dispersed in a binder. U.S. Pat. Nos. 4,769,549 and 4,963,751 disclose storage phosphor screens having deposited phosphor layers without binder, in which such screens offer a very good compromise between speed and sharpness, sharpness and sharpness. It has been suggested that no special measures are required to further increase the compromise between speeds. Surprisingly, even binderless stimulable phosphor screens having deposited phosphors that exhibit high speed combined with high sharpness already absorb at least 30% of the stimulating light, It has now been found that a better speed / sharpness compromise can be achieved when including a support that reflects at least 60% of the stimulated light. Preferably, the support absorbs at least 75% of the stimulating light and reflects at least 75% of the stimulated light.
[0014]
“Evaporated phosphor” throughout this specification means a phosphor produced by any method selected from the group consisting of thermal evaporation, chemical vapor deposition, electron beam evaporation, radio frequency evaporation and pulsed laser evaporation. I do. This deposition is preferably carried out under the conditions as described in EP-A-111458.
[0015]
Preferred supports for the storage phosphor screen of the present invention are selected from the group consisting of ceramics, glass and polymer films. Among them, polymer films are most preferred. Particularly heat-stable polymer films having a thickness of 100 to 1000 [mu] m (such as, for example, polyethylene terephthalate and polyethylene naphthalate) are preferred as supports in the screen according to the invention. In order to achieve the desired absorption and reflection properties, the support used in the screens of the present invention is such that no special layers have to be coated on the support before the deposition of the acicular phosphor. Processed in bulk. The treatment of the bulk of the support preferably comprises the inclusion of a white pigment and a pigment that absorbs light of a wavelength of 600 nm or more in the bulk of the support. Useful white pigment is _{TiO 2, ZnS, Al 2 O} 3, MgO and BaSO ₄ for example, but not limited to them. TiO ₂ of anatase crystal type is preferred white pigment for use in a support for a phosphor screen according to the present invention. Useful blue pigments are, for example, ZAPON FAST BLUE 3G (manufactured by Hoechst AG.), ESTROL BRILL BLUE N-3RL (manufactured by Sumitomo Kagaku Co., Ltd.), and SUMIACRYL BLUE F-GSL (Sumigam. Manufacturing), D & C BLUE NO. 1 (manufactured by National Aniline Co., Ltd.), SPIRIT BLUE (manufactured by Hodogaya Kagaku Co., Ltd.), OIL BLUE NO. 603 (manufactured by Orient Co., Ltd.), KITON BLUE A (manufactured by Ciba Geigy AG.), AIZEN CATHILON BLUE GLH (manufactured by Hodoyaya Kagaku Co., Ltd.), LAKEBL. F. H. (Manufactured by Kyowa Sankyo Co., Ltd.), RODALIN BLUE 6GX (manufactured by Kyowa Sankyo Co., Ltd.), PRIMOCIANINE 6GX (manufactured by Inaha Sanyo Co., Ltd. LGBHgA.Rg.A., Ltd., LGA. Ltd.), CYANINE BLUE BNRS (manufactured by Toyo Ink Co., Ltd.), LIONOL BLUE SL (manufactured by Toyo Ink Co., Ltd.) and organic brands such as MACROLEX BLUE (Bayer AG, Levus of Bayer AG, etc.) Pigments, but not limited thereto.
[0016]
Inorganic coloring agent may be used in the radiation image storage panel of the present invention is ultramarine blue, cobalt blue, cerulean blue, chromium oxide, including pigment TiO ₂ -ZnO-CoO-NiO-based, but are not limited to. Commercially available, very useful blue and blue-green inorganic pigments are, for example, SICOCE A, SICOCERB, SICOCE E, SICOCE F, SICOCE G, SICOCE I, SICOCE P, SICOCE R, SICOCE S, SICO CER U (all BASF, Blue or blue-green pigments selected from the series (Ludwigshafe, sold by Germany).
[0017]
When the support for use in the storage phosphor screen of the present invention is glass, the glass particles or fibers are heated at a temperature high enough to melt them together in a manner sufficient to form a plate. It is preferred to use frit glass made by this. The surface of such a plate of frit glass is non-uniform and its profile depends on the diameter of the glass beads used to form the frit glass plate. Such non-uniformities in the support for depositing the phosphor are highly desirable. Because it helps to deposit the phosphor crystals in needle-like form. The pigments used in the bulk of the glass are preferably inorganic white and blue pigments in the present invention.
[0018]
The binderless phosphor screens according to the invention are prepared by vacuum deposition of phosphor crystals on a substrate as well as mixing the components for the phosphor (phosphor precursor), and then evaporating this mixture in situ during evaporation. It can be manufactured by forming a phosphor.
[0019]
It is further preferred according to the present invention to provide a binderless stimulable phosphor screen on a polymer film as a substrate, wherein said polymer film has an embossed surface to form a fine relief pattern.
[0020]
The phosphor in the binderless phosphor screen according to the present invention may be any known stimulable metal phosphor. Preferably, the storage phosphor used in the binderless phosphor screen of the present invention is an alkali metal phosphor.
[0021]
Highly suitable phosphors are, for example, phosphors according to formula I:
M ¹⁺ X. aM ²⁺ X ′ ₂ bM ³⁺ X ″ ₃ : cZ (I)
^Wherein M ¹⁺ is at least one element selected from the group consisting of Li, Na, K, Cs and Rb, and M ²⁺ is Be, Mg, Ca, Sr, Ba, Zn, Cd, Cu, Pb and At least one element selected from the group consisting of Ni, wherein M ³⁺ is Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Z is at least one element selected from the group consisting of Lu, Al, Bi, In and Ga, and Z is at least one element selected from the group consisting of Ga ¹⁺ , Ge ²⁺ , Sn ²⁺ , Sb ³⁺ and As ^3+. And X, X ′ and X ″ may be the same or different, each of which represents a halogen atom selected from the group consisting of F, Br, Cl, I, 0 ≦ a ≦ 1, 0 ≦ b ≦ 1 and 0 < ≦ 0.2. Such phosphors have been disclosed in US-A 5736069, for example.
[0022]
A highly preferred phosphor for use in the binderless phosphor screen of the present invention is a CsX: Eu stimulable phosphor, wherein X represents a halide selected from the group consisting of Br and Cl, wherein the phosphor is Is produced by a method comprising the following steps:
- EuX _{'2, EuX' 3} and EuOX '(where, X' is F, Cl, an element of one selected from the group consisting of Br and I) ¹⁰ of europium compound selected from the group consisting of ^-3 Mixing the CsX with ~ 5 mol%;
Burning the mixture at a temperature of 450 ° C. or higher;
-Cooling the mixture; and-recovering the CsX: Eu phosphor.
[0023]
Most preferably a CsBr: Eu stimulable phosphor prepared by a method comprising the following steps is used:
- EuX _{'2, EuX' 3} and EuOX '(where, X' is F, Cl, an element of one selected from the group consisting of Br and I) ¹⁰ of europium compound selected from the group consisting of ^-3 Mixing the CsX with ~ 5 mol%;
Burning the mixture at a temperature of 450 ° C. or higher;
-Cooling the mixture; and-recovering the CsX: Eu phosphor.
[0024]
A binderless screen is produced by bringing the finished phosphor onto a support by any method selected from the group consisting of thermal evaporation, chemical vapor deposition, electron beam evaporation, radio frequency evaporation and pulsed laser evaporation. Can be Alternatively, the alkali metal halide and dopant can be brought together and co-evaporated on a support in such a way that the alkali metal phosphor is doped during the manufacture of the screen.
[0025]
The present invention is a method of making a phosphor screen containing a CsX: Eu stimulable phosphor, wherein X represents a halide selected from the group consisting of Br and Cl, including a method comprising the following steps. Do:
- EuX _{'2, EuX' 3} and EuOX '(where, X' is F, Cl, a is selected halides from the group consisting of Br and I) Europium compound selected from the group consisting of and the number of CsX In a state of vapor deposition; and-doped with ^{10-3 to 5} mol% of europium by a method selected from the group consisting of thermal vapor deposition, chemical vapor deposition, electron beam vapor deposition, radio frequency vapor deposition and pulsed laser vapor deposition. Both the CsX and the europium compound are deposited on the substrate in a ratio such that the resulting CsX phosphor is formed on the substrate.
[0026]
The deposition can be performed from a single vessel containing the mixture of the starting compounds in the desired proportions. The method is a method of making a phosphor screen containing a CsX: Eu stimulable phosphor (where X represents a halide selected from the group consisting of Br and Cl), further comprising a method comprising the following steps. Do:
- EuX _{'2, EuX' 3} and EuOX '(where, X' is F, Cl, a is selected halides from the group consisting of Br and I) ^{10 -3} ~ europium compound selected from the group consisting of Mixing 5 mol% with the CsX;
-Bringing the mixture into a state of deposition; and-depositing the mixture on a substrate by a method selected from the group consisting of physical vapor deposition, thermal vapor deposition, chemical vapor deposition, electron beam vapor deposition, radio frequency vapor deposition and pulsed laser vapor deposition. .

Claims (6)

A binderless stimulable phosphor screen comprising a phosphor layer deposited on a support that absorbs at least 30% of the stimulating light and reflects at least 60% of the stimulated light. The binderless stimulable phosphor screen of claim 1, wherein said support is selected from the group consisting of ceramics, glass and polymer films. 3. The binderless stimulable phosphor screen of claim 2, wherein said support is a pigmented polymer film. The phosphor screen with no binding agent according to claim 2 polymer film is a PET film containing TiO ₂ and MACROLEX BLUE. 5. A binderless stimulable phosphor screen according to any of claims 1 to 4, wherein the deposited phosphor is a needle phosphor. A binderless stimulable phosphor screen according to any of claims 1 to 5, wherein the acicular phosphor crystals are alkali metal phosphor crystals.