JP2004251882A - Storage phosphor screen using no bonding agent equipped with support containing amorphous carbon layer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a support which is suitable for the evaporation of a phosphor layer and has high mechanical strength and low absorbency of transmitted radiation in a storage phosphor screen which includes a phosphor layer evaporated onto the support in a vacuum, and is free from a bonding agent. <P>SOLUTION: A support 2 includes an amorphous carbon (a-C) layer 23. As needed, the support 2 may further include one or more of a polymer assistance layer 24 which is placed farther away from the phosphor layer 1 than the amorphous carbon layer 23, a reflective assistance layer 25 placed between the amorphous carbon layer 23 and the phosphor layer 1 and a protective assistance layer 26 placed between the reflective assistance layer 25 and the phosphor layer 1. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００３９】
表１で得られた結果から、非晶質炭素（ａ−Ｃ）支持体は例えばＦｅ（たった１００μｍの層厚さに対してでなくても使用のために適さない）及びアルミニウム（１００μｍの薄い燐光体層に対して８００μｍまで使用に適する）と比較すると、ほとんど吸収を生じないので優れている：非晶質炭素は最も厚い燐光体層（１５０μｍ）であっても光度計の位置に十分な線量を与え、２０００μｍの厚さは使用のために完全に適している。非晶質炭素は図１に示されたようなガラスと匹敵しうるが、ガラスに対してより優れている。なぜならば非晶質炭素は本発明の燐光体パネル又はスクリーンの製造に適用されるのにずっと適しているからである。
【００４０】
本発明の好ましい例を詳細に記載したが、添付の特許請求の範囲に規定された発明の範囲から逸脱せずに多数の変更をその中でなしうることは当業者に明らかであろう。
【図面の簡単な説明】
【００４１】
【図１】本発明の貯蔵燐光体パネル又はスクリーンの一例を概略的に示す。
【図２】本発明の貯蔵燐光体パネル又はスクリーンのさらなる例を概略的に示す。
【図３】本発明の貯蔵燐光体パネル又はスクリーンの他例を概略的に示す。[0001]
FIELD OF THE INVENTION The present invention relates to binderless phosphor screens having a support comprising an amorphous carbon (a-C) layer.
[0002]
BACKGROUND OF THE INVENTION A well-known application of phosphors is in the production of X-ray images. In conventional radiographic systems, radiographs are obtained by x-rays that have passed image-wise through an object and have been converted in a so-called intensifying screen (X-ray conversion screen) into light of a corresponding intensity, where the phosphor particles are Absorbs transmitted X-rays and converts them into visible and / or ultraviolet light, which photographic films are more sensitive to direct X-ray impact.
[0003]
According to another method of recording and reproducing X-ray patterns, described for example in US-A 3,585,527, a special type of phosphor known as photostimulable phosphor is used, which is mixed into a panel or screen, Exposure to an X-ray beam modulated according to the pattern results in a temporary storage of the energy contained in the X-ray radiation pattern. At some interval after exposure, a beam of visible or infrared light scans the panel or screen to stimulate the emission of stored energy as light. The light is detected and sequentially converted to an electrical signal, which can be processed to produce a visible image. For this purpose, the phosphor should store as much as possible of the incident X-ray energy 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 (CR)".
[0004]
The exposure given for inspection in both types of radiography is often adjusted by a "photometer". A "photometer" is a radiometer and radiographic imaging system for measuring the amount of radiation passing through an object (patient) and a penetrating radiation source for switching off the transmitted radiation source as soon as a preset dose is reached. Includes connections to sources. In systems using such photometers, it is important that a sufficiently measurable dose reaches the radiometer in the photometer. This is because the reproducibility of switching off the source of transmitted radiation when the dose reaching the photometer is too low should not be taken from an image quality standpoint. Thus, the imaging system only absorbs the transmitted radiation to the extent necessary for good speed and image quality, and thus-with the immediate indication of the examination and with the lowest possible patient dose- Is achieved with a sufficiently high exposure dose for reproducible switching of the source of transmitted radiation.
[0005]
In a practical setting, the amount of radiation reaching the "photometer" is determined by the absorption of the transmitted radiation by the tube side of the cassette containing the object, storage phosphor panel or screen and the back side of the cassette. The absorption of the storage phosphor panel or screen is determined by the phosphor used, the amount of phosphor and the support. The higher the absorption in the phosphor layer, the better the image quality and speed of the radiographic imaging system, and therefore it is necessary to increase the thickness (absorption) of the phosphor layer, It can only be done when the total absorption of the layers and the support remains almost constant. Therefore, the increase in the thickness of the phosphor layer must be compensated for by reducing the absorption of transmitted radiation in the support. In radiographic techniques, especially where low energy penetrating radiation is used (eg, mammography, certain non-destructive testing applications, etc.), the contribution of the phosphor screen or panel or support to the absorption of the screen cannot be neglected.
[0006]
Reduction of the absorption of transmitted radiation by the support can be achieved by reducing the thickness of the support, using a support with low absorption, and the like. On the other hand, the support of the storage phosphor panel or screen should have high mechanical strength, low brittleness, and should be able to withstand the temperatures encountered during deposition when vacuum depositing the phosphor thereon. It is. Thus, there is still a need for a support that provides a good compromise between often incompatible properties as cited above.
[0007]
OBJECTS AND SUMMARY OF THE INVENTION It is an object of the present invention to provide a storage phosphor panel or screen that can be used in applying phosphor deposition and that includes a support having high mechanical strength and low absorption of transmitted radiation. It is to provide.
[0008]
A further object of the present invention is a storage phosphor panel which can be used when applying phosphor deposition and comprises a support having a low mechanical absorption of less than 70 keV and a low absorption of X-rays. Or providing a screen, the panel or screen of which is suitable for use in mammography.
[0009]
The object of the present invention is achieved by providing a storage phosphor panel or screen according to claim 1. Specific features for preferred embodiments of the invention are disclosed in the dependent claims.
[0010]
Further advantages and embodiments of the present invention will become apparent from the following description.
[0011]
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 schematically shows an example of a storage phosphor panel or screen of the present invention.
FIG. 2 schematically illustrates a further example of a storage phosphor panel or screen of the present invention.
FIG. 3 schematically illustrates another example of the storage phosphor panel or screen of the present invention.
[0012]
DETAILED DESCRIPTION OF THE INVENTION In the manufacture of binderless phosphor screens by chemical vapor deposition in vacuum, the support on which the phosphor is deposited can be heated to a temperature of about 400 ° C. Therefore, the use of a heat stable support is necessary. Therefore, polymeric supports are not very suitable, even for supports containing only elements with low atomic numbers. The inclusion of an amorphous carbon film in the support means that the binder-free storage phosphor on the support having low X-ray absorption, even if the storage phosphor layer is applied by vacuum deposition at a rather high temperature. We found that opening the prospects for generating a screen. Amorphous carbon films suitable for use in the present invention are commercially available through Tokyo, Japan, for example, Tokyo Carbon Co, LTD, Nissinbo Industries, Tokyo, Japan; they are "glassy carbon films", Or, it is called "glassy carbon".
[0013]
In a binderless phosphor panel or screen according to the present invention, the thickness of the layer of amorphous carbon ranges from 100 μm to 3000 μm, with a thickness of 500 μm to 2000 μm providing flexibility, strength and X-ray absorption. Preferred as a compromise.
[0014]
First Example of the Invention In the binderless storage phosphor screen of the present invention, the storage phosphor layer is adjacent to the amorphous carbon layer, for example, by vacuum depositing the storage phosphor on an amorphous carbon film. It can be positioned directly and the screen can be used without the addition of further layers to the screen, which is a very simple example of the storage phosphor screen of the present invention. This example is shown in FIG. 1, where the storage phosphor layer (1) on the support (2) is adjacent to the amorphous carbon layer (23).
[0015]
Second Example of the Invention In a further example of a storage phosphor screen or panel according to the invention, an auxiliary layer can be added to the screen on the side of the amorphous carbon layer facing away from the phosphor layer. Such a screen is shown in FIG. 2, where a phosphor layer (1) on a support (2) is schematically shown, the support comprising an amorphous carbon layer (23) and an auxiliary layer (24). including. This auxiliary layer is preferably a polymer layer laminated on the amorphous carbon layer. Doing so enhances the mechanical strength of the panels or screens of the present invention, especially those relating to brittleness and flexibility. The need for extremely high mechanical strength exists especially in radiographic systems that utilize storage phosphor panels, where the panels are automatically removed from the cassette during the readout of the energy stored in the panels, often with wavy paths. Through the reader and then back into the cassette. In such a reader, it is very advantageous to use a screen or panel according to the invention having an auxiliary layer laminated on an amorphous carbon layer. This auxiliary layer can be any known polymer film, such as a polyester film, polyvinyl chloride, polycarbonate, syntactic polystyrene and the like. Preferred polymer films are polyester films, such as polyethylene terephthalate film, polyethylene naphthalate film and the like. The thickness of the auxiliary layer (24) can be 1 μm to 500 μm. Using a very thin amorphous carbon film (eg, 400 μm) and laminating a 500 μm thick auxiliary film onto it, and using a thick amorphous carbon film (eg, 2000 μm thickness) with a 6 μm thin polymer Films can be laminated. The relative thickness of the amorphous carbon and polymer films can be varied widely, depending on the required physical strength of the amorphous carbon during the deposition of the phosphor layer and the required flexibility during use of the panel. It is only dominated.
[0016]
Third Example of the Invention For example, European patent application no. 02100763.8 shows that adding a specular layer between the phosphor layer and the amorphous carbon layer can enhance both image quality and speed of the screen or panel. In addition, in the panel according to the present invention, the addition of such a regular reflection auxiliary layer may be beneficial. When such a layer is added, it preferably reflects at least 80% of the light impinging on it with specular reflection. More preferably, said layer reflects 90% of the impinging light with specular reflection. Such a layer is preferably an extremely thin (less than 20 μm, preferably less than 10 μm) metal layer. When a specular reflection layer is present in the screen or panel according to the invention, it is preferred that the layer is a thin aluminum layer (preferably no more than 10 μm, more preferably no more than 5 μm). Since such thin metal layers can be very corrosion sensitive, when a specular metal layer is present in the panels or screens of the present invention, this layer may be a barrier layer that blocks water and / or moisture from reaching the reflective auxiliary layer. (Auxiliary layer). Such a barrier layer may be any known moisture barrier layer, but is preferably a parylene layer. The most preferred polymer for use in the barrier layer of the present invention is a vacuum deposited, preferably chemically vacuum deposited, poly-p-xylylene film. Poly-p-xylylene has a repeating unit in the range of 10 to 10000, each repeating unit having a substituted or unsubstituted aromatic nucleus group. As a base agent, Union Carbide Co. under the trademark "PARYLENE". Preferred are the commercially available di-p-xylylene compositions sold by R. Preferred compositions for the barrier layer are unsubstituted "PARYLENE N", monochlorinated "PARYLENE C", dichlorinated "PARYLENE D", and "PARYLENE HT"("PARYLENEN"). Fluorine-substituted type, which has heat resistance up to a temperature of 400 ° C. and ultraviolet light resistance as opposed to other “parylene”; moisture resistance is almost the same as that of “PARYLENE C”). The most preferred polymer for use in making the barrier layer in the panels of the present invention is poly (p-2-chloroxylylene), a PARYLENE C film, poly (p-2,6-dichloroxylylene), a PARYLENE D. Film and "PARYLENE HT" (a completely fluorine-substituted type of PALYLENE N). An advantage of the parylene layers as moisture barrier layers in the panels or screens of the present invention is the heat resistance of the layers, such that they can withstand the temperatures required to vacuum deposit the storage phosphor. Things. The use of parylene layers in storage phosphor screens is disclosed, for example, in EP-A 128,362, 128,363, 128,364 and 128,365.
[0017]
A screen or panel according to the third embodiment of the invention as described above (FIG. 3) has a phosphor layer (1) and a support (2), where the support is an amorphous carbon layer (23) and a phosphorescent layer. A specular reflection layer (22) adjacent to the amorphous carbon layer between the body and the amorphous carbon layer and a parylene layer (21) over the reflection layer. The polymer layer (24) is laminated on the amorphous carbon layer. In a preferred embodiment according to the present invention, the reflection auxiliary layer (22) is an aluminum layer having a thickness of 0.2 μm to 200 μm.
[0018]
The present invention further includes a method of manufacturing a storage phosphor panel comprising the following steps:
Providing an amorphous carbon film;
-Vacuum depositing a storage phosphor layer on said amorphous carbon film;
-Optionally laminating a polymer film on the side of the amorphous carbon film not covered by the phosphor.
[0019]
The present invention further includes a method of manufacturing a storage phosphor panel comprising the following steps:
Providing an amorphous carbon film;
-Applying a specular reflection layer on said amorphous carbon film;
-Vacuum depositing a storage phosphor layer on said amorphous carbon film;
-Optionally laminating a polymer film on the side of the amorphous carbon film not covered by the phosphor.
[0020]
The present invention further includes a method of manufacturing a storage phosphor panel comprising the following steps:
Providing an amorphous carbon film;
-Applying a specular reflection layer on said amorphous carbon film;
-Chemically vacuum depositing a parylene layer on top of said specular reflection layer;
-Vacuum depositing a storage phosphor layer on said amorphous carbon film;
-Optionally laminating a polymer film on the side of the amorphous carbon film not covered by the phosphor.
[0021]
The screen or panel of the present invention can include any known protective layer on top of the phosphor layer. Particularly preferred for use are the protective layers disclosed in EP-A 1 286 363; 1316969 and 136970. A screen or panel according to the invention in which a moisture repellent layer is present between the support and the phosphor layer is advantageously used, furthermore a moisture repellent layer is coated as outermost layer adjacent to the phosphor layer. More preferred is a screen or panel according to the invention. In particular, said screen or panel having a moisture repelling parylene layer is recommended. A screen or panel in which the phosphor layer is sandwiched between two moisture repelling parylene layers provides excellent protection.
[0022]
The screens or panels according to the invention can also have reinforcing edges, for example as described in US-A 5,334,842 and US-A 5,340,661.
[0023]
The surface of the phosphor layer (1) in the panel or screen of the present invention can be made smaller than the surface of the support (2) so that the phosphor layer does not reach the edge of the support. Such a screen is disclosed, for example, in EP-A 1 286 363.
[0024]
Preferably, the storage phosphor used in the panels or screens of the present invention is an alkali metal storage phosphor. Such phosphors are disclosed in US Pat. No. 5,736,069 and correspond to the following formula:
M ¹⁺ X. aM ²⁺ X ′ ₂ bM ³⁺ X ″ ₃ : cZ
^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+. X, X ′ and X ″ may be the same or different and each represents a halogen atom selected from the group consisting of F, Br, Cl and I, and 0 ≦ a ≦ 1, 0 ≦ b ≦ 1 and 0 <c ≦ 0. It is.
[0025]
A particularly preferred phosphor for use in the panel or 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 comprises the following steps: Produced by a method that includes:
- EuOX _', EuX' ₂ and EuX _'3 (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.
[0026]
Such phosphors are disclosed in EP-A 1203394.
[0027]
Preferably, the phosphor is vacuum deposited on a support under the conditions disclosed in EP-A-111458 and EP-A-1118540.
[0028]
In a preferred embodiment, the panel or screen according to the invention is a binderless phosphor panel or screen, wherein said phosphor layer is a needle-like CsX: Eu phosphor, wherein X is selected from the group consisting of Br and Cl. Represents a halide).
[0029]
The invention further comprises a method for exposing an object to X-rays comprising the following steps:
An X-ray tube equipped to emit X-rays having an energy of 70 keV or less, and a photometer coupled to the X-ray tube for switching the tube on and off according to the X-ray dose reaching the photometer Providing an X-ray device comprising:
Placing an object between the X-ray tube and the photometer;
Placing a binderless storage phosphor panel or screen according to the present invention between the object and the photometer; and- the object, the cassette and the cassette until the photometer switches off the X-ray tube. Activate the X-ray tube to expose the photometer.
[0030]
The invention further comprises a method as described above, wherein said X-ray tube is provided for emitting X-rays having an energy of 40 keV or less.
[0031]
The screens or panels of the present invention are very well suited for use in mammography and certain non-destructive testing applications where low keV X-ray equipment is used.
[0032]
Parts list 1 phosphor layer 2 support 21 auxiliary layer, moisture barrier layer 22 auxiliary layer, specular reflection layer 23 amorphous carbon layer 24 auxiliary layer, polymer layer
EXAMPLES While the invention will be described below in connection with preferred embodiments thereof, it will be understood that it is not intended to limit the invention to those embodiments.
[0034]
An X-ray cassette with a phosphor screen or panel was exposed with X-rays having an energy of 28 keV from a Mo anode (30 μmMo, each with intern filtering and no filtering).
[0035]
A Mammory Detail R® screen from Agfa-Gevaert, Morstel, Belgium was used as a comparison screen: the system (for absorption of X-ray exposure energy as described in the detailed description above). The use of a "photometer" is permitted. The absorption for all investigated cassettes with screens or panels should not exceed the absorption measured for the aforementioned comparative screen.
[0036]
An X-ray dose of 10 mR reaching the cassette (X-rays pass through a 4 cm layer of polymethyl methacrylate polymer and further into the cassette bottom (3 mm polyethylene), panel or screen (change composition in experiments as described below) and Starting from the cassette cover (continuously passing through 4.1 mm of polyethylene)), in order to obtain an acceptable and accurate action of the "photometer", 0 It has been determined that doses in the range of .75 to 0.85 mR are required.
[0037]
In the panel or screen, the CsBr: Eu phosphor layer (which varies in thickness (in μm as shown in Table 1) as shown in Table 1) is coated in various supports (in μm in Table 1) The X-ray energy (dose mR) reaching the "photometer" coated on aluminum, a-C "amorphous carbon", glass and iron) is shown in Table 1 for each panel or screen examined. It was put together. The thickness of the support is given in Table 1 below, for various thicknesses of the CsBr: Eu phosphor layer, which still provides a sufficient dose at the photometer location after the X-rays have passed through the cassette.
[0038]
[Table 1]

[0039]
From the results obtained in Table 1, it can be seen that amorphous carbon (a-C) supports are, for example, Fe (not suitable for use if not only for a layer thickness of only 100 μm) and aluminum (100 μm thin). (Suitable for use up to 800 μm for the phosphor layer) because it hardly produces any absorption: amorphous carbon is sufficient for the photometer even with the thickest phosphor layer (150 μm) Given the dose, a thickness of 2000 μm is perfectly suitable for use. Amorphous carbon is comparable to glass as shown in FIG. 1, but is superior to glass. This is because amorphous carbon is much more suitable for being applied in the manufacture of the phosphor panel or screen of the present invention.
[0040]
While the preferred embodiment of the invention has been described in detail, it will be apparent to those skilled in the art that numerous changes may be made therein without departing from the scope of the invention as defined in the appended claims.
[Brief description of the drawings]
[0041]
FIG. 1 schematically illustrates an example of a storage phosphor panel or screen of the present invention.
FIG. 2 schematically illustrates a further example of a storage phosphor panel or screen of the present invention.
FIG. 3 schematically illustrates another example of a storage phosphor panel or screen of the present invention.

Claims (8)

A binderless storage phosphor panel or screen comprising a phosphor layer (1) vacuum deposited on a support (2), characterized in that said support comprises a layer (23) of amorphous carbon. Storage phosphor panels or screens without a binder. The binderless storage phosphor panel or screen of claim 1, wherein said support further comprises a polymer auxiliary layer (24) further from said phosphor layer than said layer of amorphous carbon. 3. A binderless storage phosphor panel or screen according to claim 1 or 2, wherein the support further comprises a reflective auxiliary layer (22). 4. A binderless storage phosphor panel or screen according to claim 3, wherein said support further comprises a protective auxiliary layer (21) between said reflective auxiliary layer and said phosphor layer. 5. The binderless storage phosphor panel or screen according to claim 4, wherein said protective auxiliary layer is a layer of parylene, wherein said parylene is selected from the group consisting of Parylene C, Parylene D and Parylene HT. 6. A binderless storage phosphor according to any one of claims 1 to 5, wherein said phosphor layer comprises a needle-shaped CsX: Eu phosphor and X represents a halide selected from the group consisting of Br and Cl. Body panel or screen. A method for exposing an object to X-rays, comprising the steps of:
An X-ray tube provided for emitting X-rays having an energy of less than or equal to 70 keV, and coupled to the X-ray tube to switch the X-ray tube on and off according to the X-ray dose reaching the photometer Providing an X-ray device including a photometer;
Placing an object between the X-ray tube and the photometer;
-Placing a binderless storage phosphor panel or screen according to any one of claims 1 to 6 between the object and the photometer;
Activating the X-ray tube to expose the object, the cassette and the photometer until the photometer switches off the X-ray tube. Use of a screen or panel according to any one of claims 1 to 6 in mammography.

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