CN102760506A - Phosphor sheet - Google Patents

Abstract

The invention relates to a phosphor plate with a substrate (1) and an additional layer (2) located thereon, on which a layer of phosphor is applied, wherein the additional layer (2) is as follows gridded in such a way that separate protrusions (8) are generated by the grooves (3-7), the luminescent material needles of the luminescent material forming the luminescent material layer are formed on the surface of the protrusions (8), wherein the first protrusion (8) First structures are formed, the second protrusions (9) form second structures geometrically different from the first structures, and the second structures are disposed between the first structures. Such a phosphor plate has a good imaging quality even with thick phosphor layers.

Description

Luminescent material plate

technical field

The invention relates to a phosphor plate with a substrate and an additional layer thereon, on which a layer of phosphor is applied, wherein the additional layer is rasterized in such a way that The separate protrusions are formed by the grooves, on the surface of which the phosphor needles of the phosphor forming the phosphor layer are produced.

Background technique

In such a phosphor plate, the phosphor can be an energy-storage phosphor or a scintillator.

Common scintillators include CsI:Tl, CsI:Na, NaI:Tl or similar materials containing alkali-halides, with CsI being particularly suitable as a scintillator material because it can grow into a needle shape. This results in a good spatial resolution of the x-ray representation even with relatively large layer thicknesses which ensure optimal absorption of the x-rays. Good positional resolution is produced by so-called "photoguiding" via the air spaces between the scintillator needles.

Scintillators, which convert X-rays and gamma rays into light, are used, for example, in medical imaging, when inspecting goods and packages, and in non-destructive material inspection. These luminescent substances should have a high absorption in the "harder" X-rays caused by the increased 3D use of so-called C-arcs in radiology.

As shown in Figure 1, compared with the radiation quality of the common CsI:Tl-scintillator, when the "radiation hardness" increases, the absorption (Absorption) is almost halved from 87% at RQA3 to 44% at RQA9.

RQA stands for Radiation Quality based on aluminum-added filters (from standard IEC 61267).

For comparison, in addition to the absorption curves of the scintillator CsI:Tl shown in Figure 1, the absorption curves of four other scintillators are also shown, wherein the measurements were performed under the condition of a mixed radiation beam with a diameter of 20 mm.

The absorption curves A1 to A5 shown in Figure 1 and the given RQA-value represent:

Absorption curve of A1 unstructured luminescent material UFC,

Absorption curve of A2 structured luminescent material UFC,

The absorption curve of A3 luminescent material CsI:Tl (400μm),

Absorption curve of A4 luminescent material GOS, and

The absorption curve of the luminescent material GOS with A5 layer thickness smaller than A4,

Among them, UFC means Ultra Fast Ceramic and GOS means gadolinium oxysulfide.

RQA3 50kV/10mmAl,

RQA5 70kV/21mmAl,

RQA7 90kV/30mmAl and

RQA9 120kV/40mmAl.

The scintillator material UFC must be structured so as to reduce light propagation from the sides. This reduces the absorbance at various radiation qualities. Despite the structuring, the resolution is usually 1 line pair/mm (Linienpaar pro mm) in the case of UFC. Correspondingly, the resolution of CsI:Tl at 400 μm is typically 4 line pairs/mm, and is therefore preferred.

In order to compensate for the significantly lower absorption with increased radiation hardness, the thickness of the phosphor layer must be significantly increased in the case of conventional CsI:Tl scintillators. In order to achieve an absorption of 90% in the case of RQA9, the layer thickness must be about 1.8 mm.

A problem here is that, although the diameter of the scintillator-needles (needles of luminescent material) can remain smaller than 10 μm with increasing layer thickness if the substrate temperature is not too high, in the luminescent material layer Around each scintillator-needle formed the desired crack indefinitely. These cracks create a limited spacing between the scintillator-needle, which ideally has a pitch of half the emission wavelength of the scintillator. In the case of cesium iodide (CsI), this spacing is approximately 250 nm to 300 nm.

Conversely, shrinkage cracks are generated in the luminescent material layer due to the low coefficient of expansion when cooling the evaporated substrate. This leads to a superimposed irregular crack structure with a crack width above 1 μm that encloses the entire needle core (Nadelpakete), as shown in Figure 2, which shows the known CsI-layer under a grating electron microscope Enlarge the photo 50 times. The distance between the cracks in this case is on the order of size from 0.5 mm to 1.5 mm, and the cracks have a width of up to about 10 μm.

At grain boundaries, gaps and cracks, it is known that more light is coupled out of the phosphor layer than from the phosphor needles themselves. Therefore, the halo (Lichthof) of the focused beam, as shown in Fig. 3, shows a clear halo (Halo, i.e. a relatively uniform over-illumination Variation of (Verlauf). This problem is also significantly exacerbated with increasing layer thickness, since more energy is required to separate the phosphor needles.

A phosphor plate in which the phosphor layer consists of an energy-storage phosphor is known, for example, from DE 10 24 2006 A1. The additional layer applied on the substrate is used to balance the different coefficients of thermal expansion between the substrate and the layer of luminescent material and therefore consists of a polymer such as polyimide or Parylen and has a regular, An n-angle structure is preferred.

In the phosphor plate according to DE 10242006 A1, due to the regular polygonal structure, "lines" are produced along which cracks form and continue without separation into individual structural elements (linear crack propagation). Due to the increase in the layer thickness of the energy-storage luminescent material, the formation of superimposed crack structures is aggravated. This is the case not only for layers of energy-storage luminescent materials such as cesium bromide (CsBr), but also for scintillator layers such as cesium iodide (CsI).

In FIGS. 4 and 5, superimposed crack structures at, for example, two different polygonal structures (squares in FIG. 4 and hexagons in FIG. 5) in a luminescent material layer made of cesium iodide with a thickness of already clearly visible. The structuring of the additional layer results in a channelization of the cracks, so that although undesirably wide cracks are avoided, the cracks are clearly visible in the preferred orientation.

Furthermore, DE 68906478 T2 describes a phosphor plate (scintillator plate) having a scintillator as phosphor. The scintillator was coated on an aluminum substrate. The aluminum substrate has a honeycomb-shaped surface structure, which is carried out by the Eloxal method (electrolytic oxidation of aluminum).

Independently of the type of phosphor, ie in the case of energy-storage phosphor plates as well as in the case of scintillator plates, the formation of superimposed crack structures should be avoided as much as possible for the above reasons.

Contents of the invention

The object of the present invention is to provide a phosphor plate which has a good image quality even with large phosphor layer thicknesses

This object is solved according to the invention by a phosphor plate according to claim 1 . Advantageous embodiments of the phosphor plate according to the invention are in each case the subject-matter of the further claims.

The luminescent material plate of claim 1 comprising a substrate and an additional layer thereon, on which the luminescent material layer is applied, wherein the additional layer is gridded in such a way that separate protrusions are formed by grooves forming Luminescent material needles of the luminescent material of the luminescent material layer are produced on the surface of the protrusions, wherein the first protrusions form a first structure, the second protrusions form a second structure geometrically different from the first structure, and the second structure disposed between the first structures.

The solution of the present invention is characterized in that the first protrusion forms a first structure, and the second protrusion forms a second structure, wherein the first structure and the second structure are formed in a geometrically different manner, and the second structure is arranged at the second between a structure. As a result, the first protrusions and the second protrusions each have a shorter distance than the first protrusions and the second protrusions from each other.

This additional layer enables the structuring according to the invention to be realized in a simple manner by the usual structuring methods for polymers, oxides and metals.

The term "forming geometrically different structures" is understood to mean that the formed structures have, for example, different sizes and/or different shapes. This can be the case within the first structure and/or within the second structure, and it can also be the case when the first structure and the second structure are compared (claim 8 and/or claim 9).

Since the first protrusion and the second protrusion are arranged directly adjacent to each other, the groove formed by the first protrusion is "interfered" by the second protrusion.

Undesirable superimposed crack structures in the additional layer and thus damage to the imaging properties can be reliably prevented by the solution according to the invention, and instead favorable crack formation around the phosphor needles is ensured. The phosphor plate according to the invention therefore has a good image quality even in the case of large layer thicknesses of the phosphor layer.

Advantageously, the first structure formed by the first protrusions constitutes a lattice structure and/or the second structure formed by the second protrusions constitutes a lattice structure (claims 2 and 3).

Within the scope of the invention, one or more separate phosphor needles may be formed on the protrusion (claim 4).

According to an advantageous embodiment of the phosphor plate, the thickness of the additional layer is approximately 10 μm to 50 μm (claim 5 ).

The grid size of the structure is preferably in the range of 10 μm to 100 μm, preferably between 20 μm and 50 μm (claim 6 ).

According to an advantageous embodiment of the phosphor plate according to the invention, the groove has a width in the range of 10 μm to 50 μm (claim 7 ), wherein the protrusions are separated from one another by the groove.

The formation of undesired superimposed crack structures can be avoided in the case of additional layers with the above-mentioned disadvantages by:

- the first structure is at least partly of regular shape, the second structure is at least partly of regular shape (claim 10), and/or

- the first structure has an at least partially irregular shape, the second structure has an at least partially irregular shape (claim 11), and/or

- the first structure has an at least partially regular shape and the second structure has an at least partially irregular shape (claim 12), and/or

- The first structure has an at least partially irregular shape and the second structure has an at least partially regular shape (claim 13).

The structures formed by the protrusions and/or the protrusions themselves may have, for example, an n-eckig structure or shape. This holds for both the first protrusion and the first structure and the second protrusion and the second structure (claims 14 to 17).

The solution according to the invention can advantageously be realized in panels of energy-storage luminescent materials (claim 18 ), as well as in scintillator panels (claim 19 ).

Additional layers can be applied, for example, by PVD methods (Physical Vapor Deposition) or by CVD methods (Chemical Vapor Deposition). Furthermore, the sol-gel method and the spin-on-coating method (spin-on-coating) are suitable for producing the intermediate layer.

的光刻法而生成。根据附加层的组成，借助激光或腐蚀的结构化为其他的结构化方法。Additional layers of structuring can be achieved, for example, by having a subsequent decomposition

produced by photolithography. Depending on the composition of the additional layer, structuring by means of laser or etching are other structuring methods.

Description of drawings

Schematic embodiments of the invention are explained in more detail below with reference to the drawings, without however restricting the invention. In the attached picture:

Figure 1 shows the radiation mass-dependent absorption of X-rays in the case of different scintillators,

Figure 2 shows a 50X magnification of the known CsI:Tl-layer under a grating electron microscope to show the crack spacing,

Figure 3 shows a photomicrograph of a CsI:Tl-layer halo,

Figure 4 shows a known CsI:Tl-layer with a tetragonal structure under a grating electron microscope at 50X magnification,

Figure 5 shows a 50x magnification photograph of a known hexagonal structured CsI:Tl-layer under a grating electron microscope,

Figure 6 shows a partial top view of a first embodiment structured according to the invention,

Figure 7 shows a partial top view of a second embodiment structured according to the invention.

Detailed ways

In the case of CsI:Tl scintillators, the layer thickness has to be significantly increased due to the already explained absorbance ( FIG. 1 ). This increase resulted in a superimposed irregular crack structure (Fig. 2) and a pronounced halo (Fig. 3). Although the n-corner structured additional layer proposed in DE 10242006 A1 already suppresses the undesirably wide cracks at n=4 and n=6, the cracks are still clearly visible at the preferred orientation ( FIGS. 4 and 5 ).

FIG. 6 shows a plan view of a first embodiment of a substrate 1 of an inventive phosphor plate. The phosphor plate comprises a substrate 1 on which an additional layer 2 is applied. The additional layer 2 is gridded in such a way that the trenches 3 to 7 form separate protrusions 8 , on the surface of which the phosphor needles of the phosphor forming the phosphor layer are evaporated in a further process step. This additional layer 2 makes it possible to implement the structuring provided by the invention in a simple manner by means of conventional structuring methods.

In the embodiment described, the protrusions 8 each have an octagonal base.

According to the invention, the protrusions 8 separated by the grooves 3 to 7 form a first protrusion and define a first structure. The second protrusions 9 , each having, for example, a quadrangular base in the embodiment shown, form the second structure.

According to the invention, the first structure formed by the first protrusion 8 and the second structure formed by the protrusion 9 are formed in a geometrically different manner. Furthermore, a second structure is disposed between the first structures. As a result, the first protrusions 8 and the second protrusions 9 each have a shorter distance than the distances between the first protrusions 8 and the second protrusions 9 . To this end, the second protrusions 9 are arranged in the grooves 3 to 7 . As a result, the grooves 3 to 7 formed by the protrusion 8 are “interrupted” by the second protrusion 9 .

FIG. 7 shows a plan view of a second embodiment of a substrate 1 of an inventive phosphor plate. The structure of the substrate 1 is basically the same as that of the substrate 1 shown in FIG. 6 . Only the second protrusion 9 is rotated by an angle of 45° relative to the base 1 according to FIG. 6 . As a result, the corners of the protrusions 9 approach the protrusions 8 .

The invention is described in FIGS. 6 and 7 using the example of a protrusion 8 with an octagonal base and a protrusion 9 with a quadrangular base (two polygons arranged regularly). Within the scope of the invention, further configurations can also be realized for the first configuration and the second configuration by means of a differently shaped first protrusion 8 and/or a differently shaped second protrusion 9 . Here, the first protrusions 8 and the second protrusions 9 may have any structure, and may be arranged regularly or irregularly. Furthermore, the first protrusions 8 and/or the second protrusions 9 can also be provided as a structure which varies over the entire surface of the additional layer 2 .

The inventive solution illustrated by these two embodiments reliably prevents an undesired superimposed crack structure in the additional layer 2 and thus reliably prevents damage to the imaging properties and instead ensures favorable crack formation and acicular shape of the luminescent material thing. The phosphor plate according to the invention therefore has a good imaging quality even with a large layer thickness of the phosphor layer.

The measures according to the invention thus take into account the "linear degrees of freedom" in the case of the additional layer 2 . This suggests that for example "interfering elements" (formed by second protrusions 9) between regularly arranged polygonal structures (formed by first protrusions 8) block the "path" of linear crack propagation and thereby force the crack to change direction . The formation of superimposed crack structures in the additional layer 2 is thus reliably prevented.

Various forms of polygonal or irregular structures can be arranged arbitrarily in the additional layer 2 coated on the substrate 1 . Within the scope of the present invention, the term “polygon” includes arbitrarily shaped n-angles with side length a, where n≧3. When n→∞ (that is, a→0), a nearly circular shape can be obtained. In the case of the first structure formed by the first protrusions 8 and in the case of the second structure formed by the second protrusions 9, the invention also includes other geometries, such as elliptical or star-shaped structures.

The luminescent materials that can be structured in this way are not limited to scintillators (eg CsI:Tl, CsF, CsI:Na, NaI:Tl), but also extend to energy-storage luminescent materials (eg CsBr:Eu).

By selecting a suitable structured additional layer 2 on the substrate 1, the scintillator layer or the energy-storage luminescent material layer can be evaporated under suitable parameters (pressure, substrate temperature) and cooled in the desired manner not only at the The coarser structuring of the first protrusions 8 and/or the second protrusions 9 takes place as well as the finer structuring of the first protrusions 8 and/or the second protrusions 9 .

Claims (19)

1. luminescent material plate; It has substrate (1) and position extra play (2) on it; On said extra play (2), be coated with luminous material layer, wherein said extra play (2) gridding as follows generates the projection (8) of separating through groove (3-7); The luminescent material spicule that forms the luminescent material of luminous material layer is created on the surface of projection (8); Wherein first projection (8) forms first structure, and second projection (9) forms second structure that is different from first structure on how much, and said second structure is arranged between first structure.

2. according to the luminescent material plate of claim 1, it is characterized in that said first structure that is formed by first projection (8) constitutes cell structure.

3. according to the luminescent material plate of claim 1 or 2, it is characterized in that said second structure that is formed by second projection (9) constitutes cell structure.

4. according to the luminescent material plate of claim 1, it is characterized in that, in projection (8,9) but go up to form the luminescent material spicule of the separation of predetermined quantity.

5. according to the luminescent material plate of claim 1, it is characterized in that thick about 10 μ m to the 50 μ m of said extra play (2).

6. according to the luminescent material plate of claim 1 or 2, it is characterized in that the grid size of said structure is in the scope of 10 μ m to 100 μ m, preferably between 20 μ m to 50 μ m.

7. according to the luminescent material plate of claim 1, it is characterized in that the width of said groove (3-7) is in the scope of 10 μ m to 50 μ m.

8. according to the luminescent material plate of claim 1, it is characterized in that said first structure and second structure are of different sizes.

9. according to the luminescent material plate of claim 1, it is characterized in that said first structure has different shapes with second structure.

10. according to the luminescent material plate of claim 1, it is characterized in that said first structure part at least has regular shape, and said second structure at least partly has the shape of rule.

11. the luminescent material plate according to claim 1 is characterized in that, said first structure part at least has irregular shape, and said second structure at least partly has irregular shape.

12. the luminescent material plate according to claim 1 is characterized in that, said first structure part at least has regular shape, and said second structure at least partly has irregular shape.

13. the luminescent material plate according to claim 1 is characterized in that, said first structure part at least has irregular shape, and said second structure at least partly has the shape of rule.

14. the luminescent material plate according to claim 1 is characterized in that, said first structure that is formed by first projection (8) has the structure at n-angle.

15. the luminescent material plate according to claim 1 is characterized in that, said second structure that is formed by second projection (9) has the structure at n-angle.

16. the luminescent material plate according to claim 1 is characterized in that, said first projection (8) has the n-angular shape.

17. the luminescent material plate according to claim 1 is characterized in that, said second projection (9) has the n-angular shape.

18. the luminescent material plate according to claim 1 is characterized in that said luminous material layer is made up of the accumulating type luminescent material.

19. the luminescent material plate according to claim 1 is characterized in that said luminous material layer is made up of scintillator.

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