JP4345460B2 - Radiation image conversion panel - Google Patents

Description

  In the present invention, a photostimulable phosphor layer made of a columnar crystal containing a photostimulable phosphor is formed on a support by a vapor deposition method, and the photostimulable phosphor layer is covered with a protective layer. The present invention relates to a radiation image conversion panel.

Conventionally, so-called radiography using a silver salt is used to obtain a radiographic image, but a method for imaging a radiographic image without using a silver salt has been developed. That is, the radiation transmitted through the subject is absorbed by the stimulable phosphor, and then the stimulable phosphor is excited with a certain energy to excite the radiation energy accumulated in the stimulable phosphor. A method of emitting as a fluorescent material and detecting and imaging this fluorescence is disclosed.
As a specific method, a radiation image conversion method using a panel having a photostimulable phosphor layer on a support and using one or both of visible light and infrared light as excitation energy is known (Patent Document 1). reference).

  By the way, in recent years, as a radiation image conversion method using a high-luminance, high-sensitivity, high-sharp stimulable phosphor, radiation using a stimulable phosphor in which Eu is activated with an alkali halide such as CsBr as a base material. Image conversion panels have been proposed. In particular, by using Eu as an activator, X-ray conversion efficiency, which has been impossible in the past, can be improved.

On the other hand, there is a demand for a high-sensitivity and high-quality radiation image conversion panel by improving the light collection efficiency of stimulated emission light in the analysis of diagnostic images. As a means for this purpose, for example, it is formed on a support. A radiation image conversion panel has been proposed in which the stimulable phosphor layer has a columnar structure composed of columnar crystals, and the ends of the columnar crystals (the top on the side opposite to the support) are convex (Patent Document 2). reference).
US Pat. No. 3,859,527 JP 2002-181997 A

However, even if the shape of the crystal tip is controlled as in the radiation image conversion panel described in Patent Document 2, only the light emission efficiency of the surface layer portion is improved, so the image granularity (noise) is not excellent, and the image quality As it was insufficient.
The present invention has been made in view of the above circumstances, and an object thereof is to provide a radiation image conversion panel excellent in image granularity by increasing the uniformity of light emission.

In order to solve the above-mentioned problems, the invention of claim 1 is characterized in that a stimulable phosphor layer comprising a columnar crystal containing a stimulable phosphor is formed on a support by a vapor deposition method. A radiation image conversion panel in which a phosphor layer is covered with a protective layer,
The photostimulable phosphor layer is a single-layer columnar crystal formed by activating an activator on the matrix of the photostimulable phosphor,
On the side of the columnar crystal of the photostimulable phosphor layer, the linearity in the portion corresponding to 5% to 15% of the film thickness from the protective layer side with respect to the film thickness of the photostimulable phosphor layer is as follows: From the above, the linearity at the portion corresponding to 0% to 10% of the film thickness is better.

  According to the invention of claim 1, since the linearity on the protective layer side is better than the linearity on the support side on the columnar crystal side surface, the light is prevented from going out from the crystal, and the light is transmitted within the crystal. By reflecting or refracting the light, it is possible to easily scatter the stimulated light emission and increase the uniformity of the light emission of each crystal, thereby obtaining a panel having excellent image graininess. Therefore, the image quality of the radiation image can be significantly improved.

The invention of claim 2 is the radiation image conversion panel according to claim 1,
The average columnar diameter of the columnar crystals at the portion corresponding to 5% to 15% of the film thickness from the protective layer side with respect to the film thickness of the photostimulable phosphor layer is 0% to 15% of the film thickness from the support side. It is characterized by being larger than the average columnar diameter of the columnar crystals in the portion corresponding to%.

  According to the invention of claim 2, since the average columnar diameter of the columnar crystal on the protective layer side is larger than the average columnar diameter of the columnar crystal on the support side, the width of the columnar crystal increases toward the protective layer side. The area in the take-out direction is increased, the light emission efficiency is increased, and the image granularity can be improved.

The invention of claim 3 is the radiation image conversion panel according to claim 1 or 2,
The stimulable phosphor layer has a thickness of 50 μm or more and 1000 μm or less.

According to the invention of claim 3, since the thickness of the photostimulable phosphor layer is 50 μm or more and 1000 μm or less, the required amount of radiation absorption can be satisfied, and an image quality excellent in image granularity can be obtained. Can do.
Here, the film thickness of the photostimulable phosphor layer is set to 50 μm or more and 1000 μm or less because when the film thickness is less than 50 μm, the radiation absorption amount is small and the transmission amount is large. This is because the image quality deteriorates. On the other hand, when the film thickness is thicker than 1000 μm, scattering of the photostimulable luminescent component is increased, leading to deterioration in image quality.

Invention of Claim 4 is a radiation image conversion panel as described in any one of Claims 1-3,
The stimulable phosphor layer, CsBr: characterized in that it is composed of CsBr columnar crystals formed by depositing Eu.

  According to the invention of claim 4, since the photostimulable phosphor layer is composed of CsBr columnar crystals, it can be a photostimulable phosphor layer having both high sensitivity and high sharpness. The image quality can be significantly improved.

Hereinafter, the radiation image conversion panel according to the present invention will be described in detail.
As shown in FIG. 1, the radiation image conversion panel of the present invention is a stimulable phosphor comprising a support 11 and a columnar crystal formed on the support 11 by a vapor deposition method and containing a stimulable phosphor. A layer 12 and a protective layer (not shown) for covering the photostimulable phosphor layer 12 are provided.
And in the columnar crystal side surface of the photostimulable phosphor layer 12, the linearity in the portion 12a corresponding to 5% to 15% of the film thickness from the protective layer side with respect to the film thickness of the photostimulable phosphor layer 12 is supported. It is better than the linearity at the part 12b corresponding to 0% to 10% of the film thickness from the body 11 side.
Moreover, the average columnar diameter of the columnar crystal 12a on the protective layer side in the above range is larger than the average columnar diameter of the columnar crystal 12b on the support 11 side in the above range.
As described above, the present inventors increase the uniformity of light emission by controlling the side shape of the columnar crystal 12a on the protective layer side of the stimulable phosphor layer 12 and the columnar crystal 12b on the support 11 side. As a result, it has been found that a radiation image conversion panel excellent in image granularity can be obtained.

Here, the portion corresponding to 5% to 15% of the film thickness from the protective layer side with respect to the film thickness of the photostimulable phosphor layer 12 means that the photostimulable phosphor layer 12 has a pointed tip. Therefore, it refers to the crystal 12a corresponding to the 10% film thickness from the part excluding this protrusion (the part corresponding to 5% from the protective layer side with respect to the film thickness of the stimulable phosphor layer 12).
On the other hand, the portion corresponding to 0% to 10% of the film thickness from the support 11 side with respect to the film thickness of the photostimulable phosphor layer 12 is the crystal 12b corresponding to the 10% film thickness from the upper surface of the support 11. Say.

Also, “good linearity” means that the shape of the side surface of the columnar crystal is substantially vertical, that is, the shape having less undulation is better. Specifically, as shown in FIG. 3, the width (waviness width) of the undulations on the side surface of the columnar crystal is the portion protruding outward (maximum protruding portion) and the portion recessed inward (maximum dent portion). The shorter the line, the better the linearity. In this embodiment, which will be described later, the linearity is evaluated by measuring the width of the waviness described above.
Furthermore, the columnar diameter of the columnar crystals refers to the widths D and d of the columnar crystals 12a and 12b shown in FIG.

The support used in the present invention can be arbitrarily selected from known materials as a support for a conventional radiation image conversion panel. However, in the case of forming a phosphor layer by a vapor deposition method, In particular, a quartz glass sheet, a metal sheet made of aluminum, iron, tin, chromium, or the like, and a carbon fiber reinforced sheet are preferable.
The support preferably has a resin layer in order to make the surface smooth.
The resin layer preferably contains a compound such as polyimide, polyethylene terephthalate, paraffin, graphite, and the film thickness is preferably about 5 μm to 50 μm. This resin layer may be provided on the front surface, the back surface, or both surfaces of the support.
Examples of means for providing the resin layer on the support include means such as a bonding method and a coating method.
Bonding is performed using heating and a pressure roller. The heating condition is preferably about 80 to 150 ° C. The pressure condition is 4.90 × 10 to 2.94 × 10 ² N / cm, and the conveyance speed is 0. .1 to 2.0 m / sec is preferable.

  The film thickness of the photostimulable phosphor layer of the present invention is 50 μm to 2000 μm from the viewpoint of obtaining the effects of the present invention, although it varies depending on the intended use of the radiation image conversion panel and the type of stimulable phosphor. Preferably they are 50 micrometers-1000 micrometers, More preferably, they are 100 micrometers-800 micrometers.

The stimulable phosphor layer preferably contains a stimulable phosphor represented by the following general formula (1).
General formula (1)
M ¹ X · aM ² X ′ ₂ · bM ³ X ″ ₃ : eA [wherein M ¹ is at least one alkali metal atom selected from Li, Na, K, Rb and Cs atoms; ² is at least one divalent metal atom selected from the atoms of Be, Mg, Ca, Sr, Ba, Zn, Cd, Cu and Ni, and M ³ is Sc, Y, La, Ce, Pr, Nd. , Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Al, Ga, and In, at least one trivalent metal atom, and X, X ′, X ″ is at least one halogen atom selected from F, Cl, Br, and I atoms, and A is Eu, Tb, In, Ce, Tm, Dy, Pr, Ho, Nd, Yb, Er, Gd , Lu, Sm, Y, Tl, Na, Ag, Cu and Mg It is at least one kind of metal atom, and a, b and e each represent a numerical value in the range of 0 ≦ a <0.5, 0 ≦ b <0.5, and 0 <e ≦ 0.2. ]

In the photostimulable phosphor represented by the general formula (1), M ¹ represents at least one alkali metal atom selected from each atom such as Li, Na, K, Rb and Cs. At least one alkaline earth metal atom selected from each atom of Cs is preferable, and a Cs atom is more preferable.

M ² represents at least one divalent metal atom selected from atoms such as Be, Mg, Ca, Sr, Ba, Zn, Cd, Cu, and Ni, and among these, Be, It is a divalent metal atom selected from each atom such as Mg, Ca, Sr and Ba.

M ³ is selected from atoms such as Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Al, Ga, and In. At least one trivalent metal atom is represented, but among them, a trivalent metal atom selected from each atom such as Y, Ce, Sm, Eu, Al, La, Gd, Lu, Ga and In is preferable. It is.

  A is at least one selected from each atom of Eu, Tb, In, Ce, Tm, Dy, Pr, Ho, Nd, Yb, Er, Gd, Lu, Sm, Y, Tl, Na, Ag, Cu, and Mg. It is a seed metal atom.

  From the viewpoint of improving the photostimulable emission brightness of the photostimulable phosphor, X, X ′ and X ″ represent at least one halogen atom selected from F, Cl, Br and I atoms. At least one halogen atom selected from Br is preferable, and at least one halogen atom selected from Br and I atoms is more preferable.

In the general formula (1), the b value is 0 ≦ b <0.5, and preferably 0 ≦ b <10 ⁻² .

In particular, in the present invention, it is preferable to use a stimulable phosphor having, as a base, CsBr which is a combination of atoms (M ¹ ; Cs, X; Br) in the general formula (1).

The photostimulable phosphor represented by the general formula (1) of the present invention is produced, for example, by the method described below.
As a phosphor material,
(A) At least one compound selected from NaF, NaCl, NaBr, NaI, KF, KCl, KBr, KI, RbF, RbCl, RbBr, RbI, CsF, CsCl, CsBr and CsI is used.

_{(B) MgF 2, MgCl 2} , MgBr 2, MgI 2, CaF 2, CaCl 2, CaBr 2, CaI 2, SrF 2, SrCl 2, SrBr 2, SrI 2, BaF 2, BaCI 2, BaBr 2, BaBr 2 2H ₂ O, BaI ₂ , ZnF ₂ , ZnCl ₂ , ZnBr ₂ , ZnI ₂ , CdF ₂ , CdCl ₂ , CdBr ₂ , CdI ₂ , CuF ₂ , CuCl ₂ , CuBr ₂ , CuI, NiF ₂ , NiCl ₂ , NiBr _At least one or two or more compounds selected from ₂ and NiI ₂ compounds are used.

  (C) In the general formula (1), Eu, Tb, In, Cs, Ce, Tm, Dy, Pr, Ho, Nd, Yb, Er, Gd, Lu, Sm, Y, Tl, Na, Ag, Cu And a compound having a metal atom selected from each atom such as Mg.

The phosphor materials (a) to (c) are weighed so as to have a mixed composition in the above numerical range, and dissolved in pure water.
At this time, the mixture may be sufficiently mixed using a mortar, ball mill, mixer mill or the like.
Next, a predetermined acid is added so that the pH value C of the obtained aqueous solution is adjusted to 0 <C <7, and then water is evaporated.
Next, the obtained raw material mixture is filled in a heat-resistant container such as a quartz crucible or an alumina crucible and fired in an electric furnace. The firing temperature is preferably 500 to 1000 ° C. The firing time varies depending on the filling amount of the raw material mixture, the firing temperature and the like, but is preferably 0.5 to 6 hours.
The firing atmosphere includes a nitrogen gas atmosphere containing a small amount of hydrogen gas, a weak reducing atmosphere such as a carbon dioxide atmosphere containing a small amount of carbon monoxide, a neutral atmosphere such as a nitrogen gas atmosphere and an argon gas atmosphere, or a small amount of oxygen gas. A weak oxidizing atmosphere is preferred.

  After firing once under the above firing conditions, the fired product is taken out from the electric furnace and pulverized, and then the fired product powder is again filled in a heat-resistant container and placed in the electric furnace, and again under the same firing conditions as described above. If the firing is performed, the luminous brightness of the photostimulable phosphor can be further increased, and when the fired product is cooled to the room temperature from the firing temperature, the fired product is taken out of the electric furnace and allowed to cool in the air. Although the desired photostimulable phosphor can be obtained, it may be cooled in the same weakly reducing atmosphere or neutral atmosphere as in the firing.

  In addition, by moving the fired product from the heating part to the cooling part in an electric furnace and quenching in a weakly reducing atmosphere, neutral atmosphere or weakly oxidizing atmosphere, the resulting stimulable phosphor is excited. The emission luminance can be further increased, which is preferable.

The photostimulable phosphor layer of the present invention is formed by a vapor deposition method.
As the vapor phase deposition method of the photostimulable phosphor, an evaporation method, a sputtering method, a CVD method, an ion plating method, and others can be used. In the present invention, the evaporation method is particularly preferable.

Hereinafter, the vapor deposition method suitable for the present invention will be described. Here, the stimulable phosphor is vapor-deposited on the support using the vapor deposition apparatus shown in FIG. 2 and will be described together with the explanation of the vapor deposition apparatus.
As shown in FIG. 2, the vapor deposition apparatus 1 includes a vacuum vessel 2, an evaporation source 3 that is provided in the vacuum vessel 2 and deposits vapor on the support 11, and a support holder 4 that holds the support 11. A support rotating mechanism 5 for depositing vapor from the evaporation source 3 by rotating the support holder 4 with respect to the evaporation source 3, a vacuum pump 6 for introducing the exhaust in the vacuum vessel 2 and introducing the atmosphere, etc. It has.

Since the evaporation source 3 contains a stimulable phosphor and is heated by a resistance heating method, the evaporation source 3 may be composed of an alumina crucible wound with a heater, a boat, or a heater made of a refractory metal. May be. In addition to the resistance heating method, the stimulable phosphor may be heated by an electron beam or a high frequency induction method. However, in the present invention, it is easy to handle with a relatively simple structure and is inexpensive. In addition, the resistance heating method is preferable because it is applicable to a large number of substances. The evaporation source 3 may be a molecular beam source by a molecular source epitaxial method.
The support rotation mechanism 5 includes, for example, a rotation shaft 5a that supports the support holder 4 and rotates the support holder 4, and a motor (not shown) that is disposed outside the vacuum vessel 2 and serves as a drive source for the rotation shaft 5a. Etc.
The support holder 4 is preferably provided with a heater (not shown) for heating the support 11. By heating the support 11, the adsorbate on the surface of the support 11 is separated and removed, and the generation of an impurity layer between the surface of the support 11 and the photostimulable phosphor is prevented, the adhesion is enhanced and the brightness is increased. The film quality of the stimulable phosphor layer can be adjusted.
Furthermore, a shutter (not shown) that blocks a space from the evaporation source 3 to the support 11 may be provided between the support 11 and the evaporation source 3. Substances other than the target substance attached to the surface of the photostimulable phosphor by the shutter can be prevented from evaporating at the initial stage of vapor deposition and adhering to the support 11.

In order to form the photostimulable phosphor layer on the support 11 using the vapor deposition apparatus 1 configured as described above, first, the support 11 is attached to the support holder 4.
Next, the vacuum container 2 is evacuated. Thereafter, the support holder 4 is rotated with respect to the evaporation source 3 by the support rotating mechanism 5, and when the vacuum container 2 reaches a vacuum degree capable of vapor deposition, the stimulable phosphor is evaporated from the heated evaporation source 3. Then, a stimulable phosphor is grown on the surface of the support 11 to a desired thickness. In this case, the distance between the support 11 and the evaporation source 3 is preferably set to 100 mm to 1500 mm.

In this vapor deposition, for example, by adjusting the vapor deposition rate, the linearity of the columnar crystal side surface on the protective layer side is controlled to be better than the linearity of the columnar crystal side surface on the support side. The average columnar diameter of the columnar crystals on the layer side is controlled to be larger than the average columnar diameter of the columnar crystals on the support side. Specifically, the deposition rate is gradually decreased to improve the linearity of the columnar crystal side surface on the protective layer side, and the deposition rate is gradually increased to increase the average columnar diameter of the columnar crystal on the protective layer side. It is preferable to make it faster.
In addition, the linearity and the average columnar diameter can also be controlled by increasing the number of evaporation sources and performing deposition from a plurality of locations, and it is preferable to control these conditions in appropriate combination.

The stimulable phosphor used as the evaporation source is preferably processed into a tablet shape by pressure compression.
Further, instead of the photostimulable phosphor, a raw material or a raw material mixture may be used.

  1 and 2, the stimulable phosphor layer 12 is deposited on the support 11 so that the incident angle of the vapor flow is 0 °, and the columnar crystals 12 a and 12 b are in contact with the surface of the support 11. Although formed so as to be substantially vertical, the incident angle of the vapor flow is appropriately set by changing the position of the evaporation source 3, and the angle of the formed columnar crystals 12a, 12b with respect to the normal direction of the surface of the support 11 is set. You can change it.

  Further, here, a stimulable phosphor layer not containing a binder is formed. However, the gap formed between the columnar crystals may be filled with a filler such as a binder. In addition to reinforcing the phosphor layer, a highly light-absorbing substance or a highly reflecting substance may be filled. This provides a reinforcing effect and is effective in reducing the light diffusion in the lateral direction of the stimulated excitation light incident on the stimulable phosphor layer.

  In the vapor deposition step, the photostimulable phosphor layer can be formed in a plurality of times. Further, in the vapor deposition step, it is possible to co-evaporate using a plurality of resistance heaters or electron beams to synthesize the desired photostimulable phosphor on the support and simultaneously form the photostimulable phosphor layer. is there.

In the vapor deposition method, the vapor deposition target (support, protective layer, or intermediate layer) may be cooled or heated as necessary during vapor deposition.
Further, the stimulable phosphor layer may be heat-treated after the vapor deposition. In the vapor deposition method, reactive vapor deposition may be performed in which vapor deposition is performed by introducing a gas such as O ₂ or H _{2 as} necessary.

  In forming the photostimulable phosphor layer by the vapor deposition method, the temperature of the support on which the photostimulable phosphor layer is formed is preferably set to room temperature (rt) to 300 ° C., more preferably 50-200 ° C.

  Furthermore, the vapor deposition apparatus is not limited to a rotary apparatus that performs vapor deposition by rotating the support as described above. For example, a deposition plate having a slit is disposed between the support and the evaporation source. A transport type vapor deposition apparatus (not shown) that deposits the stimulable phosphor through the slit while reciprocating the support in the horizontal direction with respect to the evaporation source may be used.

  After forming the photostimulable phosphor layer as described above, the radiation image conversion panel of the present invention is provided by providing a protective layer on the side opposite to the support of the photostimulable phosphor layer as necessary. To manufacture. The protective layer may be formed by directly applying a coating solution for the protective layer to the surface of the photostimulable phosphor layer, or a protective layer separately formed in advance may be adhered to the photostimulable phosphor layer. .

  Materials for the protective layer include cellulose acetate, nitrocellulose, polymethyl methacrylate, polyvinyl butyral, polyvinyl formal, polycarbonate, polyester, polyethylene terephthalate, polyethylene, polyvinylidene chloride, nylon, polytetrafluoroethylene, polytrifluoride-chloride. Usual protective layer materials such as ethylene, ethylene tetrafluoride-hexafluoropropylene copolymer, vinylidene chloride-vinyl chloride copolymer, vinylidene chloride-acrylonitrile copolymer are used. In addition, a transparent glass substrate can be used as the protective layer.

Further, this protective layer may be formed by laminating inorganic substances such as SiC, SiO ₂ , SiN, Al ₂ O ₃ by vapor deposition, sputtering, or the like. The thickness of these protective layers is preferably 0.1 μm to 2000 μm.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, the embodiment of this invention is not limited to this.
Radiation image conversion panels of Examples 1 to 5 and Comparative Examples 1 to 2 were prepared according to the following method.
[Example 1]
(Production of radiation image conversion panel)
A stimulable phosphor layer was formed by vapor-depositing a stimulable phosphor (CsBr: 0.0002Eu) on one side of a support made of a carbon fiber reinforced resin sheet using the vapor deposition apparatus 1 shown in FIG.
That is, first, the above-mentioned phosphor raw material was filled in a resistance heating crucible as an evaporation material, and the support 11 was placed on the rotating support holder 4, and the distance between the support 11 and the evaporation source 3 was adjusted to 500 mm. Subsequently, the inside of the vapor deposition apparatus 1 was once evacuated, Ar gas was introduced and the degree of vacuum was adjusted to 0.01 Pa, and then the temperature of the support 11 was maintained at 100 ° C. while rotating the support 11 at a speed of 10 rpm. . Next, the resistance heating crucible was heated to deposit a stimulable phosphor, and the deposition was terminated when the thickness of the stimulable phosphor layer reached 500 μm. In addition, it adjusted so that it might become desired linearity and an average particle diameter by adjusting a vapor deposition rate to 1 micrometer / min during this vapor deposition.
Next, the stimulable phosphor layer was placed in a protective layer bag in dry air to obtain a radiation image conversion panel having a structure in which the stimulable phosphor layer was sealed.

About the radiation image conversion panel obtained at this time, the width of the waviness of the columnar crystal side surface corresponding to the above range (5% to 15%) on the protective layer side and the columnar crystal side surface corresponding to the above range (0% to 10%) on the support side The width of the swell was measured.
The width of the waviness of the columnar crystal side surface is measured by exposing the cross section of the photostimulable phosphor layer, observing the columnar side surface with a scanning electron microscope (SEM), and measuring the maximum protruding portion with respect to the center line of the columnar crystal side surface. A line was drawn in parallel with respect to the center line for the maximum recessed portion, and the interval between the lines was defined as the undulation width (see FIG. 3). As a result of the measurement, the protective layer side was 0.1 μm, and the support side was 0.5 μm. Similarly, when the average columnar diameter was measured, the protective layer side was 3 μm and the support side was 2 μm.

[Example 2]
It was produced in the same manner as in Example 1 except that the distance between the support and the evaporation source was 400 mm. At this time, the waviness width (linearity) of the obtained radiation image conversion panel was 0.3 μm on the protective layer side and 0.5 μm on the support side. The average columnar diameter was 3 μm on the protective layer side and 2 μm on the support side.

[Example 3]
The distance between the support and the evaporation source was 400 mm, the deposition rate was initially 1 μm / min, and when the stimulable phosphor layer thickness was approximately halved, the deposition rate was changed to 5 μm / min. The others were produced in the same manner as in Example 1. At this time, the waviness width (linearity) of the obtained radiation image conversion panel was 0.3 μm on the protective layer side and 0.5 μm on the support side. The average columnar diameter was 6 μm on the protective layer side and 2 μm on the support side.

[Example 4]
When the distance between the support and the evaporation source is 400 mm, the deposition rate is 5 μm / min in the initial stage, and the film thickness of the stimulable phosphor layer is almost halved, the deposition rate is changed to 1 μm / min. The others were produced in the same manner as in Example 1. At this time, the waviness width (linearity) of the obtained radiation image conversion panel was 0.3 μm on the protective layer side and 0.5 μm on the support side. The average columnar diameter was 2 μm on the protective layer side and 3 μm on the support side.

[Example 5]
The initial deposition rate was 5 μm / min. When the photostimulable phosphor layer thickness was approximately halved, the deposition rate was changed to 1 μm / min. . At this time, the waviness width (linearity) of the obtained radiation image conversion panel was 0.1 μm on the protective layer side and 0.5 μm on the support side. The average columnar diameter was 2 μm on the protective layer side and 3 μm on the support side.

[Comparative Example 1]
It was produced in the same manner as in Example 1 except that the distance between the support and the evaporation source was 200 mm. At this time, the waviness width (linearity) of the obtained radiation image conversion panel was 1.5 μm on the protective layer side and 1 μm on the support side. The average columnar diameter was 3 μm on the protective layer side and 2 μm on the support side.

[Comparative Example 2]
It was produced in the same manner as in Example 1 except that the distance between the support and the evaporation source was 300 mm. At this time, the waviness width (linearity) of the obtained radiation image conversion panel was 1 μm on the protective layer side and 0.5 μm on the support side. The average columnar diameter was 3 μm on the protective layer side and 2 μm on the support side.

And the following evaluation was performed about the radiation image conversion panel obtained as mentioned above.
<< Granularity (Noise) >>
The graininess is stimulated emission emitted from the stimulable phosphor layer by irradiating the radiation image conversion panel with X-rays having a tube voltage of 80 kVp and then exciting the panel with He-Ne laser light (633 nm). Is received by a photoreceiver (photomultiplier tube with spectral sensitivity S-5) and converted into an electrical signal, which is reproduced as an image by an image reproducing device and output by a laser imager, and the obtained image is visually observed. Noise was evaluated. The noise was evaluated in five stages from 1 to 5 as follows. Table 1 shows the results.
5: Almost no noise 4: Noise is present but no problem 3: Some noise is observed 2: There is a little noise 1: There is a lot of noise and cannot withstand the evaluation If it is 3 or more in the above rank, it is practical It was determined that there was no problem.

表１の結果から明らかなように、保護層側の柱状結晶側面におけるうねりの幅が、支持体側の柱状結晶側面におけるうねりの幅に比べて短く、保護層側における柱状結晶側面の直線性の方が良好である実施例１〜実施例５は、支持体側における柱状結晶側面の直線性の方が良好である比較例１〜比較例２に比べて、ノイズのランクも良く粒状性に優れていた。
また、特に実施例１〜実施例３のように、保護層側における柱状結晶の平均柱状径が支持体側における柱状結晶の平均柱状径より大きい場合に、粒状性に優れることがわかる。
このように、保護層側及び支持体側の柱状結晶の側面形状を制御することにより、ノイズを実用上問題のない程度とすることができ、放射線画像の画質を格段に向上させることが可能となる。

As is clear from the results in Table 1, the width of the undulation on the columnar crystal side surface on the protective layer side is shorter than the width of the undulation on the columnar crystal side surface on the support side, and the linearity of the columnar crystal side surface on the protective layer side is In Examples 1 to 5 in which the linearity of the columnar crystal on the support side is better, the noise rank is better and the graininess is better than Comparative Examples 1 to 2 in which the linearity of the columnar crystal side surface on the support side is better. .
Moreover, it turns out that it is excellent in granularity especially when the average columnar diameter of the columnar crystal on the protective layer side is larger than the average columnar diameter of the columnar crystal on the support side as in Examples 1 to 3.
In this way, by controlling the side surface shape of the columnar crystals on the protective layer side and the support side, noise can be reduced to a practically no problem level, and the image quality of the radiation image can be remarkably improved. .

It is a schematic sectional drawing which shows an example of the photostimulable fluorescent substance layer formed on the support body. It is sectional drawing which shows schematic structure of a vapor deposition apparatus. It is sectional drawing of the columnar crystal for demonstrating the width | variety of the waviness of a columnar crystal side surface.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vapor deposition apparatus 2 Vacuum vessel 3 Evaporation source 5 Support body rotation mechanism 11 Support body 12 Stimulable phosphor layer 12a Protective layer side columnar crystal 12b Support side columnar crystal

Claims (3)

A radiation image conversion panel in which a photostimulable phosphor layer comprising a columnar crystal containing a photostimulable phosphor is formed on a support by a vapor deposition method, and the photostimulable phosphor layer is covered with a protective layer. Because
The photostimulable phosphor layer is a single-layer columnar crystal formed by activating an activator on the matrix of the photostimulable phosphor,
On the side of the columnar crystal of the photostimulable phosphor layer, the linearity in the portion corresponding to 5% to 15% of the film thickness from the protective layer side with respect to the film thickness of the photostimulable phosphor layer is as follows: The radiation image conversion panel characterized by being better than the linearity in the region corresponding to 0% to 10% of the film thickness.   The average columnar diameter of the columnar crystals at the portion corresponding to 5% to 15% of the film thickness from the protective layer side with respect to the film thickness of the photostimulable phosphor layer is 0% to 15% of the film thickness from the support side. 2. The radiation image conversion panel according to claim 1, wherein the radiation image conversion panel is larger than an average columnar diameter of columnar crystals at a portion corresponding to%.   3. The radiation image conversion panel according to claim 1, wherein the stimulable phosphor layer has a thickness of 50 μm or more and 1000 μm or less.

Images