JP2006029852A - Method for manufacturing radiation image conversion panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a radiation image conversion panel which gives radiation images of good image qualities. <P>SOLUTION: The method for manufacturing the radiation image conversion panel includes a process for forming a phosphor layer by evaporating and laying up phosphor ingredients generated through the heating of an evaporation source containing phosphor materials on a substrate in an evaporator. The method is characterized in that the chronological change rate of a lay-up speed of the phosphor ingredients in an arbitrary point on the substrate ranges between 0.03 and 2 μm/sec<SP>2</SP>. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a radiation image conversion panel used in a radiation image recording / reproducing method using a stimulable phosphor.

  When irradiated with radiation such as X-rays, it absorbs and accumulates part of the radiation energy, and then emits light according to the accumulated radiation energy when irradiated with electromagnetic waves (excitation light) such as visible light and infrared rays. Using a stimulable phosphor having properties (such as a stimulable phosphor exhibiting stimulating luminescence), the specimen is transmitted through the sheet-shaped radiation image conversion panel containing the stimulable phosphor or the subject. The radiation image information of the subject is once accumulated and recorded by irradiating the radiation emitted from the laser beam, and then the panel is scanned with excitation light such as laser light and emitted sequentially as emitted light, and this emitted light is read photoelectrically. Thus, a radiation image recording / reproducing method comprising obtaining an image signal has been widely put into practical use. After the reading of the panel is completed, the remaining radiation energy is erased, and then the panel is prepared and used repeatedly for the next imaging.

  A radiation image conversion panel (also referred to as an accumulative phosphor sheet) used in a radiation image recording / reproducing method includes a support and a phosphor layer provided thereon as a basic structure. However, a support is not necessarily required when the phosphor layer is self-supporting. In addition, a protective layer is usually provided on the upper surface of the phosphor layer (the surface not facing the support) to protect the phosphor layer from chemical alteration or physical impact.

  The phosphor layer is composed of a stimulable phosphor and a binder containing and supporting the phosphor in a dispersed state, and only aggregates of the stimulable phosphor without a binder formed by vapor deposition or sintering. And those in which a polymer substance is impregnated in the gaps between the aggregates of the stimulable phosphor are known.

  In addition, as another method of the above-described radiographic image recording / reproducing method, Patent Document 1 discloses at least a storage phosphor (energy storage phosphor) by separating a radiation absorption function and an energy storage function of a conventional storage phosphor. A radiation image forming method using a combination of a radiation image conversion panel containing a phosphor and a phosphor screen containing a phosphor (radiation absorbing phosphor) that absorbs radiation and emits light in the ultraviolet to visible region has been proposed. . In this method, radiation that has passed through a subject is first converted into light in the ultraviolet or visible region by the screen or panel radiation-absorbing phosphor, and then the light is imaged by the panel's energy storage phosphor. Accumulate and record as information. Next, the panel is scanned with excitation light to emit emitted light, and the emitted light is read photoelectrically to obtain an image signal. Such a radiation image conversion panel and a fluorescent screen are also included in the present invention.

  The radiographic image recording / reproducing method (and the radiographic image forming method) is a method having a number of excellent advantages as described above. However, the radiographic image conversion panel used in this method is as sensitive as possible. In addition, it is desired to provide an image with good image quality (sharpness, graininess, etc.).

  For the purpose of improving sensitivity and image quality, a method of forming a phosphor layer of a radiation image conversion panel by a vapor deposition method has been proposed. The vapor deposition method includes a vapor deposition method and a sputtering method. For example, the vapor deposition method evaporates and scatters the evaporation source by heating the evaporation source made of the phosphor or its raw material by irradiation with a resistance heater or an electron beam. By depositing the evaporated material on the surface of a substrate such as a metal sheet, a phosphor layer made of columnar crystals of the phosphor is formed.

  The phosphor layer formed by the vapor deposition method does not contain a binder and is composed only of the phosphor, and there are voids between the columnar crystals of the phosphor. For this reason, since the entrance efficiency of excitation light and the extraction efficiency of emitted light can be increased, the sensitivity is high, and the scattering of the excitation light in the plane direction can be prevented, so that a high sharpness image can be obtained. .

  Patent Document 2 discloses a method for manufacturing a radiation image conversion panel in which a phosphor layer is formed by increasing the deposition rate over time when a photostimulable phosphor layer is formed by a vapor deposition method. It is disclosed. In this patent document, the average deposition rate of the phosphor is taken up.

  In Patent Document 3, there is provided a regulating member that has a slit between the evaporation source and the support that moves relative to the evaporation source, and that regulates an intersection angle at which the evaporation flow from the evaporation source enters the support surface. A phosphor deposition apparatus is disclosed. The example describes that the support is reciprocated at a speed of 50 cm / min.

  In Patent Document 4, when the phosphor layer is formed by vapor deposition on the substrate, the phosphor layer is deposited so that the density of the phosphor layer is lower than the density of the phosphor as a solid. A method of forming a phosphor layer having a needle-like structure is disclosed. This patent document describes that the substrate is rotated at a rotational speed of 12 rpm.

  However, none of the above patent documents describes the stability (that is, the rate of change) of the deposition rate at any point on the substrate.

JP 2001-255610 A Japanese Patent No. 3070941 Japanese Patent No. 2789194 US Patent Application Publication No. 2001 / 0007352A1

  When the phosphor layer of the radiation image conversion panel is formed by vapor deposition, a phosphor layer composed of a phosphor having a columnar crystal structure is generally obtained, and the average column diameter of the columnar crystals is several μm to several tens μm. However, the phosphor crystal may grow locally and abnormally during the columnar crystal growth process, and the crystal size of this abnormally grown crystal (also called abnormal crystal or Hillock) is the pixel size at the time of panel reading or image reproduction. It has been found that if the image size is exceeded, it can be confirmed as a point defect on the reconstructed radiographic image, which hinders various diagnoses and examinations.

  On the other hand, when a substance that evaporates from the evaporation source is deposited on the substrate while moving the substrate, the evaporation substance is deposited on the substrate even if the evaporation flow rate (evaporation rate) from the evaporation source is constant. The rate of deposition (deposition rate) is maximum at a position directly above the evaporation source and decreases with distance from the evaporation source. Therefore, when a certain place on the substrate is considered, the change in the deposition rate with time increases as the moving speed of the substrate increases. And it turned out that said abnormal crystal increases, so that the time change rate of a deposition rate is large.

  Accordingly, it is an object of the present invention to provide a method of manufacturing a radiation image conversion panel that provides a radiation image with good image quality with few point defects and no image unevenness.

  As a result of repeated investigations on the above-mentioned problems, the present inventor has found that abnormal crystals can be remarkably reduced when the temporal rate of change of the deposition rate is within a certain value at any location on the substrate. It has come.

Accordingly, the present invention provides a radiation image conversion including a step of forming a phosphor layer by vapor deposition of a phosphor component generated by heating an evaporation source including a phosphor material in a vapor deposition apparatus. A method for manufacturing a radiation image conversion panel, characterized in that the temporal change rate of the deposition rate of the phosphor component at an arbitrary position on the substrate is in the range of 0.03 to 2 μm / second ^2. is there.

  The manufacturing method of the present invention suitably adjusts the moving speed of the substrate, the evaporation speed of the evaporation flow, the deposition range of the evaporation substance, etc., and suppresses the time change rate of the deposition speed of the evaporation substance within a certain value, Abnormal crystals (Hillock) that cause image point defects can be remarkably reduced. Furthermore, the film thickness of the deposited film can be made uniform, and the occurrence of image unevenness can be prevented. Therefore, the radiation image conversion panel manufactured by the method of the present invention gives a radiation image with good image quality and can be used advantageously for medical radiation image diagnosis.

In the method for producing a radiation image conversion panel of the present invention, the temporal change rate of the deposition rate of the phosphor component is preferably in the range of 0.03 to 1 μm / second ² .

  It is preferable that the substrate is reciprocated in a linear direction at a speed in the range of 3 to 250 mm / sec in the vapor deposition apparatus.

  Alternatively, it is preferable to rotate the substrate around an arbitrary position on the substrate so that the moving speed at an arbitrary position on the substrate is within 250 mm / second. Furthermore, it is preferable to rotate the substrate around an arbitrary position on the substrate so that the maximum moving speed of the substrate is in the range of 3 to 250 mm / second.

  The degree of vacuum in the vapor deposition apparatus is preferably maintained in the range of 0.1 to 10 Pa. Moreover, it is preferable to perform vapor deposition by a resistance heating system.

The phosphor is preferably a stimulable phosphor, and particularly preferably an alkali metal halide-based stimulable phosphor having the following basic composition formula (I). In the basic composition formula (I), M ^I is Cs, X is Br, A is Eu, and z is preferably a numerical value in the range of 1 × 10 ⁻⁴ ≦ z ≦ 0.1. .

M ^I X · aM ^II X ' ₂ · bM ^III X " ₃ : zA (I)

[Wherein M ^I represents at least one alkali metal selected from the group consisting of Li, Na, K, Rb, and Cs; M ^II represents Be, Mg, Ca, Sr, Ba, Ni, Cu, Zn, and Cd. M ^III represents Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, and at least one alkaline earth metal or divalent metal selected from the group consisting of Represents at least one rare earth element or trivalent metal selected from the group consisting of Tm, Yb, Lu, Al, Ga and In; X, X ′ and X ″ are from the group consisting of F, Cl, Br and I, respectively. Represents at least one halogen selected; A represents Y, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Cu, Ag, Tl, and Bi Less selected Each represents a kind of rare earth element or metal; and a, b and z represent numerical values in the range of 0 ≦ a <0.5, 0 ≦ b <0.5 and 0 <z <1.0, respectively]

  Hereinafter, the method for producing the radiation image conversion panel of the present invention will be described in detail, taking as an example the case where the phosphor is a storage phosphor and the vapor deposition method using the resistance heating method is used.

  The substrate for forming the vapor deposition film usually serves also as a support for the radiation image conversion panel, and can be arbitrarily selected from known materials as a support for the conventional radiation image conversion panel. A quartz glass sheet, a sapphire glass sheet; a metal sheet made of aluminum, iron, tin, chromium or the like; a resin sheet made of aramid or the like. In a known radiation image conversion panel, in order to improve the sensitivity or image quality (sharpness, graininess) of the panel, a light reflecting layer made of a light reflecting material such as titanium dioxide, or a light absorbing material such as carbon black It is known to provide a light absorption layer made of or the like. These various layers can also be provided on the substrate used in the present invention, and the configuration thereof can be arbitrarily selected according to the desired purpose and application of the radiation image conversion panel. Further, for the purpose of enhancing the columnar crystallinity of the deposited film, the surface of the substrate on which the deposited film is formed (an auxiliary layer such as an undercoat layer (adhesion-imparting layer), a light reflecting layer or a light absorbing layer on the surface of the substrate). May be formed on the surface of these auxiliary layers).

  The stimulable phosphor is preferably a stimulable phosphor that exhibits stimulated emission in a wavelength range of 300 to 500 nm when irradiated with excitation light having a wavelength of 400 to 900 nm.

Among them, basic composition formula (I):
M ^I X · aM ^II X ' ₂ · bM ^III X " ₃ : zA (I)
An alkali metal halide photostimulable phosphor represented by the formula (1) is particularly preferred. M ^I represents at least one alkali metal selected from the group consisting of Li, Na, K, Rb, and Cs, and M ^II consists of Be, Mg, Ca, Sr, Ba, Ni, Cu, Zn, and Cd. at least one rare earth element or trivalent metal selected from the group, M ^III is Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm Represents at least one rare earth element or trivalent metal selected from the group consisting of Yb, Lu, Al, Ga and In, and A represents Y, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho Represents at least one rare earth element or metal selected from the group consisting of Er, Tm, Yb, Lu, Mg, Cu and Bi. X, X ′ and X ″ each represent at least one halogen selected from the group consisting of F, Cl, Br and I. a, b and z are 0 ≦ a <0.5 and 0 ≦ b <, respectively. It represents a numerical value within the range of 0.5 and 0 <z <1.0.

In the basic composition formula (I), z is preferably in the range of 1 × 10 ⁻⁴ ≦ z ≦ 0.1. M ^I preferably contains at least Cs. X preferably contains at least Br. A is preferably Eu or Bi, and particularly preferably Eu. In addition, in the basic composition formula (I), if necessary, a metal oxide such as aluminum oxide, silicon dioxide, zirconium oxide or the like is added in an amount of 0.5 mol or less with respect to 1 mol of M ^I X. May be added.

The basic composition formula (II):
M ^II FX: zLn (II)
Also preferred are rare earth activated alkaline earth metal fluoride halide stimulable phosphors. M ^II represents at least one alkaline earth metal selected from the group consisting of Ba, Sr and Ca, and Ln represents Ce, Pr, Sm, Eu, Tb, Dy, Ho, Nd, Er, Tm and Yb. Represents at least one rare earth element selected from the group consisting of X represents at least one halogen selected from the group consisting of Cl, Br and I. z represents a numerical value within the range of 0 <z ≦ 0.2.

As M ^II in the basic composition formula (II), Ba preferably accounts for more than half. Ln is particularly preferably Eu or Ce. Further, in the basic composition formula (II), it appears as F: X = 1: 1 on the notation, but this indicates that it has a BaFX-type crystal structure, and the stoichiometric value of the final composition. It does not indicate composition. In general, a state in which many F ⁺ (X ⁻ ) centers, which are X ⁻ ion vacancies, are generated in a BaFX crystal is preferable in order to increase the photostimulation efficiency with respect to light of 600 to 700 nm. At this time, F is often slightly more excessive than X.

Although omitted in the basic composition formula (II), one or more of the following additives may be added to the basic composition formula (II) as necessary.
bA, wN ^I , xN ^II , yN ^III
However, A represents a metal oxide such as Al ₂ O _3, SiO ₂ and ZrO _2. In preventing sintering between M ^II FX particles, it is preferable to use an average particle size of the primary particles has low reactivity with M ^II FX in the following ultrafine particles 0.1 [mu] m. N ^I represents at least one alkali metal compound selected from the group consisting of Li, Na, K, Rb and Cs, N ^II represents an alkaline earth metal compound composed of Mg and / or Be, N ^III represents a compound of at least one trivalent metal selected from the group consisting of Al, Ga, In, Tl, Sc, Y, La, Gd, and Lu. As these metal compounds, halides are preferably used, but are not limited thereto.

In addition, b, w, x, and y are the amounts added to the feed when the number of moles of M ^II FX is 1, and 0 ≦ b ≦ 0.5, 0 ≦ w ≦ 2, 0 ≦ x ≦ 0. 3 represents a numerical value within each range of 0 ≦ y ≦ 0.3. These numerical values do not represent the ratio of elements contained in the final composition with respect to the additive that is reduced by firing or subsequent cleaning treatment. Some of the compounds remain as added in the final composition, while others react with or be taken up by M ^II FX.

In addition, in the above basic composition formula (II), if necessary, Zn and Cd compounds; TiO ₂ , BeO, MgO, CaO, SrO, BaO, ZnO, Y ₂ O ₃ , La ₂ O ₃ , In ₂ O ₃ , GeO ₂ , SnO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , ThO _{2 and} other metal oxides; Zr and Sc compounds; B compounds; As and Si compounds; tetrafluoroboric acid compounds; Hexafluorotitanic acid and a hexafluoro compound composed of a monovalent or divalent salt of hexafluorozirconic acid; compounds of transition metals such as V, Cr, Mn, Fe, Co and Ni may be added. Furthermore, in the present invention, not only the phosphor containing the above-mentioned additives, but any material having a composition basically regarded as a rare earth activated alkaline earth metal fluoride halide stimulable phosphor. It may be.

Basic composition formula (III):
M ^II S: A, Sm (III)
Also preferred are rare earth activated alkaline earth metal sulfide photostimulable phosphors. M ^II represents at least one alkaline earth metal selected from the group consisting of Mg, Ca and Sr. A represents Eu and / or Ce.

Basic composition formula (IV):
M ^III OX: Ce (IV)
A cerium-activated trivalent metal oxide halide photostimulable phosphor represented by M ^III represents at least one rare earth element or trivalent metal selected from the group consisting of Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb, and Bi. X represents at least one halogen selected from the group consisting of Cl, Br and I.

However, in the present invention, the phosphor is not limited to the stimulable phosphor, and may be a phosphor that absorbs radiation such as X-rays and emits (instantaneous) emission in the ultraviolet to visible region. Examples of such phosphors include LnTaO ₄ : (Nb, Gd), Ln ₂ SiO ₅ : Ce, LnOX: Tm (Ln is a rare earth element), CsX (X is a halogen). Gd ₂ O ₂ S: Tb, Gd ₂ O ₂ S: Pr, Ce, ZnWO ₄ , LuAlO ₃ : Ce, Gd ₃ Ga ₅ O ₁₂ : Cr, Ce, HfO _{2 and the} like.

  In the case of forming a deposited film by multi-source deposition (co-evaporation), at least two evaporation sources comprising a matrix component of the stimulable phosphor and an activator component are prepared as evaporation sources. . In the multi-source deposition, when the melting point and vapor pressure of the phosphor base material and the activator component are greatly different, the evaporation rate can be controlled so that the activator can be uniformly contained in the phosphor base. preferable. Each evaporation source may be composed only of the host component and the activator component of the phosphor, or may be a mixture with an additive component, depending on the composition of the stimulable phosphor desired. Good. Further, the number of evaporation sources is not limited to two, and for example, three or more evaporation sources may be added by separately adding evaporation sources composed of additive components.

  The matrix component of the phosphor may be the compound itself constituting the matrix, or may be a mixture of two or more raw materials that can react to form a matrix compound. The activator component is generally a compound containing an activator element. For example, a halide or oxide of the activator element is used.

When the activator is Eu, the molar ratio of the Eu ²⁺ compound to the Eu compound as the activator component is preferably as high as possible. This is because the desired stimulated light emission (or even instantaneous light emission) is emitted from a phosphor using Eu ²⁺ as an activator. In general, commercially available Eu compounds often contain a mixture of Eu ²⁺ and Eu ³⁺ due to oxygen contamination. In such a case, the Eu compound is previously contained in a Br gas atmosphere. in and melting treatment to remove oxygen content, and it is desirable to use the resulting EuBr _2.

  The evaporation source preferably has a water content of 0.5% by weight or less. It is important from the standpoint of preventing bumping, especially when the phosphor matrix component and activator component that is the evaporation source is hygroscopic, such as EuBr and CsBr, for example, to suppress the water content to such a low value. It is. The evaporation source is preferably dehydrated by subjecting each phosphor component to a heat treatment at a temperature range of 100 to 300 ° C. under reduced pressure. Alternatively, each phosphor component may be heated and melted for several tens of minutes to several hours at a temperature equal to or higher than the melting point of the component in an atmosphere containing no moisture such as a nitrogen gas atmosphere.

  Furthermore, in the present invention, the evaporation source, particularly the evaporation source containing the phosphor matrix component, has an alkali metal impurity (alkali metal other than the constituent elements of the phosphor) of 10 ppm or less, and an alkaline earth metal impurity (fluorescence). The content of the alkaline earth metal other than the constituent elements of the body is desirably 5 ppm (weight) or less. In particular, it is desirable when the phosphor is an alkali metal halide-based stimulable phosphor having the basic composition formula (I). Such an evaporation source can be prepared by using a raw material having a low impurity content such as an alkali metal or an alkaline earth metal.

  In the present invention, for example, a vapor deposition apparatus having a resistance heater as shown in FIG. 1 can be used to form a phosphor vapor deposition film on a substrate.

  FIG. 1 is a schematic cross-sectional view showing a configuration example of a vapor deposition apparatus used in the present invention. In FIG. 1, a vapor deposition apparatus includes a chamber 1, a substrate heater 2, a substrate holding / moving member 3, a shutter 5, resistance heaters 6 and 7, a gas introduction pipe 8, a vapor deposition rate monitor 9, a vacuum gauge 10, and a gas analyzer. 11, a main exhaust valve 12, and an auxiliary exhaust valve 13.

The plurality of evaporation sources are filled in the heating containers 6a and 7a of the resistance heaters 6 and 7 of the vapor deposition apparatus shown in FIG. Further, the substrate 4 is held and fixed to the substrate holding / moving member 3. The inside of the chamber 1 of the apparatus is evacuated by the main exhaust valve 12 and the auxiliary exhaust valve 13 to a medium vacuum degree of about 0.1 to 10 Pa. The degree of vacuum is preferably 0.1 to 4 Pa. Particularly preferably, after the chamber 1 is evacuated to a high vacuum level of about 1 × 10 ⁻⁵ to 1 × 10 ⁻² Pa, an inert gas such as Ar gas, Ne gas, N ₂ gas or the like is introduced from the gas introduction pipe 8. A gas is introduced to make the pressure of the inert gas 0.1 to 10 Pa, preferably 0.1 to 4 Pa. Thereby, the water pressure, oxygen partial pressure, etc. in the apparatus can be lowered. The degree of vacuum is detected by the vacuum gauge 10, and the gas partial pressure is detected by the gas analyzer 11. As the exhaust device, a rotary pump, a turbo molecular pump, a diffusion pump, a cryopump, a mechanical booster, or the like can be used in appropriate combination.

  The distance between the evaporation sources in the heating containers 6a and 7a and the substrate 4 varies depending on the size of the substrate, but generally ranges from 10 to 1000 mm, and the distance between the evaporation sources ranges from 10 to 1000 mm.

  The substrate 4 is reciprocated in the linear direction by the substrate holding / moving member 3 or is rotated about the rotation axis on the substrate.

  FIG. 2 is a top view showing a typical example when the substrate is linearly moved, and FIG. 3 is a cross-sectional view taken along the line II of FIG. 2 and 3, the evaporation source is a set of two, and three sets (61, 71, 62, 72, 63, 73) are arranged at equal intervals, and have vapor deposition areas 81, 82, 83, respectively. . Here, the deposition area (deposition range) means a region where a deposition rate of 10% or more is maintained with respect to the maximum deposition rate at the substrate position directly above the evaporation source. The substrate (size m × n) 41 reciprocates in the direction of the arrow 21. h is the distance between the substrate 41 and the evaporation sources 62 and 72, and i is the diameter of the deposition area 82.

  For example, when the distance between the substrate and the evaporation source is h = 150 mm, the deposition area diameter is i = 120 mm, and the substrate size is m × n = 45 cm × 45 cm, the position directly above the evaporation source (center position of the deposition area) a Assuming that the deposition rate (maximum rate) at 100% is 100%, the deposition rate at the end b of the deposition area is about 10%. When the substrate moves 60 mm from the area end b to the center position a, the deposition rate changes 10 times (inversely 1/10 times) and shows the maximum change.

In the present invention, the rate of change of the deposition rate with time at an arbitrary location on the substrate 41 is 2 μm / second ^{2 or} less. Therefore, the linear movement speed of the substrate 41 is preferably in the range of 3 to 250 mm / second. Moreover, it is preferable that the distance which passes the inside of a vapor deposition area with respect to the total distance which the board | substrate 41 moves linearly shall be 60% or less at maximum. The total travel distance of the substrate is usually approximately equal to the length m of the substrate. This is because a large number of evaporation sources are required to widen the deposition area, resulting in an increase in manufacturing cost, and it is technically more difficult to uniformly control a large number of evaporation sources.

  FIG. 4 is a top view showing a typical example in the case of rotating the substrate, and FIG. 5 is a cross-sectional view taken along the line II of FIG. 4 and 5, two evaporation sources are arranged in pairs (64, 74, 65, 75), and have evaporation areas 84 and 85, respectively. The substrate (size m × n) 42 rotates in the direction of the arrow 22 with the center of the substrate as the rotation axis. h is the distance between the substrate 42 and the evaporation sources 64 and 74, and i is the diameter of the deposition area 84.

  For example, when the distance between the substrate and the evaporation source is h = 150 mm, the deposition area diameter is i = 120 mm, and the substrate size is m × n = 45 cm × 45 cm, the position directly above the evaporation source (center position of the deposition area) a Assuming that the deposition rate (maximum rate) at 100% is 100%, the deposition rate at the end b of the deposition area is about 10%. When the substrate moves from the end b of the area to the center position a, the deposition speed changes 10 times (inversely 1/10 times).

In the present invention, the temporal change rate of the deposition rate at an arbitrary position on the substrate 42 is within 2 μm / second ² . Therefore, it is preferable that the rotational movement speed at an arbitrary position of the substrate 42 is within 250 mm / second. It depends on the size of the substrate 42. In order to reduce the rate of change of the deposition rate, it is better that the rotational movement speed is slow, but if it is too slow, the film thickness of the vapor deposition film formed becomes non-uniform, so that the rotational movement speed becomes maximum (FIG. 4). In the corner portion c) of the substrate 42, the rotational movement speed is preferably in the range of 3 to 250 mm / second. For the same reason as described above, it is preferable that the distance passing through the deposition area with respect to the total distance that the outer peripheral portion of the substrate 42 moves is within 60% at the maximum.

  Note that the movement of the substrate and the arrangement of the evaporation sources according to the present invention are not limited to the configurations shown in FIGS. 2 to 5, and the number of evaporation sources (the number in the case of single deposition) and the arrangement thereof. Can be appropriately determined according to the vapor deposition apparatus, the size of the substrate, the manner of movement, and the like. Further, the direction of linear movement of the substrate and the position of the central axis in the case of rotational movement can be arbitrarily determined.

  Next, vapor deposition is performed by a resistance heating method. The resistance heating method has an advantage that vapor deposition can be performed at a moderate degree of vacuum, and a vapor deposition film having a good columnar crystal can be easily obtained. Electric current is supplied to the resistance heaters 6 and 7 in FIG. 1 to heat the evaporation sources in the heating containers 6a and 7a. Prior to vapor deposition, it is desirable to heat each evaporation source sufficiently to completely melt it.

  It is considered that point defects generated due to abnormal growth of the phosphor crystal become larger due to a change in evaporation rate or a change in deposition rate, starting from bumping or splashing of the substance evaporated from the evaporation source. The size of the abnormal crystal (Hillock) is determined by the size of the starting point, the shape of the abnormal crystal, and the thickness of the deposited film. Therefore, large bumping and splash can be prevented by sufficiently melting the evaporation source before vapor deposition. Further, it is possible to stabilize the evaporation flow and maintain a constant evaporation rate.

  The matrix component, activator component, and the like of the stimulable phosphor that is the evaporation source are heated to evaporate and scatter, and react to form the phosphor and deposit on the surface of the substrate 4. At this time, the substrate 4 may be heated from the back surface by the substrate heater 2. Alternatively, the substrate 4 may be cooled. The substrate temperature is generally in the range of 20 to 350 ° C., preferably in the range of 100 to 300 ° C. The evaporation rate of each evaporation source can be controlled by adjusting the resistance current of the heaters 6 and 7. In order to reduce the rate of change of the deposition rate, it is desirable that the evaporation rate be constant during vapor deposition.

  During deposition, the deposition rate at a position directly above the evaporation source is detected by the deposition rate monitor 9 as needed. This deposition rate is generally in the range of 0.001 to 16 μm / second, preferably in the range of 0.01 to 1.6 μm / second. This corresponds to the evaporation rate of the evaporation source.

  As described above, the temporal rate of change of the phosphor deposition rate generally becomes maximum when the substrate moves through the deposition area through the center position of the area. This maximum change rate is the difference between the deposition rate at the center position of the deposition area (position just above the evaporation source) and the deposition speed at the end position, and the substrate moves from the center to the end of the deposition area. It is possible to calculate by dividing by the time required for.

In the present invention, the rate of change of the deposition rate at any location on the substrate is within 2 μm / sec ² . Thereby, generation | occurrence | production of an abnormal crystal | crystallization (Hillock) can be reduced significantly. From the standpoint of reducing abnormal crystals, it is better that the rate of change of the deposition rate is small, that is, it is better that the moving speed of the substrate is slow, but if the moving speed is too slow, the film thickness of the deposited film becomes uneven. As a result, image unevenness occurs, columnar crystallinity deteriorates (it becomes difficult to grow straight in the vertical direction), and the sensitivity is lowered. Although the deposition rate and the rate of change differ depending on the position on the substrate, the maximum rate of change of the deposition rate is preferably in the range of 0.03 to 2 μm / sec ² .

  Note that two or more phosphor layers can be formed by performing heating by a resistance heater in a plurality of times. The deposited film may be heat-treated (annealed) after the deposition. The heat treatment is generally performed at a temperature of 100 ° C. to 300 ° C. for 0.5 to 3 hours, preferably at a temperature of 150 ° C. to 250 ° C. for 0.5 to 2 hours. As the heat treatment atmosphere, an inert gas atmosphere or an inert gas atmosphere containing a small amount of oxygen gas or hydrogen gas is used.

  Prior to forming the vapor deposition film made of the phosphor, a vapor deposition film made only of the phosphor matrix compound may be formed. The matrix compound vapor deposition film generally comprises a columnar crystal structure or an aggregate of spherical crystals, and the columnar crystallinity of the phosphor vapor deposition film formed thereon can be further improved. Depending on the substrate heating during vapor deposition and / or heat treatment after vapor deposition, additives such as an activator in the phosphor vapor-deposited film diffuse into the matrix compound vapor-deposited film, so the boundary between them is not always clear.

  In the case of single vapor deposition, the phosphor itself or the phosphor raw material mixture is used as an evaporation source and heated by a single resistance heater. The evaporation source is prepared in advance to contain a desired concentration of activator. Alternatively, it is possible to perform vapor deposition while supplying the phosphor matrix component to the evaporation source in consideration of the vapor pressure difference between the phosphor matrix component and the activator component.

  In this way, a phosphor layer is obtained in which the columnar crystals of the phosphor are grown substantially in the thickness direction. The phosphor layer does not contain a binder and is composed only of the phosphor, and there are voids between the columnar crystals of the phosphor. The layer thickness of the phosphor layer varies depending on the characteristics of the intended radiation image conversion panel, the means for carrying out the vapor deposition method, conditions, etc., but is usually in the range of 50 μm to 1 mm, preferably in the range of 200 μm to 700 μm. .

  The substrate does not necessarily have to serve as a support for the radiation image conversion panel. After forming the phosphor layer, the phosphor layer is peeled off from the substrate and bonded to the prepared support using an adhesive or the like. A method of providing a phosphor layer on a support may be used. Alternatively, the support (substrate) may not be attached to the phosphor layer.

  The vapor deposition method used in the present invention is not limited to the vapor deposition method using the resistance heating method, and a vapor deposition method using an electron beam irradiation method or the like can also be used.

  It is desirable to provide a protective layer on the surface of the phosphor layer in order to facilitate transportation and handling of the radiation image conversion panel and avoid characteristic changes. It is desirable that the protective layer be transparent so that it does not affect the incidence of excitation light and emission of emitted light, and the radiation image conversion panel is sufficiently protected from physical impacts and chemical effects given from the outside. It is desirable to be chemically stable, highly moisture-proof, and have high physical strength.

  As the protective layer, a solution prepared by dissolving a transparent organic polymer substance such as cellulose derivative, polymethyl methacrylate, organic solvent-soluble fluorine-based resin in an appropriate solvent is applied on the phosphor layer. Formed, or separately formed a protective layer forming sheet such as an organic polymer film such as polyethylene terephthalate or a transparent glass plate, and provided with an appropriate adhesive on the surface of the phosphor layer, or inorganic A compound formed on the phosphor layer by vapor deposition or the like is used. In addition, in the protective layer, various additives such as light scattering fine particles such as magnesium oxide, zinc oxide, titanium dioxide and alumina, slipping agents such as perfluoroolefin resin powder and silicone resin powder, and crosslinking agents such as polyisocyanate. May be dispersed and contained. The thickness of the protective layer is generally in the range of about 0.1 to 20 μm when it is made of a polymer substance, and is in the range of 100 to 1000 μm when it is made of an inorganic compound such as glass.

  A fluororesin coating layer may be further provided on the surface of the protective layer in order to increase the stain resistance of the protective layer. The fluororesin coating layer can be formed by coating a fluororesin solution prepared by dissolving (or dispersing) a fluororesin in an organic solvent on the surface of the protective layer and drying. Although the fluororesin may be used alone, it is usually used as a mixture of a fluororesin and a resin having a high film forming property. In addition, an oligomer having a polysiloxane skeleton or an oligomer having a perfluoroalkyl group can be used in combination. The fluororesin coating layer can be filled with a fine particle filler in order to reduce interference unevenness and further improve the image quality of the radiation image. The thickness of the fluororesin coating layer is usually in the range of 0.5 μm to 20 μm. In forming the fluororesin coating layer, additive components such as a cross-linking agent, a hardener, and a yellowing inhibitor can be used. In particular, the addition of a crosslinking agent is advantageous for improving the durability of the fluororesin coating layer.

  Although the radiation image conversion panel of the present invention is obtained as described above, the configuration of the panel of the present invention may include various known variations. For example, for the purpose of improving the sharpness of an image, at least one of the above layers may be colored with a colorant that absorbs excitation light and does not absorb emitted light.

[Example 1] Linear movement of substrate (1) Evaporation source As an evaporation source, cesium bromide (CsBr) powder having a purity of 4N or more and europium bromide (EuBr ₂ ) powder having a purity of 3N or more were prepared. As a result of analyzing trace elements in each powder by ICP-MS method (inductively coupled plasma spectroscopy-mass spectrometry), alkali metals (Li, Na, K, Rb) other than Cs in CsBr are each 10 ppm or less. Yes, and other elements such as alkaline earth metals (Mg, Ca, Sr, Ba) were 2 ppm or less. Further, rare earth elements other than Eu in EuBr ₂ were each 20 ppm or less, and other elements were 10 ppm or less. Since these powders have high hygroscopicity, they were stored in a desiccator that maintained a dry atmosphere with a dew point of -20 ° C. or less, and were taken out immediately before use.

(2) Formation of phosphor layer As a support, a glass substrate (size: 45 cm × 45 cm) 4 subjected to alkali cleaning, pure water cleaning, and IPA (isopropyl alcohol) cleaning in order was prepared, and the vapor deposition shown in FIG. It was fixed to the substrate holding / moving member 3 in the apparatus. The CsBr evaporation source was filled in the crucible container 6 a of the resistance heater 6, and the EuBr ₂ evaporation source was filled in the crucible container 7 a of the resistance heater 7.

  As shown in FIGS. 2 and 3, three sets of evaporation sources were arranged at equal intervals so that the film thickness distribution of the deposited film was within ± 10%. The distance h between the substrate and each evaporation source was 150 mm. The vapor deposition area diameter i was 120 mm. The substrate was reciprocated in the direction of the arrow. The linear moving speed of the substrate was 200 mm / second.

Next, the inside of the chamber 1 was evacuated by the main exhaust valve 12 and the auxiliary exhaust valve 13 to obtain a vacuum degree of 1 × 10 ⁻³ Pa. At this time, a combination of a rotary pump, a mechanical booster, and a turbo molecular pump was used as a vacuum exhaust device. Ar gas (purity 5N) was introduced into the chamber 1 from the gas introduction pipe 8 to obtain a vacuum degree (Ar gas pressure) of 1.0 Pa. The glass substrate 4 was heated to 100 ° C. by the substrate heater 2.

With the shutter 5 provided between the substrate 4 and each evaporation source closed, an electric current was passed through the resistance heaters 6 and 7 to heat each evaporation source and melt it completely. Thereafter, only the shutter 5 on the CsBr evaporation source side was opened, and a CsBr phosphor matrix was deposited on the surface of the substrate 4 to form a coating layer. Three minutes later, the shutter 5 on the EuBr ₂ evaporation source side was also opened, and a CsBr: Eu photostimulable phosphor was deposited on the coating layer. During deposition, the deposition rate directly above the evaporation source was constant at 0.6 μm / sec. Further, the current values of the resistance heaters 6 and 7 were adjusted to control the Eu / Cs molar concentration ratio in the photostimulable phosphor to 0.003 / 1. After vapor deposition, the inside of the apparatus was returned to atmospheric pressure, and the substrate was taken out from the apparatus. On the substrate, an accumulative phosphor layer (layer thickness: 700 μm, area 43 cm × 43 cm) having a structure in which the columnar crystals of the phosphor were densely planted in a substantially vertical direction was formed.
Thus, the radiation image conversion panel according to the present invention comprising the support and the stimulable phosphor layer was manufactured by co-evaporation.

[Example 2] Linear movement of substrate A radiation image conversion panel according to the present invention was manufactured in the same manner as in Example 1 except that the linear movement speed of the substrate was changed to 20 mm / sec.

[Example 3] Linear movement of substrate A radiation image conversion panel according to the present invention was manufactured in the same manner as in Example 1, except that the linear movement speed of the substrate was changed to 4 mm / second.

Comparative Example 1 Linear Movement of Substrate A radiation image conversion panel for comparison was manufactured in the same manner as in Example 1 except that the linear movement speed of the substrate was changed to 300 mm / sec.

[Comparative Example 2] Linear movement of substrate In Example 1, the linear movement speed of the substrate was changed to 4 mm / second, and the deposition speed directly above the evaporation source was 0.6 μm / second and 0 μm every 0.1 second. A radiation image conversion panel for comparison was manufactured in the same manner as in Example 1 except that it was changed between 1 second / second.

[Performance evaluation 1 of radiation image conversion panel]
About each obtained radiation image conversion panel, the point defect, the image nonuniformity, and the sensitivity were evaluated as follows.
(1) Point defect of radiographic image The radiographic image conversion panel was accommodated in a cassette capable of shielding room light and irradiated with X-rays (10 mR). Next, after removing the panel from the cassette, the image data is obtained from the panel using a line scan reader (excitation light: semiconductor laser array (wavelength: 660 nm), CCD line sensor), and the obtained image data is reproduced. It output as an image film with the apparatus (image size: 200 micrometers). On this output film, a 10 cm × 10 cm region with many point defects was selected, and the number of point defects was counted visually.

(2) Image unevenness The above output film was visually observed to check for the presence of image unevenness.
A: No image unevenness B: Some image unevenness C: Image unevenness is extremely problematic

(3) Sensitivity The radiation image conversion panel was housed in a cassette capable of shielding room light, and irradiated with X-rays having a tube voltage of 80 kVp and a tube current of 16 mA. Next, after removing the panel from the cassette, the surface of the panel was excited with a semiconductor laser beam (wavelength: 660 nm), and the stimulated emission light emitted from the panel was detected by a photomultiplier. The sensitivity was evaluated based on the relative value as a reference.

Also, the maximum rate of change in the deposition rate of the phosphor is determined by the deposition rate (V, 100%) at the center position (position directly above the evaporation source) of the deposition area and the deposition rate (10%) at the end position. V), from the deposition area size i, and the substrate movement speed (v _1), it was determined by the following equation.
Maximum rate of change of deposition rate = (V-0.1V)
0.5i / v ₁
The results obtained are summarized in Table 1.

[Example 4] Rotational movement of substrate A radiation image conversion panel according to the present invention was produced in the same manner as in Example 1 except that (2) the phosphor layer of Example 1 was formed as follows. did.
A glass substrate (size: 45 cm × 45 cm) 4 subjected to alkali cleaning, pure water cleaning, and IPA cleaning in this order was prepared as a support, and fixed to the substrate holding / moving member 3 in the vapor deposition apparatus shown in FIG. . The CsBr evaporation source was filled in the crucible container 6 a of the resistance heater 6, and the EuBr ₂ evaporation source was filled in the crucible container 7 a of the resistance heater 7.

  As shown in FIGS. 4 and 5, two sets of evaporation sources were arranged so that the film thickness distribution of the deposited film was within ± 10%. The distance h between the substrate and each evaporation source was 150 mm. The vapor deposition area diameter i was 120 mm. The substrate was rotated in the direction of the arrow. The rotational movement speed of the corner c of the substrate was about 166 mm / second (rotation speed 10 rpm).

Next, the inside of the chamber 1 was evacuated by the main exhaust valve 12 and the auxiliary exhaust valve 13 to obtain a vacuum degree of 1 × 10 ⁻³ Pa. At this time, a combination of a rotary pump, a mechanical booster, and a turbo molecular pump was used as a vacuum exhaust device. Ar gas (purity 5N) was introduced into the chamber 1 from the gas introduction pipe 8 to obtain a vacuum degree (Ar gas pressure) of 1.0 Pa. The glass substrate 4 was heated to 100 ° C. by the substrate heater 2.

With the shutter 5 provided between the substrate 4 and each evaporation source closed, an electric current was passed through the resistance heaters 6 and 7 to heat each evaporation source and melt it completely. Thereafter, only the shutter 5 on the CsBr evaporation source side was opened, and a CsBr phosphor matrix was deposited on the surface of the substrate 4 to form a coating layer. Three minutes later, the shutter 5 on the EuBr ₂ evaporation source side was also opened, and a CsBr: Eu photostimulable phosphor was deposited on the coating layer. During deposition, the deposition rate directly above the evaporation source was constant at 0.6 μm / sec. Further, the current values of the resistance heaters 6 and 7 were adjusted to control the Eu / Cs molar concentration ratio in the photostimulable phosphor to 0.003 / 1. After vapor deposition, the inside of the apparatus was returned to atmospheric pressure, and the substrate was taken out from the apparatus. On the substrate, an accumulative phosphor layer (layer thickness: 700 μm, area 43 cm × 43 cm) having a structure in which the columnar crystals of the phosphor were densely planted in a substantially vertical direction was formed.
Thus, the radiation image conversion panel according to the present invention comprising the support and the stimulable phosphor layer was manufactured by co-evaporation.

[Example 5] Rotational movement of substrate The radiation according to the present invention is the same as in Example 4 except that the rotational movement speed of the corner of the substrate is changed to about 83 mm / second (rotation speed 5 rpm) in Example 4. An image conversion panel was manufactured.

[Comparative Example 3] Rotational movement of substrate In Example 4, the rotational movement speed of the corner portion of the substrate was changed to about 833 mm / sec (rotational speed 50 rpm) in the same manner as in Example 4 for comparison. A radiation image conversion panel was manufactured.

[Comparative Example 4] Rotational Movement of Substrate For comparison, in Example 4, except that the rotational movement speed of the corner of the substrate was changed to about 300 mm / second (rotation speed 18 rpm). A radiation image conversion panel was manufactured.

[Performance evaluation 2 of radiation image conversion panel]
Each obtained radiation image conversion panel was evaluated for point defects and sensitivity in the same manner as described above. There were many point defects near the corners of the substrate.

Moreover, the temporal rate of change (maximum rate of change) of the phosphor deposition rate at the corner of the substrate is the difference between the deposition rate at which the corner of the substrate is maximum in the vapor deposition area and the deposition rate at the end position, It was determined by dividing by the time required for the corner of the substrate to move from its maximum deposition rate position to the edge.
The results obtained are summarized in Table 2.

As is clear from the results shown in Tables 1 and 2, all of the radiation image conversion panels (Examples 1 to 5) manufactured according to the method of the present invention with the temporal change rate of the deposition rate within 2 μm / second ² were used. As compared with the radiation image conversion panels (Comparative Examples 1 to 4) for comparison in which the rate of change of the deposition rate is outside the above range, the point defects are remarkably reduced. In addition, the panel of the present invention (Examples 1 to 3) exhibited almost no image unevenness and good sensitivity. On the other hand, from Comparative Example 2, if the evaporation rate (corresponding to the deposition rate directly above the evaporation source) changes even if the substrate moving speed is constant, the rate of change of the deposition rate increases, resulting in point defects. It can be seen that it increases.

It is a schematic sectional drawing which shows the structural example of the vapor deposition apparatus used for this invention. It is a top view which shows the typical example of the linear movement of a board | substrate. It is sectional drawing along the II line | wire of FIG. It is a top view which shows the typical example of the rotational movement of a board | substrate. It is sectional drawing along the II line | wire of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Chamber 2 Substrate heater 3 Substrate holding / moving member 4, 41, 42 Substrate 5 Shutter 6, 7 Resistance heater 6a, 7a Heating vessel 8 Gas introduction pipe 9 Deposition rate monitor 10 Vacuum gauge 11 Gas analyzer 12 Main exhaust valve 13 Auxiliary exhaust valve 61, 62, 63, 64, 65, 71, 72, 73, 74, 75 Evaporation source 81, 82, 83, 84, 85 Deposition area

Claims (9)

In a method for manufacturing a radiation image conversion panel, the method includes forming a phosphor layer by vapor-depositing a phosphor component generated by heating an evaporation source containing a phosphor material in a vapor deposition apparatus. A method for producing a radiation image conversion panel, wherein the temporal change rate of the deposition rate of the phosphor component at an arbitrary location on the substrate is in the range of 0.03 to 2 μm / sec ² . ^2. The method for manufacturing a radiation image conversion panel according to claim 1, wherein the temporal change rate of the deposition rate of the phosphor component is in the range of 0.03 to 1 [mu] m / sec < ² >.   The method for producing a radiation image conversion panel according to claim 1 or 2, wherein the substrate is reciprocated in a linear direction at a speed in the range of 3 to 250 mm / sec in the vapor deposition apparatus.   The radiation according to claim 1 or 2, wherein the substrate is rotated around an arbitrary position on the substrate so that a moving speed at an arbitrary position on the substrate in the vapor deposition apparatus is in a range of 3 to 250 mm / sec. An image conversion panel manufacturing method.   The manufacturing method of the radiation image conversion panel of any one of Claims 1 thru | or 4 which maintains the vacuum degree in a vapor deposition apparatus in the range of 0.1 thru | or 10 Pa.   The method for manufacturing a radiation image conversion panel according to any one of claims 1 to 5, wherein vapor deposition is performed by a resistance heating method. The method for manufacturing a radiation image conversion panel according to any one of claims 1 to 6, wherein the phosphor is a stimulable phosphor. The stimulable phosphor has a basic composition formula (I):

M ^I X · aM ^II X ' ₂ · bM ^III X " ₃ : zA (I)

[Wherein M ^I represents at least one alkali metal selected from the group consisting of Li, Na, K, Rb, and Cs; M ^II represents Be, Mg, Ca, Sr, Ba, Ni, Cu, Zn, and Cd. M ^III represents Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, and at least one alkaline earth metal or divalent metal selected from the group consisting of Represents at least one rare earth element or trivalent metal selected from the group consisting of Tm, Yb, Lu, Al, Ga and In; X, X ′ and X ″ are from the group consisting of F, Cl, Br and I, respectively. Represents at least one selected halogen; A represents Y, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Na, Mg, Cu, Ag, Tl and Bi Selected from the group consisting of And at least one kind of rare earth element or metal; and a, b, and z represent numerical values in the range of 0 ≦ a <0.5, 0 ≦ b <0.5, and 0 <z <1.0, respectively. ]
The method for producing a radiation image conversion panel according to claim 7, wherein the phosphor is an alkali metal halide-based stimulable phosphor. 9. In the basic composition formula (I), M ^I is Cs, X is Br, A is Eu, and z is a numerical value in the range of 1 × 10 ⁻⁴ ≦ z ≦ 0.1. The manufacturing method of the radiation image conversion panel of description.

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