JP2004325214A - Radiological image conversion panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radiological image conversion panel having notably-improved sensitivity and adhesiveness. <P>SOLUTION: In this radiological image conversion panel, a phosphor layer formed by a vapor-phase sedimentation method comprises a columnar crystal of a phosphor, and the orientation constant (hkl) specified by the formula has an orientation face satisfying the conditions: the orientation constant (hkl)≥2.5; and (the orientation constant (hkl)/N)×100≥35%. In this case, I(hkl)/I<SB>0</SB>(hkl) is an X-ray diffraction intensity ratio of a specified exponential face (hkl) of a sample, and N is an integer on condition of N≥6 which is a number on the specified exponential face, and Σ<SB>N</SB>(I(hkl)/I<SB>0</SB>(hkl)) includes specified exponential faces (100), (110) and (111). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

［ただし、Ｉ（ｈｋｌ）／Ｉ_０（ｈｋｌ）は、試料の規約された指数面（ｈｋｌ）のＸ線回折強度比であり、Ｎは、規約された指数面の数を表し、Ｎ≧６の整数であり、そしてΣ_Ｎ（Ｉ（ｈｋｌ）／Ｉ_０（ｈｋｌ））は、規約された指数面（１００）、（１１０）及び（１１１）を含む］
該蛍光体層が、配向定数（ｈｋｌ）≧２．５および（配向定数（ｈｋｌ）／Ｎ）×１００≧３５％を満足する配向面（ｈｋｌ）を少なくとも一つ有することを特徴とする放射線像変換パネルにある。
【００１５】
ここで、規約された指数面（ｈｋｌ）とは、後で詳しく説明するように、指数が同一の面や縮退している面を考慮に入れた指数面（ｈｋｌ）を意味し、配向定数（ｈｋｌ）は、その規約された指数面について上記の組織係数ＴＣ（ｈｋｌ）を求めたものである。
【００１６】
【発明の実施の形態】
本発明の放射線像変換パネルの蛍光体層は、配向定数（ｈｋｌ）≧３．５および（配向定数（ｈｋｌ）／Ｎ）×１００≧４０％を満足する配向面（ｈｋｌ）を少なくとも一つ有することが好ましく、特に好ましくは、配向定数（ｈｋｌ）≧４．０および（配向定数（ｈｋｌ）／Ｎ）×１００≧５０％を満足する配向面（ｈｋｌ）を少なくとも一つ有する。また、これらのいずれかの条件を満足する配向面が、（１１１）面、（２１０）面、（２１１）面、（２２１）面、（３１０）面および（３２０）面のいずれかであることが好ましい。なかでも、配向定数の最も大きい配向面が（１１１）面であることが好ましい。
【００１７】
蛍光体は、塩化セシウム型または岩塩型結晶構造を示す蛍光体であることが好ましい。また、蛍光体は、蓄積性蛍光体であることが好ましく、特に下記基本組成式（Ｉ）を有するアルカリ金属ハロゲン化物系輝尽性蛍光体であることが好ましい。基本組成式（Ｉ）においてＭ^ＩはＣｓであり、ＸはＢｒであり、ＡはＥｕであり、そしてｚは１×１０^−４≦ｚ≦０．１の範囲内の数値であることが好ましい。
【００１８】
Ｍ^ＩＸ・ａＭ^ＩＩＸ’_２・ｂＭ^ＩＩＩＸ”_３：ｚＡ ‥‥（Ｉ）
［ただし、Ｍ^ＩはＬｉ、Ｎａ、Ｋ、Ｒｂ及びＣｓからなる群より選ばれる少なくとも一種のアルカリ金属を表し；Ｍ^ＩＩはＢｅ、Ｍｇ、Ｃａ、Ｓｒ、Ｂａ、Ｎｉ、Ｃｕ、Ｚｎ及びＣｄからなる群より選ばれる少なくとも一種のアルカリ土類金属又は二価金属を表し；Ｍ^ＩＩＩはＳｃ、Ｙ、Ｌａ、Ｃｅ、Ｐｒ、Ｎｄ、Ｐｍ、Ｓｍ、Ｅｕ、Ｇｄ、Ｔｂ、Ｄｙ、Ｈｏ、Ｅｒ、Ｔｍ、Ｙｂ、Ｌｕ、Ａｌ、Ｇａ及びＩｎからなる群より選ばれる少なくとも一種の希土類元素又は三価金属を表し；Ｘ、Ｘ’及びＸ”はそれぞれ、Ｆ、Ｃｌ、Ｂｒ及びＩからなる群より選ばれる少なくとも一種のハロゲンを表し；ＡはＹ、Ｃｅ、Ｐｒ、Ｎｄ、Ｓｍ、Ｅｕ、Ｇｄ、Ｔｂ、Ｄｙ、Ｈｏ、Ｅｒ、Ｔｍ、Ｙｂ、Ｌｕ、Ｎａ、Ｍｇ、Ｃｕ、Ａｇ、Ｔｌ及びＢｉからなる群より選ばれる少なくとも一種の希土類元素又は金属を表し；そしてａ、ｂ及びｚはそれぞれ、０≦ａ＜０．５、０≦ｂ＜０．５、０＜ｚ＜１．０の範囲内の数値を表す］
【００１９】
以下に、本発明の放射線像変換パネルについて詳細に説明する。
本発明において、放射線像変換パネルの蛍光体層は、気相堆積法により形成されたものであり、よって結合剤を含有せず、蛍光体のみからなる。蛍光体層は、蛍光体の柱状結晶がほぼ厚み方向に成長した層であり、柱状結晶と柱状結晶の間には空隙（クラック）が存在する。そして、蛍光体層の柱状結晶は、Ｘ線回折法（ＸＲＤ）に基づいて次のようにして決定された配向度を有する。
【００２０】
ＸＲＤに基づいて試料の配向度を評価する一般的な方法として、組織係数ＴＣ（ｈｋｌ）を用いる方法がある。
【００２１】

【００２２】
［ただし、Ｉ（ｈｋｌ）は、試料の（ｈｋｌ）面のＸ線回折強度であり、Ｉ_０（ｈｋｌ）は、同一化合物の無配向の粉末Ｘ線回折強度であってＪＣＰＤＳカードから得られる標準強度であり、Ｎは、回折線の数を表す］
【００２３】
上記組織係数ＴＣで、ＴＣ（ｈｋｌ）＝１であるとき、試料は（ｈｋｌ）面に無配向であることを意味し、全てのＴＣ＝１であるとき、試料は全く無配向（ランダム）であることを意味する。ＴＣ（ｈｋｌ）＝Ｎであるとき、試料は（ｈｋｌ）面に完全配向であることを意味する。よって、ＴＣ（ｈｋｌ）＞１であるとき、試料は（ｈｋｌ）面に選択的に配向し、そしてＴＣ（ｈｋｌ）が大きくなるほど（ｈｋｌ）面への配向の程度が高いことを示す。なお、ＴＣ（ｈｋｌ）＜１であるとき（ｈｋｌ）面への配向の程度は小さい。すなわち、組織係数ＴＣは、無配向の粉末Ｘ線回折強度で規格されたＸＲＤの強度であり、その数値で配向度を定量化できるものである。
【００２４】
実際には、ＸＲＤの回折線には指数が同一の面や縮退している面が含まれるので、本発明においては、Ｉ（ｈｋｌ）／Ｉ_０（ｈｋｌ）の算出方法に以下のような修正を加えた。同一指数の場合には、各Ｉ（ｈｋｌ）／Ｉ_０（ｈｋｌ）を平均し、より低次の指数とする。例えば、（１１１）面と（２２２）面の場合には、Ｉ（１１１）／Ｉ_０（１１１）とＩ（２２２）／Ｉ_０（２２２）の平均値を求め、その値を（１１１）面の強度比、Ｉ（１１１）／Ｉ_０（１１１）とする。
【００２５】
縮退の場合には、例えば塩化セシウム型結晶構造の試料では、（２２１）面と（３００）面はその回折線が同一の回折角に現れる。（２２１）面と（３００）面によるＩ（ｈｋｌ）／Ｉ_０（ｈｋｌ）の値が、（１００）面と（２００）面のＩ（ｈｋｌ）／Ｉ_０（ｈｋｌ）の平均値と比べて大きければ、その差がＩ（２２１）／Ｉ_０（２２１）である。反対に小さければ、その値をＩ（３００）／Ｉ_０（３００）として、再度Ｉ（１００）／Ｉ_０（１００）とＩ（２００）／Ｉ_０（２００）とＩ（３００）／Ｉ_０（３００）の平均値を求め、その値を（１００）面の強度比、Ｉ（１００）／Ｉ_０（１００）とする。
【００２６】
このようにして指数が同一の面や縮退している面を規約して得られた指数面とその強度比に基づいて、上記組織係数ＴＣを算出して得られた値を、本発明においては配向定数と定義する。従って、配向定数（ｈｋｌ）は、次のように定義される。
【００２７】

【００２８】
［ただし、Ｉ（ｈｋｌ）／Ｉ_０（ｈｋｌ）は、試料の規約された指数面（ｈｋｌ）のＸ線回折強度比であり、Ｎは、規約された指数面の数を表す］
【００２９】
本発明においては特に、ＮはＮ≧６の整数であり、そしてΣ_Ｎ（Ｉ（ｈｋｌ）／Ｉ_０（ｈｋｌ））には規約された指数面（１００）、（１１０）及び（１１１）が含まれる。
【００３０】
本発明の配向定数は、組織係数ＴＣと同様に試料の配向度を定量化して表すものであるが、規約された指数に基づいているので、結晶学的イメージをより一層明確にすることができる。配向定数が有意義であるためには、指数面の数Ｎが多いことが望ましく、それによって精度も高くなる。よって、Ｎは６以上の整数であり、一般には７乃至１２の範囲内の整数である。また、規約された指数面として（１００）面、（１１０）面および（１１１）面を含ませることにより、配向定数の信頼性および精度を更に高めることができる。
【００３１】
本発明において、蛍光体層は、
配向定数（ｈｋｌ）≧２．５、および
（配向定数（ｈｋｌ）／Ｎ）×１００≧３５％
を満足する配向面（ｈｋｌ）を少なくとも一つ有する。ここで、配向定数（ｈｋｌ）は、蛍光体層の柱状結晶の指数面（ｈｋｌ）への配向の程度（最大値＝Ｎ）を表し、（配向定数（ｈｋｌ）／Ｎ）×１００は、指数面（ｈｋｌ）に配向している結晶の割合を表している。従って、本発明では蛍光体層の配向度は、配向の程度と割合の両方で規定され、そして配向の程度は多数の面を考慮に入れて定量化されるので、従来よりも高い信頼性および精度を有する。
【００３２】
好ましくは、蛍光体層は、
配向定数（ｈｋｌ）≧３．５、および
（配向定数（ｈｋｌ）／Ｎ）×１００≧４０％
を満足する配向面（ｈｋｌ）を少なくとも一つ有する。特に好ましくは、
配向定数（ｈｋｌ）≧４．０、および
（配向定数（ｈｋｌ）／Ｎ）×１００≧５０％
を満足する配向面（ｈｋｌ）を少なくとも一つ有する。
【００３３】
上記の配向定数を満足する配向面は（１１１）面、（２１０）面、（２１１）面、（２２１）面、（３１０）面および（３２０）面のいずれかであることが好ましい。なかでも、配向定数の最も大きい配向面が（１１１）面であることが好ましい。
【００３４】
蛍光体層がこのように高い配向度を有することにより、柱状結晶の配向が揃っているので結晶中の付活剤の周囲環境が均一になり、各柱状結晶からの発光（輝尽発光）にばらつきがなく、発光量が増加する。また、基板との密着性も増大する。
【００３５】
本発明において、蛍光体層に用いられる蛍光体は、塩化セシウム型又は岩塩型の結晶構造を示す蛍光体であることが好ましく、また蓄積性蛍光体であることが好ましい。そのような好ましい蓄積性蛍光体としては、下記基本組成式（Ｉ）を有するアルカリ金属ハロゲン化物系輝尽性蛍光体、および硫化物系輝尽性蛍光体（ＢａＳ、ＳｒＳ、ＣａＳ等）を挙げることができる。
【００３６】
Ｍ^ＩＸ・ａＭ^ＩＩＸ’_２・ｂＭ^ＩＩＩＸ”_３：ｚＡ ‥‥（Ｉ）
［ただし、Ｍ^ＩはＬｉ、Ｎａ、Ｋ、Ｒｂ及びＣｓからなる群より選ばれる少なくとも一種のアルカリ金属を表し；Ｍ^ＩＩはＢｅ、Ｍｇ、Ｃａ、Ｓｒ、Ｂａ、Ｎｉ、Ｃｕ、Ｚｎ及びＣｄからなる群より選ばれる少なくとも一種のアルカリ土類金属又は二価金属を表し；Ｍ^ＩＩＩはＳｃ、Ｙ、Ｌａ、Ｃｅ、Ｐｒ、Ｎｄ、Ｐｍ、Ｓｍ、Ｅｕ、Ｇｄ、Ｔｂ、Ｄｙ、Ｈｏ、Ｅｒ、Ｔｍ、Ｙｂ、Ｌｕ、Ａｌ、Ｇａ及びＩｎからなる群より選ばれる少なくとも一種の希土類元素又は三価金属を表し；Ｘ、Ｘ’及びＸ”はそれぞれ、Ｆ、Ｃｌ、Ｂｒ及びＩからなる群より選ばれる少なくとも一種のハロゲンを表し；ＡはＹ、Ｃｅ、Ｐｒ、Ｎｄ、Ｓｍ、Ｅｕ、Ｇｄ、Ｔｂ、Ｄｙ、Ｈｏ、Ｅｒ、Ｔｍ、Ｙｂ、Ｌｕ、Ｎａ、Ｍｇ、Ｃｕ、Ａｇ、Ｔｌ及びＢｉからなる群より選ばれる少なくとも一種の希土類元素又は金属を表し；そしてａ、ｂ及びｚはそれぞれ、０≦ａ＜０．５、０≦ｂ＜０．５、０＜ｚ＜１．０の範囲内の数値を表す。］
【００３７】
上記基本組成式（Ｉ）中のＭ^Ｉとしては少なくともＣｓを含んでいることが好ましい。Ｘとしては少なくともＢｒを含んでいることが好ましい。Ａとしては特にＥｕ又はＢｉであることが好ましい。また、基本組成式（Ｉ）には、必要に応じて、酸化アルミニウム、二酸化珪素、酸化ジルコニウムなどの金属酸化物を添加物として、Ｍ^ＩＸ１モルに対して、０．５モル以下の量で加えてもよい。
【００３８】
次に、本発明の放射線像変換パネルを製造する方法について、蛍光体が蓄積性蛍光体であって、気相堆積法として蒸着法を用いる場合を例にとり、詳細に説明する。蛍光体層の配向は、特には気相堆積時の雰囲気や真空度、基板の種類や温度、および気相堆積方向などによって制御することができる。
【００３９】
蒸着膜形成のための基板は通常、放射線像変換パネルの支持体を兼ねるものであり、従来の放射線像変換パネルの支持体として公知の材料から任意に選ぶことができるが、特に好ましい基板は、石英ガラスシート、サファイアガラスシート；アルミニウム、鉄、スズ、クロムなどからなる金属シート；アラミドなどからなる耐熱性樹脂シートである。公知の放射線像変換パネルにおいて、パネルとしての感度もしくは画質（鮮鋭度、粒状性）を向上させるために、二酸化チタンなどの光反射性物質からなる光反射層、もしくはカーボンブラックなどの光吸収性物質からなる光吸収層などを設けることが知られている。本発明で用いられる基板についても、これらの各種の層を設けることができ、それらの構成は所望の放射線像変換パネルの目的、用途などに応じて任意に選択することができる。さらに、柱状結晶性を高める目的で、基板の蒸着膜が形成される側の表面（支持体の蛍光体層側の表面に下塗層（接着性付与層）、光反射層あるいは光吸収層などの補助層が設けられている場合には、それらの補助層の表面であってもよい）には微小な凹凸が設けられていてもよい。また、基板表面にプラズマ洗浄を施してもよい。
【００４０】
多元蒸着（共蒸着）により蒸着膜を形成する場合には、まず蒸発源として、蓄積性蛍光体の母体成分を含むものと付活剤成分を含むものからなる少なくとも二個の蒸発源を用意する。多元蒸着は、蛍光体の母体成分と付活剤成分の蒸気圧が大きく異なる場合に、その蒸発速度を各々制御することができるので好ましい。各蒸発源は、所望とする蓄積性蛍光体の組成に応じて、蛍光体の母体成分および付活剤成分それぞれのみから構成されていてもよいし、添加物成分などとの混合物であってもよい。また、蒸発源は二個に限定されるものではなく、例えば別に添加物成分などからなる蒸発源を加えて三個以上としてもよい。
【００４１】
蛍光体の母体成分は、母体を構成する化合物それ自体であってもよいし、または反応して母体化合物となりうる二以上の原料の混合物であってもよい。また、付活剤成分は、一般には付活剤元素を含む化合物であり、例えば付活剤元素のハロゲン化物や酸化物が用いられる。
【００４２】
付活剤がＥｕである場合に、付活剤成分のＥｕ化合物におけるＥｕ^２＋化合物のモル比が７０％以上であることが好ましい。一般に、Ｅｕ化合物にはＥｕ^２＋とＥｕ^３＋が混合して含まれているが、所望とする輝尽発光（あるいは瞬時発光であっても）はＥｕ^２＋を付活剤とする蛍光体から発せられるからである。Ｅｕ化合物はＥｕＸ_ｍであることが好ましく、その場合には、ｍは２．０≦ｍ≦２．３の範囲内の数値であることが好ましい。ｍは、２．０であることが望ましいが、２．０に近づけようとすると酸素が混入しやすくなる。よって、実際にはｍは２．２付近でＸの比率が比較的高い状態が安定している。
【００４３】
蒸発源は、その含水量が０．５重量％以下であることが好ましい。蒸発源となる蛍光体母体成分や付活剤成分が、例えばＥｕＢｒ、ＣｓＢｒのように吸湿性である場合には特に、含水量をこのような低い値に抑えることは突沸防止などの点から重要である。蒸発源の脱水は、上記の各蛍光体成分を減圧下で１００〜３００℃の温度範囲で加熱処理することにより行うことが好ましい。あるいは、各蛍光体成分を窒素ガス雰囲気などの水分を含まない雰囲気中で、該成分の融点以上の温度で数十分乃至数時間加熱溶融してもよい。
【００４４】
蒸発源の相対密度は、８０％以上、９８％以下であることが好ましく、より好ましくは９０％以上、９６％以下である。蒸発源が相対密度の低い粉体状態であると、蒸着の際に粉体が飛散するなどの不都合が生じたり、蒸発源の表面から均一に蒸発しないで蒸着膜の膜厚が不均一となったりする。よって、安定した蒸着を実現するためには蒸発源の密度がある程度高いことが望ましい。上記相対密度とするには一般に、粉体を２０ＭＰａ以上の圧力で加圧成形したり、あるいは融点以上の温度で加熱溶融して、タブレット（錠剤）の形状にする。ただし、蒸発源は必ずしもタブレットの形状である必要はない。
【００４５】
また、蒸発源、特に蛍光体母体成分を含む蒸発源は、アルカリ金属不純物（蛍光体の構成元素以外のアルカリ金属）の含有量が１０ｐｐｍ以下であり、そしてアルカリ土類金属不純物（蛍光体の構成元素以外のアルカリ土類金属）の含有量が１ｐｐｍ以下であることが望ましい。このような蒸発源は、アルカリ金属やアルカリ土類金属など不純物の含有量の少ない原料を使用することにより調製することができる。これによって、不純物の混入が少ない蒸着膜を形成することができるとともに、そのような蒸着膜は発光量が増加する。
【００４６】
上記蒸発源および基板を蒸着装置内に配置し、装置内を排気して１×１０^−５〜１×１０^−２Ｐａ程度の真空度とする。このとき、真空度をこの程度に保持しながら、Ａｒガス、Ｎｅガス、Ｎ_２ガスなどの不活性ガスを導入してもよい。また、装置内の雰囲気中の水分圧を、ディフュージョンポンプ（またはターボ分子ポンプ）とコールドトラップ（クライオコイル、クライオポンプ等）との組合せなどを用いることにより、７．０×１０^−３Ｐａ以下にすることが好ましい。あるいは、抵抗加熱による場合には、水分圧をこの程度に保持しながら不活性ガスを導入して０．１〜２．０Ｐａ程度の真空度にしてもよい。
【００４７】
次に、電子線蒸着の場合には、二つの電子銃から電子線をそれぞれ発生させて各蒸発源に照射する。このとき、電子線の加速電圧を１．５ｋＶ以上で、５．０ｋＶ以下に設定することが望ましい。電子線の照射により、蒸発源である蓄積性蛍光体の母体成分や付活剤成分等は加熱されて蒸発、飛散し、そして反応を生じて蛍光体を形成するとともに基板表面に堆積する。抵抗加熱による蒸着の場合には、抵抗加熱器に電流を流すことにより蒸発源を加熱する。蒸発源である蓄積性蛍光体の母体成分や付活剤成分等は加熱されて蒸発、飛散する。そして、両者は反応を生じて蛍光体を形成するとともに基板表面に堆積する。不活性ガスを導入して蒸着を行う際には抵抗加熱器の使用が好ましい。蒸着の際に基板を加熱することが好ましい。基板温度は、一般には５０〜３００℃の範囲にある。蛍光体の堆積する速度、すなわち蒸着速度は、一般には０．１〜１０００μｍ／分の範囲にあり、好ましくは０．２〜１００μｍ／分の範囲にある。蒸発流に対する基板の傾斜角度は、蒸発流に垂直な方向を０度とすると一般には０〜４０度の範囲にある。
【００４８】
なお、電子線の照射および／または抵抗加熱器による加熱を複数回に分けて行って二層以上の蛍光体層を形成することもできる。また、蒸着終了後に蒸着膜を熱処理（アニール処理）してもよい。
【００４９】
なお、上記蓄積性蛍光体からなる蒸着膜を形成するに先立って、蛍光体の母体のみからなる蒸着膜を形成してもよい。これによって、より一層柱状結晶性の良好な蒸着膜を得ることができる。なお、蛍光体からなる蒸着膜中の付活剤など添加物は、特に蒸着時の加熱および／または蒸着後の熱処理によって、蛍光体母体からなる蒸着膜中に拡散するために、両者の境界は必ずしも明確ではない。
【００５０】
一元蒸着（疑似一元蒸着）の場合には、蒸発流に垂直な方向（基板に平行な方向）に上記蛍光体母体成分と付活剤成分とを分離して含む一個の蒸発源を用意することが好ましい。そして、蒸着に際しては、一つの電子線を用いて、蒸発源の母体成分領域および付活剤成分領域各々に電子線を照射する時間（滞在時間）を制御することにより、所望の付活剤濃度を有し、かつ組成の均一な蓄積性蛍光体からなる蒸着膜を形成することができる。あるいは、蒸発源として蛍光体自体または蛍光体原料混合物を用いて、これに電子線を照射するか、または抵抗加熱器で加熱する一元蒸着であってもよい。その場合には、予め、所望の濃度の付活剤を含有するように蛍光体を調製する。もしくは、蛍光体母体成分と付活剤成分との蒸気圧差を考慮して、蒸発源に蛍光体の母体成分を補給しながら蒸着を行うことも可能である。
【００５１】
このようにして、蓄積性蛍光体の柱状結晶がほぼ厚み方向に成長した蛍光体層が得られる。蛍光体層は、結合剤を含有せず、蓄積性蛍光体のみからなり、蛍光体の柱状結晶と柱状結晶の間には空隙（クラック）が存在する。蛍光体層の層厚は、目的とする放射線像変換パネルの特性、蒸着法の実施手段や条件などによっても異なるが、通常は５０μｍ〜１ｍｍの範囲にあり、好ましくは２００μｍ〜７００μｍの範囲にある。
【００５２】
本発明に用いられる気相堆積法は、上記の蒸着法に限定されるものではなく、スパッタ法、化学蒸着（ＣＶＤ）法、イオンプレーティング法など公知の各種の方法を利用することができる。
【００５３】
なお、基板は必ずしも放射線像変換パネルの支持体を兼ねる必要はなく、蛍光体層形成後、蛍光体層を基板から引き剥がし、別に用意した支持体上に接着剤を用いるなどして接合して、支持体上に蛍光体層を設ける方法を利用してもよい。あるいは、蛍光体層に支持体（基板）が付設されていなくてもよい。
【００５４】
この蛍光体層の表面には、放射線像変換パネルの搬送および取扱い上の便宜や特性変化の回避のために、保護層を設けることが望ましい。保護層は、励起光の入射や発光光の出射に殆ど影響を与えないように、透明であることが望ましく、また外部から与えられる物理的衝撃や化学的影響から放射線像変換パネルを充分に保護することができるように、化学的に安定で防湿性が高く、かつ高い物理的強度を持つことが望ましい。
【００５５】
保護層としては、セルロース誘導体、ポリメチルメタクリレート、有機溶媒可溶性フッ素系樹脂などのような透明な有機高分子物質を適当な溶媒に溶解して調製した溶液を蛍光体層の上に塗布することで形成されたもの、あるいはポリエチレンテレフタレートなどの有機高分子フィルムや透明なガラス板などの保護層形成用シートを別に形成して蛍光体層の表面に適当な接着剤を用いて設けたもの、あるいは無機化合物を蒸着などによって蛍光体層上に成膜したものなどが用いられる。また、保護層中には酸化マグネシウム、酸化亜鉛、二酸化チタン、アルミナ等の光散乱性微粒子、パーフルオロオレフィン樹脂粉末、シリコーン樹脂粉末等の滑り剤、およびポリイソシアネート等の架橋剤など各種の添加剤が分散含有されていてもよい。保護層の層厚は一般に、高分子物質からなる場合には約０．１〜２０μｍの範囲にあり、ガラス等の無機化合物からなる場合には１００〜１０００μｍの範囲にある。
【００５６】
保護層の表面にはさらに、保護層の耐汚染性を高めるためにフッ素樹脂塗布層を設けてもよい。フッ素樹脂塗布層は、フッ素樹脂を有機溶媒に溶解（または分散）させて調製したフッ素樹脂溶液を保護層の表面に塗布し、乾燥することにより形成することができる。フッ素樹脂は単独で使用してもよいが、通常はフッ素樹脂と膜形成性の高い樹脂との混合物として使用する。また、ポリシロキサン骨格を持つオリゴマーあるいはパーフルオロアルキル基を持つオリゴマーを併用することもできる。フッ素樹脂塗布層には、干渉むらを低減させて更に放射線画像の画質を向上させるために、微粒子フィラーを充填することもできる。フッ素樹脂塗布層の層厚は通常は０．５μｍ乃至２０μｍの範囲にある。フッ素樹脂塗布層の形成に際しては、架橋剤、硬膜剤、黄変防止剤などのような添加成分を用いることができる。特に架橋剤の添加は、フッ素樹脂塗布層の耐久性の向上に有利である。
【００５７】
上述のようにして本発明の放射線像変換パネルが得られるが、本発明のパネルの構成は、公知の各種のバリエーションを含むものであってもよい。例えば、放射線画像の鮮鋭度を向上させることを目的として、上記の少なくともいずれかの層を、励起光を吸収し発光光は吸収しないような着色剤によって着色してもよい。
【００５８】
【実施例】
［実施例１］
（１）蒸発源
蒸発源として、純度４Ｎ以上の臭化セシウム（ＣｓＢｒ）粉末、及び純度３Ｎ以上の臭化ユーロピウム（ＥｕＢｒ_ｍ、ｍ≒２．２）粉末を用意した。各粉末中の微量元素をＩＣＰ−ＭＳ法（誘導結合高周波プラズマ分光分析−質量分析法）により分析した結果、ＣｓＢｒ中のＣｓ以外のアルカリ金属（Ｌｉ、Ｎａ、Ｋ、Ｒｂ）は各々１０ｐｐｍ以下であり、アルカリ土類金属（Ｍｇ、Ｃａ、Ｓｒ、Ｂａ）など他の元素は２ｐｐｍ以下であった。また、ＥｕＢｒ_ｍ中のＥｕ以外の希土類元素は各々２０ｐｐｍ以下であり、他の元素は１０ｐｐｍ以下であった。これらの粉末は、吸湿性が高いので露点−２０℃以下の乾燥雰囲気を保ったデシケータ内で保管し、使用直前に取り出すようにした。
【００５９】
（２）蛍光体層の形成
支持体として、順にアルカリ洗浄、純水洗浄、およびＩＰＡ（イソプロピルアルコール）洗浄を施した後、更にプラズマ洗浄を施した合成石英基板を用意し、蒸着装置内の基板ホルダーに設置した。上記ＣｓＢｒ蒸発源およびＥｕＢｒ_ｍ蒸発源を装置内の所定位置に配置した後、装置内を排気して１×１０^−４Ｐａの真空度とした。このとき、真空排気装置としてロータリーポンプ、メカニカルブースターおよびターボ分子ポンプの組合せを用いた。次いで、基板の蒸着面とは反対側に位置したシーズヒータで、石英基板を３００℃に加熱した。蒸発源それぞれに電子銃からの電子線を照射して共蒸着させ、基板上にＣｓＢｒ：Ｅｕ輝尽性蛍光体を堆積させた。このとき、基板の傾斜角度は０度であった。また、各々の電子銃のエミッション電流を調整して、輝尽性蛍光体におけるＥｕ／Ｃｓモル濃度比が０．００３／１となるように制御ししながら、４μｍ／分の速度で堆積させた。
【００６０】
蒸着終了後、装置内を大気圧に戻し、装置から石英基板を取り出した。石英基板上には、蛍光体の柱状結晶がほぼ垂直方向に密に林立した構造の蒸着膜（膜厚：約２００μｍ、面積１０ｃｍ×１０ｃｍ）が形成されていた。
このようにして、共蒸着により支持体と蛍光体層とからなる本発明の放射線像変換パネルを製造した。
【００６１】
［実施例２、３］
実施例１の（２）蛍光体層の形成において、基板のプラズマ洗浄、基板の加熱温度、蒸着速度、および／または基板の傾斜角度をそれぞれ表１に示すように変更したこと以外は実施例１と同様にして、本発明の二種の放射線像変換パネルを製造した。
【００６２】
【表１】

【００６３】
［実施例４］
実施例１の（１）蒸発源において、蒸発源として純度３Ｎ以上の酸化臭化ユーロピウム（ＥｕＯＢｒ）粉末を用意したこと、および（２）蛍光体層の形成において、基板の加熱温度と蒸着速度を表１に示すように変更したこと以外は実施例１と同様にして、本発明の放射線像変換パネルを製造した。なお、ＥｕＯＢｒ中のＥｕ以外の希土類元素は各々２０ｐｐｍ以下であり、他の元素は１０ｐｐｍ以下であった。
【００６４】
［実施例５］
実施例１の（２）蛍光体層の形成を以下のようにして行ったこと以外は実施例１と同様にして、本発明の放射線像変換パネルを製造した。
支持体として、順にアルカリ洗浄、純水洗浄、およびＩＰＡ（イソプロピルアルコール）洗浄を施した合成石英基板を用意し、蒸着装置内の基板ホルダーに設置した。上記ＣｓＢｒ蒸発源およびＥｕＢｒ_ｍ蒸発源を装置内の所定位置に配置した後、装置内を排気して１×１０^−４Ｐａの真空度とした。このとき、真空排気装置としてロータリーポンプ、メカニカルブースターおよびターボ分子ポンプの組合せを用いた。石英基板の蒸着とは反対側に位置したシーズヒータで、基板を２００℃に加熱した。ＣｓＢｒ蒸発源には電子銃からの電子線を照射し、一方ＥｕＢｒ_ｍ蒸発源は抵抗加熱器で加熱して、基板上にＣｓＢｒ：Ｅｕ輝尽性蛍光体を堆積させた。このとき、基板の傾斜角度は０度であった。また、電子銃のエミッション電流および加熱器の抵抗電流を調整して、輝尽性蛍光体におけるＥｕ／Ｃｓモル濃度比が０．００３／１となるように制御ししながら、４μｍ／分の速度で堆積させた。
【００６５】
［実施例６］
実施例５において、基板の傾斜角度を２０度に変更したこと以外は実施例５と同様にして、本発明の放射線像変換パネルを製造した。
【００６６】
［実施例７］
実施例１の（２）蛍光体層の形成を以下のようにして行ったこと以外は実施例１と同様にして、本発明の放射線像変換パネルを製造した。
支持体として、順にアルカリ洗浄、純水洗浄、およびＩＰＡ（イソプロピルアルコール）洗浄を施した後、更にプラズマ洗浄を施した合成石英基板を用意し、蒸着装置内の基板ホルダーに設置した。上記ＣｓＢｒ蒸発源およびＥｕＢｒ_ｍ蒸発源を装置内の坩堝容器に充填した後、装置内を排気して１×１０^−４Ｐａの真空度とした。このとき、真空排気装置としてロータリーポンプ、メカニカルブースターおよびターボ分子ポンプの組合せを用いた。石英基板の蒸着とは反対側に位置したシーズヒータで、基板を３００℃に加熱した。蒸発源それぞれを抵抗加熱器で加熱して、基板上にＣｓＢｒ：Ｅｕ輝尽性蛍光体を堆積させた。このとき、基板の傾斜角度は０度であった。また、各々の加熱器の抵抗電流を調整して、輝尽性蛍光体におけるＥｕ／Ｃｓモル濃度比が０．００３／１となるように制御ししながら、４μｍ／分の速度で堆積させた。
【００６７】
［実施例８］
実施例７において、装置内を排気して１×１０^−４Ｐａの真空度とした後、Ａｒガスを導入して真空度を表１に示すように変更したこと、および基板の加熱温度を表１に示すように変更したこと以外は実施例７と同様にして、本発明の放射線像変換パネルを製造した。
【００６８】
［実施例９］
実施例１において、蒸発源としてＣｓＢｒ：Ｅｕ輝尽性蛍光体を用いて、表１に示す条件で一元蒸着で、基板上にＣｓＢｒ：Ｅｕ輝尽性蛍光体（Ｅｕ／Ｃｓモル濃度比＝０．００３／１）を堆積させたこと以外は実施例１と同様にして、本発明の放射線像変換パネルを製造した。
【００６９】
［比較例１、２］
実施例１の（２）蛍光体層の形成において、基板のプラズマ洗浄、基板の加熱温度および／または蒸着速度をそれぞれ表１に示すように変更したこと以外は実施例１と同様にして、比較のための二種の放射線像変換パネルを製造した。
【００７０】
［放射線像変換パネルの性能評価］
得られた各放射線像変換パネルの蛍光体層について、以下のようにして配向定数を決定した。Ｘ線回折（ＸＲＤ）装置（リガク社製）を用いてＸＲＤ測定を行ってＸＲＤパターンを得た。ＸＲＤパターンに現れた各回折線についてＸ線回折強度Ｉ（ｈｋｌ）を測定し、一方ＪＣＰＤＳカード（Ｎｏ．５−０５８８）からＣｓＢｒの無配向の粉末Ｘ線強度Ｉ_０（ｈｋｌ）を得て、各強度比Ｉ（ｈｋｌ）／Ｉ_０（ｈｋｌ）を算出した。次いで、同一指数の面および縮退している面について、前述したようにして規約された指数面およびその強度比を求めた。得られた強度比を下記式に導入して、各指数面の配向定数（ｈｋｌ）を算出した。なお、指数面の数Ｎは、実施例９でＮ＝１０であり、それ以外の実施例ではＮ＝７であった。
得られた結果をまとめて表２に示す。
【００７１】

【００７２】
【表２】

【００７３】
また、各放射線像変換パネルの感度および密着性について以下のようにして評価を行った。
（１）感度
放射線像変換パネルを室内光を遮蔽可能なカセッテに収納し、これに管電圧８０ｋＶｐ、管電流１６ｍＡのＸ線を照射した。次いで、パネルをカセッテから取り出した後、パネルを半導体レーザ光（波長：６６０ｎｍ）で励起し、パネルから放出された輝尽発光光をフォトマルチプライヤで検出し、その発光量（比較例１を基準とした相対値）により感度を評価した。
【００７４】
（２）密着性
権田俊一監修、「薄膜の作成・評価とその応用技術ハンドブック」、フジテクノシステム、１９８４年、ｐ．２１１に記載のスコッチテープ法を参考にして、蛍光体層の表面に粘着テープ（ニチバン製セロハンテープ）を貼り付けた後、粘着テープを剥がして蛍光体層の支持体からの剥離の程度を観察し、密着性を以下の基準にて評価した。
ＡＡ：極めて良好、 Ａ：良好、 Ｂ：やや良好、
Ｃ：不良であって実用上問題がある
得られた結果をまとめて表３に示す。
【００７５】
【表３】
【００７６】

【００７７】
表２および表３に示した結果から、蛍光体層が配向定数≧２．５および（配向定数／Ｎ）×１００≧３５％である配向面を有する本発明の放射線像変換パネル（実施例１〜９）はいずれも、感度が高く、蛍光体層と支持体との密着性も良好であった。そして、蛍光体層の配向度が高いほど、高感度であって優れた密着性を示した。特に、配向面が（１１１）面で配向度の高いパネル（実施例１、２、５）は優れた特性を示した。
【００７８】
【発明の効果】
配向定数で規定した配向度の高い蛍光体層を有する本発明の放射線像変換パネルは、感度が高く、そして蛍光体層と支持体との密着性においても優れている。従って、本発明の放射線像変換パネルは、医療用放射線画像診断などに有利に使用することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a radiation image conversion panel used in a radiation image recording / reproducing method using a stimulable phosphor.
[0002]
[Prior art]
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.
[0003]
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.
[0004]
The phosphor layer includes a stimulable phosphor and a binder containing and supporting the phosphor in a dispersed state, and does not contain a binder formed by a vapor deposition method or a sintering method. There are known those composed only of aggregates, and those in which polymer substances are impregnated in the gaps between aggregates of stimulable phosphors.
[0005]
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 is also included in the present invention.
[0006]
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.).
[0007]
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.
[0008]
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 (cracks) 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. .
[0009]
In Patent Document 2, the stimulable phosphor layer was measured on the crystal lattice plane perpendicular to the direction of the fastest growth rate by a powder X-ray diffractometer in an X-ray incident angle range of 10 ° to 35 °. in X-ray diffraction pattern of the time, the second peak intensity I ₂ so that the ratio I _{2 /} I ₁ of the first peak intensity I ₁ is less than 0.3, the radiation image conversion direction of the crystal lattice plane are aligned A panel is disclosed.
[0010]
Patent Document 3 describes alkali metal-preserving phosphors that exhibit an XRD-spectrum having a (100) diffraction line having an intensity I ₁₀₀ such that I ₁₀₀ / I ₁₁₀ ≧ 1 and a (110) diffraction line having an intensity I _110. A binderless storage phosphor screen comprising a phosphor is disclosed.
[0011]
[Patent Document 1]
JP 2001-255610 A [Patent Document 2]
Japanese Patent No. 3130632 [Patent Document 3]
Japanese Patent Laid-Open No. 2001-249198
[Problems to be solved by the invention]
As a result of repeated examinations of vapor deposition films such as phosphor vapor-deposited films, the present inventor greatly changes the physical properties of the vapor deposition films depending on the degree of orientation, even if the vapor deposition films are columnar crystalline. That is, it has been found that the higher the degree of orientation, the more the light emission amount such as the stimulated light emission amount, and the better the adhesion with the support (substrate). And the degree of orientation of the vapor-deposited film is not sufficient simply by specifying the diffraction intensity ratio between the two specific surfaces as in the prior art, or the ratio between the maximum diffraction intensity and the second diffraction intensity, It has been found that the degree of orientation can be obtained quantitatively and with high reliability by using a texture coefficient (TC, Texture Coefficient), and the present invention has been achieved.
[0013]
Accordingly, it is an object of the present invention to provide a radiation image conversion panel with significantly improved sensitivity and adhesion.
[0014]
[Means for Solving the Problems]
The present invention relates to a radiation image conversion panel having a phosphor layer formed by a vapor deposition method, wherein the phosphor layer is composed of a columnar crystal of the phosphor, and a prescribed index plane is defined based on an X-ray diffraction pattern. When the orientation constant (hkl) of (hkl) is defined by the following equation:

[Where I (hkl) / I ₀ (hkl) is the X-ray diffraction intensity ratio of the prescribed exponential surface (hkl) of the sample, N represents the number of prescribed exponential surfaces, and N ≧ 6 And Σ _N (I (hkl) / I ₀ (hkl)) includes the prescribed exponential surfaces (100), (110) and (111)]
The phosphor layer has at least one orientation plane (hkl) satisfying an orientation constant (hkl) ≧ 2.5 and (orientation constant (hkl) / N) × 100 ≧ 35%. In the conversion panel.
[0015]
Here, the regulated index plane (hkl) means an index plane (hkl) that takes into account a plane having the same index or a degenerate plane, as will be described in detail later. hkl) is the above-described organization coefficient TC (hkl) obtained for the specified index plane.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
The phosphor layer of the radiation image conversion panel of the present invention has at least one orientation plane (hkl) that satisfies the orientation constant (hkl) ≧ 3.5 and (orientation constant (hkl) / N) × 100 ≧ 40%. It is particularly preferable to have at least one orientation plane (hkl) that satisfies the orientation constant (hkl) ≧ 4.0 and (orientation constant (hkl) / N) × 100 ≧ 50%. In addition, the orientation plane that satisfies any of these conditions is any one of the (111) plane, the (210) plane, the (211) plane, the (221) plane, the (310) plane, and the (320) plane. Is preferred. Especially, it is preferable that the orientation plane with the largest orientation constant is a (111) plane.
[0017]
The phosphor is preferably a phosphor exhibiting a cesium chloride type or rock salt type crystal structure. 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. .
[0018]
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. comprising represents at least one alkaline 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, 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 Consist of Represents at least one rare earth element or metal selected from the group; and a, b and z are in the range of 0 ≦ a <0.5, 0 ≦ b <0.5 and 0 <z <1.0, respectively. Represents a numerical value]
[0019]
The radiation image conversion panel of the present invention will be described in detail below.
In the present invention, the phosphor layer of the radiation image conversion panel is formed by a vapor deposition method, and therefore does not contain a binder and is made of only a phosphor. The phosphor layer is a layer in which columnar crystals of the phosphor are grown substantially in the thickness direction, and there are voids (cracks) between the columnar crystals. The columnar crystals of the phosphor layer have an orientation degree determined as follows based on the X-ray diffraction method (XRD).
[0020]
As a general method for evaluating the degree of orientation of a sample based on XRD, there is a method using a tissue coefficient TC (hkl).
[0021]

[0022]
[Where I (hkl) is the X-ray diffraction intensity of the (hkl) plane of the sample, and I ₀ (hkl) is the non-oriented powder X-ray diffraction intensity of the same compound, which is a standard obtained from the JCPDS card. Intensity, N represents the number of diffraction lines]
[0023]
When the texture coefficient TC is TC (hkl) = 1, it means that the sample is not oriented in the (hkl) plane, and when all TC = 1, the sample is completely unoriented (random). It means that there is. When TC (hkl) = N, it means that the sample is perfectly oriented in the (hkl) plane. Therefore, when TC (hkl)> 1, the sample is selectively oriented in the (hkl) plane, and the larger the TC (hkl), the higher the degree of orientation in the (hkl) plane. When TC (hkl) <1, the degree of orientation to the (hkl) plane is small. That is, the texture coefficient TC is the XRD intensity standardized by the non-oriented powder X-ray diffraction intensity, and the degree of orientation can be quantified by the numerical value.
[0024]
Actually, since the XRD diffraction lines include surfaces having the same index or degenerate surfaces, in the present invention, the following correction is made to the calculation method of I (hkl) / I ₀ (hkl). Was added. In the case of the same index, each I (hkl) / I ₀ (hkl) is averaged to obtain a lower-order index. For example, in the case of the (111) plane and the (222) plane, an average value of I (111) / I ₀ (111) and I (222) / I ₀ (222) is obtained, and the value is calculated as the (111) plane. The intensity ratio is I (111) / I ₀ (111).
[0025]
In the case of degeneracy, for example, in a sample having a cesium chloride type crystal structure, the diffraction lines of the (221) plane and the (300) plane appear at the same diffraction angle. The value of I (hkl) / I ₀ (hkl) by the (221) plane and the (300) plane is compared with the average value of I (hkl) / I ₀ (hkl) of the (100) plane and the (200) plane. If so, the difference is I (221) / I ₀ (221). On the contrary, if it is smaller, the value is set to I (300) / I ₀ (300), and again I (100) / I ₀ (100) and I (200) / I ₀ (200) and I (300) / I ₀ An average value of (300) is obtained, and the value is defined as an intensity ratio of (100) plane, I (100) / I ₀ (100).
[0026]
In the present invention, the value obtained by calculating the texture coefficient TC based on the index surface obtained by defining the surface having the same index or the degenerate surface and the intensity ratio thereof in the present invention is as follows. It is defined as an orientation constant. Accordingly, the orientation constant (hkl) is defined as follows.
[0027]

[0028]
[Where I (hkl) / I ₀ (hkl) is the X-ray diffraction intensity ratio of the prescribed exponential surface (hkl) of the sample, and N represents the number of prescribed exponential surfaces]
[0029]
In particular, in the present invention, N is an integer of N ≧ 6, and Σ _N (I (hkl) / I ₀ (hkl)) has the prescribed exponential surfaces (100), (110), and (111). included.
[0030]
The orientation constant of the present invention represents the degree of orientation of the sample in the same manner as the texture coefficient TC, but is based on a prescribed index, so that the crystallographic image can be further clarified. . In order for the orientation constant to be meaningful, it is desirable that the number N of the index surfaces is large, thereby increasing the accuracy. Therefore, N is an integer of 6 or more, and is generally an integer in the range of 7 to 12. In addition, by including (100) plane, (110) plane, and (111) plane as the regulated index plane, the reliability and accuracy of the alignment constant can be further improved.
[0031]
In the present invention, the phosphor layer is
Orientation constant (hkl) ≧ 2.5 and (orientation constant (hkl) / N) × 100 ≧ 35%
At least one orientation plane (hkl) satisfying the above. Here, the orientation constant (hkl) represents the degree of orientation (maximum value = N) of the columnar crystals of the phosphor layer toward the index plane (hkl), and (orientation constant (hkl) / N) × 100 is an index. It represents the proportion of crystals oriented in the plane (hkl). Therefore, in the present invention, the degree of orientation of the phosphor layer is defined by both the degree and ratio of the orientation, and the degree of orientation is quantified taking into account a number of surfaces, so that higher reliability and Have accuracy.
[0032]
Preferably, the phosphor layer is
Orientation constant (hkl) ≧ 3.5 and (orientation constant (hkl) / N) × 100 ≧ 40%
At least one orientation plane (hkl) satisfying the above. Particularly preferably,
Orientation constant (hkl) ≧ 4.0 and (orientation constant (hkl) / N) × 100 ≧ 50%
At least one orientation plane (hkl) satisfying the above.
[0033]
The orientation plane that satisfies the above-mentioned orientation constant is preferably any of the (111) plane, the (210) plane, the (211) plane, the (221) plane, the (310) plane, and the (320) plane. Especially, it is preferable that the orientation plane with the largest orientation constant is a (111) plane.
[0034]
Since the phosphor layer has such a high degree of orientation, the orientation of the columnar crystals is uniform, so the surrounding environment of the activator in the crystals becomes uniform, and light emission from each columnar crystal (stimulated luminescence). There is no variation, and the amount of light emission increases. In addition, adhesion with the substrate is increased.
[0035]
In the present invention, the phosphor used in the phosphor layer is preferably a phosphor exhibiting a cesium chloride type or rock salt type crystal structure, and is preferably a storage phosphor. Examples of such preferable stimulable phosphors include alkali metal halide-based stimulable phosphors having the following basic composition formula (I) and sulfide-based stimulable phosphors (BaS, SrS, CaS, etc.). be able to.
[0036]
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. comprising represents at least one alkaline 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, 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 Consist of Represents at least one rare earth element or metal selected from the group; and a, b and z are in the range of 0 ≦ a <0.5, 0 ≦ b <0.5 and 0 <z <1.0, respectively. Represents a numerical value.]
[0037]
In the basic composition formula (I), M ^I preferably contains at least Cs. X preferably contains at least Br. A is particularly preferably Eu or Bi. 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.
[0038]
Next, 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 is used as the vapor deposition method. The orientation of the phosphor layer can be controlled particularly by the atmosphere and the degree of vacuum during vapor deposition, the type and temperature of the substrate, the vapor deposition direction, and the like.
[0039]
The substrate for forming the vapor deposition film usually serves 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 heat-resistant 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. Furthermore, for the purpose of enhancing the columnar crystallinity, the surface of the substrate on which the deposited film is formed (the undercoat layer (adhesion-imparting layer) on the surface of the support on the phosphor layer side, the light reflecting layer, the light absorbing layer, etc.) If the auxiliary layer is provided, the surface of the auxiliary layer may be provided with minute irregularities. Further, plasma cleaning may be performed on the substrate surface.
[0040]
In the case of forming a deposited film by multi-source deposition (co-evaporation), first prepare at least two evaporation sources comprising a matrix component containing a stimulable phosphor and an activator component as evaporation sources. . Multi-source deposition is preferable because the evaporation rate can be controlled when the vapor pressures of the matrix component and the activator component of the phosphor are greatly different. Each evaporation source may be composed only of the host component and the activator component of the phosphor, or may be a mixture with additive components, depending on the desired composition of the stimulable phosphor. 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.
[0041]
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.
[0042]
When the activator is Eu, the molar ratio of the Eu ²⁺ compound in the Eu compound of the activator component is preferably 70% or more. In general, Eu compounds contain a mixture of Eu ²⁺ and Eu ^3+, but the desired stimulating luminescence (or even instantaneous light emission) is emitted from a phosphor using Eu ²⁺ as an activator. Because. The Eu compound is preferably EuX _m . In that case, m is preferably a numerical value within the range of 2.0 ≦ m ≦ 2.3. m is preferably 2.0, but oxygen tends to be mixed if it is close to 2.0. Therefore, in practice, the state where m is around 2.2 and the ratio of X is relatively high is stable.
[0043]
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.
[0044]
The relative density of the evaporation source is preferably 80% or more and 98% or less, more preferably 90% or more and 96% or less. If the evaporation source is in a powder state with a low relative density, there will be inconveniences such as powder scattering during vapor deposition, or the film thickness of the vapor deposition film will be non-uniform without evaporating uniformly from the surface of the evaporation source. Or Therefore, it is desirable that the density of the evaporation source is high to some extent in order to realize stable vapor deposition. In order to obtain the above relative density, generally, the powder is pressure-molded at a pressure of 20 MPa or more, or heated and melted at a temperature of the melting point or more to form a tablet (tablet). However, the evaporation source is not necessarily in the form of a tablet.
[0045]
Further, 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 (the phosphor composition). The content of (alkaline earth metals other than elements) is desirably 1 ppm or less. 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. As a result, it is possible to form a vapor-deposited film with few impurities and to increase the amount of light emitted from such a vapor-deposited film.
[0046]
The said evaporation source and a board | substrate are arrange | positioned in a vapor deposition apparatus, and the inside of an apparatus is exhausted and it is set as the vacuum degree of about 1 * 10 ^{< -5} > ^-1 * 10 ^<-2 > Pa. At this time, an inert gas such as Ar gas, Ne gas, or N ₂ gas may be introduced while maintaining the degree of vacuum at this level. Moreover, the moisture pressure in the atmosphere in the apparatus is reduced to 7.0 × 10 ⁻³ Pa or less by using a combination of a diffusion pump (or turbo molecular pump) and a cold trap (cryocoil, cryopump, etc.). It is preferable to do. Alternatively, in the case of resistance heating, an inert gas may be introduced while the moisture pressure is maintained at this level to obtain a degree of vacuum of about 0.1 to 2.0 Pa.
[0047]
Next, in the case of electron beam evaporation, electron beams are respectively generated from two electron guns and irradiated to each evaporation source. At this time, it is desirable to set the acceleration voltage of the electron beam to 1.5 kV or more and 5.0 kV or less. By irradiation with an electron beam, 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 substrate surface. In the case of vapor deposition by resistance heating, the evaporation source is heated by passing an electric current through the resistance heater. The matrix component, activator component, and the like of the stimulable phosphor that is the evaporation source are heated to evaporate and scatter. Both of them react to form phosphors and deposit on the substrate surface. When vapor deposition is performed by introducing an inert gas, it is preferable to use a resistance heater. It is preferable to heat the substrate during vapor deposition. The substrate temperature is generally in the range of 50 to 300 ° C. The deposition rate of the phosphor, that is, the vapor deposition rate is generally in the range of 0.1 to 1000 μm / min, and preferably in the range of 0.2 to 100 μm / min. The inclination angle of the substrate with respect to the evaporation flow is generally in the range of 0 to 40 ° when the direction perpendicular to the evaporation flow is 0 °.
[0048]
Note that two or more phosphor layers can be formed by performing electron beam irradiation and / or heating by a resistance heater in a plurality of times. Further, the deposited film may be heat-treated (annealed) after completion of the deposition.
[0049]
Prior to the formation of the deposited film made of the stimulable phosphor, a deposited film made only of the phosphor base material may be formed. As a result, it is possible to obtain a vapor deposition film with even better columnar crystallinity. In addition, since additives such as an activator in the vapor deposition film made of the phosphor diffuse into the vapor deposition film made of the phosphor base material by heating during vapor deposition and / or heat treatment after vapor deposition, the boundary between the two is Not necessarily clear.
[0050]
In the case of single vapor deposition (pseudo single vapor deposition), prepare a single evaporation source that contains the phosphor matrix component and activator component separately in a direction perpendicular to the evaporation flow (direction parallel to the substrate). Is preferred. In vapor deposition, a desired activator concentration is controlled by controlling the time (stay time) for irradiating the base component region and the activator component region of the evaporation source with the electron beam using one electron beam. It is possible to form a deposited film made of a stimulable phosphor having a uniform composition. Alternatively, single vapor deposition may be used in which the phosphor itself or the phosphor raw material mixture is used as an evaporation source, and this is irradiated with an electron beam or heated by a resistance heater. In that case, the phosphor is prepared in advance so as to contain a desired concentration of activator. Alternatively, it is also possible to perform vapor deposition while supplying the matrix component of the phosphor to the evaporation source in consideration of the vapor pressure difference between the phosphor matrix component and the activator component.
[0051]
In this way, a phosphor layer is obtained in which columnar crystals of the stimulable phosphor are grown substantially in the thickness direction. The phosphor layer does not contain a binder and is composed only of a stimulable phosphor, and there are voids (cracks) 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. .
[0052]
The vapor deposition method used in the present invention is not limited to the above evaporation method, and various known methods such as a sputtering method, a chemical vapor deposition (CVD) method, and an ion plating method can be used.
[0053]
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.
[0054]
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.
[0055]
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.
[0056]
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 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.
[0057]
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 the radiographic image, at least one of the above layers may be colored with a colorant that absorbs excitation light and does not absorb emitted light.
[0058]
【Example】
[Example 1]
(1) Evaporation source As an evaporation source, cesium bromide (CsBr) powder having a purity of 4N or more and europium bromide (EuBr _m , m≈2.2) 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. Also, rare earth elements other than Eu in EuBr _m is at each 20ppm or less, other elements were 10ppm 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.
[0059]
(2) As a support for forming the phosphor layer, a synthetic quartz substrate that has been subjected to alkaline cleaning, pure water cleaning, and IPA (isopropyl alcohol) cleaning in order and then plasma cleaning is prepared, and the substrate in the vapor deposition apparatus is prepared. Installed in the holder. After the CsBr evaporation source and the EuBr _m evaporation source were arranged at predetermined positions in the apparatus, the inside of the apparatus was evacuated to a vacuum degree of 1 × 10 ⁻⁴ 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. Next, the quartz substrate was heated to 300 ° C. with a sheathed heater located on the side opposite to the deposition surface of the substrate. Each evaporation source was irradiated with an electron beam from an electron gun and co-evaporated to deposit a CsBr: Eu photostimulable phosphor on the substrate. At this time, the inclination angle of the substrate was 0 degree. Further, the emission current of each electron gun was adjusted so that the Eu / Cs molar concentration ratio in the stimulable phosphor was controlled to 0.003 / 1, and deposition was performed at a rate of 4 μm / min. .
[0060]
After vapor deposition, the inside of the apparatus was returned to atmospheric pressure, and the quartz substrate was taken out from the apparatus. On the quartz substrate, a deposited film (thickness: about 200 μm, area 10 cm × 10 cm) having a structure in which phosphor columnar crystals were densely grown in a substantially vertical direction was formed.
Thus, the radiation image conversion panel of the present invention comprising the support and the phosphor layer was produced by co-evaporation.
[0061]
[Examples 2 and 3]
Example 1 (2) Example 1 except that the plasma cleaning of the substrate, the heating temperature of the substrate, the deposition rate, and / or the tilt angle of the substrate were changed as shown in Table 1, respectively, in the formation of the phosphor layer. In the same manner, two types of radiation image conversion panels of the present invention were produced.
[0062]
[Table 1]

[0063]
[Example 4]
In Example 1, (1) the evaporation source, europium oxide bromide (EuOBr) powder having a purity of 3N or more was prepared as the evaporation source, and (2) in the formation of the phosphor layer, the substrate heating temperature and the deposition rate were set. A radiation image conversion panel of the present invention was produced in the same manner as in Example 1 except that the changes were made as shown in Table 1. In addition, rare earth elements other than Eu in EuOBr were each 20 ppm or less, and other elements were 10 ppm or less.
[0064]
[Example 5]
A radiation image conversion panel of 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.
As a support, a synthetic quartz substrate subjected to alkali cleaning, pure water cleaning, and IPA (isopropyl alcohol) cleaning in order was prepared and placed on a substrate holder in a vapor deposition apparatus. After the CsBr evaporation source and the EuBr _m evaporation source were arranged at predetermined positions in the apparatus, the inside of the apparatus was evacuated to a vacuum degree of 1 × 10 ⁻⁴ 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. The substrate was heated to 200 ° C. with a sheathed heater located on the opposite side of the quartz substrate from vapor deposition. The CsBr evaporation source was irradiated with an electron beam from an electron gun, while the EuBr _m evaporation source was heated with a resistance heater to deposit a CsBr: Eu photostimulable phosphor on the substrate. At this time, the inclination angle of the substrate was 0 degree. In addition, by adjusting the emission current of the electron gun and the resistance current of the heater to control the Eu / Cs molar concentration ratio in the stimulable phosphor to be 0.003 / 1, the speed is 4 μm / min. It was deposited with.
[0065]
[Example 6]
In Example 5, the radiation image conversion panel of the present invention was manufactured in the same manner as in Example 5 except that the inclination angle of the substrate was changed to 20 degrees.
[0066]
[Example 7]
A radiation image conversion panel of 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.
As a support, a synthetic quartz substrate that was subjected to alkali cleaning, pure water cleaning, and IPA (isopropyl alcohol) cleaning in this order and then plasma cleaning was prepared and placed on a substrate holder in a vapor deposition apparatus. After filling the crucible container in the apparatus with the CsBr evaporation source and the EuBr _m evaporation source, the apparatus was evacuated to a vacuum of 1 × 10 ⁻⁴ 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. The substrate was heated to 300 ° C. with a sheathed heater located on the side opposite to the quartz substrate deposition. Each evaporation source was heated with a resistance heater to deposit a CsBr: Eu photostimulable phosphor on the substrate. At this time, the inclination angle of the substrate was 0 degree. In addition, the resistance current of each heater was adjusted so that the Eu / Cs molar concentration ratio in the photostimulable phosphor was controlled to 0.003 / 1, and deposition was performed at a rate of 4 μm / min. .
[0067]
[Example 8]
In Example 7, the inside of the apparatus was evacuated to a vacuum degree of 1 × 10 ⁻⁴ Pa, Ar gas was introduced and the degree of vacuum was changed as shown in Table 1, and the heating temperature of the substrate was shown. A radiation image conversion panel of the present invention was manufactured in the same manner as in Example 7 except that the change was made as shown in FIG.
[0068]
[Example 9]
In Example 1, CsBr: Eu photostimulable phosphor was used as the evaporation source, and CsBr: Eu photostimulable phosphor (Eu / Cs molar concentration ratio = 0) was formed on the substrate by single deposition under the conditions shown in Table 1. A radiation image conversion panel of the present invention was manufactured in the same manner as in Example 1 except that .003 / 1) was deposited.
[0069]
[Comparative Examples 1 and 2]
In the formation of the phosphor layer in Example 1 (2), a comparison was made in the same manner as in Example 1 except that the plasma cleaning of the substrate, the heating temperature of the substrate and / or the deposition rate were changed as shown in Table 1, respectively. Two kinds of radiation image conversion panels for were manufactured.
[0070]
[Performance evaluation of radiation image conversion panel]
With respect to the phosphor layers of the obtained radiation image conversion panels, orientation constants were determined as follows. XRD measurement was performed using an X-ray diffraction (XRD) apparatus (manufactured by Rigaku Corporation) to obtain an XRD pattern. The X-ray diffraction intensity I (hkl) is measured for each diffraction line appearing in the XRD pattern, while the non-oriented powder X-ray intensity I ₀ (hkl) of CsBr is obtained from the JCPDS card (No. 5-0588), Each intensity ratio I (hkl) / I ₀ (hkl) was calculated. Next, for the same index surface and the degenerate surface, the index surface defined as described above and its strength ratio were obtained. The obtained intensity ratio was introduced into the following formula, and the orientation constant (hkl) of each index plane was calculated. The number N of the index surfaces was N = 10 in Example 9, and N = 7 in the other examples.
The results obtained are summarized in Table 2.
[0071]

[0072]
[Table 2]

[0073]
Further, the sensitivity and adhesion of each radiation image conversion panel were evaluated as follows.
(1) The sensitive 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 the panel is taken out from the cassette, the panel is excited with a semiconductor laser beam (wavelength: 660 nm), the stimulated emission light emitted from the panel is detected by a photomultiplier, and the light emission amount (based on Comparative Example 1) The relative value was used to evaluate the sensitivity.
[0074]
(2) Adhesiveness Supervised by Shunichi Gonda, “Handbook of Thin Film Creation / Evaluation and its Applied Technology”, Fuji Techno System, 1984, p. Referring to the Scotch tape method described in 211, after sticking adhesive tape (Nichiban cellophane tape) on the surface of the phosphor layer, peel off the adhesive tape and observe the degree of peeling of the phosphor layer from the support The adhesion was evaluated according to the following criteria.
AA: extremely good, A: good, B: somewhat good,
C: Table 3 summarizes the results obtained that are defective and have practical problems.
[0075]
[Table 3]
[0076]

[0077]
From the results shown in Tables 2 and 3, the radiation image conversion panel of the present invention (Example 1) in which the phosphor layer has an orientation plane with orientation constant ≧ 2.5 and (orientation constant / N) × 100 ≧ 35%. All of 9 to 9) had high sensitivity and good adhesion between the phosphor layer and the support. The higher the degree of orientation of the phosphor layer, the higher the sensitivity and the better the adhesion. In particular, the panels (Examples 1, 2 and 5) having a (111) plane and a high degree of orientation exhibited excellent characteristics.
[0078]
【The invention's effect】
The radiation image conversion panel of the present invention having a phosphor layer having a high degree of orientation defined by an orientation constant is high in sensitivity and excellent in adhesion between the phosphor layer and the support. Therefore, the radiation image conversion panel of the present invention can be advantageously used for medical radiation image diagnosis and the like.

Claims (9)

In a radiation image conversion panel having a phosphor layer formed by a vapor deposition method, the phosphor layer is made of columnar crystals of the phosphor, and has a prescribed index plane (hkl) based on an X-ray diffraction pattern. When the orientation constant (hkl) is defined by the following formula,

[Where I (hkl) / I ₀ (hkl) is the X-ray diffraction intensity ratio of the prescribed exponential surface (hkl) of the sample, N represents the number of prescribed exponential surfaces, and N ≧ 6 And Σ _N (I (hkl) / I ₀ (hkl)) includes the prescribed exponential surfaces (100), (110) and (111)]
The phosphor layer has at least one orientation plane (hkl) satisfying an orientation constant (hkl) ≧ 2.5 and (orientation constant (hkl) / N) × 100 ≧ 35%. Conversion panel. The radiation image according to claim 1, wherein the phosphor layer has at least one orientation plane (hkl) satisfying an orientation constant (hkl) ≧ 3.5 and (orientation constant (hkl) / N) × 100 ≧ 40%. Conversion panel. The radiation image according to claim 2, wherein the phosphor layer has at least one orientation plane (hkl) satisfying an orientation constant (hkl) ≧ 4.0 and (orientation constant (hkl) / N) × 100 ≧ 50%. Conversion panel. The orientation planes that satisfy the conditions according to any one of claims 1 to 3 are (111) plane, (210) plane, (211) plane, (221) plane, (310) plane, and (320). ) A radiation image conversion panel comprising any one of the surfaces. 4. A radiation image conversion panel, wherein an orientation plane having the largest orientation constant among the orientation faces satisfying the condition according to claim 1 is a (111) plane. The radiation image conversion panel according to any one of claims 1 to 5, wherein the phosphor is a phosphor exhibiting a cesium chloride type or a rock salt type crystal structure. The 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. comprising represents at least one alkaline 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, 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 Consist of Represents at least one rare earth element or metal selected from the group; and a, b and z are in the range of 0 ≦ a <0.5, 0 ≦ b <0.5 and 0 <z <1.0, respectively. Represents a numerical value]
The radiation image conversion panel according to claim 7, wherein the radiation image conversion panel 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. Radiation image conversion panel described in 1.