JP2004148246A - Microcapsule composition and thermosensitive recording material using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a microcapsule composition which has high thermosensitivity and excellent raw shelf stability, has fine grain sizes, and is stable with the lapse of time, a thermosensitive recoding material which is formed by using such microcapsules in a thermosensitive recording layer and has high sensitivity, color developability and excellent raw shelf stability, and a multicolor thermosensitive recording material which has high sensitivity, excellent color reproducibility and raw shelf stability. <P>SOLUTION: The microcapsule composition is characterized in that, in manufacturing the microcapsules having polyurethane/urea walls by polymerizing an isocyanate compound with a compound having active hydrogen, (1) multifunctional isocyanate having ≥2 isocyanate groups within the molecule and (2) at least one polyether derivative of an average molecular weight 500 to 20,000 having one active hydrogen within the molecule are reacted, then by processing the the obtained reaction product with (3) at least one alcohol, to at least one kind of compounds obtained by reacting all of isocyanate groups is added to the composition, thereby forming the polyurethane/urea walls. <P>COPYRIGHT: (C)2004,JPO

Description

【００２４】
一般式（Ｉ）において、Ｒ^１はアルキル基、アリール基、アシル基を表す。
Ｒ^１で表されるアルキル基としては、置換基を有していてもよく、また分岐を有していてもよく、総炭素数が１〜３０のアルキル基が好ましく、特に総炭素数が１〜２０のアルキル基が好ましい。置換基を有する場合の上記置換基には、活性水素を有する置換基は含まれず、アリール基、アルケニル基、アルコキシ基が好ましい。この様なアルキル基の具体例としては、メチル基、エチル基、ブチル基、イソプロピル基、ベヘニル基、ベンジル基、アリル基、オレイル基、メトキシエチル基等が挙げられる。
【００２５】
Ｒ^１で表されるアリール基としては、置換基を有していてもよく、総炭素数が６〜３０のアリール基が好ましく、特に総炭素数が６〜２０のアリール基が好ましい。置換基を有する場合の上記置換基には、活性水素を有する置換基は含まれず、ハロゲン原子、アルキル基、アルケニル基、アルキニル基、アルコキシ基が好ましく、中でも特にアルキル基、アルコキシ基が好ましい。この様なアリール基の具体例としては、フェニル基、ノニルフェニル基、オクチルフェニル基、フルオロフェニル基、スチリルフェニル基、フェニルエテニルフェニル基、メトキシフェニル等が挙げられる。
【００２６】
Ｒ^１で表されるアシル基としては、脂肪族でも芳香族のアシル基でもよく、置換基を有していてもよく、また分岐を有していてもよく、総炭素数が２〜３０のアシル基が好ましく、特に総炭素数が２〜２０のアシル基が好ましい。置換基を有する場合の上記置換基には、活性水素を有する置換基は含まれず、アルキル基、アリール基、アルケニル基、アルコキシ基が好ましい。この様なアシル基の具体例としては、アセチル基、ベンゾイル基、（メタ）アクリロイル基、オレオイル基、ラウロイル基、ステアロイル基、メトキシベンゾイル基等が挙げられる。以上、この様なＲで表される基の中でも、アルキル基及びアシル基が好ましく、特にアルキル基を表すことが好ましい。
【００２７】
一般式（Ｉ）において、Ｌはアルキレンを表す。
Ｌで表されるアルキレンとしては、置換基を有していてもよく、また分岐を有していてもよく、総炭素数が２〜２０のアルキレンが好ましく、特に総炭素数が２〜１０のアルキレンが好ましい。置換基を有する場合の上記置換基には、活性水素を有する置換基は含まれず、アリール基、アルケニル基、アルコキシ基、アシル基が好ましく、中でも特にアリール基が好ましい。この様なアルキレンとしては、エチレン、プロピレン、テトラメチレン、フェニルエチレン、シクロヘキシレン、ビニルエチレン、フェノキシメチルエチレン等が挙げられる。
【００２８】
一般式（Ｉ）の繰り返し単位−（Ｌ−Ｏ）_ｎ−は、ｎ個の繰り返しにおいてそれぞれ独立の基を表してもよいが、同一の基を表すことが特に好ましい。この様な繰り返し単位を有するポリエーテルとしては、ポリエチレンオキシド、ポリプロピレンキシド、ポリテトラメチレンオキシド、ポリスチレンオキシド、ポリシクロヘキシレンオキシド、ポリエチレンオキシド−ポリプロピレンオキシド−ブロック共重合体、ポリエチレンオキシド−ポリプロピレンオキシドランダム共重合体等が挙げられる。
ｎはポリエーテル基の平均付加モル数で１１〜４４０の数を表し、１５〜３００の数が好ましく、特に１５〜２００の数が好ましい。
【００２９】
一般式（Ｉ）において、Ｒ^２は水素原子又は−（Ｘ）_ｍ−Ａ−Ｂを表す。
上記Ｘは−ＣＯ−又は−ＳＯ_２−を表し、−ＣＯ−が好ましい。
上記Ａはアルキレン又はアリーレンを表す。
Ａで表されるアリーレンとしては、置換基を有していてもよく、また分岐を有していてもよく、総炭素数が６〜３０のアリーレンが好ましく、特に総炭素数が６〜２０のアリーレンが好ましい。置換されている場合の上記置換基には、活性水素を有する置換基は含まれず、ハロゲン原子、アルキル基、アルコキシ基、アルコキシカルボニル基、アリールオキシカルボニル基、シアノ基が好ましく、特にハロゲン原子、アルキル基、アルコキシ基が好ましい。この様なアリーレンの具体例としては、フェニレン、ビフェニレン、ナフタレン、メチルフェニレン、メトキシフェニレン等が挙げられる。
【００３０】
Ａで表されるアルキレンとしては、置換基を有していてもよく、また分岐を有していてもよく、総炭素数が１〜３０のアルキレンが好ましく、特に総炭素数が１〜２０のアルキレンが好ましい。置換されている場合の上記置換基には、活性水素を有する置換基は含まれず、アリール基、アルケニル基、アルコキシ基、アルコキシカルボニル基が好ましく、中でも特にアリール基が好ましい。この様なアルキレンの具体例としては、メチレン、エチレン、プロピレン、テトラメチレン、フェニルメチレン等が挙げられる。
【００３１】
上記Ｂは水酸基又はアミノ基を表し、アミノ基が好ましい。
ｍは０又は１を表し、１が好ましい。
この様な−（Ｘ）_ｍ−Ａ−Ｂで表される基の具体例としては、アミノエチル基、アミノプロピル基、４−アミノベンゾイル基、３−アミノベンゾイル基、４−アミノベンゼンスルホニル基、アミノアセチル基、アミノエチルスルホニル基、ヒドロキシアセチル基、４−ヒドロキシベンゾイル基等が挙げられる。
以上、Ｒ^２で表される基の中では、特に水素原子が好ましい。
【００３２】
（処理用のアルコール類）
本発明において、イソシアネート基を総て反応させるための処理に用いるアルコールとしては、脂肪族アルコール、脂環式アルコール、芳香族アルコール、複素環式アルコール等の群の中から選択して使用することができる。これらの中でも、メタノール、エタノール、プロピルアルコール、イソプロピルアルコール、ブチルアルコール、イソブチルアルコール、シクロペンタノール、ベンジルアルコール、フルフリルアルコール等の炭素原子数が１〜８のアルコールが、好ましい具体例として挙げられ、中でも特に、メタノール、エタノール、プロパノール等の様に留去の容易な低沸点のアルコールが好ましい。該処理用の上記アルコール類は、２種以上を併用してもよい。
【００３３】
（水酸基を有するアミン類）
本発明に用いる、少なくとも１個の水酸基を有する１級又は２級アミンとしては、脂肪族アミン、脂環式アミン、芳香族アミン、複素環式アミン等の群の中から選択して使用することができ、これらの中でも、炭素原子数が２〜３０のアミン類が好適に使用される。
上記のアミン化合物において、水酸基はアミノ基に対して炭素原子数が２〜２０のアルキレン又は炭素原子数が６〜２０のアリーレンを介して結合していることが好ましく、特に炭素原子数が２〜１８のアルキレンを介して結合していることが好ましい。上記のアルキレン及びアリーレンは、置換基を有していてもよく、また分岐を有していてもよい。この様な水酸基を有している置換基の例として、ヒドロキシエチル基、ヒドロキシプロピル基、ヒドロキシドデシル基、ヒドロキシフェニル基等が挙げられる。
また２級アミンの場合には、アミンの窒素原子に結合する２つの置換基は同一であっても異なっていてもよく、異なる場合には、上記水酸基が結合したアルキレン又はアリーレンの他に、炭素原子数が１〜２０のアルキル基又は炭素原子数が６〜２０のアリール基が好ましい。該アルキル基、アリール基は置換基を有していてもよく、また分岐を有していてもよい。
この様な少なくとも１個の水酸基を有する１級又は２級アミンの具体例としては、エタノールアミン、ヒドロキシプロピルアミン、ヒドロキシデシルアミン、ジエタノールアミン、ｐ−アミノフェノール、Ｎ−ヒドロキシエチル−Ｎ−ドデシルアミン、Ｎ−メチル−ｐ−アミノフェノール等が挙げられる。
【００３４】
（本発明の化合物の製造方法）
第１の本発明における、（１）分子内に２個以上のイソシアネート基を有する多官能イソシアネートと（２）分子内に１個の活性水素を有し且つ平均分子量が５００〜２００００のポリエーテル誘導体の少なくとも１種とを反応させた後に、該反応物を（３）アルコールの少なくとも１種で処理することによりイソシアネート基を総て反応させた化合物の製造方法について、以下に具体的に説明する。
【００３５】
本発明の上記イソシアネート基を総て反応させた化合物は、前述した多官能イソシアネート化合物に、該化合物のイソシアネート基のモル数と等量又はそれより少ないモル数の前記ポリエーテル誘導体を反応させた後に、残存しているイソシアネート基をアルコールで処理することによりウレタン結合に変化させ、総てのイソシアネート基を消失させたものである。
この際、ポリエーテル誘導体の使用量は、多官能イソシアネート化合物のイソシアネート基１．０モルに対して０．０１〜１．０モルが好ましく、特に０．０３〜１．０モルが好ましい。
【００３６】
また上記反応で溶媒を使用してもよく、該溶媒としてはトルエン、アセトニトリル、テトラヒドロフラン、塩化メチレン、酢酸エチル等の活性水素を持たない低沸点溶媒が好ましく、特にトルエン、アセトニトリル、酢酸エチルが好ましい。溶媒を使用する場合の使用量は、多官能イソシアネート化合物１ｇに対して０．１ｍｌ〜１００ｍｌが好ましく、特に０．５ｍｌから２０ｍｌが好ましい。
本反応の温度としては、０℃〜１００℃又は使用する溶媒の還流温度が好ましく、特に３０℃〜７０℃が好ましい。
また、ポリエーテル誘導体を反応前に脱水して使用することも好ましく、脱水方法としては真空ポンプで６０℃〜１００℃に加熱下に数時間攪拌する方法、酢酸エチル等の溶媒と共沸脱水する方法等が挙げられる。
本反応に要する時間は１時間〜８時間が好ましく、特に２時間〜６時間が好ましい。
また本反応には、オクチル酸第１錫やジブチル錫ジアセテート等の触媒を添加してもよい。
【００３７】
多官能イソシアネートとポリエーテル誘導体との反応の後に処理するアルコールの使用量は、多官能イソシアネートの残存しているイソシアネート基をウレタン結合に変換するのに十分な量が好ましく、具体的には多官能イソシアネート１ｇに対して１．０ｍｌ〜１００ｍｌが好ましく、特に２．０ｍｌ〜５０ｍｌが好ましい。
該処理に必要な温度は０℃〜１００℃又は使用する溶媒の還流温度が好ましく、特に２０℃から７０℃が好ましい。
該反応に要する時間は３０分〜３０時間が好ましく、特に１時間〜８時間が好ましい。
また該反応には、オクチル酸第１錫やジブチル錫ジアセテート等の触媒を添加してもよい。
【００３８】
次に第２の本発明における、（１）分子内に２個以上のイソシアネート基を有する多官能イソシアネートと（２）分子内に１個の活性水素を有し且つ平均分子量が５００〜２００００のポリエーテル誘導体の少なくとも１種とを反応させ、更に（３）少なくとも１個の水酸基を有する１級又は２級アミンの少なくとも１種を反応させた後に、該反応物を（４）アルコールの少なくとも１種で処理することによりイソシアネート基を総て反応させた化合物の製造方法について説明する。
【００３９】
本発明の上記イソシアネート基を総て反応させた化合物は、多官能イソシアネート化合物のイソシアネート基のモル数より少ないモル数のポリエーテル誘導体を反応させた後に、更に、残存しているイソシアネート基のモル数と等量又はそれより少ないモル数の１級又は２級アミンを反応させ、その後に残存しているイソシアネート基をアルコールにより処理することによりウレタン結合に変化させることにより、総てのイソシアネート基を消失させたものである。
この際、ポリエーテル誘導体の使用量は、多官能イソシアネート化合物のイソシアネート基１．０モルに対して０．０１〜０．９９モルが好ましく、特に０．０３〜０．５モルが好ましい。
その他の多官能イソシアネートとポリエーテル誘導体の反応については上記に記載したものと同様にできる。
【００４０】
更に第３の本発明における、（１）分子内に２個以上のイソシアネート基を有する多官能イソシアネートと（２）分子内に１個の活性水素を有し且つ平均分子量が３００〜５０００のポリエーテル誘導体の少なくとも１種を、後者の活性水素のモル数が前者のイソシアネート基のモル数を下回らないモル比で反応させることにより、イソシアネート基を総て反応させた化合物の製造方法について説明する。
【００４１】
本発明の上記イソシアネート基を総て反応させた化合物は、ポリエーテル誘導体の活性水素のモル数が多官能イソシアネート化合物のイソシアネート基のモル数を下回らないモル比で反応させることにより、総てのイソシアネート基を消失させたものである。
この際、ポリエーテル誘導体の使用量は、多官能イソシアネート化合物のイソシアネート基１．０モルに対して１．０〜１０モルが好ましく、特に１．０〜３．０モルが好ましい。
その他の多官能イソシアネートとポリエーテル誘導体の反応については上記に記載したものと同様にできる。
【００４２】
第１及び第２の本発明の前記反応に続く、水酸基を有し１級又は２級アミンとの反応は、上記の反応溶液に１級又は２級アミンを添加してもよいし、多官能イソシアネート化合物とポリエーテル誘導体を別途に反応させておき、当該反応溶液を１級又は２級アミンに添加してもよい。
上記１級又は２級アミンとの反応における１級又は２級アミンの使用量は、ポリエーテル誘導体との反応後に残存しているイソシアネート基１．０モルに対して０．１〜１．０モルが好ましく、特に０．５〜１．０モルが好ましい。
【００４３】
上記反応には溶媒を使用してもよく、該溶媒としてはトルエン、アセトニトリル、テトラヒドロフラン、塩化メチレン、酢酸エチル等の活性水素を持たない低沸点溶媒が好ましく、特にトルエン、アセトニトリル、酢酸エチルが好ましい。溶媒を使用する場合の使用量は、１級又は２級アミン１ｇに対して１ｍｌ〜２００ｍｌが好ましく、特に１０ｍｌ〜１００ｍｌが好ましい。
上記反応の温度は０℃〜１００℃又は使用する溶媒の還流温度が好ましく、特に０℃から５０℃が好ましい。
上記反応に要する時間は３０分間〜８時間が好ましく、特に３０分間〜３時間が好ましい。
引き続くアルコールとの処理については、前記に記載と同様にして行なう。
【００４４】
（マイクロカプセル組成物）
次に、本発明のマイクロカプセル組成物について説明する。
マイクロカプセルの形成は多官能イソシアネート化合物の重合、例えば分子内に２個以上の活性水素を有する化合物との反応で行なわれる。この様な活性水素を有する化合物の例としては、例えば水の他、エチレングリコール、グリセリン等の多価アルコール系化合物、エチレンジアミン、ジエチレントリアミン等の多価アミン系化合物等、又はこれらの混合物等が挙げられる。これらの中でも、特に水を用いて重合させることが好ましい。この結果としてポリウレタン／ポリウレア壁が形成される。
【００４５】
本発明のマイクロカプセル組成物は、該マイクロカプセルの製造の際に、（１）分子内に２個以上のイソシアネート基を有する多官能イソシアネートと、（２）分子内に１個の活性水素を有し且つ平均分子量が５００〜２００００のポリエーテル誘導体の少なくとも一種を反応させた後に、（３）炭素原子数１〜８のアルコールの少なくとも一種で処理することによりイソシアネート基を総て反応させた化合物、又は、（１）分子内に２個以上のイソシアネート基を有する多官能イソシアネートと、（２）分子内に１個の活性水素を有し且つ平均分子量が５００〜２００００のポリエーテル誘導体の少なくとも一種を反応させ、更に（３）少なくとも１個の水酸基を有する炭素原子数２〜３０の１級又は２級アミンの少なくとも一種を反応させた後に、（４）炭素原子数１〜８のアルコールの少なくとも一種で処理することによりイソシアネート基を総て反応させた化合物、又は第３の発明の化合物を、油相又は／及び水相に添加したものである。
【００４６】
上記のイソシアネート基を総て反応させた化合物はカプセル化の際に、油相又は水相のいずれか一方、又は両方に添加してもよいが、これらの化合物が溶解する方に添加するのが好ましい。また、これらの化合物は１種単独でも２種以上を併用しても構わない。
上記イソシアネート基を総て反応させた化合物の添加量は、油相又は水相の全質量の０．５％〜５０％が好ましく、特に１．０％〜３０％が好ましい。
【００４７】
本発明において、マイクロカプセルの製造に必要な他の成分、即ち、カプセルに封入する物質、疎水性溶媒、水媒体等は、当該技術の現状に対応するものが使用可能である。
本発明のマイクロカプセルに封入することの可能な物質の例は、例えば、香料油、植物保護剤、反応性接着剤及び医薬等を挙げられるが、ジアゾニウム塩化合物又は電子供与性染料前駆体等の発色成分を内包するマイクロカプセルを製造するのに好適である。ジアゾニウム塩化合物又は電子供与性染料前駆体を内包する場合には、高沸点溶媒に溶解されてマイクロカプセルに封入されている態様が好ましい。
【００４８】
また本発明の感熱記録材料は、支持体上に上記マイクロカプセルを含む感熱記録層が設けられた基本構成を有する。更に、本発明の多色感熱記録材料は、透明支持体上にシアン、マゼンタ及びイエローのマイクロカプセルを含む感熱記録層が設けられ、これらの中の少なくとも１種は上記マイクロカプセルからなる基本構成を有する。ここで、所望により透明支持体の裏面にブラックの感熱記録層が設けられてもよい。
【００４９】
（発色成分及び顕色剤）
本発明のマイクロカプセルに内包される電子供与性染料前駆体としては、トリアリールメタン系化合物、ジフェニルメタン系化合物、チアジン系化合物、キサンテン系化合物、スピロピラン系化合物等が挙げられるが、特にトリアリールメタン系化合物及びキサンテン系化合物が、発色濃度が高く有用である。
【００５０】
これらの具体例としては、３，３−ビス（ｐ−ジメチルアミノフェニル）−６ジメチルアミノフタリド（即ちクリスタルバイオレットラクトン）、３，３−ビス（ｐ−ジメチルアミノ）フタリド、３−（ｐ−ジメチルアミノフェニル）−３−（１，３−ジメチルインドール−３−イル）フタリド、３−（ｐ−ジメチルアミノフェニル）−３−（２−メチルインドール−３−イル）フタリド、３−（ｏ−メチル−ｐ−ジメチルアミノフェニル）−３−（２−メチルインドール−３−イル）フタリド、３−（ｏ−メチル−ｐ−ジエチルアミノフェニル）−３−（１′−エチル−２−メチルインドール−３−イル）フタリド、４，４′−ビス（ジメチルアミノ）ベンズヒドリンベンジルエーテル、Ｎ−ハロフェニルロイコオーラミン、Ｎ−２，４，５−トリクロロフェニルロイコオーラミン；
【００５１】
ローダミン−Ｂ−アニリノラクタム、ローダミン（ｐ−ニトロアニリノ）ラクタム、ローダミン−Ｂ−（ｐ−クロロアニリノ）ラクタム、２−ベンジルアミノ−６−ジエチルアミノフルオラン、２−アニリノ−６−ジエチルアミノフルオラン、２−アニリノ−３−メチル−６−ジエチルアミノフルオラン、２−アニリノ−３−メチル−６−シクロヘキシルメチルアミノフルオラン、２−アニリノ−３−メチル−６−イソアミルエチルアミノフルオラン、２−（ｏ−クロロアニリノ）−６−ジエチルアミノフルオラン、２−オクチルアミノ−６−ジエチルアミノフルオラン、２−エトキシエチルアミノ−３−クロロ−２−ジエチルアミノフルオラン、２−アニリノ−３−クロロ−６−ジエチルアミノフルオラン、ベンゾイルロイコメチレンブルー、ｐ−ニトロベンジルロイコメチレンブルー、３−メチル−スピロ−ジナフトピラン、３−エチル−スピロ−ジナフトピラン、３，３′−ジクロロ−スピロ−ジナフトピラン、３−ベンジルピロジナフトピラン、３−プロピル−スピロ−ジベンゾピラン等が挙げられる。
【００５２】
上記電子供与性染料前駆体と組み合わせて用いられる電子受容性化合物（顕色剤とも言われ、通常はマイクロカプセルには内包されない。）としては、フェノール誘導体、サリチル酸誘導体、ヒドロキシ安息香酸エステル等が挙げられる。これらの中でも特に、ビスフェノール類、ヒドロキシ安息香酸エステル類が好ましい。例えば、２，２−ビス（ｐ−ヒドロキシフェニル）プロパン（ビスフェノールＡ）、２，２−ビス（ｐ−ヒドロキシフェニル）ペンタン、２，２−ビス（ｐ−ヒドロキシフェニル）エタン、２，２−ビス（ｐ−ヒドロキシフェニル）ブタン、２，２−ビス（４′−ヒドロキシ−３′，５′−ジクロロフェニル）プロパン、１，１−（ｐ−ヒドロキシフェニル）シクロヘキサン、１，１−（ｐ−ヒドロキシフェニル）プロパン、１，１−（ｐ−ヒドロキシフェニル）ペンタン、１，１−（ｐ−ヒドロキシフェニル）−２−エチルヘキサン、３，５−ジ（α−メチルベンジル）サリチル酸及びその多価金属塩、３，５−ジ（ｔｅｒｔ−ブチル）サリチル酸及びその多価金属塩、３−α，α−ジメチルベンジルサリチル酸及びその多価金属塩、ｐ−ヒドロキシ安息香酸ブチル、ｐ−ヒドロキシ安息香酸ベンジル、ｐ−ヒドロキシ安息香酸−２−エチルヘキシル、ｐ−フェニルフェノール及びｐ−クミルフェノール等を挙げることができる。これらの電子受容性化合物は１種単独でも、２種以上を任意の比率で併用することもできる。
【００５３】
本発明の感熱記録層には、その反応を促進するために増感剤を添加することが好ましい。この様な増感剤としては、分子内に芳香族性の基と極性基を適度に有している低融点有機化合物が好ましい。その具体例としては、ｐ−ベンジルオキシ安息香酸ベンジル、α−ナフチルベンジルエーテル、β−ナフチルベンジルエーテル、β−ナフトエ酸フェニルエステル、α−ヒドロキシ−β−ナフトエ酸フェニルエステル、β−ナフトール−（ｐ−クロロベンジル）エーテル、１，４−ブタンジオールフェニルエーテル、１，４−ブタンジオール−ｐ−メチルフェニルエーテル、１，４−ブタンジオール−ｐ−エチルフェニルエーテル、１，４−ブタンジオール−ｍ−メチルフェニルエーテル、１−フェノキシ−２−（ｐ−トリルオキシ）エタン、１−フェノキシ−２−（ｐ−エチルフェノキシ）エタン、１−フェノキシ−２−（ｐ−クロロフェノキシ）エタン、ｐ−ベンジルビフェニル、ｐ−トルエンスルホンアミド、４−（２−エチルヘキシルオキシ）フェニルスルホンアミド、４−ｎ−ペンチルオキシフェニルスルホンアミド等が挙げられる。本発明においては、これらの増感剤を２種以上任意の比率で併用することもできる。
【００５４】
マイクロカプセルに内包されるジアゾニウム塩化合物は、公知のものを使用することができる。該ジアゾニウム塩化合物としては、下記一般式
Ａｒ−Ｎ_２ ^＋・Ｘ⁻
で表わされる化合物をいう。ここで、上式中のＡｒはアリール基を表わし、Ｘ⁻ は酸アニオンを表す。
【００５５】
上記ジアゾニウム塩化合物は、フェノール化合物或いは活性メチレンを有する化合物と反応し、いわゆる染料を形成可能であり、更に光（一般的には紫外線）照射により分解し、脱窒素してその反応活性を失うものである。この様なジアゾニウム塩の具体例としては、２，５−ジブトキシ−４−モルホリノベンゼンジアゾニウム、２，５−オクトキシ−４−モルホリノベンゼンジアゾニウム、２，５−ジブトキシ−４−（Ｎ−（２−エチルヘキサノイル）ピペラジノ）ベンゼンジアゾニウム、２，５−ジエトキシ−４−（Ｎ−（２−（２，４−ジ−ｔｅｒｔ−アミルフェノキシ）ブチリル）ピペラジノ）ベンゼンジアゾニウム、２，５−ジブトキシ−４−トリルチオベンゼンジアゾニウム、２，５−ジブトキシ−４−クロルベンゼンチオジアゾニウム、２，５−ジヘプチルオキシ−４−クロルベンゼンチオジアゾニウム、３−（２−オクチルオキシエトキシ）−４−モロホリノベンゼンジアゾニウム、４−Ｎ，Ｎ−ジヘキシルアミノ−２−ヘキシルオキシベンゼンジアゾニウム、４−（Ｎ−ヘキシル−Ｎ−（１−メチル−２−（ｐ−メトキシフェノキシ）エチル）アミノ）−２−ヘキシルオキシベンゼンジアゾニウム及び４−Ｎ−ヘキシル−Ｎ−トリルアミノ−２−ヘキシルオキシベンゼンジアゾニウムの塩等を挙げることができる。
【００５６】
上記ジアゾニウム塩化合物の酸アニオンには、ヘキサフルオロフォスフェート塩、テトラフルオロボレート塩、１，５−ナフタレンスルホネート塩、パーフルオロアルキルカルボネート塩、パーフルオロアルキルスルフォネート塩、塩化亜鉛塩、及び塩化錫塩等を用いることができる。中でも好ましくは、ヘキサフルオロフォスフェート塩、テトラフルオロボレート塩、及び１，５−ナフタレンスルホネート塩が、水溶性が低く有機溶剤に可溶であるので好適である。本発明においては、異なる２種以上のジアゾニウム塩化合物を任意の比率で混合して用いることもできる。
【００５７】
ジアゾニウム塩化合物を内包するマイクロカプセルを用いた感熱記録層においては、アリールスルフォンアミド化合物等の公知の熱増感剤が添加されていてもよい。具体的には、トルエンスルホンアミドやエチルベンゼンスルホンアミドなどが好適に挙げられる。また本発明においては、異なる２種以上の熱増感剤を混合して用いることもできる。
【００５８】
ジアゾニウム塩化合物と反応して色素を形成するカプラー化合物は、通常、乳化分散及び／又は固体分散することにより微粒子化して使用される。該カプラーの具体例としては、例えば、レゾルシン、フルルグルシン、２，３−ジヒドロキシナフタレン−６−スルホン酸ナトリウム、１−ヒドロキシ−２−ナフトエ酸モルホリノプロピルアミド、１，５−ジヒドロキシナフタレン、２，３−ジヒドロキシナフタレン、２，３−ジヒドロキシ−６−スルファニルナフタレン、２−ヒドロキシ−３−ナフトエ酸アニリド、２−ヒドロキシ−３−ナフトエ酸エタノールアミド、２−ヒドロキシ−３−ナフトエ酸オクチルアミド、２−ヒドロキシ−３−ナフトエ酸−Ｎ−ドデシルオキシプルピルアミド、２−ヒドロキシ−３−ナフトエ酸テトラデシルアミド、アセトアニリド、アセトアセトアニリド、ベンゾイルアセトアニリド、２−クロロ−５−オクチルアセトアセトアニリド、２，５−ジ−ｎ−ヘプチルオキシアセトアニリド；
【００５９】
１−フェニル−３−メチル−５−ピラゾロン、１−（２’−オクチルフェニル）−３−メチル−５−ピラゾロン、１−（２’，４’，６’−トリクロロフェニル）−３−ベンズアミド−５−ピラゾロン、１−（２’，４’，６’−トリクロロフェニル）−３−アニリノ−５−ピラゾロン、１−フェニル−３−フェニルアセトアミド−５−ピラゾロン、１−（２−ドデシルオキシフェニル）−２−メチルカーボネイトシクロヘキサン−３，５−ジオン、１−（２−ドデシルオキシフェニル）シクロヘキサン−３，５−ジオン、Ｎ−フェニル−Ｎ−ドデシルバルビツール酸、Ｎ−フェニル−Ｎ−（２，５−ジオクチルオキシフェニル）バルビツール酸及びＮ−フェニル−Ｎ−（３−ステアリルオキシ）ブチルバルビツール酸等を挙げることができる。これらのカプラー化合物は、２種以上を併用して目的とする発色色相を得ることもできる。
【００６０】
更に、色素形成反応を促進させるために、乳化分散及び／又は固体分散して微粒子化した塩基化合物を添加するのが好ましい。該塩基物質としては無機或いは有機の塩基化合物の他、加熱時に分解等によりアルカリ物質を放出するような化合物も含まれる。代表的な塩基化合物としては、有機アンモニウム塩、有機アミン、アミド、尿素及びチオ尿素、更にそれらの誘導体、チアゾール類、ピロール類、ピリミジン類、ピペラジン類、グアニジン類、インドール類、イミダゾール類、イミダゾリン類、トリアゾール類、モルホリン類、ピペリジン類、アミジン類、フォルムアジン類、ピリジン類等の含窒素化合物が挙げられる。
【００６１】
これらの具体例としてはトリシクロヘキシルアミン、トリベンジルアミン、オクタデシルベンジルアミン、ステアリルアミン、アリル尿素、チオ尿素、メチルチオ尿素、アリルチオ尿素、エチレンチオ尿素、２−ベンジルイミダゾール、４−フェニルイミダゾール、２−フェニル−４−メチルイミダゾール、２−ウンデシルイミダゾリン、２，４，５−トリフリル−２−イミダゾリン、１，２−ジフェニル−４，４−ジメチル−２−イミダゾリン、２−フェニル−２−イミダゾリン、１，２，３−トリフェニルグアニジン、１，２−ジシクロヘキシルグアニジン、１，２，３−トリシクロヘキシルグアニジン、グアニジントリクロロ酢酸塩、Ｎ，Ｎ’−ジベンジルピペラジン、４，４’−ジチオモルホリン、モルホリニウムトリクロロ酢酸塩、２−アミノベンゾチアゾール、及び２−ベンゾイルヒドラジノベンゾチアゾール等を挙げることができる。これらの塩基化合物は、２種以上を併用することもできる。
【００６２】
（マイクロカプセルの形成及び感熱記録材料）
本発明のマイクロカプセル組成物は、例えば下記の様にして具体的に作製することができる。マイクロカプセルの芯を形成するための疎水性溶媒としては、沸点１００〜３００℃の高沸点有機溶媒が好ましい。具体的には、アルキルナフタレン、アルキルジフェニルエタン、アルキルジフェニルメタン、ジフェニルエタンアルキル付加物、アルキルビフェニル、塩素化パラフィン、トリクレジルフォスフェート等の燐酸系誘導体、マレイン酸−ジ−２−エチルヘキシル等のマレイン酸エステル類、及びアジピン酸エステル類などを挙げることができる。これらは２種以上を混合して用いてもよい。前記ジアゾニウム塩化合物や電子供与性染料前駆体の上記疎水性溶媒に対する溶解度が充分でない場合は、更に低沸点有機溶剤を併用することができる。併用する低沸点有機溶媒としては、沸点４０〜１００℃の有機溶媒が好ましく、具体的には酢酸エチル、酢酸ブチル、メチレンクロライド、テトラヒドロフラン及びアセトン等を挙げることができる。また、これらの低沸点有機溶媒を２種以上混合して用いてもよい。低沸点（沸点約１００℃以下のもの）の溶媒のみをカプセル芯に用いた場合には、該溶媒は揮発して、カプセル壁とジアゾニウム塩化合物や電子供与性染料前駆体のみが存在する所謂コアレスカプセルが形成され易い。
【００６３】
ジアゾニウム塩の種類によってはマイクロカプセル化反応中の水相側へ移動する場合があり、これを抑制するために、予め酸アニオンを水溶性高分子溶液中に適宜添加してもよい。この様な酸アニオンとしては、ＰＦ_６ ⁻、Ｂ（−Ｐｈ）_４ ⁻（該Ｐｈはフェニル基）、ＺｎＣｌ_２ ⁻、Ｃ_ｎＨ_２ｎ＋１ＣＯＯ⁻（該ｎは１〜９の整数）及びＣ_ｐＦ_２ｐ＋１ＳＯ_３ ⁻（該ｐは１〜９の整数）を挙げることができる。
また、保存安定性や発色感度調整等のために種々の添加剤を併用することも可能である。
【００６４】
本発明においてマイクロカプセル化の際、マイクロカプセル壁を形成するためのイソシアネート化合物の重合に用いる活性水素を有する化合物としては、一般に水が使用されるが、ポリオールを芯となる有機溶媒中或いは分散媒となる水溶性高分子溶液中に添加しておき、上記活性水素を有する化合物（マイクロカプセル壁の原料の一つ）として用いることができる。具体的にはプロピレングリコール、グリセリン及びトリメチロールプロパン等が挙げられる。またポリオールの代わりに、或いは併用してジエチレントリアミン、テトラエチレンペンタミン等のアミン化合物を使用してもよい。これらの化合物も先の「ポリウレタン樹脂ハンドブック」に記載されている。
【００６５】
マイクロカプセルの油相を水相中に分散するための水溶性高分子としては、ポリビニルアルコールおよびその変成物、ポリアクリル酸アミドおよびその誘導体、エチレン／酢酸ビニル共重合体、スチレン／無水マレイン酸共重合体、エチレン／無水マレイン酸共重合体、イソブチレン／無水マレイン酸共重合体、ポリビニルピロリドン、エチレン／アクリル酸共重合体、酢酸ビニル／アクリル酸共重合体、カルボキシメチルセルロース、メチルセルロース、カゼイン、ゼラチン、澱粉誘導体、アラビヤゴム及びアルギン酸ナトリウムを挙げることができる。これらの水溶性高分子は、イソシアネート化合物との反応しないか、極めて反応し難いものが好ましく、たとえばゼラチンのように分子鎖中に反応性のアミノ基を有するものは予め反応性をなくしておくことが必要である。
本発明に係る化合物は、少なくとも油相あるいは水相のいずれか一方に添加されている必要がある。
【００６６】
本発明では、界面活性剤を油相あるいは水相の何れに添加して使用しても良いが、有機溶媒に対する溶解度が低いために水相に添加する方が容易である。添加量は油相の重量に対し０．１〜５重量％、特に０．５〜２重量％が好ましい。一般に乳化分散に用いる界面活性剤は、比較的長鎖の疎水基を有する界面活性剤が優れているとされており「界面活性剤便覧」（西一郎ら、産業図書発行（１９８０））、アルキルスルホン酸、アルキルベンゼンスルホン酸などのアルカリ金属塩を用いることができる。
【００６７】
本発明において、界面活性剤（乳化助剤）として芳香族スルホン酸塩のホルマリン縮合物や芳香族カルボン酸塩のホルマリン縮合物などの化合物を使用することもできる。具体的には、下記一般式（Ａ）で表される化合物が挙げられる。
【化２】

〔一般式（Ａ）において、Ｒは炭素原子数が１〜４のアルキル基を表し、Ｘは−ＳＯ_３ ⁻又は−ＣＯＯ⁻を表し、Ｍはナトリウム原子又はカリウム原子を表す。ｑは１〜２０の整数を表わす］
上記化合物については特開平６−２９７８５６号公報（←特願平５−８３７２１号）に記載されている。
【００６８】
また、アルキルグルコシド系化合物も同様に使用することができる。具体的には、下記一般式（Ｂ）で表される化合物である。
【化３】

〔一般式（Ｂ）において、Ｒは炭素原子数が４〜１８のアルキル基を表す。ｑは０〜２の整数を表わす。］
本発明においては、いずれの界面活性剤とも単独で使用しても２種以上を適宜に併用してもよい。
【００６９】
上記ジアゾニウム塩化合物（あるいは電子供与性染料前駆体）、高沸点溶媒等からなる溶液と多官能イソシアネート化合物との混合液（油相）を、界面活性剤及び水溶性高分子からなる水溶液（水相）に添加する。その際、水溶液をホモジナイサー等の高シェア攪拌装置で攪拌させながら、添加することにより乳化分散させする。乳化後、イソシアネート化合物の重合反応触媒を添加するか、乳化物の温度を上昇させてカプセル壁形成反応を行なう。
【００７０】
調製されたジアゾニウム塩を内包したマイクロカプセル液には、更にカップリング反応失活剤を適宜添加することができる。この反応失活剤としての例としては、ハイドロキノン、重亜硫酸ナトリウム、亜硝酸カリウム、次亜リン酸、塩化第１スズ及びホルマリンを挙げることができる。これらの化合物については、特開昭６０−２１４９９２号公報に記載されている。また通常、カプセル化の過程で、水相中にジアゾニウム塩化合物が溶出することが多いが、これを除去する方法として、濾過処理、イオン交換処理、電気泳動処理、クロマト処理、ゲル濾過処理、逆浸透処理、限外濾過処理、透析処理、活性炭処理などの方法を利用することができる。この中でもイオン交換処理、逆浸透処理、限外濾過処理及び透析処理が好ましく、特に、陽イオン交換体による処理、陽イオン交換体と陰イオン交換体の併用による処理が好ましい。これらの方法については、特開昭６１−２１９６８８号公報に記載されている。
【００７１】
本発明においては、感熱発色層中に電子受容性化合物、熱増感剤、カプラー及び塩基性化合物などを添加することができる。これらは、適宜混合して、別々に乳化分散、あるいは固体分散、微粒化して添加、あるいは適宜混合してから、乳化分散あるいは固体分散、微粒化して添加することができる。乳化分散する方法は、有機溶媒中にこれらの化合物を溶解し、水溶性高分子水溶液をホモジナイザー等で攪拌中に添加する。微粒子化を促進するにあたり、前述の疎水性有機溶媒、界面活性剤、水溶性高分子を使用することが好ましい。
【００７２】
カプラーおよび塩基性物質、電子受容性化合物、熱増感剤などを固体分散するには、これらの粉末を水溶性高分子水溶液中に投入しボールミル等の公知の分散手段を用いて微粒子化し、使用することができる。微粒子化に際しては、熱感度、保存性、記録層の透明性、製造適性などの多色感熱記録材料及びその製造方法に必要な特性を満足しうる粒子直径を得るように行なうことが好ましい。
【００７３】
上記マイクロカプセル液と、上記熱増感剤、電子受容性化合物、カプラー及び塩基性化合物等の調製液とは、適当な割合で混合され支持体上に塗布される。一般には、ジアゾニウム塩化合物１モルに対して、カプラー１〜１０モル、好ましくは２〜６モルが適当である。塩基性化合物の最適添加量は塩基性の強度により異なるがジアゾニウム塩化合物の０．５〜５モルが一般的である。電子受容性化合物（顕色剤）は、電子供与性染料前駆体１モルに対して０．５〜３０モルの範囲内で一般に添加するが、好ましくは１〜２０モルの範囲で適宜添加する。さらに好ましく３〜１５モルの範囲内で添加する。熱増感剤は、電子供与性染料前駆体に対して一般に０．１〜２０モルの範囲内で添加するが、好ましくは０．５〜１０モルの範囲で適宜添加する。
【００７４】
これらの塗布液を塗布する支持体としては、感熱記録材料の支持体として公知の材料を使用することができる。例えば、紙、紙上にクレー等を塗布した塗工紙、ポリエチレン、ポリエステル等を紙上にラミネートしたラミネート紙、合成紙、ポリエチレンテレフタレート、ポリイミド、トリアセチルセルロース等のプラスチックフィルムを挙げることができる。また透明支持体としては、上記のポリエチレンテレフタレート、トリアセチルセルロース、さらにポリスチレン、ポリプロピレン、ポリエチレン等のプラスチックフィルムを挙げることができる。
【００７５】
本発明には、光堅牢性などを更に改善するために感熱発色層の上に保護層を設けてもよい。また、多色感熱材料においては、色再現性を更に良くするために感熱記録層の間に中間層を設けてもよい。これらに用いられる層の素材としては、水溶性高分子化合物もしくは疎水性高分子化合物のエマルジョン（ラテックス）が好ましい。
【００７６】
多色感熱記録材料及びその記録方法について述べる。まず初めに低エネルギーの熱記録でジアゾニウム化合物を含有する最外層の感熱層（第１感熱記録層、通常イエロー発色層）を発色させた後、該感熱層に含有されるジアゾニウム化合物の吸収波長域の光を放出する光源を用いて全面光照射して、最上層の感熱層中に残存するジアゾニウム化合物を光分解させる。
【００７７】
次いで、前回より高エネルギーで、第１層に含有されるジアゾニウム化合物の吸収波長域の光とは異なった光吸収波長域を有するジアゾニウム化合物を含有する第２層目の感熱層（第２感熱記録層、通常マゼンタ発色層）を発色させた後、該ジアゾニウム化合物の吸収波長域の光を放出する光源を用いて再度全面光照射し、これによって第２層目の加熱層中に残存するジアゾニウム化合物を光分解させる。最後に、更に高エネルギーで、最内層（第３感熱記録層、通常シアン発色層）の電子供与性染料前駆体を含有する層（第３層）を発色させて画像記録を完了する。
【００７８】
上記の場合には、最外層及び第２層を透明な感熱層とすることが、各発色が鮮やかになるので好ましい。また本発明においては、支持体として透明な支持体を用い、上記３層のうち何れか一層を透明な支持体の裏面に塗布することにより、多色画像を得ることもできる。この場合には、画像を見る側と反対側の最上層の感熱層は透明である必要はない。
【００７９】
上記ジアゾニウム化合物の光分解に使用する光源としては、通常紫外線ランプを使用する。紫外線ランプは管内に水銀蒸気を充填した蛍光管であり、管の内壁に塗布する蛍光体の種類により種々の発光波長を有する蛍光管を得ることができる。
【００８０】
多色感熱記録材料においては、上記第３感熱記録層を適当なジアゾニウム塩化合物とカプラー化合物との組合せで作成することも可能である。
【００８１】
【実施例】
以下に実施例を示し、本発明を更に具体的に説明するが、本発明はこれらの実施例により限定されるものではない。尚、本実施例において「部」及び「％」は全て、「質量部」及び「質量％」を表す。
【００８２】
［合成例１］：本発明の化合物（１）の合成
ポリエチレングリコールモノメチルエーテル（日本油脂（株）製の「ユニオックスＭ−４０００」、平均分子量：４３５０）２０部を外温１１０℃で窒素気流下において乾燥した後に、外温を６０℃に戻し、乾燥酢酸エチル１５ｍｌ、及び多価イソシアネート化合物としてキシリレンジイソシアネート／トリメチロールプロパン付加物（三井武田ケミカル（株）製の「タケネートＤ１１０Ｎ」、７５％酢酸エチル溶液）１．６８部を添加して、６０℃で３時間撹拌を行なった。この反応液にメタノール２０ｍｌを添加し６０℃で２時間撹拌を行なった後に、溶媒を留去し、本発明に係る化合物（１）を２０．３ｇ得た。該化合物（１）につきＩＲ吸収スペクトル（ＫＢｒセル使用）を測定したところ、ＮＣＯ基の吸収は認められなかった。
【００８３】
［合成例２］：本発明の化合物（２）の合成
合成例１において、多価イソシアネート化合物「タケネートＤ１１０Ｎ」１．６８部の代わりに、ジ（４−イソシアネートフェニル）メタンの０．５８部を使用したこと以外は、合成例１と同様にして本発明に係る化合物（２）を１９．８ｇ得た。該化合物（２）にも、ＩＲ吸収スペクトルでＮＣＯ基の吸収は認められなかった。
【００８４】
［合成例３］：本発明の化合物（３）の合成
合成例１において、多価イソシアネート化合物「タケネートＤ１１０Ｎ」１．６８部の代わりに、多価イソシアネート化合物（日本ポリウレタン工業（株）製の「ミリオネートＭＲ−２００」）の０．６０部を使用したこと以外は、合成例１と同様にして本発明に係る化合物（３）を２０．６ｇ得た。該化合物（３）にも、ＩＲ吸収スペクトルでＮＣＯ基の吸収は認められなかった。
【００８５】
［合成例４］：本発明の化合物（４）の合成
合成例１において、ポリエチレングリコールモノメチルエーテル「ユニオックスＭ−４０００」をポリエチレングリコールモノメチルエーテル（Ａｌｄｒｉｃｈ社製の「２０，２５０−９」、平均分子量：２０００）に変更し、多価イソシアネート化合物「タケネートＤ１１０Ｎ」の添加量１．６８部を３．６５部に変更したこと以外は、合成例１と同様にして本発明に係る化合物（４）を２１．６ｇ得た。該化合物（４）にも、ＩＲ吸収スペクトルでＮＣＯ基の吸収は認められなかった。
【００８６】
［合成例５］：本発明の化合物（５）の合成
合成例１において、ポリエチレングリコールモノメチルエーテル「ユニオックスＭ−４０００」をポリエチレングリコールモノメチルエーテル（Ａｌｄｒｉｃｈ社製の「２０，２４９−５」、平均分子量：７５０）に変更し、多価イソシアネート化合物「タケネートＤ１１０Ｎ」の添加量１．６８部を９．７４部に変更したこと以外は、合成例１と同様にして本発明に係る化合物（５）を２６．１ｇ得た。該化合物（５）にも、ＩＲ吸収スペクトルでＮＣＯ基の吸収は認められなかった。
【００８７】
［合成例６］：本発明の化合物（６）の合成
ポリエチレングリコールモノメチルエーテル（「ユニオックスＭ−４０００」）５０部と多価イソシアネート化合物（「タケネートＤ１１０Ｎ」）５０部の反応混合物（５０％酢酸エチル溶液）１０部とアセトニトリル２０ｍｌの混合物を、氷浴下にエタノールアミン０．５２部とアセトニトリル３０ｍｌの混合物に２２分かけて滴下した。そのまま２２分攪拌した後にメタノール２０ｍｌを添加し、５０℃で３０分間攪拌した。溶媒を溜去した後に酢酸エチルとｎ−ヘキサンを添加し生じた沈殿を濾取して、本発明に係る化合物（６）を５．５５ｇ得た。該化合物（６）にも、ＩＲ吸収スペクトルでＮＣＯ基の吸収は認められなかった。
【００８８】
［合成例７］：本発明の化合物（７）の合成
合成例６において、エタノールアミン０．５２部を、ジエタノールアミンの０．９０部に変更したこと以外は、合成例６と同様にして本発明に係る化合物（７）を５．９７ｇ得た。該化合物（７）にも、ＩＲ吸収スペクトルでＮＣＯ基の吸収は認められなかった。
【００８９】
［実施例１］
（Ｉ）感熱記録層（Ａ）の塗布液の調製
（１）ジアゾニウム塩内包カプセル液の調製
ジアゾニウム塩化合物として、４２０ｎｍに分解の最大吸収波長をもつ下記の化合物（Ａ−１）３．５部及び化合物（Ａ−２）０．９部を酢酸エチル１６．４部に溶解し、更に高沸点溶媒としてイソプロピルビフェニル７．３部及びフタル酸ジフェニル２．５部を添加し、加熱して均一に混合した。
【００９０】
【化４】

【００９１】
上記の混合溶液に、カプセル壁剤として、キシリレンジイソシアネート／トリメチロールプロパン付加物（三井武田ケミカル（株）製の「タケネートＤ１１０Ｎ」、７５％酢酸エチル溶液、）４．５部と特開平７−８８３５６号公報（←特願平５−２３３５３６号）に記載の方法に従って合成したキシリレンジイソシアネート／ビスフェノールＡ付加物の３０％酢酸エチル溶液４．５部からなる混合物の８．６部を添加し、均一に攪拌した。
別途、「ＳｃｒａｐｈＡＧ−８」（日本精化（株）製）０．３６部が添加された８％フタル化ゼラチン水溶液７７部と合成例１で得られた本発明に係る化合物（１）１．２部からなる混合物を用意し、上記ジアゾニウム塩化合物とイソシアネート化合物の混合溶液を添加し、ホモジナイザーにて乳化分散した。得られた乳化分散液に水２０部を加え均一化した後、４０℃にて攪拌しながら３時間かけてカプセル化反応を行なった。この後３５℃に液温を下げ、イオン交換樹樹脂「アンバーライトＩＲＡ６８」（オルガノ社製）４．１部、「アンバーライトＩＲＣ５０」（オルガノ社製）８．２部を加え、更に１時間撹拌した。その後、イオン交換樹脂を濾過して取り除き、カプセル液の固形分濃度が２０％になる様に濃度を調整して、ジアゾニウム塩内包マイクロカプセル液を得た。得られたマイクロカプセルの粒径は、堀場製作所（株）製の粒径分布測定装置「ＬＡ−７００」で測定した結果、メジアン径で０．８５μｍであった。
【００９２】
（２）カプラー乳化分散液の調製
カプラー化合物として、２，５−ジ−ｎ−ヘプチルオキシアセトアニリド２．４部とトリフェニルグアニジン２．５部、４−（２−エチルヘキシルオキシ）フェニルスルホンアミド３．３部、４−ｎ−ペンチルオキシフェニルスルホンアミド１．７部、及び４，４′−（ｍ−フェニレンジイソプロピリデン）ジフェノール５．０部を、酢酸エチル８．０部に溶解し、「パイオニンＡ４１Ｃ」（竹本油脂（株）製）１．０部を添加した後、加熱し均一に混合した。この混合物を、別途、調製したゼラチン（新田ゼラチン（株）製の「＃７５０ゼラチン」）１０％水溶液７５．０部中に加えて、ホモジナイザーにて４０℃で乳化分散した。この乳化分散液から残存する酢酸エチルを蒸発させ、固形分濃度が２６．５％になる様に濃度を調整した。
更に、上記カプラー乳化分散液１００部に対して、ＳＢＲラテックス（住化エイビーエスラテックス（株）製の商品名「ＳＮ−３０７」、４８％液）を２６．５％に濃度調整したもの９部を添加して、均一に撹拌してカプラー乳化分散液を得た。
【００９３】
（３）感熱記録層（Ａ）用塗布液の調製
前記ジアゾニウム塩化合物内包マイクロカプセル液及び上記カプラー乳化分散液を、内包しているジアゾ化合物／カプラー化合物の質量比が１．０／３．２になる様に混合し、感熱記録層（Ａ）用塗布液を得た。
【００９４】
（ＩＩ）感熱保護層（Ｄ）の塗布液の調製
５．０％のイタコン酸変性ポリビニルアルコール（クラレ（株）製の「ＫＬ−３１８」）水溶液６１部に、２０．５％のステアリン酸亜鉛分散液（中京油脂（株）製の「ハイドリンＦ１１５」）２．０部を添加し、下記に示す化合物（Ｄ−１）の２％水溶液８．４部、フッ素系離型剤（ダイキン（株）製の「ＭＥ−３１３」）８．０部、小麦粉澱粉（籠島澱粉（株）製の「ＫＦ−４」）０．５部を添加し均一に撹拌した。この液を母液と呼ぶ。
【００９５】
化合物（Ｄ−１） Ｃ_１２Ｈ_２５Ｏ−（Ｃ_２Ｈ_４Ｏ）_１０−Ｈ
【００９６】
別途、イオン交換した２０％の「カオグロス」（白石工業（株）製）水溶液１２．５部、「ポイズ５３２Ａ」（花王（株）製）０．０６部、「ハイドリンＺ−７（中京油脂（株）製）１．８７部、１０％のポリビニルアルコール（クラレ（株）の「ＰＶＡ１０５」）水溶液１．２５部、２％のドデシルスルホン酸ナトリウム水溶液０．３９部を混合し、ダイノミルにて微分散を行なった。この液を顔料液と呼ぶ。上記の母液８０部に、この顔料液４．４部を加え、３０分以上撹拌した。その後、「Ｗｅｔｍａｓｔｅｒ５００」（東邦化学（株）製）２．８部を添加し、更に３０分以上撹拌して目的とする感熱保護層（Ｄ）用塗布液を得た。
【００９７】
（ＩＩＩ）感熱記録材料の作製
上質紙上にポリエチレンがラミネートされた印画紙用支持体の表面に、ワイヤーバーで前記感熱記録層（Ａ）用塗布液及び上記保護層（Ｄ）用塗布液をこの順に塗布し乾燥を行い、目的とする感熱記録材料を得た。この際、固形分としての塗布量は１ｍ^２当たりそれぞれ４．５ｇと１．０ｇであった。
【００９８】
（ＩＶ）熱記録及び評価
京セラ（株）製のサーマルヘッド「ＫＳＴ型」を用い、下記の様にして上記の感熱記録材料の熱記録特性を評価した。
（１）単位面積あたりの記録エネルギーが３４ｍＪ／ｍｍ^２となる様にサーマルヘッドに対する印加電力とパルス幅を設定し、該感熱記録材料に印字して、イエローの画像を記録した。
（２）その記録材料を発光中心波長４２０ｎｍ、出力４０Ｗの紫外線ランプで１０秒間照射し、未印字部分の画像を定着させた。このイエロー画像の発色濃度は、マクベス濃度計「ＲＤ９１８型」にて発色部分の光学反射濃度を測定した。その結果を下記の表１の発色濃度として示した。
（３）またシェルフライフ（生保存性）の評価は、得られた感熱記録材料を、温度４０℃、相対湿度９０％に保った恒温恒湿槽に２４時間保存した後、非印字部分を定着して地肌部分の光学反射濃度を測定した。その結果を下記表１のカブリ濃度として示した。
【００９９】
［実施例２］
実施例１において、ジアゾニウム塩内包カプセル液の調製で用いた本発明に係る化合物（１）の代わりに、合成例２で得られた本発明に係る化合物（２）を用いたこと以外は、実施例１と同様にして実施例２の感熱記録材料を作製した。ここで、該ジアゾニウム塩内包カプセルの平均粒径は０．８６μｍであった。
【０１００】
［実施例３］
実施例１において、ジアゾニウム塩内包カプセル液の調製で用いた本発明に係る化合物（１）の代わりに、合成例３で得られた本発明に係る化合物（３）を用いたこと以外は、実施例１と同様にして実施例３の感熱記録材料を作製した。ここで、該ジアゾニウム塩内包カプセルの平均粒径は０．４６μｍであった。
【０１０１】
［実施例４］
実施例１において、ジアゾニウム塩内包カプセル液の調製で用いた本発明に係る化合物（１）の代わりに、合成例４で得られた本発明に係る化合物（４）を用いたこと以外は、実施例１と同様にして実施例４の感熱記録材料を作製した。ここで、該ジアゾニウム塩内包カプセルの平均粒径は０．７７μｍであった。
【０１０２】
［実施例５］
実施例１において、ジアゾニウム塩内包カプセル液の調製で用いた本発明に係る化合物（１）の代わりに、合成例６で得られた本発明に係る化合物（６）を用いたこと以外は、実施例１と同様にして実施例５の感熱記録材料を作製した。ここで、該ジアゾニウム塩内包カプセルの平均粒径は０．７５μｍであった。
【０１０３】
［実施例６］
実施例１において、ジアゾニウム塩内包カプセル液の調製で用いた本発明に係る化合物（１）の代わりに、合成例７で得られた本発明に係る化合物（７）を用いたこと以外は、実施例１と同様にして実施例６の感熱記録材料を作製した。ここで、該ジアゾニウム塩内包カプセルの平均粒径は０．５７μｍであった。
【０１０４】
［実施例７］
実施例１において、ジアゾニウム塩内包カプセル液の調製で用いたカプセル壁剤として、キシリレンジイソシアネート／トリメチロールプロパン付加物（「タケネートＤ１１０Ｎ」）４．５部と特開平７−８８３５６号公報に記載の方法に従って合成したキシリレンジイソシアネート／ビスフェノールＡ付加物の３０％酢酸エチル溶液４．５部からなる混合物の８．６部の代わりに、キシリレンジイソシアネート／トリメチロールプロパン付加物（「タケネートＤ１１０Ｎ」）４．５部と特開平７−８８３５６号公報に記載の方法に従って合成したキシリレンジイソシアネート／ビスフェノールＡ付加物の３０％酢酸エチル溶液４．５部からなる混合物の８．６部及び合成例４で得られた本発明に係る化合物（４）の１．７部を用い、且つ、「ＳｃｒａｐｈＡＧ−８」（日本精化（株）製）０．３６部が添加された８％フタル化ゼラチン水溶液７７部と合成例１の本発明に係る化合物（１）１．２部からなる混合物の代わりに、「ＳｃｒａｐｈＡＧ−８」（日本精化（株）製）０．３６部が添加された８％フタル化ゼラチン水溶液の７７部だけを用いたこと以外は、実施例１と同様にして実施例７の感熱記録材料を作製した。ここで、上記ジアゾニウム塩内包カプセルの平均粒径は０．８９μｍであった。
【０１０５】
［実施例８］
実施例７において、ジアゾニウム塩内包カプセル液の調製で用いたカプセル壁剤として、合成例４の本発明に係る化合物（４）の代わりに合成例５で得られた本発明に係る化合物（５）を用いたこと以外は、実施例７と同様にして実施例８の感熱記録材料を作製した。ここで、上記ジアゾニウム塩内包カプセルの平均粒径は０．４４μｍであった。
【０１０６】
［比較例１］
実施例１において、ジアゾニウム塩内包カプセル液の調製で用いたカプセル壁剤として、キシリレンジイソシアネート／トリメチロールプロパン付加物（「タケネートＤ１１０Ｎ」）４．５部と特開平７−８８３５６号公報）に記載の方法に従って合成したキシリレンジイソシアネート／ビスフェノールＡ付加物の３０％酢酸エチル溶液４．５部からなる混合物の１０．３部を用い、且つ、「ＳｃｒａｐｈＡＧ−８」（日本精化（株）製）０．３６部が添加された８％フタル化ゼラチン水溶液７７部と合成例１の本発明に係る化合物（１）１．２部からなる混合物の代わりに、「ＳｃｒａｐｈＡＧ−８」（日本精化（株）製）０．３６部が添加された８％フタル化ゼラチン水溶液の７７部だけを用いたこと以外は、実施例１と同様にして実施例７の感熱記録材料を作製した。ここで、上記ジアゾニウム塩内包カプセルの平均粒径は０．６０μｍであった。
【０１０７】
上記で得られた感熱記録材料（実施例２〜８及び比較例１）についても、実施例１の熱記録及び評価と同様にして、画像部の発色濃度及び非発色部のカブリ濃度を測定した。その結果を下記の表１に示す。
【０１０８】
【表１】

【０１０９】
表１から明らかな様に、マイクロカプセルの形成の際に、本発明の手順に従ってイソシアネート基を総て反応させた本発明に係わる化合物を添加して製造したマイクロカプセル組成物を用いた感熱記録材料（実施例１〜８）は、本発明の化合物を添加しない比較例１のものに較べて、画像部の発色濃度が高く、地肌部のカブリ濃度が低いことが分かった。
【０１１０】
［実施例８］
（Ｖ）感熱記録層（Ｂ）の塗布液の調製
（１）ジアゾニウム塩内包カプセル液の調製
ジアゾニウム塩化合物として３６５ｎｍに分解の最大吸収波長をもつ下記化合物（Ｂ−１）２．８部、硫酸ジブチル２．８部、及び２，２−ジメトキシ−１，２−ジフェニルエタン−１−オン（チバ・ガイギー（株）製の「イルガキュア６５１」）０．５６部を、酢酸エチル１０．０部に溶解した。更に高沸点溶媒としてイソプロピルビフェニルを５．９部及びリン酸トリクレジル２．５部を添加し、加熱して均一に混合した。
【０１１１】
【化５】

【０１１２】
カプセル壁剤として、キシリレンジイソシアネート／トリメチロールプロパン付加物（三井武田ケミカル（株）製の「タケネートＤ１１０Ｎ」、７５％酢酸エチル溶液）７．６部を、上記混合液に更に添加して均一に攪拌した。
別途、１０％ドデシルスルホン酸ナトリウム水溶液２．０部を加えた６％ゼラチン（ニッピゼラチン工業（株）製の商品名「ＭＧＰ−９０６６」）水溶液６４部を用意し、上記ジアゾニウム塩化合物の混合液を添加し、ホモジナイザーにて乳化分散した。
【０１１３】
上記で得られた乳化分散液に水２０部を加え均一化した後、攪拌しながら４０℃で３０分反応させ、この後６０℃に昇温し、３時間かけてカプセル化反応を行なった。この後３５℃に液温を下げ、イオン交換樹樹脂「アンバーライトＩＲＡ６８」（オルガノ社製）４．１部、「アンバーライトＩＲＣ５０」（オルガノ社製）８．２部を加え、更に１時間撹拌した。その後イオン交換樹脂を濾過して、目的とするジアゾニウム塩内包カプセル液を得た。このマイクロカプセルの平均粒径は０．６４μｍであった。
【０１１４】
（２）カプラー乳化分散液の調製
カプラー化合物として、下記に示す化合物（Ｂ−２）３．０部、トリフェニルグアニジン８．０部、１，１−（ｐ−ヒドロキシフェニル）−２−エチルヘキサンを８．０部、４，４′−（ｐ−フェニレンジイソプロピリデン）ジフェノール８．０部、下記に示す化合物（Ｂ−３）２．０部、及び１，１，３−トリス（２−メチル−４−ヒドロキシ−５−ｔ−ブチルフェニル）ブタン２．０部を、酢酸エチル１０．５部に溶解し、更に高沸点溶媒としてりん酸トリクレジル０．４８部、マレイン酸ジエチル０．２４部及び「パイオニンＡ４１Ｃ」（竹本油脂（株）製）１．２７部を添加した後、加熱し均一に混合した。この混合物を、８％ゼラチン（新田ゼラチン（株）製の「＃７５０ゼラチン」）水溶液９３部中に加えて、ホモジナイザーにて乳化分散した。この乳化分散液から残存する酢酸エチルを蒸発させ、目的とするカプラー乳化分散液を得た。
【０１１５】
【化６】

【０１１６】
【化７】

【０１１７】
（３）感熱記録層（Ｂ）用塗布液の調製
前記ジアゾニウム塩内包マイクロカプセル液及び上記カプラー乳化分散液を、内包しているジアゾ化合物／カプラー化合物の質量比が１．０／３．２になる様に混合し、目的とする感熱記録層（Ｂ）用塗布液を得た。
【０１１８】
（ＶＩ）感熱記録層（Ｃ）の塗布液の調製
（１）電子供与性染料前駆体内包カプセル液の調製
電子供与性染料前駆体として３−（ｏ−メチル−ｐ−ジエチルアミノフェニル）−３−（１′−エチル−２−メチルインドール−３−イル）フタリド０．３９部、紫外線吸収剤として２８５ｎｍに最大吸収波長を持つ２−ヒドロキシ−４−メトキシベンゾフェノン０．１９部、及び酸化防止剤として２、５−ｔｅｒｔ−オクチルハイドロキノン０．２９部を、酢酸エチル０．９３部に溶解し、更に高沸点溶媒であるフェネチルクメン０．５４部を添加し、加熱して均一に混合した。カプセル壁剤として、キシリレンジイソシアネート／トリメチロールプロパン付加物（「タケネートＤ１１０Ｎ」）１．０部を、この溶液に更に添加し、均一に撹拌した。
別途、１０％ドデシルスルホン酸ナトリウム水溶液０．０７部が添加された６％ゼラチン（ニッピゼラチン工業（株）製の「ＭＧＰ−９０６６」）水溶液３６．４部を用意し、上記の電子供与性染料前駆体溶液を添加し、ホモジナイザーにて乳化分散した。この様にして得られた乳化分散液を一次乳化分散液と呼ぶ。
【０１１９】
別途３−（ｏ−メチル−ｐ−ジエチルアミノフェニル）−３−（１′−エチル−２−メチルインドール−３−イル）フタリド６．０部、２−ヒドロキシ−４−メトキシベンゾフェノン３．０部、及び２、５−ｔｅｒｔ−オクチルハイドロキノン４．４部を、酢酸エチル１４．４部に溶解し、更に高沸点溶媒としてフェネチルクメン８．４部を添加し、均一に撹拌した溶液に、先に用いた「タケネートＤ１１０Ｎ」を７．８部及びメチレンジイソシアネート（日本ポリウレタン（株）製の「ミリオネートＭＲ２００」）５．９部を添加し、均一に撹拌した。この様にして得られた溶液と、１０％ドデシルスルホン酸ナトリウム水溶液１．２部を上記の一次乳化分散液に添加し、ホモジナイザーにて乳化分散した。この液を二次乳化分散液と呼ぶ。この二次乳化分散液に、水６０．０部及びジエチレントリアミン０．４部を加えて均一化した後、攪拌しながら６５℃に昇温し、３．５時間かけてカプセル化反応を行い、目的とする電子供与性染料前駆体内包マイクロカプセル乳化液を得た。このマイクロカプセルの平均粒子径は１．９μｍであった。
【０１２０】
（２）電子受容性化合物分散液の調製
電子受容性化合物として、「ビスフェノールＰ」３０部をゼラチン（ニッピゼラチン工業（株）製の「ＭＧＰ−９０６６」）２．０％水溶液８２．５部中に添加し、更に２％の２−エチルヘキシルスルホコハク酸ナトリウム水溶液７．５部を加え、得られた混合物をボールミルにて２４時間分散して分散液を作製した。この分散液に１５％ゼラチン（新田ゼラチン（株）製の「＃７５０ゼラチン」）水溶液３６．０部を加え均一に撹拌して、電子受容性化合物分散液を得た。この分散液中の電子受容性化合物の平均粒径は０．５μｍであった。
【０１２１】
（３）感熱記録層（Ｃ）用塗布液の調製
次に、前記の電子供与性染料前駆体内包マイクロカプセル液、上記の電子受容性化合物分散液、１５％のゼラチン（新田ゼラチン（株）製の「＃７５０ゼラチン」）水溶液及びスチルベン系蛍光増白剤（住友化学（株）製の「Ｗｈｉｔｅｘ−ＢＢ」）を、電子供与性染料前駆体／電子受容性化合物の質量比率が１／１４、電子供与性染料前駆体／「＃７５０ゼラチン」の質量比率が１．１／１、且つ電子供与性染料前駆体／蛍光増白剤の質量比率が５．３／１となる様に混合し、目的とする感熱記録層（Ｃ）用塗布液を調製した。
【０１２２】
（ＶＩＩ）中間層（Ｅ）用塗布液の調液
１４％のゼラチン（新田ゼラチン（株）製の「＃７５０ゼラチン」）水溶液に４％ほう酸水溶液８．２部、（４−ノニルフェノキシトリオキシエチレン）ブチルスルホン酸ナトリウムの２％水溶液１．２部、及び下記化合物（Ｅ−１）の２％水溶液７．５部を添加し均一に撹拌して、目的とする中間層（Ｅ）用の塗布液を調製した。
【０１２３】
（Ｅ−１） （ＣＨ_３ＣＨ_２ＳＯ_２ＣＨ_２ＣＯＮＨＣＨ_２）_２−
【０１２４】
（ＶＩＩＩ）多色感熱記録材料の作製
上質紙上にポリエチレンがラミネートされた印画紙用支持体の表面に、ワイヤーバーで上記感熱記録層（Ｃ）用塗布液、上記中間層（Ｅ）用塗布液、上記感熱記録層（Ｂ）用塗布液、上記中間層（Ｅ）用塗布液、実施例１記載の感熱記録層（Ａ）用塗布液及び前記保護層（Ｄ）用塗布液を、この順に塗布し乾燥を行い、目的とする多色感熱記録材料を得た。ここで、固形分としての塗布量は１ｍ^２あたり各々９．０ｇ、３．０ｇ、８．０ｇ、３．０ｇ、４．７ｇ、１．０ｇであった。
【０１２５】
（ＩＸ）熱記録及び評価
京セラ（株）製のサーマルヘッド「ＫＳＴ型」を用いて、下記の様に上記感熱記録材料の熱記録特性を評価した。
（１）単位面積あたりの記録エネルギーが３５ｍＪ／ｍｍ^２となる様にサーマルヘッドに対する印加電力とパルス幅を調整し、上記感熱記録材料に印字して、イエローの画像を記録した。（２）その記録材料を発光中心波長４２０ｎｍ、出力４０Ｗの紫外線ランプで１０秒間照射し、（３）再度単位面積あたりの記録エネルギーが８０ｍＪ／ｍｍ^２となる様にサーマルヘッドに対する印加電力とパルス幅を決め、印字して、マゼンタの画像を記録した。更に（４）発光中心波長３６５ｎｍ、出力４０Ｗの紫外線ランプで１５秒間照射し、（５）再度単位面積あたりの記録エネルギーが１４０ｍＪ／ｍｍ^２となる様にサーマルヘッドに対する印加電力とパルス幅を調整し、印字してシアンの画像を記録した。この結果、イエロー、マゼンタ、シアンの各発色画像の他に、イエローとマゼンタの記録が重複した記録部分は赤色に、マゼンタとシアンが重複した部分は青色に、イエローとシアンが重複した部分は緑色に、そしてイエロー、マゼンタ、シアンの記録が重複した画像部分は黒色に発色した。未記録部は、灰白色であった。イエロー、マゼンタ、シアンの各発色部分の光学反射濃度を「マクベスＲＤ９１８」型濃度計で測定した。シェルフライフ（生保存性）の評価は、得られた多色感熱記録材料を温度４０℃、相対湿度９０％に保った恒温恒湿槽に２４時間放置した後、定着し、地肌部分の光学反射濃度を測定して評価した。
【０１２６】
【表２】

【０１２７】
表２より明らかな様に、多色記録材料においても、マイクロカプセルの形成の際に、本発明の手順に従ってイソシアネート基を総て反応させた本発明に係わる化合物を添加して製造したマイクロカプセル組成物を用いた感熱記録材料は、イエロー、マゼンタ、シアンの画像部の発色濃度が高く、地肌部のカブリ濃度が低いことが分かった。
【０１２８】
【発明の効果】
本発明のマイクロカプセル組成物は、熱に対する感度が高く、カプラー或いは顕色剤との接触により高い発色性示し、また芯材料としてジアゾ化合物を用いた場合は優れた生保存性（長いシェルフライフ）を示す等の優れた特性を有する。従って、上記マイクロカプセルを感熱記録材料の感熱記録層に用いた場合、感熱感度及び発色性が高く、また芯材料としてジアゾ化合物を用いた場合は、生保存性に優れた記録材料を得ることができる。更に、上記マイクロカプセルを感熱記録層に用いると、色再現性及び生保存性に優れた多色感熱記録材料を得ることができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a microcapsule composition that can be used as a heat-sensitive recording material, a heat-sensitive recording material using the microcapsule, and a multicolor heat-sensitive recording material.
[0002]
[Prior art]
Thermal recording materials that are widely used as recording media such as facsimiles and printers mainly use materials obtained by applying a solid dispersion of an electron-donating dye precursor on a support and drying it. The recording method using an electron donating dye precursor has advantages such as easy acquisition of materials and high color density and color development speed, but it tends to develop color due to storage conditions after recording, heating or adhesion of solvent, etc. However, there are problems with the storability and reliability of recorded images, and many improvements have been studied.
[0003]
As one method for improving the storability of the recorded image, an electron donating dye precursor is encapsulated in a microcapsule, and the developer and the electron donating dye precursor are separated from each other in the recording layer. A method for improving the storage stability of an image has been proposed. By this method, high color developability and image stability can be obtained.
[0004]
As other heat-sensitive recording materials, so-called diazo-type heat-sensitive recording materials using a diazonium salt compound have been studied. This diazonium salt compound reacts with a phenol derivative, a compound having an active methylene group or the like (coupler) to form a dye, but also has photosensitivity and loses its activity upon irradiation with light. Utilizing these properties, it has recently been applied to heat-sensitive recording materials. A photo-fixing type heat-sensitive recording material that can react with a diazo compound and a coupler with heat to form an image and then fix it by light irradiation. Has been proposed (see, for example, Non-Patent Document 1).
[0005]
However, since the recording material using such a diazonium salt compound has high chemical activity, the diazonium salt compound and the coupler gradually react even at a low temperature, and the shelf life is too short. There were drawbacks. As one solution to this problem, a method of including a diazonium salt compound in a microcapsule and isolating it from a coupler, water, and a basic compound has been proposed (see, for example, Non-Patent Document 2).
[0006]
In addition, multicolor thermal recording materials have attracted attention as one application field of thermal recording materials. Reproduction of multicolor images by thermal recording has been said to be difficult compared to electrophotographic recording methods and ink jet recording methods, but in this regard, an electron-donating dye precursor and a developer have already been provided on a support. A multicolor thermosensitive recording material can be obtained by laminating two or more thermosensitive coloring layers containing a thermosensitive coloring layer or a diazonium salt compound as a main component and a coupler compound that reacts with the diazonium salt compound to cause color development upon heating. Have been found. In such a multicolor thermosensitive recording material, in order to obtain excellent color reproducibility, it is necessary to highly control the thermochromic characteristics of the microcapsules.
[0007]
Conventionally, in order to include an electron-donating dye precursor and a diazonium salt compound in a microcapsule, these compounds are generally dissolved in an organic solvent (oil phase), and this is dissolved in an aqueous solution (water phase) containing a water-soluble polymer. ) And then emulsified and dispersed. At this time, by adding a monomer or prepolymer as a wall agent to either the organic solvent (oil phase) side or the aqueous phase side, a polymer wall is formed at the interface between the organic solvent phase and the aqueous phase. It can be microencapsulated (see, for example, Non-Patent Documents 3 and 4). As the microcapsule wall formed here, various materials such as gelatin, alginate, celluloses, polyurea, polyurethane, melamine resin, and nylon can be used. Polyurea and urethane resin have a glass transition temperature of about room temperature to about 200 ° C., so that the capsule wall exhibits thermal responsiveness and is suitable for designing a heat-sensitive recording material.
[0008]
As a method for forming the microcapsule, in the case of a microcapsule having a polyurethane or polyurea wall, first, a coloring component such as a diazonium salt or an electron-donating dye precursor is dissolved in an organic solvent, and a polyvalent isocyanate compound is added thereto. The organic phase solution is dispersed and emulsified in an aqueous phase containing a water-soluble polymer. Thereafter, a catalyst for promoting the polymerization reaction is added to the aqueous phase side, or the temperature of the dispersion emulsion is increased to polymerize the polyvalent isocyanate compound with a compound having active hydrogen such as water to form a microcapsule wall. Methods are conventionally known.
[0009]
As the polyurea compound which is a material for forming the above polyurea or polyurethane wall, for example, an adduct of 2,4-tolylene diisocyanate and trimethylolpropane and an adduct of xylylene diisocyanate and trimethylolpropane are mainly used. (For example, refer to Patent Documents 1 and 2.)
However, even the polyurea or polyurethane capsule wall using the polyisocyanate compound as described above has not been sufficiently improved with respect to the short shelf life when the diazonium salt compound is used. That is, a thermal recording material having a shelf life that is not sufficiently long develops a background color called “fogging” when it is exposed to high-temperature and high-humidity conditions, for example, before it is manufactured and used. Reduce the visibility of the image. In order to solve such a problem, there is a means for increasing the wall thickness of the microcapsule, for example. However, when such a method is used, the color development sensitivity during thermal printing is reduced. Therefore, it was very difficult to further improve the shelf life while maintaining the color developability.
[0010]
In view of such problems, at least one compound (A) having one active hydrogen in the molecule and an average molecular weight of 500 to 20,000, and (B) two or more isocyanate groups in the molecule There is disclosed a thermoresponsive microcapsule comprising a polymer obtained by polymerization of an isocyanate compound containing an adduct with a polyfunctional isocyanate having a microcapsule having both fog and sensitivity ( For example, see Patent Document 3.) However, the free isocyanate group remains in the reaction product of (A) and (B) here, and in the microcapsule formation reaction, due to the reactivity of the isocyanate group with water, it is preliminarily added to the oil phase. Although it is necessary to add, the compound (A) often has a higher solubility in the water phase than the oil phase, which may cause a problem in terms of production suitability.
[0011]
There is also disclosed a microcapsule having a polyurea shell, wherein the isocyanate used for the production is a reaction product of at least a difunctional isocyanate and a monovalent poly (ethylene oxide) alcohol ( For example, see Patent Document 4), the isocyanate group remains in the reaction product, and in the microcapsule formation reaction, it is added to the oil phase in advance because of the reactivity of the isocyanate group with water. Although it is necessary, monovalent poly (ethylene oxide) alcohol is often more soluble in the aqueous phase than the oil phase, which may be problematic in terms of production suitability.
[0012]
[Patent Document 1]
Japanese Unexamined Patent Publication No. Sho 62-212190
[Patent Document 2]
JP-A-4-26189
[Patent Document 3]
Japanese Patent Laid-Open No. 10-114153
[Patent Document 4]
Japanese Patent No. 3266330
[Non-Patent Document 1]
Koji Sato et al., “Journal of the Institute of Image Electronics Engineers”, Vol. 11, No. 4, 290-296, 1982, etc.
[Non-Patent Document 2]
Usami Tomomasa et al., “The Journal of Electrophotographic Society”, Vol. 26, No. 2, pp. 115-125, 1987
[Non-Patent Document 3]
Asahi Kondo "Microcapsule", Nikkan Kogyo Shimbun, 1970
[Non-Patent Document 4]
Kondo et al. “Microcapsules”, Sankyo Publishing, 1977
[0013]
[Problems to be solved by the invention]
In view of the above circumstances, the present inventors have reached the present invention as a result of intensive studies from the viewpoint of further improving shelf life while maintaining high color developability with respect to the formation of microcapsules in a heat-sensitive recording material. . That is,
An object of the present invention is to provide a microcapsule composition that can be suitably used for a heat-sensitive recording material and a multicolor heat-sensitive recording material, exhibits high color developability upon contact with a coupler or a developer, and is excellent in raw storability. It is to provide.
Another object of the present invention is to provide a heat-sensitive recording material having high color developability and excellent raw shelf life (long shelf life).
Another object of the present invention is to provide a multicolor thermosensitive recording material excellent in color reproducibility and raw storage.
[0014]
[Means for Solving the Problems]
The above problems can be solved by the following microcapsule composition and heat-sensitive recording material of the present invention. That is,
<1> In producing a microcapsule having a polyurethane / urea wall by polymerizing an isocyanate compound with a compound having active hydrogen, (1) a polyfunctional isocyanate having two or more isocyanate groups in the molecule and (2) a molecule After reacting with at least one polyether derivative having one active hydrogen and having an average molecular weight of 500 to 20000, the reaction product is treated with (3) at least one of alcohols to obtain isocyanate. A microcapsule composition, wherein the polyurethane / urea wall is formed by adding at least one compound obtained by reacting all groups.
<2> In producing a microcapsule having a polyurethane / urea wall by polymerizing an isocyanate compound with a compound having active hydrogen, (1) a polyfunctional isocyanate having two or more isocyanate groups in the molecule and (2) a molecule And reacting with at least one polyether derivative having one active hydrogen and having an average molecular weight of 500 to 20,000, and (3) at least one primary or secondary amine having at least one hydroxyl group. After reacting the seeds, the reaction product was treated with at least one of (4) alcohols to add at least one compound that had all isocyanate groups reacted to form the polyurethane / urea wall. A microcapsule composition characterized by the above.
<3> In producing a microcapsule having a polyurethane / urea wall by polymerizing an isocyanate compound with a compound having active hydrogen, (1) a polyfunctional isocyanate having two or more isocyanate groups in the molecule and (2) a molecule At least one polyether derivative having one active hydrogen and having an average molecular weight of 300 to 5,000 is reacted in a molar ratio in which the number of moles of the latter active hydrogen is not less than the number of moles of the former isocyanate group A microcapsule composition, wherein the polyurethane / urea wall is formed by adding at least one compound obtained by reacting all isocyanate groups.
<4> A thermosensitive material comprising a support and (1) a microcapsule and a coupler encapsulating a diazo compound provided thereon, or (2) a microcapsule and a developer encapsulating an electron-donating dye precursor. A thermosensitive recording material comprising a recording layer, wherein the microcapsule composition containing the microcapsule is the microcapsule composition according to any one of <1> to <3>. .
<5> Support, and cyan, magenta, and yellow thermosensitive recording layers provided thereon, each thermosensitive recording layer (1) microcapsules and couplers containing diazo compounds, or (2) electron donation A multicolor thermosensitive recording material comprising a microcapsule encapsulating a functional dye precursor and a developer, wherein at least one of the microcapsule compositions comprising the microcapsule comprises the above <1> to <3 > A multicolor thermosensitive recording material, wherein the microcapsule is any one of the above.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
In producing a microcapsule having a polyurethane / urea wall, the microcapsule composition of the first aspect of the present invention comprises (1) a polyfunctional isocyanate having two or more isocyanate groups in the molecule and (2) one in the molecule. After reacting with at least one polyether derivative having a number of active hydrogens and an average molecular weight of 500 to 20000, the reaction product is treated with (3) at least one of alcohols to remove all of the isocyanate groups. The polyurethane / urea wall is formed by adding at least one of the reacted compounds.
In producing a microcapsule having a polyurethane / urea wall, the microcapsule composition of the second present invention comprises (1) a polyfunctional isocyanate having two or more isocyanate groups in the molecule and (2) one in the molecule. Reaction with at least one polyether derivative having one active hydrogen and an average molecular weight of 500 to 20,000, and (3) reacting with at least one primary or secondary amine having at least one hydroxyl group Then, the polyurethane / urea wall is formed by adding at least one compound obtained by treating all of the isocyanate groups by treating the reactant with at least one of (4) alcohol. And
In producing a microcapsule having a polyurethane / urea wall, the microcapsule composition of the third aspect of the present invention comprises (1) a polyfunctional isocyanate having two or more isocyanate groups in the molecule and (2) one in the molecule. By reacting at least one polyether derivative having one active hydrogen and an average molecular weight of 300 to 5,000 in a molar ratio in which the number of moles of the latter active hydrogen is not less than the number of moles of the former isocyanate group The polyurethane / urea wall is formed by adding at least one compound obtained by reacting all the groups.
[0016]
In the microcapsule composition of the present invention, when producing a microcapsule having a polyurethane / urea wall, at least one compound having all isocyanate groups reacted as described above is added. Other components required for the production of the above-mentioned isocyanate group, such as substances encapsulated in the capsule, hydrophobic organic solvent, low boiling point organic solvent, water-soluble medium, capsule wall agent, active hydrogen compound, various additives, etc. All of the reacted compounds can be appropriately added before or after the addition of the reacted compounds as needed or as required.
The microcapsule composition of the present invention is a composition containing a microcapsule having a polyurethane / urea wall formed according to the above-described configuration and procedure. Even if it is a particle size, it is stable over time, has a long shelf life, has high heat sensitivity, and the microcapsule encapsulating the color developing component exhibits high color developability upon contact with a coupler or developer, In addition, it has excellent properties for shelf life.
Hereinafter, main components and manufacturing procedures of the present invention will be described in detail.
[0017]
(Polyfunctional isocyanate compound)
First, the polyfunctional isocyanate compound having two or more isocyanate groups in the molecule used in the present invention will be described.
Examples of such a polyfunctional isocyanate compound include compounds having two isocyanate groups in the molecule, such as m-phenylene diisocyanate, p-phenylene diisocyanate, 2,6-tolylene diisocyanate, and 2,4-tolylene diisocyanate. , Naphthalene-1,4-diisocyanate, diphenylmethane-4,4′-diisocyanate, 3,3′-dimethoxy-biphenyl diisocyanate, 3,3′-dimethyldiphenylmethane-4,4′-diisocyanate, xylylene-1,4-diisocyanate , Xylylene-1,3-diisocyanate, 4-chloroxylylene-1,3-diisocyanate, 2-methylxylylene-1,3-diisocyanate, 4,4′-diphenylpropane diisocyanate, 4,4′-diph Nylhexafluoropropane diisocyanate, trimethylene diisocyanate, hexamethylene diisocyanate, propylene-1,2-diisocyanate, butylene-1,2-diisocyanate, cyclohexylene-1,2-diisocyanate, cyclohexylene-1,3-diisocyanate, cyclohexylene -1,4-diisocyanate, dicyclohexylmethane-4,4′-diisocyanate, 1,4-bis (isocyanatemethyl) cyclohexane and 1,3-bis (isocyanatemethyl) cyclohexane, isophorone diisocyanate, lysine diisocyanate and the like.
Furthermore, addition reaction products of these bifunctional isocyanate compounds with bifunctional alcohols such as ethylene glycols and bisphenols, and phenols can also be used.
[0018]
Furthermore, trifunctional or higher functional isocyanate compounds can also be used. As an example of such a polyfunctional isocyanate, the above bifunctional isocyanate compound is used as a main raw material, and these trimers (burette or isocyanurate), an adduct of a polyol such as trimethylolpropane and a bifunctional isocyanate compound are used. A polyfunctional isocyanate, a formalin condensate of benzene isocyanate, a polymer of an isocyanate compound having a polymerizable group such as methacryloyloxyethyl isocyanate, lysine triisocyanate, and the like can also be used.
In particular, xylene diisocyanate and hydrogenated products thereof, hexamethylene diisocyanate, tolylene diisocyanate and hydrogenated products thereof are used as main raw materials, and adducts with trimethylolpropane in addition to these trimers (burette or isosinurate). Also preferred are functional isocyanates. These compounds are described in detail in “Polyurethane Resin Handbook” edited by Keiji Iwata (published by Nikkan Kogyo Shimbun, 1987).
[0019]
Among these, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, xylylene-1,4-diisocyanate, xylylene-1,3-diisocyanate, trimethylolpropane and xylylene-1,4-diisocyanate or xylylene- Adducts with 1,3-diisocyanate are preferred, in particular xylylene-1,4-diisocyanate and xylylene-1,3-diisocyanate, trimethylolpropane and xylylene-1,4-diisocyanate or xylylene-1,3-diisocyanate. Adducts are preferred.
As mentioned above, these polyfunctional isocyanate compounds may be used individually by 1 type, or 2 or more types may be mixed and used for them.
[0020]
(Polyether derivative)
Next, a polyether derivative having one active hydrogen in the molecule and having an average molecular weight of 500 to 20000, or 300 to 5000 will be described.
Examples of the functional group having active hydrogen include a hydroxyl group, an amino group, and a carboxyl group, and among these, a hydroxyl group and an amino group are particularly preferable.
Such a polyether derivative having active hydrogen is not particularly limited, and examples thereof include derivatives of polyethers having active hydrogen at one end. When the molecular weight of the polyether derivative is smaller than 300, fog is increased due to the introduction of these compounds. On the other hand, when the molecular weight of the polyether derivative is larger than 20000, it becomes difficult to synthesize these compounds, and since the viscosity becomes high, liquid preparation for capsule production and capsule formation become difficult.
[0021]
Specific examples of the polyether derivative include various derivatives such as polyethylene oxide, polypropylene oxide, polytetramethylene oxide, polystyrene oxide, polycyclohexylene oxide, and poly (ethylene thioglycol).
[0022]
In the present invention, the polyether derivative may have one repeating unit or a copolymer composed of two or more repeating units. Further, these polyether derivatives may have a melting point, and in such a case, a compound having a melting point of 40 to 180 ° C. is particularly preferable. Examples of the polyether derivative having such a melting point include derivatives of polyethylene oxide, polystyrene oxide, polycaprolactone, and the like. Since the melting point varies depending on the molecular weight, it cannot be said unconditionally. For example, a polyethylene oxide derivative has such a melting point when the molecular weight is about 1000 or more.
[0023]
In the present invention, from the viewpoints of stability of the microcapsule composition and control of the capsule particle size, etc., as a polyether derivative having one active hydrogen in the molecule and an average molecular weight of 500 to 20000 or 300 to 5000, A polyether derivative represented by the following general formula (I) is particularly preferred.
[Chemical 1]

[0024]
In general formula (I), R¹Represents an alkyl group, an aryl group, or an acyl group.
R¹As the alkyl group represented by formula (1), the alkyl group may have a substituent or may have a branch, and is preferably an alkyl group having 1 to 30 carbon atoms in total, particularly 1 to 20 carbon atoms in total. Are preferred. In the case of having a substituent, the above substituent does not include a substituent having active hydrogen, and is preferably an aryl group, an alkenyl group, or an alkoxy group. Specific examples of such an alkyl group include a methyl group, an ethyl group, a butyl group, an isopropyl group, a behenyl group, a benzyl group, an allyl group, an oleyl group, and a methoxyethyl group.
[0025]
R¹The aryl group represented by the formula (1) may have a substituent, is preferably an aryl group having 6 to 30 carbon atoms, and particularly preferably an aryl group having 6 to 20 carbon atoms. In the case of having a substituent, the above substituent does not include a substituent having active hydrogen, and is preferably a halogen atom, an alkyl group, an alkenyl group, an alkynyl group or an alkoxy group, and particularly preferably an alkyl group or an alkoxy group. Specific examples of such an aryl group include phenyl group, nonylphenyl group, octylphenyl group, fluorophenyl group, styrylphenyl group, phenylethenylphenyl group, methoxyphenyl and the like.
[0026]
R¹The acyl group represented by may be an aliphatic or aromatic acyl group, may have a substituent, may have a branch, and is an acyl group having 2 to 30 carbon atoms in total. In particular, an acyl group having 2 to 20 carbon atoms is preferred. In the case of having a substituent, the substituent does not include a substituent having active hydrogen, and is preferably an alkyl group, an aryl group, an alkenyl group, or an alkoxy group. Specific examples of such an acyl group include an acetyl group, a benzoyl group, a (meth) acryloyl group, an oleoyl group, a lauroyl group, a stearoyl group, and a methoxybenzoyl group. As described above, among such groups represented by R, an alkyl group and an acyl group are preferable, and an alkyl group is particularly preferable.
[0027]
In general formula (I), L represents alkylene.
The alkylene represented by L may have a substituent or may have a branch, and is preferably an alkylene having 2 to 20 carbon atoms, particularly 2 to 10 carbon atoms. Alkylene is preferred. In the case of having a substituent, the above substituent does not include a substituent having active hydrogen, and is preferably an aryl group, an alkenyl group, an alkoxy group, or an acyl group, and particularly preferably an aryl group. Examples of such alkylene include ethylene, propylene, tetramethylene, phenylethylene, cyclohexylene, vinylethylene, and phenoxymethylethylene.
[0028]
Repeating unit of general formula (I)-(LO)_n-May represent an independent group in n repetitions, but it is particularly preferable to represent the same group. Polyethers having such repeating units include polyethylene oxide, polypropylene oxide, polytetramethylene oxide, polystyrene oxide, polycyclohexylene oxide, polyethylene oxide-polypropylene oxide-block copolymer, polyethylene oxide-polypropylene oxide random copolymer. Examples include coalescence.
n is the average number of added moles of the polyether group and represents a number of 11 to 440, preferably a number of 15 to 300, and particularly preferably a number of 15 to 200.
[0029]
In general formula (I), R²Is a hydrogen atom or-(X)_m-AB is represented.
X is —CO— or —SO.₂-Represents -CO-.
A represents alkylene or arylene.
The arylene represented by A may have a substituent or may have a branch, and is preferably an arylene having a total carbon number of 6 to 30, particularly a total carbon number of 6 to 20. Arylene is preferred. In the case of substitution, the above substituent does not include a substituent having active hydrogen, and is preferably a halogen atom, an alkyl group, an alkoxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, or a cyano group, particularly a halogen atom or an alkyl group. Group and an alkoxy group are preferable. Specific examples of such arylene include phenylene, biphenylene, naphthalene, methylphenylene, methoxyphenylene, and the like.
[0030]
The alkylene represented by A may have a substituent or may have a branch, and is preferably an alkylene having 1 to 30 carbon atoms, particularly 1 to 20 carbon atoms in total. Alkylene is preferred. In the case of substitution, the above substituent does not include a substituent having active hydrogen, and is preferably an aryl group, an alkenyl group, an alkoxy group, or an alkoxycarbonyl group, and particularly preferably an aryl group. Specific examples of such alkylene include methylene, ethylene, propylene, tetramethylene, phenylmethylene and the like.
[0031]
B represents a hydroxyl group or an amino group, and an amino group is preferred.
m represents 0 or 1, and 1 is preferable.
-(X) like this_mSpecific examples of the group represented by -A-B include aminoethyl group, aminopropyl group, 4-aminobenzoyl group, 3-aminobenzoyl group, 4-aminobenzenesulfonyl group, aminoacetyl group, aminoethylsulfonyl group. , Hydroxyacetyl group, 4-hydroxybenzoyl group and the like.
R²Of these groups, a hydrogen atom is particularly preferable.
[0032]
(Treatment alcohols)
In the present invention, the alcohol used in the treatment for reacting all the isocyanate groups may be selected from the group of aliphatic alcohol, alicyclic alcohol, aromatic alcohol, heterocyclic alcohol and the like. it can. Among these, alcohols having 1 to 8 carbon atoms such as methanol, ethanol, propyl alcohol, isopropyl alcohol, butyl alcohol, isobutyl alcohol, cyclopentanol, benzyl alcohol, furfuryl alcohol and the like can be mentioned as preferred specific examples. Of these, low boiling alcohols that can be easily distilled off, such as methanol, ethanol, propanol and the like, are particularly preferable. Two or more kinds of the alcohols for the treatment may be used in combination.
[0033]
(Amines having a hydroxyl group)
The primary or secondary amine having at least one hydroxyl group used in the present invention is selected from the group of aliphatic amine, alicyclic amine, aromatic amine, heterocyclic amine and the like. Among these, amines having 2 to 30 carbon atoms are preferably used.
In the above amine compound, the hydroxyl group is preferably bonded to the amino group via an alkylene having 2 to 20 carbon atoms or an arylene having 6 to 20 carbon atoms, particularly 2 to 2 carbon atoms. Bonding is preferably via 18 alkylenes. The above alkylene and arylene may have a substituent or may have a branch. Examples of the substituent having such a hydroxyl group include a hydroxyethyl group, a hydroxypropyl group, a hydroxydodecyl group, and a hydroxyphenyl group.
In the case of a secondary amine, the two substituents bonded to the nitrogen atom of the amine may be the same or different. If they are different, in addition to the alkylene or arylene to which the hydroxyl group is bonded, carbon An alkyl group having 1 to 20 atoms or an aryl group having 6 to 20 carbon atoms is preferable. The alkyl group and aryl group may have a substituent or may have a branch.
Specific examples of such primary or secondary amines having at least one hydroxyl group include ethanolamine, hydroxypropylamine, hydroxydecylamine, diethanolamine, p-aminophenol, N-hydroxyethyl-N-dodecylamine, N-methyl-p-aminophenol and the like can be mentioned.
[0034]
(Method for producing the compound of the present invention)
In the first invention, (1) a polyfunctional isocyanate having two or more isocyanate groups in the molecule and (2) a polyether derivative having one active hydrogen in the molecule and an average molecular weight of 500 to 20000 A method for producing a compound in which all of the isocyanate groups are reacted by reacting at least one of the above and then reacting the reactant with at least one of (3) alcohol will be specifically described below.
[0035]
The compound in which all of the isocyanate groups of the present invention have been reacted is obtained by reacting the above-described polyfunctional isocyanate compound with the above-mentioned polyether derivative in an amount equal to or less than the number of moles of the isocyanate group of the compound. The remaining isocyanate groups are changed to urethane bonds by treating with alcohol, and all isocyanate groups are lost.
Under the present circumstances, 0.01-1.0 mol is preferable with respect to 1.0 mol of isocyanate groups of a polyfunctional isocyanate compound, and, as for the usage-amount of a polyether derivative, 0.03-1.0 mol is especially preferable.
[0036]
A solvent may be used in the above reaction, and the solvent is preferably a low boiling point solvent having no active hydrogen such as toluene, acetonitrile, tetrahydrofuran, methylene chloride, ethyl acetate, and particularly preferably toluene, acetonitrile, and ethyl acetate. When the solvent is used, the amount used is preferably 0.1 ml to 100 ml, more preferably 0.5 ml to 20 ml, with respect to 1 g of the polyfunctional isocyanate compound.
As temperature of this reaction, 0 to 100 degreeC or the reflux temperature of the solvent to be used is preferable, and 30 to 70 degreeC is especially preferable.
It is also preferable to use the polyether derivative after dehydration before the reaction. As a dehydration method, a method of stirring for several hours while heating at 60 ° C. to 100 ° C. with a vacuum pump, or azeotropic dehydration with a solvent such as ethyl acetate. Methods and the like.
The time required for this reaction is preferably 1 hour to 8 hours, particularly preferably 2 hours to 6 hours.
In this reaction, a catalyst such as stannous octylate or dibutyltin diacetate may be added.
[0037]
The amount of alcohol used after the reaction between the polyfunctional isocyanate and the polyether derivative is preferably an amount sufficient to convert the remaining isocyanate group of the polyfunctional isocyanate into a urethane bond. 1.0 ml-100 ml are preferable with respect to 1 g of isocyanate, and 2.0 ml-50 ml are especially preferable.
The temperature required for the treatment is preferably 0 ° C. to 100 ° C. or the reflux temperature of the solvent used, and particularly preferably 20 ° C. to 70 ° C.
The time required for the reaction is preferably from 30 minutes to 30 hours, particularly preferably from 1 hour to 8 hours.
In addition, a catalyst such as stannous octylate or dibutyltin diacetate may be added to the reaction.
[0038]
Next, in the second invention, (1) a polyfunctional isocyanate having two or more isocyanate groups in the molecule and (2) one active hydrogen in the molecule and an average molecular weight of 500 to 20000 After reacting with at least one ether derivative, and (3) reacting at least one primary or secondary amine having at least one hydroxyl group, the reaction product is converted into (4) at least one alcohol. The manufacturing method of the compound which made all the isocyanate groups react by processing by is demonstrated.
[0039]
The compound in which all of the isocyanate groups of the present invention have reacted is reacted with a polyether derivative having a number of moles smaller than the number of moles of the isocyanate group of the polyfunctional isocyanate compound, and then the number of moles of the remaining isocyanate groups. All isocyanate groups disappeared by reacting with primary or secondary amines of the same or less mole number with primary and secondary amines, and then changing the remaining isocyanate groups to urethane bonds by treating with alcohol. It has been made.
In this case, the amount of the polyether derivative used is preferably from 0.01 to 0.99 mol, particularly preferably from 0.03 to 0.5 mol, per 1.0 mol of the isocyanate group of the polyfunctional isocyanate compound.
Other polyfunctional isocyanates and polyether derivatives can be reacted in the same manner as described above.
[0040]
Furthermore, in the third aspect of the present invention, (1) a polyfunctional isocyanate having two or more isocyanate groups in the molecule and (2) a polyether having one active hydrogen in the molecule and an average molecular weight of 300 to 5,000 A method for producing a compound in which all of the isocyanate groups are reacted by reacting at least one of the derivatives at a molar ratio in which the number of moles of the latter active hydrogen is not less than the number of moles of the former isocyanate group will be described.
[0041]
The compounds obtained by reacting all of the above isocyanate groups of the present invention are obtained by reacting all the isocyanate groups by reacting them in a molar ratio in which the number of active hydrogens in the polyether derivative is not less than the number of isocyanate groups in the polyfunctional isocyanate compound. The group is lost.
Under the present circumstances, 1.0-10 mol is preferable with respect to 1.0 mol of isocyanate groups of a polyfunctional isocyanate compound, and, as for the usage-amount of a polyether derivative, 1.0-3.0 mol is especially preferable.
Other polyfunctional isocyanates and polyether derivatives can be reacted in the same manner as described above.
[0042]
Subsequent to the reaction of the first and second inventions, the reaction with a primary or secondary amine having a hydroxyl group may be performed by adding a primary or secondary amine to the above reaction solution. The isocyanate compound and the polyether derivative may be reacted separately, and the reaction solution may be added to the primary or secondary amine.
The amount of the primary or secondary amine used in the reaction with the primary or secondary amine is 0.1 to 1.0 mol with respect to 1.0 mol of the isocyanate group remaining after the reaction with the polyether derivative. Is preferable, and 0.5 to 1.0 mol is particularly preferable.
[0043]
A solvent may be used in the above reaction, and the solvent is preferably a low-boiling solvent having no active hydrogen such as toluene, acetonitrile, tetrahydrofuran, methylene chloride, ethyl acetate, and particularly preferably toluene, acetonitrile, and ethyl acetate. When the solvent is used, the amount used is preferably 1 ml to 200 ml, more preferably 10 ml to 100 ml, with respect to 1 g of the primary or secondary amine.
The reaction temperature is preferably 0 ° C. to 100 ° C. or the reflux temperature of the solvent used, and particularly preferably 0 ° C. to 50 ° C.
The time required for the reaction is preferably 30 minutes to 8 hours, particularly preferably 30 minutes to 3 hours.
Subsequent treatment with alcohol is carried out in the same manner as described above.
[0044]
(Microcapsule composition)
Next, the microcapsule composition of the present invention will be described.
Microcapsules are formed by polymerization of a polyfunctional isocyanate compound, for example, reaction with a compound having two or more active hydrogens in the molecule. Examples of such active hydrogen-containing compounds include water, polyhydric alcohol compounds such as ethylene glycol and glycerin, polyhydric amine compounds such as ethylenediamine and diethylenetriamine, and mixtures thereof. . Among these, it is particularly preferable to perform polymerization using water. This results in the formation of polyurethane / polyurea walls.
[0045]
When the microcapsule composition of the present invention is produced, the microcapsule composition has (1) a polyfunctional isocyanate having two or more isocyanate groups in the molecule, and (2) one active hydrogen in the molecule. And after reacting at least one polyether derivative having an average molecular weight of 500 to 20,000, (3) a compound in which all isocyanate groups are reacted by treatment with at least one kind of alcohol having 1 to 8 carbon atoms, Or (1) a polyfunctional isocyanate having two or more isocyanate groups in the molecule, and (2) at least one polyether derivative having one active hydrogen in the molecule and an average molecular weight of 500 to 20,000. And (3) reacting at least one primary or secondary amine having 2 to 30 carbon atoms having at least one hydroxyl group. Then, (4) a compound obtained by reacting all isocyanate groups by treatment with at least one kind of alcohol having 1 to 8 carbon atoms, or a compound of the third invention is added to the oil phase and / or the aqueous phase. It is what.
[0046]
The compound in which all the isocyanate groups are reacted may be added to either one or both of the oil phase and the aqueous phase at the time of encapsulation, but it should be added to those in which these compounds are dissolved. preferable. These compounds may be used alone or in combination of two or more.
The addition amount of the compound obtained by reacting all the isocyanate groups is preferably 0.5% to 50%, particularly preferably 1.0% to 30%, based on the total mass of the oil phase or the aqueous phase.
[0047]
In the present invention, as other components necessary for the production of the microcapsules, that is, substances encapsulated in the capsule, hydrophobic solvent, aqueous medium, etc., those corresponding to the current state of the art can be used.
Examples of substances that can be encapsulated in the microcapsules of the present invention include, for example, perfume oils, plant protection agents, reactive adhesives, pharmaceuticals, etc., such as diazonium salt compounds or electron donating dye precursors. It is suitable for producing a microcapsule that encapsulates a coloring component. When the diazonium salt compound or the electron donating dye precursor is encapsulated, an embodiment in which the diazonium salt compound or the electron donating dye precursor is dissolved in a high boiling point solvent and encapsulated in a microcapsule is preferable.
[0048]
The heat-sensitive recording material of the present invention has a basic structure in which a heat-sensitive recording layer containing the microcapsules is provided on a support. Furthermore, the multicolor thermosensitive recording material of the present invention is provided with a thermosensitive recording layer containing cyan, magenta and yellow microcapsules on a transparent support, and at least one of these has a basic structure comprising the microcapsules. Have. Here, if desired, a black thermosensitive recording layer may be provided on the back surface of the transparent support.
[0049]
(Coloring component and developer)
Examples of the electron donating dye precursor encapsulated in the microcapsule of the present invention include triarylmethane compounds, diphenylmethane compounds, thiazine compounds, xanthene compounds, spiropyran compounds, and the like. Compounds and xanthene compounds are useful because of their high color density.
[0050]
Specific examples thereof include 3,3-bis (p-dimethylaminophenyl) -6dimethylaminophthalide (that is, crystal violet lactone), 3,3-bis (p-dimethylamino) phthalide, 3- (p- Dimethylaminophenyl) -3- (1,3-dimethylindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-methylindol-3-yl) phthalide, 3- (o- Methyl-p-dimethylaminophenyl) -3- (2-methylindol-3-yl) phthalide, 3- (o-methyl-p-diethylaminophenyl) -3- (1'-ethyl-2-methylindole-3) -Yl) phthalide, 4,4'-bis (dimethylamino) benzhydrin benzyl ether, N-halophenylleucooramine, N-2,4 - trichlorophenyl leuco auramine;
[0051]
Rhodamine-B-anilinolactam, rhodamine (p-nitroanilino) lactam, rhodamine-B- (p-chloroanilino) lactam, 2-benzylamino-6-diethylaminofluorane, 2-anilino-6-diethylaminofluorane, 2- Anilino-3-methyl-6-diethylaminofluorane, 2-anilino-3-methyl-6-cyclohexylmethylaminofluorane, 2-anilino-3-methyl-6-isoamylethylaminofluorane, 2- (o-chloroanilino) ) -6-diethylaminofluorane, 2-octylamino-6-diethylaminofluorane, 2-ethoxyethylamino-3-chloro-2-diethylaminofluorane, 2-anilino-3-chloro-6-diethylaminofluorane, benzoyl Leucomethylene bull P-nitrobenzyl leucomethylene blue, 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3,3'-dichloro-spiro-dinaphthopyran, 3-benzylpyrodinaftpyran, 3-propyl-spiro-dibenzo Examples include pyran.
[0052]
Examples of the electron-accepting compound used in combination with the electron-donating dye precursor (also referred to as a color developer and usually not encapsulated in microcapsules) include phenol derivatives, salicylic acid derivatives, hydroxybenzoic acid esters, and the like. It is done. Among these, bisphenols and hydroxybenzoic acid esters are particularly preferable. For example, 2,2-bis (p-hydroxyphenyl) propane (bisphenol A), 2,2-bis (p-hydroxyphenyl) pentane, 2,2-bis (p-hydroxyphenyl) ethane, 2,2-bis (P-hydroxyphenyl) butane, 2,2-bis (4'-hydroxy-3 ', 5'-dichlorophenyl) propane, 1,1- (p-hydroxyphenyl) cyclohexane, 1,1- (p-hydroxyphenyl) ) Propane, 1,1- (p-hydroxyphenyl) pentane, 1,1- (p-hydroxyphenyl) -2-ethylhexane, 3,5-di (α-methylbenzyl) salicylic acid and its polyvalent metal salt, 3,5-di (tert-butyl) salicylic acid and its polyvalent metal salt, 3-α, α-dimethylbenzylsalicylic acid and its polyvalent metal salt, p-hy Proxy-butylbenzoic acid, p- hydroxybenzoic acid benzyl, p- hydroxybenzoate, 2-ethylhexyl can be mentioned p- phenylphenol and p- cumylphenol and the like. These electron-accepting compounds can be used alone or in combination of two or more in any ratio.
[0053]
It is preferable to add a sensitizer to the heat-sensitive recording layer of the present invention in order to accelerate the reaction. As such a sensitizer, a low-melting-point organic compound having moderately aromatic groups and polar groups in the molecule is preferable. Specific examples thereof include p-benzyloxybenzoic acid benzyl, α-naphthylbenzyl ether, β-naphthylbenzyl ether, β-naphthoic acid phenyl ester, α-hydroxy-β-naphthoic acid phenyl ester, β-naphthol- (p -Chlorobenzyl) ether, 1,4-butanediol phenyl ether, 1,4-butanediol-p-methylphenyl ether, 1,4-butanediol-p-ethylphenyl ether, 1,4-butanediol-m- Methyl phenyl ether, 1-phenoxy-2- (p-tolyloxy) ethane, 1-phenoxy-2- (p-ethylphenoxy) ethane, 1-phenoxy-2- (p-chlorophenoxy) ethane, p-benzylbiphenyl, p-toluenesulfonamide, 4- (2-ethylhexylo) ) Phenyl sulfonamide, include 4-n-pentyloxyphenyl sulfonamide. In the present invention, these sensitizers can be used in combination of two or more at any ratio.
[0054]
As the diazonium salt compound encapsulated in the microcapsule, a known compound can be used. The diazonium salt compound includes the following general formula:
Ar-N₂ ⁺・ X⁻
The compound represented by these. Here, Ar in the above formula represents an aryl group, and X⁻  Represents an acid anion.
[0055]
The diazonium salt compound reacts with a phenol compound or a compound having active methylene to form a so-called dye, and further decomposes by irradiation with light (generally ultraviolet rays) and denitrifies to lose its reaction activity. It is. Specific examples of such a diazonium salt include 2,5-dibutoxy-4-morpholinobenzenediazonium, 2,5-octoxy-4-morpholinobenzenediazonium, 2,5-dibutoxy-4- (N- (2-ethyl). Hexanoyl) piperazino) benzenediazonium, 2,5-diethoxy-4- (N- (2- (2,4-di-tert-amylphenoxy) butyryl) piperazino) benzenediazonium, 2,5-dibutoxy-4-tri Ruthiobenzenediazonium, 2,5-dibutoxy-4-chlorobenzenethiodiazonium, 2,5-diheptyloxy-4-chlorobenzenethiodiazonium, 3- (2-octyloxyethoxy) -4-morpholinobenzenediazonium, 4-N, N-dihexylamino-2-hexyloxybenzene Azonium, 4- (N-hexyl-N- (1-methyl-2- (p-methoxyphenoxy) ethyl) amino) -2-hexyloxybenzenediazonium and 4-N-hexyl-N-tolylamino-2-hexyloxy Examples thereof include benzenediazonium salts.
[0056]
The acid anions of the diazonium salt compounds include hexafluorophosphate salts, tetrafluoroborate salts, 1,5-naphthalene sulfonate salts, perfluoroalkyl carbonate salts, perfluoroalkyl sulfonate salts, zinc chloride salts, and chloride salts. A tin salt or the like can be used. Among these, hexafluorophosphate salts, tetrafluoroborate salts, and 1,5-naphthalene sulfonate salts are preferable because of their low water solubility and solubility in organic solvents. In the present invention, two or more different diazonium salt compounds may be mixed and used at an arbitrary ratio.
[0057]
In a heat-sensitive recording layer using microcapsules enclosing a diazonium salt compound, a known heat sensitizer such as an arylsulfonamide compound may be added. Specific examples include toluenesulfonamide and ethylbenzenesulfonamide. In the present invention, two or more different heat sensitizers can be mixed and used.
[0058]
A coupler compound that reacts with a diazonium salt compound to form a dye is usually used after being finely divided by emulsifying dispersion and / or solid dispersion. Specific examples of the coupler include, for example, resorcin, flurglucin, sodium 2,3-dihydroxynaphthalene-6-sulfonate, 1-hydroxy-2-naphthoic acid morpholinopropylamide, 1,5-dihydroxynaphthalene, 2,3- Dihydroxynaphthalene, 2,3-dihydroxy-6-sulfanylnaphthalene, 2-hydroxy-3-naphthoic acid anilide, 2-hydroxy-3-naphthoic acid ethanolamide, 2-hydroxy-3-naphthoic acid octylamide, 2-hydroxy- 3-naphthoic acid-N-dodecyloxypurpyramide, 2-hydroxy-3-naphthoic acid tetradecylamide, acetanilide, acetoacetanilide, benzoylacetanilide, 2-chloro-5-octylacetoacetanilide, 2,5-di-n Heptyloxy acetanilide;
[0059]
1-phenyl-3-methyl-5-pyrazolone, 1- (2′-octylphenyl) -3-methyl-5-pyrazolone, 1- (2 ′, 4 ′, 6′-trichlorophenyl) -3-benzamide 5-pyrazolone, 1- (2 ′, 4 ′, 6′-trichlorophenyl) -3-anilino-5-pyrazolone, 1-phenyl-3-phenylacetamido-5-pyrazolone, 1- (2-dodecyloxyphenyl) 2-methyl carbonate cyclohexane-3,5-dione, 1- (2-dodecyloxyphenyl) cyclohexane-3,5-dione, N-phenyl-N-dodecylbarbituric acid, N-phenyl-N- (2, And 5-dioctyloxyphenyl) barbituric acid and N-phenyl-N- (3-stearyloxy) butylbarbituric acid. . These coupler compounds can be used in combination of two or more to obtain the desired color hue.
[0060]
Furthermore, in order to promote the pigment formation reaction, it is preferable to add a basic compound finely divided by emulsification dispersion and / or solid dispersion. As the basic substance, in addition to an inorganic or organic basic compound, a compound that releases an alkaline substance by decomposition or the like when heated is also included. Typical base compounds include organic ammonium salts, organic amines, amides, urea and thiourea, and derivatives thereof, thiazoles, pyrroles, pyrimidines, piperazines, guanidines, indoles, imidazoles, imidazolines. , Nitrogen-containing compounds such as triazoles, morpholines, piperidines, amidines, formazines and pyridines.
[0061]
Specific examples thereof include tricyclohexylamine, tribenzylamine, octadecylbenzylamine, stearylamine, allylurea, thiourea, methylthiourea, allylthiourea, ethylenethiourea, 2-benzylimidazole, 4-phenylimidazole, 2-phenyl- 4-methylimidazole, 2-undecylimidazoline, 2,4,5-trifuryl-2-imidazoline, 1,2-diphenyl-4,4-dimethyl-2-imidazoline, 2-phenyl-2-imidazoline, 1,2 , 3-triphenylguanidine, 1,2-dicyclohexylguanidine, 1,2,3-tricyclohexylguanidine, guanidine trichloroacetate, N, N′-dibenzylpiperazine, 4,4′-dithiomorpholine, morpholinium trichloro Acetate 2-amino-benzothiazole, and 2-benzoyl-hydrazino-benzothiazole and the like. Two or more of these basic compounds can be used in combination.
[0062]
(Formation of microcapsules and heat-sensitive recording materials)
The microcapsule composition of the present invention can be specifically prepared as follows, for example. As the hydrophobic solvent for forming the core of the microcapsule, a high boiling organic solvent having a boiling point of 100 to 300 ° C. is preferable. Specifically, alkyl naphthalene, alkyl diphenyl ethane, alkyl diphenyl methane, diphenyl ethane alkyl adduct, alkyl biphenyl, chlorinated paraffin, tricresyl phosphate and other maleic acid derivatives, maleic acid-di-2-ethylhexyl maleic Examples include acid esters and adipic acid esters. You may use these in mixture of 2 or more types. When the solubility of the diazonium salt compound or the electron donating dye precursor in the hydrophobic solvent is not sufficient, a low boiling point organic solvent can be used in combination. The low boiling organic solvent used in combination is preferably an organic solvent having a boiling point of 40 to 100 ° C., and specific examples thereof include ethyl acetate, butyl acetate, methylene chloride, tetrahydrofuran and acetone. Moreover, you may use these low boiling point organic solvents in mixture of 2 or more types. When only a solvent having a low boiling point (boiling point of about 100 ° C. or lower) is used for the capsule core, the solvent is volatilized, so-called coreless in which only the capsule wall and the diazonium salt compound or the electron donating dye precursor exist. Capsules are easily formed.
[0063]
Depending on the type of diazonium salt, it may move to the aqueous phase side during the microencapsulation reaction, and in order to suppress this, an acid anion may be appropriately added to the water-soluble polymer solution in advance. Such acid anions include PF₆ ⁻, B (-Ph)₄ ⁻(Where Ph is a phenyl group), ZnCl₂ ⁻, C_nH_{2n + 1}COO⁻(Where n is an integer from 1 to 9) and C_pF_{2p + 1}SO₃ ⁻(Wherein p is an integer of 1 to 9).
Various additives may be used in combination for storage stability, color development sensitivity adjustment, and the like.
[0064]
In the present invention, at the time of microencapsulation, water is generally used as a compound having active hydrogen used for polymerization of an isocyanate compound for forming a microcapsule wall. It can be used as a compound having one of the active hydrogens (one of the raw materials for the microcapsule wall). Specific examples include propylene glycol, glycerin and trimethylolpropane. Further, an amine compound such as diethylenetriamine or tetraethylenepentamine may be used instead of or in combination with the polyol. These compounds are also described in the above “Polyurethane Resin Handbook”.
[0065]
Water-soluble polymers for dispersing the oil phase of the microcapsules in the aqueous phase include polyvinyl alcohol and its modified products, polyacrylic acid amide and its derivatives, ethylene / vinyl acetate copolymer, styrene / maleic anhydride copolymer. Polymer, ethylene / maleic anhydride copolymer, isobutylene / maleic anhydride copolymer, polyvinylpyrrolidone, ethylene / acrylic acid copolymer, vinyl acetate / acrylic acid copolymer, carboxymethylcellulose, methylcellulose, casein, gelatin, Mention may be made of starch derivatives, arabic gum and sodium alginate. These water-soluble polymers are preferably those that do not react with isocyanate compounds or are extremely difficult to react. For example, those having a reactive amino group in the molecular chain such as gelatin should be made inactive beforehand. is required.
The compound according to the present invention needs to be added to at least one of the oil phase and the aqueous phase.
[0066]
In the present invention, the surfactant may be added to either the oil phase or the aqueous phase, but it is easier to add to the aqueous phase because of its low solubility in organic solvents. The addition amount is 0.1 to 5% by weight, particularly 0.5 to 2% by weight, based on the weight of the oil phase. In general, surfactants used for emulsification and dispersion are considered to be superior surfactants having a relatively long-chain hydrophobic group. “Surfactant Handbook” (Nishi Ichiro et al., Sangyo Tosho (1980)), alkyl Alkali metal salts such as sulfonic acid and alkylbenzene sulfonic acid can be used.
[0067]
In the present invention, compounds such as aromatic sulfonate formalin condensates and aromatic carboxylate formalin condensates can also be used as surfactants (emulsification aids). Specific examples include compounds represented by the following general formula (A).
[Chemical 2]

[In General Formula (A), R represents an alkyl group having 1 to 4 carbon atoms, and X represents -SO₃ ⁻Or -COO⁻M represents a sodium atom or a potassium atom. q represents an integer of 1 to 20]
The above compounds are described in JP-A-6-297856 (← Japanese Patent Application No. 5-83721).
[0068]
Alkyl glucoside compounds can also be used in the same manner. Specifically, it is a compound represented by the following general formula (B).
[Chemical 3]

[In General Formula (B), R represents an alkyl group having 4 to 18 carbon atoms. q represents an integer of 0-2. ]
In the present invention, any surfactant may be used alone, or two or more kinds may be used in combination as appropriate.
[0069]
A mixed liquid (oil phase) of a solution composed of the diazonium salt compound (or electron donating dye precursor), a high boiling point solvent, and the like and a polyfunctional isocyanate compound is converted into an aqueous solution (aqueous phase) composed of a surfactant and a water-soluble polymer. ). At that time, the aqueous solution is emulsified and dispersed by adding it while stirring with a high shear stirring device such as a homogenizer. After emulsification, a polymerization reaction catalyst for an isocyanate compound is added, or the temperature of the emulsion is increased to perform a capsule wall forming reaction.
[0070]
A coupling reaction quencher can be added as appropriate to the microcapsule solution encapsulating the prepared diazonium salt. Examples of the reaction quencher include hydroquinone, sodium bisulfite, potassium nitrite, hypophosphorous acid, stannous chloride and formalin. These compounds are described in JP-A-60-214992. In general, during the encapsulation process, diazonium salt compounds often elute in the aqueous phase. As a method for removing this, filtration, ion exchange, electrophoresis, chromatography, gel filtration, reverse Methods such as osmosis treatment, ultrafiltration treatment, dialysis treatment, and activated carbon treatment can be used. Among these, ion exchange treatment, reverse osmosis treatment, ultrafiltration treatment and dialysis treatment are preferred, and treatment with a cation exchanger and treatment with a combination of a cation exchanger and an anion exchanger are particularly preferred. These methods are described in JP-A-61-219688.
[0071]
In the present invention, an electron accepting compound, a thermal sensitizer, a coupler, a basic compound, and the like can be added to the thermosensitive coloring layer. These can be mixed as appropriate and added separately after being emulsified and dispersed, or solid dispersed and atomized, or mixed as appropriate, and then added after being emulsified and dispersed, solid dispersed and atomized. In the emulsifying and dispersing method, these compounds are dissolved in an organic solvent, and a water-soluble polymer aqueous solution is added while stirring with a homogenizer or the like. In promoting the formation of fine particles, it is preferable to use the aforementioned hydrophobic organic solvent, surfactant, and water-soluble polymer.
[0072]
To solidly disperse couplers and basic substances, electron accepting compounds, thermal sensitizers, etc., these powders are put into a water-soluble polymer aqueous solution, and finely divided using a known dispersing means such as a ball mill. can do. The microparticulation is preferably carried out so as to obtain a particle diameter satisfying the characteristics required for the multicolor thermosensitive recording material such as thermal sensitivity, storage stability, transparency of the recording layer and production suitability, and the production method thereof.
[0073]
The microcapsule solution and the preparation solution of the thermal sensitizer, electron accepting compound, coupler, basic compound and the like are mixed at an appropriate ratio and coated on a support. In general, 1 to 10 moles, preferably 2 to 6 moles of the coupler is appropriate for 1 mole of the diazonium salt compound. The optimum addition amount of the basic compound varies depending on the basic strength, but is generally 0.5 to 5 mol of the diazonium salt compound. The electron-accepting compound (developer) is generally added in the range of 0.5 to 30 mol, preferably in the range of 1 to 20 mol, per 1 mol of the electron-donating dye precursor. More preferably, it is added within the range of 3 to 15 mol. The thermal sensitizer is generally added within a range of 0.1 to 20 mol with respect to the electron donating dye precursor, but is preferably added within a range of 0.5 to 10 mol.
[0074]
As the support on which these coating solutions are applied, known materials can be used as the support for the heat-sensitive recording material. Examples thereof include paper, coated paper obtained by applying clay or the like on paper, laminated paper obtained by laminating polyethylene, polyester or the like on paper, synthetic paper, plastic film such as polyethylene terephthalate, polyimide, or triacetyl cellulose. Examples of the transparent support include the polyethylene terephthalate, triacetyl cellulose, and plastic films such as polystyrene, polypropylene, and polyethylene.
[0075]
In the present invention, a protective layer may be provided on the thermosensitive coloring layer in order to further improve the light fastness and the like. In a multicolor thermosensitive material, an intermediate layer may be provided between the thermosensitive recording layers in order to further improve color reproducibility. As a material for the layer used in these, an emulsion (latex) of a water-soluble polymer compound or a hydrophobic polymer compound is preferable.
[0076]
A multicolor thermal recording material and a recording method thereof will be described. First, the outermost heat-sensitive layer containing the diazonium compound (first heat-sensitive recording layer, usually yellow color-developing layer) is developed by low-energy thermal recording, and then the absorption wavelength range of the diazonium compound contained in the heat-sensitive layer The entire surface is irradiated with a light source that emits the light to photodecompose the diazonium compound remaining in the uppermost heat-sensitive layer.
[0077]
Next, a second heat-sensitive layer (second heat-sensitive recording) containing a diazonium compound having a higher energy than the previous light and having a light absorption wavelength range different from that of the absorption wavelength range of the diazonium compound contained in the first layer. Layer, usually a magenta coloring layer), and then irradiating the entire surface again with a light source that emits light in the absorption wavelength range of the diazonium compound, whereby the diazonium compound remaining in the second heating layer Is photolyzed. Finally, the layer (third layer) containing the electron donating dye precursor of the innermost layer (third heat-sensitive recording layer, usually cyan coloring layer) is developed with higher energy to complete image recording.
[0078]
In the above case, it is preferable that the outermost layer and the second layer are transparent heat-sensitive layers because each color is brilliant. In the present invention, a multicolor image can also be obtained by using a transparent support as the support and applying any one of the three layers to the back of the transparent support. In this case, the uppermost heat-sensitive layer on the side opposite to the image viewing side does not need to be transparent.
[0079]
As a light source used for photolysis of the diazonium compound, an ultraviolet lamp is usually used. An ultraviolet lamp is a fluorescent tube in which mercury vapor is filled in a tube, and fluorescent tubes having various emission wavelengths can be obtained depending on the type of phosphor applied to the inner wall of the tube.
[0080]
In the multicolor thermosensitive recording material, the third thermosensitive recording layer can be formed by combining an appropriate diazonium salt compound and a coupler compound.
[0081]
【Example】
The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to these examples. In the present embodiment, “parts” and “%” all represent “parts by mass” and “mass%”.
[0082]
[Synthesis Example 1]: Synthesis of Compound (1) of the Present Invention
After drying 20 parts of polyethylene glycol monomethyl ether (“Uniox M-4000” manufactured by NOF Corporation, average molecular weight: 4350) at an external temperature of 110 ° C. under a nitrogen stream, the external temperature is returned to 60 ° C. and dried. 15 ml of ethyl acetate and 1.68 parts of xylylene diisocyanate / trimethylolpropane adduct (“Takenate D110N”, 75% ethyl acetate solution manufactured by Mitsui Takeda Chemical Co., Ltd.) as a polyvalent isocyanate compound were added, For 3 hours. After adding 20 ml of methanol to this reaction liquid and stirring at 60 ° C. for 2 hours, the solvent was distilled off to obtain 20.3 g of Compound (1) according to the present invention. When the IR absorption spectrum (using KBr cell) of the compound (1) was measured, no NCO group absorption was observed.
[0083]
[Synthesis Example 2]: Synthesis of Compound (2) of the Present Invention
In Synthesis Example 1, the present invention was carried out in the same manner as in Synthesis Example 1 except that 0.58 parts of di (4-isocyanatophenyl) methane was used instead of 1.68 parts of the polyvalent isocyanate compound “Takenate D110N”. 19.8 g of the compound (2) according to the above was obtained. Also in the compound (2), no NCO group absorption was observed in the IR absorption spectrum.
[0084]
[Synthesis Example 3]: Synthesis of Compound (3) of the Present Invention
In Synthesis Example 1, 0.60 part of a polyvalent isocyanate compound (“Millionate MR-200” manufactured by Nippon Polyurethane Industry Co., Ltd.) was used instead of 1.68 parts of the polyvalent isocyanate compound “Takenate D110N”. Except for the above, 20.6 g of the compound (3) according to the present invention was obtained in the same manner as in Synthesis Example 1. Also in the compound (3), NCO group absorption was not observed in the IR absorption spectrum.
[0085]
[Synthesis Example 4]: Synthesis of Compound (4) of the Present Invention
In Synthesis Example 1, polyethylene glycol monomethyl ether “Uniox M-4000” was changed to polyethylene glycol monomethyl ether (“20,250-9”, average molecular weight: 2000, manufactured by Aldrich), and polyvalent isocyanate compound “Takenate D110N”. 21.6 g of the compound (4) according to the present invention was obtained in the same manner as in Synthesis Example 1 except that the amount of addition of 1.68 parts was changed to 3.65 parts. Also in the compound (4), NCO group absorption was not observed in the IR absorption spectrum.
[0086]
[Synthesis Example 5]: Synthesis of compound (5) of the present invention
In Synthesis Example 1, polyethylene glycol monomethyl ether “Uniox M-4000” was changed to polyethylene glycol monomethyl ether (“20,249-5”, average molecular weight: 750, manufactured by Aldrich), and polyvalent isocyanate compound “Takenate D110N”. 26.1 g of the compound (5) according to the present invention was obtained in the same manner as in Synthesis Example 1 except that the amount of 1.68 parts was changed to 9.74 parts. Also in the compound (5), NCO group absorption was not observed in the IR absorption spectrum.
[0087]
[Synthesis Example 6]: Synthesis of Compound (6) of the Present Invention
A mixture of 50 parts of polyethylene glycol monomethyl ether (“Uniox M-4000”) and 50 parts of a polyisocyanate compound (“Takenate D110N”) (10 parts of a 50% ethyl acetate solution) and 20 ml of acetonitrile was placed in an ice bath. Was added dropwise to a mixture of 0.52 parts of ethanolamine and 30 ml of acetonitrile over 22 minutes. After stirring as it was for 22 minutes, 20 ml of methanol was added and stirred at 50 ° C. for 30 minutes. After the solvent was distilled off, ethyl acetate and n-hexane were added and the resulting precipitate was collected by filtration to obtain 5.55 g of the compound (6) according to the present invention. Also in the compound (6), NCO group absorption was not observed in the IR absorption spectrum.
[0088]
[Synthesis Example 7]: Synthesis of compound (7) of the present invention
In Synthesis Example 6, 5.97 g of Compound (7) according to the present invention was obtained in the same manner as in Synthesis Example 6, except that 0.52 part of ethanolamine was changed to 0.90 part of diethanolamine. Also in the compound (7), NCO group absorption was not observed in the IR absorption spectrum.
[0089]
[Example 1]
(I) Preparation of coating solution for thermosensitive recording layer (A)
(1) Preparation of capsule solution containing diazonium salt
As a diazonium salt compound, 3.5 parts of the following compound (A-1) having a maximum absorption wavelength of decomposition at 420 nm and 0.9 part of compound (A-2) are dissolved in 16.4 parts of ethyl acetate. 7.3 parts of isopropyl biphenyl and 2.5 parts of diphenyl phthalate were added as boiling solvents and heated to mix uniformly.
[0090]
[Formula 4]

[0091]
In the above mixed solution, 4.5 parts of xylylene diisocyanate / trimethylolpropane adduct (“Takenate D110N”, 75% ethyl acetate solution, manufactured by Mitsui Takeda Chemical Co., Ltd.) as capsule wall agent and JP-A-7- 8.6 parts of a mixture comprising 4.5 parts of a 30% ethyl acetate solution of xylylene diisocyanate / bisphenol A adduct synthesized according to the method described in Japanese Patent No. 88356 (← Japanese Patent Application No. 5-233536), Stirred uniformly.
Separately, 77 parts of an 8% phthalated gelatin aqueous solution to which 0.36 part of “ScraphAG-8” (manufactured by Nippon Seika Co., Ltd.) was added and the compound (1) according to the present invention obtained in Synthesis Example 1 A mixture consisting of 2 parts was prepared, a mixed solution of the diazonium salt compound and the isocyanate compound was added, and the mixture was emulsified and dispersed with a homogenizer. After adding 20 parts of water to the obtained emulsified dispersion and homogenizing it, an encapsulation reaction was carried out over 3 hours with stirring at 40 ° C. Thereafter, the temperature of the solution is lowered to 35 ° C., and 4.1 parts of ion-exchange resin “Amberlite IRA68” (manufactured by Organo) and 8.2 parts of “Amberlite IRC50” (manufactured by Organo) are added and further stirred for 1 hour. did. Thereafter, the ion exchange resin was removed by filtration, and the concentration was adjusted so that the solid content of the capsule solution was 20%, thereby obtaining a diazonium salt-encapsulating microcapsule solution. The obtained microcapsules had a median diameter of 0.85 μm as a result of measurement using a particle size distribution measuring device “LA-700” manufactured by Horiba, Ltd.
[0092]
(2) Preparation of coupler emulsion dispersion
As coupler compounds, 2.4 parts of 2,5-di-n-heptyloxyacetanilide, 2.5 parts of triphenylguanidine, 3.3 parts of 4- (2-ethylhexyloxy) phenylsulfonamide, 4-n-pentyloxy 1.7 parts of phenylsulfonamide and 5.0 parts of 4,4 ′-(m-phenylenediisopropylidene) diphenol were dissolved in 8.0 parts of ethyl acetate to obtain “Pionin A41C” (Takemoto Yushi Co., Ltd.). (Product made) After adding 1.0 part, it heated and mixed uniformly. This mixture was added to 75.0 parts of a separately prepared 10% aqueous solution of gelatin (“# 750 gelatin” manufactured by Nitta Gelatin Co., Ltd.), and emulsified and dispersed at 40 ° C. with a homogenizer. The remaining ethyl acetate was evaporated from this emulsified dispersion, and the concentration was adjusted so that the solid content concentration was 26.5%.
Further, 9 parts of SBR latex (trade name “SN-307”, 48% liquid manufactured by Sumika ABS latex Co., Ltd.) adjusted to 26.5% with respect to 100 parts of the coupler emulsified dispersion 9 parts Was added and stirred uniformly to obtain a coupler emulsified dispersion.
[0093]
(3) Preparation of coating solution for thermosensitive recording layer (A)
For the thermosensitive recording layer (A), the diazonium salt compound-encapsulated microcapsule liquid and the coupler emulsified dispersion are mixed so that the mass ratio of the encapsulated diazo compound / coupler compound is 1.0 / 3.2. A coating solution was obtained.
[0094]
(II) Preparation of coating solution for heat-sensitive protective layer (D)
In 61 parts of a 5.0% aqueous solution of itaconic acid-modified polyvinyl alcohol (“KL-318” manufactured by Kuraray Co., Ltd.), 20.5% zinc stearate dispersion (“Hydrin F115” manufactured by Chukyo Yushi Co., Ltd.) ) 2.0 parts, 8.4 parts of a 2% aqueous solution of the compound (D-1) shown below, 8.0 parts of a fluorine-based mold release agent (“ME-313” manufactured by Daikin Corporation), 0.5 parts of wheat starch (“KF-4” manufactured by Kakishima Starch Co., Ltd.) was added and stirred uniformly. This liquid is called mother liquor.
[0095]
Compound (D-1) C₁₂H₂₅O- (C₂H₄O)₁₀-H
[0096]
Separately, 12.5 parts of ion-exchanged 20% aqueous solution of “Kao Gloss” (manufactured by Shiroishi Kogyo Co., Ltd.), 0.06 part of “Poise 532A” (manufactured by Kao Co., Ltd.), “Hydrin Z-7 (Chukyo Yushi ( 1.87 parts of 10% polyvinyl alcohol (Kuraray Co., Ltd. “PVA105”) aqueous solution 1.25 parts, 2% sodium dodecyl sulfonate aqueous solution 0.39 parts were mixed and finely mixed with Dino Mill. Dispersion was performed. This liquid is called a pigment liquid. To 80 parts of the above mother liquor, 4.4 parts of this pigment solution was added and stirred for 30 minutes or more. Thereafter, 2.8 parts of “Wetmaster 500” (manufactured by Toho Chemical Co., Ltd.) was added, and the mixture was further stirred for 30 minutes or more to obtain the intended coating solution for the thermal protection layer (D).
[0097]
(III) Production of thermosensitive recording material
The heat-sensitive recording layer (A) coating solution and the protective layer (D) coating solution are applied in this order to the surface of a photographic paper support in which polyethylene is laminated on a high-quality paper, and dried. A heat-sensitive recording material was obtained. At this time, the coating amount as a solid content is 1 m.²It was 4.5 g and 1.0 g, respectively.
[0098]
(IV) Thermal recording and evaluation
A thermal head “KST type” manufactured by Kyocera Corporation was used to evaluate the thermal recording characteristics of the thermal recording material as described below.
(1) Recording energy per unit area is 34 mJ / mm²The power applied to the thermal head and the pulse width were set so as to be, and printing was performed on the thermal recording material to record a yellow image.
(2) The recording material was irradiated with an ultraviolet lamp having a light emission center wavelength of 420 nm and an output of 40 W for 10 seconds to fix an image of an unprinted portion. The color density of this yellow image was measured by measuring the optical reflection density of the colored portion with a Macbeth densitometer “RD918 type”. The results are shown as the color density in Table 1 below.
(3) In addition, shelf life (raw preservation) was evaluated by storing the obtained thermosensitive recording material in a constant temperature and humidity chamber maintained at a temperature of 40 ° C. and a relative humidity of 90% for 24 hours, and then fixing the non-printing portion. Then, the optical reflection density of the background portion was measured. The results are shown as fog density in Table 1 below.
[0099]
[Example 2]
In Example 1, except that the compound (2) according to the present invention obtained in Synthesis Example 2 was used instead of the compound (1) according to the present invention used in the preparation of the diazonium salt-encapsulating capsule liquid. A thermosensitive recording material of Example 2 was produced in the same manner as Example 1. Here, the average particle size of the diazonium salt-encapsulating capsules was 0.86 μm.
[0100]
[Example 3]
In Example 1, except that the compound (3) according to the present invention obtained in Synthesis Example 3 was used instead of the compound (1) according to the present invention used in the preparation of the diazonium salt-encapsulating capsule solution. A thermosensitive recording material of Example 3 was produced in the same manner as Example 1. Here, the average particle diameter of the diazonium salt-encapsulating capsules was 0.46 μm.
[0101]
[Example 4]
In Example 1, except that the compound (4) according to the present invention obtained in Synthesis Example 4 was used instead of the compound (1) according to the present invention used in the preparation of the diazonium salt-encapsulating capsule solution. A heat-sensitive recording material of Example 4 was produced in the same manner as Example 1. Here, the average particle diameter of the diazonium salt-encapsulating capsules was 0.77 μm.
[0102]
[Example 5]
In Example 1, except that the compound (6) according to the present invention obtained in Synthesis Example 6 was used instead of the compound (1) according to the present invention used in the preparation of the diazonium salt-encapsulating capsule solution. A thermosensitive recording material of Example 5 was produced in the same manner as Example 1. Here, the average particle diameter of the diazonium salt-encapsulating capsules was 0.75 μm.
[0103]
[Example 6]
In Example 1, except that the compound (7) according to the present invention obtained in Synthesis Example 7 was used instead of the compound (1) according to the present invention used in the preparation of the diazonium salt-encapsulating capsule solution. A heat-sensitive recording material of Example 6 was produced in the same manner as Example 1. Here, the average particle diameter of the diazonium salt-encapsulating capsules was 0.57 μm.
[0104]
[Example 7]
In Example 1, 4.5 parts of xylylene diisocyanate / trimethylolpropane adduct (“Takenate D110N”) and a capsule wall agent used in the preparation of the diazonium salt-encapsulating capsule solution described in JP-A-7-88356 Instead of 8.6 parts of a mixture consisting of 4.5 parts of a 30% ethyl acetate solution of xylylene diisocyanate / bisphenol A adduct synthesized according to the process, xylylene diisocyanate / trimethylolpropane adduct (“Takenate D110N”) 4 8.6 parts of a mixture comprising 4.5 parts of 30% ethyl acetate solution of xylylene diisocyanate / bisphenol A adduct synthesized according to the method described in JP-A-7-88356 and obtained in Synthesis Example 4 1.7 parts of the obtained compound (4) according to the present invention, and A mixture of 77 parts of an 8% aqueous solution of phthalated gelatin to which 0.36 part of “ScraphAG-8” (manufactured by Nippon Seika Co., Ltd.) and 1.2 parts of compound (1) according to the invention of Synthesis Example 1 was added. Instead, it was carried out in the same manner as in Example 1 except that only 77 parts of an 8% phthalated gelatin aqueous solution to which 0.36 part of “ScraphAG-8” (manufactured by Nippon Seika Co., Ltd.) was added was used. The heat-sensitive recording material of Example 7 was produced. Here, the average particle size of the diazonium salt-encapsulating capsules was 0.89 μm.
[0105]
[Example 8]
In Example 7, as the capsule wall agent used in the preparation of the diazonium salt-encapsulating capsule solution, the compound (5) according to the present invention obtained in Synthesis Example 5 instead of the compound (4) according to the present invention in Synthesis Example 4 was used. A heat-sensitive recording material of Example 8 was produced in the same manner as Example 7 except that was used. Here, the average particle diameter of the above-mentioned diazonium salt-encapsulating capsules was 0.44 μm.
[0106]
[Comparative Example 1]
In Example 1, 4.5 parts of xylylene diisocyanate / trimethylolpropane adduct (“Takenate D110N”) and JP-A-7-88356 described as capsule wall agents used in the preparation of the diazonium salt-encapsulating capsule solution And 10.3 parts of a mixture consisting of 4.5 parts of a 30% ethyl acetate solution of xylylene diisocyanate / bisphenol A adduct synthesized according to the above method, and “ScraphAG-8” (manufactured by Nippon Seika Co., Ltd.) Instead of 77 parts of 8% phthalated gelatin aqueous solution to which 0.36 parts were added and 1.2 parts of the compound (1) according to the invention of Synthesis Example 1, “ScraphAG-8” (Nippon Seika ( Made in the same manner as Example 1 except that only 77 parts of 8% phthalated gelatin aqueous solution with 0.36 parts added was used. 7 thermosensitive recording material was prepared. Here, the average particle size of the above-mentioned diazonium salt-encapsulating capsules was 0.60 μm.
[0107]
For the heat-sensitive recording materials (Examples 2 to 8 and Comparative Example 1) obtained above, the color density in the image area and the fog density in the non-color area were measured in the same manner as in the thermal recording and evaluation in Example 1. . The results are shown in Table 1 below.
[0108]
[Table 1]

[0109]
As is apparent from Table 1, a heat-sensitive recording material using a microcapsule composition produced by adding a compound according to the present invention in which all isocyanate groups were reacted in accordance with the procedure of the present invention when microcapsules were formed. In Examples 1 to 8, it was found that the color density of the image area was high and the fog density of the background area was low compared to that of Comparative Example 1 in which the compound of the present invention was not added.
[0110]
[Example 8]
(V) Preparation of coating solution for thermosensitive recording layer (B)
(1) Preparation of capsule solution containing diazonium salt
As a diazonium salt compound, 2.8 parts of the following compound (B-1) having a maximum absorption wavelength of decomposition at 365 nm, 2.8 parts of dibutyl sulfate, and 2,2-dimethoxy-1,2-diphenylethane-1-one ( 0.56 parts of “Irgacure 651” manufactured by Ciba-Geigy Co., Ltd. was dissolved in 10.0 parts of ethyl acetate. Furthermore, 5.9 parts of isopropyl biphenyl and 2.5 parts of tricresyl phosphate were added as a high boiling point solvent, and the mixture was heated and mixed uniformly.
[0111]
[Chemical formula 5]

[0112]
As a capsule wall agent, 7.6 parts of xylylene diisocyanate / trimethylolpropane adduct (“Takenate D110N” manufactured by Mitsui Takeda Chemical Co., Ltd., 75% ethyl acetate solution) is further added to the above mixed solution and uniformly added. Stir.
Separately, 64 parts of a 6% gelatin aqueous solution (trade name “MGP-9066” manufactured by Nippi Gelatin Industries Co., Ltd.) to which 2.0 parts of a 10% sodium dodecyl sulfonate aqueous solution was added were prepared, and a mixed solution of the above diazonium salt compound Was added and emulsified with a homogenizer.
[0113]
After adding 20 parts of water to the emulsified dispersion obtained above and homogenizing it, the mixture was reacted at 40 ° C. for 30 minutes with stirring, then heated to 60 ° C. and encapsulated for 3 hours. Thereafter, the temperature of the solution is lowered to 35 ° C., and 4.1 parts of ion-exchange resin “Amberlite IRA68” (manufactured by Organo) and 8.2 parts of “Amberlite IRC50” (manufactured by Organo) are added and further stirred for 1 hour. did. Thereafter, the ion exchange resin was filtered to obtain a target diazonium salt-encapsulating capsule solution. The average particle size of the microcapsules was 0.64 μm.
[0114]
(2) Preparation of coupler emulsion dispersion
As a coupler compound, 3.0 parts of the following compound (B-2), 8.0 parts of triphenylguanidine, 8.0 parts of 1,1- (p-hydroxyphenyl) -2-ethylhexane, 4,4 '-(P-phenylenediisopropylidene) diphenol 8.0 parts, 2.0 parts of the following compound (B-3), and 1,1,3-tris (2-methyl-4-hydroxy-5- 2.0 parts of t-butylphenyl) butane is dissolved in 10.5 parts of ethyl acetate, and 0.48 parts of tricresyl phosphate, 0.24 parts of diethyl maleate and “Pionine A41C” (Takemoto Yushi) as high-boiling solvents. After adding 1.27 parts, it was heated and mixed uniformly. This mixture was added to 93 parts of an aqueous solution of 8% gelatin (“# 750 gelatin” manufactured by Nitta Gelatin Co., Ltd.) and emulsified and dispersed with a homogenizer. The remaining ethyl acetate was evaporated from the emulsion dispersion to obtain the desired coupler emulsion dispersion.
[0115]
[Chemical 6]

[0116]
[Chemical 7]

[0117]
(3) Preparation of coating solution for thermosensitive recording layer (B)
The diazonium salt-encapsulated microcapsule liquid and the coupler emulsified dispersion are mixed so that the mass ratio of the encapsulated diazo compound / coupler compound is 1.0 / 3.2, and the target thermosensitive recording layer (B ) Coating solution was obtained.
[0118]
(VI) Preparation of coating solution for thermosensitive recording layer (C)
(1) Preparation of an electron donating dye precursor encapsulated capsule solution
0.39 part of 3- (o-methyl-p-diethylaminophenyl) -3- (1′-ethyl-2-methylindol-3-yl) phthalide as electron donating dye precursor, maximum at 285 nm as UV absorber 0.19 part of 2-hydroxy-4-methoxybenzophenone having an absorption wavelength and 0.29 part of 2,5-tert-octylhydroquinone as an antioxidant are dissolved in 0.93 part of ethyl acetate, and a high boiling point solvent. 0.54 part of phenethylcumene was added and heated to mix uniformly. As a capsule wall agent, 1.0 part of xylylene diisocyanate / trimethylolpropane adduct (“Takenate D110N”) was further added to this solution and stirred uniformly.
Separately, 36.4 parts of a 6% gelatin aqueous solution (“MGP-9066” manufactured by Nippi Gelatin Industries Co., Ltd.) to which 0.07 part of 10% sodium dodecyl sulfonate aqueous solution was added were prepared, and the above-mentioned electron-donating dye was prepared. The precursor solution was added and emulsified and dispersed with a homogenizer. The emulsion dispersion thus obtained is referred to as a primary emulsion dispersion.
[0119]
Separately, 6.0 parts of 3- (o-methyl-p-diethylaminophenyl) -3- (1′-ethyl-2-methylindol-3-yl) phthalide, 3.0 parts of 2-hydroxy-4-methoxybenzophenone, In addition, 4.4 parts of 2,5-tert-octylhydroquinone is dissolved in 14.4 parts of ethyl acetate, and 8.4 parts of phenethylcumene is further added as a high-boiling solvent, and the solution is stirred for uniform use. 7.8 parts of “Takenate D110N” and 5.9 parts of methylene diisocyanate (“Millionate MR200” manufactured by Nippon Polyurethane Co., Ltd.) were added and stirred uniformly. The solution thus obtained and 1.2 parts of a 10% aqueous sodium dodecylsulfonate solution were added to the above primary emulsified dispersion, and the mixture was emulsified and dispersed with a homogenizer. This liquid is called a secondary emulsified dispersion. After adding 60.0 parts of water and 0.4 parts of diethylenetriamine to this secondary emulsified dispersion, the mixture was homogenized, heated to 65 ° C. with stirring, and encapsulated over 3.5 hours. An electron donating dye precursor-encapsulated microcapsule emulsion was obtained. The average particle size of the microcapsules was 1.9 μm.
[0120]
(2) Preparation of electron-accepting compound dispersion
As an electron-accepting compound, 30 parts of “bisphenol P” was added to 82.5 parts of a 2.0% aqueous solution of gelatin (“MGP-9066” manufactured by Nippi Gelatin Industries Co., Ltd.), and further 2% 2-ethylhexyl. 7.5 parts of an aqueous sodium sulfosuccinate solution was added, and the resulting mixture was dispersed for 24 hours with a ball mill to prepare a dispersion. 36.0 parts of a 15% gelatin (“# 750 gelatin” manufactured by Nitta Gelatin Co., Ltd.) aqueous solution was added to this dispersion and stirred uniformly to obtain an electron-accepting compound dispersion. The average particle size of the electron-accepting compound in this dispersion was 0.5 μm.
[0121]
(3) Preparation of coating solution for thermosensitive recording layer (C)
Next, the above electron-donating dye precursor-encapsulated microcapsule solution, the above-described electron-accepting compound dispersion, a 15% gelatin (“# 750 gelatin” manufactured by Nitta Gelatin Co., Ltd.) aqueous solution, and a stilbene-based fluorescent enhancement A white agent (“Whiteex-BB” manufactured by Sumitomo Chemical Co., Ltd.) is used. The mass ratio of electron donating dye precursor / electron accepting compound is 1/14, electron donating dye precursor / “# 750 gelatin”. Mixing is performed so that the mass ratio is 1.1 / 1 and the mass ratio of electron donating dye precursor / fluorescent brightening agent is 5.3 / 1, and the target coating solution for the thermal recording layer (C) is prepared. Prepared.
[0122]
(VII) Preparation of coating solution for intermediate layer (E)
A 14% gelatin aqueous solution (“# 750 gelatin” manufactured by Nitta Gelatin Co., Ltd.) in an aqueous solution containing 8.2% 4% boric acid aqueous solution and (4-nonylphenoxytrioxyethylene) butyl sulfonate 2% aqueous solution 1.2% And 7.5 parts of a 2% aqueous solution of the following compound (E-1) were added and stirred uniformly to prepare a coating solution for the desired intermediate layer (E).
[0123]
(E-1) (CH₃CH₂SO₂CH₂CONHCH₂)₂−
[0124]
(VIII) Preparation of multicolor thermal recording material
On the surface of a photographic paper support in which polyethylene is laminated on fine paper, the above-mentioned coating solution for the thermal recording layer (C), the coating solution for the intermediate layer (E), and the coating for the thermal recording layer (B) with a wire bar. The coating solution for the intermediate layer (E), the coating solution for the thermosensitive recording layer (A) described in Example 1 and the coating solution for the protective layer (D) are applied in this order and dried to obtain the desired multi-layer. A color thermosensitive recording material was obtained. Here, the coating amount as a solid content is 1 m²It was 9.0 g, 3.0 g, 8.0 g, 3.0 g, 4.7 g, and 1.0 g, respectively.
[0125]
(IX) Thermal recording and evaluation
A thermal head “KST type” manufactured by Kyocera Corporation was used to evaluate the thermal recording characteristics of the thermal recording material as described below.
(1) Recording energy per unit area is 35 mJ / mm²The power applied to the thermal head and the pulse width were adjusted so as to obtain a yellow image by printing on the thermal recording material. (2) The recording material was irradiated for 10 seconds with an ultraviolet lamp having an emission center wavelength of 420 nm and an output of 40 W. (3) The recording energy per unit area was again 80 mJ / mm.²Then, the power applied to the thermal head and the pulse width were determined, printed, and a magenta image was recorded. (4) Irradiation with an ultraviolet lamp with an emission center wavelength of 365 nm and an output of 40 W for 15 seconds. (5) Recording energy per unit area is 140 mJ / mm again.²The power applied to the thermal head and the pulse width were adjusted so that a cyan image was recorded. As a result, in addition to the yellow, magenta, and cyan color images, the recorded portion where the yellow and magenta records overlap is red, the overlapping portion of magenta and cyan is blue, and the overlapping portion of yellow and cyan is green In addition, the image portion where the yellow, magenta and cyan recordings overlapped was colored black. The unrecorded part was grayish white. The optical reflection density of each colored portion of yellow, magenta, and cyan was measured with a “Macbeth RD918” type densitometer. The shelf life (raw storage) was evaluated by leaving the obtained multicolor thermosensitive recording material in a constant temperature and humidity chamber maintained at a temperature of 40 ° C. and a relative humidity of 90% for 24 hours, and then fixing and optical reflection of the background portion. The concentration was measured and evaluated.
[0126]
[Table 2]

[0127]
As is apparent from Table 2, even in a multicolor recording material, a microcapsule composition produced by adding a compound according to the present invention in which all isocyanate groups were reacted according to the procedure of the present invention when forming microcapsules. It was found that the heat-sensitive recording material using the material has a high color density in the yellow, magenta and cyan image areas and a low fog density in the background area.
[0128]
【The invention's effect】
The microcapsule composition of the present invention has high sensitivity to heat, exhibits high color developability upon contact with a coupler or developer, and has excellent raw shelf life (long shelf life) when a diazo compound is used as a core material. It has excellent characteristics such as showing. Therefore, when the above microcapsules are used in a heat-sensitive recording layer of a heat-sensitive recording material, a heat-sensitive sensitivity and color developability are high, and when a diazo compound is used as a core material, a recording material excellent in raw storability can be obtained. it can. Furthermore, when the above microcapsules are used in a heat-sensitive recording layer, a multicolor heat-sensitive recording material excellent in color reproducibility and raw storage can be obtained.

Claims (5)

In producing a microcapsule having a polyurethane / urea wall by polymerizing an isocyanate compound with a compound having active hydrogen, (1) a polyfunctional isocyanate having two or more isocyanate groups in the molecule and (2) 1 in the molecule. After reacting with at least one polyether derivative having a number of active hydrogens and an average molecular weight of 500 to 20000, the reaction product is treated with (3) at least one of alcohols to remove all of the isocyanate groups. A microcapsule composition comprising the polyurethane / urea wall formed by adding at least one of the reacted compounds. In producing a microcapsule having a polyurethane / urea wall by polymerizing an isocyanate compound with a compound having active hydrogen, (1) a polyfunctional isocyanate having two or more isocyanate groups in the molecule and (2) 1 in the molecule. Reaction with at least one polyether derivative having one active hydrogen and an average molecular weight of 500 to 20,000, and (3) reacting at least one primary or secondary amine having at least one hydroxyl group. Then, the polyurethane / urea wall is formed by adding at least one compound obtained by treating all of the isocyanate groups by treating the reaction product with (4) at least one alcohol. A microcapsule composition. In producing a microcapsule having a polyurethane / urea wall by polymerizing an isocyanate compound with a compound having active hydrogen, (1) a polyfunctional isocyanate having two or more isocyanate groups in the molecule and (2) one in the molecule. By reacting at least one polyether derivative having one active hydrogen and having an average molecular weight of 300 to 5,000 in a molar ratio in which the number of moles of the latter active hydrogen is not less than the number of moles of the former isocyanate group A microcapsule composition, wherein the polyurethane / urea wall is formed by adding at least one compound obtained by reacting all groups. From a thermosensitive recording layer containing a support and (1) microcapsules and couplers encapsulating a diazo compound, or (2) microcapsules encapsulating an electron-donating dye precursor and a developer provided thereon. A heat-sensitive recording material, wherein the microcapsule composition containing the microcapsule is the microcapsule composition according to any one of claims 1 to 3. A support and a cyan, magenta and yellow thermosensitive recording layer provided thereon, each thermosensitive recording layer comprising (1) a microcapsule and a coupler containing a diazo compound, or (2) an electron donating dye precursor A multicolor thermosensitive recording material comprising a microcapsule enclosing a body and a developer, wherein at least one microcapsule composition comprising the microcapsule is according to any one of claims 1 to 3. A multicolor thermosensitive recording material characterized by being a microcapsule.