JP2004255842A - Heat sensitive recording material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat sensitive recording material which has an excellent recording sensitivity, storage stability, and texture fogging resistance. <P>SOLUTION: This heat sensitive recording material comprises a heat sensitive recording layer provided on a support. The heat sensitive recording layer is composed mainly of an electron-donating dye precursor, which is colorless or light-colored in an ordinary state, and an electron-accepting compound which, upon heating, reacts with the dye precursor to cause a color development of the dye precursor. In the heat sensitive recording layer, a urea urethane compound represented by general formula (1) is contained as the electron-accepting compound, and 4-hydroxy-4'-allyloxydiphenylsulfone is also contained. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００１４】
また、該感熱記録層中に、補助増感剤として、一般式（２）で表される飽和脂肪酸モノアミドを含有することを特徴とする前記記載の感熱記録材料である。
【化４】

（式中、Ｒ_１は炭素数１１〜２１のアルキル基を示す。）
【００１５】
【発明の実施の形態】
本発明の内容を更に具体的に説明する。
支持体上に電子供与性である通常無色ないし淡色である染料前駆体と、加熱時反応して該染料前駆体を発色させる電子受容性化合物とを含有する感熱記録層を設けた感熱記録材料において、該感熱記録層中に該電子受容性化合物として、一般式（１）で表されるウレアウレタン化合物を用いることにより、他の電子受容性化合物を用いた場合と比較して、画像部の保存安定性が改善されるが、高い熱応答性、ならびに発色濃度は得られない。
しかし、本発明の感熱記録材料は、上記の一般式（１）で表されるウレアウレタン化合物に４−ヒドロキシ−４’−アリルオキシジフェニルスルホンを併用することによって、該電子受容性化合物の画像部の保存安定性を損なうことなく、高い熱応答性、ならびに発色濃度が得られる。また、従来、電子受容性化合物の併用は、感熱記録材料の未発色部の白色度を低下、いわゆる地肌カブリを起こす傾向にあるが、上記の一般式（１）で表されるウレアウレタン化合物と４−ヒドロキシ−４’−アリルオキシジフェニルスルホンの併用は、そのような白色度の低下が見られない上に耐熱性においても優れた白色度を有する感熱記録材料を提供する。
【００１６】
該電子受容性化合物と、４−ヒドロキシ−４’−アリルオキシジフェニルスルホンの含有量質量比は、該電子受容性化合物１質量部に対して１〜２０質量部程度が好ましく、さらに好ましくは、５〜１０質量部程度である。
【００１７】
また、本発明の感熱記録材料は、該感熱記録層中に、補助増感剤として、上記の一般式（２）で表される飽和脂肪酸モノアミドを用いる。これによって、発色感度が著しく向上する。
【００１８】
本発明における感熱記録層に用いられる電子受容性化合物である上記の一般式（１）で表されるウレアウレタン化合物の具体的な例としては、４、４’−ビス［（４−メチル−３−フェノキシカルボニルアミノフェニル）ウレイド］ジフェニルスルホン、４、４’−ビス［（２−メチル−５−フェノキシカルボニルアミノフェニル）ウレイド］ジフェニルスルホン、［４−（２−メチル−５−フェノキシカルボニルアミノフェニル）−４’−（４−メチル−３−フェノキシカルボニルアミノフェニル）ウレイド］ジフェニルスルホンなどを挙げることができるが、本発明に係わるウレアウレタン化合物は、これに限定されるものではなく、また、これらのウレアウレタン化合物は必要に応じて単独、または２種以上併用して使用することができる。
【００１９】
本発明における感熱記録層に用いられる補助増感剤である上記一般式（２）で表される飽和脂肪酸モノアミドの具体的な例としては、ラウリン酸アミド、ミリスチン酸アミド、パルミチン酸アミド、ステアリン酸アミド、アラギン酸アミド、べへニン酸アミドなどを挙げることができるが、本発明に係わる飽和脂肪酸モノアミドは、これに限定されるものではなく、また、これらの飽和脂肪酸モノアミドは必要に応じて単独、または２種以上併用して使用することができる。
【００２０】
本発明の感熱記録材料は、一般に支持体上に電子供与性の通常無色ないし淡色の染料前駆体、及び本発明の電子受容性化合物である共反応体を主成分とし、これらをバインダーなどに分散した後、支持体上に塗工して感熱記録層を設け、熱ヘッド、熱ペン、レーザー光などで加熱することにより、染料前駆体、電子受容性化合物が瞬時反応し記録画像が得られるものである。上記感熱記録層には顔料、増感剤、バインダー、酸化防止剤、及びスティッキング防止剤などが必要に応じて添加される。
【００２１】
本発明の感熱記録材料に用いられる染料前駆体としては、一般に感圧記録材料、または感熱記録材料に用いられているものに代表されるが、これらに制限されることはない。
【００２２】
このような染料前駆体の具体的な例を挙げれば、次の通りである。
（１）トリアリールメタン系化合物：３，３−ビス（４−ジメチルアミノフェニル）−６−ジメチルアミノフタリド（クリスタルバイオレットラクトン）、３，３−ビス（４−ジメチルアミノフェニル）フタリド、３−（４−ジメチルアミノフェニル）−３−（１，２−ジメチルインドール−３−イル）フタリド、３−（４−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−（４−ジメチルアミノフェニル）−３−（２−フェニルインドール−３−イル）フタリド、３，３−ビス（１，２−ジメチルインドール−３−イル）−５−ジメチルアミノフタリド、３，３−ビス（１，２−ジメチルインドール−３−イル）−６−ジメチルアミノフタリド、３，３−ビス（９−エチルカルバゾール−３−イル）−５−ジメチルアミノフタリド、３，３−ビス（２−フェニルインドール−３−イル）−５−ジメチルアミノフタリド、３−（４−ジメチルアミノフェニル）−３−（１−メチルピロール−２−イル）−６−ジメチルアミノフタリドなど、
【００２３】
（２）ジフェニルメタン系化合物：４，４’−ビス（ジメチルアミノフェニル）ベンズヒドリルベンジルエーテル、Ｎ−クロ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など、
【００２４】
（３）キサンテン系化合物：ローダミンＢアニリノラクタム、ローダミンＢ−４−クロロアニリノラクタム、３−ジエチルアミノ−７−ジベンジルアミノフルオラン、３−ジエチルアミノ−７−オクチルアミノフルオラン、３−ジエチルアミノ−７−フェニルフルオラン、３−ジエチルアミノ−７−クロロフルオラン、３−ジエチルアミノ−６−クロロ−７−メチルフルオラン、３−ジエチルアミノ−７−（３，４−ジクロロアニリノ）フルオラン、３−ジエチルアミノ−７−（２−クロロアニリノ）フルオラン、３−ジエチルアミノ−６−メチル−７−アニリノフルオラン、３−ジブチルアミノ−６−メチル−７−アニリノフルオラン、３−ジペンチルアミノ−６−メチル−７−アニリノフルオラン、３−ピペリジノ−６−メチル−７−アニリノフルオラン、３−（Ｎ−エチル−Ｎ−トリル）アミノ−６−メチル−７−フェネチルフルオラン、３−ジエチルアミノ−７−（４−ニトロアニリノ）フルオラン、３−（Ｎ−メチル−Ｎ−プロピル）アミノ−６−メチル−７−アニリノフルオラン、３−（Ｎ−エチル−Ｎ−イソアミル）アミノ−６−メチル−７−アニリノフルオラン、３−（Ｎ−メチル−Ｎ−シクロヘキシル）アミノ−６−メチル−７−アニリノフルオラン、３−（Ｎ−エチル−Ｎ−テトラヒドロフルフリル）アミノ−６−メチル−７−アニリノフルオラン、３−ジエチルアミノ−６−メチル−７−（３−トルイジノ）フルオランなど、
【００２５】
（４）チアジン系化合物：ベンゾイルロイコメチレンブルー、４−ニトロベンゾイルロイコメチレンブルーなど、
【００２６】
（５）スピロ系化合物：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−ベンジルスピロジナフトピラン、３−メチルナフト−（３−メトキシベンゾ）スピロピラン、３−プロピルスピロベンゾピランなどを挙げることができる。またこれらの染料前駆体は必要に応じて単独、もしくは２種以上混合して使用することができる。
【００２７】
本発明の感熱記録材料を構成する感熱記録層に含まれる発色成分の分散液は、発色成分を構成する化合物を乾式粉砕して分散媒中に分散する方法、または発色成分を構成する化合物を分散媒に混入し湿式粉砕する方法などにより得られる。
【００２８】
該分散液中の発色成分を構成する化合物の粒径は、通常７μｍ以下であり、０．１〜５μｍが好ましく、特に０．１〜２μｍの範囲が好ましい。平均粒子径が７μｍを超える場合には、光散乱が起こりやすく、感熱記録層の透明度が損なわれると共に、発色画像を得るためのエネルギーがより多く必要となる。
【００２９】
本発明では、本発明の効果を阻害しない限り、従来公知の増感剤を使用することが可能である。この場合、６０℃〜１８０℃の融点を有するものが好ましく、特に、８０℃〜１４０℃の融点を持つものがより好ましい。具体的な例を挙げれば、次の通りである。
Ｎ−ヒドロキシメチルステアリン酸アミド、Ｎ−ステアリルステアリン酸アミド、エチレンビスステアリン酸アミド、オレイン酸アミド、メチレンビス水添牛脂脂肪酸アミド、リシノール酸アミドなどの脂肪酸アミド類、パラフィンワックス、マイクロクリスタリンワックス、ポリエチレンワックス、カルナバワックスなどの合成、および天然ワックス類、Ｎ−ステアリル尿素などの脂肪族尿素化合物、ビス（４−メトキシフェニル）エーテル、２，２’−ビス（４−メトキシフェノキシ）ジエチルエーテル、１，２−ビス（３−メチルフェノキシ）エタン、１，２−ジフェノキシエタン、１，２−ビス（フェノキシメチル）ベンゼン、ナフチルエーテル誘導体、アントリルエーテル誘導体、脂肪族エーテルなどのエーテル化合物、アジピン酸ジフェニル、シュウ酸ジベンジル、シュウ酸ジ（４−クロルベンジル）、シュウ酸ジ（４−メチルベンジル）、炭酸ジフェニル、テレフタル酸ジメチル、テレフタル酸ジベンジル、ベンゼンスルホン酸フェニル、４−アセチルアセトフェノンなどのエステル化合物、３−ターフェニル、４−ベンジルビフェニル、４−アセチルビフェニル、４−アリルオキシビフェニルなどのビフェニル誘導体、ビス（４−アリルオキシフェニル）スルホン、アセト酢酸アニリド、４−メチルアセチルアニリド、脂肪酸アニリド類などの熱可融性化合物が挙げられるが、これらに限定されるものではなく、また必要に応じて単独、もしくは２種以上混合して使用することができる。
【００３０】
その他本発明の感熱記録材料の感熱記録層には、顔料として、ケイソウ土、タルク、カオリン、焼成カオリン、炭酸カルシウム 、炭酸マグネシウム、酸化チタン、酸化亜鉛、酸化ケイ素、水酸化アルミニウム、尿素−ホルマリン樹脂などの無機、ならびに有機顔料を用いることができる。その中でも特に、炭酸カルシウム、酸化ケイ素、水酸化アルミニウムが好ましく用いられる。
【００３１】
本発明の感熱記録材料に用いられる樹脂としては、デンプン類、ヒドロキシメチルセルロース、ヒドロキシエチルセルロース、メチルセルロース、エチルセルロース、カルボキシメチルセルロースなどのセルロース誘導体、ゼラチン、カゼイン、キトサン、ポリビニルアルコール、変性ポリビニルアルコール、アルギン酸ソーダ、ポリビニルピロリドン、ポリアクリルアミド、ポリアクリル酸ソーダ、アクリル酸アミド／アクリル酸エステル共重合体、アクリル酸アミド／アクリル酸エステル／メタクリル酸３元共重合体、ポリアクリル酸のアルカリ塩、ポリマレイン酸のアルカリ塩、スチレン／無水マレイン酸共重合体のアルカリ塩、エチレン／無水マレイン酸共重合体のアルカリ塩、イソブチレン／無水マレイン酸共重合体のアルカリ塩などの水溶性樹脂、ポリ酢酸ビニル、ポリウレタン、ポリアクリル酸エステル、スチレン−ブタジエン共重合体、アクリロニトリル／ブタジエン共重合体、アクリル酸メチル／ブタジエン共重合体、アクリロニトリル／ブタジエン／スチレン三元共重合体、ポリ酢酸ビニル、酢酸ビニル／アクリル酸エステル共重合体、エチレン／酢酸ビニル共重合体、ポリアクリル酸エステル、スチレン／アクリル酸エステル共重合体、ポリウレタンなどの水分散性樹脂が挙げられる。
【００３２】
その他の添加剤としては、加熱印字ヘッドの摩耗防止、またはスティッキング防止などの目的でステアリン酸亜鉛、ステアリン酸カルシウムなどの高級脂肪酸金属塩、パラフィン、酸化パラフィン、ポリエチレン、酸化ポリエチレンなどのワックス類、また、ジオクチルスルホコハク酸ナトリウムなどの分散剤、ベンゾフェノン系、ベンゾトリアゾール系などの紫外線吸収剤、さらにはアニオン性、ノニオン性の高分子量のものを含む界面活性剤、蛍光染料、消泡剤などを必要に応じて添加することができる。
【００３３】
感熱記録層の塗工量は、通常染料前駆体の塗工量で０．１〜２ｇ／ｍ^２が適当である。上記の範囲でより優れた熱応答性と記録画像が得られる。
【００３４】
本発明の感熱記録材料は、必要に応じて支持体と感熱記録層の間に単層あるいは複数層の顔料あるいは樹脂からなるアンダーコート層を１層以上設けることができる。本発明における感熱記録材料がアンダーコート層を設けたものである場合、そのアンダーコート層の塗工量は、１〜３０ｇ／ｍ^２が好ましく、３〜２０ｇ／ｍ^２がより好ましい。
【００３５】
アンダーコート層の顔料としては、一般的には焼成カオリンが用いられるが、それ以外にもケイソウ土、タルク、カオリン、重質炭酸カルシウム、沈降炭酸カルシウム、炭酸マグネシウム、酸化亜鉛、酸化アルミニウム、水酸化アルミニウム、水酸化マグネシウム、二酸化チタン、硫酸バリウム、硫酸亜鉛、非晶質シリカ、非晶質ケイ酸カルシウム、コロイダルシリカ等の無機顔料、メラミン樹脂フィラー、尿素−ホルマリン樹脂フィラー、ポリエチレンパウダー、ナイロンパウダー、有機中空粒子、有機椀型粒子、貫通孔を有する有機粒子等の有機顔料を用いることができる。
【００３６】
アンダーコート層の樹脂としては、通常の塗工で用いられる種々の水溶性樹脂または水分散性樹脂を用いることができる。具体例についてはすでに述べたような感熱記録材料に用いられる樹脂が挙げられる。
【００３７】
本発明の感熱記録材料は、感熱記録層を設けた後、さらにその上に水溶性樹脂または水分散性樹脂を主成分とする保護層を１層以上設けて、画像保存性を向上させることができる。保護層の乾燥塗工量は０．２〜１０ｇ／ｍ^２が好ましく、０．５〜５ｇ／ｍ^２がより好ましい。
【００３８】
保護層の水溶性樹脂または水分散性樹脂としては、従来公知の水溶性高分子または水分散性樹脂から適宜選択される。具体例についてはすでに述べたような感熱記録材料に用いられる樹脂が挙げられる。また、電子線、紫外線により皮膜を形成する樹脂を使用してもよい。
【００３９】
保護層には、記録走行性、筆記性等を向上させる目的で、顔料を含有させることが可能である。顔料の具体例としては、ケイソウ土、タルク、カオリン、焼成カオリン、重質炭酸カルシウム、沈降炭酸カルシウム、炭酸マグネシウム、酸化亜鉛、酸化アルミニウム、水酸化アルミニウム、水酸化マグネシウム、二酸化チタン、硫酸バリウム、硫酸亜鉛、非晶質シリカ、非晶質ケイ酸カルシウム、コロイダルシリカ等の無機顔料、メラミン樹脂フィラー、尿素−ホルマリン樹脂フィラー、ポリエチレンパウダー、ナイロンパウダー等の有機顔料を使用することができる。
【００４０】
また、保護層には、ヘッド摩耗防止、スティッキング防止等記録走行性向上の目的から、ステアリン酸亜鉛、ステアリン酸カルシウム等の高級脂肪酸金属塩、ステアリン酸アミド等の高級脂肪酸アミド、パラフィン、ポリエチレンワックス、酸化ポリエチレン、カットワックスなどの滑剤が必要に応じて添加される。
【００４１】
さらに、感熱記録層が設けられている面と反対側の面に、電気的、光学的、磁気的に情報が記録可能な材料を含んでもよい。また、感熱記録層が設けられている面と反対側の面に、インクジェットプリンター適性を有するインク受理層や、ブロッキング防止、カール防止、帯電防止を目的としたバックコート層を設けることもできる。
【００４２】
感熱記録層、保護層、アンダーコート層、またはバックコート層の形成方法は、特に限定されるものではなく、従来公知の技術に従って形成することができる。具体的な例としては、エアナイフ塗工、ロッドブレード塗工、バー塗工、ブレード塗工、グラビア塗工、カーテン塗工、Ｅバー塗工などの方法により塗工液を塗工し、乾燥により感熱記録層、保護層、アンダーコート層、またはバックコート層を形成させることができる。
【００４３】
また、平版、凸版、フレキソ、グラビア、スクリーン、ホットメルトなどの方式による各種印刷機などによって各層を形成しても良い。
【００４４】
また、必要に応じて、アンダーコート層塗工後、感熱記録層塗工後、または保護層塗工後、スーパーカレンダー処理をし、画質を向上させることもできる。
【００４５】
なお、本発明に使用される支持体としては、紙が主として用いられるが、不織布、プラスチックフィルム、合成紙、金属箔など、あるいはこれらを組み合わせた複合シートを任意に用いることができる。
【００４６】
【実施例】
次に、本発明を実施例により、さらに詳細に説明する。ただし、これらに限定されるものではない。なお、以下に示す「部」、ならびに「％」は、特に断らない限りそれぞれ「質量部」、「質量％」を示し、塗工量は絶乾塗工量である。
【００４７】
実施例１
下塗り層用塗液の調製
焼成カオリン１００部、固形分濃度５０％のスチレン／ブタシエン系ラテックス２４部、固形分濃度２０％のリン酸エステル化澱粉３０部、および水２００部からなる組成物を混合攪拌して下塗り層用の塗液を得た。
【００４８】
感熱記録層用塗液の調製
＜分散液Ａ＞
３−ジブチルアミノ−６−メチル−７−アニリノフルオラン２００ｇを１０％スルホン基変性ポリビニルアルコール水溶液２００ｇ、水６００ｇの混合物中に分散し、ビーズミルで平均粒子径が１μｍになるまで粉砕し分散液Ａを得た。
【００４９】
＜分散液Ｂ＞
４、４’−ビス［（４−メチル−３−フェノキシカルボニルアミノフェニル）ウレイド］ジフェニルスルホン２００ｇを１０％スルホン基変性ポリビニルアルコール水溶液２００ｇ、水６００ｇの混合物中に分散し、ビーズミルで平均粒子径が０．７μｍになるまで粉砕し分散液Ｃを得た。
【００５０】
＜分散液Ｃ＞
４−ヒドロキシ−４’−アリルオキシジフェニルスルホン２００ｇを１０％スルホン基変性ポリビニルアルコール水溶液２００ｇ、水６００ｇの混合物中に分散し、ビーズミルで平均粒子径が０．７μｍになるまで粉砕し分散液Ｂを得た。
【００５１】
＜分散液Ｄ＞
１，２−ビス（３−メチルフェノキシ）エタン２００ｇを１０％スルホン基変性ポリビニルアルコール水溶液２００ｇ、水６００ｇの混合物中に分散し、ビーズミルで平均粒子径が１μｍになるまで粉砕し分散液Ｄを得た。
【００５２】
＜分散液Ｅ＞
非晶質シリカ２００ｇを０．５％ポリアクリル酸ナトリウム塩水溶液８００ｇ中に分散し、ホモミキサーで１０分間撹拌し分散液Ｄを得た。
【００５３】
＜分散液Ｆ＞
水酸化アルミニウム２００ｇを０．５％ポリアクリル酸ナトリウム塩水溶液８００ｇ中に分散し、ホモミキサーで１０分間撹拌し分散液Ｄを得た。
【００５４】
上記の分散液を用い、各々の素材を下記に示す割合で混合し、感熱塗工液濃度が１５％水溶液になるように添加水を加え、充分撹拌して感熱記録層塗液を調製した。
分散液Ａ ４０部
分散液Ｂ １０部
分散液Ｃ ７０部
分散液Ｄ ２０部
分散液Ｅ ６０部
分散液Ｆ ６０部
４０％ステアリン酸亜鉛分散液 １０部
１０％完全鹸化ＰＶＡ水溶液 ４０部
【００５５】
感熱記録材料の作製
坪量６０ｇ／ｍ^２の上質の中性紙の片面に、下塗り層用塗液の固形分塗抹量が１０ｇ／ｍ^２、感熱記録層用塗液の固形分塗抹量が染料前駆体の塗工量で０．３ｇ／ｍ^２となるように順次塗布乾燥して下塗り層、感熱記録層を形成して感熱記録材料を作製した。
【００５６】
実施例２
実施例１の感熱記録層用塗液の調製において、３０％ステアリン酸アミド分散液を３０部加えた以外は、実施例１と同様にして感熱記録材料を作製した。
【００５７】
実施例３
実施例１の感熱記録層用塗液の調製において、分散液Ｂの添加量を１０部から１３部に変更し、分散液Ｃの添加量を７０部から６７部に変更した以外は、実施例１と同様にして感熱記録材料を作製した。
【００５８】
実施例４
実施例３の感熱記録層用塗液の調製において、３０％ステアリン酸アミド分散液を３０部加えた以外は、実施例３と同様にして感熱記録材料を作製した。
【００５９】
実施例５
実施例１の感熱記録層用塗液の調製において、分散液Ｂの添加量を１０部から８部に変更し、分散液Ｃの添加量を７０部から７２部に変更した以外は、実施例１と同様にして感熱記録材料を作製した。
【００６０】
実施例６
実施例５の感熱記録層用塗液の調製において、３０％ステアリン酸アミド分散液を３０部加えた以外は、実施例５と同様にして感熱記録材料を作製した。
【００６１】
実施例７
実施例１の感熱記録層用塗液の調製において、分散液Ｂの添加量を１０部から４部に変更し、分散液Ｃの添加量を７０部から７６部に変更した以外は、実施例１と同様にして感熱記録材料を作製した。
【００６２】
実施例８
実施例１の感熱記録層用塗液の調製において、分散液Ｂの添加量を１０部から４０部に変更し、さらに分散液Ｃの添加量を７０部から４０部に変更した以外は、実施例１と同様にして感熱記録材料を作製した。
【００６３】
実施例９
実施例１の感熱記録層用塗液の調製において、分散液Ｂの添加量を１０部から６０部に変更し、さらに分散液Ｃの添加量を７０部から２０部に変更した以外は、実施例１と同様にして感熱記録材料を作製した。
【００６４】
実施例１０
実施例１の感熱記録層用塗液の調製において、分散液Ｂの添加量を１０部から２部に変更し、さらに分散液Ｃの添加量を７０部から７８部に変更した以外は、実施例１と同様にして感熱記録材料を作製した。
【００６５】
比較例１
実施例１の感熱記録層用塗液の調製において、分散液Ｂの添加量を１０部から８０部に変更し、かつ、分散液Ｃを加えなかった以外は、実施例１と同様にして感熱記録材料を作製した。
【００６６】
比較例２
実施例１の感熱記録層用塗液の調製において、分散液Ｂを加えず、かつ、分散液Ｃの添加量を７０部から８０部に変更した以外は、実施例１と同様にして感熱記録材料を作製した。
【００６７】
比較例３
＜分散液Ｇ＞
２、２−ビス（４−ヒドロキシフェニル）プロパン２００ｇを１０％スルホン基変性ポリビニルアルコール水溶液２００ｇ、水６００ｇの混合物中に分散し、ビーズミルで平均粒子径が０．７μｍになるまで粉砕し分散液Ｇを得た。
【００６８】
実施例１の感熱記録層用塗液の調製において、分散液Ｃを分散液Ｇに置き換えた以外は、実施例１と同様にして感熱記録材料を作製した。
【００６９】
比較例４
＜分散液Ｈ＞
４−ヒドロキシ−４’−イソプロポキシジフェニルスルホン２００ｇを１０％スルホン基変性ポリビニルアルコール水溶液２００ｇ、水６００ｇの混合物中に分散し、ビーズミルで平均粒子径が０．７μｍになるまで粉砕し分散液Ｈを得た。
【００７０】
実施例１の感熱記録層用塗液の調製において、分散液Ｃを分散液Ｈに置き換えた以外は、実施例１と同様にして感熱記録材料を作製した。
【００７１】
比較例５
＜分散液Ｉ＞
ビス（３−アリル−４−ヒドロキシフェニル）スルホン２００ｇを１０％スルホン基変性ポリビニルアルコール水溶液２００ｇ、水６００ｇの混合物中に分散し、ビーズミルで平均粒子径が０．７μｍになるまで粉砕し分散液Ｉを得た。
【００７２】
実施例１の感熱記録層用塗液の調製において、分散液Ｃを分散液Ｉに置き換えた以外は、実施例１と同様にして感熱記録材料を作製した。
【００７３】
比較例６
＜分散液Ｊ＞
２、４’−ジヒドロキシジフェニルスルホン２００ｇを１０％スルホン基変性ポリビニルアルコール水溶液２００ｇ、水６００ｇの混合物中に分散し、ビーズミルで平均粒子径が０．７μｍになるまで粉砕し分散液Ｊを得た。
【００７４】
実施例１の感熱記録層用塗液の調製において、分散液Ｃを分散液Ｊに置き換えた以外は、実施例１と同様にして感熱記録材料を作製した。
【００７５】
比較例７
＜分散液Ｋ＞
４、４’−ジヒドロキシジフェニルスルホン２００ｇを１０％スルホン基変性ポリビニルアルコール水溶液２００ｇ、水６００ｇの混合物中に分散し、ビーズミルで平均粒子径が０．７μｍになるまで粉砕し分散液Ｋを得た。
【００７６】
実施例１の感熱記録層用塗液の調製において、分散液Ｃを分散液Ｋに置き換えた以外は、実施例１と同様にして感熱記録材料を作製した。
【００７７】
以上の実施例１〜１０、比較例１〜７で作製した感熱記録材料を感熱記録層塗工面のベック平滑度が３００〜８００秒になるようにカレンダー処理した後、以下の評価に供した。評価結果を表１に示す。
【００７８】
［熱応答性］
大倉電機製ファクシミリ試験機ＴＨ−ＰＭＤを用いて印字テストを行った。ドット密度８ドット／ｍｍ、ヘッド抵抗１６８５Ωのサーマルヘッドを使用し、ヘッド電圧２１Ｖ、パルス幅１．０ｍｓｅｃで通電して印字し、未印字部（地肌部）の濃度と印字部（記録部）の濃度をマクベスＲＤ−９１８型反射濃度計（ビジュアルフィルター）で測定した。数値の大きい方が熱応答性に優れる。
【００７９】
［耐可塑剤性試験］
熱応答性特性の評価で用いたパルス幅１．０ｍｓｅｃで印字した記録部の上に軟質塩ビシートを密着させ、４０℃の条件下に２４時間保存した後の濃度をマクベスＲＤ−９１８型反射濃度計（ビジュアルフィルター）で測定した。記録部の濃度の数値が大きいほど耐可塑剤画像保存性に優れる。
【００８０】
［耐水性試験］
熱応答性特性の評価で用いたパルス幅１．０ｍｓｅｃで印字した感熱記録材料を２０℃の水道水に２４時間浸漬した後、記録部の濃度をマクベスＲＤ−９１８型反射濃度計（ビジュアルフィルター）で測定した。記録部の濃度の数値が大きいほど耐水画像保存性に優れる。
【００８１】
［耐酒性試験］
熱応答性特性の評価で用いたパルス幅１．０ｍｓｅｃで印字した感熱記録材料を２０℃の日本酒に２４時間浸漬した後、記録部の濃度をマクベスＲＤ−９１８型反射濃度計（ビジュアルフィルター）で測定した。記録部の濃度の数値が大きいほど耐酒画像保存性に優れる。
【００８２】
［耐熱性試験］
熱応答性特性の評価で用いたパルス幅１．０ｍｓｅｃで印字した感熱記録材料を７０℃の環境下に２４時間置いた後、地肌部と記録部の濃度をマクベスＲＤ−９１８型反射濃度計（ビジュアルフィルター）で測定した。地肌部の濃度の数値が小さい程、耐熱地肌部保存性に優れ、記録部の濃度の数値が大きいほど耐熱画像保存性に優れる。
【００８３】
【表１】

【００８４】
上記表１から明らかなごとく、支持体上に電子供与性の通常無色ないし淡色の染料前駆体と、加熱時反応して該染料前駆体を発色させる電子受容性化合物とを含有する感熱記録層を設けた感熱記録材料において、該感熱記録層中に該電子受容性化合物として、一般式（１）で表されるウレアウレタン化合物を含有する実施例１〜１０は、該電子受容性化合物を含有しない比較例２と比較して、画像部の保存安定性が著しく向上しているのが判る。
【００８５】
また、実施例１〜１０は、本発明における感熱記録層に用いられる４−ヒドロキシ−４’−メチルジフェニルスルホンを含有することから、４−ヒドロキシ−４’−メチルジフェニルスルホンを含有しない比較例１と比べて熱応答性が著しく向上しているのが判る。
【００８６】
また、支持体上に電子供与性の通常無色ないし淡色の染料前駆体と、加熱時反応して該染料前駆体を発色させる電子受容性化合物とを含有する感熱記録層を設けた感熱記録材料において、該感熱記録層中に該電子受容性化合物として、一般式（１）で表されるウレアウレタン化合物に加えて、４−ヒドロキシ−４’−アリルオキシジフェニルスルホン以外の他の電子受容性化合物を含有する比較例３〜７は、実施例１〜１０と比較して、熱応答性は遜色ない程に優れるが、画像部の保存安定性が実施例１〜１０より劣る上、地肌部の白さが低めで、耐熱性試験後の地肌部の白さに劣る。
【００８７】
また、本発明の感熱記録材料に、更にステアリン酸アミドを加えて用いた実施例２、４、及び６は、各々、実施例１，３、及び５と比較して、熱応答性が大きく向上し、画像の保存安定性も向上している。
【００８８】
【発明の効果】
支持体上に電子受容性の通常無色ないし淡色の染料前駆体と、加熱時反応して該染料前駆体を発色させる電子受容性化合物とを含有する感熱記録層を設けた感熱記録材料において、感熱記録層中に電子受容性化合物として、一般式（１）で表されるウレアウレタン化合物を用い、該電子受容性化合物と４−ヒドロキシ−４’−アリルオキシジフェニルスルホンを併用することにより、熱応答性、発色濃度、画像部の保存安定性に優れ、良好な地肌白色度を有する感熱記録材料が得られる。該電子受容性化合物と、４−ヒドロキシ−４’−アリルオキシジフェニルスルホンの含有量質量比は、該電子受容性化合物１質量部に対して１〜２０質量部程度が好ましく、さらに好ましくは、５〜１０質量部程度である。
また、本発明の感熱記録材料は、該感熱記録層中に、補助増感剤として、一般式（２）で表される飽和脂肪酸モノアミドを用いることによって、発色感度が著しく向上する。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a heat-sensitive recording material, and more particularly, to a heat-sensitive recording material having excellent recording sensitivity, image storage stability, and background fog resistance.
[0002]
[Prior art]
The heat-sensitive recording material is generally a material in which a support is provided with a heat-sensitive recording layer mainly composed of an electron-donating, usually colorless or light-colored dye precursor, and an electron-accepting developer. By heating with a pen, laser light, or the like, the dye precursor and the developer react instantaneously to obtain a recorded image. A recording device for recording on such a thermosensitive recording material has advantages such as relatively inexpensive, compact, easy maintenance, and no generation of noise. It is used in a wide range of fields as a recording medium for facsimile machines, printers, computer terminals, labels, vending machines for tickets, and the like.
[0003]
In particular, in recent years, heat-sensitive recording materials have been used for financial-related recording paper, such as receipts for gas, water, electricity, etc., ATM usage statements of financial institutions, and various receipts.
[0004]
As the uses and demands of the heat-sensitive recording material have been expanding in various ways, high heat responsiveness and storage stability of the image area have been required.
[0005]
However, the heat-sensitive recording material obtains a recorded image by heating, and when a high sensitivity, that is, thermal responsiveness is realized, the recorded image deteriorates when exposed to high temperature, high humidity, or both conditions for a long time. There is a drawback that the uncolored portion becomes discolored, that is, the background fog increases. Due to the deterioration of the recorded image and the background fog, the contrast between the image portion and the background is lost. Therefore, development of a heat-sensitive recording material having high thermal responsiveness, low color fog, low background fog, and excellent image storage stability is desired.
[0006]
As a means for obtaining a heat-sensitive recording material having high thermal responsiveness, as well as having less background fog while having a color density, and having excellent storage stability of an image, a urea urethane compound as an electron-accepting compound is used in the heat-sensitive recording layer. Thermal recording materials characterized in that they are used together with various electron-accepting compounds and sensitizers, for example, diphenylsulfone derivatives (for example, see Patent Document 1), diphenylsulfonic acid derivatives (for example, Patent Document 2, 3), a combination of a sulfonamide derivative or a diphenylsulfone derivative and a diphenylsulfonic acid derivative (for example, see Patent Document 4).
[0007]
However, the urea urethane compound described in the publication is used alone as an electron-accepting compound or, even when used in combination with other electron-accepting compounds, has a problem that the color-forming sensitivity is low. Is done.
[0008]
In order to improve the thermal responsiveness of the heat-sensitive recording material, it contains, as main components, an electron-donating, usually colorless or pale-colored dye precursor, and an electron-accepting compound that reacts upon heating to form the dye precursor. A heat-sensitive recording material provided with a heat-sensitive recording layer, characterized in that the heat-sensitive recording layer contains 4-hydroxy-4'-isopropoxydiphenyl sulfone as the electron-accepting compound (for example, see Patent Document 1). 5) has been proposed, but a high thermal response and a high color density can be obtained, but a heat-sensitive recording material having excellent storage stability in an image area has not yet been obtained.
[0009]
Further, in order to improve the thermal responsiveness of the heat-sensitive recording material, various sensitizers are added as required in addition to the diphenylsulfone derivative and the sulfonamide derivative. When the sensitizer itself is melted by the transferred thermal energy, it dissolves the nearby dye precursor and the electron-accepting compound, or has an action of promoting the color-forming reaction by encapsulating the sensitizer. Increasing the thermal responsiveness or the compatibility with the dye precursor and the electron-accepting compound is also one means for increasing the sensitivity of the heat-sensitive recording material.
[0010]
As this method, waxes (for example, see Patent Document 6), nitrogen-containing compounds, carboxylic acid esters and the like (for example, see Patent Document 7), naphthol derivatives (for example, see Patent Document 8), and naphthoic acid derivatives (for example, see Patent Document 8) For example, see Patent Document 9), benzoic acid ester derivatives (for example, see Patent Document 10), parabenzylbiphenyl (for example, see Patent Document 11), and diphenoxyethanes (for example, see Patent Document 12). Examples of addition are disclosed. However, heat-sensitive recording materials produced by these disclosed methods are still insufficient in color density and thermal response at low temperatures.
[0011]
[Patent Document 1]
JP 2001-1646 A
[Patent Document 2]
JP 2001-341424 A
[Patent Document 3]
JP 2002-178645 A
[Patent Document 4]
JP 2002-178646 A
[Patent Document 5]
JP-A-60-13852
[Patent Document 6]
JP-A-48-19231
[Patent Document 7]
JP-A-49-34842
[Patent Document 8]
JP-A-57-64593
[Patent Document 9]
JP-A-57-64592
[Patent Document 10]
JP-A-57-148688
[Patent Document 11]
JP-A-60-122193
[Patent Document 12]
JP-A-60-56588
[0012]
[Problems to be solved by the invention]
An object of the present invention is to provide a heat-sensitive recording material that is excellent in color density of a recording portion, storage stability, and background fog resistance.
[0013]
[Means for Solving the Problems]
As a result of intensive studies, the present inventors have invented a heat-sensitive recording material of the present invention which can solve the above-mentioned problems.
That is, the heat-sensitive recording material of the present invention is a heat-sensitive recording layer containing, as a main component, an electron-donating, usually colorless or pale-colored dye precursor, and an electron-accepting compound that reacts upon heating to form the dye precursor. Wherein the urea urethane compound represented by the general formula (1) is contained in the heat-sensitive recording layer as the electron-accepting compound, and 4-hydroxy-4'-allyloxydiphenyl sulfone is provided. Which is a thermosensitive recording material.
Embedded image

[0014]
The thermosensitive recording material as described above, further comprising a saturated fatty acid monoamide represented by the general formula (2) as an auxiliary sensitizer in the thermosensitive recording layer.
Embedded image

(Where R ₁ Represents an alkyl group having 11 to 21 carbon atoms. )
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
The contents of the present invention will be described more specifically.
In a heat-sensitive recording material provided with a heat-sensitive recording layer containing an electron-donating usually colorless to light-colored dye precursor on a support and an electron-accepting compound that reacts upon heating to form the dye precursor. By using a urea urethane compound represented by the general formula (1) as the electron-accepting compound in the heat-sensitive recording layer, the preservation of the image area can be reduced as compared with the case where another electron-accepting compound is used. Although stability is improved, high thermal responsiveness and color density cannot be obtained.
However, the heat-sensitive recording material of the present invention can be obtained by using 4-urea-4′-allyloxydiphenyl sulfone in combination with the urea urethane compound represented by the general formula (1) to form an image area of the electron-accepting compound. High thermal responsiveness and color density can be obtained without impairing the storage stability of the compound. Conventionally, the combined use of an electron-accepting compound tends to reduce the whiteness of the uncolored portion of the heat-sensitive recording material and cause so-called background fogging, but the urea-urethane compound represented by the above general formula (1) The combined use of 4-hydroxy-4′-allyloxydiphenyl sulfone provides a heat-sensitive recording material having no such decrease in whiteness and excellent heat resistance.
[0016]
The content ratio by mass of the electron-accepting compound to 4-hydroxy-4′-allyloxydiphenylsulfone is preferably about 1 to 20 parts by mass, more preferably 5 to 20 parts by mass, per 1 part by mass of the electron-accepting compound. About 10 to 10 parts by mass.
[0017]
In the heat-sensitive recording material of the present invention, a saturated fatty acid monoamide represented by the above general formula (2) is used as an auxiliary sensitizer in the heat-sensitive recording layer. Thereby, the coloring sensitivity is significantly improved.
[0018]
Specific examples of the urea urethane compound represented by the above general formula (1), which is an electron-accepting compound used in the thermosensitive recording layer according to the invention, include 4,4′-bis [(4-methyl-3). -Phenoxycarbonylaminophenyl) ureido] diphenylsulfone, 4,4′-bis [(2-methyl-5-phenoxycarbonylaminophenyl) ureido] diphenylsulfone, [4- (2-methyl-5-phenoxycarbonylaminophenyl) -4 '-(4-methyl-3-phenoxycarbonylaminophenyl) ureido] diphenylsulfone, and the like, but the ureaurethane compound according to the present invention is not limited to these compounds. The urea urethane compounds can be used alone or in combination of two or more as necessary.
[0019]
Specific examples of the saturated fatty acid monoamide represented by the above general formula (2), which is an auxiliary sensitizer used in the heat-sensitive recording layer in the present invention, include lauric amide, myristic amide, palmitic amide, stearic acid, and the like. Examples thereof include amide, araginic acid amide, and behenic acid amide, but the saturated fatty acid monoamide according to the present invention is not limited thereto, and these saturated fatty acid monoamides may be used alone if necessary. Or two or more of them can be used in combination.
[0020]
The heat-sensitive recording material of the present invention generally comprises, as a main component, an electron-donating usually colorless or pale-color dye precursor on a support, and a co-reactant which is an electron-accepting compound of the present invention, and these are dispersed in a binder or the like. After that, a thermosensitive recording layer is applied by coating on the support, and the dye precursor and the electron-accepting compound react instantaneously by heating with a thermal head, a hot pen, a laser beam, etc. to obtain a recorded image. It is. Pigments, sensitizers, binders, antioxidants, anti-sticking agents and the like are added to the heat-sensitive recording layer as needed.
[0021]
The dye precursor used in the heat-sensitive recording material of the present invention is typically represented by a pressure-sensitive recording material or a heat-sensitive recording material, but is not limited thereto.
[0022]
Specific examples of such a dye precursor are as follows.
(1) Triarylmethane compounds: 3,3-bis (4-dimethylaminophenyl) -6-dimethylaminophthalide (crystal violet lactone), 3,3-bis (4-dimethylaminophenyl) phthalide, 3- (4-dimethylaminophenyl) -3- (1,2-dimethylindol-3-yl) phthalide, 3- (4-dimethylaminophenyl) -3- (2-methylindol-3-yl) phthalide, 3- (4-dimethylaminophenyl) -3- (2-phenylindol-3-yl) phthalide, 3,3-bis (1,2-dimethylindol-3-yl) -5-dimethylaminophthalide, 3,3 -Bis (1,2-dimethylindol-3-yl) -6-dimethylaminophthalide, 3,3-bis (9-ethylcarbazol-3-yl)- -Dimethylaminophthalide, 3,3-bis (2-phenylindol-3-yl) -5-dimethylaminophthalide, 3- (4-dimethylaminophenyl) -3- (1-methylpyrrol-2-yl ) -6-dimethylaminophthalide,
[0023]
(2) Diphenylmethane compounds: 4,4'-bis (dimethylaminophenyl) benzhydrylbenzyl ether, N-chlorophenylleucouramine, N-2,4,5-trichlorophenylleucouramine, etc.
[0024]
(3) Xanthene compounds: rhodamine B anilinolactam, rhodamine B-4-chloroanilinolactam, 3-diethylamino-7-dibenzylaminofluoran, 3-diethylamino-7-octylaminofluoran, 3-diethylamino- 7-phenylfluoran, 3-diethylamino-7-chlorofluoran, 3-diethylamino-6-chloro-7-methylfluoran, 3-diethylamino-7- (3,4-dichloroanilino) fluoran, 3-diethylamino -7- (2-chloroanilino) fluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-dibutylamino-6-methyl-7-anilinofluoran, 3-dipentylamino-6-methyl- 7-anilinofluoran, 3-piperidino-6-methyl-7-a Linofluoran, 3- (N-ethyl-N-tolyl) amino-6-methyl-7-phenethylfluoran, 3-diethylamino-7- (4-nitroanilino) fluoran, 3- (N-methyl-N-propyl) amino -6-methyl-7-anilinofluoran, 3- (N-ethyl-N-isoamyl) amino-6-methyl-7-anilinofluoran, 3- (N-methyl-N-cyclohexyl) amino-6 -Methyl-7-anilinofluoran, 3- (N-ethyl-N-tetrahydrofurfuryl) amino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7- (3-toluidino ) Fluoran etc.
[0025]
(4) Thiazine compounds: benzoyl leucomethylene blue, 4-nitrobenzoyl leucomethylene blue, etc.
[0026]
(5) Spiro compounds: 3-methylspirodinaphthopyran, 3-ethylspirodinaphthopyran, 3,3′-dichlorospirodinaphthopyran, 3-benzylspirodinaphthopyran, 3-methylnaphtho- (3-methoxy Benzo) spiropyran, 3-propylspirobenzopyran and the like can be mentioned. These dye precursors can be used alone or as a mixture of two or more, if necessary.
[0027]
The dispersion of the color-forming component contained in the heat-sensitive recording layer constituting the heat-sensitive recording material of the present invention is a method of dry-pulverizing the compound constituting the color-forming component and dispersing it in a dispersion medium, or dispersing the compound constituting the color-forming component. It is obtained by a method of mixing in a medium and wet grinding.
[0028]
The particle size of the compound constituting the color-forming component in the dispersion is usually 7 μm or less, preferably 0.1 to 5 μm, particularly preferably 0.1 to 2 μm. If the average particle size exceeds 7 μm, light scattering is likely to occur, the transparency of the heat-sensitive recording layer is impaired, and more energy is required to obtain a color image.
[0029]
In the present invention, conventionally known sensitizers can be used as long as the effects of the present invention are not impaired. In this case, those having a melting point of 60 ° C to 180 ° C are preferable, and those having a melting point of 80 ° C to 140 ° C are more preferable. A specific example is as follows.
Fatty acid amides such as N-hydroxymethylstearic acid amide, N-stearylstearic acid amide, ethylenebisstearic acid amide, oleic acid amide, methylenebishydrogenated tallow fatty acid amide, ricinoleic acid amide, paraffin wax, microcrystalline wax, polyethylene wax And natural waxes, aliphatic urea compounds such as N-stearyl urea, bis (4-methoxyphenyl) ether, 2,2'-bis (4-methoxyphenoxy) diethyl ether, 1,2 Ether compounds such as -bis (3-methylphenoxy) ethane, 1,2-diphenoxyethane, 1,2-bis (phenoxymethyl) benzene, naphthyl ether derivatives, anthryl ether derivatives and aliphatic ethers, adipic acid Ester compounds such as diphenyl, dibenzyl oxalate, di (4-chlorobenzyl) oxalate, di (4-methylbenzyl) oxalate, diphenyl carbonate, dimethyl terephthalate, dibenzyl terephthalate, phenyl benzenesulfonate, and 4-acetylacetophenone , 3-terphenyl, 4-benzylbiphenyl, 4-acetylbiphenyl, 4-allyloxybiphenyl and other biphenyl derivatives, bis (4-allyloxyphenyl) sulfone, acetoacetic anilide, 4-methylacetylanilide, fatty acid anilide and the like However, the present invention is not limited to these, and may be used alone or as a mixture of two or more as necessary.
[0030]
Others In the heat-sensitive recording layer of the heat-sensitive recording material of the present invention, diatomaceous earth, talc, kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, titanium oxide, zinc oxide, silicon oxide, aluminum hydroxide, urea-formalin resin are used as pigments. Inorganic and organic pigments can be used. Among them, calcium carbonate, silicon oxide and aluminum hydroxide are particularly preferably used.
[0031]
As the resin used in the heat-sensitive recording material of the present invention, starches, hydroxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose, ethyl cellulose, cellulose derivatives such as carboxymethyl cellulose, gelatin, casein, chitosan, polyvinyl alcohol, modified polyvinyl alcohol, sodium alginate, polyvinyl Pyrrolidone, polyacrylamide, sodium polyacrylate, acrylamide / acrylate copolymer, acrylamide / acrylate / methacrylic acid terpolymer, alkali salt of polyacrylic acid, alkali salt of polymaleic acid, Alkali salt of styrene / maleic anhydride copolymer, alkaline salt of ethylene / maleic anhydride copolymer, alkaline salt of isobutylene / maleic anhydride copolymer Which water-soluble resin, polyvinyl acetate, polyurethane, polyacrylate, styrene-butadiene copolymer, acrylonitrile / butadiene copolymer, methyl acrylate / butadiene copolymer, acrylonitrile / butadiene / styrene terpolymer, Water-dispersible resins such as polyvinyl acetate, vinyl acetate / acrylate copolymer, ethylene / vinyl acetate copolymer, polyacrylate, styrene / acrylate copolymer, and polyurethane.
[0032]
As other additives, for the purpose of preventing wear of the heating print head, or preventing sticking, zinc stearate, higher fatty acid metal salts such as calcium stearate, paraffin, paraffin oxide, polyethylene, waxes such as polyethylene oxide, If necessary, dispersants such as dioctyl sodium sulfosuccinate, UV absorbers such as benzophenones and benzotriazoles, as well as surfactants, including high molecular weight anionic and nonionic surfactants, fluorescent dyes, defoamers, etc. Can be added.
[0033]
The coating amount of the heat-sensitive recording layer is usually 0.1 to 2 g / m2 as the coating amount of the dye precursor. ² Is appropriate. In the above range, excellent thermal responsiveness and a recorded image can be obtained.
[0034]
The heat-sensitive recording material of the present invention may have, if necessary, one or more undercoat layers composed of a single layer or a plurality of pigments or resins between the support and the heat-sensitive recording layer. When the heat-sensitive recording material in the present invention has an undercoat layer, the coating amount of the undercoat layer is 1 to 30 g / m. ² Is preferably 3 to 20 g / m ² Is more preferred.
[0035]
As the pigment for the undercoat layer, calcined kaolin is generally used. In addition, diatomaceous earth, talc, kaolin, heavy calcium carbonate, precipitated calcium carbonate, magnesium carbonate, zinc oxide, aluminum oxide, and hydroxide Inorganic pigments such as aluminum, magnesium hydroxide, titanium dioxide, barium sulfate, zinc sulfate, amorphous silica, amorphous calcium silicate, colloidal silica, melamine resin filler, urea-formalin resin filler, polyethylene powder, nylon powder, Organic pigments such as organic hollow particles, organic bowl-shaped particles, and organic particles having through holes can be used.
[0036]
As the resin of the undercoat layer, various water-soluble resins or water-dispersible resins used in ordinary coating can be used. Specific examples include the resins used for the heat-sensitive recording material as described above.
[0037]
In the heat-sensitive recording material of the present invention, after the heat-sensitive recording layer is provided, one or more protective layers containing a water-soluble resin or a water-dispersible resin as a main component are further provided thereon to improve image storability. it can. The dry coating amount of the protective layer is 0.2 to 10 g / m ² Is preferred, and 0.5 to 5 g / m ² Is more preferred.
[0038]
The water-soluble resin or water-dispersible resin of the protective layer is appropriately selected from conventionally known water-soluble polymers or water-dispersible resins. Specific examples include the resins used for the heat-sensitive recording material as described above. Further, a resin that forms a film with an electron beam or ultraviolet light may be used.
[0039]
The protective layer may contain a pigment for the purpose of improving recording runnability, writing properties, and the like. Specific examples of the pigment include diatomaceous earth, talc, kaolin, calcined kaolin, heavy calcium carbonate, precipitated calcium carbonate, magnesium carbonate, zinc oxide, aluminum oxide, aluminum hydroxide, magnesium hydroxide, titanium dioxide, barium sulfate, and sulfuric acid. Inorganic pigments such as zinc, amorphous silica, amorphous calcium silicate and colloidal silica, and organic pigments such as melamine resin filler, urea-formalin resin filler, polyethylene powder and nylon powder can be used.
[0040]
Further, the protective layer is provided with a higher fatty acid metal salt such as zinc stearate and calcium stearate, a higher fatty acid amide such as stearic acid amide, paraffin, polyethylene wax, and oxidized material for the purpose of improving recording running properties such as head abrasion prevention and sticking prevention. Lubricants such as polyethylene and cut wax are added as needed.
[0041]
Further, the surface opposite to the surface on which the heat-sensitive recording layer is provided may include a material capable of recording information electrically, optically, and magnetically. Further, on the surface opposite to the surface on which the heat-sensitive recording layer is provided, an ink receiving layer having suitability for an ink jet printer and a back coat layer for the purpose of preventing blocking, curling and charging can be provided.
[0042]
The method for forming the heat-sensitive recording layer, the protective layer, the undercoat layer, or the backcoat layer is not particularly limited, and can be formed according to a conventionally known technique. As a specific example, a coating liquid is applied by a method such as air knife coating, rod blade coating, bar coating, blade coating, gravure coating, curtain coating, E-bar coating, and drying. A heat-sensitive recording layer, a protective layer, an undercoat layer, or a backcoat layer can be formed.
[0043]
Further, each layer may be formed by various printing machines using a method such as planographic printing, letterpress printing, flexographic printing, gravure printing, screen printing, and hot melt printing.
[0044]
Further, if necessary, after the undercoat layer is applied, the heat-sensitive recording layer is applied, or after the protective layer is applied, a super calender treatment may be performed to improve the image quality.
[0045]
As the support used in the present invention, paper is mainly used, but nonwoven fabric, plastic film, synthetic paper, metal foil, and the like, or a composite sheet combining these can be used arbitrarily.
[0046]
【Example】
Next, the present invention will be described in more detail with reference to examples. However, it is not limited to these. In the following, “parts” and “%” indicate “parts by mass” and “% by mass”, respectively, unless otherwise specified, and the coating amounts are absolutely dry coating amounts.
[0047]
Example 1
Preparation of coating liquid for undercoat layer
A composition consisting of 100 parts of calcined kaolin, 24 parts of a styrene / butadiene-based latex having a solid content of 50%, 30 parts of a phosphorylated starch having a solid content of 20%, and 200 parts of water is mixed and stirred to form an undercoat layer. A coating liquid was obtained.
[0048]
Preparation of coating solution for thermal recording layer
<Dispersion A>
200 g of 3-dibutylamino-6-methyl-7-anilinofluoran was dispersed in a mixture of 200 g of a 10% aqueous solution of a sulfonate-modified polyvinyl alcohol and 600 g of water, pulverized by a bead mill until the average particle diameter became 1 μm, and the dispersion was dispersed. A was obtained.
[0049]
<Dispersion B>
200 g of 4,4′-bis [(4-methyl-3-phenoxycarbonylaminophenyl) ureido] diphenyl sulfone was dispersed in a mixture of 200 g of a 10% aqueous solution of a sulfonate-modified polyvinyl alcohol and 600 g of water, and the average particle diameter was adjusted with a bead mill. The mixture was pulverized to 0.7 μm to obtain a dispersion C.
[0050]
<Dispersion C>
200 g of 4-hydroxy-4′-allyloxydiphenyl sulfone was dispersed in a mixture of 200 g of an aqueous solution of 10% sulfone group-modified polyvinyl alcohol and 600 g of water, pulverized by a bead mill until the average particle diameter became 0.7 μm, and dispersion B was dispersed. Obtained.
[0051]
<Dispersion D>
200 g of 1,2-bis (3-methylphenoxy) ethane was dispersed in a mixture of 200 g of a 10% aqueous solution of a sulfonate-modified polyvinyl alcohol and 600 g of water, and pulverized by a bead mill until the average particle diameter became 1 μm to obtain a dispersion D. Was.
[0052]
<Dispersion E>
200 g of amorphous silica was dispersed in 800 g of a 0.5% aqueous solution of sodium polyacrylate, and the mixture was stirred with a homomixer for 10 minutes to obtain a dispersion D.
[0053]
<Dispersion F>
200 g of aluminum hydroxide was dispersed in 800 g of a 0.5% aqueous solution of sodium polyacrylate and stirred with a homomixer for 10 minutes to obtain a dispersion D.
[0054]
Using the above dispersion, the respective materials were mixed at the following ratios, added with water so that the concentration of the heat-sensitive coating solution became a 15% aqueous solution, and sufficiently stirred to prepare a heat-sensitive recording layer coating solution.
Dispersion A 40 parts
Dispersion B 10 parts
Dispersion C 70 parts
Dispersion D 20 parts
Dispersion E 60 parts
Dispersion F 60 parts
10 parts of 40% zinc stearate dispersion
10% completely saponified PVA aqueous solution 40 parts
[0055]
Preparation of thermal recording material
Basis weight 60g / m ² On one side of high quality neutral paper, the amount of the solid content of the undercoat layer coating solution is 10 g / m ² The solid coating amount of the heat-sensitive recording layer coating liquid is 0.3 g / m2 in terms of the coating amount of the dye precursor. ² Then, an undercoat layer and a heat-sensitive recording layer were formed by coating and drying in order to obtain a heat-sensitive recording material.
[0056]
Example 2
A heat-sensitive recording material was prepared in the same manner as in Example 1, except that 30 parts of a 30% stearamide dispersion was added in the preparation of the coating solution for the heat-sensitive recording layer of Example 1.
[0057]
Example 3
In the preparation of the coating solution for the heat-sensitive recording layer of Example 1, the addition amount of the dispersion B was changed from 10 parts to 13 parts, and the addition amount of the dispersion C was changed from 70 parts to 67 parts. In the same manner as in Example 1, a thermosensitive recording material was produced.
[0058]
Example 4
A heat-sensitive recording material was prepared in the same manner as in Example 3, except that 30 parts of a 30% stearamide dispersion was added in the preparation of the coating solution for the heat-sensitive recording layer of Example 3.
[0059]
Example 5
In the preparation of the thermosensitive recording layer coating liquid of Example 1, the addition amount of the dispersion B was changed from 10 parts to 8 parts, and the addition amount of the dispersion C was changed from 70 parts to 72 parts. In the same manner as in Example 1, a thermosensitive recording material was produced.
[0060]
Example 6
A heat-sensitive recording material was prepared in the same manner as in Example 5, except that 30 parts of a 30% stearamide dispersion was added in the preparation of the coating solution for the heat-sensitive recording layer of Example 5.
[0061]
Example 7
In the preparation of the heat-sensitive recording layer coating liquid of Example 1, the addition amount of the dispersion B was changed from 10 parts to 4 parts, and the addition amount of the dispersion C was changed from 70 parts to 76 parts. In the same manner as in Example 1, a thermosensitive recording material was produced.
[0062]
Example 8
In the preparation of the heat-sensitive recording layer coating liquid of Example 1, the procedure was performed except that the addition amount of the dispersion B was changed from 10 parts to 40 parts and the addition amount of the dispersion C was changed from 70 parts to 40 parts. A heat-sensitive recording material was produced in the same manner as in Example 1.
[0063]
Example 9
In the preparation of the heat-sensitive recording layer coating liquid of Example 1, the procedure was performed except that the addition amount of the dispersion B was changed from 10 parts to 60 parts, and the addition amount of the dispersion C was changed from 70 parts to 20 parts. A heat-sensitive recording material was produced in the same manner as in Example 1.
[0064]
Example 10
In the preparation of the coating solution for the heat-sensitive recording layer of Example 1, except that the addition amount of the dispersion B was changed from 10 parts to 2 parts and the addition amount of the dispersion C was changed from 70 parts to 78 parts. A heat-sensitive recording material was produced in the same manner as in Example 1.
[0065]
Comparative Example 1
In the preparation of the coating solution for the heat-sensitive recording layer of Example 1, the heat-sensing was performed in the same manner as in Example 1 except that the addition amount of the dispersion liquid B was changed from 10 parts to 80 parts, and the dispersion liquid C was not added. A recording material was prepared.
[0066]
Comparative Example 2
In the preparation of the thermosensitive recording layer coating liquid of Example 1, the thermosensitive recording was performed in the same manner as in Example 1 except that the dispersion B was not added and the amount of the dispersion C was changed from 70 parts to 80 parts. Materials were made.
[0067]
Comparative Example 3
<Dispersion G>
Dispersion G was prepared by dispersing 200 g of 2,2-bis (4-hydroxyphenyl) propane in a mixture of 200 g of a 10% aqueous solution of a sulfonated polyvinyl alcohol and 600 g of water, and pulverizing with a bead mill until the average particle diameter became 0.7 μm. Got.
[0068]
A heat-sensitive recording material was prepared in the same manner as in Example 1, except that Dispersion C was replaced with Dispersion G in the preparation of the coating solution for the heat-sensitive recording layer of Example 1.
[0069]
Comparative Example 4
<Dispersion H>
200 g of 4-hydroxy-4′-isopropoxydiphenylsulfone was dispersed in a mixture of 200 g of an aqueous solution of 10% sulfone group-modified polyvinyl alcohol and 600 g of water, pulverized by a bead mill until the average particle diameter became 0.7 μm, and the dispersion H was dispersed. Obtained.
[0070]
A heat-sensitive recording material was prepared in the same manner as in Example 1, except that Dispersion C was replaced with Dispersion H in the preparation of the coating solution for the heat-sensitive recording layer of Example 1.
[0071]
Comparative Example 5
<Dispersion I>
200 g of bis (3-allyl-4-hydroxyphenyl) sulfone was dispersed in a mixture of 200 g of an aqueous solution of 10% sulfone group-modified polyvinyl alcohol and 600 g of water, pulverized by a bead mill until the average particle diameter became 0.7 μm, and Dispersion I Got.
[0072]
A heat-sensitive recording material was produced in the same manner as in Example 1, except that Dispersion C was replaced with Dispersion I in the preparation of the coating solution for the heat-sensitive recording layer of Example 1.
[0073]
Comparative Example 6
<Dispersion J>
200 g of 2,4′-dihydroxydiphenylsulfone was dispersed in a mixture of 200 g of a 10% aqueous solution of a sulfonate-modified polyvinyl alcohol and 600 g of water, and pulverized by a bead mill until the average particle diameter became 0.7 μm to obtain a dispersion J.
[0074]
A heat-sensitive recording material was prepared in the same manner as in Example 1, except that Dispersion C was replaced with Dispersion J in the preparation of the coating solution for the heat-sensitive recording layer in Example 1.
[0075]
Comparative Example 7
<Dispersion K>
200 g of 4,4'-dihydroxydiphenylsulfone was dispersed in a mixture of 200 g of a 10% aqueous solution of a sulfonate-modified polyvinyl alcohol and 600 g of water, and pulverized by a bead mill until the average particle diameter became 0.7 μm to obtain a dispersion liquid K.
[0076]
A heat-sensitive recording material was prepared in the same manner as in Example 1, except that Dispersion C was replaced with Dispersion K in the preparation of the coating solution for the heat-sensitive recording layer of Example 1.
[0077]
The heat-sensitive recording materials prepared in Examples 1 to 10 and Comparative Examples 1 to 7 were calendered so that the coated surface of the heat-sensitive recording layer had a Beck smoothness of 300 to 800 seconds, and were subjected to the following evaluation. Table 1 shows the evaluation results.
[0078]
[Thermal response]
A printing test was performed using a facsimile tester TH-PMD manufactured by Okura Electric. Using a thermal head with a dot density of 8 dots / mm and a head resistance of 1685Ω, printing is performed by energizing with a head voltage of 21 V and a pulse width of 1.0 msec, and the density of the unprinted portion (background portion) and the printing portion (recording portion) The density was measured with a Macbeth RD-918 reflection densitometer (visual filter). The larger the value, the better the thermal response.
[0079]
[Plasticizer resistance test]
A soft PVC sheet was adhered to the recording portion printed with a pulse width of 1.0 msec used in the evaluation of the thermal responsiveness, and the density after storage at 40 ° C. for 24 hours was used to determine the Macbeth RD-918 reflection density. It was measured with a meter (visual filter). The higher the density value of the recording portion, the better the plasticizer image storage stability.
[0080]
[Water resistance test]
After immersing the thermosensitive recording material printed with a pulse width of 1.0 msec used in the evaluation of the thermal responsiveness in tap water at 20 ° C. for 24 hours, the density of the recording portion was measured with a Macbeth RD-918 reflection densitometer (visual filter). Was measured. The higher the density value of the recording portion, the better the water-resistant image storage stability.
[0081]
[Alcohol resistance test]
After immersing the heat-sensitive recording material printed with a pulse width of 1.0 msec used in the evaluation of the thermal response characteristics in sake at 20 ° C. for 24 hours, the density of the recording portion was measured with a Macbeth RD-918 reflection densitometer (visual filter). It was measured. The higher the numerical value of the density of the recording portion, the better the liquor image storage stability.
[0082]
[Heat resistance test]
After placing the thermosensitive recording material printed with a pulse width of 1.0 msec used in the evaluation of the thermal response characteristics in an environment of 70 ° C. for 24 hours, the densities of the background portion and the recording portion were measured with a Macbeth RD-918 reflection densitometer ( (Visual filter). The lower the numerical value of the density of the background portion, the better the storage stability of the heat-resistant background portion.
[0083]
[Table 1]

[0084]
As is clear from Table 1, a heat-sensitive recording layer containing an electron-donating, usually colorless or light-colored dye precursor and an electron-accepting compound that reacts upon heating to form the dye precursor is formed on the support. In the provided heat-sensitive recording material, Examples 1 to 10 containing the urea urethane compound represented by the general formula (1) as the electron-accepting compound in the heat-sensitive recording layer do not contain the electron-accepting compound. It can be seen that the storage stability of the image area is significantly improved as compared with Comparative Example 2.
[0085]
Further, since Examples 1 to 10 contain 4-hydroxy-4'-methyldiphenylsulfone used in the heat-sensitive recording layer in the present invention, Comparative Example 1 containing no 4-hydroxy-4'-methyldiphenylsulfone was used. It can be seen that the thermal response is remarkably improved as compared with.
[0086]
Further, a thermosensitive recording material provided with a thermosensitive recording layer containing an electron-donating usually colorless to light-colored dye precursor on a support and an electron-accepting compound that reacts upon heating to form the dye precursor. In the thermosensitive recording layer, as the electron accepting compound, in addition to the urea urethane compound represented by the general formula (1), another electron accepting compound other than 4-hydroxy-4′-allyloxydiphenyl sulfone is used. Comparative Examples 3 to 7 contained therein were excellent in thermal responsiveness as much as Examples 1 to 10, but were inferior in storage stability of the image area to Examples 1 to 10 and had a white background. It is low, and is inferior in whiteness of the background after the heat resistance test.
[0087]
In Examples 2, 4, and 6, in which stearic acid amide was further added to the heat-sensitive recording material of the present invention, the thermal responsiveness was greatly improved as compared with Examples 1, 3, and 5, respectively. In addition, the storage stability of the image is improved.
[0088]
【The invention's effect】
In a heat-sensitive recording material provided with a heat-sensitive recording layer containing an electron-accepting usually colorless to light-colored dye precursor and an electron-accepting compound that reacts upon heating to develop the dye precursor, By using a urea urethane compound represented by the general formula (1) as an electron-accepting compound in the recording layer and using the electron-accepting compound in combination with 4-hydroxy-4′-allyloxydiphenyl sulfone, A heat-sensitive recording material having excellent properties, color density, and storage stability of an image area, and having good background whiteness can be obtained. The content ratio by mass of the electron-accepting compound to 4-hydroxy-4′-allyloxydiphenylsulfone is preferably about 1 to 20 parts by mass, more preferably 5 to 20 parts by mass, per 1 part by mass of the electron-accepting compound. About 10 to 10 parts by mass.
Further, in the heat-sensitive recording material of the present invention, by using a saturated fatty acid monoamide represented by the general formula (2) as an auxiliary sensitizer in the heat-sensitive recording layer, the coloring sensitivity is remarkably improved.

Claims (2)

Thermal recording in which a heat-sensitive recording layer containing, as a main component, an electron-donating usually colorless to light-colored dye precursor and an electron-accepting compound that reacts upon heating to form the dye precursor is formed on a support. In the material, it is preferable that the heat-sensitive recording layer contains, as the electron-accepting compound, a urea urethane compound represented by the general formula (1) and 4-hydroxy-4′-allyloxydiphenyl sulfone. Characteristic thermal recording material.

2. The thermosensitive recording material according to claim 1, wherein the thermosensitive recording layer contains a saturated fatty acid monoamide represented by the general formula (2) as an auxiliary sensitizer.

(In the formula, R ₁ represents an alkyl group having 11 to 21 carbon atoms.)