JP3597253B2 - Thermal recording material - Google Patents

Description

【０００９】
式中、Ｒ^１ 及びＲ^２ は各々同一でも異なっていてもよく、炭素数１〜８のアルキル基を表す。
【００１０】
また、請求項２に係る本発明の感熱記録材料は、前記電子受容性化合物が、下記一般式（２）で表されるサリチル酸誘導体多価金属塩を含有することを特徴とする。
【００１１】
【化４】

【００１２】
式中、Ｒ^３ は水素原子、アルキル基、アリール基、アラルキル基、アルコキシ基又はアリールオキシ基を表し、Ｍは、Ｚｎ、Ｃａ及びＡｌを表し、ｍは１〜４の整数を表し、ｎは２又は３の整数を表す。
【００１３】
請求項３に係る本発明の感熱記録材料は、前記ベンゾトリアゾール系紫外線吸収剤が前記式（１−Ｉ）又は（１− II ）で表されることを特徴とする。
【００１４】
以下に本発明を詳細に説明する。
本発明の感熱記録材料においては、特に、前記サリチル酸誘導体多価金属塩及び、前記一般式（１）で表されるベンゾトリアゾール系紫外線吸収剤を乳化物として使用することを要する。乳化物の調製法は特に制限されるものではなく、従来公知の方法により調製することができる。
【００１５】
本発明の感熱記録材料に用いられる一般式（１）で表されるベンゾトリアゾール系紫外線吸収剤において、Ｒ¹ 及びＲ² は各々同一でも異なっていてもよく、炭素数１〜８のアルキル基を表すものであるが、各々のアルキル基は、直鎖状であっても分岐を有するものであってもよい。このアルキル基の具体例としては、メチル基、エチル基、ｎ−プロピル基、イソプロピル基、ｎ−ブチル基、イソブチル基、ｓｅｃ−ブチル基、tert−ブチル基、２−メチルブチル基、ｎ−ペンチル基、ｉ−ペンチル基、ｎ−ヘキシル基、ｎ−オクチル基、２−エチルヘキシル基、シクロペンチル基、シクロヘキシル基等が挙げられる。Ｒ¹ 及びＲ² は、メチル基、エチル基、tert−ブチル基、２−エチルヘキシル基等が好ましい。
【００１６】
本発明の感熱記録材料に含まれる一般式（１）で表されるベンゾトリアゾール系紫外線吸収剤は１種であっても、２種以上の混合物として含まれてもよい。
【００１７】
次に本発明に係る一般式（１）で表されるベンゾトリアゾール系紫外線吸収剤の具体的な化合物を例示するが、本発明はこれにより限定されるものではない。
【００１８】
【化５】

【００１９】
本発明の感熱記録材料に含まれるサリチル酸誘導体多価金属塩には特に制限はなく、例えば、特公平６−１５２９２号に例示されたもの等が好適に使用できる。中でも前記一般式（２）で表されるサリチル酸誘導体多価金属塩が好ましく用いられ、これは、本発明の感熱記録材料において電子受容性化合物としての機能を有する。
【００２０】
前記一般式（２）において、Ｒ^３ は、水素原子、アルキル基、アリール基、アラルキル基、アルコキシ基又はアリールオキシ基を表し、炭素数１から１８の直鎖又は分岐を有するアルキル基及び炭素数４から１２のシクロアルキル基、炭素数７から１８のアラルキル基、炭素数６から２０のアリール基、炭素数１から１８のアルコキシ基、炭素数６から１０のアリール基、炭素数６から１０のアリールオキシ基が好ましく、特に、炭素数１から１２のアルキル基、炭素数５から６のシクロアルキル基、炭素数７から１２のアラルキル基、炭素数６から１２のアリール基が好ましい。これらは更に炭素数１から８のアルキル基、炭素数１から８のアルコキシ基、炭素数６から１０のアリール基、炭素数６から１０のアリールオキシ基、ハロゲン原子などで置換されていてもよい。
【００２１】
Ｒ^３ として具体的にはメチル基、エチル基、ｎ−プロピル基、ｉ−プロピル基、ｎ−ブチル基、ｉ−ブチル基、ｓｅｃ−ブチル基、ｎ−ペンチル基、ｉ−ペンチル基、ｎ−ヘキシル基、ｎ−オクチル基、２−エチルヘキシル基、ｎ−デシル基、ｎ−ドデシル基、シクロペンチル基、シクロヘキシル基、ベンジル基、２−フェネチル基、１−フェネチル基、フェニル基、ｐ−トリル基、ｐ−メトキシフエニル基、ｐ−クロロフェニル基、２−メトキシエチル基、２−（２−メトキシエトキシ）エチル基、２−フェノキシエチル基、２−フェノキシプロピル基、３−フェノキシプロピル基等が挙げられる。ｍは１〜４の整数を表すが、ここで、Ｒ^３ はサリチル酸の基本骨格に付加する１乃至４個の官能基を示し、ｍは付加する官能基の数を表し、好ましくは１又は２である。
【００２２】
Ｍは、Ｚｎ、Ｃａ及びＡｌを表し、好ましくはＺｎであり、ｎは前記多価金属が２価或いは３価であることを表し、ＭがＺｎの場合、ｎは２を表す。
【００２３】
本発明の感熱記録材料に含まれるサリチル酸誘導体は、好ましくは一般式（２）で表されるサリチル酸誘導体を含み、１種のみが含まれていても、２種以上含まれてもよい。
【００２４】
次に本発明に係る一般式（２）で表されるサリチル酸誘導体の具体的な化合物を例示するが、本発明はこれにより限定されるものではない。
【００２５】
【化６】

【００２６】
サリチル酸誘導体の好ましい添加量は、電子受容性化合物の２０〜７０重量％である。
【００２７】
本発明の感熱記録材料に用いられる他の電子受容性化合物（顕色剤）としては、フェノール誘導体、前記一般式（２）で表される以外のサリチル酸誘導体、芳香族カルボン酸の金属塩、酸性白土、ベントナイト、ノボラック樹脂、金属処理ノボラック樹脂、金属錯体などが挙げられる。
【００２８】
これらの例は特公昭４０−９３０９号、特公昭４５−１４０３９号、特開昭５２−１４０４８３号、特開昭４８−５１５１０号、特開昭５７−２１０８８６号、特開昭５８−８７０８９号、特開昭５９−１１２８６号、特開昭６０−１７６７９５号、特開昭６１−９５９８８号等に記載されている。
【００２９】
この電子受容性化合物は、必要に応じて添加剤を単独又は混合して、スチレンブタジエンラテックス、ポリビニールアルコールの如きバインダー中に分散させ、顔料とともに紙、プラスチックシート、樹脂コートテッド紙などの支持体に塗布することにより顕色剤シートを得ることができる。
【００３０】
バインダーとしてはカルボキシ変性スチレンブタジエンラテックスと水溶性高分子を併用することが、耐光性、耐水性の点から好ましい。また顔料としては平均粒径５．０μ以下の炭酸カルシウムを、全顔料の６０重量％以上用いるのが、顕色能の点から好ましい。
【００３１】
本発明の感熱記録材料において用いられる電子供与性無色染料には特に制限はなく、従来より公知のトリフェニルメタンフタリド系化合物、フルオラン系化合物、フェノチアジン系化合物、インドリルフタリド系化合物、ロイコオーラミン系化合物、ローダミンラクタム系化合物、トリフェニルメタン系化合物、トリアゼン系化合物、スピロピラン系化合物、フルオレン系化合物など各種の染料化合物を用いることができる。フタリド類の具体例は米国再発行特許明細書第２３，０２４号、米国特許明細書第３，４９１，１１１号、同第３，４９１，１１２号、同第３，４９１，１１６号及び同第３，５０９，１７４号、フルオラン類の具体例は米国特許明細書第３，６２４，１０７号、同第３，６２７，７８７号、同第３，６４１，０１１号、同第３，４６２，８２８号、同第３，６８１，３９０号、同第３，９２０，５１０号、同第３，９５９，５７１号、スピロジピラン類の具体例は米国特許明細書第３，９７１，８０８号、ピリジン系及びピラジン系化合物類は米国特許明細書第３，７７５，４２４号、同第３，８５３，８６９号、同第４，２４６，３１８号、フルオレン系化合物の具体例は特開昭６３−９４８７８号等に記載されている。
【００３２】
本発明に係る電子供与性無色染料の塗布量は特には限定されないが、総量で０．１〜３．０ｇ／ｍ^２ 、特には１．０〜２．５ｇ／ｍ^２ が好ましい。
【００３３】
前記電子供与性無色染料は、マイクロカプセル中に内包されて感熱記録層に含まれることが、印字画像を長期的に安定化させる、即ち、経時的に消色しにくいという観点から好ましい。
【００３４】
カプセルの製造方法については、米国特許２，８００，４５７号、同２，８００，４５８号に記載された親水性コロイドゾルのコアセルベーションを利用した方法、米国特許３，２８７，１５４号、英国特許８６７，７９７号、同９５０，４４３号、同９８９，２６４号、同９９０，４４３号、同１，０９１，０７６号、特公昭３８−１９５７４号、同４２−４４６号、同４２−７７１号などに記載された界面重合法、米国特許３，４１８，２５０号、同３，６６０，３０４号に記載されたポリマーの析出による方法、米国特許３，４１８，２５０号に記載されたイソシアネートポリオール壁材料を用いる方法、米国特許３，９１４，５１１号に記載されたイソシアネート壁材料を用いる方法、米国特許４，００１，１４０号、同４，０８７，３７６号、同４，０８９，８０２号に記載された尿素−ホルムアルデヒド系、尿素ホルムアルデヒド−レゾルシノール系壁材料を用いるメラミン−ホルムアルデヒド樹脂、ヒドロキシプロピルピルセルロース等の壁形成材料を用いる方法、特公昭３６−９１６８号、特開昭５１−９０７９号に記載されたモノマーの重合によるｉｎ−ｓｉｔｕ法、英国特許９５２，８０７号、同９６５，０７４号に記載された電解分散冷却法、米国特許３，１１１，４０７号、英国特許９３０，４２２号に記載されたスプレードライング法などがある。これらに限定されるものではないが、芯物質を乳化した後マイクロカプセル壁として高分子膜を形成することが好ましい。
【００３５】
一般的には、電子供与性無色染料を、溶媒（アルキル化ナフタレン、アルキル化ジフェニル、アルキル化ジフェニルメタン、アルキル化ターフェニル、塩素化パラフィンなどの合成油：木綿油、ヒマシ油などの植物油：動物油：鉱物油あるいはこれらの混合物など）に溶解し、これをマイクロカプセル中に含有させ、紙、上質紙、プラスチックシート、樹脂コートテッド紙などに塗布することにより感熱記録層が形成された発色剤シートをうる。
【００３６】
本発明の感熱記録材料においては、電子供与性無色染料は従来より公知の蛍光増白剤、酸化防止剤及び一般式（１）で表されるベンゾトリアゾール系紫外線吸収剤以外の紫外線吸収剤と併用してもよい。
【００３７】
併用できる紫外線吸収剤として好ましいものは、ベンゾフエノン系紫外線吸収剤、一般式（１）で表される以外のベンゾトリアゾール系紫外線吸収剤、サリチル酸系紫外線吸収剤、シアノアクリレート系紫外線吸収剤、オキザリックアシッドアニリド系紫外線吸収剤などが挙げられる。これらの例は特開昭４７−１０５３７号、同５８−１１１９４２号、同５８−２１２８４４号、同５９−１９９４５号、同５９−４６６４６号、同５９−１０９０５５号、同６３−５３５４４号、特公昭３６−１０４６６号、同４２−２６１８７号、同４８−３０４９２号、同４８−３１２５５号、同４８−４１５７２号、同４８−５４９６５号、同５０−１０７２６号、米国特許２，７１９，０８６号、同３，７０７，３７５号、同３，７５４，９１９号、同４，２２０，７１１号などに記載されている。
【００３８】
併用できる蛍光増白剤として好ましいものは、クマリン系蛍光増白剤などが挙げられる。これらの例は特公昭４５−４６９９号、同５４−５３２４号などに記載されている。
【００３９】
併用できる酸化防止剤として好ましいものは、ヒンダードアミン系酸化防止剤、ヒンダードフエノール系酸化防止剤、アニリン系酸化防止剤、キノリン系酸化防止剤などが挙げられる。これらの例は特開昭５９−１５５０９０号、同６０−１０７３８３号、同６０−１０７３８４号、同６１−１３７７７０、同６１−１３９４８１号、同６１−１６０２８７などに記載されている。
【００４０】
併用できる紫外線吸収剤、蛍光増白剤、酸化防止剤の使用量としては０．０５〜１．０ｇ／ｍ^２ 、特には０．１〜０．４ｇ／ｍ^２ が好ましい。
【００４１】
使用される電子供与性無色染料と電子受容性化合物の比は、重量比で１：１０から１：１の間が好ましく、さらには１：５から２：３の間が特に好ましい。
【００４２】
前記の各配合成分で感熱記録材料を構成する場合には、特開昭６２−１４４９８９号、特開平１−８７２９１号明細書等に記載されているような形態をとる。具体的には、カプセルに内包された電子供与性無色染料と共に分散される電子受容性化合物は分散媒中で１０μ以下、好ましくは３μ以下の粒径まで粉砕分散して用いられる。分散媒としては、一般に０．５ないし１０％程度の濃度の水溶高分子水溶液が用いられ、分散はボールミル、サンドミル、横型サンドミル、アトライタ、コロイダルミル等を用いて行われる。
【００４３】
その際、熱応答性を改良するために熱可融性物質を感熱発色層に含有させることができる。熱可融性物質としては、芳香族エーテル、チオエーテル、エステル及び又は脂肪族アミド又はウレイドなどがその代表である。
【００４４】
これらの例は特開昭５８−５７９８９号、同５８−８７０９４号、同６１−５８７８９号、同６２−１０９６８１号、同６２−１３２６７４号、同６３−１５１４７８号、同６３−２３５９６１号、特開平２−１８４４８９号、同２−２１５５８５号などに記載されている。
【００４５】
これらは電子供与性無色染料と同時又は電子受容性化合物と同時に微分散して用いられる。これらの使用量、電子受容性化合物に対して、２０％以上３００％以下の重量比で添加され、特に４０％以上１５０％以下が好ましい。
【００４６】
このようにして得られた塗液には、さらに種々の要求を満たす為に必要に応じて添加剤が加えられる。添加剤の例としては記録時の記録ヘッドの汚れを防止するために、バインダー中に無機顔料、ポリウレアフィラー等の吸油性物質を分散させておくことが行われ、さらにヘッドに対する離型性を高めるために脂肪酸、金属石鹸などが添加される。したがって一般には、発色に直接寄与する電子供与性無色染料、電子受容性化合物の他に、熱可融性物質、顔料、ワックス、帯電防止剤、紫外線吸収剤、消泡剤、導電剤、蛍光染料、界面活性剤などの添加剤が支持体上に塗布され、記録材料が構成されることになる。さらに必要に応じて感熱記録層の表面に保護層を設けてもよい。
【００４７】
通常、電子供与性無色染料及び電子受容性化合物は、バインダー中に分散して塗布される。バインダーとしては水溶性のものが一般的であり、ポリビニルアルコ−ル、ヒドロキシエチルセルロース、ヒドロキシプロピルセルロース、エピクロルヒドリン変性ポリアミド、エチレン−無水マレイン酸共重合体、スチレン−無水マレイン酸共重合体、イソブチレン−無水マレインサリチル酸共重合体、ポリアクリル酸、ポリアクリル酸アミド、メチロール変性ポリアクリルアミド、デンプン誘導体、カゼイン、ゼラチン等があげられる。またこれらのバインダーに耐水性を付与する目的で耐水化剤を加えたり、疎水性ポリマーのエマルジョン、具体的には、スチレン−ブタジエンゴムラテックス、アクリル樹脂エマルジョン等を加えることもできる。これらの使用量としては、０．４〜５ｇ／ｍ^２ が好ましく、さらには０．８〜１．６ｇ／ｍ^２ が好ましい。
【００４８】
得られた感熱塗液は、上質紙、下塗り層を有する上質紙、合成紙、プラスチックフィルム等に塗布される。この際ＪＩＳ−８１１９で規定される平滑度が５００秒以上特に８００秒以上の支持体を用いるのがドット再現性の点から特に好ましい。
【００４９】
本発明の感熱記録材料においてはその必要に応じて、公知のワックス、帯電防止剤、消泡剤、導電剤、蛍光染料、界面活性剤、紫外線吸収剤プリカーサーなど各種添加剤を使用することができる。
【００５０】
本発明の感熱記録材料には必要に応じて感熱記録層の表面に保護層を設けてもよい。保護層は必要に応じて二層以上積層してもよい。保護層に用いる材料としては、ポリビニルアルコール、カルボキシ変性ポリビニルアルコール、酢酸ビニル−アクリルアミド共重合体、珪素変性ポリビニルアルコール、澱粉、変性澱粉、メチルセルロース、カルボキシメチルセルロース、ヒドロキシメチルセルロース、ゼラチン類、アラビアゴム、カゼイン、スチレン−マレイン酸共重合体加水分解物、スチレン−マレイン酸共重合物ハーフエステル加水分解物、イソブチレン−無水マレイン酸共重合体加水分解物、ポリアクリルアミド誘導体、ポリビニルピロリドン、ポリスチレンスルホン酸ソーダ、アルギン酸ソーダなどの水溶性高分子化合物、及びスチレン−ブタジエンゴムラテックス、アクリロニトリル−ブタジエンゴムラテックス、アクリル酸メチル−ブタジエンゴムラテックス、酢酸ビニルエマルジョン等のラテックス類が用いられる。保護層の水溶性高分子化合物を架橋してより一層保存安定性を向上させることもでき、その架橋剤としては公知の架橋剤を使用することができる。具体的にはＮ−メチロール尿素、Ｎ−メチロールメラミン、尿素−ホルマリン等の水溶性初期縮合物、グリオキザール、グルタルアルデヒド等のジアルデヒド化合物類、硼酸、硼砂等の無機系架橋剤、ポリアミドエピクロルヒドリンなどが挙げられる。保護層には、さらに公知の顔料、金属石鹸、ワックス、界面活性剤などを使用することもできる。保護層の塗布量は０．２〜５ｇ／ｍ^２ が好ましく、さらには０．５〜２ｇ／ｍ^２ が好ましい。またその膜厚は０．２〜５μｍが好ましく、特に０．５〜２μｍが好ましい。
【００５１】
本発明の感熱記録材料に保護層を使用する場合、保護層中に公知の紫外線吸収剤や紫外線吸収剤プレカーサーを含有してもよい。
【００５２】
本発明の記録材料に使用できる支持体としては、酸性紙、中性紙、コート紙、プラスチックフィルムラミネート紙、合成紙、プラスチックフィルムなどを使用することができる。さらにこれら支持体に公知の下塗り層を設けてもよい。この下塗り層は上記保護層と同様にして設けることができる。
【００５３】
支持体のカールバランスを補正するため或いは、裏面からの耐薬品性を向上させる目的で、バックコート層を設けてもよく、また裏面に接着剤層を介して剥離紙を組み合わせてラベルの形態にしてもよい。このバックコート層についても上記保護層と同様にして設けることができる。
【００５４】
【実施例】
以下、実施例によって本発明を記述するが、本発明はこれにより限定されるものではない。
（実施例１）
顕色剤（電子受容性化合物）乳化分散液（Ａ）の調製
前記式（２−Ｉ）で表される化合物、下記式（Ｅ−１）、（Ｅ−２）、（Ｅ−３）、（Ｅ−４）、（Ｅ−５）で表わされる化合物及び前記式（１−Ｉ）で表わされる化合物を、それぞれ１６．２ｇ、１０．４ｇ、５．８ｇ、１．４ｇ、２．２ｇ、１．４ｇ及び４．２ｇをＴＣＰ（大八化学社製オイル）１．０ｇＤＥＭ（大八化学社製オイル）０．５ｇ及び酢酸エチル２０ｇを混合した溶液を加熱し溶解させた。
【００５５】
【化７】

【００５６】
得られた溶液をポリビニルアルコール１５％溶液（ＰＶＡ２０５Ｃ：クラレ社製）２５．０ｇ、ポリビニルアルコール８％溶液（ＰＶＡ２１７Ｃ）４６．０ｇ、ドデシルスルホン酸ナトリウム０．５ｇ及び水７５．０ｇを混合した水相に投入し、エースホモジナイザー（商品名：日本精機（株）製）を使用し１００００ｒｐｍで３分間乳化し、平均粒子径が０．６μｍの電子受容性化合物（以下、適宜顕色剤と称する）乳化分散液を得た。
【００５７】
なお平均粒径は、レーザー回析粒度分布測定装置（ＬＡ７００：商品名、（株）堀場製作所製）を用いて測定した５０％体積平均粒子径である。以下において特に断らない限り、平均粒子径は上記の５０％体積平均粒子径を表す。
（実施例２）
顕色剤乳化分散液（Ｂ）の調製
前記実施例１記載中の顕色剤乳化分散液（Ａ）の調製において前記式（１−Ｉ）で表される化合物（ベンゾトリアゾール系紫外線吸収剤）の代わりに前記式（１−ＩＩ）で表される化合物を同重量用いた以外同様な方法により、平均粒子が０．６μｍである顕色剤乳化分散液（Ｂ）を得た。
（比較例１）
顕色剤乳化分散液（Ｃ）の調製
前記実施例１記載中の顕色剤乳化分散液（Ａ）の調製において式（１−Ｉ）で表される化合物の代わりに下記式（Ｅ−６）で表される化合物（本発明の範囲外のベンゾトリアゾール系紫外線吸収剤）を同重量用いた以外同様な方法により、平均粒子が０．６μｍである顕色剤乳化分散液（Ｃ）を得た。
【００５８】
【化８】

【００５９】
（比較例２）
顕色剤乳化分散液（Ｄ）の調製
前記実施例１記載中の顕色剤乳化分散液（Ａ）の調製において、式（１−Ｉ）で表される化合物の代わりに下記式（Ｅ−７）で表される化合物（本発明の範囲外のベンゾトリアゾール系紫外線吸収剤）を同重量用いた以外同様な方法により、平均粒子が０．６μｍである顕色剤乳化分散液（Ｄ）を得た。
【００６０】
【化９】

【００６１】
（比較例３）
顕色剤乳化分散液（Ｅ）の調製
前記実施例１記載中の顕色剤乳化分散液（Ａ）の調製において式（１−Ｉ）で表される化合物の代わりに下記式（Ｅ−８）で表される化合物（本発明の範囲外のベンゾトリアゾール系紫外線吸収剤）を同重量用いた以外同様な方法により、平均粒子が０．６μｍである顕色剤乳化分散液（Ｅ）を得た。
【００６２】
【化１０】

【００６３】
（比較例４）
顕色剤乳化分散液（Ｆ）の調製
前記実施例１記載中の顕色剤乳化分散液（Ａ）の調製において、式（２−Ｉ）、（Ｅ−１）、（Ｅ−２）、（Ｅ−３）、（Ｅ−４）及び（Ｅ−５）で表わされる化合物、それぞれ１６．２ｇ、１０．４ｇ、５．８ｇ、１．４ｇ、２．２ｇ及び１．４ｇのところを、式（Ｅ−１）、（Ｅ−２）、（Ｅ−３）、（Ｅ−４）及び（Ｅ−５）で表わされる化合物、それぞれを１８．３ｇ、１０．１ｇ、２．６ｇ、３．８ｇ及び２．６ｇに変えた以外同様な方法で平均粒子径０．６μｍの顕色剤乳化分散液（Ｆ）を得た。
（比較例５）
顕色剤乳化分散液（Ｇ）の調製
前記実施例１記載中の顕色剤乳化分散液（Ａ）の調製において、式（２−Ｉ）、（Ｅ−１）、（Ｅ−２）、（Ｅ−３）、（Ｅ−４）及び（Ｅ−５）で表わされる化合物、それぞれ１６．２ｇ、１０．４ｇ、５．８ｇ、１．４ｇ、２．２ｇ及び１．４ｇのところを、式（Ｅ−１）、（Ｅ−２）、（Ｅ−３）、（Ｅ−４）及び（Ｅ−５）で表わされる化合物、それぞれ１８．３ｇ、１０．１ｇ、２．６ｇ、３．８ｇ及び２．６ｇに変え、式（１−Ｉ）で表わされる化合物の代わりに式（１−ＩＩ）で表わされる化合物を同重量用いた以外同様な方法で、平均粒子径０．６μｍの顕色剤乳化分散液（Ｇ）を得た。
（比較例６）
顕色剤乳化分散液（Ｈ）の調製
前記実施例１記載中の顕色剤乳化分散液（Ａ）の調製において、式（２−Ｉ）、（Ｅ−１）、（Ｅ−２）、（Ｅ−３）、（Ｅ−４）及び（Ｅ−５）で表わされる化合物、それぞれ１６．２ｇ、１０．４ｇ、５．８ｇ、１．４ｇ、２．２ｇ及び１．４ｇのところを、式（Ｅ−１）、（Ｅ−２）、（Ｅ−３）、（Ｅ−４）及び（Ｅ−５）で表わされる化合物、それぞれ１８．３ｇ、１０．１ｇ、２．６ｇ、３．８ｇ及び２．６ｇに変え、式（１−Ｉ）で表わされる化合物の代わりに式（Ｅ−６）で表わされる化合物を同重量用いた以外同様な方法で、平均粒子径０．６μｍの顕色剤乳化分散液（Ｈ）を得た。
（比較例７）
顕色剤乳化分散液（Ｉ）の調製
前記実施例１記載中の顕色剤乳化分散液（Ａ）の調製において、式（２−Ｉ）、（Ｅ−１）、（Ｅ−２）、（Ｅ−３）、（Ｅ−４）及び（Ｅ−５）で表わされる化合物、それぞれ１６．２ｇ、１０．４ｇ、５．８ｇ、１．４ｇ、２．２ｇ及び１．４ｇのところを式（Ｅ−１）、（Ｅ−２）、（Ｅ−３）、（Ｅ−４）及び（Ｅ−５）、それぞれを１８．３ｇ、１０．１ｇ、２．６ｇ、３．８ｇ及び２．６ｇに変え、式（１−Ｉ）で表わされる化合物の代わりに式（Ｅ−７）で表わされる化合物を同重量用いた以外同様な方法で平均粒子径０．６μｍの顕色剤乳化分散液（Ｉ）を得た。
（比較例８）
顕色剤乳化分散液（Ｊ）の調製
前記実施例１記載中の顕色剤乳化分散液（Ａ）の調製において、式（２−Ｉ）、（Ｅ−１）、（Ｅ−２）、（Ｅ−３）、（Ｅ−４）及び（Ｅ−５）で表わされる化合物、それぞれ１６．２ｇ、１０．４ｇ、５．８ｇ、１．４ｇ、２．２ｇ及び１．４ｇのところを、式（Ｅ−１）、（Ｅ−２）、（Ｅ−３）、（Ｅ−４）及び（Ｅ−５）それぞれ、１８．３ｇ、１０．１ｇ、２．６ｇ、３．８ｇ及び２．６ｇに変え、式（１−Ｉ）で表わされる化合物の代わりに式（Ｅ−８）で表わされる化合物を同重量用いた以外同様な方法で平均粒子径０．６μｍの顕色剤乳化分散液（Ｊ）を得た。
（比較例９）
顕色剤乳化分散液（Ｋ）の調製
前記実施例１記載中の顕色剤乳化分散液（Ａ）の調製において、式（１−Ｉ）で表わされる化合物４．２ｇを取り除いた以外同様な方法により平均粒子径０．６μｍの顕色剤乳化分散液を得た。
（比較例１０）
顕色剤乳化分散液（Ｌ）の調製
前記比較例５記載の顕色剤乳化分散液（Ｇ）の調製において、式（１−ＩＩ）で表される化合物４．２ｇを取り除いた以外同様な方法により平均粒子径０．６μｍの顕色剤乳化分散液（Ｌ）を得た。
※評価１：乳化物の安定性検討
得られた顕色剤乳化分散液について乳化液作成後室温にて静置させ、１日後、その液の様子を観察した。下記表１にその結果を示す。
【００６４】
【表１】

【００６５】
析出を生じた顕色剤乳化分散液では後記の透明な感熱記録材料を提供できず、以降の評価を打ち切った。乳化物が安定に存在しえた実施例１及び２、比較例２及び９の顕色剤乳化分散液について以下に記載する評価２及び評価３を考察した。
※評価２：透過率及び目視による評価
透明な厚さ７５μｍのポリエチレンテレフタレートの一方の面に、ＳＢＲラテックスを固形分重量で０．３ｇ／ｍ^２ となるように塗布した後、下記の下塗層用塗布液を片面当たりの固形分重量が０．１ｇ／ｍ^２ となるように塗布して、下塗層を設けた透明支持体を得た。
＜塗層用塗布液の調製＞
ゼラチン５％水溶液（＃８１０：商品名、新田ゼラチン株式会社製）２００ｇ、粒子径２μｍのポリメチルメタクリレート樹脂粒子を５％分散したゼラチン分散物０．５ｇ、１，２−ベンゾチアゾリン−３−オン３％水溶液１．０ｇ及びスルホン酸ジ（２−エチル）ヘキシル２％水溶液１０ｇを混合して下塗り層塗布液を得た。
＜サンプルの調製＞
以上の方法で調製したクリアーな透明支持体上に評価１で析出を生じなかった顕色剤乳化分散液をそれぞれ固形分で５．０ｇ／ｍ^２ となる様に塗布した。（４水準）
サンプルの透過率測定
得られたサンプルの透過率スペクトルを、分光光度計Ｕ−３４００（日立製作所（株）製）を用いて、波長３２０ｍｍ〜５００ｍｍの領域で測定した。
【００６６】
得られた結果を図１に示した。
目視の印象
上記４種のサンプルをシヤーカスチン（精光社製）越しに観察したところ、比較例２は明らかに黄色いが、実施例１及び２はわずかに黄色く見え、比較例９は黄色く見えなかった。
評価３：感熱記録材料の耐光性検討
評価１で安定に存在することを確認した実施例１・２、比較例２及び９の顕色剤乳化分散物を用いて実際に感熱記録材料を作成した。
◎実施例１の顕色剤乳化分散物（Ａ）を用いた感熱記録材料の作成
＜電子供与性染料前駆体を内包したカプセル液の調製＞
下記式（Ｅ−９）、（Ｅ−１０）、（Ｅ−１１）、（Ｅ−１２）、（Ｅ−１３）、（Ｅ−１４）及び（Ｅ−６）で表される化合物、それぞれ９．８ｇ、１．４ｇ、１．９ｇ、３．０ｇ、１．０ｇ、０．４ｇ及び０．４ｇを、酢酸エチル２０ｇ中で加熱溶解させ、４０°Ｃまで徐冷させた後、タケネートＤ１１０Ｎ（商品名：武田薬品製カプセル壁剤）２．０ｇ及びタケネートＤ１２７Ｎ（同上）１１．６ｇ及びｎ−ブタノール０．４ｇを添加し、４０°Ｃで４０分間攪拌させた。
【００６７】
【化１１】

【００６８】
得られた溶液を、ポリビニルアルコール８％溶液（ＰＶＡ２１７Ｃ：クラレ株式会社製の商品名）４０ｇと水１３ｇを混合した水相に添加した後、エースホモジナイザーを用い、１００００μｍで５分間乳化分散を行った。
【００６９】
得られた乳化液に、更に水７０ｇ及びテトラエチレンペンタミン０．５ｇを添加した後、６０°Ｃで３時間カプセル化反応を行わせて、平均粒子径が０．６μｍのカプセル液を得た。
＜保護層塗布液の調製＞
水３０ｇ、ポリビニルアルコール６％水溶液（ＰＶＡ１２４Ｃ：クラレ製）２０ｇ、スルホコハク酸ジオクチルのナトリウ塩２％水溶液０．３ｇ、カオリン分散物（ポリビニルアルコール３ｇを水１００ｇに混合した液にカオリン３５ｇをポールミルで分散させたもの）３．０ｇ及びハイドリンＺ（商品名：中京油脂株式会社製）０．５ｇを混合して保護層塗布液を得た。
＜下塗層を設けた透明支持体の調製＞
透明な厚さ１７５μｍのポリエテレンテレフタレートの一方の面に、ＳＢＲラテックスを固形分重量で０．３ｇ／ｍ^２ となるように塗布した後、下記の下塗層用塗布液を片面当たりの固形分重量が０．１ｇ／ｍ^２ となるように塗布して、下塗層を設けた透明支持体を得た。
＜塗層用塗布液の調製＞
ゼラチン５％水溶液（＃８１０：新田ゼラチン株式会社製）２００ｇ、粒子径２μｍのポリメチルメタクリレート樹脂粒子を５％分散したゼラチン分散物０．５ｇ、１，２−ベンゾチアゾリン−３−オン３％水溶液１．０ｇ、スルホン酸ジ（２−エチル）ヘキシル２％水溶液１０ｇを混合して下塗り層塗布液を得た。
＜感熱記録層用塗布液の調製＞
既に調製したカプセル液（ＭＣ）５．０ｇ、顕色剤乳化分散液（Ａ）（乳化分散後１日放置したもの）１５ｇ及び水１０ｇを混合して感熱記録用塗布液（１）を得た。
＜感熱記録材料の調製＞
既に調製した下塗り層を設けた透明支持体の一方の面に、感熱記録用塗布液（１）を固形分重量で１４ｇ／ｍ^２ となるように塗布・乾燥した後、その上に調製済の保護層用塗布液を固形分重量で２．５ｇ／ｍ^２ となる様に塗布・乾燥して、本発明の感熱記録材料を得た。
◎実施例２の顕色剤乳化分散液（Ｂ）を用いた感熱記録材料の作成
前記実施例１の顕色剤乳化分散液（Ａ）を用いた感熱記録材料の作成において、感熱記録用塗布液の調製時に顕色剤乳化分散液（Ａ）の代わりに顕色剤乳化分散液（Ｂ）を同重量用いた以外同様な方法で、感熱記録材料を得た。
◎比較例２の顕色剤乳化分散液（Ｄ）を用いた感熱記録材料の作成
前記実施例１の顕色剤乳化分散液（Ａ）を用いた感熱記録材料の作成において、感熱記録用塗布液の調製時に顕色剤乳化分散液（Ａ）の代わりに顕色剤乳化分散液（Ｄ）を同重量用いた以外同様な方法で、感熱記録材料を得た。
◎比較例９の顕色剤乳化分散液（Ｋ）を用いた感熱記録材料の作成
前記実施例１の顕色剤乳化分散液（Ａ）を用いた感熱記録材料の作成において、感熱記録用塗布液の調製時に顕色剤乳化分散液（Ａ）の代わりに顕色剤乳化分散液（Ｋ）を同重量用いた以外同様な方法で感熱記録材料を得た。
※耐光性評価
得られた４種の感熱記録材料を未印字のままウェザー・オ・メーター（ＡＴＬＡＳ（ｉ６５）：商品名、東洋精機社製）中で２４ｈｒ光照射した。この際、光照射前後の材料の透過濃度（Ｙｅｌｌｏｗ値）をＴＤ９０４（マクベス社製）を用いて測定した。結果を下記表２に示す。
【００７０】
【表２】

【００７１】
実施例１、２に用いた顕色剤乳化分散液を用いた感熱記録材料は、材料の地肌の黄味をおさえ、なおかつ、２４時間の光照射後の黄変も極めて少なく、地肌耐光性向上に寄与する顕色剤乳化分散液であることが分かる。
【００７２】
【発明の効果】
本発明の感熱記録材料は、地肌即ち白地部分の着色、黄変がなく、耐光性に優れ、さらには、電子受容性化合物乳化物の安定性に優れ、良好な発色を達成しうるという優れた効果を示した。
【図面の簡単な説明】
【図１】透明支持体上に顕色剤乳化分散液塗布したサンプルの透過率スペクトルを示すグラフである。[0001]
[Industrial applications]
The present invention relates to a heat-sensitive recording material, and in particular, includes a salicylic acid derivative polyvalent metal salt as an electron-accepting compound and a specific benzotriazole-based ultraviolet absorber, without yellowing of the background, and emulsification of the electron-accepting compound. The present invention relates to a thermosensitive recording material having a stable material.
[0002]
[Prior art]
Recording materials using an electron-donating colorless dye and an electron-accepting compound are already well known as pressure-sensitive paper, heat-sensitive paper, photosensitive pressure-sensitive paper, energized heat-sensitive recording paper, heat-sensitive transfer paper, and the like. For example, British Patent 2,140,449, U.S. Pat. No. 4,480,052, U.S. Pat. No. 4,436,920, JP-B-60-23992, JP-A-57-179636, JP-A-60-123556, and JP-A-60-123557 are detailed. .
[0003]
In recent years, as a recording material, researches on (1) improvement of characteristics such as (1) color density and color sensitivity and (2) robustness of a color body have been earnestly conducted.
[0004]
In particular, heat-sensitive recording materials are described in detail in Japanese Patent Publication No. 43-4160, and these heat-sensitive recording systems have been applied to various fields such as facsimile machines and printers, and needs have been expanding. Since these heat-sensitive recording materials are primary colors, the reaction between the electron-donating colorless dye and the electron-accepting compound is caused not only by heat but also by a solvent or the like, or the color formed by the heat reaction is discolored. Had the disadvantages of Attempts have been made to solve this problem, as disclosed in JP-B-51-43386, JP-A-53-17347, and JP-A-56-72996, all of which have insufficient effect of preventing discoloration and fading. Although it is effective, it has a drawback such as generation of color (fog) on a white background portion.
[0005]
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to provide a heat-sensitive recording material which is free from coloring or yellowing of the background, that is, a white background, and has excellent light fastness. An object of the present invention is to provide a heat-sensitive recording material capable of achieving color development.
[0006]
[Means for Solving the Problems]
As a result of intensive studies, the present inventors have found that a polyvalent metal salt of a salicylic acid derivative and a specific benzotriazole-based ultraviolet absorber are contained.Electron-donating colorless using emulsified dispersionDye is encapsulated in microcapsulesIncludingIt has been found that the above-mentioned object can be achieved by having the present invention, and the present invention has been completed.
[0007]
That is, the heat-sensitive recording material of the present invention is a heat-sensitive recording material provided with a heat-sensitive recording layer containing a colorless electron-donating dye and an electron-accepting compound encapsulated in microcapsules on a support. , Microcapsules containing an electron-donating colorless dyeA dispersion, andEmulsified dispersion containing salicylic acid derivative polyvalent metal salt and benzotriazole-based ultraviolet absorber represented by the following general formula (1)Formed by applying and drying a coating solution containingIt is characterized by the following.
[0008]
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[0009]
Where R¹  And R²  May be the same or different and each represents an alkyl group having 1 to 8 carbon atoms.
[0010]
The heat-sensitive recording material of the present invention according to claim 2 is characterized in that the electron-accepting compound contains a salicylic acid derivative polyvalent metal salt represented by the following general formula (2).
[0011]
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[0012]
Where R³Represents a hydrogen atom, an alkyl group, an aryl group, an aralkyl group, an alkoxy group or an aryloxy group, M represents Zn, Ca and Al, m represents an integer of 1 to 4, and n represents an integer of 2 or 3 Represents
[0013]
The heat-sensitive recording material of the present invention according to claim 3, whereinThe benzotriazole-based ultraviolet absorber is represented by the formula (1-I) or (1- II )It is characterized by the following.
[0014]
Hereinafter, the present invention will be described in detail.
In the heat-sensitive recording material of the present invention, in particular, the salicylic acid derivative polyvalent metal salt and the benzotriazole-based ultraviolet absorber represented by the general formula (1) are used as an emulsion.It takes.The method for preparing the emulsion is not particularly limited, and the emulsion can be prepared by a conventionally known method.
[0015]
In the benzotriazole-based ultraviolet absorber represented by the general formula (1) used in the heat-sensitive recording material of the present invention, R¹ And R^Two May be the same or different, CharcoalIt represents an alkyl group having a prime number of 1 to 8, and each alkyl group may be linear or branched. Specific examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a 2-methylbutyl group, and an n-pentyl group. , I-pentyl, n-hexyl, n-octyl, 2-ethylhexyl, cyclopentyl, cyclohexyl and the like. R¹ And R^Two Is preferably a methyl group, an ethyl group, a tert-butyl group, a 2-ethylhexyl group, or the like.New
[0016]
The benzotriazole-based ultraviolet absorber represented by the general formula (1) contained in the heat-sensitive recording material of the present invention may be used alone or as a mixture of two or more.
[0017]
Next, specific compounds of the benzotriazole-based ultraviolet absorber represented by the general formula (1) according to the present invention will be exemplified, but the present invention is not limited thereto.
[0018]
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[0019]
The salicylic acid derivative polyvalent metal salt contained in the heat-sensitive recording material of the present invention is not particularly limited, and for example, those exemplified in JP-B-6-15292 can be suitably used. Above all, a salicylic acid derivative polyvalent metal salt represented by the general formula (2) is preferably used, and has a function as an electron accepting compound in the heat-sensitive recording material of the present invention.
[0020]
In the general formula (2), R³Represents a hydrogen atom, an alkyl group, an aryl group, an aralkyl group, an alkoxy group or an aryloxy group, and is a linear or branched alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 4 to 12 carbon atoms, An aralkyl group having 7 to 18 carbon atoms, an aryl group having 6 to 20 carbon atoms, an alkoxy group having 1 to 18 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aryloxy group having 6 to 10 carbon atoms are preferable. An alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 6 carbon atoms, an aralkyl group having 7 to 12 carbon atoms, and an aryl group having 6 to 12 carbon atoms are preferable. These may be further substituted with an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, an aryl group having 6 to 10 carbon atoms, an aryloxy group having 6 to 10 carbon atoms, a halogen atom, or the like. .
[0021]
R³Specifically, methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, sec-butyl, n-pentyl, i-pentyl, n-hexyl , N-octyl group, 2-ethylhexyl group, n-decyl group, n-dodecyl group, cyclopentyl group, cyclohexyl group, benzyl group, 2-phenethyl group, 1-phenethyl group, phenyl group, p-tolyl group, p- Examples include a methoxyphenyl group, a p-chlorophenyl group, a 2-methoxyethyl group, a 2- (2-methoxyethoxy) ethyl group, a 2-phenoxyethyl group, a 2-phenoxypropyl group, and a 3-phenoxypropyl group. m represents an integer of 1 to 4, where R³Represents 1 to 4 functional groups added to the basic skeleton of salicylic acid, and m represents the number of functional groups to be added, and is preferably 1 or 2.
[0022]
M represents Zn, Ca and Al, preferably Zn, and n represents that the polyvalent metal is divalent or trivalent. When M is Zn, n represents 2.
[0023]
The salicylic acid derivative contained in the thermosensitive recording material of the present invention preferably contains a salicylic acid derivative represented by the general formula (2), and may contain only one kind or two or more kinds.
[0024]
Next, specific examples of the salicylic acid derivative represented by the general formula (2) according to the present invention are illustrated, but the present invention is not limited thereto.
[0025]
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[0026]
The preferred addition amount of the salicylic acid derivative is 20 to 70% by weight of the electron accepting compound.
[0027]
Other electron-accepting compounds (developers) used in the heat-sensitive recording material of the present invention include phenol derivatives, salicylic acid derivatives other than those represented by the general formula (2), metal salts of aromatic carboxylic acids, and acid salts. Examples include clay, bentonite, novolak resin, metal-treated novolak resin, and metal complexes.
[0028]
These examples are described in JP-B-40-9309, JP-B-45-14039, JP-A-52-140483, JP-A-48-51510, JP-A-57-210886, JP-A-58-87089, It is described in JP-A-59-11286, JP-A-60-176799, JP-A-61-95988, and the like.
[0029]
This electron-accepting compound is dispersed alone in a binder such as styrene-butadiene latex or polyvinyl alcohol, if necessary, alone or in combination with an additive, and together with the pigment, paper, a plastic sheet, a resin-coated paper or other support. To form a color developer sheet.
[0030]
It is preferable to use a carboxy-modified styrene-butadiene latex and a water-soluble polymer in combination from the viewpoint of light resistance and water resistance. As the pigment, it is preferable to use calcium carbonate having an average particle size of 5.0 μm or less in an amount of 60% by weight or more of the total pigment from the viewpoint of color developing ability.
[0031]
The electron donating colorless dye used in the heat-sensitive recording material of the present invention is not particularly limited, and conventionally known triphenylmethanephthalide compounds, fluoran compounds, phenothiazine compounds, indolylphthalide compounds, leucoura Various dye compounds such as a min-based compound, a rhodamine lactam-based compound, a triphenylmethane-based compound, a triazene-based compound, a spiropyran-based compound, and a fluorene-based compound can be used. Specific examples of phthalides are described in U.S. Pat. No. Re. 23,024, U.S. Pat. Nos. 3,491,111, 3,491,112, 3,491,116 and 3,491,116. 3,509,174 and specific examples of fluorans are described in U.S. Pat. Nos. 3,624,107, 3,627,787, 3,641,011, and 3,462,828. No. 3,681,390, No. 3,920,510, No. 3,959,571, and specific examples of spirodipyrans are described in US Pat. No. 3,971,808, pyridine and Pyrazine compounds are described in U.S. Pat. Nos. 3,775,424, 3,853,869 and 4,246,318, and specific examples of fluorene compounds are described in JP-A-63-94878. It is described in.
[0032]
Although the coating amount of the electron donating colorless dye according to the present invention is not particularly limited, the total amount is 0.1 to 3.0 g / m2.²  , Especially 1.0 to 2.5 g / m²  Is preferred.
[0033]
It is preferable that the electron-donating colorless dye is included in the heat-sensitive recording layer by being encapsulated in microcapsules from the viewpoint of stabilizing a printed image for a long period of time, that is, it is difficult to lose color over time.
[0034]
Methods for producing capsules are described in U.S. Pat. Nos. 2,800,457 and 2,800,458, which use coacervation of hydrophilic colloid sol, U.S. Pat. No. 3,287,154, and British Patent 867,797, 950,443, 989,264, 990,443, 1,091,076, JP-B-38-19574, 42-446, 42-771, etc. Interfacial polymerization method described in US Pat. Nos. 3,418,250 and 3,660,304, and a method by precipitation of a polymer described in US Pat. No. 3,418,250, and isocyanate polyol wall material described in US Pat. No. 3,418,250. A method using an isocyanate wall material described in U.S. Pat. No. 3,914,511, and U.S. Pat. Nos. 4,001,140 and 4,087. Nos. 376 and 4,089,802, and melamine-formaldehyde resins using urea-formaldehyde-based, urea-formaldehyde-resorcinol-based wall materials, and methods using wall-forming materials such as hydroxypropylpyrucellulose. No. 9168, JP-A-51-9079, in-situ method by polymerization of monomers, British Patents 952,807 and 965,074, electrolytic dispersion cooling method, U.S. Pat. No. 407 and British Patent No. 930,422. Although not limited thereto, it is preferable to form a polymer film as a microcapsule wall after emulsifying the core substance.
[0035]
Generally, a solvent (alkylated naphthalene, alkylated diphenyl, alkylated diphenylmethane, alkylated terphenyl, chlorinated paraffin, etc., synthetic oil: vegetable oil such as cotton oil, castor oil, animal oil: Mineral oil or a mixture thereof), dissolve it in microcapsules, apply it to paper, woodfree paper, plastic sheet, resin coated paper, etc. to form a color former sheet on which a heat-sensitive recording layer is formed. sell.
[0036]
In the heat-sensitive recording material of the present invention, the electron-donating colorless dye is used in combination with a conventionally known fluorescent brightener, an antioxidant, and an ultraviolet absorber other than the benzotriazole-based ultraviolet absorber represented by the general formula (1). May be.
[0037]
Preferred as the UV absorber which can be used in combination are a benzophenone UV absorber, a benzotriazole UV absorber other than represented by the general formula (1), a salicylic acid UV absorber, a cyanoacrylate UV absorber, and oxalic. Acid anilide-based ultraviolet absorbers. Examples of these are described in JP-A-47-10537, JP-A-58-111942, JP-A-58-212844, JP-A-59-19945, JP-A-59-46646, JP-A-59-109055, JP-A-63-53544, and No. 36-10466, No. 42-26187, No. 48-30492, No. 48-31255, No. 48-41572, No. 48-54965, No. 50-10726, U.S. Pat. No. 2,719,086, Nos. 3,707,375, 3,754,919, and 4,220,711.
[0038]
Preferred examples of the fluorescent whitening agent that can be used in combination include a coumarin fluorescent whitening agent. Examples of these are described in JP-B Nos. 45-4699 and 54-5324.
[0039]
Preferred examples of the antioxidant that can be used in combination include a hindered amine antioxidant, a hindered phenol antioxidant, an aniline antioxidant, and a quinoline antioxidant. Examples thereof are described in JP-A-59-155090, JP-A-60-107383, JP-A-60-107384, JP-A-61-137770, JP-A-61-139481, and JP-A-61-160287.
[0040]
The amount of the UV absorber, the fluorescent whitening agent and the antioxidant which can be used together is 0.05 to 1.0 g / m.²  , Especially 0.1 to 0.4 g / m²  Is preferred.
[0041]
The ratio of the electron-donating colorless dye to the electron-accepting compound used is preferably between 1:10 and 1: 1 by weight, more preferably between 1: 5 and 2: 3.
[0042]
When a heat-sensitive recording material is composed of the above-mentioned components, it takes a form as described in JP-A-62-144989, JP-A-1-87291 and the like. Specifically, the electron-accepting compound dispersed together with the electron-donating colorless dye encapsulated in the capsule is used after being pulverized and dispersed in a dispersion medium to a particle size of 10 μm or less, preferably 3 μm or less. As the dispersion medium, a water-soluble polymer aqueous solution having a concentration of about 0.5 to 10% is generally used, and the dispersion is performed using a ball mill, a sand mill, a horizontal sand mill, an attritor, a colloidal mill, or the like.
[0043]
At that time, a heat-fusible substance can be contained in the thermosensitive coloring layer in order to improve the thermal response. Representative examples of the heat-fusible substance include aromatic ethers, thioethers, esters, and / or aliphatic amides and ureides.
[0044]
These examples are described in JP-A-58-57989, JP-A-58-87094, JP-A-61-58789, JP-A-62-109681, JP-A-62-132684, JP-A-63-151478, JP-A-63-233591, and JP-A-63-235961. Nos. 2-184489 and 2-215585.
[0045]
These are used in a finely dispersed state simultaneously with the electron-donating colorless dye or simultaneously with the electron-accepting compound. It is added at a weight ratio of 20% or more and 300% or less with respect to the used amount and the electron accepting compound, and particularly preferably 40% or more and 150% or less.
[0046]
Additives may be added to the thus obtained coating liquid as needed to further satisfy various requirements. Examples of the additive include dispersing an oil-absorbing substance such as an inorganic pigment or a polyurea filler in a binder in order to prevent a recording head from being stained at the time of recording, and further enhance the releasability from the head. For this purpose, fatty acids and metal soaps are added. Therefore, in general, in addition to electron donating colorless dyes and electron accepting compounds that directly contribute to color development, heat fusible substances, pigments, waxes, antistatic agents, ultraviolet absorbers, defoamers, conductive agents, fluorescent dyes Then, an additive such as a surfactant is applied on the support to form a recording material. Further, if necessary, a protective layer may be provided on the surface of the heat-sensitive recording layer.
[0047]
Usually, the colorless electron-donating dye and the electron-accepting compound are applied by being dispersed in a binder. Water-soluble binders are generally used, such as polyvinyl alcohol, hydroxyethyl cellulose, hydroxypropyl cellulose, epichlorohydrin-modified polyamide, ethylene-maleic anhydride copolymer, styrene-maleic anhydride copolymer, and isobutylene-anhydride. Maleic salicylic acid copolymer, polyacrylic acid, polyacrylamide, methylol-modified polyacrylamide, starch derivatives, casein, gelatin and the like. For the purpose of imparting water resistance to these binders, a water-proofing agent may be added, or an emulsion of a hydrophobic polymer, specifically, a styrene-butadiene rubber latex, an acrylic resin emulsion or the like may be added. The amount of these used is 0.4 to 5 g / m²  Is preferred, and more preferably 0.8 to 1.6 g / m.²  Is preferred.
[0048]
The obtained heat-sensitive coating liquid is applied to a high quality paper, a high quality paper having an undercoat layer, a synthetic paper, a plastic film or the like. In this case, it is particularly preferable to use a support having a smoothness specified by JIS-8119 of 500 seconds or more, particularly 800 seconds or more, from the viewpoint of dot reproducibility.
[0049]
In the heat-sensitive recording material of the present invention, various additives such as known waxes, antistatic agents, antifoaming agents, conductive agents, fluorescent dyes, surfactants, and ultraviolet absorber precursors can be used as necessary. .
[0050]
The heat-sensitive recording material of the present invention may have a protective layer on the surface of the heat-sensitive recording layer, if necessary. Two or more protective layers may be laminated as necessary. Materials used for the protective layer include polyvinyl alcohol, carboxy-modified polyvinyl alcohol, vinyl acetate-acrylamide copolymer, silicon-modified polyvinyl alcohol, starch, modified starch, methyl cellulose, carboxymethyl cellulose, hydroxymethyl cellulose, gelatins, gum arabic, casein, Styrene-maleic acid copolymer hydrolyzate, styrene-maleic acid copolymer half ester hydrolyzate, isobutylene-maleic anhydride copolymer hydrolyzate, polyacrylamide derivative, polyvinylpyrrolidone, polystyrene sodium sulfonate, sodium alginate Water-soluble polymer compounds such as styrene-butadiene rubber latex, acrylonitrile-butadiene rubber latex, methyl acrylate-butadiene rubber latex Latexes such as vinyl acetate emulsion is used. The storage stability can be further improved by crosslinking the water-soluble polymer compound of the protective layer, and a known crosslinking agent can be used as the crosslinking agent. Specifically, N-methylol urea, N-methylol melamine, water-soluble initial condensates such as urea-formalin, glyoxal, dialdehyde compounds such as glutaraldehyde, boric acid, inorganic crosslinking agents such as borax, polyamide epichlorohydrin and the like. No. For the protective layer, known pigments, metal soaps, waxes, surfactants and the like can be further used. The coating amount of the protective layer is 0.2 to 5 g / m²  Is more preferable, and more preferably 0.5 to 2 g / m²  Is preferred. Further, the film thickness is preferably from 0.2 to 5 μm, particularly preferably from 0.5 to 2 μm.
[0051]
When a protective layer is used in the heat-sensitive recording material of the present invention, the protective layer may contain a known ultraviolet absorber or a precursor of an ultraviolet absorber.
[0052]
As a support that can be used for the recording material of the present invention, acid paper, neutral paper, coated paper, plastic film laminated paper, synthetic paper, plastic film, and the like can be used. Further, a known undercoat layer may be provided on these supports. This undercoat layer can be provided in the same manner as the above protective layer.
[0053]
In order to correct the curl balance of the support or to improve the chemical resistance from the back surface, a back coat layer may be provided, and a release paper is combined with an adhesive layer on the back surface to form a label. You may. This back coat layer can be provided in the same manner as the above protective layer.
[0054]
【Example】
Hereinafter, the present invention will be described by way of examples, but the present invention is not limited thereto.
(Example 1)
Preparation of developer (electron accepting compound) emulsified dispersion (A)
A compound represented by the formula (2-I), a compound represented by the following formula (E-1), (E-2), (E-3), (E-4), (E-5) 16.2 g, 10.4 g, 5.8 g, 1.4 g, 2.2 g, 1.4 g, and 4.2 g of the compound represented by the formula (1-I) were respectively transferred to TCP (oil made by Daihachi Chemical Co., Ltd.). A solution obtained by mixing 1.0 g of DEM (oil made by Daihachi Chemical Co., Ltd.) and 20 g of ethyl acetate was heated and dissolved.
[0055]
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[0056]
An aqueous phase obtained by mixing 25.0 g of a 15% polyvinyl alcohol solution (PVA205C: manufactured by Kuraray Co., Ltd.), 46.0 g of an 8% solution of polyvinyl alcohol (PVA217C), 0.5 g of sodium dodecylsulfonate and 75.0 g of water And emulsified at 10,000 rpm for 3 minutes using an ace homogenizer (trade name: manufactured by Nippon Seiki Co., Ltd.) to emulsify an electron-accepting compound having an average particle diameter of 0.6 μm (hereinafter, appropriately referred to as a developer). A dispersion was obtained.
[0057]
The average particle size is a 50% volume average particle size measured using a laser diffraction particle size distribution analyzer (LA700: trade name, manufactured by Horiba, Ltd.). Unless otherwise specified below, the average particle size represents the above 50% volume average particle size.
(Example 2)
Preparation of developer emulsified dispersion (B)
In the preparation of the developer emulsified dispersion (A) described in Example 1, the compound represented by the formula (1-II) is used instead of the compound represented by the formula (1-I) (benzotriazole-based ultraviolet absorber). A developer emulsified dispersion (B) having an average particle size of 0.6 μm was obtained by the same method except that the compound represented by the same weight was used.
(Comparative Example 1)
Preparation of developer emulsified dispersion (C)
A compound represented by the following formula (E-6) instead of the compound represented by the formula (1-I) in the preparation of the developer emulsion dispersion (A) described in Example 1 (the scope of the present invention) A developer emulsified dispersion (C) having an average particle size of 0.6 μm was obtained in the same manner except that the same weight of the other benzotriazole-based ultraviolet absorber was used.
[0058]
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[0059]
(Comparative Example 2)
Preparation of developer emulsified dispersion (D)
In the preparation of the developer emulsified dispersion (A) described in Example 1, a compound represented by the following formula (E-7) instead of the compound represented by the formula (1-I) (the present invention) A developer emulsified dispersion (D) having an average particle size of 0.6 μm was obtained by the same method except that the same weight of the benzotriazole-based ultraviolet absorber out of the range was used.
[0060]
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[0061]
(Comparative Example 3)
Preparation of developer emulsified dispersion (E)
A compound represented by the following formula (E-8) in place of the compound represented by the formula (1-I) in the preparation of the developer emulsified dispersion (A) described in Example 1 (the scope of the present invention) A developer emulsified dispersion (E) having an average particle size of 0.6 μm was obtained by the same method except that the same weight of the other benzotriazole-based UV absorber was used.
[0062]
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[0063]
(Comparative Example 4)
Preparation of developer emulsified dispersion (F)
In the preparation of the developer emulsion dispersion (A) described in Example 1, the formulas (2-I), (E-1), (E-2), (E-3), and (E-4) And 16.2 g, 10.4 g, 5.8 g, 1.4 g, 2.2 g and 1.4 g of the compounds represented by the formulas (E-1) and (E-2), respectively. ), (E-3), (E-4) and the compounds represented by (E-5), except that each was changed to 18.3 g, 10.1 g, 2.6 g, 3.8 g and 2.6 g, respectively. A developer emulsified dispersion (F) having an average particle diameter of 0.6 μm was obtained by the following method.
(Comparative Example 5)
Preparation of developer emulsified dispersion (G)
In the preparation of the developer emulsion dispersion (A) described in Example 1, the formulas (2-I), (E-1), (E-2), (E-3), and (E-4) And 16.2 g, 10.4 g, 5.8 g, 1.4 g, 2.2 g and 1.4 g of the compounds represented by the formulas (E-1) and (E-2), respectively. ), (E-3), (E-4) and (E-5), 18.3 g, 10.1 g, 2.6 g, 3.8 g and 2.6 g, respectively, and the formula (1 A developer emulsified dispersion (G) having an average particle size of 0.6 μm was obtained in the same manner except that the compound represented by the formula (1-II) was used in the same weight instead of the compound represented by -I). .
(Comparative Example 6)
Preparation of developer emulsified dispersion (H)
In the preparation of the developer emulsion dispersion (A) described in Example 1, the formulas (2-I), (E-1), (E-2), (E-3), and (E-4) And 16.2 g, 10.4 g, 5.8 g, 1.4 g, 2.2 g and 1.4 g of the compounds represented by the formulas (E-1) and (E-2), respectively. ), (E-3), (E-4) and (E-5), 18.3 g, 10.1 g, 2.6 g, 3.8 g and 2.6 g, respectively, and the formula (1 A developer emulsified dispersion (H) having an average particle size of 0.6 μm was obtained in the same manner as described above except that the compound represented by the formula (E-6) was used in place of the compound represented by the formula (E-6). .
(Comparative Example 7)
Preparation of developer emulsified dispersion (I)
In the preparation of the developer emulsion dispersion (A) described in Example 1, the formulas (2-I), (E-1), (E-2), (E-3), and (E-4) And 16.2 g, 10.4 g, 5.8 g, 1.4 g, 2.2 g and 1.4 g of the compounds represented by formulas (E-1) and (E-2), respectively. , (E-3), (E-4), and (E-5), respectively, to 18.3 g, 10.1 g, 2.6 g, 3.8 g, and 2.6 g. A developer emulsified dispersion (I) having an average particle diameter of 0.6 μm was obtained in the same manner except that the compound represented by the formula (E-7) was used in place of the compound represented by the same weight.
(Comparative Example 8)
Preparation of developer emulsified dispersion (J)
In the preparation of the developer emulsion dispersion (A) described in Example 1, the formulas (2-I), (E-1), (E-2), (E-3), and (E-4) And 16.2 g, 10.4 g, 5.8 g, 1.4 g, 2.2 g and 1.4 g of the compounds represented by the formulas (E-1) and (E-2), respectively. ), (E-3), (E-4), and (E-5), respectively, to 18.3 g, 10.1 g, 2.6 g, 3.8 g, and 2.6 g. A developer emulsified dispersion (J) having an average particle diameter of 0.6 μm was obtained in a similar manner except that the compound represented by the formula (E-8) was used in place of the compound represented by the same weight.
(Comparative Example 9)
Preparation of developer emulsified dispersion (K)
A color developer having an average particle size of 0.6 μm was prepared in the same manner as in Example 1, except that 4.2 g of the compound represented by the formula (1-I) was removed. An emulsified dispersion was obtained.
(Comparative Example 10)
Preparation of developer emulsified dispersion (L)
A color developer having an average particle diameter of 0.6 μm was prepared in the same manner as in the preparation of the developer emulsion dispersion (G) described in Comparative Example 5, except that 4.2 g of the compound represented by the formula (1-II) was removed. An emulsified dispersion (L) was obtained.
* Evaluation 1: Examination of stability of emulsion
The resulting developer emulsified dispersion was allowed to stand at room temperature after the preparation of the emulsion, and one day later, the state of the liquid was observed. The results are shown in Table 1 below.
[0064]
[Table 1]

[0065]
With the developer emulsified dispersion liquid in which precipitation occurred, a transparent heat-sensitive recording material described later could not be provided, and the subsequent evaluation was terminated. Evaluations 2 and 3 described below were considered for the developer emulsified dispersions of Examples 1 and 2 and Comparative Examples 2 and 9 in which the emulsion could be stably present.
* Evaluation 2: Evaluation by transmittance and visual observation
One side of a transparent 75 μm thick polyethylene terephthalate was coated with 0.3 g / m 2 of SBR latex in solid content weight.²Then, the following coating solution for an undercoat layer was applied so that the solid content weight per side was 0.1 g / m 2.²To obtain a transparent support provided with an undercoat layer.
<Preparation of coating liquid for coating layer>
200 g of a 5% aqueous solution of gelatin (# 810: trade name, manufactured by Nitta Gelatin Co., Ltd.), 0.5 g of a gelatin dispersion in which 5% of polymethyl methacrylate resin particles having a particle diameter of 2 μm are dispersed, 1,2-benzothiazoline-3- An undercoat layer coating solution was obtained by mixing 1.0 g of a 3% aqueous solution and 10 g of a 2% aqueous solution of di (2-ethyl) hexyl sulfonate.
<Sample preparation>
On the clear transparent support prepared by the above method, each of the developer emulsified dispersions which did not cause precipitation in Evaluation 1 was 5.0 g / m2 in solid content.²It applied so that it might become. (4 levels)
Sample transmittance measurement
The transmittance spectrum of the obtained sample was measured using a spectrophotometer U-3400 (manufactured by Hitachi, Ltd.) in a wavelength range of 320 mm to 500 mm.
[0066]
The results obtained are shown in FIG.
Visual impression
Observation of the above four types of samples through Sherkastin (manufactured by Seiko Co., Ltd.) revealed that Comparative Example 2 was clearly yellow, Examples 1 and 2 appeared slightly yellow, and Comparative Example 9 did not appear yellow.
Evaluation 3: Examination of light resistance of heat-sensitive recording material
A thermosensitive recording material was actually prepared using the developer emulsified dispersions of Examples 1 and 2 and Comparative Examples 2 and 9, which were confirmed to be stably present in Evaluation 1.
◎Preparation of heat-sensitive recording material using developer emulsified dispersion (A) of Example 1
<Preparation of capsule solution containing electron-donating dye precursor>
Compounds represented by the following formulas (E-9), (E-10), (E-11), (E-12), (E-13), (E-14) and (E-6), respectively. 9.8 g, 1.4 g, 1.9 g, 3.0 g, 1.0 g, 0.4 g and 0.4 g were dissolved by heating in 20 g of ethyl acetate, and gradually cooled to 40 ° C., and then Takenate D110N 2.0 g (trade name: Takeda Pharmaceutical capsule wall material), 11.6 g of Takenate D127N (same as above) and 0.4 g of n-butanol were added, and the mixture was stirred at 40 ° C. for 40 minutes.
[0067]
Embedded image

[0068]
The resulting solution was added to an aqueous phase obtained by mixing 40 g of an 8% polyvinyl alcohol solution (PVA217C: trade name of Kuraray Co., Ltd.) and 13 g of water, and emulsified and dispersed at 10,000 μm for 5 minutes using an ace homogenizer. .
[0069]
After 70 g of water and 0.5 g of tetraethylenepentamine were further added to the obtained emulsion, an encapsulation reaction was performed at 60 ° C. for 3 hours to obtain a capsule liquid having an average particle diameter of 0.6 μm. .
<Preparation of protective layer coating solution>
30 g of water, 20 g of a 6% aqueous solution of polyvinyl alcohol (PVA124C: manufactured by Kuraray), 0.3 g of a 2% aqueous solution of sodium salt of dioctyl sulfosuccinate, and kaolin dispersion (35 g of kaolin dispersed in a mixture of 3 g of polyvinyl alcohol and 100 g of water with a pole mill) 3.0 g of Hydrin Z (trade name: manufactured by Chukyo Yushi Co., Ltd.) was mixed to obtain a coating solution for a protective layer.
<Preparation of transparent support provided with undercoat layer>
On one side of a transparent 175 μm thick polyethylene terephthalate, 0.3 g / m 2 of solid content weight of SBR latex was applied.²Then, the following coating solution for an undercoat layer was applied so that the solid content weight per side was 0.1 g / m 2.²To obtain a transparent support provided with an undercoat layer.
<Preparation of coating liquid for coating layer>
200 g of a 5% aqueous solution of gelatin (# 810: manufactured by Nitta Gelatin Co., Ltd.), 0.5 g of a gelatin dispersion in which 5% of polymethyl methacrylate resin particles having a particle diameter of 2 μm are dispersed, 3% of 1,2-benzothiazolin-3-one 1.0 g of an aqueous solution and 10 g of a 2% aqueous solution of di (2-ethyl) hexyl sulfonate were mixed to obtain an undercoat layer coating solution.
<Preparation of coating solution for heat-sensitive recording layer>
5.0 g of the already prepared capsule liquid (MC), 15 g of the developer emulsified dispersion liquid (A) (one day left after emulsification and dispersion) and 10 g of water were mixed to obtain a thermosensitive recording coating liquid (1). .
<Preparation of thermal recording material>
On one surface of the previously prepared transparent support provided with an undercoat layer, the thermosensitive recording coating solution (1) was applied at a solid content of 14 g / m2.²After coating and drying, the prepared coating solution for the protective layer is coated thereon with a solid content of 2.5 g / m2.²Was applied and dried to obtain a heat-sensitive recording material of the present invention.
の Preparation of heat-sensitive recording material using developer emulsified dispersion (B) of Example 2
In the preparation of the thermosensitive recording material using the developer emulsified dispersion (A) of Example 1, the developer emulsified dispersion was used instead of the developer emulsified dispersion (A) at the time of preparing the coating solution for thermosensitive recording. A thermosensitive recording material was obtained in the same manner except that (B) was used in the same weight.
の Preparation of heat-sensitive recording material using developer emulsified dispersion (D) of Comparative Example 2
In the preparation of the thermosensitive recording material using the developer emulsified dispersion (A) of Example 1, the developer emulsified dispersion was used instead of the developer emulsified dispersion (A) at the time of preparing the coating solution for thermosensitive recording. A thermosensitive recording material was obtained in the same manner except that (D) was used in the same weight.
の Preparation of heat-sensitive recording material using developer emulsified dispersion (K) of Comparative Example 9
In the preparation of the thermosensitive recording material using the developer emulsified dispersion (A) of Example 1, the developer emulsified dispersion was used instead of the developer emulsified dispersion (A) at the time of preparing the coating solution for thermosensitive recording. A heat-sensitive recording material was obtained in the same manner except that (K) was used in the same weight.
* Lightfastness evaluation
The obtained four kinds of heat-sensitive recording materials were irradiated with light for 24 hours in a weather o meter (ATLAS (i65): trade name, manufactured by Toyo Seiki Co., Ltd.) without printing. At this time, the transmission density (Yellow value) of the material before and after light irradiation was measured using TD904 (manufactured by Macbeth). The results are shown in Table 2 below.
[0070]
[Table 2]

[0071]
The thermosensitive recording material using the developer emulsified dispersion used in Examples 1 and 2 suppressed the yellowishness of the background of the material, had very little yellowing after 24 hours of light irradiation, and improved the background light resistance. It can be seen that this is a developer emulsified dispersion that contributes to the above.
[0072]
【The invention's effect】
The heat-sensitive recording material of the present invention is excellent in that there is no coloring or yellowing of the background, that is, a white background, light resistance is excellent, and further, the stability of the electron accepting compound emulsion is excellent, and good coloring can be achieved. The effect was shown.
[Brief description of the drawings]
FIG. 1 is a graph showing a transmittance spectrum of a sample obtained by applying a developer emulsified dispersion on a transparent support.

Claims (3)

On a support, a heat-sensitive recording material provided with a heat-sensitive recording layer containing an electron-donating colorless dye and an electron-accepting compound encapsulated in microcapsules,
A microcapsule dispersion in which the heat-sensitive recording layer contains an electron-donating colorless dye , and an emulsion containing a salicylic acid derivative polyvalent metal salt and a benzotriazole-based ultraviolet absorber represented by the following general formula (1): A thermosensitive recording material formed by applying and drying a coating solution containing a dispersion.

In the formula, R ¹ and R ² may be the same or different and each represents an alkyl group having 1 to 8 carbon atoms. The heat-sensitive recording material according to claim 1, wherein the electron-accepting compound contains a salicylic acid derivative polyvalent metal salt represented by the following general formula (2).

In the formula, R ³ represents a hydrogen atom, an alkyl group, an aryl group, an aralkyl group, an alkoxy group or an aryloxy group, M represents Zn, Ca and Al, m represents an integer of 1 to 4, and n represents Represents an integer of 2 or 3. 3. The heat-sensitive recording material according to claim 1, wherein the benzotriazole-based ultraviolet absorber is represented by the following formula (1-I) or (1-II).

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