JP2004322435A - Thermosensitive recording material and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermosensitive recording material, by which image density can be kept constant even under different humidity atmosphere and little sticking and blocking develops, and its manufacturing method. <P>SOLUTION: In the manufacturing method of the thermosensitive recording material formed by laminating at least a thermosensitive recording layer on a support, after the coating and drying of all the coating liquids of laminated layers including the thermosensitive recording layer, the packaging of the material is performed by conditioning humidity so as to become the equilibrium moisture content of the thermosensitive recording material equal to that realized under the condition that the material is left in the atmosphere having the equilibrium humidity of 35-65% at 25°C. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００８７】
本発明において、感熱記録層又は中間層上に均一に保護層を形成させるために、保護層形成用塗布液に界面活性剤を添加することが好ましい。該界面活性剤としては、スルホコハク酸系のアルカリ金属塩、フッ素含有界面活性剤等が好ましく、具体的には、ジ−（２−エチルヘキシル）スルフォコハク酸、ジ−（ｎ−ヘキシル）スルフォコハク酸等のナトリウム塩、カリウム塩、又はアンモニウム塩、アセチレングリコール誘導体、パーフルオロアルキル硫酸ナトリウム塩、カリウム塩、又はアンモニウム塩、パーフルオロアルキルベタイン化合物等が挙げられる。
【００８８】
更に上記保護層中には、感熱記録材料の帯電防止の目的で、金属酸化物微粒子、無機電解質、高分子電解質等を添加してもよい。また、上記保護層は単層構造であってもよいし、２層以上の積層構造であってもよい。
上記保護層の乾燥塗布量は０．２〜７ｇ／ｍ^２が好ましく、１〜４ｇ／ｍ^２がより好ましい。
【００８９】
本発明の感熱記録材料は、支持体上に、その他の層として、中間層、下塗り層、紫外線フィルター層、光反射防止層（バック層）等を設けることができる。
【００９０】
［中間層］
中間層は、前記感熱記録層上に形成されることが好ましい。該中間層は層の混合防止や画像保存性に対して有害なガス（酸素等）の遮断のために設けられる。使用するバインダーは特に制限はなく、系に応じてポリビニルアルコール、ゼラチン、ポリビニルピロリドン、セルロース誘導体等を用いることができる。中でもゼラチンは、高温では水溶液が流動性を有しているが、低温（例えば３５℃以下）にすると流動性を失いゲル化する性質（セット性）に優れるため、支持体上に複数の層を形成するための塗布液を塗布、乾燥して前記層を設ける場合、複数の層を順次塗布乾燥する方法でも、また押し出しダイ方式等で一度に重層塗布、乾燥する方法においても、隣接する２つの層が相互に混合することが有効に防止され、得られる感熱記録材料の面状が良好になり、高品位な画像形成が可能な感熱記録材料を得ることができるため、細部まで明瞭な画像を形成する必要のある医療診断用記録材料に好適である。更に高い風速で乾燥しても面状が悪化しないので、製造効率が向上する。
この様なゼラチンとしては、無修飾（未処理）ゼラチンあるいは修飾（処理）ゼラチンがいずれも支障なく用いられる。修飾ゼラチンとしては石灰処理ゼラチン、酸処理ゼラチン、フタル化処理ゼラチン、脱イオン処理ゼラチン、酵素処理低分子量ゼラチン等が挙げられる。また塗布性付与のため、種々の界面活性剤を添加してもよい。またガスバリアー性をより高めるために雲母等の無機微粒子を前記バインダーに対し２〜２０質量％より好ましくは５〜１０質量％添加してもよい。中間層用塗布液のバインダー濃度は３〜２５質量％、好ましくは５〜１５質量％程度が適切である。また中間層の乾燥塗布量は０．５〜６ｇ／ｍ^２、好ましくは１〜４ｇ／ｍ^２が適切である。
【００９１】
［下塗り層］
本発明の感熱記録材料においては、支持体から感熱記録層が剥がれることを防止する目的で、マイクロカプセル等を含有する感熱記録層や光反射防止層等を塗布する前に、支持体上に下塗り層を設けることができる。
該下塗り層としては、アクリル酸エステル共重合体、ポリ塩化ビニリデン、ＳＢＲ、水性ポリエステル等を用いることができ、層の厚みは０．０５〜０．５μｍが好ましい。
【００９２】
上記下塗り層上に感熱記録層を塗布する際、感熱記録層用塗布液に含まれる水分により下塗り層が膨潤して、感熱記録層に記録された画像が悪化することがあるので、下塗り層にはグルタルアルデヒド、２，３−ジヒドロキシ−１，４−ジオキサン等のジアルデヒド類及びホウ酸等の硬膜剤を用いて硬化させることが好ましい。これらの硬膜剤の添加量は、下塗り素材の質量に応じて０．２〜３．０質量％の範囲で、所望の硬化度に合わせて適宜に添加することができる。
【００９３】
［紫外線フィルター層］
本発明の感熱記録材料においては、画像の光による褪色および地肌かぶり防止のために紫外線フィルター層を設けてもよい。紫外線フィルター層は結合剤中に紫外線吸収剤を均一に分散させたものであり、この均一に分散した紫外線吸収剤が有効に紫外光を吸収することにより、紫外光によって地肌が変色したり、画像部が変色または褪色することを防止する。紫外線フィルター層の形成方法及び用いる化合物等については、ベンゾトリアゾール系、ベンゾフェノン系、ヒンダードアミン系等の紫外線吸収剤のほか、特開平４−１９７７７８号公報に記載されているものが利用できる。
【００９４】
［光反射防止層］
本発明の感熱記録材料は支持体の一面にマイクロカプセルを含む感熱記録層を有し、他方の面に光反射防止層（バック層）を有する片面感材であることが好ましい。光反射防止層（バック層）には搬送性付与および光反射防止の目的でマット剤を添加することが好ましい。マット剤の添加により、入射光角２０°で測定した光沢度を５０％以下にすることが好ましく、３０％以下にすることがより好ましい。
上記マット剤としては、大麦、小麦、コーン、米、豆類等より得られる澱粉等の微粒子の他、セルロースファイバー、ポリスチレン樹脂、エポキシ樹脂、ポリウレタン樹脂、尿素ホルマリン樹脂、ポリ（メタ）アクリレート樹脂、ポリメチル（メタ）アクリレート樹脂、塩化ビニルまたは酢酸ビニル等の共重合体樹脂、ポリオレフィン等の合成高分子の微粒子、炭酸カルシウム、酸化チタン、カオリン、スメクタイト粘度、水酸化アルミニウム、シリカ、酸化亜鉛等の無機物の微粒子等が挙げられる。該マット剤の平均粒径は０．５〜２０μｍ、好ましくは０．５〜１０μｍの範囲が好ましい。上記マット材は１種単独でも、２種以上併用してもよい。
また、感熱記録材料の透明性を良好なものとする観点から、屈折率が１．４〜１．８の範囲にあることが好ましい。バック層には、色相改良の観点から、各種染料（例えば、Ｃ．Ｉ．Ｐｉｇｍｅｎｔ Ｂｌｕｅ ６０、Ｃ．Ｉ．Ｐｉｇｍｅｎｔ Ｂｌｕｅ ６４、Ｃ．Ｉ．Ｐｉｇｍｅｎｔ Ｂｌｕｅ １５：６）を用いることができる。またバック層には硬膜剤を用いても良い。該硬膜剤の例としては、Ｔ．Ｈ．Ｊａｍｅｓ著「ＴＨＥ ＴＨＥＯＲＹ ＯＦ ＴＨＥ ＰＨＯＴＯＧＲＡＰＨＩＣ ＰＲＯＣＥＳ ４ｔｈ ＥＤＩＴＩＯＮ」（７７頁〜８７頁）に記載のある各方法があり、ビニルスルフォン系化合物が好ましい。
【００９５】
本発明の感熱記録材料は、後述する本発明の感熱記録材料の製造方法により製造されたものであるから、平衡含水率が均一に保たれていて、そのため、画像濃度を一定に保つことができる。
【００９６】
＜感熱記録材料の製造方法＞
次いで、本発明の感熱記録材料の製造方法について説明する。
本発明の感熱記録材料の製造方法は、支持体上に、前記感熱記録層形成用塗布液を塗布して感熱記録層を形成し、必要に応じて、該感熱記録層上に、保護層形成用塗布液を塗布して保護層を形成し、更に必要に応じて、その他の層を形成してなる。
ここで、上記感熱記録層及びその他の層は同時に形成してもよく、その場合、該感熱記録層形成用塗布液とその他の層の形成用塗布液とを支持体上に同時に重層塗布することにより、感熱記録層及びその上に保護層を同時に形成する工程を有する。
【００９７】
ここで使用される支持体は、本発明の感熱記録材料に使用される既に説明した支持体を用いることができる。また、上記感熱記録層形成用塗布液としては、前述した前記感熱記録層用塗布液を用いることができ、更に、上記保護層形成用塗布液も、前述した顔料及びバインダーを含有する保護層用塗布液を用いることができる。
また、上記その他の層としては、前述した中間層や下塗り層等のその他の層が挙げられる。
本発明の感熱記録材料の製造方法では、支持体上に、下塗り層、感熱記録層、中間層、保護層等を順次形成するために、ブレード塗布法、エアナイフ塗布法、グラビア塗布法、ロールコーティング塗布法、スプレー塗布法、ディップ塗布法、バー塗布法等の公知の塗布方法が用いられる。
【００９８】
（サーマルヘッド）
感熱記録に用いられるサーマルヘッドは、感熱記録材料に接触する最上層の炭素比率が９０％以上となる様に、既知の製膜装置を用いてグレーズ層上に発熱抵抗体と電極を具備する加熱素子に保護層を設けたものが好ましい。該ヘッド保護層は、２層以上でもよいが、少なくとも最上層は炭素比率が９０％以上であることが望ましい。
【００９９】
本発明の感熱記録材料の製造方法においては、前記感熱記録層を含む、積層される層の塗布液をすべて塗布・乾燥した後、前記感熱記録材料の平衡含水率が、２５℃における平衡相対湿度で３５〜６５％の雰囲気に放置したときの平衡含水率となるように調湿して包装する。
【０１００】
本発明において、感熱記録材料を２５℃における平衡相対湿度で３５〜６５％の雰囲気に放置したときの平衡含水率にするためには、通常、上記雰囲気下に感熱記録材料を２４時間以上放置することにより平衡に到達させることで達成することができる。また、感熱記録材料の表面に、上記雰囲気の風を風速０．１ｍ／ｓｅｃ以上で当てることで調湿時間を１６時間に短縮することが可能である。
【０１０１】
感熱記録材料を前述のように調湿した後、包装する手法としては、感熱記録材料をポリプロピレンあるいは天然パルプ原紙からできている保湿レートをコの字上に折曲成形したものに装填した後、包装袋につめて密封するという手法が挙げられる。
また、包装に用いる包装袋あるいは包装箱の材質としては、耐湿性の点から、ポリエチレン、ナイロン、ポリエチレンテレフタレートを積層したポリエチレンが好ましい。
【０１０２】
本明細書において平衡含水率は、以下のようにして測定して得られる数値である。即ち、感熱記録材料を所定の温湿度雰囲気下に２４時間以上放置したときの感熱記録材料の質量を測定した後、１０５℃条件下で１６時間以上加熱して感熱記録材料の水分をすべて蒸発させた後、その質量を測定して蒸発した水分質量を算出し、この水分質量を加熱前の感熱記録材料の質量で割って得られる含水率が所定温湿度における平衡含水率となる。
【０１０３】
以上のように、感熱記録材料を前記平衡含水率とすることにより、季節や、冊内のどの位置かに関わらず、感熱記録材料を均一な平衡含水率に保つことができ、適度な平衡含水率により、画像濃度を一定に保つことができるとともに、スティッキングやブロッキングを防止することができる。
【０１０４】
【実施例】
以下に、実施例を示し本発明を具体的に説明するが、本発明は以下の実施例のみに限定されるものではない。文中で使用する濃度は、全て質量％である。また、乳化分散液とは、水中油滴分散型分散物を意味する。
【０１０５】
≪実施例１≫
＜保護層用塗布液の調製＞
［保護層用顔料分散液Ａの調製］
水１１０ｇに、顔料としてステアリン酸処理水酸化アルミニウム（商品名：ハイジライトＨ４２Ｓ，昭和電工（株）製）３０ｇを加え３時間撹拌した後、これに分散助剤（商品名：ポイズ５３２Ａ，花王（株）製）０．８ｇ、１０％ポリビニルアルコール水溶液（商品名：ＰＶＡ１０５，（株）クラレ製）３０ｇ、２％に調整した下記構造式［１００］で表される化合物の水溶液１０ｇを加えサンドミルで分散し、平均粒径０．３０μｍの保護層用顔料分散液Ａを得た。
尚、「平均粒径」は、用いる顔料を分散助剤共存下で分散し、その分散直後の顔料分散物に水を加えて０．５％に希釈した被検液を、４０℃の温水中に投入し光透過率が７５±１．０％になるように調整した後、３０秒間超音波処理しレーザー回折粒度分布測定装置（商品名：ＬＡ７００，（株）堀場製作所製）により測定した、全顔料の５０体積％に相当する顔料粒子の平均粒径を使用し、以下に記載の「平均粒径」は全て同様の方法により測定した平均粒径を表す。
【０１０６】
【化２】

【０１０７】
［保護層用塗布液の調製］
水６５ｇに、
８％ポリビニルアルコール水溶液
（商品名：ＰＶＡ１２４Ｃ，（株）クラレ製） ９０ｇ
２０．５％ステアリン酸亜鉛分散物
（商品名：Ｆ１１５，中京油脂（株）製） ５．５ｇ
２１．５％ステアリン酸アミド化合物
（商品名：Ｇ−２７０，中京油脂（株）製） ３．８ｇ
１８．０％ステアリン酸分散物
（商品名：セロゾール９２０，中京油脂（株）製） ２．８ｇ
４％ホウ酸水溶液 １０ｇ
前記保護層用顔料分散液Ａ ７０ｇ
３５％シリコーンオイル水分散液
（ポリジメチルシロキサン，商品名：ＢＹ２２−８４０，
東レ・ダウコーニング（株）製） ４．７ｇ
１０％ドデシルベンゼンスルフォン酸Ｎａ塩水溶液 ６．５ｇ
７５％ジ−２−エチルヘキシルスルフォコハク酸
アンモニウム塩水溶液
（商品名：ニッサンエレクトールＳＡＬ１、日本油脂（株）製） ３．２８ｇ
６％スチレン−マレイン酸共重合体アンモニウム塩
水溶液（商品名：ポリマロン３８５，荒川化学（株）製） １７．５ｇ
２０％コロイダルシリカ
（商品名：スノーテックス，日産化学（株）製） １４ｇ
１０％サーフロンＳ１３１Ｓ（旭ガラス（株）製） １６ｇ
プライサーフＡ２１７Ｅ（第一工業製薬（株）製） １．１ｇ
２％酢酸 ８ｇ
を混合して保護層用塗布液を得た。
【０１０８】
＜中間層用塗布液の調製＞
石灰処理ゼラチン１ｋｇに、水７８４８ｇを加え、溶解した後に、ジ−２−エチルヘキシルスルフォコハク酸Ｎａ塩（商品名：ニッサンラピゾールＢ９０、日本油脂（株）製）の５％溶解液（水／メタノール＝１／１体積混合溶媒）を１３７ｇ加え、中間層用塗布液を調製した。
【０１０９】
＜感熱記録層用塗布液の調製＞
以下のようにして、マイクロカプセル塗布液、顕色剤乳化分散液の各液を調製した。
［マイクロカプセル塗布液Ａの調製］
発色成分として、
下記構造式［２０１］で表される化合物 １１．７ｇ
下記構造式［２０２］で表される化合物 １．５ｇ
下記構造式［２０３］で表される化合物 ２．２ｇ
下記構造式［２０４］で表される化合物 ５．６５ｇ
下記構造式［２０５］で表される化合物 １．２ｇ
下記構造式［２０６］で表される化合物 １．１ｇ
下記構造式［２０７］で表される化合物 ０．５７ｇ
を酢酸エチル２４．３ｇに添加して７０℃に加熱、溶解した後、４５℃まで冷却した。これに、カプセル壁材（商品名：タケネートＤ１４０Ｎ，三井武田ケミカル（株）製）１５．４ｇを加え、混合した。
【０１１０】
【化３】

【０１１１】
【化４】

【０１１２】
【化５】

【０１１３】
この溶液を、水１６ｇに８％のポリビニルアルコール水溶液（商品名：ＭＰ−１０３、（株）クラレ製）４８ｇを混合した水相中に加えた後、エースホモジナイザー（日本精機（株）製）を用い回転数１５０００ｒｐｍで５分間乳化を行った。得られた乳化液に、更に水１１０ｇ及びテトラエチレンペンタミン１．０ｇを添加した後、６０℃で４時間カプセル化反応を行い、平均粒径０．８０μｍのマイクロカプセル塗布液Ａを調製した。
得られたマイクロカプセル塗布液Ａのカプセル壁のガラス転移温度（以下、「Ｔｇ」という。）をＤＭＴＡ（Ｄｙｎａｍｉｃ Ｍｅｃｈａｎｉｃａｌ Ｔｈｅｒｍａｌ Ａｎａｌｙｚｅｒ）（ポリマーラボラトリー社製のガラス転移温度測定器の商品名）を用いて測定したところ、１９３℃であった。
【０１１４】
［マイクロカプセル塗布液Ｂの調製］
構造式［２０１］で表される化合物 １２．２ｇ
構造式［２０２］で表される化合物 １．６ｇ
構造式［２０３］で表される化合物 ２．４ｇ
構造式［２０４］で表される化合物 ３．３ｇ
構造式［２０５］が表される化合物 １．５ｇ
構造式［２０６］で表される化合物 ０．２ｇ
構造式［２０７］が表される化合物 ０．５ｇ
を酢酸エチル２１ｇに添加し、７０℃に加熱、溶解した後、３５℃に冷却した。これにカプセル壁材（商品名：タケネートＤ１２７Ｎ、三井武田ケミカル（株）製）１６．６ｇ、を加え、混合した。
【０１１５】
この溶液を水１６．６ｇに８％のポリビニルアルコール（ＭＰ−１０３、（株）クラレ製）４８．１ｇを混合した水相中に加え、エースホモジナイザー（日本精機（株）製）を用い、１５０００ｒｐｍで５分間乳化を行なった。得られた乳化液に更に水１１２ｇ及びテトラエチレンペンタミン０．９ｇを添加した後、６０℃で４時間カプセル化反応を行ない、平均粒径０．３０μｍのマイクロカプセル塗布液Ｂを調製した。
得られたマイクロカプセル塗布液Ｂのカプセル壁のＴｇを、マイクロカプセル液Ａと同様に測定したところ、１５３℃であった。
【０１１６】
［顕色剤乳化分散液の調製］
顕色剤として
下記構造式［３０１］で表される化合物 ６．７ｇ
下記構造式［３０２］で表される化合物 ８．０ｇ
下記構造式［３０３］で表される化合物 ５．８ｇ
下記構造式［３０４］で表される化合物 １．５ｇ
下記構造式［３０５］で表される化合物 ２．２ｇ
下記構造式［３０６］で表される化合物 ０．８ｇ
下記構造式［３０７］で表される化合物 ４．３ｇ
をトリクレジルフォスフェート１．０ｇ、マレイン酸ジエチル０．５ｇと共に、酢酸エチル１６．５ｇに添加し、７０℃に加熱して溶解した。
【０１１７】
【化６】

【０１１８】
【化７】

【０１１９】
この溶液を、水７０ｇ、８％ポリビニルアルコール水溶液（ＰＶＡ２１７Ｃ、（株）クラレ製）５７ｇ、１５％のポリビニルアルコール水溶液（商品名：ＰＶＡ２０５Ｃ，（株）クラレ製）２０ｇ、下記構造式［４０１］で挙げられる化合物及び下記構造式［４０２］で表される化合物の２％水溶液１１．５ｇを混合した水相中に加えた後、エースホモジナイザー（日本精機（株）製）を用いて回転数１００００ｒｐｍで平均粒径０．７μｍになるように乳化し、顕色剤乳化分散液Ｃを得た。
【０１２０】
【化８】

【０１２１】
［感熱記録層用塗布液Ａの調製］
マイクロカプセル塗布液Ａ（固形分濃度２３％） １２ｇ
マイクロカプセル塗布液Ｂ（固形分濃度２４％） ２．５ｇ
顕色剤乳化分散液Ｃ（固形分濃度２２％） ５０ｇ
下記構造式［４０３］で表される化合物の５０％水溶液 ０．７ｇ
コロイダルシリカ（スノーテックス 日産化学（株）製）１．８ｇ
を混合して、感熱記録層用塗布液Ａを調製した。
【０１２２】
【化９】

【０１２３】
［感熱記録層用塗布液Ｂの調製］
マイクロカプセル塗布液Ａ（固形分濃度２３％） ２．３ｇ
マイクロカプセル塗布液Ｂ（固形分濃度２４％） ６．６ｇ
顕色剤乳化分散液Ｃ（固形分濃度２２％） ３３ｇ
コロイダルシリカ（スノーテックス、日産科学（株）製） １．５ｇ
構造式［４０３］で表される化合物の５０％水溶液 ０．４ｇ
を混合し、感熱記録層用塗布液Ｂを調製した。
【０１２４】
［バック層用塗布液Ａの調製］
石灰処理ゼラチンを１ｋｇ、平均粒子径５．７μｍの球形ＰＭＭＡ粒子１２％を含むゼラチン分散物を７５７ｇ、構造式［５０１］〜［５０５］で表わされる化合物を以下の含有率で含む紫外線吸収剤の乳化物を３７６１ｇ（乳化物１ｋｇ当たりの紫外線吸収剤含有量は、

【０１２５】
【化１０】

【０１２６】
［バック層用塗布液Ｂの調製］
石灰処理ゼラチンを１ｋｇ、平均粒子径０．７μｍの球形ＰＭＭＡ粒子１２％を含むゼラチン分散物を２０００ｇ、メタノールを１２６８ｍｌ、１，２−ベンズイソチアゾリン−３−オンを１．７５ｇ、ポリアクリル酸ナトリウム（分子量約１０万）を６４．４ｇ、ポリ（ｐ−ビニルベンゼンスルホン酸ナトリウム）（分子量約４０万）を５４ｇ、ｐ−ｔｅｒｔ−オクチルフェノキシポリオキシエチレン−エチレンスルホン酸ナトリウムを２５．２ｇ、Ｎ−プロピル−Ｎ−ポリオキシエチレン−パーフルオロオクタンスルホン酸アミドブチルスルホン酸ナトリウムを５．３ｇ、パールフルオロオクタンスルフォン酸カリウムを７．１ｇを、苛性ソーダでｐＨ＝７．０に調整した後、水を加えて全量を６６．７９リットルとなるように調製した。
【０１２７】
上記のバック層用塗布液Ａ及びバック層用塗布液Ｂを、ＪＩＳ−Ｚ８７０１記載の方法により規定された色度座標でｘ＝０．２８５０、ｙ＝０．２９９５に青色染色した厚み１８０μｍの二軸延伸ポリエチレンテレフタレート支持体の片面に、支持体に近い側から、バック層用塗布液Ａ、バック層用塗布液Ｂの順でそれぞれ塗布量が４４．０ｍｌ／ｍ^２、１８．５ｍｌ／ｍ^２となるようにスライドビード法により同時重層塗布、乾燥した。
塗布乾燥条件は以下の通りである。塗布スピードは１６０ｍ／分とし、コーティングダイ先端と支持体との間隔を０．１０〜０．３０ｍｍとし、減圧室の圧力を大気圧に対して２００〜１０００Ｐａ低く設定した。支持体は塗布前にイオン風にて除電した。引き続くチリングゾーンにおいて、乾球温度０〜２０℃の風で塗布液を冷却した後、無接触で搬送して、つるまき式無接触型乾燥装置により、乾球温度２３〜４５℃、湿球温度１５〜２１℃の乾燥風で乾燥させた。
【０１２８】
＜感熱記録材料の作製＞
上記バック層を塗設した支持体のバック層と反対の面に、支持体に近い側から感熱記録層用塗布液Ａ、感熱記録層用塗布液Ｂ、中間層用塗布液、及び保護層用塗布液の順で、それぞれ塗布量が５０ｍｌ／ｍ^２、２０ｍｌ／ｍ^２、２７ｍｌ／ｍ^２、２５ｍｌ／ｍ^２になるように塗布・乾燥した。乾燥後の感熱記録材料を、２５℃における平衡相対湿度で５０％の雰囲気に放置したときの平衡含水率となるように調湿した後包装し、２９℃／７０％の夏場の雰囲気に放置した。
【０１２９】
≪実施例２≫
バック層の塗設までは実施例１と同様に実施し、バック層を塗設した支持体のバック層と反対の面に、支持体に近い側から感熱記録層用塗布液Ａ、感熱記録層用塗布液Ｂ、中間層用塗布液、及び保護層用塗布液の順で、それぞれの塗布量５０ｍｌ／ｍ^２、２０ｍｌ／ｍ^２、２７ｍｌ／ｍ^２、２５ｍｌ／ｍ^２になるように塗布・乾燥した。乾燥後の感熱記録材料を、２５℃における平衡相対湿度で５０％の雰囲気に放置したときの平衡含水率となるように調湿した後包装し、２０℃／３０％の冬場の雰囲気に放置した。
【０１３０】
≪比較例１≫
バック層を塗設した支持体のバック層と反対の面に実施例１と同様に各層の塗布液を塗布・乾燥した後、２５℃における平衡相対湿度で５０％の雰囲気に放置したときの平衡含水率となるように調湿した後包装し、２９℃／７０％の雰囲気に放置した。
【０１３１】
≪比較例２≫
バック層を塗設した支持体のバック層と反対の面に実施例１と同様に各層の塗布液を塗布・乾燥した後、２５℃における平衡相対湿度で５０％の雰囲気に放置したときの平衡含水率となるように調湿した後包装し、２０℃／３０％の雰囲気に放置した。
【０１３２】
以上の実施例１〜２、及び比較例１〜２において作製した、感熱記録材料を包装袋から取り出し、富士写真フイルム（株）製のドライ画像記録装置（ＤＲＹＰＩＸ）にセットし２５℃／４５％条件下にて８０ｍＪの印画エネルギーにて印画して、画像濃度を比較した。発色濃度はマクベス濃度計ＴＤ−４０４（マクベス社製）を用いて測定した。結果を表１に示す。
【０１３３】
【表１】

【０１３４】
表１より、実施例１〜２の感熱記録材料は、夏場の雰囲気でも、冬場の雰囲気でも、ほぼ一定の発色濃度で記録できたことが分かる。これに対して、比較例の感熱記録材料は、実施例のものとは平衡含水率が異なり、発色濃度に隔たりがあった。
【０１３５】
≪実施例３≫
実施例１の＜感熱記録材料の作製＞において、感熱記録層用塗布液Ａ、感熱記録層用塗布液Ｂ、中間層用塗布液、及び保護層用塗布液を塗布・乾燥させて作製した感熱記録材料を、２５℃における平衡相対湿度で３５％の雰囲気に放置したときの平衡含水率となるように調湿して包装したこと以外は実施例１と同様にして実施例３の感熱記録材料を作製した。
【０１３６】
≪実施例４≫
実施例１の＜感熱記録材料の作製＞において、感熱記録層用塗布液Ａ、感熱記録層用塗布液Ｂ、中間層用塗布液、及び保護層用塗布液を塗布・乾燥させて作製した感熱記録材料を、２５℃における平衡相対湿度で５０％の雰囲気に放置したときの平衡含水率となるように調湿して包装したこと以外は実施例１と同様にして実施例４の感熱記録材料を作製した。
【０１３７】
≪実施例５≫
実施例１の＜感熱記録材料の作製＞において、感熱記録層用塗布液Ａ、感熱記録層用塗布液Ｂ、中間層用塗布液、及び保護層用塗布液を塗布・乾燥させて作製した感熱記録材料を、２５℃における平衡相対湿度で６５％の雰囲気に放置したときの平衡含水率となるように調湿した後包装したこと以外は実施例１と同様にして実施例５の感熱記録材料を作製した。
【０１３８】
≪比較例３≫
実施例１の＜感熱記録材料の作製＞において、塗布・乾燥させて作製した感熱記録材料を、２５℃における平衡相対湿度で３０％の雰囲気に放置したときの平衡含水率となるように調湿した後包装したこと以外は実施例１と同様にして比較例３の感熱記録材料を作製した。
【０１３９】
≪比較例４≫
実施例１の＜感熱記録材料の作製＞において、塗布・乾燥させて作製した感熱記録材料を、２５℃における平衡相対湿度で７０％の雰囲気に放置したときの平衡含水率となるように調湿した後包装したこと以外は実施例１と同様にして比較例４の感熱記録材料を作製した。
【０１４０】
［評価］
１．スティッキングの評価
実施例３〜５及び比較例３〜４で得られた感熱記録材料に対し、京セラ（株）製のサーマルヘッド（商品名：ＫＧＴ、２６０−１２ＭＰＨ８）の最上層に厚さ２μｍで炭素含有率が９８質量％のカーボン層を物理蒸着法により設けたサーマルヘッドを用いてヘッド圧が１０ｋｇ／ｃｍ^２で記録エネルギーが１２０ｍＪ／ｍｍ^２の条件で記録し、その際、印画時に該サーマルヘッドと感熱記録材料の保護層との間で接着ないしは融着する現象（スティッキング）を起こすか否かを目視により観察し、下記の評価基準に従い評価した。結果を表２に示す。
［評価］
○：スティッキングが発生しなかった。
△：スティッキングが少し発生した。
×：スティッキングがかなり発生した。
【０１４１】
２．ブロッキング評価
各実施例及び比較例で得られた感熱記録材料を、１冊をＢ４サイズにて１０１枚の包装単位にしたものを、机の上に５冊積み上げた状態にして、２週間放置した後、１番下の冊の感熱記録材料同士にブロッキングが生じているか否かを目視にて下記評価基準に従い評価した。結果を表２に示す。
［評価基準］
○：ブロッキングしていない。
△：感熱記録材料同士がわずかにブロッキングしている。
×：ブロッキングしている。
【０１４２】
【表２】

【０１４３】
表２より、実施例３〜５の感熱記録材料は、スティッキングもブロッキングも発生していないのに対し、比較例３〜４の感熱記録材料は、スティッキング及びブロッキングのいずれかが発生していた。
【０１４４】
【発明の効果】
本発明によれば、異なる湿度雰囲気下においても画像濃度を一定に保つことができ、スティッキングやブロッキングの発生の少ない感熱記録材料、及びその製造方法を提供することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a heat-sensitive recording material and a method for producing the same.
[0002]
[Prior art]
Conventionally, a silver salt film has been used for digital image output. However, since the silver salt film is a wet process, an automatic machine is required in addition to the output device. For this reason, the silver salt film is accompanied by complicated operations such as developing solution replacement, waste liquid processing, maintenance of the self-machine, and darkroom operation. Therefore, in recent years, a heat-sensitive recording material simpler than this silver salt film has been used. This heat-sensitive recording material has an advantage that a development process is not required as compared with a conventional silver salt film, since a video signal from each apparatus can be received and an image can be directly formed on the heat-sensitive recording material by a thermal head. In addition, since images are recorded with heat instead of light, it is possible to work in a bright room. The device is small and light and can be carried, and when necessary, it can output images where needed. There are various advantages such as no maintenance of the apparatus.
[0003]
Many recording methods using heat as an input signal are known. Among them, what can be called thermal recording is a method of recording an image by color development using only Joule heat as an input signal. Recording methods used for thermal recording can be divided into those using physical changes for recording and those using chemical changes. The former, in which the physical change is applied to the recording, is a type using a ribbon, in which the dye is transferred from the ribbon by heat and recorded, which is called a transfer thermal method. The latter using a chemical change is a type that does not require a ribbon, and an image is directly formed on recording paper by heat, which is called a direct thermal method.
[0004]
The basic structure of the heat-sensitive recording material used in the direct heat-sensitive method is composed of materials such as a color former and a developer, all of which are combined with a binder in the form of particles finely divided to several μm or less. It is coated on the support. A light or colorless color former is a precursor of a dye, and dissociates itself by donating electrons to form a dye and develop a color. The developer plays a role in causing the dye formation reaction by taking electrons from the color former. Both are dispersed in the binder polymer. The binder plays a role of fixing the color former and the developer to the support and is adsorbed on each surface to prevent both from coming into direct contact and reacting. When heat is directly applied to the heat-sensitive recording material having such a structure from the thermal head, the developer having a low melting point generally melts, breaks the adsorption layer of the binder polymer, diffuses and comes into contact with the color former, where the reaction occurs. Occurs, and a dye is formed and develops color. Recording is performed by a thermal head having a structure in which minute heating resistors are linearly arranged according to the required dot density. Recording is performed by heating and cooling a minute heating resistor in a very short time in accordance with signals from various devices and repeating this in the feed direction. The direct thermal method using such a thermal recording material has recently been attracting attention because it covers the drawbacks of silver salt film and exhibits the same high image quality as silver salt film.
[0005]
However, some of the heat-sensitive recording materials have the property that the sensitivity varies depending on the moisture content depending on the type of the heat-sensitive recording material. The moisture content of the heat-sensitive recording material greatly depends on the humidity of the recording atmosphere. For example, when the humidity is low, the image density decreases, and conversely, when the humidity is high, the image density increases. It was.
[0006]
On the other hand, if the moisture content of the heat-sensitive recording material is low, torque is increased when the thermal head is run, and sticking is likely to occur. Conversely, if the moisture content is high, blocking between the heat-sensitive recording materials occurs. It was.
[0007]
Therefore, conventionally, measures have been taken to insert a humidity control agent having a humidity control function during processing and packaging so that the heat-sensitive recording material has a constant moisture content (see, for example, Patent Document 1). ) In the book of the thermal recording material of the packaged product, a moisture content difference occurs between the thermal recording material close to the humidity control agent and the thermal recording material in the book, resulting in a change in density during printing between the films in the book. There was a problem.
[0008]
[Patent Document 1]
JP 2000-263933 A
[0009]
[Problems to be solved by the invention]
This invention is made | formed in view of the said conventional problem, and makes it a subject to achieve the following objectives. That is,
An object of the present invention is to provide a heat-sensitive recording material capable of maintaining a constant image density even under different humidity atmospheres and causing less sticking and blocking, and a method for producing the same.
[0010]
[Means for Solving the Problems]
Means for solving the problems are as follows. That is,
<1> A method for producing a heat-sensitive recording material in which at least a heat-sensitive recording layer is laminated on a support, wherein the heat-sensitive recording material is coated and dried after coating and drying all the coating liquids of the layer including the heat-sensitive recording layer. A method for producing a heat-sensitive recording material, wherein the material is conditioned and packaged so that the equilibrium moisture content of the material is an equilibrium moisture content when left in an atmosphere of 35 to 65% at an equilibrium relative humidity at 25 ° C. is there.
<2> The thermosensitive recording material further includes a group consisting of stearic acid, zinc stearate, calcium stearate, stearamide, ethylene bisstearamide, hydrogenated castor oil, silicon, alkyl phosphate ester, and fluorine-containing compound. The method for producing a heat-sensitive recording material according to <1>, further comprising a protective layer containing at least one selected lubricant, an inorganic pigment, and a binder.
<3> A heat-sensitive recording material produced by the method for producing a heat-sensitive recording material according to <1> or <2>.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
The method for producing a heat-sensitive recording material of the present invention is a method for producing a heat-sensitive recording material in which at least a heat-sensitive recording layer is laminated on a support, and all the coating liquids for the layers including the heat-sensitive recording layer are applied. After drying, the thermosensitive recording material is packaged by adjusting the humidity so that the equilibrium moisture content of the thermosensitive recording material is an equilibrium moisture content when left in an atmosphere of 35 to 65% at an equilibrium relative humidity at 25 ° C. Yes. The heat-sensitive recording material of the present invention is manufactured by the method for manufacturing a heat-sensitive recording material of the present invention.
Hereinafter, the heat-sensitive recording material of the present invention will be described first.
[0012]
<Thermal recording material>
The heat-sensitive recording material of the present invention has at least a heat-sensitive recording layer on a support and, if necessary, a protective layer, an undercoat layer, an intermediate layer, and the like. Hereinafter, the support and each layer will be described.
[0013]
[Support]
Examples of the support include polyester films such as polyethylene terephthalate and polybutylene terephthalate, cellulose derivative films such as cellulose triacetate film, polyolefin films such as polystyrene film, polypropylene film, polyethylene film, polyimide film, polyvinyl chloride film, poly Examples thereof include synthetic polymer films such as vinylidene chloride film, polyacrylic acid copolymer film, and polycarbonate film, and paper, synthetic paper, and paper having a plastic resin layer.
The said support body can be used individually or by bonding.
[0014]
The paper having the plastic resin layer is preferably one in which a layer containing a thermoplastic resin is formed on both surfaces of the base paper or at least the surface on which the heat-sensitive recording layer is formed. As such a support, for example, (1) a thermoplastic resin is melt-extruded and coated on a base paper, and (2) a gas barrier layer is coated on a thermoplastic resin that is melt-extruded and coated on a base paper. , (3) A base film with a plastic film with low oxygen permeability, (4) A base sheet with a plastic film bonded to it, and a thermoplastic resin by melt extrusion, (5) Base paper Examples include those obtained by melt-extruding a thermoplastic resin and then adhering a plastic film.
[0015]
Examples of the thermoplastic resin that is melt-extruded and applied to the base paper include olefin resins, for example, α-olefin homopolymers such as polyethylene and polypropylene, and mixtures of these various polymers, or random copolymers of ethylene and vinyl alcohol. Polymers are preferred. Examples of the polyethylene include LPDE (low density polyethylene), HDPE (high density polyethylene), L-LPDE (linear low density polyethylene) and the like.
[0016]
The method of laminating the plastic film to the base paper can be appropriately selected from known lamination methods described in “New Laminating Handbook” (Edited by Processing Technology Research Group), etc., but so-called dry lamination, solventless dry lamination, electron beam Alternatively, dry lamination or hot dry lamination using an ultraviolet curable resin is preferable.
[0017]
Among the various supports described above, a synthetic polymer film is preferable, and polyethylene terephthalate is more preferable.
[0018]
The synthetic polymer film may be colored in an arbitrary hue. As a method of coloring the polymer film, (1) a method in which a dye is kneaded in advance with a resin before film formation, and (2) ▼ Prepare a coating solution in which the dye is dissolved in an appropriate solvent, and apply this to a transparent and colorless resin film by a known coating method, such as a gravure coating method, a roller coating method, a wire coating method, etc. It is done. Among them, a polyester resin such as polyethylene terephthalate or polyethylene naphthalate kneaded with a blue dye is preferably formed into a film and subjected to heat treatment, stretching treatment and antistatic treatment.
[0019]
As thickness of the said support body, 25-300 micrometers is preferable and 50-250 micrometers is more preferable.
A thermal recording layer, a protective layer, an ultraviolet filter layer, an intermediate layer, etc., which will be described later, are coated on a support by blade coating, air knife coating, gravure coating, roll coating coating, spray coating, dip coating, bar coating. It can apply | coat by well-known coating methods, such as a method, and can dry and form.
[0020]
In the heat-sensitive recording material of the present invention, a transparent heat-sensitive recording material can be obtained by using a transparent support. Examples of the transparent support include polyester films such as polyethylene terephthalate (PET) and polybutylene terephthalate, cellulose triacetate films, and synthetic polymer films such as polyolefin films such as polypropylene and polyethylene. These may be used alone or in combination. Can be used.
In the case of medical use, the transparent support may be colored with a blue dye (for example, dye-1 described in Examples of JP-A-8-240877) or may be uncolored. The support is preferably primed with gelatin or water-soluble polyester. In this case, the thickness of the support is preferably 25 to 250 μm, more preferably 50 to 210 μm.
[0021]
The synthetic polymer film may be colored in an arbitrary hue. As a method of coloring a polymer film, a method of forming a film by kneading a dye into a resin before forming a resin film, preparing a coating solution in which a dye is dissolved in an appropriate solvent, and preparing this as a colorless transparent resin Examples of the coating method include a known coating method on the film, for example, a gravure coating method, a roller coating method, a wire coating method, and the like. Among them, a polyester resin such as polyethylene terephthalate or polyethylene naphthalate kneaded with a blue dye is preferably formed into a film and subjected to heat treatment, stretching treatment, and antistatic treatment.
[0022]
In particular, when the heat-sensitive recording material of the present invention is observed from the support side on a schacus ten, illusion may occur due to the schacus ten light transmitted through a transparent non-image portion, resulting in an image that is difficult to see.
In order to avoid this, as the transparent support, A (x = 0.8055, y = 0.3005), B (x = 0.820, on the chromaticity coordinates defined by the method described in JIS-Z8701. y = 0.2970), C (x = 0.2885, y = 0.015), D (x = 0.2870, y = 0.04040) is colored blue in a rectangular region formed by four points It is particularly preferable to use a synthetic polymer film prepared.
[0023]
[Thermosensitive recording layer]
The heat-sensitive recording layer contains at least a coloring component, and can further contain other components as required.
[0024]
(Coloring component)
The heat-sensitive recording layer can be used in any composition as long as it has excellent transparency when not processed and has a property of being colored by heating.
As such a heat-sensitive recording layer, a so-called two-component heat-sensitive recording layer containing a substantially colorless coloring component A and a substantially colorless coloring component B that reacts with the coloring component A to develop a color. The coloring component A or the coloring component B is preferably encapsulated in microcapsules. Examples of the combination of the two components constituting the two-component heat-sensitive recording layer include the following (a) to (m).
[0025]
(A) A combination of an electron donating dye precursor and an electron accepting compound.
(B) A combination of a photodegradable diazo compound and a coupler.
(C) A combination of an organic metal salt such as silver behenate or silver stearate and a reducing agent such as protocatechinic acid, spiroindane or hydroquinone.
(D) A combination of a long-chain aliphatic salt such as ferric stearate or ferric myristate and a phenol such as gallic acid or ammonium salicylate.
(E) Organic acid heavy metal salts such as salts with nickel, cobalt, lead, copper, iron, mercury, silver, etc. such as acetic acid, stearic acid, palmitic acid, and alkaline earths such as calcium sulfide, strontium sulfide, potassium sulfide, etc. A combination of a metal sulfide or a combination of the organic acid heavy metal salt and an organic chelating agent such as s-diphenylcarbazide or diphenylcarbazone.
(F) A combination of a (heavy) metal sulfate such as silver sulfide, lead sulfide, mercury sulfide, or sodium sulfide and a sulfur compound such as Na-tetrathionate, sodium thiosulfate, or thiourea.
(G) A combination of an aliphatic ferric salt such as ferric stearate and an aromatic polyhydroxy compound such as 3,4-dihydroxytetraphenylmethane.
(H) A combination of an organic noble metal salt such as silver oxalate or mercury oxalate and an organic polyhydroxy compound such as polyhydroxy alcohol, glycerin or glycol.
(I) A combination of an aliphatic ferric salt such as ferric pelargonate or ferric laurate, and a thiocesylcarbamide or isothiocecilcarbamide derivative.
(J) A combination of an organic acid lead salt such as lead caproate, lead pelargonate or lead behenate and a thiourea derivative such as ethylenethiourea or N-dodecylthiourea.
(K) A combination of a higher fatty acid heavy metal salt such as ferric stearate or copper stearate and zinc dialkyldithiocarbamate.
(L) A substance that forms an oxazine dye such as a combination of resorcin and a nitroso compound.
(M) A combination of a formazan compound and a reducing agent and / or a metal salt.
[0026]
Among these, in the heat-sensitive recording material of the present invention, (a) a combination of an electron donating dye precursor and an electron accepting compound, (b) a combination of a photodegradable diazo compound and a coupler, and (c) an organic It is preferable to use a combination of a metal salt and a reducing agent, and it is particularly preferable to use a combination of the above (a) and (b).
[0027]
Further, the heat-sensitive recording material of the present invention is an image having excellent transparency by constituting the heat-sensitive recording layer so as to lower the haze value calculated from (diffuse transmittance / total light transmittance) × 100 (%). Can be obtained. The haze value is an index representing the transparency of the material, and is generally calculated from the total light transmission amount, the diffuse transmission light amount, and the parallel transmission light amount using a haze meter.
In the present invention, as a method for lowering the haze value, for example, (1) the 50% volume average particle size of both the coloring components (A, B) contained in the heat-sensitive recording layer is 1.0 μm or less, preferably , 0.6 μm or less, and a method of containing a binder in the range of 30 to 60% by mass of the total solid content of the heat-sensitive recording layer, or (2) either one of the color developing components (A, B) in a microcapsule Examples include a method of encapsulating the other and forming the substantially continuous layer after coating and drying, for example, as an emulsion. Also effective is (3) a method in which the refractive index of the component used in the thermosensitive recording layer is as close to a constant value as possible.
[0028]
Next, combinations (a), (b), and (c) of the color forming components that are preferably used in the heat-sensitive recording layer will be described in detail below.
(A) Combination of electron-donating dye precursor and electron-accepting compound
The electron donating dye precursor preferably used in the present invention is not particularly limited as long as it is substantially colorless. However, the electron donating dye precursor is colored by donating electrons or accepting protons such as acids. In particular, it has a partial skeleton such as lactone, lactam, sultone, spiropyran, ester, amide, etc., and when this is contacted with an electron accepting compound, these partial skeletons are opened or cleaved. Those which are colorless compounds are preferred.
[0029]
Examples of the electron-donating dye precursor include triphenylmethane phthalide compounds, fluoran compounds, phenothiazine compounds, indolyl phthalide compounds, leucooramine compounds, rhodamine lactam compounds, and triphenylmethane compounds. Examples thereof include compounds, triazene compounds, spiropyran compounds, fluorene compounds, pyridine compounds, pyrazine compounds.
[0030]
Specific examples of the phthalides include U.S. Reissue Patent No. 23,024, U.S. Pat. Nos. 3,491,111, 3,491,112, and 3,491,116. And the compounds described in JP 3,509,174.
Specific examples of the fluorans include U.S. Pat. Nos. 3,624,107, 3,627,787, 3,641,011, 3,462,828, 3, 681, 390, 3,920, 510, 3,959, 571 and the like.
Specific examples of the spiropyrans include compounds described in US Pat. No. 3,971,808.
Examples of the pyridine-based and pyrazine-based compounds include compounds described in US Pat. Nos. 3,775,424, 3,853,869, 4,246,318, and the like.
Specific examples of the fluorene compound include compounds described in JP-A-63-94878.
Among these, black-colored 2-arylamino-3- [H, halogen, alkyl, or alkoxy-6-substituted aminofluorane] is particularly preferable.
[0031]
Specifically, for example, 2-anilino-3-methyl-6-diethylaminofluorane, 2-anilino-3-methyl-6-Ncyclohexyl-N-methylaminofluorane, 2-p-chloroanilino-3-methyl -6-dibutylaminofluorane, 2-anilino-3-methyl-6-dioctylaminofluorane, 2-anilino-3-chloro-6-diethylaminofluorane, 2-anilino-3-methyl-6-N-ethyl -N-isoamylaminofluorane, 2-anilino-3-methyl-6-N-ethyl-N-dodecylaminofluorane, 2-anilino-3-methoxy-6-dibutylaminofluorane, 2-o-chloroanilino- 6-dibutylaminofluorane, 2-p-chloroanilino-3-ethyl-6-N-ethyl-N-isoamylaminofluor Lan, 2-o-chloroanilino-6-p-butylanilinofluorane, 2-anilino-3-pentadecyl-6-diethylaminofluorane, 2-anilino-3-ethyl-6-dibutylaminofluorane, 2-o -Toluidino-3-methyl-6-diisopropylaminofluorane, 2-anilino-3-methyl-6-N-isobutyl-N-ethylaminofluorane, 2-anilino-3-methyl-6-N-ethyl-N -Tetrahydrofurfurylaminofluorane, 2-anilino-3-chloro-6-N-ethyl-N-isoamylaminofluorane, 2-anilino-3-methyl-6-N-methyl-N-γ-ethoxypropylamino Fluorane, 2-anilino-3-methyl-6-N-ethyl-N-γ-ethoxypropylaminofluorane, 2-anilino- -Methyl-6-N-ethyl-N-γ-propoxypropylaminofluorane, 3,6-bis (hexyloxy))-2- (2-thienyl) spiro [4H-3,1-benzoxazine-4, 9 ′-[9H] xanthrene], 3 ′, 6′-bis (hexyloxy) -2- (2-phenyl) -spiro [4H-3,1-benzoxazine-4,9 ′-[9H] xanthrene] Etc.
[0032]
Examples of the electron-accepting compound that acts with the electron-donating dye precursor include acidic substances such as phenol compounds, organic acids or metal salts thereof, and oxybenzoic acid esters. For example, JP-A-61-291183. Can be mentioned.
Specifically, 2,2-bis (4′-hydroxyphenyl) propane (generic name: bisphenol A), 2,2-bis (4′-hydroxyphenyl) pentane, 2,2-bis (4′-hydroxy) -3 ', 5'-dichlorophenyl) propane, 1,1-bis (4'-hydroxyphenyl) cyclohexane, 2,2-bis (4'-hydroxyphenyl) hexane, 1,1-bis (4'-hydroxyphenyl) ) Propane, 1,1-bis (4′-hydroxyphenyl) butane, 1,1-bis (4′-hydroxyphenyl) pentane, 1,1-bis (4′-hydroxyphenyl) hexane, 1,1-bis (4′-hydroxyphenyl) heptane, 1,1-bis (4′-hydroxyphenyl) octane, 1,1-bis (4′-hydroxyphenyl) -2-methyl -Pentane, 1,1-bis (4'-hydroxyphenyl) -2-ethyl-hexane, 1,1-bis (4'-hydroxyphenyl) dodecane, 1,4-bis (p-hydroxyphenylcumyl) benzene 1,3-bis (p-hydroxyphenylcumyl) benzene, bis (p-hydroxyphenyl) sulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, bis (p-hydroxyphenyl) acetic acid benzyl ester, etc. Bisphenols;
[0033]
Salicylic acid derivatives such as 3,5-di-α-methylbenzylsalicylic acid, 3,5-di-tertiarybutylsalicylic acid, 3-α-α-dimethylbenzylsalicylic acid, 4- (β-p-methoxyphenoxyethoxy) salicylic acid;
[0034]
Or a polyvalent metal salt thereof (in particular, zinc or aluminum is preferable); p-hydroxybenzoic acid benzyl ester, p-hydroxybenzoic acid-2-ethylhexyl ester, β-resorcinic acid- (2-phenoxyethyl) ester, etc. Oxybenzoates; phenols such as p-phenylphenol, 3,5-diphenylphenol, cumylphenol, 4-hydroxy-4'-isopropoxy-diphenylsulfone, 4-hydroxy-4'-phenoxy-diphenylsulfone Is mentioned. Among these, bisphenols are particularly preferable from the viewpoint of obtaining good color development characteristics.
Moreover, said electron-accepting compound may be used individually by 1 type, and may use 2 or more types together.
[0035]
(B) Combination of photodegradable diazo compound and coupler
The above photodegradable diazo compound is a compound that reacts with a coupler, which is a coupling component described later, to develop a desired hue, decomposes when receiving light in a specific wavelength region before the reaction, and is no longer coupled. It is a photodegradable diazo compound that does not have a coloring ability even in the presence of a component.
The hue in this color developing system is determined by a diazo dye formed by the reaction of a diazo compound and a coupler. Therefore, the color hue can be easily changed by changing the chemical structure of the diazo compound or coupler, and an arbitrary color hue can be obtained depending on the combination.
[0036]
Examples of the photodegradable diazo compound preferably used in the present invention include aromatic diazo compounds, and specifically include aromatic diazonium salts, diazosulfonate compounds, diazoamino compounds and the like.
Examples of the aromatic diazonium salt include, but are not limited to, compounds represented by the following general formula. In addition, the aromatic diazonium salt is preferably used since it has excellent photofixability, little generation of colored stain after fixing, and a stable color developing portion.
Ar-N₂ ⁺X⁻
In the above formula, Ar represents a substituted or unsubstituted aromatic hydrocarbon ring group, and N₂ ⁺Is a diazonium group, X⁻Represents an acid anion.
[0037]
As the diazosulfonate compound, many compounds have been known in recent years, and each diazonium salt can be obtained by treating each diazonium salt with a sulfite, and can be suitably used for the heat-sensitive recording material of the present invention.
[0038]
The diazoamino compound can be obtained by coupling a diazo group with dicyandiamide, sarcosine, methyltaurine, N-ethylanthranic acid-5-sulfonic acid, monoethanolamine, diethanolamine, guanidine, etc. It can be suitably used for the heat-sensitive recording material of the invention.
Details of these diazo compounds are described in detail, for example, in JP-A-2-136286.
[0039]
On the other hand, examples of couplers that undergo a coupling reaction with the above-mentioned diazo compound include those described in JP-A-62-146678, including resorcin, in addition to 2-hydroxy-3-naphthoic acid anilide. It is done.
[0040]
In the thermosensitive recording layer, when using a combination of a diazo compound and a coupler, these coupling reactions can be further promoted by performing them in a basic atmosphere. Basic substances may be added.
Examples of the basic substance include water-insoluble or hardly soluble basic substances and substances that generate alkali by heating, such as inorganic or organic ammonium salts, organic amines, amides, urea, thiourea or derivatives thereof, Nitrogenous compounds such as thiazoles, pyrroles, pyrimidines, piperazines, guanidines, indoles, imidazoles, imidazolines, triazoles, morpholines, piperidines, amidines, forimazines or pyridines. .
Specific examples thereof include those described in JP-A No. 61-291183.
[0041]
Next, (c) a combination of an organic metal salt and a reducing agent will be described.
Specific examples of the organic metal salts include silver salts of long chain aliphatic carboxylic acids such as silver laurate, silver myristate, silver palmitate, silver stearate, silver arachidate or silver behenate; benzotriazole silver Silver salts of organic compounds having an imino group such as salts, benzimidazole silver salts, carbazole silver salts or phthalazinone silver salts; silver salts of sulfur-containing compounds such as s-alkylthioglycolates; aromas such as silver benzoate and silver phthalate A silver salt of an aromatic carboxylic acid; a silver salt of a sulfonic acid such as silver ethanesulfonate; a silver salt of a sulfinic acid such as silver o-toluenesulfinate; a silver salt of a phosphoric acid such as silver silver phenylphosphate; a silver barbiturate; Examples include silver saccharinate, silver salt of salicyl asdoxime, or any mixture thereof.
Of these, long-chain aliphatic carboxylic acid silver salts are preferable, and silver behenate is more preferable. Further, behenic acid may be used together with silver behenate.
[0042]
The reducing agent can be appropriately used based on the description in JP-A-53-1020, page 227, lower left column, line 14 to page 229, upper right column, line 11. Among them, mono, bis, tris or tetrakisphenols, mono or bisnaphthols, di or polyhydroxynaphthalenes, di or polyhydroxybenzenes, hydroxy monoethers, ascorbic acids, 3-pyrazolidones, pyrazolines, pyrazolones It is preferable to use reducing sugars, phenylenediamines, hydroxylamines, reductones, hydroxamic acids, hydrazides, amide oximes, N-hydroxyureas and the like.
Of the above, aromatic organic reducing agents such as polyphenols, sulfonamidophenols or naphthols are particularly preferred.
[0043]
In order to ensure sufficient transparency of the heat-sensitive recording material, (a) a combination of an electron-donating dye precursor and an electron-accepting compound, or (b) a photodegradable diazo compound and a coupler, It is preferable to use a combination of In the present invention, it is preferable to use one of the coloring component A and the coloring component B in a microencapsulated form, and the electron donating dye precursor or the photodegradable diazo compound is used in a microencapsulated form. More preferably.
[0044]
(Microcapsule)
Next, the manufacturing method of a microcapsule is explained in full detail.
There are an interfacial polymerization method, an internal polymerization method, an external polymerization method and the like in the production of microcapsules, and any method can be adopted.
As described above, the heat-sensitive recording material of the present invention preferably includes an electron-donating dye precursor or a photodegradable diazo compound in a microcapsule, and in particular, an electron-donating dye precursor or a light that becomes the core of the capsule. An oil phase prepared by dissolving or dispersing a degradable diazo compound in a hydrophobic organic solvent is put into an aqueous phase in which a water-soluble polymer is dissolved, emulsified and dispersed by stirring means such as a homogenizer, and then heated. Therefore, it is preferable to employ an interfacial polymerization method in which a polymer forming reaction is caused at the oil droplet interface to form a microcapsule wall made of a polymer substance.
[0045]
The reactant that forms the polymer substance is added inside the oil droplet and / or outside the oil droplet. Specific examples of the polymer substance include polyurethane, polyurea, polyamide, polyester, polycarbonate, urea-formaldehyde resin, melamine resin, polystyrene, styrene methacrylate copolymer, styrene-acrylate copolymer, and the like. Among these, polyurethane, polyurea, polyamide, polyester, and polycarbonate are preferable, and polyurethane and polyurea are particularly preferable.
[0046]
For example, when polyurea is used as a capsule wall material, polyisocyanates such as diisocyanate, triisocyanate, tetraisocyanate and polyisocyanate prepolymer, polyamines such as diamine, triamine and tetraamine, two or more amino acids A microcapsule wall can be easily formed by reacting a prepolymer having a group, piperazine or a derivative thereof, or a polyol with the interfacial polymerization method in the aqueous phase.
[0047]
In addition, for example, a composite wall made of polyurea and polyamide or a composite wall made of polyurethane and polyamide is made of, for example, polyisocyanate and a second substance (for example, acid chloride, polyamine, or polyol) that reacts with it to form a capsule wall. It can be prepared by mixing in a water-soluble polymer aqueous solution (aqueous phase) or an oily medium to be encapsulated (oil phase), emulsifying and dispersing them, and then heating. Details of the method for producing the composite wall composed of polyurea and polyamide are described in, for example, JP-A-58-66948.
[0048]
The polyisocyanate compound is preferably a compound having a trifunctional or higher functional isocyanate group, but a bifunctional isocyanate compound may be used in combination. Specifically, diisocyanates such as xylene diisocyanate and hydrogenated products thereof, hexamethylene diisocyanate, tolylene diisocyanate and hydrogenated products thereof, isophorone diisocyanate and the like, and dimers thereof. In addition to a trimer (burette or isocyanurate), a polyfunctional adduct of a polyol such as trimethylolpropane and a bifunctional isocyanate such as xylylene diisocyanate, a polyol such as trimethylolpropane and a xylylene Examples thereof include a compound in which a high molecular weight compound such as polyether having active hydrogen such as polyethylene oxide is introduced into an adduct with a bifunctional isocyanate such as range isocyanate, and a formalin condensate of benzene isocyanate.
The compounds described in JP-A-62-212190, JP-A-4-26189, JP-A-5-317694, JP-A-10-114153 and the like are preferable.
[0049]
The polyisocyanate is preferably added so that the average particle size of the microcapsules is 0.3 to 12 μm and the thickness of the capsule wall is 0.01 to 0.3 μm. The dispersed particle size is generally about 0.2 to 10 μm.
[0050]
Specific examples of polyols and / or polyamines that react with the polyisocyanate and are added to the water phase and / or the oil phase as one of the components of the microcapsule wall include propylene glycol, glycerin, trimethylolpropane, Examples include ethanolamine, sorbitol, hexamethylenediamine, and the like. When a polyol is added, a polyurethane wall is formed. In the above reaction, it is preferable to keep the reaction temperature high or to add an appropriate polymerization catalyst from the viewpoint of increasing the reaction rate.
The polyisocyanate, polyol, reaction catalyst, polyamine for forming a part of the wall agent, and the like are detailed in, for example, “Polyurethane Handbook” (Nikkan Kogyo Shimbun, 1987) edited by Keiji Iwata.
[0051]
In addition, a metal-containing dye, a charge control agent such as nigrosine, or any other additive substance can be added to the microcapsule wall as necessary. These additives can be included in the wall of the capsule at the time of wall formation or at any time. Further, a monomer such as a vinyl monomer may be graft-polymerized in order to adjust the chargeability of the capsule wall surface as necessary.
[0052]
Furthermore, it is preferable to use a plasticizer suitable for the polymer used as the wall material, in order to make the wall of the microcapsule excellent in material permeability even under lower temperature conditions and rich in color development. The plasticizer preferably has a melting point of 50 ° C. or higher, and more preferably has a melting point of 120 ° C. or lower. Of these, those that are solid at room temperature can be suitably selected and used.
For example, when the wall material is made of polyurea or polyurethane, a hydroxy compound, a carbamic acid ester compound, an aromatic alkoxy compound, an organic sulfonamide compound, an aliphatic amide compound, an arylamide compound, or the like is preferably used.
[0053]
In preparing the oil phase, the hydrophobic organic solvent used for dissolving the electron-donating dye precursor or the photodegradable diazo compound to form the core of the microcapsule is an organic solvent having a boiling point of 100 to 300 ° C. Is preferred.
Specifically, in addition to esters, dimethylnaphthalene, diethylnaphthalene, diisopropylnaphthalene, dimethylbiphenyl, diisopropylbiphenyl, diisobutylbiphenyl, 1-methyl-1-dimethylphenyl-2-phenylmethane, 1-ethyl-1-dimethylphenyl -1-phenylmethane, 1-propyl-1-dimethylphenyl-1-phenylmethane, triallylmethane (eg, tritoluylmethane, toluyldiphenylmethane), terphenyl compound (eg, terphenyl), alkyl compound, alkylated diphenyl ether (For example, propyl diphenyl ether), hydrogenated terphenyl (for example, hexahydroterphenyl), diphenyl ether, and the like. Among these, it is particularly preferable to use esters from the viewpoint of emulsion stability of the emulsion dispersion.
[0054]
Examples of the esters include phosphate esters such as triphenyl phosphate, tricresyl phosphate, butyl phosphate, octyl phosphate, and cresyl phenyl phosphate; dibutyl phthalate, 2-ethylhexyl phthalate, ethyl phthalate, Phthalic acid esters such as octyl phthalate and butyl benzyl phthalate; Dioctyl tetrahydrophthalate; Benzoic acid esters such as ethyl benzoate, propyl benzoate, butyl benzoate, isopentyl benzoate and benzyl benzoate; Ethyl abietic acid, abietic acid Abietic acid esters such as benzyl; dioctyl adipate; isodecyl succinate; dioctyl azelate; oxalic acid esters such as dibutyl oxalate and dipentyl oxalate; diethyl malonate; dimethyl maleate, diethyl maleate, di maleate Maleic acid esters such as chill; Tributyl citrate; Sorbic acid esters such as methyl sorbate, ethyl sorbate, and butyl sorbate; Sebacic acid esters such as dibutyl sebacate and dioctyl sebacate; Formic acid monoesters and diesters, butyric acid monoester And ethylene glycol esters such as diester, lauric acid monoester and diester, palmitic acid monoester and diester, stearic acid monoester and diester, oleic acid monoester and diester; triacetin; diethyl carbonate; diphenyl carbonate; ethylene carbonate; propylene carbonate And boric acid esters such as tributyl borate and tripentyl borate.
[0055]
Among these, in particular, when tricresyl phosphate is used alone or in combination, the stability of the emulsion is most favorable, which is preferable. It is also possible to use the above oils in combination with other oils.
[0056]
When the electron-donating dye precursor to be encapsulated or the photodegradable diazo compound has poor solubility in the hydrophobic organic solvent, a low-boiling solvent having high solubility can be supplementarily used together. Preferred examples of such a low boiling point solvent include ethyl acetate, isopropyl acetate, butyl acetate, and methylene chloride.
[0057]
In the present invention, when the electron donating dye precursor or the photodegradable diazo compound is used in a heat sensitive recording layer of a heat sensitive recording material, the content of the electron donating dye precursor is 0.1 to 5.0 g / m²Is preferable, 1.0-4.0 g / m²Is more preferable.
The content of the photodegradable diazo compound is 0.02 to 5.0 g / m.²0.10 to 4.0 g / m in terms of color density²Is more preferable.
The content of the electron donating dye precursor is 0.1 to 5.0 g / m.²In this range, a sufficient color density can be obtained, and the content of both is 5.0 g / m.²Within the range, a sufficient color density can be maintained and the transparency of the thermosensitive recording layer can be maintained.
[0058]
On the other hand, an aqueous solution in which a water-soluble polymer is dissolved as a protective colloid is used for the aqueous phase to be used, and after the oil phase is added thereto, emulsification and dispersion are performed by means of a homogenizer or the like. And a dispersion medium that stabilizes the emulsified and dispersed aqueous solution. Here, in order to more uniformly emulsify and disperse and stabilize, a surfactant may be added to at least one of the oil phase and the aqueous phase. As the surfactant, a known surfactant for emulsification can be used. 0.1-5% is preferable with respect to the mass of an oil phase, and, as for the addition amount of this surfactant, 0.5-2% is more preferable.
[0059]
As the surfactant to be contained in the aqueous phase, an anionic or nonionic surfactant that does not cause precipitation or aggregation by acting with the protective colloid can be suitably selected and used.
Preferable surfactants include, for example, sodium alkylbenzene sulfonate, sodium alkyl sulfate, dioctyl sulfosuccinate sodium salt, polyalkylene glycol (for example, polyoxyethylene nonyl phenyl ether) and the like.
[0060]
For emulsification, the oil phase containing the above components and the aqueous phase containing the protective colloid and the surfactant are stirred by means of normal fine particle emulsification such as high-speed stirring and ultrasonic dispersion, such as a homogenizer, Manton Gorey, It can be easily carried out using a known emulsifying device such as an ultrasonic disperser, a dissolver, a teddy mill or the like. After the emulsification, the emulsion is preferably heated to 30 to 70 ° C. in order to promote the capsule wall formation reaction. Further, during the reaction, in order to prevent aggregation between the capsules, it is preferable to add water to reduce the collision probability between the capsules or perform sufficient stirring.
[0061]
Further, a dispersion for preventing aggregation may be added again during the reaction. As the polymerization reaction proceeds, the generation of carbon dioxide gas is observed, and the end of the generation can be regarded as the end point of the capsule wall formation reaction. Usually, the target microcapsule can be obtained by reacting for several hours.
[0062]
(Emulsified dispersion)
When an electron donating dye precursor or a photodegradable diazo compound is encapsulated as a core substance, the electron accepting compound or coupler to be used is, for example, a water-soluble polymer and an organic base, other color forming aids, etc. At the same time, it can be used as a solid dispersion by means of a sand mill or the like. However, after previously dissolving in a high-boiling organic solvent that is hardly soluble or insoluble in water, this is used as a protective colloid with a surfactant and / or a water-soluble polymer. It is more preferable to use as an emulsified dispersion mixed with the aqueous polymer solution (aqueous phase) contained and emulsified with a homogenizer or the like. In this case, a low boiling point solvent can be used as a dissolution aid, if necessary.
Further, the coupler and the organic base can be emulsified and dispersed separately, or mixed and then dissolved in a high boiling point organic solvent to be emulsified and dispersed. A preferable emulsified and dispersed particle size is 1 μm or less.
[0063]
The high boiling point organic solvent used in this case can be appropriately selected from, for example, high boiling point oils described in JP-A-2-141279.
Among them, it is preferable to use esters from the viewpoint of emulsion stability of the emulsion dispersion, and tricresyl phosphate is particularly preferable. The above oils can be used together with other oils.
[0064]
The water-soluble polymer contained as the protective colloid can be appropriately selected from known anionic polymers, nonionic polymers, and amphoteric polymers, and has a solubility in water at the temperature to be emulsified. A water-soluble polymer of 5% or more is preferable, and specific examples thereof include polyvinyl alcohol or a modified product thereof, polyacrylic acid amide or a derivative thereof, ethylene-vinyl acetate copolymer, styrene-maleic anhydride copolymer, ethylene -Maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, polyvinylpyrrolidone, ethylene-acrylic acid copolymer, vinyl acetate-acrylic acid copolymer, cellulose derivatives such as carboxymethylcellulose, methylcellulose, casein, gelatin, Starch derivatives, arabic gum, sodium alginate Etc. The.
Among these, polyvinyl alcohol and modified products thereof, gelatin and modified products thereof, cellulose derivatives and the like are particularly preferable.
[0065]
Moreover, 0.02-0.6 are preferable and, as for the mixing ratio (oil phase mass / aqueous phase mass) with respect to the water phase of an oil phase, 0.1-0.4 are more preferable. When the mixing ratio is in the range of 0.02 to 0.6, an appropriate viscosity can be maintained, the production suitability is excellent, and the coating solution stability is excellent.
[0066]
When an electron-accepting compound is used in the heat-sensitive recording material of the present invention, the electron-accepting compound is preferably 0.5 to 30 parts by mass with respect to 1 part by mass of the electron-donating dye precursor, and 1.0 to 10 parts by mass is more preferable.
Further, when a coupler is used in the heat-sensitive recording material of the present invention, the amount of the coupler is preferably 0.1 to 30 parts by mass with respect to 1 part by mass of the diazo compound.
[0067]
(Coating solution for thermal recording layer)
The thermal recording layer coating liquid can be prepared, for example, by mixing the microcapsule liquid prepared as described above and an emulsified dispersion. Here, the water-soluble polymer used as the protective colloid in the preparation of the microcapsule liquid and the water-soluble polymer used as the protective colloid in the preparation of the emulsified dispersion are used as the binder in the thermosensitive recording layer. Function. In addition to these protective colloids, a binder may be added and mixed to prepare a thermal recording layer coating solution.
The binder to be added is generally a water-soluble binder, such as polyvinyl alcohol, hydroxyethyl cellulose, hydroxypropyl cellulose, epichlorohydrin-modified polyamide, ethylene-maleic anhydride copolymer, styrene-maleic anhydride copolymer. Examples of the polymer include isobutylene-maleic salicylic acid copolymer, polyacrylic acid, polyacrylic acid amide, methylol-modified polyacrylamide, starch derivative, casein, and gelatin.
In addition, a water-resistant agent may be added for the purpose of imparting water resistance to these binders, or an emulsion of a hydrophobic polymer, specifically, a styrene-butadiene rubber (SBR) latex, an acrylic resin emulsion, or the like may be added. .
[0068]
When applying the above-mentioned heat-sensitive recording layer coating solution on the support, known coating means used for aqueous or organic solvent-based coating solutions are used. In this case, the heat-sensitive recording layer coating solution is applied safely and uniformly. In addition, in order to maintain the strength of the coating film, in the heat-sensitive recording material of the present invention, methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, starches, gelatin, polyvinyl alcohol, carboxy-modified polyvinyl alcohol, polyacrylamide, polystyrene, or a co-polymer thereof. Polymer, polyester or copolymer thereof, polyethylene or copolymer thereof, epoxy resin, acrylate resin or copolymer thereof, methacrylate resin or copolymer thereof, polyurethane resin, polyamide resin, polyvinyl butyral resin, etc. are used. can do.
[0069]
(Other ingredients)
Hereinafter, other components that can be used in the thermosensitive recording layer will be described.
The other components are not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include known heat-fusible substances, ultraviolet absorbers and antioxidants.
[0070]
The heat-fusible substance can be contained in the heat-sensitive recording layer for the purpose of improving thermal response. Examples of the heat-fusible substance include aromatic ethers, thioethers, esters, aliphatic amides, ureidos and the like.
Examples of these are disclosed in JP-A Nos. 58-57989, 58-87094, 61-58789, 62-109682, 62-132673, 63-151478, and 63-235961. It is described in Japanese Laid-Open Patent Publication Nos. 2-184289 and 2-215585.
[0071]
Preferred examples of the UV absorber include benzophenone UV absorbers, benzotriazole UV absorbers, salicylic acid UV absorbers, cyanoacrylate UV absorbers, and oxalic acid anilide UV absorbers. Examples of these are disclosed in JP-A-47-10537, 58-111942, 58-21284, 59-19945, 59-46646, 59-109555, 63-53544, JP-A 36-10466, 42-26187, 48-30492, 48-31255, 48-41572, 48-54965, and 50-10726, U.S. Pat. No. 086, No. 3,707,375, No. 3,754,919, No. 4,220,711, and the like.
[0072]
Preferable examples of the antioxidant include hindered amine antioxidants, hindered phenol antioxidants, aniline antioxidants, and quinoline antioxidants. Examples of these are described in JP-A Nos. 59-155090, 60-107383, 60-107384, 61-137770, 61-139481, 61-160287, and the like. Yes.
[0073]
The coating amount of these other components is 0.05 to 1.0 g / m.²The degree is preferable, 0.1 to 0.4 g / m²Is more preferable. The other components may be added inside the microcapsule or outside the microcapsule.
[0074]
In the present invention, the heat-sensitive recording layer suppresses density unevenness caused by a slight difference in thermal conductivity of the thermal head and the like, so that a high-quality image can be obtained._t-maxIt is preferable that the recording layer be a heat-sensitive recording layer having a wide energy amount range, that is, a wide dynamic range. The heat-sensitive recording material of the present invention has the heat-sensitive recording layer as described above, and is 90 to 150 mJ / mm.²The saturated transmission density (D_t-max) = 3.0 is preferable.
[0075]
The heat-sensitive recording layer has a solid coating amount of 1 to 25 g / m after coating and drying.²It is preferable to apply so that the thickness of the layer becomes 1 to 25 μm. Further, two or more thermosensitive recording layers can be laminated and used. In this case, the solid coating amount after application / drying of the entire thermosensitive recording layer is 1 to 25 g / m.²Is preferred.
[0076]
[Protective layer]
The heat-sensitive recording material of the present invention is preferably provided with a protective layer, and the protective layer is formed on the heat-sensitive recording layer or when the intermediate layer is provided on the heat-sensitive recording layer as another layer. Is done. This protective layer is usually formed by applying a protective layer coating solution. The protective layer is at least selected from the group consisting of stearic acid, zinc stearate, calcium stearate, stearamide, ethylene bisstearamide, hydrogenated castor oil, silicon, alkyl phosphate ester, and fluorine-containing compound. The inclusion of one type of lubricant, an inorganic pigment, and a binder is preferable for the reasons of preventing sticking during conveyance of the thermal head and obtaining good print image quality.
[0077]
(lubricant)
The lubricant is at least one selected from the group consisting of stearic acid, zinc stearate, calcium stearate, stearic acid amide, ethylene bisstearamide, hydrogenated castor oil, silicone, alkyl phosphate ester, and fluorine-containing compound. Preferably there is.
[0078]
Lubricant content is 0.05-2.0 g / m²Is preferably 0.2 to 1.0 g / m.²It is more preferable that
[0079]
When the lubricant used in the heat-sensitive recording material of the present invention is insoluble in water, it is preferably added to the protective layer in the form of dispersion or emulsion. In the case of a solid, (1) an aqueous dispersion dispersed with a known disperser such as a homogenizer, dissolver or sand mill in the presence of a water-soluble polymer such as polyvinyl alcohol or a dispersant such as various surfactants. (2) Emulsified after being dissolved in a solvent and then emulsified and dispersed with a known emulsifying device such as a homogenizer, dissolver or colloid mill in the presence of a dispersing agent such as a water-soluble polymer or various surfactants Used in the form of In the case of a liquid, it is used in the form of an emulsion as described above. A preferable average particle size of the dispersion or emulsion is 0.1 to 5.0 μm, and more preferably 0.1 to 2.0 μm. Here, the average particle diameter refers to, for example, a 50% volume average particle diameter measured at a transmittance of 71 ± 1% using a laser diffraction particle size distribution measuring device “LA-700” manufactured by Horiba, Ltd. .
[0080]
(Inorganic pigment)
The inorganic pigment contained in the protective layer is usually used for the purpose of making recording with a thermal head suitable, that is, suppressing the occurrence of sticking or abnormal noise.
[0081]
As the inorganic pigment used for the protective layer, the average particle diameter, specifically, 50% volume average particle diameter measured by a laser diffraction method (pigment measured by a laser diffraction particle size distribution measuring device “LA700” manufactured by Horiba, Ltd.) The average particle diameter of pigment particles corresponding to 50% volume in the medium, hereinafter referred to simply as “average particle diameter”) is preferably 0.10 to 5 μm. At this time, it is more preferable that the 50% volume average particle diameter is in the range of 0.20 to 0.50 μm from the viewpoint of preventing the occurrence of sticking or abnormal noise between the thermal head and the thermal recording material. When this 50% volume average particle size is in the range of 0.10 to 5.0 μm, the effect of reducing friction with respect to the thermal head is large, and as a result, the thermal head and the protective layer of the thermal recording material adhere to each other at the time of printing. The so-called sticking phenomenon can be effectively prevented.
[0082]
The inorganic pigment that can be used in the protective layer is not particularly limited, and examples thereof include known inorganic pigments. In particular, calcium carbonate, titanium oxide, kaolin, aluminum hydroxide, amorphous silica, oxidized Inorganic pigments such as zinc are preferred. Of these, kaolin, aluminum hydroxide, and amorphous silica are more preferable. These inorganic pigments may be used alone or in combination of two or more.
[0083]
These inorganic pigments include, for example, sodium metametaphosphate, partially saponified or fully saponified polyvinyl alcohol, polyacrylic acid copolymers, dispersion aids such as various surfactants, preferably partially saponified or fully saponified polyvinyl alcohol, In the presence of an acrylic acid copolymer ammonium salt, it is preferably used by dispersing to the above-mentioned average particle size with a known disperser such as a dissolver, sand mill, or ball mill. That is, the pigment is preferably used after being dispersed until the 50% volume average particle size is in the range of 0.1 to 5.0 μm.
[0084]
The content of the inorganic pigment is 0.1 to 3.0 g / m²Is preferably 0.2 to 2.0 g / m.²It is more preferable that
[0085]
(binder)
From the viewpoint of improving the transparency of the protective layer, it is preferable to use polyvinyl alcohol, carboxy-modified polyvinyl alcohol, silica-modified polyvinyl alcohol, gelatin or the like as a binder.
[0086]
(Other ingredients)
The protective layer may contain a known hardener or the like. Examples of the hardener include inorganic compounds such as boric acid, borax, and colloidal silica, and dialdehyde derivatives represented by the following structural formula [001].
[Chemical 1]

[0087]
In the present invention, in order to form a protective layer uniformly on the heat-sensitive recording layer or the intermediate layer, it is preferable to add a surfactant to the protective layer-forming coating solution. As the surfactant, sulfosuccinic acid-based alkali metal salts, fluorine-containing surfactants, and the like are preferable. Specific examples include di- (2-ethylhexyl) sulfosuccinic acid and di- (n-hexyl) sulfosuccinic acid. Examples include sodium salts, potassium salts, or ammonium salts, acetylene glycol derivatives, sodium perfluoroalkyl sulfate, potassium salts, ammonium salts, perfluoroalkyl betaine compounds, and the like.
[0088]
Furthermore, metal oxide fine particles, inorganic electrolytes, polymer electrolytes, and the like may be added to the protective layer for the purpose of preventing charging of the thermosensitive recording material. The protective layer may have a single layer structure or a laminated structure of two or more layers.
The dry coating amount of the protective layer is 0.2 to 7 g / m.²1 to 4 g / m²Is more preferable.
[0089]
In the heat-sensitive recording material of the present invention, an intermediate layer, an undercoat layer, an ultraviolet filter layer, an antireflection layer (back layer), and the like can be provided on the support as other layers.
[0090]
[Middle layer]
The intermediate layer is preferably formed on the thermosensitive recording layer. The intermediate layer is provided to prevent mixing of layers and to block gases (oxygen and the like) harmful to image storage stability. The binder to be used is not particularly limited, and polyvinyl alcohol, gelatin, polyvinyl pyrrolidone, cellulose derivatives and the like can be used depending on the system. Among them, gelatin has fluidity at high temperatures, but has a property (set property) that loses fluidity and gels at low temperatures (for example, 35 ° C. or lower), so that a plurality of layers are formed on a support. In the case of providing the layer by applying and drying a coating solution for forming, the two adjacent layers may be applied by a method in which a plurality of layers are sequentially applied and dried, or in a method in which multiple layers are applied and dried at once by an extrusion die method or the like. The layers can be effectively prevented from mixing with each other, the surface shape of the resulting heat-sensitive recording material is improved, and a heat-sensitive recording material capable of high-quality image formation can be obtained. It is suitable for a medical diagnostic recording material that needs to be formed. Further, even when dried at a high wind speed, the surface condition is not deteriorated, so that the production efficiency is improved.
As such gelatin, unmodified (untreated) gelatin or modified (treated) gelatin can be used without any problem. Examples of modified gelatin include lime-processed gelatin, acid-processed gelatin, phthalated-processed gelatin, deionized-processed gelatin, and enzyme-processed low-molecular-weight gelatin. Further, various surfactants may be added for imparting coatability. In order to further improve the gas barrier properties, inorganic fine particles such as mica may be added to the binder in an amount of 2 to 20% by mass, more preferably 5 to 10% by mass. The binder concentration of the intermediate layer coating solution is 3 to 25% by mass, preferably about 5 to 15% by mass. The dry coating amount of the intermediate layer is 0.5 to 6 g / m.², Preferably 1 to 4 g / m²Is appropriate.
[0091]
[Undercoat layer]
In the heat-sensitive recording material of the present invention, for the purpose of preventing the heat-sensitive recording layer from being peeled off from the support, before coating the heat-sensitive recording layer containing the microcapsules or the like, the light reflection preventing layer, etc. A layer can be provided.
As the undercoat layer, an acrylate copolymer, polyvinylidene chloride, SBR, aqueous polyester, or the like can be used, and the thickness of the layer is preferably 0.05 to 0.5 μm.
[0092]
When applying the heat-sensitive recording layer on the undercoat layer, the undercoat layer may swell due to moisture contained in the heat-sensitive recording layer coating solution, and the image recorded on the heat-sensitive recording layer may deteriorate. Is preferably cured using dialdehydes such as glutaraldehyde, 2,3-dihydroxy-1,4-dioxane, and hardeners such as boric acid. The amount of these hardeners can be appropriately added according to the desired degree of curing in the range of 0.2 to 3.0% by mass depending on the mass of the undercoat material.
[0093]
[UV filter layer]
In the heat-sensitive recording material of the present invention, an ultraviolet filter layer may be provided to prevent discoloration of the image and background fogging. The UV filter layer is obtained by uniformly dispersing an UV absorber in a binder, and the uniformly dispersed UV absorber absorbs UV light effectively. Prevents parts from discoloring or fading. As the method for forming the ultraviolet filter layer and the compound used, those described in JP-A-4-197778 can be used in addition to ultraviolet absorbers such as benzotriazole, benzophenone, and hindered amine.
[0094]
[Antireflection layer]
The heat-sensitive recording material of the present invention is preferably a single-sided light-sensitive material having a heat-sensitive recording layer containing microcapsules on one side of the support and an antireflection layer (back layer) on the other side. It is preferable to add a matting agent to the light antireflection layer (back layer) for the purpose of imparting transportability and preventing light reflection. By adding a matting agent, the glossiness measured at an incident light angle of 20 ° is preferably 50% or less, and more preferably 30% or less.
Examples of the matting agent include fine particles such as starch obtained from barley, wheat, corn, rice, beans, etc., cellulose fiber, polystyrene resin, epoxy resin, polyurethane resin, urea formalin resin, poly (meth) acrylate resin, polymethyl (Meth) acrylate resin, copolymer resin such as vinyl chloride or vinyl acetate, fine particles of synthetic polymer such as polyolefin, calcium carbonate, titanium oxide, kaolin, smectite viscosity, inorganic substances such as aluminum hydroxide, silica, zinc oxide Examples thereof include fine particles. The average particle size of the matting agent is 0.5 to 20 μm, preferably 0.5 to 10 μm. The mat materials may be used alone or in combination of two or more.
Further, from the viewpoint of improving the transparency of the heat-sensitive recording material, the refractive index is preferably in the range of 1.4 to 1.8. Various dyes (for example, CI Pigment Blue 60, CI Pigment Blue 64, CI Pigment Blue 15: 6) can be used for the back layer from the viewpoint of improving the hue. Further, a hardener may be used for the back layer. Examples of the hardener include T.W. H. There are various methods described in “THE THEORY OF THE PHOTOGRAPHIC PROCESS 4th EDITION” by James (pages 77 to 87), and vinyl sulfone compounds are preferred.
[0095]
Since the heat-sensitive recording material of the present invention is produced by the method for producing the heat-sensitive recording material of the present invention, which will be described later, the equilibrium moisture content is kept uniform, so that the image density can be kept constant. .
[0096]
<Method for producing thermosensitive recording material>
Next, a method for producing the heat-sensitive recording material of the present invention will be described.
The method for producing a heat-sensitive recording material of the present invention comprises forming a heat-sensitive recording layer by applying the heat-sensitive recording layer-forming coating solution on a support, and forming a protective layer on the heat-sensitive recording layer, if necessary. A protective layer is formed by applying a coating solution for coating, and other layers are formed as necessary.
Here, the heat-sensitive recording layer and other layers may be formed at the same time, and in that case, the heat-sensitive recording layer forming coating solution and the other layer forming coating solution are simultaneously coated on the support. Thus, there is a step of simultaneously forming a heat-sensitive recording layer and a protective layer thereon.
[0097]
As the support used here, the support described above used in the heat-sensitive recording material of the present invention can be used. Further, as the heat-sensitive recording layer forming coating solution, the above-mentioned heat-sensitive recording layer coating solution can be used. Further, the protective layer-forming coating solution is also for the protective layer containing the pigment and the binder described above. A coating solution can be used.
Moreover, as said other layer, other layers, such as the intermediate | middle layer mentioned above and undercoat, are mentioned.
In the method for producing a heat-sensitive recording material of the present invention, a blade coating method, an air knife coating method, a gravure coating method, a roll coating are used to sequentially form an undercoat layer, a heat-sensitive recording layer, an intermediate layer, a protective layer, etc. on a support. Known coating methods such as a coating method, a spray coating method, a dip coating method, and a bar coating method are used.
[0098]
(Thermal head)
The thermal head used for thermal recording is a heating comprising a heating resistor and an electrode on the glaze layer using a known film forming apparatus so that the carbon ratio of the uppermost layer in contact with the thermal recording material is 90% or more. What provided the protective layer in the element is preferable. The head protective layer may be two or more layers, but at least the uppermost layer preferably has a carbon ratio of 90% or more.
[0099]
In the method for producing the heat-sensitive recording material of the present invention, after all the coating liquids of the laminated layers including the heat-sensitive recording layer are applied and dried, the equilibrium moisture content of the heat-sensitive recording material is an equilibrium relative humidity at 25 ° C. Then, the humidity is adjusted and packaged so as to obtain an equilibrium moisture content when left in an atmosphere of 35 to 65%.
[0100]
In the present invention, in order to obtain an equilibrium moisture content when the thermosensitive recording material is left in an atmosphere of 35 to 65% at an equilibrium relative humidity at 25 ° C., the thermosensitive recording material is usually left in the above atmosphere for 24 hours or more. This can be achieved by reaching equilibrium. Further, the humidity adjustment time can be shortened to 16 hours by applying the wind of the above atmosphere to the surface of the heat sensitive recording material at a wind speed of 0.1 m / sec or more.
[0101]
After conditioning the heat-sensitive recording material as described above, as a method of packaging, after loading the heat-sensitive recording material into a U-shaped bent shape of a moisture retention rate made of polypropylene or natural pulp base paper, A method of sealing by sealing in a packaging bag can be mentioned.
Moreover, as a material of the packaging bag or packaging box used for packaging, polyethylene laminated with polyethylene, nylon, or polyethylene terephthalate is preferable from the viewpoint of moisture resistance.
[0102]
In this specification, the equilibrium water content is a numerical value obtained by measurement as follows. That is, after measuring the mass of the thermal recording material when the thermal recording material is left in a predetermined temperature and humidity atmosphere for 24 hours or more, it is heated at 105 ° C. for 16 hours or more to evaporate all the moisture of the thermal recording material. Then, the mass of moisture is measured by calculating its mass, and the moisture content obtained by dividing the mass of moisture by the mass of the heat-sensitive recording material before heating is the equilibrium moisture content at a predetermined temperature and humidity.
[0103]
As described above, by setting the thermal recording material to the above-mentioned equilibrium moisture content, the thermal recording material can be kept at a uniform equilibrium moisture content regardless of the season or any position in the booklet. Depending on the rate, the image density can be kept constant, and sticking and blocking can be prevented.
[0104]
【Example】
EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited only to the following examples. All concentrations used in the text are mass%. The emulsified dispersion means an oil-in-water dispersion type dispersion.
[0105]
Example 1
<Preparation of coating solution for protective layer>
[Preparation of pigment dispersion A for protective layer]
To 110 g of water, 30 g of stearic acid-treated aluminum hydroxide (trade name: Heidilite H42S, Showa Denko KK) was added as a pigment and stirred for 3 hours, and then a dispersion aid (trade name: Poise 532A, Kao ( 0.8 g, 10% polyvinyl alcohol aqueous solution (trade name: PVA105, manufactured by Kuraray Co., Ltd.) 30 g, 10 g of an aqueous solution of a compound represented by the following structural formula [100] adjusted to 2%, and added with a sand mill. Dispersion was performed to obtain a pigment dispersion A for protective layer having an average particle size of 0.30 μm.
The “average particle size” means that the test solution in which the pigment to be used is dispersed in the presence of a dispersion aid and diluted to 0.5% by adding water to the pigment dispersion immediately after the dispersion is added to warm water at 40 ° C. , And adjusted so that the light transmittance is 75 ± 1.0%, and then subjected to ultrasonic treatment for 30 seconds and measured with a laser diffraction particle size distribution measuring device (trade name: LA700, manufactured by Horiba, Ltd.) The average particle diameter of pigment particles corresponding to 50% by volume of the total pigment is used, and the “average particle diameter” described below represents the average particle diameter measured by the same method.
[0106]
[Chemical 2]

[0107]
[Preparation of coating solution for protective layer]
To 65 g of water,
8% polyvinyl alcohol aqueous solution
(Product name: PVA124C, manufactured by Kuraray Co., Ltd.) 90g
20.5% zinc stearate dispersion
(Product name: F115, manufactured by Chukyo Yushi Co., Ltd.) 5.5 g
21.5% stearamide compound
(Product name: G-270, manufactured by Chukyo Yushi Co., Ltd.) 3.8 g
18.0% stearic acid dispersion
(Product name: Cellosol 920, manufactured by Chukyo Yushi Co., Ltd.) 2.8 g
4% boric acid aqueous solution 10g
70 g of pigment dispersion A for protective layer
35% silicone oil aqueous dispersion
(Polydimethylsiloxane, trade name: BY22-840,
Toray Dow Corning Co., Ltd.) 4.7g
6.5% sodium dodecylbenzenesulfonic acid sodium salt aqueous solution 6.5g
75% di-2-ethylhexylsulfosuccinic acid
Ammonium salt aqueous solution
(Product name: Nissan Electol SAL1, manufactured by NOF Corporation) 3.28 g
6% styrene-maleic acid copolymer ammonium salt
Aqueous solution (trade name: Polymaron 385, manufactured by Arakawa Chemical Co., Ltd.) 17.5 g
20% colloidal silica
(Product name: Snowtex, manufactured by Nissan Chemical Co., Ltd.) 14g
10% Surflon S131S (Asahi Glass Co., Ltd.) 16g
PRISURF A217E (Daiichi Kogyo Seiyaku Co., Ltd.) 1.1g
2% acetic acid 8g
Were mixed to obtain a coating solution for protective layer.
[0108]
<Preparation of coating solution for intermediate layer>
After adding 7848 g of water to 1 kg of lime-processed gelatin and dissolving it, a 5% solution (water / 137 g of methanol = 1/1 volume mixed solvent) was added to prepare an intermediate layer coating solution.
[0109]
<Preparation of coating solution for thermosensitive recording layer>
Each liquid of the microcapsule coating liquid and the developer emulsified dispersion was prepared as follows.
[Preparation of microcapsule coating solution A]
As coloring component,
11.7 g of a compound represented by the following structural formula [201]
1.5 g of the compound represented by the following structural formula [202]
Compound represented by Structural Formula [203] 2.2 g
5.65 g of a compound represented by the following structural formula [204]
1.2 g of the compound represented by the following structural formula [205]
1.1 g of the compound represented by the following structural formula [206]
0.57 g of a compound represented by the following structural formula [207]
Was added to 24.3 g of ethyl acetate, heated to 70 ° C and dissolved, and then cooled to 45 ° C. To this, 15.4 g of capsule wall material (trade name: Takenate D140N, manufactured by Mitsui Takeda Chemical Co., Ltd.) was added and mixed.
[0110]
[Chemical 3]

[0111]
[Formula 4]

[0112]
[Chemical formula 5]

[0113]
This solution was added to an aqueous phase obtained by mixing 48 g of an aqueous 8% polyvinyl alcohol solution (trade name: MP-103, manufactured by Kuraray Co., Ltd.) with 16 g of water, and then an ace homogenizer (manufactured by Nippon Seiki Co., Ltd.). The resulting mixture was emulsified for 5 minutes at 15,000 rpm. To the obtained emulsion, 110 g of water and 1.0 g of tetraethylenepentamine were further added, followed by an encapsulation reaction at 60 ° C. for 4 hours to prepare a microcapsule coating solution A having an average particle size of 0.80 μm.
The glass transition temperature (hereinafter referred to as “Tg”) of the capsule wall of the obtained microcapsule coating liquid A was measured using DMTA (Dynamic Mechanical Thermal Analyzer) (trade name of a glass transition temperature measuring instrument manufactured by Polymer Laboratory). It was 193 degreeC when measured.
[0114]
[Preparation of microcapsule coating solution B]
Compound represented by Structural Formula [201] 12.2 g
1.6 g of the compound represented by the structural formula [202]
Compound represented by Structural Formula [203] 2.4 g
Compound represented by Structural Formula [204] 3.3 g
Compound represented by Structural Formula [205] 1.5 g
Compound represented by Structural Formula [206] 0.2 g
Compound represented by Structural Formula [207] 0.5 g
Was added to 21 g of ethyl acetate, heated to 70 ° C. and dissolved, and then cooled to 35 ° C. To this, 16.6 g of capsule wall material (trade name: Takenate D127N, manufactured by Mitsui Takeda Chemical Co., Ltd.) was added and mixed.
[0115]
This solution was added to an aqueous phase in which 48.1 g of 8% polyvinyl alcohol (MP-103, manufactured by Kuraray Co., Ltd.) was mixed with 16.6 g of water, and an ace homogenizer (manufactured by Nippon Seiki Co., Ltd.) was used at 15000 rpm. For 5 minutes. 112 g of water and 0.9 g of tetraethylenepentamine were further added to the obtained emulsion, followed by an encapsulation reaction at 60 ° C. for 4 hours to prepare a microcapsule coating solution B having an average particle size of 0.30 μm.
It was 153 degreeC when Tg of the capsule wall of the obtained microcapsule coating liquid B was measured similarly to the microcapsule liquid A.
[0116]
[Preparation of developer emulsified dispersion]
As a developer
6.7 g of a compound represented by the following structural formula [301]
Compound represented by Structural Formula [302] 8.0 g
5.8 g of a compound represented by the following structural formula [303]
1.5 g of the compound represented by the following structural formula [304]
Compound represented by the following structural formula [305] 2.2 g
0.8 g of the compound represented by the following structural formula [306]
4.3 g of the compound represented by the following structural formula [307]
Was added to 16.5 g of ethyl acetate together with 1.0 g of tricresyl phosphate and 0.5 g of diethyl maleate, and dissolved by heating to 70 ° C.
[0117]
[Chemical 6]

[0118]
[Chemical 7]

[0119]
70 g of water, 57 g of 8% polyvinyl alcohol aqueous solution (PVA217C, manufactured by Kuraray Co., Ltd.), 20 g of 15% polyvinyl alcohol aqueous solution (trade name: PVA205C, manufactured by Kuraray Co., Ltd.), and the following structural formula [401] After adding 11.5 g of a 2% aqueous solution of the compound represented by the following formula and the compound represented by the following structural formula [402] into a mixed aqueous phase, it was rotated at 10,000 rpm using an ace homogenizer (manufactured by Nippon Seiki Co., Ltd.). The developer was emulsified to an average particle size of 0.7 μm to obtain a developer emulsified dispersion C.
[0120]
[Chemical 8]

[0121]
[Preparation of coating solution A for thermosensitive recording layer]
Microcapsule coating liquid A (solid concentration 23%) 12g
Microcapsule coating liquid B (solid content 24%) 2.5g
Developer emulsified dispersion C (solid content 22%) 50 g
0.7 g of a 50% aqueous solution of a compound represented by the following structural formula [403]
Colloidal silica (Snowtex Nissan Chemical Co., Ltd.) 1.8g
Were mixed to prepare a coating solution A for a thermosensitive recording layer.
[0122]
[Chemical 9]

[0123]
[Preparation of thermal recording layer coating solution B]
Microcapsule coating liquid A (solid content concentration 23%) 2.3 g
Microcapsule coating liquid B (solid content concentration 24%) 6.6 g
Developer emulsified dispersion C (solid content 22%) 33 g
Colloidal silica (Snowtex, manufactured by Nissan Science Co., Ltd.) 1.5g
0.4 g of a 50% aqueous solution of the compound represented by the structural formula [403]
Were mixed to prepare a coating solution B for a heat-sensitive recording layer.
[0124]
[Preparation of Back Layer Coating Liquid A]
An ultraviolet absorber comprising 1 kg of lime-processed gelatin, 757 g of a gelatin dispersion containing 12% of spherical PMMA particles having an average particle size of 5.7 μm, and a compound represented by structural formulas [501] to [505] at the following contents 3761 g of the emulsion (the ultraviolet absorber content per kg of the emulsion is

[0125]
Embedded image

[0126]
[Preparation of Back Layer Coating Liquid B]
1 kg of lime-processed gelatin, 2000 g of gelatin dispersion containing 12% spherical PMMA particles having an average particle diameter of 0.7 μm, 1268 ml of methanol, 1.75 g of 1,2-benzisothiazolin-3-one, sodium polyacrylate ( 64.4 g of molecular weight of about 100,000), 54 g of poly (sodium p-vinylbenzenesulfonate) (molecular weight of about 400,000), 25.2 g of sodium p-tert-octylphenoxypolyoxyethylene-ethylenesulfonate, N- After adjusting 5.3 g of sodium propyl-N-polyoxyethylene-perfluorooctanesulfonate amidobutylsulfonate and 7.1 g of potassium perfluorooctanesulfonate to pH = 7.0 with caustic soda, water was added. The total amount was adjusted to 66.79 liters.
[0127]
The back layer coating solution A and the back layer coating solution B were blue-stained with x = 0.2850 and y = 0.2995 in chromaticity coordinates defined by the method described in JIS-Z8701, and the thickness was 180 μm. On one side of the axially stretched polyethylene terephthalate support, the coating amount is 44.0 ml / m in the order of the back layer coating solution A and the back layer coating solution B from the side close to the support.²18.5 ml / m²Then, simultaneous multi-layer coating and drying were performed by the slide bead method.
The coating and drying conditions are as follows. The coating speed was 160 m / min, the distance between the coating die tip and the support was 0.10 to 0.30 mm, and the pressure in the decompression chamber was set to be 200 to 1000 Pa lower than the atmospheric pressure. The support was neutralized with an ion wind before coating. In the subsequent chilling zone, the coating solution is cooled with a wind at a dry bulb temperature of 0 to 20 ° C., then conveyed in a non-contact manner, and dried at a dry bulb temperature of 23 to 45 ° C. and a wet bulb temperature by a helical contactless dryer. It dried with the dry wind of 15-21 degreeC.
[0128]
<Preparation of thermal recording material>
On the surface opposite to the back layer of the support coated with the back layer, from the side close to the support, the thermal recording layer coating liquid A, the thermal recording layer coating liquid B, the intermediate layer coating liquid, and the protective layer In the order of coating solution, the coating amount is 50 ml / m²20 ml / m²27 ml / m²25ml / m²It was applied and dried. The dried heat-sensitive recording material was conditioned and packaged so as to have an equilibrium water content when left in an atmosphere of 50% at an equilibrium relative humidity at 25 ° C., and then left in an atmosphere of summer at 29 ° C./70%. .
[0129]
<< Example 2 >>
The coating up to the back layer was carried out in the same manner as in Example 1. On the surface opposite to the back layer of the support on which the back layer was coated, the coating solution A for the thermal recording layer and the thermal recording layer from the side close to the support. Coating solution B, intermediate layer coating solution, and protective layer coating solution in that order, each coating amount 50 ml / m²20 ml / m²27 ml / m²25ml / m²It was applied and dried. The dried heat-sensitive recording material was packaged after being conditioned so as to have an equilibrium moisture content when left in an atmosphere of 50% at an equilibrium relative humidity at 25 ° C. and left in a winter atmosphere at 20 ° C./30%. .
[0130]
≪Comparative example 1≫
Equilibrium when the coating liquid of each layer was applied and dried on the surface opposite to the back layer of the support on which the back layer had been coated, and then allowed to stand in an atmosphere of 50% at an equilibrium relative humidity at 25 ° C. The moisture content was adjusted to a moisture content and then packaged and left in an atmosphere of 29 ° C./70%.
[0131]
≪Comparative example 2≫
Equilibrium when the coating liquid of each layer was applied and dried on the surface opposite to the back layer of the support on which the back layer had been coated, and then allowed to stand in an atmosphere of 50% at an equilibrium relative humidity at 25 ° C. The moisture content was adjusted so that the moisture content was reached, and then packaged and left in an atmosphere of 20 ° C./30%.
[0132]
The heat-sensitive recording materials prepared in Examples 1 and 2 and Comparative Examples 1 and 2 were taken out of the packaging bag, set in a dry image recording apparatus (DRYPIX) manufactured by Fuji Photo Film Co., Ltd., and 25 ° C./45%. Printing was performed at a printing energy of 80 mJ under the conditions, and the image densities were compared. The color density was measured using a Macbeth densitometer TD-404 (manufactured by Macbeth). The results are shown in Table 1.
[0133]
[Table 1]

[0134]
From Table 1, it can be seen that the heat-sensitive recording materials of Examples 1 and 2 were able to record at a substantially constant color density in both summer and winter atmospheres. In contrast, the heat-sensitive recording material of the comparative example had an equilibrium water content different from that of the example and had a difference in color density.
[0135]
Example 3
In Example 1 <Preparation of thermosensitive recording material>, a thermosensitive recording layer was prepared by applying and drying the thermosensitive recording layer coating solution A, the thermosensitive recording layer coating solution B, the intermediate layer coating solution, and the protective layer coating solution. The heat-sensitive recording material of Example 3 was the same as Example 1 except that the recording material was conditioned and packaged so as to have an equilibrium moisture content when left in an atmosphere with an equilibrium relative humidity at 25 ° C. of 35%. Was made.
[0136]
Example 4
In Example 1 <Preparation of thermosensitive recording material>, a thermosensitive recording layer was prepared by applying and drying the thermosensitive recording layer coating solution A, the thermosensitive recording layer coating solution B, the intermediate layer coating solution, and the protective layer coating solution. The heat-sensitive recording material of Example 4 was used in the same manner as in Example 1 except that the recording material was conditioned and packaged so as to have an equilibrium moisture content when left in an atmosphere with an equilibrium relative humidity at 25 ° C. of 50%. Was made.
[0137]
Example 5
In Example 1 <Preparation of thermosensitive recording material>, a thermosensitive recording layer was prepared by applying and drying the thermosensitive recording layer coating solution A, the thermosensitive recording layer coating solution B, the intermediate layer coating solution, and the protective layer coating solution. The heat-sensitive recording material of Example 5 was the same as Example 1 except that the recording material was conditioned and packaged so as to have an equilibrium moisture content when left in an atmosphere of 65% at an equilibrium relative humidity at 25 ° C. Was made.
[0138]
«Comparative Example 3»
In Example 1 <Preparation of thermosensitive recording material>, the thermosensitive recording material prepared by coating and drying was adjusted to have an equilibrium moisture content when left in an atmosphere of 30% at an equilibrium relative humidity at 25 ° C. Then, a heat-sensitive recording material of Comparative Example 3 was produced in the same manner as in Example 1 except that it was packaged.
[0139]
<< Comparative Example 4 >>
In Example 1 <Preparation of thermosensitive recording material>, the thermosensitive recording material prepared by coating and drying was controlled to have an equilibrium moisture content when left in an atmosphere of 70% at an equilibrium relative humidity at 25 ° C. Then, a heat-sensitive recording material of Comparative Example 4 was produced in the same manner as in Example 1 except that it was packaged.
[0140]
[Evaluation]
1. Evaluation of sticking
With respect to the heat-sensitive recording materials obtained in Examples 3 to 5 and Comparative Examples 3 to 4, the carbon content was 2 μm in thickness at the uppermost layer of a thermal head (trade name: KGT, 260-12MPH8) manufactured by Kyocera Corporation. The head pressure is 10 kg / cm using a thermal head in which a carbon layer of 98 mass% is provided by physical vapor deposition.²Recording energy is 120mJ / mm²When recording, observe visually whether or not a phenomenon of sticking or fusing (sticking) occurs between the thermal head and the protective layer of the heat-sensitive recording material during printing, and in accordance with the following evaluation criteria evaluated. The results are shown in Table 2.
[Evaluation]
○: Sticking did not occur.
Δ: A little sticking occurred.
X: A lot of sticking occurred.
[0141]
2. Blocking evaluation
The heat-sensitive recording material obtained in each of the examples and comparative examples, one book in B4 size in 101 packaging units, was stacked on a desk and left for two weeks, Whether or not blocking occurred between the heat-sensitive recording materials of the bottom book was visually evaluated according to the following evaluation criteria. The results are shown in Table 2.
[Evaluation criteria]
○: Not blocking.
Δ: The heat-sensitive recording materials are slightly blocked.
X: Blocking.
[0142]
[Table 2]

[0143]
From Table 2, the heat-sensitive recording materials of Examples 3 to 5 had neither sticking nor blocking, whereas the heat-sensitive recording materials of Comparative Examples 3 to 4 had either sticking or blocking.
[0144]
【The invention's effect】
According to the present invention, it is possible to provide a heat-sensitive recording material that can maintain a constant image density even under different humidity atmospheres and that is less susceptible to sticking and blocking, and a method for manufacturing the same.

Claims (3)

A method for producing a thermosensitive recording material in which at least a thermosensitive recording layer is laminated on a support,
After coating and drying all the coating liquids for the layers including the thermal recording layer, the equilibrium moisture content of the thermal recording material is left in an atmosphere of 35 to 65% at an equilibrium relative humidity at 25 ° C. A method for producing a heat-sensitive recording material, characterized in that the moisture is conditioned and packaged to achieve an equilibrium moisture content. The heat-sensitive recording material is further selected from the group consisting of stearic acid, zinc stearate, calcium stearate, stearamide, ethylene bisstearamide, hydrogenated castor oil, silicon, alkyl phosphate ester, and fluorine-containing compound. The method for producing a heat-sensitive recording material according to claim 1, further comprising a protective layer containing at least one lubricant, an inorganic pigment, and a binder. A heat-sensitive recording material produced by the method for producing a heat-sensitive recording material according to claim 1.