JP4678459B2 - Laminate for thermal transfer and magnetic recording medium - Google Patents

Description

【００１８】
やむを得ず、上記セルロ−ス誘導体樹脂と化学構造の基本構造で異なる樹脂を使用しなければならないときは、相溶性に問題がない範囲内で適宜選択し、添加・使用することができる。そのような樹脂の種類としては、ポリ塩化ビニル、アクリル樹脂、エポキシ樹脂、ポリカ−ボネ−ト等があり、その使用量は、前述の樹脂組成比で、任意成分樹脂・Ａに相当する0〜25質量％である。
【００１９】
また、剥離性保護層用樹脂として上記セルロース誘導体樹脂を使用する場合は、通常、保護層の機械的特性、例えば擦過性などを向上させるために、架橋促進剤としてのイソシアネート化合物を添加し、架橋反応を起し硬化を促進する。このイソシアネート化合物の使用量は、結着剤樹脂100質量部に対し2〜30質量部が好ましい。
【００２０】
またさらに、剥離性保護層には、転写用支持体と保護層との剥離性をより良好にするために、公知慣用の離型剤を含有させることが出来る。離型剤としては、例えばフッ素樹脂、ポリオレフィンワックス、天然ワックス、シリコン系離型剤等が挙げられる。
【００２１】
剥離性保護層形成用塗料の調製は、アセトン、酢酸エチル、酢酸ブチル、トルエン、シクロヘキサノン等の混合溶剤に、上記セルロース誘導体樹脂および離型剤その他の添加剤を加え、それらが５〜４０質量％の濃度になるように溶解・懸濁して行なう。
【００２２】
剥離性保護層の形成は、上記塗料を転写用支持体（ＰＥＴフィルム）上に、乾燥塗膜厚が０．４〜２．５μｍとなるように塗布し、窒素雰囲気中で乾燥の後、空気中、100〜120℃、10秒〜５分間の条件下で熱硬化処理して行う。塗布方式としては、特に制限はなく、公知慣用の方式を使用できる。単層または複数層構成の塗布物製造方式を採用して製造することができる。具体的には、例えばグラビア方式、リバース方式、エアドクターコーター方式、ブレードコーター方式、エアナイフコーター方式、スクイズコーター方式、含浸コーター方式、トランスファロールコーター方式、キスコーター方式、キャストコーター方式、スプレイコーター方式、ダイ方式等が挙げられる。
【００２３】
磁性層形成用塗料に用いられる結着樹脂としては、公知慣用の、例えばポリ塩化ビニル系樹脂、アクリル系樹脂、アクリルウレタン樹脂、ニトロセルロース樹脂、ポリウレタン、ポリエステル等を、単独であるいは混合して、用いることが出来る。
【００２４】
磁性層形成用塗料に用いられる磁性材料としては、公知慣用の、例えばγ−酸化鉄、マグネタイト、コバルト被着酸化鉄、２酸化クロム、鉄系メタル磁性粉、ストロンチュウムフェライト、バリウムフェライト等の磁性粉末を使用することができる。
【００２５】
磁性層形成用塗料の調製は、上記磁性粉末およびそれに対して20〜30質量％の上記結着剤樹脂、さらには必要に応じて、公知慣用の分散安定剤、界面活性剤、樹脂フィラー等を、メチルエチルケトン、トルエン、シクロヘキサノン等の混合溶剤中に溶解・分散させて行なう。そのときの塗料の固形分濃度は25〜50質量％であることが好ましい。また、溶解・分散には、公知慣用の、例えばボールミル、サンドグラインドミル等の分散機を使用することができる。
【００２６】
磁性層の形成は、上記磁性層形成用塗料に、硬化剤としてイソシアネート化合物を添加し、前述の剥離性保護層の上に、乾燥塗膜厚が2〜20μｍとなるように塗布し、窒素雰囲気中で乾燥後、空気中において100〜120℃、10秒〜5分間、熱硬化処理する。塗布方式としては、特に制限はなく、公知慣用の方式を使用できる。単層または複数層構成の塗布物製造に使用される方法に準じて製造することができる。具体的には、例えばグラビア方式、リバース方式、エアドクターコーター方式、ブレードコーター方式、エアナイフコーター方式、スクイズコーター方式、含浸コーター方式、トランスファロールコーター方式、キスコーター方式、キャストコーター方式、スプレイコーター方式、ダイ方式等が挙げられる。
【００２７】
接着層用の結着剤樹脂としては、常温でタックフリーであるが加熱により粘接着性を発現する熱可塑性結着剤樹脂であれば良く、公知慣用の、例えばポリ塩化ビニル系樹脂、ポリウレタン系樹脂等を用いることができる。
【００２８】
接着層形成用塗料の調製は、上記結着剤樹脂が3〜70重量％となるように、メチルエチルケトン、トルエン等の混合溶剤に溶解して調製する。またこの際、高温環境下でのブロッキング防止剤として、シリカやポリエチレンワックス等を添加することができる。
【００２９】
接着層の形成は、上記接着層形成用塗料を、磁性層上に、乾燥塗膜厚が0.3〜10μｍとなるように塗布し、空気中、50〜120℃で乾燥して行なう。塗布方式としては、特に制限はなく、公知慣用の方式を使用できる。単層または複数層構成の塗布物製造に使用される方法に準じて製造することができる。具体的には、例えばグラビア方式、リバース方式、エアドクターコーター方式、ブレードコーター方式、エアナイフコーター方式、スクイズコーター方式、含浸コーター方式、トランスファロールコーター方式、キスコーター方式、キャストコーター方式、スプレイコーター方式、ダイ方式等が挙げられる。
【００３０】
本発明の磁気記録媒体：磁気カードは、前述したように、磁気記録媒体基体の表面に上記熱転写用積層体を熱転写して得られる。基体は、通常、積層物であって、コアシートと呼ぶ印刷等が可能な芯材とその上下に設けられたオ−バ−レイシ−トと呼ぶカバーシートなどから成っている。
【００３１】
【実施例】
以下に、本発明の具体的な実施例および比較例を挙げ、更に詳細に説明する。
しかし、本発明はこれら実施例に限定されるものではない。なお、以下において、部は質量部を表すものとする。
【００３２】
（実施例１）
＜剥離性保護層形成用塗料の組成＞
酢酸セルロース ： Ｂ樹脂 ７．５部
（ダイセル化学社製『Ｌ−ＡＣ Ｌ−２０』）
セルロースアセテートプロピオネート ： Ｃ樹脂 １．８部
（イーストマンケミカル社製『ＣＡＰ５０４−０．２』）
ポリエチレンワックス ２．０部
（三井石油化学（株）製『ハイワックス２００ＰＦ』）
大豆レシチン ０．１部
アセトン ２４．３部
酢酸エチル ２４．３部
シクロヘキサノン １９部
トルエン １９部
イソシアネート化合物 ２部
（大日本インキ化学工業（株）製『バ−ノックＤ−７５０』）
【００３３】
＜磁性層形成用塗料の組成＞
Ｂａフェライト磁性粉 ４０部
（戸田工業（株）製『ＭＣ−１２７』）
塩化ビニル系樹脂 ６部
（日本ゼオン社製『ＭＲ−１１０』）
ポリウレタン樹脂 ４部
（大日本インキ化学工業（株）製『Ｔ−５２０６』）
メチルエチルケトン ２０部
トルエン ２０部
シクロヘキサノン ８部
イソシアネート化合物 ２部
（大日本インキ化学工業（株）製『バ−ノックＤ−７５０』）
【００３４】
＜接着層形成用塗料の組成＞
塩化ビニル−プロピオン酸ビニル共重合体樹脂 １０部
（東ソー（株）製『リューロンＱＣ６４０』）
メチルエチルケトン ４５部
トルエン ４５部
【００３５】
＜熱転写用積層体の調製＞
転写用支持体（ＰＥＴフィルム）上に、乾燥塗膜厚が１．０μｍとなるようにリバース塗工方式塗工機で、剥離性保護層形成用塗料を塗布し、窒素雰囲気中で乾燥後、空気中、１０５±５℃、３０秒間、熱硬化処理して剥離性保護層を形成した。その剥離性保護層の上に、乾燥塗膜厚が１４μｍとなるようにリバース塗工方式塗工機で磁性層形成用塗料を塗布し、窒素雰囲気中で乾燥後、１０５±５℃、３０秒間、熱硬化処理して磁性層を形成した。さらにその磁性層の上に、乾燥塗膜厚が１．５μｍとなるようにリバース塗工方式塗工機で接着層形成用塗料を塗布し、窒素雰囲気中で乾燥して接着層を形成した。この積層体が、本発明の熱転写用積層体である。
【００３６】
＜磁気記録媒体：磁気カード基体の材料と基体の調製＞
三菱樹脂（株）製『ビニホイルＣ−８１９５』
（透明オーバーレイシート用、厚さ１００μｍ）
三菱樹脂（株）製『ビニホイルＣ−４６３６Ｎ』
（白色コアシート用、厚さ２８０μｍ）
上記材料を順次積層し、120℃にて熱プレスする常法にて基体を得た。
【００３７】
＜磁気記録媒体：磁気カードの調製＞
上記で得た基体に、常法により、前記熱転写用積層体を転写し、磁気記録媒体：磁気カードを得た。実際に用いた装置は、オアシス社製・簡易カ−ド作製機『卓上ラミネータ ＯＬＡ６型』である。ラミネートは、温度８０℃、固定時間１２０秒、圧力メモリ４５の条件で仮転写を行い、転写用支持体であるＰＥＴフィルムを除去した後、再度、温度１６０℃、固定時間１２０秒、圧力メモリ６５で本プレスすることにより行った。
【００３８】
（比較例１）
剥離性保護層形成用塗料の組成を以下のようにした以外は、実施例１と同様にして熱転写用積層体および磁気記録媒体を作製した。
【００３９】
酢酸セルロース ： Ｂ樹脂 ９．３部
（ダイセル化学社製『Ｌ−ＡＣ Ｌ−２０』）
ポリエチレンワックス ２．０部
（三井石油化学（株）製『ハイワックス２００ＰＦ』）
大豆レシチン ０．１部
アセトン ２４．３部
酢酸エチル ２４．３部
シクロヘキサノン １９部
トルエン １９部
イソシアネート化合物 ２部
（大日本インキ化学工業（株）製『バ−ノックＤ−７５０』）
【００４０】
（比較例２）
剥離性保護層形成用塗料の組成を以下のようにした以外は、実施例１と同様にして熱転写用積層体および磁気記録媒体を作製した。
【００４１】
セルロースアセテートプロピオネート ： Ｃ樹脂 ９．３部
（イーストマンケミカル社製『ＣＡＰ５０４−０．２』）
ポリエチレンワックス ２．０部
（三井石油化学（株）製『ハイワックス２００ＰＦ』）
大豆レシチン ０．１部
アセトン ２４．３部
酢酸エチル ２４．３部
シクロヘキサノン １９部
トルエン １９部
イソシアネート化合物 ２部
（大日本インキ化学工業（株）製『バ−ノックＤ−７５０』）
【００４２】
（比較例３）
剥離性保護層形成用塗料の組成を以下のようにした以外は、実施例１と同様にして熱転写用積層体および磁気記録媒体を作製した。
【００４３】
酢酸セルロース ： Ｂ樹脂 ７．５部
（ダイセル化学社製『Ｌ−ＡＣ Ｌ−２０』）
セルロースアセテートブチレート ： Ａ樹脂 １．８部
（イーストマンケミカル社製『ＣＡＢ３８１−０．１』）
ポリエチレンワックス ２．０部
（三井石油化学（株）製『ハイワックス２００ＰＦ』）
大豆レシチン ０．１部
アセトン ２４．３部
酢酸エチル ２４．３部
シクロヘキサノン １９部
トルエン １９部
イソシアネート化合物 ２部
（大日本インキ化学工業（株）製『バ−ノックＤ−７５０』）
【００４４】
（比較例４）
剥離性保護層形成用塗料の組成を以下のようにした以外は、実施例１と同様にして熱転写用積層体および磁気記録媒体を作製した。
【００４５】
酢酸セルロース ： Ｂ樹脂 ４．７部
（ダイセル化学社製『Ｌ−ＡＣ Ｌ−２０』）
セルロースアセテートプロピオネート ： Ｃ樹脂 ４．６部
（イーストマンケミカル社製『ＣＡＰ５０４−０．２』）
ポリエチレンワックス ２．０部
（三井石油化学（株）製『ハイワックス２００ＰＦ』）
大豆レシチン ０．１部
アセトン ２４．３部
酢酸エチル ２４．３部
シクロヘキサノン １９部
トルエン １９部
イソシアネート化合物 ２部
（大日本インキ化学工業（株）製『バ−ノックＤ−７５０』）
【００４６】
（試験項目及び試験結果）
＜Ｉ．剥離性試験（剥離強度：支−保層・層間接着力）＞
転写用支持体（ＰＥＴフィルム）と剥離性保護層との剥離性、すなわち、剥離強度：支−保層・層間接着力を測定する。この値より、剥離性の難易を見極め、剥離強度値が10〜80mNの範囲にあれば、易剥離性と判定する。
熱転写用積層体を１０ｍｍ幅に裁断し、テープ状熱転写用積層体を作製する。このテープ状熱転写用積層体をオーバーレイシートに熱転写して剥離試験サンプルを得た。熱転写装置および熱転写条件は次の通りである。装置：ヒートシーラー（テスター産業株式会社製）、条件：１２０℃、９．９秒、０．４ＭＰａで熱プレス。次に、ここで得た剥離試験サンプルを剥離試験機にかけ、保護層から、転写用支持体であるＰＥＴフィルムを引き剥がす力、すなわち、剥離強度を測定した。剥離試験機は、高速剥離試験機（テスター産業株式会社製）を使用した。
【００４７】
＜II．接着性試験（保−磁層・層間接着力）＞
剥離性保護層と磁性層との接着性（保−磁層・層間接着力）を試験し、所定の接着性が有るか否かを見極める。
上記実施例および比較例で作製した磁気記録媒体を用いて、JIS K 5400-1990記載の碁盤目テープ法に準じて評価し、接着性の良否を判定した。
【００４８】
＜III．耐熱性試験＞
上記実施例および比較例で作製した磁気記録媒体を平圧プレス機（東洋精機社製）で熱プレスすることにより試験した。すなわち、磁気記録媒体をステンレス板で挟み、温度１８０℃、圧力８ＭＰａ、加熱時間３０分で熱プレス（平圧プレス機：東洋精機社製）する。その後、ステンレス板を取り外し、磁気テープと接していた側のステンレス板（他のステンレス板はオーバーレイシートとのみ接していた）の表面観察を行い、磁性層のステンレス板への焼き付き状態を確認する。ステンレス板を確認して磁気記録媒体の磁性層がステンレス板に転移しているか否かを目視にて確認し、耐熱性の良否を判定した。
【００４９】
＜IV．耐薬品性試験＞
上記実施例および比較例で作製した磁気記録媒体を用いて、薬品にて保護層を溶解・擦り落とすことにより試験した。試験薬品には、▲１▼メチルエチルケトン（ＭＥＫ）、▲２▼トルエン、▲３▼アルコールの各有機溶剤を使用する。室温および溶剤温度を２５±５℃として、試験溶剤を浸した綿棒で磁気記録媒体の保護層表面の同一箇所を擦る。１０回擦る毎に、綿棒の擦り面を目視にて観察し、磁気記録媒体の磁気層が綿棒に付着して茶色から黒色の着色が有るか否かを評価する。着色が認められたときの擦り回数を比較して耐溶剤性の良否を判定した。
【００５０】
＜Ｖ．耐擦過性（機械的強度）試験＞
上記実施例および比較例で作製した磁気記録媒体を磁気カード状に打ち抜き、カード書き込み機にて情報を書き込んだ後、カード読みとり機で一定回数の繰り返し読み取りを行い、読み取り情報の出力低下の状況と磁気カード上の磁気テープ部分の表面削れ状況とを目視観察し、耐擦過性（機械的強度）の良否を判定した。
【００５１】
＜試験結果＞
上記Ｉ〜Ｖの５項目の試験結果を、以下の表１に示す。
【００５２】
【表１】
表１．実施例における剥離性保護層の試験結果

（注）表において、
▲１▼▲２▼▲３▼は薬品の種類：▲１▼メチルエチルケトン、▲２▼トルエン、▲３▼エタノール を表わし、
データ数値は実測値、記号(○,×)は評価結果の良(○)、否(×) を示す。
【００５３】
（評価結果のまとめ）
表１の結果より、実施例１（セルロース誘導体樹脂のＢ、Ｃ樹脂を２種類併用かつ規定量遵守）のみが、目的の易剥離性（20mN）を示すと共に剥離性保護層に要求される他の特性[II〜Ｖ]も満足していることが判った。また、Ｂ、Ｃ樹脂のそれぞれ１種類・単独で使用した比較例１および比較例２では、Ｉ．剥離性はかなりの水準にあるが、II．接着性ないしＶ．擦過性では問題となる評価結果であり、目的未達であった。さらに、２種類の樹脂を併用した比較例３(ＡとＢの併用)および比較例４(ＢとＣの併用)においては、II．接着性は良であるが、目的のＩ．剥離性が大きくて不十分、他の特性[III〜Ｖ]にも否があって同様に目的未達であった。さらにまた、この比較例３，４より、Ｃ樹脂が必須成分樹脂であり、かつ樹脂組成比に規定量が有ること(Ｂ樹脂の下限量)が判った。
なお、経時変化の有無についても評価し、１ヶ月後に上記と同様の試験を行なった結果、試験結果に有意差は見られなかった。特に、実施例１では、易剥離性かつ他の特性も良であって、経時安定性が高いことを確認した。
【００５４】
【発明の効果】
本発明の熱転写用積層体およびそれを使用した磁気記録媒体は、最終製品製造工程中の剥離操作工程において、不要となるため除去の必要がある転写用支持体を剥離性保護層から剥離するとき、易剥離性である。そのため、剥離不良による転写用支持体（ＰＥＴフィルム）の破断や保護層中への残存などが起きず、不良品の発生や工程トラブルを防止することができる。これにより、磁気記録媒体の製造工程および製品品質の安定化、製品のコストダウンおよび資源の節約化ないしは廃棄物の低減化などに顕著な効果を奏する。
【図面の簡単な説明】
【図１】本発明における熱転写用積層体の縦断面図である。
【図２】磁気記録媒体基体上に熱転写用積層体を転写し、最上層の転写用支持体を剥離・除去した後の、本発明における磁気記録媒体の縦断面図である。
【符号の説明】
１ 転写用支持体
２ 剥離性保護層
３ 磁性層
４ 接着層
５ 磁気記録媒体基体[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a thermal transfer laminate used as a component of a magnetic recording medium such as a magnetic card, and a magnetic recording medium using the same. Here, in a broad sense, the magnetic recording medium is equipped with a magnetic layer portion having a magnetic recording / reproducing function on a base made of metal, plastic, paper, etc. having various functions such as required outer shape and mechanical characteristics. It is a general term for the product group. For example, magnetic disks and tapes as hardware components for computers, magnetic cards such as plastic credit cards or cash cards, magnetic passbooks made of synthetic paper such as banks, or magnetic tickets such as paper tickets and toll tickets Etc. At the same time, in a narrow sense, only the magnetic layer portion having a magnetic recording / reproducing function or the ancillary portion necessary for ensuring its function, such as a magnetic tape used as a built-in component of the card in the above-described magnetic card. (Also referred to as a magnetic stripe) is directly referred to as a magnetic recording medium, and a “heat transfer laminate” described later may be referred to as a magnetic recording medium.
[0002]
“Laminate for thermal transfer” is a magnetic recording / reproducing sheet with magnetic layers and other functional layers that are mainly used as components such as magnetic cards. In particular, the magnetic recording / reproducing sheet is prepared so that it can be loaded onto a substrate of a magnetic recording medium by a processing method called “transfer”. The thermal transfer laminate basically consists of (1) a transfer support, (2) a protective layer that protects the functional layer from various stains in the final product, and (3) magnetic recording. A laminated structure comprising at least four layers of a magnetic layer which is a substantially functional layer for reproduction and an adhesive layer for thermal transfer (4) is adopted. In addition, the thermal transfer laminate is generally prepared as one product (part) different from the plastic sheet or synthetic paper that is the base of the magnetic recording medium, and is used during the commercialization process in magnetic card manufacturing. As a component raw material, it is incorporated into the inside or surface portion of a magnetic recording medium.
[0003]
The technique of the present invention relates to the protective layer (2), which is one of the constituent layers in the thermal transfer laminate. This (2) protective layer is located between (1) the transfer support and (3) the magnetic layer which is a substantially functional layer, and between the above (1) and (3) serving as the upper and lower layers. Special suitability is required for mutual adhesiveness-interlayer adhesiveness. There are two types of adhesive strengths for interlaminar adhesiveness: [1]: (1) Interlayer adhesive strength at the interface between the transfer support and (2) protective layer (hereinafter referred to as “support-holding layer / interlayer adhesive strength”) And [2]: (2) Interlayer adhesive force at the interface between the protective layer and (3) the magnetic layer which is a substantially functional layer (hereinafter referred to as “coercive magnetic layer / interlayer adhesive force”) It is. Of these, the latter [2] is generally sufficient if the adhesion is strong, whereas the former [1] is required to have “appropriate adhesion”. The adhesiveness, which is this “appropriate adhesive strength”, is a requirement of “easy peeling property and small peeling force” when expressed from the operation surface of peeling off the transfer support. The present invention relates to a technology related to difficulty of peelability.
The present invention also relates to a technique of a magnetic recording medium using the thermal transfer laminate having the above-described peelable protective layer.
[0004]
[Prior art]
As such a protective layer (peelable protective layer) having both moderate adhesiveness and good peelability at the same time as the support-holding layer / interlayer adhesive force, its structure has been studied, and 65356 and JP 2000-293837 A. And in the synthetic resin composition consisting of a binder resin, an abrasion resistance improver, a mold release agent, a cross-linking accelerating curing agent, etc., which is a conventional protective layer configuration, as the particularly preferable binder resin, The use of a resin composition composed of an acrylic resin / salt-vinyl acetate resin / isocyanate compound is proposed, and in the latter case, one type of cellulose derivative resin is used alone.
[0005]
However, it has been difficult to obtain a peelable protective layer sufficient for practical use only with the configuration according to the above-described disclosure. That is, in both the former and the latter, the peeling strength is still too high, and when the transfer support is peeled off, it breaks and remains in the final product, resulting in a defective product. There was a problem of poor sexuality. In addition, the preparation of an acrylic resin composition for preventing the occurrence of defects and the selection of a cellulose derivative resin are accompanied by difficulties, and in addition of a release agent for reducing the peel strength, other important characteristics In order not to cause a decrease in the coercive layer / interlayer adhesion, there is a drawback that it is difficult to adjust the addition amount.
[0006]
[Problems to be solved by the invention]
An object of the present invention relates to a protective layer of a laminate for thermal transfer, and in a peeling operation for peeling and removing an unnecessary transfer support from the protective layer, a support-holding layer / interlayer adhesive force is appropriate. Peeling strength is small and easy to peel, and does not impair other properties required for the protective layer. In addition, peeling with these easy peelability and other properties stable over time It is providing the laminated body for thermal transfer which has a property protection layer. Another object of the present invention is to provide a magnetic recording medium using the thermal transfer laminate having the easily peelable protective layer.
[0007]
[Means for Solving the Problems]
As a result of intensive studies on the resin constituting the protective layer for the purpose of improving the peelability of the thermal transfer laminate, the present inventors specify the type, method, functional group amount and composition ratio, etc. of the resin to be used. Thus, a laminate for thermal transfer having a protective layer having a small peel strength and a desired easy peelability can be obtained, and further, by using the laminate to prepare a magnetic recording medium as a magnetic card The evaluation of various other properties required for the protective layer was confirmed to be at a practical level, and the present invention was completed.
[0008]
That is, the present invention provides a cellulose derivative as compared with the conventional construction in which one kind of cellulose derivative resin, which is relatively hard, has good film properties, and is excellent in releasability, is used as a binder resin for a protective layer. A plurality of types, preferably two types of resins are used in combination. The reason why a plurality of types are used in combination is based on the reason that the degree of freedom in adjusting the peel strength is remarkably improved as compared with the case where one cellulose derivative resin is used alone. Usually, when a cellulose derivative resin is used as a resin for a protective layer, in order to improve mechanical strength such as scratch resistance, a hydroxyl group (-OH) that is a functional group present in the cellulose derivative resin is used as a reaction point. Isocyanate compound is added and crosslinked. Due to this cross-linking, the properties of the resin change, and the peel strength changes accordingly. At this time, the adjustment of the peel strength is difficult when one kind of resin is used alone, whereas it is easy when there are plural kinds of resins.
Here, combined use of a resin different from the cellulose derivative resin in the basic structure of the chemical structure, such as an acrylic resin, is possible, but it is not practical as a protective layer. This is because the compatibility between the resins is often poor, and this causes a non-uniform peel strength, resulting in poor peelability. For this reason, all the resins used in combination need to be derivative resins in which the basic structure is a cellulose structure and a part thereof is substituted with an appropriate substituent. Here, the cellulose structure has a glucose unit-bound glucose as a structural unit.
[0009]
In the present invention, attention is paid to the hydroxyl group (—OH), which is a functional group of the cellulose derivative resin, and the cellulose derivative resin is classified based on the hydroxyl group content indicating the amount of the hydroxyl group in the resin and used as a basis for combined use. However, the hydroxyl group content is the ratio of the hydroxyl group content to the average molecular weight of the resin, and the unit is mass%. For example, when 50 hydroxyl groups are present in a resin having an average molecular weight of 30000, the hydroxyl group content is 2.8 [(50 × 17/30000) × 100] mass%. And the essential component resin and arbitrary component resin as resin for protective layer structure are defined by the division. The contents of the classification are the following three classifications of A, B, and C resins. A resin: hydroxyl group content = 0 to 2.4 mass% (optional component resin), B resin: hydroxyl group content = 2.5 to 3.5 mass% (first essential component resin), C resin: hydroxyl group content = 3.6 mass% or more ( Second essential component resin).
The amount of hydroxyl groups in the cellulose derivative resin can also be represented by the number of hydroxyl groups bonded to a predetermined resin structural unit. For example, when the cellulose constituent unit is glucose having a glucoside bond and any four consecutive glucose units are another unit, the number of hydroxyl groups bound thereto. The number of bonds of the A, B, and C resins in the present invention is the center value, which is 1, 2.3, and 4, respectively.
[0010]
Furthermore, in this invention, the resin composition ratio in a protective layer is prescribed | regulated regarding the above-mentioned A, B, C resin. Here, the resin composition ratio is the ratio of each of the A, B, and C resins to the total amount of the cellulose derivative resin used in the protective layer, and the unit is expressed in mass%.
The specific composition ratio is as follows: composition ratio Ar of the optional component resin A: 0 to 25 mass%, composition ratio Br of the first essential component resin B: 60 to 85 mass%, composition ratio Cr of the second essential component resin C: 15 to 40% by mass.
When deviating from this range, the peel strength: the support-holding layer / interlayer adhesive force increases, and the desired easy peelability cannot be obtained. In addition, various properties required for the protective layer cannot be satisfied. That is, the peel strength becomes 100 mN or more, exceeds the target value of “easy peelability” “10 to 80 mN”, and cannot be evaluated as easy peelability. In addition, mechanical properties such as a coercive magnetic layer / adhesive force, heat resistance, chemical resistance, and scratch resistance are deteriorated, resulting in a defect as a protective layer. These behaviors are as described in Examples and test results in Table 1 described later.
[0011]
In addition to the thermal transfer laminate / protective layer inventions described above, the present invention uses the thermal transfer laminate and adopts / uses known transfer techniques and materials to produce a magnetic recording medium in the form of a magnetic card. Can be manufactured.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
The laminated body for thermal transfer of the present invention is produced by applying a peelable protective layer having peelability, a magnetic layer, and an adhesive layer in this order on a transfer support and applying and drying the coating materials prepared for forming each layer in this order. Further, the magnetic recording medium: magnetic card of the present invention is produced by transferring the adhesive layer side of the thermal transfer laminate to the surface of the magnetic recording medium substrate so as to be fused and fixed, and then peeling the transfer support.
[0013]
As a substance involved in improving the peelability of the protective layer for thermal transfer laminate, which is an object of the present invention, there is a transfer support material. The transfer support material is generally a synthetic resin film or a synthetic paper called a release paper, and can be selected without any limitation as long as it matches the use conditions.
In the present invention, a synthetic resin film is suitable, and in particular, a PET (polyethylene terephthalate) film having a thickness of 3 to 100 μm is more suitable from the viewpoint of heat resistance and tensile strength. This is used in the embodiment of the present invention.
[0014]
As the binder resin used in the paint for forming the peelable protective layer, a known and commonly used resin can be used. As a property thereof, when a coating film is formed, the film / film-forming property is high and relatively hard, Those excellent in releasability from a PET film are preferred. Examples of such resins include cellulose derivative resins such as cellulose acetate, cellulose acetate butyrate, cellulose acetate nitrate, and cellulose acetate propionate.
[0015]
The cellulose derivative resin used for the peelable protective layer of the present invention is a cellulose derivative resin having a weight average molecular weight of 10,000 to 70,000. Here, if the molecular weight is too small, characteristics such as easy releasability and time-dependent release stability are not exhibited. Conversely, if the molecular weight is too large, the viscosity of the coating becomes high and thin film coating becomes difficult.
[0016]
The high and low hydroxyl group content in the cellulose derivative resin used in the peelable protective layer of the present invention has the following adverse effects, so the hydroxyl group content in actual use is in the range of 1 to 7%. . That is, when the hydroxyl group content is low, the heat resistance and mechanical strength characteristics (scratch resistance) are poor, which causes seizure during hot press processing and destruction of the protective layer during recording head travel. On the other hand, when the hydroxyl group content is high, it becomes difficult to form a coating because it is hardly soluble in an organic solvent, or the coating is thickened with respect to the addition of a crosslinking accelerator, making application difficult.
[0017]
In the cellulose derivative resin used in the peelable protective layer of the present invention, representative examples of each of the A, B and C resins classified by the hydroxyl group content are as follows: The hydroxyl group content and molecular weight are described. These are also used in examples described later.

[0018]
When it is unavoidable to use a resin having a chemical structure different from that of the cellulose derivative resin, it can be appropriately selected, added, and used within a range where there is no problem in compatibility. Examples of such resins include polyvinyl chloride, acrylic resin, epoxy resin, polycarbonate, etc., and the amount used is 0 to 0 corresponding to the optional component resin A in the above resin composition ratio. 25% by mass.
[0019]
In addition, when the cellulose derivative resin is used as the resin for the peelable protective layer, an isocyanate compound as a crosslinking accelerator is usually added to improve the mechanical properties of the protective layer, for example, the scratching property. Causes a reaction to accelerate curing. The amount of the isocyanate compound used is preferably 2 to 30 parts by mass with respect to 100 parts by mass of the binder resin.
[0020]
Furthermore, the release protective layer can contain a known and commonly used release agent in order to improve the peelability between the transfer support and the protective layer. Examples of the release agent include a fluororesin, a polyolefin wax, a natural wax, and a silicon release agent.
[0021]
The coating material for forming the peelable protective layer is prepared by adding the above cellulose derivative resin and a release agent and other additives to a mixed solvent such as acetone, ethyl acetate, butyl acetate, toluene, cyclohexanone, and the like. Dissolve and suspend so that the concentration becomes.
[0022]
The peelable protective layer is formed by applying the coating material on a transfer support (PET film) so that the dry coating thickness is 0.4 to 2.5 μm, drying in a nitrogen atmosphere, and then air. The heat curing treatment is performed under conditions of 100 to 120 ° C. and 10 seconds to 5 minutes. There is no restriction | limiting in particular as an application | coating system, A well-known and usual system can be used. It can be manufactured by adopting a single-layer or multi-layer coating manufacturing method. Specifically, for example, gravure method, reverse method, air doctor coater method, blade coater method, air knife coater method, squeeze coater method, impregnation coater method, transfer roll coater method, kiss coater method, cast coater method, spray coater method, die The method etc. are mentioned.
[0023]
As a binder resin used for the magnetic layer-forming coating material, known and commonly used, for example, polyvinyl chloride resin, acrylic resin, acrylic urethane resin, nitrocellulose resin, polyurethane, polyester, etc., alone or in combination, Can be used.
[0024]
As a magnetic material used for the coating material for forming a magnetic layer, known and commonly used materials such as γ-iron oxide, magnetite, cobalt-coated iron oxide, chromium oxide, iron-based metal magnetic powder, strontium ferrite, barium ferrite, etc. Magnetic powder can be used.
[0025]
The magnetic layer-forming coating material is prepared by adding the above-mentioned magnetic powder and 20-30% by mass of the above-mentioned binder resin, and further, if necessary, known and commonly used dispersion stabilizers, surfactants, resin fillers, etc. , Dissolved and dispersed in a mixed solvent such as methyl ethyl ketone, toluene and cyclohexanone. The solid content concentration of the paint at that time is preferably 25 to 50% by mass. In addition, for the dissolution / dispersion, a known and commonly used dispersing machine such as a ball mill or a sand grind mill can be used.
[0026]
The magnetic layer is formed by adding an isocyanate compound as a curing agent to the magnetic layer forming coating material, applying the dried protective film on the above-described peelable protective layer so that the dry coating thickness is 2 to 20 μm, and a nitrogen atmosphere. After drying in the air, it is heat-cured in air at 100 to 120 ° C. for 10 seconds to 5 minutes. There is no restriction | limiting in particular as an application | coating system, A well-known and usual system can be used. It can manufacture according to the method used for the coating material manufacture of a single layer or multiple layers structure. Specifically, for example, gravure method, reverse method, air doctor coater method, blade coater method, air knife coater method, squeeze coater method, impregnation coater method, transfer roll coater method, kiss coater method, cast coater method, spray coater method, die The method etc. are mentioned.
[0027]
The binder resin for the adhesive layer may be any thermoplastic binder resin that is tack-free at room temperature but develops adhesiveness when heated. For example, polyvinyl chloride resin and polyurethane A resin or the like can be used.
[0028]
The coating material for forming the adhesive layer is prepared by dissolving in a mixed solvent such as methyl ethyl ketone and toluene so that the binder resin is 3 to 70% by weight. At this time, silica, polyethylene wax or the like can be added as an anti-blocking agent under a high temperature environment.
[0029]
The adhesive layer is formed by applying the adhesive layer-forming coating material on the magnetic layer so that the dry coating thickness is 0.3 to 10 μm, and drying in air at 50 to 120 ° C. There is no restriction | limiting in particular as an application | coating system, A well-known and usual system can be used. It can manufacture according to the method used for the coating material manufacture of a single layer or multiple layers structure. Specifically, for example, gravure method, reverse method, air doctor coater method, blade coater method, air knife coater method, squeeze coater method, impregnation coater method, transfer roll coater method, kiss coater method, cast coater method, spray coater method, die The method etc. are mentioned.
[0030]
Magnetic recording medium of the present invention: As described above, the magnetic card is obtained by thermally transferring the thermal transfer laminate to the surface of the magnetic recording medium substrate. The substrate is usually a laminate, and is composed of a core material called a core sheet that can be printed and a cover sheet called an overlay sheet provided above and below the core material.
[0031]
【Example】
Hereinafter, specific examples and comparative examples of the present invention will be given and described in more detail.
However, the present invention is not limited to these examples. In the following, “part” represents “part by mass”.
[0032]
Example 1
<Composition of paint for forming peelable protective layer>
Cellulose acetate: 7.5 parts of B resin
("L-AC L-20" manufactured by Daicel Chemical Industries)
Cellulose acetate propionate: C resin 1.8 parts
(Eastman Chemical's “CAP504-0.2”)
Polyethylene wax 2.0 parts
("High Wax 200PF" manufactured by Mitsui Petrochemical Co., Ltd.)
Soybean lecithin 0.1 parts
Acetone 24.3 parts
24.3 parts of ethyl acetate
19 parts of cyclohexanone
19 parts of toluene
Isocyanate compound 2 parts
("Barnock D-750" manufactured by Dainippon Ink & Chemicals, Inc.)
[0033]
<Composition of magnetic layer forming coating>
40 parts of Ba ferrite magnetic powder
("MC-127" manufactured by Toda Kogyo Co., Ltd.)
6 parts of vinyl chloride resin
("MR-110" manufactured by Zeon Corporation)
4 parts of polyurethane resin
("T-5206" manufactured by Dainippon Ink & Chemicals, Inc.)
20 parts of methyl ethyl ketone
20 parts of toluene
8 parts of cyclohexanone
Isocyanate compound 2 parts
("Barnock D-750" manufactured by Dainippon Ink & Chemicals, Inc.)
[0034]
<Composition of adhesive layer forming coating>
10 parts of vinyl chloride-vinyl propionate copolymer resin
("Lulon QC640" manufactured by Tosoh Corporation)
45 parts of methyl ethyl ketone
45 parts of toluene
[0035]
<Preparation of laminate for thermal transfer>
On the support for transfer (PET film), apply a peelable protective layer-forming coating with a reverse coating system coating machine so that the dry coating thickness is 1.0 μm, and after drying in a nitrogen atmosphere, A peelable protective layer was formed by heat curing in air at 105 ± 5 ° C. for 30 seconds. On the peelable protective layer, a magnetic layer forming coating is applied with a reverse coating system coating machine so that the dry coating thickness is 14 μm, dried in a nitrogen atmosphere, and then at 105 ± 5 ° C. for 30 seconds. Then, a heat curing treatment was performed to form a magnetic layer. Further, an adhesive layer-forming coating material was applied on the magnetic layer with a reverse coating system coating machine so that the dry coating thickness was 1.5 μm, and dried in a nitrogen atmosphere to form an adhesive layer. This laminated body is the laminated body for thermal transfer of the present invention.
[0036]
<Magnetic recording medium: Magnetic card substrate material and substrate preparation>
"Vini foil C-8195" manufactured by Mitsubishi Plastics Co., Ltd.
(For transparent overlay sheet, thickness 100μm)
“Vini foil C-4636N” manufactured by Mitsubishi Plastics Co., Ltd.
(For white core sheet, thickness 280μm)
The above materials were sequentially laminated, and a substrate was obtained by a conventional method in which hot pressing was performed at 120 ° C.
[0037]
<Magnetic recording medium: Preparation of magnetic card>
The laminate for thermal transfer was transferred to the substrate obtained above by a conventional method to obtain a magnetic recording medium: magnetic card. The apparatus actually used is a simple card making machine “Desktop Laminator OLA6 type” manufactured by Oasis. The laminate was temporarily transferred under the conditions of a temperature of 80 ° C., a fixed time of 120 seconds, and a pressure memory 45, and after removing the PET film as a transfer support, the temperature was 160 ° C., a fixed time of 120 seconds, and a pressure memory 65 again. This was done by pressing this.
[0038]
(Comparative Example 1)
A laminate for thermal transfer and a magnetic recording medium were produced in the same manner as in Example 1 except that the composition of the paint for forming the peelable protective layer was as follows.
[0039]
Cellulose acetate: B resin 9.3 parts
("L-AC L-20" manufactured by Daicel Chemical Industries)
Polyethylene wax 2.0 parts
("High Wax 200PF" manufactured by Mitsui Petrochemical Co., Ltd.)
Soybean lecithin 0.1 parts
Acetone 24.3 parts
24.3 parts of ethyl acetate
19 parts of cyclohexanone
19 parts of toluene
Isocyanate compound 2 parts
("Barnock D-750" manufactured by Dainippon Ink & Chemicals, Inc.)
[0040]
(Comparative Example 2)
A laminate for thermal transfer and a magnetic recording medium were produced in the same manner as in Example 1 except that the composition of the paint for forming the peelable protective layer was as follows.
[0041]
Cellulose acetate propionate: 9.3 parts of C resin
(Eastman Chemical's “CAP504-0.2”)
Polyethylene wax 2.0 parts
("High Wax 200PF" manufactured by Mitsui Petrochemical Co., Ltd.)
Soybean lecithin 0.1 parts
Acetone 24.3 parts
24.3 parts of ethyl acetate
19 parts of cyclohexanone
19 parts of toluene
Isocyanate compound 2 parts
("Barnock D-750" manufactured by Dainippon Ink & Chemicals, Inc.)
[0042]
(Comparative Example 3)
A laminate for thermal transfer and a magnetic recording medium were produced in the same manner as in Example 1 except that the composition of the paint for forming the peelable protective layer was as follows.
[0043]
Cellulose acetate: 7.5 parts of B resin
("L-AC L-20" manufactured by Daicel Chemical Industries)
Cellulose acetate butyrate: 1.8 parts of A resin
(Eastman Chemical's “CAB381-0.1”)
Polyethylene wax 2.0 parts
("High Wax 200PF" manufactured by Mitsui Petrochemical Co., Ltd.)
Soybean lecithin 0.1 parts
Acetone 24.3 parts
24.3 parts of ethyl acetate
19 parts of cyclohexanone
19 parts of toluene
Isocyanate compound 2 parts
("Barnock D-750" manufactured by Dainippon Ink & Chemicals, Inc.)
[0044]
(Comparative Example 4)
A laminate for thermal transfer and a magnetic recording medium were produced in the same manner as in Example 1 except that the composition of the paint for forming the peelable protective layer was as follows.
[0045]
Cellulose acetate: 4.7 parts of B resin
("L-AC L-20" manufactured by Daicel Chemical Industries)
Cellulose acetate propionate: 4.6 parts of C resin
(Eastman Chemical's “CAP504-0.2”)
Polyethylene wax 2.0 parts
("High Wax 200PF" manufactured by Mitsui Petrochemical Co., Ltd.)
Soybean lecithin 0.1 parts
Acetone 24.3 parts
24.3 parts of ethyl acetate
19 parts of cyclohexanone
19 parts of toluene
Isocyanate compound 2 parts
("Barnock D-750" manufactured by Dainippon Ink & Chemicals, Inc.)
[0046]
(Test items and test results)
<I. Peelability test (peel strength: support-retaining layer / interlayer adhesion)>
The peelability between the transfer support (PET film) and the peelable protective layer, that is, peel strength: support-holding layer / interlayer adhesion is measured. From this value, the difficulty of peelability is determined, and if the peel strength value is in the range of 10 to 80 mN, it is determined as easy peelability.
The laminated body for thermal transfer is cut into a width of 10 mm to produce a laminated body for thermal transfer with tape. This tape-shaped thermal transfer laminate was thermally transferred to an overlay sheet to obtain a peel test sample. The thermal transfer apparatus and thermal transfer conditions are as follows. Apparatus: Heat sealer (manufactured by Tester Sangyo Co., Ltd.), Conditions: 120 ° C., 9.9 seconds, hot press at 0.4 MPa. Next, the peel test sample obtained here was subjected to a peel tester, and the force to peel off the PET film as the transfer support from the protective layer, that is, the peel strength was measured. As the peel tester, a high speed peel tester (manufactured by Tester Sangyo Co., Ltd.) was used.
[0047]
<II. Adhesion test (coercive layer / interlayer adhesion)>
The adhesion between the peelable protective layer and the magnetic layer (coercive layer / interlayer adhesion) is tested to determine whether or not there is a predetermined adhesion.
Using the magnetic recording media prepared in the above examples and comparative examples, evaluation was made according to the cross-cut tape method described in JIS K 5400-1990, and the quality of the adhesiveness was determined.
[0048]
<III. Heat resistance test>
The magnetic recording media produced in the above examples and comparative examples were tested by hot pressing with a flat pressure press (manufactured by Toyo Seiki Co., Ltd.). That is, the magnetic recording medium is sandwiched between stainless plates and hot pressed (flat pressure press machine: manufactured by Toyo Seiki Co., Ltd.) at a temperature of 180 ° C., a pressure of 8 MPa, and a heating time of 30 minutes. Thereafter, the stainless steel plate is removed, and the surface of the stainless steel plate on the side in contact with the magnetic tape (the other stainless steel plates were in contact only with the overlay sheet) is observed to confirm the state of the magnetic layer being burned onto the stainless steel plate. The stainless steel plate was checked to visually check whether the magnetic layer of the magnetic recording medium had been transferred to the stainless steel plate, and the heat resistance was judged.
[0049]
<IV. Chemical resistance test>
The magnetic recording media prepared in the above examples and comparative examples were tested by dissolving and rubbing off the protective layer with chemicals. As test chemicals, organic solvents (1) methyl ethyl ketone (MEK), (2) toluene, and (3) alcohol are used. The room temperature and the solvent temperature are set to 25 ± 5 ° C., and the same portion on the surface of the protective layer of the magnetic recording medium is rubbed with a cotton swab dipped in the test solvent. The rubbing surface of the cotton swab is visually observed after every 10 rubbing, and it is evaluated whether the magnetic layer of the magnetic recording medium adheres to the cotton swab and has a brown to black coloring. The number of rubbing when coloring was observed was compared to determine whether the solvent resistance was good or bad.
[0050]
<V. Scratch resistance (mechanical strength) test>
After punching out the magnetic recording media produced in the above examples and comparative examples into a magnetic card shape and writing information with a card writing machine, the card reading machine repeatedly reads a certain number of times, The surface abrasion of the magnetic tape portion on the magnetic card was visually observed to determine whether the scratch resistance (mechanical strength) was good or bad.
[0051]
<Test results>
The test results of the above five items I to V are shown in Table 1 below.
[0052]
[Table 1]
Table 1. Test results of peelable protective layer in Examples

(Note) In the table,
(1) (2) (3) represents the type of chemical: (1) methyl ethyl ketone, (2) toluene, (3) ethanol,
Data numerical values indicate actual measurement values, and symbols (◯, ×) indicate good (◯) or no (×) evaluation results.
[0053]
(Summary of evaluation results)
From the results of Table 1, only Example 1 (two types of B and C resins of cellulose derivative resin are used in combination and comply with the prescribed amount) shows the desired easy peelability (20 mN) and is required for the peelable protective layer. It was found that the characteristics [II to V] were also satisfied. In Comparative Example 1 and Comparative Example 2 where each one of B and C resins was used alone, Although peelability is at a considerable level, II. Adhesiveness or V. It was an evaluation result that caused a problem with scratching, and the purpose was not achieved. Furthermore, in Comparative Example 3 (combined use of A and B) and Comparative Example 4 (combined use of B and C) using two types of resins together, II. Although the adhesiveness is good, the desired I.D. The peelability was large and insufficient, and other properties [III to V] were also unsatisfactory, and the purpose was not achieved. Furthermore, from Comparative Examples 3 and 4, it was found that the C resin is an essential component resin and that the resin composition ratio has a specified amount (the lower limit amount of the B resin).
In addition, the presence or absence of a change with time was also evaluated, and as a result of conducting the same test as described above after one month, no significant difference was found in the test results. In particular, in Example 1, it was confirmed that easily peelable and other characteristics were good, and the stability over time was high.
[0054]
【The invention's effect】
The laminate for thermal transfer of the present invention and the magnetic recording medium using the same are not required in the peeling operation step in the final product manufacturing process, and therefore when the transfer support that needs to be removed is peeled from the peelable protective layer It is easy to peel. Therefore, the transfer support (PET film) is not broken or left in the protective layer due to defective peeling, and the occurrence of defective products and process troubles can be prevented. As a result, the magnetic recording medium manufacturing process and product quality are stabilized, product costs are reduced, resources are saved, and waste is reduced.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a thermal transfer laminate in the present invention.
FIG. 2 is a longitudinal sectional view of a magnetic recording medium according to the present invention after a thermal transfer laminate is transferred onto a magnetic recording medium substrate, and an uppermost transfer support is peeled off and removed.
[Explanation of symbols]
1 Transfer support
2 Peelable protective layer
3 Magnetic layer
4 Adhesive layer
5 Magnetic recording medium substrate

Claims (2)

Two types of cellulose derivatives having different chemical structures as binder resins for the peelable protective layer in a thermal transfer laminate in which at least a peelable protective layer, a magnetic layer and an adhesive layer are laminated in this order on a transfer support A resin is contained, cellulose acetate having a hydroxyl group content of 2.5 to 3.5% by mass as one of the two types is 60 to 85% by mass, and another type having a hydroxyl group content of 3.6% by mass or more. heat transfer laminate characterized that you containing 15 to 40 wt% cellulose acetate propionate.   A magnetic recording medium obtained by thermal transfer using the thermal transfer laminate according to claim 1.

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