JP3856107B2 - Protective film on polycarbonate board - Google Patents
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- JP3856107B2 JP3856107B2 JP2001346157A JP2001346157A JP3856107B2 JP 3856107 B2 JP3856107 B2 JP 3856107B2 JP 2001346157 A JP2001346157 A JP 2001346157A JP 2001346157 A JP2001346157 A JP 2001346157A JP 3856107 B2 JP3856107 B2 JP 3856107B2
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Description
【０００１】
【発明の属する技術分野】
本発明は、ポリカーボネート板、あるいはポリカーボネート板を外層に持ち、偏光特性やフォトクロミック特性などの機能性を有した積層体を、加熱下にて加圧および／または減圧しながら予め所望の形状にかたどられた型に密着させて賦形させる熱曲げ加工を施す際に、該ポリカーボネート板の表面を保護するために貼られている保護フィルムを装着したままの状態で、ポリカーボネート板あるいはその積層体を熱曲げ加工する際に用いられる保護フィルムに関する。
【０００２】
【従来の技術】
合成樹脂基板、例えばポリカーボネートやアクリルなどのシートを取り扱う際に、キズや汚れおよび異物がつきやすいことから表面を保護する為に、ポリオレフィン系フィルム、例えばポリエチレンやポリプロピレンなどの保護フィルムが貼られている。
【０００３】
また、予め所望される形状に掘り込み加工が施された金型や木型あるいは樹脂型などを用いて、加熱環境下（一般的には、該合成樹脂基板のガラス転移温度近辺の温度下）のもと、加圧あるいは減圧（真空下）によって、該合成樹脂板を前記金型などを用いて賦形する、いわゆる合成樹脂基板の二次加工としての熱曲げ加工が従来より行われている。
【０００４】
しかしながら、例えばポリカーボネート板の熱曲げ加工に際して、ポリカーボネートのガラス転移温度近辺（１３５〜１５５℃）の高温環境下で、減圧あるいは加圧下にて曲げ加工を施す際に、従来の保護フィルムを装着したままでポリカーボネート板の熱曲げ加工を行うと、耐熱性の低い保護フィルムを使用した場合は保護フィルムが溶けてしまい、金型や木型あるいは樹脂型等の型やポリカーボネート板に溶着してしまうという問題があり、また逆に耐熱性の高い保護フィルムを使用した場合は、保護フィルムの溶着等の問題はなく曲げ加工ができるものの、曲げ加工品にシワやゆず肌等が発生しやすかった。
【０００５】
それゆえ、ポリカーボネート板より予め保護フィルムを剥いで、ポリカーボネートのガラス転移温度近辺の高温加熱下での曲げ加工を行わざるをえなかった。このように保護フィルムをポリカーボネート板から剥がして曲げ加工を行うと、加工時にポリカーボネート板にキズや汚れあるいは異物の付着などが発生しやすい状況であった。
【０００６】
また、特開平８−１９２５０１号公報には、低密度ポリエチレン層とエチレン−酢酸ビニル共重合体（ＥＶＡ）層の二層構成の保護フィルムが特にアクリル基板用の一体熱曲げ加工用保護フィルムとして開示されているが、ポリカーボネート基板に該保護フィルムを装着したまま、１５０℃で４〜１０分かけて熱曲げ加工を行った際は、型に密着させて熱曲げ加工を行うと低密度ポリエチレン層の型への溶着が起こり、使用に耐えないものであった。
【０００７】
このように、ポリカーボネート板、あるいはポリカーボネート板を外層に持ち機能性を有した積層体を用いて、加圧および／または減圧下にて、予め所望の形状にかたどられた型に密着させて賦形する熱曲げ加工を容易に施すために、ポリカーボネートのガラス転移温度近辺の高温環境下まで加熱して曲げ加工が行われるが、このような熱曲げ加工の環境下に耐えて、外観性の良好な曲げ加工品を容易に得られることを可能としたポリカーボネート板用の保護フィルムは未だ提供されていないのが現状である。
【０００８】
【発明が解決しようとする課題】
本発明は、保護フィルムを装着したままのポリカーボネート板、あるいはポリカーボネート板を外層に持つ機能性を有した積層体を、加熱下にて加圧および／または減圧しながら、予め所望の形状にかたどられた型に密着させて賦形させる熱曲げ加工を施す際に、ポリカーボネートのガラス転移温度近辺の高温加熱環境下でも、保護フィルム付きポリカーボネート板をそのまま熱曲げ加工を行なっても、外観の良好なポリカーボネート曲げ加工品が容易に得られる保護フィルムを提供することである。
【０００９】
【課題を解決するための手段】
本発明者らは、鋭意検討した結果、ポリカーボネート板に用いられる保護フィルムを、少なくとも型に接する側に配置された第一フィルム層とポリカーボネート板に接する側に配置された第二フィルム層からなり、該第一フィルム層の融点が１５０℃以上のポリオレフィン系フィルム層であり、該第二フィルム層の融点が１２５〜１４５℃のポリオレフィン系フィルム層である保護フィルムを用いることにより、該保護フィルムを装着したままのポリカーボネート板を、ポリカーボネートのガラス転移温度近辺の高温環境下にて、加圧および／または減圧しながら予め所望の形状にかたどられた型に密着させて賦形しても、該保護フィルムをポリカーボネート板より剥がした際に、保護フィルムの曲げ加工品や型への溶着が無く、且つ得られた曲げ加工品がシワ等の発生も無く外観性が良好であることを見出し、本発明に至った。
【００１０】
【発明の実施の形態】
本発明における第一フィルム層としての役割は、前述したポリカーボネートのガラス転移温度近辺の高温環境下にて固層を維持できる耐熱性を有すること、耐薬品性、耐侯性、耐擦傷性などに優れること、また熱曲げ加工でポリカーボネート板が金型や木型などにより賦形される際に、ポリカーボネート板と同様に賦形できる良好な転写性を有することなどが挙げられる。これらの諸要求を満たす第一フィルム層としては、融点が１５０℃以上のポリオレフィン系フィルムが一般的に安価で手に入りやすく、本発明の第一フィルム層として好ましい。
【００１１】
第一フィルム層に用いるポリオレフィン系フィルム層としては、実質的な融点が１５０℃以上のポリプロピレンやポリエチレン、あるいはこれらの混合品や共重合体が挙げられる。
【００１２】
また、必要に応じてエチレン−プロピレン共重合体、エチレン−α―オレフィン共重合体、プロピレン−α−オレフィン共重合体、エチレン−酢酸ビニル共重合体、エチレン−エチルアクリレート共重合体、エチレン−メチルメタクリレート共重合体、およびエチレン−ｎ−ブチルアクリレート共重合体などを前記ポリオレフィン系にブレンドしても良い。前記のα−オレフィンとしては、１−ヘキセン、４−メチル−１−ペンテン、１−オクテン、１−ブテン、１−ペンテン、または１−ヘプテンなどが挙げられる。
【００１３】
前記のポリオレフィン系フィルムの中から、熱曲げ加工時に固層を維持するように、使用する熱曲げ加工時の温度条件よりも、少なくとも５℃以上高い融点を有するものを第一フィルム層として適宜選定する。従って、第一フィルム層の選定は、熱曲げ加工時の温度条件（一般的には１３５〜１５５℃の温度範囲内）に基づくが、第一フィルム層としては融点が１５０℃以上のものを使用することが好ましい。特に融点が１６０℃程度を示すポリプロピレンまたはポリプロピレンとポリエチレンの混合品や、プロピレン、エチレンおよびα−オレフィン（プロピレンを除く）から選ばれる２種類以上の共重合体で、ポリプロピレンの配合量が５０重量％以上のものは、前述のポリカーボネート板の熱曲げ加工に要望される耐熱性を有しており、耐薬品に優れ、安価で手に入れやすく、前記の諸条件を満足しており、本発明の第一フィルム層として、より好ましいものである。
【００１４】
次に、本発明における第二フィルム層としての役割は、ポリカーボネートのガラス転移温度近辺の温度にて粘性を持った溶融状態にあることであり、言い換えると熱曲げ加工の温度変化に伴って生じる第一フィルム層の加熱収縮による影響（応力）を該ポリカーボネート板に伝わらないようにすることである。これは該ポリカーボネート板がポリカーボネートのガラス転移温度近辺の高温環境下に曝され、且つ第一フィルム層の伸縮による影響を受けると、曲げ加工品の表面にシワなどの外観不良が発生してしまうからである。従って、第二フィルム層には実質的な融点がポリカーボネートのガラス転移温度以下のものが要求されるが、逆に融点がポリカーボネートのガラス転移温度よりあまりにも低くなりすぎると、曲げ加工時に第一フィルム層が曲げ加工品からズレてしまったり、保護フィルムを剥離した後の曲げ加工品に保護フィルムの一部が残ってしまう（糊残り）などの外観不良が発生しやすくなる等の問題があるため、第二フィルム層の融点は熱曲げ加工温度より若干低い（５℃〜２５℃低い）程度であることが要求される。また、その他には耐薬品性や耐擦傷性などが挙げられる。
【００１５】
それ故に、第二フィルム層の選定は第一フィルム層と同様に、使用する熱曲げ加工時の温度条件に基づいて選定されるが、前述した諸要求を満たす第二フィルム層としては、融点が１２５〜１４５℃の範囲であるポリオレフィン系フィルム層を使用することが好ましい。第二フィルム層として用いるポリオレフィン系フィルムは、第一フィルム層のポリオレフィン系フィルムで例示したもので、融点が１２５〜１４５℃の範囲のものであれば本発明の保護フィルムに適用できるが、特に第一フィルム層との親和性の関係から融点が１３０℃程度を示すポリエチレン、エチレン−プロピレン共重合体およびエチレン−α−オレフィン共重合体から選ばれる１種または２種以上の混合品であって、第二フィルム層中のエチレン成分が５０重量％以上であることがより好ましい。
【００１６】
第一フィルム層の厚みとしては、１０μｍ〜１００μｍの範囲が好ましく、１０μｍより薄いと特に深絞り形状品などの曲げ加工において伸び不足などによる破れが発生しやすくなり、また１００μｍを超えるとフィルムとしての柔軟性が小さくなるため取り扱い難く嵩張り、また経済性も悪くなる。
【００１７】
第二フィルム層の厚みは、１０μｍ〜１００μｍの範囲が好ましく、第二フィルム層の厚みが１０μｍより薄いとポリカーボネート板の熱曲げ加工品にシワが発生しやすくなり、１００μｍより厚いと熱曲げ加工時に第二フィルム層がポリカーボネート板よりはみ出しやすくなる。
【００１８】
本発明の保護フィルムの第一フィルム層と第二フィルム層を合わせた全体の厚みは、２５μｍ〜１５０μｍが好ましく、より好ましくは３０〜１２０μｍである。全体の厚みが２５μｍを下回る場合フィルムの剛性が非常に低く、曲げ加工時や剥離時に破れやすくなり、また外部からの擦傷などで容易に製品であるポリカーボネート板にキズがついてしまう。膜厚が１５０μｍを超えると、ポリカーボネート板への熱伝導に時間がかかり、熱曲げ加工サイクルが長くなると共に、過剰のフィルムを使用するため経済性が悪い。
【００１９】
次に、本発明の保護フィルムの第一フィルム層と第二フィルム層のそれぞれの内側に、各々粘着層を設けることは、取り扱いや曲げ加工時に本発明の保護フィルムの層間剥離やポリカーボネート板からの離脱を防ぐことができ、好ましい対応である。
【００２０】
前記の粘着層は、２個のロール間で挟む圧接による方法により、室温下にて低い圧力（１０ｋｇ／ｃｍ2 以下）でも、容易に第一フィルム層と第二フィルム層、あるいは第二フィルム層とポリカーボネート板を密着することができ、また安価に入手できるものが好ましい。
【００２１】
また、第二フィルム層の内側に使用する粘着層としては、該ポリカーボネート板との剥離力が１００ｇ／２５mm（２５℃における９０゜剥離強度試験）以下と低く、熱曲げ加工後の剥離力が上昇しないものが作業性の観点から望まれており、特にポリエチレン、エチレン−プロピレン共重合体、エチレン−α−オレフィン共重合体等が前記の剥離力を満足することができ、本発明の保護フィルムに好ましく使用できる。
【００２２】
第一フィルム層の内側に使用する粘着層としては、一般的に保護フィルムに使用されている粘着剤であれば加熱後に粘着力が上昇してもポリカーボネート板と保護フィルムの剥離には何ら関係しないので、何れを使用してもかまわない。
【００２３】
また、第一フィルム層の型の接する側に、シリコーン系、長鎖アルキル系、アクリル系あるいはステアリン酸系などの背面処理剤を塗布して離型性を付与したものは、金型からの曲げ加工品の離脱が容易となり、好ましい対応である。
【００２４】
更には、酸化防止剤、光安定剤、帯電防止剤などの各種添加剤を本発明の保護フィルムの第一フィルム層に練りこませたフィルムを用いることや、第一フィルム層の型に接する側にこれらの各種添加剤を塗布したフィルムを用いることも、長期に渡りポリカーボネート板や曲げ加工品を保管する際には好ましい対応である。
【００２５】
ポリカーボネート板に本発明の保護フィルムを積層する方法は、最終的に本発明の保護フィルムの構成となるような積層方法であれば特に限定されるものではないが、例えば第二フィルム層とポリカーボネート板を、第二フィルム層が粘着層を有する場合は粘着層側がポリカーボネート板と接するようにして、室温下にて２個のロール間で圧着（荷重１０ｋｇ／ｃｍ2 以下）しポリカーボネート板に第二フィルム層を積層させ、その後同様にして第一フィルム層を該第二フィルム層が積層されたポリカーボネート板の第二フィルム層と接するようにして、室温下にて２個のロール間で圧着（荷重１０ｋｇ／ｃｍ2 以下）して積層する、第二フィルム層と第一フィルム層とを別々に該ポリカーボネート板に積層する方法が挙げられる。
【００２６】
あるいはまた、本発明の保護フィルムの構成となるように第一フィルム層と第二フィルム層を同時にポリカーボネート板の上に、室温下にて２個のロール間で圧着（荷重１０ｋｇ／ｃｍ2 以下）する方法もある。
【００２７】
【実施例】
以下に、本発明を実施例にて更に詳細に説明するが、本発明はこれらに限定されるものではない。
【００２８】
実施例１
２枚の厚みがそれぞれ４００μｍで幅３００ｍｍのポリカーボネートシートの間に介在する厚み３０μｍの偏光膜を持った積層体（三菱瓦斯化学（株）製、ユーピロンポーラ）を用い、該ポリカーボネート積層体の両面に、まず保護フィルムの第二フィルム層としてポリエチレン系の粘着層を有する融点が１３２℃、厚みが４５μｍで幅３００ｍｍのポリエチレン系保護フィルム（東レ合成フィルム、ＦＭ７７２１）を室温下にて２個のロール間で圧着（荷重５ｋｇ／ｃｍ2 ）した。その後、更に保護フィルムの第一フィルム層として融点が１６３℃、厚み４２μｍで幅３００ｍｍのゴム系の粘着層を有し長鎖アルキル系の背面処理が施されたポリプロピレンとポリエチレンの混合品である耐熱性のポリオレフィン系保護フィルム（日東電工（株）製、ＳＰＶ−ＪＢ５００）を、第二フィルム層が貼られた該ポリカーボネート積層体の両面に室温下にて２個のロール間で圧着（荷重５ｋｇ／ｃｍ2 ）した。その後、第一フィルム層と第二フィルム層からなる保護フィルムが両面に貼られた該ポリカーボネート積層体を外径φ８０ｍｍにプレス機で打ち抜いた。次いで、該打ち抜きサンプルを、熱風乾燥機にて１３０℃×５分間の予備乾燥を行った。次に、該打ち抜きサンプルを球面半径が９０ｍｍの半球状の金型上（下型）に載せ、１５０℃の温度雰囲気下にて５秒間５ｋｇ／ｃｍ2 の圧力で上型により押さえると共に下型より５分間真空引きした状態で該下型に打ち抜きサンプルを密着させて熱曲げ加工を施した。出来上がった曲げ加工品は、金型の球面形状が転写されて賦形された球面半径９０ｍｍに湾曲したものであった。更に保護フィルムの剥離強度をばね秤を用いて測定したところ、剥離強度は表１に示すように非常に小さかった。また保護フィルムを剥がした後のポリカーボネート曲げ加工品の外観は良好で、更には良好な偏光特性を有しており、何ら不良が見当たらなかった。
【００２９】
実施例２
第一フィルム層として厚み４０μｍで幅３００ｍｍのアクリル系粘着層（粘着層厚み５μｍ）を有する融点が１６４℃のポリプロピレン系保護フィルムを用いた以外は、実施例１と同様にして保護フィルム付きのポリカーボネート積層体を作製し曲げ加工品を得た。保護フィルムの剥離強度をばね秤を用いて測定したところ、剥離強度は表１に示すようにかなり小さかった。また、保護フィルムを剥がした後のポリカーボネート曲げ加工品の外観は良好で、更には良好な偏光特性を有しており、何ら不良が見当たらなかった。
【００３０】
実施例３
実施例１において、第二フィルム層のＦＭ７７２１の代わりにポリエチレンを粘着層に有する融点が１３２℃、厚み３０μｍで幅３００ｍｍのポリエチレン系フィルム（東レ合成フィルム（株）製、ＦＭ５０３０）を用いた以外は、実施例１と同様にして曲げ加工品を作製した。保護フィルムの剥離強度をばね秤を用いて測定したところ、剥離強度は表１に示すようにかなり小さかった。また、保護フィルムを剥がした後のポリカーボネート曲げ加工品の外観は良好で、更には良好な偏光特性を有しており、何ら不良が見当たらなかった。
【００３１】
実施例４
２枚の厚みがそれぞれ４００μｍ、幅３００ｍｍのポリカーボネートシートの間に介在するスピロオキサジン系の有機フォトクロミック色素を１％含有した厚み１１０μｍのポリウレタン層を持った積層体を用いた以外は実施例１と同様の保護フィルムを使用して、保護フィルム付きの積層体を作製し、外径φ８０ｍｍにプレス機で打ち抜いた。該打ち抜きサンプルを熱風乾燥機に入れて１３０℃×５分間の予備乾燥を行った。その後１４５℃の環境下にて該打ち抜きサンプルを球面半径が９０ｍｍの下型に載せ、更に上型と下型により該打ち抜きサンプルを挟み圧力１０ｋｇ／ｃｍ2 を４分間加えた。次いで該金型を開きサンプルを取りだした。保護フィルムの剥離強度をばね秤を用いて測定したところ、剥離強度は表１に示すようにかなり小さかった。
また、保護フィルムを剥がした後のポリカーボネート曲げ加工品の外観は良好で、何ら不良が見当たらなかった。更には太陽光下に曝すと１０秒程度でオレンジに発色し、暗所に移すと１分程度で消色する良好なフォトクロミック特性を有していた。
【００３２】
実施例５
実施例１の保護フィルム付きポリカーボネート積層体を用いて熱曲げ加工時に下型に該積層体を載せ上型を下降させ、１４７℃の温度雰囲気下にて上型と下型により該積層体を挟み、その後上型よりの圧力は加えずに下型より８分間真空引きすることにより熱曲げ加工を行った以外は実施例１と同様にして曲げ加工品を得た。
保護フィルムの剥離強度をばね秤を用いて測定したところ、剥離強度は表１に示すようにかなり小さかった。
また、保護フィルムを剥がした後のポリカーボネート曲げ加工品の外観は良好で、更には良好な偏光特性を有しており、何ら不良が見当たらなかった。
【００３３】
比較例１
実施例１の第一フィルム層であるポリオレフィン系フィルム層を積層せずに、厚み４５μｍで幅３００ｍｍのポリエチレン系保護フィルム（東レ合成フィルム（株）製、ＦＭ７７２１）のみを使用した以外は、実施例１と同様にして熱曲げ加工を行った。出来上がった曲げ加工品はポリエチレン系フィルムが曲げ加工品に溶着しており外観の悪いものであった。
【００３４】
比較例２
実施例１の第二フィルム層であるポリオレフィン系フィルム層を積層せずに、厚み４２μｍで幅３００ｍｍのポリオレフィン系保護フィルム（日東電工（株）製、ＳＰＶ−ＪＢ５００）のみを使用した以外は、実施例１と同様にして熱曲げ加工を行った。
得られた曲げ加工品は保護フィルムの溶着は無かったが、ばね秤を用いて保護フィルムの剥離強度を測定したところ、非常に剥離しにくく剥離強度が２５０ｇ／２５ｍｍ（２５℃）もあった。
また剥離後の曲げ加工品の外観は、若干のゆず肌（シワ）が見られ外観の悪いものであった。
【００３５】
【表１】
【発明の効果】
本発明の保護フィルムによれば、該保護フィルムを装着したままのポリカーボネート板およびポリカーボネート板を外層に持つ積層体を、ポリカーボネートのガラス転移温度近辺の高温環境下にて、加圧および／または減圧しながら予め所望の形状にかたどられた型に密着させて賦形しても、該保護フィルムをポリカーボネート板より剥がした際に、保護フィルムの曲げ加工品や型への溶着が無く、熱曲げ加工後の剥離も非常に容易であり、且つ得られた曲げ加工品にシワ等の発生も無く外観性が良好である。
【図面の簡単な説明】
【図１】 本発明の保護フィルムをポリカーボネート板（積層体）に貼った状態の断面図
【符号の説明】
１ ポリカーボネート板、またはポリカーボネート板を外層に持つ積層体
２ 第二フィルム層のポリオレフィン系フィルム層
３ 第一フィルム層のポリオレフィン系フィルム層[0001]
BACKGROUND OF THE INVENTION
In the present invention, a polycarbonate plate or a laminate having a polycarbonate plate as an outer layer and having functionality such as polarization characteristics and photochromic properties is shaped in advance into a desired shape while being pressurized and / or decompressed under heating. When a thermal bending process is performed in which the polycarbonate plate is brought into close contact with the mold, the polycarbonate plate or laminate thereof is subjected to thermal bending with the protective film applied to protect the surface of the polycarbonate plate still attached. The present invention relates to a protective film used for processing.
[0002]
[Prior art]
When handling synthetic resin substrates such as polycarbonate and acrylic sheets, polyolefin films such as polyethylene and polypropylene protective films are applied to protect the surface from scratches, dirt, and foreign matter. .
[0003]
Also, using a mold, a wooden mold, or a resin mold that has been dug into a desired shape in advance, under a heating environment (generally, at a temperature near the glass transition temperature of the synthetic resin substrate). Under the circumstances, a heat bending process as a secondary process of a so-called synthetic resin substrate, in which the synthetic resin plate is shaped using the mold or the like by pressurization or reduced pressure (under vacuum), has been conventionally performed. .
[0004]
However, for example, when heat-bending a polycarbonate plate, a conventional protective film remains attached when bending is performed under reduced pressure or pressure in a high-temperature environment near the glass transition temperature of polycarbonate (135 to 155 ° C.). If the heat-bending process of the polycarbonate plate is used, the protective film will be melted if a protective film with low heat resistance is used, and it will be welded to molds, wooden molds, resin molds, etc. and polycarbonate plates. On the other hand, when a protective film having high heat resistance was used, there was no problem of welding of the protective film and bending could be performed, but wrinkles and yuzu skin were likely to occur in the bent product.
[0005]
Therefore, the protective film has been peeled off from the polycarbonate plate in advance, and bending processing has to be performed under high-temperature heating near the glass transition temperature of polycarbonate. When the protective film is peeled off from the polycarbonate plate and bent as described above, the polycarbonate plate is likely to be scratched, soiled, or adhered with foreign matter during processing.
[0006]
JP-A-8-192501 discloses a protective film having a two-layer structure of a low-density polyethylene layer and an ethylene-vinyl acetate copolymer (EVA) layer as a protective film for integral heat bending processing particularly for an acrylic substrate. However, when the heat bending process is performed over 4 to 10 minutes at 150 ° C. while the protective film is mounted on the polycarbonate substrate, the low density polyethylene layer is formed by performing the heat bending process in close contact with the mold. Welding to the mold occurred and it could not be used.
[0007]
In this way, using a polycarbonate plate or a laminate having a polycarbonate plate as an outer layer and having functionality, it is shaped by being brought into close contact with a mold that has been previously shaped into a desired shape under pressure and / or reduced pressure. In order to easily perform hot bending, the bending is performed by heating to a high temperature environment near the glass transition temperature of polycarbonate. The present situation is that the protective film for polycarbonate plates which made it possible to obtain a bent product easily is not yet provided.
[0008]
[Problems to be solved by the invention]
In the present invention, a polycarbonate plate with a protective film attached or a laminate having the functionality of having a polycarbonate plate as an outer layer is shaped in advance into a desired shape while being pressurized and / or decompressed under heating. Polycarbonate with good appearance, even when subjected to hot bending near the glass transition temperature of polycarbonate, even when subjected to hot bending of the polycarbonate plate with protective film, It is to provide a protective film from which a bent product can be easily obtained.
[0009]
[Means for Solving the Problems]
As a result of intensive studies, the inventors of the present invention have a protective film used for a polycarbonate plate, comprising at least a first film layer disposed on the side in contact with the mold and a second film layer disposed on the side in contact with the polycarbonate plate, The first film layer is a polyolefin film layer having a melting point of 150 ° C. or higher, and the second film layer has a melting point of 125 to 145 ° C. The protective film can be formed by adhering the as-prepared polycarbonate plate to a mold previously formed into a desired shape while applying pressure and / or reduced pressure in a high temperature environment near the glass transition temperature of the polycarbonate. When the film is peeled off from the polycarbonate plate, the protective film is not welded to the bent product or mold, and is obtained. Bending workpieces found that even without the appearance of generation of wrinkles is good, leading to the present invention.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The role as the first film layer in the present invention has heat resistance capable of maintaining a solid layer in a high temperature environment near the glass transition temperature of the polycarbonate described above, and is excellent in chemical resistance, weather resistance, scratch resistance, and the like. In addition, when the polycarbonate plate is formed by a metal mold or a wooden mold by hot bending, it has good transferability that can be formed in the same manner as the polycarbonate plate. As the first film layer satisfying these requirements, a polyolefin film having a melting point of 150 ° C. or higher is generally inexpensive and easily available, and is preferable as the first film layer of the present invention.
[0011]
Examples of the polyolefin film layer used for the first film layer include polypropylene and polyethylene having a substantial melting point of 150 ° C. or higher, or a mixture or copolymer thereof.
[0012]
If necessary, ethylene-propylene copolymer, ethylene-α-olefin copolymer, propylene-α-olefin copolymer, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-methyl A methacrylate copolymer, an ethylene-n-butyl acrylate copolymer, or the like may be blended with the polyolefin system. Examples of the α-olefin include 1-hexene, 4-methyl-1-pentene, 1-octene, 1-butene, 1-pentene, and 1-heptene.
[0013]
From the above polyolefin films, a film having a melting point that is at least 5 ° C. higher than the temperature condition during the heat bending process is appropriately selected as the first film layer so as to maintain a solid layer during the heat bending process. To do. Therefore, the selection of the first film layer is based on the temperature conditions during the heat bending process (generally within a temperature range of 135 to 155 ° C.), but the first film layer having a melting point of 150 ° C. or more is used. It is preferable to do. In particular, polypropylene having a melting point of about 160 ° C. or a mixture of polypropylene and polyethylene, or two or more types of copolymers selected from propylene, ethylene and α-olefin (excluding propylene), and the blending amount of polypropylene is 50% by weight. The above has the heat resistance required for the heat bending process of the aforementioned polycarbonate plate, is excellent in chemical resistance, is inexpensive and easy to obtain, satisfies the above-mentioned conditions, The first film layer is more preferable.
[0014]
Next, the role of the second film layer in the present invention is that it is in a molten state having a viscosity at a temperature in the vicinity of the glass transition temperature of the polycarbonate, in other words, the second film layer that occurs with the temperature change of the hot bending process. It is to prevent the influence (stress) due to heat shrinkage of one film layer from being transmitted to the polycarbonate plate. This is because when the polycarbonate plate is exposed to a high temperature environment near the glass transition temperature of polycarbonate and affected by the expansion and contraction of the first film layer, appearance defects such as wrinkles occur on the surface of the bent product. It is. Therefore, the second film layer is required to have a substantial melting point below the glass transition temperature of the polycarbonate. Conversely, if the melting point is too low than the glass transition temperature of the polycarbonate, the first film is bent during the bending process. Due to problems such as the appearance of defective layers such as the layer being misaligned from the bent product or part of the protective film remaining on the bent product after peeling off the protective film (residue residue). The melting point of the second film layer is required to be slightly lower (5 ° C. to 25 ° C.) than the heat bending temperature. Other examples include chemical resistance and scratch resistance.
[0015]
Therefore, the selection of the second film layer is selected based on the temperature conditions during the hot bending process to be used, as in the case of the first film layer. It is preferable to use a polyolefin film layer having a temperature range of 125 to 145 ° C. The polyolefin film used as the second film layer is exemplified by the polyolefin film of the first film layer, and can be applied to the protective film of the present invention as long as the melting point is in the range of 125 to 145 ° C. One or a mixture of two or more selected from polyethylene, an ethylene-propylene copolymer and an ethylene-α-olefin copolymer showing a melting point of about 130 ° C. from the affinity relationship with one film layer, The ethylene component in the second film layer is more preferably 50% by weight or more.
[0016]
The thickness of the first film layer is preferably in the range of 10 μm to 100 μm, and if it is thinner than 10 μm, the film tends to be broken due to insufficient elongation especially in bending of a deep-drawn product, and if it exceeds 100 μm, Since flexibility becomes small, it is difficult to handle and bulky, and economical efficiency is also deteriorated.
[0017]
The thickness of the second film layer is preferably in the range of 10 μm to 100 μm. If the thickness of the second film layer is less than 10 μm, wrinkles are likely to occur in the heat-bending product of the polycarbonate plate. It becomes easier for the second film layer to protrude from the polycarbonate plate.
[0018]
The total thickness of the first film layer and the second film layer of the protective film of the present invention is preferably 25 μm to 150 μm, more preferably 30 to 120 μm. When the total thickness is less than 25 μm, the rigidity of the film is very low, it is easily broken at the time of bending or peeling, and the product polycarbonate plate is easily scratched by external scratches. If the film thickness exceeds 150 μm, it takes time to conduct heat to the polycarbonate plate, the heat bending process cycle becomes long, and an excessive film is used, which is not economical.
[0019]
Next, providing an adhesive layer inside each of the first film layer and the second film layer of the protective film of the present invention means that the protective film of the present invention is peeled off from the delamination or polycarbonate plate during handling or bending. It is possible to prevent detachment, which is a preferable measure.
[0020]
The pressure-sensitive adhesive layer can be easily formed by the first film layer and the second film layer, or the second film layer even at a low pressure (less than 10 kg / cm 2 ) at room temperature by a method of pressure welding sandwiched between two rolls. A polycarbonate plate that can be brought into close contact with each other and can be obtained at low cost is preferable.
[0021]
The adhesive layer used on the inside of the second film layer has a peel strength as low as 100 g / 25 mm (90 ° peel strength test at 25 ° C.) or less, and the peel strength after hot bending is increased. In view of workability, polyethylene, ethylene-propylene copolymer, ethylene-α-olefin copolymer and the like can satisfy the above-mentioned peeling force, and the protective film of the present invention can be used. It can be preferably used.
[0022]
The adhesive layer used inside the first film layer is not related to the separation of the polycarbonate plate and the protective film even if the adhesive strength increases after heating if the adhesive is generally used for the protective film. So, either one can be used.
[0023]
In addition, a silicone, long-chain alkyl, acrylic, or stearic acid-based back treatment agent is applied to the side of the first film layer that comes into contact with the mold to release it. This is a preferable measure because the workpiece can be easily detached.
[0024]
Furthermore, a film in which various additives such as an antioxidant, a light stabilizer, and an antistatic agent are kneaded into the first film layer of the protective film of the present invention is used, or the side in contact with the mold of the first film layer It is also preferable to use a film coated with these various additives when storing a polycarbonate plate or a bent product for a long period of time.
[0025]
The method of laminating the protective film of the present invention on the polycarbonate plate is not particularly limited as long as it is a laminating method that finally becomes the configuration of the protective film of the present invention. For example, the second film layer and the polycarbonate plate When the second film layer has an adhesive layer, the adhesive layer side is in contact with the polycarbonate plate, and is crimped between two rolls at room temperature (load of 10 kg / cm 2 or less), and the second film is applied to the polycarbonate plate. The layers are laminated, and thereafter the first film layer is pressed between the two rolls at room temperature so that the first film layer is in contact with the second film layer of the polycarbonate plate on which the second film layer is laminated (load 10 kg). / Cm 2 or less), and a method of laminating the second film layer and the first film layer separately on the polycarbonate plate.
[0026]
Alternatively, the first film layer and the second film layer are simultaneously pressed on a polycarbonate plate between two rolls at room temperature so as to form the protective film of the present invention (load: 10 kg / cm 2 or less). There is also a way to do it.
[0027]
【Example】
EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to these examples.
[0028]
Example 1
Using a laminate (Iupilon Polar, manufactured by Mitsubishi Gas Chemical Co., Inc.) having a polarizing film having a thickness of 30 μm interposed between two polycarbonate sheets each having a thickness of 400 μm and a width of 300 mm, both sides of the polycarbonate laminate are used. First, a polyethylene protective film (Toray Synthetic Film, FM7721) having a melting point of 132 ° C., a thickness of 45 μm and a width of 300 mm having a polyethylene adhesive layer as the second film layer of the protective film is placed between two rolls at room temperature. And crimped with a load of 5 kg / cm @ 2. Thereafter, the first film layer of the protective film is a mixed product of polypropylene and polyethylene having a rubber adhesive layer having a melting point of 163 ° C., a thickness of 42 μm and a width of 300 mm and subjected to a long-chain alkyl backside treatment. -Based polyolefin protective film (SPV-JB500, manufactured by Nitto Denko Corporation) is pressed between two rolls at room temperature on both sides of the polycarbonate laminate on which the second film layer is pasted (load 5 kg / cm @ 2). Thereafter, the polycarbonate laminate on which the protective films composed of the first film layer and the second film layer were stuck on both sides was punched out with a press to an outer diameter of φ80 mm. Next, the punched sample was pre-dried at 130 ° C. for 5 minutes in a hot air dryer. Next, the punched sample is placed on a hemispherical mold having a spherical radius of 90 mm (lower mold), and is pressed by the upper mold at a pressure of 5 kg / cm @ 2 for 5 seconds under a temperature atmosphere of 150 DEG C. In a state where a vacuum was drawn for a minute, the punched sample was brought into close contact with the lower mold and subjected to hot bending. The finished bent product was curved to a spherical radius of 90 mm formed by transferring the spherical shape of the mold. Furthermore, when the peel strength of the protective film was measured using a spring balance, the peel strength was very small as shown in Table 1. Moreover, the appearance of the polycarbonate bent product after peeling off the protective film was good, and it had good polarization characteristics, and no defect was found.
[0029]
Example 2
A polycarbonate with a protective film in the same manner as in Example 1 except that a polypropylene protective film having a melting point of 164 ° C. having an acrylic adhesive layer (adhesive layer thickness 5 μm) having a thickness of 40 μm and a width of 300 mm was used as the first film layer. A laminate was produced to obtain a bent product. When the peel strength of the protective film was measured using a spring balance, the peel strength was considerably small as shown in Table 1. Moreover, the appearance of the polycarbonate bent product after peeling off the protective film was good, and it had a good polarization property, and no defect was found.
[0030]
Example 3
In Example 1, instead of FM7721 of the second film layer, a polyethylene film having a melting point of 132 ° C., a thickness of 30 μm and a width of 300 mm having a polyethylene of 300 μm (FM5030, manufactured by Toray Synthetic Film Co., Ltd.) was used instead of FM7721. A bent product was prepared in the same manner as in Example 1. When the peel strength of the protective film was measured using a spring balance, the peel strength was considerably small as shown in Table 1. Moreover, the appearance of the polycarbonate bent product after peeling off the protective film was good, and it had a good polarization property, and no defect was found.
[0031]
Example 4
The same as Example 1 except that a laminate having a polyurethane layer with a thickness of 110 μm containing 1% of a spirooxazine-based organic photochromic pigment interposed between polycarbonate sheets having a thickness of 400 μm and a width of 300 mm was used. Using the protective film, a laminate with a protective film was prepared and punched out with a press to an outer diameter of φ80 mm. The punched sample was put in a hot air dryer and preliminarily dried at 130 ° C. for 5 minutes. Thereafter, the punched sample was placed on a lower die having a spherical radius of 90 mm under an environment of 145 ° C., and the punched sample was sandwiched between the upper die and the lower die, and a pressure of 10 kg / cm 2 was applied for 4 minutes. Next, the mold was opened and a sample was taken out. When the peel strength of the protective film was measured using a spring balance, the peel strength was considerably small as shown in Table 1.
Moreover, the appearance of the polycarbonate bent product after peeling off the protective film was good, and no defect was found. Furthermore, it had a good photochromic property that developed orange in about 10 seconds when exposed to sunlight, and disappeared in about 1 minute when moved to a dark place.
[0032]
Example 5
Using the polycarbonate laminate with protective film of Example 1, the laminate was placed on the lower mold during the heat bending process, the upper mold was lowered, and the laminate was sandwiched between the upper mold and the lower mold in a temperature atmosphere of 147 ° C. Thereafter, a bent product was obtained in the same manner as in Example 1 except that heat bending was performed by evacuating the lower die for 8 minutes without applying pressure from the upper die.
When the peel strength of the protective film was measured using a spring balance, the peel strength was considerably small as shown in Table 1.
Moreover, the appearance of the polycarbonate bent product after peeling off the protective film was good, and it had a good polarization property, and no defect was found.
[0033]
Comparative Example 1
Except for laminating the polyolefin film layer, which is the first film layer of Example 1, and using only a polyethylene protective film having a thickness of 45 μm and a width of 300 mm (manufactured by Toray Synthetic Film Co., Ltd., FM7721). In the same manner as in No. 1, hot bending was performed. The finished bent product had a poor appearance because a polyethylene film was welded to the bent product.
[0034]
Comparative Example 2
Except for laminating the polyolefin film layer, which is the second film layer of Example 1, with a thickness of 42 μm and a width of 300 mm, only a polyolefin protective film (manufactured by Nitto Denko Corporation, SPV-JB500) was used. Hot bending was performed in the same manner as in Example 1.
The obtained bent product did not have a protective film welded, but when the peel strength of the protective film was measured using a spring balance, it was very difficult to peel off and the peel strength was 250 g / 25 mm (25 ° C.).
In addition, the appearance of the bent product after peeling had a slight appearance of wrinkles and was poor in appearance.
[0035]
[Table 1]
【The invention's effect】
According to the protective film of the present invention, the polycarbonate plate with the protective film attached and a laminate having the polycarbonate plate as an outer layer are pressurized and / or depressurized in a high-temperature environment near the glass transition temperature of polycarbonate. However, even if it is formed in close contact with a mold that has been shaped into a desired shape in advance, when the protective film is peeled off from the polycarbonate plate, there is no welding of the protective film to the bent product or mold, and after the heat bending process Is very easy to peel off, and the obtained bent product has no appearance of wrinkles and has good appearance.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a protective film of the present invention attached to a polycarbonate plate (laminate).
DESCRIPTION OF
Claims (5)
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| JP2001346157A JP3856107B2 (en) | 2001-11-12 | 2001-11-12 | Protective film on polycarbonate board |
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| Application Number | Priority Date | Filing Date | Title |
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| JP2001346157A JP3856107B2 (en) | 2001-11-12 | 2001-11-12 | Protective film on polycarbonate board |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2013210476A (en) * | 2012-03-30 | 2013-10-10 | Sumitomo Bakelite Co Ltd | Method of manufacturing polarizing plate formed body, polarizing plate formed body, anti-glare product, and protection product |
| WO2020179524A1 (en) | 2019-03-07 | 2020-09-10 | 三菱瓦斯化学株式会社 | Resin sheet for high hardness molding and molded article using same |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
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2001
- 2001-11-12 JP JP2001346157A patent/JP3856107B2/en not_active Expired - Fee Related
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| JP2013210476A (en) * | 2012-03-30 | 2013-10-10 | Sumitomo Bakelite Co Ltd | Method of manufacturing polarizing plate formed body, polarizing plate formed body, anti-glare product, and protection product |
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| KR20210136004A (en) | 2019-03-07 | 2021-11-16 | 미쯔비시 가스 케미칼 컴파니, 인코포레이티드 | Resin sheet for high hardness molding and molded article using same |
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