JP2004058435A - Laminated polyester film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a laminated polyester film excellent in processability, adhesiveness and scratch resistance and also excellent in wheatherability. <P>SOLUTION: In the laminated polyester film continuously formed using a coextrusion method and containing three or more polyester layers, light transmittance at a wavelength of 370 nm is not more than 3%, haze is not more than 3%, a refractive index in a thickness direction is 1.490-1.505, surface roughness Ra is 3-30 nm and the concentration of an ultraviolet absorber in each of layers satisfies a specific range. <P>COPYRIGHT: (C)2004,JPO

Description

【００２４】
式中、Ｘ^１は上記式に表わされたＸ^１からの２本の結合手が１位、２位の位置関係にある、２価の芳香族残基であり；ｎは１、２または３であり；Ｒ^１はｎ価の炭化水素残基で、これは更にヘテロ原子を含有していてもよい、またはＲ^１はｎ＝２のとき直接結合であることができる。
【００２５】
【化６】

【００２６】
式中、Ａは下記式（ＩＩ）−ａで表わされる基であるかまたは下記式（ＩＩ）−ｂで表わされる基であり；Ｒ^２およびＲ^３は同一もしくは異なり１価の炭化水素残基であり；Ｘ^２は４価の芳香族残基で、これは更にヘテロ原子を含有していてもよい。
【００２７】
【化７】

【００２８】
【化８】

【００２９】
前記一般式（Ｉ）中、Ｘ^１は式（Ｉ）に表わされたＸ^１からの２本の結合手が１位、２位の位置関係にある２価の芳香族残基であり；ｎは１、２または３であり；Ｒ^１はｎ価の炭化水素残基で、これは更にヘテロ原子を含有していてもよい、またはＲ^１はｎ＝２のとき直接結合であることができる。
【００３０】
Ｘ^１としては、好ましくは例えば１，２−フェニレン、１，２−ナフチレン、２，３−ナフチレン、下記式（ａ）または（ｂ）で表わされる基を挙げることができる。これらのうち、特に１，２−フェニレンが好ましい。なお式（ａ）または（ｂ）中、Ｒは−Ｏ−、−ＣＯ−、−Ｓ−、−ＳＯ_２−、−ＣＨ_２−、−（ＣＨ_２）−または−Ｃ（ＣＨ_３）_２−である。
【００３１】
【化９】

【００３２】
Ｘ^１について例示した上記芳香族残基は、例えば炭素数１〜１０のアルキル例えばメチル、エチル、プロピル、ヘキシル、デシル等；炭素数６〜１２のアリール例えばフェニル、ナフチル等；炭素数５〜１２のシクロアルキル例えばシクロペンチル、シクロヘキシル等；炭素数８〜２０のアラルキル例えばフェニルエチル等；炭素数１〜１０のアルコキシ例えばメトキシ、エトキシ、デシルオキシ等；ニトロ；ハロゲン例えば塩素、臭素等；炭素数２〜１０のアシル例えばアセチル、プロポニル、ゼンゾイル、デカノイル等；などの置換基で置換されていてもよい。
【００３３】
Ｒ^１はｎ価（ただし、ｎは１、２または３である）の炭化水素残基であるか、またはｎが２であるときに限り直接結合であることができる。
【００３４】
１価の炭化水素残基（ｎ＝１の場合）としては、第一に、例えば炭素数１〜１０の未置換脂肪族基、炭素数６〜１２の未置換芳香族基、炭素数５〜１２の未置換脂環族基が挙げられる。
【００３５】
炭素数１〜１０の未置換脂肪族基としては、例えばメチル、エチル、プロピル、ヘキシル、デシル等を、炭素数６〜１２の未置換芳香族基としては、例えばフェニル、ナフチル、ビフェニル等を；炭素数５〜１２の未置換脂環族基としては、例えばシクロペンチル、シクロヘキシル等を挙げることができる。
【００３６】
また、上記１価の炭化水素残基としては、第二に、例えば下記式（ｃ）〜（ｆ）で表わすことのできる、置換された脂肪族残基または芳香族残基を挙げることができる。これら式中で、Ｒ^４は炭素数２〜１０のアルキレン、フェニレンまたはナフチレンである。Ｒ^５は炭素数１〜１０のアルキル基、フェニル基またはナフチル基である。Ｒ^６は水素原子またはＲ^５に定義された基のいずれかである。Ｒ^７は水素原子またはＲ^５に定義された基のいずれかである。
【００３７】
【化１０】

【００３８】
【化１１】

【００３９】
【化１２】

【００４０】
【化１３】

【００４１】
また、上記１価の炭化水素残基としては、第三に、上記未置換の芳香族残基が例えば上記Ｘ^１を表わす芳香族残基の置換基として例示したと同じ置換基で置換されているものを挙げることができる。それ故、かかる置換基で置換された場合の例としては、例えばトリル、メチルナフチル、ニトロフェニル、ニトロナフチル、クロロフェニル、ベンゾイルフェニイル、アセチルフェニルまたはアセチルナフチル等を挙げることができる。
【００４２】
１価の炭化水素残基としては、上記式（ｃ）、（ｄ）、（ｅ）または（ｆ）で表わされる基、すなわち置換された脂肪族残基または芳香族残基、特にそのうち置換された芳香族残基が好ましい。
【００４３】
２価の炭化水素残基（ｎ＝２の場合）としては、第一に、例えば２価の、炭素数２〜１０の未置換の脂肪族残基、炭素数６〜１２の未置換の芳香族残基、炭素数５〜１２の未置換の脂環族残基基が挙げられる。
【００４４】
２価の炭素数２〜１０の未置換の脂肪族基としては、例えばエチレン、トリメチレン、テトラメチレン、デカメチレン等を、２価の炭素数６〜１２の未置換の芳香族残基としては、例えばフェニレン、ナフチレン、Ｐ，Ｐ’−ビフェニレン等を；２価の炭素数５〜１２の未置換の脂環族残基としては、例えばシクロペンチレン、シクロヘキシレン等を挙げることができる。
【００４５】
また、上記２価の炭化水素残基としては、第二に、例えば下記式（ｇ）で表わされる基、または下記式（ｈ）で表される、置換された脂肪族残基または芳香族残基を挙げることができる。式中、Ｒ^８はＲ^４に定義された基のいずれかである。Ｒ^９はＲ^４に定義された基のいずれかであり、そしてＲ^１０はＲ^６に定義された基のいずれかである。
【００４６】
【化１４】

【００４７】
【化１５】

【００４８】
また、上記２価の炭化水素残基としては、第三に、上記未置換の２価の芳香族残基が、例えば上記Ｘ^１を表わす芳香族基の置換基として例示したと同じ置換基で置換されているものを挙げることができる。
【００４９】
ｎが２の場合には、Ｒ^１としては、これらのうち直接結合または上記第一〜第三の群の未置換または置換された２価の芳香族炭化水素残基が好ましく、特に２本の結合手が最も離れた位置から出ている第一または第三の群の未置換または置換された芳香族炭化水素残基が好ましく、就中Ｐ−フェニレン、Ｐ，Ｐ’−ビフェニレンまたは２，６−ナフチレンが好ましい。
【００５０】
３価の炭化水素残基（ｎ＝３の場合）としては、例えば３価の炭素数６〜１２の芳香族残基を挙げることができる。
【００５１】
かかる芳香族残基としては、例えば次に示す４種類の基を挙げることができる。かかる芳香族残基は、上記１価の芳香族残基の置換基として例示したと同じ置換基で置換されていてもよい。
【００５２】
【化１６】

【００５３】
前述の一般式（Ｉ）中、Ｒ^２およびＲ^３は同一もしくは異なり１価の炭化水素残基であり、Ｘ^２は４価の芳香族炭化水素残基である。
【００５４】
Ｒ^２およびＲ^３としては、上記式（Ｉ）の説明において、ｎ＝１の場合のＲ^１について例示したと同じ基を例として挙げることができる。
【００５５】
４価の芳香族炭化水素残基としては、例えば次に示す８種類の基を挙げることができる。ここで、Ｒの定義は前述の一般式（ａ）に同じである。
【００５６】
【化１７】

【００５７】
上記４価の芳香族残基は、上記式（Ｉ）の説明において、Ｒ^１を表わす１価の芳香族残基の置換基として例示したと同じ置換基で置換されていてもよい。
【００５８】
本発明において用いられる上記式（Ｉ）および（ＩＩ）で表わされる環状イミノエステルの具体例としては、例えば下記の化合物を挙げることができる。
【００５９】
上記式（Ｉ）の化合物　ｎ＝１の場合
２−メチル−３，１−ベンゾオキサジン−４−オン、２−ブチル−３，１−ベンゾオキサジン−４−オン、２−フェニル−３，１−ベンゾオキサジン−４−オン、２−（１−または２−ナフチル）−３，１−ベンゾオキサジン−４−オン、２−（４−ビフェニル）−３，１−ベンゾオキサジン−４−オン、２−ｐ−ニトロフェニル−３，１−ベンゾオキサジン−４−オン、２−ｍ−ニトロフェニル−３，１−ベンゾオキサジン−４−オン、２−ｐ−ベンゾイルフェニル−３，１−ベンゾオキサジン−４−オン、２−ｐ−メトキシフェニル−３，１−ベンゾオキサジン−４−オン、２−ｏ−メトキシフェニル−３，１−ベンゾオキサジン−４−オン、２−シクロヘキシル−３，１−ベンゾオキサジン−４−オン、２−ｐ−（またはｍ−）フタルイミドフェニル−３，１−ベンゾオキサジン−４−オン、Ｎ−フェニル−４−（３，１−ベンゾオキサジン−４−オン−２−イル）フタルイミド、Ｎ−ベンゾイル−４−（３，１−ベンゾオキサジン−４−オン−２−イル）アニリン、Ｎ−ベンゾイル−Ｎ−メチル−４−（３，１−ベンゾオキサジン−４−オン−２−イル）アニリン、２−（ｐ−（Ｎ−メチルカルボニル）フェニル）−３，１−ベンゾオキサジン−４−オン。
【００６０】
上記式（Ｉ）の化合物　ｎ＝２の場合
２，２’−ビス（３，１−ベンゾオキサジン−４−オン）、２，２’−エチレンビス（３，１−ベンゾオキサジン−４−オン）、２，２’−テトラメチレンビス（３，１−ベンゾオキサジン−４−オン）、２，２’−デカメチレンビス（３，１−ベンゾオキサジン−４−オン）、２，２’−ｐ−フェニレンビス（３，１−ベンゾオキサジン−４−オン）、２，２’−ｍ−フェニレンビス（３，１−ベンゾオキサジン−４−オン）、２，２’−（４，４’−ジフェニレン）ビス（３，１−ベンゾオキサジン−４−オン）、２，２’−（２，６−または１，５−ナフチレン）ビス（３，１−ベンゾオキサジン−４−オン）、２，２’−（２−メチル−ｐ−フェニレン）ビス（３，１−ベンゾオキサジン−４−オン）、２，２’−（２−ニトロ−ｐ−フェニレン）ビス（３，１−ベンゾオキサジン−４−オン）、２，２’−（２−クロロ−ｐ−フェニレン）ビス（３，１−ベンゾオキサジン−４−オン）、２，２’−（１，４−シクロヘキシレン）ビス（３，１−ベンゾオキサジン−４−オン）、Ｎ−ｐ−（３，１−ベンゾオキサジン−４−オン−２−イル）フェニル、４−（３，１−ベンゾオキサジン−４−オン−２−イル）フタルイミド、Ｎ−ｐ−（３，１−ベンゾオキサジン−４−オン−２−イル）ベンゾイル、４−（３，１−ベンゾオキサジン−４−オン−２−イル）アニリン。
【００６１】
上記式（Ｉ）の化合物　ｎ＝３の場合
１，３，５−トリ（３，１−ベンゾオキサジン−４−オン−２−イル）ベンゼン、１，３，５−トリ（３，１−ベンゾオキサジン−４−オン−２−イル）ナフタレン、２，４，６−トリ（３，１−ベンゾオキサジン−４−オン−２−イル）ナフタレン。
【００６２】
上記式（ＩＩ）の化合物
２，８−ジメチル−４Ｈ，６Ｈ−ベンゾ（１，２−ｄ；５，４−ｄ’）ビス（１，３）−オキサジン−４，６−ジオン、２，７−ジメチル−４Ｈ，９Ｈ−ベンゾ（１，２−ｄ；４，５−ｄ’）ビス（１，３）−オキサジン−４，９−ジオン、２，８−ジフェニル−４Ｈ，８Ｈ−ベンゾ（１，２−ｄ；５，４−ｄ’）ビス（１，３）−オキサジン−４，６−ジオン、２，７−ジフェニル−４Ｈ，９Ｈ−ベンゾ（１，２−ｄ；４，５−ｄ’）ビス（１，３）−オキサジン−４，６−ジオン、６，６’−ビス（２−メチル−４Ｈ，３，１−ベンゾオキサジン−４−オン）、６，６’−ビス（２−エチル−４Ｈ，３，１−ベンゾオキサジン−４−オン）、６，６’−ビス（２−フェニル−４Ｈ，３，１−ベンゾオキサジン−４−オン）、６，６’−メチレンビス（２−メチル−４Ｈ，３，１−ベンゾオキサジン−４−オン）、６，６’−メチレンビス（２−フェニル−４Ｈ，３，１−ベンゾオキサジン−４−オン）、６，６’−エチレンビス（２−メチル−４Ｈ，３，１−ベンゾオキサジン−４−オン）、６，６’−エチレンビス（２−フェニル−４Ｈ，３，１−ベンゾオキサジン−４−オン）、６，６’−ブチレンビス（２−メチル−４Ｈ，３，１−ベンゾオキサジン−４−オン）、６，６’−ブチレンビス（２−フェニル−４Ｈ，３，１−ベンゾオキサジン−４−オン）、６，６’−オキシビス（２−メチル−４Ｈ，３，１−ベンゾオキサジン−４−オン）、６，６’−オキシビス（２−フェニル−４Ｈ，３，１−ベンゾオキサジン−４−オン）、６，６’−スルホニルビス（２−メチル−４Ｈ，３，１−ベンゾオキサジン−４−オン）、６，６’−スルホニルビス（２−フェニル−４Ｈ，３，１−ベンゾオキサジン−４−オン）、６，６’−カルボニルビス（２−メチル−４Ｈ，３，１−ベンゾオキサジン−４−オン）、６，６’−カルボニルビス（２−フェニル−４Ｈ，３，１−ベンゾオキサジン−４−オン）、７，７’−メチレンビス（２−メチル−４Ｈ，３，１−ベンゾオキサジン−４−オン）、７，７’−メチレンビス（２−フェニル−４Ｈ，３，１−ベンゾオキサジン−４−オン）、７，７’−ビス（２−メチル−４Ｈ，３，１−ベンゾオキサジン−４−オン）、７，７’−エチレンビス（２−メチル−４Ｈ，３，１−ベンゾオキサジン−４−オン）、７，７’−オキシビス（２−メチル−４Ｈ，３，１−ベンゾオキサジン−４−オン）、７，７’−スルホニルビス（２−メチル−４Ｈ，３，１−ベンゾオキサジン−４−オン）、７，７’−カルボニルビス（２−メチル−４Ｈ，３，１−ベンゾオキサジン−４−オン）、６，７’−ビス（２−メチル−４Ｈ，３，１−ベンゾオキサジン−４−オン）、６，７’−ビス（２−フェニル−４Ｈ，３，１−ベンゾオキサジン−４−オン）、６，７’−メチレンビス（２−メチル−４Ｈ，３，１−ベンゾオキサジン−４−オン）、６，７’−メチレンビス（２−フェニル−４Ｈ，３，１−ベンゾオキサジン−４−オン）。
【００６３】
上記例示化合物のうち、上記式（Ｉ）の化合物、より好ましくはｎ＝２の場合の上記式（Ｉ）の化合物、特に好ましくは下記式（Ｉ）−１で表わされる化合物が有利に用いられる。式中、Ｒ^１１は２価の芳香族炭化水素残基である。
【００６４】
【化１８】

【００６５】
式（Ｉ）−１の化合物としては、就中２，２’−ｐ−フェニレンビス（３，１−ベンゾオキサジン−４−オン）、２，２’−（４，４’−ジフェニレン）ビス（３，１−ベンゾオキサジン−４−オン）および２，２’−（２，６−ナフチレン）ビス（３，１−ベンゾオキサジン−４−オン）が好ましい。
【００６６】
これら環状イミノエステルの紫外線吸収特性は、例えばその代表的化合物について特開昭５９−１２９５２号公報に記載されているので、それを援用する。
【００６７】
前記環状イミノエステルは、ポリエステルに対して優れた相溶性を有するが、前記特開昭５９−１２９５２号公報や米国特許第４２９１１５２号明細書に記載されているように、ポリエステルの末端水酸基と反応する能力を有する。そこで、環状イミノエステルが実質的に未反応な状態で含有されるように、環状イミノエステルとポリエステルとを注意深く混合させることが求められる。ただし、ポリエステルとして、主たる割合の末端基がカルボキシル基であるポリエステルや、末端水酸基が該環状イミノエステルと反応性の無い末端封鎖剤で封鎖されているポリエステルを用いる場合、環状イミノエステルを未反応の状態で含有する組成物を製造するのに特別の注意を払う必要は無い。末端基の主たる割合が水酸基であるポリエステルを用いる場合には、溶融混合の時間は、次の２つの計算式（４）、（５）を満足するように、短時間で完了するようにするのが望ましい。
【００６８】
【数３】
Ｌｏｇｔ≦−０．００８Ｔ＋４．８　　…（４）
Ｔｍ＜Ｔ＜３２０　　　　　　　　　　…（５）
（４）及び（５）式中、ｔは溶融混合時間（秒）、Ｔは溶融混合温度（℃）及びＴｍはポリエステルの溶融温度（℃）である。
【００６９】
この場合、環状イミノエステルとポリエステルとが少しの割合で反応する可能性があるが、この反応によってポリエステルの分子量は大きくなるので、この割合によっては可視光吸収剤によるポリエステルの劣化による分子量低下を防ぐことが可能である。なお、環状イミノエステルがポリエステルと反応した場合、紫外線吸収波長領域が、一般に、未反応の状態の紫外線吸収波長領域より低波長側にずれる傾向を示し、それ故高波長側の紫外線を透過する傾向をもつ。
【００７０】
前記環状イミノエステルは、適量を添加する場合、昇華物が殆どないので、製膜でダイ周辺を汚すことが少なく、紫外線から３７０ｎｍ付近の光線を吸収するのでフィルムの着色が無く、可視光線吸収剤やフィルムの劣化を防止する特性に優れている。
【００７１】
前記紫外線吸収剤は、下記式（１）〜（３）を同時に満足するように積層フィルム中に添加する必要がある。
【００７２】
【数４】
０．１≦ＣＡ≦５．０　　　…（１）
０．１≦ＣＢ≦５．０　　　…（２）
０．２≦ＣＡ／ＣＢ≦５　　　　　…（３）
（上記式（１）〜（３）中、ＣＡ　は中間層中の紫外線吸収剤濃度（中間層が複数ある場合は両側の最外層を除いた各層の平均値；重量％）、ＣＢ　は最外層中の紫外線吸収剤濃度（最外層中の紫外線吸収剤濃度が異なる場合は濃度の高い方の最外層中の紫外線吸収剤濃度；重量％）を表わす。
【００７３】
更に好ましい範囲は０．２≦ＣＡ≦３．０、０．２≦ＣＢ≦３．０、０．３≦ＣＡ／ＣＢ≦３である。ＣＡ、ＣＢのいずれかが０．１重量％未満であると耐候性が劣り、また５重量％を超えると添加した紫外線吸収剤がフィルム表面に湧き出る現象（ブリードアウト）、及びそれが昇華する現象が発生しやすく、これによってフィルム製膜機が汚染されやすかったり、フィルム表層の湧出物が加工工程で悪影響を及ぼすため、好ましくない。またＣＡ／ＣＢが０．２未満であるとブリードアウト現象が発生したり、紫外線吸収性能が劣り、一方、５を超えると最外層が劣化しやすくなり、好ましくない。
【００７４】
前記紫外線吸収剤のポリエステルへの添加方法は特に限定されないが、ポリエステル重合工程、フィルム製膜前の溶融工程でのポリマー中への練込み、二軸延伸フィルムへの含浸、などを挙げることができ、特にポリエステル重合度低下を防止する意味でもフィルム製膜前の溶融工程でのポリマー中への練込みが好ましい。その際、紫外線吸収剤の練込みは、化合物粉体の直接添加法、マスターバッチ法などにより行うことができる。
【００７５】
本発明における積層ポリエステルフィルムの、３７０ｎｍでの光線透過率は、３％以下、好ましくは２％以下である必要がある。３％を超える場合は紫外線に対する耐候性が不足する。
【００７６】
＜被膜層＞
本発明の積層ポリエステルフィルムは、接着性や耐ブロッキング性を向上させるために、共押出法を用いて連続製膜された少なくとも３層のポリエステル層の少なくとも一方の最外層上には、被膜層を設けることもできる。この被膜層を形成させる樹脂としては特に限定されないが、共重合ポリエステル系樹脂を主成分とすることが好ましい。共重合ポリエステル樹脂としては、例えば多塩基酸成分として、テレフタル酸、イソフタル酸、フタル酸、無水フタル酸、２、６−ナフタレンジカルボン酸、１、４−シクロヘキサンジカルボン酸、アジピン酸、セバシン酸、トリメリット酸、ピロメリット酸、ダイマー酸、５−ナトリウムスルホイソフタル酸等が挙げられ、また、ポリオール成分としては、エチレングリコール、１、４−ブタンジオール、ジエチレングリコール、ジプロピレングリコール、１、６−ヘキサンジオール、１、４−シクロヘキサンジメタノール、キシレングリコール、ジメチロールプロパン、ポリ（エチレンオキシド）グリコール、ポリ（テトラメチレンオキシド）グリコール等が挙げられる。特にガラス転移点が４０〜１００℃の範囲にあるポリエステル樹脂が好ましい。また、アクリル系樹脂との接着性を向上させ、且つ被膜層の耐スクラッチ性を向上させるために、アルキルアクリレート、アルキルアクリレート等のモノマーと主成分とするアクリル系樹脂、エポキシ系樹脂、架橋剤等を含有させてもよい。
【００７７】
本積層ポリエステルフィルムの被膜層は、耐スクラッチ性、ハンドリング性付与のために不活性粒子を含有してもよい。不活性粒子の平均粒径は１０〜３００ｎｍの範囲であり、含有量は０．１〜２０重量％であることが好ましい。平均粒径が１０ｎｍ未満であるか、被膜層中の不活性粒子の含有量が０．１重量％より少ないとフィルムが滑りにくくなり、スクラッチ傷耐性やハンドリング性が不十分となる。不活性粒子の粒子径が３００ｎｍを超えるか、含有量が２０重量％を超えると不活性粒子の脱落が起こりやすくなり、また被膜層の透明性が損なわれ、ディスプレイ用途等に使用しにくくなる。かかるフィラーは有機または無機の微粒子であり、炭酸カルシウム、酸化カルシウム、酸化アルミニウム、カオリン、酸化珪素、酸化亜鉛、架橋アクリル樹脂粒子、架橋ポリスチレン樹脂粒子、メラミン樹脂粒子、架橋シリコーン樹脂粒子等が例示される。
【００７８】
本発明で用いられる被膜層は、水溶性、水分散性、或いは乳化液等の水性塗液の形態で使用されることが好ましい。被膜を形成するために、必要に応じて、上記組成物以外の他の樹脂や化合物、例えば帯電防止剤、着色剤、界面活性剤、ワックス、架橋剤、紫外線吸収剤などを添加することができる。
【００７９】
本発明の積層ポリエステルフィルムでは被膜層を設けた場合は、表面粗さは被膜層を設けた外表面の表面粗さのことを指す。
【００８０】
＜積層ポリエステルフィルムの製造方法＞
積層ポリエステルフィルムは、従来から知られている逐次二軸延伸法、同時二軸延伸法、インフレーション法等によって製造することができる。逐次二軸延伸法や同時二軸延伸法においては、先ず、所定の組成のポリエステルチップを充分に乾燥した後、複数台の押出機、複数層のマルチマニホールドダイまたはフィードブロックを用い、それぞれのポリエステルフィルムを積層して口金から複数層の溶融シートを押出し、予め２０〜４０℃程度に設定されたキャスティングドラム上にて急冷固化させて未延伸フィルムを得る。得られる未延伸フィルムの厚みは０．５ｍｍ以上であることが好ましい。未延伸フィルムは、その後、一般によく知られた条件で二軸方向に延伸するが、熱収と屈折率を所望の範囲とするために、フィルムの連続製膜方向（縦方向）に３．０〜４．５倍、これと直角方向（横方向）に３．０〜４．５倍、面積倍率で９〜２０倍に延伸するのが好ましい。延伸温度は、９０℃〜１４０℃が好ましい。また二軸延伸後、必要に応じて熱固定を行うことができる。熱固定温度は１８０〜２５０℃が好ましく、２１０〜２４０℃がより好ましい。
【００８１】
本発明における積層ポリエステルフィルムに被膜層を形成する方法は、通常の塗工工程、即ち二軸延伸熱固定した積層ポリエステルフィルムに該フィルムの製造工程と切り離した工程で行うと、芥、塵埃等を巻込み易く、好ましくない。かかる観点より、クリーンな雰囲気での塗布、即ちフィルム製造工程での塗布が好ましい。そして、この塗布によれば、被膜（塗膜）の積層ポリエステルフィルムへの密着性が向上する。
【００８２】
塗布方法としては、公知の任意の塗布法が適用できる。例えばロールコート法、グラビアコート法、ロールブラッシュ法、スプレーコート法、エアーナイフコート法、含浸法及びカーテンコート法などを単独または組合せて用いることができる。塗布量は走行しているフィルム１ｍ^２当り、０．５〜２０ｇ、さらには１〜１０ｇが好ましい。水性液は水分散液または乳化液として用いるのが好ましい。乾燥、延伸後の被膜層の厚さは０．０２〜１μｍであることが好ましい。なお、被膜は、必要に応じ、フィルムの片面のみに形成してもよいし、両面に形成してもよい。
【００８３】
また、積層ポリエステルフィルムを構成する各層の厚みや不活性粒子の添加状態を前述のように制御することで、積層ポリエステルフィルムに必要な光学特性を達成できる。
【００８４】
【実施例】
以下、実施例により本発明を更に説明する。なお、各特性値は以下の方法で測定した。
【００８５】
（１）粒子の平均粒径
試料フィルム小片を走査型電子顕微鏡用試料台に固定し、スパッターリング装置（日本電子（株）製の商品名「ＪＩＳ−１１００型イオンスパッターリング装置」）を用いてフィルム表面をイオンエッチング処理し、高分解能電界放出形走査型電子顕微鏡にて１〜３万倍で観測し、ニレコ（株）製ルーゼックスＦＳにて、５０個の粒子の面積相当粒径を求め、数平均値を平均粒径とした。
【００８６】
（２）屈折率
アッベ屈折計を用いナトリウムＤ線（５８９ｎｍ）を光源としてフィルムの屈折率を求めた。
【００８７】
（３）表面粗さＲａ
三次元粗さ計（小坂研究所製の商品名「ＳＥ−３ＣＫ」）を用いて、針径２μｍＲ、針圧３０ｍｇ、測定長さ１ｍｍ、サンプリングピッチ２μｍ、カットオフ０．２５ｍｍ、縦方向拡大率２万倍、横方向拡大率２００倍、走査本数１００本の条件にて測定し、Ｒａを測定する。両面に被膜層を設けた場合は、両面を測定し平均値を求めた。
【００８８】
（４）全光線透過率、ヘーズ値
ヘーズ測定器（日本電色工業社製の商品名「ＮＤＨ―２０００」）を使用してフィルムの全光線透過率及びヘーズ値を測定した。尚、フィルムのヘーズ値は下記の基準で評価した。
◎：ヘーズ値≦１．５％　…フィルムのヘーズ極めて良好
○：１．５％＜ヘーズ値≦３．０％　…フィルムのヘーズ良好
×：３．０％＜ヘーズ値　…フィルムのヘーズ不良。
【００８９】
（５）３７０ｎｍ光線透過率
ダブルビーム型分光光度計（島津製作所（株）製の商品名「ＵＶ−３１０１ＰＣ」）により、スリット幅；２０ｎｍ、スキャン速度；中速、サンプリングピッチ；１ｎｍの条件で、波長３００〜５００ｎｍ領域の光線透過率を連続的に測定し、３７０ｎｍ波長での光線透過率を検出し、以下の基準で評価した。
○：３％未満
△：３％以上、５％未満
×：５％以上。
【００９０】
（６）フィルムの積層厚み
フィルム小片をエポキシ樹脂にて固定成形した後、ミクロトームで切断し、フィルムの断面を透過電子顕微鏡（日本電子（株）製の商品名「ＪＥＭ２０１０」）にて写真撮影した。その断面のうちフィルム表面とほぼ平行に２本、明暗によって界面が観察される。その２本の界面とフィルム表面までの距離を１０枚の写真から測定し、平均値を積層厚さとした。
【００９１】
（７）耐スクラッチ性
光学易接着フィルムを幅１００ｍｍにスリットしたものをフィルム走行性試験機を使用して、直径１００ｍｍ、回転抵抗１ｋｇのハードクロムメッキ処理されたフリーロール（表面粗度：Ｒａで１００ｎｍ）上を走行させる。この時の走行条件は、走行速度：１０ｍ／分、巻き付け角：９０゜、走行張力：２０ｋｇとした。この処理によりフィルム表面に入った傷を、白金蒸着後、顕微鏡で観察し、幅２μｍ以上でかつ長さ３００μｍ以上の傷の０．４ｍ^２あたり本数をカウントし、下記基準で評価した。
○：１０個未満
△：１０個以上２０個未満
×：２０個以上。
【００９２】
（８）摩擦係数（μｓ）
重ね合わせた２枚のフィルムの下側に固定したガラス板を置き、重ね合わせたフィルムの下側（ガラス板と接しているフィルム）のフィルムを低速ロールにて引取り（約１０ｃｍ／分）、上側のフィルムの一端（下側フィルムの引取り方向と逆端）に検出器を固定してフィルム／フィルム間のスタート時の引張力を検出する。尚、そのときに用いるスレッドは重さ１．５ｋｇ、下側面積７５ｃｍ^２のものを使用する。
【００９３】
なお、摩擦係数（μｓ）は次式より求める。
μｓ＝スタート時の引張力（ｋｇ）／荷重１ｋｇ
評価は下記の基準で行う。
○：０．４未満
△：０．４以上　０．６未満
×：０．６以上。
【００９４】
（９）接着性
積層ポリエステルフィルムの被膜形成面にハードコート剤（大日精化社製の商品名「セイカビームＥＸＦ０１（Ｂ）」）を＃８ワイヤバーにより塗布し、７０℃で１分間乾燥し溶剤を除去した後、高圧水銀灯で２００ｍＪ／ｃｍ^２、照射距離１５ｃｍ、走行速度５ｍ／分の条件下で、厚み５μｍのハードコート層を形成した。得られたフィルムをＪＩＳ−Ｋ５４００の８．５．１の記載に準じた試験方法で接着性を求めた。具体的には、被膜層を貫通して基材フィルムに達する１００個の升目状の切り傷を、隙間間隔１ｍｍのカッターガイドを用いて付けた。次いで、セロハン粘着テープ（ニチバン社製４０５番；２４ｍｍ幅）を升目状の切り傷面に張り付け、消しゴムでこすって完全に付着させた後、１８０°の剥離角度で急激に剥がした後、剥離面を観察し、下記の基準で評価した。
○：剥離面積が３０％未満
△：剥離面積が３０％以上５０％未満
×：剥離面積が５０％を超えるもの。
【００９５】
（１０）耐候性
接着性評価同様、積層ポリエステルフィルムに厚さ５μｍのハードコート層を形成する。このサンプルを、サンシャインウェザーメーター（スガ試験機（株）性、ＷＥＬ−ＳＵＮ−ＨＣＬ型）を使用し、ＪＩＳ−Ｋ−６７８３ｂに準じて、１０００時間（屋外曝露１年間に相当）照射することにより屋外曝露促進試験を行う。処理後、日本電色工業社製のヘーズ測定器（ＮＤＨ―２０００）を使用してフィルムのヘーズ値を測定し、処理前後の差を求め、下記の基準で評価した。
○：１．０％未満
△：１．０％以上、２．０％未満
×：２．０％以上。
【００９６】
［実施例１］
式（イ）に示す紫外線吸収剤を１．０重量％含有したポリエチレンテレフタレートチップＡ（固有粘度０．６３）を用意した。さらに、式（イ）に示す紫外線吸収剤を１．０重量％と、平均粒径１．５μｍの多孔質シリカ（一次粒子の径０．００４μｍ、細孔容積１．２ｍｌ／ｇ）を０．０１重量％含有したポリエチレンテレフタレートチップＢ（固有粘度０．６２）も用意した。それぞれ１６０℃で３時間乾燥した。
【００９７】
【化１９】

【００９８】
また、ポリエステル８５重量部と、フィラー５重量部と、濡れ剤１０重量部とからなる塗剤も用意した。ここで塗剤用に用いたポリエステルは、酸成分が２，６−ナフタレンジカルボン酸６５モル％／イソフタル酸３０モル％／５−ナトリウムスルホイソフタル酸５モル％、グリコール成分がエチレングリコール９０モル％／ジエチレングリコール１０モル％で構成（Ｔｇ＝８０℃）される。フィラーは架橋アクリルフィラー（６０ｎｍ）である。濡れ剤はポリオキシエチレン（ｎ＝７）ラウリルエーテルである。
【００９９】
そして前述の二種類のチップを、別々の押出機に供給し、２９０℃で溶融押出し、マルチマニホールドダイを用いてポリエチレンテレフタレートチップＡから得た層を内層に、ポリエチレンテレフタレートチップＢから得た層を表層にして３層に積層し、２０℃に保持した冷却ドラム上で急冷固化せしめて未延伸フィルムを得た。続いて、該未延伸フィルムを９５℃で縦方向に３．２倍に延伸し、次いで両面に前述の塗剤を乾燥後の厚みがそれぞれ０．０４μｍになるように塗布し、さらに１１０℃で横方向に３．６倍に延伸したのち、２３０℃で５秒間熱固定し、更に１９０℃の温度で幅方向に０．５％弛緩させ、厚みが１００μｍの積層ポリエステルフィルムを得た。表層Ｂ層の厚みは５μｍ、内層の厚みは９０μｍとした。得られたフィルムの特性を表１に示す。
【０１００】
［実施例２、３および比較例１］
ポリエチレンテレフタレートチップＡ，Ｂに含有させる紫外線吸収剤を下記の通り変更する他は、実施例１と同様にして積層ポリエステルフィルムを得た。実施例２では、下記式（ロ）の紫外線吸収剤をポリエチレンテレフタレートチップＡ，Ｂとも１．０重量％含有させた。実施例３では、下記式（ハ）の紫外線吸収剤を、ポリエチレンテレフタレートチップＡに１．２重量％、ポリエチレンテレフタレートチップＢに０．４重量％含有させた。比較例１では、ポリエチレンテレフタレートチップＡ，Ｂとも紫外線吸収性剤を含有させなかった。得られたフィルムの特性を表１に示す。
【０１０１】
【化２０】

【０１０２】
【化２１】

【０１０３】
［実施例８および比較例６、７］
ポリエチレンテレフタレートチップＡ、Ｂに含有させる紫外線吸収剤の含有量を下記の通り変更する他は、実施例１と同様にして積層ポリエステルフィルムを得た。実施例８では、ポリエチレンテレフタレートチップＡに０．５重量％、ポリエチレンテレフタレートチップＢに１．５重量％、比較例６では、ポリエチレンテレフタレートチップＡに１．１重量％、ポリエチレンテレフタレートチップＢには含有させず、比較例７では、ポリエチレンテレフタレートチップＡに０．５重量％、ポリエチレンテレフタレートチップＢに３．０重量％含有させた。得られたフィルムの特性を表１に示す。
【０１０４】
［実施例４］
フィルム厚みを１８８μｍとし、そのうちの外層厚を１０μｍ、内層厚を１６８μｍとする以外は実施例１と同様にして積層ポリエステルフィルムを得た。得られたフィルムの特性を表１に示す。
【０１０５】
［実施例５］
外層の厚を１２μｍ、内層の厚を７６μｍとする以外は、実施例１と同様にして積層ポリエステルフィルムを得た。得られたフィルムの特性を表１に示す。
【０１０６】
［実施例６］
ポリエチレンテレフタレートチップＢに含有させる多孔質シリカの含有量を０．０４重量％とする以外は、実施例１と同様にして積層ポリエステルフィルムを得た。得られたフィルムの特性を表１に示す。
【０１０７】
［実施例７］
ポリエチレンテレフタレートチップＢに含有させたのと同じ種類の多孔質シリカを、ポリエチレンテレフタレートチップＡにも０．００３重量％含有させた以外は、実施例１と同様にして積層ポリエステルフィルムを得た。得られたフィルムの特性を表１に示す。
【０１０８】
［比較例２］
ポリエチレンテレフタレートチップＡには、紫外線吸収剤に加えて、平均粒径０．１２μｍの球状シリカを０．１重量％加える以外は実施例１と同様にして積層ポリエステルフィルムを得た。得られたフィルムの特性を表１に示す。
【０１０９】
［比較例３］
ポリエチレンテレフタレートチップＢに含まれる多孔質シリカの含有量を０．０８重量％とし、外層の厚みを２０μｍ、内層の厚みを６０μｍに変更する以外は実施例１と同様にして積層ポリエステルフィルムを得た。得られたフィルムの特性を表１に示す。
【０１１０】
［比較例４］
縦方向の延伸倍率を３．７倍、横方向の延伸倍率を３．９倍とし、熱固定温度を２０５℃とする以外は実施例１と同様にして積層ポリエステルフィルムを得た。得られたフィルムの特性を表１に示す。
【０１１１】
［比較例５］
実施例１と同じ紫外線吸収剤を１．０重量％、平均粒径１．５μｍの多孔質シリカ（一次粒子の径０．００４μｍ、細孔容積１．２ｍｌ／ｇ）を０．００３重量％含有したポリエチレンテレフタレートチップ（固有粘度０．６３）を用意した。これを１６０℃で３時間乾燥したのち押出機に供給し、２９０℃で溶融押出し、他は実施例１と同様にして単層のポリエステルフィルムを得た。得られたフィルムの特性を表１に示す。
【０１１２】
【表１】

【０１１３】
【発明の効果】
表１に示された結果から明らかなように、本発明の積層ポリエステルフィルムは耐候性に優れ、かつ加工性、接着性、耐スクラッチ性に優れ、積層ポリエステルフィルムとして有用である。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a laminated polyester film having excellent weather resistance and excellent transparency, handling properties, scratch resistance, and processing characteristics, and more specifically, a base film for a prism lens sheet used for a liquid crystal display device and a base for a touch panel. The present invention relates to a laminated polyester film used for optical applications such as a film, a base film for a backlight, a base film for an AR (anti-reflection) film, and a shatterproof film for a CRT.
[0002]
[Prior art]
Polyester films, especially biaxially stretched films of polyethylene terephthalate and polyethylene naphthalate, have excellent mechanical properties, heat resistance, and chemical resistance, so they can be used for magnetic tapes, ferromagnetic metal thin film tapes, photographic films, packaging films, and electronics. It is widely used as a material for parts films, electric insulating films, films for laminating metal plates, films to be attached to surfaces of glass displays, etc., and films for protecting various members. In recent years, various optical films have been used in particular, and there are uses such as prism lens sheets for liquid crystal display devices, base films for touch panels and backlights, base films for antireflection films, and explosion-proof base films for displays. . These are often used outdoors, such as notebook PCs and PDAs. However, if the film also has poor weather resistance, the strength of the film is reduced, the transparency is reduced, and the like, and it cannot be used for a long time. .
[0003]
In addition, in order to maintain the transparency of the polyester film, it is preferable to minimize the amount of particles and additives contained in the polyester film as much as possible. There was a problem that the handling properties, scratch resistance, and blocking resistance during processing were poor.
[0004]
[Problems to be solved by the invention]
An object of the present invention is to solve such a conventional problem and to provide a laminated polyester film having excellent weather resistance and excellent transparency, handling properties, scratch resistance and blocking resistance.
[0005]
[Means for Solving the Problems]
According to the present invention, (1) a laminated polyester film containing three or more polyester layers continuously formed by a coextrusion method has a light transmittance at a wavelength of 370 nm of 3% or less. The haze is 3% or less, the refractive index in the thickness direction is 1.490 or more and 1.505 or less, the surface roughness Ra is 3 nm or more and 30 nm or less, and the concentration of the ultraviolet absorber in the layer is represented by the following formulas (1) to (3). This is achieved by a laminated polyester film that satisfies (1).
[0006]
(Equation 2)
0.1 ≦ CA ≦ 5.0 (1)
0.1 ≦ CB ≦ 5.0 (2)
0.2 ≦ CA / CB ≦ 5 (3)
(In the above formulas (1) to (3), CA is the concentration of the ultraviolet absorber in the intermediate layer (when there are a plurality of intermediate layers, the average value of each layer excluding the outermost layers on both sides; weight%), CB is the outermost layer The concentration of the ultraviolet absorbent in the middle (when the concentration of the ultraviolet absorbent in the outermost layer is different, the concentration of the ultraviolet absorbent in the outermost layer having the higher concentration; wt%) is shown.
[0007]
Furthermore, the subject of the present invention is (2) the lamination according to (1), wherein the heat shrinkage at 150 ° C. is 2% or less in both the continuous film forming direction and the direction perpendicular to the continuous film forming direction. (3) the laminated polyester film according to any one of (1) and (2), wherein the total light transmittance is 80% or more; and (4) the refractive index in the thickness direction is 1.493 or more and 1.502 or less. The laminated polyester film according to any one of (1) to (3), wherein (5) the refractive index in the continuous film forming direction is 1.620 or more and 1.680 or less, and refraction in the direction perpendicular to the continuous film forming direction. The laminated polyester film according to any one of (1) to (4), wherein the ratio is 1.640 to 1.700, and (6) three or more polyester layers continuously formed using a coextrusion method. Coating on at least one outermost layer (8) The laminated polyester film according to any one of (1) to (5), (7) the laminated polyester film according to (6), wherein the coating layer contains inert particles having an average particle size of 10 nm or more and 300 nm or less, (8) The polyester layer according to any one of (1) to (7), wherein the polyester layer is mainly composed of polyethylene terephthalate or polyethylene-2,6-naphthalate; The laminated polyester film according to any one of (1) to (8), which is at least one compound selected from the cyclic imino esters represented by the formula (II), and (10) used for optics. It can be preferably achieved by the laminated polyester film according to any one of (1) to (9).
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail.
[0009]
<Laminated polyester film>
The at least three polyester layers constituting the laminated polyester film of the present invention refer to a layer obtained by stretching a material extruded by a coextrusion method in which all the layers are melt-extruded from a die and then heat-fixing the resultant as necessary. Hereinafter, a three-layered film will be described as a laminated polyester film. However, the laminated polyester film of the present invention is not limited to a three-layered polyester film as long as the purpose is satisfied, and is a multilayer of four or more layers. You may.
[0010]
The main component of the polyester constituting the laminated polyester film in the present invention is an aromatic dicarboxylic acid component selected from terephthalic acid, isophthalic acid, 2,6-naphthalene dicarboxylic acid and 4,4′-diphenyl dicarboxylic acid, ethylene glycol, Aromatic polyester composed of a glycol component selected from 2,4-butanediol, 1,4-cyclohexanedimethanol, and 1,6-hexanediol is preferred, and polyethylene terephthalate and polyethylene-2,6-naphthalene dicarboxylate are particularly preferred. Is preferred. Further, a copolymerized polyester such as the above components may be used. When the structure of the polyester film is a single layer, it is difficult to achieve both transparency and scratch resistance.
[0011]
In the laminated polyester film of the present invention, the outermost layer is a layer constituting two exposed surfaces immediately after being extruded from the die, and the other layers are referred to as inner layers. The intrinsic viscosity (IV: measured at 35 ° C. in an orthochlorophenol solution) of the polyester composition constituting the inner layer and the outermost layer is usually 0.45 to 0.80, preferably 0.50 to 0.75, and furthermore Preferably it is 0.55 to 0.70. When the IV value is less than 0.45, the polyester film as a film tends to have inferior excellent characteristics such as heat resistance and mechanical strength. If the IV value exceeds 0.80, the load in the extrusion step during the production of the polyester film tends to be too large, and the productivity may be reduced.
[0012]
The thickness of the laminated polyester film in the present invention is from 50 μm to 200 μm, preferably from 75 μm to 175 μm. If the thickness is less than 50 μm, the stiffness is weak, and flatness is easily lost during processing, and scratches are likely to occur. On the other hand, if the thickness is more than 200 μm, the stiffness is too strong, and the workability is poor, and the transparency is lowered, which is not preferable.
[0013]
The thickness of the outermost layer of the laminated film of the present invention is generally 0.5 to 30 μm, preferably 1 to 20 μm on one side only. If the thickness is less than 0.5 μm, it is necessary to contain a high concentration of inert particles in order to achieve the desired surface roughness, and coarse projections due to aggregates are likely to occur, which is not preferable. On the other hand, when the thickness is more than 30 μm, the haze value due to the inert particles added to the outermost layer film for improving the winding property of the film and the scratch resistance is increased, and the transparency of the film is deteriorated. Tend. The thickness of the inner layer is 30 μm to 190 μm, preferably 20 μm to 170 μm.
[0014]
The laminated polyester film of the present invention needs to have a surface roughness Ra of 3 nm or more and less than 30 nm, and preferably 5 nm or more and less than 20 nm. When Ra is less than 3 nm, the coefficient of friction of the film surface increases, and the handling properties and scratch resistance are poor, which is not preferable. On the other hand, if Ra exceeds 30 nm, the surface of the film becomes rough, the surface reflection increases, and the total light transmittance decreases.
[0015]
As a method for keeping the roughness within this range, a method of adding fine inert particles to the outermost layer of the laminated polyester film is preferably used. The inert particles added to the outermost layer preferably have an average particle size in the range of 0.01 to 2.0 μm, and more preferably 0.1 to 1.0 μm. Further, the addition amount of the particles in the outermost layer is preferably in the range of 0.003 to 0.5% by weight, more preferably 0.005 to 0.1% by weight.
[0016]
Examples of the inert particles used in the present invention include organic or inorganic particles, such as calcium carbonate, calcium oxide, aluminum oxide, kaolin, silicon oxide, zinc oxide, crosslinked acrylic resin particles, crosslinked polystyrene resin particles, and urea. Resin particles, melamine resin particles, crosslinked silicone resin particles and the like are exemplified. The inert particles may be a single component selected from those exemplified above, and the timing of adding the inert particles is not particularly limited as long as it is a stage until the polyester is formed into a film. And may be added at the time of film formation.
[0017]
In the laminated polyester film of the present invention, the content of inert particles in the inner layer is preferably smaller than that in the outermost layer, but is more preferably 0.1% by weight or less from the viewpoint of transparency. The kind of the inert particles may be the same as or different from the particles contained in the outermost layer, and may be one kind or two or more kinds. The average particle size is preferably 2.0 μm or less, more preferably 1.0 μm or less. If the average particle size exceeds 2.0 μm, the transparency may be impaired.
[0018]
The laminated polyester film of the present invention, in any layer, in addition to the inert particles, a coloring agent, an antistatic agent, an antioxidant, a lubricant, a catalyst, polyethylene, polypropylene, ethylene-propylene-polymer, such as an olefin-based ionomer. Other resins and the like can be arbitrarily contained as long as the transparency is not impaired.
[0019]
The laminated polyester film of the present invention has a heat shrinkage at 150 ° C. of 2.0% or less in both the continuous film forming method (longitudinal direction) and the direction perpendicular to the continuous film forming direction (width direction). Preferably, it is 1.5% or less. If the heat shrinkage in the longitudinal direction at 150 ° C. exceeds 2.0%, when the hard coat agent is dried in the hard coat treatment step, the shrinkage characteristics between the film and the hard coat layer are different, resulting in adhesion to the hard coat layer. Properties tend to decrease. Further, when the film passes through a process involving heating during processing, it is not preferable because wrinkles, curls, and irregularities in flatness are generated. The method of adjusting the heat shrinkage of the polyester film is not particularly limited, and a known method can be used. For example, a method of shrinking in a heat treatment step as disclosed in JP-A-57-57628, A method of relaxing the film in a suspended state as disclosed in Japanese Unexamined Patent Publication No. 1-275031 can be exemplified.
[0020]
The haze of the laminated polyester film in the present invention needs to be 3% or less, preferably 2% or less. If this haze exceeds 3% or more, it may not be suitable for optical use such as impairing visibility in various display applications. Further, the total light transmittance is preferably 80% or more, and if it is less than 80%, the sharpness of the screen deteriorates, which is not preferable.
[0021]
Further, the laminated polyester film of the present invention needs to have a refractive index in the thickness direction of 1.490 or more and 1.505 or less, and preferably 1.493 or more and 1.502 or less. When the refractive index is less than 1.490, delamination tends to occur, and when used as an optical film, the adhesiveness to the hard coat layer is insufficient. Further, the flatness is deteriorated and the flatness is deteriorated, which is not preferable. On the other hand, when the refractive index exceeds 1.505, transparency tends to be impaired. Further, the refractive index in the longitudinal direction is preferably from 1.620 to 1.680, and more preferably from 1.630 to 1.670. Further, the refractive index in the width direction is preferably 1.640 to 1.700, and more preferably 1.650 to 1.690. Outside this range, it is difficult to control the refractive index in the thickness direction within the range.
[0022]
<Ultraviolet absorber>
The polyester constituting the laminated polyester film in the present invention needs to contain an ultraviolet absorber in order to improve the weather resistance of the film. The type of the ultraviolet absorber is not particularly specified, but at least one compound selected from a cyclic imino ester represented by the following formula (I) and a cyclic imino ester represented by the following formula (II) is reacted with an unreacted compound. It is preferred to use it in form. Such a cyclic imino ester is a compound known as an ultraviolet absorber, and is described in, for example, JP-A-59-12952.
[0023]
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[0024]
In the formula, X ¹ is a divalent aromatic residue in which two bonds from X ¹ represented by the above formula are in a 1-position or 2-position relationship; n is 1, 2 or 3; R ¹ is an n-valent hydrocarbon residue, which may further contain a heteroatom, or R ¹ can be a direct bond when n = 2.
[0025]
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[0026]
In the formula, A is a group represented by the following formula (II) -a or a group represented by the following formula (II) -b; R ² and R ³ are the same or different and are monovalent hydrocarbon residues X ² is a tetravalent aromatic residue, which may further contain a heteroatom.
[0027]
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[0028]
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[0029]
In the general formula (I), X ¹ is a divalent aromatic residue in which two bonds from X ¹ represented by the formula (I) are in a 1-position or 2-position positional relationship; n is 1, 2 or 3; R ¹ is an n-valent hydrocarbon residue, which may further contain a heteroatom, or R ¹ is a direct bond when n = 2 it can.
[0030]
X ¹ preferably includes, for example, 1,2-phenylene, 1,2-naphthylene, 2,3-naphthylene, and a group represented by the following formula (a) or (b). Of these, 1,2-phenylene is particularly preferred. Note in the formula (a) or (b), R is -O -, - CO -, - S -, - SO 2 -, - CH 2 -, - (CH 2) - or -C _{(CH 3) 2} - It is.
[0031]
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[0032]
Examples of the aromatic residue exemplified for X ¹ include alkyl having 1 to 10 carbons such as methyl, ethyl, propyl, hexyl, and decyl; aryl having 6 to 12 carbons such as phenyl and naphthyl; C8 to C20 aralkyl such as phenylethyl; C1 to C10 alkoxy such as methoxy, ethoxy, decyloxy and the like; nitro; Halogen such as chlorine, bromine and the like; For example, acetyl, proponyl, zenzoyl, decanoyl and the like.
[0033]
R ¹ can be an n-valent (where n is 1, 2 or 3) hydrocarbon residue, or can be a direct bond only when n is 2.
[0034]
Examples of the monovalent hydrocarbon residue (when n = 1) include, for example, an unsubstituted aliphatic group having 1 to 10 carbon atoms, an unsubstituted aromatic group having 6 to 12 carbon atoms, and 5 to 5 carbon atoms. And 12 unsubstituted alicyclic groups.
[0035]
Examples of the unsubstituted aliphatic group having 1 to 10 carbon atoms include methyl, ethyl, propyl, hexyl, and decyl, and examples of the unsubstituted aromatic group having 6 to 12 carbon atoms include phenyl, naphthyl, and biphenyl; Examples of the unsubstituted alicyclic group having 5 to 12 carbon atoms include cyclopentyl and cyclohexyl.
[0036]
Secondly, examples of the monovalent hydrocarbon residue include a substituted aliphatic residue or an aromatic residue represented by the following formulas (c) to (f). . In these formulas, R ⁴ is alkylene, phenylene or naphthylene having 2 to 10 carbon atoms. R ⁵ is an alkyl group having 1 to 10 carbon atoms, a phenyl group or a naphthyl group. R ⁶ is either a hydrogen atom or a group defined as R ⁵ . R ⁷ is either a hydrogen atom or a group defined as R ⁵ .
[0037]
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[0038]
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[0039]
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[0040]
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[0041]
Moreover, as the monovalent hydrocarbon residue, third, substituted by the same substituents as the aromatic residue of the unsubstituted, for example, exemplified as the substituent of the aromatic residues representing the X ¹ Can be mentioned. Therefore, examples of substitution with such a substituent include, for example, tolyl, methylnaphthyl, nitrophenyl, nitronaphthyl, chlorophenyl, benzoylphenyl, acetylphenyl or acetylnaphthyl.
[0042]
As the monovalent hydrocarbon residue, a group represented by the above formula (c), (d), (e) or (f), that is, a substituted aliphatic residue or an aromatic residue, Preferred are aromatic residues.
[0043]
Examples of the divalent hydrocarbon residue (when n = 2) include, for example, a divalent unsubstituted aliphatic residue having 2 to 10 carbon atoms and an unsubstituted aromatic residue having 6 to 12 carbon atoms. And an unsubstituted alicyclic group having 5 to 12 carbon atoms.
[0044]
Examples of the divalent unsubstituted aliphatic group having 2 to 10 carbon atoms include, for example, ethylene, trimethylene, tetramethylene, decamethylene and the like. Examples of the unsubstituted aromatic residue having 2 to 12 carbon atoms include, for example, Phenylene, naphthylene, P, P'-biphenylene and the like; Examples of the divalent unsubstituted alicyclic group having 5 to 12 carbon atoms include cyclopentylene and cyclohexylene.
[0045]
Secondly, the divalent hydrocarbon residue is, for example, a group represented by the following formula (g) or a substituted aliphatic residue or aromatic residue represented by the following formula (h). Groups can be mentioned. Wherein R ⁸ is any of the groups defined for R ⁴ . R ⁹ is any of the groups defined for R ⁴ , and R ¹⁰ is any of the groups defined for R ⁶ .
[0046]
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[0047]
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[0048]
Further, as the divalent hydrocarbon residue, third, divalent aromatic residues of the non-substituted, for example by the same substituents as exemplified as the substituent for the aromatic group representing the X ¹ Substituted ones can be mentioned.
[0049]
When n is 2, R ¹ is preferably a direct bond or an unsubstituted or substituted divalent aromatic hydrocarbon residue of the above-mentioned first to third groups. Unsubstituted or substituted aromatic hydrocarbon residues of the first or third group in which the bond comes from the furthest position are preferred, especially P-phenylene, P, P'-biphenylene or 2,6 -Naphthylene is preferred.
[0050]
Examples of the trivalent hydrocarbon residue (when n = 3) include a trivalent aromatic residue having 6 to 12 carbon atoms.
[0051]
Examples of such an aromatic residue include the following four types of groups. Such aromatic residues may be substituted with the same substituents as those exemplified above as the substituent for the monovalent aromatic residue.
[0052]
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[0053]
In the general formula (I), R ² and R ³ are the same or different and are monovalent hydrocarbon residues, and X ² is a tetravalent aromatic hydrocarbon residue.
[0054]
As R ² and R ³ , the same groups as those exemplified for R ¹ when n = 1 in the description of the above formula (I) can be mentioned as examples.
[0055]
Examples of the tetravalent aromatic hydrocarbon residue include the following eight types of groups. Here, the definition of R is the same as that of the above-mentioned general formula (a).
[0056]
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[0057]
The tetravalent aromatic residue may be substituted with the same substituent as that exemplified for the monovalent aromatic residue represented by R ¹ in the description of the formula (I).
[0058]
Specific examples of the cyclic imino esters represented by the above formulas (I) and (II) used in the present invention include, for example, the following compounds.
[0059]
Compound of the above formula (I) When n = 1, 2-methyl-3,1-benzoxazin-4-one, 2-butyl-3,1-benzoxazin-4-one, 2-phenyl-3,1- Benzoxazin-4-one, 2- (1- or 2-naphthyl) -3,1-benzoxazin-4-one, 2- (4-biphenyl) -3,1-benzoxazin-4-one, 2- p-nitrophenyl-3,1-benzoxazin-4-one, 2-m-nitrophenyl-3,1-benzoxazin-4-one, 2-p-benzoylphenyl-3,1-benzoxazin-4- On, 2-p-methoxyphenyl-3,1-benzoxazin-4-one, 2-o-methoxyphenyl-3,1-benzoxazin-4-one, 2-cyclohexyl-3,1-benzoxazine-4 -E 2-p- (or m-) phthalimidophenyl-3,1-benzoxazin-4-one, N-phenyl-4- (3,1-benzoxazin-4-one-2-yl) phthalimide, N -Benzoyl-4- (3,1-benzoxazin-4-one-2-yl) aniline, N-benzoyl-N-methyl-4- (3,1-benzoxazin-4-one-2-yl) aniline , 2- (p- (N-methylcarbonyl) phenyl) -3,1-benzoxazin-4-one.
[0060]
When the compound of the formula (I) is n = 2, 2,2′-bis (3,1-benzoxazin-4-one) and 2,2′-ethylenebis (3,1-benzoxazin-4-one) 2,2′-tetramethylenebis (3,1-benzoxazin-4-one), 2,2′-decamethylenebis (3,1-benzoxazin-4-one), 2,2′-p- Phenylenebis (3,1-benzoxazin-4-one), 2,2′-m-phenylenebis (3,1-benzoxazin-4-one), 2,2 ′-(4,4′-diphenylene) Bis (3,1-benzoxazin-4-one), 2,2 ′-(2,6- or 1,5-naphthylene) bis (3,1-benzoxazin-4-one), 2,2′- (2-methyl-p-phenylene) bis (3,1-benzoxazin-4-one), 2,2 ′ (2-nitro-p-phenylene) bis (3,1-benzoxazin-4-one), 2,2 ′-(2-chloro-p-phenylene) bis (3,1-benzoxazin-4-one) 2,2 ′-(1,4-cyclohexylene) bis (3,1-benzoxazin-4-one), Np- (3,1-benzoxazin-4-one-2-yl) phenyl, 4- (3,1-benzoxazin-4-one-2-yl) phthalimide, Np- (3,1-benzoxazin-4-one-2-yl) benzoyl, 4- (3,1-benzo Oxazin-4-one-2-yl) aniline.
[0061]
When the compound of the formula (I) is n = 3, 1,3,5-tri (3,1-benzoxazin-4-one-2-yl) benzene, 1,3,5-tri (3,1-benzo) Oxazin-4-one-2-yl) naphthalene, 2,4,6-tri (3,1-benzoxazin-4-one-2-yl) naphthalene.
[0062]
Compound of the above formula (II) 2,8-dimethyl-4H, 6H-benzo (1,2-d; 5,4-d ') bis (1,3) -oxazine-4,6-dione, 2,7 -Dimethyl-4H, 9H-benzo (1,2-d; 4,5-d ') bis (1,3) -oxazine-4,9-dione, 2,8-diphenyl-4H, 8H-benzo (1 , 2-d; 5,4-d ') bis (1,3) -oxazine-4,6-dione, 2,7-diphenyl-4H, 9H-benzo (1,2-d; 4,5-d ') Bis (1,3) -oxazine-4,6-dione, 6,6'-bis (2-methyl-4H, 3,1-benzoxazin-4-one), 6,6'-bis (2 -Ethyl-4H, 3,1-benzoxazin-4-one), 6,6′-bis (2-phenyl-4H, 3,1-benzoxazin-4-one), 6,6′-methylenebis (2-methyl-4H, 3,1-benzoxazin-4-one), 6,6′-methylenebis (2-phenyl-4H, 3,1-benzoxazin-4-one), 6,6′-ethylenebis (2-methyl-4H, 3,1-benzoxazin-4-one), 6,6′-ethylenebis (2-phenyl-4H, 3,1-benzoxazin-4-one) ), 6,6′-butylenebis (2-methyl-4H, 3,1-benzoxazin-4-one), 6,6′-butylenebis (2-phenyl-4H, 3,1-benzoxazin-4-one) ), 6,6′-oxybis (2-methyl-4H, 3,1-benzoxazin-4-one), 6,6′-oxybis (2-phenyl-4H, 3,1-benzoxazin-4-one) ), 6,6'-sulfonylbis (2-methyl -4H, 3,1-benzoxazin-4-one), 6,6'-sulfonylbis (2-phenyl-4H, 3,1-benzoxazin-4-one), 6,6'-carbonylbis (2 -Methyl-4H, 3,1-benzoxazin-4-one), 6,6′-carbonylbis (2-phenyl-4H, 3,1-benzoxazin-4-one), 7,7′-methylenebis ( 2-methyl-4H, 3,1-benzoxazin-4-one), 7,7′-methylenebis (2-phenyl-4H, 3,1-benzoxazin-4-one), 7,7′-bis ( 2-methyl-4H, 3,1-benzoxazin-4-one), 7,7′-ethylenebis (2-methyl-4H, 3,1-benzoxazin-4-one), 7,7′-oxybis (2-methyl-4H, 3,1-benzoxazine- 4-one), 7,7′-sulfonylbis (2-methyl-4H, 3,1-benzoxazin-4-one), 7,7′-carbonylbis (2-methyl-4H, 3,1-benzo) Oxazin-4-one), 6,7′-bis (2-methyl-4H, 3,1-benzoxazin-4-one), 6,7′-bis (2-phenyl-4H, 3,1-benzo) Oxazin-4-one), 6,7′-methylenebis (2-methyl-4H, 3,1-benzoxazin-4-one), 6,7′-methylenebis (2-phenyl-4H, 3,1-benzo) Oxazin-4-one).
[0063]
Among the above exemplified compounds, the compound of the above formula (I), more preferably the compound of the above formula (I) when n = 2, particularly preferably the compound of the following formula (I) -1 is advantageously used. . In the formula, R ¹¹ is a divalent aromatic hydrocarbon residue.
[0064]
Embedded image

[0065]
Compounds of the formula (I) -1 include, among others, 2,2′-p-phenylenebis (3,1-benzoxazin-4-one), 2,2 ′-(4,4′-diphenylene) bis ( 3,1-benzoxazin-4-one) and 2,2 ′-(2,6-naphthylene) bis (3,1-benzoxazin-4-one) are preferred.
[0066]
The UV-absorbing properties of these cyclic imino esters are described in, for example, JP-A-59-12952 for typical compounds thereof, which are incorporated herein by reference.
[0067]
The cyclic imino ester has excellent compatibility with the polyester, but reacts with the terminal hydroxyl group of the polyester as described in JP-A-59-12952 and US Pat. No. 4,291,152. Have the ability. Therefore, it is required to carefully mix the cyclic imino ester and the polyester so that the cyclic imino ester is contained in a substantially unreacted state. However, when a polyester having a major proportion of a terminal group having a carboxyl group or a polyester having a terminal hydroxyl group blocked with a terminal blocking agent having no reactivity with the cyclic imino ester is used as the polyester, the cyclic imino ester is unreacted. No special precautions need to be taken in preparing the compositions to be contained as-is. In the case of using a polyester in which the main proportion of the terminal group is a hydroxyl group, the melt mixing time should be completed in a short time so as to satisfy the following two formulas (4) and (5). Is desirable.
[0068]
[Equation 3]
Logt ≦ −0.008T + 4.8 (4)
Tm <T <320 (5)
In the formulas (4) and (5), t is the melt mixing time (second), T is the melt mixing temperature (° C.), and Tm is the polyester melting temperature (° C.).
[0069]
In this case, there is a possibility that the cyclic imino ester and the polyester react at a small ratio, but the molecular weight of the polyester is increased by this reaction, and depending on this ratio, the molecular weight reduction due to the deterioration of the polyester by the visible light absorber is prevented. It is possible. When the cyclic imino ester reacts with the polyester, the ultraviolet absorption wavelength region generally shows a tendency to shift to a lower wavelength side than the unreacted ultraviolet absorption wavelength region, and therefore tends to transmit the higher wavelength ultraviolet light. With.
[0070]
When the cyclic imino ester is added in an appropriate amount, there is almost no sublimation, so that the periphery of the die is hardly stained during film formation, and the film absorbs light of about 370 nm from ultraviolet light, so that the film is not colored, and a visible light absorbing agent is used. And excellent properties to prevent film deterioration.
[0071]
The ultraviolet absorber needs to be added to the laminated film so as to simultaneously satisfy the following formulas (1) to (3).
[0072]
(Equation 4)
0.1 ≦ CA ≦ 5.0 (1)
0.1 ≦ CB ≦ 5.0 (2)
0.2 ≦ CA / CB ≦ 5 (3)
(In the above formulas (1) to (3), CA is the concentration of the ultraviolet absorber in the intermediate layer (when there are a plurality of intermediate layers, the average value of each layer excluding the outermost layers on both sides; weight%), CB is the outermost layer The concentration of the ultraviolet absorbent in the middle (when the concentration of the ultraviolet absorbent in the outermost layer is different, the concentration of the ultraviolet absorbent in the outermost layer having the higher concentration; wt%) is shown.
[0073]
More preferred ranges are 0.2 ≦ CA ≦ 3.0, 0.2 ≦ CB ≦ 3.0, and 0.3 ≦ CA / CB ≦ 3. If either CA or CB is less than 0.1% by weight, the weather resistance is inferior, and if it exceeds 5% by weight, the added ultraviolet absorbent bleeds out on the film surface (bleed out) and the phenomenon of sublimation. This is not preferable because the film is easily contaminated and the film forming machine is apt to be contaminated by this, and the exudate on the surface of the film adversely affects the processing step. If CA / CB is less than 0.2, a bleed-out phenomenon occurs or the ultraviolet absorption performance is poor. On the other hand, if CA / CB is more than 5, the outermost layer tends to deteriorate, which is not preferable.
[0074]
The method of adding the ultraviolet absorber to the polyester is not particularly limited, and examples thereof include a polyester polymerization step, kneading into a polymer in a melting step before film formation, and impregnation into a biaxially stretched film. In particular, kneading into a polymer in a melting step before film formation is also preferable from the viewpoint of preventing a decrease in the degree of polyester polymerization. At that time, the kneading of the ultraviolet absorber can be performed by a direct addition method of the compound powder, a master batch method or the like.
[0075]
The light transmittance at 370 nm of the laminated polyester film in the present invention needs to be 3% or less, preferably 2% or less. If it exceeds 3%, the weather resistance to ultraviolet rays will be insufficient.
[0076]
<Coating layer>
The laminated polyester film of the present invention has a coating layer on at least one outermost layer of at least three polyester layers continuously formed by using a co-extrusion method in order to improve adhesion and blocking resistance. It can also be provided. The resin for forming the coating layer is not particularly limited, but it is preferable to use a copolymer polyester resin as a main component. Examples of the copolymerized polyester resin include, for example, terephthalic acid, isophthalic acid, phthalic acid, phthalic anhydride, 2,6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, adipic acid, sebacic acid, tribasic acid as a polybasic acid component. Examples include melitic acid, pyromellitic acid, dimer acid, 5-sodium sulfoisophthalic acid, and the polyol component is ethylene glycol, 1,4-butanediol, diethylene glycol, dipropylene glycol, 1,6-hexanediol. And 1,4-cyclohexanedimethanol, xylene glycol, dimethylolpropane, poly (ethylene oxide) glycol, poly (tetramethylene oxide) glycol and the like. Particularly, a polyester resin having a glass transition point in the range of 40 to 100 ° C is preferable. In addition, in order to improve the adhesiveness with the acrylic resin and improve the scratch resistance of the coating layer, an acrylic resin, an epoxy resin, a cross-linking agent, and the like, which are mainly composed of monomers such as alkyl acrylate and alkyl acrylate. May be contained.
[0077]
The coating layer of the present laminated polyester film may contain inert particles for imparting scratch resistance and handling property. The average particle size of the inert particles is in the range of 10 to 300 nm, and the content is preferably 0.1 to 20% by weight. When the average particle size is less than 10 nm or the content of the inert particles in the coating layer is less than 0.1% by weight, the film becomes difficult to slip and the scratch resistance and the handling property become insufficient. If the particle size of the inert particles exceeds 300 nm or the content exceeds 20% by weight, the inert particles are likely to fall off, and the transparency of the coating layer is impaired, making it difficult to use for display applications and the like. Such fillers are organic or inorganic fine particles, and examples thereof include calcium carbonate, calcium oxide, aluminum oxide, kaolin, silicon oxide, zinc oxide, crosslinked acrylic resin particles, crosslinked polystyrene resin particles, melamine resin particles, crosslinked silicone resin particles, and the like. You.
[0078]
The coating layer used in the present invention is preferably used in the form of a water-soluble, water-dispersible, or aqueous coating liquid such as an emulsion. In order to form a film, other resins and compounds other than the above-described composition, for example, an antistatic agent, a coloring agent, a surfactant, a wax, a crosslinking agent, and an ultraviolet absorber can be added as needed. .
[0079]
When the coating layer is provided in the laminated polyester film of the present invention, the surface roughness refers to the surface roughness of the outer surface provided with the coating layer.
[0080]
<Production method of laminated polyester film>
The laminated polyester film can be produced by a conventionally known sequential biaxial stretching method, simultaneous biaxial stretching method, inflation method and the like. In the sequential biaxial stretching method and the simultaneous biaxial stretching method, first, after sufficiently drying a polyester chip of a predetermined composition, using a plurality of extruders, a multi-layer multi-manifold die or a feed block, each polyester The film is laminated, a plurality of layers of a molten sheet are extruded from a die, and rapidly cooled and solidified on a casting drum set at about 20 to 40 ° C. in advance to obtain an unoriented film. The thickness of the obtained unstretched film is preferably 0.5 mm or more. The unstretched film is then stretched biaxially under generally well-known conditions. However, in order to keep the heat yield and the refractive index in the desired ranges, the unstretched film is stretched to 3.0 in the continuous film forming direction (longitudinal direction). It is preferable that the film be stretched to 4.5 times, 3.0 to 4.5 times in a direction (lateral direction) perpendicular thereto, and 9 to 20 times in area magnification. The stretching temperature is preferably from 90C to 140C. After the biaxial stretching, heat setting can be performed as necessary. The heat setting temperature is preferably from 180 to 250 ° C, more preferably from 210 to 240 ° C.
[0081]
The method of forming a coating layer on the laminated polyester film in the present invention is performed in a normal coating step, that is, in a step separated from the film production step on the biaxially stretched heat-set laminated polyester film, to remove refuse, dust, and the like. It is not preferable because it is easy to get involved. From such a viewpoint, application in a clean atmosphere, that is, application in a film manufacturing process is preferable. According to this coating, the adhesion of the coating film (coating film) to the laminated polyester film is improved.
[0082]
As a coating method, any known coating method can be applied. For example, a roll coating method, a gravure coating method, a roll brushing method, a spray coating method, an air knife coating method, an impregnation method, a curtain coating method and the like can be used alone or in combination. The coating amount film 1 m ² per the running, 0.5 to 20 g, more 1~10g is preferred. The aqueous liquid is preferably used as an aqueous dispersion or an emulsion. The thickness of the coating layer after drying and stretching is preferably 0.02 to 1 μm. The coating may be formed on only one side of the film or on both sides as necessary.
[0083]
Also, by controlling the thickness of each layer constituting the laminated polyester film and the state of addition of the inert particles as described above, the optical characteristics required for the laminated polyester film can be achieved.
[0084]
【Example】
Hereinafter, the present invention will be further described with reference to examples. In addition, each characteristic value was measured by the following method.
[0085]
(1) A sample film piece having an average particle diameter of a sample is fixed to a sample table for a scanning electron microscope, and a sputter device (trade name “JIS-1100 type ion sputter device” manufactured by JEOL Ltd.) is used. The film surface was subjected to ion etching treatment, observed at a magnification of 1 to 30,000 times with a high-resolution field emission scanning electron microscope, and the area equivalent particle size of 50 particles was determined by Luzex FS manufactured by Nireco Co., Ltd. The number average value was defined as the average particle size.
[0086]
(2) Refractive index Using a Abbe refractometer, the refractive index of the film was determined using sodium D line (589 nm) as a light source.
[0087]
(3) Surface roughness Ra
Using a three-dimensional roughness tester (trade name “SE-3CK” manufactured by Kosaka Laboratory), needle diameter 2 μmR, needle pressure 30 mg, measurement length 1 mm, sampling pitch 2 μm, cutoff 0.25 mm, vertical magnification The measurement is performed under the conditions of 20,000 times, a magnification of 200 in the horizontal direction, and 100 scanning lines, and Ra is measured. When a coating layer was provided on both sides, both sides were measured and the average value was obtained.
[0088]
(4) Total light transmittance and haze value The total light transmittance and haze value of the film were measured using a haze measuring device (trade name “NDH-2000” manufactured by Nippon Denshoku Industries Co., Ltd.). The haze value of the film was evaluated according to the following criteria.
：: Haze value ≦ 1.5%: very good haze of the film ○: 1.5% <haze value ≦ 3.0%: good haze of the film ×: 3.0% <haze value: poor haze of the film.
[0089]
(5) Using a 370 nm light transmittance double beam spectrophotometer (trade name “UV-3101PC” manufactured by Shimadzu Corporation) under the conditions of a slit width: 20 nm, a scan speed; a medium speed, a sampling pitch; The light transmittance in the wavelength range of 300 to 500 nm was continuously measured, and the light transmittance at the wavelength of 370 nm was detected and evaluated according to the following criteria.
：: less than 3% △: 3% or more and less than 5% X: 5% or more.
[0090]
(6) Lamination Thickness of Film A small piece of film was fixed and molded with epoxy resin, cut with a microtome, and a cross section of the film was photographed with a transmission electron microscope (trade name “JEM2010” manufactured by JEOL Ltd.). . Of the cross sections, two of them are almost parallel to the film surface, and the interface is observed by light and dark. The distance between the two interfaces and the film surface was measured from ten photographs, and the average value was defined as the lamination thickness.
[0091]
(7) Scratch resistance A free roll having a diameter of 100 mm and a rotation resistance of 1 kg and hard chrome plating (surface roughness: Ra 100 nm). The running conditions at this time were a running speed of 10 m / min, a winding angle of 90 °, and a running tension of 20 kg. The scratches entering the film surface due to this treatment were observed under a microscope after platinum deposition, and the number of scratches having a width of 2 μm or more and a length of 300 μm or more was counted per 0.4 m ² and evaluated according to the following criteria.
：: less than 10 △: 10 or more and less than 20 ×: 20 or more
[0092]
(8) Friction coefficient (μs)
The fixed glass plate is placed under the two superposed films, and the film on the lower side of the superposed film (the film in contact with the glass plate) is taken up by a low-speed roll (about 10 cm / min), A detector is fixed to one end of the upper film (the end opposite to the direction in which the lower film is pulled out), and the tensile force at the start between the films is detected. The thread used at that time has a weight of 1.5 kg and a lower area of 75 cm ² .
[0093]
The coefficient of friction (μs) is obtained from the following equation.
μs = tensile force (kg) at start / load 1 kg
The evaluation is performed according to the following criteria.
：: less than 0.4 Δ: 0.4 or more and less than 0.6 x: 0.6 or more
[0094]
(9) A hard coat agent (trade name “Seika Beam EXF01 (B)” manufactured by Dainichi Seika Co., Ltd.) is applied to the film-forming surface of the adhesive laminated polyester film using a # 8 wire bar, dried at 70 ° C. for 1 minute to remove the solvent. After the removal, a hard coat layer having a thickness of 5 μm was formed using a high-pressure mercury lamp under the conditions of 200 mJ / cm ² , irradiation distance of 15 cm, and running speed of 5 m / min. The adhesiveness of the obtained film was determined by a test method according to JIS-K5400, 8.5.1. Specifically, 100 square cuts that penetrate the coating layer and reach the base film were made using a cutter guide with a gap of 1 mm. Then, a cellophane adhesive tape (Nichiban No. 405; 24 mm width) was attached to the cut-shaped cut surface of the grid, rubbed with an eraser and completely adhered, and then rapidly peeled at a peel angle of 180 °. It was observed and evaluated according to the following criteria.
：: Peeled area is less than 30% Δ: Peeled area is 30% or more and less than 50% X: Peeled area exceeds 50%.
[0095]
(10) A hard coat layer having a thickness of 5 μm is formed on the laminated polyester film in the same manner as in the evaluation of weather resistance and adhesion. This sample was irradiated for 1000 hours (corresponding to one year of outdoor exposure) according to JIS-K-6783b using a sunshine weather meter (Suga Test Instruments Co., Ltd., WEL-SUN-HCL type). Conduct an outdoor exposure acceleration test. After the treatment, the haze value of the film was measured using a haze measuring device (NDH-2000) manufactured by Nippon Denshoku Industries Co., Ltd., and the difference before and after the treatment was determined.
：: less than 1.0% Δ: 1.0% or more, less than 2.0% ×: 2.0% or more
[0096]
[Example 1]
A polyethylene terephthalate chip A (intrinsic viscosity: 0.63) containing 1.0% by weight of the ultraviolet absorbent represented by the formula (A) was prepared. Further, 1.0% by weight of the ultraviolet absorbent represented by the formula (A) and 0.1% of porous silica having an average particle diameter of 1.5 μm (primary particle diameter 0.004 μm, pore volume 1.2 ml / g) were added. A polyethylene terephthalate chip B (intrinsic viscosity: 0.62) containing 01% by weight was also prepared. Each was dried at 160 ° C. for 3 hours.
[0097]
Embedded image

[0098]
Further, a coating agent composed of 85 parts by weight of polyester, 5 parts by weight of filler, and 10 parts by weight of wetting agent was prepared. The polyester used here for the coating agent had an acid component of 65 mol% of 2,6-naphthalenedicarboxylic acid / 30 mol% of isophthalic acid / 5 mol% of 5-sodium sulfoisophthalic acid, and a glycol component of 90 mol% of ethylene glycol / It is composed of 10 mol% of diethylene glycol (Tg = 80 ° C.). The filler is a crosslinked acrylic filler (60 nm). The wetting agent is polyoxyethylene (n = 7) lauryl ether.
[0099]
Then, the two types of chips described above are supplied to separate extruders, melt-extruded at 290 ° C., and a layer obtained from the polyethylene terephthalate chip B is formed as an inner layer using a multi-manifold die, and a layer obtained from the polyethylene terephthalate chip B is formed. The surface layer was laminated in three layers, and quenched and solidified on a cooling drum maintained at 20 ° C. to obtain an unstretched film. Subsequently, the unstretched film is stretched 3.2 times in the longitudinal direction at 95 ° C., and then the above-mentioned coating composition is applied to both sides so that the thickness after drying becomes 0.04 μm, and further at 110 ° C. The film was stretched 3.6 times in the transverse direction, heat-set at 230 ° C. for 5 seconds, and further relaxed by 0.5% in the width direction at a temperature of 190 ° C. to obtain a laminated polyester film having a thickness of 100 μm. The thickness of the surface layer B was 5 μm, and the thickness of the inner layer was 90 μm. Table 1 shows the properties of the obtained film.
[0100]
[Examples 2, 3 and Comparative Example 1]
A laminated polyester film was obtained in the same manner as in Example 1, except that the ultraviolet absorber contained in the polyethylene terephthalate chips A and B was changed as described below. In Example 2, the polyethylene terephthalate chips A and B each contained 1.0% by weight of an ultraviolet absorber represented by the following formula (B). In Example 3, the polyethylene terephthalate chip A contained 1.2% by weight of the ultraviolet absorber of the following formula (C), and the polyethylene terephthalate chip B contained 0.4% by weight. In Comparative Example 1, neither the polyethylene terephthalate chips A nor B contained an ultraviolet absorbent. Table 1 shows the properties of the obtained film.
[0101]
Embedded image

[0102]
Embedded image

[0103]
[Example 8 and Comparative Examples 6, 7]
A laminated polyester film was obtained in the same manner as in Example 1, except that the content of the ultraviolet absorber contained in the polyethylene terephthalate chips A and B was changed as follows. In Example 8, the polyethylene terephthalate chip A contained 0.5% by weight and the polyethylene terephthalate chip B contained 1.5% by weight. In Comparative Example 6, the polyethylene terephthalate chip A contained 1.1% by weight and the polyethylene terephthalate chip B contained the same. In Comparative Example 7, the polyethylene terephthalate chip A contained 0.5% by weight and the polyethylene terephthalate chip B contained 3.0% by weight. Table 1 shows the properties of the obtained film.
[0104]
[Example 4]
A laminated polyester film was obtained in the same manner as in Example 1 except that the film thickness was 188 μm, of which the outer layer thickness was 10 μm and the inner layer thickness was 168 μm. Table 1 shows the properties of the obtained film.
[0105]
[Example 5]
A laminated polyester film was obtained in the same manner as in Example 1, except that the thickness of the outer layer was 12 μm and the thickness of the inner layer was 76 μm. Table 1 shows the properties of the obtained film.
[0106]
[Example 6]
A laminated polyester film was obtained in the same manner as in Example 1, except that the content of the porous silica contained in the polyethylene terephthalate chip B was changed to 0.04% by weight. Table 1 shows the properties of the obtained film.
[0107]
[Example 7]
A laminated polyester film was obtained in the same manner as in Example 1, except that the same kind of porous silica as that contained in the polyethylene terephthalate chip B was also contained in the polyethylene terephthalate chip A at 0.003% by weight. Table 1 shows the properties of the obtained film.
[0108]
[Comparative Example 2]
To the polyethylene terephthalate chip A, a laminated polyester film was obtained in the same manner as in Example 1 except that 0.1% by weight of spherical silica having an average particle size of 0.12 μm was added in addition to the ultraviolet absorber. Table 1 shows the properties of the obtained film.
[0109]
[Comparative Example 3]
A laminated polyester film was obtained in the same manner as in Example 1 except that the content of the porous silica contained in the polyethylene terephthalate chip B was changed to 0.08% by weight, the thickness of the outer layer was changed to 20 μm, and the thickness of the inner layer was changed to 60 μm. . Table 1 shows the properties of the obtained film.
[0110]
[Comparative Example 4]
A laminated polyester film was obtained in the same manner as in Example 1 except that the stretching ratio in the longitudinal direction was 3.7 times, the stretching ratio in the transverse direction was 3.9 times, and the heat setting temperature was 205 ° C. Table 1 shows the properties of the obtained film.
[0111]
[Comparative Example 5]
1.0% by weight of the same ultraviolet absorber as in Example 1 and 0.003% by weight of porous silica having an average particle size of 1.5 μm (primary particle diameter 0.004 μm, pore volume 1.2 ml / g) A prepared polyethylene terephthalate chip (intrinsic viscosity: 0.63) was prepared. After drying at 160 ° C. for 3 hours, this was supplied to an extruder and melt-extruded at 290 ° C., and the other steps were the same as in Example 1 to obtain a single-layer polyester film. Table 1 shows the properties of the obtained film.
[0112]
[Table 1]

[0113]
【The invention's effect】
As is clear from the results shown in Table 1, the laminated polyester film of the present invention is excellent in weather resistance, excellent in processability, adhesion, and scratch resistance, and is useful as a laminated polyester film.

Claims (10)

In a laminated polyester film including three or more polyester layers continuously formed by a co-extrusion method, the light transmittance at a wavelength of 370 nm is 3% or less, the haze is 3% or less, and the refractive index in the thickness direction is 1 or less. A laminated polyester film having a thickness of from 490 to 1.505, a surface roughness Ra of from 3 nm to 30 nm, and an ultraviolet absorber concentration in the layer satisfying the following formulas (1) to (3).

(In the above formulas (1) to (3), CA is the concentration of the ultraviolet absorber in the intermediate layer (when there are a plurality of intermediate layers, the average value of each layer excluding the outermost layers on both sides; weight%), CB is the outermost layer The concentration of the ultraviolet absorbent in the middle (when the concentration of the ultraviolet absorbent in the outermost layer is different, the concentration of the ultraviolet absorbent in the outermost layer having the higher concentration; wt%) is shown. 2. The laminated polyester film according to claim 1, wherein the heat shrinkage at 150 ° C. is 2% or less in both the continuous film forming direction and the direction perpendicular to the continuous film forming direction. The laminated polyester film according to any one of claims 1 to 2, having a total light transmittance of 80% or more. The laminated polyester film according to any one of claims 1 to 3, wherein a refractive index in a thickness direction is from 1.493 to 1.502. The refractive index in the continuous film forming direction is 1.620 or more and 1.680 or less, and the refractive index in the direction perpendicular to the continuous film forming direction is 1.640 or more and 1.700 or less. Laminated polyester film. The laminated polyester film according to any one of claims 1 to 5, wherein a coating layer is provided on at least one outermost layer of three or more polyester layers continuously formed by a coextrusion method. The laminated polyester film according to claim 6, wherein the coating layer contains inert particles having an average particle size of 10 nm or more and 300 nm or less. The laminated polyester film according to any one of claims 1 to 7, wherein the polyester layer is mainly composed of polyethylene terephthalate or polyethylene-2,6-naphthalate. The laminated polyester film according to any one of claims 1 to 8, wherein the ultraviolet absorbent is at least one compound selected from cyclic imino esters represented by the following formula (I) or (II).

(Where X ¹ is a divalent aromatic residue in which the two bonds from X ¹ represented by the above formula have a 1-position or 2-position relationship; n is 1, 2 or 3; R ¹ is an n-valent hydrocarbon residue, which may further contain a heteroatom, or R ¹ can be a direct bond when n = 2.)

(Where A is a group represented by the following formula (II) -a or a group represented by the following formula (II) -b; R ² and R ³ are the same or different and are monovalent hydrocarbon residues) X ² is a tetravalent aromatic residue, which may further contain a heteroatom.)

The laminated polyester film according to any one of claims 1 to 9, which is used for optics.