JP4289586B2 - Solution casting die and solution casting method - Google Patents

Description

【００５７】
２４時間経過しても皮張りは発生しなかった。支持体上の剥ぎ残り汚れは、ほとんどなかった。
【００５８】
［実施例２］
下記の条件にて、共流延した。リップ端部への溶剤滴下条件は下記の通りである。

【００５９】
２４時間経過しても皮張りは発生しなかった。支持体上の剥ぎ残り汚れは、ほとんどなかった。
【００６０】
［実施例３］
下記のドープ処方にて、単層流延した。リップ端部への溶剤滴下条件は下記の通りである。
セルローストリアセテート １００重量部
トリフェニルフォスフェート １０重量部
ビフェニルジフェニルフォスフェート ５重量部
酢酸メチル ３１５重量部
エタノール ６０重量部
ｎ−ブタノール １０重量部
【００６１】
溶媒にてセルローストリアセテートを３０分間膨潤させ、セルローストリアセテート溶液をスクリュー押出し機で送液して、−７０℃で３分間維持されるように冷却部分を通過させた。冷却は冷凍機で冷却した−８０℃の冷媒（３Ｍ社製Ｎｏｖａｃ ＦＣ−７７、あるいはＨＦＥ−７１００）を用いて実施した。そして、冷却により得られた溶液はステンレス製の容器に移送し、５０℃で２時間攪拌した。そして、絶対濾過精度０．０１ｍｍの濾紙（東洋濾紙（株）製、＃６３）で濾過した。
【００６２】
１）滴下流量を０．２ｍｌ／分
２）滴下ノズル内径がφ０．１ｍｍ、滴下ノズル外径がφ０．３ｍｍ、滴下ノズルの吐出流速を４２．５ｃｍ／秒
３）溶剤の粘度が０．３６ｃｐ
４）溶剤の表面張力が、２５ｄｙｎ／ｃｍ
５）溶剤と滴下ノズル先端およびダイリップ先端との接触角が３０度
６）吐出ドープ端部と滴下ノズル先端との距離が１．０ｍｍ
７）滴下する位置はリップ先端ドープ端部より幅方向水平方向の位置
８）溶剤組成 酢酸メチル １００重量％
９）ノズル材質はＳＵＳ３１６
【００６３】
２４時間経過しても皮張りは発生しなかった。支持体上の剥ぎ残り汚れは、ほとんどなかった。
【００６４】
［比較例１］
下記の条件にて、単層流延した。リップ端部への溶剤滴下条件は下記の通りである。

【００６５】
２４時間経過しても皮張りは発生しなかった。支持体上の剥ぎ残り汚れは多かった。
【００６６】
［比較例２］
比較例１の条件に対して、リップ端部への溶剤滴下条件を滴下流量０．６ｍｌ／分とし、流延した。その結果、１０時間後に皮張りが発生し、流延続行不能となった。
【００６７】
［実施例４］
実施例３のドープ処方に、さらに下記処方のドープを副流として用い、共流延を行った。

送る溶剤の組成は、酢酸メチル９０重量部、アセトン１０重量部である。
結果は、２４時間経過しても皮張りは発生しなかった。支持体上の剥ぎ残り汚れもほとんどなかった。
【００６８】
［実施例５］
実施例１の条件にて、図２に示す流延ダイを用いて、溶剤の流量変動率を１Ｈｚの周期で、±５０％以内に制御した。これにより、製膜中に流延ダイから吐出された流延膜の端部の乱れが抑制され、流延を続行することが可能であった。
【００６９】
［実施例６］
実施例１の条件にて、図２に示す流延ダイを用いて、溶剤の流量変動率を１Ｈｚの周期で、±１０％以内に制御した。これにより、製膜中に流延ダイから吐出された流延膜の端部に乱れはなく、流延膜全体の厚み変動が生じなかった。また、乾燥後のフイルムには、厚みムラによる外観不良も生じなかった。
【００７０】
［比較例３］
実施例１の条件にて、図２に示す流延ダイを用いて、溶剤の流量変動率を１Ｈｚの周期で、±５５％以内に制御した。この場合には、製膜中に流延ダイから吐出された流延膜の端部が大きく乱れ、流延を続行することが不可能になった。
【００７１】
さらに、上記の方法により流延製膜した実施例３及び実施例４のフイルムを使って、塗工による反射防止膜を下記の手順により作製した。
【００７２】
（防眩層用塗布液Ａの調製）
ジペンタエリスリトールペンタアクリレートとジペンタエリスリトールヘキサアクリレートの混合物（ＤＰＨＡ、日本化薬（株）製）１２５ｇ、ビス（４−メタクリロイルチオフェニル）スルフィド（ＭＰＳＭＡ、住友精化（株）製）１２５ｇを、４３９ｇのメチルエチルケトン／シクロヘキサノン＝５０／５０重量％の混合溶媒に溶解した。得られた溶液に、光重合開始剤（イルガキュア９０７、チバガイギー社製）５．０ｇおよび光増感剤（カヤキュアーＤＥＴＸ、日本化薬（株）製）３．０ｇを４９ｇのメチルエチルケトンに溶解した溶液を加えた。この溶液を塗布、紫外線硬化して得られた塗膜の屈折率は１．６０であった。さらにこの溶液に平均粒径２μｍの架橋ポリスチレン粒子（商品名：ＳＸ−２００Ｈ、綜研化学（株）製）１０ｇを添加して、高速ディスパにて５０００ｒｐｍで１時間攪拌、分散した後、孔径３０μｍのポリプロピレン製フィルターでろ過して防眩層の塗布液Ａを調製した。
【００７３】
（防眩層用塗布液Ｂの調製）
シクロヘキサノン１０４．１ｇ、メチルエチルケトン６１．３ｇの混合溶媒に、エアディスパで攪拌しながら酸化ジルコニウム分散物含有ハードコート塗布液（デソライトＫＺ−７８８６Ａ、ＪＳＲ（株）製）２１７．０ｇ、を添加した。この溶液を塗布、紫外線硬化して得られた塗膜の屈折率は１．６１であった。さらにこの溶液に平均粒径２μｍの架橋ポリスチレン粒子（商品名：ＳＸ−２００Ｈ、綜研化学（株）製）５ｇを添加して、高速ディスパにて５０００ｒｐｍで１時間攪拌、分散した後、孔径３０μｍのポリプロピレン製フィルターでろ過して防眩層の塗布液Ｂを調製した。
【００７４】
（防眩層用塗布液Ｃの調製）
ジペンタエリスリトールペンタアクリレートとジペンタエリスリトールヘキサアクリレートの混合物（ＤＰＨＡ、日本化薬（株）製）９１ｇ、酸化ジルコニウム分散物含有ハードコート塗布液（デソライトＫＺ−７１１５、ＪＳＲ（株）製）１９９ｇ、および酸化ジルコニウム分散物含有ハードコート塗布液（デソライトＫＺ−７１６１、ＪＳＲ（株）製）１９ｇを、５２ｇのメチルエチルケトン／シクロヘキサノン＝５４／４６重量％の混合溶媒に溶解した。得られた溶液に、光重合開始剤（イルガキュア９０７、チバガイギー社製）１０ｇを加えた。この溶液を塗布、紫外線硬化して得られた塗膜の屈折率は１．６１であった。さらにこの溶液に平均粒径２μｍの架橋ポリスチレン粒子（商品名：ＳＸ−２００Ｈ、綜研化学（株）製）２０ｇを８０ｇのメチルエチルケトン／シクロヘキサノン＝５４／４６重量％の混合溶媒に高速ディスパにて５０００ｒｐｍで１時間攪拌分散した分散液２９ｇを添加、攪拌した後、孔径３０μｍのポリプロピレン製フィルターでろ過して防眩層の塗布液Ｃを調製した。
【００７５】
（ハードコート層用塗布液Ｄの調製）
紫外線硬化性ハードコート組成物（デソライトＫＺ−７６８９、７２重量％、ＪＳＲ（株）製）２５０ｇを６２ｇのメチルエチルケトンおよび８８ｇのシクロヘキサノンに溶解した溶液を加えた。この溶液を塗布、紫外線硬化して得られた塗膜の屈折率は１．５３であった。さらにこの溶液を孔径３０μｍのポリプロピレン製フィルターでろ過してハードコート層の塗布液Ｄを調製した。
【００７６】
（低屈折率層用塗布液の調製）
屈折率１．４２の熱架橋性含フッ素ポリマー（ＴＮ−０４９、ＪＳＲ（株）製）２００９３ｇにＭＥＫ−ＳＴ（平均粒径１０〜２０ｎｍ、固形分濃度３０重量％のＳｉＯ２ゾルのＭＥＫ分散物、日産化学（株）製）８ｇ、およびメチルエチルケトン１００ｇを添加、攪拌の後、孔径１μｍのポリプロピレン製フィルターでろ過して、低屈折率層用塗布液を調製した。
【００７７】
実施例３で作製した８０μｍの厚さのトリアセチルセルロースフイルム、上記のハードコート層用塗布液Ｄをバーコーターにて塗布し、１２０℃で乾燥の後、１６０Ｗ／ｃｍの空冷メタルハライドランプ（アイグラフィックス（株）製）を用いて、照度４００ｍＷ／ｃｍ² 、照射量３００ｍＪ／ｃｍ² の紫外線を照射して塗布層を硬化させ、厚さ２．５μｍのハードコート層を形成した。その上に、上記防眩層用塗布液Ａをバーコーターにて塗布し、上記ハードコート層と同条件にて乾燥、紫外線硬化して、厚さ約１．５μｍの防眩層を形成した。その上に、上記低屈折率層用塗布液をバーコーターにて塗布し、８０℃で乾燥の後、さらに１２０℃で１０分間熱架橋し、厚さ０．０９６μｍの低屈折率層を形成した。
【００７８】
次に実施例３のフイルムを用いて、防眩層用塗布液Ａを防眩層用塗布液Ｂに代え、その他の条件は同じにした反射防止膜を作成した。さらに、防眩層用塗布液Ａを防眩層用塗布液Ｃに代え、その他の条件は同じにした反射防止膜も作成した。
【００７９】
さらに、実施例４のフイルムからも、防眩層用塗布液Ａ，Ｂ，Ｃを１つずつ用いて前述した反射防止膜を作成条件は同じで作成した。
【００８０】
［反射防止膜の評価］
前述した作成方法で、実施例３のフイルム（防眩層Ａ，Ｂ，Ｃ）及び実施例４のフイルム（防眩層Ａ，Ｂ，Ｃ）から形成された６種類の反射防止膜について以下の項目の評価を行った。以下の評価方法から得られた結果については後に表１にまとめて示す。
【００８１】
（反射防止膜の評価）
得られたフイルムについて、以下の項目の評価を行った。
【００８２】
（１）鏡面反射率及び色味
分光光度計Ｖ−５５０（日本分光（株）製）にアダプターＡＲＶ−４７４を装着して、３８０〜７８０ｎｍの波長領域において、入射角５°における出射角−５度の鏡面反射率を測定し、４５０〜６５０ｎｍの平均反射率を算出し、反射防止性を評価した。さらに、測定された反射スペクトルから、ＣＩＥ標準光源Ｄ６５の５度入射光に対する正反射光の色味を表わすＣＩＥ１９７６Ｌ＊ａ＊ｂ＊色空間のＬ＊値、ａ＊値、ｂ＊値を算出し、反射光の色味を評価した。
【００８３】
（２） 積分反射率
分光光度計Ｖ−５５０（日本分光（株）製）にアダプターＩＬＶ−４７１を装着して、３８０〜７８０ｎｍの波長領域において、入射角５°における積分反射率を測定し、４５０〜６５０ｎｍの平均反射率を算出した。
【００８４】
（３）ヘイズ
得られたフイルムのヘイズをヘイズメーターＭＯＤＥＬ １００１ＤＰ（日本電色工業（株）製）を用いて測定した。
【００８５】
（４）鉛筆硬度評価
耐傷性の指標としてＪＩＳ Ｋ ５４００に記載の鉛筆硬度評価を行った。反射防止膜を温度２５℃、湿度６０％ＲＨで２時間調湿した後、ＪＩＳ Ｓ ６００６に規定する３Ｈの試験用鉛筆を用いて、１ｋｇの荷重にて
ｎ＝５の評価において傷が全く認められない ：○
ｎ＝５の評価において傷が１または２つ ：△
ｎ＝５の評価において傷が３つ以上 ：×
【００８６】
（５）接触角測定
表面の耐汚染性の指標として、光学材料を温度２５℃、湿度６０％ＲＨで２時間調湿した後、水に対する接触角を測定し、指紋付着性の指標とした。
【００８７】
（６）動摩擦係数測定
表面滑り性の指標として動摩擦係数にて評価した。動摩擦係数は試料を２５℃、相対湿度６０％で２時間調湿した後、ＨＥＩＤＯＮ−１４動摩擦測定機により５ｍｍφステンレス鋼球、荷重１００ｇ、速度６０ｃｍ／ｍｉｎにて測定した値を用いた。
【００８８】
（７）防眩性評価
作成した防眩性フイルムにルーバーなしのむき出し蛍光灯（８０００ｃｄ／ｍ² ）を映し、その反射像のボケの程度を以下の基準で評価した。
蛍光灯の輪郭が全くわからない ：◎
蛍光灯の輪郭がわずかにわかる ：○
蛍光灯はぼけているが、輪郭は識別できる ：△
蛍光灯がほとんどぼけない ：×
【００８９】
（８）塗膜の面状評価
蛍光灯の反射光および透過光にて角度を変化させて検査し、フイルムの厚みムラに起因する塗膜表面の凹凸の強さを官能評価した。
凹凸がほとんどない ：◎
凹凸が弱く、少ない ：○
凹凸が弱いが多い ：△
凹凸の強いものがある ：×
【００９０】
【表１】

【００９１】
実施例３及び実施例４のフイルムから形成された反射防止膜は、いずれも防眩性、反射防止性に優れ、且つ色味が弱く、また、鉛筆硬度、指紋付着性、動摩擦係数のような膜物性を反映する評価の結果も良好であった。
【００９２】
次に、実施例４のフイルムを用いて防眩性反射防止偏光板を作成した。この偏光板を用いて反射防止層を最表層に配置した液晶表示装置を作成したところ、外光の映り込みがないために優れたコントラストが得られ、防眩性により反射像が目立たず優れた視認性を有し、指紋付も良好であった。
【００９３】
また、前述した実施例３と実施例４とにおいてドープ調製用の混合溶媒の組成比を変えている。実施例３で、酢酸メチルが８２重量％、ケトン類が０重量％、アルコール類（エタノール，ｎ−ブタノール）が１８重量％であった。また、実施例４では、酢酸メチル７５重量％、ケトン類（シクロペンタノン，アセトン）１５重量％、アルコール類（メタノール，エタノール）１０重量％であった。このように本発明において、酢酸メチル、ケトン類、アルコール類の混合比を変えた溶媒からもドープを調製することができる。
【００９４】
【発明の効果】
本発明の溶液製膜法により、ダイリップ端部の皮張りを防止するために溶剤を滴下しながら流下流延する溶液製膜方法について、リップ先端における濡れ広がりや、風などの外乱による液流路の乱れを発生させず、必要最小限の液量をリップ端部ドープに供給し、流延膜に悪影響を及ぼすことなく、支持体からの端部剥離点で乾燥不足により発生する剥ぎ残りを定期的に洗浄する必要がなく、生産能率を向上することができた。
【００９５】
本発明の溶液製膜方法は、前記溶剤の流量変動率が±５０％以内、より好ましくは±１０％以内にすることで、流延膜の振れや伸縮の発生を抑制でき、製膜したフイルムの厚みムラによる外観不良も抑制できる。
【００９６】
また、本発明では、酢酸メチル、ケトン類、アルコール類の混合溶媒により、セルロースアシレートを効率良く溶解できる。そのセルロースアシレート溶液には、各種の添加剤を添加することができ、その溶液から前記溶液製膜法により得られたフイルムは優れた光学的性質や物性を有する。
【００９７】
さらに、このフイルムから作成された偏光板保護膜、偏光板、光学機能製膜、液晶表示装置は優れた光学的性質や物性を有すると共に耐久性にも優れている。
【図面の簡単な説明】
【図１】本発明の一実施例である溶液製膜方法において流延ダイからドープを流延している状態を示す部分正面図である。
【図２】本発明に係る流延ダイの側面図である。
【図３】図１の要部拡大図である。
【図４】図１の流延ダイ部分の側面図である。
【図５】図１において減圧チャンバーを付設した状態の側面図である。
【図６】図１の流延ダイを用いた流延バンド式の流延装置の要部構成を示す部分側面図である。
【図７】図１に示す流延バンド式の流延装置の要部平面図である。
【図８】図１の流延ダイを流延ドラム式の流延装置に適用した例を示す部分側面図である。
【図９】図８に示す適用例の要部平面図である。
【図１０】本発明が適用される流延ダイの一例の縦断面図である。
【図１１】本発明が適用される流延ダイの別の例の縦断面図である。
【図１２】本発明が適用される流延ダイの別の例の縦断面図である。
【図１３】従来の溶液製膜方法において流延ダイからドープを流延している状態を示す部分正面図である。
【図１４】その流延ダイ部分の側面図である。
【符号の説明】
１ 流延ダイ
２ 流延バンド
３ 回転ドラム
４ 流延ドラム
５ 剥取ローラー
６ 減圧チャンバー
７ 吸引ダクト
８ バッファーチャンバー
９ 吸引ブロワー
１０ 流延ドープ
１１ マニホールド
１２ ドープ供給口
１３ スロット
１４ パッキン
１５ 側板
１６ ダイリップ
１７ 皮張り
１９ フィードブロック
２０ 溶剤給液配管
２１ 溶剤タンク
２２ 送液ポンプ
２３ 給液ノズル
２４ 溶剤[0001]
BACKGROUND OF THE INVENTION
  The present invention prevents skinning occurring at both ends in the casting die width direction in solution castingThe present invention relates to a casting die for solution casting and a solution casting method using the casting die.
[0002]
[Prior art]
In general, a part of a support film such as cellulose acetate, polycarbonate and cellophane is produced by a solution casting method. In most cases, the skin 17 is generated at both ends of the casting die lip as shown in FIG. 14 by drying of the polymer solution (hereinafter referred to as “dope”). This skin growth grows in a wiggle shape at both ends of the lip tip, disturbs the flow of dope from the lip, and inhibits stable film formation.
[0003]
When skinning occurs, the casting speed must be reduced to a speed that does not cut even if the casting film becomes unstable due to disturbance, and the skinning must be removed, which causes a significant reduction in productivity. It was.
[0004]
Conventionally, as a countermeasure against this, there are known methods for preventing the problem by blowing a solvent saturated gas into both ends of the die lip or flowing down a solvent soluble in the dope.
[0005]
For example, in Japanese Patent Laid-Open No. 2-208650, the occurrence of skinning is prevented by providing a solvent flow path inside the both ends of a die for casting a cellulose triacetate solution and supplying a solvent such as methylene chloride therefrom. A method is disclosed. The lower end of this flow path joins at the cellulose triacetate solution discharge end, and the solvent is discharged together with the cellulose triacetate solution.
[0006]
Also, in Japanese Patent No. 2687260, a solvent such as methylene chloride is supplied so as to be placed on both ends of the dope cast slightly inward from the dope discharge ends at both ends of the die for casting a solution such as cellulose triacetate. A method for preventing the occurrence of skinning is disclosed.
[0007]
[Problems to be solved by the invention]
However, these methods are easily affected by the wind speed around the die lip, temperature conditions, and the like, and it is difficult to control the gas concentration and the solvent flow position. That is, when the gas concentration is low, skinning occurs, and even if the saturation concentration is maintained, condensation occurs due to fluctuations in the temperature around the die, and the gas flow causes adverse effects such as non-uniformity of the cast film thickness. There is a failure on the appearance of the film. Also, under the flow of the solvent, if the flow rate is low, skinning occurs, and the dope discharge part at the tip of the lip spreads in the width direction, so it is rather a solvent to supply the necessary amount to the lip end where the skinning occurs. It becomes excessive, causing peeling off on the support and causing a foreign matter adhesion failure. If unseparation occurs on the support, the casting speed must be reduced and the support must be cleaned, which significantly reduces productivity. Furthermore, if the flow rate of the flowing solvent fluctuates, it may cause disturbance of the cast film discharged from the casting die, and the cast film may be shaken or stretched to change the film thickness of the formed film. Cause product defects.
[0008]
The object of the present invention is to eliminate the above-mentioned problems in the prior art in solution casting, and to periodically remove any residue remaining due to insufficient drying at the end peeling point from the support without adversely affecting the casting film. It is an object of the present invention to provide a method for preventing the occurrence of skinning without improving the production efficiency.
[0009]
Another object of the present invention is to provide a solution film-forming method of a film excellent in optical properties by adding various additives to a cellulose acylate solution.
[0010]
Furthermore, another object of the present invention is to provide a polarizing plate protective film, a polarizing plate, an optical functional film, and a liquid crystal display device which are excellent in optical characteristics using the film.
[0011]
[Means for Solving the Problems]
The present invention has been made to solve the above-mentioned problems, and the casting die for solution casting according to the present invention is a casting die for solution casting in which a solution is cast by casting a solution. It is preferable that a solvent supply nozzle is provided outside the discharge end with an interval of 0.5 to 3.0 mm. Further, it is more preferable that the liquid supply nozzle is disposed between a nozzle substantially vertical state where the angle formed by the liquid supply nozzle with respect to the cast solution is 10 degrees and a nozzle horizontal state where the angle is 90 degrees. The present invention also includes a solution casting method using any one of the above casting dies for solution casting.
[0012]
The solution casting method of the present invention is a solution casting method in which a solution is cast using a casting die, and the solution is cast from the outside of both ends of the lip of the casting die. It is preferable to flow at a flow rate of 5 ml / min. In addition, when flowing the solvent, it is preferable that the rate of change of the flow rate within 0.002 seconds to 100 seconds is within ± 50%. More preferably, when the solvent is flowed, the fluctuation rate of the flow rate from 0.005 seconds to 10 seconds is within ± 10%.
[0013]
It is preferable to increase or decrease the flow rate of the solvent according to the flow rate of the solution to be cast. Further, it is more preferable that the solvent is soluble in the solute of the solution to be cast, the viscosity is 0.2 to 3 cp, and the surface tension is 15 to 50 dyn / cm. Further, it is more preferable that the solvent supply nozzle for flowing the solvent is between a nozzle substantially vertical state where the nozzle is 10 degrees with respect to the solution to be cast and a horizontal state where the nozzle is 90 degrees. Furthermore, in the solution casting method, a solution casting method using a co-casting method is also included in the present invention.
[0014]
In the solution casting method of the present invention, the solute of the solution is preferably cellulose acetate. Further, a solution film forming method using a cellulose acylate solution is also included in the present invention.
[0015]
The solvent of the cellulose acylate solution is composed of methyl acetate, ketones and alcohols, and the solvent ratio is 20 to 90% by weight for methyl acetate, 0 to 60% by weight for ketones and 5 to 30% by weight for alcohols. Preferably there is.
[0016]
The cellulose acylate solution preferably contains 0.1 to 20% by weight of at least one plasticizer with respect to cellulose acylate. Moreover, it is preferable that the said cellulose acylate solution contains 0.001 to 5 weight% of at least 1 type of ultraviolet absorber with respect to a cellulose acylate. Furthermore, it is preferable that the cellulose acylate solution contains 0.001 to 5% by weight of at least one fine particle powder with respect to the cellulose acylate. Furthermore, it is preferable that the cellulose acylate solution contains 0.002 to 2% by weight of at least one release agent with respect to the cellulose acylate. Moreover, it is preferable that the said cellulose acylate solution contains 0.001-2 weight% of at least 1 type of fluorosurfactant with respect to a cellulose acylate.
[0017]
The present invention also includes a solution casting method that is a manufacturing process in which two or more types of cellulose acylate solutions are co-cast in the casting process.
[0018]
The film formed by the solution casting method of the present invention is preferably used as a polarizing plate protective film, a polarizing plate, an optical functional film, and a liquid crystal display device. In this case, an excellent durability can be obtained.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
[polymer]
Examples of the polymer that can be used for the polymer solution (dope) in the solution casting method of the present invention include cellulose ester and polycarbonate. The cellulose ester is typically a lower fatty acid ester of cellulose (for example, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, etc.). Lower fatty acid means a fatty acid having 6 or less carbon atoms. Cellulose acetate includes cellulose triacetate (TAC) and cellulose diacetate (DAC). In particular, in the present invention, it is preferable to prepare a dope from a cellulose acylate solution, and the cellulose acylate is more preferably cellulose triacetate.
[0020]
[solvent]
As the dope solvent, a lower aliphatic hydrocarbon chloride or a lower aliphatic alcohol is generally used. Examples of lower aliphatic hydrocarbon chlorides include methylene chloride and chloroform. Examples of lower aliphatic alcohols include carbon atoms such as methanol, ethanol, n-propanol, iso-propanol, 1-butanol, t-butanol, 2-methyl-2-butanol, 2-methoxyethanol and 2-butoxyethanol. Although alcohol is mentioned to number 1-6, it is not limited to these. Examples of other solvents include ketones such as acetone substantially free of halogenated hydrocarbons, for example, ketones having 4 to 12 carbon atoms such as methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclohexanone and methylcyclohexanone. However, it is not limited to these. Also, esters having 3 to 12 carbon atoms can be used. Examples include, but are not limited to, ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, pentyl acetate and 2-ethoxy-ethyl acetate. Furthermore, ethers having 3 to 12 carbon atoms can also be used. Examples include, but are not limited to, diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, anisole and phenetole. Furthermore, cyclic hydrocarbons having 5 to 8 carbon atoms can also be used. Examples include, but are not limited to, cyclopentane, cyclohexane, cycloheptane, and cyclooctane.
[0021]
As the solvent, methylene chloride is particularly preferable. Moreover, you may mix and use another solvent for a methylene chloride. However, the mixing ratio of methylene chloride is preferably 70% by weight or more. Particularly preferred mixing ratios are 75 to 93% by weight for methylene chloride and 7 to 25% by weight for other solvents. The solvent is removed in the process of forming the cellulose ester film, and the residual amount of the solvent is generally less than 5% by weight. However, the residual amount is preferably less than 1% by weight, and more preferably less than 0.5% by weight.
[0022]
Moreover, when the influence on a human body and an environment is considered, it is preferable to use the solvent which does not use a methylene chloride. In this case, it is preferable to use a mixed solvent of methyl acetate and the aforementioned ketones and alcohols. In particular, when cellulose acylate is selected as the polymer for preparing the dope, it is preferable from the viewpoint of solubility that methyl acetate is used as the solvent as the main solvent. Also, methyl acetate can be mixed with a ketone or alcohol solvent for the purpose of improving the solubility of the polymer. In this case, the component ratio of each solvent is preferably 20 to 90% by weight for methyl acetate, 0 to 60% by weight for ketones, and 5 to 30% by weight for alcohols.
[0023]
[Additive]
You may add additives, such as a plasticizer, a ultraviolet absorber, and a degradation inhibitor, to dope. Below, these each additive is demonstrated in detail.
[0024]
(Plasticizer)
The plasticizer that can be used in the present invention is not particularly limited, but in the phosphate ester type, triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl Phosphate, etc., for phthalate esters, diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, etc., for glycolate esters, triacetin, tributyrin, butyl phthalyl butyl glycolate, ethyl phthalyl ethyl glycolate, methyl phthalyl Ethyl glycolate, butyl phthalyl butyl glycolate and the like are preferably used alone or in combination. Further, plasticizers described in JP-A-11-80381, JP-A-11-124445, and JP-A-11-248940 can also be added. These plasticizers are desirably mixed in the dope so as to contain 0.1 to 20% by weight with respect to cellulose acylate.
[0025]
(UV absorber)
In addition, an ultraviolet absorber can be added to the dope. In particular, it preferably contains one or more ultraviolet absorbers. From the viewpoint of preventing deterioration of the liquid crystal, the ultraviolet absorbent for liquid crystal is preferably excellent in the ability to absorb ultraviolet rays having a wavelength of 370 nm or less, and from the viewpoint of liquid crystal display properties, the absorption of visible light having a wavelength of 400 nm or more is small. Examples include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and the like. Particularly preferred ultraviolet absorbers are benzotriazole compounds and benzophenone compounds. Among these, a benzotriazole-based compound is preferable because unnecessary coloring with respect to the cellulose ester is small. Furthermore, a benzotriazole type ultraviolet absorber described in JP-A-8-29619 or an ultraviolet absorber described in JP-A-8-239509 can be added. In addition, a known ultraviolet absorber may be added. These ultraviolet absorbers are desirably mixed in the dope so as to contain 0.001 to 5% by weight with respect to cellulose acylate. For example, a benzotriazole-based ultraviolet absorber described in JP-A-8-29619 or an ultraviolet absorber described in JP-A-8-239509 can be added.
[0026]
As preferred UV inhibitors, 2,6-di-tert-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], triethylene glycol -Bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) ) Propionate], 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-tert-butylanilino) -1,3,5-triazine, 2,2-thio-diethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di tert-butyl-4-hydroxyphenyl) propionate, N, N'-hexamethylenebis (3,5-di-tert-butyl-4-hydroxy-hydrocinnamide), 1,3,5-trimethyl-2,4,6 -Tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, tris- (3,5-di-tert-butyl-4-hydroxybenzyl) -isocyanurate and the like. In particular, 2,6-di-tert-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3 -(3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate] is most preferred. Further, for example, metal deactivators of hydrazine compounds such as N, N′-bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyl] hydrazine and tris (2,4-di- A phosphorus processing stabilizer such as tert-butylphenyl) phosphite may be used in combination. The amount of these compounds added is preferably 0.001 to 5% by weight based on cellulose acylate.
[0027]
(Fine particle powder)
For the dope, a matting agent, which is a fine particle powder, can be used in order to improve the slipperiness of the film and the adhesion resistance under high humidity. The average height of the protrusions on the surface of the matting agent is preferably 0.005 to 10 μm, more preferably 0.01 to 5 μm. In addition, it is better that there are many protrusions on the surface, but if there are more protrusions than necessary, it becomes a problem and becomes a problem. As the matting agent used, both inorganic compounds and organic compounds can be used. Inorganic compounds include fine powders of inorganic substances such as barium sulfate, manganese colloid, titanium dioxide, strontium barium sulfate, silicon dioxide, aluminum oxide, tin oxide, zinc oxide, calcium carbonate, barium sulfate, talc, kaolin and calcium sulfate. However, for example, silicon dioxide such as synthetic silica obtained by a wet method or gelation of silicic acid, titanium dioxide (rutile type or anatase type) produced by titanium slug and sulfuric acid, and the like can be mentioned. It can also be obtained by pulverizing from an inorganic substance having a relatively large particle diameter, for example, 20 μm or more, followed by classification (vibration filtration, wind classification, etc.). Examples of organic compounds include polytetrafluoroethylene, cellulose acetate, polystyrene, polymethyl methacrylate, polypropyl methacrylate, polymethyl acrylate, polyethylene carbonate, acrylic styrene resin, silicone resin, polycarbonate resin, benzoguanamine resin, melamine resin, Examples thereof include pulverized and classified products of organic polymer compounds such as polyolefin resin, polyester resin, polyamide resin, polyimide resin, polyfluorinated ethylene resin, and starch. Alternatively, a polymer compound synthesized by a suspension polymerization method, a polymer compound made spherical by a spray dry method or a dispersion method, or an inorganic compound can be used. Further, if the fine particle powder is added in an excessive amount, there are also problems such as the loss of flexibility of the film. Therefore, the fine particle powder is preferably contained in an amount of 0.001 to 5% by weight based on the cellulose acylate.
[0028]
(Release agent)
In addition, a release agent for facilitating the release operation can be added to the dope. Release agents include, but are not limited to, high melting point waxes, higher fatty acids and their salts and esters, silicone oil, polyvinyl alcohol, low molecular weight polyethylene, vegetable protein derivatives and the like. Since the addition amount of the release agent affects the gloss and smoothness of the film surface, it is preferably contained in an amount of 0.002 to 2% by weight based on the cellulose acylate.
[0029]
(Fluorosurfactant)
A fluorine-based surfactant can also be added to the dope. A fluorosurfactant is a surfactant having a fluorocarbon chain as a hydrophobic group, and is used as a coating agent in an organic solvent or an antistatic agent because it significantly reduces the surface tension. Fluorosurfactants include C₈F₁₇CH₂CH₂O- (CH₂CH₂O)_Ten-OSO_ThreeNa, C₈F₁₇SO₂N (C_ThreeH₇) (CH₂CH₂O)₁₆-H, C₈F₁₇SO₂N (C_ThreeH₇) CH₂COOK, C₇F₁₅COONH_Four, C₈F₁₇SO₂N (C_ThreeH₇) (CH₂CH₂O)_Four-(CH₂)_Four-SO_ThreeNa, C₈F₁₇SO₂N (C_ThreeH₇) (CH₂)_Three-N⁺(CH_Three)_Three・ I^-, C₈F₁₇SO₂N (C_ThreeH₇) CH₂CH₂CH₂N⁺(CH_Three)₂-CH₂COO^-, C₈F₁₇CH₂CH₂O (CH₂CH₂O)₁₆-H, C₈F₁₇CH₂CH₂O (CH₂)_Three-N⁺(CH_Three)_Three・ I^-, H (CF₂)₈-CH₂CH₂OCOCH₂CH (SO_Three) COOCH₂CH₂CH₂CH₂-(CF₂)₈-H, H (CF₂)₆CH₂CH₂O (CH₂CH₂O)₁₆-H, H (CF₂)₈CH₂CH₂O (CH₂)_Three-N⁺(CH_Three)_Three・ I^-, H (CF₂)₈CH₂CH₂OCOCH₂CH (SO_Three) COOCH₂CH₂CH₂CH₂C₈F₁₇, C₉F₁₇-C₆H_Four-SO₂N (C_ThreeH₇) (CH₂CH₂O)₁₆-H, C₉F₁₇-C₆H_Four-CSO₂N (C_ThreeH₇) (CH₂)_Three-N⁺(CH_Three)_Three・ I^-However, it is not necessarily limited to these. The addition amount of the fluorosurfactant is preferably 0.001 to 2% by weight based on the cellulose acylate.
[0030]
In addition, various additives may be further added to the dope at any stage after preparation of the solution from before preparation. Heat stabilizers such as alkaline earth metal salts such as calcium and magnesium, antistatic agents, flame retardants, lubricants, oils and the like.
[0031]
[Preparation of dope]
(Swelling process)
About the preparation of dope, the case where a cellulose triacetate is used for a polymer is demonstrated. First, the cellulose triacetate particles and a solvent are mixed, and a swelling process is performed in which the cellulose triacetate particles are swollen with the solvent. It is preferable that the temperature of a swelling process is -10-55 degreeC, and it implements normally at room temperature. The ratio of cellulose triacetate and solvent is determined according to the concentration of the solution finally obtained. In general, the amount of cellulose triacetate in the mixture is preferably 5 to 30% by weight, more preferably 8 to 20% by weight, and most preferably 10 to 15% by weight. The mixture of the solvent and cellulose triacetate is preferably stirred until the cellulose triacetate is sufficiently swollen. Usually, the mixing and stirring time is 1 to 180 minutes. There are cases where the process proceeds from swelling to dissolution only by mixing and stirring, and in this case, a step of dissolving cellulose triacetate in a solvent such as a heating step described later is not necessarily performed. In the swelling step, components other than the solvent and cellulose triacetate, for example, a plasticizer, a deterioration inhibitor, a dye, and an ultraviolet absorber may be added.
[0032]
(Heating process)
Next, a heating step for heating the dope to 130 ° C. or higher is performed. The heating temperature is 130 ° C. or higher, desirably 160 ° C. or higher, and most desirably 180 ° C. or higher. However, if it exceeds 250 ° C., the cellulose triacetate in the dope is decomposed, so that the quality of the film is impaired, which is not preferable. In this case, the heating rate is preferably 1 ° C./min or more, more preferably 2 ° C./min or more, further preferably 4 ° C./min or more, and more preferably 8 ° C./min or more. Most preferred. The higher the heating rate, the better. However, 10,000 ° C./second is the theoretical upper limit, 1000 ° C./second is the technical upper limit, and 100 ° C./second is the practical upper limit. The heating rate is a value obtained by dividing the difference between the temperature at the start of heating and the final heating temperature by the time from the start of heating to the final heating temperature. The heating method may be any method such as an autoclave system, a multi-tube heat exchanger, a screw extruder, and a static mixer.
[0033]
The heating time is preferably 20 seconds or longer and 4 hours or shorter. If the heating time is less than 20 seconds, insoluble materials remain in the heated and dissolved dope, and a high-quality film cannot be produced. Moreover, even when this insoluble matter is removed by filtration, it is disadvantageous because the filter life is extremely shortened. The beginning of the heating time is measured when the target temperature is reached, and the end is when the cooling starts from the target temperature. The cooling of the device may be natural cooling or forced cooling.
[0034]
(Pressure process)
In the heating step, the dope is preferably heated to a temperature equal to or higher than the boiling point at the atmospheric pressure of the solvent under a pressure adjusted so that the solution does not boil. By applying pressure, foaming of the dope can be prevented and a uniform dope can be obtained. At this time, the pressure to pressurize is determined by the relationship between the heating temperature and the boiling point of the solvent.
[0035]
(Cooling process)
Performing a cooling step of cooling the dope to −100 to −10 ° C. before the heating step is also effective for obtaining a film having good optical properties. In a system that cannot be easily dissolved at room temperature and a system that has a large amount of insoluble matter, a good dope can be prepared by using cooling, heating, or a combination of both. By cooling, the solvent can be rapidly and effectively infiltrated into cellulose triacetate, and dissolution is promoted. An effective temperature condition is −100 to −10 ° C. In the cooling process, it is desirable to use an airtight container in order to avoid moisture mixing due to condensation during cooling. Further, if the pressure is reduced during cooling, the cooling time can be shortened. In order to perform decompression, it is desirable to use a pressure resistant container. It is also effective in the present invention that this cooling step is performed after the heating step. If the dissolution is insufficient, the cooling process to the heating process may be repeated. Whether the dissolution is sufficient or not can be judged by visually observing the appearance of the solution.
[0036]
[Solution casting method]
The dope obtained as described above is injected into a mixing tank and stirred with a stirring blade to form a uniform solution. At this time, additives such as a hydrophobic plasticizer and an ultraviolet absorber can be mixed in the dope. The dope is sent to a filtration device by a pump to remove impurities. A solution casting method is performed using this dope, but typical methods are divided into a method using a casting band and a method using a casting drum.
[0037]
[Casting die]
First, a method using a casting band will be described. An example of a band-type solution casting apparatus is shown in FIG. In this apparatus, an endless casting band 2 having a mirror-finished surface is wound around a pair of rotating drums 3 (only one is shown). A casting die 1 is provided on one side of the rotating drum 3 at a distance from the peripheral surface. A decompression chamber 6 is provided behind the casting die 1, that is, on the right side of the drawing. The decompression chamber 6 is sucked by a suction blower 9 via a suction duct 7 and a buffer chamber 8. The dope is extruded from the casting die 1 as shown in FIG. 4 or FIG. 5 and cast on the casting band 2 running to the left of the drawing, solidified during the running and stripped after approximately one round. It is peeled off by the roller 5 and sent to a tenter stretching machine (not shown). The present invention can also be applied to an apparatus without the above-described decompression chamber.
[0038]
The film is stretched and dried while being conveyed by the tenter stretching machine. The film exiting the tenter stretching machine is sent to the drying zone, dried while being conveyed by a plurality of rollers, then passed through the cooling zone, cooled to room temperature, and taken up by a winder. It is preferable that knurling or ear cutting is performed before winding. However, in the present invention, the method for drying the film may be any known method.
[0039]
The apparatus shown in FIG. 8 uses a casting drum 4 instead of the casting band 2. FIG. 9 shows a plan view of the main part of the apparatus shown in FIG.
[0040]
As said casting die 1, what is shown in FIG.10, FIG.11, FIG.12 can be used.
[0041]
The casting die shown in FIG. 10 is used when a single layer film is formed, and the casting die 1 is provided with one manifold 11. The casting die of FIG. 11 is a multi-manifold type co-casting die, and this co-casting die 1 has three manifolds 111, 112, and 113, and can form a film having a three-layer structure. . The manifold 11 has a coat hanger shape as shown in FIG. 1, and a dope supply port 12 is provided at the center thereof. The lower side of the manifold 11 is a slot 13 from which the dope is extruded in the form of a film. Packing 14 is provided on both sides of the die 1, and is closed by a side plate 15 via the packing 14. The casting die of FIG. 12 is a feed block type co-casting die. The co-casting die 1 is provided with a manifold 11 and a feed block 19, and is joined at the feed block 19. Thus, the dope having a plurality of layers (three layers in FIG. 12) is cast. In the above casting die, a coat hanger die is used, but the die is not limited to this, and may be a die having another shape such as a T die.
[0042]
In FIG. 3, the principal part enlarged view of the casting die 1 is shown. With reference to FIG.1 and FIG.3, the attachment position of the liquid supply nozzle 23 of the solvent 24 is demonstrated in detail. Moreover, in FIG. 7, the principal part top view of the casting apparatus shown in FIG. 1 is shown. The casting dope 10 is cast from a die lip 16 at the tip of the casting die 1 onto a casting band (not shown). The liquid supply nozzle 23 is installed along the outer peripheral surface of the packing 14, and the distance L1 between the tip 23a of the nozzle 23 and the discharge end of the casting dope 10 is set to 0.5 to 3.0 mm. ing. The angle θ formed by the tip of the liquid supply nozzle 23 with respect to the casting dope 10 is 90 degrees. The liquid supply nozzle 23 can be installed so that the angle θ is 10 to 90 degrees. The liquid supply nozzle 23 is not limited to the above-described installation method as long as it is in the range of L1 and θ, and can be attached to the casting die by any known installation method.
[0043]
The die lip clearance in the solution casting method is usually set in the range of 0.2 mm to 3 mm, preferably in the range of 0.5 mm to 2.5 mm, but is not limited thereto.
[0044]
The distance between the casting die and the support (casting band or casting die) is usually set in the range of 1 mm to 10 mm, preferably in the range of 1.5 mm to 6 mm, but is not limited to this. Is not to be done.
[0045]
An example in which the solvent supply pipe 20 is provided on the casting die 1 is shown in FIGS. As shown in these drawings, the conventional solvent dropping method is a method in which a solvent is dropped from the direction perpendicular to the tip of the lip at or inside both ends of the dope discharged from the casting die lip 16. It was. On the other hand, the present invention is characterized in that the solvent is dropped from the lip tip horizontal direction to 90 degrees, preferably from the horizontal direction to 45 degrees, outside both ends of the dope. The solvent used was a corrosion-resistant material against chlorine-based solvents such as metals such as stainless steel, ceramics, and resin materials such as fluororesin having an inner diameter of 0.1 to 0.8 mm and an outer diameter of 0.2 to 2.0 mm. The nozzle is supplied to the dope at both ends of the lip. The solvent passage may be inside or outside the die, but the solvent outlet needs to be 0.5 to 3.0 mm away from the end of the casting dope. The distance between the solvent supply port at the nozzle tip and the casting dope end is preferably about 0.5 to 3.0 mm, particularly preferably about 1.0 to 2.0 mm. The solvent discharged from the nozzle accumulates at the lip tip and is supplied to the discharged dope. At this time, if the wettability between the nozzle and lip tip and the solvent is poor, the solvent becomes droplets and falls to the upper end of the support or is sucked into the decompression chamber and falls to the center of the support, resulting in a failure in the appearance of the product. Is generated. Moreover, even if it gets wet too much, the solvent spreads in the width direction of the lip tip, and the dope that has become a dilute solution dries in the solvent retention portion, and a solute such as a polymer precipitates, which adversely affects stable casting. As a result of diligent research, the viscosity of the solvent is 0.2 to 3.0 cp, particularly 0.3 to 1.0 cp, the surface tension of the solvent is 15 to 50 dyn / cm, preferably 20 to 30 dyn / cm, and the solvent and dropping nozzle. It has been discovered that the contact angle at the tip and die lip tip may be 10 to 90 degrees, particularly 20 to 50 degrees. Moreover, in order to form a stable meniscus between the tip of the dropping nozzle and the dope end, the discharge flow rate of the dropping nozzle is 10 to 110 cm / second, particularly 20 to 60 cm / second, the discharge dope end and the tip of the dropping nozzle It has been found that the distance for forming a meniscus between the first and second layers may be 0.5 to 3.0 mm, particularly 1.0 to 2.0 mm. The dropping flow rate is suitably 0.05 to 0.5 ml / min, particularly 0.1 to 0.2 ml / min.
[0046]
As a control method for each of the above factors, the viscosity can be adjusted by adjusting the mixing ratio of each solvent using a mixed solvent as a solvent, or by adjusting the temperature of the solvent, and the surface tension can also be adjusted by using a mixed solvent. It can be adjusted by adjusting the mixing ratio of the solvent. The contact angle between the solvent and the tip of the dropping nozzle and the tip of the die lip can be adjusted by changing the roughness of the tip of the dropping nozzle and the tip of the die lip and the surface material (by plating, fluororesin coating, etc.).
[0047]
The decompression degree p of the decompression chamber is usually set in the range of −500 to −10 Pa, and preferably set to −400 to −20 Pa, but is not limited thereto.
[0048]
The casting speed v is usually set in the range of 3 m / min to 150 m / min, and preferably in the range of 10 m / min to 100 m / min, but is not limited thereto.
[0049]
The thickness t of the film is preferably 20 to 500 μm, more preferably 30 to 300 μm, most preferably 35 to 200 μm, but is not limited thereto.
[0050]
The solvent is soluble in the solute of the solution to be cast, and can be either a good solvent for a solute such as methylene chloride or methyl acetate, or a mixed solvent of a good solvent and a poor solvent such as methanol, ethanol, butanol, or acetone. good. The ratio of the poor solvent is 0 to 90% by weight, preferably 0 to 60% by weight. According to the present invention, there is no wetting and spreading of the solvent on the lip surface as in the prior art, and the flow rate of the solvent may be the minimum necessary amount. As a result of intensive studies, it was found that an appropriate flow rate is 0.05 to 0.5 ml / min. In other words, if the flow rate is too small, stretching or instability due to drying of the dope end tends to occur, and if the flow rate is too high, it tends to peel off on the surface of the support, significantly hindering stable casting. become. This flow rate is preferably 0.1 to 0.2 ml / min.
[0051]
With reference to FIG. 2, the means for suppressing fluctuations in the speed of the solvent when the solvent is supplied to the die lip at the tip of the casting die will be described. A solvent supply pipe 20 is attached to the die lip 16 of the casting die 1, and the solvent injected into the solvent tank 21 is sent and fed by a liquid feed pump 22. In the present invention, it is preferable to suppress fluctuations in the flow rate of the solvent so as not to cause the cast film to sway or expand and contract. As a means for controlling fluctuations in the speed of the solvent, the liquid feed pump 22 can be a rotary pump such as a gear pump, a reciprocating pump such as a diaphragm pump, or a plunger pump. Is preferable in terms of flow rate accuracy. In the present invention, it is also possible to use a feedback control method in which the liquid flow rate is detected by a flow meter and the pump liquid flow rate is controlled. In the present invention, the fluctuation rate of the flow rate of the solvent is the average flow rate v of the solvent flowing within a certain period._aveAnd the maximum flow rate v within a certain period_maxAnd minimum flow rate v_minMeans the value calculated from the ratio. In the present invention, the variation rate is preferably controlled to be within ± 50% (from 0.002 seconds to 100 seconds), more preferably within ± 10% (from 0.005 seconds to 10 seconds). It is.
[0052]
[Product]
The obtained film can be used as a polarizing plate protective film. A polarizing plate can be formed by pasting this polarizing plate protective film on both surfaces of a polarizing film made of polyvinyl alcohol or the like. Furthermore, it can also be used as an optical functional film such as an optical compensation film having an optical compensation sheet affixed on a film, or an antireflection film having an antiglare layer laminated on the film. From these products, it is also possible to constitute a part of a liquid crystal display device.
[0053]
[Co-casting]
The solution casting method of the present invention can also be applied to a solution casting method by preparing two or more types of dopes and applying simultaneous multilayer coating. For example, when a film is formed by simultaneous three-layer coating, a large amount of cellulose triacetate is contained in the inner layer dope, and a relatively small amount of cellulose triacetate is included in the outer layer dope formed on the front and back surfaces of the inner layer. Contain. A film formed by applying three layers of these dopes simultaneously by the co-casting method has good flatness, transparency or moldability. However, the co-casting method in the solution casting method of the present invention is not limited to this embodiment.
[0054]
【Example】
The raw materials used in the solution casting process are as follows.
100 parts by weight of cellulose triacetate
10 parts by weight of triphenyl phosphate
5 parts by weight of biphenyl diphenyl phosphate
315 parts by weight of methylene chloride
60 parts by weight of methanol
10 parts by weight of n-butanol
Product thickness after drying 40,80μm
Decompression chamber decompression degree 0-500Pa
Sidestream dope composition during co-casting
100 parts by weight of cellulose triacetate
10 parts by weight of triphenyl phosphate
5 parts by weight of biphenyl diphenyl phosphate
400 parts by weight of methylene chloride
75 parts by weight of methanol
n-Butanol 13 parts by weight
Total product thickness after drying 80μm
Mainstream thickness 76μm
Side flow thickness (upper and lower layers) 2μm each
Distance between casting die and support h = 3.5mm
Die lip clearance d = 1.0mm
Casting speed 50m / min
[0055]
Under each condition of the examples, the time and degree of occurrence of skinning at both ends of the lip, and the remaining dirt on the support were evaluated.
[0056]
[Example 1]
Single layer casting was performed under the following conditions. The solvent dripping conditions to the lip end are as follows.

[0057]
Skinning did not occur after 24 hours. There was almost no unremoved dirt on the support.
[0058]
[Example 2]
Co-casting was performed under the following conditions. The solvent dripping conditions to the lip end are as follows.

[0059]
Skinning did not occur after 24 hours. There was almost no unremoved dirt on the support.
[0060]
[Example 3]
Single layer casting was carried out with the following dope formulation. The solvent dripping conditions to the lip end are as follows.
100 parts by weight of cellulose triacetate
10 parts by weight of triphenyl phosphate
5 parts by weight of biphenyl diphenyl phosphate
315 parts by weight of methyl acetate
60 parts by weight of ethanol
10 parts by weight of n-butanol
[0061]
Cellulose triacetate was swollen with a solvent for 30 minutes, and the cellulose triacetate solution was fed by a screw extruder and passed through the cooling part so as to be maintained at -70 ° C for 3 minutes. Cooling was performed using a −80 ° C. refrigerant (3vac Novac FC-77 or HFE-7100) cooled by a refrigerator. The solution obtained by cooling was transferred to a stainless steel container and stirred at 50 ° C. for 2 hours. And it filtered with the filter paper (Toyo Filter Paper Co., Ltd. product # 63) with an absolute filtration precision of 0.01 mm.
[0062]
1) Dropping flow rate is 0.2 ml / min
2) The inner diameter of the dropping nozzle is 0.1 mm, the outer diameter of the dropping nozzle is 0.3 mm, and the discharge speed of the dropping nozzle is 42.5 cm / second.
3) The viscosity of the solvent is 0.36 cp
4) The surface tension of the solvent is 25 dyn / cm
5) The contact angle between the solvent and the tip of the dropping nozzle and the tip of the die lip is 30 degrees.
6) The distance between the discharge dope end and the tip of the dropping nozzle is 1.0 mm.
7) Dropping position is horizontal position in the width direction from the lip tip dope end.
8) Solvent composition Methyl acetate 100% by weight
9) The nozzle material is SUS316.
[0063]
Skinning did not occur after 24 hours. There was almost no unremoved dirt on the support.
[0064]
[Comparative Example 1]
Single layer casting was performed under the following conditions. The solvent dripping conditions to the lip end are as follows.

[0065]
Skinning did not occur after 24 hours. There was a lot of unstriped dirt on the support.
[0066]
[Comparative Example 2]
With respect to the conditions in Comparative Example 1, the solvent was dropped onto the lip end at a dropping flow rate of 0.6 ml / min. As a result, skinning occurred after 10 hours, making it impossible to continue casting.
[0067]
[Example 4]
The dope formulation of Example 3 was further co-cast using a dope of the following formulation as a side stream.

The composition of the solvent to be sent is 90 parts by weight of methyl acetate and 10 parts by weight of acetone.
As a result, no skinning occurred even after 24 hours. There was almost no residue remaining on the support.
[0068]
[Example 5]
Under the conditions of Example 1, the flow rate fluctuation rate of the solvent was controlled within ± 50% at a cycle of 1 Hz using the casting die shown in FIG. Thereby, the disorder of the edge part of the casting film discharged from the casting die during film formation was suppressed, and it was possible to continue casting.
[0069]
[Example 6]
Under the conditions of Example 1, the flow rate fluctuation rate of the solvent was controlled within ± 10% at a period of 1 Hz using the casting die shown in FIG. Thereby, there was no disorder in the edge part of the casting film discharged from the casting die during film formation, and the thickness variation of the whole casting film did not arise. In addition, the film after drying did not have a poor appearance due to uneven thickness.
[0070]
[Comparative Example 3]
Under the conditions of Example 1, the flow rate fluctuation rate of the solvent was controlled within ± 55% with a period of 1 Hz using the casting die shown in FIG. In this case, the end of the casting film discharged from the casting die during film formation is greatly disturbed, making it impossible to continue casting.
[0071]
Further, an antireflection film by coating was produced by the following procedure using the films of Example 3 and Example 4 cast by the above method.
[0072]
(Preparation of coating solution A for antiglare layer)
439 g of a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate (DPHA, Nippon Kayaku Co., Ltd.) 125 g, bis (4-methacryloylthiophenyl) sulfide (MPSMA, Sumitomo Seika Co., Ltd.) 125 g Of methyl ethyl ketone / cyclohexanone = 50/50% by weight in a mixed solvent. In the obtained solution, a solution obtained by dissolving 5.0 g of a photopolymerization initiator (Irgacure 907, manufactured by Ciba Geigy) and 3.0 g of a photosensitizer (Kayacure DETX, manufactured by Nippon Kayaku Co., Ltd.) in 49 g of methyl ethyl ketone. added. The refractive index of the coating film obtained by applying this solution and curing with ultraviolet rays was 1.60. Furthermore, 10 g of crosslinked polystyrene particles having an average particle diameter of 2 μm (trade name: SX-200H, manufactured by Soken Chemical Co., Ltd.) was added to this solution, and the mixture was stirred and dispersed at 5000 rpm for 1 hour with a high-speed dispaper. A coating solution A for the antiglare layer was prepared by filtering with a polypropylene filter.
[0073]
(Preparation of coating solution B for antiglare layer)
To a mixed solvent of 104.1 g of cyclohexanone and 61.3 g of methyl ethyl ketone, 217.0 g of a hard coat coating solution containing zirconium oxide dispersion (Desolite KZ-7886A, manufactured by JSR Corporation) was added while stirring with an air disperser. The refractive index of the coating film obtained by applying this solution and curing with ultraviolet rays was 1.61. Further, 5 g of crosslinked polystyrene particles having an average particle diameter of 2 μm (trade name: SX-200H, manufactured by Soken Chemical Co., Ltd.) was added to this solution, and the mixture was stirred and dispersed at 5000 rpm for 1 hour with a high speed dispaper. The coating liquid B of the anti-glare layer was prepared by filtering with a polypropylene filter.
[0074]
(Preparation of coating solution C for antiglare layer)
91 g of a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate (DPHA, manufactured by Nippon Kayaku Co., Ltd.), zirconium oxide dispersion-containing hard coat coating solution (Desolite KZ-7115, manufactured by JSR Co., Ltd.) 199 g, and 19 g of a zirconium oxide dispersion-containing hard coat coating solution (Desolite KZ-7161, manufactured by JSR Corporation) was dissolved in a mixed solvent of 52 g of methyl ethyl ketone / cyclohexanone = 54/46% by weight. 10 g of a photopolymerization initiator (Irgacure 907, manufactured by Ciba Geigy) was added to the resulting solution. The refractive index of the coating film obtained by applying this solution and curing with ultraviolet rays was 1.61. Furthermore, 20 g of crosslinked polystyrene particles having an average particle diameter of 2 μm (trade name: SX-200H, manufactured by Soken Chemical Co., Ltd.) were added to this solution in a mixed solvent of 80 g of methyl ethyl ketone / cyclohexanone = 54/46% by weight at 5000 rpm with a high speed disperser. After adding and stirring 29 g of the dispersion obtained by stirring and dispersing for 1 hour, the mixture was filtered through a polypropylene filter having a pore size of 30 μm to prepare a coating solution C for an antiglare layer.
[0075]
(Preparation of coating liquid D for hard coat layer)
A solution prepared by dissolving 250 g of an ultraviolet curable hard coat composition (Desolite KZ-7689, 72% by weight, manufactured by JSR Corporation) in 62 g of methyl ethyl ketone and 88 g of cyclohexanone was added. The refractive index of the coating film obtained by applying this solution and curing with ultraviolet rays was 1.53. Further, this solution was filtered through a polypropylene filter having a pore diameter of 30 μm to prepare a coating solution D for a hard coat layer.
[0076]
(Preparation of coating solution for low refractive index layer)
MEK-ST (MEK dispersion of SiO2 sol having an average particle size of 10 to 20 nm and a solid content concentration of 30% by weight) was added to 20093 g of a heat-crosslinkable fluorine-containing polymer (TN-049, manufactured by JSR Corporation) having a refractive index of 1.42. 8 g of Nissan Chemical Co., Ltd.) and 100 g of methyl ethyl ketone were added. After stirring, the mixture was filtered through a polypropylene filter having a pore size of 1 μm to prepare a coating solution for a low refractive index layer.
[0077]
The 80 μm-thick triacetyl cellulose film prepared in Example 3 and the above hard coat layer coating solution D were applied by a bar coater, dried at 120 ° C., and then air-cooled metal halide lamp (eye graphic of 160 W / cm). Illuminance 400 mW / cm², Irradiation amount 300mJ / cm²The ultraviolet ray was irradiated to cure the coating layer, and a hard coat layer having a thickness of 2.5 μm was formed. Furthermore, the antiglare layer coating solution A was applied with a bar coater, dried and UV cured under the same conditions as the hard coat layer, to form an antiglare layer having a thickness of about 1.5 μm. On top of that, the above-mentioned coating solution for the low refractive index layer was applied by a bar coater, dried at 80 ° C., and further thermally crosslinked at 120 ° C. for 10 minutes to form a low refractive index layer having a thickness of 0.096 μm. .
[0078]
Next, using the film of Example 3, the anti-glare layer coating liquid A was replaced with the anti-glare layer coating liquid B, and an antireflection film having the same conditions was prepared. Furthermore, the anti-glare layer coating liquid A was replaced with the anti-glare layer coating liquid C, and an antireflection film was also prepared under the same conditions.
[0079]
Furthermore, the antireflection film described above was prepared from the film of Example 4 using the coating liquids A, B, and C for the antiglare layer one by one under the same conditions.
[0080]
[Evaluation of antireflection film]
Six types of antireflection films formed from the film of Example 3 (antiglare layers A, B, C) and the film of Example 4 (antiglare layers A, B, C) by the above-described production method are as follows. Items were evaluated. The results obtained from the following evaluation methods are summarized in Table 1 later.
[0081]
(Evaluation of antireflection film)
The obtained film was evaluated for the following items.
[0082]
(1) Specular reflectance and color
A spectrophotometer V-550 (manufactured by JASCO Corporation) is equipped with an adapter ARV-474, and in the wavelength region of 380 to 780 nm, the specular reflectance at an incident angle of 5 ° at an incident angle of 5 ° is measured. An average reflectance of 450 to 650 nm was calculated, and antireflection properties were evaluated. Further, CIE 1976 L * a * b * color space L * value, a * value, and b * value representing the color of the specularly reflected light with respect to the 5 degree incident light of the CIE standard light source D65 are calculated from the measured reflection spectrum. The color of reflected light was evaluated.
[0083]
(2) Integral reflectance
An adapter ILV-471 is attached to a spectrophotometer V-550 (manufactured by JASCO Corporation), and an integrated reflectance at an incident angle of 5 ° is measured in a wavelength region of 380 to 780 nm, and an average reflection of 450 to 650 nm. The rate was calculated.
[0084]
(3) Haze
The haze of the obtained film was measured using a haze meter MODEL 1001DP (manufactured by Nippon Denshoku Industries Co., Ltd.).
[0085]
(4) Pencil hardness evaluation
The pencil hardness evaluation described in JIS K 5400 was performed as an index of scratch resistance. After conditioning the antireflection film at a temperature of 25 ° C. and a humidity of 60% RH for 2 hours, using a 3H test pencil specified in JIS S 6006, with a load of 1 kg
No scratch is observed in the evaluation of n = 5: ○
In evaluation of n = 5, 1 or 2 scratches:
In evaluation of n = 5, 3 or more scratches: ×
[0086]
(5) Contact angle measurement
As an index of surface contamination resistance, the optical material was conditioned at a temperature of 25 ° C. and a humidity of 60% RH for 2 hours, and then the contact angle with water was measured to obtain an index of fingerprint adhesion.
[0087]
(6) Dynamic friction coefficient measurement
The coefficient of dynamic friction was evaluated as an index of surface slipperiness. As the dynamic friction coefficient, a sample was conditioned at 25 ° C. and a relative humidity of 60% for 2 hours, and then a value measured with a HEIDON-14 dynamic friction measuring machine at a 5 mmφ stainless steel ball, a load of 100 g, and a speed of 60 cm / min was used.
[0088]
(7) Anti-glare evaluation
Bare fluorescent light (8000 cd / m) without louver on the antiglare film²) And the degree of blur of the reflected image was evaluated according to the following criteria.
I do not know the outline of the fluorescent lamp at all: ◎
Slightly understand the outline of the fluorescent lamp: ○
The fluorescent lamp is blurred, but the outline can be identified: △
Fluorescent lamp is hardly blurred: ×
[0089]
(8) Evaluation of surface condition of coating film
Inspection was performed by changing the angle with reflected light and transmitted light of a fluorescent lamp, and the strength of the unevenness on the surface of the coating film due to film thickness unevenness was sensory evaluated.
There is almost no unevenness: ◎
Unevenness is weak and few: ○
Unevenness is weak but often △
Some have strong irregularities: ×
[0090]
[Table 1]

[0091]
The antireflection films formed from the films of Example 3 and Example 4 are both excellent in antiglare property and antireflection property, and have a weak color, and also have pencil hardness, fingerprint adhesion, dynamic friction coefficient, etc. Evaluation results reflecting film properties were also good.
[0092]
Next, an antiglare antireflection polarizing plate was prepared using the film of Example 4. Using this polarizing plate, a liquid crystal display device in which an antireflection layer was disposed on the outermost layer was created. As a result, there was no reflection of external light, and excellent contrast was obtained. Visibility was good and fingerprinting was good.
[0093]
Further, the composition ratio of the mixed solvent for preparing the dope is changed between the above-described Example 3 and Example 4. In Example 3, methyl acetate was 82% by weight, ketones were 0% by weight, and alcohols (ethanol, n-butanol) were 18% by weight. In Example 4, methyl acetate was 75% by weight, ketones (cyclopentanone, acetone) were 15% by weight, and alcohols (methanol, ethanol) were 10% by weight. Thus, in this invention, dope can be prepared also from the solvent which changed the mixing ratio of methyl acetate, ketones, and alcohols.
[0094]
【The invention's effect】
The solution film forming method of the present invention is a solution film forming method in which a solvent is dropped to prevent the skin of the die lip end from being peeled. The required minimum amount of liquid is supplied to the lip end dope without causing turbulence of the lip, and without causing adverse effects on the casting film, the remaining peeling due to insufficient drying at the end peeling point from the support is periodically The production efficiency could be improved without the need for cleaning.
[0095]
In the solution casting method of the present invention, the fluctuation rate of the flow rate of the solvent is within ± 50%, more preferably within ± 10%. Appearance defects due to uneven thickness can be suppressed.
[0096]
In the present invention, cellulose acylate can be efficiently dissolved with a mixed solvent of methyl acetate, ketones, and alcohols. Various additives can be added to the cellulose acylate solution, and the film obtained from the solution by the solution casting method has excellent optical properties and physical properties.
[0097]
Furthermore, a polarizing plate protective film, a polarizing plate, an optical functional film, and a liquid crystal display device prepared from this film have excellent optical properties and physical properties and are excellent in durability.
[Brief description of the drawings]
FIG. 1 is a partial front view showing a state in which a dope is cast from a casting die in a solution casting method according to an embodiment of the present invention.
FIG. 2 is a side view of a casting die according to the present invention.
FIG. 3 is an enlarged view of a main part of FIG. 1;
4 is a side view of the casting die portion of FIG. 1. FIG.
5 is a side view showing a state in which a decompression chamber is attached in FIG. 1. FIG.
6 is a partial side view showing a configuration of a main part of a casting band type casting apparatus using the casting die of FIG. 1. FIG.
FIG. 7 is a plan view of an essential part of the casting band type casting apparatus shown in FIG. 1;
FIG. 8 is a partial side view showing an example in which the casting die of FIG. 1 is applied to a casting drum type casting apparatus.
9 is a plan view of relevant parts of the application example shown in FIG. 8;
FIG. 10 is a longitudinal sectional view of an example of a casting die to which the present invention is applied.
FIG. 11 is a longitudinal sectional view of another example of a casting die to which the present invention is applied.
FIG. 12 is a longitudinal sectional view of another example of a casting die to which the present invention is applied.
FIG. 13 is a partial front view showing a state in which a dope is cast from a casting die in a conventional solution casting method.
FIG. 14 is a side view of the casting die portion.
[Explanation of symbols]
1 Casting die
2 Casting band
3 Rotating drum
4 Casting drum
5 Stripping roller
6 Vacuum chamber
7 Suction duct
8 Buffer chamber
9 Suction blower
10 Casting dope
11 Manifold
12 Dope supply port
13 slots
14 Packing
15 Side plate
16 Die lip
17 Skinning
19 Feed block
20 Solvent supply piping
21 Solvent tank
22 Liquid feed pump
23 Liquid supply nozzle
24 Solvent

Claims (12)

A slot for discharging a dope containing a polymer and a solvent toward the support, a lip tip having a discharge port of the slot, and the polymer on both sides of the discharged dope on both sides in the longitudinal direction of the discharge port In a casting die for solution casting comprising a supply nozzle for supplying a soluble solvent that is soluble,
  The liquid supply nozzle is provided at the lip tip so as to sandwich the discharge port from the longitudinal direction, and supplies the soluble solvent to the dopes on both sides via the lip tip between the discharge port,
  The casting die for solution casting, wherein a distance between the both side dopes and the liquid supply nozzle is 0.5 to 3.0 mm. Claim 1, characterized in that it comprises in that a said liquid supply nozzle between a nozzle horizontal position angle is 90 degrees from the nozzle substantially vertical state in which the 10 degrees of the liquid supply nozzle relative to the two side dope The casting die for solution casting as described. The casting die for solution casting according to claim 1 or 2, wherein a contact angle of the soluble solvent at the liquid supply nozzle and the lip tip is 10 to 90 °. The viscosity of the soluble solvent is 0.2 to 3 cp, the surface tension of the soluble solvent is 15 to 50 dyn / cm,
The liquid feed pump for adjusting the discharge amount of the soluble solvent discharged from the liquid supply nozzle forms a stable meniscus at the tip of the lip between the liquid supply nozzle and the dopes on both sides. The discharge flow rate of the soluble solvent in the liquid supply nozzle is 10 to 110 cm / second, and the soluble solvent is flowed to the dope on both sides at a flow rate of 0.05 to 0.5 ml / min. The casting die for solution casting according to any one of claims 1 to 3. 5. The solution casting die according to claim 4, wherein the flow rate fluctuation rate is 0.0050% or less within 0.002 seconds to 100 seconds when flowing the soluble solvent . 5. The casting die for solution casting according to claim 4, wherein when the soluble solvent is flowed, a fluctuation rate of the flow rate from 0.005 seconds to 10 seconds is within ± 10% . 7. The solution casting die according to claim 1, wherein the liquid supply nozzle is provided downstream of the discharge port in the running direction of the support. The casting die for solution casting according to any one of claims 1 to 7, wherein the polymer contains cellulose acylate . The solvent comprises methyl acetate, ketones and alcohols, and the solvent ratio is 20 to 90% by weight of methyl acetate, 0 to 60% by weight of ketones and 5 to 30% by weight of alcohols. The casting die for solution casting according to any one of claims 1 to 8. 10. The casting die for solution casting according to any one of claims 1 to 9, wherein the soluble solvent contains methylene chloride or methyl acetate. Using the casting die for solution casting according to claim 1 to 10, the dope is discharged onto the support, and the dope solidified on the support is peeled off as a film and dried. Solution casting method. The solution casting method according to claim 11 , wherein a co-casting method is used.

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