JP2004131637A - Cellulose ester film, polarizing plate and method for producing the same and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a visual field angle-widening polarizing plate capable of simply improving visual field angle characteristics of TN type LCD such as TN-TFT, namely contrast, coloring and reversal phenomenon of light and shade in a vertical direction of screen in the case when viewed from an oblique direction, and a cellulose film used for the polarizing plate and further to provide a liquid display device in which the visual field angle in the vertical direction is improved by a simple constitution by using the visual field angle-widening polarizing plate. <P>SOLUTION: The cellulose ester film has one or more aromatic rings and comprises a compound having one or more kinds of reactive groups reacting with a residual hydroxy group of the cellulose ester and binding the group in the molecule and has an optically biaxial property. <P>COPYRIGHT: (C)2004,JPO

Description

【０１８２】
表１の結果から明らかなように、本発明のセルロースエステルフィルム１〜８は比較のセルロースエステルフィルム９と同等のＲ０、Ｒｔを得るために、延伸倍率が１．４から１．２に低下させることが可能である。また、芳香族環を一つ以上有し、かつヒドロキシル基と結合する基を分子内に一つ以上有する化合物が導入されていることから、水分率が低く、可塑剤の添加量の減量が可能である。
【０１８３】
《偏光板の作製》
（偏光板１）
厚さ１２０μｍのポリビニルアルコールフィルムをヨウ素１部、ヨウ化カリウム２部、ホウ酸４部を含む水溶液に浸漬し、５０℃で４倍に延伸して偏光膜を得た。次に、この偏光膜に上述のセルロースエステルフィルム１を以下の手順でラミネートして本発明の偏光板１を得た。
（１）保護フィルムとして、図２に示すように３０ｃｍ×１８ｃｍの長方形ＡＢＣＤの形状に切り取った上述のセルロースエステルフィルム２枚を２ｍｏｌ／Ｌの水酸化ナトリウム溶液に６０℃で１分間浸漬し、さらに水洗、乾燥させた。
【０１８４】
図２は、流延製膜により作製された本発明の長尺のセルロースエステルフィルムの模式図である。流延製膜され、作製された本発明の長尺のセルロースエステルフィルム１０において、流延方向１１は流延製膜時の流延方向、幅手方向１２は流延製膜時の幅手方向を表す。偏光板作製に用いられるセルロースエステルフィルムは、例えば、長方形ＡＢＣＤのように切り取られて使用されるが、長方形ＡＢＣＤの一辺ＡＢとセルロースエステルフィルム１０の流延方向１１とのなす角度は４５度であるように切り取られる。
（２）２枚のセルロースエステルフィルムと同サイズに調整した上記記載の偏光膜（偏光子）を固形分２質量％のポリビニルアルコール接着剤槽中に１〜２秒間浸漬する。
（３）前記の偏光膜（偏光子）に付着した過剰の接着剤を軽く取り除き、図３のような配置でセルロースエステルフィルムの面上に載せ、さらにもう１枚のセルロースエステルフィルムの面と接着剤とが接するように積層し配置する。
【０１８５】
図３は、本発明の偏光板の模式図である。偏光板６ａは、偏光子２ａを２枚の本発明のセルロースエステルフィルム１ａが挟みこむ状態に配置、構成されている。セルロースエステルフィルム１ａの流延製膜時の流延方向と偏光子２ａの延伸方向は平行である。
（４）ハンドローラで積層された偏光膜とセルロースエステルフィルムとの積層物の端部から過剰の接着剤及び気泡を取り除き貼り合わせる。ハンドローラは、２０〜３０Ｎ／ｃｍ^２の圧力をかけて、ローラスピードは約２ｍ／分とした。
（５）得られた試料を８０℃の乾燥器中に２分間放置し、偏光板１を作製した。次いで、偏光板１を下記に示す方法で液晶セルに組み込み、表示装置としての特性の一つである視野角を評価した。
【０１８６】
（偏光板２）
セルロースエステルフィルム２を用いて、セルロースエステルフィルム１と同様にして偏光板２を作製し、偏光板１と同様にして視野角測定を行った。
【０１８７】
（偏光板３）
セルロースエステルフィルム３を用いて、セルロースエステルフィルム１と同様にして偏光板３を作製し、偏光板１と同様にして視野角測定を行った。
【０１８８】
（偏光板４）
セルロースエステルフィルム４を用いて、セルロースエステルフィルム１と同様にして偏光板４を作製し、偏光板１と同様にして視野角測定を行った。
【０１８９】
（偏光板５）
セルロースエステルフィルム５を用いて、セルロースエステルフィルム１と同様にして偏光板５を作製し、偏光板１と同様にして視野角測定を行った。
【０１９０】
（偏光板６）
セルロースエステルフィルム１０を用いて、セルロースエステルフィルム１と同様にして偏光板６を作製し、偏光板１と同様にして視野角測定を行った。
【０１９１】
（偏光板７）
セルロースエステルフィルム１１（セルローストリアセテートフィルム）とセルロースエステルフィルム１の組み合わせをラミネート用の支持体として、以下の手順で偏光板７を作製した。
【０１９２】
まず、厚さ１２０μｍのポリビニルアルコールフィルムをヨウ素１部、ヨウ化カリウム２部、ホウ酸４部を含む水溶液に浸漬し、５０℃で４倍に延伸して偏光膜を得た。次に、
（１）保護フィルムとして、図２に示したように、３０ｃｍ×１８ｃｍの長方形ＡＢＣＤに各々、切り取ったセルロースエステルフィルム１とセルロースエステルフィルム１１をそれぞれ２ｍｏｌ／Ｌの水酸化ナトリウム溶液に６０℃で１分間浸漬し、さらに水洗、乾燥させた。
（２）これらの２枚のセルロースエステルフィルムと同サイズに調整した上記記載の偏光膜を固形分２質量％のポリビニルアルコール接着剤槽中に１〜２秒間浸漬する。
（３）前記の偏光膜に付着した過剰の接着剤を軽く取り除き、図３の２枚のセルロースエステルフィルム１ａの１枚をセルロースエステルフィルム１、他の１枚をセルロースエステルフィルム１１とし、図３と同様な配置で偏光子上にセルロースエステルフィルムを積層した。
（４）ハンドローラで積層された偏光膜とセルロースエステルフィルムとの積層物の端部から過剰の接着剤及び気泡を取り除き貼り合わせる。ハンドローラは、２０〜３０Ｎ／ｃｍ^２の圧力をかけて、ローラスピードは約２ｍ／分とした。
（５）８０℃の乾燥器中に得られた試料を２分間放置し、偏光板７を作製した。次に、偏光板１と同様にして視野角測定を行った。
【０１９３】
（偏光板８）
平均重合度３８００、けん化度９９．５モル％のポリビニルアルコール１００部を水に溶解し、５．０質量％の溶液を得た。これをポリエチレンテレフタレート上に流延後乾燥して原反フィルムを得た。このフィルムをヨウ素０．２ｇ／Ｌ、ヨウ化カリウム６０ｇ／Ｌよりなる水溶液中に３０℃にて２４０秒浸漬し、次いでホウ酸７０ｇ／Ｌ、ヨウ化カリウム３０ｇ／Ｌの組成の水溶液に浸漬すると共に、同時に搬送方向に６．０倍に一軸延伸しつつ搬送しながら、５分間ホウ酸処理を行い乾燥した。一方、上述のセルロースエステルフィルム１をコア径２００ｍｍのガラス繊維強化樹脂製のコアに巾１ｍ、長さ１０００ｍのフィルムロール状に巻き取ったセルロースエステル原反フィルムを２ｍｏｌ／Ｌの水酸化ナトリウム溶液に６０℃で１分間浸漬し、さらに水洗、乾燥させた。このけん化処理セルロースエステル原反フィルムを、前述の延伸して巻き取り済みのポリビニルアルコールフィルムの両面に保護膜としてポリビニルアルコール系接着剤を用いて、ロール・ツー・ロールで連続的に貼合した。図２に示すように、３０ｃｍ×１８ｃｍの長方形ＡＢＣＤを切り取った。
【０１９４】
次に、偏光板１と同様にして視野角測定を行った。
（偏光板９）
セルロースエステルフィルム１１を用いて、セルロースエステルフィルム１と同様にして偏光板９を作製し、偏光板１と同様にして視野角測定を行った。
【０１９５】
（視野角測定）
偏光板を液晶セルの両面に、以下のように配置して貼合し、パネルで評価した。すなわち本発明の偏光板は、液晶セルの近接する基板面のラビング軸方向と偏光板透過軸が直交するように貼合した。液晶セルは、ＮＥＣ製１５インチディスプレイＭｕｌｔｉ　Ｓｙｎｃ　ＬＣＤ１５２５Ｊの予め貼合されていた光学補償フィルム及び偏光板を剥がしたものを使用した。こうして得られた液晶表示装置を、ＥＬＤＩＭ社製ＥＺ−ｃｏｎｔｒａｓｔにより視野角を測定した。視野角は、液晶セルの白表示と黒表示時のコントラスト比が１０以上を示すパネル面に対する法線方向からの傾き角の範囲で表した。測定結果を表２に示す。
【０１９６】
【表２】

【０１９７】
表２から、比較例に比べて本発明の偏光板は、著しく視野角が改善されていることが明らかである。
【０１９８】
実施例２
下記のようにして、偏光板１０〜１４を作製した。
【０１９９】
（偏光板１０）
（セルロースエステルフィルムＡの作製）
以下の手順により、偏光板保護フィルム用のセルローストリアセテートフィルム（セルロースエステルフィルムＡ）を作製した。
【０２００】
アセチル基の置換度２．００、プロピオニル基の置換度０．６０、粘度平均重合度３５０のセルロースアセテートプロピオネート１０質量部、塩化メチレン２９０質量部を密閉容器に入れ、完全に溶解した。次にジフェニルイソシアネート５質量部を加え８０℃に加熱し、攪拌しながら反応させた。反応後ドープを室温に戻し、アセチル基の置換度２．００、プロピオニル基の置換度０．６０、粘度平均重合度３５０のセルロースアセテートプロピオネート９０質量部、エチルフタリルエチルグリコレート５質量部、トリフェニルフォスフェイト３質量部、エタノール６０質量部を加え、混合物をゆっくり攪拌しながら徐々に昇温し、６０分かけて４５℃まで上げ溶解した。容器内は１２０ｋＰａとなった。このドープを安積濾紙（株）製の安積濾紙Ｎｏ．２４４を使用して濾過した後、２４時間静置しドープ中の泡を除いた。
【０２０１】
また、これとは別に、上記セルロースアセテートプロピオネート５質量部、チヌビン３２６（チバ・スペシャルティ・ケミカルズ（株）製）６質量部、チヌビン１０９（チバ・スペシャルティ・ケミカルズ（株）製）４質量部、チヌビン１７１（チバ・スペシャルティ・ケミカルズ（株）製）５質量部を塩化メチレン９４質量部とエタノール８質量部を混合した溶媒に加え撹拌溶解し、紫外線吸収剤溶液を調製した。
【０２０２】
上記ドープ１００質量部に対して前記紫外線吸収剤溶液を２質量部の割合で加え、スタチックミキサーにより十分混合した後、ダイからステンレスベルト上にドープ温度３０℃で流延した。ステンレスベルトの裏面から２５℃の温水を接触させて温度制御されたステンレスベルト上で１分間乾燥した後、更にステンレスベルトの裏面に、１５℃の冷水を接触させて１５秒間保持した後、ステンレスベルトから剥離した。
【０２０３】
剥離時のウェブ中の残留溶媒量は１００質量％であった。次いで延伸テンターを用いて剥離したウェブの両端をクリップで掴み、クリップ間隔の巾方向を変化させることで、１２０℃で巾方向のみに１．０７倍延伸した。更にローラー搬送しながら１３０℃で１０分間乾燥させ、膜厚８０μｍのセルロースエステルフィルムＡを得た。
【０２０４】
得られたセルロースエステルフィルムＡと、実施例１に記載のセルロースエステル７を用いて、実施例１の偏光板１と同様にして偏光板１０を作製した。
【０２０５】
（偏光板１１）
剥離後の幅方向の延伸倍率を１．１５倍とした以外はセルロースエステルフィルムＡと同様の手順により、偏光板保護フィルム用のセルローストリアセテートフィルム（セルロースエステルフィルムＢ）を作製した。
【０２０６】
このセルロースエステルフィルムＢを用いて、偏光板１０の場合と同様にして偏光板１１を作製した。
【０２０７】
（偏光板１２）
剥離後の幅方向の延伸倍率を１．２０倍とした以外はセルロースエステルフィルムＡと同様の手順により、偏光板保護フィルム用のセルローストリアセテートフィルム（セルロースエステルフィルムＣ）を作製した。
【０２０８】
このセルロースエステルフィルムＣを用いて、偏光板１０の場合と同様にして偏光板１２を作製した。
【０２０９】
（偏光板１３）
剥離後の幅方向の延伸倍率を１．０２倍とした以外はセルロースエステルフィルムＡと同様の手順により、偏光板保護フィルム用のセルローストリアセテートフィルム（セルロースエステルフィルムＤ）を作製した。
【０２１０】
このセルロースエステルフィルムＤを用いて、偏光板１０の場合と同様にして偏光板１３を作製した。
【０２１１】
（偏光板１４）
ジフェニルイソシアネートを添加せず、剥離後の幅方向の延伸を行わなかったこと以外はセルロースエステルフィルムＡと同様の手順により、偏光板保護フィルム用のセルローストリアセテートフィルム（セルロースエステルフィルムＥ）を作製した。
【０２１２】
このセルロースエステルフィルムＥを用いて、偏光板１０の場合と同様にして偏光板１４を作製した。
【０２１３】
（偏光板の評価）
得られた偏光板について、実施例１に記載の方法で視野角測定を行い（強制劣化処理なし）、次に作製後の偏光板を８０℃、９０％ＲＨ条件下で５００時間静置（強制劣化処理あり）した後、同様にして視野角測定を行った。強制劣化処理した偏光板については目視でカール特性を観察した。その結果を表３に示す。
【０２１４】
【表３】

【０２１５】
表３から、本発明のセルロースエステルフィルムを有する偏光板１０〜１４は、良好な視野角改善効果が見られることが明らかである。また、強制劣化処理をした場合、偏光板を構成する２枚のセルロースエステルフィルムのうち、本発明のセルロースエステルフィルムを１枚のみ使用した偏光板１４については、保存後の視野角の劣化がやや観察され、また、黒表示時に光漏れ等が観察されたが、２枚とも本発明のセルロースエステルフィルムを用いた偏光板１０〜１３は経時保存後も保存前と同様に優れた視野角改善効果を示していることが判る。
【０２１６】
また、偏光板１０〜１４は、一方の面を延伸倍率１．２０のセルロースエステルフィルム７を各々用いているが、強制劣化処理（６０℃、９０％、５００時間処理）後の偏光板のカール特性を目視で観察した結果、延伸操作を行わなかったセルロースエステルフィルムＥを片面の保護フィルムに使用した偏光板１４は偏光板自身の寸法変化によるカールが観察されたのに対し、延伸倍率２％（セルロースエステルフィルムＤ）、２０％（セルロースエステルフィルムＣ）、１５％（セルロースエステルフィルムＢ）、７％（セルロースエステルフィルムＡ）のセルロースエステルフィルムを各々、片面の保護フィルムとした場合は、延伸倍率２％、２０％のもので改善が見られ、１５％、７％ではほとんどカールは発生しなかった。
【０２１７】
【発明の効果】
本発明により、ＴＮ−ＴＦＴ等のＴＮ型ＬＣＤの視野角特性、すなわち、斜め方向から見た場合の画面上下方向のコントラスト、着色、明暗の反転現象を簡便に改善できる視野角拡大偏光板とその偏光板に用いられるセルロースエステルフィルムを提供することであり、更に、前記視野角拡大偏光板を用いて、簡単な構成で上下方向の視野角が改善される液晶表示装置を提供することができた。
【図面の簡単な説明】
【図１】本発明の液晶表示装置の構成を示す模式図である。
【図２】流延製膜により作製された本発明の長尺のセルロースエステルフィルムの模式図である。
【図３】本発明の偏光板の構成を示す模式図である。
【符号の説明】
１ａ、１ｂ　セルロースエステルフィルム
２ａ、２ｂ　偏光子
３ａ、３ｂ、１１　流延方向
４ａ、４ｂ　延伸方向
５ａ、５ｂ　ラビング軸
６ａ、６ｂ　偏光板
７　液晶セル
８ａ、８ｂ　光透過軸
９　液晶表示装置
１０　長尺のセルロースエステルフィルム
１２　幅手方向[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a cellulose ester film, a polarizing plate, a method for producing the same, and a liquid crystal display device.
[0002]
[Prior art]
Conventionally, the following four types of configurations have been tried as optical compensation films used for expanding the viewing angle of a liquid crystal display device, and each of them has been proposed as an effective method.
(1) A method of supporting a discotic liquid crystalline compound, which is a compound having negative uniaxiality, on a support (for example, see Patent Document 1)
(2) A method in which a nematic-type polymer liquid crystalline compound having positive optical anisotropy and having a hybrid orientation in which the pretilt angle of liquid crystal molecules changes in the depth direction is supported on a support (for example, see Patent Document 1). 2)
(3) By forming a nematic liquid crystal compound having a positive optical anisotropy into a two-layer structure on a support and setting the orientation direction of each layer to about 90 °, pseudo-negative uniaxial similarity is obtained. Method for imparting optical characteristics (for example, see Patent Document 3)
(4) A method in which an optically biaxial cellulose ester film is attached to a polarizer by stretching (for example, see Patent Document 4).
[0003]
However, each of the above-described configurations has the following problems. In the method (1), when applied to a TN mode liquid crystal cell, a disadvantage peculiar to the discotic liquid crystal compound that a screen when viewed from an oblique direction is colored yellow appears.
[0004]
In the method (2), the liquid crystal development temperature is high, and the orientation of the liquid crystal cannot be fixed on an isotropic transparent support such as TAC (cellulose triacetate). Thereafter, it is necessary to transfer to a support such as TAC, which complicates the process and extremely lowers productivity.
[0005]
As an example of the above method (3), for example, JP-A-8-15681 discloses a method in which a rod-shaped positive uniaxial low-molecular liquid crystal compound is used as an optically anisotropic layer through a polarizer having alignment ability. A layer of a rod-shaped positive uniaxial low-molecular liquid crystalline compound oriented and formed is fixed, fixed on the layer, and further re-oriented via a polarizer having an alignment ability on this layer. Discloses a four-layer optically anisotropic layer in which a layer made of a uniaxial low-molecular liquid crystal compound is formed and fixed. In this case, by giving the alignment directions projected in the plane of the two liquid crystal layers, for example, shifted by 90 degrees, it is possible to give a pseudo disk-like characteristic.
[0006]
Therefore, the method described in the above (3) has no coloring problem unlike the case of the discotic liquid crystalline compound, and therefore has a very advantageous feature in applications such as a liquid crystal TV (television) where importance is placed on color reproduction. Have.
[0007]
However, this method is achieved by using two liquid crystal layers daringly to achieve the discotic liquid crystal compound with one layer, and has a problem that the efficiency is extremely low.
[0008]
Furthermore, all of these methods (1) to (3) have more fundamental and common problems. That is, according to these methods, it is necessary to precisely apply a liquid crystal compound in a thin film in order to obtain optical compensation ability. In order to orient and apply the liquid crystal compound, a process (rubbing treatment, polarization exposure treatment, etc.) for applying an orientation layer in advance and imparting an alignment regulating force is performed. Means that the cost is very high in the method of improving the viewing angle. In addition, as a method without using a liquid crystal compound, a biaxially oriented retardation plate is prepared by stretching a resin usually used as a retardation plate such as a polycarbonate, and the post-laminating treatment is performed on a polarizing plate. There is a method of increasing the viewing angle by forming a so-called elliptically polarizing plate. For example, a commercially available VAC film or NewVAC film is available from Sumitomo Chemical Co., Ltd. However, it is very difficult to uniformly stretch such a biaxially oriented retardation plate in terms of material, and requires an advanced stretching technique. There was also a problem that the yield was low. Further, since this retardation plate is used after being bonded and bonded to a polarizing plate, the number of manufacturing steps is increased, and the increase in cost cannot be avoided. As described above, there has been no polarizing plate having a viewing angle expanding effect at low cost by the same manufacturing method as that of the conventional polarizing plate.
[0009]
In the method (4), the viewing angle can be easily improved by using the stretched cellulose ester film as the polarizer protective film. However, this method has a problem that the draw ratio is large and the production cost is increased.
[0010]
[Patent Document 1]
JP-A-7-325221
[0011]
[Patent Document 2]
JP-A-10-186356
[0012]
[Patent Document 3]
JP-A-8-15681
[0013]
[Patent Document 4]
JP 2002-187960 A
[0014]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION An object of the present invention is to provide a viewing angle widening polarizer that can easily improve viewing angle characteristics of a TN type LCD such as a TN-TFT, that is, contrast in the vertical direction of the screen, coloring, and inversion of light and dark when viewed from an oblique direction. And a cellulose ester film used for the polarizing plate, and further, by using the viewing angle-enlarging polarizing plate, to provide a liquid crystal display device in which the vertical viewing angle is improved with a simple configuration. is there.
[0015]
[Means for Solving the Problems]
The above object of the present invention is achieved by the following configurations.
[0016]
1. Contains a compound that has at least one aromatic ring and at least one reactive group in the molecule that reacts and bonds with the residual hydroxyl group of the cellulose ester, and is optically biaxial. Cellulose ester film.
[0017]
2. It is characterized by containing 0.1 to 20 parts by mass of a compound having at least one aromatic ring and having at least one group bonding to a hydroxyl group in a molecule with respect to 100 parts by mass of the cellulose ester. 2. The cellulose ester film as described in 1 above.
[0018]
3. 3. The cellulose ester film as described in 1 or 2 above, which is long.
[0019]
4. 4. The cellulose ester film as described in any one of the above items 1 to 3, wherein the in-plane retardation value R0 is 30 to 300 nm.
[0020]
5. The cellulose ester film according to any one of the above items 1 to 4, wherein the retardation value Rt in the thickness direction is 30 to 300 nm.
[0021]
6. The cellulose ester film according to any one of the above items 1 to 5, which satisfies the formulas (1) and (2) simultaneously.
[0022]
7. A polarizing plate, comprising the cellulose ester film according to any one of the above items 1 to 6.
[0023]
8. A polarizing plate having a cellulose ester film according to any one of the above 1 to 6 and a polarizer containing a dichroic substance, wherein the light transmission axis of the polarizer and the maximum refractive index in the plane of the cellulose ester film. A polarizing plate, wherein an angle between the direction and a direction to be given is −10 ° to 10 °.
[0024]
9. The cellulose ester film according to any one of the above 1 to 6, a cellulose ester film b different from or the same as the cellulose ester film, and a polarizing plate having a polarizer containing a dichroic substance, wherein the cellulose ester film b. The polarizing plate, wherein b is stretched in the same direction as the cellulose ester film.
[0025]
10. 10. The polarizing plate according to the above item 9, wherein the cellulose ester film b is stretched in the width direction during or after film formation.
[0026]
11. The polarizing plate according to the above item 9 or 10, wherein the cellulose ester film or the cellulose ester film b is stretched so that the stretching ratio becomes 1.02 to 1.2 times.
[0027]
12. 12. The liquid crystal display device having the polarizing plate and the liquid crystal cell according to any one of the items 7 to 11, wherein the cellulose ester film of the polarizing plate is formed of a polarizer containing the dichroic substance of the polarizing plate and the liquid crystal cell. A liquid crystal display device, which is disposed between them.
[0028]
13. 13. The liquid crystal display device according to the above item 12, wherein a light transmission axis of the polarizing plate is orthogonal to a rubbing axis or a liquid crystal alignment axis on a side where the polarizing plate of the liquid crystal cell is arranged.
[0029]
14． The angle between the direction in which the refractive index of the cellulose ester film of the polarizing plate disposed on the bonding surface side of the polarizing plate and the liquid crystal cell and the light transmission axis of the polarizing plate is −10 ° to 10 °. 14. The liquid crystal display device according to the above 13, wherein the liquid crystal display device is adjusted to:
[0030]
15. The method for producing a cellulose ester film according to any one of the above 1 to 6, wherein an operation of optically imparting biaxiality to the cellulose ester film is performed, and the cellulose ester film is produced as a long roll. Of producing a cellulose ester film.
[0031]
16. The method for producing a polarizing plate according to any one of the above 7 to 11,
(1) A step of producing an elongated roll of a cellulose ester film by performing an operation of optically imparting biaxiality and adjusting the refractive index in the width direction at the time of casting film formation to be maximum.
(2) Step of forming polarizer containing dichroic substance
(3) a step of laminating the polarizer on the long roll
A method for producing a polarizing plate, comprising:
[0032]
Hereinafter, the present invention will be described in detail.
The cellulose ester film of the present invention will be described. Conventionally, the optical compensation film used is a method in which a liquid crystal compound is uniformly coated and aligned on a transparent support, or a biaxial stretching retardation is carried out by making use of a complicated stretching technique for a resin such as polycarbonate. Optical films having such complicated optical anisotropy, such as a method using a plate, have been used by being bonded to a polarizing plate. After that, it was found that the optically biaxial cellulose ester film has sufficient optical compensating ability and can maintain stable optical compensating ability even under high temperature and high humidity conditions, and is used as a protective film. The obtained elliptically polarizing plate was found. However, there is a problem that the stretching ratio at the time of producing the cellulose ester film is as large as 1.4 times.
[0033]
This time, the present inventors, in the cellulose ester film, having at least one aromatic ring, and containing a compound having at least one group in the molecule that binds to the hydroxyl group, the draw ratio of the conventional. The inventors have found that an elliptically polarizing plate using a cellulose ester film prepared as a protective film for a polarizer, which has been manufactured at a magnification of 1.2 times, can provide the same optical compensation effect as the elliptically polarizing plate. The polarizing plate of the present invention can include a so-called elliptically polarizing plate having a phase difference function.
[0034]
The polarizing plate using the cellulose film of the present invention has a high contrast when viewed from an oblique direction, and not only has a wide viewing angle, but also has no coloring on the screen when viewed from an oblique direction, and also has an inversion area. It was found that excellent optical compensating ability such as narrowing was exhibited.
[0035]
Furthermore, the cellulose ester film used for the polarizing plate having a viewing angle widening effect of the present invention has a feature of being optically biaxial, but when a cellulose ester film is used, it is necessary to obtain such optical characteristics. It is not necessary to perform biaxial stretching, and optically biaxiality can be obtained only by performing uniaxial stretching. This means that the cast cellulose ester film itself is originally negative uniaxial (nx = ny>nz; nx, ny are the in-plane X and Y directions of refractive index, and nz is the film thickness Z direction). (Refractive index). Here, having optically biaxiality means that nx ≠ ny ≠ nz.
[0036]
When producing a polarizing plate, an optically biaxial cellulose ester film can be used as a protective film on the liquid crystal cell side (between the dichroic substance constituting the polarizing plate and the liquid crystal cell), Since the optical property of the support on the opposite side (outermost side) is not particularly limited, a cellulose triacetate film (TAC film) which is usually used may be used as the type of the protective film. In this case, for example, an elliptically polarizing plate capable of maintaining very stable optical characteristics even under high temperature and high humidity conditions can be obtained by performing stretching operation of the TAC film at least in a width direction at a certain magnification.
[0037]
The compound having at least one aromatic ring in the present invention and having at least one group bonded to a hydroxyl group in a molecule is a compound having at least one aromatic ring and an unreacted hydroxyl group of a cellulose ester. Is a compound having a group that reacts and bonds with, for example, aldehyde compounds such as monoaldehyde and dialdehyde represented by benzaldehyde, phenyl isocyanate, phenylthioisocyanate, tolyl isocyanate, tolylthioisocyanate, pentafluorophenylisocyanate, Pentafluorophenylthioisocyanate, 1-naphthyl isocyanate, 2-naphthyl isocyanate, 2-naphthylthioisocyanate, 2-fluorene isocyanate, 4-phenylcyanoisocyanate, 2,4-difluorophenyliso Anate, 4-fluorophenylthioisocyanate, 2,5-dichlorophenylisocyanate, 4-iodophenylthioisocyanate, 4-pyridylisocyanate, tolylenediisocyanate (also called "TDI"), 4,4'-diphenylmethanediisocyanate ("MDI") ), Mono-isocyanates such as xylylene diisocyanate, meta-xylylene diisocyanate, 1,5-naphthalenedi isocyanate, monothioisocyanate, diisocyanate, dithioisocyanate compounds, and adduct polyisocyanate compounds such as Coronate HL (manufactured by Nippon Polyurethane Co., Ltd.) Can be mentioned. These can be used alone or in combination of two or more.
[0038]
Furthermore, monoglycidyl ether of bisphenol A, diglycidyl ether represented by Epikote 827, epoxyphenol novolak represented by Epikote 152, and epoxycresol novolac represented by Araldite ECN1235 can be exemplified.
[0039]
Other, for example,
(1) Bisphenol F monoglycidyl ether and diglycidyl ether
(2) Diglycidyl ester compounds obtained by reacting a dibasic acid such as phthalic acid and dihydrophthalic acid with epihalohydrin
(3) Epoxy compounds obtained by reacting an aromatic amine such as aminophenol or bis (4-aminophenyl) methane with epihalohydrin
(4) aromatic-containing silane alkoxide compounds such as phenyltriethoxysilane and diphenyldiethoxysilane
(5) Acid chloride compounds such as acetoacetic acid phenyl chloride
However, the present invention is not limited to these. It is also conceivable to add these functional groups to the side chains of cellulose by a technique such as transesterification.
[0040]
Among compounds having one or more aromatic rings and one or more groups bonded to a hydroxyl group in the molecule, particularly preferred are monoisocyanates, monothioisocyanates, diisocyanates, and dithioisocyanate compounds. .
[0041]
The addition amount of the compound having at least one of these aromatic rings and having at least one group bonding to a hydroxyl group in the molecule is not particularly limited, but the stretching ratio of the film, the film strength, and the flatness are not particularly limited. Is preferably in the range of 0.1 to 20% by mass, more preferably 1 to 10% by mass, based on the substrate polymer.
[0042]
By producing a polarizing plate using the cellulose ester film of the present invention, just by replacing the type of cellulose ester film used for the support, by using the conventional polarizing plate production process as it is a normal polarizing plate and A polarizing plate with a wide viewing angle can be manufactured by the same method, and there is a great practical advantage. That is, the cellulose ester film is an extremely suitable support because it can be bonded to the polarizer by being subjected to an alkali saponification treatment in the polarizing plate production step, and has excellent water removal properties after bonding. As the polarizer, usually, a stretched polyvinyl alcohol film doped with a dichroic substance is preferably used.
[0043]
The present invention includes a viewing angle expanding polarizing plate having a viewing angle expanding function only with a polarizing plate, a compound having at least one aromatic ring used for it, and having at least one group in a molecule that binds to a hydroxyl group. And a method for manufacturing a long optically biaxial cellulose ester film, a polarizing plate with a wide viewing angle, and a liquid crystal display device using the polarizing plate with a wide viewing angle. More specifically, the present invention is to improve the change in contrast due to the viewing angle peculiar to the twisted nematic (TN) type liquid crystal, and in particular, the viewing angle dependence of the display of an active matrix TN type liquid crystal display device used as a full color display.
[0044]
The optical properties of the cellulose ester film of the invention will be described. In the present invention, a cellulose ester film having optically biaxial properties is used, but the above-mentioned optical properties are usually obtained by applying tension in a certain direction in the process of producing a cellulose ester by casting. Can be. For example, it is particularly effective to perform an operation such as stretching under the condition that a residual solvent is present after casting the cellulose ester film. Further, it can also be produced by stretching a heated cellulose ester film.
[0045]
As the cellulose ester, for example, cellulose triacetate can be used, but the total degree of substitution may be more than 2.0, and in particular, a cellulose ester having a total degree of substitution of all acyl groups of 2.8 or less is preferably used. Can be Furthermore, in order to obtain a certain level of optical compensation performance, it is extremely effective to use a lower fatty acid cellulose ester having a specific substituent, that is, an acetyl group and a propionyl group.
[0046]
The cellulose ester used for producing the cellulose ester film of the present invention preferably has an acyl group having 2 to 4 carbon atoms as a substituent and satisfies the above formulas (1) and (2) simultaneously.
[0047]
Further, in the present invention, a cellulose ester film satisfying the following formulas (3) and (4) at the same time is preferably used.
[0048]
Formula (3) 2.5 ≦ A + B ≦ 2.75
Formula (4) 1.7 ≦ A ≦ 1.95
These acyl groups may be substituted at the 2-, 3-, and 6-positions of the glucose unit on average, or may be substituted at a high ratio in the 6-position. Good.
[0049]
Here, the degree of substitution refers to the percentage of the amount of bound fatty acid, and is a numerical value calculated according to the measurement and calculation of the degree of acetylation in ASTM-D817-91 (test method for cellulose acetate or the like). The degree of acyl group substitution can be measured according to ASTM-D817-96.
[0050]
When the sum of the substitution degree of the acetyl group and the acyl group having 3 to 4 carbon atoms is within the above range, there is a property that the retardation becomes larger as the wavelength becomes longer, and it has a good moisture content and water barrier property. Cellulose ester film can be obtained. In particular, it is preferable that the average degree of substitution of the acetyl group is 2.0 or less, since the dispersion of the retardation during stretching is small.
[0051]
In addition, from the viewpoint of obtaining an optical compensation film having excellent mechanical strength, the viscosity average degree of polymerization (hereinafter, also simply referred to as degree of polymerization) of the cellulose ester used in the present invention is preferably from 200 to 700, and particularly preferably from 250 to 500. Are preferred.
[0052]
The viscosity average degree of polymerization (DP) described above is determined by the following method.
<< Measurement of viscosity average degree of polymerization (DP) >>
0.2 g of absolutely dried cellulose ester is precisely weighed and dissolved in 100 ml of a mixed solvent of methylene chloride and ethanol (mass ratio 9: 1). This is measured for drop seconds at 25 ° C. using an Ostwald viscometer, and the degree of polymerization is determined by the following equation.
[0053]
(1) ηrel = T / Ts
(2) [η] = (lnηrel) / C
(3) DP = [η] / Km
Here, T is the number of seconds of falling of the measurement sample, Ts is the number of seconds of falling of the solvent, C is the concentration of cellulose ester (g / L), Km = 6 × 10 ^-4 It is.
[0054]
From the viewpoint that the viewing angle expanding effect can be more preferably obtained, the cellulose ester film according to the present invention preferably has the relationship defined by the formula (I).
[0055]
Formula (I) (nx + ny) / 2-nz> 0
Here, nx is the refractive index in the direction in which the refractive index is maximum in the plane of the cellulose ester film, ny is the refractive index in the plane and in the direction perpendicular to nx, and nz is the refractive index of the film in the thickness direction. Rate.
[0056]
Further, the optically biaxial cellulose ester support of the present invention has a viewing angle improving effect as long as it is optically biaxial, but the preferred condition is a retardation value Rt value in the thickness direction. The in-plane retardation value R0 can be specified, and by appropriately controlling these values, the viewing angle enlarging effect can be significantly improved. As a specific control method, a stretching method described later or the like can be used.
[0057]
Regarding the retardation value Rt in the thickness direction, the retardation value (Rt value) defined by the following formula (II) is preferably from 30 to 300 nm, and more preferably from 60 to 250 nm.
[0058]
Formula (II) ((nx + ny) / 2-nz) × d
Further, the retardation value R0 in the in-plane direction is represented by the following equation.
[0059]
R0 = (nx−ny) × d
Here, d is the thickness (nm) of the film.
[0060]
In the present invention, R0 is preferably from 0 to 300 nm, more preferably from 40 to 150 nm.
[0061]
<< Measurement of retardation values Rt and R0 >>
The retardation values Rt and R0 described above were measured using an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments) at a wavelength of 590 nm under an environment of 23 ° C. and 55% RH. It can be obtained by performing a two-dimensional refractive index measurement and determining the refractive indexes nx, ny, and nz.
[0062]
The optically biaxial cellulose ester film of the present invention is preferably a transparent support having a light transmittance of 80% or more, more preferably 92% or more. Further, the cellulose ester film of the present invention preferably has a thickness of 30 to 150 μm.
[0063]
The mixed fatty acid ester of cellulose used in the present invention can be synthesized using an acid anhydride or an acid chloride as an acylating agent. When the acylating agent is an acid anhydride, an organic acid (eg, acetic acid) or methylene chloride is used as a reaction solvent. As the catalyst, an acidic catalyst such as sulfuric acid is used. When the acylating agent is an acid chloride, a basic compound is used as a catalyst. According to the most common synthetic method in industry, cellulose is treated with an organic acid corresponding to acetyl group and propionyl group (acetic acid, propionic acid) or a mixed organic acid component containing their acid anhydride (acetic anhydride, propionic anhydride). It is esterified to synthesize a cellulose ester. The amounts of the acetylating agent and the propionylating agent are adjusted so that the ester to be synthesized falls within the above-mentioned substitution degree. The amount of the reaction solvent to be used is preferably 100 to 1000 parts by mass, more preferably 200 to 600 parts by mass, based on 100 parts by mass of the cellulose. The amount of the acidic catalyst is preferably from 0.1 to 20 parts by mass, more preferably from 0.4 to 10 parts by mass, based on 100 parts by mass of the cellulose.
[0064]
The reaction temperature is preferably from 10 to 120C, more preferably from 20 to 80C. Note that another acylating agent (eg, a butylating agent) or an esterifying agent (eg, a sulfuric esterifying agent) may be used in combination. After the acylation reaction is completed, the degree of substitution may be adjusted by hydrolysis (saponification) as necessary. After completion of the reaction, the reaction mixture is separated by a conventional means such as precipitation, washed and dried to obtain a mixed fatty acid ester of cellulose (cellulose acetate propionate).
[0065]
As the cellulose ester used in the present invention, either cellulose triacetate synthesized from cotton linter or cellulose triacetate synthesized from wood pulp can be used alone or in combination. It is preferable to use a large amount of cellulose ester synthesized from a cotton linter having good releasability from a belt or a drum because the production efficiency is high. When the proportion of cellulose ester synthesized from cotton linter is 60% by mass or more, the effect of releasability becomes remarkable, preferably 60% by mass or more, more preferably 85% by mass or more, and most preferably used alone. preferable.
[0066]
Further, the cellulose ester acylated with an acetyl group and an acyl group having 3 or 4 carbon atoms used in the present invention is also called a mixed fatty acid ester of cellulose.
[0067]
Examples of the acyl group having 3 or 4 carbon atoms include a propionyl group and a butyryl group. A propionyl group or an n-butyryl group is preferable from the viewpoint of mechanical strength and ease of dissolution when formed into a film, and a propionyl group is particularly preferable.
[0068]
Solvents for dissolving the fatty acid cellulose ester to form a dope include methylene chloride, methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran, 1,3-dioxolan, cyclohexanone, 2,2,2-trifluoroethanol, Examples thereof include 2,3,3-hexafluoro-1-propanol and 1,3-difluoro-2-propanol.
[0069]
Among them, chlorinated solvents such as methylene chloride can be preferably used, but methyl acetate, ethyl acetate, acetone and the like are also preferably used. In particular, it is preferable that methyl acetate is contained in an amount of 50% by mass or more based on the total organic solvent, and it is preferable to use 5 to 30% by mass of acetone based on the total organic solvent in combination with methyl acetate because the viscosity of the dope solution can be reduced.
[0070]
The fatty acid cellulose ester dope used in the present invention preferably contains 1 to 30% by mass of an alcohol having 1 to 4 carbon atoms in addition to the organic solvent. After the alcohol is contained, after the dope is cast on the casting support, the solvent starts to evaporate, and when the ratio of the alcohol increases, the web (dope film) gels to make the web strong and the casting support. From the organic solvent, and further has an effect of promoting the dissolution of the fatty acid cellulose ester in the organic solvent. Examples of the alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol and tert-butanol. Of these, ethanol is preferred because it has good stability of the dope, a relatively low boiling point, good drying properties, and no toxicity.
[0071]
Usually, the solid concentration of the dope is preferably from 10 to 40% by mass, and the viscosity of the dope is preferably adjusted to a range of from 10 to 50 Pa · sec, from the viewpoint of obtaining good film flatness.
[0072]
The dope adjusted as described above is filtered by a filter medium, defoamed, and sent to the next step by a pump. In the dope, a plasticizer, a matting agent, an ultraviolet absorber, an antioxidant, a dye, a moisture permeability improving agent and the like may be added.
[0073]
Since the fatty acid cellulose ester having an acetyl group and a propionyl substituent used in the present invention itself exhibits an effect as a plasticizer, sufficient film properties can be obtained without adding a plasticizer or with a small addition amount. Although it is obtained, a plasticizer may be added for other purposes. For example, for the purpose of improving the moisture resistance of the film, alkylphthalylalkylglycolates, phosphates, carboxylate esters, citrate esters, and the like can be mentioned.
[0074]
Examples of the alkylphthalylalkyl glycolates include, for example, methylphthalylmethyl glycolate, ethylphthalylethyl glycolate, propylphthalylpropyl glycolate, butylphthalylbutyl glycolate, octylphthalyloctyl glycolate, and methylphthalyl Ethyl glycolate, ethyl phthalyl methyl glycolate, ethyl phthalyl propyl glycolate, methyl phthalyl butyl glycolate, ethyl phthalyl butyl glycolate, butyl phthalyl methyl glycolate, butyl phthalyl ethyl glycolate, propyl phthalyl butyl Glycolate, butylphthalylpropyl glycolate, methylphthalyloctyl glycolate, ethylphthalyloctyl glycolate, octylphthalylmethyl glycolate, octylphthalate Ethyl glycolate, and the like.
[0075]
Examples of the phosphate esters include triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, phenyl diphenyl phosphate, octyl diphenyl phosphate, trioctyl phosphate, tributyl phosphate, and the like.
[0076]
Examples of the carboxylic acid ester include phthalic acid esters and citric acid esters. Examples of the phthalic acid esters include dimethyl phthalate, diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, and di-2. -Ethylhexyl phthalate and the like.
[0077]
Examples of the citrate esters include acetyltriethyl citrate, acetyltriethyl citrate, and acetyltributyl citrate.
[0078]
In addition, butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, triacetin and the like are preferably used alone or in combination. If necessary, two or more plasticizers may be used in combination. When used for a cellulose ester, the use ratio of a phosphate ester-based plasticizer is preferably 50% by mass or less because hydrolysis of the cellulose ester film hardly occurs and durability is excellent. It is more preferable that the ratio of the phosphate plasticizer is smaller, and it is particularly preferable to use only the phthalate or glycolate plasticizer. Among them, methyl phthalyl methyl glycolate, ethyl phthalyl ethyl glycolate, propyl phthalyl propyl glycolate, butyl phthalyl butyl glycolate, octyl phthalyl octyl glycolate is preferable, and particularly ethyl phthalyl ethyl glycolate is preferably used. . Further, two or more of these alkylphthalylalkyl glycolates may be used as a mixture. The amount of the plasticizer used for this purpose is preferably from 1 to 30% by mass, particularly preferably from 4 to 13% by mass, based on the cellulose ester.
[0079]
These compounds may be added together with the cellulose ester and the solvent when preparing the cellulose ester solution, or may be added during or after the solution is prepared.
[0080]
A dye may be added for the purpose of improving the yellowness of the film. It is preferable that the color can be colored gray as seen in a usual photographic support. However, unlike photographic supports, it is not necessary to prevent light piping, so that the content may be small, and the content is preferably 1 to 100 ppm, more preferably 2 to 50 ppm, by mass relative to the cellulose ester.
[0081]
Since the cellulose ester has a slightly yellow tint, a blue or purple dye is preferably used. A plurality of dyes may be combined as appropriate to make them gray.
[0082]
If the films are not slippery, the films may block each other, resulting in poor handling. In that case, the film according to the present invention, silicon dioxide, titanium dioxide, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, calcium phosphate and other inorganic fine particles and a matting agent such as a crosslinked polymer. It is preferable to include them.
[0083]
Fine particles such as silicon dioxide are preferably surface-treated with an organic substance because the haze of the film can be reduced. Preferred organic materials for the surface treatment include halosilanes, alkoxysilanes, silazanes, siloxanes and the like. The larger the average diameter of the fine particles, the greater the matting effect, and the smaller the average diameter, the better the transparency. Therefore, the average diameter of the primary particles of the fine particles is preferably 5 to 50 nm, more preferably 7 to 14 nm. These fine particles are usually present as an aggregate in the film, and it is preferable to form irregularities of 0.01 to 1.0 μm on the film surface. Examples of the fine particles of silicon dioxide include AEROSIL 200, 300, R972, R974, R202, R812, OX50, TT600, and the like, preferably AEROSIL R972V, 200V, R972, R974, R202, R812, and the like. .
[0084]
It is preferable to mix the matting agent so that the haze of the film is 0.6% or less and the dynamic friction coefficient is 0.5 or less.
[0085]
The content of the matting agent used for this purpose is preferably from 0.005 to 0.3% by mass based on the fatty acid cellulose ester.
[0086]
Further, since the cellulose ester film of the present invention is incorporated in a liquid crystal display device and is often used outdoors, it is preferable that the cellulose ester film has a function of cutting off ultraviolet rays. From such a viewpoint, the cellulose ester film support according to the present invention preferably contains an ultraviolet absorber.
[0087]
As the ultraviolet absorber, those which are excellent in the ability to absorb ultraviolet light having a wavelength of 370 nm or less from the viewpoint of deterioration of the liquid crystal and absorb as little as possible visible light having a wavelength of 400 nm or more from the viewpoint of good liquid crystal display properties are preferably used. Can be In particular, the transmittance at a wavelength of 370 nm needs to be 10% or less, and more preferably 5% or less.
[0088]
The ultraviolet absorber used for this purpose preferably has no absorption in the visible light region, and examples thereof include benzotriazole-based compounds, benzophenone-based compounds, and salicylate-based compounds.
[0089]
Examples of these compounds include 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) benzotriazole, (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) benzotriazole, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-n-octoxybenzophenone, 4-dodecyloxy-2-hydroxybenzophenone, 2,2 ', 4,4'-tetrahydroxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, phenyl salicylate, methyl salicylate and the like.
[0090]
In the present invention, one or more of these ultraviolet absorbers are preferably used, and two or more different ultraviolet absorbers may be contained.
[0091]
As a method of adding the ultraviolet absorber, the ultraviolet absorber may be dissolved in an organic solvent such as alcohol, methylene chloride, or dioxolane and then added to the dope, or may be directly added to the dope composition. Those which do not dissolve in an organic solvent, such as inorganic powders, are dispersed in an organic solvent and a cellulose ester using a dissolver or a sand mill and then added to the dope.
[0092]
The amount of the UV absorber used is 0.1 to 5% by mass, preferably 0.5 to 2.5% by mass, more preferably 0.8 to 2.0% by mass based on the cellulose ester. If the amount of the ultraviolet absorber is more than 2.5% by mass, the transparency tends to deteriorate, which is not preferable.
[0093]
For the purpose of improving the heat resistance of the film, hindered phenol-based compounds are preferably used, and the addition amount of these compounds is preferably 1 ppm to 1.0% by mass relative to the cellulose ester, and 10 to 1000 ppm. More preferred. In addition, a heat stabilizer such as a salt of an alkaline earth metal such as calcium and magnesium may be added.
[0094]
In addition to the above, an antistatic agent, a flame retardant, a slipping agent, and the like may be appropriately added. Further, since the cellulose ester film according to the present invention is disposed between the polarizing plates, a foreign substance that generates abnormally refracted light causes performance degradation. At that point, a so-called bright spot-like abnormality becomes a problem.
[0095]
In the present invention, the luminescent spot recognized in the polarization crossed Nicols state is observed when two polarizing plates are set in a crossed (crossed Nicols) state, and a cellulose ester film is interposed therebetween and light from a light source is applied from the opposite side. Means something. In the polarization crossed Nicol state, such bright spots are observed only in the bright spots in the dark field, so that their size and number can be easily identified.
[0096]
The number of bright spots is 250 mm ² It is preferable that 200 or less bright spots having a size of 5 to 50 μm and 0 bright spots having a size of 50 μm or more are recognized in a polarized cross nicol state. More preferably, the number of luminescent spots of 5 to 50 μm is 100 or less, particularly preferably 0 to 10. If there are many such bright spots, it will have a serious adverse effect on the image on the liquid crystal display.
[0097]
The method for producing the cellulose ester film of the present invention will be described. As a method for producing a cellulose ester film, a dope solution is cast on a support for casting, a film is formed, the obtained film is peeled off from the support, and then, while being transported through a drying zone under tension. A solution casting film forming method of drying is preferred. The solution casting method will be described below.
[0098]
(1) Dissolution step: This is a step of dissolving the flakes in an organic solvent mainly containing a good solvent for the cellulose ester flakes in a dissolving vessel with stirring to form a cellulose ester solution (dope). The dissolution is carried out at normal pressure, at a temperature below the boiling point of the main solvent, at a pressure at or above the boiling point of the main solvent, M. G. FIG. Makromol. chem. 143, p. 105 (1971), and a cooling dissolution method of dissolving at a low temperature, a method of high-pressure dissolution, and the like described in JP-A-9-95544 and JP-A-9-95557. There is a dissolution method. After dissolution, the dope is filtered with a filter medium, defoamed, and sent to the next step by a pump.
[0099]
(2) Casting step: The dope is fed to a pressurizing die through a pressurized metering gear pump and, at a casting position, an endless metal belt or a casting support for a rotating metal drum (hereinafter simply referred to as a casting support). This is a step of casting a dope from a pressure die onto a support. The surface of the casting support is a mirror surface. Other casting methods include a doctor blade method of adjusting the film thickness of the cast dope film with a blade, and a reverse roll coater method of adjusting the film with a counter-rotating roll. A pressure die that can be adjusted and is easy to make the film thickness uniform is preferable. Examples of the pressure die include a coat hanger die and a T die, and any of them is preferably used. In order to increase the film forming speed, two or more pressure dies may be provided on the casting support, and the doping amount may be divided to form an overlying layer. Alternatively, a cellulose ester film having a laminated structure can be formed by using a co-casting method.
[0100]
(3) Solvent evaporation step: a step of evaporating the solvent by heating the web (the web is referred to as a dope film after casting the dope on the casting support) on the casting support. . In order to evaporate the solvent, there are a method of blowing air from the web side and / or a method of transferring heat with liquid from the back surface of the support, a method of transferring heat from the front and back by radiant heat, and the like. Drying efficiency is good and preferable. A method of combining them is also preferable.
[0101]
(4) Peeling step: This is a step of peeling the web, on which the solvent has evaporated on the support, at the peeling position. The peeled web is sent to the next step. If the residual solvent amount (the following formula) of the web at the time of peeling is too large, it is difficult to peel the web, or conversely, if the web is sufficiently dried on the support and then peeled, a part of the web is peeled in the middle.
[0102]
As a method of increasing the film forming speed, there is a gel casting method (gel casting) that can peel even if the residual solvent is large (the film forming speed can be increased because the film is separated while the amount of the residual solvent is as large as possible). Examples of the method include a method in which a poor solvent for the cellulose ester is added to the dope, gelling is performed after casting the dope, and a method in which the temperature of the support is lowered to gelate. There is also a method of adding a metal salt to the dope. By gelling on the support and strengthening the film, separation can be accelerated and the film forming speed can be increased. If the residual solvent amount is greater at the time of peeling, if the web is too soft, the flatness at the time of peeling will be impaired, or the shear and vertical stripes due to the peel tension are likely to occur, and the amount of the residual solvent peeling will be reduced in consideration of economic speed and quality. I can decide.
[0103]
(5) Drying step: a step of drying the web using a drying device that alternately transports the web through rolls arranged in a staggered manner and / or a tenter device that transports the web by clipping both ends of the web with clips. In general, hot air is blown to both sides of the web as a drying means, but there is also a method of heating by applying a microwave instead of the wind. Very rapid drying tends to impair the flatness of the resulting film. Drying at a high temperature is preferably performed when the residual solvent is at most about 8% by mass. In general, the drying temperature is usually 40 to 250C, preferably 70 to 180C. The drying temperature, the amount of drying air, and the drying time vary depending on the solvent used, and the drying conditions may be appropriately selected according to the type and combination of the solvents used.
[0104]
In the drying step after peeling off from the surface of the casting support, the web tends to shrink in the width direction due to evaporation of the solvent. The quicker it dries at higher temperatures, the greater the shrinkage. Drying while suppressing this shrinkage as much as possible is preferable for improving the flatness of the resulting film. From this viewpoint, for example, a method of drying all the steps or a part of the steps as described in Japanese Patent Application Laid-Open No. Sho 62-46625 while holding both ends of the width of the web with clips in the width direction (tenter method) Is preferred.
[0105]
(6) Winding step: This is a step of winding the web as a film after the residual solvent amount becomes 2% by mass or less. By setting the amount of the residual solvent to 0.4% by mass or less, a film having good dimensional stability can be obtained. As the winding method, a generally used method may be used, and there are a constant torque method, a constant tension method, a taper tension method, a program tension control method with constant internal stress, and the like.
[0106]
To adjust the thickness of the fatty acid cellulose ester film, control the dope concentration, pump feed rate, die slit gap, die extrusion pressure, and casting support speed to achieve the desired thickness. Good to do. Further, as means for making the film thickness uniform, it is preferable that the programmed feedback information is fed back to each of the above-mentioned devices using a film thickness detecting means for adjustment.
[0107]
In the process from immediately after casting through the solution casting film forming method to drying, the atmosphere in the drying apparatus may be air, or may be performed in an inert gas atmosphere such as nitrogen gas or carbon dioxide gas. . However, the danger of the explosion limit of the evaporated solvent in the dry atmosphere must always be considered.
[0108]
The cellulose ester film having an optically biaxial property according to the present invention can employ any method for obtaining an optically biaxial (or nx>ny> nz) orientation. However, a stretching method can be employed as one of the most effective methods.
[0109]
In the cellulose ester film of the present invention, during its production, by controlling the residual solvent in the film as described below, it is possible to stretch even at a high temperature, but if this method is not used, at a high temperature Stretching is also possible. In the case of stretching at a high temperature, the stretching is performed at a temperature equal to or higher than the glass transition temperature of the cellulose ester.However, in the case of the above-described plasticizer, the effect may be weakened and the stretchability may not be sufficiently obtained. is there. A plasticizer capable of imparting sufficient stretchability even at a high temperature is required, and it has been found that a non-volatile plasticizer can be preferably used as such a plasticizer. The non-volatile plasticizer is a compound having a vapor pressure at 200 ° C. of 1,330 Pa or less, has a very low vapor pressure, and has a low volatility. The vapor pressure is more preferably 665 Pa or less, and even more preferably 133 Pa or less. For example, arylene bis (diaryl phosphate) esters are preferred. In addition, tricresyl phosphate (38.6 Pa, 200 ° C.), tris (2-ethylhexyl) trimellitate (66.5 Pa, 200 ° C.) and the like are also preferably used. Alternatively, a non-volatile phosphate ester described in JP-A-6-501040 is also preferably used. In addition, high molecular weight plasticizers such as polymers or oligomers such as polyesters, acrylic resins, and copolymers containing polyvinyl acetate can also be preferably used. In this case, the content of the plasticizer is preferably 0.1 to 30% by mass, more preferably 0.5 to 15% by mass, based on the cellulose ester. By using a plasticizer in this manner, the stretchability of the cellulose ester at a high temperature can be improved, and in particular, a cellulose ester film having excellent surface quality and flatness can be produced with high productivity.
[0110]
As a method for imparting optical biaxiality to the cellulose ester film of the present invention, a method of performing a stretching operation in a state containing a solvent as described above is used as an example of a preferable method. Hereinafter, the stretching method will be described.
[0111]
In the production of the cellulose ester film of the present invention, the dope solution of the cellulose ester is cast on a casting support, and then the web (film) peeled from the casting support is treated with a residual solvent amount in the web of 100. It is preferred that the film be stretched 1.0 to 4.0 times in at least one direction while being in the range of 10% by mass or less, particularly 10 to 100% by mass.
[0112]
The residual solvent amount can be expressed by the following equation.
Residual solvent amount (% by mass) = ((M−N) / N) × 100
Here, M is the mass of the web at an arbitrary point, and N is the mass of M when dried at 110 ° C. for 3 hours.
[0113]
If the amount of the residual solvent in the web is too large, the effect of stretching cannot be obtained, and if it is too small, the stretching becomes extremely difficult, and the web may be broken. A more preferable range of the amount of the residual solvent in the web is 10 to 50% by mass, particularly 12 to 40% by mass. On the other hand, if the stretching ratio is too small, a sufficient phase difference cannot be obtained, while if it is too large, stretching becomes difficult and breakage may occur. A more preferred range of the stretching ratio is in the range of 1.0 to 3.5 times.
[0114]
The solution cast film formed using the cellulose ester according to the present invention can be stretched without heating to a high temperature as long as the residual solvent amount is within a specific range. It is preferable because it can be short. However, if the temperature of the web is too high, the plasticizer volatilizes, so the temperature is preferably in the range of room temperature (15 ° C) to 180 ° C.
[0115]
Stretching in biaxial directions orthogonal to each other is an effective method for keeping the refractive indexes nx, ny, and nz of the film within the scope of the present invention.
[0116]
Further, the film thickness variation of the film obtained by stretching in biaxial directions perpendicular to each other can be reduced. If the thickness variation of the cellulose ester film support is too large, the phase difference becomes uneven, and when used as an optical compensation film, problems such as coloring occur. The thickness variation of the cellulose ester film support is preferably in the range of ± 3%, more preferably ± 1%. For the above purpose, a method of stretching in biaxial directions orthogonal to each other is effective, and the stretching ratios in biaxial directions orthogonal to each other are 0.8 to 4.0 times and 0.4 to 1.2 times, respectively. It is preferable that the range be twice as large.
[0117]
The method for stretching the web is not particularly limited. For example, a method in which a plurality of rolls are provided with a difference in peripheral speed, a method of stretching in the longitudinal direction using the difference in roll peripheral speed between them, fixing both ends of the web with clips or pins, and widening a gap between the clips and pins in a traveling direction. And a method in which the film is spread in the horizontal direction and stretched in the horizontal direction, or a method in which the film is simultaneously spread in the vertical and horizontal directions and stretched in both the vertical and horizontal directions. Of course, these methods may be used in combination. Further, in the case of the so-called tenter method, it is preferable to drive the clip portion by the linear drive method because smooth stretching can be performed and the risk of breakage can be reduced.
[0118]
The film obtained as described above preferably has a residual solvent content of 2% by mass or less, more preferably 0.4% by mass or less in the final finished film, in order to obtain a film having good dimensional stability.
[0119]
In the present invention, at the time of casting, it is preferable to adjust the above-mentioned various conditions so that the refractive index in the width direction of the cellulose ester film formed on the casting support is maximized.
[0120]
As described above, in the optically biaxial cellulose ester support according to the present invention, the refractive indices nx, ny, and nz of the film satisfy the relationship of nx>ny> nz. In the present invention, the expression "the refractive index in the width direction is maximized" means that the direction nx is substantially equal to the width direction. Here, that the directions are substantially equal indicates that the directions of the axes are substantially parallel. Here, "substantially parallel" means that the angle between the respective axes is within ± 10 °, preferably within ± 3 °, and more preferably within ± 1 °.
[0121]
Further, in the polarizing plate of the present invention, the width of the light transmission axis of the dichroic substance-containing polarizer and the width of the optically biaxial cellulose ester film to be bonded to the polarizer during casting. It is preferable that the lamination is performed so that the stretching direction is substantially parallel to the stretching direction. In the present invention, orthogonal means that the axes are substantially orthogonal to each other as described above, and that the directions are the same means that the directions of the axes are substantially parallel to each other. Is shown.
[0122]
Furthermore, during the production of the polarizing plate, a polarizer containing a dichroic substance and a cellulose ester film having optically biaxial properties are laminated, but from the viewpoint of improving production efficiency, it was produced as a long roll. Cellulose ester films are preferably used. In the present invention, the length is 500 m or more, preferably 1000 m or more, and particularly preferably 1000 m to 4000 m.
[0123]
The polarizing plate and the liquid crystal display of the present invention will be described. As the polarizer used for the polarizing plate of the present invention, a conventionally known polarizer can be used. For example, a film made of a hydrophilic polymer such as polyvinyl alcohol and stretched by treating with a dichroic dye such as iodine, or a film obtained by treating and orienting a plastic film such as vinyl chloride is used. The polarizer thus obtained is bonded with a cellulose ester film. At this time, at least one of the cellulose ester films needs to use the cellulose ester film of the present invention. However, a cellulose triacetate (TAC) film conventionally used as a support for a polarizing plate may be used. You may use it for bonding of the other surface of a polarizer. In order to maximize the effects described in the present invention, from the viewpoint of the same physical properties on both surfaces of the polarizing plate protective film, the cellulose ester film of the present invention is used as all cellulose ester films constituting the polarizing plate. Is preferred.
[0124]
When the polarizing plate is formed by laminating the cellulose ester film of the present invention, the polarizer, and the cellulose triacetate (TAC) film in this order, when the cellulose triacetate film is stretched in the width direction, the temperature and humidity can be increased. It is possible to obtain a polarizing plate with a retardation function that maintains excellent optical characteristics with little dimensional change (shape change) with respect to environmental changes. The stretching operation may be performed at the time of casting film formation, or may be performed offline after film formation, but may be continuously performed during casting film formation from the viewpoint of uniformity of stretching, productivity, and the like. preferable. The stretching ratio is preferably in the range of 1.02 to 1.2 times, particularly preferably 1.03 to 1.15 times, and most preferably 1.05 to 1.10 times.
[0125]
Furthermore, at the time of producing a polarizing plate, the stretch ratio A of the cellulose ester film of the present invention to be bonded to one surface of the polarizer and the cellulose ester film to be bonded to the other surface on the opposite side across the polarizer. Regarding the relationship with the stretching ratio B, A / B is preferably in the range of 1000 to 0.001, more preferably 200 to 0.005, and particularly preferably 100 to 0.01. is there.
[0126]
Further, at the time of producing the polarizing plate, it is preferable that the casting direction at the time of casting the cellulose ester film of the present invention and the stretching direction of the polarizer are substantially parallel. The polarizing plate thus obtained is bonded to both sides of the liquid crystal cell, preferably arranged as follows.
[0127]
The polarizing plate of the present invention is bonded so that the rubbing axis direction of the substrate surface close to the liquid crystal cell and the polarizing plate transmission axis (here, the stretching direction of the polarizer and the light transmission axis are perpendicular). Thus, a liquid crystal display device can be obtained. Here, FIG. 1 is a schematic diagram showing the configuration of the liquid crystal display device of the present invention. The liquid crystal display device 9 shown in FIG. 1 includes one liquid crystal cell 7 and two polarizing plates 6a and 6b. The polarizing plate 6a is composed of two cellulose ester films 1a and one polarizer 2a, and the polarizing plate 6b is composed of two cellulose ester films 1b and one polarizer 2b. In the polarizing plates 6a and 6b, the casting directions 3a and 3b represent the casting directions during casting of the cellulose ester films 1a and 1b, respectively. The stretching directions 4a and 4b represent the stretching directions of the polarizers 2a and 2b, respectively. The light transmission axes 8a and 8b represent the light transmission axes of the polarizing plates 6a and 6b, respectively, and are orthogonal to the rubbing axes 5a and 5b of the liquid crystal cell 7, respectively. With the simple configuration as described above, a liquid crystal display device with a remarkably improved viewing angle can be obtained.
[0128]
The thickness of the cellulose ester film of the present invention is preferably from 10 to 300 μm. If the film thickness is less than 10 μm, the mechanical strength becomes insufficient, and if it exceeds 300 μm, the handleability and workability deteriorate, which is not preferable. The thickness of the cellulose ester film is more preferably 40 to 160 μm, and particularly preferably a thin film of 40 to 80 μm. This is because the effect of reacting a compound having at least one aromatic ring and having at least one group bonded to a hydroxyl group in a molecule is particularly remarkable in a thin cellulose ester film. The mechanical strength of the cellulose ester film is preferably 2500 N / mm when the tensile modulus at room temperature is represented as an index. ² And more preferably 3000 N / mm ² That is all. The tensile modulus at room temperature can be measured based on JIS-K-6911.
[0129]
Further, the retardation film of the present invention has at least one aromatic ring, and from the improvement of the crosslink density by reaction with a compound having at least one group bonded to a hydroxyl group in the molecule, a plasticizer or ultraviolet light A film having good storage stability without physical property change due to bleed-out or volatilization of an additive such as an absorbent can be provided. Further, a compound having at least one aromatic ring and having at least one group bonded to a hydroxyl group in a molecule can reduce the amount of a plasticizer due to a decrease in moisture permeability of a cellulose ester film.
[0130]
【Example】
Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited thereto.
[0131]
Example 1
<< Preparation of cellulose ester film >>
(Cellulose ester film 1)
Ten parts by mass of cellulose acetate propionate having a degree of substitution of acetyl group of 2.00, a degree of substitution of propionyl group of 0.60, and a viscosity average polymerization degree of 350, and 290 parts by mass of methylene chloride were completely dissolved in a closed vessel. Next, 5 parts by mass of diphenyl isocyanate was added, heated to 80 ° C., and reacted while stirring. After the reaction, the dope was returned to room temperature, 90 parts by mass of cellulose acetate propionate having a degree of substitution of acetyl group of 2.00, a degree of substitution of propionyl group of 0.60, and a viscosity average degree of polymerization of 350, and 5 parts by mass of ethyl phthalylethyl glycolate. Then, 3 parts by mass of triphenyl phosphate and 60 parts by mass of ethanol were added, and the mixture was gradually heated while slowly stirring, and heated to 45 ° C. over 60 minutes to dissolve. The inside of the container became 120 kPa. Azumi filter paper No. No. manufactured by Azumi Filter Paper Co., Ltd. After filtration using 244, the mixture was allowed to stand for 24 hours to remove bubbles in the dope.
[0132]
Separately, 5 parts by mass of the above-mentioned cellulose acetate propionate, 6 parts by mass of Tinuvin 326 (manufactured by Ciba Specialty Chemicals Co., Ltd.), and 4 parts by mass of Tinuvin 109 (manufactured by Ciba Specialty Chemicals Co., Ltd.) 5 parts by mass of Tinuvin 171 (manufactured by Ciba Specialty Chemicals Co., Ltd.) was added to a solvent obtained by mixing 94 parts by mass of methylene chloride and 8 parts by mass of ethanol and dissolved by stirring to prepare an ultraviolet absorbent solution.
[0133]
The ultraviolet absorbent solution was added at a ratio of 2 parts by mass with respect to 100 parts by mass of the dope, and the mixture was sufficiently mixed by a static mixer, and then cast from a die onto a stainless steel belt at a dope temperature of 30 ° C. After drying for 1 minute on a temperature-controlled stainless steel belt by contacting hot water of 25 ° C. from the back surface of the stainless steel belt, further contacting cold water of 15 ° C. with the back surface of the stainless steel belt and holding for 15 seconds, Was peeled off. The residual solvent amount in the web at the time of peeling was 100% by mass. Next, both ends of the peeled web were gripped with clips using a stretching tenter, and the width of the clip interval was changed, whereby the web was stretched 1.2 times only in the width direction at 120 ° C. Further, the film was dried at 130 ° C. for 10 minutes while being transported by a roller to obtain a cellulose ester film 1 having a thickness of 80 μm.
[0134]
The cellulose ester film 1 was wound by a taper tension method into a film roll having a width of 1 m and a length of 1000 m around a glass fiber reinforced resin core having a core diameter of 200 mm. At this time, an emboss ring at a temperature of 250 ° C. was pressed against the edge of the film, and the film was subjected to thickness processing to prevent adhesion between the films.
[0135]
The obtained film roll was sampled from the center in the width direction, and the refractive index nx in the slow axis direction, the refractive index ny in the fast axis direction, and the refractive index nz in the thickness direction were measured as follows, and the in-plane retardation was measured. When the value R0 and the retardation value Rt in the thickness direction were calculated, they were 52 nm and 132 nm at the center, respectively. The retardation values R0 and Rt are defined by the following equations.
[0136]
R0 = (nx−ny) × d
Rt = ((nx + ny) / 2−nz) × d
Here, d is the thickness (nm) of the film.
[0137]
Further, the direction of the slow axis was within ± 0.8 degrees with respect to the width direction of the film for each sample.
[0138]
(Measurement of refractive index nx, ny, nz)
Using an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments), a three-dimensional refractive index is measured at a wavelength of 590 nm in an environment of 23 ° C. and 55% RH, and the refractive indices nx, ny, nz was determined.
[0139]
The water content was measured by the following to be 0.9%.
(Moisture percentage measurement method)
10cm cellulose ester film ² And left for 48 hours under the conditions of 23 ° C. and 80% RH, and the mass was measured to be W1. Next, the film was subjected to a heat-drying treatment at 120 ° C. for 45 minutes, and the mass was measured to be W2. The water content at 23 ° C. and 80% RH is determined from the measured values obtained by the following formula.
[0140]
Moisture percentage (%) = ((W1-W2) / W2) × 100
(Cellulose ester film 2)
10 parts by mass of cellulose acetate propionate having a degree of substitution of acetyl group of 1.60, a degree of substitution of propionyl group of 1.00 and a viscosity average polymerization degree of 400, and 290 parts by mass of methylene chloride were completely dissolved in a closed vessel. Next, 5 parts by mass of pentafluorophenyl isocyanate was added, heated to 80 ° C., and reacted while stirring. After the reaction, the dope was returned to room temperature, 90 parts by mass of cellulose acetate propionate having a degree of substitution of acetyl group of 2.00, a degree of substitution of propionyl group of 0.80, and a viscosity average degree of polymerization of 350, and 5 parts by mass of ethyl phthalylethyl glycolate. Then, 3 parts by mass of triphenyl phosphate and 60 parts by mass of ethanol were added, and the mixture was gradually heated while slowly stirring, and heated to 45 ° C. over 60 minutes to dissolve. The inside of the container became 120 kPa. Azumi filter paper No. No. manufactured by Azumi Filter Paper Co., Ltd. After filtration using 244, the mixture was allowed to stand for 24 hours to remove bubbles in the dope.
[0141]
Separately, 5 parts by mass of the above-mentioned cellulose acetate propionate, 6 parts by mass of Tinuvin 326 (manufactured by Ciba Specialty Chemicals Co., Ltd.), and 4 parts by mass of Tinuvin 109 (manufactured by Ciba Specialty Chemicals Co., Ltd.) , Tinuvin 171 (manufactured by Ciba Specialty Chemicals Co., Ltd.) and AEROSIL R972V (manufactured by Nippon Aerosil Co., Ltd.) were added to a solvent obtained by mixing 94 parts by mass of methylene chloride and 8 parts by mass of ethanol, and dissolved by stirring. An absorbent solution was prepared. R972V was previously dispersed and added to the ethanol.
[0142]
The ultraviolet absorbent solution was added at a ratio of 2 parts by mass with respect to 100 parts by mass of the dope, and the mixture was sufficiently mixed by a static mixer, and then cast from a die onto a stainless steel belt at a dope temperature of 30 ° C. After drying for 1 minute on a temperature-controlled stainless steel belt by contacting hot water of 25 ° C. from the back surface of the stainless steel belt, further contacting cold water of 15 ° C. with the back surface of the stainless steel belt and holding for 15 seconds, Was peeled off. The residual solvent amount in the web at the time of peeling was 80% by mass. Next, both ends of the peeled web were gripped with clips using a stretching tenter, and the width of the clip interval was changed, whereby the web was stretched 1.2 times in the width direction at 120 ° C. Further, the film was dried at 130 ° C. for 10 minutes while being transported by a roller to obtain a cellulose ester film 2 having a thickness of 80 μm.
[0143]
The cellulose ester film 2 was wound by a taper tension method into a film roll having a width of 1 m and a length of 1000 m around a glass fiber reinforced resin core having a core diameter of 200 mm. At this time, an emboss ring at a temperature of 250 ° C. was pressed against the edge of the film, and the film was subjected to thickness processing to prevent adhesion between the films.
[0144]
Sampling was performed from the center in the width direction of the obtained film roll, and the refractive index nx in the slow axis direction, the refractive index ny in the fast axis direction, and the refractive index nz in the thickness direction were measured in the same manner as the cellulose ester film 1. , R0, and Rt were calculated to be 50 nm and 130 nm, respectively, at the center. Further, the direction of the slow axis was within a range of ± 0.4 degrees with respect to the width direction of the film in each sample. The water content was 1.0%.
[0145]
(Cellulose ester film 3)
10 parts by mass of cellulose acetate propionate having a degree of substitution of acetyl group of 2.00, a degree of substitution of propionyl group of 0.60, and a viscosity average degree of polymerization of 350 were put in a closed vessel and completely dissolved. Next, 5 parts by mass of Coronate L (Nippon Polyurethane) was added, heated to 80 ° C., and reacted while stirring. After the reaction, the dope was returned to room temperature, 90 parts by mass of cellulose acetate propionate having a degree of substitution of acetyl group of 2.00, a degree of substitution of propionyl group of 0.60, and a viscosity average degree of polymerization of 350, and 5 parts by mass of ethyl phthalylethyl glycolate. , 3 parts by mass of triphenyl phosphate and 75 parts by mass of ethanol were added to a closed vessel, and the mixture was gradually heated while slowly stirring, and then heated to 65 ° C. over 60 minutes to dissolve. The inside of the container became 120 kPa. Azumi filter paper No. No. manufactured by Azumi Filter Paper Co., Ltd. After filtration using 244, the mixture was allowed to stand for 24 hours to remove bubbles in the dope.
[0146]
Separately, 5 parts by mass of the above-mentioned cellulose acetate propionate, 6 parts by mass of Tinuvin 326 (manufactured by Ciba Specialty Chemicals Co., Ltd.), and 4 parts by mass of Tinuvin 109 (manufactured by Ciba Specialty Chemicals Co., Ltd.) And 5 parts by mass of Tinuvin 171 (manufactured by Ciba Specialty Chemicals Co., Ltd.) were added to a solvent obtained by mixing 94 parts by mass of methyl acetate and 8 parts by mass of ethanol, and dissolved by stirring to prepare an ultraviolet absorbent solution.
[0147]
The ultraviolet absorbent solution was added at a ratio of 2 parts by mass with respect to 100 parts by mass of the dope, and the mixture was sufficiently mixed by a static mixer, and then cast from a die onto a stainless steel belt at a dope temperature of 50 ° C. After contacting hot water of 55 ° C. from the back of the stainless steel belt and drying it on a temperature-controlled stainless steel belt for 1 minute, further contacting cold water of 15 ° C. with the back of the stainless steel belt for 15 seconds, Was peeled off. The residual solvent amount in the web at the time of peeling was 70% by mass. Then, using a simultaneous biaxial stretching tenter, the both ends of the peeled web are gripped with clips, and the clip interval is simultaneously changed in the width direction and the casting direction (length direction). The film was stretched 1.05 times in the casting direction (length direction). Further, the film was dried at 130 ° C. for 10 minutes while being transported by a roller to obtain a cellulose ester film 3 having a thickness of 80 μm.
[0148]
The cellulose ester film 3 was wound around a glass fiber reinforced resin core having a core diameter of 200 mm into a film roll having a width of 1 m and a length of 1000 m by a taper tension method. At this time, an emboss ring at a temperature of 250 ° C. was pressed against the edge of the film, and the film was subjected to thickness processing to prevent adhesion between the films.
[0149]
The obtained film roll was sampled from the center in the width direction, and the refractive index nx in the slow axis direction, the refractive index ny in the fast axis direction, and the refractive index nz in the thickness direction were measured in the same manner as in the cellulose ester film 1. , R0, and Rt were 52 nm and 135 nm, respectively. The direction of the slow axis was within ± 1.2 degrees with respect to the width direction of the film for each sample. The water content was 0.8%.
[0150]
(Cellulose ester film 4)
10 parts by mass of cellulose acetate propionate having a degree of substitution of acetyl groups of 2.30, a degree of substitution of propionyl groups of 0.3, and a viscosity average degree of polymerization of 300, and 290 parts by mass of methylene chloride were completely dissolved in a closed vessel. Next, 5 parts by mass of phenyltriethoxysilane, 0.1 parts by mass of acetic acid and 1 part by mass of water were added, and the mixture was heated to 80 ° C. and reacted while stirring. After the reaction, the dope was returned to room temperature, 90 parts by mass of cellulose acetate propionate having a degree of substitution of acetyl groups of 2.30, a degree of substitution of propionyl groups of 0.3, and a viscosity average degree of polymerization of 300, and 5 parts by mass of ethyl phthalylethyl glycolate. , 3 parts by mass of triphenyl phosphate and 60 parts by mass of ethanol were added to a closed vessel, and the mixture was gradually heated while slowly stirring, and then heated to 45 ° C. over 60 minutes to dissolve. The inside of the container became 120 kPa. Azumi filter paper No. No. manufactured by Azumi Filter Paper Co., Ltd. After filtration using 244, the mixture was allowed to stand for 24 hours to remove bubbles in the dope.
[0151]
Separately, 3 parts by mass of the cellulose acetate propionate, 3 parts by mass of Tinuvin 326 (manufactured by Ciba Specialty Chemicals), and 4 parts by mass of Tinuvin 109 (manufactured by Ciba Specialty Chemicals). And 5 parts by mass of Tinuvin 171 (manufactured by Ciba Specialty Chemicals Co., Ltd.) were added to a solvent obtained by mixing 90 parts by mass of methylene chloride and 10 parts by mass of ethanol, and dissolved by stirring to prepare an ultraviolet absorbent solution.
[0152]
The ultraviolet absorbent solution was added at a ratio of 2 parts by mass with respect to 100 parts by mass of the dope, and the mixture was sufficiently mixed by a static mixer, and then cast from a die onto a stainless steel belt at a dope temperature of 35 ° C. After drying for 1 minute on a stainless steel belt whose temperature is controlled by contacting warm water of 35 ° C. from the back surface of the stainless steel belt, further contacting cold water of 15 ° C. with the back surface of the stainless steel belt and holding for 15 seconds, Was peeled off. The residual solvent amount in the web at the time of peeling was 70% by mass.
[0153]
Next, while the roll is conveyed in an oven at 120 ° C., the peripheral speed of the roll immediately before the exit of the oven is 2.1 times the peripheral speed of the roll immediately after the entrance of the oven. ) And stretched 1.2 times. After stretching, it was immediately cooled to 60 ° C. Further, both ends of the web were gripped with clips using a tenter, and the web was dried at 140 ° C. for 5 minutes while keeping the clip interval fixed to obtain a cellulose ester film 4 having a thickness of 160 μm.
[0154]
The cellulose ester film 4 was wound by a taper tension method into a film roll having a width of 1 m and a length of 1000 m around a glass fiber reinforced resin core having a core diameter of 200 mm. At this time, an embossing ring at a temperature of 270 ° C. was pressed against the end of the film, and a 10 μm thickness embossing process was performed to prevent adhesion between the films.
[0155]
Sampling was performed from the center in the width direction of the obtained film roll, and the refractive index nx in the slow axis direction, the refractive index ny in the fast axis direction, and the refractive index nz in the thickness direction were measured in the same manner as in the cellulose ester film 1. Then, when R0 and Rt were calculated, they were 101 nm and 203 nm at the center, respectively. Further, the direction of the slow axis was within ± 0.5 degrees with respect to the width direction of the film for each sample. The water content was 1.0%.
[0156]
(Cellulose ester film 5)
Except that the cellulose ester used for the cellulose ester film was changed to cellulose acetate butyrate having a substitution degree of an acetyl group of 1.90, a substitution degree of a butyryl group of 0.55, and a viscosity average polymerization degree of 300, the same procedure as in the production of the cellulose ester film 1 was performed. Thus, a cellulose ester film 5 having a thickness of 80 μm and a film roll thereof were produced.
[0157]
From the obtained film roll, a sample was taken from the center in the width direction of the film, and the refractive index nx in the slow axis direction, the refractive index ny in the fast axis direction, and the refractive index nz in the thickness direction were set in the same manner as in the cellulose ester film 1. R0 and Rt were calculated and found to be 54 nm and 130 nm, respectively, at the center. The direction of the slow axis was within ± 1.2 degrees with respect to the width direction of the film for each sample. The water content was 0.7%.
[0158]
(Cellulose ester film 6)
10 parts by mass of cellulose acetate propionate having a degree of substitution of acetyl group of 1.90, a degree of substitution of propionyl group of 0.55, and a viscosity average polymerization degree of 350, and 290 parts by mass of methylene chloride were completely dissolved in a closed vessel. Next, 5 parts by mass of diphenylisothiocyanate was added, heated to 80 ° C., and reacted while stirring. After the reaction, the dope was returned to room temperature, 2 parts by mass of ethyl phthalylethyl glycolate, 8.5 parts by mass of triphenyl phosphate, and 60 parts by mass of ethanol were added to a closed vessel, and the mixture was gradually heated while slowly stirring. The temperature was raised to 45 ° C. over 60 minutes to dissolve. The inside of the container became 120 kPa. Azumi filter paper No. No. manufactured by Azumi Filter Paper Co., Ltd. After filtration using 244, the mixture was allowed to stand for 24 hours to remove bubbles in the dope.
[0159]
Separately, 5 parts by mass of the above-mentioned cellulose acetate propionate, 6 parts by mass of Tinuvin 326 (manufactured by Ciba Specialty Chemicals Co., Ltd.), and 4 parts by mass of Tinuvin 109 (manufactured by Ciba Specialty Chemicals Co., Ltd.) 5 parts by mass of Tinuvin 171 (manufactured by Ciba Specialty Chemicals Co., Ltd.) was added to a solvent obtained by mixing 94 parts by mass of methylene chloride and 8 parts by mass of ethanol and dissolved by stirring to prepare an ultraviolet absorbent solution.
[0160]
The ultraviolet absorbent solution was added at a ratio of 2 parts by mass with respect to 100 parts by mass of the dope, and the mixture was sufficiently mixed by a static mixer, and then cast from a die onto a stainless steel belt at a dope temperature of 30 ° C. After drying for 1 minute on a stainless steel belt whose temperature is controlled by contacting hot water of 25 ° C. from the back surface of the stainless steel belt, further contacting cold water of 15 ° C. with the back surface of the stainless steel belt and holding for 15 seconds, Was peeled off. The residual solvent amount in the web at the time of peeling was 70%. Next, both ends of the peeled web were gripped by clips using a stretching tenter, and the width of the clip interval was changed, whereby the web was stretched 1.30 times only in the width direction at 115 ° C. Further, the film was dried at 130 ° C. for 10 minutes while being transported by a roller to obtain a cellulose ester film 6 having a thickness of 80 μm.
[0161]
The cellulose ester film 6 was wound by a taper tension method into a film roll having a width of 1 m and a length of 1000 m around a glass fiber reinforced resin core having a core diameter of 200 mm. At this time, an emboss ring at a temperature of 250 ° C. was pressed against the edge of the film, and the film was subjected to thickness processing to prevent adhesion between the films.
[0162]
The obtained film roll was sampled from the center in the width direction, and the refractive index nx in the slow axis direction, the refractive index ny in the fast axis direction, and the refractive index nz in the thickness direction were measured in the same manner as in the cellulose ester film 1. , R0, and Rt were calculated to be 70 nm and 148 nm, respectively, at the center. Further, the direction of the slow axis was within a range of ± 0.7 degrees with respect to the width direction of the film for each sample. The water content was 0.9%.
[0163]
(Cellulose ester film 7)
A cellulose ester film 7 having a thickness of 80 μm was produced in the same manner as the cellulose ester film 6, except that the stretching ratio was 1.20 times in the width direction.
[0164]
Sampling was performed from the center in the width direction of the obtained film roll, and the refractive index nx in the slow axis direction, the refractive index ny in the fast axis direction, and the refractive index nz in the thickness direction were measured in the same manner as in the cellulose ester film 1. Then, when R0 and Rt were calculated, they were 56 nm and Rt 135 nm, respectively, at the center. Further, the direction of the slow axis was within a range of ± 0.7 degrees with respect to the width direction of the film for each sample. The water content was 0.9%.
[0165]
(Cellulose ester film 8)
A cellulose ester film 8 was produced in the same manner as the cellulose ester film 6, except that the final film thickness after stretching was 40 μm.
[0166]
Sampling was performed from the center in the width direction of the obtained film roll, and the refractive index nx in the slow axis direction, the refractive index ny in the fast axis direction, and the refractive index nz in the thickness direction were measured in the same manner as in the cellulose ester film 1. Then, when R0 and Rt were calculated, they were 38 nm and 91 nm, respectively, at the center. Further, the direction of the slow axis was within a range of ± 0.7 degrees with respect to the width direction of the film for each sample. The water content was 0.6%.
[0167]
(Cellulose ester film 9)
100 parts by mass of cellulose acetate propionate having a degree of substitution of acetyl groups of 2.00, a degree of substitution of propionyl groups of 0.60, and a viscosity average degree of polymerization of 350, 5 parts by mass of ethylphthalylethyl glycolate, and 3 parts by mass of triphenyl phosphate , 290 parts by mass of methylene chloride and 60 parts by mass of ethanol were placed in a closed container, and the mixture was gradually heated while slowly stirring, and then heated to 45 ° C over 60 minutes to dissolve. The inside of the container became 120 kPa. Azumi filter paper No. No. manufactured by Azumi Filter Paper Co., Ltd. After filtration using 244, the mixture was allowed to stand for 24 hours to remove bubbles in the dope.
[0168]
Separately, 5 parts by mass of the above-mentioned cellulose acetate propionate, 6 parts by mass of Tinuvin 326 (manufactured by Ciba Specialty Chemicals Co., Ltd.), and 4 parts by mass of Tinuvin 109 (manufactured by Ciba Specialty Chemicals Co., Ltd.) 5 parts by mass of Tinuvin 171 (manufactured by Ciba Specialty Chemicals Co., Ltd.) was added to a solvent obtained by mixing 94 parts by mass of methylene chloride and 8 parts by mass of ethanol and dissolved by stirring to prepare an ultraviolet absorbent solution.
[0169]
The ultraviolet absorbent solution was added at a ratio of 2 parts by mass with respect to 100 parts by mass of the dope, and the mixture was sufficiently mixed by a static mixer, and then cast from a die onto a stainless steel belt at a dope temperature of 30 ° C. After drying for 1 minute on a stainless steel belt whose temperature is controlled by contacting hot water of 25 ° C. from the back surface of the stainless steel belt, further contacting cold water of 15 ° C. with the back surface of the stainless steel belt and holding for 15 seconds, Was peeled off. The residual solvent amount in the web at the time of peeling was 100% by mass. Next, both ends of the peeled web were gripped with clips using a stretching tenter, and the width of the clip interval was changed, whereby the web was stretched 1.4 times only in the width direction at 120 ° C. Further, the film was dried at 130 ° C. for 10 minutes while being transported by a roller to obtain a cellulose ester film 9 having a thickness of 80 μm.
[0170]
The cellulose ester film 9 was wound by a taper tension method into a film roll having a width of 1 m and a length of 1000 m around a glass fiber reinforced resin core having a core diameter of 200 mm. At this time, an emboss ring at a temperature of 250 ° C. was pressed against the edge of the film, and the film was subjected to thickness processing to prevent adhesion between the films.
[0171]
The obtained film roll was sampled from the center in the width direction, and the refractive index nx in the slow axis direction, the refractive index ny in the fast axis direction, and the refractive index nz in the thickness direction were measured in the same manner as in the cellulose ester film 1. , R0, and Rt were calculated to be 51 nm and 131 nm, respectively, at the center. Further, the direction of the slow axis was within ± 0.8 degrees with respect to the width direction of the film for each sample. The water content was 1.8%.
[0172]
(Cellulose ester film 10)
A cellulose ester film 10 having a thickness of 80 μm was produced in the same manner as the cellulose ester film 9 except that the stretching ratio in the width direction was set to 1.2.
[0173]
The obtained film roll was sampled from the center in the width direction, and the refractive index nx in the slow axis direction, the refractive index ny in the fast axis direction, and the refractive index nz in the thickness direction were measured in the same manner as in the cellulose ester film 1. , R0, and Rt were 34 nm and 115 nm, respectively, at the center. Further, the direction of the slow axis was within ± 0.8 degrees with respect to the width direction of the film for each sample. The water content was 1.6%.
[0174]
(Cellulose ester film 11)
According to the following procedure, a cellulose triacetate film 11 conventionally used as a support for a polarizing plate was produced.
[0175]
100 parts by mass of cellulose triacetate having an acetyl group substitution degree of 2.92 and a viscosity average degree of polymerization of 300, 2 parts by mass of ethylphthalylethyl glycolate, 10 parts by mass of triphenyl phosphate, 350 parts by mass of methylene chloride, and 50 parts by mass of ethanol The mixture was placed in a closed container, and the temperature of the mixture was gradually raised while being slowly stirred, and raised to 45 ° C. over 60 minutes to dissolve the mixture. The inside of the container became 120 kPa. Azumi filter paper No. No. manufactured by Azumi Filter Paper Co., Ltd. After filtration using 244, the mixture was allowed to stand for 24 hours to remove bubbles in the dope.
[0176]
Separately, 5 parts by mass of the above cellulose triacetate, 3 parts by mass of Tinuvin 326 (manufactured by Ciba Specialty Chemicals), 7 parts by mass of Tinuvin 109 (manufactured by Ciba Specialty Chemicals), and 171 5 parts by mass (manufactured by Ciba Specialty Chemicals Co., Ltd.) and 1 part by mass of AEROSIL 200V (manufactured by Nippon Aerosil Co., Ltd.) were added to a mixed solvent of 90 parts by mass of methylene chloride and 10 parts by mass of ethanol, and the mixture was stirred and dissolved. A UV absorber solution was prepared.
[0177]
The ultraviolet absorbent solution was added at a ratio of 2 parts by mass with respect to 100 parts by mass of the dope, and the mixture was sufficiently mixed by a static mixer, and then cast from a die onto a stainless steel belt at a dope temperature of 35 ° C. After drying for 1 minute on a stainless steel belt whose temperature is controlled by contacting warm water of 35 ° C. from the back surface of the stainless steel belt, further contacting cold water of 15 ° C. with the back surface of the stainless steel belt and holding for 15 seconds, Was peeled off.
[0178]
The residual solvent amount in the web at the time of peeling was 70% by mass. Next, the peeled web was dried at 120 ° C. for 10 minutes while fixing both ends of the peeled web to obtain a cellulose triacetate film 11 having a thickness of 80 μm.
[0179]
The obtained film roll was sampled from the center in the width direction, and the refractive index nx in the slow axis direction, the refractive index ny in the fast axis direction, and the refractive index nz in the thickness direction were measured in the same manner as in the upper cellulose ester film 1. Then, when R0 and Rt were calculated, they were 2 nm and 42 nm, respectively, at the center. Further, the direction of the slow axis was below the measurement limit because the R0 value was small. The water content was 1.6%.
[0180]
Table 1 shows the stretch ratio in width, R0, Rt, film thickness, direction of the slow axis, and moisture content of the produced cellulose ester films 1 to 10.
[0181]
[Table 1]

[0182]
As is clear from the results in Table 1, the draw ratio of the cellulose ester films 1 to 8 of the present invention is reduced from 1.4 to 1.2 in order to obtain R0 and Rt equivalent to those of the comparative cellulose ester film 9. It is possible. In addition, since a compound having at least one aromatic ring and having at least one group that binds to a hydroxyl group in the molecule is introduced, the water content is low and the amount of the plasticizer added can be reduced. It is.
[0183]
<< Preparation of polarizing plate >>
(Polarizing plate 1)
A polyvinyl alcohol film having a thickness of 120 μm was immersed in an aqueous solution containing 1 part of iodine, 2 parts of potassium iodide, and 4 parts of boric acid, and stretched 4 times at 50 ° C. to obtain a polarizing film. Next, the above-mentioned cellulose ester film 1 was laminated on this polarizing film by the following procedure to obtain the polarizing plate 1 of the present invention.
(1) As a protective film, as shown in FIG. 2, two pieces of the above-mentioned cellulose ester films cut into a rectangular ABCD of 30 cm × 18 cm were immersed in a 2 mol / L sodium hydroxide solution at 60 ° C. for 1 minute. Washed and dried.
[0184]
FIG. 2 is a schematic view of a long cellulose ester film of the present invention produced by casting. In the long cellulose ester film 10 of the present invention, which is cast and produced, the casting direction 11 is the casting direction at the time of casting, and the width direction 12 is the width direction at the time of casting. Represents The cellulose ester film used for producing the polarizing plate is cut and used, for example, as a rectangular ABCD, and the angle between one side AB of the rectangular ABCD and the casting direction 11 of the cellulose ester film 10 is 45 degrees. Is cut off.
(2) The above-mentioned polarizing film (polarizer) adjusted to the same size as the two cellulose ester films is immersed in a polyvinyl alcohol adhesive tank having a solid content of 2% by mass for 1 to 2 seconds.
(3) The excess adhesive adhering to the polarizing film (polarizer) is gently removed, placed on the surface of the cellulose ester film in an arrangement as shown in FIG. 3, and further adhered to the surface of another cellulose ester film. They are laminated and arranged so that they come into contact with the agent.
[0185]
FIG. 3 is a schematic view of the polarizing plate of the present invention. The polarizing plate 6a is arranged and configured so that the polarizer 2a is sandwiched between two cellulose ester films 1a of the present invention. The casting direction at the time of casting the cellulose ester film 1a and the stretching direction of the polarizer 2a are parallel.
(4) Excessive adhesive and air bubbles are removed from the end of the laminated product of the polarizing film and the cellulose ester film laminated by a hand roller, and they are bonded together. Hand roller is 20-30N / cm ² At a roller speed of about 2 m / min.
(5) The obtained sample was left in a dryer at 80 ° C. for 2 minutes to produce a polarizing plate 1. Next, the polarizing plate 1 was incorporated into a liquid crystal cell by the method described below, and the viewing angle, which is one of the characteristics as a display device, was evaluated.
[0186]
(Polarizing plate 2)
Using the cellulose ester film 2, a polarizing plate 2 was produced in the same manner as in the cellulose ester film 1, and the viewing angle was measured in the same manner as in the polarizing plate 1.
[0187]
(Polarizing plate 3)
Using the cellulose ester film 3, a polarizing plate 3 was produced in the same manner as in the cellulose ester film 1, and the viewing angle was measured in the same manner as in the polarizing plate 1.
[0188]
(Polarizing plate 4)
Using the cellulose ester film 4, a polarizing plate 4 was prepared in the same manner as in the cellulose ester film 1, and the viewing angle was measured in the same manner as in the polarizing plate 1.
[0189]
(Polarizing plate 5)
Using the cellulose ester film 5, a polarizing plate 5 was prepared in the same manner as in the cellulose ester film 1, and the viewing angle was measured in the same manner as in the polarizing plate 1.
[0190]
(Polarizing plate 6)
Using the cellulose ester film 10, a polarizing plate 6 was prepared in the same manner as in the cellulose ester film 1, and the viewing angle was measured in the same manner as in the polarizing plate 1.
[0191]
(Polarizing plate 7)
Using the combination of the cellulose ester film 11 (cellulose triacetate film) and the cellulose ester film 1 as a support for lamination, a polarizing plate 7 was produced in the following procedure.
[0192]
First, a polyvinyl alcohol film having a thickness of 120 μm was immersed in an aqueous solution containing 1 part of iodine, 2 parts of potassium iodide, and 4 parts of boric acid, and stretched 4 times at 50 ° C. to obtain a polarizing film. next,
(1) As a protective film, as shown in FIG. 2, a cellulose ester film 1 and a cellulose ester film 11 cut into rectangular ABCD of 30 cm × 18 cm were respectively placed in a 2 mol / L sodium hydroxide solution at 60 ° C. The sample was immersed for another minute, washed with water and dried.
(2) The above-mentioned polarizing film adjusted to the same size as the two cellulose ester films is immersed in a polyvinyl alcohol adhesive tank having a solid content of 2% by mass for 1 to 2 seconds.
(3) The excess adhesive adhering to the polarizing film was lightly removed, and one of the two cellulose ester films 1a in FIG. 3 was used as the cellulose ester film 1 and the other one was used as the cellulose ester film 11, and FIG. The cellulose ester film was laminated on the polarizer in the same arrangement as in the above.
(4) Excessive adhesive and air bubbles are removed from the end of the laminated product of the polarizing film and the cellulose ester film laminated by a hand roller, and they are bonded together. Hand roller is 20-30N / cm ² At a roller speed of about 2 m / min.
(5) The obtained sample was left in a dryer at 80 ° C. for 2 minutes to produce a polarizing plate 7. Next, the viewing angle was measured in the same manner as in the polarizing plate 1.
[0193]
(Polarizing plate 8)
100 parts of polyvinyl alcohol having an average degree of polymerization of 3800 and a degree of saponification of 99.5 mol% was dissolved in water to obtain a 5.0 mass% solution. This was cast on polyethylene terephthalate and dried to obtain a raw film. This film is immersed in an aqueous solution comprising 0.2 g / L of iodine and 60 g / L of potassium iodide at 30 ° C. for 240 seconds, and then immersed in an aqueous solution having a composition of 70 g / L of boric acid and 30 g / L of potassium iodide. At the same time, a boric acid treatment was carried out for 5 minutes while the film was conveyed while being uniaxially stretched 6.0 times in the conveying direction, and dried. On the other hand, the above-mentioned cellulose ester film 1 was wound on a glass fiber reinforced resin core having a core diameter of 200 mm and wound into a film roll having a width of 1 m and a length of 1000 m into a 2 mol / L sodium hydroxide solution. It was immersed at 60 ° C. for 1 minute, further washed with water and dried. This saponified cellulose ester raw film was continuously bonded on both sides of the above-mentioned stretched and wound polyvinyl alcohol film by roll-to-roll using a polyvinyl alcohol-based adhesive as a protective film. As shown in FIG. 2, a rectangular ABCD of 30 cm × 18 cm was cut out.
[0194]
Next, the viewing angle was measured in the same manner as in the polarizing plate 1.
(Polarizing plate 9)
Using the cellulose ester film 11, a polarizing plate 9 was prepared in the same manner as in the cellulose ester film 1, and the viewing angle was measured in the same manner as in the polarizing plate 1.
[0195]
(Viewing angle measurement)
A polarizing plate was arranged and bonded on both sides of the liquid crystal cell as follows, and evaluated by a panel. That is, the polarizing plate of the present invention was bonded so that the rubbing axis direction of the substrate surface adjacent to the liquid crystal cell was perpendicular to the polarizing plate transmission axis. As the liquid crystal cell, the one obtained by peeling off the optical compensation film and the polarizing plate previously bonded to the NEC 15 inch display Multi Sync LCD 1525J was used. The viewing angle of the thus obtained liquid crystal display device was measured by EZ-contrast manufactured by ELDIM. The viewing angle was represented by a range of the inclination angle from the normal direction to the panel surface where the contrast ratio between the white display and the black display of the liquid crystal cell was 10 or more. Table 2 shows the measurement results.
[0196]
[Table 2]

[0197]
From Table 2, it is clear that the polarizing plate of the present invention has significantly improved viewing angle as compared with the comparative example.
[0198]
Example 2
Polarizing plates 10 to 14 were produced as described below.
[0199]
(Polarizing plate 10)
(Preparation of cellulose ester film A)
According to the following procedure, a cellulose triacetate film (cellulose ester film A) for a polarizing plate protective film was produced.
[0200]
Ten parts by mass of cellulose acetate propionate having a degree of substitution of acetyl group of 2.00, a degree of substitution of propionyl group of 0.60, and a viscosity average polymerization degree of 350, and 290 parts by mass of methylene chloride were completely dissolved in a closed vessel. Next, 5 parts by mass of diphenyl isocyanate was added, heated to 80 ° C., and reacted while stirring. After the reaction, the dope was returned to room temperature, 90 parts by mass of cellulose acetate propionate having a degree of substitution of acetyl group of 2.00, a degree of substitution of propionyl group of 0.60, and a viscosity average degree of polymerization of 350, and 5 parts by mass of ethyl phthalylethyl glycolate. Then, 3 parts by mass of triphenyl phosphate and 60 parts by mass of ethanol were added, and the mixture was gradually heated while slowly stirring, and heated to 45 ° C. over 60 minutes to dissolve. The inside of the container became 120 kPa. Azumi filter paper No. No. manufactured by Azumi Filter Paper Co., Ltd. After filtration using 244, the mixture was allowed to stand for 24 hours to remove bubbles in the dope.
[0201]
Separately, 5 parts by mass of the above-mentioned cellulose acetate propionate, 6 parts by mass of Tinuvin 326 (manufactured by Ciba Specialty Chemicals Co., Ltd.), and 4 parts by mass of Tinuvin 109 (manufactured by Ciba Specialty Chemicals Co., Ltd.) 5 parts by mass of Tinuvin 171 (manufactured by Ciba Specialty Chemicals Co., Ltd.) was added to a solvent obtained by mixing 94 parts by mass of methylene chloride and 8 parts by mass of ethanol and dissolved by stirring to prepare an ultraviolet absorbent solution.
[0202]
The ultraviolet absorbent solution was added at a ratio of 2 parts by mass with respect to 100 parts by mass of the dope, and the mixture was sufficiently mixed by a static mixer, and then cast from a die onto a stainless steel belt at a dope temperature of 30 ° C. After drying for 1 minute on a stainless steel belt whose temperature is controlled by contacting hot water of 25 ° C. from the back surface of the stainless steel belt, further contacting cold water of 15 ° C. with the back surface of the stainless steel belt and holding for 15 seconds, Was peeled off.
[0203]
The residual solvent amount in the web at the time of peeling was 100% by mass. Next, both ends of the peeled web were gripped with clips using a stretching tenter, and the web was stretched 1.07 times only in the width direction at 120 ° C. by changing the width direction of the clip interval. Further, the film was dried at 130 ° C. for 10 minutes while being transported by a roller to obtain a cellulose ester film A having a thickness of 80 μm.
[0204]
Using the obtained cellulose ester film A and the cellulose ester 7 described in Example 1, a polarizing plate 10 was produced in the same manner as the polarizing plate 1 of Example 1.
[0205]
(Polarizing plate 11)
A cellulose triacetate film (cellulose ester film B) for a polarizing plate protective film was prepared in the same procedure as for the cellulose ester film A, except that the stretching ratio in the width direction after peeling was 1.15 times.
[0206]
Using this cellulose ester film B, a polarizing plate 11 was produced in the same manner as in the case of the polarizing plate 10.
[0207]
(Polarizing plate 12)
A cellulose triacetate film (cellulose ester film C) for a polarizing plate protective film was produced in the same procedure as for the cellulose ester film A except that the stretching ratio in the width direction after peeling was 1.20 times.
[0208]
Using this cellulose ester film C, a polarizing plate 12 was produced in the same manner as in the case of the polarizing plate 10.
[0209]
(Polarizing plate 13)
A cellulose triacetate film (cellulose ester film D) for a polarizing plate protective film was prepared in the same procedure as for the cellulose ester film A except that the stretching ratio in the width direction after peeling was changed to 1.02.
[0210]
Using this cellulose ester film D, a polarizing plate 13 was produced in the same manner as in the case of the polarizing plate 10.
[0211]
(Polarizing plate 14)
A cellulose triacetate film for a polarizing plate protective film (cellulose ester film E) was produced in the same procedure as for the cellulose ester film A, except that diphenyl isocyanate was not added and stretching in the width direction after peeling was not performed.
[0212]
Using this cellulose ester film E, a polarizing plate 14 was produced in the same manner as in the case of the polarizing plate 10.
[0213]
(Evaluation of polarizing plate)
The viewing angle of the obtained polarizing plate was measured by the method described in Example 1 (without forced degradation treatment), and the polarizing plate after the production was allowed to stand at 80 ° C. and 90% RH for 500 hours (forced). After the deterioration treatment), the viewing angle was measured in the same manner. The curling characteristics of the polarizing plate subjected to the forced deterioration treatment were visually observed. Table 3 shows the results.
[0214]
[Table 3]

[0215]
From Table 3, it is clear that the polarizing plates 10 to 14 having the cellulose ester film of the present invention have a good viewing angle improving effect. When the forced deterioration treatment is performed, the polarizing plate 14 using only one cellulose ester film of the present invention among the two cellulose ester films constituting the polarizing plate slightly deteriorates the viewing angle after storage. Although light leakage and the like were observed during black display, both of the polarizing plates 10 to 13 using the cellulose ester film of the present invention exhibited excellent viewing angle improvement effects after storage over time as well as before storage. It turns out that it shows.
[0216]
Further, the polarizing plates 10 to 14 each use a cellulose ester film 7 having a stretching ratio of 1.20 on one surface, but the curling of the polarizing plates after the forced deterioration treatment (treatment at 60 ° C., 90%, 500 hours). As a result of visually observing the characteristics, the polarizing plate 14 using the cellulose ester film E, which had not been subjected to the stretching operation, as a protective film on one side showed curl due to a dimensional change of the polarizing plate itself, whereas the stretching ratio was 2%. When each of the cellulose ester films (cellulose ester film D), 20% (cellulose ester film C), 15% (cellulose ester film B) and 7% (cellulose ester film A) was used as a single-sided protective film, Improvement was observed at 2% and 20% magnification, and almost no curl occurred at 15% and 7%.
[0217]
【The invention's effect】
INDUSTRIAL APPLICABILITY According to the present invention, viewing angle characteristics of a TN type LCD such as a TN-TFT, that is, a viewing angle widening polarizing plate and a viewing angle widening polarizing plate capable of easily improving the contrast in the vertical direction of the screen when viewed from an oblique direction, coloring, and the reversal of light and dark. The present invention is to provide a cellulose ester film used for a polarizing plate. Furthermore, by using the viewing angle-enlarging polarizing plate, it was possible to provide a liquid crystal display device in which the vertical viewing angle is improved with a simple configuration. .
[Brief description of the drawings]
FIG. 1 is a schematic diagram illustrating a configuration of a liquid crystal display device of the present invention.
FIG. 2 is a schematic view of a long cellulose ester film of the present invention produced by casting.
FIG. 3 is a schematic diagram illustrating a configuration of a polarizing plate of the present invention.
[Explanation of symbols]
1a, 1b Cellulose ester film
2a, 2b Polarizer
3a, 3b, 11 Casting direction
4a, 4b Stretching direction
5a, 5b rubbing shaft
6a, 6b Polarizing plate
7 Liquid crystal cell
8a, 8b Light transmission axis
9 Liquid crystal display
10 Long cellulose ester film
12 Width direction

Claims (16)

Contains a compound that has at least one aromatic ring and at least one reactive group in the molecule that reacts and bonds with the residual hydroxyl group of the cellulose ester, and is optically biaxial. Cellulose ester film. It is characterized by containing 0.1 to 20 parts by mass of a compound having at least one aromatic ring and having at least one group bonding to a hydroxyl group in a molecule with respect to 100 parts by mass of the cellulose ester. The cellulose ester film according to claim 1. 3. The cellulose ester film according to claim 1, which is long. The cellulose ester film according to any one of claims 1 to 3, wherein the in-plane retardation value R0 is 30 to 300 nm. The cellulose ester film according to any one of claims 1 to 4, wherein a retardation value Rt in a thickness direction is 30 to 300 nm. The cellulose ester film according to any one of claims 1 to 5, wherein the following formulas (1) and (2) are simultaneously satisfied.
Formula (1) 2.4 ≦ A + B ≦ 2.8
Formula (2) 1.4 ≦ A ≦ 2.0
(In the formula, A represents the degree of substitution of an acetyl group, and B represents the degree of substitution of an acyl group having 3 or 4 carbon atoms.) A polarizing plate comprising the cellulose ester film according to claim 1. A polarizing plate comprising the cellulose ester film according to any one of claims 1 to 6 and a polarizer containing a dichroic substance, wherein the light transmission axis of the polarizer and the maximum refractive index in the plane of the cellulose ester film. Wherein the angle formed with the direction giving the angle is −10 ° to 10 °. A polarizing plate comprising a cellulose ester film according to any one of claims 1 to 6, a cellulose ester film b different from or the same as the cellulose ester film, and a polarizer containing a dichroic substance, wherein the cellulose ester A polarizing plate, wherein the film b is stretched in the same direction as the cellulose ester film. The polarizing plate according to claim 9, wherein the cellulose ester film (b) is stretched in the width direction during or after film formation. The polarizing plate according to claim 9, wherein the cellulose ester film or the cellulose ester film b is stretched so that the stretching ratio becomes 1.02 to 1.2 times. 12. A liquid crystal display device comprising the polarizing plate and the liquid crystal cell according to any one of claims 7 to 11, wherein the cellulose ester film of the polarizing plate comprises a polarizer containing the dichroic substance of the polarizing plate, and the liquid crystal cell. A liquid crystal display device, which is arranged between the liquid crystal display devices. 13. The liquid crystal display device according to claim 12, wherein a light transmission axis of the polarizing plate is orthogonal to a rubbing axis or a liquid crystal alignment axis on a side of the liquid crystal cell where the polarizing plate is disposed. The angle between the direction in which the refractive index of the cellulose ester film of the polarizing plate disposed on the bonding surface side of the polarizing plate and the liquid crystal cell and the light transmission axis of the polarizing plate is −10 ° to 10 °. The liquid crystal display device according to claim 13, wherein the liquid crystal display device is adjusted to: The method for producing a cellulose ester film according to any one of claims 1 to 6, wherein an operation of optically imparting biaxiality to the cellulose ester film is performed, and the cellulose ester film is manufactured as a long roll. A method for producing a cellulose ester film. The method for producing a polarizing plate according to any one of claims 7 to 11,
(1) A step of producing an elongated roll of a cellulose ester film by performing an operation of optically imparting biaxiality and adjusting the refractive index in the width direction at the time of casting film formation to be maximum. (2) a step of forming a polarizer containing a dichroic substance; and (3) a step of laminating the polarizer on the long roll.

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