JP4032721B2 - Cellulose ester film, polarizing plate and liquid crystal display device using the cellulose ester film, and method for producing the cellulose ester film - Google Patents

Description

【００８４】
＜フィルム試料２１＞
フィルム試料１の作製においてドーブ組成物１を下記のドープ組成物２１に変えた以外はフィルム試料１の作製と同様の方法で、フィルム試料２１を作製した。
〔ドープ組成物２１〕
トリアセチルセルロース（酢化度６１．０％） １００質量部
２−（２′−ヒドロキシ−３′，５′−ジ−ｔ−ブチル
フェニル）ベゾトリアゾール １質量部
トリフェニルフォスフェート １５質量部
メチレンクロライド ４７５質量部
エタノール ５０質量部
＜フィルム試料２２＞
フィルム試料１の作製においてドーブ組成物１を下記のドープ組成物２２に変えた以外は同様の方法で、フィルム試料２２を作製した。
〔ドープ組成物２２〕
トリアセチルセルロース（酢化度６１．０％） １００質量部
２−（２′−ヒドロキシ−３′，５′−ジ−ｔ−ブチル
フェニル）ベゾトリアゾール １質量部
エチルフタリルエチルグリコレート ４質量部
メチレンクロライド ４７５質量部
エタノール ５０質量部
＜フィルム試料２３＞
フィルム試料１の作製においてドーブ組成物１を下記のドープ組成物２３に変えた以外は同様の方法で、フィルム試料２３を作製した。
〔ドープ組成物２３〕
トリアセチルセルロース（酢化度６１．０％） １００質量部
２−（２′−ヒドロキシ−３′，５′−ジ−ｔ−ブチル
フェニル）ベゾトリアゾール １質量部
トリフェニルフォスフェート １０質量部
ラウリルベンゼンスルホネート ２質量部
メチレンクロライド ４７５質量部
エタノール ５０質量部
２．偏光板試料１〜２３の作製
フィルム試料１を４０℃の２．５Ｍ−水酸化ナトリウム水溶液で６０秒間アルカリ処理し、３分間水洗して鹸化処理層を形成し、アルカリ処理フィルムを得た。
【００８５】
次に厚さ１２０μｍのポリビニルアルコールフィルムを沃素１質量部、ホウ酸４質量部を含む水溶液１００質量部に浸漬し、５０℃で４倍に延伸して偏光膜を作った。この偏光膜の両面に前記アルカリ処理フィルムを完全鹸化型ポリビニルアルコール５％水溶液を粘着剤として各々貼り合わせ偏光板試料１を作製した。フィルム試料２〜２３についても上記と同様の方法で偏光板試料２〜２３を作製した。
３．フィルム試料１〜２３、偏光板試料１〜２３の評価
フィルム試料１〜２３について下記（１）〜（６），偏光板試料１〜２３について下記（７）の評価を行った。
（１）ヘイズ
東京電色（株）製のＴＵＲＢＩＤＩＴＹ ＭＥＴＥＲ Ｔ−２６００ＤＡを用いてヘイズ値を測定した。
（２）引裂強度
エレメンドルフ法の引き裂き荷重をＪＩＳ Ｋ ７１２８−１９９１に従い東洋精機（株）製の軽荷重引き裂き装置で引裂強度を測定した。
（３）透湿性
ＪＩＳ Ｚ ０２０８に記載の方法に従い各フィルム試料の透湿性を測定した。試験を行った温湿度条件は、２５℃、９０％ＲＨである。
（４）保留性（可塑剤の析出性）
フィルム試料を、幅手方向に１０ｃｍ、長手方向に１０ｃｍのサイズでサンプルを切出し、２３℃、５５％ＲＨで２４時間放置後の質量を測定した後、８０℃、９０％ＲＨの条件下で４８時間処理した。さらに処理後のフィルム試料を２３℃、５５％ＲＨで２４時間放置後の質量を測定して以下の方法で保留性を計算した。
【００８６】
保留性＝（処理前の質量−処理後の質量）／処理前の質量×１００％
（５）ブリードアウト値
フィルム試料を、幅手方向に１０ｃｍ、長手方向に１０ｃｍのサイズでサンプルを切出し、８０℃、９０％ＲＨの条件下で４８時間処理後、東京電色（株）製のＴＵＲＢＩＤＩＴＹ ＭＥＴＥＲ Ｔ−２６００ＤＡを用いて測定したヘイズ値をブリードアウト値とした。
（６）リターデーション値（Ｒｔ値）
自動複屈折率計ＫＯＢＲＡ−２１ＡＨ（王子計測機器（株）製）を用いて、フィルム試料を、２３℃、５５％ＲＨの条件下で、５９０ｎｍの波長において３次元屈折率測定を行い、屈折率Ｎｘ、Ｎｙ、Ｎｚを求める。
【００８７】
下記式に従って厚み方向のリターデーション値Ｒｔを算出した。
Ｒｔ＝｛（Ｎｘ＋Ｎｙ）／２−Ｎｚ｝＊ｄ
式中、Ｎｘはフィルムの製膜方向に平行な方向におけるフィルムの屈折率、Ｎｙはフィルムの製膜方向に垂直な方向におけるフィルムの屈折率、Ｎｚはフィルムの厚み方向におけるフィルムの屈折率、ｄはフィルムの厚み（ｎｍ）をそれぞれ表す。
（７）偏光板耐久性テスト
１０ｃｍ×１０ｃｍの偏光板試料２枚を高温高湿処理（条件：８０℃−９０％ＲＨ、５０時間）し、その表面状態を観察した。
【００８８】
◎：偏光板表面がブリードアウトによって曇った部分が５％未満
（偏光板として問題ないレベル）
○：偏光板表面がブリードアウトによって曇った部分が５％以上１０％未満
（偏光板として問題ないレベル）
△：偏光板表面がブリードアウトによって曇った部分が１０％以上２０％未満
（偏光板として何とか使えるレベル）
×：偏光板表面がブリードアウトによって曇った部分が２０％以上
（偏光板として問題のあるレベル）
△以上であれば実技上問題ないレベルである。
【００８９】
結果を表２、表３に示す。
【００９０】
【表２】

【００９１】
【表３】

【００９２】
さらに偏光板試料３，２２については、ＩＰＳモジュールに組み込み、色味の評価を行った。結果を表４に示す。
【００９３】
【表４】

【００９４】
表２、表３の結果より、本発明のフィルム試料は、ヘイズが０．１％と透明性が非常に高いことから、特に液晶表示装置の偏光板等に用いると、非常に有用であることが分かった。
【００９５】
また、本発明のフィルム試料は、引裂強度が高く耐久性が高いことから、特に液晶表示装置の偏光板等に用いると、非常に有用であることが分かった。
【００９６】
さらに、本発明のフィルム試料は、保留性が小さいことから、特に液晶表示装置の偏光板等に用いると、非常に有用であることが分かった。
【００９７】
さらに、本発明のフィルム試料は、水蒸気透過率が低いことから、特に液晶表示装置の偏光板等に用いると、水蒸気の侵入による液晶表示装置の機能の低下を防止することができるので、耐久性を向上させることができることが分かった。
【００９８】
さらに、本発明のフィルム試料は、ブリードアウトの発生を抑えていることから、特に液晶表示装置の偏光板等に用いると、非常に有用であることが分かった。
【００９９】
さらに、本発明の偏光板試料３は、特にＲｔが小さく、ＩＰＳ方式の液晶表示装置の偏光板に用いると色濁りが抑えられて非常に有用であることが分かった。
【０１００】
さらに、本発明のフィルム試料は溶液流延製膜法を用いて製造されいているので、平面性が高く、液晶表示装置の偏光板保護フィルムに用いると非常に有用である。
【０１０１】
さらに、本発明の偏光板試料は、ブリードアウトの発生を抑えることができていることから、液晶表示装置の偏光板保護フィルムに用いると非常に有用であることが分かった。
【０１０２】
さらに、本発明の偏光板試料のそれぞれを液晶表示装置にセットして使用してみたが、上述した効果により、非常に有用であることを確認した。
【０１０３】
【発明の効果】
本発明のセルロースエステルフィルムの少なくとも一つによって、十分な耐久性を有し、ブリードアウトの発生を低減させたセルロースエステルフィルムを提供することができた。
【０１０４】
本発明のセルロースエステルフィルムの少なくとも一つによって、透明性の高いセルロースエステルフィルムを提供することができた。
【０１０５】
本発明のセルロースエステルフィルムの少なくとも一つによって、保留性の小さいセルロースエステルフィルムを提供することができた。
【０１０６】
本発明のセルロースエステルフィルムの少なくとも一つによって、ＩＰＳ方式の液晶表示装置において、色濁りが少ないセルロースエステルフィルムを提供することができた。
【０１０７】
本発明のセルロースエステルフィルムの少なくとも一つによって、平面性の高いセルロースエステルフィルムを提供することができた。
【０１０８】
上記の効果を少なくとも一つ有する本発明のセルロースエステルフィルムを用いた偏光板及び液晶表示装置及び該セルロースエステルフィルムの製造方法を提供することができた。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cellulose ester film, a polarizing plate and a liquid crystal display device using the cellulose ester film, and a method for producing the cellulose ester film.
[0002]
[Prior art]
Cellulose ester films are preferably used in silver halide photographic light-sensitive materials and liquid crystal image display devices because of their transparency and characteristics free from optical defects. In particular, it is used as a protective film for polarizing plates in liquid crystal image display devices.
[0003]
In recent years, information devices equipped with liquid crystal image display devices such as notebook PCs, car navigation systems, and mobile phones have been developed for thinning. For the protective films for polarizing plates used in liquid crystal image display devices However, thinning is required. Therefore, the cellulose ester film is also thinned.
[0004]
However, when the cellulose ester film is thinned, the tear strength is lowered, resulting in a problem that durability is lowered.
[0005]
As measures against this, Japanese Patent Publication No. 47-760 and Japanese Patent Publication No. 44-32672 disclose a technique for increasing the tear strength by incorporating a polyurethane resin having polyester as a component into a cellulose ester film.
[0006]
[Problems to be solved by the invention]
In the polarizing plate protective film of the liquid crystal display device, the durability of the polarizing plate protective film is also necessary, but it is important that the liquid crystal screen etc. is sufficiently easy to see, and therefore sufficient transparency, retentivity, Flatness is required. Further, it is required that the viewing angle dependency is small.
[0007]
In addition, the cellulose ester film containing a polyurethane resin having a polyester as a component is a phenomenon in which the ester bond portion of the polyester in the polyurethane resin is hydrolyzed with time, and the surface of the cellulose ester film becomes white turbid (bleed out) ) May occur, which may reduce the visibility of a liquid crystal display screen or the like.
[0008]
The present invention has been made in view of the above problems, and a first object of the present invention is to provide a cellulose ester film having sufficient durability and reduced occurrence of bleed out.
[0009]
The second object of the present invention is to provide a highly transparent cellulose ester film.
[0010]
The third object of the present invention is to provide a cellulose ester film having a low retentivity.
[0011]
A fourth object of the present invention is to provide a cellulose ester film with little color turbidity in an IPS liquid crystal display device.
[0012]
The fifth object of the present invention is to provide a cellulose ester film having high flatness.
[0013]
The sixth object of the present invention is to provide a polarizing plate and a liquid crystal display device using a cellulose ester film that achieves at least one of the above objects, and a method for producing the cellulose ester film.
[0014]
The present invention achieves at least one of the above objects.
[0015]
[Means for Solving the Problems]
The above object has been achieved by the following constitution.
[0016]
(1) A cellulose ester film containing a urethane resin having a polyester as a component and a weight average molecular weight of 100,000 or more.
[0017]
(2) A cellulose ester film containing a urethane resin having a polyester as a component and an antioxidant.
[0018]
(3) A cellulose ester film containing a urethane resin having a polyester as a component and a plasticizer.
[0019]
(4) The cellulose ester film according to (2) or (3), wherein the urethane resin has a weight average molecular weight of 100,000 or more.
[0020]
(5) The cellulose ester film as described in (3) or (4), which contains an antioxidant.
[0021]
(6) The cellulose ester film according to any one of (1) to (5), wherein the urethane resin is contained in an amount of 1 to 30% by mass.
[0022]
(7) The cellulose ester film according to any one of (1) to (6), wherein the urethane resin is synthesized from polyester and toluene diisocyanate.
[0023]
(8) The cellulose ester film according to any one of (1) to (6), wherein the urethane resin is synthesized from polyester and p, p′-diphenylmethane diisocyanate.
[0024]
(9) The cellulose ester film according to any one of (1) to (8), wherein the polyester is synthesized with adipic acid and ethylene glycol.
[0025]
(10) The cellulose ester film according to any one of (1) to (9), wherein a urethane group concentration of the urethane resin is 0.3 to 1.50 mmol / g.
[0026]
(11) The cellulose ester film according to any one of (1) to (10), wherein a haze value is 0.01 to 0.2%.
[0027]
(12) The cellulose ester film according to any one of (1) to (11), wherein the tear strength according to the Elmendle method when converted to a thickness of 40 μm is 0.05 N or more.
[0028]
(13) A polarizing plate having the cellulose ester film according to any one of (1) to (12).
[0029]
(14) A liquid crystal display device comprising the cellulose ester film according to any one of (1) to (12).
[0030]
(15) A method for producing a cellulose ester film, wherein the cellulose ester film according to any one of (1) to (12) is produced using a solution casting film forming method.
[0031]
The present invention is described in more detail below. The present inventor has found that when a urethane resin having a polyester as a component and having a weight average molecular weight of 100,000 or more is contained in the cellulose ester film, the cellulose ester film is less likely to bleed out.
[0032]
Moreover, this inventor also discovered that the bleed-out of a cellulose-ester film becomes difficult to occur by making a cellulose-ester film contain the urethane resin which has polyester as a component, and antioxidant. At this time, it has also been found that it is preferable to make the weight average molecular weight of the urethane resin to be contained 100000 or more because the bleedout of the cellulose ester is more difficult to occur.
[0033]
Furthermore, this inventor also discovered that the bleed-out of a cellulose-ester film becomes difficult to occur by making a cellulose-ester film contain the urethane resin which has polyester as a component, and a plasticizer. At this time, it was also found that it is preferable to make the weight average molecular weight of the urethane resin to be contained 100000 or more because the bleedout of the cellulose ester film is less likely to occur. Furthermore, it has been found that the inclusion of an antioxidant is particularly preferable because it is more difficult for bleeding out to occur.
[0034]
In the cellulose ester film of the present invention, it is more preferable that the weight average molecular weight of the urethane resin is 200,000 or more, which makes it more difficult for bleeding out to occur.
[0035]
Since the cellulose ester film of the present invention contains a urethane resin, it has high tear strength and excellent durability.
[0036]
The material of the urethane resin used in the cellulose ester film of the present invention is not particularly limited as long as it contains high tear strength and durability, but it is synthesized by reacting polyester with toluene diisocyanate. It is preferable to be a urethane resin. When this urethane resin is used, the tear strength is further increased, bleeding out can be further suppressed, and the transparency can be increased. Furthermore, moisture permeability can be suppressed.
[0037]
Even if a urethane resin synthesized by reacting polyester and p, p'-diphenylmethane diisocyanate as a urethane resin is used, the tear strength is further increased, bleeding out can be further suppressed, and the transparency is increased. be able to. Furthermore, moisture permeability can be suppressed.
[0038]
Furthermore, the polyester used for the urethane resin is preferably synthesized with adipic acid and ethylene glycol. As a result, the tear strength is further increased, bleeding out can be further suppressed, and the transparency can be further increased.
[0039]
The urethane group concentration of the urethane resin contained in the cellulose ester film of the present invention is preferably 0.3 to 1.50 mmol / g, more preferably 0.7 to 1.20 mmol / g. , The tear strength increases and the transparency also increases. The urethane group concentration can be measured by NMR (JEOL Ltd .: Lambda400).
[0040]
The cellulose ester film of the present invention preferably contains 1 to 30% by mass of urethane resin, more preferably 15 to 25% by mass. As a result, the tear strength is further increased, bleeding out can be further suppressed, and the transparency can be increased.
[0041]
Examples of the plasticizer contained in at least one of the cellulose ester films of the present invention include alkyl phthalyl alkyl glycolates, phosphate esters and carboxylic acid esters.
[0042]
Examples of alkyl phthalyl alkyl glycolates include methyl phthalyl methyl glycolate, ethyl phthalyl ethyl glycolate, propyl phthalyl propyl glycolate, butyl phthalyl butyl glycolate, octyl phthalyl octyl glycolate, methyl phthalyl ethyl Glycolate, ethyl phthalyl methyl glycolate, ethyl phthalyl propyl glycolate, propyl phthalyl ethyl glycolate, methyl phthalyl propyl glycolate, methyl phthalyl butyl glycolate, ethyl phthalyl butyl glycolate, butyl phthalyl methyl glycol Butyl phthalyl ethyl glycolate, propyl phthalyl butyl glycolate, butyl phthalyl propyl glycolate, methyl phthalyl octyl glycolate, ethyl phthalyl Chi le glycolate, octyl phthalyl methyl glycolate, and the like octyl phthalyl ethyl glycolate. Examples of phosphate esters include triphenyl phosphate, tricresyl phosphate, phenyl diphenyl phosphate, and the like. Examples of the carboxylic acid ester include phthalic acid ester and citric acid ester. Examples of the phthalic acid ester include dimethyl phthalate, diethyl phosphate, dioctyl phthalate, and diethyl hexyl phthalate. Examples of the citrate ester include acetyl triethyl citrate and citric acid. Mention may be made of acetyltributyl. Other examples include butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, and triacetin.
[0043]
Among them, methyl phthalyl methyl glycolate, ethyl phthalyl ethyl glycolate, propyl phthalyl propyl glycolate, butyl phthalyl butyl glycolate, octyl phthalyl octyl glycolate are preferable, and ethyl phthalyl ethyl glycolate is particularly preferable. . These alkyl phthalyl alkyl glycolates may be used in combination of two or more.
[0044]
1-30 mass% is preferable with respect to a cellulose ester, and, as for the quantity of the plasticizer contained in the cellulose ester film of this invention, 4-13 mass% is especially preferable. By setting it as this range, durability can be improved, maintaining the retentivity of a cellulose-ester film.
[0045]
The antioxidant contained in at least one of the cellulose ester films of the present invention is specifically a phenylenediamine antioxidant (Ouchi Shinsei Chemical Co., Ltd .: Nocrack CD, Nocrack TO, Nocrack GI, Aspic ), Imidazole antioxidants (Ouchi Shinsei Chemical Co., Ltd .: Nocrack MB, Nocrack MMB, etc.), hindered phenol antioxidants (BHT, etc.), dithiocarbamate antioxidants, and the like. Di-t-butylmethylphenol (BHT) is preferred.
[0046]
The cellulose ester film of the present invention contains a cellulose ester. Examples of the cellulose ester include cellulose triacetate, cellulose diacetate, cellulose ester propionate, and cellulose propionate. It may contain an acyl group having 4 or more carbon atoms, such as cellulose acetate butyrate and cellulose acetate propionate butyrate. Of these, those consisting only of an acyl group having 2 to 3 carbon atoms are preferred, and cellulose triacetate and cellulose acetate propionate are particularly preferred. The substitution degree of the acyl group is preferably 2.6 to 3.0. By setting the degree of substitution within this range, a film having good durability can be obtained. If the degree of substitution of the acetyl group is too small, the breaking strength of the film may be too low, so it is preferably 1.4 or more. The measuring method of the substitution degree of an acyl group can be measured by ASTM-D817-96.
[0047]
The cellulose ester used in the present invention can be synthesized by an ordinary method. For example, it can be synthesized by the method described in JP-A-10-45804.
[0048]
The cellulose as a raw material for the cellulose ester is not particularly limited, and examples thereof include cotton linter, wood pulp, and kenaf. Moreover, the cellulose ester obtained from them can be mixed and used in arbitrary ratios, respectively. Cellulose esters obtained from cotton linters are preferred because they have particularly good releasability from the support during film formation.
[0049]
The weight average molecular weight of the cellulose ester used in the present invention is preferably in the range of 70,000 to 300,000 because the mechanical strength when molded is strong. Furthermore, 80,000-200,000 are preferable.
[0050]
When the cellulose ester film of the present invention is used, for example, in a liquid crystal display device, the opportunity to be used outdoors has increased, and it is also important to impart a function of cutting ultraviolet rays to a protective film for a polarizing plate. . For this purpose, it is preferable to contain an ultraviolet absorber, and the ultraviolet absorber used preferably has no absorption in the visible light region, and examples thereof include benzotriazole compounds, benzophenone compounds, and salicylic acid compounds. For example, 2- (2′-hydroxy-5-methylphenyl) benzotriazole, 2- (2′-hydroxy-3 ′, 5′-di-t-butylphenyl) benzotriazole, 2- (2′-hydroxy- 3'-di-t-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.
[0051]
The addition amount of the ultraviolet absorber is preferably in the range of 0.5 to 20% by mass, more preferably in the range of 0.6 to 5% by mass with respect to the cellulose ester.
[0052]
For the purpose of improving the heat and heat resistance of the film, hindered phenol compounds are preferably used, and 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di- t-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino) -1 , 3,5-triazine, 2,2-thio-diethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octa Sil-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, N, N'-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-hydrocinnamamide) 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tris- (3,5-di-t-butyl-4-hydroxy Benzyl) -isocyanurate and the like. In particular, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] is preferred. Further, for example, hydrazine-based metal deactivators such as N, N′-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine and tris (2,4-di-t A phosphorus-based processing stabilizer such as -butylphenyl) phosphite may be used in combination. The amount of these compounds added is preferably 1 ppm to 1.0%, more preferably 10 to 1,000 ppm in terms of mass ratio with respect to the cellulose ester. In addition, a heat stabilizer such as a salt of an alkaline earth metal such as calcium or magnesium may be added.
[0053]
In addition, a dye may be added to the cellulose ester film of the present invention for the purpose of improving the yellowness of the film. The tint is preferably one that can be colored gray as seen on a normal photographic support. However, unlike the photographic support, it is not necessary to prevent light piping, so the content may be small, and the mass ratio to the cellulose ester is preferably 1 to 100 ppm, more preferably 2 ppm to 50 ppm. Since the cellulose ester is slightly yellowish, a blue or purple dye is preferably used. A plurality of dyes may be appropriately combined so as to become gray.
[0054]
If the film is difficult to slip, the films may block and handleability may be poor. In this case, inorganic fine particles such as silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, kaolin, talc, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, calcium phosphate, etc. It is preferable to include a matting agent such as a molecule. Of these, silicon dioxide is preferable because it can reduce the haze of the film. The matting agent is preferably blended so that the haze of the film is 0.6% or less and the dynamic friction coefficient is 0.5 or less. The matting agent used for this purpose preferably has an average particle size of 0.01 to 1.0 μm and a content of 0.005 to 0.3% by mass with respect to the cellulose ester.
[0055]
In addition to the above, an antistatic agent, a flame retardant, a lubricant, an oil agent, and the like may be added as appropriate.
The cellulose ester film of the present invention preferably has a haze value of 0.01 to 0.2% in consideration of use for a protective film for a polarizing plate such as a liquid crystal display device. This makes it easier to see the liquid crystal display device. The haze value can be measured with a commercially available measuring instrument such as TURBIDITY METER T-2600DA manufactured by Tokyo Denshoku Co., Ltd.
[0056]
The cellulose ester film of the present invention needs to have a certain degree of strength and improved durability in order to cope with the reduction in thickness in consideration of use for a protective film for a polarizing plate such as a liquid crystal display device. Therefore, the tear strength according to the Elmendle method when converted to a thickness of 40 μm is preferably 0.05 N or more. Here, the tear strength according to the Elmendle method when converted to a thickness of 40 μm is 0.05 N or more, as described in JIS K7128-1991, method A (trouser tear method), method B (element It shows that the value measured using a 40 μm thick film using the B method of the Dorf tear method and the C method (right angle tear method) is 0.05 N or more.
[0057]
The cellulose ester film of the present invention has a moisture permeability of 300 g / m in consideration of use for a protective film for a polarizing plate such as a liquid crystal display device. ² -It is preferable that it is 24 hours or less. Thereby, the penetration | invasion of the water vapor | steam from a polarizing plate can be suppressed and durability of a liquid crystal display device can be improved. The moisture permeability is a value measured under conditions of 25 ° C. and 90% RH according to JIS Z0208-76.
[0058]
Since the cellulose acetate film of the present invention has the above performance, it is useful when used as a protective film for a polarizing plate, and particularly useful when used as a protective film for a polarizing plate of a liquid crystal display device.
[0059]
The cellulose ester film of the present invention is preferably manufactured using a solution casting film forming method. Thereby, it can be set as the cellulose-ester film which was more excellent in planarity, and the visibility of a liquid crystal display device etc. can be improved.
[0060]
The manufacturing method of the cellulose ester film by the solution casting film forming method concerning this invention is demonstrated.
[0061]
The solution casting film forming method includes a dissolution step, a casting step, a solvent evaporation step, a peeling step, a drying step, and a winding step.
[0062]
{Circle around (1)} Dissolution step: This is a step of forming a dope by dissolving the flakes in an organic solvent mainly composed of a good solvent for cellulose ester flakes in a dissolution vessel while stirring.
[0063]
The dissolution method useful in the present invention is a method performed at a temperature not lower than the boiling point of the main solvent and under a pressure that does not boil (hereinafter referred to as a high temperature dissolution method), cooling the cellulose ester and the organic solvent to −100 ° C. to −10 ° C. Or after mixing the cellulose ester with an organic solvent at −100 ° C. to −10 ° C. and then heating to 0 ° C. to 120 ° C. (hereinafter referred to as cooling dissolution method), the cellulose ester and the organic solvent at 50 atm. Examples include a method of pressurizing to 2,000 atmospheres (hereinafter referred to as a high-pressure dissolution method).
[0064]
For example, in the case of using methyl acetate (boiling point 56.32 ° C.) as the main solvent in the high temperature dissolution method, the temperature is preferably 56.32 ° C. to 120 ° C., more preferably 60 ° C. to 90 ° C. At this time, the pressure that does not boil may be about 2 atm or more, and there is no particular upper limit, but the effect is saturated at about 50 atm, so 2 to 50 atm is preferable. Further, 2 to 10 atm is preferable.
[0068]
The cellulose ester dope preferably contains 0.1 to 30% by mass of an alcohol having 1 to 4 carbon atoms. As a result, after the dope is cast on the casting support, the solvent starts to evaporate, and when the alcohol ratio increases, the web (dope film) gels, making the web strong and easy to peel off from the casting support. Furthermore, the effect of promoting the dissolution of the cellulose ester of the non-chlorine organic solvent can be obtained. 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 most preferable because of the stability of the dope, the boiling point is relatively low, the drying property is good, and there is no toxicity.
[0069]
The solid content concentration of the dope is usually preferably 10 to 40% by mass, and the dope viscosity is preferably adjusted to a range of 100 to 500 poise from the viewpoint of obtaining good film flatness.
[0070]
The dope prepared as described above is filtered with a filter medium, defoamed, and sent to the next process with a pump.
[0071]
(2) Casting step: The dope is fed to a pressurizing die through a pressurization type fixed gear pump, and an endless metal belt for infinite transfer or a support for casting a rotating metal drum at the casting position (hereinafter simply referred to as “casting”). 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 in which the film thickness of the cast dope film is adjusted with a blade, or a reverse roll coater method in which the film is adjusted with a reverse rotating roll, but the slit shape of the die part is adjusted. A pressure die that is easy to make uniform in film thickness 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 dope amount may be divided and stacked.
[0072]
(3) Solvent evaporation step: This is a step of evaporating the solvent by heating the web (the dope film is referred to as the web after the dope is cast 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 from the back side of the support by a liquid, a method of transferring heat from the front and back by radiant heat, and the like. The drying efficiency is good and preferable. A method of combining them is also preferable.
[0073]
(4) Peeling step: This is a step of peeling the web where the solvent has evaporated on the support at the peeling position. The peeled web is sent to the next process. If the residual solvent amount (the following formula) of the web at the time of peeling is too large, peeling is difficult, or conversely, if it is peeled off after sufficiently drying on the support, part of the web is peeled off.
[0074]
As a method for increasing the film forming speed (the film forming speed can be increased because the film is peeled off while the residual solvent amount is as large as possible), there is a gel casting method (gel casting) in which even a large amount of residual solvent can be removed. For example, a poor solvent for the cellulose ester is added to the dope, and after the dope is cast, the gel is formed, and the temperature of the support is lowered to form a gel. There is also a method of adding a metal salt in the dope. By gelling on the support and strengthening the film, it is possible to speed up the peeling and increase the film forming speed. When peeling at a time when the amount of residual solvent is larger, if the web is too soft, the flatness at the time of peeling will be impaired, or slippage and vertical stripes due to peeling tension are likely to occur, and the amount of residual solvent that is peeled off is a balance between economic speed and quality. It is decided.
[0075]
(5) Drying step: A step of drying the web using a drying device that alternately conveys the web through rolls arranged in a staggered manner and / or a tenter device that clips and conveys both ends of the web with a clip. As a drying means, hot air is generally blown on both sides of the web, but there is also a means for heating by applying a microwave instead of the wind. Too much drying tends to impair the flatness of the finished film. Drying at a high temperature is preferably performed from about 8% by mass or less of the residual solvent. Throughout, the drying temperature is usually 40 to 250 ° C, preferably 70 to 180 ° C. The drying temperature, the amount of drying air, and the drying time differ depending on the solvent used, and the drying conditions may be appropriately selected according to the type and combination of the solvents used.
[0076]
In the drying step after peeling from the casting support surface, the web tends to shrink in the width direction due to evaporation of the solvent. Shrinkage increases as the temperature rapidly dries. Drying while suppressing this shrinkage as much as possible is preferable for improving the flatness of the finished film. From this point of view, for example, a method of drying the entire drying process or a part of the process as shown in Japanese Patent Application Laid-Open No. 62-46625 while holding the width at both ends of the web with a clip in the width direction (tenter method) ) Is preferred.
[0077]
(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 residual solvent amount to 0.4% by mass or less, a film having good dimensional stability can be obtained. As a winding method, a generally used method may be used. There are a constant torque method, a constant tension method, a taper tension method, a program tension control method with a constant internal stress, and the like.
[0078]
The amount of residual solvent can be expressed by the following formula.
Residual solvent amount (% by mass) = {(MN) / N} × 100
Here, M is the mass of the web at any point, and N is the mass when M is dried at 110 ° C. for 3 hours.
[0079]
To adjust the film thickness of the cellulose ester film, adjust the dope concentration, the pumping amount, the slit gap of the die base, the extrusion pressure of the die, the speed of the casting support, etc. It is good to control. Further, as a means for making the film thickness uniform, it is preferable to use a film thickness detection means to feed back and adjust the programmed feedback information to each of the above devices.
[0080]
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. .
[0081]
【Example】
EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.
1. Production of film samples 1 to 23
<Film samples 1-20>
A dope composition 1 having the following composition was put into a sealed container, heated to 70 ° C., and stirred to completely dissolve cellulose triacetate (TAC) to obtain a dope. The time required for dissolution was 4 hours. After the dope composition was filtered, it was uniformly cast on a stainless band support having a dope temperature of 35 ° C. and a temperature of 22 ° C. using a belt casting apparatus. The temperature of the stainless steel band support was 20 ° C.
[0082]
Then, after making it dry to the range which can be peeled, dope was peeled from the stainless steel band support body. At this time, the residual solvent amount of the dope was 25%. The time required from casting the dope to peeling was 3 minutes. After peeling from the stainless steel band support, after drying at 120 ° C while holding in the width direction, release the width holding and finish drying at 120 ° C and 135 ° C drying zones while transporting with many rolls. Then, a knurling process having a width of 10 mm and a height of 5 μm was applied to both ends of the film to prepare a cellulose triacetate film sample 1 having a thickness of 40 μm. The film width of the film sample was 1300 mm, and the winding length was 3000 m. The winding tension was an initial tension of 1.5 N / 1300 mm and a final winding tension of 1 N / 1300 mm. In the same manner, film samples 2 to 20 were prepared for the dope compositions 2 to 20. In this way, film samples 1 to 20 were obtained.
[Dope Compositions 1-20]
Triacetyl cellulose (acetylation degree 61.0%) 100 parts by mass
2- (2'-hydroxy-3 ', 5'-di-t-butyl
Phenyl) bezotriazole 2 parts by mass
20 parts by mass of urethane resin described in Table 1 below
5 parts by mass of a plasticizer described in Table 1 below
0.5 mass parts of antioxidants listed in Table 1 below
475 parts by mass of methylene chloride
50 parts by mass of ethanol
[0083]
[Table 1]

[0084]
<Film sample 21>
A film sample 21 was produced in the same manner as the production of the film sample 1 except that the dope composition 1 was changed to the following dope composition 21 in the production of the film sample 1.
[Dope composition 21]
Triacetyl cellulose (acetylation degree 61.0%) 100 parts by mass
2- (2'-hydroxy-3 ', 5'-di-t-butyl
Phenyl) bezotriazole 1 part by mass
15 parts by mass of triphenyl phosphate
475 parts by mass of methylene chloride
50 parts by mass of ethanol
<Film sample 22>
A film sample 22 was produced in the same manner except that the dove composition 1 was changed to the following dope composition 22 in the production of the film sample 1.
[Dope composition 22]
Triacetyl cellulose (acetylation degree 61.0%) 100 parts by mass
2- (2'-hydroxy-3 ', 5'-di-t-butyl
Phenyl) bezotriazole 1 part by mass
4 parts by mass of ethyl phthalyl ethyl glycolate
475 parts by mass of methylene chloride
50 parts by mass of ethanol
<Film sample 23>
A film sample 23 was produced in the same manner except that the dope composition 1 was changed to the following dope composition 23 in the production of the film sample 1.
[Dope composition 23]
Triacetyl cellulose (acetylation degree 61.0%) 100 parts by mass
2- (2'-hydroxy-3 ', 5'-di-t-butyl
Phenyl) bezotriazole 1 part by mass
10 parts by weight of triphenyl phosphate
Laurylbenzenesulfonate 2 parts by weight
475 parts by mass of methylene chloride
50 parts by mass of ethanol
2. Preparation of polarizing plate samples 1 to 23
Film sample 1 was alkali-treated with a 2.5 M sodium hydroxide aqueous solution at 40 ° C. for 60 seconds and washed with water for 3 minutes to form a saponification-treated layer to obtain an alkali-treated film.
[0085]
Next, a 120 μm-thick polyvinyl alcohol film was immersed in 100 parts by mass of an aqueous solution containing 1 part by mass of iodine and 4 parts by mass of boric acid, and stretched 4 times at 50 ° C. to form a polarizing film. A polarizing plate sample 1 was prepared by laminating the alkali-treated film on both surfaces of this polarizing film with a 5% aqueous solution of a completely saponified polyvinyl alcohol as an adhesive. Regarding the film samples 2 to 23, polarizing plate samples 2 to 23 were prepared in the same manner as described above.
3. Evaluation of film samples 1 to 23 and polarizing plate samples 1 to 23
The following (1) to (6) for the film samples 1 to 23 and the following (7) for the polarizing plate samples 1 to 23 were evaluated.
(1) Haze
The haze value was measured using TURBIDITY METER T-2600DA manufactured by Tokyo Denshoku Co., Ltd.
(2) Tear strength
The tear strength of the Elmendorf method was measured with a light load tear device manufactured by Toyo Seiki Co., Ltd. according to JIS K 7128-1991.
(3) Moisture permeability
The moisture permeability of each film sample was measured according to the method described in JIS Z 0208. The temperature and humidity conditions for the test are 25 ° C. and 90% RH.
(4) Retention (plasticizer precipitation)
A film sample was cut out in a size of 10 cm in the width direction and 10 cm in the longitudinal direction, and the mass after standing for 24 hours at 23 ° C. and 55% RH was measured. Then, the sample was 48 under the conditions of 80 ° C. and 90% RH. Time processed. Further, the mass of the treated film sample after standing for 24 hours at 23 ° C. and 55% RH was measured, and the retention was calculated by the following method.
[0086]
Retention property = (mass before treatment−mass after treatment) / mass before treatment × 100%
(5) Bleed out value
A film sample was cut out in a size of 10 cm in the width direction and 10 cm in the longitudinal direction, treated for 48 hours under conditions of 80 ° C. and 90% RH, and then TURBIDITY METER T-2600DA manufactured by Tokyo Denshoku Co., Ltd. The haze value measured using this was taken as the bleed-out value.
(6) Retardation value (Rt value)
Using an automatic birefringence meter KOBRA-21AH (manufactured by Oji Scientific Instruments), a three-dimensional refractive index measurement is performed at a wavelength of 590 nm on a film sample under the conditions of 23 ° C. and 55% RH. Nx, Ny, and Nz are obtained.
[0087]
The retardation value Rt in the thickness direction was calculated according to the following formula.
Rt = {(Nx + Ny) / 2−Nz} * d
In the formula, Nx is the refractive index of the film in the direction parallel to the film forming direction, Ny is the refractive index of the film in the direction perpendicular to the film forming direction, Nz is the refractive index of the film in the film thickness direction, d Represents the thickness (nm) of the film.
(7) Polarizing plate durability test
Two 10 cm × 10 cm polarizing plate samples were subjected to high temperature and high humidity treatment (conditions: 80 ° C.-90% RH, 50 hours), and the surface state was observed.
[0088]
A: Less than 5% of the part of the polarizing plate clouded by bleed-out
(No problem for polarizing plate)
○: The portion where the surface of the polarizing plate becomes cloudy due to bleeding out is 5% or more and less than 10%
(No problem for polarizing plate)
Δ: The portion of the polarizing plate clouded by bleed-out is 10% or more and less than 20%
(A level that can be used as a polarizing plate)
×: 20% or more of the portion of the polarizing plate clouded by bleed-out
(Problem level as a polarizing plate)
If it is more than △, it is a level where there is no practical problem.
[0089]
The results are shown in Tables 2 and 3.
[0090]
[Table 2]

[0091]
[Table 3]

[0092]
Further, the polarizing plate samples 3 and 22 were incorporated in an IPS module and evaluated for color. The results are shown in Table 4.
[0093]
[Table 4]

[0094]
From the results of Tables 2 and 3, the film sample of the present invention has very high transparency with a haze of 0.1%, so that it is very useful particularly when used for a polarizing plate of a liquid crystal display device. I understood.
[0095]
Moreover, since the film sample of this invention has high tear strength and high durability, it turned out that it is very useful especially when used for the polarizing plate etc. of a liquid crystal display device.
[0096]
Furthermore, since the film sample of the present invention has low retentivity, it has been found that it is very useful particularly when used for a polarizing plate of a liquid crystal display device.
[0097]
Further, since the film sample of the present invention has a low water vapor transmission rate, it can prevent deterioration of the function of the liquid crystal display device due to the intrusion of water vapor, particularly when used for a polarizing plate of a liquid crystal display device. It was found that can be improved.
[0098]
Furthermore, since the film sample of the present invention suppresses the occurrence of bleed-out, it has been found that the film sample is very useful particularly when used for a polarizing plate of a liquid crystal display device.
[0099]
Further, it was found that the polarizing plate sample 3 of the present invention has a particularly small Rt and is very useful when used for a polarizing plate of an IPS liquid crystal display device because color turbidity is suppressed.
[0100]
Furthermore, since the film sample of the present invention is manufactured using a solution casting film forming method, it has high flatness and is very useful when used for a polarizing plate protective film of a liquid crystal display device.
[0101]
Furthermore, since the polarizing plate sample of this invention can suppress generation | occurrence | production of bleed-out, it turned out that it is very useful when used for the polarizing plate protective film of a liquid crystal display device.
[0102]
Furthermore, each of the polarizing plate samples of the present invention was set and used in a liquid crystal display device, and was confirmed to be very useful due to the above-described effects.
[0103]
【The invention's effect】
With at least one of the cellulose ester films of the present invention, it was possible to provide a cellulose ester film having sufficient durability and reduced occurrence of bleed out.
[0104]
With at least one of the cellulose ester films of the present invention, a highly transparent cellulose ester film could be provided.
[0105]
With at least one of the cellulose ester films of the present invention, a cellulose ester film with low retentivity could be provided.
[0106]
With at least one of the cellulose ester films of the present invention, it was possible to provide a cellulose ester film with little color turbidity in an IPS liquid crystal display device.
[0107]
With at least one of the cellulose ester films of the present invention, a highly planar cellulose ester film could be provided.
[0108]
It was possible to provide a polarizing plate, a liquid crystal display device using the cellulose ester film of the present invention having at least one of the above effects, and a method for producing the cellulose ester film.

Claims (5)

A urethane resin containing methylene chloride and cellulose ester, synthesized by reacting polyester with toluene diisocyanate or p, p′-diphenylmethane diisocyanate, and having a weight average molecular weight of 100,000 or more, and a plasticizer. A method for producing a cellulose ester film, which comprises producing a dope contained by a solution casting film forming method. A cellulose ester film produced by the method for producing a cellulose ester film according to claim 1. A polarizing plate comprising the cellulose ester film according to claim 2. A liquid crystal display device comprising the polarizing plate according to claim 3. The liquid crystal display device according to claim 4, wherein the liquid crystal display device is an IPS system.