JP6024479B2 - Optical film, circularly polarizing plate, and image display device - Google Patents

Description

  The present invention relates to an optical film, a circularly polarizing plate, and an image display device.

  The λ / 4 retardation film can convert linearly polarized light into circularly polarized light and elliptically polarized light, or convert circularly polarized light and elliptically polarized light into linearly polarized light. Such a λ / 4 retardation film is widely used for various optical applications in image display devices and optical pickup devices.

  A retardation film used in an optical device using a laser light source of a specific wavelength, such as an optical pickup device, can impart a quarter-wave phase difference (hereinafter also referred to as retardation) to only light of a specific wavelength. Good. However, the retardation film constituting the antireflection film (circular polarizing plate) of the image display device (including the organic EL display) can give a quarter-wave retardation to the light in the entire visible light range. Desired. Therefore, the λ / 4 retardation film used in the image display device has a negative wavelength dispersibility (reverse) in which the retardation imparted to the long wavelength light is larger than the retardation imparted to the short wavelength light. It is required to have (wavelength dispersion).

  A stretched film made of cellulose acetate having a specific degree of acetylation has been proposed as a retardation film having a retardation of λ / 4 and exhibiting negative wavelength dispersion (for example, Patent Document 1). However, a film whose phase difference and wavelength dispersion are adjusted only with a resin such as cellulose acetate, which is the main component of the film, has a problem that its optical characteristics are likely to fluctuate greatly due to slight environmental changes such as humidity, temperature, and external pressure. It was.

  On the other hand, a retardation film containing a retardation increasing agent having a wavelength dispersion adjusting function, having a retardation of λ / 4, and exhibiting negative wavelength dispersion has been proposed (for example, Patent Document 2). As described above, by adding the additive and adjusting the phase difference and the wavelength dispersibility, the fluctuation of the optical characteristics due to the environmental change as described above can be suppressed to some extent.

  By the way, in a circularly polarizing plate including a polarizer and a λ / 4 retardation film, the polarizer is laminated so that the absorption axis of the polarizer and the slow axis of the λ / 4 retardation film are at an angle of about 45 degrees. Need to be. Usually, since the polarizing film used as a polarizer is obtained by extending polyvinyl alcohol colored with a pigment at a high magnification in the longitudinal direction, the polarizing film has an absorption axis parallel to the longitudinal direction. On the other hand, the retardation film is usually obtained by stretching the resin film in the longitudinal direction or the transverse direction and orienting the molecules of the resin or additive to adjust the retardation, so that the longitudinal direction or the transverse direction is obtained. Has a slow axis parallel to the axis. Therefore, conventionally, a circularly polarizing plate is obtained by cutting out a film to an appropriate size from a long polarizer film and a long λ / 4 retardation film, and bonding them obliquely (batch). method). However, since the batch method has low productivity and a large loss of chips and the like, improvement has been demanded particularly when manufacturing a circularly polarizing plate used for a large display or the like.

  On the other hand, the resin film is stretched in an oblique direction (a direction that is neither 0 ° nor 90 °) with respect to the longitudinal direction (or the width direction) of the film, and relative to the longitudinal direction (or the width direction) of the film. A method for producing a long retardation film having a slow axis in an oblique direction has been proposed (for example, Patent Document 3). In this way, by using a stretched film having a slow axis in an oblique direction, a long circular polarizing plate can be obtained by laminating with a roll-toe-roll instead of a conventional batch-type laminating. It can be manufactured and productivity is dramatically improved.

  By the way, a circularly polarizing plate is usually manufactured by laminating a λ / 4 retardation film and a polarizer film via an adhesive. For example, in the case of a retardation film mainly composed of cellulose ester, an aqueous adhesive such as polyvinyl alcohol is used as the adhesive used for bonding. In recent years, a method using an active energy ray-curable adhesive has been proposed from the viewpoint of suppressing water unevenness of a circularly polarizing plate and increasing productivity (for example, Patent Document 4). As described above, the retardation film is required to be able to adhere to the polarizer film regardless of whether the aqueous adhesive or the active energy ray-curable adhesive is used.

JP 2000-137116 A International Publication No. 2000/065384 JP 2010-173261 A JP 2009-193047 A

  However, a circularly polarizing plate in which an obliquely stretched film containing a cellulose ester, a retardation increasing agent having a wavelength dispersion adjusting function, and a polarizer film are bonded together via an ultraviolet curable adhesive is used as an antireflection film. There is a problem in that the contrast of the organic EL display device included in the above is lowered or color variation is caused.

  As a result of intensive studies, the inventors of the present invention have a decrease in contrast and color variation of an organic EL display device caused by a phase difference film constituting a circularly polarizing plate contracting and a phase difference and wavelength dispersion being changed. I found out. The shrinkage of the retardation film is caused by the irradiation of ultraviolet rays for curing the active energy ray-curable adhesive in the manufacturing process of the circularly polarizing plate, so that the wavelength dispersion adjusting agent contained in the retardation film absorbs ultraviolet rays and heats it. It was found to be caused by the heat.

  The present invention has been made in view of the above circumstances, and has an optical film having a high phase difference and good reverse wavelength dispersion, and capable of suppressing thermal shrinkage during ultraviolet irradiation, and a circularly polarized light including the same The purpose is to provide a board. Another object of the present invention is to provide an image display device that includes the above optical film, suppresses a decrease in contrast, and has little color fluctuation.

  The present inventors include a wavelength dispersion adjusting agent whose absorption peak is adjusted in the range of 300 to 360 nm, and the obliquely stretched film having a transmittance at 380 nm of 20 to 90% has a high retardation in the in-plane direction. The present inventors have found that they exhibit good light resistance and wavelength dispersion and are less likely to cause phase difference fluctuations during ultraviolet irradiation. As a result, the image display device including the obliquely stretched film has been found to have little reduction in contrast, color variation, and the like, and is excellent in light resistance. That is, the said subject concerning this invention is solved by the following means.

（一般式（１）中、
Ａは、芳香族炭化水素環、非芳香族炭化水素環、芳香族複素環または非芳香族複素環を表し；
Ｌ_１およびＬ_２は、それぞれ独立に単結合または−Ｒ_Ｌ−Ｏ−、−Ｏ−Ｒ_Ｌ−、−Ｏ−Ｃ（＝Ｏ）−Ｒ_Ｌ−、−Ｃ（＝Ｏ）−Ｏ−Ｒ_Ｌ−（Ｒ_Ｌは、フェニレン基、アルキレン基、アルケニレン基またはアルキニレン基を示す）、−Ｏ−、−（Ｃ＝Ｏ）−、−（Ｃ＝Ｓ）−、−（Ｃ＝Ｏ）−Ｏ−、−ＮＲ_Ｍ−、−Ｓ−、−ＳＯ_２−、−（Ｃ＝Ｏ）−ＮＲ_Ｍ−および−ＮＲ_Ｍ−（Ｃ＝Ｏ）−（Ｒ_Ｍは、水素原子またはアルキレン基を表す）からなる群より選ばれる２価の連結基またはそれらの組合せを表し；
Ｒ_２およびＲ_３は、それぞれ独立にアルキレン基、アルケニレン基、アルキニレン基、−（Ｒ_Ｎ）ｎ−（Ｒ_Ｎは、シクロアルキレン基を示し、ｎは１〜４の整数を示す）、−（ＯＲ_Ｏ）ｎ−（Ｒ_Ｏは、アルキレン基を示し、ｎは１〜４の整数を示す）、フェニレン基、ヘテロアルキレン基またはヘテロアリ−レン基を表し；
Ｒ_４およびＲ_５は、水素原子または置換基を表し；
Ｒ_１は、置換基を表し；
ｋは、０〜４の整数を表し；
複数のＲ_１は、互いに結合して環を形成してもよい）
［２］ 前記一般式（１）で表される波長分散調整剤が、下記一般式（２）で表される化合物である、［１］に記載の光学フィルム。
一般式（２）

（一般式（２）中、
Ｌ_2１およびＬ_2２は、それぞれ独立に単結合または−Ｒ_Ｌ−Ｏ−、−Ｏ−Ｒ_Ｌ−、−Ｏ−Ｃ（＝Ｏ）−Ｒ_Ｌ−、−Ｃ（＝Ｏ）−Ｏ−Ｒ_Ｌ−（Ｒ_Ｌは、フェニレン基、アルキレン基、アルケニレン基またはアルキニレン基を示す）、−Ｏ−、−（Ｃ＝Ｏ）−、−（Ｃ＝Ｓ）−、−（Ｃ＝Ｏ）−Ｏ−、−ＮＲ_Ｍ−、−Ｓ−、−ＳＯ_２−、−（Ｃ＝Ｏ）−ＮＲ_Ｍ−および−ＮＲ_Ｍ−（Ｃ＝Ｏ）−（Ｒ_Ｍは、水素原子またはアルキレン基を表す）からなる群より選ばれる２価の連結基またはそれらの組合せを表し；
Ｒ_２２およびＲ_２３は、それぞれ独立にアルキレン基、アルケニレン基、アルキニレン基、−（Ｒ_Ｎ）ｎ−（Ｒ_Ｎは、シクロアルキレン基を示し、ｎは１〜４の整数を示す）、−（ＯＲ_Ｏ）ｎ−（Ｒ_Ｏは、アルキレン基を示し、ｎは１〜４の整数を示す）、フェニレン基、ヘテロアルキレン基またはヘテロアリ−レン基を表し；
Ｒ_２４およびＲ_２５は、水素原子または置換基を表し；
Ｒ_２１は、−（Ｃ＝Ｏ）Ｒｐ、−（Ｃ＝Ｏ）−Ｏ−Ｒｐ、−Ｏ−（Ｃ＝Ｏ）−Ｒｐ、−（Ｃ＝Ｏ）−Ｓ−Ｒｐ、−Ｓ−（Ｃ＝Ｏ）−Ｒｐ（Ｒｐは、アルキル基またはアリール基を示す）、−Ｃ（＝Ｏ）−ＮＲｑ（Ｒｑは、アルキル基を表す）、アリール基、ヘテロアリール基、または前記Ｒ_２１が結合するベンゼン環と縮合した２，５−ジオン−ピロリジン環を表し；
ｋ_２は、１〜４の整数を表す）
［３］ 前記一般式（１）で表される波長分散調整剤が、下記一般式（３）で表される化合物である、［１］に記載の光学フィルム。
一般式（３）

（一般式（３）中、
Ｌ_３１およびＬ_３２は、それぞれ独立に単結合または−Ｒ_Ｌ−Ｏ−、−Ｏ−Ｒ_Ｌ−、−Ｏ−Ｃ（＝Ｏ）−Ｒ_Ｌ−、−Ｃ（＝Ｏ）−Ｏ−Ｒ_Ｌ−（Ｒ_Ｌは、フェニレン基、アルキレン基、アルケニレン基またはアルキニレン基を示す）、−Ｏ−、−（Ｃ＝Ｏ）−、−（Ｃ＝Ｓ）−、−（Ｃ＝Ｏ）−Ｏ−、−ＮＲ_Ｍ−、−Ｓ−、−ＳＯ_２−および−（Ｃ＝Ｏ）−ＮＲ_Ｍ−、−ＮＲ_Ｍ−（Ｃ＝Ｏ）−（Ｒ_Ｍは、水素原子またはアルキレン基を表す）からなる群より選ばれる２価の連結基またはそれらの組合せを表し；
Ｒ_３３およびＲ_３４は、それぞれ独立にアルキレン基、アルケニレン基、アルキニレン基、−（Ｒ_Ｎ）ｎ−（Ｒ_Ｎは、シクロアルキレン基を示し、ｎは１〜４の整数を示す）、−（ＯＲ_Ｏ）ｎ−（Ｒ_Ｏは、アルキレン基を示し、ｎは１〜４の整数を示す）、フェニレン基、ヘテロアルキレン基またはヘテロアリ−レン基を表し；
Ｒ_３６およびＲ_３７は、それぞれ独立に水素原子または置換基を表し；
Ｒ_３１およびＲ_３２は、それぞれ独立に水素原子または−（Ｃ＝Ｏ）−Ｏ−Ｒｔ（Ｒｔは、アルキル基、オキシアルキレン基またはアリール基を示す）、−Ｃ（＝Ｏ）−Ｒｖ（Ｒｖは、アルキル基またはアリール基を示す）、−Ｃ（＝Ｏ）−ＮＲｗＲｘ（Ｒｗは、水素原子またはアルキル基を示し；Ｒｘは、アルキル基を示す）、シアノ基またはハロゲン原子を表し；Ｒ_３１とＲ_３２は、互いに結合して環を形成してもよく；
Ｒ_３５は、置換基を表し；
ｊ_３は、０〜３の整数を表す）
［４］ 前記一般式（１）で表される波長分散調整剤が、下記一般式（４）で表される化合物である、［１］に記載の光学フィルム。
一般式（４）

（一般式（４）中、
Ｂ_１およびＢ_２は、それぞれ独立に−Ｏ−、−ＮＲ−（Ｒは、水素原子または置換基を示す）、−Ｓ−、−Ｓ（＝Ｏ）−および−Ｃ（＝Ｏ）−からなる群から選ばれる２価の基を表し；
破線部は、単結合または二重結合を表し；
Ｌ_４１およびＬ_４２は、それぞれ独立に単結合または−Ｒ_Ｌ−Ｏ−、−Ｏ−Ｒ_Ｌ−、−Ｏ−Ｃ（＝Ｏ）−Ｒ_Ｌ−、−Ｃ（＝Ｏ）−Ｏ−Ｒ_Ｌ−（Ｒ_Ｌは、フェニレン基、アルキレン基、アルケニレン基またはアルキニレン基を示す）、−Ｏ−、−（Ｃ＝Ｏ）−、−（Ｃ＝Ｓ）−、−（Ｃ＝Ｏ）−Ｏ−、−ＮＲ_Ｍ−、−Ｓ−、−ＳＯ_２−、−（Ｃ＝Ｏ）−ＮＲ_Ｍ−および−ＮＲ_Ｍ−（Ｃ＝Ｏ）−（Ｒ_Ｍは、水素原子またはアルキレン基を表す）からなる群より選ばれる２価の連結基またはそれらの組合せを表し；
Ｒ_４２およびＲ_４３は、それぞれ独立にアルキレン基、アルケニレン基、アルキニレン基、−（Ｒ_Ｎ）ｎ−（Ｒ_Ｎは、シクロアルキレン基を示し、ｎは１〜４の整数を示す）、−（ＯＲ_Ｏ）ｎ−（Ｒ_Ｏは、アルキレン基を示し、ｎは１〜４の整数を示す）、フェニレン基、ヘテロアルキレン基またはヘテロアリ−レン基を表し；
Ｒ_４５およびＲ_４６は、それぞれ独立に水素原子または置換基を表し；
Ｒ_４１は、＝Ｒ_４１１Ｒ_４１２またはアリール基を表し；
＝Ｒ_４１１Ｒ_４１２におけるＲ_４１１およびＲ_４１２は、それぞれ独立にシアノ基または−Ｃ（＝Ｏ）−Ｏ−Ｒ（Ｒは、アルキル基またはアリール基を示す）を表し；
Ｒ_４４は、置換基を表し；
ｊ_４は、０〜２の整数を表し；ｊ_４が２である場合、２つのＲ_４４は互いに結合して環を形成してもよい）
［５］ ３８０ｎｍにおける透過率が、４０〜８５％の範囲内である、［１］〜［４］のいずれか一項に記載の光学フィルム。
［６］ 前記熱可塑性樹脂が、セルロースエステルである、［１］〜［５］のいずれか一項に記載の光学フィルム。
［７］ 前記セルロースエステルの、アセチル基置換度Ｘおよびプロピオニル基またはブチリル基の合計置換度Ｙが、下記式を満たす、［６］に記載の光学フィルム。
式（Ｉ） １．５≦Ｘ＋Ｙ≦２．６
式（ＩＩ） ０≦Ｙ≦１．５
［８］ 膜厚が２０〜４５μｍの範囲内である、［１］〜［７］のいずれか一項に記載の光学フィルム。
［９］ 前記一般式（１）で表される波長分散調整剤の含有量が、前記熱可塑性樹脂１００重量部に対して１〜３０重量部である、［１］〜［８］のいずれか一項に記載の光学フィルム。
［１０］ 前記光学フィルムの面内の遅相軸と、前記光学フィルムの幅方向とのなす角度が４０°以上５０°以下である、［１］〜［９］のいずれか一項に記載の光学フィルム。 [1] An optical film comprising a thermoplastic resin and a wavelength dispersion adjusting agent represented by the following general formula (1) and having an absorption peak in the range of 300 to 360 nm in the ultraviolet-visible absorption spectrum of the solution, The slow axis direction in the plane of the optical film is oblique to the width direction of the film, and retardation values in the in-plane direction measured at wavelengths of 450 nm, 550 nm, and 650 nm are R0 (450) and R0 (550, respectively. ) And R0 (650), an optical film satisfying the formulas (a) to (c) and having a transmittance of 20 to 90% at a wavelength of 380 nm.
(A) 110 nm ≦ R0 (550) ≦ 170 nm
(B) 0.72 ≦ R0 (450) / R0 (550) ≦ 1.00
(C) 0.83 ≦ R0 (550) / R0 (650) ≦ 1.00
General formula (1)

(In general formula (1),
A represents an aromatic hydrocarbon ring, a non-aromatic hydrocarbon ring, an aromatic heterocyclic ring or a non-aromatic heterocyclic ring;
L ₁ and L ₂ are each independently a single bond or —R _L —O—, —O—R _L —, —O—C (═O) —R _L —, —C (═O) —O—R. _L— (R _L represents a phenylene group, an alkylene group, an alkenylene group or an alkynylene group), —O—, — (C═O) —, — (C═S) —, — (C═O) —O _{-, - NR M -, -} S -, - SO 2 -, - (C = O) -NR M - and _{-NR M - (C = O)} - (R M represents a hydrogen atom or an alkylene group) Represents a divalent linking group selected from the group consisting of or a combination thereof;
R ₂ and R ₃ each independently represent an alkylene group, an alkenylene group, an alkynylene group,-(R _N ) n- (R _N represents a cycloalkylene group, and n represents an integer of 1 to 4),-( OR _O ) n- (R _O represents an alkylene group, n represents an integer of 1 to 4), a phenylene group, a heteroalkylene group or a heteroarylene group;
R ₄ and R ₅ represent a hydrogen atom or a substituent;
R ₁ represents a substituent;
k represents an integer of 0 to 4;
A plurality of R ₁ may be bonded to each other to form a ring)
[2] The optical film according to [1], wherein the wavelength dispersion adjusting agent represented by the general formula (1) is a compound represented by the following general formula (2).
General formula (2)

(In general formula (2),
L ₂₁ and L ₂₂ are each independently a single bond or —R _L —O—, —O—R _L —, —O—C (═O) —R _L —, —C (═O) —O—R. _L— (R _L represents a phenylene group, an alkylene group, an alkenylene group or an alkynylene group), —O—, — (C═O) —, — (C═S) —, — (C═O) —O _{-, - NR M -, -} S -, - SO 2 -, - (C = O) -NR M - and _{-NR M - (C = O)} - (R M represents a hydrogen atom or an alkylene group) Represents a divalent linking group selected from the group consisting of or a combination thereof;
R ₂₂ and R ₂₃ each independently represent an alkylene group, an alkenylene group, an alkynylene group,-(R _N ) n- (R _N represents a cycloalkylene group, and n represents an integer of 1 to 4),-( OR _O ) n- (R _O represents an alkylene group, n represents an integer of 1 to 4), a phenylene group, a heteroalkylene group or a heteroarylene group;
R ₂₄ and R ₂₅ represent a hydrogen atom or a substituent;
R ₂₁ represents — (C═O) Rp, — (C═O) —O—Rp, —O— (C═O) —Rp, — (C═O) —S—Rp, —S— (C ═O) —Rp (Rp represents an alkyl group or an aryl group), —C (═O) —NRq (Rq represents an alkyl group), an aryl group, a heteroaryl group, or the R ₂₁ bonded thereto. Represents a 2,5-dione-pyrrolidine ring fused with a benzene ring;
k ₂ represents an integer of 1 to 4)
[3] The optical film according to [1], wherein the wavelength dispersion adjusting agent represented by the general formula (1) is a compound represented by the following general formula (3).
General formula (3)

(In general formula (3),
L ₃₁ and L ₃₂ are each independently a single bond or —R _L —O—, —O—R _L —, —O—C (═O) —R _L —, —C (═O) —O—R. _L— (R _L represents a phenylene group, an alkylene group, an alkenylene group or an alkynylene group), —O—, — (C═O) —, — (C═S) —, — (C═O) —O _{-, - NR M -, -} S -, - SO 2 - and _{- (C = O) -NR M} -, - NR M - (C = O) - (R M represents a hydrogen atom or an alkylene group) Represents a divalent linking group selected from the group consisting of or a combination thereof;
R ₃₃ and R ₃₄ each independently represent an alkylene group, an alkenylene group, an alkynylene group,-(R _N ) n- (R _N represents a cycloalkylene group, and n represents an integer of 1 to 4),-( OR _O ) n- (R _O represents an alkylene group, n represents an integer of 1 to 4), a phenylene group, a heteroalkylene group or a heteroarylene group;
R ₃₆ and R ₃₇ each independently represents a hydrogen atom or a substituent;
R ₃₁ and R ₃₂ are each independently a hydrogen atom or — (C═O) —O—Rt (Rt represents an alkyl group, an oxyalkylene group or an aryl group), —C (═O) —Rv (Rv Represents an alkyl group or an aryl group), —C (═O) —NRwRx (Rw represents a hydrogen atom or an alkyl group; Rx represents an alkyl group), a cyano group or a halogen atom; R ₃₁ And R ₃₂ may combine with each other to form a ring;
R ₃₅ represents a substituent;
j ₃ represents an integer of 0 to 3)
[4] The optical film according to [1], wherein the wavelength dispersion adjusting agent represented by the general formula (1) is a compound represented by the following general formula (4).
General formula (4)

(In general formula (4),
B ₁ and B ₂ are each independently —O—, —NR— (R represents a hydrogen atom or a substituent), —S—, —S (═O) — and —C (═O) —. Represents a divalent group selected from the group consisting of:
The dashed portion represents a single bond or a double bond;
L ₄₁ and L ₄₂ are each independently a single bond or —R _L —O—, —O—R _L —, —O—C (═O) —R _L —, —C (═O) —O—R. _L— (R _L represents a phenylene group, an alkylene group, an alkenylene group or an alkynylene group), —O—, — (C═O) —, — (C═S) —, — (C═O) —O _{-, - NR M -, -} S -, - SO 2 -, - (C = O) -NR M - and _{-NR M - (C = O)} - (R M represents a hydrogen atom or an alkylene group) Represents a divalent linking group selected from the group consisting of or a combination thereof;
R ₄₂ and R ₄₃ each independently represent an alkylene group, an alkenylene group, an alkynylene group, — (R _N ) n— ( _RN represents a cycloalkylene group, and n represents an integer of 1 to 4), — ( OR _O ) n- (R _O represents an alkylene group, n represents an integer of 1 to 4), a phenylene group, a heteroalkylene group or a heteroarylene group;
R ₄₅ and R ₄₆ each independently represents a hydrogen atom or a substituent;
R ₄₁ represents _{═R 411} R ₄₁₂ or an aryl group;
= _{R 411} and _{R 412} in _R 411 _{R 412} is (are R, represents an alkyl group or an aryl group) independently cyano or -C (= O) -O-R represents;
R ₄₄ represents a substituent;
j ₄ represents an integer of 0 to 2; when j ₄ is 2, two R _44s may be bonded to each other to form a ring)
[5] The optical film according to any one of [1] to [4], wherein the transmittance at 380 nm is in the range of 40 to 85%.
[6] The optical film according to any one of [1] to [5], wherein the thermoplastic resin is a cellulose ester.
[7] The optical film according to [6], wherein the cellulose ester has an acetyl group substitution degree X and a total substitution degree Y of propionyl group or butyryl group satisfying the following formula.
Formula (I) 1.5 ≦ X + Y ≦ 2.6
Formula (II) 0 ≦ Y ≦ 1.5
[8] The optical film according to any one of [1] to [7], wherein the film thickness is in a range of 20 to 45 μm.
[9] Any of [1] to [8], wherein the content of the wavelength dispersion adjusting agent represented by the general formula (1) is 1 to 30 parts by weight with respect to 100 parts by weight of the thermoplastic resin. The optical film according to one item.
[10] The angle formed by the in-plane slow axis of the optical film and the width direction of the optical film is 40 ° or more and 50 ° or less, according to any one of [1] to [9]. Optical film.

[11] A circularly polarizing plate comprising a polarizer and the optical film according to any one of [1] to [10].
[12] The circularly polarizing plate according to [11], wherein the polarizer and the optical film are bonded via a cured product layer of an active energy ray adhesive.
[13] An image display device comprising the circularly polarizing plate according to [11] or [12].

  The optical film of the present invention has a high retardation and good reverse wavelength dispersion, and can suppress thermal shrinkage during ultraviolet irradiation. Therefore, in the image display device including the optical film of the present invention, a decrease in contrast and color variation can be reduced.

It is explanatory drawing which shows an example of diagonal extending | stretching. It is a schematic diagram which shows an example of the diagonal stretch apparatus. It is a schematic diagram which shows the other example of the diagonal stretch apparatus. It is a schematic diagram which shows the other example of the diagonal stretch apparatus. It is a schematic diagram which shows an example of a structure of an organic electroluminescence display. It is a schematic diagram explaining the reflection preventing function by a circularly-polarizing plate. It is a schematic diagram which shows an example of a structure of a liquid crystal display device.

  In order to suppress thermal shrinkage of an optical film during ultraviolet irradiation, the present inventors make it difficult for an optical film containing a wavelength dispersion adjusting agent to absorb ultraviolet light; that is, an optical film containing a wavelength dispersion adjusting agent. We focused on increasing the transmittance at 380 nm. For this purpose, it has been found that it is effective to shift the absorption peak of the wavelength dispersion adjusting agent contained in the optical film to a shorter wavelength side than 380 nm.

  On the other hand, when the absorption peak of the wavelength dispersion adjusting agent is extremely shifted to the short wavelength side, there is a tendency that it is difficult to impart sufficient reverse wavelength dispersion to the film. Therefore, the present inventors can impart reverse wavelength dispersion to the film by setting the absorption peak of the wavelength dispersion adjusting agent in the range of 300 nm or more; and depending on the content of the wavelength dispersion adjusting agent, etc., at 380 nm of the optical film. It was found that heat shrinkage of the optical film during ultraviolet irradiation can be suppressed by setting the transmittance within the above range.

  That is, the optical film of the present invention includes a thermoplastic resin and at least one or more types of specific wavelength dispersion adjusting agents, and is in-plane obliquely with respect to the width direction of the film (an angle that is neither 0 ° C. nor 90 ° C.). Has a slow axis. And 1) that the absorption peak of the wavelength dispersion adjusting agent is adjusted in the range of 300 to 360 nm in the ultraviolet-visible absorption spectrum of the solution, and 2) the transmittance of the optical film at 380 nm is 20 to 90% (preferably 40 to 85%) is the main feature.

  The optical film of the present invention is preferably used for polarizing plates and image display devices. In particular, in an organic EL display device having a circularly polarizing plate including the optical film of the present invention, a decrease in contrast and color variation can be reduced.

  Hereinafter, the present invention, its components, and modes for carrying out the present invention will be described in detail. In addition, in this application, "-" is used in the meaning which includes the numerical value described before and behind that as a lower limit and an upper limit.

1. Optical film The optical film of this invention contains a thermoplastic resin and a specific wavelength dispersion regulator as above-mentioned, and may further contain other arbitrary components as needed.

About the thermoplastic resin The thermoplastic resin contained in the optical film of the present invention is not particularly limited, but is a cellulose ester resin, polycarbonate resin, polystyrene resin, polysulfone resin, polyester resin, polyarylate resin, acrylic resin. Examples thereof include resins and olefin resins (norbornene resins, cyclic olefin resins, cyclic conjugated diene resins, vinyl alicyclic hydrocarbon resins, and the like). Among these, cellulose ester resins, polycarbonate resins, acrylic resins, and cyclic olefin resins are more preferable, and cellulose ester resins (cellulose esters) are particularly preferable.

  The total acyl group substitution degree of the cellulose ester is preferably 1.5 or more and 2.9 or less from the viewpoint of enhancing the compatibility with the wavelength dispersion adjusting agent represented by the general formula (1) described later. More preferably, it is 5 or more and 2.6 or less. The measuring method of the substitution degree of an acyl group can be measured according to ASTM-D817-96.

The cellulose ester preferably satisfies the following formulas (a) and (b) at the same time when the substitution degree of the acetyl group is X and the total substitution degree of the propionyl group or butyryl group is Y.
Formula (a) 1.5 ≦ X + Y ≦ 2.6
Formula (b) 0 ≦ Y ≦ 1.5

  Preferred examples of the cellulose ester include cellulose acetate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate propionate butyrate and the like. Among these, cellulose acetate and cellulose acetate propionate are particularly preferable.

  The cellulose ester contained in the optical film of the present invention may contain a plurality of cellulose esters having different degrees of substitution in order to obtain desired optical properties. For example, when two types of cellulose esters having different degrees of substitution are included, the mixing ratio thereof can be in the range of 10:90 to 90:10 by mass ratio.

The number average molecular weight of the cellulose ester is preferably in the range of 6 × 10 ^{4 to} 3 × 10 ⁵ and preferably in the range of 7 × 10 ⁴ to 2 × 10 ⁵ because the mechanical strength of the resulting film is high. It is more preferable.

The weight average molecular weight Mw and the number average molecular weight Mn of the cellulose ester can be measured by gel permeation chromatography (GPC). An example of the measurement conditions is shown below, but not limited to this, an equivalent measurement method can also be used.
Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three products manufactured by Showa Denko KK)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (manufactured by GL Sciences)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corporation) Mw = 100000 to 500 calibration curves with 13 samples are used. Thirteen samples are used at approximately equal intervals.

  The cellulose ester can be produced by a known method. Specifically, it can be synthesized with reference to the method described in JP-A-10-45804. The cellulose used as a raw material is not particularly limited, but may be cotton linter, wood pulp, kenaf, and the like. Moreover, as above-mentioned, the cellulose ester obtained from them can be used, mixing each in arbitrary ratios.

Wavelength dispersion adjusting agent The wavelength dispersion adjusting agent contained in the optical film of the present invention is preferably represented by the following general formula (1).
General formula (1)

  A in the general formula (1) represents an aromatic hydrocarbon ring, a non-aromatic hydrocarbon ring, an aromatic heterocyclic ring or a non-aromatic heterocyclic ring.

  The aromatic hydrocarbon ring may be a single ring or a condensed ring, but in order to make the absorption peak of the compound shorter, it is preferable to have a structure in which conjugation does not spread, Is more preferably a monocycle. Preferred examples of the aromatic hydrocarbon ring include benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, perylene ring, tetracene ring, pyrene ring, benzopyrene ring, chrysene ring, triphenylene ring, acenaphthene ring, fluoranthene ring, fluorene ring, etc. More preferably, it is a benzene ring.

  Preferred examples of the non-aromatic hydrocarbon ring include a cyclopropane ring, a cyclobutane ring, a cyclopentane ring, a cyclohexane ring, a cycloheptane ring, a cyclooctane ring, a norbornene ring, and the like, more preferably a cyclohexane ring and a cyclopentane ring. It is.

  The aromatic heterocyclic ring may be a single ring or a condensed ring, and preferably has a structure in which conjugation does not spread, and more specifically, it is more preferably a single ring. Preferred examples of the aromatic heterocycle include furan ring, benzofuran ring, thiophene ring, benzothiophene ring, pyrrole ring, pyrazole ring, imidazole ring, oxadiazole ring, indole ring, carbazole ring, triazole ring, benzimidazole ring, Benzoxazole ring, benzothiazole ring, pyridine ring, pyrazine ring, pyridazine ring, pyrimidine ring, triazine ring, quinoline ring, perimidine ring, quinazoline ring, azulene ring, dibenzofuran ring, dibenzothiophene ring, dibenzocarbazole ring, benzodifuran ring, benzo A dithiophene ring, a phenanthroline ring, and the like are included, and a pyridine ring, a benzothiazole ring, and a benzoxazole ring are preferable.

  Preferred examples of the non-aromatic heterocycle include tetrahydrofuran ring, tetrahydropyran ring, dioxolane ring, dioxane ring, pyrrolidine ring, pyridone ring, pyridazinone ring, imide ring, piperidine ring, dihydropyrrole ring, dihydropyridine ring, tetrahydropyridine ring, Piperazine ring, morpholine ring, piperidine ring and the like are included, and pyridone ring, imide ring and pyrrolidine ring are more preferable.

L ₁ and L _{2 in} the general formula (1) are each independently a single bond or —R _L —O—, —O—R _L —, —O—, — (C═O) —, — (C═S ) -, - (C = O ) -O -, - NR M -, - S -, - SO 2 - and _{- (C = O) -NR M} -, - NR M - (C = O) - consisting of A divalent linking group selected from the group or a combination thereof is shown.

_{-R L -O -, - O-} R L -, - O-C (= O) -R L -, - C (= O) -O-R L - in _{R L} are a phenylene group, an alkylene group, An alkenylene group or an alkynylene group is shown. Carbon number of an alkylene group becomes like this. Preferably it is 1-10, More preferably, it may be 1-2. The alkenylene group and the alkynylene group may preferably have 2 to 10 carbon atoms.

Examples of combinations of two or more groups described above include — (C═O) —O—, —O— (C═O) —, — (C═O) —NR _M —, —NR _M — (C ═O) —, —O— (C═S) —, —O— (S═O) ₂ —, —S— (C═O) — and the like.

Among these, from the viewpoint of having good compatibility with the thermoplastic resin and imparting sufficient reverse wavelength dispersion to the film, -O-,-(C = O)-,-(C = O) —O—, —NR _M —, —S—, and — (C═O) —NR _M — are preferred.

R ₂ and R _{3 in} the general formula (1) are each independently an alkylene group, an alkenylene group, an alkynylene group,-(R _N ) n- (R _N represents a cycloalkylene group),-(OR _O ) n - (R _O represents an alkylene group), a phenylene group, heteroalkylene group or heteroaryl - shows the alkylene group.

  Carbon number of an alkylene group becomes like this. Preferably it is 1-10, More preferably, it may be 2-8. The alkenylene group and the alkynylene group may preferably have 2 to 10 carbon atoms.

- _(R N) n-in _{R N} represents a cycloalkylene group. The carbon number of the cycloalkylene group may preferably be 4-10. Preferred examples of the cycloalkylene group include a cyclohexylene group. n represents an integer of 1 to 4, and preferably 1 to 2 in order to obtain sufficient reverse wavelength dispersion.

  Ro in — (ORo) n— represents an alkylene group, preferably an alkylene group having 1 to 10 carbon atoms, and more preferably an alkylene group having 2 to 3 carbon atoms. n represents an integer of 1 to 4, and preferably 1 to 2 in order to obtain sufficient reverse wavelength dispersion.

  The carbon number of the heteroalkylene group may preferably be 1-10. Examples of heteroalkylene groups include piperidinylene groups. The carbon number of the heteroarylene group may preferably be 4-10. Examples of the heteroarylene group include a thiophenylene group.

Among these, from the viewpoint of enhancing the wavelength dispersibility, _{R 2} and _{R 3} is an alkylene group, heteroalkylene _{group, - (R N) n- (} R N is a cycloalkylene group), a phenylene group, heteroaryl - Len group Is preferred.

R ₄ and R _{5 in} the general formula (1) represent a hydrogen atom or a substituent. The molecular weight of the substituent is preferably 1 or more and 300 or less.

Such substituents are not particularly limited, and specific examples thereof include:
Halogen atom (fluorine atom, chlorine atom, bromine atom, iodine atom, etc.),
Alkyl groups (methyl group, ethyl group, n-propyl group, isopropyl group, tert-butyl group, n-octyl group, 2-ethylhexyl group, etc.),
A cycloalkyl group (a cyclohexyl group, a cyclopentyl group, a 4-n-dodecylcyclohexyl group, etc.),
Alkenyl group (vinyl group, allyl group, etc.),
Cycloalkenyl groups (such as 2-cyclopenten-1-yl and 2-cyclohexen-1-yl groups), alkynyl groups (such as ethynyl groups and propargyl groups),
An aryl group (phenyl group, p-tolyl group, naphthyl group, etc.),
Heteroaryl group (2-pyrrole group, 2-furyl group, 2-thienyl group, pyrrole group, imidazolyl group, oxazolyl group, thiazolyl group, benzoimidazolyl group, benzoxazolyl group, 2-benzothiazolyl group, pyrazolinone group, pyridyl group , Pyridinone group, 2-pyrimidinyl group, etc.),
Cyano group, hydroxyl group, nitro group, carboxyl group,
Alkoxy groups (methoxy group, ethoxy group, isopropoxy group, tert-butoxy group, n-octyloxy group, 2-methoxyethoxy group, etc.),
Aryloxy groups (phenoxy group, 2-methylphenoxy group, 4-tert-butylphenoxy group, 3-nitrophenoxy group, 2-tetradecanoylaminophenoxy group, etc.),
An acyl group (acetyl group, pivaloylbenzoyl group, etc.),
Acyloxy groups (formyloxy group, acetyloxy group, pivaloyloxy group, stearoyloxy group, benzoyloxy group, p-methoxyphenylcarbonyloxy group, etc.),
Amino group (amino group, methylamino group, dimethylamino group, anilino group, N-methyl-anilino group, diphenylamino group, etc.), acylamino group (formylamino group, acetylamino group, pivaloylamino group, lauroylamino group, benzoylamino) Group),
Alkyl and arylsulfonylamino groups (methylsulfonylamino group, butylsulfonylamino group, phenylsulfonylamino group, 2,3,5-trichlorophenylsulfonylamino group, p-methylphenylsulfonylamino group, etc.),
Mercapto group,
Alkylthio groups (methylthio group, ethylthio group, n-hexadecylthio group, etc.), arylthio groups (phenylthio group, p-chlorophenylthio group, m-methoxyphenylthio group, etc.),
Sulfamoyl group (N-ethylsulfamoyl group, N- (3-dodecyloxypropyl) sulfamoyl group, N, N-dimethylsulfamoyl group, N-acetylsulfamoyl group, N-benzoylsulfamoyl group, N -(N 'phenylcarbamoyl) sulfamoyl group etc.),
A sulfo group,
A carbamoyl group (carbamoyl group, N-methylcarbamoyl group, N, N-dimethylcarbamoyl group, N, N-di-n-octylcarbamoyl group, N- (methylsulfonyl) carbamoyl group, etc.) and the like are included. These groups may be further substituted with the same group.

Among these, hydrogen atom, alkyl group, alkenyl group, alkoxy group, aryloxy group, cycloalkyl group, aryl group, heteroaryl group, acyl group, acyloxy group, alkylthio group, arylthio group, acylamino group, carbamoyl group, cyano A group and an amino group are preferable, and a hydrogen atom, an alkyl group, an alkenyl group, an alkoxy group, an aryloxy group, an acyl group, and an acyloxy group are more preferable. The substituents represented by R ₄ and R ₅ may be further substituted with the aforementioned substituents.

R _{1 in the} general formula (1) represents a substituent. The substituent is selected so that the absorption peak of the wavelength dispersion adjusting agent represented by the general formula (1) is in the range of 300 to 360 nm. Examples of the substituent include not only the substituent represented by R ₄ and R ₅ in the general formula (1), but also an alkyloxycarbonyl group, an aryloxycarbonyl group, an alkylcarbonylamino group, an alkyloxycarbonyl. An amino group, an alkylcarbonylthiol group, an arylcarbonylthiol group and the like are included.

In the general formula (1), k represents an integer of 0 to 4, and is preferably 1 to 4 and more preferably 1 or 2 in order to improve the chromatic dispersion. When the ring represented by A has R ₁ on two or more adjacent ring-constituting carbon atoms, a plurality of R ₁ may be bonded to each other to form a ring.

The wavelength dispersion adjusting agent represented by the general formula (1) may preferably be a compound represented by the following general formula (2), (3) or (4).
General formula (2)

L ₂₁ , L ₂₂ , R ₂₂ , R ₂₃ , R ₂₄ and R ₂₅ in the general formula (2) are respectively represented by L ₁ , L ₂ , R ₂ , R ₃ , R ₄ and R _{5 in the} general formula (1). Each can be defined similarly. R ₂₂ and R _{23 in} the general formula (2) are preferably an alkylene group, a cycloalkylene group, or a phenylene group from the viewpoint of enhancing wavelength dispersibility.

R _{21 in the} general formula (2) represents — (C═O) —Rp, — (C═O) —O—Rp, —O— (C═O) —Rp, — (C═O) —S—. Rp, —S— (C═O) —Rp, —C (═O) —NRq, an aryl group, a heteroaryl group, or a 2,5-dione-pyrrolidine ring fused to the benzene ring to which R ₂₁ is bonded. Indicates.

-(C = O) -Rp,-(C = O) -O-Rp, -O- (C = O) -Rp,-(C = O) -S-Rp and -S- (C = O). Rp in —Rp represents an alkyl group or an aryl group. The number of carbon atoms of the alkyl group represented by Rp is preferably 1-20, more preferably 1-4. The number of carbon atoms of the aryl group represented by Rp may preferably be 6-10. These alkyl groups and aryl groups may have a substituent. Examples of the substituent include those similar to the substituents represented by R ₄ and R ₅ in the general formula (1).

  Rq in —C (═O) —NRq represents an alkyl group. The alkyl group represented by Rq can be defined in the same manner as the alkyl group represented by Rp described above.

  Examples of the aryl group include a phenyl group. It is preferable that carbon number of a heteroaryl group is 3-10. Examples of the heteroaryl group include a pyrazole group and a benzothiazole group.

In the 2,5-dione-pyrrolidine ring condensed with the benzene ring to which R ₂₁ is bonded, the nitrogen atom constituting the ring may further have a substituent. Such a substituent includes the substituents represented by R ₄ and R ₅ in the general formula (1), and may preferably be an alkyl group which may be substituted with an oxyalkylene group or the like.

_{K 2} of the general formula (2) represents an integer of 1 to 4, in view of enhancing the reverse wavelength dispersion, preferably 1 to 2.

The wavelength dispersion adjusting agent represented by the general formula (1) may be a compound represented by the following general formula (3).
General formula (3)

L ₃₁ , L ₃₂ , R ₃₃ , R ₃₄ , R ₃₆ and R ₃₇ in the general formula (3) are respectively represented by L ₁ , L ₂ , R ₂ , R ₃ , R ₄ and R _{5 in the} general formula (1). Each can be defined similarly. R ₃₃ and R _{34 in} the general formula (3) are preferably an alkylene group, a cycloalkylene group, or a phenylene group from the viewpoint of enhancing wavelength dispersibility.

R ₃₁ and R _{32 in} the general formula (3) are each independently a hydrogen atom or — (C═O) —O—Rt, —C (═O) —Rv, —C (═O) —NRwRx, cyano group Or a halogen atom is shown.

Rt in — (C═O) —O—Rt represents an alkyl group, an oxyalkylene group or an aryl group. The oxyalkylene group can contain a plurality of repeating units. These groups may further have the same substituent as the substituents represented by R ₄ and R ₅ in the general formula (1). Rw in —C (═O) —NRwRx represents a hydrogen atom or an alkyl group; Rx represents an alkyl group. These groups may further have the same substituent as the substituents represented by R ₄ and R ₅ in the general formula (1).

R ₃₁ and R ₃₂ may combine with each other to form a ring. Examples of the ring formed by combining R ₃₁ and R ₃₂ include 2,4,6-trione-pyrimidine ring, 4-one-pyrimidine ring and the like. These rings may further have a substituent (for example, an alkylamino group).

R _{35 in the} general formula (3) represents a substituent. Examples of the substituent include those similar to the substituents represented by R ₄ and R ₅ in the general formula (1).

J _{3 in the} general formula (3) represents an integer of 0 to _{3, and} is preferably 1 to 2 from the viewpoint of enhancing reverse wavelength dispersion.

The wavelength dispersion adjusting agent represented by the general formula (1) may be a compound represented by the following general formula (4).
General formula (4)

B ₁ and B _{2 in} the general formula (4) are each independently selected from the group consisting of —O—, —NR—, —S—, —S (═O) —, and —C (═O) —. Indicates a valent group. A broken line part shows a single bond or a double bond.

R in —NR— represents a hydrogen atom or a substituent. Examples of the substituent include an alkyl group. When B ₁ is —S— and B ₂ is —NR—, the ring corresponding to A in the general formula (1) may be a benzothiazole ring.

  Among these, -NR-, -S-, and -C (= O)-are preferable from the viewpoint of enhancing wavelength dispersion.

L ₄₁ , L ₄₂ , R ₄₂ , R ₄₃ , R ₄₅ and R ₄₆ in the general formula (4) are respectively represented by L ₁ , L ₂ , R ₂ , R ₃ , R ₄ and R _{5 in the} general formula (1). Each can be defined similarly. R ₄₂ and R _{43 in} the general formula (4) are preferably an alkylene group, a cycloalkylene group, or a phenylene group from the viewpoint of enhancing wavelength dispersion.

R _{41 in the} general formula (4) represents = R ₄₁₁ R ₄₁₂ or an aryl group. = _{R 411} and _{R 412} in _R 411 _{R 412} is a cyano group, or -C (= O) -O-R independently. R in —C (═O) —O—R represents an alkyl group or an aryl group. These alkyl groups and aryl groups may further have a substituent such as a hydroxyl group.

The aryl group is preferably an aryl group having 6 to 10 carbon atoms, more preferably a phenyl group. The aryl group may further have a substituent. Examples of such substituents include those similar to the substituents represented by R ₄ and R ₅ in the general formula (1), preferably alkyl groups, alkoxy groups, alkylcarbonyloxy groups, alkylcarbonyls. It may be an amino group, an alkylsulfonyloxy group, an alkylamino group, an aryl group, or the like.

R _{44 in the} general formula (4) represents a substituent. Examples of the substituent include the same substituents as those represented by R ₄ and R ₅ in the general formula (1).

J _{4 in the} general formula (4) represents an integer of 0 to 2, and is preferably 0. When j ₄ is 2, two R ₄₄ may be bonded to each other to form a ring.

Examples of the wavelength dispersion adjusting agent represented by the general formula (1) include the following. Of the following exemplary compounds, exemplary compounds B-001 to B-042 are also examples of compounds represented by general formula (4); exemplary compounds C-001 to C-026 are represented by general formula (2). Example compounds D-001 to D-025 are also examples of compounds represented by general formula (3).

  The wavelength dispersion adjusting agent represented by the general formula (1) can be synthesized by a known method.

  The molecular weight of the wavelength dispersion adjusting agent represented by the general formula (1) is preferably 200 or more and 1500 or less.

  In the wavelength dispersion adjusting agent in the present invention, R0 of a stretched film F1 obtained by stretching a film containing a thermoplastic resin and a 3% by mass of the wavelength dispersion adjusting agent with a stretching ratio of 1.3 times has a wavelength of R0 (450) / R0 (550) of the stretched film F1 that is 1.1 times or more of R0 of the stretched film F0 that does not contain the dispersion modifier and that contains the wavelength dispersion regulator does not contain the wavelength dispersion modifier. It is a compound which becomes 1.05 times or less with respect to R0 (450) / R0 (550) of stretched film F0.

In the present invention, the wavelength dispersion adjusting agent represented by the general formula (1) has an absorption peak in the range of 300 to 360 nm in the ultraviolet-visible absorption spectrum of the solution containing the same. Specifically, the UV-visible absorption spectrum of the solution is tetrahydrofuran (no polymerization inhibitor) containing the wavelength dispersion adjusting agent represented by the general formula (1) so as to have a concentration of 1.0 × 10 ⁻⁵ mol / L. The solution is determined from an ultraviolet-visible absorption spectrum obtained by measuring the solution at 25 ° C. with a normal absorption spectrophotometer.

  A wavelength dispersion adjusting agent having an absorption peak in the range of 300 to 360 nm is unlikely to be a trade-off between retardation development and reverse wavelength dispersion. Therefore, the wavelength dispersion adjusting agent can have a sufficient retardation and reverse wavelength dispersion even if the optical film including the wavelength dispersion adjusting agent has a transmittance within the above range.

  That is, by setting the absorption peak to 360 nm or less, the retardation development property is enhanced and the absorption at a long wavelength is relatively small, so that the light resistance can be enhanced. Thereby, the phase difference fluctuation | variation of the diagonally stretched film obtained can be suppressed. On the other hand, the reverse wavelength dispersion can be improved by setting the absorption peak to 300 nm or more.

The wavelength of the absorption peak of the wavelength dispersion adjusting agent represented by the general formula (1) can be preferably adjusted by the structure of L ₁ and L ₂ or the structure of R _{1 in} the general formula (1).

For example, L ₁ and L ₂ of the general formula (1) (L ₂₁ and L _{22 of} the general formula (2), L ₃₁ and L _{32 of} the general formula (3), L ₄₁ and L ₄₂ of the general formula (4)) the -O- (C = O) -, - SO 2 - and doing, it is possible to the absorption peak of the wavelength dispersion adjusting agent to the short wavelength side. On the other hand, L ₁ and L ₂ in the general formula (1) are represented by —O—, — (C═O) —O—, — (C═O) —, — (C═O) —NR _M —, —NR _M. By setting it as (C = O)-, the absorption peak of the wavelength dispersion adjusting agent can be on the long wavelength side.

R ₁ of the general formula (1) (R _{21 of} the general formula (2), R ₃₁ and R _{32 of} the general formula (3), R ₄₁ of the general formula (4)) is represented by —C (═O ) —, —C (═O) —O—, —SO ₂ — A substituent having no conjugated structure or a substituent having a conjugated structure so that the absorption peak of the wavelength dispersion adjusting agent is on the short wavelength side. Can do. On the other hand, when R ₁ in the general formula (1) is a substituent having a conjugated structure, the absorption peak of the wavelength dispersion adjusting agent can be on the long wavelength side.

  0.1-30 mass parts is preferable with respect to 100 mass parts of thermoplastic resins, as for content of the wavelength dispersion regulator represented by General formula (1), 1-20 mass parts is more preferable, and 2-10 Part by mass is more preferable. When the content of the wavelength dispersion adjusting agent is less than 0.1 parts by mass, there is a possibility that a certain phase difference or more and negative wavelength dispersion cannot be sufficiently imparted. On the other hand, when the content of the wavelength dispersion adjusting agent is more than 30 parts by mass, the transmittance of the optical film at 380 nm may be lowered.

  The optical film of the present invention may further contain an optional component as necessary in addition to the cellulose ester and the wavelength dispersion adjusting agent represented by the general formula (1). The optional component may be at least one or more of the group consisting of, for example, a sugar ester compound, a plasticizer, an ultraviolet absorber, an antioxidant, and fine particles.

(Sugar ester compound)
The optical film of the present invention can further contain a sugar ester compound other than the cellulose ester described above from the viewpoint of improving the plasticity of the optical film.

The sugar ester compound may be a compound having 1 to 12 furanose structures or pyranose structures, in which all or part of the hydroxy groups in the compound are esterified. Preferable examples of such sugar ester compounds include sucrose esters represented by the following general formula (FA).

R _{1 to} R _{8 in} formula (FA) each independently represent a hydrogen atom, a substituted or unsubstituted alkylcarbonyl group, or a substituted or unsubstituted arylcarbonyl group. R _{1 to} R ₈ may be the same as or different from each other.

  The substituted or unsubstituted alkylcarbonyl group is preferably a substituted or unsubstituted alkylcarbonyl group having 2 or more carbon atoms. Examples of the substituted or unsubstituted alkylcarbonyl group include a methylcarbonyl group (acetyl group). Examples of the substituent that the alkyl group has include an aryl group such as a phenyl group.

  The substituted or unsubstituted arylcarbonyl group is preferably a substituted or unsubstituted arylcarbonyl group having 7 or more carbon atoms. Examples of the arylcarbonyl group include a phenylcarbonyl group. Examples of the substituent that the aryl group has include an alkyl group such as a methyl group, an alkoxyl group such as a methoxy group, and the like.

  The average substitution degree of the acyl group of the sucrose ester is preferably in the range of 3.0 to 7.5. When the average substitution degree of the acyl group is within this range, sufficient compatibility with the cellulose ester is easily obtained.

Specific examples of the sucrose ester represented by the general formula (FA) include the following exemplary compounds (FA-1) to (FA-24). The table below, the _R 1 to R ₈ in the general formula of the exemplified compound (FA-1) ~ (FA -24) (FA), shows the average degree of substitution of acyl groups.

  Examples of other sugar ester compounds include those described in JP-A Nos. 62-42996 and 10-237084.

  The content of the sugar ester compound is preferably 0.5 to 35.0% by mass and more preferably 5.0 to 30.0% by mass with respect to the cellulose ester.

  The optical film of the present invention may further contain a plasticizer in order to improve the fluidity of the composition during film production and the flexibility of the film. Examples of plasticizers include polyester plasticizers, polyhydric alcohol ester plasticizers, polycarboxylic acid ester plasticizers (including phthalate ester plasticizers), glycolate plasticizers, ester plasticizers ( Citrate ester plasticizers, fatty acid ester plasticizers, phosphate ester plasticizers, trimellitic ester plasticizers, etc.). Of these, polyester plasticizers and phosphate ester plasticizers are preferred. These may be used alone or in combination of two or more.

  The polyester plasticizer is a compound obtained by reacting a 1-4 carboxylic acid and a 1-6 valent alcohol, preferably a compound obtained by reacting a divalent carboxylic acid with a glycol. It is.

  Examples of the divalent carboxylic acid include glutaric acid, itaconic acid, adipic acid, phthalic acid, azelaic acid, sebacic acid and the like. In particular, a compound using adipic acid, phthalic acid or the like as the divalent carboxylic acid can impart good plasticity.

  Examples of glycols include ethylene glycol, propylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, 1,6-hexamethylene glycol, neopentylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol and the like. included. Each of the divalent carboxylic acid and glycol may be one kind, or two or more kinds may be used in combination.

  The polyester plasticizer may be any of ester, oligoester, and polyester. The molecular weight of the polyester plasticizer is preferably in the range of 100 to 10000, and more preferably in the range of 600 to 3000 since the effect of imparting plasticity is great.

  The viscosity of the polyester plasticizer depends on the molecular structure and molecular weight, but in the case of an adipic acid plasticizer, the compatibility with the cellulose ester is high and the effect of imparting plasticity is high. It is preferably in the range of s (25 ° C.). The polyester plasticizer may be used alone or in combination of two or more.

  Examples of the phosphate ester plasticizer include triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate and the like.

  It is preferable that content of a plasticizer is 0.5-30.0 mass% with respect to a cellulose ester. If the content of the plasticizer is 30.0% by mass or less, the optical film hardly causes bleed out.

(UV absorber)
The optical film of the present invention may further contain an ultraviolet absorber. The ultraviolet absorber may be benzotriazole, 2-hydroxybenzophenone, salicylic acid phenyl ester, or the like. Specifically, 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2- Triazoles such as (3,5-di-t-butyl-2-hydroxyphenyl) benzotriazole; 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2,2′-dihydroxy-4 -Benzophenones such as methoxybenzophenone.

  Especially, the ultraviolet absorber whose molecular weight is 400 or more is hard to volatilize at a high boiling point, and is not easily scattered during high temperature molding. Therefore, even if the addition amount is relatively small, weather resistance can be imparted to the obtained film.

Examples of ultraviolet absorbers having a molecular weight of 400 or more include 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole, 2,2-methylenebis [4- Benzotriazoles such as (1,1,3,3-tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol];
Hindered amines such as bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate;
2- (3,5-di-t-butyl-4-hydroxybenzyl) -2-n-butylmalonate bis (1,2,2,6,6-pentamethyl-4-piperidyl), 1- [2- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy] ethyl] -4- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy]- A hybrid system having both hindered phenol and hindered amine structures in the molecule such as 2,2,6,6-tetramethylpiperidine;
Preferably, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole or 2,2-methylenebis [4- (1,1,3, 3-tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol]. These may be used alone or in combination of two or more.

(Antioxidant)
As the antioxidant, a known one can be used, and may be a lactone compound, a sulfur compound, a phenol compound, a double bond compound, a hindered amine compound, a phosphorus compound, or the like.

  Examples of lactone compounds include Irgafos XP40 and Irgafos XP60 (BASF Japan Ltd.). Examples of the sulfur-based compound may include Sumilizer TPL-R and Sumilizer TP-D (Sumitomo Chemical Co., Ltd.). The phenolic compound preferably has a 2,6-dialkylphenol structure, and examples thereof include Irganox 1076, Irganox 1010 (BASF Japan Ltd.), ADK STAB AO-50 (Adeka). Examples of the double bond compound include Sumilizer GM and Sumilizer GS (Sumitomo Chemical Co., Ltd.). Examples of the hindered amine compounds include Tinuvin 144, Tinuvin 770 (BASF Japan Co., Ltd.), and ADK STAB LA-52 (ADEKA Corporation). Examples of phosphorus compounds include Sumitizer GP (Sumitomo Chemical Co., Ltd.), ADK STAB PEP-24G, ADK STAB PEP-36 and ADK STAB 3010 (ADEKA), IRGAFOS P-EPQ (BASF Japan Ltd.), GSY- P101 (Sakai Chemical Industry Co., Ltd.) can be mentioned.

  The content of the antioxidant can be about 0.05 to 5% by mass, preferably 0.1 to 4% by mass with respect to the above-described thermoplastic resin.

(Fine particles)
The optical film of the present invention may contain fine particles composed of an inorganic compound or an organic compound.

  Examples of inorganic compounds include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate , Calcium phosphate and the like.

  Examples of the organic compound include polytetrafluoroethylene, polystyrene, polymethyl methacrylate, polypropyl methacrylate, polymethyl acrylate, polyethylene carbonate, acrylic styrene resin, silicone resin, and the like.

  Especially, since the haze of the film obtained is hard to increase, fine particles of silicon dioxide are preferable. Examples of the fine particles of silicon dioxide include Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (above, Nippon Aerosil Co., Ltd.) and the like. Among these, Aerosil 200V and Aerosil R972V are particularly preferable because they can easily increase the slipperiness of the film surface while keeping the haze of the optical film low.

  The average particle diameter of the primary particles of the fine particles is preferably in the range of 5 to 400 nm, more preferably in the range of 10 to 300 nm. The fine particles may mainly form secondary aggregates having a particle size in the range of 0.05 to 0.30 μm. If the average particle size of the fine particles is in the range of 100 to 400 nm, they can exist as primary particles without agglomeration.

  The content of the fine particles is preferably in the range of 0.01 to 1.00% by mass, more preferably in the range of 0.05 to 0.50% by mass with respect to the cellulose ester.

Physical properties of optical film The transmittance at 380 nm of the optical film of the present invention is preferably 20 to 90%, more preferably 40 to 85%. In a film having a transmittance of less than 20% at 380 nm, the wavelength dispersion adjusting agent represented by the above-described formula (1) easily absorbs ultraviolet rays when irradiated with ultraviolet rays and generates heat, and heat shrinkage of the film easily occurs. . When thermal shrinkage of the film occurs, fluctuations in the retardation of the film are likely to occur. On the other hand, if the transmittance at 380 nm exceeds 90%, sufficient reverse wavelength dispersion is difficult to obtain. The transmittance at 380 nm may preferably be the transmittance when the thickness of the optical film is 40 μm.

  The transmittance at 380 nm of the optical film can be measured with Spectrophotometer U-3200 (manufactured by Hitachi, Ltd.) at 25 ° C. and 55% RH.

  The transmittance at 380 nm of the optical film can be adjusted by the structure of the wavelength dispersion adjusting agent (the wavelength range of the absorption peak of the wavelength dispersion adjusting agent) and the content thereof. In order to increase the transmittance at 380 nm, for example, a wavelength dispersion adjusting agent having an absorption peak on the short wavelength side may be selected, or the content of the wavelength dispersion adjusting agent may be reduced.

The retardation value R0 (550) in the in-plane direction measured at a wavelength of 550 nm under the condition of 23 ° C. and 55% RH of the optical film of the present invention preferably satisfies the following (a).
(A) 110 nm ≦ R0 (550) ≦ 170 nm

  An optical film in which R0 (550) satisfies the following range can preferably function as, for example, a λ / 4 retardation film. The optical film of the present invention preferably satisfies 120 nm ≦ R0 (550) ≦ 160 nm, and more preferably satisfies 130 nm ≦ R0 (550) ≦ 150 nm.

  In the optical film of the present invention, the retardation value Rth (550) in the thickness direction measured at a wavelength of 550 nm under the condition of 23 ° C. and 55% RH preferably satisfies 50 nm ≦ Rth (550) ≦ 250 nm.

When the retardation values in the in-plane direction measured at wavelengths of 450 nm and 650 nm under conditions of 23 ° C. and 55% RH are R0 (450) and R0 (650), respectively, the optical film of the present invention has the following ( It is preferable that b) and (c) are further satisfied.
(B) 0.72 ≦ R0 (450) / R0 (550) ≦ 1.00
(C) 0.83 ≦ R0 (550) / R0 (650) ≦ 1.00

  An optical film in which R0 (450) / R0 (550) or R0 (550) / R0 (650) satisfies the above range can preferably function as a λ / 4 retardation film for light in a wide wavelength region, for example. Further, light leakage or the like when the display device displays black can be reduced. In particular, when (b) 0.72 ≦ R0 (450) / R0 (550) ≦ 0.95 is satisfied, blue reproducibility is high; (c) 0.83 ≦ R0 (550) / R0 (650) ≦ When 0.95 is satisfied, red reproducibility is high, which is more preferable.

R0 and Rt are defined by the following formulas (I) and (II), respectively.
Formula (I): R0 = (nx−ny) × d
Formula (II): Rt = {(nx + ny) / 2−nz} × d
[In the formulas (I) and (II), nx represents the refractive index in the slow axis direction x where the refractive index is maximum in the in-plane direction of the optical film. ny represents the refractive index in the direction y orthogonal to the slow axis direction x in the in-plane direction of the optical film. nz represents the refractive index in the thickness direction z of the optical film. d represents the film thickness (nm) of the optical film. ]

R0 and Rt can be measured using an automatic birefringence meter, for example, AxoScan manufactured by Axometric, and KOBRA-21ADH manufactured by Oji Scientific Instruments. When using AxoScan, specifically, it can be measured by the following method.
1) Condition the optical film at 23 ° C. and 55% RH. The average refractive index of the optical film after humidity adjustment at each of wavelengths of 450 nm, 550 nm and 650 nm is measured using an Abbe refractometer and a spectral light source. Moreover, the film thickness d (nm) of an optical film is measured using a film thickness meter.
2) Retardation values R0 (450) and R0 (550) in the in-plane direction when light having a wavelength of 450 nm, 550 nm or 650 nm is incident on the optical film after humidity adjustment in parallel with the normal line of the film surface. And R0 (650) are measured with an AxoScan. The measurement is performed under the conditions of 23 ° C. and 55% RH.
3) Using an AxoScan manufactured by Axometric, the slow axis in the plane of the optical film is the tilt axis (rotation axis), and the wavelength from the angle normal to the surface of the optical film (incident angle (φ)) is 450 nm. The retardation value R (φ) when light of 550 nm and 650 nm is incident is measured. R (φ) can be measured at 6 points every 10 ° in the range of 0 to 50 °. The measurement is performed under the conditions of 23 ° C. and 55% RH. The in-plane slow axis of the optical film can be confirmed with an AxoScan manufactured by Axometric.
4) R0 (450), R0 (550) and R0 (650) measured in 2) above, R (φ) measured in each wavelength of 450 nm, 550 nm or 650 nm in 3) above, and 1) above Nx, ny and nz are calculated by AxoScan from the average refractive index and the film thickness d measured in step (1). Then, retardation values Rt (450), Rt (550), and Rt (650) in the thickness direction at wavelengths of 450 nm, 550 nm, and 650 nm are calculated based on the following formulas.
Rth (λ) = {(nx (λ) + ny (λ)) / 2−nz (λ)} × d (nm)
(In the above formula, nx (λ) represents the refractive index in the slow axis direction x at which the refractive index is maximum in the in-plane direction of the optical film when light of wavelength λ is incident; ny (λ) Represents the refractive index in the direction y perpendicular to the slow axis direction x in the in-plane direction of the optical film when light of wavelength λ is incident; nz (λ) is incident of light of wavelength λ Represents the refractive index in the thickness direction z of the optical film; d (nm) represents the thickness of the optical film)

  R0 (450) / R0 (550) is calculated from the obtained R0 (450) and R0 (550); R0 (550) / R0 (650) is obtained R0 (550) and R0 (650) It can be calculated from

In the optical film of the present invention, Nz defined by the following formula (d1) preferably satisfies the following formula (d2).
(D1) Nz = Rt (550) / Ro (550) +0.5
(D2) 0 ≦ Nz ≦ 1
If Nz satisfies the formula (d2), the retardation value Rt in the thickness direction is relatively smaller than the retardation value R0 in the in-plane direction, so that the image display device including the optical film of the present invention is inclined. It is possible to reduce the change in color when observed from above.

  The angle θ (orientation angle) formed by the in-plane slow axis of the optical film of the present invention and the width direction of the film is preferably 40 ° or more and 50 ° or less. When the orientation angle is within the above range, the optical film is unwound from the roll body and has a slow axis in an oblique direction with respect to the long direction, and the transmission axis is unwound from the roll body and parallel to the long direction. A circularly polarizing plate can be easily manufactured by laminating the polarizers having a roll-to-roll so that the longitudinal directions thereof overlap each other. Thereby, there is little cut loss of a film and it is advantageous on production. The orientation angle θ is more preferably 45 ± 2 °, and particularly preferably 45 °.

  The orientation angle θ of the optical film can be measured with an AxoScan manufactured by Axometric.

  The film thickness of the optical film is preferably 150 μm or less, more preferably 60 μm or less, and even more preferably 45 μm or less in order to reduce the variation in retardation due to heat and humidity. On the other hand, the film thickness of the optical film is preferably 10 μm or more, and more preferably 20 μm or more, in order to express a certain level of film strength or retardation. When the film thickness of the optical film is within these ranges, it is preferable from the viewpoint of thinning and productivity of the image display device.

  The haze (total haze) of the optical film is preferably less than 1%, more preferably 0.5% or less, and even more preferably 0.2% or less. If the haze is less than 1%, the transparency of the film does not decrease and the film functions sufficiently as an optical film.

  The haze (total haze) of the optical film can be measured with a haze meter NDH-2000 (manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K-7136. The light source of the haze meter may be a 5V9W halogen sphere, and the light receiving portion may be a silicon photocell (with a relative visibility filter). The haze can be measured under conditions of 23 ° C. and 55% RH.

  In the optical film of the present invention, the elongation at break in at least one direction measured in accordance with JIS-K7127-1999 is preferably 10% or more, more preferably 20% or more, and further preferably 30. % Or more.

  As described above, the absorption peak of the wavelength dispersion adjusting agent contained in the optical film of the present invention is adjusted to the short wavelength side; specifically, in the range of 300 to 360 nm. Therefore, the film of the present invention has a high retardation and good reverse wavelength dispersion.

  In the optical film of the present invention, the transmittance at 380 nm is adjusted to a range of 20 to 90%. For this reason, the optical film of the present invention hardly absorbs ultraviolet rays, and heat generated thereby is suppressed. Thereby, the thermal contraction of the optical film due to the ultraviolet irradiation when producing the circularly polarizing plate can be suppressed, and the phase difference fluctuation can be reduced.

  Specifically, on the optical film, the retardation in the in-plane direction at a wavelength of 550 nm before irradiation with ultraviolet rays for 2 minutes with a weather resistance tester (I Super UV Tester, Iwasaki Electric Co., Ltd.) is R0 (550), When the retardation in the in-plane direction at a wavelength of 550 nm after irradiation is R0 ′ (550), the amount of change ΔR0 in phase difference (phase difference R0 (550) before irradiation−phase difference R0 ′ (550) after irradiation) ) Is preferably 5 nm or less, more preferably 3 nm or less, and even more preferably 2 nm or less.

  The optical film of the present invention is used as an optical film of an image display device such as an organic EL display or a liquid crystal display device; specifically, a polarizing plate protective film, a retardation film, an optical compensation film, or an antireflection film, preferably Used as a λ / 4 retardation film.

  The λ / 4 retardation film has an in-plane retardation R0 of about ¼ of a predetermined wavelength of light (usually in the visible light region). The λ / 4 retardation film is preferably composed of a single layer of the optical film of the present invention. The λ / 4 retardation film is preferably used as an antireflection film for an organic EL display.

2. Method for Producing Optical Film The optical film of the present invention can be produced by a solution casting method or a melt casting method. The solution casting method is preferable from the viewpoint of suppressing optical defects such as coloring of the optical film, foreign matter defects, and die lines, and the melt casting method is preferable from the viewpoint of suppressing the solvent from remaining in the optical film.

A) Solution casting method An optical film containing a cellulose ester is produced by a solution casting method. A1) At least a cellulose ester and a wavelength dispersion adjusting agent represented by the above formula (1) are dissolved in a solvent. A step of obtaining a dope, A2) a step of casting the dope on an endless metal support, A3) a step of evaporating the solvent from the cast dope, and obtaining a film, and A4) a step of peeling the film from the metal support. And A5) a step of stretching the film after drying.

A1) Step of obtaining a dope In a dissolution vessel, a dope is prepared by dissolving a cellulose ester and, if necessary, other additives in a solvent.

  A solvent can be used without a restriction | limiting, if a cellulose ester, another additive, etc. are melt | dissolved. For example, as a chlorinated organic solvent, methylene chloride, as a non-chlorinated organic solvent, methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, cyclohexanone, ethyl formate, 2,2,2-trifluoroethanol, 2,2,3,3-hexafluoro-1-propanol, 1,3-difluoro-2-propanol, 1,1,1,3,3,3-hexafluoro- Examples include 2-methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1-propanol, and nitroethane. Preferably, methylene chloride, methyl acetate, ethyl acetate, acetone or the like can be used.

  The dope preferably further contains 1 to 40% by mass of a linear or branched aliphatic alcohol having 1 to 4 carbon atoms. When the ratio of the alcohol in the dope is high, the film obtained by drying the dope film gels, and peeling from the metal support becomes easy. On the other hand, when the ratio of alcohol in the dope is small, dissolution of cellulose acetate in a non-chlorine organic solvent system can be promoted.

Examples of the linear or branched aliphatic alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, tert-butanol and the like. Of these, ethanol is preferred because of high dope stability, relatively low boiling point, and high drying properties.
Especially, it is preferable that dope contains the methylene chloride of a solvent, and a C1-C4 linear or branched aliphatic alcohol.

  The concentration of the cellulose ester in the dope is preferably high in order to reduce the drying load, but if the concentration of the cellulose ester is too high, it is difficult to filter. Therefore, the concentration of the cellulose ester in the dope is preferably in the range of 10 to 35% by mass, more preferably in the range of 15 to 25% by mass.

  The method for dissolving the cellulose ester in a solvent may be, for example, a method for dissolving under heating and pressure. A higher heating temperature is preferable from the viewpoint of increasing the solubility of the cellulose ester. If the temperature is too high, the pressure needs to be increased, and the productivity is lowered. Therefore, the heating temperature is preferably within the range of 45 to 120 ° C.

  The additive may be added batchwise to the dope, or an additive solution may be separately prepared and added inline. In particular, it is preferable to add all or part of the fine particles in-line in order to reduce the load on the filter medium.

  When the additive solution is added in-line, it is preferable to dissolve a small amount of cellulose ester to facilitate mixing with the dope. The content of the preferred thermoplastic resin can be in the range of 1 to 10 parts by mass, more preferably in the range of 3 to 5 parts by mass with respect to 100 parts by mass of the solvent.

  For in-line addition and mixing, for example, a static mixer (manufactured by Toray Engineering), an in-line mixer such as SWJ (Toray Static In-Pipe Mixer Hi-Mixer), or the like is preferably used.

  The obtained dope may contain insoluble matters such as impurities contained in the cellulose ester as a raw material, for example. Such an insoluble matter can become a bright spot foreign material in the obtained film. In order to remove insoluble matter, it is preferable to further filter the obtained dope.

The dope filtration is preferably performed so that the number of bright spot foreign substances in the obtained film is a certain value or less. Specifically, the number of bright spot foreign matters having a diameter of 0.01 mm or more is 200 / cm ² or less, preferably 100 / cm ² or less, more preferably 50 / cm ² or less, and still more preferably 30 Filtration is performed so that the number of particles / cm ² or less, particularly preferably 10 / cm ² or less.

The bright spot foreign matter having a diameter of 0.01 mm or less is also preferably 200 pieces / cm ² or less, more preferably 100 pieces / cm ² or less, further preferably 50 pieces / cm ² or less, It is more preferably 30 pieces / cm ² or less, particularly preferably 10 pieces / cm ² or less, and most preferably none.

The number of bright spot foreign matter on the film can be measured by the following procedure.
1) Two polarizing plates are arranged in a crossed Nicol state, and the obtained film is arranged between them.
2) When light is applied from the side of one polarizing plate and observed from the side of the other polarizing plate, the number where the light appears to leak is counted as a foreign object.

A2) Casting step The dope is cast on the endless metal support from the slit of the pressure die.

  As the metal support, a stainless steel belt or a drum whose surface is plated with a casting is preferably used. The surface of the metal support is preferably mirror-finished.

  The width of the cast can be in the range of 1-4 m. The surface temperature of the metal support in the casting process is set to −50 ° C. or higher and below the temperature at which the solvent boils and does not foam. A higher temperature is preferable because the drying speed of the dope film can be increased, but it is within a temperature range in which foaming of the dope film and deterioration of planarity can be prevented.

  The surface temperature of the metal support is preferably in the range of 0 to 100 ° C, more preferably in the range of 5 to 30 ° C. Alternatively, the metal support may be cooled to gel the dope film so that it can be peeled off from the drum in a state containing a large amount of residual solvent.

  The method for adjusting the temperature of the metal support is not particularly limited, and there are a method of blowing hot air or cold air, and a method of bringing hot water into contact with the back side of the metal support. It is preferable to use warm water because heat transfer is performed efficiently, so that the time until the temperature of the metal support becomes constant is short.

  When using warm air, considering the temperature drop of the film due to the latent heat of vaporization of the solvent, while using warm air above the boiling point of the solvent, there may be cases where air at a temperature higher than the target temperature is used while preventing foaming. . In particular, it is preferable to efficiently dry by changing the temperature of the metal support and the temperature of the drying air during the period from casting to peeling.

A3) Solvent evaporation step The dope film cast on the metal support is heated on the metal support to evaporate the solvent to obtain a film. The drying method and drying conditions of the dope film can be the same as in the above-described A2) casting step.

A4) Peeling process The film obtained by evaporating the solvent on the metal support is peeled off at the peeling position on the metal support. The amount of residual solvent of the film when peeling at the peeling position on the metal support is preferably within the range of 10 to 150% by mass, in order to improve the flatness of the film, 20 to 40% by mass or 60%. It is more preferable to set it in the range of -130 mass%, and it is further more preferable to set it in the range of 20-30 mass% or 70-120 mass%.

The residual solvent amount of the film is defined by the following formula.
Residual solvent amount (%) = (mass before heat treatment of film−mass after heat treatment of film) / (mass after heat treatment of film) × 100
Note that the heat treatment for measuring the residual solvent amount means a heat treatment at 115 ° C. for 1 hour.

A5) Drying and stretching process (oblique stretching process)
The film peeled from the metal support is dried as necessary and then stretched. The film may be dried while being transported by a number of rollers arranged above and below, or may be dried while being transported while fixing both ends of the film with clips.

  The method of drying the film may be a method of drying with hot air, infrared rays, a heating roller, microwaves, or the like, and a method of drying with hot air is preferable because it is simple.

  Then, an optical film having a desired retardation is obtained by stretching the film. The retardation of the optical film can be controlled by adjusting the magnitude of tension on the film.

  In the present invention, in order to set the slow axis in the plane of the optical film to an oblique direction with respect to the width direction (or transport direction) of the film, the film is stretched in an oblique direction with respect to the width direction (or transport direction) of the film. (Draw diagonally). The oblique direction is a direction having an angle in the range of 40 to 50 ° with respect to the film transport direction, and is preferably stretched in a direction at an angle of 45 ° with respect to the film transport direction.

  As described above, a polarizing film unwound from a roll body and having a transmission axis in the longitudinal direction, and an optical film unwound from the roll body and having a slow axis in a direction at an angle of 45 ° with respect to the longitudinal direction. Can be easily manufactured by simply laminating them in a roll-to-roll manner so that their longitudinal directions overlap each other. Moreover, the cut loss of the film can be reduced, which is advantageous in production.

  The draw ratio is represented by the ratio W / W0 of the width of the film before and after stretching (W is before stretching, W0 is the width after stretching), and the film thickness of the obtained optical film and the required retardation However, it is preferably in the range of 1.3 to 3.0 times, more preferably in the range of 1.5 to 2.8 times.

  The stretching temperature is preferably in the range of 120 to 230 ° C, more preferably in the range of 150 to 220 ° C, and even more preferably greater than 150 ° C and 210 ° C or less.

  It does not restrict | limit especially as a method of producing the film in which a slow axis inclines within the range of 40-50 degrees with respect to a conveyance direction. For example, there is a method in which the right and left in the width direction are gripped by the gripping means, and the film is stretched using a tenter that can independently control the gripping length (distance from the start of gripping to the end of gripping) on the left and right.

  Examples of the stretching apparatus having a mechanism for stretching in an oblique direction include the stretching apparatus described in Example 1 of Japanese Patent Application Laid-Open No. 2003-340916, the stretching apparatus illustrated in FIG. The stretching apparatus described in 2007-30466, the stretching apparatus used in Example 1 of JP 2007-94007 A, and the like are included.

  Moreover, the method of using the linear diagonal stretch apparatus (simultaneous biaxial stretching apparatus) and not having to incline the direction which draws out a film, and the direction which winds up the film after extending | stretching is also mentioned. Specifically, gripping both ends of the film with a plurality of gripping tools, and conveying the film, the difference in travel speed between the gripping tool gripping one end and the gripping tool gripping the other end. And a method of obliquely stretching the film. For example, the method described in JP2008-23775A can be mentioned.

  The residual solvent of the film at the start of stretching is preferably 20% by mass or less, more preferably 15% by mass or less.

Hereinafter, the oblique stretching process will be described more specifically.
(Oblique stretching process)
As described above, in the oblique stretching step, the formed long film is stretched in an oblique direction with respect to the width direction. The stretched film (stretched film) is formed into a long film, wound around a core once to form a wound body, and then the film is unwound from the wound body and obliquely stretched. Or may be obtained by continuously stretching the film without winding it up. Continuously performing the film-forming process and the oblique stretching process feeds back the film thickness and optical value results of the stretched film to change the film-forming conditions, thereby obtaining a long stretched film having desired optical characteristics. It is preferable because it is reduced.

  In the oblique stretching step, the film is stretched in an oblique direction with respect to the width direction (an angle of greater than 0 ° and less than 90 ° with respect to the width direction), and a long shape having a slow axis in the oblique direction with respect to the width direction. A stretched film is produced. The angle with respect to the width direction of the film is an angle in the plane of the film. The slow axis in the plane of the film usually develops in the stretching direction or in a direction perpendicular to the stretching direction.

  The angle formed by the width direction of the film and the in-plane slow axis; that is, the orientation angle can be set to an arbitrary angle in the range of more than 0 ° and less than 90 °.

  As will be described later, the oblique stretching apparatus for performing the oblique stretching apparatus usually has a pair of gripping tools disposed on both ends in the width direction of the film and a pair of gripping tool travel support tools for running the gripping tool. Then, the film is stretched in the heating zone while both ends of the long film are gripped with a gripping tool and run.

  FIG. 1 is an explanatory diagram showing an example of oblique stretching. The embodiment of FIG. 1 is merely an example of oblique stretching, and is not limited to this. As shown in FIG. 1, generally, in an oblique stretching apparatus, the feeding direction D1 of the long film is different from the winding direction D2 of the film after stretching, and the feeding direction D1 of the film and after stretching The film winding direction D2 forms a feeding angle θi. The feeding angle θi can be arbitrarily set to a desired angle within a range of more than 0 ° and less than 90 °.

  At the entrance of the oblique stretching machine (position A in the figure), the both ends of the long film described above are gripped by the right and left grippers (tenters) and run. The left and right gripping tools Ci and Co facing the direction substantially orthogonal to the film transport direction (feeding direction D1) at the entrance of the oblique stretching machine (position A in the drawing) are: Each travels on asymmetrical rails Ri and Ro. Then, the left and right gripping tools release the stretched film (stretched film) gripped at the position at the end of stretching (position B in the figure).

  As the left and right gripping tools facing at the entrance of the oblique stretching machine (position A in the figure) travel on the left and right asymmetric rails Ri and Ro, the gripping tool Ci traveling on the Ri side travels on the Ro side. Proceed with respect to the gripping tool Co. That is, at the entrance of the oblique stretching machine (holding start position by the gripping tool) A, a straight line connecting the gripping tools Ci and Co is substantially perpendicular to the film feeding direction D1. On the other hand, in the state at the position B at the end of stretching of the film, the straight line connecting the grippers Ci and Co is inclined by an angle θL with respect to a direction substantially perpendicular to the film winding direction D2. . Thereby, the film is stretched obliquely in the direction of θL. The term “substantially vertical” indicates a range of 90 ± 1 °.

  And the zone which drive | works with the space | interval of the holding tool which hold | gripped both ends among the zones formed between a pair of rails maintaining a fixed space | interval becomes a "preheating zone." Further, the interval between the gripping tools gripping both ends is opened, and a section until the predetermined interval is reached becomes an “extension zone”. Furthermore, in a period in which the interval between the gripping tools after the stretching zone becomes constant again, a section in which the gripping tools at both ends travel while being parallel to each other is a “heat fixing zone or heat fixing / cooling zone”.

  The temperature of the preheating zone and the stretching zone is preferably in the range of Tg to Tg + 30 ° C. when the glass transition temperature of the cellulose ester is Tg; the temperature of the heat setting zone or heat setting / cooling zone is Tg-30 It is preferable to set within the range of ~ Tg ° C.

  The lengths of the preheating zone, the stretching zone, and the heat setting zone can be appropriately selected. The length of the preheating zone can usually be in the range of 100-150% with respect to the length of the drawing zone; the length of the heat setting zone should normally be in the range of 50-100% Can do.

  As described above, the oblique stretching apparatus used for oblique stretching includes a plurality of gripping tools that travel by gripping both ends in the width direction of the long film, and an endless shape that guides and supports the travel of the gripping tools. A gripping tool travel support tool.

  Then, both ends of the long film to be supplied are gripped by the gripping tool at the entrance of the stretching apparatus and stretched in the oblique direction in the heating zone, and then the gripping tool is opened at the exit of the stretching apparatus. On the other hand, the gripping tool that has opened the stretched film travels on an endless gripping tool travel support tool and is returned to the entrance of the stretching device again.

  The gripping tool travel support tool may have, for example, an endless chain and a guide rail or gear that regulates the path thereof, or may be an endless guide rail (without an endless chain). Good. In other words, the gripping tool travel support tool may be an endless or endless guide rail having an endless chain, or may be an endless guide rail having no endless chain.

  The path of the gripping tool travel support tool has an asymmetric shape on the left and right, and can be adjusted manually or automatically in accordance with the orientation angle and stretch ratio of the optical film to be manufactured.

  The gripper travels on the gripper travel support when the gripper travel support has a chain, and travels through the chain when the gripper travel support does not have a chain.

  The traveling speed of the gripping tool can be set as appropriate, but is preferably 1 to 150 m / min. When the traveling speed of the gripping tool exceeds 150 m / min, the local stress applied to both ends in the width direction of the film increases at the location where the conveyance of the long film is oblique, and wrinkles and Misalignment is likely to occur. Thereby, there exists a tendency for the effective width which can be used among the full width of the film obtained after extending | stretching to become narrow.

  The difference in travel speed between the gripping tool that grips one of the both ends in the width direction of the film and the gripping tool that grips the other is usually 1% or less, preferably 0.5% or less, more preferably 0, of the travel speed. 0.1% or less, more preferably substantially zero (constant velocity). If there is a running speed difference between the pair of gripping tools that grip the left and right of the elongated stretched film (stretched film) at the outlet of the oblique stretching apparatus, the film will be wrinkled or offset at the outlet of the oblique stretching apparatus. It is easy to occur. In a general stretching device, there is a speed variation that occurs in the order of seconds or less depending on the period of the sprocket (gear) tooth that drives the chain, the frequency of the drive motor, etc. However, these do not correspond to the speed difference described in this embodiment.

  FIG. 2 is a schematic diagram illustrating an example of an oblique stretching apparatus. In this embodiment, the length of the path of the inner gripping tool travel support tool and the length of the path of the outer gripping tool travel support tool are the same, and the straight line connecting the pair of gripping release points is the width direction of the stretched film Is not parallel to the example. As shown in FIG. 2, in the oblique stretching apparatus T1, the gripping tools (the gripping tool 1i and the gripping tool 1o) grip both ends in the width direction of the long film at the grip start point on the straight line A. The gripping tool 1i that travels along the path of the inner gripping tool travel support tool Ri and 1o that travels along the path of the outer gripping tool travel support tool Ro are aligned on the straight line A.

  Each gripping tool travel support tool has an endless continuous track. The gripping tool travels on the aforementioned gripping tool travel support tool. The gripper grips the supplied film at the grip start point, and after stretching, releases the stretched film F at the grip release point on the straight line B. Each gripping tool that has released the stretched film F continues to travel on the gripping tool travel support tool, reaches the gripping start point again, and grips the continuously supplied film. In this way, the gripper circulates the gripper travel support tool and repeats gripping, stretching, and releasing of the supplied film. In these operations, one gripping tool that travels along the route of the inner gripping tool travel support tool Ri and one gripping tool that travels along the path of the outer gripping tool travel support tool Ro form a gripping tool pair. And it is done continuously.

  The distance between the gripping tools forming the gripping tool pair corresponds to the width of the supplied film. A film is conveyed with the holding | gripping tool to drive | work and passes the preheating zone, extending | stretching zone, heat setting zone, and cooling zone which are not shown in figure. The gripping tool traveling on the inner gripping tool travel support tool Ri reaches the grip release point earlier than the gripping tool traveling on the outer gripping tool travel support tool Ro, and releases the film after stretching. To do. Note that when the gripping tool traveling on the inner gripping tool travel support tool Ri reaches the grip release point, the other gripping tool that forms a grip tool pair at the grip start point is still gripping and releasing. It does not arrive at the point, but travels along the route of the outer gripping tool travel support tool Ro.

  In FIG. 2, a straight line connecting the grip release point of the gripping tool 1i traveling on the route of the inner gripping tool travel support tool Ri and the grip release point of the gripping tool 1o traveling on the path of the outer gripping tool travel support tool Ro. B is not parallel to the width direction of the traveling film F. The length of the path of the inner gripping tool travel support tool Ri and the length of the path of the outer gripping tool travel support tool Ro are the same.

  As shown in FIG. 2, in order to make the path length of the inner gripping tool travel support tool Ri the same as the path length of the outer gripping tool travel support tool Ro, the inner gripping tool travel support tool Ri Is provided with an adjusting gear G3. The adjustment gear G3 is a gear for stretching the inner gripping tool travel support tool Ri outward in the circumferential direction.

  As shown in FIG. 2, the folding gear G1 provided near the grip release point of the inner gripping tool travel support tool is more than the folding gear G2 provided near the grip release point of the outer gripping tool travel support tool. The film F is disposed on the downstream side in the conveyance direction. As a result, the angle θ formed by the straight line B and the conveyance direction of the film F exceeds 0 ° and is less than 90 °. In this case, the stress applied to the stretched film F when the gripping tool 1i traveling on the route of the inner gripping tool travel support tool Ri is released and the gripping tool 1o traveling on the path of the outer gripping tool travel support tool Ro stretched when released. The stress applied to the subsequent film F is not canceled out. As a result, thickness unevenness may occur in the obtained stretched film F. Therefore, the straight line B connecting the grip release points is preferably parallel to the width direction of the stretched film F as shown in FIG.

  FIG. 3 is a schematic diagram illustrating another example of the oblique stretching apparatus. In this embodiment, the length of the path of the inner gripping tool travel support tool and the length of the path of the outer gripping tool travel support tool are the same, and the straight line connecting the pair of gripping release points is the width direction of the stretched film It is an example which becomes parallel to.

  As shown in FIG. 3, in the oblique stretching apparatus T2, the angle θa formed by the straight line connecting the grip release points and the transport direction of the film F is 90 °. The folding gear G1a provided in the vicinity of the grip release point of the inner gripping tool traveling support tool is arranged on the upstream side in the traveling direction of the film F compared to the folding gear G1 of FIG. As a result, the straight line B is formed to be parallel to the width direction of the film F.

  In this case, the gripping tool travel support tool may bend in the inner gripping tool travel support tool. Therefore, as shown in FIG. 3, the inner gripping tool travel support tool is provided with an adjustment gear G3a as described above. The adjustment gear G3a is a gear for stretching the inner gripping tool travel support tool to the outer side in the circumferential direction in order to eliminate bending generated in the inner gripping tool travel support tool by changing the position of the folding gear G1a. .

  By producing the stretched film F using the stretching apparatus T2 shown in FIG. 3, when the gripping tool releases the stretched film F particularly at the grip release point, the stress applied thereto is affected by the width direction of the film. Since both ends cancel each other, the thickness unevenness of the obtained stretched film F is reduced.

  FIG. 4 is a schematic view showing still another example of the oblique stretching apparatus. This aspect is an example in which the path lengths of the two gripping tool travel support tools are different. As shown in FIG. 4, when the path lengths of the two gripping tool travel support tools are different, the oblique stretching apparatus T3 is a speed at which the travel speed of the grip tool is increased or decreased by one or both grip tool travel support tools. You may further have an adjustment mechanism (not shown). The figure shows an example in which a speed adjusting mechanism for increasing the traveling speed of the gripping tool is provided on the route of the outer gripping tool travel support tool Ro.

  The speed adjusting mechanism is a mechanism that adjusts the traveling speed until the gripping tool 1o that has released the grip of the stretched film F returns to the grip start point again at the grip release point. The method for adjusting the travel speed of the gripping tool is not particularly limited. For example, the gripping tool travel support tool is provided with an inclination, the wind is blown, the magnetic field is generated, and the gripping tool travel support tool has a different coefficient of friction. It may be a method of dividing into a plurality of sections.

  Whether the traveling speed of the gripping tool is to slow down the speed of the gripping tool traveling on the path of the gripping tool traveling support tool having the short overall length or to increase the speed of the gripping tool traveling on the path of the gripping tool traveling support tool having the long overall length. It can be adjusted by combining both of them. In FIG. 4, reference symbol C indicates a section in which the traveling speed of the gripping tool is adjusted by the speed adjustment mechanism. In FIG. 4, section C in which the traveling speed of the gripping tool is adjusted by the speed adjustment mechanism is a section in which the gripping tool that has released the film at the grip release point travels to the grip start point.

  As shown in FIG. 4, the gripping tool 1 o accelerated by the speed adjustment mechanism travels in the section C. In this way, by adjusting the traveling speed of the gripping tool, it is not necessary to make the entire length of the path of the gripping tool travel support tool the same, and a significant design change of the apparatus is not necessary. In addition, it is possible to calculate in advance how much the traveling speed of the gripping tool needs to be adjusted when adjusting the path pattern and the stretching angle of the gripping tool travel support tool. As a result, even when the diagonally extending angle or the like is changed, the traveling speed of the gripping tool can be adjusted so that the same gripping tool pair is always aligned at the gripping start point accordingly. 4 shows a case where the angle θb formed by the straight line connecting the grip release points and the transport direction of the stretched film F is 90 °, the angle θb is the same as that shown in FIG. May be greater than 0 ° and less than 90 °.

  In the oblique stretching apparatus shown in FIG. 4, the path of the gripping tool travel support tool may have a bent portion having a large bending rate, particularly at a location where the conveyance of the long film is oblique. In order to avoid interference between gripping tools due to sudden bending or local stress concentration, it is desirable that the trajectory of the gripping tool draws an arc at the bent portion.

  The stretched film is dried as necessary and then wound. As described above, the film may be dried while being transported by a large number of rollers arranged on the top and bottom (roller system), or both ends of the film are fixed with clips and dried while being transported. Also good (tenter method).

B) Melt Casting Method The method for producing the optical film of the present invention by the melt casting method is as follows: B1) Step of producing molten pellets (pelletizing step), B2) Step of extruding after melting and kneading the molten pellets (melting) Extruding step), B3) a step of cooling and solidifying the molten resin to obtain a film (cooling solidification step), and B4) a step of stretching the film (stretching step).

B1) Pelletization process It is preferable that the resin composition containing the cellulose ester which is the main component of the optical film is previously kneaded and pelletized. Pelletization can be performed by a known method. For example, a resin composition containing the aforementioned cellulose ester and, if necessary, an additive such as a plasticizer, is melt-kneaded with an extruder, and then from a die. Extrude into a strand. The molten resin extruded in a strand form can be cooled with water or air, and then cut to obtain pellets.

  The pellet raw material is preferably dried before being supplied to the extruder in order to prevent decomposition.

  The mixture of the antioxidant and the cellulose ester may be mixed with each other, or the cellulose ester may be mixed with an antioxidant dissolved in a solvent, or the antioxidant may be mixed with the cellulose ester. You may spray and mix. The atmosphere around the feeder part of the extruder and the outlet part of the die is preferably an atmosphere of dehumidified air or nitrogen gas in order to prevent deterioration of the raw material of the pellet.

  In an extruder, kneading is preferably performed at a low shearing force or at a low temperature so as not to cause deterioration of the resin (decrease in molecular weight, coloring, gel formation, etc.). For example, when kneading with a twin screw extruder, it is preferable to use a deep groove type screw and to rotate the two screws in the same direction. In order to knead uniformly, it is preferable that two screw shapes mesh with each other.

  Instead of pelletizing the resin composition containing cellulose ester, an optical film may be produced by melt-kneading a cellulose ester not melt-kneaded as a raw material with an extruder.

B2) Melt extrusion step The obtained molten pellets and other additives as required are supplied from the hopper to the extruder. The supply of pellets is preferably performed under vacuum, reduced pressure, or an inert gas atmosphere in order to prevent oxidative decomposition of the pellets. And it melt-kneads the melt pellet which is a film material, and another additive as needed with an extruder.

  The melting temperature of the film material in the extruder is preferably in the range of Tg to (Tg + 100) ° C., more preferably when the glass transition temperature of the film is Tg (° C.), although it depends on the type of film material. Is within the range of (Tg + 10) to (Tg + 90) ° C.

  Furthermore, when additives such as plasticizers and fine particles are added in the middle of the extruder, a mixing device such as a static mixer is further arranged on the downstream side of the extruder to uniformly mix these components. May be.

  The molten resin extruded from the extruder is filtered through a leaf disc filter or the like as necessary, and further mixed with a static mixer or the like, and extruded from a die into a film.

  The extrusion flow rate is preferably stabilized using a gear pump. Moreover, it is preferable that the leaf disk filter used for removal of a foreign material is a stainless fiber sintered filter. The stainless steel fiber sintered filter is an integrated, intricately intertwined stainless steel fiber body that is compressed and sintered by integrating the contact points. The density is changed according to the thickness of the fiber and the amount of compression, and the filtration accuracy is adjusted. it can.

  The melting temperature of the resin at the exit portion of the die can be in the range of about 200-300 ° C.

B3) Cooling and solidifying step The resin extruded from the die is nipped between the cooling roller and the elastic touch roller to make the film-like molten resin a predetermined thickness. Then, the film-like molten resin is cooled and solidified stepwise by a plurality of cooling rollers.

  The surface temperature of the cooling roller can be Tg (° C.) or lower when the glass transition temperature of the film is Tg (° C.). The surface temperatures of the plurality of cooling rollers may be different.

  The elastic touch roller is also called a pinching rotary body. A commercially available elastic touch roller can also be used. The film surface temperature on the elastic touch roller side can be in the range of Tg to (Tg + 110) ° C. of the film.

  The film-like molten resin solidified from the cooling roller is peeled off with a peeling roller or the like to obtain a film. When peeling the film-like molten resin, it is preferable to adjust the tension in order to prevent deformation of the obtained film.

B4) Stretching step As in the solution casting method, the obtained film is stretched in an oblique direction with a stretching machine to obtain a film. The stretching method, stretching ratio and stretching temperature of the film can be the same as in the solution casting method.

3. Circularly polarizing plate The circularly polarizing plate of this invention has a polarizer (linearly-polarizing film) and the optical film of this invention arrange | positioned on the at least one surface. The optical film of the present invention may be disposed directly on the polarizer or may be disposed via another layer or film.

  The polarizer may be an iodine polarizing film, a dye polarizing film using a dichroic dye, or a polyene polarizing film. The iodine-based polarizing film and the dye-based polarizing film may be generally a film obtained by uniaxially stretching a polyvinyl alcohol-based film and then dyeing with iodine or a dichroic dye; After the film is dyed with iodine or a dichroic dye, it may be a uniaxially stretched film (preferably a film further subjected to a durability treatment with a boron compound). The absorption axis of the polarizer is parallel to the stretching direction of the film.

  The polyvinyl alcohol film may be a film formed from a polyvinyl alcohol aqueous solution. The polyvinyl alcohol film is preferably an ethylene-modified polyvinyl alcohol film because it is excellent in polarizing performance and durability performance, and has few color spots.

  Examples of dichroic dyes include azo dyes, stilbene dyes, pyrazolone dyes, triphenylmethane dyes, quinoline dyes, oxazine dyes, thiazine dyes and anthraquinone dyes.

  The thickness of the polarizer is preferably in the range of 5 to 30 μm, and more preferably in the range of 10 to 20 μm.

  In order to obtain the function as a circularly polarizing plate, the angle formed by the absorption axis (or transmission axis) of the polarizer and the in-plane slow axis of the optical film of the present invention is within the range of 40 to 50 °. It is preferable that it is 45 °, and more preferably 45 °.

  A reflective polarizing plate may be further disposed between the polarizer and the optical film of the present invention. The reflective polarizing plate transmits linearly polarized light in a direction parallel to the transmission axis of the polarizer and reflects linearly polarized light in a direction different from the transmission axis. The organic EL display device having such a circularly polarizing plate can emit more light emitted from the light emitting layer to the outside.

  Examples of the reflective polarizing plate include a birefringent optical polarizer (described in JP-A-8-503313) in which polymer thin films having different refractive indexes in one direction are alternately laminated, and a polarization separation film having a cholesteric structure (special Described in Kaihei 11-44816). Moreover, you may arrange | position a protective film further on the surface of a polarizer.

  When the optical film of the present invention is disposed on one surface of the polarizer, a transparent protective film other than the optical film of the present invention may be disposed on the other surface of the polarizer. The transparent protective film is not particularly limited, and may be a normal cellulose ester film or the like. Examples of the cellulose ester film include commercially available cellulose ester films (for example, Konica Minoltak KC8UX, KC5UX, KC8UCR3, KC8UCR4, KC8UCR5, KC8UY, KC6UY, KC4UY, KC4UE, KC8UE, KC8UY-X8 -C, KC8UXW-RHA-NC, KC4UXW-RHA-NC (manufactured by Konica Minolta Advanced Layer Co., Ltd.) and the like are preferably used.

  The thickness of the transparent protective film is not particularly limited, but can be in the range of about 10 to 200 μm, preferably in the range of 10 to 100 μm, and more preferably in the range of 10 to 70 μm.

  When the optical film or the transparent protective film of the present invention is disposed on the outermost surface of the display, a transparent hard coat layer, an antiglare layer, an antireflection layer, or the like may be further provided on the outermost surface of these films. .

  The circularly polarizing plate can be manufactured through a step of laminating the polarizer and the optical film of the present invention. The adhesive used for bonding can be, for example, a water-based adhesive (completely saponified polyvinyl alcohol aqueous solution), an active energy ray-curable adhesive, or the like. An active energy ray-curable adhesive is preferable because the moisture permeability of the obtained polarizing plate can be effectively reduced.

  The active energy ray-curable adhesive contains a curable compound, and may further contain a photopolymerization initiator as necessary. When the active energy ray curable adhesive is an electron beam curable type, it is not particularly necessary to contain a photopolymerization initiator, but when it is an ultraviolet ray curable type, it is preferable to contain a photopolymerization initiator. .

  The curable compound may be a cationic polymerizable compound such as an epoxy compound, or may be a radical polymerizable compound such as a (meth) acrylic compound.

Radical polymerization type active energy ray curable adhesive The curable compound contained in the radical polymerization type active energy ray curable adhesive is a radical polymerizable compound, for example, a compound having a (meth) acryloyl group. Etc. are included.

  The compound having a (meth) acryloyl group can be various epoxy (meth) acrylates, urethane (meth) acrylates, polyester (meth) acrylates, various (meth) acrylate monomers, and the like.

Examples of compounds having a (meth) acryloyl group include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth ) Acrylate, lauryl (meth) acrylate, etc. having 1 to 12 carbon atoms (meth) acrylate;
(Meth) acrylic acid alkoxyalkyl monomers such as (meth) acrylic acid methoxyethyl and (meth) acrylic acid ethoxyethyl;
2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, Examples thereof include hydroxy group-containing monomers such as (meth) acrylic acid 10-hydroxydecyl, (meth) acrylic acid 12-hydroxylauryl and (4-hydroxymethylcyclohexyl) -methyl acrylate. A sclerosing | hardenable component can also be used 1 type or in combination of 2 or more types.

  The photopolymerization initiator is a photoradical polymerization initiator when combined with a radically polymerizable compound. Examples of photo radical polymerization initiators include acetophenones such as 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 4- (2-hydroxyethoxy) phenyl (2-hydroxy-2-propyl) ketone Benzoin ether compounds such as benzoin ethyl ether; benzophenone compounds such as 3,3′-dimethyl-4-methoxybenzophenone and the like.

  Content of a photoinitiator is about 0.1-10 mass parts normally per 100 mass parts of sclerosing | hardenable components, Preferably it is the range of 0.5-3 mass parts.

  Hereinafter, an example of the manufacturing method of the circularly-polarizing plate using an active energy ray hardening-type adhesive agent is demonstrated. The circularly polarizing plate is 1) a pretreatment step for easily bonding the adhesive surface of the optical film of the present invention, and 2) a step of applying the above-mentioned active energy ray-curable adhesive to at least one of the polarizer and the optical film ( Adhesive application step), 3) a step of bonding the polarizer and the optical film through the obtained adhesive layer (bonding step), and 4) the polarizer and the optical film bonded through the adhesive layer It can manufacture by the manufacturing method including the process (hardening process) of hardening an adhesive bond layer in the state put together.

(Pretreatment process)
In the pretreatment step, the surface of the optical film to be bonded to the polarizer is subjected to easy adhesion treatment. Examples of easy adhesion treatment include corona treatment. In the next adhesive application step, the surface subjected to the easy adhesion treatment becomes an adhesion surface with the polarizer.

(Adhesive application process)
In the adhesive application step, the aforementioned active energy ray-curable adhesive is applied to at least one of the adhesive surfaces of the polarizer and the optical film. The application method of the active energy ray curable adhesive is not particularly limited, and may be, for example, a doctor blade, a wire bar, a die coater, a comma coater, a gravure coater, or the like. Moreover, after casting an active energy ray hardening-type adhesive between a polarizer and an optical film, the method of pressurizing with a roll etc. and spreading uniformly can also be utilized.

(Bonding process)
After applying an active energy ray-curable adhesive on a polarizer or an optical film, they are laminated together. And the obtained laminated body is pinched | interposed with a roll etc., and it bonds together. As the material of the roll, metal, rubber or the like can be used. The rolls arranged on both sides may be the same material or different materials.

(Curing process)
In the curing step, the active energy ray-curable adhesive coating layer is cured by irradiating the laminate bonded together with active energy rays. Thereby, a polarizer and an optical film are adhere | attached through the hardened | cured material layer of an active energy ray hardening-type adhesive agent. Irradiation of active energy rays can be performed from one side or both sides of a laminate of a polarizer or an optical film.

  Visible light, ultraviolet rays, X-rays, electron beams, and the like can be used as the active energy rays, but ultraviolet rays are generally preferably used because they are easy to handle and have a sufficient curing rate. The light source of the active energy ray is not particularly limited, and has a light emission distribution at a wavelength of 400 nm or less. A lamp, an LED lamp, or the like can be used.

The irradiation intensity of the active energy ray is determined for each target composition and is not particularly limited. However, the irradiation intensity in the wavelength region effective for activating the polymerization initiator is UV-B (280 It is preferable to adjust so that it may become the range of 1-3000 mW / cm < ² > as -320 nm medium wavelength range ultraviolet rays). When the irradiation intensity is less than 1 mW / cm ² , the reaction time becomes too long, and when the irradiation intensity exceeds 3,000 mW / cm ^{2, due} to heat generated during polymerization of the active energy ray-curable adhesive radiated from the lamp, There is a possibility of causing yellowing of the photocurable adhesive and deterioration of the polarizer.

The irradiation time of the active energy ray is controlled for each composition to be cured and is not particularly limited. However, the integrated light amount represented by the product of the irradiation intensity and the irradiation time is in the range of 10 to 5000 mJ / cm ² . It is preferable to set so as to be. When the integrated light quantity is less than 10 mJ / cm ² , active species derived from the polymerization initiator are not sufficiently generated, and the adhesive layer may be insufficiently cured. On the other hand, if the integrated light quantity exceeds 5000 mJ / cm ² , the irradiation time becomes very long, which is disadvantageous for improving productivity.

  The irradiation condition of the active energy ray is preferably in a range that does not lower the polarization degree, transmittance, hue, transparency of the optical film, and the like of the polarizer.

  As described above, the transmittance of the optical film of the present invention is adjusted to a range of 20 to 90% at 380 nm. For this reason, the optical film of the present invention hardly absorbs ultraviolet rays, and heat generated thereby is suppressed. Thereby, in the curing step when producing the circularly polarizing plate, the thermal contraction of the optical film due to the ultraviolet irradiation can be suppressed, and the retardation fluctuation caused thereby can be reduced.

  In the polarizing plate obtained as described above, the thickness of the cured layer of the active energy ray-curable adhesive is not particularly limited, but is usually 50 μm or less, preferably 20 μm or less, more preferably 10 μm or less. More preferably, it is 5 μm or less.

  The circularly polarizing plate is preferably used for an image display device described later.

4). Image display device The image display device of the present invention has the optical film of the present invention. The image display device can be, for example, an organic EL display device or a liquid crystal display device.

  FIG. 5 is a schematic diagram illustrating an example of the configuration of an organic EL display device. As shown in FIG. 5, the organic EL display device 10 includes a light reflecting electrode 12, a light emitting layer 14, a transparent electrode layer 16, a transparent substrate 18, and a circularly polarizing plate 20 in this order.

  The light reflecting electrode 12 is preferably made of a metal material having a high light reflectance. Examples of the metal material include Mg, MgAg, MgIn, Al, LiAl, and the like. The flatter surface of the light reflecting electrode 12 is preferable because irregular reflection of light can be prevented.

  The light reflecting electrode 12 can be formed by a sputtering method. The light reflecting electrode 12 may be patterned. Patterning can be performed by etching.

  The light emitting layer 14 includes R (red), G (green), and B (blue) light emitting layers. Each light emitting layer contains a light emitting material. The light emitting material may be an inorganic compound or an organic compound, and is preferably an organic compound.

  Each of the R, G, and B light-emitting layers further includes a charge transport material, and may further have a function as a charge transport layer. Each of the R, G, and B light emitting layers further includes a hole transport material, and may further have a function as a hole transport layer. When each of the R, G, and B light emitting layers does not include a charge transport material or a hole transport material, the organic EL display device 10 may further include a charge transport layer or a hole transport layer.

  The light emitting layer 14 can be formed by evaporating a light emitting material. Each of the R, G, and B light emitting layers is obtained by patterning. Patterning can be performed using a photomask or the like.

  The transparent electrode layer 16 can generally be an ITO (indium tin oxide) electrode. The transparent electrode layer 16 can be formed by a sputtering method or the like. The transparent electrode layer 16 may be patterned. Patterning can be performed by etching.

  The transparent substrate 18 may be any material that can transmit light, and may be a glass substrate, a plastic film, or the like.

  The circularly polarizing plate 20 is disposed such that the λ / 4 retardation film 20A is located on the transparent substrate 18 side and the polarizer 20B is located on the viewing side.

  When the organic EL display device 10 is energized between the light reflecting electrode 12 and the transparent electrode layer 16, the light emitting layer 14 emits light and can display an image. In addition, since each of the R, G, and B light-emitting layers is configured to be energized, a full-color image can be displayed.

  The circularly polarizing plate 20 includes a λ / 4 retardation film 20A and a polarizer 20B. The λ / 4 retardation film 20A can be used as the optical film of the present invention. The polarizer 20B is a linearly polarizing film.

  The optical film of the present invention or the circularly polarizing plate including the optical film is not limited to the organic EL display device having the above-described configuration, but also includes international patent applications WO96 / 34514, JP-A-9-127858, and 11-45058. The present invention can also be applied to the organic EL display device described in the publication. In that case, the optical film or the circularly polarizing plate of the present invention may be disposed in place of or together with the antireflection means of the organic EL display device provided in advance. The optical film or circularly polarizing plate of the present invention can also be applied to an inorganic EL display device described in, for example, “Electroluminescence Display” (Toshio Higuchi, Sangyo Tosho Co., Ltd., published in 1991).

  FIG. 6 is a schematic diagram for explaining the antireflection function of the circularly polarizing plate 20. As shown in FIG. 6, when light including linearly polarized light a1 and b1 enters from the outside in parallel to the normal line of the display screen of the organic EL display device 10, linearly polarized light b1 parallel to the transmission axis direction of the polarizer 20B. Only passes through the polarizer 20B. The other linearly polarized light a1 that is not parallel to the transmission axis of the polarizer 20B is absorbed by the polarizer 20B. The linearly polarized light b2 that has passed through the polarizer 20B is converted to circularly polarized light c2 by passing through the λ / 4 retardation film 20A. When the circularly polarized light c2 is reflected by the light reflecting electrode 12 (see FIG. 5) of the organic EL display device 10, the circularly polarized light c2 becomes reverse circularly polarized light c3. The reversely polarized circularly polarized light c3 passes through the λ / 4 retardation film 20A and is converted into linearly polarized light b3 orthogonal to the transmission axis of the polarizer 20B. This linearly polarized light b3 is absorbed by the polarizer 20B and cannot pass through.

  Thus, since all the light (including linearly polarized light a1 and b1) incident on the organic EL display device 10 from the outside is absorbed by the polarizer 20B, it is reflected by the light reflecting electrode 12 of the organic EL display device 10. However, it does not exit to the outside. Therefore, it is possible to prevent a decrease in image display characteristics due to the reflection of the background.

  As described above, the λ / 4 retardation film 20A made of the optical film of the present invention includes the compound represented by the formula (1). Therefore, the λ / 4 retardation film 20A exhibits sufficient reverse wavelength dispersion, and the unevenness of wavelength dispersion is reduced. Thereby, it can have a phase difference of λ / 4 with respect to light in a wide wavelength region. Therefore, most of the light incident from the outside can be prevented from leaking outside the organic EL display device 10. Therefore, the light leakage in the front direction when the organic EL display device 10 is displayed in black can be suppressed, and reflection can be prevented.

  Furthermore, since the λ / 4 retardation film 20A made of the optical film of the present invention has a high retardation, the thickness of the film can be reduced. As a result, it is possible to reduce the difference between the color in the front direction and the color in the oblique direction in the display device, and to improve the visibility from the oblique direction.

  Moreover, the light from the inside of the organic EL display device 10, that is, the light from the light emitting layer 14, includes two circularly polarized components of circularly polarized light c3 and c4. One circularly polarized light c3 is converted to linearly polarized light b3 by passing through the λ / 4 retardation film 20A as described above, and is absorbed without passing through the polarizer 20B. The other circularly polarized light c4 passes through the λ / 4 retardation film 20A and is converted into linearly polarized light b4 parallel to the transmission axis of the polarizer 20B. The linearly polarized light b4 passes through the polarizer 20B and becomes linearly polarized light b4, which is recognized as an image.

  A reflective polarizing plate (not shown) may be further disposed between the polarizer 20B and the λ / 4 retardation film 20A to reflect the linearly polarized light b3 orthogonal to the transmission axis of the polarizer 20B. The reflective polarizing plate can reflect the linearly polarized light b3 without being absorbed by the polarizer 20B, reflect it again by the light reflecting electrode 12, and convert it into linearly polarized light b4 parallel to the transmission axis of the polarizer 20B. . By further disposing the reflective polarizing plate, all of the light emitted by the light emitting layer 14 (circularly polarized light c3 and c4) can be emitted to the outside.

  The circularly polarizing plate of the present invention includes the optical film of the present invention in which the phase difference variation is reduced as described above. Therefore, the organic EL display device including the circularly polarizing plate of the present invention can reduce the decrease in contrast and color variation.

  FIG. 7 is a schematic diagram illustrating an example of the configuration of the liquid crystal display device. As shown in FIG. 7, the liquid crystal display device 30 includes a liquid crystal cell 40, two polarizing plates 50 and 60 that sandwich the liquid crystal cell 40, and a backlight 70.

  The display method of the liquid crystal cell 40 is not particularly limited, and is a TN (Twisted Nematic) method, STN (Super Twisted Nematic) method, IPS (In-Plane Switching) method, OCB (Optically Compensated Birefringence) method, VA (Vertical Alignment). There are methods (including MVA: Multi-domain Vertical Alignment, PVA: Patterned Vertical Alignment), and HAN (Hybrid Aligned Nematic). In order to increase the contrast, the VA (MVA, PVA) method is preferable.

  A VA liquid crystal cell includes a pair of transparent substrates and a liquid crystal layer sandwiched between them.

  Of the pair of transparent substrates, one transparent substrate is provided with a pixel electrode for applying a voltage to the liquid crystal molecules. The counter electrode may be disposed on one transparent substrate (transparent substrate on which the pixel electrode is disposed) or may be disposed on the other transparent substrate.

  The liquid crystal layer includes liquid crystal molecules having negative or positive dielectric anisotropy. When the liquid crystal molecules are not applied with voltage due to the alignment regulating force of the alignment film provided on the liquid crystal layer side surface of the transparent substrate and no electric field is generated between the pixel electrode and the counter electrode, the liquid crystal molecules The major axis is oriented so as to be substantially perpendicular to the surface of the transparent substrate.

  In the liquid crystal cell configured as described above, an electric field is generated between the pixel electrode and the counter electrode by applying a voltage corresponding to the image signal to the pixel electrode. Thereby, the liquid crystal molecules initially aligned perpendicularly to the surface of the transparent substrate are aligned so that the major axis thereof is in the horizontal direction with respect to the substrate surface. In this way, the liquid crystal layer is driven, and the image display is performed by changing the transmittance and reflectance of each sub-pixel.

  The polarizing plate 50 is disposed on the viewing side of the liquid crystal cell 40, and includes a polarizer 52, a protective film 54 disposed on the viewing side of the polarizer 52, and a protective film disposed on the liquid crystal cell side of the polarizer 52. 56. The polarizing plate 60 is disposed on the backlight 70 side of the liquid crystal cell 40, is disposed on the backlight side of the polarizer 62, the protective film 64 disposed on the surface of the polarizer 62 on the liquid crystal cell side, and the polarizer 62. And a protective film 66. One of the protective films 56 and 64 may be omitted as necessary.

  Any of the protective films 54, 56, 64 and 66; preferably the protective film 66 can be the optical film of the present invention.

  In the following, the invention will be described in more detail with reference to examples. These examples do not limit the scope of the present invention.

1. Optical Film Material 1) Cellulose Ester The cellulose ester shown in the table below was prepared.
Cellulose ester A: Cellulose diacetate having a degree of acetyl group substitution of 2.40 (number average molecular weight 70000)
Cellulose ester B: cellulose acetate propionate having a degree of acetyl group substitution of 1.58, a degree of substitution of propionyl group of 0.9, and a degree of substitution of total acyl group of 2.48 (number average molecular weight 70,000)
Cellulose ester C: cellulose triacetate having a degree of acetyl group substitution of 2.85 (number average molecular weight 70000)

2) Wavelength dispersing agent Compound represented by formula (1) Exemplary compounds A-002, A-018, A-020,
Exemplary compounds B-002, B-013, B-023,
Illustrative compounds C-001, C-010, C-025, C-026,
Exemplified compounds D-001, D-004, D-016, D-018, D-019, D-025

Synthesis of Exemplary Compound A-002 Exemplary Compound A-002 was synthesized according to the following scheme.

  That is, 6.4 mL of thionyl chloride was added to a toluene (45 mL) solution containing 7.0 g of Compound A, and after stirring at 60 ° C. for 2 hours, the solvent and thionyl chloride were distilled off under reduced pressure to obtain Compound B. On the other hand, 2 g of 2,3-dichloro-1,4-dihydroxy-5-nitronaphthalene and 0.1 g of dimethylaminopyridine were added to 100 mL of tetrahydrofuran, and after cooling in an ice-water cooling bath, a solution of compound B in tetrahydrofuran (5 mL) was added. It was dripped. After stirring at room temperature for 3 hours, water and ethyl acetate were added and extracted. The solvent was distilled off from the organic layer under reduced pressure, and the resulting crude crystals were purified by silica gel chromatography (ethyl acetate / heptane) to obtain 3.5 g of Exemplified Compound A-002. The obtained compound was identified by NMR spectrum and MASS spectrum.

Synthesis of Exemplified Compound B-002 Exemplified Compound B-002 was synthesized in the same manner as Example 12 in paragraph 0170 of JP-A-2008-107767.

Synthesis of Exemplary Compound C-001 Exemplary Compound C-001 was synthesized according to the following scheme.

  5.0 g of 2,5-dihydroxyterephthalic acid, 10 g of boron trifluoride-ethyl ether complex and 30 ml of n-butanol were stirred at 130 ° C. for 3 hours and then cooled. To this, 200 ml of ethyl acetate and 100 ml of water were further added, followed by liquid separation until neutrality. This was dried over magnesium sulfate and concentrated under reduced pressure. The obtained solid was purified by silica gel chromatography (toluene / acetone) to obtain 3.5 g of Compound C.

  Compound C (2.0 g), compound D (6.0 g), and potassium carbonate (10 g) were reacted in DMF (50 ml) at 100 ° C. for 10 hours. After completion of the reaction, the reaction solution was added dropwise to water, and the resulting solid was filtered. The obtained solid was purified by silica gel chromatography (toluene / acetone) to obtain 1.2 g of exemplary compound C-001. The obtained compound was identified by NMR spectrum and MASS spectrum.

Synthesis of Exemplary Compound D-016 Exemplary Compound D-016 was synthesized according to the following scheme.

  Into a reaction vessel equipped with an ester tube, 125 ml of toluene, 12.5 g of malonic acid, 30 ml of n-propanol and 11.42 g of p-toluenesulfonic acid monohydrate are added and stirred for 5 hours while heating under reflux in a nitrogen atmosphere. did. Distillation of water was confirmed as the reaction progressed. Thereafter, the solvent was distilled off from the resulting reaction solution under reduced pressure, and the residue was purified by silica gel chromatography (ethyl acetate / heptane) to obtain 19.8 g of Compound E.

  To 100 ml of pyridine, 5 g of 2,5-dihydroxybenzaldehyde was added, and 12.2 g of paramethoxybenzoic acid chloride was added dropwise at 10 ° C. over 2 hours. After completion of dropping, the mixture was stirred at room temperature for 5 hours. After completion of the reaction, pyridine was distilled off under reduced pressure and suspended in 100 ml of methanol. The suspension was filtered and then purified by silica gel chromatography (dichloromethane / toluene) to obtain 6.3 g of Compound F.

  A reaction vessel equipped with an ester tube was charged with 50 ml of toluene, 5.0 g of compound E, 3.1 g of compound F and 1.5 g of piperidine, and stirred for 5 hours while heating under reflux in a nitrogen atmosphere. As the reaction progresses, water is distilled off. After cooling the obtained reaction liquid, water and dichloromethane were added and extracted. The solvent was distilled off from the organic layer under reduced pressure, and the resulting crude crystals were purified by silica gel chromatography (dichloromethane / toluene) to obtain 3.3 g of Exemplified Compound D-016. The obtained compound was identified by NMR spectrum and MASS spectrum.

Synthesis of Other Exemplary Compounds Exemplary compounds A-018 and A-020 are the same as the synthetic method of exemplary compound A-002 described above; exemplary compounds B-013 and B-023 are synthetic methods of exemplary compound B-001 Exemplified compounds C-010, C-025, and C-026 are the same as the synthetic methods of Exemplified compound C-001 described above; Exemplified compounds D-001, D-004, D-018, D-019 , D-025 was synthesized in the same manner as the synthesis method of the exemplified compound D-016 described above.

Comparative compounds The following comparative compounds E-001 and E-002

  The solution absorption spectra of the above exemplary compounds and comparative compounds were measured by the following method.

[Measurement of solution absorption spectrum]
The above exemplary compounds and comparative compounds were dissolved in tetrahydrofuran (without stabilizer) to obtain a solution having a concentration of 1.0 × 10 ⁻⁵ mol / L. The obtained solution is put into a quartz cell (10 mm long square cell), and the absorbance in the wavelength region of 250 to 400 nm of the solution is measured using an ultraviolet visible infrared spectrophotometer (U-570, manufactured by JASCO Corporation). Was measured. And the absorption peak in the obtained solution absorption spectrum was calculated | required. When there are a plurality of absorption peaks in the above wavelength range, the peak on the longest wavelength side was taken as the absorption peak.
A: Absorption peak in the range of 320 nm or more and less than 350 nm B: Absorption peak in the range of 300 nm or more and less than 320 nm, 350 nm or more and 360 nm or less C: Absorption peak in the range of less than 300 nm or more than 360 nm

2. Production of optical film ( Reference Example 1)
Preparation of Fine Particle Dispersion 1 The following components were stirred and mixed with a dissolver for 50 minutes and then dispersed with Manton Gorin to obtain fine particle dispersion 1.
(Composition of fine particle dispersion 1)
Fine particles (Aerosil R972V manufactured by Nippon Aerosil Co., Ltd.): 11 parts by mass Ethanol: 89 parts by mass

Preparation of Fine Particle Additive Solution 1 The obtained fine particle dispersion 1 was slowly added to a dissolution tank charged with methylene chloride with sufficient stirring, and then dispersed with an attritor. The obtained solution was filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd., and a fine particle additive solution 1 was obtained.
(Composition of fine particle additive liquid 1)
Methylene chloride: 99 parts by mass Fine particle dispersion 1: 5 parts by mass

Preparation of Main Dope Solution Methylene chloride and ethanol were added to a pressure dissolution tank, and cellulose ester A, exemplary compound A-002, sugar ester compound FA-7, and fine particle additive solution 1 were added while stirring. The resulting solution was heated and completely dissolved with stirring. The obtained solution was used as Azumi filter paper No. manufactured by Azumi Filter Paper Co., Ltd. Filtration using 244 gave a main dope solution.
(Main dope composition)
Methylene chloride: 340 parts by mass Ethanol: 64 parts by mass Cellulose ester A: 100 parts by mass Illustrative compound A-002: 4 parts by mass Sugar ester compound FA-7: 5 parts by mass Fine particle additive solution 1: 1 part by mass

  The obtained main dope solution was put into a sealed container, kept at 80 ° C. under pressure, and completely dissolved with stirring to obtain a dope solution.

  The obtained dope solution was uniformly cast on a stainless steel belt support using an endless belt casting apparatus. After the solvent in the cast film cast on the stainless steel belt support was evaporated until the residual solvent amount became 75%, the obtained film was peeled off from the stainless steel belt support. The obtained film was conveyed while being held by a clip of a tenter stretching apparatus. The obtained film was dried while being transported by a number of rolls in a drying zone to obtain a long film (raw fabric) having a width of 1000 mm. The film thickness of the long film was 100 μm.

  The obtained film was stretched in an oblique direction (45 ° with respect to the width direction of the film) at a stretch rate of 2.5 times at a glass transition temperature of the film + 20 ° C. to obtain an optical film 101. The film thickness of the obtained optical film 101 was 40 μm. The angle θ formed by the in-plane slow axis of the obtained optical film 101 and the width direction of the film was 45 °. The in-plane slow axis of the optical film was confirmed by AxoScan manufactured by Axometric.

(Reference Example 2-7, Example 8-20, Comparative Example 1-4)
Optical films 102 to 124 were obtained in the same manner as in Reference Example 1 except that any one or more of the type of thermoplastic resin, the type and addition amount of the wavelength dispersion adjusting agent, and the film thickness were changed as shown in Table 1. .

  The transmittance of the obtained optical film at 380 nm, R0, wavelength dispersion characteristics (R0 (450) / R0 (550), R0 (550) / R0 (650)), phase difference variation and weather resistance during UV irradiation, Evaluation was made by the following method.

[Transmissivity]
The transmittance of the obtained optical film at 25 ° C. and 55% RH at a wavelength of 380 nm was measured with Spectrophotometer U-3200 (manufactured by Hitachi, Ltd.).

[R0 and wavelength dispersion characteristics]
1) The optical film was conditioned at 23 ° C. and 55% RH. The average refractive index at 450 nm, 550 nm and 650 nm of the optical film after humidity control was measured using an Abbe refractometer and a spectral light source, respectively. Moreover, the thickness of the optical film was measured using the film thickness meter.
2) In-plane phase difference R0 (450), R0 (550) when light having a measurement wavelength of 450 nm, 550 nm, or 650 nm is incident on the optical film after humidity adjustment in parallel with the normal line of the film surface R0 (650) was measured with an AxoScan manufactured by Axometric.
3) R0 (450) / R0 (550) is calculated from the obtained R0 (450) and R0 (550); from the obtained R0 (550) and R0 (650), R0 (550) / R0 ( 650) was calculated.

[Phase variation during UV irradiation]
After irradiating the optical film with ultraviolet rays for 2 minutes with a weather resistance tester (eye super UV tester manufactured by Iwasaki Electric Co., Ltd.), R0 ′ (550) at a wavelength of 550 nm was measured in the same manner as described above. Then, the amount of change ΔR0 in phase difference (phase difference R0 (550) before irradiation−phase difference R0 ′ (550) after irradiation) was obtained and evaluated according to the following criteria.
A: Phase difference change ΔR0 is 2 nm or less B: Phase difference change ΔR0 is more than 2 nm and less than 3 nm C: Phase difference change ΔR0 is more than 3 nm and less than 5 nm D: Phase difference change ΔR0 is more than 5 nm A˜ C was accepted.

[Weatherability]
The transmittance T1 at a wavelength of 400 nm of the produced optical film was measured with Spectrophotometer U-3200 (manufactured by Hitachi, Ltd.) in the same manner as described above. Then, after irradiating the optical film with ultraviolet rays for 500 hours with a weather resistance tester (Isuper UV Tester, Iwasaki Electric Co., Ltd.), the transmittance T2 at a wavelength of 400 nm was measured. Then, a difference ΔT = T1-T2 in transmittance was obtained, and the weather resistance was evaluated according to the following criteria.
A: ΔT is less than 2% B: ΔT is 2% or more and less than 4% C: ΔT is 4% or more

Table 1 shows the evaluation results of the optical films of Reference Examples 1 to 7, Examples 8 to 20, and Comparative Examples 1 to 4.

As shown in Table 1, the wavelength dispersion adjusting agent contained in Reference Examples 1 to 7 and Examples 8 to 20 has an absorption peak in the range of 300 nm to 360 nm. Therefore, it turns out that an optical film has a high phase difference and reverse wavelength dispersion. Further, the optical film of Reference Examples 1-7 and Examples 8-20, the transmittance at 380nm is adjusted to 20% or more. Therefore, it can be seen that the optical films of Reference Examples 1 to 7 and Examples 8 to 20 have little phase difference fluctuation during UV irradiation and high weather resistance.

  On the other hand, since the wavelength dispersion adjusting agent used in Comparative Example 1 has an absorption peak on the extremely short wavelength side of less than 300 nm, it can be seen that it does not exhibit reverse wavelength dispersion. Since the wavelength dispersion adjusting agent used in Comparative Example 2 has an absorption peak at a wavelength longer than 360 nm, the transmittance at 380 nm of the film containing the absorption peak is low, and it is understood that the phase difference variation during UV irradiation is large. . Since the optical film of Comparative Example 3 has a large content of the wavelength dispersion adjusting agent, it can be seen that the transmittance at 380 nm is low, and the phase difference variation occurs during UV irradiation. It can be seen that the optical film of Comparative Example 4 has a high transmittance at 380 nm but a low retardation because the content of the wavelength dispersion adjusting agent is small.

3. Fabrication of circularly polarizing plate and display device ( Reference Example 8 )
Production of Polarizer A polyvinyl alcohol film having a thickness of 120 μm was uniaxially stretched under conditions of a stretching temperature of 110 ° C. and a stretching ratio of 5 times. The obtained film was immersed in an aqueous solution consisting of 0.075 g of iodine, 5 g of potassium iodide and 100 g of water for 60 seconds, and then immersed in an aqueous solution of 68 ° C. consisting of 6 g of potassium iodide, 7.5 g of boric acid and 100 g of water. . The obtained film was washed with water and dried to obtain a polarizer having a thickness of 20 μm.

Preparation of UV Adhesive 100 parts by weight of 2-hydroxyethyl acrylate and 5 parts by weight of polyfunctional polyester acrylate (manufactured by Sartomer Japan Co., Ltd., trade name CN2302; number of acrylates: 16) are combined, and UV adhesive Was prepared.

Production of Circular Polarizing Plate 201 On the produced optical film 101, the above UV adhesive is cured using a micro gravure coater (gravure roll: # 300, rotation speed: 140% / line speed) to a thickness after curing of 5 μm. It apply | coated so that it might become, It was set as the optical film with an adhesive agent. Similarly, the UV adhesive was applied onto Konica Minolta Tack Film KC6UA (manufactured by Konica Minolta Opto Co., Ltd.) to obtain a transparent protective film with an adhesive.

  The optical film 101 with an adhesive was disposed on one surface of the polarizer prepared above; the transparent protective film with an adhesive was disposed on the other surface, and were bonded together by a roll machine. The optical film 101 and the polarizer were bonded so that the angle formed by the absorption axis of the polarizer and the slow axis of the optical film 101 was 45 °. Both surfaces of the obtained laminate were irradiated with an electron beam to cure the UV adhesive to obtain a circularly polarizing plate. The line speed was 20 m / min, the acceleration voltage was 250 kV, and the irradiation dose was 20 kGy.

Production of Display Device 301 A light-reflecting electrode made of chromium having a thickness of 80 nm was formed on a glass substrate by a sputtering method. An ITO thin film having a thickness of 40 nm was formed as an anode on the light reflecting electrode. Next, a hole transport layer made of poly (3,4-ethylenedioxythiophene) -polystyrene sulfonate (PEDOT: PSS) having a thickness of 80 nm was formed on the anode by sputtering. On the hole transport layer, RGB light emitting layers (red light emitting layer, green light emitting layer, and blue light emitting layer) were respectively formed by patterning using a shadow mask. The thickness of the light emitting layer was 100 nm for each color. The red light-emitting layer contains tris (8-hydroxyquinolinate) aluminum (Alq3) as a host and a light-emitting compound [4- (dicyanomethylene) -2-methyl-6 (p-dimethylaminostyryl) -4H-pyran] (DCM). Was formed by co-evaporation (mass ratio 99: 1). The green light-emitting layer is formed by co-evaporation (mass ratio 99: 1) of Alq3 and the luminescent compound coumarin 6 as a host; the blue light-emitting layer is co-evaporated (mass of BAlq and the luminescent compound Perylene as a host). Ratio 90:10).

  On the obtained RGB light emitting layer, a thin film having a thickness of 4 nm made of calcium having a low work function was formed as a first cathode capable of efficiently injecting electrons by vacuum deposition. On this 1st cathode, the thin film which consists of aluminum with a thickness of 2 nm was formed as a 2nd cathode, and the organic light emitting layer was obtained. The aluminum used as the second cathode has a role of preventing the first cathode calcium from being chemically altered when a transparent electrode is formed thereon by sputtering.

  Next, a transparent conductive film made of ITO and having a thickness of 80 nm (the first cathode, the second cathode, and the transparent conductive film were combined to form a transparent electrode layer) was formed on the second cathode by sputtering. Furthermore, a thin film having a thickness of 200 nm made of silicon nitride was formed on the transparent conductive film by a CVD method to obtain an insulating film (transparent substrate).

  On the obtained insulating film (transparent substrate), the circularly polarizing plate 201 was bonded via an adhesive to obtain an organic EL display device 301. The circularly polarizing plate 201 was bonded so that the optical film 101 was on the insulating film side.

(Reference Example 9-14, Example 28-40, Comparative Examples 5 to 8)
Circular polarizing plates 202 to 224 and display devices 302 to 324 were obtained in the same manner as in Reference Example 8 except that the optical film 101 was changed to the optical films 102 to 124.

  The light leakage in the front direction and the color in the oblique direction of the obtained organic EL display device were evaluated by the following methods.

[Light leakage in the front direction]
With a commercially available desk stand (MITSUBISHI inverter BB giraffe) installed at a position 60 cm away from the display screen of the display device, a black image was displayed on the display device for 1 hour while the display screen was irradiated with light. The black image was displayed in a state where the light emitting layer did not emit light. Thereafter, the luminance in the direction of the tilt angle of 0.2 ° with respect to the normal of the display screen was measured with a luminance meter (manufactured by Konica Minolta: CS-2000) installed at a position 1 m away from the display screen of the display device. . In addition, at a position 1 m away from the display screen of the display device, the observer performed sensory evaluation on the blackness and color shift of the display screen. Evaluation of light leakage in the front direction was performed based on the following criteria.
◎: luminance is less than 2cd / ^{m 2,} and look tight black ○: brightness is at 2cd / ^{m 2} or more 3 cd / ^{m 2} or less, and black toned look ×: luminance 3 cd / ^{m 2} or larger, Or it doesn't look black and looks colored

[Color variation]
Displayed in a constant temperature and humidity room of 23 ° C and 55% RH with a commercial desk stand (MITSUBISHI inverter BB giraffe) installed 60 cm away from the display screen of the display device, with the display screen illuminated by light. A black image was displayed on the device for 1 hour. The black image was displayed in a state where the light emitting layer did not emit light. Then, the sensory evaluation of the black level when observed from the front direction of the display screen of the display device and the black level when observed from the direction of 45 ° with respect to the normal line of the display screen, The difference was compared. The evaluation of the color in the oblique direction was performed based on the following criteria.
◎: No change in blackness is observed between the front direction and the diagonal direction. ○: A slight difference in blackness is observed between the front direction and the diagonal direction. I am worried about the difference in external light reflection depending on the direction

Table 2 shows the evaluation results of the organic EL display devices of Reference Examples 8 to 14, Examples 28 to 40, and Comparative Examples 5 to 8.

As shown in Table 2, it is shown that the display devices of Reference Examples 8 to 14 and Examples 28 to 40 have less light leakage and color variation in the front direction than the display devices of Comparative Examples 5 to 8. .

  ADVANTAGE OF THE INVENTION According to this invention, it can provide the optical film which has a high phase difference and favorable reverse wavelength dispersion, and can suppress the thermal contraction at the time of ultraviolet irradiation.

DESCRIPTION OF SYMBOLS 10 Organic electroluminescent display device 12 Light reflection electrode 14 Light emitting layer 16 Transparent electrode layer 18 Transparent substrate 20 Circularly-polarizing plate 20A (lambda) / 4 phase difference film 20B Polarizer 30 Liquid crystal display device 40 Liquid crystal cell 50, 60 Polarizing plate 70 Backlight 52, 62 Polarizer 54, 56, 64, 66 Protective film

Claims (9)

Cellulose ester, an optical film comprising a wavelength dispersion regulator having an absorption peak in the range of 300~360nm in ultraviolet-visible absorption spectrum of the solvent solution,
The wavelength dispersion adjusting agent is a compound represented by the following general formula (2) or (3):
The slow axis direction in the plane of the optical film is oblique to the width direction of the film,
When the retardation values in the in-plane direction measured at wavelengths of 450 nm, 550 nm and 650 nm are R0 (450), R0 (550) and R0 (650), respectively, the expressions (a) to (c) are satisfied,
An optical film having a transmittance of 20 to 90% at a wavelength of 380 nm.
(A) 110 nm ≦ R0 (550) ≦ 170 nm
(B) 0.72 ≦ R0 (450) / R0 (550) ≦ 1.00
(C) 0.83 ≦ R0 (550) / R0 (650) ≦ 1.00

(In general formula (2),
L ₂₁ and L ₂₂ are each independently a single bond or —R _L —O—, —O—R _L —, —O —C (═O) —R _L —, —C (═O) —O—R. _L— (R _L represents a phenylene group, an alkylene group, an alkenylene group or an alkynylene group), —O—, — (C═O) —, — (C═S) —, — (C═O) —O _{-, - NR M -, -} S -, - SO 2 -, - (C = O) -NR M - and _{-NR M - (C = O)} - (R M represents a hydrogen atom or an alkylene group) Represents a divalent linking group selected from the group consisting of or a combination thereof;
R ₂₂ and R ₂₃ each independently represent an alkylene group, an alkenylene group, an alkynylene group,-(R _N ) n- (R _N represents a cycloalkylene group, and n represents an integer of 1 to 4),-( OR _O ) n- (R _O represents an alkylene group, n represents an integer of 1 to 4), a phenylene group, a heteroalkylene group or a heteroarylene group;
R ₂₄ and R ₂₅ represent a hydrogen atom or a substituent;
R ₂₁ represents a heteroaryl group or a 2,5-dione-pyrrolidine ring condensed with a benzene ring to which R ₂₁ is bonded;
k ₂ represents an integer of 1 to 4)

(In general formula (3),
L ₃₁ and L ₃₂ are each independently a single bond or —R _L —O—, —O—R _L —, —O —C (═O) —R _L —, —C (═O) —O—R. _L— (R _L represents a phenylene group, an alkylene group, an alkenylene group or an alkynylene group), —O—, — (C═O) —, — (C═S) —, — (C═O) —O _{-, - NR M -, -} S -, - SO 2 - and _{- (C = O) -NR M} -, - NR M - (C = O) - (R M represents a hydrogen atom or an alkylene group) Represents a divalent linking group selected from the group consisting of or a combination thereof;
R ₃₃ and R ₃₄ each independently represent an alkylene group, an alkenylene group, an alkynylene group,-(R _N ) n- (R _N represents a cycloalkylene group, and n represents an integer of 1 to 4),-( OR _O ) n- (R _O represents an alkylene group, n represents an integer of 1 to 4), a phenylene group, a heteroalkylene group or a heteroarylene group;
R ₃₆ and R ₃₇ each independently represents a hydrogen atom or a substituent;
R ₃₁ and R ₃₂ are each independently a hydrogen atom or — (C═O) —O—Rt (Rt represents an alkyl group, an oxyalkylene group or an aryl group), —C (═O) —Rv (Rv Represents an alkyl group or an aryl group), —C (═O) —NRwRx (Rw represents a hydrogen atom or an alkyl group; Rx represents an alkyl group), a cyano group or a halogen atom; R ₃₁ And R ₃₂ may combine with each other to form a ring;
R ₃₅ represents a substituent;
j ₃ represents an integer of 0 to 3) Transmittance at 380nm is within a range of 40% to 85%, the optical film according to claim 1. The optical film according to claim 1 or 2 , wherein the cellulose ester has an acetyl group substitution degree X and a total substitution degree Y of propionyl group or butyryl group satisfying the following formula.
Formula (I) 1.5 ≦ X + Y ≦ 2.6
Formula (II) 0 ≦ Y ≦ 1.5 The optical film as described in any one of Claims 1-3 whose film thickness exists in the range of 20-45 micrometers. The optical according to any one of claims 1 to 4 , wherein the content of the wavelength dispersion adjusting agent represented by the general formula (1) is 1 to 30 parts by weight with respect to 100 parts by weight of the cellulose ester. the film. The optical film according to any one of claims 1 to 5 , wherein an angle formed by an in-plane slow axis of the optical film and a width direction of the optical film is 40 ° or more and 50 ° or less. The circularly-polarizing plate containing a polarizer and the optical film as described in any one of Claims 1-6 . The circularly polarizing plate according to claim 7 , wherein the polarizer and the optical film are bonded via a cured product layer of an active energy ray adhesive. Including a circularly polarizing plate according to claim 7 or 8, the image display device.

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