JP2007025649A - Laminated optical film, laminated polarizing plate and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminated optical film which improves the angle dependency of retardation of a retardation film and also improves the uniformity of the retardation. <P>SOLUTION: The laminated optical film is configured by laminating: a nearly uniaxial negative optical layer including an amorphous polymer of which the molecular polarizability anisotropy is positive and having an optical axis in a thickness direction; and a nearly uniaxial negative optical film including a thermoplastic polymer of which the molecular polarizability anisotropy is negative and having an optical axis in a plane. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a laminated optical film having excellent viewing angle characteristics, a laminated polarizing plate using the laminated optical film, and a liquid crystal display device.

  A retardation film, which is one of optical films, is indispensable for improving the performance of a liquid crystal display device, and plays a role such as color compensation and viewing angle compensation. In the retardation film, the retardation value generally varies depending on the incident angle, and this phenomenon is referred to as a viewing angle problem of the retardation film herein. Several methods have already been proposed to solve the viewing angle problem of the retardation film.

  For example, the main refractive index in three directions that are parallel or orthogonal to each other and orthogonal to each other in the plane of the retardation film is controlled. Specifically, the main refractive index in the thickness direction is changed to two main refractive indexes in the plane. Patent Documents 1 to 4 listed below disclose techniques for reducing the viewing angle dependency of the retardation of the retardation film by making it larger than any one of these and making it smaller than the remaining one. Also, a proposal for a technique for improving the viewing angle dependency of a retardation film by laminating a positive uniaxial optical film having an optical axis in the plane and a negative uniaxial optical film having an optical axis in the plane. Is described in Patent Document 5 below.

Japanese Patent No. 2612196 Japanese Patent No. 2999413 Japanese Patent No. 2818983 Japanese Patent No. 3168850 Japanese Patent No. 2809712

  In Patent Documents 1 to 4, only one retardation film is used to control the three-dimensional refractive index to improve the viewing angle dependency of the retardation film. In order to control the refractive index in the thickness direction, this improving method generally requires application of stress in the thickness direction, and a special manufacturing method as described in Patent Documents 1 to 4 described above is used. It is difficult to obtain a large-area, uniform retardation film with high productivity.

  On the other hand, in Patent Document 5, two sheets of retardation film having an in-plane retardation are used, and in order to bond the slow axes in parallel, two films are prepared in separate steps, respectively. It is necessary to laminate by lamination. Since there are two in-plane slow axes and two in-plane retardation values, the dispersion of each retardation film increases the dispersion of the laminated retardation films, resulting in high performance liquid crystal display devices. It is not easy to ensure the uniformity of required optical elements.

  The objective of this invention is providing the optical film which improves the angle dependence of the phase difference of a phase difference film, and improves the uniformity of phase difference.

  As a result of examining the problems of the conventional methods, the present inventors have found that there are problems in the configuration, material, manufacturing method, and the like of the retardation film. The above-mentioned method for improving the viewing angle dependency of the retardation film by controlling the three-dimensional refractive index by using only one retardation film is mass production because the manufacturing method, particularly the stretching method, is special. It is difficult to obtain a well uniform retardation film. On the other hand, the method of laminating two retardation films having an in-plane retardation is not necessarily suitable for the configuration of the retardation film, so that essentially uniform optical properties can be obtained as described above. It's hard to be done. In view of these problems, the present inventors have intensively studied a solution, and found that it is possible to improve the angle dependency of the retardation of the retardation film and to improve the uniformity of the retardation. That is, the present invention is as follows.

[1] A negative substantially uniaxial optical layer made of an amorphous polymer having a positive molecular polarizability anisotropy and having an optical axis in the thickness direction, and heat having a negative molecular polarizability anisotropy A laminated optical film comprising a plastic polymer and a negative substantially uniaxial optical film having an optical axis in a plane.
[2] Rth _NEC (λ) is a thickness direction retardation value of a negative substantially uniaxial optical layer having an optical axis in the thickness direction, and a negative substantially uniaxial optical film having an optical axis in the plane. When the in-plane retardation value is Γ _NEA (λ), the above laminated optical film satisfies the relationship of the following formula (1).
−100 <Γ _NEA (λ) / 2 + Rth _NEC (λ) <100 nm (1)
(However, λ = 550 nm)
[3] The laminated optical film as described above, wherein the thermoplastic polymer having negative molecular polarizability anisotropy is a polycarbonate having a fluorene skeleton.
[4] The amorphous polymer having positive molecular polarizability anisotropy is selected from the group consisting of polycarbonate, polyimide, polyamide, polyester, polyetherketone, polyarylate, polyaryletherketone, polyamideimide and polyesterimide. The above laminated optical film comprising at least one polymer.
[5] The laminated optical film as described above, wherein the thickness of the negative substantially uniaxial optical layer having an optical axis in the thickness direction is 10 μm or less.
Said retardation film.
[6] The laminated optical film as described above, wherein the amorphous polymer having a positive molecular polarizability anisotropy is a polyimide containing a fluorine atom.
[7] A polyimide containing a fluorine atom is 2,2′-bis (3,4-dicarboxyphenyl) -1,1,1,3,3,3, -hexafluoropropane dianhydride and 2,2 The above laminated optical film obtained by polymerizing '-bistrifluoromethyl-4,4'-diamino-biphenyl.
[8] A laminated polarizing plate in which the laminated optical film described above and a polarizing plate are integrated.
[9] A polarizing plate, a negative substantially uniaxial optical layer having an optical axis in the thickness direction, and a negative substantially uniaxial optical film having an optical axis in the plane are laminated in at least this order, and The laminated polarizing plate described above, wherein the absorption axis of the polarizing plate and the optical axis of the negative substantially uniaxial optical film having an optical axis in the plane are substantially orthogonal to each other.
[10] A liquid crystal display device using the above laminated optical film and / or laminated polarizing plate.

  The present invention is a laminated optical film using two layers of a substantial retardation film (hereinafter referred to as an optical film). Specifically, a negative substantially uniaxial optical layer having an optical axis in the thickness direction and a negative substantially uniaxial optical film having an optical axis in the plane are laminated and used. Since the negative substantially uniaxial optical layer having an optical axis in the thickness direction of the former has an in-plane retardation value of substantially 0, control of the in-plane slow axis and retardation value is the latter. The optical film is a negative substantially uniaxial optical film having an optical axis in the plane, and is essentially a configuration capable of minimizing the variation of the laminated optical film functioning as a retardation film. . Further, these negative substantially uniaxial optical films have no particular difficulty in production in the production process as will be described later, and as a result, it is possible to obtain a laminated optical film having high mass productivity and excellent uniformity. is there.

In the present invention, an optically anisotropic film having refractive index anisotropy is referred to as an optical film or a retardation film. A uniaxial optical film and a biaxial optical film are classified according to their three-dimensional refractive index, and these are the categories of retardation films. The retardation film is expressed by a refractive index ellipsoid, and only the case where the orientations of the three main refractive indexes are parallel or perpendicular to the film plane is considered here. Here we consider the orthogonal coordinate system axes are parallel or perpendicular to the surface of the film as shown in FIG. 3, defines three refractive index corresponding to the orientation of the coordinate n _x, n _y, and n _z. When the slow axis direction in the plane is set as the x axis, the y axis is set in the plane and the z axis is set in the thickness direction. Accordingly, the negative substantially uniaxial optical film having an optical axis in plane of the present invention, with three refractive _{index, n z ≒ n x> n} y , and the late phase n _x is the film plane It becomes an axis. Further, the negative substantially uniaxial optical film having an optical axis in the thickness direction (or an optical film layer) is defined as _{n z <n x ≒ n y} . All three biaxial optical films are defined as having different refractive indexes. On the other hand, a positive uniaxial optical film having an in-plane optical axis is _nx > _ny = _nz in this definition. Further, a positive uniaxial optical film having an optical axis in the thickness direction _{satisfies nz} > _nx = _{ny in} this definition.

The in-plane retardation value Γ of the optical film in the present invention is defined by the following formula (2) or (3).
When the optical film of the n _z ≧ _{n x} is
_{Γ (λ) = (n y} -n x) × d (2)
When the optical film of the n _{z <n x} is
_{Γ (λ) = (n x} -n y) × d (3)
Here, d is the thickness (nm) of the film.

Strictly speaking, it is preferable that the negative substantially uniaxial optical film having an in-plane optical axis in the present invention satisfies the relationship of n _z = n _x > _ny , but n _z ≈n _x > _ny . If you can, you can use it without any problems. In addition, since there is a variation in refractive index in an actual optical film, the range of the term of negative substantially uniaxial is defined using the following formula (4) using these three refractive indexes.
_{Nz = (n x -n z)} / (n x -n y) (4)

What is a negative substantially uniaxial optical film having an optical axis in a plane in the present invention?
−0.7 <Nz <0.1 (5)
Is preferably defined as
−0.4 <Nz <0.1 (5 ′)
And more preferably
−0.4 <Nz <0.05 (6)
And more preferably
−0.30 <Nz <0.03 (7)
And even more preferably
−0.10 <Nz <0.02 (8)
It is. Rth (λ) is defined as follows.
Rth (λ) = {(n _x + _ny ) / 2−n _z } × d (9)
In the above formula (9), d (nm) is the thickness of the optical film. In the present invention, the phase difference value Γ (λ), Rth (λ), Nz value, and the like are measured at a wavelength of 550 nm unless otherwise specified.

  The in-plane retardation value of the negative substantially uniaxial optical film having an optical axis in the thickness direction in the present invention is preferably 0, but is required to be 20 nm or less, preferably 10 nm or less. More preferably, it is 5 nm or less, and further preferably 3 nm or less. The angle formed by the slow axis of the negative substantially uniaxial optical film having the optical axis in the plane and the slow axis of the negative substantially uniaxial optical film having the optical axis in the thickness direction is approximately 0 ° or It is preferably approximately 90 °. The slow axis alignment angle is preferably the above-mentioned angle, but the allowable range is within ± 3 °, preferably within ± 2 °, more preferably ± 1 °, centering on the set angle. Is more preferably within ± 0.5 °. When the in-plane retardation value of the negative substantially uniaxial optical film having an optical axis in the thickness direction is 5 nm or less, the angle of the slow axis is not questioned. It becomes possible to obtain a laminated optical film excellent in.

  When an amorphous polymer having a positive molecular polarizability anisotropy is used, a negative substantially uniaxial optical having an optical axis in the thickness direction is obtained simply by solution casting without using the stretching step. It is possible to produce a layer, and it is relatively easy to obtain a target retardation value in the thickness direction by reducing the in-plane retardation value depending on the material design. One reason why this configuration is excellent in retardation uniformity is to use a negative substantially uniaxial optical layer having an optical axis in the thickness direction made of an amorphous polymer having positive molecular polarizability anisotropy. In addition, the present invention has found a configuration capable of improving the viewing angle dependency of a laminated optical film that is a retardation film.

  An amorphous polymer having a positive molecular polarizability anisotropy refers to a polymer in which the maximum orientation of the in-plane refractive index appears in the stretching direction by stretching the width freely uniaxially in the vicinity of the glass transition point. On the other hand, an amorphous polymer having a negative molecular polarizability anisotropy means that the maximum orientation of the in-plane refractive index appears in the vertical direction in the stretching direction by stretching the width freely uniaxially in the vicinity of the glass transition point. Say things.

  By stretching an amorphous polymer having a positive molecular polarizability anisotropy in the biaxial direction, a negative substantially uniaxial optical layer having an optical axis in the thickness direction can be obtained. In addition, as described above, this polymer is dissolved in a solvent and cast into stainless steel, etc. A negative substantially uniaxial optical layer having an axis can be obtained. It is possible to obtain an optical layer only by such coating (casting) without using a stretching process, and if a polymer having a high birefringence is selected, a sufficiently large thickness that is sufficiently practical without stretching. It is possible to obtain an optical layer having a direction retardation value and being a thin film. Such a negative substantially uniaxial optical layer having an optical axis in the thickness direction can be formed by coating on a negative uniaxial optical film having an optical axis in the plane.

  According to the present invention, it is possible to provide a laminated optical film as a retardation film that improves the angle dependency of retardation and improves the uniformity of retardation. Furthermore, it is possible to achieve both high functionalization and thinning of the retardation film, such as improved viewing angle dependency.

In order to obtain the effect of the invention, a negative substantially uniaxial optical layer made of an amorphous polymer having a positive molecular polarizability anisotropy and having an optical axis in the thickness direction, and a different molecular polarizability are obtained. It is a laminated optical film made of a thermoplastic polymer having a negative directionality, and a negative substantially uniaxial optical film having an optical axis in the plane is laminated,
And,
The retardation value in the thickness direction of the negative substantially uniaxial optical layer having the optical axis in the thickness direction is Rth _NEC (λ), and the in-plane position of the negative substantially uniaxial optical film having the optical axis in the plane. When the retardation value is Γ _NEA (λ), the retardation film preferably satisfies the relationship of the following formula (1).
−100 <Γ _NEA (λ) / 2 + Rth _NEC (λ) <100 nm (1)
(However, λ = 550 nm)

The optimum value of Γ _NEA (λ) / 2 + Rth _NEC (λ) is, as a result of examination, a negative substantially uniaxial optical layer having an optical axis in the thickness direction and a negative substantially 1 having an optical axis in the plane. It has been found that if the refractive index of the axial optical film is the same, the angle dependence is the smallest at 0 nm. However, the material actually used is not necessarily the same refractive index and may be combined with other optical elements. In consideration, the preferable range is to satisfy the above formula (1). More preferably, the following formula (10)
−80 <Γ _NEA (λ) / 2 + Rth _NEC (λ) <80 nm (10)
More preferably, the following formula (11) is satisfied.
−60 <Γ _NEA (λ) / 2 + Rth _NEC (λ) <60 nm (11)
And most preferably
−40 <Γ _NEA (λ) / 2 + Rth _NEC (λ) <40 nm (12)
Is satisfied.

  Each of the substantially uniaxial optical layer and the film may be configured by laminating a single film as a single film or two or more films as long as it has necessary characteristics. A single film is preferable from the viewpoint of productivity because the thickness of the entire retardation film can be reduced, and a laminating process between the films is unnecessary.

  The in-plane retardation value of the negative substantially uniaxial optical film having an optical axis in the plane is preferably 30 to 800 nm, more preferably 50 to 700 nm, although it depends on the application. On the other hand, the retardation value in the thickness direction of the negative substantially uniaxial optical layer having the optical axis in the thickness direction is the surface of the negative substantially uniaxial optical film having the optical axis in the plane depending on the application. It is preferable to control within the range of the inner phase difference value and the above formula (1).

  Examples of the thermoplastic polymer having negative molecular polarizability anisotropy that gives a negative uniaxial optical film having an optical axis in the plane include polycarbonate, polystyrene, syndiotactic polystyrene, amorphous polyolefin, and norbornene skeleton. Examples thereof include polymers, organic acid-substituted cellulose series, polyethersulfone, polyarylate, polyester, olefin maleimide, and copolymerized olefin maleimide having a phenyl group. These materials can be made into a negative uniaxial optical film having an optical axis in a plane by, for example, uniaxial stretching after film formation.

  The amorphous polymer having negative molecular polarizability anisotropy is preferably a polycarbonate having a fluorene skeleton. Since the fluorene skeleton is oriented perpendicular to the polymer main chain by a stretching operation or the like, it can have a large negative molecular polarizability anisotropy.

ここで、Ｒ^１〜Ｒ^８は、互いに独立に、水素原子、ハロゲン原子、炭素数１〜６の炭化水素基および炭素数１〜６の炭化水素−Ｏ−基よりなる群から選ばれる基であり、そしてＸは下記式（１）−１

で表わされる基であり、Ｒ^３０およびＲ^３１は、互いに独立に、ハロゲン原子または炭素数１〜３のアルキル基であり、そしてｎおよびｍは互いに独立に、０〜４の整数である。 A preferable chemical structure of the polycarbonate having a fluorene skeleton is composed of a polymer or a polymer mixture containing a repeating unit represented by the following formula (I).

Here, R ^{1 to} R ⁸ are each independently a group selected from the group consisting of a hydrogen atom, a halogen atom, a hydrocarbon group having 1 to 6 carbon atoms, and a hydrocarbon group having 1 to 6 carbon atoms. And X is the following formula (1) -1

R ³⁰ and R ³¹ are each independently a halogen atom or an alkyl group having 1 to 3 carbon atoms, and n and m are each independently an integer of 0 to 4.

  Here, the polymer and the polymer mixture preferably contain 50 to 95 mol%, more preferably 60 to 95 mol% of the repeating units represented by the above formula (I), respectively, based on the total repeating units of the polymer or polymer mixture. More preferably, it is 70-90 mol%.

  These polycarbonate materials having a fluorene skeleton have excellent physical properties as an optical film in the present invention in terms of high glass transition temperature, handling, stretch moldability and the like.

で示される繰返し単位からなり、かつ上記式（Ｉ）および（ＩＩ）の合計に基づき上記式（Ｉ）で表される繰返し単位は５０〜９５モル％含有するものが好ましく、より好ましくは６０〜９５モル％、さらに好ましくは７０〜９０モル％である共重合体または混合物である。 More preferable polycarbonate materials include the repeating unit represented by the above formula (I) and the following formula (II):

And the repeating unit represented by the formula (I) based on the sum of the formulas (I) and (II) is preferably contained in an amount of 50 to 95 mol%, more preferably 60 to The copolymer or mixture is 95 mol%, more preferably 70 to 90 mol%.

よりなる群から選ばれる少なくとも一種の基である。ここで、Ｙ中のＲ^１７〜Ｒ^１９、Ｒ^２１およびＲ^２２は、それぞれ独立に、水素原子、ハロゲン原子、またはアルキル基、アリール基の如き炭素数１〜２２の炭化水素基であり、Ｒ^２０およびＲ^２３はアルキル基、アリール基の如き炭素数１〜２０の炭化水素基であり、また、Ａｒ^１〜Ａｒ^３は、それぞれ独立に、フェニル基の如き炭素数６〜１０のアリール基である。 In the above formula (II), R ^{9 to} R ¹⁶ are each independently at least one group selected from the group consisting of a hydrogen atom, a halogen atom, and a hydrocarbon group having 1 to 22 carbon atoms, and Y represents the following formula: Groups represented by each of the groups:

And at least one group selected from the group consisting of: Here, R ^{17 to} R ¹⁹ , R ²¹ and R ²² in Y are each independently a hydrogen atom, a halogen atom, or a hydrocarbon group having 1 to 22 carbon atoms such as an alkyl group or an aryl group. ²⁰ and R ²³ are each a hydrocarbon group having 1 to 20 carbon atoms such as an alkyl group or an aryl group, and Ar ^{1 to} Ar ³ are each independently an aryl group having 6 to 10 carbon atoms such as a phenyl group. is there.

  The above-mentioned polycarbonate is suitably produced by a method by polycondensation of a dihydroxy compound and phosgene, a melt polycondensation method, a solid phase polymerization method or the like. In the case of blends, compatible blends are preferred, but even if they are not completely compatible, it is possible to suppress light scattering between components and improve transparency by matching the refractive index between components.

  Examples of the polymer which is made of an amorphous polymer having a positive molecular polarizability anisotropy and has a negative uniaxial optical film having an optical axis in the thickness direction include polycarbonate, organic acid-substituted cellulose, and polyimide. It is preferably at least one polymer selected from the group consisting of polyamide, polyimide, polyester, polyetherketone, polyarylate, polyaryletherketone, polyamideimide and polyesterimide.

  These polymers are preferable because, for example, they are excellent in heat resistance, chemical resistance, transparency, and rigidity. Any one of these polymers may be used alone, or a mixture of two or more having different functional groups such as a mixture of polyaryletherketone and polyamide may be used. . Among such polymers, polyimide and the like are preferable because high birefringence can be obtained. This is because, when such a high birefringence is exhibited, a large birefringence value can be obtained, and therefore, for example, a comparable compensation effect can be achieved with a thin layer as compared with other polymers.

As the polyimide, for example, a polyimide that has high in-plane orientation and is soluble in an organic solvent is preferable.
Furthermore, examples of the polyimide include a copolymer obtained by appropriately copolymerizing acid dianhydride or diamine.

  Examples of the acid dianhydride include aromatic tetracarboxylic dianhydrides. Examples of the aromatic tetracarboxylic dianhydride include pyromellitic dianhydride, benzophenone tetracarboxylic dianhydride, naphthalene tetracarboxylic dianhydride, heterocyclic aromatic tetracarboxylic dianhydride, 2, And 2'-substituted biphenyltetracarboxylic dianhydride. Examples of the pyromellitic dianhydride include pyromellitic dianhydride, 3,6-diphenylpyromellitic dianhydride, 3,6-bis (trifluoromethyl) pyromellitic dianhydride, and 3,6-dibromo. Examples include pyromellitic dianhydride and 3,6-dichloropyromellitic dianhydride. Examples of the benzophenone tetracarboxylic dianhydride include 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 2,3,3 ′, 4′-benzophenone tetracarboxylic dianhydride, 2 2,2 ', 3,3'-benzophenone tetracarboxylic dianhydride and the like. Examples of the naphthalenetetracarboxylic dianhydride include 2,3,6,7-naphthalene-tetracarboxylic dianhydride, 1,2,5,6-naphthalene-tetracarboxylic dianhydride, 2,6 -Dichloro-naphthalene-1,4,5,8-tetracarboxylic dianhydride and the like. Examples of the heterocyclic aromatic tetracarboxylic dianhydride include thiophene-2,3,4,5-tetracarboxylic dianhydride and pyrazine-2,3,5,6-tetracarboxylic dianhydride. Pyridine-2,3,5,6-tetracarboxylic dianhydride and the like. Examples of the 2,2′-substituted biphenyltetracarboxylic dianhydride include, for example, 2,2′-dibromo-4,4 ′, 5,5′-biphenyltetracarboxylic dianhydride, 2,2′-dichloro. -4,4 ', 5,5'-biphenyltetracarboxylic dianhydride, 2,2'-bis (trifluoromethyl) -4,4', 5,5'-biphenyltetracarboxylic dianhydride, etc. can give.

  Other examples of the aromatic tetracarboxylic dianhydride include 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and bis (2,3-dicarboxyphenyl) methane dianhydride. Bis (2,5,6-trifluoro-3,4-dicarboxyphenyl) methane dianhydride, 2,2-bis (3,4-dicarboxyphenyl) -1,1,1,3,3 3-hexafluoropropane dianhydride, 4,4 '-(3,4-dicarboxyphenyl) -2,2-diphenylpropane dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, 4 , 4'-oxydiphthalic dianhydride, bis (3,4-dicarboxyphenyl) sulfonic dianhydride, (3,3 ', 4,4'-diphenylsulfonetetracarboxylic dianhydride), 4,4 '-[4,4'- Sopropylidene-di (p-phenyleneoxy)] bis (phthalic anhydride), N, N- (3,4-dicarboxyphenyl) -N-methylamine dianhydride, bis (3,4-dicarboxyphenyl) And diethylsilane dianhydride.

  Examples of the diamine include aromatic diamines, and specific examples include benzene diamine, diaminobenzophenone, naphthalene diamine, heterocyclic aromatic diamines, and other aromatic diamines.

  Examples of the benzenediamine include o-, m- and p-phenylenediamine, 2,4-diaminotoluene, 1,4-diamino-2-methoxybenzene, 1,4-diamino-2-phenylbenzene, and 1, Examples include diamines selected from the group consisting of benzenediamines such as 3-diamino-4-chlorobenzene. Examples of the diaminobenzophenone include 2,2′-diaminobenzophenone and 3,3′-diaminobenzophenone. Examples of the naphthalene diamine include 1,8-diaminonaphthalene and 1,5-diaminonaphthalene. Examples of the heterocyclic aromatic diamine include 2,6-diaminopyridine, 2,4-diaminopyridine, and 2,4-diamino-S-triazine.

  In addition to these, the aromatic diamine includes 4,4′-diaminobiphenyl, 4,4′-diaminodiphenylmethane, 4,4 ′-(9-fluorenylidene) -dianiline, 2,2′-bis ( Trifluoromethyl) -4,4′-diaminobiphenyl, 3,3′-dichloro-4,4′-diaminodiphenylmethane, 2,2′-dichloro-4,4′-diaminobiphenyl, 2,2 ′, 5 5′-tetrachlorobenzidine, 2,2-bis (4-aminophenoxyphenyl) propane, 2,2-bis (4-aminophenyl) propane, 2,2-bis (4-aminophenyl) -1,1, 1,3,3,3-hexafluoropropane, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 1,3-bis (3-aminophenol Xyl) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 4,4'-bis (4-aminophenoxy) biphenyl, 4,4'-bis (3-aminophenoxy) biphenyl, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] -1,1,1,3 , 3,3-hexafluoropropane, 4,4'-diaminodiphenyl thioether, 4,4'-diaminodiphenyl sulfone and the like.

  The negative substantially uniaxial optical layer having an optical axis in the thickness direction made of polyimide, for example, forms a coating film by coating the polyimide on a certain substrate, and the polyimide in the coating film Can be formed on the substrate. Alternatively, as described above, the polyimide is directly coated on a negative substantially uniaxial optical film made of a thermoplastic polymer having negative molecular polarizability anisotropy and having an optical axis in the plane. It can also be formed by forming a film and solidifying the polyimide in the coating film. Due to its property, polyimide is a negative, substantially uniaxial optical film (layer) that spontaneously orients during coating and has an optical axis in the thickness direction without using a stretching step.

  The laminated optical film of the present invention has a structure in which the negative substantially uniaxial optical film having an optical axis in the thickness direction is peeled from the substrate and then the negative substantially uniaxial optical film having an optical axis in the plane. Or may be used in a state of being applied directly on a negative substantially uniaxial optical film having an optical axis in the plane.

  The polyimide is preferably a fluorine-containing polyimide, more preferably 2,2-bis (3,4-dicarboxyphenyl) -1,1,1,3,3,3, -hexafluoropropane. Polymerized from dianhydride and 2,2′-bistrifluoromethyl-4,4′-diamino-biphenyl. Since the optical layer formed by coating using this polyimide has a large retardation in the thickness direction, it is possible to produce an optical layer of 10 μm or less.

  In the optical film in the present invention (refers to both a negative substantially uniaxial optical layer having an optical axis in the thickness direction and a negative substantially uniaxial optical film having an optical axis in the plane), phenyl is further included. You may contain low molecular additives, such as ultraviolet absorbers, such as a salicylic acid, 2-hydroxybenzophenone, and a triphenyl phosphate, a bluing agent for changing a color, and antioxidant.

The thickness of the negative substantially uniaxial optical layer having an optical axis in the thickness direction in the present invention is preferably 0.1 to 20 μm, more preferably 1 to 10 μm.
The thickness of the negative substantially uniaxial optical film having an optical axis in the plane in the present invention is preferably 10 μm to 150 μm, more preferably 20 μm to 100 μm.

  The thickness of the laminated optical film of the present invention is preferably 1 μm to 400 μm. In addition, the laminated optical film in the present invention is used to include any of the so-called “sheet” and “plate”. Considering the handling of the film, the thickness is preferably 20 to 130 μm, more preferably 30 to 100 μm, still more preferably 40 to 70 μm.

According to the present invention, a laminated polarizing plate can be obtained by integrating the laminated optical film and the polarizing plate.
The polarizing plate may be composed of only a polarizing layer, but in general, a polarizing film between a pair of films made of cellulose acetate or the like as a film for protecting the polarizing layer (hereinafter sometimes referred to as a protective film for a polarizing layer). The thing of the structure which pinched | interposed the layer is used suitably. As the polarizing layer of the polarizing plate, an appropriate layer capable of obtaining light in a predetermined polarization state can be used. In particular, those capable of obtaining transmitted light in a linearly polarized state are preferable. Examples of polarizing layers include iodine and / or dichroic dye adsorbed on hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and ethylene / vinyl acetate copolymer partially saponified films. And a polarizing layer composed of a polyene-oriented film such as a dehydrated product of polyvinyl alcohol or a dehydrochlorinated product of polyvinyl chloride.

  When a protective film for a polarizing layer is present on the polarizing plate, the optical anisotropy is preferably as small as possible. Specifically, the in-plane retardation is 10 nm or less, more preferably 7 nm or less, and most preferably 5 nm or less. Rth (λ) is preferably 70 nm or less, more preferably 50 nm or less, and most preferably 40 nm or less. Furthermore, it is preferable that the slow axis in the film plane of the protective film for polarizing layers is orthogonal or parallel to the absorption axis of a polarizing plate, and it is more preferable to perform parallel production of a polarizing plate. Examples of the protective film for the polarizing layer include polycarbonate, polystyrene, syndiotactic polystyrene, amorphous polyolefin, polymer having norbornene skeleton, organic acid-substituted cellulose, polyethersulfone, polyarylate, polyester, olefin maleimide And a copolymerized olefin maleimide-based organic acid-substituted cellulose having a phenyl group are used, and cellulose acetate is preferred.

  In the laminated polarizing plate of the present invention, the protective film for the polarizing layer may be omitted, and the laminated optical film of the present invention may also serve as the protective film for the polarizing layer. This also has the advantage that the optical design becomes easier.

  In addition, when intensive studies were made on the order of lamination of the laminated polarizing plates and the relationship between the optical axes, the polarizing plate, a negative substantially uniaxial optical layer having an optical axis in the thickness direction, and a negative having an optical axis in the plane. The substantially uniaxial optical film is laminated at least in this order, and the absorption axis of the polarizing plate and the optical axis of the negative substantially uniaxial optical film having an in-plane optical axis are substantially orthogonal to each other. It turned out to be most preferable. That is, when this laminated structure is used in a liquid crystal display device, particularly in an in-plane switching mode, a display device with less color change even when the viewing angle characteristic, particularly the viewing angle changes, can be obtained as compared with other structures. It turns out that there is an advantage. In addition, since this structure allows the polarizing plate and the laminated optical film to be bonded together by roll rolls, it is effective not only for improving productivity but also for preventing the optical axis from being displaced during bonding, and is also expected to improve contrast. . In addition, in order to bond the laminated polarizing plate of this structure with a roll-to-roll, it is preferable to produce the negative substantially uniaxial optical film which has an in-plane optical axis by longitudinal uniaxial stretching. Since the substantially uniaxial optical film thus produced has a negative molecular polarizability anisotropy, the optical axis exists in a direction substantially perpendicular to the stretching direction (long direction), Since a polarizing plate using iodine is generally produced by longitudinal uniaxial stretching, an absorption axis is present in a substantially long direction, and therefore, they can be bonded by roll-to-roll. On the other hand, the negative substantially uniaxial optical layer made of an amorphous polymer having a positive molecular polarizability anisotropy and having an optical axis in the thickness direction is optically on the polarizing plate or in-plane as described above. It can form by application | coating, for example on the negative substantially uniaxial optical film which has an axis | shaft. As an example, FIG. 8 shows an example in which the present laminated polarizing plate is applied to an in-plane switching mode liquid crystal display device. In FIG. 8, the light source may be on either one of the upper and lower polarizing plates.

  As a method for producing a negative uniaxial optical film having an optical axis in the plane, it is preferable to produce a material having negative molecular polarizability anisotropy by uniaxial stretching. The azimuth of the slow axis can be controlled depending on whether the longitudinal uniaxial stretching or the transverse uniaxial stretching is performed.

  When laminating the polarizing plate and the laminated optical film, they can be fixed via an adhesive or the like, if necessary. From the standpoint of preventing axial misalignment, it is preferable to bond and fix. For the adhesion, for example, a transparent adhesive such as polyvinyl alcohol, modified polyvinyl alcohol, organic silanol, acrylic or silicone, polyester or polyurethane, polyether or rubber can be used. There is no particular limitation on. From the standpoint of preventing changes in optical properties, those that do not require high-temperature processes during curing and drying are preferred, and those that do not require long-time curing or drying treatments are desirable. Moreover, the thing which does not produce peeling etc. on heating or humidification conditions is preferable.

  When triacetyl cellulose (TAC) is used as the protective film for the polarizing layer, TAC and retardation film adhesives include butyl (meth) acrylate, methyl (meth) acrylate, ethyl (meth) acrylate and ( An acrylic pressure-sensitive adhesive composed of an acrylic polymer having a weight average molecular weight of 100,000 or more and a glass transition temperature of 0 ° C. or less, which contains a monomer such as (meth) acrylic acid, can be particularly preferably used. An acrylic pressure-sensitive adhesive is also preferable from the viewpoint of excellent transparency, weather resistance, heat resistance, and the like.

  Adhesives may be appropriately selected from fillers and pigments made of natural or synthetic resins, glass fibers and glass beads, metal powders and other inorganic powders, colorants, antioxidants, and the like as required. Additives can also be blended. In addition, each layer such as the above polarizer, retardation film, polarizing plate protective film, adhesive layer is, for example, a salicylic acid ester compound, a benzophenol compound, a benzotriazole compound, a cyanoacrylate compound, a nickel complex compound, etc. An ultraviolet absorbing function can be provided by a method of treating with an ultraviolet absorber.

  Further, by using the laminated optical film or laminated polarizing plate of the present invention for a liquid crystal display device, display performance such as viewing angle characteristics of the liquid crystal display device can be improved.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.
(Evaluation method)
The material characteristic values and the like described in the present specification are obtained by the following evaluation methods.

(1) Measurement of retardation value Γ (λ) (nm), Rth (λ) value (nm), Nz Phase difference Γ (λ) value, Rth (λ), which is the product of birefringence Δn and film thickness d ) And Nz were measured by a trade name “M150” manufactured by JASCO Corporation, which is a spectroscopic ellipsometer. The Γ value was measured with the incident light beam and the film surface orthogonal. In addition, the Nz and Rth values are obtained by measuring the phase difference value at each angle by changing the angle between the incident light beam and the film surface, and by curve fitting with a known refractive index ellipsoidal expression, A certain _nx , _ny , _nz was calculated | required and substituted by following formula (4), (9).
_{Nz = (n x -n z)} / (n x -n y) (4)
Rth (λ) = {(n _x + _ny ) / 2−n _z } × d (9)

を８６対１４のモル比で溶解させ、少量のハイドロサルファイトを加えた。次にこれに塩化メチレンを加え、２０℃でホスゲンを約６０分かけて吹き込んだ。さらに、ｐ−ｔｅｒｔ−ブチルフェノールを加えて乳化させた後、トリエチルアミンを加えて３０℃で約３時間攪拌して反応を終了させた。反応終了後有機相分取し、塩化メチレンを蒸発させてポリカーボネート共重合体を得た。得られた共重合体の組成比は仕込み量比とほぼ同様であった。 (2) Method for producing substantially uniaxial optical film having optical axis in plane As a polymer material of the optical film, a polycarbonate copolymer having a fluorene skeleton was used. The polymerization of the polycarbonate copolymer was performed by an interfacial polycondensation method using a known phosgene. Monomers [A] and [B] having the above structure are charged with a sodium hydroxide aqueous solution and ion-exchanged water in a reaction vessel equipped with a stirrer, a thermometer and a reflux condenser.

Was dissolved in a molar ratio of 86:14 and a small amount of hydrosulfite was added. Next, methylene chloride was added thereto, and phosgene was blown in at about 20 ° C. over about 60 minutes. Further, p-tert-butylphenol was added to emulsify, and then triethylamine was added and stirred at 30 ° C. for about 3 hours to complete the reaction. After completion of the reaction, the organic phase was collected, and methylene chloride was evaporated to obtain a polycarbonate copolymer. The composition ratio of the obtained copolymer was almost the same as the charged amount ratio.

  This copolymer was dissolved in methylene chloride to prepare a dope solution having a solid concentration of 18% by weight. A cast film was produced from this dope solution to obtain an unstretched film. The residual solvent amount of this unstretched film was 0.9% by weight. The film was stretched at a temperature of 225 ° C., and the stretching ratio was set so that the retardation values shown in Table 1 were obtained. The film was uniaxially stretched to obtain an optical film having a thickness of 70 μm.

を有する、重量平均分子量６万のポリイミドの１７重量％のシクロヘキサノン溶液を、前記（２）で作製した面内に光学軸を有する負の略１軸性光学フィルム上に塗布し、乾燥させて本発明の積層光学フィルムを作製した（厚みの異なるように３種類を作製（実施例１〜３に対応））。 (3) Method for producing negative substantially uniaxial optical layer having optical axis in thickness direction and method for laminating with substantially uniaxial optical film having optical axis in plane 2,2′-bis (3,4) -Dicarboxyphenyl) -1,1,1,3,3,3, -hexafluoropropane dianhydride and 2,2'-bistrifluoromethyl-4,4'-diamino-biphenyl [C]

A 17% by weight cyclohexanone solution of polyimide having a weight average molecular weight of 60,000 is applied on a negative substantially uniaxial optical film having an optical axis in the plane prepared in the above (2), and dried. The laminated optical film of the invention was produced (three kinds were produced so as to have different thicknesses (corresponding to Examples 1 to 3)).

The retardation value of the negative substantially uniaxial optical layer having an optical axis in the plane is Γ _NEA (λ), and the retardation value of the negative substantially uniaxial optical film having the optical axis in the thickness direction is thickness direction. Rth _NEC (λ), and these values and the value of Γ _NEA (λ) / 2 + Rth _NEC (λ) of the laminated optical film are shown in Table 1. In-plane retardation values were all 2 nm or less. Furthermore, although the dispersion | variation in the phase difference of this laminated | stacked optical film was confirmed, it turned out that it is excellent in uniformity with about ± 1 nm in an in-plane phase difference in the range of 10 cm square.

[Examples 1 to 3]
As shown in FIG. 1, polarizing plates were arranged on both sides of the laminated optical film prepared in (3) to prepare an optical element. In the optical element having the structure shown in FIG. 1, Jones matrix calculation corresponding to oblique incidence was first performed. In the following calculations, calculation results at a wavelength of 550 nm are all shown. The calculation results of Examples 1 to 3 are shown in FIGS. 4 to 6, the incident angle dependency of the transmittance spectrum is calculated, and the incident angle dependency of the color difference ΔE ^* in the L ^* a ^* b ^* space of CIE1976 is obtained by calculation. The color difference between the polar angle 0 ° and the oblique incidence is plotted. In other words, this evaluation shows that the smaller the color difference at oblique incidence, the better the viewing angle dependency of the laminated optical film. In the figure, darker portions indicate smaller color differences. Further, in the range where the polar angle is smaller than that of the black solid line, the color difference is 3 or less, indicating that the region has little color change. It can be seen that the area where the color change is small is greatly expanded as compared with the comparative example described later. Moreover, although the structure of FIG. 1 was actually produced and the color change was visually observed, it was confirmed that the color change was small in a wide viewing angle range.

[Comparative example]
Evaluation was performed in the same manner as in Example 1 except that the negative substantially uniaxial optical layer having an optical axis in the thickness direction was not used and the configuration of FIG. 2 was used. As can be seen from FIG. 7 of the calculation result, it can be seen that the region where the color difference change is 3 or less is very small and the viewing angle characteristics are not excellent. Moreover, although the structure of FIG. 7 was actually produced and the color change was confirmed visually, it turned out that a color changes a lot by a polar angle change.

  The laminated optical film of the present invention is excellent in phase difference viewing angle characteristics and phase difference uniformity, and by using these in a liquid crystal display device, high performance of the display device, particularly wide viewing angle, can be realized.

It is an arrangement plan of optical elements in Examples 1 to 3. It is an arrangement plan of optical elements in a comparative example. It is a figure explaining the orthogonal coordinate for the definition of the three-dimensional refractive index of the phase difference film in this invention. It is a figure showing the incident angle dependence of the color difference in Example 1. FIG. It is a figure showing the incident angle dependence of the color difference in Example 2. FIG. It is a figure showing the incident angle dependence of the color difference in Example 3. FIG. It is a figure showing the incident angle dependence of the color difference in a comparative example. It is the conceptual diagram which applied the laminated optical film of this invention to the liquid crystal display device of the in-plane switching mode.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Polarizing plate 2 Negative substantially uniaxial optical layer 3 having an optical axis in the thickness direction Negative substantially uniaxial optical film having an optical axis in the plane 4 Polarizing plate 5 Light emitted from a light source and incident on a polarizing plate Light 6 Absorption axis 7 of polarizing plate Slow axis 21 in the plane of the laminated optical film Polarizing plate 22 Negative substantially uniaxial optical layer 23 having an optical axis in the plane Polarizing plate 24 Light emitted from the light source to the polarizing plate Incident light 25 Absorption axis 26 of polarizing plate Optical axis (slow axis)
30 (Laminated) Optical Film 31 (Laminated) Optical Film Surface 40 Polarizing Plate 41 Liquid Crystal Cell 42 Negative substantially uniaxial optical film 43 having an optical axis in the plane Negative substantially uniaxial having an optical axis in the thickness direction Optical layer 44 Polarizing plate 45 Absorption axis 46 of polarizing plate Slow axis of liquid crystal cell (liquid crystal major axis alignment direction)
47 Optical axis (slow axis)
48 Absorption axis of polarizing plate

Claims (10)

  A negative substantially uniaxial optical layer having an optical axis in the thickness direction, and a thermoplastic polymer having a negative molecular polarizability anisotropy, comprising an amorphous polymer having a positive molecular polarizability anisotropy A laminated optical film comprising a negative substantially uniaxial optical film having an optical axis in a plane. The retardation value in the thickness direction of the negative substantially uniaxial optical layer having the optical axis in the thickness direction is Rth _NEC (λ), and the in-plane position of the negative substantially uniaxial optical film having the optical axis in the plane. 2. The laminated optical film according to claim 1, wherein when the phase difference value is Γ _NEA (λ), the relationship of the following formula (1) is satisfied.
−100 <Γ _NEA (λ) / 2 + Rth _NEC (λ) <100 nm (1)
(However, λ = 550 nm)   The laminated optical film according to claim 1 or 2, wherein the thermoplastic polymer having a negative molecular polarizability anisotropy is a polycarbonate having a fluorene skeleton.   The amorphous polymer having a positive molecular polarizability anisotropy is at least selected from the group consisting of polycarbonate, polyimide, polyamide, polyester, polyetherketone, polyarylate, polyaryletherketone, polyamideimide and polyesterimide. The laminated optical film according to claim 1, comprising a kind of polymer.   The laminated optical film according to claim 1, wherein the thickness of the negative substantially uniaxial optical layer having an optical axis in the thickness direction is 10 μm or less.   6. The laminated optical film according to claim 4, wherein the amorphous polymer having a positive molecular polarizability anisotropy is a polyimide containing a fluorine atom.   The polyimide containing fluorine atoms is 2,2′-bis (3,4-dicarboxyphenyl) -1,1,1,3,3,3, -hexafluoropropane dianhydride and 2,2′-bistri The laminated optical film according to claim 6, which is obtained by polymerizing fluoromethyl-4,4′-diamino-biphenyl.   A laminated polarizing plate in which the laminated optical film according to claim 1 and a polarizing plate are integrated.   A polarizing plate, a negative substantially uniaxial optical layer having an optical axis in the thickness direction, and a negative substantially uniaxial optical film having an in-plane optical axis are laminated at least in this order. The laminated polarizing plate according to claim 8, wherein the optical axis of the negative uniaxial optical film having an optical axis in the plane and the optical axis of the optical axis are substantially orthogonal to each other.   A liquid crystal display device comprising the laminated optical film according to claim 1 and / or the laminated polarizing plate according to any one of claims 8 to 9.

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