JP4224390B2 - Method for producing birefringent film - Google Patents

Description

The present invention relates to a method for producing a birefringent film .

  In order to improve the characteristics of a display screen in various image display devices such as a liquid crystal display device, a birefringent optical film is usually used.

  Many of the optical films that are currently widely used industrially are birefringent films that are optically uniaxial, and generally have positive or negative axiality, and those that have an optical axis in the film plane. Some are in the thickness direction (normal direction) of the film. For example, a birefringent film used in an STN (Super Twisted Nematic) liquid crystal display is a positive uniaxial birefringent film having an optical axis in the plane. In addition, for negative uniaxial birefringent films, for example, a simple manufacturing method is disclosed in which a specific polymer solution is dried on a substrate and the polymer is surface-oriented so that the optical axis is in the film normal direction. (For example, see Patent Document 1, Patent Document 2, and Patent Document 3). However, such a uniaxial birefringent film naturally has a limit in effects such as polarization control when used in a liquid crystal display device.

  On the other hand, since the effect of polarization control is excellent, the importance of an optically biaxial birefringent film having birefringence in the in-plane direction and thickness direction is increasing. Is produced by biaxial stretching. However, when producing a birefringent film by such biaxial stretching, for example, it is necessary to control the refractive index in three directions (that is, in two orthogonal directions and the thickness direction in the plane) by the balance of stretching in two directions. Therefore, it is very difficult to control the refractive index. Further, the obtained birefringent film has a problem that the refractive index distribution tends to be non-uniform in the plane, and it is difficult to form a uniform film in terms of optical characteristics.

  Therefore, in recent years, a new manufacturing method using a film forming material such as polyimide has been disclosed as a new manufacturing method of the optical biaxial birefringent film. That is, the film-forming material is coated on a substrate, and the coated film is dried to cause anisotropy in molecular orientation, to form a plane-oriented optically negative uniaxial film, and This is a method of forming a negative biaxial film by stretching this film (see, for example, Patent Document 4). According to such a method, compared with the method of realizing optical biaxiality by adjusting the complicated biaxial stretching conditions as described above, optical uniaxiality is expressed only by coating and drying, In addition, since optical biaxiality can be exhibited only by performing at least uniaxial stretching, it is possible to precisely control the refractive index, simplify the setting of conditions associated with the control, and facilitate the manufacturing itself.

However, even with such a new method, the obtained optical biaxial birefringent film may have uneven refractive index distribution due to variations in the orientation axis angle. For this reason, the further improvement of the quality, such as the uniformity of an optical characteristic, is calculated | required.
US Pat. No. 5,344,916 US Pat. No. 6,480,964 US Pat. No. 5,580,950 JP 2000-190385 A

  Therefore, an object of the present invention is to provide a method for producing an optical biaxial birefringent film that can easily control the refractive index and is excellent in quality such as homogeneity of the refractive index.

In order to achieve the above object, the method for producing an optical biaxial birefringent film according to the present invention includes a step of coating a birefringent material on a substrate, and fixing the coated film on the substrate. Forming an optically uniaxial birefringent layer, and changing the birefringence index of the birefringent layer to optically biaxially. There,
The step of changing the birefringence of the birefringent layer to optical biaxiality is the optical uniaxiality under a temperature condition not lower than the glass transition temperature of the substrate and not higher than the glass transition temperature of the birefringent material. Is a step of subjecting the birefringent layer to stretching treatment,
The difference between the elastic modulus of the substrate and the elastic modulus of the birefringent material during the stretching treatment is in the range of 500 to 900 MPa.

The step of changing the birefringence of the birefringent layer to optical biaxiality is not less than the glass transition temperature of the base material and not more than the glass transition temperature of the birefringent material, instead of the stretching treatment. A step of shrinking the optically uniaxial birefringent layer under temperature conditions;
The difference between the elastic modulus of the base material and the elastic modulus of the birefringent material during the shrinkage treatment may be in the range of 500 to 900 MPa.

  Thus, the temperature in the stretching process is equal to or higher than the glass transition temperature of the base material and is equal to or lower than the glass transition temperature of the birefringent material, and the base material and the birefringent material are used during the stretching process. If the difference between the respective elastic moduli is in the range of 500 to 900 MPa, the variation in the axial angle distribution is suppressed and the refractive index is uniformly controlled, so that the birefringence, the in-plane direction, and the thickness can be controlled. The optical biaxial birefringent film of the present invention having a uniform retardation in the direction and excellent optical characteristics can be obtained. Thus, the birefringent film excellent in optical characteristics with uniform birefringence, retardation, etc. is useful for various optical films, for example, and excellent when applied to various image display devices such as liquid crystal display devices. Display characteristics can be realized.

  Thus, the condition that “the difference between the elastic modulus of the substrate and the elastic modulus of the birefringent material in the stretching treatment is in the range of 500 to 900 MPa” is a technique that the inventors have found for the first time. In other words, when curling or warping occurs in an optical film that is a laminate of a base material and a birefringent film, there is a problem that an appearance defect and variation in optical properties are caused accordingly. In general, it is common sense to prevent the curling and the like by matching the elastic moduli of the base material and the birefringent film, and the upper limit of the difference between the two elastic moduli is set. However, as a result of diligent research, the inventors of the present invention formed a birefringent layer directly on the base material, and when the birefringent layer was stretched, the elastic modulus of the base material and the birefringent material was Instead of matching them as in the prior art, on the contrary, it has been found that by providing a certain degree of difference, that is, a difference of 500 MPa or more, it is possible to achieve a uniform birefringence and the like. This is a matter contrary to the technical common sense of those skilled in the art, that is, the technical common sense of matching the elastic moduli of the two, and the present invention is established for the first time by finding a matter that violates such technical common sense. To do. The same applies to the case where the contraction process is performed instead of the stretching process.

As described above, the method for producing an optical biaxial birefringent film according to the present invention includes a step of coating a birefringent material on a substrate, an optical uniaxial on the substrate by fixing the coated film. Forming a birefringent layer and changing the birefringence of the birefringent layer into optical biaxiality, wherein the birefringence of the birefringent layer is optically birefringent. The step of changing to an axial property is a step of subjecting the optically uniaxial birefringent layer to a stretching process under a temperature condition not lower than the glass transition temperature of the substrate and not higher than the glass transition temperature of the birefringent material. ,
The difference between the elastic modulus of the base material and the elastic modulus of the birefringent material during the stretching process is in the range of 500 to 900 MPa.

  The difference between the elastic modulus of the birefringent material and the elastic modulus of the base material at the time of stretching may be 500 to 900 MPa as described above. If the difference in elastic modulus is less than 500 MPa, there is a problem that the base material and the birefringent layer are cut during stretching, and if it exceeds 900 MPa, stretching is difficult. The difference in elastic modulus between the two is preferably 600 to 900 MPa, more preferably 650 to 850 MPa, and particularly preferably 700 to 800 MPa. It is known that the elastic modulus is a property determined according to the type of the forming material, and shows a value corresponding to the stretching temperature at the time of stretching. For this reason, for example, if the birefringent material is determined, a substrate satisfying the condition can be selected according to the elastic modulus, and if the base material is determined, a compound satisfying the condition according to the elastic modulus can be selected. The refractive material can be determined. Specific examples of the combination of the birefringent material and the substrate will be described later.

  The type of the birefringent material is not particularly limited as long as the above conditions are satisfied. For example, a non-liquid crystalline polymer is preferable. If such a non-liquid crystalline polymer is used, for example, unlike a liquid crystalline material, it is applied only by coating regardless of the orientation of the substrate, and optically negative uniaxiality (nx> nz) and (ny> nz) can be formed. For this reason, for example, the base material to be used is not limited to the alignment base material. For example, even if it is an unaligned base material, an alignment film is formed on the surface as in the case of using a liquid crystal material. There is no need to form or laminate by coating. In addition, nx, ny, and nz respectively indicate the refractive indexes in the X-axis (slow axis), Y-axis, and Z-axis directions of the birefringent layer, and the X-axis direction is within the plane of the birefringent layer. It is an axial direction showing the maximum refractive index, the Y-axis direction is an axial direction perpendicular to the X-axis in the plane, and the Z-axis indicates a thickness direction perpendicular to the X-axis and the Y-axis. .

  Examples of the non-liquid crystalline polymer include heat resistance, chemical resistance, transparency, and rigidity, so that polyamide, polyimide, polyester, polyether ketone, polyaryl ether ketone, polyamide imide, polyester imide, etc. The polymer is preferred. 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.

  The molecular weight of the polymer is not particularly limited. For example, the weight average molecular weight (Mw) is preferably in the range of 1,000 to 1,000,000, more preferably in the range of 2,000 to 500,000. is there.

  As the polyimide, for example, a polyimide that has high in-plane orientation and is soluble in an organic solvent is preferable. Specifically, for example, a condensation polymerization product of 9,9-bis (aminoaryl) fluorene and aromatic tetracarboxylic dianhydride disclosed in JP 2000-511296 A, specifically, A polymer containing one or more repeating units represented by the following formula (1) can be used.

前記式（１）中、Ｒ³〜Ｒ⁶は、水素、ハロゲン、フェニル基、１〜４個のハロゲン原子またはＣ₁〜₁₀アルキル基で置換されたフェニル基、およびＣ₁〜₁₀アルキル基からなる群からそれぞれ独立に選択される少なくとも一種類の置換基である。好ましくは、Ｒ³〜Ｒ⁶は、ハロゲン、フェニル基、１〜４個のハロゲン原子またはＣ₁〜₁₀アルキル基で置換されたフェニル基、およびＣ₁〜₁₀アルキル基からなる群からそれぞれ独立に選択される少なくとも一種類の置換基である。

In the formula (1), R ³ to R ⁶ are hydrogen, halogen, a phenyl group, 1-4 halogen atoms, or C ₁ ~ ₁₀ alkyl-substituted phenyl, and C ₁ ~ ₁₀ alkyl group And at least one substituent selected independently from the group. Preferably, R ³ to R ⁶ is a halogen, a phenyl group, each independently from the group consisting of one to four halogen atoms or C ₁ ~ ₁₀ alkyl-substituted phenyl, and C ₁ ~ ₁₀ alkyl group It is at least one type of substituent selected.

In the formula (1), Z represents a tetravalent aromatic group C ₆ ~ _20, preferably a pyromellitic group, a polycyclic aromatic group, a derivative of a polycyclic aromatic group, or, It is group represented by following formula (2).

前記式（２）中、Ｚ’は、例えば、共有結合、Ｃ(Ｒ⁷)₂基、ＣＯ基、Ｏ原子、Ｓ原子、ＳＯ₂基、Ｓｉ(Ｃ₂Ｈ₅)₂基、または、ＮＲ⁸基であり、複数の場合、それぞれ同一であるかまたは異なる。また、ｗは、１から１０までの整数を表す。Ｒ⁷は、それぞれ独立に、水素またはＣ（Ｒ⁹）₃である。Ｒ⁸は、水素、炭素原子数１〜約２０のアルキル基、またはＣ₆〜₂₀アリール基であり、複数の場合、それぞれ同一であるかまたは異なる。Ｒ⁹は、それぞれ独立に、水素、フッ素、または塩素である。

In the formula (2), Z ′ represents, for example, a covalent bond, C (R ⁷ ) ₂ group, CO group, O atom, S atom, SO ₂ group, Si (C ₂ H ₅ ) ₂ group, or NR ^{There are 8} groups, and when there are multiple groups, they are the same or different. W represents an integer from 1 to 10. Each R ⁷ is independently hydrogen or C (R ⁹ ) ₃ . R ⁸ is hydrogen, an alkyl group or a C ₆ ~ ₂₀ aryl group, the carbon atom number from 1 to about 20, for a plurality, it may be the same or different. Each R ⁹ is independently hydrogen, fluorine, or chlorine.

Examples of the polycyclic aromatic group include a tetravalent group derived from naphthalene, fluorene, benzofluorene or anthracene. The substitution Examples of the substituted derivatives of polycyclic aromatic group, for example, an alkyl group of C ₁ ~ _10, at least one group selected from the group consisting of fluorinated derivatives, and F or a halogen such as Cl And the above-mentioned polycyclic aromatic group.

  In addition, for example, a homopolymer described in JP-A-8-511812, wherein the repeating unit is represented by the following general formula (3) or (4), or the repeating unit is represented by the following general formula (5): The polyimide etc. which are shown are mention | raise | lifted. In addition, the polyimide of following formula (5) is a preferable form of the homopolymer of following formula (3).

前記一般式（３）〜（５）中、ＧおよびＧ’は、例えば、共有結合、ＣＨ₂基、Ｃ(ＣＨ₃)₂基、Ｃ(ＣＦ₃)₂基、Ｃ(ＣＸ₃)₂基（ここで、Ｘは、ハロゲンである。）、ＣＯ基、Ｏ原子、Ｓ原子、ＳＯ₂基、Ｓｉ(ＣＨ₂ＣＨ₃)₂基、および、Ｎ(ＣＨ₃)基からなる群から、それぞれ独立して選択される基を表し、それぞれ同一でも異なってもよい。

In the general formulas (3) to (5), G and G ′ are, for example, a covalent bond, a CH ₂ group, a C (CH ₃ ) ₂ group, a C (CF ₃ ) ₂ group, or a C (CX ₃ ) ₂ group. (Where X is halogen), from the group consisting of CO, O, S, SO ₂ , Si (CH ₂ CH ₃ ) ₂ and N (CH ₃ ) groups, respectively It represents independently selected groups, and may be the same or different.

In the above formulas (3) and (5), L is a substituent, and d and e represent the number of substitutions. L is, for example, halogen, C ₁ ~ ₃ alkyl group, C ₁ ~ ₃ halogenated alkyl group, a phenyl group, or a substituted phenyl group, in the case of multiple or different are each identical. Examples of the substituted phenyl group, for example, halogen, a substituted phenyl group having at least one substituent selected from C ₁ ~ ₃ alkyl group, and C ₁ ~ ₃ the group consisting of halogenated alkyl groups. Examples of the halogen include fluorine, chlorine, bromine and iodine. d is an integer from 0 to 2, and e is an integer from 0 to 3.

  In the formulas (3) to (5), Q is a substituent, and f represents the number of substitutions. Q is, for example, selected from the group consisting of hydrogen, halogen, alkyl group, substituted alkyl group, nitro group, cyano group, thioalkyl group, alkoxy group, aryl group, substituted aryl group, alkyl ester group, and substituted alkyl ester group And when Q is plural, they are the same or different. Examples of the halogen include fluorine, chlorine, bromine and iodine. Examples of the substituted alkyl group include a halogenated alkyl group. Examples of the substituted aryl group include a halogenated aryl group. f is an integer from 0 to 4, and g and h are integers from 0 to 3 and 1 to 3, respectively. Further, g and h are preferably larger than 1.

In the formula (4), R ¹⁰ and R ¹¹ are groups independently selected from the group consisting of hydrogen, halogen, phenyl group, substituted phenyl group, alkyl group, and substituted alkyl group. Among these, R ¹⁰ and R ¹¹ are preferably each independently a halogenated alkyl group.

In the formula (5), M ¹ and M ² are identical or different, for example, halogen, C ₁ ~ ₃ alkyl group, C ₁ ~ ₃ halogenated alkyl group, a phenyl group or a substituted phenyl group is there. Examples of the halogen include fluorine, chlorine, bromine and iodine. The above-mentioned substituted phenyl group, for example, halogen, a substituted phenyl group having at least one substituent selected from the group consisting of C ₁ ~ ₃ alkyl group, and C ₁ ~ ₃ halogenated alkyl group and the like .

  Specific examples of the polyimide represented by the formula (3) include those represented by the following formula (6).

さらに、前記ポリイミドとしては、例えば、前述のような骨格（繰り返し単位）以外の酸二無水物やジアミンを、適宜共重合させたコポリマーがあげられる。

Furthermore, examples of the polyimide include a copolymer obtained by appropriately copolymerizing an acid dianhydride other than the skeleton (repeating unit) as described above and a 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 ′, 3,3′-benzophenonetetracarboxylic 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 2,2′-dibromo-4,4 ′, 5,5′-biphenyltetracarboxylic dianhydride and 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′-bis (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′-diphenylsulfone tetracarboxylic 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.

  Among these, the aromatic tetracarboxylic dianhydride is preferably 2,2′-substituted biphenyltetracarboxylic dianhydride, more preferably 2,2′-bis (trihalomethyl) -4,4. ', 5,5'-biphenyltetracarboxylic dianhydride, more preferably 2,2'-bis (trifluoromethyl) -4,4', 5,5'-biphenyltetracarboxylic dianhydride It is.

  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, as the aromatic diamine, 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-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 4,4′-bis (4-aminophenoxy) biphenyl, 4,4′-bis (3-amino) Phenoxy) 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.

  Examples of the polyether ketone which is a material for forming the birefringent layer include polyaryl ether ketones represented by the following general formula (7) described in JP-A No. 2001-49110.

前記式（７）中、Ｘは、置換基を表し、ｑは、その置換数を表す。Ｘは、例えば、ハロゲン原子、低級アルキル基、ハロゲン化アルキル基、低級アルコキシ基、または、ハロゲン化アルコキシ基であり、Ｘが複数の場合、それぞれ同一であるかまたは異なる。

In the formula (7), X represents a substituent, and q represents the number of substitutions. X is, for example, a halogen atom, a lower alkyl group, a halogenated alkyl group, a lower alkoxy group, or a halogenated alkoxy group, and when there are a plurality of Xs, they are the same or different.

Examples of the halogen atom include a fluorine atom, a bromine atom, a chlorine atom, and an iodine atom, and among these, a fluorine atom is preferable. Examples of the lower alkyl group, for example, preferably a lower alkyl group having a straight-chain or branched C ₁ ~ _6, more preferably a straight-chain or branched alkyl group of C ₁ ~ _4. Specifically, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, and a tert-butyl group are preferable, and a methyl group and an ethyl group are particularly preferable. Examples of the halogenated alkyl group include halides of the lower alkyl group such as a trifluoromethyl group. Examples of the lower alkoxy group, for example, preferably a straight chain or branched chain alkoxy group of C ₁ ~ _6, more preferably a straight chain or branched chain alkoxy group of C ₁ ~ _4. Specifically, a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, an isobutoxy group, a sec-butoxy group, and a tert-butoxy group are more preferable, and a methoxy group and an ethoxy group are particularly preferable. . Examples of the halogenated alkoxy group include halides of the lower alkoxy group such as a trifluoromethoxy group.

  In the formula (7), q is an integer from 0 to 4. In the above formula (7), it is preferable that q = 0 and that the carbonyl group bonded to both ends of the benzene ring and the oxygen atom of the ether are present in the para position.

In the formula (7), R ¹ is a group represented by the following formula (8), and m is an integer of 0 or 1.

前記式（８）中、Ｘ’は置換基を表し、例えば、前記式（７）におけるＸと同様である。前記式（８）において、Ｘ’が複数の場合、それぞれ同一であるかまたは異なる。ｑ’は、前記Ｘ’の置換数を表し、０から４までの整数であって、ｑ’＝０が好ましい。また、ｐは、０または１の整数である。

In the formula (8), X ′ represents a substituent, and is the same as X in the formula (7), for example. In the formula (8), when there are a plurality of X ′, they are the same or different. q ′ represents the number of substitutions of X ′ and is an integer from 0 to 4, preferably q ′ = 0. P is an integer of 0 or 1.

In the formula (8), R ² represents a divalent aromatic group. Examples of the divalent aromatic group include an o-, m- or p-phenylene group, or naphthalene, biphenyl, anthracene, o-, m- or p-terphenyl, phenanthrene, dibenzofuran, biphenyl ether, or And divalent groups derived from biphenylsulfone. In these divalent aromatic groups, hydrogen directly bonded to the aromatic group may be substituted with a halogen atom, a lower alkyl group or a lower alkoxy group. Among these, R ² is preferably an aromatic group selected from the group consisting of the following formulas (9) to (15).

前記式（７）中、前記Ｒ¹としては、下記式（１６）で表される基が好ましく、下記式（１６）において、Ｒ²およびｐは前記式（８）と同義である。

In the formula (7), the R ¹ is preferably a group represented by the following formula (16). In the following formula (16), R ² and p have the same meanings as the formula (8).

さらに、前記式（７）中、ｎは重合度を表し、例えば、２〜５０００の範囲であり、好ましくは、５〜５００の範囲である。また、その重合は、同じ構造の繰り返し単位からなるものであってもよく、異なる構造の繰り返し単位からなるものであってもよい。後者の場合には、繰り返し単位の重合形態は、ブロック重合であってもよいし、ランダム重合でもよい。

Furthermore, in said Formula (7), n represents a polymerization degree, for example, is the range of 2-5000, Preferably, it is the range of 5-500. Further, the polymerization may be composed of repeating units having the same structure, or may be composed of repeating units having different structures. In the latter case, the polymerization mode of the repeating unit may be block polymerization or random polymerization.

  Furthermore, the end of the polyaryl ether ketone represented by the formula (7) is preferably fluorine on the p-tetrafluorobenzoylene group side and a hydrogen atom on the oxyalkylene group side. Can be represented by the following general formula (17). In the following formula, n represents the same degree of polymerization as in formula (7).

前記式（７）で示されるポリアリールエーテルケトンの具体例としては、下記式（１８）〜（２１）で表されるもの等があげられ、下記各式において、ｎは、前記式（７）と同様の重合度を表す。

Specific examples of the polyaryletherketone represented by the formula (7) include those represented by the following formulas (18) to (21). In each formula below, n represents the formula (7). Represents the same degree of polymerization.

また、これらの他に、前記複屈折層の形成材料である前記ポリアミドまたはポリエステルとしては、例えば、特表平１０−５０８０４８号公報に記載されるポリアミドやポリエステルがあげられ、それらの繰り返し単位は、例えば、下記一般式（２２）で表すことができる。

In addition to these, examples of the polyamide or polyester that is the material for forming the birefringent layer include polyamides and polyesters described in JP-T-10-508048, and their repeating units are: For example, it can be represented by the following general formula (22).

前記式（２２）中、Ｙは、ＯまたはＮＨである。また、Ｅは、例えば、共有結合、Ｃ₂アルキレン基、ハロゲン化Ｃ₂アルキレン基、ＣＨ₂基、Ｃ(ＣＸ₃)₂基（ここで、Ｘはハロゲンまたは水素である。）、ＣＯ基、Ｏ原子、Ｓ原子、ＳＯ₂基、Ｓｉ(Ｒ)₂基、および、Ｎ(Ｒ)基からなる群から選ばれる少なくとも一種類の基であり、それぞれ同一でもよいし異なってもよい。前記Ｅにおいて、Ｒは、Ｃ_1-3アルキル基およびＣ_1-3ハロゲン化アルキル基の少なくとも一種類であり、カルボニル官能基またはＹ基に対してメタ位またはパラ位にある。

In the formula (22), Y is O or NH. E is, for example, a covalent bond, a C ₂ alkylene group, a halogenated C ₂ alkylene group, a CH ₂ group, a C (CX ₃ ) ₂ group (where X is a halogen or hydrogen), a CO group, It is at least one kind of group selected from the group consisting of O atom, S atom, SO ₂ group, Si (R) ₂ group, and N (R) group, and may be the same or different. In E, R is at least one of a C _1-3 alkyl group and a C _1-3 halogenated alkyl group, and is in a meta position or a para position with respect to a carbonyl functional group or a Y group.

  Moreover, in said (22), A and A 'are substituents, and t and z represent the number of each substitution. P is an integer from 0 to 3, q is an integer from 1 to 3, and r is an integer from 0 to 3.

Wherein A is selected from hydrogen, a halogen, C ₁ ~ ₃ alkyl group, C ₁ ~ ₃ halogenated alkyl group, OR (wherein, R represents those defined above.) The alkoxy group represented by aryl group, a substituted aryl group by a halogen, etc., C ₁ ~ ₉ alkoxycarbonyl group, C ₁ ~ ₉ alkylcarbonyloxy group, C ₁ ~ ₁₂ aryloxycarbonyl group, C ₁ ~ ₁₂ arylcarbonyloxy group and a substituted derivative thereof, C _1-12 arylcarbamoyl group, and is selected from the group consisting of C _1-12 arylcarbonylamino group and a substituted derivative thereof, in the case of a plurality, they may be the same or different. Wherein A 'is, for example, halogen, C ₁ ~ ₃ alkyl group, C ₁ ~ ₃ halogenated alkyl group, selected from the group consisting of phenyl group and a substituted phenyl group and when there are plural, they may be the same or different. The substituent on the phenyl ring of the substituted phenyl group, for example, halogen, C ₁ ~ ₃ alkyl group, C ₁ ~ ₃ alkyl halide groups and combinations thereof. The t is an integer from 0 to 4, and the z is an integer from 0 to 3.

  Among the repeating units of polyamide or polyester represented by the formula (22), those represented by the following general formula (23) are preferable.

前記式（２３）中、Ａ、Ａ’およびＹは、前記式（２２）で定義したものであり、ｖは０から３の整数、好ましくは、０から２の整数である。ｘおよびｙは、それぞれ０または１であるが、共に０であることはない。

In the formula (23), A, A ′ and Y are those defined in the formula (22), and v is an integer of 0 to 3, preferably 0 to 2. x and y are each 0 or 1, but are not 0 at the same time.

On the other hand, as the substrate, various resin films, metal substrates and the like can be used, and the material thereof is not particularly limited, but for example, a resin having excellent transparency is preferable. If the resin is excellent in transparency as described above, for example, as described later, a birefringent film (hereinafter referred to as “the present invention”) obtained by the base material and the production method of the invention formed on the base material . This is because it may be used as it is as a laminate. In addition, a thermoplastic resin is preferable because it is suitable for a stretching process and a shrinking process described later. Specifically, for example, polyolefins such as polyethylene, polypropylene, and poly (4-methylpentyne-1), polyimide, polyamideimide, polyamide, polyetherimide, polyetheretherketone, polyketone sulfide, polyethersulfone, polysulfone, and polyphenylene sulfide. , Polyphenylene oxide, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyacetal, polycarbonate, polyarylate, acrylic resin, polyvinyl alcohol, polypropylene, cellulosic glass tex, epoxy resin, phenol resin, triacetyl cellulose (TAC), etc. Acetate resin, polyester resin, acrylic resin, polynorbornene resin, cellulose Fat, polystyrene resins, polyvinyl alcohol resins, polyvinyl chloride resins, polyvinylidene chloride resins, and polyacrylic resins, mixtures thereof and the like, also, the liquid crystal polymer or the like can be used. Among these, for example, polypropylene, polyethylene terephthalate, polyethylene naphthalate and the like are preferable from the viewpoint of solvent resistance and heat resistance. Further, for example, as described in JP-A-2001-343529 (WO 01/37007), a thermoplastic resin having a substituted imide group or an unsubstituted imide group in the side chain, and a substituted phenyl group in the side chain Alternatively, a mixture of a thermoplastic resin having an unsubstituted phenyl group and a nitrile group can also be used. Specific examples include a resin composition having an alternating copolymer composed of isobutene and N-methylmaleimide and an acrylonitrile / styrene copolymer. Among these forming materials, for example, a thermoplastic resin having a substituted imide group or an unsubstituted imide group in the aforementioned side chain, and a thermoplastic resin having a substituted phenyl group or an unsubstituted phenyl group and a nitrile group in the side chain; Is preferred. Further, the resin film may be subjected to a hydrophilic treatment, a hydrophobic treatment, a treatment for reducing solubility with a solvent, or the like on the surface.

  The method for producing the resin film as described above is not particularly limited, and examples thereof include a casting method, a method of performing a stretching treatment after forming a resin melt, and a film produced by the latter method is described later. In such a birefringent layer stretching treatment, it is preferable because it exhibits sufficient strength and can contribute to precise deformation of the birefringent layer.

  In addition, since the coating film formed from the non-liquid crystalline polymer as described above is optically negative uniaxial, when the non-liquid crystalline polymer is used as a birefringent material, It is not necessary to use the orientation of the substrate for the formation. For this reason, as the base material, both an oriented base material and a non-oriented base material can be used. Further, for example, a phase difference due to birefringence may be generated, or a phase difference due to birefringence may not be generated. As a base material which produces the phase difference by the said birefringence, a stretched film etc. are mention | raise | lifted, for example, and the thing etc. which the refractive index of the thickness direction was controlled can be used. The refractive index can be controlled by, for example, a method in which a polymer film is bonded to a heat-shrinkable film and then heated and stretched.

  Examples of the combination of the birefringent material and the base material include a combination of polyimide and TAC. For example, when the stretching temperature is 150 ° C., the elastic modulus of polyimide is 1000 MPa, and the elastic modulus of TAC is 300 MPa. The difference is 700 MPa.

  Next, although an example of the manufacturing method of the birefringent film of the present invention is shown, it is not limited thereto. First, the birefringent material is dispersed or dissolved in a solvent to prepare a coating solution. The concentration of the birefringent material in the coating liquid is not particularly limited. For example, since the viscosity is easy to apply, for example, the birefringent material is preferably 0.5 to 50% by weight, Preferably it is 1 to 40 weight%, Most preferably, it is 2 to 30 weight%. Specifically, when the birefringent material is a non-liquid crystalline polymer, the amount of the polymer added is preferably, for example, 5 to 50 parts by weight of the forming material with respect to 100 parts by weight of the solvent, more preferably 10 to 40 parts by weight.

  The solvent is not particularly limited and can be appropriately selected depending on the birefringent material. For example, a solvent that can dissolve the birefringent material and hardly erodes the base material is preferable. For example, specifically, for example, halogenated hydrocarbons such as chloroform, dichloromethane, carbon tetrachloride, dichloroethane, tetrachloroethane, trichloroethylene, tetrachloroethylene, chlorobenzene, orthodichlorobenzene, phenols such as phenol and parachlorophenol, benzene, Aromatic hydrocarbons such as toluene, xylene, methoxybenzene, 1,2-dimethoxybenzene, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, cyclopentanone, 2-pyrrolidone, N-methyl-2-pyrrolidone Solvents, ester solvents such as ethyl acetate and butyl acetate, t-butyl alcohol, glycerin, ethylene glycol, triethylene glycol, ethylene glycol monomethyl Ether, diethylene glycol dimethyl ether, propylene glycol, dipropylene glycol, alcohol solvents such as 2-methyl-2,4-pentanediol, amide solvents such as dimethylformamide and dimethylacetamide, nitrile solvents such as acetonitrile and butyronitrile, diethyl ether , Ether solvents such as dibutyl ether and tetrahydrofuran, carbon disulfide, ethyl cellosolve, butyl cellosolve, sulfuric acid and the like can be used. These solvents may be used alone or in combination of two or more.

  For example, the coating liquid may further contain various additives such as a surfactant, a stabilizer, a plasticizer, and metals as required.

  Further, the coating liquid may contain other different resins as long as the orientation of the birefringent material is not significantly lowered. Examples of the other resin include various general-purpose resins, engineering plastics, thermoplastic resins, and thermosetting resins.

  Examples of the general-purpose resin include polyethylene (PE), polypropylene (PP), polystyrene (PS), polymethyl methacrylate (PMMA), ABS resin, and AS resin. Examples of the engineering plastic include polyacetate (POM), polycarbonate (PC), polyamide (PA: nylon), polyethylene terephthalate (PET), and polybutylene terephthalate (PBT). Examples of the thermoplastic resin include polyphenylene sulfide (PPS), polyethersulfone (PES), polyketone (PK), polyimide (PI), polycyclohexanedimethanol terephthalate (PCT), polyarylate (PAR), and liquid crystal polymer. (LCP) and the like. Examples of the thermosetting resin include an epoxy resin and a phenol novolac resin. Thus, when mix | blending the said other resin etc. with the said coating liquid, the compounding quantity is 0-50 weight% with respect to the said polymer material, for example, Preferably, it is 0-30 weight %.

  Next, the prepared coating solution is applied to the surface of the substrate to form a coating film of the birefringent material. Examples of the coating method include spin coating, roll coating, printing, dipping and lifting, curtain coating, wire bar coating, doctor blade method, knife coating method, tie coating method, and gravure coating. Method, micro gravure coating method, offset gravure coating method, lip coating method, spray coating method and the like. Moreover, in the case of coating, the superposition | polymerization method of a polymer layer is also employable as needed.

  The thickness of the substrate is not particularly limited, but is usually 10 μm or more, preferably in the range of 10 to 200 μm, more preferably in the range of 20 to 150 μm, and particularly preferably in the range of 30 to 100 μm. If it is 10 μm or more, sufficient strength is exhibited in the stretching treatment and shrinkage treatment as described later, and therefore stretching and shrinkage unevenness in the stretching treatment and shrinkage treatment can be sufficiently suppressed. Moreover, if it is 200 micrometers or less, since an extending | stretching process is possible with moderate tension, it is preferable.

  Then, the coating film formed on the substrate is dried. By this drying, the birefringent material such as polyimide is fixed on the base material, and an optically uniaxial birefringent layer is formed. That is, as described above, if the birefringent material is the non-liquid crystal polymer, the orientation of the base material (for example, the coating film shrinks in the film thickness direction during drying) regardless of the orientation of the substrate. , A phenomenon in which anisotropic layer properties occur in molecular orientation), and a birefringent layer that exhibits optically negative uniaxiality (nx> nz, ny> nz). The refractive indexes of nx, ny, and nz are usually determined by the material used, production conditions, and the like. By adjusting the film thickness (d) of the birefringent layer, the retardation value (nx−nz) in the thickness direction is adjusted. ) · D can be controlled.

  The drying method is not particularly limited, and examples thereof include natural drying and heat drying. The conditions can also be appropriately determined according to, for example, the type of the birefringent material, the type of the solvent, etc. For example, the temperature is usually 40 ° C. to 250 ° C., preferably 50 ° C. to 200 ° C. is there. The coating film may be dried at a constant temperature or may be performed while increasing or decreasing the temperature stepwise. The drying time is not particularly limited, but is usually 10 seconds to 60 minutes, preferably 30 seconds to 30 minutes.

  Since the solvent of the polymer liquid remaining in the birefringent layer after the drying treatment may change the optical characteristics of the birefringent layer over time in proportion to the amount thereof, the residual amount is, for example, 5% or less is preferable, More preferably, it is 2% or less, More preferably, it is 0.2% or less.

  The thickness of the birefringent layer formed on the substrate is not particularly limited, but is, for example, in the range of 0.5 to 40 μm, preferably in the range of 1 to 20 μm, more preferably in the range of 1 to 10 μm. It is.

  As described above, the optical characteristics of the birefringent layer are “nx> nz” and “ny> nz”, and nz and ny are almost the same, and usually 0 ≦ (nx−ny) ≦ 0.001. It can be said that it is optically uniaxial if it is a grade.

  On the other hand, (nx−nz) is preferably set to 0.002 or more, more preferably 0.005 or more, still more preferably 0.01 or more, and particularly preferably 0.02 or more. If 0.02 ≦ (nx−nz), it is not necessary to increase the film thickness in order to obtain a desired retardation value (nx−nz) · d, and sufficiently uniform stretching is performed even in the stretching process described later. This is because it becomes possible. In addition, (nx-nz) · d of this optically uniaxial birefringent layer is usually 20 to 2000 nm, preferably 20 to 2000 nm, more preferably 50 to 1000 nm, and particularly preferably 100 to 600 nm. In general, (nx−nz) · d set in the birefringent layer exhibits the same range in the optical biaxial birefringent layer described later.

  The thickness of the birefringent layer formed on the substrate is usually preferably set to 0.2 to 100 μm, more preferably 0.5 to 50 μm, and particularly preferably 1 to 20 μm. If the thickness is 0.2 μm or more, a sufficient phase difference is obtained for the birefringent film finally obtained, and if it is 100 μm or less, the uniformity during formation is also excellent. In addition, since the relationship between the thickness of the birefringent layer and the substrate is excellent in uniformity when a stretching process is performed as described later, the thickness of the birefringent layer is preferably smaller than the thickness of the substrate. The thickness of the birefringent layer is more preferably half or less of the thickness of the substrate.

  Subsequently, the optically uniaxial birefringent layer formed on the substrate is further subjected to stretching treatment. Thus, if the birefringent layer is stretched in one direction within the plane, only nx can be greatly changed without greatly changing ny and nz, so that optical uniaxiality (nx> nz, The birefringent layer exhibiting ny> nz) further causes a difference in refractive index within the surface, and exhibits optical biaxiality (nx> ny> nz). Therefore, the thickness direction retardation value represented by (nx−nz) · d (d is the thickness) in the optically uniaxial birefringent layer is not significantly changed, and is represented by (nx−ny) · d. The in-plane retardation value can be controlled by the stretching process. That is, by this stretching treatment, the in-plane birefringence can be further changed to change the optical characteristics.

  As described above, the stretching temperature in the stretching treatment may be not less than the glass transition temperature of the base material and not more than the glass transition temperature of the birefringent material. If the stretching temperature is lower than the glass transition temperature, enormous tension is required for stretching, and the stretching conditions of the optically uniaxial birefringent layer may not be controlled. On the other hand, when the stretching temperature exceeds the glass transition temperature of the birefringent material, the temperature with respect to the substrate is too high, and thus stretching of the optically uniaxial birefringent layer may not be controlled. The stretching temperature only needs to satisfy such conditions, and can be set, for example, by selecting the type of the base material and the type of the birefringent material. Specifically, the base material and the birefringent material are preferably selected so that the stretching temperature is in the range of 40 to 250 ° C, more preferably in the range of 80 to 220 ° C, and still more preferably in the range of 100 to 200 ° C. It is.

  The method for stretching the birefringent layer is not particularly limited, and for example, only the birefringent layer may be stretched, or it can be performed by pulling the laminate of the base material and the birefringent layer together. For this reason, it is preferable to directly stretch only the base material. When only the base material is stretched, the birefringent layer on the base material is indirectly stretched by the tension generated in the base material by this stretching. And, since stretching the single layer body is usually uniform stretching rather than stretching the laminate, if only the base material is stretched uniformly as described above, the base material This is because the above birefringent layer can also be stretched uniformly. In addition, after peeling a birefringent layer from the said base material, only the said birefringent layer can also be extended | stretched.

  Moreover, it is preferable to cool an optical biaxial birefringent layer to room temperature as needed after completion | finish of extending | stretching. At this time, if the tension at the time of stretching is suddenly released, wrinkles are likely to occur. For example, it is preferable to release the tension after cooling in a state where the tension is applied.

  The stretching method is not particularly limited, and examples thereof include uniaxial stretching that applies tension in one direction and biaxial stretching that applies tension in two orthogonal directions. In the present invention, since the birefringent layer on the substrate already exhibits optically uniaxiality, uniaxial stretching is sufficient to change to optically biaxiality, but the optical properties are further adjusted. For example, the biaxial stretching is effective.

  The draw ratio is not particularly limited, and can be appropriately determined according to, for example, the type of the base material or the birefringent material, desired optical characteristics (for example, in-plane retardation), and the like. Specifically, the draw ratio is, for example, preferably 1.01 to 2 times, more preferably 1.01 to 1.5 times, and still more preferably 1.01 to 1.3 times. If the draw ratio is 1.01 times, the birefringent film to be formed can be practically used as an optical biaxial film. Nonuniformity can be sufficiently suppressed.

  Thus, the birefringent layer on the substrate changes to optical biaxiality, and the birefringent film of the present invention is obtained. The thickness of the birefringent film of the present invention on this substrate is not particularly limited, but is, for example, in the range of 0.5 to 40 μm, preferably in the range of 1 to 20 μm, more preferably 1 to 10 μm. It is a range. Moreover, the thickness of the base material after extending | stretching is 5-150 micrometers, for example, Preferably it is 10-100 micrometers, Most preferably, it is 30-80 micrometers.

  In addition, when the production method of the present invention is industrially performed, for example, an optically uniaxial birefringent layer as described above is formed on a roll base material, and further continuously stretched. It is preferable to carry out. When uniaxial stretching is performed as the stretching treatment, longitudinal stretching or lateral stretching may be performed. The longitudinal stretching means stretching along the direction in which the film advances by the rotation of the roll, and the lateral stretching refers to a direction perpendicular to the traveling direction of the film and stretching along the width direction of the roll. Means that. In the case of longitudinal stretching, the X-axis direction of the obtained birefringent film is usually the longitudinal direction of the film (traveling direction = stretching direction), while in the case of lateral stretching, the width direction of the film (width direction of the roll = normally). (Stretching direction) becomes the X-axis direction, and the X-axis directions of the two differ by 90 °. Longitudinal stretching and transverse stretching are preferred because they are industrially easy to operate and the apparatus is simplified. On the other hand, for example, when the roll-shaped birefringent film obtained by the production method of the present invention and another roll-shaped optical film are continuously bonded, the transverse stretching is easily continuous from the viewpoint of optical properties. It is preferable because it can be easily laminated. This is because when a plurality of films are laminated, the optical performance varies depending on the direction of the maximum refractive index direction of the birefringent film. Further, in the case of transverse stretching, a certain amount of tension may be required in the longitudinal direction of the film for conveyance, but by setting the tension in the width direction sufficiently larger than the tension in the longitudinal direction, Uniaxial stretching in the width direction can be performed.

  In addition, the production method of the present invention does not apply the stretching treatment as described above, but uses the shrinkage of the base material to form an optically uniaxial birefringent layer formed on the base material. It can also be changed to biaxial. Specifically, an optically uniaxial birefringent layer is formed on a base material that exhibits contractibility in at least one direction in the plane, and the birefringent layer contracts as the base material contracts. It is a method to make it. According to this method, the optically uniaxial birefringent layer formed on the base material as described above contracts similarly in the plane direction as the base material contracts. For this reason, the birefringent layer further has a refractive difference in the plane, and exhibits optical biaxiality (nx> ny> nz). Also in this shrinkage treatment, the treatment temperature is not less than the glass transition temperature of the base material and not more than the glass transition temperature of the birefringent material, as in the stretching treatment. The difference between the elastic modulus and the elastic modulus of the birefringent material is in the range of 500 to 900 MPa. When the difference in elastic modulus is less than 500 MPa, for example, there is a problem that wrinkles enter and the appearance is poor, and when it exceeds 900 MPa, there is a problem that shrinkage does not occur.

  The shrinkability of the base material can be imparted, for example, by fixing one end of the base material in advance and stretching in any one direction in the plane prior to the application of the birefringent material. In this way, by stretching in advance, a contraction force is generated in the direction opposite to the stretching direction. By utilizing the in-plane shrinkage difference of the base material, an in-plane refractive index difference is imparted to the birefringent material. Specific conditions are shown below.

  First, an optically uniaxial birefringent layer is formed on the shrinkable substrate in the same manner as described above. And the said base material is contracted by heat-processing to the said base material. As the base material contracts, the birefringent layer on the base material contracts, so that the birefringent layer exhibits optical biaxiality from optical uniaxiality. Thus, the birefringent film of the present invention is obtained. In addition, it does not restrict | limit especially as conditions of the said heat processing, For example, although it can determine suitably with the kind etc. of the material of the said base material, For example, it is the same as the extending | stretching temperature in the above-mentioned extending | stretching process.

  According to the manufacturing method as described above, the refractive index is precisely controlled by suppressing the variation of the shaft angle, and the optical characteristics such as the refractive index, the birefringence, the in-plane direction and the thickness direction phase difference are provided. A uniform optical biaxial birefringent film of the present invention can be obtained.

The birefringent film obtained by the production method of the present invention has an in-plane retardation value “(nx-ny) · d”, that is, the variation in retardation is, for example, −8% to + 8%, Preferably, it is -7% to + 7%, more preferably -6% to + 6%. The accuracy of the thickness direction retardation value “(nx-nz) · d” is, for example, −5% to + 5%, preferably −4% to + 4%, more preferably −3% to + 3%. The accuracy of each phase difference can be measured as follows. First, it is an intermediate point in the direction (Y-axis direction) perpendicular to the stretching direction (or shrinkage direction: X-axis direction) of the birefringent film, and is equally divided into 14 equal parts in the stretching direction (X-axis direction). The in-plane retardation and the thickness direction retardation are measured at 13 points excluding the end at the time. Then, assuming that the average value is 100%, the difference between each measured value and the average value is calculated as the accuracy (%) of the in-plane retardation and the thickness direction retardation.

The birefringent film obtained by the production method of the present invention preferably has an axial angle distribution in the X-axis direction of ± 1 ° or less, more preferably ± 0.5 ° or less. According to the above-described method, since the axial angle distribution can be controlled within such a range, the refractive index can be made uniform. The axial angle distribution can be calculated, for example, by measuring the axial angle at the 13 points in the same manner as the phase difference and calculating the difference between the measured values with respect to the average value. The axial angle distribution can be automatically calculated using, for example, an automatic birefringence meter (trade name KOBRA-21ADH; manufactured by Oji Scientific Instruments).

When the birefringent film obtained by the production method of the present invention is formed on a substrate by the production method of the present invention as described above, for example, it may be used as a laminate with the substrate, It can also be used as a single layer peeled from the substrate. In addition, after peeling from the base material (hereinafter referred to as “first base material”), the base material (hereinafter referred to as “second base material”) that does not interfere with the optical properties thereof is again passed through the adhesive layer. It can also be used after being laminated (transferred).

  The second substrate is not particularly limited as long as it has appropriate flatness, and for example, glass, a transparent polymer film having optical isotropy, and the like are preferable. Examples of the polymer film include polymethacrylate, polystyrene, polycarbonate, polyethersulfone, polyphenylene sulfide, polyarylate, amorphous polyolefin, TAC, epoxy resin, isobutene / N-methylmaleimide copolymer and acrylonitrile / styrene as described above. Examples thereof include a film formed from a resin composition with a copolymer. Among these, polymethyl methacrylate, polycarbonate, polyarylate, TAC, polyether sulfone, a resin composition of an isobutene / N-methylmaleimide copolymer and an acrylonitrile / styrene copolymer, and the like are preferable. Moreover, even if it is a base material which shows optical anisotropy, it can be used according to the objective. Examples of such an optically anisotropic substrate include a retardation film obtained by stretching a polymer film such as polycarbonate polystyrene or norbornene resin, a polarizing film, and the like.

  The adhesive layer in the transfer as described above may be used for optical purposes. For example, acrylic, epoxy, urethane adhesives and pressure-sensitive adhesives can be used.

  The method for peeling the birefringent film from the substrate is not particularly limited, and can be selected according to the adhesion between the birefringent film and the substrate. For example, a method of mechanically peeling using a roll or the like, pasting A method of mechanically peeling after dipping in a poor solvent for all the materials of the combined structure, a method of peeling by ultrasonic treatment in the poor solvent, and a difference in thermal expansion coefficient between the substrate and the birefringent film The method of peeling by temperature change using it etc. is mention | raise | lifted.

Next, the optical film of the present invention only needs to include the birefringent film obtained by the production method of the present invention as described above, and the configuration thereof is not limited, for example, including a substrate as described above. .

  The optical film of the present invention preferably further has a pressure-sensitive adhesive layer in the outermost layer. This is because it becomes easy to bond the optical film of the present invention to other members such as other optical layers and liquid crystal cells, and the optical film of the present invention can be prevented from peeling off. Moreover, the one surface of the optical film of this invention may be sufficient as the said adhesive layer, and it may be arrange | positioned at both surfaces.

  The material for the adhesive layer is not particularly limited, and for example, acrylic, silicone, polyester, rubber-based adhesives can be used. Alternatively, these materials may contain fine particles to form a layer exhibiting light diffusibility. Among these, for example, a material excellent in hygroscopicity and heat resistance is preferable. With such a property, for example, when used in a liquid crystal display device, it can prevent foaming and peeling due to moisture absorption, deterioration of optical characteristics due to a difference in thermal expansion, warpage of the liquid crystal cell, etc., and high quality and durability. The display device is also excellent.

The optical film of the present invention may be a birefringent film alone obtained by the production method of the present invention as described above, or may be a laminate combined with other optical members as necessary. The other optical member is not particularly limited, and examples thereof include other birefringent films, other retardation films, liquid crystal films, light scattering films, lens sheets, diffraction films, and polarizing plates.

  When the optical film of the present invention includes the polarizing plate, the polarizing plate may be only a polarizer, or a transparent protective layer may be laminated on one side or both sides of the polarizer.

  The optical film of the present invention is preferably used for forming various devices such as a liquid crystal display device. For example, the optical film can be disposed on one side or both sides of a liquid crystal cell to form a liquid crystal panel and used for a liquid crystal display device. In addition, the arrangement | positioning method in particular of an optical film is not restrict | limited, It is the same as that of the optical film containing the conventional birefringent film.

  The type of the liquid crystal cell forming the liquid crystal display device can be arbitrarily selected. For example, it is represented by an active matrix driving type such as a thin film transistor or MIM, an IPS driving type, a plasma addressing driving type, a twisted nematic type or a super twisted nematic type. Various types of liquid crystal cells such as a simple matrix driving type can be used. Specifically, for example, STN (Super Twisted Nematic) cell, TN (Twisted Nematic) cell, IPS (In-Plan Switching) cell, VA (Vertical Nematic) cell, OCB (Optically Controlled Birefringence) cell, HAN (Hybrid Aligned) Nematic) cell, ASM (Axially Symmetric Aligned Microcell) cell, ferroelectric / antiferroelectric cell, and those obtained by regular alignment division and those obtained by random alignment division.

  As such a liquid crystal display device provided with the optical film of the present invention, for example, a transmissive type provided with a back lime system, a reflective type provided with a reflective plate, a projection type, or the like may be used.

  In addition, the optical film of this invention is not limited to the above liquid crystal display devices, For example, it can be used also for self-luminous display devices, such as an organic electroluminescent (EL) display, PDP, and FED. In this case, the configuration is not limited except that the optical film of the present invention is used instead of the conventional optical film.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples. Various characteristics were measured by the following methods.

(Measurement of birefringence, phase difference, shaft angle distribution)
The value at a wavelength of 590 nm was measured using an automatic birefringence meter (trade name: KOBRA-21ADH; manufactured by Oji Scientific Instruments).

(Thickness measurement)
The film thickness of the birefringent layer was measured using an instantaneous multi-photometry system (trade name MCPD-2000; manufactured by Otsuka Electronics Co., Ltd.).

  Using 2,2'-bis (3,4-dicarboxyphenyl) hexafluoropropanoic dianhydride (6FDA) and 2,2'-bis (trifluoromethyl) -4,4'-diaminobiphenyl (PFMB) Thus, a polyimide (Mw = 120000) composed of a repeating unit represented by the following general formula (6) was synthesized. This polyimide was dissolved in MIBK so that it might become 20 weight%, and the polyimide solution was prepared. This polyimide solution was continuously applied to a TAC film (length 200 m, width 1330 mm, thickness 80 μm; manufactured by Fuji Film Co., Ltd.) by a blade coating method. The coated film was dried at 130 ° C. for 2 minutes to form a 6.2 μm thick polyimide film. This polyimide film exhibited optically uniaxial (nx = ny> nz) birefringence. Furthermore, at a temperature (150 ° C.) that is not lower than the glass transition temperature (150 ° C.) of the substrate and not higher than the glass transition temperature (300 ° C.) of the polyimide, uniaxial stretching (longitudinal stretching) is performed in the longitudinal direction of the film. (Stretching ratio: 1.04 times). By this stretching treatment, the film was stretched 3.2% with respect to the film before stretching in the longitudinal direction of the film, and contracted 4.8% with respect to the film before stretching in the width direction of the film. The elastic modulus of the base material at a stretching temperature of 150 ° C. was 300 MPa, and the elastic modulus of the polyimide was 1000 MPa.

前記ＴＡＣフィルム上に形成された延伸後のポリイミドフィルムを、粘着剤を介してガラス基板に接着してから、前記ＴＡＣフィルムを剥離除去した。ガラス基板上の延伸ポリイミドフィルムは、光学二軸性（ｎｘ＞ｎｙ＞ｎｚ）を示す複屈折フィルムであり、面内最大の屈折率を示すＸ軸方向は、延伸方向と同一であった。このガラスと複屈折フィルムとの積層体について、前述のように、延伸方向（Ｘ軸方向）に１０ｃｍ間隔で合計１３点、ポリイミドフィルムの膜厚、位相差、軸角度分布の測定を行った。

After the stretched polyimide film formed on the TAC film was adhered to a glass substrate via an adhesive, the TAC film was peeled off. The stretched polyimide film on the glass substrate is a birefringent film exhibiting optical biaxiality (nx>ny> nz), and the X-axis direction indicating the maximum in-plane refractive index was the same as the stretching direction. As above-mentioned, about the laminated body of this glass and a birefringent film, a total of 13 points | pieces were carried out at a 10-cm space | interval in the extending | stretching direction (X-axis direction), and the film thickness, phase difference, and axial angle distribution of the polyimide film were measured.

  As a result, the birefringent film has an axial angle distribution of ± 0.6 °, an in-plane retardation (nx-ny) · d of 72.1 ± 3 nm, an accuracy of ± 5%, and a thickness direction retardation (nx− nz) · d was 234.0 ± 5 nm, and the accuracy was ± 2.5%.

(Comparative Example 1)
Except that the temperature at the time of stretching was set to a temperature (135 ° C.) that is lower than the glass transition temperature (150 ° C.) of the substrate and not higher than the glass transition temperature (300 ° C.) of the polyimide, the same as in Example 1 above. A birefringent film was manufactured and its characteristics were investigated. The elastic modulus of the base material at a stretching temperature of 135 ° C. was 700 MPa, and the elastic modulus of the polyimide was 1000 MPa.

  As a result, the birefringent film exhibits optical biaxiality of nx> ny> nz, the axial angle distribution is ± 2 °, the in-plane retardation (nx-ny) · d is 55.4 ± 10 nm, and its accuracy ± 18%, thickness direction retardation (nx-nz) · d was 238.0 ± 20 nm, and the accuracy was ± 8.4%.

(Comparative Example 2)
The temperature during stretching is set to a temperature (180 ° C.) that is not lower than the glass transition temperature (150 ° C.) of the substrate and not higher than the glass transition temperature (300 ° C.) of the polyimide, and the elasticity of the substrate at a stretching temperature of 180 ° C. A birefringent film was produced in the same manner as in Example 1 except that the modulus was 2 MPa and the modulus of elasticity of the polyimide was 950 MPa, and the characteristics thereof were examined. As a result, since the elastic modulus of the substrate was too small and the difference in elastic modulus was high, when the polyimide was stretched through the substrate, it was broken and an optical biaxial birefringent film could not be obtained.

  As described above, according to Example 1 that satisfies the above-described conditions regarding the stretching temperature and the elastic modulus, the in-plane retardation and the thickness direction retardation are more varied than those in Comparative Example 1 that does not satisfy the conditions of the stretching temperature and the elastic modulus. Was extremely suppressed. For this reason, according to the manufacturing method of this invention, it can be said that the optical biaxial birefringent film excellent in optical uniformity is obtained.

As described above, by setting the temperature in the stretching process and the elastic modulus of the base material and the birefringent material to the above-described conditions, the refractive index can be uniformly controlled, and the birefringence, in-plane direction, and thickness direction can be controlled. The optical biaxial birefringent film of the present invention having a uniform retardation and excellent optical characteristics can be obtained. Thus, the birefringent film excellent in optical characteristics is useful for various optical films, for example, and when applied to various image display devices such as liquid crystal display devices, excellent display characteristics can be realized.

Claims (5)

A step of coating a birefringent material on a substrate, a step of fixing the coating film to form an optically uniaxial birefringent layer on the substrate, and an optical birefringence of the birefringent layer A method for producing an optically biaxial birefringent film, the method comprising:
The step of changing the birefringence of the birefringent layer to optical biaxiality is the optical uniaxiality under a temperature condition not lower than the glass transition temperature of the substrate and not higher than the glass transition temperature of the birefringent material. Is a step of subjecting the birefringent layer to stretching treatment,
The method for producing a birefringent film, wherein a difference between an elastic modulus of the base material and an elastic modulus of the birefringent material during the stretching treatment is in a range of 500 to 900 MPa. The step of changing the birefringence of the birefringent layer to optical biaxiality is a temperature condition that is not less than the glass transition temperature of the base material and not more than the glass transition temperature of the birefringent material, instead of the stretching treatment. Below, a step of applying a shrinkage treatment to the optically uniaxial birefringent layer,
The method according to claim 1, wherein a difference between an elastic modulus of the base material and an elastic modulus of the birefringent material during the shrinkage treatment is in a range of 500 to 900 MPa. The manufacturing method according to claim 1, wherein the birefringent material is a non-liquid crystalline material . The method according to claim 3, wherein the non-liquid crystalline material is at least one polymer material selected from the group consisting of polyamide, polyimide, polyester, polyetherketone, polyamideimide, and polyesterimide. The said base material is a transparent polymer film, The manufacturing method as described in any one of Claims 1-4.