JP4260571B2 - Birefringent layer manufacturing method, birefringent layer, and polarizing plate using the same - Google Patents

Description

  The present invention relates to a method for producing a birefringent layer, a birefringent layer, a laminated polarizing plate using the birefringent layer, and various image display devices.

  Conventionally, in various liquid crystal display devices, an optical uniaxial or optical biaxial birefringent film is used for the purpose of visual field compensation.

  The uniaxial birefringent film is usually used by laminating a plurality of sheets. For example, a stretched polymer film (Patent Document 1), an unstretched polyimide film (Patent Document 2, Patent Document 3, Patent Literature 4, Patent Literature 5) and the like are disclosed. On the other hand, a biaxial birefringent film prepared by biaxial stretching of a polymer film is disclosed (Patent Document 6).

  Such various birefringent films usually control the birefringence by changing the stretching ratio and the stretching direction, but there is a problem that the control is very difficult. Specifically, for example, by increasing the stretch ratio, the birefringence increases, but the film becomes extremely thin, so the strength decreases and the birefringence uniformity also decreases. There is. On the other hand, in order to avoid such a problem, there is a method of preparing a thick film in advance and stretching it to ensure the thickness of the birefringent film to be produced to a practical level. The formation of the film is liable to cause uneven thickness and is extremely difficult in terms of technology. Even if a thick film can be formed, further advanced technology is required for precisely stretching the thick film itself. In addition, the stretching method itself, which is a means for controlling the birefringence, has a disadvantage that the yield is poor.

In addition, for birefringent films made of polyimide, it is also shown that the birefringence value can be increased by changing the polyimide structure, specifically, by increasing the linearity and rigidity of the polyimide main chain. Yes. However, there is a problem that the raw material monomers (for example, diamine, acid dianhydride, etc.) necessary for changing the structure of polyimide are limited in availability.
US Pat. No. 5,138,474 US Pat. No. 513847 US Pat. No. 5,480,964 US Pat. No. 5,580,950 US Pat. No. 6,387,753B1 JP 2000-190385 A

  Accordingly, an object of the present invention is to provide a method for producing a birefringent layer in which the birefringence can be easily controlled.

In order to achieve the above object, the method for producing a birefringent layer according to the present invention forms a coating film by applying a forming material solution in which a forming material of a birefringent layer is dispersed or dissolved in a solvent onto a substrate. A step of forming a birefringent layer on the substrate by solidifying the coating film,
By selecting the solvent to be used according to its volatilization rate, the birefringence of the birefringent layer is controlled,
In controlling the birefringence of the birefringent layer, a solvent having a relatively high volatilization rate is selected from five types of solvents in which the volatilization rate is in the order of acetone> ethyl acetate>toluene>2-methylpentanone> cyclohexanone. Thus, the birefringence is set to a large value, and by selecting a solvent having a relatively low volatilization rate, the birefringence is set to a small value .

  Thus, the birefringence of the birefringent layer to be formed can be easily controlled by selecting the solvent according to the volatilization rate. Specifically, for example, if a solvent having a relatively high volatilization rate is used, a birefringent layer having a larger birefringence than a birefringent layer using a solvent having a relatively low volatilization rate can be obtained. On the other hand, if a solvent having a relatively low volatilization rate is used, a birefringent layer having a smaller birefringence than a birefringent layer using a solvent having a relatively high volatilization rate can be obtained. Therefore, when setting a desired birefringence according to the purpose of use of the birefringent layer, the birefringence can be easily controlled by selecting the type of solvent. For this reason, for example, the problem due to the stretching process as described above can be avoided and can be used together with the stretching process, so that the problem due to the stretching process that has conventionally occurred can be reduced. According to such a manufacturing method, the birefringence can be easily controlled, and variations of the birefringence that can be set are widened. For example, the birefringence layer applied to various image display devices, particularly VA mode liquid crystal display devices. It can be said that this is a very useful method.

  In the birefringence control method of the present invention, a forming material liquid in which a forming material of a birefringent layer is dispersed or dissolved in a solvent is applied onto a substrate to form a coating film, and the coating film is solidified. Thus, when the birefringent layer is formed on the substrate, the birefringence of the birefringent layer is controlled by selecting the solvent to be used according to its volatilization rate. And the manufacturing method of this invention is a manufacturing method of a birefringent layer which controls a birefringence using the control method of the said this invention. That is, as described above, a process of forming a coating film by coating a forming material liquid in which a forming material of a birefringent layer is dispersed or dissolved in a solvent on a substrate, and solidifying the coating film Forming a birefringent layer on the substrate according to the method for producing a birefringent layer, wherein the solvent to be used is selected according to its volatilization rate, whereby the birefringence of the birefringent layer is determined. It is a manufacturing method to control. Thus, by selecting the solvent according to the volatilization rate, the birefringence of the birefringent layer can be controlled, specifically, the birefringence ΔNxz in the thickness direction of the birefringent layer can be controlled, In particular, by controlling the refractive index nz, ΔNxz shown in the following formula can be controlled.

ΔNxz = nx−nz
In the above formula, nx and nz respectively indicate the refractive indexes of the X-axis and the Z-axis in the birefringent layer, and the X-axis is an axial direction indicating the maximum refractive index in the plane of the birefringent layer. Yes, the Z-axis indicates the thickness direction perpendicular to the X-axis. In addition, ny mentioned later shows the refractive index of the Y-axis in the said birefringent layer, and the said Y-axis shows the axial direction perpendicular | vertical to the said X-axis in the surface of the said birefringent layer.

  The mechanism by which the birefringence of the birefringent layer increases when the solvent volatilization rate is relatively high is unknown, but is presumed as follows. That is, when a non-liquid crystalline polymer as described later is used as the material for forming the birefringent layer, the polymer self-orients depending on its properties when the solvent volatilizes, but the self-orientation time is controlled by the solvent volatilization rate. As a result, it is considered that the degree of orientation of the polymer and the birefringence index associated therewith are controlled.

  In the present invention, the volatilization rate of the solvent can be relatively determined by measuring the volatilization rates of various solvents under the same conditions. For this reason, the measuring method of the volatilization rate of the solvent is not limited at all except that it is measured under the same conditions, and examples thereof include the following methods. The volatilization rate measurement method is used only for specifying the relative relationship of volatilization rates of various solvents. The production method of the present invention, the birefringent layer produced by this method, its use, and usage There are no restrictions.

The volatilization rate is measured by, for example, putting a constant weight of solvent in a container, placing the container under a predetermined temperature condition, and measuring a decrease amount (weight) when a predetermined time elapses. sec). Specifically, 2.0 g of solvent is weighed into an aluminum container (bottom area 30 cm ² ), and this container is placed on a hot plate at 100 ° C. and heated. Then, the amount of weight loss (Xg) 20 seconds after the start of heating is measured, and the volatilization rate (g / sec) is obtained from the formula “Xg / 20 sec”.

  The volatilization rates of various solvents measured by this method are shown in Table 1 below. For the solvents shown in Table 1 below, the volatilization rate increases in the order of acetone> ethyl acetate> toluene> 2-methylpentanone> cyclohexanone. Therefore, when selecting a solvent from these five types, acetone may be selected when setting the highest birefringence. Then, the birefringence can be set to be smaller as the upper acetone is changed to the lower cyclohexane in Table 1 below, and the lowest birefringence is obtained when cyclohexane is selected.

  The material for forming the birefringent layer is not particularly limited, but is preferably a non-liquid crystalline material, particularly a non-liquid crystalline polymer. If such a non-liquid crystalline material is used, for example, unlike a liquid crystalline material, the optically negative uniaxiality (nx> nz), (ny> nz) can be formed. For this reason, for example, the transparent polymer substrate to be used is not limited to the alignment substrate. For example, even if it is an unaligned substrate, the alignment film is formed on the surface thereof as in the case of using a liquid crystal material. There is no need to form or laminate by coating.

  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, a halogen, a C _1-3 alkyl group, a C _1-3 halogenated alkyl group, a phenyl group, or a substituted phenyl group, and in a plurality of cases, they are the same or different. Examples of the substituted phenyl group include substituted phenyl groups having at least one kind of substituent selected from the group consisting of halogen, C _1-3 alkyl group, and C _1-3 halogenated alkyl group. 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 the same or different and are, for example, halogen, C _1-3 alkyl group, C _1-3 halogenated alkyl group, phenyl group, or substituted phenyl group. is there. Examples of the halogen include fluorine, chlorine, bromine and iodine. Examples of the substituted phenyl group include substituted phenyl groups having at least one type of substituent selected from the group consisting of halogen, C _1-3 alkyl groups, and C _1-3 halogenated alkyl groups. .

  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 2,2 ', 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′-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, 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-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.

A represents, for example, hydrogen, halogen, C _1-3 alkyl group, C _1-3 halogenated alkyl group, an alkoxy group represented by OR (where R is as defined above), aryl Group, substituted aryl group by halogenation, C _1-9 alkoxycarbonyl group, C _1-9 alkylcarbonyloxy group, C _1-12 aryloxycarbonyl group, C _1-12 arylcarbonyloxy group and substituted derivatives thereof, C It is selected from the group consisting of a _1-12 arylcarbamoyl group and a C _1-12 arylcarbonylamino group and substituted derivatives thereof, and in the plurality of cases, they are the same or different. The A ′ is, for example, selected from the group consisting of halogen, C _1-3 alkyl group, C _1-3 halogenated alkyl group, phenyl group and substituted phenyl group, and in a plurality of cases, they are the same or different. Examples of the substituent on the phenyl ring of the substituted phenyl group include halogen, C _1-3 alkyl group, C _1-3 halogenated alkyl group, 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, glass 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, the base material and the birefringence index of the present invention formed on the base material can be used as a laminate. It is. 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.

  In addition, since the coating film formed from the polymer as described above is optically negative uniaxial as described above, when the non-liquid crystal polymer is used as a birefringent layer forming material, It is not necessary to use the orientation of the substrate for forming the birefringent layer. 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.

  The base material is, for example, a base material having a low glass transition point (Tg), a base material having a high elastic modulus, a base material having the same or larger linear expansion as the birefringent layer forming material, and a high heat transfer coefficient. A substrate, a substrate having a high aspect ratio, a substrate having a small thickness, and the like are preferable.

  Next, although an example of the manufacturing method of the birefringent layer of this invention is shown, it does not restrict | limit to this.

  First, the forming material liquid (coating liquid) is prepared by dispersing or dissolving the forming material of the birefringent layer in a solvent. In the present invention, the birefringence ΔNxz of the formed birefringent layer is controlled by appropriately selecting the type of the solvent as described above. Therefore, the correlation between the volatilization rates between the respective solvents may be examined in advance as described above, and the solvent may be selected as described above.

  The concentration of the forming material in the coating liquid is not particularly limited. For example, since the viscosity is easy to apply, the forming material is, for example, 5 to 50 parts by weight with respect to 100 parts by weight of the solvent. Is preferable, and more preferably 10 to 40 parts by weight. Specifically, when the forming material is a non-liquid crystalline polymer, the amount of the polymer added is preferably, for example, 5 to 50 parts by weight, more preferably 10 parts by weight with respect to 100 parts by weight of the solvent. ~ 40 parts by weight.

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

  In addition, the coating liquid may contain other different resins as long as, for example, the orientation of the forming material is not significantly reduced. 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 said other resin etc. with the said coating liquid, the compounding quantity is 0-50 mass% with respect to the said polymer material, for example, Preferably, it is 0-30 mass. %.

  Next, the prepared coating solution is applied to the surface of the substrate to form a coating film of the forming 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 20 μm or more, more preferably 30 μm or more. In addition, after the formation of the coating film, in the case where a stretching treatment is performed as described later, for example, it is in the range of 10 to 200 μm, preferably in the range of 20 to 150 μm, particularly preferably in the range of 30 to 100 μm. is there.

  Then, the coating film formed on the substrate is dried. By this drying, the forming material such as polyimide is solidified on the base material, and a birefringent layer is formed.

  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 layer forming material, the type of the solvent, etc. For example, the temperature is usually 40 ° C. to 400 ° C., preferably 50 ° C. to 300 ° C. It is 60 degreeC, More preferably, it is 60 to 200 degreeC. 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 30 minutes, preferably 30 seconds to 25 minutes, and more preferably 1 minute to 20 minutes or less.

  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.

  Thus, the birefringent layer formed on the base material is nx> nz, ny> nz regardless of the orientation of the substrate due to the nature of the non-liquid crystal polymer, and is optically negative uniaxial. This is a birefringent layer exhibiting properties (nx≈ny> nz). As for the birefringence obtained by such a manufacturing method, the birefringence ΔNxz is controlled by appropriately selecting the type of the solvent as described above.

  The production method of the present invention may further include a step of stretching or shrinking the coating film after the coating film is solidified. As described above, the coating film exhibiting optical uniaxiality (nx≈ny> nz) as described above can be further reduced in the in-plane refractive difference by stretching or shrinking the coating film in one direction in the plane. Resulting in optical biaxiality (nx> ny> nz). For this reason, not only the birefringence in the thickness direction but also the birefringence in the in-plane direction can be further changed, and a more useful birefringent layer can be formed.

  The stretching method of the coating film is not particularly limited, and for example, only the coating film may be stretched, or it can be performed by pulling the laminate of the base material and the coating film together. For this reason, it is preferable to directly stretch only the base material. When only the base material is stretched, the coating film on the base material is stretched indirectly 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 upper coating film can also be stretched uniformly.

  The stretching method is not particularly limited. For example, free end longitudinal stretching that is uniaxially stretched in the longitudinal direction, fixed end lateral stretching that is uniaxially stretched in the width direction in a state where the longitudinal direction of the base material is fixed, the longitudinal direction and the width direction Examples of the method include sequential or simultaneous biaxial stretching in which stretching is performed in both of the above.

  The stretching conditions are not particularly limited, and can be appropriately determined according to, for example, the type of the base material or the birefringent layer forming material. As a specific example, the draw ratio is preferably greater than 1 and not greater than 5 times, more preferably greater than 1 and not greater than 4 times, and particularly preferably greater than 1 and not greater than 3 times. The thickness of the base material after stretching is, for example, 5 to 150 μm, preferably 10 to 100 μm, and particularly preferably 30 to 80 μm.

  The thickness of the birefringent layer thus formed 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. is there.

  In addition, the birefringent layer exhibiting negative biaxiality can be formed on the base material by utilizing the shrinkage of the base material instead of performing the stretching treatment as described above. Specifically, a coating film is formed by directly coating the coating liquid on a base material that exhibits shrinkage in one direction in the plane, and the coating film is formed along with the shrinkage of the base material. This is a method of contraction. According to this method, the coating film showing negative uniaxiality formed on the base material as described above is similarly contracted in the surface direction as the base material contracts. For this reason, the coating film further has an in-plane refractive difference and exhibits optical biaxiality (nx> ny> nz).

  The shrinkability of the substrate can be imparted, for example, by fixing one end of the base material in advance and stretching in any one direction within the surface prior to the application of the forming 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 substrate, an in-plane refractive index difference is imparted to the coating film forming material. Specific conditions are shown below.

  Although the thickness of the said base material before extending | stretching is not restrict | limited in particular, For example, it is the range of 10-200 micrometers, Preferably it is the range of 20-150 micrometers, Especially preferably, it is the range of 30-100 micrometers. The stretching ratio is not particularly limited as long as the birefringent layer formed on the stretched substrate exhibits optical biaxiality (nx> ny> nz). The method for imparting shrinkage to the substrate is not limited to this.

  Next, a coating film 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. With the shrinkage of the base material, the coating film on the base material shrinks, whereby the coating film exhibits negative biaxiality. The conditions for the heat treatment are not particularly limited and can be appropriately determined depending on, for example, the type of material of the base material. For example, the heating temperature is in the range of 25 to 300 ° C, preferably 50 to 200 ° C. The range is particularly preferably 60 to 180 ° C.

  In addition, although the said forming material which forms a coating film is solidified on a base material, for example by drying etc., the heat processing which shrinks this base material may serve as the solidification process of a forming material.

The birefringent layer (hereinafter referred to as “birefringent layer of the present invention”) produced by the above production method has a birefringence controlled by the selection of the solvent. Compared with the case where the refractive index is controlled, the birefringence uniformity is excellent, and the manufacturing yield is also excellent.

  The birefringent layer of the present invention may be used, for example, as a laminate with the substrate, or may be used as a single layer peeled from the substrate after being formed on the substrate.

  The birefringent layer of the present invention preferably further has an adhesive layer. This is because adhesion between the birefringent layer of the present invention and other members such as other optical layers and liquid crystal cells can be facilitated, and peeling of the birefringent layer of the present invention can be prevented. The pressure-sensitive adhesive layer may be one surface of the birefringent layer of the present invention or may be laminated on 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 birefringent layer of the present invention can be used for the purpose of visual compensation alone or as a laminate in combination 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, diffraction films, and polarizing films (polarizers).

  The laminated polarizing plate of the present invention is characterized by including the birefringent layer of the present invention, and the configuration is not particularly limited as long as it has the birefringent layer and polarizing plate of the present invention. As the polarizing plate, for example, only a polarizer may be used, or a transparent protective layer may be laminated on one side or both sides of the polarizer.

  As described above, the birefringent layer and the laminated polarizing plate of the present invention are preferably used for forming various devices such as a liquid crystal display device. For example, the birefringent layer and the laminated polarizing plate of the present invention are used on one side of a liquid crystal cell. Alternatively, a liquid crystal panel can be arranged on both sides and used for a liquid crystal display device.

  The type of the liquid crystal cell forming the liquid crystal display device can be arbitrarily selected, for example, an active matrix drive type represented by a thin film transistor type, a simple matrix drive type represented by a twist nematic type or a super twist nematic type. Various types of liquid crystal cells 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 Compensated Birefringence) cell, HAN (Hybrid Aligned) Nematic) cells, ASM (Axially Symmetric Aligned Microcell) cells, ferroelectric / antiferroelectric cells, and those in which regular alignment division is performed on these cells, and those in which random alignment division is performed are applicable. Among these, the birefringent layer and the polarizing plate of the present invention are very excellent particularly in optical compensation of VA (Vertical Aligned) cells, so that they are very useful as viewing angle compensation films for VA mode liquid crystal display devices. Useful.

  In addition, the birefringent layer and the laminated polarizing plate of the present invention are not limited to the liquid crystal display device as described above, and are also used for self-luminous display devices such as an organic electroluminescence (EL) display, PDP, and FED. it can.

  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. The characteristics of the obtained birefringent layer were evaluated by the following methods. The volatilization rates (g / sec) of toluene, 2-methylpentanone, cyclohexanone, ethyl acetate, and acetone are as shown in Table 1.

(Measurement of refractive index)
The refractive index at 590 nm was measured using a trade name KOBRA21ADH manufactured by Oji Scientific Instruments.

(Thickness measurement)
Measurement was performed using an Anritsu brand name digital micrometer K-351C type.

(Example 1)
The following formula (6) synthesized from 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride and 2,2′-bis (trifluoromethyl) -4,4′-diaminobiphenyl The polyimide having a weight average molecular weight (Mw) of 110,000 represented by 1) was dissolved in a cyclohexane solvent and a 2-methylpentanone solvent, respectively, to prepare two types of polyimide solutions of 10% by weight. For the preparation of polyimide and the like, the method in the literature (F. Li et al. Polymer 40 (1999) 4571-4583) was referred. These polyimide solutions were spin-coated on a triacetyl cellulose (TAC) film having a thickness of 80 μm and dried at 150 ° C. for 15 minutes. The polyimide coating film and the TAC film were stretched 1.15 times by free end uniaxial stretching to form a biaxial birefringent layer on the TAC film. And about the birefringent layer peeled from the said TAC film, the refractive index was measured and birefringence index (DELTA) Nxz was computed. The results are shown in Table 2 below. In addition, the birefringent layer produced using the cyclohexane solvent was set to A, and the birefringent layer produced using the 2-methylpentanone solvent was set to B.

（実施例２）
下記式（１８）で表される重量平均分子量（Ｍｗ）１１０,０００のポリエーテルケトン（商品名ポリアリールエーテルケトンＡ、日本触媒社製）を、トルエン溶剤、酢酸エチル、２−メチルペンタノン溶剤溶剤にそれぞれ溶解し、１０重量％の三種類のポリエーテルケトン液を調製した。前記ポリイミド液に代えてこれらのポリエーテルケトン液を使用した以外は、前記実施例１と同様にしてＴＡＣ基材上に複屈折層を形成した。この複屈折層について、屈折率を測定し、複屈折率ΔＮｘｚを算出した結果を下記表２に示す。なお、２−メチルペンタノン溶剤を使用して作製した複屈折層をＣ、トルエン溶剤を使用して作製した複屈折層をＤ、酢酸エチル溶剤を使用して作製した複屈折層をＥとした。

(Example 2)
Polyetherketone (trade name: Polyaryletherketone A, manufactured by Nippon Shokubai Co., Ltd.) having a weight average molecular weight (Mw) of 110,000 represented by the following formula (18), toluene solvent, ethyl acetate, 2-methylpentanone solvent Each was dissolved in a solvent to prepare 10% by weight of three types of polyetherketone solutions. A birefringent layer was formed on the TAC substrate in the same manner as in Example 1 except that these polyetherketone solutions were used instead of the polyimide solution. Table 2 below shows the results of measuring the refractive index of the birefringent layer and calculating the birefringence ΔNxz. In addition, the birefringent layer produced using the 2-methylpentanone solvent was set to C, the birefringent layer produced using the toluene solvent was set to D, and the birefringent layer produced using the ethyl acetate solvent was set to E. .

（表２）
複屈折層 溶剤 揮発速度 nx ny nz ΔNxz
(g/sec)
Ａ シクロヘキサノン 0.17 1.56077 1.55208 1.52577 0.035
Ｂ 2-メチルヘ゜ンタノン 0.39 1.56518 1.55264 1.52118 0.044
Ｃ 2-メチルヘ゜ンタノン 0.39 1.55182 1.54785 1.53882 0.013
Ｄ トルエン 0.50 1.55213 1.54803 1.53814 0.014
Ｅ 酢酸エチル 0.83 1.55328 1.54850 1.53630 0.017
前記表２に示すように、ポリイミド製の複屈折層ＡおよびＢ、ポリエーテルケトン製の複屈折層Ｃ〜Ｄは、溶剤の揮発速度が早くなるにしたがって、その厚み方向の複屈折率ΔNxzが大きくなった。この結果から、溶剤の種類を揮発速度によって選択することによって、複屈折層の厚み方向複屈折率を制御できるといえる。

(Table 2)
Birefringent layer Solvent Volatilization rate nx ny nz ΔNxz
(g / sec)
A Cyclohexanone 0.17 1.56077 1.55208 1.52577 0.035
B 2-Methylhentanone 0.39 1.56518 1.55264 1.52118 0.044
C 2-methylhentanone 0.39 1.55182 1.54785 1.53882 0.013
D Toluene 0.50 1.55213 1.54803 1.53814 0.014
E Ethyl acetate 0.83 1.55328 1.54850 1.53630 0.017
As shown in Table 2, the birefringence layers A and B made of polyimide and the birefringence layers C to D made of polyether ketone have a birefringence index ΔNxz in the thickness direction as the solvent volatilization rate becomes faster. It became bigger. From this result, it can be said that the birefringence in the thickness direction of the birefringent layer can be controlled by selecting the type of solvent according to the volatilization rate.

As described above, according to the method for producing a birefringent layer of the present invention , the volatilization rate is relative from five types of solvents in the order of acetone> ethyl acetate>toluene>2-methylpentanone> cyclohexanone. The birefringence of the resulting birefringent layer can be set by selecting a fast solvent, setting the birefringence large, selecting a solvent with a relatively low volatilization rate, and setting the birefringence small. Can be controlled easily.

Claims (8)

A process for forming a coating film by coating a forming material solution in which a forming material for the birefringent layer is dispersed or dissolved in a solvent on the substrate, and a step of forming a coating film on the substrate by solidifying the coating film. A method for producing a birefringent layer, comprising the step of forming a refractive layer,
By selecting the solvent to be used according to its volatilization rate, the birefringence of the birefringent layer is controlled,
In controlling the birefringence of the birefringent layer, a solvent having a relatively high volatilization rate is selected from five types of solvents in which the volatilization rate is in the order of acetone> ethyl acetate>toluene>2-methylpentanone> cyclohexanone. The manufacturing method which sets a birefringence small by selecting a solvent with a relatively slow volatilization rate by setting a birefringence large by this . The manufacturing method of Claim 1 which controls thickness direction birefringence (DELTA) Nxz shown by the following formula in the said birefringent layer.
ΔNxz = nx−nz
In the above formula, nx and nz respectively indicate the refractive indexes of the X-axis and the Z-axis in the birefringent layer, and the X-axis is an axial direction indicating the maximum refractive index in the plane of the birefringent layer. , Z-axis indicates the thickness direction perpendicular to the X-axis. Material for forming the birefringent layer, polyamide, polyimide, polyester, polyaryletherketone, polyetherketone, to claim 1 or 2 is a non-liquid crystal polymer of at least one selected from the group consisting of polyamideimide and polyesterimide The manufacturing method as described. The manufacturing method according to any one of claims 1 to 3 , wherein the birefringent layer exhibits negative optical uniaxiality. The manufacturing method according to any one of claims 1 to 3 , further comprising a step of stretching or shrinking the coating film after solidifying the coating film. The manufacturing method according to claim 5 , wherein the coating film on the substrate is stretched or contracted by stretching or shrinking the substrate. The manufacturing method according to claim 5 or 6 , wherein the birefringent layer exhibits negative optical biaxiality. Furthermore, the manufacturing method as described in any one of Claims 1-7 including the process of peeling and removing the said base material from the laminated body of the said base material and a birefringent layer.