JP3349173B2 - Phase difference compensation film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a retardation compensating film, and more particularly to a high-performance optical retardation compensating film useful as a retardation compensating film for a liquid crystal panel.

[0002]

2. Description of the Related Art Polycarbonate is generally used as a material in various fields because it is excellent in mechanical strength, heat resistance and the like, and is also excellent in optical properties such as transparency and dimensional stability. ing. Nevertheless, with the expansion of applications in recent years, there is a demand for the development of a device having even better performance.

[0003] The most typical polycarbonates are those obtained by the reaction of bisphenol A with phosgene, and a wide variety of others are known. However, at present, the basic point of what structure polycarbonate is preferably used is not clarified for some applications. Therefore, from the viewpoint of application development, it is necessary to select a type of polycarbonate that is more suitable for each application, and furthermore, to make it suitable for the application.

[0004] Incidentally, as one of uses of polycarbonate, recently, there is an optical retardation compensating film (a sheet-like or plate-like film, and various names such as a retardation sheet and a retardation plate. Unless otherwise stated, the use of these materials as optical retardation compensating films is attracting attention. The optical retardation compensation film has birefringence, has a function of causing a phase difference in the direction perpendicular to the incident light of linearly polarized light, and has a function of converting transmitted light into circularly polarized light or elliptically polarized light, for example, And various optical devices and devices for liquid crystal panels and the like.

When an optical retardation compensating film is used for such a purpose, usually, one of its characteristics is a retardation value (hereinafter referred to as an R value. The R value is determined by the thickness t of the film or sheet. Is defined as a product of its birefringence Δn, that is, R = t × Δn, expressed by a numerical value in nm.) Is about 135 nm, so-called １ ／ wavelength or more, for example, an optical path of about 600 nm. A retardation film that produces a difference is suitable. In order to obtain a high-performance retardation film, it is also important to manufacture the stretched film or the stretched sheet so that the R value does not vary in all parts.

[0006] Such optical retardation compensation films include:
Conventionally, cellulose acetate-based films and sheets have been used. Recently, it has been proposed to use a polycarbonate-based film or sheet as an optical retardation compensating film from the viewpoint of dimensional stability and thickness reduction (for example, JP-A-63-189804, Kaiping 1
-201608). However, in stretched films and sheets made of these conventional materials,
In general, depending on the portion of the stretched film or sheet, for example, the difference in optical properties between the center and both ends is large,
For this reason, there has been a problem that the retardation compensation film as a product can be taken out only from the central part of the stretched film or sheet.

Further, when using a polycarbonate-based film or sheet as an optical retardation compensating film, a polycarbonate material, its stretching method, stretching conditions, and the like have been studied, particularly with the aim of obtaining a uniform R value. (See, for example, JP-A-4-84107). However, the conventional techniques do not achieve a sufficiently satisfactory uniform R value, and in particular, have no optically variable R value under orthogonal Nicols, that is, no color unevenness. At present, the development of a high-performance retardation compensation film is required.

[0008]

SUMMARY OF THE INVENTION The present invention has been made based on the above circumstances. An object of the present invention is to solve the above-mentioned problems and to easily control the R value to an appropriate range.
An object of the present invention is to provide a high-performance polycarbonate-based optical retardation compensation film which has advantages such as remarkable reduction in variation in R value and can be suitably used as a retardation compensation film for a liquid crystal panel.

[0009]

Means for Solving the Problems The present inventors have made intensive studies to achieve the above object, and as a result, obtained by stretching a material comprising a polycarbonate having a repeating unit represented by a specific general formula. Alternatively, it has been found that a high-performance optical retardation compensation film satisfying the above object can be realized by using a sheet. The present inventors have completed the present invention based on the above findings.

That is, the present invention provides a compound represented by the following general formula [I]:

[0011]

Embedded image Wherein R ¹ and R ² each independently represent a halogen atom, an alkyl group having 1 to 6 carbon atoms or a substituted or unsubstituted aryl group having 6 to 12 carbon atoms, and a and b each independently represent X represents an integer of 0 to 4, and X is

[0012]

Embedded image (Wherein, R ³ , R ⁷ , R ⁸ , R ⁹ and R ¹⁰ each independently represent a halogen atom, an alkyl group having 1 to 6 carbon atoms or a substituted or unsubstituted aryl group having 1 to 12 carbon atoms. Show,
R ⁴ represents a hydrogen atom, an alkyl group having 1 to 12 carbon atoms or a cycloalkyl group, and c , f and i each independently represent 0 to 4
G and h each independently represent an integer of 0 to 2, Z is a single bond, -O-, -CO-, -S-, -SO
—, —SO ₂ — or —CH ₂ —. ). Or a repeating unit [I] represented by the following general formula [II]:

[0013]

Embedded image Wherein R ¹¹ and R ¹² are each independently a halogen atom, an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms, or a substituted or unsubstituted aryl having 6 to 12 carbon atoms. Represents a group, j and k each independently represent an integer of 0 to 4, Y represents a single bond, -O-, -CO-, -S-,-
SO—, —SO ₂ —, —CR ¹³ R ¹⁴ — (wherein, R ¹³ and R ¹⁴ are each independently a hydrogen atom, a trifluoromethyl group, an alkyl group having 1 to 6 carbon atoms, or an alkyl group having 6 to 12 carbon atoms. A substituted or unsubstituted aryl group), a cycloalkylidene group having 5 to 8 carbon atoms, or an α, ω-alkylene group having 2 to 12 carbon atoms. And a concentration of 0.5 g / dl using methylene chloride as a solvent.
Reduced viscosity [η _sp / c] at 20 ° C. of the solution of
An object of the present invention is to provide a retardation compensation film comprising a stretched polycarbonate film or stretched sheet in the range of 2.5 dl / g.

As the retardation compensation film of the present invention, a stretched film or sheet made of the above-mentioned polycarbonate is used, and the polycarbonate is formed from the repeating unit [I] represented by the general formula [I]. It is important to use at least one of a polycarbonate comprising the repeating unit [I] and a repeating unit [II] represented by the general formula [II]. Examples of the polycarbonate include various polycarbonate homopolymers and copolymers composed of only one or two or more of the repeating units [I], and one or more of the repeating units [I] and the repeating unit [I]. I
Various types of polycarbonate copolymers comprising one or more of the above [I] can be used. Further, other repeating units may be further contained within a range not to impair the achievement of the object of the present invention. In particular, in the case of a copolymer having the repeating unit [I] and the repeating unit [II], the content ratio of the repeating unit [I] to the total content of the repeating unit [I] and the repeating unit [II] is usually 1 mol. % Is preferable.

These polycarbonates may be used alone or, if necessary, as a mixture of two or more. Further, when stretching these polycarbonates, desired components such as other polymer components and additives can be appropriately added as needed, and used as a composition.

In the general formula [I], R ¹ , R ² , R ³ ,
R ⁷ , R ⁸ , R ⁹ and R ¹⁰ each independently represent a halogen atom, an alkyl group having 1 to 6 carbon atoms or a substituted or unsubstituted aryl group having 1 to 12 carbon atoms.

Specific examples of the substituents R ¹ , R ² , R ³ , R ⁷ , R ⁸ , R ⁹ and R ¹⁰ are as follows.

Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom. Examples of the alkyl group include a methyl group, an ethyl group and an n-
Propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, isobutyl group, n-pentyl group, isopentyl group, sec-pentyl group, ter
t-pentyl group, neopentyl group, n-hexyl group, isohexyl group, sec-hexyl group, tert-hexyl group, neohexyl group, cyclopentylmethyl group and the like.Examples of the substituted or unsubstituted aryl group include, for example, , Phenyl group, methylphenyl group, ethylphenyl group, propylphenyl group, butylphenyl group,
Examples thereof include a dimethylphenyl group, a trimethylphenyl group, a cyclohexylphenyl group, a p-biphenylyl group, an m-biphenylyl group, a 1-naphthyl group, a 2-naphthyl group, a methylnaphthyl group, a dimethylnaphthyl group, and an ethylnaphthyl group.

In the general formula [I], R ⁴ is a hydrogen atom,
And represents an alkyl group having 1 to 12 carbon atoms or a cycloalkyl group. Specific examples of the alkyl group include, in addition to those exemplified above, an octyl group, a nonyl group, a decyl group, an undecyl group,
A dodecyl group and the like can be mentioned. As the cycloalkyl group, one having 4 to 8 carbon atoms is preferable, and a cyclohexyl group is particularly preferable.

In the general formula [II], R ¹¹ and R ¹² are each independently a halogen atom, an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms or a cycloalkyl group having 6 to 1 carbon atoms.
2 represents a substituted or unsubstituted aryl group, and specific examples of a halogen atom, an alkyl group having 1 to 6 carbon atoms, and an aryl group having 6 to 12 carbon atoms are those exemplified in the description of the above general formula [I]. Can be mentioned. 5 carbon atoms
As cycloalkyl 7, a cyclohexyl group is preferred.

In the general formula [II], Y is a single bond,-
O -, - CO -, - S -, - SO -, - SO 2 -, - C
R ¹³ R ¹⁴ — represents a cycloalkylidene group having 5 to 8 carbon atoms or an α, ω-alkylene group having 2 to 12 carbon atoms.

Here, R ¹³ and R ^{14 in} —CR ¹³ R ¹⁴ —
Each independently represents a hydrogen atom, a trifluoromethyl group, an alkyl group having 1 to 6 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 12 carbon atoms. Examples of the alkyl group and the aryl group include Examples can be given.

Examples of the cycloalkylidene group as Y include a 1,1-cyclopentylidene group, a 1,1-cyclohexylidene group, and a 1,1-cycloheptylidene group.
Among these, a 1,1-cyclohexylidene group is preferable.

Examples of the α, ω-alkylene group having 2 to 12 carbon atoms as Y include various polymethylene groups ranging from a dimethylene group to a decamethylene group.

These various repeating units [I] and [II] can be formed from monomers having the corresponding structures, for example, bisphenols (dihydric phenols) having the corresponding structures. It can be formed by reacting phosgene. Therefore, instead of directly showing specific examples of these various repeating units [I] and [II], specific examples of bisphenols corresponding to them are given below.

The bisphenols forming the repeating unit [I] are represented by the following general formula [III]:

[0027]

Embedded image (Wherein, R ¹ , R ² , a, b and X have the same meaning as described above), and specific examples thereof include the following.

[0028]

Embedded image Bisphenols forming the repeating unit [II] include
The following general formula [IV]

[0029]

Embedded image (Wherein, R ¹¹ , R ¹² , j, k, and Y have the same meaning as described above). Specific examples thereof include, for example,
Bis (4-hydroxyphenyl) methane, 1,1-bis (4-hydroxyphenyl) ethane, 1,2-bis (4
-Hydroxyphenyl) ethane, 2,2-bis (4-hydroxyphenyl) propane, 2,2-bis (3-methyl-4-hydroxyphenyl) butane, 2,2-bis (4-hydroxyphenyl) butane, , 2-bis (4
-Hydroxyphenyl) octane, 4,4-bis (4-
Hydroxyphenyl) heptane, 4,4'-dihydroxytetraphenylmethane, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 1,1-bis (4
-Hydroxyphenyl) -1-phenylmethane, bis (4-hydroxyphenyl) ether, bis (4-hydroxyphenyl) sulfide, bis (4-hydroxyphenyl) sulfone, 1,1-bis (4-hydroxyphenyl) cyclopentane , 1,1-bis (4-hydroxyphenyl) cyclohexane, 2,2-bis (3-methyl-4-hydroxyphenyl) propane, 2- (3-methyl-4-hydroxyphenyl) -2- (4-hydroxy Phenyl) -1-phenylethane, bis (3-methyl-
4-hydroxyphenyl) sulfide, bis (3-methyl-4-hydroxyphenyl) sulfone, bis (3-methyl-4-hydroxyphenyl) methane, 1,1-bis (3-methyl-4-hydroxyphenyl) cyclohexane, 2,2-bis (2-methyl-4-hydroxyphenyl) propane, 1,1-bis (2-butyl-4-hydroxy-5-methylphenyl) butane, 1,1-bis (2
-Tert-butyl-4-hydroxy-3-methylphenyl) ethane, 1,1-bis (2-tert-butyl-
4-hydroxy-5-methylphenyl) propane, 1,
1-bis (2-tert-butyl-4-hydroxy-5
-Methylphenyl) butane, 1,1-bis (2-ter
t-butyl-4-hydroxy-5-methylphenyl) isobutane, 1,1-bis (2-tert-butyl-4-
(Hydroxy-5-methylphenyl) heptane, 1,1-
Bis (2-tert-butyl-4-hydroxy-5-methylphenyl) -1-phenylmethane, 1,1-bis (2-tert-amyl-4-hydroxy-5-methylphenyl) butane, bis (3- Chloro-4-hydroxyphenyl) methane, bis (3,5-dibromo-4-hydroxyphenyl) methane, 2,2-bis (3-chloro-
4-hydroxyphenyl) propane, 2,2-bis (3
-Fluoro-4-hydroxyphenyl) propane, 2,
2-bis (3-bromo-4-hydroxyphenyl) propane, 2,2-bis (3,5-difluoro-4-hydroxyphenyl) propane, 2,2-bis (3,5-dichloro-4-hydroxyphenyl) ) Propane, 2,2-bis (3,5-dibromo-4-hydroxyphenyl) propane, 2,2-bis (3-bromo-4-hydroxy-5)
-Chlorophenyl) propane, 2,2-bis (3,5-
Dichloro-4-hydroxyphenyl) butane, 2,2-
Bis (3,5-dibromo-4-hydroxyphenyl) butane, 1-phenyl-1,1-bis (3-fluoro-4
-Hydroxyphenyl) ethane, bis (3-fluoro-
4-hydroxyphenyl) ether, 3,3'-difluoro-4,4'-dihydroxybiphenyl, 1,1-bis (3-cyclohexyl-4-hydroxyphenyl) cyclohexane, 2,2-bis (4-hydroxyphenyl) Hexafluoropropane, 1,1-bis (4-hydroxyphenyl) -1-phenyl-2,2,2-trifluoroethane, 2,2-bis (3-phenyl-4-hydroxyphenyl) propane, 1,1 -Bis (3-phenyl-4-hydroxyphenyl) cyclohexane, bis (3-phenyl-4-hydroxyphenyl) sulfone,
4,4'-dihydroxybenzophenonone, bis (4-
(Hydroxyphenyl) sulfoxide, 4,4'-dihydroxybiphenyl, 4,4'-dihydroxy-3,3 '
-Dimethylbiphenyl, 4,4'-dihydroxy-2,
2'-dimethylbiphenyl, 4,4'-dihydroxy-
3,3'-dicyclohexylbiphenyl and the like.

Among the bisphenols represented by the general formula [IV], 2,2-bis (4-hydroxyphenyl) propane, 4,4-dihydroxytetraphenylmethane, 1-phenyl-1,1-bis ( 4-hydroxyphenyl) ethane, bis (4-hydroxyphenyl) sulfone, 1,1-bis (4-hydroxyphenyl) cyclohexane, 2,2-bis (3-methyl-4-hydroxyphenyl) propane, 4,4- Dihydroxybiphenyl, 2,2-bis (3-phenyl-4-hydroxyphenyl) propane and the like are preferred.

The polycarbonate used in the present invention may be a straight-chained one, a branched one, a one having a branched structure, a cyclic one or a ring-shaped one, and further, a special structure at the polycarbonate terminal. Those having various molecular structures such as those introduced are applicable.

The polycarbonate used in the present invention is:
Reduced viscosity [η _sp / c] at 20 ° C. of a solution having a concentration of 0.5 g / dl using methylene chloride as a solvent is 0.5 to 2.5 d.
1 / g. If the reduced viscosity is less than 0.5 dl / g, the strength of the film or sheet decreases, and
If it exceeds / g, molding may be difficult.

The method for producing these polycarbonates is not particularly limited. For example, the above-mentioned various bisphenols may be used as monomers in the presence of an acid acceptor such as an alkali metal compound or pyridine (if necessary). And phosgene gas (in an appropriate solvent) to react with phosgene gas (interfacial polycondensation method, pyridine method, etc.), or by a known method such as a chloroformate method, a transesterification method, etc. Applicable. In the case of this phosgene method, the desired bisphenols and phosgene may be reacted at once to obtain a desired polycarbonate, or a portion of the bisphenols as a reaction raw material may be reacted with phosgene in advance to form a chloro group at the molecular end. A two-step method may be used in which an oligomer having a formate group is produced, and then the remaining reaction materials are added to complete the polycondensation to obtain a desired polycarbonate.

The retardation compensation film of the present invention is a film obtained by molding and stretching a material comprising at least one of the above-mentioned repeating unit [I] or a polycarbonate comprising the repeating unit [I] and the repeating unit [II]. And a sheet. At that time, the polycarbonate can be used alone or as a mixture in an arbitrary ratio, and if necessary, can also be used as a mixture with other components such as a mixture with another polymer. it can.

The above-mentioned polycarbonate can be formed into a film or sheet by various known film-forming methods, for example, a solvent casting method, an extrusion method, a calendering method and the like. It is to be noted that stretching may be performed simultaneously or continuously with the molding to obtain a desired stretched film or sheet. Further, the film or sheet thus formed may be used after being stretched. In any case, this stretching can be performed by various methods such as a known stretching method using a stretching roll or a known forming stretching method.

The stretching temperature is suitably a temperature somewhat higher than the glass transition temperature of the polycarbonate.

The stretching of the film or sheet is usually carried out by
The stretching in the uniaxial direction may be performed, and the stretching ratio in the uniaxial direction (percentage of the stretched length to the original length) is usually in the range of 1 to 10%, preferably 3 to 5%. Is preferred. This stretching may be performed in one step, or may be performed in multiple steps.

The thickness of the stretched film or sheet thus obtained cannot be determined uniformly because the optimum value varies depending on the properties (particularly, optical properties such as birefringence) of the polycarbonate used and the degree of stretching. , And 50 to 300 μm. That is, considering the birefringence Δn of the stretched film or sheet,
By appropriately selecting the thickness t, a retardation compensation film having a desired R value can be easily manufactured.

The phase difference compensating film of the present invention obtained as described above has particularly small variation in the R value (for example, this variation can be easily reduced to an extremely small range of usually 3% or less, more preferably 2% or less). This is a high-performance optical retardation compensation film, and can be advantageously used in various applications including liquid crystal panel applications.

[0040]

The present invention will be described below in detail with reference to examples, but the present invention is not limited to these examples.

Example 1 The following structure was used as a starting monomer.

[0042]

Embedded image Bisphenol compound (15.4 g, 0.051 mol)
And 42.6 g (0.205 mol) of 2,2-bis (4-hydroxyphenyl) propane, 550 ml of an 8% aqueous sodium hydroxide solution, 400 ml of methylene chloride, and p-tert- as a terminal stopper (molecular weight regulator). 0.15 g of butylphenol and 3 ml of a 10% aqueous triethylamine solution as a catalyst were introduced into a reactor equipped with baffles, and phosgene gas was supplied at a rate of 100 ml / min for 15 minutes while vigorously stirring while maintaining the temperature of the reaction solution at around 10 ° C. The polycondensation reaction was performed by blowing.

After completion of the reaction, the organic layer was diluted by adding 1 liter of methylene chloride, washed with water, dilute hydrochloric acid and water in that order, and then poured into methanol to obtain a polycarbonate.

The polycarbonate thus obtained has a reduced viscosity [η _sp / c] of 0.78 dl at 20 ° C. in a solution of 0.5 g / dl in methylene chloride as a solvent.
/ G. ^{By 1} H-NMR spectrum analysis, it was confirmed that the obtained polycarbonate was a polycarbonate having the following repeating units [Ia] and [IIa] in the following molar ratio.

[0045]

Embedded image The above polycarbonate is extruded to a thickness of 120
A transparent film having a thickness of 500 μm and a width of 500 mm was uniaxially stretched at 160 ° C. by 5% to obtain a uniform phase difference compensation film having a thickness of 100 μm. The obtained retardation compensation film was cut into a width of 400 mm and a length of 1 m, and the length and width were each 50 m.
The birefringence was measured at 8 × 20 = 160 points at m intervals using a Senarmon compensator attached to a polarizing microscope.
The R value was calculated. A halogen lamp was used as a light source. The measurement results are shown in Table 1. This film also exhibited a uniform color tone under crossed Nicols.

Example 2 The following structure was used as a monomer

[0047]

Embedded image 20.0 g (0.051 mol) of bisphenol compound
A polycarbonate was obtained in the same manner as in Example 1 except that 54.9 g (0.205 mol) of 1,1-bis (4-hydroxyphenyl) cyclohexane was used.

The polycarbonate thus obtained has a reduced viscosity [η _sp / c] of 0.81 dl at 20 ° C. for a solution having a concentration of 0.5 g / dl using methylene chloride as a solvent.
/ G. ^{According to 1} H-NMR spectrum analysis, the obtained polycarbonate was represented by the following repeating unit [Ib]
And [IIb] in the following molar ratio.

[0049]

Embedded image Using this polycarbonate, a retardation compensation film was produced in the same manner as in Example 1, and the R value was measured. The measurement results are as shown in Table 1. This film also exhibited a uniform color tone under crossed Nicols.

[0050]

[0051]

[0052]

[0053]

Comparative Example 1 Reaction of a commercially available polymer, 2,2-bis (4-hydroxyphenyl) propane, with phosgene (the terminal terminator was p
Example 1 using a polycarbonate ([η _sp /c]=0.76 dl / g) composed of the following repeating unit [IIa] produced by (tert-butylphenol).
Production of a retardation compensation film was attempted in the same manner as in Example 1, and the R value of the obtained film was measured in the same manner as in Example 1. The measurement results are as shown in Table 1. This film showed remarkable color tone unevenness under crossed Nicols.

[0055]

Embedded image

[0056]

[Table 1]

[0057]

According to the present invention, since a stretched film or a stretched sheet made of a polycarbonate having a specific structure is used, the R value can be easily controlled to an appropriate range, and the variation of the R value is, for example, within 3%. Further, it can be easily reduced to a remarkably low range of 2% or less, so that a high-performance retardation compensation film which can be suitably and advantageously used as a retardation compensation film for a liquid crystal panel or the like can be provided. .

Further, according to the present invention, quality unevenness such as R value variation can be significantly reduced not only within the same film but also between various products, so that product yield and productivity can be significantly improved. it can.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI B29L 7:00 B29L 7:00 (72) Inventor Tomohiro Nagao 1280 Kamiizumi, Sodegaura-shi, Chiba Idemitsu Kosan Co., Ltd. (56) References JP-A-6-25398 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B 5/30 C08G 63/00-64/42

Claims (1)

(57) [Claims] [Claim 1] The following general formula [I] Wherein R ¹ and R ² each independently represent a halogen atom, an alkyl group having 1 to 6 carbon atoms or a substituted or unsubstituted aryl group having 6 to 12 carbon atoms, and a and b each independently represent X represents an integer of 0 to 4, and X is (Wherein, R ³ , R ⁷ , R ⁸ , R ⁹ and R ¹⁰ each independently represent a halogen atom, an alkyl group having 1 to 6 carbon atoms or a substituted or unsubstituted aryl group having 1 to 12 carbon atoms. Show,
R ⁴ represents a hydrogen atom, an alkyl group having 1 to 12 carbon atoms or a cycloalkyl group, and c , f and i each independently represent 0 to 4
G and h each independently represent an integer of 0 to 2, Z is a single bond, -O-, -CO-, -S-, -SO
—, —SO ₂ — or —CH ₂ —. ). Or a repeating unit [I] represented by the following general formula [II]: Wherein R ¹¹ and R ¹² are each independently a halogen atom, an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms, or a substituted or unsubstituted aryl having 6 to 12 carbon atoms. Represents a group, j and k each independently represent an integer of 0 to 4, Y represents a single bond, -O-, -CO-, -S-,-
SO—, —SO ₂ —, —CR ¹³ R ¹⁴ — (wherein, R ¹³ and R ¹⁴ are each independently a hydrogen atom, a trifluoromethyl group, an alkyl group having 1 to 6 carbon atoms, or an alkyl group having 6 to 12 carbon atoms. A substituted or unsubstituted aryl group), a cycloalkylidene group having 5 to 8 carbon atoms, or an α, ω-alkylene group having 2 to 12 carbon atoms. And a concentration of 0.5 g / dl using methylene chloride as a solvent.
Reduced viscosity [η _sp / c] at 20 ° C. of the solution of
A retardation compensation film comprising a stretched polycarbonate film or stretched sheet in the range of 2.5 dl / g.