JPH06322094A - Phase contract compensation film - Google Patents

Abstract

PURPOSE:To obtain the subject film suitable for use in a liquid-crystal panel having a widened view angle by reacting a mixture of a specific dihydric phenol and a polyfunctional organic compound with a carbonate-forming compound and stretching the resulting branched polycarbonate. CONSTITUTION:A mixture of a dihydric phenol represented by the formula {wherein R<1> and R<2> each is a halogen, a 1-6C alkyl, a 5-8C cycloalkyl, or a 6-12C (substituted)aryl; (a) and (b) each is 0-4; and X is a single bond, a divalent connecting member such as O, CO, S, SO2, or CR<3>R<4> [where R<3> and R<4> each is a 1-6C alkyl, a 5-8C cycloalkyl, or a 6-12C (substituted)aryl], a (substituted) cycloalkylidene, a 2-10C alpha,omega-alkylene, or fluorene, provided that when a=b=0, X is not C(CH3)2} and an organic compound having three or more phenolic hydroxyl groups is reacted with a carbonate-forming compound to obtain a branched polycarbonate. This polycarbonate is stretched to obtain the objective film.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a retardation compensation film, and more particularly to a high performance retardation compensation film useful as a retardation compensation film for STN liquid crystal display devices.

[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 recent expansion of applications, there is a demand for the development of higher performance products.

The most typical polycarbonate (PC) is one obtained by the reaction of bisphenol A and phosgene, and various other types are known. However, in the present situation, even the basic point of which structure of polycarbonate is preferably used has not been clarified depending on the application. Therefore, in terms of application development, it is necessary to select a type of polycarbonate that is better suited for each application, and further to make it possible to exhibit the performance suitable for the application.

By the way, recently, as one of the uses of polycarbonate, there are optical retardation compensation films (sheet-like and plate-like ones, for example, various names such as retardation sheet and retardation plate, but here, in particular, Unless otherwise stated, the application as a phase difference compensating film including these is generally noted). The retardation compensation film has a birefringent property, has a function of causing a phase difference in a direction orthogonal to incident light of linearly polarized light, and has a function of converting transmitted light into circularly polarized light or elliptically polarized light. It is used in various optical devices and devices such as panels. In particular, it is used for compensating the phase difference due to the birefringence effect of the STN liquid crystal display element and making the display black and white. Conventionally, it is manufactured by uniaxially orienting linear polymer materials such as polycarbonate, polyvinyl alcohol and polystyrene. There is.

When the optical retardation compensating film is used for such an application, the retardation value (hereinafter referred to as R value), which is one of its characteristics, is usually referred to as the R value. And its birefringence Δn, that is, R = t × Δn is expressed as a numerical value in nm.) Is around 135 nm, a so-called quarter wavelength or more, for example, an optical path around 600 nm. A retardation film that causes a difference is suitable. Further, in order to obtain a high-performance retardation film, it is also important to manufacture it so that the R value does not vary.

A conventional retardation compensation film utilizing the birefringence of a polymer material has a large change in retardation value when viewed obliquely. The field of view is limited because when it is seen, it causes remarkable coloring and inversion of the display.

In order to reduce the angle dependence of the retardation value of this retardation compensation film, materials, stretching methods, stretching conditions, etc. have also been investigated (for example, Japanese Patent Laid-Open No. Hei 4-
84107, Japanese Patent Laid-Open No. 4-195103). However, the conventional techniques have the drawbacks that sufficient effects cannot be obtained, they are technically difficult, and the material cost is high.

[0008]

SUMMARY OF THE INVENTION The object of the present invention is to solve the above-mentioned problems and to reduce the angle dependence of the retardation value by using a new material as a material to achieve a wide viewing angle. It is to provide a high-performance polycarbonate retardation compensation film that can be suitably used as a retardation compensation film for liquid crystal panels.

[0009]

Means for Solving the Problems As a result of intensive studies to achieve the above-mentioned object, the present inventors have achieved the above-mentioned object by using a film or sheet formed by stretching a material made of a specific polycarbonate polymer. It was found that a high-performance optical retardation compensation film satisfying the above conditions can be realized, and the present invention has been completed based on this finding.

That is, the present invention provides the following general formula [I]:

[0011]

[Chemical 2](However, R in the formula [I]¹And R²Each independently
Rogen atom, alkyl group having 1 to 6 carbon atoms, 5 to 8 carbon atoms
Or a cycloalkyl group of 6 to 12 carbon atoms, or
Represents an unsubstituted aryl group, and a and b each independently represent 0 to
4 represents an integer of 4 and X represents a single bond, -O-, -CO-,-.
S-, -SO-, -SO₂-, -CR³R^Four -(Where
R³And R^FourAre each independently an alkyl having 1 to 6 carbons.
Group, substituted or unsubstituted cycloalkyl having 5 to 8 carbon atoms
Group or a substituted or unsubstituted aryl group having 6 to 12 carbon atoms
Represents a radical. ), Cycloalkylidene having 5 to 11 carbon atoms
Group or α, ω-alkylene group having 2 to 10 carbon atoms or full
Represents an orene group, provided that in the above case a = b = 0
X is -C (CH₃)₂-Should never be
It ) Dihydric phenol [I] and phenol
With a trifunctional or higher-functional polyfunctional organic compound having a functional hydroxyl group
Branched poly obtained by reacting with carbonate forming compound
A stretched film or sheet of carbonate
To provide a retardation compensation film characterized by
It is a thing.

These polycarbonate polymers may be used alone or in combination of two or more as a mixture or the like, if necessary.
In addition, when these polycarbonate-based polymers are stretched, other polymer components and desired components such as additives can be added as necessary and used as a composition.

Specific examples of the substituents R ¹ and R ² include the following. That is, for R ¹ and R ² , examples of the halogen atom include a fluorine atom, chlorine atom, bromine atom and iodine atom, and 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, tert-pentyl group, neopentyl group, n-
Hexyl group, isohexyl group, sec-hexyl group, t
An ert-hexyl group, a neohexyl group, a cyclopentylmethyl group and the like can be mentioned. Examples of the cycloalkyl group include a cyclopentyl group, a cyclohexyl group, a methylcyclopentyl group, a cycloheptyl group, a methylcyclohexyl group, a dimethylcyclopentyl group and ethyl. Examples of the aryl group include a phenyl group, a methylphenyl group, an ethylphenyl group, a propylphenyl group, a butylphenyl group, a dimethylphenyl group, a trimethylphenyl group, a cyclohexylphenyl group, and p-. Biphenylyl group,
Examples thereof include m-biphenylyl group, 1-naphthyl group, 2-naphthyl group, methylnaphthyl group, dimethylnaphthyl group and ethylnaphthyl group.

Examples of the cycloalkylidene group as X include a 1,1-cyclopentylidene group, a 1,1-cyclohexylidene group, a 1,1-cycloheptylidene group and a 1,1-cyclooctylidene group. is there. Of these, a 1,1-cyclohexylidene group is particularly preferable.

Α, ω-having 2 to 10 carbon atoms as X
Examples of the alkylene group include various polymethylene groups ranging from a dimethylene group to a decamethylene group.

Specific examples of the dihydric phenols represented by the general formula [I] include, for example, bis (4-hydroxyphenyl) methane, 1,1-bis (4-hydroxyphenyl) ethane and 1,2-bis ( 4-hydroxyphenyl)
Ethane, 2,2-bis (3-methyl-4-hydroxyphenyl) butane, 2,2-bis (4-hydroxyphenyl) butane, 2,2-bis (4-hydroxyphenyl)
Octane, 4,4-bis (4-hydroxyphenyl) heptane, 1,1-bis (4-hydroxyphenyl)-
1,1-diphenylmethane, 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-hydroxyphenyl) -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, 4,4′-dihydroxybiphenyl, 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-tert-butyl-4)
-Hydroxy-5-methylphenyl) isobutane, 1,
1-bis (2-tert-butyl-4-hydroxy-5)
-Methylphenyl) heptane, 1,1-bis (2-te
rt-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 (3,3
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'-hydroxybiphenyl, 1,1-bis (3-cyclohexyl-4-hydroxyphenyl) cyclohexane, bis (4-hydroxyphenyl) sulfoxide,
2,2-bis (3-phenyl-4-hydroxyphenyl) propane, 1,1-bis (3-phenyl-4-hydroxyphenyl) cyclohexane, bis (3-phenyl-4-hydroxyphenyl) sulfone, 4,4 Examples thereof include'-dihydroxybenzophenone.

Among these, particularly as a monomer,
1,1-bis (4-hydroxyphenyl) -1,1-diphenyl, 1,1-bis (4-hydroxyphenyl)-
1-phenylethane, 1,1-bis (4-hydroxyphenyl) cyclohexane, 2,2-bis (3-methyl-)
4-hydroxyphenyl) propane, 1,1-bis (3
-Methyl-4-hydroxyphenyl) cyclohexane,
4,4'-dihydroxybiphenyl, 2,2-bis (3
Various polycarbonate-based polymers obtained by using -phenyl-4-hydroxyphenyl) propane or the like are preferably used. Further, a polycarbonate polymer obtained by using these monomers and 2,2-bis (4-hydroxyphenyl) propane (bisphenol A) is also used. The proportion of 2,2-bis (4-hydroxyphenyl) propane used is preferably less than 98 mol%.

Although bisphenol A polycarbonate can be used in combination as an additive component as will be described later, it is impossible to obtain a retardation compensation film having a wide viewing angle as in the present invention even if it is used alone. .

The polyfunctional organic compound used in the present invention has a role as a branching agent, and specific examples thereof include:
Phloroglysin, 1,1,1-tri (4-hydroxyphenyl) ethane, 1,3,5-tri (4-hydroxyphenyl) benzol, 2,6-dimethyl-2,4,6-
Tri (4-hydroxyphenyl) heptene-3,4,6
-Dimethyl-2,4,6-tri (4-hydroxyphenyl) heptene-2,2,6-bis (2-hydroxy-5)
-Methylbenzyl) -4-methylphenol, α,
α ′, α ″ -tri (4-hydroxyphenyl) -1,
Polyhydroxy compounds exemplified by 3,5-triisopropylbenzene and the like, 3,3-bis (4-hydroxyaryl) oxindole [= isatin bisphenol], 5-chloroisatin, 5,7-dichloroisatin, 5-bromoisatin, etc. Is mentioned. The amount of the polyfunctional organic compound used is preferably 0.01 to 10 mol%, more preferably 0.05 with respect to the amount of the dihydric phenol used.
~ 5 mol%.

The polycarbonate polymer used in the present invention has a concentration of 0.5 g / dl in methylene chloride as a solvent.
Solution has a reduced viscosity [η _sp / c] of 0.2 at 20 ° C.
It is preferably in the range of to 5.0 dl / g. More preferably, it is 0.3 to 4.0 dl / g. 0.2 dl /
If it is less than g, the strength of the film or sheet decreases,
If it exceeds 5.0 dl / g, molding or the like may be difficult.

The method for producing these polycarbonate-based polymers is also not particularly limited. For example, various dihydric phenols exemplified above are used as monomers in the presence of an alkali metal compound or an acid acceptor such as pyridine. Produced by various methods such as known polymerization methods such as phosgene method (interfacial polycondensation method, pyridine method, etc.) of reacting with phosgene gas (in a suitable solvent as necessary), or chloroformate method, transesterification method, etc. Those that have been applied are applicable.
In the case of the phosgene method, the divalent phenol as a raw material, the polyfunctional organic compound and phosgene may be reacted at once to obtain a desired polycarbonate, or a part of the dihydric phenol as a reaction raw material and phosgene may be previously prepared. A two-step method may be used in which the reaction is carried out to form an oligomer having a chloroformate group at the molecular end, and then the remaining reaction raw materials are added to complete the polycondensation to obtain the desired polycarbonate.

The retardation compensation film of the present invention is constituted by using a film or sheet formed by molding and stretching a material made of at least one of the branched polycarbonates obtained as described above. In that case, the branched polycarbonate can be used alone or as a mixture in an arbitrary ratio, and further, if necessary, a mixture with another polymer (for example, bisphenol A polycarbonate, polyether, etc.), It can also be used as a mixture with other components.

Here, forming into a film or sheet is performed by
It can be carried out by various known film forming methods, and for example, it can be suitably carried out by a solvent casting method, an extrusion method, a calendering method or the like. Incidentally, the desired stretched film or sheet may be obtained by stretching simultaneously or continuously with this molding. Further, the film or sheet thus formed may be stretched and used.

In any case, this stretching can be carried out by various methods such as known stretching or molding stretching method.

The film or sheet may be stretched usually in a uniaxial direction, and the stretching ratio in the uniaxial direction (percentage of the stretched length relative to the original length) is usually 1 to It is suitable to select in the range of 10%, preferably 3 to 5%.

The thickness of the stretched film or sheet thus obtained cannot be uniformly set because the optimum value varies depending on the characteristics of the polycarbonate polymer used (especially optical characteristics such as birefringence) and the degree of stretching. However, it is usually preferable to select it in the range of 50 to 300 μm.

That is, a retardation compensation film having a desired R value can be easily realized by appropriately selecting the thickness t in consideration of the birefringence Δn of the stretched film or sheet.

The retardation compensating film of the present invention may be constituted solely by appropriately arranging the stretched film or sheet produced as described above by cutting it into a desired size. Alternatively, a plurality of them may be combined and configured, and further, they may be appropriately combined with other components as required.

The retardation compensation film of the present invention obtained as described above is a high-performance optical retardation compensation film having a wide viewing angle, and is advantageously used in various applications including liquid crystal panels. be able to.

[0030]

EXAMPLES The present invention will be described in more detail below with reference to examples of the present invention and comparative examples thereof, but the present invention is not limited to these examples.

Example 1 2,2-bis (4-hydroxy-3) as a raw material monomer
-Phenylphenyl) propane (bisphenol PH)
95.0 g (0.25 mol) was dissolved in 550 ml of a 10% aqueous potassium hydroxide solution, and 400 ml of methylene chloride, 0.25 g of p-tert-butylphenol as a terminal stopper, and 0.10 g of phloroglucin as a branching agent were dissolved in this aqueous solution. Was introduced into a reactor with a baffle, 5 ml of 10% triethylamine aqueous solution was added, and the temperature of the reaction solution was adjusted to 10 ° C.
Phosgene gas was blown at a rate of 450 ml / min for 30 minutes to carry out a polycondensation reaction while vigorously stirring while maintaining the temperature in the vicinity. After stopping the phosgene gas, the reaction was terminated by further stirring for 1 hour.

After completion of the reaction, the organic layer was diluted with 1 liter of methylene chloride, washed with water, diluted hydrochloric acid and water in this order, and then poured into methanol to obtain polycarbonate 99.5.
g was obtained.

The polymer thus obtained has a reduced viscosity [η _sp / c] of 0.78 dl / g at 20 ° C. in a solution of methylene chloride at a concentration of 0.5 g / dl, and ¹ H -From NMR spectrum analysis, it was confirmed that the polycarbonate was composed of the following repeating units.

[0034]

[Chemical 3] The above polycarbonate was dissolved in methylene chloride to form a varnish having a solid content of 20% by weight, and the thickness was 70% by a casting method.
A μm film was prepared. Furthermore, this film was heated to 150 ° C. by a tenter type stretching machine and stretched 1.2 times.

When the optical characteristics of the obtained film were evaluated, the retardation was 410 nm, and the angle dependency of the retardation was 9% on average in the phase increasing direction and the phase decreasing direction at an incident angle of 45 degrees. When this retardation compensation film was attached to an STN liquid crystal cell, a wide viewing angle was obtained.

Example 2 As a raw material monomer, 5,2-bis (4-hydroxyphenyl) propane (bisphenol A) 59.3 g (0.
26 mol) and an aqueous solution of sodium hydroxide having a concentration of 8% 550
250 ml of methylene chloride was introduced into a reactor equipped with a baffle, and the solution was stirred violently while maintaining the temperature of the reaction solution at about 10 ° C., and phosgene gas was adjusted to 95%.
The polycondensation reaction was carried out by blowing for 15 minutes at a rate of 0 ml / min. After the reaction solution was allowed to stand, the organic layer was separated and the polymerization degree was 2
A methylene chloride solution of a bisphenol A oligomer having a chloroformate group at the molecular end of -4 was obtained.

This oligomer solution and 1,1-bis (4-hydroxyphenyl) -1, as a post-added monomer,
1-diphenylmethane (bisphenol TP) 11.3
g (0.032 mol) and 150 ml of an 8% aqueous sodium hydroxide solution in which 0.32 g of 1,1,1-tris (4-hydroxyphenylethane) as a branching material were introduced into a reactor with a baffle plate, Furthermore, p-te is used as a terminal stopper.
rt-Butylphenol (0.15 g) and 10% triethylamine aqueous solution (5 ml) were added, and the mixture was kept at around 10 ° C. and vigorously stirred to carry out a polycondensation reaction.

After completion of the reaction, 1 liter of methylene chloride was added to the organic layer to dilute it, and the organic layer was washed with water, diluted hydrochloric acid and water in this order, and then poured into methanol to obtain polycarbonate 71.5.
g was obtained.

The polymer thus obtained had a reduced viscosity [η _sp / c] of 0.69 dl / g at 20 ° C. in a solution of methylene chloride at a concentration of 0.5 g / dl, and ¹ H -From NMR spectrum analysis, it was confirmed that the polycarbonate was composed of the following repeating units.

[0040]

[Chemical 4] The above polycarbonate was dissolved in methylene chloride to form a varnish having a solid content of 20% by weight, and the thickness was 70% by a casting method.
A μm film was prepared. Furthermore, this film was heated to 150 ° C. by a tenter type stretching machine and stretched 1.2 times.

When the optical characteristics of the obtained film were evaluated, the retardation was 370 nm, and the angle dependency of the retardation was 9% on average in the phase increasing direction and the phase decreasing direction at an incident angle of 45 degrees. When this retardation compensation film was attached to an STN liquid crystal cell, a wide viewing angle was obtained.

Comparative Example 1 Reaction of 2,2-bis (4-hydroxyphenyl) propane, which is a commercially available polymer, with phosgene (the terminator is p
-Tert-butylphenol) was used to prepare a retardation compensation film in the same manner as in Example 1 except that a polycarbonate ([η _sp /c]=0.65 dl / g) was used. When the optical characteristics were evaluated in the same manner as in Example 1, the retardation was 450 nm, and the angle dependence of the retardation was
25% on average in the increasing and decreasing directions at 45 degree incidence
Met. When this phase difference compensating film was attached to an STN liquid crystal cell, the viewing angle was narrow and the field of view was easily inverted, resulting in poor displayability.

[0043]

INDUSTRIAL APPLICABILITY The retardation compensation film obtained by the present invention has a small angle dependence of retardation value, and when mounted in a liquid crystal device, a wide field of view can be achieved. Particularly, it is preferably used as a retardation compensation film for STN liquid crystal display device.

Claims (1)

[Claims] 1. The following general formula [I]:(However, R in the formula [I]¹And R²Each independently
Rogen atom, alkyl group having 1 to 6 carbon atoms, 5 to 8 carbon atoms
Or a cycloalkyl group of 6 to 12 carbon atoms, or
Represents an unsubstituted aryl group, and a and b each independently represent 0 to
4 represents an integer of 4 and X represents a single bond, -O-, -CO-,-.
S-, -SO-, -SO₂ -, -CR³R^Four -(Where
R³And R^FourAre each independently an alkyl having 1 to 6 carbons.
Group, cycloalkyl group having 5 to 8 carbon atoms or 6 to 1 carbon atoms
2 represents a substituted or unsubstituted aryl group. ),carbon
Substituted or unsubstituted cycloalkylidene of the number 5 to 11
Group or α, ω-alkylene group having 2 to 10 carbon atoms or full
Represents an orene group, provided that in the above case a = b = 0
X is -C (CH₃)₂-Should never be
It ) Dihydric phenol [I] and phenol
With a trifunctional or higher-functional polyfunctional organic compound having a functional hydroxyl group
Branched poly obtained by reacting with carbonate forming compound
A stretched film or sheet of carbonate
A retardation compensation film characterized by the following.