JP3499838B2 - Film for retardation film formed from high refractive index and low birefringence polycarbonate resin and use thereof - 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 film formed of a high-refractive index, low-birefringence polycarbonate resin having improved refractive index and birefringence, and its use. More specifically, it relates to a film for retardation film formed from a high refractive index, low birefringence and excellent transparency having a specific amount of 9,9-bis (4-oxyphenylene) fluorene structural unit, and use thereof. . Such a resin is extremely useful as a material for a CD pickup lens, an optical lens such as a Fresnel lens, a screen for a projection television, a film such as a retardation film, and a disc by utilizing its characteristics.

[0002]

2. Description of the Related Art Conventionally, a polycarbonate resin obtained by reacting a carbonate precursor substance with 2,2-bis (4-hydroxyphenyl) propane has excellent transparency, heat resistance, mechanical properties and dimensional stability. Therefore, it is widely used in many fields as engineering plastics. In particular, it has many uses as an optical material because of its excellent transparency. However, such a polycarbonate resin has a drawback that it has a large birefringence as an optical material.

By the way, it is well known that a polycarbonate resin film may be uniaxially stretched to form a retardation film used for liquid crystal display or the like from the polycarbonate resin film. Such a technique has been known for a long time, and, for example, in Japanese Patent Publication No. 41-12.
No. 190 (Applicant: Mitsubishi Electric Corporation), JP-A-6
No. 3-189804 (Applicant: Sumitomo Chemical Co., Ltd.), JP-A No. 1-201608 (Applicant: Fujifilm Co., Ltd.), JP-A No. 2-12205 (Applicant: Sumitomo Chemical Co., Ltd.) JP-A-2-59702 (Applicant: Sumitomo Chemical Co., Ltd.), JP-A-4-8
Japanese Patent No. 4107 (Applicant: Toyo Kagaku Co., Ltd.) also discloses a technique of uniaxially stretching a polycarbonate resin film to form a retardation film. In particular, JP-A-6
In the lower left column of page 2 of Japanese Patent Laid-Open No. 3-189804, "To make the above polycarbonate polymer a retardation film, the polycarbonate polymer is formed into a film by a known film forming method, that is, a solvent casting method, a calendar method, or an extrusion method. Alternatively, it can be achieved by forming a sheet and then appropriately stretching it in the uniaxial direction. ”

In addition, in the general literature, for example, in the "STN-LCD phase difference film" report of Fuji Film Research Report No. 37 (March 20, 1992, issued by Fuji Film Co., Ltd.), Part 82. On page 83, a technology for producing a retardation film is disclosed, "We manufacture retardation films using polycarbonate as a raw material, and the following two points can be mentioned as the features of the technology ... ... By widening the film in the width direction free shrinking, the refractive index characteristic of the retardation film in the triaxial direction is increased to the limit performance of the uniaxial stretching, thereby realizing a wide viewing angle of the LCD. " Also, pages 183-184 of "Handbook of Liquid Crystal Display Manufacturing Technology" (published on April 30, 1992, Science Fall Co., Ltd.) ("2.1.1
"What is a retardation plate?", "The retardation plate used in the LCD is the latter, which is a uniaxially stretched polycarbonate or polyvinyl alcohol film." In addition, in June 1992, "Yano Economic Research Institute Co., Ltd.," Actual Conditions of Demand for Optical Functional Films for LCDs and Development Strategy, "in the middle of page 17," What is a retardation film? It is obtained by precision stretching in the direction .... 1989, Nitto Denko commercialized a uniaxially stretched film of polycarbonate as an STN-LCD discoloration film, and was in the spotlight. ”

As described above, the technique for producing a retardation film from a polycarbonate resin by uniaxial stretching is well known in the art.

[0006]

The object of the present invention is to provide a film for retardation film formed from a polycarbonate resin having excellent transparency, high refractive index and low birefringence, and its use. To do.

The present inventor has conducted earnest studies to achieve this object, and as a result, a polycarbonate copolymer in which a specific proportion of 9,9-bis (4-oxyphenylene) fluorene structural unit is introduced achieves the above object. Find out that
The present invention has been reached.

9,9-bis (4-hydroxyphenyl)
Aromatic polycarbonate resins obtained by reacting fluorene with a carbonate precursor are known, and it is also known that this polymer has a high refractive index and good heat resistance. However, when this homopolymer was synthesized, a large amount of a gel-like substance insoluble in the solvent was produced, and the yield of the solvent-soluble component was at most 60 to 70%, which was poor in practicality. Also,
When attempting to melt mold this, there was a problem that the melt viscosity was too high to mold.

However, the aromatic polycarbonate resin obtained by copolymerizing a specific amount of 9,9-bis (4-oxyphenylene) fluorene constitutional unit does not have such a defect, but also has a high refractive index and a low birefringence. It is surprising to show.

In general, a retardation film made of a polycarbonate resin film having a high photoelastic constant has a low stretching ratio, so that it is greatly affected by variations in the stretching ratio and unevenness. On the other hand, low birefringence, that is, low photoelastic constant (50 × 10 ⁻¹⁴ cm ² /
An aromatic polycarbonate resin film having a μN (50 × 10 ⁻¹³ cm ² / dyne or less) necessarily increases the uniaxial stretching ratio. As a result, variations in birefringence,
A retardation film with less spots can be obtained. In addition, since it is sufficiently stretched, it is less likely to be deformed by the tension received in the process of laminating the retardation film on the polarizing plate, etc., and it is less likely to induce the change in birefringence during the process and the occurrence of variation than the conventional product. .

[0011]

The present invention provides the following general formula [1]:

[0012]

[Chemical 3]

[Wherein R _{1 to} R ₄ are a hydrogen atom, a halogen atom, a phenyl group or an alkyl group having 1 to 3 carbon atoms,
It may be the same or different. ] And the following general formula [2]

[0014]

[Chemical 4]

[Wherein W is a single bond, an alkylidene group, a cycloalkylidene group, a phenyl group-substituted alkylidene group, a sulfone group, a sulfide group or an oxide group, and R ₅ and R ₆ are a hydrogen atom, a halogen atom, a phenyl group, It is an alkyl group having 1 to 3 carbon atoms and may be the same or different, and m and n are each an integer of 1 to 4. ] Containing 41 to 95 mol% of the structural unit represented by the general formula [1], the photoelastic constant is 50 × 10 5.
^-14 cm ² / μN (50 × 10 ^-13 cm ² / dyne) or less and 0.7 g is dissolved in 100 ml of methylene chloride, and 2
A high refractive index having a specific viscosity of 0.19 or more measured at 0 ° C.,
The present invention relates to a film for retardation film formed of a low birefringence polycarbonate resin and its use.

Polycarbonate resins of interest in the present invention are prepared by reacting 9,9-bis (4-hydroxyphenyl) fluorenes with one or more other dihydric phenol compounds, endcapping agents and carbonate precursor materials. Manufactured. It is usually produced by an interfacial polycondensation method using phosgene or a transesterification reaction using a carbonic acid diester.

9,9-bis (4-hydroxyphenyl)
Examples of fluorenes include 9,9-bis (4-hydroxyphenyl) fluorene, 9,9-bis (3-methyl-4-hydroxyphenyl) fluorene, and 9,9-bis (3-ethyl-4-hydroxyphenyl). ) Fluorene and the like, and particularly 9,9-bis (4-hydroxyphenyl) fluorene is preferable.

Other dihydric phenols include, for example, bis (4-hydroxyphenyl) methane and 2,2-bis (4
-Hydroxyphenyl) propane [commonly known as bisphenol A], 2,2-bis (4-hydroxy-3-methylphenyl) propane, 4,4-bis (4-hydroxyphenyl) heptane, 2,2-bis (4-hydroxy) -3,5
-Dichlorophenyl) propane, 2,2-bis (4-hydroxy-3,5-dibromophenyl) propane, bis (4-hydroxyphenyl) oxide, bis (3,5
-Dichloro-4-hydroxyphenyl) oxide,
4,4'-dihydroxydiphenyl, 3,3'-dichloro-4,4'-dihydroxydiphenyl, bis (4-hydroxyphenyl) sulfone, bis (3,5-dimethyl-4-hydroxyphenyl) sulfone, bis (4 -Hydroxyphenyl) sulfide, bis (4-hydroxyphenyl) sulfoxide and the like are mentioned, and bisphenol A is particularly preferable. Examples of the terminal terminator include p-ter.
A monohydric phenol such as t-butylphenol is used. The amount used is usually 0.01 to 10 mol%, preferably 0.03 to 8 mol% based on the dihydric phenol used.
Is.

In the interfacial polycondensation reaction using phosgene,
Usually, 9,9-bis (4-hydroxyphenyl) fluorenes and other dihydric phenol are dissolved in an aqueous solution of an acid binder and reacted in the presence of an organic solvent. As the acid binder, for example, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide are used, and as the organic solvent, halogenated hydrocarbons such as methylene chloride and chlorobenzene are used. The reaction is usually 0 to 40 ° C., preferably 20
The process is completed in about 10 minutes to 10 hours at -30 ° C. It is preferable to keep the pH of the reaction system at 10 or higher as the reaction progresses. A catalyst may be used to accelerate the reaction, and examples of the catalyst include triethylamine and tetra-n.
Examples include tertiary amines such as -butylammonium bromide and tetra-n-butylphosphonium bromide, quaternary ammonium compounds, and quaternary phosphonium compounds. Furthermore, if necessary, an antioxidant such as hydrosulfite can be added.

In the transesterification reaction using a carbonic acid diester, 9,9-bis (4-hydroxyphenyl) fluorenes and other dihydric phenol compounds are produced by stirring the carbonic acid diester with heating in an inert gas atmosphere. It is carried out by distilling alcohol or phenol.
The reaction temperature varies depending on the boiling point of the alcohol or phenol to be produced, but is usually in the range of 120 to 350 ° C.
In the latter stage of the reaction, the system is depressurized to facilitate the distillation of the alcohol or phenol produced and complete the reaction. Examples of the carbonic acid diester include diphenyl carbonate, dinaphthyl carbonate, bis (diphenyl) carbonate, dimethyl carbonate, diethyl carbonate, dibutyl carbonate and the like. Of these, diphenyl carbonate is particularly preferable.

A polymerization catalyst may be used to accelerate the polymerization rate. As the polymerization catalyst, hydroxides of alkali metals and alkaline earth metals such as sodium hydroxide and potassium hydroxide, and hydroxides of boron and aluminum are used. Alkaline metal salts, alkaline earth metal salts, quaternary ammonium salts, alkali metal and alkaline earth metal alkoxides, alkali metal and alkaline earth metal organic acid salts,
Zinc compounds, boron compounds, silicon compounds, germanium compounds, organotin compounds, lead compounds, antimony compounds, manganese compounds, titanium compounds,
It is possible to use a catalyst which is usually used for esterification reaction and transesterification reaction of zirconium compounds and the like.
The catalyst may be used alone or in combination of two or more kinds. The amount of these catalysts used is 0.0001 to 1% by weight, preferably 0.000, based on the dihydric phenol as a raw material.
It is selected in the range of 5 to 0.5% by weight.

The molecular weight of the polycarbonate resin is 0.19 or more, preferably 0.26, as a specific viscosity measured at 20 ° C. in a methylene chloride solution having a concentration of 0.7 g / dl.
.About.0.45. If it is less than 0.19, the obtained molded product becomes brittle, which is not suitable.

In the polycarbonate resin of the present invention, the content ratio of the constitutional unit represented by the general formula [1] and the constitutional unit represented by the general formula [2] is 41 to 95 mol% of the former and 59 to 5 of the latter. Mol%. The former is 50 to 85 mol% and the latter is 50 to 15 mol%. If the content of the structural unit represented by the general formula [1] is less than 41 mol%, the birefringence will not be sufficiently low, and if it exceeds 95 mol%, the birefringence will be significantly reduced, but the transparency will be poor.

In the polycarbonate resin of the present invention, if necessary, for example, triphenyl phosphite, tris (nonylphenyl) phosphite, distearyl pentaerythritol diphosphite, diphenyl hydrogen phosphite, Irganox 1076 [stearyl-β -(3,5-di-tert-butyl-4-
Hydroxyphenyl) propionate] and the like, for example 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-
3 ', 5'-di-tert-amylphenyl) benzotriazole, 2- (2'-hydroxy-4'-octoxyphenyl) benzotriazole, 2-hydroxy-4
-Additives such as weathering agents such as octoxybenzophenone, colorants, antistatic agents, release agents and lubricants may be added. Further, any method such as injection molding, extrusion molding, and heat press molding is adopted to mold the polycarbonate resin of the present invention, but the method of film formation by the casting method is most suitable for increasing transparency. is there. The polycarbonate resin of the present invention obtained as described above has a high refractive index, low birefringence, and excellent transparency.

[0025]

EXAMPLES The present invention will be further described with reference to the following examples. The parts and% in the examples are parts by weight and% by weight, unless otherwise specified. The specific viscosity, total light transmittance, refractive index and photoelastic coefficient were measured by the following methods. Specific viscosity: 0.7 g of the polymer was dissolved in 100 ml of methylene chloride and measured at 20 ° C. Total light transmittance: Measured by Σ80 manufactured by Nippon Denshoku Co., Ltd. according to ASTM D-1003. Refractive index: wavelength 59 by Abbe refractometer manufactured by Atago Co., Ltd.
It was measured at 25 ° C. using a D line of 8.3 nm. Photoelastic coefficient (birefringence): 30 mm × 10 mm × 100
The film was measured with a photoelasticity measuring device PA-150 manufactured by Riken Keiki Co., Ltd. using a film of μm.

Example 1 21.5 parts of 9,9-bis (4-hydroxyphenyl) fluorene, bisphenol A
2.47 parts, 43.8% caustic soda aqueous solution 23.8 parts and distilled water 361 parts were charged into a reactor equipped with a stirrer and dissolved. To this, 162 parts of methylene chloride was added, and the mixed solution became
It was cooled to 0 ° C., and 10.0 parts of phosgene was blown thereinto in 40 minutes. Thereafter, 0.108 parts of p-tert-butylphenol was added to the reaction solution as a solution in methylene chloride, 2.98 parts of a 48.5% aqueous sodium hydroxide solution and 0.05 parts of triethylamine were added, and the mixture was stirred for 2 hours to continue the reaction. finished. After completion of the reaction, a lower layer methylene chloride solution of polycarbonate was separated from the reaction solution, the solution was washed with an aqueous solution of hydrochloric acid and distilled water, and then methylene chloride was removed by evaporation to obtain a polycarbonate powder. The specific viscosity of the obtained powder was 0.850. This powder was dissolved in methylene chloride to form a film. The total light transmittance of this product is 89%, the refractive index is 1.636, and the photoelastic coefficient is 24 × 10 ^-14 cm ² / μN (24 × 10 ^-13
was cm ² / dyne). By applying a known technique to this film, it was found that this film is effective as a film for retardation film.

[Example 2] A powder was obtained in the same manner as in Example 1 except that 19.0 parts of 9,9-bis (4-hydroxyphenyl) fluorene and 4.11 parts of bisphenol A were used. The specific viscosity of this powder was 0.863. When this powder was molded and evaluated in the same manner as in Example 1, the total light transmittance was 89% and the refractive index was 1.631.
Photoelastic coefficient is 30 × 10 ^-14 cm ² / μN (30 × 10
^-13 cm ² / dyne). By applying a known technique to this film, it was found that this film is effective as a film for retardation film.

[Example 3] A powder was obtained in the same manner as in Example 1 except that 12.6 parts of 9,9-bis (4-hydroxyphenyl) fluorene and 8.23 parts of bisphenol A were used. The specific viscosity of this powder was 0.755. When this powder was molded and evaluated in the same manner as in Example 1, the total light transmittance was 90% and the refractive index was 1.616.
Photoelastic coefficient is 48 × 10 ^-14 cm ² / μN (48 × 10
^-13 cm ² / dyne). By applying a known technique to this film, it was found that this film is effective as a film for retardation film.

[Comparative Example 1] A powder was obtained in the same manner as in Example 1 except that 2.53 parts of 9,9-bis (4-hydroxyphenyl) fluorene and 14.8 parts of bisphenol A were used. The specific viscosity of this powder was 1.024. When this powder was molded and evaluated in the same manner as in Example 1, the total light transmittance was 90% and the refractive index was 1.592.
The photoelastic coefficient is 74 × 10 ^-14 cm ² / μN (74 × 10
^-13 cm ² / dyne).

[Comparative Example 2] Bisphenol A polycarbonate powder having a specific viscosity of 0.451 [Teijin Kasei Co., Ltd.]
Panlite L-1250] was molded and evaluated in the same manner as in Example 1. The total light transmittance was 90% and the refractive index was 1.5.
89, the photoelastic coefficient is 83 × 10 ⁻¹⁴ cm ² / μN (83 ×
It was 10 ^-13 cm ² / dyne).

[0031]

The film for retardation film formed from the polycarbonate resin of the present invention has a high refractive index, low birefringence and excellent transparency, and is therefore extremely useful as a retardation film.

Continuation of front page (56) Reference JP-A-63-182336 (JP, A) JP-A-2-304741 (JP, A) JP-A-4-84106 (JP, A) JP-A-3-281524 (JP , A) JP 5-11115 (JP, A) JP 6-18701 (JP, A) JP 6-25399 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB) Name) C08J 5/18 C08G 64/00-64/42 G02B 5/30 C08L 69/00

Claims (7)

(57) [Claims] 1. The following general formula [1]: [In the formula, R _{1 to} R ₄ are a hydrogen atom, a halogen atom, a phenyl group or an alkyl group having 1 to 3 carbon atoms and may be the same or different. ] And the following general formula [2] [Wherein W is a single bond, an alkylidene group, a cycloalkylidene group, a phenyl group-substituted alkylidene group, a sulfone group, a sulfide group or an oxide group, and R ₅ and R ₆ are a hydrogen atom, a halogen atom, a phenyl group, and a carbon number of 1 ~ 3 alkyl groups, which may be the same or different, m and n
Are integers of 1 to 4, respectively. ] Containing 41 to 95 mol% of the structural unit represented by the general formula [1] and having a photoelastic constant of 50 × 10 ⁻¹⁴ cm ² / μN.
(50 × 10 ^-13 cm ² / dyne) or less and 0.7 g
A film for retardation film formed from a high-refractive index, low-birefringence polycarbonate resin having a specific viscosity of 0.19 or more when dissolved in 100 ml of methylene chloride and measured at 20 ° C. 2. The film for retardation film according to claim 1, wherein R _{1 to} R ₄ are the same or different and each is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. 3. W is an alkylidene group, R ₅ and R ₆
Is a hydrogen atom, The film for retardation films of Claim 1 or 2. 4. The film for retardation film according to claim 1, which contains 50 to 85 mol% of the structural unit represented by the general formula [1]. 5. The film for retardation film according to claim 1, wherein the monohydric phenol end-stopping agent is used in an amount of 0.01 to 10 mol% based on all dihydric phenols. . 6. The film according to claim 1, wherein the film is a retardation film. 7. Use of the film according to claim 1 as a retardation film.