KR102181206B1 - Resin composition for optical materials, optical film and liquid crystal display device - Google Patents

Abstract

(식 중, A¹, A²는 각각 독립적으로 탄소 원자수 1∼8의 알킬기 또는 탄소 원자수 6∼18의 아릴기이다. R¹∼R⁴은, 각각 독립적으로 탄소 원자수 1∼3의 알킬기이다. X¹, X²는 각각 독립적으로 2가의 연결기이다)으로 표시되는 화합물(B)을 함유하는 광학 재료용 수지 조성물을 제공한다.The present invention has a small change in birefringence due to an external force, and aims to provide a resin composition that can be suitably used for manufacturing an optical member, an optical film obtained by using the resin composition, and a liquid crystal display device using the same, ( Polymer (A) obtained using meth)acrylic acid or (meth)acrylic acid alkyl ester, and the following general formula (1)

(In the formula, A ¹ and A ² are each independently an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 18 carbon atoms. R ¹ to R ⁴ each independently have 1 to 3 carbon atoms. It is an alkyl group. Each of X ¹ and X ² independently represents a divalent linking group) to provide a resin composition for an optical material containing the compound (B).

Description

A resin composition for optical materials, an optical film, and a liquid crystal display device TECHNICAL FIELD TECHNICAL FIELD [RESIN COMPOSITION FOR OPTICAL MATERIALS, OPTICAL FILM AND LIQUID CRYSTAL DISPLAY DEVICE}

The present invention relates to a resin composition that has a small change in birefringence due to an external force and can be suitably used for manufacturing an optical member, an optical film obtained by using the resin composition, and a liquid crystal display device using the same.

In recent years, for example, with the expansion of the display market, the demand to view images more clearly is increasing, and an optical material with more advanced optical properties is required, rather than a simple transparent material.

In general, a polymer causes birefringence because the refractive index is different in the direction of the molecular main chain and the direction perpendicular to it. Depending on the application, it is required to strictly control this birefringence, and in the case of a protective film used for a polarizing plate of a liquid crystal, it is believed that a molded article of a polymer material having a smaller birefringence is required even if the total light transmittance is the same, and triacetylcellulose is a representative Used as a material.

Among these, in recent years, as liquid crystal displays have grown in size and molded polymeric optical materials required for them have increased in size, in order to reduce the distribution of birefringence caused by the bias of external force, a material having a small change in birefringence due to external force is required. .

A material from which a molded article having a small change in birefringence due to an external force is obtained, that is, a polymer optical material from which a molded article having a small photoelastic coefficient is obtained, and among these materials, acrylic resins are attracting attention as inexpensive materials. Specifically, a resin composition containing an acrylic resin and an aliphatic polyester resin as a plasticizer is known (for example, see Patent Document 1). However, even when the optical material disclosed in Patent Document 1 is used, it has been difficult to obtain an optical film having a sufficiently small photoelastic coefficient.

International Publication No. 2006/077776 pamphlet

The problem to be solved by the present invention is to provide a resin composition that has a small change in birefringence due to an external force and can be suitably used for manufacturing an optical member, an optical film obtained using the resin composition, and a liquid crystal display device using the same. There is one.

As a result of intensive investigation, the present inventors used a composition containing an acrylic resin and a compound having a biphenyl skeleton, and the terminal of the compound having a structure sealed with a hydrocarbon group or an aryl group. An optical member having a small change in birefringence due to is obtained, the resin composition is particularly suitable when manufacturing an optical film, and the optical film can be suitably used as a member when manufacturing a liquid crystal display device. We found out, and came to complete the present invention.

That is, the present invention is a polymer (A) obtained using (meth)acrylic acid or (meth)acrylic acid alkyl ester, and the following general formula (1)

(In the formula, A ¹ and A ² are each independently an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 18 carbon atoms. R ¹ to R ⁴ each independently have 1 to 3 carbon atoms. It is an alkyl group, X ¹ and X ² are each independently a divalent linking group)

It is to provide the resin composition for optical materials characterized by containing the compound (B) represented by.

In addition, the present invention provides an optical film comprising the resin composition for optical materials.

Further, the present invention is to provide a liquid crystal display device having the optical film.

ADVANTAGE OF THE INVENTION According to this invention, the change in birefringence by an external force is small, and the resin composition which can be used suitably for manufacture of an optical member can be provided by using the acrylic resin which is an inexpensive material. By using this resin composition, an optical film with a small change in birefringence due to external force can be easily obtained. And, by using this optical film, it is possible to obtain a liquid crystal display device in which the visibility of the screen is hardly changed by an external force.

The polymer (A) used in the present invention is obtained using (meth)acrylic acid or (meth)acrylic acid alkyl ester, and specifically, (meth)acrylic acid or (meth)acrylic acid alkyl ester is required, It is obtained by polymerization by using other polymerizable monomers together. Examples of the (meth)acrylic acid or (meth)acrylic acid alkyl ester include acrylic acid; Methacrylic acid: alkyl methacrylate esters such as cyclohexyl methacrylate, t-butylcyclohexyl methacrylate, and methyl methacrylate; And alkyl acrylate esters such as methyl acrylate, ethyl acrylate, butyl acrylate, isopropyl acrylate, and 2-ethylhexyl acrylate.

Among the polymers (A) used in the present invention, a homopolymer of methyl methacrylate or a copolymer of methyl methacrylate and other monomers is preferable because a film having excellent optical properties is obtained and also excellent in economic efficiency.

As said other monomer, For example, (meth)acrylic acid or (meth)acrylic acid ester other than methyl methacrylate; Aromatic vinyl compounds such as styrene, vinyl toluene, and α-methylstyrene; Vinyl cyanides such as acrylonitrile and methacrylonitrile; Maleimides such as N-phenylmaleimide and N-cyclohexylmaleimide; Unsaturated carboxylic anhydrides such as maleic anhydride; Unsaturated acids, such as maleic acid, etc. are mentioned.

Monomers such as aromatic vinyl compounds, vinyl cyanides, maleimides, unsaturated carboxylic anhydrides, and unsaturated acids exemplified as the other monomers are within a range that does not impair the effects of the present invention even when methyl methacrylate is not used. Can be used.

When the above methyl methacrylate and other monomers are copolymerized to obtain a polymer to be used as the polymer (A), aromatic vinyl compounds are preferable since an optical film excellent in heat resistance and economy is obtained as other monomers. Among them, styrene and α -Methylstyrene is more preferable. Here, the amount of aromatic vinyl compounds used is preferably 1 to 50 parts by mass, more preferably 2 to 30 parts by mass, based on 100 parts by mass of methyl methacrylate.

In addition, the effect of obtaining an optical film excellent in heat resistance can be expected by using an unsaturated carboxylic anhydride as the other monomer. Among the unsaturated carboxylic anhydrides, maleic anhydride is preferable. Here, the amount of unsaturated carboxylic anhydride used is preferably 1 to 100 parts by mass, more preferably 5 to 90 parts by mass, based on 100 parts by mass of methyl methacrylate.

As the polymer (A) used in the present invention, (meth)acrylic acid or (meth)acrylic acid alkyl ester may be used alone, or two or more may be used in combination. Moreover, you may use independently also about said other monomer, and may use 2 or more types together.

The weight average molecular weight of the polymer (A) used in the present invention is preferably 50,000 to 200,000, since a molded article such as an optical film having strength is obtained, and a resin composition having sufficient fluidity and excellent molding processability is obtained. , 70,000 to 150,000 are more preferable.

In addition, the number average molecular weight of the polymer (A) used in the present invention is preferably 15,000 to 100,000, and more preferably 20,000 to 50,000.

Here, in the present invention, the weight average molecular weight (Mw) and the number average molecular weight (Mn) are values converted into polystyrene based on GPC measurement. In addition, the measurement conditions of GPC are as follows.

[GPC measurement conditions]

Measuring device: "HLC-8220 GPC" manufactured by Tosoh Corporation

Column: Tosoh Corporation guard column "HHR-H" (6.0mm ID×4cm) + Tosoh Corporation's "TSK-GEL GMHHR-N" (7.8mm ID×30cm) + Tosoh Corporation "TSK-GEL GMHHR-N" (7.8mm ID×30cm) made by Shiki Co., Ltd.+ “TSK-GEL GMHHR-N” (7.8mm ID×30cm) made by Tosoh Co., Ltd. TSK-GEL GMHHR-N"(7.8mm ID×30cm)

Detector: ELSD (“ELSD2000” manufactured by Ortech)

Data processing: "GPC-8020 Model II Data Analysis Version 4.30" manufactured by Tosoh Corporation

Measurement conditions: column temperature 40°C

Developing solvent tetrahydrofuran (THF)

Flow rate 1.0ml/min

Sample: 1.0 mass% tetrahydrofuran solution in terms of resin solid content was filtered through a micro filter (5 µl).

Standard sample: In accordance with the measurement manual of the "GPC-8020 Model II Data Analysis Version 4.30", the following monodisperse polystyrene having a known molecular weight was used.

(Monodisperse polystyrene)

``A-500'' manufactured by Tosoh Corporation

``A-1000'' manufactured by Tosoh Corporation

``A-2500'' manufactured by Tosoh Corporation

``A-5000'' manufactured by Tosoh Corporation

``F-1'' manufactured by Tosoh Corporation

``F-2'' made by Tosoh Corporation

``F-4'' made by Tosoh Corporation

``F-10'' manufactured by Tosoh Corporation

``F-20'' manufactured by Tosoh Corporation

``F-40'' manufactured by Tosoh Corporation

``F-80'' manufactured by Tosoh Corporation

``F-128'' manufactured by Tosoh Corporation

``F-288'' manufactured by Tosoh Corporation

``F-550'' manufactured by Tosoh Corporation

As a method for producing the polymer (A) used in the present invention, various polymerization methods such as cast polymerization, bulk polymerization, suspension polymerization, solution polymerization, emulsion polymerization, and anionic polymerization can be used. Among the manufacturing methods, bulk polymerization and solution polymerization are preferable because a polymer with little mixing of minute foreign matters is obtained. In the case of performing solution polymerization, a solution prepared by dissolving a mixture of raw materials in a solvent of an aromatic hydrocarbon such as toluene and ethylbenzene can be used. In the case of polymerization by bulk polymerization, polymerization can be initiated by irradiation of free radicals or ionizing radiation generated by heating, as is usually performed.

As the initiator used in the polymerization reaction, any initiator generally used in radical polymerization can be used, and examples thereof include azo compounds such as azobisisobutylnitrile; Organic peroxides, such as benzoyl peroxide, lauroyl peroxide, and t-butyl peroxy-2-ethylhexanoate, etc. are used. When polymerization is carried out at a high temperature of 90°C or higher, solution polymerization is common, so a 10-hour half-life temperature of 80°C or higher and a peroxide, azobis initiator, etc. soluble in the organic solvent used are used. Preferably, 1,1-bis(t-butylperoxy)3,3,5-trimethylcyclohexane, cyclohexane peroxide, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane , 1,1-azobis(1-cyclohexanecarbonitrile), 2-(carbamoylazo)isobutyronitrile, etc. are mentioned. These initiators are used in the range of 0.005 to 5% by mass.

When polymerizing the polymer (A) used in the present invention, a molecular weight modifier may be used if necessary. Any of the molecular weight modifiers used in general radical polymerization is used, and for example, mercaptan compounds such as butyl mercaptan, octyl mercaptan, dodecyl mercaptan, and 2-ethylhexyl thioglycolic acid are particularly preferred. It can be mentioned as one. These molecular weight modifiers are added in a concentration range such that the degree of polymerization is controlled within the above range.

Compound (B) used in the present invention is the following general formula (1)

(In the formula, A ¹ and A ² are each independently an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 18 carbon atoms. R ¹ to R ⁴ each independently have 1 to 3 carbon atoms. It is an alkyl group, X ¹ and X ² are each independently a divalent linking group)

As represented by, it contains a biphenol skeleton. By having a biphenyl skeleton, an effect of reducing the absolute value of the photoelastic coefficient of the acrylic resin can be expected. In addition, since the terminal is sealed with A ¹ or A ^{2 described} above, a resin composition having excellent stability such as storage stability is obtained.

X ¹ and X ² in the compound (B) used in the present invention (including a non-phenolic skeleton) may be the same or different. Examples of X ¹ and X ² include an ester group, an ether group, a thioether group, an amino group, and an imino group. Among them, an ester group or an ether group is preferable for compatibility with acrylic resins.

Examples of the alkyl group having 1 to 8 carbon atoms that are specific examples of A ¹ and A ² include, for example, methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, t- Butyl group, n-pentyl group, isopentyl group, t-pentyl group, cyclopentyl group, n-hexyl group, isohexyl group, 2-hexyl group, dimethylbutyl group, ethylbutyl group, cyclohexyl group, heptyl group, Octyl group, etc. are mentioned. Examples of the aryl group having 6 to 18 carbon atoms include phenyl group, benzyl group, tolyl group, 2,4,6-trimethylphenyl group, tert-butylphenyl, 2,4-ditert-butylphenyl group, 2,6 -Ditert-butylphenyl group, naphthyl group, etc. are mentioned. Among them, a phenyl group and a tolyl group are preferable since it becomes a resin composition excellent in stability such as storage stability.

As a specific example of the compound (B) used in the present invention, for example, a compound represented by the following general formula can be preferably exemplified because it exhibits the effects of the present invention and can be easily obtained.

(In the formula, L ¹ and L ² are each independently an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 18 carbon atoms. R ¹ to R ⁴ each independently have 1 to 3 carbon atoms. Is an alkyl group)

The compound represented by the above general formula (1-1) is, for example, an epoxy compound having a biphenyl skeleton, a monocarboxylic acid having an alkyl group having 2 to 8 carbon atoms, or an aromatic monocarboxylic acid having 7 to 18 carbon atoms. It can be obtained by reacting a carboxylic acid. In addition, the compound represented by the general formula (1-2) is, for example, an epoxy compound having a biphenyl skeleton, a monoalcohol having an alkyl group having 1 to 8 carbon atoms or an alkoxide derivative thereof, and a carbon atom number. It can be obtained by reacting 6 to 18 aromatic monoalcohols.

Examples of the epoxy compound having a biphenyl skeleton include a diglycidyl ether type epoxy compound obtained by reaction of biphenols and epichlorohydrin. As a specific example of this epoxy compound, 3,3',5,5'-tetramethyl-4,4'-diglycidyloxybiphenyl (commercially available product is ``jER YX-4000 manufactured by Japan Epoxy Resin Co., Ltd. "(Epoxy equivalent 180 to 192)) and other non-phenolic epoxy compounds can be used.

Examples of the monocarboxylic acid having an alkyl group having 2 to 8 carbon atoms include acetic acid, propionic acid, butanoic acid, hexanoic acid, and octanoic acid. Examples of the aromatic monocarboxylic acid having 7 to 18 carbon atoms include benzoic acid, dimethylbenzoic acid, trimethylbenzoic acid, tetramethylbenzoic acid, ethylbenzoic acid, propylbenzoic acid, cumic acid, o-toluic acid, m-toluic acid, p- Toluic acid, anisic acid, ethoxybenzoic acid, propoxybenzoic acid, cyanobenzoic acid, fluorobenzoic acid, nitrobenzoic acid, 4-phenylbenzoic acid, 4-(3-methylphenyl)benzoic acid, 4-(4-methylphenyl)benzoic acid, 4- (3,5-dimethylphenyl)benzoic acid, 2-methyl-4-phenylbenzoic acid, 2,6-dimethyl-4-phenylbenzoic acid, 2,6-dimethyl-4-(3,5-dimethylphenyl)benzoic acid, naphthoic acid , Nicotinic acid, furoic acid, 1-naphthalenecarboxylic acid, 2-naphthalenecarboxylic acid, and the like. The monocarboxylic acid having an alkyl group having 2 to 8 carbon atoms and the aromatic monocarboxylic acid having 7 to 18 carbon atoms may be used alone or in combination of two or more. In addition, in the present invention, the number of carbon atoms in the "monocarboxylic acid having an alkyl group having 2 to 8 carbon atoms" includes the number of carbon atoms in the carbonyl group. In addition, the number of carbon atoms of the carbonyl group is also included in the number of carbon atoms in the "aromatic monocarboxylic acid having 7 to 18 carbon atoms".

As the monoalcohol having an alkyl group having 1 to 8 carbon atoms, for example, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutyl alcohol, sec-butyl alcohol, t-butyl alcohol, n-pentane Ol, isopentyl alcohol, t-pentyl alcohol, cyclopentanol, n-hexanol, isohexanol, cyclohexanol, heptanol, octanol, and the like. Examples of the aromatic monoalcohol having 6 to 18 carbon atoms include phenol, benzyl alcohol, methylphenol, 2,4,6-trimethylphenol, tert-butylphenol, 2,4-ditert-butylphenol, and 2 ,6-ditert-butylphenol, 1-naphthol, 2-naphthol, and the like.

As described above, the compound represented by the general formula (1-1) is, for example, an epoxy compound having a biphenyl skeleton, a monocarboxylic acid having an alkyl group having 2 to 8 carbon atoms, or 7 to 18 carbon atoms. It can be obtained by reacting an aromatic monocarboxylic acid of.

Further, the compound represented by the general formula (1-2) is, for example, an epoxy compound having a biphenyl skeleton, a mono alcohol having an alkyl group having 1 to 8 carbon atoms, or an aromatic mono alcohol having 6 to 18 carbon atoms. It can be obtained by reacting alcohol. The reaction temperature when reacting the epoxy compound with the monocarboxylic acid or monoalcohol is preferably in the range of 80 to 130°C, and more preferably in the range of 100°C to 115°C. The reaction time is preferably in the range of 10 to 25 hours. In addition, the ratio of the epoxy compound to the monocarboxylic acid or monoalcohol is the ratio of the number of moles of the epoxy group of the epoxy compound and the number of moles of the monocarboxylic acid or the number of moles of monoalcohol (number of moles of epoxy group)/(number of moles of monocarboxylic acid or mono). It is preferable that the number of moles of alcohol) is in the range of 1/0.9 to 1.1.

In the reaction, the epoxy group of the epoxy compound and the carboxy group of the monocarboxylic acid or the hydroxyl group of the monoalcohol may use a catalyst as necessary. Examples of this catalyst include phosphine compounds such as trimethylphosphine, triethylphosphine, tributylphosphine, trioctylphosphine, and triphenylphosphine; Imidazole-based compounds such as 2-methylimidazole, 2-ethylimidazole, 2-isopropylimidazole, 2-ethyl-4-methylimidazole, and 4-phenyl-2-methylimidazole; Triethylamine, tributylamine, trihexylamine, triamylamine, triethanolamine, dimethylaminoethanol, triethylenediamine, dimethylphenylamine, dimethylbenzylamine, 2-(dimethylaminomethyl)phenol, 1,8-diazabi Amine compounds such as cyclo(5,4,0)undecene-7; Pyridine compounds, such as dimethylaminopyridine, etc. are mentioned. These catalysts are preferably used in an amount of 0.05 to 1 parts by mass based on 100 parts by mass in total of the epoxy compound and the aromatic monocarboxylic acid.

Among the compounds represented by the general formula (1-1) or the compounds represented by the general formula (1-2), it is preferable that L ¹ and L ² each be a phenyl group or a tolyl group because of good compatibility with an acrylic resin. . Among them, in the compound represented by General Formula (1-1), it is more preferable that L ¹ is a phenyl group or a tolyl group.

In addition, in the compound represented by the general formula (1-1) and the compound represented by the general formula (1-2), R ¹ to R ⁴ are each a compound having a methyl group having excellent compatibility with the polymer (A). It is desirable.

The properties of the compound (B) used in the present invention vary depending on factors such as composition, but are usually liquid, solid, paste, etc. at room temperature.

The content of the compound (B) in the resin composition for an optical material of the present invention also depends on the photoelastic coefficient of the polymer (A) to be used, but since the absolute value of the photoelastic coefficient of the resin composition can be reduced, it is 1 per 100 parts by mass of the polymer. -10 parts by mass is preferable, and 2 to 8 parts by mass are more preferable.

The optical film of the present invention is characterized by containing the resin composition for optical materials of the present invention. The optical film of the present invention has a feature of an extremely small photoelastic coefficient, and specifically, the absolute value of the photoelastic coefficient is 2.0×10 ^-12 /Pa or less, more preferably 1.0×10 ^-12 /Pa or less. Thus, the optical film of the present invention has a small photoelastic coefficient, and as a result, a change in birefringence due to an external force is small, and thus a liquid crystal display device in which the visibility of a screen is difficult to change due to an external force can be provided.

In the present invention, the photoelastic coefficient was measured by the method shown below.

<Measurement method of photoelastic coefficient (C _R )>

Using the optical film obtained by stretching as an example of the optical film of the present invention, this optical film is cut out in a width of 15 mm in the stretching direction to obtain a measurement sample. This measurement sample is fixed to a tensile jig for photoelastic measurement (manufactured by Oji-Isokugi Co., Ltd.), and the weight when the measurement sample is stretched every 100 g·f from 127.3 g·f to 727.3 g·f It was changed and the in-plane retardation change at 588 nm when each weight was applied was measured with a retardation measuring device KOBRA-WR (manufactured by Ojisokugiki Co., Ltd.). The measurement is performed under an atmosphere of 23°C and a relative humidity of 55%.

By using the composition for optical materials of the present invention, it can be used for manufacturing various optical molded articles. Among them, the composition for optical materials of the present invention can be used to produce a film-shaped molded article (optical film). In the optical film, for example, an optical film that is stretched in at least one axial direction and has an absolute value of photoelastic coefficient of 2 (×10 ^-12 /Pa) or less requires a retardation such as a retardation film, and It can be used suitably for applications requiring small changes in birefringence. As the phase difference film, an optical film having an absolute value of a photoelastic coefficient of 1 (×10 ^-12 /Pa) or less is preferable, and an optical film having an absolute value of a photoelastic coefficient of 0.5 (×10 ^-12 /Pa) or less is more preferable. The stretching ratio in the TD direction and the MD direction of such an optical film is appropriately selected according to the purpose, and by adjusting the amount of the compound (B), a phase difference in which birefringence is large from an optically isotropic optical film with small birefringence. You can even get a film.

In the resin composition for optical materials of the present invention, polymers other than the polymer (A) can be mixed within a range that does not impair the object of the present invention. Examples of polymers other than the polymer (A) include polyolefins such as polyethylene and polypropylene; Styrene resins such as polystyrene and styrene acrylonitrile copolymer; Thermoplastic resins such as polyamide, polyphenylene sulfide resin, polyetheretherketone resin, polyester resin, polysulfone, polyphenylene oxide, polyimide, polyetherimide, and polyacetal; And thermosetting resins such as phenol resin, melamine resin, silicone resin, and epoxy resin. These may mix 1 type and may mix 2 or more types.

In addition, arbitrary additives can be blended according to various purposes within a range not significantly impairing the effects of the present invention. The type of additive is not particularly limited as long as it is generally used for blending resins or rubbery polymers. Examples of additives include inorganic fillers and pigments such as iron oxide; Lubricants such as stearic acid, behenic acid, zinc stearate, calcium stearate, magnesium stearate, and ethylene bis stearoamide; Hyungje Rhee(離型劑); Softeners and plasticizers such as paraffinic process oil, naphthenic process oil, aromatic process oil, paraffin, organic polysiloxane, and mineral oil; Antioxidants such as hindered phenol-based antioxidants, phosphorus-based thermal stabilizers, lactone-based thermal stabilizers, and vitamin E-based thermal stabilizers; Light stabilizers such as hindered amine light stabilizers and benzoate light stabilizers; UV absorbers such as benzophenone UV absorbers, triazine UV absorbers, and benzotriazole UV absorbers; Flame retardant; Antistatic agent; Reinforcing agents such as organic fibers, glass fibers, carbon fibers, and metal whiskers; Coloring agents, other additives, or mixtures thereof.

The resin composition for an optical material of the present invention should just contain the polymer (A) and the compound (B), and the manufacturing method is not particularly limited. Specifically, for example, the polymer (A) and compound (B), and if necessary, the additives are mixed with a melt kneader such as a single screw extruder, a twin screw extruder, a Banbury mixer, a Brabender, and various kneaders. It can be obtained by using and melt-kneading.

The optical film of the present invention is characterized by containing the resin composition for optical materials of the present invention. In order to obtain the optical film of the present invention, methods such as extrusion molding and cast molding are used, for example. Specifically, for example, an unstretched optical film can be extruded using an extruder equipped with a T-die, a circular die, or the like. When obtaining the optical film of the present invention by extrusion molding, the resin composition for optical materials of the present invention obtained by melt-kneading the polymer (A) and the compound (B) in advance may be used, or the polymer ( A) and compound (B) can also be melt-kneaded and extruded as it is. Further, using a solvent that dissolves the polymer (A) and compound (B) components, the polymer (A) and compound (B) are dissolved in the solvent to obtain a so-called dope solution, and then cast-molded. The optical film of the present invention in an unstretched state can also be obtained by a method (solvent casting method).

Hereinafter, the solution casting method will be described in detail. The optical film obtained by the solution casting method shows optical isotropy substantially. The film exhibiting optical isotropy can be used, for example, for an optical material such as a liquid crystal display, and is particularly useful for a protective film for polarizing plates. Further, the film obtained by the above method is difficult to form irregularities on its surface, and is excellent in surface smoothness.

The solution casting method is generally included in the first step of dissolving the polymer (A) and the compound (B) in an organic solvent to cast the obtained resin solution onto a metal support, and the cast resin solution. The organic solvent is distilled off and dried to form a film, followed by a third step of peeling the film formed on the metal support from the metal support and drying by heating.

As the metal support used in the first step, an endless belt-like or drum-like metal can be exemplified. For example, a stainless steel and a mirror-finished surface can be used.

When casting a resin solution on the metal support, it is preferable to use a resin solution filtered through a filter in order to prevent foreign matters from being mixed in the resulting film.

The drying method of the second step is not particularly limited, for example, by blowing wind in a temperature range of 30 to 50°C to the upper and/or lower surfaces of the metal support, A method of evaporating 50 to 80% by mass of the organic solvent contained therein to form a film on the metal support is mentioned.

Next, the third step is a step of peeling the film formed in the second step from the metal support, and drying by heating under a temperature condition higher than that of the second step. As the heat drying method, for example, a method of increasing the temperature step by step under a temperature condition of 100 to 160°C is preferable because good dimensional stability can be obtained. By heating and drying under the above temperature conditions, the organic solvent remaining in the film after the second step can be almost completely removed.

Further, in the first to third steps, the organic solvent may be recovered and reused.

The organic solvent that can be used when the polymer (A) and the compound (B) are mixed and dissolved in an organic solvent is not particularly limited as long as it can dissolve them. For example, chloroform, methylene dichloride, methylene chloride, etc. And a solvent.

The concentration of the polymer (A) in the resin solution is preferably 10 to 50% by mass, more preferably 15 to 35% by mass.

The film thickness of the optical film of the present invention is preferably in the range of 20 to 120 µm, more preferably in the range of 25 to 100 µm, and particularly preferably in the range of 25 to 80 µm.

In the present invention, for example, the optical film in the unstretched state obtained by the above method is stretched by uniaxial longitudinal stretching in the mechanical flow direction and uniaxial transverse stretching in a direction straight to the mechanical flow direction, if necessary. You can get a film. In addition, a biaxially stretched stretched film can be obtained by stretching by a sequential biaxial stretching method of roll stretching and tenter stretching, a simultaneous biaxial stretching method by tenter stretching, a biaxial stretching method by tubular stretching, or the like. The draw ratio is preferably 0.1% or more and 1000% or less in at least one direction, more preferably 0.2% or more and 600% or less, and particularly preferably 0.3% or more and 300% or less. By designing in this range, a stretched optical film preferable from the viewpoint of birefringence, heat resistance and strength is obtained.

The optical film according to the present invention, as an optical material, is a polarizing plate protective film used in displays such as a liquid crystal display device, a plasma display, an organic EL display, a field emission display, and a rear projection television, a 1/4 wavelength plate, and a 1/2 It can be suitably used for a wave plate, a viewing angle control film, a retardation film such as a liquid crystal optical compensation film, and a front panel of a display. In addition, the resin composition for an optical material of the present invention, in the fields of optical communication systems, optical exchange systems, optical measurement systems, waveguides, lenses, optical fibers, optical fibers substrates, coating materials, LED lenses, lens covers, etc. Can also be used.

[Example]

Hereinafter, the present invention will be described in more detail based on examples. Parts and percentages in the examples are by mass unless otherwise noted.

Synthesis Example 1 [Synthesis of Compound (B)]

To a 1-liter four-necked flask equipped with a thermometer, stirrer, reflux condenser and nitrogen inlet tube, 299 g of tetramethylbiphenol-type epoxy resin (epoxy equivalent 187), 195 g of benzoic acid and 1 g of triphenylphosphine as a catalyst were added, and at 115° C. It was made to react for 20 hours, and the compound (B1) represented by the said general formula (1-1) was obtained. The acid value of Compound (B1) was 0.7, and the hydroxyl value was 178.

Synthesis Example 2 (Synthetic phase)

To a 1-liter four-necked flask equipped with a thermometer, stirrer, reflux condenser and nitrogen inlet tube, 299 g of tetramethylbiphenol-type epoxy resin (epoxy equivalent 187), 195 g of phenol and 1 g of triphenylphosphine as a catalyst were added, and at 115°C It was made to react for 20 hours, and the compound (B2) represented by the said general formula (1-2) was obtained. The acid value of Compound (B2) was 0.7, and the hydroxyl value was 178.

Synthesis Example 3 (frost phase)

To a 1-liter four-necked flask equipped with a thermometer, a stirrer, a reflux condenser and a nitrogen inlet tube, 299 g of tetramethylbiphenol-type epoxy resin (epoxy equivalent 187), 217 g of paratoluic acid, and 1 g of triphenylphosphine as a catalyst were added, and 115 The reaction was carried out at °C for 24 hours to obtain a compound (B3) represented by the general formula (1-1). The acid value of Compound (B3) was 0.2, and the hydroxyl value was 171.

Synthesis Example 4 [Synthesis of Comparative Polyester Resin (b')]

In a 1-liter four-necked flask equipped with a thermometer, a stirrer, and a reflux condenser, 341 g of ethylene glycol and 659 g of adipic acid were added. Further, 30 ppm of tetraisopropyl titanate was added to the total amount of ethylene glycol and adipic acid, heated to 220° C. while stirring under a nitrogen stream, and reacted for 24 hours, the number average molecular weight was 1,100, and the acid value was 0.19, A polyester resin (b'1) for comparison and control having a hydroxyl value of 112 was obtained.

Synthesis Example 5 (frost phase)

In the same manner as in Synthesis Example 3, except that 770 g of succinic acid, 595 g of 1,2-propylene glycol, and tetraisopropyl titanate were used with respect to the total amount of succinic acid and 1,2-propylene glycol, the number average molecular weight was 11,000, and the acid value was 0.7. And a polyester resin (b'2) for comparison and control having a hydroxyl value of 8.

Example 1 (Preparation of resin composition for optical material)

100 parts of acrylic resin (A1) [copolymer of methyl methacrylic acid/maleic anhydride/styrene = 50/40/10 (molar ratio), number average molecular weight 27,800], 5 parts of polyester resin (B1), 270 parts of methylene chloride, and It was added to and dissolved in a mixed solvent consisting of 30 parts of methanol to obtain the resin composition for optical materials (dope solution) of the present invention.

This dope solution was cast on a glass plate so as to have a thickness of 0.5 mm, dried at room temperature for 16 hours, and then dried at 50°C for 30 minutes and further at 100°C for 60 minutes to obtain an unstretched film having a thickness of 100 μm.

The obtained unstretched film was uniaxially stretched at a temperature of +5° C. of the glass transition temperature (Tg) of the resin composition for an optical material (1) determined by a differential scanning calorimeter (DSC) (2 times the draw ratio, the draw rate 100%/min. ) Was performed, and the stretched film 1 was created. Here, the measurement of Tg using a differential scanning calorimeter (DSC) followed the following conditions.

<Measurement conditions of glass transition temperature Tg>

Differential scanning calorimetry DSC822e (made by METTLER TOLEDO) was used. Specifically, 5 mg of the resin composition was put in a lightweight aluminum pan, heated from 25°C to 150°C at 10°C per minute (1st run) under a nitrogen atmosphere, and then rapidly cooled to 0°C, and again, from 0°C to 150°C. The temperature was raised to 10 ℃ every minute to ℃ (2nd run). The glass transition temperature Tg was determined by the midpoint method from the DSC curve obtained in the 2nd run.

The optical properties of the obtained stretched film 1, specifically, in-plane birefringence (Δn), out-of-plane birefringence (ΔP) photoelastic coefficient (C _R ), and haze were evaluated according to the methods shown below. Table 1 shows the evaluation results.

<Evaluation method of in-plane birefringence (Δn) and out-of-plane birefringence (ΔP)>

After obtaining the refractive index at 588 nm using the phase difference measuring device KOBRA-WR (manufactured by Ojisokugiki Co., Ltd.), in-plane birefringence (Δn) and out-of-plane birefringence (ΔP) were determined according to the following equation.

In-plane birefringence (Δn)=(n _x )-(n _y )

Out-of-plane birefringence (ΔP)=[(n _x )+(n _y )]/2-(n _z )

〔(N _x ): refractive index in the stretching direction, (n _y ): refractive index in the direction orthogonal to the stretching direction, (n _z ): refractive index in the film thickness direction]

In addition, the measurement was performed in an atmosphere of 23°C and a relative humidity of 55%.

<Evaluation method of photoelastic coefficient (C _R )>

A stretched film cut out in a width of 15 mm parallel to the stretching direction was fixed to a tensile jig for measuring photoelasticity (manufactured by Oji-Isokugiki Co., Ltd.), and from 127.3 g·f to 727.3 g·f to 100 g·f The change in the in-plane retardation (Re) at 588 nm when the weight was changed for each time was measured with a retardation measuring device KOBRA-WR (manufactured by Ojisokugiki Co., Ltd.). The measurement was performed in an atmosphere of 23°C and a relative humidity of 55%. The in-plane phase difference (Re) was calculated according to the following equation.

Re=(n _x -n _y )×d

((N _x ): refractive index in the stretching direction, (n _y ): refractive index in the direction orthogonal to the stretching direction, d: thickness of the film (µm))

For the measured values, the stress (σ) on the horizontal axis and the in-plane phase difference (Re) on the vertical axis were plotted, and the photoelastic coefficient (C _R ) was obtained from the slope of a straight line in a linear region by least square approximation. The smaller the absolute value of the inclination indicates that the photoelastic coefficient is close to 0, and indicates that the optical film has a small change in birefringence due to an external force.

<Evaluation of Haze>

Nihon Denshoku Kogyo Co., Ltd. NDH-5000 was used to comply with JIS K 7136.

Examples 2 to 8 and Comparative Examples 1 to 6

Optical films (2) to (8) and stretched film (1') for comparison and control in the same manner as in Example 1 except that the resin composition for optical materials (dope solution) was obtained under the blending and stretching conditions shown in Tables 1 to 2 -(5') was obtained. The same evaluation as in Example 1 was performed, and the results are shown in Tables 1 to 2.

[Table 1]

Footnotes in Table 1

Inability to measure: The film's haze was so large that optical properties could not be measured.

[Table 2]

Footnotes in Table 2

Acrylic film (A2): Copolymer of methyl methacrylate/α-methylstyrene = 93/7 (molar ratio), number average molecular weight 30,000)

Inability to measure: The film's haze was so large that optical properties could not be measured.

The optical film obtained by using the resin composition for optics of the present invention is a film having a small optical elastic modulus and a small change in birefringence due to an external force. On the other hand, the optical film of the comparative example has a large absolute value of the optical elastic modulus and a large change in birefringence due to an external force.

Claims (10)

Polymer (A) obtained using (meth)acrylic acid or (meth)acrylic acid alkyl ester and having a number average molecular weight of 15,000 to 100,000, and the following general formula (1)

(In the formula, A ¹ and A ² are each independently an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 18 carbon atoms. R ¹ to R ⁴ each independently have 1 to 3 carbon atoms. It is an alkyl group, X ¹ and X ² are each independently a divalent linking group)
A resin composition for optical materials containing the compound (B) represented by, wherein the content of the compound (B) is 1 to 10 parts by mass with respect to 100 parts by mass of the polymer (A). . The method of claim 1,
The compound (B) is the following general formula (1-1) or general formula (1-2)

(In the formula, L ¹ and L ² are each independently an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 18 carbon atoms. R ¹ to R ⁴ each independently have 1 to 3 carbon atoms. Is an alkyl group)
The resin composition for optical materials represented by. The method of claim 2,
The resin composition for optical materials wherein L ¹ and L ² are each a phenyl group or a tolyl group. The method of claim 2,
The resin composition for an optical material, wherein each of R ¹ to R ⁴ is a methyl group. The method of claim 1,
The resin composition for optical materials, wherein the polymer (A) is obtained by using methyl methacrylate. The method of claim 1,
The resin composition for optical materials in which the polymer (A) has a number average molecular weight of 20,000 to 50,000. An optical film containing the resin composition for optical materials according to any one of claims 1 to 6. The method of claim 7,
Optical film for polarizing plate protection. The method of claim 7,
An optical film which is stretched in at least one axial direction and has an absolute value of a photoelastic coefficient of 2×10 ^-12 /Pa or less. A liquid crystal display device comprising the optical film according to claim 7.