JP2008225452A5 - - Google Patents

Description

Molded body for optical element

  The present invention relates to an optical element molded body for producing an optical element such as a polarizing plate.

  With the recent expansion of the thin display market represented by liquid crystal televisions, there is an increasing demand for clearer images at a lower price. What is important for realizing this is an optical element such as a polarizing plate.

In some cases, a protective film is laminated on the optical element in order to enhance durability against an external environment such as humidity. And since the protective film of such an optical element requires high transparency, many triacetyl cellulose films have been used until now (nonpatent literature 1).
However, since the triacetyl cellulose film has a high moisture permeability, it has a disadvantage that the durability under high-temperature and high-humidity conditions is poor. In particular, when the optical element is a polarizing plate in which a protective film is laminated on both sides of a polarizing film, the polarizing film has a coordination structure in which iodine or a dichroic dye is adsorbed on a polyvinyl alcohol resin film or the like. Since the coordination structure is easily damaged by moisture, when a protective film having a low moisture permeability is used, the polarizing plate is significantly deteriorated.

  In order to solve this problem, an attempt has been made to use an amorphous polyolefin resin (thermoplastic saturated norbornene resin) as a protective film for an optical element having a low moisture permeability. However, since the moisture permeability of the amorphous polyolefin-based resin is extremely low, the moisture inside the optical element is not released to the outside. As a result, the optical element is deformed, and the optical element is used as an optical element. The problem of loss of function arises.

Supervised by Fumio Ide, “Optical Film for Display”, CM Publishing, 2004 JP-A-8-43812

  From such a situation, a molded body for an optical element that can adjust water absorption and water vapor permeability to desired values is desired.

  The subject of this invention is providing the molded object for optical elements which can adjust a water absorption and water vapor permeability to a desired value.

  As a result of intensive studies on materials that can be used for a protective film of an optical element, the present inventors have found that a resin composition containing an acrylic resin (A) and a styrene resin (B) is an acrylic resin ( By adjusting the mass ratio between A) and the styrene-based resin (B), when this is molded, a molded product having a low moisture absorption and an appropriate moisture permeability can be obtained. I found.

  Furthermore, since the present inventors can easily give a desired retardation to a molded product of a resin composition containing an acrylic resin (A) and a styrene resin (B), It was also found that it can function as a phase difference film. Specifically, a protective film is obtained by using a molded product of a resin composition containing an acrylic resin (A) and a styrene resin (B) not only as a protective film for a polarizing plate but also as a retardation film. It has been found that a polarizing plate having excellent productivity and durability can be produced while the thickness of the polarizing plate is reduced by omitting the adhesion of the retardation film separately.

ADVANTAGE OF THE INVENTION According to this invention, the control of retardation is easy, and also the molded object for optical elements which can control water vapor permeability to an appropriate value can be manufactured.
Moreover, according to the present invention, a polarizing plate excellent in productivity and durability can be produced.

The resin composition for optical materials used in the present invention contains an acrylic resin (A) and a styrene resin (B).
In the present invention, the acrylic resin refers to a polymer containing acrylic acid, methacrylic acid or a derivative thereof as a monomer component.
Specific examples of the acrylic resin (A) in the present invention include, for example, methacrylic acid esters such as cyclohexyl methacrylate, t-butyl cyclohexyl methacrylate, and methyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, and acrylic. Examples thereof include those obtained by polymerizing one or more monomers selected from acrylic acid esters such as isopropyl acid and 2-ethylhexyl acrylate.

  The acrylic resin (A) includes those obtained by copolymerizing acrylic acid, methacrylic acid or their derivatives and other monomer components. The content of such other monomer components ( The copolymerization ratio) is preferably less than 50% by mass relative to the acrylic resin (A), more preferably less than 40% by mass, and even more preferably less than 30% by mass.

  Among these, the polymer containing methyl methacrylate as a monomer component is a preferred example of the styrene resin (B), which is a styrene-acrylonitrile copolymer (B-1), a styrene-methacrylic acid copolymer ( Since B-2) and the compatibility with a styrene-maleic anhydride copolymer (B-3) are high, it is especially preferable.

The polymer containing methyl methacrylate as a monomer component may be either a homopolymer of methyl methacrylate or a copolymer with other monomers.
Monomers copolymerizable with methyl methacrylate include methacrylic acid alkyl esters other than methyl methacrylate, acrylic acid alkyl esters, styrene, o-methyl styrene, p-methyl styrene, 2,4-dimethyl styrene, Aromatic vinyl compounds such as ethyl styrene, p-tert-butyl styrene, etc., nuclear alkyl-substituted styrene, α-methyl styrene, α-alkyl-substituted styrene, such as α-methyl-p-methyl styrene; acrylonitrile, methacrylonitrile, etc. Examples thereof include vinyl cyanides; maleimides such as N-phenylmaleimide and N-cyclohexylmaleimide; unsaturated carboxylic acid anhydrides such as maleic anhydride; unsaturated acids such as acrylic acid, methacrylic acid and maleic acid.
These monomers can be used alone or in combination of two or more.

Among these monomers that can be copolymerized with methyl methacrylate, acrylic acid alkyl esters are particularly excellent in heat decomposability, and acrylic resins obtained by copolymerizing these have high fluidity during molding. Therefore, it is preferable. The amount of alkyl acrylates used when methyl acrylate is copolymerized with methyl methacrylate is preferably 0.1% by weight or more from the viewpoint of thermal decomposition resistance, and 15% from the viewpoint of heat resistance. % Or less is preferable. The content is more preferably 0.2% by weight or more and 14% by weight or less, and particularly preferably 1% by weight or more and 12% by weight or less.
Among the alkyl acrylates, methyl acrylate and ethyl acrylate are most preferable because the effect of improving the fluidity at the time of the molding process can be remarkably obtained only by copolymerizing with a small amount of methyl methacrylate.

  The weight average molecular weight of the acrylic resin (A) is desirably 50,000 to 200,000. The weight average molecular weight of the acrylic resin (A) is preferably 50,000 or more from the viewpoint of the strength of the molded product, and preferably 200,000 or less from the viewpoint of molding processability and fluidity. A more desirable range is 70,000 to 150,000.

  In the present invention, isotactic polymethacrylate and syndiotactic polymethacrylate can be used simultaneously.

As a method for producing the acrylic resin (A), for example, generally used polymerization methods such as cast polymerization, bulk polymerization, suspension polymerization, solution polymerization, emulsion polymerization, anionic polymerization, and the like can be used. It is preferable to avoid the introduction of minute foreign substances as much as possible. From this viewpoint, bulk polymerization or solution polymerization without using a suspending agent or an emulsifier is desirable.
When solution polymerization is performed, a solution prepared by dissolving a mixture of monomers in an aromatic hydrocarbon solvent such as toluene or ethylbenzene can be used. In the case of polymerization by bulk polymerization, the polymerization can be started by irradiation with free radicals generated by heating or ionizing radiation as is usually done.

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, benzoyl peroxide, lauroyl peroxide, and t-butyl peroxide. Organic peroxides such as oxy-2-ethylhexanoate can be used.
In particular, when polymerization is carried out at a high temperature of 90 ° C. or higher, solution polymerization is common, so that the 10-hour half-life temperature is 80 ° C. or higher and a peroxide that is soluble in the organic solvent used, An azobis initiator is preferred. Specifically, 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane, cyclohexane peroxide, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, 1, Examples thereof include 1-azobis (1-cyclohexanecarbonitrile) and 2- (carbamoylazo) isobutyronitrile. These initiators can be used in the range of 0.005 to 5 wt%, for example.

As the molecular weight regulator used as necessary for the polymerization reaction, any one generally used in radical polymerization can be used. For example, mercaptan compounds such as butyl mercaptan, octyl mercaptan, dodecyl mercaptan, 2-ethylhexyl thioglycolate, etc. Particularly preferred.
These molecular weight regulators are added in a concentration range such that the polymerization degree of the acrylic resin (A) is controlled within a preferable range.

As a specific production method, a method described in JP-B 63-1964 and the like can be used.
Further, as the acrylic resin (A), two or more kinds having different molecular weights, compositions, etc. can be used at the same time.

The photoelastic coefficient of the acrylic resin (A) when not stretched at 23 ° C. is −60 × 10 ^−12.
It is preferably Pa ⁻¹ or more, more preferably −30 × 10 ⁻¹² Pa ⁻¹ or more, and particularly preferably −6 × 10 ⁻¹² Pa ⁻¹ or more. When the photoelastic coefficient of the acrylic resin (A) is in this range, the photoelastic coefficient of the molded article made of the composition for optical resin of the present invention can be reduced, and a desired thickness direction retardation (Rth) is obtained. Can be imparted, which is preferable.

The “photoelastic coefficient” in the present invention is a coefficient representing the ease with which birefringence changes due to external force, and is described in various literatures (for example, Chemical Review, No. 39, 1998 (Academic Publishing Center) Issue)), defined by the following formula.
C _R [Pa ⁻¹ ] = Δn / σ _R Δn = nx−ny
(In the formula, C _R : Photoelastic coefficient, σ _R : Extension stress [Pa], Δn: Birefringence when stress is applied, nx
: Refractive index in the direction parallel to the stretching direction, ny: refractive index in the direction perpendicular to the stretching direction)
The closer the value of the photoelastic coefficient is to zero, the smaller the change in birefringence due to external force. This means that the birefringence designed for each application is small in change due to external force, and has superior optical characteristics. .

In the present invention, the styrene resin (B) refers to a polymer containing at least a styrene monomer as a monomer component. Here, the styrene monomer is a monomer having a styrene skeleton in its structure, for example, styrene; o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene. And vinyl aromatic compound monomers such as α-alkyl-substituted styrene such as α-methylstyrene and α-methyl-p-methylstyrene, and nuclear alkyl-substituted styrene such as ethylstyrene and p-tert-butylstyrene, A typical one is styrene.

The styrene resin (B) includes those obtained by copolymerizing a styrene monomer component with another monomer component. Examples of the copolymerizable monomer include alkyl methacrylates such as methyl methacrylate, cyclohexyl methacrylate, methylphenyl methacrylate, and isopropyl methacrylate, and alkyl acrylates such as methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, and cyclohexyl acrylate. Unsaturated carboxylic acid alkyl ester monomers; methacrylic acid, acrylic acid, itaconic acid, maleic acid, fumaric acid, cinnamic acid and other unsaturated carboxylic acid monomers; maleic anhydride, itaconic acid, ethyl maleic acid, methyl Unsaturated dicarboxylic acid anhydride monomers such as itaconic acid and chloromaleic acid; unsaturated nitrile monomers such as acrylonitrile and methacrylonitrile; 1,3-butadiene, -Conjugated dienes such as methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, and the like. It is also possible to polymerize.
The content of such other monomer components is preferably 50% by weight or less, more preferably 30% by weight or less, still more preferably 20% by weight or less, based on the styrene resin (B). It is.

  As the styrene resin (B), in particular, a styrene-acrylonitrile copolymer (B-1), a styrene-methacrylic acid copolymer (B-2), and a styrene-maleic anhydride copolymer (B-3). It is preferable because it has properties required for optical materials such as heat resistance and transparency.

  In the case of the styrene-acrylonitrile copolymer (B-1), the acrylonitrile content in the copolymer is preferably 1 to 40% by mass. A more preferable range is 1 to 30% by mass, and an especially preferable range is 1 to 25% by mass. When the content of acrylonitrile in the copolymer is 1 to 40% by mass, it is preferable because of excellent transparency.

  In the case of a styrene-methacrylic acid copolymer (B-2), the methacrylic acid content in the copolymer is preferably 0.1 to 50% by mass. A more preferable range is 0.1 to 40% by mass, and a further preferable range is 0.1 to 30% by mass. If the methacrylic acid content in the copolymer is 0.1% by mass or more, the heat resistance is excellent, and if it is in the range of 50% by mass or less, the transparency is excellent, which is preferable.

  In the case of the styrene-maleic anhydride copolymer (B-3), the maleic anhydride content in the copolymer is preferably 0.1 to 50% by mass. A more preferable range is 0.1 to 40% by mass, and a further preferable range is 0.1 to 30% by mass. If the maleic anhydride content in the copolymer is 0.1% by mass or more, the heat resistance is excellent, and if it is in the range of 50% by mass or less, the transparency is excellent, which is preferable.

  As the styrene resin (B), a plurality of types of styrene resins having different compositions and molecular weights can be used in combination.

  The styrene resin (B) can be obtained by a known anion, block, suspension, emulsion or solution polymerization method. Moreover, the unsaturated double bond of the benzene ring of the conjugated diene or the styrene monomer may be hydrogenated in the styrene resin (B). The hydrogenation rate can be measured by a nuclear magnetic resonance apparatus (NMR).

The photoelastic coefficient when the styrene resin (B) is not stretched at 23 ° C. is 60 × 10 ⁻¹² P.
It is preferably a ⁻¹ or less, more preferably 30 × 10 ⁻¹² Pa ⁻¹ or less, and particularly preferably 6 × 10 ⁻¹² Pa ⁻¹ or less. Styrenic resin (
When the photoelastic coefficient of B) is in this range, the photoelastic coefficient of the molded article made of the resin composition for optical materials of the present invention can be reduced, and the resin composition for optical materials of the present invention can be reduced. Since it becomes possible to give a desired thickness direction retardation (Rth) to the molded object which consists of this, it is preferable.

  In the present invention, the mass ratio ((A) / (B) of the acrylic resin (A) and the styrene resin (B) in the resin composition for an optical material containing the acrylic resin (A) and the styrene resin (B). )) Is a mass ratio ((A) / (B)) of the acrylic resin (A) and the styrene resin (B) of 20/80 to 60/40 in terms of moisture permeability and optical properties, The mass ratio ((A) / (B)) is more preferably 30/70 to 50/50.

In the resin composition for an optical material used in the present invention, when the mass ratio ((A) / (B)) of the acrylic resin (A) and the styrene resin (B) is increased, the water absorption of the molded product obtained therefrom is increased. In contrast, when the mass ratio ((A) / (B)) is decreased, the water absorption rate of the molded product obtained therefrom tends to decrease.
Moreover, when the mass ratio ((A) / (B)) of the acrylic resin (A) and the styrene resin (B) is increased, the water absorption rate of the molded product obtained therefrom tends to increase and the water vapor permeability tends to decrease. On the contrary, when the mass ratio ((A) / (B)) is decreased, the water absorption rate of the molded product obtained from this decreases, and the water vapor permeability tends to increase.
Therefore, by adjusting the mass ratio ((A) / (B)) of the resin composition, a molded product having a desired water absorption rate and a desired water vapor permeability can be easily produced.

Moreover, in this invention, polymers other than acrylic resin (A) and a styrene resin (B) can be mixed with the resin composition for optical materials in the range which does not impair the objective of this invention. Polymers that can be mixed include polyolefins such as polyethylene and polypropylene, polyamides, polyphenylene sulfide resins, polyether ether ketone resins, polyesters, polysulfones, polyphenylene oxides, polyimides, polyether imides, polyacetals and other thermoplastic resins, and Examples thereof include thermosetting resins such as phenol resin, melamine resin, silicone resin, and epoxy resin, and one or more of these can be added.
From the viewpoint of the photoelastic coefficient, the amount of these polymers added is 20% by weight or less, more preferably based on the resin composition for optical materials containing the acrylic resin (A) and the styrene resin (B). It is preferably 10% by weight or less, more preferably 5% by weight or less.

  Furthermore, in the range which does not impair the effect of this invention remarkably, arbitrary additives are mix | blended with the resin composition for optical materials containing acrylic resin (A) and styrene resin (B) according to various objectives. be able to. The additive that can be blended is not particularly limited as long as it is generally used for blending resins and rubber-like polymers.

Examples of such additives include inorganic fillers such as silicon dioxide; lubricants such as pigments such as iron oxide, stearic acid, behenic acid, zinc stearate, calcium stearate, magnesium stearate, and ethylene bisstearamide; Mold release agents: Softeners and plasticizers such as paraffinic process oil, naphthenic process oil, aromatic process oil, paraffin, organic polysiloxane, mineral oil; hindered phenolic antioxidants, phenolic compounds with acrylate groups Antioxidants, antioxidants such as phosphorus heat stabilizers, hindered amine light stabilizers, UV absorbers, flame retardants, antistatic agents, organic fibers, glass fibers, carbon fibers, metal whiskers and other reinforcing agents; colorants Benzotriazole compounds, benzotriazine compounds, benzoate compounds , Benzophenone compounds, phenol compounds, oxazole compounds, malonic acid ester compounds, lactone compounds, other additives or mixtures thereof. The additive amount of these additives is 0.01 parts by mass or more and 50 parts by mass or less, more preferably 100 parts by mass of the resin composition for an optical material containing the acrylic resin (A) and the styrene resin (B). The amount is preferably 0.1 parts by mass or more and 10 parts by mass or less, more preferably 0.1 parts by mass or more and 2 parts by mass or less.
By adjusting the amounts of these additives, it is possible to adjust the water absorption rate and water vapor permeability of the resulting molded article.

Among these additives, in particular, benzotriazole compounds, benzotriazine compounds, benzoate compounds, benzophenone compounds, phenol compounds, oxazole compounds, malonic acid ester compounds, lactone compounds, salicylic acid ester compounds, A benzoxazinone-based compound is preferable because it has the effect of reducing the absolute value of the photoelastic coefficient of the resin composition to which it is added. Of these, benzotriazole compounds and benzotriazine compounds are particularly preferable.
These may be used alone or in combination of two or more.

  Hereinafter, as specific examples of the benzotriazole-based compound which is an additive preferably used in the present invention, the compounds represented by the general formulas [2] and [3] are used, and as specific examples of the benzotriazine-based compound, the general formula [4] is used. The compound shown by these is shown.

General formula [2]

T

T

General formula [3]

T

T

T General formula [4]

T

  In general formula [2], X1 represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms or an alkoxy group, and R1 to R4 are each a hydrogen atom or a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms. Represents. In general formula [3], X2 and X3 are each a hydrogen atom, a halogen atom, R5 and R6 are each a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, and R7 is an alkylene group having 1 to 4 carbon atoms. Represents. In the general formula [4], R8 represents an alkyl group having 1 to 20 carbon atoms or an alkoxy group, and R9 and R10 each represents a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms.

Moreover, in this invention, it is preferable to use a phenolic antioxidant. Among phenolic antioxidants, those having an acrylate group in the molecule are particularly preferable. Phenolic antioxidants, especially phenolic antioxidants that have acrylate groups in the molecule, cause the high molecular weight resin in the resin composition to gel by heating during molding and generate foreign matter in the molded body. In addition, even if a large amount is added to the resin composition, the photoelastic coefficient is not greatly changed.
As a phenolic antioxidant which has an acrylate group in a molecule | numerator, the compound represented, for example by the following general formula is preferable.

T General formula [5]

T

  In General Formula [5], R11 represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and R12 and R13 each independently represents an alkyl group having 1 to 8 carbon atoms.

The alkyl group having 1 to 10 carbon atoms of R11 in the general formula [5] may be linear or have a branched structure or a ring structure. R12 and R13 are preferably a structure represented by “* — (CH 3) 2 —R ′” containing a quaternary carbon (* represents a site connected to an aromatic ring, and R ′ represents 1 to 1 carbon atoms. Represents an alkyl group of 5).
R12 is more preferably a t-butyl group, a t-amyl group or a t-octyl group. R13 is more preferably a t-butyl group or a t-amyl group.

  As a compound represented by the above general formula [5], commercially available products include Sumilizer GM (general formula [6]), Sumilizer GS (general formula [7]) (both trade names, manufactured by Sumitomo Chemical Co., Ltd.). It is done.

T General formula [6]

T

T General formula [7]

T

When the vapor pressure (P) at 20 ° C. of the additive is 1.0 × 10 ⁻⁴ Pa or less, the processability is excellent and preferable. A more preferable range is a vapor pressure (P) of 1.0 × 10 ⁻⁶ Pa or less, and a particularly preferable range is a vapor pressure (P) of 1.0 × 10 ⁻⁸ Pa or less. Here, being excellent in moldability means that, for example, the adhesion of the additive to the roll is small during film formation. When the additive adheres to the roll, for example, it adheres to the surface of the molded body and deteriorates the appearance and optical characteristics, which is not preferable as an optical material.

The melting point (Tm) of the ultraviolet absorber is preferably 80 ° C. or higher, which is excellent in molding processability. A more preferable range is a melting point (Tm) of 130 ° C. or higher, and a particularly preferable range is a melting point (Tm) of 160 ° C. or higher.
The ultraviolet absorber is excellent in molding processability when the weight reduction rate when the temperature is increased from 23 ° C. to 260 ° C. at a rate of 20 ° C./min is 50% or less. A more preferable range is a weight reduction rate of 15% or less, and a particularly preferable range is a weight reduction rate of 2% or less.

  The manufacturing method of the resin composition for optical materials used in the present invention is not particularly limited, and a known method can be used. For example, using a melt kneader such as a single screw extruder, twin screw extruder, Banbury mixer, Brabender, various kneaders, etc., adding a resin component, if necessary, adding a hydrolysis resistance inhibitor and the above other components to melt It can be produced by kneading.

Next, the molded body for optical elements of the present invention will be described.
When the molded article for optical elements of the present invention is used as a film, the water absorption is preferably 0.01% or more and 0.5% or less. Since the moisture permeability of the protective film is preferably low in order to protect the optical element from external humidity under high temperature and high humidity conditions, the water absorption is preferably 0.5% or less. On the other hand, in order to release moisture generated from the inside of the optical element to the outside, even a protective film preferably has some moisture permeability, and its water absorption rate is 0.01% or more. preferable.

Here, the water absorption rate of the molded product is the dry mass of the test sample with the amount of water absorbed by the test piece when the test piece is exposed to infiltrated air at 23 ° C. and 50% RH until the water absorption reaches equilibrium. It is a ratio with respect to and is shown by the following formula.
Water absorption rate (%) = (M1 / M2) × 100
(M1: water absorption of the test piece, M2: dry weight of the test piece)

Specifically, the water absorption rate can be measured by the following method.
The test piece was dried, for example, allowed to stand in a thermostat kept at 50 ° C. for 24 hours, and then allowed to stand for a long time, for example, 24 hours or more until water absorption reached equilibrium in an infiltrated air atmosphere at 23 ° C. and 50% RH. The mass of the test piece placed and absorbed is measured. Next, the water absorption test piece is heated to a high temperature, for example, 180 ° C. under an air stream such as dry nitrogen, and the amount of water released from the test piece is quantified by the Karl Fischer method. In the case of this measuring method, the water absorption is obtained by the following formula.
Water absorption (%) = (W2 / (W1-W2)) × 100
(W1: Mass of test piece after exposure to humid air, W2: Mass of released water)

  The water absorption rate of the molded body is controlled by adjusting the type of acrylic resin (A) and styrene resin (B) in the resin composition for optical materials and the mass ratio ((A) / (B)) between the two. it can.

When the molded article for an optical element of the present invention is used as a film, the water vapor permeability is preferably 15 g / m ² · 24 h (g / m ² · day) or more and 100 g / m ² · 24 h. More preferably, it is preferably 20 g / m ² · 24 h or more and 80 g / m ² · 24 h, and particularly preferably 20 g / m ² · 24 h or more and 60 g / m ² · 24 h.
Here, the water vapor permeability of the molded body is water vapor that passes through a test piece of a unit area per unit time at 40 ° C. and a relative humidity of 90% RH determined according to JIS K 7129 B (1992) method (infrared sensor method). Amount.

  The method for producing the molded article for optical elements of the present invention is not limited, and can be molded by known methods such as injection molding, sheet molding, blow molding, injection blow molding, inflation molding, extrusion molding, and foam molding. Secondary processing molding methods such as pressure forming and vacuum forming can also be used.

  When the optical element molded body of the present invention is a film or a sheet, for example, an unstretched film can be extruded using an extruder or the like equipped with a T die, a circular die, or the like. When obtaining a molded body by extrusion molding, the acrylic resin (A) and the styrene resin (B) may be melt-kneaded in advance, but may be molded through melt-kneading at the time of extrusion molding. it can. It is also possible to obtain an unstretched film or sheet by cast molding using a good solvent common to the acrylic resin (A) and the styrene resin (B), for example, a solvent such as chloroform.

Further, if necessary, the unstretched film or sheet can be stretched uniaxially in the machine flow direction (MD) and uniaxially stretched in the direction (TD) perpendicular to the mechanical flow direction. For example, industrially, a uniaxial stretching method by roll stretching or tenter stretching, a sequential biaxial stretching method by a combination of roll stretching and tenter stretching, a simultaneous biaxial stretching method by tenter stretching, a biaxial stretching method by tubular stretching, etc. A stretched film can be produced.
The draw ratio is preferably 0.1% or more and 300% or less in at least one of the directions, more preferably 1% or more and 200% or less, and particularly preferably 2% or more and 100% or less. By designing in this range, a stretched molded article preferable in terms of birefringence and strength can be obtained.
Here, the draw ratio can be obtained by the following equation by shrinking the obtained stretched film or sheet at a temperature 20 ° C. or higher than the glass transition temperature. The glass transition temperature can also be determined by DSC method or viscoelastic method.
Stretch ratio (%) = [(length before shrinkage / length after shrinkage) −1] × 100

  In the present invention, a film means a film having a thickness of 300 μm or less, and a sheet has a thickness exceeding 300 μm. In the present invention, the thickness of the film is desirably 1 μm or more, more desirably 5 μm or more, and the thickness of the sheet is desirably 10 mm or less, more desirably 5 mm or less.

  The molded article for optical element of the present invention may be subjected to surface functionalization treatment such as antireflection treatment, transparent conductive treatment, electromagnetic wave shielding treatment, gas barrier treatment and the like.

  Since the molded article for optical elements of the present invention has high mechanical strength, it can also be used as a protective film for various optical elements. In particular, the molded article for an optical element of the present invention can be used as a polarizing plate protective film because it can be optically anisotropic. Below, the case where the molded object for optical elements of this invention is used as a polarizing plate protective film is demonstrated.

A polarizing plate can be produced by laminating the polarizing plate protective film of the present invention on a polarizing film. In the present invention, it is preferable to laminate a protective film with Re of 10 nm or more on one surface of the polarizing film and laminate a protective film with Re of 10 nm or less on the other surface.
Usually, since the protective film aims at protecting the polarizing film, a film having optical isotropy such as a triacetyl cellulose-based film is used.
On the other hand, in a preferred embodiment of the present invention, the protective film having optical anisotropy of the present invention is laminated on one surface and the protective film having optical isotropy is laminated on the other surface. As a result, the protective film on one side also serves as the retardation film, so that the retardation film made of polycarbonate resin or cycloolefin-based resin usually attached on the protective film of the polarizing plate is omitted. Thinning can be achieved.
Moreover, since there is no process which adhere | attaches another retardation film on a protective film, it is excellent in productivity.

From such a viewpoint, the in-plane retardation Re of the protective film laminated on one surface of the polarizing film is preferably 10 nm or more, more preferably 20 to 1000 nm, still more preferably 30 to 900 nm.
In this case, the protective film with Re of 10 nm or more laminated on one surface also has a function as a quarter-wave plate, a half-wave plate, and other retardation films.

  The optically isotropic protective film laminated on the other surface of the polarizing film preferably has a smaller Re, preferably Re is 10 nm or less, more preferably 8 nm or less, and even more preferably 5 nm or less.

Here, the in-plane retardation (Re) is defined by the following equation.
Re = (nx−ny) × d
In the formula, nx: main refractive index in the x direction when the direction in which the refractive index is maximum in the molded body surface is x, ny: y direction in the direction perpendicular to the x direction in the molded body surface is y Main refractive index d: thickness (nm) of the molded product.

  In the present invention, it is preferable to use a film containing an acrylic resin (d) as an optically isotropic protective film laminated on the other surface.

  Specific examples of the acrylic resin (d) include methacrylic acid alkyl ester such as cyclohexyl methacrylate, t-butyl cyclohexyl methacrylate, methyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, isopropyl acrylate, acrylic What polymerized 1 or more types of monomers chosen from acrylic acid alkylesters, such as acid 2-ethylhexyl, is mentioned.

Among these, a homopolymer of methyl methacrylate or a copolymer of methyl methacrylate and other monomers is particularly preferable.
Examples of monomers copolymerizable with methyl methacrylate include other alkyl alkyl methacrylates, alkyl acrylates, aromatic vinyl compounds such as styrene, vinyl toluene and α-methyl styrene; acrylonitrile, methacrylonitrile, etc. Vinyl cyanides; maleimides such as N-phenylmaleimide and N-cyclohexylmaleimide; unsaturated carboxylic acid anhydrides such as maleic anhydride; unsaturated acids such as acrylic acid, methacrylic acid and maleic acid . These may be used alone or in combination of two or more.

Among these monomers that are copolymerizable with methyl methacrylate, alkyl acrylates are particularly excellent in heat decomposability and have high fluidity during the molding of methacrylic resins obtained by copolymerizing these. Therefore, it is preferable.
The amount of alkyl acrylates used when methyl acrylate is copolymerized with methyl methacrylate is preferably 0.1% by mass or more from the viewpoint of heat decomposability, and 15 from the viewpoint of heat resistance. It is preferable that it is below mass%. More preferably, it is 0.2-14 mass%, and it is especially preferable that it is 1-12 mass%.
As alkyl acrylates, methyl acrylate and ethyl acrylate are preferred because the effect of improving the fluidity during the molding process described above can be remarkably obtained only by copolymerizing with a small amount of methyl methacrylate.

  The mass average molecular weight of the acrylic resin (d) is preferably 50,000 to 200,000. The mass average molecular weight is preferably 50,000 or more from the viewpoint of the strength of the molded product, and preferably 200,000 or less from the viewpoint of molding processability and fluidity. A more preferable range is 70,000 to 150,000. In the present invention, isotactic polymethacrylate and syndiotactic polymethacrylate can be used simultaneously.

As a method for producing the acrylic resin (d), for example, generally used polymerization methods such as cast polymerization, bulk polymerization, suspension polymerization, solution polymerization, emulsion polymerization, and anionic polymerization can be used. It is preferable to avoid the introduction of minute foreign substances as much as possible. From this viewpoint, bulk polymerization and solution polymerization without using a suspending agent or an emulsifier are preferable. Specifically, the method described in Japanese Patent Publication No. 63-1964 can be used.
When solution polymerization is performed, a solution prepared by dissolving a mixture of monomers in an aromatic hydrocarbon solvent such as toluene or ethylbenzene can be used. In the case of polymerization by bulk polymerization, the polymerization can be started by irradiation with free radicals generated by heating or ionizing radiation as is usually done.

As the initiator used in the polymerization reaction, any initiator used in radical polymerization can be used. For example, azo compounds such as azobisisobutylnitrile, benzoyl peroxide, lauroyl peroxide, t-butylperoxy- An organic peroxide such as 2-ethylhexanoate can be used.
In particular, when polymerization is carried out at a high temperature of 90 ° C. or higher, solution polymerization is generally used. Therefore, a peroxide, azobis, which has a 10-hour half-life temperature of 80 ° C. or higher and is soluble in the organic solvent used. Initiators and the like are preferred. Specifically, 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 and the like can be mentioned. These initiators can be used in the range of 0.005 to 5 mass%, for example.

  As the molecular weight regulator used as necessary in the polymerization reaction, any of those used in radical polymerization can be used. For example, mercaptan compounds such as butyl mercaptan, octyl mercaptan, dodecyl mercaptan, 2-ethylhexyl thioglycolate are particularly preferable. It is mentioned as a thing. These molecular weight regulators are added in a concentration range such that the polymerization degree of the acrylic resin (d) is controlled within a preferable range.

  As acrylic resin (d) used by this invention, the copolymer which has a methacrylic ester and / or an acrylate ester unit, an aromatic vinyl compound unit, and the compound unit represented by following General formula [1] is preferable.

  General formula [1]

T
（ＸはＯまたは、Ｎ−Ｒを示す。Ｏは酸素原子、Ｎは窒素原子、Ｒは水素原子、アルキル基、アリール基またはシクロアルカン基である）

T
(X represents O or N—R. O is an oxygen atom, N is a nitrogen atom, R is a hydrogen atom, an alkyl group, an aryl group, or a cycloalkane group)

As the methacrylic acid ester and / or acrylic acid ester copolymerized with the compound represented by the general formula [1], methyl methacrylate is preferable. Examples of the aromatic vinyl compound include α-alkyl-substituted styrene such as α-methylstyrene and α-methyl-p-methylstyrene, and styrene is preferable.

  As the compound represented by the general formula [1], a compound in which X = O, that is, maleic anhydride is preferable. Furthermore, from the viewpoint of heat resistance and photoelastic coefficient, the methyl methacrylate unit in the copolymer is 40 to 90% by mass, the styrene unit is 5 to 40% by mass, the maleic acid unit is 5 to 20% by mass, and It is preferable that the copolymerization ratio of the styrene unit to the copolymerization ratio of the maleic acid unit is 1 to 3 times. More preferably, the methyl methacrylate unit in the copolymer is 40 to 90% by mass, the maleic anhydride unit is 5 to 19% by mass, and the styrene unit is 10 to 40% by mass, and particularly preferably in the copolymer. The methyl methacrylate unit is 45 to 88% by mass, the maleic anhydride unit is 6 to 15% by mass, and the styrene unit is 16 to 40% by mass.

Another preferred example of the acrylic resin (d) is a copolymer containing a methacrylic ester and / or an acrylic ester unit, an aromatic vinyl compound unit, and an acid anhydride unit having a 6-membered ring structure. The copolymer containing an acid anhydride unit having a 6-membered ring structure is suitable for an optical material because it is excellent in heat resistance and the retardation design of a molded product obtained therefrom is easy.
As the methacrylic acid ester and / or acrylic acid ester which is the first monomer component of the copolymer containing an acid anhydride unit having a 6-membered ring structure, methyl methacrylate is preferable, and the second monomer component is Examples of the aromatic vinyl compound include α-alkyl-substituted styrene such as α-methylstyrene and α-methyl-p-methylstyrene, and styrene is preferable.
Further, the acid anhydride unit having a 6-membered ring structure, which is the third unit of the copolymer containing an acid anhydride unit having a 6-membered ring structure, includes an unsaturated carboxylic acid monomer and, if necessary, an unsaturated carboxylic acid. After polymerization with an acid alkyl ester monomer and other monomer components to form a copolymer, the copolymer is heated in the presence or absence of an appropriate catalyst to remove alcohol and / or dehydrate. It can produce | generate by performing intramolecular cyclization reaction by. In this case, typically, the carboxyl group of the unsaturated carboxylic acid unit of 2 units is dehydrated by heating the copolymer, or the alcohol of the alcohol from the unsaturated carboxylic acid unit and the unsaturated carboxylic acid alkyl ester unit adjacent to each other is dehydrated. One unit of an acid anhydride unit having a 6-membered ring structure is generated by elimination.
Examples of the unsaturated carboxylic acid monomer for producing a 6-membered ring acid anhydride unit include methacrylic acid, acrylic acid, itaconic acid, maleic acid, fumaric acid, cinnamic acid, and the like. Examples of the carboxylic acid alkyl ester monomer include methyl methacrylate and methyl acrylate.
A copolymer containing an acid anhydride unit having a 6-membered ring structure is disclosed in JP-B-02-26641, JP-A-2006-266543, JP-A-2006-274069, JP-A-2006-274071, and JP-A-2006-274071. The composition ratio can be determined, manufactured, and evaluated with reference to the methods described in JP 2006-283013 A and JP 2005-162835 A.

  The melt index (ASTM D1238; I condition) of the acrylic resin (d) used in the present invention is preferably 10 g / 10 min or less from the viewpoint of the strength of the protective film obtained by molding the acrylic resin (d). More preferably, it is 6 g / 10 minutes or less, More preferably, it is 3 g / 10 minutes or less.

The protective film with Re of 10 nm or less laminated on the other surface of the polarizing film in the present invention may contain an aliphatic polyester resin (e) in addition to the acrylic resin (d).
Examples of the aliphatic polyester-based resin (e) include a polymer mainly composed of an aliphatic hydroxycarboxylic acid and a polymer mainly composed of an aliphatic polycarboxylic acid and an aliphatic polyhydric alcohol. It is done.
Specific examples of the polymer mainly containing an aliphatic hydroxycarboxylic acid include polyglycolic acid, polylactic acid, poly-3-hydroxybutyric acid, poly-4-hydroxybutyric acid, poly-4-hydroxyvaleric acid, and poly-3-hydroxyhexane. Examples of the polymer mainly composed of aliphatic polycarboxylic acid and aliphatic polyhydric alcohol include polyethylene adipate, polyethylene succinate, polybutylene adipate and polybutylene succinate. Etc. These aliphatic polyester resins (e) can be used alone or in combination of two or more.

  Among these aliphatic polyester resins (e), a polymer containing hydroxycarboxylic acid as a main constituent component is preferable, and a polylactic acid resin is particularly preferably used. These (e) components can use 1 or more types.

  Examples of the polylactic acid-based resin include polymers having L-lactic acid and / or D-lactic acid as main constituent components.

In the polylactic acid-based resin, the constituent molar ratio of the L-lactic acid unit and the D-lactic acid unit is preferably 100% for both the L-form and the D-form, and either the L-form or the D-form is preferably 85% or more. More preferably, one is 90% or more, and still more preferably one is 94% or more. In the present invention, poly-L lactic acid mainly composed of L-lactic acid and poly-D lactic acid mainly composed of D-lactic acid can be used simultaneously.
The polylactic acid-based resin may be copolymerized with lactic acid derivative monomers other than L-form or D-form or other components copolymerizable with lactide. Examples of such components include dicarboxylic acids, polyhydric alcohols, hydroxycarboxylic acids. Examples include acids and lactones. The polylactic acid resin can be polymerized by a known polymerization method such as direct dehydration condensation or ring-opening polymerization of lactide. Moreover, it can also be made high molecular weight using binders, such as polyisocyanate, as needed.
The mass average molecular weight range of the polylactic acid-based resin is preferably 30,000 or more from the viewpoint of mechanical properties, and more preferably 1,000,000 or less from the viewpoint of workability. More preferably, it is 50,000-500,000, Most preferably, it is 100,000-280,000.

In addition, the polylactic acid-based resin may contain 0.1 to 30% by mass of a copolymer component other than lactic acid as long as the object of the present invention is not impaired. Examples of such other copolymer component units include polyvalent carboxylic acids, polyhydric alcohols, hydroxycarboxylic acids, lactones, and the like. Specifically, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid , Azelaic acid, sebacic acid, dodecanedioic acid, fumaric acid, cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 5-sodium sulfoisophthalic acid, 5-tetrabutylphosphonium sulfoisophthalic acid Polyvalent carboxylic acids such as ethylene glycol, propylene glycol, butanediol, heptanediol, hexanediol, octanediol, nonanediol, decanediol, 1,4-cyclohexanedimethanol, neopentylglycol, glycerin, trimethyl Aromatic propane, pentaerythritol, bisphenol A, polyhydric alcohols such as aromatic polyhydric alcohol obtained by addition reaction of bisphenol with ethylene oxide, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol; glycolic acid, 3- Hydroxycarboxylic acids such as hydroxybutyric acid, 4-hydroxybutyric acid, 4-hydroxyvaleric acid, 6-hydroxycaproic acid, hydroxybenzoic acid; glycolide, ε-caprolactone glycolide, ε-caprolactone, β-propiolactone, δ-butyrolactone, Lactones such as β- or γ-butyrolactone, pivalolactone, and δ-valerolactone can be used. These copolymer components can be used alone or in combination of two or more.

  As a method for producing the aliphatic polyester resin (e), a known polymerization method can be used. In particular, for a polylactic acid resin, a direct polymerization method from lactic acid, a ring-opening polymerization method via lactide, or the like is employed. be able to.

  In the present invention, when the protective film having Re of 10 nm or less contains the acrylic resin (d) and the aliphatic polyester resin (e), the proportion (parts by mass) of the acrylic resin (d) is the acrylic resin (d ) And aliphatic polyester-based resin (e) in a total amount of 100 parts by mass, it is preferably 0.1 to 99.9 parts by mass in terms of photoelastic coefficient, strength, heat resistance, and haze value. More preferably, it is -99.9 mass parts, and it is especially preferable that it is 60-95 mass parts. When it is 50 parts by mass or more, the haze value in a moist heat atmosphere becomes small, which is preferable. When the haze value is small or the change is small, it can be suitably used for display applications.

  The ratio (parts by mass) of the aliphatic polyester-based resin (e) is 100 parts by mass of the total amount of the acrylic resin (d) and the aliphatic polyester-based resin (b), photoelastic coefficient, strength, heat resistance, It is preferable that it is 0.1-99.9 mass part from the point of a haze value, It is more preferable that it is 0.1-50 mass part, It is especially preferable that it is 5-40 mass part. When it is 50 parts by mass or less, the haze value in a moist and heat atmosphere is preferably reduced. When the haze value is small or the change is small, it can be suitably used for display applications.

  In the present invention, the thickness of the protective film having Re of 10 nm or less is preferably 0.1 μm or more from the viewpoint of handling properties, and preferably 300 μm or less from the viewpoint of thinning. For the same reason, the range of 0.2 to 250 μm is more preferable, and the range of 0.3 to 200 μm is particularly preferable.

  For the bonding of the polarizing film and the protective film, it is preferable to use an optically isotropic adhesive. Examples of such an adhesive include a polyvinyl alcohol-based adhesive, a urethane-based adhesive, an epoxy-based adhesive, Examples include acrylic adhesives. When the adhesion between the polarizing film and the protective film is poor, it is preferable that the protective film is appropriately bonded with the polarizing film after an easy adhesion treatment such as a corona treatment, a primer treatment or a coating treatment.

  When a polarizing plate protective film made of the resin composition for optical materials of the present invention is used on one surface of the polarizing film, and a protective film having an acrylic resin (d) of 10 nm or less is used on the other surface, The occurrence of problems such as warping and curling due to the difference in characteristics and stress due to the difference in hygroscopicity are reduced.

In the present invention, the polarizing film is not particularly limited. For example, a polarizing film obtained by adsorbing and orienting a dichroic dye on a uniaxially stretched resin film is preferable.
Such a polarizing film can be manufactured using a well-known method, for example, can be manufactured by the method described in Unexamined-Japanese-Patent No. 2002-174729 etc. Specifically, it is as follows.
As the resin constituting the polarizing film, a polyvinyl alcohol resin is preferable, and a polyvinyl alcohol resin obtained by saponifying a polyvinyl acetate resin is preferable. Here, examples of the polyvinyl acetate resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith. Examples of other monomers copolymerized with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, and unsaturated sulfonic acids. Moreover, it is preferable that the saponification degree of a polyvinyl alcohol-type resin is 85-100 mol%, More preferably, it is 98-100 mol%. This polyvinyl alcohol-based resin may be further modified, and for example, polyvinyl formal and polyvinyl acetal modified with aldehydes may be used. The degree of polymerization of the polyvinyl alcohol-based resin is preferably 1000 to 10,000, and more preferably 1500 to 10,000.

For example, a polarizing film is a process of producing a film from a resin and uniaxially stretching the film, a process of dyeing a stretched polyvinyl alcohol-based resin film with a dichroic dye, and adsorbing iodine or a dichroic dye, a dichroic dye Can be produced through a step of treating the polyvinyl alcohol-based resin film adsorbed with boric acid aqueous solution and a step of washing with water after the treatment with boric acid aqueous solution.
Uniaxial stretching may be performed before dyeing with a dichroic dye, may be performed simultaneously with dyeing with a dichroic dye, or may be performed after dyeing with a dichroic dye. When uniaxial stretching is performed after dyeing with a dichroic dye, uniaxial stretching may be performed before boric acid treatment or during boric acid treatment. It is also possible to perform uniaxial stretching in a plurality of stages.
For uniaxial stretching, rolls having different peripheral speeds may be uniaxially stretched or uniaxially stretched using a hot roll. Moreover, the dry-type extending | stretching which extends | stretches in air | atmosphere may be sufficient, and the wet extending | stretching which extends | stretches in the state swollen with the solvent may be sufficient. The draw ratio is usually about 4 to 8 times.

In order to dye the resin film with the dichroic dye, for example, the resin film may be immersed in an aqueous solution containing the dichroic dye. Here, examples of the dichroic dye include iodine and dichroic dyes.
When iodine is used as the dichroic dye, a method of immersing and dyeing a resin film in an aqueous solution containing iodine and potassium iodide can be employed. The iodine content in this aqueous solution is preferably about 0.01 to 0.5 parts by mass per 100 parts by mass of water, and the potassium iodide content is 0.5 to 10 parts by mass per 100 parts by mass of water. It is preferable that it is a grade. The temperature of this aqueous solution is preferably about 20 to 40 ° C., and the immersion time in this aqueous solution is preferably about 30 to 300 seconds.
When a dichroic dye is used as the dichroic dye, a method of immersing and dyeing a polyvinyl alcohol-based resin film in an aqueous solution containing the dichroic dye can be employed. The content of the dichroic dye in this aqueous solution is preferably about 1 × 10 ⁻³ to 1 × 10 ⁻² parts by mass per 100 parts by mass of water. This aqueous solution may contain an inorganic salt such as sodium sulfate. The temperature of this aqueous solution is preferably about 20 to 80 ° C., and the immersion time in this aqueous solution is preferably about 30 to 300 seconds.

  The boric acid treatment after dyeing with the dichroic dye is performed by immersing the dyed resin film in an aqueous boric acid solution. The boric acid content in the boric acid aqueous solution is preferably about 2 to 15 parts by mass, more preferably about 5 to 12 parts by mass per 100 parts by mass of water. When iodine is used as the dichroic dye, the aqueous boric acid solution preferably contains potassium iodide. The content of potassium iodide in the boric acid aqueous solution is preferably about 2 to 20 parts by mass, more preferably 5 to 15 parts by mass per 100 parts by mass of water. The immersion time in the boric acid aqueous solution is preferably about 100 to 1200 seconds, more preferably about 150 to 600 seconds, and further preferably about 200 to 400 seconds. Moreover, it is preferable that the temperature of boric-acid aqueous solution is 50 degreeC or more, More preferably, it is 50-85 degreeC.

The resin film after the boric acid treatment is preferably washed with water. The water washing treatment is performed, for example, by immersing a boric acid-treated polyvinyl alcohol resin film in water. After washing with water, a drying process is appropriately performed to obtain a polarizing film. The water temperature in the water washing treatment is preferably about 5 to 40 ° C., and the immersion time is preferably about 2 to 120 seconds. It is preferable that the drying process performed after that is performed using a hot air dryer or a far-infrared heater. The drying temperature is preferably 40 to 100 ° C. The treatment time in the drying treatment is preferably about 120 seconds to 600 seconds.
The final film thickness is preferably 5 to 200 [mu] m, more preferably 10 to 150 [mu] m, and particularly preferably 15 to 100 [mu] m from the viewpoint of easy handling of the film and the requirement for thinning the display.

Next, the present invention will be described specifically by way of examples.
The evaluation methods used in the present invention and examples will be described.
(I) Evaluation Method (1) Measurement of Birefringence and Photoelastic Coefficient A birefringence measuring device described in detail in Macromolecules 2004, 37, 1062-1066 was used. A film tensioning device was placed in the laser beam path, and birefringence was measured while applying a tensile stress at 23 ° C. The strain rate during stretching was 20% / min (chuck interval: 30 mm, chuck moving speed: 6 mm / min), and the test piece width was 7 mm. Plotting birefringence (Δn) as the y-axis and stretching stress (σ _R ) as the x-axis, the photoelastic coefficient (C _R ) was calculated by obtaining the slope of the straight line in the linear region by least square approximation.
(2) Measurement of in-plane retardation (Re) The thickness d (nm) of the film was measured using a thickness gauge. This value is input to a birefringence measuring apparatus RETS-100 manufactured by Otsuka Electronics Co., Ltd., a sample is placed so that the measurement surface is perpendicular to the measurement light, and in-plane retardation (Re ) Was measured and calculated.
(3) Method for measuring water absorption rate After placing the film at 23 ° C. and 50% RH for 24 hours or longer, use a CA-06 type Karl Fischer moisture meter manufactured by Mitsubishi Chemical Corporation to determine the volatile components when heated to 180 ° C. The water absorption was determined.
(4) Water vapor transmission rate measurement method Using PERMATRAN-W3 / 33 manufactured by MOCON, the water vapor transmission rate was measured under the conditions of 40 ° C./90% RH according to JIS K 7129 B (1992) method (infrared sensor method).
(5) Measurement of warpage of polarizing plate The polarizing plate is cut into a square of 200 mm × 200 mm, placed on a horizontal and flat base so that the center of the film is in contact with the base, and in an atmosphere of 23 ° C. and 50% RH. The height at which the four corners of the cut film were allowed to warp from the table was calculated by averaging.
(6) Measurement of durability of polarizing plate at high temperature and high humidity The degree of polarization before and after being held at 60 ° C. and 90% RH for 1000 hours is obtained according to the following formula, and the degree of polarization holding rate is calculated using this value to be durable. Sex was evaluated.
Degree of polarization (%) = {[(H ₂ −H ₁ ) / (H ₂ + H ₁ )] × ½} × 100
Here, H ₂ is a value (parallel transmittance) measured using a spectrophotometer in a state in which the orientation directions of the two polarizing plates are aligned so as to be the same direction, and H ₁ is the two polarizations. It is a value (orthogonal transmittance) measured in a state where the orientation directions of the plates are superposed so as to be orthogonal to each other. Shimadzu UV-3150 spectrophotometer was used for the measurement of the degree of polarization.
The degree of polarization retention is a value obtained by multiplying 100 by the value obtained by dividing the degree of polarization after the retention test at 60 ° C. and 90% RH by the degree of polarization before the test. The larger the value, the better the durability.

(7) Measurement of acrylonitrile content in styrene-acrylonitrile copolymer A styrene-acrylonitrile copolymer as a sample was formed into a film using a hot press machine, and FT-410 manufactured by JASCO Corporation was used to obtain 1603 cm of the film. ^{-1, 2245cm -
The} absorbance derived from the acrylonitrile group in ¹ was measured. The acrylonitrile content in the styrene-acrylonitrile copolymer previously determined using a styrene-acrylonitrile copolymer with a known acrylonitrile content, and 1603 cm ⁻¹ , 2245 cm ^−.
Using the relationship with the absorbance ratio of ¹ , the acrylonitrile content in the styrene-acrylonitrile copolymer was quantified.
(8) Measurement of maleic anhydride content in styrene-maleic anhydride copolymer A styrene-maleic anhydride copolymer as a sample was dissolved in deuterated chloroform, and 1H-NMR (JNM ECA-500) manufactured by JEOL Ltd. NMR measurement was performed at a frequency of 500 MHz and at room temperature. From the measurement results, the area ratio between the proton peak of the benzene ring in the styrene unit (near 7 ppm) and the proton peak of the alkyl group in the maleic anhydride unit (near 1 to 3 ppm), the styrene unit and maleic anhydride unit in the sample The molar ratio of was determined. From the obtained molar ratio and the mass ratio of each monomer unit (styrene unit: maleic anhydride unit = 104: 98), the content of maleic anhydride in the styrene-maleic anhydride copolymer was determined.
(9) Measurement of methacrylic acid content in styrene-methacrylic acid copolymer A styrene-methacrylic acid copolymer as a sample was dissolved in deuterated chloroform, and 1H-NMR (JNM ECA-500) manufactured by JEOL Ltd. was used. NMR measurement was performed at a frequency of 500 MHz and at room temperature. From the measurement results, the molar ratio of the styrene unit and the methacrylic acid unit in the sample was determined from the area ratio of the proton peak of the benzene ring in the styrene unit (around 7 ppm) and the proton peak of the alkyl group in the methacrylic acid unit (around 1 to 3 ppm). The ratio was determined. The content of methacrylic acid in the styrene-methacrylic acid copolymer was determined from the obtained molar ratio and the mass ratio of each monomer unit (styrene unit: methacrylic acid unit = 104: 86).
(10) Measurement of each content in methyl methacrylate-maleic anhydride-styrene copolymer A methyl methacrylate-maleic anhydride-styrene copolymer as a sample was dissolved in deuterated chloroform, and 1H- manufactured by JEOL Ltd. NMR measurement was performed using NMR (JNM ECA-500) at a frequency of 500 MHz and at room temperature. From the measurement results, the proton peak of the benzene ring in the styrene unit (around 7 ppm), the proton peak of the alkyl group in the maleic anhydride unit (around 1-3 ppm), and the proton peak of the methyl group in the methyl methacrylate unit (0. The molar ratio of styrene units, maleic anhydride units and methyl methacrylate units in the sample was determined from the area ratio of about 5 to 1 ppm. From the obtained molar ratio and the mass ratio of each monomer unit (styrene unit: maleic anhydride unit: methyl methacrylate = 104: 86: 100), each of the methyl methacrylate-maleic anhydride-styrene copolymers The content was determined.

(II) Preparation of raw materials (1) Acrylic resin (A)
i) Methyl methacrylate-methyl acrylate copolymer 1
1,1-di-t-butylperoxy-3,3,3-trimethyl was added to a monomer mixture consisting of 89.2 parts by weight of methyl methacrylate, 5.8 parts by weight of methyl acrylate, and 5 parts by weight of xylene. 0.0294 parts by weight of cyclohexane and 0.115 parts by weight of n-octyl mercaptan were added and mixed uniformly. This solution is continuously supplied to a closed pressure-resistant reactor having an internal volume of 10 liters, polymerized with stirring at an average temperature of 130 ° C. and an average residence time of 2 hours, and then continuously sent to a reservoir connected to the reactor. The volatile matter was removed under a certain condition, and the volatile matter was continuously transferred to an extruder in a molten state to obtain a methyl methacrylate / methyl acrylate copolymer pellet as an acrylic resin (A). The resulting copolymer had a methyl acrylate content of 6.0%, a weight average molecular weight of 145,000, and a melt flow value measured at 230 ° C. of 3.8 kg measured according to ASTM-D1238 was 1.0 g / Minutes. The photoelastic coefficient (unstretched) at 23 ° C. was −5.2 × 10 ⁻¹² / Pa.
ii) Methyl methacrylate-methyl acrylate copolymer 2
1,1-di-t-butylperoxy-3,3,3 was added to a monomer mixture consisting of 93.2 parts by weight of methyl methacrylate, 2.3 parts by weight of methyl acrylate, and 3.3 parts by weight of xylene. Add 0.03 parts by weight of trimethylcyclohexane and 0.12 parts by weight of n-octyl mercaptan and mix uniformly. This solution was continuously supplied to a sealed pressure-resistant reactor having an internal volume of 10 L, polymerized with stirring at an average temperature of 130 ° C. and an average residence time of 2 hours, and then continuously sent to a reservoir connected to the reactor, Volatiles were removed under certain conditions. Furthermore, it was continuously transferred to an extruder in a molten state, and methyl methacrylate-methyl acrylate copolymer pellets were obtained.
The resulting methyl methacrylate-methyl acrylate copolymer has a methyl acrylate content of 2.0%, a mass average molecular weight of 102,000, and a 230 ° C. 3.8 kg load melt measured in accordance with ASTM-D1238. The flow value was 2.0 g / 10 min. The photoelastic coefficient (unstretched) at 23 ° C. was −4.5 × 10 ⁻¹² / Pa.

(2) Styrenic resin (B)
i) Styrene-acrylonitrile copolymer (B-1)
A monomer mixture composed of 72% by mass of styrene, 13% by mass of acrylonitrile, and 15% by mass of ethylbenzene was continuously fed into a complete mixing reactor equipped with a stirrer, and a polymerization reaction was performed at 150 ° C. and a residence time of 2 hours.
The obtained polymerization solution was continuously supplied to an extruder, and unreacted monomers and a solvent were collected by the extruder to obtain pellets of a styrene-acrylonitrile copolymer (B-1).
The obtained styrene-acrylonitrile copolymer (B-1) was colorless and transparent, and as a result of compositional analysis by neutralization titration, the styrene content was 80% by mass, the acrylonitrile content was 20% by mass, and 220 ° C. in accordance with ASTM-D1238. The melt flow rate value at 10 kg load was 13 g / 10 min. The photoelastic coefficient (unstretched) is 5.0 × 10 ⁻¹² Pa ^−1.
The intrinsic birefringence was negative.

ii) Styrene-methacrylic acid copolymer (B-2)
Continuous solution polymerization was carried out using all the equipment made of stainless steel. 75.2% by mass of styrene, 4.8% by mass of methacrylic acid, and 20% by mass of ethylbenzene are used as a preparation liquid, and 1,1-tert-butylperoxy-3,3,5-trimethylcyclohexane is used as a polymerization initiator. This prepared solution was added at 1 L / hr. The mixture was continuously fed at a rate of 1 to a completely mixed polymerization reactor with an internal volume of 2 L and equipped with a stirrer, and polymerization was carried out at 136 ° C.
A polymerization solution containing 49% of solid content is continuously taken out, first preheated to 230 ° C., kept at 230 ° C., and supplied to a devolatilizer depressurized to 20 torr. It discharged continuously from the gear pump at the lower part of the volatilizer.
The obtained styrene-methacrylic acid copolymer (B-2) was colorless and transparent, and as a result of compositional analysis by neutralization titration, the styrene content was 92 mass% and the methacrylic acid content was 8 mass%. The melt flow rate value measured at 230 ° C. under a load of 3.8 kg measured in accordance with ASTM-D1238 was 5.2 g / 10 minutes. The photoelastic coefficient (unstretched) is 4.8 × 10 ⁻¹² Pa.
^The intrinsic birefringence was negative.

iii) Styrene-maleic anhydride copolymer (B-3)
Continuous solution polymerization was carried out using all the equipment made of stainless steel. A total of 100 parts by mass was prepared at a ratio of 91.7 parts by mass of styrene and 8.3 parts by mass of maleic anhydride. (However, the two are not mixed.) 5 parts by mass of methyl alcohol and 0.03 parts by mass of 1,1-tert-butylperoxy-3,3,5-trimethylcyclohexane as a polymerization initiator are mixed with styrene. It was set as the preparation liquid. 0.95 kg / hr. Was continuously supplied to a jacketed complete mixing polymerization machine having an internal volume of 4 L.
On the other hand, maleic anhydride heated to 70 ° C. was used as the second preparation liquid at 0.10 kg / hr. To the same polymerization machine at a rate of 1 ° C., and polymerization is carried out at 111 ° C. When the polymerization conversion rate became 54%, the polymerization solution was continuously removed from the polymerization machine, first preheated to 230 ° C., kept at 230 ° C., and supplied to a devolatilizer reduced to 20 torr, with an average retention of 0 After 3 hours, it was continuously discharged from the lower gear pump of the devolatilizer to obtain a styrene-maleic anhydride copolymer (B-3). The obtained styrene-maleic anhydride copolymer (B-3) was colorless and transparent, and as a result of compositional analysis by neutralization titration, the styrene content was 85% by mass and the maleic anhydride unit was 15% by mass. The melt flow rate value measured at 230 ° C. under a load of 2.16 kg measured according to ASTM-D1238 was 2.0 g / 10 min. The photoelastic coefficient (unstretched) is 4.1 × 10 ^−.
12 Pa ⁻¹ and the intrinsic birefringence was negative.

(3) Preparation of cycloolefin-based film (COP) For comparison, a cycloolefin-based resin film, which is an amorphous polyolefin-based resin, was produced as follows as a representative example of a conventional polarizing plate protective film.
Addition polymerization of ethylene and norbornene was performed as a cyclic polyolefin to produce an ethylene-norbornene random copolymer (ethylene content: 65 mol%, MFR: 31 g / 10 min, number average molecular weight: 68000). 100 parts by mass of the resin obtained here was dissolved in a mixed solvent of 80 parts by mass of cyclohexane, 80 parts by mass of toluene, and 80 parts by mass of xylene, and a film having a thickness of 101 μm was produced by a casting method.

(4) Preparation of triacetyl cellulose (TAC) film For comparison, a triacetyl cellulose film (manufactured by Fuji Photo Film Co., Ltd.) (100 μm) was used.

(5) Additive (i) ADK STAB LA-31
Adeka Stub LA-31 (melting point (Tm): 195 ° C.) manufactured by Asahi Denka Co., Ltd., which is a benzotriazole ultraviolet absorber represented by the general formula [3] was used.
(Ii) Sumilyzer-GS
Sumitizer-GS (melting point (Tm): ≧ 115 ° C.) manufactured by Sumitomo Chemical Co., Ltd., which is a phenolic antioxidant having an acrylate group, was used.

[ Reference Examples 1 to 7, Comparative Examples 1 and 2]
Using the resin composition having the blending ratio shown in Table 1, using a Technobel T-die mounting extruder (KZW15TW-25MG-NH type / width 150 mmT die mounting / lip thickness 0.5 mm), screw rotation speed, extruder The unstretched film was obtained by adjusting the resin temperature in the cylinder and the temperature of the T die to the conditions shown in Table 1 and performing extrusion molding. The flow (extrusion direction) of the film was defined as the MD direction, and the direction perpendicular to the MD direction was defined as the TD direction.
Then, the unstretched film was cut out to have a width of 50 mm, and uniaxial stretching (between chucks: 50 mm, chuck moving speed: 500 mm / min) was performed using the tensile tester under the conditions shown in Table 1, Reference Example 1 4, 7 uniaxially stretched films were obtained.
Also, cut out such that the width of the uniaxial stretched film is 50 mm, uniaxial stretching under the conditions shown in Table 1 (between chucks: 50 mm, chuck moving speed: 500 mm / min) was performed using a tensile tester, reference example 2, 3, 5, 6 biaxially stretched films were obtained.

Table 1 shows the composition of each stretched film, extrusion molding conditions, film thickness, retardation (Re), absolute value of photoelastic coefficient, and water absorption.
For comparison, a cycloolefin resin film (COP) (photoelastic coefficient is positive, intrinsic birefringence is positive) is Comparative Example 1, a commercially available TAC (triacetyl cellulose) film (LOFO High Tech Film, Inc.) Table 1 shows the thickness, the in-plane retardation Re, the absolute value of the photoelastic coefficient, and the water absorption rate as Comparative Example 2 in which the name TACPHAN, the photoelastic coefficient is positive, and the intrinsic birefringence is positive.

  From Table 1, it was confirmed that the film produced from the resin composition for an optical material of the present invention has a higher water absorption rate than the cycloolefin-based resin and a lower water absorption rate than the triacetyl cellulose (TAC) film.

[Examples 8 to 13]
Using the resin composition having the blending ratio shown in Table 2, using a Technobel T-die mounting extruder (KZW15TW-25MG-NH type / width 150 mmT die mounting / lip thickness 0.5 mm), screw rotation speed, extruder The unstretched film was obtained by adjusting the resin temperature in the cylinder and the temperature of the T die to the conditions shown in Table 2 and performing extrusion molding. The flow (extrusion direction) of the film was defined as the MD direction, and the direction perpendicular to the MD direction was defined as the TD direction.
Then, the unstretched film was cut out to have a width of 50 mm, and uniaxial stretching (between chucks: 50 mm, chuck moving speed: 500 mm / min) was performed using the tensile tester under the conditions shown in Table 2, Example 8 ˜13 uniaxially stretched films were obtained.

  Table 2 shows the composition of each stretched film, extrusion molding conditions, film thickness, retardation (Re), absolute value of photoelastic coefficient, water absorption, and water vapor permeability.

From Table 1 and Table 2, the film manufactured from the resin composition for optical materials of the present invention (Examples 8 to 13) to which the additive was added was compared with the film manufactured from those not added ( Reference Examples 1 to 7). It was confirmed that the water vapor permeability was small.

[ Reference Examples 14 to 16, Examples 17 to 19, Comparative Examples 3 and 4]
(Manufacture of polarizing film)
Polyvinyl acetate is saponified (saponification degree: 98 mol%), molded, and the resulting polyvinyl alcohol film (thickness 75 μm) is an aqueous solution comprising 1000 parts by mass of water, 7 parts by mass of iodine, and 105 parts by mass of potassium iodide. For 5 minutes to adsorb iodine to the film. Next, this film was stretched uniaxially in the machine direction 5 times in a 4% by mass boric acid aqueous solution at 40 ° C., and then dried in a tension state to obtain a polarizing film.

(Manufacture of acrylic resin (d) protective film)
A methyl methacrylate-maleic anhydride-styrene copolymer was obtained by the method described in Japanese Patent Publication No. 63-1964.
The composition of the obtained methyl methacrylate-maleic anhydride-styrene copolymer was 74% by mass of methyl methacrylate, 10% by mass of maleic anhydride, and 16% by mass of styrene, and the copolymer melt flow rate value (ASTM- D1238; 230 ° C., 3.8 kg load) was 1.6 g / 10 min.
This methyl methacrylate-maleic anhydride-styrene copolymer was molded and stretched under the conditions shown in Table 1 to produce a protective film of Prototype Example 1.
(Manufacture of polarizing plates)
Using a 10% aqueous solution of a polyvinyl alcohol-based resin as an adhesive, the films of Reference Examples 1, 5, 7, Examples 8, 10, 13, Reference Examples 14, 16 and Comparative Example 2 were formed on one surface of the polarizing film. The COP film of Example 1, the triacetyl cellulose film of Comparative Example 1 and the protective film of Prototype Example 1 were bonded to the other surface to obtain polarizing plates of Reference Examples 14 to 16, Examples 17 to 19, and Comparative Examples 3 to 4. It was.

Table 3 shows the warpage and polarization degree retention of the polarizing plates of Reference Examples 14 to 16, Examples 17 to 19, and Comparative Examples 3 and 4.
From Table 3, it was confirmed that the polarizing plate using the film produced from the resin composition for an optical material of the present invention as a protective film has little warpage and excellent durability at high temperature and high humidity.

The resin composition for an optical material of the present invention is a waveguide in the fields of a display front plate, a display substrate, a touch panel, a transparent substrate used for solar cells, and other optical communication systems, an optical switching system, an optical measurement system, etc. It can be used as an optical material for manufacturing various optical elements such as lenses, optical fibers, optical fiber coating materials, LED lenses, and lens covers.
In particular, the resin composition for optical materials of the present invention can be used suitably as an optical material for manufacturing protective films for various optical elements because it can produce a molded article having an appropriate moisture permeability.
In particular, since the molded article of the optical resin composition of the present invention can easily provide retardation, it can serve both as a protective film and as a retardation film, and as a polarizing plate protective film. It can be used suitably.

Claims (14)

The acrylic resin (A) and the styrene resin (B) are included, and the mass ratio ((A) / (B)) of the acrylic resin (A) and the styrene resin (B) is 20/80 to 60/40. It is composed of a composition containing 0.01 parts by mass or more and 2 parts by mass or less of an additive with respect to 100 parts by mass of the resin composition for an optical material. A molded article for an optical element having a degree of 15 g / m ² · day or more and 100 g / m ² · day.   2. The optical element according to claim 1, wherein the additive is at least one additive selected from the group consisting of a benzotriazole compound, a benzotriazine compound, and a phenolic antioxidant having an acrylate group in the molecule. Molded body. The molded article for an optical element according to claim 1 or 2 , wherein the styrene resin (B) is a styrene-acrylonitrile copolymer. The molded article for an optical element according to claim 3 , wherein an acrylonitrile content in the styrene-acrylonitrile copolymer is 1 to 40% by mass. The molded article for an optical element according to claim 1, wherein the styrene resin (B) is a styrene-methacrylic acid copolymer. The molded article for an optical element according to claim 5 , wherein a methacrylic acid content in the styrene-methacrylic acid copolymer is 0.1 to 50% by mass. The molded article for an optical element according to claim 1 or 2 , wherein the styrene resin (B) is a styrene-maleic anhydride copolymer. The molded article for an optical element according to claim 7 , wherein the maleic anhydride content in the styrene-maleic anhydride copolymer is 0.1 to 50% by mass.   Water vapor permeability is 20g / m ² ・ Day and above 60g / m ² It is day or less, The molded object for optical elements of any one of Claims 1-8.   Water vapor permeability is 30g / m ² ・ Day over 40g / m ² It is day or less, The molded object for optical elements of any one of Claims 1-8. Polarizing plate protective film composed of a molded article for an optical element according to any one of claims 1-10. A retardation film consisting of the molded body for optical element according to any one of claims 1-10. A polarizing film;
The polarizing plate protective film according to claim 11 , wherein the polarizing film is laminated on one surface of the polarizing film and Re is 10 nm or more.
A polarizing plate having Furthermore, the polarizing plate of Claim 13 which has an acrylic resin (d) protective film laminated | stacked on the other surface of the said polarizing film, and Re being 10 nm or less.