JP2008291136A - Molding for optical material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a molding for an optical material having a low absolute value of photo-elastic coefficient and excellent in molding stability, when used for a liquid crystal display or the like. <P>SOLUTION: This molding for the optical material is formulated at a specified ratio of wt.% with a resin composition containing (a) 100 pts.wt. of acrylic resin comprising 25 wt.% or more-85 wt.% or less of acrylic compound, 10 wt.% or more-50 wt.% or less of aromatic vinyl compound, and 5 wt.% or more-25 wt.% or less of six-membered ring acid anhydride, (b) 0.1 pt.wt. or more-10 pts.wt. or less of ultraviolet absorber, and (c) 0.1 pt.wt. or more-10 pts.wt. or less of thermal stabilizer. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a molded article for an optical material having excellent optical characteristics.

Recently, with the expansion of the display market, there is an increasing demand for clearer images, and there is a demand for optical materials with higher optical properties than simple transparent materials.
Currently, in liquid crystal displays that are widely used as display elements, the liquid crystal elements that make up liquid crystals and the polarizers that make up polarizing plates are deteriorated by ultraviolet rays. Performance is required. In addition, the polymer has birefringence because the refractive index differs between the molecular main chain direction and the direction perpendicular thereto. Depending on the application, it is required to strictly control this birefringence. In the case of a protective film used for a polarizing plate of a liquid crystal, a polymer material having a smaller birefringence even if the total light transmittance is the same. A molded body is required. In this application, an example in which a film of cellulose triacetate or polylactic acid is studied as a polarizing plate protective film is known (see Patent Document 1), and cellulose triacetate is a representative material. On the other hand, a retardation film such as a quarter-wave plate having a function of converting light polarized by a polarizing plate into circularly polarized light in a liquid crystal display functions by consciously generating birefringence in a polymer material molded body. As a typical material, polycarbonate or the like can be given.

  In recent years, with the increase in size of liquid crystal displays, the required size of polymer optical material moldings has increased. In order to reduce the distribution of birefringence caused by bias of external force, the change in birefringence due to external force, that is, photoelasticity A material with a small coefficient is required. However, cellulose acetate and polycarbonate that are generally used as optical films at present have a large photoelastic coefficient and are not satisfactory for these requirements.

  Therefore, a birefringent optical material having a small photoelastic coefficient instead of these is desired. As a technique for controlling optical properties by using an additive in combination with an acrylic resin, a birefringence was controlled by adding a low molecular weight compound to an acrylic resin containing a glutaric anhydride unit and having a glass transition temperature of 120 ° C. or higher. It is shown (refer patent document 2). However, the photoelastic coefficient is not suggested, and there is a demand for an optical material having a small absolute value of the photoelastic coefficient and further improved moldability.

JP 2002-82223 A JP 2006-241197 A

  An object of the present invention is to provide a molded article for an optical material having a small absolute value of a photoelastic coefficient and excellent molding stability, and a method for producing the same.

  As a result of intensive studies on the above problems, the present inventors have found that a resin composition containing an acrylic resin (a) having a specific composition ratio, an ultraviolet absorber (b) and a heat stabilizer (c). It was found that by blending and producing at a specific ratio, the optical material has a small absolute value of the photoelastic coefficient and can provide a molded article for optical material having excellent molding stability, and the present invention has been completed.

（式中、Ｒ₁、Ｒ₂は、それぞれ独立して、水素原子又は炭素数１〜５のアルキル基を表す。）
（３）光弾性係数の絶対値が３．０×１０^-12/Ｐａ以下である（１）又は（２）に記載の光学材料用成形体
（４）前記紫外線吸収剤（ｂ）がベンゾトリアゾール系化合物又はベンゾトリアジン系化合物であることを特徴とする（１）〜（３）のいずれかに記載の光学材料用成形体
（５）前記熱安定剤（ｃ）がヒンダードフェノール系酸化防止剤又はリン系加工安定剤である（１）〜（４）のいずれかに記載の光学材料用成形体
（６）少なくとも一方向の延伸倍率が０．１％以上３００％以下である（１）〜（５）のいずれかに記載の光学材料用成形体
（７）（１）〜（６）のいずれかに記載の光学材料用成形体からなる偏光板保護フィルム
（８）（１）〜（６）のいずれかに記載の光学材料用成形体からなる位相差フィルム
（９）アクリル系化合物単位２５質量％以上８５質量％以下、芳香族ビニル系化合物単位１０質量％以上５０質量％以下、六員環酸無水物単位５質量％以上２５質量％以下からなるアクリル系樹脂（ａ）に、紫外線吸収剤（ｂ）及び熱安定剤（ｃ）を添加し、樹脂組成物を得る工程と、
前記樹脂組成物を、少なくとも一方向に延伸させる工程と、を含む光学材料用成形体の製造方法であって、
前記アクリル系樹脂（ａ）１００質量部に対して、前記紫外線吸収剤（ｂ）が０．１質量部以上１０質量部以下、及び前記熱安定剤（ｃ）が０．１質量部以上１０質量部以下である製造方法
を提供する。 That is, the present invention
(1) Acrylic compound unit comprising 25% by mass or more and 85% by mass or less of an acrylic compound unit, 10% by mass or more and 50% by mass or less of an aromatic vinyl compound unit, and 5% by mass or more and 25% by mass or less of a six-membered cyclic acid anhydride unit. Resin (a);
A molded article for an optical material, stretched in at least one direction, comprising a resin composition comprising an ultraviolet absorber (b) and a heat stabilizer (c),
The ultraviolet absorber (b) is 0.1 to 10 parts by mass and the thermal stabilizer (c) is 0.1 to 10 parts by mass with respect to 100 parts by mass of the acrylic resin (a). The molded article for optical material according to (1), wherein the six-membered cyclic acid anhydride unit is a six-membered cyclic acid anhydride unit represented by the formula [1]. Formula [1]

(In formula, R < ₁ >, R < ₂ > represents a hydrogen atom or a C1-C5 alkyl group each independently.)
(3) The molded article for optical material according to (1) or (2), wherein the absolute value of the photoelastic coefficient is 3.0 × 10 ⁻¹² / Pa or less (4) The ultraviolet absorber (b) is benzotriazole (5) The molded article for an optical material according to any one of (1) to (3), wherein the heat stabilizer (c) is a hindered phenol antioxidant Or the molded object for optical materials according to any one of (1) to (4), which is a phosphorus-based processing stabilizer (6) The stretch ratio in at least one direction is 0.1% to 300% (1) to (5) Polarized material protective film (8) (1)-(6) which consists of a molded object for optical materials in any one of (7) (1)-(6). ) Retardation film comprising the molded article for optical material according to any one of (9) Acrylic Acrylic resin (a) comprising 25% by mass to 85% by mass of compound unit, 10% by mass to 50% by mass of aromatic vinyl compound unit, and 5% by mass to 25% by mass of 6-membered cyclic acid anhydride unit. A step of adding a UV absorber (b) and a heat stabilizer (c) to obtain a resin composition;
Stretching the resin composition in at least one direction, and a method for producing a molded article for an optical material,
The ultraviolet absorber (b) is 0.1 to 10 parts by mass and the thermal stabilizer (c) is 0.1 to 10 parts by mass with respect to 100 parts by mass of the acrylic resin (a). A manufacturing method is provided.

According to the present invention, it is possible to provide a molded article for an optical material having a small absolute value of a photoelastic coefficient and excellent molding stability.
Further, when used in a liquid crystal display device or the like, since the absolute value of the photoelastic coefficient is small, it is possible to provide a molded article for an optical material that is excellent in color reproducibility, screen uniformity, and contrast.

  Hereinafter, although this invention is demonstrated in detail with desirable embodiment, this invention is not limited to these aspects.

  The molded article for an optical material of the present invention is a molded article for an optical material stretched in at least one direction comprising a resin composition containing an acrylic resin (a), an ultraviolet absorber (b) and a heat stabilizer (c). Is the body.

  The acrylic resin (a) used in the present invention is a copolymer comprising an acrylic compound unit, an aromatic vinyl compound unit, and a six-membered cyclic acid anhydride unit.

  Examples of acrylic compound units include units derived from methacrylic monomers and acrylic monomers, and as methacrylic monomers and acrylic monomers ((meth) acrylic monomers) Methacrylic acid, acrylic acid and derivatives thereof, preferably methacrylic acid, methacrylic acid ester and acrylic acid ester.

  Specific examples of the methacrylic acid ester include butyl methacrylate, ethyl methacrylate, methyl methacrylate, propyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, 2-ethylhexyl methacrylate, t-butylcyclohexyl methacrylate, benzyl methacrylate, And 2,2,2-trifluoroethyl methacrylate and the like, and a typical one is methyl methacrylate.

  Specific examples of the acrylate ester include methyl acrylate, ethyl acrylate, butyl acrylate, isopropyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, and phenyl acrylate.

  The (meth) acrylic monomers can be used alone or in combination of two or more.

  When it contains methacrylic acid, it is preferably 2% by mass or more and 20% by mass or less, more preferably 2% by mass or more and 15% by mass or less, and further preferably 3% by mass or more and 10% by mass or less in the acrylic resin (a).

  Examples of the aromatic vinyl compound unit include units derived from a styrene compound monomer, an isopropenylbenzene compound monomer, and the like.

  Specific examples of the styrene compound monomer include, in addition to styrene, for example, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, 2,5-dimethylstyrene, 3,4 -Alkyl-substituted styrenes such as dimethyl styrene, 3,5-dimethyl styrene, p-ethyl styrene, m-ethyl styrene, о-ethyl styrene, and p-tert-butyl styrene; 1,1-diphenylethylene and the like A typical one is styrene.

  Specific examples of the isopropenylbenzene compound monomer include, for example, isopropenylbenzene (α-methylstyrene), isopropenyltoluene, isopropenylethylbenzene, isopropenylpropylbenzene, isopropenylbutylbenzene, isopropenylpentylbenzene, Examples thereof include alkyl-substituted isopropenylbenzenes such as propenylhexylbenzene and isopropenyloctylbenzene, and a typical one is isopropenylbenzene.

  The above styrene compound monomers and isopropenyl benzene compound monomers can be used alone or in combination of two or more.

The 6-membered cyclic acid anhydride unit may be any unit as long as it has a 5- or 6-membered ring in its structure, and may be an unsaturated carboxylic acid monomer and, if necessary, an unsaturated carboxylic acid. Examples include units derived from compounds obtained by intramolecular or intermolecular cyclization of alkyl ester monomers. Specific examples of the unsaturated carboxylic acid monomer for producing a six-membered ring acid anhydride unit include, for example, methacrylic acid, acrylic acid, itaconic acid, maleic acid, fumaric acid, and cinnamic acid. Specific examples of the unsaturated carboxylic acid alkyl ester monomer include, for example, methyl methacrylate and methyl acrylate.
The unsaturated carboxylic acid and unsaturated carboxylic acid alkyl ester monomer may be used alone or in combination of two or more.

（式中、Ｒ₁、Ｒ₂は、それぞれ独立して、水素原子又は炭素数１〜５のアルキル基を表す。） The six-membered cyclic acid anhydride unit is preferably a six-membered cyclic acid anhydride unit represented by the formula [1].
Formula [1]

(In formula, R < ₁ >, R < ₂ > represents a hydrogen atom or a C1-C5 alkyl group each independently.)

From the viewpoints of heat resistance and photoelastic coefficient, the acrylic compound unit in the acrylic resin (a) is 25% by mass to 85% by mass, the aromatic vinyl compound unit is 10% by mass to 50% by mass, and six members. The cyclic acid anhydride unit is 5% by mass or more and 25% by mass or less.
Preferably, the acrylic compound unit in the acrylic resin (a) is 40% by mass to 75% by mass, the aromatic vinyl compound unit is 15% by mass to 40% by mass, and the six-membered cyclic acid anhydride unit is 10%. The acrylic compound unit in the acrylic resin (a) is 45% by mass to 68% by mass and the aromatic vinyl compound unit is 20% by mass to 37% by mass. Hereinafter, the 6-membered cyclic acid anhydride unit is 12% by mass or more and 18% by mass or less.

As a method for producing the acrylic resin (a), generally used polymerization methods such as cast polymerization, bulk polymerization, suspension polymerization, solution polymerization, emulsion polymerization, and anionic polymerization can be used. Among them, bulk polymerization and solution polymerization without using a suspending agent or an emulsifier are preferable because it is possible to reduce the mixing of minute foreign matters that are inconvenient for optical applications.
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, and t-butyl Organic peroxides such as peroxy-2-ethylhexanoate can be used.
When polymerization is performed at a high temperature of 90 ° C. or higher, solution polymerization is generally used. Therefore, the initiator has a 10-hour half-life temperature of 80 ° C. or higher, and is a peroxide that is soluble in the organic solvent used. It is preferable to use an azobis initiator or the like. Specifically, 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, cyclohexane peroxide, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, , 1-azobis (1-cyclohexanecarbonitrile), 2- (carbamoylazo) isobutyronitrile, and the like. These initiators are preferably used in the range of 0.005 to 5% by mass with respect to 100% by mass of the whole monomer, for example.

  As the molecular weight regulator used as necessary in 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, and 2-ethylhexyl thioglycolate. Etc.

Examples of the acrylic resin (a) containing a 6-membered cyclic acid anhydride unit include Japanese Patent Publication No. 02-26641, Japanese Patent Application Laid-Open No. 2006-265543, Japanese Patent Application Laid-Open No. 2006-274069, and Japanese Patent Application Laid-Open No. 2006-274071. It can be produced with reference to the method described in JP-A-2006-283013.
For the purpose of improving the yield and performance of the acrylic resin (a), it is preferable to adjust the polymerization conditions. Such polymerization conditions can be adjusted, for example, by suppressing the thermal history during polymerization to shorten the thermal treatment time, reducing the amount of oxygen present in the polymerization system during polymerization, and devolatilizing low molecular weight products. For example, increasing the degree of vacuum at the time.

  The acrylic resin (a) may be a block polymer or a random polymer, and is preferably a statistical random polymer from the viewpoints of heat resistance, rigidity, and recyclability.

The molecular weight distribution range of the acrylic resin (a) is preferably such that the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is in the range of 1.6 to 4.0. More preferably, it is 1.7-3.7, More preferably, it is the range of 1.8-3.5. When Mw / Mn is smaller than 1.6, the balance between resin film processability and mechanical properties is deteriorated. On the other hand, when Mw / Mn is larger than 4.0, melt fluidity is deteriorated and workability is deteriorated.
As a method for controlling Mw / Mn, for example, acrylic resin (a) in the range of 1.6 to 2.3 can be obtained by controlling the rotation speed of the stirring blade in the reactor by a continuous polymerization method. Moreover, Mw / Mn can be controlled between 2.0-4.0 by carrying out the solution or melt blending of the high molecular weight component.
The ratio (Mw / Mn) between the weight average molecular weight (Mw) and the number average molecular weight (Mn) in the present invention is a value determined by gel conversion using gel permeation chromatography (GPC).
The weight average molecular weight (Mw) measured by GPC is preferably 50,000 to 500,000, more preferably 10 to 350,000, and still more preferably 150 to 300,000. By using the acrylic resin (a) having a weight average molecular weight of 500,000 or less, sufficient fluidity can be obtained for the extrusion stretching process, melt extrusion and stretching film formation can be performed without any major trouble, and the weight average molecular weight is 5 By using 10,000 or more acrylic resins (a), it is possible to give sufficient stability to the stretching stability and the film.

  Examples of the ultraviolet absorber (b) include benzotriazole compounds, benzotriazine compounds, benzoate compounds, benzophenone compounds, oxybenzophenone compounds, phenol compounds, oxazole compounds, malonic acid ester compounds, cyanoacrylate compounds. , Lactone compounds, salicylic acid ester compounds, benzoxazinone compounds, and the like, and benzotriazole compounds and benzotriazine compounds are preferable. These may be used alone or in combination of two or more.

The ultraviolet absorber (b) is excellent in moldability when the vapor pressure (P) at 20 ° C. is 1.0 × 10 ⁻⁴ Pa or less. A preferable range is a vapor pressure (P) of 1.0 × 10 ⁻⁶ Pa or less, and a more preferable range is a vapor pressure (P) of 1.0 × 10 ⁻⁸ Pa or less. “Excellent molding processability” means, for example, that there is little adhesion of a low molecular compound to a roll during film formation. For example, when a low molecular weight compound adheres to a roll, the low molecular weight compound adheres to the surface of the molded article for optical material via the roll, which deteriorates the appearance and optical characteristics of the molded article for optical material. It becomes.
The ultraviolet absorber (b) is excellent in moldability when the melting point (Tm) is 80 ° C. or higher. A preferable range is a melting point (Tm) of 130 ° C. or higher, and a more preferable range is a melting point (Tm) of 160 ° C. or higher.
The ultraviolet absorbent (b) is excellent in moldability when the weight reduction rate of the ultraviolet absorbent (b) is 50% or less when the temperature is increased from 23 ° C. to 260 ° C. at a rate of 20 ° C./min. A preferred range is a weight reduction rate of 15% or less, and a more preferred range is a weight reduction rate of 2% or less.

The molded article for optical material of the present invention preferably has a spectral transmittance at 380 nm of 5% or less and a spectral transmittance at 400 nm of 65% or more. The lower the spectral transmittance at 380 nm in the ultraviolet region, the lower the deterioration of the polarizer and the liquid crystal element, and the higher the 400 nm spectral transmittance in the visible region, the better the color reproducibility. Therefore, it can be preferably used as an optical film. In order to design within this range, the amount of the ultraviolet absorber (b) needs to be 0.1 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the acrylic resin (a). When the amount is more than 0.1 parts by mass, the spectral transmittance at 380 nm is small, and when the amount is less than 10 parts by mass, the increase in the photoelastic coefficient is small, and the moldability and mechanical strength are also improved. A preferable range of the amount of the ultraviolet absorber (b) is 0.3 part by mass or more and 8 parts by mass or less, and a more preferable range is 0.5 part by mass or more and 5 parts by mass or less.
The amount of the ultraviolet absorber (b) is determined by measuring proton NMR with a nuclear magnetic resonance apparatus (NMR) and obtaining from the ratio of integral values of peak signals, or by extracting from a resin using a good solvent and then gas chromatograph (GC). It can be quantified by the method of measuring by

Examples of the heat stabilizer (c) include antioxidants such as hindered phenol antioxidants or phosphorus processing stabilizers, and preferably hindered phenol antioxidants. Specific examples of the hindered phenol antioxidant include pentaerythritol terakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], thiodiethylenebis [3- (3,5- Di-tert-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, N, N′-hexane-1,6-diylbis [3 -(3,5-di-tert-butyl-4-hydroxyphenylpropionamide], 3,3 ′, 3 ″, 5,5 ′, 5 ″ -hexa-tert-butyl-a, a ′, a ''-(Mesitylene-2,4,6-triyl) tri-p-cresol, 4,6-bis (octylthiomethyl) -o-cresol, 4,6-bis (dodecylthiomethyl) -o-cresol, Ethylene bi (Oxyethylene) bis [3- (5-tert-butyl-4-hydroxy-m-tolyl) propionate, hexamethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] 1,3,5-tris (3,5-di-tert-butyl-4-hydroxybenzyl) -1,3,5-triazine-2,4,6 (1H, 3H, 5H) -trione, 3,5-tris [(4-tert-butyl-3-hydroxy-2,6-xylin) methyl] -1,3,5-triazine-2,4,6 (1H, 3H, 5H) -trione, 2, , 6-di-tert-butyl-4- (4,6-bis (octylthio) -1,3,5-triazin-2-ylamine) phenol, and more preferably pentaerythritol terakis [3- (3,5-di-tert-butyl-4 Is hydroxy phenyl) propionate].
In order to improve the molding thermal stability of the film, the amount of the heat stabilizer (c) needs to be 0.1 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the acrylic resin (a). It is. When the amount is more than 0.1 parts by mass, the melt fluidity is improved at the time of film forming and the moldability is stabilized. A preferable range of the amount of the heat stabilizer (c) is 0.3 part by mass or more and 8 parts by mass or less, and a more preferable range is 0.5 part by mass or more and 5 parts by mass or less.

The “photoelastic coefficient” in the present invention is a coefficient representing the ease with which birefringence changes due to external force, and is defined by the following equation.
C _R [/ Pa] = Δn / σ _R
Here, σ _R is extensional stress [Pa], Δn is birefringence when stress is applied, and Δn is defined by the following equation.
Δn = n ₁ −n ₂
Here, n ₁ is the refractive index in the direction parallel to the stretching direction, and n ₂ is the refractive index in the direction perpendicular to the stretching direction.
It shows that the change in birefringence due to external force is smaller as the value of the photoelastic coefficient is closer to zero. The absolute value of the photoelastic coefficient is preferably 3.0 × 10 ⁻¹² / Pa or less, and more preferably 1.0 × 10 ⁻¹² / Pa or less. If the photoelastic coefficient is within this range, the change in birefringence due to stress is small, so that the contrast and the uniformity of the screen are excellent when used in a liquid crystal display device or the like. In the present invention, the absolute value of the photoelastic coefficient can be controlled within a preferable range by designing the amount of the ultraviolet absorber (b) and the draw ratio within a preferable range.

  The polymer for optical material of the present invention can be mixed with other polymers as long as the object of the present invention is not impaired. Examples of such polymers include polyolefins such as polyethylene and polypropylene, polyamides, polyphenylene sulfide resins, polyether ether ketone resins, polyesters, polysulfones, polyphenylene oxides, polyimides, polyether imides, and thermoplastic resins such as polyacetals, And thermosetting resins such as phenol resins, melamine resins, silicone resins, and epoxy resins.

  Moreover, arbitrary additives can be mix | blended with the molded object for optical materials of this invention according to various objectives within the range which does not impair the objective of this invention. The type of additive is not particularly limited as long as it is generally used for blending resins and rubber-like polymers. Inorganic fillers such as silicon dioxide, pigments such as iron oxide, lubricants such as stearic acid, behenic acid, zinc stearate, calcium stearate, magnesium stearate, ethylene bisstearamide, mold release agents, paraffinic process oil, naphthene -Based process oil, aromatic process oil, paraffin, organic polysiloxane, mineral softener / plasticizer, flame retardant, antistatic agent, organic fiber, glass fiber, carbon fiber, metal whisker reinforcing agent, coloring Agents, other additives, or a mixture thereof.

  The method for producing the molded article for optical material in the present invention is not particularly limited, and a known method can be used. For example, the resin composition can be produced using a melt kneader such as a single screw extruder, a twin screw extruder, a Banbury mixer, a Brabender, or various kneaders. In the case where the form of the molded article for optical material of the present invention is a film or sheet, it is manufactured by extruding an unstretched film or sheet using an extruder or the like equipped with a T die, a circular die, etc. can do. When obtaining a molded product by extrusion molding, it is possible to use a material in which an acrylic resin (a, an ultraviolet absorber (b), and a heat stabilizer (c) is previously melt-kneaded. It can also be molded after that.

The molded article for optical material in the present invention can be obtained by stretching an unstretched molded article in at least one direction. The stretching method is not particularly limited, and a longitudinal uniaxial stretching in the mechanical flow direction (MD), a transverse uniaxial stretching in a direction orthogonal to the mechanical flow direction (TD), and the like can be used. For example, industrially, by uniaxial stretching method by roll stretching or tenter stretching, sequential biaxial stretching method by combination of roll stretching and tenter stretching, simultaneous biaxial stretching method by tenter stretching, 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 direction. More preferably, it is 1% or more and 200% or less, More preferably, it is the range which does not exceed 130% exceeding 10%. By designing in this range, a stretched molded article preferable in terms of photoelastic coefficient and mechanical strength can be obtained.
The thickness of the molded article for optical material in the present invention is 300 μm or less, preferably 1 μm or more, more preferably 5 μm or more.

In the present invention, the planar retardation (Re) is controlled by designing the composition of the acrylic resin (a) and the ultraviolet absorber (b), the draw ratio, and the thickness of the molded article for the optical material within a preferable range. Can do.
The planar retardation (Re) is defined by the following formula.
Re = (nx−ny) × d
(Where, nx, ny: main refractive index of plane, d: thickness)
In the case of a polarizing plate protective film comprising the molded article for optical material of the present invention, the absolute value of Re of the molded article for optical material is preferably 0 nm or more and 50 nm or less, more preferably 30 nm or less, and still more preferably. It is 10 nm or less, and particularly preferably 5 nm or less.
In the case of a quarter-wave plate comprising the molded article for optical material of the present invention, the absolute value of Re of the molded article for optical material is preferably 100 nm or more and 180 nm or less, more preferably 120 nm or more and 160 nm or less, and still more preferably. Is 130 nm or more and 150 nm or less.

The draw ratio can be determined from the following relational expression by shrinking the obtained stretched film at a temperature 20 ° C. or higher than the glass transition temperature.
Stretch ratio (%) = [(length before shrinkage / length after shrinkage) −1] × 100
The glass transition temperature can be determined by a DSC method or a viscoelastic method.

Moreover, this invention is a manufacturing method of the molded object for optical materials extended | stretched at least to one direction which consists of a resin composition containing acrylic resin (a), a ultraviolet absorber (b), and a heat stabilizer (c). Also related.
The method for producing a molded article for an optical material according to the present invention is an acrylic compound unit of 25 mass% to 85 mass%, an aromatic vinyl compound unit of 10 mass% to 50 mass%, and a 6-membered cyclic acid anhydride unit of 5 mass. The step of adding a UV absorber (b) and a heat stabilizer (c) to an acrylic resin (a) comprising 25% by mass or more and 25% by mass or less to obtain a resin composition, and the resin composition at least in one direction And a method of producing a molded body for an optical material, which comprises a step of stretching the film.
The molded article for an optical material obtained by the production method of the present invention has an ultraviolet absorber (b) of 0.1 part by mass or more and 10 parts by mass or less, and a thermal stabilizer with respect to 100 parts by mass of the acrylic resin (a). Since the resin composition is obtained with (c) being 0.1 parts by mass or more and 10 parts by mass or less, it is a molded article for optical materials having a small absolute value of photoelastic coefficient and excellent molding stability.
[Example]

EXAMPLES Next, although an Example is given and demonstrated in detail, this invention is not restrict | limited to these Examples.
The evaluation method used in the examples will be described.
<Evaluation method>
(1) Tensile in the path of the measurement the measurement beam of the photoelastic coefficient (C _R) apparatus (Imoto Seisakusho) arranged, with RETS-RFI (manufactured by Otsuka Electronics) The birefringence while applying a tensile stress to the test piece Measured. The strain rate during stretching was 0.3% / min (between chucks: 30 mm, chuck moving speed 0.1 mm / min), and the specimen width was 10 mm. The absolute value of birefringence (| Δn |) in the strain range of 0 to 0.5% of the specimen at 25 ° C. is plotted as the y-axis and the tensile stress (σ _R ) as the x-axis. The slope of the straight line was obtained, and the absolute value (| C _R |) of the photoelastic coefficient was calculated.
(2) Measurement of planar retardation (Re) Using a birefringence measuring apparatus RETS-100 manufactured by Otsuka Electronics Co., Ltd., planar retardation (Re) at 25 ° C. was measured by a rotating analyzer method.
(3) Spectral transmittance The spectral spectrum was measured using U-3310 manufactured by Hitachi, Ltd., and the transmittance at 380 nm was determined.
(4) Glass transition temperature (Tg) measurement Using a DSC-7 type (manufactured by Perkin Elmer Co., Ltd.), in the temperature rise measurement from room temperature to 200 ° C., the raw film sample weight is 8. 0-10 mg Tg was measured.
(5) Measurement of film thickness The center part of each stretched film was measured using a micrometer (manufactured by Mitutoyo Corporation).
(6) Film molding evaluation method A: Melt viscosity is reduced, low temperature processing is possible, and moldability is very good.
◯: Melt viscosity is reduced, low temperature processing is possible, and moldability is good.
(Triangle | delta): A melt viscosity rises and a moldability will not be stabilized unless it is high temperature processing.

(1) Acrylic resin (a)
(Raw material I) Preparation of acrylic resin (methyl methacrylate-styrene-methacrylic acid-six-membered cyclic acid anhydride) Methyl methacrylate 35 wt%, styrene 25 wt%, methacrylic acid 20 wt%, metaxylene 20 wt%, perhexa C (1 , 1-di (tert-butylperoxy) cyclohexane) 50ppm, n-octyl mercaptan 1500ppm mixed liquid prepared continuously at a rate of 1.5L / hr, with a jacket of 3L capacity, complete mixing The polymerization was carried out at a temperature of 125 ° C. by feeding the reactor. Further, the polymerization solution was continuously supplied to a high-temperature deaerator set at 260 ° C., and stayed for 2 hours and deaerated and cyclized to remove unreacted substances and produce a six-membered cyclic acid anhydride. The results of composition analysis by neutralization titration, IR spectrum, and ¹³ CNMR of this acrylic resin were methyl methacrylate unit 45 wt%, styrene unit 30 wt%, six-membered cyclic acid anhydride unit 18 wt%, and methacrylic acid unit 7 wt%. . The resulting acrylic resin had a melt flow rate value (ASTM-D1238; 230 ° C., 3.8 kg load) of 1.1 g / 10 min and Tg = 135 ° C.

(Raw material II) Preparation of acrylic resin (methyl methacrylate-α-methylstyrene-methacrylic acid-six-membered cyclic acid anhydride) Methyl methacrylate 48 wt%, α-methylstyrene 6 wt%, methacrylic acid 6 wt%, t-butanol A mixed liquid consisting of 40 wt%, 1,1-di-tert-butylperoxy-3,3,5-trimethylcyclohexane 500 ppm, and n-octyl mercaptan 200 ppm was prepared and continuously mixed at a rate of 1.5 L / hr. Then, the mixture was supplied to a complete mixing reactor equipped with a jacket having an internal volume of 3 L, and polymerization was carried out at a temperature of 125 ° C. Further, the polymerization solution was continuously supplied to a high-temperature degassing apparatus set at 260 ° C., and retained for 2 hours and degassed and cyclized to remove unreacted substances and produce a six-membered ring anhydride. The results of composition analysis by neutralization titration, IR spectrum, and ¹³ C NMR of this polymer were as follows: methyl methacrylate unit 80 wt%, α-methyl styrene unit 11 wt%, six-membered cyclic acid anhydride unit 6 wt%, and methacrylic acid unit 3 wt%. there were. The resulting acrylic resin had a melt flow rate value (ASTM-D1238; 230 ° C., 3.8 kg load) of 1.5 g / 10 min and Tg = 132 ° C.

(2) UV absorber (b)
Adekastab LA-31 (melting point (Asahi Denka Co., Ltd.), a benzotriazole compound.
Tm): 195 ° C) was used. ThermoPlus TG8120 manufactured by Rigaku Denki Co., Ltd.
Was used to measure the weight reduction rate when the temperature was increased from 23 ° C. to 260 ° C. at a rate of 20 ° C./min, and it was 0.03%.

(3) Thermal stabilizer (c)
IRGANOX 1010 (white powder, melting point (Tm): 110-125 ° C., vapor pressure: 1.3 × 10 ⁻¹⁰ Pa (20 ° C.)) manufactured by Ciba Specialty Chemicals Co., Ltd. was used.

[Examples 1 to 4 and Comparative Examples 1 and 2]
Using a T-die mounting extruder (BT-30-C-36-L type / width 400 mm, T-die mounting / lip thickness 0.8 mm) manufactured by the Institute of Plastics Engineering, screw rotation speed, resin temperature in the cylinder of the extruder, T An unstretched film was obtained by adjusting the temperature of the die 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. In Examples 1 to 4, each resin, LA-31, and IRGANOX 1010 were dry blended and extruded.
Next, longitudinal (MD direction) uniaxial stretching of the obtained unstretched film was performed using a roll-type longitudinal stretching machine manufactured by Ichikin Kogyo Co., Ltd. In order to obtain a target set stretching ratio, stretching was performed between rolls by changing the rotation speed of two rolls (low speed side roll / high speed side roll). Subsequently, transverse (TD direction) stretching of the obtained longitudinally uniaxially stretched film was performed using a tenter stretching machine manufactured by Ichikin Kogyo Co., Ltd. Stretching was performed by changing the distance between the tenter chucks at a flow rate of 2 m / min in order to obtain a target set stretching ratio. The composition, molding conditions, and film optical properties are shown in Table 1.
[Example 1]

LA-31 (1.5 parts by weight) and IRGANOX 1010 (1.0 parts by weight) were mixed with the raw material I to prepare a raw film. Thereafter, the film was stretched 100% in the MD direction and 100% in the TD direction to obtain a biaxially stretched film.
[Example 2]

LA-31 (1.0 part by weight) and IRGANOX 1010 (0.5 part by weight) were mixed with the raw material I to prepare a raw film. Thereafter, 100% stretching was performed in the MD direction to obtain a uniaxially stretched film.
[Example 3]

LA-31 (1.5 parts by weight) and IRGANOX 1010 (1.0 parts by weight) were mixed with the raw material II to prepare a raw film. Thereafter, the film was stretched 50% in the MD direction and 50% in the TD direction to obtain a biaxially stretched film.
[Example 4]

  LA-31 (1.0 part by weight) and IRGANOX 1010 (0.5 part by weight) were mixed with the raw material II to prepare a raw film. Thereafter, 100% stretching was performed in the MD direction to obtain a uniaxially stretched film.

(Comparative Example 1)
It carried out like Example 1 except not having mixed LA-31 and IRGANOX1010.

(Comparative Example 2)
It carried out like Example 3 except not having mixed LA-31 and IRGANOX1010.

In Examples 1 to 4, a resin composition having a small absolute value of the photoelastic coefficient and excellent film forming stability is obtained by blending at specific composition ratios of acrylic resin, LA-31, and IRGANOX 1010. It was. Moreover, in Example 1, 3, the polarizing plate protective film was obtained with small plane retardation by controlling extending | stretching process. Further, in Examples 2 and 4, the planar retardation is in the vicinity of λ / 4 (nm), which is suitable for a retardation film.
In Comparative Example 1, since LA-31 was not mixed, the spectral transmittance at 380 nm was 89%, and IRGANOX 1010 was not mixed. Therefore, the film molding was not stabilized unless the temperature was 250 ° C. or higher. .
In Comparative Example 2, since no mixing LA-31, the absolute value of the photoelastic coefficient is larger than 3.0 × 10- ¹² / Pa, not mixed with IRGANOX1010, during film forming, 250 The film forming was not stabilized unless it was over ℃.

  The molded article for an optical material of the present invention includes a light guide plate, a diffusion plate, a polarizing plate protective film, a quarter-wave plate, which are used in a display such as a liquid crystal display, a plasma display, an organic EL display, a field emission display, and a rear projection TV. It has applicability to half-wave plates, viewing angle control films, retardation films such as liquid crystal optical compensation films, display front plates, display substrates, lenses, touch panels, and transparent substrates used in solar cells. . In addition, in the fields of optical communication systems, optical switching systems, and optical measurement systems, the present invention can also be used for waveguides, lenses, optical fibers, optical fiber coating materials, LED lenses, lens covers, and the like. The molded article for an optical material of the present invention can be subjected to surface functionalization treatment such as antireflection treatment, transparent conductive treatment, electromagnetic wave shielding treatment, gas barrier treatment and the like.

Claims (9)

Acrylic resin (a) comprising 25% by mass to 85% by mass of acrylic compound units, 10% by mass to 50% by mass of aromatic vinyl compound units, and 5% by mass to 25% by mass of 6-membered cyclic acid anhydride units. )When,
A molded article for an optical material, stretched in at least one direction, comprising a resin composition comprising an ultraviolet absorber (b) and a heat stabilizer (c),
The ultraviolet absorber (b) is 0.1 to 10 parts by mass and the thermal stabilizer (c) is 0.1 to 10 parts by mass with respect to 100 parts by mass of the acrylic resin (a). The molded part for optical materials which is less than the part. The molded article for an optical material according to claim 1, wherein the six-membered cyclic acid anhydride unit is a six-membered cyclic acid anhydride unit represented by the formula [1].
Formula [1]

(In formula, R < ₁ >, R < ₂ > represents a hydrogen atom or a C1-C5 alkyl group each independently.) The molded article for an optical material according to claim 1 or 2, wherein the absolute value of the photoelastic coefficient is 3.0 × 10 ^-12 / Pa or less.   The said ultraviolet absorber (b) is a benzotriazole type compound or a benzotriazine type compound, The molded object for optical materials of any one of Claims 1-3 characterized by the above-mentioned.   The molded article for an optical material according to any one of claims 1 to 4, wherein the thermal stabilizer (c) is a hindered phenol-based antioxidant or a phosphorus-based processing stabilizer.   The molded article for an optical material according to any one of claims 1 to 5, wherein a stretch ratio in at least one direction is 0.1% or more and 300% or less.   The polarizing plate protective film which consists of a molded object for optical materials of any one of Claims 1-6.   The retardation film which consists of a molded object for optical materials of any one of Claims 1-6. Acrylic resin (a) comprising 25% by mass to 85% by mass of acrylic compound units, 10% by mass to 50% by mass of aromatic vinyl compound units, and 5% by mass to 25% by mass of 6-membered cyclic acid anhydride units. ), An ultraviolet absorber (b) and a heat stabilizer (c) are added to obtain a resin composition;
Stretching the resin composition in at least one direction, and a method for producing a molded article for an optical material,
The ultraviolet absorber (b) is 0.1 to 10 parts by mass and the thermal stabilizer (c) is 0.1 to 10 parts by mass with respect to 100 parts by mass of the acrylic resin (a). Part or less of the manufacturing method.