JP5403777B2 - Molded body for optical materials - Google Patents

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.
The polymer has birefringence because the refractive index differs between the molecular main chain direction and the perpendicular direction. 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 (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 generally used as an optical film at present have a large photoelastic coefficient and are not satisfactory for these requirements.
An acrylic resin is known as a material having a small photoelastic coefficient and a negative birefringence. However, acrylic resins are inferior in toughness (trimming properties) and are brittle and easily broken, and cracks occur when the film is broken, resulting in poor productivity. In order to solve this problem, a composition containing a toughness improving agent in an acrylic resin is disclosed (Patent Document 2). However, since the toughness improving agent is used in a large amount, the stretched film has a problem that it loses transparency.

Further, for the purpose of improving mechanical strength, a method in which an acrylic resin contains a styrene elastomer, a styrene-butadiene rubber or the like is disclosed (Patent Document 3). However, since the haze value exceeds 1.0% in spite of a relatively small amount of styrene elastomer and the raw fabric, the stretched film has a problem that the haze value is further increased.
Furthermore, as a thermoplastic resin composition with improved mechanical strength and transparency, a technique of incorporating a rubber polymer into a thermoplastic resin containing a glutaric anhydride unit having a six-membered ring structure is disclosed. (Patent Document 4). However, since the rubber dispersibility varies depending on the copolymer composition, the haze value increases during styrene copolymerization.

Further, as an acrylic resin film imparted with heat resistance and toughness, a technique is disclosed in which a cross-linked elastic body having a multilayer structure is contained in an acrylic resin containing a glutaric anhydride unit (Patent Document 5). Since the cross-linked elastic body is contained in a large amount for improving the bending property, there is a concern that the haze value is increased accordingly.
From the above prior art, it was not possible to find an effect related to the maintenance of transparency at the time of stretching described in the present application and the solution to the generation of microcracks and cracks in the trimming process (trimming property), and this was achieved for the first time by the present application. Is.
JP 2002-82223 A Japanese Patent Laid-Open No. 5-119217 JP 2006-284881 A JP 2004-292812 A JP 2000-178399 A

  The problem to be solved by the present invention is to provide an optical material molded article having an excellent trimming property and having a small photoelastic coefficient that maintains transparency during stretching.

As a result of intensive studies on the above problems, the present inventors have blended the rubber-containing copolymer particles (b) having a three-layer structure with the acrylic resin (a) having a specific composition ratio. The present invention has been completed.
That is, the present invention
(1) Acrylic resin comprising 25% by mass to 85% by mass of acrylic compound units, 10 % by mass to 45% by mass of aromatic vinyl compound units, and 5% by mass to 35% by mass of 6-membered ring compound units ( a) with respect to 100 parts by mass, the rubber-containing polymer particles (b) is a hard layer from the inner - soft layer - consisting of three-layer structure of the hard layer the rubber-containing polymer particles (b) 0.1 part by mass or more A molded article for an optical material comprising a resin composition containing 10 parts by mass or less and stretched in at least one direction.
(2) The molded article for an optical material according to (1), wherein the six-membered cyclic acid anhydride unit is a six-membered cyclic acid anhydride unit represented by the following chemical formula.


(In formula, R < ₁ >, R < ₂ > represents a hydrogen atom or a C1-C5 alkyl group each independently.)
( 3 ) The refractive index difference between the acrylic resin (a) and the rubber-containing polymer particles (b) is 0.02 or less, and the optical material according to any one of (1) to ( 2 ) Molded body.
( 4 ) The molded article for an optical material according to any one of (1) to ( 3 ), wherein a draw ratio in at least one direction is 0.1% or more and 200% or less.
( 5 ) The haze value is 1.0% or less, and the absolute value of the photoelastic coefficient is 5.0 × 10 ⁻¹² / Pa or less, according to any one of (1) to ( 4 ), Molded body for optical materials.
( 6 ) A polarizing plate protective film comprising the molded article for an optical material according to any one of (1) to ( 5 ).
( 7 ) A retardation film comprising the molded article for optical material according to any one of (1) to ( 5 ).

According to the present invention, it is possible to provide a molded article for an optical material having excellent trimming properties and transparency at the time of stretching, and a small photoelastic coefficient. Since the optical film of the present invention has excellent trimming properties, it is possible to reduce the occurrence of microcracks, cracks, and the like in the trimming step, and the productivity of the optical film can be improved.
Further, when used in a liquid crystal display device or the like, since transparency can be maintained by stretching, a wide range of retardation can be designed, and it can be suitably used for a retardation film and a polarizing plate protective film.

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 according to the present invention is a molded article for an optical material stretched in at least one direction comprising a resin composition comprising an acrylic resin (a) and a rubber-containing polymer particle (b) having a three-layer structure. is there.
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, methacrylic acid (t-butylcyclohexyl), and methacrylic acid. Examples include benzyl and methacrylic acid (2,2,2-trifluoroethyl), 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 a mixture with methyl methacrylate, and the methacrylic acid content in that case is preferably 2% by mass or more and 20% by mass or less in the acrylic resin (a). The content is more preferably 15% by mass or less and further preferably 3% by mass or more and 10% by mass or less.
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 dimethylstyrene, 3,5-dimethylstyrene, p-ethylstyrene, m-ethylstyrene, о-ethylstyrene, and p-tert-butylstyrene; 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 six-membered ring compound unit may be any unit as long as the object of the present invention is not impaired, and examples thereof include a six-membered ring structure such as a pyran ring, a lactone ring, a glutarimide ring, and a glutaric anhydride structure. A glutaric acid structure is preferred.

  Among the six-membered ring compound units, preferably a six-membered cyclic acid anhydride unit, an unsaturated carboxylic acid monomer, and optionally an unsaturated carboxylic acid alkyl ester monomer, and other monomer components After polymerization to form a copolymer, the copolymer may be heated in the presence or absence of a suitable catalyst to cause an intramolecular cyclization reaction by dealcoholization and / or dehydration. it can. 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 generating the acid anhydride unit having a six-membered ring structure 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.
The unsaturated carboxylic acid and unsaturated carboxylic acid alkyl ester monomer may be used alone or in combination of two or more.
A copolymer containing an acid anhydride unit having a six-membered ring structure is obtained by the method described in Japanese Patent Publication Nos. 02-26641, 2006-265543, 2006-274069, and 2006-274071. With reference to the composition ratio, the composition ratio can be determined, manufactured, and evaluated.

  The six-membered cyclic acid anhydride unit is excellent in thermal stability and heat resistance, and because the retardation design of the molded product obtained therefrom is easy, the six-membered cyclic acid anhydride unit represented by the following chemical formula [1] It is preferably a physical unit.

(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 5% by mass to 45% by mass, and six members. It is necessary that the ring compound unit be 5 mass% or more and 35 mass% or less.
Preferably, the acrylic compound unit in the acrylic resin (a) is 25% by mass to 75% by mass, the aromatic vinyl compound unit is 7% by mass to 45% by mass, and the six-membered cyclic acid anhydride unit is 5%. The acrylic compound unit in the acrylic resin (a) is preferably 30% by mass to 70% by mass and the aromatic vinyl compound unit is 7% by mass to 40% by mass. Hereinafter, the 6-membered cyclic acid anhydride unit is 7% by mass or more and 30% by mass or less. More preferably, the acrylic compound unit in the acrylic resin (a) is 35% by mass to 70% by mass, the aromatic vinyl compound unit is 7% by mass to 35% by mass, and the six-membered cyclic acid anhydride unit is 10% by mass to 30% by mass, particularly preferably 45% by mass to 70% by mass of the acrylic compound unit in the acrylic resin (a), and 10% by mass to 30% by mass of the aromatic vinyl compound unit. The 6-membered cyclic acid anhydride unit is 15% by mass or more and 25% by mass or less.

For practical use, the Tg (glass transition temperature) of the acrylic resin (a) is preferably 120 ° C. or higher, more preferably 125 ° C. or higher, and most preferably 130 ° C. or higher.
As a method for producing the acrylic resin (a), generally used polymerization methods such as cast polymerization, bulk polymerization, suspension polymerization, solution polymerization and emulsion 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 performing solution polymerization, there is no particular limitation as long as the mixture of monomers can be dissolved and the reaction is not hindered. As a preferred solvent, a solution prepared by dissolving 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, an azo compound such as azobisisobutylnitrile; benzoyl peroxide, lauroyl peroxide, and t-butyl. An organic peroxide 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-di (t-butylperoxy) -3,3,5-trimethylcyclohexane, cyclohexane peroxide, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, , 1-azobis (1-cyclohexanecarbonitrile), 2- (carbamoylazo) isobutyronitrile, 1,1-di (tert-butylperoxy) cyclohexane, and the like. These initiators are preferably used in the range of 0.001 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.
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. If Mw / Mn is 1.6 or more, the balance between resin film processability and mechanical properties is improved. Moreover, if Mw / Mn is 4.0 or less, melt fluidity will improve and workability will become favorable.

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 100,000 to 500,000, more preferably 12 to 300,000, still more preferably 140 to 200,000. 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 stretch film formation can be performed without any major trouble, and the weight average molecular weight is 10 By using 10,000 or more acrylic resins (a), it is possible to give sufficient stability to the stretching stability and the film.

In the molded article for optical material of the present invention, it is necessary to use rubber copolymer particles (b) having a three-layer structure. By using a rubber having a three-layer structure, deformation of the rubber copolymer particles due to stretching is suppressed, and the designed particle diameter and refractive index are maintained. Therefore, an increase in haze value can be reduced when the film is stretched. On the other hand, for example, when core-shell two-layer structured particles are used, the structure is deformed by stretching, and the particle diameter and / or the refractive index are changed, which may raise the haze value.
The rubber copolymer particle (b) having a three-layer structure refers to a rubber particle having a multilayer structure in which a soft layer made of a rubber-like polymer and a hard layer made of a glass-like polymer are laminated in three layers. Although it is not particularly defined as long as it can be exhibited, it is preferably a three-layer structure in the order of hard layer-soft layer-hard layer from the inside. By having a hard layer in the innermost layer and the outermost layer, deformation of the rubber copolymer can be suppressed, and toughness can be imparted by having a soft component in the central layer.

  Preferably, the innermost layer (b-1) of the rubber copolymer particles (b) having a three-layer structure is 70 to 100 parts by mass of methyl methacrylate, and another copolymerizable monomer that can be copolymerized therewith. It is a copolymer obtained by copolymerizing -30 parts by mass and 0.01-5 parts by mass of a copolymerizable polyfunctional monomer, and the central layer (b-2) is 70-100 parts by mass of an acrylate ester. A rubber elastic copolymer obtained by copolymerizing 0-30 parts by mass of other copolymerizable monomers copolymerizable with this and 0.1-5 parts by mass of a copolymerizable polyfunctional monomer. And the outermost layer (b-3) is made of a copolymer consisting of 70 to 100 parts by mass of methyl methacrylate and 0 to 30 parts by mass of at least one other vinyl monomer copolymerizable therewith. .

  The other monomer copolymerized with methyl methacrylate in the innermost layer (b-1) of the rubber copolymer particle (b) having a three-layer structure is any monomer that does not impair this purpose. There may be. Further, the polyfunctional monomer is not particularly limited, but preferably ethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, 1,4-butane. One or more of diol di (meth) acrylate, allyl (meth) acrylate, triallyl isocyanurate, diallyl maleate, divinylbenzene and the like are used. Particularly preferred is allyl (meth) acrylate.

  The central layer (b-2) of the rubber copolymer particles (b) having a three-layer structure is preferably a copolymer exhibiting soft rubber elasticity in order to impart toughness to the resin composition. As acrylic acid ester used, methyl acrylate, ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, etc. are used alone or in combination of two or more, Particularly preferred are n-butyl acrylate and 2-hexyl acrylate. Further, as the other vinyl monomer copolymerized with the acrylate ester, the same monomers as those used for the acrylic resin (a) can be used, but preferably the (b-2) layer In order to adjust the refractive index of the resin composition to improve the transparency of the resin composition, styrene or a derivative thereof is used. The polyfunctional monomer is the same as the polyfunctional monomer used in the innermost layer (b-1), but has a crosslinking effect at 0.1% by mass or more, and 5% by mass. If it is below, the crosslinking is moderate, both of which are preferable because the rubber elasticity effect is increased and the toughness of the resin composition is improved.

Further, the outermost layer (b-3) of the rubber-containing copolymer particles (b) having a three-layer structure is a single monomer used for the acrylic resin (a). The same thing as a mer can be used.
The method for producing the rubber-containing copolymer particles (b) is not particularly limited, and can be obtained by a known polymerization method such as bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization. It is particularly preferable to obtain it by an emulsion polymerization method. In this case, in the presence of an emulsifier and an initiator, the monomer mixture of layer (b-1) is first added to complete the polymerization, and then the monomer mixture of layer (b-2) is added to perform polymerization. And then the monomer mixture of layer (b-3) is added to complete the polymerization, whereby the multilayer structure particles can be easily obtained as a latex. The rubber-containing copolymer particles (b) can be recovered from the latex as a powder by a known method such as salting out, spray drying, freeze drying and the like.

Moreover, as an average particle diameter of rubber-containing copolymer particle (b), it is preferable that it is 0.05-0.5 micrometer, and toughness of material can be maintained from being 0.05 or more, 0.5 micrometer or less Thus, the transparency of the molded product can be maintained.
Moreover, when the refractive indexes of the acrylic resin (a) and the rubber-containing copolymer particles (b) are close to each other, it is preferable because a molded body excellent in transparency can be obtained. The difference is preferably 0.05 or less, more preferably 0.02 or less, and still more preferably 0.01 or less. In order to satisfy such a refractive index condition, a method of adjusting the unit composition ratio of each monomer of the acrylic resin (a) and / or rubber used for the rubber-containing copolymer particles (b) Examples include a method of adjusting the composition ratio of the polymer or monomer.

  Further, the difference in refractive index here means that in the rubber-containing copolymer particles (b), a medium having a refractive index of 1.59 and 1.49 is mixed and mixed with (b) while changing the ratio. The point at which white turbidity disappeared was defined as its refractive index (23 ° C., 550 nm). And the difference with the refractive index of the press-molded acrylic resin (a) separately measured with the laser refractometer was calculated.

  The rubber-containing copolymer particles (b) in the resin composition of the present invention are 0.1 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the acrylic resin (a) from the viewpoint of trimming properties and transparency. It is necessary to include, preferably 0.1 to 30 parts by mass, more preferably 0.1 to 10 parts by mass. When the content of the rubber-containing copolymer particles (b) is 0.1 parts by mass or more, the trimming property of the optical film is excellent, and microcracks and cracks can be suppressed in the trimming process. Transparency can be maintained when stretched.

In addition, a trimming process means the process of cutting off both ends, in order to make the width | variety of a film uniform, when manufacturing an optical film. At this time, if the film is inferior in trimming properties, microcracks or cracking phenomena occur during the process, and the productivity of the optical film is significantly reduced.
In the molded article for optical material of the present invention, the haze value (turbidity), which is one of the indexes representing transparency, is preferably 1.0% or less, more preferably 0.8% or less, and still more preferably 0. .6% or less. Thereby, it has high transparency.

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 5.0 × 10 ⁻¹² / Pa or less, more preferably 3.0 × 10 ⁻¹² / Pa or less, and 1.0 × 10 ⁻¹² / Pa or less. More preferably. 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, when the composition ratio per unit of the acrylic resin (a) and the draw ratio are designed in a preferable range, the absolute value of the photoelastic coefficient can be controlled in 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 polystyrene, polyethylene, and polypropylene, thermoplastics such as polyamide, polyphenylene sulfide resin, polyether ether ketone resin, polyester, polysulfone, polyphenylene oxide, polyimide, polyetherimide, and polyacetal. Examples thereof include thermosetting resins such as resins, 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. 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.

Furthermore, an ultraviolet absorber can be added as long as the object of the present invention is not impaired.
Examples of ultraviolet absorbers that can be mixed include benzotriazole compounds, benzotriazine compounds, benzoate compounds, benzophenone compounds, oxybenzophenone compounds, phenol compounds, oxazole compounds, malonic ester compounds, cyanoacrylates. Compounds, lactone compounds, salicylic acid ester compounds, benzoxazinone compounds, hindered amine compounds, triazine compounds, and the like.
These may be used alone or in combination of two or more.

The method for producing the molded article for optical material in the present invention is not particularly limited, and melt-kneading the acrylic resin (a) and the rubber-containing copolymer particles (b) having a three-layer structure by a known method. Can be obtained. 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 a sheet, it is manufactured by extruding the original film or sheet using an extruder equipped with a T die, a circular die or the like. can do. When a molded product is obtained by extrusion molding, it is possible to use a material obtained by melting and kneading the acrylic resin (a) and the rubber-containing polymer particles (b) in advance, or molding by melt kneading at the time of extrusion molding. You can also. Moreover, it can manufacture by shape | molding by well-known methods, such as injection molding, blow molding, injection blow molding, inflation molding, foaming molding, and can also use secondary processing molding methods, such as pressure forming and vacuum forming.

The molded article for optical material in the present invention is obtained by stretching 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), etc. can be used. Uniaxial or biaxial stretching It is preferable to stretch by. For example, industrially, 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 molded body can be produced.
The draw ratio is preferably 0.1% or more and 200% or less in at least one direction. More preferably, they are 1% or more and 150% or less, More preferably, they are 10% or more and 130% or less. By designing in this range, a stretched molded article preferable in terms of photoelastic coefficient and mechanical strength can be obtained.

When used as a film, the thickness of the molded article for optical material in the present invention is preferably 300 μm or less, more preferably 1 μm or more and 200 μm or less, further preferably 5 μm or more and 150 μm or less, and most preferably 10 μm or more and 130 μm or less.
The draw ratio can be determined from the following relational expression by shrinking the obtained stretched molded product at a temperature 20 ° C. or more higher than the glass transition temperature.
Stretch ratio (%) = [(length before shrinkage / length after shrinkage) −1] × 100
Moreover, as preferable extending | stretching temperature, Tg (glass transition temperature) -5 degreeC-+40 degreeC is preferable, More preferably, it is the range of Tg + 0 degreeC-30 degreeC, More preferably, it is the range of Tg + 5 degreeC-20 degreeC.

The glass transition temperature can be determined by a DSC method or a viscoelastic method.
The molded article for an optical material of the present invention can be suitably used for a polarizing plate protective film or a retardation film imparted with toughness.
In-plane retardation (Re) can be controlled by designing the copolymerization ratio, stretch ratio, and thickness of the acrylic resin (a) within the preferred ranges.
In-plane retardation (Re) is defined by the following formula.
Re = (nx−ny) × d
(Where nx, ny: in-plane main refractive index, d: thickness)
A preferable absolute value of Re of the molded article for an optical material obtained in the present invention is 0 nm or more and 50 nm or less, and more preferably 40 nm or less. By designing Re in this range, it can be preferably used as a polarizing plate protective film.

  A preferable absolute value of Re of the molded article for an optical material obtained in the present invention is 100 nm to 180 nm, more preferably 120 nm to 160 nm. By designing Re within this range, it can be preferably used as a quarter-wave plate.

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) Planar retardation (Re) at 25 ° C. was measured by a rotating analyzer method using a birefringence measuring apparatus RETS-100 manufactured by Otsuka Electronics Co., Ltd.
(3) Measurement of glass transition temperature (Tg) In 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.

(4) Evaluation of trimming property The presence or absence of occurrence of microcracks, cracks and avoidance of the optical film in the trimming process is observed.
The state of microcracks, cracks and tears is evaluated using the following evaluation criteria.
○: Microcracks, cracks and tears are not observed ×: Microcracks, cracks and tears are observed (5) Film thickness measurement The center of each stretched film is measured using a micrometer (Mitutoyo) did.
(6) Refractive Index Measurement The average refractive index at 23 ° C. and 550 nm of the acrylic resin (a) film was measured using a laser refractometer Model 2010 manufactured by Metricon.
(7) Haze measurement The haze value of each stretched film was measured according to JIS-K7136.

<Resin manufacturing method>
(1) Acrylic resin (a)
(Raw material I) Preparation of acrylic resin (methyl methacrylate-styrene-methacrylic acid-six-membered cyclic acid anhydride) Methyl methacrylate 35% by mass, styrene 25% by mass, methacrylic acid 20% by mass, metaxylene 20% by mass, A mixture of 50 ppm of perhexa C (1,1-di (tert-butylperoxy) cyclohexane) and 1500 ppm of n-octyl mercaptan was prepared, and this was continuously added at a rate of 1.5 L / hr to a jacket having an inner volume of 3 L The polymerization was carried out at a temperature of 125 ° C. by feeding to a complete mixing 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 compositional analysis by neutralization titration, IR spectrum, and ¹³ C NMR of this acrylic resin were as follows: methyl methacrylate unit 45% by mass, styrene unit 30% by mass, 6-membered cyclic acid anhydride unit 18% by mass, methacrylic acid unit 7%. %Met. The resulting acrylic resin had a melt flow rate value (ASTM-D1238; 230 ° C., 3.8 kg load) of 1.1 g / 10 minutes and Tg = 135 ° C. The refractive index was 1.528.

(Raw material II) Preparation of acrylic resin (methyl methacrylate-α-methylstyrene-methacrylic acid-six-membered cyclic acid anhydride) Methyl methacrylate 48% by mass, α-methylstyrene 6% by mass, methacrylic acid 6% by mass, A liquid mixture comprising 40% by mass of t-butanol, 500 ppm of 1,1-di (tert-butylperoxy) -3,3,5-trimethylcyclohexane and 200 ppm of n-octyl mercaptan was prepared, and this was added to 1.5 L / hr. The mixture was continuously fed at a rate of 3 L 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 compositional analysis by neutralization titration, IR spectrum, and ¹³ CNMR of this polymer were as follows: methyl methacrylate unit 80% by mass, α-methylstyrene unit 11% by mass, 6-membered cyclic acid anhydride unit 6% by mass, methacrylic acid unit It was 3 mass%. 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. The refractive index was 1.504.

<Rubber copolymer production method>
(1) Three-layer rubber-containing polymer particles (b)
The reaction vessel was charged with 300 parts of ion-exchanged water, heated to 70 ° C. while being purged with nitrogen, and then charged with 0.3 part of sodium dihexylsulfosuccinate and 0.3 part of potassium persulfate. Subsequently, a monomer mixture consisting of 23 parts of methyl methacrylate, 2 parts of n-acrylic acid-n-butyl and 0.03 part of allyl methacrylate was charged and held for 1 hour to complete the reaction. Next, a monomer mixture consisting of 22 parts of n-butyl acrylate, 28 parts of styrene, and 1.0 part of allyl methacrylate was added over 2 hours, and then the reaction was completed by maintaining for 2 hours. Next, a monomer mixture consisting of 22 parts of methyl methacrylate, 3 parts of n-butyl acrylate, and 0.05 part of n-octyl mercaptan was added over 1 hour, and then held for 1 hour to complete the reaction. After salting out the obtained latex using sodium sulfate as a salting-out agent, the rubber-containing copolymer (b) was recovered as a powder by dehydration, washing with water, dehydration and drying. The particle size of the obtained rubber-containing copolymer (b) was 0.25 μm. The refractive index was 1.519.

(2) Two-layer rubber-containing copolymer particles (c)
In a reaction vessel equipped with a stirrer, 300 parts of ion-exchanged water was charged, and the temperature was raised to 70 ° C. while purging with nitrogen. Then, 0.3 part of sodium dihexylsulfosuccinate and 0.3 part of potassium persulfate were charged. Subsequently, a monomer mixture consisting of 24 parts of n-butyl acrylate, 28 parts of styrene, and 2.0 parts of allyl methacrylate was added over 2 hours, and then the reaction was completed by maintaining for 2 hours. Next, a monomer mixture consisting of 45 parts of methyl methacrylate, 3 parts of n-butyl acrylate, and 0.05 part of n-octyl mercaptan was added over 1 hour, and then held for 1 hour to complete the reaction. The obtained latex was salted out using sodium sulfate as a salting-out agent, and then dehydrated, washed with water, dehydrated and dried to recover a rubber-containing copolymer consisting of two layers as a powder. The particle size of the obtained two-layer rubber-containing copolymer was 0.25 μm. The refractive index was 1.518.

[Examples 1 to 4, Reference Example 5 and Comparative Examples 1 to 4]
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 original 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 and Reference Example 5 , each resin and a three-layer rubber-containing copolymer were dry-blended, and in Comparative Examples 2 and 4, each resin and a two-layer rubber-containing copolymer were dry-blended and extruded. . Moreover, in Comparative Examples 1 and 3, extrusion molding was performed without blending a rubber copolymer.

Next, longitudinal (MD direction) uniaxial stretching of the obtained raw 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 stretch ratio.
Table 1 shows the blending ratio, molding conditions, trimming evaluation, and film optical property results.

In Examples 1 to 4 and Reference Example 5 , by blending rubber-containing copolymer particles having a three-layer structure with an acrylic resin having a specific composition ratio, the trimming property is maintained while maintaining transparency even during stretching. An optical film having a small absolute value of the photoelastic coefficient was obtained. Further, by controlling the stretching process, in Examples 1 and 3 and Reference Example 5 , those having a small plane retardation and suitable for a polarizing plate protective film were obtained. Furthermore, 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 the rubber-containing copolymer was not mixed, the trimming property was insufficient. In Comparative Example 2, the haze value at the time of stretching was increased although the trimming property was good although the two-layer rubber-containing copolymer particles having a refractive index close to that of the acrylic resin were blended. The same phenomenon occurred in the acrylic resins in Comparative Examples 3 and 4.

  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 (7)

Acrylic resin (a) 100 comprising 25% by mass to 85% by mass of an acrylic compound unit, 10 % by mass to 45% by mass of an aromatic vinyl compound unit, and 5% by mass to 35% by mass of a 6-membered ring compound unit. relative to the weight parts, the rubber-containing polymer particles (b) is a hard layer from the inner - soft layer - 10 parts by mass or more 0.1 part by weight of tri-layer consisting of structure the rubber-containing polymer particles (b) of the rigid layer A molded article for an optical material, comprising a resin composition comprising the following and stretched in at least one direction. 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 following chemical formula.


(In formula, R < ₁ >, R < ₂ > represents a hydrogen atom or a C1-C5 alkyl group each independently.) For optical materials molded body according to any one of claims 1-2 in which the refractive index difference is equal to or than 0.02 acrylic resin (a) and rubber-containing polymer particles (b). The molded article for an optical material according to any one of claims 1 to 3 , wherein a draw ratio in at least one direction is 0.1% or more and 200% or less. Haze value is 1.0% or less, an optical material according to any one of claims 1 to 4, wherein the absolute value of the photoelastic coefficient is 5.0 × 10 ^-12 / Pa or less Molded body. The polarizing plate protective film which consists of a molded object for optical materials of any one of Claims 1-5 . The retardation film which consists of a molded object for optical materials of any one of Claims 1-5 .