JP2008121002A - Molded article for optical use - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a molded article for optical use having small optical birefringence after molding and excellent in transparency and impact resistance. <P>SOLUTION: The molded article for optical use is constituted of a styrenic resin composition containing at least one kind of block copolymer (1) having 40-99 mass% vinylaromatic hydrocarbon content and composed of a polymer block A mainly consisting of at least one vinylaromatic hydrocarbon and a polymer block B mainly consisting of at least one conjugated diene. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical molded body excellent in optical characteristics obtained from a sheet having low birefringence.

In recent years, with the development of optical technology, new optical equipment products such as displays, optical discs, laser printers, optical fibers, etc., have been developed, and transparent plastics with excellent optical properties are optical lenses, prisms, optical discs, etc. It is widely used in optical products.
Generally, a polymer has birefringence due to the orientation of the molecular chain because the refractive index differs between the molecular main chain direction and the perpendicular direction. PMMA is known as a transparent material having a small birefringence (Non-Patent Document 1), but since the impact resistance is low, a material having a low birefringence and a good impact resistance is required.

As shown in Patent Document 1, a retardation plate using a block copolymer having a lamellar structure is known. Patent Document 1 discloses an optical film made of a styrene-isoprene block copolymer, but the present situation is that a molded product having low birefringence and good rigidity has not been obtained.
Moreover, the sheet | seat and film which consist of a resin composition comprised from a vinyl aromatic hydrocarbon-conjugated diene block copolymer and an acrylate ester copolymer are disclosed (patent document 2). However, there is no description that sheets and films obtained from these compositions are excellent in optical properties.
Chemical Review, No. 39, 1998 (published by Academic Publishing Center) JP-A-5-164920 JP2001-2870

  An object of the present invention is to provide an optical molded body that has a small change in birefringence after molding and is excellent in transparency, rigidity, and impact resistance.

Surprisingly, the inventors of the present invention have an optical molded body obtained by using a block copolymer having a specific structure, which has a small change in birefringence even after molding such as extrusion and stretching, and has transparency, rigidity, The inventors have found that the impact performance is excellent and have completed the present invention.
That is, the present invention
[1] The vinyl aromatic hydrocarbon content of the polymer block A mainly composed of at least one vinyl aromatic hydrocarbon and the polymer block B mainly composed of at least one conjugated diene is 40 to 99 mass. % Of a block copolymer (1), which is composed of a styrene-based resin composition containing at least one, and is obtained from a sheet having a thickness exceeding 300 μm.
[2] The block ratio of the vinyl aromatic hydrocarbon polymer block to the total vinyl aromatic hydrocarbon in the block copolymer (1) is 50 to 100%, and the vinyl aromatic carbonization of the block copolymer (1) The optical molded article according to [1], wherein the number average molecular weight Mn of the hydrogen polymer block is 10,000 to 150,000.
[3] The optically molded article according to [1] or [2], wherein the styrene-based resin composition contains 10 to 99% by mass of the block copolymer (1) and 90 to 1% by mass of a thermoplastic resin. .
[4] The optically molded article according to [1] or [2], wherein the styrene-based resin composition contains 30 to 80% by mass of a block copolymer (1) and 70 to 20% by mass of a thermoplastic resin. .
[5] The optical molded body according to [3] or [4], wherein the thermoplastic resin is a vinyl aromatic hydrocarbon- (meth) acrylic ester copolymer.
[6] The optical molded article according to [5], wherein the aromatic hydrocarbon content of the vinyl aromatic hydrocarbon- (meth) acrylic acid ester copolymer is 70 to 90% by mass.
[7] The optically molded article according to any one of [1] to [6], wherein the block copolymer (1) has an aromatic hydrocarbon content of 70 to 90% by mass.
[8] The optical molded body according to any one of [1] to [7], wherein the retardation is 1 nm to 2000 nm.
It is.

  According to the present invention, it is possible to provide a molded article having small birefringence after molding such as extrusion and stretching, that is, retardation is small and excellent in impact resistance, rigidity, and transparency.

Hereinafter, the present invention will be specifically described.
The block copolymer (1) used in the present invention comprises a block copolymer having a polymer block A mainly composed of at least one vinyl aromatic hydrocarbon and a polymer block B mainly composed of at least one conjugated diene. It is a polymer.
Here, the polymer block A mainly composed of vinyl aromatic hydrocarbon is a copolymer block of vinyl aromatic hydrocarbon and conjugated diene containing vinyl aromatic hydrocarbon content of 50% by mass or more and / or vinyl aromatic. A polymer block B mainly showing a conjugated diene is a conjugated diene and vinyl aromatic hydrocarbon copolymer block and / or conjugated containing a conjugated diene in an amount exceeding 50% by mass. This refers to a diene homopolymer block.

When a random copolymer portion of vinyl aromatic hydrocarbon and conjugated diene is present in polymer block A mainly composed of vinyl aromatic hydrocarbon or polymer block B mainly composed of conjugated diene, The vinyl aromatic hydrocarbon may be distributed uniformly in the polymer block or may be distributed in a tapered shape. Further, the copolymer portion may coexist with a plurality of portions where vinyl aromatic hydrocarbons are uniformly distributed and / or portions where they are distributed in a tapered shape.
When the block copolymer (1) of the present invention has a plurality of polymer blocks A (or B), they may be different in molecular weight, composition, type and the like.

  The block copolymer (1) used in the present invention can basically be produced by a conventionally known method. For example, Japanese Patent Publication No. 36-19286, Japanese Patent Publication No. 43-171979, Japanese Patent Publication No. 48-2423. The methods described in Japanese Patent Publication No. 49-36957, Japanese Patent Publication No. 57-49567, Japanese Patent Publication No. 58-11446, etc. can be mentioned. Must be set. All of the above known methods are methods in which a conjugated diene and a vinyl aromatic hydrocarbon are block copolymerized using an anionic initiator such as an organic lithium compound in a hydrocarbon solvent.

The polymer structure of the block copolymer used in the present invention is, for example,
A- (BA) _n , A- (BA) _n -B, B- (AB) _{n + 1}
[In the above formula, A is a polymer block mainly composed of vinyl aromatic hydrocarbons, and B is a polymer block mainly composed of conjugated dienes. The boundary between the A block and the B block does not necessarily have to be clearly distinguished. n is an integer of 1 or more, generally 1 to 5. ] A linear block copolymer represented by
[(AB) _k ] _m -X, [(AB) _k -A] _m -X, [(BA) _k ] _m -X,
[(B−A) _k −B] _m −X
[In the above formula, A and B are the same as described above, and k and m are integers of 1 or more, generally 1 to 5. X represents a residue of a coupling agent such as silicon tetrachloride or tin tetrachloride or a residue of an initiator such as a polyfunctional organolithium compound. Or a mixture of these block copolymers having any polymer structure can be used.

  Examples of the vinyl aromatic hydrocarbon used in the present invention include styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 1,3-dimethylstyrene, α-methylstyrene, vinylnaphthalene, vinylanthracene, 1,1-diphenylethylene and the like can be mentioned, and styrene is particularly commonly mentioned. These may be used alone or in combination of two or more. The conjugated diene is a diolefin having a pair of conjugated double bonds, such as 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene. 1,3-pentadiene, 1,3-hexadiene and the like. Representative conjugated dienes include 1,3-butadiene, isoprene and the like. These may be used alone or in combination of two or more.

When 1,3-butadiene and isoprene are used in combination, 1,3-butadiene is preferably 10% by mass or more, more preferably 25% by mass or more, and particularly preferably 40% by mass or more. When 1,3-butadiene is 10% by mass or more, thermal decomposition does not occur during molding and the molecular weight does not decrease, so that it can be preferably used as an optical molded body.
Examples of the hydrocarbon solvent include aliphatic hydrocarbons such as butane, pentane, hexane, isopentane, heptane, and octane, alicyclic hydrocarbons such as cyclopentane, methylcyclopentane, cyclohexane, methylcyclohexane, and ethylcyclohexane, or benzene, Aromatic hydrocarbons such as toluene, ethylbenzene and xylene can be used. These may be used alone or in combination of two or more.

Examples of the organic lithium compound include an organic monolithium compound, an organic dilithium compound, and an organic polylithium compound in which one or more lithium atoms are bonded in the molecule. Specific examples of these include ethyl lithium, n-propyl lithium, isopropyl lithium, n-butyl lithium, sec-butyl lithium, tert-butyl lithium, hexamethylene dilithium, butadienyl dilithium, isoprenyl dilithium, and the like. Can be mentioned. These may be used alone or in combination of two or more.
In the present invention, polar compounds or the like are used for the purpose of adjusting the polymerization rate, changing the microstructure of the polymerized conjugated diene moiety (ratio of cis, trans, vinyl), adjusting the reaction ratio of conjugated diene and vinyl aromatic hydrocarbon, and the like. Randomizing agents can be used. Examples of polar compounds and randomizing agents include ethers such as tetrahydrofuran, diethylene glycol dimethyl ether and diethylene glycol dibutyl ether, amines such as triethylamine and tetramethylethylenediamine, thioethers, phosphines, phosphoramides, alkylbenzene sulfonates, potassium and sodium. An alkoxide etc. are mentioned.

  The polymerization temperature for producing the block copolymer (1) in the method of the present invention is generally in the range of -10 ° C to 150 ° C, preferably 40 ° C to 120 ° C. The time required for polymerization varies depending on the conditions, but is usually within 48 hours, and particularly preferably in the range of 1 to 10 hours. The polymerization atmosphere is preferably replaced with an inert gas such as nitrogen gas. The polymerization pressure is not particularly limited as long as the polymerization pressure is in a range sufficient to maintain the monomer and solvent in the liquid layer within the above polymerization temperature range. Furthermore, care must be taken not to mix impurities, such as water, oxygen, carbon dioxide, etc., that inactivate the catalyst and living polymer into the polymerization system.

The range of vinyl aromatic hydrocarbon content of the block copolymer (1) used in the present invention is 40 to 99% by mass, preferably 65 to 95% by mass, more preferably 70 to 90% by mass. It is. When the vinyl aromatic hydrocarbon content of the block copolymer is 40% by mass or more, the resin composition molded article is excellent in rigidity and transparency. It is preferable that the content is in the range of 70 to 90% by mass because the retardation becomes smaller.
In the present invention, the preferred range of the block ratio of the vinyl aromatic hydrocarbon polymer block incorporated in the block copolymer (1) is 50 to 100%. A block ratio of 50% or more is preferable because the rigidity of the resin composition molded article is excellent. The block ratio of the vinyl aromatic hydrocarbon block is the weight and weight ratio of the vinyl aromatic hydrocarbon and the conjugated diene in the process of copolymerizing at least a part of the vinyl aromatic hydrocarbon and the conjugated diene during the production of the block copolymer. It can be controlled by changing the polymerization reactivity ratio and the like.

As a concrete method,
(A) A mixture of a vinyl aromatic hydrocarbon and a conjugated diene is continuously supplied to the polymerization system for polymerization, and / or (b) a vinyl aromatic hydrocarbon using a polar compound or a randomizing agent. And a method of copolymerizing a conjugated diene and the like.
Examples of polar compounds and randomizing agents include ethers such as tetrahydrofuran, diethylene glycol dimethyl ether and diethylene glycol dibutyl ether, amines such as triethylamine and tetramethylethylenediamine, thioethers, phosphines, phosphoramides, alkylbenzene sulfonates, potassium and sodium. An alkoxide etc. are mentioned. The block ratio of the vinyl aromatic hydrocarbon polymer block incorporated in the block copolymer in the present invention means that the block copolymer is oxidized with di-tertiary butyl hydroperoxide using osmium tetroxide as a catalyst. Decomposition method [I. M.M. KOLTHOFF, et al. , J .; Polym. Sci. 1,429 (1946)], and the vinyl aromatic hydrocarbon polymer block component (excluding vinyl aromatic hydrocarbon polymer components having an average degree of polymerization of about 30 or less) was determined. The value obtained from the following equation.

Vinyl aromatic of block copolymer (1)
Mass% of hydrocarbon polymer block
Block rate (%) = ――――――――――――――――― × 100
Total vinyl of block copolymer (1)
% By mass of aromatic hydrocarbon

  The number average molecular weight Mn of the vinyl aromatic hydrocarbon polymer block of the block copolymer (1) used in the present invention is preferably 10,000 to 150,000, more preferably 20,000 to 120,000. When the number average molecular weight Mn of the vinyl aromatic hydrocarbon polymer block is 10,000 or more, it is preferable because of excellent rigidity and impact resistance, and when it is 150,000 or less, it is preferable because of excellent molding processability and transparency.

The number average molecular weight of the block copolymer (1) is measured in the same manner as described above by oxidatively decomposing the block copolymer with di-tertiary butyl hydroperoxide using osmium tetroxide as a catalyst [I. M.M. KOLTHOFF, et al. , J .; Polym. Sci. 1,429 (1946)] can be obtained by gel permeation chromatography (GPC). The molecular weight is obtained by GPC measurement of monodisperse polystyrene for GPC, creating a calibration curve between the peak count and the molecular weight of the monodisperse polystyrene, and calculating according to conventional methods (for example, “Gel Chromatography <Basics> Issued by Kodansha”) To do.
The block copolymer (1) may be a mixture of two or more.
The styrenic resin composition used in the optical molded body of the present invention comprises a block copolymer (1) and a thermoplastic resin in order to enhance rigidity, heat resistance or processability while maintaining transparency and impact resistance. A composition is preferred.

Examples of the thermoplastic resin include polyolefin resins such as polyethylene, polypropylene, and polybutene, polystyrene, rubber-modified high impact polystyrene (HIPS), styrene-butyl acrylate copolymer, styrene-acrylonitrile copolymer, and styrene-maleic anhydride copolymer. Polymer, acrylonitrile-butadiene-styrene copolymer (ABS), methacrylate-butadiene-styrene copolymer (MBS), polyvinyl chloride resin, polymethacrylate resin, polycarbonate resin, polyethylene terephthalate, poly Polyester resins such as trimethylene terephthalate and polybutylene terephthalate, polyamide resins, polyphenylene sulfide resins, polyether ether ketone resins, polysulfone resins, Polyphenylene oxide resins, polyimide resins, polyetherimide resins, polyacetal resins, cyclic olefin resins, norbornene resins.
Preferred thermoplastic resins include vinyl aromatic hydrocarbon- (meth) acrylic acid ester copolymers and polystyrene resins.

  Particularly preferred thermoplastic resins include vinyl aromatic hydrocarbon- (meth) acrylic acid ester copolymers. From the viewpoint of reducing the transparency and retardation of the final composition, the content of the vinyl aromatic hydrocarbon is preferably 70 to 90 mass%, more preferably 75 to 88 mass%. Moreover, the other monomer of 0.1 to 2% may be included. Vinyl aromatic hydrocarbons used in the vinyl aromatic hydrocarbon- (meth) acrylic acid ester copolymer are styrene, α-methylstyrene, p-methylstyrene, pt-butylstyrene, and the like (meth) Acrylic acid esters include methacrylic acid methyl ester, ethyl ester, n-butyl ester, i-butyl ester, t-butyl ester, 2-ethylhexyl ester, acrylic acid methyl ester, ethyl ester, n-butyl ester, 2- It is an ester of (meth) acrylic acid and an alcohol having 1 to 8 carbon atoms such as ethylhexyl ester. In order to improve rigidity and heat resistance among vinyl aromatic hydrocarbon- (meth) acrylic acid ester copolymers, styrene-methyl methacrylate copolymer is preferable, and high transparency is maintained and rigidity is simultaneously improved. In order to improve processability, a styrene-butyl acrylate copolymer is preferred. The blending amount of the block copolymer (1) and the vinyl aromatic hydrocarbon- (meth) acrylic acid ester is preferably 10/90 to 99/1, more preferably 30/70 to 80/20, in terms of mass%. It is. A resin composition having a blending amount of 90% by mass or less is preferable because of excellent impact resistance, small retardation, which is a feature of the optical molded article of the present application, and excellent rigidity.

  Furthermore, arbitrary additives can be blended in accordance with various purposes within a range that does not significantly impair the effects of the present 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, pigments such as iron oxide, stearic acid, behenic acid, zinc stearate, calcium stearate, magnesium stearate, ethylene bisstearoamide and other lubricants, mold release agents, paraffinic process oil, naphthenic process oil, Softeners and plasticizers such as aromatic process oils, paraffins, organic polysiloxanes and mineral oils, hindered phenol antioxidants, antioxidants such as phosphorus heat stabilizers, hindered amine light stabilizers, benzotriazoles Examples include ultraviolet absorbers, flame retardants, antistatic agents, reinforcing agents such as organic fibers, glass fibers, carbon fibers, and metal whiskers, colorants, other additives, and mixtures thereof.

  The optical molded body of the present invention is obtained from a resin composition having excellent optical properties with low birefringence, and can be suitably used for optical products such as optical lenses, prisms, and optical disks. In particular, the optical molded body of the present invention can be used without impairing the characteristics of light when light is allowed to pass through, and thus is useful as a protective material for optical devices that are used by allowing light to pass through. For example, when the optical disk is used as a protective cover that protects against dust or the like, the information recorded on the optical disk can be read without impairing the light characteristics because of its low birefringence. In addition, the optical molded body 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.

The method for producing the optical molded body is not particularly limited, and a known method can be used. For example, it 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. The molded body in the present invention can be molded by a known method such as injection molding, sheet molding, blow molding, injection blow molding, extrusion molding, foam molding, etc., and secondary processing such as pressure molding or vacuum molding. A molding method can also be used.
As a preferable production method of the optical molded body of the present invention, techniques such as press molding, vacuum molding, blow molding, injection molding, and profile extrusion molding are used. For example, a method in which a sheet extruded from a T die is heated again to form a box-shaped molded product of various shapes by press molding, vacuum molding, or the like, a method of molding a hollow molded product by blow molding, By molding, a molded body can be obtained by a method of shaping a lens shape or various complicated shapes. The thickness of the optical sheet which is one form of the optical molded body of the present invention is preferably in the range of 1 mm or less so that the retardation is 2000 nm or less.

Further, an optical molded body obtained from a sheet having a thickness exceeding 300 μm is preferable because of excellent impact resistance and excellent rigidity. Furthermore, an optical molded body exceeding 300 μm obtained from the composition of the block copolymer (1) and the vinyl aromatic hydrocarbon- (meth) acrylic acid ester copolymer has excellent impact resistance, and the optical properties of the present application. This is preferable because the retardation, which is a characteristic of the molded body, is small and the rigidity is excellent.
As described above, the optical molded body obtained from the sheet is, for example, a plate-shaped molded product that is extruded using a T die or the like, or a box-shaped molded product of various shapes that is formed by vacuum molding or the like. Can be given. The optical molded body may partially have a thin portion having a thickness of 300 μm or less as long as it has a shaped shape with a thick portion having a thickness of 300 μm or more. Further, the sheet obtained by the T-die can be further longitudinally uniaxially stretched in the mechanical flow direction and transversely uniaxially stretched in the direction orthogonal to the mechanical flow direction, and a sequential biaxial stretching method of roll stretching and tenter stretching. A biaxially stretched sheet can be produced by stretching by a simultaneous biaxial stretching method by tenter stretching, a biaxial stretching method by tubular stretching, or the like. The strength of the sheet can be improved by stretching. The final draw ratio can be determined from the thermal shrinkage rate of the obtained sheet.

Next, the present invention will be described by way of examples.
First, the evaluation methods used in the present invention and examples will be described.
(A) Evaluation (1) Retardation measurement Using RETS-100 manufactured by Otsuka Electronics Co., Ltd., a wavelength of 400 to 800 nm was measured by a rotating analyzer method. The absolute value (| Δn |) of birefringence and retardation (Re) are in the following relationship.
Re = | Δn | × d
(| Δn |: absolute value of birefringence, Re: retardation, d: thickness of sample (nm))
The absolute value (| Δn |) of birefringence is a value shown below.
| Δn | = | nx−ny |
(Nx: refractive index in the stretching direction, ny: refractive index perpendicular to the stretching direction in the plane)

(2) Block ratio and number average molecular weight of vinyl aromatic hydrocarbon polymer block of block copolymer (1) Oxidative decomposition of block copolymer with di-tert-butyl hydroperoxide using osmium tetroxide as a catalyst Method [I. M.M. KOLTHOFF, et al. , J .; Polym. Sci. 1,429 (1946)] was quantified and determined from the following formula.

Vinyl aromatic of block copolymer (1)
Mass% of hydrocarbon polymer block
Block rate (%) = ――――――――――――――――― × 100
Total vinyl of block copolymer (1)
% By mass of aromatic hydrocarbon

Moreover, the number average molecular weight was obtained for the vinyl aromatic hydrocarbon polymer block component obtained by this method using GPC.

(3) Drop weight impact test Measured according to ASTM D1709 using a dirt impact tester manufactured by Toyo Seiki Co., Ltd.
(4) Tensile modulus Based on ASTM D638, it was measured at a test speed of 5 mm / min using a TG-5KN type tester manufactured by Minebea Co., Ltd.
(5) Total light transmittance and haze Based on JIS K7105, the Nippon Denshoku Co., Ltd. haze meter (1001DP) was used. The measurement was performed by liquid paraffin coating.
(6) DuPont impact tester A DuPont impact tester manufactured by Toyo Seiki Co., Ltd. was used.

(B) Raw material (1) Block copolymer (1-a)
Using an autoclave equipped with a stirrer, 0.080 parts by mass of n-butyllithium was added to a cyclohexane solution containing 25 parts by mass of styrene under a nitrogen gas atmosphere and polymerized at 80 ° C. for 20 minutes.
Next, ii) a cyclohexane solution containing 15 parts by mass of styrene and 24 parts by mass of 1,3-butadiene was continuously added for 60 minutes to polymerize at 80 ° C.
Next, iii) A cyclohexane solution containing 36 parts by mass of styrene was continuously added for 25 minutes and polymerized at 80 ° C., and then kept at 80 ° C. for 10 minutes. Thereafter, the polymerization was stopped by adding methanol to the polymerization vessel at a 0.9-fold mole relative to n-butyllithium, and 2- [1- (2-hydroxy-3,5-di-t-pentylphenyl) was used as a stabilizer. ) Ethyl] -4,6-di-t-pentylphenyl acrylate is added in an amount of 0.5 parts by mass to 100 parts by mass of the block copolymer, and then the solvent is removed to obtain the block copolymer (A-1). Obtained. The block copolymer A-1 is a polymer block A in which styrene / 1,3-butadiene = 100/0 mass ratio, and a polymer in which styrene / 1,3-butadiene = 38.5 / 61.5 mass ratio. This is an ABA block polymer composed of polymer block A in which block B and styrene / 1,3-butadiene = 100/0 mass ratio. The obtained block copolymer A-1 has a number average molecular weight of 85,000, a styrene content of 77.5% by mass, a block rate of 80%, and a melt flow rate of 7 g / 10 min (according to ASTM D1238). , 200 ° C., load 5 kg).

(2) Block copolymer (1-b to 1-g)
Using the same method as for the block copolymer (1-a), the amount of styrene and 1,3-butadiene added in i), ii) and iii) of (1-a), and n-butyllithium The block copolymer (1-b to 1-g) was prepared by appropriately controlling the amount of addition.
In addition, when the addition amount of n-butyl lithium is decreased, the molecular weight is increased. When the amount of styrene added in ii) is increased with respect to the amount of styrene added in i) and iii), the styrene block rate decreases.
Properties of the obtained block copolymers (1-a) to (1-g) are shown in Table 1.

(3) Block copolymer (1-h)
After the block copolymers (1-a) and (1-b) were dry blended at a 50/50 mass ratio, they were melt kneaded at a cylinder temperature of 200 ° C. using a single screw extruder having a cylinder diameter of 40 mmφ. A block copolymer (1-h) composed of a blend of seed block copolymers was obtained.
(4) Thermoplastic resin (2-a); polystyrene Polystyrene 685 (manufactured by PS Japan Ltd.) was used as polystyrene.
(5) Thermoplastic resin (2-b); vinyl aromatic hydrocarbon-acrylic acid ester copolymer Styrene-n-butyl acrylate copolymer (styrene content 84 mass%, melt flow rate is 6.5 g / 10 min (200 ° C., 5 kg load)) was used.
(6) Thermoplastic resin (2-c): Vinyl aromatic hydrocarbon-methacrylic acid ester copolymer A styrene-methyl methacrylate copolymer (styrene content 80% by mass) was used.
(7) Thermoplastic resin (2-d): Polymethylmethacrylate Delaglass 80N (manufactured by Asahi Kasei Chemicals Corporation) was used.

[Examples 1 to 14 and Comparative Examples 1 to 6]
Each raw material pellet was charged according to the formulation shown in Table 2 or Table 3 into a hopper of Union Plastics T-die mounting extruder (USV type / barrel diameter 40 mmφ, L / D = 28, width 400 mm T-die mounting). The resin temperature in the cylinder of the extruder and the temperature of the T-die were adjusted, and about 300 μm, 700 μm, and 1000 μm thick sheets were extruded and the retardation was measured. Furthermore, the obtained sheet was pressed at 200 ° C. and 150 kg / cm ² for 5 minutes using a press molding machine to obtain a sheet with relaxed orientation. The orientation relaxation sheet was further subjected to uniaxial stretching (stretching speed 0.3 m / min) twice and three times using a biaxial stretching device manufactured by Toyo Seiki Co., Ltd., and the retardation was measured.
Nx necessary for obtaining | Δn | = | nx−ny | is the extrusion direction (MD) of the sheet in the case of an extruded sheet, MD of the sheet before pressing in the case of a press-formed product, and uniaxial stretching in the case of a uniaxially stretched sheet. The refractive index in the direction is ny, and ny is the refractive index in the direction perpendicular to the nx direction.
Moreover, about the 300 micrometers extruded sheet | seat, the falling weight impact strength, the tensile elasticity modulus, the total light transmittance, and the haze were measured.
Tables 2 and 3 show the composition, extrusion conditions, stretching conditions, sheet thickness, retardation (550 nm), absolute value of birefringence, falling weight impact strength, tensile elastic modulus, total light transmittance, and haze.
The sheets of Comparative Examples 1 to 4 were significantly inferior in impact resistance compared to the examples. The sheet of Comparative Example 5 had high retardation, extremely low rigidity and transparency, and the sheet of Comparative Example 6 was cloudy and was not evaluated.

[Examples 15 to 17 and Comparative Examples 7 to 10]
The 1000 μm thick sheets used in Examples 1, 4, 9 and Comparative Examples 1 to 4 were formed into a cup shape having a thick part of about 1000 μm and a thin part of about 250 μm using a vacuum forming machine. The thin part was cut out and fixed in a flat shape, and then the retardation was measured. In addition, the cup was crushed to determine whether it was difficult to break.
The results are shown in Table 4.

[Examples 18 to 20 and Comparative Examples 11 to 14]
Using raw materials used in Examples 1, 4, 9 and Comparative Examples 1 to 4 by an injection molding machine (FE-120) manufactured by Nissei Plastic Industry Co., Ltd., a 1/8 inch thick strip and a 2 mm thick business card plate A size flat plate was injection molded, and dumbbell retardation (550 nm) and a DuPont impact test with a business card plate were performed. The results are shown in Table 5.

  The optical molded body of the present invention can be suitably used in the field of optical products such as optical lenses, prisms and optical disks. In particular, the optical molded body of the present invention is a material useful as a protective cover for an optical device because it can be used without impairing the characteristics of light when light is allowed to pass through.

Claims (8)

  A block having a vinyl aromatic hydrocarbon content of 40 to 99% by mass comprising a polymer block A mainly composed of at least one vinyl aromatic hydrocarbon and a polymer block B mainly composed of at least one conjugated diene. An optical molded body obtained from a sheet comprising a styrene resin composition containing at least one copolymer (1) and having a thickness exceeding 300 μm.   The block ratio of the vinyl aromatic hydrocarbon polymer block to the total vinyl aromatic hydrocarbon in the block copolymer (1) is 50 to 100%, and the vinyl aromatic hydrocarbon polymer of the block copolymer (1) 2. The optical molded body according to claim 1, wherein the block has a number average molecular weight Mn of 10,000 to 150,000.   The optically molded article according to claim 1 or 2, wherein the styrene-based resin composition contains 10 to 99 mass% of the block copolymer (1) and 90 to 1 mass% of the thermoplastic resin.   3. The optical molded body according to claim 1, wherein the styrenic resin composition contains 30 to 80 mass% of the block copolymer (1) and 70 to 20 mass% of the thermoplastic resin. 4.   The optical molded body according to claim 3 or 4, wherein the thermoplastic resin is a vinyl aromatic hydrocarbon- (meth) acrylic ester copolymer.   6. The optical molded body according to claim 5, wherein the aromatic hydrocarbon content of the vinyl aromatic hydrocarbon- (meth) acrylic acid ester copolymer is 70 to 90% by mass.   The optical molded body according to any one of claims 1 to 6, wherein the block copolymer (1) has an aromatic hydrocarbon content of 70 to 90 mass%.   Retardation is 1 nm or more and 2000 nm or less, The optical molded object in any one of Claims 1-7 characterized by the above-mentioned.