WO2013146708A1 - Molded object for optical use - Google Patents

Description

Optical molded body

The present invention relates to an optical molded body.

A polymer material having both heat resistance, flexibility, and transparency is assumed to be used, for example, as an optical molded body. Optical molded bodies with controlled optical anisotropy are used for liquid crystal display elements, electroluminescence elements, and the like.

There are many types of optical molded bodies. For example, there is an optical film. As one of the optical films, there is a film called a retardation film that plays a role of compensating for a phase difference of a liquid crystal of a liquid crystal display or improving a viewing angle. As the retardation film, those having positive orientation birefringence such as polycarbonate and amorphous cyclic polyolefin have been generally used. On the other hand, it is known that a further improvement in viewing angle can be achieved by laminating a film having negative orientation birefringence with a film having positive orientation birefringence.

Although films with negative orientation birefringence are under development, styrenic polymers have negative orientation birefringence. However, since polystyrene is brittle, a material with excellent mechanical strength is required. For example, as in Patent Document 1, there is known a method of forming an optical molded article having impact resistance by block copolymerization of a styrene monomer and a conjugated diene monomer.

On the other hand, examples of the block copolymer of a heat-resistant styrene monomer and a conjugated diene monomer include α-methylstyrene and a conjugated diene monomer such as those disclosed in Patent Documents 2, 3, and 4, for example. And block copolymers of α-methylstyrene and styrene and a conjugated diene monomer such as those disclosed in Non-Patent Document 1 are known.

JP 2006-283010 A Japanese Patent Laid-Open No. 2003-73433 JP 2003-73434 A JP 2009-84458 A L. H. Tung et al., Ance “Advances in Elastomers and Rubber Elasticity”, Lal, J. etc .; Plenum: New York, 1986, p129-142

However, Patent Document 1 has no description regarding heat resistance, and is considered to be insufficient in heat resistance as an optical molded article. Patent Documents 2, 3, and 4 do not mention control of the phase difference expression. Further, since no other monomer is copolymerized in the α-methylstyrene block, it is considered that the thermal stability is low and the molding by melting cannot be tolerated. Furthermore, it is considered that the vinyl bond amount of the conjugated diene monomer increases to make an optical molded body, and the appearance is not good. Non-Patent Document 1 does not mention control of the phase difference expression. In addition, since styrene is charged together with α-methylstyrene, the composition of styrene is increased and the effect of improving heat resistance is decreased, or the amount of styrene charged is limited, so that the productivity is considered to be low.

An object of the present invention is to provide an optical molded article that has heat resistance, flexibility, and transparency and solves at least one of the above-mentioned conventional problems.
In one aspect, the present invention provides an optical molded article having good appearance, thermal stability, and retardation development property and low photoelastic birefringence. It is another object of the present invention to provide an optical molded body suitable for obtaining a stretched film exhibiting negative orientation birefringence.

According to the main aspect of the present invention, a polymer block A comprising an α-methylstyrene unit and a styrene unit and having a glass transition temperature of 115 to 145 ° C. measured by DSC (differential scanning calorimeter), and a conjugated diene unit A block structure ABA or (AB) mX (wherein X is a residue of a coupling agent and m is an integer of 2 or more) comprising a polymer block B having 40 to 85% by volume of (a), component (b) of block structure AB and component (c) of block structure A in a total of 15 to 60% by volume, respectively, and components (a), (b) and The total of the total of (c) has a number average molecular weight of 50,000 or more, the sum of α-methylstyrene units and styrene units is 35 to 85 mol%, conjugated diene units are 15 to 65 mol%, conjugated diene units 15 ~ An optical molded body obtained by molding a block copolymer composition having a 1,4-bond amount of 15 to 50 mol% and a vinyl bond amount of 15 mol% or less of 65 mol% is provided.

In the above, the conjugated diene unit is, for example, a 1,3-butadiene unit. The optical molded body is, for example, a film having a thickness of 10 to 300 μm, such as a melt-extruded film. In a particularly preferred embodiment, the optical molded body is a stretched film, particularly a retardation film.

According to another aspect of the present invention, a polymer block A comprising an α-methylstyrene unit and a styrene unit and having a glass transition temperature of 115 to 145 ° C. measured by DSC (differential scanning calorimeter), and a conjugated diene A block structure ABA or (AB) mX (wherein X is a residue of a coupling agent and m is an integer of 2 or more) comprising a polymer block B having units Component (a) has a volume of 40 to 85% by volume, component (b) of block structure AB and component (c) of block structure A has a total of 15 to 60% by volume, and components (a) and (b) And (c) as a whole, the number average molecular weight is 50,000 or more, the sum of α-methylstyrene units and styrene units is 35 to 85 mol%, conjugated diene units are 15 to 65 mol%, conjugated diene units 15 to 65 mole A block copolymer composition having a 1,4-bond content of 15 to 50 mol% and a vinyl bond content of 15 mol% or less is also provided.

The optical molded body of the present invention has good heat resistance, flexibility, transparency, appearance, thermal stability, and low photoelastic double-fold, and in particular, a retardation film, a polarizing film protective film, and a viewing angle improvement. It can be suitably used for a film, a polarizing film, an antireflection film and the like. Especially, since the retardation development property of negative birefringence is favorable, it can use especially suitably for the retardation film which shows negative orientation birefringence.

An optical molded article according to an embodiment of the present invention has a block structure ABA or (AB) mX (where X is a residue of a coupling agent and m is an integer of 2 or more). And a block copolymer composition containing the component (a) of the above and the component (b) of the block structure AB and / or the component (c) of the block A.

<Block copolymer composition>
The polymer block A comprises α-methylstyrene units and styrene units, and has a glass transition temperature of 115 to 145 ° C. measured by DSC. The polymer blocks A may have a mixture of glass transition temperatures and molecular weights different from each other, or may be the same. By copolymerizing α-methylstyrene with styrene, the glass transition temperature can be raised to 115 ° C. or higher, and heat resistance can be obtained. By setting the glass transition temperature to 145 ° C. or lower, the depolymerization seen in the α-methylstyrene homopolymer can be prevented, so that thermal stability can be obtained. The glass transition temperature can be controlled by adjusting the respective amounts charged in the polymerization of α-methylstyrene and styrene.
Here, the glass transition temperature was measured by DSC under the following measurement conditions.
Device name: Robot DSC6200 manufactured by Seiko Instruments Inc.
Measurement conditions: heating rate 10 ° C / min, under nitrogen flow

Polymer block B is a polymer block having a conjugated diene monomer unit. The polymer block B may be a mixture of monomer units having different types, ratios, and molecular weights, or may be the same.

Examples of the conjugated diene compound constituting the conjugated diene unit in the polymer block B include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, and the like. These compounds may be used alone or in combination of two or more. Among these, 1,3-butadiene can be preferably used.

Other monomer units may be present in the polymer block B. As other monomer units, styrene monomer units are preferable, and styrene is more preferable. The amount of the other monomer unit is preferably 50% by mass or less because film strength can be secured. These may be introduced into the polymer block B in a random or tapered manner.

The block copolymer composition of the present invention comprises a component of a block structure ABA or (AB) mX (where X is a residue of a coupling agent and m is an integer of 2 or more) ( 40% by volume to 85% by volume of a), and the component (b) of the block structure AB and the component (c) of the block structure A are included in a total amount of 15% by volume to 60% by volume. Flexibility can be ensured by setting the component (a) to 40% by volume or more and the components (b) and (c) to 60% by volume or less in total. Moreover, on the polymerization technique, the component (a) is 85% by volume or less, and the sum of the component (b) and the component (c) is 15% by volume or more.

The number average molecular weight (Mn) is 50000 or more for the whole of the components (a), (b) and (c). Flexibility can be secured by setting Mn to 50000 or more.

Mn of the present invention is Mn in terms of polystyrene measured by gel permeation chromatography (hereinafter referred to as GPC), and was measured under the following measurement conditions.
Equipment: Shimadzu GPC system (LC-20AD, CBM-20A, RID-10A, SPD-M20A, CTO-20A, SIL-20A _HT , DGU-20A ₃ connected)
Column: Showa Denko Shodex GPC KF-404HQ and KF-402.5HQ are connected in series Measurement temperature: 40 ° C
Detector: RI (differential refractive index)
Developing solvent: Chloroform Concentration: 1% by mass
Calibration curve: Standard polystyrene (Shodex Standard SM-105)
The attribution of each peak of components (a), (b) and (c) can be made by comparison with the measurement results of the samples collected in the process of synthesizing each component, and the volume ratio of each component Can be calculated from the respective peak area ratios.

The total of the components (a), (b) and (c) is 35 to 85 mol% in total of α-methylstyrene units and styrene units, 15 to 65 mol% in conjugated diene units, conjugated diene. Of the units 15 to 65 mol%, the 1,4-bond amount is 15 to 50 mol%, and the vinyl bond amount is 15 mol% or less. Flexibility can be ensured by setting the amount of 1,4-bond in 15 to 65 mol% of the conjugated diene unit to 15 mol% or more, and retardation development can be ensured by setting it to 50 mol% or less. By setting the vinyl bond amount of the conjugated diene unit to 15% or less, flexibility can be ensured, generation of gel can be suppressed, and good appearance can be secured.

<Preparation of block copolymer composition>
The polymerization of the block copolymer of the present invention is preferably by a production method having the steps (1), (2), (3-1), or (1), (2), (3-2):
・ Process (1)
Α-methylstyrene is mixed with a nonpolar solvent, and an organic lithium compound is used as an initiator, and polymerization is performed at a temperature of 0 to 60 ° C. while continuously adding styrene to form a living copolymer composed of block structure A. Process / Process (2)
A process in which a conjugated diene is added to a living copolymer composed of block structure A at a temperature of 60 ° C. or lower and polymerized at a temperature of 30 to 70 ° C. to form a living copolymer composed of block structure AB. Step (3-1)
The living copolymer consisting of block structure AB is mixed by mixing α-methylstyrene with the living copolymer consisting of block structure AB and polymerizing at a temperature of 0-60 ° C. while continuously adding styrene. Process and process for forming polymer (3-2)
A step of performing coupling by adding a coupling agent to a living copolymer having a block structure AB at a temperature of 30 ° C. or higher.

For the polymerization of the block copolymer, it is preferable to use a nonpolar solvent. Examples of the nonpolar solvent include aliphatic hydrocarbons such as cyclohexane, methylcyclohexane, n-hexane, and n-heptane, and aromatic hydrocarbons such as benzene, toluene, and xylene. These may be used alone or in combination of two or more.

In the polymerization of the block copolymer, a small amount of a polar compound may be dissolved in a solvent in order to improve the efficiency of the initiator. The polar compounds include ethers such as tetrahydrofuran, diethylene glycol dimethyl ether and diethylene glycol dibutyl ether, amines such as triethylamine and tetramethylethylenediamine, thioethers, phosphines, phosphoramides, alkyl benzene sulfonates, potassium and sodium alkoxides. The preferred polar compound is tetrahydrofuran. The addition amount of the polar compound is preferably 500 ppm or less with respect to the nonpolar solvent because the vinyl bond amount of the conjugated diene unit can be suppressed.

Examples of the organic lithium compound used in step (1) include lithium compounds such as n-butyllithium, sec-butyllithium and tert-butyllithium. These compounds may be used alone or in combination of two kinds. You may use above.
The amount of the organic lithium compound used can be appropriately determined depending on the molecular weight of the desired polymer to be obtained by anionic polymerization. In addition, the minimum amount of organolithium compound that develops color of α-methylstyryl anion is added, and factors that deactivate the anion such as moisture, air, polymerization inhibitor, etc. in nonpolar solvent and α-methylstyrene in advance are added. It is preferable to add an organolithium compound to be used for the initiation reaction after inactivation.

In step (1), the flow rate of styrene may be changed every time.

The polymerization temperature in step (1) is preferably 0 to 60 ° C. By setting the polymerization temperature to 0 ° C. or higher, the polymerization rate of α-methylstyrene and styrene can be secured. By setting the polymerization temperature to 60 ° C. or lower, it is possible to suppress the deactivation reaction at the terminal of the living copolymer to be generated, and to secure the content of the target component (a).

In step (2), it is preferable to add conjugated diene at a temperature of 60 ° C. or lower and polymerize at a temperature of 30 ° C. or higher. By setting the temperature at which the conjugated diene is added to 60 ° C. or less, it is possible to suppress the deactivation reaction at the end of the living copolymer to be produced. By setting the polymerization temperature to 30 ° C. or higher, the polymerization rate of the conjugated diene can be ensured.

The polymerization temperature in step (3-1) is preferably 0 to 60 ° C. By setting the polymerization temperature to 0 ° C. or higher, the polymerization rate of α-methylstyrene and styrene can be secured. By setting the polymerization temperature to 60 ° C. or lower, the terminal of the living copolymer to be generated can suppress the deactivation reaction.

By adding an active hydrogen compound such as alcohols, carboxylic acids and water to the living copolymer after step (3-1) to stop the polymerization reaction, the block copolymer having the block structure ABA is blocked. A polymer can be obtained.

In step (3-2), a coupling agent is added to obtain a block copolymer having a block structure (AB) mX. The block structure AB before coupling may be one type or a mixture of 2 types or more and m types or less.

As the coupling agent to be added, a bifunctional coupling agent may be used or a polyfunctional coupling agent may be used. A plurality of types of coupling agents may be used in combination. The coupling agent preferably used in the present invention includes chlorosilane compounds such as silicon tetrachloride and 1,2-bis (methyldichlorosilyl) ethane, alkoxysilane compounds such as tetramethoxysilane and tetraphenoxysilane, and the like. Examples include tin chloride, polyhalogenated hydrocarbons, carboxylic acid esters, polyvinyl compounds, epoxidized fats and oils such as epoxidized soybean oil and epoxidized linseed oil, and epoxidized soybean oil is particularly preferred.

The reaction temperature of the coupling agent is preferably 30 ° C. or higher because the reaction rate can be secured.

If necessary, the block copolymer composition includes a heat resistant stabilizer such as a hindered phenol compound, a lactone compound, a phosphorus compound, and a sulfur compound, and a light resistant stabilizer such as a hindered amine compound and a benzotriazole compound. Additives such as lubricants, plasticizers, colorants, antistatic agents and mineral oils may be included. The addition amount is preferably less than 1 part by mass with respect to 100 parts by mass of the copolymer resin.

<Molded body of block copolymer composition>
The block copolymer composition is molded into an optical molded body. As the shape of the optical molded body, a known molded body such as an injection molded body, a sheet or a film can be used, but it is preferably molded into a film having a thickness of 10 to 300 μm. A method for forming a film having such a thickness is not particularly limited, but a method of melt extrusion using a film extruder is preferred.

The film molded as the molded article of the present invention can be used for known optical film applications such as retardation films, antireflection films, and liquid crystal protective films. The film molded as the molded body of the present invention can be stretched and oriented by a known method. The stretched and oriented film generates negative orientation birefringence, and is most preferable for use as a retardation film.

Hereinafter, the present invention will be further described with reference to examples and comparative examples, but these are illustrative only and do not limit the contents of the present invention. In the polymerization reaction, solvents and monomers that were sufficiently deaerated and dried were used.

<Measurement method>
(1) Method for Determining the Composition of Monomer Units Determined by the proton nuclear magnetic resonance ( ¹ H-NMR) method.
Equipment: JEOL-ECX400 (resolution 400MHz)
Solvent: Deuterated chloroform Reference: TMS or chloroform Temperature: 20 ° C

The signal shift positions necessary for quantification are as follows. Since the shift position may move depending on the solvent, temperature measurement conditions, and polymer structure, appropriate assignment is made for the entire monomer unit contained in the block copolymer composition.

[Signals used for quantification]
(A) 4.8 to 5.0 ppm
Butadiene vinyl bond (= CH2). Contains 2H per unit of 1,2-vinyl group by vinyl bond.

(B) 5.0 to 5.6 ppm
1,2-vinyl group (—CH═) and butadiene 1,4-bond (double bond in the main chain) (—CH═) by butadiene vinyl bond. It contains 1H per 1,2-vinyl group unit by vinyl bond and 2H per 1,4-bond unit.

(C) 6.3 to 7.3 ppm
α-methylstyrene, benzene ring H in styrene. Contains α-methylstyrene and 5H per styrene unit. When chloroform is used as a standard, this range (7.2 ppm) includes one H1 in chloroform.

[Quantitative method]
When the integral values in the ranges (a), (b), and (c) are I _a , I _b , I _c , and the integral value of chloroform is I _ch , mol% M _x of the butadiene vinyl bond amount, butadiene 1 , 4-bond mol% M _y and α-methylstyrene and styrene total mol% M _z can be calculated by the following equations, respectively.

[Example 1]
(1) To a reaction vessel having a volume of 50 L, 17 kg of cyclohexane containing 150 ppm of tetrahydrofuran was added, and 5400 g of α-methylstyrene was added.
(2) Next, a cyclohexane solution containing 10% by mass of n-butyllithium (initiator) was gradually added, and 50 mL was further added and the temperature was raised to 40 ° C. from the time when the color development of α-methylstyryl anion was observed.
(3) While maintaining the internal temperature of the container at 40 ° C., 650 g of styrene was charged and added at a speed of 650 g / h.
(4) While maintaining the internal temperature at 40 ° C., 450 g of styrene was charged and added at a rate of 450 g / h.
(5) 760 g of butadiene was added all at once. After completion of the addition, the internal temperature was raised to 50 ° C. and stirred for 1 hour.
(6) A solution obtained by diluting 5.4 g of epoxidized soybean oil (manufactured by Adeka) with 60 mL of cyclohexane was added and stirred for 30 minutes.
(7) 10 g of methanol was added to deactivate the polymerization active terminal to obtain a polymerization solution.
(8) The polymerization liquid was supplied to a twin screw extruder with a vent and devolatilized to obtain a block copolymer composition.
A 100 μm-thick film was extruded from this block copolymer composition at a cylinder temperature of 240 ° C. and a die temperature of 240 ° C. using a film extruder equipped with a T-die, and wound on a roll. The resulting melt-extruded film was uniaxially stretched 2.5 times at a glass transition temperature of + 10 ° C. using a tenter transverse stretching machine to obtain a stretched film.
Table 1 shows the measurement results of the obtained block copolymer composition, melt-extruded film, and stretched film.

[Example 2]
5500 g of α-methylstyrene, 750 g of styrene was added at a feed rate of 750 g / h in Step (3) of Example 1, 520 g of styrene was added at a feed rate of 520 g / h in Step (4) of Example 1, and 520 g of butadiene was added. A block copolymer composition, a melt-extruded film, and a stretched film were obtained in the same manner as in Example 1 except that. These measurement results are shown in Table 1.

[Example 3]
4800 g of α-methylstyrene, 560 g of styrene was added at a feed rate of 560 g / h in Step (3) of Example 1, 390 g of styrene was added at a feed rate of 390 g / h in Step (4) of Example 1, and 1400 g of butadiene was added. A block copolymer composition, a melt-extruded film, and a stretched film were obtained in the same manner as in Example 1 except that. These measurement results are shown in Table 1.

[Example 4]
5800 g of α-methylstyrene, 430 g of styrene were added at a charging rate of 430 g / h in Step (3) of Example 1, 300 g of styrene was added at a charging rate of 300 g / h in Step (4) of Example 1, and 750 g of butadiene was added. A block copolymer composition, a melt-extruded film, and a stretched film were obtained in the same manner as in Example 1 except that. These measurement results are shown in Table 1.

[Example 5]
5,000 g of α-methylstyrene, 870 g of styrene was added at a feed rate of 870 g / h in step (3) of Example 1, 600 g of styrene was added at a feed rate of 600 g / h in step (4) of Example 1, and 760 g of butadiene was added. A block copolymer composition, a melt-extruded film, and a stretched film were obtained in the same manner as in Example 1 except that. These measurement results are shown in Table 1.

[Example 6]
In Example 1 (1), a cyclohexane solution (initiator) containing 10% by mass of n-butyllithium was gradually added, and 72 mL was further added from the time when the color development of α-methylstyryl anion was observed. A block copolymer composition, a melt-extruded film and a stretched film were obtained in the same manner as in Example 1 except that the bean oil was changed to 7.8 g. These measurement results are shown in Table 1.

[Example 7]
(1) To a reaction vessel having a volume of 50 L, 17 kg of cyclohexane containing 150 ppm of tetrahydrofuran and 5400 g of α-methylstyrene were added.
(2) Next, a cyclohexane solution (initiator) containing 10% by mass of n-butyllithium was gradually added until color formation of α-methylstyryl anion was confirmed, and then 25 mL was further added and the temperature was raised to 40 ° C.
(3) While maintaining the internal temperature of the container at 40 ° C., 650 g of styrene was charged and added at a speed of 650 g / h.
(4) 760 g of butadiene was added all at once. After completion of the addition, the internal temperature was raised to 50 ° C. and stirred for 1 hour. The internal temperature was lowered to 40 ° C.
(5) While maintaining the internal temperature at 40 ° C., 450 kg of styrene was charged and added at a rate of 450 g / h.
(7) The polymerization active terminal was deactivated with methanol to obtain a polymerization solution.
(8) The reaction solution was supplied to a vented twin screw extruder and devolatilized to obtain a copolymer resin.
A film having a thickness of 100 μm was extruded from this resin at a cylinder temperature of 240 ° C. and a die temperature of 240 ° C. using a film extruder equipped with a T die, and wound on a roll. The obtained film was uniaxially stretched 2.5 times at a glass transition temperature of + 10 ° C. using a tenter transverse stretching machine to obtain a stretched optical film.
Table 1 shows the measurement results of the obtained block copolymer composition, melt-extruded film, and stretched film.

[Comparative Example 1]
(1) 17 kg of cyclohexane containing 150 ppm of tetrahydrofuran and 6100 g of α-methylstyrene were added to a reaction vessel having a volume of 50 L.
(2) Then, a cyclohexane solution (initiator) containing 10% by mass of n-butyllithium was gradually added until the color development of α-methylstyryl anion was confirmed, and then 26 mL was further added and the temperature was raised to 40 ° C.
(3) While maintaining the internal temperature of the container at 40 ° C., 700 g of styrene was charged and added at a rate of 700 g / h.
(4) While maintaining the internal temperature at 40 ° C., 490 kg of styrene was charged and added at a rate of 490 g / h.
(5) The polymerization active terminal was deactivated with methanol to obtain a polymerization solution.
(6) The reaction solution was supplied to a vented twin screw extruder and devolatilized to obtain a copolymer resin.
A film having a thickness of 100 μm was extruded from this resin at a cylinder temperature of 240 ° C. and a die temperature of 240 ° C. using a film extruder equipped with a T die, and wound on a roll. The obtained film was uniaxially stretched 2.5 times at a glass transition temperature of + 10 ° C. using a tenter transverse stretching machine to obtain a stretched optical film.
Table 2 shows the measurement results of the obtained block copolymer composition, melt-extruded film, and stretched film.

[Comparative Example 2]
5900 g of α-methylstyrene, 690 g of styrene was added at a feed rate of 690 g / h in Step (3) of Example 1, 480 g of styrene was added at a feed rate of 480 g / h in Step (4) of Example 1, and 250 g of butadiene was added. A block copolymer composition, a melt-extruded film, and a stretched film were obtained in the same manner as in Example 1 except that. The measurement results are shown in Table 2.

[Comparative Example 3]
A block copolymer composition, a melt-extruded film and a stretched film were obtained in the same manner as in Example 1 except that 7 kg of tetrahydrofuran, 10 kg of cyclohexane and 5400 g of α-methylstyrene were added in the step (1) of Example 1. . The measurement results are shown in Table 2.

[Comparative Example 4]
A block copolymer composition, a melt-extruded film, and stretched in the same manner as in Example 1 except that 100 mL of a cyclohexane solution (initiator) containing 10% by mass of n-butyllithium and 10.8 g of epoxidized soybean oil were added. A film was obtained. The measurement results are shown in Table 2.

[Comparative Example 5]
A block copolymer composition, a melt-extruded film, and a stretched film were obtained in the same manner as in Example 1 except that epoxidized soybean oil was not added. The measurement results are shown in Table 2.

[Comparative Example 6]
(1) To a reaction vessel having a volume of 50 L, 7 kg of tetrahydrofuran, 10 kg of cyclohexane, 2300 g of α-methylstyrene, and 500 g of styrene were added while maintaining the internal temperature at −40 ° C.
(2) Next, a cyclohexane solution (initiator) containing 10% by mass of n-butyllithium was gradually added until the color development of α-methylstyryl anion was confirmed, and then 60 mL was further added and stirred for 3 hours.
(3) The temperature was raised to 40 ° C., and 740 g of butadiene was added all at once. After completion of the addition, the internal temperature was raised to 50 ° C. and stirred for 1 hour.
(4) 7.5 g of epoxidized soybean oil (manufactured by Adeka) diluted with 60 L of cyclohexane was added and stirred for 1 hour.
(5) The polymerization active terminal was deactivated with methanol to obtain a polymerization solution.
(6) The reaction solution was supplied to a twin screw extruder with a vent and devolatilized to obtain a block copolymer composition.
A film having a thickness of 100 μm was extruded from this resin at a cylinder temperature of 240 ° C. and a die temperature of 240 ° C. using a film extruder equipped with a T die, and wound on a roll. The obtained film was uniaxially stretched 2.5 times at a glass transition temperature of + 10 ° C. using a tenter transverse stretching machine to obtain a stretched film.
Table 2 shows the measurement results of the obtained block copolymer composition, melt-extruded film, and stretched film.

[Comparative Example 7]
2700 g of α-methylstyrene, 310 g of styrene were added at a feed rate of 310 g / h in Step (3) of Example 1, 210 g of styrene was added at a feed rate of 210 g / h in Step (4) of Example 1, and 1500 g of butadiene was added. A block copolymer composition, a melt-extruded film, and a stretched film were obtained in the same manner as in Example 1 except that. The measurement results are shown in Table 2.

Various evaluations were based on the following methods.
(1) Flexibility As the flexibility, the bending strength of the melt-extruded film was measured under the following conditions, and judged according to the following criteria. The folding number of 200 times or more was regarded as acceptable.
Measurement conditions Measuring instrument: MIT-D HOLDING ENDURANCE TESTER (Toyo Seiki Co., Ltd.)
Load (tension): 500 g weight Bending speed: 175 times / min Bending angle: 45 degrees each left and right Folding device tip radius: 0.38 mm
Specimen width: 15mm
Bending direction: Film extrusion direction Number of sample points: 5 points (2 points for bending times of 1000 times or more)
(2) Transparency Based on ASTM D1003, the haze (unit:%) of the film was measured using a haze meter (NDH-1001DP type manufactured by Nippon Denshoku Industries Co., Ltd.). 2% or less was accepted.
(3) Appearance The melt-extruded film was observed using an image processing apparatus (LUZEX SE manufactured by Nireco), and the quality was judged according to the following criteria. “Excellent” and “Good” were accepted.
“Excellent”: 0 film defects with a length of 50 μm or more / m ²
“Good”: 1 to 4 film defects with a length of 50 μm or more / m ²
“Not possible”: Film defects with a length of 50 μm or more are 5 pieces / m ² or more. Here, “film defects” appear to be uneven with the surroundings due to foreign matters, unmelted spots, etc. Refers to the part.
(4) Thermal stability Using a TG / DTA 220TGA manufactured by Seiko Denshi Kogyo Co., Ltd., a decrease in heating weight was measured under the following conditions. The temperature when the weight decreased by 5% was determined to be 320 ° C or higher.
Flow gas: N2 100 ml / min Temperature rising condition: 30 ° C. to 400 ° C. 10 ° C./min (5) Photoelastic birefringence Applying a tensile stress to the melt-extruded film with a photoelastic coefficient indicating the photoelastic birefringence In this state, the retardation (unit: nm) was measured with a phase difference measuring device. When the retardation with the load f applied is Re (f) and the test piece width is w, the photoelastic coefficient C is C = dRe (f) / df × w
Therefore, it calculated by calculating | requiring the inclination of the value of the retardation with respect to the load added to the test piece. The phase difference measuring device used was KOBRA-WR manufactured by Oji Scientific Co., Ltd., and stress was applied by a digital force gauge Z2S-DPU-50N manufactured by Imada. A photoelastic coefficient having an absolute value of 5 × 10 ⁻¹² 1 / Pa or less was accepted.
(6) Retardation expression The retardation (unit: nm) of the stretched film was measured using a phase difference measuring device (KOBRA-WR manufactured by Oji Scientific Co., Ltd.). An absolute value of retardation was determined to be 100 nm or more. Moreover, by observing with a phase-contrast microscope, it confirmed that the sign of orientation birefringence was negative about all the samples in an Example and a comparative example.

Since the optical molded body of the present invention has good heat resistance, flexibility, transparency, appearance, thermal stability and low photoelastic birefringence, in particular, a retardation film, a polarizing film protective film, a viewing angle improving film It can be suitably used for polarizing films, antireflection films and the like. Especially, since the retardation development property of negative birefringence is favorable, it can use especially suitably for the retardation film which shows negative orientation birefringence.

Claims (6)

Consists of a polymer block A composed of α-methylstyrene units and styrene units and having a glass transition temperature of 115 to 145 ° C. measured by DSC (differential scanning calorimeter), and a polymer block B having conjugated diene units. 40 to 85% by volume of component (a) of the block structure ABA or (AB) mX (wherein X is a residue of a coupling agent and m is an integer of 2 or more) The total of components (a), (b), and (c) having a total of 15 to 60% by volume of component (b) of block structure AB and component (c) of block structure A, The number average molecular weight is 50,000 or more, the total of α-methylstyrene units and styrene units is 35 to 85 mol%, conjugated diene units are 15 to 65 mol%, and conjugated diene units are 15 to 65 mol%, and 1,4 -Join An optical molded article obtained by molding a block copolymer composition having an amount of 15 to 50 mol% and a vinyl bond content of 15 mol% or less. 2. The molded article for optics according to claim 1, wherein a block copolymer composition in which the conjugated diene unit is a 1,3-butadiene unit is molded. 3. The optical molded body according to claim 1, wherein the optical molded body is a film having a thickness of 10 to 300 μm. The optical molded body according to claim 3, wherein the film is a melt-extruded film. The optical molded body according to claim 3 or 4, wherein the film is a stretched film. 6. The molded article for optics according to claim 5, wherein the stretched film is a retardation film.