JP5416438B2 - Light guide made of methacrylic resin composition - Google Patents

Description

  The present invention relates to a light guide composed of an acrylic resin composition, and more specifically, impact resistance, surface hardness, heat resistance while retaining the features such as good moldability and high transparency inherent in methacrylic resins. The present invention relates to a light guide having excellent rigidity.

  Conventionally, as a light source device used for a thin signboard, a display device, a back light source of a liquid crystal display device, etc., a backlight device that makes light incident on a light guide and emits light is known. A backlight system in which a light source such as a cold cathode tube or a hot cathode tube is arranged on the end face of the light guide so as to emit light in an arbitrary shape or pattern has become the mainstream. A light source device called a front light type has also been developed.

  This type of light source device is required to be more compact, lighter and thinner, with higher brightness. As a material for the light guide in such a light source device, it is desirable to have as little transmittance loss as possible in the light guide such as absorption, scattering, and reflection of light, and a transparent resin having high light transmittance is suitable. . Therefore, at present, acrylic resin is often used, and an acrylic resin molded into an arbitrary shape or an acrylic resin plate itself is used as a light guide.

  In recent years, studies on the use of LEDs in edge light type light sources have begun, and the demand for thinner light guides has become stronger. However, the current situation is that conventional acrylic resins are brittle and have not fully met the demand for thinning.

  Patent Document 1 discloses a method of blending methacrylic resin with multilayer structure acrylic rubber particles produced by an emulsion polymerization method as a method for improving the impact resistance of an acrylic resin. This method is now widely practiced industrially. This multilayer structure acrylic rubber particle is composed of two or more layers, and a hard layer mainly composed of methyl methacrylate and a soft layer mainly composed of an acrylate ester such as n-butyl acrylate are substantially In other words, it has a spherical core-shell structure that alternately overlaps. However, the effect of improving the impact resistance of the acrylic resin by this method cannot be said to be sufficient, and the rigidity and heat resistance are greatly reduced. In addition, the methacrylic resin produced by this method may cause a mass (gel colony) of the multi-layered acrylic rubber particles when the multi-layered acrylic rubber particles are blended with the methacrylic resin. As a result, the molded product may have a flaw (fish eye), and particularly when used for optical member applications, the commercial value may be significantly impaired.

  Patent Document 2 discloses a method of polymerizing a monomer having methyl methacrylate as a main component in the presence of a rubber-like substance composed of a butadiene-butyl acrylate copolymer. However, in this method, the appearance defect of the molded body caused by the poor dispersion of the rubber-like substance still remains.

  Patent Document 3 discloses a method of polymerizing a monomer mainly composed of methyl methacrylate in the presence of a partially hydrogenated conjugated diene polymer. However, since the partially hydrogenated conjugated diene polymer used in the method does not dissolve in methyl methacrylate, it must be dissolved in another solvent, and the manufacturing process becomes complicated. Furthermore, in this method, it may be difficult to form dispersed particles by phase inversion, particularly to control the dispersed particle size.

Japanese Examined Patent Publication No.59-36645 Japanese Examined Patent Publication No. 45-26111 Republished WO96 / 32440

  An object of the present invention is to provide a light guide comprising a methacrylic resin composition having excellent surface hardness, heat resistance, rigidity, and impact resistance while maintaining the features such as good moldability and high transparency inherent in methacrylic resins. Is to provide a body.

  The present inventors have made various studies in order to solve the above problems. As a result, by using a methacrylic resin in which a specific block copolymer rubber is dispersed, a light guide made of a methacrylic resin composition having excellent surface hardness, rigidity, transparency, and impact resistance can be obtained. The headline and the present invention were completed.

That is, the present invention
A polymer block (b) comprising a polymer block (a) comprising a (meth) acrylic acid alkyl ester unit and a conjugated diene compound unit on a matrix comprising a methacrylic resin (A) having 50% by mass or more of methyl methacrylate units And the block copolymer (B) is 1 to 80 parts by mass with respect to 100 parts by mass of the methacrylic resin (A), and the block copolymer (B ) Is a polymer block (a) 30 to 65% by mass comprising an acrylic acid alkyl ester unit and having a glass transition temperature of 23 ° C. or less, and a polymer block comprising a conjugated diene compound unit and having a glass transition temperature of 0 ° C. or less. (b) and a 35 to 70 wt%, a refractive index Ri Do methacrylic resin composition is from 1.48 to 1.50, and, 2 mm thickness About light guide is below.
In the methacrylic resin (A), the molecular weight distribution (weight average molecular weight / number average molecular weight) measured by GPC is in the range of 1.9 to 3.0, and the number average of the block polymer (B). The molecular weight is preferably in the range of 5,000 to 1,000,000, and the side chain vinyl bond content of the polymer block (b) is preferably in the range of 10 mol% to 60 mol%.

  Since the light guide of the present invention uses a methacrylic resin composition excellent in molding processability, it is easy to form with a high transfer rate of a fine light scattering pattern on the exit surface and the opposite exit surface, and is transparent. That is, light guide performance, surface hardness, heat resistance, and rigidity are good. Furthermore, since the light guide of the present invention is composed of a methacrylic resin composition having excellent impact resistance, it is excellent in process passability when assembling a surface light source element, and is also suitable for a thin light guide.

  Hereinafter, preferred embodiments of the present invention will be described, but the present invention is not limited to the following descriptions.

  The methacrylic resin composition constituting the light guide of the present invention is obtained by dispersing a block copolymer (B) described later in a matrix composed of a methacrylic resin (A).

[Methacrylic resin (A)]
The methacrylic resin (A) constituting the matrix is a resin having 50% by mass or more of methyl methacrylate units. The methyl methacrylate unit is preferably 80% by mass or more, and more preferably 90% by mass or more.
Examples of monomer units other than methyl methacrylate units include alkyl acrylates such as methyl acrylate, ethyl acrylate and butyl acrylate, alkyl methacrylates other than methyl methacrylate such as ethyl methacrylate and butyl methacrylate, Examples thereof include monomer units such as non-crosslinkable monomers having only one alkenyl group in one molecule such as acrylamide, methacrylamide, acrylonitrile, methacrylonitrile, styrene, α-methylstyrene and the like. The mass ratio of the methyl methacrylate unit and the other monomer units is preferably 80:20 to 99: 1, and more preferably 90:10 to 98: 2.

  The weight average molecular weight measured by GPC of the methacrylic resin (A) is preferably 70,000 to 200,000, more preferably 80,000 to 150,000, and still more preferably 90,000 to 120,000. . If the weight average molecular weight is less than 70,000, the impact resistance and toughness of the methacrylic resin composition are lowered, and it is not preferable because it becomes brittle. Moreover, when a weight average molecular weight exceeds 200,000, the fluidity | liquidity of a methacrylic resin composition falls and a moldability may fall, and it is unpreferable.

  The molecular weight distribution (weight average molecular weight / number average molecular weight) measured by GPC of the methacrylic resin (A) is preferably 1.9 to 3.0, more preferably 2.1 to 2.8, More preferably, it is 2.2 to 2.7. If the molecular weight distribution is less than 1.9, the moldability of the methacrylic resin composition may be lowered, which is not preferable. On the other hand, if the molecular weight distribution exceeds 3.0, the impact resistance of the methacrylic resin composition may be lowered, and it may become brittle.

[Block copolymer (B)]
The block copolymer (B) used in the present invention is a block copolymer having a polymer block (a) composed of (meth) acrylic acid alkyl ester units and a polymer block (b) composed of conjugated diene compound units. It is. The above “(meth) acryl” means a generic name of “methacryl” and “acryl”.

  The polymer block (a) constituting the block copolymer (B) comprises (meth) acrylic acid alkyl ester units. Examples of the alkyl methacrylate include methyl methacrylate, ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate and the like. Examples of the alkyl acrylate include methyl acrylate, ethyl acrylate, n-butyl acrylate, i-butyl acrylate, 2-ethylhexyl acrylate and the like. These can be used alone or in combination of two or more. Among these, a monomer that gives a polymer block (a) having a glass transition temperature (Tg) of 23 ° C. or less is preferred, and a monomer that gives a polymer block (a) having a Tg of 0 ° C. or less is more preferred, A monomer that gives a polymer block (a) having a Tg of −10 ° C. or lower is more preferable. As such a monomer, n-butyl acrylate or 2-ethylhexyl acrylate is more preferable, and n-butyl acrylate is particularly preferable.

  The polymer block (b) constituting the block copolymer (B) is composed of a conjugated diene compound unit. Examples of the conjugated diene compound include 1,3-butadiene, isoprene, pentadiene, 2,3-dimethylbutadiene and the like. These can be used alone or in combination of two or more. Among these, a monomer that gives a polymer block (b) having a glass transition temperature (Tg) of 0 ° C. or lower is preferable, and 1,3-butadiene and / or isoprene are preferred from the viewpoints of versatility, economy, and handleability. More preferred is 1,3-butadiene.

  Conjugated diene compounds include those that undergo 1,4-addition polymerization and those that undergo 1,2- or 3,4-addition polymerization. When the conjugated diene compound undergoes 1,4-addition polymerization, it has a carbon-carbon double bond in the molecular main chain. When the conjugated diene compound is subjected to 1,2- or 3,4-addition polymerization, the conjugated diene compound has a vinyl group (side chain vinyl bond) bonded to the molecular main chain. The carbon-carbon double bond and / or the vinyl group bonded to the molecular main chain in the molecular main chain is a starting point for the graft reaction or the crosslinking reaction. The amount of side chain vinyl bonds in the polymer block (b) is preferably 10 mol% to 60 mol%, more preferably 10 mol% to 50 mol%, and even more preferably 10 mol% to 35 mol%. The amount of side chain vinyl bonds can be increased by adding a polar compound such as ethers to the polymerization reaction system.

  When the amount of side chain vinyl bonds is less than 10 mol%, the impact resistance tends to decrease as a result of insufficient graft bonding with the matrix. On the other hand, when it exceeds 60 mol%, the transparency and rigidity of the methacrylic resin composition tend to be lowered because the diameter of the dispersed phase becomes too large due to aggregation during polymerization.

  The polymer block (b) may be obtained by partially hydrogenating a carbon-carbon double bond in the molecular main chain and / or a vinyl group bonded to the molecular main chain. From the viewpoint of maintaining the effects of the present invention, the hydrogenation rate of the polymer block (b) is preferably less than 70 mol%, and more preferably less than 50 mol%. The method of hydrogenation is not particularly limited, and can be achieved by, for example, the method disclosed in Japanese Patent Publication No. 5-20442.

  The polymer block constituting the block copolymer (B) is a polymer block (a) (hereinafter sometimes simply referred to as (a)) and a polymer block (b) (hereinafter simply referred to as (b). As long as it has ().), It is not limited by the bonding mode. Specifically, (a)-(b) type diblock copolymer, (a)-(b)-(a) type triblock copolymer, (b)-(a)-(b) Type triblock copolymer, (a)-(b)-(a)-(b) type tetrablock copolymer, and (a) and (b) multiblock copolymer in which tetrablock or more is bonded And a linear block copolymer.

  The mass ratio of the polymer block (a) and the polymer block (b) is not particularly limited, but when the total of the polymer block (a) and the polymer block (b) is 100% by mass, The combined block (a) is usually 30 to 65% by mass, preferably 40 to 60% by mass. A polymer block (b) is 70-35 mass% normally, Preferably it is 60-40 mass%.

  In the block copolymer (B) used in the present invention, the glass transition temperature of the polymer block (a) and / or the polymer block (b) is preferably 0 ° C. or lower, more preferably −10 ° C. or lower. Thus, the monomer to be subjected to polymerization and the composition ratio thereof are selected.

  The block copolymer (B) is not particularly limited by its refractive index, but since the light guide is required to have transparency, a methacrylic resin in which the refractive index of the block copolymer (B) constitutes the matrix. It is preferable to match the refractive index of (A). Specifically, the refractive index of the block copolymer (B) is preferably 1.48 to 1.50, more preferably 1.485 to 1.495.

  As this block copolymer (B), a plurality of arm polymer blocks composed of the above-mentioned linear block copolymer is a group (cup) derived from a polyfunctional monomer, a polyfunctional coupling agent or the like. A star block copolymer (B ′) linked by a ring agent residue) is preferably used.

The plurality of arm polymer blocks constituting the star block copolymer (B ′) may be the same type of block copolymer or different types of block copolymers.
In particular, the star-shaped block copolymer (B ′) suitable for the present invention has a chemical structural formula:
(Polymer block (b) -polymer block (a)-) _n X
(Wherein X represents a coupling agent residue, and n represents a number exceeding 2).

A star-shaped block copolymer (B ′) suitable for the present invention has a formula:
[Number average molecular weight of star block copolymer]> 2 × [Number average molecular weight of arm polymer block].
The ratio of [number average molecular weight of star block copolymer] / [number average molecular weight of arm polymer block] is sometimes referred to as the number of arms.
Dispersion of the star block copolymer (B ′) dispersed in the methacrylic resin by setting the number average molecular weight of the star block copolymer to more than twice the number average molecular weight of the arm polymer block The mechanical strength against shearing of the phase is increased, and the desired performance can be obtained. A star block copolymer (B ′) having a number average molecular weight larger than 100 times the number average molecular weight of the arm polymer block is difficult to synthesize, so that an industrially preferred star block copolymer (B The number average molecular weight of ') is greater than 2 times and less than 100 times the number average molecular weight of the arm polymer block, more preferably 2.5 to 50 times, and even more preferably 3 to 10 times.
The star-shaped block copolymer (B ′) may contain a linear block copolymer composed only of arm polymer blocks that are not linked by a coupling agent residue.

  The number average molecular weight (Mn) of the block copolymer (B) used in the present invention is from 5,000 to 5,000 from the viewpoint of improving the impact resistance of the resulting methacrylic resin composition and improving the handleability of the light guide. It is preferably 1,000,000, more preferably 10,000 to 800,000, and even more preferably 50,000 to 500,000.

  The production method of the block copolymer (B) used in the present invention is not particularly limited as long as a block copolymer satisfying the requirements of the present invention concerning the chemical structure is obtained, and a method according to a known method is adopted. can do. In general, as a method for obtaining a star-shaped block copolymer having a narrow molecular weight distribution, a method of living polymerizing monomers as constituent units is employed. Examples of such living polymerization methods include a method of polymerizing using an organic rare earth metal complex as a polymerization initiator, an alkali metal or alkaline earth metal mineral salt using an organic alkali metal compound as a polymerization initiator, and the like. And a method of anionic polymerization in the presence of an organic alkali metal compound as a polymerization initiator, an anion polymerization in the presence of an organoaluminum compound, an atom transfer radical polymerization (ATRP) method, and the like.

  Among the above production methods, the method of using an organic alkali metal compound as a polymerization initiator and anionic polymerization in the presence of an organoaluminum compound can produce a block copolymer having a narrower molecular weight distribution and less residual monomers. It can be carried out under relatively mild temperature conditions, and is preferable in that the environmental load in industrial production (mainly the power consumption of the refrigerator necessary for controlling the polymerization temperature) is small.

  As the polymerization initiator for the anionic polymerization, an organic alkali metal compound is usually used. Examples of the organic alkali metal compound include methyl lithium, ethyl lithium, n-propyl lithium, isopropyl lithium, n-butyl lithium, sec-butyl lithium, isobutyl lithium, tert-butyl lithium, n-pentyl lithium, n-hexyl lithium, tetra Alkyllithium and alkyldilithium such as methylenedilithium, pentamethylenedilithium and hexamethylenedilithium; aryllithium and aryldilithium such as phenyllithium, m-tolyllithium, p-tolyllithium, xylyllithium and lithium naphthalene; Benzyl lithium, diphenylmethyl lithium, trityl lithium, 1,1-diphenyl-3-methylpentyl lithium, α-methylstyryl lithium, diisopropenylbenzene Aralkyllithium and aralkyldilithium such as dilithium produced by the reaction of butyllithium; lithium amides such as lithium dimethylamide, lithium diethylamide and lithium diisopropylamide; methoxylithium, ethoxylithium, n-propoxylithium, isopropoxylithium, n-butoxy Lithium, sec-butoxylithium, tert-butoxylithium, pentyloxylithium, hexyloxylithium, heptyloxylithium, octyloxylithium, phenoxylithium, 4-methylphenoxylithium, benzyloxylithium, 4-methylbenzyloxylithium, etc. Organic lithium compounds such as alkoxides can be mentioned. These may be used alone or in combination of two or more.

Examples of the organoaluminum compound used in the above anionic polymerization include the following general formula:
AlR ¹ R ² R ³
Wherein R ¹ , R ² and R ³ are each independently an alkyl group which may have a substituent, a cycloalkyl group which may have a substituent, or an aryl group which may have a substituent. Represents an aralkyl group which may have a substituent, an alkoxyl group which may have a substituent, an aryloxy group which may have a substituent or an N, N-disubstituted amino group, or R ¹ Represents one of the groups described above, and R ² and R ³ together represent an aryleneoxy group which may have a substituent.

  Specific examples of the organoaluminum compound represented by the above general formula include isobutylbis (2,6-di-tert-butyl-4-methylphenoxy) aluminum, isobutylbis (2,6-di-tert-butylphenoxy) aluminum. Isobutyl [2,2′-methylenebis (4-methyl-6-tert-butylphenoxy)] aluminum is easy to handle and allows the anionic polymerization reaction to proceed without deactivation under relatively mild temperature conditions It is preferable in that it can be performed.

  In the reaction system of the anionic polymerization, if necessary, ethers such as dimethyl ether, dimethoxyethane, diethoxyethane, 12-crown-4; triethylamine, N, N, N ′, N′-tetramethylethylenediamine, Nitrogen-containing compounds such as N, N, N ′, N ″, N ″ -pentamethyldiethylenetriamine, 1,1,4,7,10,10-hexamethyltriethylenetetramine, pyridine, 2,2′-dipyridyl, It can coexist for stabilization of a polymerization reaction.

As a method for obtaining a star-shaped block copolymer (B ′) suitable for the present invention, there is a method in which a small amount of a polyfunctional monomer, a polyfunctional coupling agent or the like is added to an anionic polymerization reaction system for polymerization. Can be mentioned.
The polyfunctional monomer is a compound having two or more ethylenically unsaturated groups, and specifically includes allyl methacrylate, ethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, divinylbenzene, 1 , 6-hexanediol diacrylate and the like.

  The polyfunctional coupling agent is a compound having 3 or more reactive groups, specifically, trichloromethylsilane, tetrachlorosilane, butyltrichlorosilane, bis (trichlorosilyl) ethane, tetrachlorotin, butyltrichlorotin, Examples include tetrachlorogermanium.

[Methacrylic resin composition]
In the methacrylic resin composition constituting the light guide of the present invention, the rubbery block copolymer (B) is dispersed in a methacrylic resin (A) constituting the matrix in the form of particles. It is. Content of a block copolymer (B) is 1-80 mass parts with respect to 100 mass parts of methacrylic resin (A), Preferably it is 2-30 mass parts, More preferably, it is 3-20 mass parts. When the amount of the block copolymer (B) is small, the light guide made of the methacrylic resin composition becomes brittle and the handleability tends to decrease. Conversely, when the amount is large, not only the surface hardness, heat resistance and rigidity tend to decrease. The block copolymer (B) is not preferable because it is difficult to uniformly disperse in the methacrylic resin (A), and transparency and surface properties may be deteriorated (scratches are generated).

  The size of the dispersed particles of the block copolymer (B) is preferably 0.05 to 2 μm, more preferably 0.05 to 1 μm, still more preferably 0.08 to 0.5 μm. If the average diameter of the dispersed particles is smaller than 0.05 μm, the light guide becomes brittle and the handling property tends to be lowered, and if the average diameter of the dispersed particles is larger than 2 μm, the transparency and surface properties tend to be lowered.

  The acryl-based resin composition used in the present invention is not particularly limited by its production method. For example, the block copolymer (B) is added to the methacrylic resin (A) constituting the matrix, and the uniaxial or biaxial is formed. Although it can be obtained by melt kneading in a melt extruder or the like, in the present invention, those obtained by the production method (in situ method) described below are preferable. In-situ method is to generate a material that becomes continuous phase (matrix) or dispersed phase (rubber particles) in the presence of the material that becomes dispersed phase or continuous phase, and directly form a composition consisting of continuous phase and dispersed phase. It is a method to do.

A suitable method for producing the above methacrylic resin composition is that in the presence of 1 to 80 parts by mass of the block copolymer (B), 50 to 100% by mass of methyl methacrylate and other copolymerizable with methyl methacrylate A method comprising bulk polymerization or solution polymerization of 100 parts by mass of a monomer mixture (A _m ) composed of 0 to 50% by mass of a vinyl monomer until polymerization conversion of the monomer reaches 70% by mass or more. It is.

More specifically, 1 to 80 parts by mass of a block copolymer (B) having a polymer block (a) composed of (meth) acrylic acid alkyl ester units and a polymer block (b) composed of conjugated diene compound units. 50 to 100% by weight of methyl methacrylate, preferably 80 to 100% by weight, more preferably 90 to 100% by weight, 0 to 50% by weight of other vinyl monomers copolymerizable with methyl methacrylate, preferably Is dissolved in a liquid consisting of 100 parts by mass of a monomer mixture (A _m ) consisting of 0 to 20% by mass, more preferably 0 to 10% by mass, and 0 to 100 parts by mass of a solvent. It is a method including a step of bulk polymerization or solution polymerization until the conversion becomes 70% by mass or more.

In order to obtain a methacrylic resin composition in which the block copolymer (B) is dispersed in the methacrylic resin (A), shear is applied to the monomer mixture (A _m ) solution in which the block copolymer (B) is dissolved. Polymerization is preferably performed while stirring so as to be added. By the polymerization reaction while applying shear to the monomer mixture (A _m) solution of the block copolymer (B), the block copolymer (B), and obtained by polymerization of monomer mixture (A _m) Phase inversion with the methacrylic resin (A) occurred, and the monomer mixture (A _m ) solution phase in which the methacrylic resin (A) was dissolved dissolved the block copolymer (B) in the continuous phase (matrix). The monomer mixture (A _m ) solution phase becomes a dispersed phase (domain). The polymerization conversion rate of the monomer that causes this phase inversion is the volume ratio between the block copolymer (B) and the monomer mixture (A _m ), the molecular weight of the block copolymer (B), the block copolymer weight. In the case of adding a graft body with the combined body (B) and further a solvent, it can be adjusted depending on the amount of solvent and the type of solvent.

As the polymerization method, a bulk polymerization method or a solution polymerization method is preferable from the initial stage of polymerization until phase inversion occurs. When polymerization is performed by the bulk polymerization method or the solution polymerization method, a methacrylic resin is generated in the monomer mixture (A _m ) solution of the block copolymer (B) at the initial stage of polymerization. In the bulk polymerization method or solution polymerization method, a shearing force due to stirring is applied to the block copolymer (B) side more, and a monomer mixture of methacrylic resin (A _m ) formed by phase separation as the polymerization conversion increases. ) The solution phase and the monomer mixture (A _m ) solution phase of the block copolymer (B) are inverted, the solution phase of the methacrylic resin becomes a continuous phase, and the solution phase of the block copolymer (B) becomes It becomes a dispersed phase. Examples of the apparatus for performing the bulk polymerization method or the solution polymerization method include a tank reactor with a stirrer, a cylindrical reactor with a stirrer, and a cylindrical reactor having a static stirring ability. One or more of these apparatuses may be used, or a combination of two or more different reactors may be used. The polymerization may be either batch or continuous.

  The size of the dispersed phase depends on factors such as the number of revolutions of stirring in the case of a reactor equipped with a stirrer; in the case of a static stirring reactor represented by a tower reactor, the linear velocity of the reaction solution, the viscosity of the polymerization system, the phase It can be controlled by various factors such as the graft ratio to the block copolymer (B) before inversion. In addition, after the phase inversion has occurred, a bulk polymerization method or a solution polymerization method can be applied, but in addition to these, a suspension polymerization method can also be applied.

The method of dissolving the block copolymer (B) in the liquid composed of the monomer mixture (A _m ) and the solvent used as necessary is a method capable of uniformly dissolving the block copolymer (B). It is not specifically limited, For example, a block copolymer (B) can be melt | dissolved by heating a monomer mixture ( _Am ) and the solvent used as needed to about 30-60 degreeC, and stirring. .

As a solvent used for the solution polymerization, a monomer mixture (A _m ) containing 50% by mass or more of methyl methacrylate, a methacrylic resin (A) obtained by the monomer mixture, and a block copolymer (B) If it is a solvent which has solubility with respect to it, it will not restrict | limit in particular, For example, aromatic hydrocarbons, such as benzene, toluene, ethylbenzene, etc. are mentioned. Moreover, you may use 2 or more types of mixed solvents as needed. When using a solvent mixture, the monomer mixture (A _m), as long as the mixed solvent can dissolve the methacrylic resin (A) and the block copolymer (B), the monomer mixture (A _m), methacrylic The solvent which cannot melt | dissolve a system resin (A) or a star-shaped block copolymer (B) may be included. For example, alcohols such as methanol, ethanol, and butanol; ketones such as acetone and methyl ethyl ketone; hydrocarbons such as hexane; alicyclic hydrocarbons such as cyclohexane may be included.

  The amount of a preferable solvent that can be used in the present invention is from 0 to 90% by mass, based on 100% by mass of a mixture of methyl methacrylate, another vinyl monomer copolymerizable with the methyl methacrylate, and the solvent. It is a range.

The polymerization reaction of the monomer mixture containing 50% by mass or more of methyl methacrylate is accompanied by a graft reaction or a crosslinking reaction starting from a carbon-carbon unsaturated bond in the block copolymer (B). In particular, since the crosslinking reaction mainly proceeds when the polymerization conversion rate of the monomer becomes high, in the present invention, the polymerization conversion rate of the monomer is 70% by mass or more, preferably 80% by mass or more. Polymerization can be performed.
By setting the polymerization conversion rate of the monomer to 70% by mass or more, it is possible to improve the handleability of the light guide obtained by improving the impact resistance of the methacrylic resin composition.

  The polymerization initiator used in the present invention is not particularly limited as long as it generates a reactive radical. For example, azo compounds such as azobisisobutyronitrile and azobiscyclohexylcarbonitrile; benzoyl peroxide, t-butyl Peroxybenzoate, di-t-butyl peroxide, dicumyl peroxide, 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane, t-butyl peroxyisopropyl carbonate, 1,1- Examples thereof include organic peroxides such as bis (t-butylperoxy) cyclohexane, di-t-butyl peroxide, and t-butylperoxybenzoate. These may be used alone or in combination of two or more. The addition amount and addition method of the polymerization initiator are not particularly limited as long as they are appropriately set according to the purpose.

  When polymerizing a monomer mixture containing 50% by mass or more of methyl methacrylate, a chain transfer agent may be added to the reaction system as necessary. For example, n-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, 1,4-butanedithiol, 1,6-hexanedithiol, ethylene glycol bisthiopropionate, butanediol bisthioglycolate, butanediol bisthiol Alkyl mercaptans such as propionate, hexanediol bisthioglycolate, hexanediol bisthiopropionate, trimethylolpropane tris- (β-thiopropionate), pentaerythritol tetrakisthiopropionate and α-methylstyrene A dimer, terpinolene, etc. can be mentioned. These can be used alone or in combination of two or more.

  After completion of the polymerization, the unreacted monomer and solvent are usually removed. The removal method is not particularly limited, but heating devolatilization is preferable. Examples of the devolatilization method include an equilibrium flash method and an adiabatic flash method. In particular, in the adiabatic flash method, devolatilization is preferably performed at a temperature of 200 to 300 ° C, more preferably 220 to 270 ° C. If it is less than 200 ° C., it takes time for devolatilization, and if the devolatilization is insufficient, the molded product may have poor appearance such as silver. On the other hand, when the temperature exceeds 300 ° C., the methacrylic resin composition may be colored due to oxidation, burning or the like.

According to the above production method, the monomer mixture (A _m ) solution phase of the block copolymer (B), which has become a dispersed phase through phase inversion, is further added to the methacrylic resin inside the dispersed phase by the polymerization. (A) is phase-separated from the block copolymer (B) to form a sea-island structure of a sea phase composed of the block copolymer (B) and an island phase composed of the methacrylic resin (A). From the viewpoint of improving the impact resistance of the resulting methacrylic resin composition, the total area of the island phase composed of the methacrylic resin (A) in the dispersed phase is 30% or more of the dispersed phase area in transmission electron micrograph observation. Preferably. Moreover, it is preferable that the dispersed phase particles in which the total area of the island phases in the dispersed phase occupy 30% or more of the dispersed phase area is 30% by mass or more of the total dispersed phase particles.

  As long as the methacrylic resin composition is within the range defined by the mass ratio of the block copolymer (B) to the methacrylic resin (A), the product obtained by the above production method is separately produced separately. The methacrylic resin (A) may be diluted. The melt flow rate of the methacrylic resin composition is preferably 10 g / 10 min or more from the viewpoint of good moldability to a light guide having a thin, large area and fine light scattering pattern. More preferably, it is 10 minutes or more.

  For the light guide comprising the methacrylic resin composition of the present invention, an antioxidant, an ultraviolet absorber, a light stabilizer, a lubricant, a mold release agent, a polymer processing aid, an antistatic agent, a flame retardant, if necessary. , Dyes and pigments, light diffusing agents, matting agents, impact resistance modifiers, phosphors and the like can be added.

The light guide made of the methacrylic resin composition may contain 0.001 to 0.1 parts by mass of an ultraviolet absorber with respect to 100 parts by mass of the methacrylic resin composition.
In order to further improve the durability, the methacrylic resin composition obtained by the present invention may contain hindered amines such as compounds having a 2,2,6,6-tetraalkylpiperidine skeleton as a light stabilizer. Good. In that case, it is preferable to contain 0.001-0.1 mass part of light stabilizer with respect to 100 mass parts of methacrylic-type resin compositions.

  Furthermore, you may make the light guide which consists of a methacrylic-type resin composition contain 0.001-0.5 mass part of antioxidant with respect to 100 mass parts of methacrylic-type resin compositions. The antioxidant used in the present invention has an effect for preventing thermal deterioration of the resin by itself, and examples thereof include phosphorus-based, hindered phenol-based, thioether-based antioxidants, etc. Can be used singly or in combination of two or more. Among them, phosphorus antioxidants and hindered phenols are preferably used from the viewpoint of the effect of preventing deterioration of optical properties due to coloring.

  Furthermore, in order to improve the mold releasability in light guide molding by injection molding, the light guide of the present invention contains higher alcohol and / or glycerin monoester with respect to 100 parts by mass of the methacrylic resin composition. You may contain 0.5 mass part or less in total. Examples of the higher alcohol include cetyl alcohol and stearyl alcohol. Examples of the glycerin monoester include glycerides of higher fatty acids such as stearic acid monoglyceride and stearic acid diglyceride.

  Examples of organic dyes include terphenyl having a function of converting ultraviolet rays, which are considered harmful to resins, into visible light. Examples of the light diffusing agent and matting agent include glass fine particles, polysiloxane-based crosslinked fine particles, crosslinked polymer fine particles, talc, calcium carbonate, and barium sulfate. Examples of phosphors include fluorescent pigments, fluorescent dyes, fluorescent white dyes, fluorescent brighteners, fluorescent bleaches and the like.

[Light guide]
The method for producing a light guide comprising the methacrylic resin composition of the present invention includes an injection molding method, a press molding method, a melt molding method such as an extrusion method via a T-die or a roll unit, and a cast molding method by cast polymerization. However, from the viewpoint of economical efficiency, an injection molding method or an extrusion molding method using a T die is preferable.

  The light guide made of the methacrylic resin composition of the present invention is suitably used for a backlight of a liquid crystal display device having a diagonal length of 10 to 20 inches, preferably 14 to 20 inches.

  The thickness of the light guide is usually 2 mm or less on the incident end face side from a light source such as a cold cathode tube, and preferably 0.5 to 1.5 mm. For thin light guides having a thickness within this range, the impact resistance of the methacrylic resin composition, which is a feature of the present invention, is exhibited well, which is advantageous for process passability when assembling a surface light source element. . The cross-sectional shape of the light guide is generally a wedge-shaped cross section when the incident surface thickness is 1 mm or more in the case of single side incidence, and a flat plate cross section that is easy to mold if the thickness is less than 1 mm. It can be. You may give a fine light-scattering pattern to the output surface or anti-output surface of a light guide by shaping, such as a prism shape, or dot printing.

  EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited thereto. In addition, the measurement or evaluation of the physical property value in an Example and a comparative example was performed with the following method.

(1) Measurement of number average molecular weight (Mn), weight average molecular weight (Mw), molecular weight distribution (Mw / Mn) and block copolymer production rate by gel permeation chromatography (GPC) Apparatus: Gel Perm manufactured by Tosoh Corporation Eation chromatograph (HLC-8020)
Column: Tosoh TSKgel GMHXL, G4000HXL and G5000HXL connected in series Eluent: Tetrahydrofuran Eluent flow rate: 1.0 mL / min Column temperature: 40 ° C.
Detection method: differential refractive index (RI) meter Calibration curve: created using standard polystyrene

(2) Measurement of polymerization conversion rate of charged monomer by gas chromatography (GC) Apparatus: Gas chromatograph GC-14A manufactured by Shimadzu Corporation
Column: GL Sciences Inc. INERT CAP 1 (df = 0.4 μm, 0.25 mm ID × 60 m)
Analysis conditions: injection temperature 180 ° C., detector temperature 180 ° C., 60 ° C. (5 minutes hold) → temperature increase rate 10 ° C./min→200° C. (10 minutes hold)

(3) Amount of side chain vinyl bonds The block copolymer was dissolved in deuterated chloroform to obtain a test solution, and the test solution was analyzed using ¹ H-NMR (JEOL's magnetic resonance apparatus (JNM-LA400)). Chemical shift 4.7 to 5.2 ppm (hereinafter referred to as signal C ₀ ) 1,2-vinyl proton (= C H ₂ ) and chemical shift 5.2 to 5.8 ppm (hereinafter referred to as signal D ₀ ). )) Was determined by calculating the integral intensity of vinyl protons (= C H- ) and calculating the side chain vinyl bond amount V ₀ [mol%] by the following formula.
V ₀ = _{[(C 0/2) / {} C 0/2 + (D 0 -C 0/2) / 2} ] × 100

(4) Glass transition temperature (Tg)
The glass transition temperature (Tg) of n-butyl polyacrylate used as the polymer block (a) is the value described in “POLYMER HANDBOOK FOURTH Edition”, page VI / 199, Wiley Interscience (1998) (polyacrylic acid). n-butyl: -49 ° C) was used.
The glass transition temperature (Tg) of poly1,3-butadiene used as the polymer block (b) is 1,2-vinyl bond amount described in “ANIONIC POLYMERIZATION”, page 434, MARCEL DEKKER (1996). A value derived from the relationship between Tg and Tg was used. The glass transition temperature (Tg) of the styrene polymer block of the styrene-butadiene block copolymer used in the comparative example was 100 ° C.

(5) Refractive index (n _d )
The block copolymer (B) was uniformly dissolved in toluene so as to be 30% by mass. The density of the solution and toluene and the refractive index with an Abbe refractometer were measured at room temperature, and the refractive index of the block copolymer (B) was determined using the following formulas (Formula 1) to (Formula 3). Further, polymethyl methacrylate having a known refractive index (n _d = 1.492) is measured by the same method, a calibration coefficient for refractive index measurement by this method is obtained, and the refractive index of the block copolymer (B) is calibrated. did.
[(N _d ² −1) / (n _d ² +2)] × V = r = constant (Expression 1)
r ₃ = w ₁ r ₁ + w ₂ r ₂ (Formula 2)
V ₂ = (1 / ρ ₁ ) − (1 / w ₂ ) × [(1 / ρ ₁ ) − (1 / ρ ₃ )] (Expression 3)
[N _d : refractive index, V: specific volume, r: molecular refraction, w: mass fraction, ρ: density,
Subscript 1: Toluene, Subscript 2: Block copolymer (B), Subscript 3: Solution,
Actual measurement: V ₃ , n _d3 , V ₁ , n _d1 ]
Formula (1), Formula (2) Source: Polymer Experimental Studies Vol. 12, “Thermodynamic, Electrical, and Optical Properties” published in 1984 Kyoritsu Publishing Formula (3) Source: Polymer Experimental Studies, Vol. 11 “ Polymer solution "published in 1982 Kyoritsu Publishing

(6) Average particle diameter The molded product was cut out using a diamond knife to obtain an ultrathin slice, this slice was stained with osmium tetroxide (polybutadiene part was stained), and an observation image was obtained using a transmission electron microscope. I took a photo. Thirty rubber particles that were randomly shown as a whole were selected, and the individual particle diameters were measured and then expressed as an average value thereof.

(7) Measurement of impact resistance of molded article Charpy impact strength with a notch was measured according to ISO 179-1eA.

(8) Measurement of flexural modulus of molded body The flexural modulus was measured according to ISO178.

(9) Measurement of deflection temperature under load of molded article The deflection temperature under load was measured according to ISO75.

(10) Evaluation of surface hardness of molded body The pencil hardness of the scratch-resistant extruded plate obtained with a 0.75 kg load was measured according to JIS K5600-5-4.

(11) Long optical path spectrophotometric measurement of the molded body (transparency evaluation)
Using a UV-2550 type spectrophotometer manufactured by Shimadzu Corporation, a plate-shaped molded product of 190 mm × 50 mm × 5 mm molded by an injection molding machine was used to transmit light through a length of 190 mm in the longitudinal direction inside the plate-shaped molded product ( The transmittance (%) of 450, 550, and 650 nm) was measured.

Reference Example 1 Production of Star Block Copolymer (B′-1) (1) 801 ml of toluene and 0.007 ml of 1,2-dimethoxyethane were charged into a 1.5 liter autoclave container equipped with a stirrer. A nitrogen purge was performed for a minute. Thereto was added 1.9 ml of a cyclohexane solution of sec-butyllithium having a concentration of 1.3 mol / l, then 97 ml of 1,3-butadiene was added and reacted at 30 ° C. for 3 hours to obtain a 1,3-butadiene polymer. A reaction mixture containing was obtained.
As a result of sampling analysis of a part of the obtained reaction mixture, the 1,3-butadiene polymer in the reaction mixture has a number average molecular weight (Mn) of 48,700 and a molecular weight distribution (Mw / Mn) of 1.06. The side chain vinyl bond content was 30 mol%, and the glass transition temperature of the 1,3-butadiene polymer (polymer block (b)) was -77 ° C.

(2) The reaction mixture obtained in (1) above is cooled to −30 ° C., and toluene containing 0.45 mol / l isobutylbis (2,6-di-t-butyl-4-methylphenoxy) aluminum 18.1 ml of the solution and 8.1 ml of 1,2-dimethoxyethane were added and stirred for 10 minutes to obtain a homogeneous solution.

(3) Next, 71 ml of n-butyl acrylate was added while vigorously stirring the solution obtained in the above (2), and polymerized at −15 ° C. for 3 hours. A part of the obtained reaction mixture was sampled, and the molecular weight was analyzed by GPC (polystyrene conversion). As a result, the butadiene-n-butyl diblock copolymer (arm polymer block) in the reaction mixture had a number average molecular weight. The weight average molecular weight / number average molecular weight ratio (Mw / Mn) was 1.02. The glass transition temperature of the polymer block (a) obtained by polymerization of n-butyl acrylate was −49 ° C.

(4) The reaction mixture obtained in the above (3) was kept at −15 ° C., and with vigorous stirring, 2.1 ml of 1,6-hexanediol diacrylate was added and polymerized for 30 minutes. Then about 1 ml of methanol was added to stop the polymerization.

(5) The reaction mixture obtained in the above (4) was deposited in 8000 ml of methanol to obtain a block copolymer (B′-1). The yield of the obtained block copolymer (B′-1) was almost 100%.

The obtained block copolymer (B′-1) was a mixture of a star block copolymer and an arm polymer block. In the block copolymer (B′-1), the ratio of the star block copolymer calculated from the area ratio of GPC was 92% by mass.
The star block copolymer had a number average molecular weight (Mn) of 310,000 (number of arms = 3.88) and an Mw / Mn of 1.16. The block copolymer (B′-1) is a polymer block (b) consisting of 49% by mass of a repeating unit derived from 1,3-butadiene and a polymer block consisting of a repeating unit derived from n-butyl acrylate. (A) A diblock copolymer comprising 51% by mass was contained as an arm polymer block.
The refractive index of the block copolymer (B′-1) was 1.492. Table 1 shows the characteristics of the block copolymer (B′-1). In the table, BA means n-butyl acrylate, and Bd means 1,3-butadiene.

Reference Example 2 Production of Star Block Copolymer (B′-2) (1) 801 ml of toluene was put into a 1.5 liter autoclave vessel equipped with a stirrer and purged with nitrogen for 20 minutes. Then, 1.9 ml of a cyclohexane solution of sec-butyllithium having a concentration of 1.3 mol / l was added, and then 105 ml of 1,3-butadiene was added and reacted at 30 ° C. for 3 hours to obtain a 1,3-butadiene polymer. A reaction mixture containing was obtained.
As a result of sampling analysis of a part of the obtained reaction mixture, the 1,3-butadiene polymer in the reaction mixture has a number average molecular weight (Mn) of 46,700 and a molecular weight distribution (Mw / Mn) of 1.06. The side chain vinyl bond content was 10 mol%, and the glass transition temperature of the 1,3-butadiene polymer (polymer block (b)) was -95 ° C.

(2) The reaction mixture obtained in (1) above is cooled to −30 ° C., and toluene containing 0.45 mol / l isobutylbis (2,6-di-t-butyl-4-methylphenoxy) aluminum 18.1 ml of the solution and 8.1 ml of 1,2-dimethoxyethane were added and stirred for 10 minutes to obtain a homogeneous solution.

(3) Next, while vigorously stirring the solution obtained in the above (2), 65 ml of n-butyl acrylate was added and polymerized at −15 ° C. for 3 hours. A part of the obtained reaction mixture was sampled, and the molecular weight was analyzed by GPC (polystyrene conversion). As a result, the butadiene-n-butyl diblock copolymer (arm polymer block) in the reaction mixture had a number average molecular weight. The weight average molecular weight / number average molecular weight ratio (Mw / Mn) was found to be 1.02. The glass transition temperature of the polymer block (a) obtained by polymerization of n-butyl acrylate was −49 ° C.

(4) The reaction mixture obtained in the above (3) was kept at −15 ° C., and with vigorous stirring, 2.1 ml of 1,6-hexanediol diacrylate was added and polymerized for 30 minutes. Then about 1 ml of methanol was added to stop the polymerization.

(5) The reaction mixture obtained in the above (4) was deposited in 8000 ml of methanol to obtain a block copolymer (B′-2). The yield of the obtained block copolymer (B′-2) was almost 100%.

The obtained block copolymer (B′-2) was a mixture of a star-shaped block copolymer and an arm polymer block. In the block copolymer (B′-2), the ratio of the star block copolymer calculated from the area ratio of GPC was 93% by mass.
The star block copolymer had a number average molecular weight (Mn) of 308,000 (number of arms = 3.88) and an Mw / Mn of 1.16. The block copolymer (B′-2) is a polymer block (b) consisting of 53% by mass of a repeating unit derived from 1,3-butadiene and a polymer block consisting of a repeating unit derived from n-butyl acrylate. (A) A diblock copolymer comprising 47% by mass was contained as an arm polymer block.
The refractive index of the block copolymer (B′-2) was 1.492. Table 1 shows the characteristics of the block copolymer (B′-2).

Reference Example 3 Production of Diblock Copolymer (B-1) (1) 801 ml of toluene and 0.007 ml of 1,2-dimethoxyethane were charged into a 1.5 liter autoclave vessel equipped with a stirrer and nitrogen was added for 20 minutes. Purging was performed. Then, 1.9 ml of a cyclohexane solution of sec-butyllithium having a concentration of 1.3 mol / l was added, and then 95 ml of 1,3-butadiene was added and reacted at 30 ° C. for 3 hours to obtain a 1,3-butadiene polymer. A reaction mixture containing was obtained.
As a result of sampling analysis of a part of the obtained reaction mixture, the 1,3-butadiene polymer in the reaction mixture has a number average molecular weight (Mn) of 48,700 and a molecular weight distribution (Mw / Mn) of 1.06. The side chain vinyl bond content was 30 mol%, and the glass transition temperature of the 1,3-butadiene polymer (polymer block (b)) was -77 ° C.

(2) The reaction mixture obtained in (1) above is cooled to −30 ° C., and toluene containing 0.45 mol / l isobutylbis (2,6-di-t-butyl-4-methylphenoxy) aluminum 18.1 ml of the solution and 8.1 ml of 1,2-dimethoxyethane were added and stirred for 10 minutes to obtain a homogeneous solution.

(3) Next, while vigorously stirring the solution obtained in the above (2), 72 ml of n-butyl acrylate was added and polymerized at −15 ° C. for 3 hours. A part of the obtained reaction mixture was sampled, and the molecular weight was analyzed by GPC (polystyrene conversion). As a result, the butadiene-n-butyl diblock copolymer (arm polymer block) in the reaction mixture had a number average molecular weight. The weight average molecular weight / number average molecular weight ratio (Mw / Mn) was 1.02. The glass transition temperature of the polymer block (a) obtained by polymerization of n-butyl acrylate was −49 ° C.

(4) The block copolymer (B-1) was obtained by putting the reaction mixture obtained by said (3) in 8000 ml of methanol, and precipitating. The yield of the obtained block copolymer (B-1) was almost 100%.

Reference Example 4 Production of Star Block Copolymer (B′-3) Synthesis Example 1 except that the amount of 1,3-butadiene was changed to 40 ml and the amount of n-butyl acrylate was changed to 111 ml. By the same method, a block copolymer (B′-3) was obtained. The block copolymer (B′-3) is mainly a star block copolymer comprising 20% by mass of repeating units derived from 1,3-butadiene and 80% by mass of repeating units derived from n-butyl acrylate. The polymer block (b) composed of 1,3-butadiene has a vinyl bond content of 30 mol%, a glass transition temperature of −77 ° C., and a polymer block composed of n-butyl acrylate ( a) had a glass transition temperature of −49 ° C. The butadiene-n-butyl acrylate diblock copolymer (arm polymer block) has a number average molecular weight of 69,000 and a weight average molecular weight / number average molecular weight ratio (Mw / Mn) of 1.02. It was. The number average molecular weight (Mn) of the star block copolymer is 272,000 (number of arms = 3.94), and its Mw / Mn is 1.15, and the star block copolymer calculated from the area ratio of GPC is used. The proportion of the polymer was 90% by mass. The refractive index of the block copolymer (B′-3) is 1.473. Table 1 shows the characteristics of the block copolymer (B′-3).

Example 1
An autoclave with a stirrer and a sampling tube was charged with 60.7 parts by weight of purified methyl methacrylate, 1.9 parts by weight of methyl acrylate, and 35 parts by weight of toluene, and a star block copolymer (B′-1) Was added and stirred at 30 ° C. for 8 hours to uniformly dissolve the star block copolymer (B′-1) as a (meth) acrylic elastomer. Thereafter, 0.035 parts by mass of 1,1-di (t-butylperoxy) cyclohexane and 0.1 parts by mass of n-octyllmercaptan were added and dissolved uniformly, and oxygen in the reaction system was removed with nitrogen. Polymerization was carried out by continuously supplying the raw material monomer to a 3 L complete mixing reactor controlled at a polymerization temperature of 125 ° C. Polymerization was carried out with an average residence time in the reaction zone of 45 minutes. The polymerization solution was collected from the collection tube to obtain a reaction solution. The reaction solution had a polymerization conversion of 42% by mass as measured by gas chromatography.

  Subsequently, the reaction mixture was continuously withdrawn from the reactor, and 0.001% by mass of 1,1-di (t-butylperoxy) cyclohexane was further added in a piping part equipped with a static mixer manufactured by Noritake Engineering. Polymerization was carried out by continuously feeding to a 5 L complete mixing reactor controlled at 0 ° C. Polymerization was carried out with an average residence time in the reaction zone of 90 minutes. The polymerization solution was collected from the collection tube to obtain a reaction solution. The reaction solution had a polymerization conversion of 72% by mass as measured by gas chromatography.

  Subsequently, the reaction mixture was continuously withdrawn from the reactor, and 0.02% by mass of t-butyl peroxybenzoate was further added to a pipe part equipped with a static mixer manufactured by Noritake Engineering Co., so that the inner wall temperature of the tubular reactor was increased. It was supplied to a tubular reactor (plug flow reactor) equipped with a static mixer manufactured by Noritake Engineering Co., Ltd. at 135 ° C. The average residence time was 45 minutes. The internal pressure was 0.7 MPa. The polymerization rate was 81%.

  Subsequently, the reaction mixture was continuously withdrawn from the reactor and supplied to a tubular reactor (plug flow reactor) equipped with a static mixer manufactured by Noritake Engineering Co., Ltd. having an inner wall temperature of 140 ° C .. The average residence time was 50 minutes. The internal pressure was 0.7 MPa. The polymerization rate was 89%.

Next, the reaction mixture was continuously fed from this tubular reactor to the twin screw extruder at 230 ° C., and volatile components mainly composed of unreacted monomers were separated and removed at 260 ° C. A polymer block (a) consisting of butyl acrylate units and a polymer block (b) consisting of butadiene units are added to 96 parts by mass of a methacrylic resin (A) consisting of 3% by mass and 3% methyl acrylate units. A pellet-shaped methacrylic resin composition obtained by dispersing 4 parts by mass of the block copolymer (B) was obtained.
A plate-shaped molded product was injection-molded from the obtained pellet and evaluated by the method described above. The evaluation results are shown in Table 2. In observation with a transmission electron micrograph, the rubber particles in which the total island phase area dispersed in the rubber particles accounted for 30% or more of the rubber particle area accounted for 30% by mass or more of the total rubber particles.
Further, injection molding is performed by a high-speed injection molding machine having a clamping force of 450 tons, and a diagonal length of 15.4 inches, an incident end face thickness of 1.5 mm, and a fine prism-shaped light scattering pattern on the exit surface and the opposite exit surface. A wedge-shaped light guide was obtained.

<< Examples 2-3, Comparative Example 1 >>
In Example 1, the pellet-form methacrylic resin composition was obtained by the same method as Example 1 except changing a star-shaped block copolymer (B'-1). The resulting pellet-like methacrylic resin composition was obtained, and the residual volatile content was 0.1% by mass. A plate-shaped molded article and a light guide were injection molded from the obtained pellets and evaluated by the method described above. The evaluation results are shown in Table 2. In the obtained pellet, rubber particles in which the total island phase area dispersed in the rubber particles accounted for 30% or more of the rubber particle area accounted for 30% by mass or more of the total rubber particles.

<< Comparative Example 2 >> (Core-shell polymer particles)
A pellet of a composition comprising 30 parts by mass of core-shell type polymer particles containing 40% by mass of styrene-n-butyl acrylate random copolymer rubber and 70 parts by mass of the methacrylic resin (A) as in Example 1. It was injection molded and evaluated by the method described above. The evaluation results are shown in Table 2.

  From the result of Table 2, it consists of the polymer block (a) which consists of a (meth) acrylic-acid alkylester unit, and a conjugated diene compound unit in the matrix which consists of a methacrylic resin (A) which has 50 mass% or more of methyl methacrylate units. The light guides (Examples 1 to 3) made of the resin composition in which the block copolymer (B) having the polymer block (b) is dispersed are more transparent than the comparative examples 1 and 2. Shows excellent hardness, heat resistance, rigidity, and impact resistance

Claims (4)

A polymer block (b) comprising a polymer block (a) comprising a (meth) acrylic acid alkyl ester unit and a conjugated diene compound unit on a matrix comprising a methacrylic resin (A) having 50% by mass or more of methyl methacrylate units And the block copolymer (B) is 1 to 80 parts by mass with respect to 100 parts by mass of the methacrylic resin (A), and the block copolymer (B ) Is a polymer block (a) 30 to 65% by mass comprising an acrylic acid alkyl ester unit and having a glass transition temperature of 23 ° C. or less, and a polymer block comprising a conjugated diene compound unit and having a glass transition temperature of 0 ° C. or less. (b) and a 35 to 70 wt%, a refractive index Ri Do methacrylic resin composition is from 1.48 to 1.50, and, 2 mm thickness The light guide is below. In the methacrylic resin (A), the molecular weight distribution (weight average molecular weight / number average molecular weight) measured by GPC is in the range of 1.9 to 3.0, and the number average molecular weight of the block polymer (B) is 2. The light guide according to claim 1, wherein the light guide is in a range of 5,000 to 1,000,000, and a side chain vinyl bond content of the polymer block (b) is in a range of 10 mol% to 60 mol%. The block copolymer (B) is a star block copolymer (B ′) composed of a plurality of arm polymer blocks, and is a number average molecular weight in terms of polystyrene calculated by gel permeation chromatography (GPC). But the formula:
[Number average molecular weight of star block copolymer]> 2 × [Number average molecular weight of arm polymer block]
The light guide according to claim 1 or 2 , wherein: The star block copolymer (B ′) has the chemical structural formula:
(Polymer block (b) -polymer block (a)-) _n X
The light guide according to claim 3 , wherein X is a coupling residue, and n is a number exceeding 2.