JP7294922B2 - Methacrylic resin, molding, optical parts or automobile parts - Google Patents

Description

The present invention relates to a methacrylic resin that has high heat resistance and highly controlled birefringence and is suitable for injection molding, a molded article obtained from the methacrylic resin, and an optical part or an automobile part obtained from the molded article. .

In the past, glass was used for optical parts such as lenses and prisms, but in recent years plastic has been used due to the high degree of freedom in design, such as weight reduction and miniaturization, as well as the use of aspherical lenses. It has become to. Methacrylic resins, styrene resins, polycarbonates, cyclic olefin resins, and the like are generally known as plastics used for optical parts.

In general, plastics tend to have birefringence due to orientation during molding, which adversely affects imaging performance when used as an optical component. Furthermore, when injection molding, which has high productivity, is used as a molding method, a greater degree of orientation is likely to occur, and the effect on imaging performance becomes significant. Methacrylic resins, typified by polymethyl methacrylate, have been favorably used as optical components because of their low intrinsic birefringence and relatively low orientation birefringence. However, due to the increasing demand for higher optical performance, there is a demand for materials capable of reducing the orientation birefringence.

For example, Patent Documents 1 and 2 disclose orientation birefringence and photoelastic birefringence by copolymers obtained by copolymerizing monomers including methyl methacrylate, 2,2,2-trifluoroethyl methacrylate, and benzyl methacrylate. can be lowered. This is done by selecting a plurality of monomers having different signs of intrinsic birefringence and photoelastic coefficient when they are homopolymers, combining them and copolymerizing them to adjust the composition, thereby obtaining orientation birefringence and It is based on the idea of reducing photoelastic birefringence. However, since this copolymer has a low glass transition temperature, there is a problem that its use in electronic equipment, automobiles, etc., where the interior temperature is high, is limited.

Therefore, as a resin for injection molding with improved orientation birefringence and heat resistance, the aromatic double bond of a copolymer obtained by polymerizing a monomer composition containing a (meth)acrylic acid ester monomer and an aromatic vinyl monomer (Patent Document 3) and a (meth)acrylic resin having a ring-structured glutarimide unit in the main chain (Patent Document 4) have been proposed. However, although the orientation birefringence of these resins is low, the photoelastic coefficient is not sufficiently reduced, so there is a drawback that birefringence occurs due to residual strain during molding and stress generated when optical parts are fixed to equipment. rice field.

Therefore, a non-birefringent resin material (Patent Document 5) composed of a composition containing a resin such as a glutarimide acrylic resin and a graft copolymer, or a methacrylate monomer and two or more N-substituted maleimide monomers are used. Resin materials that reduce both orientation birefringence and photoelasticity in injection molded pieces and have high heat resistance, such as methacrylic copolymers (Patent Document 6) having a ring structure in the main chain obtained from monomers containing Proposed. However, a composition containing a plurality of completely incompatible resins, such as that disclosed in Patent Document 5, has limited application as an optical component because the thicker the molded article, the higher the haze and the worse the transparency. In addition, the methacrylic resin of Patent Document 6 has low orientation birefringence and photoelastic coefficient even as an injection molded product, but it can There is room for improvement with regard to the birefringence that occurs when used in molded articles.

Japanese Patent Application Laid-Open No. 2006-308682 WO2015/098980 JP 2008-15199 A JP-A-2006-328330 WO2015/098775 WO2011/149088

The present invention provides a methacrylic resin having high heat resistance, highly controlled birefringence, and suitable for injection molding, a methacrylic resin molded article containing the methacrylic resin, and an optical component comprising the methacrylic resin molded article. Or for the purpose of providing automobile parts.

The inventors of the present invention have made intensive studies to solve the above-described problems of the prior art. , it was found that even if the composition is designed so that the orientation birefringence at a certain degree of orientation becomes zero, it does not become zero at other degrees of orientation. In addition, the present inventors have found that as a resin material for molding an injection molded article, particularly a molded article having a complicated shape such as a change in thickness or a thin molded article, it is more expensive than conventional film applications. We have found that it is important to control the orientation birefringence at the degree of orientation as well. It has also been found that the above problem can be solved by using a resin in which the sign of orientation birefringence differs between a low orientation degree and a high orientation degree.

That is, the present invention is as follows.
[1]
A methacrylic resin having a ring structure in its main chain,
A glass transition temperature of more than 120° C. and 160° C. or less,
The sign of the orientation birefringence when oriented so that the degree of orientation is 0.03 and the sign of the orientation birefringence when oriented so that the degree of orientation is 0.08 are different,
Contains structural units derived from N-substituted maleimide monomers
A methacrylic resin characterized by:
[2]
The absolute value of the orientation birefringence when oriented so that the degree of orientation is 0.03 is 0.1 × 10 ^-5 or more and 5.0 × 10 ^-5 or less,
The absolute value of the orientation birefringence when oriented so that the degree of orientation is 0.08 is 8.0 × 10 ^-5 or less.
The methacrylic resin according to [1].
[3]
The absolute value of the orientation birefringence when oriented so that the degree of orientation is 0.03 is 0.1 × 10 ^-5 or more and 3.0 × 10 ^-5 or less,
The absolute value of the orientation birefringence when oriented so that the degree of orientation is 0.08 is 5.0 × 10 ^-5 or less.
The methacrylic resin according to [2].
[4]
The methacrylic resin according to any one of [1] to [3], wherein a molded piece obtained by injection molding the methacrylic resin has a yellowness index (YI) of 20 or less measured at an optical path length of 80 mm.
[5]
The methacrylic resin according to any one of [1] to [4], wherein the methacrylic resin has a photoelastic coefficient of −3×10 ⁻¹² to +3×10 ⁻¹² Pa ⁻¹ .
[6 ]
Molding characterized by comprising the methacrylic resin according to any one of [ 1] to [ 5 ] or a methacrylic resin composition containing the methacrylic resin according to any one of [1] to [ 5 ] body.
[ 7 ]
The molded article according to [ 6 ], which has a thickness of 1.5 mm or less.
[ 8 ]
An optical component or an automobile component comprising the molded article according to [ 6] or [ 7 ].

According to the present invention, a methacrylic resin that has high heat resistance and highly controlled birefringence and is suitable for injection molding, a molded article containing the methacrylic resin, and an optical component or an automobile part comprising the molded article. can provide.

FIG. 4 is a diagram showing a flat plate mold having a fan gate used in phase difference measurement of an injection-molded piece of an example. (A) shows a plan view, and (B) shows a cross-sectional view taken along the line AA in (A).

Hereinafter, the mode for carrying out the present invention (hereinafter referred to as "this embodiment") will be described in detail, but the present invention is not limited to the following description, and within the scope of the gist Various modifications can be made.

(methacrylic resin)
The methacrylic resin of the present embodiment is a methacrylic resin containing a methacrylic acid ester monomer unit (A) and a structural unit (B) having a ring structure in its main chain. The structural unit (B) having a ring structure in the main chain includes a structural unit (B-1) derived from an N-substituted maleimide monomer, a glutarimide structural unit (B-2), and a lactone ring structural unit (B-3 ), etc. Optionally, other vinyl-based monomer units (C) copolymerizable with methacrylic acid ester monomers are also included.

Each monomer structural unit will be described below.

-Structural unit (A) derived from methacrylic acid ester monomer-
First, the structural unit (A) derived from the methacrylate monomer will be described.
The structural unit (A) derived from a methacrylic acid ester monomer is formed, for example, from a monomer selected from methacrylic acid esters shown below.
Examples of methacrylates include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, and methacrylic acid. Cyclopentyl, cyclohexyl methacrylate, cyclooctyl methacrylate, tricyclodecyl methacrylate, dicyclooctyl methacrylate, tricyclododecyl methacrylate, isobornyl methacrylate, phenyl methacrylate, benzyl methacrylate, 1-phenylethyl methacrylate, methacrylic acid 2-phenoxyethyl, 3-phenylpropyl methacrylate, 2,4,6-tribromophenyl methacrylate and the like.
These monomers may be used alone or in combination of two or more.
Among the above methacrylic acid esters, methyl methacrylate and benzyl methacrylate are preferable because the methacrylic resin to be obtained has excellent transparency and weather resistance.
Structural units (A) derived from methacrylic acid ester monomers may be contained alone or in combination of two or more.

The content of the structural unit (A) derived from the methacrylic acid ester monomer is, from the viewpoint of sufficiently imparting heat resistance to the methacrylic resin by the structural unit (B) having a ring structure in the main chain described later, The methacrylic resin is 100% by mass, preferably 50 to 97% by mass, more preferably 55 to 97% by mass, even more preferably 55 to 95% by mass, still more preferably 60 to 93% by mass, particularly preferably 60% by mass. ~90% by mass.
The content of the structural unit (A) derived from the methacrylic acid ester monomer can be determined by ¹ H-NMR measurement and ¹³ C-NMR measurement. ¹ H-NMR measurement and ¹³ C-NMR measurement can be performed, for example, using CDCl ₃ or DMSO-d ₆ as a measurement solvent at a measurement temperature of 40°C.

The structural unit (B) having a ring structure in its main chain is described below.

-Structural unit (B) having a ring structure in the main chain-
-- Structural unit (B-1) derived from N-substituted maleimide monomer --
Next, the structural unit (B-1) derived from the N-substituted maleimide monomer will be described.
The structural unit (B-1) derived from the N-substituted maleimide monomer is at least selected from monomers represented by the following formula (1) and/or monomers represented by the following formula (2) It may be one, and is preferably formed from both monomers represented by the following formula (1) and the following formula (2).

式（１）中、Ｒ^１は、炭素数７～１４のアリールアルキル基、炭素数６～１４のアリール基のいずれかを示し、Ｒ^２及びＲ^３は、それぞれ独立に、水素原子、炭素数１～１２のアルキル基、炭素数６～１４のアリール基のいずれかを示す。
また、Ｒ^２がアリール基の場合には、Ｒ^２は、置換基としてハロゲンを含んでいてもよい。
また、Ｒ^１は、ハロゲン原子、炭素数１～６のアルキル基、炭素数１～６のアルコキシ基、ニトロ基、ベンジル基等の置換基で置換されていてもよい。

In formula (1), R ¹ represents either an arylalkyl group having 7 to 14 carbon atoms or an aryl group having 6 to 14 carbon atoms, and R ² and R ³ each independently represent a hydrogen atom or a carbon number. It represents either an alkyl group of 1 to 12 or an aryl group of 6 to 14 carbon atoms.
In addition, when R ² is an aryl group, R ² may contain halogen as a substituent.
In addition, R ¹ may be substituted with a substituent such as a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a nitro group, or a benzyl group.

式（２）中、Ｒ^４は、水素原子、炭素数３～１２のシクロアルキル基、炭素数１～１２のアルキル基のいずれかを示し、Ｒ^５及びＲ^６は、それぞれ独立に、水素原子、炭素数１～１８のアルキル基、炭素数６～１４のアリール基のいずれかを示す。

In formula (2), R ⁴ represents a hydrogen atom, a cycloalkyl group having 3 to 12 carbon atoms, or an alkyl group having 1 to 12 carbon atoms, and R ⁵ and R ⁶ each independently represent a hydrogen atom. , an alkyl group having 1 to 18 carbon atoms, or an aryl group having 6 to 14 carbon atoms.

Specific examples are shown below.
Examples of the monomer represented by formula (1) include N-phenylmaleimide, N-benzylmaleimide, N-(2-chlorophenyl)maleimide, N-(4-chlorophenyl)maleimide, N-(4-bromo Phenyl)maleimide, N-(2-methylphenyl)maleimide, N-(2-ethylphenyl)maleimide, N-(2-methoxyphenyl)maleimide, N-(2-nitrophenyl)maleimide, N-(2,4 , 6-trimethylphenyl)maleimide, N-(4-benzylphenyl)maleimide, N-(2,4,6-tribromophenyl)maleimide, N-naphthylmaleimide, N-anthracenylmaleimide, 3-methyl-1 -phenyl-1H-pyrrole-2,5-dione, 3,4-dimethyl-1-phenyl-1H-pyrrole-2,5-dione, 1,3-diphenyl-1H-pyrrole-2,5-dione, 1 , 3,4-triphenyl-1H-pyrrole-2,5-dione and the like.
Among these monomers, N-phenylmaleimide and N-benzylmaleimide are preferred because the obtained methacrylic resin has excellent heat resistance and optical properties such as birefringence.
These monomers may be used alone or in combination of two or more.

Examples of the monomer represented by formula (2) include N-methylmaleimide, N-ethylmaleimide, Nn-propylmaleimide, N-isopropylmaleimide, Nn-butylmaleimide, N-isobutylmaleimide, Ns-butylmaleimide, Nt-butylmaleimide, Nn-pentylmaleimide, Nn-hexylmaleimide, Nn-heptylmaleimide, Nn-octylmaleimide, N-laurylmaleimide, N-stearyl maleimide, N-cyclopentylmaleimide, N-cyclohexylmaleimide, 1-cyclohexyl-3-methyl-1-phenyl-1H-pyrrole-2,5-dione, 1-cyclohexyl-3,4-dimethyl-1-phenyl-1H- pyrrole-2,5-dione, 1-cyclohexyl-3-phenyl-1H-pyrrole-2,5-dione, 1-cyclohexyl-3,4-diphenyl-1H-pyrrole-2,5-dione and the like.
Among these monomers, N-methylmaleimide, N-ethylmaleimide, N-isopropylmaleimide, and N-cyclohexylmaleimide are preferred from the viewpoint of excellent weather resistance of methacrylic resins. N-cyclohexylmaleimide is particularly preferred because of its excellent hygroscopicity.
These monomers can be used alone or in combination of two or more.

In the methacrylic resin of the present embodiment, the combined use of the monomer represented by the formula (1) and the monomer represented by the formula (2) provides highly controlled birefringence properties. It is particularly preferable because it can be expressed.
The molar ratio (B1/ B2) is preferably greater than 0 and 15 or less, more preferably greater than 0 and 10 or less.
When the molar ratio B1/B2 is in this range, the methacrylic resin molded article of the present embodiment maintains transparency, does not yellow, and does not impair environmental resistance, and has good heat resistance and good heat resistance. It expresses photoelastic properties.

The content of the structural unit (B-1) derived from the N-substituted maleimide monomer is not particularly limited as long as the resulting composition satisfies the range of the glass transition temperature of the present embodiment. 100% by mass, preferably in the range of 5 to 40% by mass, more preferably in the range of 5 to 35% by mass.
Within this range, the methacrylic resin molded article has a more sufficient effect of improving heat resistance, and more favorable effects of improving weather resistance, low water absorption, and optical properties. When the content of the structural unit derived from the N-substituted maleimide monomer is 40% by mass or less, the reactivity of the monomer component is lowered during the polymerization reaction, and the amount of unreacted residual monomer is large. It is effective in preventing deterioration of the physical properties of the methacrylic resin molded product due to deterioration.

-- Glutarimide structural unit (B-2) --
Methacrylic resins having a glutarimide-based structural unit in the main chain, for example, JP-A-2006-249202, JP-A-2007-009182, JP-A-2007-009191, JP-A-2011-186482, Re It is a methacrylic resin having a glutarimide-based structural unit, which is described in Japanese Patent Publication No. 2012/114718, etc., and can be formed by the method described in the publication.

The glutarimide-based structural unit that constitutes the methacrylic resin of this embodiment may be formed after the resin is polymerized.
Specifically, the glutarimide-based structural unit may be represented by the following general formula (3).

上記一般式（３）において、好ましくはＲ^７及びＲ^８は、それぞれ独立して、水素又はメチル基であり、Ｒ^９は、水素、メチル基、ブチル基、シクロヘキシル基のいずれかであり、より好ましくは、Ｒ^７は、メチル基であり、Ｒ^８は、水素であり、Ｒ^９は、メチル基である。
グルタルイミド系構造単位は、単一の種類のみを含んでいてもよいし、複数の種類を含んでいてもよい。
グルタルイミド系構造単位を有するメタクリル系樹脂において、グルタルイミド系構造単位の含有量については、本実施形態の組成物として好ましいガラス転移温度の範囲を満たすものであれば特に制限はないが、メタクリル系樹脂を１００質量％として、好ましくは５～７０質量％の範囲、より好ましくは５～６０質量％の範囲である。
グルタルイミド系構造単位の含有量が上記範囲にあると、成形加工性、耐熱性、及び光学特性の良好な樹脂が得られることから好ましい。
グルタルイミド系構造単位を有するメタクリル系樹脂は、必要に応じて、芳香族ビニル単量体単位をさらに含んでいてもよい。
芳香族ビニル単量体としては特に限定されないが、スチレン、α－メチルスチレンが挙げられ、スチレンが好ましい。
グルタルイミド系構造単位を有するメタクリル系樹脂における芳香族ビニル単位の含有量としては、特に限定されないが、グルタルイミド系構造単位を有するメタクリル系樹脂を１００質量％として、０～２０質量％が好ましい。
芳香族ビニル単位の含有量が上記範囲にあると、耐熱性と優れた光弾性特性との両立が可能となり好ましい。

In general formula (3) above, preferably R ⁷ and R ⁸ are each independently hydrogen or a methyl group, R ⁹ is hydrogen, a methyl group, a butyl group, or a cyclohexyl group, and more Preferably, ^R7 is a methyl group, ^R8 is hydrogen and ^R9 is a methyl group.
The glutarimide-based structural unit may contain only a single type, or may contain a plurality of types.
In the methacrylic resin having a glutarimide-based structural unit, the content of the glutarimide-based structural unit is not particularly limited as long as it satisfies the preferred glass transition temperature range for the composition of the present embodiment. Based on 100% by mass of the resin, it is preferably in the range of 5 to 70% by mass, more preferably in the range of 5 to 60% by mass.
When the content of the glutarimide-based structural unit is within the above range, it is preferable because a resin having excellent moldability, heat resistance, and optical properties can be obtained.
A methacrylic resin having a glutarimide structural unit may further contain an aromatic vinyl monomer unit, if necessary.
Examples of the aromatic vinyl monomer include, but are not limited to, styrene and α-methylstyrene, with styrene being preferred.
The content of the aromatic vinyl unit in the methacrylic resin having a glutarimide structural unit is not particularly limited, but is preferably 0 to 20% by mass based on 100% by mass of the methacrylic resin having a glutarimide structural unit.
When the content of the aromatic vinyl unit is within the above range, it is possible to achieve both heat resistance and excellent photoelastic properties, which is preferable.

上記一般式（４）において、Ｒ^１０、Ｒ^１１及びＲ^１２は、互いに独立して、水素原子、又は炭素数１～２０の有機残基である。
有機残基としては、例えば、メチル基、エチル基、プロピル基等の炭素数１～２０の飽和脂肪族炭化水素基（アルキル基等）；エテニル基、プロペニル基等の炭素数２～２０の不飽和脂肪族炭化水素基（アルケニル基等）；フェニル基、ナフチル基等の炭素数６～２０の芳香族炭化水素基（アリール基等）；これら飽和脂肪族炭化水素基、不飽和脂肪族炭化水素基、芳香族炭化水素基における水素原子の一つ以上が、ヒドロキシ基、カルボキシル基、エーテル基、エステル基からなる群から選ばれる少なくとも１種の基により置換された基；等が挙げられる。
ラクトン環構造は、例えば、ヒドロキシ基を有するアクリル酸系単量体と、メタクリル酸メチル等のメタクリル酸エステル単量体とを共重合して、分子鎖にヒドロキシ基とエステル基又はカルボキシル基とを導入した後、これらヒドロキシ基とエステル基又はカルボキシル基との間で、脱アルコール（エステル化）又は脱水縮合（以下、「環化縮合反応」ともいう）を生じさせることにより形成することができる。
重合に用いるヒドロキシ基を有するアクリル酸系単量体としては、例えば、２－（ヒドロキシメチル）アクリル酸、２－（ヒドロキシエチル）アクリル酸、２－（ヒドロキシメチル）アクリル酸アルキル（例えば、２－（ヒドロキシメチル）アクリル酸メチル、２－（ヒドロキシメチル）アクリル酸エチル、２－（ヒドロキシメチル）アクリル酸イソプロピル、２－（ヒドロキシメチル）アクリル酸ｎ－ブチル、２－（ヒドロキシメチル）アクリル酸ｔ－ブチル）、２－（ヒドロキシエチル）アクリル酸アルキル等が挙げられ、好ましくは、ヒドロキシアリル部位を有する単量体である２－（ヒドロキシメチル）アクリル酸や２－（ヒドロキシメチル）アクリル酸アルキルであり、特に好ましくは２－（ヒドロキシメチル）アクリル酸メチル、２－（ヒドロキシメチル）アクリル酸エチルである。 --Lactone ring structural unit (B-3)--
Methacrylic resins having a lactone ring structural unit in the main chain, for example, JP-A-2001-151814, JP-A-2004-168882, JP-A-2005-146084, JP-A-2006-96960, JP-A-2006-96960 It can be formed by methods described in JP-A-2006-171464, JP-A-2007-63541, JP-A-2007-297620, JP-A-2010-180305, and the like.
The lactone ring structural unit constituting the methacrylic resin of the present embodiment may be formed after resin polymerization.
The lactone ring structural unit in the present embodiment is preferably a 6-membered ring because the stability of the ring structure is excellent.
As the 6-membered lactone ring structural unit, for example, a structure represented by the following general formula (4) is particularly preferred.

In general formula (4) above, R ¹⁰ , R ¹¹ and R ¹² are each independently a hydrogen atom or an organic residue having 1 to 20 carbon atoms.
Examples of organic residues include saturated aliphatic hydrocarbon groups (alkyl groups, etc.) having 1 to 20 carbon atoms such as methyl group, ethyl group and propyl group; saturated aliphatic hydrocarbon groups (alkenyl groups, etc.); aromatic hydrocarbon groups having 6 to 20 carbon atoms such as phenyl groups and naphthyl groups (aryl groups, etc.); these saturated aliphatic hydrocarbon groups, unsaturated aliphatic hydrocarbons a group in which one or more hydrogen atoms in an aromatic hydrocarbon group are substituted with at least one group selected from the group consisting of a hydroxy group, a carboxyl group, an ether group, and an ester group; and the like.
The lactone ring structure is obtained, for example, by copolymerizing an acrylic monomer having a hydroxy group and a methacrylic acid ester monomer such as methyl methacrylate to form a hydroxy group and an ester group or a carboxyl group in the molecular chain. After introduction, it can be formed by causing dealcoholization (esterification) or dehydration condensation (hereinafter also referred to as "cyclization condensation reaction") between these hydroxy groups and ester groups or carboxyl groups.
Examples of acrylic acid-based monomers having a hydroxy group used for polymerization include 2-(hydroxymethyl)acrylic acid, 2-(hydroxyethyl)acrylic acid, and alkyl 2-(hydroxymethyl)acrylate (e.g., 2- (Hydroxymethyl) methyl acrylate, 2-(hydroxymethyl) ethyl acrylate, 2-(hydroxymethyl) isopropyl acrylate, 2-(hydroxymethyl) n-butyl acrylate, 2-(hydroxymethyl) t-acrylate butyl), 2-(hydroxyethyl)alkyl acrylate, etc., preferably 2-(hydroxymethyl)acrylic acid or 2-(hydroxymethyl)alkyl acrylate, which are monomers having a hydroxyallyl moiety. , and particularly preferably methyl 2-(hydroxymethyl)acrylate and ethyl 2-(hydroxymethyl)acrylate.

The content of the lactone ring structural unit in the methacrylic resin having the lactone ring structural unit in the main chain is not particularly limited as long as it satisfies the range of the glass transition temperature of the methacrylic resin of the present embodiment. It is preferably 5 to 40% by mass, more preferably 5 to 35% by mass, based on 100% by mass.
When the content of the lactone ring structural unit is within this range, effects of introducing the ring structure, such as improved solvent resistance and improved surface hardness, can be exhibited while maintaining moldability.
In addition, the content of the lactone ring structure in the methacrylic resin can be determined using the method described in the aforementioned patent document.

The content of the structural unit (B) having a ring structure in the main chain is 3, based on 100% by mass of the methacrylic resin, from the viewpoint of the heat resistance, thermal stability, strength, and fluidity of the methacrylic resin of the present embodiment. to 40% by mass, the lower limit is more preferably 5% by mass or more, still more preferably 7% by mass or more, and even more preferably 8% by mass or more, and the upper limit is more preferably It is 30% by mass or less, more preferably 28% by mass or less, even more preferably 25% by mass or less, particularly preferably 20% by mass or less, even more preferably 18% by mass or less, and most preferably less than 15% by mass.

-Other vinyl-based monomer unit (C) copolymerizable with methacrylic acid ester monomer-
Other vinyl-based monomer units (C) copolymerizable with methacrylic acid ester monomers that can constitute the methacrylic resin of the present embodiment (hereinafter sometimes referred to as (C) monomer units) .) include an aromatic vinyl-based monomer unit (C-1), an acrylic ester monomer unit (C-2), a vinyl cyanide-based monomer unit (C-3), and other units A mer unit (C-4) is included.
Other vinyl-based monomer units (C) copolymerizable with methacrylic acid ester monomers may be used singly or in combination of two or more.

The (C) monomer unit can be appropriately selected according to the properties required for the methacrylic resin, but properties such as thermal stability, fluidity, mechanical properties, and chemical resistance are particularly required. is selected from the group consisting of an aromatic vinyl-based monomer unit (C-1), an acrylate monomer unit (C-2), and a vinyl cyanide-based monomer unit (C-3) At least one is preferred.

[Aromatic vinyl-based monomer unit (C-1)]
The monomer forming the aromatic vinyl-based monomer unit (C-1) constituting the methacrylic resin of the present embodiment is not particularly limited, but is represented by the following general formula (5) Aromatic vinyl monomers are preferred.

前記一般式（４）中、Ｒ^１３は、水素原子、又は炭素数が１～６のアルキル基を表し、当該アルキル基は、例えば、水酸基で置換されていてもよい。
Ｒ^１４は、水素原子、炭素数が１～１２のアルキル基、炭素数が１～１２のアルコキシ基、炭素数が６～８のアリール基、炭素数が６～８のアリーロキシ基からなる群より選択されるいずれかであり、Ｒ^２は、全て同じ基であっても、異なる基であってもよい。また、Ｒ^１４同士で環構造を形成してもよい。
ｎは、０～５の整数を表す。

In general formula (4), R ¹³ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and the alkyl group may be substituted with, for example, a hydroxyl group.
R ¹⁴ is selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group having 6 to 8 carbon atoms, and an aryloxy group having 6 to 8 carbon atoms. Any selected, and R ² may all be the same group or different groups. Also, R ¹⁴ may form a ring structure together.
n represents an integer of 0 to 5;

Specific examples of the monomer represented by the general formula (5) are not particularly limited, but styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethyl styrene, 2,5-dimethylstyrene, 3,4-dimethylstyrene, 3,5-dimethylstyrene, p-ethylstyrene, m-ethylstyrene, o-ethylstyrene, p-tert-butylstyrene, 1-vinylnaphthalene, 2-vinylnaphthalene, 1,1-diphenylethylene, isopropenylbenzene (α-methylstyrene), isopropenyltoluene, isopropenylethylbenzene, isopropenylpropylbenzene, isopropenylbutylbenzene, isopropenylpentylbenzene, isopropenylhexylbenzene, isopropenyloctylbenzene, α-hydroxymethylstyrene, α-hydroxyethylstyrene and the like.
Among the above, styrene and isopropenylbenzene are preferable, and styrene is more preferable from the viewpoints of imparting fluidity and reducing unreacted monomers by improving polymerization conversion.
These may be appropriately selected according to the properties required for the methacrylic resin of the present embodiment.

When the aromatic vinyl-based monomer unit (C-1) is used, the content is, considering heat resistance, reduction of residual monomer species, and balance of fluidity, (A) monomer unit and (B) When the total amount with the structural unit is 100% by mass, it is preferably 23% by mass or less, more preferably 20% by mass or less, still more preferably 18% by mass or less, and even more preferably 15% by mass or less. Even more preferably, it is 10% by mass or less.

When the aromatic vinyl-based monomer unit (C-1) is used in combination with the maleimide-based structural unit (B-1) described above, the ratio of (C-1) monomer to the content of (B-1) structural unit The ratio (mass ratio) of the unit content (that is, (C-1) content / (B-1) content) is determined from the viewpoint of processing fluidity and the effect of reducing silver streaks by reducing residual monomers. , 0.3 to 5.
Here, from the viewpoint of maintaining good color tone and heat resistance, the upper limit is preferably 5 or less, more preferably 3 or less, and even more preferably 1 or less. From the viewpoint of reducing residual monomers, the lower limit is preferably 0.3 or more, more preferably 0.4 or more.
The aromatic vinyl-based monomer (C-1) described above may be used alone or in combination of two or more.

[Acrylic acid ester monomer unit (C-2)]
The monomer forming the acrylic acid ester monomer unit (C-2) constituting the methacrylic resin of the present embodiment is not particularly limited, but acrylic represented by the following general formula (6) Acid ester monomers are preferred.

前記一般式（６）中、Ｒ^１５は、水素原子、又は炭素数が１～１２のアルコキシ基を表し、Ｒ^１６は、炭素数が１～１８のアルキル基、炭素数が３～１２のシクロアルキル基、炭素数が６～１４のアリール基のいずれかを表す。

In the general formula (6), R ¹⁵ represents a hydrogen atom or an alkoxy group having 1 to 12 carbon atoms, R ¹⁶ represents an alkyl group having 1 to 18 carbon atoms, a cyclo It represents either an alkyl group or an aryl group having 6 to 14 carbon atoms.

As a monomer for forming the acrylic acid ester monomer unit (C-2), in the methacrylic resin for the film of the present embodiment, the weather resistance, heat resistance, fluidity, and heat stability are improved. From the point of view, methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, sec-butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, phenyl acrylate and the like are preferable. More preferred are methyl acrylate, ethyl acrylate and n-butyl acrylate, and from the viewpoint of availability, methyl acrylate and ethyl acrylate are even more preferred.
The acrylic acid ester monomer units (C-2) may be used singly or in combination of two or more.

The content when the acrylic acid ester monomer unit (C-2) is used is, from the viewpoint of heat resistance and thermal stability, the total amount of the (A) monomer unit and the (B) structural unit to 100. In terms of % by mass, it is preferably 5% by mass or less, more preferably 3% by mass or less.

[Vinyl cyanide-based monomer unit (C-3)]
The monomer forming the vinyl cyanide monomer unit (C-3) constituting the methacrylic resin of the present embodiment is not particularly limited, but examples include acrylonitrile, methacrylonitrile, ethacrylonitrile, Nitrile, vinylidene cyanide, etc., may be mentioned, and among them, acrylonitrile is preferable from the viewpoint of availability and imparting chemical resistance.
The vinyl cyanide-based monomer units (C-3) may be used alone or in combination of two or more.

When the vinyl cyanide-based monomer unit (C-3) is used, the content is the total amount of the (A) monomer unit and (B) structural unit from the viewpoint of maintaining solvent resistance and heat resistance. 100% by mass, the content is preferably 15% by mass or less, more preferably 12% by mass or less, and even more preferably 10% by mass or less.

[monomer unit (C-4) other than (C-1) to (C-3)]
The monomer forming the monomer unit (C-4) other than (C-1) to (C-3) constituting the methacrylic resin of the present embodiment is not particularly limited. , acrylamide, amides such as methacrylamide; glycidyl compounds such as glycidyl (meth)acrylate, allyl glycidyl ether; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, and their half esters compounds or anhydrides; unsaturated alcohols such as methallyl alcohol and allyl alcohol; olefins such as ethylene, propylene and 4-methyl-1-pentene; vinyl acetate, 2-hydroxymethyl-1-butene, methyl vinyl ketone, Vinyl compounds other than those mentioned above, such as N-vinylpyrrolidone and N-vinylcarbazole, and vinylidene compounds are included.
Furthermore, crosslinkable compounds having multiple reactive double bonds include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, and the like. Esterification of both terminal hydroxyl groups of ethylene glycol or its oligomer with acrylic acid or methacrylic acid; neopentyl glycol di(meth)acrylate, di(meth)acrylate, etc., with acrylic acid or methacrylic acid for the hydroxyl groups of two alcohols esterified ones; polyhydric alcohol derivatives such as trimethylolpropane and pentaerythritol esterified with acrylic acid or methacrylic acid; and polyfunctional monomers such as divinylbenzene.

Among the monomers constituting the (C) monomer unit described above, at least one selected from the group consisting of methyl acrylate, ethyl acrylate, styrene, and acrylonitrile is preferable from the viewpoint of availability.

The content of other vinyl-based monomer units (C) that can be copolymerized with the methacrylic acid ester monomer is 100% by mass of the methacrylic resin from the viewpoint of enhancing the effect of imparting heat resistance by the structural unit (B). is 0 to 20% by mass, preferably 0 to 18% by mass, more preferably 0 to 15% by mass.
In particular, when using a crosslinkable polyfunctional (meth)acrylate having a plurality of reactive double bonds as the monomer unit (C), the content of the monomer unit (C) is the fluidity of the polymer. From the viewpoint of , it is preferably 0.5% by mass or less, more preferably 0.3% by mass or less, and still more preferably 0.2% by mass or less.

In particular, in the present embodiment, from the viewpoint of the heat resistance and optical properties of the methacrylic resin molded product, when the total amount of the (B) structural unit and the (C) monomer unit is 100% by mass, (B) The content of structural units is 45 to 100% by mass. At this time, the content of the (C) structural unit is 0 to 55% by mass. The content of the (B) structural unit is preferably 50 to 100% by mass, more preferably 50 to 90% by mass, still more preferably 50 to 80% by mass.

The properties of the methacrylic resin of this embodiment are described below.

The glass transition temperature (Tg) of the methacrylic resin in this embodiment is more than 120° C. and 160° C. or less.
If the glass transition temperature of the methacrylic resin exceeds 120 ° C., it is easier to obtain necessary and sufficient heat resistance for optical parts such as lens moldings in recent years, automotive parts such as in-vehicle displays, and film moldings for liquid crystal displays. can get to The glass transition temperature (Tg) is more preferably 125° C. or higher, and still more preferably 130° C. or higher, from the viewpoint of dimensional stability under the environmental temperature of use.
On the other hand, when the glass transition temperature (Tg) of the methacrylic resin is 160° C. or less, melt processing at extremely high temperatures is avoided, thermal decomposition of the resin is suppressed, and good products can be obtained. The glass transition temperature (Tg) is preferably 150° C. or less for the reasons described above.
The glass transition temperature (Tg) can be determined by measuring according to JIS-K7121. Specifically, it can be measured using the method described in the examples below.

The methacrylic resin containing a structural unit having a ring structure in the main chain of the present embodiment has a sign of orientation birefringence when oriented such that the degree of orientation is 0.03, and a degree of orientation of 0.08. The sign of the orientation birefringence is different from that when oriented as shown in FIG.

Furthermore, the absolute value of the orientation birefringence when oriented so that the degree of orientation is 0.03 is preferably 0.1×10 ⁻⁵ or more and 5.0×10 ⁻⁵ or less, and 0.1 ×10 ⁻⁵ or more and 3.0×10 ⁻⁵ or less, more preferably 0.3×10 ⁻⁵ or more and 2.0×10 ⁻⁵ or less, and 0.5×10 ⁻⁵ More preferably, it is equal to or greater than 1.5×10 ⁻⁵ and equal to or less than 1.5×10 −5 .
The absolute value of orientation birefringence when oriented so that the degree of orientation is 0.08 is preferably 8.0×10 ⁻⁵ or less, and 5.0×10 ⁻⁵ or less. is more preferably 0.1×10 ⁻⁵ or more and 4.0×10 ⁻⁵ or less, and even more preferably 0.3×10 ⁻⁵ or more and 3.0×10 ⁻⁵ or less. .
Furthermore, the absolute value of the orientation birefringence when oriented so that the degree of orientation is 0.03 and the absolute value of the orientation birefringence when oriented so that the degree of orientation is 0.08 The absolute value of the difference is preferably 5.0×10 ⁻⁵ or less, more preferably 4.0×10 ⁻⁵ or less, even more preferably 3.0×10 ⁻⁵ or less, and 2 0×10 ⁻⁵ or less, and even more preferably 1.0×10 ⁻⁵ or less.
Specifically, the orientation birefringence of the methacrylic resin can be determined by the method described in Examples below.

For example, orientation birefringence when oriented so that the orientation degree is 0.03: 0.4 × 10 ^-5 Orientation birefringence when oriented so that the orientation degree is 0.08: -2.4 × 10 ^-5 and orientation birefringence when oriented so that the orientation degree is 0.03: -0.4 × 10 ^-5 , so that the orientation degree is 0.08 Orientation birefringence when oriented to: 2.4 × 10 ^-5 The resin is technically capable of canceling the in-plane birefringence due to the orientation degree distribution in the thickness direction when formed into a molded body. It has the same meaning.

Birefringence Δn is defined as follows.
Δn=nx−ny (a)
nx is the refractive index in the stretching direction, and ny is the refractive index in the direction perpendicular to the stretching direction. If nx is larger than ny, Δn is positive, and if it is smaller, Δn is negative.
Assuming that the intrinsic birefringence is Δn ⁰ and the degree of orientation is f, the orientation birefringence Δn ^or is expressed by the following equation.
Δn ^or =f×Δn ⁰ (b)

本実施形態におけるメタクリル系樹脂の配向度は、メタクリル酸エステル単位がメタクリル酸メチルの場合、メタクリル酸メチル単位中のＣＨ_２の横揺れ振動に対応する波数７５０ｃｍ^－１の吸収を用い、αを１７°として求めることができる。また、α－メチルの対称変角振動に対応する１３８８ｃｍ^－１の吸収を用い、αを９０°として求めることもできる。 Here, the degree of orientation f is an index representing the degree of orientation of the main chain of the polymer, and the state in which the polymer is completely oriented in one direction is represented by f=1. The orientation birefringence at this time corresponds to the intrinsic birefringence ^Δn0 . The degree of orientation f can be obtained by infrared dichroism measurement.
_A methacrylic resin molded into a film is stretched and irradiated with infrared light polarized in the direction of stretching and in the horizontal or vertical direction _. ,
D= _A / A _⊥ (c)
is represented.
Assuming that the angle formed by the direction of the vibrational transition moment regarding the absorption of the functional group of interest and the orientation direction or elongation direction of the main chain is α, the degree of orientation f is expressed by the following formula.

The degree of orientation of the methacrylic resin in this embodiment, when the methacrylate ester unit is methyl methacrylate, uses absorption at a wave number of 750 cm ⁻¹ corresponding to the lateral vibration of CH ₂ in the methyl methacrylate unit, and α is 17. ° can be obtained. It can also be determined using the absorption at 1388 cm ⁻¹ corresponding to the symmetrical bending vibration of α-methyl, with α set to 90°.

In a methacrylic resin having a ring structure, the thickness and the degree of orientation are higher than those of films for conventional applications, and the intrinsic birefringence, which is a measure of orientation birefringence, is used in injection-molded products that require a high level of birefringence reduction. and the photoelastic coefficient, which is a measure of photoelastic birefringence, to be close to zero.
In the process, we investigated a resin material that exhibits lower orientation birefringence over a higher and wider range of orientation degrees. First, for example, even when the composition of the methacrylic resin having a ring structure is adjusted so that the orientation birefringence at a low orientation degree becomes zero, the orientation birefringence at a high orientation degree does not become zero.
Therefore, by selecting a plurality of monomers having different signs of intrinsic birefringence and photoelastic coefficient when they are homopolymers, combining them and copolymerizing them to adjust the composition, orientation birefringence and optical It has been found that the conventional methods for reducing elastic birefringence cannot completely eliminate the birefringence of an injection-molded article having an orientation distribution inside the molded article.
Although the reason why the orientation birefringence in methacrylic resins with a ring structure exhibits orientation dependence is unknown, the easiness of movement when an external force is applied between the methacrylic comonomer unit and the comonomer unit with a ring structure is unknown. This is because when the orientation is low, the comonomer units that are easy to move move, and as the orientation increases, the comonomer units that are difficult to move also move. It is estimated to be.
Therefore, the present inventors have determined the sign of the intrinsic birefringence at the degree of orientation corresponding to the low-orientation site near the center in the thickness direction inside the injection molded body, and the high-orientation site slightly inside the surface. It has been found that by preparing a copolymer having a different sign of intrinsic birefringence in the degree of orientation, the orientation birefringence can be canceled in the injection molded article and the birefringence of the injection molded article can be reduced.

Although the optimum magnitude of orientation birefringence differs depending on the shape of the injection molded article, the absolute value of orientation birefringence is 0.1×10 ⁻⁵ or more when oriented so that the degree of orientation is 0.03. 0 × 10 ^-5 or less, and if the absolute value of the orientation birefringence when oriented so that the degree of orientation is 0.08 is 8.0 × 10 ^-5 or less, especially a thin thickness of 1.5 mm or less In the case of a molded article having a complicated shape such as a variable thickness, an injection molded article having a low birefringence can be obtained.

The absolute value of the photoelastic coefficient C _R of the methacrylic resin containing a structural unit having a ring structure in the main chain of the present embodiment is preferably 3.0×10 ⁻¹² Pa ⁻¹ or less, and 2.0× It is more preferably 10 ⁻¹² Pa ⁻¹ or less, further preferably 1.0×10 ⁻¹² Pa ⁻¹ or less.
Photoelastic coefficients are described in various documents (see, for example, Kagaku Sosetsu, No. 39, 1998 (published by Gakkai Publishing Center)), and are defined by the following formulas (ia) and (ib) is. It can be seen that the closer the value of the photoelastic coefficient _CR is to zero, the smaller the change in birefringence due to external force.
C _R =Δn/σ _R (e)
Δn=nx−ny (f)
(In the formula, _CR is the photoelastic coefficient, _σR is the tensile stress, Δn is the birefringence, nx is the refractive index in the stretching direction, and ny is the refractive index in the plane perpendicular to the stretching direction.)
If the absolute value of the photoelastic coefficient C _R of the methacrylic resin of the present embodiment is 3.0×10 ⁻¹² Pa ⁻¹ or less, the residual stress during injection molding and the injection molded body as a part are embedded in the product. The birefringence caused by the stress that occurs in the case is sufficiently small.
The photoelastic coefficient _CR of the methacrylic resin can be specifically determined by the method described in Examples below.

In the methacrylic resin of the present embodiment, the weight average molecular weight (Mw) in terms of polymethyl methacrylate measured by gel permeation chromatography (GPC) is preferably in the range of 65,000 to 220,000, more preferably It is in the range of 80,000 to 180,000, more preferably in the range of 90,000 to 150,000.
When the weight average molecular weight (Mw) is within the above range, the balance between mechanical strength and fluidity is also excellent.
Further, regarding the ratio among the Z-average molecular weight (Mz), the weight-average molecular weight (Mw), and the number-average molecular weight (Mn), which are parameters representing the molecular weight distribution, the methacrylic resin in the present embodiment has fluidity and mechanical Considering the balance with strength, Mw / Mn is preferably 1.5 to 3.0, more preferably 1.6 to 2.5, and 1.6 to 2.3 Mz/Mw is more preferably 1.3 to 2.0, more preferably 1.3 to 1.8, even more preferably 1.4 to 1.7.
The weight average molecular weight and number average molecular weight of the methacrylic resin can be measured by the methods described in Examples below.
The sign of the orientation birefringence when oriented so that the degree of orientation is 0.03 is different from the sign of the orientation birefringence when oriented so that the degree of orientation is 0.08, and more preferably The absolute value of the orientation birefringence when oriented so that the degree of orientation is 0.03 is 0.1 × 10 ^-5 or more and 5.0 × 10 ^-5 or less, and the degree of orientation is 0.08 A methacrylic resin containing a structural unit having a ring structure having a characteristic that the absolute value of orientation birefringence when oriented in the direction is 8.0 × 10 ^-5 or less is the composition of the ring structure in the methacrylic resin The distribution tends to be uniform.
The composition distribution of the ring structure in the methacrylic resin can be determined by looking at the molecular weight dependence of the composition ratio of the structural units containing the ring structure in the methacrylic resin. It is obtained by determining the abundance ratio of structural units having a ring structure for each component obtained by fractionation. Fraction components having peak top molecular weights of 40,000 to 50,000 and peak top The difference in abundance ratio of the structural unit having a ring structure between the fraction component having a molecular weight of 240,000 to 260,000 is preferably 3.0% by mass or less, and is 2.5% by mass or less. is more preferably 2.0% by mass or less, and even more preferably 1.5% by mass or less. Here, the fraction component having a peak top molecular weight of 40,000 to 50,000 refers to any fraction component having a peak top molecular weight within this range, and a peak top molecular weight of 240,000 to 260,000. is defined as any fraction component having a peak top molecular weight within this range.
The method for molecular weight fractionation of the methacrylic resin and the abundance ratio of the structural unit having a ring structure in each fractionated component can be measured by the method described in Examples below.
Furthermore, the difference between the absolute value of the orientation birefringence when oriented so that the degree of orientation is 0.03 and the absolute value of the orientation birefringence when oriented so that the degree of orientation is 0.08 Obtaining a methacrylic resin from which a molded article with low birefringence can be obtained as an injection molded article by adjusting the composition of structural units containing a ring structure in the methacrylic resin so that the absolute value is 5.0×10 ⁻⁵ or less. be able to.
By reducing the difference in the composition of the structural unit containing the ring structure between the methacrylic resin components having different molecular weights and by setting the composition of the structural unit containing the ring structure in the entire methacrylic resin to an appropriate value, The orientation birefringence has a different sign between the orientation degree and the high orientation degree, and the value can be suppressed. Although the factors that enable such control are not clear, the following reasons are conceivable. That is, in general, a structural unit having a ring structure exhibiting a sign of birefringence opposite to that of a methacrylate monomer unit has low mobility in the molecular chain. Therefore, when there is an imbalance in the bond composition of structural units containing a ring structure, the molecular chains in which many methacrylate monomers are bonded are preferentially oriented due to external stress, and the orientation birefringence increases in one direction. It is difficult to obtain different codes depending on the degree of orientation. In addition, it is thought that there is a difference in the orientation of the low-molecular-weight component and the high-molecular-weight component due to the flow during molding. It is also conceivable that it can be made smaller.

The yellowness index (YI) at an optical path length of 80 mm of an injection-molded piece of a methacrylic resin containing a structural unit having a structural unit having a ring structure in the main chain of the present embodiment is preferably 20 or less, more preferably 18 or less. , more preferably 16 or less, still more preferably 15 or less.
When the yellowness index of the methacrylic resin of the present embodiment is within the above range, a molded product with excellent color tone can be obtained.
The yellowness index (YI) can be measured by the method described in Examples below.

(Method for producing methacrylic resin)
A method for producing the methacrylic resin of the present embodiment will be described below.

In the production method of the present embodiment, a batch (batch) system, a semi-batch system, or a continuous system can be used as the polymerization system. Here, the batch system is a process in which the reaction is started and progressed after the total amount of raw material is introduced into the reactor, and the product is recovered after completion. It is a process in which one of them is carried out simultaneously while the reaction is in progress, and the continuous type is a process in which both raw material input and product recovery are carried out simultaneously while the reaction is in progress. As the method for producing the methacrylic resin having a ring structure in the main chain in the present embodiment, a semi-batch method in which a part of the raw materials is added after the reaction is started is preferable from the viewpoint of precisely controlling the copolymer composition.
The continuous method is not preferable as the manufacturing method in this embodiment for the following reasons. When the polymerization reaction is carried out in a single complete mixing reactor, there is an advantage in that the difference in monomer composition between the fractions with different molecular weights in the methacrylic resin can be reduced. Since a large amount of the polymer remains, it tends to have an adverse effect on the color tone. On the other hand, when a plug flow reactor is used, the amount of unreacted monomer can be reduced, but the difference in monomer composition between fractions with different molecular weights in the methacrylic resin is tend to be large. Even when a plurality of complete mixing reactors or a complete mixing reactor and a plug flow reactor are combined in series, the amount of unreacted monomer can be reduced, but the difference in monomer composition between the above fractions is large. tend to be large.
In the method for producing a methacrylic resin according to the present embodiment, polymerization of monomers by radical polymerization is used.

Hereinafter, a method for producing a methacrylic resin containing an N-substituted maleimide structural unit (B-1) as the structural unit (B) having a ring structure in the main chain will be described in detail.

Hereinafter, as an example of a method for producing a methacrylic resin having a structural unit derived from an N-substituted maleimide monomer (hereinafter sometimes referred to as a "maleimide copolymer"), radical The case of production by polymerization will be specifically described.

The polymerization solvent to be used is not particularly limited as long as it can increase the solubility of the maleimide copolymer obtained by polymerization and maintain the viscosity of the reaction solution appropriately for the purpose of preventing gelation or the like.
Specific polymerization solvents include aromatic hydrocarbons such as toluene, xylene, ethylbenzene and isopropylbenzene; ketones such as methylisobutylketone, butylcellosolve, methylethylketone and cyclohexanone; polar solvents such as dimethylformamide and 2-methylpyrrolidone. can be used.
Alcohols such as methanol, ethanol, and isopropanol may also be used as a polymerization solvent as long as they do not inhibit the dissolution of the polymerization product during polymerization.

The amount of the solvent used during polymerization is not particularly limited as long as the polymerization proceeds, the copolymer and the monomer used do not precipitate during production, and the amount can be easily removed. When the total amount is 100 parts by mass, it is preferably 10 to 200 parts by mass. More preferably 25 to 200 parts by mass, still more preferably 50 to 200 parts by mass, still more preferably 50 to 150 parts by mass.

The polymerization temperature is not particularly limited as long as it is a temperature at which polymerization proceeds. More preferably 90 to 150°C, still more preferably 100 to 150°C. From the viewpoint of productivity, the temperature is preferably 70° C. or higher, and preferably 180° C. or lower in order to suppress side reactions during polymerization and obtain a polymer having a desired molecular weight and quality.

In addition, the polymerization time is not particularly limited as long as it is a time that can obtain the required degree of polymerization at the required conversion rate, but from the viewpoint of productivity etc., it is preferably 2 to 15 hours. More preferably 3 to 12 hours, still more preferably 4 to 10 hours.

The polymerization conversion rate at the end of polymerization of the methacrylic resin having a structural unit derived from an N-substituted maleimide monomer in the main chain in the present embodiment is preferably 93 to 99.9%, preferably 95 to 99.9. %, more preferably 97 to 99.8%.
Here, the polymerization conversion rate is the value obtained by subtracting the total mass of the monomers remaining at the end of the polymerization from the total mass of the monomers added to the polymerization system. is the ratio to the total mass of

Further, the amount of the N-substituted maleimide monomer remaining in the solution after polymerization (N-substituted maleimide residual amount) is preferably 50 to 5000 ppm by mass, more preferably 100 to 3000 ppm by mass. More preferably, it is 200 to 1000 ppm by mass.
The higher the polymerization conversion rate and the lower the residual amount of N-substituted maleimide, the less the monomer that goes into the solvent recovery system, so the load on the purification system is reduced, and the unit consumption is increased, which is economical. If the polymerization conversion rate is too high or if the amount of residual N-substituted maleimide is too low, the amount of coloring low-molecular-weight components increases, which may adversely affect color tone and moldability.

During the polymerization reaction, if necessary, a polymerization initiator or a chain transfer agent may be added for polymerization.

Any initiator generally used in radical polymerization can be used as the polymerization initiator. Examples include cumene hydroperoxide, diisopropylbenzene hydroperoxide, di-t-butyl peroxide, lauroyl peroxide, and benzoyl peroxide. organic peroxides such as oxide, t-butylperoxyisopropyl carbonate, t-amylperoxy-2-ethylhexanoate, t-amylperoxyisononanoate, 1,1-di-t-butylperoxycyclohexane; 2,2'-azobis(isobutyronitrile), 1,1'-azobis(cyclohexanecarbonitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), dimethyl-2,2'-azobis azo compounds such as isobutyrate; and the like.
These may be used alone or in combination of two or more.
These polymerization initiators may be added at any stage as long as the polymerization reaction is in progress.
The amount of the polymerization initiator to be added may be 0.01 to 1 part by mass, preferably 0.05 to 0.5 part by mass, when the total amount of monomers used for polymerization is 100 parts by mass.

As the chain transfer agent, a chain transfer agent used in general radical polymerization can be used. mercaptan compounds; halogen compounds such as carbon tetrachloride, methylene chloride and bromoform; unsaturated hydrocarbon compounds such as α-methylstyrene dimer, α-terpinene, dipentene and terpinolene;
These may be used alone or in combination of two or more.
These chain transfer agents may be added at any stage as long as the polymerization reaction is in progress, and are not particularly limited.
The amount of chain transfer agent to be added may be 0.01 to 1 part by mass, preferably 0.05 to 0.5 part by mass, when the total amount of monomers used for polymerization is 100 parts by mass.

In solution polymerization, it is important to reduce the dissolved oxygen concentration in the polymerization solution as much as possible. For example, the dissolved oxygen concentration is preferably 10 ppm or less.
The dissolved oxygen concentration can be measured using, for example, a dissolved oxygen meter DO meter B-505 (manufactured by Iijima Denshi Kogyo Co., Ltd.).
As a method for reducing the dissolved oxygen concentration, a method of bubbling an inert gas into the polymerization solution, and an operation of pressurizing the container containing the polymerization solution to about 0.2 MPa with an inert gas before polymerization and then releasing the pressure are repeated. A method such as passing an inert gas through a container containing a polymerization solution can be selected as appropriate.

During the polymerization of the methacrylic resin having a ring structural unit derived from the N-substituted maleimide monomer in the present embodiment, the distribution of the ring structure in the methacrylic resin is controlled to achieve the desired orientation birefringence at a specific degree of orientation. In order to obtain it, it is preferable to narrow the copolymer composition distribution in the copolymer.

In general radical polymerization, the concentration of radicals and the concentration of monomers in the system fluctuate from the beginning to the end of polymerization. Then, a difference occurs in the average molecular weight of the polymer produced at each time point. On the other hand, methacrylic acid ester monomers generally have a high copolymerizability ratio with respect to N-substituted maleimide, and polymerization tends to proceed first. Therefore, when the finally obtained copolymer is fractionated by molecular weight, the ratio of the monomer units in the copolymer differs between fractions. By reducing the difference in monomer composition in copolymers having different molecular weights, the difference in orientation birefringence between low orientation degree and high orientation degree can be suppressed. Furthermore, by controlling the composition of the entire copolymer, the sign of orientation birefringence at an orientation degree of 0.03, which is required for the methacrylic resin containing a structural unit having a ring structure in the main chain of the present embodiment, and , the sign of the orientation birefringence when the degree of orientation is 0.08, and preferably the absolute value of the orientation birefringence when the degree of orientation is 0.03 is 0.1×10 ⁻⁵ or more5. 0×10 ⁻⁵ or less, and the absolute value of orientation birefringence when the degree of orientation is 0.08 can be 8.0×10 ⁻⁵ or less.

In order to reduce the difference in monomer composition in copolymers with different molecular weights, some monomer units are additionally added so that the monomer composition in the polymerization system during polymerization becomes as uniform as possible. It is preferable to polymerize while

For example, at least one point in time when 60 to 70% of the total amount of methacrylic acid ester monomers added to the polymerization system is consumed, the difference in consumption rate from each other monomer added to the polymerization system However, the type, amount and timing of the additionally added monomers are adjusted so that the content is preferably 10% or less, more preferably 5% or less, and still more preferably 3% or less.
In addition, the consumption rate of a certain monomer at one time refers to the ratio of the total amount of the added monomer that is consumed in the polymerization reaction, and the total amount of the added monomer is , including those that have already been added and those that have not yet been added at the above point in time.

Furthermore, the difference in the final conversion rate of each monomer added to the polymerization system at the end of the polymerization is preferably 10% or less, more preferably 5% or less, and still more preferably 3% or less. to implement.

Also, the final conversion rate of the N-substituted maleimide monomer is preferably 97% or higher, more preferably 98% or higher, even more preferably 99% or higher, still more preferably 99.2% or higher. A methacrylic resin excellent in color tone can be obtained by setting it as such a range.

The method for recovering the polymer from the polymerization liquid obtained by solution polymerization is not particularly limited. After adding the polymerization liquid in the presence of an excess amount, treatment with a homogenizer (emulsification dispersion) is performed, and unreacted monomers are subjected to pretreatment such as liquid-liquid extraction and solid-liquid extraction. a method of separating from the polymerization solution; or a method of separating the polymerization solvent and unreacted monomers through a step called devolatilization step to recover the polymerization product; and the like.
Here, the devolatilization step refers to a step of removing volatile matter such as a polymerization solvent, residual monomers, and reaction by-products under heating and reduced pressure conditions.

Devices used in the devolatilization process include, for example, a devolatilization device consisting of a tubular heat exchanger and a devolatilization tank; thin film evaporators such as Wyblen and Exeva manufactured by Kobelco Eco-Solutions Co., Ltd., Contra and inclined blade Contra manufactured by Hitachi; A vented extruder with sufficient residence time and surface area to exhibit vaporization performance;
A devolatilization step or the like using a devolatilization device in which two or more of these devices are combined can also be used.

From the viewpoint of improving the color tone, it is preferable to use a devolatilization device having a heat exchanger and a decompression vessel as its main structure and not having a rotating part.
Specifically, a devolatilization tank having a configuration in which a decompression unit is attached to a decompression vessel having a size that allows devolatilization and a heat exchanger disposed on the top thereof, and a gear pump for discharging the polymer after devolatilization. It is possible to employ a devolatilization device composed of a discharge device such as
The devolatilization device transfers the polymerization solution to a heat exchanger placed in the upper part of the decompression vessel and heated. After being preheated in a heat exchanger or the like, the mixture is supplied to a devolatilization tank under heating and reduced pressure to separate and remove the polymerization solvent, unreacted raw material mixture, polymerization by-products, etc., and the copolymer. It is preferable to use a devolatilization device that does not have a rotating part as described above, because a methacrylic resin having a good color tone can be obtained.

The treatment temperature in the devolatilizer is preferably 150 to 350°C, more preferably 170 to 300°C, still more preferably 200 to 280°C. By setting the temperature to the lower limit temperature or higher, residual volatile matter can be suppressed, and by setting the temperature to the upper limit temperature or lower, coloring and decomposition of the obtained acrylic resin can be suppressed.

The degree of vacuum in the devolatilizer is preferably in the range of 10 to 500 Torr, more preferably in the range of 10 to 300 Torr. By making the degree of vacuum equal to or lower than the upper limit, the residual amount of volatile matter can be suppressed. A degree of vacuum equal to or higher than the lower limit is practical for industrial implementation.
The treatment time is appropriately selected depending on the amount of residual volatile matter, but the shorter the treatment time, the better, in order to suppress the coloring and decomposition of the obtained acrylic resin.

The polymer recovered through the devolatilization process is processed into pellets in a process called granulation process.
In the granulation step, a molten resin is extruded through a multi-hole die in the form of strands, and processed into pellets by a cold cut method, an air hot cut method, and an underwater cut method.

When a vented extruder is employed as the devolatilization device, the devolatilization step and the granulation step may be combined. Also, in other devolatilizing devices, the molten resin can be granulated by pressurizing it with a gear pump or the like and discharging it, at the same time passing it through a multi-hole die to make it into a strand shape.

Next, an example of a method for producing a methacrylic resin having a glutarimide structural unit will be described.

Methacrylic resins having a glutarimide-based structural unit in the main chain are, for example, JP-A-2006-249202, JP-A-2007-009182, JP-A-2007-009191, JP-A-2011-186482, International It is a methacrylic resin having a glutarimide-based structural unit, which is described in Japanese Unexamined Patent Publication No. 2012/114718, etc., and can be formed by the method described in the publication.
Hereinafter, as an example of a method for producing a methacrylic resin having a glutarimide-based structural unit, a case of production by radical polymerization using a solution polymerization method will be specifically described.

First, a (meth)acrylate polymer is produced by polymerizing a (meth)acrylate such as methyl methacrylate. When an aromatic vinyl unit is included in a methacrylic resin having a glutarimide-based structural unit, a (meth)acrylic acid ester and an aromatic vinyl (e.g., styrene) are copolymerized to form a (meth)acrylic acid ester-aromatic to produce a group vinyl copolymer.

Next, the (meth)acrylic acid ester polymer or the methacrylic acid ester-aromatic vinyl copolymer is reacted with an imidizing agent to perform an imidization reaction (imidization step). Thereby, a methacrylic resin having a glutarimide structural unit can be produced.

The imidizing agent is not particularly limited as long as it can form the glutarimide-based structural unit represented by the general formula (3).
Specifically, ammonia or primary amine can be used as the imidizing agent. Examples of the primary amine include aliphatic hydrocarbon group-containing primary amines such as methylamine, ethylamine, n-propylamine, i-propylamine, n-butylamine, i-butylamine, tert-butylamine, and n-hexylamine; alicyclic hydrocarbon group-containing primary amines such as cyclohexylamine;
Among the above imidization agents, ammonia, methylamine, and cyclohexylamine are preferably used, and methylamine is particularly preferably used, from the viewpoint of cost and physical properties.

In this imidization step, the content of the glutarimide-based structural unit in the obtained methacrylic resin having the glutarimide-based structural unit can be adjusted by adjusting the addition ratio of the imidizing agent.

The method for carrying out the imidization reaction is not particularly limited, but a conventionally known method can be used. For example, the imidization reaction can be advanced by using an extruder or a batch reaction tank.
Although the extruder is not particularly limited, for example, a single-screw extruder, a twin-screw extruder, a multi-screw extruder, or the like can be used.

Among them, it is preferable to use a twin-screw extruder. A twin-screw extruder can facilitate mixing of the starting polymer and the imidizing agent.
Examples of the twin-screw extruder include non-intermeshing co-rotating, intermeshing co-rotating, non-intermeshing counter-rotating and intermeshing counter-rotating.

The extruders exemplified above may be used alone, or may be used by connecting a plurality of them in series.
In addition, the extruder to be used is equipped with a vent port that can be reduced to atmospheric pressure or less, because it is possible to remove the imidizing agent of the reaction, by-products such as methanol, or monomers. preferable.

In producing a methacrylic resin having a glutarimide structural unit, in addition to the imidization step, an esterification step of treating the carboxyl groups of the resin with an esterification agent such as dimethyl carbonate can be included. In that case, a catalyst such as trimethylamine, triethylamine or tributylamine may be used in combination for the treatment.
The esterification step can be advanced by using, for example, an extruder or a batch-type reaction tank, like the imidization step. For the purpose of removing excessive esterifying agent, by-products such as methanol, or monomers, the apparatus used is preferably equipped with a vent port capable of reducing pressure to atmospheric pressure or lower.

The methacrylic resin that has undergone the imidization process and, if necessary, the esterification process, is melted and extruded into strands from an extruder equipped with a multi-hole die. and processed into pellets.
Further, in order to reduce the number of foreign substances in the resin, the methacrylic resin is dissolved in an organic solvent such as toluene, methyl ethyl ketone, methylene chloride, etc., the resulting methacrylic resin solution is filtered, and then the organic solvent is devolatilized. It is also preferred to use a method.

The difference in the composition of the glutarimide ring structural unit between the methacrylic resin components having glutarimide structural units with different molecular weights is reduced, the orientation birefringence has different signs at the low orientation degree and the high orientation degree, and From the viewpoint of suppressing the value, it is preferable to imidize the solution of the (meth)acrylic acid ester polymer or the methacrylic acid ester-aromatic vinyl copolymer in a batch-type reactor. It is not clear why imidization in a solution state enables a uniform ring structure composition to be obtained, but compared to the imidization reaction performed in an extruder, the imidization agent and the polymer can be mixed well. , the contact frequency between the imidizing agent and the polymer is improved regardless of the molecular weight of the polymer. On the other hand, when the cyclization reaction is carried out in an extruder, the frequency of contact with polymer terminals with high mobility is high, so it is thought that polymer components with a high terminal ratio and a low molecular weight are more susceptible to cyclization.

The imidization reaction is preferably carried out at 130-250°C, more preferably at 150-230°C. The reaction time is preferably 10 minutes to 5 hours, more preferably 30 minutes to 2 hours. After the imidization step, if necessary, the product is subjected to an esterification step, followed by devolatilization and granulation steps.

From the viewpoint of improving the color tone, it is preferable to use a devolatilization device having a heat exchanger and a decompression vessel as its main structure and not having a rotating part.
Specifically, a devolatilization tank having a configuration in which a decompression unit is attached to a decompression vessel having a size that allows devolatilization and a heat exchanger disposed on the top thereof, and a gear pump for discharging the polymer after devolatilization. It is possible to employ a devolatilization device composed of a discharge device such as
The devolatilization device transfers the polymerization solution to a heat exchanger placed in the upper part of the decompression vessel and heated. After being preheated in a heat exchanger or the like, the mixture is supplied to a devolatilization tank under heating and reduced pressure to separate and remove the polymerization solvent, unreacted raw material mixture, polymerization by-products, etc., and the copolymer. It is preferable to use a devolatilization device that does not have a rotating part as described above, because a methacrylic resin having a good color tone can be obtained.

Hereinafter, a method for producing a methacrylic resin containing a lactone ring structural unit (B-2) as the structural unit (B) having a ring structure in the main chain will be described in detail.

Methacrylic resins having a lactone ring structural unit in the main chain, for example, JP-A-2001-151814, JP-A-2004-168882, JP-A-2005-146084, JP-A-2006-96960, JP-A-2006-96960 It can be formed by methods described in JP-A-2006-171464, JP-A-2007-63541, JP-A-2007-297620, JP-A-2010-180305, and the like.

Hereinafter, as an example of a method for producing a methacrylic resin having a lactone ring structural unit, a case of producing by radical polymerization using a solution polymerization method will be specifically described.

As the method for producing the methacrylic resin having the lactone ring structural unit (B-2) in the main chain in the present embodiment, solution polymerization using a solvent is preferable in terms of promoting the cyclization reaction. Here, the lactone ring structure may be formed by a cyclization reaction after polymerization.

A methacrylic resin having a lactone ring structural unit in the present embodiment can be obtained by performing a cyclization reaction after completion of the polymerization reaction. Therefore, it is preferable to subject the polymerization reaction solution to the lactone cyclization reaction in a state containing the solvent without removing the polymerization solvent.
The copolymer obtained by polymerization is heat-treated to cause a cyclization condensation reaction between the hydroxyl group (hydroxyl group) and the ester group present in the molecular chain of the copolymer to form a lactone ring structure. to form
In the heat treatment for forming the lactone ring structure, a reaction apparatus equipped with a vacuum device or a devolatilization device, an extruder equipped with a devolatilization device, or the like can be used to remove alcohol that may be by-produced by cyclization condensation. .

When forming the lactone ring structure, if necessary, heat treatment may be performed using a cyclization condensation catalyst in order to promote the cyclization condensation reaction.
Specific examples of cyclization condensation catalysts include methyl phosphite, ethyl phosphite, phenyl phosphite, dimethyl phosphite, diethyl phosphite, diphenyl phosphite, trimethyl phosphite, Phosphite monoalkyl esters, dialkyl esters or triesters such as triethyl phosphate; methyl phosphate, ethyl phosphate, 2-ethylhexyl phosphate, octyl phosphate, isodecyl phosphate, lauryl phosphate, stearyl phosphate, phosphoric acid isostearyl phosphate, dimethyl phosphate, diethyl phosphate, di-2-ethylhexyl phosphate, diisodecyl phosphate, dilauryl phosphate, distearyl phosphate, diisostearyl phosphate, trimethyl phosphate, triethyl phosphate, triisodecyl phosphate, phosphoric acid monoalkyl esters, dialkyl esters or trialkyl esters such as trilauryl phosphate, tristearyl phosphate and triisostearyl phosphate;
These may be used alone or in combination of two or more.

The amount of the cyclization condensation catalyst used is not particularly limited. 1 part by mass.
If the amount used is less than 0.01 part by mass, the reaction rate of the cyclization condensation reaction may not be sufficiently improved. Conversely, if the amount of the catalyst used exceeds 3 parts by mass, the resulting polymer may be colored or the polymer may be crosslinked, making melt molding difficult.

The timing of addition of the cyclization condensation catalyst is not particularly limited. For example, it may be added at the beginning of the cyclization condensation reaction, during the reaction, or both. good.
It is also preferable to perform devolatilization at the same time when the cyclization condensation reaction is performed in the presence of a solvent.
The device used when the cyclization condensation reaction and the devolatilization step are performed at the same time is not particularly limited, but a devolatilization device consisting of a heat exchanger and a devolatilization tank, a vented extruder, or a devolatilization A device and an extruder arranged in series are preferred, and a vented twin-screw extruder is more preferred.
As the vented twin-screw extruder to be used, a vented extruder having a plurality of vent ports is preferable.

When using a vented extruder, the reaction processing temperature is preferably 150 to 350°C, more preferably 200 to 300°C. If the reaction treatment temperature is lower than 150°C, the cyclization condensation reaction may be insufficient and the residual volatile matter may increase. Conversely, if the reaction treatment temperature exceeds 350° C., the resulting polymer may be colored or decomposed.
The degree of vacuum when using a vented extruder is preferably 10 to 500 Torr, more preferably 10 to 300 Torr. When the degree of vacuum exceeds 500 Torr, volatile matter tends to remain. Conversely, if the degree of vacuum is less than 10 Torr, industrial implementation may become difficult.

For the purpose of deactivating the remaining cyclization condensation catalyst during the cyclization condensation reaction, it is also preferable to add an alkaline earth metal and/or amphoteric metal salt of an organic acid during granulation.
Examples of alkaline earth metal and/or amphoteric metal salts of organic acids that can be used include calcium acetylacetate, calcium stearate, zinc acetate, zinc octylate, and zinc 2-ethylhexylate.

After passing through the cyclization condensation reaction process, the methacrylic resin is melted and extruded into strands from an extruder equipped with a multi-hole die, and processed into pellets by a cold cut method, an air hot cut method, and an underwater cut method. .
The lactonization for forming the lactone ring structural unit described above may be performed after the production of the resin and before the production of the resin composition (described later). It may be performed in conjunction with melt-kneading with.

The methacrylic resin in the present embodiment preferably has at least one ring structural unit selected from the group consisting of N-substituted maleimide monomer-derived structural units, glutarimide structural units, and lactone ring structural units. In particular, it is particularly preferable to have a structural unit derived from an N-substituted maleimide monomer, because optical properties such as photoelastic coefficient can be controlled to a high degree without blending with other thermoplastic resins.

(Methacrylic resin composition)
The methacrylic resin composition of the present embodiment may contain a methacrylic resin composition containing the methacrylic resin of the present embodiment described above. The methacrylic resin composition may optionally contain additives in addition to the methacrylic resin of the present embodiment described above, and may also contain thermoplastic resins other than methacrylic resins, rubbery polymers etc. may be included.

-Additive-
The methacrylic resin composition according to this embodiment may contain various additives as long as the effects of the present invention are not significantly impaired.
Additives are not particularly limited, but include, for example, antioxidants, light stabilizers such as hindered amine light stabilizers, ultraviolet absorbers, release agents, other thermoplastic resins, paraffin-based process oils, and naphthene-based process oils. Oil, aromatic process oil, paraffin, organic polysiloxane, softeners and plasticizers such as mineral oil, flame retardants, antistatic agents, organic fibers, inorganic fillers such as pigments such as iron oxide, glass fiber, carbon fiber , reinforcing agents such as metal whiskers, coloring agents; organic phosphorous compounds such as phosphites, phosphonites, and phosphates; other additives; or mixtures thereof.

--Antioxidant--
The methacrylic resin composition according to this embodiment preferably contains an antioxidant that suppresses deterioration and coloration during molding or during use.
Examples of the antioxidant include, but are not limited to, hindered phenol-based antioxidants, phosphorus-based antioxidants, sulfur-based antioxidants, and the like. The methacrylic resin of the present embodiment is suitably used in various applications such as melt extrusion, injection molding, and film molding. The heat history received during processing differs depending on the processing method, but it ranges from several tens of seconds for extruders to tens of minutes to several hours for thick product molding and sheet molding. Various.
When subjected to a long heat history, it is necessary to increase the amount of heat stabilizer added in order to obtain the desired heat stability. From the viewpoint of suppressing the bleeding out of the heat stabilizer and preventing the film from sticking to the roll during film formation, it is preferable to use a plurality of types of heat stabilizers in combination, such as a phosphorus antioxidant and a sulfur antioxidant. It is preferable to use together at least one selected from the antioxidants and a hindered phenol-based antioxidant.
These antioxidants may be used singly or in combination of two or more.

Examples of hindered phenol antioxidants include, but are not limited to, pentaerythritol tetrakis [3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate], thiodiethylene bis [3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 3,3′,3 '',5,5',5''-hexa-tert-butyl-a,a',a''-(mesitylene-2,4,6-triyl)tri-p-cresol, 4,6-bis( octylthiomethyl)-o-cresol, 4,6-bis(dodecylthiomethyl)-o-cresol, ethylenebis(oxyethylene)bis[3-(5-tert-butyl-4-hydroxy-m-tolyl)propionate ], hexamethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl) -1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 1,3,5-tris[(4-tert-butyl-3-hydroxy-2,6-xylin)methyl ]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 2,6-di-tert-butyl-4-(4,6-bis(octylthio)-1,3 ,5-triazin-2-ylamine)phenol, 2-[1-(2-hydroxy-3,5-di-tert-pentylphenyl)ethyl]-4,6-di-tert-pentylphenyl acrylic acid, acrylic acid 2-tert-butyl-4-methyl-6-(2-hydroxy-3-tert-butyl-5-methylbenzyl)phenyl and the like.
In particular pentaerythritol terakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 2-[1-(2-Hydroxy-3,5-di-tert-pentylphenyl)ethyl]-4,6-di-tert-pentylphenyl acrylate is preferred.

In addition, the hindered phenol-based antioxidant as the antioxidant may be a commercially available phenol-based antioxidant, and such a commercially available phenol-based antioxidant is limited to the following. However, for example, Irganox 1010 (Irganox 1010: pentaerythritol tetrakis [3-(3,5-di-t-butyl-4-hydroxyphenyl) propionate], manufactured by BASF), Irganox 1076 (Irganox 1076: Octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, manufactured by BASF), Irganox 1330 (Irganox 1330: 3,3′,3″,5,5′,5′) '-Hexa-t-butyl-a,a',a''-(mesitylene-2,4,6-triyl)tri-p-cresol, manufactured by BASF), Irganox 3114 (Irganox3114: 1,3,5 -tris(3,5-di-t-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, manufactured by BASF), Irganox 3125 (Irganox 3125, manufactured by BASF), Adekastab AO-60 (pentaerythritol tetrakis [3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], manufactured by ADEKA), Adekastab AO-80 (3 , 9-bis{2-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]-1,1-dimethylethyl}-2,4,8,10-tetraoxaspiro [5.5] Undecane, manufactured by ADEKA), Sumilizer BHT (Sumilizer BHT, manufactured by Sumitomo Chemical), Cyanox 1790 (Cyanox 1790, manufactured by Cytec), Sumilizer GA-80 (Sumilizer GA-80, manufactured by Sumitomo Chemical), Sumilizer GS (Sumilizer GS: 2-[1-(2-hydroxy-3,5-di-tert-pentylphenyl)ethyl]-4,6-di-tert-pentylphenyl acrylate, manufactured by Sumitomo Chemical), Sumilizer GM (Sumilizer GM: 2-tert-butyl-4-methyl-6-(2-hydroxy-3-tert-butyl-5-methylbenzyl)phenyl acrylate, manufactured by Sumitomo Chemical), vitamin E (manufactured by Eisai), and the like.
Among these commercially available phenolic antioxidants, Irganox 1010, Adekastab AO-60, Adekastab AO-80, Irganox 1076, Sumilizer GS, etc. are preferable from the viewpoint of the effect of imparting thermal stability to the resin.
These may be used individually by 1 type, or may be used in combination of 2 or more types.

Further, the phosphorus-based antioxidant as the antioxidant is not limited to the following, but for example, tris(2,4-di-t-butylphenyl)phosphite, bis(2,4- Bis(1,1-dimethylethyl)-6-methylphenyl)ethyl ester phosphorous acid, tetrakis(2,4-di-t-butylphenyl)(1,1-biphenyl)-4,4'-diylbisphosph Phonite, bis(2,4-di-t-butylphenyl)pentaerythritol diphosphite, bis(2,6-di-t-butyl-4-methylphenyl)pentaerythritol diphosphite, bis(2,4 -dicumylphenyl)pentaerythritol-diphosphite, tetrakis(2,4-t-butylphenyl)(1,1-biphenyl)-4,4'-diylbisphosphonite, di-t-butyl-m-cresyl- Phosphonite, 4-[3-[(2,4,8,10-tetra-tert-butyldibenzo[d,f][1,3,2]dioxaphosphepin)-6-yloxy]propyl]-2 -methyl-6-tert-butylphenol and the like.
Furthermore, a commercially available phosphorus antioxidant may be used as the phosphorus antioxidant, and examples of such commercially available phosphorus antioxidants include, but are not limited to, Irgafos 168 ( Irgafos 168: tris (2,4-di-t-butylphenyl) phosphite, manufactured by BASF), Irgafos 12 (Irgafos 12: tris [2-[[2,4,8,10-tetra-t-butyldibenzo[ d, f][1,3,2]dioxaphosphefin-6-yl]oxy]ethyl]amine, manufactured by BASF), Irgafos 38 (Irgafos 38: bis(2,4-bis(1,1-dimethyl Ethyl)-6-methylphenyl) ethyl ester phosphorous acid, manufactured by BASF), Adekastab 329K (ADK STAB-229K, manufactured by ADEKA), Adekastab PEP-36 (ADK STAB PEP-36, manufactured by ADEKA), Adekastab PEP-36A ( ADK STAB PEP-36A, manufactured by ADEKA), ADEKA STAB PEP-8 (ADK STAB PEP-8, manufactured by ADEKA), ADEKA STAB HP-10 (ADK STAB HP-10, manufactured by ADEKA), ADEKA STAB 2112 (ADK STAB 2112, manufactured by ADEKA) ), ADEKA STAB 1178 (ADKA STAB 1178, made by ADEKA), ADEKA STAB 1500 (ADK STAB 1500, made by ADEKA), Sandstab P-EPQ (made by Clariant), Weston 618 (Weston 618, made by GE), Weston 619G (Weston 619G, made by GE ), Ultranox 626 (manufactured by GE), Sumilizer GP: 4-[3-[(2,4,8,10-tetra-tert-butyldibenzo[d,f][1,3, 2] Dioxaphosphepin)-6-yloxy]propyl]-2-methyl-6-tert-butylphenol, manufactured by Sumitomo Chemical), HCA (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10 - oxide, manufactured by Sanko Co., Ltd.) and the like.
Among these commercially available phosphorus-based antioxidants, Irgafos 168, Adekastab PEP-36, Adekastab PEP-36A, and Adekastab HP are considered effective in imparting thermal stability to the resin and in combination with various antioxidants. -10 and Adekastab 1178 are preferred, and Adekastab PEP-36A and Adekastab PEP-36 are particularly preferred.
These phosphorus-based antioxidants may be used alone or in combination of two or more.

Further, the sulfur-based antioxidant as the antioxidant is not limited to the following, but for example, 2,4-bis(dodecylthiomethyl)-6-methylphenol (Irganox 1726, BASF ), 2,4-bis(octylthiomethyl)-6-methylphenol (Irganox 1520L, manufactured by BASF), 2,2-bis{[3-(dodecylthio)-1-oxoporopoxy]methyl}propane-1 ,3-diylbis[3-dodecylthio]propionate] (adekastab AO-412S, manufactured by ADEKA), 2,2-bis{[3-(dodecylthio)-1-oxoporopoxy]methyl}propane-1,3-diylbis[3 -dodecylthio]propionate] (Cheminox PLS, manufactured by Chemipro Kasei Co., Ltd.), di(tridecyl) 3,3′-thiodipropionate (AO-503, manufactured by ADEKA), and the like.
Among these commercially available sulfur antioxidants, Adekastab AO-412S and Cheminox PLS are preferred from the viewpoints of thermal stability imparting effect in the resin, combined effect with various antioxidants, and handleability.
These sulfur-based antioxidants may be used alone or in combination of two or more.

The content of the antioxidant may be any amount as long as the effect of improving the thermal stability is obtained, and if the content is excessive, problems such as bleeding out during processing may occur. Based on 100 parts by mass of the system resin, it is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, still more preferably 1 part by mass or less, even more preferably 0.8 parts by mass or less. It is preferably 0.01 to 0.8 parts by mass, particularly preferably 0.01 to 0.5 parts by mass.

The timing of adding the antioxidant is not particularly limited, a method of starting polymerization after adding it to the monomer solution before polymerization, a method of adding and mixing with the polymer solution after polymerization and then subjecting it to a devolatilization step, and devolatilization. Examples thereof include a method of adding and mixing with the polymer in a molten state and then pelletizing, and a method of adding and mixing the pellets after devolatilization and pelletizing when they are melt-extruded again. Among these, from the viewpoint of preventing thermal deterioration and coloration in the devolatilization process, it is possible to add and mix the polymer solution after polymerization, add an antioxidant before the devolatilization process, and then subject it to the devolatilization process. preferable.

--Hindered amine light stabilizer--
The methacrylic resin composition of this embodiment can contain a hindered amine light stabilizer.
Although the hindered amine light stabilizer is not particularly limited, it is preferably a compound containing three or more ring structures. Here, the ring structure is preferably at least one selected from the group consisting of aromatic rings, aliphatic rings, aromatic heterocycles and non-aromatic heterocycles, and two or more ring structures are contained in one compound. If so, they may be the same or different from each other.

Examples of the hindered amine light stabilizer include, but are not limited to, bis(1,2,2,6,6-pentamethyl-4-piperidyl)[[3,5-bis (1,1-dimethylethyl)-4-hydroxyphenyl]methyl]butylmalonate, bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and methyl 1,2,2,6,6 -pentamethyl-4-piperidyl sebacate mixture, bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, N,N'-bis(2,2,6,6-tetramethyl-4- piperidyl)-N,N'-diformylhexamethylenediamine, dibutylamine/1,3,5-triazine/N,N'-bis(2,2,6,6-tetramethyl-4-piperidyl-1,6 -Polycondensate of hexamethylenediamine and N-(2,2,6,6-tetramethyl-4-piperidyl)butylamine, poly[{6-(1,1,3,3-tetramethylbutyl)amino-1 ,3,5-triazine-2,4-diyl}{2,2,6,6-tetramethyl-4-piperidyl)imino}hexamethylene {(2,2,6,6-tetramethyl-4-piperidyl) imino}], tetrakis(1,2,2,6,6-pentamethyl-4-piperidyl)butane-1,2,3,4-tetracarboxylate, tetrakis(2,2,6,6-tetramethyl-4 -piperidyl)butane-1,2,3,4-tetracarboxylate, 1,2,2,6,6-pentamethyl-4-piperidiol and β,β,β',β'-tetramethyl-2,4, 8,10-tetraoxaspiro[5.5]undecane-3,9-diethanol reactants, 2,2,6,6-tetramethyl-4-piperidiol and β,β,β',β'-tetramethyl -2,4,8,10-tetraoxaspiro[5.5]undecane-3,9-diethanol reactant, bis(1-undecanoxy-2,2,6,6-tetramethylpiperidin-4-yl) carbonate, 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate, 2,2,6,6-tetramethyl-4-piperidyl methacrylate and the like.
Among them, bis(1,2,2,6,6-pentamethyl-4-piperidyl)[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl containing 3 or more ring structures ] Butylmalonate, dibutylamine/1,3,5-triazine/N,N′-bis(2,2,6,6-tetramethyl-4-piperidyl-1,6-hexamethylenediamine and N-(2 , 2,6,6-tetramethyl-4-piperidyl)butylamine polycondensate, poly[{6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2, 4-diyl}{2,2,6,6-tetramethyl-4-piperidyl)imino}hexamethylene {(2,2,6,6-tetramethyl-4-piperidyl)imino}], 1,2,2 ,6,6-pentamethyl-4-piperidiol and β,β,β',β'-tetramethyl-2,4,8,10-tetraoxaspiro[5.5]undecane-3,9-diethanol reactant , 2,2,6,6-tetramethyl-4-piperidiol and β,β,β',β'-tetramethyl-2,4,8,10-tetraoxaspiro[5.5]undecane-3,9 - the diethanol reactant is preferred.

The content of the hindered amine light stabilizer may be any amount as long as the effect of improving the light stability is obtained, and if the content is excessive, problems such as bleeding out during processing may occur. , with respect to 100 parts by mass of the methacrylic resin, it is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, still more preferably 1 part by mass or less, still more preferably 0.8 parts by mass or less, More preferably 0.01 to 0.8 parts by mass, particularly preferably 0.01 to 0.5 parts by mass.

--Ultraviolet absorber--
The methacrylic resin composition of this embodiment can contain an ultraviolet absorber.
Although the ultraviolet absorber is not particularly limited, it is preferably an ultraviolet absorber having a maximum absorption wavelength of 280 to 380 nm. Examples include benzotriazole compounds, benzotriazine compounds, benzophenone compounds, and oxybenzophenone compounds. , benzoate-based compounds, phenol-based compounds, oxazole-based compounds, cyanoacrylate-based compounds, benzoxazinone-based compounds, and the like.

Benzotriazole compounds include 2,2′-methylenebis[4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazol-2-yl)phenol], 2-(3, 5-di-tert-butyl-2-hydroxyphenyl)-5-chlorobenzotriazole, 2-(2H-benzotriazol-2-yl)-p-cresol, 2-(2H-benzotriazol-2-yl)- 4,6-bis(1-methyl-1-phenylethyl)phenol, 2-benzotriazol-2-yl-4,6-di-tert-butylphenol, 2-[5-chloro(2H)-benzotriazole-2 -yl]-4-methyl-6-t-butylphenol, 2-(2H-benzotriazol-2-yl)-4,6-di-t-butylphenol, 2-(2H-benzotriazol-2-yl)- 4-(1,1,3,3-tetramethylbutyl)phenol, 2-(2H-benzotriazol-2-yl)-4-methyl-6-(3,4,5,6-tetrahydrophthalimidylmethyl) ) phenol, reaction product of methyl 3-(3-(2H-benzotriazol-2-yl)-5-t-butyl-4-hydroxyphenyl)propionate/polyethylene glycol 300, 2-(2H-benzotriazole-2 -yl)-6-(linear and branched dodecyl)-4-methylphenol, 2-(5-methyl-2-hydroxyphenyl)benzotriazole, 2-[2-hydroxy-3,5-bis(α, α-dimethylbenzyl)phenyl]-2H-benzotriazole, 3-(2H-benzotriazol-2-yl)-5-(1,1-dimethylethyl)-4-hydroxy-C7-9 side chain and linear alkyl esters.
Among these, benzotriazole-based compounds having a molecular weight of 400 or more are preferable. registered trademark) 234 (manufactured by BASF).

Benzotriazine compounds include 2-mono(hydroxyphenyl)-1,3,5-triazine compounds, 2,4-bis(hydroxyphenyl)-1,3,5-triazine compounds, 2,4,6-tris (Hydroxyphenyl)-1,3,5-triazine compounds, specifically 2,4-diphenyl-6-(2-hydroxy-4-methoxyphenyl)-1,3,5-triazine, 2 ,4-diphenyl-6-(2-hydroxy-4-ethoxyphenyl)-1,3,5-triazine, 2,4-diphenyl-(2-hydroxy-4-propoxyphenyl)-1,3,5-triazine , 2,4-diphenyl-(2-hydroxy-4-butoxyphenyl)-1,3,5-triazine, 2,4-diphenyl-6-(2-hydroxy-4-butoxyphenyl)-1,3,5 -triazine, 2,4-diphenyl-6-(2-hydroxy-4-hexyloxyphenyl)-1,3,5-triazine, 2,4-diphenyl-6-(2-hydroxy-4-octyloxyphenyl) -1,3,5-triazine, 2,4-diphenyl-6-(2-hydroxy-4-dodecyloxyphenyl)-1,3,5-triazine, 2,4-diphenyl-6-(2-hydroxy- 4-benzyloxyphenyl)-1,3,5-triazine, 2,4-diphenyl-6-(2-hydroxy-4-butoxyethoxy)-1,3,5-triazine, 2,4-bis(2- hydroxy-4-butoxyphenyl)-6-(2,4-dibutoxyphenyl)-1,3-5-triazine, 2,4,6-tris(2-hydroxy-4-methoxyphenyl)-1,3, 5-triazine, 2,4,6-tris(2-hydroxy-4-ethoxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-4-propoxyphenyl)-1, 3,5-triazine, 2,4,6-tris(2-hydroxy-4-butoxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-4-butoxyphenyl)- 1,3,5-triazine, 2,4,6-tris(2-hydroxy-4-hexyloxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-4-octyl oxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-4-dodecyloxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy -4-benzyloxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-4-ethoxyethoxyphenyl)-1,3,5-triazine, 2,4,6-tris (2-hydroxy-4-butoxyethoxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-4-propoxyethoxyphenyl)-1,3,5-triazine, 2,4 ,6-tris(2-hydroxy-4-methoxycarbonylpropyloxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-4-ethoxycarbonylethyloxyphenyl)-1,3 ,5-triazine, 2,4,6-tris(2-hydroxy-4-(1-(2-ethoxyhexyloxy)-1-oxopropan-2-yloxy)phenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-3-methyl-4-methoxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-3-methyl-4-ethoxyphenyl )-1,3,5-triazine, 2,4,6-tris(2-hydroxy-3-methyl-4-propoxyphenyl)-1,3,5-triazine, 2,4,6-tris(2- hydroxy-3-methyl-4-butoxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-3-methyl-4-butoxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-3-methyl-4-hexyloxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-3-methyl-4-octyl oxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-3-methyl-4-dodecyloxyphenyl)-1,3,5-triazine, 2,4,6-tris (2-hydroxy-3-methyl-4-benzyloxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-3-methyl-4-ethoxyethoxyphenyl)-1,3 ,5-triazine, 2,4,6-tris(2-hydroxy-3-methyl-4-butoxyethoxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-3- methyl-4-propoxyethoxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-3-methyl-4-methoxycarbonylpropyloxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-3-methyl-4-ethoxycarbonylethyloxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-3-methyl-4 -(1-(2-ethoxyhexyloxy)-1-oxopropan-2-yloxy)phenyl)-1,3,5-triazine and the like.
As the benzotriazine-based compound, commercially available products may be used, for example, Kemisorb 102 (manufactured by Chemipro Kasei Co., Ltd.), LA-F70 (manufactured by ADEKA Corporation), LA-46 (manufactured by ADEKA Corporation), Tinuvin 405 (BASF Corporation). (manufactured by BASF), Tinuvin 460 (manufactured by BASF), Tinuvin 479 (manufactured by BASF), Tinuvin 1577FF (manufactured by BASF) and the like can be used.
Among them, 2,4-bis(2,4-dimethylphenyl)-6-[2-hydroxy-4-(3-alkyloxy -2-hydroxypropyloxy)-5-α-cumylphenyl]-s-triazine skeleton ("alkyloxy" means a long-chain alkyloxy group such as octyloxy, nonyloxy, decyloxy, etc.). It can be preferably used.

As the UV absorber, benzotriazole-based compounds and benzotriazine-based compounds having a molecular weight of 400 or more are preferable from the viewpoint of compatibility with resins and volatility when heated. Benzotriazine-based compounds are particularly preferred from the viewpoint of inhibiting decomposition by.

Further, the melting point (Tm) of the ultraviolet absorber is preferably 80° C. or higher, more preferably 100° C. or higher, still more preferably 130° C. or higher, and further preferably 160° C. or higher. more preferred.
The UV absorber preferably has a weight loss rate of 50% or less, more preferably 30% or less, and 15% or less when the temperature is increased from 23° C. to 260° C. at a rate of 20° C./min. is more preferably 10% or less, and even more preferably 5% or less.

These ultraviolet absorbers may be used alone or in combination of two or more.
By using two kinds of ultraviolet absorbers having different structures together, it is possible to absorb ultraviolet rays in a wide wavelength range.

The content of the ultraviolet absorber is not particularly limited as long as it does not impair heat resistance, moist heat resistance, thermal stability, and molding processability, and is an amount that exhibits the effects of the present invention. It is preferably 0.1 to 5 parts by mass, preferably 0.2 to 4 parts by mass or less, more preferably 0.25 to 3 parts by mass, and even more preferably 0.3 to 3 parts by mass. Within this range, the balance between ultraviolet absorption performance, moldability, and the like is excellent.

--Release agent--
The methacrylic resin composition of this embodiment can contain a release agent. Examples of the release agent include, but are not limited to, fatty acid esters, fatty acid amides, fatty acid metal salts, hydrocarbon-based lubricants, alcohol-based lubricants, polyalkylene glycols, carboxylic acid esters, carbonized Hydrogen-based paraffinic mineral oils and the like are included.

Fatty acid esters that can be used as the release agent are not particularly limited, and conventionally known ones can be used.
Examples of fatty acid esters include fatty acids having 12 to 32 carbon atoms such as lauric acid, palmitic acid, heptadecanoic acid, stearic acid, oleic acid, arachidic acid and behenic acid, and monovalent acids such as palmityl alcohol, stearyl alcohol and behenyl alcohol. Ester compounds with fatty alcohols and polyhydric fatty alcohols such as glycerin, pentaerythritol, dipentaerythritol and sorbitan; Complex esters of fatty acids, polybasic organic acids and monohydric fatty alcohols or polyhydric fatty alcohols A compound or the like can be used.
Examples of such fatty acid ester lubricants include cetyl palmitate, butyl stearate, stearyl stearate, stearyl citrate, glycerin monocaprylate, glycerin monocaprate, glycerin monolaurate, glycerin monopalmitate, glycerin dipalmi. Tate, Glycerin Monostearate, Glycerin Distearate, Glycerin Tristearate, Glycerin Monooleate, Glycerin Dioleate, Glycerin Trioleate, Glycerin Monolinoleate, Glycerin Monobehenate, Glycerin Mono 12-Hydroxystearate, Glycerin Di-12-hydroxystearate, glycerin tri-12-hydroxystearate, glycerin diacetomonostearate, glycerin citric acid fatty acid ester, pentaerythritol adipate stearate, montanic acid partially saponified ester, pentaerythritol tetrastearate, dipenta Erythritol hexastearate, sorbitan tristearate and the like can be mentioned.
These fatty acid ester-based lubricants can be used singly or in combination of two or more.
Examples of commercially available products include Rikemal series, Poem series, Rikester series, Rikemaster series manufactured by Riken Vitamin Co., Ltd., Excel series manufactured by Kao Corporation, Rheodor series, Exceparl series, Coconard series, and more specific examples. Rikemar S-100, Rikemar H-100, Poem V-100, Rikemar B-100, Rikemar HC-100, Rikemar S-200, Poem B-200, Rikester EW-200, Rikester EW-400, Excel S -95, Rheodol MS-50 and the like.

Fatty acid amide-based lubricants are also not particularly limited, and conventionally known ones can be used.
Examples of fatty acid amide lubricants include saturated fatty acid amides such as lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, and hydroxystearic acid amide; unsaturated fatty acid amides such as oleic acid amide, erucic acid amide, and ricinoleic acid amide. fatty acid amides; substituted amides such as N-stearyl stearamide, N-oleyl oleic acid amide, N-stearyl oleic acid amide, N-oleyl stearic acid amide, N-stearyl erucic acid amide, N-oleyl palmitic acid amide; methylol Methylolamides such as stearic acid amide and methylolbehenic acid amide; Bishydroxystearic acid amide, ethylenebisbehenic acid amide, hexamethylenebisstearic acid amide, hexamethylenebisbehenic acid amide, hexamethylenebishydroxystearic acid amide, N,N'-distearyladipic acid amide, N,N'- Saturated fatty acid bisamides such as distearylsebacamide; unsaturated fatty acids such as ethylenebisoleic acid amide, hexamethylenebisoleic acid amide, N,N'-dioleyladipate, and N,N'-dioleylsebacic acid amide Bisamides; aromatic bisamides such as m-xylylenebisstearic acid amide and N,N'-distearyl isophthalic acid amide.
These fatty acid amide release agents can be used singly or in combination of two or more.
Examples of commercially available products include Diamid series (manufactured by Nippon Kasei Co., Ltd.), Amide series (manufactured by Nippon Kasei Co., Ltd.), Nikka Amide series (manufactured by Nippon Kasei Co., Ltd.), Methylolamide series, Bisamide series, and Slipax series (Nippon Kasei Co., Ltd.). Co., Ltd.), Kaowax series (manufactured by Kao Corporation), fatty acid amide series (manufactured by Kao Corporation), ethylenebisstearate amides (manufactured by Dainichi Chemical Industry Co., Ltd.), and the like.

Fatty acid metal salts refer to metal salts of higher fatty acids, such as lithium stearate, magnesium stearate, calcium stearate, calcium laurate, calcium ricinoleate, strontium stearate, barium stearate, barium laurate, barium ricinoleate, zinc stearate, zinc laurate, zinc ricinoleate, zinc 2-ethylhexoate, lead stearate, dibasic lead stearate, lead naphthenate, calcium 12-hydroxystearate, lithium 12-hydroxystearate, Among these, calcium stearate, magnesium stearate, and zinc stearate are particularly preferred because the resulting transparent resin composition has excellent processability and extremely excellent transparency.
Examples of commercially available products include SZ series, SC series, SM series, SA series manufactured by Sakai Chemical Industry Co., Ltd., and the like.
When using the fatty acid metal salt, the content is preferably 0.2% by mass or less with respect to 100% by mass of the methacrylic resin composition from the viewpoint of maintaining transparency.

The release agents may be used singly or in combination of two or more.

The release agent to be used preferably has a decomposition initiation temperature of 200° C. or higher. Here, the decomposition initiation temperature can be measured by the 1% weight loss temperature by TGA.
The content of the release agent may be any amount as long as it is effective as a release agent. If the content is excessive, problems such as bleeding out during processing and extrusion failure due to screw slippage will occur. Therefore, it is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, still more preferably 1 part by mass or less, and still more preferably 0.8 parts by mass with respect to 100 parts by mass of the methacrylic resin. parts by mass or less, more preferably 0.01 to 0.8 parts by mass, and particularly preferably 0.01 to 0.5 parts by mass. When added in an amount within the above range, a decrease in transparency due to the addition of a release agent is suppressed, and mold release failure during injection molding and sticking to metal rolls during sheet molding tend to be suppressed. preferable.

-Other thermoplastic resins-
The methacrylic resin composition of the present embodiment may contain a thermoplastic resin other than the methacrylic resin for the purpose of adjusting the birefringence and improving flexibility without impairing the object of the present invention.
Other thermoplastic resins include, for example, polyacrylates such as polybutyl acrylate; polystyrene, styrene-methyl methacrylate copolymer, styrene-butyl acrylate copolymer, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene Styrene-based polymers such as block copolymers; etc., acrylic rubber particles having a three- to four-layer structure; JP-B-60-17406, a rubbery polymer disclosed in JP-A-8-245854; , methacrylic rubber-containing graft copolymer particles obtained by multistage polymerization;
Among these, from the viewpoint of obtaining good optical properties and mechanical properties, it is preferable to use a composition compatible with a styrene-acrylonitrile copolymer or a methacrylic resin containing a structural unit (X) having a ring structure in the main chain. A rubber-containing graft copolymer particle having a graft portion on its surface layer is preferred.
The average particle size of the acrylic rubber particles, the methacrylic rubber-containing graft copolymer particles, and the rubbery polymer mentioned above enhances the impact strength, optical properties, etc. of the molded article obtained from the composition of the present embodiment. From the point of view, it is preferably 0.03 to 1 μm, more preferably 0.05 to 0.5 μm.

The content of the other thermoplastic resin is preferably 0 to 50 parts by mass, more preferably 0 to 25 parts by mass, based on 100 parts by mass of the methacrylic resin.

(Method for producing methacrylic resin composition)
Examples of the method for producing the methacrylic resin composition include a method of kneading using a kneader such as an extruder, a heating roll, a kneader, a roller mixer, or a Banbury mixer. Among them, kneading by an extruder is preferable in terms of productivity. The kneading temperature may follow the preferred processing temperature of the polymer constituting the methacrylic resin and other resins to be mixed, and is generally in the range of 140 to 300.degree. Also, the extruder is preferably provided with a vent port for the purpose of reducing volatile matter.
The glass transition temperature (Tg), weight average molecular weight (Mw), number average molecular weight (Mn), orientation birefringence, and photoelastic coefficient _CR of the methacrylic resin composition are the same as those described above for the methacrylic resin. you can

(Molded body)
The molded article of the present embodiment may contain the methacrylic resin of the present embodiment, or may contain the methacrylic resin composition of the present embodiment.

(Method for manufacturing molded body)
Various molding methods such as extrusion molding, injection molding, compression molding, calender molding, inflation molding, and blow molding can be used as the method for producing the molded article of the present embodiment. Among them, it is preferable to apply injection molding and injection compression molding from the viewpoint of productivity.
In general, the injection molding method consists of (1) an injection process in which the resin is melted and filled into the temperature-controlled cavity of the mold, and (2) pressure is applied to the cavity until the gate is sealed, and the injection process fills the cavity. (3) A cooling process in which the molded product is held until the resin is cooled after releasing the holding pressure, ( 4) It consists of opening the mold and removing the cooled part.

At this time, the molding temperature is preferably in the range of Tg+100° C. to Tg+160° C., preferably Tg+110° C. to Tg+150° C., based on the glass transition temperature of the methacrylic resin composition. Here, the molding temperature refers to the controlled temperature of the band heater wound around the injection nozzle.
The mold temperature is in the range of Tg-70°C to Tg, preferably in the range of Tg-50°C to Tg-20°C, based on the glass transition temperature (Tg) of the methacrylic resin composition. preferable.

Also, the injection speed can be appropriately selected depending on the thickness and dimensions of the injection molded article to be obtained, and can be appropriately selected, for example, from the range of 200 to 1000 mm/sec.
Further, the pressure for holding pressure can be appropriately selected depending on the shape of the injection molded article to be obtained, and can be appropriately selected within the range of, for example, 30 to 120 MPa. In the case of a thin molded body with a high solidification speed, there is a case where no holding pressure is applied.
Here, the pressure for holding pressure is the pressure held by the screw for further sending out the molten resin from the gate after the molten resin is filled.

Injection compression molding involves opening the mold slightly at the start of injection molding and filling the mold with molten resin at high speed and low pressure. It is an injection molding method in which a compression and holding pressure step is added, and it is possible to mold a molded product with excellent surface characteristics and optical characteristics.
When it is desired to obtain a thinner injection-molded article, for example, a thickness of less than 1 mm and a diagonal dimension of more than 100 mm, injection compression molding is employed to obtain a molded article having excellent optical characteristics and color tone. It is particularly preferred because it can be obtained.

In addition, when the injection-molded article obtained using the methacrylic resin composition of the present embodiment is used as a light guide plate, the article may have fine irregularities formed on its surface. By providing such fine unevenness, it is preferable that there is no need to separately provide a reflective layer by printing or the like. Fine unevenness is not particularly limited, but unevenness with clear structural units such as cuboids, cylinders, elliptical cylinders, triangular prisms, spherical surfaces, and aspherical surfaces, and uneven shapes such as satin-like and hairline-like shapes. Concavities and convexities whose structural units are unclear or a combination thereof, and concavities and convexities whose structural units are clear but whose shapes, particularly sizes, are varied. As for the shape of the unevenness, the height of the shape or the concave portion is 0.1 to 500 μm, and the pitch distance between the unevenness is 10 to 1000 μm.

Surface functions such as hard coat treatment, anti-glare treatment, anti-reflection treatment, transparent conductive treatment, electromagnetic wave shielding treatment, gas barrier treatment, etc. are applied to the surface of various molded products using the methacrylic resin of the present embodiment and its resin composition. Further processing can be performed.
Although the thickness of these functional layers is not particularly limited, it is usually used in the range of 0.01 to 10 μm.

When hard coating is applied to the surface of the molded product, examples of the hard coating layer to be applied to the surface include silicone-based curable resins, organic polymer composite inorganic fine particle-containing curable resins, urethane acrylates, epoxy acrylates, polyfunctional acrylates, and the like. A coating liquid obtained by dissolving or dispersing the acrylate and the photopolymerization initiator in an organic solvent is applied to the film or sheet obtained from the methacrylic resin composition of the present embodiment by a conventionally known coating method, and dried. It is formed by applying and photocuring.
In addition, before applying the hard coat layer, in order to improve the adhesiveness, for example, a method of forming the hard coat layer after previously providing an easy adhesion layer, a primer layer, an anchor layer, etc. containing inorganic fine particles in its composition. can also be used.
The anti-glare layer to be applied to the surface is formed by forming an ink from fine particles of silica, melamine resin, acrylic resin, etc., applying the ink onto another functional layer by a conventionally known coating method, and curing the ink with heat or light. Let
The antireflection layer to be applied to the surface includes thin films of inorganic substances such as metal oxides, fluorides, silicides, borides, nitrides and sulfides, and resins having different refractive indices such as acrylic resins and fluorine resins. can be exemplified by lamination of a single layer or multiple layers, and a lamination of thin layers containing fine composite particles of an inorganic compound and an organic compound can also be used.

(Characteristics of compact)
The characteristics of the molded article of this embodiment are described below.

In the molded body of the present embodiment, the average value of the absolute values of the in-plane retardation (Re) of the molded body is preferably 5.0 nm or less, more preferably 4.0 nm or less per 1 mm of thickness. more preferably 3.0 nm or less, and still more preferably 1.5 nm or less.
In addition, the standard deviation of the absolute value of the in-plane retardation (Re) of the molded body is preferably 2.0 nm or less, more preferably 1.5 nm or less, and still more preferably 1.0 nm or less per 1 mm of thickness. 0 nm or less.
The in-plane retardation of the molded article can be measured by the method described in Examples below.

The thickness of the molded article of the present embodiment is preferably 1.5 mm or less, more preferably 1.2 mm or less, and even more preferably 1.0 mm or less.

(Application of compact)
A molded article made of the methacrylic resin composition of the present invention can be suitably used for applications such as optical parts in household goods, OA equipment, AV equipment, battery electrical components, lighting equipment, automobile parts, and the like.
Optical parts in household goods, OA equipment, AV equipment, battery electrical components, lighting equipment, etc. include, for example, smartphones, PDAs, tablet PCs, light guide plates used in displays such as liquid crystal televisions, display front plates, touch panels, and more. Lenses for smartphones, tablet PC cameras, etc., optical lens parts for head-mounted displays, liquid crystal projectors, etc., such as prism elements, waveguides, lenses, especially small thin and uneven thickness optical lenses, optical fibers, optical fiber coating materials , lenses, Fresnel lenses, phase plates with microlens arrays, optical cover components, and the like.
Optical parts for automobile parts include light guide plates for in-vehicle displays; in-vehicle meter panels; car navigation front panels, combiners, optical cover parts and other optical parts for head-up displays; in-vehicle camera lenses, light guide bars, etc. be done.
In addition to the above, it can also be used as parts for digital signage display devices that transmit information to thin displays connected to networks for the purpose of publicity, advertising, etc., in places such as camera focal plates, outdoors, stores, public institutions, and transportation facilities. It can be preferably used.

EXAMPLES The content of the present invention will be specifically described below with reference to examples , reference examples , and comparative examples. In addition, the present invention is not limited to the following examples.

<1. Measurement of polymerization conversion>
A part of the polymerization liquid in Examples , Reference Examples and Comparative Examples was sampled, and the amount of monomer remaining in this polymerization liquid sample was dissolved in chloroform to prepare a 5% by mass solution, and an internal standard Add n-decane as a substance, using gas chromatography (Shimadzu Corporation GC-2010), to measure the concentration of the monomers remaining in the sample, the total mass of the monomers remaining in the polymerization solution ( a) was sought. Then, from this total mass (a) and the total mass (b) when it is assumed that the total amount of the added monomers remained in the polymerization solution by the time the sample was collected, the calculation formula (ba)/ The polymerization conversion rate (%) was calculated from b×100.

<2. Analysis of Structural Units>
Unless otherwise specified in each example and reference example described later, the structural unit of the produced methacrylic resin was identified by ¹ H-NMR measurement and ¹³ C-NMR measurement, and the abundance was calculated. The measurement conditions for ¹ H-NMR measurement and ¹³ C-NMR measurement are as follows.
・Measurement equipment: DPX-400 manufactured by Bruker
・Measurement solvent: CDCl ₃ or DMSO-d ₆
・Measurement temperature: 40°C
When the ring structure of the methacrylic resin is a lactone ring structure, it was confirmed by the methods described in JP-A-2001-151814 and JP-A-2007-297620.

<3. Measurement of molecular weight and molecular weight distribution>
The weight-average molecular weight (Mw) and number-average molecular weight (Mn) of the methacrylic resins produced in Examples, Reference Examples, and Comparative Examples described below were measured using the following equipment and conditions.
・ Measuring device: Gel permeation chromatography (HLC-8320GPC) manufactured by Tosoh Corporation
·Measurement condition:
Columns: One TSKguard column SuperH-H, two TSKgel SuperHM-M, and one TSKgel SuperH2500 were connected in series and used. Column temperature: 40°C
Developing solvent: tetrahydrofuran, flow rate: 0.6 mL/min, 0.1 g/L of 2,6-di-t-butyl-4-methylphenol (BHT) was added as an internal standard.
Detector: RI (differential refraction) detector, detection sensitivity: 3.0 mV/min Sample: 0.02 g of methacrylic resin or tetrahydrofuran solution of methacrylic resin in 20 mL. Injection volume: 10 μL
Standard sample for calibration curve: The following 10 types of polymethyl methacrylate (manufactured by Polymer Laboratories; PMMACalibration Kit MM-10) with known monodisperse weight peak molecular weights and different molecular weights were used.
Weight peak molecular weight (Mp)
Standard sample 1 1,916,000
Standard sample 2 625,500
Standard sample 3 298,900
Standard sample 4 138,600
Standard sample 5 60,150
Standard sample 6 27,600
Standard sample 7 10,290
Standard sample 8 5,000
Standard sample 9 2,810
Standard sample 10 850
Under the above conditions, the RI detection intensity was measured with respect to the elution time of the methacrylic resin.
The weight average molecular weight (Mw) and number average molecular weight (Mn) of the methacrylic resin were obtained based on the calibration curve obtained by measuring the standard sample for calibration curve.

<4. Glass transition temperature>
The glass transition temperature (Tg) (°C) of the methacrylic resin was measured according to JIS-K7121.
First, from a sample that had been conditioned under standard conditions (23° C., 65% RH) (left at 23° C. for 1 week), 4 points (4 locations) were cut out of about 10 mg each as test pieces.
Next, a differential scanning calorimeter (Diamond DSC manufactured by PerkinElmer Japan Co., Ltd.) was used under the condition of a nitrogen gas flow rate of 25 mL / min, where the temperature was raised from room temperature (23 ° C.) to 200 ° C. at 10 ° C. / min. After heating (primary temperature rise) and holding at 200 ° C. for 5 minutes to completely melt the sample, the temperature was lowered from 200 ° C. to 40 ° C. at 10 ° C./min, held at 40 ° C. for 5 minutes, and further , Among the DSC curves drawn during the temperature increase (secondary temperature increase) under the above temperature increase conditions, the stepwise change partial curve at the time of the secondary temperature increase and the extension line of each baseline are equidistant in the vertical axis direction The point of intersection with a straight line (midpoint glass transition temperature) was measured as the glass transition temperature (Tg) (°C). Measurement was performed at 4 points per sample, and the arithmetic average of the 4 points (rounded off to the nearest whole number) was used as the measured value.

<5. Measurement of Composition Distribution of Structural Units>
The methacrylic resins obtained in Examples , Reference Examples and Comparative Examples were subjected to molecular weight fractionation using the following equipment and conditions.
・Preparation device: LC-908 manufactured by Nippon Analytical Industry Co., Ltd.
・Preparation conditions:
Column: SHODEX K-2004
Eluent: chloroform, flow rate: 3 mL/min Detector: UV detector (254 nm)
Sample: 3% by mass chloroform solution 3 mL of sample was injected and fractionated at 1-minute intervals from 18 to 43 minutes of elution time.
The fractionation operation was repeated three times, and fractions with the same elution time were pooled together.
For each sample selected from the obtained fractions, the above <2. Analysis of Structural Units>, the composition ratio of each structural unit was obtained. Further, regarding each of the above samples, the aforementioned <3. The molecular weight distribution of the methacrylic resin was measured according to Measurement of Molecular Weight and Molecular Weight Distribution>, and the peak top molecular weight (Mp) was obtained from the position of the peak apex of the molecular weight distribution curve.

本実施例及び参考例では、メタクリル酸メチル単位中のＣＨ_２の横揺れ振動に対応する波数７５０ｃｍ^－１の吸収を用い、αを１７°として求めた。
配向複屈折の測定は、王子計測機器製ＫＯＢＲＡ－ＷＲを用いて波長５８７ｎｍで求めた。
複屈折Δｎは次式のように定義される。
Δｎ＝ｎｘ－ｎｙ ・・・（ａ）
（ｎｘは伸長方向の屈折率、ｎｙは伸長方向と垂直方向の屈折率）
配向複屈折Δｎ^ｏｒは次式のように表される。
Δｎ^ｏｒ＝ｆ×Δｎ^０ ・・・（ｂ）
（Δｎ^０は固有複屈折、配向度はｆ） <6. Measurement of orientation birefringence>
The methacrylic resins obtained in Examples , Reference Examples , and Comparative Examples were first formed into press films using a vacuum compression molding machine to prepare unstretched samples.
As a specific sample preparation condition, a methacrylic resin was placed in a polyimide frame with a thickness of 150 μm, sandwiched between two polyimide films and two iron plates, and a vacuum compression molding machine (manufactured by Shindo Kinzoku Kogyosho, SFV-30 type), preheated at 260 ° C. under reduced pressure (about 10 kPa) for 10 minutes, then compressed at 260 ° C. and about 10 MPa for 5 minutes, released the reduced pressure and press pressure, and cooled compression molding machine and cooled to solidify.
The obtained press film was aged for 24 hours or more in a constant temperature and humidity room adjusted to 23° C. and humidity of 60% to obtain an unstretched sample.
The unstretched sample was cut into a thickness of 40 mm and a length of 60 mm to obtain a test piece for measurement. After uniaxial free stretching with a distance of 40 mm, a stretching temperature of Tg + 20 ° C., and a stretching speed of 500 mm / min, it was immediately taken out to room temperature and cooled, and then placed in a constant temperature and humidity room adjusted to 23 ° C. and humidity of 60% for 24 hours. A stretched film was produced by curing.
Several films were prepared at a draw ratio of 100% and 300%, respectively, and the degree of orientation was measured by the infrared dichroic ratio described later, and the orientation birefringence was measured. The orientation birefringence was determined.
The degree of orientation was determined by an infrared dichroic ratio by a transmission method using an infrared spectrometer Tensor27 manufactured by Bruker.
The measurement was performed with a wavelength resolution of 2 cm ⁻¹ and 16 integration times. Infrared light polarized in the horizontal direction and the vertical direction with respect to the stretching direction of the stretched film was irradiated through a polarizing filter, and the absorbance thereof was measured to obtain _A∥ and _A⊥ , respectively.
The infrared dichroic ratio D is represented by the following formula.
D= _A / A _⊥ (c)
Assuming that the angle formed by the direction of the vibrational transition moment regarding the absorption of the functional group of interest and the orientation direction or elongation direction of the main chain is α, the degree of orientation f is expressed by the following formula.

In this example and reference example , absorption at a wavenumber of 750 cm ⁻¹ corresponding to the rolling vibration of CH ₂ in methyl methacrylate units was used, and α was determined as 17°.
The orientation birefringence was measured at a wavelength of 587 nm using KOBRA-WR manufactured by Oji Scientific Instruments.
Birefringence Δn is defined as follows.
Δn=nx−ny (a)
(nx is the refractive index in the stretching direction, ny is the refractive index in the stretching direction and the vertical direction)
Orientation birefringence Δn ^or is expressed by the following equation.
Δn ^or =f×Δn ⁰ (b)
(Δn ⁰ is intrinsic birefringence, degree of orientation is f)

<7. Measurement of photoelastic coefficient _CR >
The above <6. Measurement of Orientation Birefringence> Using a film-shaped test piece obtained by cutting the unstretched sample to a width of 6 mm, using a birefringence measuring apparatus described in detail in Polymer Engineering and Science 1999, 39, 2349-2357 , the photoelastic coefficient C _R (Pa ⁻¹ ) was measured.
A film-shaped test piece was similarly placed in a film tensioning device (manufactured by Imoto Seisakusho) installed in a constant temperature and humidity chamber with a chuck distance of 50 mm. Next, the birefringence measuring device (RETS-100, manufactured by Otsuka Electronics Co., Ltd.) was placed so that the optical path of the device was positioned at the center of the film. The birefringence of the test piece was measured at a wavelength of 550 nm while applying .
From the relationship between the birefringence (Δn) and the tensile stress (σ _R ) obtained from the measurement, the slope of the straight line was determined by least squares approximation, and the photoelastic coefficient (C _R ) (Pa ⁻¹ ) was calculated. For the calculation, the data when the tensile stress is between 2.5 MPa≦σ _R ≦10 MPa was used.
C _R =Δn/σ _R
Here, the birefringence (Δn) is the value shown below.
Δn=nx−ny
(nx: refractive index in the stretching direction, ny: refractive index in the direction perpendicular to the stretching direction in the plane)

<8. Phase difference measurement in the in-plane direction of an injection molded piece>
Using the methacrylic resins obtained in Examples 1 to 7 and Comparative Examples 1 and 2, an injection molding machine (AUTO SHOT C Series MODEL 15A, manufactured by FANUC Co., Ltd.) has a fan gate as shown in FIG. Injection molding was performed using a flat plate mold having a thickness of 1 mm, a width of 60 mm, and a length of 45 mm.
FIG. 1(A) shows a plan view of the flat plate mold, and FIG. 1(B) shows a cross-sectional view of the flat plate mold in FIG. 1(A) taken along line AA.
First, the cylinder temperature is 270°C, the mold temperature is 90°C, the cooling time is 20 seconds, the injection screw speed is 50 mm/s, and the holding pressure is 0 kgf/ ^cm2 . The lowest injection pressure (short shot point, SSP) at which is completely filled was determined. Next, by injection molding with the injection pressure set to SSP+50 kgf/cm ² , a flat plate molded piece for in-plane retardation measurement was obtained.
The in-plane retardation distribution of the obtained flat plate molded piece was measured at a wavelength of 520 nm using PA-200-L manufactured by Photonic Lattice. The in-plane retardation distribution measurement is performed by observing a region of width 55 mm × length 40 mm in the center of the plate (shaded area in FIG. 1) from above, and the average value of the absolute values of the in-plane retardation (Re) in the region And the standard deviation was obtained as an index for evaluation.

<9. Measurement of color tone of molded piece>
The methacrylic resins obtained in Examples , Reference Examples , and Comparative Examples were molded using an injection molding machine (AUTO SHOT C Series MODEL 15A, manufactured by FANUC Co., Ltd.) at a molding temperature of 250°C and a mold temperature of 90°C. , a strip-shaped test piece having a thickness of 4 mm, a width of 10 mm, and a length of 80 mm was prepared.
The mold was mirror-finished, and the end face on the short side had a slide core structure with no draft.
Using a color difference meter (manufactured by Nippon Denshoku Industries Co., Ltd., ASA-1), the obtained test piece was measured for YI at a C light source of 2° and an optical path length of 80 mm.

<10. Color Reproducibility of Simulated Light Guide Unit>
The methacrylic resins obtained in Examples , Reference Examples , and Comparative Examples were subjected to injection press molding using an injection molding machine with a mold clamping force of 50 tons at a molding temperature of 270°C and a mold temperature of 90°C. A light guide plate having a thickness of 0.6 mm, a width of 115 mm, a length of 80 mm, and a dot shape formed on the lower surface at a pitch of 100 to 300 μm was produced. A simulated light guide unit in which light is emitted to the upper surface was fabricated by installing a light source on the end face on the long side and further by installing a reflective sheet under the lower surface of the light guide plate. Using a spectral radiance meter, the chromaticity x and y of the emitted light at a position of 5 mm from the end face on the light source side and a position of 75 mm (that is, a position of 5 mm from the end face on the opposite side to the end face where the light source is installed) Δx and Δy were obtained by subtracting the value at the position of 5 mm from the value at the position of 75 mm. It can be said that the smaller the values of Δx and Δy, the smaller the color deviation and the higher the color tone reproducibility.

[material]
Raw materials used in production examples , production reference examples , and production comparative examples, which will be described later, are shown below.
[[monomer]]
・Methyl methacrylate: manufactured by Asahi Kasei Corporation ・N-Phenylmaleimide (phMI): manufactured by Nippon Shokubai Co., Ltd. ・N-Cyclohexylmaleimide (chMI): manufactured by Nippon Shokubai Co., Ltd. [[polymerization initiator]]
・ 1,1-di (t-butylperoxy) cyclohexane: "Perhexa C" manufactured by NOF Corporation
[[chain transfer agent]]
・ n-octyl mercaptan: manufactured by Kao Corporation [[Antioxidant]]
・ Pentaerythritol = tetrakis [3-(3',5'-di-tert-butyl-4'-hydroxyphenyl) propionate]: BASF "Irganox1010"
- Tris (2,4-di-t-butylphenyl) phosphite: "Irgafos168" manufactured by BASF

[Example 1]
358.6 kg of methyl methacrylate (hereinafter referred to as MMA), 29.4 kg of N-phenylmaleimide (hereinafter referred to as phMI), 67.7 kg of N-cyclohexylmaleimide (hereinafter referred to as chMI), and n-octyl mercaptan as a chain transfer agent. 0.77 kg and 224.3 kg of meta-xylene (hereinafter referred to as mXy) were weighed and added to a 1.25 m ³ reactor equipped with a jacket temperature control device and stirring blades and stirred to obtain a mixed monomer solution.
Then, 88.0 kg of MMA, 6.3 kg of phMI and 142.4 kg of mXy were weighed and added to tank 1 and stirred to obtain a mixed monomer solution for addition.
The contents of the reactor were bubbled with nitrogen at a rate of 30 L/min for 1 hour, and the tank 1 was bubbled with nitrogen at a rate of 10 L/min for 30 minutes to remove dissolved oxygen.
After that, steam was blown into the jacket to raise the temperature of the solution in the reactor to 115° C., and while stirring at 50 rpm, 0.470 kg of 1,1-di(t-butylperoxy)cyclohexane was dissolved in 1.905 kg of mXy. Polymerization was initiated by adding the polymerization initiator solution obtained at a rate of 1.0 kg/hour.
During the polymerization, the temperature of the solution in the reactor was controlled at 115±2° C. by adjusting the temperature with a jacket. Thirty minutes after the start of the polymerization, the initiator solution addition rate was reduced to 0.5 kg/h.
Further, the total amount of the additional mixed monomer solution was added from tank 1 at a constant speed over 4 hours from 1 hour after the initiation of polymerization.
Furthermore, the addition rate of the initiator solution was reduced to 0.25 kg/hour after 3.5 hours from the start of polymerization, and the addition was stopped after 5 hours from the start of polymerization.
After 12 hours had passed since the initiation of polymerization, a polymer solution containing a methacrylic resin having a ring structure in the main chain was obtained to complete the polymerization.
After 2 hours and 12 hours from the initiation of polymerization, the polymer solution was sampled, respectively, and the polymerization conversion rate was analyzed from the concentration of the remaining monomers. , phMI 77.3%, chMI 70.4%, and the polymerization conversion rate after 12 hours was MMA 97.9%, phMI 99.4%, chMI 99.2%. Considering the monomers added after 2 hours from the start of polymerization, the polymerization conversion rate after 2 hours was converted into the consumption rate with respect to the total amount of each monomer added by the end of the polymerization, MMA 67.2%, pHMI 67. .1%, chMI 70.4%.
This polymer solution was devolatilized by supplying it to a concentrating device consisting of a tubular heat exchanger preheated to 250° C. and a vaporization tank. The degree of vacuum in the vaporization tank was set to 10 to 15 Torr. The resin flowing down the vaporization tank was discharged by a gear pump, extruded from a strand die, cooled with water, and pelletized to obtain a methacrylic resin.
When the composition of the obtained pellet-shaped polymer was confirmed, the structural units derived from MMA, phMI, and chMI monomers were 81.0% by mass, 6.6% by mass, and 12.4% by mass, respectively. there were. Moreover, the weight average molecular weight was 108,000 and Mw/Mn was 2.04.
Other physical properties are shown in Table 1.

[Example 2]
The amount of MMA added to the reactor was changed to 357.0 kg, the amount of phMI to 30.1 kg, and the amount of chMI to 68.9 kg, and the amount of MMA added to tank 1 was changed to 87.6 kg and the amount of phMI to 6.4 kg. A methacrylic resin was obtained in the same manner as in Example 1 except for the above. Table 1 shows the physical properties obtained.

[Example 3]
Change the amount of MMA added to the reactor to 355.4 kg, the amount of phMI to 30.8 kg, the amount of chMI to 70.1 kg, the amount of MMA added to tank 1 to 87.2 kg, and the amount of phMI to 6.5 kg, Furthermore, 0.550 kg of Irganox 1010 and 0.825 kg of Irgafos 168 were added as antioxidants before devolatilization, and a methacrylic resin was obtained in the same manner as in Example 1, except that they were stirred and mixed. Table 1 shows the physical properties obtained.

[Example 4]
Change the amount of MMA added to the reactor to 353.8 kg, the amount of phMI to 31.5 kg, the amount of chMI to 70.3 kg, the amount of MMA added to tank 1 to 86.8 kg, and the amount of phMI to 6.6 kg, Furthermore, 0.550 kg of Irganox 1010 and 0.825 kg of Irgafos 168 were added as antioxidants before devolatilization, and a methacrylic resin was obtained in the same manner as in Example 1, except that they were stirred and mixed. Table 1 shows the physical properties obtained.

[Example 5]
A methacrylic resin was obtained in the same manner as in Example 2, except that 0.41 kg of n-octylmercaptan was added to the reactor. Table 1 shows the physical properties obtained.

[Example 6]
A methacrylic resin was obtained in the same manner as in Example 1 except that the amount of phMI added to the reactor was changed to 28.2 kg and the amount of phMI added to tank 1 was changed to 7.5 kg.
The polymer solution was sampled 2 hours and 12 hours after the start of polymerization, and the polymerization conversion rate was analyzed from the concentration of the remaining monomers. , phMI 77.0%, chMI 70.6%, and the polymerization conversion rate after 12 hours was MMA 97.8%, phMI 99.3%, chMI 99.1%. Considering the monomers added after 2 hours from the start of the polymerization, the polymerization conversion rate after 2 hours was converted into the consumption rate for the total amount of each monomer added by the end of the polymerization, MMA 67.3%, pHMI 64 .9% and chMI 70.6%.
Other physical properties are shown in Table 1.

[Example 7]
A methacrylic resin was obtained in the same manner as in Example 1 except that the amount of phMI added to the reactor was changed to 27.2 kg and the amount of phMI added to tank 1 was changed to 8.5 kg.
After 2 hours and 12 hours from the initiation of polymerization, the polymer solution was sampled, respectively, and the polymerization conversion rate was analyzed from the concentration of the remaining monomers. , phMI 77.2%, chMI 70.7%, and the polymerization conversion rate after 12 hours was MMA 97.9%, phMI 99.3%, chMI 99.2%. Considering the monomers added after 2 hours from the start of polymerization, the polymerization conversion rate after 2 hours was converted into the consumption rate with respect to the total amount of each monomer added by the end of the polymerization, MMA 67.2%, pHMI 63. .4% and chMI 70.7%.
Other physical properties are shown in Table 1.

[ Reference Example 8]
40 parts by mass of MMA, 60 parts by mass of mXy, and 0.08 parts by mass of n-octyl mercaptan, which is a chain transfer agent, were charged into a reactor equipped with a temperature control device using a jacket and stirring blades, and bubbled with nitrogen for 1 hour to dissolve. Oxygen was removed. After that, steam is blown into the jacket to raise the solution temperature in the reactor to 120° C., and while stirring at 50 rpm, 0.02 parts by mass of 1,1-di(t-butylperoxy)cyclohexane is added to 0.10 parts by mass of mXy. Polymerization was carried out by adding a polymerization initiator solution dissolved in the solution at a constant rate for 5 hours, followed by aging at 120° C. for 3 hours. rice field. After the polymerization was completed, the liquid temperature was lowered to 50°C.
Next, a mixed liquid consisting of 12 parts by mass of monomethylamine and 12 parts by mass of methanol was added dropwise into the reactor at room temperature, the liquid temperature was raised to 170°C, and the mixture was stirred under pressure for 1 hour to proceed with the glutarimide cyclization reaction. let me The liquid temperature was lowered to 120° C., the pressure in the reactor was reduced, unreacted monomethylamine and methanol, and a part of mXy were distilled off to obtain an approximately 50 mass % mXy solution of the glutarimide cyclized methacrylic polymer. Obtained.
This polymer solution was devolatilized by supplying it to a concentrating device consisting of a tubular heat exchanger preheated to 250° C. and a vaporization tank. The degree of vacuum in the vaporization tank was set to 10 to 15 Torr. The resin flowing down the vaporization tank was discharged by a gear pump, extruded from a strand die, cooled with water, and pelletized to obtain a methacrylic resin.
When the composition of the obtained methacrylic resin composition was checked, the amount of glutarimide structural units was 5.2% by mass. Moreover, the weight average molecular weight was 93,000 and Mw/Mn was 1.79.
Other physical properties are shown in Table 1.

[Comparative Example 1]
440.0 kg of MMA, 37.0 kg of phMI, 73.0 kg of chMI, 1.12 kg of n-octyl mercaptan as a chain transfer agent, and 450 kg of mXy were weighed and added to a 1.25 ^m3 reactor equipped with a jacket temperature control device and stirring blades. It was stirred to obtain a mixed monomer solution.
The solution in the reactor was bubbled with nitrogen at a rate of 30 L/min for 1 hour to remove dissolved oxygen. After that, steam was blown into the jacket to raise the temperature of the solution in the reactor to 125° C., and while stirring at 50 rpm, 0.231 kg of 1,1-di(t-butylperoxy)cyclohexane was dissolved in 5.769 kg of mXy. The polymerization initiator solution was added at a rate of 1 kg/hour for 6 hours to initiate polymerization.
During the polymerization, the temperature of the solution in the reactor was controlled at 125±2° C. by adjusting the temperature with a jacket. Eight hours after the initiation of polymerization, a polymerization solution containing a methacrylic resin having a ring structure in its main chain was obtained. After 2.5 hours, 4 hours, and 8 hours (at the end of polymerization) of polymerization initiation, the polymer solution was sampled, and the polymerization conversion rate was analyzed from the remaining monomer concentration. The polymerization conversion rate after 5 hours was MMA 68.2%, phMI 66.1%, chMI 54.1%, and the polymerization conversion rate after 4 hours was MMA 83.8%, phMI 81.5%, chMI 71.3%. After 8 hours, the polymerization conversion was MMA 95.9%, phMI 96.8%, and chMI 93.3%.
This polymer solution was devolatilized by supplying it to a concentrating apparatus consisting of a tubular heat exchanger preheated to 250° C. and a vaporization tank. The degree of vacuum in the vaporization tank was set to 10 to 15 Torr. The resin flowing down the vaporization tank was discharged by a gear pump, extruded through a strand die, cooled with water, and pelletized to obtain a methacrylic resin.
When the composition of the obtained pellet-shaped polymer was confirmed, the structural units derived from MMA, phMI, and chMI monomers were 80.2% by mass, 6.8% by mass, and 13.0% by mass, respectively. there were. Moreover, the weight average molecular weight was 131,000 and Mw/Mn was 2.26.
Other physical properties are shown in Table 1.

[Comparative Example 2]
335.5 kg of MMA, 37.4 kg of phMI, 67.1 kg of chMI, 0.30 kg of n-octyl mercaptan as a chain transfer agent, and 236.9 kg of mXy were weighed, and a 1.25 m ³ reactor equipped with a jacket temperature control device and stirring blades. and stirred to obtain a mixed monomer solution.
Next, 123.1 kg of mXy was weighed to prepare tank 1 for additional solvent.
Further, 110.0 kg of MMA and 90.0 kg of mXy were weighed into tank 2 and stirred to obtain an additional MMA solution.
The contents of the reactor were bubbled with nitrogen at a rate of 30 L/min for 1 hour, and the tanks 1 and 2 were bubbled with nitrogen at a rate of 10 L/min for 30 minutes to remove dissolved oxygen.
After that, steam was blown into the jacket to raise the temperature of the solution in the reactor to 123° C., and while stirring at 50 rpm, 0.481 kg of 1,1-di(t-butylperoxy)cyclohexane was dissolved in 2.644 kg of mXy. Polymerization was initiated by adding the polymerization initiator solution obtained at a rate of 1.0 kg/hour.
During the polymerization, the temperature of the solution in the reactor was controlled at 123±2° C. by adjusting the temperature with a jacket. Thirty minutes after the start of the polymerization, the initiator solution addition rate was reduced to 0.25 kg/h. Furthermore, over 3.5 hours from 30 minutes after the start of polymerization, the total amount of the additive solvent was added from tank 1 at a constant rate.
Then, 4 hours after the initiation of the polymerization, the addition rate of the initiator solution was increased to 0.75 kg/hour, and the entire amount of the additional MMA solution was added from tank 2 at a constant rate for 2 hours.
Furthermore, 6 hours after the initiation of polymerization, the addition rate of the initiator solution was reduced to 0.25 kg/hour, and 7 hours after the initiation of polymerization, the addition was stopped.
After 8 hours had passed since the initiation of the polymerization, a polymer solution containing a methacrylic resin was obtained to complete the polymerization.
After 2.5 hours and 8 hours from the start of polymerization, the polymer solution was sampled, and the polymerization conversion rate was analyzed from the concentration of the remaining monomer. .5%, phMI 80.1%, chMI 71.9%, and the polymerization conversion rate after 8 hours was MMA 92.0%, phMI 99.1%, chMI 97.8%. Taking into account the monomers added after 2.5 hours from the start of the polymerization, the polymerization conversion rate after 2.5 hours was converted into a consumption rate with respect to the total amount of each monomer added until the end of the polymerization, resulting in MMA62. 9%, phMI 80.1%, chMI 71.9%.
This polymer solution was devolatilized by supplying it to a concentrating device consisting of a tubular heat exchanger preheated to 250° C. and a vaporization tank. The degree of vacuum in the vaporization tank was set to 10 to 15 Torr. The resin flowing down the vaporization tank was discharged by a gear pump, extruded from a strand die, cooled with water, and pelletized to obtain a methacrylic resin.
When the composition of the obtained pellet-shaped polymer was confirmed, the structural units derived from MMA, phMI, and chMI monomers were 80.0% by mass, 7.2% by mass, and 12.8% by mass, respectively. there were. Moreover, the weight average molecular weight was 137,000 and Mw/Mn was 2.32.
Other physical properties are shown in Table 1.

[Comparative Example 3]
141.2 kg of MMA, 14.6 kg of phMI, 27.5 kg of chMI, 0.174 kg of n-octyl mercaptan as a chain transfer agent, and 147.0 kg of mXy were weighed, and a 1.25 m ³ reactor equipped with a jacket temperature control device and stirring blades. and stirred to obtain a mixed monomer solution.
Next, 262.3 kg of MMA, 27.1 kg of phMI, 51.1 kg of chMI and 273.0 kg of mXy were weighed and added to tank 1 and stirred to obtain a mixed monomer solution for addition.
In addition, 56.1 kg of MMA was weighed into Tank 2.
The contents of the reactor are bubbled with nitrogen at a rate of 30 L/min for 1 hour, and each of tanks 1 and 2 is bubbled with nitrogen at a rate of 10 L/min for 30 minutes to remove dissolved oxygen. bottom.
After that, steam was blown into the jacket to raise the temperature of the solution in the reactor to 124° C., and while stirring at 50 rpm, 0.348 kg of 1,1-di(t-butylperoxy)cyclohexane was dissolved in 4.652 kg of mXy. Polymerization was initiated by adding the polymerization initiator solution obtained at a rate of 2 kg/hour.
During the polymerization, the temperature of the solution in the reactor was controlled at 124±2° C. by adjusting the temperature with a jacket. Thirty minutes after the initiation of the polymerization, the addition rate of the initiator solution was reduced to 1 kg/hour, and the mixed monomer solution for addition was added from tank 1 at 306.8 kg/hour for 2 hours.
Then, 2 hours and 45 minutes after the initiation of polymerization, the entire amount of MMA was added from tank 2 at a rate of 112.1 kg/hour over 30 minutes.
Further, the initiator solution was added at a rate of 0.5 kg/hour after 3.5 hours of polymerization, 0.25 kg/hour after 4.5 hours, and 0.125 kg/hour after 6 hours. Addition stopped.
After 10 hours from the initiation of polymerization, a polymerization solution containing a methacrylic resin having a ring structure in its main chain was obtained.
After 3.25 hours and 10 hours from the initiation of polymerization, the polymer solution was sampled, and the polymerization conversion rate was analyzed from the remaining monomer concentration. The polymerization conversion rate after 3.25 hours was MMA was 69.5%, phMI was 68.9% and chMI was 63.1%, and the polymerization conversion rate after 10 hours was MMA 96.6%, phMI 96.0% and chMI 91.8%. Considering the monomers added after 2 hours from the start of the polymerization, the polymerization conversion rate after 2 hours was converted into the consumption rate with respect to the total amount of each monomer added by the end of the polymerization, MMA 69.5%, pHMI 68 .9% and chMI 63.1%.
This polymer solution was devolatilized by supplying it to a concentrating device consisting of a tubular heat exchanger preheated to 250° C. and a vaporization tank. The degree of vacuum in the vaporization tank was set to 10 to 15 Torr. The resin flowing down the vaporization tank was discharged by a gear pump, extruded from a strand die, cooled with water, and pelletized to obtain a methacrylic resin.
When the composition of the obtained pellet-shaped polymer was confirmed, the structural units derived from MMA, phMI, and chMI monomers were 79.8% by mass, 7.2% by mass, and 13.0% by mass, respectively. there were. Also, the weight average molecular weight was 141,000 and the Mw/Mn was 1.96.
Other physical properties are shown in Table 1.

[Comparative Example 4]
A methacrylic resin composition having a glutarimide structure was obtained by imidizing polymethyl methacrylate with monomethylamine using a co-rotating twin-screw extruder.
Using a co-rotating twin-screw extruder with a screw diameter of 40 mm, the temperature of the extruder cylinder is set to 270° C., the screw rotation speed is set to 150 rpm, and polymethyl methacrylate having an Mw of 108,000 is supplied from a hopper at 20 kg/hour. At the same time, nitrogen was flowed into the extruder at a flow rate of 200 mL/min. After the resin was melted and filled in the kneading block, 1.8 parts by mass of monomethylamine was injected from the nozzle into the raw material resin to carry out an imidization reaction. A reverse flight was placed at the end of the reaction zone (before the vent port) to fill the resin. By-products and excess methylamine after the reaction were removed by reducing the pressure at the vent port to 50 Torr. The resin coming out as a strand from the die provided at the exit of the extruder was cooled in a water tank and then pelletized by a pelletizer to obtain an imide resin.
Then, using a co-rotating twin-screw extruder with a screw diameter of 40 mm, the extruder cylinder temperature was set to 250° C. and the screw rotation speed was set to 150 rpm. After the resin was melted and filled, a mixture of dimethyl carbonate and triethylamine was injected from the nozzle as an esterifying agent to reduce the carboxylic acid groups in the resin. Dimethyl carbonate was 3.2 parts by mass and triethylamine was 0.8 parts by mass with respect to 100 parts by mass of the imide resin. A reverse flight was placed at the end of the reaction zone to fill with resin. By-products and excess dimethyl carbonate after the reaction were removed by reducing the pressure at the vent port to 50 Torr. The resin that came out as a strand from the die provided at the exit of the extruder was cooled in a water tank and then pelletized by a pelletizer to obtain a methacrylic resin composition having a glutarimide structure.
When the composition of the obtained methacrylic resin composition was checked, the amount of glutarimide structural units was 5.2% by mass. Moreover, the weight average molecular weight was 102,000 and Mw/Mn was 1.76.
Other physical properties are shown in Table 1.

As is clear from Examples and Comparative Examples, in methacrylic resins having a ring structural unit derived from an N-substituted maleimide monomer, the consumption rate with respect to the total amount of each monomer added by the end of polymerization is Furthermore, in the examples in which the monomers were additionally added and polymerized so that the difference in the consumption rate between N-phenylmaleimide and N-cyclohexylmaleimide becomes small at one point in time when the consumption rate of methyl methacrylate is 60 to 70%. , the composition distribution of structural units having a ring structure is small, and when the composition is adjusted so that the orientation birefringence at an orientation degree of 0.03 is positive, the orientation birefringence at an orientation degree of 0.08 is negative. Such a composition range exists, and when this resin is injection molded, a molded article with low birefringence can be obtained.
On the other hand, at one point in time when the consumption rate of methyl methacrylate is 60 to 70%, the composition distribution of the structural units having a ring structure is large in the comparative examples, in which the difference in the consumption rate between N-phenylmaleimide and N-cyclohexylmaleimide is large. The composition cannot be adjusted so that the sign of the orientation birefringence differs between the degree of orientation of 0.03 and the degree of orientation of 0.08, and the birefringence of the molded product cannot be sufficiently reduced.
Further, in a methacrylic resin having a glutarimide-based structural unit, a polymer having a uniform composition distribution of a ring structure can be obtained by carrying out a cyclization reaction in a solution state. Compositions with different signs of orientation birefringence at 0.08 can be present to obtain compacts with low birefringence.

[Example 9]
On both sides of the injection molded plate obtained in Example 1, Acier E50PG manufactured by Nidek Co., Ltd. was spray-coated, dried, and then irradiated with ultraviolet rays of about 1000 mJ/cm ² using a high-pressure mercury lamp to obtain a film thickness of about 3 μm. A hard coat layer was formed.
Furthermore, an antireflection layer was formed by depositing TiO ₂ (thickness 13 nm), SiO ₂ (thickness 36 nm), TiO ₂ (thickness 119 nm), and SiO ₂ (thickness 88 nm) in this order by vacuum deposition.

The total light transmittance of the injection-molded plate obtained in Example 1 was 92.5%, while the total light transmittance of the injection-molded plate formed with the hard coat layer and the antireflection layer was 97.5%. and was good.
Further, when a cross-cut test was conducted according to JIS K5600-5-6, no peeling of the hard coat layer was observed.
Next, the injection molded plate on which the hard coat layer and the antireflection layer were formed was placed in a constant temperature and humidity chamber at a temperature of 85° C. and a relative humidity of 85% for 500 hours, and then the total light transmittance was measured and the cross-cut test was performed in the same manner. However, there was no change from before being placed in the constant temperature and humidity chamber.

The methacrylic resin of the present embodiment has high heat resistance, and birefringence is highly controlled when the methacrylic resin and its composition are injection molded.
The methacrylic resin molded article of the present invention is used as an optical member in household goods, OA equipment, AV equipment, battery electrical components, lighting equipment, etc., for example, in displays such as smartphones, PDAs, tablet PCs, and liquid crystal televisions. Light guide plate, display front panel, touch panel, smart phone, tablet PC camera lens, etc., optical lens parts for head mounted display, liquid crystal projector, etc. For example, prism element, waveguide, lens, especially small thin and uneven thickness shape optical lenses, optical fibers, coating materials for optical fibers, lenses, Fresnel lenses, phase plates with microlens arrays, optical cover parts, and the like.
Optical parts for automobiles include: light guide plates for in-vehicle displays; in-vehicle meter panels; front panels of car navigation systems, combiners, optical parts for head-up displays such as optical cover parts; in-vehicle camera lenses, light guide bars, etc. .
In addition to the above, advertising on camera focusing screens, outdoors, stores, public facilities, transportation, etc.
It can also be preferably used as parts for a display device for digital signage that transmits information to a thin display connected to a network for the purpose of advertisement or the like.

Claims (8)

A methacrylic resin having a ring structure in its main chain,
A glass transition temperature of more than 120° C. and 160° C. or less,
The sign of the orientation birefringence when oriented so that the degree of orientation is 0.03 and the sign of the orientation birefringence when oriented so that the degree of orientation is 0.08 are different,
Contains structural units derived from N-substituted maleimide monomers
A methacrylic resin characterized by: The absolute value of the orientation birefringence when oriented so that the degree of orientation is 0.03 is 0.1 × 10 ^-5 or more and 5.0 × 10 ^-5 or less,
The absolute value of the orientation birefringence when oriented so that the degree of orientation is 0.08 is 8.0 × 10 ^-5 or less.
The methacrylic resin according to claim 1. The absolute value of the orientation birefringence when oriented so that the degree of orientation is 0.03 is 0.1 × 10 ^-5 or more and 3.0 × 10 ^-5 or less,
The absolute value of the orientation birefringence when oriented so that the degree of orientation is 0.08 is 5.0 × 10 ^-5 or less.
The methacrylic resin according to claim 2. The methacrylic resin according to any one of claims 1 to 3, wherein a molded piece obtained by injection molding the methacrylic resin has a yellowness index (YI) of 20 or less measured at an optical path length of 80 mm. 5. The methacrylic resin according to claim 1, wherein the methacrylic resin has a photoelastic coefficient of −3×10 ⁻¹² to +3×10 ⁻¹² Pa ⁻¹ . Molding characterized by comprising the methacrylic resin according to any one of claims 1 to 5 or a methacrylic resin composition containing the methacrylic resin according to any one of claims 1 to 5 . body. 7. The molded article according to claim 6 , having a thickness of 1.5 mm or less. An optical part or an automobile part comprising the molded article according to claim 6 or 7 .

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