JP2022020372A - Transparent molded body for optical elements - Google Patents

Abstract

To provide a transparent molded body for optical elements, in which deterioration in visibility due to minute bright spot foreign matter is reduced.SOLUTION: A transparent molded body for optical elements is provided, containing 1/cm3 or less of bright spot foreign matter of 10 micrometer or larger per unit volume, which act as bright spots by diffuse reflection when light is incident.SELECTED DRAWING: None

Description

The present invention relates to a transparent molded product for an optical element.

In the past, glass was used for optical components 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, miniaturization, and asphericalization of lenses. It has become to. As the plastic used for the optical component, a methacrylic resin, a styrene resin, a polycarbonate, a cyclic olefin resin and the like are generally known.

In general, optical plastics include impurities contained in raw materials, gels generated during polymerization, foreign substances mixed in during the manufacturing process, resin discoloration due to heat history such as molding processing, foreign substances generated and mixed from molding machines and external environments, etc. Since it is greatly affected by the quality of optical products, thorough measures against foreign substances and management are carried out.
Among foreign substances, bright spot foreign substances that become bright spots by diffusely reflecting light may be regarded as important in optical applications. For example, most black or brown foreign substances that are thought to be derived from resin discoloration due to the above-mentioned heat history do not easily become bright spots because they absorb light, but they are mainly composed of inorganic compositions that are thought to be derived from the external environment. It is considered that the foreign matter to be removed tends to be a bright spot because it easily reflects light.

As a measure against foreign matter, in order to reduce foreign matter of several micrometers or more or 20 micrometers or more, regardless of whether it is a bright spot foreign matter or not, for example, filtration accuracy of about 5 micrometers or 10 micrometers is used. A method of filtering and removing foreign matter with a polymer filter or the like has been implemented.
For example, in Patent Document 1, an acrylic resin package having a diameter of 2 micrometers or more and less than 500 pieces / g measured by a particle counter in a liquid by filtering a molten acrylic resin with a polymer filter. The body is disclosed.
Further, Patent Document 2 describes that a heat-resistant acrylic resin is filtered by a polymer filter having a filtration accuracy of 10 micrometers or less, and a particle diameter of 20 microns per gram measured using a particle counter is used. A pellet of an acrylic resin composition having 100 or less foreign substances of meters or more is disclosed.

However, since filtration by the polymer filter as described above is intended to remove impurities contained in the raw material of the resin, gel generated during polymerization, and foreign substances mixed in during the manufacturing process, the molding process, transportation, and external environment are targeted. Foreign matter of origin may remain unremoved.

As described above, the amount of bright spot foreign matter in the resin is not clearly measured and controlled, and a transparent molded body for an optical element in which bright spot foreign matter is highly reduced is desired.

Japanese Patent No. 4819952 Japanese Patent No. 5536011

Therefore, an object of the present invention is to provide a transparent molded article for an optical element in which a decrease in visibility due to a minute foreign matter with a bright spot is reduced.

As a result of diligent studies to solve the above-mentioned problems of the prior art, the present inventors have constructed a clean environment in each process of manufacturing and molding, and eliminated static electricity in the entire space to eliminate bright spot foreign substances mainly derived from the external environment. It was clarified that the above-mentioned problems could be solved by reducing the amount, and the present invention was completed.

That is, the present invention is as follows.
[1]
A transparent molded body for an optical element, characterized in that the content of a bright spot foreign substance having a bright spot of 10 micrometers or more, which becomes a bright spot due to diffuse reflection when light is incident, is 1 piece / cm ³ or less per unit volume.
[2]
The transparent molded article for an optical element according to [1], which comprises a resin composition containing a methacrylic resin having a ring structure in a main chain.
[3]
The transparent molded article for an optical element according to [2], wherein the glass dislocation temperature of the resin composition is more than 120 ° C. and 160 ° C. or lower.
[4]
The transparent molded article for an optical element according to [2] or [3], wherein the photoelastic coefficient of the resin composition is −3.0 × ^10-12 to +3.0 × ^10-12 Pa ^-1 .

According to the present invention, it is possible to provide a transparent molded product for an optical element in which a decrease in visibility due to a minute foreign matter with a bright spot is reduced.

Hereinafter, embodiments for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described in detail, but the present invention is not limited to the following description and is within the scope of the gist thereof. It can be modified in various ways.

<Transparent molded body for optical elements> The transparent molded body for optical elements of the present embodiment contains one bright spot foreign substance of 10 micrometer or more, which becomes a bright spot due to diffuse reflection when light is incident on it, per unit volume. It is characterized by being less than / ^cm3 .
In the present disclosure, the "bright spot" is a point where the brightness is higher than that of the surroundings by diffusely reflecting light, and is observed, for example, when light is incident on an arbitrary surface of a transparent molded body. It can be detected as a bright part in a state where the illumination light does not reach the person (dark field). More specifically, the "bright spot" is a portion where the luminance in dark field observation is 3 mcd / m ² or more, which is a range in which a person can confirm the contour.
Further, in the present disclosure, the "bright spot foreign substance" is a foreign substance that becomes a bright spot due to diffuse reflection when light is incident on the transparent molded body.

The size of the bright spot foreign matter targeted by the transparent molded body for an optical element of the present embodiment is set to 10 micrometers or more in consideration of the brightness that can be recognized as a bright spot by a person. It is preferable to reduce the amount of bright spot foreign matter less than 10 micrometers as much as possible from the viewpoint of quality improvement, but it is considered that about 10 micrometers is the lower limit of control as the actual control range in consideration of mass productivity.
The transparent molded body for an optical element of the present embodiment has a content of bright spot foreign matter of 10 micrometer or more of 1 piece / cm ³ or less per unit volume, preferably 0.9 piece / cm ³ or less, more preferably. Is 0.8 pieces / cm ³ or less. When the content of the bright spot foreign matter of 10 micrometers or more is in the above range, the visibility of the transparent molded product for an optical element is improved.
As a method of controlling the content of bright spot foreign matter within the above range, filtration and purification is performed by a polymer filter or the like in the resin polymerization process, and cleanliness is obtained in each step from the resin manufacturing process to the molding process of the transparent molded article for an optical element. It is possible to build a clean environment by installing a booth, etc., and to reduce the amount of bright spot foreign matter mainly derived from the external environment by removing static electricity from the entire space using an ionizer or the like. In particular, in the area where static electricity is removed, it is effective to eliminate static electricity not only in a local place such as each device but also in the entire space to reduce foreign substances in bright spots.
The size of the bright spot foreign matter is a value expressed as the size (maximum diameter) of the bright spot measured with a digital microscope in a dark field.

As a criterion for determining whether a foreign substance is a bright spot foreign substance, if the reflected light is a bright spot foreign substance that diffusely reflects light in a dark field when light is incident on an arbitrary surface of a transparent molded body, the reflected light is used. Since it reaches the observer, it means that the foreign matter observed in the dark field with higher brightness than the surroundings is the bright spot foreign matter. Therefore, the foreign matter that absorbs or transmits the incident light is judged not to be a bright spot foreign matter because the reflected light does not reach the observer and does not become a bright spot. For example, black or brown foreign substances such as resin burns generated by heat history in the manufacturing process, and transparent foreign resins that are thought to have been mixed from the outside during transportation, etc., absorb or transmit light, so they are bright spot foreign substances. It is thought that it is difficult to become. On the other hand, inorganic foreign substances such as those derived from metals and minerals and colored foreign substances such as fibers are observed as bright spots because they diffuse and reflect light, although they differ depending on the type and surface shape, and are judged to be bright spot foreign substances.

The method of observing bright spot foreign matter may be visually confirmed by a person, but the smaller the bright spot foreign matter, the more difficult it is to detect, so observation is performed with a microscope such as a stereomicroscope or a digital microscope. It is preferable, and from the viewpoint of quantitative evaluation and time reduction, the determination may be made by automatic measurement such as an automatic appearance inspection device.

As a more specific method for inspecting internal bright spot foreign matter in a transparent molded body, a depth composite image in which only the inside of the transparent molded body is imaged is acquired by depth synthesis of a digital microscope, and transparent molding is performed from this depth composite image. Only bright spot foreign substances existing inside the transparent molded body excluding the surface portion of the body can be extracted.
In the present disclosure, the "inside of the transparent molded product" and the "surface portion of the transparent molded product" are the "surface portion of the transparent molded product" from the surface to a specific distance in the direction perpendicular to the surface. The portion other than the above is the “inside of the transparent molded product”, which may be determined according to the desired inspection range of the transparent molded product. For example, the part from the surface to less than 2 mm in the direction perpendicular to the surface is the surface part of the transparent molded body, and the other part (the part separated from the surface by 2 mm or more in the direction perpendicular to the surface) is "transparent molding". For example, "inside the body".

Here, regarding the relationship between the lens magnification and the depth of focus (depth of field), the lower the lens magnification, the wider the field of view, but the depth of focus (depth of field) becomes shallower, and the higher the lens magnification, the wider the field of view. It becomes narrower, but the depth of focus (depth of field) becomes deeper.
On the other hand, as for the resolution of the image to be captured, the higher the lens magnification, the smaller the projected area per pixel of the captured depth-of-field image side sensor, and the higher the resolution. In other words, for the transparent molded body you want to observe, select the lens magnification of the digital microscope appropriately, and adjust the height range of the depth of focus synthesis of the digital microscope from the range of resolution and depth of focus (depth of field). , It is possible to obtain a depth-of-focus composite image only inside the transparent molded body excluding the surface portion.

Quantitative evaluation of internal bright spot foreign matter including minute internal bright spot foreign matter of about 10 micrometers by separately preparing external lighting as a light source for incident light on any surface of the transparent molded body. It can be performed.
External lighting for incident light on any surface of the transparent molded body includes a diffusive light source such as an LED, a highly straight light source such as a laser, and a parallel light source focused by an optical fiber or a lens. Can be mentioned.

Further, the wavelength of the light source to be irradiated is not particularly limited as long as it is light having a wavelength that can be identified as a bright spot in the acquired image, such as white light or monochromatic light, and can be freely selected. However, from the viewpoint of determining a bright spot foreign substance, there is a situation in which it is easier for a person to judge a bright spot foreign substance by using a light source of monochromatic light. In addition, white LEDs are usually made white by mixing a blue LED with a yellow phosphor, and depending on the light distribution characteristics, due to the anisotropy of the emitted color derived from blue with high directivity and yellow with strong diffusivity. It is possible that there will be a difference in the appearance of bright spot foreign matter. Therefore, it is preferable to use a monochromatic light source.

Furthermore, removing noise light (stray light) caused by reflections on foreign matter and scratches on the surface makes it possible to detect bright spots more clearly in dark field observation, and detects bright spot foreign matter more accurately. can do. Therefore, in the method for inspecting bright spot foreign matter, it is preferable to have a means for removing noise light caused by the surface of the transparent molded product.
As a means for removing noise light caused by the surface of the transparent molded body, it is preferable to provide an optical slit between the light source for incident light on an arbitrary surface of the transparent molded body and the transparent molded body. By making the slit width of this optical slit narrower than the width of the surface on which the light of the transparent molded body is incident, external lighting does not hit foreign substances and scratches existing on the surface of the transparent molded body. Noisy light is reduced, and bright spot foreign matter inside the transparent molded body can be clearly detected.
Further, instead of providing a slit, the external lighting to be irradiated is set to highly parallel lighting, and the noise light is removed by irradiating only the inside of the transparent molded body without irradiating the surface of the transparent molded body with light. It doesn't matter. However, it is not easy to prepare strict parallel light, and when the thickness and size of the transparent molded body change, it is necessary to prepare a suitable light source each time, but if it is an optical slit, it is necessary to prepare a suitable light source. It is sufficient to prepare several types of optical slits having a slit width according to the size of the transparent molded body, and it is possible to easily cope with the situation.

[Resin composition containing a methacrylic resin having a ring structure in the main chain]
The transparent molded article for an optical element of the present embodiment preferably contains a resin composition containing a methacrylic resin having a ring structure in the main chain.
The resin composition containing a methacrylic resin having a ring structure in the main chain may optionally contain an additive, and a thermoplastic resin other than the methacrylic resin having a ring structure in the main chain, It may contain a rubbery polymer or the like, or may be only a methacrylic resin having a ring structure in the main chain.

(Methyl resin having a ring structure in the main chain)
The methacrylic resin having a ring structure in the main chain of the present embodiment is a methacrylic resin containing a structural unit (A) derived from a methacrylic acid ester monomer and containing a structural unit (B) having a ring structure in the main chain. be. The structural unit (B) having a ring structure in the main chain is a structural unit derived from an N-substituted maleimide monomer (B-1), a glutarimide-based structural unit (B-2), and a lactone ring structural unit (B-). 3) etc. are selected. It also optionally includes other vinyl-based monomer units (C) that can be copolymerized with the methacrylic acid ester monomer.
The content of the methacrylic resin having a ring structure in the main chain in 100% by mass of the resin composition is preferably 50% by mass or more, more preferably 60% by mass or more, still more preferably 70% by mass or more, particularly. It is preferably 80% by mass or more.

Hereinafter, each monomer structural unit will be described.

-Structural unit derived from methacrylic acid ester monomer (A)-
First, the structural unit (A) derived from the methacrylic acid ester monomer will be described.
The structural unit (A) derived from the methacrylic acid ester monomer is formed from, for example, a monomer selected from the following methacrylic acid esters.
Examples of the methacrylic acid ester 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 Examples thereof include 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 in that the obtained methacrylic acid resin having a ring structure in the main chain is excellent in transparency and weather resistance.
The structural unit (A) derived from the methacrylic acid ester monomer may contain only one kind or two or more kinds.

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

Hereinafter, the structural unit (B) having a ring structure in the main chain will be described.

-Structural unit (B) having a ring structure in the main chain-
－－N－Structural unit derived from substituted maleimide monomer (B-1) －－
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 the monomer represented by the following formula (1) and / or the monomer represented by the following formula (2). As one, it is preferably formed from both the monomers represented by the following formulas (1) and (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 the formula (1), R ¹ represents any of an arylalkyl group having 7 to 14 carbon atoms and an aryl group having 6 to 14 carbon atoms, and R ² and R ³ are independent hydrogen atoms and carbon atoms, respectively. An alkyl group having 1 to 12 or an aryl group having 6 to 14 carbon atoms is shown.
Further, when R ² is an aryl group, R ² may contain a halogen as a substituent.
Further, 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 and 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１～１２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。

In the 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 are independent hydrogen atoms. , An alkyl group having 1 to 12 carbon atoms or an aryl group having 6 to 14 carbon atoms.

A specific example is shown below.
Examples of the monomer represented by the formula (1) include N-phenylmaleimide, N-benzylmaleimide, N- (2-chlorophenyl) maleimide, N- (4-chlorophenyl) maleimide, and 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-anthrasenylmaleimide, 3-methyl-1 -Phenyl-1H-Phenyl-2,5-dione, 3,4-dimethyl-1-phenyl-1H-Phenyl-2,5-dione, 1,3-diphenyl-1H-Pyrol-2,5-dione, 1 , 3,4-Triphenyl-1H-pyrrole-2,5-dione and the like.
Among these monomers, N-phenylmaleimide and N-benzylmaleimide are preferable because they are excellent in heat resistance of the obtained methacrylic resin having a ring structure in the main chain 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 the formula (2) include N-methylmaleimide, N-ethylmaleimide, Nn-propylmaleimide, N-isopropylmaleimide, Nn-butylmaleimide, and 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- Examples thereof include pyrrol-2,5-dione, 1-cyclohexyl-3-phenyl-1H-pyrol-2,5-dione, 1-cyclohexyl-3,4-diphenyl-1H-pyrol-2,5-dione.
Among these monomers, N-methylmaleimide, N-ethylmaleimide, N-isopropylmaleimide, and N-cyclohexylmaleimide are preferable because of the excellent weather resistance of the methacrylic resin having a ring structure in the main chain. N-cyclohexylmaleimide is particularly preferable because it is excellent in the low moisture absorption required for the material.
These monomers may be used alone or in combination of two or more.

In the methacrylic resin having a ring structure in the main chain of the present embodiment, it is highly possible to use the monomer represented by the formula (1) and the monomer represented by the formula (2) in combination. It is particularly preferable in that it is possible to develop controlled birefringence characteristics.
The molar ratio (B1 /) of the content (B1) of the structural unit derived from the monomer represented by the formula (1) to the content (B2) of the structural unit derived from the monomer represented by the formula (2). B2) is preferably more than 0 and 15 or less, and more preferably more than 0 and 10 or less.
When the molar ratio B1 / B2 is in this range, the molded product containing the methacrylic resin having a ring structure in the main chain of the present embodiment maintains transparency, does not cause yellowing, and impairs environmental resistance. It exhibits good heat resistance and good 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 obtained composition satisfies the glass transition temperature range of the present embodiment, but is not particularly limited. Is 100% by mass, preferably in the range of 5 to 40% by mass, and more preferably in the range of 5 to 35% by mass.
Within this range, the molded product containing a methacrylic resin having a ring structure in the main chain can obtain a more sufficient heat resistance improving effect, and more preferable improving effects on weather resistance, low water absorption, and optical properties. can get. If the content of the structural unit (B-1) derived from the N-substituted maleimide monomer is 40% by mass or less, the reactivity of the monomer component decreases during the polymerization reaction and remains unreacted. It is effective in preventing deterioration of the physical properties of a molded product containing a methacrylic resin having a ring structure in the main chain due to an increase in the amount of the body.

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

The glutarimide-based structural unit (B-2) constituting the methacrylic resin having a ring structure in the main chain of the present embodiment may be formed after the resin polymerization.
Specifically, the glutarimide-based structural unit (B-2) 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（Ｂ－２）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（Ｂ－２）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（Ｂ－２）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（Ｂ－２）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（Ｂ－２）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（Ｂ－２）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（Ｂ－２）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 the above general formula (3), preferably R ⁷ and R ⁸ are independently hydrogen or methyl groups, and R ⁹ is any of hydrogen, methyl group, butyl group and cyclohexyl group. Preferably, R ⁷ is a methyl group, R ⁸ is hydrogen and R ⁹ is a methyl group.
The glutarimide-based structural unit (B-2) may contain only a single type or may contain a plurality of types.
In the methacrylic resin having the glutarimide-based structural unit (B-2), the content of the glutarimide-based structural unit (B-2) satisfies the range of the glass transition temperature preferable for the composition of the present embodiment. If there is no particular limitation, the methacrylic resin is 100% by mass, preferably in the range of 5 to 70% by mass, and more preferably in the range of 5 to 60% by mass.
When the content of the glutarimide-based structural unit (B-2) is within the above range, a resin having good molding processability, heat resistance, and optical properties can be obtained, which is preferable.
The methacrylic resin having the glutarimide-based structural unit (B-2) may further contain an aromatic vinyl monomer unit, if necessary.
The aromatic vinyl monomer is not particularly limited, and examples thereof include styrene and α-methylstyrene, and styrene is preferable.
The content of the aromatic vinyl unit in the methacrylic resin having the glutarimide-based structural unit (B-2) is not particularly limited, but 100% by mass of the methacrylic resin having the glutarimide-based structural unit (B-2). It is preferably 0 to 20% by mass.
When the content of the aromatic vinyl unit is in the above range, it is possible to achieve both heat resistance and excellent photoelastic properties, which is preferable.

--Lactone ring structure unit (B-3) ---
Examples of the methacrylic resin having a lactone ring structural unit (B-3) in the main chain include JP-A-2001-151814, JP-A-2004-168882, JP-A-2005-146804, and JP-A-2006-96960. It can be formed by the 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 (B-3) constituting the methacrylic resin of the present embodiment may be formed after the resin polymerization.
The lactone ring structure unit (B-3) in the present embodiment is preferably a 6-membered ring because of its excellent ring structure stability.
As the lactone ring structural unit (B-3) which is a 6-membered ring, for example, the structure represented by the following general formula (4) is particularly 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。

In the above general formula (4), R ¹⁰ , R ¹¹ and R ¹² are hydrogen atoms or organic residues having 1 to 20 carbon atoms independently of each other.
Examples of the organic residue include a saturated aliphatic hydrocarbon group having 1 to 20 carbon atoms (alkyl group, etc.) such as a methyl group, an ethyl group, and a propyl group; and a non-saturated aliphatic hydrocarbon group having 2 to 20 carbon atoms such as an ethenyl group and a propenyl group. Saturated aliphatic hydrocarbon group (alkenyl group, etc.); Aromatic hydrocarbon group having 6 to 20 carbon atoms (aryl group, etc.) such as phenyl group and naphthyl group; these saturated aliphatic hydrocarbon group, unsaturated aliphatic hydrocarbon Examples include a group in which one or more of the hydrogen atoms in the group and the 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.
In the lactone ring structure, for example, an acrylic acid-based monomer having a hydroxy group and a methacrylic acid ester monomer such as methyl methacrylate are copolymerized 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 an ester group or a carboxyl group.
Examples of the hydroxy group-containing acrylic acid-based monomer used for polymerization include 2- (hydroxymethyl) acrylic acid, 2- (hydroxyethyl) acrylic acid, and 2- (hydroxymethyl) alkyl acrylate (for example, 2-). Methyl (hydroxymethyl) acrylate, ethyl 2- (hydroxymethyl) acrylate, isopropyl 2- (hydroxymethyl) acrylate, n-butyl 2- (hydroxymethyl) acrylate, t- (hydroxymethyl) acrylate Examples thereof include butyl) and alkyl 2- (hydroxyethyl) acrylate, preferably 2- (hydroxymethyl) acrylate and alkyl 2- (hydroxymethyl) acrylate, which are monomers having a hydroxyallyl moiety. , Particularly preferred are methyl 2- (hydroxymethyl) acrylate and ethyl 2- (hydroxymethyl) acrylate.

The content of the lactone ring structure unit (B-3) in the methacrylic resin having the lactone ring structure unit (B-3) in the main chain is the glass transition temperature of the methacrylic resin having the ring structure in the main chain of the present embodiment. There is no particular limitation as long as it satisfies the above range, but it is preferably 5 to 40% by mass, more preferably 5 to 35% by mass, based on 100% by mass of the methacrylic resin.
When the content of the lactone ring structure unit (B-3) is in this range, the ring structure introduction effect such as improvement of solvent resistance and surface hardness can be exhibited while maintaining molding processability.
The content of the lactone ring structure unit (B-3) in the methacrylic resin having a ring structure in the main chain can be determined by using the method described in the above-mentioned patent document.

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

-Other vinyl-based monomer unit (C) that can be copolymerized with a methacrylic acid ester monomer-
Other vinyl-based monomer units (C) (hereinafter, (C) monomers copolymerizable with the methacrylic acid ester monomer, which can constitute a methacrylic resin having a ring structure in the main chain of the present embodiment. (Sometimes referred to as a unit) includes an aromatic vinyl-based monomer unit (C-1), an acrylic acid ester monomer unit (C-2), and a vinyl cyanide-based monomer unit (C-). 3), and monomeric units (C-4) other than these can be mentioned.
As the other vinyl-based monomer unit (C) copolymerizable with the methacrylic acid ester monomer, only one type may be used alone, or two or more types may be combined.

The material of the (C) monomer unit can be appropriately selected according to the characteristics required for the methacrylic resin having a ring structure in the main chain, but thermal stability, fluidity, mechanical characteristics, and chemical resistance can be appropriately selected. When properties such as properties are particularly required, aromatic vinyl-based monomer unit (C-1), acrylic acid ester monomer unit (C-2), and vinyl cyanide-based monomer unit (C-3) At least one selected from the group consisting of) is suitable.

[Aromatic vinyl-based monomer unit (C-1)]
The monomer forming the aromatic vinyl-based monomer unit (C-1) constituting the methacrylic resin having a ring structure in the main chain of the present embodiment is not particularly limited, but is not limited to the following general formula. The aromatic vinyl-based monomer represented by (5) is preferable.

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^１４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 the 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 composed of a 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. Whichever is selected, R ¹⁴ may be all the same group or different groups. Further, a ring structure may be formed between R ^14s .
n represents an integer of 0 to 5.

Specific examples of the monomer represented by the general formula (5) are not particularly limited, but are styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, and 2,4-dimethyl. Styrene, 2,5-dimethylstyrene, 3,4-dimethylstyrene, 3,5-dimethylstyrene, p-ethylstyrene, m-ethylstyrene, о-ethylstyrene, p-tert-butylstyrene, 1-vinylnaphthalene, 2-vinylnaphthalene, 1,1-diphenylethylene, isopropenylbenzene (α-methylstyrene), isopropenyltoluene, isopropenylethylbenzene, isopropenylpropylbenzene, isopropenylbutylbenzene, isopropenylpentylbenzene, isopropenylhexylbenzene, Examples thereof include isopropenyloctylbenzene, α-hydroxymethylstyrene and α-hydroxyethylstyrene.
Among the above, styrene and isopropenylbenzene are preferable, and styrene is more preferable from the viewpoint of imparting fluidity and reducing unreacted monomers by improving the polymerization conversion rate.
These may be appropriately selected depending on the required characteristics in the methacrylic resin having a ring structure in the main chain of the present embodiment.

When the aromatic vinyl-based monomer unit (C-1) is used, the content is (A) monomer unit and (B) in consideration of the balance between heat resistance, reduction of residual monomer species, and fluidity. 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, still 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 (C-1) monomer with respect to the content of the (B-1) structural unit The unit content ratio (mass ratio) (that is, (C-1) content / (B-1) content) is the processing fluidity during molding of the film and silver streak due to the reduction of residual monomers. From the viewpoint of the effect of reducing the amount of monomer, it is preferably 0.3 to 5.
Here, from the viewpoint of maintaining good color tone and heat resistance, the upper limit value is preferably 5 or less, more preferably 3 or less, and further preferably 1 or less. Further, from the viewpoint of reducing the residual monomer, the lower limit value is preferably 0.3 or more, and more preferably 0.4 or more.
As the above-mentioned aromatic vinyl-based monomer (C-1), only one kind may be used alone, or two or more kinds may be used in combination.

[Acrylic acid ester monomer unit (C-2)]
The monomer forming the acrylic acid ester monomer unit (C-2) constituting the methacrylic acid resin having a ring structure in the main chain of the present embodiment is not particularly limited, but is not limited to the following general formula ( The acrylic acid ester monomer represented by 6) is preferable.

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, and R ¹⁶ is an alkyl group having 1 to 18 carbon atoms and a cyclo having 3 to 12 carbon atoms. Represents any of an alkyl group and an aryl group having 6 to 14 carbon atoms.

As the monomer for forming the acrylic acid ester monomer unit (C-2), the methacrylic resin for the film of the present embodiment enhances weather resistance, heat resistance, fluidity, and thermal stability. From the viewpoint, 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. Methyl acrylate, ethyl acrylate, and n-butyl acrylate are more preferable, and methyl acrylate and ethyl acrylate are even more preferable from the viewpoint of availability.
As the acrylic acid ester monomer unit (C-2), only one type may be used alone, or two or more types may be used in combination.

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

[Vinyl cyanide monomer unit (C-3)]
The monomer forming the vinyl cyanide-based monomer unit (C-3) constituting the methacrylic resin having a ring structure in the main chain of the present embodiment is not particularly limited, but is not particularly limited, for example, acrylonitrile. , Methacrylonitrile, etacrylonitrile, vinylidene cyanide and the like, and among them, acrylonitrile is preferable from the viewpoint of easy availability and imparting chemical resistance.
As the vinyl cyanide-based monomer unit (C-3), only one type may be used alone, or two or more types may be used in combination.

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

[Monomer units (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 having a ring structure in the main chain of the present embodiment is particularly limited. Although not, for example, amides such as acrylamide and methacrylic acid; glycidyl compounds such as glycidyl (meth) acrylate and allylglycidyl ether; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, maleic acid and fumaric acid. Acids and their semi-esters or anhydrides; unsaturated alcohols such as methacrylic alcohol and allyl alcohol; olefins such as ethylene, propylene and 4-methyl-1-pentene; vinyl acetate, 2-hydroxymethyl-1 -Vinyl compounds other than those described above such as butene, methylvinylketone, N-vinylpyrrolidone, N-vinylcarbazole and the like, vinylidene compounds and the like can be mentioned.
Further, examples of the crosslinkable compound having a plurality of reactive double bonds include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, and tetraethylene glycol di (meth) acrylate. Esterated hydroxyl groups at both ends of ethylene glycol or its oligomer with acrylic acid or methacrylic acid; hydroxyl groups of two alcohols such as neopentyl glycol di (meth) acrylate and di (meth) acrylate with acrylic acid or methacrylic acid. Esterated products; polyhydric alcohol derivatives such as trimethylolpropane and pentaerythritol esterified with acrylic acid or methacrylic acid; polyfunctional monomers such as divinylbenzene and the like can be mentioned.

Among the monomers constituting the above-mentioned (C) monomer unit, 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 the other vinyl-based monomer unit (C) copolymerizable with the methacrylic acid ester monomer is 100% by mass of the methacrylic acid-based resin from the viewpoint of enhancing the effect of imparting heat resistance by the structural unit (B). It is preferably 0 to 20% by mass, preferably 0 to 18% by mass, and more preferably 0 to 15% by mass.
In particular, when (C) a crosslinkable polyfunctional (meth) acrylate having a plurality of reactive double bonds is used as the monomer unit, the content of the (C) monomer unit is the fluidity of the polymer. From the viewpoint of the above, it is preferably 0.5% by mass or less, more preferably 0.3% by mass or less, and further preferably 0.2% by mass or less.

In particular, in the present embodiment, the total amount of the (B) structural unit and the (C) monomer unit is 100 from the viewpoint of heat resistance and optical properties of the molded body containing the methacrylic resin having a ring structure in the main chain. When taken as% by mass, the content of the structural unit (B) is 45 to 100% by mass. At this time, the content of (C) the structural unit is 0 to 55% by mass. The content of the structural unit (B) is preferably 50 to 100% by mass, more preferably 50 to 90% by mass, and further preferably 50 to 80% by mass.

Hereinafter, the characteristics of the methacrylic resin having a ring structure in the main chain of the present embodiment will be described.

(Glass transition temperature of methacrylic resin having a ring structure in the main chain)
The glass transition temperature (Tg) of the methacrylic resin having a ring structure in the main chain of the present embodiment is preferably more than 120 ° C and 160 ° C or less.
If the glass transition temperature of the methacrylic resin having a ring structure in the main chain exceeds 120 ° C., it is possible to more easily obtain the necessary and sufficient heat resistance as a transparent molded body for an optical element. The glass transition temperature (Tg) is more preferably 125 ° C. or higher, still more preferably 130 ° C. or higher, from the viewpoint of dimensional stability under the operating environment temperature.
On the other hand, when the glass transition temperature (Tg) of the methacrylic resin having a ring structure in the main chain is 160 ° C. or lower, melting processing at an extremely high temperature is avoided, thermal decomposition of the resin or the like is suppressed, and a good product is obtained. Can be obtained. The glass transition temperature (Tg) is preferably 150 ° C. or lower for the above-mentioned reasons.
The glass transition temperature (Tg) can be determined by measuring in accordance with JIS-K7121. Specifically, it can be measured by using the method described in Examples described later.

(Photoelastic coefficient of methacrylic resin having a ring structure in the main chain)
The photoelastic coefficient C of the methacrylic resin having a ring structure in the main chain of the present embodiment is preferably −3.0 × ^10-12 to +3.0 × ^10-12 Pa ^-1 , preferably −2.0. It is more preferably × 10 ^{-12 to +2.0 × 10 -12 Pa -1, and further preferably −1.0 × 10 -12 to +1.0 ×} 10 ^-12 Pa ^-1 . When the photoelastic coefficient C is in the above range, it can be suitably used as an optical resin having excellent transparency, low birefringence, and high heat resistance, which is suitable for applications requiring high optical characteristics among optical elements.
Photoelastic coefficients are described in various documents (see, for example, Review Articles of Chemistry, No. 39, 1998 (published by the Society 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 C is to zero, the smaller the birefringence change due to the external force.
C = Δn / σ ... (e)
Δn = nx-ny ... (f)
(In the equation, C is the photoelastic coefficient, σ is the elongation stress, Δn is birefringence, nx is the refractive index in the extension direction, and ny is the refractive index in the direction perpendicular to the extension direction in the plane.)
When the absolute value of the photoelastic coefficient C of the methacrylic resin having a ring structure in the main chain of the present embodiment is 3.0 × ^10-12 Pa ^-1 or less, when the injection molded product is fitted into the product as a part. The birefringence generated by the generated stress is sufficiently small.
The photoelastic coefficient C of the methacrylic resin having a ring structure in the main chain can be specifically obtained by the method described in Examples described later.

The methacrylic resin having a ring structure in the main chain of the present embodiment has a weight average molecular weight (Mw) in terms of polymethylmethacrylate measured by gel permeation chromatography (GPC), preferably 65,000 to 220,000. It is in the range, more preferably in the range of 80,000 to 180,000, and even more preferably in the range of 90,000 to 150,000.
When the weight average molecular weight (Mw) is in the above range, the balance between mechanical strength and fluidity is also excellent.
Further, regarding the ratio between the Z average molecular weight (Mz), the weight average molecular weight (Mw), and the number average molecular weight (Mn) as parameters representing the molecular weight distribution, the methacrylic resin in the present embodiment has fluidity and machine. Considering the balance with the 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 preferably 1.3 to 2.0, more preferably 1.3 to 1.8, and even more preferably 1.4 to 1.7.
The weight average molecular weight and the number average molecular weight of the methacrylic resin can be measured by the methods described in Examples described later.

The composition distribution of the ring structure in the methacrylic resin having a ring structure in the main chain of the present embodiment can be determined by observing the molecular weight dependence of the composition ratio of the structural unit including the ring structure in the methacrylic resin, and is concrete. Is obtained by obtaining the abundance ratio of the structural unit having a ring structure for each component obtained by fractionating the molecular weight of the methacrylic resin with a preparative GPC. When the abundance ratio of the structural unit having a ring structure in the methacrylic resin component obtained by molecular weight fractionation is expressed by mass%, the peak top molecular weight is 40,000 to 50,000, and the peak top. The difference in the abundance ratio of the structural units having a ring structure between the fraction components having a molecular weight of 240,000 to 260,000 is preferably 3.0% by mass or less, preferably 2.5% by mass or less. It is more preferably 2.0% by mass or less, still more preferably 1.5% by mass or less. Here, the fraction component having a peak top molecular weight of 40,000 to 50,000 means an arbitrary fraction component having a peak top molecular weight in this range, and the peak top molecular weight is 240,000 to 260,000. The fractional component of is defined as any fractional component having a peak top molecular weight in this range.
The method of molecular weight fractionation of the methacrylic resin and the abundance ratio of the structural units having a ring structure in each fractionated component can be measured by the method described in Examples described later.

(Manufacturing method of methacrylic resin)
Hereinafter, a method for producing a methacrylic resin having a ring structure in the main chain of the present embodiment will be described.

In the production method in the present embodiment, a batch type, a semi-batch type, and a continuous type can be used as the polymerization type. Here, the batch type is a process in which the reaction is started / progressed after the entire amount of the raw material is charged into the reactor, and the product is recovered after the completion, and the semi-batch type is either the raw material charging or the product recovery. A process in which one of them is simultaneously performed while the reaction is in progress, and the continuous method is a process in which both raw material input and product recovery are simultaneously performed during the reaction progress. As a method for producing a 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 material is added after the reaction is started is preferable from the viewpoint of precisely controlling the copolymer composition.
In the method for producing a methacrylic resin having a ring structure in the main chain in the present embodiment, it is preferable to use polymerization of a monomer by radical polymerization.

Hereinafter, a method for producing a methacrylic resin containing an N-substituted maleimide-based structural unit (B-1) as the structural unit (B) having a ring structure in the main chain will be described in detail.
As a method for producing a methacrylic resin having a structural unit (B-1) derived from an N-substituted maleimide monomer in the main chain in the present embodiment, a solution polymerization method is preferable.

The polymerization solvent to be used is not particularly limited as long as it can increase the solubility of the maleimide copolymer obtained by the polymerization and maintain the viscosity of the reaction solution appropriately for the purpose of preventing gelation and the like.
Specific polymerization solvents include, for example, aromatic hydrocarbons such as toluene, xylene, ethylbenzene and isopropylbenzene; ketones such as methyl isobutyl ketone, butyl cellosolve, methyl ethyl ketone and cyclohexanone; and polar solvents such as dimethylformamide and 2-methylpyrrolidone. Can be used.
Further, an alcohol such as methanol, ethanol or isopropanol may be used in combination as the polymerization solvent as long as it does not inhibit the dissolution of the polymerization product at the time of polymerization.
These may be used alone or in combination of two or more.

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

The polymerization temperature is not particularly limited as long as it is a temperature at which the polymerization proceeds, but is preferably 70 to 180 ° C, more preferably 80 to 160 ° C, still more preferably 90 to 150 ° C, and even more preferably 100. It is ~ 150 ° C. From the viewpoint of productivity, the temperature is preferably 70 ° C. or higher, and the temperature is preferably 180 ° C. or lower in order to suppress side reactions during polymerization and obtain a polymer having a desired molecular weight and quality.

The polymerization time is not particularly limited as long as the required degree of polymerization can be obtained at the required conversion rate, but it is preferably 2 to 15 hours from the viewpoint of productivity and the like. It is 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 the structural unit (B-1) derived from the N-substituted maleimide monomer in the main chain in the present embodiment is preferably 93 to 99.9%. It is more preferably 95 to 99.9%, and even more preferably 97 to 99.8%.
Here, the polymerization conversion rate is a 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 in the polymerization system, and the monomer added in the polymerization system. Is the ratio to the total mass of.

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

At the time of the polymerization reaction, a chain transfer agent may be added as needed for polymerization.
As the chain transfer agent, any chain transfer agent used in general radical polymerization can be used, for example, n-butyl mercaptan, n-octyl mercaptan, n-decyl mercaptan, n-dodecyl mercaptan, thioglycol. Examples thereof include mercaptan compounds such as 2-ethylhexyl acid; halogen compounds such as carbon tetrachloride, methylene chloride and bromoform; unsaturated hydrocarbon compounds such as α-methylstyrene dimer, α-terpinene, dipentene and turpinolene; and the like.
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 the chain transfer agent added may be 0.01 to 1 part by mass, preferably 0.05 to 0.5 part by mass, when the total amount of the monomers used for the polymerization is 100 parts by mass.

Further, a polymerization initiator may be added at the time of the polymerization reaction.
As the polymerization initiator, any initiator generally used in radical polymerization can be used, and for example, cumene hydroperoxide, diisopropylbenzene hydroperoxide, di-t-butyl peroxide, lauroyl peroxide, benzoylper. Organic peroxides such as oxides, t-butylperoxyisopropyl carbonate, t-amylperoxy-2-ethylhexanoate, t-amylperoxyisononanoate, 1,1-dit-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 can be mentioned.
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 added may be 0.01 to 1 part by mass, preferably 0.05 to 0.5 part by mass, when the total amount of the monomers used for the 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 in the polymerization solution and an operation of pressurizing the inside of the container containing the polymerization solution with the inert gas to about 0.2 MPa and then releasing the pressure are repeated before the polymerization. A method such as a method or a method of passing an inert gas through a container containing a polymerization solution can be appropriately selected.

In order to reduce the difference in the bonded monomer composition in copolymers having different molecular weights, some monomer units are additionally added so that the monomer composition in the polymerization system during polymerization is as uniform as possible. It is preferable to polymerize while doing so. For example, the difference in the consumption rate of each monomer at the time when about 70% of the total amount of the monomers finally added into the system is consumed is preferably 10% or less, more preferably 5% or less. The type, amount, and timing of the monomer to be additionally added are adjusted so as to be more preferably 3% or less.
The consumption rate of a certain monomer at a certain point in time means the ratio of the total amount of the added monomer consumed in the polymerization reaction, and the total amount of the added monomer is included in the total amount of the monomer added. It includes those that have already been added at a certain point in time and those that have not yet been added.

Further, the polymerization is carried out so that the difference in the final conversion rate between the monomers at the end of the polymerization is 10% or less, more preferably 5% or less, still more preferably 3% or less.

The method for recovering the polymer from the polymerization solution obtained by solution polymerization is not particularly limited, but for example, a poor solvent such as a hydrocarbon solvent or an alcohol solvent that does not dissolve the polymerization product obtained by the polymerization. After adding the polymerization solution in the presence of an excessive amount of solvent, the unreacted monomer is treated with a homogenizer (emulsion dispersion), and the unreacted monomer is subjected to pretreatment such as liquid-liquid extraction and solid-liquid extraction. Examples thereof include a method of separating from the polymerization solution; or a method of separating the polymerization solvent and the unreacted monomer via a step called a devolatile step and recovering the polymerization product.
Here, the devolatile step refers to a step of removing volatile components such as a polymerization solvent, a residual monomer, and a reaction by-product under heating and reduced pressure conditions.

As the device used in the devolatilization process, for example, a devolatilization device consisting of a tubular heat exchanger and a devolatilization tank; a thin film evaporator such as Wybren and Exeba manufactured by Kobelco Eco-Solutions Co., Ltd., a contra and a tilted blade contra manufactured by Hitachi, Ltd .; Extruders with vents that have sufficient residence time and surface area to exhibit volatilization performance; and the like.
A volatilization step using a devolatilization device in which any two or more of these devices are combined can also be used.

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

The degree of vacuum in the devolatilizer is preferably in the range of 10 to 500 Torr, and more preferably in the range of 10 to 300 Torr. By setting this degree of vacuum to the upper limit or less, the residual amount of volatile matter can be suppressed. Moreover, the degree of vacuum above the lower limit is realistic in industrial implementation.
The treatment time is appropriately selected depending on the amount of residual volatile matter, but a shorter treatment time is preferable in order to suppress coloring and decomposition of the obtained acrylic resin.

The polymer recovered through the devolatile step may be processed into pellets in a step called a granulation step.
In the granulation step, the molten resin may be extruded into a strand shape from a porous die and processed into a pellet shape by a cold cut method, an aerial hot cut method, or an underwater cut method.

When an extruder with a vent is used as the devolatilization device, the devolatilization step and the granulation step may be combined.

Next, an example of a method for producing a methacrylic resin having a glutarimide-based structural unit (B-2) will be described.

First, a (meth) acrylic acid ester polymer is produced by polymerizing a (meth) acrylic acid ester such as methyl methacrylate. When the aromatic vinyl unit is contained in the methacrylic resin having the glutarimide-based structural unit (B-2), the (meth) acrylic acid ester and the aromatic vinyl (for example, styrene) are copolymerized to (meth). Acrylic acid ester-Aromatic vinyl copolymer is produced.

Next, an imidization reaction is carried out by reacting the (meth) acrylic acid ester polymer or the methacrylic acid ester-aromatic vinyl copolymer with an imidizing agent (imidization step). This makes it possible to produce a methacrylic resin having a glutarimide-based structural unit (B-2).

The imidizing agent is not particularly limited as long as it can generate a glutarimide-based structural unit (B-2) represented by the general formula (3).
Specifically, as the imidizing agent, ammonia or a primary amine can be used. 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; and the like.
Among the above imidizing agents, ammonia, methylamine and cyclohexylamine are preferably used, and methylamine is particularly preferable, from the viewpoint of cost and physical properties.

In this imidization step, the content of the glutarimide-based structural unit (B-2) in the methacrylic resin having the glutarimide-based structural unit (B-2) obtained by adjusting the addition ratio of the imidizing agent. Can be adjusted.

The method for carrying out the imidization reaction is not particularly limited, but a conventionally known method can be used, and for example, the imidization reaction can be allowed to proceed by using an extruder or a batch type reaction tank.
The extruder is not particularly limited, and for example, a single-screw extruder, a twin-screw extruder, a multi-screw extruder, or the like can be used.
Above all, it is preferable to use a twin-screw extruder. According to the twin-screw extruder, mixing of the raw material polymer and the imidizing agent can be promoted.
Examples of the twin-screw extruder include a non-meshing type same-direction rotation type, a meshing type same-direction rotation type, a non-meshing type different-direction rotation type, and a non-meshing type different-direction rotation type.

The extruder exemplified above may be used alone or may be used by connecting a plurality of extruders in series.
Further, the extruder to be used is particularly equipped with a bent port capable of reducing the pressure below atmospheric pressure because the imidizing agent for the reaction, by-products such as methanol, or monomers can be removed. preferable.

In producing a methacrylic resin having a glutarimide-based structural unit (B-2), in addition to the above-mentioned imidization step, an esterification step of treating the carboxyl group of the resin with an esterifying agent such as dimethyl carbonate is included. be able to. At that time, a catalyst such as trimethylamine, triethylamine, or tributylamine can be used in combination for treatment.
The esterification step can be carried out in the same manner as the imidization step by using, for example, an extruder or a batch type reaction vessel.
Further, for the purpose of removing excess esterifying agent, by-products such as methanol, or monomers, it is preferable to equip the device to be used with a valve opening capable of reducing the pressure below atmospheric pressure.

The methacrylic resin that has undergone the imidization step and, if necessary, the esterification step is melted and extruded into strands from an extruder equipped with a porous die, and is used for cold cut method, aerial hot cut method, underwater cut method, etc. 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 and methylene chloride, the obtained methacrylic resin solution is filtered, and then the organic solvent is devolatile. It is also preferable to use the method.

The imidization reaction is preferably carried out at 130 to 250 ° C, more preferably 150 to 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 esterification step is performed, and then the devolatile and granulation steps are performed.

Hereinafter, a method for producing a methacrylic resin containing a lactone ring structural unit (B-3) as a structural unit (B) having a ring structure in the main chain will be described in detail.
As a method for producing a methacrylic resin having a lactone ring structure unit (B-3) in the main chain in the present embodiment, solution polymerization using a solvent is preferable in order to promote the cyclization reaction. Here, a method of forming the lactone ring structural unit (B-3) by a cyclization reaction after polymerization may be used.

Examples of the polymerization solvent used include aromatic hydrocarbons such as toluene, xylene and ethylbenzene; and ketones such as methyl ethyl ketone and methyl isobutyl ketone;
These solvents may be used alone or in combination of two or more.
The amount of the solvent at the time of polymerization is not particularly limited as long as the polymerization proceeds and gelation can be suppressed. For example, when the total amount of the monomers to be blended is 100 parts by mass, the amount is 50 to 200 mass. The amount is preferably 100 to 200 parts by mass, more preferably 100 to 200 parts by mass.
In order to sufficiently suppress the gelation of the polymerization solution and promote the cyclization reaction after the polymerization, the polymerization is carried out so that the concentration of the produced polymer in the reaction mixture obtained after the polymerization is 50% by mass or less. Is preferable.
Further, it is preferable to appropriately add a polymerization solvent to the reaction mixture to control the content to 50% by mass or less. The method of appropriately adding the polymerization solvent to the reaction mixture is not particularly limited, and for example, the polymerization solvent may be continuously added or the polymerization solvent may be added intermittently. The polymerization solvent to be added may be a single solvent of only one kind or a mixed solvent of two or more kinds.

The polymerization temperature is not particularly limited as long as it is a temperature at which the polymerization proceeds, but is preferably 50 to 200 ° C., more preferably 80 to 180 ° C. from the viewpoint of productivity.

The polymerization time is not particularly limited as long as the desired conversion rate is satisfied, but is preferably 0.5 to 10 hours, more preferably 1 to 8 hours from the viewpoint of productivity and the like.

The polymerization conversion rate of the methacrylic resin having a lactone ring structural unit (B-3) in the main chain in the present embodiment at the end of polymerization has the structural unit (B-1) derived from the N-substituted maleimide monomer. It may be the polymerization conversion rate disclosed in the method for preparing a methacrylic resin.

At the time of the polymerization reaction, a chain transfer agent may be added and polymerized, if necessary.
As the chain transfer agent, a chain transfer agent used in general radical polymerization can be used, and for example, the chain disclosed in the method for preparing a methacrylic resin having a structural unit (B-1) derived from the N-substituted maleimide monomer. Transfer agents etc. can be used.
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 the chain transfer agent added is not particularly limited as long as the desired degree of polymerization can be obtained under the polymerization conditions used, but preferably the total amount of the monomers used for the polymerization is 100 parts by mass. In this case, the amount may be 0.01 to 1 part by mass, preferably 0.05 to 0.5 part by mass.

The dissolved oxygen concentration in the polymerization solution may be, for example, the value disclosed in the method for preparing a methacrylic resin having a structural unit (B-1) derived from the N-substituted maleimide monomer.

At the time of the polymerization reaction, a polymerization initiator may be added to polymerize.
The polymerization initiator is not particularly limited, but for example, the polymerization initiator disclosed in the method for preparing a methacrylic resin having a structural unit (B-1) derived from the N-substituted maleimide monomer can be used. can.
These polymerization initiators may be used alone or in combination of two or more.
The amount of the polymerization initiator added may be appropriately set according to the combination of monomers, reaction conditions, etc., and is not particularly limited, but when the total amount of the monomers used for polymerization is 100 parts by mass. In addition, it may be 0.01 to 1 part by mass, preferably 0.05 to 0.5 part by mass.

In the polymerization of the methacryl-based resin having the lactone ring structure unit (B-3) in the present embodiment, a polymerization initiator and a monomer are added in the middle of the polymerization as needed, and the addition amount thereof is controlled. It is possible to reduce the fluctuation of the ratio between the concentration of the monomer in the system during the polymerization and the concentration of the radical, suppress the formation of low molecular weight components at the final stage of the polymerization, and improve the coloring property and the molding processability. ..
The methacrylic resin having the lactone ring structure unit (B-3) in the present embodiment can be obtained, for example, by carrying out a cyclization reaction after the completion of the above-mentioned polymerization reaction. Therefore, it is preferable to carry out the lactone cyclization reaction in a state containing the solvent without removing the polymerization solvent from the polymerization reaction solution.
The copolymer obtained by the polymerization undergoes a cyclization condensation reaction between a hydroxyl group (hydroxyl group) existing in the molecular chain of the copolymer and an ester group by heat treatment, and has a lactone ring structure. Form.
During the heat treatment for forming the lactone ring structure, a vacuum device for removing alcohol that may be by-produced by cyclization condensation, a reaction device equipped with a devolatilization device, an extruder equipped with a volatilization device, or the like can also be used. ..

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 the cyclization condensation catalyst include, for example, methyl phosphite, ethyl phosphite, phenyl phosphite, dimethyl phosphite, diethyl phosphite, diphenyl phosphite, trimethyl trimethyl phosphite, and sub-phosphite. Phosphate monoalkyl ester such as triethyl phosphate, dialkyl ester or triester; methyl phosphate, ethyl phosphate, 2-ethylhexyl phosphate, octyl phosphate, isodecyl phosphate, lauryl phosphate, stearyl phosphate, phosphoric acid Isostearyl, dimethyl phosphate, diethyl phosphate, di-2-ethylhexyl phosphate, diisodecyl phosphate, dilauryl phosphate, disstearyl phosphate, diisostearyl phosphate, trimethyl phosphate, triethyl phosphate, triisodecyl phosphate, Examples thereof include phosphoric acid monoalkyl esters such as trilauryl phosphate, tristearyl phosphate, and triisostearyl phosphate, dialkyl esters, and trialkyl esters.
These may be used alone or in combination of two or more.

The amount of the cyclization condensation catalyst used is not particularly limited, but is preferably 0.01 to 3 parts by mass, more preferably 0.05 to 3 parts by mass with respect to 100 parts by mass of the methacrylic resin, for example. It is 1 part by mass.
If the amount used is less than 0.01 parts by mass, the reaction rate of the cyclization condensation reaction may not be sufficiently improved. On the contrary, if the amount of the catalyst used exceeds 3 parts by mass, the obtained 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, and for example, it may be added at the initial stage of the cyclization condensation reaction, during the reaction, or at both of them. good.
When the cyclization condensation reaction is carried out in the presence of a solvent, it is also preferably used to carry out devolatile reaction at the same time.
The apparatus used when the cyclization condensation reaction and the devolatilization step are performed at the same time is not particularly limited, but is a devolatilization apparatus consisting of a heat exchanger and a devolatilization tank, an extruder with a vent, and devolatilization. It is preferable that the device and the extruder are arranged in series, and a twin-screw extruder with a vent is more preferable.
As the twin-screw extruder with a vent to be used, an extruder with a vent having a plurality of vent ports is preferable.

When an extruder with a vent is used, the reaction treatment temperature is preferably 150 to 350 ° C, more preferably 200 to 300 ° C. If the reaction treatment temperature is less than 150 ° C., the cyclization condensation reaction may be insufficient and the residual volatile matter may increase. On the contrary, when the reaction treatment temperature exceeds 350 ° C., coloring or decomposition of the obtained polymer may occur.
When the extruder with a vent is used, the degree of vacuum is preferably 10 to 500 Torr, more preferably 10 to 300 Torr. If the degree of vacuum exceeds 500 Torr, volatile matter may easily remain. On the contrary, if the degree of vacuum is less than 10 Torr, industrial implementation may be difficult.

It is also preferable to add an alkaline earth metal and / or an amphoteric metal salt of an organic acid at the time of granulation for the purpose of inactivating the remaining cyclization condensation catalyst when the above cyclization condensation reaction is carried out.
As the alkaline earth metal and / or amphoteric metal salt of the organic acid, for example, calcium acetyl acetate, calcium stearate, zinc acetate, zinc octylate, zinc 2-ethylhexylate and the like can be used.

After undergoing the cyclization condensation reaction step, the methacrylic resin is melted and extruded into strands from an extruder equipped with a porous die, and processed into pellets by a cold cut method, an aerial hot cut method, and an underwater cut method. ..
The lactonization for forming the above-mentioned lactone ring structure unit (B-3) may be performed after the production of the resin and before the production of the resin composition (described later), and during the production of the resin composition, the resin may be formed. It may be carried out in combination with melting and kneading with a component other than the resin.

The methacrylic resin having a ring structure in the main chain in the present embodiment is a structural unit (B-1) derived from an N-substituted maleimide monomer, a glutarimide-based structural unit (B-2), and a lactone ring structural unit (B). It is preferable to have at least one kind of ring structure unit selected from the group consisting of -3), and among them, in particular, it is easy to highly control optical properties such as photoelastic coefficient without blending with other thermoplastic resins. From the point of view, it is particularly preferable to have a structural unit (B-1) derived from an N-substituted maleimide monomer.

-Additive-
The resin composition containing a methacrylic resin having a ring structure in the main chain according to the present embodiment may contain various additives as long as the effects of the present invention are not significantly impaired.
The additives are not particularly limited, but are, for example, light stabilizers such as antioxidants and hindered amine-based light stabilizers, ultraviolet absorbers, mold release agents, other thermoplastic resins, paraffin-based process oils, and naphthen-based processes. Oils, aromatic process oils, paraffins, organic polysiloxanes, softeners / plasticizers such as mineral oils, flame retardants, antistatic agents, organic fibers, inorganic fillers such as pigments such as iron oxide, glass fibers, carbon fibers , Reinforcing agents such as metal whiskers, coloring agents; organic phosphorus compounds such as phosphites, phosphoric acid esters, other additives, or mixtures thereof.

--Antioxidant--
The resin composition containing a methacrylic resin having a ring structure in the main chain according to the present embodiment preferably contains an antioxidant that suppresses deterioration and coloring during molding and 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 varies depending on the processing method, but it ranges from several tens of seconds like an extruder to tens of minutes to several hours of heat history such as thick-walled molding and sheet molding. There are various.
When receiving a long heat history, it is necessary to increase the amount of the heat stabilizer added in order to obtain the desired heat stability. From the viewpoint of suppressing the bleed-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, for example, a phosphorus-based antioxidant and a sulfur-based antioxidant. It is preferable to use at least one selected from the agents in combination with a hindered phenol-based antioxidant.
These antioxidants may be used alone or in combination of two or more.

The hindered phenolic antioxidant is not limited to the following, but is, for example, pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], thiodiethylenebis. [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''-(methitylen-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-Triazine-2-ylamine) phenol, acrylic acid 2- [1- (2-hydroxy-3,5-di-tert-pentylphenyl) ethyl] -4,6-di-tert-pentylphenyl, acrylic acid Examples thereof include 2-tert-butyl-4-methyl-6- (2-hydroxy-3-tert-butyl-5-methylbenzyl) phenyl.
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 is preferred.

Further, as the hindered phenol-based antioxidant as the antioxidant, a commercially available phenol-based antioxidant may be used, 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''-(methicylene-2,4,6-triyl) tri-p-cresol, manufactured by BASF), Irganox 3114 (Irganox 3114: 1,3,5) -Tris (3,5-di-t-butyl-4-hydroxybenzyl) -1,3,5-triazine-2,4,6 (1H, 3H, 5H) -Torion, manufactured by BASF), Irganox 3125 (Irganox 3125, manufactured by BASF), Adecastab AO-60 (pentaerythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], manufactured by ADEKA), Adecastab AO-80 (3) , 9-bis {2- [3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionylxyoxy] -1,1-dimethylethyl} -2,4,8,10-tetraoxaspiro [5.5] Undecan (manufactured by ADEKA), Sumilizer BHT (Sumilizer BHT, manufactured by Sumitomo Chemical), Cyanox 1790 (Cyanox 1790, manufactured by Cytec), Sumilizer GA-80 (manufactured by 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, manufactured by Sumitomo Chemical Co., Ltd.), Sumilizer GM (Sumilizer) GM: 2-tert-butyl-4-methyl-6- (2-hydroxy-3-tert-butyl-5-methylbenzyl) phenyl acrylate, manufactured by Sumitomo Chemical Co., Ltd.), vitamin E (manufactured by Eisai) and the like can be mentioned.
Among these commercially available phenolic antioxidants, Irganox 1010, Adecastab AO-60, Adecastab AO-80, Irganox 1076, Sumilyzer GS and the like are preferable from the viewpoint of the effect of imparting thermal stability with the resin.
These may be used alone or in combination of two or more.

The phosphorus-based antioxidant as the antioxidant is not limited to the following, but is, for example, tris (2,4-di-t-butylphenyl) phosphite, bis (2,4-). Bis (1,1-dimethylethyl) -6-methylphenyl) ethyl ester phosphite, tetrakis (2,4-di-t-butylphenyl) (1,1-biphenyl) -4,4'-diylbisphos 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] dioxaphosphepine) -6-yloxy] propyl] -2 -Methyl-6-tert-butylphenol and the like can be mentioned.
Further, a commercially available phosphorus-based antioxidant may be used as the phosphorus-based antioxidant, and such a commercially available phosphorus-based antioxidant is not limited to the following, but is, for example, Irgafos 168 ( Irgafos 168: Tris (2,4-di-t-butylphenyl) phosphite, manufactured by BASF), Irgafos 12: Tris [2-[[2,4,8,10-tetra-t-butyldibenzo [2,4,8,10-tetra-t-butyldibenzo [ d, f] [1,3,2] dioxaphosfefin-6-yl] oxy] ethyl] amine, manufactured by BASF), Irgafos 38: bis (2,4-bis (1,1-dimethyl) Ethyl) -6-methylphenyl) ethyl ester phosphite, made by BASF), ADEKA STAB 329K (ADK STAB-229K, made by ADEKA), ADEKA STAB PEP-36 (ADK STAB PEP-36, made by ADEKA), ADEKA STAB PEP-36A (made by ADEKA) ADK STAB PEP-36A, made by ADEKA), ADEKA STAB PEP-8 (ADK STAB PEP-8, made by ADEKA), ADEKA STAB HP-10 (ADK STAB HP-10, ADEKA), ADEKA STAB 2112 (ADK STAB 2112, ADEKA). ), ADEKA STAB 1178 (ADKA STAB 1178, ADEKA), ADEKA STAB 1500 (ADK STAB 1500, ADEKA) Sandstab P-EPQ (Clariant), Weston 618 (Weston 618, GE), Weston 619G (Weston) ), Ultranox 626 (Ultranox 626, manufactured by GE), Sumilizer GP: 4- [3-[(2,4,8,10-tetra-tert-butyldibenzo [d, f] [1,3]) 2] Dioxaphosfepine) -6-yloxy] propyl] -2-methyl-6-tert-butylphenol, manufactured by Sumitomo Chemical Co., Ltd.), 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, Adecastab PEP-36, Adecastab PEP-36A, Adecastab HP from the viewpoint of the effect of imparting thermal stability in the resin and the effect of combined use with various antioxidants. -10, Adecastab 1178 are preferable, and Adecastab PEP-36A and Adecastab PEP-36 are particularly preferable.
These phosphorus-based antioxidants may be used alone or in combination of two or more.

The sulfur-based antioxidant as the antioxidant is not limited to the following, but is, 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] (ADEKA STAB 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, Adecastab AO-412S and Cheminox PLS are preferable from the viewpoints of the effect of imparting thermal stability in the resin, the effect of being used in combination with various antioxidants, and the viewpoint of 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 it has the effect of improving thermal stability, and if the content is excessive, problems such as bleeding out during processing may occur. It is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, further preferably 1 part by mass or less, still more preferably 0.8 parts by mass or less, still more preferably, with respect to 100 parts by mass of the based resin. It is preferably 0.01 to 0.8 parts by mass, and particularly preferably 0.01 to 0.5 parts by mass.

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

－－Hindered amine-based light stabilizer －－
The resin composition containing a methacrylic resin having a ring structure in the main chain of the present embodiment can contain a hindered amine-based light stabilizer.
The hindered amine-based light stabilizer is not particularly limited, but 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 an aromatic ring, an aliphatic ring, an aromatic heterocycle and a non-aromatic heterocycle, and two or more ring structures are contained in one compound. If they have, they may be the same or different from each other.

The hindered amine-based light stabilizer is not limited to the following, but specifically, for example, 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- Piperidine) -N, N'-diformylhexamethylenediamine, dibutylamine 1,3,5-triazine N, N'-bis (2,2,6,6-tetramethyl-4-piperidyl-1,6) -A 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-piperididiol 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-diethanol reaction product, bis (1-undecanoxy-2,2,6,6-tetramethylpiperidine-4-yl) Examples thereof include carbonate, 1,2,2,6,6-pentamethyl-4-piperidylmethacrylate, 2,2,6,6-tetramethyl-4-piperidylmethacrylate and the like.
Among them, bis (1,2,2,6,6-pentamethyl-4-piperidyl) [[3,5-bis (1,1-dimethylethyl) -4-hydroxyphenyl] methyl containing three 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 reaction product , 2,2,6,6-Tetramethyl-4-piperidiol and β, β, β', β'-Tetramethyl-2,4,8,10-Tetraoxaspiro [5.5] Undecane-3,9 -A reaction product of diethanol is preferred.

The content of the hindered amine-based light stabilizer may be an amount that can improve the light stability, and if the content is excessive, problems such as bleeding out during processing may occur. , 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, based on 100 parts by mass of the methacrylic resin. It is even more preferably 0.01 to 0.8 parts by mass, and particularly preferably 0.01 to 0.5 parts by mass.

－－UV absorber －－
The resin composition containing a methacrylic resin having a ring structure in the main chain of the present embodiment can contain an ultraviolet absorber.
The ultraviolet absorber is not particularly limited, but is preferably an ultraviolet absorber having a maximum absorption wavelength of 280 to 380 nm, and is, for example, a benzotriazole-based compound, a benzotriazine-based compound, a benzophenone-based compound, or an oxybenzophenone-based compound. , Benzoate-based compounds, phenol-based compounds, oxazole-based compounds, cyanoacrylate-based compounds, benzoxadinone-based compounds and the like.

Examples of benzotriazole compounds include 2,2'-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazole-2-yl) phenol], 2- (3). 5-Di-tert-butyl-2-hydroxyphenyl) -5-chlorobenzotriazole, 2- (2H-benzotriazole-2-yl) -p-cresol, 2- (2H-benzotriazole-2-yl)- 4,6-bis (1-methyl-1-phenylethyl) phenol, 2-benzotriazole-2-yl-4,6-di-tert-butylphenol, 2- [5-chloro (2H) -benzotriazole-2 -Il] -4-Methyl-6-t-butylphenol, 2- (2H-benzotriazole-2-yl) -4,6-di-t-butylphenol, 2- (2H-benzotriazole-2-yl)- 4- (1,1,3,3-tetramethylbutyl) phenol, 2- (2H-benzotriazole-2-yl) -4-methyl-6- (3,4,5,6-tetrahydrophthalimidylmethyl) ) Phenol, methyl 3- (3- (2H-benzotriazole-2-yl) -5-t-butyl-4-hydroxyphenyl) propionate / reaction product of polyethylene glycol 300, 2- (2H-benzotriazole-2) -Il) -6- (Linear and side chain dodecyl) -4-methylphenol, 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- [2-hydroxy-3,5-bis (α,) α-dimethylbenzyl) phenyl] -2H-benzotriazole, 3- (2H-benzotriazole-2-yl) -5- (1,1-dimethylethyl) -4-hydroxy-C7-9 side chain and linear alkyl Esther can be mentioned.
Among these, benzotriazole-based compounds having a molecular weight of 400 or more are preferable, and for example, in the case of a commercially available product, Chemisorb (registered trademark) 2792 (Cemipro Kasei), ADEKA STAB (registered trademark) LA31 (made by ADEKA Co., Ltd.), Tinubin (manufactured by ADEKA Co., Ltd.) Examples thereof include (registered trademark) 234 (manufactured by BASF).

Examples of benzotriazine compounds include 2-mono (hydroxyphenyl) -1,3,5-triazine compounds, 2,4-bis (hydroxyphenyl) -1,3,5-triazine compounds, and 2,4,6-tris. Examples thereof include (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 (2,4,6-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-octyloxyphenyl) -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-methoxycarbonylpropyloxy) Phenyl) -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 can be mentioned.
Commercially available products may be used as the benzotriazine compound, for example, Chemisorb102 (manufactured by Chemipro Kasei Co., Ltd.), LA-F70 (manufactured by ADEKA Corporation), LA-46 (manufactured by ADEKA Corporation), and Tinubin 405 (manufactured by BASF). , Chinubin 460 (manufactured by BASF), Chinubin 479 (manufactured by BASF), Chinubin 1577FF (manufactured by BASF) and the like can be used.
Among them, 2,4-bis (2,4-dimethylphenyl) -6- [2-hydroxy-4- (3-alkyloxy) is excellent in compatibility with acrylic resins and excellent ultraviolet absorption characteristics. -2-Hydroxypropyloxy) -5-α-cumylphenyl] -s-triazine skeleton (“alkyloxy” means long-chain alkyloxy groups such as octyloxy, nonyloxy, decyloxy, etc.) It can be preferably used.

As the ultraviolet absorber, benzotriazole-based compounds and benzotriazine-based compounds having a molecular weight of 400 or more are preferable from the viewpoint of compatibility with the resin and volatilization during heating, and the ultraviolet absorber itself is heated during extrusion processing. Benzotriazine-based compounds are particularly preferable from the viewpoint of suppressing decomposition by UV rays.

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

Only one kind of these ultraviolet absorbers may be used alone, or two or more kinds thereof may be used in combination.
By using two kinds of ultraviolet absorbers having different structures in combination, 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, moisture heat resistance, thermal stability, and molding processability and exhibits the effects of the present invention, but is 100 mass of methacrylic resin. 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. 3 parts by mass. Within this range, the balance of ultraviolet absorption performance, moldability, etc. is excellent.

--Release agent--
The resin composition containing a methacrylic resin having a ring structure in the main chain of the present embodiment can contain a mold release agent. The release agent is not limited to the following, and is, for example, a fatty acid ester, a fatty acid amide, a fatty acid metal salt, a hydrocarbon-based lubricant, an alcohol-based lubricant, polyalkylene glycols, carboxylic acid esters, and carbonic acid. Examples thereof include hydrocarbons such as paraffin-based mineral oils.

The fatty acid ester that can be used as the release agent is not particularly limited, and conventionally known fatty acid esters can be used.
Examples of the fatty acid ester include fatty acids having 12 to 32 carbon atoms such as lauric acid, palmitic acid, heptadecanoic acid, stearic acid, oleic acid, araquinic acid and behenic acid, and monovalent fatty acids such as palmityl alcohol, stearyl alcohol and behenyl alcohol. Ester compounds with fatty alcohols and polyvalent fatty alcohols such as glycerin, pentaerythritol, dipentaerythritol, sorbitan; complex esters of fatty acids, polybasic organic acids and monovalent fatty alcohols or polyhydric alcohols. Compounds and the like can be used.
Examples of such fatty acid ester-based lubricants include cetyl palmitate, butyl stearate, stearyl stearate, stearyl citrate, glycerin monocaprilate, glycerin monocaplate, glycerin monolaurate, glycerin monopalmitate, and glycerin dipalmi. Tate, glycerin monostearate, glycerin distearate, glycerin tristearate, glycerin monooleate, glycerin dioleate, glycerin trioleate, glycerin monolinoleate, glycerin monobehenate, glycerin mono12-hydroxystearate, glycerin Di12-hydroxystearate, glycerintri 12-hydroxystearate, glycerin diacet monostearate, glycerin quinic acid fatty acid ester, pentaerythritol adipic acid stearic acid ester, montanic acid partially saponified ester, pentaerythritol tetrastearate, dipenta Examples thereof include erythritol hexastearate and sorbitan tristearate.
These fatty acid ester-based lubricants can be used alone or in combination of two or more.
Examples of commercially available products include Riken Vitamin's Rikemar series, Poem series, Riquester series, Rikemaster series, Kao's Exel series, Leodor series, Exepearl series, and Coconard series. Rikemar S-100, Rikemar H-100, Poem V-100, Rikemar B-100, Rikemar HC-100, Rikemar S-200, Poem B-200, Rikestar EW-200, Rikestar EW-400, Exel S -95, Leodor MS-50 and the like can be mentioned.

The fatty acid amide-based lubricant is not particularly limited, and conventionally known lubricants can be used.
Examples of the fatty acid amide-based lubricant include saturated fatty acid amides such as lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, and hydroxystearic acid amide; Fatty acid amide; substituted amides such as N-stearyl stearyl amide, N-oleyl oleic acid amide, N-stearyl oleic acid amide, N-oleyl stealic acid amide, N-stearyl erucate amide, N-oleyl palmitate amide; methylol Methylolamides such as stearate amides and methylolbechenic acid amides; methylene bisstearic acid amides, ethylene biscapric acid amides, ethylene bislauric acid amides, ethylene bisstearic acid amides (ethylene bisstearyl amides), ethylene bisisostearic acid amides, ethylene. Bishydroxystearic acid amide, ethylene bisbechenic acid amide, hexamethylene bisstearic acid amide, hexamethylene bisbechenic acid amide, hexamethylene bishydroxystearic acid amide, N, N'-dystearyl adipic acid amide, N, N'- Saturated fatty acid bisamides such as distearyl sevacinic acid amide; unsaturated fatty acids such as ethylene bisoleic acid amides, hexamethylene bisoleic acid amides, N, N'-diorail adipic acid amides, N, N'-diorail sevacinic acid amides. Bisamides; aromatic bisamides such as m-xylylene bisstearic acid amides and N, N'-distearylisophthalic acid amides can be mentioned.
These fatty acid amide-based release agents can be used alone or in combination of two or more.
Commercially available products include, for example, Diamid series (manufactured by Nihon Kasei), Amide series (manufactured by Nihon Kasei), Nikka Amide series (manufactured by Nihon Kasei), Methylol amide series, Bis Amide series, Slipax series (Nihon Kasei). , Kao wax series (manufactured by Kao), fatty acid amide series (manufactured by Kao), ethylene bisstearic acid amides (manufactured by Dainichi Chemical Industry Co., Ltd.) and the like.

The fatty acid metal salt refers to a metal salt of a higher fatty acid, for example, lithium stearate, magnesium stearate, calcium stearate, calcium laurate, calcium ricinolate, strontium stearate, barium stearate, barium laurate, barium ricinolate, etc. Zinc stearate, zinc laurate, zinc ricinolate, zinc 2-ethylhexoate, lead stearate, lead dibasic stearate, lead naphthenate, calcium 12-hydroxystearate, lithium 12-hydroxystearate and the like can be mentioned. Among them, calcium stearate, magnesium stearate, and zinc stearate are particularly preferable because the obtained transparent resin composition has excellent processability and extremely excellent transparency.
Examples of commercially available products include SZ series, SC series, SM series, and SA series manufactured by Sakai Chemical Industry Co., Ltd.
When the fatty acid metal salt is used, the content should be 0.2% by mass or less with respect to 100% by mass of the resin composition containing the methacrylic resin having a ring structure in the main chain from the viewpoint of maintaining transparency. Is preferable.

The above-mentioned mold release agent may be used alone or in combination of two or more.

As the release agent to be used, those having a decomposition start temperature of 200 ° C. or higher are preferable. Here, the decomposition start temperature can be measured by the 1% mass loss temperature by TGA.
The content of the mold release agent may be any amount as long as the effect as a mold release agent can be obtained, and if the content is excessive, problems such as bleed-out occurrence during processing and extrusion failure due to screw slippage 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, still more preferably 0.8 parts by mass with respect to 100 parts by mass of the methacrylic resin. The amount is less than or equal to parts, more preferably 0.01 to 0.8 parts by mass, and particularly preferably 0.01 to 0.5 parts by mass. When the amount is added in the above range, the decrease in transparency due to the addition of the mold release agent is suppressed, and the mold release defect during injection molding and the sticking to the metal roll during sheet molding tend to be suppressed. preferable.

--Other thermoplastic resins ---
The resin composition containing a methacrylic resin having a ring structure in the main chain of the present embodiment may contain a thermoplastic resin other than the methacrylic resin as long as the object of the present invention is not impaired.
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. A styrene-based polymer such as a block copolymer; further, for example, JP-A-59-20221, JP-A-63-27516, JP-A-51-129449, JP-A-52-56150. , Etc.; Acrylic rubber particles having a three- to four-layer structure; a rubbery polymer disclosed in Japanese Patent Application Laid-Open No. 60-17406, Japanese Patent Application Laid-Open No. 8-245854; International Publication No. 2014-002491. , Acrylate-based rubber-containing graph copolymer particles obtained by multi-stage polymerization; and the like.
Among these, from the viewpoint of obtaining good optical properties and mechanical properties, the composition is compatible with the styrene-acrylonitrile copolymer and the methacrylic resin containing the structural unit (B) having a ring structure in the main chain. Rubber-containing graft copolymer particles having a graft portion on the surface layer thereof are preferable.
As the average particle size of the acrylic rubber particles, the methacrylic rubber-containing graph copolymer particles, and the rubbery polymer described above, the impact strength and optical properties of the molded product obtained from the composition of the present embodiment are enhanced. From the viewpoint, 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, when the methacrylic resin is 100 parts by mass.

(Method for producing a resin composition containing a methacrylic resin having a ring structure in the main chain)
Examples of the method for producing a resin composition containing a methacrylic resin having a ring structure in the main chain include a method of kneading using a kneader such as an extruder, a heating roll, a kneader, a roller mixer, and a Banbury mixer. .. Among them, kneading with an extruder is preferable in terms of productivity. The kneading temperature may be in accordance with the preferable processing temperature of the polymer constituting the methacrylic resin and other resins to be mixed, and is in the range of 140 to 300 ° C., preferably 180 to 280 ° C. as a guide. Further, it is preferable that the extruder is provided with a vent port for the purpose of reducing the volatile content.

(Glass transition temperature of a resin composition containing a methacrylic resin having a ring structure in the main chain)
The glass transition temperature (Tg) of the resin composition of the present embodiment is preferably more than 120 ° C and 160 ° C or less.
When the glass transition temperature of the resin composition exceeds 120 ° C., it is possible to more easily obtain heat resistance necessary and sufficient as a transparent molded product for an optical element. The glass transition temperature (Tg) is more preferably 125 ° C. or higher, still more preferably 130 ° C. or higher, from the viewpoint of dimensional stability under the operating environment temperature.
On the other hand, when the glass transition temperature (Tg) of the resin composition is 160 ° C. or lower, melt processing at an extremely high temperature can be avoided, thermal decomposition of the resin or the like can be suppressed, and a good product can be obtained. The glass transition temperature (Tg) is preferably 150 ° C. or lower for the above-mentioned reasons.
The glass transition temperature (Tg) can be determined by measuring in accordance with JIS-K7121. Specifically, it can be measured by using the method described in Examples described later.

(Photoelastic coefficient of a resin composition containing a methacrylic resin having a ring structure in the main chain)
The photoelastic coefficient C of the resin composition of the present embodiment is preferably −3.0 × ^10-12 to +3.0 × ^10-12 Pa ^-1 , preferably −2.0 × ^10-12 to +2. It is more preferably 0 × 10 ^-12 Pa ^-1 , and further preferably −1.0 × 10 ^-12 to +1.0 × 10 ^-12 Pa ^-1 . When the photoelastic coefficient C is in the above range, it can be suitably used as an optical resin composition having excellent transparency, low birefringence, and high heat resistance, which is suitable for applications requiring high optical characteristics among optical elements. can.
Photoelastic coefficients are described in various documents (see, for example, Review Articles of Chemistry, No. 39, 1998 (published by the Society 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 C is to zero, the smaller the birefringence change due to the external force.
C = Δn / σ ... (e)
Δn = nx-ny ... (f)
(In the equation, C is the photoelastic coefficient, σ is the elongation stress, Δn is birefringence, nx is the refractive index in the extension direction, and ny is the refractive index in the direction perpendicular to the extension direction in the plane.)
If the absolute value of the photoelastic coefficient C of the resin composition of the present embodiment is 3.0 × ^10-12 Pa ^-1 , a birefringence generated by stress generated when the injection molded product is fitted into the product as a component. The refraction is small enough.
Specifically, the photoelastic coefficient C of the resin composition can be obtained by the method described in Examples described later.

(Manufacturing method of transparent molded product for optical elements)
As a method for manufacturing a transparent molded article for an optical element of the present embodiment, various molding methods such as extrusion molding, injection molding, compression molding, calendar molding, inflation molding, and hollow molding can be used. Among them, it is preferable to apply injection molding and injection compression molding from the viewpoint of productivity.
Normally, the injection molding method consists of (1) an injection process in which the resin is melted and the cavity of the mold whose temperature is controlled is filled with the molten resin, and (2) pressure is applied to the inside of the cavity until the gate is sealed, and the cavity is filled in the injection process. A pressure holding step of injecting a resin corresponding to the amount of the molten resin that has been cooled and shrunk in contact with the mold, (3) a cooling step of holding the molded product until the resin is cooled after releasing the holding pressure, (3) 4) It consists of a step of opening a mold and taking out a cooled molded product.

At this time, the molding temperature is in the range of Tg + 100 ° C. to Tg + 160 ° C., preferably in the range of Tg + 110 ° C. to Tg + 150 ° C., based on the glass transition temperature of the resin composition containing the methacrylic resin having a ring structure in the main chain. It is preferable to have. Here, the molding temperature refers to the control temperature of the band heater wound around the injection nozzle.
The mold temperature is in the range of Tg-70 ° C to Tg, preferably from Tg-50 ° C, based on the glass transition temperature (Tg) of the resin composition containing a methacrylic resin having a ring structure in the main chain. It is preferably in the range of Tg-20 ° C.

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 from the range of, for example, 200 to 1000 mm / sec.
The pressure for holding the pressure can be appropriately selected depending on the shape of the injection-molded article to be obtained, and can be appropriately selected, for example, in the range of 30 to 120 MPa. If the solidified body is a thin-walled molded product and the solidification rate is high, the holding pressure may not be applied.
Here, the pressure for holding pressure is the pressure held by the screw for further feeding the molten resin from the gate after filling the molten resin.

In injection compression molding, the mold is opened slightly in advance at the start of injection molding, the molten resin is filled in the mold at high speed and low pressure, and then the mold clamping pressure is increased at high speed to keep the entire surface of the resin uniform. It is an injection molding method to which a compression holding step of pressing is added, and it becomes possible to mold a molded body having excellent surface characteristics and optical characteristics.
When an injection molded product having a thinner wall thickness, for example, a thickness of less than 1 mm and a diagonal dimension of more than 100 mm is to be obtained, injection compression molding is used to obtain a molded product having excellent optical characteristics and color tone. It is particularly preferable because it can be obtained.

Further, when an injection-molded article obtained by using a resin composition containing a methacrylic resin having a ring structure in the main chain is used as a light guide plate, some have fine irregularities on the surface thereof. included. By providing such fine irregularities, it is not necessary to separately provide a reflective layer by printing or the like, which is preferable. The fine unevenness is not particularly limited, but is an unevenness having a clear structural unit such as a rectangular parallelepiped, a cylinder, an elliptical column, a triangular prism, a spherical surface, or an aspherical surface, or an uneven shape such as a satin finish or a hairline. Examples include unevenness or a combination thereof in which the structural unit is not clear, and unevenness in which the structural unit is clear but the shape, in particular, the size is changing. As 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.

Various molded bodies using a methacrylic resin having a ring structure in the main chain of the present embodiment and the resin composition thereof are subjected to surface functionalization treatments such as antireflection treatment, transparent conductive treatment, electromagnetic wave shielding treatment, and gas barrier treatment. Can also be done further.

(Applications for transparent molded products for optical elements)
According to the transparent molded body for an optical element of the present embodiment, not only the bright spot foreign matter which becomes a bright spot due to diffuse reflection is highly reduced, but also the transparency and heat resistance are excellent, and the birefringence is highly controlled. A molded body containing a methacrylic resin composition can be obtained, and it can be suitably used for applications such as household goods, OA equipment, AV equipment, battery electrical components, lighting equipment, optical members in automobiles and the like.
Optical members in household products, OA equipment, AV equipment, battery electrical components, lighting equipment, etc. include, for example, a light guide plate used for displays such as smartphones, PDA, tablet PCs, and liquid crystal televisions, display front plates, touch panels, and further. Is a lens for smartphones, tablet PC cameras, and optical lens components such as head mount displays and liquid crystal projectors, such as prism elements, waveguides, lenses, especially small thin-walled uneven thickness optical lenses, optical fibers, and optical fiber coating materials. , Lenses, Fresnel lenses, phase plates with microlens arrays, optical cover components and the like.
Examples of optical members in automobiles include a light guide plate for an in-vehicle display; an in-vehicle meter panel; an optical component for a head-up display such as a front plate of a car navigation system, a combiner, and an optical cover component; an in-vehicle camera lens, a light guide rod, and the like. ..
In addition to the above, it can also be used as a display device component for digital signage that sends information to a thin display connected to the network for the purpose of advertising, advertising, etc. in places such as camera focal plates, outdoors, stores, public institutions, and transportation. It can be preferably used.

Hereinafter, the contents of the present invention will be specifically described with reference to Examples and Comparative Examples. The present invention is not limited to the following examples.

<1. Measurement of polymerization conversion rate>
A part of the polymerization solution in Examples and Comparative Examples was collected, and the amount of the monomer remaining in the polymerization solution sample was dissolved in chloroform to prepare a 5% by mass solution, which was used as an internal standard substance. -Decan is added, and the concentration of the monomer remaining in the sample is measured by gas chromatography (GC-2010 manufactured by Shimadzu Corporation), and the total mass (a) of the monomer remaining in the polymerization solution is determined. I asked. Then, the total mass (a), the total mass (b) assuming that the total amount of the monomers added by the time the sample was collected remained in the polymerization solution, and the simple addition by the end of the polymerization step. From the total mass (c) of the monomer, the polymerization conversion rate (%) was calculated by the calculation formula (ba) / c × 100.

<2. Analysis of structural units>
By ^{1 1} H-NMR measurement and ¹³ C-NMR measurement, the structural unit of the methacrylic resin having a ring structure in the produced main chain was identified, and the abundance thereof was calculated. The measurement conditions for ^{1 1} H-NMR measurement and ¹³ C-NMR measurement are as follows.
・ Measuring equipment: Bruker DPX-400
-Measuring solvent: CDCl ₃ or DMSO-d ₆
・ Measurement temperature: 40 ° C

<3. Measurement of molecular weight and molecular weight distribution>
The weight average molecular weight (Mw) and the number average molecular weight (Mn) of the methacrylic resin having a ring structure in the main chain produced in Examples and Comparative Examples described later were measured by the following devices and conditions.
-Measuring device: Gel Permeation Chromatography (HLC-8320GPC) manufactured by Tosoh Corporation
·Measurement condition:
Columns: 1 TSKguardcolum SuperH-H, 2 TSKgel SuperHM-M, and 1 TSKgel SuperH2500 were connected in series and used. Column temperature: 40 ° C
The developing solvent: tetrahydrofuran, the flow rate: 0.6 mL / min, and 0.1 g / L of 2,6-di-t-butyl-4-methylphenol (BHT) as an internal standard were added.
Detector: RI (differential refractometer) detector, detection sensitivity: 3.0 mV / min Sample: 0.02 g of methacrylic resin or a 20 mL solution of methacryl resin in tetrahydrofuran. Injection volume: 10 μL
Standard sample for calibration curve: Weight peak of monodisperse The following 10 types of methyl methacrylate (manufactured by Polymer Laboratories; PMMACalibration Kit M-10) having a known molecular weight 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 with respect to the elution time of the methacrylic resin was measured.
Based on the calibration curve obtained by the measurement of the standard sample for the calibration curve, the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the methacrylic resin were determined.

<4. Glass transition temperature>
The glass transition temperature (Tg) (° C.) of the methacrylic resin having a ring structure in the main chain was measured according to JIS-K7121.
First, about 10 mg of each of 4 test pieces (4 points) was cut out from a sample whose state was adjusted (leaved at 23 ° C. for 1 week) in a standard state (23 ° C., 65% RH).
Next, using a differential scanning calorimeter (Diamond DSC manufactured by Perkin Elmer Japan Co., Ltd.) under the condition of a nitrogen gas flow rate of 25 mL / min, the temperature rises from room temperature (23 ° C) to 200 ° C at 10 ° C / min. Warm (primary temperature rise) and hold at 200 ° C. for 5 minutes to completely thaw the sample, then cool down from 200 ° C. to 40 ° C. at 10 ° C./min, hold at 40 ° C. for 5 minutes, and then Of the DSC curves drawn during the temperature rise again (secondary temperature rise) under the above temperature rise conditions, the stepwise change partial curve at the time of the second temperature rise and each baseline extension line are equidistant in the vertical axis direction. The intersection with a certain straight line (intermediate point glass transition temperature) was measured as the glass transition temperature (Tg) (° C.). Four points were measured per sample, and the arithmetic mean of the four points (rounded to the nearest whole number) was used as the measured value.

<5. Measurement of composition distribution of structural units>
The molecular weight fractions of the methacrylic resins having a ring structure in the main chain obtained in Examples and Comparative Examples were carried out under the following equipment and conditions.
-Preparation device: LC-908 manufactured by Nippon Analytical Industry Co., Ltd.
・ Distribution conditions:
Column: SHODEX K-2004
Eluent: chloroform, flow rate: 3 mL / min Detector: UV detector (254 nm)
Sample: 3% by mass chloroform solution Separation method: 3 mL of the sample was injected, and the elution time of 18 to 43 minutes was separated at 1-minute intervals.
The preparative operation was repeated 3 times, and the sample selected from the obtained fractions was selected from the above <2. Obtain the composition ratio of the structural unit according to <Analysis of structural unit>, and also <3. The molecular weight distribution was measured according to the measurement of molecular weight and molecular weight distribution>, and the peak top molecular weight (Mp) was obtained from the position of the apex of the peak.

<6. Measurement of bright spot foreign matter in transparent molded product>
The four strip-shaped molded pieces obtained in Examples and Comparative Examples were inspected for bright spot foreign matter in a dark field using VHX-7000 manufactured by KEYENCE Co., Ltd. as a digital microscope. The lens magnification is set to 80 times so that the width direction of the strip-shaped molded piece is perpendicular to the stage of the digital microscope and the length direction of the strip-shaped molded piece is the left-right direction of the digital microscope. Then, the strip-shaped molded piece was installed in a digital microscope. Next, light was incident on each of the two opposite side surfaces of the strip-shaped molded piece of 20 mm × 3 mm from the external illumination to generate a bright spot. Of the height (width) of 20 mm of the strip-shaped molded piece, the range of 16 mm excluding the range of 2 mm from the upper and lower surfaces as the surface part of the strip-shaped molded piece is taken as the inside of the strip-shaped molded piece, and the depth composition is performed by imaging. went. Further, the obtained depth composite images were concatenated over a total range of 50 mm from the center of the strip-shaped molded piece to 25 mm in the length direction.
As the external lighting for generating bright spots, two blue LED lightings (line LED lighting "LDL2-158X16BL2" manufactured by CCS Co., Ltd., peak emission wavelength 467 nm) were used. The blue LED lighting, the strip-shaped molded piece, with the 20 mm x 3 mm side surface and the light emitting surface of the blue LED lighting facing each other so that light is incident on each of the two opposite 20 mm × 3 mm side surfaces of the strip-shaped molded piece. The blue LED lights were arranged in a row at intervals of about 1 mm in this order.
Further, for each of the four strip-shaped molded pieces, among the connected depth composite images, the bright spot foreign substances of 10 micrometers or more existing in the area of thickness 2.5 mm × width 16 mm × length 50 mm are counted and 1 cm. Calculated as the number per ³ volumes.

<7. Measurement of photoelasticity coefficient>
An unstretched sample was prepared by first using the methacrylic resin obtained in Examples and Comparative Examples into a press film using a vacuum compression molding machine.
As a specific sample preparation condition, a vacuum compression molding machine (manufactured by Kondo Metal Industry Co., Ltd.) with a methacrylic resin placed in a 150 μm-thick polyimide frame and sandwiched between two polyimide films and two iron plates. Set in SFV-30 type), preheat at 260 ° C. under reduced pressure (about 10 kPa) for 10 minutes, compress at 260 ° C. at about 10 MPa for 5 minutes, release the reduced pressure and press pressure, and then cool the compression molding machine. It was transferred to and cooled and solidified. The obtained press film was cured in a constant temperature and humidity chamber adjusted to 23 ° C. and a humidity of 50% for 24 hours or more, and then used as an unstretched sample.
Using a film-shaped test piece cut out from this unstretched sample to a width of 6 mm, and using the birefringence measuring device described in detail in Polymer Engineering and Science 1999, 39, 2349-2357, the photoelastic coefficient C (Pa- ⁾ . ¹ ) was measured.
The film-shaped test piece was placed in a film tensioning device (manufactured by Imoto Seisakusho) similarly installed in a constant temperature and humidity chamber so that the chuck distance was 50 mm. Next, the device was arranged so that the optical path of the birefringence measuring device (ReTS-100 manufactured by Otsuka Electronics) was located at the center of the film, and the stretch stress was set at a chuck spacing of 50 mm and a chuck moving speed of 0.1 mm / min. The birefringence of the test piece was measured at a wavelength of 550 nm.
From the relationship between the birefringence (Δn) and the elongation stress (σ) obtained from the measurement, the slope of the straight line was obtained by the minimum square approximation, and the photoelastic coefficient (C) (Pa ^-1 ) was calculated. For the calculation, data with an elongation stress between 2.5 MPa ≤ σ ≤ 10 MPa was used.
C = Δn / σ
Here, the birefringence (Δn) is a 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. Visibility evaluation>
The strip molded pieces obtained in Examples and Comparative Examples were evaluated for visual visibility with white LED illumination applied to the side surface (20 mm × 3 mm surface) of the molded body. The evaluation result was judged as good visibility (〇) or poor visibility (×).

[material]
The raw materials used in the production examples 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-butyl peroxy) cyclohexane: "Perhexa C" manufactured by NOF CORPORATION

[[Chain Transfer Agent]]
・ N-octyl mercaptan: manufactured by Kao Corporation

[Example 1]
Methyl methacrylate (hereinafter referred to as MMA) 358.6 kg, N-phenylmaleimide (hereinafter referred to as phMI) 29.4 kg, N-cyclohexylmaleimide (hereinafter referred to as chMI) 67.7 kg, chain transfer agent n-octyl mercaptan. 0.77 kg and 224.3 kg of methaxylene (hereinafter referred to as mXy) were weighed, added to a 1.25 m3 reactor equipped with a temperature control device using a jacket and a stirring blade, 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, added to the tank 1 and stirred to obtain a mixed monomer solution for addition.
The contents of the reactor were bubbling with nitrogen at a rate of 30 L / min for 1 hour, and the tank 1 was bubbling with nitrogen at a rate of 10 L / min for 30 minutes to remove dissolved oxygen.
After that, steam is blown into the jacket to raise the solution temperature in the reactor to 115 ° C., and 0.487 kg of 1,1-di (t-butylperoxy) cyclohexane is dissolved in mXy 1.888 kg while stirring at 50 rpm. Polymerization was started by adding the polymerization initiator solution 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. After 30 minutes from the start of polymerization, the rate of addition of the initiator solution was reduced to 0.5 kg / hour. Further, from 1 hour after the start of the polymerization to 4 hours, the total amount of the mixed monomer solution for addition was added from the tank 1 at a constant velocity.
Further, the addition rate of the initiator solution was reduced to 0.25 kg / hour 3.5 hours after the start of polymerization, and the addition was stopped 5 hours after the start of polymerization.
After 12 hours had passed from the start of the polymerization, a polymer solution containing a methacrylic resin having a structural unit having a ring structure in the main chain was obtained.
The polymer solution was sampled 2 hours and 12 hours after the start of polymerization, and the polymerization conversion rate was analyzed from the remaining monomer concentration. The polymerization conversion rate after 2 hours was MMA78.9%. , PhMI 77.3%, chMI 70.4%, and after 12 hours, MMA was 97.9%, phMI 99.4%, and chMI 99.3%. When the monomer added after 2 hours from the start of polymerization is added and the conversion conversion rate after 2 hours is converted into the consumption rate with respect to the total amount of each monomer added by the end of polymerization, MMA 67.2%, phMI67 It was .1% and chMI 70.4%.
This polymer solution was supplied to a concentrator consisting of a tubular heat exchanger and a vaporization tank preheated to 250 ° C. to perform devolatileization. The vacuum degree of 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. The environment where the manufacturing equipment is located is a space controlled by class 6 (ISO146441) cleanliness, and a bar-type ionizer is installed to eliminate static electricity in the entire space.
When the composition of the obtained pellet-shaped polymer was confirmed, the structural units derived from the MMA, phMI, and chMI monomers were 81.0% by mass, 6.6% by mass, and 12.4% by mass, respectively. there were.
The weight average molecular weight was 108,000 and Mw / Mn was 2.04.
The glass transition temperature was 134 ° C.
The measurement results of the composition distribution of the structural unit are Mp: 253,000 (MMA: 81.4% by mass, phMI: 6.5% by mass, chMI: 12.1% by mass), Mp: 176,000 (MMA:: 81.1% by mass, phMI: 6.6% by mass, chMI: 12.3% by mass), Mp: 111,000 (MMA: 80.9% by mass, phMI: 6.7% by mass, chMI: 12.4) Mp: 88,000 (MMA: 80.8% by mass, phMI: 6.7% by mass, chMI: 12.5% by mass), Mp: 48,000 (MMA: 80.4% by mass, phMI) : 6.8% by mass, chMI: 12.8% by mass).
A press film was prepared using the obtained methacrylic resin, and the photoelastic coefficient was evaluated. As a result, the photoelastic coefficient was −0.3 × ^10-12 Pa ^-1 .
Next, using the obtained methacrylic resin, a cylinder temperature of 280 was used by an injection molding machine (EC-100SX manufactured by Toshiba Machine Co., Ltd.) and a strip molding die having a thickness of 3 mm, a width of 20 mm, and a length of 220 mm having a side gate. By injection molding at ° C. and a mold temperature of 70 ° C., a strip molded piece for measuring bright spot foreign matter was obtained.
The environment where the injection molding machine is located is a space controlled by class 6 (ISO146441) cleanliness. In particular, a bar-type ionizer is installed to eliminate static electricity from the entire space, and for foreign matter adhering to the packaging surface due to exposure to the external environment after pellet packaging, molding is performed after removing the adhering foreign matter with an air gun with a static elimination function. Moved to the environment.
When the above-mentioned bright spot foreign matter was measured for four strip molded bodies, a total of seven bright spot foreign matter having a diameter of 10 μm or more were measured. That is, when calculated as the number of bright spot foreign substances per 1 cm ³ volume, it was 0.875 / cm ³ .
Moreover, when the visibility was evaluated, the visibility was good (〇).

[Example 2]
A methacrylic resin was prepared in the same manner as in Example 1 except that the polymer solution was filtered and purified with a polymer filter having a pore size of 10 μm.
Similarly, when the bright spot foreign matter was measured for 4 strips, a total of 6 bright spot foreign matter of 10 μm or more were measured, and when calculated as the number of bright spot foreign matter per 1 cm ³ volume, 0.75 pieces / cm ³ Met.
Moreover, when the visibility was evaluated, the visibility was good (〇).
The polymerization conversion rate, structural unit, weight average molecular weight (Mw), molecular weight distribution (Mw / Mn), glass transition temperature, composition distribution of structural unit, and photoelastic coefficient were the same results as in Example 1.

[Comparative Example 1]
A methacrylic resin was prepared from the same raw material as the polymerization formulation described in Example 1 in a general environment in which a clean booth or the like was not installed. In the injection molding using the obtained methacrylic resin, molding was performed in a space controlled to have the same cleanliness as the clean environment described in Example 1.
When the bright spot foreign matter was measured on the four strips obtained, a total of 76 bright spot foreign matter of 10 μm or more were measured, and when calculated as the number of bright spot foreign matter per 1 cm ³ volume, 9.5 pieces / It was cm ³ .
Moreover, when the visibility was evaluated, the visibility was poor (x).
The polymerization conversion rate, structural unit, weight average molecular weight (Mw), molecular weight distribution (Mw / Mn), glass transition temperature, composition distribution of structural unit, and photoelastic coefficient were the same results as in Example 1.

[Comparative Example 2]
Using the methacrylic resin obtained in Comparative Example 1, a strip molded piece was obtained by injection molding in a general environment where a clean booth or the like was not installed.
When the bright spot foreign matter was measured on the four strips obtained, a total of 192 bright spot foreign matter of 10 μm or more was measured, and when calculated as the number of bright spot foreign matter per 1 cm ³ volume, 24 pieces / cm ³ Met.
Moreover, when the visibility was evaluated, the visibility was poor (x).
The polymerization conversion rate, structural unit, weight average molecular weight (Mw), molecular weight distribution (Mw / Mn), glass transition temperature, composition distribution of structural unit, and photoelastic coefficient were the same results as in Example 1.

It can be seen that the transparent molded product for an optical element of the embodiment has a high degree of reduction in bright spot foreign matter and has good visibility.

The transparent molded body in which the bright spot foreign matter of the present invention is highly reduced can be used as an optical member in household products, OA equipment, AV equipment, battery electrical components, lighting equipment, etc., for example, a smartphone, a PDA, a tablet PC, or a liquid crystal. Light guide plates, display front plates, touch panels, lenses for smartphones, tablet PC cameras, etc. used for displays such as televisions, and optical lens components such as head mount displays and liquid crystal projectors, such as prism elements, waveguides, lenses, etc. In particular, small thin-walled uneven-walled optical lenses, optical fibers, optical fiber coating materials, lenses, Frenel lenses, phase plates equipped with microlens arrays, optical cover parts, and the like can be mentioned.
Examples of optical members in automobiles include a light guide plate for an in-vehicle display; an in-vehicle meter panel; an optical component for a head-up display such as a front plate of a car navigation system, a combiner, and an optical cover component; an in-vehicle camera lens, a light guide rod, and the like. ..
In addition to the above, it can also be used as a display device component for digital signage that sends information to a thin display connected to the network for the purpose of advertising, advertising, etc. in places such as camera focal plates, outdoors, stores, public institutions, and transportation. It can be preferably used.

Claims (4)

A transparent molded body for an optical element, characterized in that the content of a bright spot foreign substance having a bright spot of 10 micrometers or more, which becomes a bright spot due to diffuse reflection when light is incident, is 1 piece / cm ³ or less per unit volume. The transparent molded article for an optical element according to claim 1, which comprises a resin composition containing a methacrylic resin having a ring structure in a main chain. The transparent molded article for an optical element according to claim 2, wherein the glass dislocation temperature of the resin composition is more than 120 ° C. and 160 ° C. or lower. The transparent molded article for an optical element according to claim 2 or 3, wherein the photoelastic coefficient of the resin composition is −3.0 × 10 ^-12 to +3.0 × ^10-12 Pa ^-1 .