JP2013019957A - Polarization light transmitting optical component and optical projection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a material having low birefringence and heat resistance, a polarization light transmitting optical component excellent in heat resistance, inorganic adhesion, and hardness, and having optical isotropy (low birefringence), and an optical projection device using the material and the polarization light transmitting optical component.SOLUTION: The polarization light transmitting optical component is formed of an acrylic thermoplastic resin containing 50-95 mass% of a first structural unit selected from a methacrylic acid monomer, a methacrylic acid ester and the like; 0.1-20 mass% of a second structural unit selected from an N-substituted maleimide compound such as N-phenyl maleimide; and 0.1-49.9 mass% of a third structural unit selected from the N-substituted maleimide compound such as N-cyclohexyl maleimide compound.

Description

  The present invention relates to a polarization transmission optical component and an optical projection apparatus.

  Highly transparent optical materials are widely used as useful optical components. Examples thereof include a spherical convex lens, a spherical concave lens, an aspherical lens, a spherical lens, a Fresnel lens, a fly-eye lens, a collimator lens, an optical fiber, a reflection sheet, a brightness enhancement film, a Gram Thompson polarizer, a beam splitter, and the like.

  In particular, with the development of liquid crystal technology and laser light source technology, in recent years, a polarization beam splitter has attracted attention as an optical component that separates and transmits polarized light in optical pickup applications, various optical communication devices, and various projection apparatuses (Patent Document 1). .

  The polarization beam splitter includes a prism type, a planar type, a wedge substrate type, and the like. Of the prism types, a simple configuration generally has a cubic shape in which two prisms each having a transparent dielectric multilayer film or a metal thin film formed on the overlapping surfaces to be joined are overlapped. Also known is a sheet-like one formed by forming a transparent dielectric multilayer film on an inclined surface formed by opposed minute prism-like protrusions (Patent Documents 2 and 3).

  These polarizing beam splitter components have high optical isotropy, so-called low birefringence, that allows the polarized light separated at the interface to pass through without being broken, along with high transparency for sufficiently maintaining the amount of transmitted light. Required.

  In the case of a polymer, birefringence is the sum of orientation birefringence due to the orientation of polymer chains and photoelastic birefringence generated by stress within an elastic range applied from the outside, and is usually considerably larger than that of optical glass. Therefore, precision optical parts have been molded through a process of performing post-processing methods such as polishing after molding, using optical glass with sufficient strain as a material. As a result, it can be said that it is not necessarily manufactured by a method having excellent productivity.

  In general, a polymer injection molding method is a method with excellent productivity, and a method of forming various optical components by injection molding of polymethyl methacrylate or polycarbonate having high optical transparency has been studied. However, in injection molding, photoelastic birefringence occurs due to orientation birefringence due to resin orientation during molding and the stress derived from molding distortion that remains after annealing, and it is difficult to obtain a high-quality product. .

  On the other hand, productivity is inferior to the injection molding method as a method of using a polymer as an optical component, but a bulk polymerization method is widely known as a product quality superior to the injection molding. In the bulk polymerization method, orientation birefringence does not occur as compared with injection molding. However, on the other hand, the volumetric shrinkage during polymerization is large. It was difficult to sufficiently remove strain after polymerization by annealing, and furthermore, it was difficult to completely remove internal foam. As a result, even in polymethyl methacrylate having a relatively small photoelastic coefficient, it is difficult to sufficiently and sufficiently suppress birefringence in recent optical applications.

  On the other hand, Patent Document 4 discloses an acrylic composition capable of radical polymerization. In Patent Document 4, the volumetric shrinkage rate of the polymethyl methacrylate composition is suppressed by using an acryloyl oligomer having a polyfunctional radically polymerizable group, and the polymerization solution has a viscosity that can be poured into a mold even in a molding method. After reacting, the product is poured into a mold and a photoinitiator is used to achieve a product with high optical uniformity. However, even with these methods, there remains a problem that productivity is low and photoelastic birefringence that occurs due to external stress strain, installation state, and the like caused by various processing that the product receives after molding remains. . For this reason, it is difficult to say that birefringence is sufficiently and sufficiently suppressed for recent optical applications.

  The use of an optical material including a transparent elastic body having a glass transition temperature of room temperature or lower is disclosed as a method for suppressing the strain that is the cause of the photoelastic birefringence (Patent Document 5). However, transparency is not necessary and sufficient for recent optical applications.

  On the other hand, as a completely different approach, a material composition that does not cause orientation birefringence and photoelastic birefringence during injection molding is disclosed (Patent Document 5). This material composition exhibits extremely low birefringence and can be sufficiently injection molded.

JP 2010-191173 A Japanese Patent Laid-Open No. 6-51399 JP-A-8-15525 WO2007 / 094953 JP-A-7-120621 JP 2006-308682 A

  However, this material composition has a low glass transition temperature of less than 100 ° C. and is not heat resistant enough to be installed around an HID (High Intensity Discharge) lamp that has been conventionally used as a light source for a polarizing beam splitter. Also, in recent years, even when installed around LED light sources, which are increasingly adopted in various display devices, heat resistance of 120 ° C. or higher is required, so that the heat resistance is not sufficient. Moreover, when the glass transition temperature is 100 ° C. or lower, it is difficult to deposit a transparent multilayer dielectric having high adhesion and excellent quality as a polarizing beam splitter.

  As described above, various polarized light transmission optical parts required in recent years are desired to satisfy low birefringence, heat resistance, high heat melt moldability, heat resistance, and inorganic adhesion.

  Accordingly, the present invention provides a polarization transmitting optical component having high optical isotropy (low birefringence), heat resistance, and inorganic adhesion, from a material having low birefringence and heat resistance, and an optical device using the same. An object is to provide a projection device.

  As a result of intensive studies to solve the above-mentioned problems, the present inventor has developed highly optical isotropy (low birefringence) and heat resistance from a specific acrylic thermoplastic resin as a material for a polarized light transmission optical component. The inventors have found that a polarized light transmitting optical component having inorganic adhesion can be obtained, and that an optical projection apparatus comprising the same can be obtained, and the present invention has been completed based on this finding.

［式中、Ｒ^１は、水素原子、炭素数１〜１２のアルキル基、炭素数５〜１２のシクロアルキル基、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、又は、下記Ａ群より選ばれる少なくとも一種の置換基を有する炭素数６〜１４のアリール基、を示す。
Ａ群：ハロゲン原子、ヒドロキシル基、ニトロ基、炭素数１〜１２のアルコキシ基及び炭素数１〜１２のアルキル基。］

［式中、Ｒ^２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、又は、下記Ｂ群より選ばれる少なくとも一種の置換基を有する炭素数６〜１４のアリール基、を示し、Ｒ^３及びＲ^４はそれぞれ独立に、水素原子、炭素数１〜１２のアルキル基又は炭素数６〜１４のアリール基を示す。
Ｂ群：ハロゲン原子、ヒドロキシル基、ニトロ基、炭素数１〜１２のアルコキシ基、炭素数１〜１２のアルキル基及び炭素数７〜１４のアリールアルキル基。］

［式中、Ｒ^５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、又は、下記Ｃ群より選ばれる少なくとも一種の置換基を有する炭素数１〜１２のアルキル基、を示し、Ｒ^６及びＲ^７はそれぞれ独立に、水素原子、炭素数１〜１２のアルキル基又は炭素数６〜１４のアリール基を示す。
Ｃ群：ハロゲン原子、ヒドロキシル基、ニトロ基及び炭素数１〜１２のアルコキシ基。］
［２］アクリル系熱可塑性樹脂の光弾性係数の絶対値が、３．０×１０^−１２Ｐａ^−１以下である［１］に記載の偏光透過光学部品。
［３］アクリル系熱可塑性樹脂のハロゲン原子含有率が、アクリル系熱可塑性樹脂の総量基準で０．４７質量％未満である［１］又は［２］に記載の偏光透過光学部品。
［４］第二の構造単位の含有量の、第三の構造単位の含有量に対するモル比が０より大きく１５以下である［１］〜［３］のいずれか１つに記載の偏光透過光学部品。
［５］ 上記Ｒ^１が、メチル基又はベンジル基であり、上記Ｒ^２が、フェニル基又は上記Ｂ群より選ばれる少なくとも一種の置換基を有するフェニル基であり、上記Ｒ^５が、シクロヘキシル基である［１］〜［４］のいずれか１つに記載の偏光透過光学部品。
［６］アクリル系熱可塑性樹脂は、フィルム成形した場合の面内方向の位相差Ｒｅの絶対値が、１００μｍ厚み換算で３０ｎｍ以下となる樹脂である、［１］〜［５］のいずれか１つに記載の偏光透過光学部品。
［７］アクリル系熱可塑性樹脂は、フィルム成形した場合の厚み方向の位相差Ｒｔｈの絶対値が１００μｍ厚み換算で、３０ｎｍ以下となる樹脂である、［１］〜［６］のいずれか１つに記載の偏光透過光学部品。
［８］アクリル系熱可塑性樹脂は、フィルム成形した場合の延伸倍率（Ｓ）と、該延伸倍率での１００μｍ厚み換算複屈折（Δｎ（Ｓ））との最小二乗法近似直線関係式（ａ）における傾きαの値が、下記式（ｂ）を満たす樹脂である、［１］〜［７］のいずれか１つに記載の偏光透過光学部品。
Δｎ（Ｓ）＝α×Ｓ＋β ・・・（ａ）
−０．３０×１０^−５≦α≦０．３０×１０^−５ ・・・（ｂ）
［式中、βは定数であり、無延伸時の複屈折を示す。］
［９］アクリル系熱可塑性樹脂のガラス転移温度が１３０℃以上である［１］〜［８］のいずれか１つに記載の偏光透過光学部品。
［１０］表面の鉛筆硬度が３Ｈ以上である［１］〜［９］のいずれか１つに記載の偏光透過光学部品。
［１１］光路長が１０〜１０００００μｍである、［１］〜［１０］のいずれか１つに記載の偏光透過光学部品。
［１２］表面に無機層を蒸着した、［１］〜［１１］のいずれか１つに記載の偏光透過光学部品。
［１３］無機層が透明多層誘電体である［１２］に記載の偏光透過光学部品。
［１４］［１２］又は［１３］に記載の偏光透過光学部品を備える、光学投影装置。 That is, the present invention relates to the following.
[1] An acrylic having a first structural unit represented by the following formula (1), a second structural unit represented by the following formula (2), and a third structural unit represented by the following formula (3) An acrylic thermoplastic resin based on the total amount thereof, 50 to 95% by mass of the first structural unit, 0.1 to 20% by mass of the second structural unit; A polarized light transmission optical component having 1 to 49.9% by mass of a third structural unit.

[Wherein, R ¹ represents a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, an arylalkyl group having 7 to 14 carbon atoms, an aryl group having 6 to 14 carbon atoms, or And an aryl group having 6 to 14 carbon atoms and having at least one substituent selected from the following group A.
Group A: a halogen atom, a hydroxyl group, a nitro group, an alkoxy group having 1 to 12 carbon atoms, and an alkyl group having 1 to 12 carbon atoms. ]

[Wherein, R ² represents an arylalkyl group having 7 to 14 carbon atoms, an aryl group having 6 to 14 carbon atoms, or an aryl group having 6 to 14 carbon atoms having at least one substituent selected from the following group B: R ³ and R ⁴ each independently represent a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, or an aryl group having 6 to 14 carbon atoms.
Group B: a halogen atom, a hydroxyl group, a nitro group, an alkoxy group having 1 to 12 carbon atoms, an alkyl group having 1 to 12 carbon atoms, and an arylalkyl group having 7 to 14 carbon atoms. ]

[Wherein, R ⁵ represents a hydrogen atom, a cycloalkyl group having 3 to 12 carbon atoms, an alkyl group having 1 to 12 carbon atoms, or at least one substituent having at least one substituent selected from the following group C. R ⁶ and R ⁷ each independently represents a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, or an aryl group having 6 to 14 carbon atoms.
Group C: a halogen atom, a hydroxyl group, a nitro group, and an alkoxy group having 1 to 12 carbon atoms. ]
[2] The polarized light transmitting optical component according to [1], wherein the absolute value of the photoelastic coefficient of the acrylic thermoplastic resin is 3.0 × 10 ⁻¹² Pa ⁻¹ or less.
[3] The polarized light transmitting optical component according to [1] or [2], wherein the halogen atom content of the acrylic thermoplastic resin is less than 0.47% by mass based on the total amount of the acrylic thermoplastic resin.
[4] The polarized light transmission optics according to any one of [1] to [3], wherein the molar ratio of the content of the second structural unit to the content of the third structural unit is greater than 0 and 15 or less. parts.
[5] The R ¹ is a methyl group or a benzyl group, the R ² is a phenyl group or a phenyl group having at least one substituent selected from the group B, and the R ⁵ is a cyclohexyl group. The polarized light transmission optical component according to any one of [1] to [4].
[6] The acrylic thermoplastic resin is any one of [1] to [5], in which the absolute value of the retardation Re in the in-plane direction when the film is formed is 30 nm or less in terms of 100 μm thickness. Polarized light transmission optical component as described in one.
[7] The acrylic thermoplastic resin is a resin in which the absolute value of the retardation Rth in the thickness direction when a film is formed is 30 nm or less in terms of thickness of 100 μm, and any one of [1] to [6] The polarized light transmission optical component according to 1.
[8] The acrylic thermoplastic resin is a least-squares approximate linear relational expression (a) between the draw ratio (S) when film-forming and 100 μm-thickness converted birefringence (Δn (S)) at the draw ratio. The polarized light transmission optical component according to any one of [1] to [7], wherein the value of the slope α is a resin that satisfies the following formula (b).
Δn (S) = α × S + β (a)
−0.30 × 10 ⁻⁵ ≦ α ≦ 0.30 × 10 ⁻⁵ (b)
[In the formula, β is a constant and indicates birefringence at the time of non-stretching. ]
[9] The polarized light transmitting optical component according to any one of [1] to [8], wherein the glass transition temperature of the acrylic thermoplastic resin is 130 ° C. or higher.
[10] The polarized light transmitting optical component according to any one of [1] to [9], wherein the pencil hardness of the surface is 3H or more.
[11] The polarized light transmitting optical component according to any one of [1] to [10], wherein the optical path length is 10 to 100,000 μm.
[12] The polarized light transmitting optical component according to any one of [1] to [11], wherein an inorganic layer is deposited on the surface.
[13] The polarized light transmitting optical component according to [12], wherein the inorganic layer is a transparent multilayer dielectric.
[14] An optical projection device comprising the polarization transmission optical component according to [12] or [13].

  According to the present invention, it is possible to provide a polarized light transmitting optical component having high optical isotropy (low birefringence), heat resistance, and inorganic adhesion, and a small and light optical projection apparatus can be obtained by using it. Can be provided.

It is a schematic diagram of an optical projector.

  Hereinafter, preferred embodiments of the present invention will be described in detail.

[Acrylic thermoplastic resin]
The polarized light transmitting optical component of this embodiment is made of an acrylic thermoplastic resin. The acrylic thermoplastic resin has a first structural unit, a second structural unit, and a third structural unit. Hereinafter, each structural unit will be described.

(First structural unit)
The first structural unit is a structural unit represented by the following formula (1).

式中、Ｒ^１は、水素原子、炭素数１〜１２のアルキル基、炭素数５〜１２のシクロアルキル基、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、又は、下記Ａ群より選ばれる少なくとも一種の置換基を有する炭素数６〜１４のアリール基、を示す。ここで、Ａ群は、ハロゲン原子、ヒドロキシル基、ニトロ基、炭素数１〜１２のアルコキシ基及び炭素数１〜１２のアルキル基からなる群である。

In the formula, R ¹ is a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, an arylalkyl group having 7 to 14 carbon atoms, an aryl group having 6 to 14 carbon atoms, or The C6-C14 aryl group which has at least 1 type of substituent chosen from the following A group is shown. Here, group A is a group consisting of a halogen atom, a hydroxyl group, a nitro group, an alkoxy group having 1 to 12 carbon atoms, and an alkyl group having 1 to 12 carbon atoms.

  In the present specification, the alkyl group may be linear or branched. Further, the alkyl group in the arylalkyl group and the alkyl group in the alkoxy group may be linear or branched.

Examples of the alkyl group having 1 to 12 carbon atoms in R ^1, preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms. The alkyl group having 1 to 12 carbon atoms in ^{R 1,} a methyl group, an ethyl group, n- propyl group, an isopropyl group, n- butyl group, an isobutyl group, t- butyl, 2-ethylhexyl, nonyl , Decanyl group, lauryl group, etc. Among these, in terms of further improving the transparency and weather resistance of acrylic thermoplastic resin, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl Group, isobutyl group, t-butyl group and 2-ethylhexyl group are preferable, and methyl group is more preferable.

Examples of the cycloalkyl group having 5 to 12 carbon atoms in R ¹ include a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a tricyclodecyl group, a bicyclooctyl group, a tricyclododecyl group, an isobornyl group, and an adamantyl group. And tetracyclododecyl group. Among these, a cyclopentyl group, a cyclohexyl group, a cyclooctyl group, a tricyclodecyl group, a bicyclooctyl group, a tricyclododecyl group, and an isobornyl group are preferable.

Examples of the arylalkyl group having 7 to 14 carbon atoms in R ¹ include benzyl group, 1-phenylethyl group, 2-phenylethyl group, 3-phenylpropyl group, 6-phenylhexyl group, and 8-phenyloctyl group. Among these, benzyl group, 1-phenylethyl group, 2-phenylethyl group, and 3-phenylpropyl group are preferable.

The aryl group having 6 to 14 carbon atoms in R ^1, a phenyl group, a naphthyl group, anthracenyl group and the like, among these, phenyl groups are preferred.

R ¹ may be an aryl group having 6 to 14 carbon atoms having a substituent, wherein the substituent is a halogen atom, a hydroxyl group, a nitro group, an alkoxy group having 1 to 12 carbon atoms, or 1 carbon atom. A group selected from the group consisting of ˜12 alkyl groups (Group A).

In R ¹ , the aryl group having 6 to 14 carbon atoms having a substituent is preferably a phenyl group having a substituent. Examples of the aryl group having 6 to 14 carbon atoms having a substituent include 2,4,6-tribromophenyl group, 2-chlorophenyl group, 4-chlorophenyl group, 2-bromophenyl group, 4-bromophenyl group, 2-methylphenyl group, 4-methylphenyl group, 2-ethylphenyl group, 4-ethylphenyl group, 2-methoxyphenyl group, 4-methoxyphenyl group, 2-nitrophenyl group, 4-nitrophenyl group, 2, Examples include 4,6-trimethylphenyl group. Among these, 2,4,6-tribromophenyl group is preferable in terms of imparting flame retardancy.

  The content of the first structural unit is 50 to 95% by mass, preferably 60 to 92% by mass, more preferably 70 to 90% by mass, based on the total amount of the acrylic thermoplastic resin. When the content of the first structural unit is 50% by mass or more, high total light transmittance and environmental resistance are exhibited.

  The acrylic thermoplastic resin may contain only one kind of the first structural unit, or may contain two or more kinds of the first structural unit.

For example, the acrylic thermoplastic resin may have a structural unit in which R ¹ is an alkyl group and a structural unit in which R ¹ is an arylalkyl group or an aryl group. At this time, the content of the latter structural unit is preferably 0.1 to 10% by mass, more preferably 0.1 to 8% by mass, based on the total amount of the acrylic thermoplastic resin. More preferably, it is -6 mass%. According to the acrylic thermoplastic resin in this range, an effect of improving optical characteristics such as birefringence can be obtained without a large decrease in heat resistance.

  The first structural unit is formed from, for example, a first monomer selected from methacrylic acid monomers and methacrylic acid esters. The first monomer can be represented by the following formula (1-a).

式中、Ｒ^１は式（１）におけるＲ^１と同義である。

Wherein, ^{R 1} has the same meaning as ^{R 1} in Formula (1).

  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; methacrylic acid. Cyclopentyl, cyclohexyl methacrylate, cyclooctyl methacrylate, tricyclodecyl methacrylate, fine cyclooctyl methacrylate, tricyclododecyl methacrylate, isobornyl methacrylate, phenyl methacrylate, benzyl methacrylate, 1-phenylethyl methacrylate, methacrylic acid Examples include 2-phenoxyethyl, 3-phenylpropyl methacrylate, 2,4,6-tribromophenyl methacrylate, and the like. These first monomers may be used alone or in combination of two or more. Of the methacrylic acid esters, methyl methacrylate and benzyl methacrylate are preferred because the acrylic thermoplastic resin obtained has excellent transparency and weather resistance.

(Second structural unit)
The second structural unit is a structural unit represented by the following formula (2).

式中、Ｒ^２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、又は、下記Ｂ群より選ばれる少なくとも一種の置換基を有する炭素数６〜１４のアリール基、を示し、Ｒ^３及びＲ^４はそれぞれ独立に、水素原子、炭素数１〜１２のアルキル基又は炭素数６〜１４のアリール基を示す。Ｂ群は、ハロゲン原子、ヒドロキシル基、ニトロ基、炭素数１〜１２のアルコキシ基、炭素数１〜１２のアルキル基及び炭素数７〜１４のアリールアルキル基からなる群である。

In the formula, R ² is an arylalkyl group having 7 to 14 carbon atoms, an aryl group having 6 to 14 carbon atoms, or an aryl group having 6 to 14 carbon atoms having at least one substituent selected from the following group B; R ³ and R ⁴ each independently represent a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, or an aryl group having 6 to 14 carbon atoms. Group B is a group consisting of a halogen atom, a hydroxyl group, a nitro group, an alkoxy group having 1 to 12 carbon atoms, an alkyl group having 1 to 12 carbon atoms, and an arylalkyl group having 7 to 14 carbon atoms.

Examples of the arylalkyl group having 7 to 14 carbon atoms in R ² include benzyl group, 1-phenylethyl group, 2-phenylethyl group, 3-phenylpropyl group, 6-phenylhexyl group, and 8-phenyloctyl group. Of these, a benzyl group is preferred in terms of further improving optical properties such as heat resistance and low birefringence.

Examples of the aryl group having 6 to 14 carbon atoms in R ² include a phenyl group, a naphthyl group, and an anthracenyl group, and among these, optical characteristics such as heat resistance and low birefringence are further improved. In the formula, a phenyl group is preferred.

R ² may be an aryl group having 6 to 14 carbon atoms having a substituent, wherein the substituent is a halogen atom, a hydroxyl group, a nitro group, an alkoxy group having 1 to 12 carbon atoms, or 1 carbon atom. A group selected from the group consisting of ˜12 alkyl groups and arylalkyl groups having 7 to 14 carbon atoms (Group B).

  Examples of the halogen atom as a substituent include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

  As a C1-C12 alkoxy group as a substituent, a C1-C10 alkoxy group is preferable and a C1-C8 alkoxy group is more preferable. Moreover, as a C1-C12 alkoxy group as a substituent, a methoxy group, an ethoxy group, n-propyloxy group, isopropyloxy group, n-butyloxy group, isobutyloxy group, t-butyloxy group, 2-ethylhexyl An oxy group, 1-decyloxy group, 1-dodecyloxy group, etc. are mentioned.

Examples of the alkyl group having 1 to 12 carbon atoms and the arylalkyl group having 7 to 14 carbon atoms as the substituent are exemplified as the alkyl group having 1 to 12 carbon atoms and the arylalkyl group having 7 to 14 carbon atoms in R ¹ . Groups are exemplified as well.

In R ² , the aryl group having 6 to 14 carbon atoms having a substituent is preferably a phenyl group having a substituent or a naphthyl group having a substituent. Examples of the aryl group having 6 to 14 carbon atoms having a substituent include 2,4,6-tribromophenyl group, 2-chlorophenyl group, 4-chlorophenyl group, 2-bromophenyl group, 4-bromophenyl group, 2-methylphenyl group, 4-methylphenyl group, 2-ethylphenyl group, 4-ethylphenyl group, 2-methoxyphenyl group, 4-methoxyphenyl group, 2-nitrophenyl group, 4-nitrophenyl group, 2, Examples include 4,6-trimethylphenyl group. Among these, 2,4,6-tribromophenyl group is preferable in that flame retardancy is imparted.

Examples of the alkyl group having 1 to 12 carbon atoms in R ³ and ^{R 4,} preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms. Moreover, as a C1-C12 alkyl group in R < ³ > and R < ⁴ >, a methyl group, an ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group , Nonyl group, decanyl group, lauryl group, etc. Among these, in terms of further improving the transparency and weather resistance of the acrylic thermoplastic resin, methyl group, ethyl group, n-propyl group, isopropyl group, An n-butyl group, an isobutyl group, a t-butyl group and a 2-ethylhexyl group are preferable, and a methyl group is more preferable.

Examples of the aryl group having 6 to 14 carbon atoms in R ³ and R ⁴ include a phenyl group, a naphthyl group, and an anthracenyl group, and among these, optical characteristics such as heat resistance and low birefringence are further improved. In this respect, a phenyl group is preferred.

R ³ and R ⁴ are preferably a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or a phenyl group, and more preferably a hydrogen atom.

  The content of the second structural unit is 0.1 to 49.9% by mass, preferably 0.1 to 35% by mass, more preferably 0.1% by mass based on the total amount of the acrylic thermoplastic resin. ˜20 mass%. If the content of the second monomer is within this range, the transparency of the acrylic thermoplastic resin is maintained, and the heat resistance is improved without yellowing and without impairing the environmental resistance.

  The acrylic thermoplastic resin may contain only one second structural unit, or may contain two or more second structural units.

  The second structural unit is formed from, for example, a second monomer selected from N-substituted maleimide compounds represented by the following formula (2-a).

^Wherein, R 2, ^{R 3} and ^{R 4} have the same meaning as ^R 2, ^{R 3} and ^{R 4} in each formula (2).

  As the second monomer, N-phenylmaleimide, N-benzylmaleimide, N- (2-chlorophenyl) maleimide, N- (4-chlorophenyl) maleimide, N- (4-bromophenyl) maleimide, N- ( 2-methylphenyl) maleimide, N- (2-ethylphenyl) maleimide, N- (2-methoxyphenyl) maleimide, N- (2-nitrophenyl) maleimide, N- (2,4,6-trimethylphenyl) maleimide N- (4-benzylphenyl) maleimide, N- (2,4,6-tribromophenyl) maleimide, N-naphthylmaleimide, N-anthracenylmaleimide, 3-methyl-1-phenyl-1H-pyrrole 2,5-dione, 3,4-dimethyl-1-phenyl-1H-pyrrole-2,5-dione, 1,3-diph Sulfonyl -1H- pyrrole-2,5-dione, 1,3,4-triphenyl -1H- pyrrole-2,5-dione, and the like. Of these second monomers, N-phenylmaleimide and N-benzylmaleimide are preferred because they are excellent in the heat resistance of the acrylic thermoplastic resin and the excellent optical properties such as birefringence. These second monomers may be used alone or in combination of two or more.

(Third structural unit)
The third structural unit is a structural unit represented by the following formula (3).

式中、Ｒ^５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、又は、下記Ｃ群より選ばれる少なくとも一種の置換基を有する炭素数１〜１２のアルキル基、を示し、Ｒ^６及びＲ^７はそれぞれ独立に、水素原子、炭素数１〜１２のアルキル基又は炭素数６〜１４のアリール基を示す。Ｃ群は、ハロゲン原子、ヒドロキシル基、ニトロ基及び炭素数１〜１２のアルコキシ基からなる群である。

In the formula, R ⁵ is a hydrogen atom, a C 3-12 cycloalkyl group, a C 1-12 alkyl group, or a C 1-12 having at least one substituent selected from the following group C. An alkyl group, and R ⁶ and R ⁷ each independently represent a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, or an aryl group having 6 to 14 carbon atoms. Group C is a group consisting of a halogen atom, a hydroxyl group, a nitro group, and an alkoxy group having 1 to 12 carbon atoms.

Examples of the cycloalkyl group having 3 to 12 carbon atoms in R ⁵ include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a tricyclodecyl group, a bicyclooctyl group, a tricyclododecyl group, Isobornyl group, adamantyl group, tetracyclododecyl group, etc., among them, cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group, cyclooctyl group are preferred, and acrylic thermoplastic resin A cyclohexyl group is more preferable in terms of further improving optical properties such as weather resistance and transparency and imparting low water absorption.

The alkyl group having 1 to 12 carbon atoms in ^{R 5,} preferably an alkyl group having 1 to 10 carbon atoms, more preferably an alkyl group having 1 to 8 carbon atoms. The alkyl group having 1 to 12 carbon atoms in ^{R 5,} a methyl group, an ethyl group, n- propyl group, an isopropyl group, n- butyl group, an isobutyl group, t- butyl group, n- pentyl group, n- Hexyl group, n-octyl group, n-dodecyl group, n-octadecyl group, 2-ethylhexyl group, 1-decyl group, 1-dodecyl group, and the like. Among these, weather resistance of acrylic thermoplastic resin and A methyl group, an ethyl group, and an isopropyl group are preferable because optical properties such as transparency are further improved.

R ⁵ may be a C 1-12 alkyl group having a substituent, wherein the substituent is a group consisting of a halogen atom, a hydroxyl group, a nitro group and a C 1-12 alkoxy group ( Group C).

  Examples of the halogen atom as a substituent include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

  As a C1-C12 alkoxy group as a substituent, a C1-C10 alkoxy group is preferable and a C1-C8 alkoxy group is more preferable. Moreover, as a C1-C12 alkoxy group as a substituent, a methoxy group, an ethoxy group, n-propyloxy group, isopropyloxy group, n-butyloxy group, isobutyloxy group, t-butyloxy group, 2-ethylhexyl An oxy group, 1-decyloxy group, 1-dodecyloxy group, etc. are mentioned.

In R ⁵ , examples of the alkyl group having 1 to 12 carbon atoms having a substituent include a dichloromethyl group, a trichloromethyl group, a trifluoroethyl group, and a hydroxyethyl group, and among these, a trifluoroethyl group is preferable. It is.

Examples of the alkyl group having 1 to 12 carbon atoms in R ⁶ and ^{R 7,} preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms. The alkyl group having 1 to 12 carbon atoms in ^{R 6} and ^{R 7,} methyl group, ethyl group, n- propyl group, an isopropyl group, n- butyl group, an isobutyl group, t- butyl group, a 2-ethylhexyl group , Nonyl group, decanyl group, lauryl group, etc. Among these, in terms of further improving the transparency and weather resistance of the acrylic thermoplastic resin, methyl group, ethyl group, n-propyl group, isopropyl group, An n-butyl group, an isobutyl group, a t-butyl group and a 2-ethylhexyl group are preferable, and a methyl group is more preferable.

Examples of the aryl group having 6 to 14 carbon atoms in R ⁶ and R ⁷ include a phenyl group, a naphthyl group, and an anthracenyl group, and among these, optical characteristics such as heat resistance and low birefringence are further improved. In this respect, a phenyl group is preferred.

R ⁶ and R ⁷ are preferably a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or a phenyl group, and more preferably a hydrogen atom.

  The content of the third structural unit is 0.1 to 49.9% by mass, preferably 0.1 to 35% by mass, and more preferably 0.1 to 35% by mass based on the total amount of the acrylic thermoplastic resin. 30% by mass. If content of a 3rd structural unit is this range, transparency will be maintained and low hygroscopicity will be exhibited.

  The acrylic thermoplastic resin may contain only one third structural unit, or may contain two or more third structural units.

  The third structural unit is formed of, for example, a third monomer selected from N-substituted maleimide compounds represented by the following formula (3-a).

^Wherein, R 5, ^{R 6} and ^{R 7} have the same meanings as ^R 5, ^{R 6} and ^{R 7} in each formula (3).

  Examples of the third monomer include N-methylmaleimide, N-ethylmaleimide, Nn-propylmaleimide, N-isopropylmaleimide, Nn-butylmaleimide, N-isobutylmaleimide, and Ns-butyl. Maleimide, Nt-butylmaleimide, Nn-pentylmaleimide, Nn-hexylmaleimide, Nn-heptylmaleimide, Nn-octylmaleimide, N-laurylmaleimide, N-stearylmaleimide, N-cyclo Propylmaleimide, N-cyclobutylmaleimide, N-cyclopentylmaleimide, N-cyclohexylmaleimide, N-cycloheptylmaleimide, N-cyclooctylmaleimide, 1-cyclohexyl-3-methyl-1-phenyl-1H-pyrrole-2,5 -Dione, 1-cyclohex 3,4-dimethyl-1-phenyl-1H-pyrrole-2,5-dione, 1-cyclohexyl-3-phenyl-1H-pyrrole-2,5-dione, 1-cyclohexyl-3,4-diphenyl- 1H-pyrrole-2,5-dione and the like can be mentioned. These third monomers may be used alone or in combination of two or more. N-methylmaleimide, N-ethylmaleimide, N-isopropylmaleimide, and N-cyclohexylmaleimide are preferable because of the excellent weather resistance of the acrylic thermoplastic resin, and low hygroscopicity that is recently required for optical materials is excellent. N-cyclohexylmaleimide is particularly preferred.

  In the acrylic thermoplastic resin, the total content of the second structural unit and the third structural unit is preferably 5 to 50% by mass based on the total amount of the acrylic thermoplastic resin. More preferably, it is 5-40 mass%, More preferably, it is 10-35 mass%, More preferably, it is 10-30 mass%, Most preferably, it is 15-30 mass%. When it is within this range, the acrylic thermoplastic resin has a more sufficient heat resistance improvement effect, and more preferable improvement effects in terms of weather resistance, low water absorption, and optical properties. In addition, when the content of the second structural unit and the content of the third structural unit exceeds 50% by mass, the reactivity of the monomer component is reduced during the polymerization reaction, and the monomer that remains unreacted The amount increases, and the physical properties of the acrylic thermoplastic resin may decrease.

In the acrylic thermoplastic resin, the molar ratio C ₂ / C ₃ between the content C ₂ of the _second structural unit and the content C ₃ of the third structural unit is desirably greater than 0 and 15 or less. From the viewpoint of optical characteristics (low birefringence, low photoelastic coefficient) described later, the molar ratio C ₂ / C ₃ is more preferably 10 or less. When the molar ratio C ₂ / C ₃ is in this range, the acrylic thermoplastic resin of the present invention exhibits even better optical properties.

  In the acrylic thermoplastic resin, the total content of the first structural unit, the second structural unit, and the third structural unit may be 80% by mass or more based on the total amount of the acrylic thermoplastic resin. . As a result, the acrylic thermoplastic resin exhibits better optical characteristics.

(Fourth structural unit)
The acrylic thermoplastic resin may further contain a structural unit other than the above. For example, the acrylic thermoplastic resin further has a structural unit derived from another monomer copolymerizable with the first, second, and third monomers as long as the object of the invention is not impaired. You may do it. Hereinafter, structural units other than the first, second, and third structural units in the acrylic thermoplastic resin are referred to as fourth structural units.

  Other monomers that can be copolymerized include aromatic vinyl; unsaturated nitrile; cyclohexyl group, benzyl group, or acrylic acid ester having an alkyl group having 1 to 18 carbon atoms; olefin; diene; vinyl ether; vinyl ester; Examples thereof include vinyl chloride; allyl ester or methallyl ester of saturated fatty acid monocarboxylic acid such as allyl propionate; polyvalent (meth) acrylate; polyvalent arylate; glycidyl compound; unsaturated carboxylic acid. The other monomer may be one or a combination of two or more selected from these groups.

  Examples of the aromatic vinyl include styrene, α-methylstyrene, divinylbenzene, and the like. Examples of the unsaturated nitrile include acrylonitrile, methacrylonitrile, ethacrylonitrile, phenylacrylonitrile and the like. Examples of the acrylic ester include methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, isobutyl acrylate, tert-butyl acrylate, amyl acrylate, isoamyl acrylate, and acrylic acid. Examples include octyl, 2-ethylhexyl acrylate, decyl acrylate, lauryl acrylate, cyclohexyl acrylate, and benzyl acrylate.

  Examples of the olefin include ethylene, propylene, isobutylene, diisobutylene and the like. Examples of the diene include butadiene and isoprene. Examples of the vinyl ether include methyl vinyl ether and butyl vinyl ether. Examples of the vinyl ester include vinyl acetate and vinyl propionate. Examples of the vinyl fluoride include vinylidene fluoride.

  Examples of the polyvalent (meth) acrylate include ethylene glycol (meth) acrylate, diethylene glycol (meth) acrylate, trimethylolpropane tri (meth) acrylate, hexanediol di (meth) acrylate, pentaerythritol tetra (meth) acrylate, and dipenta Erythritol hexa (meth) acrylate, di (meth) acrylate of bisphenol A ethylene oxide or propylene oxide adduct, di (meth) acrylate of halogenated bisphenol A ethylene oxide or propylene oxide adduct, isocyanurate ethylene oxide or propylene Examples thereof include di- or tri (meth) acrylates of oxide adducts.

  Examples of the polyvalent arylate monomer include diallyl phthalate and triallyl isocyanurate. Examples of the glycidyl compound monomer include glycidyl (meth) acrylate and allyl glycidyl ether. Examples of the unsaturated carboxylic acid monomer include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, and half-esterified products or anhydrides thereof.

  The content of the fourth structural unit in the acrylic thermoplastic resin is preferably 0.1 to 20% by mass, and preferably 0.1 to 15% by mass, based on the total amount of the acrylic thermoplastic resin. Is more preferable, and it is still more preferable that it is 0.1-10 mass%. When the content is in the above range, the hygroscopicity of the acrylic thermoplastic resin is further improved. From the viewpoint of weather resistance, the content is preferably less than 10% by mass, and more preferably less than 7% by mass.

  The acrylic thermoplastic resin may have only one kind of the fourth structural unit, or may have two or more kinds.

    An example of the fourth structural unit is a structural unit represented by the following formula (4).

In the formula, R ⁸ represents a hydrogen atom or an alkyl group having 1 to 12 carbon atoms, and R ⁹ represents a halogen atom, a hydroxyl group, a nitro group, an alkyl group having 1 to 12 carbon atoms or an alkoxy group having 1 to 12 carbon atoms. A represents an integer of 1 to 3.

Examples of the alkyl group having 1 to 12 carbon atoms in R ^8, preferably an alkyl group having 1 to 10 carbon atoms, more preferably an alkyl group having 1 to 8 carbon atoms. Examples of the alkyl group having 1 to 12 carbon atoms in R ⁹ include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group, 1- A decyl group, 1-dodecyl group, etc. are mentioned, Among these, a methyl group is suitable.

Examples of the halogen atom for R ⁹ include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

The alkyl group having 1 to 12 carbon atoms in ^{R 9,} preferably an alkyl group having 1 to 10 carbon atoms, more preferably an alkyl group having 1 to 8 carbon atoms. Examples of the alkyl group having 1 to 12 carbon atoms in R ⁹ include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group, 1- Decyl group, 1-dodecyl group and the like. Among these, in terms of further improving the transparency and weather resistance of the acrylic thermoplastic resin, methyl group, ethyl group, n-propyl group, isopropyl group, n- A butyl group, an isobutyl group, a t-butyl group, and a 2-ethylhexyl group are preferable, and a methyl group is more preferable.

Further, the alkoxy group having 1 to 12 carbon atoms in ^{R 9,} preferably an alkoxy group having 1 to 10 carbon atoms, more preferably an alkoxy group having 1 to 8 carbon atoms. Moreover, as a C1-C12 alkoxy group as a substituent, a methoxy group, an ethoxy group, n-propyloxy group, isopropyloxy group, n-butyloxy group, isobutyloxy group, t-butyloxy group, 2-ethylhexyl Examples thereof include an oxy group, a 1-decyloxy group, and a 1-dodecyloxy group, and among these, a methoxy group is preferable.

  The structural unit represented by the formula (4) can be formed from, for example, a monomer represented by the following formula (4-a).

式中、Ｒ^８、Ｒ^９及びａはそれぞれ式（４）におけるＲ^８、Ｒ^９及びａと同義である。

^Wherein, R 8, ^{R 9} and a have the same meanings as ^R 8, ^{R 9} and a in each formula (4).

  Examples of the fourth monomer include styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2,4-dimethylstyrene, 2,5-dimethylstyrene, and 2-methyl-4-chlorostyrene. 2,4,6-trimethylstyrene, α-methylstyrene, cis-β-methylstyrene, trans-β-methylstyrene, 4-methyl-α-methylstyrene, 4-fluoro-α-methylstyrene, 4-chloro -Α-methylstyrene, 4-bromo-α-methylstyrene, 4-t-butylstyrene, 2-fluorostyrene, 3-fluorostyrene, 4-fluorostyrene, 2,4-difluorostyrene, 2-chlorostyrene, 3 -Chlorostyrene, 4-chlorostyrene, 2,4-dichlorostyrene, 2,6-dichlorostyrene, 2-bromostyrene Down, 3-bromostyrene, 4-bromostyrene, 2,4-dibromostyrene, alpha-bromostyrene, beta-bromostyrene, 2-hydroxystyrene, 4-hydroxystyrene, and the like. From the point that it is excellent in copolymerizability with the first monomer, the second monomer and the third monomer constituting the acrylic thermoplastic resin, and the optical properties can be adjusted with a small amount of use. Styrene and α-methylstyrene are particularly preferred. These fourth monomers may be used alone or in combination of two or more.

  The acrylic thermoplastic resin according to the present embodiment may be composed of one kind of copolymer, or one or more kinds of the first structural unit, the second structural unit, and the third structural unit. It may be a blend of two or more copolymers having structural units. For example, the acrylic thermoplastic resin may be a resin composed of one kind of copolymer having a first structural unit, a second structural unit, and a third structural unit. Alternatively, the acrylic thermoplastic resin may be a blend composed of two or more types of copolymers having a first structural unit, a second structural unit, and / or a third structural unit. Alternatively, it may be a blend composed of a polymer having the first structural unit, a polymer having the second structural unit, and a polymer having the third structural unit. From the viewpoint of transparency and uniformity, the acrylic thermoplastic resin is a copolymer having the first structural unit, the second structural unit, and the third structural unit, or the first structural unit, It is preferably a blend composed of two or more kinds of copolymers having the second structural unit and / or the third structural unit. The first structural unit, the second structural unit, and the first structural unit A copolymer having three structural units is particularly preferred.

  The content of halogen atoms in the acrylic thermoplastic resin is preferably less than 0.47% by mass and more preferably 0.45% by mass or less based on the total amount of the acrylic thermoplastic resin. Because acrylic thermoplastic resin contains less than 0.47% by mass of halogen atoms, it is difficult to generate halogen gas even when acrylic thermoplastic resin is handled at high temperatures during melt molding, etc. Corrosion of equipment to be used and work environment deterioration are prevented. In addition, when the acrylic thermoplastic resin (or a molded product thereof) is discarded, there is an advantage that it is difficult to generate a halogen-based gas having a relatively large environmental load.

  It is preferable that the weight average molecular weight (Mw) of polymethylmethacrylate conversion by the GPC measuring method of an acrylic thermoplastic resin is 3000-1 million. If Mw is 3000 or more, an optically isotropic polarizing film protective film having a required strength can be obtained by molding. Moreover, if Mw is 1000000 or less, necessary and sufficient heat fluidity can be obtained at the time of various melt molding. Mw is more preferably 30,000 to 800,000, still more preferably 60000 to 600,000. Particularly preferably, it is 100,000 to 400,000.

  It is preferable that the molecular weight distribution (Mw / Mn) in terms of polymethyl methacrylate by GPC measurement method of the acrylic thermoplastic resin is 1-10. The acrylic thermoplastic resin can be polymerized by a living radical polymerization method, and the molecular weight distribution can be adjusted as necessary. From the viewpoint of adjusting the resin viscosity suitable for molding processing, the molecular weight distribution (Mw / Mn) is more preferably 1.1 to 7.0, further preferably 1.2 to 5.0, It can also be set to 1.5 to 4.0.

  The glass transition temperature (Tg) of the acrylic thermoplastic resin is preferably 120 ° C. or higher. When Tg is 120 ° C. or higher, the film has necessary and sufficient heat resistance as a recent liquid crystal display film molded body. Tg is preferably 130 ° C. or higher, more preferably 135 ° C. or higher. On the other hand, the upper limit of Tg is preferably 180 ° C. or lower.

(Optical characteristics of acrylic thermoplastic resin)
(I) Absolute value of photoelastic coefficient C The absolute value of the photoelastic coefficient C of the acrylic thermoplastic resin is preferably 3.0 × 10 ⁻¹² Pa ⁻¹ or less, more preferably 2.0 ×. It is 10 <^-12> Pa < ^{-1 >} or less, More preferably, it is 1.0 * 10 <^-12> Pa <^-1> or less.

Here, the photoelastic coefficient is described in various documents (see, for example, Chemical Review, No. 39, 1998 (published by the Academic Publishing Center)), and is defined by the following formulas (i-1) and (i-2). It is what is done. As the value of photoelastic coefficient C _R is close to zero, it can be seen that change in birefringence due to an external force is small.
C _R = | Δn | / σ _R (i-1)
| Δn | = nx−ny (i−2)
Wherein, C _R photoelastic coefficient, sigma _R is tensile stress, | [Delta] n | is the absolute value of the birefringence, nx is the refractive index of stretching direction, ny is the refractive index of stretching direction perpendicular to the direction in the plane, the Each is shown.

  The photoelastic coefficient C of the acrylic thermoplastic resin is sufficiently small as compared with existing resins (for example, PMMA, PC, triacetyl cellulose resin, cyclic olefin resin, etc.). Therefore, since it does not cause birefringence due to external force (photoelasticity), it is difficult to undergo birefringence change. In addition, since birefringence caused by residual stress at the time of molding (photoelasticity) hardly occurs, the birefringence distribution in the molded body is also small.

(Ii) In-plane phase difference Re
For example, the acrylic thermoplastic resin preferably has an absolute value of the retardation Re in the in-plane direction of 30 nm or less when formed into a film. Here, the phase difference Re is a value obtained by converting a value measured as a film into a thickness of 100 μm.

  The absolute value of the phase difference Re is more preferably 20 nm or less, further preferably 15 nm or less, and particularly preferably 11 nm or less.

  In general, the absolute value of the phase difference Re is an index representing the magnitude of birefringence. The birefringence of the acrylic thermoplastic resin is sufficiently small compared to the birefringence when the existing resin (for example, PMMA, PC, triacetyl cellulose resin, cyclic olefin resin, etc.) is used. Suitable for applications requiring zero birefringence.

  On the other hand, when the absolute value of the in-plane phase difference Re exceeds 30 nm, it means that the refractive index anisotropy is high, and it cannot be used for applications requiring low birefringence or zero birefringence as an optical material. There is. Moreover, in order to improve the mechanical strength of an optical material (for example, a film, a sheet, etc.), it may be stretched, but when the absolute value of the retardation in the in-plane direction after the stretching process exceeds 30 nm, No low birefringence or zero birefringence material is obtained as an optical material.

(Iii) Thickness direction retardation Rth
For example, the acrylic thermoplastic resin preferably has an absolute value of the retardation Rth in the thickness direction of 30 nm or less when formed into a film. Here, the retardation Rth is a value obtained by converting a value measured as a film into a thickness of 100 μm.

  The absolute value of the phase difference Rth is more preferably 20 nm or less, further preferably 15 nm or less, and particularly preferably 11 nm or less.

  The retardation Rth in the thickness direction is an index that correlates with the viewing angle characteristics of a display device incorporating the optical film when an optical material, particularly an optical film is used. More specifically, the smaller the absolute value of the thickness direction retardation Rth, the better the viewing angle characteristics, and the smaller the change in the color tone of the display color depending on the viewing angle and the lower the contrast.

  The acrylic thermoplastic resin is an absolute value of the retardation Rth in the thickness direction when used as an optical film, compared to the case where an existing resin (for example, PMMA, PC, triacetyl cellulose resin, cyclic olefin resin, etc.) is used. Is very small.

(Iv) Total light transmittance The acrylic thermoplastic resin preferably has, for example, a total light transmittance of 85% or more, more preferably 88% or more, and 90% or more when film-formed. More preferably. Here, the total light transmittance is a value obtained by converting to a thickness of 100 μm. When the total light transmittance is less than 85%, the transparency is lowered, and it may not be used for applications requiring high transparency.

  As described above, the acrylic thermoplastic resin has a sufficiently small photoelastic coefficient C (approximately zero). For example, when it is formed into a film shape, it is evaluated as an optical film regardless of whether or not it is stretched. Even in this case, the absolute values of the in-plane phase difference Re and the thickness direction phase difference Rth are both small (approximately zero). The acrylic thermoplastic resin according to the embodiment of the present invention can realize optically complete isotropic property (so-called zero / zero birefringence) that cannot be achieved by a conventionally known resin, and also has high heat resistance. Can be achieved at the same time.

[Method for producing acrylic thermoplastic resin]
The acrylic thermoplastic resin of this embodiment can be obtained by polymerizing a monomer group including a first monomer, a second monomer, and a third monomer. As a technique for obtaining an acrylic thermoplastic resin, for example, commonly used polymerization methods such as cast polymerization, bulk polymerization, suspension polymerization, solution polymerization, emulsion polymerization, living radical polymerization, anionic polymerization, etc. can be used. Usually, radical polymerization without catalyst deashing is selected.

  In order to use an acrylic thermoplastic resin as an optical material, it is preferable to avoid the inclusion of minute foreign matters and impurities as much as possible. From this point of view, a radical that does not use a suspending agent or an emulsifier is used in the polymerization method of the acrylic thermoplastic resin. It is desirable to use cast polymerization or radical solution polymerization.

  Moreover, as a polymerization form, any of a batch polymerization method and a continuous polymerization method can be used, for example. The batch polymerization method is desirable from the viewpoint of simple polymerization operation, and the continuous polymerization method is desirably used from the viewpoint of obtaining a polymer having a more uniform composition.

  The temperature and polymerization time at the time of the polymerization reaction can be appropriately adjusted according to the type and ratio of the monomer used, for example, the polymerization temperature is 0 to 160 ° C., the polymerization time is 0.5 to 24 hours, Preferably, the polymerization temperature is 80 to 160 ° C. and the polymerization time is 1 to 8 hours.

  At the time of radical polymerization reaction, a polymerization initiator is added as necessary. As the polymerization initiator, a general radical polymerization initiator can be used depending on the polymerization temperature. For example, cumene hydroperoxide, diisopropylbenzene hydroperoxide, di-t-butyl peroxide, lauroyl peroxide, Organic peroxides such as benzoyl peroxide, t-butylperoxyisopropyl carbonate, t-amylperoxy-2-ethylhexanoate; 2,2′-azobis (isobutyronitrile), 1,1′-azobis Examples include azo compounds such as (cyclohexanecarbonitrile), 2,2′-azobis (2,4-dimethylvaleronitrile), dimethyl-2,2′-azobisisobutyrate. These polymerization initiators may be used alone or in combination of two or more.

  The amount of the polymerization initiator used may be appropriately set according to the combination of the monomers and reaction conditions, and is not particularly limited, but is preferably used in the range of 0.005 to 5% by mass.

  As the molecular weight regulator used as necessary in the polymerization reaction, any one used in general radical polymerization may be used. Can be mentioned. These molecular weight regulators are added so that the degree of polymerization is controlled within a desired range.

  Examples of the polymerization solvent in the case of radical solution polymerization include aromatic hydrocarbon solvents such as toluene, xylene and ethylbenzene, ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone, and ether solvents such as tetrahydrofuran. These solvents may be used alone or in combination of two or more. A solvent having a boiling point of 50 to 200 ° C. is preferable in view of polymerization temperature, ease of handling, and ease of separation and removal of the resin and the solvent.

  In radical solution polymerization, it is desirable that the polymerization solution concentration (concentration of resin) be 10 to 95% by mass. If it is 10 mass% or more, adjustment of molecular weight and molecular weight distribution is easy. If it is 95 mass% or less, a high molecular weight polymer can be obtained. Further, from the viewpoint of heat removal during polymerization, in order to make the viscosity of the reaction solution appropriate, it is more preferably 75% by mass or less, and further preferably 60% by mass or less.

  Further, from the viewpoint of appropriately maintaining the viscosity of the polymerization reaction solution, a polymerization solvent can be appropriately added during the polymerization. By appropriately maintaining the viscosity of the reaction solution, it is easy to control heat removal and suppress side reactions in the reaction solution. In particular, in the latter half of the polymerization reaction in which the viscosity increases, it is more preferable to add a polymerization solvent as appropriate and control it to be 50% by mass or less.

  The acrylic thermoplastic resin obtained by solution polymerization needs to be separated from the solvent and the remaining monomer, except when the solution is used as it is to form an optically isotropic polarizing film protective film by a solution casting method. Separation methods include devolatilization treatment that volatilizes the solvent and residual monomer by heating or depressurizing the solution, extraction and removal of the solvent and residual monomer in a poor solvent of the resin, etc. A known method can be used.

  In the present embodiment, since the acrylic thermoplastic resin is used for a polarized light transmitting optical component that is a precise optical application, the number of foreign matters to be mixed is preferably as small as possible. As a method of reducing the number of foreign substances, a method of filtering a polymerization solution or a melt with, for example, a leaf disk polymer filter having a filtration accuracy of 1.5 to 15 μm in a polymerization reaction step, a devolatilization treatment step, and a molding step Etc.

  In the present embodiment, the acrylic thermoplastic resin has a thermal stabilizer, an ultraviolet absorber, and optical isotropy (having birefringence) within a range that does not affect the final polarized light transmitting optical component. Other resins can be added including less expensive resins. The adding method is not particularly limited as long as it is a known method. For example, it can be added by a method of adding at the time of polymerization, a method of adding to the solution after polymerization, a method of adding the resin by melt kneading or the like, or a method of combining these.

  The acrylic thermoplastic resin composition is within a range that does not impair the object of the present invention. For example, polyolefin resin such as polyethylene and polypropylene; polystyrene, styrene / acrylonitrile copolymer, styrene / maleic anhydride copolymer, styrene / Styrenic resin such as methacrylic acid copolymer; Polymethacrylate ester resin; Polyamide; Polyphenylene sulfide resin; Polyether ether ketone resin; Polyester resin; Polysulfone; Polyphenylene oxide; Polyimide; Polyetherimide; Polyacetal; Resin; Norbornene resin; Thermoplastic resin such as cellulose resin such as triacetyl cellulose; and phenol resin; melamine resin; silicone resin; thermosetting resin such as epoxy resin Even without it may contain one or more.

[Molding of polarization transmission optical parts]
The acrylic thermoplastic resin of this embodiment can be processed into a polarized light transmitting optical component by melt molding. As the melt molding method, a melt hot press method, an injection molding method, or the like can be used. From the viewpoint of productivity, the injection molding method is preferable. It is also possible to extrude into a plate shape once by a melt extrusion method, and then form a prism shape on the surface by a melt hot press method.

  Regarding this surface-attached shape, it may have a regular periodic structure or a structure with no particular regularity. Moreover, when it has a regular periodic structure, it is desirable that one period of the periodic structure is 10 to 500 μm. If the periodic structure is 10 μm or more, the light can be controlled as a light beam.

[Polarized transmission optical components]
The polarized light transmissive optical component of the present embodiment is a molded product that can be produced by melt molding the acrylic thermoplastic resin, and refers to an optical component that transmits and / or separates polarized light.

The polarized light transmitting optical component of this embodiment is preferably made of an acrylic thermoplastic resin having a photoelastic coefficient (C) of −3.0 × 10 ⁻¹² to + 3.0 × 10 ⁻¹² Pa ⁻¹ or less. In the present invention, the photoelastic coefficient (C) is R = (C) × where R is the phase difference observed when polarized light is applied to an object whose magnitude and direction of the strain S change when an external force σ is applied. It is a physical coefficient denoted by σ. The photoelastic coefficient (C) is a value specific to each transparent material. The absolute value of the photoelastic coefficient C is more preferably 2.0 × 10 ⁻¹² Pa ⁻¹ or less, and further preferably 1.0 × 10 ⁻¹² Pa ⁻¹ or less. Within this range, polarization disturbance due to external stress caused by a difference in linear expansion from the housing supporting the polarized light transmitting optical component is less likely to occur.

  The polarized light transmitting optical component of this embodiment is preferably made of an acrylic thermoplastic resin having a glass transition temperature of 130 ° C. or higher. If it is 130 degreeC or more, it can fully arrange | position around the LED light source used for the optical projection apparatus of recent years. In addition, it can be suitably used in applications that require high durability such as in-vehicle use. The glass transition temperature is preferably 135 ° C. or higher, more preferably 140 ° C. or higher. On the other hand, the upper limit of the glass transition temperature is preferably 180 ° C.

  The surface hardness of the polarized light transmitting optical component of the present invention is preferably a pencil hardness of 3H or more. A pencil hardness of 3H or more is sufficient as a scratch property when used as a polarized light transmitting optical component. More preferably, it is 4H or more. On the other hand, the upper limit of pencil hardness is about 6H.

  The optical path length of the polarized light transmitting optical component of the present invention is preferably 10 to 100,000 μm, more preferably 25 to 10,000 μm, and particularly preferably 50 to 5000 μm. If the optical path length of the polarized light transmitting optical component is 25 μm or more, it can be easily handled as a molded body. Moreover, if it is 100000 micrometers or less, sufficient transparency is securable.

[Post-processing of polarized light transmission optical components]
The polarized light transmitting optical component can be subjected to dielectric vapor deposition treatment, antireflection treatment, metal vapor deposition treatment, hard coat treatment, anchor coat treatment, and transparent conductive treatment as necessary.

  The polarized light transmitting optical component can be provided with an inorganic layer on the surface by vapor deposition, and the inorganic layer is preferably a transparent multilayer dielectric.

[Polarized beam splitter]
The polarizing beam splitter of the present embodiment includes any of a plurality of types such as a prism type, a planar type, and a wedge substrate type, and a prism type is particularly preferable. The prism-type polarization beam splitter is composed of two prisms, and a multilayer transparent dielectric film or a metal thin film is formed on an overlapping surface to be bonded to each other.

In order to manufacture the polarizing beam splitter of this embodiment, silicon dioxide (SiO ₂ ) or titanium dioxide (TiO ₂ ) is deposited in multiple layers on the surface of the polarized light transmitting optical component, and a multilayer transparent dielectric film is applied to the surface. . In some cases, a multilayer film having a hybrid structure of a chromium layer and a silicon dioxide layer may be used.

  As a method for forming the multilayer transparent dielectric film, any of the conventionally known techniques such as vacuum deposition, sputtering, and ion plating can be used. However, the uniformity of the film and the adhesion of the thin film to the anchor coat layer can be used. From the viewpoint, thin film formation by sputtering is preferable.

  The required number of layers varies depending on the application, but can be from one to 1,000 layers. Twenty or more layers are preferable for efficient polarization separation. Further, it is desirable to apply an antireflection treatment to the entrance surface and the exit surface. In the case of performing such various surface treatments, the adhesion can be enhanced by treatment with corona discharge or plasma discharge, or primer coating surface treatment having an epoxy group, an isocyanate group, or the like, if necessary.

[Optical Projector]
The polarized light transmitting optical component of this embodiment can form an optical projection device together with other lenses. FIG. 1 is a diagram schematically showing a general optical projection apparatus 1. As shown in FIG. 1, the optical projection apparatus according to the present embodiment includes a light source 10, a spherical reflector 12, a collimator lens 14, an infrared removing filter 16, a quarter-wave plate 18, and the polarizing beam splitter 20 according to the present embodiment. Are aligned in series. The polarizing beam splitter 20 is constructed by joining 45 ° inclined surfaces of two right-angle prisms, and the multilayer transparent dielectric film is formed on the joining surface 20a. This multilayer transparent dielectric film reflects the S wave polarization component of the incident light and transmits the P wave polarization component p.

  Light emitted from the light source 10 such as a xenon lamp becomes parallel rays by the spherical reflecting mirror 12 and the collimator lens 14. Thereafter, the parallel light passes through the infrared removing filter 16 and the quarter wavelength plate 18 and is incident on the polarization beam splitter 20. The P-wave polarization component p transmitted through the joint surface 20a of the polarization beam splitter 20 is incident on a liquid crystal panel (not shown) on which an image to be projected is displayed. Then, image light is formed by transmission through the liquid crystal panel, and this image light is enlarged and projected onto a screen (not shown) by a projection lens.

  On the other hand, the S-wave polarization component s reflected by the joint surface 20a is reflected by the mirror 22 disposed at the output portion of the reflected light and enters the polarization beam splitter 20 again. The S-wave polarization component s incident from the mirror 22 is reflected by the joint surface 20a and returns to the light source 1 side. At this time, the return light is circularly polarized by passing through the quarter-wave plate 18 disposed between the polarization beam splitter 20 and the light source 10, and the return light that has become the circular polarization is spherical. The circularly polarized wave is reversely rotated by the reflection at the reflecting mirror 2 and passes through the quarter-wave plate 18 again to be converted into the P-wave polarization component p.

  Therefore, the component converted into the P wave is transmitted through the joint surface 20a, and eventually all the components of the light from the light source 10 become the P wave polarization component p and enter the liquid crystal panel side. Image light based on an image displayed on the liquid crystal panel can be formed.

  The preferred embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment.

  Hereinafter, the contents of the present invention will be described more specifically with reference to examples and comparative examples. In addition, this invention is not limited to the following Example.

[Analysis of acrylic thermoplastic resin composition]
Acrylic thermoplastic resin obtained by polymerization was dissolved in CDCl ₃ , and ¹ H-NMR, ¹³ C-NMR (measurement temperature: 40 ° C.) measurement was carried out using a DPX-400 apparatus manufactured by Bruker, Inc. The amounts of (i) the first structural unit, (ii) the second structural unit, (iii) the third structural unit, and (iv) the fourth structural unit were identified, and the composition was confirmed from the ratio. .

[Measurement of glass transition temperature of acrylic thermoplastic resin]
The glass transition temperature (Tg) of the acrylic thermoplastic resin obtained by polymerization was determined using α-alumina as a reference in a nitrogen gas atmosphere using a differential scanning calorimeter (Diamond DSC, manufactured by Perkin Elmer Japan Co., Ltd.). Based on JIS-K-7121, it was calculated by a midpoint method from a DSC curve obtained by heating about 10 mg of a sample from room temperature to 200 ° C. at a rate of temperature increase of 10 ° C./min.

[Weight average molecular weight measurement of acrylic thermoplastic resin]
The weight average molecular weight (Mw) and the number average molecular weight (Mn) of the acrylic thermoplastic resin obtained by polymerization were measured using a gel permeation chromatograph (HLC-8220 manufactured by Tosoh Corporation), the solvent being tetrahydrofuran, and the set temperature. It calculated | required by 40 degreeC by conversion of commercially available standard PMMA.

[Optical property evaluation of acrylic thermoplastic resin]
<Preparation of sample for optical evaluation of acrylic thermoplastic resin>
The acrylic thermoplastic resin obtained by polymerization was formed into a film by melt vacuum press molding. A Kapton sheet was placed on an iron plate, and a 150 μm-thick gold frame cut into a 15 cm square was placed thereon, and an acrylic thermoplastic resin was placed thereon. Furthermore, the Kapton sheet was stacked and the iron plate was arrange | positioned. Put it in a vacuum compression molding machine (SFV-30, manufactured by Shindo Metal Industry Co., Ltd.) while sandwiching it between the two metal plates, and start reducing pressure and reach 10 kPa. The temperature was raised, then held at 260 ° C. for 5 minutes, then compressed at a press pressure of 10 MPa for 5 minutes, and then cooling started. When the temperature reached 50 ° C., the inside of the vacuum dryer was returned to atmospheric pressure, and a sample was taken out. . The sample was then peeled once from the Kapton sheet, sandwiched again with a new Kapton sheet, held in a dryer filled with nitrogen and maintained at a temperature 10 ° C. above the glass transition temperature (Tg) for 8 hours.

<Measurement of photoelastic coefficient of acrylic thermoplastic resin>
A birefringence measuring apparatus described in detail in Polymer Engineering and Science 1999, 39, 2349-2357 was used. A film made of an acrylic thermoplastic resin (thickness: about 150 μm, width: 6 mm) that has been cured for 24 hours or more in a constant temperature and humidity chamber adjusted to 23 ° C. and a humidity of 60%, and similarly installed in the constant temperature and humidity chamber A film was placed on a tensioning apparatus (manufactured by Imoto Seisakusho Co., Ltd.) so that the distance between chucks was 50 mm. Next, a laser beam path of a birefringence measuring apparatus (RETS-100 manufactured by Otsuka Electronics Co., Ltd.), which will be described later, is set to the center of the film, and a strain rate of 50% / min (between chucks: 50 mm, chuck moving speed: 5 mm / min). The birefringence was measured while applying an extensional stress. From the relationship between the absolute value of birefringence (| Δn |) and the extensional stress (σ _R ), the slope of the straight line was obtained by least square approximation, and the photoelastic coefficient (C _R ) was calculated. For the calculation, data with an extensional stress between 2.5 MPa ≦ σR ≦ 10 MPa was used.
C _R = | Δn | / σ _R
| Δn | = | nx−ny |
(C _R : photoelastic coefficient, σ _R : stretching stress, | Δn |: absolute value of birefringence, nx: refractive index in the stretching direction, ny: vertical refractive index in the stretching direction)

<Measurement of birefringence of acrylic thermoplastic resin>
Using the Otsuka Electronics RETS-100, the birefringence of the polarization transmission optical component was measured by the rotation analyzer method. The value of birefringence is a value of light having a wavelength of 550 nm. Birefringence (Δn) was calculated by the following formula. The obtained value was converted to a film thickness of 100 μm to obtain a measured value.
Δn = nx−ny
(Δn: birefringence, nx: refractive index in the stretching direction, ny: refractive index perpendicular to the stretching direction)

The absolute value (| Δn |) of birefringence (Δn) was determined as follows.
| Δn | = | nx−ny |

<Phase difference Re measurement of acrylic thermoplastic resin>
Birefringence of polarized light transmission optical components in the wavelength range from 400 nm to 800 nm by rotating analyzer method using RETS-100 manufactured by Otsuka Electronics Co., Ltd. installed in a constant temperature and humidity chamber adjusted to 23 ° C. and humidity 60%. Measurements were performed. Regarding 30 sheets of 4 cm square films, in-plane retardation Re was measured at the center of the sample, and then the thickness of the center of the sample was measured to obtain the in-plane retardation Re converted to a thickness of 100 μm. Next, after conversion to an absolute value, an average was taken, and the absolute value of the phase difference Re in the in-plane direction of the polarized light transmitting optical component was obtained by converting it to the total thickness obtained above.

In addition, conversion from each thickness to 100 micrometers thickness was performed based on the following numerical formula.
The absolute value of birefringence (| Δn |) and the phase difference Re have the following relationship.
Re = | Δn | × d
(| Δn |: absolute value of birefringence, Re: phase difference, d: thickness of sample)

The absolute value (| Δn |) of birefringence is a value shown below.
| Δn | = | nx−ny |
(Nx: refractive index in the stretching direction, ny: refractive index perpendicular to the stretching direction in the plane)

<Measurement of retardation Rth of acrylic thermoplastic resin>
The birefringence measurement of the polarized light transmitting optical component was performed at a wavelength of 589 nm using a phase difference measuring device (KOBRA-21ADH) manufactured by Oji Scientific Instruments Co., Ltd. installed in a constant temperature and humidity chamber adjusted to 23 ° C. and humidity 60%. The measurement is performed on 30 samples of 4 cm square, and the thickness direction retardation Rth is measured at the center of the sample, and then the thickness of the sample at the center is measured to obtain the thickness direction retardation Rth converted to a thickness of 100 μm. It was. Subsequently, after converting into an absolute value, the average was taken, and it converted into the whole thickness calculated | required above again, and the absolute value of phase difference Rth of the thickness direction of polarized light transmission optical components was calculated | required.

In addition, conversion from each thickness to 100 micrometers thickness was performed based on the following numerical formula. The absolute value of birefringence (| Δn |) and the phase difference Rth have the following relationship.
Rth = | Δn | × d
(| Δn |: absolute value of birefringence, Rth: phase difference, d: thickness of sample)

The absolute value (| Δn |) of birefringence is a value shown below.
| Δn | = | (nx + ny) / 2−nz |
(Nx: refractive index in the stretching direction, ny: refractive index in the plane perpendicular to the stretching direction, nz: refractive index in the thickness direction out of the plane perpendicular to the stretching direction)

<Measurement of slope α of relational expression of distortion and birefringence of acrylic thermoplastic resin>
An acrylic thermoplastic resin film (thickness: about 150 μm, width: 40 mm) was formed by uniaxial free stretching at a stretching temperature (Tg + 20) ° C. and a stretching speed (500 mm / min) with an Instron 10t tensile tester. The draw ratio was drawn at 100%, 200%, and 300%. Subsequently, the birefringence of the obtained stretched sample was measured by the above-described method, and the birefringence (Δn (S)) expressed when uniaxially stretched was determined.

The value of the slope α from the least squares approximate linear relationship (A) obtained by plotting the value of birefringence (Δn (S)) expressed in the obtained stretched sample against the stretch ratio (S) Asked. It means that the smaller the value of the inclination α, the smaller the birefringence (Δn (S)) and its change.
Δn (S) = α × S + β (β is a constant: birefringence value when not stretched) (A)

  Here, the birefringence is a value obtained by converting a measured value to a thickness of 100 μm.

The draw ratio (S) is a value represented by the following formula, where L _{0 is} the distance between chucks before stretching and L ₁ is the distance between chucks after stretching.

  In a stretched sample that completely satisfies optical isotropy, both the in-plane retardation Re and the thickness direction retardation Rth are “zero”, and there is no variation in the retardation.

[Melting thermoforming of polarized light transmission optical components]
Resin predrying conditions: 80 ° C., 6 hours. Two prismatic molds with a short side of 40mm and a depth of 40mm are used, and injection molding is performed under injection molding conditions (cylinder temperature 265 ° C, injection speed 20mm / sec, injection pressure 110MPa, mold temperature 115 ° C). Carried out.

[Method for Applying Multilayer Transparent Dielectric Layer to Polarized Transmission Optical Component]
The inclined surface of the injection-transmitted polarized light transmitting optical component is subjected to corona discharge treatment with an energy of 50 W · min / m ² in the atmosphere, and the surface is hydrophilized. A multilayer transparent dielectric layer was formed using a SiO ₂ target.

[Production method of polarization beam splitter]
The multilayer transparent dielectric layers of the two prisms were brought into close contact with each other so that air could not enter, and a Kubrick type polarization beam splitter was produced.

[Contrast evaluation of polarization beam splitter]
The light from the LED light source was collimated with a collimator lens, and then turned into a 10 mm square white light through a flyhole lens. Next, the produced Kubrick beam splitter was placed on an XY stage, and a polarizing plate was placed at a position where the transmitted polarized light was quenched. Next, the XY stage was moved to visually evaluate polarization leakage at 9 points.

  ◎ indicates that there is no change in polarization leakage when the XY stage is moved, Δ indicates that a slight change in light and darkness is observed, and × indicates that there is clear polarization leakage.

[Measurement of surface hardness of polarized light transmission optical components]
Using an electric pencil scratch hardness tester (manufactured by Yasuda Seiki Seisakusho Co., Ltd.) according to JIS K5600-5-4, the pencil hardness of the polarized light transmission optical component was measured with a load of 500 g with respect to the orthogonal plane of the injection molded body. .

[Measurement of adhesion of multilayer transparent dielectric layer]
The adhesion of the multilayer transparent dielectric layer was evaluated by a cross-cut method according to JIS-K5600-5-6. The evaluation criteria were as follows.
0: The cut wrinkles are smooth and there is no peeling on the lattice surface.
1: Slight peeling occurs at the cut intersection.
2: When peeled off at the intersection along the cut ridges and the influence is about 5 to 15% of the total area.
3: About 15% to 35% peeling at the crosscut portion.
4: Peeling partly on the front and peeling up to about 35% at the crosscut part.
5: Peeling more than 4 classifications.

[Evaluation of display quality of optical projector]
An optical projection apparatus having the configuration shown in FIG. 1 is manufactured, and ◎ indicates that the color tone reproducibility and image resolution of the projected image is excellent, ○ indicates that the color reproducibility is excellent, and ○ indicates that there is a change in color and the image resolution. Those inferior to were marked with x.

[Example 1]
An acrylic thermoplastic resin was produced by the following method. Methyl methacrylate (Wako Pure Chemicals, hereinafter referred to as MMA) was distilled at a reduced pressure of 0.01 MPa and 40 ° C. to remove the inhibitor. Next, 24.30 kg of distilled methyl methacrylate, 2.40 kg of N-phenylmaleimide (special grade of Wako Pure Chemicals, hereinafter phMI), 3.30 kg of N-cyclohexylmaleimide (special grade of Wako Pure Chemicals, hereinafter chMI), 20 kg of metaxylene (Wako Pure Chemicals) A special grade, hereinafter mXy) was weighed and added to a 50 L tank to obtain a mixed monomer solution. Subsequently, nitrogen was bubbled at a rate of 100 mL / min for 12 hours to remove dissolved oxygen. The mixed monomer solution was added to a 60 L reactor purged with nitrogen and the temperature was raised to 130 ° C. Next, polymerization was carried out by adding an initiator solution in which 0.06 kg of perbutyl O (Japanese oil) was dissolved in 6 kg of mXy at a rate of 1 kg / hour, and the reactor was cooled to 50 ° C. after 8 hours. .

Subsequently, 500 L of methanol was added to a 1 m ³ reactor, and the above polymerization solution was poured over 5 hours to precipitate a polymer. Thereafter, the mixture was further stirred for 2 hours and filtered under reduced pressure. 300 L of methanol was further poured into the methanol-containing polymer powder after filtration under reduced pressure and stirred again. Thereafter, filtration under reduced pressure was performed, and the methanol-containing powder was collected and dried in a 0.3 m ³ conical vacuum dryer under conditions of a degree of vacuum of 0.03 MPa and a temperature of 80 ° C. The powder after drying was pelletized with a twin-screw extruder at 250 ° C. to obtain a pellet-shaped acrylic thermoplastic resin.

When the composition of this acrylic thermoplastic resin was confirmed, the structural units derived from MMA, phMI, and chMI monomers were 81.3 mass%, 7.9 mass%, and 10.8 mass%, respectively. . Moreover, when Tg was measured, it was 135 degreeC and Mw was 225,000. The photoelastic coefficient was + 0.4 × 10 ⁻¹² Pa ⁻¹ . Re in terms of thickness of 100 μm was 9 nm, and Rth was 26 nm. α was 0.03 × 10 ⁻⁵ .

  Injection molding was performed to produce a polarizing beam splitter. Pencil hardness is 4H. The result of the polarization leakage test is ◎. The adhesion test result was 2.

[Example 2]
Styrene (Wako Pure Chemicals, hereinafter St) was distilled at a reduced pressure of 0.01 MPa and 52 ° C. to remove the inhibitor. Next, 21.0 kg of distilled MMA, 2.18 kg of phMI (special grade of Wako Pure Chemical), 5.0 kg of chMI (special grade of Wako Pure Chemical), 1.72 kg of distilled St (special grade of Wako Pure Chemical), 20 kg of mXy (special grade of Wako Pure Chemical) and mixed monomer solution Except that, polymerization was performed in the same manner as in Example 1 to obtain a pellet-shaped acrylic thermoplastic resin.

When the composition of this acrylic thermoplastic resin was confirmed, the structural units derived from the monomers MMA, phMI, chMI, and St were 70.2% by mass, 5.2% by mass, and 19.8% by mass, respectively. It was 4.8% by mass. Moreover, when the glass transition temperature was measured, it was 141 degreeC and the weight average molecular weight was 150,000. The photoelastic coefficient was + 0.1 × 10 ⁻¹² Pa ⁻¹ . Re in terms of 100 μm thickness was 24 nm and Rth was 16 nm. α was −0.2 × 10 ⁻⁵ .

  Injection molding was performed to produce a polarizing beam splitter. Pencil hardness is 3H. A polarization leakage test was performed. The result was ○. The adhesion test result was 1.

[Example 3]
Benzyl methacrylate (special grade of Wako Pure Chemicals, hereinafter referred to as BzMA) was distilled at a reduced pressure of 0.01 MPa and 52 ° C. to remove the inhibitor. Distilled MMA 24.0 kg, phMI 2.40 kg (Wako Pure Chemical), chMI 3.30 kg (Wako Pure Chemical), BzMA 0.30 kg (Wako Pure Chemical), mXy 20 kg (Wako Pure Chemical) were used as mixed monomer solutions. Was polymerized in the same manner as in Example 1 to obtain a pellet-shaped acrylic thermoplastic resin. When the composition of this acrylic thermoplastic resin was confirmed, the structural units derived from the monomers MMA, phMI, chMI, and BzMA were 80.3% by mass, 7.9% by mass, and 10.8% by mass, respectively. 1.0% by mass. Moreover, when the glass transition temperature was measured, it was 142 degreeC and the weight average molecular weight was 22 million. The photoelastic coefficient was + 0.7 × 10 ⁻¹² Pa ⁻¹ . Re in terms of thickness of 100 μm was 2 nm, and Rth was 2 nm. α was −0.02 × 10 ⁻⁵ .

  Injection molding was performed to produce a polarizing beam splitter. Pencil hardness is 2H. A polarization leakage test was performed. The result was ○. The adhesion test result was 1.

[Comparative Example 1]
It was + 5.0 * 10 < ^-12 > Pa < ^-1 > which measured the photoelastic coefficient regarding ZEONOR 480R (Nippon Zeon Corporation). The glass transition temperature was 130 ° C. Re in terms of thickness of 100 μm was 50 nm, and Rth was 55 nm. α was 0.6 × 10 ⁻⁵ .

  Injection molding was performed to produce a polarizing beam splitter. The pencil hardness is HB. A polarization leakage test was performed. The result was x. The adhesion test result was 2.

[Comparative Example 2]
Polymerization and the polymer were recovered in the same manner as in Example 1 using MMA alone as the monomer solution. It was -4.7 * 10 < ^-12 > Pa < ^-1 > as a result of measuring a photoelastic coefficient. The molecular weight was 102,000. The glass transition temperature was 98 ° C.
Re in terms of 100 μm thickness was 10 nm and Rth was 9 nm. α was −0.33 × 10 ⁻⁵ .

  Injection molding was performed to produce a polarizing beam splitter. The pencil hardness is H. The result of conducting the polarization leakage test was Δ.

  Tables 1 below summarize the characteristics of Examples 1, 2, and 3 and Comparative Examples 1 and 2.

  It can be seen that the optical characteristics (low birefringence) are excellent by comparing Examples 1, 2, and 3 with Comparative Examples 1 and 2. In particular, it can be seen that the ternary composition of MMA, phMI, and chMI is excellent as a polarization transmission optical component. Moreover, it turns out that it is excellent in inorganic adhesiveness by comparing Examples 1, 2, and 3 with Comparative Examples 1 and 2. Moreover, it turns out that hardness is high and it is hard to be damaged by comparing Examples 1, 2, and 3 with Comparative Examples 1 and 2.

  Since the polarized light transmitting optical component of the present invention has heat resistance, inorganic adhesion, high hardness, and high optical isotropy (low birefringence), as a polarizing beam splitter installed around the LED light source Is preferred. Further, it is particularly suitable for an optical projection apparatus by combining with other lenses.

  DESCRIPTION OF SYMBOLS 1 ... Optical projection apparatus, 10 ... Light source, 12 ... Spherical reflector, 14 ... Collimator lens, 16 ... Infrared removal filter, 18 ... / 4 wavelength plate, 20 ... Polarizing beam splitter (PBS), 20a ... Multilayer transparent dielectric film , 22 ... Mirror.

Claims (14)

Acrylic thermoplastic having a first structural unit represented by the following formula (1), a second structural unit represented by the following formula (2), and a third structural unit represented by the following formula (3) Formed from resin,
The acrylic thermoplastic resin is, based on the total amount, 50 to 95% by mass of the first structural unit, 0.1 to 20% by mass of the second structural unit, and 0.1 to 49.9. A polarized light transmitting optical component comprising the third structural unit in mass%.

[Wherein, R ¹ represents a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, an arylalkyl group having 7 to 14 carbon atoms, an aryl group having 6 to 14 carbon atoms, or And an aryl group having 6 to 14 carbon atoms and having at least one substituent selected from the following group A.
Group A: a halogen atom, a hydroxyl group, a nitro group, an alkoxy group having 1 to 12 carbon atoms, and an alkyl group having 1 to 12 carbon atoms. ]

[Wherein, R ² represents an arylalkyl group having 7 to 14 carbon atoms, an aryl group having 6 to 14 carbon atoms, or an aryl group having 6 to 14 carbon atoms having at least one substituent selected from the following group B: R ³ and R ⁴ each independently represent a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, or an aryl group having 6 to 14 carbon atoms.
Group B: a halogen atom, a hydroxyl group, a nitro group, an alkoxy group having 1 to 12 carbon atoms, an alkyl group having 1 to 12 carbon atoms, and an arylalkyl group having 7 to 14 carbon atoms. ]

[Wherein, R ⁵ represents a hydrogen atom, a cycloalkyl group having 3 to 12 carbon atoms, an alkyl group having 1 to 12 carbon atoms, or at least one substituent having at least one substituent selected from the following group C. R ⁶ and R ⁷ each independently represents a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, or an aryl group having 6 to 14 carbon atoms.
Group C: a halogen atom, a hydroxyl group, a nitro group, and an alkoxy group having 1 to 12 carbon atoms. ] The polarized light transmission optical component according to claim 1, wherein an absolute value of a photoelastic coefficient of the acrylic thermoplastic resin is 3.0 × 10 ⁻¹² Pa ⁻¹ or less.   The polarized light transmission optical component according to claim 1 or 2, wherein a halogen atom content of the acrylic thermoplastic resin is less than 0.47% by mass based on a total amount of the acrylic thermoplastic resin.   The polarized light transmission optical component according to any one of claims 1 to 3, wherein a molar ratio of the content of the second structural unit to the content of the third structural unit is greater than 0 and 15 or less. R ¹ is a methyl group or a benzyl group,
R ² is a phenyl group or a phenyl group having at least one substituent selected from the group B;
The polarized light transmission optical component according to claim 1, wherein R ⁵ is a cyclohexyl group.   The said acrylic thermoplastic resin is resin whose absolute value of the phase difference Re of the in-plane direction at the time of film forming will be 30 nm or less in conversion of 100 micrometer thickness of any one of Claims 1-5. Polarized transmission optical components.   The polarized light according to any one of claims 1 to 6, wherein the acrylic thermoplastic resin is a resin in which an absolute value of a retardation Rth in a thickness direction when a film is formed is 30 nm or less in terms of a thickness of 100 µm. Transmission optics. The acrylic thermoplastic resin has a slope in the least squares approximate linear relationship (a) between the stretch ratio (S) when film-molded and the 100 μm-thickness converted birefringence (Δn (S)) at the stretch ratio. The polarized light transmission optical component according to claim 1, wherein the value of α is a resin that satisfies the following formula (b).
Δn (S) = α × S + β (a)
−0.30 × 10 ⁻⁵ ≦ α ≦ 0.30 × 10 ⁻⁵ (b)
[In the formula, β is a constant and indicates birefringence at the time of non-stretching. ]   The polarized light transmission optical component according to any one of claims 1 to 8, wherein a glass transition temperature of the acrylic thermoplastic resin is 130 ° C or higher.   The polarized light transmission optical component according to any one of claims 1 to 9, wherein the surface has a pencil hardness of 3H or more.   The polarized light transmission optical component according to claim 1, wherein the optical path length is 10 to 100,000 μm.   The polarized light transmission optical component according to claim 1, wherein an inorganic layer is deposited on the surface.   The polarized light transmission optical component according to claim 12, wherein the inorganic layer is a transparent multilayer dielectric.   An optical projection apparatus comprising the polarized light transmitting optical component according to claim 12 or 13.

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