JP5901158B2 - Conductive substrate - Google Patents

Description

  The present invention relates to a conductive substrate having excellent transparency and conductivity.

  Conventionally, as a transparent optical material, a methacrylic resin represented by a homopolymer of methyl methacrylate (PMMA), polystyrene (PS), styrene / methyl methacrylate copolymer (MS), polycarbonate (PC), etc. Examples thereof include amorphous resins and semicrystalline resins such as polyethylene terephthalate (PET).

  In recent years, various optical products such as flat panel displays such as liquid crystal displays, plasma displays, organic EL displays, small infrared sensors, fine optical waveguides, ultra-small lenses, pickups for DVD / BlueRayDisk that handle short-wavelength light. With the development of lenses, optical resins for optical materials not only have excellent transparency, but also have high heat resistance and higher birefringence control (phase difference control (positive / negative / zero) ) And photoelastic coefficient control (zero)) have been required (Non-Patent Documents 1 and 2).

  Recently, portable information terminals represented by smartphones, tablet PCs, and the like have been widely used. For such portable information terminals, an input device in which a transparent touch panel is mounted on a liquid crystal display element is used. Then, for the purpose of reducing the thickness and weight of the portable information terminal and improving the display quality, technical development of incorporating the touch panel function into the liquid crystal display element has been carried out. At present, the polarizing plate constituting the liquid crystal display element and An inner touch panel (On-cell method) incorporating a touch panel function between glass substrates and an inner touch panel (In-cell method) incorporating a touch panel function between the liquid crystal in the liquid crystal display element and the glass substrate have appeared. (Non-patent Document 3).

  In the inner touch panel, since the members constituting the touch panel function exist between the two polarizing plates of the liquid crystal display element, high isotropy (that is, low birefringence and low photoelasticity) is provided as an optical material characteristic. The optical resin which has is desired (patent document 1). Further, a metal oxide (for example, a composite oxide of indium and tin (ITO), etc.) is formed as a transparent conductive film by a DC sputtering method on the surface of an optical material (film, sheet) formed by molding an optical resin, A transparent conductive film for a touch panel and a transparent conductive substrate are obtained (Patent Document 2).

  As an optical resin for a transparent conductive film and a transparent conductive substrate, generally used PET has a problem that low birefringence is not satisfactory, and PC has a problem that both low birefringence and durability are not satisfactory. . In addition, the cyclic olefin resin has heat resistance and low birefringence, but it has a problem that it is fragile and difficult to handle.

  On the other hand, PMMA as an optical resin is excellent in transparency, weather resistance, etc., but because of low heat resistance, transparency and flatness deteriorate when forming a conductive film by sputtering or other conductive films. There was a problem to do.

  For example, Patent Document 3 discloses a styrene copolymer comprising a predetermined amount of styrene, maleic anhydride and methyl methacrylate as a transparent novel styrene copolymer having improved heat resistance. Patent Document 4 discloses a method for producing a heat-resistant acrylic resin having good optical purity by washing a copolymer comprising a predetermined amount of a methyl methacrylate unit and an N-alkyl-substituted maleimide unit by a predetermined method. Have been described. However, all the copolymers have problems in coloring during heating and low birefringence.

  For example, Non-Patent Documents 4 and 5 disclose methyl methacrylate / methacrylic acid-2,2,2-trifluoroethyl / benzyl methacrylate terpolymer (= 52/42/6 wt%). . However, the acrylic resin can control the birefringence and the photoelastic coefficient at the same time, and the absolute value of the birefringence and the photoelastic coefficient can be simultaneously zero (zero-zero birefringence), but the heat resistance is insufficient. There was a problem of being.

  Furthermore, for example, Patent Document 5 discloses a terpolymer comprising methyl methacrylate, N-cyclohexylmaleimide, and benzyl methacrylate. However, although the acrylic resin can control a certain degree of low birefringence, there is a problem that the heat resistance is not always sufficient.

  Patent Document 2 discloses an optical resin mainly composed of an acrylic resin having a lactone ring structure in the main chain and a glass transition temperature of 120 ° C. or higher. Although the acrylic resin has heat resistance and low birefringence is controlled to some extent, it is not satisfactory, has a problem that it is fragile and difficult to handle.

JP-A-11-53118 JP 2008-179677 A JP-A-55-102614 JP 61-252211 Japanese Patent Laid-Open No. 06-25359

Chemical Review, 1988, No. 39 (Academic Publishing Center) Monthly display, April 2005 issue Forefront of touch panel, 2010, (Nikkei BP) Molding, 2009, Vol. 21, No. 7, p. 426 Macromolecules, 2006, 39, 3019-3023

  As described above, within the scope of the prior art, it is excellent in transparency and heat resistance, and its birefringence (low birefringence and low photoelastic coefficient) is highly controlled as its optical characteristics, and as its molded product There is no technology that can provide an acrylic resin excellent in handleability, and therefore there is no transparent conductive substrate excellent in transparency, heat resistance, optical properties, and mechanical properties suitable for a touch panel including an inner touch panel.

  Therefore, the present invention provides an acrylic thermoplastic resin composition that is excellent in transparency, heat resistance, low birefringence, and handleability as a molded article, and has transparency, heat resistance, optical properties, and mechanical properties. An object is to provide an excellent conductive substrate.

  In the present invention, a resin layer containing a specific acrylic resin is excellent in transparency, its low birefringence can be highly controlled, and transparent even when a transparent conductive layer is provided on one surface thereof. It has been found that transparent conductivity is exhibited without impairing the properties and low birefringence.

［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］ 前記アクリル系樹脂の光弾性係数の絶対値が３．０×１０^−１２Ｐａ^−１以下である、［１］に記載の導電性基板。
［３］ 前記アクリル系樹脂は、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厚換算で、３０ｎｍ以下となる樹脂である、［１］又は［２］に記載の導電性基板。
［４］ 前記アクリル系樹脂は、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厚換算で、３０ｎｍ以下となる樹脂である、［１］〜［３］のいずれかに記載の導電性基板。
［５］ 前記アクリル系樹脂のガラス転移温度Ｔｇが１２０℃以上である、［１］〜［４］のいずれかに記載の導電性基板。
［６］ 前記アクリル系樹脂は、フィルム成形した場合の全光線透過率が、１００μｍ厚換算で８５％以上となる樹脂である、［１］〜［５］のいずれかに記載の導電性基板。
［７］ 前記導電層がインジウム−錫酸化物を含有する、［１］〜［６］のいずれかに記載の導電性基板。
［８］ 前記アクリル系樹脂が、その総量基準で、５０〜９５質量％の前記第一の構造単位と、０．１〜４９．９質量％の前記第二の構造単位と、０．１〜４９．９質量％の前記第三の構造単位とを有する、［１］〜［７］のいずれかに記載の導電性基板。
［９］ 前記アクリル系樹脂が、その総量基準で、５０〜９５質量％の前記第一の構造単位と、０．１〜２０質量％の前記第二の構造単位と、０．１〜４９．９質量％の前記第三の構造単位とを有する、［１］〜［８］のいずれかに記載の導電性基板。
［１０］ 前記Ｒ^１が、メチル基又はベンジル基であり、
前記Ｒ^２が、フェニル基又は前記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、
前記Ｒ^５が、シクロヘキシル基である、［１］〜［９］のいずれか一項に記載の導電性基板。
［１１］ 前記アクリル系樹脂は、ＧＰＣ測定法により測定されるポリメタクリル酸メチル換算の重量平均分子量Ｍｗが３０００〜１００００００であり、数平均分子量Ｍｎに対する重量平均分子量Ｍｗの比Ｍｗ／Ｍｎが１〜１０である、［１］〜［１０］のいずれか一項に記載の導電性基板。
［１２］ 前記樹脂層が、前記アクリル系樹脂を含有する樹脂シートを、少なくとも一軸方向に延伸してなるフィルム状又はシート状の成形体からなる層である、［１］〜［１１］のいずれかに記載の導電性基板。
［１３］ ［１］〜［１３］のいずれかに記載の導電性基板を備える、タッチパネル。 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) A conductive substrate comprising a resin layer containing a resin and a conductive layer provided on one surface of the resin layer.

[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 conductive substrate according to [1], wherein an absolute value of a photoelastic coefficient of the acrylic resin is 3.0 × 10 ⁻¹² Pa ⁻¹ or less.
[3] The conductive resin according to [1] or [2], wherein the acrylic resin is a resin in which an absolute value of an in-plane phase difference Re when formed into a film is 30 nm or less in terms of a thickness of 100 μm. Substrate.
[4] The acrylic resin is a resin according to any one of [1] to [3], in which an absolute value of a thickness direction retardation Rth when formed into a film is 30 nm or less in terms of a thickness of 100 μm. Conductive substrate.
[5] The conductive substrate according to any one of [1] to [4], wherein the acrylic resin has a glass transition temperature Tg of 120 ° C. or higher.
[6] The conductive substrate according to any one of [1] to [5], wherein the acrylic resin is a resin having a total light transmittance of 85% or more in terms of a thickness of 100 μm when formed into a film.
[7] The conductive substrate according to any one of [1] to [6], wherein the conductive layer contains indium-tin oxide.
[8] The acrylic resin is, based on the total amount, 50 to 95% by mass of the first structural unit, 0.1 to 49.9% by mass of the second structural unit, The conductive substrate according to any one of [1] to [7], comprising 49.9% by mass of the third structural unit.
[9] The acrylic resin, based on the total amount thereof, is 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.%. The conductive substrate according to any one of [1] to [8], comprising 9% by mass of the third structural unit.
[10] The 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 conductive substrate according to any one of [1] to [9], wherein R ⁵ is a cyclohexyl group.
[11] The acrylic resin has a weight average molecular weight Mw in terms of polymethyl methacrylate measured by GPC measurement method of 3000 to 1000000, and a ratio Mw / Mn of the weight average molecular weight Mw to the number average molecular weight Mn is 1 to 1. The conductive substrate according to any one of [1] to [10], which is 10.
[12] Any of [1] to [11], wherein the resin layer is a layer formed of a film-like or sheet-like molded body obtained by stretching the resin sheet containing the acrylic resin in at least a uniaxial direction. A conductive substrate according to any one of the above.
[13] A touch panel comprising the conductive substrate according to any one of [1] to [13].

  According to the present invention, an acrylic thermoplastic resin composition excellent in transparency, heat resistance, low birefringence, and handleability as a molded article can be provided, and by using the composition, transparency, heat resistance, optical characteristics, and mechanical characteristics can be provided. It is possible to provide a conductive substrate that is excellent in resistance.

It is a perspective view which shows one Embodiment of the electroconductive board | substrate of this invention. It is a schematic cross section which shows the cross section along the cutting line II of FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments.

  FIG. 1 is a perspective view showing an embodiment of a conductive substrate of the present invention, and FIG. 2 is a schematic cross-sectional view showing a cross section taken along a cutting line II in FIG. 1 and 2, the conductive substrate 100 includes a resin layer 10 and a conductive layer 12 provided on one surface of the resin layer.

  The resin layer 10 contains an acrylic resin having a first structural unit, a second structural unit, and a third structural unit. For example, an acrylic thermoplastic resin composition containing the acrylic resin is formed into a film. Or it is a layer which consists of a molded object obtained by shape | molding in a sheet form.

[Acrylic resin]
The acrylic resin contained in the resin layer 10 has a first structural unit, a second structural unit, and a third structural unit. Hereinafter, each structural unit will be described in detail.

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

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 , A decanyl group, a lauryl group, etc. Among these, in terms of further improving the transparency and weather resistance of the resin layer 10, a methyl group, an ethyl group, an n-propyl group, an 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 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.

  In the acrylic resin, it is preferable that the first structural unit is contained in a dominant amount over the other structural units in order to maintain the excellent transparency, weather resistance and mechanical properties of the methacrylic resin. The content of the first structural unit is 50 to 95% by mass based on the total amount of the acrylic resin. Preferably it is 60-95 mass%, More preferably, it is 65-90 mass%, More preferably, it is 70-90 mass%, Most preferably, it is 70-85 mass%. When the content of the first structural unit is within this range, the acrylic resin is more excellent in transparency, weather resistance and mechanical properties, and a preferable heat resistance improving effect is obtained.

  The acrylic 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 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 resin, and 0.1 to 6%. More preferably, it is mass%. According to the acrylic resin in this range, the 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).

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

  Examples of methacrylic acid esters include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, and the like. Methacrylic acid alkyl ester; methacrylic acid cycloalkyl ester such as cyclopentyl methacrylate, cyclohexyl methacrylate, cyclooctyl methacrylate, tricyclodecyl methacrylate, bicyclooctyl methacrylate, tricyclododecyl methacrylate, isobornyl methacrylate; phenyl methacrylate, Benzyl methacrylate, 1-phenylethyl methacrylate, 2-phenylethyl methacrylate, 3-phenylpropyl methacrylate, 2, methacrylate , Methacrylic acid aryl based ester such as 6-tribromophenyl; and the like. These first monomers may be used alone or in combination of two or more.

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

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 resin layer, 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 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 in the acrylic resin is preferably 0.1 to 49.9% by mass and more preferably 0.1 to 35% by mass based on the total amount of the acrylic resin. Preferably, it is 0.1-20 mass%. When the content of the second monomer is within this range, the heat resistance and optical characteristics of the resin layer 10 are further improved.

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

  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. 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).

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, Examples thereof include an isobornyl group, an adamantyl group, a tetracyclododecyl group, and among these, a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group are preferable, and the weather resistance of the resin layer 10 In addition, a cyclohexyl group is more preferable from the viewpoint of further improving optical properties such as transparency and imparting low water absorption to the resin layer 10.

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- Examples include 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 and transparency of resin layer 10 From the viewpoint of further improving optical characteristics such as methyl group, ethyl group and isopropyl group are preferable.

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 resin layer, 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 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 in the acrylic resin is preferably 0.1 to 49.9% by mass and more preferably 0.1 to 40% by mass based on the total amount of the acrylic resin. Preferably, it is 0.1-35 mass%. If the content of the third monomer is within this range, the optical properties such as weather resistance, water absorption resistance and transparency of the resin layer 10 are further improved.

  The acrylic 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).

  As the third monomer, N-methylmaleimide, N-ethylmaleimide, Nn-propylmaleimide, N-isopropylmaleimide, Nn-butylmaleimide, N-isobutylmaleimide, Ns-butylmaleimide, Nt-butylmaleimide, Nn-pentylmaleimide, Nn-hexylmaleimide, Nn-heptylmaleimide, Nn-octylmaleimide, N-laurylmaleimide, N-stearylmaleimide, N-cyclopropylmaleimide N-cyclobutylmaleimide, N-cyclopentylmaleimide, N-cyclohexylmaleimide, N-cycloheptylmaleimide, N-cyclooctylmaleimide, 1-cyclohexyl-3-methyl-1H-pyrrole-2,5-dione, 1-cyclohexyl -3,4-dimethyl 1H-pyrrole-2,5-dione, 1-cyclohexyl-3-phenyl-1H-pyrrole-2,5-dione, 1-cyclohexyl-3,4-diphenyl-1H-pyrrole-2,5-dione, etc. It is done. These third monomers may be used alone or in combination of two or more.

  In the acrylic resin, the total content of the second structural unit and the third structural unit is 5 to 50% by mass based on the total amount of the acrylic resin. Preferably it is 5-40 mass%, More preferably, it is 10-35 mass%, More preferably, it is 10-30 mass%, More preferably, it is 15-30 mass%. When it is within this range, the acrylic resin can provide a more sufficient heat resistance improving effect, and more preferable effects for improving weather resistance, low water absorption, and optical properties. When the total content of the second structural unit and the third structural unit exceeds 50% by mass, the reactivity of the monomer component is reduced during the polymerization reaction, and the amount of monomer remaining unreacted is reduced. In some cases, the physical properties of the acrylic resin may decrease.

In the acrylic resin, the molar ratio C ₂ / C ₃ of the content C ₂ of the _second structural unit and the content C ₃ of the third structural unit is preferably more than 0 and 15 or less, and more than 0. More preferably, it is 10 or less. When the molar ratio C ₂ / C ₃ is in this range, the acrylic resin exhibits better optical characteristics.

  In the acrylic 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 resin. As a result, the acrylic resin exhibits better optical properties.

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

  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 resin is preferably 0.1 to 20% by mass, more preferably 0.1 to 15% by mass, based on the total amount of the acrylic resin. More preferably, it is 0.1-10 mass%. When the content of the fourth structural unit is in the above range, the hygroscopicity of the resin layer 10 made of an acrylic resin is further improved. From the viewpoint of the weather resistance of the resin layer 10, the content of the fourth structural unit is preferably less than 10% by mass, and more preferably less than 7% by weight.

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

  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 ⁸ 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- Examples include decyl group, 1-dodecyl group, etc. Among them, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group in that the transparency and weather resistance of the resin layer 10 are further improved. , Isobutyl group, t-butyl group and 2-ethylhexyl group are preferable, and 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).

^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 , 3-bromostyrene, 4-bromostyrene, 2,4-dibromostyrene, α-bromostyrene, β-bromostyrene, 2-hydroxystyrene, 4-hydroxystyrene, and the like. Since it is easy, styrene and α-methylstyrene are preferable. These fourth monomers may be used alone or in combination of two or more.

  The weight average molecular weight Mw in terms of polymethylmethacrylate by GPC measurement method of acrylic resin is preferably 3000 to 1000000. When the weight average molecular weight Mw is within the above range, sufficient strength can be imparted to the resin layer 10. Moreover, if the weight average molecular weight Mw is 1000000 or less, it can be set as the molded object by press molding. The weight average molecular weight Mw is more preferably from 4,000 to 800,000, and even more preferably from 5,000 to 5,000,000.

  It is preferable that the molecular weight distribution (Mw / Mn) in terms of polymethyl methacrylate by GPC measurement method of acrylic resin is 1-10. The acrylic 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 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.

  The content of halogen atoms in the acrylic 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 resin. The acrylic resin contains less than 0.47% by mass of halogen atoms, so that even when the acrylic resin is handled at a high temperature during melt molding or the like, the halogen gas is hardly generated, and the corrosion of the equipment caused by the halogen gas. And the work environment is prevented from deteriorating. Further, when the acrylic 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.

(Method for producing acrylic resin)
The acrylic resin can be obtained, for example, by the following polymerization step. Moreover, it can refine | purify by the following devolatilization process.

(Polymerization process)
The acrylic resin can be obtained by polymerizing a monomer group including the first monomer, the second monomer, and the third monomer. As the polymerization method, for example, generally used polymerization methods such as cast polymerization, bulk polymerization, suspension polymerization, solution polymerization, emulsion polymerization, living radical polymerization, and anionic polymerization can be used.

  In order to use an acrylic resin as an optical material, it is preferable to avoid the introduction of minute foreign substances as much as possible. From this viewpoint, the polymerization method of the acrylic resin uses cast polymerization or solution polymerization without using a suspending agent or an emulsifier. It is desirable.

  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 during the polymerization reaction and the polymerization time can be appropriately adjusted according to the type and ratio of the monomer used, for example, the polymerization temperature is 0 to 150 ° C., the polymerization time is 0.5 to 24 hours, Preferably, the polymerization temperature is 80 to 150 ° C. and the polymerization time is 1 to 12 hours.

  When a solvent is used during the polymerization reaction, examples of the polymerization solvent include aromatic hydrocarbon solvents such as toluene, xylene, and ethylbenzene; ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone; ether solvents such as tetrahydrofuran; It is done. These solvents may be used alone or in combination of two or more. If the boiling point of the solvent to be used is too high, the residual volatile content of the finally obtained acrylic resin will increase, so a solvent having a boiling point of 50 to 200 ° C. is preferred.

  During the polymerization reaction, a polymerization initiator may be added as necessary. As the polymerization initiator, any initiator generally used in radical polymerization can be used. For example, cumene hydroperoxide, diisopropylbenzene hydroperoxide, di-t-butyl peroxide, lauroyl peroxide, benzoyl peroxide Organic peroxides such as oxide, t-butylperoxyisopropyl carbonate, t-amylperoxy-2-ethylhexanoate; 2,2′-azobis (isobutyronitrile), 1,1′-azobis (cyclohexane Carbonitrile), 2,2′-azobis (2,4-dimethylvaleronitrile), azo compounds such as 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 is used. It is mentioned as preferable. These molecular weight regulators are added in a concentration range such that the degree of polymerization is controlled within the aforementioned range.

  Moreover, you may add an organophosphorus compound and an organic acid as needed at the time of a polymerization reaction. By coexisting with these compounds, favorable effects such as suppression of side reactions and reduction of the amount of unreacted N-substituted maleimide can be expected. Thereby, when shape | molding the acrylic resin obtained or the acrylic thermoplastic resin composition containing the same, the coloring at the time of a process may be reduced.

  Examples of the organic phosphorus compound include alkyl (aryl) phosphonous acid and diesters or monoesters thereof; dialkyl (aryl) phosphinic acid and esters thereof; alkyl (aryl) phosphonic acids and diesters or monoesters thereof; alkyl Phosphinic acid and esters thereof; phosphorous acid diester, phosphorous acid monoester, phosphorous acid triester; phosphoric acid diester, phosphoric acid monoester, phosphoric acid triester and the like. These organophosphorus compounds may be used alone or in combination of two or more. The amount of the organophosphorus compound used is preferably 0.001 to 5.0 mass% with respect to the total amount of monomers.

  On the other hand, as the organic acid, for example, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, caprylic acid, capric acid, lauric acid, stearic acid, oleic acid, linoleic acid, linolenic acid, benzoic acid, cyclohexanecarboxylic acid, Examples thereof include phthalic acid, isophthalic acid, terephthalic acid and the like, and acid anhydrides thereof. These organic acids may be used alone or in combination of two or more. The amount of the organic acid used is preferably 0.001 to 1.0% by mass with respect to the total amount of monomers.

  When carrying out the polymerization reaction, it is desirable that the polymer concentration is 10% by mass or more and 95% by mass or less. When the polymer concentration is 10% by mass or more, the molecular weight and the molecular weight distribution can be easily adjusted, and when the polymer concentration is 95% by mass or less, a high molecular weight polymer can be obtained. Further, from the viewpoint of heat removal management of polymerization reaction heat, the polymer concentration is preferably 75% by mass or less, more preferably 60% by mass or less.

  On the other hand, it is desirable to add a polymerization solvent as appropriate from the viewpoint of maintaining the viscosity of the obtained polymerization reaction solution appropriately. By maintaining the reaction solution viscosity appropriately, it is easy to control heat removal, and microgel generation in the reaction solution can be suppressed. In particular, in the latter half of the polymerization reaction in which the viscosity increases, it is preferable to control the polymer concentration to be 50% by mass or less by appropriately adding a polymerization solvent.

  The form in which the polymerization solvent is appropriately added to the polymerization reaction solution is not particularly limited, and for example, the polymerization solvent may be added continuously or the polymerization solvent may be added intermittently. By controlling the concentration of the acrylic resin produced in the polymerization reaction solution in this way, the temperature uniformity inside the reactor can be improved and the gelation of the reaction solution can be more sufficiently suppressed. The polymerization solvent to be added may be, for example, the same type of solvent used during the initial charging of the polymerization reaction or a different type of solvent, but the solvent used during the initial charging of the polymerization reaction. It is preferable to use the same type of solvent. Moreover, the polymerization solvent to be added may be only one kind of single solvent or two or more kinds of mixed solvents.

  When the acrylic resin is polymerized by the suspension polymerization method, it is carried out in an aqueous medium, and a suspending agent and, if necessary, a suspending aid are added. Examples of the suspending agent include water-soluble polymers such as polyvinyl alcohol, methylcellulose, and polyacrylamide, and inorganic substances such as calcium phosphate and magnesium pyrophosphate. The water-soluble polymer is preferably used in an amount of 0.03 to 1% by mass based on the total amount of monomers, and the inorganic substance is used in an amount of 0.05 to 0.5% by mass based on the total amount of monomers. Is preferred. As the suspension aid, there are anionic surfactants such as sodium dodecylbenzenesulfonate. When an inorganic substance is used as the suspension agent, it is preferable to use a suspension aid. The suspension aid is preferably used in an amount of 0.001 to 0.02% by mass based on the total amount of monomers.

(Devolatilization process)
The devolatilization step means a step of removing a volatile component such as a polymerization solvent, a residual monomer and moisture under reduced pressure heating conditions as necessary. If this removal treatment is insufficient, residual volatile components in the resulting acrylic resin increase, and coloring due to alteration during molding, or molding defects such as bubbles and silver streaks may occur. The residual volatile content is preferably 0.5% by mass or less, more preferably 0.4% by mass or less, and still more preferably 0.3% by mass or less, with respect to 100% by mass of the acrylic resin. The amount of residual volatile matter corresponds to the total amount of residual monomer, polymerization solvent, and side reaction product that did not react during the polymerization reaction described above.

  As an apparatus used for a devolatilization process, the devolatilizer which consists of a heat exchanger and a devolatilization tank; Extruder with a vent; What arranged the devolatilizer and the extruder in series etc. are mentioned, for example. When using an extruder with a vent, one or a plurality of vents may be used, but it is preferable to have a plurality of vents.

  The temperature in the devolatilization step is preferably 150 to 350 ° C, more preferably 170 to 330 ° C, and further preferably 200 to 300 ° C. If this temperature is less than 150 ° C., the residual volatile matter may increase. Conversely, when this temperature exceeds 350 ° C., the resulting acrylic resin may be colored or decomposed.

  The pressure in the devolatilization step is preferably 931 to 1.33 hPa (700 to 1 mmHg), more preferably 800 to 13.3 hPa (600 to 10 mmHg), and further preferably 667 to 20.0 hPa (500 to 15 mmHg). When this pressure exceeds 931 hPa (700 mmHg), volatile matter may remain easily. Conversely, if the pressure is less than 1.33 hPa (1 mmHg), industrial implementation may be difficult.

  The treatment time is appropriately selected depending on the amount of residual volatile matter, but a shorter time is preferable in order to suppress coloring and decomposition of the resulting acrylic resin.

  When the monomer reaction conversion rate during the polymerization reaction is low, a large amount of unreacted monomer remains in the polymerization solution. In that case, in order to reduce the residual volatile content of the resulting acrylic resin, the treatment is performed at a high treatment temperature for a long time, but there is a problem that coloring and decomposition are likely to occur. When processing a polymerization reaction solution containing a large amount of unreacted monomer, the monomer in question is, for example, an aromatic hydrocarbon solvent, a hydrocarbon solvent, or an alcohol solvent in the polymerization solution. After the addition, a homogenizer (emulsification dispersion) treatment is performed, and the unreacted monomer can be separated from the polymerization reaction solution by a pretreatment such as liquid-liquid extraction or solid-liquid extraction. When the polymerization reaction liquid after monomer separation by pretreatment is subjected to the devolatilization step described above, the total amount of monomers remaining in 100% by mass of the obtained acrylic resin is easily suppressed to 0.5% by mass or less. be able to.

  The total amount of monomers remaining in the acrylic resin is preferably 0.5% by mass or less, more preferably 0.4% by mass or less, and still more preferably 0.3% by mass with respect to 100% by mass of the acrylic resin. It is as follows. When the total amount of the remaining monomers exceeds 0.5% by mass, a molded product that is not suitable for practical use may be obtained, such as being colored when heated during molding processing, and the heat resistance and weather resistance of the molded product are reduced.

  The number of foreign substances contained in the acrylic resin is preferably as small as possible when used for optics. As a method for reducing the number of foreign substances, in the polymerization reaction step, the devolatilization step, and the molding step described later, an acrylic resin solution or melt is used, for example, a leaf disk type polymer filter having a filtration accuracy of 1.5 to 15 μm. And the like, and the like.

(Optical characteristics of acrylic resin)
(I) Absolute value of photoelastic coefficient C The acrylic resin preferably has an absolute value of photoelastic coefficient C of 3.0 × 10 ⁻¹² Pa ⁻¹ or less, and 2.0 × 10 ⁻¹² Pa ^−1. Or less, more preferably 1.0 × 10 ⁻¹² Pa ⁻¹ or less.

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 (ia) and (ib). It is. 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 of the acrylic resin is sufficiently small as compared with the case where an existing resin (for example, PMMA, PC, triacetyl cellulose resin, cyclic olefin resin, etc.) is used. 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
The acrylic resin preferably has an absolute value of the phase difference 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 resin is sufficiently small compared to the birefringence when using existing resins (for example, PMMA, PC, triacetyl cellulose resin, cyclic olefin resin, etc.). Suitable for applications requiring refraction.

  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
The acrylic resin preferably has an absolute value of the thickness direction retardation Rth 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.

  Compared to the case of using existing resins (for example, PMMA, PC, triacetyl cellulose resin, cyclic olefin resin, etc.), the acrylic resin has an extremely large absolute value of the retardation Rth in the thickness direction when it is used as an optical film. It has a feature of being small.

(Iv) Glass transition temperature Tg
The acrylic resin desirably has high heat resistance from the viewpoint of dimensional stability under the use environment temperature. Since the heat resistance is excellent, the glass transition temperature Tg of the acrylic resin is preferably 120 ° C. or higher, more preferably 130 ° C. or higher, and further preferably 135 ° C. or higher.

(V) Total light transmittance The acrylic resin preferably has a total light transmittance of 85% or more, more preferably 88% or more, and even more preferably 90% or more when film-formed. . 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 resin has a sufficiently small photoelastic coefficient C (approximately zero), and an in-plane retardation Re and a thickness retardation as an optical film regardless of whether or not stretching is performed. It is characterized by a small absolute value of Rth (approximately zero), and can realize optically complete isotropic property that cannot be achieved by conventionally known resins. Furthermore, the acrylic resin can achieve high heat resistance at the same time.

[Acrylic thermoplastic resin composition]
The acrylic thermoplastic resin composition contains the acrylic resin and is excellent in transparency, heat resistance, and low birefringence. Moreover, the molded object formed by shape | molding an acrylic thermoplastic resin composition has favorable mechanical characteristics, and is excellent in handleability.

  The acrylic thermoplastic resin composition may contain various additives as long as the effects of the present invention are not significantly impaired. The type of additive is not particularly limited as long as it is generally used for blending resins and rubber-like polymers.

  Examples of additives include inorganic fillers; pigments such as iron oxides; lubricants and mold release agents such as stearic acid, behenic acid, zinc stearate, calcium stearate, magnesium stearate, and ethylene bisstearamide; paraffinic processes Softeners and plasticizers such as oils, naphthenic process oils, aromatic process oils, paraffins, organic polysiloxanes and mineral oils; hindered phenolic antioxidants, antioxidants such as phosphorus thermal stabilizers, hindered amines Examples thereof include light stabilizers, benzotriazole-based ultraviolet absorbers, flame retardants, antistatic agents; reinforcing agents such as organic fibers, glass fibers, carbon fibers, and metal whiskers; colorants; other additives; The content of the additive is preferably 0 to 5% by mass, more preferably 0 to 2% by mass, and still more preferably 0 to 1% by mass.

  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 resin; Polyamide; Polyphenylene sulfide resin; Polyether ether ketone resin; Polyester resin; Polysulfone; Polyphenylene oxide; Polyimide; 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.

[Molded body]
The resin layer 10 is a layer formed of a molded body obtained by molding an acrylic thermoplastic resin composition into a film shape or a sheet shape.

  The acrylic thermoplastic resin composition is formed into, for example, an extrusion-molded body such as a sheet, film, strand, or pipe, an injection-molded body such as a disk, cube, or plate, and a press-molded body. be able to. These molded articles have characteristics according to the characteristics of the acrylic resin.

  When the molded body is in the form of a sheet or film, the thickness is preferably 1 to 10,000 μm, more preferably 1 to 5000 μm, and even more preferably 1 to 3000 μm.

  As a method for forming an acrylic thermoplastic resin composition into a molded body, for example, a method such as extrusion molding or solution cast molding can be used for molding into a film-shaped or sheet-shaped molded body.

  Specifically, for example, in extrusion molding, an acrylic thermoplastic resin composition can be melted and formed into a sheet or film using an extruder equipped with a T die, a circular die or the like. At this time, a thermoplastic resin other than various additives and the acrylic thermoplastic resin composition can be melted and kneaded together with the acrylic thermoplastic resin composition to obtain a molded article.

  In solution cast molding, for example, an acrylic thermoplastic resin composition is dissolved in a solvent such as chloroform or methylene dichloride to form a polymer solution, and then cast, dried and solidified to form a sheet or film. .

  The sheet-like or film-like molded body can be stretched continuously by extrusion molding and cast molding. For example, an unstretched film or sheet is longitudinally uniaxially stretched in the mechanical flow direction, transversely uniaxially stretched in a direction perpendicular to the mechanical flow direction, or by simultaneous biaxial stretching method of roll stretching and tenter stretching, and tenter stretching simultaneously. A biaxially stretched film can be obtained by stretching by a biaxial stretching method, a biaxial stretching method by tubular stretching, or the like.

  The strength of the molded body can be improved by stretching. The draw ratio is 0.1% or more and 300% or less in at least one direction, preferably 0.2% or more and 290% or less, and more preferably 0.3% or more and 280% or less. By extending into this range, a molded article having further excellent optical properties such as strength, transparency and birefringence can be obtained.

  A heat treatment (annealing) or the like can be performed on the stretched molded body for the purpose of stabilizing its mechanical properties and optical properties. The conditions for the heat treatment may be appropriately selected similarly to the conditions for the heat treatment performed on a conventionally known sheet or film, and are not particularly limited.

  The molded body can be subjected to surface functionalization treatment such as antireflection treatment, transparent conductive treatment, electromagnetic wave shielding treatment, and gas barrier treatment.

  The molded body is, for example, a polarizing plate protective film used for a display such as a liquid crystal display, a plasma display, an organic EL display, a field emission display, and a rear projection television, a retardation plate such as a quarter-wave plate and a half-wave plate It can be suitably used for liquid crystal optical compensation films such as viewing angle control films, display front plates, display substrates, lenses, etc., transparent substrates used in solar cells, transparent conductive substrates such as touch panels, and the like. In addition, the molded body can be used for waveguides, lenses, lens arrays, optical fibers, optical fiber coating materials, LED lenses, lens covers, etc. in the fields of optical communication systems, optical switching systems, and optical measurement systems. it can.

[Conductive layer]
The conductive substrate according to the present embodiment has a conductive layer 12 on at least one surface of the resin layer 10. The conductive layer 12 is preferably a layer having excellent transparency, and can also be referred to as a “transparent conductive layer”.

  As the material constituting the conductive layer 12, any material conventionally used as a conductive material in the field can be used. Specifically, an organic conductive compound, an organic conductive polymer, indium oxide, Metal oxides such as tin oxide, zinc oxide, indium-tin oxide (ITO), antimony-tin oxide (ATO), zinc-aluminum oxide, indium-zinc oxide (IZO); gold, silver, copper, Examples include metals such as copper, palladium, and aluminum.

  Among these, those containing zinc oxide or indium oxide as a main component are preferable, and those containing indium oxide as a main component are particularly preferable. Among these, indium-tin oxide is preferable because it has both high transparency and conductivity. Here, the “main component” means that 60% by mass or more is contained in the conductive layer 12, and preferably 80 to 99% by mass.

  The conductive layer 12 preferably contains 80 to 99% by mass of indium oxide and more preferably 90 to 95% by mass based on the total amount of the conductive layer 12.

  The thickness of the conductive layer 12 is preferably 20 to 300 nm. More preferably, it is 25-200 nm, More preferably, it is 30-100 nm. If the thickness of the conductive layer 12 is too thin, the thickness and composition may be non-uniform. On the other hand, if it is too thick, the transparency may be lost.

  In the present invention, the method for forming the conductive layer 12 on the resin layer 10 includes thin film forming means such as a coating method, a vacuum deposition method, a sputtering method, and an ion plating method. Among these, it is preferable to employ a sputtering method in which the thickness and composition of the conductive layer 12 can be easily controlled, and the adhesion to the surface of the resin layer 10 and the productivity are excellent.

  When employing a sputtering method, a normal sputtering method using a metal oxide target having the same composition as the desired conductive layer, or a target using a metal target and a mixture of sputtering gas with oxygen, nitrogen, etc. Alternatively, a conductive layer having a desired composition may be formed by reacting on the substrate (resin layer 10).

  The sputtering method is not particularly limited, and plasma methods such as dipole sputtering, tripolar sputtering, quadrupole sputtering, magnetron sputtering, opposed target sputtering (FTS) method, unbalanced magnetron sputtering, ion beam sputtering, ECR (electron). (Cyclotron resonance) Beam method such as sputtering. Among these, the magnetron sputtering method and the opposed target sputtering (FTS) method are preferable. The power source to be used may be either a high frequency power source (RF) or a direct current power source (DC).

  A rare gas such as argon, helium, or neon is used as a sputtering gas when forming the conductive layer 12 by sputtering. Further, oxygen or nitrogen may be used as the reactive gas.

  In addition, it is preferable that the vacuum degree at the time of sputtering shall be 0.01-2.0 Pa, More preferably, it is 0.1-1.0 Pa. If the degree of vacuum is within the above range, discharge occurs stably, so that sputtering is stable, and the conductive layer 12 having a uniform film thickness and composition is easily obtained. In addition, the adhesion between the conductive layer 12 and the resin layer 10 tends to be good.

  In the step of laminating the conductive layer 12, it is preferable that the surface temperature of the resin layer 10 is within a range not exceeding the glass transition temperature of the acrylic resin constituting the resin layer 10 + 30 ° C. More preferably, the glass transition temperature of the acrylic resin constituting the resin layer 10 does not exceed + 20 ° C., and still more preferably, the glass transition temperature of the acrylic resin constituting the resin layer 10 is not exceeded. If the glass transition temperature of the acrylic resin exceeds + 30 ° C., the resin layer 10 may be deformed or the surface smoothness of the resin layer 10 may be lost.

[Conductive substrate]
The conductive substrate 100 includes a resin layer 10 and a conductive layer 12 provided on one surface of the resin layer 10. And the resin layer 10 is a layer which consists of a molded object obtained by shape | molding the acrylic thermoplastic resin composition containing the said acrylic resin in the shape of a film or a sheet, for example.

  The optical properties of a molded article of an acrylic thermoplastic resin composition used as the resin layer 10 (hereinafter sometimes referred to as “film-like molded article”) are shown below.

(I) Absolute value of photoelastic coefficient C The acrylic thermoplastic resin composition constituting the film-shaped molded body preferably has an absolute value of the photoelastic coefficient C of 3.0 × 10 ⁻¹² Pa ⁻¹ or less. 2.0 × 10 ⁻¹² Pa ⁻¹ or less, more preferably 1.0 × 10 ⁻¹² Pa ⁻¹ or less.

(Ii) In-plane phase difference Re
The acrylic thermoplastic resin composition constituting the film-shaped molded body preferably has an absolute value of retardation Re in the in-plane direction of 30 nm or less. 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.

(Iii) Thickness direction retardation Rth
The acrylic thermoplastic resin composition constituting the film-shaped molded body preferably has an absolute value of the retardation Rth in the thickness direction of 30 nm or less. 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.

(Iv) Glass transition temperature Tg
It is desirable that the film-shaped molded body has high heat resistance from the viewpoint of dimensional stability under the use environment temperature. Since the heat resistance is excellent, the glass transition temperature Tg of the acrylic thermoplastic resin composition constituting the film-shaped molded body is preferably 120 ° C. or higher, more preferably 130 ° C. or higher, and 135 ° C. More preferably, it is the above.

(V) Total light transmittance The acrylic thermoplastic resin composition constituting the film-shaped molded body preferably has a total light transmittance of 85% or more, more preferably 88% or more, and 90%. More preferably, it is the above. Here, the total light transmittance is a value obtained by converting to a thickness of 100 μm.

  As described above, the acrylic thermoplastic resin composition constituting the film-shaped molded body has a sufficiently small photoelastic coefficient C (approximately zero), and is in-plane as an optical film regardless of the presence or absence of stretching. It is characterized by the fact that the absolute values of the direction retardation Re and the thickness direction retardation Rth are both small (approximately zero), and realizes optically complete isotropic property that cannot be achieved by conventionally known resins. be able to. Furthermore, the film-like molded body can simultaneously achieve high heat resistance.

  And by using such a film-shaped molded object as the resin layer 10, the electroconductive board | substrate 100 which is excellent in transparency, heat resistance, an optical characteristic, and a mechanical characteristic can be obtained.

[Touch panel]
Since the conductive substrate 100 has both high transparency and low birefringence, the conductive substrate 100 is suitably used for a touch panel used in combination with various display devices.

  In addition, since the conductive substrate 100 has good adhesion between the resin layer 10 and the conductive layer 12, even when repeated input is performed with a pen or the like, the conductive layer 12 does not easily peel due to friction between the electrodes. .

  The touch panel using the conductive substrate 100 is such that, for example, the upper and lower conductive substrates 100 face each other with the conductive layer 12 facing each other and a predetermined gap is maintained between the upper and lower conductive layers 12. It has the structure laminated | stacked through the spacer.

  When the laminated structure is used as a touch panel, the conductive layer non-formation surface (the surface opposite to the surface on which the conductive layer 12 is formed) of one (upper) conductive substrate 100 is pressed with a finger or a pen. When the upper and lower conductive layers 12 come into contact with each other, the input information by the finger or the pen is recognized. That is, since the upper and lower conductive layers 12 are short-circuited at the contact portion, this is processed as an electric signal, and the input content by the finger or the pen is recognized.

  In addition, as described above, the touch panel according to the present invention may be composed of two conductive substrates 100. Further, the surface of the film is glaring or reflected, scratch resistance, fingerprint resistance, and repeated use. In order to improve durability at the time, a surface treatment (hard coat treatment, fingerprint adhesion treatment) may be applied to the surface where the conductive layer is not formed, or a functional layer may be provided. Moreover, in order to ensure the ease of input at the time of use, glass and a polymer resin film can also be laminated | stacked on a conductive layer non-formation surface.

  Since the touch panel according to the present invention uses the conductive substrate 100 which is excellent in transparency and optically isotropic (substantially has no birefringence), it is used as a liquid crystal display panel. In addition, even when used over a display device such as a plasma display panel or a CRT, or when used as a constituent member of an inner touch panel, the contrast is unlikely to decrease, and it has high visibility. Indicates the display quality.

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

  EXAMPLES Hereinafter, although an Example demonstrates this invention more concretely, this invention is not limited to an Example. First, the measurement method for each measurement value will be described below.

(A) Analysis of acrylic resin (a-1) Analysis of structural unit
The first structural unit, the second structural unit, the third structural unit, and the fourth structural unit were identified by ¹ H-NMR measurement and ¹³ C-NMR measurement, and the abundance thereof was calculated. The measurement conditions for ¹ H-NMR measurement and ¹³ C-NMR measurement are as follows.
Measuring instrument: DPX-400 manufactured by Blue Car Co., Ltd.
Measurement solvent: CDCl _3, ^or, d 6-DMSO
Measurement temperature: 40 ° C

(A-2) Measurement of glass transition temperature Tg The glass transition temperature (Tg) was measured using a differential scanning calorimeter (Diamond DSC, manufactured by PerkinElmer Japan Co., Ltd.) under a nitrogen gas atmosphere and α-alumina as a reference. Based on JIS-K-7121, it calculated by the midpoint method from the DSC curve obtained by heating about 10 mg of samples from normal temperature to 200 degreeC with the temperature increase rate of 10 degree-C / min.

(A-3) Measurement of molecular weight The weight average molecular weight and the number average molecular weight were measured using a gel permeation chromatograph (HLC-8220, manufactured by Tosoh Corporation), the solvent was tetrahydrofuran, at a set temperature of 40 ° C, and converted into a standard commercial PMMA. Asked.

(B) Evaluation of optical properties A press film and a stretched film were prepared from the acrylic thermoplastic resin composition by the following method, and the optical properties of the stretched film were evaluated by the following method.

[Production of press film]
Using a vacuum compression molding machine (SFV-30 manufactured by Shindo Metal Industries Co., Ltd.), preheat at 260 ° C under atmospheric pressure for 25 minutes, then under vacuum (about 10 kPa), 260 ° C, about 10 MPa for 5 minutes Compressed to form a press film.

[Production of stretched film]
About the said press film, using a 5t tensile tester manufactured by Instron, a uniaxial free stretching is performed at a stretching temperature (Tg + 20) ° C., a stretching speed (500 mm / min) and a stretching ratio of 100%, and a stretched film is formed. It used for evaluation.

(B-1) Measurement of birefringence Using RETS-100 manufactured by Otsuka Electronics Co., Ltd., measurement was performed by a rotating 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 and used as a measured value. The absolute value (| Δn |) of birefringence (Δn) was determined as follows.
Δn = nx−ny
| Δn | = | nx−ny |
(In the formula, Δn represents birefringence, nx represents the refractive index in the stretching direction, and ny represents the refractive index in the direction perpendicular to the stretching direction in the plane.)

(B-2) Measurement of phase difference Re in in-plane direction Using RETS-100 manufactured by Otsuka Electronics Co., Ltd., measurement was performed in a wavelength range of 400 to 800 nm by a rotating analyzer method. The obtained value was converted to a film thickness of 100 μm to obtain a measured value. The absolute value of birefringence (| Δn |) and the phase difference (Re) have the following relationship. The absolute value (| Δn |) of birefringence is a value shown below.
Re = | Δn | × d
(Where | Δn | is the absolute value of birefringence, Re is the phase difference, and d is the thickness of the sample.)
| Δn | = | nx−ny |
(In the formula, nx represents the refractive index in the stretching direction, and ny represents the refractive index perpendicular to the stretching direction in the plane.)

(B-3) Measurement of thickness direction retardation Rth Using Oji Scientific Instruments Co., Ltd. phase difference measuring device (KOBRA-21ADH), the phase difference at a wavelength of 589 nm was measured, and the obtained value was used as the film thickness. The measured value was converted to 100 μm. The absolute value of birefringence (| Δn |) and the phase difference (Rth) have the following relationship. The absolute value (| Δn |) of birefringence is a value shown below.
Rth = | Δn | × d
(Where | Δn | is the absolute value of birefringence, Rth is the phase difference, and d is the thickness of the sample.)
| Δn | = | (nx + ny) / 2−nz |
(In the formula, nx represents the refractive index in the stretching direction, ny represents the refractive index in the plane perpendicular to the stretching direction, and nz represents the refractive index in the thickness direction out of the plane perpendicular to the stretching direction.)

  In an ideal film that is completely isotropic in the three-dimensional direction, both the in-plane retardation (Re) and the thickness direction retardation (Rth) are zero.

(B-4) Measurement of Photoelastic Coefficient A birefringence measuring apparatus described in detail in Polymer Engineering and Science 1999, 39, 2349-2357 was used. A film tensioning device (manufactured by Imoto Seisakusho) was placed in the laser beam path, and birefringence was measured while applying an extensional stress at 23 ° C. The strain rate during stretching was 50% / min (between chucks: 50 mm, chuck moving speed: 5 mm / min), and the test piece width was 6 mm. 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 a tensile stress between 2.5 MPa ≦ σ _R ≦ 10 MPa was used.
C _R = | Δn | / σ _R
| Δn | = | nx−ny |
(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 represents a vertical refractive index of stretching direction in the plane. )

(Production Example 1: Production of acrylic resin (A-1))
A SUS reactor (capacity 0.5 L) equipped with a stirrer, a temperature sensor, a cooling pipe, a nitrogen gas introduction nozzle, a raw material solution introduction nozzle, an initiator solution introduction nozzle, and a polymerization solution discharge nozzle was used. The pressure in the polymerization reactor was slightly pressurized, and the reaction temperature was controlled at 130 ° C. with an oil bath.

  After mixing 576 g of methyl methacrylate, 61 g of N-phenylmaleimide, 83 g of N-cyclohexylmaleimide, and 480 g of methyl isobutyl ketone, a raw material solution was prepared by replacing with nitrogen gas. Further, 8.63 g of Perhexa C (manufactured by NOF Corporation; concentration 75 wt%) was dissolved in 91.37 g of methyl isobutyl ketone, and then substituted with nitrogen gas to prepare an initiator solution.

  The raw material solution was introduced from the raw material solution introduction nozzle at 8.25 ml / min using a pump. The initiator solution was introduced from the initiator solution introduction nozzle at 0.08 ml / min using a pump. After 30 minutes, the polymer solution was discharged from the polymerization solution discharge nozzle at a constant flow rate of 500 ml / hr using a pump. The polymer solution was collected separately in the initial flow tank for 1.5 hours after discharge. The polymer solution was collected for 2.5 hours after 1.5 hours from the start of discharge. The obtained polymer solution and methanol as an extraction solvent were simultaneously supplied to a homogenizer and subjected to emulsion dispersion extraction. The separated and precipitated polymer was collected and dried under vacuum at 130 ° C. for 2 hours to obtain the desired acrylic resin (A-1).

About the obtained acrylic resin (A-1), the analysis of a structural unit, the measurement of glass transition temperature, and the measurement of molecular weight were performed by said method. The results were as follows. Hereinafter, in some cases, the structural unit derived from methyl methacrylate is represented by “MMA”, the structural unit derived from N-phenylmaleimide is represented by “N-PheMI”, and the structural unit derived from N-cyclohexylmaleimide is represented by “N-CyMI”. ".
Structural unit: MMA / N-PheMI / N-CyMI = 81/8/11 (mass%), N-PheMI / N-CyMI (molar ratio) = 0.75
Molecular weight: Mw = 22.5 × 10 ⁴ , Mw / Mn = 2.09
Tg: 135 ° C

(Production Example 2: Production of acrylic resin (A-2))
A glass reactor (capacity 1.0 L) equipped with a stirrer, a temperature sensor, a cooling pipe, a nitrogen gas introduction nozzle, a raw material solution introduction nozzle, and an initiator solution introduction nozzle was used. The pressure in the polymerization reactor was slightly pressurized, and the reaction temperature was controlled at 100 ° C. with an oil bath.

  After mixing 140 g of methyl methacrylate, 14 g of N-phenylmaleimide, 34 g of N-cyclohexylmaleimide, 12 g of styrene and 200 g of methyl isobutyl ketone, a raw material solution was prepared by substituting with nitrogen gas. Further, after dissolving 0.32 g of Perhexa C (manufactured by NOF Corporation; concentration 75 wt%) in 1.00 g of methyl isobutyl ketone, the initiator solution was prepared by replacing with nitrogen gas.

  The raw material solution was introduced from the raw material solution introduction nozzle into the glass reactor by pressure feeding. The initiator solution was introduced from the initiator solution introduction nozzle with a syringe to start the polymerization reaction. After 3 hours from the start of the reaction, the reaction was terminated, and the polymer solution was recovered. The obtained polymer solution and methanol as a poor solvent were simultaneously supplied to a homogenizer, and emulsified, dispersed and extracted. The separated and precipitated polymer was collected and dried under vacuum at 130 ° C. for 2 hours to obtain the desired acrylic resin (A-2).

About the obtained acrylic resin (A-2), the analysis of a structural unit, the measurement of glass transition temperature, and the measurement of molecular weight were performed by said method. The results were as follows. Hereinafter, in some cases, a structural unit derived from styrene is represented as “St”.
Structural unit: MMA / N-PheMI / N-CyMI / St = 70/5/20/5 (mass%), N-PheMI / N-CyMI (molar ratio) = 0.26
Molecular weight: Mw = 15.6 × 10 ⁴ , Mw / Mn = 2.01
Tg: 141 ° C

(Reference Example 1)
Using the acrylic resin (A-1) obtained in Production Example 1, a press film was produced according to the method described above. In addition, a 100% stretched film was produced from the press film according to the above-described method to obtain a stretched transparent film (A-1).

  About the obtained extending | stretching transparent film (A-1), the optical characteristic was evaluated by the above-mentioned method. The evaluation results are as shown in Table 1.

(Reference Example 2)
Using the acrylic resin (A-2) obtained in Production Example 2, a press film was produced according to the method described above. In addition, a 100% stretched film was produced from the press film according to the above-described method to obtain a stretched transparent film (A-2).

  About the obtained stretched transparent film (A-2), the optical characteristic was evaluated by the above-mentioned method. The evaluation results are as shown in Table 1. In the table, “> 85” indicates that it is greater than 85.

  As shown in Table 1, it was confirmed that the transparent film obtained from the acrylic resin of each production example had extremely small absolute values of retardation and photoelastic coefficient, which are optical characteristics. In particular, it can be seen that the transparent film of Reference Example 1 has high optical isotropy, so-called zero-zero birefringence, which cannot be achieved by existing resins, even though the transparent film is stretched. Moreover, it is confirmed that it has excellent heat resistance. This feature does not cause (orientation) birefringence due to the orientation of polymer chains due to the flow during melt molding during molding or stretching, and (photoelastic) birefringence due to residual stress or external force during molding Is extremely advantageous for industrial application in that

(Example 1)
An ITO layer was formed on the stretched transparent film (A-1) obtained in Reference Example 1 using a sputtering apparatus (opposite target type sputtering apparatus, manufactured by Osaka Vacuum Equipment Co., Ltd.). For the sputtering, an indium oxide-tin oxide target containing 10% by mass of tin oxide was used, and the vacuum was 0.5 Pa and an argon gas atmosphere containing 5% by volume of oxygen was added at a rate of 0.4 liter / sec. Sputtering was performed for 20 minutes to obtain a transparent conductive substrate (A-1) having an ITO transparent conductive layer (thickness 50 nm).

(Example 2)
The ITO layer (thickness 50 nm) was used in the same manner and conditions as in Example 1 except that the stretched transparent film (A-2) obtained in Reference Example 2 was used instead of the stretched transparent film (A-1). The transparent conductive substrate (A-2) was obtained.

(Comparative Example 1)
A cyclic olefin resin (COP) film (manufactured by Nippon Zeon Co., Ltd.) is molded into a stretched transparent film (B-1) stretched 100% according to the method described above, and the stretched transparent film is subjected to the same method and conditions as in Example 1. An ITO layer (thickness 50 nm) was formed on the film (B-1) to obtain a transparent conductive substrate (B-1).

(Comparative Examples 2 and 3)
A PC film (manufactured by Teijin Ltd.) and a PET film (manufactured by Toray Industries, Inc.) were used, respectively, and an ITO layer (thickness 50 nm) was formed on each film in the same manner and conditions as in Example 1. A transparent conductive substrate (B-2) and a transparent conductive substrate (B-3) were obtained.

  The physical properties of the transparent conductive substrates obtained in Examples and Comparative Examples are as shown in Table 2. In the table, “<1” indicates less than 1.

  From Table 2, the transparent conductive substrate of an Example has a small photoelastic coefficient and a phase difference compared with the transparent conductive substrate of a comparative example. In particular, the transparent conductive substrate (A-1) of Example 1 has high optical isotropy, which should be zero-zero characteristics. The total light transmittance is also sufficient for use in applications that require transparency. Therefore, the transparent conductive substrate of the present invention is suitable for a touch panel used in combination with various display elements.

  The conductive substrate of the present invention uses, as a base material (resin layer), a molded body made of a specific acrylic resin having excellent heat resistance and various optical properties (transparency, optical isotropy, low birefringence). Therefore, excellent optical characteristics (transparency, optical isotropy, low birefringence) are maintained even after formation of a conductive layer made of a metal oxide such as an ITO layer, so that display elements such as liquid crystal displays and plasma displays It is suitable as a touch panel used in combination.

  DESCRIPTION OF SYMBOLS 10 ... Resin layer, 12 ... Conductive layer, 100 ... Conductive substrate.

Claims (9)

An acrylic resin 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): A conductive substrate comprising: a resin layer containing; and a conductive layer provided on one surface of the resin layer ,
The acrylic resin is
The content of the first structural unit is 50 to 95% by mass based on the total amount of the acrylic resin,
The content of the second structural unit is 0.1 to 20% by mass based on the total amount of the acrylic resin,
The content of the third structural unit is 0.1 to 49.9% by mass based on the total amount of the acrylic resin,
The molar ratio C ₂ / C ₃ of the content C _{2 of the second} structural unit and the content C ₃ of the third structural unit is 0.26 or more and 15 or less,
The total content of the first structural unit, the second structural unit, and the third structural unit is 80% by mass or more based on the total amount of the acrylic resin,
The absolute value of the photoelastic coefficient is 3.0 × 10 ⁻¹² Pa ⁻¹ or less,
The absolute value of the phase difference Re in the in-plane direction when film-forming is 30 nm or less in terms of 100 μm thickness, and
A conductive substrate having a halogen atom content of less than 0.47% by mass based on the total amount of the acrylic resin.

[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 conductive substrate according to claim 1 , wherein the acrylic resin is a resin having an absolute value of a thickness direction retardation Rth of 30 nm or less in terms of a thickness of 100 μm when a film is formed. The electroconductive board | substrate of Claim 1 or 2 whose glass transition temperature Tg of the said acrylic resin is 120 degreeC or more. The acrylic resin has a total light transmittance in the case of film molding, a resin comprising 85% or more at 100μm thick terms, a conductive substrate according to any one of claims 1-3. Wherein the conductive layer of indium - containing tin oxide, a conductive substrate according to any one of claims 1-4. 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;
Wherein R ⁵ is a cyclohexyl group, a conductive substrate according to any one of claims 1-5. The acrylic resin has a polymethyl methacrylate equivalent weight average molecular weight Mw measured by GPC measurement method of 3000 to 1000000, and a ratio Mw / Mn of weight average molecular weight Mw to number average molecular weight Mn is 1 to 10. The electroconductive board | substrate as described in any one of Claims 1-6 . The resin layer is a resin sheet containing the acrylic resin, a layer made of at least formed by stretching uniaxially a film-like or sheet-like shaped body, according to any one of claims 1-7 Conductive substrate. A touch panel provided with the electroconductive board | substrate as described in any one of Claims 1-8 .

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