JP2017078840A - Protective film, film laminate and polarizing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a protective film having a low retardation value in a film plane direction and in a thickness direction and having a high tensile elastic modulus and tensile strength.SOLUTION: The protective film relating to the present invention is formed of: an urethane (meth)acrylate I that is a reaction product of a hydroxyl group-containing alkyl (meth)acrylate and diol and diisocyanate or an urethane (meth)acrylate II that is a reaction product of an isocyanate group-containing alkyl (meth)acrylate and diol and diisocyanate; a (meth)acrylate group-containing raw material having a (meth)acryl equivalent of 90 g/eq or more and 500 g/eq or less; and a thioether structure. The urethane (meth)acrylate I and II have a plurality of types of saturated cyclic aliphatic structures. The protective film has a low retardation value in a plane direction and in a thickness direction.SELECTED DRAWING: None

Description

  The present invention relates to a protective film, a film laminate, and a polarizing plate using an energy beam curable composition.

  In recent years, displays such as liquid crystal and organic EL used in TVs and mobile devices are becoming thinner and thinner, and technological development is progressing with the aim of making the components used in these displays, especially polarizing plates, extremely thin. ing. In general, a polarizing plate is adhered to both sides of a polarizing film made of a polyvinyl alcohol film uniaxially stretched by adsorbing iodine with an adhesive such as an optical film such as triacetyl cellulose (hereinafter referred to as TAC) as a protective film. It has a combined configuration.

  The protective film used for such a polarizing plate has different functions depending on its application. For example, in the case of a liquid crystal display, the polarizing film to be bonded to both surfaces of the liquid crystal cell is different from the liquid crystal cell. As a protective film (so-called retardation film) installed between the films, a film in which the retardation value is controlled three-dimensionally is used in order to obtain good contrast and a wide viewing angle.

  These polarizing plates have an environment in which stress relaxation and moisture absorption and dehumidification occur due to residual stress due to uniaxial stretching of the polarizing film and high hydrophilicity due to the constituent materials (for example, at high temperature, high temperature and high humidity, low temperature, high temperature) Protective films are also required to have a function to suppress this dimensional change when exposed to a low-temperature cycle, etc.). Especially in retardation films, the cohesive force between molecules is increased by molecular orientation. By increasing the tensile modulus and tensile strength of the film, it helps to suppress the dimensional change of the polarizing film.

  Here, although the material and manufacturing method of the retardation film differ depending on the driving mode of the liquid crystal cell to be used, in general, a film made of a thermoplastic resin or a refractive index anisotropic material is stretched, irradiated with ultraviolet rays, It can be obtained by performing molecular orientation treatment by external stimulation such as heating or magnetic field application.

  On the other hand, in a liquid crystal display with a liquid crystal cell driving mode of IPS or FFS, a wide viewing angle can be obtained in terms of driving principle, so it is not necessary to use a retardation film. In this case, a portion corresponding to the retardation film For the film, a film having a low retardation value in the in-plane direction and thickness direction of the film (so-called low retardation film) can be used.

  The low retardation film is generally obtained by forming a film without stretching a thermoplastic resin or the like, but since these are not stretched, the cohesive force due to the molecular orientation as described above cannot be obtained. The dimensional change of the polarizing film cannot be sufficiently suppressed.

  On the other hand, an acrylic resin is cited as a resin having a high cohesive force, and Patent Document 1 proposes forming an acrylic resin into a film without performing a molecular orientation treatment.

JP 2011-242581 A

  However, in the above method, although a film having a low retardation value can be obtained, since the tensile elastic modulus is excessively high, the film is brittle and easily damaged. The film is given flexibility by adding rubber elastic particles in order to modify this brittle property, and as a result, the tensile elastic modulus of the resulting acrylic resin film eventually becomes low. End up. Polarizing plates with such low tensile modulus films can be polarized by exposing them to environments where stress relaxation and moisture absorption / dehumidification occur (for example, under high temperature, high temperature and high humidity, low temperature, and high temperature / low temperature cycle). There was a problem that the film was greatly changed in dimensions.

  In view of the above problems, an object of the present invention is to provide a protective film having a low retardation value in the film in-plane direction and a thickness direction and a high tensile elastic modulus and high tensile strength without performing molecular orientation treatment. It is in.

  As a result of intensive studies on the above problems, the inventors of the present invention applied a specific energy ray-curable composition to a base film and cured the protective film in an in-plane direction and a thickness direction. The inventors have found that the phase difference value of is low, and has a high tensile elastic modulus and tensile strength without the need for molecular orientation treatment, thereby completing the present invention.

The present invention includes the following forms.
A block A consisting of repeating units I or II having a structure derived from urethane (meth) acrylate I or II as a monomer, and a block B consisting of repeating units having a structure derived from a (meth) acrylate group-containing raw material as a monomer, A protective film formed by a thioether structure,
The urethane (meth) acrylate I is a reaction product of a hydroxyl group-containing alkyl (meth) acrylate, a diol and a diisocyanate,
The urethane (meth) acrylate II is a reaction product of an isocyanate group-containing alkyl (meth) acrylate, a diol, and a diisocyanate,
The urethane (meth) acrylates I and II have a plurality of types of saturated cycloaliphatic structures,
The (meth) acrylate group-containing raw material has a (meth) acryl equivalent of 90 g / eq or more and 500 g / eq or less,
The thioether structure is present in the polymer chain composed of block A and block B, at least in the polymer chain, or via the thioether bond with the end of the polymer chain,
The in-plane retardation value (Re) at 23 ° C. at a wavelength of 590 nm is 0 nm to 10 nm, and the thickness direction retardation value (Rth) at 590 nm at 23 ° C. is from −10 nm to 10 nm. A protective film.
On at least one side of the protective film,
(1) A film substrate that supports the protective film,
(2) a hard coat layer having scratch resistance;
(3) an antiglare layer that scatters light, and
(4) A film comprising any one of an antireflection layer composed of a high refractive index layer provided on the protective film and a low refractive index layer provided on the high refractive index layer. Laminated body.
A polarizing plate comprising the protective film on at least one surface of a polarizing film.

  The protective film according to the present invention has a low retardation value in the in-plane direction and the thickness direction, and has a high tensile elastic modulus and tensile strength without performing a molecular orientation treatment. Even in an environment where stress relaxation or moisture absorption / dehumidification occurs in the film (for example, under high temperature, high temperature and high humidity, low temperature, or high temperature / low temperature cycle), the dimensional change of the polarizing film is suppressed.

  Hereinafter, although the protective film, film laminated body, polarizing plate, and these manufacturing methods concerning this invention are demonstrated, this invention is limited to these description and is not interpreted.

"Protective film"
The protective film according to the present invention includes a block A composed of a repeating unit having a structure derived from a urethane (meth) acrylate I or II which is a monomer, and a repeating unit having a structure derived from a (meth) acrylate group-containing raw material which is a monomer. A block B and a copolymer formed by a thioether structure, wherein the repeating unit of the block A has a plurality of types of saturated cycloaliphatic structures, and the repeating unit of the block B has a (meth) acrylic equivalent Is a raw material containing a (meth) acrylate group of 90 g / eq or more and 500 g / eq or less, and the thioether bond is at least in the polymer chain of the block A and the block B or at the end of the polymer chain And is present through a thioether bond.
That is, in the protective film, the matrix forming the copolymer has a block A composed of repeating units having a structure derived from urethane (meth) acrylate I or II, and a (meth) acrylic equivalent of 90 g / eq or more and 500 g / eq. The block B is composed of the following (meth) acrylate group-containing raw material monomer units and a thioether structure. In addition, the monomer may be a structural isomer thereof or a mixture of the monomer and the structural isomer.

[Block A]
The structure derived from urethane (meth) acrylate I or II according to block A is a urethane (meth) acrylate I or II monomer unit, that is, (meth) acrylate in urethane (meth) acrylate I or II as a monomer This means a structure in which the double bond of the group is cleaved, and it has bifunctionality because it mainly has a site where the double bond of the (meth) acrylate group is cleaved at both ends.

  The repeating unit of the block A has a urethane bond (—NH—CO—O—). The number of the urethane bonds is not particularly limited, and is 1 to 8, for example. The urethane bond is a polar group, and the urethane bonds in each repeating unit are close to each other by intermolecular force. On the other hand, the saturated cycloaliphatic structure is a non-polar cyclic structure and thus has a high molecular weight and is a hard skeleton from the viewpoint of the molecular structure compared to the saturated aliphatic chain. It is considered that the intermolecular force generates a high cohesive force by the contribution of the high molecular weight and hardness of the saturated cycloaliphatic structure in the intermolecular interaction between the urethane bonds. As a result, the protective film constituted by the above repeating unit has a high tensile elastic modulus and tensile strength even without stretching.

  The urethane (meth) acrylate I and II monomer units have a plurality of types of saturated cycloaliphatic structures. Although it does not specifically limit as a saturated cycloaliphatic structure, From a viewpoint of raising the cohesion force resulting from molecular weight, it is preferable that it is a saturated cycloaliphatic structure more than 5 membered ring. Although the upper limit of the number of member rings is not particularly limited, it is, for example, 15-membered ring or less, preferably 10-membered ring or less, from the viewpoint of easy synthesis of a monomer that is a raw material for the protective film. When the saturated cyclic aliphatic structure has a plurality of cyclic structures, the number of member rings represents the maximum number of member rings of the cyclic structure, and the saturated cyclic aliphatic structure has a bicyclo ring or a tricyclo ring. This means the number of ring members in the ring structure excluding the bridge carbon connecting the bridgehead carbon. For example, in the case of a tricyclodecane ring, the number of member rings is nine.

  The main chain of the cyclic structure of the saturated cycloaliphatic structure may be formed only by carbon atoms, or may be formed by oxygen atoms and / or nitrogen atoms in addition to carbon atoms. In addition, a linear and / or branched chain structure having 1 to 10 carbon atoms may be added to the carbon atom of the cyclic structure.

Examples of the saturated cycloaliphatic structure include 3,5,5-trimethylcyclohexane ring, tricyclodecane ring, adamantane ring, norbornene ring and the like. The saturated cycloaliphatic structure may be bonded to a urethane bonding group via a saturated aliphatic chain, and the rigidity of the repeating unit can be suitably adjusted by changing the carbon number of the saturated aliphatic chain. The saturated aliphatic chain includes a straight chain structure and a branched chain structure, and an example of the straight chain structure includes — (CH ₂ ) _n — (n is an integer of 1 to 10), From the viewpoint of reducing flexibility and increasing rigidity, in particular, —CH ₂ — or — (CH ₂ ) ₂ — is preferable. On the other hand, examples of the branched chain structure include a structure in which hydrogen on at least one carbon of the linear structure is substituted with a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, or the like.

  When the 3,5,5-trimethylcyclohexane ring described above is bonded to two urethane bonds via a methylene chain, the 3-methylene-3,5,5-trimethylcyclohexane ring is bonded to each urethane bond. Thus, when the tricyclodecane ring is bonded to two urethane bonds via a methylene chain, the dimethylene tricyclodecane ring is bonded to each urethane bond.

  The 3-methylene-3,5,5-trimethylcyclohexane ring and the dimethylenetricyclodecane ring are preferred ring structures, and in a protective film containing the ring structure in a polymer chain, a high tensile elastic modulus without stretching. And tensile strength is suitably expressed.

  The main chain of the repeating unit preferably contains a saturated aliphatic chain having 5 to 10 carbon atoms in addition to the saturated cycloaliphatic structure. When the saturated aliphatic chain has 5 or more carbon atoms, flexibility is imparted to the repeating unit by the saturated aliphatic chain having a long chain length and flexibility, and the brittleness of the protective film is reduced. On the other hand, when the number of carbon atoms is 10 or less, it is possible to suppress a decrease in tensile elastic modulus due to excessive flexibility. The saturated aliphatic chain may have a straight chain structure or a branched chain structure. The saturated aliphatic chain constitutes a part of the repeating unit, for example, in a structure via a urethane bond or an ester bond.

Examples of the straight chain _{structure, - (CH 2) n1 -} (n1 is an integer of 5-10) include, in particular, - _{(CH 2) 5} - is preferably. On the other hand, examples of the branched chain structure include a structure in which hydrogen on at least one carbon of the linear structure is substituted with a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, or the like.

As an example of the above repeating unit, the following structure A including the saturated cycloaliphatic structure R ¹ and the structure including the following structure C including the saturated cycloaliphatic structure R ³ can be exemplified.
—CO—NH—R ¹ —NH—CO— (Structure A)
—O—R ³ —O— (Structure C)
As the repeating unit, for example, (1) a diisocyanate containing R ¹ , (2) a diol containing R ³ , and (3) a hydroxyl group-containing alkyl (meth) acrylate, or an isocyanate group-containing alkyl (meth) acrylate is used. It can be obtained from urethane (meth) acrylate obtained in this way and can be easily manufactured. As an example, the ratio of the structure A and the structure C can be m + 1: m or m: m + 1, and the m represents an integer of 1 to 4.

Further, the repeating units may further comprise the following structure B comprising the following saturated aliphatic chain R ^2.
—O—R ² —CO— (Structure B)
The repeating unit includes, for example, a diisocyanate containing R ¹ , an ester containing R ² (optionally used), a diol containing R ³ , a hydroxyl group-containing alkyl (meth) acrylate, or an isocyanate group-containing alkyl ( It can be obtained from urethane (meth) acrylate obtained by using (meth) acrylate, and can be easily produced. As an example, the ratio of the structure A, the structure B, and the structure C may be m + 1: m (r + s): m, m: m (r + s): m + 1, and m: k + n: m + 1. M represents an integer of 1 to 4, r and s each represent an integer of 0 to 2, and the sum of r and s is 1 to 2, k represents an integer of 0 to 2, n Represents an integer of 0-2.

（一般式（１）中、Ｒ^１は飽和環状脂肪族構造を示し、Ｒ^２は炭素数５〜１０の直鎖または分岐鎖状の飽和脂肪族鎖を示し、Ｒ^３は、Ｒ^１と異なる飽和環状脂肪族構造を示し、Ｒ^４は水素原子またはメチル基を示し、Ｒ^５は、水素原子、メチル基またはエチル基を示し、ｍは１〜４の整数を示し、ｒおよびｓはそれぞれ０〜２の整数を示し、かつ、ｒとｓとの和は１〜２であり、ｘは０〜３の整数を示す） Specific examples of the repeating unit having the saturated cycloaliphatic structure and the saturated aliphatic chain described above are shown below. As shown in the general formula (1), the structure derived from (meth) acrylate is a (meth) acrylate structure H ₂ C═CH—CO ₂ — (or H ₂ C═C (CH ₃ ) —CO ₂ —. ) Of the carbon-carbon double bond is cleaved to form a single bond.

(In the general formula (1), R ¹ represents a saturated cycloaliphatic structure, R ² represents a linear or branched saturated aliphatic chain having 5 to 10 carbon atoms, and R ³ is different from R ^1. R ⁴ represents a hydrogen atom or a methyl group, R ⁵ represents a hydrogen atom, a methyl group or an ethyl group, m represents an integer of 1 to 4, and r and s are each 0. ) Represents an integer of ˜2, and the sum of r and s is 1 to 2, and x represents an integer of 0 to 3)

  When m in the said General formula (1) is an integer of 1-4, a tensile elasticity modulus is raised more. m is more preferably 1 or 2, and even more preferably 1. The same applies to general formulas (2) and (3) described later.

In the general formula (1), R ¹ is a 3-methylene-3,5,5-trimethylcyclohexane ring, R ² is — (CH ₂ ) ₅ —, and R ³ is a dimethylene tricyclodecane ring. A preferred structure in which R ⁴ and R ⁵ are hydrogen atoms, r and s are 1 and x is 1 is shown below.

（一般式（２）中、Ｒ^１は飽和環状脂肪族構造を示し、Ｒ^２は炭素数５〜１０の直鎖または分岐鎖状の飽和脂肪族鎖を示し、Ｒ^３は、Ｒ^１と異なる飽和環状脂肪族構造を示し、Ｒ^４は水素原子またはメチル基を示し、Ｒ^５は、水素原子、メチル基またはエチル基を示し、ｍは１〜４の整数を示し、ｒおよびｓはそれぞれ０〜２の整数を示し、かつ、ｒとｓとの和は１〜２であり、ｘは０〜３の整数を示す） Other specific examples of the repeating unit are shown below.

(In General Formula (2), R ¹ represents a saturated cycloaliphatic structure, R ² represents a linear or branched saturated aliphatic chain having 5 to 10 carbon atoms, and R ³ is different from R ^1. R ⁴ represents a hydrogen atom or a methyl group, R ⁵ represents a hydrogen atom, a methyl group or an ethyl group, m represents an integer of 1 to 4, and r and s are each 0. ) Represents an integer of ˜2, and the sum of r and s is 1 to 2, and x represents an integer of 0 to 3)

In the general formula (2), R ¹ is a 3-methylene-3,5,5-trimethylcyclohexane ring, R ² is — (CH ₂ ) ₅ —, and R ³ is a dimethylene tricyclodecane ring. Preferred repeating units in which R ⁴ and R ⁵ are hydrogen atoms, r and s are 1 and x is 1 are shown below.

（一般式（３）中、Ｒ^１は飽和環状脂肪族構造を示し、Ｒ^２は炭素数５〜１０の直鎖または分岐鎖状の飽和脂肪族鎖を示し、Ｒ^３は、Ｒ^１と異なる飽和環状脂肪族構造を示し、Ｒ^４は水素原子またはメチル基を示し、Ｒ^５は、水素原子、メチル基またはエチル基を示し、ｍは１〜４の整数を示し、ｋは０〜２の整数を示し、ｎは０〜２の整数を示し、ｘは０〜３の整数を示す） Other specific examples of the repeating unit are shown below.

(In General Formula (3), R ¹ represents a saturated cycloaliphatic structure, R ² represents a linear or branched saturated aliphatic chain having 5 to 10 carbon atoms, and R ³ is different from R ^1. R ⁴ represents a hydrogen atom or a methyl group, R ⁵ represents a hydrogen atom, a methyl group or an ethyl group, m represents an integer of 1 to 4, and k represents an integer of 0 to 2. Represents an integer, n represents an integer of 0 to 2, and x represents an integer of 0 to 3)

In the general formula (3), R ¹ is a 3-methylene-3,5,5-trimethylcyclohexane ring, R ² is — (CH ₂ ) ₅ —, and R ³ is a dimethylene tricyclodecane ring. Preferred repeating units in which R ⁴ and R ⁵ are hydrogen atoms, k and n are 1, and x is 1 are shown below.

[Block B]
The structure derived from the (meth) acrylate group-containing raw material according to Block B is a (meth) acrylate group-containing raw material monomer unit, that is, 2 of the (meth) acrylate group in the (meth) acrylate group-containing raw material that is a monomer. It means a structure in which a double bond is cleaved.

  The (meth) acrylate group-containing raw material for producing the block B preferably has a (meth) acrylic equivalent of 90 g / eq or more and 500 g / eq or less, and 90 g / eq or more and 400 g in order to keep the tensile modulus of the protective film at a high level. / Eq or less is more preferable, and 90 g / eq or more and 300 g / eq or less is particularly preferable. When the (meth) acrylic equivalent is greater than 500 g / eq, the three-dimensional cross-linked structure formed by cleavage of the (meth) acrylate group is reduced, and as a result, the tensile modulus of the protective film made of the copolymer and The tensile strength will decrease.

  The (meth) acrylate group-containing raw material is not particularly limited as long as the (meth) acrylic equivalent is in the range of 90 g / eq or more and 500 g / eq or less, and includes a plurality of types of (meth) acrylate group-containing raw materials. May be. At this time, the (meth) acryl equivalent of the (meth) acrylate group-containing raw material is calculated as a value obtained by averaging the (meth) acryl equivalent of a plurality of types of (meth) acrylate group-containing raw materials by a mass ratio (for example, When (meth) acrylic equivalent 200 g / eq is 70% by mass and (meth) acrylic equivalent 400 g / eq is 30% by mass, (meth) acrylic equivalent is 260 g / eq).

  Here, the (meth) acrylic equivalent is a value obtained by dividing the molecular weight in the theoretical structure of the (meth) acrylate group-containing raw material by the number of (meth) acrylic functional groups, and when the value is large, the (meth) acrylic functionality contained in the monomer Since the group ratio decreases, the three-dimensional cross-linking structure formed by cleavage of the (meth) acrylate group decreases.

An example of the said (meth) acrylate group containing raw material is shown. In addition, if a (meth) acryl equivalent is in the range of 90 g / eq or more and 500 g / eq or less, the structure is not limited to the following.
Monofunctional (meth) acrylate group-containing raw materials include: alkyl (meth) acrylates such as methyl methacrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate,
Cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, 3,3,5-trimethylcyclohexyl (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyl (meth) acrylate, benzyl (meth) acrylate, etc. Saturated / unsaturated cyclic (meth) acrylate,
Hydroxyl group content such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, polycaprolactone-modified hydroxyethyl (meth) acrylate, pentaerythritol mono (meth) acrylate, etc. Examples include (meth) acrylate.
The bifunctional (meth) acrylate group-containing raw materials include 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, 1 , 10-decanediol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, pentaerythritol di (meth) acrylate, tricyclodecane dimethanol di (meth) acrylate, bisphenol A type di Polyester composed of (meth) acrylate, bisphenol F type di (meth) acrylate, polybutadiene di (meth) acrylate, hydrogenated polybutadiene di (meth) acrylate, isocyanuric acid di (meth) acrylate, diol and dicarboxylic acid Di (meth) acrylate, polyurethane di (meth) acrylate comprising a diol and a diisocyanate.
Polyfunctional (meth) acrylate group-containing raw materials include pentaerythritol tri (meth) acrylate, ethoxy-modified pentaerythritol tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, ditrimethylol Propane tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, isocyanuric acid tri (meth) acrylate, polyester (meth) acrylate composed of polyol and polycarboxylic acid, polyurethane (meth) acrylate composed of polyol and polyisocyanate, dendrimer Examples include (meth) acrylate having a structure and acrylic oligomer having (meth) acrylate in a side chain.

[Thioether structure]
The thioether structure has a thioether bond and has at least a —S—R structure (R is a hydrocarbon). The single bond on the opposite side of R of the thioether structure is bonded to the structure derived from the (meth) acrylate of the repeating unit, and a hydrogen bond is generated between the —S— of the thioether bond and the urethane bond in the repeating unit. The tensile strength of the protective film can be increased.

  The thioether structure may have at least one or more thioether bonds (-S-). However, the inclusion of a plurality of thioether bonds is preferable because strong hydrogen bonds are generated and the tensile strength of the protective film is further increased. .

The hydrocarbon R having a thioether structure has a cyclic structure and / or a chain structure. The main chain of the cyclic structure and the chain structure may be formed of only carbon atoms, or may be formed of oxygen atoms and / or nitrogen atoms in addition to carbon atoms. Examples of the cyclic structure include a 1,2,3-triazine ring, a 1,2,4-triazine ring, a 1,3,5-triazine ring, a maleimide ring, and the like. As the chain structure, — (CH ₂ ) _n2 - (n2 alkyl chain is exemplified represented by is an integer of 1 to 10). The hydrogen atom bonded to the carbon atom and / or the nitrogen atom constituting the main chain of the cyclic structure and the chain structure may be substituted with a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, or the like.

  Further, the thioether structure may have a substituent, and examples thereof include a carbonyl group, a carboxyl group, an amino group, an amide group, and a hydroxyl group.

The thioether structure is bonded to (1) a polymer chain constituted by a plurality of repeating units, or (2) to an end of the polymer chain.
In the case of (1), the thioether structure has a plurality of thioether bonds, one thioether bond is bonded to the structure derived from the (meth) acrylate of the repeating unit, and the other thioether bond is bonded to the other repeating unit. Bonded to (meth) acrylate-derived structure. The bonding state of (1) when the repeating unit has a site derived from (meth) acrylate is shown below. In addition, when a thioether structure has 3 or 4 or more -S-, it couple | bonds with a some repeating unit.

上記Ｒは炭化水素を示す。 On the other hand, in the case of (2) above, a thioether structure is bonded to the end of the polymer chain, and the thioether structure is bonded to one repeating unit. The bonding state of (2) when the repeating unit has a site derived from (meth) acrylate is shown below.

R represents a hydrocarbon.

[Relationship between Block A, B and Thiol]
As described above for the bonding state between the repeating unit and the thioether structure, when the polymer chain is formed of the block A and the block B that are repeating units,
(1 ′) The thioether structure may be bonded to block A and block B, may be bonded to block A and another block A, or may be bonded to block B and another block B. You may do it.
The (2 ′) thioether structure is bonded to the block A and may not be bonded to the other block A or the block B, or is bonded to the block B, and the block A or the other block B is bonded. It does not have to be joined.

（一般式（４）中、Ｒ^６は、水素原子がメチル基によって置換されていてもよい炭素数１または２のアルキル鎖を示し、Ｘはそれぞれ独立して−Ｓ−または−Ｓ−Ｈを示し、ｎは１〜４の整数を示す） A thioether structure having one or more thioether bonds has been described above. Specific examples of such a thioether structure having both a cyclic structure and a chain structure are shown below.

(In the general formula (4), R ⁶ represents an alkyl chain having 1 or 2 carbon atoms in which a hydrogen atom may be substituted by a methyl group, and each X independently represents —S— or —S—H. N represents an integer of 1 to 4)

In the general formula (4), specific examples of R ⁶ include —CH ₂ — and — (CH ₂ ) ₂ —, and the hydrogen atom of the alkyl chain includes a methyl group, an ethyl group, a propyl group, and the like. It may be substituted with a substituent.

X is —S— or —S—H, and the structure in which two X are —S— is represented by the following general formula (4a), and one X is —S— and the other X is — The structure which is S—H is represented by the following general formula (4b), and the structure in which two X are —S—H is represented by the following general formula (4c). -S- of the thioether structure is bonded to a structure derived from (meth) acrylate as a repeating unit.

（一般式（５）中、Ｒ^７は、水素原子がアルキル基によって置換されていてもよい炭素数１または２のアルキル鎖を示し、Ｘはそれぞれ独立して−Ｓ−または−Ｓ−Ｈを示し、Ｒ^８は水素原子またはメチル基を示し、ｐは１〜３の整数を示す） Furthermore, specific examples of the thioether structure having a chain structure are shown below.

(In the general formula (5), R ⁷ represents an alkyl chain having 1 or 2 carbon atoms in which a hydrogen atom may be substituted with an alkyl group, and each X independently represents —S— or —S—H. R ⁸ represents a hydrogen atom or a methyl group, and p represents an integer of 1 to 3)

In the general formula (5), specific examples of R ⁷ include —CH ₂ — and — (CH ₂ ) ₂ — alkyl chains, and the hydrogen atom of the alkyl chain includes a methyl group, an ethyl group, and a propyl group. It may be substituted with a substituent such as a group.

In the general formula (5), among the structures in which p is 3, the structure in which three Xs are -S- is represented by the following general formula (5a), the two Xs are -S-, A structure in which one X is —S—H is represented by the following general formula (5b). A structure in which one X is —S— and the other two X are —S—H is A structure represented by the formula (5c) and having three Xs —S—H is represented by the following general formula (5d). -S- of the thioether structure is bonded to a structure derived from (meth) acrylate as a repeating unit.

  In particular, since the thioether structure represented by the general formula (5d) is tetrafunctional and forms a complicated three-dimensional structure with the repeating unit, the resulting protective film can have higher tensile strength.

  The mass ratio between the total amount of monomers that are the repeating units of the block A and the block B and the thiol that generates the thioether structure is not particularly limited, but the tensile elastic modulus and tensile strength of the protective film resulting from the thioether structure Is preferably a total monomer amount of block A and block B: thiol = 95: 5 to 50:50, more preferably 95: 5 to 70:30, and particularly preferably 90:10 to 80:20. .

  Further, it is desirable that the ratio of the copolymer (block A and block B which are repeating units and the thioether structure) in the protective film according to the present invention is high from the viewpoint of increasing the tensile elastic modulus and tensile strength of the protective film. It is preferable that it is 70 to 99.5 mass% with respect to the total mass of a film, and it is more preferable that it is 80 to 99.5 mass%.

  It is determined by analyzing the protective film by pyrolysis GC-MS and FT-IR what structure the repeating film (block A and block B and thioether structure) is formed in according to the present invention. Is possible. In particular, pyrolysis GC-MS is useful because it can detect a monomer unit contained in a protective film as a monomer component.

  The protective film contains various additives such as UV absorbers, leveling agents and antistatic agents, as long as the film formability of the protective film, in-plane direction and thickness direction retardation values, tensile modulus and tensile strength are not impaired. You may make it contain. Thereby, it is possible to give an ultraviolet absorption characteristic, a peeling characteristic, and an antistatic characteristic to a protective film.

  As the ultraviolet absorber, known ones can be used. For example, benzophenone series such as 2-hydroxy-4-octoxybenzophenone and 2-hydroxy-4-methoxy-5-sulfobenzophenone, 2- (2′-hydroxy) Examples include benzotriazoles such as -5-methylphenyl) benzotriazole, hindered amines such as phenyl salsylate, and pt-butylphenyl salsylate. Known leveling agents and antistatic agents can also be used.

  Since the protective film according to the present invention is formed into a thin film, for example, the film thickness is 5 μm or more and 80 μm or less, more preferably 6 μm or more and 50 μm or less, and particularly preferably 7 μm or more and 30 μm or less.

The retardation value of the protective film according to the present invention is such that the refractive index in the direction in which the in-plane refractive index is maximum (that is, the slow axis direction) is nx, and the refractive index in the direction orthogonal to the slow axis is in the plane. When ny, the refractive index in the thickness direction is nz, and the thickness is d, the in-plane retardation value (Re) and the thickness direction retardation value (Rth) are expressed by the following equations (i) and (ii), respectively. Defined.
Re = (nx−ny) × d (i)
Rth = [(nx + ny) / 2−nz] × d (ii)

  The in-plane retardation value (Re) at 23 ° C. and a wavelength of 590 nm of the protective film according to the present invention is 0 nm or more and 10 nm or less, more preferably 0 nm or more and 5 nm or less. The thickness direction retardation value (Rth) at 23 ° C. and a wavelength of 590 nm is −10 nm to 10 nm, more preferably −5 nm to 5 nm.

  The protective film according to the present invention is excellent in tensile elastic modulus, and the tensile elastic modulus is, for example, 1500 MPa or more, and more preferably 2500 MPa or more. Although an upper limit is not specifically limited, For example, it is 4500 MPa.

  The protective film according to the present invention is excellent in tensile strength, and the tensile strength is, for example, 25 MPa or more, and more preferably 50 MPa or more. Although an upper limit is not specifically limited, For example, it is 100 MPa.

<Film laminate>
Next, a film laminated body is demonstrated. The film laminate according to the present invention is provided on at least one side of the protective film.
(1) A film substrate that supports the protective film,
(2) a hard coat layer having scratch resistance;
(3) an antiglare layer that scatters light, and
(4) One of an antireflection layer including a high refractive index layer provided on the protective film and a low refractive index layer provided on the high refractive index layer is provided. Of course, the said film laminated body may be equipped with arbitrary said (1)-(4) on both surfaces of a protective film. That is, the same type of layers on both sides (for example, (1) on the surface of the protective film, (1) on the back side) or different layers (for example, (1) on the front side of the protective film, (2) on the back side, or the surface (2) and (3)) may be provided on the back surface. Furthermore, (1) to (4) are provided with other layers (1) to (4), and may have a laminated structure. Hereinafter, (1) to (4) will be described.

[Film base]
The protective film which concerns on this invention can be handled integrally in the state laminated | stacked with the other film. In addition, when manufacturing a film laminate by forming a protective film on a film substrate by a coating method such as a roll coating method or a gravure coating method, the film substrate should be used as part of the film laminate. You can also.

  The film base material plays a role of supporting the protective film, and finally has a release layer on the side where the protective film is laminated in order to peel and remove. In addition, when a film base material is equipped with a functional layer via a release layer, after the film base material is bonded to the functional layer side of the protective film and then removed by removing the film base material, the functional layer is usually Is not transferred to the film substrate side but transferred to the protective film side.

  Usually, since a protective film and a polarizing film are bonded together with an ultraviolet curable adhesive, it is preferable that the film base material does not have ultraviolet absorbing ability so as not to prevent ultraviolet irradiation. Furthermore, the optical properties may be inspected in various manufacturing processes in which other films are provided on the polarizing plate and processed up to the display device, and this influences the measurement of the optical properties of the polarizing film and the protective film, which is the basic configuration of the polarizing plate. It is preferable that the film substrate has transparency so as to minimize the thickness. From such a viewpoint, a polyester film substrate having a release layer is preferably used as the film substrate.

  As described above, the polyester film substrate may have a release layer, and other functional layers may be formed in addition to the release layer. Examples of the functional layer include a hard coat layer (HC layer), an antiglare layer (AG layer), and an antireflection layer (LR layer). These layers are formed on the release layer of the polyester film, laminated on the protective film, and then peeled off the polyester substrate from the release layer, whereby each functional layer and the protective film are laminated. The body is easily obtained.

[Hard coat layer]
The hard coat layer has a hard coat property. The hard coat property in the present invention is based on JIS K5600: 1999, and the scratch hardness according to the pencil method under a load of 500 g and a speed of 1 mm / s is 2H or more.

  As the resin component constituting the hard coat layer, an ionizing radiation curable resin is suitable because it can be cured efficiently with a simple processing operation, and after curing, a coating having sufficient strength and transparency is provided. An ionizing radiation curable resin can be used without any particular limitation.

  Examples of the ionizing radiation curable resin include monomers and oligomers having radical polymerizable functional groups such as acryloyl group, methacryloyl group, acryloyloxy group, and methacryloyloxy group, and cationic polymerizable functional groups such as epoxy group, vinyl ether group, and oxetane group. , Prepolymers, and compositions obtained by mixing polymers alone or as appropriate are used. Examples of monomers include methyl acrylate, methyl methacrylate, methoxy polyethylene methacrylate, cyclohexyl methacrylate, phenoxyethyl methacrylate, ethylene glycol dimethacrylate, dipentaerythritol hexaacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, and the like. it can. As oligomers and prepolymers, polyester acrylate, polyurethane acrylate, polyfunctional urethane acrylate, epoxy acrylate, polyether acrylate, acrylate compounds such as alkit acrylate, melamine acrylate, silicone acrylate, unsaturated polyester, tetramethylene glycol diglycidyl ether, Epoxy compounds such as propylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, bisphenol A diglycidyl ether and various alicyclic epoxies, 3-ethyl-3-hydroxymethyloxetane, 1,4-bis {[((3- Oxeta such as ethyl-3-oxetanyl) methoxy] methyl} benzene, di [1-ethyl (3-oxetanyl)] methyl ether Mention may be made of the compound. Examples of the polymer include polyacrylate, polyurethane acrylate, and polyester acrylate. These can be used alone or in combination. Among these ionizing radiation curable resins, in particular, a polyfunctional monomer having 3 or more functional groups can increase the curing speed and improve the hardness of the cured product. Furthermore, by using polyfunctional urethane acrylate, the hardness and flexibility of the cured product can be imparted.

  The ionizing radiation curable resin can be cured by irradiation with ionizing radiation as it is, but in the case of curing by ultraviolet irradiation, it is necessary to add a photopolymerization initiator. Photopolymerization initiators include radical polymerization initiators such as acetophenone, benzophenone, thioxanthone, benzoin, and benzoin methyl ether, and cationic polymerization starts such as aromatic diazonium salts, aromatic sulfonium salts, aromatic iodonium salts, and metallocene compounds. The agents can be used alone or in appropriate combination.

  The thickness of the hard coat layer is not particularly limited as long as the hard coat property is exhibited, but is generally 1 μm or more and 10 μm or less.

  In order to provide functions other than hard coat properties, various additives can be added to the hard coat layer. Examples include fluorine or silicone leveling agents added to improve releasability when peeling from polyester film substrates, and electrons added to prevent dust adhesion due to peeling charge during peeling. A conjugated, metal oxide or ionic antistatic agent may be appropriately selected and used according to the required function. The point which can use an additive agent is the same also about the following glare-proof layer and a low refractive index layer.

(Anti-glare layer)
The antiglare layer has an antiglare function that scatters light, and realizes the antiglare function by external haze and / or internal haze. It contains translucent fine particles, or both.

  There is no particular limitation on the method of forming the unevenness on the surface of the antiglare layer, but the method of applying an ionizing radiation curable resin on the polyester film substrate on which the unevenness is formed, and curing after application is It is preferable because the shape can be easily controlled.

  The shape of the surface irregularities on the polyester substrate side of the antiglare layer is determined by the required antiglare property. A more preferable uneven shape can be defined by the roughness parameters Ra and Sm and the average inclination angle. Ra: 0.01 μm or more, Sm: 50 μm or more and 500 μm or less, Average inclination angle: 0.1 ° or more 3 More preferably, it is 0 ° or less.

  The thickness of the antiglare layer is not particularly limited, but if it is too thin, the uneven shape formed on the support side remains on the uneven surface formed on the support side, which is not preferable in terms of preventing glare. On the other hand, if it is too thick, curling and cracking due to curing shrinkage of the resin occur, which is not preferable in terms of handling. Therefore, it is preferably in the range of 1 μm to 12 μm.

  On the other hand, the translucent fine particles added to the ionizing radiation curable resin to cause internal haze include, for example, acrylic resin, polystyrene resin, styrene-acrylic copolymer, nylon resin, silicone resin, melamine resin, polyether. Organic resin fine particles such as sulfone resin and inorganic fine particles such as silica can be used. Here, the translucent fine particles preferably have a refractive index difference of 0.04 or less from the resin component, and more preferably 0.01 or less. A large difference in refractive index from the resin component is not preferable because internal scattering occurs in the antiglare layer and the contrast is lowered.

  The film thickness of the antiglare layer is not particularly limited as long as the antiglare property is exhibited, but is generally 1 μm or more and 10 μm or less. In addition to the antiglare property, the antiglare layer can also have a hard coat property. In this case, the hard coat property is imparted by adjusting the resin component used.

(Antireflection layer)
The antireflection layer is composed of a low refractive index layer and a high refractive index layer. The low refractive index layer is a layer having a lower refractive index than the adjacent high refractive index layer (hard coat layer, antiglare layer or protective film), and has a low refractive index in a state of being laminated with the high refractive index layer. This contributes to preventing reflection of light from the layer side. Here, the high refractive index and the low refractive index do not define an absolute refractive index, but rather specify that the refractive indices of the two layers are relatively high or low compared. It is said that the reflectance is lowest when both have the following relationship (iii).
n2 = (n1) ^1/2 (iii)
(N1 is the refractive index of the high refractive index layer, n2 is the refractive index of the low refractive index layer)

In order to suitably exhibit the antireflection function, the refractive index of the low refractive index layer is preferably 1.45 or less. Examples of the material having these characteristics include LiF (refractive index n = 1.4), MgF ₂ (n = 1.4), 3NaF · AlF ₃ (n = 1.4), AlF ₃ (n = 1. 4) Inorganic low-reflective material in which inorganic material such as Na ₃ AlF ₆ (n = 1.33) is finely divided and contained in acrylic resin or epoxy resin, fluorine-based, silicone-based organic compound, heat Examples thereof include organic low reflection materials such as plastic resins, thermosetting resins, and radiation curable resins. Among them, in particular, the fluorine-based fluorine-containing material is excellent in antifouling property, and therefore, it is preferable in terms of preventing contamination when the low refractive index layer becomes the surface.

  Examples of the fluorine-containing material include vinylidene fluoride copolymers, fluoroolefin / hydrocarbon copolymers, fluorine-containing epoxy resins, fluorine-containing epoxy acrylates, fluorine-containing silicones, which are easily dissolved in organic solvents. , Fluorine-containing alkoxysilane, fluorine-containing polysiloxane, and the like. These can be used alone or in combination. The fluorine-containing polysiloxane is obtained by curing a hydrolyzable silane compound and / or a mixture containing at least a hydrolyzate thereof and a curing accelerator, as a hydrolyzable silane compound, as a film forming agent and an antistatic agent. A cation-modified silane compound having the above function can also be contained.

  The thickness of the low refractive index layer is not particularly limited as long as the antireflection function is exhibited in relation to the high refractive index layer, but is generally 0.05 μm or more and 0.2 μm or less. Is generally preferably 0.05 μm or more and 10 μm or less. The low refractive index layer exhibits an antireflection function in relation to the high refractive index layer, but can also have a hard coat property by selecting a raw material. Further, the high refractive index layer may have a hard coat property or may have an antiglare property depending on the selection of raw materials.

"Polarizer"
Next, a polarizing plate provided with the protective film of the present invention will be described. The polarizing plate according to the present invention is provided with the protective film on at least one surface of the polarizing film.

  The polarizing film is made of a polyvinyl alcohol resin (PVA resin), and has a property of transmitting light having a vibration surface in a certain direction out of light incident on the polarizing film and absorbing light having a vibration surface orthogonal to the direction. A dichroic dye is typically adsorbed and oriented on a PVA resin. The PVA resin constituting the polarizing film can be obtained by saponifying a polyvinyl acetate resin. The polyvinyl acetate resin used as the raw material for the PVA resin may be a copolymer of polyvinyl acetate, which is a homopolymer of vinyl acetate, or a copolymer of vinyl acetate and other monomers copolymerizable therewith. Good. A polarizing film can be produced by subjecting the film made of the PVA resin to uniaxial stretching, dyeing with a dichroic dye, and boric acid crosslinking treatment after dyeing. As the dichroic dye, iodine or a dichroic organic dye is used. Uniaxial stretching may be performed before dyeing with a dichroic dye, may be performed simultaneously with dyeing with a dichroic dye, or after dyeing with a dichroic dye, for example, during a boric acid crosslinking treatment. May be. Thus, the polarizing film which consists of PVA resin which is manufactured and the dichroic dye adsorbs and becomes one of the constituent materials of a polarizing plate.

  An ultraviolet curable adhesive is preferably used for pasting the polarizing film and the protective film. As long as the ultraviolet curable adhesive is supplied in a liquid coatable state, a known one that has been conventionally used in the production of polarizing plates can be used, but from the viewpoint of weather resistance, polymerizability, etc. A polymerizable compound, for example, one containing an epoxy compound as one of the ultraviolet curable components is preferable.

  In addition to cationically polymerizable compounds such as epoxy compounds as representative examples of ultraviolet curable adhesives, polymerization initiators, particularly to generate cationic species or Lewis acids upon irradiation with ultraviolet rays, initiate polymerization of cationically polymerizable compounds. The photocationic polymerization initiator is blended. Further, a thermal cationic polymerization initiator that initiates polymerization by heating, and various other additives such as a photosensitizer may be blended.

  The polarizing plate which concerns on this invention is equipped with the said protective film on at least one surface, and the structure provided with a protective film on both surfaces of a polarizing plate is contained. The protective film has a low retardation value in the in-plane direction and a thickness direction, and has a high tensile elastic modulus and tensile strength without performing a molecular orientation treatment. Therefore, an environment in which stress relaxation and moisture absorption / dehumidification occur in the polarizing film ( Even under high temperature, high temperature and high humidity, low temperature, high temperature and low temperature cycle, etc.), the dimensional change of the polarizing film is suppressed.

<< Method for producing protective film and film laminate >>
[Protective film forming step]
Although the manufacturing method of the protective film which concerns on this invention will not be specifically limited if the said protective film can be manufactured, The method including the protective film formation process containing the following processes (A1) and (A2) as an example is mentioned.
Step (A1): The energy beam curable composition is applied on the film substrate or the release layer of the film substrate.
Step (A2): After coating, the energy beam curable composition is cured to form a protective film.

  The energy ray curable composition contains urethane (meth) acrylate according to block A, (meth) acrylate group-containing raw material according to block B, and thiol as essential components. The urethane (meth) acrylate and (meth) acrylate group-containing raw material and thiol that are monomers are raw materials for the protective film, and the monomer is copolymerized to form the repeating unit described in the above << Protective film >>. The

Examples of the urethane (meth) acrylate I or II of the block A, the following structure A having a saturated cyclic aliphatic structure R ^1, (optionally contained in) the structure B having the following saturated aliphatic chain R ^2, and, a structure containing the structure C having a saturated cyclic aliphatic structure R ³ can be exemplified. The structure B is an optional component.
—CO—NH—R ¹ —NH—CO— (Structure A)
—O—R ² —CO— (Structure B)
—O—R ³ —O— (Structure C)

The urethane (meth) acrylate is, for example, a diisocyanate containing R ¹ , an ester containing R ² (optionally used), a diol containing R ³ , a hydroxyl group-containing alkyl (meth) acrylate, or an isocyanate group. It can be obtained using the alkyl (meth) acrylate contained and can be easily produced.

  As an example, the ratio of the structure A, the structure B, and the structure C can be m + 1: m (r + s): m, m: m (r + s): m + 1, or m: k + n: m + 1. M represents an integer of 1 to 4, r and s each represent an integer of 0 to 2, and the sum of r and s is 1 to 2, k represents an integer of 0 to 2, n Represents an integer of 0-2.

  Although the method for synthesizing urethane (meth) acrylate is not particularly limited, as an example, first, a bifunctional intermediate is synthesized, and hydroxyl group-containing alkyl (meth) acrylate or isocyanate group-containing alkyl (meth) acrylate is intermediated. A method of synthesizing at both ends of the body is mentioned.

（一般式（６）中、Ｒ^１は飽和環状脂肪族構造を示し、Ｒ^２は炭素数５〜１０の直鎖または分岐鎖状の飽和脂肪族鎖を示し、Ｒ^３は、Ｒ^１と異なる飽和環状脂肪族構造を示し、Ｒ^４は水素原子またはメチル基を示し、Ｒ^５は、水素原子、メチル基またはエチル基を示し、ｍは１〜４の整数を示し、ｒおよびｓはそれぞれ０〜２の整数を示し、かつ、ｒとｓとの和は１〜２であり、ｘは０〜３の整数を示す） Specifically, when a method for synthesizing a urethane (meth) acrylate corresponding to the repeating unit of the general formula (1) described above is exemplified, [1] an ester having R ² and a diol having R ³ are represented by m ( r + s): m is reacted at a molar ratio of m, and further m + 1 mole of diisocyanate having R ¹ is reacted to obtain an intermediate having —N═C═O groups at both ends. [2] Thereafter, urethane (meth) acrylate represented by the following general formula (6) is obtained by reacting 1 mol of the intermediate with 2 mol of a hydroxyl group-containing alkyl (meth) acrylate.

(In General Formula (6), R ¹ represents a saturated cycloaliphatic structure, R ² represents a linear or branched saturated aliphatic chain having 5 to 10 carbon atoms, and R ³ is different from R ^1. R ⁴ represents a hydrogen atom or a methyl group, R ⁵ represents a hydrogen atom, a methyl group or an ethyl group, m represents an integer of 1 to 4, and r and s are each 0. ) Represents an integer of ˜2, and the sum of r and s is 1 to 2, and x represents an integer of 0 to 3)

（一般式（７）中、Ｒ^１は飽和環状脂肪族構造を示し、Ｒ^２は炭素数５〜１０の直鎖または分岐鎖状の飽和脂肪族鎖を示し、Ｒ^３は、Ｒ^１と異なる飽和環状脂肪族構造を示し、Ｒ^４は水素原子またはメチル基を示し、Ｒ^５は、水素原子、メチル基またはエチル基を示し、ｍは１〜４の整数を示し、ｒおよびｓはそれぞれ０〜２の整数を示し、かつ、ｒとｓとの和は１〜２であり、ｘは０〜３の整数を示す） An example of a method for synthesizing a urethane (meth) acrylate corresponding to the repeating unit of the general formula (2) is as follows. [1] A diisocyanate having R ¹ and an ester having R ² are converted into m: m (r + s) moles. The reaction is carried out in a ratio, and further m + 1 mol of diol having R ³ is reacted to obtain an intermediate having hydroxyl groups at both ends. [2] Thereafter, urethane (meth) acrylate corresponding to the repeating unit represented by the general formula (7) by reacting 2 mol of an isocyanate group-containing alkyl (meth) acrylate with 1 mol of an intermediate. Is obtained.

(In the general formula (7), R ¹ represents a saturated cycloaliphatic structure, R ² represents a linear or branched saturated aliphatic chain having 5 to 10 carbon atoms, and R ³ is different from R ^1. R ⁴ represents a hydrogen atom or a methyl group, R ⁵ represents a hydrogen atom, a methyl group or an ethyl group, m represents an integer of 1 to 4, and r and s are each 0. ) Represents an integer of ˜2, and the sum of r and s is 1 to 2, and x represents an integer of 0 to 3)

（一般式（８）中、Ｒ^１は飽和環状脂肪族構造を示し、Ｒ^２は炭素数５〜１０の直鎖または分岐鎖状の飽和脂肪族鎖を示し、Ｒ^３は、Ｒ^１と異なる飽和環状脂肪族構造を示し、Ｒ^４は水素原子またはメチル基を示し、Ｒ^５は、水素原子、メチル基またはエチル基を示し、ｍは１〜４の整数を示し、ｋは０〜２の整数を示し、ｎは０〜２の整数を示し、ｘは０〜３の整数を示す） An example of a method for synthesizing a urethane (meth) acrylate corresponding to the repeating unit of the general formula (3) is as follows: [1] A diisocyanate having R ¹ and a diol having R ³ are reacted at a molar ratio of m: m + 1. Thus, an intermediate having hydroxyl groups at both ends is obtained. [2-1] Then, 2 mol of an isocyanate group-containing alkyl (meth) acrylate is reacted with 1 mol of the intermediate, or [2-2] k + n mol with respect to 1 mol of the intermediate. after reacting the ester with an R ² of, it is reacted with 2 moles of isocyanate group-containing alkyl (meth) acrylate, relative to [2-3] 2 moles of isocyanate group-containing alkyl (meth) acrylate, k + n mol The urethane (meth) acrylate obtained by reacting the ester having R ² is reacted with 1 mol of the above intermediate, or by any method, the repeating unit represented by the general formula (8) The corresponding urethane (meth) acrylate is obtained.

(In General Formula (8), R ¹ represents a saturated cycloaliphatic structure, R ² represents a linear or branched saturated aliphatic chain having 5 to 10 carbon atoms, and R ³ is different from R ^1. R ⁴ represents a hydrogen atom or a methyl group, R ⁵ represents a hydrogen atom, a methyl group or an ethyl group, m represents an integer of 1 to 4, and k represents an integer of 0 to 2. Represents an integer, n represents an integer of 0 to 2, and x represents an integer of 0 to 3)

  Although the synthetic | combination procedure of each said raw material was shown, the synthetic | combination procedure of the urethane (meth) acrylate based on this invention is not limited to these, Each raw material may be mixed simultaneously. However, the above synthesis procedure is excellent in that the molecular weight can be easily controlled.

  Since the monomer for generating the block B is described as a specific example in the example of the (meth) acrylate group-containing raw material, description thereof will not be repeated.

  The thiol (R-SH) that produces the thioether structure is the thioether structure (described above) except that H on S becomes a single bond during the reaction with the urethane (meth) acrylate and the (meth) acrylate group-containing raw material. R-S-) and hydrocarbon R are common, and specific examples of hydrocarbon R have already been described in the above-described thioether structure, and therefore description on hydrocarbon R will not be repeated.

（一般式（１１）中、Ｒ^６は、水素原子がメチル基によって置換されていてもよい炭素数１または２のアルキル鎖を示し、ｎは１〜４の整数を示す） Representative thiols that give rise to thioether structures are shown below.

(In the general formula (11), R ⁶ represents an alkyl chain having 1 or 2 carbon atoms in which a hydrogen atom may be substituted with a methyl group, and n represents an integer of 1 to 4)

（一般式（１０）中、Ｒ^７は、水素原子がアルキル基によって置換されていてもよい炭素数１または２のアルキル鎖を示し、Ｒ^８は水素原子またはメチル基を示し、ｑは１〜４の整数を示す） Other structures of typical thiols that give rise to thioether structures are shown below.

(In the general formula (10), R ⁷ represents an alkyl chain having 1 or 2 carbon atoms in which a hydrogen atom may be substituted with an alkyl group, R ⁸ represents a hydrogen atom or a methyl group, and q represents 1 to 2) Indicates an integer of 4)

In the above general formula (10), R ⁷ is an ethyl chain, a methyl group is bonded to the β carbon of the ethyl chain, and a suitable thiol having q of 4 is shown below. This thiol is tetrafunctional and gives rise to a thioether structure that forms a complex three-dimensional structure with the repeating unit.

The energy ray-curable composition is prepared by adding a photopolymerization initiator that initiates polymerization of the monomer and thiol to the monomer and thiol that generate the repeating units of the block A, block B, and thioether structure.
Photopolymerization initiators include radical polymerization initiators such as acetophenone, benzophenone, thioxanthone, benzoin, and benzoin methyl ether, and cationic polymerization starts such as aromatic diazonium salts, aromatic sulfonium salts, aromatic iodonium salts, and metallocene compounds. The agents can be used alone or in appropriate combination.

  You may add various additives, such as the ultraviolet absorber mentioned above by << protective film >>, a leveling agent, and an antistatic agent, to an energy-beam curable composition.

  In the energy ray curable composition, each ratio of the monomer (the total amount of monomers that generate the block A and the block B), the thiol, the photopolymerization initiator, and any of various additives varies depending on the type of each material, and is uniquely Although it is difficult to define, as an example, monomer and thiol are 50% by mass to 99% by mass, photopolymerization initiator is 0.5% by mass to 10% by mass, and various additives are 0.01% by mass. It can be made 50 mass% or less. Moreover, you may add organic solvents, such as toluene, to an energy-beam curable composition.

  The mass ratio of the urethane (meth) acrylate that is the monomer that generates the block A and the (meth) acrylate group-containing raw material that is the monomer that generates the block B is the degree of improvement in the tensile elastic modulus of the protective film resulting from the block B Is preferably urethane (meth) acrylate: (meth) acrylate group-containing raw material = 90: 10 to 10:90, more preferably 80:20 to 20:80, and 70:30 to 30:70. Is particularly preferred.

  The mass ratio of the total amount of monomers that are the repeating units of block A and block B and the thiol that produces the thioether structure should be suitable for the degree of tensile modulus and tensile strength of the protective film resulting from the thioether structure. , Block A and Block B total monomer amount: thiol = 95: 5 to 50:50 is preferable, 95: 5 to 70:30 is more preferable, and 90:10 to 80:20 is particularly preferable.

  In order to apply the prepared energy ray curable composition on the film substrate or the release layer of the film substrate, considering continuous productivity, a coating method such as a roll coating method or a gravure coating method is used. It is preferable to use it. By the coating method, the energy ray curable composition can be applied so as to form a protective film having a thin layer, for example, 80 μm or less, preferably 50 μm or less, more preferably 30 μm or less.

  Curing in the step (A2) can be performed by irradiating ultraviolet rays from an ultraviolet irradiation device. The ultraviolet light source to be used is not particularly limited, but has a light emission distribution at a wavelength of 400 nm or less, such as a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a chemical lamp, a black light lamp, a microwave excitation mercury lamp, a metal halide lamp, etc. Can be used. In the case of using a composition having an acrylic compound as an active energy ray-curable component, a high-pressure mercury lamp or a metal halide lamp having a lot of light of 400 nm or less is preferably used as an ultraviolet light source in consideration of an absorption wavelength exhibited by a general polymerization initiator. It is done.

  By curing the energy ray-curable composition, a protective film is formed on the film substrate or the release layer of the film substrate, and a film laminate in which the protective film is laminated on the film substrate is obtained. . Furthermore, a single protective film can be obtained by peeling the protective film from the film laminate.

[Functional layer formation process]
As a variation of the manufacturing method of a film laminated body, the manufacturing method which contains a functional layer formation process (B) before a protective film formation process (A1) and (A2) is mentioned. In the functional layer forming step (B), the energy ray curable composition that is the raw material of the functional layer is applied to the film base material or the release layer of the film base material and cured to function on the film base material. Form a layer.

  Although it does not specifically limit as said functional layer, The hard-coat layer, glare-proof layer, and antireflection layer which were mentioned above are mentioned. The energy ray curable composition that is a raw material of the functional layer includes the resin described above in the description of the hard coat layer, the antiglare layer, and the antireflection layer. An organic solvent such as methyl ethyl ketone, cyclohexanone, methyl isobutyl ketone (MIBK), isopropyl alcohol (IPA), or toluene may be added.

  In order to apply the energy ray curable composition, which is the raw material of the functional layer, on the film substrate or the release layer of the film substrate, considering continuous productivity, roll coating method, gravure coating method, etc. It is preferable to use this coating method. According to the energy ray curable composition to be used, a method of arbitrarily heating and then crosslinking and curing by ultraviolet irradiation or the like may be used.

  When a functional layer is formed on the film substrate in the functional layer forming step, an energy ray curable composition containing urethane (meth) acrylate is applied to the functional layer side of the film substrate in the protective film forming step (A1). . When the functional layer is a plurality of layers, it is usually applied to the last formed functional layer side.

  When the film base material in which unevenness | corrugation was formed is used, an unevenness | corrugation is formed in the functional layer formed in the said film base material, and it functions as an anti-glare layer which has anti-glare property. The shape of the unevenness is determined by the required antiglare property, and a more preferable uneven shape can be defined by the roughness parameters Ra and Sm and the average inclination angle. Ra: 0.01 μm or more, Sm: More preferably, it is 50 μm or more and 500 μm or less, and the average inclination angle is 0.1 ° or more and 3.0 ° or less.

  When forming the functional layer, a plurality of layers can be formed. For example, when forming a plurality of hard coat layers, the first hard coat layer is formed on the film substrate or the release layer of the film substrate, and the second hard coat layer is formed on the first hard coat layer. Form. Thereafter, in the step (A1), an energy ray curable composition containing urethane (meth) acrylate is applied to the second hard coat layer side. An antiglare layer may be formed in place of the second hard coat layer.

  Moreover, when forming an antireflection layer, a low refractive index layer is formed on a film base material or a release layer of the film base material, and a high refractive index layer is formed on the low refractive index layer. Furthermore, the energy ray-curable composition containing urethane (meth) acrylate is applied to the high refractive index layer side in the step (A1). Thereby, the film laminated body laminated | stacked in order of the film base material, the functional layer, and the protective film is obtained.

<< Polarizing plate manufacturing method >>
The polarizing plate according to the present invention includes the protective film according to the present invention on at least one surface of the polarizing film. In the method for producing a polarizing plate according to the present invention, it is important that the protective film is bonded to a polarizing film, and the bonding method may be a known method, and is not particularly limited.

  As the protective film, the protective film may be used alone, but it is preferable to use the protective film together with the film laminate, that is, the film base material, for ease of handling.

  For example, after a protective film forming step or after obtaining a laminate including a protective film after a functional layer forming step and a protective film forming step, the polarizing film is bonded to the protective film side of the film laminate. A polarizing plate according to the present invention is obtained.

  The process which concerns on the manufacturing method of a polarizing plate is demonstrated more concretely. The following steps (C1) to (C4) are performed after the protective film forming step or after the functional layer forming step and the protective film forming step.

(C1) a coating step of applying an ultraviolet curable adhesive to the protective film side (or polarizing film) of the film laminate,
(C2) A laminating step in which a polarizing film (or a protective film side of the film laminate) is applied to the UV curable adhesive surface applied in the coating step and pressed.
(C3) A curing step of curing the ultraviolet curable adhesive by irradiating ultraviolet rays from an ultraviolet irradiation device to the film laminate in which the protective film is bonded to the polarizing film via the ultraviolet curable adhesive,
(C4) The peeling process which peels and removes a film base material (support base material) from a laminated | multilayer film as needed.

  In the coating step (C1), an ultraviolet curable adhesive is applied to the protective film side of the film laminate, which becomes the bonding surface of the polarizing film (or instead of the protective film side of the film laminate, the polarizing film is applied to the polarizing film). Apply UV curable adhesive). When the applied ultraviolet curable adhesive is diluted with water or an organic solvent, it is appropriately dried by a method such as heating. As a coating machine used here, a well-known thing can be used suitably, for example, the coating machine using a gravure roll etc. are mentioned.

  In the bonding step (C2), after passing through the coating step (C1), the polarizing film is laminated on the adhesive-coated surface of the film laminate, and the bonding is performed while pressing (polarization in the coating step (C1)). When an ultraviolet curable adhesive is applied to the film, the film is laminated while pressing the protective film side of the film laminate on the surface of the ultraviolet curable adhesive). A known means can be used for pressurization in the bonding step, but from the viewpoint that pressurization while continuous conveyance is possible, a method of sandwiching between a pair of nip rolls is preferably used. Is preferably about 150 to 500 N / cm as a linear pressure when sandwiched between a pair of nip rolls.

  In a hardening process (C3), after bonding a film laminated body to a polarizing film, an ultraviolet-ray is irradiated from an ultraviolet irradiation device, and an ultraviolet curable adhesive is hardened. Ultraviolet rays are irradiated through the film laminate. The ultraviolet light source to be used is not particularly limited, but has a light emission distribution at a wavelength of 400 nm or less, such as a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a chemical lamp, a black light lamp, a microwave excitation mercury lamp, a metal halide lamp, etc. Can be used. When using an adhesive having an epoxy compound as an energy ray curable component, a high-pressure mercury lamp or metal halide lamp having a large amount of light of 400 nm or less is preferably used as an ultraviolet light source in consideration of the absorption wavelength exhibited by a general polymerization initiator. .

  The peeling step (C4) is a step that is appropriately performed as necessary. The film base material laminated on the protective film by this step is peeled off and removed (if the film base material has a plurality of layers, the film base A part of the material is peeled and removed), whereby a polarizing plate is obtained. When the polarizing plate is further processed, when the surface of the protective film is desired to be protected in the post-processing step, the film substrate may be peeled after the completion of the processing.

  EXAMPLES Hereinafter, although this invention is demonstrated based on an Example and a comparative example, this invention is not limited to the content of an Example. The protective film from which the polyester film substrate was peeled from the obtained film laminate was measured, and the film thickness, in-plane direction and thickness direction retardation value, tensile modulus, and tensile strength of the protective film were measured as follows. Measured by the method.

[Film thickness]
The film thickness of the protective film was measured using a digital linear gauge D-10HS and a digital counter C-7HS (manufactured by Ozaki Manufacturing Co., Ltd.).

[In-plane direction and thickness direction retardation values]
Using a phase difference measuring device KOBRA-WR (manufactured by Oji Scientific Instruments Co., Ltd.), based on the above formulas (i) and (ii), the phase difference value (Re) in the in-plane direction at a measurement wavelength of 590 nm at 23 ° C. The thickness direction retardation value (Rth) was measured.

[Tensile modulus, tensile strength]
The sample film was cut so that the protective film was cut to a size of 15 mm x 160 mm, using “Tensilon RTF-24” (manufactured by Yamato Kagaku) with the long side as the tensile direction, so that the gap between the grips was 100 mm. Holding the both ends of the wire with a gripper, the tensile modulus of elasticity is determined from the maximum slope of the stress-strain curve at a measurement load range of 40 N and a measurement speed of 20 mm / min at a temperature of 23 ° C. ± 5 ° C. and a relative humidity of 50% RH ± 10% RH. The tensile strength was determined from the maximum stress in the stress-strain curve.

[Production Example 1: Synthesis of block A monomer]
Synthesis of Compound 1:
196.29 g (1 mol) of tricyclodecane dimethanol and 228.28 g (2 mol) of ε-caprolactone were charged into a flask, the temperature was raised to 120 ° C., and 50 ppm of monobutyltin oxide was added as a catalyst. Thereafter, the reaction was carried out under a nitrogen stream until the remaining ε-caprolactone was 1% or less by gas chromatography to obtain diol (1).

  In another flask, 44.56 g (2 mol) of isophorone diisocyanate was charged, and at a reaction temperature of 70 ° C., 424.57 g (1 mol) of diol (1) was added. When the remaining isocyanate group became 5.7%, 2-hydroxyethyl was added. 23.24 g (2 mol) of acrylate and 0.35 g of dibutyltin laurate were added, and the reaction was carried out until the remaining isocyanate group became 0.1% to obtain urethane acrylate (compound 1), which is a monomer that generates repeating units (compound 1) Is common with the structure in which m is 1 in the general formula (1a) except that both ends are acrylate groups.

[Production Example 2: Synthesis of Comparative Block A Monomer]
Synthesis of compound 2:
196.29 g (1 mol) of tricyclodecane dimethanol and 228.28 g (2 mol) of ε-caprolactone were charged into a flask, the temperature was raised to 120 ° C., and 50 ppm of monobutyltin oxide was added as a catalyst. Thereafter, the reaction was carried out under a nitrogen stream until the remaining ε-caprolactone was 1% or less by gas chromatography to obtain diol (2).

To another flask was charged 420.54 g (2 mol) of trimethylhexamethylene isocyanate, 424.57 g (1 mol) of diol (2) was added at a reaction temperature of 70 ° C., and when the remaining isocyanate group reached 5.7%, 2- Hydroxyl acrylate 232.24 g (2 mol) and dibutyltin laurate 0.35 g are added, and the reaction is carried out until the remaining isocyanate group reaches 0.1%, which is a monomer that generates a repeating unit represented by the following general formula (11a) Urethane acrylate (compound 2, acrylic equivalent 538 g / eq) was obtained. Compound 2 has one kind of saturated cycloaliphatic structure and does not generate block A.

[Example 1: Polyester film substrate / protective film]
Using an applicator, the following energy ray curable composition for forming a protective film (P1) was applied to the release layer side of non-silicone release PET SG-1 (38 μm thickness) manufactured by Panac. Compound 3 which produces block B is a monomer having an acrylic equivalent of 196 g / eq, and the structure thereof is represented by the following general formula (12a). Compound 4 is a thiol that generates a thioether structure, and the structure is represented by the following general formula (13a). The energy ray curable composition (P1) contains toluene and has a solid content (NV) of 60%.

The coating thickness of the energy beam curable composition (P1) was adjusted so that the film thickness after drying was 10 μm to 15 μm. The coating film is dried in a clean oven set at a drying furnace temperature of 100 ° C., and then irradiated with a high-pressure mercury lamp under a nitrogen atmosphere under conditions of a peak illuminance of 326 mW / cm ² and an integrated light quantity of 192 mJ / cm ^2. Was cured with UV to obtain a film laminate in which a protective film was formed on one side of the PET film. The evaluation results for this film laminate are shown in Table 2.

[Example 2: Polyester film substrate / protective film]
PET in the same manner as in Example 1 except that the monomers (Compound 1 and Compound 3) used in Example 1 were changed to 42.525 parts by mass of Compound 1 and 42.525 parts by mass of Compound 3, and the thiol was changed to 9.45 parts by mass. A film laminate in which a protective film was formed on one side of the film was obtained. The evaluation results for this film laminate are shown in Table 2.

[Example 3: Polyester film substrate / protective film]
PET in the same manner as in Example 1 except that the monomers (Compound 1 and Compound 3) used in Example 1 were changed to 33.075 parts by mass of Compound 1 and 33.075 parts by mass of Compound 3 and thiol was changed to 28.35 parts by mass. A film laminate in which a protective film was formed on one side of the film was obtained. The evaluation results for this film laminate are shown in Table 2.

[Example 4: Polyester film substrate / protective film]
PET in the same manner as in Example 1 except that the monomers (Compound 1 and Compound 3) used in Example 1 were changed to 23.625 parts by weight of Compound 1 and 23.625 parts by weight of Compound 3 and the thiol was changed to 47.25 parts by weight. A film laminate in which a protective film was formed on one side of the film was obtained. The evaluation results for this film laminate are shown in Table 2.

[Comparative Example 1]
A PET film was prepared in the same manner as in Example 1 except that the monomers (Compound 1 and Compound 3) used in Example 1 were changed to 47.25 parts by mass of Compound 1 and 47.25 parts by mass of Compound 3, and no thiol was added. The film laminated body in which the protective film was formed in the single side | surface was obtained. The evaluation results for this film laminate are shown in Table 2.

[Comparative Example 2]
PET in the same manner as in Example 1 except that the monomers (Compound 1 and Compound 3) used in Example 1 were changed to 14.175 parts by weight of Compound 1 and 14.175 parts by weight of Compound 3, and the thiol was changed to 66.15 parts by weight. A film laminate in which a protective film was formed on one side of the film was obtained. The evaluation results for this film laminate are shown in Table 2.

[Comparative Example 3]
A PET film was prepared in the same manner as in Example 1 except that the monomers (Compound 1 and Compound 3) used in Example 1 were changed to 47.25 parts by mass of Compound 2 and 47.25 parts by mass of Compound 3, and no thiol was added. The film laminated body in which the protective film was formed in the single side | surface was obtained. The evaluation results for this film laminate are shown in Table 2.

[Comparative Example 4]
The monomer (Compound 1 and Compound 3) used in Example 1 was changed to 94.5 parts by mass of Compound 3, and a cured film was formed on one side of the PET film in the same manner as in Example 1 except that no thiol was added. And a film laminate was obtained. The evaluation results for this film laminate are shown in Table 2.

  As shown in Table 2, in Examples 1 to 4, since the compound 3 having an acrylic equivalent of 196 g / eq and the thiol of Compound 4 were used as the compound for generating the block B, both Re and Rth were small, and A protective film having a high tensile elastic modulus and tensile strength was obtained.

  On the other hand, the cured film formed in Comparative Example 1 was hard, and a protective film having a high tensile elastic modulus and a low tensile strength was obtained. Since the structure of the protective film of Comparative Example 1 does not contain a thiol, a hydrogen bond cannot be generated between —S— of the thioether bond and the urethane bond in the repeating unit, and the acrylic group of Compound 3 is cured. This is thought to be due to the fact that the three-dimensional cross-linking structure is densely formed.

  The cured film formed in Comparative Example 2 was very soft, and a protective film having a low tensile modulus was obtained. In the protective film of Comparative Example 2, the acrylic group, which is a component that contributes to the hardness of the cured film, is contained in the monomer that generates the block A and the block B, but the ratio thereof is not sufficient, so that the three-dimensional This is considered to be due to the insufficient formation of the crosslinked structure.

  The cured film formed in Comparative Example 3 was very soft, and a protective film having a low tensile modulus was obtained. When synthesizing compound 2 that gives rise to comparative block A, a diisocyanate having a branched saturated aliphatic chain that is a flexible skeleton and ε-caprolactone that becomes a linear and flexible skeleton when cleaved by a synthesis reaction are synthesized. By using it, the effect of high molecular weight and molecular structure hardness as when using a saturated cycloaliphatic structure in the intermolecular interaction between urethane bonds is not obtained, the cohesive force between repeating units is weakened, It is thought that a flexible cured film was formed.

  The cured film formed in Comparative Example 4 was very hard and fragile, and collapsed when peeled from the PET film. Therefore, the film thickness, retardation value, tensile modulus, and tensile strength could not be measured. Since compound 4 does not have a urethane bond (—NH—CO—O—), cohesion between repeating units cannot be obtained, and due to the effect that only a three-dimensional cross-linked structure is formed due to the acrylic group being cured, It is considered that a highly brittle cured film was formed.

  As is clear from the above Examples and Comparative Examples, the repeating unit forming the protective film is made from urethane (meth) acrylate and (meth) acrylate group-containing raw materials and thiols, and plural types of urethane (meth) acrylates. It is very important that the (meth) acrylate equivalent of the (meth) acrylate group-containing raw material is 90 g / eq or more and 500 g / eq or less, and the protective film according to the present invention is useful. Sex is understood.

  Since the protective film according to the present invention has a high tensile elastic modulus and tensile strength without performing molecular orientation treatment, it is used for applications requiring high durability against severe temperature and humidity environments, particularly for polarizing plates. It is useful as a component and can be used in various fields.

Claims (12)

A block A consisting of repeating units I or II having a structure derived from urethane (meth) acrylate I or II as a monomer, and a block B consisting of repeating units having a structure derived from a (meth) acrylate group-containing raw material as a monomer, A protective film formed by a thioether structure,
The urethane (meth) acrylate I is a reaction product of a hydroxyl group-containing alkyl (meth) acrylate, a diol and a diisocyanate,
The urethane (meth) acrylate II is a reaction product of an isocyanate group-containing alkyl (meth) acrylate, a diol, and a diisocyanate,
The urethane (meth) acrylates I and II have a plurality of types of saturated cycloaliphatic structures,
The (meth) acrylate group-containing raw material has a (meth) acryl equivalent of 90 g / eq or more and 500 g / eq or less,
The thioether structure is present in the polymer chain composed of block A and block B, at least in the polymer chain, or via the thioether bond with the end of the polymer chain,
The in-plane retardation value (Re) at 23 ° C. at a wavelength of 590 nm is 0 nm to 10 nm, and the thickness direction retardation value (Rth) at 590 nm at 23 ° C. is from −10 nm to 10 nm. A protective film. The repeating units I and II are
Following structure A containing saturated cyclic aliphatic structure R ^1, and,
The protective film according to claim 1, comprising the following structure C including a saturated cycloaliphatic structure R ³ .
—CO—NH—R ¹ —NH—CO— (Structure A)
—O—R ³ —O— (Structure C) The repeating units I and II are
The protective film according to claim 2, further comprising the following structure B containing a saturated aliphatic chain R ² .
—O—R ² —CO— (Structure B) The said repeating unit I is a structure represented by following General formula (1), The protective film of Claim 3 characterized by the above-mentioned.

(In the general formula (1), R ¹ represents a saturated cycloaliphatic structure, R ² represents a linear or branched saturated aliphatic chain having 5 to 10 carbon atoms, and R ³ is different from R ^1. R ⁴ represents a hydrogen atom or a methyl group, R ⁵ represents a hydrogen atom, a methyl group or an ethyl group, m represents an integer of 1 to 4, and r and s are each 0. ) Represents an integer of ˜2, and the sum of r and s is 1 to 2, and x represents an integer of 0 to 3) The protective film according to claim 3, wherein the repeating unit II has a structure represented by the following general formula (2).

(In General Formula (2), R ¹ represents a saturated cycloaliphatic structure, R ² represents a linear or branched saturated aliphatic chain having 5 to 10 carbon atoms, and R ³ is different from R ^1. R ⁴ represents a hydrogen atom or a methyl group, R ⁵ represents a hydrogen atom, a methyl group or an ethyl group, m represents an integer of 1 to 4, and r and s are each 0. ) Represents an integer of ˜2, and the sum of r and s is 1 to 2, and x represents an integer of 0 to 3) The protective film according to claim 2, wherein the repeating unit II has a structure represented by the following general formula (3).

(In General Formula (3), R ¹ represents a saturated cycloaliphatic structure, R ² represents a linear or branched saturated aliphatic chain having 5 to 10 carbon atoms, and R ³ is different from R ^1. R ⁴ represents a hydrogen atom or a methyl group, R ⁵ represents a hydrogen atom, a methyl group or an ethyl group, m represents an integer of 1 to 4, and k represents an integer of 0 to 2. Represents an integer, n represents an integer of 0 to 2, and x represents an integer of 0 to 3) The R ¹ is a 3-methylene-3,5,5-trimethylcyclohexane ring, and the R ³ is a dimethylenetricyclodecane ring, according to any one of claims 2 to 6. Protective film. The said thioether structure is a structure represented by following General formula (4), The protective film of Claim 1 characterized by the above-mentioned.

(In the general formula (4), R ⁶ represents an alkyl chain having 1 or 2 carbon atoms in which a hydrogen atom may be substituted by a methyl group, and each X independently represents —S— or —S—H. N represents an integer of 1 to 4) The protective film according to claim 1, wherein the thioether structure is a structure represented by the following general formula (5).

(In the general formula (5), R ⁷ represents an alkyl chain having 1 or 2 carbon atoms in which a hydrogen atom may be substituted with an alkyl group, and each X independently represents —S— or —S—H. R ⁸ represents a hydrogen atom or a methyl group, and p represents an integer of 1 to 3)   The protective film according to any one of claims 1 to 9, wherein a tensile elastic modulus is 1500 MPa or more and a tensile strength is 25 MPa or more. At least one side of the protective film according to any one of claims 1 to 10,
(1) A film substrate that supports the protective film,
(2) a hard coat layer having scratch resistance;
(3) an antiglare layer that scatters light, and
(4) A film comprising any one of an antireflection layer composed of a high refractive index layer provided on the protective film and a low refractive index layer provided on the high refractive index layer. Laminated body.   A polarizing plate comprising the protective film according to claim 1 on at least one side of a polarizing film.