WO2018168402A1

WO2018168402A1 - Optical film, polarizing plate having same, and display device

Info

Publication number: WO2018168402A1
Application number: PCT/JP2018/006732
Authority: WO
Inventors: 里誌森井; 崇南條
Original assignee: コニカミノルタ株式会社
Priority date: 2017-03-13
Filing date: 2018-02-23
Publication date: 2018-09-20
Also published as: JP6996552B2; JPWO2018168402A1

Abstract

The present invention relates to an optical film which is characterized by containing a cycloolefin resin, a retardation reducing agent which is formed from a cinnamic acid ester derivative-fumaric acid diester copolymer, and core-shell particles, and which is also characterized in that, with respect to the core-shell particles, the glass transition temperature of the polymer that constitutes the shell is higher than the glass transition temperature of the polymer that constitutes the core by 150°C to 290°C (inclusive). The present invention provides an optical film which has sufficient bondability, while having improved brittleness.

Description

Optical film, polarizing plate having the same, and display device

The present invention relates to an optical film containing a retardation reducing agent and a core-shell particle comprising a copolymer having a specific structural unit, a polarizing plate having the same, and a display device. More particularly, the present invention relates to a technique for improving adhesion and brittleness in an optical film.

Various systems such as a TN (Twisted Nematic) system, a VA (Virtual Alignment) system, and an IPS (In-Place-Switching) system have been developed for liquid crystal display devices (Liquid Crystal Display, LCD). Among them, the IPS method is superior in viewing angle performance compared to the TN method and VA method, and is used for various applications. Note that the IPS liquid crystal cell is a type in which a nematic liquid crystal is switched by applying a horizontal electric field. IDRC (Asia Display 1995), pages 777-580 and pages 707-710.

As an optical film for a polarizing plate used for an IPS system, an optical film for a polarizing plate having optical isotropy (hereinafter also referred to as “zero retardation”) is required due to the characteristics of the IPS system. Conventionally, a cellulose triacetate (TAC) film has been widely used as an optical film for a polarizing plate exhibiting isotropic properties (zero retardation) due to its good handleability. However, since the value of the phase difference is not completely zero, improvement has been demanded.

In recent years, an optical film using a cycloolefin resin is also used as an optical film for a polarizing plate exhibiting zero retardation. Japanese Patent Application Laid-Open No. 2011-128356 discloses an optical film having zero retardation using a cycloolefin resin.

Currently, cycloolefin resins for optical films used in various display devices have positive intrinsic birefringence. Accordingly, when an optical film is produced by the melt film-forming method, a phase difference derived from positive orientation birefringence is exhibited by elongation in the transport direction or thermal stretching. It is difficult to completely suppress the development of such a phase difference only by adjusting the process conditions at the time of manufacture.

In addition, when producing optical films by the solution casting method, in addition to the above reasons, a phase difference is manifested by the orientation of the resin chain during the drying process after casting from a pressure die slit onto a drum or belt. To do. Furthermore, when the optical film with the solvent remaining is transported while being held in the width direction with a clip, the optical film contracts due to drying and is stretched in a pseudo manner, resulting in a phase difference. Sometimes.

Therefore, it was necessary to maintain zero retardation by adding a polymer material having a negative intrinsic birefringence to the cycloolefin resin to compensate for unnecessary retardation.

Conventionally, acrylic resin and polystyrene are known as a polymer material having a negative intrinsic birefringence, but acrylic resin has a small phase difference and an effect of developing zero phase difference is not sufficient. In addition, since polystyrene has a large photoelastic coefficient in a low temperature region, it has a problem of stability of phase difference in which the phase difference is changed by a slight stress and a practical problem of low heat resistance.

WO 2014/013982 (US Patent Application Publication No. 2015/0232599) includes fumaric acid diesters and cinnamic acid ester derivatives as new polymer materials having a negative intrinsic birefringence. Copolymers are disclosed.

However, a copolymer synthesized by the present inventors using a monomer having a cyclic alkyl group based on the above-mentioned International Publication No. 2014/013982 (US Patent Application Publication No. 2015/0232599) is a cycloolefin-based copolymer. When an optical film with zero retardation is produced by adding to a resin, the resulting optical film has low adhesion to a polarizer and the like, and a new problem arises that the optical film itself is brittle. There was found.

Therefore, an object of the present invention is to provide an optical film having sufficient adhesiveness and improved brittleness.

The present inventors have conducted intensive studies in view of the above problems. As a result, in addition to the cycloolefin resin and the copolymer of the fumaric acid diester and the cinnamic acid ester derivative, the core-shell type particles containing a polymer having a specific glass transition temperature are included, thereby solving the above-mentioned problem. The present invention has been completed.

That is, the optical film of the present invention has the following formula (1):

In formula (1), A ¹ to A ⁴ are each independently the following (i) to (iv):
(I) a hydrogen atom (ii) a halogen atom,
(Iii) a hydrocarbon group, or (iv) a hydrogen bond accepting group,
Or (v) or (vi) below:
(V) A ¹ and A ² , or A ³ and A ⁴ are bonded to each other to form an alkylidene group, and A ¹ to A ⁴ not participating in the bond are independently selected from the above (i) to ( iv) represents a group selected from
(Vi) A ¹ and A ³ , A ¹ and A ⁴ , A ² and A ³ , or A ² and A ⁴ are bonded to each other to form a cyclic structure together with the carbon atoms to which they are bonded; A ¹ to A ⁴ not involved each independently represents a group selected from the above (i) to (iv);
B represents 0 or 1, c represents an integer of 0 or more;
A cycloolefin-based resin having a structural unit derived from a monomer represented by:
Following formula (2):

In Formula (2), X ¹ each independently represents a linear alkyl group, a branched alkyl group, or a cyclic alkyl group, and X ² each independently represents an alkoxy group, an aryloxy group, or an ester group. Represents a hydroxyl group, a carboxyl group, a halogen atom, or a cyano group, and a represents an integer of 0 to 5;
And a structural unit represented by the following formula (3):

In formula (3), X ³ and X ⁴ each independently represent a linear alkyl group, a branched alkyl group, or a cyclic alkyl group;
(However, X ¹ in the formula (2) and at least one of X ³ and X ^{4 in} the formula (3) represents a cyclic alkyl group). A phase difference reducing agent;
And a core-shell type particle having a glass transition temperature of a polymer forming a shell that is higher by 150 ° C. or more and 290 ° C. or less than a glass transition temperature of a polymer forming a core.

Hereinafter, modes for carrying out the present invention will be described.

In this specification, “X to Y” indicating a range means “X or more and Y or less”. Unless otherwise specified, operations and physical properties are measured under conditions of room temperature (20 to 25 ° C.) and relative humidity of 40 to 50% RH. In addition, the notation “(meth) acrylic acid” means both acrylic acid and methacrylic acid, or either acrylic acid or methacrylic acid.

<Optical film>
The optical film according to the present invention has the following formula (1):

In formula (3), X ³ and X ⁴ each independently represent a linear alkyl group, a branched alkyl group, or a cyclic alkyl group;
(However, at least one of X ¹ in formula (2) and X ³ and X ^{4 in} formula (3) represents a cyclic alkyl group)
A retardation reducing agent comprising a copolymer having a structural unit represented by:
And a core-shell type particle having a glass transition temperature of a polymer forming a shell that is higher by 150 ° C. or more and 290 ° C. or less than a glass transition temperature of a polymer forming a core.

According to the present invention, it is possible to obtain an optical film having sufficient adhesiveness with a polarizer and improved brittleness. The mechanism by which these effects are achieved by the present invention is not clear, but the present inventors presume as follows.

That is, when the copolymer constituting the retardation reducing agent includes a structural unit having a cyclic alkyl group, the cycloolefin portion of the side chain of the cycloolefin resin, and the cyclic alkyl group contained in the retardation reducing agent Are thought to stack due to intermolecular interactions to form a dense structure. Thereby, it is estimated that the adhesive is prevented from penetrating into the optical film and the adhesiveness of the optical film is lowered. Further, it is presumed that the flexibility of the optical film is lost and the brittleness is increased.

The optical film of the present invention further includes core-shell type particles in addition to the cycloolefin resin and the retardation reducing agent, and the glass transition temperature of the polymer forming the shell of the core-shell type particle is that of the polymer forming the core. It is characterized by being 150 to 290 ° C. higher than the glass transition temperature. The core has a soft property because it has a relatively low glass transition temperature, and the shell has a hard property because it has a relatively high glass transition temperature. Therefore, the core-shell type particle has a property that has appropriate flexibility and strength by being surrounded by a hard shell with a soft core. By blending such core-shell particles, the intermolecular interaction between the cycloolefin-based resin and the retardation reducing agent is relaxed, making it difficult to form a dense structure. Thereby, it is considered that the adhesive easily penetrates into the optical film, and the adhesiveness of the optical film is improved. Moreover, this is considered that the softness | flexibility of an optical film is maintained and brittleness is improved. In addition, the said mechanism is based on estimation to the last, and the correctness or incorrectness does not affect the patentability of the present invention.

Hereinafter, each component contained in the optical film according to the present invention will be described in detail.

[Cycloolefin resin]
The cycloolefin-based resin has a structural unit derived from a monomer represented by the following formula (1).

In formula (1), A ¹ to A ⁴ are each independently the following (i) to (iv):
(I) a hydrogen atom (ii) a halogen atom,
(Iii) a hydrocarbon group, or (iv) a hydrogen bond accepting group,
Or (v) or (vi) below:
(V) A ¹ and A ² , or A ³ and A ⁴ are bonded to each other to form an alkylidene group, and A ¹ to A ⁴ not participating in the bond are independently selected from the above (i) to ( iv) represents a group selected from
(Vi) A ¹ and A ³ , A ¹ and A ⁴ , A ² and A ³ , or A ² and A ⁴ are bonded to each other to form a cyclic structure together with the carbon atoms to which they are bonded; A ¹ to A ⁴ not involved each independently represents a group selected from the above (i) to (iv);
, B represents 0 or 1, and c represents an integer of 0 or more.

In formula (1), examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

In the formula (1), examples of the hydrocarbon group include hydrocarbon groups having 1 to 30 carbon atoms, such as alkyl groups such as methyl group, ethyl group, and propyl group; cycloalkyl groups such as cyclopentyl group and cyclohexyl group. Alkenyl groups such as vinyl group, allyl group and propenyl group; aromatic groups such as phenyl group, biphenyl group, naphthyl group and anthracenyl group. These hydrocarbon groups may be substituted, and examples of the substituent include halogen atoms such as fluorine atom, chlorine atom and bromine atom, phenylsulfonyl group and the like.

In the present specification, the “hydrogen-accepting group” means a group containing a negative atom such as a fluorine atom, an oxygen atom or a nitrogen atom and capable of forming a hydrogen bond.

Examples of the hydrogen bond accepting group include an alkoxy group having 1 to 10 carbon atoms, an acyloxy group having 1 to 10 carbon atoms, an alkoxycarbonyl group having 2 to 10 carbon atoms, an aryloxycarbonyl group, a cyano group, an amide group, and an imide. Examples thereof include a ring-containing group, a triorganosiloxy group, a triorganosilyl group, an acyl group, an alkoxysilyl group having 1 to 10 carbon atoms, a sulfonyl-containing group, and a carboxy group. More specifically, these hydrogen-accepting groups include alkoxy groups such as methoxy and ethoxy groups; acyloxy groups such as alkylcarbonyloxy groups such as acetoxy and propionyloxy groups. And arylcarbonyloxy groups such as benzoyloxy group; examples of the alkoxycarbonyl group include methoxycarbonyl group and ethoxycarbonyl group; examples of the aryloxycarbonyl group include, for example, phenoxycarbonyl group and naphthyloxy A carbonyl group, a fluorenyloxycarbonyl group, a biphenylyloxycarbonyl group, and the like; examples of the triorganosiloxy group include a trimethylsiloxy group, a triethylsiloxy group, and the like; a triorganosilyl group And is a trimethylsilyl group, triethylsilyl group and the like; the alkoxysilyl group, for example, trimethoxysilyl groups, triethoxysilyl group, and the like.

In the formula (1), one or two of A ¹ to A ⁴ are preferably hydrogen bond accepting groups. By having such a structure, it can be easily dissolved in a solvent, and film formation with a solution flow is facilitated. The ratio of hydrogen bond accepting groups present in A ¹ to A ⁴ in formula (1) can be identified using, for example, ¹³ C nuclear magnetic resonance ( ¹³ CNMR) spectroscopy.

In formula (1), A ¹ and A ³ are preferably a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms from the viewpoint of improving solubility and facilitating film formation by solution pouring. More preferably, it is a hydrocarbon group having 1 to 4 carbon atoms, more preferably a hydrocarbon group having 1 to 2 carbon atoms, and at least one of A ² and A ⁴ is a hydrogen bond accepting group. Preferably there is. From the viewpoint of increasing the glass transition temperature and improving the mechanical strength, it is preferable that b = 0 and c = 1.

Furthermore, from the viewpoint that film formation by the solution casting method is easy and thinning can be easily performed, in formula (1), A ¹ and A ² are hydrogen atoms, and A ³ is a methyl group. A ⁴ is a methoxycarbonyl group, b is 0, and c is preferably 1.

The number average molecular weight (Mn) of the cycloolefin resin is preferably 8000 to 100,000, more preferably 10,000 to 80,000, and even more preferably 12,000 to 50,000. The weight average molecular weight (Mw) is preferably 20000 to 300000, more preferably 30000 to 250,000, and further preferably 40000 to 200000. When the number average molecular weight (Mn) or the weight average molecular weight (Mw) is within the above range, the heat resistance, water resistance, chemical resistance and mechanical properties of the cycloolefin resin are improved, and molding as an optical film is performed. Property is improved. In addition, a weight average molecular weight (Mw) and a number average molecular weight (Mn) are calculated | required by polystyrene conversion from the result measured by gel permeation chromatography (GPC).

The intrinsic viscosity [η] inh (measurement temperature: 30 ° C.) of the cycloolefin resin is preferably 0.2 to 5 cm ³ / g, more preferably 0.3 to 3 cm ³ / g, and More preferably, it is 4 to 1.5 cm ³ / g. When the intrinsic viscosity [η] inh is within the above range, the heat resistance, water resistance, chemical resistance and mechanical properties of the cycloolefin resin are improved, and the moldability as an optical film is improved. Intrinsic viscosity [η] inh is obtained by measuring (measurement temperature: 30 ° C.) a resin solution obtained by dissolving a cycloolefin resin to be measured in chloroform using an Ubbelohde viscometer.

The glass transition temperature (Tg) of the cycloolefin resin is usually 110 ° C. or higher, preferably 110 to 350 ° C., more preferably 120 to 250 ° C., and particularly preferably 120 to 220 ° C. preferable. A glass transition temperature (Tg) of 110 ° C. or higher is preferred because deformation under secondary processing such as use under high temperature conditions, coating, printing, etc. is suppressed. Moreover, it is preferable for the glass transition temperature (Tg) to be 350 ° C. or lower because resin degradation due to heat during molding and molding is suppressed. In addition, a glass transition temperature (Tg) is calculated | required by measuring using a differential scanning calorimeter.

As the cycloolefin resin, one synthesized by a known method may be used, or a commercially available product may be used. Examples of commercially available products include ARTON G, ARTON F, ARTON R, and ARTON RX (ARTON is a registered trademark) manufactured by JSR Corporation.

The content of the cycloolefin resin contained in the optical film is not particularly limited, but from the viewpoint of improving the heat resistance of the optical film, it is 51 to 99% by mass with respect to 100% by mass of the total solid content of the optical film. Preferably there is.

[Phase difference reducing agent]
The phase difference reducing agent is represented by a structural unit represented by the formula (2) (hereinafter also referred to as “structural unit (2)”) and a formula (3) (hereinafter also referred to as “structural unit (3)”). A copolymer having a structural unit. The retardation reducing agent has a negative value of the intrinsic birefringence, thereby reducing the retardation of a film made of cycloolefin resin having a positive intrinsic birefringence, and zero retardation in an optical film. Has the function of expressing

First, the structure of the structural unit (2) is shown below.

In Formula (2), X ¹ each independently represents a linear alkyl group, a branched alkyl group, or a cyclic alkyl group, and X ² each independently represents an alkoxy group, an aryloxy group, or an ester group. Represents a hydroxyl group, a carboxyl group, a halogen atom, or a cyano group, and a represents an integer of 0 to 5.

Examples of the linear alkyl group, branched alkyl group, or cyclic alkyl group represented by X ¹ include a linear alkyl group having 1 to 12 carbon atoms, a branched alkyl group having 3 to 12 carbon atoms, and a 3 to 12 carbon atom group. A cyclic alkyl group is mentioned. Specifically, examples of the linear alkyl group having 1 to 12 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, and an n-hexyl group; Examples of the branched alkyl group having 3 to 12 include isopropyl group, isobutyl group, sec-butyl group, tert-butyl group, etc .; examples of the cyclic alkyl group having 3 to 12 carbon atoms include cyclopropyl group, cyclobutyl group, A cyclohexyl group etc. are mentioned. Among these, from the viewpoint of polymerizability, X ¹ is preferably a methyl group, an ethyl group, an n-propyl group, or an isopropyl group, and more preferably a methyl group or an ethyl group.

Examples of the alkoxy group represented by X ² include alkoxy groups having 1 to 10 carbon atoms. Specific examples include a methoxy group, an ethoxy group, and an isopropoxy group.

Examples of the aryloxy group represented by X ² include a phenoxy group, a naphthyloxy group, a fluorenyloxy group, and a biphenylyloxy group.

Examples of the ester group represented by X ² include groups represented by the formula: —O—C (═O) —R or C (═O) —O—R. In this case, R is an alkyl group or an aromatic group. Examples of the alkyl group herein include a linear alkyl group having 1 to 12 carbon atoms, a branched alkyl group having 3 to 12 carbon atoms, and a cyclic alkyl group having 3 to 12 carbon atoms. Specifically, examples of the linear alkyl group having 1 to 12 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, and an n-hexyl group; Examples of the branched alkyl group having 3 to 12 include isopropyl group, isobutyl group, sec-butyl group, tert-butyl group, etc .; examples of the cyclic alkyl group having 3 to 12 carbon atoms include cyclopropyl group, cyclobutyl group, A cyclohexyl group etc. are mentioned. Examples of the aromatic group herein include aryl groups having 6 to 24 carbon atoms. Specific examples include a phenyl group, a p-tolyl group, a naphthyl group, a biphenyl group, a fluorenyl group, an anthryl group, a pyrenyl group, an azulenyl group, an acenaphthylenyl group, a terphenyl group, and a phenanthryl group.

Examples of the halogen atom represented by X ² include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

a represents an integer of 0 to 5. Among these, from the viewpoint of polymerizability, a is preferably from 0 to 3, more preferably from 0 to 2, and even more preferably 0. When a is 2 or more, the groups represented by X ² may be the same as or different from each other.

As for the structural unit (2) contained in the copolymer, only one kind may be contained alone, or two or more kinds may be contained in combination.

Next, the structure of the structural unit (3) is shown below.

In formula (3), X ³ and X ⁴ each independently represent a linear alkyl group, a branched alkyl group, or a cyclic alkyl group.

Examples of the linear alkyl group, branched alkyl group, or cyclic alkyl group represented by X ³ and X ⁴ include a linear alkyl group having 1 to 12 carbon atoms, a branched alkyl group having 3 to 12 carbon atoms, and a carbon number of 3 ˜12 cyclic alkyl groups. Specifically, the linear alkyl group having 1 to 12 carbon atoms specifically includes a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, and an n-hexyl group. Examples of the branched alkyl group having 3 to 12 carbon atoms include isopropyl group, isobutyl group, sec-butyl group, and tert-butyl group; examples of the cyclic alkyl group having 3 to 12 carbon atoms include , Cyclopropyl group, cyclobutyl group, cyclohexyl group and the like. Among these, from the viewpoint of solubility in a solvent, a sec-butyl group, a tert-butyl group, a cyclopropyl group, a cyclobutyl group, and a cyclohexyl group are preferable, and a tert-butyl group and a cyclohexyl group are more preferable.

As for the structural unit (3) contained in the copolymer, only one kind may be contained alone, or two or more kinds may be contained in combination.

In this embodiment, it is essential that at least one of X ¹ in formula (2) and X ³ and X ^{4 in} formula (3) is a cyclic alkyl group. Among these, at least 2 to 3 of X ¹ , X ³ , and X ⁴ are preferably cyclic alkyl groups, and more preferably 2 are cyclic alkyl groups. As described above, by including a structural unit having a cyclic alkyl group in at least a part of the copolymer constituting the retardation reducing agent, a higher retardation reduction effect can be obtained (that is, retardation reduction). The negative value of the intrinsic birefringence of the agent becomes smaller (the absolute value of the negative value becomes larger in the negative direction)). Although the mechanism by which the effect is obtained has not been clarified, the present inventors presume as follows. That is, when the side chain of the copolymer constituting the phase difference reducing agent includes a cyclic alkyl group, the cyclic alkyl groups tend to face in the direction perpendicular to the main chain due to steric hindrance due to their bulk. As a result, it is considered that a higher phase difference reduction effect can be obtained by developing birefringence in a direction perpendicular to the main chain.

When the retardation reducing agent is a copolymer having the structural unit (2) and the structural unit (3), the content ratio of each structural unit is not particularly limited, but improves the zero retardation in the optical film. From the viewpoint of reducing brittleness, the mass of the structural unit (2) part is 2 to 90% by mass relative to the total mass of the structural unit (2) part and the structural unit (3) part of 100% by mass. 3) The mass of the part is preferably 10 to 98% by mass, the mass of the structural unit (2) part is 5 to 70% by mass, and the mass of the structural unit (3) part is 30 to 95% by mass. More preferably, the mass of the structural unit (2) part is 10 to 70% by mass, the mass of the structural unit (3) part is 30 to 90% by mass, and the mass of the structural unit (2) part is 30 to 90% by mass. 60% by mass, quality of structural unit (3) Particularly preferably but 40 to 70 wt%, structural units (2) part of the mass of 40 to 55% by weight, and most preferred weight of the structural unit (3) moiety is 45 to 60 mass%. That is, a monomer represented by the following formula (2a) that is a raw material of the copolymer constituting the retardation reducing agent according to the present embodiment (hereinafter also referred to as “monomer (2a)”) and a formula (3a) The ratio of each of the monomer (2a) and the monomer (3a) to the total mass of 100% by mass of the monomer (hereinafter also referred to as “monomer (3a)”) is 2 to 90% by mass of the monomer (2a) (3a) is preferably 10 to 98% by mass, monomer (2a) is preferably 5 to 70% by mass, monomer (3a) is more preferably 30 to 95% by mass, and monomer (2a) is 10 to 98% by mass. More preferably, it is 70% by mass, and the monomer (3a) is 30 to 90% by mass, particularly the monomer (2a) is 30 to 60% by mass, and the monomer (3a) is 40 to 70% by mass. Preferred, monomers (2a) from 40 to 55% by weight, and most preferred monomer (3a) is 45 to 60 mass%.

In the formula (2a), the definitions of X ¹ , X ² and a are the same as those in the formula (2).

Examples of the monomer (2a) include methyl cinnamate, ethyl cinnamate, tert-butyl cinnamate, cyclohexyl cinnamate, methyl 4-methylcinnamate, ethyl 4-methylcinnamate, and 3,4-dimethyl. Examples include, but are not limited to, methyl cinnamate, 3,5-dimethylethyl cinnamate, and methyl 4-tert-butyl cinnamate.

Only one type of monomer (2a) may be used alone, or two or more types may be used in combination.

In formula (3a), the definitions of X ³ and X ⁴ are the same as in formula (3).

Examples of the monomer (3a) include, but are not limited to, di-sec-butyl fumarate, di-tert-butyl fumarate, dicyclopropyl fumarate, dicyclohexyl fumarate, and the like.

Only one type of monomer (3a) may be used alone, or two or more types may be used in combination.

The copolymer constituting the retardation reducing agent is derived from a monomer having at least one radical polymerizable group (hereinafter also referred to as “other monomer”) in addition to the structural unit (2) and the structural unit (3). You may further have a unit (henceforth "other structural unit"). By including other structural units, the solubility of the retardation reducing agent in the solvent can be improved.

Examples of monomers having at least one radical polymerizable group (other monomers) include the following monomers.

(1) Styrene monomer Styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-phenylstyrene, p-ethylstyrene, pn-butylstyrene, p-tert-butyl Styrene, pn-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene, 2,4-dimethyl styrene, divinylbenzene, dibilyl maleate Propanediol divinyl ether, etc.

(2) (Meth) acrylic acid ester monomers Methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate , Lauryl acrylate, phenyl acrylate phenyl, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, lauryl methacrylate , Phenyl methacrylate, diethylamino Noethyl methacrylate, dimethylaminoethyl methacrylate, isobornyl methacrylate, isobornyl acrylate, dicyclopentanyl methacrylate, dicyclopentanyl acrylate, 1,6-hexanediol diacrylate, tricyclodecane dimethanol methacrylate, trimethylolpropane Trimethacrylate, ethylene glycol dimethacrylate, ditrimethylolpropane tetraacrylate, etc.

(3) Olefins Ethylene, propylene, isobutylene, vinylcyclohexane and the like.

(4) Vinyl esters Vinyl propionate, vinyl acetate, vinyl benzoate and the like.

(5) Vinyl ethers Vinyl methyl ether, vinyl ethyl ether, vinyl cyclohexyl ether and the like.

(6) Vinyl ketones Vinyl methyl ketone, vinyl ethyl ketone, vinyl hexyl ketone and the like.

(7) N-vinyl compounds N-vinylcarbazole, N-vinylindole, N-vinylpyrrolidone and the like.

(8) Others Vinyl compounds such as butadiene, vinyl naphthalene, vinyl pyridine, acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, maleic anhydride, N-phenylmaleimide, N-cyclohexylmaleimide, etc. .

Among these, from the viewpoint of improving the retardation reduction effect, the monomer having at least one radical polymerizable group is preferably a (meth) acrylic acid ester monomer, an olefin, or a vinyl ether, and (meth) acrylic acid. An ester monomer is more preferable.

The other structural units contained in the copolymer may be contained alone or in combination of two or more.

In the case where the copolymer constituting the retardation reducing agent further includes other structural units, the content ratio of the other structural units is not particularly limited, but from the viewpoint of improving the solubility, the structural unit (2) portion In addition, with respect to 100 parts by mass of the total mass of the structural unit (3) part, the mass of the other structural unit parts is preferably 1 to 50 parts by mass, more preferably 3 to 40 parts by mass. The amount is more preferably 30 parts by mass, and particularly preferably 10 to 20 parts by mass.

The weight average molecular weight (Mw) of the retardation reducing agent is preferably 5000 to 300,000, more preferably 8000 to 100,000, from the viewpoint of solubility in a solvent and compatibility with a cycloolefin resin. More preferably, it is 10,000 to 80,000. In this specification, the weight average molecular weight (Mw) or the number average molecular weight (Mn) is a polystyrene equivalent value measured by gel permeation chromatography (GPC).

The content of the retardation reducing agent contained in the optical film is not particularly limited, but is 5 to 45% by mass with respect to 100% by mass of the total solid content of the optical film from the viewpoint of improving the zero retardation. It is preferably 10 to 30% by mass.

[Method for producing retardation reducing agent]
The retardation reducing agent according to this embodiment can be produced by appropriately referring to a conventionally known method. More specifically, it can be produced by polymerizing the monomer (2a) and the monomer (3a) and / or a monomer having at least one radical polymerizable group by radical polymerization.

The radical polymerization initiator used for radical polymerization is not particularly limited, and known compounds such as organic peroxides that generate free radicals and azobis-based radical polymerization initiators can be appropriately employed.

Organic peroxides include diacetyl peroxide, dibenzoyl peroxide (benzoyl peroxide), diisobutyroyl peroxide, di (2,4-dichlorobenzoyl) peroxide, di (3,5,5-trimethylhexanoyl) ) Diacyl peroxides such as peroxide, dioctanoyl peroxide, dilauroyl peroxide, distearoyl peroxide, bis {4- (m-toluoyl) benzoyl} peroxide;
Ketone peroxides such as methyl ethyl ketone peroxide, cyclohexanone peroxide, methylcyclohexanone peroxide, acetylacetone peroxide;
Hydrogen peroxide, tert-butyl hydroperoxide, α-cumene hydroperoxide, p-menthane hydroperoxide, diisopropylbenzene hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, tert-hexyl hydro Hydroperoxides such as peroxides;
Di-tert-butyl peroxide, dicumyl peroxide, dilauryl peroxide, α, α'-bis (tert-butylperoxy) diisopropylbenzene, 2,5-dimethyl-2,5-bis (tert-butyl peroxide) Dialkyl peroxides such as oxy) hexane, tert-butylcumyl peroxide, 2,5-dimethyl-2,5-bis (tert-butylperoxy) hexyne-3;
tert-butyl peroxyacetate, tert-butyl peroxypivalate, tert-hexyl peroxypivalate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, 2,5-dimethyl- 2,5-bis (2-ethylhexanoylperoxy) hexane, 1-cyclohexyl-1-methylethylperoxy-2-ethylhexanoate, tert-hexylperoxy-2-ethylhexanoate, tert-butyl Peroxy-2-ethylhexanoate, tert-butylperoxyisobutyrate, tert-butylperoxymaleate, tert-butylperoxy-3,5,5-trimethylhexanoate, tert-butylperoxylaur Rate, 2,5-dimethyl-2,5-bis (m Toluoylperoxy) hexane, α, α'-bis (neodecanoylperoxy) diisopropylbenzene, cumylperoxyneodecanoate, 1,1,3,3-tetramethylbutylperoxyneodecanoate, 1 -Cyclohexyl-1-methylethylperoxyneodecanoate, tert-hexylperoxyneodecanoate, tert-butylperoxyneodecanoate, tert-butylperoxybenzoate, tert-hexylperoxybenzoate, bis ( tert-butylperoxy) isophthalate, 2,5-dimethyl-2,5-bis (benzoylperoxy) hexane, tert-butylperoxy m-toluoyl benzoate, 3,3 ′, 4,4′-tetra ( tert-butylperoxycarbonyl) ben Peroxy esters such as phenone;
1,1-bis (tert-hexylperoxy) 3,3,5-trimethylcyclohexane, 1,1-bis (tert-hexylperoxy) cyclohexane, 1,1-bis (tert-butylperoxy) 3,3 , 5-trimethylcyclohexane, 1,1-bis (tert-butylperoxy) cyclohexane, 1,1-bis (tert-butylperoxy) cyclododecane, 2,2-bis (tert-butylperoxy) butane, n Peroxyketals such as butyl-4,4-bis (tert-butylperoxy) pivalate, 2,2-bis (4,4-di-tert-butylperoxycyclohexyl) propane;
Peroxymonocarbonates such as tert-hexylperoxyisopropyl monocarbonate, tert-butylperoxyisopropyl monocarbonate, tert-butylperoxy-2-ethylhexyl monocarbonate, tert-butylperoxyallyl monocarbonate;
Di-sec-butyl peroxydicarbonate, di-n-propyl peroxydicarbonate, diisopropyl peroxydicarbonate, bis (4-tert-butylcyclohexyl) peroxydicarbonate, di-2-ethoxyethyl peroxydicarbonate Peroxydicarbonates such as di-2-ethylhexyl peroxydicarbonate, di-2-methoxybutyl peroxydicarbonate, di (3-methyl-3-methoxybutyl) peroxydicarbonate;
Other examples include tert-butyltrimethylsilyl peroxide, but the organic peroxide used in the present invention is not limited to these exemplified compounds.

As the azobis-based radical polymerization initiator, azobisisobutyronitrile, azobisisovaleronitrile, 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2,2′-azobis (2 , 4-dimethylvaleronitrile), 2,2′-azobis (2-methylbutyronitrile), 1,1′-azobis (cyclohexane-1-carbonitrile), 2- (carbamoylazo) isobutyronitrile, , 2′-azobis [2-methyl-N- {1,1-bis (hydroxymethyl) -2-hydroxyethyl} propionamide], 2,2′-azobis [2-methyl-N- {2- (1 -Hydroxybutyl)} propionamide], 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) -propionamide], 2,2′-azo [N- (2-propenyl) -2-methylpropionamide], 2,2′-azobis (N-butyl-2-methylpropionamide), 2,2′-azobis (N-cyclohexyl-2-methylpropion) Amide), 2,2′-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride, 2,2′-azobis [2- (2-imidazolin-2-yl) propane Dihydrochloride, 2,2′-azobis [2- (2-imidazolin-2-yl) propane] disulfate dihydrate, 2,2′-azobis [2- (3,4,5,6-tetrahydropyrimidine -2-yl) propane] dihydrochloride, 2,2′-azobis [2- {1- (2-hydroxyethyl) -2-imidazolin-2-yl} propyl Pan] dihydrochloride, 2,2′-azobis [2- (2-imidazolin-2-yl) propane], 2,2′-azobis (2-methylpropionamidine) dihydrochloride, 2,2′-azobis [N- (2-carboxyethyl) -2-methyl-propionamidine], 2,2′-azobis (2-methylpropionamidoxime), dimethyl 2,2′-azobisbutyrate, 4,4′-azobis ( 4-cyanopentanoic acid), 2,2′-azobis (2,4,4-trimethylpentane), 1,1′-azobis (1-acetoxy-1-phenylethane), dimethyl 2,2′-azo Bisisobutyrate (2,2′-azobis (isobutyric acid) dimethyl) and the like, and the azobis radical polymerization initiator used in the present invention is It is not limited to these exemplified compounds.

The amount of the radical polymerization initiator used is usually 0.01 to 20 mol%, preferably 0.05 to 10 mol%, preferably 0.1 to 5 mol%, based on 100 mol% of the total amount of monomers. preferable.

A catalyst may be used for radical polymerization. A catalyst is not specifically limited, For example, a well-known anion polymerization catalyst, a coordination polymerization catalyst, a cationic polymerization catalyst etc. are mentioned.

In radical polymerization, in the presence of a radical polymerization initiator or a catalyst, the above monomers are mixed with conventional monomers such as bulk polymerization, solution polymerization, precipitation polymerization, emulsion polymerization, suspension polymerization, or bulk-suspension polymerization. It is carried out by copolymerization by a known method.

[Core-shell type particles]
The optical film according to the present invention includes core-shell type particles in which the glass transition temperature of the polymer forming the shell is higher by 150 ° C. or more and 290 ° C. or less than the glass transition temperature of the polymer forming the core. By including such core-shell type particles, the intermolecular interaction between the cycloolefin resin and the retardation reducing agent is moderately relaxed, and the adhesiveness between the polarizer and the retardation reducing agent is improved and the brittleness is improved. It is thought that it is done.

The core-shell type particle has at least a shell that forms a surface and a core that is covered with the shell and forms a central portion of the particle. The core-shell type particles are not limited to a structure in which the shell completely covers the core, and may have a structure in which the core is partially exposed. Hereinafter, each part (core, shell) will be described in detail.

(core)
The core is preferably an elastic core having properties as a rubber in order to moderately relax the intermolecular interaction between the cycloolefin-based resin and the retardation reducing agent, and to improve adhesion and brittleness. In order to have properties as rubber, the gel content is preferably 60% by mass or more, more preferably 80% by mass or more, further preferably 90% by mass or more, and 95% by mass or more. It is particularly preferred. In addition, the gel content referred to in the present specification means that 0.5 g of crumb obtained by coagulation and drying is immersed in 100 g of toluene and left to stand at 23 ° C. for 24 hours, and then insoluble and soluble components are separated. The ratio of insoluble matter to the total amount of insoluble matter and soluble matter is meant.

As a polymer capable of forming an elastic core having properties as a rubber, at least one monomer (first monomer) selected from natural rubber and diene monomers (conjugated diene monomers) and (meth) acrylate monomers is used. A rubber elastic body comprising 50 to 100% by mass and 0 to 50% by mass of other copolymerizable vinyl monomer (second monomer), a polysiloxane rubber elastic body, or a combination thereof Is mentioned. Among these, a diene rubber using a diene monomer is preferable. The elastic core is also preferably a (meth) acrylate rubber or a polysiloxane rubber elastic body. In the present invention, (meth) acrylate means acrylate and / or methacrylate.

Examples of the monomer (conjugated diene monomer) constituting the diene rubber used for the elastic core include 1,3-butadiene, 2-chloro-1,3-butadiene, and 2-methyl-1,3-butadiene (isoprene). Etc. These diene monomers may be used alone or in combination of two or more.

1,3-butadiene rubber, which is a polymer of 1,3-butadiene, in order to moderately relax the intermolecular interaction between the cycloolefin resin and the retardation reducing agent, and to improve adhesion and brittleness, or A butadiene-styrene rubber which is a copolymer of 1,3-butadiene and styrene is preferable, and 1,3-butadiene rubber is more preferable.

Examples of the monomer constituting the (meth) acrylate rubber used for the elastic core include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and octyl (meta). ) Acrylates, alkyl (meth) acrylates such as dodecyl (meth) acrylate, stearyl (meth) acrylate, behenyl (meth) acrylate; aromatic ring-containing (meth) acrylates such as phenoxyethyl (meth) acrylate and benzyl (meth) acrylate Hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate; glycidyl (meth) acrylate and glycidylalkyl (meth) acrylate Glycidyl (meth) acrylates such as alkoxide; alkoxyalkyl (meth) acrylates; allylalkyl (meth) acrylates such as allyl (meth) acrylate and allylalkyl (meth) acrylate; monoethylene glycol di (meth) acrylate, Examples include polyfunctional (meth) acrylates such as triethylene glycol di (meth) acrylate and tetraethylene glycol di (meth) acrylate. These (meth) acrylate monomers may be used alone or in combination of two or more. Particularly preferred are ethyl (meth) acrylate, butyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate.

Examples of the vinyl monomer (second monomer) copolymerizable with the first monomer include vinyl arenes such as styrene, α-methyl styrene, monochlorostyrene and dichlorostyrene; vinyl carboxylic acids such as acrylic acid and methacrylic acid. Vinyl vinyls such as acrylonitrile and methacrylonitrile; vinyl halides such as vinyl chloride, vinyl bromide and chloroprene; vinyl acetate; alkenes such as ethylene, propylene, butylene and isobutylene; diallyl phthalate, triallyl cyanurate, And polyfunctional monomers such as triallyl isocyanurate and divinylbenzene. These vinyl monomers may be used alone or in combination of two or more. Particularly preferred is styrene.

The above copolymerizable vinyl monomer can be contained in the range of 0 to 50% by mass of the core, preferably in the range of 0 to 30% by mass, more preferably in the range of 0 to 10% by mass.

Examples of the polysiloxane rubber elastic body that can constitute the elastic core include alkyl or aryl 2 such as dimethylpolysiloxane, diethylpolysiloxane, methylphenylpolysiloxane, diphenylpolysiloxane, dimethylpolysiloxane-diphenylpolysiloxane, and the like. Polysiloxane polymers composed of alkyl or aryl 1-substituted silyloxy units, such as polysiloxane polymers composed of substituted silyloxy units and organohydrogenpolysiloxanes in which part of the side chain alkyl is substituted with hydrogen atoms Is mentioned. These polysiloxane polymers may be used alone or in combination of two or more. Of these, dimethylpolysiloxane, methylphenylpolysiloxane, and dimethylpolysiloxane-diphenylpolysiloxane are preferable for imparting heat resistance to the cured product, and dimethylpolysiloxane is most preferable because it is easily available and economical.

In an embodiment in which the elastic core is formed from a polysiloxane rubber elastic body, the polysiloxane polymer portion is 80% by mass or more (more preferably) in order not to impair the heat resistance of the cured product. 90% by mass or more) is preferable.

The glass transition temperature (Tg) of the polymer forming the core is preferably 0 ° C. or less, more preferably −20 ° C. or less, and further preferably −40 ° C. or less, from the viewpoint of improving the adhesiveness and brittleness of the optical film. The temperature is preferably −60 ° C. or less. In addition, in this specification, the value measured by the method described in the below-mentioned Example is employ | adopted for glass transition temperature (Tg).

The volume average particle diameter (Mv) of the core (hereinafter also simply referred to as “particle diameter”) is preferably 0.03 to 1 μm, more preferably 0.05 to 0.5 μm, and even more preferably 0.07 to 0.3 μm. . A volume average particle diameter of 0.03 μm or more is preferable in that it is easy to obtain homogeneous core particles. On the other hand, when it is 1 μm or less, it is preferable in that it is easy to obtain the brittle improvement effect. In addition, in this specification, the value measured by the method described in the below-mentioned Example is employ | adopted for a volume average particle diameter.

The mass of the core is preferably 40 to 97% by mass, more preferably 60 to 95% by mass, still more preferably 70 to 93% by mass, and more preferably 80 to 90% by mass with respect to 100% by mass of the total mass of the core-shell particles. Particularly preferred. When the core is 40% by mass or more, the effect of improving adhesiveness and improving brittleness is satisfactorily exhibited in the optical film. On the other hand, when the core is 97% by mass or less, aggregation of the core-shell type particles is suppressed, and it is possible to prevent the dope when manufacturing the optical film from becoming highly viscous and difficult to handle.

(shell)
The shell exists on the outermost side (surface) of the core-shell type particle. The shell is made of a material having a glass transition temperature higher by 150 ° C. or more and 290 ° C. or less than the core. Thus, when the core (elastic core) is covered with a material having a high glass transition temperature (that is, a hard material), the intermolecular interaction between the cycloolefin resin and the phase difference reducing agent can be moderately moderated. Conceivable.

The covering form of the shell may be physically adsorbed to the core or chemically bonded, but is preferably chemically bonded. The core-shell type particles in a form in which the shell and the core are chemically bonded are obtained by polymerizing a monomer (shell-forming monomer) that is a constituent component of the shell with a latex containing a polymer that forms the core. Can do.

Examples of the shell-forming monomer include aromatic vinyl monomers, vinyl cyan monomers, (meth) acrylate monomers, and nitrogen-containing vinyl monomers from the viewpoint of glass transition temperature and the like. These shell-forming monomers may be used alone or in appropriate combination.

Specific examples of the aromatic vinyl monomer include vinylbenzenes such as styrene, α-methylstyrene, p-methylstyrene, o-hydroxystyrene, m-hydroxystyrene, p-hydroxystyrene, divinylbenzene and the like.

Specific examples of the vinylcyan monomer include acrylonitrile or methacrylonitrile.

Specific examples of the (meth) acrylate monomer include (meth) acrylic acid alkyl esters such as methyl (meth) acrylate, ethyl (meth) acrylate, and butyl (meth) acrylate; hydroxyethyl (meth) acrylate and hydroxybutyl (meth) Examples include (meth) acrylic acid hydroxyalkyl esters such as acrylate.

Specific examples of the nitrogen-containing cyclic vinyl monomer include N-vinyl-2-pyrrolidone and N-vinyl-ε-caprolactam.

In addition to the above, a polymer having a structural unit represented by the following formula disclosed in JP-A-2008-179677 can also be used.

In the formula, R ¹ , R ² and R ³ are each independently a hydrogen atom or an organic residue having 1 to 20 carbon atoms (for example, methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, Represents an alkyl group having 1 to 20 carbon atoms such as an isobutyl group, a t-butyl group, and a cyclohexyl group; and the organic residue contains hydrogen, oxygen, nitrogen, sulfur, phosphorus, and halogen atoms. May be.

Among these, the shell is preferably composed of a polymer having a structural unit containing an aromatic ring having a hydroxyl group or a structural unit containing a nitrogen-containing ring. More specifically, the shell-forming monomer is an aromatic vinyl monomer having a hydroxyl group such as o-hydroxystyrene, m-hydroxystyrene, p-hydroxystyrene; N-vinyl-2-pyrrolidone, N-vinyl-ε Nitrogen-containing ring vinyl monomers such as caprolactam are preferable, and nitrogen-containing ring vinyl monomers such as N-vinyl-2-pyrrolidone and N-vinyl-ε-caprolactam are more preferable. By including such a structural unit having a hetero atom (oxygen atom or nitrogen atom), the rigidity of the core-shell particle is improved, and it acts on the bulky cyclic alkyl group portion of the cycloolefin resin or retardation reducing agent. Thereby, the resin density of the film surface can be lowered and the penetration of the adhesive can be promoted.

The glass transition temperature (Tg) of the polymer forming the shell is preferably 100 ° C. or higher, more preferably 130 ° C. or higher, and even more preferably 160 ° C. or higher, from the viewpoint of improving the adhesiveness and brittleness of the optical film.

The core-shell type particle according to this embodiment requires that the glass transition temperature of the polymer forming the shell is 150 ° C. or more and 290 ° C. or less higher than the glass transition temperature of the polymer forming the core. It is preferable that the temperature is 170 ° C. or higher and 270 ° C. or lower. When the difference in the glass transition temperature (shell-core) is less than 150 ° C., for example, the glass transition temperature of the shell is low, so that there is a possibility that the optical film is not suitable for film formation. Further, when the difference in the glass transition temperature (shell-core) exceeds 290 ° C., for example, due to the high glass transition temperature of the shell (the shell is hard), the cycloolefin resin and the retardation reducing agent The intermolecular interaction with can not be sufficiently reduced, and there is a possibility that the effect of improving adhesiveness and improving brittleness cannot be sufficiently exhibited. In addition, the compatibility between the cycloolefin resin and the retardation reducing agent may be deteriorated.

The content of the core-shell type particles contained in the optical film is not particularly limited, but is preferably 1 to 35% by mass with respect to 100% by mass of the total solid content of the optical film, and preferably 3 to 10% by mass. It is more preferable. When the content of the core-shell type particle is 1% by mass or more, the adhesiveness and brittleness of the optical film can be sufficiently improved. On the other hand, when the content is 35% by mass or less, it is possible to prevent a part from agglomerating and light scattering due to too many core-shell particles, thereby impairing transparency.

[Method for producing core-shell particles]
(Core manufacturing method)
When the polymer forming the core constituting the core-shell type particle includes at least one monomer (first monomer) selected from a diene monomer (conjugated diene monomer) and a (meth) acrylate monomer The core can be formed, for example, by emulsion polymerization, suspension polymerization, microsuspension polymerization, or the like. For example, the method described in International Publication No. 2005/028546 can be used.

When the polymer forming the core is composed of a polysiloxane-based polymer, the core can be formed by, for example, emulsion polymerization, suspension polymerization, microsuspension polymerization, etc. The method described in No. 2006/070664 can be used.

(Shell formation method)
The shell can be formed by polymerizing a shell-forming monomer by known radical polymerization. When the core is obtained as an emulsion, the polymerization of the shell-forming monomer is preferably carried out by an emulsion polymerization method, and can be produced, for example, according to the method described in International Publication No. 2005/0285546.

As an emulsifier (dispersant) that can be used in emulsion polymerization, alkyl or aryl sulfonic acid represented by dioctyl sulfosuccinic acid and dodecylbenzene sulfonic acid, alkyl or aryl ether sulfonic acid, alkyl or aryl represented by dodecyl sulfate, and the like. Sulfuric acid, alkyl or aryl ether sulfuric acid, alkyl or aryl substituted phosphoric acid, alkyl or aryl ether substituted phosphoric acid, N-alkyl or aryl sarcosine acid typified by dodecyl sarcosine acid, oleic acid and stearic acid Various acids such as alkyl or aryl carboxylic acids, alkyl or aryl ether carboxylic acids, anionic emulsifiers (dispersing agents) such as alkali metal salts or ammonium salts of these acids; alkyl or aryl substituted polyethylene Nonionic emulsifiers such as glycol (dispersing agent); polyvinyl alcohol, alkyl substituted cellulose, polyvinyl pyrrolidone, dispersants such as polyacrylic acid derivatives. These emulsifiers (dispersants) may be used alone or in combination of two or more.

It is preferable to reduce the amount of emulsifier (dispersant) used so long as the dispersion stability of the aqueous latex of core-shell particles is not hindered. Moreover, an emulsifier (dispersant) is so preferable that the water solubility is high. If the water solubility is high, the emulsifier (dispersant) can be easily removed by washing with water, and adverse effects on the finally obtained cured product can be easily prevented.

When the emulsion polymerization method is employed, a known initiator, that is, 2,2′-azobisisobutyronitrile, hydrogen peroxide, potassium persulfate, ammonium persulfate, or the like can be used as the thermal decomposition type initiator. .

Organic peroxides such as tert-butylperoxyisopropyl carbonate, paramentane hydroperoxide, cumene hydroperoxide, dicumyl peroxide, tert-butyl hydroperoxide, di-tert-butyl peroxide, tert-hexyl peroxide, etc. Oxides; peroxides such as inorganic peroxides such as hydrogen peroxide, potassium persulfate, and ammonium persulfate; reducing agents such as sodium formaldehyde sulfoxylate and glucose as necessary; and iron sulfate (II as necessary) ) And other transition metal salts, and if necessary, a chelating agent such as ethylenediaminetetraacetic acid disodium, and if necessary, a redox initiator using a phosphorus-containing compound such as sodium pyrophosphate. Kill.

When a redox type initiator system is used, the polymerization can be performed at a low temperature at which the peroxide is not substantially thermally decomposed, and the polymerization temperature can be set in a wide range, which is preferable. Of these, organic peroxides such as cumene hydroperoxide, dicumyl peroxide, and tert-butyl hydroperoxide are preferably used as the redox initiator. When the amount of the initiator used, or the redox type initiator is used, the amount of the reducing agent / transition metal salt / chelating agent used may be within a known range. In the polymerization of a monomer having two or more radical polymerizable double bonds, a known chain transfer agent can be used within a known range. In addition, a surfactant can be used, but this is also within a known range. The polymerization temperature, pressure, deoxygenation, and other conditions during the polymerization can be within the known ranges.

In the optical film according to the present embodiment, the content of the core-shell type particles is not particularly limited, but is 3 parts by mass to 50 parts by mass with respect to 100 parts by mass of the total mass of the cycloolefin resin and the phase difference reducing agent. It is preferably 5 to 40 parts by mass, more preferably 10 to 30 parts by mass. When the content of the core-shell type particles is 3 parts by mass or more, the effects of the present invention, that is, the improvement in adhesiveness and the improvement in brittleness are satisfactorily exhibited. On the other hand, when the content of the core-shell type particles is 50 parts by mass or less, it is possible to prevent a part of the core-shell type particles from agglomerating and light scattering to impair the transparency.

The particle diameter of the core-shell type particle is not particularly limited, but the volume average particle diameter (Mv) is preferably 0.05 to 1.1 μm, more preferably 0.07 to 0.7 μm, and further preferably 0.1 to 0.5 μm. preferable. A volume average particle diameter of 0.05 μm or more is preferable in terms of improving adhesiveness. On the other hand, if it is 1.1 μm or less, it is preferable in terms of improving brittleness.

[Additive]
The optical film may contain the following additives (mat agent, plasticizer, ultraviolet absorber) in addition to the retardation reducing agent and the resin.

(Matting agent)
The optical film preferably contains a matting agent in order to prevent the manufactured optical film from being damaged and the transportability from being deteriorated. As the matting agent, it is particularly preferable to contain silica particles.

Silica particles are particles mainly composed of silicon dioxide. The main component means to contain 50% or more of the components constituting the particles, preferably 70% or more, more preferably 80% or more, and particularly preferably 90% or more.

It is also preferable to add fine particles of silicon dioxide-based particles whose surface has been hydrophobized by alkylation treatment, since the dispersibility in a solvent is good and the generation of foreign matters can be suppressed.

The hydrophobization treatment for the silica particles is preferably an alkylation treatment. The surface of the alkylated fine particles has an alkyl group, and the alkyl group preferably has 1 to 20 carbon atoms, more preferably 1 to 12 carbon atoms, and particularly preferably The range is from 1 to 8 carbon atoms.

Silica particles having an alkyl group having 1 to 20 carbon atoms on the surface can be obtained, for example, by treating silicon dioxide particles with alkylsilane. Moreover, as an example of what has an alkyl group on the surface, it is marketed by the brand name (Aerosil is a registered trademark) of Aerosil R812 (made by Nippon Aerosil Co., Ltd.), and is preferably used.

The average particle size of the primary particles of the silica particles is preferably within the range of 5 to 400 nm, and more preferably within the range of 10 to 300 nm.

The average particle diameter of the secondary particles of the silica particles is preferably in the range of 100 to 400 nm, and if it is in the range of 100 to 400 nm, it is also preferable that they are contained as primary particles without agglomeration.

As the silica particles, commercially available products can be preferably used. Besides the above-mentioned Aerosil R812, for example, Aerosil R972, R972V, R974, R976S, R805, R812S, RY300, 300, R202, OX50, TT600 (above, Nippon Aerosil Co., Ltd.) Company name) (Aerosil is a registered trademark) and can be used.

Among these, Aerosil R805, R812, and R976S are preferable because they can improve the handleability during handling and keep the haze of the optical film low.

(Plasticizer)
Examples of the plasticizer include polyester, polyhydric alcohol ester, polyvalent carboxylic acid ester (including phthalic acid ester), glycolate, and ester (including fatty acid ester and phosphoric acid ester). Especially, it is preferable that it is polyester containing the repeating unit obtained by making dicarboxylic acid and diol react. These may be used alone or in combination of two or more.

The dicarboxylic acid constituting the polyester is an aromatic dicarboxylic acid, an aliphatic dicarboxylic acid or an alicyclic dicarboxylic acid, preferably an aromatic dicarboxylic acid. The dicarboxylic acid may be one type or a mixture of two or more types.

The diol constituting the polyester is an aromatic diol, an aliphatic diol or an alicyclic diol, preferably an aliphatic diol, and more preferably a diol having 1 to 4 carbon atoms. The diol may be one type or a mixture of two or more types.

Among these, the polyester preferably contains a repeating unit obtained by reacting at least a dicarboxylic acid containing an aromatic dicarboxylic acid and a diol having 1 to 4 carbon atoms. The polyester contains an aromatic dicarboxylic acid and an aliphatic dicarboxylic acid. More preferably, it contains a repeating unit obtained by reacting a dicarboxylic acid containing with a diol having 1 to 4 carbon atoms.

Both ends of the polyester molecules may or may not be sealed, but are preferably sealed from the viewpoint of reducing the moisture permeability of the optical film.

Further, the polyhydric alcohol ester is an ester (alcohol ester) of a dihydric or higher aliphatic polyhydric alcohol and a monocarboxylic acid, preferably a divalent to 20-valent aliphatic polyhydric alcohol ester. The polyhydric alcohol ester preferably has an aromatic ring or a cycloalkyl ring in the molecule.

Preferred examples of the aliphatic polyhydric alcohol include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1,2- Butanediol, 1,3-butanediol, 1,4-butanediol, dibutylene glycol, 1,2,4-butanetriol, 1,5-pentanediol, 1,6-hexanediol, hexanetriol, trimethylolpropane , Pentaerythritol, trimethylolethane, xylitol and the like. Of these, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, sorbitol, trimethylolpropane, xylitol and the like are preferable.

The monocarboxylic acid is not particularly limited, and may be an aliphatic monocarboxylic acid, an alicyclic monocarboxylic acid, an aromatic monocarboxylic acid, or the like. In order to increase the moisture permeability of the optical film and make it difficult to volatilize, alicyclic monocarboxylic acid or aromatic monocarboxylic acid is preferred. One type of monocarboxylic acid may be sufficient and a 2 or more types of mixture may be sufficient as it. Further, all of the OH groups contained in the aliphatic polyhydric alcohol may be esterified, or a part of the OH groups may be left as they are.

The aliphatic monocarboxylic acid is preferably a fatty acid having a straight chain or a side chain having 1 to 32 carbon atoms. The number of carbon atoms of the aliphatic monocarboxylic acid is more preferably 1-20, and still more preferably 1-10. Examples of aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanoic acid, undecylic acid, lauric acid, tridecylic acid Saturated fatty acids such as myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, melicic acid, and laccelic acid; undecylenic acid, Examples include unsaturated fatty acids such as oleic acid, sorbic acid, linoleic acid, linolenic acid, and arachidonic acid.

Examples of the alicyclic monocarboxylic acid include cyclopentane carboxylic acid, cyclohexane carboxylic acid, cyclooctane carboxylic acid and the like.

Examples of aromatic monocarboxylic acids include benzoic acid; one having 1 to 3 alkyl groups or alkoxy groups (for example, methoxy group or ethoxy group) introduced into the benzene ring of benzoic acid (for example, toluic acid); Aromatic monocarboxylic acids having two or more benzene rings (for example, biphenylcarboxylic acid, naphthalenecarboxylic acid, tetralincarboxylic acid, etc.) are included, and benzoic acid is preferable.

Specific examples of the polyhydric alcohol ester include compounds described in paragraphs “0058” to “0061” of JP-A-2006-113239.

The polyvalent carboxylic acid ester is an ester of a divalent or higher, preferably 2 to 20 valent polycarboxylic acid and an alcohol. The polyvalent carboxylic acid is preferably a divalent to 20-valent aliphatic polyvalent carboxylic acid, a 3- to 20-valent aromatic polyvalent carboxylic acid, or a 3- to 20-valent alicyclic polyvalent carboxylic acid. .

Examples of polycarboxylic acid esters include triethyl citrate, tributyl citrate, acetyl triethyl citrate (ATEC), acetyl tributyl citrate (ATBC), benzoyl tributyl citrate, acetyl triphenyl citrate, acetyl tribenzyl citrate , Dibutyl tartrate, diacetyl dibutyl tartrate, tributyl trimellitic acid, tetrabutyl pyromellitic acid and the like.

Examples of glycolates include alkyl phthalyl alkyl glycolates. Examples of alkyl phthalyl alkyl glycolates include methyl phthalyl methyl glycolate, ethyl phthalyl ethyl glycolate, propyl phthalyl propyl glycolate, butyl phthalyl butyl glycolate, octyl phthalyl octyl glycolate, methyl phthalyl Ethyl glycolate, ethyl phthalyl methyl glycolate, ethyl phthalyl propyl glycolate, methyl phthalyl butyl glycolate, ethyl phthalyl butyl glycolate, butyl phthalyl methyl glycolate, butyl phthalyl ethyl glycolate, propyl phthalyl butyl Glycolate, butyl phthalyl propyl glycolate, methyl phthalyl octyl glycolate, ethyl phthalyl octyl glycolate, octyl phthalyl methyl glycolate, octyl phthalyl ethyl Glycolate and the like, preferably ethyl phthalyl ethyl glycolate.

Esters include fatty acid esters, citrate esters and phosphate esters. Examples of the fatty acid ester include butyl oleate, methylacetyl ricinoleate, and dibutyl sebacate. Examples of the citrate ester include acetyltrimethyl citrate, acetyltriethyl citrate, and acetyltributyl citrate. Examples of the phosphate ester include triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, biphenyl diphenyl phosphate, trioctyl phosphate, tributyl phosphate, and the like, and preferably triphenyl phosphate.

Of these, polyester, glycolate, and phosphate ester are preferable, and polyester is particularly preferable.

The content of the plasticizer is preferably in the range of 1 to 20 parts by mass, more preferably in the range of 1.5 to 15 parts by mass with respect to 100 parts by mass of the resin (particularly cycloolefin resin). When the content of the plasticizer is within the above range, the effect of imparting plasticity can be exhibited, and the resistance to the plasticizer from seeping out from the optical film is excellent.

(UV absorber)
The optical film preferably contains an ultraviolet absorber in order to shield unnecessary ultraviolet rays irradiated to the polarizing plate and the liquid crystal display device. By containing the ultraviolet absorber, the deterioration of the liquid crystal molecules in the liquid crystal cell can be prevented, so that the polarizing function can be maintained even when the polarizing plate or the display device is exposed to sunlight or the like for a long time.

Examples of ultraviolet absorbers include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and the like, but less benzotriazole compounds Compounds are preferred. Further, ultraviolet absorbers described in JP-A-10-182621 and JP-A-8-337574 and polymer ultraviolet absorbers described in JP-A-6-148430 are preferably used.

When the optical film is used as a protective film for a polarizing plate in addition to the optical compensation film, the ultraviolet absorber is excellent in the ability to absorb ultraviolet rays having a wavelength of 370 nm or less and a liquid crystal from the viewpoint of preventing deterioration of a polarizer and liquid crystal. From the viewpoint of display properties, it is preferable to have a characteristic that the absorption of visible light having a wavelength of 400 nm or more is small.

The addition amount of the ultraviolet absorber is preferably in the range of 0.1 to 5.0 parts by mass, preferably 0.5 to 3.0 parts by mass with respect to 100 parts by mass of the total solid content in the optical film. More preferably, it is in the range.

Examples of the benzotriazole ultraviolet absorber include 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2- (2′-hydroxy-3 ′, 5′-di-tert-butylphenyl) benzo Triazole, 2- (2′-hydroxy-3′-tert-butyl-5′-methylphenyl) benzotriazole, 2- (2′-hydroxy-3 ′, 5′-di-tert-butylphenyl) -5 Chlorobenzotriazole, 2- [2′-hydroxy-3 ′-(3 ″, 4 ″, 5 ″, 6 ″ -tetrahydrophthalimidomethyl) -5′-methylphenyl] benzotriazole, 2,2- Methylenebis [4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol], 2- (2′- Droxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2H-benzotriazol-2-yl) -6- (straight and side chain dodecyl) -4-methylphenol Octyl-3- [3-tert-butyl-4-hydroxy-5- (chloro-2H-benzotriazol-2-yl) phenyl] propionate and 2-ethylhexyl-3- [3-tert-butyl-4-hydroxy Examples include, but are not limited to, a mixture of -5- (5-chloro-2H-benzotriazol-2-yl) phenyl] propionate.

Also, as commercially available products, “TINUVIN 109”, “TINUVIN 171”, “TINUVIN 326”, “TINUVIN 328”, “TINUVIN 928” (above, trade names, BASF Japan) (TINUVIN is a registered trademark) can be preferably used.

<Physical properties of optical film>
[Haze]
The optical film preferably has a haze of less than 1%, and more preferably less than 0.5%. By setting the haze to less than 1%, there is an advantage that the transparency of the optical film becomes higher and it becomes easier to use as a film for optical applications. In the optical film, when a matting agent is used, it is preferable to disperse and use silica particles having a uniform particle diameter from the viewpoint of haze. Thereby, the grade of the light scattering by particle | grains can be made low and the optical film excellent in transparency can be obtained. In addition, in this specification, the value measured by the method as described in the below-mentioned Example is employ | adopted for haze.

[Film length, width, film thickness]
The optical film is preferably long, specifically, preferably has a length of about 100 to 40,000 m, and is wound into a roll. The width of the optical film is preferably 1 m or more, more preferably 1.3 m or more, and particularly preferably 1.3 to 4 m.

The film thickness of the stretched optical film is in the range of 5 to 20 μm. More preferably, it is 10 to 15 μm. If a film thickness is 5 micrometers or more, the optical film intensity | strength more than fixed can be expressed, and it is preferable from a viewpoint of crack tolerance. If the film thickness is 20 μm or less, it can be applied to make the polarizing plate and the display device thinner. In particular, when the optical film contains a cycloolefin-based resin, even a thin film has good crack resistance, and variation in retardation due to the location of the optical film surface can be reduced.

<Method for producing optical film>
Although there is no restriction | limiting in particular in the manufacturing method of the optical film which concerns on this form, Since it is easy to manufacture the film of a transparent thin film, manufacturing by the solution casting film forming method is preferable.

In particular, when a thin optical film of a cycloolefin resin is produced by a solution casting film forming method, the resin chains are loosened more than the melt casting, so that the entanglement between the resin chains is large. As a result, it is estimated that compatibility is improved and a transparent film can be produced.

In forming a film by the solution casting film forming method, after the core-shell type particles are previously dispersed in a cycloolefin-based resin to obtain a dispersion, a dope containing the dispersion, a retardation reducing agent, and an organic solvent is obtained. It is preferable to prepare the solution within a range of 15 to 50 ° C.

The optical film includes a step of preparing a dope containing a dispersion in which at least core-shell type particles are previously dispersed in a cycloolefin resin and a retardation reducing agent (dope preparation step), and casting the dope on a support. Forming a web (also called casting film) (casting process), evaporating the solvent from the web on the support (solvent evaporation process), and peeling the web from the support (peeling process). And a step of drying the obtained optical film (preliminary drying step), a step of further drying the optical film after stretching (drying step), a step of winding up the obtained optical film (winding step), It is preferable that it is manufactured by. Moreover, in consideration of the removal efficiency from the produced optical film roll, a step (stretching step) of stretching the optical film may be provided after the preliminary drying step and then stretched.

[Dope preparation process]
Examples of the solvent used in the solution casting method include chlorinated solvents such as chloroform and dichloromethane; aromatic solvents such as toluene, xylene, benzene, and mixed solvents thereof; methanol, ethanol, isopropanol, n-butanol, Examples thereof include alcohol solvents such as 2-butanol; methyl cellosolve, ethyl cellosolve, butyl cellosolve, dimethylformamide, dimethyl sulfoxide, dioxane, cyclohexanone, tetrahydrofuran, acetone, methyl ethyl ketone (MEK), ethyl acetate, and diethyl ether. These solvents may be used alone or in combination of two or more.

When the solvent is a mixed solvent of a good solvent and a poor solvent, the good solvent is, for example, dichloromethane as a chlorinated organic solvent, methyl acetate, ethyl acetate, amyl acetate, acetone, methyl ethyl ketone, as a non-chlorine organic solvent, Tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, cyclohexanone, ethyl formate, 2,2,2-trifluoroethanol, 2,2,3,3-hexafluoro-1-propanol, 1,3-difluoro- 2-propanol, 1,1,1,3,3,3-hexafluoro-2-methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2, Examples include 3,3,3-pentafluoro-1-propanol, nitroethane, and the like. Among them, dichloromethane is preferable. As the poor solvent, an alcohol solvent is preferably used. Especially, it is preferable to select from methanol, ethanol, and butanol from a viewpoint which improves peelability and enables high-speed casting, and is more preferable than ethanol.

When the solvent is a mixed solvent of a good solvent and a poor solvent, it is preferable to use 55% by mass or more, and 70% by mass or more of the good solvent with respect to the total amount of the solvent, from the viewpoint of easily obtaining a uniform dope. It is preferable to use 80% by mass or more.

[Casting process]
The dope is fed to a pressure die through a liquid feed pump (for example, a pressurized metering gear pump) and transferred to an endless metal support such as a stainless steel belt or a metal support such as a rotating metal drum. It is a step of casting a web from a pressure die slit at a casting position.

[Solvent evaporation step]
It is a step of heating the web on the metal support for casting and evaporating the solvent, and is a step of controlling the amount of residual solvent at the time of peeling described later.

To evaporate the solvent, there are a method of blowing air from the web side, a method of transferring heat from the back side of the support, a method of transferring heat from the front and back by radiant heat, etc. Is preferable.

[Peeling process]
In this step, the web in which the solvent is evaporated on the metal support is peeled at the peeling position. The peeled web is sent to the next step as an optical film.

The temperature at the peeling position on the metal support is preferably in the range of 10 to 40 ° C, more preferably in the range of 11 to 30 ° C.

The residual solvent amount of the web on the metal support at the time of peeling is preferably in the range of 15 to 100 parts by mass with respect to 100 parts by mass of the solid content of the web. The residual solvent amount is preferably controlled by the drying temperature and drying time in the solvent evaporation step. When the residual solvent amount is 15 parts by mass or more, the silica particles do not have a distribution in the thickness direction and are uniformly dispersed in the optical film in the drying process on the support, which is preferable. Further, if the amount of residual solvent is within 100 parts by mass, the optical film has self-supporting properties, can avoid poor peeling of the optical film, and can maintain the mechanical strength of the web, thus improving the flatness at the time of peeling. , It is possible to suppress occurrence of slippage and vertical stripes due to peeling tension.

[Drying and stretching process]
A drying process can also be performed by dividing into a preliminary drying process and a main drying process.

The optical film obtained by peeling the web from the metal support is preliminarily dried. The preliminary drying of the optical film may be performed while the optical film is transported by a large number of rollers arranged above and below, or is dried while being transported by fixing both ends of the optical film with clips like a tenter dryer. You may let them.

The means for drying the web is not particularly limited, and can be generally performed with hot air, infrared rays, a heating roller, microwave, or the like, but it is preferably performed with hot air in terms of simplicity.

The drying temperature in the web pre-drying step is preferably a glass transition point of the optical film of −5 ° C. or lower, and it is effective to perform a heat treatment at a temperature of 30 ° C. or higher for 1 minute or longer and 30 minutes or shorter. Drying is carried out at a drying temperature in the range of 40 to 150 ° C., more preferably in the range of 50 to 100 ° C.

[Stretching process]
The optical film may be stretched under a residual solvent amount with a stretching device to produce a thin optical film, a wide optical film, or improve the flatness of the optical film. it can. Further, the retardation values Ro and Rt can be adjusted by controlling the orientation of molecules in the optical film.

In the production of an optical film, when stretching in the stretching step, the residual solvent amount at the start of stretching is preferably 5% by mass or more and less than 30% by mass. More preferably, it is in the range of 10 to 25% by mass. If the amount of residual solvent at the start of stretching is 5% by mass or more, the stress generated in the optical film during stretching is lowered, the development of retardation due to the orientation of the resin chain is suppressed, and the retardation value is zero retardation. Easy to adjust to the range. If the amount of residual solvent at the start of stretching is less than 30% by mass, the stability of the optical film containing the residual solvent, for example, the transport direction (also referred to as the longitudinal direction, MD direction, or casting direction), or the width It is preferable from the viewpoint of suppressing the talmi in the direction (direction orthogonal to the transport direction, also referred to as the TD direction).

The stretching operation may be performed in multiple stages. When biaxial stretching is performed, simultaneous biaxial stretching may be performed or may be performed stepwise. In this case, stepwise means that, for example, stretching in different stretching directions can be sequentially performed, stretching in the same direction is divided into multiple stages, and stretching in different directions is added to any one of the stages. Is also possible.

Thus, for example, the following stretching steps are possible:
-Stretch in longitudinal direction-> Stretch in width direction-> Stretch in longitudinal direction-> Stretch in longitudinal direction-Stretch in width direction-> Stretch in width direction-> Stretch in longitudinal direction-> Stretch in longitudinal direction--Stretch in width direction-> Stretching in an oblique direction In addition, simultaneous biaxial stretching includes stretching in one direction and contracting the other while relaxing the tension.

[Drying process]
In the drying step, the stretched optical film is heated and dried by a drying device.

In order to adjust the amount of the organic solvent contained in the optical film, it is preferable to appropriately adjust the conditions of the drying step.

When heating the optical film with hot air or the like, a means for preventing the mixing of used hot air by installing a nozzle that can exhaust used hot air (air containing solvent or wet air) is also preferably used. The hot air temperature is more preferably in the range of 40 to 350 ° C. The drying time is preferably about 5 seconds to 60 minutes, and more preferably 10 seconds to 30 minutes.

In the drying step, it is preferable to dry the optical film until the residual solvent amount is generally 2% by mass or less.

[Winding process]
This is a step of winding as an optical film after the amount of residual solvent in the optical film becomes 2% by mass or less, and obtaining an optical film with good dimensional stability by making the residual solvent amount preferably 1% by mass or less. Can do.

As a winding method, a commonly used one may be used, and there are a constant torque method, a constant tension method, a taper tension method, a program tension control method with a constant internal stress, etc., and these may be used properly.

<Use of optical film>
The optical film is preferably a functional film used for various display devices such as liquid crystal display devices and organic EL display devices and touch panels. Specifically, the optical film is a polarizing plate protective film, a retardation film, an antireflection film, a brightness enhancement film, a hard coat film, an antiglare film, an antistatic film or the like for a liquid crystal display device or an organic EL display device. sell. Here, the retardation film includes a film in a retardation region having zero retardation.

Particularly preferred applications are optical films for IPS liquid crystal display devices. The optical film can also be used as a polarizing plate protective film that also serves as the retardation film.

<Polarizing plate>
According to one aspect of the present invention, there is provided a polarizing plate in which the optical film is disposed on at least one surface of a polarizer.

[Polarizer]
A polarizer is an element that passes only light having a plane of polarization in a certain direction. Examples thereof include a polyvinyl alcohol polarizing film.

Polyvinyl alcohol polarizing films include those obtained by dyeing iodine on polyvinyl alcohol films and those obtained by dyeing dichroic dyes.

The polarizer can be obtained by uniaxially stretching a polyvinyl alcohol film and then dyeing or dying a polyvinyl alcohol film and then uniaxially stretching, preferably by further performing a durability treatment with a boron compound.

The film thickness of the polarizer is preferably in the range of 5 to 30 μm, and more preferably in the range of 5 to 15 μm.

A coating-type polarizer obtained by stretching polyvinyl alcohol on a support and then stretching is preferable in that it can be made thinner.

Examples of the polyvinyl alcohol film include an ethylene unit content of 1 to 4 mol%, a degree of polymerization of 2000 to 4000, a degree of saponification of 99.0 to 99 described in JP2003-248123A, JP2003-342322A, and the like. 99 mol% ethylene-modified polyvinyl alcohol is preferably used. In addition, it is preferable to produce a polarizer by producing a polarizer by the method described in JP2011-1000016A, JP4691205, and JP48080489, and bonding the optical polarizer of the present invention.

(adhesive)
Water paste The polarizing plate is preferably bonded to the polarizer using a completely saponified aqueous polyvinyl alcohol solution (water paste). Another polarizing plate protective film can be bonded to the other surface. When the optical film is a liquid crystal display device, the optical film is preferably provided on the liquid crystal cell side of the polarizer. The optical film on the side opposite to the liquid crystal cell of the polarizer is the optical film according to this embodiment and the conventional polarizing film. Either of the plate protective films can be used.

For example, as a conventional polarizing plate protective film, a commercially available cellulose ester film (for example, Konica Minoltak KC8UX, KC5UX, KC8UCR3, KC8UCR4, KC8UCR5, KC8UY, KC6UY, KC6UA, KC4UY, KC8U, KC8U, XCU RHA, KC8UXW-RHA-C, KC8UXW-RHA-NC, KC4UXW-RHA-NC, and the like, manufactured by Konica Minolta, Inc.) are preferably used.

Active energy ray-curable adhesive In addition, in the polarizing plate, the optical film and the polarizer are preferably bonded with an active energy ray-curable adhesive.

The active energy ray-curable adhesive is preferably an ultraviolet curable adhesive. By applying an ultraviolet curable adhesive to the bonding of the optical film and the polarizer, it is possible to obtain a polarizing plate with high strength and excellent flatness even in a thin film. There is no restriction | limiting in particular in the manufacturing method of the polarizing plate using a ultraviolet curing adhesive, It can manufacture by a conventionally well-known method.

Protective film It is preferable that the film arrange | positioned on the opposite side to an optical film on both sides of a polarizer is a film which functions as a protective film of a polarizer.

As such a protective film, an optical film according to the present embodiment may be used. For example, a commercially available cellulose ester film (for example, Konica Minoltak KC8UX, KC5UX, KC4UX, KC8UCR3, KC4SR, KC4BR, KC4CR, KC4DR, KC4FR, KC4KR, KC8UY, KC6UY, KC4UY, KC4UE, KC8UE, KC8UY-HA, KC2UA, KC4UA, KC6UAKC, KC2UAH, KC4UAH, KC6UAH, KC6UAH, KC6UAY Fujitac TD60UL, Fujitac TD40UL, Fujitac R02, Fujitac R06, and more, manufactured by Fuji Film Co., Ltd.) Preferably it can be used. An optical film may be used as a protective film, and the optical film may be disposed on both sides of the polarizer.

In addition, for example, resin films such as polyethylene terephthalate, polyethylene naphthalate, and polycarbonate, alicyclic polyolefins (for example, ZEONOR (registered trademark) manufactured by Nippon Zeon Co., Ltd., polyarylate, polyethersulfone, polysulfone, cycloolefin copolymer, polyimide (For example, Mitsubishi Gas Chemical Co., Ltd., Neoprim (registered trademark)), resin films such as fluorene ring-modified polycarbonate, alicyclic modified polycarbonate, acryloyl compound, etc. Among these resin base materials, cost and availability are easy. In terms of properties, films such as polyethylene terephthalate (abbreviation: PET), polybutylene terephthalate, polyethylene naphthalate (abbreviation: PEN), polycarbonate (abbreviation: PC), etc. are used as protective films. Used Mashiku.

The thickness of the protective film is not particularly limited, but can be about 10 to 200 μm, preferably in the range of 10 to 100 μm, more preferably in the range of 10 to 70 μm.

<Display device>
According to one embodiment of the present invention, a display device including the optical film or the polarizing plate is provided.

[Liquid Crystal Display]
By using the polarizing plate bonded with the optical film for a liquid crystal display device, various liquid crystal display devices with excellent visibility can be manufactured.

The polarizing plate on which the optical film is bonded can be used for liquid crystal display devices of various drive systems such as STN, TN, OCB, HAN, VA (MVA, PVA), IPS, OCB and the like. An IPS liquid crystal display device is preferable.

In a liquid crystal display device, normally two polarizing plates, a polarizing plate on the viewing side and a polarizing plate on the backlight side, are used, but it is also preferable to use the polarizing plate as both polarizing plates, and to use as a polarizing plate on one side. Is also preferable. In particular, the polarizing plate is preferably used as a polarizing plate on the viewing side that directly touches the external environment. When the optical film according to the present embodiment is a protective film, the viewing side surface or the optical film according to the present embodiment is an optical compensation film. In the case, it is preferable to be disposed on the liquid crystal cell side. When used as an optical compensation film for an IPS liquid crystal display device, it is preferably disposed on both sides of the liquid crystal cell.

In addition, as the polarizing plate on the backlight side, a polarizing plate other than that of this embodiment can be used. , KC4SR, KC4BR, KC4CR, KC4DR, KC4FR, KC4KR, KC8UY, KC6UY, KC4UY, KC4UE, KC8UE, KC8UY-HA, KC2UA, KC4UA, KC6UA, KC2UAH, KC2UAH Fujifilm, T60UZ, Fujitac T80UZ, Fujitac TD80UL, Fujitac TD60UL, Fujitac TD40UL, Fujitac R02, Fujitac R06 Polarizing plate stuck Formula Company Ltd. and the like) are preferably used.

Moreover, as the polarizing plate on the backlight side, the optical film according to the present embodiment is used on the liquid crystal cell side of the polarizer, and the commercially available protective film or retardation film, polyester film, acrylic film, polycarbonate film, Or the polarizing plate which bonded the other cycloolefin film can also be used preferably.

By using the polarizing plate bonded with the optical film according to this embodiment, a liquid crystal excellent in visibility such as display unevenness, front contrast, viewing angle, even in a large-screen liquid crystal display device with a screen of 30 type or more. A display device can be obtained.

[Organic electroluminescence display]
The optical film according to this embodiment (in particular, an optical film containing a cycloolefin-based resin) is suitable for an organic electroluminescence display device because it is suitable for freeform punching.

For the outline of the organic EL element applicable to the organic electroluminescence display device, for example, JP2013-157634A, JP2013-168552A, JP2013-177361A, JP2013-187221A. JP, 2013-191644, JP, 2013-191804, JP, 2013-225678, JP, 2013-235994, JP, 2013-243234, JP, 2013-243236, JP JP 2013-242366, JP 2013-243371, JP 2013-245179, JP 2014-003249, JP 2014-003299, JP 2014-013910, JP 2014. -014933, It can be mentioned arrangement described in the open 2014-017494 Patent Publication.

The present invention will be described in further detail using the following examples and comparative examples. However, the technical scope of the present invention is not limited to the following examples. Unless otherwise specified, “%” and “part” mean “% by mass” and “part by mass”, respectively. The mixing ratio of the monomers is the charging mass ratio.

<Synthesis of retardation reducing agent (co) polymer>
[Phase difference reducing agent A-1]
To 500 ml of 3 Kolben, 50 g of dicyclohexyl fumarate, 50 g of ethyl cinnamate, 0.56 g of benzoyl peroxide, and 200 ml of pure water were added and stirred vigorously at room temperature for 1 hour while flowing nitrogen. Thereafter, the temperature was raised to 70 ° C. and stirring was continued for 24 hours. After completion of the reaction, water was removed under reduced pressure, and 100 ml of tetrahydrofuran was added and dissolved by heating. At that time, the precipitated insoluble matter was removed by filtration, and the resulting solution was dropped into 5 L of stirring methanol for reprecipitation purification. After sufficiently stirring, the precipitate was filtered and dried to obtain 34 g of retardation reducing agent A-1. The weight average molecular weight (Mw) of the retardation reducing agent A-1 measured by GPC was 32000.

[Comparative phase difference reducing agents a-1 to a-2]
Comparative phase difference reduction consisting of a single monomer in the same manner as the phase difference reducing agent A-1, except that the monomers are those listed in Table 2 (but adjusted so that the total amount of monomers is 100 g). Agents a-1 and a-2 were synthesized.

<Preparation of core-shell type particles>
[Preparation of core-shell type particle L-1]
(Preparation of latex containing core particle R-1)
In a 100 L pressure-resistant polymerization machine, 200 parts by mass of deionized water, 0.03 parts by mass of tripotassium phosphate, 0.25 parts by mass of potassium dihydrogen phosphate, 0.002 parts by mass of disodium ethylenediaminetetraacetate (EDTA), sulfuric acid After adding 0.001 part by mass of ferrous heptahydrate (FE) and 1.5 part by mass of sodium dodecylbenzenesulfonate (SDS), the nitrogen substitution was sufficiently performed while stirring to remove oxygen, 100 parts by mass of 1,3-butadiene (BD) and 34 parts by mass of styrene were charged into the system, and the temperature was raised to 45 ° C. 0.015 parts by mass of paramentane hydroperoxide (PHP) and then 0.04 parts by mass of sodium formaldehyde sulfoxylate (SFS) were added to initiate polymerization. At 4 hours from the start of polymerization, 0.01 parts by weight of PHP, 0.0015 parts by weight of EDTA and 0.001 parts by weight of FE were added. At 10 hours after polymerization, the residual monomer was removed by devolatilization under reduced pressure to complete the polymerization, and a latex containing core particles R-1 was obtained. The volume average particle diameter (Mv) of the core particle R-1 contained in the obtained latex was 0.10 μm.

(Preparation of latex containing core-shell type particles L-1)
Into a 3 L glass container, 1575 parts by mass of latex containing the core particle R-1 obtained above (equivalent to 510 parts by mass of poly1,3-butadiene rubber particles) and 315 parts by mass of deionized water were charged, and the nitrogen substitution was performed. Stir at ° C. After adding EDTA 0.024 parts by mass, FE 0.006 parts by mass, and SFS 1.2 parts by mass, a mixture of methyl methacrylate 90 parts by mass and cumene hydroperoxide (CHP) 0.3 parts by mass was continuously added over 2 hours. Added and polymerized. After completion of the addition, the reaction was terminated by further stirring for 2 hours to obtain a latex containing core-shell type particles L-1. The volume average particle diameter (Mv) of the core-shell type particle L-1 contained in the obtained latex was 0.11 μm.

The volume average particle diameter (Mv) of the core particle R-1 and the volume average particle diameter (Mv) of the core-shell type particle L-1 were measured using Microtrac UPA150 (manufactured by Nikkiso Co., Ltd.). A sample diluted with deionized water was used as a measurement sample. The measurement was performed by inputting the refractive index of water and the refractive index of each particle, and adjusting the sample concentration so that the measurement time was 600 seconds and the Signal Level was in the range of 0.6 to 0.8.

The glass transition temperature (Tg) of each of the polymer forming the core of the core-shell type particle L-1 and the polymer forming the shell was measured by the following method. The glass transition temperature (Tg) of the polymer forming the core was measured based on the method described in JIS K6240 (2011) with an onset temperature of −140 ° C. About the polymer which comprises a shell, the midpoint glass transition temperature (Tmg) measured based on the method of JISK7121 (1987) was made into the glass transition temperature (Tg).

[Preparation of Latex Containing Core-Shell Type Particles L-2 to L-5 and Comparative Core-Shell Type Particles 1-1 to 1-2]
Core-shell type particle L-1 except that the monomer for forming the core (core-forming monomer) and the monomer for forming the shell (shell-forming monomer) are the materials shown in Table 1, respectively. In the same manner, latexes containing core-shell type particles L-2 to L-5 and comparative core-shell type particles 1-1 to 1-2 were prepared.

The polymer X used for the preparation of the latex containing the core-shell type particle L-4 is a structural unit represented by the following formula having a lactone structure in the main chain (wherein R ¹ is H and R ² is CH ₃ and R ³ is CH ₃ ).

<Production of optical film>
[Optical film B-1]
(Preparation of cycloolefin resin containing core-shell type particles)
15.8 g of methyl ethyl ketone (MEK) was introduced into a 1 L mixing tank at 25 ° C., and 15.8 g of the latex of the core-shell type particle L-1 obtained above was stirred (corresponding to 4.8 g of the core-shell type particle L-1). I put it in. After mixing uniformly, 200 g of water was added at a feed rate of 80 g / min. When the stirring was stopped immediately after the completion of the supply, a slurry liquid composed of an aqueous phase partially containing a floating aggregate and an organic solvent was obtained. Next, an agglomerate containing a part of the aqueous phase was left, and the aqueous phase was discharged from the discharge port at the bottom of the tank. 45 g of MEK and 225 g of dichloromethane were added to the obtained aggregate and mixed uniformly to obtain a dispersion in which core-shell type particles were uniformly dispersed. To this dispersion, 80 g of cycloolefin resin (ARTON (registered trademark) G7810, number average molecular weight (Mn) 45000, weight average molecular weight (Mw) 140000, glass transition temperature (Tg) 165 ° C., manufactured by JSR Corporation) is mixed. did. From this mixture, the liquid component was removed using a rotary evaporator. Thus, a dispersion (M-1) in which the core-shell type particles were dispersed in the cycloolefin resin was obtained.

(Preparation of fine particle additive solution)
11.3 parts by mass of fine particles (Aerosil (registered trademark) R812, manufactured by Nippon Aerosil Co., Ltd.) and 84 parts by mass of ethanol were stirred and mixed with a dissolver for 50 minutes, and then dispersed with Manton Gorin. Obtained. 5 parts by weight of the fine particle dispersion was slowly added to dichloromethane (100 parts by weight) that was sufficiently stirred in the dissolution tank. Further, the particles were dispersed by an attritor so that the secondary particles had a predetermined particle size. This was filtered through Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle additive solution.

(Preparation of main dope)
A main dope having the following composition was prepared. First, dichloromethane and ethanol were added to the pressure dissolution tank. In a pressurized dissolution tank containing dichloromethane, the dispersion (M-1) in which the core-shell type particles are dispersed in the cycloolefin resin obtained above, the phase difference reducing agent A-1 synthesized above, and the fine particle addition liquid are stirred. While throwing. This was heated to 35 ° C., and the cycloolefin-based resin and the retardation reducing agent A-1 were completely dissolved while stirring, and this was dissolved in Azumi Filter Paper No. The main dope was prepared by filtration using 244. The ratio of the core-shell type particles contained in the main dope was 5 parts by mass relative to 100 parts by mass of the total mass of the cycloolefin resin and the phase difference reducing agent A-1.

Dispersion in which core-shell type particles are dispersed in cycloolefin resin (M-1)
84.8 parts by mass Dichloromethane 300 parts by mass Ethanol 20 parts by mass Phase difference reducing agent A-1 16 parts by mass Fine particle additive solution 7.6 parts by mass.

(Production of optical film)
Using an endless belt casting apparatus, the main dope prepared above was uniformly cast on a stainless belt support at a temperature of 31 ° C. and a width of 1800 mm. The temperature of the stainless steel belt was controlled at 28 ° C. The conveyance speed of the stainless steel belt was 20 m / min. On the stainless steel belt support, the solvent was evaporated until the amount of residual solvent in the cast (cast) film reached 40% by mass. Next, the film was peeled from the stainless steel belt support with a peeling tension of 128 N / m. The peeled film was stretched 1.15 times in the width direction under the condition of 175 ° C. The residual solvent at the start of stretching was 5% by mass. Next, drying was completed while transporting the drying zone with a number of rollers, and the end sandwiched between tenter clips was slit with a laser cutter, and then wound up to produce an optical film B-1 having a thickness of 10 μm.

[Preparation of optical films B-2 to B-7 and comparative optical films b-1 to b-5]
The optical films B-2 to B-7 were compared with the optical films B-2 to B-7 in the same manner as the optical film B-1, except that the type of retardation reducing agent, the type of core-shell particles, and the addition amount were set to the values shown in Table 2, respectively. Optical films b-1 to b-5 were produced.

<Preparation of polarizing plate>
[Production of Polarizing Plate PL-1]
(Production of laminate)
The surface of the 120 μm-thick amorphous polyethylene terephthalate sheet subjected to the antistatic treatment was subjected to corona treatment to obtain a thermoplastic resin layer A. As a hydrophilic polymer, polyvinyl alcohol powder (trade name: JC-25, average polymerization degree 2500, saponification degree 99.0 mol% or more, manufactured by NIPPON BI POVAL Co., Ltd.) is dissolved in 95 ° C. hot water. A polyvinyl alcohol aqueous solution having a concentration of 8% by mass was prepared. The obtained aqueous polyvinyl alcohol solution is coated on the thermoplastic resin layer A for lamination using a lip coater, dried at 80 ° C. for 20 minutes, and is made of a hydrophilic material composed of the thermoplastic resin layer A and polyvinyl alcohol. The laminated body 1 which laminated | stacked the conductive resin layer (polarizer 1) was produced. In addition, the thickness of the hydrophilic resin layer (polarizer 1) was 12.0 μm.

(Stretching process)
The laminate 1 was subjected to a 5.3 times free end uniaxial stretching treatment at 160 ° C. in the transport direction (MD direction) to produce a stretched laminate 1. In addition, the thickness of the hydrophilic resin layer (polarizer 1) in the stretched laminate 1 was 5.6 μm.

<Dyeing process>
The stretched laminate 1 was immersed in a 60 ° C. warm bath for 60 seconds, and immersed in an aqueous solution containing 0.05 parts by mass of iodine and 5 parts by mass of potassium iodide per 100 parts by mass of water at a temperature of 28 ° C. for 60 seconds. Next, while maintaining the tension state, it was immersed in a boric acid aqueous solution containing 7.5 parts by mass of boric acid and 6 parts by mass of potassium iodide per 100 parts by mass of water at a temperature of 73 ° C. for 300 seconds. Then, it wash | cleaned for 10 second with 15 degreeC pure water. While maintaining the film washed with water in a tension state, the film was dried at 70 ° C. for 300 seconds to obtain a stretched laminate 1 composed of the thermoplastic resin layer A and the polarizer 1.

(Preparation of polarizing plate 1)
According to the following steps 1 to 6, the stretched laminate 1 produced above and the optical film B-1 of the present invention were bonded, and then the thermoplastic resin layer A was peeled off to produce a polarizing plate PL-1a.
Step 1: The optical film B-1 was subjected to corona discharge treatment. The corona discharge treatment was performed at a corona output intensity of 2.0 kW and a line speed of 18 m / min.
Step 2: A polyvinyl alcohol adhesive having a solid content of 2% by mass was applied to the surface of the stretched laminate 1 having the polarizer 1.
Step 3: The surface on which the polyvinyl alcohol adhesive was applied in Step 2 (the surface on which the polarizer 1 was formed) and the optical film B-1 treated in Step 1 were arranged to face each other. The optical film B-1 was bonded so that the absorption axis of the polarizer 1 and the slow axis of the optical film B-1 were perpendicular.
Step 4: The sample superimposed in Step 3 was bonded at a pressure of 20 to 30 N / cm ² and a conveyance speed of about 2 m / min.
Step 5: The bonded sample prepared in Step 4 was dried for 2 minutes in a dryer at 80 ° C. to obtain a laminate composed of the optical film B-1, the polarizer 1, and the thermoplastic resin layer A.
Step 6: The thermoplastic resin layer A was peeled from the obtained laminate to obtain a polarizing plate PL-1a.

(Preparation of polarizing plate 2)
In accordance with the following steps 7 to 11, the polarizing plate PL-1a produced above is bonded to Konica Minolta Tuck 2UAH (trade name) (manufactured by Konica Minolta Co., Ltd.) (hereinafter referred to as “KC2UAH”), and polarizing plate PL -1 was produced.
Step 7: KC2UAH was immersed in a 2 mol / L sodium hydroxide solution at 60 ° C. for 90 seconds, then washed with water and dried to saponify the side to be bonded to the polarizer.
Step 8: A polyvinyl alcohol adhesive having a solid content of 2 mass% was applied to the surface of the polarizer 1 on the side where the optical film B-1 of the polarizing plate PL-1a is not bonded.
Step 9: The surface of the polarizing plate PL-1a on which the polyvinyl alcohol adhesive was applied in Step 8 and the surface to which the hard coat layer of KC2UAH treated in Step 7 was not applied were arranged to face each other.
Step 10: The sample superposed in Step 9 was bonded at a pressure of 20 to 30 N / cm ² and a conveyance speed of about 2 m / min.
Step 11: The bonded sample prepared in Step 10 in a dryer at 80 ° C. is dried for 2 minutes, and is composed of polarizing plates PL-1a and KC2UAH (that is, optical film B-1, polarizer 1, polarizing plate protective film) A polarizing plate PL-1 (made of KC2UAH) was obtained.

[Production of Polarizing Plates PL-2 to PL-7 and Comparative Polarizing Plates pl-1 to pl-3]
Polarizing plates PL-2 to PL-7 and comparative polarizing plates pl-1 to pl-3 were prepared in the same manner as the polarizing plate PL-1, except that the types of optical films were as shown in Table 2. .

<Evaluation of optical film>
[Adhesiveness with polarizer]
100 grid-shaped cuts were made on the optical film surface of the polarizing plate produced above using a cutter guide with a gap interval of 1 mm so as to penetrate the optical film. Next, the optical film was placed on the outside and attached to a cylinder having a diameter of 80 mm with double-sided tape. In that state, a 18 mm tape (Cellotape (registered trademark) CT-18 manufactured by Nichiban Co., Ltd.) was applied to the cut surface of the grid, and a 2.0 kg roller was reciprocated 20 times from above to remove the air remaining at the interface. Pressed with an eraser to ensure complete contact. And it peeled off rapidly, keeping the peeling angle at 180 degrees. After peeling off, the operation of applying a new tape and peeling off was repeated 10 times in the same manner as described above. The peeling rate of the optical film at the end of 10 times was determined, and the adhesiveness was evaluated according to the following criteria.
A: Peeling area is less than 3% B: Peeling area is 3% or more and less than 5% X: Peeling area is 5% or more.

[Brittleness (crack rate)]
The outer periphery of each of the optical films produced above was overlapped, and the outer periphery of a cut piece obtained by punching 100 sheets with a 10 cm square Thomson blade was observed to detect punching defects such as cracks, cracks, and chips. The number of (n) was divided by the number of observed outer peripheral parts (m), and the crack occurrence rate was expressed as a percentage as follows.

Crack occurrence rate (%) = 100 × (n / m).

[Transparency (Haze)]
The haze value is measured at 10 points at equal intervals in the width direction of the optical film with a haze meter (NDH2000, manufactured by Nippon Denshoku Industries Co., Ltd.) in an environment of 23 ° C. and a relative humidity of 50% RH. The average value was obtained and used as haze.

The results are shown in Table 2.

From the results of Table 2, it was shown that the optical film according to the present invention was excellent in adhesiveness with a polarizer and improved in brittleness. In particular, it was shown that optical films B-1 to B-6 in which the amount of core-shell type particles added is 10 parts by mass or less are optical films having small haze and excellent transparency.

On the other hand, comparative optical film b-1 containing no core-shell type particles, comparative optical film b in which the difference (Tg difference) between the glass transition temperature of the polymer forming the shell and the glass transition temperature of the polymer forming the core is 140 ° C. -2, The comparative optical film b-3 having a Tg difference of 310 ° C. did not have sufficient adhesiveness to the polarizer and had a high crack generation rate due to brittleness.

In addition, in the example using only ethyl cinnamate as the monomer component of the retardation reducing agent, it was not possible to polymerize only ethyl cinnamate. Further, in the example using only dicyclohexyl fumarate as the monomer component of the retardation reducing agent, the optical film itself could not be produced due to brittleness.

This application is based on Japanese Patent Application No. 2017-047706 filed on March 13, 2017, the disclosure content of which is referenced and incorporated as a whole.

Claims

Following formula (1):

In formula (1), A 1 to A 4 are each independently the following (i) to (iv):
(I) a hydrogen atom (ii) a halogen atom,
(Iii) a hydrocarbon group, or (iv) a hydrogen bond accepting group,
Or (v) or (vi) below:
(V) A 1 and A 2 , or A 3 and A 4 are bonded to each other to form an alkylidene group, and A 1 to A 4 not participating in the bond are independently selected from the above (i) to ( iv) represents a group selected from
(Vi) A 1 and A 3 , A 1 and A 4 , A 2 and A 3 , or A 2 and A 4 are bonded to each other to form a cyclic structure together with the carbon atoms to which they are bonded; A 1 to A 4 not involved each independently represents a group selected from the above (i) to (iv);
B represents 0 or 1, c represents an integer of 0 or more;
A cycloolefin-based resin having a structural unit derived from a monomer represented by:
Following formula (2):

In Formula (2), X 1 each independently represents a linear alkyl group, a branched alkyl group, or a cyclic alkyl group, and X 2 each independently represents an alkoxy group, an aryloxy group, or an ester group. Represents a hydroxyl group, a carboxyl group, a halogen atom, or a cyano group, and a represents an integer of 0 to 5;
And a structural unit represented by the following formula (3):

In formula (3), X 3 and X 4 each independently represent a linear alkyl group, a branched alkyl group, or a cyclic alkyl group;
(However, at least one of X 1 in formula (2) and X 3 and X 4 in formula (3) represents a cyclic alkyl group)
A retardation reducing agent comprising a copolymer having a structural unit represented by:
Core-shell type particles in which the glass transition temperature of the polymer forming the shell is higher by 150 ° C. or more and 290 ° C. or less than the glass transition temperature of the polymer forming the core;
Including an optical film.
The optical film according to claim 1, wherein the polymer forming the shell of the core-shell type particle has a structural unit including an aromatic ring having a hydroxyl group.
The optical film according to claim 1, wherein the polymer forming the shell of the core-shell type particle has a structural unit containing a nitrogen-containing ring.
The optical film according to any one of claims 1 to 3, wherein a content of the retardation reducing agent is 5 to 45 mass% with respect to a total solid content of 100 mass% of the optical film.
The optical film according to any one of claims 1 to 4, wherein the content of the core-shell type particles is 1 to 35 mass% with respect to a total amount of 100 mass% of the solid content of the optical film.
A polarizing plate comprising the optical film according to any one of claims 1 to 5 disposed on at least one surface of a polarizer.
A display device comprising the optical film according to any one of claims 1 to 5 or the polarizing plate according to claim 6.