JP6737287B2 - Optical film, polarizing plate and display device - Google Patents

Description

TECHNICAL FIELD The present invention relates to an optical film, a polarizing plate and a display device, and more particularly to an optical film and the like in which, when used as an optical film for a polarizing plate, generation of cracks and chips when punching the polarizing plate is reduced.

Various types of liquid crystal display devices (LCDs) such as a TN (Twisted Nematic) system, a VA (Virtual Alignment) system, and an IPS (In-Place-Switching) system have been developed. Among them, the IPS method is superior in viewing angle performance to the TN method and the VA method and is used for various purposes. The IPS type liquid crystal cell is a type in which a nematic liquid crystal is applied with a lateral electric field to perform switching. IDRC (Asia Display 1995), pp. 577-580 and pp. 707-710.

The polarizing plate optical film used in the IPS system is required to have an optically isotropic (hereinafter referred to as “zero retardation”) polarizing plate optical film due to the characteristics of the IPS system. As an optical film for a polarizing plate exhibiting isotropic property (zero retardation), a cellulose triacetate (TAC) film has been widely used because of its good handleability. However, there is a problem that the cellulose triacetate film is inferior in moisture resistance and has a large performance fluctuation due to humidity fluctuation. Further, since the phase difference value is not completely zero, its improvement has been required.

In recent years, an optical film using a cycloolefin resin has also been used as an optical film for a polarizing plate having good moisture resistance and zero retardation.

Patent Document 1 discloses an optical film using a cycloolefin resin having zero retardation.

On the other hand, in recent years, display devices such as liquid crystal display devices (LCD) and organic electroluminescence display devices (OLED) have become thinner. Along with this, there is an increasing demand for thinning the polarizing plate provided in the display device.

Therefore, thinning is also required for the optical film using the above-mentioned zero retardation cycloolefin resin.

Therefore, the present inventor has studied to reduce the film thickness to 5 to 20 μm with an optical film using a cycloolefin resin having zero retardation as described in Patent Document 1.

As a cycloolefin optical film exhibiting zero retardation, an optical film produced mainly by a melt film forming method is known. However, it has been found that when thinning is performed by melt film formation, cracks and cutting chips are generated on the surface of the optical film during punching of the optical film and the polarizing plate. Further, similar problems have occurred in solution film formation.

The cracks thus generated make it easier for water present in the storage environment to permeate when a polarizing plate or a liquid crystal display device is manufactured, and promote deterioration of the polarizing plate or the liquid crystal display device. Therefore, the wet heat durability of the polarizing plate and the liquid crystal display device is deteriorated.

Furthermore, cycloolefin resins for optical films currently used in various display devices have a positive intrinsic birefringence. Therefore, when an optical film is produced by the melt-casting film forming method, a retardation derived from the positive orientation birefringence is exhibited due to elongation in the transport direction and thermal stretching. It is difficult to completely suppress the occurrence of such a phase difference only by adjusting the process conditions during manufacturing.
Further, in the case of producing by the solution casting film forming method, in addition to the same reason, the phase difference is developed by the resin chains being oriented in the drying process after being cast on the drum or belt from the pressure die slit. .. Furthermore, when the optical film in a state in which the solvent remains is conveyed while being held in the width direction by a clip, the optical film shrinks due to drying and is pseudo-stretched, resulting in a phase difference. Sometimes.

Therefore, it has been necessary to add a compound having a negative intrinsic birefringence to the cycloolefin resin to compensate for an unnecessary phase difference generated in the cycloolefin resin, thereby maintaining the zero retardation property.

However, when a compound having a negative intrinsic birefringence index is added to a cycloolefin resin and an optical film having a thin film with zero retardation is produced, cracks and chips during punching are further generated. A new problem has been found that the value of the phase difference tends to fluctuate depending on the position on the surface of the optical film.

JP, 2011-128356, A

The present invention has been made in view of the above problems and circumstances, and the problem to be solved is that the generation of cracks and chips at the time of punching does not occur, and the fluctuation of the retardation value due to the location of the optical film surface is small. An object of the present invention is to provide an optical film having zero retardation. Further, it is to provide a polarizing plate and a display device provided with the optical film.

The present inventor, in order to solve the above problems, in the process of examining the cause of the above problems, an optical film containing a cycloolefin resin and a compound having a negative intrinsic birefringence, the intrinsic birefringence Since the weight average molecular weight of the compound having a negative index is within a specific range, and the compound having a negative intrinsic birefringence is contained at a specific mass ratio, both exhibit good compatibility, It was speculated that the strain on the surface of the optical film and the microscopic phase separation were alleviated. The present invention has been found out that by adopting the constitution of the present invention, it is possible to provide an optical film of zero retardation in which cracks and chips are not generated during punching.

That is, the above-mentioned subject concerning the present invention is solved by the following means.
1. At least cycloolefin resin and intrinsic birefringence An optical film doped containing was cast negative, compound, the cycloolefin resin has a structure represented by the following general formula (I) It is a polymer derived from a cycloolefin-based monomer, the weight average molecular weight of the compound having a negative intrinsic birefringence is in the range of 500 to 14000, and the compound having a negative intrinsic birefringence is 1 to 49 mass. %, the thickness of the film of the optical film is in the range of 5 to 20 μm, and the retardation value Ro of the optical film in the film plane defined by the following formula (i) is (Nm) and the retardation value Rt (nm) in the film thickness direction defined by the following formula (ii) satisfy the conditions defined by the following formulas (iii) and (iv).
_{(I) Ro = (n x} -n y) × d
_{(Ii) Rt = ((n} x + n y) / 2-n z) × d
(Iii) 0≦Ro≦5
(Iv) −10≦Rt≦10
[In the formula, Ro and Rt are phase difference values measured with light having a wavelength of 590 nm under an environment of a temperature of 23° C. and a relative humidity of 55%.
n _x is the refractive index in the slow axis direction in the plane of the film.
n _y is the refractive index in the direction perpendicular to the slow axis direction in the plane of the film.
_nz is the refractive index in the direction perpendicular to the film surface.
d is the film thickness (nm). ]

上記一般式（Ｉ）において、ｐは０又は１であり、ｍは０又は１以上の整数である。Ｒ^１〜Ｒ^４は、それぞれ独立に、水素原子、炭化水素基、ハロゲン原子、又は水素結合受容性基を表す。また、Ｒ^１〜Ｒ^４は、二つ以上が互いに結合して、不飽和結合、単環又は多環を形成していてもよく、この単環又は多環は、二重結合を有していても、芳香環を形成してもよい。

In the general formula (I), p is 0 or 1, and m is 0 or an integer of 1 or more. R ^{1 to} R ⁴ each independently represent a hydrogen atom, a hydrocarbon group, a halogen atom, or a hydrogen bond-accepting group. Two or more of R ^{1 to} R ⁴ may be bonded to each other to form an unsaturated bond, a monocycle or a polycycle, and the monocycle or the polycycle has a double bond. Alternatively, it may form an aromatic ring.

2. P of the cycloolefin-based monomer having the structure represented by the general formula (I) is 0, R ¹ and R ² are hydrogen atoms, R ³ is a methyl group, and R ⁴ is a methoxycarbonyl group. The optical film as described in the above item 1, which is characterized.

3. The glass transition temperature (Tg) of the optical film is in the range of 130 to 210° C., The optical film according to the first or second aspect.

4. The optical film according to any one of items 1 to 3, wherein the compound having a negative intrinsic birefringence is an oligomer derived from an aromatic vinyl compound or an acrylic oligomer.

5. A polarizing plate comprising the polarizer and the optical film according to any one of the above items 1 to 4 on at least one surface of the polarizer.

6. A display device using the polarizing plate according to item 5.

According to the above-mentioned means of the present invention, it is possible to provide an optical film having a zero retardation property in which the generation of cracks and chips during punching is small. It is also possible to provide a zero retardation optical film in which the retardation value does not vary depending on the location of the optical film surface.

The mechanism of action or mechanism of action of the present invention has not been clarified, but is presumed as follows.

When an optical film of a cycloolefin resin is produced by a solution casting film forming method, residual solvent remains on the surface of the optical film due to quick drying of the solvent, and the film is formed. It is speculated that when the film is thinned, the proportion of the surface layer where the residual stress remains increases, and cracks are more likely to occur.

However, when the weight average molecular weight of the compound having a negative intrinsic birefringence is in the range of 500 to 14000, the compound forms a good compatibility state with the cycloolefin resin and is uniform with the polymer chain of the resin. Will be mixed in. It is presumed that this causes an effect of alleviating the strain of the cycloolefin-based resin chain of the surface layer where residual stress remains, and contributes to the suppression of the occurrence of cracks (hereinafter referred to as crack resistance).

On the other hand, if the compound having a negative intrinsic birefringence has a weight average molecular weight of more than 14,000, it is presumed that the compatibility is insufficient, the above-mentioned relaxation effect is insufficient, and crack generation is not sufficiently suppressed.

Further, generally, a compound having a small molecular weight cannot form a film, or even if it can be formed, it becomes very fragile. When the compound having a negative intrinsic birefringence of the present invention has a weight average molecular weight of less than 500, the effect of embrittlement is stronger than the effect of improving crack resistance, and therefore, the crack resistance of the film is opposite. It is speculated that it will not improve or will decrease.

In addition, when a compound having a negative intrinsic birefringence is added and a thin film zero retardation optical film is produced, the value of the retardation tends to fluctuate depending on the position of the optical film surface. Raises new problems peculiar to.

The reason for this is presumed as follows. A cycloolefin resin and a compound having a negative intrinsic birefringence tend to cause microscopic phase separation. Further, when heating, lowering the temperature or stretching is performed in the manufacturing process of the thin optical film, this micro phase separation increases. It is speculated that this causes a variation in the retardation value depending on the location of the optical film surface.

However, when the weight average molecular weight of the compound having a negative intrinsic birefringence is in the range of 500 to 14000, micro phase separation between the cycloolefin resin and the compound having a negative intrinsic birefringence is less likely to occur. .. Therefore, it is estimated that the unevenness of the optical film surface is improved.

Schematic cross section of polarizing plate

The optical film of the present invention is an optical film is doped to at least cycloolefin resin and intrinsic birefringence is negative compound was cast, the cycloolefin resin is the general formula (I) Is a polymer derived from a cycloolefin-based monomer having a structure represented by, wherein the compound having a negative intrinsic birefringence has a weight average molecular weight in the range of 500 to 14000, and the intrinsic birefringence is negative. A certain compound is contained in the range of 1 to 49% by mass, the film thickness of the optical film is in the range of 5 to 20 μm,
The in-plane retardation value Ro (nm) defined by the formula (i) and the retardation value Rt (nm) in the film thickness direction defined by the formula (ii) of the optical film are It is characterized by satisfying the conditions defined by the formulas (iii) and (iv).

This feature is a technical feature common to the inventions according to each claim.

As an embodiment of the present invention, from the viewpoint of exhibiting the effect of the present invention, p of the cycloolefin-based monomer having the structure represented by the general formula (I) is 0, and R ¹ and R ² are hydrogen atoms. , R ³ is a methyl group, and R ⁴ is a methoxycarbonyl group, which is more preferable because a film can be easily formed by a solution casting film forming method and a thin film can be easily formed.

Furthermore, the glass transition temperature (Tg) of the optical film is preferably in the range of 130 to 210° C. because the optical film has excellent heat resistance.

Further, it is more preferable that the compound having a negative intrinsic birefringence is either an oligomer derived from an aromatic vinyl compound or an acrylic oligomer because the effect of exhibiting zero retardation is large.

In addition, a polarizing plate having the optical film of the present invention as a polarizer or a display device having the polarizing plate has a good moisture resistance of the optical film, is a thin film, and has a zero phase difference, and therefore has a viewing angle for IPS. Is preferable in that a polarizing plate and a display device having a wide range and excellent moisture resistance can be obtained.

In the present invention, the zero retardation means that the in-plane retardation value Ro is in the range of 0 to 5 nm, and the retardation value Rt in the optical film thickness direction is -10. It is defined to be within the range of 10 nm.

Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail. In addition, in this application, "-" is used by the meaning including the numerical value described before and after that as a lower limit and an upper limit.
<<Outline of the optical film of the present invention>>
The optical film of the present invention is an optical film is doped to at least cycloolefin resin and intrinsic birefringence is negative compound was cast, the cycloolefin resin is represented by the following general formula (I) Is a polymer derived from a cycloolefin-based monomer having a structure represented by, wherein the compound having a negative intrinsic birefringence has a weight average molecular weight in the range of 500 to 14000, and the intrinsic birefringence is negative. The compound is in the range of 1 to 49 mass%, the film thickness of the optical film is in the range of 5 to 20 μm,
The in-plane retardation value Ro (nm) defined by the following formula (i) and the retardation value Rt (nm) in the film thickness direction defined by the following formula (ii) of the optical film are as follows: It is characterized by satisfying the conditions defined by the formulas (iii) and (iv).

_{(I) Ro = (n x} -n y) × d
_{(Ii) Rt = ((n} x + n y) / 2-n z) × d
(Iii) 0≦Ro≦5
(Iv) −10≦Rt≦10
[In the formula, Ro and Rt are phase difference values measured with light having a wavelength of 590 nm under an environment of a temperature of 23° C. and a relative humidity of 55%. n _x is the refractive index in the slow axis direction in the plane of the film. n _y is the refractive index in the direction perpendicular to the slow axis direction in the plane of the film. _nz is the refractive index in the direction perpendicular to the film surface. d is the film thickness (nm). ]
The in-plane retardation value Ro and the retardation value Rt in the thickness direction are measured using an automatic birefringence meter Axoscan (Axo Scan Mueller Matrix Polarimeter: manufactured by Axometrics Co.) under an environment of 23° C. and 55% RH. The three-dimensional refractive index is measured at a wavelength of 590 nm, and the refractive index nx, ny, and nz thus obtained are calculated using the following formula.

<Cycloolefin resin>
The optical film of the present invention is characterized by containing a polymer derived from a cycloolefin-based monomer having a structure represented by the general formula (I).

〔式中、ｐは０又は１であり、ｍは０又は１以上の整数である。Ｒ^１〜Ｒ^４は、それぞれ独立に、水素原子、炭化水素基、ハロゲン原子、又は水素結合受容性基である。また、Ｒ^１〜Ｒ^４は、二つ以上が互いに結合して、不飽和結合、単環又は多環を形成していてもよく、この単環又は多環は、二重結合を有していても、芳香環を形成してもよい。〕
本発明において、シクロオレフィン系樹脂の好ましい水素結合受容性基の保有比率は一般式（Ｉ）でＲ^１〜Ｒ^４のうち１〜２個が水素結合受容性基を有することが好ましい。

[In the formula, p is 0 or 1, and m is an integer of 0 or 1 or more. R ^{1 to} R ⁴ are each independently a hydrogen atom, a hydrocarbon group, a halogen atom, or a hydrogen bond-accepting group. Two or more of R ^{1 to} R ⁴ may be bonded to each other to form an unsaturated bond, a monocycle or a polycycle, and the monocycle or the polycycle has a double bond. Alternatively, it may form an aromatic ring. ]
In the present invention, the preferred holding ratio of the hydrogen bond-accepting group of the cycloolefin resin is that in General Formula (I), ^{1 to} 2 of R ^{1 to} R ⁴ have a hydrogen bond-accepting group.

The ratio of hydrogen bond-accepting groups held in the cycloolefin resin can be identified using, for example, carbon-13 nuclear magnetic resonance ( ¹³ CNMR) spectroscopy.

Further, in the general formula (I), R ¹ and R ³ are a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms, more preferably 1 to 4 carbon atoms, and particularly preferably 1 to 2 carbon atoms. At least one of R ² and R ⁴ is preferably a hydrogen bond-accepting group having polarity, from the viewpoint of facilitating solution casting film formation. From the viewpoints of high glass transition temperature and excellent mechanical strength, p and m are preferably m=1 and p=0.

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, and an amide. Examples thereof include groups, imide ring-containing groups, triorganosiloxy groups, triorganosilyl groups, acyl groups, alkoxysilyl groups having 1 to 10 carbon atoms, sulfonyl-containing groups, and carboxy groups. More specifically describing these polar groups, examples of the alkoxy group include a methoxy group and an ethoxy group; examples of the acyloxy group include an acetoxy group and an alkylcarbonyloxy group such as a propionyloxy group; And an arylcarbonyloxy group such as a benzoyloxy group; examples of the alkoxycarbonyl group include a methoxycarbonyl group and an ethoxycarbonyl group; examples of the aryloxycarbonyl group include a phenoxycarbonyl group and a naphthyloxycarbonyl group. Group, a fluorenyloxycarbonyl group, a biphenylyloxycarbonyl group, etc.; a triorganosiloxy group, for example, a trimethylsiloxy group, a triethylsiloxy group, etc.; a triorganosilyl group, a trimethylsilyl group, triethyl Examples thereof include a silyl group and the like; examples of the alkoxysilyl group include a trimethoxysilyl group and a triethoxysilyl group.

Examples of the halogen atom include a fluorine atom, a chlorine atom and a bromine atom. Examples of the hydrocarbon group having 1 to 30 carbon atoms include 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. Group; aromatic groups such as phenyl group, biphenyl group, naphthyl group, anthracenyl group, and the like. These hydrocarbon groups may be substituted, and examples of the substituent include a halogen atom such as a fluorine atom, a chlorine atom and a bromine atom, and a phenylsulfonyl group.

P of the cycloolefin-based monomer having the structure represented by the general formula (I) is 0, R ¹ and R ² are hydrogen atoms, R ³ is a methyl group, and R ⁴ is a methoxycarbonyl group. Since it is easy to form a film by a solution casting method, a thin film is easily formed, which is more preferable.

The cycloolefin resin according to the present invention is preferably contained in the optical film within the range of 51 to 99 mass% from the viewpoint of heat resistance.

The preferred molecular weight of the cycloolefin resin according to the present invention is such that the polystyrene equivalent number average molecular weight (Mn) measured by gel permeation chromatography (GPC) is 8000 to 100,000, more preferably 10,000 to 80,000, and particularly preferably 12,000. The weight average molecular weight (Mw) is preferably 20,000 to 300,000, more preferably 30,000 to 250,000, and particularly preferably 40,000 to 200,000.

The cycloolefin resin according to the present invention has a preferable intrinsic viscosity [η] inh (measurement temperature of 30° C.) of 0.2 to ⁵ cm ³ /g, more preferably 0.3 to ³ cm ³ /g, and particularly preferably 0. It is 4-1.5 cm< ³ >/g.

The intrinsic viscosity [η] inh can be measured (measurement temperature 30° C.) using a Ubbelohde viscometer for the resin solution.

When the intrinsic viscosity [η] inh, the number average molecular weight and the weight average molecular weight are within the above ranges, the heat resistance, water resistance, chemical resistance and mechanical properties of the cycloolefin resin, and the molding process as the optical film of the present invention The property is good.

The glass transition temperature (Tg) of the cycloolefin resin according to the present invention is usually 110°C or higher, preferably 110 to 350°C. The temperature is more preferably 120 to 250°C, and particularly preferably 120 to 220°C.

When the Tg of the cycloolefin resin is 110° C. or higher, deformation due to use under high temperature conditions or secondary processing such as coating and printing is suppressed, which is preferable. Further, when Tg is 350° C. or less, resin deterioration due to molding and heat during molding is suppressed, which is preferable.

The optical film of the present invention preferably has a glass transition temperature (Tg) of 130 to 210° C. in the optical film. When the glass transition temperature (Tg) of the optical film is 210° C. or less, increase in internal stress is small and crack resistance is large, which is preferable.

When Tg is 130° C. or higher, the heat resistance of the optical film is further improved. The Tg of the optical film is preferably within the range of 150 to 180° C. because the effect of the present invention is greater.

The glass transition temperature Tg referred to herein is the midpoint glass transition temperature (Tmg) measured according to JIS K7121 (1987) by measuring at a temperature rising rate of 20° C./min using a commercially available differential scanning calorimeter. Is. A specific method for measuring the glass transition temperature Tg of the optical film is measured using a differential scanning calorimeter DSC220 manufactured by Seiko Instruments Inc. according to JISK7121 (1987).

As the cycloolefin-based resin described above, a commercially available product can be preferably used, and examples of the commercially available products include JSR Corporation's Arton G, Arton F, Arton R, and Arton RX product names (Arton RX). Is a registered trademark), and these can be used.

<Compound having a negative intrinsic birefringence>
The compound having a negative intrinsic birefringence according to the present invention is a compound that is used in combination with a cycloolefin resin and exhibits zero retardation, and the weight average molecular weight of the compound is in the range of 500 to 14,000.

The compound having a negative intrinsic birefringence is an oligomer derived from an aromatic vinyl compound or an acrylic compound, in that the effect of the present invention (crack resistance and improvement in retardation value variation depending on the location of the optical film surface) is large. It is preferably an oligomer.

<Oligomer derived from aromatic vinyl compound>
The compound having a negative intrinsic birefringence is preferably an oligomer derived from an aromatic vinyl compound because the effect of the present invention is large. The weight average molecular weight of the oligomer is in the range of 500 to 14,000, and more preferably in the range of 1,000 to 10,000.

The weight average molecular weight of the oligomer can be changed by adjusting the ratio of the amount of the polymerization initiator added to the monomer in the polymerization reaction of the oligomer, the reaction time, the reaction temperature and the like. In the present invention, the oligomer derived from an aromatic vinyl compound means an oligomer which is derived by polymerizing an aromatic vinyl compound as a component.

The aromatic vinyl compound-derived oligomer is more preferably a polystyrene-based oligomer having a structure represented by the following general formula (II).

（式中、Ｒは水素原子又はメチル基を表す。）
本発明に係る一般式（II）で表される構造を有する化合物のオリゴマーは、ゲルパーミエーションクロマトグラフィー（ＧＰＣ）で測定されるポリスチレン換算の重量平均分子量Ｍｗが５００〜１４０００の範囲内であり、より好ましくは、１０００〜１００００の範囲内であることである。

(In the formula, R represents a hydrogen atom or a methyl group.)
The oligomer of the compound having a structure represented by the general formula (II) according to the present invention has a polystyrene equivalent weight average molecular weight Mw measured by gel permeation chromatography (GPC) of 500 to 14000, More preferably, it is in the range of 1,000 to 10,000.

When the weight average molecular weight of the aromatic vinyl compound-derived oligomer is 500 or more, the crack resistance of the optical film is improved by relaxing the strain of the surface layer of the cycloolefin resin.

The weight average molecular weight of the aromatic vinyl compound-derived oligomer is more preferably 1,000 or more. When the weight average molecular weight is 1,000 or more, the glass transition temperature (Tg) of the optical film can be kept higher in addition to the improvement of crack resistance. When the weight average molecular weight of the aromatic vinyl compound-derived oligomer is 14,000 or less, crack resistance is improved by relaxing strain of the surface layer of the cycloolefin resin. More preferably, the weight average molecular weight is 10,000 or less, and the effect of improving crack resistance is further enhanced. In addition, the problem that the value of the retardation easily changes depending on the location of the optical film surface is solved.

Furthermore, the molecular weight distribution (Mw/Mn) of the oligomer of the compound having the structure represented by the general formula (II) is usually 1.0 to 10, preferably 1.2 to 5.0, and more preferably 1.2. Is ~4.0.

The measurement conditions of GPC are as follows.

Solvent: Dichloromethane Column: Shodex K806, K805, K803G (3 Showa Denko KK were used by connecting them)
Column temperature: 25°C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (GL Science Co., Ltd.)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0 ml/min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corp.) A calibration curve of 13 samples with a weight average molecular weight (Mw) of 500 to 2800000 was used. The 13 samples are preferably used at substantially equal intervals.

Specific examples of the monomer (hereinafter, also referred to as styrene-based monomer) that induces the oligomer of the compound having the structure represented by the general formula (II) are styrene, α-methylstyrene, and p-methyl. Styrene, o-methylstyrene, p-trifluoromethylstyrene, p-methoxystyrene, p-hydroxystyrene, p-chlorostyrene, p-nitrostyrene, p-aminostyrene, p-carboxystyrene, p-phenylstyrene, p. -Tert-butoxystyrene, 2,4,6-trimethylstyrene, p-isopropenylphenol and the like can be mentioned. These monomers may be used alone or in combination of two or more. Of these monomers, styrene, α-methylstyrene, p-hydroxystyrene, and p-isopropenylphenol are preferably used alone or in combination, and styrene is particularly preferable.

The compound having the structure represented by the general formula (1) is preferably produced by a method of polymerizing each of the above monomers in the presence of a suitable polymerization initiator. Although the details of the polymerization initiator will be described later, it is preferable to use a radical polymerization initiator, an anionic polymerization catalyst, a coordination polymerization catalyst, a cationic polymerization catalyst, or the like, and it is particularly preferable to use a radical polymerization initiator.

<Polymerization reaction>
As the radical initiator used in the polymerization reaction, a known organic peroxide that generates a free radical or an azobis-based radical polymerization initiator can be used.

Examples of organic peroxides include diacetyl peroxide, dibenzoyl peroxide, diisobutyroyl peroxide, di(2,4-dichlorobenzoyl) peroxide, di(3,5,5-trimethylhexanoyl) peroxide, and di(3,5,5-trimethylhexanoyl) peroxide. Diacyl peroxides such as octanoyl peroxide, dilauroyl peroxide, distearoyl peroxide, and bis{4-(m-toluoyl)benzoyl}peroxide;
Ketone peroxides such as methyl ethyl ketone peroxide, cyclohexanone peroxide, methyl cyclohexanone peroxide, acetylacetone peroxide and the like;
Hydrogen peroxide, t-butyl hydroperoxide, α-cumene hydroperoxide, p-menthane hydroperoxide, diisopropylbenzene hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, t-hexyl hydro Hydroperoxides such as peroxides;
Di-t-butyl peroxide, dicumyl peroxide, dilauryl peroxide, α,α′-bis(t-butylperoxy)diisopropylbenzene, 2,5-dimethyl-2,5-bis(t-butylperoxide) (Oxy)hexane, t-butylcumyl peroxide, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexyne-3 and other dialkyl peroxides;
t-butylperoxyacetate, t-butylperoxypivalate, t-hexylperoxypivalate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, 2,5-dimethyl- 2,5-bis(2-ethylhexanoylperoxy)hexane, 1-cyclohexyl-1-methylethylperoxy-2-ethylhexanoate, t-hexylperoxy-2-ethylhexanoate, t-butyl Peroxy-2-ethylhexanoate, t-butylperoxyisobutyrate, t-butylperoxymaleate, t-butylperoxy-3,5,5-trimethylhexanoate, t-butylperoxylaurate Rate, 2,5-dimethyl-2,5-bis(m-toluoylperoxy)hexane, α,α′-bis(neodecanoylperoxy)diisopropylbenzene, cumylperoxy neodecanoate, 1,1 , 3,3-Tetramethylbutylperoxyneodecanoate, 1-cyclohexyl-1-methylethylperoxyneodecanoate, t-hexylperoxyneodecanoate, t-butylperoxyneododecanoate, t-butylperoxybenzoate, t-hexylperoxybenzoate, bis(t-butylperoxy)isophthalate, 2,5-dimethyl-2,5-bis(benzoylperoxy)hexane, t-butylperoxy m- Peroxyesters such as toluoyl benzoate and 3,3',4,4'-tetra(t-butylperoxycarbonyl)benzophenone;
1,1-bis(t-hexylperoxy)3,3,5-trimethylcyclohexane, 1,1-bis(t-hexylperoxy)cyclohexane, 1,1-bis(t-butylperoxy)3,3 ,5-trimethylcyclohexane, 1,1-bis(t-butylperoxy)cyclohexane, 1,1-bis(t-butylperoxy)cyclododecane, 2,2-bis(t-butylperoxy)butane, n -Butyl-4,4-bis(t-butylperoxy)pivalate, peroxyketals such as 2,2-bis(4,4-di-t-butylperoxycyclohexyl)propane;
Peroxymonocarbonates such as t-hexylperoxyisopropylmonocarbonate, t-butylperoxyisopropylmonocarbonate, t-butylperoxy-2-ethylhexylmonocarbonate, t-butylperoxyallylmonocarbonate;
Di-sec-butyl peroxydicarbonate, di-n-propyl peroxydicarbonate, diisopropyl peroxydicarbonate, bis(4-t-butylcyclohexyl) peroxydicarbonate, di-2-ethoxyethyl peroxydicarbonate Peroxydicarbonates such as di-2-ethylhexyl peroxydicarbonate, di-2-methoxybutyl peroxydicarbonate and di(3-methyl-3-methoxybutyl)peroxydicarbonate;
Other examples include t-butyltrimethylsilyl peroxide, but the organic peroxide used in the present invention is not limited to these exemplified compounds.

Azobis-isobutyronitrile, 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 ,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'-azobis[N-(2-propenyl)-2- Methylpropionamide], 2,2'-azobis(N-butyl-2-methylpropionamide), 2,2'-azobis(N-cyclohexyl-2-methylpropionamide), 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-tetrahydropyrimidin-2-yl)propane]dihydrochloride, 2 ,2'-Azobis[2-{1-(2-hydroxyethyl)-2-imidazolin-2-yl}propane]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 ) And the like, but the azobis radical polymerization initiator used in the present invention is not limited to these exemplified compounds.

The amount of these radical initiators used is usually 0.01 to 5 mol%, preferably 0.03 to 3 mol%, and more preferably 0.05 to 2 mol% with respect to 100 mol% of the total amount of the monomers.

Further, a catalyst may be used in the polymerization reaction. The catalyst is not particularly limited, and examples thereof include known anionic polymerization catalysts, coordination polymerization catalysts, and cationic polymerization catalysts.

In the presence of the above-mentioned polymerization initiator or catalyst, the above-mentioned polymerization reaction is carried out by subjecting the above-mentioned monomer to a bulk polymerization method, a solution polymerization method, a precipitation polymerization method, an emulsion polymerization method, a suspension polymerization method or a bulk-suspension polymerization method. It is carried out by copolymerizing by a conventionally known method of.

The aromatic vinyl compound-derived oligomer of the present invention is preferably contained in the optical film in a range of 5 to 20% by mass. When it is 5 mass% or more, the crack resistance of the present invention is greatly improved, and when it is 20 mass% or less, the glass transition temperature (Tg) is not low and the heat resistance is good.

Further, when the content is 5% by mass or more, an optical film with less variation in retardation value can be easily obtained.

Therefore, it is easy to solve the unique problem that occurs when a thin zero retardation optical film is produced by adding a compound having a negative intrinsic birefringence.
<Acrylic oligomer>
As the compound having a negative intrinsic birefringence according to the present invention, an acrylic oligomer is also preferable because the effect of the present invention is large. Among them, polymethylmethacrylate (PMMA) is preferably used.

The acrylic oligomer according to the present invention is not particularly limited as a resin. It may consist of one type of acrylic monomer. Alternatively, it may be composed of 50 to 99% by mass of a methyl methacrylate unit and 1 to 50% by mass of another monomer unit copolymerizable therewith.

Other copolymerizable monomers include alkyl methacrylates having 2 to 18 carbon atoms, alkyl acrylates having 1 to 18 carbon atoms, acrylic acid, methacrylic acid, and the like. Saturated acid, maleic acid, fumaric acid, unsaturated group-containing divalent carboxylic acid such as itaconic acid, styrene, α-methylstyrene, aromatic vinyl compounds such as nucleus-substituted styrene, acrylonitrile, methacrylonitrile and the like α,β- Unsaturated nitrile, maleic anhydride, maleimide, N-substituted maleimide, glutaric anhydride and the like can be mentioned, and these can be used alone or in combination of two or more kinds.

Among these, methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, s-butyl acrylate, 2-ethylhexyl acrylate and the like are preferable from the viewpoint of thermal decomposition resistance and fluidity of the copolymer, and methyl acrylate and n-Butyl acrylate is particularly preferably used. More preferably, it is a methyl methacrylate oligomer.

The acrylic oligomer according to the present invention is a polymer having a weight average molecular weight of 500 to 14,000. This improves the crack resistance and the variation of the retardation value depending on the location of the optical film surface.

When the weight average molecular weight of the acrylic oligomer is 500 or more, the crack resistance of the optical film is improved by alleviating the strain of the surface layer of the cycloolefin resin.

More preferably, the acrylic oligomer has a weight average molecular weight of 1,000 or more. When the weight average molecular weight is 1,000 or more, the glass transition temperature (Tg) of the optical film can be kept higher in addition to the improvement of crack resistance. Further, when the weight average molecular weight of the acrylic oligomer is 14,000 or less, the crack resistance is improved by relaxing the strain of the surface layer of the cycloolefin resin. More preferably, the weight average molecular weight is 10,000 or less, and the effect of improving crack resistance is further enhanced. In addition, the problem that the value of the retardation easily changes depending on the location of the optical film surface is solved.

The acrylic oligomer according to the present invention is preferably contained in the optical film in the range of 5 to 20% by mass. When it is 5 mass% or more, the crack resistance of the present invention is greatly improved, and when it is 20 mass% or less, the glass transition temperature (Tg) is not low and the heat resistance is good.

Further, when the content is 5% by mass or more, an optical film with less variation in retardation value can be easily obtained.

The method for producing the acrylic oligomer in the present invention is not particularly limited, and any known method such as suspension polymerization, emulsion polymerization, bulk polymerization, or solution polymerization may be used. Here, as the polymerization initiator, usual peroxide-type and azo-type polymerization initiators can be used, and also redox-type polymerization initiators can be used. The polymerization temperature may be 30 to 100°C for suspension polymerization or emulsion polymerization, and 80 to 160°C for bulk polymerization or solution polymerization. Further, in order to control the reduced viscosity of the produced copolymer, it is possible to carry out the polymerization by using alkyl mercaptan or the like as a chain transfer agent.

The weight average molecular weight of the oligomer can be changed by adjusting the ratio of the amount of the polymerization initiator added to the monomer during the polymerization reaction of the oligomer, the reaction time, the reaction temperature, and the like.

The optical film of the present invention has an in-plane retardation value Ro (nm) defined by the following formula (i) and a retardation value Rt (nm) in the film thickness direction defined by the following formula (ii): It is characterized by satisfying the conditions defined by the following formulas (iii) and (iv).

_{(I) Ro = (n x} -n y) × d
_{(Ii) Rt = ((n} x + n y) / 2-n z) × d
(Iii) 0≦Ro≦5
(Iv) −10≦Rt≦10
[In the formula, Ro and Rt are phase difference values measured with light having a wavelength of 590 nm under an environment of a temperature of 23° C. and a relative humidity of 55%. n _x is the refractive index in the slow axis direction in the plane of the film. n _y is the refractive index in the direction perpendicular to the slow axis direction in the plane of the film. _nz is the refractive index in the direction perpendicular to the film surface. d is the film thickness (nm). ]
By having the above-mentioned characteristic (zero retardation), it is possible to impart an optimal retardation as a polarizing plate for an IPS liquid crystal display device.

The in-plane retardation value Ro (nm) of the optical film is preferably 0 to +3 nm. The retardation value Rt in the optical film thickness direction is preferably -5 to +5 nm.

In the present invention, even a thin cycloolefin resin optical film has good crack resistance, and fluctuations in the value of the retardation depending on the location of the optical film surface can be reduced. The thickness of the optical film is preferably in the range of 10 to 15 μm, and by making it thin, it can contribute to the thinning of the IPS type liquid crystal display device.

The in-plane retardation value Ro and the retardation value Rt in the thickness direction are measured using an automatic birefringence meter Axoscan (Axo Scan Mueller Matrix Polarimeter: manufactured by Axometrics) under an environment of 23° C. and 55% RH. Three-dimensional refractive index measurement is performed at a wavelength of 590 nm, and it can be calculated from the obtained refractive indices n _x , n _y , and _nz .

Other additives that may be contained in the optical film of the present invention include the following.

<Mat agent>
The optical film of the present invention preferably further contains a matting agent in order to prevent scratches and deterioration in transportability when the manufactured optical film is handled. It is particularly preferable that the matting agent contains silica particles.

Silica particles are particles containing silicon dioxide as a main component. The main component means that it contains 50% or more of the components constituting the particles, preferably 70% or more, more preferably 80% or more, and particularly preferably 90% or more.

Further, it is preferable to add fine particles of silicon dioxide particles whose surface is hydrophobized by an alkylation treatment because the dispersibility in a solvent is good and the generation of foreign matter can be suppressed.

The hydrophobic treatment on the silica particles is preferably an alkylation treatment. The surface of the alkylated fine particles has an alkyl group, and the carbon number of the alkyl group is preferably in the range of 1 to 20, more preferably in the range of 1 to 12, and particularly preferably, It has a carbon number of 1 to 8.

The silica particles having an alkyl group having 1 to 20 carbon atoms on the surface thereof can be obtained, for example, by treating the silicon dioxide particles with octylsilane. Further, as an example of those having an octyl group on the surface, it is commercially available under the trade name of Aerosil R805 (manufactured by Nippon Aerosil Co., Ltd.), and is preferably used.

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

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

As the silica particles, commercially available products can be preferably used, and in addition to the above Aerosil R805, for example, Aerosil R972, R972V, R974, R976S, R812, R812S, RY300, 300, R202, OX50, TT600 (above, Nippon Aerosil Co., Ltd. It is commercially available under the trade name of (made by company) (Aerosil is a registered trademark) and can be used.

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

<Plasticizer>
Examples of plasticizers include polyesters, polyhydric alcohol esters, polyhydric carboxylic acid esters (including phthalic acid esters), glycolates, and esters (including fatty acid esters and phosphoric acid esters). Be done. These may be used alone or in combination of two or more.

A preferred plasticizer for the optical film of the present invention is a polyester containing a repeating unit obtained by reacting a dicarboxylic acid and a diol.

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 C1-4 diol. The diol may be one kind or a mixture of two or more kinds.

Among them, the polyester preferably contains a repeating unit obtained by reacting a dicarboxylic acid containing at least an aromatic dicarboxylic acid with a diol having 1 to 4 carbon atoms, and contains an aromatic dicarboxylic acid and an aliphatic dicarboxylic acid. It is more preferable to contain a repeating unit obtained by reacting a dicarboxylic acid and a diol having 1 to 4 carbon atoms.

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

The polyhydric alcohol ester is an ester (alcohol ester) of an aliphatic polyhydric alcohol having a valency of 2 or more and a monocarboxylic acid, and preferably an aliphatic polyhydric alcohol ester having a valency of 2 to 20. 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. An alicyclic monocarboxylic acid or an aromatic monocarboxylic acid is preferable in order to increase the moisture permeability of the optical film and to make it less likely to volatilize. The monocarboxylic acid may be one kind or a mixture of two or more kinds. Further, all of the OH groups contained in the aliphatic polyhydric alcohol may be esterified, or some of them 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 carbon number of the aliphatic monocarboxylic acid is more preferably 1-20, and further preferably 1-10. Examples of the aliphatic monocarboxylic acid include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanoic acid, undecyl acid, lauric acid, tridecyl acid. Saturated fatty acids such as myristic acid, pentadecylic acid, palmitic acid, heptadecyl acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid, heptacosanoic acid, montanic acid, melissic acid, laxeric acid; undecylenic acid, It includes unsaturated fatty acids such as oleic acid, sorbic acid, linoleic acid, linolenic acid and arachidonic acid.

Examples of the alicyclic monocarboxylic acid include cyclopentanecarboxylic acid, cyclohexanecarboxylic acid, cyclooctanecarboxylic acid and the like.

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

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

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

Examples of the polycarboxylic acid ester include triethyl citrate, tributyl citrate, acetyl triethyl citrate (ATEC), acetyl tributyl citrate (ATBC), benzoyl tributyl citrate, acetyl triphenyl citrate, acetyl tribenzyl citrate. , Dibutyl tartrate, diacetyldibutyl tartrate, tributyl trimellitate, tetrabutyl pyromellitic acid and the like.

Examples of glycolates include alkylphthalylalkyl glycolates. Examples of alkylphthalylalkylglycolates include methylphthalylmethylglycolate, ethylphthalylethylglycolate, propylphthalylpropylglycolate, butylphthalylbutylglycolate, octylphthalyloctylglycolate, methylphthalyl. 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, butylphthalylpropyl glycolate, methylphthalyloctylglycolate, ethylphthalyloctylglycolate, octylphthalylmethylglycolate, octylphthalylethylglycolate, etc. are included, preferably ethylphthalylethylglycolate. Is.

The ester includes fatty acid ester, citric acid ester, phosphoric acid ester and the like. Examples of the fatty acid ester include butyl oleate, methylacetyl ricinoleate, dibutyl sebacate and the like. Examples of the citric acid ester include acetyltrimethyl citrate, acetyltriethyl citrate, acetyltributyl citrate, and the like. Examples of the phosphoric acid 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.

Among them, polyester, glycolate, and phosphoric acid ester are preferable, and polyester is particularly preferable.

The content of the plasticizer is preferably 1 to 20% by mass, and more preferably 1.5 to 15% by mass, based on 100 parts by mass of the cycloolefin resin. When the content of the plasticizer is within the above range, the effect of imparting plasticity can be exhibited, and the exudation resistance of the plasticizer from the optical film is also excellent.

<Ultraviolet absorber>
The optical film of the present invention preferably contains an ultraviolet absorber in order to shield unnecessary ultraviolet rays with which the polarizing plate and the liquid crystal display device are irradiated. By containing the ultraviolet absorber, deterioration of 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 for a long time.

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

When the optical film of the present invention is used as a protective film for a polarizing plate in addition to an optical compensation film, the ultraviolet absorber has an excellent ability to absorb ultraviolet rays having a wavelength of 370 nm or less from the viewpoint of preventing deterioration of a polarizer or liquid crystal. In addition, from the viewpoint of the displayability of the liquid crystal, it is preferable that the liquid crystal display device has a property of absorbing less visible light having a wavelength of 400 nm or more.

The addition amount of the ultraviolet absorber is preferably in the range of 0.1 to 5.0 mass% with respect to the polymer composition, and more preferably in the range of 0.5 to 3.0 mass %. preferable.

Examples of the benzotriazole-based ultraviolet absorber useful in the present invention include 2-(2'-hydroxy-5'-methylphenyl)benzotriazole and 2-(2'-hydroxy-3',5'-di-t. -Butylphenyl)benzotriazole, 2-(2'-hydroxy-3'-t-butyl-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3',5'-di-t-butyl Phenyl)-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'-hydroxy-3'-t-butyl-5 '-Methylphenyl)-5-chlorobenzotriazole, 2-(2H-benzotriazol-2-yl)-6-(linear and side chain dodecyl)-4-methylphenol, octyl-3-[3-t- Butyl-4-hydroxy-5-(chloro-2H-benzotriazol-2-yl)phenyl]propionate and 2-ethylhexyl-3-[3-t-butyl-4-hydroxy-5-(5-chloro-2H- Examples thereof include, but are not limited to, a mixture of benzotriazol-2-yl)phenyl]propionate.

In addition, as commercially available products, "TINUVIN 109", "TINUVIN 171", "TINUVIN 326", "TINUVIN 328", "TINUVIN 928" (above, product name, BASF Japan Ltd.) (TINUVIN is a registered trademark) can be preferably used.

<Method for producing optical film>
In the method for producing an optical film of the present invention, it is preferable to produce it by a solution casting film forming method because it is easy to produce a thin optical film having crack resistance.

When a thin optical film of a cycloolefin resin is produced by the solution casting film forming method, the degree of entanglement between the resin chains is large because the unraveling of the resin chains is larger than that in the melt casting film forming method. As a result, it is presumed that the mechanical properties are strong and cracks are less likely to occur at the ends due to processing such as punching and cutting.
Further, in the solution casting film forming method, since the unraveling of the resin chain is larger than that in the melt casting film forming method, each compound having a negative intrinsic birefringence in the range of the weight average molecular weight of 500 to 14,000 is negative. It is presumed that the effect of improving the crack resistance will be large because it easily interacts with the resin chain and eventually exhibits good compatibility.

When the optical film of the present invention is formed into a film by a solution casting film forming method, the cycloolefin resin and the dope containing an organic solvent containing a compound having a negative intrinsic birefringence are dissolved at a melting temperature of 15 to 50. It is preferably prepared within the range of °C.

The optical film of the present invention comprises a step of preparing a dope containing at least a cycloolefin resin and a compound having a negative intrinsic birefringence (dope preparing step), and casting the dope on a support to form a web. A step of forming (also referred to as a casting film) (casting step), a step of evaporating the solvent from the web on the support (solvent evaporation step), a step of peeling the web from the support (peeling step), It is preferably manufactured by a step of drying the obtained optical film (preliminary drying step), a step of further drying the stretched optical film (drying step), and a step of winding the obtained optical film (winding step). .. Further, in consideration of the efficiency of taking out from the manufactured optical film roll, a step of stretching the optical film (stretching step) may be provided and stretched after the preliminary drying step.

<Dope adjusting step>
Examples of the solvent used in the solution casting film forming method include chlorine-based solvents such as chloroform and dichloromethane; aromatic solvents such as toluene, xylene, benzene, and mixed solvents thereof; methanol, ethanol, isopropanol, n- Alcohol solvents such as butanol and 2-butanol; methyl cellosolve, ethyl cellosolve, butyl cellosolve, dimethylformamide, dimethyl sulfoxide, dioxane, cyclohexanone, tetrahydrofuran, acetone, methyl ethyl ketone (MEK), ethyl acetate, diethyl ether; These solvents may be used alone or in combination of two or more.

When the solvent according to the present invention is a mixed solvent of a good solvent and a poor solvent, the good solvent is, for example, dichloromethane as a chlorine-based organic solvent, methyl acetate, ethyl acetate, amyl acetate as a non-chlorine-based organic solvent. , Acetone, methyl ethyl ketone, 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 , 2,2,3,3,3-pentafluoro-1-propanol, nitroethane, methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, tert-butanol and the like, and among them, dichloromethane. Is preferred.

An alcohol solvent is preferably used as the poor solvent. It is preferable to select from methanol, ethanol and butanol, from the viewpoints of improving the peelability and enabling high speed casting together with the effect of the present invention. Of these, ethanol is preferable from the above viewpoint.

In the present invention, in the case of a mixed solvent, it is preferable to use 55% by mass or more, more preferably 70% by mass or more, and further preferably 80% by mass or more of the good solvent with respect to the total amount of the solvent.

<Casting process>
On a metal support such as an endless metal support, for example, a stainless belt or a rotating metal drum, which transfers the dope to a pressure die through a liquid supply pump (for example, a pressure-type metering gear pump) and transfers it infinitely. It is a step of casting the dope from the pressure die slit at the casting position.

<Solvent evaporation process>
It is a step of heating the web on the casting metal support to evaporate the solvent, and a step of controlling the residual solvent amount 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 surface of the support by a liquid, a method of transferring heat from the front and back sides by radiant heat, etc. Is preferable and preferable.

<Peeling process>
It is a step of peeling the web where the solvent is evaporated on the metal support 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 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 mass %. The amount of residual solvent is preferably controlled by the drying temperature and the drying time in the solvent evaporation step.

When the amount of the residual solvent is 15% by mass or more, the silica particles have no distribution in the thickness direction and are uniformly dispersed in the optical film during the drying process on the support, which is preferable.

Further, when the residual solvent amount is 100% by mass or less, the optical film has self-supporting property, it is possible to avoid the peeling defect of the optical film, and the mechanical strength of the web can be maintained, so that the flatness at the time of peeling is improved. However, it is possible to suppress the generation of cracks and vertical lines due to peeling tension.

<Drying and stretching process>
The drying step can be performed separately in a preliminary drying step and a main drying step.

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

The means for drying the web is not particularly limited, and generally, hot air, infrared rays, a heating roller, microwaves or the like can be used, but hot air is preferable in terms of simplicity.

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

<Stretching process>
The optical film of the present invention is subjected to a stretching treatment in a stretching device under a residual solvent amount to produce a thin optical film, a wide optical film, or improve the flatness of the optical film. Alternatively, the retardation values Ro and Rt can be adjusted by controlling the orientation of molecules in the optical film.

In the production of the optical film of the present invention, when stretching is performed 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 within the range of 10 to 25 mass %. If the residual solvent amount at the start of stretching is 5% or more, the stress generated in the optical film at the time of stretching is reduced, the expression of the retardation due to the orientation of the resin chains is suppressed, and the retardation value becomes zero retardation. Easy to adjust to the range. In addition, if the residual solvent amount at the start of stretching is 30% or less, the stability of the optical film containing the residual solvent, for example, the transport direction (also referred to as the longitudinal direction, MD direction, casting direction), or the width direction It is preferable from the viewpoint of suppressing Talumi (also referred to as TD direction).

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

Thus, for example, the following stretching steps are possible:
Stretching in the longitudinal direction → Stretching in the width direction → Stretching in the longitudinal direction → Stretching in the longitudinal direction ・Stretching in the lateral direction → Stretching in the lateral direction → Stretching in the longitudinal direction → Stretching in the longitudinal direction ・Stretching in the lateral direction → Stretching in an oblique direction Simultaneous biaxial stretching also includes the case of stretching in one direction and relaxing the other by contracting 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 organic solvent contained in the optical film, it is preferable to appropriately adjust the conditions of the drying step.

When the optical film is heated by hot air or the like, a means for preventing used hot air from being mixed by installing a nozzle capable of exhausting 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, 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 0.5% by mass or less.

<Winding process>
It is a step of winding the optical film after the residual solvent amount in the optical film becomes 2% by mass or less, and by obtaining the residual solvent amount preferably 1% by mass or less, an optical film having good dimensional stability can be obtained. You can

As a winding method, a generally 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, and the like, and these may be used properly.

<Physical properties of optical film>
<Haze>
The optical film of the present invention preferably has a haze of less than 1%, 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 use.
When a matting agent is used in the optical film of the present invention, it is preferable that silica particles having a uniform particle size are dispersed and used from the viewpoint of the haze. Thereby, the degree of light scattering by the particles is reduced, and an optical film having excellent transparency can be obtained.
The haze value is measured at an equal interval in the width direction of the optical film at 10 points with a haze meter (NDH2000, manufactured by Nippon Denshoku Industries Co., Ltd.) under an environment of 23° C. and 50% RH, and the average value thereof. And ask for haze.

<Equilibrium water content>
The equilibrium water content of the optical film of the present invention at 25° C. and 60% relative humidity is preferably 4% or less, more preferably 3% or less. By setting the equilibrium water content to 4% or less, it is easy to respond to changes in humidity, and it is more difficult for optical characteristics and dimensions to change, which is preferable.

Equilibrium moisture content is determined by leaving the sample film in a room conditioned at 23°C and 20% RH for 4 hours or more, and then in a room conditioned at 23°C and 80% RH for 24 hours. Using a meter (for example, CA-20 type manufactured by Mitsubishi Chemical Analytech Co., Ltd.), water is dried and vaporized at a temperature of 150° C., and then quantified by the Karl Fischer method.

<Film length, width, film thickness>
The optical film of the present invention is preferably long, specifically, about 100 to 40,000 m long and wound into a roll. The width of the optical film of the present invention 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 optical film after stretching of the present invention is in the range of 5 to 20 μm. More preferably, it is 10 to 15 μm. When the film thickness is 5 μm or more, a certain optical film strength or more can be exhibited, which is preferable from the viewpoint of crack resistance. When the film thickness is 20 μm or less, it can be applied to thin the polarizing plate and the display device. By adopting the constitution of the present invention, it is possible to obtain an optical form of a cycloolefin resin which has a good crack resistance even in a thin film and has a small variation in retardation depending on the location of the optical film surface.

<Application of optical film>
The optical film of the present invention 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 of the present invention is a polarizing plate protective film for liquid crystal display device or organic EL display device, retardation film, antireflection film, brightness enhancement film, hard coat film, antiglare film, antistatic film. And so on. Here, the retardation film also includes a film in the retardation region of zero retardation of the present invention.

A particularly preferable application is an optical film for an IPS type liquid crystal display device. The optical film of the present invention can also be used as a polarizing plate protective film that doubles as the retardation film.

<Polarizing plate>
<Polarizer>
The polarizer is an element that allows only light having a polarization plane in a certain direction to pass therethrough, and examples thereof include a polyvinyl alcohol-based polarizing film.

Polyvinyl alcohol-based polarizing films include those obtained by dyeing a polyvinyl alcohol-based film with iodine and those obtained by dyeing a dichroic dye.

The polarizer can be obtained by uniaxially stretching a polyvinyl alcohol film and then dyeing it, or by dyeing a polyvinyl alcohol film and then uniaxially stretching it, and preferably further performing 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 coating polyvinyl alcohol on a support and then stretching is preferable in terms of further thinning.

As the polyvinyl alcohol film, the content of ethylene units described in JP-A-2003-248123, JP-A-2003-342322, etc., 1 to 4 mol %, the degree of polymerization: 2000 to 4000, and the degree of saponification: 99.0 to 99. Ethylene-modified polyvinyl alcohol of .99 mol% is preferably used. In addition, it is preferable that a polarizer is prepared by the method described in JP 2011-100161 A, JP 4691205 A, and JP 4804589 A, and is laminated with the optical of the present invention to prepare a polarizing plate.

<Adhesive>
<Water paste>
In the polarizing plate used in the present invention, it is preferable that the optical film of the present invention is attached to a polarizer using a completely saponified polyvinyl alcohol aqueous solution (water glue). Another polarizing plate protective film can be attached to the other surface. When the optical film of the present invention is used as a liquid crystal display device, it is preferably provided on the liquid crystal cell side of the polarizer, and the optical film on the side opposite to the liquid crystal cell of the polarizer is the optical film of the present invention, and a conventional one. Any of these polarizing plate protective films can be used.

For example, the conventional polarizing plate protective film, commercially available cellulose ester film (for example, Konica Minolta TAC KC8UX, KC5UX, KC8UCR3, KC8UCR4, KC8UCR5, KC8UY, KC6UY, KC6UA, KC4UY, KC4UE, KC8UE, KC8UY-HA, KC8UX- RHA, KC8UXW-RHA-C, KC8UXW-RHA-NC, KC4UXW-RHA-NC, manufactured by Konica Minolta Co., Ltd. are preferably used.

<Active energy ray curable adhesive>
In addition, in the polarizing plate used in the present invention, it is preferable that the optical film of the present invention and the polarizer are attached to each other with an active energy ray-curable adhesive.

As the active energy ray curable adhesive, it is preferable to use an ultraviolet curable adhesive.

In the present invention, by applying an ultraviolet-curable adhesive to the optical film and the polarizer, it is possible to obtain a polarizing plate having high strength and excellent flatness even with a thin film. There is no particular limitation on the method for producing the polarizing plate using the ultraviolet curable adhesive, and it can be produced by a conventionally known method.

<Protective film>
The film arranged on the side opposite to the optical film of the present invention with the polarizer interposed therebetween is preferably a film which functions as a protective film for the polarizer.

As such a protective film, the optical film of the present invention may be used, but for example, a commercially available cellulose ester film (for example, Konica Minolta Tuck KC8UX, KC5UX, KC4UX, KC8UCR3, KC4SR, KC4BR, KC4CR, KC4DR, KC4FR). , KC4KR, KC8UY, KC6UY, KC4UY, KC4UE, KC8UE, KC8UY-HA, KC2UA, KC4UA, KC6UAKC, 2UAAH, KC4UAHZ, 80T, TJT, TUT, TITU, TUT, TITU, TUT, TITO, TITO, TITO, TITO, TITO, TITO, TITO, TITO, TITO, TITO, TITO, TITO, TITO, TITO, TITO, TITO, TITO, TITO, TITO, TITO, TITO, TITO, TITO, TITO, TITO, TITO, TITO, TITO, TITO, TITO, TITO, TITO, TITO, TITO, TITO, TITO, TUT, TUT TD60UL, FUJI TAC TD40UL, FUJI TAC R02, FUJI TAC R06, and those manufactured by Fuji Film Co., Ltd. can also be preferably used. The optical film of the present invention may be used as a protective film, and the optical film of the present invention may be arranged on both sides of the polarizer.

Further, 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, polyether sulfone, polysulfone, cycloolefin copolymer, polyimide) (For example, Neoprim (registered trademark) manufactured by Mitsubishi Gas Chemical Co., Inc.), fluorene ring-modified polycarbonate, alicyclic-modified polycarbonate, acryloyl-based compound, and other resin films are mentioned. Among these resin substrates, cost and easy availability In terms of properties, a film of polyethylene terephthalate (abbreviation: PET), polybutylene terephthalate, polyethylene naphthalate (abbreviation: PEN), polycarbonate (abbreviation: PC), or the like is preferably used as the protective film.

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

<Polarizing plate>
FIG. 1 is a schematic sectional view of a polarizing plate according to a preferred embodiment of the present invention. In the embodiment of FIG. 1, the polarizing plate 101 includes a polarizer 10 and an optical film 20 and a protective film 30 arranged on both surfaces of the polarizer 10. The polarizer 10, the optical film 20, and the protective film 30 are bonded together via an optional adhesive layer (not shown).

<Liquid crystal display>
By using the polarizing plate to which the optical film of the present invention is attached in a liquid crystal display device, various liquid crystal display devices used in the present invention having excellent visibility can be manufactured.

Further, the optical film of the present invention is preferably used for a polarizing plate for display applications having a polygonal shape or a curved line, and when a free form is punched, cracks such as crispy and cracks are generated on the end face, and cutting chips by cutting. It is possible to solve the conventional problem that is likely to occur.

The polarizing plate used in the present invention can be used in liquid crystal display devices of various drive systems such as STN, TN, OCB, HAN, VA (MVA, PVA), IPS and OCB. Preferred is an IPS type liquid crystal display device.

A liquid crystal display device usually uses two polarizing plates, a polarizing plate on the viewing side and a polarizing plate on the backlight side, but it is also preferable to use the polarizing plate used in the present invention as both polarizing plates. It is also preferably used as a polarizing plate. Particularly, the polarizing plate used in the present invention is preferably used as a polarizing plate on the viewing side that directly contacts the external environment, and when the optical film of the present invention is a protective film, the viewing side surface or the optical film of the present invention is optically compensated. In the case of a film, it is preferably arranged on the liquid crystal cell side. When used as an optical compensation film of an IPS type liquid crystal display device, it is preferably arranged on both sides of a liquid crystal cell.

Further, a polarizing plate other than the present invention can be used as the polarizing plate on the backlight side. In that case, for example, a commercially available cellulose ester film (for example, Konica Minolta Tack KC8UX, KC5UX, KC4UX, KC8UCR3) may be used on both surfaces of the polarizer. , KC4SR, KC4BR, KC4CR, KC4DR, KC4FR, KC4KR, KC8UY, KC6UY, KC4UY, KC4UE, KC8UE, KC8UY-HA, KC2UA, KC4UA, KC6UA, KC2UAH, KC4UAH, KC6UAH, or Konica Minolta Co., FUJITAC T40UZ, A polarizing plate to which Fuji Tac T60UZ, Fuji Tac T80UZ, Fuji Tac TD80UL, Fuji Tac TD60UL, Fuji Tac TD40UL, Fuji Tac R02, Fuji Tac R06, etc. (manufactured by Fuji Film Co., Ltd.) is preferably used.

Further, as the polarizing plate on the backlight side, the optical film of the present invention 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 on the opposite surface. A polarizing plate laminated with another cycloolefin film can also be preferably used.

By using the polarizing plate used in the present invention, it is possible to obtain a liquid crystal display device having excellent visibility such as display unevenness, front contrast, and viewing angle, even in the case of a liquid crystal display device having a large screen of 30-inch or more. You can

<Organic electroluminescence display device>
The optical film using the cycloolefin-based resin of the present invention has high suitability for punching in free form, and is therefore suitable for an organic electroluminescence display device.

Regarding the outline of the organic EL element applicable to the organic electroluminescence display device used in the present invention, for example, JP 2013-157634 A, JP 2013-168552 A, JP 2013-177361 A, JP 2013-187211, JP2013-191644A, JP2013-191804A, JP2013-225678A, JP2013-235994A, JP2013-243234A, JP2013-2013A. No. 243236, JP2013-242366A, JP2013-243371A, JP2013-245179A, JP2014-003249A, JP2014-003299A, JP2014-013910A. The configurations described in Japanese Patent Laid-Open No. 2014-017493, Japanese Patent Laid-Open No. 2014-017494 and the like can be mentioned.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In the examples, “parts” or “%” is used, but unless otherwise specified, “parts by mass” or “% by mass” is shown.

[Example 1]
A compound having a negative intrinsic birefringence was synthesized as an additive to the cycloolefin resin used in the examples.

Oligomers derived from aromatic vinyl compounds and comparative compounds were synthesized as follows. (Synthesis of styrene oligomer (S-1) (weight average molecular weight 700))
Using styrene 146.53 g (1.407 mol), toluene 75 g as a solvent, and 1,1′-azobis(cyclohexane-1-carbonitrile) 0.70 g (2.8 mmol) as a radical initiator, the mixture was heated to 90° C. Polymerization was carried out by heating and reacting for 3 hours. 150 g of toluene was added to the obtained polymerization reaction solution to dilute it, then 43.6 g (1.36 mol) of methanol and 1.338 g (0.0136 mol) of concentrated sulfuric acid were added and heated to 60° C. for 2 hours. It was made to react. The obtained reaction liquid was diluted with tetrahydrofuran and coagulated in a large amount of methanol to collect and purify the polymer, which was dried in a vacuum dryer at 80° C. for 2 days to obtain a styrene copolymer. The weight average molecular weight of the obtained polymer was Mw=700 (Mw/Mn=1.96), and the yield was 80%.

(Synthesis of Styrene Oligomer (S-2 to S-5 and S-11 to S-12))
The conditions of the polymerization reaction were adjusted in the same manner as in the synthesis example of the styrene-based oligomer (S-1) to obtain styrene-based oligomers having different weight average molecular weights. The weight average molecular weight Mw of the obtained polymer is as follows, and the yield was 80%, respectively.

S-2: Weight average molecular weight Mw=7500 (Mw/Mn=1.95)
S-3: Weight average molecular weight Mw=12000 (Mw/Mn=1.97)
S-4: Weight average molecular weight Mw=14000 (Mw/Mn=1.95)
S-5: Weight average molecular weight Mw=500 (Mw/Mn=1.96)
S-11: Weight average molecular weight Mw=350 (Mw/Mn=1.99)
S-12: Weight average molecular weight Mw=20,000 (Mw/Mn=1.94)
(Synthesis of acrylic oligomer)
The synthesis of acrylic oligomers and comparative compounds as compounds having a negative intrinsic birefringence will be described below.

(Synthesis of acrylic oligomer (A-1) (weight average molecular weight 500))
The monomers that are the raw materials for the acrylic oligomer are shown below.

Methyl methacrylate (MMA): Asahi Kasei Chemicals Corporation
An acrylic oligomer was synthesized using the above-mentioned monomer materials.

Methyl methacrylate (MMA) and 2,2′-azobis(2-methylpropionitrile) (AIBN) as a polymerization initiator were placed in a 10 L catalyst dissolution tank (SUS304, with paddle impeller agitator, with jacket) described below. It was added so as to be 0.982 mass% with respect to the monomer components contained in the catalyst liquid and the monomer mixed liquid. These components were mixed by stirring to completely dissolve AIBN to obtain a catalyst liquid. A refrigerant was passed through the jacket to adjust the temperature in the catalyst dissolution tank to 5°C. The obtained catalyst solution was continuously fed to a 10 L polymerization reactor (SUS304, with a helical ribbon impeller, with a jacket) at a flow rate of 1.47 kg/Hr by a pump.

From the lower part of the polymerization reactor, the above-mentioned catalyst liquid and monomer mixed liquid were charged, and a polymerization reaction was carried out at an average residence time of 9 minutes and a temperature of 175° C.±2° C. until the average polymerization rate reached 49 mass %. A liquid polymer composition was obtained. Then, the obtained liquid polymer composition was taken out from the upper part of the polymerization reactor and fed to a heater (inner diameter 16.7 mm×length 3 m, with a jacket).

While the liquid polymer composition was heated to 20 kg/cm ² G and 200° C. in a heater, the obtained polymer composition was fed to a devolatilizing extruder. As the devolatilizing extruder, a twin-screw extruder (TEX-30) manufactured by Japan Steel Works, Ltd., different direction rotation system, screw diameter 30 mm, cylinder length 1200 mm, 1 rear vent, 3 for vents are used. Using. The vents of the devolatilizing extruder were depressurized, the cylinder temperature was about 250° C., the liquid polymer composition was devolatilized, and the volatile components containing unreacted monomer as the main component were taken out from the vents. The unreacted monomer taken out was recovered in a monomer recovery tower (inner diameter 100 mm, length 3 m, SUS304, 3/8 inch SUS Raschig ring packed tower, concentration part length 0.7 m, recovery part length 0.3 m).

The obtained polymer in a molten state was extruded into a strand and cooled with water. In this way, acrylic oligomer A-1 was obtained.

(Synthesis of acrylic oligomers (A-2 to A-5 and A-11, A-12))
The conditions of the polymerization reaction were adjusted in the same manner as in the synthesis example of the acrylic oligomer (A-1) to obtain acrylic oligomers having different weight average molecular weights. The weight average molecular weight Mw of the obtained polymer is as follows, and the yield was 80%, respectively.

A-2: Weight average molecular weight Mw=700 (Mw/Mn=1.98)
A-3: Weight average molecular weight Mw=7000 (Mw/Mn=1.97)
A-4: Weight average molecular weight Mw=13000 (Mw/Mn=1.98)
A-5: Weight average molecular weight Mw=14000 (Mw/Mn=1.97)
A-11: Weight average molecular weight Mw=20,000 (Mw/Mn=1.97)
A-12: Weight average molecular weight Mw=350 (Mw/Mn=2.00)
(Synthesis of oligomer (F-1) (weight average molecular weight 7500)
Polymerization of polycarbonate was carried out by an interfacial polycondensation method using known phosgene.

A reaction vessel equipped with a stirrer, a thermometer and a reflux condenser was charged with an aqueous sodium hydroxide solution and ion-exchanged water, and the monomers [A] and [B] having the following structures were dissolved in a molar ratio of 86:14. , A small amount of hydrosulfite was added. Then, methylene chloride was added thereto, and phosgene was blown thereinto at 20° C. for about 60 minutes. Further, p-tert-butylphenol was added to emulsify, triethylamine was added, and the mixture was stirred at 30° C. for about 50 minutes to terminate the reaction.

After completion of the reaction, the organic phase was separated and methylene chloride was evaporated to obtain a polycarbonate copolymer. The composition ratio of the obtained copolymer was almost the same as the charging amount ratio. The glass transition temperature was 162°C. The intrinsic viscosity of this copolymer was 0.8 when measured at 20° C. in methylene chloride using an Ubbelohde viscosity tube.

（オリゴマー（Ｆ−２）の合成（重量平均分子量７５００）
固有複屈折値が負である材料として、フルオレン骨格を有するノルボルネン系開環共重合体を用いた。

(Synthesis of oligomer (F-2) (weight average molecular weight 7500)
A norbornene ring-opening copolymer having a fluorene skeleton was used as a material having a negative intrinsic birefringence value.

According to the synthesis method described in [0161] to [0164] of JP-A-2005-36201, spiro[fluorene-9,8'-tricyclo[4.3.0.1 ^2.5 ] represented by the following formula (A): ] [3] Decene] (exo form) was synthesized.

3.67 g of the above-mentioned monomer, 8-methoxycarbonyl-8-methyltetracyclo[4.4.0.1 ^2,5 . 1 ^7,10] -3-dodecene 3.0 g, molecular weight modifier of 1-hexene 0.63 g, and toluene 20.0 g, were charged into a reaction vessel purged with nitrogen, and heated to 80 ° C.. To this, 0.068 mL of a toluene solution of triethylaluminum (0.6 mol/L) and 0.21 mL of a toluene solution of methanol-modified WCl ₆ (0.025 mol/L) were added, and reacted at 80° C. for about 20 minutes. A ring-opening copolymer solution was obtained. The weight average molecular weight (Mw) of the obtained ring-opening copolymer was 7,500, and the molecular weight distribution (Mw/Mn) was 6.08.

<Production of optical film>
<Production of Optical Film F-A1>
<Preparation of fine particle dispersion>
11.3 parts by mass of fine particles (Aerosil 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.

5 parts by mass of the fine particle dispersion was slowly added to dichloromethane (100 parts by mass) which was sufficiently stirred in the dissolution tank. Furthermore, dispersion was performed with an attritor so that the particle size of the secondary particles would be a predetermined size. This was filtered through Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle additive liquid.

<Preparation of main dope>
A main dope having the following composition was prepared. First, dichloromethane and ethanol were added to the pressure dissolution tank. The cycloolefin resin, the additive A and the fine particle additive liquid were charged into a pressure dissolution tank containing dichloromethane while stirring. This was heated and completely dissolved with stirring, and this was mixed with Azumi filter paper No. The main dope was prepared by filtration using 244.

<Production of optical film>
Cycloolefin resin (ARTON G7810, manufactured by JSR Corporation)
90 parts by mass Dichloromethane 200 parts by mass Ethanol 10 parts by mass Compound A-1 having a negative intrinsic birefringence 1 part by mass Fine particle additive liquid 7.6 parts by mass Then, using an endless belt casting device, the main dope was heated at a temperature of 31°C. It was uniformly cast on a stainless belt support with a width of 1800 mm. The temperature of the stainless belt was controlled at 28°C. The transport speed of the stainless belt was 20 m/min.

The solvent was evaporated on the stainless belt support until the amount of residual solvent in the cast optical film became 40%. Then, it was peeled from the stainless belt support with a peeling tension of 128 N/m. The peeled optical film was stretched 1.15 times in the width direction under the condition of 170°C. The residual solvent at the start of stretching was 5% by mass. Then, the drying was completed while the drying zone was conveyed by a large number of rollers, the ends sandwiched by the tenter clips were slit by a laser cutter, and then the film was wound to produce an optical film F-A1 having a film thickness of 10 μm.

[Production of Optical Films F-A2 to F-A22 and F-B1 to F-B18]
In the production of the optical film FA-1, the type of additive, the amount added, and the film thickness are changed as shown in Table 1 and Table 2, respectively, and the optical films F-A2 to F-A22 and F-B1 to F-B18 was produced. When changing the amount of the additive, the total amount of the cycloolefin resin and the additive was adjusted to 100 parts by mass.

[Production of Optical Films F-B19 and F-A23]
As a comparative sample, an optical film F-B19 was prepared as follows.

A cycloolefin resin (ARTON G7810, manufactured by JSR Corporation) was kneaded with a twin-screw extruder, extruded into a strand, and cut with a pelletizer to produce a cycloolefin resin. Hereinafter referred to as "resin A1".

A silica filler FS-3DC (average particle size 2.9 μm) manufactured by Denki Kagaku Kogyo Co., Ltd. was put into a ball mill and pulverized to prepare a pulverized silica filler having an irregular shape. The average primary particle diameter of the produced pulverized silica filler was measured and found to be 0.8 μm. The refractive index at 25°C was 1.43.

99.7% by mass of resin A1 and silica beads made by Admatechs Co., Ltd. as spherical silica fine particles Admafine SO-E2 (average primary particle diameter 0.5 μm, aspect ratio 1.1, refractive index at 25° C. 1. 43) was mixed with 0.3% by mass and melt-kneaded with a twin-screw extruder to prepare a resin A'.

The prepared resin A′ was supplied to a single-screw extruder and melt-extruded to obtain an optical film FB-19 having a thickness of 10 μm.

As a sample of the present invention, an optical film F-A23 was prepared as follows.

Styrene oligomer S-4 was mixed in an amount of 10% by mass and the resin A′ was 90% by mass, and melt-kneaded with a twin-screw extruder to prepare a resin B.

The resin B was supplied to a single-screw extruder and melt-extruded to obtain an optical film FA-23 having a thickness of 10 μm.

For the optical films FA-1 to FA-23 and FB-1 to FB-19 produced as described above, the following glass transition temperature (Tg), crack occurrence rate, phase difference value, and phase difference fluctuation degree were measured. It was measured.

<Heat resistance (Tg)>
A differential scanning calorimeter DSC220 manufactured by Seiko Instruments Inc. was used to measure at a temperature rising rate of 20° C./min, and the midpoint glass transition temperature determined according to JIS K7121 (1987) was defined as Tg.

<Crack occurrence rate>
The number of corners (n) in which five optical films were overlapped (same configuration) and 100 pieces were punched with a 10 cm square Thomson blade, and punching defects such as cracks, cracks and chips were detected (n) were observed ( It was divided by m) and the crack occurrence rate was shown in percentage as follows.
Crack occurrence rate (%)=100×(n/m)
<Phase difference value>
The retardation value Ro in the in-plane direction of the optical film, and the retardation value Rt in the thickness direction are measured by using an automatic birefringence meter Axoscan (Axo Scan Mueller Matrix Polarimeter: manufactured by Axometrics Co., Ltd.) at 23° C. and 55%. Three-dimensional refractive index measurement is performed at a wavelength of 590 nm under the environment of RH, and the refractive index n _x , n _y , and n _z thus obtained are calculated using the following formula.

Formula _{(i): Ro = (n} x -n y) × d (nm)
Formula (ii): Rt={(n _x +n _y )/2−n _z }×d (nm)
[In the formulas (i) and (ii), n _x represents the refractive index in the slow axis direction in the in-plane direction of the film. n _y represents the refractive index in the direction y orthogonal to the direction x in the in-plane direction of the film. _nz represents the refractive index in the thickness direction z of the film. d represents the thickness (nm) of the film. ]
<Phase difference variation>
An optical film having a width direction of 1800 mm was prepared, and in-plane retardation values Ro were measured at 35 points every 5 cm. The above measurement was performed on three optical films having a width direction of 1800 mm, and a total of 105 points were measured. The average value of Ro was calculated, and the number of points where the phase difference value was separated from the average value by 2 nm or more out of 105 measurement points was defined as the phase difference variation degree.

The structure of the optical film and the above results are summarized in Tables 1 and 2.

なお表中のシクロオレフィン系樹脂Ｐ−１は、ＪＳＲ社製Ｇ７８１０（商品名）、Ｐ−２はＪＳＲ社製Ｒ５０００（商品名）、Ｐ−３はＪＳＲ社製ＲＸ４５００（商品名）を表す。

In the table, cycloolefin resin P-1 is G7810 (trade name) manufactured by JSR, P-2 is R5000 (trade name) manufactured by JSR, and P-3 is RX4500 (trade name) manufactured by JSR.

From the results shown in Tables 1 and 2, it can be seen that the optical film of the present invention has a low crack generation rate and a zero retardation optical film having a small degree of retardation variation.

[Example 2]
A sample similar to the optical film F-A10 of Example 1 was prepared and designated as F-A24, except that 1% by mass of TINUVIN928 (manufactured by BASF) (registered trademark) was added as an ultraviolet absorber in the optical film. As in Example 1, the glass transition temperature (Tg), crack occurrence rate, retardation value, and retardation variation value were measured.

The structure of the optical film F-A24 and the measurement results are summarized in Table 3.

光学フィルムＦ−Ａ２４は、Ｆ−Ａ１０と同様にガラス転移温度（Ｔｇ）、クラック発生率、位相差値、位相差変動度が良好であった。

Like the F-A10, the optical film F-A24 had good glass transition temperature (Tg), crack occurrence rate, retardation value, and retardation variation.

[Example 3]
<Production of polarizing plate>
<Production of Stretched Laminate 1 Having Polarizer>
<Preparation of laminated body 1>
The surface of the 120 μm-thick amorphous polyethylene terephthalate sheet that had been subjected to antistatic treatment was corona-treated to form a thermoplastic resin layer A.
As a hydrophilic polymer, polyvinyl alcohol powder (manufactured by Nippon Vinegar Bipovar Co., Ltd., average degree of polymerization: 2500, saponification degree: 99.0 mol% or more, trade name: JC-25) is dissolved in hot water at 95°C to obtain a concentration. An 8 mass% polyvinyl alcohol aqueous solution was prepared. The obtained polyvinyl alcohol aqueous solution is applied onto the thermoplastic resin layer A for lamination using a lip coater and dried at 80° C. for 20 minutes to obtain a hydrophilic property composed of the thermoplastic resin layer A and polyvinyl alcohol. A laminate 1 in which resin layers (polarizer 1) were laminated was produced. The thickness of the hydrophilic resin layer (polarizer 1) was 12.0 μm.

<Stretching process>
The laminated body 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 laminated body 1. The thickness of the hydrophilic resin layer (polarizer 1) in the stretched laminate 1 was 5.6 μm.

<Dyeing process>
Next, the stretched laminate 1 is immersed in a warm bath of 60° C. for 60 seconds, and immersed in an aqueous solution containing 0.05 part 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. did. Then, while maintaining a tension state, it was immersed for 300 seconds at a temperature of 73° C. in an aqueous boric acid 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. Then, it was washed with pure water at 15° C. for 10 seconds. The film washed with water was dried at 70° C. for 300 seconds while keeping the film tensioned to obtain a stretched laminate 1 composed of the thermoplastic resin layer A and the polarizer 1.

<Production of polarizing plate 1>
According to the following steps 1 to 6, the stretched laminate 1 produced above was laminated with the optical film F-A1 of the present invention, and then the thermoplastic resin layer A was peeled off to produce a polarizing plate PL-A1'. Step 1: F-A1 was immersed in a 2 mol/L sodium hydroxide solution at 60° C. for 90 seconds, washed with water and dried to be saponified.
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 coated with the polyvinyl alcohol adhesive in Step 2 (polarizer 1 forming surface) and the optical film F-A1 treated in Step 1 were arranged so as to face each other. The optical film F-A1 was attached such that the absorption axis of the polarizer 1 and the slow axis of the optical film F-A1 were perpendicular to each other. Step 4: The samples piled up in Step 3 were laminated at a pressure of 20 to 30 N/cm ² and a transportation speed of about 2 m/min.
Step 5: The laminated sample prepared in Step 4 was dried for 2 minutes in a drier at 80° C. to obtain a polarizing plate including F-A1, polarizer 1, and thermoplastic resin layer A.
Step 6: The thermoplastic resin layer A was peeled off from the obtained polarizing plate to obtain a polarizing plate PL-A1'.
<Production of polarizing plate 2>
In accordance with the following steps 7 to 11, the PL-A1' prepared above and the Konica Minolta Tuck 2UAH (trade name) (manufactured by Konica Minolta Co., Ltd.) (hereinafter referred to as "KC2UAH") are bonded to each other, and the polarizing plate PL- A1 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 with the polarizer.
Step 8: A polyvinyl alcohol adhesive having a solid content of 2% by mass was applied to the surface of the polarizer 1 of the PL-A1' on which the F-A1 was not attached.
Step 9: The surface coated with the polyvinyl alcohol adhesive in Step 8 and the surface to which the hard coat layer of 2UAH treated in Step 7 was not applied were arranged so as to face each other.
Step 10: The samples piled up in Step 9 were laminated at a pressure of 20 to 30 N/cm ² and a transportation speed of about 2 m/min.
Step 11: The laminated sample prepared in Step 10 is dried for 2 minutes in a dryer at 80° C., and a polarizing plate composed of PL-A1′ and 2UAH, that is, optical film F-A1, polarizer 1, and polarizing plate protection. A polarizing plate PL-A1 made of the film KC2UAH was obtained.
Next, in the polarizing plate PL-A1, the same polarizing plates PL-A2 to PL-A24 and PL-B1 as the polarizing plate PL-A1 except that the type of the optical film was changed as shown in Table 4. PL-B19 was produced.

The wet heat durability of the polarizer of the thus-prepared polarizing plate was measured as follows.

<Wet heat durability (polarizer)>
In order to reproduce the state of being mounted on a liquid crystal panel, the surface of the optical film of the present invention on the side opposite to the polarizer is attached to glass via an adhesive layer, and then the environment of 40° C. and relative humidity of 90% is used. The color fading of the polarizer before and after storage for 1000 hours was visually observed and evaluated according to the following evaluation criteria.
⊚: No fading ○: Slight fading is observed, but there is no hindrance to the polarization performance ×: In order to reproduce the state of being mounted on the liquid crystal panel which is obviously fading, the polarizer of the optical film of the present invention is After sticking the opposite surface to the glass via the adhesive layer, visually observing the discoloration of the polarizer before and after storage for 1000 hours (durability treatment) in an environment of 40°C and 90% relative humidity It was observed and evaluated according to the following evaluation criteria.
◎: No fading ○: Very fading is seen ×: Obviously fading <Wet heat resistance (light leakage)>
In addition, the polarization performance was evaluated as follows. PL-A1 which was not subjected to the durability treatment was placed on the Schaukasten so that 2UAH was on the Schaukasten side and F-A1 was on the visible side. The polarizing plate attached to the glass and subjected to the durability treatment as described above was placed thereon so that the glass was on the side of Schaukasten and 2UAH was on the side of visual recognition. That is, in order from the light source, Schaukasten, 2UAH (not subjected to durability treatment), polarizer (not subjected to durability treatment), F-A1 (not subjected to durability treatment), glass, adhesive layer, F-A1 (after durability treatment) ), and a polarizer (after endurance treatment) and 2UAH (after endurance treatment). At this time, the two polarizers were arranged so that their absorption axes were perpendicular to each other (crossed Nicols). In that state, the light source was turned on, visually observed from the front, and evaluated according to the following evaluation criteria.
⊚: No light leakage ○: Very slight light leakage ×: Clearly light leakage The constitution of the polarizing plate and the above results are summarized in Table 4.

表４の結果から本発明の偏光板は湿熱耐久性が良いことがわかる。

The results in Table 4 show that the polarizing plate of the present invention has good wet heat durability.

[Example 4]
<Production of liquid crystal display device>
In order to evaluate the characteristics of the above-prepared polarizing plate, the polarizing plates attached to the viewer's front and back surfaces of the liquid crystal panel of the Hitachi liquid crystal television (Woo W32-L7000) in the IPS mode were peeled off. The polarizing plates PL-A1 to PL-A24 and PL-B1 to PL-B19 produced in Example 3 were originally attached to the light source side (rear surface) and the visual recognition side (front surface), respectively. The transparent axis of the polarizing plate was set to be the same as that of the polarizing plate, and they were bonded using an acrylic transparent adhesive to obtain liquid crystal display devices CLD-A1 to CLD-A24 and CLD-B1 to CLD-B19.

The wet heat durability of the liquid crystal display device thus manufactured was evaluated by the following measuring methods and evaluation criteria.

<Wet heat durability of liquid crystal display>
The liquid crystal display device was stored in an environment of 40° C. and 90% relative humidity for 1000 hours, and the black display portion before and after the test was visually observed.
⊚: A good black color is maintained, which is the same as before the durability test.
◯: The brightness of black is slightly decreased from that before endurance, but black is maintained.
X: The blackness is obviously reduced.

The configuration of the liquid crystal display device and the above results are summarized in Table 5.

表５の結果から本発明の液晶表示装置は湿熱耐久性が良いことがわかる。

The results in Table 5 show that the liquid crystal display device of the present invention has good wet heat durability.

The present invention does not cause the generation of cracks and chips at the time of punching, and can be used as an optical film having zero retardation with little variation in retardation value depending on the location of the optical film surface, in particular, the optical film. It can be used for a polarizing plate and a display device provided with.

10 Polarizer 20 Optical Film 30 Protective Film 101 Polarizing Plate

Claims (6)

At least cycloolefin resin and intrinsic birefringence An optical film doped containing was cast negative compounds wherein,
The cycloolefin-based resin is a polymer derived from a cycloolefin-based monomer having a structure represented by the following general formula (I),
The compound having a negative intrinsic birefringence has a weight average molecular weight in the range of 500 to 14,000,
The compound having a negative intrinsic birefringence is contained in the range of 1 to 49 mass%,
The thickness of the film of the optical film is in the range of 5 to 20 μm,
The in-plane retardation value Ro (nm) defined by the following formula (i) and the retardation value Rt (nm) in the film thickness direction defined by the following formula (ii) of the optical film are as follows: An optical film satisfying the conditions defined by the formulas (iii) and (iv).
_{(I) Ro = (n x} -n y) × d
_{(Ii) Rt = ((n} x + n y) / 2-n z) × d
(Iii) 0≦Ro≦5
(Iv) −10≦Rt≦10
[In the formula, Ro and Rt are phase difference values measured with light having a wavelength of 590 nm under an environment of a temperature of 23° C. and a relative humidity of 55%.
n _x is the refractive index in the slow axis direction in the plane of the film.
n _y is the refractive index in the direction perpendicular to the slow axis direction in the plane of the film.
_nz is the refractive index in the direction perpendicular to the film surface.
d is the film thickness (nm). ]

In the general formula (I), p is 0 or 1, and m is 0 or an integer of 1 or more. R ^{1 to} R ⁴ are each independently a hydrogen atom, a hydrocarbon group, a halogen atom, or a hydrogen bond-accepting group. Two or more of R ^{1 to} R ⁴ may be bonded to each other to form an unsaturated bond, a monocycle or a polycycle, and the monocycle or the polycycle has a double bond. Alternatively, it may form an aromatic ring. P of the cycloolefin-based monomer having the structure represented by the general formula (I) is 0, R ¹ and R ² are hydrogen atoms, R ³ is a methyl group, and R ⁴ is a methoxycarbonyl group. The optical film according to claim 1, which is characterized. The glass transition temperature (Tg) of the optical film is in the range of 130 to 210° C. 3. The optical film according to claim 1 or 2, wherein The compound having a negative intrinsic birefringence is either an aromatic vinyl compound-derived oligomer or an acrylic oligomer, and the compound according to any one of claims 1 to 3. Optical film. A polarizing plate comprising the optical film according to any one of claims 1 to 4 on at least one surface of a polarizer. A display device comprising the polarizing plate according to claim 5.

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