KR102427149B1 - Optical film and polarizing plate - Google Patents

Abstract

The optical film of this invention contains the (meth)acrylic-type copolymer and the rubber particle whose glass transition temperature is 0 degreeC or less. The (meth)acrylic copolymer has a structural unit derived from a monomer A in which the photoelastic coefficient of the homopolymer is negative, and a structural unit derived from a monomer B having a positive photoelastic coefficient of the homopolymer and having no alicyclic structure. And, the photoelastic modulus of the homopolymer is positive, has a structural unit derived from the monomer C having an alicyclic structure, and does not have a ring structure in the main chain. The optical elastic modulus of the optical film is -2.0×10 ^-12 to 2.0×10 ^-12 Pa ^-1 .

Description

Optical film and polarizer {OPTICAL FILM AND POLARIZING PLATE}

The present invention relates to an optical film and a polarizing plate.

The polarizing plate used for display apparatuses, such as a liquid crystal display device, contains a polarizer and the protective film arrange|positioned on the both surfaces. In recent years, it is calculated|required that it is hard to generate|occur|produce display nonuniformity in a display apparatus even if a polarizing plate and the protective film which comprises it by the use outdoors, such as a smartphone, even in the harsh environment of high temperature and high humidity. As a protective film from such a viewpoint, the (meth)acrylic-type resin film which is low hygroscopicity and is excellent in dimensional stability rather than the conventional cellulose-ester film is used.

The display nonuniformity of the display apparatus which is easy to generate|occur|produce under high temperature, high humidity is easy to generate|occur|produce when a protective film changes dimensionally under high temperature and high humidity, and the phase difference resulting from stress expresses in a protective film. In order to suppress such display nonuniformity, using the (meth)acrylic-type resin film which lowered the absolute value of the photoelastic coefficient is examined.

As such a (meth)acrylic resin film, for example, an optical film containing a terpolymer of a monomer having a positive photoelastic coefficient, a monomer having a negative photoelastic coefficient, and a third monomer, and having a low photoelastic coefficient. This is known Specifically, an optical film (for example, Patent Document 1) containing a methyl methacrylate (MMA)/tertbutyl methacrylate (t-BMA)/benzyl methacrylate (BzMA) copolymer, or methacrylic acid The optical film (for example, patent document 2) containing a methyl (MMA)/trifluoromethyl methacrylate (3FMA)/benzyl methacrylate (BzMA) copolymer is known.

Moreover, the optical film containing the copolymer of methyl methacrylate and a maleimide-type monomer is also known (for example, patent document 3).

International Publication No. 2013/021872 Japanese Patent Laid-Open No. 2006-308682 Japanese Patent Laid-Open No. 2014-181256

Most of these (meth)acrylic resin films are manufactured by a melt casting method (melt method), but from the viewpoint that there are few restrictions on the material to be used, such as high molecular weight resin can be used, the solution casting method (cast method) method) is preferred.

In the solution casting method, a step of casting a dope in which a (meth)acrylic resin is dissolved or dispersed in a solvent onto a support, volatilizing and removing the solvent from the flexible coating film, and then peeling from the support to obtain a membranous product, and the obtained membranous product Through the process of extending|stretching while drying, a (meth)acrylic-type resin film is obtained. However, as for the membranous substance containing a (meth)acrylic-type copolymer as disclosed by patent document 1 or 2, a solvent was difficult to volatilize and removal, and drying property was low. Since such a membranous material contains a large amount of solvent, it tends to stretch by the conveyance tension|tensile_strength at the time of drying while conveying under high temperature, and there existed a problem that it is easy to generate|occur|produce a corrugated deformation|transformation.

In order to increase the drying property, it is preferable to increase the drying temperature; In order to raise a drying temperature, it is thought effective to raise the glass transition temperature (Tg) of (meth)acrylic-type resin. For example, although the optical film which has a copolymer which has a structure derived from maleimide as disclosed in patent document 3 has a high glass transition temperature, when there is too much content of the said structural unit, it becomes brittle easily. Therefore, it is desired to be able to suppress corrugated deformation by improving dryness without making the optical film brittle (that is, without impairing toughness).

Moreover, it is also desired that the favorable adhesiveness of an optical film and a polarizer can be maintained from a viewpoint of making it easy to suppress more display nonuniformity under high temperature and high humidity.

The present invention has been made in view of the above circumstances, without impairing toughness, suppressing corrugated deformation, maintaining good adhesion with a polarizer even under high temperature and high humidity, and reducing display unevenness in a display device. An object of the present invention is to provide an optical film and a polarizing plate that can be

The said subject can be solved by the following structures.

The optical film of the present invention comprises a structural unit derived from a monomer A having a negative photoelastic coefficient of the homopolymer, a structural unit derived from a monomer B having a positive photoelastic coefficient of the homopolymer and not having an alicyclic structure, , the photoelastic coefficient of the homopolymer is positive, and has a structural unit derived from monomer C having an alicyclic structure, and contains a (meth)acrylic copolymer that does not have a ring structure in the main chain, and rubber particles, The elastic modulus is -2.0×10 ^-12 to 2.0×10 ^-12 Pa ^-1 .

The polarizing plate of this invention has a polarizer and the optical film of this invention arrange|positioned at the at least one surface.

Advantageous Effects of Invention According to the present invention, an optical film capable of suppressing corrugated deformation without impairing toughness, maintaining good adhesion with a polarizer under high temperature and high humidity, and reducing display unevenness in a display device; A polarizing plate may be provided.

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which shows the polarizing plate which concerns on one Embodiment of this invention.

The present inventors, in addition to the monomer A in which the photoelastic modulus of the homopolymer is negative, and the monomer B in which the photoelastic modulus of the homopolymer is positive, as a third component, a monomer C having an alicyclic structure (constituting a side chain) By further copolymerizing and using a (meth)acrylic copolymer which does not have a cyclic structure in the main chain, it has been found that the above problems can be solved.

Although this reason is not clear, it is guessed as follows. Since the structural unit derived from the monomer C which has an alicyclic structure shows relatively high hydrophobicity compared with the solvent used by the solution casting method, affinity with the said solvent can be made small. Further, since the structural unit derived from the monomer C having an alicyclic structure has a bulky structure, it is possible to form micro spaces (voids) through which the solvent can move. Since it can make it easy to volatilize and remove a solvent from a membranous substance when forming into a film by the solution casting method by these, drying property can be improved. Further, since the monomer C having an alicyclic structure has a bulky structure, it is easy to raise the glass transition temperature of the membranous substance. Thereby, since a drying temperature can be raised, drying property can be improved further. As described above, by improving the drying property of the membranous material, the amount of residual solvent in the membranous material can be reduced and the elongation can be made difficult, so that the corrugated plate shape deformation at the time of conveyance under high temperature can be suppressed. In addition, since the (meth)acrylic copolymer does not have a cyclic structure in the main chain, despite having a structural unit derived from the monomer C having an alicyclic structure, the movement of the main chain is hardly disturbed, and the toughness of the optical film is also impaired. hard to be In addition, since the optical film has a micro space (gap) as described above, the adhesiveness with the polarizer through the adhesive can be improved in that the adhesive or the like easily permeates appropriately.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described in detail with reference to drawings.

1. Optical film

The optical film contains a (meth)acrylic copolymer and rubber particles.

1-1. (meth)acrylic copolymer

The (meth)acrylic copolymer has a structural unit derived from a monomer A (hereinafter simply referred to as “monomer A”) in which the photoelastic coefficient of the homopolymer is negative, and a monomer B having a positive photoelastic coefficient of the homopolymer ( Hereinafter, it has a structural unit derived from a "monomer B") and a structural unit derived from a monomer C (hereinafter also simply referred to as "monomer C") having an alicyclic structure. In addition, (meth)acryl means methacryl or acryl.

(monomer A)

Monomer A is a monomer in which the photoelastic coefficient of the homopolymer becomes negative. The photoelastic coefficient of the homopolymer of the monomer A is not particularly limited as long as the photoelastic coefficient of the optical film containing the (meth)acrylic copolymer is in the range described later, but for example, -10×10 ^-12 to It is preferable that it is -2×10 ^-12 Pa ^-1 , and it is more preferable that it is -8×10 ^-12 to -4×10 ^-12 Pa ^-1 .

The photoelastic coefficient of the homopolymer of the monomer A can be measured with the following procedure.

1) A cast film with a thickness of 0.1 mm is prepared using the homopolymer of the monomer A.

2) The photoelastic modulus of the prepared film is measured by the same method as the measuring method of the photoelastic modulus of the optical film described later, except that a tensile load is applied in any one direction.

In addition, when it is difficult to measure the photoelastic modulus of the film, such as the film is extremely brittle, measure the modulus of elasticity of the film of the copolymer copolymerized with a monomer having a known photoelastic modulus such as methyl methacrylate (MMA), , you may obtain|require the photoelastic coefficient of monomer A from a copolymerization ratio.

Monomer A is not particularly limited as long as the photoelastic modulus of the homopolymer is an ethylenic double bond-containing compound satisfying the above range, and examples thereof include methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, and methacrylic acid. (meth)acrylic acid alkylester compounds, such as acid t-butyl, (alpha) methylstyrene, etc. are contained. The number of carbon atoms in the alkyl portion of the (meth)acrylic acid alkylester compound may be, for example, 1 to 7, preferably 1 to 5.

Monomer A may be a monomer in which orientation birefringence of the homopolymer is positive, or a monomer in which orientation birefringence is negative. Among them, from the viewpoint of making it easy to adjust the photoelastic coefficient of the optical film containing the (meth)acrylic copolymer to the range described later, the monomer A is preferably a monomer in which the orientation birefringence of the homopolymer is negative, meta Methyl acrylate (MMA) is particularly preferred.

The orientation birefringence (Δn) of the homopolymer of the monomer A can be specified by the following method.

Specifically,

1) A cast film with a thickness of 0.1 mm is prepared using the homopolymer of the monomer A. After this film was cut into a square with a side of 5.0 cm, both ends of the film were bitten with chucks (3.0 cm between chucks), and the film was stretched 1.5 times at (Tg+5)°C of the homopolymer.

2) The retardation (Re) at 589 nm of the film after extending|stretching is measured using the ellipsometer M-220 manufactured by Nippon Bunko Co., Ltd., and orientation birefringence ((DELTA)n) is calculated|required from the following formula.

Δn=Re/d

Δn: orientation birefringence (-)

Re: phase difference (nm)

d: film thickness (nm)

Monomer A may be used by 1 type, and may be used in combination of 2 or more type.

The content of the structural unit derived from the monomer A may be set so that the photoelastic coefficient of the optical film falls within the range described later, and is not particularly limited, but a structural unit derived from the monomer A and a structural unit derived from the monomer B; It is preferable that it is 30-70 mass % with respect to the total content of the structural unit derived from the monomer C, and it is more preferable that it is 60-70 mass %.

(monomer B)

Monomer B is a monomer in which the photoelastic coefficient of a homopolymer becomes positive, it is a monomer different from monomer C, ie, does not have an alicyclic structure, and is a monomer in which the photoelastic coefficient of this homopolymer becomes positive. The photoelastic modulus of the homopolymer of the monomer B may be in a range such that the photoelastic modulus of the optical film containing the (meth)acrylic copolymer is in the range described later, and is not particularly limited, but for example, 2×10 ^-12 It is preferable that it is Pa ^-1 or more, and it is more preferable that it is 10x10 ^-12 - 50x10 ^-12 Pa ^-1 . The photoelastic coefficient of the homopolymer of the monomer B can be specified by the method similar to the above.

Monomer B is not particularly limited as long as it does not have an alicyclic structure and is an ethylenic double bond-containing compound in which the photoelastic modulus of the homopolymer satisfies the above range, for example, an ethylenic double bond-containing compound having an aromatic ring it is preferable Examples of the ethylenic double bond-containing compound having an aromatic ring include aromatic (meth)acrylic acid ester compounds such as benzyl methacrylate (BzMA), phenyl methacrylate (PhMA), and benzyl acrylate (BzAA), and styrene (St) , and aromatic vinyl compounds such as parachlorostyrene.

Monomer B may be a monomer in which orientation birefringence of the homopolymer is positive, or a monomer in which orientation birefringence is negative. Especially, from a viewpoint of making it easy to adjust the photoelastic coefficient of an optical film to the range mentioned later, it is preferable that the monomer B is a monomer from which orientation birefringence of the homopolymer becomes positive. It is more preferable that such a monomer B is an aromatic (meth)acrylic acid ester compound, and it is especially preferable that it is benzyl methacrylate (BzMA). In addition, from the viewpoint of obtaining a (meth)acrylic copolymer having no ring structure in the main chain, monomer B having a ring structure constituting the main chain, for example, maleimides such as phenylmaleimide is not included. .

Monomer B may be used by 1 type, and may be used in combination of 2 or more type.

(monomer C)

Monomer C is a monomer which has an alicyclic structure and the photoelastic coefficient of a homopolymer becomes positive. The alicyclic structure constitutes a side chain of the (meth)acrylic copolymer. The photoelastic coefficient of the homopolymer of the monomer C may be in a range such that the photoelastic coefficient of the optical film containing the (meth)acrylic copolymer is in the range described later, and is not particularly limited, but for example, more than 0 Pa ^-1 50 It is preferable that it is less than x10 ^-12 Pa ^-1 , and it is more preferable that it is 2 x 10 ^-12 Pa ^-1 or more and less than 10 x 10 ^-12 Pa ^-1 . The photoelastic coefficient of the homopolymer of the monomer C can be specified by the method similar to the above.

Monomer C is not particularly limited as long as it is an ethylenic double bond-containing compound having an alicyclic structure and the photoelastic modulus of the homopolymer satisfies the above range, Examples thereof include cyclohexyl methacrylate (CHMA), dimethacrylate Cyclofentanyl (DCPMA), isobornyl methacrylate (IBX), (meth) acrylic acid adamantyl, (meth) acrylic acid ester having an alicyclic structure such as methacrylic acid dicyclofentanyl (CPMA), vinyl cyclohexane, etc. and vinyls having an alicyclic structure.

Especially, the (meth)acrylic acid ester compound which has a crosslinked hydrocarbon group (bicyclo ring, tricyclo ring, etc.) as an alicyclic structure is preferable. Since the cross-linked hydrocarbon group has a bulky structure, it is easy to form a space through which the solvent can move in the resin matrix during the production of the optical film. Thereby, it is easy to improve the volatilization removal property of a solvent, ie, drying property, and it is easy to suppress a corrugated deformation|transformation. Moreover, since the cross-linked hydrocarbon group contains many tertiary carbon atoms, it is easy to produce|generate a hydroxyl group by corona treatment etc., and it is easy to improve the adhesiveness of an optical film and a polarizer. Examples of the (meth)acrylic acid ester compound having a crosslinked hydrocarbon group include dicyclopentanyl methacrylate (DCPMA) and isobornyl methacrylate (IBX), and preferably dicyclopentanyl methacrylate (DCPMA). In addition, from the viewpoint of obtaining a (meth)acrylic copolymer having no ring structure in the main chain, monomer C having a ring structure constituting the main chain, for example, maleimides such as cyclohexylmaleimide is not included. does not

Monomer C may be used by 1 type, and may be used in combination of 2 or more type.

The total content of the structural unit derived from the monomer B and the structural unit derived from the monomer C may be set so that the photoelastic coefficient of the optical film is in the range described later, and is not particularly limited, but the structural unit derived from the monomer A and , It is preferable that it is 30-70 mass % with respect to the total content of the structural unit derived from monomer B, and the structural unit derived from monomer C, and it is more preferable that it is 30-40 mass %. In addition, the total content of the structural unit derived from the monomer A, the structural unit derived from the monomer B, and the structural unit derived from the monomer C may be 100 mass % with respect to all the structural units constituting the (meth)acrylic copolymer. do.

Further, when the content of the structural unit derived from the monomer B is b and the content of the structural unit derived from the monomer C is c, c/(b+c) is preferably 0.4 to 0.8 (mass ratio). When c/(b+c) is 0.4 or more, since it contains suitably a large amount of structural units derived from monomer C having a bulky structure, the resulting membranous material has a large amount of space for moving the solvent in the resin matrix. easy to form Thereby, it is easy to improve the volatilization removal property of the solvent, ie, drying property, in the solution casting method, and it is easy to suppress a corrugated deformation|transformation. Moreover, since it is easy to form many spaces in a membranous substance, it is easy to permeate an adhesive agent, and it is easy to improve adhesiveness with a polarizer as well. If c/(b+c) is 0.8 or less, since it contains many structural units derived from the monomer B suitably, it is hard to become large the absolute value of the photoelastic coefficient of a (meth)acrylic-type copolymer. Thereby, even if stress is applied to an optical film, it can make it difficult to generate|occur|produce a phase difference and it can make it difficult to generate|occur|produce display nonuniformity in a display apparatus. It is more preferable that c/(b+c) is 0.5-0.8 (mass ratio) from the said viewpoint.

Moreover, it is preferable that a (meth)acrylic-type copolymer does not have a ring structure in a main chain from a viewpoint of not impairing the toughness of an optical film. Not having a ring structure in the main chain specifically means not having a ring in which atoms constituting the main chain are ring constituent atoms. For example, the (meth)acrylic copolymer does not have a structural unit derived from a monomer having a ring structure constituting the main chain, for example, maleimides such as phenylmaleimide and cyclohexylmaleimide. As described above, in the (meth)acrylic copolymer having no ring structure in the main chain, the movement of the main chain is hardly inhibited, and thus the toughness or flexibility of the optical film is hardly impaired.

(weight average molecular weight)

It is preferable that the weight average molecular weight (Mw) of a (meth)acrylic-type copolymer is 300,000 or more. When the weight average molecular weight of the (meth)acrylic copolymer is 300,000 or more, the mechanical strength (toughness, etc.) of the optical film can be easily increased, so that corrugated deformation can be further suppressed. From the said viewpoint, it is more preferable that it is 500,000-3 million, and, as for the weight average molecular weight of a (meth)acrylic-type copolymer, it is still more preferable that it is 600,000-2 million. A weight average molecular weight can be measured by the method similar to the above.

(Glass Transition Temperature)

It is preferable that it is 90 degreeC or more, and, as for the glass transition temperature (Tg) of a (meth)acrylic-type copolymer, it is more preferable that it is 120-150 degreeC. When the Tg of the (meth)acrylic copolymer is within the above range, not only the heat resistance of the optical film can be improved, but also the drying property can be improved, so that the corrugated deformation in the drying step can be further reduced. In order to increase Tg of a (meth)acrylic-type copolymer, it is preferable to increase content of the structural unit derived from the monomer C which has an alicyclic structure, for example.

It is preferable that it is 60 mass % or more with respect to an optical film, and, as for content of a (meth)acrylic-type copolymer, it is more preferable that it is 70 mass % or more.

1-2. rubber particles

The rubber particles can impart toughness and flexibility to the optical film.

A rubber particle is a particle|grains containing a rubber-like polymer (crosslinked polymer). Examples of the rubbery polymer include butadiene-based crosslinked polymers, (meth)acrylic crosslinked polymers and organosiloxane-based crosslinked polymers. Among them, a (meth)acrylic crosslinked polymer is preferable, and an acrylic crosslinked polymer (acrylic rubbery polymer) is more preferable from the viewpoint that the refractive index difference with the methacrylic resin is small and the transparency of the optical film is hardly impaired.

That is, it is preferable that a rubber particle is particle|grains containing an acrylic rubber-like polymer (a).

(Acrylic rubbery polymer (a))

The acrylic rubber-like polymer (a) is a crosslinked polymer containing acrylic acid ester as a main component. That is, the acrylic rubber-like polymer (a) has a structural unit derived from an acrylic acid ester, a structural unit derived from a monomer copolymerizable therewith, and two or more radically polymerizable groups (non-conjugated reactive double bonds) in one molecule. It is preferable that it is a crosslinked polymer containing the structural unit derived from a polyfunctional monomer.

It is preferable that acrylic acid ester is a C1-C12 acrylic acid alkylester of alkyl groups, such as methyl acrylate and a butyl acrylate. The number of acrylic acid esters may be one, and two or more types may be sufficient as them. From a viewpoint of making the glass transition temperature of a rubber particle into -15 degrees C or less, it is preferable that acrylic acid ester contains C4-C10 acrylic acid alkylester at least.

It is preferable that it is 50-80 mass % with respect to all the structural units which comprise the acrylic rubber-like polymer (a), and, as for content of the structural unit derived from acrylic acid ester, it is more preferable that it is 60-80 mass %. When content of acrylic acid ester is in the said range, it will be easy to provide sufficient toughness to a film.

A copolymerizable monomer is a thing other than a polyfunctional monomer among monomers copolymerizable with an acrylic acid ester. That is, a copolymerizable monomer does not have two or more radically polymerizable groups. Examples of the copolymerizable monomer include methacrylic acid esters such as methyl methacrylate; styrenes such as styrene and methylstyrene; Unsaturated nitriles, such as acrylonitrile and methacrylonitrile, etc. are contained. Especially, it is preferable that the monomer which can be copolymerized contains styrene.

It is preferable that it is 5-40 mass % with respect to all the structural units which comprise the acrylic rubber-like polymer (a), and, as for content of the structural unit derived from styrene, it is more preferable that it is 10-30 mass %.

Examples of the polyfunctional monomer include allyl (meth) acrylate, triallyl cyanurate, triallyl isocyanurate, diallyl phthalate, diallyl maleate, divinyl adipate, divinylbenzene, ethylene glycol di (meth) ) acrylate, diethylene glycol (meth) acrylate, triethylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylolmethane tetra (meth) acrylate, dipropylene glycol di (meth) ) acrylate, and polyethylene glycol di(meth)acrylate.

It is preferable that it is 0.05-10 mass % with respect to all the structural units which comprise the acrylic rubber-like polymer (a), and, as for content of the structural unit derived from a polyfunctional monomer, it is more preferable that it is 0.1-5 mass %. When the content of the polyfunctional monomer is 0.05% by mass or more, the degree of crosslinking of the obtained acrylic rubber-like polymer (a) is easily increased, so the hardness and rigidity of the obtained film are not excessively impaired. hard to be

The monomer composition constituting the acrylic rubbery polymer (a) can be measured, for example, by the peak area ratio detected by thermal decomposition GC-MS.

The particle|grains which consist of an acrylic rubber-like polymer (a) may be sufficient as the particle|grains containing the acrylic rubber-like polymer (a); The particle|grains which consist of an acrylic graft copolymer obtained by superposing|polymerizing at least 1 stage or more of mixtures of monomers, such as a methacrylic acid ester, in presence of an acrylic rubber-like polymer (a) may be sufficient. The particle|grains which consist of an acrylic graft copolymer may be core-shell type particle|grains which have a core part containing the acrylic rubber-like polymer (a), and a shell part covering it.

That is, the core part of the particle|grains of a core-shell type contains the acrylic rubber-like polymer (a); The shell part contains the polymer (b) containing the structural unit derived from methacrylic acid ester.

It is preferable that the methacrylic acid ester which comprises a polymer (b) is a C1-C12 methacrylic acid alkylester of alkyl groups, such as methyl methacrylate. The number of methacrylic acid esters may be one, and two or more types may be sufficient as them.

It is preferable that content of methacrylic ester is 50 mass % or more with respect to all the structural units which comprise a polymer (b). It can be made difficult to reduce the hardness and rigidity of the film obtained as content of methacrylic acid ester is 50 mass % or more. Moreover, as for content of methacrylic acid ester from a viewpoint of improving affinity with solvents, such as a methylene chloride, it is more preferable that it is 70 mass % or more with respect to all the structural units which comprise a polymer.

The polymer (b) may further contain a structural unit derived from another copolymerizable monomer. Examples of other monomers include acrylic acid esters such as methyl acrylate, ethyl acrylate, and n-butyl acrylate; (meth)acrylic acid (meth)acrylic monomers (ring structure-containing (meth)acrylic monomers) having an alicyclic structure, a heterocyclic structure or an aromatic group, such as benzyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and phenoxyethyl (meth)acrylate Included.

The weight ratio (graft ratio) of the graft component in the rubber particles is preferably 10 to 250%, more preferably 25 to 200%, still more preferably 40 to 200%, and still more preferably 60 to 150%. It is more preferable that When the said mass ratio is 10 % or more, since the ratio of a shell part does not decrease too much, the hardness and rigidity of a film are hard to be impaired. When the said mass ratio is 250 % or less, since the ratio of a core part does not decrease too much, the toughness and brittleness improvement effect of a film are hard to be impaired.

The graft rate is measured by the following method.

1) 2 g of core-shell particles were dissolved in 50 ml of methyl ethyl ketone, and centrifuged using a centrifugal separator (manufactured by Hitachi Koki Co., Ltd., CP60E) at a rotation speed of 30000 rpm and a temperature of 12° C. for 1 hour to obtain insoluble and soluble content. Separate in minutes (3 sets of centrifugation operations in total).

2) The weight of the obtained insoluble matter is applied to the following formula to calculate the graft rate.

Graft rate (%) = [{(weight of methyl ethyl ketone insoluble matter) - (weight of acrylic rubbery polymer (a))}/(weight of acrylic rubbery polymer (a))] x 100

(About physical properties)

It is preferable that the glass transition temperature (Tg) of the rubbery polymer contained in a rubber particle is 20 degrees C or less. When the glass transition temperature (Tg) of the rubbery polymer contained in the rubber particles is 20°C or less, moderate toughness can be imparted to the film. From the viewpoint of facilitating imparting sufficient toughness to the film, the glass transition temperature (Tg) of the rubbery polymer contained in the rubber particles is more preferably 0°C or less, more preferably -10°C or less, and -20°C or less. It is particularly preferred.

The glass transition temperature (Tg) of the rubbery polymer contained in the rubber particles can be measured in the same manner as described above. Alternatively, the glass transition temperature of the rubbery polymer may be calculated as a value obtained by specifying the monomer composition of the rubbery polymer by analysis and averaging the glass transition temperature of the homopolymer of each monomer according to the monomer composition. For example, when the rubbery polymer is a copolymer of monomer A and monomer B (mass fraction of monomer A: ma, mass fraction of monomer B: mb), glass transition temperature of the rubbery polymer = TgA × ma + TgB × You may compute it as mb (TgA: the glass transition temperature of the homopolymer of the monomer A, TgB: the glass transition temperature of the homopolymer of the monomer B).

The glass transition temperature (Tg) of the rubber particles can be adjusted, for example, according to the composition and graft rate of the polymer constituting the core portion or the shell portion. In order to lower the glass transition temperature (Tg) of the rubber particles, as will be described later, for example, in the acrylic rubbery polymer (a) of the core part, the mass ratio of the acrylic acid ester/copolymerizable monomer having an alkyl group of 4 or more carbon atoms is increased. (For example, it is 3 or more, Preferably it is set as 4 or more and 10 or less) It is preferable.

The shape of the rubber particles may or may not be flat in a cross section along the thickness direction of the film (preferably a cross section parallel to the stretching direction). For example, when the optical film is a stretched one, the rubber particles may usually be flat. It is preferable that the average long diameter (average particle diameter when not flat) of a rubber particle is 100-500 nm. It is easy to provide sufficient toughness or softness|flexibility to an optical film that the average long diameter of a rubber particle is 100 nm or more, and it is easy to suppress increase in the haze of an optical film that it is 500 nm or less. As for the average long diameter of a rubber particle, it is more preferable that it is 200-400 nm. The average major axis of the rubber particles is an average value of the major diameters of the rubber particles.

The average major axis of the rubber particles can be calculated with the following method.

1) TEM observation of the cross section of the optical film. The observation region may be a region corresponding to the thickness of the optical film or a region of 5 µm x 5 µm. When making the area|region corresponded to the thickness of an optical film into an observation area|region, a measurement location can be made into one place. When the area|region of 5 micrometers x 5 micrometers is made into an observation area|region, a measurement location can be made into 4 places.

2) The major axis and minor axis of each rubber particle in the obtained TEM image are measured. Let the average value of the major axis obtained from a some rubber particle be "average major axis".

In addition, when a rubber particle is not flat, what is necessary is just to measure the circle equivalent diameter of each rubber particle, and just to set the average value as "average particle diameter".

Although content of a rubber particle is not specifically limited, It is preferable that it is 5-25 mass % with respect to a (meth)acrylic-type copolymer, and it is more preferable that it is 5-15 mass %.

1-3. other ingredients

The optical film may further contain components other than the above as needed. Examples of other components include a matting agent for imparting slidability to the film. Inorganic microparticles|fine-particles, such as a silica particle, may be sufficient as a mat agent, and 80 degreeC or more of organic microparticles|fine-particles may be sufficient as a glass transition temperature.

1-4. Properties

(photoelastic coefficient)

It is preferable that the photoelastic coefficient of an optical film is -2.0x10 ^-12 to 2.0x10 ^-12 Pa ^-1 . If the photoelastic coefficient is within the above range, for example, even if stress is generated in the optical film due to bending of the polarizing plate under high temperature and high humidity, the retardation due to the stress is difficult to express, so display unevenness such as cloud unevenness occurs. hard to do In addition, since the said display nonuniformity looks cloud-like, it is called cloud nonuniformity. The photoelastic coefficient of the optical film is more preferably -1.0×10 ^-12 to 1.0×10 ^-12 Pa ^-1 from the above viewpoint.

The photoelastic coefficient of an optical film can be measured with the following method.

That is, using KOBRA-31PRW (manufactured by Oji Keisoku Kiki), a tensile load (stress) is applied in the in-plane slow axis direction of the optical film, a tensile test is performed, and the retardation developed at that time is measured at a wavelength of 589 nm. Specifically, by plotting the phase difference (nm) with respect to the tension (N) at 10 points in the range of 1 to 15 N for the tensile load (stress), the slope when the plot is linearly approximated is calculated, and the photoelastic coefficient do it with A measurement can be performed under 23 degreeC 55%RH. In addition, when the in-plane slow axis direction cannot be specified, it shall apply a tensile load to the width direction of an optical film.

The photoelastic coefficient of the optical film can be adjusted according to the monomer composition of the (meth)acrylic copolymer. In order to make the absolute value of the photoelastic coefficient of an optical film small, for example, the content of the structural unit derived from the monomer A which becomes negative the photoelastic coefficient of a homopolymer, and the monomer B which the photoelastic coefficient of a homopolymer becomes positive derived from It is preferable to adjust ratio of content (and/or content of the structural unit derived from the monomer C which has an alicyclic structure) of the structural unit to make in the range which cancels a photoelastic coefficient as a whole.

(Glass Transition Temperature)

It is preferable that the glass transition temperature (Tg) of an optical film is 90-150 degreeC, for example. When Tg of an optical film is 90 degreeC or more, not only can the heat resistance of an optical film be improved, but at the time of manufacture of the optical film by a solution casting method, since a drying temperature can be raised, it is easy to improve drying property. Since content of the structural unit derived from a rigid monomer can be decreased as Tg of an optical film is 150 degrees C or less, the toughness of an optical film is hard to be impaired. As for Tg of an optical film, it is more preferable that it is 120-150 degreeC. The glass transition temperature of an optical film can be measured by the method similar to the above.

The glass transition temperature of the optical film is mainly adjusted according to the monomer composition of the (meth)acrylic copolymer. In order to raise the glass transition temperature of an optical film, it is preferable to increase content of the structural unit derived from the monomer C which has an alicyclic structure, for example.

(internal haze)

It is preferable that it is 1.0 % or less like the above-mentioned, as for the internal haze of an optical film, It is more preferable that it is 0.1 % or less, It is more preferable that it is 0.05 % or less. The internal haze of an optical film can be measured by the method similar to the above.

The internal haze of the optical film can be adjusted according to the content of rubber particles and the like. In order to lower the internal haze of an optical film, it is preferable to make content of a rubber particle small.

(phase difference Ro and Rt)

The optical film, for example, from the viewpoint of using it as a retardation film for IPS mode, the retardation Ro in the in-plane direction measured in an environment of a measurement wavelength of 550 nm and 23 ° C. 55% RH is preferably 0 to 10 nm, 0 to It is more preferable that it is 5 nm. It is preferable that it is -20-20 nm, and, as for retardation Rt of the thickness direction of an optical film, it is more preferable that it is -10-10 nm.

Ro and Rt are each defined by the following formula.

Equation (2a): Ro=(nx-ny)×d

Equation (2b): Rt=((nx+ny)/2-nz)×d

(During the meal,

nx represents the refractive index in the in-plane slow axis direction (direction in which the refractive index is maximized) of the film,

ny represents the refractive index in the direction orthogonal to the in-plane slow axis of the film,

nz represents the refractive index in the thickness direction of the film,

d represents the thickness (nm) of the film.)

The in-plane slow axis of the optical film can be confirmed by an automatic birefringence meter axo-scan (Axo Scan Mueller Matrix Polarimeter: manufactured by Axo Matrix).

Ro and Rt can be measured by the following method.

1) Humidity control is performed for an optical film in the environment of 23 degreeC 55%RH for 24 hours. The average refractive index of this film is measured with an Abbe refractometer, and the thickness d is measured using a commercially available micrometer.

2) Retardation Ro and Rt of the film after humidity control at a measurement wavelength of 550 nm using an automatic birefringence meter Axo Scan (Axo Scan Mueller Matrix Polarimeter: manufactured by Axo Matrix Co., Ltd.), respectively, under an environment of 23°C and 55% RH measure

The retardation Ro and Rt of an optical film can be adjusted according to the monomer composition of a (meth)acrylic-type copolymer, or extending|stretching conditions, for example.

(Residual solvent amount)

The optical film may further contain a residual solvent in that it is preferably formed into a film by a solution casting method. It is preferable that it is 700 ppm or less with respect to an optical film, and, as for the amount of residual solvent, it is more preferable that it is 30-700 ppm. Content of a residual solvent can be adjusted with the drying conditions of the dope cast|flow_spreaded on the support body in the manufacturing process of an optical film.

The amount of residual solvent of an optical film can be measured by headspace gas chromatography. In the headspace gas chromatography method, a sample is sealed in a container, heated, the gas in the container is rapidly injected into the gas chromatograph in a state where the container is filled with volatile components, and volatile components are identified while performing mass spectrometry. is to quantify In the headspace method, it is possible to observe all the peaks of volatile components with a gas chromatograph, and by using an analysis method using electromagnetic interaction, quantification of volatile substances and monomers can be performed with high precision. have.

(thickness)

Although the thickness in particular of an optical film is not restrict|limited, It is preferable that it is 10-60 micrometers, and it is more preferable that it is 10-40 micrometers.

2. Manufacturing method of optical film

Although the optical film of the present invention can be produced by any method, it is preferable to be prepared by a solution casting method from the viewpoint that a high molecular weight (meth)acrylic copolymer can be used. That is, the optical film is at least 1) a step of obtaining a dope containing the above-described (meth)acrylic copolymer, rubber particles, and a solvent, and 2) casting the obtained dope on a support, followed by drying and peeling, to form a film It can be manufactured through the process of obtaining a shape, and 3) the process of drying the obtained membranous material, extending|stretching as needed.

About the process of 1)

A (meth)acrylic copolymer and a rubber particle are melt|dissolved or disperse|distributed to a solvent, and dope is prepared.

The solvent used for dope contains the organic solvent (good solvent) which can melt|dissolve a (meth)acrylic-type copolymer at least. Examples of the good solvent include chlorine-based organic solvents such as methylene chloride; and non-chlorine-based organic solvents such as methyl acetate, ethyl acetate, acetone, and tetrahydrofuran. Especially, methylene chloride is preferable.

The solvent used for dope may contain the poor solvent further. Examples of the poor solvent include linear or branched aliphatic alcohols having 1 to 4 carbon atoms. When the ratio of alcohol in dope becomes high, a membranous substance will gelatinize easily, and peeling from a metal support body will become easy to become easy. Examples of the linear or branched aliphatic alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, and tert-butanol. Among these, stability of dope and a boiling point are also comparatively low, and points, such as good drying property, are preferable to ethanol.

2) about the process

The obtained dope is cast|flow_spread on a support body. Casting of dope can be performed by discharging from a casting die.

Then, the solvent in the dope cast on the support is evaporated to dryness. The dried dope is peeled from a support body, and a membranous substance is obtained.

It is preferable that it is 25 mass % or more, for example, and, as for the amount of residual solvent of dope at the time of peeling from a support body (amount of residual solvent at the time of peeling), it is more preferable that it is 30-37 mass %. It is easy to suppress that the membranous substance by peeling stretches too much that the amount of residual solvent at the time of peeling is 37 mass % or less.

The amount of residual solvent of dope at the time of peeling is defined by a following formula. The same applies to the following.

Residual solvent amount (mass %) of dope = (mass before heat treatment of dope - mass after heat treatment of dope) / mass after heat treatment of dope x 100

In addition, the heat treatment at the time of measuring the amount of residual solvent means heat treatment at 140 degreeC for 30 minutes.

The amount of residual solvent at the time of peeling can be adjusted with the drying temperature and drying time of dope on a support body, the temperature of a support body, etc.

3) about the process

The obtained membranous material is dried. Drying may be performed in one step, and may be performed in multiple steps. In addition, you may perform drying, extending|stretching as needed.

For example, the drying step of the membranous material includes a step of pre-drying the membranous material (pre-drying step), a step of stretching the membranous material (stretching step), and a step of drying the membranous material after stretching (main drying step) may include

(Pre-drying process)

The preliminary drying temperature (drying temperature before stretching) may be a temperature higher than the stretching temperature. Specifically, when the glass transition temperature of the (meth)acrylic copolymer is Tg, it is preferably (Tg-50) to (Tg+50)°C. When the pre-drying temperature is (Tg-50) ° C. or higher, the solvent is easily volatilized properly, so the transportability (handling property) is easy to increase. It is hard to impair the stretchability in the extending|stretching process of. Initial drying temperature can be measured as atmospheric temperature, such as a temperature inside a stretching machine, or a hot air temperature, when drying by non-contact heating type while conveying by (a) a tenter stretching machine or a roller.

(stretching process)

Stretching may be performed in accordance with the required optical properties, preferably stretching in at least one direction, and stretching in two directions orthogonal to each other (eg, the width direction (TD direction) of the membranous material, and conveyance orthogonal thereto) biaxial stretching in the direction (MD direction)).

It is preferable that it is 5 to 100 %, and, as for the draw ratio at the time of manufacturing an optical film, it is more preferable that it is 20 to 100 %. When biaxially stretching, it is preferable that the draw ratios in each direction are in the said range, respectively.

The draw ratio (%) is defined as (size in the stretching direction of the film after stretching - the magnitude in the stretching direction of the film before stretching)/(size in the stretching direction of the film before stretching) x 100. Moreover, when performing biaxial stretching, it is preferable to set it as the said draw ratio with respect to each of a TD direction and MD direction.

The stretching temperature (drying temperature during stretching) is preferably Tg (° C.) or higher, and (Tg+10) to (Tg+50) when the glass transition temperature of the (meth)acrylic copolymer is Tg as described above. )°C is more preferable. When the stretching temperature is Tg(°C) or higher, preferably (Tg+10)°C or higher, the solvent tends to volatilize appropriately, so it is easy to adjust the stretching tension to an appropriate range. Since is not volatilized too much, it is hard to impair ductility. Extending|stretching temperature can be 90 degreeC or more, for example. As for extending|stretching temperature, it is preferable to measure atmospheric temperatures, such as (a) extending|stretching machine internal temperature similarly to the above.

It is preferable that the amount of residual solvent in the membranous substance at the start of stretching is about the same as the amount of residual solvent in the membranous substance at the time of peeling, for example, it is preferable that it is 20-30 mass %, It is more preferable that it is 25-30 mass %. desirable.

Stretching in the TD direction (width direction) of the membranous material can be performed, for example, by a method (tenter method) in which both ends of the membranous material are fixed with clips or pins, and the interval between the clips or pins is widened in the advancing direction. Extending|stretching of the MD direction of a membranous substance can be performed by the method (roll method) which gives a circumferential speed difference to a some roll, and uses a roll circumferential speed difference between them, for example.

(Main drying process)

It is preferable to further dry the membranous substance obtained after extending|stretching from a viewpoint of reducing the amount of residual solvent further. For example, it is preferable to further dry the membranous substance obtained after extending|stretching, conveying with a roll etc.

This drying temperature (drying temperature in the case of unstretching) is preferably (Tg-50) to (Tg-10) °C, when the glass transition temperature of the (meth)acrylic copolymer is Tg, (Tg-40 ) to (Tg-10)°C are more preferable. When the post-drying temperature is (Tg-50)°C or higher, the solvent is easily evaporated sufficiently from the membranous material after stretching, and when the post-drying temperature is (Tg-10)°C or lower, deformation of the membranous material and the like can be highly suppressed. As for this drying temperature, it is preferable to measure atmospheric temperatures, such as (a) hot air temperature, similarly to the above.

3. Polarizer

The polarizing plate of this invention has a polarizer, the optical film of this invention arrange|positioned at the at least one surface, and the adhesive bond layer arrange|positioned between them.

1 : is sectional drawing which shows the polarizing plate 100 which concerns on one Embodiment of this invention. As shown in Fig. 1, the polarizing plate 100 is between the polarizer 110, the optical film 120 of the present invention, the counter film 130, and the polarizer 110 and the optical film 120, and an adhesive layer 140 disposed between the polarizer 110 and the opposing film 130 .

3-1. polarizer

A polarizer is an element which passes only the light of the polarization plane of a fixed direction, and is a polyvinyl alcohol type polarizing film. The polyvinyl alcohol-based polarizing film includes a polyvinyl alcohol-based polarizing film in which iodine is dyed and a dichroic dye is dyed.

The polyvinyl alcohol-based polarizing film may be a film (preferably a film further subjected to durability treatment with a boron compound) after uniaxial stretching of the polyvinyl alcohol-based film and dyeing it with iodine or a dichroic dye; After dyeing a polyvinyl alcohol-type film with iodine or a dichroic dye, the film (preferably the film which further gave durability process with a boron compound) may be sufficient as it uniaxially stretched. The absorption axis of the polarizer is usually parallel to the maximum stretching direction.

For example, ethylene-modified ethylene with a content of 1 to 4 mol% of an ethylene unit, a degree of polymerization of 2000 to 4000, and a degree of saponification of 99.0 to 99.99 mol%, described in Japanese Patent Application Laid-Open No. 2003-248123 and Japanese Patent Application Laid-Open No. 2003-342322, etc. Polyvinyl alcohol is used.

It is preferable that it is 5-30 micrometers, and, as for the thickness of a polarizer, it is more preferable that it is 5-20 micrometers in consideration for the purpose of making a polarizing plate thin.

3-2. optical film

The optical film of this invention is arrange|positioned on one surface (preferably the surface which opposes a liquid crystal cell) of a polarizer. The optical film can function as a polarizing plate protective film (preferably retardation film).

3-3. opposing film

The optical film of this invention may be sufficient as a counter film, and other optical films other than that may be sufficient as it. Examples of other optical films include commercially available cellulose ester films (eg, Konica Minolta Tack KC8UX, KC5UX, KC4UX, KC8UCR3, KC4SR, KC4BR, KC4CR, KC4DR, KC4FR, KC4KR, KC8UY, KC6UY, KC4UY, KC4UY, KC4UY, KC4UY, KC8UY-HA, KC2UA, KC4UA, KC6UA, KC8UA, KC2UAH, KC4UAH, KC6UAH, or higher Konica Minolta Co., Ltd., Fujitack T40UZ, Fujitack T60UZ, Fujitack T80UZ, Fujitack TD TD80UL, Fujitack TD40UL, FUJITAK TD40UL, FUJITACH TD60UL, Fujitag R02, Fujitag R06, and above, manufactured by Fuji Film Co., Ltd.) are included.

The thickness of the opposing film may be, for example, 5 to 100 μm, preferably 40 to 80 μm.

3-3. adhesive layer

The adhesive layer may be disposed between the polarizer and the optical film and between the polarizer and the opposing film, respectively.

A layer obtained from a water-based adhesive agent may be sufficient as an adhesive bond layer, and the hardened|cured material layer of an active energy ray-curable adhesive agent may be sufficient as it.

(Water-Based Adhesive)

Examples of the water-based adhesive include vinyl polymer-based, gelatin-based, vinyl-based latex-based, polyurethane-based, isocyanate-based, polyester-based, and epoxy-based adhesives. Among them, a water-based adhesive containing a vinyl polymer is preferable, and a water-based adhesive containing a polyvinyl alcohol-based resin (completely saponified polyvinyl) alcohol aqueous solution, etc.) is more preferable. The water-based adhesive containing polyvinyl alcohol-type resin may further contain water-soluble crosslinking agents, such as boric acid, borax, glutaraldehyde, melamine, and oxalic acid.

(Active energy ray-curable adhesive)

An active energy ray-curable adhesive agent may be an optical radical polymerizable composition, or a photocationically polymerizable composition may be sufficient as it. Especially, a photocationically polymerizable composition is preferable.

The photocationically polymerizable composition contains an epoxy compound and a photocationic polymerization initiator.

An epoxy compound is a compound which has 1 or more, Preferably it has 2 or more epoxy groups in a molecule|numerator. Examples of the epoxy compound include a hydrogenated epoxy compound (glycidyl ether of a polyol having an alicyclic ring) obtained by reacting epichlorohydrin with an alicyclic polyol; Aliphatic epoxy compounds, such as polyglycidyl ether of an aliphatic polyhydric alcohol or its alkylene oxide adduct; The alicyclic epoxy-type compound which has one or more epoxy groups couple|bonded with the alicyclic ring in a molecule|numerator is contained. An epoxy-type compound may use only 1 type and may use 2 or more types together.

The photocationic polymerization initiator is, for example, an aromatic diazonium salt; onium salts such as aromatic iodonium salts and aromatic sulfonium salts; iron-arene complex or the like.

The photocationic polymerization initiator may further contain additives, such as cationic polymerization accelerators, such as an oxetane and a polyol, a photosensitizer, and a solvent, as needed.

The thickness of the adhesive layer is not particularly limited, and is, for example, 0.01 to 10 µm, preferably about 0.01 to 5 µm.

3-4. another floor

The polarizing plate of this invention may further have other layers other than the above as needed. Examples of the other layer include a pressure-sensitive adhesive layer for fixing the polarizing plate to the liquid crystal cell. For example, when a polarizing plate is arrange|positioned so that the optical film of this invention may become a liquid crystal cell side, a polarizing plate may further have the adhesive layer arrange|positioned on the optical film.

The pressure-sensitive adhesive layer is preferably dried and partially crosslinked with a pressure-sensitive adhesive composition containing a base polymer, a crosslinking agent, and a solvent. That is, at least a portion of the pressure-sensitive adhesive composition may be cross-linked.

Examples of the pressure-sensitive adhesive composition include an acrylic pressure-sensitive adhesive composition containing a (meth)acrylic polymer as a base polymer, a silicone pressure-sensitive adhesive composition containing a silicone-based polymer as a base polymer, and a rubber pressure-sensitive adhesive composition containing rubber as a base polymer. Especially, from a viewpoint of transparency, weather resistance, heat resistance, and workability, an acrylic adhesive composition is preferable.

The thickness of an adhesive layer is about 3-100 micrometers normally, Preferably it is 5-50 micrometers.

In addition, the surface of the pressure-sensitive adhesive layer may be protected with a release film (for example, a polyester film, a fluororesin film, etc.) subjected to a release treatment.

3-5. Method of manufacturing a polarizing plate

The polarizing plate of this invention can be obtained through the process of bonding a polarizer and the optical film of this invention through an adhesive agent. From a viewpoint of improving the adhesiveness of a polarizer and an optical film, you may further perform the process of surface-treating, such as a corona treatment, as needed before the process of bonding.

For example, in the case of using a water-based adhesive, the polarizing plate of the present invention comprises: 1) a step of performing activation treatment on the surface of the optical film of the present invention; 2) applying an adhesive to the surface of the optical film subjected to activation treatment. It can be obtained through the process of laminating|stacking a polarizer through and 3) the process of drying the obtained laminated body.

About the process of 1)

An activation process is given to the surface (surface to bond with a polarizer) of an optical film. Thereby, it makes it easy to obtain adhesiveness with a polarizer. Specifically, by making the tertiary carbon atom or the like of the (meth)acrylic copolymer contained in the optical film hydrophilic by activation treatment to increase affinity with the water-based adhesive or to facilitate interaction, the optical film It makes it easy to bond and polarizer.

Examples of the activation treatment include corona treatment, plasma treatment and saponification treatment, preferably corona treatment and plasma treatment, and more preferably corona treatment.

Activation treatment conditions may be sufficient to sufficiently activate tertiary carbon atoms and the like that the (meth)acrylic copolymer may have. When the activation treatment is a corona treatment, the irradiation amount is preferably 600 to 1200 (W·min/m 2 ).

2) about the process

Next, a polarizer is laminated|stacked on the surface to which the activation process of the optical film was given via a water-based adhesive agent.

It is preferable to perform lamination|stacking of the polarizer through a water-based adhesive agent quickly after an activation process, before the activity of the surface of an optical film is impaired. Specifically, it is preferable to perform lamination|stacking of the polarizer via a water-based adhesive agent within 30 minutes after an activation process, for example. Moreover, it is preferable not to heat-process from a viewpoint of making it hard to impair the activity of the surface of an optical film.

3) about the process

Next, the obtained laminate is dried to obtain a polarizing plate.

Drying can be performed by heat drying. The drying temperature may be a temperature at which the water-based adhesive is sufficiently dried, and may be, for example, 60 to 100°C.

As described above, since the optical film of the present invention has a micro space derived from the monomer C having an alicyclic structure in the (meth)acrylic copolymer, the aqueous adhesive easily permeates appropriately. In addition, when the (meth)acrylic copolymer has a crosslinked hydrocarbon group as an alicyclic structure, the tertiary carbon atom contained in the crosslinked hydrocarbon group is activated by the activation treatment, and a hydroxyl group (with high affinity with the water-based adhesive) is activated. can create Thereby, an optical film and a polarizer can be adhere|attached favorably through a water-system adhesive agent.

4. Liquid crystal display

A liquid crystal display device of the present invention includes a liquid crystal cell, a first polarizing plate disposed on one side of the liquid crystal cell, and a second polarizing plate disposed on the other side of the liquid crystal cell.

The display mode of the liquid crystal cell is, for example, STN (Super-Twisted Nematic), TN (Twisted Nematic), OCB (Optically Compensated Bend), HAN (Hybrid aligned Nematic), VA (Vertical Alignment, MVA (Multi-domain Vertical Alignment) ), PVA (Patterned Vertical Alignment), IPS (In-Plane-Switching), and the like. For example, when a liquid crystal display device is used for a smartphone or the like, the IPS mode is preferable.

The first polarizing plate and the second polarizing plate may be arranged such that the absorption axis of the polarizer of the first polarizing plate and the absorption axis of the polarizer of the second polarizing plate are orthogonal to each other (to become cross Nicols).

At least one of a 1st polarizing plate and a 2nd polarizing plate is the polarizing plate of this invention. It is preferable that the polarizing plate of this invention is arrange|positioned so that the optical film of this invention may become a liquid crystal cell side.

In this way, at least one of the first polarizing plate and the second polarizing plate is the polarizing plate of the present invention; The optical film of this invention is arrange|positioned so that it may become a liquid crystal cell side, and can function as retardation film. Thereby, cloud nonuniformity of the liquid crystal display device under high temperature and high humidity can be suppressed.

<Example>

Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these.

1. Materials of Optical Film

(1) (meth)acrylic copolymer

(meth)acrylic copolymers X1 to X22 shown in Table 1 were prepared.

(Monomer A in which the photoelastic modulus of the homopolymer is positive)

MMA: methyl methacrylate

t-BuMA: t-butyl methacrylate

(monomer B in which the photoelastic modulus of the homopolymer is negative)

BzMA: benzyl methacrylate

PhMA: Phenyl methacrylate

St: styrene

(monomer C having an alicyclic structure)

CHMA: cyclohexyl methacrylate

DCPMA: dicyclofentanyl methacrylate

IBX: isobornyl methacrylate

(comparative monomer)

PhMI: Phenylmaleimide

CHMI: cyclohexylmaleimide

The weight average molecular weight (Mw) and glass transition temperature (Tg) of (meth)acrylic copolymers X1-X22 were measured with the following method.

(photoelastic modulus of homopolymer)

1) The homopolymer of the monomer A, the homopolymer of the monomer B, and the homopolymer of the monomer C were prepared, respectively, and a 0.1 mm-thick cast film was produced with respect to each.

2) The photoelastic modulus of the produced film is subjected to a tensile test by applying a tensile load (stress) in any one direction using KOBRA-31PRW (manufactured by Oji Keisoku Kiki Co., Ltd.), and the retardation developed at that time is measured at a wavelength of 589 nm. measured. Specifically, by plotting the phase difference (nm) with respect to the tension (N) at 10 points in the range of 1 to 15 N for the tensile load (stress), the slope when the plot is linearly approximated is calculated, and the photoelastic coefficient was done with The measurement was performed under 23 degreeC 55%RH.

(weight average molecular weight)

The weight average molecular weight (Mw) of resin was measured using gel permeation chromatography (HLC8220GPC manufactured by Tosoh Corporation) and a column (TSK-GEL G6000HXL-G5000HXL-G5000HXL-G4000HXL-G3000HXL series manufactured by Tosoh Corporation). 20 mg±0.5 mg of the sample was dissolved in 10 ml of tetrahydrofuran, and filtered through a 0.45 mm filter. 100 ml of this solution was injected into a column (temperature: 40°C), and the measurement was performed at a detector RI temperature of 40°C, and a value converted to styrene was used.

(Glass Transition Temperature)

The glass transition temperature (Tg) of the resin was measured according to JIS K 7121-2012 using DSC (Differential Scanning Colorimetry).

(2) rubber particles

<Rubber Particle R1>

The following substances were put into an 8L polymerization apparatus equipped with a stirrer.

180 parts by mass of deionized water

0.002 parts by mass of polyoxyethylene lauryl ether phosphoric acid

0.4725 parts by mass of boric acid

Sodium carbonate 0.04725 parts by mass

0.0076 parts by mass of sodium hydroxide

After sufficiently replacing the inside of the polymerization reactor with nitrogen gas, the internal temperature was set to 80°C, and 0.021 parts by mass of potassium persulfate was introduced as a 2% aqueous solution. Next, 21 mass parts of a monomer mixture (c') comprising 84.6 mass% of methyl methacrylate, 5.9 mass% of butyl acrylate, 7.9 mass% of styrene, 0.5 mass% of allyl methacrylate, and 1.1 mass% of n-octyl mercaptan is poly The liquid mixture which added 0.07 mass parts of oxyethylene lauryl ether phosphoric acid was continuously added to the said solution over 63 minutes. Further, the innermost hard polymer (c) was obtained by continuing the polymerization reaction for 60 minutes.

Then, 0.021 mass part of sodium hydroxide was added as a 2 mass % aqueous solution, and 0.062 mass parts of potassium persulfate were added as a 2 mass % aqueous solution, respectively. Next, the mixture obtained by adding 0.25 mass parts of polyoxyethylene lauryl ether phosphoric acid to 39 mass parts of monomer mixture (a') which consists of 80.0 mass % of butyl acrylate, 18.5 mass % of styrene, and 1.5 mass % of allyl methacrylate over 117 minutes was added continuously. After completion of the addition, 0.012 parts by mass of potassium persulfate was added in a 2% by mass aqueous solution, the polymerization reaction was continued for 120 minutes, and a soft layer (layer made of the acrylic rubber-like polymer (a)) was obtained. The glass transition temperature (Tg) of the soft layer was -30°C. The glass transition temperature of the soft layer was calculated by averaging the glass transition temperature of the homopolymer of each monomer constituting the acrylic rubber-like polymer (a) according to the composition ratio.

Then, 0.04 mass parts of potassium persulfate was added with 2 mass % aqueous solution, and 26.1 mass parts of monomer mixtures (b') which consist of 97.5 mass % of methyl methacrylate and 2.5 mass % of butyl acrylates were continuously added over 78 minutes. Further, the polymerization reaction was continued for 30 minutes to obtain a polymer (b).

The obtained polymer was poured into a 3 mass % sodium sulfate hot water solution, and salted out and solidified. Subsequently, after repeated dehydration and washing, it was dried to obtain acrylic graft copolymer particles having a three-layer structure (rubber particles R1). The average particle diameter of the obtained rubber particle R1 was 200 nm.

<Rubber particle R2>

Except for changing the monomer composition (composition of the monomer mixture (a')) used for formation of the soft layer to 70.0 mass % of butyl acrylate, 28.5 mass % of styrene, and 1.5 mass % of allyl methacrylate, the same procedure as for rubber particle R1 was followed. Particle R2 was obtained. The average particle diameter of rubber particle R2 was 200 nm. The glass transition temperature (Tg) of the soft layer was -10°C.

The average particle diameter of a rubber particle was measured with the following method.

(average particle diameter)

The dispersed particle size of the rubber particles in the obtained dispersion was measured with a zeta potential/particle size measuring system (ELSZ-2000ZS manufactured by Otsuka Electronics Co., Ltd.).

2. Fabrication of optical films

<Production of Optical Film 101>

(Preparation of rubber particle dispersion)

15 parts by mass of rubber particles and 185 parts by mass of methylene chloride were stirred and mixed with a dissolver for 50 minutes, and then dispersed under 1500 rpm conditions using a milder disperser (manufactured by Daiheiyou Kiko Co., Ltd.), rubber particle dispersion liquid got

(preparation of dope)

Next, dope of the following composition was prepared. First, methylene chloride and ethanol were added to the pressure dissolution tank. Then, it injected|threw-in to the pressure dissolution tank, stirring resin 2. Next, the prepared rubber particle dispersion liquid was put in, and it was completely dissolved while stirring. This was filtered using SHP150 manufactured by Rocky Techno Co., Ltd., and dope was obtained.

(meth)acrylic copolymer X1: 100 parts by mass

Methylene chloride: 200 parts by mass

Ethanol: 40 parts by mass

Rubber particle dispersion: 200 parts by mass

(Unveiling)

Using the obtained dope, using the endless belt casting apparatus, dope was cast|flow_spread uniformly on the stainless steel belt support body at the temperature of 30 degreeC and 1800 mm width|variety. The temperature of the stainless steel belt was controlled at 28°C.

On the stainless steel belt support body, the solvent was evaporated until the amount of residual solvent in cast (cast) dope became 30 mass %. Then, it peeled from the stainless belt support body with the peeling tension|tensile_strength of 128 N/m, and obtained the membranous substance. The amount of residual solvent of the membranous substance at the time of peeling was 30 mass %.

Next, while conveying the peeled film with a number of rollers, the obtained membranous material was transported in a tenter in the width direction (TD direction) under the conditions of (Tg+10)°C (Tg: Tg of (meth)acrylic copolymer, hereinafter the same). ) was stretched by 30%. Then, it further dried at (Tg-10) degreeC, conveying with a roll, the edge part picked up with the tenter clip was slitted and wound up, and the optical film 101 with a film thickness of 40 micrometers was obtained.

<Production of optical films 102 to 117>

Except having changed the composition of the (meth)acrylic-type copolymer as shown in Table 2, it carried out similarly to the optical film 105, and obtained the optical films 102-117.

<Production of optical films 118 and 119>

Except having changed the composition and weight average molecular weight (Mw) of the (meth)acrylic copolymer as shown in Table 2, it carried out similarly to the optical film 106, and obtained the optical films 118 and 119.

<Production of optical films 122 and 123>

Except having changed the composition and weight average molecular weight (Mw) of a (meth)acrylic-type copolymer as shown in Table 2, it carried out similarly to the optical film 107, and obtained the optical films 122 and 123.

<Production of optical films 120 and 124>

Except not having added the rubber particle, it carried out similarly to the optical film 118 or 122, and obtained the optical film 120 or 124.

<Production of optical films 125 and 127>

The composition of the (meth)acrylic copolymer was changed as shown in Table 2 (changed to one having a ring structure in the main chain), and optical films 125 and 127 were obtained in the same manner as in optical film 106 except that rubber particles were not added. .

<Production of optical film 126>

Except having changed the kind of rubber particle as shown in Table 2, it carried out similarly to the optical film 106, and obtained the optical film 126.

<Evaluation>

The photoelastic modulus, glass transition temperature, corrugated deformation, and MIT flexibility of the obtained optical films 101-127 were measured by the following method.

(photoelastic coefficient)

Using KOBRA-31PRW (manufactured by Oji Keisoku Kiki Co., Ltd.), a tensile load (stress) is applied in the maximum stretching direction (direction in which the stretching ratio is maximized) of the optical film, a tensile test is performed, and the phase difference developed at that time is measured Measurements were made at 589 nm. Specifically, by plotting the phase difference (nm) with respect to the tension (N) at 10 points in the range of 1 to 15 N for the tensile load (stress), the slope when the plot is linearly approximated is calculated, and the photoelastic coefficient was done with The measurement was performed under 23 degreeC 55%RH.

(Glass Transition Temperature)

The glass transition temperature (Tg) of an optical film was measured based on JISK7121-2012 similarly to the above.

(waveform deformation)

The width direction cut out only 1 m of the obtained optical film in full width and a conveyance direction, and it was set as the sample. This sample was placed on the test base, and the presence or absence of corrugated deformation was visually observed. The corrugated deformation is a plurality of wrinkles formed substantially parallel to the conveyance direction of the optical film, and is a deformation seen in a wavy shape in the cross section of the optical film in the width direction. And it evaluated based on the following criteria.

(double-circle): no corrugated plate shape deformation is seen at all

○: Very little corrugated plate shape deformation is seen

△: A level in which a corrugated plate shape deformation is slightly visible, but there is no problem in practical use

×: A lot of corrugated plate shape deformation is seen

It was judged that it was favorable if it was more than (triangle|delta).

(MIT Flexibility)

The obtained optical film was cut out in width 15mm x length 150mm, and it was set as the test piece. After this test piece was left still for 1 hour or more at a temperature of 25°C and a relative humidity of 65% RH, under the condition of a load of 500 g, an MIT bending test was performed in accordance with JIS P8115:2001, and the number of times until fracture was measured did. The MIT bending test was performed using the cut resistance tester (The Tester Sangyo Co., Ltd. make, MIT, BE-201 type, bending curvature radius 0.38 mm). And the following evaluation criteria evaluated.

◎: 20000 or more

○: 15000 or more and less than 20000

△: 5000 times or more and less than 15000 times

×: less than 5000 times

The greater the number of times until fracture, the better the flexibility and the excellent resistance to repeated bending.

If it was more than (triangle|delta), it was judged as favorable.

Moreover, using the obtained optical films 101-126, a polarizing plate and a liquid crystal display device were respectively produced by the following method, and the adhesiveness of a polarizing plate and cloud nonuniformity of a liquid crystal display device were also evaluated, respectively.

(Adhesiveness of polarizer)

1) Fabrication of polarizer

A 25-micrometer-thick polyvinyl alcohol-type film was swollen with 35 degreeC water. The obtained film was immersed in an aqueous solution composed of 0.075 g of iodine, 5 g of potassium iodide, and 100 g of water for 60 seconds, and further immersed in an aqueous solution at 45°C composed of 3 g of potassium iodide, 7.5 g of boric acid and 100 g of water. The obtained film was uniaxially stretched on the conditions of a extending|stretching temperature of 55 degreeC, and a draw ratio of 5 times. After washing this uniaxially stretched film with water, it was made to dry and the 12-micrometer-thick polarizer was obtained.

2) Preparation of polarizing plate

After drying the obtained optical film in 140 degreeC oven for 15 minutes, it corona-treated (activation process) on one side with an irradiation amount of 800 (W·min/m 2 ). Next, the optical film was bonded to one side of the polarizer through a water-based adhesive (aqueous adhesive containing a polyvinyl alcohol-based resin) so that the corona-treated surface faces the polarizer. Bonding was performed so that the absorption axis of a polarizer and the slow axis of an optical film might be orthogonal.

Further, on the other surface (surface not facing the optical film) of the polarizer, the counter film Konica Minolta Tack KC6UA (60 µm thick, cellulose triacetate film, manufactured by Konica Minolta) was bonded via the same water-based adhesive as described above. did. The obtained laminate was dried in an oven at 90°C for 10 minutes. Thereby, the polarizing plate which has the laminated structure of opposing film / adhesive bond layer / polarizer / adhesive bond layer / optical film was obtained.

3) Evaluation of adhesion

Peeling strength (adhesiveness) when the optical film of the obtained polarizing plate is peeled off at the interface of the said optical film and a polarizer under an environment of 23 degreeC and 55%RH, 90 degree peel test (based on JIS Z0237:2009) , was measured with a 90° peeling test jig (P90-200N) manufactured by Imada Corporation.

(double-circle): Peeling strength 3.0 (N/25mm) or more

○: Peel strength is 2.0 (N/25mm) or more and less than 3.0 (N/25mm)

(triangle|delta): peeling strength 1.0 (N/25mm) or more and less than 2.0 (N/25mm)

x: peel strength less than 1.0 (N/25mm)

If it was more than (triangle|delta), it was judged as favorable.

(Cloud non-uniformity of liquid crystal display)

1) Fabrication of liquid crystal display device

As a liquid crystal display device, 65-inch size liquid crystal TV (liquid crystal TV) 65SM8100PJB made by LG was prepared. From this apparatus, the previously bonded polarizing plate of 2 sheets was peeled, the produced said polarizing plate was bonded together, respectively, and the liquid crystal display device was obtained.

Bonding of a polarizing plate was performed so that an optical film might become the liquid crystal cell side. In addition, an acrylic adhesive was used for bonding.

2) Evaluation of cloud non-uniformity

The obtained liquid crystal display device was placed in an environment of 80°C and 90% RH for 100 hours. The level of cloud non-uniformity was then graded by visual observation. Evaluation of cloud nonuniformity was performed by the following reference|standard.

(double-circle): Unevenness of a display panel cannot be recognized

○: Local unevenness is seen on the display panel, but the boundary between the uneven portion and the non-uniform portion cannot be visually recognized

△: Local unevenness is seen on the display panel, and the boundary between the uneven portion and the non-uniform portion can be visually recognized

×: Non-uniformity is seen on the entire surface of the display panel, and the non-uniformity part and the non-uniform part can be clearly visually recognized.

It was judged that it was favorable if it was more than (triangle|delta).

The evaluation result of the optical films 101-127, the polarizing plate using the same, and a liquid crystal display device is shown in Table 2.

As shown in Table 2, optical films 105 to 107, 109 to 111, 113 to 115, 118, 119, 122, 123, and 125 to 126 all have good flexibility (toughness) while exhibiting little corrugated deformation. Able to know. Moreover, it turns out that this polarizing plate has favorable adhesiveness, and there are also few cloud nonuniformities of a liquid crystal display device.

In particular, the monomer C constituting the (meth)acrylic copolymer is dicyclofentanyl methacrylate (DCPMA) having a cross-linked hydrocarbon or isobornyl methacrylate (in particular, dicyclopentanyl methacrylate having many tertiary carbon atoms (DCPMA) )), it can be seen that the adhesion of the polarizing plate can be higher than that of cyclohexyl methacrylate (CHMA) having no cross-linked hydrocarbon (contrast of optical films 105 to 107, contrast of 109 to 111, 103 to contrast of 115, etc.).

In addition, if the monomer A constituting the (meth)acrylic copolymer is BzMA (having positive orientation birefringence), it is preferable in that it is easier to adjust the orientation birefringence to near zero than that of styrene (having negative orientation birefringence). do.

In addition, it can be seen that by increasing the molecular weight of the (meth)acrylic copolymer, the corrugated deformation can be more suppressed, and the MIT flexibility is further improved. This is considered to be because the toughness of the optical film became higher (contrast of optical films 118 and 119, contrast of optical films 122 and 123).

In contrast, since the optical films 101 to 104, 108 and 112 contain a (meth)acrylic copolymer having no structural unit derived from monomer C, their drying properties are low, and corrugated deformation is easy to occur, and the polarizing plate It can be seen that the adhesion of On the other hand, since the optical films 116 and 117 contain a (meth)acrylic copolymer which does not have a structural unit derived from the monomer B that imparts a positive photoelastic coefficient, the photoelastic coefficient is high, and the cloud nonuniformity of the liquid crystal display is reduced. can be seen to occur. In addition, since the optical film 125 contains a (meth)acrylic copolymer having a structural unit derived from maleimide having a ring structure in the main chain and does not contain rubber particles, it can be seen that the MIT flexibility of the film is low. . In addition, it can be seen that the film 127 having a ring structure in the main chain has lower flexibility than the film 105 having no ring structure in the main chain (comparison between the films 105 to 107 and the film 127).

This application claims priority based on Japanese Patent Application No. 2019-121615 for which it applied on June 28, 2019. All content described in the said application specification and drawing is integrated in this specification.

Advantageous Effects of Invention According to the present invention, an optical film and a polarizing plate capable of suppressing corrugated deformation without impairing toughness, maintaining good adhesion with a polarizer even under high temperature and high humidity, and reducing display unevenness in a display device can provide

100: polarizer
110: polarizer
120: optical film
130: opposing film
140: adhesive layer

Claims (12)

A structural unit derived from a monomer A in which the photoelastic modulus of the homopolymer is negative, a structural unit derived from a monomer B having a positive photoelastic modulus of the homopolymer and having no alicyclic structure, and a photoelastic modulus of the homopolymer A (meth)acrylic copolymer having a structural unit derived from the monomer C having an alicyclic structure and having no ring structure in the main chain, and
rubber particles
including,
The photoelastic modulus is -2.0×10 ^-12 to 2.0×10 ^-12 Pa ^-1 ,
optical film. According to claim 1,
The monomer A is methyl methacrylate,
optical film. 3. The method of claim 1 or 2,
The monomer C is a (meth)acrylic acid ester compound having a cross-linked hydrocarbon group as the alicyclic structure,
optical film. 4. The method of claim 3,
The monomer C is (meth) acrylic acid dicyclopentanyl,
optical film. 3. The method of claim 1 or 2,
The monomer B is a monomer in which the orientation birefringence of the homopolymer is positive,
optical film. 6. The method of claim 5,
The monomer B is an aromatic (meth) acrylic acid ester compound,
optical film. 3. The method of claim 1 or 2,
When the content of the structural unit derived from the monomer B is b and the content of the structural unit derived from the monomer C is c, c/(b+c) is 0.5 to 0.8 (mass ratio),
optical film. 8. The method of claim 7,
The total content of the structural unit derived from the monomer B and the structural unit derived from the monomer C is the structural unit derived from the monomer A, the structural unit derived from the monomer B, and the structural unit derived from the monomer C 30 to 70 mass % with respect to the total content of
optical film. 3. The method of claim 1 or 2,
The (meth)acrylic copolymer has a weight average molecular weight of 500,000 or more,
optical film. 3. The method of claim 1 or 2,
The rubber particles include a rubbery polymer,
The glass transition temperature of the rubbery polymer is 0 ℃ or less,
optical film. 3. The method of claim 1 or 2,
The glass transition temperature of the optical film is 120 to 150 ℃,
optical film. polarizer and
The optical film according to claim 1 or 2 disposed on at least one surface thereof;
An adhesive layer disposed between the polarizer and the optical film
having, a polarizing plate.

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