JPWO2018056225A1 - Multilayer film, polarizing plate, and liquid crystal display - Google Patents

Abstract

A multilayer film comprising an A layer composed of a thermoplastic resin and a B layer formed on at least one surface of the A layer, wherein the B layer has a glass transition temperature of −50 ° C. to 40 ° C. A multilayer film is provided, which is constituted using the material Y containing the polymer Y1 and the crosslinking agent, and wherein the composite elastic modulus Er of the B layer and the base component amount S in the B layer fall within a specific range. The polymer Y1 is preferably a polyurethane. There is also provided a polarizing plate and a liquid crystal display comprising the multilayer film.

Description

  The present invention relates to a multilayer film, a polarizing plate, and a liquid crystal display.

  The liquid crystal display may be provided with an optical film made of a thermoplastic resin for various purposes. For example, retardation films are widely used to compensate for retardation due to birefringence of liquid crystal cells. As the retardation film, films in which a transparent resin is oriented by drawing to develop birefringence are widely used. In addition, it is also known to use such an optical film by bonding it to a polarizer made of polyvinyl alcohol (PVA) resin or the like containing a dye such as iodine, and simultaneously serving as a polarizer protective film. .

  In such an optical film used by being bonded to a polarizer, the peel strength, that is, the strength opposed to the force peeled from the polarizer after being bonded to the polarizer may be insufficient. Patent Document 1 proposes a technique for improving the peel strength. In patent document 1, the layer for improving adhesiveness is provided in the surface of an optical film, a multilayer film is comprised, this multilayer film is bonded with a polarizer, and the polarizing plate is comprised by it.

WO 2015/098956 (Corporate Patent Publication: US Patent Application Publication No. 2017/038510)

  However, when the multilayer film shown to patent document 1 is bonded with a polarizer, in the polarizing plate obtained, the pigment | dye in a polarizer may decolorize and the function as a polarizer may fall temporally.

  Therefore, an object of the present invention is to provide a multilayer film having high adhesiveness with other members such as a polarizer and a low tendency to deteriorate other members in contact, and such a multilayer film, which is durable. Is to provide a high polarizing plate and liquid crystal display device.

  As a result of investigations to solve the above problems, the present inventor can solve such problems when the composition and physical properties of layers provided to improve adhesion on the surface of an optical film are specified. The present invention has been completed.

According to the present invention, the following are provided.
[1] A multilayer film comprising: an A layer composed of a thermoplastic resin; and a B layer formed on at least one surface of the A layer,
The layer B is configured using a material Y containing a polymer Y1 and a crosslinking agent,
The multilayer film in which the composite elastic modulus Er of the B layer satisfies the following formula (1), and the base component amount S in the B layer satisfies the following formula (2).
0.5 GPa ≦ Er ≦ 2 GPa Formula (1)
0 μg / g ≦ S ≦ 20 μg / g Formula (2)
[2] The multilayer film according to [1], wherein the polymer Y1 is a polyurethane.
[3] The multilayer film according to [2], wherein the polyurethane contains a carbonate structure in its backbone.
[4] The thermoplastic resin includes a polymer having an alicyclic structure,
The multilayer film according to any one of [1] to [3], wherein a plane orientation coefficient P of the layer A satisfies the following formula (3).
1.0 × 10 ⁻³ <P <1.0 × 10 ⁻² (3)
[5] The multilayer film according to any one of [1] to [4], wherein the thickness Ta of the layer A and the thickness Tb of the layer B satisfy the following formula (4).
5.0 × 10 ⁻³ <Tb / Ta <5.0 × 10 ⁻² (4)
[6] A polarizing plate comprising the multilayer film according to any one of [1] to [5] and a polarizing film.
[7] The polarizing plate according to [6], wherein the polarizing film contains polyvinyl alcohol, and the polarizing film, the B layer, and the A layer are provided in this order.
[8] A liquid crystal display device comprising the multilayer film according to any one of [1] to [5].

  The multilayer film according to the present invention has high adhesion to other members such as a polarizer, and has a low tendency to deteriorate other members in contact. The polarizing plate and the liquid crystal display device of the present invention can be made into a polarizing plate and a liquid crystal display device having high durability by including such a multilayer film.

  BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to the embodiment and the examples, but the present invention is not limited to the embodiments and the examples shown below, and the scope of the present invention is not limited. The embodiment can be arbitrarily changed and implemented without departing from the scope.

  In the following description, the “polarizing plate” includes not only a rigid member but also a flexible member such as a resin film (including a sheet).

  The in-plane retardation of a film or layer is a value represented by (nx-ny) x d unless otherwise specified. Further, the retardation in the thickness direction of the film or layer is a value represented by {(nx + ny) / 2-nz} × d unless otherwise specified. Here, nx represents the refractive index in the direction (in-plane direction) perpendicular to the thickness direction of the film or layer and in the direction giving the maximum refractive index. ny represents the refractive index in the in-plane direction of the film or layer, which is perpendicular to the nx direction. nz represents the refractive index in the thickness direction of the film or layer. d represents the film thickness of the film or layer. The above-mentioned retardation can be measured using a commercially available phase difference measuring device (for example, "KOBRA-21ADH" manufactured by Oji Scientific Instruments, "WPA-micro" manufactured by Photonic Lattice, Inc.) or the Senalmon method.

  In addition, “parallel”, “vertical” or “orthogonal” as component orientations include errors within a range that does not impair the effects of the present invention, for example, within ± 5 ° unless otherwise specified. It is also good.

<1. Multilayer film>
The multilayer film of the present invention comprises an A layer composed of a thermoplastic resin, and a B layer formed on at least one surface of this A layer.

<1.1. A layer>
The A layer is a layer composed of a thermoplastic resin.
Examples of the thermoplastic resin include olefin resins such as polyethylene and polypropylene; polyester resins such as polyethylene terephthalate and polybutylene terephthalate; polyarylene sulfide resins such as polyphenylene sulfide; polyvinyl alcohol resin, polycarbonate resin, polyarylate resin, cellulose ester resin, Polyether sulfone resin, polysulfone resin, polyallyl sulfone resin, polyvinyl chloride resin, resin containing polymer having alicyclic structure, rod-like liquid crystal polymer, styrene or homopolymer of styrene derivative or copolymer with comonomer And polyacrylonitrile resin, polymethyl methacrylate resin, multicomponent copolymer thereof, and the like.
As a comonomer contained in polystyrene resin, acrylonitrile, maleic anhydride, methyl methacrylate, and butadiene can be mentioned as a preferable thing. You may use these individually by 1 type or in combination of 2 or more types. In the present invention, as the thermoplastic resin, a polymer having an alicyclic structure is preferable from the viewpoint of retardation expression, low-temperature stretchability, and adhesiveness with other layers.

  The polymer having an alicyclic structure is a polymer in which a structural unit of the polymer has an alicyclic structure. The polymer having this alicyclic structure may have an alicyclic structure in the main chain, and may have an alicyclic structure in the side chain. The polymer having this alicyclic structure may be used singly or in combination of two or more at an arbitrary ratio. Among them, polymers having an alicyclic structure in the main chain are preferable from the viewpoint of mechanical strength, heat resistance and the like.

  Examples of the alicyclic structure include a saturated alicyclic hydrocarbon (cycloalkane) structure, an unsaturated alicyclic hydrocarbon (cycloalkene, cycloalkyne) structure and the like. Among them, a cycloalkane structure and a cycloalkene structure are preferable from the viewpoint of, for example, mechanical strength and heat resistance, and a cycloalkane structure is particularly preferable.

  The number of carbon atoms constituting the alicyclic structure per one alicyclic structure is preferably 4 or more, more preferably 5 or more, preferably 30 or less, more preferably 20 or less, particularly preferably Is 15 or less. When the number of carbon atoms is in this range, the mechanical strength, heat resistance and moldability of the resin containing the polymer having the alicyclic structure are highly balanced, which is preferable.

  In the polymer having an alicyclic structure, the proportion of the structural unit having an alicyclic structure may be appropriately selected according to the purpose of use, and is preferably 55% by weight or more, more preferably 70% by weight or more, particularly Preferably it is 90 weight% or more. When the ratio of the structural unit having an alicyclic structure in the polymer having an alicyclic structure is in this range, the transparency and the heat resistance of the resin containing the polymer having an alicyclic structure become good.

  Among the polymers having an alicyclic structure, cycloolefin polymers are preferable. The cycloolefin polymer is a polymer having a structure obtained by polymerizing a cycloolefin monomer. The cycloolefin monomer is a compound having a ring structure formed of carbon atoms and having a polymerizable carbon-carbon double bond in the ring structure. Examples of polymerizable carbon-carbon double bonds include polymerizable carbon-carbon double bonds such as ring-opening polymerization. Moreover, as an example of the ring structure of a cycloolefin type monomer, a single ring, a polycyclic, a condensed polycyclic, a bridged ring, the polycyclic which combined these, etc. are mentioned. Among them, polycyclic cycloolefin monomers are preferable from the viewpoint of achieving a high balance of properties such as dielectric properties and heat resistance of the obtained polymer.

  Among the above cycloolefin polymers, preferred are norbornene polymers, monocyclic cyclic olefin polymers, cyclic conjugated diene polymers, and hydrides thereof. Among these, norbornene polymers are particularly preferable because they have good moldability.

  Examples of the norbornene-based polymer include a ring-opening polymer of a monomer having a norbornene structure, a ring-opening copolymer of a monomer having a norbornene structure and a comonomer, or a hydride thereof; An addition polymer of a monomer, an addition copolymer of a monomer having a norbornene structure and a comonomer, a hydride thereof, and the like can be mentioned. Among these, a ring-opened (co) polymer hydride of a monomer having a norbornene structure is particularly preferable from the viewpoint of moldability, heat resistance, low hygroscopicity, dimensional stability, lightness, and the like. Here, "(co) polymer" refers to a polymer and a copolymer.

Examples of monomers having a norbornene structure include bicyclo [2.2.1] hept-2-ene (common name: norbornene), tricyclo [4.3.0.1 ^2,5 ] deca-3,7. -Diene (conventional name: dicyclopentadiene), 7,8-benzotricyclo [4.3.0.1 ^2,5 ] dec-3-ene (conventional name: methanotetrahydrofluorene), tetracyclo [4.4. 0.1 ^2,5 . ^{17, 10} ] dodeca-3-ene (common name: tetracyclododecene), and derivatives of these compounds (for example, those having a substituent on the ring) and the like can be mentioned. Here, as an example of a substituent, an alkyl group, an alkylene group, a polar group etc. can be mentioned. Also, these substituents may be the same or different and a plurality of these may be bonded to the ring. Moreover, the monomer which has a norbornene structure may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  Examples of types of polar groups include heteroatoms or atomic groups having heteroatoms. Examples of the hetero atom include an oxygen atom, a nitrogen atom, a sulfur atom, a silicon atom, a halogen atom and the like. Specific examples of the polar group include carboxyl group, carbonyloxycarbonyl group, epoxy group, hydroxyl group, oxy group, ester group, silanol group, silyl group, amino group, nitrile group, sulfonic acid group and the like.

  Examples of monomers having a norbornene structure and ring-opening copolymerizable comonomers include monocyclic olefins such as cyclohexene, cycloheptene and cyclooctene and derivatives thereof; cyclic conjugated dienes and derivatives thereof such as cyclohexadiene and cycloheptadiene And the like. The monomer having a norbornene structure and the ring-opening copolymerizable comonomer may be used alone or in combination of two or more at an arbitrary ratio.

  The ring-opening polymer of a monomer having a norbornene structure, and the ring-opening copolymer of a monomer having a norbornene structure and a copolymerizable comonomer are, for example, the presence of a known ring-opening polymerization catalyst. It can be produced by polymerization or copolymerization below.

  Examples of the monomer having a norbornene structure and a comonomer capable of addition copolymerizing include α-olefins having 2 to 20 carbon atoms such as ethylene, propylene and 1-butene and derivatives thereof; cyclobutene, cyclopentene, cyclohexene and the like And cycloolefins and derivatives thereof; non-conjugated dienes such as 1,4-hexadiene, 4-methyl-1,4-hexadiene, 5-methyl-1,4-hexadiene and the like; Among these, α-olefins are preferable, and ethylene is more preferable. Moreover, the monomer which has a norbornene structure, and the comonomer which can be addition-copolymerized may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  The addition polymer of a monomer having a norbornene structure, and the addition copolymer of a monomer having a norbornene structure and a copolymerizable comonomer, for example, polymerize the monomer in the presence of a known addition polymerization catalyst Or it can manufacture by copolymerizing.

  Hydrogenated product of ring-opened polymer of monomer having norbornene structure, Hydrogenated product of ring-opened copolymer of monomer having norbornene structure and ring-openable copolymerizable monomer thereof and norbornene structure The hydrogenated substance of an addition polymer of a monomer having the same, and the hydrogenated substance of an addition copolymer of a monomer having a norbornene structure and a copolymer copolymerizable with the monomer with a norbornene structure are, for example, solutions of these polymers. The carbon-carbon unsaturated bond is preferably produced by hydrogenation of 90% or more in the presence of a known hydrogenation catalyst containing a transition metal such as nickel and palladium.

  As an example of a monocyclic cyclic olefin polymer, an addition polymer of a cyclic olefin monomer having a single ring such as cyclohexene, cycloheptene, cyclooctene and the like can be mentioned.

  Examples of cyclic conjugated diene polymers include polymers obtained by the cyclization reaction of addition polymers of conjugated diene monomers such as 1,3-butadiene, isoprene and chloroprene; cyclic conjugates such as cyclopentadiene and cyclohexadiene And 1,2- or 1,4-addition polymers of diene monomers; and hydrides thereof.

  The weight average molecular weight (Mw) of the polymer having an alicyclic structure can be appropriately selected according to the purpose of use of the multilayer film. The weight average molecular weight of the polymer having an alicyclic structure is preferably 10,000 or more, more preferably 15,000 or more, particularly preferably 20,000 or more, preferably 100,000 or less, more preferably 80. Or less, particularly preferably 50,000 or less. When the weight average molecular weight is in such a range, the mechanical strength and moldability of the multilayer film are highly balanced and suitable. Here, the weight average molecular weight is polyisoprene or polystyrene conversion measured by gel permeation chromatography using cyclohexane as a solvent (however, toluene may be used if the sample is not dissolved in cyclohexane). Weight average molecular weight of

  The thermoplastic resin may contain any component as long as the effects of the present invention are not significantly impaired. Examples of optional components include colorants such as pigments and dyes; plasticizers; fluorescent brighteners; dispersants; thermal stabilizers; light stabilizers; ultraviolet absorbers; antistatic agents; Additives such as surfactants can be mentioned. One of these components may be used alone, or two or more thereof may be used in combination at an arbitrary ratio. However, the amount of the proportion of the polymer constituting the thermoplastic resin is usually 50% by weight to 100% by weight, or 70% by weight to 100% by weight.

  The glass transition temperature of the thermoplastic resin is preferably 100 ° C. or more, more preferably 110 ° C. or more, particularly preferably 120 ° C. or more, preferably 190 ° C. or less, more preferably 180 ° C. or less, particularly preferably 170 ° C. It is below. By making the glass transition temperature of the thermoplastic resin equal to or higher than the lower limit value of the above range, the durability of the multilayer film in a high temperature environment can be enhanced. Further, by setting the content to the upper limit value or less, the stretching process can be easily performed.

  In the present application, the phrase “made of” the A layer means that the A layer is produced using a thermoplastic resin. By such production, the thermoplastic resin as it is, or, if necessary, reacts with the polymer in the resin, volatilizes the solvent, and the like to constitute the A layer. The method for producing the layer A using a thermoplastic resin is not particularly limited. For example, the thermoplastic resin may be produced into a film by a melt molding method, a solution casting method or the like. Examples of the melt molding method include an extrusion molding method of molding by melt extrusion, a press molding method, an inflation molding method, an injection molding method, a blow molding method, and a stretch molding method. Among these methods, the extrusion molding method, the inflation molding method and the press molding method are preferable from the viewpoint of obtaining an A layer excellent in mechanical strength and surface accuracy. Among them, the extrusion molding method is particularly preferable because the amount of residual solvent can be reduced and efficient and easy production is possible.

  In a preferred embodiment, the A layer is a layer having a predetermined plane orientation coefficient P, and thus, a certain value of retardation develops in the A layer. Therefore, the layer A is preferably a layer that has been subjected to a stretching treatment to develop such retardation. The method of stretching and the conditions of stretching may be as described in detail later in the description of the method of producing a multilayer film.

It is preferable that the plane orientation coefficient P of the layer A satisfies the following formula (3).
1.0 × 10 ⁻³ <P <1.0 × 10 ⁻² (3)

The plane orientation coefficient P of the layer A is preferably 2.0 × 10 ⁻³ or more, more preferably 3.0 × 10 ⁻³ or more, and preferably 9.0 × 10 ⁻³ or less, more preferably 8. It is 0 × 10 ⁻³ or less. By setting the plane orientation coefficient P of the layer A to the lower limit or more, a high retardation can be obtained while reducing the thickness of the layer A. The plane orientation coefficient P is an index indicating the orientation of molecular chains contained in a layer, and is a numerical value calculated according to the following equation from the refractive indices nx, ny and nz of the layer.
P = (nx + ny) / 2-nz
The measurement wavelength of the refractive index may be 590 nm.
The plane orientation coefficient P can be adjusted to a desired value by appropriately adjusting the conditions that affect the optical anisotropy of the A layer in the production of the multilayer film of the present invention. Specifically, in the step of stretching a film of a thermoplastic resin as a material of layer A alone or with other layers, the value of P is adjusted by adjusting conditions such as stretching temperature, stretching speed, stretching ratio, etc. Can be adjusted to over 1.0 × 10 ⁻³ . Moreover, the value of P can be adjusted to more than 1.0 * 10 < ^-3 > by also adjusting the said temperature and tension in the process of applying the film heat or tension of a thermoplastic resin. For example, in the step of forming layer B on layer A, the value of P is greater than 1.0 × 10 ⁻³ by appropriately adjusting the heat and tension applied in the operation of drying the material used to form layer B. It can be adjusted to

  The total light transmittance of the layer A in terms of 1 mm thickness is preferably 80% or more, and more preferably 90% or more. The A layer preferably has a haze of 0.3% or less at a thickness of 1 mm, and more preferably 0.2% or less. When the haze exceeds the above numerical range, the transparency of the multilayer film may be reduced.

  The content of the residual volatile component in the layer A is preferably 0.1% by weight or less, more preferably 0.05% by weight or less, and still more preferably 0.02% by weight or less. By setting the content of the volatile component in the above range, the dimensional stability is improved, and the temporal change of the in-plane retardation Re of the A layer and the retardation Rth in the thickness direction can be reduced. Deterioration of a polarizing plate provided with a film, a liquid crystal display device, or the like can be suppressed, and a display screen can be stably maintained stably for a long time. The volatile component is a substance having a molecular weight of 200 or less, and includes, for example, residual monomers and solvents. The content of volatile components can be quantified by gas chromatography analysis as a total of substances having a molecular weight of 200 or less.

<1.2. B layer>
B layer is a layer comprised using material Y containing polymer Y1 and a crosslinking agent.
In the present application, the layer B being a layer “made of the material Y” means that the layer B is a layer formed by the layer forming step using the material Y as a material. By such molding, the material Y becomes a B layer as it is or, if necessary, through the reaction of the components therein, the volatilization of the solvent, and the like. For example, the material Y is a solution or dispersion containing a polymer Y1, a crosslinking agent and a volatile medium such as water, and the B layer is formed by the volatilization of the medium and the crosslinking reaction of the polymer Y1 with the crosslinking agent. Ru.
The B layer is usually in direct contact with the A layer. That is, normally, no other layer is sandwiched between the A layer and the B layer. However, as long as the effect of the present invention is not significantly impaired, an optional layer may be interposed between the A layer and the B layer, if necessary.

  The polymer Y1 contained in the material Y is preferably a polymer having a glass transition temperature of −50 ° C. to 40 ° C., and is preferably different from the polymer of the thermoplastic resin constituting the layer A. The polymer Y1 preferably has water solubility or water dispersibility, and is more preferably a polymer that can be crosslinked by a crosslinking agent.

  As polymer Y1, what introduce | transduced the functional group into various polymers, such as an acrylic polymer, a vinyl polymer, polyurethane, polyester, can be used suitably, for example. Examples of the functional group include polar groups such as a carboxyl group, a carbonyloxycarbonyl group, an epoxy group, a hydroxyl group, an oxy group, an ester group, a silanol group, a silyl group, an amino group, a nitrile group and a sulfo group. Among them, a methylol group, a hydroxyl group, a carboxyl group and an amino group are preferable, a hydroxyl group or a carboxyl group is more preferable, and a hydroxyl group is particularly preferable. The content of the polar group in the polymer Y1 is preferably 0.0001 to 1 equivalent / 1 kg, and particularly preferably 0.001 to 1 equivalent / 1 kg.

  As an acrylic polymer, acrylic acid, acrylic acid esters such as alkyl acrylate, methacrylic acid esters such as acrylamide, acrylonitrile, methacrylic acid, alkyl methacrylate etc., single weight of any monomer of methacrylamide and methacrylonitrile A copolymer, a copolymer obtained by polymerization of two or more of these monomers, a copolymer obtained by polymerization of one or more of the above monomers and a comonomer, and the like can be mentioned. Among these, as the acrylic polymer, homopolymers of monomers of acrylic acid esters such as alkyl acrylate and methacrylic acid esters such as alkyl methacrylate or polymerization of two or more of these monomers The copolymers obtained are preferred. For example, mention may be made of homopolymers of monomers of any of acrylic acid esters and methacrylic acid esters having an alkyl group having 1 to 6 carbon atoms, or copolymers obtained by polymerization of two or more of these monomers. it can. The said acrylic polymer is a polymer which has the said composition as a main component, and is obtained using a part of monomer which has the functional group mentioned above so that reaction (crosslinking reaction) with the functional group in a crosslinking agent is possible.

  As a vinyl polymer, polyvinyl alcohol, acid-modified polyvinyl alcohol, polyvinyl formal, polyvinyl butyral, polyvinyl methyl ether, polyolefin, ethylene / butadiene copolymer, polyvinyl acetate, vinyl chloride / vinyl acetate copolymer, nyl chloride / ( Mention may be made of meta) acrylic acid ester copolymers and ethylene / vinyl acetate copolymers (preferably ethylene / vinyl acetate / (meth) acrylic acid ester copolymers). Among these, polyvinyl alcohol, acid-modified polyvinyl alcohol, polyvinyl formal, polyolefin, ethylene / butadiene copolymer and ethylene / vinyl acetate copolymer (preferably, ethylene / vinyl acetate / acrylic acid ester copolymer) Is preferred. The vinyl polymer is a polyvinyl alcohol, an acid-modified polyvinyl alcohol, a polyvinyl formal, a polyvinyl butyral, a polyvinyl methyl ether and a polyvinyl acetate, for example, a vinyl alcohol so that a crosslinking reaction with a crosslinking agent (for example, a carbodiimide compound) is possible. The polymer is a polymer having a hydroxyl group by leaving the unit in the polymer, and for other polymers, for example, a polymer crosslinkable by partially using a monomer having a methylol group, a hydroxyl group, a carboxyl group and / or an amino group .

  As the polyurethane, a polyol compound (ethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, glycerin, trimethylolpropane etc.) and a polybasic acid (polycarboxylic acid (eg, adipic acid, succinic acid, etc.) By reaction with sebacic acid, glutaric acid, maleic acid, fumaric acid, phthalic acid, dicarboxylic acid such as isophthalic acid, terephthalic acid, etc., and polycarboxylic acid containing tricarboxylic acid such as trimellitic acid or anhydride thereof)) Any of aliphatic polyester-based polyols, polyether polyols (eg, poly (oxypropylene ether) polyols, poly (oxyethylene-propylene ether) polyols), polycarbonate-based polyols, and polyethylene terephthalate polyols obtained It can be mentioned polyurethane derived species or mixtures thereof and a polyisocyanate. In the polyurethane, for example, after the reaction of the polyol and the polyisocyanate, the unreacted hydroxyl group can be used as a polar group capable of the crosslinking reaction with the functional group in the crosslinking agent. Here, as the polyurethane, a polycarbonate polyurethane having a carbonate structure in its skeleton is preferable.

  As polyurethane, what is contained in the water-based emulsion marketed as water-based urethane resin can be used. The water-based urethane resin is a composition containing polyurethane and water, and usually, polyurethane and optional components contained as necessary are dispersed in water. Examples of water-based urethane resins include "Adekabontiter" series manufactured by ADEKA, "Olester" series manufactured by Mitsui Chemicals, "Bondic" series manufactured by DIC, and "Hydran (WLS 201, WLS 202 etc.)" series , Bayer 's "Implanil" series, Kao' s "Poise" series, Sanyo Chemical Industries "Sanpren" series, Daiichi Kogyo Seiyaku 's "Superflex" series, Kushimoto Kasei " It is possible to use NEOREZ (Neo Reds) series, “Sancure” series manufactured by Lubrizol, and the like. One type of polyurethane may be used alone, or two or more types may be used in combination in an arbitrary ratio.

  As the polyester, generally, a polymer obtained by the reaction of the polyol compound and the polybasic acid can be used. The polyester can be used, for example, as a functional group (polar group) capable of undergoing a crosslinking reaction with a crosslinking agent after leaving the reaction between a polyol and a polybasic acid and leaving unreacted hydroxyl groups and carboxyl groups. Of course, a third component having a polar group such as a hydroxyl group or a carboxyl group may be added to the reaction system upon polymerization. Polyester is an acrylic acid, an acrylic acid ester such as an alkyl acrylate, an acrylic acid, an acrylic acid, an acrylic acid, an acrylic acid, an acrylic acid, an acrylonitrile, a methacrylic acid ester such as an acrylic acid, an acrylic acid, an acrylic acid, etc. And a copolymer obtained by polymerizing two or more of these monomers, and an acrylic polymer such as a copolymer obtained by polymerizing one or more of the monomers and a comonomer as a composite. You may use as polymer Y1.

As the water-soluble or water-dispersible polyester, one synthesized appropriately may be used, or a commercially available product may be used. Examples of the commercially available product include "Nichigo Polyester (Nichigo Polyester W-0030, Nichigo Polyester W-0005 S30 WO, Nichigo Polyester WR-961 etc.)" series (manufactured by Nippon Synthetic Chemical Co., Ltd.), "PES Resin A (PES Resin) A-210, PES resin A-520, PES resin A-684 G, PES resin A-695 GE, etc.) series (manufactured by Takamatsu Yushi Co., Ltd.) and the like.
Material Y may contain an organic solvent, but is preferably an aqueous emulsion substantially free of organic solvent. Specifically, the organic solvent may be less than 1% by weight. Here, examples of the organic solvent include methyl ethyl ketone, N-methyl-2-pyrrolidone and butyl cellosolve.

  The material Y usually contains the polymer Y1 as a main component. Specifically, the amount of the polymer Y1 in the material Y may be 60 to 100% by weight, preferably 70 to 100% by weight, where the total solid content in the material Y is 100% by weight.

  The material Y constituting the B layer contains a crosslinking agent in addition to the polymer Y1. The crosslinking agent may be a compound having two or more functional groups capable of forming bonds by reacting with functional groups (polar groups) in the polymer Y1. As a crosslinking agent, an epoxy compound, a carbodiimide compound, an oxazoline compound, an isocyanate compound etc. can be mentioned, for example.

<Epoxy compound>
As the epoxy compound, a polyfunctional epoxy compound having two or more epoxy groups in the molecule can be used. Thereby, a crosslinking reaction can be advanced and the mechanical strength of B layer can be improved effectively.

  The epoxy compound is preferably one that is soluble in water or that can be dispersed in water and emulsified. Such epoxy compounds may be preferably used in aqueous resin compositions. Here, the aqueous resin composition refers to a composition containing solid content in a state of being dissolved or dispersed in an aqueous solvent such as water. If the epoxy group has solubility in water or can be emulsified, it becomes possible to improve the coatability of the aqueous resin composition and to easily manufacture the B layer.

  Examples of the epoxy compound include glycols such as ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, 1,4-butanediol, 1,6-hexane glycol, neopentyl glycol 1 Diepoxy compound obtained by etherification of 1 mol of epichlorohydrin and 2 mol of epichlorohydrin; obtained by etherification of 1 mol of polyhydric alcohol such as glycerin, polyglycerin, trimethylolpropane, pentaerythritol and sorbitol with 2 mol or more of epichlorohydrin Polyepoxy compound; diepo obtained by esterification of 1 mole of dicarboxylic acid such as phthalic acid, terephthalic acid, oxalic acid, adipic acid and the like with 2 moles of epichlorohydrin Shi compounds; and the like. An epoxy compound may be used individually by 1 type, and may be used combining 2 or more types by arbitrary ratios.

  More specifically, as the epoxy compound, 1,4-bis (2 ′, 3′-epoxypropyloxy) butane, 1,3,5-triglycidyl isocyanurate, 1,3-diglycidyl-5- (γ) -Acetoxy-β-oxypropyl) isocyanurate, sorbitol polyglycidyl ethers, polyglycerol polyglycidyl ethers, pentaerythritol polyglycidyl ethers, diglyceryl polyglycidyl ether, 1,3,5-triglycidyl (2-hydroxyethyl) 2.) Epoxy compounds such as isocyanurate, glycerol polyglycerol ethers and trimethylol propane polyglycidyl ethers are preferable, and as a specific example of the commercially available product, "Nenacol (Denacol EX-521, manufactured by Nagase Chemtex Co., Ltd.)" is preferred. EX-614B etc.] series etc. can be mentioned.

  The amount of the epoxy compound is usually 2 parts by weight or more, preferably 4 parts by weight or more, more preferably 5 parts by weight or more, and usually 35 parts by weight or less, preferably 30 parts by weight, based on 100 parts by weight of the polymer Y1. The following amount is more preferably 25 parts by weight or less. By setting the amount of the epoxy compound to the lower limit value or more of the above range, the reaction between the epoxy compound and the polymer Y constituting the B layer sufficiently proceeds, so that the mechanical strength of the B layer is appropriately improved. By setting the upper limit value or less, the remaining of the unreacted epoxy compound can be reduced, and the mechanical strength of the B layer can be appropriately improved.

  When a polymer having a functional group is used as the polymer Y1, the amount of the epoxy compound is preferably in a specific range relative to the functional group. The preferred range of the amount of epoxy compound in the material Y can be expressed by the relative amount to the amount of epoxy compound equivalent to the functional group of the polymer Y1. The weight of the epoxy compound in the material Y is preferably 0.2 parts by weight or more, more preferably 0.4 parts by weight or more, particularly preferably 0.6 parts by weight or more, in terms of a ratio to 1 part by weight of the equivalent Is 5 parts by weight or less, more preferably 4.5 parts by weight or less, and particularly preferably 4 parts by weight or less. Here, the amount of the epoxy compound equivalent to the functional group means the theoretical amount of the epoxy compound which can react with the total amount of the functional group in the polymer Y1 without excess or deficiency. The functional group of the polymer Y1 can react with the epoxy group of the epoxy compound. By setting the amount of the epoxy compound in the above range, the reaction between the functional group and the epoxy compound can be advanced to an appropriate degree, and the mechanical strength of the B layer can be effectively improved.

<Carbodiimide compound>
As the carbodiimide compound, a compound having two or more carbodiimide groups in the molecule can be used. Carbodiimide compounds are usually synthesized by condensation reaction of organic diisocyanates. Here, the organic group of the organic diisocyanate used in the synthesis of the compound having two or more carbodiimide groups in the molecule is not particularly limited, and any of aromatic type, aliphatic type, or a mixture thereof may be used. However, aliphatics are particularly preferable from the viewpoint of reactivity.

  Organic isocyanate, organic diisocyanate, organic triisocyanate, etc. are used as a synthetic raw material. As examples of organic isocyanates, aromatic isocyanates, aliphatic isocyanates, and mixtures thereof can be used. Specifically, 4,4'-diphenylmethane diisocyanate, 4,4-diphenyldimethylmethane diisocyanate, 1,4-phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, hexamethylene diisocyanate, cyclohexane Diisocyanate, xylylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 1,3-phenylene diisocyanate, etc. are used, and as organic monoisocyanate, isophorone isocyanate, phenyl isocyanate And cyclohexyl isocyanate, butyl isocyanate, naphthyl isocyanate and the like are used.

  As the carbodiimide compound, for example, “Carbodilite (Carbodilite V-02, V-02-L2, SV-02, V-04, E-02, etc.)” manufactured by Nisshinbo Chemical Co., Ltd. can be obtained as a commercial product. The carbodiimide compound can be added in the range of 1 to 200% by weight, more preferably 5 to 100% by weight, with respect to the polymer Y1 of the B layer.

<Oxazoline compound>
As an oxazoline compound, the general formula shown in the following (I) (wherein R ⁴ , R ⁵ , R ⁶ and R ⁷ are the same or different and is a hydrogen atom, a halogen atom, an alkyl group, an aralkyl group, a phenyl group or It is possible to use a polymer having an oxazoline group represented by As this oxazoline compound, for example, by solution polymerization in an aqueous medium according to a conventionally known polymerization method, a monomer component containing an addition-polymerizable oxazoline, and optionally further containing an optional unsaturated monomer. You can get it.

Examples of addition polymerizable oxazolines are represented by the following general formula (II): wherein R ⁴ , R ⁵ , R ⁶ and R ⁷ are as defined above, and R ⁸ is an addition polymerizable unsaturated bond. And the like, and the like. As such compounds, specifically, 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2- Examples include oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline and the like, and one or more kinds can be used. Among these, 2-isopropenyl-2-oxazoline is industrially easy to obtain and suitable.

  The amount of use of the addition polymerizable oxazoline compound is not particularly limited, and for example, it is preferably 5% by weight or more, based on 100% by weight of all the monomer components used for producing the oxazoline compound, and 50% by weight It is preferable that it is% or less. If the amount is less than 5% by weight, the degree of curing may be insufficient, and the durability, water resistance, and the like may be impaired. Further, the optional unsaturated monomer is not particularly limited as long as it is a monomer which is copolymerizable with the addition polymerizable oxazoline and which does not react with the oxazoline group. A species or two or more species can be used.

  Examples of such oxazoline compounds include Epocross WS-500 and WS-700 in the water-soluble type, and Epocross K-2010, K-2020 and K-2030 (manufactured by Nippon Shokubai Co., Ltd.) in the emulsion type. In particular, water-soluble types that are highly reactive with the main agent are preferable.

  The amount of the oxazoline compound used is such that the molar ratio (the number of moles of functional group / the number of moles of oxazoline group) of the functional group such as the carboxyl group of the reactant and the oxazoline group of the oxazoline compound is 100/100 to 100/00. It is preferable to set it to 20. If the molar ratio of functional groups to oxazoline groups exceeds 100/20, unreacted functional groups may remain. If the molar ratio is less than 100/100, excess oxazoline groups may be generated to increase hydrophilic groups. Even when other crosslinking agents are used in combination as the crosslinking agent, it is preferable to set the molar ratio as described above.

  Here, when the polymer Y1 has a carboxyl group, in the reaction of the polymer Y1 with the oxazoline compound, when the carboxyl group is neutralized, the oxazoline group and the carboxylic acid salt hardly react with each other. The reactivity can also be controlled by changing the type of amine used (the volatility).

<Isocyanate compound>
As an isocyanate compound, compounds, such as an aliphatic, an alicyclic, or an aromatic, containing 2 or more of isocyanate groups in 1 molecule can be used. The aliphatic diisocyanate compound is preferably an aliphatic diisocyanate having 1 to 12 carbon atoms, and examples thereof include hexamethylene diisocyanate, 2,2,4-trimethylhexane diisocyanate, hexane diisocyanate (HDI) and the like. The alicyclic diisocyanate compound is preferably an alicyclic diisocyanate having 4 to 18 carbon atoms. For example, 1,4-cyclohexane diisocyanate, methylcyclohexylene diisocyanate, isophorone diisocyanate (IPDI), dicyclohexylmethane diisocyanate (HMDI), etc. It can be mentioned. Examples of the aromatic isocyanate include tolylene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate and the like.

  In the material Y, in addition to the above-mentioned crosslinking agent, a curing accelerator, a curing assistant and the like may be blended. As a curing accelerator, when using, for example, an epoxy compound as a crosslinking agent, a tertiary amine compound (a compound having a 2,2,6,6-tetramethylpiperidyl group having a tertiary amine in 4-position) is used. And the like. Boron trifluoride complex compounds and the like can be suitably used. The curing accelerator can be used singly or in combination of two or more. Although the compounding quantity of a hardening accelerator can be suitably selected according to the intended purpose, For example, 0.001-30 weight part normally with respect to 100 weight part of polymer Y1 which has a functional group, Preferably 0. The amount is 0.1 to 20 parts by weight, more preferably 0.03 to 10 parts by weight.

  Curing aids include oxime-nitroso-based curing aids such as quinone dioxime, benzoquinone dioxime, p-nitrosophenol and the like; maleimide-based curing aids such as N, N-m-phenylene bismaleimide; diallyl phthalate, toriary Allylic curing aids such as lucyanurate and triallyl isocyanurate; methacrylate curing aids such as ethylene glycol dimethacrylate and trimethylolpropane trimethacrylate; vinyl curing aids such as vinyl toluene, ethyl vinyl benzene and divinyl benzene; Etc. These curing assistants can be used singly or in combination of two or more. The compounding amount of the curing assistant is usually in the range of 1 to 100 parts by weight, preferably 10 to 50 parts by weight with respect to 100 parts by weight of the crosslinking agent.

<Other ingredients>
The material Y may contain other components other than those described above as long as the effects of the present invention are not significantly impaired. The material Y usually comprises water or a water-soluble solvent. Examples of water-soluble solvents include methanol, ethanol, isopropyl alcohol, acetone, tetrahydrofuran, N-methylpyrrolidone, dimethyl sulfoxide, ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, methyl ethyl ketone, triethylamine and the like. It is preferable to use water as a solvent. A solvent may be used individually by 1 type, and may be used combining 2 or more types by arbitrary ratios. The amount of the solvent to be blended is preferably set so that the viscosity of the material Y is in a range suitable for application.

  Moreover, the material Y may contain one or more types of fine particles. According to such a configuration, as the fine particles are contained in the B layer, unevenness can be formed on the surface of the B layer. By forming such unevenness, when the multilayer film is formed in a long shape, the area in which the B layer comes in contact with other layers when the multilayer film is wound is reduced. By reducing the area as such, the slipperiness of the surface of the layer B can be improved by that amount, and the occurrence of wrinkles when winding the multilayer film of the present invention can be suppressed.

  The average particle size of the fine particles is usually 1 nm or more, preferably 5 nm or more, more preferably 10 nm or more, and usually 500 nm or less, preferably 300 nm or less, more preferably 200 nm or less. By setting the average particle diameter to the lower limit value or more of the range, the slipperiness of the layer B can be effectively enhanced, and by setting the average particle size to the upper limit value or less of the range, the haze can be suppressed low. As the average particle diameter of the fine particles, the particle diameter distribution is measured by laser diffraction method, and the particle diameter (50% volume cumulative diameter D50) at which the cumulative volume calculated from the small diameter side becomes 50% in the measured particle diameter distribution Do.

  As fine particles, either inorganic fine particles or organic fine particles may be used, but it is preferable to use water-dispersible fine particles. Materials of inorganic fine particles include, for example, inorganic oxides such as silica, titania, alumina and zirconia; calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, calcium phosphate Etc. Moreover, when the material of organic particulates is mentioned, a silicone resin, a fluorine resin, an acrylic resin etc. will be mentioned, for example. Among these, silica is preferred. The fine particles of silica are excellent in the ability to suppress the generation of wrinkles and transparency, hardly generate haze, and have no coloring, so the influence on the optical properties of the multilayer film of the present invention is smaller. In addition, it is because silica has good dispersibility in urethane resin and dispersion stability. Among the fine particles of silica, amorphous colloidal silica particles are particularly preferable.

  The amount of fine particles contained in the material Y is usually 0.5 parts by weight or more, preferably 5 parts by weight or more, more preferably 8 parts by weight or more, and usually 20 parts by weight or less based on 100 parts by weight of the polymer Y1. Preferably it is 18 parts by weight or less, more preferably 15 parts by weight or less. By setting the amount of fine particles to the lower limit value or more of the above range, generation of wrinkles can be suppressed when the multilayer film of the present invention is wound. In addition, by setting the amount of the fine particles to the upper limit value or less of the above range, the appearance without white turbidity of the multilayer film of the present invention can be maintained.

  Further, the material Y may be, for example, a heat stabilizer, a weathering stabilizer, a leveling agent, a surfactant, an antioxidant, an antistatic agent, a slip agent, an antiblocking agent, or the like, as long as the effects of the present invention are not significantly impaired. Clouding agents, lubricants, dyes, pigments, natural oils, synthetic oils, waxes, crosslinking agents other than the above, and the like may be included. One of these may be used alone, or two or more of them may be used in combination at an arbitrary ratio.

<1.3. Composite elastic modulus Er of layer B>
In the multilayer film of the present invention, the composite elastic modulus Er of the B layer satisfies the following formula (1).
0.5 GPa ≦ Er ≦ 2 GPa Formula (1)

  The composite elastic modulus Er in the present application is obtained by Oliver-Pharr analysis. The composite elastic modulus Er is measured by using a nanoindentation (TI-950) (manufactured by HYSITRON, manufactured by HYSITRON, indenter barcovitch type) at a maximum indentation depth of 20 nm, and the relationship between the load and the indentation depth at loading and unloading. It can be determined by measuring

  The composite elastic modulus Er of the B layer is 0.5 GPa or more, preferably more than 0.5 GPa, more preferably 0.6 GPa or more, still more preferably 0.7 GPa or more, particularly preferably 1 GPa or more, and preferably 2 GPa or less Is smaller than 2 GPa, more preferably 1.9 GPa or less, and still more preferably 1.8 GPa or less. By the composite elastic modulus Er being in the above range, the peel strength of the multilayer film can be increased.

<1.4. Amount of base component S in layer B>
In the multilayer film of the present invention, the base component amount S of the B layer satisfies the following formula (2).
0 μg / g ≦ S ≦ 20 μg / g Formula (2)

  The amount of the base component is a component other than the polymer Y1 among the components constituting the B layer, and is a compound having an amine, a hydrazide, and a basicity equal to or higher than any of these. An -NR- adjacent to a carbonyl group such as an amido bond (-CO-NR-, R is a hydrogen atom or an arbitrary group) and a urethane bond (-OCO-NR-) is not included in the amines referred to herein. Examples of such amines include triethylamine, adipic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, terephthalic acid dihydrazide.

  The amount S of base components can be measured by quantifying the amount of components corresponding to the base component among the components constituting the material Y in the B layer. For example, in a composition that is a source of polyurethane as the polymer Y1, triethylamine may be included as a basic component for emulsifying the polyurethane. If the material Y is prepared using a composition containing triethylamine and a B layer is formed using it, triethylamine may be included in the B layer. The triethylamine usually disappears by volatilizing most in the process of forming the B layer, but some may remain. In addition, adipic acid dihydrazide may be added as an additive to material Y for the purpose of improving the peel strength of layer B, etc. When a layer B is formed using such material Y, adipic acid dihydrazide is It can be included in layer B. Some or all of these compounds may disappear by volatilization or reaction. Therefore, the base component amount S of the B layer can be determined by quantifying the ratio of these components in the formed B layer.

  The quantification of the base component can be determined by known methods. For example, the amount S of the base component in the sample can be determined by taking the layer B from the multilayer film of the present invention, cutting it, weighing it and dissolving it as a sample and analyzing it by various analysis methods. A specific example of the analysis method is an analysis method combining liquid chromatography and mass spectrometry such as LC / MS / MS.

  The base component amount S of the layer B is 0 μg / g or more, preferably 0.1 μg / g or more, more preferably 0.2 μg / g or more, particularly preferably 0.5 μg / g or more and 20 μg / g or less, preferably It is less than 20 μg / g, more preferably 19 μg / g or less, still more preferably 18 μg / g or less, particularly preferably 12 μg / g or less. When the amount of base components S is in this range, decolorization of the dye in the polarizer can be reduced when the multilayer film is bonded to the polarizer. When the base component is added to the material Y for the purpose of improving the peel strength of the multilayer film, the addition amount is adjusted so that the base component amount S in the B layer is in the above-described range.

<1.5. Relationship between the thickness of layer A and layer B>
It is preferable that thickness Ta of A layer and thickness Tb of B layer satisfy | fill following formula (4).
5.0 × 10 ⁻³ <Tb / Ta <5.0 × 10 ⁻² (4)

The ratio Tb / Ta of the thickness Ta of the A layer to the thickness Tb of the B layer is preferably 6.0 × 10 ⁻³ or more, more preferably 7.0 × 10 ³ or more, and preferably 4.0 × 10 ⁻² or less, more preferably 3.0 × 10 ⁻² or less. When Tb / Ta is at least the lower limit value, sufficient peel strength can be easily obtained. By Tb / Ta being below the said upper limit, the problem of winding of the multilayer film by the viscosity of B layer can be reduced.

  The thickness of the layer A is preferably 8 μm or more, more preferably 9 μm or more, particularly preferably 10 μm or more, preferably 100 μm or less, more preferably 90 μm or less, particularly preferably 80 μm or less. By making thickness of A layer more than the said lower limit, the mechanical strength of a multilayer film can be improved. The thickness of the multilayer film can be reduced by setting the thickness of the layer A to the upper limit value or less.

  The thickness of the layer B is preferably 50 nm or more, more preferably 100 nm or more, still more preferably 150 nm or more, preferably 5 μm or less, more preferably 2 μm or less, still more preferably 1 μm or less. By setting the thickness of the layer B to the above lower limit value or the like, sufficient peel strength can be obtained. By setting the thickness of the layer B to the upper limit value or more, the occurrence of deformation of the layer B, which is a relatively soft layer, is suppressed, and it becomes easy to wind up the multilayer film as a long roll. When the thickness of the layer B is in the above range, sufficient peel strength between the layer A and the layer B can be obtained, and the thickness of the multilayer film can be reduced.

  When the multilayer film of the present invention comprises only one layer A, the thickness of the layer A is a thickness Ta, and when the multilayer film of the present invention comprises two or more layers of A, the thickness of the layer A The total is the thickness Ta. When the multilayer film of the present invention comprises only one B layer, the thickness of the B layer is a thickness Tb, and when the multilayer film of the present invention comprises two or more B layers, the thickness of those B layers The total of the thickness Tb.

<1.6. Other layers>
The multilayer film of the present invention may comprise any layer in addition to the A layer and the B layer. For example, in addition to one layer of A layer and one layer of B layer, an optional layer may be provided on the side of the A layer opposite to the B layer. Examples of the optional layer include an antireflective layer, a hard coat layer, an antistatic layer, an antiglare layer, an antifouling layer, a separator film and the like.

<1.7. Method of manufacturing multilayer film>
The multilayer film of the present invention can be produced, for example, by the following production method. That is, the multilayer film of the present invention comprises a step of forming a film (layer 1) composed of a thermoplastic resin, and a layer 2 is formed on the surface of this film (layer 1) using a material Y to form a multilayer film substrate. A step of forming a multilayer film, and a step of forming a multilayer film comprising a layer A corresponding to the layer 1 after stretching and a layer B corresponding to the layer 2 after stretching by stretching the multilayer film substrate And a method comprising the steps of

  The step of forming the film (layer 1) can be performed, for example, by forming a thermoplastic resin into a film by melt molding, solution casting, or the like. Examples of the melt molding method include an extrusion molding method of molding by melt extrusion, a press molding method, an inflation molding method, an injection molding method, a blow molding method, and a stretch molding method. Among these methods, the extrusion molding method, the inflation molding method and the press molding method are preferable from the viewpoint of obtaining the layer 1 excellent in mechanical strength and surface accuracy. Among these, the extrusion molding method is particularly preferable because the amount of residual solvent can be reduced and efficient and easy production is possible.

  The step of forming the layer 2 using the material Y on the surface of the layer 1 to form a multilayer film substrate can be performed, for example, by the following procedure. That is, the material Y is applied to the surface of the layer 1 to form a coating film. Next, the resin component in the coating film is cured if necessary to obtain a layer 2.

  The method of applying the material Y is not particularly limited, but any known application method may be employed. Specific examples of the coating method include wire bar coating, dipping, spraying, spin coating, roll coating, gravure coating, air knife coating, curtain coating, slide coating, extrusion coating Law etc.

  If the material Y contains a solvent, the material Y may be dried to remove the solvent upon curing. The drying method is optional, and may be, for example, any method such as vacuum drying or heat drying. Among them, it is preferable to cure the resin in the material Y by heating and drying from the viewpoint of rapidly advancing a reaction such as a crosslinking reaction in the material Y. When the resin in the material Y is cured by heating, the heating temperature may be set appropriately as long as the material Y is dried to remove the solvent and at the same time the resin component in the material Y can be cured.

  As the material Y, for example, an aqueous emulsion (aqueous dispersion) is preferably used. In this case, in the material Y, each component in the material Y, that is, each component such as the polymer Y1 and the crosslinking agent is usually dispersed as particles. The particle size of the particles is preferably 0.01 μm to 0.4 μm from the viewpoint of the optical properties of the multilayer film of the present invention. The particle size may be measured by dynamic light scattering. For example, it can be measured by a light scattering photometer DLS-8000 series manufactured by Otsuka Electronics Co., Ltd.

  When the material Y is an aqueous emulsion, its viscosity is preferably 15 mPa · s or less, more preferably 10 mPa · s or less. When the viscosity of the aqueous emulsion is in the above range, the aqueous emulsion can be uniformly applied to the surface of the layer A. The lower limit of the viscosity of the urethane composition is not particularly limited, but is preferably 1 mPa · s or more. The above-mentioned viscosity is a value measured under the condition of 25 ° C. by a tuning fork type vibration viscometer. The viscosity of the aqueous emulsion can be adjusted, for example, by the ratio of the solvent contained in the aqueous emulsion, the particle size of the particles contained in the resin, and the like.

  In the stretching step, the multilayer film base can be stretched to obtain a multilayer film comprising an A layer corresponding to the layer 1 after stretching and a B layer corresponding to the layer 2 after stretching. The stretching treatment may be performed after the material Y is cured, but from the viewpoint of preventing the falling off of fine particles and the like from the layer configured using the material Y, before the resin component in the material Y is cured, Alternatively, it is preferable to perform the stretching treatment at the same time as curing. Furthermore, from the viewpoint of forming a uniform B layer, it is more preferable to perform the stretching treatment simultaneously with the curing of the resin component in the material Y.

  In the stretching step, the layer 1 and the layer 2 are simultaneously stretched to express a desired phase difference in the layer 1 to obtain an A layer. That is, when the layer 1 is stretched, the layer 2 formed on the surface of the layer 1 is also stretched. However, since the thickness of the layer 2 is usually sufficiently smaller than the thickness of the layer 1, a large phase difference does not appear in the B layer corresponding to the layer 2 after stretching.

  The method of the stretching treatment is not particularly limited. For example, a method of uniaxially stretching in the longitudinal direction by utilizing a difference in circumferential speed between rolls (longitudinal uniaxial stretching); a method of uniaxially stretching in the width direction using a tenter (laterally Uniaxial stretching); Method of sequentially performing longitudinal uniaxial stretching and transverse uniaxial stretching (sequential biaxial stretching); method of simultaneously performing longitudinal stretching and transverse stretching (simultaneous biaxial stretching); Diagonal to the longitudinal direction of the film before stretching Methods of stretching in the direction (oblique stretching); Here, "oblique direction" means a direction that is neither parallel nor perpendicular.

  The film temperature at the time of stretching can be relatively defined based on the glass transition temperature Tg of the thermoplastic resin forming the layer A. The film temperature during stretching is preferably Tg or more, more preferably "Tg + 5" ° C or more, particularly preferably "Tg + 8" ° C or more, preferably "Tg + 35" ° C or less, more preferably "Tg + 30" ° C or less, particularly Preferably it is "Tg + 25" ° C or less. By making the film temperature at the time of stretching at least the lower limit value of the above range, it is possible to prevent the development of a large retardation in the A layer. Further, by setting the content to the upper limit value or less, desired retardation can be stably expressed in the layer A.

  The stretching ratio can be appropriately set such that the retardation of the multilayer film has a desired value. For example, when longitudinal stretching is performed, the stretching ratio is preferably 1.1 times or more, and preferably 5.0 times or less. When transverse stretching is performed, the stretching ratio is preferably 1.3 times or more, more preferably 1.5 times or more, preferably 6.0 times or less, more preferably 5.0 times or less. Uneven thickness can be prevented by setting the draw ratio to the lower limit value of the above range or more. Moreover, the load concerning the installation for extending | stretching processes can be restrained by below an upper limit carrying out. Further, the number of times of the stretching treatment may be one, or two or more.

  In the manufacturing method of a multilayer film, you may perform arbitrary processes other than the process mentioned above. As an example of the optional step, the multilayer film can be preheated before drawing. Examples of means for heating the multilayer film include an oven-type heating device, a radiation heating device, and immersion in liquid. Among them, an oven-type heating device is preferable. The heating temperature in the preheating step is preferably "stretching temperature-40 ° C" or more, more preferably "stretching temperature-30 ° C" or more, preferably "stretching temperature + 20 ° C" or less, more preferably "stretching temperature + 15 ° C Or less. Here, the stretching temperature means the set temperature of the heating device.

  As another example of the optional step, the multilayer film after the stretching process can be subjected to an immobilization process. The temperature in the immobilization treatment is preferably room temperature or more, more preferably "stretching temperature-40 ° C" or more, preferably "stretching temperature + 30 ° C" or less, more preferably "stretching temperature + 20 ° C" or less.

  As another example of the optional step, before the layer 2 is formed on the surface of the layer 1, the surface of the layer 1 may be subjected to a modification treatment to improve the adhesion between the layer 1 and the layer 2. Examples of the surface modification treatment for the layer 1 include energy beam irradiation treatment and chemical treatment. Examples of the energy ray irradiation treatment include corona discharge treatment, plasma treatment, electron beam irradiation treatment, ultraviolet ray irradiation treatment, etc. From the viewpoint of treatment efficiency etc., corona discharge treatment and plasma treatment are preferable, and corona discharge treatment is particularly preferable. preferable. Further, as an example of the chemical treatment, there is a method of immersing in an aqueous solution of an oxidizing agent such as saponification treatment, potassium dichromate solution, concentrated sulfuric acid and the like and then washing with water.

  It is preferable to perform hydrophilization surface treatment on the surface of the layer 2 corresponding to the B layer or the B layer before the stretching treatment. The surface of the layer B is usually a bonding surface when the multilayer film of the present invention is bonded to another member. Therefore, by further improving the hydrophilicity of the surface of the layer 2 corresponding to the B layer or the B layer before the stretching treatment, the adhesion between the multilayer film of the present invention and other members can be remarkably improved.

  As an example of the hydrophilization surface treatment to B layer, corona discharge treatment, plasma treatment, saponification treatment, ultraviolet irradiation treatment, etc. are mentioned. Among them, corona discharge treatment and plasma treatment are preferable in view of treatment efficiency and the like, and corona discharge treatment is more preferable. Further, as the plasma treatment, atmospheric pressure plasma treatment is preferable.

  It is preferable to make the average water contact angle of the surface of B layer into a specific range by hydrophilization surface treatment. The average water contact angle of the surface of layer B is preferably 70 ° or less, more preferably 60 ° or less, particularly preferably 50 ° or less, and preferably 20 ° or more. Moreover, the standard deviation of a water contact angle is preferably 0.01 ° to 5 °. By subjecting the surface of the B layer to such a water contact angle, the multilayer film of the present invention can be strongly adhered to other members such as a polarizer.

The water contact angle is determined by the θ / 2 method using a contact angle meter.
The average water contact angle is calculated, for example, by measuring the water contact angle of 20 points randomly selected in the range of 100 cm ^{2 on} the surface of the B layer subjected to the hydrophilized surface treatment, and calculating the average of the measured values. Be done. The standard deviation of the water contact angle is calculated from this measurement. By performing the hydrophilization treatment, functional groups such as, for example, a hydroxy group, a carboxyl group, a carbonyl group, an amino group, and a sulfonic acid group can be introduced on the surface of the layer B.

  Preferred examples of electrodes used in corona discharge treatment include wire electrodes, flat electrodes, and roll electrodes. In order to make discharge uniform, it is preferable to carry out treatment by sandwiching a dielectric between the film to be treated and the electrode. Examples of the material of the electrode include metals such as iron, copper, aluminum and stainless steel. Examples of the shape of the electrode include a thin plate, a knife edge, and a brush.

  The dielectric preferably has a relative dielectric constant of 10 or more. The arrangement of the dielectrics is preferably such that the electrodes of both electrodes are sandwiched by the dielectrics. Examples of dielectric materials include ceramics; plastics such as silicon rubber, polytetrafluoroethylene and polyethylene terephthalate; glass; quartz; silicon dioxide; metal oxides such as aluminum oxide, zirconium dioxide and titanium dioxide; barium titanate and the like And the like. In particular, interposing a solid dielectric having a relative dielectric constant of 10 or more (under an environment of 25 ° C.) is advantageous in that corona discharge treatment can be performed at low voltage and at high speed. Examples of the solid dielectric having a dielectric constant of 10 or more include metal oxides such as zirconium dioxide and titanium dioxide; oxides such as barium titanate; silicone rubber and the like. The thickness of the dielectric is preferably in the range of 0.3 mm to 1.5 mm. If the thickness of the dielectric is too thin, dielectric breakdown is likely to occur, and if the thickness is too thick, the applied voltage may be increased, which may cause the efficiency to deteriorate.

  The distance between the film to be treated and the electrode is preferably 0.5 mm to 10 mm. If it is less than 0.5 mm, only a thin film can pass between the electrodes. For this reason, for example, when there is a thick portion such as a joint or the like, the thick portion of the film may hit the electrode when passing between the electrodes, and the film may be damaged. By setting the interval to 10 mm or less, excessive applied voltage can be prevented. As a result, the power supply equipment can be reduced in size, and the possibility of discharge becoming streamer-like can be reduced.

  The output of the corona discharge treatment is preferably such that the damage to the surface to be treated is treated as little as possible. Specifically, the output is preferably 0.02 kW or more, more preferably 0.04 kW or more, preferably 5 kW or less, more preferably 2 kW or less. Moreover, it is a preferable corona discharge treatment method to perform corona discharge treatment several times at the lowest possible output within this range.

The density of the corona discharge treatment is preferably adjusted so that the average water contact angle and the standard deviation of the water contact angle of the surface of the layer 1 subjected to the corona discharge treatment fall within the preferable range of values. The preferred average water contact angle is usually 20 ° to 70 °, more preferably 20 ° to 50 °. The preferred standard deviation of water contact angle is 0.01 ° -5 °. Specifically, the density of the corona discharge treatment is preferably 1 W · min / m ² or more, more preferably 5 W · min / m ² or more, particularly preferably 10 W · min / m ² or more, preferably 1000 W ··. min / m ² or less, more preferably 500 W · min / m ² or less, particularly preferably 300 W · min / m ² or less. By setting the processing density to the above lower limit or more, the quality of application of the material Y can be improved. In addition, by setting the treatment density to the upper limit or less, the destruction of the treated surface can be suppressed and the adhesion can be improved.

  The frequency of the corona discharge treatment is preferably 5 kHz or more, more preferably 10 kHz or more, preferably 100 kHz or less, more preferably 50 kHz or less. By setting the frequency to the lower limit or more, the uniformity of the corona discharge treatment can be improved, and the treatment with less unevenness can be performed. By setting the frequency to the upper limit or less, stable processing can be performed even when performing low-output corona discharge processing, and processing with less unevenness can be easily performed.

  In the corona discharge treatment, the discharge can be generated in a finer state by enclosing the periphery of the electrode with a casing, introducing an inert gas into the interior of the casing and applying a gas to the electrode portion. Examples of inert gases include helium, argon, nitrogen and the like. One type of inert gas may be used alone, or two or more types may be used in combination at an arbitrary ratio.

  When plasma treatment is performed as the hydrophilization surface treatment, examples of plasma discharge treatment include glow discharge treatment and flame plasma treatment. As the glow discharge, any of vacuum glow discharge treatment performed under vacuum and atmospheric pressure glow discharge treatment performed under atmospheric pressure can be used. Among them, atmospheric pressure glow discharge treatment performed under atmospheric pressure is preferable from the viewpoint of productivity. The atmospheric pressure is in the range of 700 to 780 Torr.

  In the glow discharge treatment, a film to be treated is placed between opposing electrodes, a plasma-exciting gas is introduced into the apparatus, and a high frequency voltage is applied between the electrodes to plasma-excite the gas. Glow discharge is performed. This further enhances the hydrophilicity of the treated surface.

  The plasma exciting gas refers to a gas excited by plasma under the above conditions. Examples of plasma-exciting gases include noble gases such as argon, helium, neon, krypton and xenon; nitrogen; carbon dioxide; fluorocarbons such as tetrafluoromethane and mixtures thereof; inert gases such as argon and neon And those to which a reactive gas capable of imparting a polar functional group such as a carboxyl group, a hydroxyl group or a carbonyl group is added. One type of plasma-exciting gas may be used alone, or two or more types may be used in combination at an arbitrary ratio.

  The frequency of the high frequency voltage in the plasma treatment is preferably in the range of 1 kHz to 100 kHz, and the magnitude of the voltage is preferably in the range of 1 kV / cm to 100 kV / cm when the electric field strength is applied to the electrode. .

  Moreover, the manufacturing method of a multilayer film is a method including the extending | stretching process of extending | stretching said layer 1 and forming A layer, and the process of forming B layer using the material Y on the surface of said A layer. May be That is, in this embodiment, a stretched film which has been stretched in advance is prepared, this stretched film corresponds to the layer A, and the layer B is formed on the surface of the layer A using the material Y. In the case of this manufacturing method, since the layer A already has a predetermined phase difference, the phase difference developed in the layer A before the step of forming the layer B is usually maintained in the multilayer film as a product. Is preferred. For this reason, in the step of forming the B layer, the heating temperature is preferably set to a temperature at which relaxation of orientation does not occur in the A layer. Such heating temperature may be defined relative to the glass transition temperature Tg of the material forming the A layer. Specifically, the heating temperature is preferably (Tg-50 ° C) or more, more preferably (Tg-40 ° C) or more, preferably (Tg + 60 ° C) or less, more preferably (Tg + 50 ° C) or less .

<1.8. Other Properties and Shapes of Multilayer Film>
The multilayer film of the present invention usually has high adhesion to other films such as a polarizing film. Specifically, the adhesion between the surface of the layer B and other films is high.

  From the viewpoint of stably exhibiting the function as an optical member, the multilayer film preferably has a total light transmittance of 85% or more, and more preferably 90% or more. The light transmittance can be measured using a spectrophotometer (manufactured by JASCO Corporation, ultraviolet visible near infrared spectrophotometer "V-570") in accordance with JIS K7361.

  The haze of the multilayer film is preferably at most 1%, more preferably at most 0.8%, particularly preferably at most 0.5%. By setting the haze to a low value, the sharpness of the display image of the display incorporating the multilayer film can be enhanced. Here, the haze is an average value obtained by measuring at five points using “turbidimeter NDH-4000” manufactured by Nippon Denshoku Kogyo Co., Ltd. in accordance with JIS K7136.

  The in-plane retardation Re and the retardation Rth in the thickness direction of the multilayer film can be optionally set according to the application of the multilayer film. The specific range of the in-plane retardation Re is preferably 50 nm or more, and preferably 200 nm or less. The specific retardation Rth in the thickness direction is preferably 50 nm or more, and preferably 300 nm or less.

  Furthermore, the variation in in-plane retardation Re of the multilayer film is preferably within 10 nm, more preferably within 5 nm, and particularly preferably within 2 nm. By setting the variation of the in-plane retardation Re in the above-mentioned range, it is possible to make the display quality favorable when it is used as a retardation film for a liquid crystal display device. Here, the variation in the in-plane retardation Re means the in-plane retardation Re when the light incident angle is 0 ° (that is, the state in which the direction of the light beam and the main surface of the multilayer film are perpendicular), the width of the multilayer film It is the difference between the maximum value and the minimum value when measured in the direction.

  The total thickness of the multilayer film is preferably 8 μm or more, more preferably 9 μm or more, particularly preferably 10 μm or more, preferably 250 μm or less, more preferably 200 μm or less, particularly preferably 150 μm or less. By making the total thickness of the multilayer film at least the lower limit value of the above range, the mechanical strength of the multilayer film can be increased. Moreover, the thickness of the whole multilayer film can be made thin by below an upper limit carrying out.

  The unevenness in thickness of the multilayer film may affect the possibility of winding, so it is preferably 3 μm or less, more preferably 2 μm or less. Here, thickness unevenness refers to the difference between the maximum value and the minimum value of thickness.

  The multilayer film is preferably long. The long shape means one having a length of about 5 times or more with respect to the width direction of the film, preferably 10 times or more, and specifically wound in a roll shape. It has a length that can be stored or transported. In the case of forming the multilayer film in a long shape, a long layer A is prepared, and while the layer A is sequentially fed, the material Y is continuously provided on the surface by coating or the like. Is preferred. The upper limit of the ratio of length to width is not particularly limited, but may usually be 5000 or less.

  The width dimension of the multilayer film is preferably 700 mm or more, more preferably 1000 mm or more, particularly preferably 1200 mm or more, preferably 2500 mm or less, more preferably 2200 mm or less, particularly preferably 2000 mm or less.

<2. Polarizer>
The polarizing plate of the present invention comprises the above-described multilayer film and a polarizing film. The polarizing film may be one that transmits one of two linear polarizations intersecting at right angles and absorbs or reflects the other. As a specific example of the polarizing film, a film of a vinyl alcohol polymer such as polyvinyl alcohol or partially formalized polyvinyl alcohol, dyed with a dichroic material such as iodine or a dichroic dye, stretching treatment, crosslinking treatment, etc. And the appropriate treatment of in a suitable order and manner. In particular, a polarizing film containing polyvinyl alcohol as described above is preferable because it is excellent in adhesion to a multilayer film. The thickness of the polarizing film is usually 5 μm to 80 μm.

  The multilayer film may be bonded to one side of the polarizing film, or may be bonded to both sides. Further, the number of multilayer films in the polarizing plate may be one, or two or more. Furthermore, when bonding the polarizing film and the multilayer film, an adhesive may be used as needed. Moreover, you may interpose arbitrary members between a polarizing film and a multilayer film as needed. However, in order to enhance the adhesion between the polarizing film and the multilayer film, it is preferable to bond the surface on the B layer side of the multilayer film to the polarizing film. Therefore, the polarizing plate of the present invention preferably comprises a polarizing film, a B layer and an A layer in this order.

  The polarizing plate of the present invention may include a film other than the multilayer film of the present invention as a protective film. The protective film may be provided on one side or both sides of the polarizing film. The protective film may be provided in a state of being adhered to other layers via a suitable adhesive layer. As a protective film, the resin film which is excellent in transparency, mechanical strength, heat stability, moisture shielding property, etc. is preferable. Examples of the resin forming the resin film include acetate polymers such as triacetyl cellulose, polymers having an alicyclic structure, polyolefins, polycarbonates, polyesters such as polyethylene terephthalate, polyvinyl chloride, polystyrene, polyacrylonitrile, and polysulfone, Examples include resins containing polyether sulfone, polyamide, polyimide, acrylic polymer and the like.

  The polarizing plate of the present invention may further include a retardation layer other than the multilayer film of the present invention. The retardation layer may be a single layer or a plurality of layers. By setting the optical axes of the multilayer film and the retardation layer to a desired relationship, the visibility of the liquid crystal display can be improved.

<3. Liquid Crystal Display Device>
The liquid crystal display device of the present invention comprises the multilayer film described above. The multilayer film comprises A and B layers, which allows for a high degree of birefringence compensation. Therefore, various characteristics of the liquid crystal display device can be improved by providing the multilayer film in the liquid crystal display device.

  The liquid crystal display device generally includes a liquid crystal panel in which a light source side polarizing plate, a liquid crystal cell and a viewing side polarizing plate are arranged in this order, and a light source for irradiating the liquid crystal panel with light. By arranging the multilayer film of the present invention as a retardation film, for example, between the liquid crystal cell and the light source side polarizing plate, between the liquid crystal cell and the viewing side polarizing plate, etc., the visibility of the liquid crystal display device is greatly enhanced. It can improve.

  Examples of liquid crystal cell drive methods include in-plane switching (IPS) mode, vertical alignment (VA) mode, multi-domain vertical alignment (MVA) mode, continuous spin wheel alignment (CPA) mode, hybrid alignment nematic (HAN) A mode, twisted nematic (TN) mode, super twisted nematic (STN) mode, optically compensated bend (OCB) mode and the like can be mentioned.

<4. Other uses>
The multilayer film described above can be easily manufactured and can be highly compensated for birefringence, and can be used for various optical applications alone or in combination with other members. For example, the multilayer film may be used alone as a retardation plate or a viewing angle compensation film. Also, for example, a retardation film may be combined with a circularly polarizing film to be used as a brightness enhancement film. Also, these may be applied to, for example, liquid crystal display devices, organic electroluminescence display devices, plasma display devices, FED (field emission) display devices, SED (surface electric field) display devices and the like.

Hereinafter, the present invention will be specifically described by way of examples. However, the present invention is not limited to the embodiments shown below, and can be implemented with arbitrary modifications without departing from the scope of the claims of the present invention and the equivalents thereof.
In the following description, "%" and "parts" representing quantities are by weight unless otherwise specified. Moreover, unless otherwise indicated, the operation described below was performed under conditions of normal temperature and normal pressure.

<Evaluation method>
(Method of measuring glass transition temperature of polymer)
The aqueous dispersion of polyurethane used in Examples and Comparative Examples was poured into a Teflon (registered trademark) -treated container and dried at room temperature for 24 hours. Thereafter, it was further dried in an oven at 120 ° C. for 1 hour to prepare a 150 μm thick polyurethane single film. The glass transition temperature of this single film was measured from the peak of tan δ using a dynamic viscoelasticity measuring apparatus ("Rheogel-E4000" manufactured by UBM). At this time, when two peaks appeared, the lower temperature peak was adopted as the glass transition temperature.

(Measurement method of thickness)
The total thickness of the layer A, the layer B and the multilayer film was measured as follows. The refractive index of each layer of the multilayer film as a sample was measured using ellipsometry ("M-2000" manufactured by Woollam Co., Ltd.). Thereafter, using the measured refractive index, the thickness of the film was measured with a light interference type film thickness meter ("MCPD-9800" manufactured by Otsuka Electronics Co., Ltd.).

(Measurement method of plane orientation coefficient)
The refractive index nx, ny, nz of the outermost layer (A layer) of the multilayer film at a wavelength of 590 nm was measured using a prism coupler refractometer Model 2010 manufactured by Metricon Corporation, and the plane orientation coefficient was calculated according to the following formula.
P = (nx + ny) / 2-nz
Here, nx represents the in-plane maximum refractive index, ny represents the refractive index in the direction orthogonal to ny, and ny represents the refractive index in the thickness direction.

(Method of measuring complex modulus)
The composite elastic modulus Er of layer B is measured using a nanoindentation (TI-950) (made by HYSITRON, manufactured by HYSITRON, manufactured by HYSITRON, indenter barcovich type) at a maximum indentation depth of 20 nm, at loading and unloading depth and indentation depth The relationship was determined by conducting an Oliver-Pharr analysis.

(Method of measuring the amount of base component)
Among the components contained in the aqueous resin composition prepared in the examples and comparative examples, those corresponding to the base component are triethylamine and (if contained) adipic acid dihydrazide. Therefore, these amounts were measured as base component amounts.
Layer B was shredded, weighed about 0.02 g, placed in 10 mL of acetonitrile / water (1: 1), and dissolved by sonication. The resulting solution was filtered, used as a sample, and subjected to LC / MS / MS measurement under the following conditions. The amount of triethylamine and adipic acid dihydrazide was determined by comparison with measurement using a standard product as a sample.
HPLC apparatus: LC-20A (Shimadzu Corporation)
MS / MS device: API 4000 (AB / MDS Sciex)
Column: YMC Triart-PFP (3 × 150 mm, 3 μm)
Column temperature: 45 ° C
Mobile phase A: 0.1 vol% formic acid 20 mmoL / L aqueous ammonium formate solution Mobile phase B: 0.1 vol% formic acid 20 mmo L / L ammonium formate methanol solution Time program:
0.0 → 5.0 min: B% = 2 → 10
5.0 to 8.0 min: B% = 10 to 70
8.0 to 10.0 min: B% = 70
10.1 → 20.0 min: B% = 2
Flow rate: 0.3 mL / min
Injection volume: 1 μL
Ionization: ESI (electrospray ionization method)
Detection: Positive ion detection Measurement mode: SRM (Selected reaction monitoring)
Monitor ion: Q1 m / z 175.3 → Q3 m / z 143.2 (CE: 20 eV)
Measurement time: 20.0 min

(Method of evaluating iodine coloration)
As a control polarizing plate, a polarizing plate having no B layer (hereinafter referred to as a polarizing plate 2) was produced. That is, the same thermoplastic resin film as that used in (1-1) of Example 1 was stretched under the same conditions as (1-3) except that the aqueous resin composition was not applied, to obtain an A layer. Using this A layer and the same polarizer, acrylic film and UV adhesive as used in (1-4) of Example 1, (acrylic film) / (UV adhesive layer) / (polarization) A polarizing plate 2 having a layer structure of (child) / (UV adhesive layer) / (A layer) was obtained.
The polarizing plate (hereinafter referred to as polarizing plate 1) obtained in each of the examples and comparative examples, the polarizing plate 2, a glass plate with a thickness of 0.7 mm (manufactured by Corning, product number "Eagle XG"), and an adhesive (Polarizer 1) / (Pressure-sensitive adhesive layer) / (Glass plate) / (Pressure-sensitive adhesive layer) / (Polarizer 2) using (Nitto Denko Corp., product number “CS9621”) Multilayer structure 1 was obtained. In the multilayer structure 1, the polarizing plate 1 and the polarizing plate 2 were disposed such that the surface on the acrylic film side was on the outside. Further, the transmission axis of the polarizing plate 1 and the transmission axis of the polarizing plate 2 were disposed to be orthogonal to each other.
As a control multilayer structure, a multilayer structure 2 having the same structure as that of the multilayer structure 1 except that the polarizing plate 2 was used in place of the polarizing plate 1 was produced. That is, the multilayer structure 2 has a layer configuration of (polarizing plate 2) / (adhesive layer) / (glass plate) / (adhesive layer) / (polarizing plate 2).
The multilayer structure 1 and the multilayer structure 2 were placed in an environment of 60 ° C. and 90% for 500 hours, and then placed on a back light to visually observe the state of light leakage in cross nicol. When the light leakage state of the multilayer structure 1 is the same or better than that of the multilayer structure 2 is "good" and poor is "defective".

(Method of measuring peel strength)
An unstretched film (glass transition temperature: 160 ° C., thickness: 100 μm, manufactured by Nippon Zeon Co., Ltd.) made of a resin containing a norbornene-based polymer was prepared as a film instead of the polarizing plate. The surface of the multilayer film on the side of layer B and one side of the unstretched film were subjected to corona treatment. An adhesive was attached to the corona-treated surface of the multilayer film and the corona-treated surface of the unstretched film, and the surfaces to which the adhesive was attached were bonded. At this time, a UV adhesive (CRB series (made by Toyochem)) was used as an adhesive. This obtained the sample film provided with the multilayer film and the unstretched film.
Thereafter, the sample film was cut to a width of 15 mm, and the multilayer film side was bonded to the surface of the slide glass with an adhesive. At this time, as a pressure-sensitive adhesive, a double-sided pressure-sensitive adhesive tape (manufactured by Nitto Denko Corporation, product number "CS9621") was used.
The unstretched film was held at the tip of a force gauge, and pulled in the normal direction of the surface of the slide glass to conduct a 90-degree peel test. Under the present circumstances, since the force measured when peeling an unstretched film is force required in order to make a multilayer film and an unstretched film peel, the magnitude | size of this force was measured as peeling strength.

Example 1
(1-1. Production of thermoplastic resin film)
Pellets of a resin containing a norbornene-based polymer (glass transition temperature: 137 ° C .; “ZEONOR 1420R” manufactured by Nippon Zeon Co., Ltd.) were dried at 100 ° C. for 5 hours. Thereafter, the dried resin pellets were fed to a single screw extruder. The resin was melted in an extruder, passed through a polymer pipe and a polymer filter, extruded from a T-die onto a casting drum, and cooled. Thus, a film having a thickness of 70 μm and a width of 675 mm was obtained.

(1-2. Preparation of aqueous resin composition)
Water dispersion of carbonate-based polyurethane (made by ADEKA, trade name "Adekabontiter SPX0672", glass transition temperature -16 ° C, containing triethylamine as a dispersant) in an amount of 100 parts of polyurethane and epoxy compound as a crosslinking agent ( 9 parts of Nagase ChemteX, trade name "Denacol EX 521", 0 parts of adipic acid dihydrazide as a non-volatile base (that is, not added in this example), acetylene-based surfactant (air products as a wetting agent) 0.14% by weight, based on the total amount of water, and water were mixed to make a liquid aqueous resin composition having a solid content concentration of 20%. In this operation, the "total amount of water" is the total amount of water contained in the aqueous dispersion of polyurethane and the added water.

(1-3. Production of multilayer film)
The surface of the film obtained in (1-1) was subjected to discharge treatment using a corona treatment apparatus (manufactured by Kasuga Denki Co., Ltd.) under the conditions of an output of 500 W, an electrode length of 1.35 m, and a conveyance speed of 15 m / min. Using the roll coater, the aqueous resin composition obtained in (1-2) is applied to the surface of the film obtained in (1-1) on the surface subjected to discharge treatment so that the thickness after drying becomes 1.02 μm. It applied. Thereafter, using a tenter-type lateral stretching machine, both ends of the film obtained in (1-1) are gripped with clips, and transverse uniaxial stretching is continuously performed at a stretching temperature of 152 ° C. at a draw ratio of 2.91. Furthermore, the left and right end portions were cut and removed. Thereby, the step of drying the applied aqueous resin composition and the step of stretching the film are simultaneously carried out, and the layer A formed by stretching the film obtained in (1-1) and the surface thereof are formed. A multilayer film comprising B layer was obtained. The multilayer film has an A layer thickness (Ta) of 24 μm, a B layer thickness (Tb) of 0.35 μm, an A layer orientation coefficient (P) of 0.004, a B layer composite elastic modulus (Er) of 1.8 GPa, a base component amount (S ) 0 μg / g. The peel strength of the obtained multilayer film was measured.

(Production of 1-4. Polarizing Plate)
An 80 μm thick polyvinyl alcohol film was dyed in a 0.3% aqueous iodine solution. Thereafter, the dyed polyvinyl alcohol film was stretched to 5 times in a 4% aqueous boric acid solution and a 2% aqueous potassium iodide solution, and then dried at 50 ° C. for 4 minutes to produce a polarizer.
The multilayer film obtained in (1-3), a polarizer, and an acrylic film having a thickness of 40 μm are adhered via a UV adhesive, (acrylic film) / (UV adhesive layer) / (polarizer) A polarizing plate having a layer structure of (UV adhesive layer) / (multilayer film) was obtained. As the UV adhesive, the adhesive composition described in Production Example 2 of Japanese Patent No. 5971498 was used. In the polarizing plate, the multilayer film was disposed such that the surface on the B layer side was on the UV adhesive layer side. The iodine polarizing property of the obtained polarizing plate was evaluated.

Example 2
In the step (1-2), the addition amount of adipic acid dihydrazide was changed to 2.5 parts. Moreover, in the step (1-3), the dried thickness of the aqueous resin composition was changed to 0.58 μm. A multilayer film and a polarizing plate were obtained by the same operation as in Example 1 except for the above points. The multilayer film has an A layer thickness (Ta) 24 μm, a B layer thickness (Tb) 0.2 μm, an A layer orientation coefficient (P) 0.004, a B layer composite elastic modulus (Er) 1 GPa, and a base component amount (S) 12 μg It was / g. About the obtained multilayer film and polarizing plate, measurement of peeling strength and evaluation of iodine decolorization were performed.

Example 3
In the step (1-2), the addition amount of adipic acid dihydrazide was changed to 1.5 parts. Moreover, in the step (1-3), the dried thickness of the aqueous resin composition was changed to 0.67 μm. A multilayer film and a polarizing plate were obtained by the same operation as in Example 1 except for the above points. The multilayer film has an A layer thickness (Ta) of 24 μm, a B layer thickness (Tb) of 0.23 μm, an A layer orientation coefficient (P) of 0.004, a B layer composite elastic modulus (Er) of 1.2 GPa, an amount of base components (S ) 8 μg / g. About the obtained multilayer film and polarizing plate, measurement of peeling strength and evaluation of iodine decolorization were performed.

Comparative Example 1
In the step (1-2), the addition amount of the crosslinking agent was changed to 0 part. Moreover, in the step (1-3), the dried thickness of the aqueous resin composition was changed to 0.79 μm. A multilayer film and a polarizing plate were obtained by the same operation as in Example 1 except for the above points. The multilayer film has an A layer thickness (Ta) 24 μm, a B layer thickness (Tb) 0.27 μm, an A layer orientation coefficient (P) 0.004, a B layer composite elastic modulus (Er) 3.1 GPa, a base component amount (S) ) 0 μg / g. About the obtained multilayer film and polarizing plate, measurement of peeling strength and evaluation of iodine decolorization were performed.

Comparative Example 2
In the step (1-2), the addition amount of adipic acid dihydrazide was changed to 8 parts. Moreover, in the step (1-3), the dried thickness of the aqueous resin composition was changed to 2.18 μm. A multilayer film and a polarizing plate were obtained by the same operation as in Example 1 except for the above points. The multilayer film has an A layer thickness (Ta) of 24 μm, a B layer thickness (Tb) of 0.75 μm, an A layer orientation coefficient (P) of 0.004, a B layer composite elastic modulus (Er) of 0.6 GPa, a base component amount (S ) 100 μg / g. About the obtained multilayer film and polarizing plate, measurement of peeling strength and evaluation of iodine decolorization were performed.

Comparative Example 3
In the step (1-2), the addition amount of adipic acid dihydrazide was changed to 5 parts. Moreover, in the step (1-3), the dried thickness of the aqueous resin composition was changed to 0.79 μm. A multilayer film and a polarizing plate were obtained by the same operation as in Example 1 except for the above points. The multilayer film has an A layer thickness (Ta) 24 μm, a B layer thickness (Tb) 0.27 μm, an A layer surface orientation coefficient (P) 0.004, a B layer composite elastic modulus (Er) 2.7 GPa, an amount of base components (S ) 62 μg / g. About the obtained multilayer film and polarizing plate, measurement of peeling strength and evaluation of iodine decolorization were performed.

<Result>
The results of Examples and Comparative Examples are shown in Table 1. Here, the meanings of the abbreviations in the following table are as follows.
Er: Composite elastic modulus of layer B (GPa)
S: Base component amount (μg / g)
Ta: Thickness of A layer (μm)
Tb: Thickness of B layer (μm)
P: Plane orientation coefficient of A layer

<Consideration>
As can be seen from the results in Table 1, in the examples, a multilayer film having less iodine decoloration of the polarizing film and higher peel strength was obtained as compared to the comparative examples.

Claims (8)

A multilayer film comprising an A layer composed of a thermoplastic resin and a B layer formed on at least one surface of the A layer,
The layer B is configured using a material Y containing a polymer Y1 and a crosslinking agent,
The multilayer film in which the composite elastic modulus Er of the B layer satisfies the following formula (1), and the base component amount S in the B layer satisfies the following formula (2).
0.5 GPa ≦ Er ≦ 2 GPa Formula (1)
0 μg / g ≦ S ≦ 20 μg / g Formula (2)   The multilayer film according to claim 1, wherein the polymer Y1 is a polyurethane.   The multilayer film according to claim 2, wherein the polyurethane comprises a carbonate structure in its backbone. The thermoplastic resin includes a polymer having an alicyclic structure,
The multilayer film according to any one of claims 1 to 3, wherein a plane orientation coefficient P of the layer A satisfies the following formula (3).
1.0 × 10 ⁻³ <P <1.0 × 10 ⁻² (3) The multilayer film according to any one of claims 1 to 4, wherein the thickness Ta of the layer A and the thickness Tb of the layer B satisfy the following formula (4).
5.0 × 10 ⁻³ <Tb / Ta <5.0 × 10 ⁻² (4)   A polarizing plate comprising the multilayer film according to any one of claims 1 to 5 and a polarizing film.   The polarizing plate according to claim 6, wherein the polarizing film contains polyvinyl alcohol, and the polarizing film, the B layer, and the A layer are provided in this order.   The liquid crystal display device provided with the multilayer film of any one of Claims 1-5.