JP2017109374A - Film and polarizing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film which can solve various problems of a TAC film, has good adhesion to an adhesive, has less change and deterioration even under environments such as high temperature and high humidity, high total light transmittance, and can be suitably used as a protective film for a polarizing film.SOLUTION: There are provided a film obtained by forming a coat layer formed of an aqueous urethane-based resin composition containing an urethane-based resin and a crosslinking agent on at least one surface of a resin layer containing a polycarbonate resin as a main component, where the crosslinking agent is an epoxy resin-based crosslinking agent; and a polarizing plate obtained by bonding a polarizing film on the coat layer of the film through an adhesive layer.SELECTED DRAWING: None

Description

  The present invention relates to a film, and more particularly to a film that can be suitably used as a protective film for protecting a polarizing film used in a liquid crystal display. The present invention also relates to a polarizing plate using the film and a liquid crystal display device having the polarizing plate.

  In recent years, liquid crystal displays have been widely used as display devices for televisions, personal computers, digital cameras, mobile phones and the like. The liquid crystal display has a configuration of front side polarizing plate / liquid crystal / rear side polarizing plate, where the display side is the front side and the opposite side (backlight side) is the rear side. The polarizing plate is usually formed by laminating a protective film or the like on a polarizing film made of a dyed uniaxially stretched polyvinyl alcohol film, for example, a laminated film of protective film / polarizing film / protective film. The protective films disposed on the front and rear surfaces of the polarizing film constituting the front polarizing plate are designated as protective film A and protective film B, respectively, and the protective films disposed on the front and rear surfaces of the polarizing film constituting the rear polarizing plate. Assuming that the film is a protective film C and a protective film D, respectively, the overall configuration is protective film A / front side polarizing film / protective film B / liquid crystal / protective film C / rear side polarizing film / protective film D from the front side. It becomes.

  Conventionally, as a protective film, since it has high transparency and optical isotropy, a triacetyl cellulose film (hereinafter sometimes abbreviated as a TAC film) is often used.

However, since the TAC film is inferior in dimensional stability and heat-and-moisture resistance, it causes problems such as generation of stress accompanying shrinkage and deterioration of the function of the polarizer, and affects the image quality of the liquid crystal display device using this polarizing plate. It was. Further, the TAC film has a drawback that the surface must be saponified with an alkaline solution in advance in order to adhere to the polarizing film.
As liquid crystal displays increase in size and quality in recent years, improvement in mechanical strength and stability under high-temperature and high-humidity environments is required, and also due to bleed-out of low-molecular materials and increased haze due to alkali treatment The need to avoid quality degradation has emerged. Furthermore, since the alkali treatment uses a high-concentration alkaline solution, it is not preferable in terms of work safety and environmental protection.

In order to solve these problems, studies as described below have been made using a polycarbonate resin having excellent dimensional stability and heat and moisture resistance.
For example, Patent Document 1 is characterized in that a mixture containing a hydrophilic polymer compound and a crosslinkable resin compound is applied to at least one surface of a thermoplastic polymer film such as a polycarbonate resin, and then heat-treated. A manufacturing method of a polarizer protective film is disclosed. However, this method usually has a problem that it takes several minutes to cure by heat treatment, and the process time becomes long, and deformation and shrinkage of the film by heat treatment occur. In addition, since the hydrophilic polymer compound is used, the adhesion to the base film, which is an organic film, tends to be insufficient, and the OH group in the hydrophilic polymer compound and the reaction point in the crosslinkable resin compound are water-absorbing. The performance is also high, and it is necessary to block moisture with an aluminum bag or the like when the film substrate is stored. Further, there is a problem that stability (pot life) at the time of mixing the hydrophilic polymer compound and the crosslinkable resin compound is short.

  On the other hand, in Patent Document 2, after a crosslinked resin cured layer is formed on one side of a specific transparent plastic synthetic polymer film represented by polycarbonate resin, a thin layer made of a hydrophilic polymer compound is wet on the outermost surface. A method of producing a protective film for a polarizing plate by forming by a coating method and drying the solvent is disclosed. However, this method has problems such as insufficient adhesion, a hydrophilic polymer compound with poor wettability, which is easy to repel, and a longer process time depending on the time for drying the solvent. Furthermore, many solvents in forming the cured crosslinked resin layer dissolve polycarbonate resin, and there is a problem that the possibility of breakage in the line increases when a film made of polycarbonate resin is thinned.

  Patent Document 3 discloses a resin containing polyurethane, an epoxy compound, a nonvolatile base, and a nonionic surfactant on the surface of a base film made of an alicyclic structure-containing polymer resin such as polycycloolefin. A multilayer film with a cured layer is described. However, this multi-layer film has poor functionality such as elongation characteristics and toughness, so that line troubles such as breakage are liable to occur when the film is thinned, and the yield is greatly impaired. Further, the use of a non-volatile base remains in the final film stage, and influences such as alteration of the polarizer are caused by bleeding out or the like under conditions such as high temperature and high humidity. Furthermore, with the addition of the crosslinking agent, improvement in heat resistance and moisture resistance is obtained, but it is a general problem that the adhesiveness tends to decrease.

JP 2005-266463 A JP 2007-263388 A JP2013-132871A

  The present invention has been made in view of the above circumstances, and the problem to be solved is a coat layer that can solve various problems of a TAC film and can be satisfactorily adhered to a polarizing film in a short time. A film that can be suitably used as a protective film for a polarizing film, in particular, with little change or deterioration even in an environment such as high temperature and high humidity, and a high total light transmittance. It is providing the polarizing plate and liquid crystal display device using this.

  As a result of intensive studies in view of the above circumstances, the present inventors have found that the use of a film having a specific configuration can easily solve the above-described problems, and have completed the present invention.

  That is, according to the first invention of the present invention, a coat layer made of a water-based urethane resin composition containing a urethane resin and a crosslinking agent is formed on at least one surface of a resin layer mainly composed of a polycarbonate resin. The film is characterized in that the crosslinking agent is an epoxy resin-based crosslinking agent.

Furthermore, according to the second invention of the present invention, there is provided a film according to the first invention, wherein the epoxy resin-based crosslinking agent comprises an aliphatic epoxy resin derived from a polyhydric alcohol.
According to a third aspect of the present invention, there is provided the film according to the second aspect, wherein the aliphatic epoxy resin is a resin having a sorbitol polyglycidyl ether structure.

According to the fourth invention of the present invention, in any one of the first to third inventions, the content of the epoxy resin crosslinking agent in the aqueous urethane resin composition is 100 parts by weight of the urethane resin. On the other hand, a film that is 0.1 parts by weight or more and less than 30 parts by weight is provided.
According to a fifth aspect of the present invention, there is provided the film according to any one of the first to fourth aspects, wherein the urethane resin has an aliphatic polycarbonate skeleton.

  Furthermore, according to a sixth invention of the present invention, in any one of the first to fifth inventions, the polycarbonate resin contains a structural unit derived from a dihydroxy compound represented by the following formula (1). A film is provided.

  According to a seventh aspect of the present invention, there is provided the film according to the sixth aspect, wherein the polycarbonate resin further contains a structural unit derived from tricyclodecane dimethanol represented by the following formula (2). Is done.

Moreover, according to the 8th invention of this invention, the polarizing plate formed by adhere | attaching a polarizing film on the said coating layer of the film which concerns on the invention in any one of the 1st-7th through an adhesive layer is provided.
Furthermore, according to the ninth aspect of the present invention, there is provided the polarizing plate according to the eighth aspect, wherein the adhesive is a water-based adhesive.

  According to the tenth aspect of the present invention, there is provided a liquid crystal display device having the polarizing plate according to the eighth or ninth aspect.

  According to the film of the present invention, it is possible to form a coat layer having a good adhesive force with an adhesive for adhering a polarizing film in a short time, and excellent durability under high temperature and high humidity conditions, The film itself has high transparency and can provide a film having excellent total light transmittance after being used as a polarizing plate, and its industrial value is high.

The film of the present invention is a film in which a coating layer comprising a water-based urethane resin composition containing a urethane resin and a crosslinking agent is formed on at least one surface of a resin layer containing a polycarbonate resin as a main component. Is an epoxy resin-based crosslinking agent.
In the above-mentioned Patent Document 3, there is a problem that the elongation and toughness of the film are insufficient. However, the film of the present invention is a thin film because the base film is a film composed of a resin layer mainly composed of a polycarbonate resin. Yield reduction due to line troubles such as breakage at the time of conversion can be suppressed. In addition, by using a water-based urethane resin composition containing a urethane resin and an epoxy resin-based cross-linking agent for the formation of the coat layer, the adhesion with a resin layer or adhesive layer mainly composed of a polycarbonate resin is further improved. And good adhesion can be maintained even under high temperature and high humidity conditions.

1. Polycarbonate layer The resin layer mainly composed of the polycarbonate resin used in the film of the present invention (hereinafter sometimes referred to as “polycarbonate layer of the present invention” or “polycarbonate film”) is composed mainly of the polycarbonate resin. . Here, the main component means that the component in the layer is preferably 50% by weight or more, more preferably 80% by weight or more, and still more preferably 90% by weight or more. The polycarbonate layer may be a single layer structure or a multilayer structure. In the case of a multilayer structure, the multilayer of 4 layers or more is also provided as long as the gist of the present invention is not exceeded other than the two-layer or three-layer structure. There is no particular limitation.

  A typical example of the polycarbonate resin is an aromatic polycarbonate having 2,2′-bis (4-hydroxyphenyl) -propane (commonly referred to as bisphenol-A) as a structural unit. The polycarbonate resin used in the present invention. Is not limited thereto, for example, 1,1-bis (4-hydroxyphenyl) -alkylcycloalkane, 1,1-bis (3-substituted-4-hydroxyphenyl) -alkylcycloalkane, 1, Monomer component containing at least one dihydric phenol selected from the group consisting of 1-bis (3,5-substituted-4-hydroxyphenyl) -alkylcycloalkane and 9,9-bis (4-hydroxyphenyl) fluorenes Homo- or copolymer polycarbonate, dihydric phenol and bisphenol A A mixture of polycarbonate and mer component, such as a copolycarbonate of the above dihydric phenol and the bisphenol A monomers components.

  The polycarbonate resin used in the polycarbonate layer of the present invention preferably has an aliphatic polycarbonate skeleton from the viewpoints of high transparency, high strength, high heat resistance, high weather resistance, and the like. A polycarbonate resin containing a structural unit derived from a dihydroxy compound having a site represented by (1) is preferred.

  More specifically, examples of the dihydroxy compound represented by the above formula (1) include isosorbide, isomannide, and isoide which are in a stereoisomeric relationship.

  The dihydroxy compound represented by the formula (1) is an ether diol that can be produced from a saccharide using a biogenic material as a raw material. In particular, isosorbide can be produced at low cost by hydrogenating and then dehydrating D-glucose obtained from starch, and can be obtained in abundant resources. Under these circumstances, isosorbide is most preferable as the dihydroxy compound represented by the above formula (1).

  The polycarbonate resin may further contain a structural unit other than the structural unit derived from the dihydroxy compound having the site represented by the formula (1). By further including a structural unit other than the structural unit derived from the dihydroxy compound having the site represented by the formula (1), it becomes possible to improve processability and impact resistance.

  Of the structural units other than the structural unit derived from the dihydroxy compound having the site represented by the formula (1), a structural unit derived from a dihydroxy compound having no aromatic ring is preferably used.

  More specifically, for example, structural units derived from aliphatic dihydroxy compounds described in International Publication No. 2004/111106 and structural units derived from alicyclic dihydroxy compounds described in International Publication No. 2007/148604. it can.

  Among the structural units derived from the aliphatic dihydroxy compound, at least one selected from ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol. It preferably contains a structural unit derived from a dihydroxy compound.

  Among the structural units derived from the alicyclic dihydroxy compound, those containing a 5-membered ring structure or a 6-membered ring structure are preferable. The six-membered ring structure may be fixed in a chair shape or a boat shape by a covalent bond.

  By including a structural unit derived from an alicyclic dihydroxy compound having a 5-membered ring structure or a 6-membered ring structure, the heat resistance of the obtained polycarbonate resin can be increased.

  The number of carbon atoms contained in the alicyclic dihydroxy compound is usually preferably 70 or less, more preferably 50 or less, and even more preferably 30 or less.

Examples of the alicyclic dihydroxy compound containing the 5-membered ring structure or the 6-membered ring structure include those described in the above-mentioned International Publication No. 2007/148604.
Among these, cyclohexane dimethanol, tricyclodecane dimethanol, adamantanediol, and pentacyclopentadecane dimethanol can be preferably exemplified. Among these, cyclohexane dimethanol or tricyclodecane dimethanol is more preferable in view of economy and heat resistance. In particular, it is most preferable to contain a structural unit derived from tricyclodecane dimethanol represented by the following formula (2) from the viewpoint of balance between economic efficiency, heat resistance and optical properties.

  In addition, these other structural units may contain only 1 type in polycarbonate resin, and may contain 2 or more types.

  The content ratio of the structural unit derived from the dihydroxy compound having the site represented by the formula (1) in a part of the structure of the polycarbonate resin is based on the structural unit derived from all the dihydroxy compounds in the polycarbonate resin. It is preferably 30 mol% or more, more preferably 40 mol% or more, particularly preferably 50 mol% or more, and preferably 90 mol% or less, more preferably 80 mol% or less.

  If the content ratio of the structural unit derived from the dihydroxy compound having the site represented by the formula (1) in a part of the structure of the polycarbonate resin is equal to or higher than the lower limit, the heat resistance is improved by maintaining the glass transition temperature. Is preferable. On the other hand, by being below the upper limit, coloring derived from a carbonate structure, coloring derived from impurities contained in a trace amount because a biogenic substance is used as a raw material, etc. can be suppressed, and transparency usually required for a polycarbonate layer There is a possibility not to impair the sex. In addition, appropriate molding processability, mechanical strength and heat resistance, which are difficult to achieve with a polycarbonate resin composed only of a structural unit derived from a dihydroxy compound having a site represented by the above formula (1) in a part of the structure. You can balance gender.

  The polycarbonate resin includes a structural unit derived from a dihydroxy compound having a site represented by the formula (1) in a part of the structure, and a structural unit derived from an aliphatic dihydroxy compound and / or an alicyclic dihydroxy compound. Although it is preferable to consist of derived structural units, structural units derived from other dihydroxy compounds may be further included within the range not impairing the object of the present invention.

  The polycarbonate resin can be produced by a generally used polymerization method. The polycarbonate resin may be produced by either a phosgene method or a transesterification method in which it is reacted with a carbonic acid diester. Among them, in the presence of a polymerization catalyst, a dihydroxy compound having a site represented by the above formula (1) in a part of the structure, an aliphatic and / or alicyclic dihydroxy compound, and other used as necessary A transesterification method in which the dihydroxy compound is reacted with a carbonic acid diester is preferred.

  The transesterification method includes one or more dihydroxy compounds having a site represented by the formula (1) in a part of the structure and one or more aliphatic and / or alicyclic dihydroxy compounds. In addition, one or two or more other dihydroxy compounds used as necessary and a carbonic acid diester are added with a basic catalyst, and further, an acidic substance that neutralizes the basic catalyst is added to carry out a transesterification reaction. It is a manufacturing method to be performed.

  Representative examples of carbonic acid diesters include diphenyl carbonate, ditolyl carbonate, bis (chlorophenyl) carbonate, m-cresyl carbonate, dinaphthyl carbonate, bis (biphenyl) carbonate, diethyl carbonate, dimethyl carbonate, dibutyl carbonate, and dicyclohexyl carbonate. Is mentioned. These may be used alone or in combination of two or more. Of these, diphenyl carbonate is particularly preferably used.

The molecular weight of the polycarbonate resin used in the present invention can be represented by a reduced viscosity, and the lower limit of the reduced viscosity is preferably 0.20 dl / g or more, more preferably 0.30 dL / g or more, and 0.35 dL / g or more. More preferably, the upper limit of the reduced viscosity is preferably 2.00 dL / g or less.
If the reduced viscosity of the polycarbonate resin is too low, the mechanical strength of the molded product may be small. If it is too large, the fluidity at the time of molding tends to decrease, and the productivity and moldability tend to decrease.

The reduced viscosity of the polycarbonate resin is precisely adjusted so that the concentration of the polycarbonate resin is 0.60 g / dl using an Ubbelohde viscometer with a DT-504 type automatic viscometer manufactured by Chuo Rika Co., Ltd. After the adjustment, the temperature is calculated from the measured value based on the following at a temperature of 20.0 ° C. ± 0.1 ° C.
From the passage time t _{0 of the} solvent and the passage time t of the solution, the following formula:
η _rel = t / t ₀
More seek relative viscosity eta _rel, from the relative viscosity eta _rel, the formula:
η _sp = (η−η ₀ ) / η ₀ = η _rel −1
Further, the specific viscosity ηsp is determined.
By dividing the specific viscosity η _sp by the concentration c (g / dl), the following formula:
η _red = η _sp / c
From this, the reduced viscosity (converted viscosity) η _red is determined.

  An ultraviolet absorber may be added to the polycarbonate layer of the present invention. As the ultraviolet absorber added to the polycarbonate layer, known ones such as various commercially available ones can be used without particular limitation. Especially, what is normally used for the addition to well-known aromatic polycarbonate resin can be used conveniently.

  Examples of the ultraviolet absorber include 2- (2′-hydroxy-5′-tert-octylphenyl) benzotriazole and 2- (3-tert-butyl-5-methyl-2-hydroxyphenyl) -5-chlorobenzo. Triazole, 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole and 2,2′- Benzotriazole ultraviolet absorbers such as methylenebis (4-cumyl-6-benzotriazolephenyl); benzoxazine ultraviolet absorbers such as 2,2′-p-phenylenebis (1,3-benzoxazin-4-one) 2- (4,6-diphenyl-1,3,5-triazin-2-yl) -5- (hexyl) oxy-pheno; And the like, and the like.

  The melting point of the ultraviolet absorber is particularly preferably in the range of 120 ° C to 250 ° C. When using a UV absorber with a melting point of 120 ° C. or higher, the film surface becomes dirty due to a bleed-out phenomenon in which the UV absorber aggregates on the film surface over time, or when forming a film using a die or a metal roll, Bleed-out prevents them from becoming dirty and reduces and improves film surface haze.

  From these viewpoints, as the ultraviolet absorber, 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2- (2′-hydroxy-3′-tert-butyl-5′-methylphenyl)- 5-chlorobenzotriazole, 2- [2′-hydroxy-3 ′-(3 ″, 4 ″, 5 ″, 6 ″ -tetrahydrophthalimidomethyl) -5′-methylphenyl] benzotriazole, 2,2-methylenebis [ 4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl)] phenol and 2- (2-hydroxy-3,5-dicumylphenyl) benzotriazole Benzotriazole ultraviolet absorber and 2- (4,6-diphenyl-1,3,5-triazin-2-yl) -5- (hexyl) oxy-pheno It can be preferably used hydroxyphenyl triazine-based UV absorbers such as Le.

Among these, 2- (2-hydroxy-3,5-dicumylphenyl) benzotriazole, 2,2-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzo Triazol-2-yl)] phenol, 2- (4,6-diphenyl-1,3, -triazin-2-yl) -5- (hexyl) oxy-phenol are particularly preferred.
These ultraviolet absorbers may be used alone or in combination of two or more.

The UV absorber is preferably added in a proportion of 0.0001 parts by weight or more and 20 parts by weight or less with respect to 100 parts by weight of the polycarbonate resin, and is added in a proportion of 0.0005 parts by weight or more and 15 parts by weight or less. More preferably, it is more preferably added in a proportion of 0.001 part by weight or more and 10 parts by weight or less.
By adding the ultraviolet absorber in such a range, the weather resistance of the film of the present invention can be improved without causing bleeding of the ultraviolet absorber to the surface of the polycarbonate layer and deterioration of the mechanical properties of the polycarbonate layer.

  As long as the object of the present invention is not impaired, the polycarbonate layer is also added with an appropriate amount of other various additives such as a silane coupling agent, an antioxidant and a weathering stabilizer as an additive component other than the ultraviolet absorber. May be. Moreover, you may add resin other than polycarbonate resin in the range which does not impair the objective of this invention.

  The film thickness of the polycarbonate layer is preferably 200 μm or less, more preferably 150 μm or less, and even more preferably 100 μm or less, from the viewpoint of thinning the film of the present invention and the polarizing plate of the present invention using the film. From the viewpoint of mechanical strength, it is preferably 3 μm or more, more preferably 5 μm or more, and further preferably 10 μm or more.

  As a method for forming a polycarbonate film to be a polycarbonate layer of the present invention, a known method, for example, extrusion casting using a T-die having a melt mixing facility such as a single screw extruder, a multi-screw extruder, a Banbury mixer, a kneader, etc. A method such as a calendering method or a calendering method can be employed, and although not particularly limited, in the present invention, an extrusion casting method using a T-die is preferably used in terms of handling properties and productivity. The molding temperature in the extrusion casting method using a T-die is appropriately adjusted depending on the flow characteristics and film forming properties of the polycarbonate resin to be used, but is generally 80 ° C. or higher, preferably 100 ° C. or higher, more preferably 120 ° C. or higher. Preferably, the temperature is 140 ° C. or higher, and is generally 320 ° C. or lower, preferably 300 ° C. or lower, more preferably 280 ° C. or lower, more preferably 260 ° C. or lower. When a silane coupling agent or the like is added, the reaction is accompanied. In order to suppress an increase in resin pressure and an increase in fish eye, it is preferable to lower the molding temperature. Various additives such as silane coupling agents, antioxidants, UV absorbers, and weathering stabilizers may be dry blended together with the polycarbonate resin and then supplied to the hopper. Pellets may be supplied after melting and mixing, or a master batch in which only the additive is concentrated in advance in a resin such as polycarbonate resin may be supplied.

  The polycarbonate layer of the present invention may be subjected to a surface treatment for enhancing adhesion with a urethane coat layer described later. Examples of the surface treatment in this case include energy ray 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, and the like. From the viewpoint of treatment efficiency, corona discharge treatment and plasma treatment are preferable, and corona discharge treatment is particularly preferable. preferable. Examples of the chemical treatment include saponification treatment, immersion in an aqueous oxidizing agent solution such as potassium dichromate solution and concentrated sulfuric acid, and then washing with water.

2. Urethane Coat Layer Next, a coat layer (hereinafter, referred to as “urethane coating composition”) comprising a water-based urethane resin composition (hereinafter sometimes referred to as “urethane coating composition”) containing the urethane resin and the epoxy resin crosslinking agent in the present invention. The “urethane coat layer” may be referred to.
In the present invention, it is an essential requirement to form a urethane coat layer on at least one surface of the polycarbonate film using a water-based urethane coating composition containing a urethane resin and an epoxy resin crosslinking agent.

  The urethane coat layer functions as an easy-adhesion layer and reinforces the adhesion between the polycarbonate film and other members by the adhesive when the polycarbonate film is bonded to another member (for example, a polarizer, etc.) via the adhesive. To make it adhere more firmly. That is, the urethane coat layer functions as a primer layer for reinforcing the function of the adhesive.

Usually, the urethane coat layer is directly provided on the surface of the polycarbonate film without any other layer such as an adhesive layer.
The urethane coat layer may be provided on one surface of the polycarbonate film or on both surfaces. By providing a urethane coat layer on both sides of the polycarbonate film, the handleability of the polycarbonate film can be effectively improved.

2-1. Urethane-based resin Examples of the urethane-based resin used in the present invention include (1) a component containing 2 or more active hydrogens in average in one molecule (hereinafter sometimes referred to as “component (1)”) and ( 2) A urethane-based resin obtained by reacting a polyvalent isocyanate component (hereinafter sometimes referred to as “component (2)”); or the above-mentioned component (1) and component (2) are in excess of isocyanate groups. Under the reaction, it is urethanated in an organic solvent that is inert to the reaction and has a high affinity for water to obtain an isocyanate group-containing prepolymer, and then the prepolymer is neutralized and chain-extended using a chain extender. And urethane resin produced by adding water to form a dispersion. These urethane resins may contain an acid structure (acid residue).

  As the chain extension method of the isocyanate group-containing prepolymer, a known method can be adopted. For example, water, a water-soluble polyamine, glycols or the like is used as the chain extender, and the isocyanate group-containing prepolymer and the chain extender are used. May be reacted in the presence of a catalyst, if necessary.

  The component (1) is not particularly limited, but preferably has a hydroxylic active hydrogen. Specific examples of such compounds include those exemplified in the following (1-1) to (1-5).

(1-1) Polyol compound As the polyol compound, for example, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, 1,2-butylene glycol, 1,3-butylene glycol, 2,3-butylene glycol, 1,4- Butylene glycol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 2,5-hexanediol, 1,8-octanediol, dipropylene glycol, 2,2,4-trimethyl-1,3 -Pentanediol, tricyclodecane dimethanol, 1,4-cyclohexanedimethanol, 2,2-dimethylpropanediol and the like.

(1-2) Polyether polyol As the polyether polyol, for example, an alkylene oxide adduct of the polyol compound of (1-1) above; a ring-opening (co) polymer of an alkylene oxide and a cyclic ether (for example, tetrahydrofuran); And polyethylene glycol, polypropylene glycol, ethylene glycol-propylene glycol copolymer; glycols such as glycol, polytetramethylene glycol, polyhexamethylene glycol, polyoctamethylene glycol; and the like.

(1-3) Polyester polyol As the polyester polyol, for example, dicarboxylic acid such as adipic acid, succinic acid, sebacic acid, glutaric acid, maleic acid, fumaric acid, phthalic acid or the anhydride thereof and the above (1-1) It can be obtained by polycondensing the above-mentioned polyol compounds such as ethylene glycol, propylene glycol, 1,4-butylene glycol, 1,6-hexanediol, 1,8-octanediol, neopentyl glycol and the like under the condition of excess hydroxyl group. Etc. More specifically, for example, ethylene glycol-adipic acid condensate, butanediol-adipine condensate, hexamethylene glycol-adipic acid condensate, ethylene glycol-propylene glycol-adipic acid condensate, or lactone with glycol as an initiator. And polylactone diol obtained by ring-opening polymerization.

(1-4) Polyether ester polyol As the polyether ester polyol, for example, an ether group-containing polyol (for example, the polyether polyol or diethylene glycol of the above (1-2)) or a mixture of this with other glycols is used. Examples include those obtained by reacting an alkylene oxide in addition to the dicarboxylic acid exemplified in (1-3) or its anhydride. More specifically, examples include polytetramethylene glycol-adipic acid condensate.

(1-5) Polycarbonate polyol As the polycarbonate carbonate polyol, for example, the general formula HO—R— (O—C (O) —O—R) _n —OH (wherein, R has 1 to 12 carbon atoms) A saturated fatty acid polyol residue, and n represents the number of repeating units of the molecule, and is usually an integer of 5 to 50). These are a transesterification method in which a saturated aliphatic polyol and a substituted carbonate (for example, diethyl carbonate, diphenyl carbonate, etc.) are reacted under the condition that the hydroxyl group is excessive; the saturated aliphatic polyol and phosgene are reacted, or If necessary, it can be obtained by a method of further reacting a saturated aliphatic polyol thereafter.

  The compounds as exemplified in the above (1-1) to (1-5) may be used alone or in combination of two or more at any ratio.

  Examples of the component (2) to be reacted with the component (1) include an aliphatic, alicyclic or aromatic compound containing an average of two or more isocyanate groups in one molecule.

  As the aliphatic diisocyanate compound, an aliphatic diisocyanate having 1 to 12 carbon atoms is preferable, and examples thereof include hexamethylene diisocyanate, 2,2,4-trimethylhexane diisocyanate, and hexane diisocyanate (HDI). The alicyclic diisocyanate compound is preferably an alicyclic diisocyanate compound having 4 to 18 carbon atoms, such as 1,4-cyclohexane diisocyanate, methylcyclohexylene diisocyanate, isophorone diisocyanate (IPDI), dicyclohexylmethane diisocyanate (HMDI), and the like. Can be mentioned. Examples of the aromatic diisocyanate compound include tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate, and the like. One of these may be used alone, or two or more of these may be used in combination at any ratio.

  In the present invention, the urethane-based resin can form a urethane coat layer excellent in heat resistance and water resistance, and therefore has an aliphatic polycarbonate skeleton, specifically, the polycarbonate of (1-5) above. A urethane resin obtained by a reaction between a polyol and an aliphatic diisocyanate compound is preferred.

  The urethane resin preferably has an acid structure. Urethane resin having an acid structure can be dispersed in water without using a surfactant or even if the amount of the surfactant is small, so that the water resistance of the urethane coat layer is improved. There is expected. This is called a self-emulsifying type, which means that the urethane-based resin can be dispersed and stabilized in water only by molecular ionicity without using a surfactant. A urethane coat layer using such a urethane resin is preferable because it is excellent in adhesiveness with a polycarbonate film and can maintain high transparency. Further, it is preferable to perform crosslinking using this acid structure as a starting point, since the hydrophobicity, heat resistance, and wet heat properties can be further improved.

Examples of the acid structure include acid groups such as a carboxyl group (—COOH) and a sulfonic acid group (—SO ₃ H). Moreover, the acid structure may exist in the side chain of a urethane-type resin, and may exist in the terminal. In addition, 1 type may be used for an acid structure and it may use it combining 2 or more types by arbitrary ratios.

  The content of the acid structure is preferably 5 mgKOH / g or more, more preferably 10 mgKOH / g or more, preferably 250 mgKOH / g or less, more preferably 150 mgKOH / g or less as the acid value of the urethane resin. If the acid value is less than 5 mgKOH / g, the water dispersibility tends to be insufficient. On the other hand, if the acid value is more than 250 mgKOH / g, the water resistance of the urethane coat layer tends to be inferior.

  As a method for introducing an acid structure into a urethane resin, a conventionally used method can be used without any particular limitation. Preferred examples include polyether polyol, polyester polyol, polyether ester in advance by replacing dimethylol alkanoic acid with part or all of the glycol component described in (1-2) to (1-4) above. The method of introduce | transducing a carboxyl group into a polyol etc. is mentioned. Examples of the dimethylol alkanoic acid used here include dimethylol acetic acid, dimethylol propionic acid, and dimethylol butyric acid. In addition, dimethylol alkanoic acid may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  The number average molecular weight of the urethane-based resin is preferably 1,000 or more, more preferably 20,000 or more, preferably 1,000,000 or less, and more preferably 200,000 or less.

  The urethane-based coating composition used in the present invention is preferably prepared using a water-based urethane resin. A water-based urethane resin is an aqueous dispersion of a urethane-based resin. Usually, a urethane-based resin, water, and other components contained as necessary are dissolved or dispersed in water. The minute (urethane resin) concentration is usually about 10 to 50% by weight.

  A commercially available water-based urethane resin may be used. Examples of commercially available water-based urethane resins include the “Adeka Bon titer” series manufactured by Asahi Denka Kogyo, the “Olestar” series manufactured by Mitsui Toatsu Chemicals, and the “Bondic” manufactured by Dainippon Ink & Chemicals, Inc. Series, `` Hydran '' series, `` Imprunil '' series manufactured by Bayer, `` Sofranate '' series manufactured by Sofran Japan, `` Poise '' series manufactured by Kao Corporation, `` Samprene '', `` Ucote '' manufactured by Sanyo Chemical Industries, "Euporin" series, "Rezamin" series by Dainichi Seika Kogyo Co., Ltd., "Izelux" series by Hodogaya Chemical Co., Ltd., "Superflex" series by Daiichi Kogyo Seiyaku Co., Ltd. Series, “Sancure” series by Lubrizol, “RU” series by Stahl Japan Co., Ltd., etc. It can be used. In particular, “RU-40-350” and “EX-RU-92-605” manufactured by Stahl Japan Co., Ltd., “Yukot 368” manufactured by Sanyo Chemical Industries, Ltd., and “Rezamin D-6031” manufactured by Dainichi Seika Kogyo Co., Ltd. "Is suitable for the present invention because it has an aliphatic polycarbonate skeleton and is dispersed in water with a volatile base described later.

  In addition, the urethane type coating composition may contain only 1 type of urethane type resin, and may contain 2 or more types by arbitrary ratios.

2-2. Epoxy resin crosslinking agent As the epoxy resin crosslinking agent, a polyfunctional epoxy resin having two or more epoxy groups in the molecule can be used. Thereby, a crosslinking reaction can be advanced and the mechanical strength of a urethane coat layer can be improved effectively. Moreover, the effect | action which improves adhesive force with the polar structure which an epoxy resin type crosslinking agent has can also be anticipated.

  As the epoxy resin-based crosslinking agent, those which are soluble in water or can be emulsified by being dispersed in water are preferable. If the epoxy resin-based crosslinking agent is soluble in water or can be emulsified, the coating property of the water-based urethane resin can be improved and a urethane coat layer can be easily formed. .

  Examples of the epoxy resin-based crosslinking agent include sorbitol polyglycidyl ethers, polyglycerol polyglycidyl ethers, pentaerythritol polyglycidyl ethers, diglyceryl polyglycidyl ether, 1,3,5-triglycidyl (2-hydroxyethyl) isocyanate. Nurate, glycerol polyglycerol ethers, trimethylolpropane polyglycidyl ethers, and the like. Specific commercial products thereof include, for example, “CR-5L” manufactured by DIC Corporation, “Denacol (manufactured by Nagase ChemteX Corporation) Denacol EX-521, EX-614B etc.) ”series and the like.

  As the epoxy resin-based crosslinking agent, those containing an aliphatic epoxy resin are particularly preferred from the viewpoints of transparency, weather resistance, etc. Among them, those having a sorbitol polyglycidyl ether structure are preferably mixed with water or reactive ( From the viewpoint of (crosslinkability), commercially available products include “CR-5L” manufactured by DIC and “Denacol EX-614B” manufactured by Nagase ChemteX.

  These epoxy resin crosslinking agents may be used alone or in combination of two or more.

  The content of the epoxy resin-based crosslinking agent in the urethane-based coating composition is a urethane-based resin (where the urethane-based resin is an aqueous urethane-based resin when a water-based urethane resin is used to prepare the urethane-based coating composition). This is the ratio of the pure urethane resin as a solid that does not contain water in the resin.) It is formed by sufficiently cross-linking the urethane resin to 100 parts by weight or more. From the viewpoint of sufficiently increasing the mechanical strength of the urethane coat layer to be formed. On the other hand, from the viewpoint of increasing the mechanical strength, heat resistance, moisture resistance, etc. of the urethane coating layer by reducing the residual unreacted epoxy resin crosslinking agent, the epoxy resin crosslinking agent is used in 100 parts by weight of the urethane resin. And less than 30 parts by weight. The epoxy resin-based crosslinking agent in the urethane-based coating composition is more preferably 1 to 25 parts by weight, further preferably 1 to 20 parts by weight, and particularly preferably 2 to 15 parts by weight with respect to 100 parts by weight of the urethane-based resin. It is.

  When the urethane resin has an acid structure, the amount of the epoxy resin crosslinking agent is preferably 0.2 on the weight basis with respect to the amount of the epoxy resin crosslinking agent equivalent to the acid structure of the urethane resin. Times or more, more preferably 0.4 times or more, particularly preferably 0.6 times or more, preferably 5.0 times or less, more preferably 3.0 times or less, particularly preferably 2.0 times or less. . Here, the amount of the epoxy resin-based crosslinking agent equivalent to the acid structure of the urethane-based resin refers to the theoretical amount of the epoxy resin-based crosslinking agent that can react without excess or deficiency with the total amount of the acid structure of the urethane-based resin. When the urethane resin has an acid structure, the acid structure can react with the epoxy group of the epoxy resin crosslinking agent. At this time, by keeping the amount of the epoxy resin-based crosslinking agent in the above range, the reaction between the acid structure and the epoxy resin-based crosslinking agent proceeds to an appropriate level, and the mechanical strength of the urethane coat layer to be formed can be increased. Heat resistance, moisture resistance, etc. can be improved effectively.

2-3. Other components The urethane coating composition for forming the urethane coating layer contains other components within the range not impairing the object of the present invention, if necessary, in addition to the urethane resin and the epoxy resin crosslinking agent. May be.

2-3-1. Volatile base The urethane-based coating composition preferably contains a volatile base.
The volatile base is not particularly limited as long as it is a water-soluble base compound having volatility. In addition, a base here is a Bronsted base.

  Examples of the volatile base include ammonia and volatile primary to tertiary amines.

  As the volatile base, a volatile tertiary alkylamine is preferable, and a volatile tertiary trialkylamine is more preferable.

  The volatile tertiary alkylamine is preferably trimethylamine (TMA; CAS registration number 75-50-3) or triethylamine (TEA; CAS registration number 121-44-8), more preferably triethylamine.

  When the urethane-based coating composition contains a volatile base, the stability is improved. This is considered to be because the acid structure and volatile base of the urethane-based resin contribute to the improvement of dispersion stability in the urethane-based coating composition.

  Further, it is considered that at least a part of the volatile base is present in the form of a conjugate acid in the emulsion of the water-based urethane resin.

  The volatile base can be contained in the urethane-based coating composition without any particular limitation, but the urethane-based resin (wherein the urethane-based resin refers to a water-based urethane-based resin for the preparation of the urethane-based coating composition). When used, it is the ratio of the pure urethane resin as a solid content that does not contain water in the aqueous urethane resin.) With respect to 1 mol of the acid structure, a volatile base such as a tertiary alkylamine is present. It is preferable to contain so that it may become 0.1-6 mol, and it is more preferable to contain so that it may become 0.5-4 mol. Within this range, the stability of the urethane-based coating composition is further improved.

  The volatile base, when the urethane coating composition is cured, only a trace amount remains in the urethane coat layer, and does not impair the adhesion between the urethane coat layer and the adhesive layer according to the present invention. Bleed-out does not occur even under conditions where the influence of moisture is large, such as high-temperature and high-humidity conditions that are a concern for non-volatile bases, and there is almost no effect on polarizing plates.

2-3-2. Nonionic surfactant Urethane coating composition is a nonionic surfactant that is an acetylene glycol in which hydroxyl groups and methyl groups are substituted on two adjacent carbon atoms of a triple bond and / or its ethylene oxide adduct May be contained. By including such a nonionic surfactant, wetting can be improved while suppressing foaming of the uncured urethane-based coating composition, and thus occurrence of repellency unevenness when applied to a polycarbonate film can be prevented. .

As this nonionic surfactant, what is represented by following formula (i) is mentioned.
R ³ —C (CH ₃ ) (OR ¹ ) —C≡C—C (CH ₃ ) (OR ² ) —R ⁴ (i)
(In the formula, R ¹ and R ² each independently represent — (CH ₂ ) _m —H. M represents an integer of 0 or more, preferably 0 to 400, and 0 or 20 to 100. More preferably, it is particularly preferably 40 to 70. R ³ and R ⁴ each independently represents a hydrogen atom or an alkyl group which may have a substituent. Group, propyl group, isopropyl group, butyl group, isobutyl group, t-butyl group, pentyl group, hexyl group and the like, and isopropyl group is preferred.
As such a nonionic surfactant, for example, Surfynol 104 series, Surfynol 400 series manufactured by Nissin Chemical Industry Co., Ltd. can be used.

When the urethane-based coating composition contains a nonionic surfactant, the content of the nonionic surfactant is preferably 10 ppm on a weight basis with respect to the total amount of all solids in the urethane-based coating composition. As mentioned above, More preferably, it is 100 ppm or more, Preferably it is 10,000 ppm or less, More preferably, it is 1,000 ppm or less. By making the content of the nonionic surfactant equal to or higher than the above lower limit value, occurrence of repelling unevenness can be suppressed, and when the content is equal to or lower than the upper limit value, foaming can be suppressed and defects due to bubbles can be prevented.
Here, the total solid content in the urethane-based coating composition corresponds to the total of components other than the solvent in the urethane-based coating composition.

2-3-3. Fine particle The urethane-based coating composition may contain fine particles, and by containing fine particles, irregularities are formed on the surface of the urethane coat layer to be formed. The area in contact with the layer is reduced, and the slipperiness of the surface of the urethane coat layer is improved by that amount, and the generation of wrinkles when the film of the present invention is wound can be suppressed.

  The average particle diameter 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 400 nm or less, more preferably 300 nm or less. By making the average particle diameter equal to or higher than the lower limit value of the above range, the slipping property of the urethane coat layer to be formed can be effectively increased. It is possible to prevent the occurrence of winding misalignment when wound around. In addition, as an average particle diameter of microparticles | fine-particles, a particle size distribution is measured by the laser diffraction method, and the particle size from which the cumulative volume calculated from the small diameter side in the measured particle size distribution becomes 50% (50% volume cumulative diameter D50) Is adopted.

  As the fine particles, either inorganic fine particles or organic fine particles may be used, but it is preferable to use water-dispersible fine particles. Examples of inorganic fine particles include inorganic oxides such as silica, titania, alumina, zirconia; calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, calcium phosphate Etc. Examples of the organic fine particle material include silicone resin, fluororesin, and acrylic resin. Among these, the ability to suppress the generation of wrinkles and transparency are excellent, it is difficult to produce haze, and there is no coloration, so the influence on the optical properties of the film of the present invention is smaller, and the water-based urethane resin From the viewpoint of good dispersibility and dispersion stability, silica fine particles are preferable, and among the silica fine particles, amorphous colloidal silica particles are particularly preferable.

  In addition, fine particle may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.

  When the urethane-based coating composition contains the fine particles as described above, the content of the fine particles is the urethane-based resin (where the urethane-based resin is a case where a water-based urethane-based resin is used to prepare the urethane-based coating composition). Is the ratio of the pure content of the urethane-based resin as a solid content not containing water in the water-based urethane-based resin.) Usually 0.5 parts by weight or more, preferably 1 part by weight or more, relative to 100 parts by weight. The amount is preferably 2 parts by weight or more, usually 30 parts by weight or less, preferably 25 parts by weight or less, more preferably 20 parts by weight or less. By setting the content of the fine particles to be equal to or higher than the lower limit of the above range, the generation of wrinkles can be suppressed when the film of the present invention is wound. Moreover, the external appearance without the cloudiness of the film of this invention is maintainable by making content of microparticles below into the upper limit of the said range.

2-3-4. Other components The urethane-based coating composition is, for example, a surfactant other than the nonionic surfactant described above, a heat-resistant stabilizer, a weather-resistant stabilizer, an antistatic agent, and a slip agent, as long as the effects of the present invention are not significantly impaired. Contains anti-blocking agents, dispersion stabilizers, thixotropic agents, antioxidants, antifoaming agents, thickeners, dispersants, antifogging agents, lubricants, dyes, pigments, natural oils, synthetic oils, waxes, etc. May be. In addition, these may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.

2-3-5. Solvent The urethane-based coating composition is usually prepared as a dispersion containing the above-mentioned optional components that are used as necessary, with a urethane-based resin and an epoxy resin-based crosslinking agent as essential components.
Examples of the solvent (dispersion medium) used for preparing the urethane-based coating composition include water and / or a water-soluble solvent, preferably water, and particularly preferably ion-exchanged water.

  Examples of the water-soluble solvent include methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, t-butanol, acetone, tetrahydrofuran, N-methylpyrrolidone, dimethyl sulfoxide, ethylene glycol monomethyl ether, ethylene glycol monobutyl ether. Etc. One of these may be used alone, or two or more of these may be used in combination at any ratio.

  The solvent is preferably set so that the viscosity of the urethane-based coating composition is in a range suitable for coating, and the urethane coating composition preferably has a solid content concentration from the viewpoint of coating properties and film formability. Is prepared to be about 5 to 40% by weight, particularly preferably about 10 to 30% by weight.

2-4. Preparation of urethane coating composition The urethane coating composition is prepared by using water, preferably ion-exchanged water, and the above urethane resin, preferably water-based urethane resin, and epoxy resin-based cross-linking agent, as required. It is prepared by dissolving or dispersing the components.

  In the urethane-based coating composition, components such as a urethane-based resin are usually dispersed as particles. The particle size of the particles is preferably 0.01 to 0.4 μm from the viewpoint of the optical properties of the film of the present invention. The particle size may be measured by a dynamic light scattering method, for example, a light scattering photometer DLS-8000 series manufactured by Otsuka Electronics Co., Ltd.

  The viscosity of the urethane-based coating composition is preferably 100 mPa · s or less, and particularly preferably 50 mPa · s or less. When the viscosity of the urethane coating composition is within the above range, the urethane coating composition can be uniformly applied to the surface of the polycarbonate film. Here, the viscosity of the urethane-based coating composition is a value measured with a rotational viscometer at a rotational speed of 60 rpm under the condition of 25 ° C. The viscosity of the urethane-based coating composition can be adjusted by, for example, the ratio of the solvent contained in the urethane-based coating composition and the particle size of the particles contained in the urethane-based coating composition.

2-5. Formation method of a urethane coat layer A urethane coat layer is formed by apply | coating the above-mentioned urethane type coating composition to the at least single side | surface of a polycarbonate film, and drying and solidifying (curing) the formed coating film.

  The application method of a urethane type coating composition is not specifically limited, A well-known application method is employable. Specific coating methods include, for example, a wire bar coating method, a dip method, a spray method, a spin coating method, a roll coating method, a gravure coating method, an air knife coating method, a curtain coating method, a slide coating method, and an extrusion coating method. Etc.

  When the formed coating film is cured, the solvent in the urethane-based coating composition is dried and removed. The drying method is arbitrary, and for example, the drying may be performed by any method such as reduced pressure drying or heat drying. Especially, it is preferable to make it harden | cure by heat drying from a viewpoint of making reaction, such as a crosslinking reaction, rapidly advance in a urethane type coating composition.

  When the coating film is cured by heating, the heating temperature is appropriately set within a range in which the solvent of the urethane coating composition can be dried to cure the coating film. However, when a stretched film is used as the polycarbonate film and the retardation developed in the polycarbonate film is not desired to be changed, the heating temperature is preferably set to a temperature at which no orientation relaxation occurs in the polycarbonate film. Specifically, the upper limit temperature is (Tg-10) ° C. or lower, preferably (Tg-20) ° C. or lower, more preferably Tg, when the glass transition temperature of the material forming the polycarbonate film is Tg. Is (Tg-30) ° C. or lower, and the lower limit temperature is (Bp-50) ° C. or higher, preferably (Bp-40) ° C. or higher, and more preferably, when the boiling point of the solvent is Bp. (Bp-30) ° C. or higher.

  Although it does not specifically limit regarding specific heat drying conditions, Usually, it is good to dry for 50 to 150 degreeC for 5 to 200 seconds, Preferably it is 10 to 100 second for 60 to 130 degreeC as a standard.

  Furthermore, you may perform an extending | stretching process, after forming a urethane type coating composition on the surface of a polycarbonate film. The stretching treatment may be performed after the coating film is cured, but from the viewpoint of preventing the removal of fine particles from the urethane coat layer, the stretching treatment is performed before or simultaneously with curing the coating film. It is preferable. Furthermore, from the viewpoint of forming a uniform urethane coat layer, it is more preferable to perform a stretching treatment simultaneously with curing the coating film.

  When the polycarbonate film is stretched, the urethane coat layer formed on the surface is also stretched. However, since the thickness of the urethane coat layer is usually sufficiently smaller than the thickness of the polycarbonate film, a large retardation is not exhibited in the stretched urethane coat layer.

  The surface of the urethane coat layer thus formed may be subjected to a hydrophilic surface treatment. Since the surface of the urethane coat layer is usually a bonding surface when the film of the present invention is bonded to another member, by further improving the hydrophilicity of this surface, the film of the present invention and the other member It is possible to remarkably improve the adhesion.

  Examples of the hydrophilic surface treatment for the urethane coat layer include corona discharge treatment, plasma treatment, saponification treatment, and ultraviolet irradiation treatment. Of these, corona discharge treatment and plasma treatment are preferable from the viewpoint of processing efficiency, and corona discharge treatment is particularly preferable. As the plasma treatment, atmospheric pressure plasma treatment is preferable.

  By the hydrophilization surface treatment, the average wetness index of the surface of the urethane coat layer is preferably 40 mN / m or more, more preferably 50 mN / m or more, particularly preferably 60 mN / m or more, and usually 50 mN / m or more. desirable. By subjecting the surface of the urethane coat layer to such a wetness index, the film of the present invention can be firmly bonded to other members such as a polarizer.

2-6. Film thickness The film thickness of the urethane coat layer is 10 μm or less from the viewpoint of reducing the film thickness of the film of the present invention and the polarizing plate of the present invention and preventing distortion (curing shrinkage) of the polycarbonate film and the retardation. Preferably, it is 5 μm or less, more preferably 3 μm or less. Moreover, from a viewpoint of adhesive strength, 0.1 micrometer or more is preferable, 0.2 micrometer or more is more preferable, and 0.3 micrometer or more is further more preferable. If it is the said range, favorable adhesiveness can be acquired with respect to both a polycarbonate layer and the below-mentioned aqueous adhesive.

  The ratio (t1 / t2) of the film thickness (t1) of the polycarbonate film to the film thickness (t2) of the urethane coat layer is preferably 1 to 1000, more preferably 3 to 500, and still more preferably. 5 to 200. If t1 / t2 is in the above range, it is preferable that the strength of the polycarbonate film is not reduced, wrinkles are generated, and retardation is not increased even when the urethane coating composition is heated and dried.

  In the present invention, the urethane coat layer is formed on at least one side of the polycarbonate film, and the urethane coat layer may be formed on both sides of the polycarbonate film. The film thickness of the urethane coat layer is a value of the film thickness of the urethane coat layer per one side of the polycarbonate film. When a urethane coat layer is formed on both sides of the polycarbonate film, the thickness of the urethane coat layer per side is preferably equal to or greater than the above lower limit, and the total thickness of the urethane coat layers on both sides is equal to or less than the above upper limit. It is preferable that Moreover, it is preferable that the film thickness of a urethane coat layer of both surfaces is equal from the surface of prevention of the curvature etc. of a film.

3. Polarizing plate Although there is no restriction | limiting in particular in the use of the film of this invention, Since it is excellent in transparency, dimensional stability, and heat-and-moisture resistance, it can be used suitably especially as a protective film of the polarizing film of a polarizing plate.

When using the film of this invention as a protective film of the polarizing film in a polarizing plate, for example, generally a polarizing film is bonded together through the adhesive agent for adhere | attaching a polarizing film on the urethane coat layer side.
As the adhesive, conventionally known ones can be used, for example, water-based adhesives such as polyvinyl alcohol and urethane compounds, active energy ray-curable adhesives such as acrylic compounds, epoxy compounds, and oxazoline compounds. Can be mentioned. Among these, water-based adhesives such as polyvinyl alcohol are preferable from the viewpoints of adhesiveness with polyvinyl alcohol (PVA), which is a polarizing film, and environmental safety in wastes.

After forming an adhesive layer by applying an adhesive such as a water-based adhesive on the urethane coat layer of the film of the present invention, a polarized light such as a polyvinyl alcohol film which is uniaxially stretched and dyed with iodine or the like is formed thereon. Bond the membranes together. A protective film, a retardation film, or the like can be bonded to the opposite side of the polarizing film to form a polarizing plate.
That is, the polarizing plate of the present invention using the film of the present invention has a layer structure of a first protective film / adhesive layer / polarizing film / adhesive layer / second protective film. Of these, it is used as at least one protective film.

4). Liquid crystal display device The film of the present invention is excellent in transparency, dimensional stability and heat and humidity resistance, and can be adhered with good adhesion to a polarizing film. Therefore, the polarized light of the present invention using such a film of the present invention. The plate is excellent in the protective effect and function maintenance of the polarizing film, and can realize a high-quality display screen as a polarizing plate of a liquid crystal display device such as a television, a personal computer, a digital camera, or a mobile phone.

  As described above, the liquid crystal display has the configuration of the front side polarizing plate / liquid crystal / rear side polarizing plate, and the polarizing plate has the configuration of protective film / polarizing film / protective film, and thus constitutes the front side polarizing plate. The protective films arranged on the front side and the rear side of the polarizing film are designated as protective film A and protective film B, respectively, and the protective films arranged on the front side and the rear side of the polarizing film constituting the rear side polarizing plate are respectively protective film C, If it is set as the protective film D, the whole structure will be protective film A / front side polarizing film / protective film B / liquid crystal / protective film C / rear side polarizing film / protective film D from the front side.

  When the film of the present invention is a double-sided adhesive type having a urethane coat layer on both sides of the polycarbonate layer of the present invention, a polarizing film is adhered to one urethane coat layer side through the above-mentioned adhesive layer, and the other urethane Another functional film or a transparent substrate can be bonded to the coat layer side via the above-mentioned adhesive layer. Other functional film is not particularly limited, for example, high refractive index film, low refractive index film, antireflection film laminated with these, optical correction film such as color correction film, hard coat film, antifouling film, Examples thereof include an electromagnetic wave shielding film, an infrared ray absorbing film, and an ultraviolet ray absorbing film. Moreover, as a transparent base material, the glass as a support substrate and various transparent films are mentioned.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by these examples and comparative examples.

[Evaluation method]
In the following, measurement and evaluation of various physical properties and the like were performed as follows.

<Evaluation of initial adhesiveness with PVA film>
An aqueous adhesive obtained by mixing 0.3 part by weight of a crosslinking agent (Nihon Gosei Co., Ltd., SPM-02) with 100 g of an aqueous solution of 10% by weight of PVA resin (Nihon Gosei Co., Ltd., Gohsenx Z-200). Was made. With the urethane coating layer of the prepared coating film as the adhesive surface side, a water-based adhesive was applied to the urethane coating layer with a # 24 bar coater, and a biaxially stretched PVA film (Nippon Gosei Co., Ltd., trade name: Boblon, thickness) : 40 μm) was laminated, and the sample for evaluation was produced by heating and drying at 100 ° C. for 300 seconds. After this sample was cut at a width of 20 mm, T-type peeling was performed at a test speed of 50 mm / min using a universal tensile tester (manufactured by Intesco, model: 200X). The maximum peel strength (N / 20 mm width) at that time, the average peel strength (N / 20 mm width) of the stable portion, and the peeled state were evaluated as initial adhesiveness.

<Evaluation of adhesiveness after wet heat with PVA film>
The evaluation sample prepared in <Evaluation of initial adhesiveness with PVA film> was left in a constant temperature and humidity chamber at 85 ° C. and 85% RH for 200 hours, and then the same peel test was performed.

<Evaluation of crosslinkability>
The prepared coating composition was applied to a Teflon (registered trademark) sheet and dried at 100 ° C. for 60 seconds to prepare an evaluation sample. This sample was subjected to dynamic viscoelasticity measurement by using a dynamic viscoelasticity measuring device “DVE-V4” (manufactured by Rheology), and measured at 150 ° C. by a tensile method at a frequency of 10 Hz and a heating rate of 3 ° C./min. From the elastic modulus at, the following criteria were used.
○: Elastic modulus at 150 ° C. is 1.0 MPa or more ×: Elastic modulus at 150 ° C. is less than 1.0 MPa

<Tensile elongation>
The film used for coating was cut into a MD with a width of 6 mm to obtain a sample for evaluation. According to JIS K7161, the sample for evaluation was subjected to a tensile test at a test speed of 200 mm / min, and the tensile elongation (%) at that time was measured.

<Tear strength>
About the film used for coating, the tear strength (kg / cm) of MD direction of the sample for evaluation was measured according to JISK7128-2.

[Base film]
The base film used for the production of the coating film was produced or procured as follows.

<Polycarbonate film>
The molar ratio of the structural unit derived from isosorbide which is a dihydroxy compound and the structural unit derived from tricyclodecane dimethanol is isosorbide / tricyclodecane dimethanol = 6/4 by a method according to JP2008-024919A. A polycarbonate copolymer having a glass transition temperature of 126 ° C. was obtained.
The polycarbonate copolymer is put into a φ65 mm single screw extruder, melt-kneaded at a barrel set temperature of 220 to 240 ° C., and extruded from a die having a width of 1350 mm and a lip gap of 0.7 mm (set temperature 240 ° C.). A polycarbonate film having a thickness of 100 μm was produced by winding with a cast roll whose temperature was adjusted to 65 ° C. The polycarbonate film was subjected to corona treatment with a cumulative irradiation amount of 1000 W / m ² using a corona treatment device, and then cut into 100 mm × 200 mm with the MD direction as the longitudinal direction.

<Acrylic film>
As an acrylic film, PMMA resin (manufactured by Sumitomo Chemical Co., Ltd., “Sumipec MGSS”) is put into a φ65 mm single screw extruder, melt-kneaded at a barrel set temperature of 220 to 240 ° C., a width of 1350 mm and a lip gap of 0.7 mm. After extruding from the die (set temperature 230 ° C.), an acrylic film having a thickness of 100 μm was prepared by winding up with a cast roll adjusted to 65 ° C. The acrylic film was subjected to corona treatment with an integrated irradiation amount of 1000 W / m ² using a corona treatment apparatus, and then cut into 100 mm × 200 mm with the MD direction as the longitudinal direction.

<Cycloolefin film>
“ZF14-100” (thickness: 100 μm) manufactured by Nippon Zeon Co., Ltd. was used.

[Example 1]
Aqueous urethane resin “RU-40-350” (manufactured by Star Japan Co., Ltd., solid content (urethane resin) 40 wt%, volatile base: triethylamine) 100 parts by weight, sorbitol-type poly as an epoxy resin crosslinking agent Urethane coating composition by blending 1 part by weight of glycidyl ether resin “CR-5L” (manufactured by DIC), blending with ion-exchanged water as a diluent solvent to a solid content concentration of 20% by weight, and mixing. Was made. The coating composition is coated on the polycarbonate film using a bar coater # 8, and then dried at 100 ° C. for 1 minute to form a urethane coat layer having the thickness shown in Table 1 on the polycarbonate film. An inventive coating film was prepared. Various evaluation was implemented about this coating film.

[Example 2]
A coating film was produced in the same manner as in Example 1 except that the epoxy resin crosslinking agent was changed to 5 parts by weight. Various evaluation was implemented about this coating film.

[Example 3]
A coating film was produced in the same manner as in Example 1 except that the epoxy resin crosslinking agent was changed to 10 parts by weight. Various evaluation was implemented about this coating film.

[Example 4]
In Example 2, the aqueous urethane resin was changed to an aqueous urethane resin “EX-RU-92-605” (manufactured by Star Japan Co., Ltd., solid content (urethane resin) 40 wt%, volatile base: triethylamine). A coating film was prepared in the same manner except that the change was made. Various evaluation was implemented about this coating film.

[Comparative Example 1]
A coating film was produced in the same manner as in Example 1 except that the epoxy resin crosslinking agent was not used. Various evaluation was implemented about this coating film.

[Comparative Example 2]
A coating film was produced in the same manner as in Example 1 except that the crosslinking agent was changed to 0.5 parts by weight of the carbodiimide-based crosslinking agent “XR-5580” (manufactured by Star Japan Co., Ltd.). Various evaluation was implemented about this coating film.

[Comparative Example 3]
A coating film was produced in the same manner as in Comparative Example 2 except that the carbodiimide-based crosslinking agent was changed to 3 parts by weight. Various evaluation was implemented about this coating film.

[Comparative Example 4]
A coating film was prepared in the same manner as in Comparative Example 2 except that the carbodiimide-based crosslinking agent was changed to 5 parts by weight. Various evaluation was implemented about this coating film.

[Comparative Example 5]
A coating film was prepared in the same manner as in Example 1 except that the crosslinking agent was changed to 20 parts by weight of the oxazoline-based crosslinking agent “Epocross WS-500” (manufactured by Nippon Shokubai Co., Ltd.). Various evaluation was implemented about this coating film.

[Comparative Example 6]
A coating film was prepared in the same manner as in Comparative Example 5 except that the oxazoline-based crosslinking agent was changed to 40 parts by weight. Various evaluation was implemented about this coating film.

[Comparative Example 7]
A coating film was produced in the same manner as in Example 2 except that the film used for coating was changed to an acrylic film. Various evaluation was implemented about this coating film.

[Comparative Example 8]
A coating film was produced in the same manner as in Example 2 except that the film used for coating was changed to a cycloolefin film. Various evaluation was implemented about this coating film.

The evaluation results of the coating films in Examples 1 to 4 and Comparative Examples 1 to 6 and the film thickness of the formed coating layer are shown in Table 1.
Table 2 shows the evaluation results of the films used for coating in Example 2, Comparative Example 7 and Comparative Example 8, the evaluation results of the coating film, and the thickness of the formed coating layer. In Table 2, the polycarbonate film is described as “PC”, the acrylic film as “acryl”, and the cycloolefin film as “COP”.

As is apparent from Table 1, the films coated with the coating compositions described in Examples 1 to 4 of the present invention all have high heat resistance, and are extremely excellent in adhesion to water-based adhesives and heat and humidity resistance. The characteristics are shown. On the other hand, the films of Comparative Examples 1, 2, and 5 were insufficient in crosslinkability. In addition, the films of Comparative Examples 3, 4, and 6 resulted in poor adhesion to the water-based adhesive.
Further, as is clear from Table 2, in Comparative Examples 7 and 8 in which the film used for coating was an acrylic film or a cycloolefin film, the tensile elongation of the film used for coating was small and the tear strength was also small.

Claims (10)

  In a film formed by forming a coating layer made of a water-based urethane resin composition containing a urethane resin and a crosslinking agent on at least one surface of a resin layer containing a polycarbonate resin as a main component, the crosslinking agent is an epoxy resin crosslinking agent The film characterized by being.   The film according to claim 1, wherein the epoxy resin-based crosslinking agent includes an aliphatic epoxy resin derived from a polyhydric alcohol.   The film according to claim 2, wherein the aliphatic epoxy resin is a resin having a sorbitol polyglycidyl ether structure.   The content of the epoxy resin crosslinking agent in the water-based urethane resin composition is 0.1 parts by weight or more and less than 30 parts by weight with respect to 100 parts by weight of the urethane resin. The film of crab.   The film according to claim 1, wherein the urethane resin has an aliphatic polycarbonate skeleton. The film according to any one of claims 1 to 5, wherein the polycarbonate resin is a polycarbonate resin containing a structural unit derived from a dihydroxy compound represented by the following formula (1).

The film according to claim 6, wherein the polycarbonate resin further contains a structural unit derived from tricyclodecane dimethanol represented by the following formula (2).

  The polarizing plate formed by adhere | attaching a polarizing film on the said coating layer of the film in any one of Claims 1-7 through an adhesive bond layer.   The polarizing plate according to claim 8, wherein the adhesive is a water-based adhesive.   A liquid crystal display device comprising the polarizing plate according to claim 8.