JP5716571B2 - Multilayer film, method for producing multilayer film, polarizing plate protective film and polarizing plate - Google Patents

Description

  The present invention relates to a multilayer film, a method for producing the multilayer film, and a polarizing plate protective film and a polarizing plate provided with the multilayer film.

  For example, a film made of a resin containing an alicyclic structure-containing polymer or an acrylic polymer is known as a film used for various image display devices such as a liquid crystal display device, an organic EL display device, and a plasma display. Since these films are excellent in optical properties, for example, electrode substrates of liquid crystal cells constituting liquid crystal display devices, polarizing plates, protective films for polarizing plates, retardation films, viewing angle widening films, brightness enhancement films, touch panels Development for optical applications such as a film with a transparent electrode, a light guide plate, and an optical disk is being made.

  Films used for optical applications such as those described above are bonded to members having various other functions such as polarizers, hard coat layers, antireflection layers, antistatic layers, antiglare layers, and antifouling layers. Often used. Therefore, it is desired that the film has high adhesive strength with the member to be bonded.

  However, some films having a layer made of a resin containing an alicyclic structure-containing polymer or an acrylic polymer are inferior in adhesiveness to other members. Therefore, it has been conventionally performed to provide an easy adhesion layer on the surface of the film. The easy-adhesion layer is a layer that reinforces the adhesive force of the film and bonds it more firmly when the film is bonded to some member via an adhesive as necessary. About the easily bonding layer, what was formed with the urethane resin has been proposed conventionally (refer patent documents 1-3).

JP 2009-274390 A JP 2006-201736 A JP 2009-80177 A

  However, the easy-adhesion layer formed of a urethane resin sometimes has poor water resistance. For this reason, when a multilayer film provided with a conventional easy-adhesion layer is bonded to a polarizer, for example, and then placed in a high-temperature and high-humidity environment for a long time, the adhesive strength may be reduced.

  The present invention was devised in view of the above problems, and is a multilayer film provided with a base film having a layer made of a resin containing an alicyclic structure-containing polymer, and has a high adhesive force, and An object of the present invention is to provide a multilayer film capable of maintaining the adhesive strength for a long period even in a high temperature and high humidity environment.

As a result of intensive studies to solve the above problems, the present inventor has obtained a base film having a layer made of a resin containing an alicyclic structure-containing polymer, and a urethane resin layer obtained by curing a resin containing polyurethane. In the multilayer film provided, it was found that the adhesive strength can be maintained for a long time even in a high temperature and high humidity environment by using ether polyurethane or ester / ether polyurethane as a polyurethane in a specific ratio, and the present invention was completed. .
That is, the gist of the present invention is the following [1] to [8].

[1] A base film having a layer comprising a resin containing an alicyclic structure-containing polymer on the surface, and a urethane resin layer obtained by curing a resin containing polyurethane,
The polyurethane is
A multilayer film comprising ether polyurethane or ester / ether polyurethane in a proportion of 30 wt% to 80 wt%.
[2] The multilayer film according to [1], wherein the polyurethane further contains an ester polyurethane.
[3] The multilayer film according to [1] or [2], wherein the resin containing polyurethane further contains fine particles.

[4] A method for producing a multilayer film comprising applying a resin containing polyurethane to the surface of a base film having a layer comprising a resin containing an alicyclic structure-containing polymer on the surface and curing the resin. ,
The polyurethane is
A method for producing a multilayer film, comprising ether polyurethane or ester / ether polyurethane in a proportion of 30% by weight to 80% by weight.
[5] The production method according to [4], wherein the polyurethane further contains an ester polyurethane.
[6] The production method according to [4] or [5], wherein the resin containing polyurethane further contains fine particles.
[7] A polarizing plate protective film comprising the multilayer film according to any one of [1] to [3].
[8] A polarizing plate comprising a polarizer and the polarizing plate protective film according to [7].

ADVANTAGE OF THE INVENTION According to this invention, it is equipped with the base film which has a layer which consists of resin containing an alicyclic structure containing polymer, has high adhesive force, and can maintain the adhesive force for a long period of time also in a high temperature high humidity environment A multilayer film can be provided.
In addition, according to the present invention, a base film having a layer made of a resin containing an alicyclic structure-containing polymer is provided, and the adhesive strength is high and the adhesive strength is maintained for a long time even in a high humidity environment. The manufacturing method of the multilayer film which can be provided can be provided.
Furthermore, according to this invention, the polarizing plate protective film and polarizing plate provided with the multilayer film of this invention can be provided.

  Hereinafter, the present invention will be described in detail with reference to embodiments and examples, but the present invention is not limited to the embodiments and examples described below, and the gist of the present invention and its equivalent scope are described below. You may implement arbitrarily changing in the range which does not deviate.

[1. Overview]
The multilayer film of the present invention includes a base film and a urethane resin layer. Among these, the base film has on its surface a layer made of a resin containing an alicyclic structure-containing polymer. Hereinafter, a resin containing an alicyclic structure-containing polymer may be referred to as an “alicyclic structure-containing polymer resin”.

  The urethane resin layer is formed by curing a resin containing polyurethane, and the polyurethane contains ether polyurethane or ester / ether polyurethane in a proportion of 30 wt% to 80 wt%.

  Usually, a urethane resin layer is provided on the surface of the layer which consists of resin containing the alicyclic structure containing polymer or acrylic polymer of a base film, and this urethane resin layer improves the adhesiveness of a base film. Furthermore, in the multilayer film of the present invention, the water resistance of the urethane resin layer is improved by keeping the ratio of the ether-based polyurethane or the ester-ether-based polyurethane within the above range, even in a high temperature and high humidity environment. Adhesive strength is maintained for a long time.

[2. Base film]
The base film has a layer made of an alicyclic structure-containing polymer resin on the surface of the base film. Therefore, when a base film is a film of the single layer structure which has only 1 layer, a base film is formed only by the layer which consists of alicyclic structure containing polymer resin. Further, when the base film is a film having a multilayer structure having two or more layers, if the outermost layer of at least one of the base films is a layer made of an alicyclic structure-containing polymer resin, the base material The film may have other optional layers.

[2-1. Alicyclic structure-containing polymer resin]
The alicyclic structure-containing polymer is a polymer having an alicyclic structure in the repeating unit of the polymer, and has a polymer having an alicyclic structure in the main chain and an alicyclic structure in the side chain. Any of the polymers may be used. An alicyclic structure containing polymer may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios. Among these, a polymer containing an alicyclic structure in the main chain is preferable from the viewpoint of mechanical strength, heat resistance, and the like.

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

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

  The proportion of the repeating unit having an alicyclic structure in the alicyclic structure-containing polymer may be appropriately selected according to the purpose of use, preferably 55% by weight or more, more preferably 70% by weight or more. Particularly preferably, it is 90% by weight or more. When the ratio of the repeating unit having an alicyclic structure in the alicyclic structure-containing polymer is in this range, it is preferable from the viewpoint of the transparency and heat resistance of the base film.

  Examples of alicyclic structure-containing polymers include norbornene polymers, monocyclic olefin polymers, cyclic conjugated diene polymers, vinyl alicyclic hydrocarbon polymers, and hydrides thereof. Can be mentioned. Among these, norbornene-based polymers are preferable because of their good transparency and moldability.

  As the norbornene-based polymer, for example, a ring-opening polymer of a monomer having a norbornene structure, a ring-opening copolymer of a monomer having a norbornene structure and another monomer, or a hydride thereof; An addition polymer of a monomer having a norbornene structure, an addition copolymer of a monomer having a norbornene structure and another monomer, or a hydride thereof. Among these, a ring-opening (co) polymer hydride of a monomer having a norbornene structure is particularly suitable from the viewpoints of transparency, moldability, heat resistance, low hygroscopicity, dimensional stability, lightness, and the like. It is. Here, “(co) polymer” refers to a polymer and a copolymer.

Examples of the monomer 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 (common name: dicyclopentadiene), 7,8-benzotricyclo [4.3.0.1 ^2,5 ] dec-3-ene (common name: methanotetrahydrofluorene), tetracyclo [4.4. 0.1 ^2,5 . ^{17, 10} ] dodec-3-ene (common name: tetracyclododecene), and derivatives of these compounds (for example, those having a substituent in the ring). Here, examples of the substituent include an alkyl group, an alkylene group, and a polar group. Moreover, these substituents may be the same or different, and a plurality thereof 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 the polar group include a hetero atom or an atomic group having a hetero atom. Examples of the hetero atom include an oxygen atom, a nitrogen atom, a sulfur atom, a silicon atom, and a halogen atom. Specific examples of the polar group include 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 sulfonic acid group.

Other monomers capable of ring-opening copolymerization with a monomer having a norbornene structure include, for example, monocyclic olefins such as cyclohexene, cycloheptene, and cyclooctene and derivatives thereof; and cyclic conjugates such as cyclohexadiene and cycloheptadiene. Dienes and derivatives thereof; and the like.
As the other monomer capable of ring-opening copolymerization with a monomer having a norbornene structure, one type may be used alone, or two or more types may be used in combination at any ratio.

  A ring-opening polymer of a monomer having a norbornene structure and a ring-opening copolymer with another monomer copolymerizable with a monomer having a norbornene structure are, for example, a known ring-opening monomer. You may manufacture by superposing | polymerizing or copolymerizing in presence of a polymerization catalyst.

  Examples of other monomers that can be addition copolymerized with a monomer having a norbornene structure include α-olefins having 2 to 20 carbon atoms such as ethylene, propylene, and 1-butene, and derivatives thereof; cyclobutene, cyclopentene, And cycloolefins such as cyclohexene 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-olefin is preferable and ethylene is more preferable. Moreover, the other monomer which can carry out addition copolymerization with 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.

  An addition polymer of a monomer having a norbornene structure and an addition copolymer of another monomer copolymerizable with the monomer having a norbornene structure are, for example, a known addition polymerization catalyst. You may manufacture by superposing | polymerizing or copolymerizing in presence.

  Examples of the monocyclic olefin polymer include addition polymers of a cyclic olefin monomer having a single ring such as cyclohexene, cycloheptene, and cyclooctene.

  Examples of the cyclic conjugated diene polymer include polymers obtained by 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 their hydrides.

  Examples of vinyl alicyclic hydrocarbon polymers include polymers of vinyl alicyclic hydrocarbon monomers such as vinylcyclohexene and vinylcyclohexane and their hydrides; vinyl aromatic hydrocarbons such as styrene and α-methylstyrene. Hydrogenated product obtained by hydrogenating an aromatic ring part contained in a polymer obtained by polymerizing monomers; vinyl alicyclic hydrocarbon monomer, or vinyl aromatic hydrocarbon monomer and vinyl aromatic hydrocarbon monomer And an aromatic ring hydride of a copolymer such as a random copolymer or a block copolymer with another copolymerizable monomer. Examples of the block copolymer include a diblock copolymer, a triblock copolymer or a multi-block copolymer having more than that, a gradient block copolymer, and the like.

  The molecular weight of the alicyclic structure-containing polymer is appropriately selected according to the purpose of use, but gel permeation using cyclohexane as a solvent (however, toluene may be used when the sample does not dissolve in cyclohexane). The polyisoprene or polystyrene-equivalent weight average molecular weight (Mw) measured by chromatography is usually 10,000 or more, preferably 15,000 or more, more preferably 20,000 or more, and usually 100,000 or less, preferably Is 80,000 or less, more preferably 50,000 or less. When the weight average molecular weight is in such a range, the mechanical strength and molding processability of the multilayer film of the present invention are highly balanced and suitable.

  The molecular weight distribution (Mw / Mn) represented by the ratio of the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the alicyclic structure-containing polymer is usually 1.2 or more, preferably 1.5 or more, Preferably it is 1.8 or more, usually 3.5 or less, preferably 3.0 or less, more preferably 2.7 or less. When the molecular weight distribution exceeds 3.5, low-molecular components increase, so the components with a short relaxation time increase. Even if the base film has the same in-plane retardation Re at first glance, the relaxation during high-temperature exposure is large in a short time. It is estimated that the stability of the base film is lowered. On the other hand, when the molecular weight distribution is less than 1.2, the productivity of the polymer is reduced and the cost is increased, which is not practical from the viewpoint of practicality.

  The glass transition temperature of the alicyclic structure-containing polymer is preferably 100 ° C. or higher, more preferably 130 ° C. or higher, preferably 160 ° C. or lower, more preferably 150 ° C. or lower. If the glass transition temperature is too low, durability at high temperatures may be deteriorated. If the glass transition temperature is too high, durability may be improved, but normal stretching may be difficult.

The alicyclic structure-containing polymer preferably has an absolute value of the photoelastic coefficient of 10 × 10 ⁻¹² Pa ⁻¹ or less, more preferably 7 × 10 ⁻¹² Pa ⁻¹ or less, and 4 × 10. It is particularly preferably ⁻¹² Pa ⁻¹ or less. The photoelastic coefficient C is a value represented by “C = Δn / σ” where birefringence is Δn and stress is σ. When the photoelastic coefficient of the alicyclic structure-containing polymer exceeds 10 × 10 ⁻¹² Pa ⁻¹ , the in-plane retardation Re of the base film may vary greatly.

  The saturated water absorption of the alicyclic structure-containing polymer is preferably 0.03% by weight or less, more preferably 0.02% by weight or less, and particularly preferably 0.01% by weight or less. When the saturated water absorption is within the above range, the temporal change of the in-plane retardation Re and the thickness direction retardation Rth of the base film can be reduced. In addition, deterioration of the polarizing plate and the liquid crystal display device including the multilayer film of the present invention can be suppressed, and the display on the display can be kept stable and favorable for a long period.

  The saturated water absorption is a value expressed as a percentage with respect to the mass of the test piece before immersion, which is obtained by immersing the test piece in water at a constant temperature for a certain period of time. Usually, it is measured by immersing in 23 ° C. water for 24 hours. The saturated water absorption in the alicyclic structure-containing polymer can be adjusted to the above range, for example, by reducing the amount of polar groups in the alicyclic structure-containing polymer. From the viewpoint of lowering the saturated water absorption, the alicyclic structure-containing polymer preferably has no polar group.

  The alicyclic structure-containing polymer resin may contain other components in addition to the alicyclic structure-containing polymer as long as the effects of the present invention are not significantly impaired. Examples of other components include colorants such as pigments and dyes; plasticizers; fluorescent brighteners; dispersants; thermal stabilizers; light stabilizers; ultraviolet absorbers; antistatic agents; An additive such as a surfactant may be mentioned. These components may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  The amount of the polymer contained in the alicyclic structure-containing polymer resin is generally 50% to 100%, or 70% to 100%. In particular, even when the base film according to the present invention has a layer made of a polymer resin containing an alicyclic structure having a high hydrophobicity, by providing a urethane resin layer with other members having high hydrophilicity It has the advantage of being able to adhere firmly. From the viewpoint of effectively utilizing this advantage, the amount of the polymer contained in the alicyclic structure-containing polymer resin is, for example, 80% to 100%, more specifically, 90% to 100%. It is preferable to adjust the amount of these components.

  The alicyclic structure-containing polymer resin preferably does not substantially contain particles. Here, “substantially free of particles” means that the increase in haze of the base film from a state in which no particles are contained even when particles are included in the alicyclic structure-containing polymer resin is 0.05%. It means that amounts up to the following range are acceptable. Since the alicyclic structure-containing polymer lacks affinity with many organic particles and inorganic particles, voids are generated when the alicyclic structure-containing polymer resin containing particles exceeding the above range is stretched. As a result, the haze may be significantly reduced.

  The layer made of the alicyclic structure-containing polymer resin is not particularly limited by the production method. The layer made of the alicyclic structure-containing polymer resin is obtained by molding the alicyclic structure-containing polymer resin by a known film forming method. Examples of the film forming method include a cast forming method, an extrusion forming method, and an inflation forming method. Among these, a melt extrusion method that does not use a solvent can reduce the amount of residual volatile components efficiently, and is preferable from the viewpoints of the global environment and work environment, and excellent manufacturing efficiency. Examples of the melt extrusion method include an inflation method using a die, and among them, a method using a T die is preferable in terms of excellent productivity and thickness accuracy.

[2-2. (Structure and physical properties of base film)
The base film may be a single layer film layer having only one layer, or may be a multilayer film layer having two or more layers. A polarizing plate having various characteristics can be produced by using a base film as a film layer having a multilayer structure. However, when a base film is provided with two or more layers, it is made for the layer which consists of alicyclic structure containing polymer resin to be located in the outermost surface of a base film. Under the present circumstances, the layer which consists of alicyclic structure containing polymer resin may be located only in one outermost surface among the two outermost surfaces (front surface and back surface) of a base film, The layer which consists of alicyclic structure containing polymer resin may be located in the outermost surface.

  When the base film has two or more layers, there is no limitation on the type of layer combined with the layer made of the alicyclic structure-containing polymer resin. For example, the layer made of acrylic resin, the layer made of styrene resin, the polycarbonate Examples include a layer made of a resin and a layer made of a cellulose ester resin.

  When a base film is provided with two or more layers, there is no restriction | limiting in the manufacturing method of a base film. For example, you may manufacture a base film by bonding the film layer manufactured separately using an adhesive agent. For example, you may manufacture a base film by a coextrusion method etc., without using an adhesive agent.

  The adhesive may be appropriately selected depending on the type of resin forming the film layer to be bonded. Examples of adhesives include acrylic adhesives, urethane adhesives, polyester adhesives, polyvinyl alcohol adhesives, polyolefin adhesives, modified polyolefin adhesives, polyvinyl alkyl ether adhesives, rubber adhesives , Ethylene-vinyl acetate adhesive, vinyl chloride-vinyl acetate adhesive, SEBS (styrene-ethylene-butylene-styrene copolymer) adhesive, SIS (styrene-isoprene-styrene block copolymer) adhesive And ethylene-based adhesives such as ethylene-styrene copolymer, and acrylic acid ester-based adhesives such as ethylene- (meth) methyl acrylate copolymer and ethylene- (meth) ethyl acrylate copolymer. An adhesive agent may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  The average thickness of the adhesive layer formed of the adhesive is preferably 0.1 μm or more, more preferably 0.5 μm or more, preferably 10 μm or less, more preferably 5 μm or less.

  When manufacturing a base film without using an adhesive, for example, a coextrusion molding method such as a coextrusion T-die method, a coextrusion inflation method, a coextrusion lamination method, or a film lamination molding method such as dry lamination is used. May be. Further, for example, a coating molding method in which the surface of a certain film layer is coated with a solution containing a resin constituting another film layer may be used. Among these, the coextrusion molding method is preferable from the viewpoint of production efficiency and the volatile component such as a solvent does not remain in the base film, and the coextrusion T die method is preferable among the coextrusion molding methods. Furthermore, the co-extrusion T-die method includes a feed block method and a multi-manifold method, but the multi-manifold method is more preferable from the viewpoint that variations in film layer thickness can be reduced.

  The base film may be a non-stretched unstretched film or a stretched stretched film. In addition, when the base film has two or more layers, a stretched film may be obtained by laminating a previously stretched film layer, or a stretched film obtained by stretching a multilayer film layer obtained by coextrusion or the like. You may get

  The stretching method is not particularly limited, and for example, either a uniaxial stretching method or a biaxial stretching method may be adopted. As an example of the stretching method, as an example of the uniaxial stretching method, a method of uniaxial stretching in the longitudinal direction using a difference in peripheral speed of a roll for film conveyance; uniaxial stretching in the width direction using a tenter stretching machine And the like. In addition, as an example of the biaxial stretching method, simultaneous biaxial stretching method that stretches in the width direction according to the spread angle of the guide rail at the same time as stretching in the longitudinal direction with an interval between the clips to be fixed; roll for film conveyance The biaxial stretching method such as the sequential biaxial stretching method is used in which the two ends are clipped and stretched in the width direction using a tenter stretching machine. Can be mentioned. Further, for example, an arbitrary angle θ is formed with respect to the width direction of the film by using a tenter stretching machine that can add a feeding force, a pulling force, or a pulling force at different speeds in the width direction or the longitudinal direction. An oblique stretching method in which oblique stretching is continuously performed in the direction may be used.

Examples of the apparatus used for stretching include a longitudinal uniaxial stretching machine, a tenter stretching machine, a bubble stretching machine, and a roller stretching machine.
The stretching temperature is preferably (Tg-30 ° C) or more, more preferably (Tg-10 ° C) or more, preferably, when the glass transition temperature of the material forming the unstretched base film is Tg. (Tg + 60 ° C.) or less, more preferably (Tg + 50 ° C.) or less.
The draw ratio may be appropriately selected according to the optical characteristics of the base film used, and is usually 1.05 times or more, preferably 1.1 times or more, and usually 10.0 times or less, preferably 2. 0 times or less.

The base film preferably has a total light transmittance of 80% or more in terms of 1 mm thickness. More preferably, the total light transmittance is 90% or more.
The base film preferably has a haze at a thickness of 1 mm of 0.3% or less. More preferably, the haze is 0.2% or less. If the haze exceeds 0.3%, the transparency of the base film may be lowered.

The average thickness of the base film is preferably 5 μm or more, more preferably 20 μm or more, preferably 500 μm or less, more preferably 300 μm or less.
The thickness variation width of the base film is preferably within ± 3% of the average thickness over the longitudinal direction and the width direction. By setting the thickness variation within the above range, variations in optical characteristics such as retardation of the base film can be reduced.

  The content of residual volatile components in the base film 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 making the content of the volatile component in the above range, the dimensional stability can be improved, and the temporal change of the in-plane retardation Re and the thickness direction retardation Rth of the base film can be reduced. Deterioration of a polarizing plate or a liquid crystal display device provided with the multilayer film of the invention can be suppressed, and the display on the display can be kept stable and good for a long period. Volatile components are substances having a molecular weight of 200 or less, and examples thereof include residual monomers and solvents. The content of volatile components can be quantified by analyzing the total amount of substances having a molecular weight of 200 or less by gas chromatography.

[3. Urethane resin layer]
The urethane resin layer is a layer formed by curing a resin containing polyurethane. The urethane resin layer functions as an easy-adhesion layer. When the base film is bonded to another member (for example, a polarizer, etc.) via an adhesive, the adhesive between the base film and the other member by the adhesive is used. It is reinforced and more firmly bonded. That is, the urethane resin layer is a layer that reinforces the function of the adhesive, and is called a primer layer or the like as another name.

Usually, the urethane resin layer is provided directly on the surface of the layer made of the alicyclic structure-containing polymer resin of the base film without interposing another layer such as an adhesive layer.
The urethane resin layer may be provided on one surface of the base film or on both surfaces. By providing the urethane resin layer on both surfaces of the base film, the handleability of the base film can be effectively improved.

[3-1. Polyurethane)
Examples of the polyurethane include: (i) a polyurethane obtained by reacting a component containing an average of 2 or more active hydrogens in one molecule and (ii) a polyvalent isocyanate component; or the above (i) component and ( ii) The component is urethanated in an organic solvent that is inert to the reaction and has a high affinity for water under an excess of isocyanate groups to obtain an isocyanate group-containing prepolymer, and then the prepolymer is neutralized. A polyurethane produced by chain extension using a chain extender and adding water to form a dispersion; and the like. These polyurethanes may contain an acid structure (acid residue).

  The chain extension method of the isocyanate group-containing prepolymer may be a known method. For example, water, water-soluble polyamine, glycols, etc. are used as the chain extender, and the isocyanate group-containing prepolymer and the chain extender are required. Depending on the reaction, the reaction may be carried out in the presence of a catalyst.

  In the present invention, ether polyurethane or ester / ether polyurethane is used as the polyurethane. The ether polyurethane is a polyurethane having an ether bond in the molecular main chain, and the ester / ether polyurethane is a polyurethane having an ester bond and an ether bond in the molecular main chain. Examples of the component (i) (that is, a component containing an average of 2 or more active hydrogens in one molecule) used in the production of such a polyurethane include polyether polyols and polyether ester polyols. When a polyether polyol is used as the component (i), an ether-based polyurethane is obtained, and when a polyether ester polyol is used, an ester-ether-based polyurethane is obtained.

(1) Polyether polyol Examples of the polyether polyol include an alkylene oxide adduct of a polyol compound. Examples of the polyol compound include 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-hexane glycol, 2,5-hexanediol, dipropylene glycol, 2,2,4-trimethyl-1,3-pentanediol, tricyclodecane dimethanol, 1,4- Examples include cyclohexanedimethanol, 2,2-dimethylpropanediol, and 1,4-butanediol. In addition, a ring-opening (co) polymer of an alkylene oxide and a cyclic ether (for example, tetrahydrofuran); a copolymer of polyethylene glycol, polypropylene glycol, ethylene glycol-propylene glycol; glycol, polytetramethylene glycol, polyhexamethylene glycol, And glycols such as polyoctamethylene glycol.

(2) Polyether ester polyol As the polyether ester polyol, for example, an ether group-containing polyol (for example, the above-described polyether polyol or diethylene glycol) or a mixture of this with another glycol is converted into a dicarboxylic acid or an anhydride thereof. In addition, there may be mentioned those obtained by reacting alkylene oxide. Examples of the dicarboxylic acid or anhydride thereof include dicarboxylic acids such as adipic acid, succinic acid, sebacic acid, glutaric acid, maleic acid, fumaric acid, and phthalic acid, or anhydrides thereof. More specifically, examples include polytetramethylene glycol-adipic acid condensate.

  One of these polyether polyols and polyether ester polyols may be used alone, or two or more thereof may be used in combination at any ratio.

  The polyurethane used in the present invention is the above-mentioned ether-based polyurethane or ester / ether-based polyurethane in an amount of 30 wt% to 80 wt%, preferably 35 wt% to 70 wt%, more preferably 40 wt% to 60 wt%. It contains in the ratio. When the amount of the ether-based polyurethane or the ester / ether-based polyurethane is within this range, a urethane resin layer having both high heat resistance and moisture resistance can be obtained.

  The polyurethane used in the present invention preferably contains an ester polyurethane as another polyurethane. The content of the ester-based polyurethane is preferably 30% by weight or more and 65% by weight or less, more preferably 40% by weight or more and 60% by weight or less, with respect to the total amount of polyurethane. The ester-based polyurethane can be obtained by using a polyether ester polyol as the component (i).

(3) Polyester polyol As the polyester polyol, the dicarboxylic acid or its anhydride mentioned in (2) above, and the ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexane mentioned in (1) above. Examples thereof include those obtained by polycondensation with a polyol compound such as diol, 1,8-octamethylenediol, neopentyl glycol and the like under the condition of excess hydroxyl group. 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.

  The polyurethane used in the present invention may contain a polyurethane other than ether polyurethane, ester / ether polyurethane and ester polyurethane. Such polyurethane can be obtained by using a polyol compound or polycarbonate polyol as the component (i).

(4) Polyol compound As the polyol compound, any of the polyol compounds mentioned in the above (1) can be used.

(5) Polycarbonate polyol As a polycarbonate carbonate polyol, for example, the general formula HO-R- (OC (O) -O-R) _x -OH (wherein, R is saturated with 1 to 12 carbon atoms) A fatty acid polyol residue, and x is 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 becomes 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.

  Examples of the component (ii) to be reacted with the component (i) (that is, the polyvalent isocyanate component) include, for example, an aliphatic, alicyclic or aromatic compound containing an average of two or more isocyanate groups in one molecule. May 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, and hexane diisocyanate (HDI). The alicyclic diisocyanate compound is preferably an alicyclic diisocyanate 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 isocyanate include tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate, and the like.

  The polyurethane preferably has an acid structure. Polyurethane 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 resin layer is expected to be improved. Is done. This is called a self-emulsifying type and means that the polyurethane can be dispersed and stabilized in water only by molecular ionicity without using a surfactant. A urethane resin layer using such a polyurethane is preferable because it does not require a surfactant and is excellent in adhesion to an alicyclic structure-containing polymer resin and an acrylic resin and can maintain high transparency. .

Examples of the acid structure include acid groups such as a carboxyl group (—COOH) and a sulfonic acid group (—SO ₃ H). In addition, the acid structure may be present in the side chain or at the terminal in the polyurethane. 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 20 mgKOH / g or more, more preferably 25 mgKOH / g or more, preferably 250 mgKOH / g or less, more preferably 150 mgKOH / g or less as the acid value in the polyurethane. If the acid value is too low, water dispersibility tends to be insufficient, while if the acid value is too high, the water resistance of the urethane resin layer tends to be poor.

  As a method for introducing an acid structure into polyurethane, a conventionally used method can be used without any particular limitation. Preferable examples include dimethylol alkanoic acid by replacing some or all of the glycol components described in (1) to (3) above with a polyether polyol, polyester polyol, polyether ester polyol, etc. The method of introduce | transducing group 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 polyurethane is preferably 1,000 or more, more preferably 20,000 or more, preferably 1,000,000 or less, more preferably 200,000 or less.

  As polyurethane, you may use what is marketed as a water-based urethane resin. The water-based urethane resin is a composition containing polyurethane and water, and is usually one in which polyurethane and other components contained as necessary are dispersed in water. As water-based urethane resins, for example, “Adeka Bon titer” series manufactured by Asahi Denka Kogyo Co., Ltd., “Olestar” series manufactured by Mitsui Toatsu Chemical Co., Ltd. Series, Bayer's "Impranil" series, Japan Soflan's "Sofuranate" series, Kao's "Poise" series, Sanyo Kasei's "Samprene" series, Hodogaya Chemical Industries' The “IZerax” series, the “Superflex” series manufactured by Daiichi Kogyo Seiyaku Co., Ltd., the “Neolet” series manufactured by Zeneca, the “Sancure” series manufactured by Lubrizol, and the like can be used.

[3-2. Epoxy compound)
It is preferable that the resin containing polyurethane contains an epoxy compound. The epoxy compound is a component that functions as a crosslinking agent, and the mechanical strength of the urethane resin layer can be increased by using the epoxy compound. Moreover, the effect | action which improves adhesive force is also anticipated with the polar structure which an epoxy compound has.

  As the epoxy compound, a compound having an epoxy group is used. Usually, an epoxy compound having two or more epoxy groups per molecule is used. Thereby, a crosslinking reaction can be advanced and the mechanical strength of a urethane resin layer can be improved effectively.

  Moreover, as an epoxy compound, what is soluble in water or dispersible in water and can be emulsified is preferable. The uncured urethane resin used for forming the urethane resin layer is usually used as a fluid aqueous resin containing water. Here, the aqueous resin refers to a composition containing a solid content in a dissolved or dispersed state in an aqueous solvent such as water. If the epoxy group is soluble in water or can be emulsified, the application property of the water-based resin can be improved and the urethane resin layer can be easily produced.

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

  The amount of the epoxy compound is usually 2 parts by weight or more, preferably 5 parts by weight or more, more preferably 8 parts by weight or more, usually 20 parts by weight or less, preferably 16 parts by weight or less, based on 100 parts by weight of polyurethane. The amount is preferably 14 parts by weight or less. By making the amount of the epoxy compound equal to or higher than the lower limit of the above range, the reaction between the epoxy compound and the polyurethane sufficiently proceeds, so that the mechanical strength of the urethane resin layer can be appropriately improved, and the upper limit value or less. Thus, the residual unreacted epoxy compound can be reduced, and the mechanical strength of the urethane resin layer can be appropriately improved.

  When the polyurethane has an acid structure, the amount of the epoxy compound is preferably 0.2 times or more, more preferably 0.4 times, based on the weight, with respect to the amount of the epoxy compound equivalent to the acid structure of the polyurethane. Above, particularly preferably 0.6 times or more, preferably 1.4 times or less, more preferably 1.2 times or less, particularly preferably 1.0 times or less. Here, the amount of the epoxy compound equivalent to the acid structure of the polyurethane refers to the theoretical amount of the epoxy compound that can react with the total amount of the acid structure of the polyurethane without excess or deficiency. When the polyurethane has an acid structure, the acid structure can react with the epoxy group of the epoxy compound. At this time, by keeping the amount of the epoxy compound within the above range, the reaction between the acid structure and the epoxy compound can proceed to an appropriate level, and the mechanical strength of the urethane resin layer can be effectively improved.

[3-3. Nonvolatile base)
When the polyurethane includes an acid structure, part or all of the acid structure is preferably neutralized with a non-volatile base. It is more preferable that 20% or more of the acid structure of the acid structure-containing water-based urethane resin is neutralized with a nonvolatile base, and it is particularly preferable that 50% or more is neutralized with a nonvolatile base. 20% or more of the acid structure is neutralized by a non-volatile base, so that even if the laminated film of the present invention has a heat history exposed to high temperatures, while maintaining the properties as an optical material, When used by being laminated on another optical film, in particular, a polarizer, the adhesion with the laminated film can be further maintained. The remaining acid structure of the acid structure-containing aqueous urethane resin may not be neutralized or may be neutralized with a volatile base.

  As the non-volatile base, it is allowed to stand at 80 ° C. for 1 hour, for example, under the processing conditions when drying the aqueous dispersion of the aqueous urethane resin after neutralization used in the present invention on the surface of the base film. In this case, mention may be made of inorganic bases and organic bases which are substantially non-volatile. Examples of the substantially non-volatile inorganic base and organic base include a case where the decrease of the non-volatile base after the treatment is 80% or less.

  As the non-volatile base, those which are soluble in water or can be emulsified by dispersing in water are preferable. As a result, when an uncured urethane resin is prepared as a water-based resin, it becomes possible to improve the applicability of the water-based resin and easily manufacture the urethane resin layer.

Examples of the non-volatile base include inorganic bases such as sodium hydroxide and potassium hydroxide;
2-amino-2-methyl-1-propanol (AMP), monoethanolamine, 2-amino-2-methyl-1,3-propanediol (AMPD), 2-amino-2-hydroxymethyl-1,3- Propane potassium hydroxide, γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, N-β (aminoethyl) -γ-aminopropyltrimethoxysilane, N-β (aminoethyl) -γ-aminopropyltrimethyl Dimethoxysilane, 3-ureidopropyltrimethoxysilane, 3-aminopropyl-tris (2-methoxy-ethoxy-ethoxy) silane, cyclohexylamine, hexamethylenediamine, ethylenediamine, diethylenetriamine, tetraethylenepentamine, pentaethylenepentamine, Amino Eth Ethanolamine, 1,2-propanediamine, isophoronediamine, 4,4'-dicyclohexylmethanediamine, 3,3'-dimethyl-dicyclohexylmethanediamine, 1,2-cyclohexanediamine, 1,4-cyclohexanediamine, aminoethylethanol Amine, aminopropylethanolamine, aminohexylethanolamine, aminoethylpropanolamine, aminopropylpropanolamine, aminohexylpropanolamine, 5-aminopyrazole, 1-methyl-5-aminopyrazole, 1-isopropyl-5-aminopyrazole, 1-benzyl-5-aminopyrazole, 1,3-dimethyl-5-aminopyrazole, 1-isopropyl-3-methyl-5-aminopyrazole, 1-benzyl-3-methyl-5 -Aminopyrazole, 1-methyl-4-chloro-5-aminopyrazole, 1-methyl-4-asino-5-aminopyrazole, 1-isopropyl-4-chloro-5-aminopyrazole, 3-methyl-4-chloro Primary amines such as -5-aminopyrazole, 1-benzyl-4-chloro-5-aminopyrazole;

Secondary amines such as diethanolamine, morpholine, piperazine, 2-methylpiperazine, 2,5-dimethylpiperazine, N-phenyl-γ-aminopropyltrimethoxysilane;
N-methyl-3-aminopropyltrimethoxycarboxylic acid dihydrazide, carbodihydrazide, oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, adipic acid dihydrazide, sebacic acid dihydrazide, dodecanedioic acid dihydrazide, isophthalic acid dihydrazide, terephthalic acid dihydrazide Hydrazide compounds such as glycolic acid dihydrazide and polyacrylic acid dihydrazide;
Triethanolamine, triisopropanolamine, tri [(2-hydroxy) -1-propyl] amine, N, N-diethylmethanolamine, N, N-dimethylethanolamine, N, N, N ′, N′-tetramethyl Three such as ethylenediamine, N, N-dimethylbenzylamine, diethylaminopropylamine, N- (2-aminoethyl) piperazine, 2,4,6-tris (dimethylaminomethyl) phenol, N, N-bis (trimethylsilyl) urea Secondary amines;

Imidazole, 2-methylimidazole, 1- (2-aminoethyl) -2-methylimidazole, 1- (2-aminoethyl) -2-ethylimidazole, 2-aminoimidazole sulfate, 2- (2-aminoethyl)- Imidazole compounds such as benzimidazole;
Imidazoline compounds such as imidazoline and 2-methyl-2-imidazoline; and the like.

Among them, a compound having a hydrazino group (—NHNH ₂ group) such as a hydrazide compound has high reactivity, and therefore can appropriately improve the mechanical strength of the urethane resin layer, and has a relatively high boiling point. Since the heat resistance of a layer can be made high, it is especially preferable. Moreover, a non-volatile base may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

[3-4. solvent〕
The uncured urethane resin is usually a fluid resin containing a solvent. Specifically, it is a liquid composition in which polyurethane, an epoxy compound, a non-volatile base, and other components used as necessary are dissolved or dispersed in a solvent. At this time, water or a water-soluble solvent is used as the solvent.

  Examples of the water-soluble solvent include methanol, ethanol, isopropyl alcohol, acetone, tetrahydrofuran, N-methylpyrrolidone, dimethyl sulfoxide, ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, and the like. Among these, water is preferably used as the solvent. In addition, a solvent may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.

  The amount of the solvent is preferably set so that the viscosity of the uncured urethane resin is in a range suitable for coating.

[3-5. Other ingredients
The uncured urethane resin may contain components other than those described above as long as the effects of the present invention are not significantly impaired.

  For example, the uncured urethane resin preferably further contains fine particles. Thereby, a urethane resin layer will also contain microparticles | fine-particles and an unevenness | corrugation can be formed in the surface of a urethane resin layer. As a result, the area where the urethane resin layer comes into contact with other layers during winding is reduced, and the sliding property of the surface of the urethane resin layer is improved by that much, and when the multilayer film of the present invention is wound. The generation of wrinkles 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 making the average particle diameter equal to or greater than the lower limit value of the range, the slipperiness of the urethane resin layer can be effectively increased, and by making the average particle diameter equal to or less than the upper limit value of the range, haze can be suppressed low. 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, silica is preferable. This is because the fine particles of silica are excellent in the ability to suppress the generation of wrinkles and transparency, hardly cause haze, and are not colored, and thus have less influence on the optical properties of the multilayer film of the present invention. Further, silica is good in dispersibility and dispersion stability in urethane resin. 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.

  The amount of fine particles contained in the urethane resin layer is usually 0.5 parts by weight or more, preferably 5 parts by weight or more, more preferably 8 parts by weight or more, based on 100 parts by weight of polyurethane contained in the urethane resin layer. It is 20 parts by weight or less, preferably 18 parts by weight or less, more preferably 15 parts by weight or less. By setting the amount of fine particles to be equal to or more than the lower limit of the above range, generation of wrinkles can be suppressed when the multilayer film of the present invention is wound. Moreover, the external appearance without the cloudiness of the multilayer film of this invention is maintainable by making the quantity of microparticles | fine-particles into the upper limit of the said range.

  Furthermore, the uncured urethane resin may contain a crosslinking agent. In particular, when the thickness of the urethane resin layer is 1 μm or less, it is preferable to include a crosslinking agent from the viewpoint of improving the mechanical strength of the urethane resin layer. As the crosslinking agent, any compound having a functional group that reacts with a reactive group of a polymer present in the resin can be used without particular limitation. Among these, those that are soluble in water or that can be emulsified by dispersing in water are preferred. Examples of the crosslinking agent include water-based isocyanate compounds, water-based carbodiimide compounds, water-based oxazoline compounds, and the like.

As the aqueous isocyanate compound, a compound having two or more non-blocked isocyanate groups or blocked isocyanate groups is usually used.
Examples of the non-blocking isocyanate compound include compounds obtained by reacting a polyfunctional isocyanate compound with a monovalent or polyvalent nonionic polyalkylene ether alcohol.

  Examples of the block type isocyanate compound include 2,4-tolylene diisocyanate (2,4-TDI), 2,6-tolylene diisocyanate (2,6-TDI), 4,4′-diphenylmethane diisocyanate (MDI), Xylylene diisocyanate (XDI), isophorone diisocyanate (IPDI), methylcyclohexyl diisocyanate (H6TDI), 4,4′-dicyclohexylmethane diisocyanate (H12MDI), 1,3-bis (isocyanatomethyl) cyclohexane (H6XDI), tetramethylxylylene Range isocyanate (TMXDI), 2,2,4-trimethylhexamethylene diisocyanate (TMHDI), hexamethylene diisocyanate (HDI), norbornene diisocyanate (NBD) ), 2,4,6-triisopropylphenyl diisocyanate (TIDI), 1,12-diisocyanatododecane (DDI), 2,4, -bis- (8-isocyanatooctyl) -1,3-dioctylcyclobutane (OCDI), n-Pentane-1,4-diisocyanate and their isocyanurate-modified products, adduct-modified products, burette-modified products, allophanate-modified products, and polymers having one or more isocyanate groups are polyoxyalkylenes Examples thereof include compounds obtained by modification with a group, a carboxyl group or the like, making it water-soluble and / or water-dispersible, and masking an isocyanate group with a blocking agent (such as phenol or ε-caprolactam).

  As the aqueous carbodiimide compound, a compound having two or more carbodiimide bonds (—N═C═N—) is usually used. A compound having two or more carbodiimide bonds can be obtained, for example, by a method of forming a carbodiimide bond by decarboxylation of two isocyanate groups using two or more molecules of polyisocyanate and a carbodiimidization catalyst. . The polyisocyanate and the carbodiimidization catalyst used when producing a compound having two or more carbodiimide bonds are not particularly limited, and conventionally known ones can be used.

  A crosslinking agent may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  The amount of the crosslinking agent is usually 1 part by weight or more, preferably 5 parts by weight or more, and usually 70 parts by weight or less, preferably 65 parts by weight or less in terms of solid content with respect to 100 parts by weight of polyurethane. By blending in this way, it is possible to achieve both the mechanical strength of the urethane resin layer and the stability of the uncured urethane resin.

  Furthermore, in the uncured urethane resin, unless the effects of the present invention are significantly impaired, for example, heat resistance stabilizer, weather resistance stabilizer, leveling agent, antistatic agent, slip agent, antiblocking agent, antifogging agent, lubricant , Dyes, pigments, natural oils, synthetic oils, waxes, crosslinking agents and the like may be included. In addition, these may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.

[3-6. Method for producing urethane resin layer]
The urethane resin layer is usually produced by forming the uncured urethane resin layer on the surface of the base film, and then curing the urethane resin. The uncured urethane resin is a composition in which the above components are dissolved or dispersed, and may be in the form of, for example, an emulsion, a colloidal dispersion system, or an aqueous solution.

  In an uncured urethane resin, components such as polyurethane are 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 a dynamic light scattering method, for example, a light scattering photometer DLS-8000 series manufactured by Otsuka Electronics Co., Ltd.

  The viscosity of the uncured urethane resin is preferably 15 mPa · s or less, and particularly preferably 10 mPa · s or less. When the viscosity of the uncured urethane resin is within the above range, the uncured urethane resin can be uniformly applied to the surface of the base film. The viscosity is a value measured under a condition of 25 ° C. with a tuning fork type vibration viscometer. The viscosity of the uncured urethane resin can be adjusted by, for example, the ratio of the solvent contained in the uncured urethane resin and the particle size of the particles contained in the resin.

  Usually, when a layer of an uncured urethane resin is formed on the surface of a base film, the resin is applied by a coating method to form a coating film. A coating method is not particularly limited, and a known coating method may be employed. 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.

After the uncured urethane resin layer is formed on the base film, the resin forming the layer is cured to obtain the urethane resin layer according to the present invention.
Usually, since the uncured urethane resin contains a solvent, the solvent is removed by drying when it is cured. 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 harden resin by heat drying from a viewpoint of making reaction, such as a crosslinking reaction, advance rapidly in resin.

  When the resin is cured by heating, the heating temperature is appropriately set within a range in which the solvent can be dried to cure the uncured urethane resin. However, when a stretched film is used as the base film and it is not desired to change the retardation developed in the base film, the heating temperature may be set to a temperature at which no orientation relaxation occurs in the base film. preferable. Specifically, when the glass transition temperature of the material forming the base film is Tg, it is preferably (Tg-30) ° C or higher, more preferably (Tg-10) ° C or higher, preferably (Tg + 60). ) ° C. or lower, more preferably (Tg + 50) ° C. or lower.

  Furthermore, after an uncured urethane resin layer is formed on the surface of the substrate film, a stretching treatment may be performed. The stretching treatment may be performed after the uncured urethane resin is cured, but from the viewpoint of preventing the removal of fine particles from the urethane resin layer, or before curing the uncured urethane resin. It is preferable to perform a stretching process at the same time. Furthermore, from the viewpoint of forming a uniform urethane resin layer, it is more preferable to perform a stretching process simultaneously with curing the uncured urethane resin.

  Furthermore, after an uncured urethane resin layer is formed on the surface of the substrate film, a stretching treatment may be performed. The stretching treatment may be performed after the uncured urethane resin is cured, but from the viewpoint of preventing the removal of fine particles from the urethane resin layer, or before curing the uncured urethane resin. It is preferable to perform a stretching process at the same time. Furthermore, from the viewpoint of forming a uniform urethane resin layer, it is more preferable to perform a stretching process simultaneously with curing the uncured urethane resin.

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

  Moreover, before providing a urethane resin layer, the modification | reformation process may be given to the surface of a base film, and the adhesiveness of a base film and a urethane resin layer may be improved. Examples of the surface modification treatment for the base film 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, etc., and from the viewpoint of treatment efficiency, corona discharge treatment and plasma treatment are preferred, and corona discharge treatment is particularly preferred. preferable. Examples of the chemical treatment include a saponification treatment, a method of immersing in an aqueous oxidizing agent solution such as potassium dichromate solution and concentrated sulfuric acid, and then washing with water.

  Further, the surface of the urethane resin layer is preferably subjected to a hydrophilic surface treatment. Since the surface of the urethane resin layer is usually a bonding surface when the multilayer film of the present invention is bonded to another member, by further improving the hydrophilicity of this surface, the multilayer film of the present invention Adhesiveness with other members can be significantly improved.

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

  In the hydrophilization surface treatment, the average water contact angle of the surface of the urethane resin layer is preferably 70 ° or less, more preferably 60 ° or less, particularly preferably 50 ° or less, and usually 20 ° or more. The standard deviation of the water contact angle is preferably 0.01 ° to 5 °. By subjecting the surface of the urethane resin layer to such a water contact angle, the multilayer film of the present invention can be firmly bonded 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 determined by, for example, measuring 20 water contact angles randomly selected within the range of 100 cm ^{2 on} the surface of the urethane resin layer that has been subjected to a hydrophilic surface treatment, and calculating an average of the measured values. Calculated. The standard deviation of the water contact angle is calculated from this measured value. By performing the hydrophilization treatment, functional groups such as 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 urethane resin layer.

[3-7. Urethane resin layer structure and properties, etc.)
The thickness of the urethane resin layer is preferably 0.005 μm or more, more preferably 0.01 μm or more, particularly preferably 0.02 μm or more, preferably 5 μm or less, more preferably 2 μm or less, and particularly preferably 1 μm or less. Within the above range, sufficient adhesive strength between the base film and the urethane resin layer can be obtained, and defects such as warpage of the multilayer film of the present invention can be eliminated.

The ratio t2 / _{t 1} with thickness _{t 2} of the thickness _{t 1} and the urethane resin layer of the base film is preferably 0.0003 or more, more preferably more than 0.0010, particularly preferably 0.0025 or more, 0 0.0100 or less is preferable, 0.0080 or less is more preferable, and 0.0050 or less is particularly preferable. Thereby, the transparency of the multilayer film of the present invention can be improved. In addition, when the multilayer film of the present invention includes only _one base film, the thickness of the base film becomes the thickness t1, and when the multilayer film of the present invention includes two or more base film, these The total thickness of the base film is the thickness t ₁ . Further, the urethane resin layer thickness The thickness t ₂ next if multilayer film comprises only one layer of the urethane resin layer of the present invention, when the multilayer film of the present invention comprises a urethane resin layer two or more layers thereof the total thickness of the urethane resin layer a thickness t ₂ of the.

  The interface refractive index difference between the base film and the urethane resin layer is preferably 0.05 or less. When the interface refractive index difference is within the above range, it is possible to suppress light loss when light is transmitted through the multilayer film of the present invention.

[4. Other layers]
The multilayer film of the present invention may include other layers on the surface of the base film on the side where the urethane resin layer is not formed unless departing from the gist of the present invention. Examples thereof include an antireflection layer, a hard coat layer, an antistatic layer, an antiglare layer, an antifouling layer, a separator film and the like.

[5. Physical properties of multilayer film]
In the multilayer film of the present invention, the total light transmittance in terms of 1 mm thickness is preferably 80% or more and more preferably 90% or more from the viewpoint of stably exhibiting the function as an optical member. preferable. The light transmittance can be measured using a spectrophotometer (manufactured by JASCO Corporation, ultraviolet-visible near-infrared spectrophotometer “V-570”) in accordance with JIS K0115.

  The multilayer film of the present invention has a haze in terms of 1 mm thickness of preferably 5% or less, more preferably 3% or less, and particularly preferably 1% or less. By setting the haze to a low value, the sharpness of the display image of the display device incorporating the multilayer film according to the present invention can be enhanced. Here, haze is an average value obtained by measuring five points using a turbidimeter “NDH-300A” manufactured by Nippon Denshoku Industries Co., Ltd. in accordance with JIS K7361-1997.

The multilayer film of the present invention may be a retardation film having a retardation in the plane or in the thickness direction. The specific retardation range is set according to the use of the multilayer film of the present invention. When a specific range is given, it is usually selected appropriately from the range of 10 nm to 500 nm in the in-plane retardation Re and the range of −500 nm to 500 nm in the thickness direction retardation Rth.
The in-plane retardation Re is defined as the refractive index nx in the slow axis direction of the film, the refractive index ny in the direction perpendicular to the slow axis in the plane, the refractive index nz in the thickness direction, and the average thickness D of the film. Sometimes, it is a value defined by (nx−ny) × D. The thickness direction retardation Rth is a value defined by ((nx + ny) / 2−nz) × D.

  In the multilayer film of the present invention, the variation in the in-plane retardation Re is usually within 10 nm, preferably within 5 nm, and more preferably within 2 nm. By setting the variation of the in-plane retardation Re within the above range, it is possible to improve the display quality when the multilayer film of the present invention is used as a retardation film for a liquid crystal display device. Here, the variation in the in-plane retardation Re is obtained when the in-plane retardation Re at the light incident angle of 0 ° (in which the incident light beam and the surface of the base film are orthogonal) is measured in the width direction of the film. Is the difference between the maximum value and the minimum value of the in-plane phase difference Re.

  The content of the residual volatile component in the multilayer film of the present invention is preferably 0.1% by weight or less, more preferably 0.05% by weight or less, and further 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 and the thickness direction retardation Rth of the multilayer film of the present invention can be reduced.

  The multilayer film of this invention is good also considering the dimension of the TD direction (it is also called a horizontal direction. Usually, it corresponds to the width direction) as 1000 mm-2000 mm. Moreover, although the multilayer film of this invention does not have a restriction | limiting in the dimension of the MD direction (it is also called the vertical direction. Usually, it corresponds to a longitudinal direction), It is preferable that it is a long film. Here, the “long” film means a film having a length of at least 5 times the width of the film, preferably a length of 10 times or more, specifically a roll. It has a length enough to be wound up into a shape and stored or transported.

[6. Polarizer]
The multilayer film of this invention can be used for arbitrary uses as an optical film. Since the multilayer film of the present invention has the advantage that it is excellent in adhesiveness with other members and the adhesiveness is not easily lowered even under high temperature and high humidity, from the viewpoint of effectively utilizing this advantage, It is preferable to apply to the use used by bonding to a member. If the example of a specific use is given, it is preferable to use the multilayer film of this invention as a polarizing plate protective film.

  The polarizing plate usually includes a polarizer and a polarizing plate protective film. Accordingly, when the multilayer film of the present invention is used as a polarizing plate protective film, the multilayer film of the present invention is usually bonded to a polarizer.

  A polarizing plate can be manufactured by bonding together the urethane resin layer and polarizer of the multilayer film of this invention, for example. At the time of bonding, the polarizer may be directly bonded to the urethane resin layer without using the adhesive layer, or may be bonded through the adhesive layer. Furthermore, the multilayer film of the present invention may be bonded to only one surface of the polarizer, or may be bonded to both surfaces. When the multilayer film of the present invention is bonded to only one surface of the polarizer, another highly transparent film may be bonded to the other surface of the polarizer.

  The polarizer may be produced, for example, by adsorbing iodine or a dichroic dye on a polyvinyl alcohol film and then uniaxially stretching in a boric acid bath. Alternatively, for example, iodine or a dichroic dye may be adsorbed and stretched on a polyvinyl alcohol film, and a part of the polyvinyl alcohol unit in the molecular chain may be modified to a polyvinylene unit. Furthermore, a polarizer having a function of separating polarized light into reflected light and transmitted light, such as a grid polarizer, a multilayer polarizer, and a cholesteric liquid crystal polarizer, may be used as the polarizer. Among these, a polarizer comprising polyvinyl alcohol is preferable. The polarization degree of the polarizer is preferably 98% or more, more preferably 99% or more. The thickness (average thickness) of the polarizer is preferably 5 μm to 80 μm.

  The adhesive for adhering the polarizer and the multilayer film of the present invention is not particularly limited as long as it is optically transparent. For example, an aqueous adhesive, a solvent-type adhesive, a two-component curable adhesive, Examples thereof include an ultraviolet curable adhesive and a pressure sensitive adhesive. Among these, a water-based adhesive is preferable, and a polyvinyl alcohol-based water-based adhesive is particularly preferable. In addition, an adhesive agent may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  The average thickness of the adhesive layer is preferably 0.05 μm or more, more preferably 0.1 μm or more, preferably 5 μm or less, more preferably 1 μm or less.

  Although there is no restriction | limiting in the method of bonding the multilayer film of this invention, and a polarizer, For example, after apply | coating an adhesive agent as needed to one surface of a polarizer, a polarizer and this invention are used using a roll laminator. The method of laminating | stacking with a multilayer film and drying as needed is preferable. The drying time and drying temperature are appropriately selected according to the type of adhesive.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the examples shown below, and may be arbitrarily changed without departing from the gist of the present invention and its equivalent scope. May be implemented. In the following description, “parts” and “%” indicating amounts are based on weight unless otherwise specified. In addition, the operations described below were performed under normal temperature and normal pressure conditions unless otherwise specified.

[Production Example 1: Production of base film]
Pellets of alicyclic structure-containing polymer resin (ZEONOR 1430, manufactured by Nippon Zeon Co., Ltd .; glass transition temperature 135 ° C.) were dried at 70 ° C. for 2 hours using a hot air dryer in which air was circulated. Then, using a T-die type film melt extrusion molding machine having a resin melt kneader equipped with a 65 mm diameter screw, under a molding condition of a molten resin temperature of 270 ° C. and a T die width of 500 mm, a thickness of 100 μm and a length of 1000 m A base film was produced. This base film is a base film made of an alicyclic structure-containing polymer resin.

[Production Example 2: Production of Polarizer]
A polyvinyl alcohol film having a thickness of 80 μm was dyed in a 0.3% iodine aqueous solution. Thereafter, the film was stretched 5 times in 4% boric acid aqueous solution and 2% potassium iodide aqueous solution, and then dried at 50 ° C. for 4 minutes to produce a polarizer.

[Production Example 3: Preparation of adhesive liquid]
Water was added to goosephimer Z410 (manufactured by Nippon Synthetic Chemical Industry, polyvinyl alcohol containing an acetoacetyl group) to dilute to a solid content of 3% to produce an adhesive solution.

[Example 1]
[Preparation of aqueous dispersion of urethane resin]
Ester polyurethane water dispersion Sancure 815 (manufactured by Lubrizol, solid content 35%), ester ether polyurethane water dispersion Adekabon titer HUX-522 (manufactured by ADEKA, solid content 30%), aqueous epoxy resin Denacol EX -313 (manufactured by Nagase ChemteX), isophthalic acid dihydrazide, silica fine particle water dispersion Snowtex ZL (manufactured by Nissan Chemical Industries, Ltd., solid content 40%) and water were blended so as to have the ratio shown in Table 1. A water dispersion (solid content 5%) of an uncured urethane resin was obtained. In addition, the ratio of the compounding amount in Table 1 is all based on the solid content.

[Manufacture of multilayer films]
Using a corona treatment device (Kasuga Denki Co., Ltd.), the surface of the base film obtained in Production Example 1 was subjected to discharge treatment under the conditions of an output of 300 W, an electrode length of 240 mm, a work electrode distance of 3.0 mm, and a conveying speed of 4 m / min. Was given.

  The above-mentioned aqueous dispersion of urethane resin is applied to the surface of the base film subjected to the discharge treatment using a roll coater so that the dry film thickness becomes 0.1 μm, and dried at 120 ° C. for 3 minutes. The urethane resin was cured to obtain a multilayer film 1.

[Examples 2 and 3]
Multilayer films 2 and 3 were obtained in the same manner as in Example 1 except that the polyurethane was blended so as to have the ratio shown in Table 1.

[Example 4]
Superflex 210 (Daiichi Kogyo Seiyaku Co., Ltd., solid content 35%) is used as an aqueous dispersion of ester polyurethane instead of Sancure 815, and Adekabon titer HUX-522 is used as an aqueous dispersion of ester / ether polyurethane. Instead of Superflex 150HS (Daiichi Kogyo Seiyaku Co., Ltd., solid content 30%), instead of Denacol EX-313, which is an aqueous epoxy resin, carbodilite SV-02 (Nisshinbo Co., Ltd., solid product), which is an aqueous carbodiimide compound, is used. A multilayer film 4 was obtained in the same manner as in Example 1 except that the mixing ratio was set to the ratio shown in Table 1.

[Example 5]
Instead of Adekabon titer HUX-522, which is an aqueous dispersion of ester / ether polyurethane, Sancure 878 (manufactured by Lubrizol, solid content 38%), which is an aqueous dispersion of ether polyurethane, is used. A multilayer film 5 was obtained in the same manner as in Example 1 except that the ratios shown in Table 1 were used.

[Comparative Example 1]
A multilayer film 6 was obtained in the same manner as in Example 1 except that polyurethane was blended so as to have the ratio shown in Table 2.

[Comparative Example 2]
A multilayer film 7 was obtained in the same manner as in Example 1 except that the ester / ether polyurethane was not used and the blending ratio of each component was changed to the ratio shown in Table 2.

[Comparative Example 3]
A multilayer film 8 was obtained in the same manner as in Example 1 except that ester-based polyurethane was not used and the blending ratio of each component was changed to the ratio shown in Table 2.

[Evaluation of adhesive strength]
[Measurement of peel strength of initial polarizing plate]
Triacetyl cellulose in which the surface of the multilayer film manufactured in the example or the comparative example or the urethane resin layer of the multilayer film was applied to one side of the polarizer manufactured in Production Example 2 and the surface was saponified on the other side. A protective film having a thickness of 80 μm was bonded to each other with a roll laminator using the adhesive prepared in Production Example 3 to produce a polarizing plate. The obtained polarizing plate was cut into a width of 10 mm, the polarizer and the film were pulled in the 90 ° direction, and the tensile force (90 ° peel strength) when peeling off was measured. The measurement was performed with a length of 20 mm, and the average value (average peel strength) at that time was determined. In addition, as a measuring machine, a universal tensile compression testing machine (TCM-500CR: manufactured by Shinsei Tsushin Kogyo Co., Ltd.) was used, and the test was carried out at a tensile speed of 20 mm / min. The results are shown in Tables 1 and 2.

[Measurement of peel strength of polarizing plate after wet heat test]
The polarizing plate produced as described above was left for 1,000 hours in a constant temperature and humidity chamber at 60 ° C. and 90% RH. Thereafter, the obtained polarizing plate was cut into a width of 10 mm, and the average peel strength was determined in the same manner as in [Measurement of peel strength of initial polarizing plate]. The results are shown in Tables 1 and 2.

[Consideration]
By comparing the peel strength of the initial polarizing plates of the above-mentioned Examples and Comparative Examples, a urethane resin layer using a polyurethane containing an ether-based polyurethane or an ester-ether-based polyurethane in a proportion of 30 wt% to 80 wt% is used. According to the present invention in which is formed, in a multilayer film including a base film made of a resin containing an alicyclic structure-containing polymer, it can be seen that high adhesive force can be realized after the initial stage and after the heat and humidity resistance test.

  In other words, in Examples 1 to 5, it has a high peel strength of 0.4 N / cm or more even after being left for 1,000 hours under high temperature and high humidity, whereas it is ether polyurethane or ester / ether polyurethane. In Comparative Examples 1 and 2 in which the use ratio is small, the adhesive strength was lost after the heat and humidity resistance test, and the multilayer film spontaneously peeled from the polarizer. On the other hand, in Comparative Example 3 in which the use ratio of the ester / ether polyurethane was too large, the initial peel strength was insufficient.

Claims (8)

A base film having a layer made of a resin containing an alicyclic structure-containing polymer on the surface, and a urethane resin layer obtained by curing a resin containing polyurethane,
The polyurethane is
A multilayer film comprising ether polyurethane or ester / ether polyurethane in a proportion of 30 wt% to 80 wt%. The polyurethane is
The multilayer film according to claim 1, further comprising an ester-based polyurethane.   The multilayer film according to claim 1 or 2, wherein the resin containing polyurethane further contains fine particles. A method for producing a multilayer film comprising applying a resin containing polyurethane on the surface of a base film having a layer comprising a resin containing an alicyclic structure-containing polymer on the surface, and curing the resin.
The polyurethane is
A method for producing a multilayer film, comprising ether polyurethane or ester / ether polyurethane in a proportion of 30% by weight to 80% by weight. The polyurethane is
The manufacturing method of Claim 4 which further contains ester polyurethane.   The manufacturing method of Claim 4 or 5 with which the resin containing the said polyurethane further contains microparticles | fine-particles.   The polarizing plate protective film provided with the multilayer film as described in any one of Claims 1-3.   A polarizing plate comprising a polarizer and the polarizing plate protective film according to claim 7.