WO2017002904A1

WO2017002904A1 - Multilayer optical film and polarizing plate

Info

Publication number: WO2017002904A1
Application number: PCT/JP2016/069415
Authority: WO
Inventors: 亜希子織茂; 谷口　浩一郎; 潤西岡; 陽宮下; 勝司池田
Original assignee: 三菱樹脂株式会社
Priority date: 2015-06-30
Filing date: 2016-06-30
Publication date: 2017-01-05

Abstract

For the purpose of providing a film which has small optical anisotropy, high mechanical strength and excellent productivity and is suitable for use as a protective film for a polarizing film, the present invention proposes a multilayer optical film that comprises one or more layers mainly composed of a specific polycarbonate resin and one or more layers mainly composed of a resin which has a negative intrinsic birefringence. The present invention also proposes a polarizing plate which is obtained by bonding a polarizing film to this film.

Description

Laminated optical film and polarizing plate

The present invention relates to a laminated optical film, and more particularly to a laminated optical 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.

The protective film for this polarizing plate is required to have small optical anisotropy, high transparency, excellent moisture resistance, heat resistance, mechanical strength, and low adhesion of foreign matter. As the protective film, a triacetyl cellulose film (hereinafter sometimes abbreviated as a TAC film) produced by a solution casting method is often used because it has high transparency and optical isotropy.
However, the TAC film produced by the solution casting method has small optical anisotropy, but is inferior in productivity, the solvent remaining in the film volatilizes, and adversely affects the electronic circuit and other parts in the liquid crystal display device. There was a problem such as giving. In addition, 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, affecting the image quality of the liquid crystal display device using this polarizing plate. It was.

Therefore, as a polarizing plate protective film, instead of a film by a solution casting method, a film by a melt extrusion method of a thermoplastic resin such as an acrylic resin, a cyclic olefin resin, a styrene resin, or a polycarbonate resin has been studied. . For example, in patent document 1, the optical film which can be used for a polarizing plate protective film etc. is manufactured using acrylic resin as a thermoplastic resin.

By the way, the polarizing plate is bonded to the liquid crystal cell through an adhesive layer or the like, but if a defect is confirmed after bonding, the polarizing plate may be peeled off from the liquid crystal cell. At this time, if the polarizing plate protective film is easily torn, the peeling operation becomes difficult, and thus the polarizing film protective film is required to have high tear strength. However, the acrylic film, cyclic olefin film, and styrene film described above are excellent in optical properties and heat-and-moisture resistance, but the film does not have sufficient mechanical strength, and in order to satisfy the required mechanical strength, the film The polarizing plate using these films as a protective film has a problem that it is difficult to reduce the thickness.

On the other hand, since a protective film using a polycarbonate-based resin that is generally excellent in impact resistance is excellent in mechanical strength and has high tear strength, it can be easily thinned.
However, since polycarbonate resins generally have high intrinsic birefringence, films using polycarbonate resins tend to have large optical anisotropy, making it difficult to produce a polarizing plate protective film with small optical anisotropy. Met. Moreover, since the film using a polycarbonate-type resin has a large photoelastic coefficient, there existed a problem that a phase difference was easy to change with external stress and it was difficult to handle it.

Here, Patent Document 2 discloses laminating a film having a positive intrinsic birefringence and a negative film as a technique for controlling the optical anisotropy.

JP 2014-98133 A JP 2008-268913 A

In the method of Patent Document 2, optical anisotropy can be controlled by laminating an acrylic resin or a styrene resin having a negative intrinsic birefringence on a polycarbonate resin having a positive intrinsic birefringence. However, in order to produce a laminated film with small optical anisotropy, the optical anisotropy of the layer having negative intrinsic birefringence is also increased in order to offset the large optical anisotropy of the polycarbonate resin layer. There was a need. Therefore, in order to produce a laminated film with small optical anisotropy, for example, a film made of polycarbonate resin and a film having negative intrinsic birefringence are individually produced, and the film having negative intrinsic birefringence is produced. However, it is necessary to attach them after imparting high optical anisotropy by stretching or the like. However, this method has a problem that the number of production steps increases and productivity is inferior.

On the other hand, if a co-extrusion method in which a polycarbonate resin and a resin having negative intrinsic birefringence are simultaneously melted and laminated is used, it is possible to produce a laminated film with high productivity. In order to produce a laminated film with low properties, it is necessary to relatively increase the thickness of the resin layer having negative intrinsic birefringence in order to offset the large anisotropy of the polycarbonate resin layer. However, acrylic resins and styrene resins having negative intrinsic birefringence are generally brittle and inferior in mechanical strength, resulting in a problem that the mechanical strength of the laminated film is lowered.

Therefore, an optical film having small optical anisotropy, high mechanical strength, and excellent productivity has been demanded.

An object of the present invention is to provide an optical film having small optical anisotropy, high mechanical strength, and excellent productivity in view of the above-described problems of the prior art, and produced using the optical film. The object is to provide a polarizing plate or a liquid crystal display device.

In order to solve such problems, the present invention is a laminated optical film having one or more layers each having a polycarbonate resin as a main component and an acrylic resin as a main component,
The polycarbonate resin is a polycarbonate resin containing a structural unit derived from a dihydroxy compound represented by the following formula (1):
A laminated optical film is proposed in which the total thickness of the laminated optical film is 50 μm or less and the tear strength measured in accordance with JIS K7128-2 is 4.0 kg / cm or more.

It is preferable that the polycarbonate resin further contains a structural unit derived from tricyclodecane dimethanol represented by the following formula (2).

The laminated optical film proposed by the present invention has at least three layers of an intermediate layer and a front and back layer, the intermediate layer is a layer mainly composed of the polycarbonate resin, and the front and back layer is the acrylic resin. It can be set as the layer which has as a main component.
In addition, the laminated optical film proposed by the present invention has at least three layers of an intermediate layer and a front and back layer, the intermediate layer is a layer containing the acrylic resin as a main component, and the front and back layer is the polycarbonate. A layer containing a resin as a main component can also be used.

The laminated optical film proposed by the present invention preferably has a total thickness of 20 μm or less, and a tear strength measured according to JIS K7128-2 of 5.0 kg / cm or more.

The ratio of the total thickness of the layer mainly composed of the polycarbonate resin to the total thickness of the laminated optical film proposed by the present invention is preferably 20% or more and 95% or less, and more than 50% and more than 80%. It is preferable that:

In the laminated optical film proposed by the present invention, the layer containing the acrylic resin as a main component preferably contains a flexibility modifier.
As a preferable example of the flexibility modifier, at least one monomer unit derived from a methacrylic acid ester and an acrylic acid ester and a hard segment (HS) having a glass transition temperature of 100 ° C. or higher, and at least a methacrylic acid ester And an acrylic block copolymer having a soft segment (SS) containing one kind of monomer units derived from an acrylate ester and having a glass transition temperature of 20 ° C. or lower.

It can be set as the laminated optical film provided with the coat layer which consists of a water-system urethane type resin composition containing a urethane type resin and a melamine resin type crosslinking agent on the at least single side | surface of the said laminated optical film which this invention proposes.
In this case, examples of the melamine resin-based crosslinking agent include those containing an imino group type and / or a methylol group type melamine resin.

Furthermore, the present invention proposes a polarizing plate having a structure in which a polarizing film is bonded to the coat layer of the laminated optical film via an adhesive layer.
At this time, examples of the adhesive layer include an aqueous adhesive.
Furthermore, the present invention proposes a liquid crystal display device having the polarizing plate.

According to the laminated optical film of the present invention, an optical film having small optical anisotropy, high mechanical strength, and excellent productivity can be provided, and its industrial value is high.

It is the figure which showed the sample film at the time of heat resistance evaluation.

Hereinafter, an example of an embodiment of the present invention will be described in detail.

[This laminated optical film 1]
The laminated optical film according to an example of the embodiment of the present invention includes a layer mainly composed of a polycarbonate resin (hereinafter sometimes referred to as “A layer”) and a resin whose intrinsic birefringence is negative. A laminated optical film having at least one layer (hereinafter sometimes referred to as “B layer”), wherein the polycarbonate resin contains a structural unit derived from a dihydroxy compound represented by the following formula (1) A laminated optical film (referred to as “the present laminated optical film 1”), which is a polycarbonate resin.

<1-1. Layer mainly composed of polycarbonate resin (A layer)>
At least one layer of the laminated film of the present laminated optical film 1 is a layer mainly composed of a polycarbonate resin (hereinafter sometimes referred to as “polycarbonate resin of the present laminated optical film 1”). Here, the main component means that the component in the film is preferably 50% by mass or more, more preferably 80% by mass or more, and still more preferably 90% by mass or more. Moreover, 1 type may be used for the polycarbonate resin of this laminated optical film 1, and it may use it in combination of 2 or more types.

(1) Polycarbonate resin Polycarbonate resin is excellent in dimensional stability and moisture and heat resistance, and it is possible to enhance mechanical strength and optical characteristics by designing the raw materials. A laminated film can be obtained.

Typical examples of the polycarbonate resin include aromatic polycarbonates having a structural unit of 2,2′-bis (4-hydroxyphenyl) -propane (commonly referred to as bisphenol-A). , 1-bis (4-hydroxyphenyl) -alkylcycloalkane, 1,1-bis (3-substituted-4-hydroxyphenyl) -alkylcycloalkane, 1,1-bis (3,5-substituted-4-hydroxy 1,1-bis (4-hydroxyphenyl) -alkylcycloalkanes such as phenyl) -alkylcycloalkanes; at least one 2 selected from the group consisting of 9,9-bis (4-hydroxyphenyl) fluorenes Homo- or copolymerized polycarbonate containing a monohydric phenol as a monomer component, the above dihydric phenol and bis Mixture of phenol A polycarbonate which a monomer component, such as a copolycarbonate of the above dihydric phenol and the bisphenol A monomers components.

The polycarbonate resin of the present laminated optical film 1 is a dihydroxy compound having a part represented by the following formula (1) in a part of the structure from the viewpoint of high transparency, high strength, high heat resistance and high weather resistance. Polycarbonate resins containing structural units derived from them are preferred.

More specifically, examples of the dihydroxy compound represented by the above formula (1) include isosorbide, isomannide and isoidet which have 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 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 of the present laminated optical film 1 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 is possible to improve the optical properties, processability and impact resistance.

Among 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 further 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 from the viewpoint of low raw material costs and improved heat resistance. In particular, by containing a structural unit derived from tricyclodecane dimethanol represented by the following formula (2), the optical anisotropy is small, and when the laminated optical film described later is used, the optical anisotropy is extremely low. Can be made into a small film.
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. In addition, a film satisfying the high tear strength described later can be obtained, which is preferable. On the other hand, by being below the above 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 film There is a possibility not to impair the sex. Moreover, it is difficult to achieve with a polycarbonate resin or the like 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. Heat resistance and the like can be improved.

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 purpose of the present laminated optical film 1.

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 reduced viscosity, which is an index of the molecular weight of the polycarbonate resin, is measured at a temperature of 20.0 ° C. ± 0.1 ° C., using methylene chloride as a solvent, precisely adjusting the polycarbonate concentration to 0.60 g / dl, and is usually 0. 20 dl / g or more and 1.0 dl / g or less, preferably 0.30 dl / g or more and 0.80 dl / g or less. MFR, which is an index of melt viscosity, is measured at a temperature of 230 ° C. and a load of 37.27 N in accordance with JIS-K7210, and is usually 1.0 g / 10 min to 50 g / 10 min, preferably 3 g / 10 min to 30 g. / 10 min or less, more preferably 5 g / 10 min or more and 20 g / 10 min or less.

If the reduced viscosity of the polycarbonate resin is excessively low or the melt viscosity is excessively low (MFR is excessively high), the mechanical strength at the time of molding tends to decrease. In addition, when the reduced viscosity of the polycarbonate resin is excessively high or the melt viscosity is excessively high (MFR is excessively low), not only the fluidity at the time of molding is lowered and productivity is decreased, but also flow unevenness, etc. There is a tendency to easily cause a poor appearance.

The polycarbonate resin used in the laminated optical film 1 has a positive intrinsic birefringence. Here, the resin having positive intrinsic birefringence refers to a resin having a higher refractive index in the stretched direction when a film made of the resin is stretched.
The intrinsic birefringence is preferably 0.1 or less, more preferably 0.08 or less, and particularly preferably 0.05 or less. The closer the intrinsic birefringence is to zero, the smaller the optical anisotropy of the film, which is preferable. However, since the laminated optical film 1 takes the form of a laminated optical film described later, the intrinsic birefringence of the polycarbonate resin is zero. Even if it is larger, a laminated optical film having a very small optical anisotropy can be produced.
By including the structural formula described above, such optical characteristics can be achieved. The general birefringence of conventional general-purpose polycarbonate resins is about 0.1 to 0.2.
The method for measuring the intrinsic birefringence of the polycarbonate resin is as described in the section of Examples below.

The photoelastic coefficient of the polycarbonate resin used in the laminated optical film 1 is preferably 50 × 10 ⁻¹² Pa ⁻¹ or less, more preferably 20 × 10 ⁻¹² Pa ⁻¹ or less, and 15 × 10 ⁻¹² Pa ⁻¹ or less. Is more preferable. When the photoelastic coefficient is larger than 50 × 10 ⁻¹² Pa ⁻¹ , a change in retardation due to external stress becomes large when a laminated optical film described later is used, which is not suitable as a polarizer protective film.
By including the structural formula described above, such optical characteristics can be achieved. Note that the photoelastic coefficient of conventional polycarbonate resins is about 80 × 10 ⁻¹² Pa ⁻¹ .
The measuring method of the photoelastic coefficient of the polycarbonate resin is as described in the section of Examples described later.

The glass transition temperature of the polycarbonate resin used in the present laminated optical film 1 measured at a heating rate of 10 ° C./min according to JIS K7122 is not particularly limited, but is 100 from the viewpoint of the heat resistance of the laminated film described later. ° C or higher is preferable, 110 ° C or higher is more preferable, and 120 ° C or higher is more preferable.

<1-2. Layer whose main component is a resin having a negative intrinsic birefringence (B layer)>
At least one layer of the laminated optical film 1 is a layer mainly composed of a resin having a negative intrinsic birefringence. Here, the main component means that the component in the film is preferably 50% by mass or more, more preferably 80% by mass or more, and still more preferably 90% by mass or more. Moreover, one type of resin having a negative intrinsic birefringence, which is the main component of the B layer, may be used, or two or more types may be used in combination.

(1) Resin having a negative intrinsic birefringence A resin having a negative intrinsic birefringence means that when a film made of the resin is stretched, the refractive index in the direction perpendicular to the stretched direction increases. . The intrinsic birefringence is not particularly limited as long as it is negative, but is preferably -0.0001 or less, more preferably -0.001 or less. The measuring method of intrinsic birefringence is as described in the section of Examples described later.

The photoelastic coefficient of the resin having negative intrinsic birefringence is preferably 50 × 10 ⁻¹² Pa ⁻¹ or less, more preferably 20 × 10 ⁻¹² Pa ⁻¹ or less, and particularly preferably 15 × 10 ⁻¹² Pa ⁻¹ or less. preferable. When the photoelastic coefficient is larger than 50 × 10 ⁻¹² Pa ⁻¹ , a change in retardation due to stress becomes large when a laminated optical film described later is used, which is not suitable as a polarizer protective film.

Examples of the resin having a negative intrinsic birefringence in the laminated optical film 1 include acrylic resins and styrene resins. Although not particularly limited, it is desirable to use an acrylic resin because the refractive index is close to that of the polycarbonate resin of the present laminated optical film 1, the photoelastic coefficient is small, and the hardness is high.

As the acrylic resin used in the laminated optical film 1, an acrylic resin as a thermoplastic resin is used. The following compounds are mentioned as a monomer used for acrylic resin. For example, methyl methacrylate, methacrylic acid, acrylic acid, benzyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, Lauryl (meth) acrylate, tridecyl (meth) acrylate, stearyl (meth) acrylate, glycidyl (meth) acrylate, hydroxypropyl (meth) acrylate, 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, cyclohexyl (Meth) acrylate, isobornyl (meth) acrylate, norbornyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopent Nyloxyethyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, acrylic (meth) acrylate, 2-hydroxyethyl (meth) acrylate, succinic acid-2- (meth) acryloyloxyethyl, maleic acid-2- ( (Meth) acryloyloxyethyl, phthalic acid-2- (meth) acryloyloxyethyl, hexahydrophthalic acid-2- (meth) acryloyloxyethyl, pentamethylpiperidyl (meth) acrylate, tetramethylpiperidyl (meth) acrylate , Dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate and the like. These may be used by polymerizing alone or in combination of two or more. Further, other monomers that can be polymerized with these acrylic monomers, for example, polyolefin monomers, vinyl monomers, and the like may be used in combination.

The molecular weight of the acrylic resin is not particularly limited, but if the weight average molecular weight is in the range of 30,000 to 300,000, there is no appearance defect such as flow unevenness when molding, A laminate having excellent characteristics and heat resistance can be provided.

The glass transition temperature of the resin having a negative intrinsic birefringence used in the present laminated optical film 1 measured at a heating rate of 10 ° C./min according to JIS K7122 is not particularly limited, but the heat resistance of the laminated film is not limited. From a viewpoint, 80 degreeC or more is preferable, 90 degreeC or more is more preferable, and 100 degreeC or more is further more preferable. The upper limit of the glass transition temperature is not particularly defined, but is usually 140 ° C. Here, if it is less than 120 degreeC, since a general purpose resin can be used, it is preferable from a viewpoint that the selection range of a raw material spreads.
On the other hand, when higher heat resistance is required, the glass transition temperature of the resin having a negative intrinsic birefringence used in the laminated optical film 1 is preferably 120 ° C. or higher.

The MFR, which is an index of melt viscosity, of the resin having a negative intrinsic birefringence used in the laminated optical film 1 is measured at a temperature of 230 ° C. and a load of 37.27 N in accordance with JIS-K7210. It is 1.0 g / 10 min or more and 50 g / 10 min or less, preferably 5 g / 10 min or more and 30 g / 10 min or less, more preferably 8 g / 10 min or more and 20 g / 10 min or less. Here, in the laminated structure described later, when the A layer is the outermost layer, “MFR of the polycarbonate resin that is the main component of the A layer ≧ MFR of the resin having a negative intrinsic birefringence that is the main component of the B layer” In the laminated structure described later, when the B layer is the outermost layer, the “MFR of the polycarbonate resin that is the main component of the A layer ≦ the resin having a negative intrinsic birefringence index that is the main component of the B layer” MFR ”is preferable from the viewpoint of making the film formability and the film thickness distribution of each layer uniform.

In addition, the resin having a negative intrinsic birefringence used in the present laminated optical film 1 may contain a flexibility modifier for improving flexibility and toughness. The flexibility modifier is not particularly defined, and examples thereof include rubber elastic fine particles and soft resins. From the viewpoint of transparency and optical properties, it is preferable to select a soft resin as the flexibility modifier.
The soft resin is not particularly defined, but a polymer block having a glass transition temperature of 100 ° C. or higher (hereinafter referred to as block (i)) and a polymer block having a glass transition temperature of 30 ° C. or lower (hereinafter referred to as block (ii)). ) Is preferable from the viewpoint of achieving both flexibility and heat resistance.

When an acrylic resin is used as a resin having a negative intrinsic birefringence, the main monomer component constituting the block (i) is not particularly limited, but it is necessary to set the glass transition temperature to 100 ° C. or higher. It is preferable to mainly use an ester of acrylic acid or methacrylic acid and an alcohol having 3 or less carbon atoms, such as methyl acid, methyl methacrylate, ethyl acrylate, ethyl methacrylate, isobutyl acrylate, and isopropyl methacrylate. The syndiotacticity of the block (i) is preferably 70% or more from the viewpoint of heat resistance. In addition, the main monomer component constituting the block (ii) of the soft resin is not particularly limited. However, since it is necessary to set the glass transition temperature to 30 ° C. or lower, n-butyl acrylate, n-methacrylic acid n- It is preferable to mainly use an ester of acrylic acid or methacrylic acid and an alcohol having 4 or more carbon atoms, such as butyl, n-hexyl acrylate, or n-hexyl methacrylate.

The main chain of the soft resin is not particularly limited, but preferably contains a block (i) -block (ii) -block (i) structure from the viewpoint of heat resistance. Further, from the viewpoint of achieving both flexibility and heat resistance, the total weight ratio (block (i) / block (ii)) of block (i) and block (ii) contained in the soft resin is 5/95 to 80 It is preferably within the range of / 20, and more preferably within the range of 10/90 to 75/25.

Examples of the soft resin as described above include trade name Clarity manufactured by Kuraray Co., Ltd. and trade name NANOSTRENGTH manufactured by Arkema Co., Ltd.

From the viewpoint of flexibility, the flexibility modifier is preferably contained in an amount of 1% by mass or more, more preferably 5% by mass or more, and more preferably 10% by mass or more based on the entire resin constituting the B layer. More preferably. Moreover, although the upper limit of content is not prescribed | regulated in particular, it is 50 mass% or less normally. In addition, even if it is content of 30 mass% or less, since this laminated optical film 1 takes the laminated structure mentioned later, the softness | flexibility and toughness as a laminated optical film will become favorable.

<1-3. Other ingredients>
The A layer, the B layer, or both layers of the film of the present laminated optical film 1 may contain an ultraviolet absorber. When the ultraviolet absorber is contained, the weather resistance of the film can be improved, and ultraviolet deterioration of the liquid crystal and the polarizing film can be prevented. As an ultraviolet absorber used for this laminated optical film 1, a well-known thing, for example, various commercially available things, can be especially used without a restriction | limiting.

Examples of the ultraviolet absorber include 2- (2′-hydroxy-5′-tert-octylphenyl) benzotriazole, 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, 2,2′- Methylenebis (4-cumyl-6-benzotriazolephenyl) and 2,2'-methylenebis [6- (2H-benzotriazol-2-yl) -4- (1,1,3,3-tetramethylbutyl) phenol] Benzotriazole ultraviolet absorbers such as 2- (4,6-diphenyl-1,3,5-triazin-2-yl) -5- ( Hexyloxy) -triazine UV absorbers such as phenol, benzoxazine UV absorbers such as 2,2′-p-phenylenebis (1,3-benzoxazin-4-one); 2- (4,6- And hydroxyphenyltriazine-based UV absorbers such as diphenyl-1,3,5-triazin-2-yl) -5- (hexyl) oxy-phenol.

For the purpose of further improving and adjusting molding processability and various physical properties, other resins and additives other than resins can be blended with the resin constituting the laminated optical film 1 to obtain a resin composition. . Examples thereof include resins such as polyester resins, polyethers, and polyamides. The blending amount of other resins or additives is 1% by mass or more and 30% by mass with respect to the entire resin constituting each layer of the laminated optical film 1 as long as the effect of the laminated optical film 1 is not impaired. It is preferable to mix | blend in the following ratios, It is more preferable to mix | blend in the ratio of 3 mass% or more and 20 mass% or less, It is further more preferable to mix | blend in the ratio of 5 mass% or more and 10 mass% or less.

[Laminated optical film 2]
The laminated film (referred to as “the present laminated optical film 2”) according to an example of the second embodiment of the present invention is a layer (mainly composed of a resin having a negative intrinsic birefringence index in the present laminated optical film 1). B layer) is a laminated film characterized in that it contains, in particular, an acrylic block copolymer (A) as a flexibility modifier.

When the layer (B layer) containing a resin having a negative intrinsic birefringence as a main component contains the acrylic block copolymer (A), for example, if the B layer is a surface layer, adhesiveness, surface hardness, etc. The surface characteristics can be expressed more.

<2-1. Acrylic block copolymer (A)>
The acrylic block copolymer (A) includes at least one monomer unit derived from a methacrylic acid ester and an acrylic acid ester, a hard segment (HS) having a glass transition temperature of 100 ° C. or higher, and at least a methacrylic acid ester. And a soft segment (SS) having a glass transition temperature of 20 ° C. or lower including one kind of monomer units derived from an acrylate ester. Hereinafter, the hard segment may be simply abbreviated as “HS”, and the soft segment may be simply abbreviated as “SS”.

Here, from the viewpoint of a balance between heat resistance and flexibility, the glass transition temperature of HS is more preferably 105 ° C. or higher, and further preferably 110 ° C. or higher. The upper limit of the glass transition temperature of HS is usually 125 ° C. Further, the glass transition temperature of SS is more preferably 0 ° C. or less, and further preferably −20 ° C. or less from the viewpoint of improving flexibility and low temperature characteristics. The lower limit of the glass transition temperature of SS is usually −60 ° C.

Here, as the monomer unit contained in the hard segment (HS), for example, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, methacrylic acid Methacrylic esters such as cyclohexyl, isobornyl methacrylate, phenyl methacrylate and 2-hydroxyethyl methacrylate; methyl acrylate, tert-butyl acrylate, cyclohexyl acrylate, isobornyl acrylate, phenyl acrylate and 2-hydroxyethyl acrylate And acrylic acid esters.

In the present laminated optical film 2, from the viewpoint of improving the transparency and heat resistance of the resulting film, methyl methacrylate, ethyl methacrylate, tert-butyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate, phenyl methacrylate, 2-Hydroxyethyl methacrylate, methyl acrylate, tert-butyl acrylate, cyclohexyl acrylate, isobornyl acrylate, phenyl acrylate and 2-hydroxyethyl acrylate are particularly preferred, and transparency and industrial availability. In view of the above, methyl methacrylate is more preferable. The hard segment (HS) can be used alone or in combination of two or more of these methacrylic acid esters and acrylic acid esters. Moreover, when the acrylic block copolymer (A) contains two or more hard segments (HS), these hard segments (HS) may be the same or different. The laminated optical film 2 is preferably the same from the viewpoint of transparency, ease of polymerization, industrial availability, and the like.

Examples of monomer units contained in the soft segment (SS) include n-propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, amyl methacrylate, isoamyl methacrylate, n-hexyl methacrylate, methacrylic acid. Methacrylic acid esters such as 2-ethylhexyl acid, pentadecyl methacrylate, dodecyl methacrylate, phenoxyethyl methacrylate and 2-methoxyethyl methacrylate; methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, acrylic acid n-butyl, isobutyl acrylate, sec-butyl acrylate, amyl acrylate, isoamyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, pentadecyl acrylate, acrylic acid Decyl, benzyl acrylate, acrylic acid esters such as 2-methoxyethyl acrylate phenoxyethyl and acrylic acid.

In the present laminated optical film 2, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, acrylic acid from the viewpoint of improving the flexibility and low temperature characteristics of the obtained film. Acrylic esters such as dodecyl, phenoxyethyl acrylate and 2-methoxyethyl acrylate are preferred. The soft segment (SS) can be used alone or in combination of two or more of these methacrylic acid esters and acrylic acid esters. Moreover, when the acrylic block copolymer (A) contains two or more soft segments (SS), the soft segments (SS) may be the same or different. The laminated optical film 2 is preferably the same from the viewpoint of transparency, ease of polymerization, industrial availability, and the like.

Moreover, in this laminated optical film 2, as a monomer unit used for the said hard segment (HS) and soft segment (SS) in the range which does not impair the characteristic of an acryl-type block copolymer (A), reaction is further carried out. Methacrylic acid ester and acrylic acid ester having a group can be used. Use of a methacrylic acid ester or acrylic acid ester having a reactive group for the polymerization is preferable because the adhesiveness of the resulting acrylic block copolymer (A) may be improved. Here, examples of the methacrylic acid ester and acrylic acid ester having a reactive group include glycidyl methacrylate, allyl methacrylate, glycidyl acrylate, and allyl acrylate. These monomer units are usually used in a small amount, but the amount is preferably 40% by mass or less, more preferably 20% by mass or less, based on the total mass of the monomer units contained in each segment.

Moreover, as a monomer unit used for the said hard segment (HS) and soft segment (SS) in the range which does not impair the characteristic of the acryl-type block copolymer (A) used for this laminated optical film 2, as needed. Other monomer units can be used in combination.

Examples of these other monomer units include methacrylic acid, acrylic acid, styrene, α-methylstyrene, p-methylstyrene, m-methylstyrene, acrylonitrile, methacrylonitrile, ethylene, propylene, isobutene, 1,3 -Butadiene, isoprene, octene, vinyl acetate, maleic anhydride, vinyl chloride and vinylidene chloride. These monomer units are usually used in a small amount, but are preferably 40% by mass or less, more preferably 20% by mass or less, based on the total mass of monomers used for polymerization of each segment. .

The acrylic block copolymer (A) used in the present laminated optical film 2 can have other polymer blocks as necessary in addition to the hard segment (HS) and the soft segment (SS).
Examples of other polymer blocks include methacrylic acid, acrylic acid, styrene, α-methylstyrene, p-methylstyrene, m-methylstyrene, acrylonitrile, methacrylonitrile, ethylene, propylene, isobutene, and 1,3-butadiene. , Isoprene, octene, vinyl acetate, maleic anhydride, vinyl chloride, vinylidene chloride and other polymer blocks and copolymer blocks; polyethylene terephthalate, polybutylene terephthalate, polylactic acid, polyurethane, polydimethyl Examples thereof include a polymer block composed of siloxane. The polymer block also includes a hydrogenated product of a polymer block polymerized from a monomer unit containing a diene monomer such as 1,3-butadiene and isoprene.

The bonding form of each segment and polymer block included in the acrylic block copolymer (A) of the laminated optical film 2 is not particularly limited. In this laminated optical film 2, hard segments (HS) are bonded to both ends of at least one soft segment (SS) from the viewpoints of heat resistance, mechanical properties, and blocking resistance of raw material pellets (preventing sticking between raw material pellets). It is preferable to have the form. Specifically, a triblock copolymer of (HS) -b- (SS) -b- (HS), a tetrablock of (HS) -b- (SS) -b- (HS) -b- (SS) Examples thereof include a block copolymer. In the laminated optical film 2, a triblock copolymer of (HS) -b- (SS) -b- (HS) is more preferable from the viewpoint of blocking resistance of the raw material pellets, production cost, and the like.

The glass transition temperature of each segment of the acrylic block copolymer (A) used for the present laminated optical film 2 can be measured with a differential operation calorimeter (DSC). In addition, the monomer composition and stereoregularity of each segment can be qualitatively and quantitatively analyzed by a known analysis method such as ¹ H-NMR or ¹³ C-NMR.
The stereoregularity of HS is not particularly limited, but a syndiotactic structure is preferable because the glass transition temperature is increased and heat resistance is improved. Specifically, triad fraction mm identified by nuclear magnetic resonance measurement of the hard segment of the acrylic block copolymer ^{(A) (1 H-NMR} ), of mr and rr, the molar ratio of rr structure Higher than the molar ratio of mm and mr can be suitably used.

The molecular weight of the acrylic block copolymer (A) is not particularly limited, but is determined by gel permeation chromatography (GPC) measurement from the viewpoint of mechanical properties and moldability of the laminated optical film 2. The weight average molecular weight in terms of polystyrene is preferably 10,000 to 500,000, more preferably 20,000 to 300,000.

The composition ratio (total hard segment (HS) / total soft segment (SS)) of the hard segment (HS) and the soft segment (SS) of the acrylic block copolymer (A) is 30/70 by mass ratio. ~ 90/10 is preferable, and 40/60 to 70/30 is more preferable. Here, if the composition ratio is in the above range, a balance of transparency, heat resistance and flexibility is obtained, which is preferable.

The acrylic block copolymer (A) used for the present laminated optical film 2 can be polymerized by known anionic polymerization or radical polymerization, but a commercially available product may be used. For example, the product name Clarity manufactured by Kuraray Co., Ltd. and the product name NANOSTRENGTH manufactured by Arkema Co., Ltd. can be mentioned.
In the present laminated optical film 2, since the molecular weight distribution can be narrowed, an acrylic block copolymer (A) polymerized by anionic polymerization can be suitably used.

B layer of this laminated optical film 2 is a layer which consists of a composition which contains an acryl-type block copolymer (A) as an essential component.
The content of the acrylic block copolymer (A) in the composition may be appropriately determined in consideration of the composition ratio of each segment of the acrylic block copolymer (A) to be used and desired characteristics. Specifically, it is preferably 5 to 100% by mass, more preferably 10 to 80% by mass, and particularly preferably 15 to 50% by mass.

From the viewpoint of mechanical properties and transparency, the content of the soft segment (SS) in the B layer in the present laminated optical film 2 is 5 to 25% by mass, preferably 8 to 20% by mass. Just decide. For example, if the HS / SS mass ratio of the acrylic block copolymer (A) used is 50/50 mass%, the acrylic block copolymer (A) is contained in the B layer in an amount of 10 to 50 mass%. What is necessary is just to adjust suitably between. Further, if the HS / SS mass ratio of the acrylic block copolymer (A) used is 90/10% by mass, the acrylic block copolymer (A) is contained in 50 to 100% by mass in the B layer. What is necessary is just to adjust suitably between.

In the layer B of the present laminated optical film 2, other polymers, further lubricants, plasticizers, tackifiers, antioxidants, ultraviolet absorbers, light stabilizers, as long as the effects of the present laminated optical film 2 are not impaired. Additives such as an agent, an antistatic agent, a flame retardant, a filler and a nanofiller can be contained. These other polymers and additives can be used alone or in combination of two or more.

Here, from the viewpoint of compatibility with the acrylic block copolymer (A) used in the present laminated optical film 2, other polymers include acrylic polymers, methyl methacrylate-styrene copolymers, styrene-anhydrous maleic acid. Examples include acid copolymers, styrene-methyl methacrylate-maleic anhydride copolymers, AS resins, polylactic acid, and polyvinylidene fluoride. In the present laminated optical film 2, an acrylic polymer (B) described in detail below can be preferably used from the viewpoints of mechanical strength, transparency, heat resistance, economy, and the like.

<2-2. Acrylic polymer (B)>
It is preferable from the viewpoint of mechanical strength, transparency, heat resistance, and economy that the layer B of the laminated optical film 2 further has an acrylic polymer (B) described below.
The acrylic polymer (B) is an acrylic polymer other than the acrylic block copolymer (A), and is an acrylic polymer mainly composed of a (meth) acrylic acid ester monomer. .

Here, the (meth) acrylic acid ester monomer unit means an acrylic acid ester monomer unit or a methacrylic acid ester monomer unit. In addition, the main component here is a component having the highest molar ratio when all the monomer units constituting the acrylic polymer (B) are 100 mol%, preferably 70 mol% or more, 90 mol% or more is more preferable, 95 mol% or more is further more preferable, and 98 mol% or more is especially preferable. The upper limit is 100 mol%.

Here, the constituent monomer units include methyl methacrylate, methacrylic acid, acrylic acid, benzyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, and t-butyl (meth). Acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, tridecyl (meth) acrylate, stearyl (meth) acrylate, glycidyl (meth) acrylate, hydroxypropyl (meth) acrylate, 2-methoxyethyl (meth) acrylate, 2-Ethoxyethyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, norbornyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentanyl (meth) Chlorate, dicyclopentenyloxyethyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, acrylic (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2- (meth) acryloyloxyethyl succinate, maleic acid 2 -(Meth) acryloyloxyethyl, 2- (meth) acryloyloxyethyl phthalate, 2- (meth) acryloyloxyethyl hexahydrophthalate, pentamethylpiperidyl (meth) acrylate, tetramethylpiperidyl (meth) acrylate And dimethylaminoethyl (meth) acrylate and diethylaminoethyl (meth) acrylate. These can be used alone or in combination of two or more. Examples of other monomer units that can be polymerized with these monomer units include olefin monomer units and vinyl monomer units.

Here, in this laminated optical film 2, from the viewpoint of easy compatibility with the acrylic block copolymer (A), at least a (meth) acrylic acid ester monomer of the acrylic polymer (B). One type of unit is preferably the same as one type of monomer unit of the acrylic block copolymer (A).

Furthermore, in this laminated optical film 2, a homopolymer of methyl methacrylate or a copolymer of methyl methacrylate and methyl acrylate or ethyl acrylate is preferably used because it is easily available industrially. Can do.

Further, the stereoregularity is not particularly limited, but the stereostructure of the (meth) acrylic acid ester monomer unit is preferably a syndiotactic structure because the glass transition temperature becomes higher and the heat resistance is improved. . Specifically, among the triad fractions of mm, mr, and rr, those having a molar ratio of the rr structure higher than that of mm and mr can be suitably used. Incidentally, triad fraction, using nuclear magnetic resonance measurement apparatus ^{(1 H-NMR),} can be determined by known methods.

The molecular weight of the acrylic polymer (B) used in the present laminated optical film 2 is not particularly limited, but is usually 30,000 or more and 300,000 or less in terms of weight average molecular weight, 50,000 or more, A range of 150,000 or less is preferable because appearance defects such as flow unevenness hardly occur during molding.

The glass transition temperature is not particularly limited, but is preferably 80 ° C. or higher, more preferably 90 ° C. or higher, further preferably 100 ° C. or higher, and particularly preferably 105 ° C. or higher, from the viewpoint of heat resistance of the laminated film. preferable. The upper limit of the glass transition temperature is not particularly specified, but is usually 150 ° C. Here, if it is less than 120 degreeC, since the point which is excellent in mechanical strength and a general purpose resin can be used, it is preferable from a viewpoint that the selection range of a raw material spreads. On the other hand, when higher heat resistance is required, the glass transition temperature is preferably set to 120 ° C. or higher by adjusting the copolymer component of the acrylic polymer (B) or mixing with other polymers.

The acrylic polymer (B) used for the laminated optical film 2 may be a commercially available product. Specific examples include trade names “Acrypet” manufactured by Mitsubishi Rayon Co., Ltd., Sumitomo Chemical Co., Ltd. ) Product name “SUMIPEX” and Kuraray Co., Ltd. product name “PARAPET”.

[This laminated optical film 3]
The film according to an example of the third embodiment of the present invention (referred to as “the present laminated optical film 3”) is the above-mentioned present laminated optical film 1 or the present laminated optical film 2 (these are referred to as “base film”). It is a film provided with a configuration in which a coat layer made of a water-based urethane resin composition containing a urethane resin and a melamine resin-based crosslinking agent is formed on at least one surface.

In JP-A-2015-24511, the crosslinking agent contained in the composition used for forming the easy-adhesion layer was a crosslinking agent having an epoxy group, a carbodiimide group or an oxazoline group. On the other hand, in this laminated optical film 3, a melamine resin crosslinking agent is used for the urethane resin. A general cross-linking agent has the disadvantage that the affinity for the base material and the adhesive is lost with the progress of the cross-linking reaction, and the adhesiveness between the easy-adhesion layer and the base material tends to be lowered. However, the present laminated optical film 3 has an effect that the reduction of the adhesiveness with the base material and the adhesive is suppressed by the progress of the crosslinking reaction. This is presumably because the structure derived from the amino group or hydroxyl group in the melamine-based crosslinking agent contributes to the direction in which the affinity for the base material and the adhesive is not lost even by the progress of the crosslinking reaction.
The melamine resin-based cross-linking agent controls its cross-linking reactivity by selecting various structures involved in the cross-linking reaction such as methyl ether type, imino group type, methylol group type, and methylol / imino group type. Therefore, there is an advantage that the pot life and reactivity can be easily controlled.

<3-1. Urethane coat layer>
Next, a coat layer (hereinafter referred to as “urethane coating composition”) containing a urethane resin and a melamine resin crosslinking agent in the laminated optical film 3 (hereinafter sometimes referred to as “urethane coating composition”). , May be referred to as “urethane coat layer”).
In this laminated optical film 3, it is essential to form a urethane coat layer on at least one surface of the above-described base film using a water-based urethane coating composition containing a urethane resin and a melamine resin crosslinking agent. Requirement.

The urethane coat 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. Reinforce and bond 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 base film without any other layer such as an adhesive layer.
The urethane coat layer may be provided on one surface of the base film or on both surfaces. By providing the urethane coat layer on both surfaces of the base film, the handleability of the base film can be effectively improved.

(Urethane resin)
Examples of the urethane-based resin used in the present laminated optical film 3 include (3-1) a component containing two or more active hydrogens in average in one molecule (hereinafter referred to as “component (3-1)”). )) And (3-2) a urethane resin obtained by reacting a polyisocyanate component (hereinafter sometimes referred to as “component (3-2)”); or the above components (3-1) and The component (3-2) 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 a urethane-based resin produced by adding water and adding a dispersion 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 (3-1) is not particularly limited, but preferably has a hydroxylic active hydrogen. Specific examples of such compounds include those exemplified in the following (3-1-1) to (3-1-5).

(3-1-1) 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-hexanediol, 2,5-hexanediol, 1,8-octanediol, dipropylene glycol, 2,2,4-trimethyl-1 , 3-pentanediol, tricyclodecane dimethanol, 1,4-cyclohexane dimethanol, 2,2-dimethylpropanediol, and the like.

(3-1-2) Polyether polyol As the polyether polyol, for example, an alkylene oxide adduct of the polyol compound of (3-1-1) above; ring-opening (co-polymerization) of an alkylene oxide and a cyclic ether (eg, tetrahydrofuran) ) Polymer; glycols such as glycol, polytetramethylene glycol, polyhexamethylene glycol, polyoctamethylene glycol, polyethylene glycol, polypropylene glycol, and ethylene glycol-propylene glycol;

(3-1-3) Polyester polyol Examples of the polyester polyol include dicarboxylic acids such as adipic acid, succinic acid, sebacic acid, glutaric acid, maleic acid, fumaric acid, and phthalic acid, and anhydrides thereof (3-1) -1) and polyol compounds such as ethylene glycol, propylene glycol, 1,4-butylene glycol, 1,6-hexanediol, 1,8-octanediol, and neopentyl glycol, under the conditions of excess hydroxyl group Examples thereof include those obtained by polycondensation. 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.

(3-1-4) Polyether Ester Polyol As the polyether ester polyol, for example, an ether group-containing polyol (for example, the polyether polyol or diethylene glycol of (3-1-2) above) or this and other glycols And a mixture obtained by reacting an alkylene oxide with the dicarboxylic acid or anhydride thereof as exemplified in the above (3-1-3). More specifically, examples include polytetramethylene glycol-adipic acid condensate.

(3-1-5) Polycarbonate polyol Polycarbonate carbonate polyol includes, for example, the general formula HO—R— (O—C (O) —O—R) _n —OH (wherein R represents a carbon number of 1 to 5). 12 represents 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 (3-1-1) to (3-1-5) may be used alone, or two or more kinds may be used in combination at any ratio.

Examples of the component (3-2) to be reacted with the component (3-1) include an aliphatic, alicyclic or aromatic compound containing an average of two or more isocyanate groups in one molecule.

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 compound having 4 to 18 carbon atoms, such as 1,4-cyclohexane diisocyanate, methylcyclohexylene diisocyanate, isophorone diisocyanate (IPDI), and dicyclohexylmethane diisocyanate (HMDI). Etc. Examples of the aromatic diisocyanate compound include tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, and xylylene diisocyanate. One of these may be used alone, or two or more of these may be used in combination at any ratio.

In the present laminated optical film 3, as the urethane-based resin, a urethane coat layer having excellent heat resistance and water resistance can be formed. Therefore, those having an aliphatic polycarbonate skeleton, specifically, (3-1 A urethane resin obtained by reacting the polycarbonate polyol of −5) with an aliphatic diisocyanate compound is preferred.

Also, 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-based resin is preferable because it has excellent adhesion to the base 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-based resin, a conventionally used method can be used without any particular limitation. Preferable examples include polyether polyol and polyester polyol in advance by replacing dimethylolalkanoic acid with a part or all of the glycol component described in (3-1-2) to (3-1-4). And a method of introducing a carboxyl group into a polyether ester polyol or the like. 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 laminated optical film 3 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 concentration of the component (urethane resin) 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 of Lubrizol, and “RU” series made by Stahl Japan, Etc. can be used. In particular, “Yukot UA-368” manufactured by Sanyo Chemical Industries, “RU-40-350” and “EX-RU-92-605” manufactured by Stahl Japan Co., Ltd., “ “Rezamin D-6031” has an aliphatic polycarbonate skeleton and is dispersed in water with a volatile base, which will be described later, and thus is suitable for the present laminated optical film 3.

Note that the urethane-based coating composition may include only one type of urethane-based resin, or may include two or more types in any ratio.

(Melamine resin crosslinking agent)
Examples of the melamine resin-based crosslinking agent include methylol melamine such as dimethylol melamine, trimethylol melamine, tetramethylol melamine, pentamethylol melamine and hexamethylol melamine; alkyl etherified product of methylol melamine and alcohol; condensation of methylol melamine; An etherified product of alcohol with the product. Here, examples of the alcohol include methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol, isobutyl alcohol, and 2-ethylhexyl alcohol.

Commercial products can be used as the melamine resin crosslinking agent. Examples of commercially available products include “Symel 303”, “Symel 323”, “Symel 325”, “Symel 327”, “Symel 350”, “Symel 370”, and “Symel 380” manufactured by Ornex Japan. , “Cymel 385”, “Cymel 701”, “Cymel 212”, “Cymel 253”, “Cymel 254”, “Resimin 735”, “Resimin 740”, “Resimin 741”, “Resimin 745” manufactured by Monsanto, “RESIMIN 746”, “RESIMIN 747”, “SUMIMAL M55”, “SUMIMAL M30W”, “SUMIMAL M50W” manufactured by Sumitomo Chemical Co., Ltd. “Uban 20SE” and “Uban 28SE” manufactured by Mitsui Chemicals (Mitsui Chemicals) Manufactured).

As the melamine resin-based crosslinking agent, a resin having a melamine skeleton such as a melamine resin or a benzoguanamine resin can be used, and a methylol group of a partially or completely methylolated melamine resin is partially or partially with methyl alcohol and / or butyl alcohol. Fully etherified methyl etherified melamine resins, butyl etherified melamine resins, and methyl-butyl mixed etherified melamine resins can be used.

Of these, methyl etherified melamine resin is used from the viewpoint of moisture resistance, flexibility, stability in water and pot life, and imino group type (partially methylolated) from the viewpoint of condensation, reactivity, and hardness reactivity. ) And methylol group-type (partially etherified) -containing melamine resins can be suitably used. In this laminated optical film 3, an imino group and / or methylol group type-containing melamine resin that can be crosslinked in a short time, particularly in the drying step of the film, and has good tackiness at room temperature as the hardness increases. Is preferably used.

These melamine resin-based crosslinking agents may be used alone or in combination of two or more.

The content of the melamine 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 of the urethane coating layer by reducing the residual unreacted melamine resin crosslinking agent, the melamine resin crosslinking agent is less than 40 parts by weight with respect to 100 parts by weight of the urethane resin. It is preferable. The melamine resin-based crosslinking agent in the urethane-based coating composition is particularly preferably 1 to 30 parts by weight with respect to 100 parts by weight of the urethane-based resin.

When the urethane resin has an acid structure, the amount of the melamine resin crosslinking agent is preferably 0.2 on the weight basis with respect to the amount of the melamine 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 3.0 times or less, more preferably 2.5 times or less, particularly preferably 2.0 times or less. . Here, the amount of the melamine resin-based crosslinking agent equivalent to the acid structure of the urethane-based resin refers to the theoretical amount of the melamine resin-based crosslinking agent that can react with the total amount of the acid structure of the urethane-based resin without excess or deficiency. When the urethane resin has an acid structure, the acid structure can react with the melamine structure containing an alkyl ether group, a methylol group, or an imino group of the melamine resin crosslinking agent. At this time, by keeping the amount of the melamine resin-based crosslinking agent in the above range, the reaction between the acid structure and the melamine resin-based crosslinking agent proceeds to an appropriate level, and the mechanical strength of the formed urethane coat layer is increased. It can be improved effectively.

(Other ingredients)
The urethane coating composition for forming the urethane coating layer contains other components in addition to the above water-based urethane resin and melamine resin-based cross-linking agent as required, as long as the purpose of the laminated optical film 3 is not impaired. It may be.

(Curing catalyst)
The urethane-based coating composition may contain a curing catalyst, and by including the curing catalyst, the curability of the resulting urethane coat layer can be increased.
Moreover, as a curing catalyst, sulfonic acids such as paratoluenesulfonic acid, dodecylbenzenesulfonic acid, and dinonylnaphthalenesulfonic acid; neutralized salts of the sulfonic acid and amine; neutralization of phosphate ester compound and amine 1 type, or 2 or more types, such as a salt, can be used.

When the urethane-based coating composition contains a curing catalyst, the curing catalyst is preferably contained in an amount of 0.01 to 10% by weight, particularly 0.1 to 5% by weight, based on the melamine resin-based crosslinking agent.

(Basic substance)
The urethane-based coating composition may contain a basic substance. When the urethane-based resin in the urethane-based coating composition includes an acid structure, part or all of the acid structure is preferably neutralized with a basic substance. In particular, 20% or more of the acid structure of the acid structure-containing urethane resin is more preferably neutralized with a basic substance, and 50% or more is particularly preferably neutralized with a basic substance. 20% or more of the acid structure is neutralized with a basic substance, so that the heat history of the film of the present laminated optical film 3 obtained by forming a urethane coat layer on the base film is exposed to a high temperature. Even if it has, it can maintain the adhesiveness with the laminated film even more surely when it is used by being laminated on other optical films, particularly polarizers, while maintaining the properties as an optical material. it can. The remaining acid structure of the acid structure-containing urethane resin may not be neutralized, or may be neutralized with a basic substance. Further, either a non-volatile base or a volatile base may be used as the basic substance.

(Nonvolatile base)
Nonvolatile bases include inorganic bases and organics that are substantially non-volatile when left standing at 80 ° C. for 1 hour, for example, under the treatment conditions when the urethane-based coating composition is applied to the surface of the substrate film and then dried. A base can be mentioned. Examples of the substantially non-volatile inorganic base and organic base include those whose decrease in non-volatile base is 80% or less after the treatment.

As the non-volatile base, those which are soluble in water or can be emulsified by being dispersed in water are preferable. Thereby, the applicability of the water-based urethane resin can be improved, and the urethane coat layer can be easily formed.

Examples of the non-volatile base include the following.
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-acino-5-aminopyrazole, 1-isopropyl-4-chloro-5-aminopyrazole, 3-methyl-4-chloro Primary amines such as -5-aminopyrazole and 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 Ethylenediamine, N, N-dimethylbenzylamine, diethylaminopropylamine, N- (2-aminoethyl) piperazine, 2,4,6-tris (dimethylaminomethyl) phenol, N, N-bis (trimethylsilyl) urea, etc. Tertiary amines of

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

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 coat layer, and has a relatively high boiling point and a urethane coat layer. Since the heat resistance of can be made high, it is especially preferable.

These non-volatile bases may be used alone or in combination of two or more at any ratio.

When the urethane-based coating composition contains a non-volatile base, the content of the urethane-based coating composition is a urethane-based resin (where the urethane-based resin is water-based when a water-based urethane-based 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 urethane resin.) Usually 0.5 parts by weight or more, preferably 1 part by weight or more, more preferably 2 parts per 100 parts by weight. It is at least 40 parts by weight, preferably at most 30 parts by weight, more preferably at most 20 parts by weight. By making the amount of the non-volatile base more than the lower limit of the above range, the mechanical strength of the urethane coat layer can be appropriately improved, and by making it the upper limit or less, the residual unreacted non-volatile base can be reduced. Also, the mechanical strength of the urethane coat layer can be improved appropriately.

(Volatile 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.

As the volatile tertiary alkylamine, trimethylamine or triethylamine is preferable, and triethylamine is more preferable.

Stability is improved when the urethane-based coating composition contains a volatile base. This is considered because the acid structure and volatile base of the urethane resin contribute to the improvement of dispersion stability in the urethane 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. The content is preferably 0.1 to 6 mol, and more preferably 0.5 to 4.0 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 impairs the adhesion between the urethane coat layer and the adhesive layer according to the present laminated optical film 3. However, it is preferable because it does not bleed out under conditions where the influence of moisture is large, such as a high temperature and high humidity condition which is a concern for nonvolatile bases, and hardly affects the polarizing plate.

(Polyvinyl alcohol)
The urethane-based coating composition may contain polyvinyl alcohol, and by including polyvinyl alcohol, functions such as an improvement in tackiness of the urethane coat layer surface at room temperature and an increase in adhesion with a water-based adhesive can be expected.

When the urethane-based coating composition contains polyvinyl alcohol, the content of polyvinyl alcohol is 0.1% by weight or more, more preferably 1% by weight or more, preferably 20% by weight or less, based on the solid content. Preferably it is 10 weight% or less. The tackiness of the urethane coat layer surface and the adhesiveness with the water-based adhesive can be improved by setting the content of polyvinyl alcohol to the above lower limit value or more, and the base film and the urethane coat can be made to be the upper limit value or less. Adhesion with the layer can be maintained.
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.

(Nonionic surfactant)
The urethane-based coating composition may contain an acetylene glycol in which a hydroxyl group and a methyl group are substituted on two adjacent carbon atoms of a triple bond and / or a nonionic surfactant that is an ethylene oxide adduct thereof. Good. By including such a nonionic surfactant, wetting can be improved while suppressing foaming of the uncured urethane-based coating composition, thus preventing the occurrence of repelling unevenness when applied to a substrate film. it can.

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) (wherein R ¹ and R ² are each independently-( CH ₂ ) _m —H, m represents an integer of 0 or more, preferably 0 to 400, more preferably 0 or 20 to 100, and 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, and examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, and a t-butyl group. Group, pentyl group, hexyl group and the like, and isopropyl group is preferable.)
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.

(Fine particles)
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, whereby the urethane coat layer becomes another layer during winding. The area in contact with the surface of the urethane coating layer is reduced, and the surface slipperiness of the urethane coating layer is improved accordingly, and the generation of wrinkles when the film of the laminated optical film 3 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 water-dispersible fine particles are preferably used. Examples of inorganic fine particle materials include inorganic oxides such as silica, titania, alumina, and zirconia; calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, And calcium phosphate etc. are mentioned. Examples of the organic fine particle material include silicone resin, fluororesin, and acrylic resin. Among these, since it is excellent in the ability to suppress the generation of wrinkles and transparency, hardly causes haze, and has no coloration, the influence on the optical characteristics of the film of the present laminated optical film 3 is small, and an aqueous urethane type Silica fine particles are preferred because of their good dispersibility and dispersion stability in the resin, and among the silica fine particles, amorphous colloidal silica particles are particularly preferred.

In addition, fine particles may be used alone or in combination of two or more at an arbitrary ratio.

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, generation of wrinkles can be suppressed when the film of the present laminated optical film 3 is wound. Moreover, the external appearance without the cloudiness of the film of this laminated optical film 3 is maintainable by making content of microparticles into the upper limit of the said range or less.

(Other ingredients)
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 effect of the present laminated optical film 3 is 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.

(solvent)
The urethane-based coating composition is usually prepared as a dispersion containing the urethane-based resin and the melamine resin-based crosslinking agent as essential components and the above-described optional components used as necessary.
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, and ethylene glycol. Examples include monobutyl ether. 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. It is prepared to be 5 to 40% by weight, particularly preferably about 10 to 30% by weight.

(Preparation of urethane coating composition)
The urethane coating composition dissolves or disperses the aforementioned urethane resin, preferably water-based urethane resin, and melamine resin-based crosslinking agent, and other components used as necessary, using water, preferably ion-exchanged water. It is prepared by.

In the urethane coating composition, components such as urethane resin are usually dispersed as particles. From the viewpoint of the optical characteristics of the film of the present laminated optical film 3, the particle diameter of the particles is preferably 0.01 to 0.4 μm. 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-based coating composition is within the above range, the urethane-based coating composition can be uniformly applied to the surface of the base 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.

(Method for forming urethane coat layer)
The urethane coat layer is formed by applying the above urethane coating composition on at least one surface of the base film and drying and solidifying (curing) the formed coating film.

The application method of the urethane coating composition is not particularly limited, and a known application method can 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.

When curing the formed coating film, the solvent in the urethane 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 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, the upper limit temperature is (Tg−10) ° C. or lower, preferably (Tg−20) ° C. or lower, where Tg is the glass transition temperature of the material forming the base film. Preferably, it is (Tg-30) ° C. or lower. The lower limit temperature is (Bp-50) ° C. or higher, preferably (Bp-40) ° C. or higher, more preferably (Bp-30) ° C. or higher, when the boiling point of the solvent is Bp.

The specific heating and drying conditions are not particularly limited, but the drying is usually performed at 50 to 150 ° C. for 5 to 200 seconds, preferably at 60 to 130 ° C. for 10 to 100 seconds.

Furthermore, after the urethane-based coating composition is formed on the surface of the base film, a stretching treatment may be performed. 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 base 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 base film, a large retardation is not exhibited in the stretched urethane coat layer.

The surface of the urethane coat layer formed in this way may be subjected to a hydrophilic surface treatment. The surface of the urethane coat layer is usually a bonding surface when the laminated optical film 3 is bonded to another member. Therefore, by further improving the hydrophilicity of this surface, the laminated optical film 3 and other layers Adhesiveness with a member can be remarkably improved.

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 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 40 mN / m or more. It is desirable to make it. By subjecting the surface of the urethane coating layer to such a wetness index, the laminated optical film 3 can be firmly bonded to other members such as a polarizer.

(Film thickness)
The film thickness of the urethane coating layer is from the viewpoint of the effect on the retardation of the present laminated optical film 3 and the prevention of distortion (curing shrinkage) of the base film and the retardation of the laminated optical film 3 using this laminated optical film. 10 μm or less is preferable, 5 μm or less is more preferable, and 3 μm or less is more preferable. 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 obtained with respect to both a base material layer and the below-mentioned aqueous adhesive.

Further, the ratio (t1 / t2) of the film thickness (t1) of the base 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. Is from 5 to 200. If t1 / t2 is in the above-mentioned range, it is preferable that the strength of the base film is not reduced, wrinkles are generated, and retardation is not easily increased even when the urethane coating composition is heated and dried.

In the laminated optical film 3, the urethane coat layer is formed on at least one side of the base film, and the urethane coat layer may be formed on both sides of the base 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 base film. When the urethane coat layer is formed on both surfaces of the base film, the film thickness of the urethane coat layer per one side is preferably equal to or more than the above lower limit, and the total film thickness of the both sides urethane coat layer is the above upper limit. The following is preferable. 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.

<3-2. Polarizing plate>
Although there is no restriction | limiting in particular in the use of this laminated optical film 3, 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.

For example, when the present laminated optical film 3 is used as a protective film for a polarizing film in a polarizing plate, generally, the polarizing film is bonded to the urethane coat layer side through an adhesive for adhering the polarizing film.
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 applying an adhesive such as a water-based adhesive on the urethane coating layer of the laminated optical film 3 to form an adhesive layer, for example, a uniaxially stretched polyvinyl alcohol film dyed with iodine, etc. A polarizing film is attached. 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 using the present laminated optical film 3 has a layer configuration of first protective film / adhesive layer / polarizing film / adhesive layer / second protective film. Of these, it is used as at least one protective film.

<3-3. Liquid crystal display>
Since the present laminated optical film 3 is excellent in transparency, dimensional stability, and moist heat resistance and can be adhered to the polarizing film with good adhesion, a polarizing plate using such a laminated optical film 3 is In addition, the polarizing film is excellent in protective effect and function maintenance, and a high-quality display screen can be realized 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 laminated optical film 3 is a double-sided adhesive type having a urethane coat layer on both sides of the base material layer, a polarizing film is adhered to one urethane coat layer side through the adhesive layer, and the other urethane coat is provided. Other functional films and transparent substrates can be bonded to the 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.

<4. Laminated optical film>
Each of the laminated optical films 1, 2, and 3 has a layer (A layer) containing the above-described polycarbonate resin as a main component and a layer (B layer) containing a resin having a negative intrinsic birefringence as a main component. It is essential to have more than one layer.
Hereinafter, the physical properties of the laminated optical films 1, 2, and 3 will be specifically described.

(1) Laminate configuration The number of each layer of the present laminated optical films 1, 2, and 3 is not particularly limited, but from the viewpoint of ease of production and versatility of equipment, (B layer) / (A layer) Or a three-layer structure such as (B layer) / (A layer) / (B layer), (A layer) / (B layer) / (A layer). Here, from the viewpoint of curling suppression, a three-layer configuration of (B layer) / (A layer) / (B layer), (A layer) / (B layer) / (A layer) is more preferable.
If the emphasis is on improving the adhesion to the polarizer, a three-layer configuration of (B layer) / (A layer) / (B layer) is preferable. On the other hand, in order to improve the mechanical strength of the film, a three-layer structure of (A layer) / (B layer) / (A layer) is preferable.

The difference in refractive index between the A layer and the B layer is not particularly defined, but is preferably 0.1 or less, more preferably 0.05 or less, and 0.03 or less in order to suppress light reflection at the interface of the layers. Is more preferable. Further, the lower limit of the refractive index difference is not particularly defined, but in order to measure the film thickness of each layer non-destructively by reflectance spectroscopy, it is preferably 0.001 or more, and preferably 0.005 or more. More preferred.

The laminated optical films 1, 2, and 3 have a glass transition measured at a heating rate of 10 ° C./min in accordance with JIS K7122 of a resin constituting at least one of the A layer and the B layer from the viewpoint of heat resistance. The temperature is preferably 100 ° C. or higher, more preferably 110 ° C. or higher, and further preferably 120 ° C. or higher. From the viewpoint of improving the heat resistance, it is preferable that the glass transition temperature of the resin constituting the thicker layer of the A layer or the B layer is in the above range. In the present laminated optical films 1, 2, and 3, from the viewpoint of mechanical strength, the glass transition temperature of the A layer is preferably 100 ° C or higher, more preferably 110 ° C or higher, and 120 ° C or higher. Is more preferable.

(2) Film thickness The film thickness of the laminated optical films 1, 2, and 3 is preferably 50 μm or less, more preferably 30 μm or less, and particularly preferably 20 μm or less, from the viewpoint of thinning a polarizing plate using the laminated optical film. preferable. Since the mechanical strength described later is high, a thin film can be formed in this way. On the other hand, from the viewpoint of handling properties and strength, it is preferably 3 μm or more, and more preferably 5 μm or more.

(3) Lamination ratio In this laminated optical film 1, 2, 3, the ratio of the thickness of the layer (A layer) containing the polycarbonate resin as a main component to the total thickness of the laminated optical film is 20% or more and 95% or less. More preferably, it is 30% or more and 90% or less, and particularly preferably more than 50% and 80% or less.
Here, if the thickness ratio of the A layer is 20% or more, the mechanical strength, flexibility, toughness, and heat resistance of the laminated optical films 1, 2, and 3 are good. Moreover, if the thickness of A layer is 95% or less, the optical distortion of this laminated optical film 1, 2, 3 can be made sufficiently small. In addition, when multiple A layers are arranged, it means the total thickness of each layer.

(4) Retardation The in-plane retardation (R _O ) and thickness retardation (R _th ) of the laminated optical films 1, 2, 3 are preferably 10 nm or less, more preferably 5 nm or less, and particularly preferably 3 nm or less. When the in-plane retardation (R _O ) and thickness retardation (R _th ) are 10 nm or less, the optical anisotropy is small, which is suitable as an optical film. By adopting the configuration of the present laminated optical films 1, 2, 3, a film having such a very small optical anisotropy can be achieved.
The lower limits of the in-plane retardation (R _O ) and the thickness retardation (R _th ) are not particularly defined, but are preferably −10 nm or more, more preferably −5 nm or more, and particularly preferably −3 nm or more.
The measuring method of the in-plane retardation (R _O ) and the thickness retardation (R _th ) is as described in the section of Examples described later.

(5) Photoelastic coefficient of photoelastic coefficient present laminated optical film 1, 2 and 3 is preferably ¹⁰ × 10 -12 ^{Pa -1} or less, more preferably 8 × ¹⁰ -12 ^{Pa -1} or less, 5 × 10 ^{- 12} Pa ⁻¹ or less is particularly preferable. When the photoelastic coefficient is larger than 10 × 10 ⁻¹² Pa ⁻¹ , the change in phase difference due to stress becomes large, which is not suitable as a polarizer protective film.
In addition, the present laminated optical films 1, 2, 3 cancel the phase difference generated in the (A) layer when stress is applied, so that the phase difference generated in the (B) layer cancels out the light of the (A) layer single layer. The photoelastic coefficient of the laminated optical films 1, 2, and 3 can be made smaller than the elastic coefficient.

(6) Transparency The total light transmittance of the laminated optical films 1, 2, 3 is preferably 85% or more, more preferably 90% or more, and further preferably 92% or more. The haze is preferably 1% or less, more preferably 0.5% or less, and further preferably 0.3% or less.

(7) Tear strength The tear strength of the laminated optical films 1, 2, and 3 measured according to JIS K7128-2 is 4.0 kg / cm or more. More preferably, it is 4.5 kg / cm or more, and further preferably 5.0 kg / cm or more. By making the laminated structure of the present laminated optical films 1, 2 and 3, it is possible to obtain a film having excellent mechanical strength.
The method for measuring the tear strength is as described in the Examples section below.

(8) Tensile elongation The tensile elongation of the laminated optical films 1, 2, and 3 measured by the method of JIS K7161 is preferably 20% or more, more preferably 40% or more, still more preferably 60% or more, and particularly preferably. 100% or more. When the tensile elongation is less than 20%, the handleability is deteriorated because the film is easily broken. Although there is no restriction | limiting in particular about the upper limit of tensile elongation, Usually, it is 200% or less. By making the laminated structure of the present laminated optical films 1, 2, and 3, a film excellent in such flexibility and toughness can be obtained.
The method for measuring the tensile elongation is as described in the section of Examples described later.

(9) Heat resistance From the viewpoint of heat resistance, the laminated optical films 1, 2, and 3 preferably have a heat shrinkage rate at 100 ° C of 100 hours of 0.5% or less, and 0.4% or less. More preferably, it is more preferably 0.3% or less. By making the laminated structure of the present laminated optical films 1, 2, and 3, a film having such a high heat resistance can be obtained. The method for measuring the heat shrinkage rate is as described in the section of Examples described later.

<5. Manufacturing method of laminated optical film>
The production method of the present laminated optical films 1, 2, and 3 is not particularly limited, and a layer (A layer) mainly composed of a polycarbonate resin and a layer (B) mainly composed of a resin having a negative intrinsic birefringence index. Layer) using an adhesive, an extrusion laminating method in which the other layer in a molten state is laminated on the film of one layer by extrusion, and a coextrusion method in which the layers are melted and laminated at the same time. From the viewpoint of productivity, the coextrusion method is most preferable.
When the polycarbonate resin and the acrylic resin are coextruded, the melting temperature of the T die is 180 ° C. to 260 ° C. At this time, it is preferable to adjust the difference in die temperature between the two resins in the T die to 30 ° C. or less, preferably 20 ° C. or less, more preferably 10 ° C. or less. By setting the difference in die temperature to 30 ° C. or less, the melt viscosity at the time of co-extrusion becomes approximately the same, and the influence of thickness fluctuation of the laminated film is reduced.

<6. Polarizing plate>
Although there is no restriction | limiting in particular in the use of this laminated optical film 1,2,3, Since optical anisotropy is very small and it is excellent also in mechanical strengths, such as tearing strength, especially of the polarizing film of a polarizing plate. It can be suitably used as a protective film.

When the present laminated optical films 1, 2, and 3 are used as, for example, a protective film for a polarizing film in a polarizing plate, generally, the polarizing film is bonded through an adhesive for adhering the polarizing film.
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.

The outermost layer of the present laminated optical films 1, 2, and 3 is optical regardless of whether a layer mainly composed of polycarbonate resin or a layer mainly composed of resin having a negative intrinsic birefringence is selected. Since a film having small anisotropy can be produced, the outermost layer may be selected depending on the type of adhesive used, and as a result, many types of adhesives can be used.

<7. Liquid crystal display>
The laminated optical films 1, 2, and 3 are excellent in optical properties and mechanical strength such as tear strength, can be adhered to the polarizing film with good adhesion, and handleability when peeling the polarizing plate from the liquid crystal Therefore, the polarizing plate of the present invention using such laminated optical films 1, 2, and 3 is excellent in the protective effect and functional maintenance of the polarizing film, and is used in TVs, personal computers, digital cameras, mobile phones and the like. A high-quality display screen can be realized as a polarizing plate of a liquid crystal display device, and the workability at the time of manufacturing the liquid crystal display device is excellent.

<Explanation of words>
“Sheet” generally refers to a product that is thin by definition in JIS and has a thickness that is small and flat for the length and width. In general, “film” is thicker than the length and width. A thin flat product with an extremely small thickness and an arbitrarily limited maximum thickness, usually supplied in the form of a roll (Japanese Industrial Standard JISK6900). However, since the boundary between the sheet and the film is not clear and it is not necessary to distinguish the two in terms of the present invention, in the present invention, even when the term “film” is used, the term “sheet” is included and the term “sheet” is used. In some cases, “film” is included.
In addition, the expression “panel” such as an image display panel and a protection panel includes a plate, a sheet and a film, or a laminate thereof.

In the present specification, when “X to Y” (X and Y are arbitrary numbers) is described, it means “preferably greater than X” or “preferably,” with the meaning of “X to Y” unless otherwise specified. The meaning of “smaller than Y” is also included.
Further, when “X or more or X ≦” (X is an arbitrary number) is included, it means “preferably larger than X” unless otherwise specified, and “Y or less or Y ≧” (Y is an arbitrary number) Unless otherwise specified, it means “preferably smaller than Y”.

Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited by these examples and comparative examples. In the following, the flow direction (take-off direction) at the time of manufacturing a single layer film or a laminated optical film is described as MD, and the perpendicular direction thereof is described as TD.

[Examples 1-1 to 1-5 and Comparative Examples 1-1 to 1-2]
Examples 1-1 to 1-5 and Comparative Examples 1-1 to 1-2 will be described.

<Evaluation method>
In the following, various physical properties were measured and evaluated for Examples 1-1 to 1-5 and Comparative Examples 1-1 to 1-2 as follows.

(Intrinsic birefringence)
About 8 g of resin was pressed for 1 minute under the conditions of preheating 1 to 3 minutes and pressure 20 MPa at a hot pressing temperature of 200 ° C. using a spacer with a width of 11 cm, a length of 11 cm and a thickness of 0.5 mm. Thereafter, the entire spacer was taken out and pressure-cooled with a water tube cooling press at a pressure of 20 MPa for 3 minutes to prepare a sheet. A sample was cut out from this sheet to a width of 5 mm and a length of 20 mm.

Viscoelasticity of a device combining a birefringence measuring device comprising a He-Ne laser, a polarizer, a compensation plate, an analyzer and a photodetector and a vibration type viscoelasticity measuring device ("Rheogel E-4000" manufactured by UBM). The cut sample was fixed to the measuring device, and measurement was performed under several conditions so that a synthetic curve could be created from room temperature to near the glass transition temperature using a time-temperature conversion rule. The storage elastic modulus E ′ (ω) and the loss elastic modulus E ″ (ω) were measured from the viscoelasticity measuring device while changing the measurement frequency from 1 Hz to 133 Hz. At the same time, the emitted laser light was measured with a polarizer, a sample, and a compensation plate. , Pass through the analyzer, pick up with a photodetector (photodiode), find the phase difference with respect to the amplitude and distortion of the waveform of the angular frequency ω or 2ω through the lock-in amplifier, and from this, birefringence Δn ^* (ω) At this time, the directions of the polarizer and the analyzer were orthogonal to each other, and each was adjusted so as to form an angle of π / 4 with respect to the extending direction of the sample.
Birefringence Δn ^* (ω) = Δn ₀ × cos (ωt + δ _B )

Next, the strain optical ratio O ^* (ω) was defined and obtained for the birefringence Δn ^* (ω) as shown in the following equation.
Strain optical ratio O ^* (ω) = Δn ^* (ω) / ε ^* (ω)

Here, birefringence and stress are each composed of two component functions, and each can be expressed by the following equation, assuming that the corrected stress optical law is established.
E ′ (ω) = E ′ _R (ω) + E ′ _G (ω)
O ′ (ω) = C _R × E ′ _R (ω) + C _G × E ′ _G (ω)
E ″ (ω) = E ″ (ω) = E ″ _R (ω) + E ″ _G (ω)
O ″ (ω) = C _R × E ″ _R (ω) + C _G × E ″ _G (ω)

Using the E ′ (ω), E ″ (ω), and O ^* (ω) obtained by the measurement, the above four equations can be solved.
From this, the intrinsic birefringence (Δn ₀ ) is
Δn ₀ = 5/3 × O ′ (ω = ∞) = 5/3 × C _R × E ′ _R (ω = ∞)
As asked.
(For the principle of measurement and the measurement method, see Polymer Papers Vol. 53, No. 10, p602-613 (1996).)

(Average refractive index)
Using the sample for intrinsic birefringence measurement described above, measurement was performed using an Abbe refractometer manufactured by Atago Co., Ltd., using sodium D line (589 nm) as a light source, in accordance with JIS K7142.

(Total light transmittance and haze)
For the films obtained in Examples and Comparative Examples, total light transmittance and haze were measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., trade name: NDH-5000) according to JIS K7105. .

(Film thickness of each layer)
About the film obtained by the Example and the comparative example, the film thickness of each layer was measured nondestructively using the film thickness measuring apparatus (Firmmetrics company make, brand name: F20) by reflectance spectroscopy.

(Heat-resistant)
The films obtained in Examples and Comparative Examples were cut into 12 cm × 12 cm, and lattice lines (10 cm × 10 cm) were entered as shown in FIG. This film was hung in an oven at 100 ° C. and left for 100 hours. The shrinkage was calculated from the lattice length (a) in the MD direction before entering the oven and the lattice length (b) in the MD direction after taking out of the oven, using the following formula.
Shrinkage rate (%) = 100 × ((a) − (b)) ÷ (a)

From the shrinkage value, the heat resistance was evaluated as follows.
○: Shrinkage rate is 0.5% or less ×: Shrinkage rate is greater than 0.5%

(In-plane retardation (R _O ) and thickness retardation (R _th ))
The films obtained in Examples and Comparative Examples were measured using a phase difference measuring device (trade name: KOBRA-WR, manufactured by Oji Scientific Co., Ltd.). _Rth was calculated from the phase difference between the incident angle of 0 ° and 40 °. From the measurement results, evaluation was performed as follows.
A: Absolute values of R _O and R _th are 3 nm or less ○: Absolute values of R _O and R _th are larger than 3 nm and 10 nm or less X: Absolute values of R _O and R _th are larger than 10 nm

(Photoelastic coefficient)
For the films obtained in Examples and Comparative Examples and the above-mentioned samples for measuring intrinsic birefringence, the slow axis direction was confirmed with a phase difference measuring device (trade name: KOBRA-WR, manufactured by Oji Scientific Co., Ltd.) A test piece of 15 mm × 60 mm was cut out with the slow axis direction as the long side. While applying a load of 0 to 400 gf to this sample, the in-plane phase difference (RO) at each load was measured using a phase difference measuring device (trade name: KOBRA-WR, manufactured by Oji Scientific Co., Ltd.). The photoelastic coefficient was calculated by the following equation from the slope when gf / width 15 mm) was plotted on the x-axis and phase difference (nm) was plotted on the y-axis.
Photoelastic coefficient (Pa ⁻¹ ) = slope × 1.5 × 10 ⁻⁸ ÷ 9.8

(Tensile elongation)
From the films obtained in Examples and Comparative Examples, MD was cut out in a width of 6 mm to obtain a sample for evaluation. In accordance with JIS K7161, a 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.
◎: Elongation is 60% or more ○: Elongation is 20% or more and less than 60% ×: Elongation is less than 20%

(Tear strength)
For the films obtained in Examples and Comparative Examples, the tear strength of MD of the sample for evaluation was measured according to JIS K7128-2 and evaluated according to the following criteria.
A: Tear strength is 4.5 kg / cm or more B: Tear strength is 4.0 kg / cm or more and less than 4.5 kg / cm X: Tear strength is less than 4.0 kg / cm

<Constituent materials>
The constituent materials used in Examples 1-1 to 1-5 and Comparative Examples 1-1 to 1-2 are shown below.

(Polycarbonate resin (PC-1))
The weight ratio of the structural unit derived from isosorbide, which is a dihydroxy compound, and the structural unit derived from tricyclodecane dimethanol, obtained by a method according to JP 2008-024919 A, is isosorbide / tricyclodecane dimethanol = 66. / 34, a polycarbonate copolymer having a glass transition temperature (Tg) of 130 ° C. was used. The intrinsic birefringence of this copolymer was 0.03, the average refractive index was 1.51, and the photoelastic coefficient was 10 × 10 ⁻¹² Pa ⁻¹ .

(Aromatic polycarbonate resin (PC-2))
Caliber 301-15 manufactured by Sumika Stylon Polycarbonate Co., Ltd. was used. This resin had a glass transition temperature (Tg) of 148 ° C., an intrinsic birefringence of 0.106, an average refractive index of 1.585, and a photoelastic coefficient of 80 × 10 ⁻¹² Pa ⁻¹ .

(Acrylic resin (PMMA))
Sumipex MGSS manufactured by Sumitomo Chemical Co., Ltd. was used. This resin had a glass transition temperature (Tg) of 108 ° C., an intrinsic birefringence of −0.004, an average refractive index of 1.492, and a photoelastic coefficient of 2 × 10 ⁻¹² Pa ⁻¹ .

(Flexibility modifier)
Clarity LA4285 (methyl methacrylate-butyl acrylate-methyl methacrylate triblock copolymer, copolymerization ratio 50/50 in terms of weight) manufactured by Kuraray Co., Ltd. was used. This modifier had a glass transition temperature (Tg) (block (i)) of 115 ° C. and an average refractive index of 1.478.

<Example 1-1>
The polycarbonate resin as the material for the layer (A) (PC-1), the acrylic resin as the material for the layer (B) (PMMA), respectively, were charged φ65mm single screw extruder, a [phi] 40 mm ² screw extruder These were melt-kneaded at barrel set temperatures of 220 to 240 ° C. and 180 ° C. to 240 ° C., respectively, and coextruded from a multi-die having a width of 1350 mm and a lip gap of 0.7 mm (set temperature of 240 ° C.), and then to 20 ° C. The film was wound up with a temperature-controlled cast roll to prepare a laminated optical film having a structure of (B) layer / (A) layer / (B) layer. The film thickness of each layer was 3.5 μm / 8 μm / 3.5 μm.

<Examples 1-2 to 1-3>
A laminated optical film was produced in the same manner as in Example 1-1 except that the thickness of each layer was changed as shown in Table 1.

<Example 1-4>
(A) The polycarbonate resin (PC-1) as the material for the layer and the acrylic resin (PMMA) as the material for the (B) layer were put into a φ40 mm twin screw extruder and a φ65 mm single screw extruder, respectively. They are melt-kneaded at barrel set temperatures of 220 to 240 ° C. and 180 ° C. to 240 ° C., respectively, and coextruded from a multi-die (set temperature 240 ° C.) having a width of 1350 mm and a lip gap of 0.7 mm, and then heated to 20 ° C. It was wound up with a prepared cast roll to produce a laminated optical film having a structure of (A) layer / (B) layer / (A) layer. The film thickness of each layer was 4 μm / 7 μm / 4 μm.

<Example 1-5>
(B) As a material for the layer, except that a dry blend product of 80 parts by mass of the acrylic resin (PMMA) / 20 parts by mass of the flexibility modifier was used, the same method as in Example 1-1, A laminated optical film was produced.

<Comparative Example 1-1>
(A) As a material for the layer, the above acrylic resin (PMMA) is put into a φ65 mm single screw extruder, melt kneaded at a barrel set temperature of 180 ° C. to 240 ° C., and has a width of 1350 mm and a lip gap of 0.7 mm. After extruding from the single layer die, it was wound up with a cast roll whose temperature was adjusted to 20 ° C. to produce a single layer optical film having a film thickness of 15 μm consisting of layer (B).

<Comparative Example 1-2>
A laminated optical film was produced in the same manner as in Example 1-1 except that the polycarbonate resin (PC-1) was used as the material for the (B) layer.

Examples 1-1 to 1-5 are films having excellent mechanical strength and optical isotropy due to the constitution of the present invention. In particular, Examples 1-1 and 1-4 are films in which the phase difference and the mechanical strength are balanced because the lamination ratio is more preferable. Moreover, since the softening modifier is added to the (B) layer, Example 5 is a film with further excellent mechanical strength.
On the other hand, Comparative Example 1-1 has a low mechanical strength because it is a single-layer film. In Comparative Example 1-2, since a general-purpose polycarbonate resin is used, even a laminated film is a film having a large optical anisotropy.

[Examples 2-1 to 2-4 and Comparative Examples 2-1 to 2-2]
Next, Examples 2-1 to 2-4 and Comparative Examples 2-1 to 2-2 will be described.

<Evaluation method>
For Examples 2-1 to 2-4 and Comparative Examples 2-1 to 2-2, various physical properties were measured and evaluated as follows.

(1) Glass transition temperature (Tg)
Using a differential scanning calorimeter manufactured by PerkinElmer Co., Ltd., trade name “Pyris1 DSC”, according to JIS K7121, about 10 mg of the sample was heated from −40 ° C. to 200 ° C. at a heating rate of 10 ° C./min. After holding at 200 ° C. for 1 minute, the temperature was lowered to −40 ° C. at a cooling rate of 10 ° C./min, and again from the thermogram measured when the temperature was raised to 200 ° C. at a heating rate of 10 ° C./min, the glass transition temperature (Tg ) (° C). In addition, the value of Tg was rounded off to the first decimal place.

(2) Total light transmittance and haze For the films obtained in Examples and Comparative Examples, using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., trade name: NDH-5000) according to JIS K7105, Total light transmittance and haze were measured. In addition, the results determined by the following criteria are also shown.

(Total light transmittance)
◎: Total light transmittance is 92% or more ○: Total light transmittance is 90% or more and less than 92% Δ: Total light transmittance is 85% or more and less than 90% ×: Total light transmittance is less than 85%

(Haze)
◎: Haze is 0.3% or less ○: Haze exceeds 0.3%, 1.0% or less ×: Haze exceeds 1.0%

(3) Tensile elongation From the films obtained in the examples and comparative examples, MD and TD were cut out with a width of 6 mm to obtain evaluation samples. In accordance with JIS K7161, a 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. In addition, the results determined by the following criteria are also shown.
◎: Elongation is 60% or more for both MD and TD ○: Elongation is 20% or more and less than 60% for both MD and TD ×: Either MD or TD is less than 20%

(4) Tear Strength For the films obtained in Examples and Comparative Examples, the tear strength of MD and TD of the sample for evaluation was measured according to JIS K7128-2. In addition, the results determined by the following criteria are also shown.
A: Tear strength is 6.0 kg / cm or more for both MD and TD B: Tear strength is 6.0 kg / cm or more for either MD or TD X: Tear strength is less than 6.0 kg / cm for both MD and TD

(5) In-plane retardation (R _O ), thickness retardation (R _th )
About the film obtained by the Example and the comparative example, it measured using the phase difference measuring apparatus (The Oji Scientific Instruments Co., Ltd. make, brand name: KOBRA-WR). In addition, the results determined by the following criteria are also shown. Rth was calculated from the phase difference when the incident angle was 0 ° and 40 °.
A: Absolute values of R _O and R _th are both 3 nm or less. ○: Absolute values of R _O and R _th are more than 3 nm and 10 nm or less. X: Both absolute values of R _O and R _th are larger than 10 nm.

(6) Comprehensive Judgment In the evaluation judgments (1) to (5) above, all the items were excellent when it was ◯ or better, and one or more items were evaluated as x, and those that were inferior were rated as x.

<Constituent materials>
The main raw materials used in Examples 2-1 to 2-4 and Comparative Examples 2-1 to 2-2 are described below.

(Acrylic block copolymer (A))
(A-1); acrylic block copolymer (manufactured by Kuraray Co., Ltd., trade name: Clarity LA4285, density: 1.11 g / cm ³ , methyl methacrylate polymer block-butyl acrylate polymer block-methacrylic acid) Triblock copolymer composed of methyl polymer block, methyl methacrylate / butyl acrylate = 50/50 mass%, stereoregularity (triad fraction): mm (3 mol%), mr (29 mol%), rr (68 mol%), Tg: 115 ° C. (HS), −40 ° C. (SS), MFR (temperature: 230 ° C., load: 21.2 N): 31 g / 10 min, molecular weight (Mw): 8 × 10 ⁴ , Mw /Mn=1.14, average refractive index: 1.4783)

(Acrylic polymer (B))
(B-1); acrylic polymer (Sumitomo Chemical Co., Ltd., trade name: SUMIPEX MGSS, density: 1.19 g / cm ^3, methyl methacrylate = 100 wt%, stereoregularity (triad fraction): mm (11 mol%), mr (40 mol%), rr (49 mol%), Tg: 108 ° C., MFR (temperature: 230 ° C., load: 37.3 N): 10 g / 10 min, average refractive index: 1. 4913)

(Polycarbonate resin (C))
(C-1): The molar ratio of the monomer unit derived from isosorbide, which is a dihydroxy compound, and the monomer unit derived from tricyclodecane dimethanol, obtained by a method according to Japanese Patent Application Laid-Open No. 2008-024919. Is a polycarbonate copolymer of which isosorbide / tricyclodecanedimethanol = 70/30 mol%. Density: 1.36 g / cm ³ , Tg: 130 ° C., MFR (temperature: 230 ° C., load: 37.3 N): 9.6 g / 10 min, average refractive index: 1.5102, photoelastic coefficient: 12 × 10 ^{− 12} Pa ^-1

(Additive)
(O-1); Phosphite antioxidant (manufactured by ADEKA Corporation, trade name: ADK STAB PEP-36)

<Example 2-1>
As shown in Table 2, for both surface layers (I), 20 parts by mass of acrylic block copolymer (A-1) and 80 parts by mass of acrylic polymer (B-1) and an antioxidant as an additive (O-1) A composition mixed at a ratio of 0.15 parts by mass, and for the intermediate layer (II), 100 parts by mass of a polycarbonate resin (C-1) are separately provided with a vent function and a filter function. A three-layer multi-manifold of 255 ° C. is supplied to the same-direction twin-screw extruder and melt-kneaded at a resin temperature of 220 to 255 ° C. to form a layered structure of layer (I) / layer (II) / layer (I). After co-extrusion with a die, cast cooling is performed with a mirror roll at 50 ° C. having an edge pinning device, the total thickness is 15.0 μm, and each layer thickness is Layer (I) / Layer (II) / Layer (I) = 2 .5μm / 10.0μm / 2.5μm That to obtain a laminated film.
The resulting laminated film had good appearance and excellent flatness. The photoelastic coefficient was 5 × 10 ⁻¹² Pa ⁻¹ , 100 ° C., and the heat shrinkage (MD) at 100 hours was 0.5% or less. The average refractive indexes of the surface layer (I) and the intermediate layer (II) were 1.4890 and 1.5102, respectively. The results of evaluation using the laminated film are shown in Table 2.

<Example 2-2>
As shown in Table 2, in Example 2-1, for both surface layers (I), 30 parts by mass of acrylic block copolymer (A-1) and 70 parts by mass of acrylic polymer (B-1) were used. A laminated film having a total thickness of 15.0 μm and a thickness of each layer (layer (I) / layer (II) / layer (I) = 2.5 μm / 10.0 μm / 2.5 μm) was obtained in the same manner except for the change. .
The resulting laminated film had good appearance and excellent flatness. The photoelastic coefficient was 5 × 10 ⁻¹² Pa ⁻¹ , 100 ° C., and the heat shrinkage (MD) at 100 hours was 0.5% or less. The results of evaluation using the laminated film are shown in Table 2.

<Comparative Example 2-1>
As shown in Table 2, for both surface layers (I) in Example 2-1, the product name Metabrene W-377 manufactured by Mitsubishi Rayon Co., Ltd. (core-shell type having a graft layer outside the particulate rubber) In the same manner, the total thickness is 15.0 μm, except that the impact strength modifier is changed to 20 parts by mass and 80 parts by mass of the acrylic resin (B-1). A laminated film having a thickness of layer (I) / layer (II) / layer (I) = 2.5 μm / 10.0 μm / 2.5 μm was obtained.
The obtained laminated film had a high haze. The results of evaluation using the laminated film are shown in Table 2.

<Comparative Example 2-2>
As shown in Table 2, the total thickness was 15.0 μm in the same manner as in Example 2-1, except that the acrylic polymer (B-1) was changed to 100 parts by mass for both surface layers (I). A laminated film having a thickness of layer (I) / layer (II) / layer (I) = 2.5 μm / 10.0 μm / 2.5 μm was obtained.
Although the obtained laminated film was excellent in transparency, it was brittle. The results of evaluation using the laminated film are shown in Table 2.

<Example 2-3>
In Example 2-1, for the intermediate layer (II), 100 parts by mass of the polycarbonate resin (C-1) and an ultraviolet absorber (trade name: ADK STAB LA-31 manufactured by ADEKA) as an additive 1.4 The total thickness is 15.0 μm and the thickness of each layer is the same except that the composition is mixed at a ratio of 7.7 parts by mass with a part by mass and an ultraviolet absorber (trade name: Tinuvin 1577ED manufactured by BASF Japan Ltd.). A laminated film in which layer (I) / layer (II) / layer (I) = 2.5 μm / 10.0 μm / 2.5 μm was obtained.

The resulting laminated film had good appearance and excellent flatness. The glass transition temperature of the intermediate layer (II) to which the ultraviolet absorber was added was 121 ° C.
The laminated film had a light transmittance of 4.2% at a wavelength of 380 nm. Furthermore, a 100 mm square test piece (n = 3) was cut out from the laminated film, and the light transmittance after exposure to a temperature of 60 ° C. and a humidity of 90% RH for 500 hours was measured. The spectrum was almost unchanged before and after exposure, and the light transmittance at a wavelength of 380 nm was 4.3%.
Moreover, the dimensional change rate (MD) before and after being exposed to a temperature of 60 ° C. and a humidity of 90% RH for 500 hours was measured. It was less than 0.1%.

<Example 2-4>
A masking film (manufactured by Toray Film Processing Co., Ltd., trade name: Tretec 7332, thickness: 30 μm) having self-adhesiveness in the take-off process is placed on one side of the laminated film obtained in Example 2-1. It was slightly adhered with a nip roll, and was wound into a roll using a 6-inch ABS core to obtain a wound layer body with a width of 1000 mm and a winding length of 1000 m.

From Table 2, it can be confirmed that the laminated film of the present invention is a film having excellent transparency (total light transmittance, haze), small optical anisotropy, and high mechanical strength (tear strength, tensile elongation) ( Examples 2-1 and 2-2). On the other hand, those not containing the acrylic block copolymer defined in the present invention have transparency (total light transmittance, haze), optical anisotropy, and mechanical strength (tear strength, tensile elongation). It can be confirmed that any one or more characteristics are insufficient (Comparative Examples 2-1 and 2-2). Specifically, when a core-shell type impact strength modifier having a graft layer outside the particulate rubber is used instead of the acrylic block copolymer, the effect of improving the mechanical strength is insufficient. Yes, it can be confirmed that the haze is greatly deteriorated (Comparative Example 2-1). Those containing no acrylic block copolymer are excellent in transparency (total light transmittance, haze) and optically anisotropic. Although the properties are small, it can be confirmed that the mechanical strength (tear strength, tensile elongation) is insufficient (Comparative Example 2-2).

In Example 2-3, it can be confirmed that if a UV absorber is appropriately added, the spectral spectrum can be adjusted, and the light transmittance at a wavelength of 380 nm can be controlled. Further, in Example 2-4, it can be confirmed that the laminated film of the present invention can be formed into a roll-shaped wound layer body by being overwrapped with a masking film.

[Reference Examples 3-1 to 3-2, Examples 3-1 to 3-2 and Comparative Examples 3-1 to 3-2]
Next, Reference Examples 3-1 and 3-2, Examples 3-1 and 3-2, and Comparative Examples 3-1 and 3-2 will be described.

<Evaluation method>
In Reference Examples 3-1 to 3-2, Examples 3-1 to 3-2, and Comparative Examples 3-1 to 3-2, various physical properties and the like were measured and evaluated as follows.

<Evaluation of initial adhesiveness with PVA film>
Aqueous adhesive obtained by mixing 0.3 part by weight of a crosslinking agent (Nihon Gosei Co., Ltd., SPM-02) to 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 was measured. Further, the maximum peel strength in terms of coating thickness obtained by dividing the maximum peel strength (N / 20 mm width) by the coating thickness (μm) of the coat layer was evaluated based on the following criteria.
○: Maximum peel strength in terms of coating thickness is 2 N / 20 mm width or more ×: Maximum peel strength in terms of coating thickness is less than 2 N / 20 mm width

<Evaluation of tackiness>
The coated surface of the produced coating film was touched with fingers and evaluated according to the following criteria.
○: No tack ×: There is tack

<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 using a dynamic viscoelasticity measuring device “DVE-V4” (manufactured by Rheology), and was measured at 150 ° C. by a tensile method at a frequency of 10 Hz and a temperature rising 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

[Polymer used for base film]
<Acrylic resin>
As the acrylic resin, PMMA resin “SUMIPEX MGSS” manufactured by Sumitomo Chemical Co., Ltd. was used.

<Alicyclic structure-containing resin>
The molar ratio of the structural unit derived from isosorbide, which is a dihydroxy compound, and the structural unit derived from tricyclodecane dimethanol, produced by a method according to Japanese Patent Application Laid-Open No. 2008-024919 is isosorbide / tricyclodecanedimethanol = 6 / 4, an alicyclic structure-containing resin (polycarbonate resin) having a glass transition temperature of 126 ° C. was used.

[Preparation of base film]
(1) Substrate A
The acrylic resin 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 of 240 ° C.). A film having a thickness of 60 μm was produced by winding with a cast roll whose temperature was adjusted to ° C. This film is corona-treated 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, whereby acrylic resin films (hereinafter abbreviated as “base material A”) are obtained. Was made.

(2) Base material B
100 parts by weight of the polycarbonate resin as the material for the intermediate layer, 80 parts by weight of the acrylic resin (PMMA) as the material for the front and back layers, and an acrylic block copolymer (clarity LA4285, methyl methacrylate polymer block-butyl acrylate heavy) Triblock copolymer comprising polymer block-methyl methacrylate polymer block, methyl methacrylate / butyl acrylate = 50/50 mass%, Tg: 115 ° C. (HS), −40 ° C. (SS), MFR (temperature: 230 ° C., load: 21.2 N): 31 g / 10 min, molecular weight (Mw): 8 × 10 ⁴ , Mw / Mn = 1.14, average refractive index: 1.4783) composition mixed at a ratio of 20 parts by mass the respectively, 65 mm single screw extruder, then charged into a [phi] 40 mm ² screw extruder, respectively 220 ~ 240 ° C., and It is melt-kneaded at a barrel set temperature of 180 ° C to 240 ° C, coextruded from a multi-die (set temperature 240 ° C) with a width of 1350 mm and a lip gap of 0.7 mm, and then wound with a cast roll adjusted to 20 ° C. By taking the film, a film having a constitution of polycarbonate layer / acrylic layer / polycarbonate layer was produced. The film thickness of each layer was 3.5 μm / 8 μm / 3.5 μm. The 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 to produce a laminated film (abbreviated as base material B).

(3) Base material C
The polycarbonate resin as the material of the intermediate layer, the acrylic resin (PMMA) as the material for the front and back layers, respectively, 65 mm single screw extruder, then charged into a [phi] 40 mm ² screw extruder, respectively 220 ~ 240 ° C., and 180 After melt-kneading at a barrel set temperature of ℃ to 240 ℃, co-extrusion from a multi-die having a width of 1350 mm and a lip gap of 0.7 mm (set temperature of 240 ° C.), it is wound on a cast roll adjusted to 20 ° C. Thus, a film having a configuration of polycarbonate layer / acrylic layer / polycarbonate layer was produced. The film thickness of each layer was 3.5 μm / 8 μm / 3.5 μm. This 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, thereby producing a laminated film (abbreviated as substrate C).

[Reference Example 3-1]
Water-based polyurethane resin “Rezamin D-6031” (manufactured by Dainichi Seika Kogyo Co., Ltd., solid content (urethane resin) 30 wt%) 100 parts by weight of a methylol / imino group type melamine formaldehyde resin “Cymel 701” as a crosslinking agent "(Ornex Japan Co., Ltd.) 6 parts by weight, and as an additive, polyvinyl alcohol aqueous solution" Maltite 150 "(Taiseka Pharmaceutical Co., Ltd., solid content (polyvinyl alcohol) 15 wt%) is solid. A urethane coating composition was prepared by blending so as to be 3% by weight in terms of a fraction, mixing using ion-exchanged water as a diluent solvent so that the solid content was 20% by weight, and mixing. After coating this coating composition onto the substrate A using a bar coater # 8, the urethane coating layer having the thickness shown in Table 1 was formed on the substrate A by drying at 100 ° C. for 1 minute. A coating film of the present invention was produced. Various evaluation was implemented about this coating film.

[Reference Example 3-2]
In Reference Example 3-2, the water-based urethane resin was changed to a water-based polyurethane resin “Yukot UA-368” (manufactured by Sanyo Chemical Co., Ltd., solid content (urethane resin) 50 wt%), and a melamine resin cross-linking agent A coating film was prepared in the same manner except that the amount of was changed to 20 parts by weight. Various evaluation was implemented about this coating film.

[Example 3-1]
A coating film was prepared in the same manner as in Example 3-2 except that the base material B was used instead of the base material A. Various evaluation was implemented about this coating film.

[Example 3-2]
A coating film was produced in the same manner as in Example 3-4 except that the substrate C was used instead of the substrate A. Various evaluation was implemented about this coating film.

[Comparative Example 3-1]
A coating film was prepared in the same manner as in Reference Example 3-2 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 3-2]
A coating film was produced in the same manner as in Reference Example 3-2 except that the crosslinking agent was changed to 40 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.

Table 3 shows the evaluation results of the coating films and the thicknesses of the formed coating layers in Reference Examples 3-1 to 3-2, Examples 3-1 to 3-2 and Comparative Examples 3-1 to 3-2. .

In Table 3, the numerical value in parentheses in the column “number of parts of crosslinking agent” indicates the weight part of the crosslinking agent with respect to 100 parts by weight of the water-based urethane resin.

In Comparative Example 3-1, in which an oxazoline-based cross-linking agent was used with respect to the acrylic base material, the adhesion and cross-linking properties were inferior. On the other hand, in Comparative Example 3-2 in which the amount of the crosslinking agent was increased, the crosslinkability was improved, but no improvement in adhesion was observed. Therefore, it can be seen that when an oxazoline-based crosslinking agent is used, it is difficult to achieve both adhesion and crosslinking properties.
On the other hand, Reference Examples 3-1 and 3-2 using a melamine resin-based cross-linking agent exhibited excellent properties in adhesion and cross-linking. The effects are also exhibited in Examples 3-1 and 3-2 using a laminated film as a base material.

Claims

A laminated optical film having one or more layers each having a polycarbonate resin as a main component and an acrylic resin as a main component,
The polycarbonate resin is a polycarbonate resin containing a structural unit derived from a dihydroxy compound represented by the following formula (1):
A laminated optical film, wherein the laminated optical film has a total thickness of 50 μm or less and a tear strength measured according to JIS K7128-2 of 4.0 kg / cm or more.
The laminated optical film according to claim 1, wherein the polycarbonate resin further contains a structural unit derived from tricyclodecane dimethanol represented by the following formula (2).
It has at least three layers of an intermediate layer and front and back layers, the intermediate layer is a layer mainly composed of the polycarbonate resin, and the front and back layers are layers mainly composed of the acrylic resin. The laminated optical film according to claim 1 or 2.
It has at least three layers of an intermediate layer and front and back layers, the intermediate layer is a layer mainly composed of the acrylic resin, and the front and back layers are layers mainly composed of the polycarbonate resin. The laminated optical film according to claim 1 or 2.
5. The laminated optical film has a total thickness of 20 μm or less, and a tear strength measured in accordance with JIS K7128-2 of 5.0 kg / cm or more. Laminated optical film.
6. The laminated optical system according to claim 1, wherein the ratio of the total thickness of the layer mainly composed of the polycarbonate resin to the total thickness of the laminated optical film is 20% or more and 95% or less. the film.
6. The laminated optical system according to claim 1, wherein the ratio of the thickness of the layer mainly composed of the polycarbonate resin to the total thickness of the laminated optical film is more than 50% and 80% or less. the film.
The laminated optical film according to any one of claims 1 to 7, wherein the layer mainly composed of the acrylic resin contains a flexibility modifier.
The softness modifier includes at least one monomer unit derived from methacrylic acid ester and acrylic acid ester and includes a hard segment (HS) having a glass transition temperature of 100 ° C. or higher, and at least methacrylic acid ester and acrylic acid. The laminate according to claim 8, which is an acrylic block copolymer having a soft segment (SS) containing one kind of monomer units derived from an ester and having a glass transition temperature of 20 ° C. or lower. Optical film.
The laminated optical film according to any one of claims 1 to 9, further comprising a coat layer made of an aqueous urethane resin composition containing a urethane resin and a melamine resin crosslinking agent on at least one surface of the laminated optical film.
The laminated optical film according to claim 10, wherein the melamine resin-based crosslinking agent contains an imino group-type and / or methylol group-type melamine resin.
A polarizing plate comprising a structure in which a polarizing film is bonded to the coating layer of the laminated optical film according to claim 10 or 11 via an adhesive layer.
The polarizing plate according to claim 12, wherein the adhesive layer is made of a water-based adhesive.
A liquid crystal display device comprising the polarizing plate according to claim 12.