JP6587901B2 - Uniaxially stretched multi-layer easily adhesive film and optical member using the same - Google Patents

Description

  The present invention relates to a uniaxially stretched multi-layer easily adhesive film and an optical member using the same.

  Liquid crystal display devices (LCDs) used in portable terminals such as smartphones and tablet terminals adjust the amount of light emitted from the light source by using a liquid crystal panel with polarizing plates on both sides of the liquid crystal cell. The display is possible. As a polarizing plate to be bonded to a liquid crystal cell, an absorption polarizing plate generally called a light absorption type dichroic linear polarizing plate is used. Polarized light obtained by protecting PVA containing iodine with triacetyl cellulose (TAC). Plates are widely used.

  Such an absorption-type polarizing plate transmits polarized light in the transmission axis direction and absorbs most of the polarized light in the direction orthogonal to the transmission axis, so that about 50% of non-polarized light emitted from the light source device absorbs this absorption. It has been pointed out that the light utilization efficiency is reduced by being absorbed by the mold polarizing plate. Therefore, in order to effectively use the polarized light in the direction orthogonal to the transmission axis, a configuration in which a reflective polarizer called a brightness enhancement film (reflection polarization brightness enhancement film) is used between the light source and the liquid crystal panel has been studied. As an example of such a reflective polarizer, a polymer-type multilayer laminated film using optical interference has been studied (for example, Patent Document 1).

With the widespread use of portable terminals, there is a growing need for thinner display terminals, and the thickness of the display terminals has been made thinner than members such as reflective polarizing brightness enhancement films, diffusion films, prism films, and light guide plates installed inside displays. Therefore, a composite optical film capable of integrating these functions is desired.
As an example of such a composite optical film, as described in Patent Document 2 and the like, a reflection polarization type brightness enhancement film with a prism layer in which a prism structure is formed on a reflection polarization type brightness enhancement film has been proposed. However, when an optical layer such as a prism layer or a diffusion layer is formed on such a reflective polarization type brightness enhancement film, the adhesion may not be sufficient. For example, when the optical layer is cut and placed on a display terminal, Chipping or peeling may occur.

  On the other hand, in the case of a normal prism film that does not use a reflective polarization type brightness enhancement film as a base material, a solvent-free UV curable resin is applied to a polyethylene terephthalate (PET) film base material as a general method for forming a prism layer. In this case, the adhesion is enhanced by providing an easy-adhesion layer on the PET film substrate. Such an easy-adhesion layer is applied in the process of forming a PET film, and a thermosetting cross-linking agent is added to a binder component such as a polyester-based resin, an acrylic-based resin, or a urethane-based resin so that the base material and the prism layer are formed. Increases adhesion. In particular, in a solvent-free UV curable resin such as a prism layer, an improvement in adhesion due to dissolution of the base material by an organic solvent cannot be expected, so that the composition of the easy adhesion layer is extremely limited (Patent Documents 3 to 6). ).

JP-T 9-507308 Japanese National Patent Publication No. 9-506985 JP 2008-36868 A JP 2008-189868 A Japanese Patent Laid-Open No. 11-271503 JP 2000-141574 A

  When an easy-adhesion layer is coated on a reflective polarization-type brightness enhancement film, a polyester resin other than PET is often used as the reflective polarization-type brightness enhancement film, and further within the film forming process in order to develop reflective polarization performance. In many cases, it does not have a crystallization step, so that, for example, the reactivity of the thermosetting cross-linking agent becomes low. It may be difficult to secure enough.

  Moreover, since the surface layer of the reflective polarization type brightness enhancement film is often formed of a polyester resin other than PET and the surface layer is easily damaged, it is necessary to bond a protective film or the like during the process. Yes, the protective film has also ensured the winding property. However, in recent years, it has been demanded not to use such a protective film from the viewpoint of cost reduction, and in addition to improving the adhesion with the optical layer described above, it is desired to further secure the winding property of the film itself. . However, even with regard to the winding property, even when the surface layer is formed of a polyester resin other than PET, the same easy-adhesion layer (especially with particles added) as in the case where the substrate is a PET film is used. It is difficult to secure.

An object of the present invention is a uniaxially stretched multilayer laminate easy-adhesive film having high adhesion between an optical layer such as a prism layer and a diffusion layer formed on the film and a film in addition to reflective polarization performance in a multilayer film And providing an optical member using the same.
A second object of the present invention is to provide a uniaxially stretched multilayer laminate easy-adhesive film having a winding property in addition to the above, and an optical member using the same.

  As a result of intensive studies to solve the above problems, the present inventors have made a case of a multilayer laminated film having a polyethylene naphthalate polymer as a high refractive index layer and a copolymer polyester having a high glass transition temperature as a low refractive index layer. By limiting the composition that can be used for the easy-adhesion layer compared to the case of a PET film that is often used as the base material of the prism film, and by focusing on the aspect of the outermost layer of the multilayer laminated film, the prism layer The present inventors have found that a uniaxially stretched multilayer laminate easy-adhesion film having high adhesion between the optical layer and the film and the like and an optical member using the same can be obtained, and the present invention has been completed.

That is, the present invention employs the following configuration.
1. A uniaxially stretched multi-layer easily adhesive film in which the first layer and the second layer are alternately laminated,
1) The first layer is a layer mainly composed of polyester, and contains ethylene naphthalate units in a range of 50 mol% or more and 100 mol% or less based on the repeating units constituting the polyester,
2) The second layer is a layer mainly composed of a copolyester, and the copolyester has a glass transition temperature of 85 ° C. or higher and an average refractive index of 1.55 to 1.65. A copolymerized polyester comprising a 2,6-naphthalenedicarboxylic acid component, an ethylene glycol component, and a trimethylene glycol component as a copolymerization component,
3) The total number of alternating layers of the first layer and the second layer is 101 or more, and at least one surface has an outermost layer having a thickness of 5 to 50 μm composed of the second layer,
4) It has an easy-adhesion layer having a thickness of 0.01 to 0.50 μm on the outer surface of at least one of the outermost layers, and the easy-adhesion layer contains polyurethane resin and particles having an average particle diameter of 0.4 to 0.8 μm. 0.5 to 6.0% by weight based on the weight of the easy adhesion layer,
5) The total film thickness including the easy-adhesion layer is 20 to 150 μm,
6) A uniaxially stretched multilayer laminate easy-adhesion film in which the average value of the degree of polarization (P) calculated by the following formula (1) is 5% at an interval of 5 nm in a wavelength range of 380 to 780 nm.
Degree of polarization (P) = {(Ts−Tp) / (Tp + Ts)} × 100 (1)
(In formula (1), Tp represents the average transmittance of P-polarized light at each wavelength, and Ts represents the average transmittance of S-polarized light at each wavelength.)
2. 2. The uniaxially stretched multilayer laminate easy-adhesive film as described in 1 above, wherein the urethane resin of the easy-adhesive layer is a polyester-based polyurethane resin formed from a polyester polyol and a polyisocyanate.
3. 3. The uniaxially stretched multilayer laminate easy-adhesive film according to 1 or 2 above, wherein the easy-adhesion layer further contains a crosslinking agent containing a carbodiimide group or an oxazoline group .
4 . The uniaxially stretched multilayer laminate easily adhesive film according to any one of the above 1 to 3, wherein the content of the trimethylene glycol component is 3 to 50 mol% of all diol components constituting the copolymer polyester of the second layer. .
5 . The uniaxially stretched multilayer laminate easily adhesive film according to any one of the above 1 to 4 , wherein the polyester of the first layer contains a terephthalic acid component in a range of 20 mol% or less based on the total dicarboxylic acid component.
6 . 6. The uniaxially stretched multilayer laminated adhesive film as described in any one of 1 to 5 above, which is used as a brightness improving member or a reflective polarizing plate.
7 . 7. An optical member in which a prism layer or a diffusion layer is laminated on at least one surface of the uniaxially stretched multilayer laminated easy-adhesive film according to any one of 1 to 6 above.

  According to the present invention, in a multilayer film, in addition to the reflective polarization performance, a uniaxially stretched multilayer laminate adhesive film having high adhesion between the optical layer such as a prism layer and a diffusion layer formed on the film and the film And an optical member using the same can be provided.

It is a schematic sectional drawing of a liquid crystal display.

  The uniaxially stretched multilayer laminated easily adhesive film of the present invention has an easily adhesive layer on at least one surface of the uniaxially stretched multilayer laminated film in which the first layer and the second layer are alternately laminated. Each component of the present invention will be described in detail below, such as the resin and characteristics, polarization performance, and the like.

[Uniaxially stretched multilayer laminated film]
The uniaxially stretched multilayer laminated film in the present invention may be any film as long as its structure is adjusted so as to satisfy the degree of polarization described later. For example, the first layer has a relatively higher refractive index characteristic than the second layer. The layer and the second layer are layers having lower refractive index characteristics than the first layer. By using the following specific types of polyester for each layer, the relationship between the refractive indexes is expressed.

In the present invention, the uniaxial stretching direction is referred to as the X direction, the direction perpendicular to the X direction in the film plane is referred to as the Y direction, and the direction perpendicular to the film plane is referred to as the Z direction.
The P-polarized light in the present invention is defined as a polarized light component parallel to an incident surface including a uniaxially stretched direction (X direction) with a film surface as a reflective surface in a uniaxially stretched multilayer laminated film. The S-polarized light in the present invention is defined as a polarized light component perpendicular to an incident surface including a uniaxially stretched direction (X direction) in a uniaxially stretched multilayer laminated film with the film surface as a reflective surface.
In the present invention, the refractive index in the stretching direction (X direction) may be described as nX, the refractive index in the direction orthogonal to the stretching direction (Y direction) as nY, and the refractive index in the film thickness direction (Z direction) as nZ. .

[First layer]
The 1st layer which comprises the uniaxial stretching multilayer lamination easy-adhesion film of this invention is a layer which contains polyester as a main structural component. Here, the main component is preferably 70% by weight or more, more preferably 80% by weight or more, and still more preferably 90% by weight or more based on the weight of the first layer. The polyester contains an ethylene naphthalate unit in a range of 50 mol% or more and 100 mol% or less based on the repeating unit constituting the polyester.

(First dicarboxylic acid component)
The polyester of the first layer contains a naphthalenedicarboxylic acid component as a dicarboxylic acid component constituting it, and the content thereof is 50 mol% or more and 100 mol% or less based on the dicarboxylic acid component constituting the polyester. Examples of the naphthalene dicarboxylic acid component include components derived from 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, or combinations thereof, and derivatives thereof. In particular, 2,6-naphthalenedicarboxylic acid. An acid or a derivative component thereof is preferably exemplified. The content of the naphthalenedicarboxylic acid component is preferably 70 mol% or more, more preferably 90 mol% or more. Further, the content of the naphthalenedicarboxylic acid component is preferably less than 100 mol%, more preferably 98 mol% or less, still more preferably 95 mol% or less.

  In this way, by using a polyester containing a naphthalenedicarboxylic acid component as a main component, it is possible to realize a birefringence characteristic having a high uniaxial orientation while exhibiting a high refractive index in the X direction. The refractive index difference can be increased, contributing to high polarization. On the other hand, if the proportion of the naphthalenedicarboxylic acid component is less than the lower limit, the amorphous characteristics increase, and the refractive index nX in the stretching direction (X direction) and the refractive index in the non-stretching direction (Y direction) in the stretched film. Since the difference from nY becomes small, sufficient reflection performance may not be obtained for the P-polarized component.

  In addition to the naphthalene dicarboxylic acid component, the dicarboxylic acid component constituting the first layer polyester may further contain other dicarboxylic acid components as long as the object of the present invention is not impaired. Includes a terephthalic acid component, an isophthalic acid component, a component represented by the following formula (A), etc., among which a terephthalic acid component or a component represented by the following formula (A) is preferable.

(In the formula (A), R ^A represents an alkylene group having 2 to 10 carbon atoms)

Regarding the component represented by the formula (A), R ^A represents an alkylene group having 2 to 10 carbon atoms. Examples of the alkylene group include an ethylene group, a trimethylene group, an isopropylene group, a tetramethylene group, a hexamethylene group, and an octamethylene group, and an ethylene group is particularly preferable.
The component represented by the formula (A) is preferably 6,6 ′-(ethylenedioxy) di-2-naphthoic acid, 6,6 ′-(trimethylenedioxy) di-2-naphthoic acid, 6 '-(butylenedioxy) di-2-naphthoic acid and the like are mentioned. Among them, those having an even number of carbon atoms of R ^A in the formula (A) are preferable, and in particular, 6,6'-(ethylenedioxy) Di-2-naphthoic acid is preferred.

  These other dicarboxylic acid components are preferably 0 to 50 mol%, more preferably more than 0 mol% and 50 mol% or less, more preferably 2 to 30 mol, based on the dicarboxylic acid component constituting the polyester. %, Particularly preferably 5 to 10 mol%. These other dicarboxylic acid components may be used in combination, and in that case, the total content is in the above-mentioned range.

(Diol component)
As the diol component constituting the polyester of the first layer, an ethylene glycol component is used, and the content thereof is preferably 80 mol% or more and 100 mol% or less, more preferably based on the thiol component constituting the polyester. It is 85 mol% or more and 100 mol% or less, more preferably 90 mol% or more and 100 mol% or less, and particularly preferably 90 mol% or more and 98 mol% or less. When the ratio of the diol component is less than the lower limit, the above-described uniaxial orientation may be impaired.

  As the diol component constituting the polyester of the first layer, in addition to the ethylene glycol component, another diol component may be further contained within a range not impairing the object of the present invention. Examples of such other diol component include trimethylene glycol, tetra Examples include methylene glycol, cyclohexane dimethanol, and diethylene glycol.

(First layer polyester)
The melting point of the polyester used for the first layer is preferably in the range of 220 to 290 ° C, more preferably in the range of 230 to 280 ° C, and still more preferably in the range of 240 to 270 ° C. The melting point can be determined by measuring with DSC. When the melting point is in such a range, the melt extrusion tends to be facilitated, and the mechanical characteristics and refractive index characteristics of the film tend to be improved. If the melting point of the polyester exceeds the upper limit value, fluidity may be inferior when melt-extruded and molded, and discharge and the like may be made uneven. On the other hand, if the melting point is less than the lower limit, the film forming property is excellent, but the mechanical properties of the polyester are liable to be impaired, and the refractive index properties of the present invention tend not to be exhibited.

  The glass transition temperature (hereinafter sometimes referred to as Tg) of the polyester used for the first layer is preferably 80 to 120 ° C, more preferably 82 to 118 ° C, still more preferably 85 to 118 ° C, and particularly preferably. It exists in the range of 100-115 degreeC. When Tg is in this range, the heat resistance and dimensional stability are excellent, and the refractive index characteristics of the present invention are easily exhibited. Such melting point and glass transition temperature can be adjusted by controlling the kind and amount of copolymerization component and diethylene glycol as a by-product.

By applying uniaxial stretching using the polyester as described above for the first layer, the refractive index nX in the X direction of the first layer preferably exhibits a high refractive index characteristic such as preferably 1.80 to 1.90. be able to. When the refractive index in the X direction in the first layer is sufficiently high, for example, preferably in the above range, the refractive index difference from the second layer becomes large, and higher reflective polarization performance can be exhibited.
The difference between the refractive index nY after uniaxial stretching in the Y direction and the refractive index nZ after uniaxial stretching in the Z direction is preferably 0.05 or less.

[Second layer]
The 2nd layer which comprises the uniaxially stretched multilayer lamination easy-adhesion film of this invention has a glass transition temperature of 85 degreeC or more as a main structural component, and an average refractive index is 1.55-1.65. It is a layer containing polyester. Here, the main component is preferably 70% by weight or more, more preferably 80% by weight or more, and still more preferably 90% by weight or more based on the weight of the second layer.

(Copolymerized polyester of the second layer)
The glass transition temperature of the copolyester forming the second layer is 85 ° C. or higher, preferably 90 ° C. or higher, and preferably less than 120 ° C. When the Tg is within such a range, the heat resistance tends to be excellent, and the decrease in the degree of polarization tends to be further suppressed. Further, the birefringence of the second layer tends to be more easily suppressed, and the effect of improving the reflection performance can be enhanced. When the glass transition temperature of the copolyester of the second layer is less than the lower limit, heat resistance (particularly heat resistance at 90 ° C.) may not be obtained sufficiently, and when a process such as heat treatment near the temperature is included In addition, the haze increases due to crystallization or embrittlement of the second layer, which may be accompanied by a decrease in the degree of polarization. In addition, when the glass transition temperature of the copolymer polyester of the second layer is too high, the polyester of the second layer may also be birefringent due to stretching at the time of stretching, and accordingly, refraction with the first layer in the stretching direction. The rate difference is reduced, and the reflection performance may be reduced.

  The average refractive index of the copolyester of the second layer needs to be 1.55 to 1.65, and is preferably 1.58 or more and 1.60 or less. The average refractive index of the copolyester of the second layer is adjusted according to the refractive index in the direction (Y direction) perpendicular to the stretching direction of the first layer polyester. The average refractive index of the second layer is determined by melting the copolymer polyester forming the second layer alone and extruding it from a die to create an unstretched film in the uniaxial direction (the glass transition temperature of the copolymer polyester). A uniaxially stretched film was made by stretching 5.5 times at + 20 ° C., and the refractive index at a wavelength of 633 nm using a metricon prism coupler in each of the X, Y, and Z directions of the obtained film. And the average value thereof is defined as the average refractive index.

Further, the copolyester of the second layer is preferably optically isotropic. Here, the optical isotropy in the present invention means that the refractive index difference between the two directions of the refractive index in the X direction, the Y direction, and the Z direction is 0.05 or less, preferably 0.03 or less. Say.
Since the second layer has such an average refractive index, and preferably is an optically isotropic material having a small difference in refractive index in each direction even by stretching, the layer after stretching between the first layer and the second layer A refractive index characteristic with a large refractive index difference in the X direction and a small refractive index difference between layers in the Y direction can be obtained at the same time, and the polarization performance can be further enhanced, which is preferable.

Examples of the copolyester forming the second layer include copolyethylene terephthalate, copolyethylene naphthalene dicarboxylate, and blends thereof. Examples of the dicarboxylic acid copolymer component include an isophthalic acid component, naphthalenedicarboxylic acid component in the case of copolymerized polyethylene terephthalate, and a terephthalic acid component in the case of copolymerized polyethylene naphthalene dicarboxylate.
The copolymer polyester forming the second layer is a diol-based copolymer component such as an aliphatic diol component such as a trimethylene glycol component, a tetramethylene glycol component or a diethylene glycol component, or an alicyclic diol such as a cyclohexane dimethanol component. You may contain a component.
Among these, it is particularly preferable to include a trimethylene glycol component. When the trimethylene glycol component is included, the elasticity of the layer structure increases and delamination does not easily occur.

The trimethylene glycol component is preferably 3 to 50 mol% of the total diol component constituting the copolymer polyester of the second layer. By being in this range, the interlayer adhesion between the first layer and the second layer can be increased, and a desired refractive index and Tg can be easily obtained. The amount of such component is more preferably 5 to 40 mol%, more preferably 10 to 40 mol%, and particularly preferably 10 to 30 mol%. If the content of the trimethylene glycol component is less than the lower limit, it tends to be difficult to ensure interlayer adhesion, and if it exceeds the upper limit, it tends to be difficult to obtain a resin having a desired refractive index and glass transition temperature.
The melting point of the copolyester used in the second layer is preferably in the range of 220 to 290 ° C, more preferably in the range of 230 to 280 ° C, and still more preferably 240 to 240 ° C, from the viewpoints of melt extrudability and film forming properties. It is in the range of 270 ° C. The melting point can be determined by measuring with DSC.

[Outermost layer]
The uniaxially stretched multilayer laminated film in the present invention has an outermost layer having a thickness of 5 to 50 μm composed of the second layer on at least one surface, and the thickness is preferably 5 to 45 μm, more preferably 7 to 20 μm, and still more preferably. Is 5-15 μm. In the present invention, adhesion to the optical layer can be achieved by having such an outermost layer. When the thickness of the outermost layer composed of the second layer is less than the lower limit, the adhesion between the optical layer such as the prism layer and the diffusion layer and the uniaxially stretched multilayer laminate easy-adhesion film is insufficient, and the optical layer is easily peeled off. . The upper limit of the outermost layer thickness is preferably thick from the viewpoint of improving adhesion, but is preferably within the above-mentioned range from the viewpoint of manufacturing and from the viewpoint of thinning the entire uniaxially stretched multilayer laminated film. .

In the present invention, as a mechanism for improving optical layer adhesion by making the second layer having a constant thickness the outermost layer, the outermost layer composed of the second layer has a cushioning effect, and the optical layer and the uniaxially stretched multi-layer laminate easy adhesion It is considered that a part of the stress applied to the interface with the film is relaxed, whereby the peel strength of the optical layer is increased and the adhesion is improved. Therefore, as described above, this effect is not sufficiently exhibited unless the outermost layer thickness is less than the lower limit.
The outermost layer may be one whose layer thickness is adjusted by the slit design during the production of the uniaxially stretched multilayer laminated film, or may be further laminated in a separate step after the laminated film is produced. In addition, when increasing the number of layers of the alternating laminate using a doubling method described later, an intermediate layer (hereinafter sometimes referred to as an internal thick film layer) in which the buffer layer is located inside the uniaxially stretched multilayer laminate film; The outermost layer is preferably disposed.

  In the present invention, when increasing the number of laminated uniaxially stretched multilayer laminate films, in the initial stage of production of the uniaxially stretched multilayer laminate film, thick film layers (thickness adjustments) at both ends in the lamination direction of 101 or more alternating laminates A layer or a buffer layer), and then increasing the number of stacked layers by doubling is preferably used. For example, doubling is a technique in which a 101-layer alternating laminate is first created, and this is divided into two, three, or four parts. When the first alternating laminate is made into one block, The number of stacked blocks is called the doubling number. Such a doubling process can be performed using a branch block called a layer doubling block.

  When the doubling number is 2 or more, two buffer layers existing at both ends in the stacking direction of the first alternating laminate are laminated by doubling and arranged in the middle of the alternate laminate after doubling. Called. On the other hand, the buffer layer finally disposed on the outermost layer by doubling corresponds to the outermost layer in the present invention. Due to the presence of the intermediate layer inside the alternating laminate, the thickness of each layer constituting the first layer and the second layer can be easily adjusted without affecting the polarization function, and the reflection performance is further improved. Can do. In the present invention, when the buffer layer or the intermediate layer is disposed, the composition is preferably the same as the second layer. When the polyester forming the first layer is used for the buffer layer, physical durability such as easy tearing and easy cracking may be reduced.

[Easily adhesive layer]
The uniaxially stretched multilayer laminate easy-adhesion film of the present invention has an easy-adhesion layer having a thickness of 0.01 to 0.50 μm on the outer surface of the outermost layer composed of the second layer. And this easily bonding layer contains a polyurethane resin, and contains 0.1-6.0 weight% of particles with an average particle diameter of 0.4-0.8 micrometer with respect to the weight of this easily bonding layer. The uniaxially stretched multilayer laminate easily adhesive film of the present invention has a thick film layer composed of the composition of the second layer as the outermost layer of the uniaxially stretched multilayer laminate film, and further on the outer surface of the outermost layer composed of the second layer. Adhesion with an optical layer such as a prism layer can be enhanced by having an easy-adhesion layer described later. The possible mechanism is described above. It is difficult to reduce the peeling of the optical layer to a practical level with only one of the outermost layer and the easily adhesive layer. Here, the combination of the outermost layer and the easy-adhesion layer may be provided on at least one surface of the uniaxially stretched multilayer laminate easy-adhesion film, and may be provided on both surfaces.

(Polyurethane resin)
The polyurethane resin of the easy-adhesion layer in the present invention is preferably one that can be dissolved, emulsified or dispersed in water. Here, the polyurethane resin includes a polyol, a polyisocyanate, a chain extender, a crosslinking agent, and the like. Among these, a polyester polyurethane resin formed from a polyester polyol and a polyisocyanate is preferable. By using a polyester-based polyurethane resin, the urethane component expresses higher adhesion to an optical layer such as a prism layer due to its high polarity, and the polyester component is higher than the outermost layer consisting of the second layer. The adhesiveness is expressed, and as a result, the higher adhesiveness between the uniaxially stretched multilayer laminated film and the optical layer is expressed.

  The polyester polyol is produced by dehydration condensation of a polybasic acid component and a polyhydric alcohol component. Polybasic acid components include terephthalic acid component, isophthalic acid component, phthalic acid component, phthalic anhydride component, 2,6-naphthalenedicarboxylic acid component, 1,4-cyclohexanedicarboxylic acid component, adipic acid component, sebacic acid component, tri A merit acid component, a pyromellitic acid component, a dimer acid component, a 5-sodium sulfoisophthalic acid component, etc. are mentioned. It is synthesized using one or more of these acid components. In addition, an unsaturated polybasic acid component such as maleic acid, itaconic acid or the like, or a hydroxycarboxylic acid such as p-hydroxybenzoic acid may be used in a slight amount. Polyhydric alcohol components include ethylene glycol, 1,4-butanediol, diethylene glycol, dipropylene glycol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, xylene glycol, dimethylolpropane, poly (ethylene oxide) ) Glycol, poly (tetramethylene oxide) glycol and the like. Moreover, although these monomers are mentioned, it is not limited to these. Two or more of these monomers can be used for copolymerization.

Examples of the polyisocyanate include tolylene diisocyanate, phenylene diisocyanate, 4,4′-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, 4,4′-dicyclohexylmethane diisocyanate, isophorone diisocyanate, and the like.
Examples of chain extenders or crosslinking agents include ethylene glycol, propylene glycol, diethylene glycol, trimethylolpropane, hydrazine, ethylenediamine, diethylenetriamine, triethylenetetramine, 4,4′-diaminodiphenylmethane, 4,4′-diaminodicyclohexylmethane, Water etc. are mentioned.

The content of the polyurethane resin used in the easy-adhesion layer is preferably 10 to 99 based on the weight of the easy-adhesion layer (hereinafter sometimes referred to as the weight of the solid content of the easy-adhesion layer or the easy-adhesion layer composition). 0.5% by weight, more preferably 20 to 95% by weight, still more preferably 30 to 90% by weight. Thereby, there exists a tendency for adhesiveness to become higher, and it can contain another component. If the content is less than the lower limit, the adhesion improving effect tends to be low. On the other hand, if the content exceeds the upper limit, it tends to be difficult to contain particles, a crosslinking agent, and other additives.
The polyurethane resin of the present invention does not need to be one type, and may be a mixture of several types. In that case, what is necessary is just to make it a total content be the above-mentioned content range.

(particle)
The second layer in the present invention is preferably optically isotropic in order to increase the degree of polarization. As a method for increasing the isotropic property, the second layer is made non-orientated or is heat-fixed for production. The method of not performing is taken. Therefore, when an easy-adhesion layer is further provided on the outermost surface layer, the easy-adhesion layer can be easily mixed with the copolymerized polyester forming the second layer. Particles added to the adhesive layer sink into the outermost layer by about 0.1 to 0.2 μm. For this reason, it is necessary to add the particle | grains of the magnitude | size of the limited range with an average particle diameter of 0.4-0.8 micrometer to an easily bonding layer. By setting it as the magnitude | size of this range, the slipperiness in the state which the sinking generate | occur | produced can be ensured. If the average particle size is less than 0.4 μm, no slipperiness can be obtained no matter how much it is added due to sinking. On the other hand, even if the average particle size is greater than 0.8 μm, the number of particles per weight is the same. It becomes less and it becomes difficult to obtain easy slipperiness.

  The content of the particles used in the easy-adhesion layer is 0.5 to 6.0% by weight based on the weight of the easy-adhesion layer (hereinafter sometimes referred to as the solid content of the easy-adhesion layer or the easy-adhesion layer composition). Preferably, it is 1.0 to 4.0 weight%, More preferably, it is 2.0 to 3.0 weight%. Combined with this aspect of the average particle diameter, sufficient winding properties can be obtained. If the content of the particles is less than the lower limit, sufficient winding properties will not be exhibited. On the other hand, even if the particle content is increased from the upper limit, the effect of further improving the winding properties cannot be obtained, and the easy-adhesion layer is transparent. Tend to decrease.

  The material of the particles can be organic or inert particles, calcium carbonate particles, calcium oxide particles, aluminum oxide particles, kaolin particles, silicon oxide particles, zinc oxide particles as inorganic particles, crosslinked acrylic resin particles as organic particles, Examples thereof include crosslinked polystyrene resin particles, melamine resin particles, and crosslinked silicone resin particles. In the case of installing the easy-adhesion layer by applying a water-based coating liquid, organic particles having a light specific gravity are generally more preferable than inorganic particles for the purpose of preventing sedimentation of particles in the coating liquid. More favorable winding property is obtained by preventing sedimentation using organic particles.

(Crosslinking agent)
It is preferable that the easily bonding layer in this invention contains the crosslinking agent containing a carbodiimide group or an oxazoline group further. Here, to be precise, the easy-adhesion layer contains a crosslinking agent after at least a part of the crosslinking groups has reacted. That is, in this case, the easy-adhesion layer is formed by applying a coating liquid containing a cross-linking agent and other components for forming the easy-adhesion layer, and in the formation process, the cross-linking agent forms a cross-linked structure, Therefore, in the easy-adhesion layer, the crosslinking agent has an aspect in which at least a part of the crosslinking groups has reacted. In the present invention, the expression “the easy-adhesion layer contains a crosslinking agent” is used as described above for the sake of convenience, including such an aspect. By containing a crosslinking agent, the effect of improving the adhesion to an optical layer such as a prism layer can be enhanced. As a kind of the crosslinking agent, a crosslinking agent containing a carbodiimide group or an oxazoline group, in which the reaction proceeds at a temperature lower than about 140 ° C. in order to keep the second layer in a non-oriented state, is preferable.

  As the crosslinking agent containing a carbodiimide group, a compound containing a carbodiimide group (carbodiimide compound) is preferably used. Examples of the carbodiimide compound include a monocarbodiimide compound and a polycarbodiimide compound. Examples of the monocarbodiimide compound include dicyclohexylcarbodiimide, diisopropylcarbodiimide, dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, t-butylisopropylcarbodiimide, diphenylcarbodiimide, di-t-butylcarbodiimide, and di-β-naphthylcarbodiimide. . As the polycarbodiimide compound, those produced by a conventionally known method can be used. For example, it can be produced by synthesizing an isocyanate-terminated polycarbodiimide by a condensation reaction involving decarbonization of diisocyanate.

  Examples of the diisocyanate that is a raw material for synthesizing a polycarbodiimide compound include isomers of toluylene diisocyanate, aromatic diisocyanates such as 4,4-diphenylmethane diisocyanate, aromatic aliphatic diisocyanates such as xylylene diisocyanate, isophorone diisocyanate and 4 , 4-dicyclohexylmethane diisocyanate, alicyclic diisocyanates such as tetramethylxylylene diisocyanate, hexamethylene diisocyanate, and aliphatic diisocyanates such as 2,2,4-trimethylhexamethylene diisocyanate. From the problem of yellowing, aromatic aliphatic diisocyanates, alicyclic diisocyanates, and aliphatic diisocyanates are preferred.

The diisocyanate may be used with a molecule controlled to an appropriate degree of polymerization using a compound that reacts with a terminal isocyanate such as monoisocyanate. Examples of monoisocyanates for sealing the ends of polycarbodiimide and controlling the degree of polymerization thereof include phenyl isocyanate, toluylene isocyanate, dimethylphenyl isocyanate, cyclohexyl isocyanate, butyl isocyanate, and naphthyl isocyanate. In addition, a compound having an OH group, NH ₂ group, COOH group, or SO ₃ H group can be used as a terminal blocking agent.

As the crosslinking agent containing an oxazoline group, a compound containing an oxazoline group is preferably used. This can be produced by polymerizing an addition-polymerizable oxazoline group-containing monomer alone or with other monomers.
As addition-polymerizable oxazoline group-containing monomers, 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline. These may be used alone or in a mixture of two or more.

  Among these, 2-isopropenyl-2-oxazoline is preferred because it is easily available industrially. The other monomer is not limited as long as it is a monomer copolymerizable with an addition-polymerizable oxazoline group-containing monomer, such as alkyl acrylate, alkyl methacrylate (the alkyl group includes a methyl group, an ethyl group, an n-propyl group, an isopropyl group, (meth) acrylic acid esters such as n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group, cyclohexyl group); acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, Unsaturated carboxylic acids such as styrenesulfonic acid and its salts (sodium salt, potassium salt, ammonium salt, tertiary amine salt, etc.); Unsaturated nitriles such as acrylonitrile, methacrylonitrile; acrylamide, methacrylamide, N-alkyl Acrylamide, N-alkyl methacrylate N, N-dialkylacrylamide, N, N-dialkylmethacrylate (alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, 2-ethylhexyl Groups, cyclohexyl groups, etc.); vinyl esters such as vinyl acetate, vinyl propionate, acrylic acid, methacrylic acid with polyalkylene oxide added to the ester moiety; methyl vinyl ether, ethyl vinyl ether, etc. Vinyl ethers; α-olefins such as ethylene and propylene; Halogen-containing α and β-unsaturated monomers such as vinyl chloride, vinylidene chloride and vinyl fluoride; α and β-unsaturations such as styrene and α-methylstyrene An aromatic monomer etc. can be mentioned, These 1 type or 2 types It may be used monomers above.

  The content of the crosslinking agent used in the easy adhesion layer is preferably 0.5 to 20% by weight, more preferably 2 to 15% by weight, based on the weight of the solid content of the coating liquid for forming the easy adhesion layer. %. Thereby, the improvement effect of adhesiveness with an optical layer can be made high. If the content is less than the lower limit, the cohesive force of the easy-adhesion layer tends to be poor, and the adhesion to the optical layer and the second layer tends to be poor. Since the content ratio is low, it is excessively added, and it is difficult to further improve the adhesion.

(Other ingredients)
In the present invention, a surfactant is preferably added to the composition of the easy-adhesion layer in order to apply the coating liquid for forming the easy-adhesion layer in a thin film.
The surfactant may improve and stabilize the dispersibility of the emulsion, while lowering the adhesion with the optical layer. Therefore, it is preferable to keep the content of the surfactant to the minimum amount within the range where the effect is manifested. Specifically, 0.02 to 0.30% by weight based on the weight of the aqueous coating liquid is added. It is preferable to limit the content to 2 to 20% by weight based on the weight of the easy-adhesion layer (based on the solid content of the coating liquid for forming the easy-adhesion layer).

  As examples of the surfactant, an anionic surfactant, a cationic surfactant, a nonionic surfactant, and the like can be used. For example, polyoxyalkylene-fatty acid ether, polyoxyalkylene-aromatic acid ether, polyoxyalkylene-fatty acid ester, polyoxyalkylene-aromatic acid ester, polyoxyethylene-polyoxypropylene (copolymer) -fatty acid ester, poly Oxyethylene-polyoxypropylene (copolymer) -aromatic acid ester, sorbitan fatty acid ester, glycerin fatty acid ester, fatty acid metal soap, alkyl sulfate, alkyl sulfonate, alkyl sulfosuccinate, and other anionic and nonionic interfaces An activator can be used. Of these, polyoxyalkylene-fatty acid ethers and polyoxyalkylene-aromatic acid ethers are preferred from the viewpoint of improving the effect of improving the adhesion to the optical layer, for example, polyoxyethylene tribenzylphenyl ether, polyoxyethylene distyrenation. Examples include phenyl ether and polyoxyethylene oleyl ether.

The solid content concentration of the coating liquid for forming the easy-adhesion layer is preferably 1% by weight or more and 10% by weight or less based on the weight of the coating liquid. Thereby, applicability | paintability can be improved. If the solid content concentration is less than 1% by weight, the stability of the coating film may be lowered, and coating defects such as coating stripes and repellency are likely to occur, and if it is more than 10% by weight, adhesion may be lowered. .
As long as the object of the present invention is not impaired, other resin components such as antistatic agents, colorants, ultraviolet absorbers, acrylics, polycarbonates, and polyesters are further blended as components that form the easy-adhesion layer. May be.
In the present invention, the easy-adhesion layer has a thickness of 0.01 to 0.50 μm, preferably 0.01 to 0.20 μm, and more preferably 0.01 to 0.10 μm. If the thickness is less than the lower limit, the adhesive effect with the optical layer is not sufficiently exhibited. Further, even if the thickness exceeds the upper limit, further improvement in adhesion is difficult.

[Lamination structure of uniaxially stretched multi-layer easily adhesive film]
(Number of layers)
The uniaxially stretched multilayer laminate easy-adhesive film of the present invention has a configuration in which the above-described first layer and second layer are alternately laminated in a total of 101 layers. Thereby, sufficient reflective polarization characteristics can be achieved. When the number of stacked layers is 100 or less, the average reflectance characteristics of the polarized light component parallel to the incident surface including the stretching direction (X direction) may not exhibit a certain average reflectance over a wavelength of 380 to 780 nm. . More preferably, it is 201 layers or more. The upper limit of the number of layers is preferably 2001 layers from the viewpoint of productivity and film handling properties, but the number of layers may be further reduced from the viewpoint of productivity and handling properties as long as the desired average reflectance characteristic is obtained. For example, it may be 1001, 501 or 301 layers. The thickness of the optical member obtained by the present invention can be further reduced by setting the number of laminated layers to a smaller number within a range that satisfies the target reflection characteristics.

(Each layer thickness)
The thickness of each of the first layer and the second layer is preferably 0.01 μm or more and 0.5 μm or less. The thickness of each layer of the first layer is more preferably 0.01 μm or more and 0.1 μm or less, and the thickness of each layer of the second layer is more preferably 0.01 μm or more and 0.3 μm or less. The thickness of each layer can be determined based on a photograph taken using a transmission electron microscope.
When the uniaxially stretched multilayer laminated easily adhesive film of the present invention is used as a brightness enhancement film, the light from the light source can be efficiently reused by reflecting the light in the near infrared region from the visible light region. By setting the thickness of each layer of the first layer and the second layer in such a range, it becomes possible to selectively reflect light in a wavelength region corresponding to these by optical interference between layers. On the other hand, when the layer thickness exceeds 0.5 μm, the reflection band becomes an infrared region, which does not affect the visibility of the display, and the contribution to the light utilization efficiency is reduced. On the other hand, when the layer thickness is less than 0.01 μm, the polyester component tends to absorb light and have low reflection performance.

(Ratio of maximum layer thickness to minimum layer thickness)
In the uniaxially stretched multilayer laminate easy-adhesive film of the present invention, the ratio of the maximum layer thickness and the minimum layer thickness in each of the first layer and the second layer is preferably 2.0 or more and 5.0 or less. Preferably they are 2.0 or more and 4.0 or less, More preferably, they are 2.0 or more and 3.5 or less, Most preferably, they are 2.0 or more and 3.0 or less. The ratio of the layer thickness is specifically represented by the ratio of the maximum layer thickness to the minimum layer thickness. The maximum layer thickness and the minimum layer thickness in each of the first layer and the second layer can be obtained based on a photograph taken using a transmission electron microscope.

  In the multilayer laminated film, the wavelength to be reflected is determined by the difference in refractive index between layers, the number of layers, and the thickness of the layer. However, when each of the laminated first and second layers has a constant thickness, only a specific wavelength is reflected. The average reflectance of the polarization component parallel to the incident surface including the stretching direction (X direction) cannot be increased uniformly over a wide wavelength band of wavelengths 380 to 780 nm, It is preferable to use layers having different thicknesses so as to achieve the above ratio. When the ratio is too small, it is difficult to obtain such an effect. On the other hand, when the ratio between the maximum layer thickness and the minimum layer thickness exceeds the upper limit, the reflection band is wider than 380 to 780 nm, and the visible light region of the polarization component parallel to the incident surface including the stretching direction (X direction) May be accompanied by a decrease in reflectance.

The layer thicknesses of the first layer and the second layer may change stepwise or may change continuously. By changing each of the first layer and the second layer laminated in this way, light in a wider wavelength range can be reflected.
The method of laminating the multilayer structure in the uniaxially stretched multilayer laminate easy-adhesive film of the present invention is not particularly limited. For example, the first layer is obtained by branching 138 layers of the first layer polyester and 137 layers of the second layer polyester. And a second layer are alternately laminated, and a method of using a multilayer feed block device in which the flow path continuously changes by 2.0 to 5.0 times is mentioned.

(Average layer thickness ratio of the first layer and the second layer)
In the uniaxially stretched multilayer easily adhesive film of the present invention, the ratio of the average layer thickness of the second layer to the average layer thickness of the first layer is preferably in the range of 0.5 to 2.0 times. The lower limit of the ratio of the average layer thickness of the second layer to the average layer thickness of the first layer is more preferably 0.8. The upper limit of the ratio of the average layer thickness of the second layer to the average layer thickness of the first layer is more preferably 1.5. The most preferred range is 1.0 or more and 1.3 or less. By setting the ratio of the average layer thickness of the second layer to the average layer thickness of the first layer to an optimum thickness ratio, light leakage due to multiple reflection can be minimized. The optimum thickness ratio here is (the refractive index in the stretching direction of the first layer) × (the average layer thickness of the first layer) and (the refractive index in the stretching direction of the second layer) × The value (optical thickness) represented by (average layer thickness of the second layer) is a uniform thickness.

(Total film thickness)
The uniaxially stretched multilayer laminated easy-adhesive film of the present invention has a total film thickness including the easy-adhesive layer of 20 to 150 μm, more preferably 30 to 130 μm, and still more preferably 50 to 100 μm. By using a uniaxially stretched multilayer laminated easy-adhesion film having such a thickness as a brightness enhancement film, a thin member suitable for a display terminal member can be provided.

[Uniaxially stretched film]
The uniaxially stretched multilayer laminate easy-adhesion film of the present invention is a uniaxially stretched film that is stretched in the uniaxial direction in order to obtain the desired optical properties as a reflective polarizing film. The “uniaxially stretched film” or “uniaxially stretched film” in the present invention includes a film stretched only in the uniaxial direction and a film stretched in the biaxial direction. Films stretched in the direction are also included. The uniaxial stretching direction (X direction) may be either the film longitudinal direction or the width direction. Further, in the case of a film stretched in a biaxial direction and stretched in one direction, the direction (X direction) that is more stretched may be either the film longitudinal direction or the width direction. In the direction where the draw ratio is low, it is preferable that the draw ratio is about 1.03 to 1.20 times from the viewpoint of improving the polarization performance. In the case of a film stretched in a biaxial direction and stretched in one direction, the “stretch direction” in relation to polarized light and refractive index refers to a more stretched direction.
As the stretching method, known stretching methods such as heat stretching with a rod heater, roll heat stretching, and tenter stretching can be used, but tenter stretching is preferable from the viewpoint of reducing scratches due to contact with the roll and stretching speed.

[Refractive index characteristics between the first layer and the second layer]
The X-direction refractive index difference between the first layer and the second layer is preferably 0.10 to 0.45, more preferably 0.20 to 0.40, and particularly preferably 0.25 to 0.30. is there. When the refractive index difference in the X direction is within such a range, the reflection characteristics can be improved efficiently, and a high reflectance can be obtained with a smaller number of layers.
The difference in refractive index between the first layer and the second layer in the Y direction is preferably 0.05 or less. It is preferable that the refractive index difference between the layers in the Y direction is within such a range that the polarization performance is improved.

[Characteristics of film]
(Degree of polarization)
In the wavelength range of 380 to 780 nm, the uniaxially stretched multi-layer easy-adhesion film of the present invention has an average value of the degree of polarization (P) calculated by the following formula (1) at intervals of 5 nm (an average value of the degree of polarization (P)). May be simply referred to as the degree of polarization.) Is 70% or more, preferably 75% or more, more preferably 80% or more, and still more preferably 85% or more.
Degree of polarization (P) = {(Ts−Tp) / (Tp + Ts)} × 100 (1)
(In formula (1), Tp represents the average transmittance of P-polarized light at each wavelength, and Ts represents the average transmittance of S-polarized light at each wavelength.)

The degree of polarization in the present invention can be measured using a degree of polarization measuring device.
The higher the degree of polarization, the lower the transmission of the reflected polarization component, and the higher the transmittance of the transmitted polarization component in the orthogonal direction.The higher the degree of polarization, the less light leakage of the reflected polarization component. it can. When the uniaxially stretched multilayer laminate easy-adhesion film of the present invention has such a degree of polarization, it can be used for applications requiring reflective polarization characteristics such as a brightness enhancement film. Further, when the degree of polarization is 99.5% or more, the reflective polarizing plate alone can be applied as a polarizing plate of a liquid crystal display having a high contrast, which has been difficult to apply unless it is an absorption polarizing plate.
Such polarization degree characteristics are obtained by using the above-mentioned types of polymers constituting the first layer and the second layer, and by making the refractive indexes between the layers in the X direction, the Y direction, and the Z direction a specific relationship by uniaxial stretching. can get.

(S-polarized average transmittance)
In the uniaxially stretched multi-layer easily adhesive film of the present invention, the average transmittance Ts of S-polarized light measured at 5 nm intervals in the wavelength range of 380 to 780 nm is preferably 60% or more, more preferably 70% or more. More preferably, it is 75% or more, and particularly preferably 80% or more.
The average transmittance of S-polarized light in the present invention is the incident angle with respect to the polarization component perpendicular to the incident surface including the uniaxially stretched direction (X direction) in the uniaxially stretched multilayer laminate easy-adhesive film. It represents the average transmittance at a wavelength of 380 to 780 nm for the incident polarized light at 0 degree.
If the average transmittance of S-polarized light is less than the lower limit, when used for a brightness enhancement film, etc., a light recycling function for reflecting the reflected polarized light component to the light source side without absorbing it by the film and effectively utilizing the light again is considered. Even so, the superiority of the brightness enhancement effect may not be sufficient.

(Haze)
The uniaxially stretched multilayer laminate easily adhesive film of the present invention preferably has a haze of 1.5% or less. Since the incident light can be transmitted and reflected without diffusing by being in such a range, the luminance improvement performance is excellent. If the upper limit is exceeded, diffusion occurs when the incident light is transmitted / reflected, and therefore the brightness enhancement performance tends to be poor. From this viewpoint, it is preferably 1.2% or less, more preferably 1.0% or less.

[Method for producing uniaxially stretched multi-layer easy-adhesion film]
Below, the manufacturing method of the uniaxially stretched multilayer lamination easy-adhesion film of this invention is explained in full detail.

(Method for producing uniaxially stretched multilayer laminated film)
The uniaxially stretched multi-layer laminate film of the present invention creates an alternating laminate of 101 layers or more in total by alternately superposing the polymer constituting the first layer and the polymer constituting the second layer in a molten state, Thick film layers (buffer layers) are provided on both sides, and an alternate laminate having the buffer layer is divided into, for example, 2 to 4 using a device called layer doubling, and the alternate laminate having the buffer layer is blocked as one block. The number of stacked layers can be increased by a method of stacking again so that the number of stacked layers (doubling number) is 2 to 4 times. By such a method, an uniaxially stretched multilayer laminated film having an intermediate layer in which two buffer layers are laminated in a multilayer structure and an outermost layer composed of one buffer layer on both surfaces can be obtained.

  In addition, the uniaxially stretched multilayer laminated film in the present invention, in addition to using the above-mentioned doubling method, a total of 101 layers are formed by alternately superposing the polymer constituting the first layer and the polymer constituting the second layer in a molten state. You may laminate | stack so that it may be set as the objective lamination number mentioned above, and the thickness of each layer changes in the range of 2.0 to 5.0 times stepwise or continuously.

  The multilayer unstretched film laminated in a desired number of layers by the above-described method is stretched in the film forming direction or at least one axial direction (direction along the film surface) in the width direction perpendicular thereto. The stretching temperature is preferably in the range of the glass transition temperature of the polymer of the first layer (Tg) to (Tg + 50) ° C., and the upper limit of the stretching temperature is preferably in the range of (Tg + 20) ° C. or less. When stretched at a stretching temperature of (Tg + 20) ° C. or lower, the orientation characteristics of the film can be controlled to a higher degree.

The draw ratio at this time is preferably 2 to 10 times, more preferably 2 to 7 times, still more preferably 2.5 to 7 times, and particularly preferably 4.5 to 6.5 times. Within such a range, the larger the draw ratio, the smaller the variations in the plane direction of the individual layers in the first layer and the second layer due to the thinning by stretching, and the light interference of the multilayer stretched film is made uniform in the plane direction, Moreover, since the refractive index difference of the extending | stretching direction of a 1st layer and a 2nd layer becomes large, it is preferable.
As the stretching method at this time, known stretching methods such as heat stretching with a rod heater, roll heating stretching, and tenter stretching can be used. From the viewpoints of reducing scratches due to contact with the roll and stretching speed, tenter stretching is performed. preferable.

Moreover, when performing a extending | stretching process also in the direction (Y direction) orthogonal to this extending | stretching direction and performing biaxial stretching, it is preferable to limit to a draw ratio of about 1.03-1.20 times. If the stretch ratio in the Y direction is further increased, the polarization performance may be deteriorated.
In addition, the film may be towed out (re-stretched) in the stretching direction within a range of 5 to 15% while further being heat-set at a temperature of (Tg) to (Tg + 30) ° C. after the stretching. The orientation characteristics of the easily adhesive film can be controlled to a higher degree.

(Method of forming easy-adhesion layer)
The formation method of an easily bonding layer is not specifically limited, Although a conventionally well-known method can be employ | adopted, forming by the apply | coating method is preferable. The coating liquid can be applied to the film at any stage, but in the film production process, a coating liquid containing a component that forms an easy-adhesion layer is applied to the stretchable film, and then dried and stretched. It is preferable to carry out by doing. The coating liquid is preferably an aqueous coating liquid. Moreover, an easily bonding layer may be formed only in the single side | surface of a film as needed, and may be formed in both surfaces.

[Optical member]
The uniaxially stretched multilayer laminate easy-adhesive film of the present invention uses the polyester of the above-described composition for each of the first layer and the second layer, and alternately laminates in multiple layers and stretches in one direction so that one polarization component is Since it exhibits the performance of selectively reflecting and selectively transmitting the polarized light component and the polarized light component in the vertical direction, it can be used as a brightness enhancement film for a liquid crystal display or the like. When used as a brightness enhancement film, a good brightness enhancement rate can be obtained, and light can be reused by reflecting a polarized component that has not been transmitted to the light source side.
Further, a prism layer or a diffusion layer may be laminated on at least one surface of the uniaxially stretched multilayer laminated easy-adhesive film of the present invention. At that time, the prism layer or the diffusion layer is laminated through the above-described coating layer.

  Further, a brightness enhancement film with a prism layer in which a prism layer is provided on the uniaxially stretched multilayer laminate easy-adhesion film of the present invention is also included as a preferred embodiment of the present invention. By unitizing the brightness enhancement film and the prism layer, the number of members during assembly can be reduced, and a high-quality composite optical film that integrates the functions of the brightness enhancement film and the prism can be provided. In addition, by using the uniaxially stretched multilayer laminate easy-adhesive film of the present invention and bonding to the prism layer, it is possible to suppress the peeling of the prism layer due to external force applied during processing, etc. Can be provided.

When the uniaxially stretched multilayer laminate easy-adhesion film of the present invention is used as a brightness enhancement film, it can be used in a liquid crystal display device with a configuration as shown in FIG.
Specifically, a liquid crystal display device in which the brightness enhancement member 4 is disposed between the light source 5 of the liquid crystal display and the liquid crystal panel 6 composed of the polarizing plate 1 / liquid crystal cell 2 / polarizing plate 3 is exemplified. . Further, the installation position of the prism layer is not particularly limited, but the vertical angle of the prism is preferably about 90 degrees when installed on the panel side, and about 60 degrees when installed on the backlight side.

Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to the examples shown below.
In addition, the physical property and characteristic in an Example were measured or evaluated by the following method.

(1) Polarization degree The transmittance of P-polarized light in the wavelength range of 380 to 780 nm, S-polarized light, using a polarization degree measuring device (“VAP7070S” manufactured by JASCO Corporation) for the obtained uniaxially stretched multilayer laminated adhesive film. The transmittance and the degree of polarization were measured. The measurement was performed at intervals of 5 nm, and the average value obtained at each wavelength was adopted.
The measured value when the transmission axis of the polarizing filter is aligned with the stretching direction (X direction) of the film is P-polarized light, and the measured value when the transmission axis of the polarizing filter is disposed perpendicular to the stretching direction of the film The degree of polarization (P, unit%) when S is S-polarized light is expressed by the following formula (1).
Degree of polarization (P) = {(Ts−Tp) / (Tp + Ts)} × 100 (1)
(In formula (1), Tp represents the average transmittance of P-polarized light at each wavelength, and Ts represents the average transmittance of S-polarized light at each wavelength)
The measurement light was measured with the incident angle set to 0 degree. In the analysis program (JASCO spectrum manager Ver. 2 polarizing film evaluation program) provided in the above apparatus, the analysis was performed without using the visibility correction program.

(2) Polymer melting point (Tm) and glass transition point (Tg)
10 mg of each layer sample was sampled and used at 20 ° C./min. Using DSC (trade name: DSC Q400, manufactured by TA Instruments). The melting point and glass transition point of the polymer constituting each layer were measured at a temperature rising rate of.

(3) Identification of polymer and identification of copolymer component and amount of each component For each layer of the film, the polymer component, the copolymer component and the amount of each component were identified by ¹ H-NMR measurement.

(4) Average refractive index Each resin constituting each layer was melted and extruded from a die, and a film cast on a casting drum was prepared. In addition, a stretched film was prepared by stretching the obtained film 5.5 times in a uniaxial direction at (resin glass transition temperature) + 20 ° C. With respect to the obtained cast film and stretched film, the refractive index (respectively, nX, nY, nZ) in the stretching direction (X direction), the orthogonal direction (Y direction), and the thickness direction (Z direction) is measured. The refractive index was determined by measuring at a wavelength of 633 nm using a prism coupler made from before and after stretching.
About the average refractive index of polyester which comprises a 1st layer, the average value of the refractive index of each direction before extending | stretching was made into the average refractive index. Moreover, about the average refractive index of polyester which comprises a 2nd layer, the average value of the refractive index of each direction after extending | stretching was made into the average refractive index.

(5) Thickness of each layer A uniaxially stretched multilayer laminate easy-adhesion film was cut into 2 mm in the film longitudinal direction and 2 cm in the width direction, fixed to an embedding capsule, and then embedded in an epoxy resin (Epomount manufactured by Refine Tech Co., Ltd.). . The embedded sample was cut perpendicularly in the width direction with a microtome (LETRAC ULCT UCT manufactured by LEICA) to form a thin film slice having a thickness of 5 nm. Using a transmission electron microscope (Hitachi S-4300), the film was observed and photographed at an acceleration voltage of 100 kV, and the thickness of each layer was measured from the photograph.
Based on the thickness of each layer obtained, the ratio of the maximum layer thickness to the minimum layer thickness in the first layer and the ratio of the maximum layer thickness to the minimum layer thickness in the second layer were determined.
Moreover, based on the thickness of each obtained layer, the average layer thickness of the first layer and the average layer thickness of the second layer were determined, respectively, and the average layer thickness of the second layer relative to the average layer thickness of the first layer was calculated.
In determining the thicknesses of the first layer and the second layer, the intermediate layer and the outermost layer were excluded from the first layer and the second layer.
Moreover, about the layer of 1 micrometer or more thickness which comprises a uniaxial stretching multilayer lamination easy-adhesion film, what exists in the inside of a multilayered structure is made into an intermediate | middle layer, and what exists in the outermost layer is made into the outermost layer, The thickness was measured. When a plurality of intermediate layers existed, the intermediate layer thickness was determined from the average value thereof.
Also, the thickness of the coating layer was determined in the same manner as described above.

(6) Total film thickness A film sample was sandwiched between spindle detectors (K107C manufactured by Anritsu Electric Co., Ltd.), and 10 points of thickness were measured at different positions using a digital differential electronic micrometer (K351 manufactured by Anritsu Electric Co., Ltd.). And the average value was calculated | required and it was set as the film thickness.

(7) Average particle size of particles The same measurement as the measurement of the layer thickness was performed, the particle size of 100 particles in the coating layer was measured, and the average value was taken as the average particle size.

(8) Particle content Components other than the particles forming the easy-adhesion layer are dissolved, a solvent that does not dissolve the particles is selected, the sampled easy-adhesion layer is dissolved, the particles are centrifuged, and the entire particle The ratio of the weight (% by weight) was used as the particle content.

(9) Friction coefficient Static friction coefficient μs and dynamic friction coefficient μk were measured according to JIS-K7125. The measurement was performed 5 times, and the average value was used as the result. In addition, when both the friction coefficients were 0.5 or less, when winding a film in roll shape, it was able to wind up without a crack etc. and it was evaluated that winding property was favorable. Also, the smaller the friction coefficient, the better the winding property.

(10) Haze Measured according to JIS-K7136 using a haze meter (NDH-2000 manufactured by Nippon Denshoku Industries Co., Ltd.).

(11) Brightness improvement effect (brightness improvement rate)
Using a VA liquid crystal display panel (AQUAOS LC-20E90 manufactured by Sharp), the prism film and the upper diffusion film are removed, and the resulting brightness enhancement film with a prism layer is replaced with a white display. Was measured with an FPD viewing angle measurement and evaluation apparatus (ErgoScope 88) manufactured by Opto Design, and the rate of increase in luminance relative to the configuration before replacement was calculated, and the luminance improvement effect was evaluated according to the following criteria.
○: Brightness improvement effect is 150% or more Δ: Brightness improvement effect is 120% or more and less than 150% ×: Brightness improvement effect is less than 120%

(12) Adhesion with the prism layer A glass mold having a prism lens pattern formed thereon is poured with an ultraviolet curable acrylic resin having the following composition, and the adhesive layer side of the obtained film is adhered to the resin side. The resin is cured by irradiation for 30 seconds using a UV lamp (irradiation intensity 80 W / cm, 6.4 KW) from a distance of 30 cm on the surface side of the glass mold, and the apex angle is 90 degrees, the pitch is 50 μm, and the height is A 30 μm prism lens layer was formed to obtain a brightness enhancement sheet. A cross-cut (100 squares of 1 mm ² squares) is applied to the processed surface of the obtained brightness enhancement sheet, and a 24 mm wide cellophane tape (manufactured by Nichiban Co., Ltd.) is pasted on the processed surface of the brightness enhancement sheet, and 180 ° peeling is performed. After abrupt peeling at an angle, the peeled surface was observed and evaluated according to the following criteria.

<UV curable acrylic resin>
Ethylene oxide-modified bisphenol A dimethacrylate (FA-321M manufactured by Hitachi Chemical Co., Ltd.) 46% by weight
Neopentyl glycol-modified trimethylolpropane diacrylate (R-604, manufactured by Nippon Kayaku Chemical Co., Ltd.) 25% by weight
27% by weight of phenoxyethyl acrylate (Biscoat 192 manufactured by Osaka Organic Chemical Industry Co., Ltd.)
2-Hydroxy-2-methyl-1-phenylpropan-1-one (Darocur 1173 manufactured by Merck) 2% by weight
<Adhesion evaluation criteria>
○: Peeling area is less than 5% (adhesion is good)
Δ: peeling area is 5% or more and less than 30% ×: peeling area is 30% or more (adhesion is poor)

[Polyester component of the first layer and the second layer]
(Polyester A)
As the polyester for the first layer, dimethyl 2,6-naphthalenedicarboxylate, dimethyl terephthalate, and ethylene glycol are transesterified in the presence of titanium tetrabutoxide, followed by a polycondensation reaction to produce an acid component. Is a copolymer polyester (intrinsic viscosity 0.64 dl / g) (o-chlorophenol, 5 mol% of the acid component is terephthalic acid component and glycol component is ethylene glycol). 35 ° C., the same applies hereinafter).

(Polyester B)
As polyester for the second layer, dimethyl 2,6-naphthalenedicarboxylate, dimethyl terephthalate, and ethylene glycol and trimethylene glycol are transesterified in the presence of titanium tetrabutoxide, followed by a polycondensation reaction. A copolymer polyester (inherent viscosity 0.63 dl) in which 50 mol% of the acid component is 2,6-naphthalenedicarboxylic acid component, 50 mol% of the acid component is terephthalic acid component, and 15 mol% of the glycol component is trimethylene glycol. / G) was prepared.

(Polyester C)
As the polyester for the first layer, dimethyl 2,6-naphthalenedicarboxylate, 6,6 ′-(ethylenedioxy) di-2-naphthoic acid, and ethylene glycol were esterified and esterified in the presence of titanium tetrabutoxide. An exchange reaction is carried out, followed by a polycondensation reaction. With an intrinsic viscosity of 0.63 dl / g, 70 mol% of the acid component is 2,6-naphthalenedicarboxylic acid component and 30 mol% of the acid component is 6,6 A- (ethylenedioxy) di-2-naphthoic acid component and an aromatic polyester whose glycol component is ethylene glycol were prepared.

(Polyester D)
As a polyester for the second layer, a copolymerized polyester composed of 66 mol% of 2,6-naphthalenedicarboxylic acid, 34 mol% of terephthalic acid, 50 mol% of ethylene glycol, 15 mol% of spiroglycol, and 35 mol% of trimethylene glycol (inherent viscosity 0.70 dl / g) ) Was prepared.

[Easily adhesive layer component]
The easy-adhesion layer components in the table are as follows.
(Binder A)
A polyester copolymer polyurethane in which an aromatic carboxylic acid and an isocyanate component are composed of 46 mol% terephthalic acid / 44 mol% isophthalic acid / 10 mol% isophorone diisocyanate, and the glycol component is 60 mol% ethylene glycol / 40 mol% diethylene glycol. Solid content 35%. In addition, the binder A was manufactured according to the polymerization method of the urethane resin which uses the polyester polyol as a structural component as described in the Example of Unexamined-Japanese-Patent No. 2011-153290.

(Binder B)
The aromatic carboxylic acid and the isocyanate component are composed of 26 mol% terephthalic acid / 26 mol% isophthalic acid / 24 mol% adipic acid / 24 mol% isophorone diisocyanate, and the glycol component is composed of 60 mol% neopentyl glycol / 40 mol% ethylene glycol. Polyester copolymer polyurethane. Solid content 35%. The binder B was produced in the same manner as the binder A except that the copolymerization component was changed as described above.

(Binder C)
Copolymer in which the acid component is composed of 75 mol% of 2,6-naphthalenedicarboxylic acid / 20 mol% of isophthalic acid / 5 mol% of 5-sodium sulfoisophthalic acid, and the glycol component is composed of 90 mol% of ethylene glycol / 10 mol% of diethylene glycol. polyester. The binder C was produced according to the method described in Example 1 of JP-A-06-116487.

(Particle A)
Acrylic particles (SX8703 average particle size 0.6μm, manufactured by JSR Corporation)
(Particle B)
Melamine particles (Epester S6, average particle size 0.4μm, manufactured by Nippon Shokubai Co., Ltd.)
(Particle C)
Acrylic particles (BMSA-18GN average particle size 0.8 μm, manufactured by Sekisui Plastics Co., Ltd.)
(Particle D)
Acrylic particles (Epester MX-200W, average particle size 0.3 μm, manufactured by Nippon Shokubai Co., Ltd.)
(Particle E)
Acrylic particles (Sekisui Plastics Co., Ltd. SSX-101 average particle size 1.0 μm)

(Crosslinking agent A)
Methyl methacrylate 25 mol% / 2-isopropenyl-2-oxazoline 30 mol% / polyethylene oxide (n = 10) methacrylate 10 mol% / acrylamide 35 mol%. The crosslinking agent A was produced according to the method described in Production Examples 1 to 3 of JP-A No. 63-37167.
(Crosslinking agent B)
Carbodiimide compound (Carbodilite V-02-L2 manufactured by Nisshinbo Chemical Co., Ltd.)
(Surfactant A)
Polyoxyethylene oleyl ether

[Example 1]
Polyester A for the first layer is dried at 170 ° C. for 5 hours, and polyester B for the second layer is dried at 85 ° C. for 8 hours, then supplied to the first and second extruders and heated to 300 ° C., respectively. The first layer polyester is branched into 138 layers and the second layer polyester is branched into 137 layers, and then the first layer and the second layer are alternately laminated, and the first layer and the second layer. The first and second layers are alternated using a multi-layer feedblock device in which the maximum and minimum layer thicknesses of each of the layers continuously vary up to 3.1 times and 3.0 times at the maximum / minimum. The melt of the total number of 275 layers laminated to the melt, and the same polyester as the second layer polyester is led from the third extruder to the three-layer feed block on both sides of the melt while maintaining the laminated state. Lamination direction of 275 layered melt It was further laminated a buffer layer on both sides. The supply amount of the third extruder was adjusted so that the total of the buffer layers on both sides was 47% of the total. The layered state is further divided into two layers at a layer doubling block and laminated at a ratio of 1: 1, and the layered state of 553 layers including the intermediate layer inside and the two outermost layers in the outermost layer is maintained. Guided to a die, cast on a casting drum, adjusted so that the average layer thickness ratio of the first layer and the second layer is 1.0: 2.3, and an unstretched multi-layer laminate with a total number of 553 layers A film was created.
A coating liquid having the composition shown in Table 1 at a solid content concentration of 3% was uniformly applied to one side of the unstretched multilayer laminated film with a roll coater so that the thickness after drying was 0.02 μm.

Subsequently, this unstretched multilayer laminated film was stretched 5.2 times in the width direction at a temperature of 130 ° C. The thickness of the obtained uniaxially stretched multilayer laminate easy-adhesion film was 85 μm. Among them, the multilayer part thickness was 45 μm, the outermost layer thickness was 10 μm, and the intermediate layer thickness was 20 μm. Using the brightness enhancement film with a prism layer obtained by laminating a prism layer according to the method of the measurement method (12) on the easy adhesion layer surface of the obtained uniaxially stretched multilayer laminate easy-adhesion film, the method of the measurement method (11) The brightness enhancement effect was measured.
The uniaxially stretched multilayer laminate easy-adhesion film of the present invention has high adhesion between the prism layer and the film, and the peeling of the prism layer was reduced. Moreover, since the friction coefficient was in an appropriate range, the winding property was good.

[Examples 2 to 13, Comparative Examples 1 to 7]
As shown in Table 1, a uniaxially stretched multi-layer easily adhesive film and a brightness enhancement film with a prism layer were prepared in the same manner as in Example 1 except that the easy adhesive layer composition, the polyester composition of the first layer and the second layer were changed. Obtained. In Comparative Example 6, no easy adhesion layer was provided.

  Since the uniaxially stretched multilayer laminate easy-adhesion film of the present invention has a reflective polarization performance and a high adhesion between the optical layer such as a prism layer and a diffusion layer formed on the film and the film, the brightness enhancement film High quality composite optical film that integrates the functions of and prism.

DESCRIPTION OF SYMBOLS 1 Polarizing plate 2 Liquid crystal cell 3 Polarizing plate 4 Brightness enhancement film 5 Light source 6 Liquid crystal panel

Claims (7)

A uniaxially stretched multi-layer easily adhesive film in which the first layer and the second layer are alternately laminated,
1) The first layer is a layer mainly composed of polyester, and contains ethylene naphthalate units in a range of 50 mol% or more and 100 mol% or less based on the repeating units constituting the polyester,
2) The second layer is a layer mainly composed of a copolyester, and the copolyester has a glass transition temperature of 85 ° C. or higher and an average refractive index of 1.55 to 1.65. A copolymerized polyester comprising a 2,6-naphthalenedicarboxylic acid component, an ethylene glycol component, and a trimethylene glycol component as a copolymerization component,
3) The total number of alternating layers of the first layer and the second layer is 101 or more, and at least one surface has an outermost layer having a thickness of 5 to 50 μm composed of the second layer,
4) It has an easy-adhesion layer having a thickness of 0.01 to 0.50 μm on the outer surface of at least one of the outermost layers, and the easy-adhesion layer contains polyurethane resin and particles having an average particle diameter of 0.4 to 0.8 μm. 0.5 to 6.0% by weight based on the weight of the easy adhesion layer,
5) The total film thickness including the easy-adhesion layer is 20 to 150 μm,
6) A uniaxially stretched multilayer laminate easy-adhesion film in which the average value of the degree of polarization (P) calculated by the following formula (1) is 5% at an interval of 5 nm in a wavelength range of 380 to 780 nm.
Degree of polarization (P) = {(Ts−Tp) / (Tp + Ts)} × 100 (1)
(In formula (1), Tp represents the average transmittance of P-polarized light at each wavelength, and Ts represents the average transmittance of S-polarized light at each wavelength.)   The uniaxially stretched multilayer laminate easy-adhesion film according to claim 1, wherein the urethane resin of the easy-adhesion layer is a polyester-based polyurethane resin formed from a polyester polyol and a polyisocyanate.   The uniaxially stretched multilayer laminated easy-adhesive film according to claim 1 or 2, wherein the easy-adhesive layer further contains a crosslinking agent containing a carbodiimide group or an oxazoline group. The uniaxially stretched multilayer laminate easy adhesion according to any one of claims 1 to 3, wherein the content of the trimethylene glycol component is 3 to 50 mol% of all diol components constituting the copolymer polyester of the second layer. the film. The uniaxially stretched multilayer laminate easy-adhesive film according to any one of claims 1 to 4 , wherein the polyester of the first layer contains a terephthalic acid component in a range of 20 mol% or less based on the total dicarboxylic acid component. The uniaxially stretched multilayer laminated adhesive film according to any one of claims 1 to 5 , which is used as a brightness enhancement member or a reflective polarizing plate. The optical member by which the prism layer or the diffusion layer was laminated | stacked on the at least one surface of the uniaxially stretched multilayer lamination easy-adhesion film in any one of Claims 1-6 .