JP6311605B2 - OPTICAL LAMINATE AND METHOD FOR PRODUCING OPTICAL LAMINATE - Google Patents

Description

  The present invention is an optical laminate that can be applied as a constituent member of various image display devices such as a liquid crystal display device, and includes at least one brightness enhancement layer (X) and an absorbing polarizing layer (Y). About.

  Conventionally, as a configuration of a liquid crystal display (LCD), for example, as shown in FIG. 1, a glass substrate, a polarizing film, a brightness enhancement film, a diffusion film, a light guide plate and a light source, and a reflection are provided on the back side (back side) of the liquid crystal cell. A configuration in which sheets or the like are sequentially laminated has been adopted.

  Among polarizing films, an absorption polarizing film obtained by adsorbing and orienting iodine or a dichroic dye on a polyvinyl alcohol-based resin is widely used in liquid crystal display devices. For example, the absorptive polarizing film is also incorporated in a reflective liquid crystal display device having a reflective plate on the back side of the liquid crystal cell and a transflective liquid crystal display device having a transflective plate on the back side of the liquid crystal cell. Have been used.

  However, the absorbing polarizing film plays a role of transmitting only light of a specific polarization direction (P wave, linearly polarized light) and supplying it to the liquid crystal cell and absorbing light of other polarization directions (S wave). If only the absorptive polarizing film is used, the amount of light supplied to the liquid crystal cell decreases, and the image becomes dark.

  Therefore, by arranging a brightness enhancement film on the light source side of the polarizing film as in the above configuration, the amount of light in the polarization direction transmitted by the polarizing film is increased, and the amount of light that can be supplied to the liquid crystal cell is increased. Brightening is done.

  As the brightness enhancement film, a film using a multilayer polarizer or a scattering polarizer is known. When these polarizers are used as a brightness enhancement film, if the polarization direction of light passing through the brightness enhancement film matches the polarization direction of light passing through the polarization film, light in the polarization direction absorbed by the polarization film Is reflected on the light source side by the brightness enhancement film on the near side, and while the reflection and scattering are repeated between the brightness enhancement film and the reflection sheet, the polarization direction of the light changes and passes through the polarization film. The amount of light passing through the film can be increased and the brightness of the image can be improved.

  Regarding multilayer polarizers, conventionally, as disclosed in, for example, Patent Documents 1 to 3, a multilayer polarizer in which two kinds of materials are laminated and stretched is known. These polarizers use the reflection characteristics at the laminated interface to impart polarization reflection characteristics and to precisely control the thickness of each layer, thereby exhibiting high luminance enhancement characteristics.

As for the scattering type polarizer, conventionally, there is known a scattering type polarizer obtained by uniaxially stretching a polymer blend having a phase separation structure composed of two types of polymers having different birefringence.
Such a scattering type polarizer has scattering anisotropy in which the degree of scattering of polarized light is different between the stretching direction and the perpendicular direction, and therefore selectively transmits light in a specific polarization direction and light in other polarization directions. Can be selectively reflected or scattered. For example, Patent Documents 4 and 5 include a continuous phase and a dispersed phase, and the refractive index difference between the continuous phase and the dispersed phase is greater than 0.05 along the first axis and orthogonal to the first axis. A polarizer is disclosed that is less than 0.05 along the second axis and has a diffuse reflectance of at least 30% for polarized light, and a method for manufacturing the same.

  In any of these multilayer polarizers and scattering polarizers, that is, in any of the brightness enhancement films, it is difficult to completely reflect the light (S wave) in the polarization direction to be reflected. In order to supply only directional light (P wave) to the liquid crystal cell, it is necessary to absorb the S wave by the polarizing film.

  On the other hand, in recent years, optical films used for LCDs have been laminated in order to have a plurality of functions. For example, as disclosed in Patent Documents 6 to 9, a method is known in which films having different functions such as brightness enhancement ability are bonded to a polarizing film with a pressure-sensitive adhesive or an adhesive, laminated, and integrated. .

JP 09-506984 A Japanese Translation of National Publication No. 09-506985 JP-T 09-507308 Special Table 2000-506989 JP 2000-506990 A JP 2002-022957 A JP 2002-022958 A JP-A-2004-070344 JP 2004-271446 A

The multilayer structure type polarizers disclosed in Patent Documents 1 to 3 require uniform multilayer lamination and precise control of the thickness of each layer, which complicates the manufacturing process and increases productivity. May drop significantly.
In addition, the scattering type polarizers disclosed in Patent Documents 4 and 5 are characterized in that they exhibit polarization characteristics using scattering reflection at the interface between the continuous phase and the dispersed phase. Compared with the multilayer structure type polarizer described above, the production control is relatively easy, and thus the productivity is high. On the other hand, even if the scattering polarizer is formed in a range that determines the difference in refractive index between the continuous phase and the dispersed phase, the polarization transmission characteristics are insufficient. Furthermore, since the compatibility between the continuous phase and the dispersed phase is low, a relatively large dispersed phase is formed, and the dispersed phase is uniaxially stretched. There is a problem that tearing occurs.
In addition, as disclosed in Patent Documents 6 to 9, in a method of laminating and laminating films having different functions such as brightness enhancement ability to a polarizing film with an adhesive or an adhesive, the brightness enhancement film Since the adhesive layer and the polarizing plate are bonded to each other by the adhesive layer, there are problems that air bubbles are caught in, the phase of light is shifted by the adhesive layer, and the axis of light separated by the brightness enhancement film is shifted.

  The object of the present invention is to solve the problems that occur when the brightness enhancement film and the polarizing plate are bonded together, that is, problems such as air entrainment, light phase shift, and axis misalignment of light polarized by the brightness enhancement film. An object of the present invention is to provide an optical laminate and a method for producing the same that can be solved.

  The present inventors paid attention to solving such a problem by laminating a layer having a luminance enhancement ability and a layer having an absorption polarization ability adjacent to each other without an adhesive layer. It came to complete.

  That is, the optical layered body of the present invention is an optical layered body including at least one brightness enhancement layer (X) and an absorption polarization layer (Y), and the brightness enhancement layer (X) and the absorption polarization layer. (Y) is an optical laminate formed by adjoining without interposing an adhesive layer or an adhesive layer.

  With respect to the optical layered body of the present invention, the brightness enhancement layer (X) and the absorption-type polarizing layer (Y) are laminated in advance and then co-stretched in the uniaxial direction, so that the polarization direction is the same direction. It is preferable that

  In the optical layered body of the present invention, it is preferable that the brightness enhancement layer (X) is selected from a scattering polarizing layer (X1) or a multilayer polarizing layer (X2).

  In the optical layered body of the present invention, the scattering polarizing layer (X1) contains at least two kinds of thermoplastic resins and has a sea-island structure with a continuous phase (I) and a dispersed phase (II). It is preferable that

  In the optical laminate of the present invention, at least one of the thermoplastic resin (A) that forms the continuous phase (I) or the thermoplastic resin (B) that forms the dispersed phase (II) is formed from isosorbide. A polyester resin having a diol residue to be derived is preferable.

  In the optical layered body of the present invention, the thermoplastic resin (A) that forms the continuous phase (I) and the thermoplastic resin (B) that forms the dispersed phase (II) are both polyester resins. Moreover, it is preferable that the thermoplastic resin (A) and the thermoplastic resin (B) are different types of polyester resins.

  In the optical layered body of the present invention, one of the thermoplastic resin (A) forming the continuous phase (I) and the thermoplastic resin (B) forming the dispersed phase (II) is derived from isosorbide. It is preferable that the polyester resin has a diol residue and the other is a polyethylene naphthalate resin.

  Regarding the optical layered body of the present invention, it is preferable that the absorbing polarizing layer (Y) is mainly composed of polyvinyl alcohol containing iodine or a dichroic dye.

  In the optical layered body of the present invention, the polymerization degree of the polyvinyl alcohol is preferably 1000 or more and 8000 or less.

  Another object of the present invention is to propose a method for producing an optical laminate including at least one brightness enhancement layer (X) and an absorption-type polarizing layer (Y), and the brightness enhancement layer. (X) and the said absorption-type polarizing layer (Y) are the manufacturing methods of the optical laminated body characterized by co-extending in a uniaxial direction, after laminating | stacking by coextrusion.

  Furthermore, another gist of the present invention is to propose a method for producing an optical laminate including at least one brightness enhancement layer (X) and an absorption-type polarizing layer (Y), and the brightness enhancement layer. After the absorption polarizing layer (Y) is applied to (X), it is co-stretched in the uniaxial direction.

  The optical layered body proposed by the present invention does not cause bubble entrainment or light phase shift due to the adhesive layer as in the prior art, and the axis shift of light separated by the brightness enhancement layer (X). Therefore, it can be suitably used as an optical laminate having a low content. Therefore, the optical layered body of the present invention can be applied to various image display devices such as a liquid crystal display device alone or in combination with other optical films.

It is sectional drawing which showed an example of the general structure of a liquid crystal display (LCD).

  Hereinafter, an optical layered body (referred to as “the present layered body”) as an example of an embodiment of the present invention will be described.

<This laminate>
The laminate is an optical laminate including at least one brightness enhancement layer (X) and an absorption polarizing layer (Y), and the brightness enhancement layer (X) and the absorption polarization layer (Y) , Having a configuration in which they are laminated adjacently without interposing an adhesive layer or an adhesive layer.

In the present invention, the adhesive layer or the pressure-sensitive adhesive layer is a layer provided to ensure adhesion between the brightness enhancement layer (X) and the absorption-type polarizing layer (Y), and any layer that satisfies this condition can be used. Also includes meaning. For example, an adhesive coating layer or an adhesive layer in a laminate obtained by co-extrusion of a thermoplastic adhesive resin and another thermoplastic resin is also included in this meaning.
In addition, this laminated body has a brightness enhancement layer (X) and an absorption type in order to solve the problems such as the entrapment of bubbles, the phase shift of light, and the axis misalignment of the light separated by the brightness enhancement layer (X). It is important that the polarizing layer (Y) has a configuration in which the polarizing layer (Y) is laminated adjacently without interposing an adhesive layer or an adhesive layer.

When the brightness enhancement layer (X) and the absorption polarizing layer (Y) are bonded together by an adhesive layer or an adhesive layer, the brightness enhancement layer (X) / adhesion layer or adhesive layer, or the absorption polarization layer (Y) / In some cases, bubbles may be caught between the adhesive layer or the adhesive layer, and visibility may be lowered due to light scattering by the bubbles in the laminated body. This is a potential problem as long as it has a post-process called bonding. In addition, having an adhesive layer or an adhesive layer between the brightness enhancement layer (X) and the absorption-type polarizing layer (Y) means increasing an interface having a different refractive index, which is caused by the adhesive layer or the adhesive layer. Due to the interface, light phase shift is likely to occur, and visibility may be reduced. Furthermore, when the brightness enhancement layer (X) and the absorption-type polarizing layer (Y) are bonded together, the optical axis of light (P wave) in the polarization direction that is polarized and separated by the brightness enhancement layer (X) The optical axis shifts from the absorption-type polarizing layer (Y), and the absorption-type polarizing layer (Y) absorbs a part of the light in the polarization direction (P wave) transmitted through the brightness enhancement layer (X). As a result, light loss may occur.
In order to solve these problems, the brightness enhancement layer (X) and the absorption-type polarizing layer (Y) can be combined with the brightness enhancement layer (X) and the absorption-type polarization layer (Y) without using an adhesive layer or an adhesive layer. It is important that the layers are laminated adjacent to each other, and it is preferable that the brightness enhancement layer (X) and the absorption-type polarizing layer (Y) are laminated in advance and then co-stretched in the uniaxial direction.
The brightness enhancement layer (X) and the absorption-type polarizing layer (Y) are laminated adjacent to each other without interposing an adhesive layer or an adhesive layer. The phase shift of light can be reduced. In addition, the luminance enhancement layer (X) and the absorption-type polarizing layer (Y) are laminated in advance and then co-stretched in the uniaxial direction. The transmitted light can pass through the absorptive polarizing layer (Y).

<Brightness enhancement layer (X)>
The brightness enhancement layer (X) in the laminate is any material that transmits light of a specific polarization direction (for example, P wave) and reflects light of other polarization direction (for example, S wave). It may be a thing. In the case of a layer having such a role, reflected light (for example, S wave) is separated again into light having a specific polarization direction (for example, separated into P wave and S wave), and repeats transmission and reflection. The luminance can be improved by recycling the light.
For example, a scattering type polarizing layer (X1) formed by uniaxially stretching a polymer blend having a phase separation structure composed of two types of polymers having different birefringence, or a dielectric multilayer thin film body and a difference in refractive index anisotropy In addition to the multilayer polarizing layer (X2) such as a thin film, a cholesteric liquid crystal alignment film, a film in which the alignment liquid crystal layer is supported on a film substrate, and the like can be appropriately selected and used.
In general, the scattering polarizing layer (X1) and the multilayer polarizing layer (X2) reflect linearly polarized light. On the other hand, an alignment film of cholesteric liquid crystal or a film in which the alignment liquid crystal layer is supported on a film substrate reflects circularly polarized light. The former type of brightness enhancement layer that transmits / reflects linearly polarized light as in the former allows the transmitted light to pass through the polarizing plate as it is, with the polarization axis aligned, and efficiently transmitted while suppressing absorption loss due to the polarizing plate. Can do. On the other hand, a brightness enhancement layer of a type that transmits / reflects circularly polarized light, such as the latter, allows circularly polarized light to be incident on a polarizer as it is. It is preferable that the light is linearly polarized through a plate and then incident on the polarizing plate. As the retardation plate, circularly polarized light can be converted into linearly polarized light by using a λ / 4 plate.

The brightness enhancement layer (X) in the laminate is preferably selected from the scattering polarizing layer (X1) or the multilayer polarizing layer (X2).
When the brightness enhancement layer (X) is selected from the scattering polarization layer (X1) or the multilayer polarization layer (X2), the transmitted light polarized and separated by the brightness enhancement layer (X) becomes linearly polarized light, and is absorbed adjacently. This is preferable because the axes of transmitted light and light polarized by the polarizing plate (Y) are aligned. Further, among the polarization axes reflected by the brightness enhancement layer (X), polarized light that has been transmitted without being completely reflected can be absorbed by the adjacent absorption polarizing layer (Y), which is preferable.
In the case where priority is given to the diffusibility of transmitted light, the scattering type polarizing layer (X1) is preferably selected. In the case where priority is given to the linearity of transmitted light, the multilayer type polarizing layer (X2) is preferably selected. It is preferable to select.

<Scattering polarizing layer (X1)>
In the present laminate, the scattering polarizing layer (X1) preferably contains at least two kinds of thermoplastic resins and has a sea-island structure with a continuous phase (I) and a dispersed phase (II).
At this time, the thermoplastic resin forming the continuous phase (I) is referred to as a thermoplastic resin (A), and the thermoplastic resin forming the dispersed phase (II) is referred to as a thermoplastic resin (B). That is, the continuous phase (I) and the dispersed phase (II) are phases mainly composed of different thermoplastic resins.

The thermoplastic resin (A) that forms the continuous phase (I) and the thermoplastic resin (B) that forms the dispersed phase (II) are not particularly limited unless departing from the scope defined in the present invention. Rather, any thermoplastic resin can be used. Especially, it is preferable that the intrinsic birefringence of a thermoplastic resin (A) and a thermoplastic resin (B) is both positive.
For example, a thermoplastic resin having a negative intrinsic birefringence, such as a polystyrene resin or an acrylic resin, can also be used as the thermoplastic resin (A) and the thermoplastic resin (B). Since the side chain has a bulky molecular structure, the mechanical strength may decrease. Therefore, as the thermoplastic resin (A) and the thermoplastic resin (B), a heat having a positive intrinsic birefringence from the viewpoint of preventing a decrease in mechanical strength when the scattering type polarizing layer (X1) is formed. It is preferable to use a plastic resin. However, this does not prevent the use of a thermoplastic resin having excellent mechanical strength and a negative intrinsic birefringence.

The absolute value of the difference between the average refractive index of the thermoplastic resin (A) forming the continuous phase (I) and the average refractive index of the thermoplastic resin (B) forming the dispersed phase (II) is from 0.05. Larger is preferable.
When the intrinsic birefringence of the thermoplastic composition (A) and the thermoplastic resin (B) is both positive, the absolute value of the average refractive index difference between (A) and (B) is 0.05 or less. If there is, it is considered that a refractive index difference in an axis (S axis) parallel to the alignment direction of the continuous phase (I) and the disperse phase (II) hardly occurs when the alignment is performed.

Moreover, it is preferable that the magnitude relationship of the average refractive index of said (A) and said (B) and the magnitude relationship of the birefringence of said (A) and said (B) are equal. That is, if the average refractive index magnitude relationship between (A) and (B) is (A)> (B), the magnitude relationship between the birefringence indices in (A) and (B) is also It is preferable that (A)> (B). If the magnitude relationship does not match, it is considered that a difference in refractive index between the axis (S axis) parallel to the orientation direction of the continuous phase (I) and the dispersed phase (II) is unlikely to occur.
However, if the scattering type polarizing layer (X1) oriented in the uniaxial direction belongs to the range defined by the present invention, the absolute value of the average refractive index difference between (A) and (B) or the average refraction Matching the magnitude relationship between the refractive index and the birefringence is not an essential condition.

Moreover, it is preferable that at least one of the thermoplastic resin (A) that forms the continuous phase (I) and the thermoplastic resin (B) that forms the dispersed phase (II) is a crystalline thermoplastic resin.
If at least one of the thermoplastic resin (A) forming the continuous phase (I) and the thermoplastic resin (B) forming the dispersed phase (II) is a crystalline thermoplastic resin, it is oriented in a uniaxial direction. At this time, since the polymer chain is easily oriented and the refractive index difference between the continuous phase (I) and the dispersed phase (II) with respect to the axis parallel to the orientation direction (S axis) is easily increased, the polarization reflection characteristic at the S axis is improved. It is preferable because it is easy to improve.
The crystalline thermoplastic resin generally refers to a thermoplastic resin that has a crystal melting peak temperature (melting point), and more specifically, in differential scanning calorimetry (DSC) performed in accordance with JIS K7121. Thermoplastic resins whose melting point is observed include those in a so-called semi-crystalline state. Conversely, a thermoplastic resin whose melting point is not observed in DSC is referred to as “amorphous”.

  There is no limitation in particular as such a crystalline thermoplastic resin. For example, polyesters such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polytrimethylene terephthalate, poly-1,4-cyclohexylenedimethylene terephthalate, polyethylene succinate, polybutylene succinate, polylactic acid, poly-ε-caprolactam Resin, polyethylene resin such as high density polyethylene, low density polyethylene, linear polyethylene, ethylene-vinyl acetate copolymer, ethylene- (meth) acrylic acid copolymer, ethylene- (meth) acrylic acid ester Polymer, ethylene-vinyl alcohol copolymer, ethylene-vinyl chloride copolymer, ethylene-vinyl acetate-carbon monoxide copolymer, ethylene-vinyl acetate-vinyl chloride copolymer, ethylene-α olefin copolymer, etc. of Fluorine resins such as ethylene copolymers, polypropylene resins, polybutene resins, polyamide resins, polyoxymethylene resins, polymethylpentene resins, polyvinyl alcohol resins, polytetrafluoroethylene and polyvinylidene fluoride, Examples include cellulose-based resins, polyether ether ketone, polyether ketone, polyphenylene sulfide, engineering plastics such as polyparaphenylene terephthalamide, and super engineering plastics. Of these, polyester resins are preferable, and crystalline aromatic polyester resins are more preferable.

  In general, polyester-based resins often have a positive intrinsic birefringence, and among them aromatic polyester-based resins have a high birefringence, so that the continuous phase (I) with respect to the axis parallel to the orientation direction (S-axis) This is preferable because the refractive index difference of the dispersed phase (II) can be easily increased and the polarization reflection characteristics on the S axis can be easily improved.

In the scattering type polarizing layer (X1), one of the thermoplastic resin (A) forming the continuous phase (I) and the thermoplastic resin (B) forming the dispersed phase (II). When is a crystalline or semi-crystalline thermoplastic resin, the other thermoplastic resin is preferably an amorphous thermoplastic resin.
As will be described later, the scattering type polarizing layer (X1) is preferably subjected to heat treatment after being oriented in a uniaxial direction from the viewpoint of dimensional stability. The reason for this is that during the heat treatment, the crystalline thermoplastic resin is easily oriented and crystallized, with respect to the axis parallel to the orientation direction (S axis) and the axis perpendicular to the orientation direction and parallel to the film surface (P axis). It is heat-fixed with a large refractive index anisotropy. On the other hand, the amorphous thermoplastic resin tends to be relaxed in orientation during heat treatment, and as a result, the refractive index difference between the continuous phase (I) and the dispersed phase (II) with respect to the S axis is increased. This is because it tends to be easier.

  There is no particular limitation on the amorphous thermoplastic resin. For example, a polyester resin, a polycarbonate resin, a polyolefin resin, polyphenylene ether, and the like can be given. Among these, an amorphous polyester resin is preferable.

(Polyester resin)
In the scattering type polarizing layer (X1), a thermoplastic resin (A) that forms the continuous phase (I) and a thermoplastic resin (B) that forms the dispersed phase (II) can be suitably used. As described above. Among these, at least one of the thermoplastic resin (A) and the thermoplastic resin (B) is more preferably a polyester resin having a diol residue derived from isosorbide.
By having a diol residue derived from isosorbide, the heat resistance of the polyester resin is improved, so that the deflection and dimensional stability of the scattering-type polarizing layer (X1) can be improved. Further, the compatibility between the polyester resin having a diol residue derived from isosorbide and other thermoplastic resins is increased, and the thermoplastic resin (A) and the dispersed phase (II) forming the continuous phase (I) are added. Formation of a fine sea-island structure with the thermoplastic resin (B) to be formed can be achieved.

  Polyester resins having diol residues derived from isosorbide include aromatic polyester resins and aliphatic polyester resins derived from dicarboxylic acid residues and diol residues, polyester carbonates having carbonate bonds, etc. Is also included. In addition to the above, copolymers obtained by various combinations of various dicarboxylic acid residues and diol residues and polymer blends are also included.

  Examples of preferable dicarboxylic acid residues for constituting a polyester resin having a diol residue derived from isosorbide include terephthalic acid, isophthalic acid, 2-chloroterephthalic acid, 2,5-dichloroterephthalic acid, 2- Methyl terephthalic acid, 4,4-stilbene dicarboxylic acid, 4,4-biphenyl dicarboxylic acid, orthophthalic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, bisbenzoic acid, bis (p-carboxyphenyl) Aromatic dicarboxylic acids such as methane, anthracene dicarboxylic acid, 4,4-diphenyl ether dicarboxylic acid, 4,4-diphenoxyethane dicarboxylic acid, 5-Na sulfoisophthalic acid, ethylene-bis-p-benzoic acid, succinic acid, adipine Acid, sebacic acid, azelaic acid, dodecanedioic acid, , 3-cyclohexane dicarboxylic acid, residues derived from aliphatic dicarboxylic acids or their ester derivatives, such as 1,4-cyclohexane dicarboxylic acid. These dicarboxylic acid residues may be used alone or in combination of two or more.

  Furthermore, as a preferable mixture of diol residues for constituting a polyester resin having a diol residue derived from isosorbide, for example, an ethylene glycol residue as a first residue and 1,4- Selected from the group consisting of butanediol, neopentyl glycol, isosorbide, diethylene glycol, polytetramethylene glycol, and 1,4-cyclohexanedimethanol, spiroglycol, 2,2,4,4-tetramethylcyclobutane-1,3-diol And those using a residue derived from at least one selected from the group consisting of isosorbide. Preferred diol residues constituting a polyester resin having a diol residue derived from isosorbide include an ethylene glycol residue as the first residue, a 1,4-cyclohexanedimethanol residue as the second residue and an isosorbide residue. The thing using group is mentioned.

  Furthermore, the thermoplastic resin (A) that forms the continuous phase (I) and the thermoplastic resin (B) that forms the dispersed phase (II) are both polyester resins, and the thermoplastic resin (A) and the thermoplastic resin. It is preferable that the resin (B) is a different type of polyester resin.

As described above, in general, a polyester-based resin often has a positive intrinsic birefringence, and has a high birefringence. Therefore, a continuous phase (I) and a disperse phase with respect to an axis (S axis) parallel to the orientation direction. It is easy to increase the refractive index difference of (II).
In addition, when both the thermoplastic resin (A) and the thermoplastic resin (B) are polyester resins, and the thermoplastic resin (A) and the thermoplastic resin (B) are different types of polyester resins, Since the compatibility of (A) and (B) is high, the continuous phase (I) and the dispersed phase (II) are easy to form with a uniform and fine sea-island structure.
Among these, polyester resins having a diol residue derived from isosorbide have good compatibility with other polyester resins. Therefore, in the island structure elongated in the orientation direction of the dispersed phase (II) generated when oriented in the uniaxial direction, the dispersion diameter in the axis (P-axis) direction perpendicular to the orientation direction of the dispersed phase (II) and parallel to the film surface Tends to be in the range of less than or equal to the wavelength of visible light, and this brings about an effect of facilitating improvement in luminance in the laminate.

  The thermoplastic resin (A) that forms the continuous phase (I) and the thermoplastic resin (B) that forms the dispersed phase (II) are both polyester-based resins, and the thermoplastic resin (A) and the heat When the plastic resin (B) is a different type of polyester resin, one of the thermoplastic resin (A) and the thermoplastic resin (B) is a crystalline polyester resin, particularly a crystalline aromatic polyester resin. It is preferable that the other resin is an amorphous polyester resin.

  Polyester resins that can be preferably used in the scattering type polarizing layer (X1) are derived from dicarboxylic acid residues and diol residues, derived from hydroxycarboxylic acids such as lactic acid, and derived from ε-caprolactam. There are no particular restrictions on the items. Specifically, for example, aromatic polyester resins such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polytrimethylene terephthalate, poly-1,4-cyclohexylene dimethylene terephthalate, polyethylene succinate, polybutylene succinate. In addition to aliphatic polyester resins such as polylactic acid and poly-ε-caprolactam, polyester carbonate having a carbonate bond is also included as a concept. In addition to the above, copolymers obtained by various combinations of various dicarboxylic acid residues and diol residues and polymer blends are also included.

  Examples of preferred dicarboxylic acid residues include terephthalic acid, isophthalic acid, 2-chloroterephthalic acid, 2,5-dichloroterephthalic acid, 2-methylterephthalic acid, 4,4-stilbene dicarboxylic acid, 4,4-biphenyldicarboxylic acid Acid, orthophthalic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, bisbenzoic acid, bis (p-carboxyphenyl) methane, anthracene dicarboxylic acid, 4,4-diphenyl ether dicarboxylic acid, 4,4- Aromatic dicarboxylic acids such as diphenoxyethanedicarboxylic acid, 5-Na sulfoisophthalic acid, ethylene-bis-p-benzoic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, dodecanedioic acid, 1,3-cyclohexanedicarboxylic acid Fats such as acids and 1,4-cyclohexanedicarboxylic acid Residues derived from dicarboxylic acids or their ester derivatives. These dicarboxylic acid residues may be used alone or in combination of two or more.

  Preferred mixtures of diol residues include, for example, ethylene glycol residue as the first residue, 1,4-butanediol, neopentyl glycol, isosorbide, diethylene glycol, polytetramethylene glycol, and 1,4 as the second residue. -What used the residue induced | guided | derived from at least 1 sort (s) chosen from the group which consists of cyclohexanedimethanol, spiroglycol, 2,2,4,4-tetramethylcyclobutane-1,3-diol is mentioned. Preferably, an ethylene glycol residue is used as the first residue, and an isosorbide residue or a 1,4-cyclohexanedimethanol residue is used as the second residue.

  Among them, in the thermoplastic resin (A) that forms the continuous phase (I) and the thermoplastic resin (B) that forms the dispersed phase (II), one is a polyester-based resin having a diol residue derived from isosorbide. If the other is a polyethylene naphthalate resin, it is preferable because it has a high average refractive index and a high birefringence.

  When a polyethylene naphthalate resin is used, its weight average molecular weight is preferably 30,000 or more, its intrinsic viscosity is preferably 0.5 dl / g or more, and its glass transition temperature is 70 ° C. to 120 ° C. The range of ° C is preferred, and the melting point is preferably in the range of 240 ° C to 270 ° C.

  Moreover, when using polyethylene naphthalate type-resin, it is preferable to use what has YI value in the range of -10-10, especially in the range of 3-3. When the polyethylene naphthalate resin is made of a mixture, the YI value of each resin is preferably in the range of −10 to 10. If the YI value is in the range of −10 to 10, for example, by incorporating it into a liquid crystal display or the like as a brightness enhancement film, it is possible to further improve the image clarity, and to further increase the brightness improvement rate. it can.

A commercial item can also be used as a polyethylene naphthalate-type resin.
For example, Teonex TN8065S (polyethylene naphthalate homopolymer, manufactured by Teijin Chemicals Ltd., intrinsic viscosity 0.71 dl / g), Teonex TN8065SC (polyethylene naphthalate homopolymer, manufactured by Teijin Chemicals Ltd., intrinsic viscosity 0.55 dl) / G), Teonex TN8756C (polyethylene naphthalate and polyethylene terephthalate copolymer, manufactured by Teijin Chemicals Ltd., intrinsic viscosity 0.65 dl / g) and the like can be mentioned as preferred examples.

((A) / (B))
The scattering-type polarizing layer (X1) comprising a film having a sea-island structure composed of a continuous phase (I) and a dispersed phase (II), wherein the brightness enhancement layer (X) constituting the laminate comprises at least two types of thermoplastic resins. ), The mixing mass ratio of the thermoplastic resin (A) forming the continuous phase (I) and the thermoplastic resin (B) forming the dispersed phase (II) is (A) / (B) = 10 mass. Parts / 90 parts by mass to 90 parts by mass / 10 parts by mass, especially 25 parts by mass / 75 parts by mass to 75 parts by mass / 25 parts by mass, and especially 35 parts by mass / 65 parts by mass to 65 parts by mass / 35 parts by mass. Preferably there is. Such a mixed mass ratio is preferable because the dispersed phase does not decrease too much, and scattering at the interface between the continuous phase and the dispersed phase is reduced, and there is no fear that the polarization reflection characteristic is deteriorated.
The scattering type polarizing layer (X1) may contain other thermoplastic resin as long as it contains at least one thermoplastic resin (A) and one thermoplastic resin (B). Two or more thermoplastic resins corresponding to the thermoplastic resin (B) may be included.

(Compatibilizer (C))
Further, the brightness enhancement layer (X) constituting the laminate includes at least two kinds of thermoplastic resins, and includes a film having a sea-island structure composed of a continuous phase (I) and a dispersed phase (II). In the case of (X1), an additive such as a compatibilizing agent (C) may be added to the scattering polarizer as necessary for the purpose of improving the dispersibility of the dispersed phase (II).

  The compatibilizer (C) can be selected from conventional compatibilizers according to the type of continuous phase and dispersed phase. For example, at least one resin selected from a polycarbonate resin, an ester resin, a resin having an epoxy group, a resin having an oxazoline ring, a resin having an azlactone group, and at least one selected from a styrene resin, polyphenylene oxide, and polyamide. And a block copolymer composed of two resins or a graft copolymer. Among these, from the viewpoint of improving dispersibility, a resin having an epoxy group or an oxazoline group is particularly preferable, and an epoxy-modified one is particularly preferable.

  When the compatibilizer (C) is added, the blending ratio is preferably 0.1 to 20 parts by mass with respect to a total of 100 parts by mass of the thermoplastic resin (A) and the thermoplastic resin (B). Among these, it is preferably 0.2 parts by mass or more and 15 parts by mass or less, more preferably 0.2 parts by mass or more and 10 parts by mass or less, and particularly preferably 1 part by mass or more or 10 parts by mass or less.

  Further, as additives other than the compatibilizing agent (C), various additives such as antioxidants, heat stabilizers, light stabilizers, hydrolysis inhibitors, impact modifiers, and the like can be used as long as the properties of the present invention are not impaired. Can be added.

(Refractive index)
In the scattering type polarizing layer (X1), the absolute value of the difference between the refractive index of the continuous phase (I) and the refractive index of the dispersed phase (II) is 0.05 on the axis parallel to the orientation direction (S axis). It is preferably larger and larger than 0.05 in an axis (P axis) perpendicular to the orientation direction and parallel to the film surface.

  Since the absolute value of the difference between the refractive index of the continuous phase (I) and the refractive index of the dispersed phase (II) is larger than 0.05 in the axis parallel to the orientation direction (S axis), High scattering reflection characteristics are exhibited with respect to polarized light, and the luminance improving ability of the obtained scattering type polarizing layer (X1) can be improved. The absolute value of the difference between the refractive index of the continuous phase (I) and the refractive index of the dispersed phase (II) is more preferably greater than 0.1 and even more preferably greater than 0.15 on the S axis.

In addition, the absolute value of the difference between the refractive index of the continuous phase (I) and the refractive index of the dispersed phase (II) is larger than 0.05 in an axis (P axis) perpendicular to the orientation direction and parallel to the film surface. As a result, high transmission characteristics can be exhibited with respect to the polarized light on the P-axis.
On the other hand, the absolute value of the difference between the refractive index of the continuous phase (I) and the refractive index of the dispersed phase (II) is preferably smaller than 0.1. By being smaller than 0.1, scattering at the interface between the continuous phase (I) and the dispersed phase (II) is suppressed when the dispersed diameter in the P-axis direction of the dispersed phase (II) described later is within a preferable range in the present invention. It is preferable because the transmission characteristic on the P-axis can be expressed.

As a means for making the absolute value of the difference between the refractive index of the continuous phase (I) and the refractive index of the dispersed phase (II) greater than 0.05 in the axis parallel to the orientation direction (S axis), The thermoplastic resin so that the absolute value of the difference in average refractive index between the thermoplastic resin (A) forming (I) and the thermoplastic resin (B) forming the dispersed phase (II) is greater than 0.05. (A) and thermoplastic resin (continuous by stretching, such as selecting B and adjusting to a preferred range, free-width uniaxial stretching, constant-width uniaxial stretching, tensile stretching method, inter-roll stretching method, roll rolling method, etc. Orient the thermoplastic resin (A) that forms the phase (I) and / or the thermoplastic resin (B) that forms the dispersed phase (II), and adjust to the preferred range using the difference in birefringence Or a thermoplastic resin (A) that forms the continuous phase (I), and Or, the thermoplastic resin forming the dispersed phase (II) (B), or the like is added other thermoplastic resins and the refractive index control agent which is compatible, and a method of adjusting a preferred range.
In addition, the absolute value of the difference between the refractive index of the continuous phase (I) and the refractive index of the dispersed phase (II) is larger than 0.05 on an axis (P axis) perpendicular to the orientation direction and parallel to the film surface. As a means to do this, the absolute value of the difference in average refractive index between the thermoplastic resin (A) forming the continuous phase (I) and the thermoplastic resin (B) forming the dispersed phase (II) is from 0.05 A method of selecting the thermoplastic resin (A) and the thermoplastic resin (B) so as to increase, and adjusting to a preferable range, free width uniaxial stretching, constant width uniaxial stretching, tensile stretching method, inter-roll stretching method, Orienting the thermoplastic resin (A) that forms the continuous phase (I) and / or the thermoplastic resin (B) that forms the dispersed phase (II) by stretching such as a roll rolling method, Method of adjusting to a preferred range by using, or forming the continuous phase (I) Add other compatible thermoplastic resin or refractive index adjuster to the thermoplastic resin (A) and / or the thermoplastic resin (B) forming the dispersed phase (II), and adjust to the preferred range. The method etc. are mentioned.

In the method, for example, the intrinsic birefringence of the thermoplastic resin (A) and the thermoplastic resin (B) are both positive, and the refractive index magnitude relationship between the (A) and the (B), When the magnitude relationship between the birefringences of (A) and (B) is equal, the thermoplastic resin (A) that forms the continuous phase (I) and the thermoplastic resin (B that forms the dispersion layer (II)) ) Is oriented by stretching in a uniaxial direction, the absolute value of the refractive index difference of the axis parallel to the orientation direction (S axis) tends to be greater after stretching than before stretching. It is done.
Therefore, if the thermoplastic resin (A) and the thermoplastic resin (B) having an average refractive index difference of 0.05 or more are selected and stretched, the absolute value of the S-axis refractive index difference is larger than 0.05. can do. On the other hand, the absolute value of the refractive index difference of the axis (P axis) perpendicular to the orientation direction may be smaller after stretching than before stretching. Therefore, the thermoplastic resin (A) and the thermoplastic resin (B) having a difference in average refractive index of 0.05 or more are selected and stretched within a range where the absolute value of the difference in refractive index of the P axis is not smaller than 0.05. There is a need to.
Taking these points into consideration, the stretching ratio and the like are determined, and the film is stretched in a uniaxial direction and oriented, so that the absolute value of the difference in refractive index between the S axis and the P axis is larger than 0.05. be able to.

(Dispersion diameter)
The scattering type polarizing layer (X1) preferably has a dispersion diameter in the P-axis direction of the dispersed phase (II) of 10 nm or more and 200 nm or less. The dispersion diameter is measured by the method described later.

Since the scattering-type polarizing layer (X1) is oriented in a uniaxial direction, the dispersed phase (II) is a flat ellipsoid or a fiber. If the dispersion diameter in the P-axis direction of the disperse phase (II) is 10 nm or more and 200 nm or less, it is sufficiently smaller than the wavelength order of light, and therefore in the axis (P-axis) perpendicular to the orientation direction and parallel to the film surface Even if the refractive index difference between the continuous phase (I) and the dispersed phase (II) is large, sufficient transmission characteristics can be exhibited.
Further, in the scattering type polarizing layer (X1), the dispersion diameter in the P-axis direction of the dispersed phase (II) is 10 nm or more and 200 nm or less in order to develop higher polarization transmission characteristics with respect to the polarized light on the P-axis. It is preferable that Among these, the dispersion diameter in the P-axis direction of the dispersed phase (II) is preferably 10 nm or more and 100 nm or less because higher transmission characteristics are expressed with respect to the polarized light on the P-axis.

  On the other hand, when the dispersion diameter in the P-axis direction of the dispersed phase (II) exceeds 200 nm, scattering at the interface between the continuous phase (I) and the dispersed phase (II) tends to occur, and the polarization transmission characteristics are deteriorated. Further, anisotropy of the mechanical properties of the scattering type polarizing layer is likely to occur, and problems such as cracking and tearing are likely to occur. On the other hand, when the thickness is less than 10 nm, the continuous phase (I) and the dispersed phase (II) can be regarded as being compatible with each other, and it is difficult to develop the polarization characteristics.

  As means for setting the dispersion diameter in the P-axis direction of the dispersed phase (II) to 10 nm or more and 200 nm or less, the thermoplastic resin (A) that forms the continuous phase (I) and the thermoplastic that forms the dispersed phase (II). A technique of sufficiently kneading the resin (B) with a twin screw extruder or the like so as not to be compatible with each other, and sufficiently stretching the thermoplastic resin (B) forming the dispersed phase (II) by uniaxial stretching. When forming a film by the method, T-die casting method, by sufficiently extending the thermoplastic resin (B) forming the dispersed phase (II) by increasing the take-up speed (cast roll speed), by the inflation method A method of sufficiently stretching the thermoplastic resin (B) for forming the dispersed phase (II) by increasing the take-up speed when forming a film, a fiber having a fiber diameter of 10 nm or more and 200 nm or less, and a continuous phase (I ) A method of impregnating a thermoplastic resin formed (A).

(Polarization transmittance)
The brightness enhancement layer (X) preferably has an average polarization transmittance of 80% or more at a measurement wavelength of 400 nm to 700 nm on the P axis. Conventionally, it has been considered that high diffuse reflection characteristics with respect to polarized light are necessary in order to develop a high brightness enhancement capability. However, although the reason is not clear, the present inventors have demonstrated transmission characteristics with respect to polarized light on the P axis. It has been found that a sufficient contribution to the improvement of the luminance improvement capability is obtained by sufficiently increasing it.

  The average polarization transmittance is more preferably 81% or more, and particularly preferably 84% or more. In order to make the average polarization transmittance 80% or more, the absolute value of the difference between the refractive index of the continuous phase (I) and the refractive index of the dispersed phase (II) is adjusted to a suitable range, or the continuous phase (I ) To control the size of the dispersed phase (II) in the kneading of the thermoplastic resin (A) forming the dispersed phase (II) and the thermoplastic resin (B) forming the dispersed phase (II). This can be achieved by reducing the dispersion diameter.

(Mechanical strength)
Further, the brightness enhancement layer (X) preferably has a tear strength in the P-axis direction measured in accordance with JIS K7128-3 of 600 N / cm or more. More specifically, a test piece is prepared according to JIS K7128-3, and evaluated by the tear strength measured by the right-angled tearing method at a temperature of 23 ° C. and a test speed of 200 mm / min.
When the tear strength is 600 N / cm or more, this laminate has excellent mechanical strength when used as a brightness enhancement layer, and causes problems such as breakage during handling when incorporated in a liquid crystal display device. The possibility is very small.

As described in the prior art, the conventional scattering-type polarizing layer has a low compatibility between the continuous phase and the dispersed phase, so that a relatively large dispersed phase is formed and the dispersed phase is uniaxially stretched. Anisotropy also occurs in the mechanical strength, and when a load is applied in the P-axis direction, there is a problem that cracks and tears easily occur along the S-axis.
On the other hand, the scattering type polarizing layer (X1) of the present invention surprisingly has a mechanical strength that could not be achieved in the past, and the P-axis direction measured in accordance with JIS K7128-3. The tear strength is preferably 600 N / cm or more, more preferably 800 N / cm or more, still more preferably 900 N / cm or more, and particularly preferably 1000 N / cm or more.

  As means for setting the tear strength in the P-axis direction measured in accordance with JIS K7128-3 to 600 N / cm or more, at least two types of thermoplastic resins constituting the laminate have a positive intrinsic birefringence. It is possible to select a product or to select a product with good compatibility. In addition, by selecting a polyester-based resin having a diol residue derived from isosorbide as the at least one thermoplastic resin, the size of the dispersed phase (II) during kneading with another thermoplastic resin is selected. Can be controlled. Furthermore, when a crystalline thermoplastic resin is used for the dispersed phase (II), the dispersion diameter is finely oriented in the P-axis direction and then sufficiently crystallized, which is achieved by combining these means. You can also

<Multilayer Polarizing Layer (X2)>
In this laminate, the multilayer polarizing layer (X2) is formed by alternately laminating a plurality of layers having a low refractive index and layers having a high refractive index, and selectively selects light having a specific wavelength by structural optical interference between the layers. An optical interference layer that reflects or transmits light.
Such a multilayer laminated film can obtain a high reflectance equivalent to a film using metal by gradually changing the film thickness or by bonding films having different reflection peaks. It can also be used as a reflection mirror. Furthermore, by extending such a multilayer laminate only in one direction, it can be used as a brightness enhancement layer that reflects only a specific polarization component.

In general, the multilayer polarizing layer (X2) is composed of layers having different refractive indexes of 0.05 to 0.5 μm, and the refractive index of the layer constituting one layer and the layer constituting the other layer. Depending on the difference, the film thickness, and the number of stacked layers, a phenomenon of increased reflection that reflects light of a specific wavelength is observed. In general, the reflection wavelength is expressed by the following equation.
λ = 2 (n1 × d1 + n2 × d2)
(In the above formula, λ is the reflection wavelength (nm), n1 and n2 are the refractive indices of the respective layers, and d1 and d2 are the thicknesses (nm) of the respective layers)

In addition, by using a resin with a positive stress optical coefficient in one layer, the refractive index of the layer is birefringent by stretching in a uniaxial direction to give anisotropy, and stretching in the film plane Only a specific polarization component can be reflected by increasing the refractive index difference between the layers in the direction while reducing the refractive index difference between the layers in the direction perpendicular to the stretching direction in the film plane.
The desirable birefringence at that time is represented by the following equation.
n1X> n2X, n1Y = n2Y
(In the above formula, n1X and n2X represent the refractive index in the stretching direction in each layer, and n1Y and n2Y represent the refractive index in the direction orthogonal to the stretching direction in each layer)

  As a configuration example of the multilayer polarizing layer (X2), polyethylene-2,6-naphthalenedicarboxylate (hereinafter sometimes referred to as 2,6-PEN) is used for the layer having a high refractive index, and the refractive index A multilayer structure using PEN copolymerized with a thermoplastic elastomer or isophthalic acid is exemplified in the lower layer.

<Absorptive polarizing layer (Y)>
The absorptive polarizing layer (Y) in this laminated body transmits only light in a specific polarization direction (P wave, linearly polarized light) and supplies it to the liquid crystal cell, and absorbs light in other polarization directions (S wave). It is a layer that plays a role.

At this time, the absorptive polarizing layer (Y) is based on a suitable conventional film as a base material, and the base material is dyed, stretched or crosslinked with a dichroic substance made of iodine, dichroic dye or the like. These are appropriately processed in an appropriate order and manner.
In addition, the absorbing polarizing layer (Y) preferably transmits linearly polarized light when natural light is incident thereon, and particularly preferably has excellent light transmittance and degree of polarization. From such a viewpoint, it is preferable that the base material of the absorption polarizing layer (Y) is mainly composed of polyvinyl alcohol.

If the polymerization degree of the polyvinyl alcohol is 1000 or more, the liquid flow and uneven coating can be reduced at the time of coating, and when the aqueous solution of the polyvinyl alcohol resin is applied, the polyvinyl alcohol can be repelled even if the coating thickness is reduced. Is preferable because it does not occur. From this viewpoint, the lower limit of the degree of polymerization of polyvinyl alcohol is preferably 1000 or more, more preferably 1200 or more, and particularly preferably 1500 or more.
Moreover, if the polymerization degree of the said polyvinyl alcohol is 8000 or less, mixing of the gel and undissolved substance derived from polyvinyl alcohol can be prevented, and it is preferable. From such a viewpoint, the upper limit value of the degree of polymerization of polyvinyl alcohol is preferably 8000 or less, more preferably 7000 or less, and particularly preferably 6000 or less.

  As a base material of the absorption type polarizing layer (Y), in addition to polyvinyl alcohol, for example, polyvinyl formal, polyvinyl acetal, poly (ethylene-vinyl acetate) copolymer, partially saponified or completely saponified product thereof, polyvinyl alcohol And the partial polyene product.

As a general method for adsorbing and orienting iodine on such a substrate, a method of stretching an uniaxially stretched substrate after immersing an unstretched substrate in a solution of iodine and potassium iodide, or a uniaxially stretched substrate The method of immersing in the solution of an iodine and potassium iodide etc. can be mentioned.
At this time, light incident in a direction parallel to the axial direction extended uniaxially is absorbed, and light incident on an axis parallel to the film surface in a direction perpendicular to the axial direction extended uniaxially passes.
Therefore, the absorption-type polarizing layer (Y) in the present invention is laminated in advance from the viewpoint of light axis deviation from the luminance-enhancing layer (X). After that, it is preferable to co-stretch in the uniaxial direction because the polarization direction becomes the same direction.
That is, when co-stretched in the uniaxial direction, the brightness enhancement layer (X) reflects light incident in a direction parallel to the uniaxially stretched axial direction, but transmits light that is transmitted without being completely reflected. It can be absorbed in the absorption type polarizing layer (Y). In addition, the brightness enhancement layer (X) transmits light incident in a direction perpendicular to the uniaxially stretched axial direction and parallel to the film surface, and the polarized light transmitted through the brightness enhancement layer (X) is absorption-type polarization. It is also transmitted through the layer (Y).
Subsequently, a substrate made of a polyvinyl alcohol resin to which iodine is adsorbed and oriented is treated with an aqueous solution containing potassium iodide and boric acid in order to stabilize the crosslinking. Examples of the method include a method of immersing the base material in an aqueous solution containing potassium iodide and boric acid. The boric acid concentration and potassium iodide concentration in the aqueous solution used are 2 to 20 parts by weight of potassium iodide, preferably 5 to 12 parts by weight, and 2 to 15 parts by weight of boric acid with respect to 100 parts by weight of water. Preferably, an aqueous solution containing 7 to 10 parts by weight is used. If the amount of potassium iodide with respect to 100 parts by weight of water is less than 2 parts by weight or exceeds 20 parts by weight, it is difficult to obtain a satisfactory polarizing layer. Further, when the amount of boric acid relative to 100 parts by weight of water is less than 2 parts by weight, a satisfactory polarizing layer cannot be obtained, and when the amount exceeds 15 parts by weight, problems such as crystal precipitation occur, which is not preferable. .

When the substrate is treated with an aqueous solution containing potassium iodide and boric acid, the treatment is preferably performed at a temperature in the range of 55 to 80 ° C. More preferably, it is the range of 60-70 degreeC. Moreover, the processing time in this case is 100 to 1200 seconds normally, Preferably it is 150 to 600 seconds.
The treatment in such a temperature range and treatment time range is preferable for improving the durability performance and polarization performance of the absorbing polarizing layer (Y).

  After the treatment with an aqueous solution containing potassium iodide and boric acid, a water washing treatment is performed. The treatment temperature and time at the time of this water washing may be such that the water washing treatment is performed at a treatment temperature of 10 ° C. or less. The treatment time is preferably 60 seconds or less when the temperature exceeds 10 ° C. and 20 ° C. or less, or the treatment time is 30 seconds or less when the treatment temperature exceeds 20 ° C. This washing treatment is particularly preferably carried out at a temperature of 0 ° C. or higher and 30 ° C. or lower. In particular, when the processing temperature is 0 ° C. or higher and 10 ° C. or lower, the processing time is 5 seconds or longer and 120 seconds or shorter, and the processing temperature is 10 ° C. When the temperature is higher than 20 ° C. and lower than or equal to 20 ° C., the processing time is preferably 5 seconds or longer and 60 seconds or shorter, and when the processing temperature is higher than 20 ° C. and lower than or equal to 30 ° C. From the viewpoint of industrial production, it is preferable that the washing treatment temperature is 4 ° C. or higher and the above-mentioned treatment conditions are satisfied. A water washing treatment at a temperature higher than 30 ° C. or a water washing treatment for a time shorter than 5 seconds or longer than 120 seconds is not preferable in terms of the quality of the obtained film. After the water washing treatment, a highly transparent absorption polarizing layer (Y) having a high transparency and a high degree of polarization can be obtained by ordinary drying.

  As a general method for adsorbing and orienting the dichroic dye on the base material made of the polyvinyl alcohol resin, a specific organic direct dye having a high dichroic ratio with the base material made of the polyvinyl alcohol resin. Is dissolved in water, an organic solvent, or a mixed solvent of water and an organic solvent, and then uniaxially stretched or uniaxially stretched by a compression stretching method.

  The dichroic dye used for the absorbing polarizing layer (Y) may be any dichroic dye having a high dichroic ratio, but is generally selected from azo dyes.

  As a dichroic dye used in the present invention, represented by a color index generic name, C-I Direct Black 17 (trade name Japanol Fast Black D conc., Manufactured by Taoka Chemical Industry Co., Ltd.), C-I Direct Examples thereof include Yellow 12 (made by Taoka Chemical Industry Co., Ltd., trade name Chrysophene), C.I. Direct Blue 78 (made by Taoka Chemical Industry Co., Ltd., trade name Sumitright Supra Blue G), and the like.

  When a dichroic dye is used as the absorptive polarizing layer (Y), although it has durability against water and heat compared to the case of using iodine, there is a large unevenness of dyeing and it is difficult to obtain a uniform polarizing film. The absorptive polarizing layer (Y) is preferably composed mainly of polyvinyl alcohol containing iodine. However, the absorption polarizing layer (Y) mainly composed of polyvinyl alcohol containing iodine is weak against water and heat, and when used for a long time in a high temperature and high humidity state, the absorption polarizing layer ( Y) is preferably composed mainly of polyvinyl alcohol containing a dichroic dye.

<Method for Forming the Laminate>
As an example of the method for producing the present laminate, the brightness enhancement layer (X) and the absorption polarizing layer (Y) include at least one brightness enhancement layer (X) and an absorption polarization layer (Y). However, there is a production method in which, after being laminated by coextrusion, it is co-stretched in a uniaxial direction.

  Further, as another method for producing the laminate, at least one brightness enhancement layer (X) and an absorption polarization layer (Y) are included, and the brightness enhancement layer (X) includes the absorption polarization layer (Y ) Is applied, and a production method in which the film is co-stretched in the uniaxial direction is exemplified.

First, as the brightness enhancement layer (X), a raw material of the scattering polarizing layer (X1) or the multilayer polarizing layer (X2) is formed. At this time, the method for forming the film is not particularly limited, and examples thereof include a T-die casting method, a calendar method, and an inflation method. Among these, the T die casting method is preferable from the viewpoints of film formation stability and production efficiency.
When adopting the T-die casting method, for example, at least two kinds of thermoplastic resins are dried, supplied to an extruder, and heated to a temperature equal to or higher than the melting point of the resin to be melted. Then, the cast composition may be formed by extruding the melted composition from the slit-shaped discharge port of the T die and firmly solidifying it on a cooling roll.
Although the extrusion temperature of the sheet depends on the flow characteristics of each resin, when a polyethylene naphthalate resin is used, it is preferably about 270 ° C. to 340 ° C., more preferably 280 ° C. to 320 ° C. If the extrusion temperature is 270 ° C. or higher, the sheet can be formed sufficiently for the molten resin to flow. On the other hand, if it is 340 ° C. or lower, the sheet characteristics are less likely to deteriorate due to thermal decomposition of the resin.
Further, the ratio of the discharge amount Q (kg / h) to the screw rotation speed N (rpm); Q / N (kg / h / rpm) is preferably in the range of 0.16 to 1.00, 0.18 More preferably, it is in the range of ˜0.90.
Thus, the compatibility of the mixed resin composition can be controlled by adjusting the extrusion temperature and the discharge amount Q to suitable ranges.

  As a method of laminating the brightness enhancement layer (X) and the absorption polarizing layer (Y) adjacent to each other without interposing an adhesive layer or an adhesive layer, a polyvinyl alcohol resin is coated on the above-described brightness enhancement film. Examples thereof include a method of laminating, and a method of coextruding and laminating a polyvinyl alcohol-based resin at the time of forming the brightness enhancement film into a raw fabric.

  In forming the absorption type polarizing layer (Y), when a polyvinyl alcohol resin is coated, it is preferable that the polyvinyl alcohol resin to be coated is dissolved in water to form an aqueous solution. In addition, after immersing the coated polyvinyl alcohol resin in iodine and potassium iodide solution, it may be uniaxially co-stretched, or immersed in iodine and potassium iodide solution in uniaxial co-stretched polyvinyl alcohol resin film May be. Moreover, when coating, it is preferable to perform surface treatment such as corona treatment on the raw material of the brightness enhancement film in advance. Moreover, the preferable method of processing with the aqueous solution containing potassium iodide and boric acid of the polyvinyl alcohol-type resin after co-stretching, and the preferable method of the water washing process are as above-mentioned.

In addition, when forming the absorption polarizing layer (Y), when co-extrusion of polyvinyl alcohol resin, using a multi-manifold die or feed block, the co-extrusion with the brightness enhancement layer (X) is performed and solidified to the cooling roll. Then, a cast sheet may be formed. In general, since a polyvinyl alcohol-based resin has a very narrow temperature range capable of melting and flowing and a thermal decomposition temperature range, the extrusion temperature is preferably about 140 ° C. to 300 ° C., although it depends on the flow characteristics of the resin. It is more preferable that the temperature is in the range of from 0C to 290C. The polyvinyl alcohol resin used for coextrusion is preferably a polyvinyl alcohol resin for hot melt molding.
Examples of the above-described polyvinyl alcohol resin for hot melt molding include the Kuraray Poval CP series (manufactured by Kuraray Co., Ltd.).

<Co-stretching>
In this laminate, the brightness enhancement layer (X) and the absorption-type polarizing layer (Y) are laminated in advance and then co-stretched in the uniaxial direction, so that the polarization directions are the same. preferable.
As described above, when co-stretched in the uniaxial direction, the brightness enhancement layer (X) reflects light incident in a direction parallel to the uniaxially stretched axial direction but transmits it without being completely reflected. The absorbed light can be absorbed in the absorption polarizing layer (Y), which is preferable. In addition, the brightness enhancement layer (X) transmits light incident in a direction perpendicular to the uniaxially stretched axial direction and parallel to the film surface, and the polarized light transmitted through the brightness enhancement layer (X) is absorption-type polarization. The layer (Y) is also preferable because it is transmitted.
The direction of co-stretching may be either a film take-up (flow) direction (MD) or a direction perpendicular to MD (TD). Especially, in order to express the characteristic which brightness improvement layer (X) has more effectively, it is preferable to orient to MD. That is, in the brightness enhancement layer (X), the axis parallel to the orientation direction (S axis) is MD, and the axis perpendicular to the orientation direction and parallel to the film surface (P axis) is TD. preferable.
In addition, the orientation method is not particularly limited. As a method of orienting, for example, as described above, the laminate formed by the T die casting method is uniaxially stretched to MD or TD, or when the film is formed by the T die casting method, the take-off speed (of the cast roll) Examples include a method of drafting MD by increasing the speed), a method of drafting MD by increasing the take-up speed when forming a film by the inflation method, and the like.
Especially, the method of carrying out the uniaxial stretching of the sheet | seat formed by the T die-casting method to MD or TD as mentioned above is preferable from a viewpoint of film forming stability or production efficiency improvement.

(Stretching method)
Here, “uniaxial stretching” means stretching that is positively performed in only one direction. For example, in the process of film formation, heat treatment, winding, etc., the direction is naturally different from the one direction. It is intended to include the case of being stretched. Objectively, this is a case where the stretching ratio in one direction is two times or more of the stretching ratio in the direction orthogonal thereto.

By uniaxially stretching in this manner, the dispersed phase can be arranged and fixed in a substantially constant direction in the continuous phase, and the anisotropic scattering function can be exhibited.
In the brightness enhancement layer (X), the uniaxial stretching increases the refractive index difference between the continuous phase (I) and the dispersed phase (II) in the stretching direction, and the dispersed phase (II) is elongated in the stretching direction. The dispersion diameter in the P-axis direction of the phase is included within the preferable range of the present invention. Therefore, the polarized light in the direction in which the refractive index difference with respect to the S axis increases is scattered, and the dispersion diameter is sufficiently small with respect to the wavelength order of light for the P axis, so that the polarized light is transmitted. A brightness enhancement layer (X) can be produced.

The stretching method may be any of free-width uniaxial stretching and constant-width uniaxial stretching, and any of a stretching method, an inter-roll stretching method, a roll rolling method, and other methods may be employed.
The stretching temperature is set to a temperature within a range from about Tg to (Tg + 50 ° C.) of a resin having a high glass transition temperature (Tg) among the resins constituting the brightness enhancement layer (X) and the absorption-type polarizing layer (Y). preferable. When the stretching temperature is within this range, stretching can be performed stably without breaking during stretching.
The draw ratio is not particularly limited, but for example, it is preferably 2 times or more for MD or TD, preferably 3 to 9 times for MD or TD, particularly 4 to 7 times for MD or TD. Among these, when formed with an unstretched sheet of the brightness enhancement layer (X) formed into a film, the dispersed phase (II) is stretched to reduce the dispersed diameter in the P-axis direction of the dispersed phase (II) and stretched to MD. It is particularly preferable to do this.

<Configuration of the laminate>
It is important that the laminate includes at least one brightness enhancement layer (X) and an absorption polarizing layer (Y). The brightness enhancement layer (X) and the absorption polarization layer (Y) It is important that both layers are laminated adjacent to each other without using an adhesive layer or an adhesive layer.

To illustrate the configuration of this laminate, the simplest configuration is a configuration composed of two layers of a brightness enhancement layer (X) / absorptive polarizing layer (Y). Next, the simple structure includes other layers (Z), and is (Z) / (X) / (Y) or (X) / (Y) / (Z). The other layer (Z) is preferably a layer that does not impair the optical properties, and the other layer (Z) may be one layer, two layers, or a plurality of three or more layers. It may consist of. Moreover, a structure like (Z) / (X) / (Y) / (Z) may be sufficient. Furthermore, a brightness enhancement layer (x) that satisfies the present invention and is different from (X) and an absorbing polarizing layer (y) that satisfies the present invention and is different from (Y) were used. For example, (X) / (x) / (Y), (X) / (Y) / (y), (X) / (x) / (Y) / (y) may be used.
When incorporating this laminate into a liquid crystal display device, from the back side (back side) of the liquid crystal cell, a reflective sheet, a light guide plate and a light source, a diffusion film, a prism sheet, this laminate, a liquid crystal layer, a retardation film, a polarizing film, Examples include a structure in which glass substrates and the like are sequentially laminated. Further, at this time, it is preferable that the brightness enhancement layer (X) of the laminate is disposed on the light source side with little loss of light.

<Thickness>
The thickness of this laminated body is not specifically limited. For example, from the viewpoint of rigidity, it is preferably 50 μm to 400 μm, more preferably 100 μm or more or 200 μm or less. Further, the thickness of the brightness enhancement layer (X) is not particularly limited as long as it is within a range that satisfies the ratio (Y / X) of the thickness of the brightness enhancement layer (X) and the absorption polarizing layer (Y) described later. And 10 μm to 399.99 μm is preferable.
Further, the thickness of the absorbing polarizing layer (Y) is also limited as long as it is within a range that satisfies the ratio (Y / X) of the thickness of the luminance enhancing layer (X) and the absorbing polarizing layer (Y) described later. In particular, 0.01 μm to 40 μm is preferable. In general, when the thickness of the scattering type polarizing layer (X1) is increased, the number of scattering increases, so that the polarization reflection characteristic in the axis parallel to the orientation direction (S axis) is improved. Thus, the polarization transmission characteristics in an axis (P axis) perpendicular to the orientation direction and parallel to the film surface tend to be reduced.
However, as in the present invention, when the dispersion diameter in the P-axis direction of the dispersed phase (II) is 10 nm or more and 200 nm or less, the polarization reflection property in the S-axis is improved with respect to the increase in thickness, and This brings about an effect of suppressing a decrease in the polarization transmission characteristic on the P axis.

<Ratio of the thickness of the brightness enhancement layer (X) and the absorption-type polarizing layer (Y)>
In the present laminate, with respect to the ratio (Y / X) of the thickness of the brightness enhancement layer (X) to the absorption polarization layer (Y), the absorption polarization layer with respect to 100% of the thickness of the brightness enhancement layer (X). The lower limit of the thickness ratio of (Y) is preferably 0.3% or more. If the thickness ratio is 0.3% or more, polarization characteristics can be sufficiently exhibited. From this viewpoint, the thickness ratio is more preferably 0.4% or more, and particularly preferably 0.5% or more. On the other hand, the upper limit value is preferably 3.0% or less. When the thickness ratio is 3.0% or less, curling that occurs when the absorbing polarizing layer (Y) is cured and contracted can be reduced to a level that does not cause a problem in practice. From this viewpoint, it is more preferably 2.0% or less, and particularly preferably 1.5% or less.

<Degree of polarization>
In this laminate, the degree of polarization is preferably 95.0% or more, more preferably 99.0% or more. When the degree of polarization is 95.0% or more, there is an effect that a high contrast ratio can be obtained when incorporated in a liquid crystal display (LCD). Although there is no restriction | limiting in particular about an upper limit, It is preferable that it is 99.999% or less.

<Peel strength>
In this laminate, the peel strength between the brightness enhancement layer (X) and the absorption-type polarizing layer (Y) is preferably 30 gf / 15 mm width or more, and more preferably 40 gf / 15 mm width or more. If the peel strength is 30 gf / 15 mm width or more, when used in a liquid crystal display device, the brightness enhancement layer (X) and the absorption-type polarizing layer (Y) are peeled off, and troubles in the assembly process and usage environment are unlikely to occur. ,preferable.

<Explanation of terms>
In this invention, the form of this laminated body is not specifically limited, A plate shape, a sheet form, a film form, and other forms are included.

  In general, "film" refers to a thin flat product that is extremely small compared to its length and width and whose maximum thickness is arbitrarily limited, and is usually supplied in the form of a roll (Japan) Industrial standard JISK6900), and in general, “sheet” refers to a product that is thin by definition in JIS and generally has a thickness that is small instead of length and width. 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 “main component” in the present specification includes the meaning of allowing other components to be contained within a range that does not hinder the function of the main component unless otherwise specified.
At this time, although the content ratio of the main component is not specified, the main component (when two or more components are main components, the total amount thereof) is 50% by mass or more, preferably 70% in the composition. It occupies at least 90% by mass, particularly preferably at least 90% by mass (including 100%).

In the present invention, when expressed as “X to Y” (X and Y are arbitrary numbers), “X is preferably greater than X” and “preferably Y”, with the meaning of “X to Y” unless otherwise specified. It means “smaller”.
Further, in the present invention, when expressed as “X or more” (X is an arbitrary number), it means “preferably larger than X” unless otherwise specified, and “Y or less” (Y is an arbitrary number). ) Includes the meaning of “preferably smaller than Y” unless otherwise specified.

The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to these examples, and various applications are possible without departing from the technical idea of the present invention.
Here, the take-up (flow) direction of the sheet or film when the sheet or film is manufactured is indicated by MD, and the orthogonal direction thereof is indicated by TD.

<Measurement and evaluation method>
First, measurement methods and evaluation methods for various physical property values of samples obtained in Examples and Comparative Examples will be described.

<Total thickness>
With a dial gauge of 1/1000 mm, the in-plane of the laminated porous film was measured at five unspecified locations, and the average value was taken as the total thickness of the optical laminate.

<Thickness of the brightness enhancement layer (X)>
After peeling off the absorptive polarizing layer (Y) of the optical laminate with a tape, the in-plane measurement of the laminated porous film was performed at five unspecified locations with a 1/1000 mm dial gauge, and the average value was determined as the brightness enhancement layer. The thickness was (X).

<Absorptive polarizing layer (Y) thickness>
The cross section of the optical layered body was observed with an SEM to calculate the thickness of the absorption polarizing layer (Y).

<Evaluation method of polarization transmittance>
Polarization transmittance was measured by attaching an integrating sphere to a spectrophotometer (manufactured by Hitachi, Ltd .: U-4000). Optical laminates of examples and comparative examples by attaching a polarizing film on the incident light side of a light source having a wavelength of 300 nm to 800 nm, inserting an absorbing polarizing film on the light source side, and making the light source only linearly polarized light vertically polarized Or, by inserting a brightness enhancement film, the polarization transmittance of the optical laminate or the brightness enhancement film is determined so that the axis perpendicular to the stretching direction and parallel to the film surface (P axis), the parallel axis to the stretching direction ( Measurement was performed for each of the S-axis).
The evaluation criteria for the P-axis were evaluated as “Good” when the average polarization transmittance of 400 nm to 700 nm was 80% or more, and “X (poor)” when the average was less than 80%. The evaluation criteria for the S axis were evaluated as “◯ (good)” when the average polarization transmittance of 400 nm to 700 nm was 10% or less, and “× (poor)” when it exceeded 10%.

<Evaluation method of tear strength>
A test piece was prepared according to JIS K7128-3 (1998), and tear strength was measured by the right angle tearing method in the P-axis direction and S-axis direction at a temperature of 23 ° C. and a test speed of 200 mm / min. Based on the following criteria.
○ (good): The tear strength is 600 N / cm or more.
X (poor): The tear strength is less than 600 N / cm.

<Degree of polarization>
Polarization, said polarization evaluation method of transmittance was calculated using, _{H 90} the average value of the polarization transmittance 400nm~700nm the average of polarization transmittance 400nm~700nm in _H 0, S axis in the P-axis And determined by applying the following formula.
Polarization degree (%) = {| (H ₀ −H ₉₀ ) | / (H ₀ + H ₉₀ )} ^1/2 × 100
(Very good): The degree of polarization is 99.0% or more.
○ (good): The degree of polarization is 95.0% or more and less than 99.0%.
X (poor): Polarization degree is less than 95.0%.

<Curl evaluation method>
The optical laminate was cut into A4 size so that the longitudinal direction was the stretching direction, and allowed to stand at normal temperature and humidity. When the film after standing became cylindrical due to curling, the circumference of the overlapping portion of the cylinders was measured and evaluated according to the following criteria. Δ is above the practical level.
(Very good): The film does not spontaneously become cylindrical.
○ (good): The circumference of the overlapping part of the cylinder is 0 cm or more and less than 5 cm.
Δ (fair): The circumference of the overlapping portion of the cylinders is 5 cm or more and less than 10 cm.
X (poor): The circumference of the overlapping part of the cylinder is 10 cm or more.

<Appearance evaluation method>
The optical laminate was cut into A4 size so that the longitudinal direction was the stretching direction, and evaluated visually.
(Very good): Absorptive dyeing layer (Y) does not have uneven dyeing or peeling.
○ (good): Slight unevenness is observed in the absorption-type polarizing layer (Y), but it is at a level that causes no practical problems.
X (poor): The absorbing polarizing layer (Y) has uneven dyeing or peeling.

<Evaluation method of liquid splash>
The evaluation criteria for the liquid repellency is that an aqueous polyvinyl alcohol resin solution is applied on the brightness enhancement layer (X) of the optical laminate and dried, and the uniaxially co-stretched polyvinyl alcohol resin film is made of iodine and potassium iodide. After being immersed in the solution, it was cut into A4 size, and the number of locations where the aqueous solution was repelled was examined and judged.
○ (good): 5 or less places where the aqueous solution was repelled.
X (poor): There are more than 5 locations where the aqueous solution was repelled.

<Formation of raw fabric A of brightness enhancement film>
Polyethylene naphthalate resin (average refractive index: 1.646, intrinsic birefringence: positive, glass transition temperature (Tg): 118 ° C., Tm: 261 ° C., intrinsic viscosity 0.71 dl / g, weight average molecular weight 50,000, pellet And 60% by mass of an amorphous polyester resin (average refractive index: 1.568, intrinsic birefringence: positive, Tg: 109 ° C., dicarboxylic acid unit: terephthalic acid 100 wt%, diol unit: ethylene glycol 30% by weight, 1,4-cyclohexanedimethanol 45% by weight, isosorbide 25%) 40% by mass, sufficiently mixed, and then fed by a constant mass feeder, extrusion kneaded at 290 ° C. with a φ40 mm twin screw extruder ( The ratio of discharge amount Q (kg / h) and screw rotation speed N (rpm); Q / N = 0.26 (kg / h / rpm)) A 600 μm sheet was produced. One side of the obtained sheet was subjected to corona treatment under the conditions of a processing output of 1 kW and a processing speed of 10 m / min using a generator (product name “CP1”) manufactured by VETAPHONE.
Thus, the scattering type polarizing layer (X1) having the continuous phase (I) made of polyethylene naphthalate resin and the dispersed phase (II) made of polyester resin having a diol residue derived from isosorbide is provided. And the original fabric (henceforth the original fabric A) of the brightness enhancement film which has the surface by which the corona treatment was carried out was produced.

<Film-making of raw fabric B of brightness enhancement film>
The raw material except that the mixing weight ratio of the polyethylene naphthalate resin and the amorphous polyester resin used in the film formation of the raw fabric A was changed to 40% by mass of the polyethylene naphthalate resin and 60% by mass of the amorphous polyester resin. A sheet having a thickness of 600 μm was produced in the same manner as the film formation of A. One side of the obtained sheet was subjected to corona treatment using a generator (product name “CP1”) manufactured by VETAPHONE under the conditions of a processing output of 1 kW and a processing speed of 10 m / min.
In this way, the scattering type polarizing layer (X1) having a continuous phase (I) composed of a polyester resin having a diol residue derived from isosorbide and a dispersed phase (II) composed of a polyethylene naphthalate resin is provided. And the original fabric (henceforth the original fabric B) of the brightness enhancement film which has the surface by which the corona treatment was carried out was produced.

<Example 1>
POVAL PVA124 (manufactured by Kuraray Co., Ltd .: polymerization degree 2400) was dissolved in water to a concentration of 12 wt% and stirred overnight at 80 ° C. to prepare an aqueous solution of a polyvinyl alcohol-based resin. Then, after filtering insoluble matter, it coated on the corona treatment surface of the raw fabric A of the brightness enhancement film produced as described above at a wet thickness of 200 μm, and dried in an oven at 50 ° C. for 1 hour. Thereafter, the film was stretched 5 times in the MD direction of the brightness enhancement film at a furnace temperature of 130 ° C. and a stretching speed of 5 mm / sec using a biaxial stretching machine manufactured by Island Kogyo. The obtained laminate was immersed in warm water at 60 ° C. for 15 seconds in a state of being fixed with a fixture, and thereafter, an aqueous solution prepared with 0.05 parts iodine and 5 parts potassium iodide with respect to 100 parts by mass of water. Immersion at room temperature for 1 minute. Furthermore, after fixing a laminated body with a fixing tool, it was immersed at 65 degreeC for 5 minutes in the aqueous solution prepared to 6 parts of potassium iodide and 7.5 parts of boric acid with respect to 100 mass parts of water. Then, after being immersed and washed in pure water for 20 seconds, water droplets were removed and dried in an oven at 50 ° C. for 5 minutes to obtain the target optical laminate.

When the thickness of the obtained laminate was measured, the thickness of the brightness enhancement layer (X) was 130 μm, and the thickness of the absorption polarizing layer (Y) was 10 μm.
Further, the obtained laminate is cut into a strip shape having a width of 15 mm, and a part of the absorbing polarizing layer (Y) is peeled off using a feather blade, and the end portion of the stripped absorbing polarizing layer (Y) is peeled off. The edge of the brightness enhancement layer (X) remaining at the location where the absorbing polarizing layer (Y) was peeled off was sandwiched between chucks of a tensile tester, and a peel test was performed at a speed of 100 mm / min. The peel strength was 50 gf / 15 mm width. The evaluation results are shown in Table 1.

<Example 2>
POVAL PVA124 (manufactured by Kuraray Co., Ltd .: polymerization degree 2400) was dissolved in water to a concentration of 12 wt% and stirred overnight at 80 ° C. to prepare an aqueous solution of a polyvinyl alcohol-based resin. Then, after insoluble matter was filtered, C-I Direct Black 17 (trade name “Japanol Fast Black D conc.” Manufactured by Taoka Chemical Industry Co., Ltd.), C-I Direct Yellow 12 (Taoka Chemical Industry Co., Ltd.) was added to this solution. Product name “Chrysophene”), C Direct Blue 78 (manufactured by Taoka Chemical Industry Co., Ltd., trade name “Sumilight Supra Blue G”) with respect to Poval PVA124, 0.8 wt% and 0.4 wt%, respectively. After adding 0.7 wt% and uniformly dissolving, coat the corona-treated surface of the original film A of the brightness enhancement film prepared as described above with a wet thickness of 50 μm and dry it in an oven at 50 ° C. for 1 hour. did. Thereafter, using a biaxial stretching machine manufactured by Island Kogyo Co., Ltd., the furnace was stretched 5 times in the MD direction of the brightness enhancement film at a furnace temperature of 130 ° C. and a stretching speed of 5 mm / sec to obtain a target optical laminate.
When the thickness of the obtained laminate was measured, the thickness of the brightness enhancement layer (X) was 130 μm, and the thickness of the absorption polarizing layer (Y) was 3 μm. The evaluation results are shown in Table 1.

<Example 3>
POVAL PVA124 (manufactured by Kuraray Co., Ltd .: polymerization degree 2400) was dissolved in water to a concentration of 12 wt% and stirred overnight at 80 ° C. to prepare an aqueous solution of a polyvinyl alcohol-based resin. Then, after filtering insoluble matter, it coated on the corona treatment surface of the raw fabric B of the brightness enhancement film produced as described above at a wet thickness of 200 μm, and dried in an oven at 50 ° C. for 1 hour. Thereafter, the obtained sheet was cut out and tilted by 90 °, and then increased to a preheating temperature of 145 ° C. (preheating time of 32 seconds), a stretching temperature of 130 ° C. (stretching time of 32 seconds), and a heat treatment temperature of 130 ° C. (heat treatment time of 32 seconds). The paper was passed through a warm tenter and stretched 6 times in MD. Next, it was stretched 5 times in the MD direction of the brightness enhancement film at a furnace temperature of 130 ° C. and a stretching speed of 5 mm / sec using a biaxial stretching machine manufactured by Island Kogyo.
The obtained laminate was immersed in warm water of 60 ° C. for 15 seconds in a state of being fixed with a fixture, and thereafter, an aqueous solution prepared with 0.1 part iodine and 5 parts potassium iodide with respect to 100 parts by mass of water. Immersion at room temperature for 1 minute. Furthermore, after fixing a laminated body with a fixing tool, it immersed at 65 degreeC for 5 minutes in the aqueous solution prepared to 6 parts of potassium iodide and 7.5 parts of boric acid with respect to 100 mass parts of water. Then, after being immersed and washed in pure water for 20 seconds, water droplets were removed and dried in an oven at 50 ° C. for 5 minutes to obtain the target optical laminate.

  When the thickness of the obtained laminate was measured, the thickness of the brightness enhancement layer (X) was 115 μm, and the thickness of the absorption polarizing layer (Y) was 8 μm. The evaluation results are shown in Table 1. At this time, the cross section of the film obtained with a scanning electron microscope (SEM) was observed, and the dispersion diameter in the P-axis direction of the dispersed phase (II) made of polyethylene naphthalate resin of the brightness enhancement layer (X) was confirmed. However, it was 82 nm.

<Example 4>
In Example 1, a target optical laminate was prepared in the same manner as in Example 1 except that an aqueous polyvinyl alcohol resin solution was coated on the corona-treated surface of the original fabric A of the brightness enhancement film produced as described above at a wet thickness of 50 μm. Got the body.
When the thickness of the obtained laminate was measured, the thickness of the brightness enhancement layer (X) was 132 μm, and the thickness of the absorption polarizing layer (Y) was 1 μm. The evaluation results are shown in Table 1.

<Example 5>
In Example 1, the target optical laminate was prepared in the same manner as in Example 1 except that an aqueous polyvinyl alcohol resin solution was coated on the corona-treated surface of the original fabric A of the brightness enhancement film produced as described above at a wet thickness of 80 μm. Got the body.
When the thickness of the obtained laminate was measured, the thickness of the brightness enhancement layer (X) was 132 μm, and the thickness of the absorption polarizing layer (Y) was 1.5 μm. The evaluation results are shown in Table 1.

<Example 6>
As a polyvinyl alcohol resin, an aqueous solution was prepared using JC-40 (Nippon Acetate / Poval, degree of polymerization 4000). JC-40 and water were mixed so that the concentration was 8 wt%, and the mixture was stirred at 90 ° C. for 2 hours to prepare an aqueous solution of a polyvinyl alcohol resin. Then, after filtering an insoluble matter, it coated on the raw material of a brightness enhancement film with wet thickness of 100 micrometers, and dried for 1 hour in 50 degreeC oven. Thereafter, the film was stretched 6 times in the MD direction of the brightness enhancement film at an in-furnace temperature of 130 ° C. and a stretching speed of 5 mm / sec using a biaxial stretching machine manufactured by Island Kogyo. The obtained laminate was immersed in an aqueous solution prepared with 0.05 part of iodine and 5 parts of potassium iodide with respect to 100 parts by weight of water for 1 minute at room temperature. Furthermore, after fixing a laminated body with a fixing tool, it immersed in 65 degreeC for 5 minutes to the aqueous solution prepared to 6 parts of potassium iodide and 7.5 parts of boric acid with respect to 100 mass parts of water. Then, after being immersed and washed in pure water for 20 seconds, water droplets were removed and dried in an oven at 50 ° C. for 5 minutes to obtain the target optical laminate.
When the thickness of the obtained laminate was measured, the thickness of the brightness enhancement layer (X) was 130 μm, and the thickness of the absorption polarizing layer (Y) was 8 μm. The evaluation results are shown in Table 1.

<Example 7>
In Example 6, the target optical laminate was prepared in the same manner as in Example 6 except that an aqueous solution of a polyvinyl alcohol-based resin was prepared using JC-33 (manufactured by Nippon Acetate / Poval, degree of polymerization 3300). Obtained. The evaluation results are shown in Table 1.

<Comparative Example 1>
The original film A of the brightness enhancement film prepared as described above is 5 times in the MD direction of the brightness enhancement film at a furnace temperature of 130 ° C. and a stretching speed of 5 mm / sec using a biaxial stretching machine manufactured by Island Industries. The film was stretched to obtain a brightness enhancement film on which no absorption polarizing layer was laminated.
The thickness of the obtained brightness enhancement film was 130 μm. The evaluation results are shown in Table 1.

<Comparative example 2>
In Example 6, a target optical laminate was prepared in the same manner as in Example 6 except that an aqueous solution of a polyvinyl alcohol-based resin was prepared using JMR-10HH (manufactured by Nippon Vinegar Poval, degree of polymerization 200). Obtained. The evaluation results are shown in Table 1.

As is clear from the above results, the optical laminates of Examples 1 to 7, that is, the optical laminate of the present invention have high polarization characteristics without reducing the polarization transmission characteristics of the brightness enhancement film. I understood. That is, it was found that the axis of the light polarized and separated by the brightness enhancement film does not occur.
In addition, since it does not have an adhesive layer or an adhesive layer, there is no poor appearance such as bubbles, no optical phase shift caused by the adhesive layer or the adhesive layer, and an excellent optical laminate when incorporated in a liquid crystal display device It turns out that it can be.
Furthermore, since the polymerization degree of polyvinyl alcohol, which is the main component of the absorbing polarizing layer (Y), is 1000 or more, liquid flow and coating unevenness during coating can be reduced, and even if the coating thickness is reduced, liquid repellency can be achieved. Since it did not occur, an optical laminate having a good appearance was obtained. In particular, in Examples 4 and 5, an optical laminate in which curling was suppressed was obtained by adjusting the ratio of the thickness of the luminance light upper layer (X) and the absorption-type polarizing layer (Y).

Claims (10)

A method of manufacturing an optical laminate including at least one brightness enhancement layer (X) and an absorption polarizing layer (Y), wherein the brightness enhancement layer (X) and the absorption polarization layer (Y) Production of an optical laminate characterized in that the luminance enhancement layer (X) and the absorption-type polarizing layer (Y) are polarized in the same direction by being co-stretched in a uniaxial direction after being laminated by extrusion. Method. A method for producing an optical laminate including at least one brightness enhancement layer (X) and an absorption polarization layer (Y), wherein the absorption polarization layer (Y) is applied to the brightness enhancement layer (X). After that, the polarization direction of the brightness enhancement layer (X) and the absorption-type polarizing layer (Y) is made the same direction by co-stretching in the uniaxial direction. The optical layered body according to claim 1 or 2, wherein the brightness enhancement layer (X) and the absorption-type polarizing layer (Y) are laminated adjacent to each other without interposing an adhesive layer or an adhesive layer . Production method. The method for producing an optical laminate according to any one of claims 1 to 3, wherein the brightness enhancement layer (X) is a scattering polarizing layer (X1) or a multilayer polarizing layer (X2) . The optically laminated body according to claim 4, wherein the scattering-type polarizing layer (X1) contains at least two thermoplastic resins and has a sea-island structure composed of a continuous phase (I) and a dispersed phase (II) . Production method. A polyester system in which at least one of the thermoplastic resin (A) forming the continuous phase (I) and the thermoplastic resin (B) forming the dispersed phase (II) has a diol residue derived from isosorbide It is resin, The manufacturing method of the optical laminated body of Claim 5. The thermoplastic resin (A) that forms the continuous phase (I) and the thermoplastic resin (B) that forms the dispersed phase (II) are both polyester resins, and the thermoplastic resin (A) and the thermoplastic resin. The method for producing an optical laminate according to claim 5, wherein the resin (B) is a different type of polyester resin . In the thermoplastic resin (A) forming the continuous phase (I) and the thermoplastic resin (B) forming the dispersed phase (II), one is a polyester resin having a diol residue derived from isosorbide The method for producing an optical laminate according to claim 5, wherein the other is a polyethylene naphthalate resin . The method for producing an optical laminated body according to any one of claims 1 to 8, wherein the absorption polarizing layer (Y) is a layer mainly composed of polyvinyl alcohol containing iodine or a dichroic dye . The method for producing an optical laminate according to claim 9, wherein the degree of polymerization of the polyvinyl alcohol is 1000 or more and 8000 or less .