KR101461147B1 - Polarizer protection film, polarizing plate and liquid crystal display element - Google Patents

Abstract

A polarizer protective film which can easily and surely be adhered to a polarizer by a water-soluble adhesive while suppressing a change in retardation value by reducing a dimensional change due to humidity, a polarizer using the polarizer protective film, and a liquid crystal display element .
The polarizer protective film of the present invention is a polarizer protective film to be adhered to a polarizer of a liquid crystal display panel, comprising a base layer composed mainly of an acrylic resin, a first control layer laminated on one surface side of the base layer, And a second control layer laminated on the other surface side of the base layer and controlling moisture permeability, wherein the first control layer and the second control layer are laminated on one surface side of the first control layer, As the main component, the same resin.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a polarizer protective film, a polarizer plate,

The present invention relates to a polarizer protective film, a polarizing plate having the polarizing protective film, and a liquid crystal display element including the polarizing plate.

BACKGROUND ART [0002] A liquid crystal display (LCD) is widely used as a flat panel display by taking advantage of features such as thinness, light weight and low power consumption, and its application is an information display device such as a cellular phone, a personal digital assistant It is expanding every year.

5, a general liquid crystal display element 41 provided in a liquid crystal display device includes a liquid crystal cell 42 in which a liquid crystal layer 44 is sandwiched between two transparent medium layers 43 (for example, glass) And a polarizing plate 45 adhered to both surfaces of the liquid crystal cell 42 by an adhesive layer 48. The polarizing plate 45 is formed by bonding a polarizer protective film 46 to both surfaces of a polarizer 47 having polarizing ability. As described above, the polarizer 47 is protected by the polarizer protective film 46 from the viewpoint of improvement of the strength and ease of handling.

As the material of the polarizer, a PVA film made of polyvinyl alcohol, which is generally a hydrophilic resin, is used. The polarizer is formed by uniaxially stretching the PVA film, followed by dyeing with iodine or dichroic dye, or by stretching after dyeing, and then by crosslinking with a boron compound.

As the polarizer protective film, triacetyl cellulose (TAC) is generally used because it is optically transparent, has a small retardation value, has a smooth surface, and is required to have excellent adhesion with a polarizer made of PVA. Is used as the base layer. Triacetyl cellulose is saponified (converted into a hydroxyl group having an ester group as a hydrophilic group) by an alkali, and then bonded to a polarizer made of polyvinyl alcohol as a hydrophilic resin using a water-soluble adhesive. However, since triacetylcellulose is expensive, development of an inexpensive alternative material having equivalent properties is required.

In view of such circumstances, the present applicant has proposed a polarizer protective film having a base layer made of an acrylic resin or the like (see Japanese Patent Application Laid-Open No. 2010-181500). The polarizer protective film described in JP-A-2010-181500 has a structure in which a primer layer is arranged on one surface of a substrate layer and a hydrophilic resin layer is arranged on one surface of the primer layer, The adhesion of the polarizer to the polarizer is improved. It is also assumed that the polarizer protective film described in the above publication is mainly disposed on the outer surface side (the side remote from the liquid crystal cell, that is, the uppermost layer and the lowermost layer in Fig. 5) of the liquid crystal display element.

On the other hand, the polarizer protective film arranged on the inner surface side of the liquid crystal display element is preferably lower in retardation value than the polarizer protective film arranged on the outer surface side of the liquid crystal display element. That is, when the retardation value of the polarizer protective film is high, the linearly polarized light that has passed through the polarizer becomes elliptically polarized by the polarizer protective film and enters the liquid crystal layer, or linearly polarized light having passed through the liquid crystal layer is blocked by the polarizer protective film By the elliptically polarized light, there is a possibility that the light beam can not be used sufficiently for display. Therefore, the polarizer protective film arranged on the inner surface side of the liquid crystal display element is required to have a low retardation value as described above.

However, since the base layer made of the conventional triacetyl cellulose has high moisture permeability and high water absorbability, it is liable to cause a dimensional change under a high humidity environment. Therefore, another layer (for example, an adhesive layer) And a photoelastic effect (change in retardation value due to deformation) due to dimensional changes of the other layer and the base layer is generated, and as a result, the light of the light source is not sufficiently utilized for display There is a fear that it will cause a situation.

In order to solve such a problem, it has been considered to suppress the change in the retardation value by decreasing the absorbency and the photoelastic coefficient by employing a means using an acrylic resin, a cycloolefin resin or the like as the base layer as described in the above publication do. However, when such a means is employed, if the absorbency of the polarizer protective film is made too small, the moisture permeability becomes too small, and when the polarizer protective film is adhered to the polarizer by the water-soluble adhesive, the moisture contained in the water- There is a possibility that it will not. Even if the photoelastic coefficient of the substrate layer is made small, if the moisture permeability is excessively high, the water absorbability is also increased, and there is a fear that the above-described photoelastic effect is caused by the dimensional change due to humidity.

Japanese Laid-Open Patent Publication No. 2010-181500

DISCLOSURE OF THE INVENTION The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a polarizer protective film which can easily and surely be adhered to a polarizer by a water-soluble adhesive while suppressing a change in dimension by humidity, A polarizing plate using a polarizer protective film, and a liquid crystal display element using the polarizing plate.

In order to solve the above problems,

A polarizer protective film adhered to a polarizer of a liquid crystal display panel,

A base layer containing an acrylic resin as a main component,

A first control layer laminated on one surface side of the base layer for controlling the moisture permeability,

An easy adhesion layer laminated on one surface side of the first control layer,

A second control layer for controlling the moisture permeability, which is laminated on the other surface side of the base layer,

And,

And the first control layer and the second control layer contain the same resin as the main component.

Since the easy-to-adhere layer is disposed on one side of the polarizer-protective film, the easy-to-adhere layer and the polarizer can be surely bonded by the water-soluble adhesive. The polarizer protective film is formed by controlling the desired moisture permeability by the first control layer and the second control layer disposed on both sides of the base layer. Therefore, when the water-soluble adhesive is adhered, the moisture of the water- So that the above-described bonding step can be carried out easily and reliably. Further, since the main component of the base layer of the polarizer protective film is an acrylic resin, the dimensional change of the base layer under high humidity is less than that of triacetyl cellulose, and the photoelastic effect is hardly generated. For this reason, the polarizer protective film has a small change in the retardation value. Particularly, since the polarizer protective film is formed so that the second control layer is arranged on the other surface side of the substrate layer and is controlled and controlled to have a desired moisture permeability, the dimensional change of the substrate layer is further suppressed, And the change in the retardation value is small.

In the polarizer protective film, the first control layer may have substantially the same thickness as the second control layer. This makes it possible to prevent the occurrence of curl at the time of manufacturing or the like.

In the polarizer protective film, the second control layer may be substantially thicker than the first control layer. As a result, it is possible to impart a curl preventing function to a force that tends to be rounded with the easy-to-adhere layer side inward, and it is possible to prevent the curling of the entire polarizer protective film. As a result, the polarizer protective film can improve dimensional stability.

Art polarizer protective film is if the photoelastic coefficient of the acrylic resin than -5 × 10 ^-12 / Pa or less 5 × 10 ^-12 / Pa. By setting the photoelastic coefficient of the acrylic resin in the above range, the polarizer protective film can reduce the change in the retardation value of the base layer due to the dimensional change even when the dimensional change occurs.

The polarizer protective film may contain the cellulose ester-based resin as the main component in the easy-to-adhere layer. This makes it possible to dramatically improve the adhesiveness with the polarizer made of polyvinyl alcohol and the water-soluble adhesive of the easy-to-adhere layer. That is, since a hydrophilic group hydroxyl group is generated by saponifying the easy-to-adhere layer containing a cellulose ester-based resin as a main component with alkali, the cellulose-based resin and polyvinyl alcohol as a hydrophilic resin can be easily and reliably adhered have.

The polarizer protective film may have a number-average molecular weight (Mn) of 40000 or more and 100000 or less in the cellulose ester-based resin containing the easy-to-adhere layer as a main component. This makes it possible to prevent the transparency of the cellulose ester resin from becoming white when the easy-to-adhere layer is saponified with alkali while enhancing the coating property of the easy-to-adhere layer.

The polarizer protective film may include an acrylic-modified polyester-based resin as a main component of the first control layer and the second control layer. This makes it possible to improve the adhesion to the easy-to-adhere layer due to acrylic denaturation while making good use of properties such as transparency, toughness and heat resistance inherent in the polyester-based resin, and adhesiveness to the acrylic resin contained as a main component of the base layer .

In the polarizer protective film, the first control layer and the second control layer may contain the acrylic-modified polyester-based resin and the urethane-based resin. This makes it possible to improve the adhesion to the easy-to-adhere layer due to acrylic denaturation while making good use of properties such as transparency, toughness and heat resistance inherent in the polyester-based resin, and adhesiveness to the acrylic resin contained as a main component of the base layer It is possible to impart adhesiveness and flexibility to the base layer and the easy-to-adhere layer by the blend of the urethane-based resin.

The polarizer protective film may have a moisture permeability of 1 g / m ² 24 h or more and 250 g / m ² 24 h or less. This makes it possible to more accurately evaporate the moisture of the water-soluble adhesive at the time of adhering with the water-soluble adhesive, so that the adhesive layer and the polarizer can be more easily and reliably adhered. Further, the polarizer protective film can more suitably suppress the dimensional change of the base layer, and the change of the retardation of the base layer can be further reduced.

In the polarizer protective film, the retardation value (Re) of the base layer may be -15 nm or more and 15 nm or less. Thus, in addition to the high dimensional stability of the polarizer protective film, the influence of the polarizer protective film can be suppressed with respect to the optimization of the polarization in the transmission axis direction of the polarizer and the controllability, have.

Further, in order to solve the above problems,

The polarizer protective film,

A polarizer attached to the easy-to-adhere layer of the polarizer protective film by a water-

And a polarizing plate.

In the polarizing plate, the easy-to-adhere layer of the polarizer protective film and the polarizer are reliably bonded by the water-soluble adhesive. In addition, since the polarizer protective film is formed by controlling the desired moisture permeability by the first control layer and the second control layer, moisture of the water-soluble adhesive can be precisely evaporated at the time of adhesion by the water-soluble adhesive, It can be easily and surely performed. As a result, the polarizer can securely adhere the polarizer protective film and the polarizer. Further, since the main component of the base layer of the polarizer protective film is an acrylic resin, the dimensional change of the base layer under high humidity is less than that of triacetyl cellulose, and the photoelastic effect is less likely to occur. Therefore, the polarizer protective film has a small change in the retardation value. Particularly, in the polarizer protective film, since the second control layer is arranged on the other surface side of the substrate layer and is controlled and controlled to have desired moisture permeability, the dimensional change of the substrate layer is further suppressed and the dimensional change of the substrate layer is made smaller . Therefore, the polarizing plate can reduce the change in the retardation value of the polarizer protective film, and can exhibit desired optical characteristics.

Further, in order to solve the above problems,

A liquid crystal cell,

And the polarizing plate is laminated on one surface of the liquid crystal cell

And a liquid crystal layer.

In the liquid crystal display element of the present invention, the easy-to-adhere layer of the polarizer protective film and the polarizer are reliably bonded by the water-soluble adhesive. In addition, since the polarizer protective film is formed by controlling the desired moisture permeability by the first control layer and the second control layer, moisture of the water-soluble adhesive can be precisely evaporated at the time of adhesion by the water-soluble adhesive, It can be easily and accurately performed. As a result, the liquid crystal display element can reliably adhere the polarizer protective film and the polarizer. Further, since the main component of the base layer of the polarizer protective film is an acrylic resin, the dimensional change of the base layer under high humidity is less than that of triacetyl cellulose, and the photoelastic effect is less likely to occur. Therefore, the polarizer protective film has a small change in the retardation value. Particularly, in the polarizer protective film, since the second control layer is arranged on the other surface side of the substrate layer and is controlled and controlled to have desired moisture permeability, the dimensional change of the substrate layer is further suppressed and the dimensional change of the substrate layer is made smaller . Therefore, the liquid crystal display element can reduce the change in the retardation value of the polarizer protective film, and can exhibit desired optical characteristics. Therefore, the liquid crystal display element can accurately display light by effectively utilizing the light from the light source.

In the present invention, " the same resin " includes monomers constituting the same chemical species and having different compositions and different polymerization types. The " photoelastic coefficient " is a coefficient indicating a tendency that a change in refractive index due to an external force tends to occur, and is a value obtained by C _R [Pa ^-1 ] =? N /? _R. Here, σ _R is the elongation stress [Pa], Δn is the refractive index difference at the stress addition, and Δn is defined by the following equation.

Δn = n ₁ -n ₂

(Where n ₁ is a refractive index in a direction parallel to the elongation stress, and n ₂ is a refractive index in a direction perpendicular to the elongating direction).

The "moisture permeability" is a value obtained by measuring the number of gasses of water vapor passing through a sample having an area of 1 m ² for 24 hours in an atmosphere of a temperature of 40 ° C. and a humidity of 92% RH in accordance with the moisture permeability test (cup method) of JIS Z0208. The term " retardation value (Re) " means the direction of the fast axis and the direction of the slow axis orthogonal to the plane of the crystal axis of the polarizer protective film surface in the x and y directions, the thickness of the polarizer protective film in the d, Is a value calculated by Re = (ny-nx) d, where nx and ny (nx? Ny)

INDUSTRIAL APPLICABILITY As described above, the polarizer protective film of the present invention, the polarizing plate using the polarizing protective film, and the liquid crystal display element using the polarizing plate can reduce the dimensional change of the substrate layer of the polarizing protective film by humidity, It is possible to easily and reliably adhere the polarizer protective film and the polarizer by the water-soluble adhesive while suppressing the change in the retardation value.

1 is a schematic sectional view showing a polarizer protective film according to an embodiment of the present invention.
2 is a schematic cross-sectional view showing a polarizing plate having the polarizer protective film of FIG.
Fig. 3 is a schematic view showing an apparatus for producing the polarizing plate of Fig. 2. Fig.
FIG. 4 is a schematic cross-sectional view of a liquid crystal display element having the polarizing plate of FIG. 2. FIG.
5 is a schematic view showing the structure of a conventional liquid crystal display device.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings appropriately.

[First Embodiment]

The polarizer protective film 1 of Fig. 1 comprises a base layer 2 composed mainly of an acrylic resin, a first control layer 3 for controlling the moisture permeability, an easy adhesion layer 4, And a second control layer (5). The polarizer protective film 1 is formed as a laminate in which a second control layer 5, a base layer 2, a first control layer 3 and an easy adhesion layer 4 are arranged in this order. The polarizer protective film 1 is a protective film which is adhered to the polarizer of the liquid crystal display element from the side of the easy adhesion layer 4 and improves the impact resistance and handling property of the polarizer.

(Base layer 2)

As the main component of the substrate layer 2, an acrylic resin which is a synthetic resin having a constant moisture permeability and which maintains high transparency required as a polarizer protective film of a liquid crystal display element is used. The base layer 2 may contain other arbitrary components as long as it does not impair transparency and desired strength, but preferably contains 90 mass% or more, more preferably 98 mass% or more of the acrylic resin. Examples of the optional components include an ultraviolet absorber, a stabilizer, a lubricant, a processing aid, a plasticizer, an impact resistance auxiliary, a retardation reducing agent, a gloss removing agent, an antimicrobial agent and an antifungal agent.

The acrylic resin used as the main component of the base layer 2 is a resin having a skeleton derived from acrylic acid or methacrylic acid. Examples of the acrylic resin include, but are not limited to, poly (meth) acrylic acid esters such as polymethyl methacrylate, methyl methacrylate- (meth) acrylic acid copolymer, methacrylic acid methyl- (meth) (Meth) acrylic acid ester-methacrylic acid copolymer, a (meth) acrylic acid methyl-styrene copolymer, a polymer having an alicyclic hydrocarbon group (for example, methyl methacrylate-cyclohexyl methacrylate copolymer, methacrylic acid Methyl (meth) acrylate norbornyl copolymer). Among these acrylic resins, poly (meth) acrylate C1-6 alkyl such as poly (meth) acrylate is preferable, and methyl methacrylate resin is more preferable.

The photoelastic coefficient of the acrylic resin is not particularly limited, but it is preferably -5 10 ^-12 / Pa or more and 5 10 ^-12 / Pa or less. The upper limit value of the photoelastic coefficient of the acrylic resin is 4 × 10 ^-12 / Pa is more preferred, and more preferably 3 × 10 ^-12 / Pa. On the other hand, the lower limit value of the photoelastic coefficient of the acrylic resin was -4 × 10 ^-12 / Pa is more preferable, and more preferably -3 × 10 ^-12 / Pa. When the photoelastic coefficient of the acrylic resin is out of the above range, there is a possibility that the change of the retardation value when the dimensional change occurs is increased.

The absorption rate of the acrylic resin is not particularly limited, but is preferably 1.0% or less, more preferably 0.7% or less, further preferably 0.5% or less. When the absorption rate of the acrylic resin exceeds the above range, there is a high possibility that the dimensional change will occur when the contained water evaporates. The water absorption rate is determined according to the value measured using a film-shaped sample of 50 mm in width and 100 μm in thickness in accordance with JIS K7209.

The thickness (average thickness) of the substrate layer 2 is not particularly limited, but is preferably 10 m or more and 200 m or less. The upper limit value of the thickness of the base layer 2 is more preferably 100 m, and further preferably 80 m. On the other hand, the lower limit value of the thickness of the base layer 2 is more preferably 20 占 퐉, and further preferably 40 占 퐉. When the thickness of the substrate layer 2 exceeds the upper limit, there is a fear that the line speed, productivity, and moisture permeability at the time of production are reduced, and the demand for thinning of the liquid crystal display device may be adversely affected. On the other hand, when the thickness of the substrate layer 2 is less than the lower limit value, the strength and rigidity become small, which may cause difficulty in handling in a production line or the like.

The arithmetic mean surface roughness (Ra) of the base layer 2 is not particularly limited, but is usually 0.02 or more and 0.06 or less. The substrate layer 2 may be subjected to a mat treatment if necessary. The upper limit value of the arithmetic average surface roughness (Ra) of the substrate layer 2 subjected to such a matting treatment is preferably 2, more preferably 1. On the other hand, the lower limit of the arithmetic mean surface roughness (Ra) of the substrate layer 2 subjected to the matting treatment is preferably 0.07, more preferably 0.1. By controlling the arithmetic mean surface roughness (Ra) of the base layer 2 subjected to the matting treatment to such a range, scratches are prevented from occurring in the treatment after the original master film is produced, and handling is improved. Generally, when winding the produced original film, both ends in the width direction of the film are preferably embossed (knurled) to prevent blocking. When the film is subjected to the knurling treatment, the treated portions at both ends of the film can not be used, so the portion must be cut and discarded. In the winding work of the film, masking may be performed by a protective film in order to prevent the occurrence of a scratch. However, by setting the arithmetic average surface roughness (Ra) of the base layer 2 within the above range, blocking can be prevented without performing knurling treatment, so that the manufacturing process is simplified and both end portions in the film width direction can be used In addition, it is possible to take a long winding without causing a breakdown of the film. In addition, since the base layer 2 has an appropriate surface roughness, the occurrence of scars at the time of winding is effectively suppressed, and the above-mentioned masking becomes unnecessary.

The retardation value (Re) of the base layer (2) is not particularly limited, but is preferably -15 nm or more and 15 nm or less. The upper limit value of the retardation value (Re) of the base layer (2) is more preferably 10 nm, and further preferably 5 nm. On the other hand, the lower limit value of the retardation value Re of the base layer 2 is more preferably -10 nm, and still more preferably -5 nm. When the retardation value Re of the substrate layer 2 is out of the above range, there is a possibility that the polarization of the polarizer in the transmission axis direction can not be optimized by the action of changing the polarization direction of the transmitted light beam.

The method for producing the base layer 2 is not particularly limited, and for example, it is possible to mix the flake raw materials of the acrylic resin and the additives such as the plasticizer by a conventionally known mixing method, to prepare the thermoplastic resin composition in advance, can do. The thermoplastic resin composition is obtained by preblending with a mixer such as an omni mixer, and then extruding and kneading the obtained mixture. In this case, the kneader used for the extrusion kneading is not particularly limited, and for example, conventionally known kneaders such as an extruder such as a single-screw extruder, a twin screw extruder, or a pressurized kneader can be used.

As the film forming method of the base layer 2, known methods such as a solution casting method (solution casting method), a melt extrusion method, a calendering method and a compression molding method can be mentioned. Of these, the solution casting method (solution casting method) and the melt extrusion method are preferable. In this case, a thermoplastic resin composition previously kneaded by extrusion may be used. Alternatively, other additives such as a synthetic resin and a plasticizer may be separately dissolved in a solvent to prepare a homogeneous mixed solution, followed by solution casting (solution casting) Or may be provided in a film forming process.

Examples of the solvent used in the solution casting method (solution casting method) include chlorinated solvents such as chloroform and dichloromethane; aromatic solvents such as toluene, xylene, benzene and mixed solvents thereof; alcohols such as methanol, ethanol, isopropanol, alcohols such as methyl alcohol, ethyl alcohol, n-butanol and 2-butanol; ethers such as methyl cellosolve, ethyl cellosolve, butyl cellosolve, dimethyl formamide, dimethyl sulfoxide, dioxane, cyclohexanone, tetrahydrofuran, Ethyl ketone (MEK), ethyl acetate, diethyl ether; And the like. These solvents may be used alone or in combination of two or more. Examples of the apparatus for performing the solution casting method (solution casting method) include a drum casting machine, a band casting machine, and a spin coater.

Examples of the melt extrusion method include a T-die method and an inflation method. The molding temperature of the film upon melt extrusion is preferably 150 占 폚 or higher and 350 占 폚 or lower, more preferably 200 占 폚 or higher and 300 占 폚 or lower. In the case of film-forming by the T-die method, a T-die is attached to the tip of a known single-screw extruder or a twin-screw extruder, and a film extruded into a film is wound to obtain a roll-shaped film. At this time, the uniaxial stretching process can be also carried out by appropriately adjusting the temperature of the take-up roll and stretching in the extrusion direction. It is also possible to apply processes such as sequential biaxial stretching and simultaneous biaxial stretching by applying a process of stretching the film in the direction perpendicular to the extrusion direction.

The base layer 2 may be an unstretched film or a stretched film. In the case of stretching, it may be a uniaxially stretched film or a biaxially stretched film. When a biaxially oriented film is used, the film may be biaxially stretched at the same time, or may be stretched in a biaxial stretch. In the case of biaxially stretching, the mechanical strength is improved and the film performance is improved.

The stretching temperature in the stretching step is preferably set at a temperature in the vicinity of the glass transition temperature of the thermoplastic resin composition of the raw material of the film, and specifically, it is preferably carried out at (glass transition temperature -30) ° C to (glass transition temperature +100) (Glass transition temperature -20) ° C to (glass transition temperature +80) ° C. When the stretching temperature exceeds the upper limit value, there is a fear that the resin flows (flows) and stable stretching can not be performed. On the contrary, when the stretching temperature is lower than the lower limit value, there is a possibility that a sufficient stretching magnification may not be obtained.

The stretching magnification defined by the area ratio is preferably in the range of 1.1 times to 25 times, more preferably 1.3 times to 10 times. When the draw ratio exceeds the upper limit value, there is a fear that the effect of increasing the draw ratio is not confirmed. On the contrary, when the stretching magnification is lower than the above lower limit value, there is a possibility that the toughness due to stretching may not be improved.

The stretching speed (one direction) is preferably in the range of 10 to 20,000% / min, and more preferably in the range of 100 to 10,000% / min. When the stretching speed exceeds the upper limit value, there is a fear that the stretched film may be broken. On the other hand, when the stretching speed is lower than the lower limit value, it takes time to obtain a sufficient stretching magnification, which may increase the manufacturing cost. In order to stabilize the optical isotropy and mechanical properties of the substrate layer 2, a heat treatment (annealing) or the like may be performed after the stretching treatment.

The plasticizer is not particularly limited, but preferably has a functional group capable of interacting with a synthetic resin by hydrogen bonding or the like so as to cause haze in the base layer (2) or not to bleed out or volatilize from the base layer Do. Examples of such plasticizers include, but are not limited to, phosphoric acid ester plasticizers, phthalic acid ester plasticizers, trimellitic acid ester plasticizers, pyromellitic acid plasticizers, polyhydric alcohol plasticizers, glycolate plasticizers, citrate ester plasticizers, fatty acid esters A plasticizer, a carboxylic acid ester-based plasticizer, and a polyester-based plasticizer.

(The first control layer 3)

The first control layer 3 is laminated on one surface side of the base layer 2. As the main component of the first control layer 3, a hydrophilic resin is suitably used. The hydrophilic resin is not particularly limited as long as it is a resin having chemical affinity with the base layer 2 and the easy adhesion layer 4, but it is preferable that the side chain is modified by a group having hydrophilicity. The hydrophilic modification of the hydrophilic resin may be carried out by (co) polymerizing a monomer having a hydrophilic functional group or by (co) polymerizing a monomer serving as a main chain and graft-polymerizing a monomer having a hydrophilic group to form a side chain do. The hydrophilic resin is preferably selected from the group consisting of a polyester resin, an acrylic resin, a urethane resin and an epoxy resin. These resins may be polymerized alone or copolymerized with two or more kinds thereof. As the hydrophilic resin, for example, those having a weight average molecular weight of 300 to 30000 can be used.

The polyester resin contained as the main component of the first control layer 3 is produced by esterifying (transesterifying) a dicarboxylic acid and a diol according to a known method and polycondensation. Examples of the dicarboxylic acid include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid and naphthalenedicarboxylic acid, esters thereof, aliphatic dicarboxylic acids such as adipic acid, succinic acid, sebacic acid and dodecane diacid Hydroxycarboxylic acids such as hydroxybenzoic acid, or esters thereof can be used. As the diol, there can be used, for example, ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, cyclohexanedimethanol and bisphenols.

As the polyester resin, it is preferable that, in addition to the dicarboxylic acid and the diol described above, a component having a hydrophilic group is copolymerized to impart hydrophilicity. Examples of the component having such a hydrophilic group include a dicarboxylic acid component such as 5-sodium sulfoisophthalic acid and a diol component such as diethylene glycol, triethylene glycol, and polyethylene glycol. These components having a hydrophilic group can be used in a proportion of, for example, 2 mol% or more and 80 mol% or less with respect to the above-described dicarboxylic acid or diol. The components constituting these polyester resins may be used singly or in combination of plural kinds.

The acrylic resin contained as a main component of the first control layer 3 can be synthesized by polymerizing a reactive polymer having a skeleton derived from acrylic acid or methacrylic acid. Examples of such a reactive polymer include those having a carboxyl group such as acrylic acid, methacrylic acid, carboxyethyl (meth) acrylate and carboxyphenyl acrylate, 2-hydroxyethyl (meth) acrylate, 3-hydroxybutyl (Meth) acrylate, N-methyl (meth) acrylamide, N-ethyl (meth) acrylate, Acrylamide, N, N-dimethyl (meth) acrylamide and N-methylol (meth) acrylamide; glycidyl groups such as glycidyl (Meth) acrylate, 2-dimethylaminoethyl (meth) acrylate and the like, in addition to those having an amino group such as p-chlorostyrene, chloromethylstyrene, divinylbenzene, 4-vinylpyridine , Vinyl oxazoline, Number and the like can be mentioned maleic acid.

Examples of the copolymerization components other than those constituting the acrylic resin include acrylic acid ester, methacrylic acid ester, propylene, vinyl chloride, cellulose, ethylenic, ethyleneimine, vinyl alcohol, Diene-based, fluorine-based, and acrylonitrile-based ones. From the viewpoints of versatility and coatability, acrylic acid ester-based and methacrylic acid ester-based ones are preferable. These acrylic resins may be used alone or in combination of two or more.

The urethane resin contained as a main component of the first control layer 3 can be synthesized from a low-molecular-weight polyurethane resin containing at least two hydrogen atoms reacting with a polyhydroxyl compound, a diisocyanate and a diisocyanate by a known method have. For example, there is a method of synthesizing a polyurethane having a relatively high molecular weight in a solvent, then gradually adding water to obtain a phase emulsion, and removing the solvent by decompression, or a method in which a urethane prepolymer having a polyethylene glycol or a carboxyl group introduced into the polymer as a hydrophilic group A method of dissolving or dispersing in water, and then adding a chain extender to cause a reaction.

Examples of the polyhydroxyl compound used in the production of the urethane resin include carboxylic acids such as phthalic acid, adipic acid, diminished linoleic acid and maleic acid, glycols such as ethylene glycol, propylene glycol, butylene glycol and diethylene glycol Polyester polyols obtained by dehydration condensation reaction from trimethylol propane, hexanetriol, glycerin, trimethylol ethane, pentaerythritol and the like; polyether polyols such as polyoxypropylene glycol, polyoxybutylene glycol, polytetramethylene glycol, polyoxyethylene Polyoxypropylene polyol such as polyoxypropylene polyoxyethylene polyol and polyoxypropylene polyoxyethylene polyol such as polyoxyethylene polyoxypropylene triol, sorbitol, pentaerythritol, sucrose, starch, phosphoric acid and the like, ; Acrylic polyols, castor oil derivatives, tall oil derivatives, other hydroxyl compounds, etc. The can. These polyhydroxyl compounds may be used alone or in combination of two or more.

Examples of the diisocyanate used for the production of the urethane resin include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, m-phenylenediisocyanate, p-phenylenediisocyanate, 4,4'-diphenylmethane diisocyanate , Tetramethylene diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, lydidine diisocyanate, isophorone diisocyanate, trimethylhexamethylene diisocyanate, 1,4-cyclohexylene diisocyanate, 4,4'-dicyclohexylmethane Diisocyanate, 3,3'-dimethyl-4,4'-biphenylene diisocyanate, 3,3'-dimethoxy-4,4'-biphenylene diisocyanate, 3,3'- Biphenylene diisocyanate, 1,5-naphthalene diisocyanate, and 1,5-tetrahydronaphthalene diisocyanate. These diisocyanates may be used alone or in combination of two or more.

Examples of the chain extender used in the production of the urethane resin include ethylene glycol, 1,4-butanediol, trimethylol propane, triisopropanolamine, N, N-bis (2-hydroxypropyl) aniline, hydroquinone- Propylenediamine, hexamethylenediamine, phenylenediamine, tolylene diamine, diphenyldiamine, diaminodiphenylmethane (ethylenediamine), and the like; , Diaminodiphenylmethane, diaminodicyclohexylmethane, polyamines such as piperazine, isophoronediamine, diethylenetriamine, and dipropylenetriamine, hydrazines and water. These chain extenders may be used singly or in combination of plural kinds.

The synthesis reaction in the production of the urethane-based resin can be carried out in the presence of a catalyst such as an organic tin compound, an organic bismuth, or an amine, and it is particularly preferable to carry out the reaction in the presence of an organotin compound. Specific examples of the organic tin compound include tin carboxylate such as stannous acetate, stannous octanoate, stannous laurate, and stannous oleate; dibutyltin acetate, dibutyltin dilaurate, di Dialkyl tin salts of carboxylic acids such as butyltin maleate, dibutyltin di-2-ethylhexoate, dilauryl tin diacetate, and dioctyltin diacetate; trimethyltin dilaurate, tributyltin hydroxide, Dialkyltin tin oxides such as dibutyltin dilaurate, dibutyltin dilaurate, dibutyltin dilaurate, dibutyltin dilaurate, tributyltin dilaurate, tributyltin dilaurate, They may be used singly or in combination of two or more kinds.

The epoxy resin contained as the main component of the first control layer 3 can be synthesized by polymerizing a monomer having an epoxy group. Examples of such monomers include glycidyl acrylate, glycidyl methacrylate, and allyl glycidyl ether. As the monomer copolymerizable with these monomers, vinyl esters, unsaturated carboxylic acid esters, unsaturated carboxylic acid amides, unsaturated nitriles, allyl compounds, unsaturated hydrocarbons or vinyl silane compounds are used. Specific examples thereof include vinyl propionate, vinyl chloride, vinyl bromide, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, butyl methacrylate, butyl maleate, octyl maleate, Acrylate, hydroxyethyl acrylate, hydroxypropyl methacrylate, hydroxypropyl acrylate, ethylene glycol dimethacrylate, ethylene glycol diacrylate, polyethylene glycol dimethacrylate , Polyethylene glycol diacrylate, acrylamide, methacrylamide, methylol acrylamide, butoxymethylol acrylamide, unsaturated nitrile acrylonitrile, allyl acetate, allyl methacrylate, allyl acrylate, diallyl acrylate, , Propylene, hexane, octene, styrene, vinyltoluene, butadiene, dimethylvinylmethoxysilane, dimethyl Ethyl and the like silane, methyl vinyl dimethoxy silane, methyl vinyl diethoxy silane, γ- methacryloxypropyltrimethoxysilane trimethoxysilane, γ- methacryloxypropyltrimethoxysilane methyl dimethoxysilane. These components constituting the epoxy resin may be used singly or in combination of plural kinds thereof.

When the hydrophilic side chain is formed by graft polymerization of the hydrophilic monomer after (co) polymerization of the monomer as the main chain in the hydrophilization modification of the hydrophilic resin, it is preferable to graft polymerize the hydrophilic radical polymerizable vinyl monomer. In this case, the radical polymerizable vinyl monomer may be used in a proportion of 10 parts by mass or more and 500 parts by mass or less based on 100 parts by mass in total of the main chain components.

Examples of such hydrophilic radically polymerizable vinyl monomers include -CH ₂ -CH (R) -OH (wherein -R is -H or -CH ₃ ), -COOX (wherein X is H, an alkali metal or 2 (CH ₂ -CH (R) -O) _n - _wherein R is -H or -CH ₃ , n is a positive integer, -YN (R ₁ ) (R ₂ ) (-Y- is -C (═O) - or -CH ₂ -, and -R ₁ and -R ₂ are -H or a hydroxyl group, a sulfonyl group, an acyl group, a lower alkyl group which may have a metal salt or a quaternary ammonium _{^{salt), -N + - (R 3}} ) (R 4) (R 5) ( _{wherein, -R 3, -R 4, -R} 5 is -CH ₃ Or -C ₂ H ₅ ), -CH ₂ -CH (O) CH ₂ (O forms an epoxy ring with both carbon atoms), and the like.

Specific examples of the hydrophilic radically polymerizable vinyl monomers include hydroxyacrylic acid esters such as hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate and hydroxypropyl methacrylate, ethylene glycol acrylate, ethylene glycol methacrylate Glycol esters such as polyethylene glycol acrylate and polyethylene glycol methacrylate, acrylamide compounds such as acrylamide, methacrylamide, methylol acrylamide and methoxymethylol acrylamide, glycidyl acrylate, methacrylic acid Glycidyl acrylate-based compounds such as glycidyl, vinylidene chloride-based compounds such as vinylpyridine, vinylimidazole and vinylpyrrolidone, acrylic acid, methacrylic acid, maleic anhydride, itaconic acid, Unsaturated acids and salts thereof, aminoalkyl acrylates, aminoalkyl methacrylates and Cationic monomers such as quaternary ammonium salts, and the like.

In the hydrophilic modification of the hydrophilic resin, other vinyl monomers may be copolymerized in addition to these radical polymerizable vinyl monomers. Examples of other copolymerizable vinyl monomers include vinyl esters such as vinyl acetate and vinyl propionate; vinyl halides such as vinyl chloride and vinyl bromide; vinyl esters such as methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate Vinylsilane such as dimethylvinylmethoxysilane and? -Methacryloxypropyltrimethoxysilane; olefins and diolefin compounds such as ethylene, propylene, styrene and butadiene; and the like.

When a polyester-based resin is used as the main component of the first control layer 3, the acrylic-based radical polymerizable vinyl monomer (hereinafter referred to as "acrylic-based polymerizable vinyl monomer") having a hydrophilic group is used as the polyester- (Hereinafter referred to as " acrylic-modified polyester-based resin ") in which the side chain is modified. By using an acrylic-modified polyester-based resin as a main component of the first control layer 3, it is possible to improve the transparency, toughness, and heat resistance inherent in the polyester-based resin, The adhesive property to the easy-to-adhere layer 4 can be imparted by the above-mentioned transformer while taking advantage of the properties such as adhesiveness to the adhesive layer (resin, etc.). As the first control layer 3, a composition containing a urethane-based resin together with the acrylic-modified polyester-based resin contained as a main component is most preferable. By using a composition comprising an acrylic-modified polyester-based resin and a urethane-based resin as a main component of the first control layer 3, it is possible to provide a polyester resin having properties such as transparency, toughness, heat resistance, (2) and the adhesive layer (4) by the blend of the urethane-based resin, and the adhesiveness to the adhesive layer (4) is improved by the above- And the like.

The weight average molecular weight of the acrylic radical polymerizable vinyl monomer and the urethane resin is typically 1000 to 15000, and preferably 2000 to 10000.

The mass of the urethane-based resin in the composition is preferably 10% or more and 70% or less, more preferably 25% or more and 40% or less, with respect to the mass of the acrylic-modified polyester-based resin. By setting the mass ratio of the acrylic-modified polyester-based resin and the urethane-based resin within this range, the base layer 2 and the easy-to-adhere layer (not shown) can be obtained while maintaining the layer properties of the first control layer 3 in transparency, water resistance, 4) can be optimized.

As the hydrophilic group of the acrylic radical-polymerizable vinyl monomer which is a modifying component of the acrylic-modified polyester-based resin, those exemplified as hydrophilic groups of the above-mentioned hydrophilic radically polymerizable vinyl monomer can be used. That is, the acrylic radical-polymerizable vinyl monomer having a hydrophilic group as the representative _{-CH 2 -CH (R) -OH,} -COOX, -O- (CH 2 -CH (R) -O) n -, -YN (R 1) (R ₂ ), -N ⁺ - (R ₃ ) (R ₄ ) (R ₅ ) and -CH ₂ -CH (O) CH ₂ (definition is as described above).

As the acrylic radical polymerizable vinyl monomer, the acrylic monomer used as a specific example of the above-mentioned hydrophilic radical polymerizable vinyl monomer can be used. Specifically, specific examples of the acrylic radical polymerizable vinyl monomers include acrylic acid hydroxyethyl, methacrylic acid hydroxyethyl, acrylic acid hydroxypropyl, methacrylic acid hydroxypropyl, ethylene glycol acrylate, ethylene glycol methacrylate, polyethylene glycol acrylate , Polyethylene glycol methacrylate, acrylamide, methacrylamide, methylol acrylamide, methoxymethylol acrylamide, glycidyl acrylate, glycidyl methacrylate, acrylic acid, methacrylic acid, aminoalkyl acrylate, methacrylic And aminoalkyl alkyl esters. These acrylic radical polymerizable vinyl monomers may be used singly or in combination of plural kinds thereof.

The acryl-modified polyester-based resin may be obtained by copolymerizing the above-mentioned copolymerizable other vinyl monomer in addition to the acrylic radical-polymerizable vinyl monomer. When other vinyl monomers are copolymerized, for example, from 1 part by mass to 70 parts by mass of other vinyl monomers may be used relative to 100 parts by mass of the acrylic radical polymerizable vinyl monomers.

In the acrylic-modified polyester-based resin, the mass ratio of the acrylic radical polymerizable vinyl monomer to the polyester-based resin forming the main chain is preferably 50 parts by mass or more and 150 parts by mass or less based on 100 parts by mass of the polyester- More preferably 70 parts by mass or more and 120 parts by mass or less. By setting the mass ratio of the acrylic radical-polymerizable vinyl monomer to the polyester-based resin within this range, the chemical affinity of the first control layer 3 with respect to the base layer 2 and the easiness of adhesion of the first control layer 3 It is possible to improve the chemically affinity for (4) in a well-balanced manner.

The acrylic-modified polyester-based resin may be an aqueous solution containing polyvinyl alcohol and a water-soluble or water-dispersible polyester resin obtained by copolymerizing a component having a hydrophilic group such as a dicarboxylic acid component such as 5-sodium sulfoisophthalic acid or the like, And then copolymerizing the acrylic radical polymerizable vinyl monomer (and any other copolymerizable vinyl monomer).

In the process for producing an acrylic-modified polyester resin using the polyvinyl alcohol, for example, polyvinyl alcohol may be added in an amount of 10 parts by mass or more and 500 parts by mass or less (solid content ratio ) Can be carried out.

As a polymerization method for synthesizing the acrylic-modified polyester-based resin, for example, a polymerization initiator and, if necessary, a small amount of an emulsifying and dispersing agent are added to an aqueous solution or aqueous dispersion of the water-soluble or water-dispersible polyester and polyvinyl alcohol And the acrylic radical polymerizable vinyl monomer is gradually added while stirring at a temperature of about 70 ° C and aged for several hours to complete the polymerization reaction.

As the polymerization initiator used in the production of the acrylic-modified polyester-based resin, a general radical polymerization initiator can be used. Examples of the polymerization initiator include water-soluble peroxides such as potassium persulfate, ammonium persulfate, and hydrogen peroxide; useful peroxides such as benzoyl peroxide and t-butyl hydroperoxide; and azo compounds such as azodiisobutyronitrile.

Thickness (average thickness) of the first control layer 3 is not particularly limited, but is preferably 0.01 μm or more and 5 μm or less. The upper limit value of the thickness of the first control layer 3 is more preferably 4 占 퐉, and further preferably 3 占 퐉. On the other hand, the lower limit value of the thickness of the first control layer 3 is more preferably 0.04 mu m, and further preferably 1 mu m. When the thickness of the first control layer 3 exceeds the upper limit value, the thickness of the polarizer protective film 1 becomes thick, which may be against the demand for thinning of the liquid crystal display device. On the contrary, when the thickness of the first control layer 3 is less than the above lower limit value, there is a fear that the formation of the first control layer 3 becomes difficult.

The moisture permeability of the first control layer 3 is not particularly limited, but is preferably 1 g / m ² 24 h or more and 200 g / m ² 24 h or less. The upper limit value of the moisture permeability of the first control layer 3 is more preferably 130 g / m ² · 24 h, and more preferably 80 g / m ² · 24 h. On the other hand, the lower limit value of the moisture permeability of the first control layer 3 is more preferably 10 g / m ² 24 h, more preferably 20 g / m ² 24 h. When the moisture permeability of the first control layer 3 exceeds the upper limit value, the proportion of moisture permeating from the outside becomes large, and the possibility of causing dimensional changes of the base layer 2 or the like is increased. On the other hand, when the moisture permeability of the first control layer 3 is less than the lower limit value, it is likely that a long time is required to evaporate water contained in the water-soluble adhesive when the easy-to-adherent layer 4 and the polarizer are adhered by a water- . On the other hand, when the moisture permeability of the first control layer 3 is within the above range, moisture contained in the water-soluble adhesive is suitably evaporated to promote drying of the easy-to-adherent layer 4, And the dimensional stability of the polarizer protective film 1 can be improved.

The first control layer 3 can be formed by applying an aqueous emulsion or an aqueous solution containing a hydrophilic resin (hereinafter referred to as " aqueous emulsion ") to the base layer 2 and drying it. The solid content of the water-based emulsion and the like is generally 10% by mass or more and 50% by mass or less. Water is used as the main solvent for the water-based emulsion and the like, but a small amount of an organic solvent which can be mixed with water may be used. Examples of such organic solvents include lower alcohols, polyhydric alcohols and alkyl ethers or alkyl esters thereof. Based emulsions can be formed on a base layer (a base layer) by using a known dip coating method, air knife coating method, curtain coating method, roller coating method, wire bar coating method, gravure coating method, extrusion coating method 2). The first control layer 3 can be formed by drying the applied aqueous emulsion or the like.

It is preferable to add a crosslinking agent to the aqueous emulsion for forming the first control layer 3 as required. Examples of the crosslinking agent include aldehydes, N-methylol compounds, dioxane derivatives, active vinyl compounds, active halogen compounds, isoxazole, dialdehyde starch, isocyanate compounds and silane coupling agents. These crosslinking agents may be used alone or in combination of two or more. The addition amount of the crosslinking agent is preferably 0.1% by mass or more and 20% by mass or less, more preferably 0.5% by mass or more and 15% by mass or less based on the whole amount of the hydrophilic resin. The aqueous emulsion for forming the first control layer 3 may also contain other resin components such as an amino group-containing resin, a surfactant, a lubricant, a dye, a UV absorber, a matting agent, a preservative, a thickener, , And an antioxidant may be added.

(Easy-adhesion layer 4)

The easy-adhesion layer (4) is laminated on one surface side of the first control layer (3). The main component of the adhesive layer 4 is not particularly limited as long as it is a resin having chemical affinity with a hydrophilic resin contained as a main component of the first control layer 3 and a polyvinyl alcohol constituting a polarizer, Resins are suitably used. Since the adhesive layer 4 has a cellulose ester resin as a main component, adhesion between the polarizer made of polyvinyl alcohol as a hydrophilic resin and the easy-to-adhere layer 4 is remarkably improved. That is, by saponifying the easy-to-adhere layer (4) containing a cellulose ester-based resin as a main component with alkali, a hydrophilic group hydroxyl group is generated, whereby adhesion with polyvinyl alcohol as a hydrophilic resin is effectively improved. Accordingly, the polarizer protective film 1 can be easily and reliably bonded to the polarizer using the water-soluble adhesive agent.

The cellulose ester resin contained as a main component in the adhesive facilitating layer 4 is not particularly limited as long as it is saponified with an alkali to generate a hydroxyl group. However, triacetylcellulose, diacetylcellulose, cellulose acetate propionate and cellulose acetate butyrate Is preferably selected from the group consisting of These cellulose esters are saponified with an alkali to generate a hydrophilic group-containing hydroxyl group, whereby the affinity with the polarizer made of polyvinyl alcohol as a hydrophilic resin is enhanced and adhesion can be ensured.

The number average molecular weight (Mn) of the cellulose ester resin contained as a main component in the adhesive layer 4 is not particularly limited, but is preferably 40000 or more and 100000 or less. The upper limit of the number average molecular weight (Mn) of the cellulose ester resin is more preferably 90,000, and still more preferably 80,000. On the other hand, the lower limit value of the number average molecular weight (Mn) of the cellulose ester resin is more preferably 50,000, and still more preferably 60,000. When the number average molecular weight (Mn) exceeds the upper limit value, there is a fear that the coating property of the easy adhesion layer (4) is lowered. On the contrary, when the number average molecular weight (Mn) is lower than the lower limit value, when the easy adhesion layer (4) is saponified with alkali, the cellulose ester resin may whiten and transparency may be lowered.

The value of the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the cellulose ester based resin contained as the main component in the adhesion facilitating layer (4) is not particularly limited, Do. The upper limit of the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is more preferably 2.5, and still more preferably 2.1. On the other hand, the lower limit of the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is more preferably 1.6, When the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) exceeds the upper limit, the dimensional stability of the adhesive layer (4) may be deteriorated. On the other hand, when the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the cellulose ester resin is less than the lower limit described above, the production of the desired cellulose ester may be difficult.

The thickness (average thickness) of the easy-to-adhere layer 4 is not particularly limited, but is preferably 0.01 m or more and 5 m or less. The upper limit value of the thickness of the adhesion-facilitating layer 4 is more preferably 4 m, and further preferably 3 m. On the other hand, the lower limit value of the thickness of the adhesive layer 4 is more preferably 0.04 mu m, and further preferably 1 mu m. If the thickness of the easy-to-adhere layer 4 exceeds the upper limit value, the thickness of the polarizer protective film 1 becomes thick, which may be against the demand for thinning of the liquid crystal display device. When the thickness of the easy-to-adhering layer 4 exceeds the upper limit, the moisture-permeability of the easy-to-adhering layer 4 may deteriorate. On the other hand, when the thickness of the easy-to-adhere layer 4 is less than the above lower limit value, there is a fear that the adhesion between the easy adhesion layer 4 and the first resin layer 3 is lowered. On the other hand, when the thickness of the easy-to-adherent layer 4 is within the above-mentioned range, the thickness of the polarizer protective film 1 can be kept thin and the hydroxyl groups generated by the saponification of the cellulose ester constituting the easy- , The adhesion with the polyvinyl alcohol constituting the polarizer becomes more reliable.

The solvent of the coating liquid for the cellulose ester for forming the adhesive layer (4) is not particularly limited as long as it is an organic solvent which sufficiently dissolves the cellulose ester. Examples thereof include dioxane, acetone, methyl ethyl ketone, N, Formamide, methyl acetate, ethyl acetate, trichlorethylene, methylene chloride, ethylene chloride, tetrachloroethane, trichloroethane, chloroform and the like are used. An ultraviolet absorber, a lubricant, a matting agent, an antistatic agent, a crosslinking agent, an activator, and the like may be added to the coating liquid of the cellulose ester for forming the adhesion-facilitating layer 4 as desired. Particularly, the crosslinking agent is preferable in promoting adhesion with the polyvinyl alcohol constituting the polarizer. Examples of such cross-linking agents include polyvalent epoxy compounds, aziridine compounds, isocyanate compounds, alum, and boron compounds.

The coating liquid for forming the adhesion-facilitating layer 4 can be applied to the first control layer 3 by a known technique such as a gravure coater, a dip coater, a reverse roll coater, or an extrusion coater. The method of drying after applying the coating liquid is not particularly limited and a known means can be used. It is preferable that the residual solvent amount after drying is 5% by mass or less. If the amount of the residual solvent is large, bubbles are generated at the adhesive interface in the drying process after the polarizer protective film 1 is laminated to the polarizer, which is not preferable.

 (Second control layer 5)

The second control layer 5 is laminated on the other surface side of the substrate layer 2. [ The second control layer 5 contains the same resin as the main component with the first control layer 3. The main component of the second control layer 5 is not particularly limited as long as it contains the same resin as the first control layer 3, but is preferably the same as the main component of the first control layer 3. The moisture permeability of the second control layer 5 and the first control layer 3 are made to be closer to each other when the material for forming the main component of the second control layer 5 is the same as the material for forming the main component of the first control layer 3 And the moisture permeability of the entire polarizer protective film 1 can be more reliably controlled. When the material for forming the main component of the second control layer 5 is the same as the material for forming the main component of the first control layer 3, the ease of manufacturing the polarizer protective film 1 can be improved.

The thickness (average thickness) of the second control layer 5 is not particularly limited, but is preferably 0.01 μm or more and 5 μm or less. The upper limit value of the thickness of the second control layer 5 is more preferably 4 탆, and further preferably 3 탆. On the other hand, the lower limit value of the thickness of the second control layer 5 is more preferably 0.04 mu m, further preferably 1 mu m. When the thickness of the second control layer 5 exceeds the upper limit value, the thickness of the polarizer protective film 1 becomes thick, which may hinder a demand for thinning of the liquid crystal display device. On the contrary, when the thickness of the second control layer 5 is less than the above lower limit value, there is a fear that the formation of the second control layer 5 becomes difficult.

The total thickness (average thickness) of the first control layer 3 and the second control layer 5 is not particularly limited, but is preferably 1.0 m or more and 10 m or less. The upper limit value of the total thickness of the first control layer 3 and the second control layer 5 is more preferably 8 占 퐉, and further preferably 6 占 퐉. On the other hand, the lower limit value of the total thickness of the first control layer 3 and the second control layer 5 is more preferably 2 m, and further preferably 3 m. When the total thickness of the first control layer 3 and the second control layer 5 exceeds the upper limit value, the thickness of the polarizer protective film 1 becomes thick, which is against the requirement for thinning of the liquid crystal display device, There is a fear that moisture permeability is lowered and a long time is required to evaporate water contained in the water-soluble adhesive. On the contrary, when the total thickness of the first control layer 3 and the second control layer 5 is less than the lower limit value, there is a fear that the formation of the first control layer 3 and the second control layer 5 becomes difficult.

The thickness of the second control layer 5 is preferably substantially the same as the thickness of the first control layer 3. The thickness of the second control layer 5 is substantially equal to the thickness of the first control layer 3 so that the first control layer 3 and the second control layer 5 It is possible to prevent the occurrence of curling in the state of being laminated on the substrate layer 2, and further, the ease of manufacturing the polarizer protective film 1 can be improved.

The moisture permeability of the second control layer 5 is not particularly limited, but is preferably 1 g / m ² 24 h or more and 200 g / m ² 24 h or less. The upper limit value of the moisture permeability of the second control layer 5 is more preferably 130 g / m ² · 24 h, and more preferably 80 g / m ² · 24 h. On the other hand, the lower limit value of the moisture permeability of the second control layer 5 is more preferably 10 g / m ² 24 h, more preferably 20 g / m ² 24 h. When the moisture permeability of the second control layer 5 exceeds the upper limit value, the permeation rate of moisture present in the outside is increased, and there is a high possibility that the dimensional change of the base layer 2 or the like will occur. On the other hand, when the moisture permeability of the second control layer 5 is lower than the lower limit value, when the polarizing plate 1 and the polarizing plate 1 are bonded together by the water-soluble adhesive, There is a fear that it takes a long time to evaporate water contained therein.

The second control layer 5 can be formed on the other surface side of the base layer 2 by a method similar to that of the first control layer 3.

≪ Polarizer protective film (1) >

The moisture permeability of the polarizer protective film 1 is preferably 1 g / m ² 24 h or more and 250 g / m ² 24 h or less. The upper limit of the moisture permeability of the polarizer protective film 1 is more preferably 150 g / m ² · 24 h or less, and further preferably 100 g / m ² · 24 h. On the other hand, the lower limit value of the moisture permeability of the polarizer protective film 1 is more preferably 10 g / m ² 24 h, more preferably 20 g / m ² 24 h. When the moisture permeability of the polarizer protective film 1 exceeds the upper limit value, the proportion of moisture permeating from the outside increases, thereby increasing the possibility of causing dimensional changes of the substrate layer 2 or the like. On the other hand, when the polarizer protective film 1 has a moisture permeability lower than the lower limit value, there is a fear that it takes a long time to evaporate the water contained in the water-soluble adhesive when the polarizable adhesive is adhered with the polarizable adhesive layer .

Since the easy-to-adherent layer 4 is disposed on one surface of the polarizer protective film 1, the easy-to-adherent layer 4 and the polarizer can be reliably adhered by a water-soluble adhesive. The polarizer protective film 1 is formed so as to be controlled to have a desired moisture permeability by the first control layer 3 and the second control layer 5 disposed on both surfaces of the base layer 2, The moisture of the water-soluble adhesive can be accurately evaporated at the time of adhering by the adhesive, so that the adhering step can be easily and surely performed. Further, since the main component of the base layer 2 of the polarizer protective film 1 is an acrylic resin, the dimensional change of the base layer 2 under high humidity is less than that of triacetylcellulose, and the photoelastic effect is hard to occur. Therefore, the polarizer protective film 1 has a small change in the retardation value. Particularly, in the polarizer protective film 1, since the second control layer 5 is arranged on the other surface side of the base layer 2 and is controlled and controlled to have desired moisture permeability, the dimensional change of the base layer 2 The dimensional change of the base layer 2 can be further reduced, and the change in the retardation value is small.

≪ Polarizing plate (11) >

The polarizing plate 11 of Fig. 2 is provided with a polarizer protective film 1 of Fig. 1 on one surface of a polarizer 12 made of polyvinyl alcohol and a cellulose ester conventionally used on the other surface of the polarizer 12 And a polarizer protective film 13 made of a transparent material. Between the polarizer 12 and the polarizer protective film 1 and between the polarizer 12 and the polarizer protective film 13 are bonded by an adhesive (not shown).

The polarizer 12 is obtained by uniaxially stretching a polyvinyl alcohol resin film by dying it with a dichromatic material (for example, iodine or a dichroic dye). The polymerization degree of the polyvinyl alcohol constituting the polyvinyl alcohol resin film is preferably 500 or more, more preferably 1000 or more. The polyvinyl alcohol resin film can be formed by a known method (for example, a soft method in which a resin is dissolved in water or an organic solvent, a casting method, or the like). The thickness (average thickness) of the polarizer 12 differs depending on the purpose and application of the liquid crystal display device in which the polarizing plate 11 is used, but is typically 5 占 퐉 or more and 100 占 퐉 or less. The polarizer 12 may contain any component other than the polyvinyl alcohol resin and the dichroic material as long as it does not hinder the polarization function and the optical transparency.

As a typical manufacturing method of the polarizer 12, a series of manufacturing steps including swelling, dyeing, crosslinking, stretching, washing, and drying of a polyvinyl alcohol resin film is employed. In each treatment step except for the drying step, the treatment is carried out by immersing the polyvinyl alcohol resin film in a bath of the solution used in each step. The order, number of times, and execution of each processing of swelling, dyeing, crosslinking, stretching, washing and drying can be suitably set in accordance with the object, materials to be used and conditions. For example, the stretching process may be performed before the dyeing process, or may be performed simultaneously with the swelling process. It is also preferable to carry out the crosslinking treatment before and after the stretching treatment.

The swelling step in the series of manufacturing steps of the polarizer 12 can be performed by immersing the polyvinyl alcohol resin film in a treatment bath filled with water. Glycerin, potassium iodide, or the like may be appropriately added to the treatment bath. Typically, the temperature of the treatment bath in the swelling process is about 20 to 60 DEG C, and the immersion time in the treatment bath is about 0.1 to 10 minutes. The dyeing step can be performed by immersing a polyvinyl alcohol resin film in a treatment bath containing a dichroic substance such as iodine. As the solvent used in the solution of this treatment bath, water is generally used. The dichroic substance is used in a proportion of 0.1 to 1.0 part by mass based on 100 parts by mass of the solvent. Typically, the temperature of the treatment bath in the dyeing process is about 20 to 70 DEG C, and the immersion time is about 1 to 20 minutes.

The crosslinking step can be carried out by immersing the dye-treated polyvinyl alcohol-based resin film in a treating bath containing a crosslinking agent. Examples of the crosslinking agent include boron compounds such as boric acid, glyoxal, and glutaraldehyde. As the solvent used in the solution of this treatment bath, water is generally used. Typically, the temperature of the treatment bath in the crosslinking step is about 20 to 70 DEG C, and the immersion time is about 1 to 15 minutes. The stretching process may be performed at any stage. The stretching magnification of the polyvinyl alcohol resin film is preferably 5 times or more. As the stretching method, for example, a wet stretching method may be employed. The solution of the treatment bath in this case is preferably a solution in which various metal salts, iodine, boron or zinc compounds are added to water or an organic solvent.

The water washing step can be performed by immersing the polyvinyl alcohol resin film subjected to various treatments in a washing bath. Unnecessary residues of the polyvinyl alcohol resin film can be washed away by this water washing step. The washing bath may be pure or an aqueous solution of iodide (potassium iodide, sodium iodide, etc.). The temperature of the washing bath is preferably 10 to 60 캜. Typically, the immersion time is 1 second to 1 minute. The number of times of water washing may be one time or plural times. As the drying step, for example, natural drying, air blow drying, and heat drying may be employed. Typically, the drying temperature is 20 to 80 ° C and the drying time is 1 to 10 minutes. By performing each of the above steps, the polarizer 12 can be manufactured.

The polarizer protective film 13 is formed by dissolving a flake raw material of a cellulose ester and a plasticizer in methylene chloride to make a viscous liquid, dissolving a plasticizer thereon and doping the plasticizer film, and applying a softening agent on a metal belt such as stainless steel continuously rotating from a melt extruder Dried, peeled off from the belt in a dry condition, and then dried and wound. The cellulose ester is preferably selected from the group consisting of triacetylcellulose, diacetylcellulose, cellulose acetate propionate and cellulose acetate butyrate, and triacetylcellulose is particularly preferable.

It is preferable that the polarizer protective film 1 is saponified by alkali before the adhesive layer 4 is adhered to the polarizer 12. By this saponification, the ester group of the cellulose ester is converted into a hydroxyl group having a hydrophilic group, whereby the chemical affinity between the polarizer protective film 1 and the polarizer 12 formed of polyvinyl alcohol as a hydrophilic resin increases, The adhesiveness of the substrate is remarkably improved.

As the alkali aqueous solution used for the saponification treatment, for example, an aqueous solution of sodium hydroxide, potassium hydroxide, calcium hydroxide, lithium hydroxide or the like can be used. The concentration of these metal hydroxides is generally not less than 5 mass% and not more than 40 mass%. The temperature of the saponification treatment is preferably 10 ° C or more and 80 ° C or less. When the concentration of the metal hydroxide is 5 mass% or less, or when the temperature of the saponification treatment is 10 占 폚 or less, the time required for the saponification treatment becomes long, which is not preferable. The saponification treatment is carried out by immersing the polarizer protective film 1 in the above-described alkali aqueous solution bath for a suitable period of time.

The polarizer protective film 1 provided for the saponification treatment and the polarizer 12 made of polyvinyl alcohol are adhered by an apparatus 21 schematically shown in Fig. An apparatus 21 for bonding a plurality of films shown in Fig. 3 comprises a nip 22 for supplying a polarizer 12, a nip 23 for supplying a polarizer protective film 1, means for supplying an adhesive And a nip 25 for pressing and bonding the polarizer 12 and the polarizer protective film 1 with an adhesive.

Examples of the adhesive used for bonding the polarizing element 12 with the easy-to-adhere layer 4 of the polarizer protective film 1 by the device 21 include a polyvinyl alcohol-based adhesive such as polyvinyl alcohol and polyvinyl butyral And vinyl-based latexes such as butyl acrylate. Normally, these adhesives are used as an aqueous solution. The solid content concentration of the adhesive in the resin solution is preferably 0.1 to 15% by mass in consideration of the coatability and the stability of standing. The viscosity of the resin solution of the adhesive is preferably in the range of 1 to 50 mPa · s, for example.

In the apparatus 21, the saponified polarizer protective film 1 fed from the nip 22 and the film-form polarizer 12 fed from the nip 23 is fed in the direction toward the nip 25 The polarizer 12 and the easy-to-adhere layer 4 of the polarizer protective film 1 are adhered to each other by the application of an appropriate amount of adhesive to be sandwiched between these films, A polarizer protective film 1 is laminated on one surface of the polarizer protective film 1. The polarizing plate 11 is obtained by laminating the polarizer protective film 13 on the surface of the polarizer 12 on the side where the polarizer protective film 1 is not laminated by the same means.

In the polarizing plate 11, the easy-to-adhere layer 4 of the polarizer protective film 1 and the polarizer 12 are reliably bonded by the water-soluble adhesive. Since the polarizer protective film 1 is formed by controlling the desired moisture permeability by the first control layer 3 and the second control layer 5, it is possible to accurately evaporate water of the water-soluble adhesive at the time of adhesion by the water- So that the above-described bonding step can be carried out easily and reliably. As a result, the polarizer 11 can reliably adhere the polarizer protective film 1 and the polarizer. Further, since the main component of the base layer 2 of the polarizer protective film 1 is an acrylic resin, the dimensional change of the base layer 2 under high humidity is less than that of triacetyl cellulose, and the photoelastic effect is hard to occur. Therefore, the polarizer protective film 1 has a small change in the retardation value. Particularly, since the polarizer protective film 1 is formed so that the second control layer 5 is arranged on the other surface side of the base layer 2 and controlled to have desired moisture permeability, the dimensional change of the base layer 2 The dimensional change of the substrate layer 2 can be further reduced. Therefore, the polarizer protective film 1 of the polarizing plate 11 can reduce the change in the retardation value, and can exhibit desired optical characteristics.

<Liquid crystal display element 31>

The liquid crystal display element 31 shown in Fig. 4 has a structure in which the liquid crystal layer 34 is bonded to both surfaces of the liquid crystal cell 32 sandwiched by the transparent medium layer 33 (for example, glass) And the polarizing plate 11 of Fig. 2 according to the invention. The polarizer protective film 1 (base layer 2, first control layer 3, adhesion facilitating layer 4 and second control layer 5) according to the present invention is provided on the outer surface side of the polarizer 12 A polarizer protective film 13 made of conventionally used cellulose ester is disposed on the inner surface side of the polarizer 12 (on the side of arrangement of the liquid crystal cells 32) . The material constituting the liquid crystal layer 34, the transparent medium layer 33 and the adhesive layer 35 of the liquid crystal cell 32 is not particularly limited and a known material can be used.

In the liquid crystal display element 31 of the liquid crystal display element 31, the easy adhesion layer 4 of the polarizer protective film 1 and the polarizer 12 are reliably bonded by the water-soluble adhesive. Since the polarizer protective film 1 is formed by controlling the desired moisture permeability by the first control layer 3 and the second control layer 5, it is possible to accurately evaporate water of the water-soluble adhesive at the time of adhesion by the water- So that the above bonding step can be carried out easily and accurately. As a result, the liquid crystal display element 31 can reliably adhere the polarizer protective film 1 and the polarizer 12. Since the main component of the base layer 2 of the polarizer protective film 1 is acrylic resin, the dimensional change of the base layer 2 under high humidity is less than that of triacetylcellulose, and the photoelastic effect is less likely to occur. Therefore, the polarizer protective film 1 has a small change in the retardation value. Particularly, since the polarizer protective film 1 is formed so that the second control layer 5 is arranged on the other surface side of the base layer 2 and controlled to have desired moisture permeability, the dimensional change of the base layer 2 The dimensional change of the substrate layer 2 can be further reduced. Therefore, the liquid crystal display element 31 can reduce the change in the retardation value of the polarizer protective film 1, and can exhibit desired optical characteristics. Therefore, the liquid crystal display element 31 can accurately display light by effectively utilizing the light from the light source.

[Other Embodiments]

The polarizer protective film, the polarizing plate and the liquid crystal display element of the present invention can be carried out by various modifications and improvements other than those described above. For example, the second control layer of the polarizer protective film may be formed to be substantially thicker than the first control layer. Thus, by making the second control layer substantially thicker than the first control layer in the polarizer protective film, it is possible to impart a curl preventing function to a force which tends to be rounded with the ease of adhesion side inward, It is possible to prevent the occurrence of overall curl. As a result, the polarizer protective film can improve dimensional stability.

The polarizer protective film may be arranged on both sides (inner side and outer side) of the polarizer. As a result, the dimensional stability of the polarizer protective film arranged on the inner and outer surfaces of the polarizer can be improved. The polarizer protective film may be arranged on the inner surface side of the polarizer, and another polarizer protective film may be arranged on the outer surface side of the polarizer.

An antireflection layer, an antireflection layer, an antistatic layer, a hard coat layer (an anti-reflection layer such as an antiglare layer, an antireflection layer, an antiglare layer and a low refractive index layer) A cured resin layer), an optical compensation layer, or the like) may be arranged. For example, by providing the antiglare layer (antireflection layer) on the other surface side of the second control layer, the antiglare function can be exhibited in addition to the protective function for the polarizer. In addition, by providing the hard coat layer on the other surface side of the second control layer, the protection function against the polarizer can be enhanced.

The polarizing plate is required to be laminated on either side of the liquid crystal cell, and it is not necessarily required to be laminated on both sides of the liquid crystal cell.

As described above, the polarizer protective film of the present invention, the polarizing plate using the polarizer protective film, and the liquid crystal display element using the polarizing plate can reduce the dimensional change of the substrate layer of the polarizer protective film by humidity, It is possible to easily and surely adhere the polarizer protective film and the polarizer with the water-soluble adhesive while suppressing the change of the retardation value, It can be used in various fields ranging from large size products.

One… Polarizer protective film
2… The substrate layer
3 ... The first control layer
4… Adhesive layer
5 ... The second control layer
11 ... Polarizer
12 ... Polarizer
13 ... Polarizer protective film made of cellulose ester
21 ... Apparatus for producing a polarizing plate
22 ... Nip
23 ... Nip
24 ... Adhesive supply means
25 ... Nip
31 ... Liquid crystal display element
32 ... Liquid crystal cell
33 ... Transparent medium layer
34 ... Liquid crystal layer
35 ... Adhesive layer
41 ... Liquid crystal display element
42 ... Liquid crystal cell
43 ... Transparent medium layer
44 ... Liquid crystal layer
45 ... Polarizer
46 ... Polarizer protective film
47 ... Polarizer
48 ... Adhesive layer

Claims (12)

A polarizer protective film adhered to a polarizer of a liquid crystal display panel,
A base layer containing an acrylic resin as a main component,
A first control layer laminated on one surface side of the base layer for controlling the moisture permeability,
An easy adhesion layer laminated on one surface side of the first control layer,
A second control layer for controlling the moisture permeability, which is laminated on the other surface side of the base layer,
And,
Wherein the first control layer and the second control layer comprise an acrylic-modified polyester-based resin as a main component. The polarizer protective film of claim 1, wherein the first control layer is substantially the same thickness as the second control layer. The polarizer protective film of claim 1, wherein the second control layer is substantially thicker than the first control layer. The polarizer-protective film according to claim 1, wherein the acrylic resin has a photoelastic coefficient of -5 × 10 ^-12 / Pa or more and 5 × 10 ^-12 / Pa or less. The polarizer-protective film according to claim 1, wherein the easy-to-adhere layer comprises a cellulose ester-based resin as a main component. The polarizer protective film according to claim 5, wherein the number average molecular weight (Mn) of the cellulose ester resin is 40000 or more and 100000 or less. The polarizer protective film according to claim 1, wherein the first control layer and the second control layer further contain a urethane-based resin. The polarizer protective film according to claim 1, wherein the moisture permeability is 1 g / m ² 24 h or more and 250 g / m ² 24 h or less. The polarizer protective film according to claim 1, wherein the base layer has a retardation value (Re) of -15 nm or more and 15 nm or less. A polarizer protective film as described in any one of claims 1 to 9,
A polarizer attached to the easy-to-adhere layer of the polarizer protective film by a water-
And a polarizing plate. A liquid crystal cell,
The polarizing plate according to claim 10, which is laminated on one surface of the liquid crystal cell
And a liquid crystal layer. delete

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