JP2013160863A - Polarizer protective film, polarizing plate and liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarizer protective film capable of easily and securely adhering to a polarizer by a water-soluble adhesive while suppressing variation in a retardation value by reducing a dimensional change due to humidity, a polarizing plate using the polarizer protective film and a liquid crystal display element.SOLUTION: A polarizer protective film of the present invention is a polarizer protective film adhered to a polarizer of a liquid crystal display panel, which comprises: a base material layer consisting mainly of an acrylic resin; a first control layer which is laminated on one surface side of the base material layer and controls moisture permeability; an easily adhesive layer which is laminated on one surface side of the first control layer; and a second control layer which is laminated on the other surface side of the base material layer and controls moisture permeability, wherein the first control layer and the second control layer contain the same resin as the main component.

Description

  The present invention relates to a polarizer protective film, a polarizing plate comprising this polarizer protective film, and a liquid crystal display device comprising this polarizing plate.

  Liquid crystal display devices (LCDs) are widely used as flat panel displays taking advantage of their thin, lightweight, and low power consumption characteristics, and their applications are information on mobile phones, personal digital assistants (PDAs), personal computers, televisions, etc. It is expanding year after year as a display device.

  As shown in FIG. 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 transparent medium layers 43 (for example, glass) on both sides, and the liquid crystal cell 42. And a polarizing plate 45 bonded to the both surfaces by an adhesive layer 48. The polarizing plate 45 is configured by attaching a polarizer protective film 46 to both surfaces of a polarizer 47 having polarizing ability. Thus, the polarizer 47 is protected by the polarizer protective film 46 from the viewpoint of improving the strength and facilitating handling.

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

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

  In view of such circumstances, the present applicant has devised a polarizer protective film having a base material layer made of an acrylic resin or the like (see JP 2010-181500 A). In the polarizer protective film described in JP 2010-181500 A, a primer layer is disposed on one surface of a base material layer, and a hydrophilic resin layer is disposed on one surface of the primer layer. In addition, the adhesiveness with a polarizer when a water-soluble adhesive is used is improved. In addition, it is assumed that the polarizer protective film described in the above publication is mainly disposed on the outer surface side of the liquid crystal display element (the side away from the liquid crystal cell, that is, the uppermost layer and the lowermost layer in FIG. 5).

  On the other hand, it is said that the polarizer protective film disposed on the inner surface side of the liquid crystal display element preferably has a lower retardation value than the polarizer protective film disposed on the outer surface side of the liquid crystal display element. In other words, when the retardation value of the polarizer protective film is high, the light that has passed through the polarizer and has become linearly polarized light becomes elliptically polarized light by the polarizer protective film and enters the liquid crystal layer, or linearly polarized light that has passed through the liquid crystal layer. May become elliptically polarized light by the polarizer protective film, so that the light beam may not be sufficiently used for display. For this reason, the polarizer protective film disposed on the inner surface side of the liquid crystal display element is desired to have a low retardation value as described above.

  However, since the conventional base layer made of triacetyl cellulose has high moisture permeability and water absorption, it tends to cause a dimensional change in a high humidity environment. For this reason, another layer integrated with this base layer ( For example, the adhesive layer) also undergoes a dimensional change with the dimensional change of the base material layer, and a photoelastic effect (change in retardation value due to deformation) due to the dimensional change of the other layers and the base material layer results. There is a risk of causing a situation where the light is not fully utilized for display.

  In order to solve such problems, retardation is achieved by reducing the water absorption and photoelastic coefficient by adopting a means using an acrylic resin or a cycloolefin resin as described in the above publication as the base material layer. It is conceivable to suppress the change in value. However, when such a means is adopted, if the water absorption of the polarizer protective film is too small, the moisture permeability becomes too small. When this polarizer protective film is adhered to the polarizer with a water-soluble adhesive, it is water soluble. There is a possibility that the moisture contained in the adhesive does not evaporate accurately. Moreover, even if only the photoelastic coefficient of the base material layer is reduced, if the moisture permeability is too high, the water absorption is also increased, and the above-described photoelastic effect may be caused by a dimensional change due to humidity.

JP 2010-181500 A

  The present invention has been made in view of such circumstances, and easily and reliably adheres to a polarizer with a water-soluble adhesive while suppressing a change in retardation value by reducing a dimensional change due to humidity. An object of the present invention is to provide a polarizer protective film, a polarizing plate using the polarizer protective film, and a liquid crystal display device using the polarizing plate.

The invention made to solve the above problems is
A polarizer protective film adhered to a polarizer of a liquid crystal display panel,
A base material layer mainly composed of an acrylic resin;
A first control layer for controlling moisture permeability, laminated on one surface side of the base material layer,
An easy adhesion layer laminated on one side of the first control layer;
A second control layer for controlling moisture permeability, laminated on the other surface side of the base material layer,
The polarizer protective film is characterized in that the first control layer and the second control layer contain the same resin as a main component.

  Since the easy-adhesion layer is arranged on one surface side of the polarizer protective film, the easy-adhesion layer and the polarizer can be reliably bonded with a water-soluble adhesive. In addition, the polarizer protective film is formed to be controlled to have a desired moisture permeability by the first control layer and the second control layer disposed on both surfaces of the base material layer. At this time, the water content of the water-soluble adhesive can be accurately evaporated, and the above-described bonding process can be easily and reliably performed. Furthermore, since the main component of the base material layer of the polarizer protective film is an acrylic resin, the dimensional change of the base material layer under high humidity is less than that of triacetyl cellulose, and the photoelastic effect is hardly generated. For this reason, the said polarizer protective film has a small change of a retardation value. In particular, the polarizer protective film has a second control layer disposed on the other surface side of the base material layer and is controlled to have a desired moisture permeability. Thus, the dimensional change of the base material layer can be made smaller, 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. Thereby, it is possible to prevent the occurrence of curling during production.

  In the polarizer protective film, the second control layer may be substantially thicker than the first control layer. Thereby, the curl prevention function with respect to the force which is going to be rounded by making an easily bonding layer side into an inner side can be provided, and generation | occurrence | production of the curl as the said polarizer protective film as a whole can be prevented. As a result, the polarizer protective film can improve dimensional stability.

In the polarizer protective film, the acrylic resin preferably has a photoelastic coefficient of −5 × 10 ⁻¹² / Pa to 5 × 10 ⁻¹² / Pa. The polarizer protective film can reduce the change in the retardation value of the base material layer due to the dimensional change even when the dimensional change occurs by setting the photoelastic coefficient of the acrylic resin in the above range. it can.

  In the polarizer protective film, the easy-adhesion layer may include a cellulose ester resin as a main component. Thereby, the adhesiveness using the water-soluble adhesive of the polarizer which consists of polyvinyl alcohol, and an easily bonding layer can be improved greatly. That is, since a hydroxyl group that is a hydrophilic group is generated by saponifying an easy-adhesion layer containing a cellulose ester resin as a main component with an alkali, a cellulose resin and a polyvinyl alcohol that is a hydrophilic resin are formed by a water-soluble adhesive. Can be easily and reliably adhered.

  The said polarizer protective film is good in the number average molecular weight (Mn) of the cellulose-ester-type resin which the said easily bonding layer contains as a main component being 40000-100,000. Thereby, while improving the coating property of an easily bonding layer, when an easily bonding layer is saponified with an alkali, it can prevent that a cellulose ester resin whitens and transparency falls.

  In the polarizer protective film, the first control layer and the second control layer may include an acrylic-modified polyester resin as a main component. This makes it possible to take advantage of the properties such as transparency, toughness, heat resistance inherent to polyester resins, and adhesion to acrylic resins contained as the main component of the base material layer, while adhering to easy-adhesion layers by acrylic modification. Can be granted.

  In the polarizer protective film, the first control layer and the second control layer may contain the acrylic-modified polyester resin and the urethane resin. This makes it possible to take advantage of the properties such as transparency, toughness, heat resistance inherent to polyester resins, and adhesion to acrylic resins contained as the main component of the base material layer, while adhering to easy-adhesion layers by acrylic modification. In addition, it is possible to further impart adhesion and flexibility to the base material layer and the easy adhesion layer by blending the urethane-based resin.

The polarizer protective film may have a moisture permeability of 1 g / m ² · 24 h to 250 g / m ² · 24 h. Thereby, the water | moisture content of a water-soluble adhesive can be evaporated more correctly at the time of adhesion | attachment by a water-soluble adhesive, and an easily bonding layer and a polarizer can be adhere | attached more easily and reliably. Moreover, the said polarizer protective film can suppress the dimensional change of a base material layer more suitably, and can make the change of the retardation of a base material layer still smaller.

  In the polarizer protective film, the retardation value (Re) of the base material layer is preferably -15 nm or more and 15 nm or less. Thereby, coupled with the high dimensional stability of the polarizer protective film, the action of converting transmitted light is suppressed, and the polarization is optimized and controllable in the direction of the transmission axis of the polarizer. The influence which a child protective film exerts can be suppressed.

Moreover, the polarizing plate made in order to solve the said subject is
The polarizer protective film;
And a polarizer bonded to the easy-adhesion layer of the polarizer protective film with a water-soluble adhesive.

  In the polarizing plate, the easy-adhesion layer of the polarizer protective film and the polarizer are securely bonded with a water-soluble adhesive. Further, since the polarizer protective film is formed to be controlled to have a desired moisture permeability by the first control layer and the second control layer, the water content of the water-soluble adhesive can be accurately determined during the bonding with the water-soluble adhesive. It can evaporate and the said adhesion process can be performed easily and reliably. As a result, the polarizing plate can securely bond the polarizer protective film and the polarizer. Furthermore, since the main component of the base material layer of the polarizer protective film is an acrylic resin, the dimensional change of the base material layer under high humidity is less than that of triacetyl cellulose, and a photoelastic effect is hardly generated. For this reason, the said polarizer protective film has a small change of a retardation value. In particular, the polarizer protective film has a second control layer disposed on the other surface side of the base material layer, and is controlled to have a desired moisture permeability, thereby further suppressing the dimensional change of the base material layer. Thus, the dimensional change of the base material layer can be further reduced. Therefore, the polarizing plate can reduce a change in the retardation value of the polarizer protective film, and can exhibit desired optical characteristics.

Furthermore, the liquid crystal display element made in order to solve the said subject is
A liquid crystal cell;
A liquid crystal display element comprising the polarizing plate laminated on one surface side of the liquid crystal cell.

  In the liquid crystal display element, the easy-adhesion layer of the polarizer protective film and the polarizer are securely bonded with a water-soluble adhesive. In addition, since the polarizer protective film is formed so as to be controlled to have a desired moisture permeability by the first control layer and the second control layer, the moisture of the water-soluble adhesive is appropriately evaporated upon bonding with the water-soluble adhesive. And the above bonding process can be carried out easily and accurately. As a result, the liquid crystal display element can securely bond the polarizer protective film and the polarizer. Furthermore, since the main component of the base material layer of the polarizer protective film is an acrylic resin, the dimensional change of the base material layer under high humidity is less than that of triacetyl cellulose, and a photoelastic effect is hardly generated. For this reason, the said polarizer protective film has a small change of a retardation value. In particular, the polarizer protective film has a second control layer disposed on the other surface side of the base material layer, and is controlled to have a desired moisture permeability, thereby further suppressing the dimensional change of the base material layer. Thus, the dimensional change of the base material layer can be further reduced. Therefore, the liquid crystal display element can reduce a change in the retardation value of the polarizer protective film and can exhibit desired optical characteristics. Therefore, the liquid crystal display element can perform accurate display by effectively using the light of the light source.

In the present invention, the “same resin” includes a monomer having the same chemical species and a different composition or a different polymerization type. "Photoelastic coefficient" is a coefficient representing the resulting ease of change in refractive index due to external force is a value determined by ^{_{C R [Pa -1] = Δn}} / σ R. Here, σ _R is an extensional stress [Pa], Δn is a refractive index difference when stress is applied, and Δn is defined by the following equation.
Δn = n ₁ −n ₂
(Where n ₁ is the refractive index in the direction parallel to the tensile stress, and n ₂ is the refractive index in the direction perpendicular to the tensile direction.)

“Moisture permeability” refers to the water vapor permeability test (cup method) of JIS Z0208, measuring the number of grams of water vapor that passes through a sample of 1 m ² in 24 hours in an atmosphere of 40 ° C. and 92% RH. It is the value. The “retardation value (Re)” means that the fast axis direction and the slow axis direction orthogonal to each other among the crystal axis directions on the plane of the polarizer protective film surface are the x direction and the y direction, and the polarizer protective film The thickness is d, the refractive indexes in the x direction and y direction are nx and ny (nx ≠ ny), and the value is calculated by Re = (ny−nx) d.

  As described above, the polarizer protective film of the present invention, the polarizing plate using this polarizer protective film, and the liquid crystal display element using this polarizing plate are the dimensions of the base material layer of the polarizer protective film due to humidity. Adhesion between the polarizer protective film and the polarizer by the water-soluble adhesive can be easily and reliably performed while suppressing the change in the retardation value of the polarizer protective film by reducing the change.

It is typical sectional drawing which shows the polarizer protective film which concerns on one Embodiment of this invention. It is typical sectional drawing which shows a polarizing plate provided with the polarizer protective film of FIG. It is a schematic diagram which shows the apparatus for manufacturing the polarizing plate of FIG. It is typical sectional drawing which shows a liquid crystal display element provided with the polarizing plate of FIG. It is a schematic diagram which shows the structure of the conventional common liquid crystal display element.

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

[First embodiment]
The polarizer protective film 1 of FIG. 1 is for controlling the moisture permeability by the base material layer 2 which has acrylic resin as a main component, the 1st control layer 3 for controlling moisture permeability, the easily bonding layer 4, and. Second control layer 5. The polarizer protective film 1 is formed as a laminate in which a second control layer 5, a base material 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 that is bonded to the polarizer of the liquid crystal display element from the easy-adhesion layer 4 side and improves the impact resistance and handling properties of the polarizer.

(Base material layer 2)
As a main component of the base material layer 2, an acrylic resin that is a synthetic resin that retains high transparency required for a polarizer protective film of a liquid crystal display element and has a certain moisture permeability is used. The base material layer 2 may contain other optional components as long as the transparency and desired strength are not impaired, but preferably contains 90% by mass or more, more preferably 98% by mass or more of acrylic resin. Examples of optional components here include ultraviolet absorbers, stabilizers, lubricants, processing aids, plasticizers, impact resistance aids, phase difference reducing agents, matting agents, antibacterial agents, and fungicides.

  The acrylic resin used as the main component of the base material 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 ester such as polymethyl methacrylate, methyl methacrylate- (meth) acrylic acid copolymer, methyl methacrylate- (meth) acrylic acid ester copolymer. Polymer, methyl methacrylate-acrylic ester- (meth) acrylic acid copolymer, (meth) methyl acrylate-styrene copolymer, polymer having alicyclic hydrocarbon group (for example, methyl methacrylate-methacrylic acid) Acid cyclohexyl copolymer, methyl methacrylate- (meth) acrylate norbornyl copolymer), and the like. Among these acrylic resins, poly (meth) acrylate C1-6 alkyl such as poly (meth) methyl acrylate is preferable, and methyl methacrylate resin is more preferable.

Although it does not specifically limit as a photoelastic coefficient of the said acrylic resin, It is preferable that they are -5 * 10 < ^-12 > / Pa or more and 5 * 10 < ^-12 > / Pa or less. The upper limit of the photoelastic coefficient of the acrylic resin is more preferably 4 × 10 ⁻¹² / Pa, and further preferably 3 × 10 ⁻¹² / Pa. On the other hand, the lower limit of the photoelastic coefficient of the acrylic resin is more preferably −4 × 10 ⁻¹² / Pa, and further preferably −3 × 10 ⁻¹² / Pa. When the photoelastic coefficient of the acrylic resin is outside the above range, the change in the retardation value when a dimensional change occurs may increase.

  The water absorption rate of the acrylic resin is not particularly limited, but is preferably 1.0% or less, more preferably 0.7% or less, and further preferably 0.5% or less. When the water absorption rate of the acrylic resin exceeds the above range, there is a high possibility that a dimensional change occurs when the contained water evaporates. In addition, a water absorption rate is based on the value measured using the film-like sample of 50 mm square and thickness 100 micrometers based on JISK7209.

  Although it does not specifically limit as thickness (average thickness) of the base material layer 2, 10 micrometers or more and 200 micrometers or less are preferable. The upper limit value of the thickness of the base material layer 2 is more preferably 100 μm, and further preferably 80 μm. On the other hand, the lower limit of the thickness of the base material layer 2 is more preferably 20 μm, and further preferably 40 μm. When the thickness of the base material layer 2 exceeds the above upper limit, the line speed, productivity, and moisture permeability at the time of manufacture are reduced, and there is a possibility that it is contrary to the demand for thinning the liquid crystal display device. On the contrary, when the thickness of the base material layer 2 is less than the above lower limit value, the strength and rigidity are reduced, and there is a possibility that handling in a production line or the like becomes difficult.

  Although it does not specifically limit as arithmetic mean surface roughness (Ra) of the base material layer 2, Usually, 0.02 or more and 0.06 or less can be used. Further, the base material layer 2 can be subjected to a mat treatment as necessary. The upper limit value of the arithmetic average surface roughness (Ra) of the base material layer 2 subjected to such matting treatment is preferably 2, and more preferably 1. On the other hand, the lower limit value of the arithmetic average surface roughness (Ra) of the base material layer 2 subjected to the mat treatment is preferably 0.07, and more preferably 0.1. By controlling the arithmetic average surface roughness (Ra) of the base material layer 2 that has been subjected to the matting treatment within such a range, scratches in the processing after the production of the raw film are prevented, and handling properties are improved. Moreover, generally, when winding up the manufactured film original fabric, it is preferable to prevent blocking by embossing (knurling) both ends in the width direction of the film. When a knurling process is performed on a film, the processing points at both ends of the film cannot be used, so that part must be cut and discarded. In the film winding operation, masking may be performed with a protective film in order to prevent damage. However, by setting the arithmetic average surface roughness (Ra) of the base material layer 2 in the above range, blocking can be prevented without performing a knurling treatment, so that the manufacturing process is simplified and both ends in the film width direction are achieved. The part can also be used, and a long winding can be performed without causing film failure. Moreover, when the base material layer 2 has moderate surface roughness, the damage at the time of winding is suppressed effectively, and the above masking is also unnecessary.

  Although it does not specifically limit as a retardation value (Re) of the base material layer 2, It is preferable that they are -15 nm or more and 15 nm or less. The upper limit value of the retardation value (Re) of the base material layer 2 is more preferably 10 nm, and further preferably 5 nm. On the other hand, the lower limit of the retardation value (Re) of the base material layer 2 is more preferably −10 nm, and further preferably −5 nm. When the retardation value (Re) of the base material layer 2 is out of the above range, there is a possibility that the polarization in the transmission axis direction of the polarizer cannot be optimized by the action of converting the polarization direction of the transmitted light.

  Although the manufacturing method of the base material layer 2 is not particularly limited, for example, an acrylic resin flake raw material and an additive such as a plasticizer are mixed by a conventionally known mixing method to obtain a thermoplastic resin composition in advance. A film can be produced. This thermoplastic resin composition can be obtained, for example, by pre-blending with a mixer such as an omni mixer and then extruding and kneading the resulting mixture. In this case, the kneader used for extrusion kneading is not particularly limited, and for example, a conventionally known kneader such as an extruder such as a single screw extruder or a twin screw extruder or a pressure kneader can be used. .

  Examples of the film forming method for the base material layer 2 include known methods such as a solution casting method (solution casting method), a melt extrusion method, a calendar method, and a compression molding method. Among these, the solution casting method (solution casting method) and the melt extrusion method are preferable. At this time, a thermoplastic resin composition extruded and kneaded in advance may be used, or another additive such as a synthetic resin and a plasticizer is separately dissolved in a solvent to obtain a uniform mixed solution, and then a solution cast. You may use for the film forming process of a method (solution casting method) and a melt extrusion method.

  Solvents used in the solution casting method (solution casting method) include, for example, chlorinated solvents such as chloroform and dichloromethane; aromatic solvents such as toluene, xylene, benzene, and mixed solvents thereof; methanol, ethanol, and isopropanol And alcohol solvents such as n-butanol and 2-butanol; methyl cellosolve, ethyl cellosolve, butyl cellosolve, dimethylformamide, dimethyl sulfoxide, dioxane, cyclohexanone, tetrahydrofuran, acetone, methyl ethyl ketone (MEK), ethyl acetate, diethyl ether, etc. It is done. 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 film forming temperature during melt extrusion is preferably 150 ° C. or higher and 350 ° C. or lower, more preferably 200 ° C. or higher and 300 ° C. or lower. When film-forming by the T-die method, a T-die is attached to the tip of a known single-screw extruder or twin-screw extruder, and the film extruded into a film shape is wound to obtain a roll film. Under the present circumstances, it is also possible to set it as a uniaxial stretching process by adjusting the temperature of a winding roll suitably, and adding extending | stretching to an extrusion direction. It is also possible to add steps such as sequential biaxial stretching and simultaneous biaxial stretching by adding a step of stretching the film in a direction perpendicular to the extrusion direction.

  The base material layer 2 may be an unstretched film or a stretched film. When extending | stretching, a uniaxially stretched film may be sufficient and a biaxially stretched film may be sufficient. When a biaxially stretched film is used, it may be biaxially stretched simultaneously or sequentially biaxially stretched. In the case of biaxial stretching, the mechanical strength is improved and the film performance is improved.

  As the stretching temperature when the stretching step is performed, it is preferably performed in the vicinity of the glass transition temperature of the thermoplastic resin composition of the film raw material, specifically, (glass transition temperature-30) ° C. to (glass transition temperature + 100) ° C. It is preferable to carry out at (Glass transition temperature−20) ° C. to (Glass transition temperature + 80) ° C. When the stretching temperature exceeds the above upper limit, resin flow may occur and stable stretching may not be performed. On the other hand, when the stretching temperature is less than the lower limit, a sufficient stretching ratio may not be obtained.

  The draw ratio defined by the area ratio can be preferably in the range of 1.1 to 25 times, more preferably in the range of 1.3 to 10 times. When the draw ratio exceeds the above upper limit, there is a possibility that the effect of increasing the draw ratio may not be recognized. On the other hand, when the draw ratio is less than the lower limit, there is a possibility that the toughness accompanying the drawing will not be improved.

  The stretching speed (one direction) is preferably in the range of 10 to 20000% / min, more preferably in the range of 100 to 10000% / min. When the stretching speed exceeds the above upper limit, the stretched film may be broken. On the other hand, when the stretching speed is less than the lower limit, it takes time to obtain a sufficient stretching ratio, which may increase the production cost. In addition, in order to stabilize the optical isotropy and mechanical characteristic of the base material layer 2, heat processing (annealing) etc. can also be performed after an extending | stretching process.

  Although it does not specifically limit as said plasticizer, The functional group which can interact with a synthetic resin by a hydrogen bond etc. so that a haze may be generated in the base material layer 2, or it may not bleed out or volatilize from the base material layer 2. It is preferable to have. Examples of such plasticizers include, but are not limited to, phosphate ester plasticizers, phthalate ester plasticizers, trimellitic acid ester plasticizers, pyromellitic acid plasticizers, polyhydric alcohol plasticizers. Glycolate plasticizers, citrate plasticizers, fatty acid ester plasticizers, carboxylic acid ester plasticizers, polyester plasticizers, and the like.

(First control layer 3)
The first control layer 3 is laminated on one surface side of the base material layer 2. As the main component of the first control layer 3, a hydrophilic resin is preferably used. The hydrophilic resin is not particularly limited as long as it is a resin having a chemical affinity with the base material layer 2 and the easy-adhesion layer 4, but a resin in which the side chain is modified with a hydrophilic group is preferable. As a method for hydrophilic modification of a hydrophilic resin, a monomer having a hydrophilic functional group may be (co) polymerized in advance, or a monomer that becomes a main chain is (co) polymerized and then hydrophilic. The side chain may be formed by graft polymerization of a monomer having a group. Moreover, it is preferable that this hydrophilic resin is formed from what is selected from the group which consists of a polyester-type resin, an acrylic resin, a urethane-type resin, and an epoxy resin. These resins may be a single polymer or a copolymer of two or more. As the hydrophilic resin, for example, a resin having a weight average molecular weight of 300 to 30,000 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 and polycondensing them according to a known method. Examples of the dicarboxylic acid include aromatic dicarboxylic acids or esters such as terephthalic acid, isophthalic acid, phthalic acid, and naphthalene dicarboxylic acid, and aliphatic dicarboxylic acids such as adipic acid, succinic acid, sebacic acid, and dodecanedioic acid. Hydroxycarboxylic acids such as hydroxybenzoic acid or their esters can be used. Examples of the diol include ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, cyclohexanedimethanol, bisphenols, and the like.

  As said polyester-type resin, in addition to the above-mentioned dicarboxylic acid and diol, it is preferable to copolymerize the component which has a hydrophilic group, and to provide hydrophilicity. Examples of the component having such a hydrophilic group include dicarboxylic acid components such as 5-sodium sulfoisophthalic acid, and diol components such as diethylene glycol, triethylene glycol, and polyethylene glycol. These components having a hydrophilic group can be used, for example, in a proportion of 2 mol% or more and 80 mol% or less with respect to the above-mentioned dicarboxylic acid or diol. The component which comprises these polyester-type resin can be used individually or in combination of multiple types.

  The acrylic resin contained as the 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 reactive polymers include those having a carboxyl group such as acrylic acid, methacrylic acid, carboxyethyl (meth) acrylate, carboxyphenyl acrylate, 2-hydroxyethyl (meth) acrylate, 3-hydroxybutyl (meta ), Acrylate, 2-hydroxypropyl (meth) acrylate, those having a hydroxyl group such as 3-hydroxypropyl (meth) acrylate, (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N, Those having an amide group such as N-dimethyl (meth) acrylamide, N-methylol (meth) acrylamide, those having a glycidyl group such as glycidyl (meth) acrylate, 7-amino-3,7-dimethyloctyl (meth) a In addition to those having an amino group such as relate and 2-dimethylaminoethyl (meth) acrylate, p-chlorostyrene, chloromethylstyrene, divinylbenzene, 4-vinylpyridine, vinyloxazoline, maleic anhydride, and the like can be given. .

  As copolymerization components other than the above constituting the acrylic resin, acrylic ester, methacrylic ester, propylene, vinyl chloride, cellulose, ethylene, ethyleneimine, vinyl alcohol, peptide, Examples include vinyl pyridine, diene, fluorine, and acrylonitrile. From the viewpoints of versatility and coating properties, it is preferable to include acrylic ester and methacrylic ester. The component which comprises these acrylic resins can be used individually or in combination of multiple types.

  The urethane resin contained as the main component of the first control layer 3 is synthesized from a polyhydroxyl compound, diisocyanate and a low molecular weight chain extender containing at least two hydrogen atoms that react with the diisocyanate by a known method. Can do. For example, after synthesizing a relatively high molecular weight polyurethane in a solvent, water is added little by little to phase inversion emulsification, and the solvent is removed by decompression, or polyethylene glycol or carboxyl group is introduced as a hydrophilic group in the polymer. There is a method in which the urethane prepolymer dissolved or dispersed in water is added and reacted with a chain extender.

  Examples of the polyhydroxyl compound used for the production of the urethane resin include carboxylic acids such as phthalic acid, adipic acid, dimerized linolenic acid and maleic acid; glycols such as ethylene glycol, propylene glycol, butylene glycol and diethylene glycol; Polyester polyols obtained by dehydration condensation reaction from trimethylolpropane, hexanetriol, glycerin, trimethylolethane, pentaerythritol, etc .; polyoxypropylene glycol, polyoxybutylene glycol, polytetramethylene glycol, polyoxypropylene triol, polyoxyethylene Initiators are inorganic acids such as polyoxypropylene triol, sorbitol, pentaerythritol, shrose, starch, and phosphoric acid. Polyoxypropylene polyols, polyether polyols such as polyoxypropylene polyoxyethylene polyol, acrylic polyol, a derivative of castor oil, tall oil derivatives, other hydroxyl compounds. These polyhydroxyl compounds can be used alone or in combination of two or more.

  Examples of the diisocyanate used in the production of the urethane resin include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, tetra Methylene diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, lysine 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'-dichloro-4,4 - biphenylene diisocyanate, 1,5-naphthalene diisocyanate, 1,5-tetrahydronaphthalene diisocyanate. These diisocyanates can be used singly or in combination.

  Examples of chain extenders used in the production of the urethane resin include ethylene glycol, 1,4-butanediol, trimethylolpropane, triisopropanolamine, N, N-bis (2-hydroxypropyl) aniline, hydroquinone- Polyols such as bis (β-hydroxyethyl) ether, resorcinol-bis (β-hydroxyethyl) ether, ethylenediamine, propylenediamine, hexamethylenediamine, phenylenediamine, tolylenediamine, diphenyldiamine, diaminodiphenylmethane, diaminodiphenylmethane, diamino Examples thereof include polyamines such as dicyclohexylmethane, piperazine, isophoronediamine, diethylenetriamine, and dipropylenetriamine, hydrazines, and water. These chain extenders can be used alone or in combination of two or more.

  The synthetic reaction in the production of the urethane-based resin can be performed in the presence of a catalyst such as an organic tin compound, organic bismuth, or amine, and among these, it is particularly preferable to perform in the presence of an organic tin compound. Specific examples of organic tin compounds include stannous acetate, stannous octoate, stannous laurate, stannous oleate and the like; dibutyltin acetate, dibutyltin dilaurate, dibutyltin maleate , Dialkyltin salts of carboxylic acids such as dibutyltin di-2-ethylhexoate, dilauryltin diacetate, dioctyltin diacetate; trialkyl hydroxides such as trimethyltin hydroxide, tributyltin hydroxide, trioctyltin hydroxide Tin: Dialkyltin oxide such as dibutyltin oxide, dioctyltin oxide and dilauryltin oxide; Dialkyltin chloride such as dibutyltin dichloride and dioctyltin dichloride, etc., and these may be used alone. More than one species may be used in combination.

  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. Furthermore, as a monomer copolymerizable with these monomers, vinyl ester, unsaturated carboxylic acid ester, unsaturated carboxylic acid amide, unsaturated nitrile, allyl compound, unsaturated hydrocarbon or vinyl silane compound is 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, malein Octyl acid, butyl fumarate, octyl fumarate, hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl methacrylate, hydroxypropyl acrylate, ethylene glycol dimethacrylate, ethylene glycol diacrylate, polyethylene glycol dimethacrylate Ester, polyethylene glycol diacrylate, acrylamide, methacrylamide, methylol acrylamide, butoxymethylol acrylamide, unsaturated nitrile Acrylonitrile, allyl acetate, allyl methacrylate, allyl acrylate, diallyl itaconate, ethylene, propylene, hexane, octene, styrene, vinyl toluene, butadiene, dimethylvinylmethoxysilane, dimethylethylethoxysilane, methylvinyldimethoxysilane, methyl Examples thereof include vinyldiethoxysilane, γ-methacryloxypropyltrimethoxysilane, and γ-methacryloxypropylmethyldimethoxysilane. The component which comprises these epoxy resins can be used individually or in combination of multiple types.

  In hydrophilic modification of a hydrophilic resin, when a hydrophilic side chain is formed by (co) polymerizing a monomer as a main chain and then graft polymerizing the hydrophilic monomer, a hydrophilic radical polymerizable vinyl monomer is used. Is preferably graft polymerized. In this case, the radical polymerizable vinyl monomer can be used in a proportion of 10 parts by mass or more and 500 parts by mass or less with respect to 100 parts by mass of the 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 a secondary or tertiary amino group), —O— (CH ₂ —CH (R) —O) _n — (wherein —R is —H or —CH ₃ , n is positive of an _{integer), - Y-N (R} 1) (R 2) (- Y- is -C (= O) - or -CH _{2 -,} -R 1, -R ₂ is -H or, A lower alkyl group which may have a hydroxyl group, a sulfonyl group, an acyl group, an amino group, an alkali 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 (O forming the sides of the carbon and epoxy ring) can be used having a hydrophilic group such as.

  Specific examples of the hydrophilic radical polymerizable vinyl monomer include hydroxyacrylic acid esters such as hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, and hydroxypropyl methacrylate, ethylene glycol acrylate, ethylene glycol methacrylate, and polyethylene. Glycol esters such as glycol acrylate, polyethylene glycol methacrylate, acrylamide compounds such as acrylamide, methacrylamide, methylol acrylamide, methoxymethylol acrylamide, glycidyl acrylate compounds such as glycidyl acrylate, glycidyl methacrylate, vinyl pyridine, vinyl imidazole, vinyl pyrrolidone Nitrogen-containing vinyl compounds such as acrylic acid, meta Acrylic acid, maleic anhydride, itaconic acid, unsaturated acids and salts thereof such as crotonic acid, amino alkyl acrylate, a cationic monomer such as amino alkyl methacrylate and quaternary ammonium salts.

  In the hydrophilic modification of the hydrophilic resin, in addition to these radical polymerizable vinyl monomers, other vinyl monomers may be copolymerized. 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; methyl acrylate, ethyl acrylate, butyl acrylate, methacrylic acid Unsaturated carboxylic acid esters such as methyl, ethyl methacrylate and butyl methacrylate; vinyl silanes such as dimethylvinylmethoxysilane and γ-methacryloxypropyltrimethoxysilane; olefins such as ethylene, propylene, styrene and butadiene, and diolefin compounds. Can be mentioned.

  When a polyester resin is used as the main component of the first control layer 3, the polyester resin may be a radical polymerizable vinyl monomer derived from acrylic acid having a hydrophilic group (hereinafter referred to as “acrylic radical polymerizable vinyl monomer”). It is most preferable to use a polyester-based resin whose side chain is modified by the following (hereinafter referred to as “acrylic-modified polyester-based resin”). By using an acrylic-modified polyester resin as the main component of the first control layer 3, the transparency, toughness, heat resistance inherent in the polyester resin, and synthetic resin (for example, acrylic as the main component of the base material layer 2) Adhesiveness to the easy-adhesion layer 4 can be imparted by the above-mentioned modifying group while making use of properties such as adhesiveness to the resin. The first control layer 3 is most preferably a composition containing a urethane resin together with the acrylic-modified polyester resin contained as a main component. By using a composition containing an acrylic-modified polyester resin and a urethane resin as the main component of the first control layer 3, the transparency, toughness, heat resistance, adhesion to synthetic resin, etc. inherent to the polyester resin While taking advantage of the above properties, it is possible to impart adhesion to the easy-adhesion layer 4 with the above-mentioned modifying group, and further impart adhesion and flexibility to the base material layer 2 and the easy-adhesion layer 4 with a blend of urethane resin. It becomes.

  The weight average molecular weights of the acrylic radical polymerizable vinyl monomer and the urethane resin are typically 1000 or more and 15000 or less, and preferably 2000 or more and 10,000 or less.

  The mass of the urethane 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 resin. By making the mass ratio of the acrylic-modified polyester resin and the urethane resin in such a range, the base material layer 2 while keeping the layer properties such as transparency, water resistance and heat resistance of the first control layer 3 well. And it becomes possible to optimize the adhesive force with respect to the easily bonding layer 4. FIG.

As the hydrophilic group possessed by the acrylic radical polymerizable vinyl monomer which is a modifying component of the acrylic modified polyester resin, those exemplified as the hydrophilic group of the hydrophilic radical polymerizable vinyl monomer can be used. That is, typical hydrophilic groups possessed by the acrylic radical polymerizable vinyl monomer include —CH ₂ —CH (R) —OH, —COOX, —O— (CH ₂ —CH (R) —O) _n —. ^{_{, -Y-N (R 1)}} (R 2), - N + - (R 3) (R 4) (R 5), - CH 2 -CH (O) CH 2 ( defined as above) include It is done.

  As the acrylic radical polymerizable vinyl monomer, the acrylic monomers mentioned as specific examples of the hydrophilic radical polymerizable vinyl monomer can be used. That is, specific examples of the acrylic radical polymerizable vinyl monomer include hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, 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, aminoalkyl methacrylate ester and the like. These acrylic radical polymerizable vinyl monomers may be used alone or in combination of two or more kinds.

  In addition to the acrylic radical-polymerizable vinyl monomer, the acrylic-modified polyester-based resin may be obtained by copolymerizing another copolymerizable vinyl monomer. When the other vinyl monomer is copolymerized, for example, 1 to 70 parts by mass of the other vinyl monomer can be used with respect to 100 parts by mass of the acrylic radical polymerizable vinyl monomer.

  In the acrylic modified polyester resin, the mass ratio of the acrylic radical polymerizable vinyl monomer to the polyester resin forming the main chain is preferably 50 parts by mass or more and 150 parts by mass or less with respect to 100 parts by mass of the polyester resin. More preferably, it is set to not less than 120 parts by mass. By setting the mass ratio of the acrylic radical polymerizable vinyl monomer to the polyester resin in such a range, the chemical affinity of the first control layer 3 to the base material layer 2 and the easy adhesion layer of the first control layer 3 It is possible to improve the chemical affinity for 4 in a well-balanced manner.

  The acrylic-modified polyester resin is, for example, an aqueous solution containing 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 and polyvinyl alcohol. Alternatively, it can be produced by making an aqueous dispersion and then copolymerizing an acrylic radical polymerizable vinyl monomer (and any other copolymerizable vinyl monomer).

  In the method for producing an acrylic-modified polyester resin using polyvinyl alcohol, for example, polyvinyl alcohol is used in a proportion (solid content ratio) of 10 parts by mass or more and 500 parts by mass or less with respect to 100 parts by mass of water-soluble or water-dispersible polyester. The reaction can be performed.

  As a polymerization method for synthesizing the acrylic-modified polyester-based resin, for example, in a water-soluble or water-dispersed solution of the water-soluble or water-dispersible polyester and polyvinyl alcohol, a polymerization initiator and a small amount as required. A method of completing the polymerization reaction by adding an emulsifying dispersant, gradually adding the acrylic radical polymerizable vinyl monomer while stirring at a temperature of about 70 ° C., and aging for several hours.

  A general radical polymerization initiator can be used as the polymerization initiator used in the production of the acrylic-modified polyester resin. Examples of polymerization initiators include water-soluble peroxides such as potassium persulfate, ammonium persulfate, and hydrogen peroxide, oil-soluble peroxides such as benzoyl peroxide and t-butyl hydroperoxide, and azodiisobutyronitrile. An azo compound is mentioned.

  Although it does not specifically limit as thickness (average thickness) of the 1st control layer 3, It is preferable that they are 0.01 micrometer or more and 5 micrometers or less. The upper limit value of the thickness of the first control layer 3 is more preferably 4 μm, and further preferably 3 μm. On the other hand, the lower limit value of the thickness of the first control layer 3 is more preferably 0.04 μm, and further preferably 1 μm. When the thickness of the 1st control layer 3 exceeds the said upper limit, the thickness of the polarizer protective film 1 will become thick and there exists a possibility of contradicting the request | requirement of thickness reduction of a liquid crystal display device. On the other hand, when the thickness of the first control layer 3 is less than the lower limit, it may be difficult to form the first control layer 3.

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 · 24h, and further preferably 80 g / m ² · 24h. On the other hand, the lower limit of the moisture permeability of the first control layer 3 is more preferably ^{10g / m 2 · 24h, 20g} / m 2 · 24h is more preferred. When the moisture permeability of the first control layer 3 exceeds the above upper limit value, the ratio of moisture penetrating from the outside increases, and the possibility of causing a dimensional change of the base material layer 2 and the like increases. On the other hand, when the moisture permeability of the first control layer 3 is less than the lower limit value, the water contained in the water-soluble adhesive is evaporated when the easy-adhesive layer 4 and the polarizer are bonded with the water-soluble adhesive. May take a long time to complete. On the other hand, when the moisture permeability of the first control layer 3 is within the above range, the moisture contained in the water-soluble adhesive is suitably evaporated to promote the drying of the easy-adhesive layer 4, and the easy-adhesive layer 4 and While being able to improve adhesiveness with a polarizer, the dimensional stability of the said polarizer protective film 1 can be improved.

  The first control layer 3 can be formed by applying a water-based emulsion or an aqueous solution (hereinafter referred to as “water-based emulsion or the like”) containing a hydrophilic resin to the base material layer 2 and drying it. The solid content of the aqueous emulsion or the like is usually 10% by mass or more and 50% by mass or less. Water is used as the main solvent for the aqueous emulsion and the like, but a small amount of an organic solvent miscible with water may be used. Examples of such organic solvents include lower alcohols, polyhydric alcohols and alkyl ethers or alkyl esters thereof. Water-based emulsions, etc. are formed by using known dip coating methods, air knife coating methods, curtain coating methods, roller coating methods, wire bar coating methods, gravure coating methods, extrusion coating methods (die coating methods), etc. 2 can be applied. Next, 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 or the like for forming the first control layer 3 as necessary. 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, and more preferably 0.5% by mass or more and 15% by mass or less with respect to the total amount of the hydrophilic resin. For the water-based emulsion for forming the first control layer 3, other resin components such as an amino group-containing resin, a surfactant, a slip agent, a dye, a UV absorber, a matting agent, as necessary. , Preservatives, thickeners, film-forming aids, antistatic agents, antioxidants, and the like may be added.

(Easily adhesive layer 4)
The easy adhesion layer 4 is laminated on one surface side of the first control layer 3. The main component of the easy-adhesion layer 4 is not particularly limited as long as it is a hydrophilic resin contained as the main component of the first control layer 3 and a resin having chemical affinity with polyvinyl alcohol constituting the polarizer. However, a cellulose ester resin is preferably used. When the easy-adhesion layer 4 has a cellulose ester resin as a main component, the adhesion between the polarizer made of polyvinyl alcohol, which is a hydrophilic resin, and the easy-adhesion layer 4 is dramatically improved. That is, a hydroxyl group that is a hydrophilic group is produced by saponifying the easy-adhesion layer 4 containing a cellulose ester-based resin as a main component with an alkali, thereby effectively improving the adhesiveness with polyvinyl alcohol that is a hydrophilic resin. To do. Therefore, the said polarizer protective film 1 can adhere | attach the easily bonding layer 4 and a polarizer easily and reliably using a water-soluble adhesive agent.

  The cellulose ester resin contained as a main component in the easy-adhesion layer 4 is not particularly limited as long as it is saponified with alkali to generate a hydroxyl group, but triacetyl cellulose, diacetyl cellulose, cellulose acetate propionate, and cellulose acetate. It is preferably selected from the group consisting of butyrate. These cellulose esters generate a hydroxyl group which is a hydrophilic group by saponification with an alkali, thereby increasing the affinity with a polarizer made of polyvinyl alcohol which is a hydrophilic resin, and can be reliably bonded. .

  Although it does not specifically limit as a number average molecular weight (Mn) of the cellulose-ester-type resin contained in the easily bonding layer 4 as a main component, It is preferable that it is 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 90000, and more preferably 80000. On the other hand, the lower limit of the number average molecular weight (Mn) of the cellulose ester resin is more preferably 50000, and further preferably 60000. When the said number average molecular weight (Mn) exceeds the said upper limit, there exists a possibility that the coating property of the easily bonding layer 4 may fall. On the other hand, when the number average molecular weight (Mn) is less than the lower limit, the cellulose ester resin may be whitened and the transparency may be lowered when the easy-adhesion layer 4 is saponified with alkali.

  The ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) (Mw / Mn) of the cellulose ester resin contained as the main component in the easy adhesion layer 4 is not particularly limited, but is 1.4 or more and 3 The following is preferable. 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 further 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 and even more preferably 1.8. 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 easy adhesion layer 4 may be lowered. On the contrary, when the ratio (Mw / Mn) of the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the cellulose ester resin is less than the lower limit, it may be difficult to produce a desired cellulose ester.

  Although it does not specifically limit as thickness (average thickness) of the easily bonding layer 4, It is preferable that they are 0.01 micrometer or more and 5 micrometers or less. The upper limit value of the thickness of the easy-adhesion layer 4 is more preferably 4 μm, and further preferably 3 μm. On the other hand, the lower limit of the thickness of the easy-adhesion layer 4 is more preferably 0.04 μm, and even more preferably 1 μm. When the thickness of the easily bonding layer 4 exceeds the said upper limit, the thickness of the polarizer protective film 1 becomes thick, and there exists a possibility that it may contradict the request | requirement of thickness reduction of a liquid crystal display device. Moreover, when the thickness of the easily bonding layer 4 exceeds the said upper limit, there exists a possibility that the moisture permeability of the easily bonding layer 4 may fall. On the contrary, when the thickness of the easy-adhesion layer 4 is less than the said lower limit, there exists a possibility that the adhesiveness of the easy-adhesion layer 4 and the 1st resin layer 3 may fall. On the other hand, when the thickness of the easy-adhesion layer 4 is within the above range, the thickness of the polarizer protective film 1 can be kept thin, and the cellulose ester constituting the easy-adhesion layer 4 is saponified. The bonding between the hydroxyl group and the polyvinyl alcohol constituting the polarizer becomes more reliable.

  The solvent of the cellulose ester coating solution for forming the easy-adhesion layer 4 is not particularly limited as long as it is an organic solvent that sufficiently dissolves the cellulose ester. For example, dioxane, acetone, methyl ethyl ketone, N, N-dimethylformamide, acetic acid Methyl, ethyl acetate, trichloroethylene, methylene chloride, ethylene chloride, tetrachloroethane, trichloroethane, chloroform and the like are used. Moreover, you may add a ultraviolet absorber, a slip agent, a mat agent, an antistatic agent, a crosslinking agent, an activator, etc. to the cellulose-ester coating liquid for forming the easily bonding layer 4, if desired. In particular, a crosslinking agent is preferable for promoting adhesion with polyvinyl alcohol constituting the polarizer. Examples of such crosslinking agents include polyvalent epoxy compounds, aziridine compounds, isocyanate compounds, light vanes, boron compounds and the like.

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

(Second control layer 5)
The second control layer 5 is laminated on the other surface side of the base material layer 2. The second control layer 5 contains the same resin as the main component of 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 that of the first control layer 3, but is preferably the same forming material as the main component of the first control layer 3. When the forming material of the main component of the second control layer 5 is the same as the forming material of the main component of the first control layer 3, the moisture permeability of the second control layer 5 and the first control layer 3 can be made closer, The moisture permeability of the entire polarizer protective film 1 can be controlled more reliably. Moreover, when the formation material of the main component of the 2nd control layer 5 is the same as the formation material of the main component of the 1st control layer 3, the manufacture ease of the said 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 μm and even more preferably 3 μm. On the other hand, the lower limit value of the thickness of the second control layer 5 is more preferably 0.04 μm, and even more preferably 1 μm. When the thickness of the 2nd control layer 5 exceeds the said upper limit, the thickness of the polarizer protective film 1 will become thick and there exists a possibility of contradicting the request | requirement of thickness reduction of a liquid crystal display device. On the other hand, when the thickness of the second control layer 5 is less than the lower limit, it may be difficult to form the second control layer 5.

  Furthermore, although it does not specifically limit as total thickness (average thickness) of the 1st control layer 3 and the 2nd control layer 5, It is preferable that they are 1.0 micrometer or more and 10 micrometers or less. The upper limit of the total thickness of the first control layer 3 and the second control layer 5 is more preferably 8 μm, and even more preferably 6 μm. On the other hand, the lower limit of the total thickness of the first control layer 3 and the second control layer 5 is more preferably 2 μm and even more preferably 3 μm. When the total thickness of the first control layer 3 and the second control layer 5 exceeds the above upper limit, the thickness of the polarizer protective film 1 is increased, which is against the demand for thinning of the liquid crystal display device and the moisture permeability is reduced. Thus, it may take a long time to evaporate the 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, it may be difficult to form the first control layer 3 and the second control layer 5.

  The thickness of the second control layer 5 is preferably substantially the same as the thickness of the first control layer 3. In the polarizer protective film 1, the thickness of the second control layer 5 is substantially the same as the thickness of the first control layer 3, so that the first control layer 3 and the second control layer 5 are formed on the base material layer 2. The occurrence of curling in the laminated state can be prevented, and as a result, the manufacturability of 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 · 24h, and further preferably 80 g / m ² · 24h. On the other hand, the lower limit of the moisture permeability of the second control layer 5 is more preferably ^{10g / m 2 · 24h, 20g} / m 2 · 24h is more preferred. When the moisture permeability of the second control layer 5 exceeds the above upper limit value, the penetration rate of moisture existing outside becomes high and the possibility of causing a dimensional change of the base material layer 2 and the like increases. On the other hand, when the moisture permeability of the second control layer 5 is less than the lower limit, when the easy-adhesion layer 4 and the polarizer are bonded with a water-soluble adhesive, the water content contained in the water-soluble adhesive, etc. There is a possibility that it takes a long time to evaporate the water contained in the polarizer protective film 1.

  The second control layer 5 can be formed on the other surface side of the base material layer 2 by the same method as 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 value 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 of the moisture permeability of the polarizer protective film 1 is more preferably ^{10g / m 2 · 24h, 20g} / m 2 · 24h is more preferred. When the moisture permeability of the polarizer protective film 1 exceeds the above upper limit value, the ratio of moisture penetrating from the outside increases and the risk of causing a dimensional change of the base material layer 2 and the like increases. On the contrary, when the moisture permeability of the polarizer protective film 1 is less than the above lower limit value, the moisture contained in the water-soluble adhesive when the easy-adhesive layer 4 and the polarizer are bonded with the water-soluble adhesive. It may take a long time to evaporate.

  Since the easy-adhesion layer 4 is arranged on one surface side of the polarizer protective film 1, the easy-adhesion layer 4 and the polarizer can be reliably bonded with a water-soluble adhesive. Moreover, the said polarizer protective film 1 is formed by the 1st control layer 3 and the 2nd control layer 5 which were distribute | arranged on both surfaces of the base material layer 2 being controlled by the desired moisture permeability, Therefore For the said water-soluble When adhering with the adhesive, the water content of the water-soluble adhesive can be accurately evaporated, and the above-described adhesion process can be performed easily and reliably. Furthermore, since the main component of the base material layer 2 of the polarizer protective film 1 is an acrylic resin, the dimensional change of the base material layer 2 under high humidity is less than that of triacetyl cellulose, and a photoelastic effect is produced. hard. For this reason, the said polarizer protective film 1 has a small change of a retardation value. In particular, the polarizer protective film 1 is formed with the second control layer 5 disposed on the other surface side of the base material layer 2 and controlled to have a desired moisture permeability. The change is further suppressed, the dimensional change of the base material layer 2 can be made smaller, and the change in the retardation value is small.

<Polarizing plate 11>
The polarizing plate 11 in FIG. 2 includes the polarizer protective film 1 in FIG. 1 on one surface of a polarizer 12 made of polyvinyl alcohol, and is made of a conventionally used cellulose ester on the other surface of the polarizer 12. It has the structure provided with the polarizer protective film 13 which becomes. The polarizer 12 and the polarizer protective film 1 and the polarizer 12 and the polarizer protective film 13 are bonded by an adhesive (not shown).

  As the polarizer 12, a polyvinyl alcohol resin film that is dyed with a dichroic substance (for example, iodine or a dichroic dye) and uniaxially stretched is used. The polymerization degree of polyvinyl alcohol constituting this polyvinyl alcohol resin film is preferably 500 or more, and more preferably 1000 or more. The polyvinyl alcohol resin film can be formed by a known method (for example, a casting method or casting method in which a solution obtained by dissolving a resin in water or an organic solvent is cast into a film). The thickness (average thickness) of the polarizer 12 varies depending on the purpose and application of the liquid crystal display device in which the polarizing plate 11 is used, but is typically 5 μm or more and 100 μm or less. The polarizer 12 may contain an optional component other than the polyvinyl alcohol resin and the dichroic material as long as the polarizing function and the optical transparency are not impaired.

  As a typical manufacturing method of the polarizer 12, a series of manufacturing steps including swelling, dyeing, crosslinking, stretching, washing with water, and drying steps are employed for the polyvinyl alcohol resin film. In each processing step except the drying step, the treatment is performed by immersing the polyvinyl alcohol resin film in a solution bath used in each step. The order, number of times, and the presence / absence of each treatment of swelling, dyeing, crosslinking, stretching, washing and drying can be appropriately set according to the purpose, materials used, conditions and the like. For example, the stretching process may be performed before the dyeing process or may be performed simultaneously with the swelling process. Moreover, it is preferable to perform 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 can be appropriately added to the treatment bath. Typically, the temperature of the treatment bath in the swelling process is about 20 to 60 ° C., and the immersion time in the treatment bath is about 0.1 to 10 minutes. The dyeing step can be performed by immersing the polyvinyl alcohol resin film in a treatment bath containing a dichroic substance such as iodine. As a solvent used for the solution of the treatment bath, water is generally used. The dichroic substance is used at a ratio of 0.1 to 1.0 part by mass with respect to 100 parts by mass of the solvent. Typically, the temperature of the treatment bath in the dyeing process is about 20 to 70 ° C., and the immersion time is about 1 to 20 minutes.

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

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

  The polarizer protective film 13 is a stainless steel that is continuously rotated from a melt extruder by dissolving a cellulose ester flake raw material and a plasticizer in methylene chloride to form a viscous liquid, and dissolving the plasticizer in this solution. It is cast on a metal belt such as the like, dried, peeled off from the belt in a freshly dried state, then dried and wound up to be manufactured. As the cellulose ester, those selected from the group consisting of triacetyl cellulose, diacetyl cellulose, cellulose acetate propionate and cellulose acetate butyrate are preferable, and triacetyl cellulose is particularly preferable.

  Before the polarizer protective film 1 is bonded to the polarizer 12, it is preferable that the easy-adhesion layer 4 is saponified with alkali. By this saponification, the ester group of the cellulose ester is converted to a hydroxyl group which is a hydrophilic group, and thereby, the chemicals of the polarizer protective film 1 and the polarizer 12 formed of polyvinyl alcohol which is a hydrophilic resin are chemically changed. Affinity is increased, and the mutual adhesiveness is remarkably improved.

  As the alkaline 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 5% by mass or more and 40% by mass or less. Moreover, it is preferable that the temperature of a saponification process is 10 degreeC or more and 80 degrees C or less. When the concentration of the metal hydroxide is 5% by mass or less or when the temperature of the saponification treatment is 10 ° C. or less, the time required for the saponification treatment becomes long, which is not preferable. The saponification treatment is performed by immersing the polarizer protective film 1 in an alkaline aqueous solution bath as described above for an appropriate time.

  The polarizer protective film 1 subjected to the saponification treatment and the polarizer 12 made of polyvinyl alcohol are bonded by an apparatus 21 schematically shown in FIG. The apparatus 21 for bonding a plurality of films shown in FIG. 3 includes a nip 22 for supplying a polarizer 12, a nip 23 for supplying a polarizer protective film 1, and means for supplying an adhesive. 24, and a nip 25 for pressing and joining the polarizer 12 and the polarizer protective film 1 with an adhesive.

  Examples of the adhesive used for bonding the easy-adhesion layer 4 of the polarizer protective film 1 and the polarizer 12 by the device 21 include polyvinyl alcohol adhesives such as polyvinyl alcohol and polyvinyl butyral, and vinyl such as butyl acrylate. System latex and the like. Usually, these adhesives are used as an aqueous solution. The solid content concentration in the resin solution of the adhesive is preferably from 0.1 to 15% by mass in consideration of coating property and storage stability. Moreover, as a viscosity of the resin solution of an adhesive agent, the range of 1-50 mPa * s is preferable, for example.

  In the apparatus 21, the film-like polarizer 12 supplied from the nip 22 and the saponified polarizer protective film 1 supplied from the nip 23 are sent in a direction toward the nip 25 and sandwiched between these films. Then, the polarizer 12 and the easy-adhesion layer 4 of the polarizer protective film 1 are bonded to each other by pressing at the nip 25 so that the polarizer 12 is attached to one surface of the polarizer 12. A structure in which the protective film 1 is laminated is obtained. Subsequently, the polarizing plate 11 is obtained by laminating | stacking the polarizer protective film 13 also on the surface of the polarizer 12 in which the polarizer protective film 1 is not laminated | stacked using the same means.

  In the polarizing plate 11, the easy-adhesion layer 4 of the polarizer protective film 1 and the polarizer 12 are securely bonded with a water-soluble adhesive. Moreover, since 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, the water of the water-soluble adhesive is removed during the bonding with the water-soluble adhesive. It can evaporate exactly and can perform the said adhesion process easily and reliably. As a result, the polarizing plate 11 can reliably adhere the polarizer protective film 1 and the polarizer. Furthermore, since the main component of the base material layer 2 of the polarizer protective film 1 is an acrylic resin, the dimensional change of the base material layer 2 under high humidity is less than that of triacetyl cellulose, and a photoelastic effect is hardly generated. . For this reason, the polarizer protective film 1 has a small change in retardation value. In particular, the polarizer protective film 1 has the second control layer 5 disposed on the other surface side of the base material layer 2 and is formed so as to be controlled to have a desired moisture permeability. Can be further suppressed, and the dimensional change of the base material layer 2 can be further reduced. Therefore, the said polarizing plate 11 can make small the change of the retardation value of the polarizer protective film 1, and can exhibit a desired optical characteristic.

<Liquid crystal display element 31>
The liquid crystal display element 31 of FIG. 4 has the liquid crystal layer 34 sandwiched between transparent medium layers 33 (for example, glass) on both sides of the liquid crystal cell 32 via the adhesive layer 35 and the polarizing plate 11 of FIG. It is comprised by sticking together. The polarizer protective film 1 (base material layer 2, first control layer 3, easy-adhesion layer 4 and second control layer 5) according to the present invention is provided on the outer surface side of the polarizer 12 (on the opposite side of the arrangement direction of the liquid crystal cell 32). ) And a polarizer protective film 13 made of cellulose ester, which has been conventionally used, is arranged on the inner surface side of the polarizer 12 (the arrangement direction side of the liquid crystal cell 32). The materials constituting the liquid crystal layer 34, the transparent medium layer 33, and the adhesive layer 35 of the liquid crystal cell 32 are not particularly limited, and known materials can be used.

  In the liquid crystal display element 31, the easy-adhesion layer 4 of the polarizer protective film 1 and the polarizer 12 are securely bonded with a water-soluble adhesive. Further, since 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, the water content of the water-soluble adhesive can be accurately adjusted during the bonding with the water-soluble adhesive. Thus, the bonding process can be performed easily and accurately. As a result, the liquid crystal display element 31 can reliably adhere the polarizer protective film 1 and the polarizer 12. Furthermore, since the main component of the base material layer 2 of the polarizer protective film 1 is an acrylic resin, the dimensional change of the base material layer 2 under high humidity is less than that of triacetyl cellulose, and a photoelastic effect is hardly generated. For this reason, the polarizer protective film 1 has a small change in retardation value. In particular, the polarizer protective film 1 has the second control layer 5 disposed on the other surface side of the base material layer 2 and is formed so as to be controlled to have a desired moisture permeability. Can be further suppressed, and the dimensional change of the base material layer 2 can be further reduced. Therefore, the liquid crystal display element 31 can reduce a 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 perform accurate display by effectively using the light of the light source.

[Other Embodiments]
In addition, the polarizer protective film, polarizing plate, and liquid crystal display element of this invention can be implemented in the aspect which gave various change and improvement other than the said aspect. For example, the second control layer of the polarizer protective film may be formed to be substantially thicker than the first control layer. Thus, the said polarizer protective film provides the curl prevention function with respect to the force which tries to curl by making an easily bonding layer side into an inner side by making a 2nd control layer substantially thicker than a 1st control layer. The curling of the polarizer protective film as a whole can be prevented. As a result, the polarizer protective film can improve dimensional stability.

  The polarizer protective film may be disposed on both surfaces (inner surface side and outer surface side) of the polarizer. Thereby, the dimensional stability of the polarizer protective film arrange | positioned by the inner surface side and outer surface side of a polarizer can be improved. The polarizer protective film may be disposed on the inner surface side of the polarizer, and another polarizer protective film may be disposed on the outer surface side of the polarizer.

  In addition, another layer (antiglare layer, antireflection layer, antiglare layer, low refractive index layer, etc.) is provided on the other side of the second control layer (the side on which the base material layer is not laminated). Layer, antistatic layer, hard coat layer (cured resin layer), optical compensation layer, etc.) may be provided. For example, by providing an antiglare layer (antireflection layer) on the other surface side of the second control layer, an antiglare function can be exhibited in addition to the protective function for the polarizer. Moreover, the protective function with respect to a polarizer can be strengthened by providing the hard-coat layer in the other surface side of a 2nd control layer.

  The polarizing plate need only be laminated on either side of the liquid crystal cell, and need not necessarily 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 are dimensional changes in the base material layer of the polarizer protective film due to humidity. It is possible to easily and reliably bond the polarizer protective film and the polarizer with a water-soluble adhesive while suppressing the change in the retardation value of the polarizer protective film by reducing It can be used in various fields ranging from small products to large products such as automobile meters, PC monitors, and televisions.

DESCRIPTION OF SYMBOLS 1 Polarizer protective film 2 Base material layer 3 1st control layer 4 Easy adhesion layer 5 2nd control layer 11 Polarizing plate 12 Polarizer 13 Polarizer protective film which consists of cellulose ester 21 Apparatus for manufacturing 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 Polarizing plate 46 Polarizer protective film 47 Polarized light Child 48 Adhesive layer

Claims (12)

A polarizer protective film adhered to a polarizer of a liquid crystal display panel,
A base material layer mainly composed of an acrylic resin;
A first control layer for controlling moisture permeability, laminated on one surface side of the base material layer,
An easy adhesion layer laminated on one side of the first control layer;
A second control layer for controlling moisture permeability, laminated on the other surface side of the base material layer,
A polarizer protective film, wherein the first control layer and the second control layer contain the same resin as a main component.   The polarizer protective film according to claim 1, wherein the first control layer has substantially the same thickness as the second control layer.   The polarizer protective film according to 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 to 5 × 10 ⁻¹² / Pa.   The polarizer protective film according to any one of claims 1 to 4, wherein the easy-adhesion layer contains 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 any one of claims 1 to 6, wherein the first control layer and the second control layer include an acrylic-modified polyester resin as a main component.   The polarizer protective film according to claim 7, wherein the first control layer and the second control layer further contain a urethane resin. The polarizer protective film according to any one of claims 1 to 8, wherein the moisture permeability is 1 g / m ² · 24h or more and 250 g / m ² · 24 h or less.   The retardation protective film (Re) of the said base material layer is -15 nm or more and 15 nm or less, The polarizer protective film of any one of Claims 1-9. The polarizer protective film according to any one of claims 1 to 10,
A polarizing plate comprising: a polarizer adhered to the easy-adhesion layer of the polarizer protective film with a water-soluble adhesive. A liquid crystal cell;
A liquid crystal display device comprising: the polarizing plate according to claim 11 laminated on one surface side of the liquid crystal cell.

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