TW201333556A - Polarization plate protection film, polarization plate, and liquid crystal displaying element - Google Patents

Abstract

An object of the present invention is to provide a polarization plate protection film, a polarization plate, and a liquid crystal displaying element, in which dimensional variations caused by humidity is reduced so as to suppress variation of delay value, and enable the polarization plate can be easily and reliably to be bonded with water-soluble bonding agent. The polarization plate and the liquid crystal displaying element use the polarization plate protection film. The polarization plate protection film according to the present invention is bonded to a polarization plate of a liquid crystal display panel and consists of: a substrate layer, which comprises a primary constituent of acrylic resin; a first control layer, which is stacked on a surface of the substrate layer for controlling moisture permeability; an easy bonding layer, which is stacked on a surface of the first control layer; a second control layer, which is stacked on an opposite surface of the substrate layer for controlling moisture permeability, wherein the first control layer and the second control layer have primary constituents containing the same resin.

Description

Polarizer protective film, polarizing plate and liquid crystal display element

The present invention relates to a polarizing plate protective film, a polarizing plate including the polarizing plate protective film, and a liquid crystal display element including the polarizing plate, and particularly relates to a change in dimensional change due to humidity, thereby suppressing variation in retardation value, A polarizing plate protective film which can be easily and reliably bonded to a polarizing plate by a water-soluble binder, a polarizing plate using the polarizing plate protective film, and a liquid crystal display element using the polarizing plate.

The liquid crystal display device (LCD) is characterized by being thin, light, and low in power consumption, and the liquid crystal display device is often used as a flat panel display, and is used as a display device for information such as a mobile phone, a personal digital assistant (PDA), a personal computer, or a television. Its use is expanding year by year.

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 which is formed by sandwiching a liquid crystal layer 44 with two transparent dielectric layers 43 (for example, glass); and a polarizing plate 45; Adhesive layer 48 is bonded to both faces of the liquid crystal cell 42. The polarizing plate 45 is constituted by bonding the polarizing plate protective film 46 to both surfaces of the polarizing plate 47 having polarization properties. Thus, the polarizing plate 47 is protected by the polarizer protective film 46 from the viewpoint of improving strength and ease of use.

As a raw material of the polarizing plate, a PVA film made of polyvinyl alcohol as a hydrophilic resin is generally used. After the PVA film is uniaxially stretched, it is dyed with iodine or a dichroic dye, or after dyeing, and then crosslinked with an iodine compound, thereby forming a polarizing plate.

The polarizer protective film is required to have the following characteristics: it is optically transparent; the retardation value is small, the surface is smooth; the adhesion to the polarizing plate composed of PVA is excellent; and so on, so it is generally used to have cellulose triacetate (TAC). A polarizer protective film of the prepared substrate layer. Saponification of cellulose triacetate with hydrazine (replacement of ester groups into After the hydroxyl group of the hydrophilic group), the saponified polarizer protective film is bonded to a polarizing plate made of polyvinyl alcohol as a hydrophilic resin using a water-soluble binder. However, since the price of cellulose triacetate is high, it is required to develop a low-priced alternative material of the same nature.

In view of the above, the present applicant has proposed a polarizing plate protective film having a base material layer made of an acrylic resin or the like (refer to Japanese Laid-Open Patent Publication No. 2010-181500). The polarizer protective film described in Japanese Laid-Open Patent Publication No. 2010-181500 has a base layer provided on one surface of a base material layer, and a hydrophilic resin layer is provided on one surface of the base layer, thereby improving water solubility in use. The adhesion of the polarizer protective film to the polarizer in the case of a binder. Further, the polarizer protective film described in the above publication is conceived mainly on the side of the outer 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 preferable that the retardation value of the polarizer protective film provided on the surface side inside the liquid crystal display element is lower than the retardation value of the polarizer protective film provided on the surface side outside the liquid crystal display element. That is, if the retardation value of the polarizer protective film is high, the light that has become linearly polarized by the polarizing plate becomes elliptically polarized by the polarizer protective film, is incident on the liquid crystal layer, or is linearly polarized by the polarizing plate after passing through the liquid crystal layer. The film becomes elliptically polarized, and there is a problem that the light cannot be fully utilized for display. Therefore, as described above, it is desirable that the retardation value of the polarizer protective film provided on the surface side inside the liquid crystal display element is low.

However, the conventional base material layer made of cellulose triacetate tends to cause dimensional change in a high-humidity environment due to strong moisture permeability and water absorption, and thus causes other layers integrated with the base material layer ( The size of the adhesive layer or the like also varies depending on the size of the substrate layer, and the photoelastic effect (change in retardation due to deformation) occurs due to dimensional changes of the other layer and the substrate layer, and the result is The problem that the light of the light source cannot be fully utilized for display.

In order to solve the above problem, as described in the above-mentioned publication, it is conceivable to adopt a method of using an acrylic resin, a cycloolefin resin or the like as a substrate layer. Low water absorption and photoelastic coefficient to suppress changes in retardation values. However, in the case of adopting such a method, if the water absorption of the polarizer protective film is excessively lowered, the moisture permeability is also too small, and the polarizer protective film is bonded to the polarizing plate with a water-soluble binder. In this case, there is a problem that the moisture contained in the water-soluble binder cannot be reliably evaporated. Further, even if only the photoelastic coefficient of the base material layer is lowered, if the moisture permeability is too high, the water absorbability is also high, and there is a problem that the dimensional change due to humidity causes the photoelastic effect to occur.

Prior art literature

Patent Document 1: Japanese Patent Laid-Open Publication No. 2010-181500

In view of the problems described above, an object of the present invention is to provide a polarizer protective film which can reduce a dimensional change due to humidity, can suppress a change in retardation value, and can be easily and reliably bonded to a polarizing plate by a water-soluble adhesive. A polarizing plate using the polarizing plate protective film and a liquid crystal display element using the polarizing plate.

In order to solve the problem, the present invention provides a polarizer protective film for bonding to a polarizing plate of a liquid crystal display panel, the polarizer protective film comprising: a substrate layer, which is mainly composed of an acrylic resin; a control layer laminated on one surface side of the base material layer for controlling moisture permeability; an easy-adhesion layer laminated on one surface side of the first control layer; and a second control layer laminated on the base layer The other side of the material layer is for controlling moisture permeability, and the first control layer and the second control layer contain the same resin as a main component.

Since the polarizer protective film is provided with an easy-adhesion layer on one surface side, the easy-adhesion layer and the polarizing plate can be reliably bonded by a water-soluble adhesive. Further, the moisture permeability of the polarizer protective film is controlled to a desired moisture permeability by the first control layer and the second control layer disposed on both faces of the substrate layer, and thus is dissolved by the water. When the adhesive is bonded, the moisture of the water-soluble binder can be reliably evaporated, and the bonding process can be easily and reliably performed. Further, since the main component of the substrate layer of the polarizer protective film is an acrylic resin, it is combined with triacetate. In the case of the element, the dimensional change of the substrate layer under high humidity is small, so that the photoelastic effect is less likely to occur. Therefore, the change in the retardation value of the polarizer protective film is small. In particular, since the second control layer is provided on the other surface side of the base material layer, the moisture permeability of the polarizer protective film can be controlled to a desired moisture permeability, so that the change in the size of the base material layer can be further suppressed. The dimensional change of the substrate layer can be further reduced, and the change in the retardation value can be made small.

Preferably, in the polarizer protective film, the thickness of the first control layer is substantially the same as the thickness of the second control layer. Thereby, it is possible to prevent curling at the time of manufacture or the like.

Preferably, in the polarizer protective film, the second control layer is substantially thicker than the first control layer. Thereby, the polarizing plate protective film can be prevented from being curled against the force to curl the inner side of the easy-adhesion layer, and the entire polarizing plate protective film can be prevented from being curled. As a result, the polarizer protective film can improve dimensional stability.

Preferably, in the polarizer protective film, the acrylic resin has a photoelastic coefficient of -5 × 10 -12 / Pa or more and 5 × 10 -12 / Pa or less. By setting the photoelastic coefficient of the acrylic resin of the polarizer protective film within the above range, even in the case where the polarizer protective film is changed in size, the basis due to the dimensional change can be reduced. The change in the retardation value of the layer.

Preferably, in the polarizer protective film, the easy-adhesion layer contains a cellulose ester-based resin as a main component. Thereby, the adhesion of the polarizing plate made of polyvinyl alcohol and the easy-adhesive layer through the water-soluble binder can be remarkably improved. In other words, by saponifying an easy-adhesion layer containing a cellulose ester-based resin as a main component with a base to form a hydroxyl group as a hydrophilic group, the cellulose-based resin can be easily and reliably bonded by a water-soluble binder and hydrophilic. Resin polyvinyl alcohol.

In the polarizer protective film, the cellulose ester-based resin contained as a main component of the easy-adhesion layer preferably has a number average molecular weight (Mn) of 40,000 or more and 100,000 or less. Thereby, the coating property of the easy-adhesion layer can be improved, and the alkali is easy to use. When the adhesive layer is saponified, the transparency of the cellulose ester-based resin to be whitened can be prevented from being lowered.

Preferably, in the polarizer protective film, the first control layer and the second control layer contain, as a main component, an acrylic modified polyester resin. In this way, it is possible to impart properties such as transparency, toughness, heat resistance, and adhesion to an acrylic resin which is a main component of the base layer, and to impart an easy adhesion layer by acrylic acid modification. Adhesion.

Preferably, in the polarizer protective film, the first control layer and the second control layer contain the acrylic modified polyester resin and a urethane resin. In this way, it is possible to impart properties such as transparency, toughness, heat resistance, and adhesion to an acrylic resin which is a main component of the base layer, and to impart an easy adhesion layer by acrylic acid modification. The adhesion and the adhesion to the base layer and the easy-adhesion layer can be further imparted by mixing the urethane-based resin.

Preferably, in the polarizer protective film, the moisture permeability is 1 g/m ² ‧24 h or more and 250 g/m ² ‧24 h or less. Thereby, when bonding with a water-soluble binder, the water of the water-soluble binder can be more reliably evaporated, and the easy-adhesion layer and the polarizing plate can be bonded more easily and reliably. Further, the polarizer protective film can further suppress the dimensional change of the substrate layer well, so that the variation of the retardation value of the substrate layer can be further reduced.

Preferably, in the polarizer protective film, the substrate layer has a retardation value (Re) of -15 nm or more and 15 nm or less. Thereby, the high dimensional stability of the polarizer protective film is complemented, the conversion effect of the transmitted light can be suppressed, and the polarizing plate protective film can be prevented from polarizing the polarizing plate toward the transmission axis of the polarizing plate. The impact of optimization and control.

In addition, in order to solve the above problems, the present invention also provides a polarizing plate comprising: the polarizing plate protective film; and a polarizing plate adhered to the polarizing plate protective film by a water-soluble adhesive Floor.

The easy-adhesion layer and the polarizing plate of the polarizer protective film of the polarizing plate can be reliably bonded by a water-soluble adhesive. Further, since the moisture permeability of the polarizer protective film is controlled to a desired moisture permeability by the first control layer and the second control layer, water-soluble bonding can be achieved when bonding with the water-soluble binder The moisture of the agent is reliably evaporated, and the bonding process can be easily and reliably performed. As a result, the polarizer protective film and the polarizing plate of the polarizing plate can be reliably bonded. Further, 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 smaller than that in the case of cellulose triacetate, so that photoelastic effect is less likely to occur. . Therefore, the change in the retardation value of the polarizer protective film is small. In particular, since the polarizer protective film is provided with the second control layer on the other surface side of the substrate layer, the moisture permeability of the polarizer protective film is controlled to a desired moisture permeability, so that the substrate can be further suppressed. The dimensional change of the layer enables a smaller change in the size of the substrate layer. Therefore, variations in the retardation value of the polarizer protective film of the polarizing plate can be reduced, and the polarizing plate can exhibit desired optical characteristics.

Further, in order to solve the above problems, the present invention also provides a liquid crystal display element comprising a liquid crystal cell and the polarizing plate, the polarizing plate being laminated on one surface side of the liquid crystal cell.

The easy-adhesion layer and the polarizing plate of the polarizer protective film of the liquid crystal display element can be reliably bonded by the water-soluble binder. In addition, the moisture permeability of the polarizer protective film is controlled to a desired moisture permeability by the first control layer and the second control layer, so that when the water-soluble adhesive is bonded, the water-soluble adhesive can be obtained. The moisture is reliably evaporated, and the bonding process can be easily and reliably performed. As a result, the polarizer protective film and the polarizing plate of the liquid crystal display element can be reliably bonded. Further, 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 smaller than that in the case of cellulose triacetate, so that photoelastic effect is less likely to occur. . Therefore, the change in the retardation value of the polarizer protective film is small. In particular, since the second control layer is provided on the other surface side of the base material layer, the moisture permeability of the polarizer protective film can be controlled to a desired moisture permeability, so that it can be further suppressed. The dimensional change of the substrate layer can make the dimensional change of the substrate layer smaller. Therefore, variations in the retardation value of the polarizer protective film of the liquid crystal display element can be reduced, so that the liquid crystal display element can exhibit desired optical characteristics. Therefore, the liquid crystal display element can efficiently display light using the light source for reliable display.

Further, in the present invention, the "same resin" includes resins in which the constituent monomers are the same chemical species, and their compositions are different or different in polymerization form. The "photoelastic coefficient" is a coefficient indicating the degree of difficulty in generating a refractive index change due to an external force, and is a value obtained by CR [Pa - 1] = Δn / σ R . Here, σ R is a tensile stress [Pa], and Δn is a refractive index difference when stress is applied, and Δn is defined by the following formula.

△n=n ₁ -n ₂

(wherein n ₁ is a refractive index in a direction parallel to the tensile stress, and n ₂ is a refractive index in a direction perpendicular to the stretching direction.)

The "moisture permeability" is a moisture permeability test (cup method) according to JIS Z 0208, and the number of grams of water vapor passing through a sample of 1 m ² area is measured in an atmosphere having a temperature of 40 ° C and a humidity of 92% RH for 24 hours. The value obtained. In addition, the "delay value (Re)" means that the fast axis direction and the slow axis direction which are perpendicular to the crystal axis direction on the plane of the surface of the polarizer protective film are the x direction and the y direction, respectively, and the polarizer protective film The thickness is d, and the refractive indices in the x direction and the y direction are nx and ny(nx≠ny), respectively, and the values calculated by Re=(ny-nx)d.

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 basis of the polarizer protective film due to humidity. The dimensional change of the material layer is small, so that the change in the retardation value of the polarizer protective film can be suppressed, and the polarizer protective film and the polarizing plate can be easily and reliably bonded by the water-soluble adhesive.

1‧‧‧ polarizer protective film

2‧‧‧Substrate layer

3‧‧‧First Control Layer

4‧‧‧Easy adhesive layer

5‧‧‧Second control layer

11‧‧‧Polar plate

12‧‧‧Polarizer

13‧‧‧Poly polarizer protective film made of cellulose ester

21‧‧‧Devices for manufacturing polarizers

22‧‧‧ Roll ( )

23‧‧‧ Roll

24‧‧‧Binder supply device

25‧‧‧roll

31‧‧‧Liquid display components

32‧‧‧Liquid Crystal Box

33‧‧‧Transparent dielectric layer

34‧‧‧Liquid layer

35‧‧‧Binder layer

41‧‧‧Liquid display components

42‧‧‧Liquid Crystal Box

43‧‧‧Transparent dielectric layer

44‧‧‧Liquid layer

45‧‧‧Polar plate

46‧‧‧ polarizer protective film

47‧‧‧Polarizer

48‧‧‧Binder layer

Fig. 1 is a schematic cross-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 including the polarizer protective film of FIG. 1. Figure.

Fig. 3 is a schematic view showing an apparatus for manufacturing the polarizing plate of Fig. 2.

4 is a schematic cross-sectional view showing a liquid crystal display element including the polarizing plate of FIG. 2 .

FIG. 5 is a schematic view showing a configuration of a conventional liquid crystal display device.

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

First embodiment

The polarizer protective film 1 of FIG. 1 includes: a substrate layer 2 mainly composed of an acrylic resin; a first control layer 3 for controlling moisture permeability; an easy-adhesion layer 4; and a second control layer 5 for Control moisture permeability. The polarizer protective film 1 is configured by arranging the respective layers in the order of the second control layer 5, the base material layer 2, the first control layer 3, and the easy-adhesion layer 4. The polarizer protective film 1 is bonded to the polarizing plate of the liquid crystal display element from the side of the easy-adhesion layer 4, and the polarizer protective film 1 is a protective film for improving the impact resistance and the usability of the polarizing plate.

Substrate layer 2

An acrylic resin is used as a main component of the base material layer 2, and the acrylic resin is a synthetic resin which is required to have high transparency as a polarizing plate protective film of a liquid crystal display element and has a certain moisture permeability. The base material layer 2 may contain other optional components as long as the transparency and the desired strength are not impaired, and is preferably an acrylic resin containing 90% by mass or more, and more preferably an acrylic resin containing 98% by mass or more. Here, examples of the optional component include an ultraviolet absorber, a stabilizer, a lubricant, a processing aid, a plasticizer, an impact modifier, a phase difference reducing agent, a matting agent, an antibacterial agent, and an antifungal agent.

The acrylic resin used as a main component of the base material layer 2 is a resin having a skeleton derived from acrylic acid or methacrylic acid. The example of the acrylic resin is not particularly limited, and examples thereof include poly(meth)acrylate such as polymethyl methacrylate, methyl methacrylate-(meth)acrylic acid copolymer, and methyl methacrylate. a (meth) acrylate copolymer, a methyl methacrylate-acrylate-(meth)acrylic acid copolymer, a methyl (meth) acrylate-styrene copolymer, a polymer having an alicyclic hydrocarbon group (for example) Methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate-(meth)acrylic acid norbornene ester copolymer), and the like. Among the acrylic resins, a poly(meth)acrylic acid C1-C6 alkyl ester such as poly(methyl) acrylate is preferable, and a methyl methacrylate resin is more preferable.

The photoelastic coefficient of the acrylic resin is not particularly limited, but is preferably -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, still more 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, still more preferably -3 × 10 -12 /Pa. When the photoelastic coefficient of the acrylic resin is out of the above range, there is a problem in that the change in the retardation value at the time of occurrence of a dimensional change becomes large.

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, still more preferably 0.5% or less. When the water absorption rate of the acrylic resin exceeds the upper limit of the range, the possibility of dimensional change when the contained water evaporates or the like becomes high. Further, the water absorption rate is a value measured in accordance with JIS K 7209, using a film sample having a square length of 50 mm and a thickness of 100 μm.

The thickness (average thickness) of the base material layer 2 is not particularly limited, but is preferably 10 μm or more and 200 μm or less. The upper limit of the thickness of the base material layer 2 is more preferably 100 μm, still more preferably 80 μm. On the other hand, the lower limit of the thickness of the base material layer 2 is more preferably 20 μm, still more preferably 40 μm. When the thickness of the base material layer 2 exceeds the upper limit, the production line speed, productivity, and moisture permeability at the time of production are lowered, and there is a problem that the liquid crystal display device is required to be thinner. On the other hand, when the thickness of the base material layer 2 is less than the lower limit value, strength and rigidity are small, and there is a problem that it is difficult to use in a production line or the like.

The arithmetic mean surface roughness (Ra) of the base material layer 2 is not particularly limited, but a base material layer of 0.02 or more and 0.06 or less can be usually used. Further, the substrate layer 2 can be subjected to a matte treatment as needed. The upper limit of the arithmetic mean surface roughness (Ra) of the substrate layer 2 subjected to the matte treatment described above is preferably 2, and more preferably 1. On the other hand, the lower limit of the arithmetic mean surface roughness (Ra) of the base material layer 2 subjected to the matte treatment is preferably 0.07, and more preferably 0.1. By controlling the arithmetic mean surface roughness (Ra) of the base material layer 2 subjected to the matte treatment within the above range, damage to the treatment after the production of the original film can be prevented, and the usability can be improved. Further, in general, when winding the produced original film, it is preferable to perform embossing (knurling processing) on both ends in the film width direction to prevent lumping. When the knurling process is performed on the film, since the treated portion at both ends of the film becomes unusable, it is necessary to cut the portion and discard it. Further, in the operation of winding the film, in order to prevent the film from being damaged, the protective film may be used for shielding. However, by setting the arithmetic mean surface roughness (Ra) of the base material layer 2 within the above range, the knurling process can be prevented from being lumped, so that the manufacturing process can be simplified, and both end portions in the film width direction are also It can be used and can take up a long film without causing film failure. Further, by providing the base material layer 2 with an appropriate surface roughness, it is possible to effectively suppress damage to the film during winding, and it is not necessary to shield as described above.

The retardation value (Re) of the base material layer 2 is not particularly limited, but is preferably -15 nm or more and 15 nm or less. The upper limit of the retardation value (Re) of the base material layer 2 is more preferably 10 nm, still more 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, still more preferably -5 nm. When the retardation value (Re) of the base material layer 2 is out of the above range, there is a problem that the polarization direction of the polarizing plate cannot be optimized in the transmission axis direction due to the conversion action of the polarization direction of the transmitted light.

The method for producing the base material layer 2 is not particularly limited. For example, an additive such as a sheet-like raw material of an acrylic resin and a plasticizer may be mixed by a conventional mixing method, and a thermoplastic resin composition may be prepared in advance, and then an optical film may be produced. For example, using Australia After premixing with a mixer such as a Mito mixer, the obtained mixture is subjected to extrusion kneading to obtain the thermoplastic resin composition. In this case, the kneading machine used for the extrusion kneading is not particularly limited, and for example, a conventionally known mixing machine such as a single-screw extruder or a twin-screw extruder or a pressure kneader can be used. Refinery.

The method of forming the film of the base material layer 2 may, for example, be a conventional method such as a solution casting method (solution casting method), a melt extrusion method, a calendering method, or a compression molding method. Among them, a solution casting method (solution casting method) or a melt extrusion method is preferred. In this case, a thermoplastic resin composition which has been previously kneaded and kneaded may be used, or another additive such as a synthetic resin or a plasticizer may be dissolved in a solvent to prepare a homogeneous mixed solution, and then supplied to a solution casting method (solution Casting process) or a film forming process of a melt extrusion method.

The solvent used for the solution casting method (solution casting method) may, for example, be a chlorine solvent such as chloroform or dichloromethane; an aromatic solvent such as toluene, xylene, benzene or a mixed solvent thereof; methanol or ethanol; An alcohol solvent such as isopropyl alcohol, n-butanol or 2-butanol; methyl cellosolve, ethyl cellosolve, butyl cellosolve, dimethylformamide, dimethyl hydrazine, dioxane, Cyclohexanone, tetrahydrofuran, acetone, methyl 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 type casting machine, a belt casting machine, a spin coater, and the like.

As the melt extrusion method, a T-die method, a blown film method, or the like can be exemplified. The molding temperature of the film at the time of melt extrusion is preferably 150 ° C or more and 350 ° C or less, and more preferably 200 ° C or more and 300 ° C or less. In the case of film forming by the T-die method, the T-die is attached to the front end portion of a conventional single-screw extruder or twin-screw extruder, and the film extruded into a film form is taken up to obtain Roll-shaped film. At this time, the uniaxial stretching step can be performed by appropriately adjusting the temperature of the winding roller and extending the film in the extrusion direction. Further, a step of stretching the film in a direction perpendicular to the extrusion direction may be added, and steps such as sequential biaxial stretching and simultaneous biaxial stretching may be added.

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

The stretching temperature in the case where the stretching step is carried out is preferably carried out in the vicinity of the glass transition temperature of the thermoplastic resin composition of the film raw material, and specifically, it is preferably (glass transition temperature -30) ° C ~ (Glass transition temperature + 100) is carried out in the range of ° C, and more preferably in the range of (glass transition temperature - 20) ° C - (glass transition temperature + 80) ° C. When the stretching temperature exceeds the above upper limit value, the flow of the resin (flowing) is caused, and there is a problem that stable stretching cannot be performed. On the contrary, in the case where the stretching temperature is less than the lower limit value, there is a problem that a sufficient stretching ratio cannot be obtained.

The stretching ratio defined by the area ratio is preferably in the range of 1.1 times or more and 25 times or less, and more preferably in the range of 1.3 times or more and 10 times or less. When the draw ratio exceeds the above upper limit, there is a problem that the effect of increasing the draw ratio cannot be obtained. On the other hand, when the draw ratio is less than the lower limit, there is a problem that the toughness cannot be increased with stretching.

The stretching speed (one direction) is preferably in the range of 10 to 20000%/min, and more preferably in the range of 100 to 10000%/min. When the stretching speed exceeds the above upper limit value, there is a problem that the stretched film is broken. On the other hand, when the stretching speed is less than the lower limit value, it takes a lot of time to obtain a sufficient stretching ratio, and there is a problem that the manufacturing cost becomes high. Further, in order to stabilize the optical isotropy and mechanical properties of the base material layer 2, heat treatment may be performed after the stretching treatment ( )Wait.

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 that the base material layer 2 does not become turbid or bleed out from the base material layer 2 or Volatile. Examples of the plasticizer are not particularly limited, and examples thereof include a phosphate ester plasticizer, a phthalate plasticizer, a trimellitate plasticizer, and a pyromellitic acid system. Plasticizer, polyol A plasticizer, a glycolic acid plasticizer, a citric acid ester plasticizer, a fatty acid ester plasticizer, a carboxylic acid ester plasticizer, a polyester plasticizer, 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 suitably used. The hydrophilic resin is not particularly limited as long as it has chemical affinity with the base layer 2 and the easy-adhesion layer 4, and a resin modified with a hydrophilic group by a side chain is preferable. As a method of hydrophilization modification of a hydrophilic resin, a monomer having a hydrophilic functional group may be (co)polymerized in advance, or a monomer having a main chain may be (co)polymerized, and a monomer having a hydrophilic group may be obtained. The body is graft polymerized to form a side chain. Further, it is preferable to form the hydrophilic resin from a resin selected from the group consisting of a polyester resin, an acrylic resin, a urethane resin, and an epoxy resin. The resin may be polymerized alone or in combination of two or more. As the hydrophilic resin, for example, a hydrophilic resin having a weight average molecular weight of 300 or more and 30,000 or less can be used.

Polycondensation is carried out by esterification (transesterification) of a dicarboxylic acid and a diol by a conventional method, whereby a polyester-based resin contained as a main component of the first control layer 3 is produced. As the dicarboxylic acid, for example, an aromatic dicarboxylic acid such as terephthalic acid, isophthalic acid, phthalic acid or naphthalene dicarboxylic acid or an ester thereof; adipic acid, succinic acid, sebacic acid or dodecane can be used. An aliphatic dicarboxylic acid such as a diacid; a hydroxycarboxylic acid such as hydroxybenzoic acid or an ester thereof. Further, as the diol, for example, ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, cyclohexanedimethanol, bisphenol or the like can be used.

As the polyester resin, it is preferred to copolymerize a component having a hydrophilic group with the above dicarboxylic acid and a diol to impart hydrophilicity. Examples of the component having a hydrophilic group include a dicarboxylic acid component such as sodium isophthalate-5-sulfonate; and a diol component such as diethylene glycol, triethylene glycol or polyethylene glycol. The component having a hydrophilic group can be used, for example, in a ratio of from 2 mol% to 80 mol%, based on the dicarboxylic acid or diol. The components constituting the polyester resin may be used singly or in combination of a plurality of components.

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 the reactive polymer include a substance having a carboxyl group such as acrylic acid, methacrylic acid, carboxyethyl (meth)acrylate or carboxyphenyl acrylate; 2-hydroxyethyl (meth)acrylate, a substance having a hydroxyl group such as 3-hydroxybutyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate or 3-hydroxypropyl (meth)acrylate; (meth)acrylamide, N-methyl (Methyl) acrylamide, N-ethyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N-hydroxymethyl (meth) acrylamide, etc. An amino group-containing substance; a glycidyl group-containing substance such as glycidyl (meth)acrylate; 7-amino-3,7-dimethyloctyl (meth) acrylate, 2-dimethylaminoethyl ( A substance having an amino group such as a methyl acrylate or the like may be mentioned, and examples thereof include p-chlorostyrene, chloromethylstyrene, divinylbenzene, 4-vinylpyridine, vinyloxazoline, and maleic anhydride.

The copolymerization component other than the component constituting the acrylic resin may, for example, be an acrylate type, a methacrylate type, a propylene type, a vinyl chloride type, a cellulose type, a vinyl type, an ethylene imine type, or an ethylene. In the case of an alcohol, a peptide, a vinyl pyridine, a diene, a fluorine, or an acrylonitrile, it is preferable to contain an acrylate type or a methacrylate type from the viewpoint of versatility, applicability, and the like. The components constituting the acrylic resin may be used singly or in combination of two or more.

The urethane-based resin contained as the main component of the first control layer 3 can be synthesized from a polyhydroxy compound, a diisocyanate, and a low molecular weight chain extender containing at least two hydrogen atoms reacted with a diisocyanate by a conventional method. For example, the following method can be employed: after synthesizing a polyurethane having a relatively high molecular weight in a solvent, a little bit of water is added to carry out the reverse emulsification, and then the solvent is removed by pressure reduction; and after the polyurethane prepolymer is dissolved or dispersed in water, A method of reacting a chain extender obtained by introducing a polyethylene glycol, a carboxyl group or the like as a hydrophilic group into a polymer; and the like.

As an example of a polyhydroxy compound used for producing the polyurethane resin, Examples include carboxylic acids such as phthalic acid, adipic acid, linoleic acid dimer, and maleic acid; glycols such as ethylene glycol, propylene glycol, butylene glycol, and diethylene glycol; and trimethylolpropane and Polyester polyols obtained by dehydration condensation reaction of triol, glycerin, trimethylolethane, pentaerythritol, etc.; polyoxypropylene diol, polybutylene diol, polytetramethylene glycol, polyoxypropylene Triol, polyoxyethylene polyoxypropylene triol, sorbitol, pentaerythritol, sucrose, starch, polyoxypropylene polyol such as polyoxypropylene polyol, polyoxypropylene polyoxyethylene polyol, etc. Acrylic polyol, derivatives of castor oil, tall oil derivatives, other hydroxy compounds, and the like. The polyhydroxy compounds may be used singly or in combination of two or more.

Examples of the diisocyanate used for the production of the urethane-based resin include toluene-2,4-diisocyanate, toluene-2,6-diisocyanate, isophthalic diisocyanate, p-phenylene diisocyanate, and diphenylmethane- 4,4'-diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, benzodimethyl diisocyanate, lysine diisocyanate, isophorone diisocyanate, trimethylhexamethylene di Isocyanate, 1,4-cyclohexyl diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 3,3'-dimethyl-4,4'-biphenyl diisocyanate, 3,3'-dimethoxy Base-4,4'-biphenyldiisocyanate, 3,3'-dichloro-4,4'-biphenyldiisocyanate, 1,5-naphthalene diisocyanate, 1,5-tetrahydronaphthalene diisocyanate, and the like. The diisocyanate may be used singly or in combination of two or more.

Examples of the chain extender used for producing the urethane-based resin include ethylene glycol, 1,4-butanediol, trimethylolpropane, triisopropanolamine, and N,N-bis(2- Polyols such as hydroxypropyl)aniline, hydroquinone-bis(β-hydroxyethyl)ether, resorcinol-bis(β-hydroxyethyl)ether; ethylenediamine, propylenediamine, hexamethylenediamine, Phenylenediamine, toluenediamine, diphenyldiamine, diaminodiphenylmethane, diaminodiphenylmethane, diaminodicyclohexylmethane, pyridazine, isophoronediamine, diethylene three Polyamines such as amines and dipropylene triamines; hydrazines; and water. The chain extenders may be used singly or in combination of two or more.

The synthesis reaction for producing the urethane-based resin can be carried out in the presence of a catalyst such as an organotin compound, an organic hydrazine or an amine, and it is particularly preferred to carry out the reaction in the presence of an organotin compound. Specific examples of the organotin compound include stannous acetate, stannous octoate, stannous laurate, stannous oleate, and the like; stannous diacetate, dibutyltin dilaurate, and dibutyltin maleate; a dialkyl tin salt of a carboxylic acid such as dibutyl (bis-2-ethylhexanoate) tin, dilauryl tin diacetate or dioctyltin diacetate; trimethyltin hydroxide, tributyl hydrogen a trialkyltin hydroxide such as tin oxide or trioctyltin hydroxide; a dialkyl tin oxide such as dibutyltin oxide, dioctyltin oxide or dilauryltin oxide; dibutyltin dichloride, two The dialkyltin dichloride such as octyltin dichloride 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 the monomer described include glycidyl acrylate, glycidyl methacrylate, and allyl glycidyl ether. Further, as a monomer copolymerizable with the monomer, a vinyl ester, an unsaturated carboxylic acid ester, an unsaturated carboxylic acid decylamine, an unsaturated nitrile, an allyl compound, an unsaturated hydrocarbon or a vinyl decane may be used. Compound. Specific examples thereof include vinyl propionate, vinyl chloride, vinyl bromide, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, and butyl methacrylate. Ester, butyl maleate, octyl maleate, butyl fumarate, octyl fumarate, hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl methacrylate, hydroxypropyl acrylate, ethylene Alcohol dimethacrylate, ethylene glycol diacrylate, polyethylene glycol dimethacrylate, polyethylene glycol diacrylate, acrylamide, methacrylamide, methylol decylamine, butyl Oxymethylol decylamine, acrylonitrile as unsaturated nitrile, allyl acetate, allyl methacrylate, allyl acrylate, diallyl itaconate, ethylene, propylene, hexene, octyl Alkene, styrene, vinyl toluene, butadiene, dimethylvinyl methoxy decane, dimethyl ethyl ethoxy decane, methyl vinyl dimethoxy decane, methyl vinyl diethoxy Baseline, gamma-methyl methacrylate Oxypropyltrimethoxydecane, γ-methylpropenyloxypropylmethyldimethoxydecane, and the like. The components constituting the epoxy resin described above may be used singly or in combination of two or more.

In the hydrophilization modification of the hydrophilic resin, in the case where the hydrophilic monomer is graft-polymerized to form a hydrophilic side chain after (co)polymerization of the monomer as a main chain, it is preferred to make a hydrophilic radical. Polymerizable vinyl monomer graft polymerization. In this case, the radical polymerizable vinyl monomer can be used in a ratio of 10 parts by mass or more and 500 parts by mass or less based on the total of 100 parts by mass of the main chain component.

As an example of the hydrophilic radically polymerizable vinyl monomer, -CH2-CH(R)-OH (wherein -R is -H or -CH3), -COOX (wherein, X is H, an alkali metal or a secondary or tertiary amino group), -O-(CH2-CH(R)-O)n- (wherein -R is -H or -CH3, n is a positive integer), -YN( R1)(R2)(-Y- is -C(=O)- or -CH2-, -R1, -R2 are -H, or may have a hydroxyl group, a sulfonyl group, a fluorenyl group, an amino group, an alkali metal salt or a season Lower alkyl of ammonium salt), -N+-(R3)(R4)(R5) (wherein -R3, -R4, -R5 are -CH3 or -C2H5), -CH2-CH(O)CH2(O A substance which forms a hydrophilic group such as an epoxy ring with carbon on both sides.

Specific examples of the hydrophilic radically polymerizable vinyl monomer include hydroxy acrylates such as hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, and hydroxypropyl methacrylate; Ethylene glycol esters such as alcohol acrylate, ethylene glycol methacrylate, polyethylene glycol acrylate, polyethylene glycol methacrylate; acrylamide, methacrylamide, methylol acrylamide, A acrylamide compound such as methoxymethylol acrylamide; a glycidyl acrylate compound such as glycidyl acrylate or glycidyl methacrylate; a nitrogen-containing vinyl group such as vinyl pyridine, vinyl imidazole or vinyl pyrrolidone; Compounds; unsaturated acids and their salts such as acrylic acid, methacrylic acid, maleic anhydride, itaconic acid, crotonic acid; cationic monomers such as aminoalkyl acrylate, aminoalkyl methacrylate and quaternary ammonium salts thereof; Wait.

In the hydrophilization modification of the hydrophilic resin, in addition to the radical polymerization described In addition to the vinyl monomer, other vinyl monomers may be copolymerized. Examples of other vinyl monomers copolymerizable include vinyl acetates such as vinyl acetate and vinyl propionate; vinyl halides such as vinyl chloride and vinyl bromide; methyl acrylate, ethyl acrylate, and butyl acrylate. An unsaturated carboxylic acid ester such as methyl methacrylate, ethyl methacrylate or butyl methacrylate; dimethylvinyl methoxy decane, γ-methyl propylene methoxy propyl trimethoxy decane, etc. Vinyl decane; olefin or diene compound such as ethylene, propylene, styrene or butadiene.

In the case where a polyester-based resin is used as a main component of the first control layer 3, as the polyester-based resin, it is most preferable to use a radically polymerizable vinyl group having a hydrophilic group and derived from acrylic acid. A polyester resin (hereinafter referred to as "acrylic modified polyester resin") in which a monomer (hereinafter referred to as "acrylic radical polymerizable vinyl monomer") is modified with a side chain. By using an acrylic modified polyester resin as a main component of the first control layer 3, it is possible to utilize the original transparency, toughness, heat resistance of the polyester resin, and to the synthetic resin (for example, as the base layer 2) The adhesive property of the component, such as an acrylic resin, etc., and the adhesiveness of the 1st control layer 3 and the easy-adhesion layer 4 can be provided by the said modification group. In addition, it is most preferable that the first control layer 3 is a composition containing a urethane-based 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 a main component of the first control layer 3, it is possible to utilize the original transparency, toughness, heat resistance, and synthetic resin of the polyester resin. The adhesiveness and the like can be imparted to the first control layer 3 and the easy-adhesion layer 4 by the modifying group, and the first control layer 3 and the substrate layer 2 can be imparted by mixing the urethane-based resin. Adhesion and softness of the easy-adhesion layer 4.

The weight average molecular weight of the acrylic radical polymerizable vinyl monomer and the urethane resin is typically 1,000 or more and 15,000 or less, and preferably 2,000 or more and 10,000 or less.

The quality of the polyurethane resin in the composition is relative to the acrylic modified polyester The quality of the resin is preferably 10% or more and 70% or less, and more preferably 25% or more and 40% or less. When the quality ratio of the acrylic modified polyester resin and the urethane resin is within the above range, the properties of the layer of the first control layer 3 such as transparency, water resistance, heat resistance, and the like can be favorably maintained, and The adhesion of the first control layer 3 to the substrate layer 2 and the easy-adhesion layer 4 can be optimized.

A hydrophilic group which is an acrylic radical polymerizable vinyl monomer which is a modifying component of the acrylic modified polyester resin can be used as the hydrophilic radical polymerizable vinyl monomer. A hydrophilic group exemplified by a hydrophilic group. In other words, the representative hydrophilic group of the acrylic radical polymerizable vinyl monomer may, for example, be -CH2-CH(R)-OH, -COOX, -O-(CH2-CH(R) -O)n-, -YN(R1)(R2), -N+-(R3)(R4)(R5), -CH2-CH(O)CH2 (as defined above).

As the acrylic radical polymerizable vinyl monomer, an acrylic monomer exemplified as a specific example of the hydrophilic radically 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, and B. Glycol methacrylate, polyethylene glycol acrylate, polyethylene glycol methacrylate, acrylamide, methacrylamide, methylol acrylamide, methoxymethylol decylamine, Glycidyl acrylate, glycidyl methacrylate, acrylic acid, methacrylic acid, aminoalkyl acrylate, aminoalkyl methacrylate, and the like. The acrylic radical polymerizable vinyl monomer may be used singly or in combination of two or more.

Further, as the acrylic modified polyester resin, a resin obtained by copolymerizing and copolymerizing other copolymerizable vinyl monomers other than the acrylic radical polymerizable vinyl monomer may be used. When the other vinyl monomer is copolymerized, for example, one part by mass or more and 70 parts by mass or less of 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, acrylic radical polymerizable B The acryl-based radically polymerizable vinyl monomer 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-based resin, with respect to 100 parts by mass of the polyester-based resin. Further, it is more preferably 70 parts by mass or more and 120 parts by mass or less. By setting the quality ratio of the acrylic radical polymerizable vinyl monomer to the polyester resin within the above range, the chemical affinity of the first control layer 3 to the substrate layer 2 can be more uniformly improved and the first The chemical affinity of the control layer 3 to the easy-adhesion layer 4.

For example, preparing an aqueous solution or an aqueous dispersion containing a water-soluble or water-dispersible polyester resin and polyvinyl alcohol, and then co-polymerizing an acrylic radical polymerizable vinyl monomer (and any other copolymerizable vinyl monomer) The acrylic acid-modified polyester resin is produced by polymerization, and the water-soluble or water-soluble component is obtained by copolymerizing a component having a hydrophilic group such as a dicarboxylic acid component such as sodium isophthalate-5-sulfonate. Water-dispersible polyester resin.

In the method for producing an acrylic modified polyester resin using the polyvinyl alcohol, for example, the polyvinyl alcohol may be used in an amount of 10 parts by mass or more and 500 parts by mass based on 100 parts by mass of the water-soluble or water-dispersible polyester. The following ratio (solid content ratio) is reacted.

As a polymerization method for synthesizing the acrylic modified polyester-based resin, a method may be exemplified: for example, in the aqueous solution or aqueous dispersion of the water-soluble or water-dispersible polyester and polyvinyl alcohol, polymerization initiation is added. A small amount of the emulsified dispersant is added as needed, and the acrylic radical polymerizable vinyl monomer is slowly added while stirring at a temperature of about 70 ° C, and the polymer is aged by several hours to complete the polymerization reaction.

As a polymerization initiator for producing the acrylic modified polyester resin, a usual radical polymerization initiator can be used. Examples of the polymerization initiator include water-soluble peroxides such as potassium persulfate, ammonium persulfate, and hydrogen peroxide; oil-soluble peroxides such as benzamidine peroxide and t-butyl hydroperoxide; and azodi An azo compound such as isobutyronitrile.

The 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 of the thickness of the first control layer 3 is more preferably 4 μm, still more preferably 3 μm. On the other hand, the lower limit of the thickness of the first control layer 3 is more preferably 0.04 μm, still more preferably 1 μm. When the thickness of the first control layer 3 exceeds the upper limit value, the thickness of the polarizer protective film 1 is increased, which is in violation of the requirement for thinning of the liquid crystal display device. On the contrary, in the case where the thickness of the first control layer 3 is smaller than the lower limit value, there is a problem that it is 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 of the moisture permeability of the first control layer 3 is more preferably 130 g/m ² ‧24 h, further preferably 80 g/m ² ‧24 h. On the other hand, the lower limit of the moisture permeability of the first control layer 3 is more preferably 10 g/m ² ‧24 h, further 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 increases, and the possibility that the size of the base material layer 2 or the like changes is increased. On the other hand, in the case where the moisture permeability of the first control layer 3 is less than the lower limit value, in the case where the easy-adhesion layer 4 and the polarizing plate are bonded with a water-soluble binder, there is a need to make the water-soluble binder The evaporation of water contained in it takes a long time. On the other hand, when the moisture permeability of the first control layer 3 is within the above range, the water contained in the water-soluble binder can be favorably evaporated to promote the drying of the easy-adhesion layer 4 and can be improved. The adhesiveness of the adhesive layer 4 and the polarizing plate is improved, 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 or the like") onto 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 a main solvent such as a water-based emulsion, but a small amount of an organic solvent which can be mixed with water can also be used. Examples of such an organic solvent include lower alcohols, polyhydric alcohols, alkyl ethers or alkyl esters thereof. can The conventional dip coating method, air knife coating method, curtain coating method, roll coating method, wire bar coating method, gravure coating method, extrusion coating method (die coating method), etc. are used. The water-based emulsion or the like is applied onto the base material layer 2, and then the first aqueous control layer 3 can be formed by drying the applied aqueous emulsion or the like.

It is preferable to add a crosslinking agent as needed in the aqueous emulsion or the like for forming the first control layer 3. Examples of the crosslinking agent include formaldehyde, an N-methylol compound, a dioxane derivative, a reactive ethylene compound, an active halogen compound, isoxazole, a diformaldehyde starch, an isocyanate compound, a decane coupling agent, and the like. The crosslinking agent may be used singly or in combination of two or more. The amount of the crosslinking agent to be added is preferably 0.1% by mass or more and 20% by mass or less based on the total amount of the hydrophilic resin, and more preferably 0.5% by mass or more and 15% by mass or less. In the aqueous emulsion or the like for forming the first control layer 3, other resin components such as an amino resin, a surfactant, a lubricant, a dye, a UV absorber, a matting agent, a preservative, and the like may be added as needed. Adhesives, filming aids, antistatic agents, antioxidants, etc.

Easy 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 resin having chemical affinity with the hydrophilic resin contained in the main component of the first control layer 3 and the polyvinyl alcohol constituting the polarizing plate, and is easily bonded. A cellulose ester-based resin is preferably used as the main component of the layer 4. When the main component of the easy-adhesion layer 4 contains a cellulose ester-based resin, the adhesion between the polarizing plate made of polyvinyl alcohol as a hydrophilic resin and the easy-adhesion layer 4 can be greatly improved. In other words, by saponifying the easy-adhesion layer 4 containing a cellulose ester-based resin as a main component with a base to form a hydroxyl group as a hydrophilic group, the adhesion to polyvinyl alcohol as a hydrophilic resin can be effectively improved. Therefore, the easy-adhesion layer 4 and the polarizing plate of the polarizer protective film 1 can be easily and reliably bonded using a water-soluble binder.

The cellulose ester-based resin contained in the easy-adhesion layer 4 as a main component is not particularly limited as long as it can be saponified with an alkali to form a hydroxyl group, and it is preferably from A group consisting of cellulose triacetate, cellulose diacetate, cellulose acetate propionate and cellulose acetate butyrate is selected. The cellulose ester is formed by saponification with an alkali to form a hydroxyl group as a hydrophilic group, whereby affinity with a polarizing plate made of polyvinyl alcohol as a hydrophilic resin can be improved, and it can be reliably bonded to a polarizing plate. .

The number average molecular weight (Mn) of the cellulose ester-based resin contained in the easy-adhesion layer 4 as a main component is not particularly limited, but is preferably 40,000 or more and 100,000 or less. The upper limit of the number average molecular weight (Mn) of the cellulose ester-based resin is more preferably 90,000, still more preferably 80,000. On the other hand, the lower limit of the number average molecular weight (Mn) of the cellulose ester-based resin is more preferably 50,000, still more preferably 60,000. When the number average molecular weight (Mn) exceeds the above upper limit value, there is a problem that the coating property of the easy-adhesion layer 4 is lowered. On the other hand, when the number average molecular weight (Mn) is less than the lower limit, when the saponification treatment is performed on the easy-adhesion layer 4 with an alkali, there is a problem that the cellulose ester-based resin becomes white and the transparency is 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 in the easy-adhesion layer 4 as a main component is not particularly limited, but is preferably 1.4 or more and 3 or less. 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, 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, still 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, there is a problem that the dimensional stability of the easy-adhesion layer 4 is lowered. 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-based resin is less than the lower limit, there is a problem that it is difficult to produce a desired cellulose ester. .

The thickness (average thickness) of the easy-adhesion layer 4 is not particularly limited, but is preferably 0.01 μm or more and 5 μm or less. The upper limit of the thickness of the easy-adhesion layer 4 is more preferably 4 μm, still more preferably 3 μm. On the other hand, easy to bond The lower limit of the thickness of the layer 4 is more preferably 0.04 μm, still more preferably 1 μm. When the thickness of the easy-adhesion layer 4 exceeds the above upper limit value, the thickness of the polarizer protective film 1 becomes thick, which is a problem that the thickness of the liquid crystal display device is required to be reduced. Further, when the thickness of the easy-adhesion layer 4 exceeds the above upper limit value, there is a problem that the moisture permeability of the easy-adhesion layer 4 is lowered. On the contrary, in the case where the thickness of the easy-adhesion layer 4 is less than the lower limit value, there is a problem that the adhesion of the easy-adhesion layer 4 and the first resin layer 3 is lowered. On the other hand, in the case where 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 constituting the easy-adhesion layer 4 can be more reliably bonded. The hydroxyl group formed by saponification of the ester and the polyvinyl alcohol constituting the polarizing plate.

The solvent for forming the coating liquid of the cellulose ester of the easy-adhesion layer 4 is not particularly limited as long as it is an organic solvent capable of sufficiently dissolving the cellulose ester, and for example, dioxane, acetone, methyl ethyl ketone, or the like can be used. N,N-dimethylformamide, methyl acetate, ethyl acetate, trichloroethylene, dichloromethane, ethylene dichloride, tetrachloroethane, trichloroethane, chloroform, and the like. Further, in the coating liquid for forming the cellulose ester of the easy-adhesion layer 4, an ultraviolet absorber, a lubricant, a matting agent, an antistatic agent, a crosslinking agent, an active agent, or the like may be added as needed. Since the adhesion to the polyvinyl alcohol constituting the polarizing plate can be promoted, it is particularly preferable to add a crosslinking agent. Examples of the crosslinking agent include a polyvalent epoxy compound, an aziridine compound, an isocyanate compound, an alum, an iodine compound, and the like.

The first control layer 3 may be coated with a cellulose ester for forming the easy-adhesion layer 4 by a conventional method such as a gravure coater, a dip coater, a reverse roll coater, or an extrusion coater. Coating solution. The method of drying after applying the coating liquid described above is not particularly limited, and a conventional method can be used. However, it is preferable that the amount of the solvent remaining after drying is 5 mass% or less. If the amount of the residual solvent is large, bubbles may be generated in the adhesion interface during the drying process in which the polarizer protective film 1 is laminated on the polarizing plate, 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 main component of 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 the first control layer 3, but is preferably the same material as the main component of the first control layer 3. In the case where 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, and The moisture permeability of the entire polarizer protective film 1 is reliably controlled. Further, in the case where 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 manufacture of the polarizer protective film 1 can be made easier.

Further, 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 of the thickness of the second control layer 5 is more preferably 4 μm, still more preferably 3 μm. On the other hand, the lower limit of the thickness of the second control layer 5 is more preferably 0.04 μm, still more preferably 1 μm. When the thickness of the second control layer 5 exceeds the above upper limit value, the thickness of the polarizer protective film 1 becomes thick, which is a problem that the thickness of the liquid crystal display device is required to be reduced. On the contrary, in the case where the thickness of the second control layer 5 is smaller than the lower limit value, there is a problem that it is difficult to form the second control layer 5.

In addition, the total thickness (average thickness) of the first control layer 3 and the second control layer 5 is preferably 1.0 μm or more and 10 μm or less, although it is not particularly limited. The upper limit of the total thickness of the first control layer 3 and the second control layer 5 is more preferably 8 μm, still 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, still more preferably 3 μm. 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 is increased, which is a problem that the thickness of the liquid crystal display device is required to be reduced. Further, the moisture permeability is lowered, and there is a problem that the time required for evaporating the water contained in the water-soluble binder is prolonged. Conversely, the total thickness of the first control layer 3 and the second control layer 5 is less than the lower limit value In the case of the case, there is a problem that it is difficult to form the first control layer 3 and the second control layer 5.

As the thickness of the second control layer 5, it is preferable to be substantially the same as the thickness of the first control layer 3. By making the thickness of the second control layer 5 substantially the same as the thickness of the first control layer 3, the polarizing plate is protected in a state where the first control layer 3 and the second control layer 5 are laminated on the substrate layer 2. The film 1 can prevent curling, and the manufacturing of the polarizer protective film 1 can be made easier.

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 of the moisture permeability of the second control layer 5 is more preferably 130 g/m ² ‧24 h, further preferably 80 g/m ² ‧24 h. On the other hand, the lower limit of the moisture permeability of the second control layer 5 is more preferably 10 g/m ² ‧24 h, further preferably 20 g/m ² ‧24 h. When the moisture permeability of the second control layer 5 exceeds the upper limit value, the penetration ratio of the moisture existing outside increases, and the possibility that the size of the base material layer 2 or the like changes. On the other hand, in the case where the moisture permeability of the second control layer 5 is less than the lower limit value, in the case where the easy-adhesion layer 4 and the polarizing plate are bonded with a water-soluble binder, there is a possibility for bonding in the water-soluble bond. The evaporation of moisture contained in the agent, and the time required for evaporating the water contained in the polarizer protective film 1 may become long.

The second control layer 5 can be formed on the other face 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 of the moisture permeability of the polarizer protective film 1 is more preferably 150 g/m ² ‧24 h, still more 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 10 g/m ² ‧24 h, further preferably 20 g/m ² ‧24 h. When the moisture permeability of the polarizer protective film 1 exceeds the above upper limit value, the proportion of moisture permeating from the outside increases, and the possibility that the size of the base material layer 2 or the like changes becomes large. On the other hand, in the case where the moisture permeability of the polarizer protective film 1 is less than the lower limit, in the case where the easy-adhesion layer 4 and the polarizing plate are bonded with a water-soluble binder, there is a case where the water-soluble binder is contained. The time required for evaporation of water will become longer.

Since the polarizer protective film 1 is provided with the easy-adhesion layer 4 on one surface side, the easy-adhesion layer 4 and the polarizing plate can be reliably bonded by a water-soluble adhesive. Further, the polarizer protective film 1 controls the moisture permeability to a desired moisture permeability by the first control layer 3 and the second control layer 5 disposed on both surfaces of the base material layer 2, and thus is in use. When the water-soluble binder is bonded, the water of the water-soluble binder can be reliably evaporated, and the bonding step can be easily and reliably performed. Further, 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 smaller than that in the case of cellulose triacetate, and light is less likely to occur. Elastic effect. Therefore, the change in the retardation value of the polarizer protective film 1 is small. In particular, the polarizer protective film 1 is provided with the second control layer 5 on the other surface side of the base material layer 2, and controls the moisture permeability to a desired moisture permeability, so that the size of the base material layer 2 can be further suppressed. The change enables the dimensional change of the base material layer 2 to be smaller, and the change in the retardation value is small.

Polarizer 11

The polarizing plate 11 of Fig. 2 has a structure in which the polarizer protective film 1 of Fig. 1 is provided on one surface of a polarizing plate 12 made of polyvinyl alcohol, and is provided on the other surface of the polarizing plate 12 from the past. The polarizer protective film 13 made of cellulose ester. Between the polarizing plate 12 and the polarizing plate protective film 1, and between the polarizing plate 12 and the polarizing plate protective film 13, adhesive is adhered by an adhesive (not shown).

As the polarizing plate 12, a polarizing plate obtained by dyeing a polyvinyl alcohol resin film with a dichroic substance (for example, iodine or a dichroic dye) and uniaxially stretching is used. The degree of polymerization of the polyvinyl alcohol constituting the polyvinyl alcohol resin film is preferably 500 or more, and more preferably 1,000 or more. The polyvinyl alcohol resin film can be molded by a conventional method (for example, a casting method in which a solution obtained by dissolving a resin in water or an organic solvent is cast into a film, a solution casting method, or the like). The thickness (average thickness) of the polarizing plate 12 differs depending on the purpose and use of the liquid crystal display device using the polarizing plate 11, and is typically 5 μm or more and 100 μm or less. The polarizing plate 12 may contain any components other than the polyvinyl alcohol resin and the dichroic material as long as the polarizing function and optical transparency are not impaired.

As a typical production method of the polarizing plate 12, a series of manufacturing processes consisting of a process of swelling, dyeing, crosslinking, stretching, washing, and drying a polyvinyl alcohol resin film are employed. In each treatment step except the drying step, the polyvinyl alcohol resin film is immersed in a solution bath of the solution used in each step to perform treatment. The order, the number of times, and whether or not each treatment of swelling, dyeing, crosslinking, stretching, water washing, and drying can be carried out can be appropriately set depending on the purpose, materials used, conditions, and the like. For example, the stretching treatment may be performed before the dyeing treatment, or may be performed simultaneously with the swelling treatment or the like. Further, it is preferred to carry out the crosslinking treatment before and after the stretching treatment.

The swelling step in a series of manufacturing steps of the polarizing plate 12 can be carried out by immersing the polyvinyl alcohol resin film in a treatment bath filled with water. In the treatment bath, glycerin, potassium iodide or the like can be appropriately added. The treatment bath temperature in a typical swelling step 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 carried out by immersing the polyvinyl alcohol resin film in a treatment bath containing a dichroic substance such as iodine. As the solvent of the solution used in the treatment bath, water is usually used. The dichroic substance is used in a ratio of 0.1 to 1.0 part by mass based on 100 parts by mass of the solvent. The treatment bath temperature in a typical dyeing process is about 20 to 70 ° C, and the immersion time is about 1 to 20 minutes.

The crosslinking step can be carried out by immersing the dyed polyvinyl alcohol resin film in a treatment bath containing a crosslinking agent. Examples of the crosslinking agent include a boron compound such as boric acid, glyoxal, glutaraldehyde, and the like. As the solvent of the solution used in the treatment bath, water is usually used. The treatment bath temperature in a typical crosslinking step is about 20 to 70 ° C, and the immersion time is about 1 second to 15 minutes. The stretching process can be carried out 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 a compound of various metal salts, iodine, boron or zinc is added to water or an organic solvent is preferred.

The water washing step can be performed by immersing the polyvinyl alcohol resin film subjected to various treatments in a water bath. By the water washing step, unnecessary residues on the polyvinyl alcohol resin film can be washed away. The water bath may be pure water or an aqueous solution of iodide (potassium iodide, sodium iodide, etc.). The temperature of the water bath is preferably 10 to 60 °C. Typical immersion times are from 1 second to 1 minute. The number of times of washing may be one time or multiple times. As the drying step, for example, natural drying, air drying, and heat drying can be employed. Typical drying temperatures are 20 to 80 ° C and drying times are 1 to 10 minutes. The polarizing plate 12 can be manufactured by performing each said process.

The sheet-like raw material of the cellulose ester and the plasticizer are dissolved in methylene chloride to form a viscous liquid, and then the plasticizer is dissolved therein to form a coating, which is cast from a molten extruder on a metal belt of continuously rotating stainless steel or the like. The polarizing plate protective film 13 can be produced by drying, peeling from the tape in a semi-dry state, drying and winding. The cellulose ester is preferably a material selected from the group consisting of cellulose triacetate, cellulose diacetate, cellulose acetate propionate and cellulose acetate butyrate, and cellulose triacetate is particularly preferred.

Preferably, the easy-adhesion layer 4 is saponified with a base before the polarizer protective film 1 and the polarizing plate 12 are bonded. By the saponification, the ester group of the cellulose ester is converted into a hydroxyl group as a hydrophilic group, whereby the chemical affinity of the polarizer protective film 1 and the polarizing plate 12 formed of polyvinyl alcohol as a hydrophilic resin can be improved. The adhesion between the polarizer protective film 1 and the polarizing film 12 is greatly improved.

As the aqueous alkali solution used for the saponification treatment, for example, an aqueous solution of sodium hydroxide, potassium hydroxide, calcium hydroxide or lithium hydroxide can be used. The concentration of the metal hydroxide is usually 5% by mass or more and 40% by mass or less. Further, 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 less than 5% by mass and the temperature of the saponification treatment is less than 10 ° C, the time required for the saponification treatment increases, which is not preferable. The saponification treatment is carried out by immersing the polarizer protective film 1 in the aqueous alkali bath for a suitable period of time.

The polarization after saponification is carried out by bonding the device 21 schematically shown in FIG. The sheet protective film 1 and a polarizing plate 12 made of polyvinyl alcohol. The apparatus 21 for bonding a plurality of films shown in FIG. 3 includes: a roller 22 for providing a polarizing plate 12; a roller 23 for providing a polarizing plate protective film 1; and a binder supplying device 24 for supplying a binder; A roller 25 for pressing and bonding the polarizing plate 12 and the polarizer protective film 1 by an adhesive.

The adhesive to be used for the easy-adhesion layer 4 and the polarizing plate 12 to which the polarizer protective film 1 is adhered by the device 21 may, for example, be a polyvinyl alcohol-based adhesive such as polyvinyl alcohol or polyvinyl butyral or acrylic acid. A vinyl emulsion such as butyl ester. Usually the binder is used as an aqueous solution. The solid content concentration in the resin solution as the binder is preferably 0.1 to 15% by mass in consideration of coatability, stability of standing, and the like. Further, the viscosity of the resin solution as the binder is, for example, preferably in the range of 1 to 50 mPa·s.

In the apparatus 21, the film-shaped polarizing plate 12 supplied from the roller 22 and the saponified polarizing plate protective film 1 supplied from the roller 23 are fed in the direction of the roller 25 to provide an appropriate amount of adhesive so that the adhesive is sandwiched Between the polarizing plate 12 and the polarizer protective film 1, and then pressing by the roller 25, the polarizing plate 12 and the easy-adhesion layer 4 of the polarizer protective film 1 are bonded, whereby a polarizing plate is laminated on one surface of the polarizing plate 12. The structural member of the membrane 1. Then, on the surface of the polarizing plate 12 on which the polarizer protective film 1 is not laminated, the polarizer protective film 13 is laminated in the same manner, whereby the polarizing plate 11 is obtained.

The easy-adhesion layer 4 and the polarizing plate 12 of the polarizer protective film 1 of the polarizing plate 11 can be reliably bonded by a water-soluble adhesive. Further, since the moisture permeability of the polarizer protective film 1 is controlled to a desired moisture permeability by the first control layer 3 and the second control layer 5, when the water-soluble adhesive is bonded, it can be reliably made The water-vaporization of the water-soluble binder allows the bonding process to be easily and reliably performed. As a result, the polarizer protective film 1 and the polarizing plate of the polarizing plate 11 can be reliably bonded. Further, 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 smaller than that of the case of cellulose triacetate, so that light is less likely to be generated. Elastic effect. Therefore, the change in the retardation value of the polarizer protective film 1 is small. In particular, a second control is provided on the other side of the substrate layer 2 In the layer 5, the moisture permeability of the polarizer protective film 1 is controlled to a desired moisture permeability. Therefore, the dimensional change of the base material layer 2 can be further suppressed, and the dimensional change of the base material layer 2 can be further reduced. Therefore, the polarizing plate 11 can reduce variations in the retardation value of the polarizer protective film 1, and can exhibit desired optical characteristics.

Liquid crystal display element 31

The polarizing plate 11 of FIG. 2 of the present invention is adhered to the both surfaces of the liquid crystal cell 32 formed by sandwiching the liquid crystal layer 34 with a transparent dielectric layer 33 (for example, glass) through the adhesive layer 35, thereby constituting the liquid crystal display element of FIG. 31. The polarizer protective film 1 (the base material layer 2, the first control layer 3, the easy-adhesion layer 4, and the second control layer 5) of the present invention is disposed on the outer surface side of the polarizing plate 12 (the direction in which the liquid crystal cell 32 is provided) On the other hand, the polarizer protective film 13 made of the cellulose ester used in the past is disposed on the inner side of the polarizing plate 12 (the side on which the liquid crystal cell 32 is provided). The material of the liquid crystal layer 34, the transparent medium layer 33, and the adhesive layer 35 constituting the liquid crystal cell 32 is not particularly limited, and a conventional material can be used.

The easy-adhesion layer 4 and the polarizing plate 12 of the polarizer protective film 1 of the liquid crystal display element 31 can be reliably bonded by a water-soluble adhesive. Further, the moisture permeability of the polarizer protective film 1 is controlled to a desired moisture permeability by the first control layer 3 and the second control layer 5, so that when the water-soluble adhesive is bonded, it can be reliably made The water-vaporization of the water-soluble binder allows the bonding process to be easily and reliably performed. As a result, the polarizer protective film 1 and the polarizing plate 12 of the liquid crystal display element 31 can be reliably bonded. Further, 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 smaller than that in the case of cellulose triacetate, so that photoelastic effect is less likely to occur. . Therefore, the change in the retardation value of the polarizer protective film 1 is small. In particular, the second control layer 5 is provided on the other surface side of the base material layer 2, and the moisture permeability of the polarizer protective film 1 is controlled to a desired moisture permeability, so that the dimensional change of the base material layer 2 can be further suppressed. The dimensional change of the substrate layer 2 can be further reduced. Therefore, the liquid crystal display element 31 can reduce variations in the retardation value of the polarizer protective film 1, and can exhibit desired optical characteristics. Therefore, the liquid crystal The display element 31 can efficiently use the light of the light source to display it properly.

Other embodiments

Further, the polarizer protective film, the polarizing plate, and the liquid crystal display element of the present invention can be variously modified and improved in addition to the above-described modes. For example, the thickness of the second control layer of the polarizer protective film may be substantially thicker than the thickness of the first control layer. Thus, by making the thickness of the second control layer substantially thicker than the thickness of the first control layer, it is possible to impart a function of preventing curling of the polarizer protective film against a force to curl the inner side of the easy-adhesion layer, thereby preventing it from being prevented. The polarizer protective film as a whole is curled. As a result, the polarizer protective film can improve dimensional stability.

The polarizer protective film may be provided on both faces of the polarizing plate (the inner side and the outer side). Thereby, the stability of the size of the polarizer protective film provided on the surface side and the outer surface side of the inner side of the polarizing plate can be improved. Further, a configuration may be adopted in which the polarizer protective film is provided on the inner surface side of the polarizing plate, and another polarizer protective film is provided on the outer surface side of the polarizing plate.

Further, on the other surface side of the second control layer (the surface side on which the base material layer is not laminated), other layers (anti-glare ( An antireflection layer such as a layer, an antireflection layer, an antiglare layer, or a low refractive index layer, an antistatic layer, a hard coat layer (cured resin layer), an optical compensation layer, or the like). For example, by providing an anti-glare layer (anti-reflection layer) on the other surface side of the second control layer, in addition to the protection function for the polarizing plate, an anti-glare function can be exhibited. Further, by providing a hard coat layer on the other surface side of the second control layer, the protection function for the polarizing plate can be enhanced.

The polarizing plate may be laminated on either side of the liquid crystal cell, and does not necessarily have to be laminated on both surfaces of the liquid crystal cell.

Industrial applicability

As described above, the polarizing plate protective film of the present invention, the polarizing plate using the polarizing plate protective film, and the liquid crystal display element using the polarizing plate can reduce the basis of the polarizing plate protective film due to humidity. The size of the material layer is changed, so that the variation of the retardation value of the polarizer protective film can be suppressed, and the pass can be easily and reliably The water-soluble adhesive adheres to the polarizer protective film and the polarizer, and can be used in various fields ranging from small products such as electronic calculators and clocks to large-scale products such as automotive measuring instruments, PC monitors, and televisions.

1‧‧‧ polarizer protective film

2‧‧‧Substrate layer

3‧‧‧First Control Layer

4‧‧‧Easy adhesive layer

5‧‧‧Second control layer

Claims (12)

A polarizer protective film for bonding a polarizing plate of a liquid crystal display panel, the polarizer protective film comprising: a substrate layer comprising an acrylic resin as a main component; and a first control layer; Laminated on one surface side of the substrate layer for controlling moisture permeability; an easy-adhesion layer laminated on one surface side of the first control layer; and a second control layer laminated on the substrate layer The other side is for controlling moisture permeability, and 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 thickness of the first control layer is substantially the same as the thickness of 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 or more and 5 × 10 -12 / Pa or less. The polarizer protective film according to the first aspect of the invention, wherein the easy-adhesion layer contains a cellulose ester-based resin as a main component. The polarizer protective film according to the fifth aspect of the invention, wherein the cellulose ester-based resin has a number average molecular weight (Mn) of from 40,000 to 100,000. The polarizer protective film according to claim 1, wherein the first control layer and the second control layer contain, as a main component, an acrylic modified polyester resin. The polarizer protective film according to claim 7, wherein the first control layer and the second control layer further contain a polyurethane 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 the first aspect of the invention, wherein the substrate layer has a retardation value (Re) of -15 nm or more and 15 nm or less. A polarizing plate comprising: the polarizer protective film according to any one of claims 1 to 10; and a polarizing plate adhered to the polarizing film protective film by a water-soluble adhesive Floor. A liquid crystal display element comprising a liquid crystal cell and a polarizing plate according to claim 11, wherein the polarizing plate is laminated on one surface side of the liquid crystal cell.