WO2022059518A1

WO2022059518A1 - Method for manufacturing polarizing plate

Info

Publication number: WO2022059518A1
Application number: PCT/JP2021/032415
Authority: WO
Inventors: 慶一白川; 淳古川
Original assignee: 住友化学株式会社
Priority date: 2020-09-15
Filing date: 2021-09-03
Publication date: 2022-03-24
Also published as: JP2022048646A; TW202217372A

Abstract

The purpose of the present invention is to provide a method for manufacturing a one-side-protected polarizing plate in which appearance defects are suppressed. Provided is a method for manufacturing a polarizing plate, the method including: a first step for bonding a protective film on one surface of a polarizing film via a water-based adhesive layer and layering a release film on the other surface of the polarizing film via a volatile liquid; and a second step for drying the water-based adhesive layer by heating, and evaporating the volatile liquid, the maximum height Rz of the release film specified by JIS B0601-2001 on the polarizing-film-side surface being 70 nm or less.

Description

Method for manufacturing polarizing plate

The present invention relates to a method for manufacturing a polarizing plate in which a protective film is bonded to one surface of a polarizing film.

The polarizing plate is widely used as a polarization supply element in a display device such as a liquid crystal display device and as a polarization detection element. The polarizing plate is generally configured by laminating a protective film on a polarizing film using an adhesive.

Along with the market demand for lightening the weight of the polarizing plate thin film, various configurations of the polarizing plate that can realize this have been proposed, and one of the representative examples thereof is a protective film bonded to only one side of the polarizing film. It is a single-sided protective polarizing plate (for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2009-109860

In manufacturing a single-sided protective polarizing plate, a protective film is attached to one surface of the polarizing film via an adhesive layer, and the other surface of the polarizing film to which the protective film is not attached is temporarily protected. Generally, a peelable release film is laminated on the other surface. This release film is peeled off and removed, for example, in the step of attaching the single-sided protective polarizing plate to the liquid crystal cell.

However, the polarizing plate from which the release film has been peeled has a problem that defects such as dents occur on the surface on which the release film is laminated, resulting in poor appearance. An object of the present invention is to provide a method for manufacturing a single-sided protective polarizing plate in which poor appearance is suppressed.

The present invention provides a method for manufacturing a polarizing plate exemplified below and a single-sided protective polarizing plate.
[1] A first step of laminating a protective film on one surface of a polarizing film via a water-based adhesive layer and laminating a release film on the other surface of the polarizing film via a volatile liquid.
A second step of drying the water-based adhesive layer and volatilizing the volatile liquid by heating is included.
The release film is a method for manufacturing a polarizing plate having a maximum height Rz of 70 nm or less specified in JIS B0601-2001 on the surface of the polarizing film side.
[2] The method for manufacturing a polarizing plate according to [1], wherein the release film has a coating layer formed on the surface on the polarizing film side.
[3] The method for producing a polarizing plate according to [2], wherein the thickness of the coating layer of the release film is 30 μm or less.
[4] The method for producing a polarizing plate according to [2] or [3], wherein the coating layer of the release film is made of a cured product of a (meth) acrylic resin.
[5] The method for producing a polarizing plate according to any one of [1] to [4], wherein at least one of the protective film and the release film has a moisture permeability of 400 g / ^m 2.24 hr or more.
[6] The method for producing a polarizing plate according to any one of [1] to [5], wherein the thickness of the water-based adhesive layer is 10 nm or more and 1 μm or less.
[7] The method for producing a polarizing plate according to any one of [1] to [6], wherein the protective film has a thickness of 1 μm or more and 90 μm or less.
[8] The method for producing a polarizing plate according to any one of [1] to [7], wherein the thickness of the polarizing film is 1 μm or more and 40 μm or less.
[9] The method for producing a polarizing plate according to any one of [1] to [8], further comprising a third step of peeling the release film from the polarizing film.
[10] The method for producing a polarizing plate according to [9], wherein in the third step, the peeling force between the polarizing film and the release film is 0.01 N / 25 mm or more and 2.0 N / 25 mm or less. ..
[11] A polarizing film and a protective film bonded to one side of the polarizing film are provided.
The polarizing film is a single-sided protective polarizing plate having a maximum height Rz of 60 nm or less specified in JIS B0601-2001 on the surface opposite to the protective film.
[12] A polarizing film and a protective film bonded to one side of the polarizing film are provided.
The polarizing film has 10 or less dents having a width of 0.5 mm or more and ^2.0 mm or less and a depth of 0.1 μm or more and 1.0 μm or less on the surface opposite to the protective film. Single-sided protective polarizing plate.

According to the present invention, it is possible to manufacture a single-sided protective polarizing plate in which poor appearance is suppressed.

It is a schematic sectional drawing which shows the basic layer structure of a single-sided protection polarizing plate. It is the schematic sectional drawing which shows the other example of the single-sided protection polarizing plate. It is the schematic sectional drawing which shows the other example of the single-sided protection polarizing plate. It is a schematic sectional drawing which shows the layer structure of the double-sided protective polarizing plate which can be obtained by using a single-sided protective polarizing plate. It is a side view which shows typically an example of the manufacturing method of the single-sided protective polarizing plate which concerns on this invention, and the manufacturing apparatus used for it. In the single-sided protective polarizing plate of Example 1, it is an atomic force microscope image of the surface of the polarizing film on the side opposite to the protective film. (A) is a plan view of the surface, and (B) is a three-dimensional shape view of the surface. In the single-sided protective polarizing plate of Comparative Example 1, it is an atomic force microscope image of the surface of the polarizing film on the opposite side of the protective film. (A) is a plan view of the surface, and (B) is a three-dimensional shape view of the surface.

<Manufacturing method of polarizing plate>
The present invention relates to a method for manufacturing a single-sided protective polarizing plate. In the present invention, the "single-sided protective polarizing plate" is a polarizing plate in which a protective film is bonded to only one side of the polarizing film, and this protective film is usually bonded to the polarizing film via an adhesive layer. The basic configuration of the single-sided protective polarizing plate is shown in FIG. Like the single-sided protective polarizing plate 1 shown in FIG. 1, the single-sided protective polarizing plate according to the present invention has a polarizing film 5 and a first protection bonded to one surface of the polarizing film 5 via a first adhesive layer 25. The film 20 is included as a basic configuration.

As will be described in detail later, in the manufacturing method according to the present invention, a protective film (first protective film) is attached to one surface of a polarizing film via a water-based adhesive layer, and volatile on the other surface. It includes a first step of laminating a release film via a liquid and a second step of drying the water-based adhesive layer by heating and volatilizing the volatile liquid. The single-sided protective polarizing plate obtained through these first and second steps is a release film 10 laminated on the other surface of the polarizing film 5, like the single-sided protective polarizing plate 2 with a release film shown in FIG. Further prepare.

The release film 10 is a film that can be peeled off from the polarizing film 5, and is removed by peeling off when necessary (for example, when the single-sided protective polarizing plate is attached to the liquid crystal cell). The single-sided protective polarizing plate 1 is obtained. For example, in order to bond to a liquid crystal cell, the single-sided protective polarizing plate according to the present invention is an adhesive laminated on the other surface of the polarizing film 5 like the single-sided protective polarizing plate 3 with an adhesive layer shown in FIG. The agent layer 30 can be further provided.

Further, the single-sided protective polarizing plate 1 and the single-sided protective polarizing plate 2 with a release film according to the present invention can be suitably used as an intermediate for manufacturing a double-sided protective polarizing plate in which protective films are bonded to both sides of the polarizing film. Yes, with reference to FIG. 4, the double-sided protective polarizing plate 4 is formed by laminating the second protective film 21 on the surface of the polarizing film 5 opposite to the first protective film 20 via the second adhesive layer 26. Can be obtained.

The release film 10 has a maximum height Rz specified in JIS B0601-2001 on the surface of the polarizing film 5 side of 70 nm or less, preferably 50 nm or less, more preferably 30 nm or less, and further preferably 20 nm or less. .. The maximum height Rz can be more than 0 nm and may be 5 nm or more. When the surface roughness of the release film 10 laminated on the polarizing film 5 in the first step is within the above range, the one-sided protective polarizing plate 1 manufactured has the dent on the surface on the polarizing film 5 side suppressed, and the appearance is poor. A suppressed single-sided protective polarizing plate can be obtained. By suppressing the appearance defect of the single-sided protective polarizing plate, it is possible to suppress the deterioration of the yield in the production of the single-sided protective polarizing plate.

Hereinafter, the method for manufacturing the single-sided protective polarizing plate according to the present invention will be described in detail with reference to FIG. 5 by showing an embodiment. The method for producing a single-sided protective polarizing plate according to the present invention is described in the following step:
(1) The first protective film is attached to one surface of the polarizing film via a water-based adhesive layer, and a release film is laminated on the other surface of the polarizing film via a layer made of a volatile liquid. The first step, and (2) the second step of drying the aqueous adhesive layer and volatilizing the volatile liquid by heating.
including.

FIG. 5 is a side view schematically showing an example of a method for manufacturing a single-sided protective polarizing plate according to the present invention and a manufacturing apparatus used for the method. Generally, as shown in FIG. 5, a polarizing plate such as a single-sided protective polarizing plate is continuously unwound and conveyed as a long film by performing treatment in each step. Can be manufactured to. However, the production method of the present invention is not limited to continuous production using such a long film, and may be a method using a single-wafer film.

(1) First Step In this step, first, a roll (rolled product) of a long polarizing film 5, a roll of a long first protective film 20, and a long release film 10 are referred to in FIG. Rolls are prepared, and the film is conveyed while continuously unwinding using an unwinding device (not shown). Each film is conveyed so that its longitudinal direction is the conveying direction. A guide roll 60 for supporting the traveling film is appropriately provided in the film transport path. The arrows in FIG. 5 indicate the transport direction of the film or the rotation direction of various rolls. Normally, the transport direction of the polarizing film 5 (film longitudinal direction), the transport direction of the first protective film 20 (film longitudinal direction), and the transport direction of the release film 10 (film longitudinal direction) are parallel.

In this step, the first protective film 20 is attached to one surface of the polarizing film 5 via the first adhesive layer 25 (not shown in FIG. 5) which is a water-based adhesive layer, and the polarizing film 5 is attached. The release film 10 is laminated on the other surface via a layer made of the volatile liquid 50. In the bonding of the first protective film 20 and the lamination of the release film 10, as shown in FIG. 5, the first protective film 20, the polarizing film 5 and the release film 10 are parallel to each other in the longitudinal direction (conveyance direction). This can be done by pressing the films laminated by the bonding rolls 40, 40 from above and below by passing them between the pair of bonding rolls 40, 40 so as to be stacked.

At this time, the water-based adhesive 55 is injected between the polarizing film 5 and the first protective film 20 by using the

injection devices

80 and 81 before passing between the bonding rolls 40 and 40, and the polarizing film 5 and the polarizing film 5 are injected. By injecting the volatile liquid 50 between the release film 10 and the film, a layer made of the water-based adhesive 55 (first adhesive layer 25) and a layer made of the volatile liquid 50 are interposed between the films. Can be done.

The device for interposing the layer made of the water-based adhesive 55 (first adhesive layer 25) and the layer made of the volatile liquid 50 is limited to the

injection devices

80 and 81 as shown in FIG. Instead, for example, depending on the viscosity of the water-based adhesive 55 and the volatile liquid 50, such as the doctor blade method, the wire bar coating method, the die coating method, the comma coater method, the gravure coating method, the dip coating method, and the casting method. The coating method may be appropriately selected, and the water-based adhesive 55 and the volatile liquid 50 may be applied to the bonded surface of at least one of the films to be overlapped.

In the conventional method for manufacturing a single-sided protective polarizing plate, the release film is directly laminated without interposing a special layer on the polarizing film surface, so that the polarizing film is polarized during the process of manufacturing the single-sided protective polarizing plate. There was a problem that the film was easily broken. When a protective film is attached to one side of a polarizing film via a water-based adhesive layer, a step of drying the water-based adhesive layer is required to obtain a single-sided protective polarizing plate. Was particularly prone to breakage of the polarizing film in this drying step.

On the other hand, according to the production method of the present invention, in which a layer made of a volatile liquid 50 is interposed between the polarizing film 5 and the release film 10 and the release film 10 is laminated on the polarizing film 5, the water-based adhesive 55 Even in the step (second step) of drying the layer (first adhesive layer 25) made of the same, the breakage of the polarizing film 5 can be effectively suppressed. Further, interposing a layer made of the volatile liquid 50 between the polarizing film 5 and the release film 10 also has an effect of suppressing wrinkles on the single-sided protective polarizing plate during the process of manufacturing the single-sided protective polarizing plate. be.

Since the intervening volatile liquid 50 can be volatilized during the step of drying the first adhesive layer 25 (second step), in the production method of the present invention, for volatilizing and removing the volatile liquid 50. No separate process is required.

When the first protective film 20 is bonded to the polarizing film 5, the bonding surface of the polarizing film 5 and / or the first protective film 20 is subjected to plasma treatment, corona treatment, and ultraviolet irradiation treatment in order to improve the adhesiveness. , Frame (flame) treatment, easy adhesion treatment such as Kenning treatment can be performed. Among these, it is preferable to perform plasma treatment, corona treatment or saponification treatment. For example, when the first protective film 20 is made of a cyclic polyolefin resin, the bonded surface of the first protective film 20 can be subjected to plasma treatment or corona treatment. When the first protective film 20 is made of a cellulose ester resin, the bonded surface of the first protective film 20 can be saponified. Examples of the saponification treatment include a method of immersing in an alkaline aqueous solution such as sodium hydroxide or potassium hydroxide.

[Polarizing film]
The polarizing film 5 can be a uniaxially stretched polyvinyl alcohol-based resin film in which a dichroic dye is adsorbed and oriented. As the polyvinyl alcohol-based resin constituting the polyvinyl alcohol-based resin film, a saponified polyvinyl acetate-based resin can be used. Examples of the polyvinyl acetate-based resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and a copolymer of vinyl acetate and another monomer copolymerizable therewith. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth) acrylamides having an ammonium group.

In addition, in this specification, "(meth) acrylic" means at least one selected from acrylic and methacrylic. The same applies to the cases such as "(meth) acryloyl" and "(meth) acrylate".

The degree of saponification of the polyvinyl alcohol-based resin can be in the range of 80.0 to 100.0 mol%, preferably in the range of 90.0 to 99.5 mol%, and more preferably 94.0. It is in the range of 99.0 mol%. When the degree of saponification is less than 80.0 mol%, the water resistance and moisture heat resistance of the obtained single-sided protective polarizing plate are lowered. When a polyvinyl alcohol-based resin having a saponification degree of more than 99.5 mol% is used, the dyeing speed may be slowed down, the productivity may be lowered, and the polarizing film 5 having sufficient polarizing performance may not be obtained.

The degree of saponification is the ratio of the acetic acid group (acetoxy group: -OCOCH ₃ ) contained in the polyvinyl acetate-based resin, which is the raw material of the polyvinyl alcohol-based resin, changed to a hydroxyl group by the saponification step in terms of unit ratio (mol%). It is expressed by the following formula:
Degree of saponification (mol%) = 100 x (number of hydroxyl groups) / (number of hydroxyl groups + number of acetic acid groups)
Defined in. The degree of saponification can be determined in accordance with JIS K 6726 (1994). The higher the degree of saponification, the higher the proportion of hydroxyl groups, and therefore the lower the proportion of acetic acid groups that inhibit crystallization.

The average degree of polymerization of the polyvinyl alcohol-based resin is preferably 100 to 10000, more preferably 1500 to 8000, and further preferably 2000 to 5000. The average degree of polymerization of the polyvinyl alcohol-based resin can also be determined in accordance with JIS K 6726 (1994). If the average degree of polymerization is less than 100, it is difficult to obtain preferable polarization performance, and if it exceeds 10,000, the solubility in a solvent deteriorates, and it becomes difficult to form a polyvinyl alcohol-based resin film.

The polarizing film 5 is a step of uniaxially stretching a polyvinyl alcohol-based resin film; a step of adsorbing a dichroic dye by dyeing the polyvinyl alcohol-based resin film with a dichroic dye; polyvinyl on which a dichroic dye is adsorbed. It can be produced through a step of treating the alcohol-based resin film with an aqueous boric acid solution; and a step of washing with water after the treatment with the aqueous boric acid solution.

The polyvinyl alcohol-based resin film is a film formed from the above-mentioned polyvinyl alcohol-based resin. The film forming method is not particularly limited, and a known method such as a melt extrusion method or a solvent casting method can be adopted. The thickness of the polyvinyl alcohol-based resin film is, for example, about 1 to 150 μm.

The uniaxial stretching of the polyvinyl alcohol-based resin film can be performed before, simultaneously with, or after dyeing the dichroic dye. If the uniaxial stretching is performed after staining, the uniaxial stretching may be performed before the boric acid treatment or during the boric acid treatment. Further, uniaxial stretching may be performed at these a plurality of steps.

In uniaxial stretching, rolls having different peripheral speeds may be uniaxially stretched, or thermal rolls may be used to uniaxially stretch. Further, the uniaxial stretching may be a dry stretching in which stretching is performed in the atmosphere, or a wet stretching in which the polyvinyl alcohol-based resin film is swollen using a solvent. The draw ratio is usually about 3 to 8 times.

As a method of dyeing a polyvinyl alcohol-based resin film with a dichroic dye, for example, a method of immersing the polyvinyl alcohol-based resin film in an aqueous solution (dyeing solution) containing a dichroic dye is adopted. The polyvinyl alcohol-based resin film is preferably subjected to a dipping treatment (swelling treatment) in water before the dyeing treatment.

The dichroic dye contained (adsorption orientation) in the polarizing film 5 can be iodine or a dichroic organic dye. When iodine is used as the dichroic dye, a method of immersing a polyvinyl alcohol-based resin film in an aqueous solution containing iodine and potassium iodide for dyeing is usually adopted. The iodine content in this dyeing aqueous solution is usually about 0.01 to 1 part by weight per 100 parts by weight of water. The content of potassium iodide is usually about 0.5 to 20 parts by weight per 100 parts by weight of water. The temperature of the dyeing aqueous solution is usually about 20 to 40 ° C. The immersion time (staining time) in the dyeing aqueous solution is usually about 20 to 1800 seconds.

On the other hand, when a dichroic organic dye is used as the dichroic dye, a method of immersing a polyvinyl alcohol-based resin film in a dyeing aqueous solution containing a water-soluble dichroic organic dye and dyeing is usually adopted. The content of the dichroic organic dye in the dyeing aqueous solution is usually about 1 × 10 ^-4 to 10 parts by weight per 100 parts by weight of water, preferably about 1 × 10 ^-3 to 1 part by weight. This dyeing aqueous solution may contain an inorganic salt such as sodium sulfate as a dyeing aid. The temperature of the dyeing aqueous solution is usually about 20 to 80 ° C. The immersion time (staining time) in the dyeing aqueous solution is usually about 10 to 1800 seconds.

The boric acid treatment after dyeing with a dichroic dye can be performed by immersing the dyed polyvinyl alcohol-based resin film in a boric acid-containing aqueous solution.

The amount of boric acid in the boric acid-containing aqueous solution is usually about 2 to 15 parts by weight per 100 parts by weight of water, preferably 5 to 12 parts by weight. When iodine is used as the dichroic dye, the boric acid-containing aqueous solution preferably contains potassium iodide. The amount of potassium iodide in the boric acid-containing aqueous solution is usually about 0.1 to 15 parts by weight, preferably about 5 to 12 parts by weight, per 100 parts by weight of water. The immersion time in the boric acid-containing aqueous solution is usually about 60 to 1200 seconds, preferably about 150 to 600 seconds, and more preferably about 200 to 400 seconds. The temperature of the boric acid-containing aqueous solution is usually 50 ° C. or higher, preferably 50 to 85 ° C., more preferably 60 to 80 ° C.

The polyvinyl alcohol-based resin film after the boric acid treatment is usually washed with water. The water washing treatment can be performed, for example, by immersing a boric acid-treated polyvinyl alcohol-based resin film in water. The temperature of water in the washing treatment is usually about 1 to 40 ° C.
The immersion time is usually about 1 to 120 seconds.

After washing with water, a drying treatment is performed to obtain a polarizing film 5. As the drying treatment, there are various methods such as a method of blowing hot air, a method of contacting with a hot roll, and a method of heating with an IR heater, and any of them can be preferably used. The method of contacting with a heat roll to dry is preferable in that the drying time can be shortened because the drying efficiency is improved, and the film can be widened by suppressing shrinkage in the width direction. be. The drying temperature in the drying process means the atmospheric temperature in the drying furnace in the case of a method of blowing hot air or a drying facility provided with a drying furnace such as an IR heater, and is a contact type drying such as a heat roll. In the case of equipment, it means the surface temperature of the heat roll. The temperature of the drying treatment is usually about 30 to 100 ° C, preferably 50 to 80 ° C. The drying treatment time is usually about 60 to 600 seconds, preferably 120 to 600 seconds.

By the drying process, the moisture content of the polarizing film 5 is reduced to a practical level. The water content is usually adjusted to be 5 to 45% by weight, more preferably 8 to 40% by weight. If it is lower than 5% by weight, the flexibility of the polarizing film 5 is lost, and the polarizing film 5 may be damaged or broken after its drying. If it is higher than 45% by weight, the adhesion to the protective film is achieved. Is less likely to occur sufficiently, and problems such as poor appearance and breakage of the film in the line and contaminating the process are likely to occur.

The thickness of the polarizing film 5 is usually about 1 to 40 μm, preferably 2 to 20 μm, and more preferably 2 to 10 μm. The thickness of the polarizing film 5 is preferably thin from the viewpoint of thinning the polarizing plate, but usually, when the thickness of the polarizing film 5 is thin, the appearance defect due to the dent generated in the polarizing film 5 tends to become remarkable. According to the present invention, even when a thin polarizing film is used, it is possible to suppress appearance defects that occur in the polarizing plate.

[First protective film]
The first protective film 20 is a thermoplastic resin, for example, a polyolefin resin such as a chain polyolefin resin (polypoly resin or the like) or a cyclic polyolefin resin (norbornen resin or the like); such as cellulose triacetate or cellulose diacetate. Cellulosic ester resin; polyester resin such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate; polycarbonate resin; (meth) acrylic resin such as polymethyl methacrylate resin; or a mixture thereof, copolymerization It can be a transparent resin film made of an object or the like.

Examples of the chain polyolefin resin include homopolymers of chain olefins such as polyethylene resin and polypropylene resin, and copolymers composed of two or more kinds of chain olefins. More specific examples are polypropylene-based resins (polypropylene resin which is a homopolymer of propylene and copolymers mainly composed of propylene), polyethylene-based resins (polyethylene resin which is a homopolymer of ethylene, and ethylene as a main component). Containing a copolymer).

The cyclic polyolefin resin is a general term for resins polymerized using a cyclic olefin as a polymerization unit, and is described in, for example, JP-A No. 1-240517, JP-A-3-14882, JP-A-3-122137, and the like. The resin used is mentioned. Specific examples of the cyclic polyolefin resin include a ring-opened (co) polymer of a cyclic olefin, an addition polymer of a cyclic olefin, and a copolymer of a cyclic olefin and a chain olefin such as ethylene or propylene (typically). Is a random copolymer), a graft polymer obtained by modifying these with an unsaturated carboxylic acid or a derivative thereof, and a hydride thereof. Among them, a norbornene-based resin using a norbornene-based monomer such as a norbornene or a polycyclic norbornene-based monomer is preferably used as the cyclic olefin.

Cellulose ester resin is an ester of cellulose and fatty acid. Specific examples of the cellulose ester resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. Further, these copolymers or those in which a part of the hydroxyl group is modified with another substituent can also be used. Among these, cellulose triacetate (triacetyl cellulose: TAC) is particularly preferable.

The polyester resin is a resin having an ester bond, and is generally composed of a polyvalent carboxylic acid or a derivative thereof and a polycondensate of the polyhydric alcohol. As the polyvalent carboxylic acid or a derivative thereof, a divalent dicarboxylic acid or a derivative thereof can be used, and examples thereof include terephthalic acid, isophthalic acid, dimethyl terephthalate, and dimethyl naphthalenedicarboxylate. As the polyhydric alcohol, a divalent diol can be used, and examples thereof include ethylene glycol, propanediol, butanediol, neopentyl glycol, cyclohexanedimethanol and the like. Examples of suitable polyester-based resins include polyethylene terephthalate.

Polycarbonate-based resin is an engineering plastic made of a polymer in which a monomer unit is bonded via a carbonate group, and is a resin having high impact resistance, heat resistance, flame retardancy, and transparency. The polycarbonate-based resin may be a resin called modified polycarbonate having a polymer skeleton modified in order to lower the photoelastic coefficient, or a copolymerized polycarbonate having improved wavelength dependence.

The (meth) acrylic resin is a resin containing a compound having a (meth) acryloyl group as a main constituent monomer. Specific examples of the (meth) acrylic resin include poly (meth) acrylic acid esters such as polymethyl methacrylate; methyl methacrylate- (meth) acrylic acid copolymers; methyl methacrylate- (meth) acrylic acid. Ester copolymer; Methyl methacrylate-acrylic acid ester- (meth) acrylic acid copolymer; (meth) methyl acrylate-styrene copolymer (MS resin, etc.); Methyl methacrylate and alicyclic hydrocarbon group It contains a copolymer with a compound having (for example, a methyl methacrylate-cyclohexyl methacrylate copolymer, a methyl methacrylate- (meth) acrylate norbornyl copolymer, etc.). A polymer containing a poly (meth) acrylic acid C _1-6 alkyl ester as a main component, such as methyl poly (meth) acrylate, is preferably used, and more preferably, a polymer containing methyl methacrylate as a main component (50 to 100) is used. A methyl methacrylate-based resin having a weight of% by weight, preferably 70 to 100% by weight) is used.

The first protective film 20 can also be a protective film having an optical function such as a retardation film and a luminance improving film. For example, a retardation film to which an arbitrary retardation value is imparted by stretching a transparent resin film made of the above material (uniaxial stretching or biaxial stretching, etc.) or forming a liquid crystal layer or the like on the film. Can be.

A surface treatment layer (coating layer) such as a hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer, and an antifouling layer is formed on the surface of the first protective film 20 on the side opposite to the polarizing film 5. You can also do it. The method for forming the surface treatment layer on the surface of the protective film is not particularly limited, and a known method can be used.

The thickness of the first protective film 20 is preferably 1 to 90 μm or less, more preferably 1 to 60 μm, and further preferably 1 to 50 μm.

It is preferable that at least one of the first protective film and the release film described later has a moisture permeability of 400 g / ^m 2.24 hr or more. The moisture permeability of the first protective film 20 is preferably 400 g / ^m 2.24 hr or more, and more preferably 420 g / ^m 2.24 hr or more. When the moisture permeability is in this range, the layer made of the water-based adhesive 55 can be efficiently dried in the subsequent second step, so that the productivity can be improved. When the moisture permeability of the release film is 400 g / ^m 2.24 hr or more, the first protective film may have a moisture permeability of less than 400 g / ^m 2.24 hr or less and 100 g / ^m 2.24 hr or less. It's okay.

[Water-based adhesive]
The water-based adhesive 55 forming the first adhesive layer 25 is one in which the adhesive component is dissolved in water or one in which the adhesive component is dispersed in water. The water-based adhesive preferably used is, for example, an adhesive composition using a polyvinyl alcohol-based resin or a urethane resin as a main component. The thickness of the first adhesive layer 25 formed from the water-based adhesive is usually 10 nm to 1 μm or less.

When a polyvinyl alcohol-based resin is used as the main component of the adhesive, the polyvinyl alcohol-based resin includes partially saponified polyvinyl alcohol, fully saponified polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, acetacetyl group-modified polyvinyl alcohol, and methylol group. It may be a modified polyvinyl alcohol-based resin such as modified polyvinyl alcohol and amino group-modified polyvinyl alcohol. The polyvinyl alcohol-based resin is a vinyl alcohol homopolymer obtained by saponifying polyvinyl acetate, which is a homopolymer of vinyl acetate, as well as the co-weight of vinyl acetate and other monomers copolymerizable therewith. It may be a polyvinyl alcohol-based copolymer obtained by saponifying the coalescence.

A water-based adhesive containing a polyvinyl alcohol-based resin as an adhesive component is usually an aqueous solution of a polyvinyl alcohol-based resin. The concentration of the polyvinyl alcohol-based resin in the adhesive is usually 1 to 10 parts by weight, preferably 1 to 5 parts by weight, based on 100 parts by weight of water.

Adhesives consisting of an aqueous solution of polyvinyl alcohol-based resin include curable components such as polyhydric aldehydes, melamine-based compounds, zirconia compounds, zinc compounds, glioxal, and water-soluble epoxy resins, and cross-linking agents in order to improve adhesiveness. Is preferably added. The water-soluble epoxy resin is a polyamide polyamine epoxy resin obtained by reacting a polyamide amine obtained by reacting a polyalkylene polyamine such as diethylenetriamine or triethylenetetramine with a dicarboxylic acid such as adipic acid with epichlorohydrin. Can be preferably used. Commercially available products of such polyamide polyamine epoxy resin include "Smiley's Resin 650" (manufactured by Taoka Chemical Industry Co., Ltd.), "Smiley's Resin 675" (manufactured by Taoka Chemical Industry Co., Ltd.), and "WS-525" (Japan PMC Co., Ltd.). (Made by company), etc. The amount of the curable component and the cross-linking agent added (the total amount when both the curable component and the cross-linking agent are added) is usually 1 to 100 parts by weight, preferably 1 to 100 parts by weight, based on 100 parts by weight of the polyvinyl alcohol-based resin. 1 to 50 parts by weight. When the amount of the curable component or the cross-linking agent added is less than 1 part by weight with respect to 100 parts by weight of the polyvinyl alcohol-based resin, the effect of improving the adhesiveness tends to be small, and the curable component or the above-mentioned curable component or When the amount of the cross-linking agent added exceeds 100 parts by weight with respect to 100 parts by weight of the polyvinyl alcohol-based resin, the adhesive layer tends to be brittle.

When a urethane resin is used as the main component of the adhesive, a mixture of a polyester ionomer type urethane resin and a compound having a glycidyloxy group can be mentioned as an example of an appropriate adhesive composition. The polyester-based ionomer type urethane resin is a urethane resin having a polyester skeleton, in which a small amount of an ionic component (hydrophilic component) is introduced. Such an ionomer type urethane resin is suitable as a water-based adhesive because it is directly emulsified in water to form an emulsion without using an emulsifier.

[Release film]
The release film 10 is a film that can be peeled off at a desired timing after being laminated on the polarizing film 5. “Peelable” means that the polarizing film 5 and the peeling film 10 can be separated without damaging or damaging the polarizing film 5 and the peeling film 10.

In view of handleability, transparency, low cost and the like, the release film 10 is, for example, a chain polyolefin resin such as a polyethylene resin or a polypropylene resin; a cellulose ester resin such as a cellulose triacetate or a cellulose diacetate; a polyethylene. It can be a transparent resin film made of a polyester resin such as terephthalate, polyethylene naphthalate, polybutylene terephthalate; a (meth) acrylic resin such as a polymethyl methacrylate resin, a mixture thereof, a copolymer or the like. .. A film obtained by molding one or more of these into a single layer or a multilayer can also be used as the release film 10. Above all, a film made of polyethylene terephthalate, cellulose triacetate, and a polymethyl methacrylate resin can be preferably used.

The peeling force between the polarizing film 5 and the release film 10 is, for example, 0.01 N / 25 mm to 2.0 N / 25 mm, preferably 0.01 N / 25 mm to 0.5 N / 25 mm. When the peeling force is 0.01 N / 25 mm or more, partial peeling of the polarizing film 5 and the peeling film 10 can be prevented. When the peeling force is 2.0 N / 25 mm or less, the peeling film 10 is easily peeled from the polarizing film 5 in the third step described later.

For the above peeling force, a single-sided protective polarizing plate on which the peeling film 10 was laminated was cut to a width of 25 mm to obtain a measurement sample, and a precision universal testing machine "Autograph AGS-50NX" manufactured by Shimadzu Corporation was used. It is obtained by grasping the release film 10 of the measurement sample and the single-sided protective polarizing plate and measuring the force when the release film 10 is peeled off in the 180 ° direction. The peeling force is measured in an environment where the peeling speed is 300 mm / min, the temperature is 23 ± 2 ° C., and the relative humidity is 50 ± 5%.

The thickness of the release film 10 is, for example, about 5 to 100 μm, preferably about 10 to 80 μm, and more preferably about 10 to 60 μm.

The moisture permeability of the release film 10 is preferably 400 g / ^m 2.24 hr or more, more preferably 420 g / ^m 2.24 hr or more, still more preferably 450 g / ^m 2.24 hr or more, still more preferably 500 g / ^m 2.24 hr or more. That is all. When the moisture permeability is within this range, the volatile liquid 50 can be efficiently volatilized and removed in the second step later, so that quality defects such as deterioration of optical characteristics and poor appearance due to poor drying can be prevented. Can be done.

The release film 10 preferably has a shrinkage rate (heat shrinkage rate) of 0.15% or less, more preferably 0.1% or less, when heated at 80 ° C. for 5 minutes. If the heat shrinkage rate of the release film 10 is large, wrinkles are likely to occur on the release film 10 in the heat treatment in the second step, and accordingly, wrinkles are likely to occur on the single-sided protective polarizing plate. Examples of the resin material whose heat shrinkage rate is within the above range include polyethylene terephthalate, cellulose triacetate, and polymethyl methacrylate-based resin. "The heat shrinkage rate is 0.15% or less" means that both the MD shrinkage rate and the TD shrinkage rate are 0.15% or less.

When the contact angle of the surface of the release film 10 on the side surface of the polarizing film 5 with respect to the volatile liquid 50 is 50 to 80 °, preferably 50 to 75 °, the peeling force between the polarizing film 5 and the release film 10 is within the above range. It is advantageous in that the release film 10 can be relatively easily peeled off by making the inside appropriate. For the same reason, the contact angle of the surface of the polarizing film 5 on the side of the release film 10 with respect to the volatile liquid 50 is preferably 50 to 110 °, more preferably 50 to 100 °. The contact angle can be measured by, for example, the following method. With the measurement target surface (the surface on the release film side of the polarizing film or the surface on the polarizing film side of the release film) on the outside, the polarizing film or the release film is attached to a glass substrate with an adhesive to prepare a measurement sample. Set the measurement sample horizontally on a contact angle meter (image processing type contact angle meter manufactured by Kyowa Interface Science Co., Ltd .: FACE CA-X type) so that the surface to be measured faces the top surface, and 1 microliter on the surface to be measured. Drop the volatile liquid and measure the contact angle with respect to the volatile liquid.

The release film 10 may have a coating layer formed on the surface of the polarizing film 5 side. By forming the coating layer on the surface of the release film 10, it is possible to easily obtain a release film having a small surface roughness. Since minute foreign substances (additives, film scraps, etc.) caused by the release film tend to adhere to the surface of the release film, it may cause dents on the surface of the polarizing film. It is possible to suppress the dent on the surface of the polarizing film. Further, the release film 10 on which the coating layer is formed has a good release force with the polarizing film 5, and the release force is, for example, 0.01 N / 25 mm to 2.0 N / 25 mm, preferably 0. It is 05N / 25mm to 0.5N / 25mm.
The coating layer may be formed on both sides of the release film.

The coating layer is, for example, a cured layer of an ultraviolet curable resin. Examples of the ultraviolet curable resin include (meth) acrylic resin, silicone resin, polyester resin, urethane resin, amide resin, epoxy resin and the like. The coating layer may contain additives to improve hardness. Additives are not limited, and examples thereof include inorganic fine particles, organic fine particles, or mixtures thereof.

The thickness of the coating layer of the release film is preferably 1 μm or more and 30 μm or less, more preferably 1 μm or more and 20 μm or less, and further preferably 1 μm or more and 15 μm or less. When the thickness of the coating layer is 1 μm or more, it is easy to suppress the dent on the surface of the polarizing film caused by the foreign matter of the release film. If the coating layer is too thick, the moisture permeability tends to decrease. Therefore, from the viewpoint of obtaining a release film having good moisture permeability, the thickness of the coating layer is preferably 30 μm or less.

[Volatile liquid]
The volatile liquid 50 interposed between the polarizing film 5 and the release film 10 is a liquid that can be volatilized by the heat treatment in the second step, and is preferably a liquid that does not adversely affect the polarizing film 5. An antistatic agent may be added as long as it does not have an adverse effect. Examples of the volatile liquid 50 that can be used in the present invention include water and a mixture of water and a hydrophilic liquid. The hydrophilic liquid preferably does not remain after the heat treatment in the second step, for example, methanol, ethanol, 1-butanol, tetrohydrofuran, acetone, acetonitrile, N, N-dimethylformamide, dimethyl sulfoxide, etc. Formic acid, acetic acid and the like can be mentioned.

(2) Second Step This step is a step of drying the first adhesive layer 25, which is a water-based adhesive layer, and volatilizing and removing the volatile liquid 50 by heating. By this heat treatment, the release film 10 is directly laminated on the surface of the polarizing film 5 with an appropriate adhesive force.

With reference to FIG. 5, the heat treatment is performed by introducing a laminated film composed of a first protective film 20, a polarizing film 5, and a release film 10 that has passed between the bonding rolls 40 and 40 into the drying device 70. be able to. As a result, the single-sided protective polarizing plate 2 with a release film can be obtained. The drying device 70 is not particularly limited, and a hot air dryer, a far-infrared heater, or the like can be used.

The drying temperature is preferably 30 to 90 ° C. When the temperature is lower than 30 ° C., the first protective film 20 tends to be easily peeled from the polarizing film 5 in the obtained single-sided protective polarizing plate 2 with a release film. If the drying temperature exceeds 90 ° C., the polarization performance of the polarizing film 5 may deteriorate due to heat. The drying time can be about 10 to 1000 seconds, preferably 60 to 750 seconds, and more preferably 150 to 600 seconds from the viewpoint of productivity.

(3) Other Steps After the second step, curing may be performed at a temperature of room temperature or higher for at least half a day, usually several days or longer, to obtain sufficient adhesive strength. Such curing is typically performed in a rolled state. The preferred curing temperature is in the range of 30 to 50 ° C, more preferably 35 to 45 ° C. When the curing temperature exceeds 50 ° C., so-called “rolling tightness” is likely to occur in the roll winding state. The humidity at the time of curing is not particularly limited, but is preferably selected so that the relative humidity is in the range of about 0 to 70% RH. The curing time is usually about 1 to 10 days, preferably about 2 to 7 days.

After the second step, the release film 10 is peeled off and removed from the polarizing film 5 of the single-sided protective polarizing plate 2 with the release film, and the pressure-sensitive adhesive layer 30 is formed on the surface of the polarizing film 5 on which the release film 10 is laminated. It is also possible to provide a single-sided protective polarizing plate 3 with an adhesive layer shown in FIG. 3 by providing a fourth step of laminating. The pressure-sensitive adhesive layer 30 can be used to attach the single-sided protective polarizing plate to the liquid crystal cell.

As the pressure-sensitive adhesive used for the pressure-sensitive adhesive layer 30, a conventionally known appropriate pressure-sensitive adhesive can be used, for example, (meth) acrylic pressure-sensitive adhesive, urethane-based pressure-sensitive adhesive, silicone-based pressure-sensitive adhesive, polyester-based pressure-sensitive adhesive, and polyamide. Examples thereof include system adhesives, polyether adhesives, fluorine adhesives, rubber adhesives and the like. Among them, a (meth) acrylic pressure-sensitive adhesive is preferably used from the viewpoints of transparency, adhesive strength, reliability, reworkability and the like. The pressure-sensitive adhesive layer 30 can be provided by a method in which a pressure-sensitive adhesive is used, for example, in the form of an organic solvent solution, the pressure-sensitive adhesive is applied onto the polarizing film 5 with a die coater, a gravure coater, or the like, and the pressure-sensitive adhesive is dried. It can also be provided by a method of transferring the sheet-like adhesive formed on the plastic film (called a separate film) to which the above-mentioned material has been applied to the polarizing film 5. Regardless of which method is used, it is preferable that the separate film is attached to the surface of the pressure-sensitive adhesive layer 30. The thickness of the pressure-sensitive adhesive layer 30 can be, for example, 2 to 40 μm.

Alternatively, instead of providing the fourth step, the double-sided protective polarizing plate is formed by bonding the second protective film 21 to the surface of the polarizing film 5 on which the release film 10 is laminated via the second adhesive layer 26. You can also get 4. The second adhesive layer 26 may be a water-based adhesive layer like the first adhesive layer 25, or may be a layer made of another adhesive. Examples of other adhesives include active energy ray-curable adhesives that can be cured by irradiation with active energy rays such as ultraviolet rays, visible light, electron beams, and X-rays. In this case, the second adhesive layer 26 is a cured product layer of the adhesive.

The second protective film 21 can also be a protective film having an optical function such as a retardation film and a luminance improving film. The double-sided protective polarizing plate 4 can be attached to the liquid crystal cell by using the pressure-sensitive adhesive layer 30 laminated on the outer surface of the first protective film 20 or the second protective film 21.

Among them, as the adhesive forming the second adhesive layer 26, an active energy ray-curable adhesive containing an epoxy-based compound that is cured by cationic polymerization as a curable component can be more preferably used, and more preferably such an epoxy. It is an ultraviolet curable adhesive containing a system compound as a curable component. The epoxy compound referred to here means a compound having an average of one or more, preferably two or more epoxy groups in the molecule. Only one type of epoxy compound may be used alone, or two or more types may be used in combination.

An example of an epoxy-based compound that can be preferably used is a hydride-based epoxy compound (fat) obtained by reacting an alicyclic polyol obtained by hydrogenating the aromatic ring of an aromatic polyol with epichlorohydrin. Glycidyl ether of a polyol having a cyclic ring); an aliphatic epoxy compound such as an aliphatic polyhydric alcohol or a polyglycidyl ether of an alkylene oxide adduct thereof; one epoxy group bonded to the alicyclic ring in the molecule. It contains an alicyclic epoxy compound which is an epoxy compound having the above.

The active energy ray-curable adhesive may further contain a radically polymerizable (meth) acrylic compound as a curable component. The (meth) acrylic compound is a (meth) acrylate monomer having at least one (meth) acryloyloxy group in the molecule; obtained by reacting two or more kinds of functional group-containing compounds, and at least two in the molecule. Examples thereof include (meth) acryloyloxy group-containing compounds such as (meth) acrylate oligomers having a (meth) acryloyloxy group.

When the active energy ray-curable adhesive contains an epoxy compound that is cured by cationic polymerization as a curable component, it is preferable to contain a photocationic polymerization initiator. Examples of the photocationic polymerization initiator include aromatic diazonium salts; onium salts such as aromatic iodonium salts and aromatic sulfonium salts; and iron-allene complexes. When the active energy ray-curable adhesive contains a radically polymerizable curable component such as a (meth) acrylic compound, it is preferable to contain a photoradical polymerization initiator. Examples of the photoradical polymerization initiator include an acetophenone-based initiator, a benzophenone-based initiator, a benzoin ether-based initiator, a thioxanthone-based initiator, xanthone, fluorenone, camphorquinone, benzaldehyde, anthraquinone and the like.

When using an active energy ray-curable adhesive, a curing step is carried out to cure the adhesive layer composed of the active energy ray-curable adhesive. The adhesive layer can be cured by irradiating it with active energy rays. The active energy ray is preferably ultraviolet light.

The light source of the active energy ray is not particularly limited, but an active energy ray having a emission distribution having a wavelength of 400 nm or less is preferable, and specifically, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a chemical lamp, and a black light lamp. , Microwave-excited mercury lamp, metal halide lamp and the like are preferably used.

The intensity of irradiation with active energy rays on the adhesive layer made of the active energy ray-curable adhesive is appropriately determined by the composition of the adhesive, but the irradiation intensity in the wavelength region effective for activating the polymerization initiator is 0.1. It is preferably set to be ~ 6000 mW / cm ² . When the irradiation intensity is 0.1 mW / cm ² or more, the reaction time does not become too long, and when it is 6000 mW / cm ² or less, the heat radiated from the light source and the heat generated when the adhesive is cured causes the adhesive layer to grow. There is little risk of yellowing or deterioration of the polarizing film 5.

The irradiation time of the active energy rays is also appropriately determined by the composition of the adhesive, but the integrated light amount expressed as the product of the irradiation intensity and the irradiation time shall be set to be 10 to 10000 mJ / cm ² . Is preferable. When the integrated light amount is 10 mJ / cm ² or more, a sufficient amount of the active species derived from the polymerization initiator can be generated and the curing reaction can proceed more reliably. When the integrated light amount is 10000 mJ / cm ² or less, the irradiation time is long. It does not become too much and can maintain good productivity.

Regarding the material and composition of the second protective film 21, the content described for the first protective film 20 is quoted. The first protective film 20 and the second protective film 21 may be the same type of film or different types of films.

<Single-sided protective polarizing plate>
The single-sided protective polarizing plate 1 according to an embodiment of the present invention includes a polarizing film 5 and a protective film 20 bonded to one side of the polarizing film 5. The polarizing film 5 has a maximum height Rz specified in JIS B0601-2001 on the surface opposite to the protective film 20 of 60 nm or less, preferably 50 nm or less, more preferably 30 nm or less, still more preferably 20 nm. It is as follows. The maximum height Rz can be more than 0 nm and may be 5 nm or more. Such a single-sided protective polarizing plate suppresses poor appearance. The single-sided protective polarizing plate can be manufactured according to the above-mentioned manufacturing method of the polarizing plate.

The single-sided protective polarizing plate 1 according to an embodiment of the present invention includes a polarizing film 5 and a protective film 20 bonded to one side of the polarizing film 5. The polarizing film 5 has 10 dents / m ² or less having a width of 0.5 mm or more and 2.0 mm or less and a depth of 0.1 μm or more and 1.0 μm or less on the surface opposite to the protective film 20. More preferably, it is 5 pieces / m ² or less. The density of the dents can be more than 0 pieces / m ² and may be 1 piece / m ² or more. Such a single-sided protective polarizing plate suppresses poor appearance. The single-sided protective polarizing plate can be manufactured according to the above-mentioned manufacturing method of the polarizing plate. The width of the dent is the maximum value of the length of the polarizing film in the plane direction. The depth of the dent is the maximum value of the depth from the surface of the polarizing film (the length in the direction perpendicular to the polarizing film).

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto. Moisture permeability, thickness, peeling force and surface roughness in the examples were measured according to the following methods.

(1) Moisture Permeability of Protective Film and Release Film The moisture permeability (g / m ^2.24hr ) at 40 ° C. was measured in accordance with JIS Z0208-1976.

(2) Layer thickness The film thickness was measured using a contact-type film thickness measuring device (manufactured by Nikon Corporation: MS-5C). The thickness of the adhesive layer was measured using a laser microscope (manufactured by Olympus Corporation: OLS3000).

(3) Peeling force between the polarizing film and the release film The peeling force is obtained by cutting a single-sided protective polarizing plate on which the release film is laminated to a width of 25 mm to obtain a measurement sample, and a precision universal test manufactured by Shimadzu Corporation. It was obtained by grasping the release film of the measurement sample and the single-sided protective polarizing plate using the machine "Autograph AGS-50NX" and measuring the force when peeling in the 180 ° direction. The peeling force was measured in an environment with a peeling speed of 300 mm / min, a temperature of 23 ± 2 ° C., and a relative humidity of 50 ± 5%.

(4) Surface Roughness The surface roughness of the polarizing film and the release film (maximum height Rz specified in JIS B0601-2001) is determined by using an atomic force microscope (AFM, manufactured by Shimadzu Corporation: SPM-9700HT). It was measured.

(5) Measurement of unevenness on the surface of the polarizing film Using an optical microscope (manufactured by KEYENCE CORPORATION: model number VHX-6000), the width of the surface of the polarizing film is 0.5 mm to 2.0 mm and the depth is 0.1 μm to 1. The number of dents of 0 μm was measured.

<Example 1>
(A) Preparation of polarizing film A polyvinyl alcohol film having an average degree of polymerization of about 2400, a degree of polymerization of 99.9 mol% or more and a thickness of 20 μm was uniaxially stretched about 4 times by a dry method, and 40 while maintaining a tense state. After soaking in pure water at ° C. for 1 minute, it was immersed in an aqueous solution having a weight ratio of iodine / potassium iodide / water of 0.1 / 5/100 at 28 ° C. for 60 seconds. Then, it was immersed in an aqueous solution having a weight ratio of potassium iodide / boric acid / water of 10.5 / 7.5 / 100 at 68 ° C. for 300 seconds. Subsequently, the film was washed with pure water at 5 ° C. for 5 seconds and then dried at 70 ° C. for 180 seconds to obtain a polarizing film in which iodine was adsorbed and oriented on a uniaxially stretched polyvinyl alcohol film. The thickness of the polarizing film was 8 μm. The contact angle of the release film side surface of the polarizing film was 50 °.

(B) Preparation of water-based adhesive Polyvinyl alcohol powder (trade name "KL-318" manufactured by Kuraray Co., Ltd., average degree of polymerization of 1800) is dissolved in hot water at 95 ° C. to prepare a polyvinyl alcohol aqueous solution having a concentration of 3% by weight. did. A cross-linking agent (trade name "Smiley's Resin 650" manufactured by Taoka Chemical Industry Co., Ltd.) was mixed with the obtained aqueous solution at a ratio of 1 part by weight to 2 parts by weight of polyvinyl alcohol powder to obtain a water-based adhesive.

(C) Protective film As the protective film, a cyclic polyolefin resin (COP) film having a thickness of 27 μm was used. The moisture permeability of the protective film was 5.5 g / ^m 2.24 hr.

(D) Release film As the release film, a film (HC-TAC) having a coating layer made of a methacrylic resin cured product having a thickness of 4 μm on a triacetyl cellol (TAC) film having a thickness of 42 μm was used. The moisture permeability of the release film was 540 g / ^m 2.24 hr. The contact angle of the surface on the polarizing film side of the release film was 70 °.

(E) Preparation of Single-sided Protective Polarizing Plate with Release Film and Single-sided Protective Platelet A single-sided protective polarizing plate with a release film was produced by the following procedure using the same apparatus as the polarizing plate manufacturing apparatus shown in FIG. The polarizing film obtained in (A) above was continuously conveyed, the protective film was continuously unwound from the roll of the protective film, and the release film was continuously unwound from the roll of the release film. Next, the water-based adhesive obtained in (B) above is injected between the polarizing film and the protective film, and pure water is injected between the polarizing film and the release film, and between the bonding rolls 40 and 40. It was passed through to form a laminated film composed of a protective film / water-based adhesive layer / polarizing film / pure water / release film (first step). Subsequently, the laminated film is conveyed and passed through a drying device 70 to be heat-treated at 80 ° C. for 300 seconds to dry the water-based adhesive layer and volatilize and remove the pure water interposed between the polarizing film and the release film. Then, a single-sided protective polarizing plate with a release film was obtained (second step). The thickness of the water-based adhesive layer was 75 nm. The release film was peeled off from the polarizing film to obtain a single-sided protective polarizing plate (third step).

During the manufacture of the single-sided protective polarizing plate with a release film, the polarizing film was not broken and the polarizing plate was not wrinkled. Table 1 shows the measurement results of the thickness, peeling force and surface roughness of the polarizing film, the protective film and the peeling film used for producing the polarizing plate of Example 1.

<Comparative Example 1 and Comparative Example 2>
The single-sided protective polarizing plates of Comparative Example 1 and Comparative Example 2 were produced by the same method as in Example 1 except that the type of the release film was changed. In Comparative Example 1, a TAC film having a thickness of 60 μm without a coating layer was used as a release film. In Comparative Example 2, a TAC film having a thickness of 25 μm without a coating layer was used as a release film. Table 1 shows the measurement results of the thickness, peeling force and surface roughness of the protective film and the release film. The contact angle of the surface on the polarizing film side in the release film used in Comparative Example 1 was 65 °. The contact angle of the surface on the polarizing film side in the release film used in Comparative Example 2 was 65 °.

For the manufactured single-sided protective polarizing plate, the maximum height of the surface of the polarizing film on the opposite side of the protective film and the dent on the surface of the polarizing film were measured. The results are shown in Table 1.

The single-sided protective polarizing plate manufactured in Example 1 had suppressed dents on the surface of the polarizing film on the opposite side of the protective film as compared with the single-sided protective polarizing plates of Comparative Example 1 and Comparative Example 2. 6 and 7 show images of the single-sided protective polarizing plate of Example 1 and Comparative Example 1 in which the surface from which the release film was peeled off was observed with an atomic force microscope (manufactured by Shimadzu Corporation: SPM-9700HT), respectively.

<Reference example 1>
The single-sided protective polarizing plate of Reference Example 1 was produced by the same method as in Example 1 except that the type of the release film was changed. In Reference Example 1, a polymethylmethacrylate resin (PMMA) film having a thickness of 60 μm without a coating layer was used as a release film. The moisture permeability of the release film was 60 g / ^m 2.24 hr.

The single-sided protective polarizing plate manufactured in Example 1 had better optical characteristics than the single-sided protective polarizing plate of Reference Example 1. That is, the single-sided protective polarizing plate manufactured in Example 1 had a higher degree of polarization when compared with the single-sided protective polarizing plate of Reference Example 1 at the same transmittance. It is presumed that the release film of Example 1 had a higher moisture permeability than the release film of Reference Example 1.

1 Single-sided protective polarizing plate, 2 Single-sided protective polarizing plate with release film, 3 Single-sided protective polarizing plate with adhesive layer, 4 Double-sided protective polarizing plate, 5 Polarizing film, 10 Release film, 20 First protective film, 21 Second protective film , 25 1st adhesive layer, 26 2nd adhesive layer, 30 adhesive layer, 40 bonding roll, 50 volatile liquid, 55 water-based adhesive, 60 guide roll, 70 drying device, 80, 81 injection device.

Claims

The first step of laminating a protective film on one surface of the polarizing film via a water-based adhesive layer and laminating a release film on the other surface of the polarizing film via a volatile liquid.
A second step of drying the water-based adhesive layer and volatilizing the volatile liquid by heating is included.
The release film is a method for manufacturing a polarizing plate having a maximum height Rz of 70 nm or less specified in JIS B0601-2001 on the surface of the polarizing film side.
The method for manufacturing a polarizing plate according to claim 1, wherein the release film has a coating layer formed on the surface on the polarizing film side.
The method for manufacturing a polarizing plate according to claim 2, wherein the thickness of the coating layer of the release film is 30 μm or less.
The method for producing a polarizing plate according to claim 2 or 3, wherein the coating layer of the release film is made of a cured product of a (meth) acrylic resin.
The method for producing a polarizing plate according to any one of claims 1 to 4, wherein at least one of the protective film and the release film has a moisture permeability of 400 g / m 2.24 hr or more.
The method for producing a polarizing plate according to any one of claims 1 to 5, wherein the thickness of the water-based adhesive layer is 10 nm or more and 1 μm or less.
The method for manufacturing a polarizing plate according to any one of claims 1 to 6, wherein the thickness of the protective film is 1 μm or more and 90 μm or less.
The method for manufacturing a polarizing plate according to any one of claims 1 to 7, wherein the thickness of the polarizing film is 1 μm or more and 40 μm or less.
The method for manufacturing a polarizing plate according to any one of claims 1 to 8, further comprising a third step of peeling the release film from the polarizing film.
The method for manufacturing a polarizing plate according to claim 9, wherein in the third step, the peeling force between the polarizing film and the peeling film is 0.01 N / 25 mm or more and 2.0 N / 25 mm or less.
It has a polarizing film and a protective film bonded to one side of the polarizing film.
The polarizing film is a single-sided protective polarizing plate having a maximum height Rz of 60 nm or less specified in JIS B0601-2001 on the surface opposite to the protective film.
It has a polarizing film and a protective film bonded to one side of the polarizing film.
The polarizing film has 10 or less dents having a width of 0.5 mm or more and 2.0 mm or less and a depth of 0.1 μm or more and 1.0 μm or less on the surface opposite to the protective film. Single-sided protective polarizing plate.