TW202217372A - Method for manufacturing polarizing plate - Google Patents

Abstract

An object of the present invention is to provide a method for manufacturing single-sided protective polarizing plate in which poor appearance is suppressed. The present invention provides a method for manufacturing polarizing plate which comprises: a first step of laminating a protective film on one surface of a polarizing film via an aqueous adhesive layer and laminating a release film on the other surface of the polarizing film via a volatile liquid; and a second step of drying the aqueous adhesive layer and volatilizing the volatile liquid by heating; wherein the release film has a maximum height Rz of 70 nm or less specified in JIS B0601-2001 on the surface of the polarizing film side.

Description

Manufacturing method of polarizing plate

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

Polarizing plates are widely used as polarized light supply elements or polarized light detection elements in display devices such as liquid crystal display devices. Regarding the configuration of the polarizing plate, generally, a protective film is bonded to the polarizing film using an adhesive.

With the market demand for lightweight polarizer films, various configurations of polarizers that can achieve the lightweight have been proposed. One of the representative examples is a single-sided protective polarizer with a protective film attached to only one side of the polarizer film ( For example, Patent Document 1).

[Prior Art Literature]

[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2009-109860

When manufacturing a single-sided protective polarizer, a protective film is attached to one side of the polarizing film via an adhesive layer, and in order to temporarily protect the other side of the polarizing film that is not attached to the protective film, a layer that can Peel off the release film. The peeling film is peeled and removed, for example, in the step of bonding the single-sided protective polarizing plate to the liquid crystal cell.

However, in the polarizing plate after peeling off the peeling film, there is a problem that defects such as dents are generated on the surface on which the peeling film is originally laminated, and poor appearance occurs. The objective of this invention is to provide the manufacturing method of the single-sided protective polarizing plate which suppresses an external appearance defect.

This invention provides the manufacturing method of the polarizing plate illustrated below, and a single-sided protective polarizing plate.

[1] A method for manufacturing a polarizing plate, comprising:

The first step is to stick a protective film on one side of the polarizing film through a water-based adhesive layer, and laminate a release film on the other side of the polarizing film through a volatile liquid; and

The second step is to dry the water-based adhesive layer by heating, and to volatilize the volatile liquid;

However, the maximum height Rz specified in JIS B0601-2001 of the polarizing film side surface of the peeling film is 70 nm or less.

[2] The method for producing a polarizing plate according to [1], wherein the peeling film has a coating layer formed on the side surface of the polarizing film.

[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 formed 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 the moisture permeability of at least one of the protective film and the release film is 400 g/m ² ·24hr or more.

[6] The method for producing a polarizing plate according to any one of [1] to [5], wherein the water-based adhesive layer has a thickness of 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 single-sided protective polarizing plate, comprising: a polarizing film, and a protective film attached to one side of the polarizing film;

However, the maximum height Rz specified in JIS B0601-2001 of the surface of the polarizing film on the opposite side to the protective film is 60 nm or less.

[12] A single-sided protective polarizing plate, comprising: a polarizing film and a protective film attached to one side of the polarizing film;

The number of dents with 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 of the polarizing film on the opposite side to the protective film is 10 pieces/m ² or less.

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

1: single-sided protection polarizer

2: One-sided protective polarizer with release film

3: One-sided protective polarizer with adhesive layer

4: Double-sided protection polarizer

5: polarizing film

10: Peel off the film

20: The first protective film

21: The second protective film

25: The first adhesive layer

26: The second adhesive layer

30: Adhesive layer

40: Lamination roller

50: volatile liquid

55: Water based adhesive

60: guide roller

70: Drying device

80,81: Injection device

FIG. 1 is a schematic cross-sectional view showing the basic layer structure of a single-sided protective polarizer.

FIG. 2 is a schematic cross-sectional view showing another example of a single-sided protective polarizer.

FIG. 3 is a schematic cross-sectional view showing another example of a single-sided protective polarizing plate.

4 is a schematic cross-sectional view showing the layer structure of a double-sided protective polarizer obtainable by using a single-sided protective polarizer.

5 is a side view schematically showing an example of the manufacturing method of the single-sided protective polarizing plate of the present invention and an example of the manufacturing apparatus used for the manufacturing method.

FIG. 6 is an atomic force microscope image of the surface of the polarizing film on the opposite side of the protective film in the single-sided protective polarizing plate of Example 1. FIG. (A) is a plan view of the surface, and (B) is a three-dimensional shape view of the surface.

7 is an atomic force microscope image of the surface of the polarizing film on the opposite side of the protective film in the single-sided protective polarizing plate of Comparative Example 1. (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 producing a single-sided protective polarizing plate. In the present invention, "single-sided protective polarizing plate" refers to a polarizing plate in which a protective film is bonded only on one side of the polarizing film, and the protective film is usually bonded to the polarizing film via an adhesive layer. The basic structure of a single-sided protective polarizer is shown in Figure 1. One-sided as shown in Figure 1 Protective Polarizing Plate 1 Generally, the single-sided protective polarizing plate of the present invention includes a polarizing film 5 and a first protective film 20 bonded to one side of the polarizing film 5 via a first adhesive layer 25 as a basic structure.

As will be described later, the manufacturing method of the present invention includes a first step of laminating a protective film (first protective film) on one side of the polarizing film via a water-based adhesive layer, and laminating on the other side via a volatile liquid The peeling film; and the second step are to dry the water-based adhesive layer by heating and to volatilize the volatile liquid. The single-sided protective polarizing plate obtained through the first and second steps is similar to the single-sided protective polarizing plate 2 with peeling film shown in FIG. Release film 10 .

The peeling film 10 is a film that can be peeled off from the polarizing film 5, and when necessary (for example, when a single-sided protective polarizer is attached to a liquid crystal cell), the single side of FIG. 1 can be obtained by peeling and removing the peeling film. Protect the polarizer 1. For example, in order to fit the liquid crystal cell, the single-sided protective polarizing plate of the present invention can be similar to the single-sided protective polarizing plate 3 with the adhesive layer shown in FIG. Layer 30.

In addition, the single-sided protective polarizing plate 1 and the single-sided protective polarizing plate 2 with peeling film of the present invention can also be suitably used as intermediates for the production of double-sided protective polarizing plates with protective films attached to both sides of the polarizing film. 4 , the double-sided protective polarizing plate 4 can be obtained by bonding the second protective film 21 to the surface of the polarizing film 5 opposite to the first protective film 20 via the second adhesive layer 26 .

The maximum height Rz specified in JIS B0601-2001 of the polarizing film 5 side surface of the release film 10 is 70 nm or less, preferably 50 nm or less, more preferably 30 nm or less, and still more preferably 20 nm or less. The maximum height Rz may exceed 0 nm, or may be 5 nm or more. In the first step, when the surface roughness of the release film 10 laminated on the polarizing film 5 is in the above-mentioned range, the single-sided protective polarizing plate 1 can be manufactured so that the dents on the side surface of the polarizing film 5 can be suppressed. And a single-sided protective polarizing plate that suppresses appearance defects. By suppressing the appearance defect of the single-sided protective polarizing plate, the deterioration of the yield in the manufacture of the single-sided protective polarizing plate can be suppressed.

Hereinafter, with reference to FIG. 5 and showing an embodiment, the manufacturing method of the single-sided protective polarizing plate of this invention is demonstrated in detail. The manufacturing method of the single-sided protective polarizing plate of the present invention comprises the following steps:

(1) In the first step, a first protective film is attached to one side of the polarizing film via a water-based adhesive layer, and a release film is laminated on the other side of the polarizing film via a layer composed of a volatile liquid; and

(2) In the second step, the water-based adhesive layer is dried by heating, and the volatile liquid is volatilized.

5 is a side view schematically showing an example of the manufacturing method of the single-sided protective polarizing plate of the present invention and an example of the manufacturing apparatus used for the manufacturing method. In general, as shown in FIG. 5 , a polarizing plate such as a one-sided protective polarizing plate can be continuously rolled out and conveyed while being processed at each step, whereby a long product can be continuously produced. However, the manufacturing method of the present invention is not limited to a continuous production using such a long film, and a method using a single film may also be used.

(1) Step 1

Referring to FIG. 5 , in this step, a roll of the long polarizing film 5 (roll), a roll of the long first protective film 20 , and a roll of the long release film 10 are prepared first. , and these reels are continuously rolled out using a take-up device (not shown) and the film is transported at the same time. Each film system is conveyed so that the longitudinal direction of these films may become a conveyance direction. In the conveyance path of a film, the guide roller 60 for supporting a moving film is provided suitably. The arrows in FIG. 5 indicate the direction of conveyance of the film or the direction of rotation of various rollers. Usually, the conveyance direction (film length direction) of the polarizing film 5, the conveyance direction (film length direction) of the 1st protective film 20, and the conveyance direction (film length direction) of the release film 10 are parallel.

In this step, the first protective film 20 is pasted on one side of the polarizing film 5 via the first adhesive layer 25 (not shown in FIG. 5 ) belonging to the water-based adhesive layer, and the other side of the polarizing film 5 is pasted with a The release film 10 is laminated with a layer composed of the volatile liquid 50 . As shown in FIG. 5 , the bonding of the first protective film 20 and the lamination of the release film 10 can be performed by: the first protective film 20 , the polarizing film 5 , and the release film 10 are aligned in the longitudinal direction. (conveyance direction) overlaps so that it may become parallel, and passes between a pair of bonding rolls 40 and 40, by which the laminated film is pressed from the upper and lower sides by the bonding rolls 40 and 40.

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 laminating rollers 40 and 40 , and the polarizing film 5 and the release film 10 are injected between the polarizing film 5 and the release film 10 . By injecting the volatile liquid 50 between these films, a layer (first adhesive layer 25 ) composed of the water-based adhesive 55 and a layer composed of the volatile liquid 50 can be interposed therebetween.

In addition, the device for intervening between the layer composed of the water-based adhesive 55 (the first adhesive layer 25 ) and the layer composed of the volatile liquid 50 is not limited to the injection device 80, 81, for example, according to the viscosity of the water-based adhesive 55 and the volatile liquid 50, etc., a doctor blade method, a wire rod coating method, a die coating method, a comma coater (comma coater, also known as a doctor blade coater) can also be appropriately selected. The water-based adhesive 55 and the volatile liquid 50 are applied to the bonding surface of at least one film to be overlapped by using coating methods such as cloth machine) method, gravure coating method, dip coating method, and casting method.

In the conventional manufacturing method of a single-sided protective polarizer, since a release film is directly laminated without interposing a special layer on the surface of the polarizing film, there is a problem that the polarizing film is easily broken during the step of manufacturing a single-sided protective polarizing plate. When a protective film is attached to one side of the polarizing film through a water-based adhesive layer, in order to obtain a single-sided protective polarizer, a step of drying the water-based adhesive layer is required, but in the conventional manufacturing method, it is particularly easy to do this. Breakage of the polarizing film occurs in the drying step.

On the other hand, according to the manufacturing method of the present invention in which the peeling film 10 is laminated on the polarizing film 5 through a layer formed of the volatile liquid 50 between the polarizing film 5 and the peeling film 10, even when the water-based adhesive is used In the step (second step) of drying the layer (first adhesive layer 25 ) constituted by 55 , cracking of the polarizing film 5 can also be effectively suppressed. In addition, the fact that the gap between the polarizing film 5 and the peeling film 10 is interposed by the layer formed of the volatile liquid 50 also has the effect of suppressing the generation of wrinkles in the single-sided protective polarizing plate during the step of manufacturing the single-sided protective polarizing plate.

Since the intervening volatile liquid 50 can be volatilized in the step of drying the first adhesive layer 25 (the second step), a separate step for volatilizing and removing the volatile liquid 50 is not required in the manufacturing method of the present invention.

When bonding the first protective film 20 to the polarizing film 5, the bonding surface of the polarizing film 5 and/or the first protective film 20 may be subjected to, for example, plasma treatment, corona treatment, or ultraviolet irradiation in order to improve adhesion. Treatment, flame treatment, saponification treatment, etc. are easy to follow. Among these, plasma treatment, corona treatment or saponification treatment are preferably performed. For example, when the 1st protective film 20 consists of a cyclic polyolefin resin, a plasma treatment and a corona treatment can be performed on the bonding surface of the 1st protective film 20. Moreover, when the 1st protective film 20 consists of a cellulose ester resin, saponification treatment can be performed on the bonding surface of the 1st protective film 20. As the saponification treatment, a method of immersing in an alkaline aqueous solution such as sodium hydroxide and potassium hydroxide can be cited.

[Polarizing film]

The polarizing film 5 may be a polyvinyl alcohol-based resin film uniaxially stretched by adsorption and orientation of a dichroic dye. Regarding the polyvinyl alcohol-based resin constituting the polyvinyl alcohol-based resin film, one obtained by saponifying a polyvinyl acetate-based resin can be used. In addition to polyvinyl acetate, which is a homopolymer of vinyl acetate, polyvinyl acetate-based resins can also be exemplified by vinyl acetate and other copolymers that can be copolymerized with vinyl acetate. A copolymer of monomers. As for the other monomer which can be copolymerized with vinyl acetate, for example, unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, (meth)acrylamides having an ammonium group, etc. are mentioned.

In addition, in this specification, "(meth)acrylic acid" means at least one selected from acrylic acid and methacrylic acid. The same definition applies when describing "(meth)acryloyl" and "(meth)acrylate".

The degree of saponification of the polyvinyl alcohol-based resin may be in the range of 80.0 to 100.0 mol %, but preferably in the range of 90.0 to 99.5 mol %, more preferably in the range of 94.0 to 99.0 mol %. If the degree of saponification is less than 80.0 mol %, the water resistance and heat and humidity resistance of the obtained single-sided protective polarizing plate will be reduced. When a polyvinyl alcohol-based resin having a degree of saponification exceeding 99.5 mol is used, the dyeing speed may be slowed, 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 converting the acetate group (acetoxy group: -OCOCH ₃ ) contained in the polyvinyl acetate-based resin, which is the raw material of the polyvinyl alcohol-based resin, into a hydroxyl group due to the saponification step, expressed as a unit ratio (mol %) ) is represented by the following formula:

Degree of saponification (mol%)=100×(number of hydroxyl groups)/(number of hydroxyl groups+number of acetate groups).

The degree of saponification can be determined according to JIS K 6726 (1994). The higher the degree of saponification, the higher the ratio of hydroxyl groups is shown, and the lower the ratio of acetate groups that hinder crystallization is shown.

The average degree of polymerization of the polyvinyl alcohol-based resin is preferably 100 to 10,000, more preferably 1,500 to 8,000, and still more preferably 2,000 to 5,000. The average degree of polymerization of the polyvinyl alcohol-based resin can also be determined in accordance with JIS K 6726 (1994). When the average degree of polymerization is less than 100, it is difficult to obtain better polarization performance, and when it exceeds 10,000, the solubility to the solvent deteriorates, and it becomes difficult to form a polyvinyl alcohol-based resin film.

The polarizing film 5 can be manufactured through the following steps: a step of uniaxially extending a polyvinyl alcohol-based resin film; a step of adsorbing the dichroic dye by dyeing the polyvinyl alcohol-based resin film with a dichroic dye; The step of treating the polyvinyl alcohol-based resin film on which the dichroic dye is adsorbed with an aqueous solution of boric acid; and the step of washing with water after being treated with an aqueous solution of boric acid.

The polyvinyl alcohol-based resin film is obtained by film-forming the above-mentioned polyvinyl alcohol-based resin. The film-forming method is not particularly limited, and known methods such as melt extrusion and solvent casting can be employed. 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 may be performed before the dyeing of the dichroic dye, simultaneously with the dyeing, or after the dyeing. In the case of performing uniaxial extension after dyeing, the uniaxial extension may be performed before or during boric acid treatment. In addition, uniaxial extension may also be performed in these plural stages.

In the case of uniaxial stretching, uniaxial stretching may be performed between rolls with different rotational speeds, or uniaxial stretching may be performed using heat rolls. In addition, the uniaxial stretching may be dry stretching in which the stretching is performed in the atmosphere, or wet stretching in which the polyvinyl alcohol-based resin film is swelled using a solvent. The elongation 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 can be employed. The polyvinyl alcohol-based resin film is preferably immersed in water (swelling treatment) before the dyeing treatment.

The dichroic dye contained in the polarizing film 5 (adsorption orientation) may be iodine or a dichroic organic dye. In the case of using iodine as a dichroic dye, a method of dipping a polyvinyl alcohol-based resin film in an aqueous solution containing iodine and potassium iodide and dyeing is usually employed. The iodine content in the dyeing aqueous solution is usually about 0.01 to 1 part by weight per 100 parts by weight of water. In addition, the content of potassium iodide Usually, it is 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. In addition, the time (dyeing time) immersed in the dyeing aqueous solution is usually about 20 to 1800 seconds.

On the other hand, when using a dichroic organic dye as a dichroic dye, a method of dipping a polyvinyl alcohol-based resin film in a dyeing aqueous solution containing a water-soluble dichroic organic dye and dyeing is usually employed. . 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. The dyeing aqueous solution may contain inorganic salts such as sodium sulfate as dyeing auxiliaries. The temperature of the dyeing aqueous solution is usually about 20 to 80°C. In addition, the time (dyeing time) immersed 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 an aqueous solution containing boric acid.

The amount of boric acid in the boric acid-containing aqueous solution is usually about 2 to 15 parts by weight, preferably 5 to 12 parts by weight, per 100 parts by weight of water. In the case of using iodine 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 above 50°C, preferably 50 to 85°C, more preferably 60 to 80°C.

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

After washing with water, a drying process was performed to obtain the polarizing film 5 . There are various methods of drying treatment, 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 appropriately used. From the viewpoints that drying time can be shortened due to improved drying efficiency, and the width of the film can be suppressed from shrinking in the width direction, a method of drying in contact with a hot roll is suitable. Also, in the case of a method of blowing hot air and a drying device such as an IR heater provided with a drying furnace, the drying temperature in the drying step means the ambient temperature in the drying furnace; in the case of a contact type drying such as a hot roller In the case of equipment, the drying temperature means the surface temperature of the heat roller. The drying temperature is usually about 30 to 100°C, preferably 50 to 80°C. The drying 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 moisture content is usually adjusted to 5 to 45% by weight, more preferably 8 to 40% by weight. When the content is less than 5% by weight, the polarizing film 5 may lose flexibility and the polarizing film 5 may be damaged or cracked after the drying. When the content is more than 45% by weight, it becomes difficult to fully develop. Adhesion to the protective film, and it is prone to problems of poor appearance and film rupture in the production line to contaminate the steps.

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. From the viewpoint of thinning the polarizing plate, the thinner the polarizing film 5 is, the thinner the thickness of the polarizing film 5 is. Generally speaking, if the thickness of the polarizing film 5 becomes thinner, it will be caused by the dents generated in the polarizing film 5. The appearance of the bad will easily become apparent. According to the present invention, even when a polarizing film having a thin thickness is used, it is possible to suppress the occurrence of poor appearance in the polarizing plate.

[First protective film]

The first protective film 20 may be a transparent resin film made of a thermoplastic resin, such as a chain polyolefin-based resin (polypropylene-based resin, etc.), a cyclic polyolefin-based resin (norbornene, etc.), for example. family tree Polyolefin resins such as cellulose triacetate, cellulose diacetate, etc.); cellulose ester resins such as cellulose triacetate, cellulose diacetate, etc.; such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate Polyester resins such as diesters; polycarbonate resins; (meth)acrylic resins such as polymethyl methacrylate resins; or mixtures and copolymers of these.

Examples of the chain polyolefin-based resin include homopolymers of chain olefins such as polyethylene resins and polypropylene resins, and copolymers composed of two or more kinds of chain olefins. More specific examples include: polypropylene resins (polypropylene resins which are homopolymers of propylene, and copolymers mainly containing propylene), polyethylene resins (polyethylene resins which are homopolymers of ethylene, and ethylene-based copolymers).

Cyclic polyolefin-based resins are collectively referred to as resins obtained by polymerizing cyclic olefins as polymer units, for example, Japanese Patent Application Laid-Open No. 1-240517, Japanese Patent Application Laid-Open No. 3-14882, and Japanese Patent Application Laid-Open No. 3-122137 No. Bulletin, etc. described in the resin. Specific examples of cyclic polyolefin-based resins include ring-opening (co)polymers of cyclic olefins, addition polymers of cyclic olefins, and copolymers of cyclic olefins and chain olefins such as ethylene and propylene (representatives). These are random copolymers), graft polymers modified with unsaturated carboxylic acids or derivatives thereof, and hydrides of these. Among these, norbornene-based resins using norbornene-based monomers such as norbornene and polycyclic norbornene-based monomers as cyclic olefins are preferably used.

Cellulose ester resins are esters of cellulose and fatty acids. Specific examples of the cellulose ester-based resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. In addition, these copolymers, and those in which a part of the hydroxyl group is modified with other substituents can also be used. Among these, a particularly preferred type is triacetylcellulose (triacetylcellulose: TAC).

Polyester resins are resins having ester bonds, and are generally composed of polycondensates of polycarboxylic acids or derivatives thereof and polyols. As the polyvalent carboxylic acid or its derivative, a divalent dicarboxylic acid or its derivative can be used, and examples thereof include terephthalic acid, isophthalic acid, dimethyl terephthalate, and dimethyl naphthalene dicarboxylate. esters, etc. As the polyhydric alcohol, a divalent diol can be used, and examples thereof include ethylene glycol, propylene glycol, butylene glycol, neopentyl glycol, and cyclohexanedimethanol. Examples of suitable polyester-based resins include polyethylene terephthalate.

Polycarbonate resins are engineering plastics composed of "polymers in which monomer units are bonded through carbonate groups". They are high impact resistance, heat resistance, flame retardancy, and transparency. of resin. The polycarbonate-based resin may be a resin called a modified polycarbonate in which the polymer skeleton is modified in order to reduce the photoelastic coefficient, a copolymerized polycarbonate in which wavelength dependence is improved, or the like.

The (meth)acrylic resin is a resin containing a compound having a (meth)acryloyl group as a main constituent monomer. Specific examples of (meth)acrylic resins include, for example: poly(meth)acrylates such as polymethyl methacrylate; methyl methacrylate-(meth)acrylic acid copolymers; methyl methacrylate- (meth)acrylate copolymer; methyl methacrylate-acrylate-(meth)acrylic acid copolymer; (meth)acrylate-styrene copolymer (MS resin, etc.); methyl methacrylate and Copolymers of compounds having alicyclic hydrocarbon groups (eg methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate-norbornyl (meth)acrylate copolymer, etc.). It is preferable to use a polymer whose main component is poly(meth)acrylate C _1-6 alkyl ester such as poly(meth)acrylate, and it is more preferable to use methyl methacrylate as the main component (50 to 100% by weight, preferably 70 to 100% by weight) of methyl methacrylate-based resin.

The first protective film 20 may also be a protective film having both optical functions, such as a retardation film and a brightness enhancement film. For example, a retardation film provided with an arbitrary retardation value can be obtained by stretching a transparent resin film composed of the above-mentioned materials (uniaxial stretching, biaxial stretching, etc.), or forming a liquid crystal layer on the film.

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 can also be formed on the surface of the first protective film 20 opposite to the polarizing film 5 . The method of 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 still more preferably 1 to 50 μm.

The moisture permeability of at least one of the first protective film and the release film described later is preferably 400 g/m ² ·24 hr or more. The moisture permeability of the first protective film 20 is preferably 400 g/m ² ·24hr or more, more preferably 420 g/m ² ·24hr or more. When the water vapor transmission rate is within this range, the layer composed of the water-based adhesive 55 can be efficiently dried in the subsequent second step, so that productivity can be improved. In addition, when the moisture permeability of the release film is 400 g/m ² ·24hr or more, the moisture permeability of the first protective film may be less than 400 g/m ² ·24hr, or 100 g/m ² ·24hr or less.

[Water-based adhesive]

The water-based adhesive 55 forming the first adhesive layer 25 is obtained by dissolving the adhesive component in water or by dispersing the adhesive component in water. A suitable water-based adhesive is, for example, an adhesive composition using a polyvinyl alcohol-based resin or a urethane resin as a main component. The thickness of the 1st adhesive agent layer 25 formed with an aqueous adhesive agent is 10 nm to 1 micrometer or less normally.

In the case of using a polyvinyl alcohol-based resin as the main component of the adhesive, the polyvinyl alcohol-based resin may not only be partially saponified polyvinyl alcohol, fully saponified polyvinyl alcohol, but also modified with carboxyl groups. Modified polyvinyl alcohol-based resins such as polyvinyl alcohol modified by acetyl acetyl group, polyvinyl alcohol modified by methylol group, polyvinyl alcohol modified by amine group, etc. In the case of polyvinyl alcohol-based resins, in addition to a vinyl alcohol homopolymer obtained by saponifying polyvinyl acetate, which is a homopolymer of vinyl acetate, it may also be a vinyl acetate and an acetic acid that can be mixed with acetic acid. A polyvinyl alcohol-based copolymer obtained by saponifying a copolymer of other monomers copolymerized with vinyl ester.

The 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, relative to 100 parts by weight of water.

To the adhesive composed of an aqueous solution of a polyvinyl alcohol-based resin, it is preferable to add polyaldehyde, melamine-based compound, zirconia compound, zinc compound, glyoxal, water-soluble ring compound in order to improve the adhesiveness. Oxygen resin and other hardening components and cross-linking agents. As the water-soluble epoxy resin, for example, a polyamide-polyamine epoxy resin obtained by reacting a polyamide-based amine with epichlorohydrin can be suitably used. Polyalkylene polyamines such as tetraamine react with dicarboxylic acids such as adipic acid. Commercially available such polyamide polyamine epoxy resins include "Sumirez Resin 650" (manufactured by Tagoka Chemical Industry Co., Ltd.), "Sumirez Resin 675" (manufactured by Tagoka Chemical Co., Ltd.), "WS-525" ” (manufactured by Japan PMC Co., Ltd.), etc. The addition amount of these curable components and cross-linking agents (in the case of adding both of the curable components and cross-linking agents, the total amount of the curable components and cross-linking agents) is based on 100 parts by weight of the polyvinyl alcohol-based resin , usually 1 to 100 parts by weight, preferably 1 to 50 parts by weight. When the addition amount of the above-mentioned curable component and cross-linking agent 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 reduced. When the addition amount of a component and a crosslinking agent exceeds 100 weight part with respect to 100 weight part of polyvinyl alcohol-type resin, there exists a tendency for an adhesive layer to become weak.

In addition, in the case of using urethane resin as the main component of the adhesive, an example of a suitable adhesive composition includes a polyester-based ionomer type urethane resin and a compound having a glycidyloxy group. mixture. The polyester-based ionomer-type urethane resin refers to a urethane resin having a polyester skeleton, into which a small amount of an ionic component (hydrophilic component) is introduced. Since this ionomer type urethane resin is directly emulsified in water to form an emulsion without using an emulsifier, it is suitable as a water-based adhesive.

[Release film]

The peeling film 10 is a film which can be peeled off at a desired timing after being laminated on the polarizing film 5 . "Can be peeled off" means that the polarizing film 5 and the peeling film 10 can be separated without destroying or damaging the polarizing film 5 and the peeling film 10 .

In view of handling properties, transparency, low cost, etc., the release film 10 can be a transparent resin film composed of: a chain polyolefin-based resin such as polyethylene-based resin, polypropylene-based resin, etc.; cellulose triacetate , cellulose ester resins such as cellulose diacetate; such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate and other polyester resins; such as polymethyl methacrylate (Meth)acrylic resins such as ester resins; or mixtures, copolymers and the like of these. As the release film 10, one or two or more types of these films can also be used as the release film 10, which is formed into a single layer or a multilayer. Among them, films composed of polyethylene terephthalate, cellulose triacetate, and polymethyl methacrylate-based resins can be suitably used.

The peeling force between the polarizing film 5 and the peeling film 10 is, for example, 0.01N/25mm to 2.0N/25mm, preferably 0.01N/25mm to 0.5N/25mm. 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 can be easily peeled off from the polarizing film 5 in the third step described later.

The above-mentioned peeling force was obtained by cutting the single-sided protective polarizing plate on which the peeling film 10 was laminated into a width of 25 mm to obtain a measurement sample, and using a precision universal testing machine "Autograph AGS" manufactured by Shimadzu Corporation. -50NX" gripping the release film 10 and the single-sided protective polarizing plate of the measurement sample, and measuring the force at the time of peeling in the 180° direction. The measurement of peeling force was carried out in the environment of peeling speed 300mm/min, temperature 23±2°C, and relative humidity 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 400g/m ² ‧24hr or more, more preferably 420g/m ² ‧24hr or more, still more preferably 450g/m ² ‧24hr or more, and still more preferably 500g/m ² ‧ 24hr or more. When the water vapor transmission rate is within this range, the volatile liquid 50 can be effectively volatilized and removed in the second step described later, so that quality defects such as deterioration of optical properties and poor appearance due to poor drying can be prevented.

The shrinkage rate (heat shrinkage rate) after heating the release film 10 at 80° C. for 5 minutes is preferably 0.15% or less, more preferably 0.1% or less. When the heat shrinkage rate of the release film 10 is large, wrinkles are likely to be generated in the release film 10 in the heat treatment in the second step, and subsequently, wrinkles are likely to be formed in the single-sided protective polarizer. Examples of the resin material whose heating shrinkage ratio is within the above range include polyethylene terephthalate, cellulose triacetate, and polymethyl methacrylate-based resins. "The heating 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 side surface of the polarizing film 5 of the peeling film 10 to the volatile liquid 50 is set to 50 to 80°, preferably 50 to 75°, the peeling force between the polarizing film 5 and the peeling film 10 is It is advantageous from the viewpoint that the peeling film 10 can be peeled off relatively easily that it is moderate within the said range. Similarly, the contact angle of the side surface of the release film 10 of the polarizing film 5 with respect to the volatile liquid 50 is preferably 50 to 110°, more preferably 50 to 100°. The contact angle can be measured, for example, by the following method. The surface to be measured (the peeling film side surface of the polarizing film or the polarizing film side surface of the peeling film) is set to the outside, and the polarizing film or peeling film is attached to the glass substrate using an adhesive to serve as a measurement sample. In such a way that the surface of the object to be measured becomes the upper surface, the measurement sample is set horizontally on the contact angle meter (image processing type contact angle meter manufactured by Kyowa Interface Science Co., Ltd.: FACE CA-X type), and the measurement sample is placed on the contact angle meter in a horizontal manner. 1 μL of the volatile liquid was dropped on the surface of the object, and the contact angle to the volatile liquid was measured.

The release film 10 can form a coating layer on the side surface of the polarizing film 5 . By forming a coating layer on the surface of the release film 10, a release film with small surface roughness can be easily obtained. Since minute foreign matters (additives, film scraps, etc.) caused by the release film are easily attached to the surface of the release film, they may cause dents on the surface of the polarizing film. However, these foreign matters can be covered by a coating layer. , to suppress the dent on the surface of the polarizing film. In addition, the peeling film 10 formed with the coating layer has a good peeling force with the polarizing film 5, and the peeling force is, for example, 0.01N/25mm to 2.0N/25mm, preferably 0.05N/25mm to 0.5N/ 25mm. The coating layers may be formed on both sides of the release film.

The coating layer is, for example, a hardened layer of UV-curable resin. Examples of the ultraviolet curable resin include (meth)acrylic resins, polysiloxane-based resins, polyester-based resins, urethane-based resins, amide-based resins, epoxy-based resins, and the like. In order to increase the hardness, the coating layer may also contain additives. The additive is not limited, and examples thereof include inorganic fine particles, organic fine particles, or a mixture 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 still more 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 dents on the surface of the polarizing film caused by foreign matter in the release film. Since the moisture permeability tends to decrease when the coating layer is too thick, the thickness of the coating layer is preferably 30 μm or less from the viewpoint of obtaining a release film with good moisture permeability.

[volatile liquid]

The volatile liquid 50 interposed between the polarizing film 5 and the peeling film 10 is a liquid that can be volatilized by the heat treatment in the second step, preferably a liquid that does not adversely affect the polarizing film 5 . Antistatic agents can be added if there are no negative effects. Examples of the volatile liquid 50 that can be used in the present invention include, for example, water, a mixture of water and a hydrophilic liquid, and the like. The hydrophilic liquid system can be used in the second step Those that do not remain after the heat treatment are preferred, and examples include methanol, ethanol, 1-butanol, tetrahydrofuran, acetone, acetonitrile, N,N-dimethylformamide, dimethylsulfoxide, formic acid, and acetic acid. Wait.

(2) Step 2

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

5 , the above-mentioned heat treatment can be performed by introducing the laminated film composed of the first protective film 20 , the polarizing film 5 and the release film 10 , which has passed between the bonding rolls 40 and 40 , into the drying device 70 . Thereby, 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., in the obtained single-sided protective polarizing plate 2 with peeling film, the first protective film 20 tends to be easily peeled off from the polarizing film 5 . In addition, when the drying temperature exceeds 90° C., there is a possibility that the polarization performance of the polarizing film 5 may be deteriorated by heat. The drying time can be set to about 10 to 1000 seconds, but from the viewpoint of productivity, it is preferably 60 to 750 seconds, and more preferably 150 to 600 seconds.

(3) Other steps

After the above-mentioned second step, aging can be performed at a temperature above room temperature for at least half a day (usually several days or more) to obtain sufficient bonding strength. This maturing is typically performed in a state of being rolled into a roll shape. The preferred aging temperature is in the range of 30 to 50°C, more preferably 35 to 45°C. When the aging temperature exceeds 50°C, so-called "winding up" tends to occur in the state of being rolled up in a roll shape. In addition, the humidity at the time of aging is not particularly limited, but is preferably selected so that the relative humidity is in the range of about 0 to 70% RH. The aging time is usually about 1 to 10 days, preferably about 2 to 7 days.

After the above-mentioned second step, "the third step of peeling and removing the peeling film 10 from the polarizing film 5 of the single-sided protective polarizer 2 with the peeling film" and "the area where the peeling film 10 is laminated on the polarizing film 5" are provided. In the fourth step of layering the adhesive layer 30 ", the single-sided protective polarizer 3 with the adhesive layer shown in FIG. 3 can also be made. The adhesive layer 30 can be used to attach the single-sided protective polarizer to the liquid crystal cell.

The adhesives used in the adhesive layer 30 can be any conventionally known and suitable adhesives, such as: (meth)acrylic adhesives, urethane adhesives, polysiloxane adhesives, polyester adhesives Adhesives, polyamide-based adhesives, polyether-based adhesives, fluorine-based adhesives, rubber-based adhesives, etc. Among these, it is preferable to use a (meth)acrylic-type adhesive from the viewpoints of transparency, adhesive force, reliability, reworkability, and the like. As far as the adhesive layer 30 is concerned, in addition to applying the adhesive in the form of an organic solvent solution and coating it on the polarizing film 5 by a die coater, a gravure coater, etc. and making it In addition to the installation by the drying method, it can also be installed by the method of transferring the sheet-like adhesive formed on the plastic film (referred to as a release film) subjected to mold release treatment to the polarizing film 5 . No matter which method is used, it is preferable to attach a separation film to the surface of the adhesive layer 30 . The thickness of the adhesive layer 30 may be, for example, 2 to 40 μm.

Alternatively, instead of providing the above-mentioned fourth step, the second protective film 21 can also be attached to the surface of the polarizing film 5 on which the release film 10 is laminated through the second adhesive layer 26 to obtain a double-sided protective polarizing plate 4. The second adhesive layer 26 may be the same water-based adhesive layer as the first adhesive layer 25, or may be a layer formed 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. At this time, the second adhesive layer 26 is a cured product layer of the adhesive.

The second protective film 21 may also be a protective film having both optical functions, such as a retardation film and a brightness enhancement film. The double-sided protective polarizing plate 4 can be bonded to the liquid crystal cell using the 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 for forming the second adhesive layer 26, it is more preferable to use an active energy ray-curable adhesive which uses an epoxy compound hardened by cationic polymerization as a curable component, and it is still more preferable to use the epoxy compound as a curable component. An oxygen-based compound is an ultraviolet curable adhesive as a curable component. The epoxy-based compound 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-based compound may be used alone, or two or more types may be used in combination.

Examples of the epoxy-based compound that can be suitably used include: a hydrogenated epoxy-based compound (glycidyl ether of a polyhydric alcohol having an alicyclic ring) obtained by reacting an alicyclic polyol with epichlorohydrin, wherein the aforementioned Alicyclic polyols are obtained by hydrogenating the aromatic ring of aromatic polyols; aliphatic epoxy compounds, such as polyglycidyl ethers of aliphatic polyols or their alkylene oxide adducts, etc.; The alicyclic epoxy-based compound is an epoxy-based compound having one or more epoxy groups bonded to an alicyclic ring in the molecule.

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

When the active energy ray-curable adhesive contains the "epoxy-based compound cured by cationic polymerization" as a curable component, it is preferable to contain a photocationic polymerization initiator. Examples of photocationic polymerization initiators include aromatic diazonium salts; onium salts such as aromatic iodonium salts and aromatic perionium salts; Iron-aromatic complexes, etc. Moreover, when an active energy ray-curable adhesive agent contains a radically polymerizable curable component, such as a (meth)acrylic-type compound, it is preferable to contain a photoradical polymerization initiator. Examples of photo-radical polymerization initiators include acetophenone-based initiators, benzophenone-based initiators, benzoin ether-based initiators, 9-oxanthone-based initiators, Xanthone, fenone, camphorquinone, benzaldehyde, anthraquinone, etc.

When an active-energy-ray-curable adhesive is used, a hardening step of hardening the adhesive layer which consists of this active-energy-ray-curable adhesive is implemented. The curing of the adhesive layer can be performed by irradiating active energy rays. The active energy rays are preferably ultraviolet rays.

The light source of the active energy ray is not particularly limited, and it is preferably an active energy ray with a luminous distribution below the wavelength of 400 nm, and specifically, it is preferable to use a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, and an ultra-high-pressure mercury lamp. , chemical lamps, black light lamps, microwave excited mercury lamps, metal halide lamps, etc.

The active energy ray irradiation intensity to the adhesive layer composed of the active energy ray-curable adhesive is appropriately determined according to the composition of the adhesive, and is preferably in a wavelength region where the activation of the polymerization initiator is effective. The irradiation intensity is set to be 0.1 to 6000 mW/cm ² . When the irradiation intensity is 0.1 mW/cm ² or more, the reaction time will not be too long, and when it is 6000 mW/cm ² or less, the heat emitted from the light source and the heat generated during the curing of the adhesive will occur. There are fewer concerns about yellowing of the adhesive layer and deterioration of the polarizing film 5 .

The irradiation time of the active energy rays is appropriately determined according to the composition of the adhesive, but it is preferably set so that the cumulative light amount represented by the product of the irradiation intensity and the irradiation time becomes 10 to 10000 mJ/cm ² . When the cumulative light amount is 10 mJ/cm ² or more, a sufficient amount of active species derived from the polymerization initiator can be generated to more reliably proceed the curing reaction; when the cumulative light amount is 10,000 mJ/cm ² or less, the irradiation time It is not too long and maintains good productivity.

Regarding the material and structure of the second protective film 21 , the contents described for the first protective film 20 are cited. The first protective film 20 and the second protective film 21 may be the same type of film, or may be different types of films.

<Single-sided protection polarizer>

A single-sided protective polarizing plate 1 according to an embodiment of the present invention includes a polarizing film 5 and a protective film 20 attached to one surface of the polarizing film 5 . The maximum height Rz specified by JIS B0601-2001 of the surface of the polarizing film 5 opposite to the protective film 20 is 60 nm or less, preferably 50 nm or less, more preferably 30 nm or less, and still more preferably 20 nm or less. The maximum height Rz may exceed 0 nm, or may be 5 nm or more. In this way, the appearance defects of the single-sided protective polarizing plate system are suppressed. The single-sided protective polarizing plate can be manufactured according to the above-mentioned manufacturing method of a polarizing plate.

A single-sided protective polarizing plate 1 according to an embodiment of the present invention includes a polarizing film 5 and a protective film 20 attached to one surface of the polarizing film 5 . On the surface of the polarizing film 5 opposite to the protective film 20 , the number of dents with 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 is 10 pieces/m ² or less, more preferably 5 pieces/m ² or less . The density of dents may exceed 0 pieces/m ² , or may be 1 piece/m ² or more. In this way, the appearance defects of the single-sided protective polarizing plate system are suppressed. 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 refers to the maximum value of the length in the plane direction of the polarizing film. The depth of the dent refers to the maximum value of the depth (length in the direction perpendicular to the polarizing film) from the surface of the polarizing film.

[Example]

Hereinafter, the present invention is described in more detail by way of examples, but the present invention is not limited to these. The 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

According to JIS Z0208-1976, the water vapor transmission rate (g/m ² ·24hr) at 40°C was measured.

(2) Thickness of layer

The thickness of the film was measured using a contact film thickness measuring apparatus (manufactured by Nikon Co., Ltd.: MS-5C). The thickness of the adhesive layer was measured using a laser microscope (manufactured by Olympus Corporation: OLS3000).

(3) Peeling force between polarizing film and peeling film

The peel force was obtained by cutting the single-sided protective polarizing plate with the peeling film laminated into a width of 25 mm to obtain a measurement sample, and using a precision universal testing machine "Autograph AGS-50NX" manufactured by Shimadzu Corporation The peeling film and the single-sided protective polarizing plate of the measurement sample were held, and the force when peeled off in the 180° direction was measured. The measurement of peeling force was carried out in the environment of peeling speed 300mm/min, temperature 23±2°C, and relative humidity 50±5%.

(4) Surface roughness

The surface roughness (maximum height Rz prescribed|regulated to JIS B0601-2001) of a polarizing film and a peeling film was measured using the atomic force microscope (AFM, the Shimadzu Corporation make: SPM-9700HT).

(5) Measurement of the unevenness on the surface of the polarizing film

Using an optical microscope (manufactured by Keyence Co., Ltd.: Model VHX-6000), the number of dimples having a width of 0.5 mm to 2.0 mm and a depth of 0.1 μm to 1.0 μm existing on the surface of the polarizing film was measured.

<Example 1>

(A) Production of polarizing film

The polyvinyl alcohol film with an average degree of polymerization of about 2400, a degree of saponification of 99.9 mol% or more, and a thickness of 20 μm was uniaxially stretched to about 4 times in a dry manner, and further immersed in pure water at 40°C while maintaining tension. After 1 minute of immersion, it was immersed in an aqueous solution with a weight ratio of iodine/potassium iodide/water of 0.1/5/100 at 28° C. for 60 seconds. After that, it was immersed in an aqueous solution with a weight ratio of potassium iodide/boric acid/water of 10.5/7.5/100 at 68°C. Stain for 300 seconds. Then, after washing with pure water at 5° C. for 5 seconds, drying was performed at 70° C. for 180 seconds to obtain a polarizing film in which iodine was adsorbed and oriented in the uniaxially stretched polyvinyl alcohol film. The thickness of the polarizing film is 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 1800) was dissolved in hot water at 95°C to prepare an aqueous polyvinyl alcohol solution with a concentration of 3% by weight. In the obtained aqueous solution, a crosslinking agent (trade name "Sumirez Resin 650", manufactured by Taoka Chemical Industry Co., Ltd.) was mixed in a ratio of 2 parts by weight to 1 part by weight of the polyvinyl alcohol powder to serve as a water-based adhesive.

(C) Protective film

As the protective film, a cyclic polyolefin-based resin (COP) film with a thickness of 27 μm was used. The moisture permeability of the protective film is 5.5g/m ² ·24hr.

(D) Release film

As the release film, a film (HC-TAC) having a coating layer composed of a cured methacrylic resin with a thickness of 4 μm on a cellulose triacetate (TAC) film with a thickness of 42 μm was used. The moisture permeability of the release film was 540g/m ² ·24hr. The contact angle of the polarizing film side surface of the release film was 70°.

(E) Production of single-sided protective polarizing plate with release film and single-sided protective polarizing plate

Using the same apparatus as the polarizing plate manufacturing apparatus shown in FIG. 5 , a single-sided protective polarizing plate with a release film was produced according to the following procedure. The polarizing film obtained in the above (A) was continuously conveyed, the protective film was continuously taken out from the roll of the protective film, and the release film was continuously taken out from the roll of the peeling film. Next, the water-based adhesive obtained in the above (B) was injected between the polarizing film and the protective film, and pure water was injected between the polarizing film and the release film, and passed between the bonding rollers 40 and 40 to form a protective film/water-based adhesive. Laminated film composed of agent layer/polarizing film/pure water/release film (first step). Next, the laminated film was conveyed, passed through the drying device 70, and subjected to 80° C., Heat treatment for 300 seconds, thereby drying the water-based adhesive layer, and volatilizing and removing the pure water intervening between the polarizing film and the release film to obtain a single-sided protective polarizer with a release film (the second step) . The thickness of the water-based adhesive layer was 75 nm. The peeling film was peeled and removed from the polarizing film to obtain a single-sided protective polarizing plate (third step).

In the manufacture of the single-sided protective polarizing plate with peeling film, the cracking of the polarizing film and the wrinkling of the polarizing plate did not occur. Table 1 shows the measurement results of the thickness, peeling force, and surface roughness of the polarizing film, protective film, and peeling film used in the production of 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 in the same manner 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. The measurement results of the thickness, peeling force and surface roughness of the protective film and the release film are shown in Table 1. The contact angle of the polarizing film side surface of the peeling film used in Comparative Example 1 was 65°. The contact angle of the polarizing film side surface of the peeling film used in Comparative Example 2 was 65°.

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

Table 1

Compared with the single-sided protective polarizing plate of Comparative Example 1 and Comparative Example 2, the single-sided protective polarizing plate produced in Example 1 suppressed the dent on the surface of the polarizing film on the opposite side of the protective film. In the single-sided protective polarizing plates of Example 1 and Comparative Example 1, the images observed by the atomic force microscope (SPM-9700HT, manufactured by Shimadzu Corporation) on the surface after peeling off the release film are shown in Fig. 6 and Fig. 6 , respectively. Figure 7.

<Reference example 1>

The single-sided protective polarizing plate of Reference Example 1 was produced in the same manner as in Example 1 except that the type of release film was changed. Reference Example 1 used a polymethyl methacrylate resin (PMMA) film with a thickness of 60 μm without a coating layer as a release film. The moisture permeability of the release film was 60g/m ² ·24hr.

Compared with the single-sided protective polarizing plate of Reference Example 1, the single-sided protective polarizing plate produced in Example 1 has good optical properties. That is, the single-sided protective polarizing plate manufactured in Example 1 was compared with Reference Example 1. When compared with the single-sided protective polarizing plate, in the case of comparing with the same transmittance, the polarization degree of the single-sided protective polarizing plate produced in Example 1 is higher. It is presumed that compared with the release film of Reference Example 1, the release film of Example 1 has higher moisture permeability.

1: single-sided protection polarizer

5: polarizing film

20: The first protective film

25: The first adhesive layer

Claims (12)

A manufacturing method of a polarizing plate, comprising: The first step is to stick a protective film on one side of the polarizing film through a water-based adhesive layer, and laminate a release film on the other side of the polarizing film through a volatile liquid; and The second step is to dry the water-based adhesive layer by heating, and to volatilize the volatile liquid; However, the maximum height Rz specified in JIS B0601-2001 of the polarizing film side surface of the peeling film is 70 nm or less. The method for producing a polarizing plate according to claim 1, wherein the release film has a coating layer formed on the side surface of the polarizing film. The manufacturing method of the polarizing plate of Claim 2 whose thickness of the coating layer of the said peeling film is 30 micrometers or less. The manufacturing method of the polarizing plate of Claim 2 or 3 whose coating layer of the said peeling film consists of the hardened|cured material of (meth)acrylic resin. The method for producing a polarizing plate according to any one of claims 1 to 4, wherein the moisture permeability of at least one of the protective film and the release film is 400 g/m ² ·24hr 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 manufacturing method of the polarizing plate of any one of Claims 1-6 whose thickness of the said protective film is 1 micrometer or more and 90 micrometers or less. The method for producing 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 producing 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 producing 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. A single-sided protective polarizing plate, comprising: a polarizing film, and a protective film attached to one side of the polarizing film; However, the maximum height Rz specified in JIS B0601-2001 of the surface on the opposite side to the protective film of the polarizing film is 60 nm or less. A single-sided protective polarizing plate, comprising: a polarizing film, and a protective film attached to one side of the polarizing film; The number of 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 of the polarizing film on the opposite side to the protective film is 10 pieces/m ² or less.

Images