KR20160150025A - Method for producing polarizing plate with protective film - Google Patents

Abstract

The present invention relates to a method for producing a polarizing plate having a protect film, wherein the method comprises a process of rolling a protect film overlapping on one surface of a polarizing plate by passing the same through a pair of combining rolls. When the thickness of the protect film is T_1 (m), the tensile modulus according to MD is E_1 (MPa), the film tensile strength according to MD before passing through the combing rolls is F_1 (N/m), the thickness of the polarizing plate is T_2 (m), the tensile modulus according to MD direction is E_2 (MPa), and the film tensile strength thereof according to MD before passing through the combing rolls is F_2 (N/m), the process is performed under a condition satisfying formula, F_1/(E_1T_1)>F_2/(E_2T_2).

Description

TECHNICAL FIELD [0001] The present invention relates to a polarizing plate having a protective film,

The present invention relates to a method for producing a polarizing plate having a protective film formed by laminating a protective film on the surface of a polarizing plate.

2. Description of the Related Art In recent years, mobile terminals such as smart phones have been rapidly increasing in size and size in terms of design and portability. A polarizing plate used for realizing driving for a long time with a limited thickness is required to have a higher brightness and a thinner and lighter weight.

As a polarizing plate, a polarizing film made of a polyvinyl alcohol-based resin is conventionally used in which a protective film made of triacetylcellulose (TAC) is bonded by an adhesive. Recently, however, a protective film made of a resin other than TAC has also been used in view of thinning, durability, cost, productivity, and the like (for example, Japanese Patent Laid-Open No. 2004-245925).

Polarizing plates are sensitive to the environment in which they are placed, and are liable to cause bowing-like deformation depending on environmental conditions. In the present specification, this variation is also referred to as " curl ". There are two types of curls: "positive curl" and "reverse curl". The polarizing plate has a first main surface on a side bonded to an image display element such as a liquid crystal cell and a second main surface opposite to the first main surface. The term " positive " is curl convex on the first main surface side, Is a curl that conveys the second main surface side. If a polarized plate has a counter-current, it is liable to cause a bonding error when bonding the polarizing plate to the image display device through the pressure-sensitive adhesive layer, or to cause air bubbles to enter the interface between the pressure-sensitive adhesive layer and the image display device.

Therefore, the present invention is to provide a method for manufacturing an optical member including a polarizing plate structure, in which an optical member whose backlash is sufficiently suppressed can be produced.

The present inventors have found that (1) a polarizing plate is marketed as a polarizing plate having a protective film adhering a peelable protective film (also referred to as a surface protective film) for protecting the surface thereof, and The polarizing plate having a protective film is bonded in the form of a polarizing plate having a protective film, and 2) in order to solve the above-described problem, The invention has arrived. That is, the present invention provides a method for producing a polarizing plate having a protective film described below.

[1] A method for producing a polarizing plate having a protective film comprising a step of pressing a polarizing plate by passing the polarizing plate between a pair of bonding rolls,

The thickness of the protective film is T ₁ [탆], the tensile elastic modulus in MD is E ₁ [MPa], and the film tension in MD before passing through the pair of bonding rolls is F ₁ [N / m] , The thickness of the polarizing plate is T ₂ [탆], the tensile elastic modulus in the MD direction is E ₂ [MPa], and the film tension in MD before passing through the pair of bonding rolls is F ₂ [N / m , The pressing step is performed by the following formula (I):

Is satisfied.

[2] The method according to [

Is carried out under the conditions satisfying the following formula (1).

[3] The production method according to [1] or [2], wherein the polarizing plate causes a curl which convexes the side on which the protective film is superimposed when it is made into a wax.

[4] The polarizing plate according to any one of [1] to [3], wherein the polarizing plate comprises a polarizing film, a first thermoplastic resin film laminated on one side thereof, and a second thermoplastic resin film laminated on the other side .

[5] The production method according to [4], wherein the first thermoplastic resin film has a higher equilibrium moisture content than the second thermoplastic resin film at a temperature of 23 ° C and a relative humidity of 55%.

[6] The production method according to [5], wherein the difference between the equilibrium moisture content of the first thermoplastic resin film and the second thermoplastic resin film is 0.5 wt% or more.

[7] The production method according to any one of [4] to [6], wherein the protective film is disposed on the first thermoplastic resin film side.

[8] The production method according to any one of [4] to [7], wherein the first thermoplastic resin film has an equilibrium moisture content of 1.5 wt% or more.

[9] The production method described in any one of [1] to [8], wherein the thickness of the polarizing plate is 100 μm or less.

According to the present invention, it is possible to produce a polarizing plate having a protective film whose backlash is sufficiently suppressed. According to the polarizing plate having the protective film, the problems described above can be suppressed and the bonding to the image display element can be performed with high productivity.

1 is a side view schematically showing an example of a method for producing a polarizing plate having a protective film according to the present invention.
2 is a schematic view for explaining the MD curl, in which (a) is a side view and (b) is a plan view.
3 is a schematic cross-sectional view showing an example of the layer structure of the polarizing plate.
4 is a schematic cross-sectional view showing another example of the layer structure of the polarizing plate.
5 is a schematic cross-sectional view showing another example of the layer structure of the polarizing plate.

(1) Pressing process

1, a method of manufacturing a polarizing plate having a protective film according to the present invention is characterized in that a protective film 1 is superimposed on one side of a polarizing plate 2 and passed between a pair of bonding rolls 5, And pressing the stacked body of the protective film 1 and the polarizing plate 2 upwards and downwards. By this process, the polarizing plate 3 having a protective film is produced. Normally, the protective film 1 and the polarizing plate 2 used in the pressing process are successively unrolled from the feeding rolls, not shown, and are continuously conveyed, and are conveyed between the pair of bonding rolls 5, 5 . The transport direction of the protective film 1 and the polarizing plate 2 is the film longitudinal direction, and the transport direction of both is generally parallel.

The pressing step is preferably carried out in such a manner that the thickness of the protective film 1 is T ₁ [탆], the tensile elastic modulus of the MD is E ₁ [MPa], and the MD before passing through the pair of bonding rolls 5 and 5 of the film tension F ₁ [N / m] as, and the thickness of the polarizing plate ₍₂₎ T 2 [㎛], the tensile elastic modulus in the MD direction E ₂ [MPa], a pair of bonding rolls (5,5 (I): when the film tension in the MD before passing through the film is F ₂ [N / m]

Is satisfied. In this specification, MD means the machine direction of the film, that is, the longitudinal direction of the film. The direction orthogonal to the MD, that is, the film width direction is also referred to as TD in this specification.

The tensile modulus of elasticity E ₁ and E ₂ of the protective film 1 and the polarizing plate 2 in the MD are tensile elastic modulus under an environment of 55% relative humidity at 23 ° C and are measured in accordance with the description of Examples described later do. The film tensions F ₁ and F ₂ in the MD of the protective film 1 and the polarizing plate ₂ are the film tension before passing through the pair of bonding rolls 5 and 5, 5), and the tensile force of the film running between the upstream side and the driving roll (a pair of nip rolls) closest to the bonding rolls 5, 5.

By bonding the protective film 1 to the polarizing plate 2 under the condition satisfying the above formula (I), the shape of the polarizing plate 2 can be changed in the direction in which the main surface where the protective film 1 overlaps becomes concave (that is, (Curl correction) can be performed. Therefore, for example, when the polarizing plate 2 used in the pressing step causes a backlash (curl convex on the main surface side where the protective film 1 overlaps) when it is made into a welt, according to the present invention, As a result, it is possible to obtain the polarizing plate 3 having a protective film having a curled state sufficiently suppressed, or having no curls, or having a protective film when it is made into a wax. The polarizing plate 3 having a protective film to be obtained preferably has no curl and is flat or has a curl when it is made into a wool.

According to the study by the present inventor, the left side and the right side of the formula (I) are indexes indicating the distortion state of the protective film 1 and the polarizing plate 2 when they are bonded to each other. The fact that the polarizing plate 2 can be calibrated in the positive direction by bonding the protective film 1 to the polarizing plate 2 under the condition satisfying the above formula (I) means that a force for eliminating distortion, (1). ≪ / RTI >

The relationship of the above formula (I) is not particularly limited as long as the thickness of the protective film 1 and / or the polarizing plate 2, the tensile elastic modulus in the MD and the film in the MD before passing through the pair of bonding rolls 5, Can be realized by adjusting one or more elements selected from the tension. The element to be adjusted preferably includes the film tension of the protective film (1) and / or the polarizing plate (2).

Here, the curl will be described. The curl refers to a deformation in which an optical member (optical film) such as a polarizing plate 2 and a polarizing plate 3 having a protective film bends like an arc, and this deformation usually occurs in each of the optical members of the optical member. Curl tends to occur as the optical member becomes thinner.

The curl can be classified into two types of "curled" and "counter-curled", depending on which of the two opposed main surfaces of the optical member is curled convexly. Quot; is a curl that convexes the first main surface side when the main surface on the side to be bonded to the image display element such as the liquid crystal cell is the first main surface and the main surface on the side opposite to the first main surface is the second main surface, Is a curl which convexes the second main surface side. The polarizing plate 2 used in the production method according to the present invention causes a backlash (a curl that convexes the main surface side where the protective film 1 overlaps) when it is made into a wollaston.

The curl can be classified into two types, that is, "MD curl" and "TD curl", depending on which end (side) of the optical member is formed. Referring to Fig. 2, when an individual member of an optical member curled on a flat base is placed on the convex side downward, "MD curl" is a curl in which an end portion (typically both ends) Quot; TD curl " is a curl in which an end portion (typically both ends) in the TD occurs. The manufacturing method according to the present invention is particularly advantageous for the calibration of MD curls.

The evaluation of the curl (such as the identification of the type of the curl, the counter-current, the MD curl, and the TD curl or the curl amount) of the optical member such as the polarizing plate 2 and the polarizing plate 3 having a protective film can be obtained by cutting We will do about every leaf. The each leaf is a square leaf having a pair of opposing sides parallel to the MD and a pair of opposing sides parallel to the TD. The MD length is 300 mm and the TD length is 200 mm.

According to the present invention, it is possible to obtain a polarizing plate (3) having a protective film which is sufficiently restrained when the sheet is formed into a sheet, and is preferably flat without curling or having a protective film. According to the polarizing plate 3 having the protective film, it is possible to effectively suppress the problem of causing a bonding error when joining to the image display device through the pressure-sensitive adhesive layer, or bubbles entering the interface between the pressure-sensitive adhesive layer and the image display device So that the polarizing plate 3 having a protective film and the image display element can be bonded with good productivity. In addition, as long as the curl occurring in the polarizing plate 3 having a protective film is static, there is no particular problem in terms of the above problems and productivity, even if the curl amount is relatively large. The polarizing plate (3) having a protective film obtained by the present invention may have a backlash to the extent that the above problems can be suppressed (preferably, the above problems are not caused).

The correction amount in the normal direction according to the present invention depends on the difference between the left side and the right side of the formula (I) which is an index of distortion. The larger the difference, the larger the correction amount tends to be. Although it depends on how much the polarizing plate 2 used in the pressing step is curled to some extent, the polarizing plate 3 having the obtained protective film is not flat, (II): < EMI ID =

Is satisfied. In the case where the polarizing plate 2 used in the pressing process has a large scale, the left side of the formula (II) is set to be larger than 55 in order to make the polarizing plate 3 having the obtained protective film flat Such as 60 or more, 70 or more, 80 or more, 100 or more, 130 or more, 160 or more, or 180 or more). The left side of the formula (II) may be, for example, 1000 or less.

The left side and the right side of the above formula (I) are usually 1 × 10 ^-5 to 1000 × 10 ^-5 , and may be 5 × 10 ^-5 to 500 × 10 ^-5 , respectively.

When the protective film 1 is superimposed on one side of the polarizing plate 2 and passes between the pair of bonding rolls 5 and 5, the pressure sensitive adhesive layer of the protective film 1 is pressed against the above- Respectively. Prior to the lamination of the protective film 1 and the polarizing plate 2, a plasma treatment, a corona treatment, an ultraviolet ray irradiation treatment, a flame (a flame) is applied to a bonding surface of at least one of the pressure- ) Treatment, or a surface activation treatment such as a saponification treatment may be performed.

The pressure (nip pressure) given to the laminate of the protective film 1 and the polarizing plate 2 in the step of pressing with the pair of bonding rolls 5 and 5 is, for example, 0.01 to 0.5 MPa and preferably 0.05 to 0.3 MPa . The nip pressure does not greatly affect the curl of the polarizing plate 3 having a normally obtained protective film. As the bonding rolls 5 and 5, conventionally known ones such as a metal surface (including an alloy such as SUS) and a rubber may be used.

(2) Protective film

The protective film (1) usually comprises a base film and a pressure-sensitive adhesive layer laminated on the base film. The protective film 1 is a film for protecting the surface of the polarizing plate 2. Normally, for example, after the polarizing plate 3 having a protective film is bonded to an image display device or the like, the adhesive film is peeled off. The base film may be formed of a thermoplastic resin such as a polyolefin resin such as a polyethylene resin, a polypropylene resin and a cyclic polyolefin resin; Polyester resins such as polyethylene terephthalate and polyethylene naphthalate; Polycarbonate resin; (Meth) acrylic resin or the like. The pressure-sensitive adhesive layer can be composed of a (meth) acrylic pressure-sensitive adhesive, an epoxy pressure-sensitive adhesive, a urethane pressure-sensitive adhesive, and a silicone pressure-sensitive adhesive. It may also be composed of a resin layer having a self-adhesive property such as a polypropylene resin or a polyethylene resin. The tensile elastic modulus E ₁ in the MD direction can be adjusted mainly by selecting the material of the base film.

In the present specification, the term "(meth) acrylic resin" refers to at least one kind selected from the group consisting of an acrylic resin and a methacrylic resin. The same is true of the term "(meth)".

The thickness T ₁ of the protective film ₁ may be, for example, 5 to 200 탆, preferably 10 to 150 탆, more preferably 20 to 120 탆, and still more preferably 25 to 100 탆 Mu m or less, and further, 75 mu m or less). If the thickness T ₁ is less than 5 탆, the protection of the polarizing plate 2 may be insufficient, and the handling property is also disadvantageous. If the thickness T ₁ exceeds 200 탆, it is disadvantageous in terms of cost and reworkability of the protective film 1. When the thickness T ₁ exceeds 200 μm, it is difficult to satisfy the relational expression of the formula (I) and / or the formula (II).

(3) Polarizer

The polarizing plate 2 is a polarizing element including at least a polarizing film, and usually includes a thermoplastic resin film such as a protective film laminated on at least one surface of the polarizing film. The protective film is an optical film for protecting the polarizing film.

(3-1) Configuration Example of Polarizer

The polarizing plate 2 may include a polarizing film and a layer or film other than the protective film, for example, an optical layer or optical film having optical functions other than the polarizing film. Examples of the optical layer or optical film having another optical function include a retardation film (or retardation layer), a brightness enhancement film, and the like. Various optical films including a protective film can be laminated on a polarizing film through an adhesive layer or a pressure-sensitive adhesive layer. The polarizing plate 2 may have 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.

The thickness T ₂ of the polarizing plate ₂ is usually 200 μm or less, preferably 125 μm or less, more preferably 100 μm or less, and further preferably 75 μm or less, from the viewpoint of thinning. As the thickness T ₂ is smaller, the polarizing plate ₂ is liable to cause curling in each of its corners, but according to the present invention, the thickness T ₂ of the polarizing plate ₂ is thin and the polarizing plate 2, , It is possible to effectively correct this counterexample in the normal direction. It is difficult to adjust the mechanical properties of the polarizing film and the protective film in order to flatten or curl the curl when the polarizing plate 2 is formed into a sheet of paper from the viewpoint of thinning and optical characteristics. The polarizing plate 3 having a protective film is peeled off after being bonded, so that it is possible to adjust the mechanical characteristics for calibrating.

Examples of the layer configuration of the polarizing plate 2 will be described with reference to Figs. 3 to 5. However, the layer configuration is not limited to these examples. The polarizing plate 2a shown in Fig. 3 includes a polarizing film 10; A first thermoplastic resin film (20) bonded to one surface of the polarizing film (10); A second thermoplastic resin film (30) bonded to the other surface of the polarizing film (10); A pressure-sensitive adhesive layer (40) laminated on the outer surface of the second thermoplastic resin film (30); And a separate film (50) laminated on the outer surface of the pressure-sensitive adhesive layer (40). The separate film (50) is a peelable film for protecting the surface (outer surface) of the pressure sensitive adhesive layer (40). The first and second thermoplastic resin films 20 and 30 are, for example, protective films.

One of the first and second thermoplastic resin films 20 and 30 may be omitted like the polarizing plate 2b shown in Fig. The second thermoplastic resin film 30 is omitted in the polarizing plate 2b and the pressure sensitive adhesive layer 40 is directly attached to the outer surface of the polarizing film 10 (the surface opposite to the surface on which the first thermoplastic resin film 20 is laminated) ). The polarizing plate having a thermoplastic resin film on only one side of the polarizing film 10 is advantageous for thinning the polarizing plate. In the case where a thermoplastic resin film is laminated on only one side of the polarizing film 10, the polarizing plate 2 is liable to cause curling in each of the polarizing films, but according to the present invention, only one side of the polarizing film 10 is thermoplastic Even if the polarizing plate 2 is made of a woven fabric due to the laminated bonding of the resin film, it is possible to effectively correct the backlash in the normal direction.

As in the case of the polarizing plate 2c shown in Fig. 5, the pressure-sensitive adhesive layer 40 and the separate film 50 may be omitted. The polarizing plate 2 may have a protective film different from the protective film 1 used in the pressing step in advance on one side. In this case, the polarizing plate 3 having a protective film to be obtained is a polarizing plate having a protective film on both sides.

Although not shown in Figs. 3 to 5, the polarizing film 10 and the first and second thermoplastic resin films 20 and 30 can preferably be bonded using an adhesive.

(3-2) polarizing film

The polarizing film (10) may be one in which a dichroic dye is adsorbed and oriented on a uniaxially stretched polyvinyl alcohol resin film. As the polyvinyl alcohol-based resin constituting the polyvinyl alcohol-based resin film, a saponified polyvinyl acetate-based resin can be used. As the polyvinyl acetate resin, a copolymer of vinyl acetate and other monomers copolymerizable therewith may be mentioned in addition to polyvinyl acetate as a homopolymer of vinyl acetate. Examples of other monomers copolymerizable with vinyl acetate include (meth) acrylamides having unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and ammonium groups.

The degree of saponification of the polyvinyl alcohol-based resin may be in the range of 80.0 to 100.0 mol%, preferably 90.0 to 100.0 mol%, and more preferably 98.0 to 100.0 mol%. When the degree of saponification is less than 80.0 mol%, the water resistance and moisture resistance of the resulting polarizing plate 2 may deteriorate.

The degree of saponification indicates the unit ratio (mol%) of the ratio of the acetic acid group (acetoxy group: -OCOCH ₃ ) contained in the polyvinyl acetate-based resin as the raw material of the polyvinyl alcohol-based resin to the hydroxyl group by the saponification process, The following formula:

Saponification degree (mol%) = 100 占 (number of hydroxyl groups) / (number of hydroxyl groups + number of acetic acid groups)

. The saponification degree can be obtained according to JIS K 6726 (1994). The higher the degree of saponification, the higher the proportion of hydroxyl groups and thus 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 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 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 a desired polarizing performance. When the average degree of polymerization is more than 10,000, the solubility in a solvent deteriorates and it becomes difficult to form a polyvinyl alcohol-based resin film.

The dichroic dye contained (adsorbed orientation) in the polarizing film 10 may be iodine or a dichroic organic dye. Specific examples of the dichroic organic dyes include red BR, red LR, red R, pink LB, rubin BL, Borde GS, sky blue LG, lemon yellow, blue BR, blue 2R, navy RY, green LG, violet LB, B, Black H, Black B, Black GSP, Yellow 3G, Yellow R, Orange LR, Orange 3R, Scarlet GL, Scarlet KGL, Kongogred, Brilliant Violet BK, Supra Blue G, Supra Blue GL, Supra Orange GL, , Direct First Orange S, and First Black. The dichroic dye may be used alone, or two or more dichroic dyes may be used in combination. The dichroic dye is preferably iodine.

The polarizing film (10) comprises a step of uniaxially stretching a polyvinyl alcohol-based resin film; A step of adsorbing a dichroic dye by staining a polyvinyl alcohol-based resin film with a dichroic dye; A step of cross-linking a polyvinyl alcohol-based resin film adsorbed with a dichroic dye; And a step of washing with water after the crosslinking treatment.

The polyvinyl alcohol-based resin film is a film of 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 10 to 150 mu m, preferably 50 mu m or less, and more preferably 35 mu m or less.

The uniaxial stretching of the polyvinyl alcohol based resin film can be performed before, simultaneously with, or after dyeing the dichroic dye. In the case of uniaxial stretching after dyeing, the uniaxial stretching may be carried out before or during the crosslinking treatment. The uniaxial stretching may be performed at a plurality of these steps.

In uniaxial stretching, the film may be uniaxially stretched between rolls having different circumferential velocities, or may be uniaxially stretched using a heat roll. The uniaxial stretching may be dry stretching in which stretching is performed in the atmosphere, or wet stretching in which stretching of the polyvinyl alcohol based resin film is performed in a solution. The stretching magnification is usually about 3 to 8 times.

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

When iodine is used as the dichroic dye, a method in which a polyvinyl alcohol resin film is dipped in an aqueous solution containing iodine and potassium iodide is generally employed. The content of iodine in the dyeing aqueous solution is usually 0.01 to 1 part by weight per 100 parts by weight of water. The content of potassium iodide is usually 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.

On the other hand, when a dichroic organic dye is used as the dichroic dye, a method of dying and dyeing a polyvinyl alcohol-based resin film into a dyeing aqueous solution containing a water-soluble dichroic organic dye is generally employed. The content of the dichroic organic dye in the dyeing aqueous solution is usually 1 × 10 ^-4 to 10 parts by weight, preferably 1 × 10 ^-3 to 1 part by weight, per 100 parts by weight of water. The 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 crosslinking treatment after dyeing with a dichroic dye can be carried out by immersing the dyed polyvinyl alcohol resin film in an aqueous solution containing a crosslinking agent. A suitable example of the crosslinking agent is boric acid, but boron compounds such as borax, and other crosslinking agents such as glyoxal and glutaraldehyde may be used. The crosslinking agent may be used alone or in combination of two or more.

The amount of the crosslinking agent in the crosslinking agent-containing aqueous solution is usually 2 to 15 parts by weight, preferably 5 to 12 parts by weight, per 100 parts by weight of water. When iodine is used as the dichroic dye, it is preferable that the aqueous solution containing the crosslinking agent contains potassium iodide. The amount of potassium iodide in the aqueous solution containing a crosslinking agent is usually 0.1 to 15 parts by weight, preferably 5 to 12 parts by weight, per 100 parts by weight of water. The temperature of the crosslinking agent-containing aqueous solution is usually 50 ° C or higher, preferably 50 to 85 ° C.

The polyvinyl alcohol-based resin film after crosslinking treatment is usually subjected to water washing treatment. The water washing treatment can be carried out, for example, by immersing the cross-linked polyvinyl alcohol resin film in water. The temperature of water in the water washing treatment is usually about 1 to 40 ° C.

After washing with water, the drying treatment is performed to obtain the polarizing film 10. The drying treatment may be drying by a hot air dryer, drying by contacting with a heat roll, drying by a far infrared ray heater, or the like. The drying treatment is usually carried out at a temperature of 30 to 100 캜, preferably 50 to 90 캜.

The thickness of the polarizing film 10 is usually about 2 to 40 mu m. From the viewpoint of thinning of the polarizing plate 2, the thickness of the polarizing film 10 is preferably 20 占 퐉 or less, more preferably 15 占 퐉 or less, and further preferably 10 占 퐉 or less. The smaller the thickness of the polarizing film 10, the more easily the curling of the polarizing plate 2 occurs in each of the polarizing plates. However, according to the present invention, when the thickness of the polarizing film 10 is small and the polarizing plate 2 is made of a sheet, Even if it causes a backlash, this backlash can be effectively corrected in the normal direction.

(3-3) The first and second thermoplastic resin films

Each of the first and second thermoplastic resin films 20 and 30 is a film composed of a thermoplastic resin having transparency, preferably an optically transparent thermoplastic resin. The thermoplastic resin constituting the first and second thermoplastic resin films 20 and 30 may be a polyolefin resin such as a chain polyolefin resin (polypropylene resin, etc.), a cyclic polyolefin resin (norbornene resin, etc.) ; Cellulose-based resins such as triacetylcellulose and diacetylcellulose; Polyester-based resins such as polyethylene terephthalate and polybutylene terephthalate; Polycarbonate resin; (Meth) acrylic resins such as methyl methacrylate resins; Polystyrene type resin; Polyvinyl chloride resins; Acrylonitrile-butadiene-styrene-based resin; Acrylonitrile-styrene series resin; Polyvinyl acetate resin; Polyvinylidene chloride resins; Polyamide based resin; A polyacetal-based resin; Modified polyphenylene ether-based resin; Polysulfone resins; Polyether sulfone type resin; Polyarylate resins; Polyamideimide series resin; A polyimide-based resin, or the like.

Examples of the chain polyolefin-based resin include a homopolymer of a chain olefin such as a polyethylene resin and a polypropylene resin, and a copolymer composed of two or more chain olefins. More specific examples include a polypropylene resin (a polypropylene resin which is a homopolymer of propylene or a copolymer mainly composed of propylene), a polyethylene resin (a copolymer mainly composed of polyethylene resin or ethylene which is a homopolymer of ethylene) do.

The cyclic polyolefin-based resin is a generic name of a resin that is polymerized using a cyclic olefin as a polymerization unit. Specific examples of the cyclic polyolefin-based resin include ring-opened (co) polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers (typically, random copolymers) of cyclic olefins and chain olefins such as ethylene and propylene, Graft polymers modified with carboxylic acids or their derivatives, and hydrides thereof. Among them, a norbornene resin using a norbornene monomer such as norbornene or a polycyclic norbornene monomer as the cyclic olefin is preferably used.

The cellulose-based resin is a resin in which part or all of the hydrogen atoms in the hydroxyl group of the cellulose obtained from the raw cellulose such as cotton linters and wood pulp (hardwood pulp, softwood pulp) and the like are substituted with an acetyl group, a propionyl group and / or a butyryl group , A cellulose organic acid ester, or a cellulose mixed organic acid ester. Examples thereof include acetate esters of cellulose, propionic acid esters, butyric acid esters, and mixed esters thereof. Among them, triacetylcellulose, diacetylcellulose, cellulose acetate propionate and cellulose acetate butyrate are preferable.

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

The polycarbonate resin is an engineering plastic made of a polymer having a monomer unit bonded through a carbonate, and is a resin having high impact resistance, heat resistance, flame retardancy and transparency. The polycarbonate resin may be a resin called a modified polycarbonate such as a polymer skeleton modified to lower the photoelastic coefficient, or a copolymerized polycarbonate improved in wavelength dependency.

The (meth) acrylic resin is a polymer containing a constituent unit derived from a (meth) acrylic monomer. This polymer is typically a polymer comprising a methacrylic acid ester. Preferably, the ratio of the structural units derived from methacrylic acid ester is 50% by weight or more based on the total structural units. The (meth) acrylic resin may be a homopolymer of methacrylic acid ester, or may be a copolymer containing constituent units derived from other polymerizable monomers. In this case, the proportion of the structural units derived from other polymerizable monomers is preferably 50% by weight or less based on the total structural units.

As the methacrylic acid ester which can constitute the (meth) acrylic resin, alkyl methacrylate is preferable. Examples of the methacrylic acid alkyl ester include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, Methylcyclohexyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, 2-hydroxyethyl methacrylate, and the like. The number of carbon atoms of the alkyl group contained in the methacrylic acid alkyl ester is preferably 1 to 4. In the (meth) acrylic resin, the methacrylic acid ester may be used alone, or two or more kinds thereof may be used in combination.

Examples of the other polymerizable monomer that can constitute the (meth) acrylic resin include acrylic acid esters and other compounds having a polymerizable carbon-carbon double bond in the molecule. The other polymerizable monomers may be used alone, or two or more of them may be used in combination. As the acrylic acid ester, acrylic acid alkyl ester is preferable. Examples of the alkyl acrylate include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, And alkyl acrylate esters having 1 to 8 carbon atoms in the alkyl group. The number of carbon atoms of the alkyl group contained in the alkyl acrylate is preferably 1 to 4. In the (meth) acrylic resin, the acrylic acid ester may be used alone, or two or more kinds thereof may be used in combination.

Examples of other compounds having a polymerizable carbon-carbon double bond in the molecule include vinyl compounds such as ethylene, propylene and styrene, and vinyl cyan compounds such as acrylonitrile. The other compounds having a polymerizable carbon-carbon double bond in the molecule may be used alone, or two or more of them may be used in combination.

The first and second thermoplastic resin films 20 and 30 may be a protective film for protecting the polarizing film 10 laminated on one surface of the polarizing film 10. The first or second thermoplastic resin films 20 and 30 may be a protective film having optical functions such as a retardation film and a brightness enhancement film. For example, a phase difference film having an arbitrary retardation value can be obtained by stretching (uniaxially stretching or biaxially stretching) a thermoplastic resin film made of the above material, or forming a liquid crystal layer or the like on the film. The first and / or second thermoplastic resin films 20 and 30 may have 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 laminated on the surface thereof .

Thicknesses of the first and second thermoplastic resin films 20 and 30 are usually 1 to 100 占 퐉, but preferably 5 to 60 占 퐉 and more preferably 5 to 50 占 퐉 in view of strength and handling properties. If the thickness is within this range, it is possible to mechanically protect the polarizing film 10 to suppress shrinkage of the polarizing film 10 when the polarizing plate 2 is exposed under a humid environment. The smaller the thickness of the first thermoplastic resin film 20 or the second thermoplastic resin film 30, the more easily the curled polarizing plate 2 is formed in each of the cores. However, according to the present invention, the first thermoplastic resin film 20 ) Or the thickness of the second thermoplastic resin film 30 is, for example, not more than 40 占 퐉 and more specifically not more than 30 占 퐉 and the polarizing plate 2 is made of a woven fabric, .

The first thermoplastic resin film 20 is provided on one surface of the polarizing film 10 and the second thermoplastic resin film 30 (not shown) is provided on the other surface, as in the polarizing plates 2a and 2c shown in Figs. The first thermoplastic resin film 20 and the second thermoplastic resin film 30 may be composed of the same kind of thermoplastic resin or may be composed of different kinds of thermoplastic resins, The present invention is particularly advantageous in such a case because the curvature is particularly likely to occur in each of the corners of the polarizing plate 2 when the equilibrium moisture content and the moisture permeability of the thermoplastic resin films bonded to both surfaces are different.

For example, as the first thermoplastic resin film 20, a film having an equilibrium moisture content higher than that of the second thermoplastic resin film 30 can be used. The larger the difference in the equilibrium moisture content between the first thermoplastic resin film 20 and the second thermoplastic resin film 30 bonded to both surfaces of the polarizing film 10 is, According to the present invention, even if the difference in the equilibrium moisture content is 0.5 wt% or more, moreover 1 wt% or more, and further 1.5 wt% or more, and the polarizing plate 2 is caused to form a backlit, Direction. ≪ / RTI >

In the present specification, the equilibrium moisture content of the film is measured by a dry weight method, specifically,

Equilibrium moisture content (% by weight) = {(Film weight before drying treatment - Film weight after drying treatment) / Film weight before drying treatment} x 100

. Here, the weight of the film before the drying treatment refers to the weight after the film is stored for 24 hours in an environment of a temperature of 23 DEG C and a relative humidity of 55%, and the term drying means treatment in which the film is dried at 105 DEG C for 2 hours. Examples of the combination of thermoplastic resin films having a difference in equilibrium moisture content of 0.5 wt% or more include a combination of a cellulose resin film (TAC film, etc.) and a cyclic polyolefin resin film, a cellulose resin film (TAC film, etc.) A combination of a cellulose resin film (TAC film or the like) and a polyester resin film, a combination of a cellulose resin film (TAC film or the like) and a chain polyolefin resin film, a combination of a (meth) acrylic resin film A combination of a cyclic polyolefin resin and a combination of a (meth) acrylic resin film and a polyester resin film. The difference in equilibrium moisture content between the first thermoplastic resin film 10 and the second thermoplastic resin film 20 is usually 5 wt% or less, preferably 2.5 wt% or less.

The equilibrium moisture content of the first thermoplastic resin film 20 is, for example, 1.5% by weight or more, and may be 2% by weight or more. The equilibrium water content of the first thermoplastic resin film 20 is usually 5% by weight or less.

In the case where a film having a higher equilibrium moisture content than the second thermoplastic resin film 30 is used as the first thermoplastic resin film 20, the equilibrium moisture content of the second thermoplastic resin film 20 is usually 0.1 to 1.5 wt% Preferably 0.1 to 1% by weight. Examples of the thermoplastic resin constituting the second thermoplastic resin film 20 capable of achieving such an equilibrium moisture content are a cyclic polyolefin resin, a (meth) acrylic resin, a polyester resin, and a chain polyolefin resin.

The equilibrium moisture content of the thermoplastic resin film may be adjusted in accordance with the material (the kind of the thermoplastic resin constituting the film), the thickness of the film, the presence or the material of the surface treatment layer (coating layer)

In the case of using a film having a higher equilibrium moisture content than the second thermoplastic resin film 30 as the first thermoplastic resin film 20 from the viewpoint of calibrating countercurrents that tend to occur in the polarizing plate 2 in the normal direction, In the pressing step, the protective film 1 is disposed on the first thermoplastic resin film 20 side of the polarizing plate 2.

As the first thermoplastic resin film 20, for example, a film having higher moisture permeability than the second thermoplastic resin film 30 can be used. The larger the difference in the moisture permeability between the first thermoplastic resin film 20 and the second thermoplastic resin film 30 bonded to both sides of the polarizing film 10 is, According to the invention, the difference in the moisture permeability is 30 g / (m 2 · 24 hr) or more, more preferably 50 g / (m 2 · 24 hr) or more and furthermore 100 g / (m 2 · 24 hr) ), It is possible to effectively correct the backlash in the normal direction.

In the present specification, the moisture permeability of the film is the moisture permeability at a temperature of 40 DEG C and a relative humidity of 90% measured by the cup method defined in JIS Z 0208. Examples of the combination of thermoplastic resin films having a difference in water vapor permeability of 30 g / (m 2 · 24 hr) or more include a combination of a cellulose based resin film (such as a TAC film) and a cyclic polyolefin based resin film, A combination of a cellulose resin film (TAC film, etc.) with a polyester resin film, a combination of a cellulose resin film (TAC film, etc.) with a chain polyolefin resin film, ( A combination of a (meth) acrylic resin film and a cyclic polyolefin resin, and a combination of a (meth) acrylic resin film and a polyester resin film. The difference in the moisture permeability between the first thermoplastic resin film 10 and the second thermoplastic resin film 20 is usually 5000 g / (m 2 · 24 hr) or less.

The moisture permeability of the first thermoplastic resin film 20 is, for example, 300 g / (m 2 · 24 hr) or more and 400 g / (m 2 · 24 hr) or more. When the first thermoplastic resin film 20 and the polarizing film 10 are bonded to each other using the water based adhesive agent, the layer made of the aqueous adhesive agent is efficiently dried (the water vapor permeability is 300 g / (m 2 24 hr) It is advantageous in that productivity can be increased. The moisture permeability of the first thermoplastic resin film 20 is usually 5000 g / (m 2 · 24 hr) or less.

The second thermoplastic resin film 20 has a moisture permeability of usually 1 to 350 g / (m < 2 > / 24 hr, and preferably 5 to 200 g / (m < 2 > 24 hr). Examples of the thermoplastic resin constituting the second thermoplastic resin film 20 capable of achieving such moisture permeability include a cyclic polyolefin resin, a (meth) acrylic resin, a polyester resin, and a chain polyolefin resin.

The moisture permeability of the thermoplastic resin film can be adjusted not only by its material (the kind of the thermoplastic resin constituting the film) but also by the thickness of the film, the presence or the material of the surface treatment layer (coating layer)

In the case of using a film having a higher moisture permeability than the second thermoplastic resin film 30 as the first thermoplastic resin film 20, from the viewpoint of correcting countercurrent, which is likely to occur in the polarizing plate 2, in the normal direction, The protective film 1 is disposed on the side of the first thermoplastic resin film 20 in the polarizing plate 2. [

As described above, the polarizing film 10 and the first and second thermoplastic resin films 20 and 30 can be bonded together using an adhesive. The polarizing film 10 and / or the joining surfaces of the first and second thermoplastic resin films 20 and 30 are laminated before the first and second thermoplastic resin films 20 and 30 are laminated to the polarizing film 10, May be subjected to surface activation treatment such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame treatment, and saponification treatment. By this surface activation treatment, adhesion between the polarizing film 10 and the first and second thermoplastic resin films 20 and 30 can be enhanced.

As the adhesive, an aqueous adhesive, an active energy ray-curable adhesive or a thermosetting adhesive can be used, and preferably an aqueous adhesive and an active energy ray-curable adhesive. In the case where the thermoplastic resin film is laminated on both surfaces of the polarizing film 10, the both surfaces of the adhesive may be the same kind of adhesive or different kinds of adhesives. In the case of using different types of adhesives, the polarizing plate 2 is liable to cause curling in each of its corners, but according to the present invention, even if the polarizing plate 2 is made of a sheet, It is possible to effectively calibrate a counter-clock in the direction of the hand.

The water-based adhesive is obtained by dissolving the adhesive component in water or dispersing it 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.

When a polyvinyl alcohol resin is used as the main component of the adhesive, the polyvinyl alcohol resin may be a polyvinyl alcohol resin such as partially saponified polyvinyl alcohol or fully saponified polyvinyl alcohol, or may be a carboxyl group-modified polyvinyl alcohol, Modified polyvinyl alcohol resins such as acetoacetyl group-modified polyvinyl alcohol, methylol group-modified polyvinyl alcohol, and amino group-modified polyvinyl alcohol. The polyvinyl alcohol-based resin may be a polyvinyl alcohol-based copolymer obtained by saponifying a copolymer of vinyl acetate and another monomer copolymerizable therewith, in addition to a vinyl alcohol homopolymer obtained by saponifying polyvinyl acetate which is a homopolymer of vinyl acetate. It may be combined.

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, based on 100 parts by weight of water.

The adhesive composed of an aqueous solution of a polyvinyl alcohol resin preferably contains a curing component such as a polyvalent aldehyde, a melamine compound, a zirconia compound, a zinc compound, a glyoxal, a glyoxal derivative and a water-soluble epoxy resin or a crosslinking agent . Examples of the water-soluble epoxy resin include polyamines obtained by reacting epichlorohydrin with polyamide amines obtained by reacting polyalkylene polyamines such as diethylene triamine and triethylene tetramine with dicarboxylic acids such as adipic acid, Amide polyamine epoxy resins can be suitably used. Examples of commercially available products of such polyamide polyamine epoxy resins include Sumirez Resin 650 (Daokakagaku Kogyo Co., Ltd.), Sumirez Resin 675 (Daokakagaku Kogyo Co., Ltd.), WS-525 (Manufactured by Nippon PMC Co., Ltd.). The amount of the curable component and the amount of the crosslinking agent (the total amount when the curable component and the crosslinking agent are added together) is usually 1 to 100 parts by weight, preferably 1 to 50 parts by weight, based on 100 parts by weight of the polyvinyl alcohol resin. When the amount of the curable component or the crosslinking agent to be added is less than 1 part by weight based on 100 parts by weight of the polyvinyl alcohol resin, the effect of improving the adhesiveness tends to be small. When the addition amount is less than 100 parts by weight of the polyvinyl alcohol- When the amount exceeds 100 parts by weight, the adhesive layer tends to become fragile.

A suitable example of the case where a urethane resin is used as the main component of the adhesive is a mixture of a polyester-based ionomer-type urethane resin and a compound having a glycidyloxy group. The polyester-based ionomer-type urethane resin is a urethane resin having a polyester skeleton, and a small amount of an ionic component (hydrophilic component) is introduced into the urethane resin. Such an ionomeric urethane resin is suitable as an aqueous adhesive since it emulsifies directly in water without using an emulsifier to form an emulsion.

In the case of using the water-based adhesive, it is preferable that the polarizing film 10 and the first and / or second thermoplastic resin films 20 and 30 are bonded to each other and then a drying step for removing water contained in the water- desirable. After the drying step, a curing step may be carried out to cure at a temperature of, for example, 20 to 45 ° C.

The active energy ray-curable adhesive is an adhesive which is cured by irradiation with an active energy ray such as ultraviolet ray, visible light, electron ray or X-ray. When an active energy ray-curable adhesive is used, the adhesive layer of the polarizing plate 2 is a cured layer of the adhesive.

The active energy ray curable adhesive may be an adhesive containing an epoxy compound curable by cationic polymerization as a curable component, preferably an ultraviolet curable adhesive containing such an epoxy compound as a curable component. The epoxy compound referred to herein means a compound having an average of at least one, preferably two or more epoxy groups in the molecule. The epoxy compound may be used alone, or two or more epoxy compounds may be used in combination.

Specific examples of the epoxy compound suitably usable include a hydrogenated epoxy compound obtained by reacting an alicyclic polyol obtained by subjecting an aromatic ring of an aromatic polyol to a hydrogenation reaction with epichlorohydrin (a glycidyl ether of a polyol having an alicyclic ring Diesters); Aliphatic epoxy compounds such as polyglycidyl ethers of aliphatic polyhydric alcohols or alkylene oxide adducts thereof; And an alicyclic epoxy compound which is an epoxy compound having at least one epoxy group bonded to an alicyclic ring in the molecule.

The active energy ray-curable adhesive may contain, as a curable component, a (meth) acrylic compound which is radically polymerized instead of or in addition to the epoxy compound. Examples of the (meth) acrylic compound include (meth) acrylate monomers having at least one (meth) acryloyloxy group in the molecule; (Meth) acryloyloxy group-containing compounds such as (meth) acrylate oligomers having at least two (meth) acryloyloxy groups in the molecule which are obtained by reacting two or more kinds of functional group-containing compounds.

When the active energy ray-curable adhesive contains an epoxy compound curable by cationic polymerization as a curable component, it preferably contains 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; Iron-allene complexes and the like. When the active energy ray curable adhesive contains a radically polymerizable curable component such as a (meth) acrylic compound, it preferably contains a photo radical polymerization initiator. Examples of the photo radical polymerization initiator include an acetophenone-based initiator, a benzophenone-based initiator, a benzoin ether-based initiator, a thioxanthone-based initiator, xanthone, fluorenone, camphorquinone, benzaldehyde and anthraquinone.

When an active energy ray curable adhesive is used for the lamination bonding of the polarizing film 10 and the first and / or second thermoplastic resin films 20 and 30, after the lamination bonding, the drying step is carried out if necessary, And the curing step of curing the active energy ray-curable adhesive is performed by irradiating the energy ray. Although a light source of an active energy ray is not particularly limited, ultraviolet rays having a light emission distribution at a wavelength of 400 nm or less are preferable, and specifically, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, a high pressure mercury lamp, A mercury lamp, a metal halide lamp, or the like can be used.

The active energy ray irradiation intensity on the adhesive layer made of the active energy ray-curable adhesive is appropriately determined according to the composition of the adhesive, and the irradiation intensity in the wavelength range effective for activating the polymerization initiator is set to be 0.1 to 6000 mW / desirable. When the irradiation intensity is not less than 0.1 mW / cm 2, the reaction time does not become excessively long, and when the irradiation intensity is 6000 mW / cm 2 or less, the heat radiated from the light source and heat generated during curing of the adhesive, There is little fear of causing deterioration.

The irradiation time of the active energy ray is appropriately determined depending on the composition of the adhesive. It is preferable that the accumulated light amount, which is expressed as a product of the irradiation intensity and the irradiation time, is set to 10 to 10,000 mJ / cm 2. When the cumulative light quantity is 10 mJ / cm 2 or more, a sufficient amount of active species originating from the polymerization initiator can be generated sufficiently to allow the curing reaction to proceed more surely. When the total amount is 10,000 mJ / cm 2 or less, the irradiation time is not excessively long, ) Can be maintained.

(3-4) Pressure-sensitive adhesive layer and separate film

As shown in Figs. 3 and 4, the polarizing plate 2 may include a pressure-sensitive adhesive layer 40. Fig. The pressure-sensitive adhesive layer 40 can be laminated directly on the surface of the first or second thermoplastic resin film 20 or 30 or the polarizing film 10, and the polarizing plate 3 having a protective film can be laminated on an image display element Liquid crystal cell).

The pressure-sensitive adhesive layer 40 for bonding the polarizing plate 3 having a protective film to an image display element (e.g., liquid crystal cell) is provided on the main surface (first main surface) side of the polarizing plate to be bonded to an image display element such as a liquid crystal cell . The polarizing plate 2 includes the first and second thermoplastic resin films 20 and 30 as the first thermoplastic resin film 20 and the second thermoplastic resin film 20 has the equilibrium moisture content and / The pressure-sensitive adhesive layer 40 can be disposed on the second thermoplastic resin film 30 side.

The pressure-sensitive adhesive layer 40 can be composed of a pressure-sensitive adhesive composition containing a resin such as (meth) acrylic, rubber, urethane, ester, silicone or polyvinyl ether as a main component (base polymer). Among them, a pressure-sensitive adhesive composition comprising a (meth) acrylic resin having excellent transparency, weather resistance and heat resistance as a base polymer is suitable. The pressure-sensitive adhesive composition may be an active energy radiation curable type or a thermosetting type.

Examples of the (meth) acrylic resin used in the pressure-sensitive adhesive composition include (meth) acrylic acid esters such as (meth) acrylic acid esters such as butyl (meth) acrylate, ethyl (meth) acrylate, isooctyl (meth) acrylate and 2-ethylhexyl A polymer or a copolymer containing two or more species as a monomer is suitably used. The (meth) acrylic resin is preferably copolymerized with a polar monomer. Examples of polar monomers include (meth) acrylic acid, 2-hydroxypropyl (meth) acrylate, hydroxyethyl (meth) acrylate, (meth) acrylamide, N, N-dimethylaminoethyl A hydroxyl group, an amide group, an amino group, an epoxy group, and the like, such as dodecyl (meth) acrylate.

The pressure-sensitive adhesive composition may contain only the base polymer, but usually contains a crosslinking agent. Examples of the cross-linking agent include a metal salt having a bivalent or higher valency, which forms a carboxylic acid metal salt with a carboxyl group; As the polyamine compound, forming an amide bond with a carboxyl group; As the polyepoxy compound or the polyol, an ester bond is formed with the carboxyl group; As the polyisocyanate compound, an amide bond is formed between the polyisocyanate compound and the carboxyl group. Among them, a polyisocyanate compound is preferable.

The active energy ray-curable pressure-sensitive adhesive composition has a property of curing upon irradiation with an active energy ray such as ultraviolet rays or electron rays and has adhesiveness even before irradiation with an active energy ray so that it can be adhered to an adherend such as a film, And is capable of adjusting the adhesive force. The active energy ray-curable pressure-sensitive adhesive composition is preferably an ultraviolet curable type. The active energy ray-curable pressure-sensitive adhesive composition further contains an active energy ray-polymerizable compound in addition to the base polymer and the crosslinking agent. In some cases, a photopolymerization initiator, a photosensitizer or the like may be contained as needed.

The pressure-sensitive adhesive composition is preferably a pressure-sensitive adhesive composition comprising fine particles for imparting light scattering properties, a resin other than beads (resin beads, glass beads), glass fibers and base polymers, a tackifier, fillers (metal powder and other inorganic powders, An ultraviolet absorber, a dye, a pigment, a colorant, a defoaming agent, a corrosion inhibitor, a photopolymerization initiator, and the like.

The pressure-sensitive adhesive layer 40 is formed by applying an organic solvent diluted solution of the pressure-sensitive adhesive composition onto the pressure-sensitive adhesive layer formation surface (i.e., the polarizing film 10 or the first or second thermoplastic resin films 20 and 30) of the polarizing plate 2 Followed by drying. Alternatively, an organic solvent dilution liquid of the pressure-sensitive adhesive composition may be coated on a separate film (for example, the separate film 50) and dried to form a pressure-sensitive adhesive layer, and then transferred onto the pressure-sensitive adhesive layer formation surface of the polarizing plate 2. In any of these methods, it is preferable that the separator film is adhered to the outer surface of the pressure-sensitive adhesive layer 40 to protect the pressure-sensitive adhesive layer 40 before use. When an active energy ray-curable pressure-sensitive adhesive composition is used, a cured product having a desired degree of curing can be obtained by irradiating an active energy ray to the pressure-sensitive adhesive layer formed. The thickness of the pressure-sensitive adhesive layer 40 is usually 1 to 40 占 퐉, but it is preferably 3 to 25 占 퐉 from the viewpoint of thinning of the polarizing plate 2.

The separate film 50 is a film adhered to protect the surface of the pressure-sensitive adhesive layer 40 until the pressure-sensitive adhesive layer 40 is bonded to an image display device (e.g., a liquid crystal cell). The separate film 50 is usually made of a thermoplastic resin film having a releasing treatment applied to one surface thereof, and the releasably treated surface thereof is bonded to the pressure-sensitive adhesive layer 40. The thermoplastic resin constituting the separate film 50 may be, for example, a polyethylene-based resin such as polyethylene, a polypropylene-based resin such as polypropylene, or a polyester-based resin such as polyethylene terephthalate or polyethylene naphthalate. The thickness of the separate film 50 is, for example, 10 to 100 占 퐉.

(3-5) Other components of the polarizer

The polarizing plate 2 may include other components than those described above. As another component, an optical layer or an optical film having an optical function other than the polarizing film 10 is exemplified, and specific examples thereof are optical films such as a retardation film and a brightness enhancement film. Other optical films can be laminated and bonded through a pressure-sensitive adhesive layer or an adhesive layer.

The polarizing plate 2 may include a protective film different from the protective film 1 used in the pressing step. This protective film is disposed on one surface of the polarizing plate 2. [ Regarding the constitution of this protective film, the technique relating to the above-mentioned protective film (1) is cited.

(3-6) Curl of Polarizer

As described above, according to the present invention, the polarizing plate 2 can be calibrated in the positive direction, whereby it is possible to prevent the backlash from being sufficiently suppressed when it is made into a wool, preferably flat without curling, A polarizing plate 3 having a protective film can be obtained. The manufacturing method according to the present invention is advantageous in that when the polarizing plate 2 is made of a worm, it causes a backlash (a curl that convexes the main surface side where the protective film 1 overlaps) (that is, ). ≪ / RTI >

When the first thermoplastic resin film 20 and the second thermoplastic resin film 30 have different equilibrium moisture content and / or moisture permeability as one of the forms of the polarizing plate 2, However, the present invention is not limited to this, and the countercurrent is likely to occur even when the polarizing plate 2 has an asymmetrical layer structure with respect to the polarizing film 10.

An example of the configuration of the polarizing plate 2 which is liable to cause a counter-current is as follows.

(a) a structure in which a thermoplastic resin film (protective film or the like) is bonded to only one side of the polarizing film 10,

(b) a structure in which a protective film is bonded to one surface of the polarizing film 10 and an optical film (brightness enhancement film or the like) other than a protective film is bonded to the other surface,

(c) a constitution (a type of resin, a thickness, an equilibrium moisture content, a moisture permeability, the presence or absence of a surface treatment layer) of the thermoplastic resin film (protective film or the like) bonded to both surfaces of the polarizing film 10,

(d) a structure in which adhesive layers for bonding a thermoplastic resin film (protective film or the like) to both surfaces of the polarizing film 10 are formed of different kinds of adhesives,

(e) a structure in which a thermoplastic resin film (protective film or the like) is bonded to both surfaces of the polarizing film 10 and another optical film is bonded on one thermoplastic resin film,

(f) In addition, the total number of films and layers on one side and the total number of films and layers on the other side are different from each other with respect to the polarizing film 10.

(4) Other processes

The production method according to the present invention may further include a step of cutting the polarizing plate 3 having a protective film obtained by the pressing step to obtain each of the polarizing plates 3 having the polarizing plate 3 having a protective film. A commonly used cutting device such as a shear cutter can be used for the cutting.

The shape of each fired body is not particularly limited, but it is usually a rectangular shape, preferably a rectangular shape having long sides and short sides, more preferably a rectangular shape. The streaks are usually cut so that a pair of opposing sides are parallel to the MD and the remaining pair of opposing sides are parallel to the TD. Each side may be cut so that the sides are inclined at MD or TD. The length of the long side and the length of the short side of each leaf are not particularly limited, but usually long side is 50 mm or more and short side is 30 mm or more. Curl is more likely to occur when the size of each leaf is larger. If the size (long side and / or short side) is too small, the curl problem itself is difficult to occur.

[Example]

Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples. In the following examples, the equilibrium moisture content, the moisture permeability, the thickness and the tensile elastic modulus, and the film tension and curl amount were measured by the following methods.

(1) Equilibrium moisture content of the film

A specimen of MD length 150 mm x TD length 100 mm was cut out. The film weight after storage for 24 hours under an environment of a temperature of 23 캜 and a relative humidity of 55% was measured. Thereafter, the film was dried at 105 DEG C for 2 hours, and the weight of the film after the drying treatment was measured. From the weight of the film before and after drying,

Equilibrium moisture content (% by weight) = {(Film weight before drying treatment - Film weight after drying treatment) / Film weight before drying treatment} x 100

The equilibrium moisture content was determined.

(2) Water vapor permeability of film

(G / (m < 2 > 24 hr)] at a temperature of 40 DEG C and a relative humidity of 90% was measured by a cup method defined in JIS Z 0208. [

(3) thickness of polarizer and film

MH-15M " manufactured by Nikon Corporation.

(4) Tensile modulus in MD of polarizing plate and protective film

A rectangular test piece having a length of MD 100 mm x a length of TD 25 mm was cut out. Subsequently, both ends of the test piece in the longitudinal direction were sandwiched between upper and lower grippers of a tensile tester (AUTOGRAPH AG-1S tester manufactured by Shimadzu Seisakusho Co., Ltd.) so that the gap between the grippers was 5 cm. , The specimen was pulled out in the MD (length direction of the test piece) at a tensile speed of 1 mm / min under the environment of a load of 1 mm / min, and the slope of the initial straight line in the obtained stress- [MPa] was calculated.

(5) Film tension in MD of polarizing plate and protective film

The film tension [N / m] of the polarizing plate and the protective film running between a pair of bonding rolls for bonding the polarizing plate and the protective film and a pair of nip rolls upstream of the bonding roll and nearest to the bonding roll, Was measured using a tension detection roll provided between a roll and a pair of nip rolls closest to the bonding roll.

(6) Curl of a polarizing plate and a polarizing plate having a protective film

A rectangular test piece having a MD length of 300 mm and a TD length of 200 mm was cut out from a polarizing plate having the obtained protective film and allowed to stand under an environment of a temperature of 23 DEG C and a relative humidity of 55% for 24 hours. The specimen was placed on its reference plane (horizontal band) so that its concave side was up, that is, four end sides were formed. With respect to each of the four corners of the test piece in this state, the height from the reference plane was measured, and the curl amount [mm] was obtained as an average of the heights of the four angles. When the curl amount is a positive value, it means that the first thermoplastic resin film side is concave (positive), and when it is negative, it means that the second thermoplastic resin film side is concave. Further, the polarizing plate having the protective film of Example 2 did not cause curling even when the side of the first thermoplastic resin film side or the side of the second thermoplastic resin film was raised.

≪ Example 1 >

(A) Production of polarizing film

The film was uniaxially stretched by a dry method about four times while continuously feeding a long polyvinyl alcohol film (average degree of polymerization: about 2400, saponification degree: 99.9 mol% or more, thickness: 30 탆) continuously, Immersed in pure water for 1 minute, and then immersed in an aqueous solution having a weight ratio of iodine / potassium iodide / water of 0.1 / 5/100 at 28 DEG C for 60 seconds. Thereafter, 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 占 폚 for 5 seconds and then dried at 70 占 폚 for 180 seconds to obtain a long polarizing film in which iodine was adsorbed and aligned on the uniaxially stretched polyvinyl alcohol film. The thickness of the polarizing film was 11.1 탆.

(B) Production of Polarizing Plate

The polarizing film obtained in the above (A) was continuously conveyed, and a film having a hard coat layer formed on a long first thermoplastic resin film (TAC film " KC2UAW " manufactured by Konica Minolta Opt. And a long second thermoplastic resin film (trade name " FEKB015D3 ", which is a cyclic polyolefin-based resin film manufactured by JSR Corporation, thickness: 15.1 [micro] m, (Equilibrium moisture content: 0.8% by weight, water vapor permeability: 115 g / (m 2 .24 hr)) was continuously conveyed to form a water-based film between the polarizing film and the first thermoplastic resin film and between the polarizing film and the second thermoplastic resin film While passing through the bonding rolls while injecting the adhesive, a laminated film composed of the first thermoplastic resin film / water-based adhesive layer / polarizing film / water-based adhesive layer / second thermoplastic resin film was obtained. Then, the obtained laminated film was conveyed, passed through a hot-air dryer, and subjected to heat treatment at 80 DEG C for 300 seconds to dry the water-based adhesive layer to obtain a polarizing plate. To the above water-based adhesive, a polyvinyl alcohol aqueous solution having a concentration of 3% by weight obtained by dissolving a polyvinyl alcohol powder ("Kosepaima", trade name, manufactured by Nippon Kohaku Kagaku Kogyo Co., Ltd., average degree of polymerization: 1100) (Sodium glyoxylate, manufactured by Nippon Gohsei Kagaku Kogyo Co., Ltd.) was mixed in a ratio of 1 part by weight based on 10 parts by weight of the polyvinyl alcohol powder.

The thickness T ₂ of the polarizing plate was 58.6 탆, and the tensile elastic modulus E ₂ of the MD was 6540 MPa. The amount of curl of the polarizing plate was measured according to the above-mentioned method, and it was -10 mm (counterverse).

(C) Production of a polarizing plate having a protective film

The polarizing film obtained in the above (B) was continuously conveyed, and a long protective film (a protective film having a base film made of polyethylene terephthalate and having a (meth) acrylic pressure sensitive adhesive layer thereon, a total thickness T ₁ : 57.3 탆 and tensile elastic modulus E _{1 in} the MD: 2521 MPa) were continuously conveyed and passed between the joining rolls so that the laminate of the protective film and the polarizing plate was pressed up and down to produce a polarizing plate having a protective film . The protective film is bonded to the surface of the first thermoplastic resin film (TAC film) of the polarizing plate through the pressure-sensitive adhesive layer. In addition, the pressure (nip pressure) given to the laminate of the protective film and the polarizing plate by the bonding roll was 0.1 MPa, and this value is also substantially the same in the following examples and comparative examples.

The film tension in MD of the polarizing plate and the protective film, the value obtained by multiplying the left side of the formula (I) by 10 ⁵ , the value obtained by multiplying the right side by 10 ⁵ , the difference therebetween and the curl amount of the polarizing plate having the protective film are shown in Table 1 . In Table 1, "Δ" represents the difference between the left side of the formula (I) multiplied by 10 ⁵ and the right side multiplied by 10 ⁵ , that is, the left side of the formula (II).

≪ Examples 2 to 5 >

A polarizing plate having a protective film was produced in the same manner as in Example 1 except that the film tension in the MD of the polarizing plate and the protective film was changed as shown in Table 1. [ The left side of the formula (I) is multiplied by 10 ⁵ , the right side is multiplied by 10 ⁵ , and the difference between them and the curl amount of the polarizing plate having a protective film are shown in Table 1.

≪ Example 6 >

A long protective film having a base film of polyethylene terephthalate and having a (meth) acrylic pressure-sensitive adhesive layer and having a total thickness T ₁ of 69.3 탆 and a tensile elastic modulus E ₁ of 2743 MPa in MD was used, And the film tension in the MD of the protective film were changed as shown in Table 1, a polarizing plate having a protective film was produced in the same manner as in Example 1. The left side of the formula (I) is multiplied by 10 ⁵ , the right side is multiplied by 10 ⁵ , and the difference between them and the curl amount of the polarizing plate having a protective film are shown in Table 1.

≪ Example 7 >

(Thickness: 22.9 占 퐉, equilibrium moisture content: 0.1% by weight, water vapor permeability: 17 g / (m < 2 > 24 hr)] as a second thermoplastic resin film (trade name: "ZF14-023", a cyclic polyolefin based resin film manufactured by Nippon Zeon Co., , A polarizing plate having a thickness T ₂ of 66.8 탆 and a tensile elastic modulus E ₂ of 6080 MPa in MD was prepared. The amount of curl of the polarizing plate was measured according to the above-mentioned method, and it was -6 mm (negative).

Subsequently, a polarizing plate having a protective film was produced in the same manner as in Example 1 except that the polarizing plate obtained above was used and the film tension in MD of the polarizing plate and the protective film was changed as shown in Table 1. The left side of the formula (I) is multiplied by 10 ⁵ , the right side is multiplied by 10 ⁵ , and the difference between them and the curl amount of the polarizing plate having a protective film are shown in Table 1.

≪ Comparative Example 1 &

Except that a TAC film "KC2UAW" (thickness: 25.5 μm, equilibrium moisture content: 3.0% by weight, moisture permeability: 1207 g / (m 2 · 24 hr) manufactured by Konica Minolta Opt Co., Ltd.) was used as the first thermoplastic resin film In the same manner as in Example 1, a polarizing plate having a thickness T ₂ of 51.7 탆 and a tensile elastic modulus E ₂ of 6839 MPa in MD was produced. The amount of curl of the polarizing plate was measured according to the above-mentioned method, and it was -13 mm (counterverse).

Subsequently, a polarizing plate having a protective film was produced in the same manner as in Example 1 except that the polarizing plate obtained above was used and the film tension in MD of the polarizing plate and the protective film was changed as shown in Table 1. The left side of the formula (I) is multiplied by 10 ⁵ , the right side is multiplied by 10 ⁵ , and the difference between them and the curl amount of the polarizing plate having a protective film are shown in Table 1.

1: polarizing film, 2: first thermoplastic resin film, 2: second thermoplastic resin film, 2: polarizing plate, 2: polarizing plate, 3: polarizing plate having a protective film : Pressure-sensitive adhesive layer, 50: separate film.

Claims (9)

A process for producing a polarizing plate having a protective film comprising a step of pressing a polarizing plate by passing it between a pair of bonding rolls, wherein the protective film is superimposed on one side of the polarizing plate,
The thickness of the protective film is T ₁ [탆], the tensile elastic modulus in MD is E ₁ [MPa], and the film tension in MD before passing through the pair of bonding rolls is F ₁ [N / m] , The thickness of the polarizing plate is T ₂ [탆], the tensile elastic modulus in the MD direction is E ₂ [MPa], and the film tension in MD before passing through the pair of bonding rolls is F ₂ [N / m , The pressing step is performed by the following formula (I):

Is satisfied. The method according to claim 1,

Is satisfied. The production method according to claim 1, wherein the polarizing plate causes a curl to convex the side on which the protective film is superimposed when it is made into a wax. The method according to claim 1, wherein the polarizing plate comprises a polarizing film, a first thermoplastic resin film laminated on one surface thereof, and a second thermoplastic resin film laminated on the other surface. The production method according to claim 4, wherein the first thermoplastic resin film has an equilibrium moisture content higher than that of the second thermoplastic resin film at a temperature of 23 캜 and a relative humidity of 55%. The production method according to claim 5, wherein the difference between the equilibrium moisture content of the first thermoplastic resin film and the second thermoplastic resin film is 0.5 wt% or more. The production method according to any one of claims 4 to 6, wherein the protective film is disposed on the first thermoplastic resin film side. The production method according to any one of claims 4 to 6, wherein the first thermoplastic resin film has an equilibrium water content of 1.5% by weight or more at a temperature of 23 캜 and a relative humidity of 55%. The method according to claim 1, wherein the thickness of the polarizing plate is 100 占 퐉 or less.

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