KR20170093849A - Method for manufacturing polarizing plate - Google Patents

Abstract

A method for producing a polarizing plate having a first protective film on one side of a polarizer and a second protective film on the other side, comprising the steps of: forming a first adhesive layer comprising an active energy ray- A second bonding step of bonding the second protective film to the other side of the polarizer through a second adhesive layer made of an active energy ray curable adhesive after the first bonding step, Wherein the first protective film is a protective film disposed on the display cell side with respect to the second protective film when the polarizing plate is disposed on the display cell and the thickness after curing of the first adhesive layer is less than the hardening A method of manufacturing a polarizing plate that is smaller than a thickness after the polarizing plate is provided.

Description

METHOD FOR MANUFACTURING POLARIZING PLATE [0002]

The present invention relates to a polarizing plate manufacturing method, and more particularly, to a polarizing plate manufacturing method in which a protective film is bonded to both surfaces of a polarizer through an adhesive layer made of an active energy ray curable adhesive.

BACKGROUND ART [0002] Polarizing plates are widely used in display devices such as liquid crystal display devices, and particularly in various mobile devices such as smart phones. As a polarizing plate, a protective film is generally bonded to one side or both sides of a polarizer using an adhesive. However, as polarizers are developed in mobile devices, polarizers and protective films constituting a polarizing plate are increasingly required to be thinned.

As the adhesive, an aqueous adhesive such as a polyvinyl alcohol aqueous solution or an active energy ray curable adhesive such as an ultraviolet ray curable adhesive is known. In the case of bonding a protective film with low moisture permeability, moisture is volatilized from the adhesive layer after the protective film is bonded An active energy ray curable adhesive has been used in many cases (see, for example, JP-A-2013-205741 (Patent Document 1), JP-A-2012-203205 (Patent Document 2) Patent Publication No. 2012-203108 (Patent Document 3), Japanese Patent Application Laid-Open No. 2004-245925 (Patent Document 4)].

Japanese Patent Application Laid-Open No. 2013-205741 Japanese Patent Laid-Open Publication No. 20-20520 Japanese Patent Laid-Open Publication No. 2012-203108 Japanese Patent Application Laid-Open No. 2004-245925

The thinner the polarizer or the protective film constituting the polarizing plate is, the smaller the distortion occurs in at least one of the interface between the polarizer and the adhesive layer or the interface between the protective film and the adhesive layer, or the reflection image reflected on the polarizing plate is fine Or the reflection image is distorted, so that the surface may appear to have minute irregularities. Such a phenomenon does not directly adversely affect the optical characteristics of the polarizing plate. However, when the polarizing plate exhibiting such a phenomenon is placed on the outside (for example, the outermost surface) of the protective film when the polarizing plate is bonded to the display cell, This phenomenon remains even after the protective film is peeled off and the luster of the surface of the protective film can not be obtained. Thus, appearance problems such as insufficient quality are caused.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a method for producing a polarizing plate exhibiting a good appearance when bonded to a display cell.

The present invention provides a method for producing a polarizing plate described below and a method for producing a polarizing plate having a pressure-sensitive adhesive layer.

[1] A method of producing a polarizing plate comprising a first protective film on one side of a polarizer and a second protective film on the other side,

A first bonding step of bonding the first protective film to the one surface through a first adhesive layer made of an active energy ray curable adhesive,

A second bonding step of bonding the second protective film to the other side via a second adhesive layer made of an active energy ray curable adhesive after the first bonding step

/ RTI >

The first protective film is a protective film disposed on the display cell side with respect to the second protective film when the polarizing plate is disposed on the display cell,

Wherein a thickness of the first adhesive layer after curing is smaller than a thickness after curing of the second adhesive layer.

[2] The production method according to [1], wherein the thickness of the first adhesive layer after curing is 0.75 μm or less.

[3] The production method according to [1] or [2], wherein the thickness of the second adhesive layer after curing is larger than 0.75 μm.

[4] The production method according to any one of [1] to [3], wherein a difference between a thickness after curing of the second adhesive layer and a thickness after curing of the first adhesive layer is 0.1 탆 or more.

[5] The production method according to any one of [1] to [4], wherein the thickness of the polarizer is 20 m or less.

[6] a first bonding step of bonding a first protective film to one side of the polarizer through a first adhesive layer made of an active energy ray-

A second bonding step of bonding a second protective film to the other side of the polarizer through a second adhesive layer made of an active energy ray curable adhesive after the first bonding step,

A pressure-sensitive adhesive layer forming step of disposing a pressure-sensitive adhesive layer on the outer surface of the first protective film

/ RTI >

Wherein the pressure-sensitive adhesive layer has a thickness after curing of the first adhesive layer is smaller than a thickness after curing of the second adhesive layer.

According to the production method of the present invention, it is possible to provide a polarizing plate having a polarizing plate and a pressure-sensitive adhesive layer in which the above-mentioned irregularity appearing on the surface of the second protective film and the distortion and distortion of the reflected image are suppressed. When the polarizing plate having the polarizing plate and the pressure-sensitive adhesive layer to be obtained is arranged on the display cell so that the second protective film is outside (such that the first protective film is on the display cell side), the polarizing plate having the polarizing plate Since distortion and distortion are suppressed, the appearance is excellent.

1 is a schematic cross-sectional view showing an example of a layer structure of a polarizing plate obtained by a manufacturing method according to the present invention.
2 is a schematic cross-sectional view showing a state in which the polarizing plate shown in Fig. 1 is disposed on a display cell.
3 is a flowchart showing a preferred example of the method for producing a polarizing plate according to the present invention.
4 is a schematic cross-sectional view showing an example of the layer structure of the laminated film obtained in the resin layer forming step.
5 is a schematic cross-sectional view showing an example of the layer structure of the stretched film obtained in the stretching step.
6 is a schematic cross-sectional view showing an example of the layer structure of the polarizing laminated film obtained in the dyeing step.
7 is a schematic cross-sectional view showing an example of the layer structure of the bonding film obtained in the first bonding step.
8 is a schematic cross-sectional view showing an example of the layer structure of a polarizing plate having a single-sided protective film obtained in the peeling step.

≪ Polarizing plate production method >

1, the present invention relates to a polarizer 5, a first protective film 10 laminated on one side thereof with a first adhesive layer 15, and a second adhesive layer 25 on the other side, (A polarizing plate with a double-side protective film) 1 having a second protective film 20 laminated via a first protective film 20. 2 showing a state in which the polarizing plate 1 is disposed on the display cell 50, the first protective film 10 is arranged in the same direction as the second protective film 20, As shown in Fig. The second protective film 20 is a protective film disposed outside the first protective film 10 when the polarizing plate 1 is placed on the display cell 50 and the polarizing plate 1 is used as a display cell 50, it is typically a protective film that forms the outermost surface. 2, the polarizing plate 1 is formed on the display cell 50 by using a pressure-sensitive adhesive layer 60 provided on the outer surface of the first protective film 10 disposed on the display cell 50 side, Can be arranged and bonded.

Hereinafter, embodiments of the present invention will be described, and a method for producing a polarizing plate according to the present invention will be described in detail.

[First Embodiment]

3, a method of producing a polarizing plate according to the present embodiment is a method for producing a polarizing plate having a double-side protective film using a base film, wherein the following steps:

A resin layer forming step (S10) of forming a polyvinyl alcohol-based resin layer by coating a coating liquid containing a polyvinyl alcohol-based resin on at least one surface of a base film and then drying,

A stretching step (S20) of stretching the laminated film to obtain a stretched film,

A dyeing step (S30) of obtaining a polarizing laminated film by dying a polyvinyl alcohol-based resin layer of a stretched film with a dichroic dye to form a polarizer,

A first bonding step (S40) of bonding a first protective film to the polarizer of the polarizing laminated film through the first adhesive layer to obtain a bonded film,

A peeling step (S50) of peeling off the base film from the bonding film to obtain a polarizing plate having a one-side protective film, and

A second bonding step (S60) of bonding the second protective film to the polarizing surface of the polarizing plate having the one-side protective film through the second adhesive layer,

In this order.

Hereinafter, each step will be described with reference to Figs. 4 to 8. Fig. In addition, in the resin layer forming step (S10), the polyvinyl alcohol-based resin layer may be formed on both surfaces of the base film. In the following, a case mainly formed on one side will be described.

(1) Resin layer forming step (S10)

4, the present step is a step of forming a polyvinyl alcohol-based resin layer 6 on at least one surface of the base film 30 to obtain a laminated film 100. The polyvinyl alcohol-based resin layer 6 is a layer that becomes the polarizer 5 through the drawing step (S20) and the dyeing step (S30). The polyvinyl alcohol-based resin layer 6 can be formed by coating a coating liquid containing a polyvinyl alcohol-based resin on one side or both sides of the base film 30 and drying it. The method of forming the polyvinyl alcohol-based resin layer by such a coating is advantageous in that it is easy to obtain a polarizer 5 of a thin film.

The base film 30 may be composed of a thermoplastic resin and is preferably composed of a thermoplastic resin having excellent transparency, mechanical strength, thermal stability, stretchability, and the like. Specific examples of such a thermoplastic resin include a polyolefin-based resin such as a chain-like polyolefin-based resin, a cyclic polyolefin-based resin (norbornene-based resin and the like); Polyester-based resin; (Meth) acrylic resin; Cellulose ester-based resins such as cellulose triacetate and cellulose diacetate; Polycarbonate resin; Polyvinyl alcohol-based resin; Polyvinyl acetate resin; Polyarylate resins; Polystyrene type resin; Polyether sulfone type resin; Polysulfone resins; Polyamide based resin; Polyimide resin; And mixtures and copolymers thereof. In the present specification, the term " (meth) acrylic " means at least one selected from acrylic and methacrylic. The same applies to "(meth) acryloyl".

The base film 30 may be a single layer structure composed of one resin layer composed of one kind of thermoplastic resin or two or more kinds of thermoplastic resins and may have a multilayer structure in which a plurality of resin layers made of one kind or two or more kinds of thermoplastic resins are laminated . The base film 30 is composed of a resin that can be stretched at a drawing temperature suitable for drawing the polyvinyl alcohol type resin layer 6 when the laminated film 100 is stretched in a drawing step S20 described later .

The base film (30) may contain an additive. Specific examples of the additives include an ultraviolet absorber, an antioxidant, a lubricant, a plasticizer, a release agent, a coloring inhibitor, a flame retardant, a nucleating agent, an antistatic agent, a pigment and a colorant.

The thickness of the base film 30 is usually 1 to 500 占 퐉, preferably 1 to 300 占 퐉, more preferably 5 to 200 占 퐉, further preferably 5 to 150 占 퐉, Mu m.

The coating liquid to be coated on the base film 30 is preferably a polyvinyl alcohol-based resin solution obtained by dissolving a polyvinyl alcohol-based resin powder in a good solvent (for example, water). The coating liquid may contain an additive such as a plasticizer and a surfactant if necessary. As the polyvinyl alcohol-based resin, a saponified polyvinyl acetate-based resin can be used. Examples of the polyvinyl acetate resin include polyvinyl acetate which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth) acrylamides having an ammonium group.

The saponification degree of the polyvinyl alcohol-based resin may be in the range of 80.0 to 100.0 mol%, preferably 90.0 to 99.5 mol%, and more preferably 94.0 to 99.0 mol%. When the degree of saponification is less than 80.0 mol%, the water resistance and the moisture resistance of the resultant polarizing plate 1 deteriorate. When a polyvinyl alcohol-based resin having a degree of saponification of more than 99.5 mol% is used, the dyeing speed is slowed, the productivity is lowered, and the polarizer 5 having sufficient polarization performance may not be obtained.

The degree of saponification indicates the unit ratio (mol%) 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 x (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 percentage of acetic acid groups that inhibit crystallization.

The polyvinyl alcohol resin may be a modified polyvinyl alcohol partially modified. For example, the polyvinyl alcohol-based resin may be mixed with an olefin such as ethylene or propylene; Unsaturated carboxylic acids such as acrylic acid, methacrylic acid and crotonic acid; Alkyl esters of unsaturated carboxylic acids, (meth) acryl amides, and the like. The ratio of denaturation is preferably less than 30 mol%, more preferably less than 10%. When the modification is performed in an amount exceeding 30 mol%, it becomes difficult to adsorb the dichroic dye, and it tends to be difficult to obtain the polarizer 5 having sufficient polarization performance.

The average degree of polymerization of the polyvinyl alcohol-based resin is preferably from 100 to 10,000, more preferably from 1,500 to 8,000, and further preferably from 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).

The method of coating the coating liquid on the base film 30 may be a wire bar coating method; Roll coating methods such as reverse coating and gravure coating; Die coating method; Comma coat method; Lip coating method; Spin coating method; Screen coating method; Fountain coating method; Dipping method; Spraying method or the like.

The drying temperature and drying time of the coating layer (polyvinyl alcohol-based resin layer before drying) are set according to the type of the solvent contained in the coating liquid. The drying temperature is, for example, 50 to 200 캜, preferably 60 to 150 캜. When the solvent includes water, the drying temperature is preferably 80 DEG C or higher.

The polyvinyl alcohol-based resin layer 6 may be formed on only one side of the base film 30 or on both sides thereof. It is possible to suppress the curling of the film which may occur in the production of the polarizing laminated film 300 (see Fig. 6) and to obtain two polarizing plates from one polarizing laminated film 300 , And is also advantageous in terms of production efficiency of the polarizing plate.

The thickness of the polyvinyl alcohol-based resin layer 6 in the laminated film 100 is preferably 3 to 60 占 퐉, more preferably 5 to 40 占 퐉, further preferably 5 to 20 占 퐉 . The polyvinyl alcohol-based resin layer 6 having a thickness within this range is subjected to a stretching step (S20) and a dyeing step (S30) to be described later, whereby the dyeing property of the dichroic dye is good and the polarizing performance is excellent, (For example, a thickness of 20 탆 or less, further 10 탆 or less) can be obtained.

In order to improve the adhesion between the base film 30 and the polyvinyl alcohol resin layer 6 prior to the coating of the coating liquid, at least the surface of the base film 30 on the side where the polyvinyl alcohol-based resin layer 6 is formed A corona treatment, a plasma treatment, a flame (flame) treatment, or the like may be performed. For the same reason, the polyvinyl alcohol-based resin layer 6 may be formed on the base film 30 through a primer layer or the like.

The primer layer can be formed by coating a coating liquid for forming a primer layer on the surface of the base film 30 and then drying the primer layer. This coating liquid contains a component exhibiting a strong adhesion to some extent to both the base film 30 and the polyvinyl alcohol-based resin layer 6, and usually includes a resin component and a solvent which give such adhesion. As the resin component, a thermoplastic resin excellent in transparency, thermal stability, stretchability and the like is used, and examples thereof include (meth) acrylic resin, polyvinyl alcohol resin and the like. Among them, a polyvinyl alcohol-based resin which gives good adhesion is preferably used. More preferably, it is a polyvinyl alcohol resin. As the solvent, a general organic solvent or an aqueous solvent capable of dissolving the resin component is usually used, but it is preferable to form the primer layer from a coating solution using water as a solvent.

The primer layer may be peeled off from the polarizer 5 in a single step with the base film in a peeling step (S50) described later, or peeled off from the base film as one with the polarizer 5. If it is an electron, the primer layer can be formed from any thermoplastic resin that is easily peeled from the polyvinyl alcohol-based resin layer as described above. On the other hand, in the latter case, the primer layer is dyed together with the polyvinyl alcohol-based resin layer in the dyeing step (S30) described later, and after peeling off the base film in the peeling step (S50), the polyvinyl alcohol- And it becomes necessary to become the polarizer 5 as a single layer. For example, when a primer layer is formed with a polyvinyl alcohol-based resin, the primer layer is dyed together with the polyvinyl alcohol-based resin layer in the subsequent dyeing step (S30), and the polarizer 5 And is peeled off from the base film to become a part of the polarizer 5.

In order to increase the strength of the primer layer, a crosslinking agent may be added to the coating liquid for forming the primer layer. Specific examples of the crosslinking agent include epoxy-based, isocyanate-based, dialdehyde-based, metal-based (for example, metal salts, metal oxides, metal hydroxides, organometallic compounds) and high molecular weight crosslinking agents. When a polyvinyl alcohol-based resin is used as the resin component forming the primer layer, a polyamide epoxy resin, a methylol melamine resin, a dialdehyde-based cross-linking agent, a metal chelate-based cross-linking agent and the like are suitably used.

The thickness of the primer layer is preferably about 0.05 to 1 mu m, more preferably 0.1 to 0.4 mu m. If the thickness is smaller than 0.05 탆, the effect of improving adhesion between the base film 30 and the polyvinyl alcohol-based resin layer 6 is small, and if it is thicker than 1 탆, it is disadvantageous for making the polarizing plate 1 thinner.

The method of coating the coating liquid for forming the primer layer on the base film 30 may be the same as the coating liquid for forming the polyvinyl alcohol-based resin layer. The drying temperature of the coating layer composed of the coating liquid for forming the primer layer is, for example, 50 to 200 캜, preferably 60 to 150 캜. When the solvent includes water, the drying temperature is preferably 80 DEG C or higher.

(2) Stretching step (S20)

5, the laminated film 100 composed of the base film 30 and the polyvinyl alcohol-based resin layer 6 is stretched to form the stretched base film 30 'and the polyvinyl alcohol- (6 '). The stretching treatment is usually uniaxial stretching.

The stretching magnification of the laminated film 100 can be appropriately selected according to the desired polarization characteristics, but is preferably 5 times to 17 times or more, more preferably 5 times to more than 5 times the original length of the laminated film 100 8 times or less. If the stretching magnification is 5 times or less, the degree of polarization of the polarizer 5 may not be sufficiently increased because the polyvinyl alcohol-based resin layer 6 'is not sufficiently oriented. On the other hand, when the stretching magnification exceeds 17 times, the film tends to break at the time of stretching, and the thickness of the stretched film 200 becomes thinner than necessary, which may lower the workability and handling property in the subsequent step.

The stretching treatment is not limited to stretching in one step but may be performed in multiple steps. In this case, all of the stretching process of the multistage layer may be continuously performed before the dyeing step (S30), or the second and subsequent stretching steps may be performed simultaneously with the dyeing treatment and / or the crosslinking treatment in the dyeing step (S30) good. In the case where the stretching process is performed in such a multistage, it is preferable that the stretching process is performed so as to obtain a stretching magnification of more than 5 times the total number of steps of the stretching process.

The stretching treatment may be longitudinal stretching in which stretching is performed in the film longitudinal direction (film transport direction), transverse stretching or oblique stretching in stretching in the film width direction, or the like. Examples of the longitudinal stretching method include roll-to-roll stretching using a roll, compression stretching, and stretching using a chuck. The transverse stretching method includes a tenter method and the like. The stretching treatment can be carried out by either a wet stretching method or a dry stretching method.

The stretching temperature is set to be equal to or higher than the temperature at which the entirety of the polyvinyl alcohol resin layer 6 and the substrate film 30 can be stretched to exhibit fluidity and is preferably set at a temperature at which the base film 30 has a phase transition temperature -30 占 폚 to + 30 占 폚, more preferably -30 占 폚 to + 5 占 폚, further preferably -25 占 폚 to + 0 占 폚. When the base film 30 is composed of a plurality of resin layers, the phase transition temperature means the highest phase transition temperature among the phase transition temperatures indicated by the plurality of resin layers.

If the stretching temperature is lower than -30 캜 of the phase transition temperature, high-magnification stretching exceeding 5 times is difficult to achieve, or the flowability of the base film 30 is too low to make the stretching process difficult. If the stretching temperature exceeds + 30 ° C of the phase transition temperature, the fluidity of the base film 30 is too large, and the stretching tends to become difficult. The stretching temperature is within the above range and further preferably 120 DEG C or more since it is easier to achieve a high draw ratio of more than 5 times.

Examples of the heating method of the laminated film 100 in the stretching treatment include a zone heating method (for example, a method of heating in a stretching zone such as a heating furnace in which hot air is blown and adjusted to a predetermined temperature); A method of heating the roll itself in the case of stretching using a roll; A heater heating method (an infrared heater, a halogen heater, a panel heater or the like is disposed above and below the laminated film 100 and heated by radiant heat). In the roll-to-roll stretching method, the zone heating method is preferable from the viewpoint of the uniformity of the stretching temperature.

The stretching temperature means the atmospheric temperature in the zone (for example, in the heating furnace) in the case of the zone heating method, and the heating temperature means the atmospheric temperature in the furnace when heating is performed in the furnace. In the case of the method of heating the roll itself, it means the surface temperature of the roll.

A preheating treatment step for preheating the laminated film 100 may be provided prior to the stretching step S20. As the preheating method, the same method as the heating method in the stretching treatment can be used. The preheating temperature is preferably in the range of -50 占 폚 to 占 0 占 폚 of the stretching temperature and more preferably in the range of -40 占 폚 to -10 占 폚 of the stretching temperature.

After the stretching treatment in the stretching step (S20), a heat fixing treatment step may be provided. The heat fixation treatment is a process of performing heat treatment at a crystallization temperature or higher while keeping the end portion of the stretched film 200 in a state of being held in a state of being held by a clip. By this heat setting treatment, the crystallization of the polyvinyl alcohol-based resin layer 6 'is promoted. The heat-setting treatment temperature is preferably in the range of -0 to -80 占 폚 of the stretching temperature, and more preferably in the range of -0 to -50 占 폚 of the stretching temperature.

(3) Dyeing process (S30)

6, this step is a step of dying the polyvinyl alcohol-based resin layer 6 'of the stretched film 200 with a dichroic dye and adsorbing the dyed dye to obtain a polarizer 5. A polarizing laminated film 300 in which the polarizer 5 is laminated on one side or both sides of the base film 30 'is obtained through this step. The dichroic dye 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, Congo-red, Brilliant Violet BK, GL, Direct Sky Blue, 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 dyeing step can be performed by immersing the entire stretched film 200 in a solution (dyeing solution) containing a dichroic dye. As the dyeing solution, a solution in which a dichroic dye is dissolved in a solvent can be used. As the solvent, water is generally used, but an organic solvent having compatibility with water may be further added. The concentration of the dichroic dye in the dyeing solution is preferably 0.01 to 10% by weight, and more preferably 0.02 to 7% by weight.

When iodine is used as the dichroic dye, it is preferable to add iodide to the dyeing solution because the dyeing efficiency can be improved. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide and titanium iodide. The concentration of iodide in the dyeing solution is preferably 0.01 to 20% by weight. Among iodides, it is preferable to add potassium iodide. When potassium iodide is added, the ratio of iodine to potassium iodide is preferably from 1: 5 to 1: 100, more preferably from 1: 6 to 1:80, by weight. The temperature of the dyeing solution is preferably from 10 to 60 캜, more preferably from 20 to 40 캜.

Further, it is also possible to perform the dyeing step (S30) before the stretching step (S20) or to carry out these steps at the same time, but in order to allow the dichroic dye to be adsorbed on the polyvinyl alcohol- It is preferable to perform the dyeing step (S30) after at least some degree of drawing treatment is applied to the substrate 100.

The dyeing step (S30) may include a crosslinking treatment step which is carried out subsequent to the dyeing treatment. The crosslinking treatment can be carried out by immersing the dyed film in a solution (crosslinking solution) in which the crosslinking agent is dissolved in a solvent. Examples of the crosslinking agent include boron compounds such as boric acid and borax, glyoxal, and glutaraldehyde. The crosslinking agent may be used alone or in combination of two or more. As the solvent of the crosslinking solution, water can be used, but an organic solvent having compatibility with water may be further included. The concentration of the crosslinking agent in the crosslinking solution is preferably from 1 to 20% by weight, and more preferably from 6 to 15% by weight.

The crosslinking solution may further comprise iodide. By adding iodide, the polarization performance in the plane of the polarizer 5 can be made more uniform. Specific examples of the iodide are the same as described above. The concentration of iodide in the crosslinking solution is preferably 0.05 to 15% by weight, more preferably 0.5 to 8% by weight. The temperature of the crosslinking solution is preferably 10 to 90 占 폚.

The crosslinking treatment may be carried out simultaneously with the dyeing treatment by blending the crosslinking agent into the dyeing solution. The treatment of immersing in a crosslinking solution may be performed twice or more using two or more kinds of crosslinking solutions having different compositions.

After the dyeing step (S30), it is preferable to carry out a washing step and a drying step before the first joining step (S40) described later. The cleaning process usually includes a water cleaning process. The water washing treatment can be performed by immersing the film after the dyeing treatment or after the crosslinking treatment in pure water such as ion-exchanged water or distilled water. The water washing temperature is usually 3 to 50 占 폚, preferably 4 to 20 占 폚. The cleaning step may be a combination of a water cleaning step and a cleaning step with an iodide solution. As the drying step performed after the cleaning step, any suitable method such as natural drying, air blow drying, and heat drying can be employed. For example, in the case of heat drying, the drying temperature is usually 20 to 95 ° C.

(4) First bonding step (S40)

7, the first adhesive layer 15 is formed on the polarizer 5 of the polarizing laminated film 300, that is, on the side opposite to the base film 30 'side of the polarizer 5 The first protective film 10 is bonded to the first protective film 10 to obtain a bonding film 400. [ When the polarizing laminated film 300 has polarizers 5 on both sides of the base film 30 ', the first protective film 10 is usually bonded onto the polarizers 5 on both sides. In this case, the first protective film 10 may be a protective film of the same kind or a different type.

As described above, when the polarizing plate 1 is disposed on the display cell 50, the first protective film 10 is formed so as to cover the protective film 20, which is disposed on the display cell 50 side of the second protective film 20, to be. The first protective film 10 is preferably made of a thermoplastic resin having a light transmitting property (preferably optically transparent) such as a chain polyolefin resin (polypropylene resin, etc.), a cyclic polyolefin resin (norbornene resin, etc.) The same polyolefin-based resin; Cellulose ester-based resins such as cellulose triacetate and cellulose diacetate; Polyester-based resin; Polycarbonate resin; (Meth) acrylic resin; Polystyrene type resin; Or a mixture or copolymer thereof, or the like. Among them, the first protective film 10 (also referred to as the second protective film 20 described later) suitably used in the present invention is a protective film having low moisture permeability, such as a polyolefin resin , A polyester resin, a (meth) acrylic resin, a polystyrene resin, or the like.

The first protective film 10 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) the film made of the thermoplastic resin or forming a liquid crystal layer or the like on the film.

Examples of the chain-like 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 kinds of chain olefins.

The cyclic polyolefin-based resin is a general term for resins that are polymerized using a cyclic olefin as a polymerization unit. Specific examples of the cyclic polyolefin-based resin include a ring-opening (co) polymer of a cyclic olefin, an addition polymer of a cyclic olefin, a copolymer (typically a random copolymer) of a cyclic olefin and a chain olefin such as ethylene or propylene, A graft polymer modified with a carboxylic acid or a derivative thereof, and a hydride thereof. Among them, a norbornene-based resin using a norbornene-based monomer such as norbornene or a polycyclic norbornene-based monomer as a cyclic olefin is preferably used.

The cellulose ester resin is an ester of cellulose and a fatty acid. Specific examples of the cellulose ester-based resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. These copolymers and those obtained by modifying a part of hydroxyl groups with other substituents may also be used. Of these, cellulose triacetate (triacetylcellulose: TAC) is particularly preferable.

The polyester-based resin is a resin other than the cellulose ester-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 dicarboxylic acid or a derivative thereof can be used, and examples thereof include terephthalic acid, isophthalic acid, dimethylterephthalate, and dimethyl naphthalenedicarboxylate. As the polyhydric alcohol, a diol can be used, and examples thereof include ethylene glycol, propanediol, butanediol, neopentyl glycol, cyclohexanedimethanol and the like.

Specific examples of the polyester-based resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polycyclohexanedimethyl terephthalate, polycyclohexane Dimethyl naphthalate.

The polycarbonate resin is composed of a polymer to which a monomer unit is bonded through a carbonate group. The polycarbonate resin may be a resin called a modified polycarbonate such as a modified polymer skeleton, or a copolymerized polycarbonate.

The (meth) acrylic resin is a resin mainly composed of a compound having a (meth) acryloyl group. Specific examples of the (meth) acrylic resin include poly (meth) acrylic acid esters such as polymethyl methacrylate; Methyl methacrylate- (meth) acrylic acid copolymer; Methyl methacrylate- (meth) acrylic acid ester copolymer; Methyl methacrylate-acrylic acid ester- (meth) acrylic acid copolymer; (Meth) acrylate-styrene copolymer (MS resin or the like); A copolymer of methyl methacrylate and a compound having an alicyclic hydrocarbon group [e.g., methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate- (meth) acrylate norbornyl copolymer, etc.). Preferably, a polymer containing as a main component a poly (meth) acrylic acid C _{1 -6} alkyl ester such as poly (meth) acrylate is used, more preferably methyl methacrylate as a main component (50 to 100% By weight, preferably 70 to 100% by weight) is used.

Further, specific examples of the various thermoplastic resins as described above are specific examples of the thermoplastic resin constituting the base film (30).

The first protective film 10 may contain one or more additives such as a lubricant, a plasticizer, a dispersant, a heat stabilizer, an ultraviolet absorber, an infrared absorber, an antistatic agent and an antioxidant.

The thickness of the first protective film 10 is preferably 90 占 퐉 or less, more preferably 50 占 퐉 or less, further preferably 30 占 퐉 or less, from the viewpoint of thinning of the polarizing plate 1. The thickness of the first protective film 10 is usually 5 占 퐉 or more from the viewpoints of strength and handleability.

Examples of the adhesive forming the first adhesive layer 15 for bonding the first protective film 10 to the polarizer 5 include an adhesive having an active energy ray curability that is cured by irradiation of active energy rays such as ultraviolet rays, visible light, Adhesive is used. The active energy ray curable adhesive is preferably an ultraviolet ray curable adhesive. Use of an active energy ray-curable adhesive can be used for bonding of a protective film having a low moisture permeability because 1) it can be prepared as an adhesive for a solventless formulation, and thus a drying step can be dispensed with. 2) There are many types of protective films that can be bonded.

As the active energy ray curable adhesive, an active energy ray curable adhesive composition comprising a curable compound having a cationically polymerizable property and / or a radically polymerizable curable compound can be preferably used. The active energy ray-curable adhesive usually further comprises a cationic polymerization initiator and / or a radical polymerization initiator for initiating the curing reaction of the curable compound.

Examples of the cationically polymerizable curable compound include epoxy compounds (compounds having one or two or more epoxy groups in the molecule), oxetane compounds (compounds having one or two or more oxetane rings in the molecule) . ≪ / RTI > Examples of the radically polymerizable curable compound include (meth) acrylic compounds (compounds having one or two or more (meth) acryloyloxy groups in the molecule), other vinyl compounds having a radically polymerizable double bond, or And combinations thereof. A curable compound having a cationically polymerizable property may be used in combination with a radically polymerizable curable compound.

The active energy ray-curable adhesive may contain a catechol polymerization accelerator, an ion trapping agent, an antioxidant, a chain transfer agent, a tackifier, a thermoplastic resin, a filler, a flow regulator, a plasticizer, a defoaming agent, an antistatic agent, ≪ / RTI >

The first protective film 10 is laminated on the polarizer 5 through the active energy ray curable adhesive which becomes the first adhesive layer 15 and then irradiated with active energy rays such as ultraviolet rays, By curing the layer, the first protective film 10 can be adhesively bonded to the polarizer 5. As the light source in this case, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high pressure mercury lamp, a chemical lamp, a black light lamp, a microwave-excited mercury lamp, a metal halide lamp and the like can be used. In the polarizing plate 1 to be obtained, the first adhesive layer 15 is a cured layer of an active energy ray-curable adhesive.

In bonding the first protective film 10 to the polarizer 5, on the bonding surfaces of the first protective film 10 and / or the polarizer 5, Surface treatment (adhesion treatment) such as treatment, corona treatment, ultraviolet ray irradiation treatment, flame treatment, and saponification treatment can be performed. Preferred surface treatments are plasma treatment, corona treatment, and saponification treatment.

As described in detail later, the first adhesive layer 15 is formed so as to be thinner than the second adhesive layer in thickness after curing in order to effectively suppress the unevenness on the surface of the second protective film 20. [ For the same reason, the thickness of the first adhesive layer 15 after curing is preferably 0.75 mu m or less, more preferably 0.7 mu m or less, further preferably 0.5 mu m or less. The thickness of the first adhesive layer 15 after curing is usually 0.01 占 퐉 or more, preferably 0.1 占 퐉 or more, more preferably 0.2 占 퐉 or more, further preferably 0.3 占 퐉 or more, from the viewpoint of adhesiveness. If the thickness is too small, minute bubbles are likely to be mixed into the first adhesive layer 15 at the time of bonding the first protective film 10 and the polarizer 5. Such bubbles may cause light scattering when a polarizing plate is incorporated in a display device such as a liquid crystal display device and the display device is turned on. This light scattering may cause display problems in which light leaks (bubbles become bright spots) in a black display state.

The method of coating the active energy ray-curable adhesive on the bonding surface of the first protective film 10 and / or the polarizer 5 is not particularly limited. However, in order to reduce the thickness of the adhesive layer like the first adhesive layer 15 , A small diameter gravure, and the like. Particularly, a method of relatively increasing the rotation speed of the gravure by increasing the gravure rotation speed (ratio of the rotation speed of the gravure to the line speed) The thickness of the adhesive layer can be reduced by a method of increasing the number of meshes of the adhesive layer. Particularly, in order to reduce the thickness of the adhesive layer to 1 占 퐉 or less, gravure engraved with a laser engraving is preferably used, and it is particularly preferable to use a gravure roll having a honeycomb shape. For example, it is preferable that the number of honeycombs per inch and the number of honeycombs per inch exceeds 400 rows.

(5) Peeling step (S50)

With reference to Fig. 8, this step is a step of peeling off the base film 30 'from the bonding film 400. Through this process, a polarizing plate 500 having a one-side protective film in which the first protective film 10 is laminated on one surface of the polarizer 5 is obtained. When the polarizing laminated film 300 has polarizers 5 on both sides of the base film 30 'and the first protective film 10 is bonded to both of the polarizers 5, the peeling step S50 ), A polarizing plate 500 having two single-sided protective films from one polarizing laminated film 300 is obtained.

The method of peeling off the base film 30 'is not particularly limited, and can be peeled off in the same manner as the peeling process of a separator (peeling film) which is performed in a polarizing plate having an ordinary pressure-sensitive adhesive. The base film 30 'may be peeled off immediately after the first bonding step (S40), or may be peeled off in a roll form once in a roll form after the first bonding step (S40).

(6) Second bonding step (S60)

This step is carried out on the polarizer 5 side of the polarizing plate 500 having the one side protective film, that is, on the side opposite to the first protective film 10 bonded in the first bonding step (S40) 25 to bond the second protective film 20 to obtain a polarizing plate 1 having a double-sided protective film as shown in Fig.

As described above, the second protective film 20 is a protective film disposed outside the first protective film 10 when the polarizing plate 1 is disposed on the display cell 50. Like the first protective film 10, the second protective film 20 may be a film made of the thermoplastic resin exemplified above, or may be a protective film having optical functions such as a retardation film and a brightness enhancement film. With respect to the thickness of the additives and the film that the second protective film 20 can contain, the above description about the first protective film 10 is cited. The first protective film 10 and the second protective film 20 may be a protective film made of the same kind of resin or a protective film made of different kinds of resin.

According to the present invention, even when the thickness of the second protective film 20 is small, for example, 50 탆 or less, and furthermore 30 탆 or less, the irregularities on the surface of the second protective film 20 can be effectively suppressed.

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 may be formed on the surface of the second protective film 20 opposite to the polarizer 5. The method of forming the surface treatment layer is not particularly limited, and a known method can be used.

As the adhesive for forming the second adhesive layer 25 for bonding the second protective film 20 to the polarizer 5, an active energy ray curable adhesive is used similarly to the first adhesive layer 15. The active energy ray curable adhesive is preferably an ultraviolet ray curable adhesive. In the polarizing plate 1 to be obtained, the second adhesive layer 25 is a cured layer of an active energy ray-curable adhesive. Regarding specific examples of the active energy ray-curable adhesive, the above description on the first adhesive layer 15 is cited. The adhesive forming the first adhesive layer 15 and the adhesive forming the second adhesive layer 25 may be the same or different in composition. The bonding of the second protective film 20 through the second adhesive layer 25 can be performed in the same manner as the bonding of the first protective film 10.

The cause of the irregularity on the surface of the second protective film 20 is a shrinkage force when the adhesive forming the second adhesive layer 25 is hardened (hardening of the adhesive layer in a short time by irradiation of an active energy ray (Per unit time) in the case of using the active energy ray-curable adhesive for performing the adhesion is generally larger than that of the water-based adhesive which performs the adhesion with a relatively long time by drying of the solvent (water) The second protective film 20 and the polarizer 5 are removed from the second adhesive layer 25. Even when an active energy ray curable adhesive is used as the adhesive for forming the second adhesive layer 25 according to the present invention, Even if the thickness of the polarizer 5 and the first and second protective films 10 and 20 is small, it is possible to suppress the occurrence of the irregularities on the surface of the second protective film 20, It is possible to provide a polarizing plate having a high quality by providing a clear reflection image and excellent luster on the surface of the second protective film 20.

The second adhesive layer 25 is formed to have a thickness such that the thickness after curing of the first adhesive layer 15 becomes smaller than the thickness after curing of the second adhesive layer 25. The first and second adhesive layers 15 and 25 are formed in a thickness-wise relationship as described above on the premise that the second protective film 20 is bonded after the first protective film 10 is bonded to the polarizer 5, And it is therefore possible to effectively suppress the irregularities on the surface of the second protective film 20. [

For the same reason, the thickness of the second adhesive layer 25 after curing is preferably larger than 0.75 mu m, more preferably 1.0 mu m or larger. For the same reason, the difference between the thickness after curing of the second adhesive layer 25 and the thickness after curing of the first adhesive layer 15 is preferably 0.1 占 퐉 or more, more preferably 0.2 占 퐉 or more, and 0.3 占 퐉 or more Further preferred.

[Second embodiment]

The first embodiment is a method of forming a polarizer using a polyvinyl alcohol-based resin layer coated on a base film and then producing a polarizing plate. However, the present invention is not limited thereto, and a polarizing plate 5 made of a single (single) 1 protective film 10 and the second protective film 20 may be bonded in this order to produce the polarizing plate 1. [ The bonding of the first and second protective films 10 and 20 through the first and second adhesive layers 15 and 25 may be the same as in the first embodiment.

The polarizer 5 made of a single (single) film can be obtained by, for example, a step of producing a polyvinyl alcohol based resin film by a known method such as a melt extrusion method or a solvent casting method; Uniaxially stretching a polyvinyl alcohol-based resin film; Dyeing a polyvinyl alcohol-based resin film with a dichroic dye and adsorbing the dye; Treating a polyvinyl alcohol-based resin film adsorbed with a dichroic dye with an aqueous solution of boric acid; And a step of washing with water after treatment with an aqueous boric acid solution. Uniaxial stretching 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 the boric acid treatment or during the boric acid treatment. In addition, uniaxial stretching may be performed in these plural steps.

<Polarizer>

In the polarizing plate 1 produced as described above, the thickness of the polarizer 5 formed by adsorbing and orienting a dichroic dye to a stretched polyvinyl alcohol-based resin layer (or film) is preferably 20 m or less, Particularly, in the polarizing plate for mobile equipment, it is more preferable that it is 10 탆 or less and further preferably 8 탆 or less from the viewpoint of thinning of the polarizing plate. The thickness of the polarizer 5 is usually 2 占 퐉 or more. According to the present invention, even when such a thin film polarizer 5 is used, the irregularities on the surface of the second protective film 20 can be effectively suppressed.

The method for producing a polarizing plate includes a step of forming a pressure-sensitive adhesive layer (a pressure-sensitive adhesive layer) for adhering the polarizing plate 1 to the display cell 50 on the outer surface (the surface opposite to the polarizer 5) of the first protective film 10 of the polarizing plate 1 60) may be disposed on the polarizing plate. Thus, a polarizing plate having a pressure-sensitive adhesive layer can be obtained. The pressure-sensitive adhesive for forming the pressure-sensitive adhesive layer 60 is usually a pressure-sensitive adhesive obtained by using a (meth) acrylic resin, a styrene resin, a silicone resin or the like as a base polymer and adding thereto a crosslinking agent such as an isocyanate compound, an epoxy compound or an aziridine compound Composition. And a pressure-sensitive adhesive layer containing fine particles and exhibiting light scattering properties.

The thickness of the pressure-sensitive adhesive layer 60 may be 1 to 40 占 퐉, but it is preferable that the pressure-sensitive adhesive layer 60 is formed thinly within the range of not impairing the workability and durability characteristics, and more preferably 3 to 25 占 퐉. A thickness of 3 to 25 占 퐉 has good processability and is also suitable for suppressing the dimensional change of the polarizer 5. If the thickness of the pressure-sensitive adhesive layer 60 is less than 1 占 퐉, the pressure-sensitive adhesive property tends to deteriorate. If the pressure-sensitive adhesive layer 60 exceeds 40 占 퐉, problems such as the pressure-

The method of forming the pressure-sensitive adhesive layer 60 is not particularly limited, and a pressure-sensitive adhesive composition (pressure-sensitive adhesive solution) containing each component including the above-mentioned base polymer is coated on the surface of the first protective film 10, Alternatively, the pressure-sensitive adhesive layer 60 may be transferred onto the first protective film 10 after the pressure-sensitive adhesive layer 60 is formed on the separator (release film) in the same manner. When the pressure-sensitive adhesive layer 60 is formed on the surface of the first protective film 10, the surface of the first protective film 10 or the surface of the pressure-sensitive adhesive layer 60 is subjected to surface treatment, for example, corona treatment .

The polarizing plate 1 may further include another optical layer that is laminated on the first protective film 10 or the second protective film 20. Other optical layers include a reflective polarizing film that transmits polarized light of any kind and reflects polarized light exhibiting properties opposite to that of the polarized light; A film having an antireflection function on the surface and having an antiglare function; A film having a surface antireflection function; A reflecting film having a reflecting function on the surface; A transflective film having a reflection function and a transmission function; And a viewing angle compensation film.

<Display device>

The display device of the present invention includes a display cell (image display element) 50 and a polarizing plate 1 according to the present invention disposed on at least one side thereof, with reference to Fig. The polarizing plate 1 can be arranged and bonded on the display cell 50 by using the pressure sensitive adhesive layer 60 provided on the outer surface of the first protective film 10 disposed on the display cell 50 side. In this display device, the second protective film 20 of the polarizing plate 1 forms the outer surface (typically, the outermost surface) of the display device, but according to the present invention, Since the unevenness can be effectively suppressed, the appearance of the display device is excellent.

A representative example of the display device is a liquid crystal display device in which the display cell 50 is a liquid crystal cell, but another display device such as an organic EL device in which the display cell 50 is an organic EL image display device may be used. In the display device, the polarizing plate 1 may be disposed on at least one of the display cells 50, but may be disposed on both sides.

When the display device is a liquid crystal display device, a polarizing plate is normally disposed on both sides of the liquid crystal cell. In this case, the polarizing plate on both sides may be the polarizing plate 1 according to the present invention, and only one polarizing plate may be the polarizing plate 1 according to the present invention. In the latter case, the polarizing plate 1 according to the present invention may be a polarizing plate on the front side (viewing side) or a polarizing plate on the rear side (backlight side) based on the liquid crystal cell. As the liquid crystal cell, a conventionally known type can be used.

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.

&Lt; Example 1 >

(1) Primer layer formation process

Polyvinyl alcohol powder ("Z-200", average polymerization degree: 1100, saponification degree: 99.5 mol%) manufactured by Nihon Seika Kagaku Kogyo Co., Ltd. was dissolved in hot water at 95 ° C to prepare a polyvinyl alcohol aqueous solution having a concentration of 3% Respectively. The obtained aqueous solution was mixed with 5 parts by weight of a crosslinking agent ("Sumirez Resin 650" manufactured by Daoka Chemical Industries, Ltd.) per 6 parts by weight of polyvinyl alcohol powder to obtain a coating solution for forming a primer layer.

Next, an unoriented polypropylene film (melting point: 163 占 폚) having a thickness of 90 占 퐉 was prepared as a base film, corona treatment was performed on one side thereof, and the primer layer was formed on the corona-treated side using a small diameter gravure coater Coating liquid was coated thereon and dried at 80 캜 for 10 minutes to form a primer layer having a thickness of 0.2 탆.

(2) Production of laminated film (resin layer forming step)

A polyvinyl alcohol aqueous solution having a concentration of 8% by weight was prepared by dissolving a polyvinyl alcohol powder ("PVA 124" manufactured by Kuraray Co., Ltd., average degree of polymerization: 2400, degree of saponification: 98.0 to 99.0 mol%) in hot water at 95 ° C, This was used as a coating solution for forming a polyvinyl alcohol-based resin layer.

The coating liquid for forming a polyvinyl alcohol-based resin layer was coated on the surface of the primer layer of the base film having the primer layer prepared in the above (1) using a lip coater and then dried at 80 ° C for 20 minutes to form A polyvinyl alcohol-based resin layer was formed to obtain a laminated film comprising a base film / a primer layer / a polyvinyl alcohol-based resin layer.

(3) Production of stretched film (stretching process)

The laminated film produced in the above (2) was subjected to free end uniaxial stretching at 160 캜 at 5.8 times using a longitudinal uniaxial stretching apparatus for floatation to obtain a stretched film. The thickness of the polyvinyl alcohol-based resin layer after stretching was 6.1 占 퐉.

(4) Production of a polarizing laminated film (dyeing process)

The stretched film prepared in the above (3) was dipped in a dyeing aqueous solution (iodine was contained in 0.6 part by weight and potassium iodide in 10 parts by weight per 100 parts by weight of water) containing iodine and potassium iodide for about 180 seconds to obtain poly After the vinyl alcohol resin layer was subjected to the dyeing treatment, the extra dye aqueous solution was washed with pure water at 10 占 폚.

Subsequently, the first crosslinked aqueous solution (containing 9.5 parts by weight of boric acid per 100 parts by weight of water) containing boric acid was immersed for 120 seconds at 78 DEG C, and then a second crosslinked aqueous solution of 70 DEG C containing boric acid and potassium iodide 9.5 parts by weight of boric acid per 100 parts by weight and 4 parts by weight of potassium iodide) for 60 seconds to carry out crosslinking treatment. Thereafter, the film was washed with pure water at 10 占 폚 for 10 seconds, and finally dried at 40 占 폚 for 300 seconds to obtain a polarizing laminated film comprising a base film / polarizer.

(5) Production of polarizer with one side protective film (first bonding step and peeling step)

A circular polyolefin-based resin film having a thickness of 20 mu m was prepared as the first protective film disposed on the display cell side when the polarizing plate was placed on the display cell. The joint surface of the first protective film was subjected to corona treatment, and then an ultraviolet curable adhesive (&quot; KR-70T &quot; manufactured by ADEKA Corporation) was coated on the corona-treated surface using a small diameter gravure coater, The first protective film was bonded to the polarizing surface of the polarizing laminated film prepared in (4) using a bonding roll. Subsequently, a high pressure mercury lamp was used to cure the adhesive by irradiating ultraviolet rays at an accumulated light quantity of 200 mJ / cm &lt; 2 &gt; from the base film side to form a first adhesive layer, thereby forming a first protective film / first adhesive layer / Thereby obtaining a bonded film comprising a layer structure of a film (first bonding step). The thickness of the first adhesive layer was 0.5 mu m.

Next, the base film was peeled off from the obtained bonded film (peeling step). The base film was easily peeled off to obtain a polarizing plate having a one side protective film composed of the first protective film / first adhesive layer / polarizer layer structure.

(6) Production of a polarizing plate having a double-sided protective film (second bonding step)

An annular polyolefin-based resin film having a thickness of 50 mu m was prepared as a second protective film disposed outside (on the side opposite to the display cell side) when the polarizing plate was placed on the display cell. The joint surface of the second protective film was subjected to corona treatment, and then an ultraviolet curable adhesive ("KR-70T" manufactured by ADEKA Corporation) was coated on the corona-treated surface using a small diameter gravure coater, , The second protective film was bonded to the surface (polarizing surface) opposite to the first protective film of the polarizing plate having the single-sided protective film prepared in (5) using a bonding roll. Prior to the bonding, the polarizing surface to which the second protective film was bonded was corona-treated. Subsequently, using a high-pressure mercury lamp, ultraviolet rays were irradiated from the side of the second protective film at an accumulated light quantity of 200 mJ / cm &lt; 2 &gt; to cure the adhesive to form a second adhesive layer, and the first protective film / first adhesive layer / / Second adhesive layer / second protective film having a two-side protective film. The thickness of the second adhesive layer was 1.0 mu m.

The thicknesses of the first and second adhesive layers were measured as follows. That is, the "thickness of the first or second protective film" before coating with the ultraviolet-curable adhesive and the "total thickness of the first or second protective film and the coated adhesive layer after coating the ultraviolet-curable adhesive (before bonding with the polarizer) Were measured using a non-contact multilayer film thickness gauge ("SI-T series" manufactured by GUENNESS CO., LTD.), And the difference between them was defined as the thickness of the first and second adhesive layers. The thickness of the adhesive layer before and after bonding and curing with the polarizer obtained as described above is substantially maintained even after bonding and curing with the polarizer and substantially the same as the thickness of the adhesive layer after curing in the obtained polarizing plate The cross section of the polarizing plate was cut out, and the thickness of the adhesive layer in the cross section was observed with an SEM (scanning electron microscope) and confirmed.

&Lt; Comparative Examples 2 to 5 &

A polarizing plate having a double-side protective film was produced in the same manner as in Example 1 except that the order of bonding of the first and second protective films and the thickness after curing of the first and second adhesive layers were changed as shown in Table 1 Respectively. In Table 1, &quot; first protective film &quot; refers to a protective film (annular polyolefin-based resin film having a thickness of 20 mu m) disposed on the display cell side when the polarizing plate is placed on the display cell, Protective film &quot; refers to a protective film (annular polyolefin-based resin film having a thickness of 50 mu m) disposed on the outside (opposite to the display cell side) when the polarizing plate is placed on the display cell. The "first adhesive layer" refers to an adhesive layer to which the first protective film is bonded, and the "second adhesive layer" refers to an adhesive layer to which the second protective film is bonded.

[Evaluation of reflective image]

The polarizing plates obtained in Examples and Comparative Examples were cut to a size of 4 to 6 inches and bonded to a black acrylic plate using a pressure sensitive adhesive in order to prevent reflection from the back surface of the polarizing plate to obtain evaluation samples. At this time, the polarizing plate was bonded to the black acrylic plate at the side of the first protective film so that the second protective film faced the outside. A straight fluorescent lamp in a turned-on state was irradiated to the surface of the second protective film of the sample for evaluation by regular reflection, and the reflected image was evaluated with naked eyes according to the following evaluation criteria. The results are shown in Table 1.

A: There is no disturbance in the reflection image of the fluorescent lamp reflected on the polarizing plate, the reflection image is clear to the contour,

B: The reflected image of the fluorescent lamp reflected by the polarizing plate is slightly lacking in sharpness, and the contour line is disturbed at an irregular pitch of 1 mm or less,

C: The reflected image of the fluorescent lamp reflected on the polarizing plate is distorted, and the contour line is also disturbed.

1 polarizer, 5 polarizer, 10 first protective film, 15 first adhesive layer, 20 second protective film, 25 second adhesive layer, 6 polyvinyl alcohol based resin layer, 6 ' A polyvinyl alcohol resin layer, 30 base film, 30 'stretched base film, 50 display cell, 60 adhesive layer, 100 laminated film, 200 stretched film, 300 polarized laminated film, 400 laminated film, / RTI &gt;

Claims (6)

A method of manufacturing a polarizing plate comprising a first protective film on one side of a polarizer and a second protective film on the other side,
A first bonding step of bonding the first protective film to the one surface through a first adhesive layer made of an active energy ray curable adhesive,
A second bonding step of bonding the second protective film to the other side via a second adhesive layer made of an active energy ray curable adhesive after the first bonding step
/ RTI &gt;
The first protective film is a protective film disposed on the display cell side with respect to the second protective film when the polarizing plate is disposed on the display cell,
Wherein a thickness of the first adhesive layer after curing is smaller than a thickness after curing of the second adhesive layer. The method of manufacturing a polarizing plate according to claim 1, wherein the thickness of the first adhesive layer after curing is 0.75 占 퐉 or less. The method of manufacturing a polarizing plate according to claim 1 or 2, wherein a thickness of the second adhesive layer after curing is larger than 0.75 mu m. The method of manufacturing a polarizing plate according to any one of claims 1 to 3, wherein a difference between a thickness after curing of the second adhesive layer and a thickness after curing of the first adhesive layer is 0.1 占 퐉 or more. The method of manufacturing a polarizing plate according to any one of claims 1 to 4, wherein the thickness of the polarizer is 20 占 퐉 or less. A first bonding step of bonding a first protective film to one side of the polarizer through a first adhesive layer made of an active energy ray curable adhesive,
A second bonding step of bonding a second protective film to the other side of the polarizer through a second adhesive layer made of an active energy ray curable adhesive after the first bonding step,
A pressure-sensitive adhesive layer forming step of disposing a pressure-sensitive adhesive layer on the outer surface of the first protective film
/ RTI &gt;
Wherein the pressure-sensitive adhesive layer has a thickness after curing of the first adhesive layer is smaller than a thickness after curing of the second adhesive layer.

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