KR102467722B1 - 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, wherein a first adhesive layer composed of an active energy ray-curable adhesive is applied to the one side of the polarizer. A 1st bonding process of bonding a 1st protective film, and a 2nd bonding process of bonding a 2nd protective film to the other surface of a polarizer via the 2nd adhesive layer made of an active energy ray-curable adhesive agent after the 1st bonding process, , wherein the first protective film is a protective film disposed closer to the display cell than the second protective film when the polarizing plate is disposed on the display cell, and the thickness of the first adhesive layer after curing is the cured second adhesive layer. A manufacturing method of a polarizing plate smaller than the thickness after is provided.

Description

Manufacturing method of polarizing plate {METHOD FOR MANUFACTURING POLARIZING PLATE}

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

Polarizing plates are widely used in display devices such as liquid crystal display devices, and particularly in various mobile devices such as smart phones in recent years. As a polarizing plate, it is common to have a structure in which a protective film is bonded to one or both surfaces of the polarizer using an adhesive, but with the development to mobile devices, thinning of the polarizer and protective film constituting the polarizing plate is increasingly required.

As the adhesive, a water-based adhesive such as a polyvinyl alcohol aqueous solution and an active energy ray curable adhesive such as an ultraviolet curable adhesive are known. However, when a protective film having low moisture permeability is bonded, moisture is volatilized from the adhesive layer after bonding the protective film. Since it is difficult to remove, active energy ray-curable adhesives are frequently used [eg, Japanese Unexamined Patent Publication No. 2013-205741 (Patent Document 1), Japanese Unexamined Patent Publication No. 2012-203205 (Patent Document 2), Japan Japanese Unexamined Patent Publication No. 2012-203108 (Patent Document 3) and Japanese Unexamined Patent Publication No. 2004-245925 (Patent Document 4)].

Japanese Unexamined Patent Publication No. 2013-205741 Japanese Unexamined Patent Publication No. 2012-203205 Japanese Unexamined Patent Publication No. 2012-203108 Japanese Unexamined Patent Publication No. 2004-245925

As the polarizer or protective film constituting the polarizing plate is made thinner, the reflected image reflected on the polarizing plate is fine with a pitch of 1 mm or less, probably because fine distortion occurs at least either one of the interface between the polarizer and the adhesive layer or the interface between the protective film and the adhesive layer. In some cases, the image is distorted or the reflected image is distorted, so that it looks as if fine irregularities are formed on the surface. Although this phenomenon does not directly adversely affect the optical properties of the polarizing plate, when a polarizing plate exhibiting such a phenomenon is bonded to a cell for display, when the protective film is disposed on the outside (for example, the outermost surface), bonding Since this phenomenon remains even after the coating, and the glossiness of the surface of the protective film cannot be obtained, problems in appearance such as insufficient sense of quality arise.

Then, an object of this invention is provision of the method which can manufacture the polarizing plate which shows a favorable external appearance when it bonds to the display cell.

This invention provides the manufacturing method of the polarizing plate shown below, and the manufacturing method of the polarizing plate with an adhesive layer.

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

A first bonding step of bonding the first protective film to the one side via a first adhesive layer made of an active energy ray-curable adhesive;

After the first bonding process, a second bonding process of bonding the second protective film to the other surface via a second adhesive layer made of an active energy ray-curable adhesive.

including,

The first protective film is a protective film disposed closer to the display cell than the second protective film when the polarizing plate is disposed on the display cell;

The method of manufacturing a polarizing plate, wherein the thickness of the first adhesive layer after curing is smaller than the thickness of the second adhesive layer after curing.

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

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

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

[5] The manufacturing method according to any one of [1] to [4], wherein the polarizer has a thickness of 20 μm or less.

[6] A first bonding step of bonding a first protective film to one side of the polarizer via 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;

An adhesive layer forming process of disposing an adhesive layer on the outer surface of the first protective film

including,

The method for producing a polarizing plate having a pressure-sensitive adhesive layer, wherein the thickness of the first adhesive layer after curing is smaller than the thickness of the second adhesive layer after curing.

According to the manufacturing method of the present invention, it is possible to provide a polarizing plate and a polarizing plate having a pressure-sensitive adhesive layer in which the occurrence of the above-described unevenness appearing on the surface of the second protective film and the resulting disturbance or distortion of the reflected image are suppressed. When the obtained polarizing plate and the polarizing plate having the pressure-sensitive adhesive layer are disposed on the display cell so that the second protective film is on the outside (the first protective film is on the display cell side), the reflection image when viewed from the surface of the second protective film is Since disorder and distortion are suppressed, the external appearance is excellent.

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

<Method for producing polarizing plate>

Referring to FIG. 1, the present invention includes a polarizer 5, a first protective film 10 laminated on one side thereof through a first adhesive layer 15, and a second adhesive layer 25 on the other side. It relates to a method for manufacturing a polarizing plate (polarizing plate having a double-sided protective film) 1 having a second protective film 20 laminated through. As shown in FIG. 2 showing the state when the polarizing plate 1 is placed on the cell 50 for display, the first protective film 10 is better than the second protective film 20 in the cell 50 for display. It is a protective film placed on the side. 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, and the polarizing plate 1 is placed on the display cell ( 50), it is typically a protective film forming the outermost surface. As shown in FIG. 2 , the polarizing plate 1 is placed on the cell 50 for display using the adhesive layer 60 provided on the outer surface of the first protective film 10 disposed on the side of the cell 50 for display. Can be placed and joined.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment is shown and the manufacturing method of the polarizing plate concerning this invention is demonstrated in detail.

[First Embodiment]

Referring to FIG. 3 , the method for manufacturing a polarizing plate according to the present embodiment is a method for manufacturing a polarizing plate having a double-sided protective film using a base film, and the following steps:

A resin layer forming step (S10) of coating a coating solution containing a polyvinyl alcohol-based resin on at least one side of the base film and then forming a polyvinyl alcohol-based resin layer by drying to obtain a laminated film;

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 dyeing the polyvinyl alcohol-based resin layer of the stretched film with a dichroic dye to form a polarizer;

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

A peeling step (S50) of peeling and removing the base film from the bonding film to obtain a polarizing plate having a single-sided protective film, and

A second bonding step of bonding a second protective film on the polarizer surface of a polarizing plate having a single-sided protective film through a second adhesive layer (S60)

include in this order.

Hereinafter, each process is demonstrated, referring FIGS. 4-8. In addition, in the resin layer formation step (S10), the polyvinyl alcohol-based resin layer may be formed on both surfaces of the base film, but the case where it is mainly formed on one side will be described below.

(1) Resin layer formation step (S10)

Referring to FIG. 4 , this step is a step of obtaining the laminated film 100 by forming the polyvinyl alcohol-based resin layer 6 on at least one surface of the base film 30 . This polyvinyl alcohol-based resin layer 6 is a layer used as the polarizer 5 through an extending process (S20) and a dyeing process (S30). The polyvinyl alcohol-based resin layer 6 can be formed by coating one or both surfaces of the base film 30 with a coating liquid containing the polyvinyl alcohol-based resin and drying it. The method of forming a polyvinyl alcohol-type resin layer by such a coating is advantageous in that it is easy to obtain the polarizer 5 of a thin film.

The base film 30 can be composed of a thermoplastic resin, and among these, it is preferable to be composed of a thermoplastic resin having excellent transparency, mechanical strength, thermal stability, stretchability, and the like. Specific examples of such a thermoplastic resin include, for example, polyolefin-based resins such as chain polyolefin-based resins and cyclic polyolefin-based resins (norbornene-based resins and the like); polyester-based resin; (meth)acrylic resin; cellulose ester-based resins such as cellulose triacetate and cellulose diacetate; polycarbonate-based resin; polyvinyl alcohol-based resin; polyvinyl acetate-based resins; polyarylate-based resins; polystyrene-based resin; polyethersulfone-based resins; polysulfone-based resins; polyamide-based resin; polyimide-based resin; and mixtures and copolymers thereof. In this specification, "(meth)acryl" means at least one selected from acryl and methacryl. The same applies to "(meth)acryloyl".

The base film 30 may have a single-layer structure composed of one resin layer made of one or two or more types of thermoplastic resins, or may have a multilayer structure in which a plurality of resin layers composed of one or two or more types of thermoplastic resins are laminated. . The base film 30 is composed of a resin that can be stretched at a stretching temperature suitable for stretching the polyvinyl alcohol-based resin layer 6 when the laminated film 100 is stretched in the stretching step (S20) described later. it is desirable

The base film 30 may contain additives. Specific examples of additives include ultraviolet absorbers, antioxidants, lubricants, plasticizers, release agents, anti-coloring agents, flame retardants, nucleating agents, antistatic agents, pigments and colorants.

The thickness of the base film 30 is usually 1 to 500 μm, preferably 1 to 300 μm, more preferably 5 to 200 μm, and further preferably 5 to 150 μm, from the viewpoint of strength, handling, etc. μm.

The coating liquid to be coated on the base film 30 is preferably a polyvinyl alcohol-based resin solution obtained by dissolving powder of the polyvinyl alcohol-based resin in a good solvent (for example, water). The coating liquid may contain additives such as plasticizers and surfactants as needed. As the polyvinyl alcohol-based resin, what saponified polyvinyl acetate-based resin can be used. As a polyvinyl acetate type-resin, the copolymer of vinyl acetate and the other monomer copolymerizable with this other than the polyvinyl acetate which is a homopolymer of vinyl acetate is illustrated. 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 degree of saponification of the polyvinyl alcohol-based resin may be in the range of 80.0 to 100.0 mol%, but is preferably in the range of 90.0 to 99.5 mol%, and more preferably in the range of 94.0 to 99.0 mol%. When the degree of saponification is less than 80.0 mol%, the water resistance and heat-and-moisture resistance of the polarizing plate 1 obtained are reduced. When a polyvinyl alcohol-based resin having a saponification degree of more than 99.5 mol% is used, the dyeing rate becomes slow, productivity decreases, and the polarizer 5 having sufficient polarization performance may not be obtained.

The degree of saponification is a unit ratio (mol%) representing the rate at which the acetic acid group (acetoxy group: -OCOCH ₃ ) contained in the polyvinyl acetate-based resin, which is a raw material of the polyvinyl alcohol-based resin, is changed to a hydroxyl group by the saponification step. , the following expression:

Degree of saponification (mol%) = 100 x (number of hydroxyl groups) ÷ (number of hydroxyl groups + number of acetic acid groups)

is defined as The degree of saponification can be obtained in accordance with JIS K 6726 (1994). The higher the degree of saponification, the higher the ratio of hydroxyl groups, and thus the lower the ratio of acetic acid groups that inhibit crystallization.

The modified polyvinyl alcohol partially modified may be sufficient as the polyvinyl alcohol-based resin. For example, olefins such as ethylene and propylene for polyvinyl alcohol-based resin; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid; What was modified|denatured with the alkyl ester of an unsaturated carboxylic acid, (meth)acrylamide, etc. is mentioned. It is preferable that it is less than 30 mol%, and, as for the ratio of modification, it is more preferable that it is less than 10%. When modification exceeds 30 mol%, it becomes difficult to adsorb the dichroic dye, and it tends to be difficult to obtain a polarizer 5 having sufficient polarization performance.

The average degree of polymerization of the polyvinyl alcohol-based resin is preferably 100 to 10000, more preferably 1500 to 8000, and further preferably 2000 to 5000. The average degree of polymerization of the polyvinyl alcohol-based resin can also be determined in accordance with JIS K 6726 (1994).

A method of coating the coating liquid on the base film 30 may include a wire bar coating method; roll coating methods such as reverse coating and gravure coating; die coat method; comma coat method; lip coat method; spin coating method; screen coating method; fountain coating method; dipping method; It can select suitably from methods, such as a spray method.

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

The polyvinyl alcohol-based resin layer 6 may be formed on only one surface of the base film 30 or may be formed on both surfaces. When formed on both sides, curling of the film that may occur during the manufacture of the polarizing laminated film 300 (see FIG. 6) can be suppressed, and two polarizing plates can be obtained from one polarizing laminated film 300. , it 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 μm, more preferably 5 to 40 μm, and further preferably 5 to 20 μm. . If the polyvinyl alcohol-based resin layer 6 having a thickness within this range passes through a stretching step (S20) and a dyeing step (S30) described later, the dyeability of the dichroic dye is good, the polarization performance is excellent, and it is sufficiently thin. A polarizer 5 (for example, having a thickness of 20 μm or less and further 10 μm or less) can be obtained.

Prior to the coating of the coating liquid, in order to improve the adhesion between the base film 30 and the polyvinyl alcohol-based resin layer 6, at least the surface of the base film 30 on the side where the polyvinyl alcohol-based resin layer 6 is formed. In this case, corona treatment, plasma treatment, 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 the surface of the base film 30 with a coating liquid for forming the primer layer and then drying it. This coating liquid contains a component that exerts a certain degree of strong adhesion to both the base film 30 and the polyvinyl alcohol-based resin layer 6, and usually contains a resin component and a solvent that impart such adhesion. As the resin component, a thermoplastic resin having excellent transparency, thermal stability, stretchability, etc. is preferably used, and examples thereof include (meth)acrylic resins and polyvinyl alcohol-based resins. Among them, a polyvinyl alcohol-based resin that imparts good adhesion is preferably used. More preferably, it is a polyvinyl alcohol resin. As the solvent, a general organic solvent or aqueous solvent capable of dissolving the resin component is usually used, but it is preferable to form the primer layer from a coating liquid using water as the solvent.

In the peeling process (S50) mentioned later, a primer layer may become one with a base film and peel from the polarizer 5, and may become one with the polarizer 5 and peel from a base film. In the case of the former, the primer layer can be formed with any thermoplastic resin that is easily peeled off from the polyvinyl alcohol-based resin layer as described above. On the other hand, if it is the latter, the primer layer is dyed together with the polyvinyl alcohol-based resin layer in the dyeing step (S30) described later, and after peeling the base film in the peeling step (S50), the polyvinyl alcohol-based resin layer is dyed. It is necessary to become one with the layer to become the polarizer 5. For example, when a primer layer is formed with polyvinyl alcohol-based resin, the primer layer is dyed together with the polyvinyl alcohol-based resin layer in a subsequent dyeing step (S30), and the polarizer 5 and the polarizer 5 in a peeling step (S50). It becomes one and peels from the base film, and becomes a part of 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 (eg, metal salts, metal oxides, metal hydroxides, organometallic compounds), and polymer-based crosslinking agents. When using a polyvinyl alcohol-based resin as the resin component forming the primer layer, a polyamide epoxy resin, a methylolized melamine resin, a dialdehyde-based crosslinking agent, a metal chelate compound-based crosslinking agent, and the like are suitably used.

The thickness of the primer layer is preferably about 0.05 to 1 μm, and more preferably 0.1 to 0.4 μm. When it is thinner than 0.05 μm, the effect of improving the adhesion between the base film 30 and the polyvinyl alcohol-based resin layer 6 is small, and when it is thicker than 1 μm, the thinning of the polarizing plate 1 is disadvantageous.

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

(2) Stretching process (S20)

Referring to Fig. 5, in this step, 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-based resin layer. It is a process of obtaining the stretched film 200 which consists of (6'). The stretching treatment is usually uniaxial stretching.

The draw ratio of the laminated film 100 can be appropriately selected depending on the desired polarization characteristics, but is preferably more than 5 times and 17 times or less, more preferably more than 5 times the original length of the laminated film 100. less than 8 times Since the polyvinyl alcohol-type resin layer 6' does not fully orientate as a draw ratio is 5 times or less, the polarization degree of the polarizer 5 may not become high enough. On the other hand, if the draw ratio exceeds 17 times, breakage of the film tends to occur during stretching, and the thickness of the stretched film 200 becomes thinner than necessary, resulting in reduced processability and handling in subsequent steps.

The stretching treatment is not limited to stretching in one step, and may be performed in multiple steps. In this case, all of the multi-layer stretching treatment may be performed continuously before the dyeing step (S30), or the stretching treatment in the second and subsequent steps may be performed simultaneously with the dyeing treatment and/or the crosslinking treatment in the dyeing step (S30). good night. When the stretching treatment is performed in multiple steps as described above, it is preferable to perform the stretching treatment so that the total stretching ratio of all stages of the stretching treatment is greater than 5 times.

The stretching treatment may be longitudinal stretching in which the film is stretched in the film longitudinal direction (film transport direction), or transverse stretching or oblique stretching in which the film is stretched in the width direction. Examples of the longitudinal stretching method include inter-roll stretching using rolls, compression stretching, and stretching using a chuck (clip), and examples of the transverse stretching method include a tenter method. For the stretching treatment, either a wet stretching method or a dry stretching method can be employed.

The stretching temperature is set to a temperature equal to or higher than a temperature exhibiting fluidity to the extent that the entire polyvinyl alcohol-based resin layer 6 and the base film 30 can be stretched, and preferably the phase transition temperature (melting point or glass transition temperature) of the base film 30. ) in the range of -30°C to +30°C, more preferably in the range of -30°C to +5°C, and further preferably in the range of -25°C to +0°C. 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 exhibited by the plurality of resin layers.

If the stretching temperature is lower than -30 ° C. of the phase transition temperature, it is difficult to achieve a high-magnification stretching of more than 5 times, or the flowability of the base film 30 is too low, so the stretching treatment tends to be difficult. When the stretching temperature exceeds +30°C of the phase transition temperature, the fluidity of the base film 30 is too large, and stretching tends to be difficult. Since it is easier to achieve a high draw ratio of more than 5 times, the drawing temperature is within the above range, and is further preferably 120°C or higher.

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 adjusted to a predetermined temperature by blowing hot air); In the case of stretching using a roll, a method of heating the roll itself; There is a heater heating method [a method of installing an infrared heater, a halogen heater, a panel heater, or the like above and below the laminated film 100 to heat with radiant heat] and the like. In the roll-to-roll stretching method, the zone heating method is preferred from the viewpoint of uniformity of the stretching temperature.

In the case of the zone heating method, the stretching temperature means the ambient temperature within the zone (for example, inside the heating furnace), and also in the heater heating method, when heating is performed within the furnace, it means the ambient temperature within the furnace. In addition, in the case of the method of heating a roll itself, it means the surface temperature of a roll.

Prior to the stretching step (S20), a preheat treatment step of preheating the laminated film 100 may be provided. 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°C to ±0°C of the stretching temperature, and more preferably in the range of -40°C to -10°C of the stretching temperature.

Moreover, you may provide the heat setting treatment process after the extending|stretching process in extending process (S20). The heat setting treatment is a treatment in which a heat treatment is performed at a crystallization temperature or higher while maintaining a tensioned state in a state where an end portion of the stretched film 200 is held by a clip. Crystallization of the polyvinyl alcohol-based resin layer 6' is promoted by this heat setting treatment. The temperature of the heat setting treatment is preferably in the range of -0°C to -80°C of the stretching temperature, and more preferably in the range of -0°C to -50°C of the stretching temperature.

(3) Dyeing process (S30)

Referring to FIG. 6 , this process is a process of dyeing the polyvinyl alcohol-based resin layer 6' of the stretched film 200 with a dichroic dye, adsorbing orienting this, and using it as the polarizer 5. Through this process, the polarizing laminated film 300 in which the polarizer 5 is laminated on one side or both sides of the base film 30' is obtained. The dichroic dye may be iodine or a dichroic organic dye. Specific examples of dichroic organic dyes include Red BR, Red LR, Red R, Pink LB, Rubin BL, Bordeaux GS, Sky Blue LG, Lemon Yellow, Blue BR, Blue 2R, Navy RY, Green LG, Violet LB, Violet B, Black H, Black B, Black GSP, Yellow 3G, Yellow R, Orange LR, Orange 3R, Scarlet GL, Scarlet KGL, Congo-Red, Brilliant Violet BK, Spla Blue G, Spla Blue GL, Spla Orange Includes GL, Direct Sky Blue, Direct First Orange S, and First Black. A dichroic dye may be used individually by 1 type, and may use 2 or more types together.

The dyeing step can be performed by immersing the entire stretched film 200 in a solution containing a dichroic dye (dyeing solution). 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 compatible with water may be further added. The concentration of the dichroic dye in the dyeing solution is preferably 0.01 to 10% by weight, more preferably 0.02 to 7% by weight.

When iodine is used as the dichroic dye, it is preferable to further 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 by weight, preferably 1:5 to 1:100, more preferably 1:6 to 1:80. The temperature of the dyeing solution is preferably 10 to 60°C, more preferably 20 to 40°C.

In addition, it is possible to perform the dyeing step (S30) before the stretching step (S20) or to perform these steps simultaneously, but the laminated film so that the dichroic dye adsorbed to the polyvinyl alcohol-based resin layer can be favorably oriented. It is preferable to carry out the dyeing step (S30) after performing at least a certain degree of stretching treatment with respect to (100).

The dyeing step (S30) may include a crosslinking treatment step performed subsequent to the dyeing treatment. The crosslinking treatment can be performed by immersing the dyed film in a solution in which a crosslinking agent is dissolved in a solvent (crosslinking solution). Examples of the crosslinking agent include boric acid, boron compounds such as borax, glyoxal, and glutaraldehyde. A crosslinking agent may use only 1 type, and may use 2 or more types together. As the solvent for the crosslinking solution, water can be used, but an organic solvent compatible with water may be further included. The concentration of the crosslinking agent in the crosslinking solution is preferably 1 to 20% by weight, more preferably 6 to 15% by weight.

The crosslinking solution may further contain iodide. By adding iodide, the polarization performance within the surface of the polarizer 5 can be made more uniform. Specific examples of iodide are the same as 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°C.

Further, the crosslinking treatment may be performed simultaneously with the dyeing treatment by blending a crosslinking agent into the dyeing solution. Moreover, you may perform the process of immersing in crosslinking solution twice or more using two or more types of crosslinking solutions with different compositions.

It is preferable to perform a washing process and a drying process after a dyeing process (S30) and before a 1st bonding process (S40) mentioned later. The washing process usually includes a water washing process. The water washing treatment can be performed by immersing the film after dyeing treatment or crosslinking treatment in pure water such as ion-exchanged water or distilled water. The water washing temperature is usually 3 to 50°C, preferably 4 to 20°C. The washing process may be a combination of a water washing process and a washing process using an iodide solution. As the drying step performed after the washing step, any suitable method such as natural drying, blow drying, heat drying, or the like can be employed. For example, in the case of heat drying, the drying temperature is usually 20 to 95°C.

(4) 1st joining process (S40)

Referring to FIG. 7 , in this step, the first adhesive layer 15 is applied 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. This is a process of obtaining the bonding film 400 by bonding the first protective film 10 through the process. In the case where the polarizing laminated film 300 has the polarizers 5 on both sides of the base film 30', the first protective films 10 are usually bonded on the polarizers 5 on both sides. In this case, these first protective films 10 may be the same type of protective film or a different type of protective film.

As described above, the first protective film 10 is a protective film disposed on the side of the display cell 50 rather than the second protective film 20 when the polarizing plate 1 is disposed on the display cell 50. to be. The first protective film 10 is made of a light-transmitting (preferably optically transparent) thermoplastic resin such as a chain polyolefin-based resin (polypropylene-based resin, etc.), a cyclic polyolefin-based resin (norbornene-based resin, etc.) polyolefin-based resins such as; cellulose ester-based resins such as cellulose triacetate and cellulose diacetate; polyester-based resin; polycarbonate-based resin; (meth)acrylic resin; polystyrene-based resin; Or it may be a film made of a mixture or copolymer thereof. Among them, the first protective film 10 suitably used in the present invention (the same applies to the second protective film 20 described later) is a protective film having low moisture permeability that is difficult to adhere to with a water-based adhesive, such as a polyolefin-based resin. , It is a protective film made of a polyester-based resin, a (meth)acrylic-based resin, a polystyrene-based resin, or the like.

The first protective film 10 may also be a protective film having an optical function such as a retardation film or a brightness enhancing film. For example, a retardation film having an arbitrary retardation value can be obtained by stretching the film made of the thermoplastic resin (eg, uniaxial stretching or biaxial stretching) or forming a liquid crystal layer or the like on the film.

Examples of the chain polyolefin-based resin include homopolymers of chain olefins such as polyethylene resins and polypropylene resins, as well as copolymers composed of two or more types of chain olefins.

Cyclic polyolefin resin is a general term for resins polymerized using cyclic olefins as polymerized units. Specific examples of cyclic polyolefin-based resins include ring-opening (co)polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers of cyclic olefins and chain olefins such as ethylene and propylene (typically random copolymers), and unsaturated graft polymers modified with carboxylic acids or derivatives thereof, hydrides thereof, and the like. Among them, a norbornene-based resin using a norbornene-based monomer such as norbornene or a polycyclic norbornene-based monomer as the cyclic olefin is preferably used.

Cellulose ester-type resin is an ester of a cellulose and a fatty acid. Specific examples of the cellulose ester-based resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. Copolymers of these or those in which a part of hydroxyl groups are modified with other substituents can also be used. Among these, cellulose triacetate (triacetyl cellulose: TAC) is particularly preferred.

Polyester-type resin is resin other than the said cellulose ester-type resin which has an ester bond, and what consists of polycondensate of polyhydric carboxylic acid or its derivative(s) and polyhydric alcohol is common. Dicarboxylic acids or derivatives thereof can be used as polyhydric carboxylic acids or derivatives thereof, and examples thereof include terephthalic acid, isophthalic acid, dimethyl terephthalate, and dimethyl naphthalene dicarboxylic acid. As the polyhydric alcohol, diols can be used, and examples thereof include ethylene glycol, propanediol, butanediol, neopentyl glycol, and cyclohexanedimethanol.

Specific examples of the polyester-based resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polycyclohexane dimethyl terephthalate, and polycyclohexane. Contains dimethylnaphthalate.

A polycarbonate-type resin consists of a polymer to which monomer units are bonded via a carbonate group. The polycarbonate-based resin may be a resin called a modified polycarbonate obtained by modifying a polymer skeleton, a copolymerized polycarbonate, or the like.

A (meth)acrylic resin is a resin which uses a compound having a (meth)acryloyl group as a main constituent monomer. Specific examples of the (meth)acrylic resin include poly(meth)acrylic acid esters such as polymethyl methacrylate; methyl methacrylate-(meth)acrylic acid copolymer; methyl methacrylate-(meth)acrylic acid ester copolymer; methyl methacrylate-acrylic acid ester-(meth)acrylic acid copolymer; methyl (meth)acrylate-styrene copolymers (such as MS resin); and copolymers of methyl methacrylate and a compound having an alicyclic hydrocarbon group [eg, methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate-norbornyl (meth)acrylate copolymer, etc.]. Preferably, a polymer _containing poly(meth)acrylic acid C _1-6 alkyl ester as a main component 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) of methyl methacrylate-based resin is used.

In addition, the specific example of various thermoplastic resins mentioned above is also a specific example of the thermoplastic resin which comprises the said 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 μm or less, more preferably 50 μm or less, and further preferably 30 μm or less, from the viewpoint of reducing the thickness of the polarizing plate 1. The thickness of the first protective film 10 is usually 5 μm or more from the viewpoint of strength and handleability.

As the adhesive forming the first adhesive layer 15 for bonding the first protective film 10 to the polarizer 5, an active energy ray curable property that is cured by irradiation of active energy rays such as ultraviolet rays, visible light, electron beams, and X-rays. adhesive is used. The active energy ray curable adhesive is preferably an ultraviolet curable adhesive. The use of an active energy ray-curable adhesive is: 1) it can be prepared as a solvent-free adhesive, so a drying step is unnecessary, 2) it can be used for bonding protective films with low moisture permeability, compared to water-based adhesives There is an advantage that 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 containing a cationic polymerizable curable compound and/or a radically polymerizable curable compound can be preferably used. The active energy ray-curable adhesive usually further contains a cationic polymerization initiator and/or a radical polymerization initiator for initiating a curing reaction of the curable compound.

As a cationic polymerizable curable compound, for example, an epoxy compound (a compound having one or two or more epoxy groups in a molecule), an oxetane compound (a compound having one or two or more oxetane rings in a molecule), or these A combination of 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 radically polymerizable double bonds, or Combinations of these are exemplified. A cationic polymerizable curable compound and a radical polymerizable curable compound may be used in combination.

Active energy ray-curable adhesives, if necessary, cationic polymerization accelerator, ion trapping agent, antioxidant, chain transfer agent, tackifier, thermoplastic resin, filler, flow regulator, plasticizer, antifoaming agent, antistatic agent, leveling agent, solvent, etc. of additives may be included.

After laminating the first protective film 10 on the polarizer 5 through the active energy ray-curable adhesive that becomes the first adhesive layer 15, the adhesive is irradiated with active energy rays such as ultraviolet rays, visible light, electron beams, and X-rays. By curing the layer, the first protective film 10 can be adhesively bonded to the polarizer 5 . The active energy ray is preferably an ultraviolet ray, and as a light source in this case, a low-pressure mercury-vapor lamp, a medium-pressure mercury-vapor 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, etc. can be used. In the polarizing plate 1 obtained, the 1st adhesive bond layer 15 is a hardened|cured material layer of an active energy ray-curable adhesive agent.

In bonding the 1st protective film 10 to the polarizer 5, the bonding surface of the 1st protective film 10 and/or the polarizer 5 is plasma, in order to improve adhesiveness with the polarizer 5, Treatment, corona treatment, ultraviolet irradiation treatment, flame treatment, and surface treatment (adhesion-facilitating treatment) such as saponification treatment can be performed. Preferred surface treatments are plasma treatment, corona treatment, and saponification treatment.

As described in detail later, in order to effectively suppress the unevenness on the surface of the second protective film 20, the first adhesive layer 15 is formed to be thinner than the second adhesive layer after curing. For the same reason, the thickness of the first adhesive layer 15 after curing is preferably 0.75 μm or less, more preferably 0.7 μm or less, and further preferably 0.5 μm or less. The thickness of the first adhesive layer 15 after curing is usually 0.01 μm or more, preferably 0.1 μm or more, more preferably 0.2 μm or more, and further preferably 0.3 μm or more from the viewpoint of adhesiveness. If the thickness is too small, it is easy to cause a problem that minute air bubbles are mixed in 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 into a display device such as a liquid crystal display device and the display device is turned on. This light scattering may cause a display problem 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, but in order to reduce the thickness of the adhesive layer as in the first adhesive layer 15 , A method of coating an adhesive using a small diameter gravure, etc. is suitable, and in particular, a method of relatively increasing the rotation speed of gravure by increasing the gravure rotation draw (ratio of gravure rotation speed to line speed), or gravure The thickness of the adhesive layer can be reduced by a method such as increasing the number of lines of the mesh. In particular, in order to make the thickness of the adhesive layer 1 μm or less, it is preferable to use gravure in which a mesh is engraved by laser engraving, and it is particularly preferable to use a honeycomb-shaped gravure roll. For example, those having a honeycomb shape and having more than 400 rows of honeycombs per inch are suitably used.

(5) Peeling process (S50)

Referring to FIG. 8 , this process is a process of peeling and removing the base film 30' from the bonding film 400. Through this step, a polarizing plate 500 having a single-side protective film in which the first protective film 10 is laminated on one side 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 polarizers 5, this peeling step (S50 ), a polarizing plate 500 having two single-sided protective films is obtained from one polarizing laminated film 300.

The method of peeling and removing the base film 30' is not particularly limited, and can be peeled by a method similar to the peeling step of a separator (peeling film) performed with a polarizing plate having a normal pressure-sensitive adhesive. Substrate film 30' may be peeled immediately after the first bonding step (S40) as it is, or may be wound up once in a roll shape after the first bonding step (S40), and may be peeled while unwinding in a subsequent step.

(6) Second bonding process (S60)

In this step, the second adhesive layer ( It is a process of bonding the 2nd protective film 20 through 25) and obtaining the polarizing plate 1 which has 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 cell 50 for display. Like the first protective film 10, the second protective film 20 may be a film made of the above-exemplified thermoplastic resin, or may be a protective film having an optical function such as a retardation film or a brightness enhancing film. Regarding the additives that the second protective film 20 may contain and the thickness of the film, the above description of the first protective film 10 is cited. The first protective film 10 and the second protective film 20 may be protective films made of the same type of resin or different types of resins.

According to the present invention, when the thickness of the second protective film 20 is small, for example, 50 μm or less, and further 30 μm or less, the unevenness 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, or an antifouling layer may be formed on the surface of the second protective film 20 on the opposite side to the polarizer 5 . The method of forming the surface treatment layer is not particularly limited, and a known method can be used.

As an adhesive 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 curable adhesive. In the polarizing plate 1 obtained, the 2nd adhesive bond layer 25 is a hardened|cured material layer of an active energy ray-curable adhesive agent. For specific examples of the active energy ray-curable adhesive, the above description of 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. Bonding of the second protective film 20 through the second adhesive layer 25 can be performed in the same manner as bonding of the first protective film 10 .

As a factor causing unevenness on the surface of the second protective film 20, shrinkage force when the adhesive forming the second adhesive layer 25 is cured [curing the adhesive layer in a short time by irradiation with active energy rays to adhere The contraction force (per unit time) in the case of using an active energy ray-curable adhesive that conducts is generally greater than that of a water-based adhesive that takes a relatively long time to bond by drying the solvent (water) by heating and curing as necessary thereafter. .], the second protective film 20 and the polarizer 5 are lost, and according to the present invention, even when an active energy ray-curable adhesive is used for the adhesive forming the second adhesive layer 25, also Even when the thickness of the polarizer 5 or the first and second protective films 10 and 20 is small, the occurrence of unevenness on the surface of the second protective film 20 and the resulting disturbance or distortion of the reflected image can be suppressed. As a result, a clear reflective image is obtained and the glossiness of the surface of the second protective film 20 is excellent, so that a polarizing plate having a sense of quality can be provided.

The second adhesive layer 25 is formed to such a thickness that the thickness of the first adhesive layer 15 after curing is smaller than the thickness of the second adhesive layer 25 after curing. The first and second adhesive layers 15 and 25 with the thickness relationship as described above on the premise of successive bonding of bonding the second protective film 20 after bonding of the first protective film 10 to the polarizer 5 It is essential to form, and thereby, the unevenness of the surface of the second protective film 20 can be effectively suppressed.

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

[Second Embodiment]

1st Embodiment is a method of forming a polarizer with the polyvinyl alcohol-type resin layer coated on the base film, and then manufacturing a polarizing plate, but it is not limited to this, The polarizer 5 which consists of a single-piece|unit (single-piece) film You may manufacture polarizing plate 1 by bonding 1 protective film 10 and 2nd protective film 20 in this order. Bonding of the first and second protective films 10 and 20 via the first and second adhesive layers 15 and 25 may be the same as in the first embodiment.

Process of producing a polyvinyl alcohol-type resin film according to known methods, such as the melt-extruding method and the solvent casting method; Step of uniaxially stretching the polyvinyl alcohol-based resin film; a step of dyeing a polyvinyl alcohol-based resin film with a dichroic dye and adsorbing it; A step of treating the polyvinyl alcohol-based resin film to which the dichroic dye is adsorbed with an aqueous solution of boric acid; And, it can be manufactured by a method including a step of washing with water after treatment with an aqueous solution of boric acid. Uniaxial stretching can be performed before dyeing of the dichroic dye, simultaneously with dyeing, or after dyeing. When uniaxial stretching is performed after dyeing, this uniaxial stretching may be performed before boric acid treatment or during boric acid treatment. Moreover, you may perform uniaxial stretching in these several steps.

<Polarizer>

In the polarizing plate 1 manufactured as described above, the thickness of the polarizer 5 formed by adsorbing and orienting the dichroic dye on the stretched polyvinyl alcohol-based resin layer (or film) is preferably 20 μm or less, In particular, in a polarizing plate for mobile devices, from the viewpoint of reducing the thickness of the polarizing plate, it is more preferably 10 μm or less, and further preferably 8 μm or less. The thickness of the polarizer 5 is 2 micrometers or more normally. According to the present invention, even when such a thin film polarizer 5 is used, the unevenness on the surface of the second protective film 20 can be effectively suppressed.

A method for manufacturing a polarizing plate is a pressure-sensitive adhesive layer for bonding the polarizing plate 1 to the display cell 50 on the outer surface of the first protective film 10 of the polarizing plate 1 (the surface opposite to the polarizer 5) ( 60) may be further included, thereby obtaining a polarizing plate having a pressure-sensitive adhesive layer. The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer 60 is usually a pressure-sensitive adhesive obtained by adding a crosslinking agent such as an isocyanate compound, an epoxy compound, or an aziridine compound to a base polymer such as a (meth)acrylic resin, a styrene resin, or a silicone resin. made up of a composition Moreover, it can be set as the adhesive layer which contains microparticles|fine-particles and shows light scattering property.

Although the thickness of the pressure-sensitive adhesive layer 60 may be 1 to 40 μm, it is preferable to form a thin film within a range that does not impair workability and durability characteristics, and specifically, it is preferable that it is 3 to 25 μm. A thickness of 3 to 25 μm is suitable also when it has good processability and suppresses the dimensional change of the polarizer 5. If the pressure-sensitive adhesive layer 60 is less than 1 μm, the adhesiveness decreases, and when it exceeds 40 μm, problems such as protrusion of the pressure-sensitive adhesive tend to occur.

The method of forming the pressure-sensitive adhesive layer 60 is not particularly limited, and the surface of the first protective film 10 is coated with a pressure-sensitive adhesive composition (pressure-sensitive adhesive solution) containing each component including the base polymer, and then dried. Alternatively, the pressure-sensitive adhesive layer 60 may be formed on a separator (release film) in the same manner, and then the pressure-sensitive adhesive layer 60 may be transferred to the first protective film 10 . When forming the pressure-sensitive adhesive layer 60 on the surface of the first protective film 10, surface treatment, such as corona treatment, is performed on the surface of the first protective film 10 or the surface of the pressure-sensitive adhesive layer 60, if necessary. You can do it.

The polarizing plate 1 may further include another optical layer laminated on the first protective film 10 or the second protective film 20 . Examples of the other optical layer include a reflective polarizing film that transmits a certain type of polarized light and reflects polarized light exhibiting properties opposite to that; A film having an anti-glare function having a concavo-convex shape on the surface; A film having a surface antireflection function; a reflective film having a reflective function on its surface; a semi-transmissive reflective film having both a reflective function and a transmissive function; A viewing angle compensation film etc. are mentioned.

<Display device>

Referring to Fig. 2, 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 arranged on at least one surface thereof. The polarizing plate 1 can be disposed and bonded on the display cell 50 using the adhesive layer 60 provided on the outer surface of the first protective film 10 disposed on the display cell 50 side. In such a 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, the surface of the second protective film 20 Since the feeling of irregularities 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 other display devices such as an organic EL device in which the display cell 50 is an organic EL image display element may be used. In the display device, the polarizing plate 1 should be disposed on at least one surface of the cell 50 for display, but may be disposed on both surfaces.

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

Example

Hereinafter, the present invention will be described more specifically by showing Examples and Comparative Examples, but the present invention is not limited by these examples.

<Example 1>

(1) Primer layer formation process

Polyvinyl alcohol powder ("Z-200" manufactured by Nihongo Seikagaku Kogyo Co., Ltd., average polymerization degree 1100, saponification degree 99.5 mol%) was dissolved in hot water at 95 ° C. to prepare a polyvinyl alcohol aqueous solution having a concentration of 3% by weight did A crosslinking agent (“Sumirez Resin 650” manufactured by Taoka Chemical Industry Co., Ltd.) was mixed with the obtained aqueous solution in a ratio of 5 parts by weight to 6 parts by weight of polyvinyl alcohol powder to obtain a coating solution for forming a primer layer.

Next, as a base film, an unstretched polypropylene film (melting point: 163° C.) having a thickness of 90 μm is prepared, and one side is corona treated, and then the primer layer is formed on the corona treated side using a small diameter gravure coater A primer layer having a thickness of 0.2 μm was formed by coating the coating solution and drying at 80° C. for 10 minutes.

(2) Preparation of laminated film (resin layer formation process)

Polyvinyl alcohol powder ("PVA124" manufactured by Kuraray Co., Ltd., average polymerization degree 2400, saponification degree 98.0 to 99.0 mol%) was dissolved in hot water at 95 ° C. to prepare a polyvinyl alcohol aqueous solution having a concentration of 8% by weight, This was made into the coating liquid for forming a polyvinyl alcohol-type resin layer.

After coating the coating liquid for forming the polyvinyl alcohol-based resin layer using a lip coater on the surface of the primer layer of the base film having the primer layer prepared in (1), drying at 80 ° C. for 20 minutes, on the primer layer A polyvinyl alcohol-based resin layer was formed to obtain a laminated film composed of a base film/primer layer/polyvinyl alcohol-based resin layer.

(3) Production of stretched film (stretching process)

The laminated film prepared in (2) above was subjected to 5.8-fold free end uniaxial stretching at 160°C using a floating longitudinal uniaxial stretching device to obtain a stretched film. The thickness of the polyvinyl alcohol-based resin layer after stretching was 6.1 µm.

(4) Preparation of polarizing laminated film (dyeing process)

The stretched film produced in (3) above is immersed in a 30°C dyeing solution containing iodine and potassium iodide (0.6 parts by weight of iodine and 10 parts by weight of potassium iodide per 100 parts by weight of water) for about 180 seconds, After performing the dyeing treatment of the vinyl alcohol-based resin layer, excess dyeing aqueous solution was washed off with pure water at 10°C.

Then, it was immersed in a 78 ° C. first crosslinking aqueous solution containing boric acid (including 9.5 parts by weight of boric acid per 100 parts by weight of water) for 120 seconds, followed by 70 ° C. second crosslinking aqueous solution containing boric acid and potassium iodide (water 9.5 parts by weight of boric acid and 4 parts by weight of potassium iodide per 100 parts by weight) were immersed for 60 seconds to perform crosslinking treatment. Thereafter, it was washed with pure water at 10°C for 10 seconds and finally dried at 40°C for 300 seconds to obtain a light-polarizing laminated film composed of a base film/polarizer.

(5) Production of a polarizing plate having a single-sided protective film (first bonding process and peeling process)

A cyclic polyolefin-based resin film having a thickness of 20 µm was prepared as a first protective film disposed on the display cell side when the polarizing plate was placed on the display cell. After corona treatment was applied to the bonding surface of the first protective film, the corona-treated surface was coated with an ultraviolet curable adhesive ("KR-70T" manufactured by Adeka Co., Ltd.) using a small-diameter gravure coater, and the adhesive The first protective film was bonded to the polarizer surface of the polarizing laminated film produced in (4) above using a bonding roll through the coating layer of. Then, using a high-pressure mercury lamp, ultraviolet rays are irradiated from the base film side at a cumulative light amount of 200 mJ/cm 2 to cure the adhesive to form a first adhesive layer, and the first protective film/first adhesive layer/polarizer/substrate A bonding film consisting of a film layer structure was obtained (first bonding step). The thickness of the first adhesive layer was 0.5 µm.

Next, the base film was peeled off from the obtained bonding film (peeling step). The base film was easily peeled off to obtain a polarizing plate having a single-sided protective film composed of a layer configuration of first protective film/first adhesive layer/polarizer.

(6) Preparation of polarizing plate with double-sided protective film (2nd bonding process)

As a second protective film disposed on the outer side (on the side opposite to the display cell side) when the polarizing plate is disposed on the display cell, a 50 µm-thick cyclic polyolefin-based resin film was prepared. After corona treatment was applied to the bonding surface of the second protective film, the corona-treated surface was coated with an ultraviolet curable adhesive ("KR-70T" manufactured by Adeka Co., Ltd.) using a small-diameter gravure coater, and the adhesive The second protective film was bonded to the surface (polarizer surface) opposite to the first protective film of the polarizing plate having the single-sided protective film produced in (5) above through the coating layer of the bonding roll. Prior to bonding, corona treatment was also performed on the polarizer surface to which the second protective film was bonded. Then, using a high-pressure mercury lamp, ultraviolet rays were irradiated from the second protective film side at a cumulative light amount of 200 mJ/cm 2 to cure the adhesive to form a second adhesive layer, and the first protective film/first adhesive layer/polarizer A polarizing plate having a double-sided protective film having a layer configuration of /2nd adhesive layer/2nd protective film was obtained. The thickness of the second adhesive layer was 1.0 μm.

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 with the ultraviolet curable adhesive (before bonding with the polarizer) was measured using a non-contact multilayer film thickness meter ("SI-T series" manufactured by Keyence Corporation), and the difference between them was taken as the thickness of the first and second adhesive layers. In addition, the thickness of the adhesive layer before bonding and curing with the polarizer obtained in this way is maintained almost as it is even after bonding with the polarizer and curing, and the thickness of the adhesive layer after curing in the obtained polarizing plate is substantially the same as the obtained A cross section of the polarizing plate was cut out, and the thickness of the adhesive layer in the cross section was observed with a SEM (scanning electron microscope) to be confirmed by actual measurement.

<Comparative Examples 2 to 5>

A polarizing plate having a double-sided protective film was prepared in the same manner as in Example 1, except that the order of bonding the first and second protective films and the thickness after curing of the first and second adhesive layers were shown in Table 1. did In Table 1, "first protective film" refers to a protective film (cyclic polyolefin-based resin film having a thickness of 20 µm) disposed on the display cell side when the polarizing plate is placed on the display cell, and "second The term "protective film" refers to a protective film (cyclic polyolefin-based resin film having a thickness of 50 µm) disposed on the outer side (on the side opposite to the display cell side) when the polarizing plate is disposed on the display cell. Further, "first adhesive layer" refers to an adhesive layer to bond the first protective film, and "second adhesive layer" refers to an adhesive layer to bond the second protective film.

[Evaluation of reflective image]

The polarizing plates obtained in Examples and Comparative Examples were cut into 4 to 6 inch sizes, and in order to prevent reflection from the back side of the polarizing plate, this was bonded to a black acrylic plate using an adhesive to obtain samples for evaluation. At this time, the polarizing plate was bonded to the black acrylic plate from the first protective film side so that the second protective film faced outside. An intuitive fluorescent lamp in a lit state was projected onto the surface of the second protective film of the evaluation sample in regular reflection, and the reflected image was visually evaluated according to the following evaluation criteria. The results are shown in Table 1.

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

B: The reflected image of the fluorescent lamp reflected on the polarizing plate is slightly lacking in sharpness, and the outline 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 outline is also disturbed.

1 polarizer (polarizer with double-sided protective film), 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' stretched Polyvinyl alcohol-based resin layer, 30 base film, 30' stretched base film, 50 display cells, 60 adhesive layer, 100 laminated film, 200 stretched film, 300 polarizing laminated film, 400 bonding film, 500 single-sided protective film polarizer with

Claims (6)

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,
A first bonding step of bonding the first protective film to the one side via a first adhesive layer made of an active energy ray-curable adhesive;
After the first bonding process, a second bonding process of bonding the second protective film to the other surface via a second adhesive layer made of an active energy ray-curable adhesive.
including,
The first protective film is a protective film disposed closer to the display cell than the second protective film when the polarizing plate is disposed on the display cell;
The surface on which the second adhesive layer is formed is a bonding surface of the second protective film,
The thickness of the first adhesive layer after curing is 0.75 μm or less,
The thickness of the first adhesive layer after curing is smaller than the thickness of the second adhesive layer after curing,
The difference between the thickness of the second adhesive layer after curing and the thickness of the first adhesive layer after curing is 0.1 μm or more and 0.5 μm or less, the manufacturing method of the polarizing plate. The method of claim 1, wherein the thickness of the second adhesive layer after curing is greater than 0.75 μm. delete The method of manufacturing a polarizing plate according to claim 1 or 2, wherein the polarizer has a thickness of 20 μm 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;
An adhesive layer forming process of disposing an adhesive layer on the outer surface of the first protective film
including,
The surface on which the second adhesive layer is formed is a bonding surface of the second protective film,
The thickness of the first adhesive layer after curing is 0.75 μm or less,
The thickness of the first adhesive layer after curing is smaller than the thickness of the second adhesive layer after curing,
The method for producing a polarizing plate having a pressure-sensitive adhesive layer, wherein the difference between the thickness of the second adhesive layer after curing and the thickness of the first adhesive layer after curing is 0.1 μm or more and 0.5 μm or less. delete

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