JP2020074036A - Polarizing plate and display - Google Patents

Abstract

To provide a thin polarizing plate that has a good appearance when laminated on a display cell, and a display using the same.SOLUTION: There is provided a polarizing plate comprising: a polarizer; a first protective film that is laminated on one face of the polarizer with a first adhesive layer having a thickness of less than 2.0 μm therebetween; and a second protective film that is laminated on the other face of the polarizer with a second adhesive layer having a thickness of 2.0 μm or less therebetween. When the polarizing plate is arranged on a display cell, the second protective film is arranged closer to the display cell than the first protective film, and the thickness of the first adhesive layer is smaller than the thickness of the second adhesive layer. Also provided is a display including the polarizing plate.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a polarizing plate and a display device including the same.

  The polarizing plate is widely used in display devices such as liquid crystal display devices, and particularly in recent years in various mobile devices such as smartphones and slate PCs. Generally, a polarizing plate has a structure in which a protective film is attached to one side or both sides of a polarizer by using an adhesive, but with the development of mobile devices, it is possible to reduce the thickness of the polarizer and the protective film constituting the polarizing plate. Increasingly demanded.

  As an adhesive used for laminating the polarizer and the protective film, a photo-curable adhesive and an aqueous adhesive such as an aqueous solution of polyvinyl alcohol are known, and Patent Documents 1 to 10 disclose one or both of them. A polarizing plate in which a protective film is laminated on both surfaces of a polarizer using both of them is described.

JP, 2013-228726, A JP, 2013-210513, A JP 2012-144690 A JP 2012-2032111 A JP, 2009-109994, A JP, 2009-139585, A JP, 2009-134121, A JP, 2010-091603, A Japanese Patent Laid-Open No. 2010-091602 JP, 2008-170717, A

  When the thickness of the polarizer or the protective film constituting the polarizing plate is reduced, the surface of the protective film attached to the polarizer via the adhesive layer is distorted in a minute area, and the surface is wavy and uneven. It was revealed by the study of the present inventor that These surface irregularities do not directly affect the optical characteristics of the polarizing plate, but when the polarizing plate is attached to the display cell, the protective film is placed on the outer side (for example, the outermost surface). In this case, surface unevenness remains after bonding, and the reflection image from the surface of the protective film is distorted so that a glossy feeling cannot be obtained. However, there is a defect in appearance such that the surface unevenness is not conspicuous locally) or lack of a high-class feeling.

  Therefore, an object of the present invention is to provide a thin polarizing plate having a good appearance when attached to a display cell, and a display device using the thin polarizing plate.

The present invention provides the following polarizing plate and display device.
[1] A polarizer,
A first protective film laminated on one surface of the polarizer via a first adhesive layer having a thickness of less than 2.0 μm;
A second protective film laminated on the other surface of the polarizer via a second adhesive layer having a thickness of 2.0 μm or less;
A polarizing plate including
The second protective film is a protective film arranged on the display cell side with respect to the first protective film when the polarizing plate is arranged on the display cell,
A polarizing plate in which the thickness of the first adhesive layer is smaller than the thickness of the second adhesive layer.

  [2] The polarizing plate according to [1], wherein the first and second adhesive layers are cured product layers of a photocurable adhesive.

  [3] The polarizing plate according to [1] or [2], wherein the thickness of the first adhesive layer is 0.7 μm or less.

  [4] The polarizing plate according to any one of [1] to [3], wherein the difference between the thickness of the second adhesive layer and the thickness of the first adhesive layer is 0.3 μm or more.

  [5] The polarizing plate according to any one of [1] to [4], wherein the thickness of the polarizer is 10 μm or less.

  [6] The polarizing plate according to any one of [1] to [5], further including an adhesive layer that is laminated on the outer surface of the second protective film and is attached to the display cell.

  [7] A display device including the display cell and the polarizing plate according to any one of [1] to [6] arranged on at least one surface thereof.

  According to the present invention, it is possible to provide a polarizing plate in which the above-described unevenness on the surface of the first protective film and the resulting distortion of the reflected image are suppressed. Such a polarizing plate distorts a reflection image from the surface of the first protective film when it is arranged on the display cell so that the first protective film is on the outside (the second protective film is on the display cell side). Is suppressed, resulting in excellent appearance.

It is a schematic sectional drawing which shows an example of the laminated constitution of the polarizing plate which concerns on this invention. It is a schematic sectional drawing which shows the state when arrange | positioning the polarizing plate shown in FIG. 1 on a display cell. FIG. 2 is a schematic cross-sectional view showing an example of the layer structure of a liquid crystal display device including a display cell (liquid crystal cell) and polarizing plates (polarizing plates with double-sided protective films) arranged on the front side and the rear side thereof. It is a flow chart which shows a preferred example of a manufacturing method of a polarizing plate concerning the present invention. It is a schematic sectional drawing which shows an example of the laminated constitution of the laminated film obtained by a resin layer formation process. It is a schematic sectional drawing which shows an example of the laminated constitution of the stretched film obtained by a stretching process. It is a schematic sectional drawing which shows an example of the laminated constitution of the polarizing laminated film obtained by a dyeing process. It is a schematic sectional drawing which shows an example of the laminated constitution of the bonding film obtained by a 1st bonding process. It is a schematic sectional drawing which shows an example of the layer structure of the polarizing plate with a single-sided protective film obtained by a peeling process.

<Polarizing plate>
FIG. 1 is a schematic sectional view showing an example of the layer structure of a polarizing plate 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 arranged on the display cell. Like the polarizing plate 1 shown in FIG. 1, the polarizing plate of the present invention includes a polarizer 5, a first protective film 10 laminated on one surface of the polarizer 5 via a first adhesive layer 15, and the other. The second protective film 20 that is laminated on the surface with the second adhesive layer 25 interposed therebetween.

  As shown in FIG. 2, the first protective film 10 is a protective film that is arranged outside the second protective film 20 when the polarizing plate 1 is arranged on the display cell 50. It is a protective film that typically forms the outermost surface when placed on the display cell 50. The second protective film 20 is a protective film arranged closer to the display cell 50 side than the first protective film 10. The polarizing plate 1 can be arranged and bonded on the display cell 50 by using the adhesive layer 60 provided on the outer surface of the second protective film 20 arranged on the display cell 50 side.

(1) Thickness of Adhesive Layer In the present invention, the polarizer 5 and the first protective film 10 that forms an outer surface (typically the outermost surface) when the polarizing plate 1 is placed on the display cell 50. The thickness T ₁ of the first adhesive layer 15 interposed therebetween is the thickness T _{2 of} the second adhesive layer 25 interposed between the second protective film 20 arranged on the display cell 50 side and the polarizer 5. Smaller than. That is, the thickness T ₁ of the first adhesive layer 15 is made relatively small, while the thickness T ₂ of the second adhesive layer 25 is made relatively large.

By making the thickness T ₁ of the first adhesive layer 15 relatively small, it is possible to reduce the contracting force when the adhesive forming the first adhesive layer 15 is cured or dried, and thus the first protective film. Even if the thickness of 10 or the polarizer 5 is reduced, it is possible to prevent the first protective film 10 and the polarizer 5 from losing the shrinkage force of the adhesive and generating unevenness on the surface of the first protective film 10. it can. When the thickness of the polarizer 5 is 10 μm or less, the appearance deterioration due to the occurrence of surface irregularities is particularly remarkable, but even in such a case, according to the present invention, the occurrence of surface irregularities of the first protective film 10, And a polarizing plate capable of suppressing distortion of a reflected image due to this, obtaining a clear reflected image, and having an excellent glossiness of the surface of the first protective film 10 and having surface uniformity and a high-grade feeling. You can

The thickness T ₁ of the first adhesive layer 15 is specifically less than 2.0 μm, preferably 1.0 μm or less. When the thickness of the polarizer 5 is 10 μm or less, the thickness T ₁ of the first adhesive layer 15 is 0.7 μm or less in order to sufficiently suppress the shrinkage force of the adhesive and suppress the occurrence of surface irregularities. Is more preferable, and 0.4 μm or less is further preferable.

The thickness T ₁ of the first adhesive layer 15 is usually 0.01 μm or more, preferably 0.05 μm or more. If the thickness T ₁ is less than 0.01 μm, sufficient adhesive force may not be obtained.

As described above, according to the present invention, the appearance when the polarizing plate 1 is arranged on the display cell 50 can be affected, that is, the polarizing plate 1 can be visually recognized in the state where the polarizing plate 1 is arranged on the display cell 50. While the thickness T ₁ of the first adhesive layer 15 responsible for adhesion of the protective film 10 is made relatively small, the polarizing plate 1 is disposed on the display cell 50 on the surface of the second protective film 20. Since it is not visually recognized in the state, and even if surface irregularities occur, it has almost no adverse effect on the appearance, it is not necessary to make the thickness T ₂ of the second adhesive layer 25, which is responsible for the adhesion of the second protective film 20, relatively small. Rather, it is important to make it relatively large for the following reasons.

  That is, if the thickness of the adhesive layer is made too small, the problem that minute air bubbles are mixed in the adhesive layer when the protective film and the polarizer are attached is likely to occur. Although such bubbles cannot be visually observed by themselves, when a polarizing plate is incorporated in a display device such as a liquid crystal display device and the display device is turned on, light is scattered due to the dense bubbles, and a black display state occurs. Light leakage (air bubbles become bright spots) causes display problems.

The light leakage due to such bubbles is likely to be a problem in the second adhesive layer 25 interposed between the second protective film 20 disposed on the display cell 50 side and the polarizer 5, and is disposed outside. The first adhesive layer 15 interposed between the first protective film 10 and the polarizer 5 is unlikely to cause a problem. This will be described with reference to FIG. 3 showing a liquid crystal display device including a display cell (liquid crystal cell) 50 and polarizing plates 1 arranged on the front side (viewing side) and the rear side (backlight side) thereof. This is because the 2 adhesive layer 25 is arranged in the crossed Nicols formed between the front side polarizer 5 and the rear side polarizer 5. When light is scattered in crossed Nicols, black display is broken and light leakage occurs. Therefore, the thickness T ₂ of the second adhesive layer 25, which is less likely to affect the appearance when the polarizing plate 1 is placed on the display cell 50, may be made larger than the thickness T ₁ of the first adhesive layer 15. It is essential that light leakage in a black display state can be suppressed.

On the other hand, since the first adhesive layer 15 is disposed outside the crossed Nicols, the thickness T ₁ thereof is made relatively small, and even if bubbles are generated by this, the problem of light leakage is unlikely to occur.

The thickness T ₂ of the second adhesive layer 25 is specifically set to 2.0 μm or less, and is preferably set to 1.8 μm or less from the viewpoint of thinning the polarizing plate 1. When the thickness T ₂ exceeds 2.0 μm, it is disadvantageous for thinning the polarizing plate 1. The lower limit of the thickness T ₂ is not particularly limited as long as it is larger than the thickness T _{1 of} the first adhesive layer 15, but from the viewpoint of adhesiveness, the thickness T ₂ is usually 0.01 μm or more, preferably 0. It is at least 05 μm.

In order to effectively suppress unevenness on the surface of the first protective film 10 and effectively suppress light leakage in a black display state, the thickness T _{2 of} the second adhesive layer 25 and the first adhesive layer 15 The difference from the thickness T ₁ is preferably 0.3 μm or more, more preferably 0.5 μm or more, and further preferably 0.9 μm or more.

(2) Adhesive for forming adhesive layer As the adhesive for forming the first and second adhesive layers 15 and 25, a photo-curable adhesive or a water-based adhesive can be used. As described above, a factor that causes unevenness on the surface of the first protective film 10 is the shrinkage force when the adhesive is cured or dried, and the adhesive layer is cured in a short time by light irradiation. The shrinkage force (per unit time) in the case of using a photo-curable adhesive that causes the adhesion is generally determined by drying the solvent (water) by heating and then curing the adhesive as required over a relatively long time. Since it is larger than the water-based adhesive for carrying out the present invention, the present invention can be particularly suitably applied when the first adhesive layer 15 is formed of a photo-curable adhesive, and the resulting unevenness suppressing effect is high.

  The adhesive forming the first adhesive layer 15 and the adhesive forming the second adhesive layer 25 may be the same kind or different kinds, but for the above reason, the first adhesive layer The adhesive forming 15 is preferably a photocurable adhesive. The adhesive forming the second adhesive layer 25 is also preferably a photocurable adhesive. Since the photocurable adhesive can be prepared as 1) a solventless adhesive, a drying step can be eliminated, and 2) it can be used for laminating a protective film having low moisture permeability. As compared with water-based adhesives, there are many types of protective films that can be attached, which is also an advantage.

  The first and second adhesive layers 15 and 25 formed of a photocurable adhesive are cured product layers of the photocurable adhesive.

  The photo-curable adhesive refers to an adhesive that is cured by irradiation with active energy rays such as ultraviolet rays, for example, a polymerizable compound and a photopolymerization initiator-containing adhesive, a photoreactive resin-containing adhesive, and a binder. Examples thereof include those containing a resin and a photoreactive crosslinking agent. Examples of the polymerizable compound include a photocurable epoxy compound; a photocurable vinyl compound such as a photocurable acrylic compound; and a photocurable urethane compound. Examples of the photopolymerization initiator include a photocationic polymerization initiator (for example, when using a photocurable epoxy compound) and a photoradical polymerization initiator (for example, when using a photocurable acrylic compound). ..

  Examples of the water-based adhesive include an adhesive composed of a polyvinyl alcohol-based resin aqueous solution and a water-based two-component urethane-based emulsion adhesive. Above all, a water-based adhesive composed of a polyvinyl alcohol-based resin aqueous solution is preferably used.

  Examples of the polyvinyl alcohol-based resin include vinyl alcohol homopolymers obtained by saponifying polyvinyl acetate, which is a homopolymer of vinyl acetate, as well as copolymers of vinyl acetate and other monomers copolymerizable therewith. A polyvinyl alcohol-based copolymer obtained by saponifying a polymer, or a modified polyvinyl alcohol-based polymer obtained by partially modifying the hydroxyl groups thereof can be used. The water-based adhesive can contain additives such as polyvalent aldehydes, water-soluble epoxy compounds, melamine compounds, zirconia compounds, and zinc compounds.

(3) Polarizer The polarizer 5 may be a uniaxially stretched polyvinyl alcohol resin layer in which a dichroic dye is adsorbed and oriented. The thickness of the polarizer 5 is preferably 10 μm or less, more preferably 7 μm or less. Setting the thickness of the polarizer 5 to 10 μm or less is advantageous for thinning the polarizing plate 1, while according to the present invention, the first protective film is used even when such a thin film polarizer 5 is used. 10 It is possible to effectively suppress the unevenness on the surface.

  As the polyvinyl alcohol-based resin forming the polyvinyl alcohol-based resin layer, a saponified polyvinyl acetate-based resin can be used. Examples of the polyvinyl acetate-based resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and a copolymer of vinyl acetate and another monomer copolymerizable therewith. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

  The polarizer 5 is formed by forming a film of such a polyvinyl alcohol resin. The method for forming the polyvinyl alcohol-based resin is not particularly limited, and it can be formed by a known method. However, from the viewpoint of easily obtaining the polarizer 5 having a thickness of 10 μm or less, the polyvinyl alcohol-based resin It is preferable to coat the substrate film with the solution to form a film.

  The polarizer 5 needs to be stretched and oriented, and is preferably stretched at a stretch ratio of more than 5 times, more preferably more than 5 times and not more than 17 times.

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

The saponification degree is a unit ratio (mol%) of a ratio of acetic acid groups (acetoxy groups: —OCOCH ₃ ) contained in a polyvinyl acetate-based resin, which is a raw material of a polyvinyl alcohol-based resin, converted into hydroxyl groups by a saponification step. The following formula:
Degree of saponification (mol%) = 100 × (number of hydroxyl groups) ÷ (number of hydroxyl groups + number of acetic acid groups)
Is defined by The saponification degree can be determined according to JIS K 6726 (1994). The higher the degree of saponification, the higher the proportion of hydroxyl groups, and thus the lower the proportion of acetate groups that inhibit crystallization.

  The polyvinyl alcohol-based resin may be a modified polyvinyl alcohol which is partially modified. Examples thereof include polyvinyl alcohol resins modified with olefins such as ethylene and propylene; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid; alkyl esters of unsaturated carboxylic acids, and acrylamide. The modification ratio is preferably less than 30 mol%, more preferably less than 10%. When the modification exceeds 30 mol%, it becomes difficult to adsorb the dichroic dye, and the polarizer 5 having sufficient polarization performance cannot be obtained.

  The average degree of polymerization of the polyvinyl alcohol 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 according to JIS K 6726 (1994).

  Examples of commercially available polyvinyl alcohol-based resins preferably used in the present invention are all trade names, "PVA124" (saponification degree: 98.0 to 99.0 mol%) manufactured by Kuraray Co., Ltd. PVA117 "(saponification degree: 98.0-99.0 mol%)," PVA624 "(saponification degree: 95.0-96.0 mol%)," PVA617 "(saponification degree: 94.5-95) "AH-26" (saponification degree: 97.0-98.8 mol%), "AH-22" (saponification degree: 97.5) manufactured by Nippon Synthetic Chemical Industry Co., Ltd. 98.5 mol%), "NH-18" (saponification degree: 98.0-99.0 mol%), "N-300" (saponification degree: 98.0-99.0 mol%); Japan "JC-33" (saponification degree: 99.0 mol% or more), "JM-33" (ken Degree: 93.5-95.5 mol%), "JM-26" (saponification degree: 95.5-97.5 mol%), "JP-45" (saponification degree: 86.5-89. 5 mol%), "JF-17" (saponification degree: 98.0-99.0 mol%), "JF-17L" (saponification degree: 98.0-99.0 mol%), "JF-" 20 "(degree of saponification: 98.0 to 99.0 mol%).

  The dichroic dye contained (adsorption orientation) in the polarizer 5 may be iodine or a dichroic organic dye. Specific examples of the dichroic organic dye 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, Supra Blue G, Supra Blue GL, Supra Orange GL, Direct Includes Sky Blue, Direct First Orange S and First Black. The dichroic dyes may be used alone or in combination of two or more.

(4) First and second protective films The first and second protective films 10 and 20 are thermoplastic resins, for example, chain polyolefin resin (polypropylene resin etc.), cyclic polyolefin resin (norbornene resin etc.). ) Like polyolefin resin; cellulose triacetate, cellulose diacetate like cellulose ester resin; polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate like polyester resin; polycarbonate resin; (meth) acrylic resin; Alternatively, it may be a transparent resin film made of a mixture or copolymer of these. The first protective film 10 and the second protective film 20 may be the same kind of protective film or different kinds of protective films.

  Cyclic polyolefin resin is a general term for resins polymerized with cyclic olefin as a polymerized unit, and is described in, for example, JP-A-1-240517, JP-A-3-14882, JP-A-3-122137 and the like. Resins. Specific examples of cyclic polyolefin resins include ring-opening (co) polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers of cyclic olefins with chain olefins such as ethylene and propylene (typically Are random copolymers), graft polymers obtained by modifying these with unsaturated carboxylic acids or their derivatives, and their hydrides. Above all, 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.

  Various products of cyclic polyolefin resins are commercially available. Examples of commercial products of cyclic polyolefin resins are all trade names, "Topas" (manufactured by Topas Advanced Polymers GmbH, available from Polyplastics Co., Ltd.), "Arton" (manufactured by JSR Corporation), It includes "ZEONOR" (manufactured by Nippon Zeon Co., Ltd.), "ZEONEX" (manufactured by Nippon Zeon Co., Ltd.), and "Apel" (manufactured by Mitsui Chemicals, Inc.).

  All of them are trade names, such as "ESCINA" (manufactured by Sekisui Chemical Co., Ltd.), "SCA40" (manufactured by Sekisui Chemical Co., Ltd.), and "Zeonor Film" (manufactured by Zeon Corporation). A commercial product of the filmed cyclic polyolefin resin film may be used as the protective film.

  The cellulose ester-based resin is an ester of cellulose and fatty acid. Specific examples of the cellulose ester-based resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. Moreover, these copolymers and those in which a part of the hydroxyl groups are modified with other substituents can also be used. Among these, cellulose triacetate (triacetyl cellulose: TAC) is particularly preferable. Many products of cellulose triacetate are commercially available, which is advantageous in terms of availability and cost. Examples of commercially available products of cellulose triacetate are trade names, "Fujitac TD80" (manufactured by Fuji Film Co., Ltd.), "Fujitac TD80UF" (manufactured by Fuji Film Co., Ltd.), "Fujitac TD80UZ" (Fuji Film Co., Ltd.) )), “Fujitac TD40UZ” (manufactured by FUJIFILM Corporation), “KC8UX2M” (manufactured by Konica Minolta Opto Inc.), and “KC4UY” (manufactured by Konica Minolta Opto Inc.).

  The first protective film 10 and / or the second protective film 20 may be a protective film having an optical function as well, such as a retardation film or a brightness enhancement film. For example, a retardation film provided with an arbitrary retardation value by stretching (uniaxially stretching or biaxially stretching) a transparent resin film made of the above material or forming a liquid crystal layer or the like on the film. Can be

  The surface of the first protective film 10 and / or the second protective film 20 opposite to the polarizer 5 has a surface treatment such as a hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer, and an antifouling layer. A layer (coating layer) can also be formed. The method for forming the surface treatment layer on the surface of the protective film is not particularly limited, and a known method can be used.

  The thickness of the first and second protective films 10 and 20 is preferably thin from the viewpoint of thinning the polarizing plate 1, but if the thickness is too thin, the strength decreases and the workability deteriorates. Therefore, the thickness of the first and second protective films 10 and 20 is preferably 5 to 90 μm, more preferably 5 to 60 μm, and further preferably 5 to 50 μm. According to the present invention, irregularities on the surface of the first protective film 10 can be effectively suppressed even if the thickness of the first protective film 10 is 50 μm or less.

(5) Adhesive Layer As shown in FIG. 2, the polarizing plate 1 is provided on the outer surface (the surface opposite to the polarizer 5) of the second protective film 20 of the polarizing plate 1 with another member (for example, a display device). The pressure-sensitive adhesive layer 60 for bonding to the display cell 50) may be laminated. The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer 60 is usually a (meth) acrylic resin, a styrene resin, a silicone resin or the like as a base polymer, to which a crosslinking agent such as an isocyanate compound, an epoxy compound or an aziridine compound is added. And an adhesive composition. Furthermore, a pressure-sensitive adhesive layer that contains fine particles and exhibits a light-scattering property can be used.

  The thickness of the pressure-sensitive adhesive layer 60 can be 1 to 40 μm, but it is preferable to form the pressure-sensitive adhesive layer 60 thinly within a range that does not impair the characteristics of workability and durability, and specifically 3 to 25 μm is preferable. The thickness of 3 to 25 μm has good workability and is suitable for suppressing the dimensional change of the polarizer 5. If the pressure-sensitive adhesive layer 60 is less than 1 μm, the tackiness is lowered, and if it exceeds 40 μm, problems such as sticking out of the pressure-sensitive adhesive are likely to occur.

  The method for forming the pressure-sensitive adhesive layer 60 is not particularly limited, and the surface of the second protective film 20 is coated with a pressure-sensitive adhesive composition (adhesive solution) containing each component including the above-mentioned base polymer. Then, the adhesive layer 60 may be formed by drying, or the adhesive layer 60 may be similarly formed on the separator (release film) and then the adhesive layer 60 may be transferred to the second protective film 20. When forming the pressure-sensitive adhesive layer 60 on the surface of the second protective film 20, the surface of the second protective film 20 or the surface of the pressure-sensitive adhesive layer 60 may be subjected to a surface treatment, for example, a corona treatment, if necessary. ..

(6) Optical Layer The polarizing plate 1 may further include another optical layer laminated on the first protective film 10 or the second protective film 20. Other optical layers include a reflective polarizing film that transmits a certain kind of polarized light and reflects a polarized light having the opposite property; a film having an uneven surface with an antiglare function; a film having a surface antireflection function. A reflective film having a reflective function on the surface; a semi-transmissive reflective film having both a reflective function and a transmissive function; and a viewing angle compensation film.

  Examples of commercially available products corresponding to a reflective polarizing film that transmits a certain kind of polarized light and reflects polarized light having the opposite property include "DBEF" (manufactured by 3M, Sumitomo 3M Limited in Japan). Available), "APF" (manufactured by 3M, available from Sumitomo 3M Limited in Japan).

  Examples of the viewing angle compensation film include an optical compensation film in which a liquid crystal compound is applied to the surface of a substrate and is aligned and fixed, a retardation film made of a polycarbonate resin, a retardation film made of a cyclic polyolefin resin, and the like. ..

  Commercially available products corresponding to the optically-compensatory film in which the liquid crystal compound is applied on the surface of the base material and aligned / fixed are "WV film" (manufactured by FUJIFILM Corporation), "NH film" (JX Nikko Nisseki). Energy Co., Ltd. product, "NR film" (JX Nikko Nisseki Energy Co., Ltd. product), etc. are mentioned.

  Commercially available products equivalent to the retardation film made of a cyclic polyolefin resin include "Arton Film" (manufactured by JSR Corporation), "ESCINA" (manufactured by Sekisui Chemical Co., Ltd.), "Zeonor Film" (Nippon Zeon Co., Ltd.) and the like.

<Production method of polarizing plate>
The polarizing plate of the present invention can be suitably manufactured, for example, by the method shown in FIG. The method of manufacturing the polarizing plate shown in FIG.
(1) Resin layer forming step S10 in which a coating solution containing a polyvinyl alcohol-based resin is applied to at least one surface of the substrate film and then dried to form a polyvinyl alcohol-based resin layer to obtain a laminated film. ,
(2) Stretching step S20 in which the laminated film is stretched to obtain a stretched film,
(3) Dyeing step S30 for obtaining a polarizing laminated film by dyeing the polyvinyl alcohol resin layer of the stretched film with a dichroic dye to form a polarizer.
(4) First laminating step S40, in which one of the first and second protective films is laminated on the polarizer of the polarizing laminate film via the adhesive layer to obtain a laminated film,
(5) A peeling step S50 for peeling and removing the base film from the laminated film to obtain a polarizing plate with a single-sided protective film,
(6) A second bonding step S60 of bonding the other protective film of the first and second protective films to the polarizer surface of the polarizing plate with the single-sided protective film via the adhesive layer.
In this order. Hereinafter, each step will be described with reference to FIGS.

(1) Resin layer forming step S10
With reference to FIG. 5, this step is a step of forming the polyvinyl alcohol-based resin layer 6 on at least one surface of the base film 30 to obtain the laminated film 100. The polyvinyl alcohol resin layer 6 is a layer that becomes the polarizer 5 through the stretching step S20 and the dyeing step S30. The polyvinyl alcohol-based resin layer 6 can be formed by applying a coating liquid containing a polyvinyl alcohol-based resin on one side or both sides of the substrate film 30 and drying the coating layer. The method of forming the polyvinyl alcohol resin layer by such coating is advantageous in that the thin film polarizer 5 can be easily obtained.

[Base film]
The base film 30 can be made of a thermoplastic resin, and is preferably made of a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, stretchability and the like. Specific examples of such a thermoplastic resin include, for example, polyolefin resins such as chain polyolefin resins and cyclic polyolefin resins (norbornene resins, etc.); polyester resins; (meth) acrylic resins; cellulose triacetate, Cellulose ester resin such as cellulose diacetate; polycarbonate resin; polyvinyl alcohol resin; polyvinyl acetate resin; polyarylate resin; polystyrene resin; polyethersulfone resin; polysulfone resin; polyamide resin; polyimide System resins; and mixtures and copolymers thereof.

  The base film 30 may have a single-layer structure composed of one resin layer composed of one or two or more thermoplastic resins, or a plurality of resin layers composed of one or two or more thermoplastic resins. It may have a laminated multilayer structure. The base film 30 is preferably made 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 below.

  Examples of the chain polyolefin resin include homopolymers of chain olefins such as polyethylene resin and polypropylene resin, and copolymers of two or more chain olefins. The base film 30 made of a chain polyolefin resin is preferable because it can be stably stretched at a high magnification. Among them, the base material film 30 is made of polypropylene resin (polypropylene resin which is a homopolymer of propylene or copolymer mainly composed of propylene), polyethylene resin (polyethylene resin which is a homopolymer of ethylene, or ethylene). More preferably, it is a copolymer).

  A copolymer mainly composed of propylene, which is one of the examples suitably used as the thermoplastic resin constituting the base film 30, is a copolymer of propylene and another monomer copolymerizable therewith.

  Examples of the other monomer copolymerizable with propylene include ethylene and α-olefin. As the α-olefin, an α-olefin having 4 or more carbon atoms is preferably used, and an α-olefin having 4 to 10 carbon atoms is more preferable. Specific examples of the α-olefin having 4 to 10 carbon atoms include linear monoolefins such as 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene and 1-decene; 3 Branched monoolefins such as -methyl-1-butene, 3-methyl-1-pentene, 4-methyl-1-pentene; vinylcyclohexane. The copolymer of propylene and another monomer copolymerizable therewith may be a random copolymer or a block copolymer.

  The content of the other monomer in the copolymer is, for example, 0.1 to 20% by weight, preferably 0.5 to 10% by weight. The content of other monomers in the copolymer is determined by infrared (IR) spectrum measurement according to the method described on page 616 of "Polymer Analysis Handbook" (published by Kinokuniya Bookstore in 1995). You can ask.

  Among the above, as the polypropylene resin, a propylene homopolymer, a propylene-ethylene random copolymer, a propylene-1-butene random copolymer or a propylene-ethylene-1-butene random copolymer is preferably used.

  The stereoregularity of the polypropylene resin is preferably substantially isotactic or syndiotactic. The base film 30 made of a polypropylene resin having substantially isotactic or syndiotactic stereoregularity has relatively good handleability and excellent mechanical strength in a high temperature environment.

  The polyester resin is a resin having an ester bond, and is generally made of a polycondensate of a polyvalent carboxylic acid or its derivative and a polyhydric alcohol. As the polyvalent carboxylic acid or its derivative, a divalent dicarboxylic acid or its derivative can be used, and examples thereof include terephthalic acid, isophthalic acid, dimethyl terephthalate, and dimethyl naphthalenedicarboxylate. A divalent diol can be used as the polyhydric alcohol, and examples thereof include ethylene glycol, propanediol, butanediol, neopentyl glycol, and cyclohexanedimethanol.

  A typical example of the polyester resin is polyethylene terephthalate, which is a polycondensate of terephthalic acid and ethylene glycol. Polyethylene terephthalate is a crystalline resin, but the one before being crystallized is easier to be subjected to a treatment such as stretching. If necessary, a crystallization treatment can be performed during the stretching or by a heat treatment after the stretching. Further, a copolyester whose crystallinity is lowered (or made amorphous) by copolymerizing another type of monomer with the skeleton of polyethylene terephthalate is also preferably used. Examples of such a resin include those obtained by copolymerizing cyclohexanedimethanol and isophthalic acid. Since these resins also have excellent stretchability, they can be preferably used.

  Specific examples of polyester resins other than polyethylene terephthalate and its copolymers include, for example, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polycyclohexane dimethyl terephthalate. , Polycyclohexanedimethylnaphthalate, and mixtures and copolymers thereof.

The (meth) acrylic resin is a resin containing a compound having a (meth) acryloyl group as a main constituent monomer. Specific examples of the (meth) acrylic resin include, for example, poly (meth) acrylic acid ester such as polymethylmethacrylate; methylmethacrylate- (meth) acrylic acid copolymer; methylmethacrylate- (meth) acrylic acid. Ester copolymer; methyl methacrylate-acrylic acid ester- (meth) acrylic acid copolymer; methyl (meth) acrylate-styrene copolymer (MS resin etc.); methyl methacrylate and alicyclic hydrocarbon group It includes a copolymer with a compound having (for example, a methyl methacrylate-cyclohexyl methacrylate copolymer, a 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 methyl poly (meth) acrylate is used, and more preferably, methyl methacrylate is the main component (50 to 100). % By weight, preferably 70 to 100% by weight) is used.

  The polycarbonate resin is an engineering plastic made of a polymer in which monomer units are bonded via a carbonate group, and is a resin having high impact resistance, heat resistance, flame retardancy, and transparency. The polycarbonate-based resin forming the base film 30 may be a resin called modified polycarbonate in which the polymer skeleton is modified to lower the photoelastic coefficient, a copolymerized polycarbonate with improved wavelength dependence, or the like.

  Various products of the polycarbonate-based resin are commercially available. Commercially available examples of polycarbonate resins are trade names, "Panlite" (manufactured by Teijin Kasei Co., Ltd.), "Upilon" (manufactured by Mitsubishi Engineering Plastics Co., Ltd.), "SD Polyca" (Sumitomo Dow). Manufactured by Dow Chemical Co., Ltd., and the like.

  Among these, polypropylene resin is preferably used from the viewpoints of stretchability and heat resistance.

  Regarding the cyclic polyolefin-based resin and the cellulose ester-based resin that can be used for the base film 30, the matters described for the protective film are cited. Further, the chain polyolefin resin, polyester resin, (meth) acrylic resin, and polycarbonate resin as described above in relation to the base film 30 can be used as the constituent material of the protective film.

  In addition to the above-mentioned thermoplastic resin, any appropriate additive may be added to the base film 30. Examples of such additives include an ultraviolet absorber, an antioxidant, a lubricant, a plasticizer, a release agent, an anti-coloring agent, a flame retardant, a nucleating agent, an antistatic agent, a pigment, and a coloring agent. .. The content of the thermoplastic resin in the base film 30 is preferably 50 to 100% by weight, more preferably 50 to 99% by weight, further preferably 60 to 98% by weight, and particularly preferably 70 to 97% by weight. .. When the content of the thermoplastic resin in the base material film 30 is less than 50% by weight, the high transparency and the like inherent in the thermoplastic resin may not be sufficiently exhibited.

  The thickness of the base film 30 can be appropriately determined, but in general, 1 to 500 μm is preferable, 1 to 300 μm is more preferable, and further 5 to 200 μm is preferable, and 5 to 5 from the viewpoint of workability such as strength and handleability. Most preferred is 150 μm.

[Coating liquid containing polyvinyl alcohol resin]
The coating liquid is preferably a polyvinyl alcohol-based resin solution obtained by dissolving polyvinyl alcohol-based resin powder in a good solvent (for example, water). The details of the polyvinyl alcohol-based resin are as described above.

  The coating liquid may contain additives such as a plasticizer and a surfactant, if necessary. As the plasticizer, a polyol or a condensate thereof can be used, and examples thereof include glycerin, diglycerin, triglycerin, ethylene glycol, propylene glycol, polyethylene glycol and the like. The additive content is preferably 20% by weight or less of the polyvinyl alcohol resin.

[Coating of coating liquid and drying of coating layer]
The method of applying the above coating liquid to the base film 30 is a wire bar coating method; a roll coating method such as reverse coating or gravure coating; a die coating method; a comma coating method; a lip coating method; a spin coating method; a screen coating. Method; fountain coating method; dipping method; spray method or the like.

  When the coating liquid is applied to both sides of the base material film 30, the above-mentioned method can be used to perform the application one by one, or the dipping method, the spray coating method, or other special equipment can be used to apply the base material. It is also possible to coat both surfaces of the film 30 at the same time.

  The drying temperature and the drying time of the coating layer (the polyvinyl alcohol-based resin layer before drying) are set according to the type of solvent contained 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 drying time is, for example, 2 to 20 minutes.

  The polyvinyl alcohol 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, which may occur during manufacturing of the polarizing laminated film 300 (see FIG. 7), can be suppressed, and two polarizing plates can be obtained from one polarizing laminated film 300. It is also advantageous in terms of plate production efficiency.

  The thickness of the polyvinyl alcohol-based resin layer 6 in the laminated film 100 is preferably 3 to 30 μm, more preferably 5 to 20 μm. If the polyvinyl alcohol-based resin layer 6 has a thickness within this range, the dyeing property of the dichroic dye is good, the polarizing performance is excellent, and the polarizing film having a thickness of 10 μm or less is passed through a stretching process S20 and a dyeing process S30 described below. The child 5 can be obtained. If the thickness of the polyvinyl alcohol resin layer 6 exceeds 30 μm, the thickness of the polarizer 5 may exceed 10 μm. If the thickness of the polyvinyl alcohol-based resin layer 6 is less than 3 μm, it tends to be too thin after stretching and the dyeability tends to deteriorate.

  Prior to applying the coating liquid, in order to improve the adhesion between the base film 30 and the polyvinyl alcohol resin layer 6, at least the surface of the base film 30 on which the polyvinyl alcohol resin layer 6 is formed is formed. , Corona treatment, plasma treatment, flame (flame) treatment, etc. may be performed.

  Prior to applying the coating liquid, in order to improve the adhesion between the base film 30 and the polyvinyl alcohol-based resin layer 6, a polyvinyl alcohol-based adhesive is provided on the base film 30 via a primer layer or an adhesive layer. The resin layer 6 may be formed.

[Primer layer]
The primer layer can be formed by applying the primer layer forming coating liquid on the surface of the substrate film 30 and then drying. The primer layer forming coating liquid contains a component that exhibits a certain degree of strong adhesion to both the base film 30 and the polyvinyl alcohol resin layer 6. The primer layer-forming coating liquid 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 and the like is preferably used, and examples thereof include (meth) acrylic resin and polyvinyl alcohol resin. Above all, a polyvinyl alcohol-based resin that gives good adhesion is preferably used.

  Examples of polyvinyl alcohol-based resins include polyvinyl alcohol resins and derivatives thereof. Derivatives of polyvinyl alcohol resins include polyvinyl formal and polyvinyl acetal, as well as polyvinyl alcohol resins modified with olefins such as ethylene and propylene; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid. Examples of the modified product include those modified with an alkyl ester of an unsaturated carboxylic acid and those modified with acrylamide. Among the above polyvinyl alcohol resins, it is preferable to use a polyvinyl alcohol resin.

  As the solvent, a general organic solvent or an aqueous solvent capable of dissolving the above resin component is usually used. Examples of the solvent include aromatic hydrocarbons such as benzene, toluene and xylene; ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone; esters such as ethyl acetate and isobutyl acetate; methylene chloride, Chlorinated hydrocarbons such as trichlorethylene and chloroform; alcohols such as ethanol, 1-propanol, 2-propanol and 1-butanol. However, when the primer layer is formed using a coating liquid for forming a primer layer containing an organic solvent, the base film 30 may be dissolved, so the solvent should be selected in consideration of the solubility of the base film 30. Preferably. Considering the influence on the environment, it is preferable to form the primer layer from a coating liquid containing water as a solvent.

  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. The cross-linking agent is appropriately selected from known ones such as organic type and inorganic type depending on the kind of the thermoplastic resin used. Examples of the crosslinking agent include epoxy-based, isocyanate-based, dialdehyde-based, and metal-based crosslinking agents.

  As the epoxy-based cross-linking agent, either one-component curing type or two-component curing type can be used, and ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin di- or tri-glycidyl ether, 1,6-hexane. Examples thereof include diol diglycidyl ether, trimethylolpropane triglycidyl ether, diglycidyl aniline and diglycidyl amine.

  Examples of the isocyanate cross-linking agent include tolylene diisocyanate, hydrogenated tolylene diisocyanate, trimethylolpropane-tolylene diisocyanate adduct, triphenylmethane triisocyanate, methylenebis (4-phenylmethane) triisocyanate, isophorone diisocyanate, and ketoxime thereof. Examples include block products and phenol block products.

  Examples of the dialdehyde crosslinking agent include glyoxal, malondialdehyde, succindialdehyde, glutardialdehyde, maleic dialdehyde, phthaldialdehyde and the like.

  Examples of the metal-based cross-linking agent include metal salts, metal oxides, metal hydroxides, and organic metal compounds. Examples of the metal salt, metal oxide, and metal hydroxide include divalent or higher valent metals such as magnesium, calcium, aluminum, iron, nickel, zirconium, titanium, silicon, boron, zinc, copper, vanadium, chromium, and tin. Mention may be made of valent metal salts, oxides and hydroxides.

  The organometallic compound is a compound having in the molecule at least one structure in which an organic group is directly bonded to a metal atom or an organic group is bonded via an oxygen atom or a nitrogen atom. The organic group means a monovalent or polyvalent group containing at least a carbon element, and can be, for example, an alkyl group, an alkoxy group, an acyl group or the like. Further, the bond does not mean only a covalent bond, but may be a coordinate bond such as a chelate compound.

  Suitable examples of the organometallic compound include organotitanium compounds, organozirconium compounds, organoaluminum compounds, and organosilicon compounds. The organometallic compounds may be used alone or in combination of two or more.

  Examples of the organic titanium compound include titanium orthoesters such as tetranormal butyl titanate, tetraisopropyl titanate, butyl titanate dimer, tetra (2-ethylhexyl) titanate, and tetramethyl titanate; titanium acetylacetonate, titanium tetraacetylacetonate. , Titanium chelates such as polytitanium acetylacetonate, titanium octylene glycolate, titanium lactate, titanium triethanolaminate and titanium ethyl acetoacetate; titanium acylates such as polyhydroxytitanium stearate.

  Examples of the organic zirconium compound include zirconium normal propionate, zirconium normal butyrate, zirconium tetraacetylacetonate, zirconium monoacetylacetonate, zirconium bisacetylacetonate, and zirconium acetylacetonate bisethylacetoacetate.

  Examples of the organic aluminum compound include aluminum acetylacetonate and aluminum organic acid chelate. Examples of the organic silicon compound include compounds in which the ligands exemplified above in the organic titanium compound and the organic zirconium compound are bonded to silicon.

  In addition to the above low molecular weight crosslinking agents, it is also possible to use high molecular weight crosslinking agents such as methylolated melamine resin and polyamide epoxy resin. Examples of commercially available polyamide-epoxy resins include "Sumiraz resin 650 (30)" and "Sumiraz resin 675" (both are trade names) sold by Taoka Chemical Co., Ltd.

  When a polyvinyl alcohol-based resin is used as the resin component forming the primer layer, a polyamide epoxy resin, a methylolated melamine resin, a dialdehyde-based crosslinking agent, a metal chelate compound-based crosslinking agent, or the like is preferably used as the crosslinking agent.

  The ratio of the resin component and the cross-linking agent in the primer layer forming coating liquid is within the range of about 0.1 to 100 parts by weight of the cross-linking agent with respect to 100 parts by weight of the resin component, and the type of resin component and the type of cross-linking agent It may be appropriately determined depending on the conditions, and it is particularly preferable to select from the range of about 0.1 to 50 parts by weight. In addition, the primer layer-forming coating liquid preferably has a solid content concentration of about 1 to 25% by weight.

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

  The method of applying the coating liquid for forming the primer layer on the base film 30 can be the same as the coating liquid for forming the polyvinyl alcohol resin layer. The primer layer is applied to the surface (one side or both sides of the base film 30) on which the coating liquid for forming the polyvinyl alcohol-based resin layer is applied. The drying temperature and the drying time of the coating layer made of the coating liquid for forming a primer layer are set according to the type of solvent contained 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 drying time is, for example, 30 seconds to 20 minutes.

  When the primer layer is provided, the order of coating on the base film 30 is not particularly limited. For example, when the polyvinyl alcohol-based resin layer 6 is formed on both sides of the base film 30, the base film 30 may be formed. The polyvinyl alcohol-based resin layer 6 may be formed on both surfaces of the base film 30 after forming the primer layer on both surfaces thereof, or after the primer layer and the polyvinyl alcohol-based resin layer 6 are sequentially formed on one surface of the base film 30. The primer layer and the polyvinyl alcohol-based resin layer 6 may be sequentially formed on the other surface of the base film 30.

(2) Stretching step S20
Referring to FIG. 6, in this step, the laminated film 100 including the base film 30 and the polyvinyl alcohol-based resin layer 6 is stretched to include the stretched base film 30 ′ and the polyvinyl alcohol-based resin layer 6 ′. This is a step of obtaining the stretched film 200. The stretching treatment is usually uniaxial stretching.

  The stretching ratio of the laminated film 100 can be appropriately selected according to 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. 8 times or less. If the stretching ratio is 5 times or less, the polyvinyl alcohol-based resin layer 6 is not sufficiently oriented, so that the polarization degree of the polarizer 5 may not be sufficiently high. On the other hand, when the stretching ratio exceeds 17 times, the film is likely to be broken during stretching, and the thickness of the stretched film 200 becomes unnecessarily thin, which may deteriorate the workability and handleability in the post-process.

  The stretching treatment is not limited to one-stage stretching, and may be performed in multiple stages. In this case, all of the multi-stage stretching treatments may be continuously performed before the dyeing step S30, or the stretching treatments of the second and subsequent steps may be performed simultaneously with the dyeing treatment and / or the crosslinking treatment in the dyeing step S30. Good. When the stretching treatment is performed in multiple stages, it is preferable to perform the stretching treatment so that the stretching ratio of all stages of the stretching treatment is more than 5 times.

  The stretching treatment may be longitudinal stretching for stretching in the longitudinal direction of the film (film transport direction), or lateral stretching or diagonal stretching for stretching in the film width direction. Examples of the longitudinal stretching method include inter-roll stretching in which rolls are used for stretching, compression stretching, stretching using a chuck (clip), and the like, and examples of the lateral stretching method include a tenter method. As the stretching treatment, either a wet stretching method or a dry stretching method can be adopted, but it is preferable to use the dry stretching method because the stretching temperature can be selected from a wide range.

  The stretching temperature is set to a temperature at which the polyvinyl alcohol-based resin layer 6 and the substrate film 30 as a whole have fluidity to such an extent that they can be stretched, and preferably the phase transition temperature (melting point or glass transition temperature) of the substrate film 30. It is 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 of the plurality of resin layers.

  When the stretching temperature is lower than −30 ° C. which is the phase transition temperature, it is difficult to achieve high-strength stretching of more than 5 times, or the fluidity of the base film 30 is too low, and the stretching process tends to be difficult. If the stretching temperature exceeds + 30 ° C., which is the phase transition temperature, the flowability of the base material film 30 is so large that stretching tends to be difficult. Since it is easier to achieve a high draw ratio of more than 5 times, the draw temperature is within the above range, and more preferably 120 ° C or higher. This is because when the stretching temperature is 120 ° C. or higher, there is no difficulty in the stretching process even if the stretching ratio is higher than 5 times.

  As a heating method of the laminated film 100 in the stretching treatment, 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 to adjust the temperature to a predetermined temperature) is used. There is a method of heating the roll itself; a heater heating method (a method of installing infrared heaters, halogen heaters, panel heaters and the like above and below the laminated film 100 and heating with radiant heat). In the inter-roll drawing method, the zone heating method is preferable from the viewpoint of the drawing temperature uniformity. In this case, the two pairs of nip rolls may be installed inside the temperature-controlled stretching zone or outside the stretching zone, but they are installed outside the stretching zone in order to prevent sticking between the laminated film 100 and the nip rolls. It is preferable to do.

  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 means the atmospheric temperature in the furnace in the case of heating in the furnace also in the heater heating method. In the case of the method of heating the roll itself, it means the surface temperature of the 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. When the stretching treatment method is roll-to-roll stretching, preheating may be performed at any timing before, during, or after passing through the upstream nip roll. When the stretching treatment method is hot roll stretching, preheating is preferably performed at a timing before passing through the hot roll. When the stretching method is stretching using a chuck, preheating is preferably performed at a timing before the distance between chucks is increased. 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.

  Further, a heat-setting treatment step may be provided after the stretching treatment in the stretching step S20. The heat setting process is a process of performing heat treatment at a crystallization temperature or higher while maintaining a tension state in a state where the end portion of the stretched film 200 is held by a clip. This heat setting treatment promotes crystallization of the polyvinyl alcohol-based resin layer 6 '. The temperature of the heat setting treatment is preferably in the range of stretching temperature of −0 ° C. to −80 ° C., and more preferably in the range of stretching temperature of −0 ° C. to −50 ° C.

(3) Dyeing step S30
With reference to FIG. 7, this step is a step in which the polyvinyl alcohol resin layer 6 ′ of the stretched film 200 is dyed with a dichroic dye, and this is adsorbed and oriented to form the polarizer 5. Through this step, 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.

  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 prepared by dissolving the above dichroic dye in a solvent can be used. Water is generally used as the solvent for the dyeing solution, 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, and further preferably 0.025 to 5% by weight. preferable.

  When iodine is used as the dichroic dye, it is preferable to further add iodide to the iodine-containing dyeing solution, because the dyeing efficiency can be further 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, titanium iodide and the like. Is mentioned. The iodide concentration 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 weight ratio of iodine to potassium iodide is preferably in the range of 1: 5 to 1: 100, more preferably in the range of 1: 6 to 1:80. It is more preferably in the range of 1: 7 to 1:70.

  The immersion time of the stretched film 200 in the dyeing solution is usually in the range of 15 seconds to 15 minutes, preferably 30 seconds to 3 minutes. The temperature of the dyeing solution is preferably in the range of 10 to 60 ° C, more preferably 20 to 40 ° C.

  Although the dyeing step S30 can be performed before the stretching step S20 or these steps can be performed simultaneously, the dichroic dye to be adsorbed on the polyvinyl alcohol resin layer can be favorably aligned. As described above, it is preferable to perform the dyeing step S30 after subjecting the laminated film 100 to at least some stretching treatment. That is, the stretched film 200 obtained by subjecting the stretched film 200 to the target draw ratio in the draw process S20 can be subjected to the dyeing process S30, and after the draw process is performed at a draw ratio lower than the target in the draw process S20. In the dyeing step S30, the stretching process can be performed until the total stretching ratio reaches the target ratio. Examples of the latter embodiment include 1) a mode in which the stretching process is performed at a draw ratio lower than the target in the drawing process S20, and then the stretching process is performed so that the total draw ratio becomes the target draw ratio during the dyeing process in the dyeing process S30. As will be described later, in the case of performing the crosslinking treatment after the dyeing treatment, 2) after performing the stretching treatment at a draw ratio lower than the target in the stretching step S20, the total draw ratio is the target during the dyeing treatment in the dyeing step S30. Examples include a mode in which the stretching treatment is carried out to such an extent that the stretching ratio is not reached, and then the stretching treatment is carried out during the crosslinking treatment so that the final total stretching magnification becomes the target stretching ratio.

  The dyeing process S30 may include a crosslinking treatment process performed subsequent to the dyeing treatment. The crosslinking treatment can be carried out by immersing the dyed film in a solution containing a crosslinking agent (crosslinking solution). As the cross-linking agent, a conventionally known substance can be used, and examples thereof include boric acid, a boron compound such as borax, glyoxal, and glutaraldehyde. The crosslinking agents may be used alone or in combination of two or more.

  The cross-linking solution can be specifically a solution in which a cross-linking agent is dissolved in a solvent. As the solvent, for example, water can be used, but an organic solvent compatible with water may further be included. The concentration of the crosslinking agent in the crosslinking solution is preferably in the range of 1 to 20% by weight, more preferably 6 to 15% by weight.

  The crosslinking solution can include iodide. By adding iodide, the in-plane polarization performance of the polarizer 5 can be made more uniform. 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, titanium iodide and the like. Is mentioned. The iodide concentration in the crosslinking solution is preferably 0.05 to 15% by weight, more preferably 0.5 to 8% by weight.

  The immersion time of the dyed film in the crosslinking solution is usually 15 seconds to 20 minutes, preferably 30 seconds to 15 minutes. Further, the temperature of the crosslinking solution is preferably in the range of 10 to 90 ° C.

  The cross-linking treatment can be carried out simultaneously with the dyeing treatment by adding a cross-linking agent to the dyeing solution. Further, the stretching treatment may be performed during the crosslinking treatment. The specific mode of carrying out the stretching treatment during the crosslinking treatment is as described above. Further, the treatment of immersing in the cross-linking solution may be performed twice or more using two or more cross-linking solutions having different compositions.

  After the dyeing step S30, it is preferable to perform the washing step and the drying step before the first bonding step S40 described below. The washing step usually includes a water washing step. The water washing treatment can be carried out by immersing the dyed or crosslinked film in pure water such as ion-exchanged water or distilled water. The water washing temperature is usually in the range of 3 to 50 ° C, preferably 4 to 20 ° C. The immersion time in water is usually 2 to 300 seconds, preferably 3 to 240 seconds.

  The washing step may be a combination of a water washing step and a washing step with an iodide solution. In addition to water, the cleaning liquid used in the water cleaning step and / or the cleaning treatment with the iodide solution may appropriately contain liquid alcohol such as methanol, ethanol, isopropyl alcohol, butanol, and propanol.

  As the drying step performed after the washing step, any appropriate method such as natural drying, blast drying, and heat drying can be adopted. For example, in the case of heat drying, the drying temperature is usually 20 to 95 ° C., and the drying time is usually about 1 to 15 minutes.

(4) First bonding step S40
With reference to FIG. 8, in this step, on the polarizer 5 of the polarizing laminate film 300, that is, on the surface of the polarizer 5 opposite to the base film 30 ′ side, a first adhesive layer is formed. It is a step of bonding one of the protective film 10 and the second protective film 20 to obtain the bonded film 400. FIG. 8 shows an example in which the first protective film 10 is attached via the first adhesive layer 15, but the second protective film 20 is attached via the second adhesive layer 25. Good. When the polarizing laminate film 300 has the polarizers 5 on both sides of the base film 30 ′, the protective films are usually attached to the polarizers 5 on both sides, respectively. In this case, these protective films may be the same kind of protective film or different kinds of protective films.

  The protective film (first protective film 10 or second protective film 20) is attached to the polarizer 5 via the adhesive layer (first adhesive layer 15 or second adhesive layer 25).

  For laminating the protective film via the adhesive layer, for example, an adhesive is applied to the laminating surface of the protective film and / or the polarizer 5 by using a known means, and the adhesive layer is applied. A method in which the protective film and the polarizer 5 are superposed on each other and then bonded using a bonding roll or the like can be used.

  In order to reduce the thickness of the adhesive layer like the first adhesive layer 15, a method of applying the adhesive using a small-diameter gravure or the like is suitable. The thickness of the adhesive layer can be reduced by a method of increasing the rotation speed of the gravure, or a method of increasing the number of lines of the gravure mesh. In particular, in order to make the thickness of the adhesive layer 1 μm or less, it is preferable to use a gravure in which a mesh is engraved by laser engraving, and it is particularly preferable to use a honeycomb-shaped gravure roll. For example, a honeycomb shape having more than 400 rows of honeycombs per inch is preferably used.

  When a photo-curable adhesive is used as the adhesive, after performing the above-mentioned bonding, a curing step of curing the photo-curable adhesive by irradiating with active energy rays is performed. The light source of the active energy ray is not particularly limited, but an active energy ray (ultraviolet ray) having an emission distribution at a wavelength of 400 nm or less is preferable, and specifically, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a chemical lamp, A black light lamp, a microwave excited mercury lamp, a metal halide lamp and the like are preferably used.

The light irradiation intensity on the photocurable adhesive is appropriately determined depending on the composition of the photocurable adhesive, and the irradiation intensity in the wavelength region effective for activation of the polymerization initiator is 0.1 to 6000 mW / cm ² . It is preferable to set so that When the irradiation intensity is 0.1 mW / cm ² or more, the reaction time does not become too long, and when it is 6000 mW / cm ² or less, the light radiated from the light source and the light generated by the heat generated during the curing of the photocurable adhesive are used. There is little risk of yellowing of the curable adhesive and deterioration of the polarizer 5.

The light irradiation time to the photocurable adhesive is also appropriately determined depending on the composition of the photocurable adhesive, but the integrated light amount represented as the product of the irradiation intensity and the irradiation time is 10 to 10000 mJ / cm ² . It is preferable to set so that When the integrated light amount is 10 mJ / cm ² or more, a sufficient amount of active species derived from the polymerization initiator can be generated to allow the curing reaction to proceed more reliably, and when it is 10000 mJ / cm ² or less, the irradiation time is long. Good productivity can be maintained.

  When a water-based adhesive is used, usually, after the bonding, a drying step of drying is performed to remove water contained in the water-based adhesive. Drying can be performed by, for example, introducing the laminated film into a drying oven. The drying temperature (temperature of the drying oven) is preferably 30 to 90 ° C. If it is lower than 30 ° C, the protective film tends to be easily peeled off from the polarizer 5. If the drying temperature exceeds 90 ° C., the polarization performance of the polarizer 5 may be deteriorated by heat. The drying time can be about 10 to 1000 seconds.

  After the drying step, a curing step of curing at room temperature or a slightly higher temperature, for example, a temperature of about 20 to 45 ° C. for about 12 to 600 hours may be provided. The curing temperature is generally set lower than the drying temperature.

  When laminating the protective film on the polarizer 5, a plasma treatment, a corona treatment, an ultraviolet irradiation treatment, a flame (flame) treatment is performed on the surface of the protective film on the side of the polarizer 5 in order to improve the adhesiveness with the polarizer 5. ) Treatment, surface treatment such as saponification treatment (easy adhesion treatment), and among them, plasma treatment, corona treatment or saponification treatment is preferable. For example, when the protective film is made of a cyclic polyolefin resin, plasma treatment or corona treatment is usually performed. When it is made of a cellulose ester resin, a saponification treatment is usually performed. Examples of the saponification treatment include a method of immersing in an alkaline aqueous solution such as sodium hydroxide or potassium hydroxide.

(5) Peeling step S50
With reference to FIG. 9, this step is a step of peeling and removing the base film 30 ′ from the bonding film 400 obtained by bonding the protective film. Through this step, a polarizing plate with a single-sided protective film 500 in which a protective film (the first protective film 10 in the example of FIG. 9) is laminated on one side of the polarizer 5 is obtained. When the polarizing laminate film 300 has the polarizers 5 on both sides of the base film 30 ′ and the protective films are attached to both of these polarizers 5, the peeling step S50 causes one polarizing laminate film to be formed. Two polarizing plates 500 with a single-sided protective film are obtained from the film 300.

  The method of peeling and removing the base film 30 'is not particularly limited, and the base film 30' can be peeled by the same method as the peeling step of the separator (peeling film) that is performed in a normal polarizing plate with an adhesive. The base material film 30 ′ may be immediately peeled off as it is after the first bonding step S40, or may be rolled up once after the first bonding step S40 and peeled off while being unwound in the subsequent steps. May be.

(6) Second bonding step S60
This step is performed on the polarizer 5 of the single-sided protective film-attached polarizing plate 500, that is, on the surface opposite to the protective film laminated in the first laminating step S40 via the adhesive layer. This is a step of bonding the other protective film of the protective films 10 and 20 to obtain the polarizing plate 1 according to the present invention with a double-sided protective film as shown in FIG. Regarding the method of laminating the protective film and the surface treatment (easy adhesion treatment) in laminating, the contents described in the first laminating step S40 are cited.

<Display device>
The display device of the present invention includes, as shown in FIG. 2, a display cell 50 and the above-described polarizing plate 1 according to the present invention which is disposed on at least one surface thereof. The polarizing plate 1 can be arranged and bonded on the display cell 50 by using the adhesive layer 60 provided on the outer surface of the second protective film 20 arranged on the display cell 50 side. In such a display device, the first protective film 10 of the polarizing plate 1 forms the outer surface (typically the outermost surface) of the display device. According to the present invention, unevenness on the surface of the first protective film 10 is effective. Therefore, the appearance of the display device is excellent. Also, light leakage in the black display state can be effectively suppressed.

  A typical example of the display device is a liquid crystal display device in which the display cell 50 is a liquid crystal cell, but it may be another display device such as an organic EL device. In the display device, the polarizing plate may be arranged on at least one surface of the display cell 50, but may be arranged on both surfaces.

  When the display device is a liquid crystal display device, polarizing plates are usually arranged on both surfaces of the liquid crystal cell. In this case, the polarizing plates on both sides may be the polarizing plate according to the present invention, or only one polarizing plate may be the polarizing plate according to the present invention. In the latter, the polarizing plate according to the present invention may be a front side (viewing side) polarizing plate or a rear side (backlight side) polarizing plate based on the liquid crystal cell. A conventionally known type can be used as the liquid crystal cell.

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

<Example 1>
(1) Primer layer forming step Polyvinyl alcohol powder ("Z-200" manufactured by Nippon Synthetic Chemical Industry Co., Ltd., average degree of polymerization 1100, degree of saponification 99.5 mol%) was dissolved in hot water at 95 ° C, A polyvinyl alcohol aqueous solution having a concentration of 3% by weight was prepared. A cross-linking agent (“SUMIREZ RESIN 650” manufactured by Taoka Chemical Industry Co., Ltd.) is mixed with the obtained aqueous solution at a ratio of 5 parts by weight with respect to 6 parts by weight of polyvinyl alcohol powder to prepare a coating liquid for forming a primer layer. Got

  Next, an unstretched polypropylene (PP) film having a thickness of 90 μm (melting point: 163 ° C.) was prepared as a substrate film, and one side thereof was subjected to corona treatment, and then the corona-treated surface was treated with a small-diameter gravure coater as described above. The primer layer forming coating liquid was applied and dried at 80 ° C. for 10 minutes to form a primer layer having a thickness of 0.2 μm.

(2) Production of laminated film (resin layer forming step)
Polyvinyl alcohol powder ("PVA124" manufactured by Kuraray Co., Ltd., average degree of polymerization 2400, degree of saponification 98.0 to 99.0 mol%) was dissolved in hot water at 95 ° C, and a polyvinyl alcohol aqueous solution having a concentration of 8% by weight was obtained. Was prepared, and this was used as a coating liquid for forming a polyvinyl alcohol resin layer.

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

(3) Preparation of stretched film (stretching step)
The laminated film produced 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 resin layer after stretching was 6.1 μm.

(4) Production of polarizing laminated film (dyeing step)
About the stretched film produced in the above (3) in a dyeing aqueous solution containing iodine and potassium iodide at 30 ° C. (0.6 parts by weight of iodine and 10 parts by weight of potassium iodide are included per 100 parts by weight of water). After immersing for 180 seconds to dye the polyvinyl alcohol resin layer, the excess dyeing aqueous solution was washed off with pure water at 10 ° C.

  Then, it is immersed in a first cross-linking aqueous solution containing boric acid at 78 ° C. (containing 9.5 parts by weight of boric acid per 100 parts by weight of water) for 120 seconds, and then at 70 ° C. containing boric acid and potassium iodide. 2 Cross-linking treatment was carried out by immersing in a cross-linking aqueous solution (containing 9.5 parts by weight of boric acid and 4 parts by weight of potassium iodide per 100 parts by weight of water) for 60 seconds. Then, it was washed with pure water at 10 ° C. for 10 seconds and finally dried at 40 ° C. for 300 seconds to obtain a polarizing laminated film composed of a base film / primer layer / polarizer.

(5) Production of polarizing plate (first bonding step, peeling step, second bonding step)
A cyclic polyolefin resin film (“ZF14” manufactured by Nippon Zeon Co., Ltd., thickness 23 μm) was prepared as a first protective film to be arranged on the outside (viewing side) when the polarizing plate was arranged on the display cell. .. After the corona treatment is applied to the bonding surface of the first protective film, a photocurable adhesive (“KR-70T” manufactured by ADEKA Co., Ltd.) is applied to the corona-treated surface using a small diameter gravure coater. Then, the first protective film was placed on the polarizer of the polarizing laminated film produced in (4) above via the coating layer of the adhesive, and then the first protective film was laminated using a laminating roll. Then, the adhesive is cured by ultraviolet irradiation to form a first adhesive layer, and a laminated film having a layer structure of first protective film / first adhesive layer / polarizer / primer layer / base film is obtained. (First bonding step). The thickness T ₁ of the first adhesive layer was 0.2 μm.

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

A cyclic polyolefin resin film (“ZF14” manufactured by Nippon Zeon Co., Ltd., thickness 23 μm) was prepared as a second protective film arranged on the display cell side when the polarizing plate was arranged on the display cell. After performing the corona treatment on the bonding surface of the second protective film, a photocurable adhesive (“KR-70T” manufactured by ADEKA Co., Ltd.) is applied to the corona-treated surface using a small-diameter gravure coater. Then, after arranging the second protective film on the surface opposite to the first protective film of the obtained polarizing plate with a single-sided protective film through the coating layer of the adhesive, it is laminated using a laminating roll. It matched. Then, the adhesive is cured by irradiation with ultraviolet rays to form a second adhesive layer, and the layer structure of the first protective film / first adhesive layer / polarizer / primer layer / second adhesive layer / second protective film is formed. A polarizing plate consisting of The thickness T ₂ of the second adhesive layer was 1.3 μm.

The thicknesses T ₁ and T ₂ of the first and second adhesive layers were measured as follows. That is, the "thickness of the first or second protective film" before the photo-curable adhesive coating and the "first or second protective film after the photo-curable adhesive coating (before bonding with the polarizer)". And the total thickness of the coated adhesive layer "was measured using a non-contact optical interference type film thickness meter (" F-20 "manufactured by Filmetrics Co., Ltd.), and the difference between them was measured. 2 The thickness of the adhesive layer was T ₁ and T ₂ . In addition, the thickness of the adhesive layer before bonding and curing with the polarizer thus obtained is maintained almost as it is after bonding and curing with the polarizer, and adhesion after curing in the obtained polarizing plate. It is confirmed that the thickness is substantially the same as the thickness of the adhesive layer by cutting out a cross section of the obtained polarizing plate, observing the thickness of the adhesive layer in the cross section with an SEM (scanning electron microscope), and actually measuring the thickness. ing.

<Examples 2-5, Comparative Examples 1-2>
A polarizing plate was produced in the same manner as in Example 1 except that the thicknesses T ₁ and T ₂ of the first and second adhesive layers were set as shown in Table 1.

[Evaluation of distortion of reflected image and light leakage]
(1) Evaluation of Distortion of Reflected Image The polarizing plates obtained in Examples and Comparative Examples were cut into a 4 ″ size, and the cut pieces were attached to one surface of the liquid crystal cell through the adhesive layer on the second protective film side for evaluation. A fluorescent lamp was imaged by specular reflection on the surface of the first protective film of the evaluation sample, and the distortion of the reflected image was visually evaluated according to the following evaluation criteria.

A: There is no distortion, and the reflected image is extremely clear,
B: Almost no distortion, the reflected image is clear,
C: It is slightly distorted, but a relatively clear reflection image is obtained,
D: Large distortion.

(2) Evaluation of Light Leakage In the same manner, the other surface of the liquid crystal cell in the evaluation sample used in the above (1) was laminated with a polarizing plate of 4 "size. The polarizing plate of No. 1 was laminated so as to form crossed Nicols (so that the absorption axes of the polarizers were orthogonal to each other.) In the obtained sample for evaluation, light was irradiated from the first protective film surface side of one polarizing plate. Then, the presence or absence (light leakage) of light transmitted to the first protective film side of the other polarizing plate in the black display state was visually evaluated according to the following evaluation criteria, and the results are shown in Table 1.

A: No light leakage,
B: Light leakage is recognized (there are bright spots).

  DESCRIPTION OF SYMBOLS 1 polarizing plate, 5 polarizer, 10 1st protective film, 15 1st adhesive layer, 20 2nd protective film, 25 2nd adhesive layer, 6 polyvinyl alcohol type resin layer, 6'stretched polyvinyl alcohol type resin Layer, 30 Base film, 30 'Stretched base film, 50 Display cell, 60 Adhesive layer, 100 Laminated film, 200 Stretched film, 300 Polarizable laminated film, 400 Laminated film, 500 With one-sided protective film Polarizer.

Claims (7)

A polarizer,
A first protective film laminated on one surface of the polarizer via a first adhesive layer having a thickness of less than 2.0 μm;
A second protective film laminated on the other surface of the polarizer via a second adhesive layer having a thickness of 2.0 μm or less;
A polarizing plate including
The first and second protective films are transparent resin films,
The second protective film is a protective film arranged on the display cell side with respect to the first protective film when the polarizing plate is arranged on the display cell,
The thickness of the first and second protective films is 23 μm or less,
A polarizing plate in which the thickness of the first adhesive layer is smaller than the thickness of the second adhesive layer.   The polarizing plate according to claim 1, wherein the first and second adhesive layers are cured product layers of a photocurable adhesive.   The polarizing plate according to claim 1, wherein the polarizer has a thickness of 10 μm or less.   The polarizing plate according to claim 1, further comprising a pressure-sensitive adhesive layer that is laminated on the outer surface of the second protective film and is attached to the display cell.   A display device comprising a display cell and the polarizing plate according to claim 1 disposed on at least one surface thereof.   A display device comprising a display cell and the polarizing plate according to claim 4 disposed on at least one surface thereof, wherein the polarizing plate is bonded to the display cell via the pressure-sensitive adhesive layer. A method of using the polarizing plate according to any one of claims 1 to 4,
A method of using a polarizing plate, wherein, when arranging the polarizing plate on a display cell, the second protective film is disposed on the display cell side with respect to the first protective film.

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