JP6653729B2 - Polarizing plate and display device - Google Patents

Description

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

  Polarizing plates are widely used in display devices such as liquid crystal display devices, in particular, in recent years, various mobile devices such as smartphones and slate PCs. In general, a polarizing plate has a configuration in which a protective film is attached to one or both surfaces of a polarizer using an adhesive, but with the development of mobile devices, the thickness of the polarizer and the protective film constituting the polarizing plate has been reduced. There is a growing need.

  As an adhesive used for bonding the polarizer and the protective film, a photocurable 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 these. A polarizing plate in which protective films are bonded to both surfaces of a polarizer using both of them is described.

JP 2013-228726 A JP 2013-210513 A JP 2012-144690 A JP-A-2012-203211 JP 2009-109994 A JP 2009-139585 A JP 2009-134121 A JP 2010/091603 A JP 2010/091602 A JP 2008-170717 A

  When the thickness of the polarizer and the protective film constituting the polarizing plate is reduced, the surface of the protective film bonded to the polarizer via the adhesive layer is distorted in a minute area, and the surface has irregularities such as wavy. It has been clarified by the present inventor's investigation that this occurs. Although the surface irregularities do not directly affect the optical characteristics of the polarizing plate, the protective film is arranged on the outside (for example, the outermost surface) when such a polarizing plate is bonded to a display cell. In such cases, the surface unevenness remains even after lamination, and the reflected image from the protective film surface is distorted and glossiness cannot be obtained. And the surface irregularities are not conspicuous locally) or lack in luxury.

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

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 comprising:
The second protective film is a protective film that is disposed closer to the display cell than the first protective film when the polarizing plate is disposed on the display cell,
A polarizing plate wherein 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 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 a difference between a thickness of the second adhesive layer and a 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 laminated on an outer surface of the second protective film and bonded to the display cell.

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

  According to the present invention, it is possible to provide a polarizing plate in which the occurrence of the above-mentioned unevenness on the surface of the first protective film and the distortion of the reflected image due to the occurrence are suppressed. When such a polarizing plate is disposed on a display cell such that the first protective film is on the outside (the second protective film is on the display cell side), the distortion of the reflected image from the surface of the first protective film is reduced. Is suppressed, so that the appearance is excellent.

FIG. 2 is a schematic sectional view illustrating an example of a layer configuration of a polarizing plate 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 arranged on a display cell. FIG. 2 is a schematic cross-sectional view illustrating an example of a layer configuration of a liquid crystal display device including a display cell (liquid crystal cell) and polarizing plates (polarizing plates with a double-sided protective film) disposed on the front side and the rear side. 4 is a flowchart illustrating a preferred example of a method for manufacturing a polarizing plate according to the present invention. It is a schematic sectional drawing which shows an example of the layer structure of the laminated film obtained by a resin layer formation process. It is a schematic sectional drawing which shows an example of the layer structure of the stretched film obtained by a stretching process. It is a schematic sectional drawing which shows an example of the layer structure of the polarizing laminated film obtained by a dyeing process. It is a schematic sectional drawing which shows an example of the layer structure of the bonding film obtained by a 1st bonding process. It is a schematic sectional drawing which shows an example of the layer constitution of the polarizing plate with a single-sided protective film obtained by a peeling process.

<Polarizing plate>
FIG. 1 is a schematic cross-sectional view illustrating an example of the layer configuration of the polarizing plate 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 arranged on a 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. And a second protective film 20 laminated on the surface with a second adhesive layer 25 interposed therebetween.

  As shown in FIG. 2, the first protective film 10 is a protective film that is disposed outside the second protective film 20 when the polarizing plate 1 is disposed on the display cell 50. When disposed on the display cell 50, the protective film typically forms the outermost surface. The second protective film 20 is a protective film disposed closer to the display cell 50 than the first protective film 10 is. The polarizing plate 1 can be arranged and pasted on the display cell 50 using the pressure-sensitive 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, when the polarizing plate 1 is arranged on the display cell 50, the first protective film 10 and the polarizer 5, which form the outer surface (typically, the outermost surface), are formed. The thickness T ₁ of the first adhesive layer 15 interposed therebetween is changed to the thickness T _{2 of} the second adhesive layer 25 interposed between the second protective film 20 disposed 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, the shrinkage force when the adhesive forming the first adhesive layer 15 is cured or dried can be reduced. Even when the thickness of the first protective film 10 and the polarizer 5 is reduced, it is possible to prevent the first protective film 10 and the polarizer 5 from losing the above-described shrinkage force of the adhesive and generating irregularities 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 is particularly deteriorated due to the occurrence of surface irregularities. In such a case, according to the present invention, the occurrence of the surface irregularities of the first protective film 10 is improved. And to provide a polarizing plate that can suppress distortion of a reflected image associated therewith, provides a clear reflected image, has excellent glossiness on the surface of the first protective film 10, and has surface uniformity and high-grade appearance. Can be.

The thickness T ₁ of the first adhesive layer 15 is specifically less than 2.0 μm, and 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 set to 0.7 μm or less in order to sufficiently suppress the shrinkage force of the adhesive and suppress the occurrence of surface irregularities. More preferably, it is still more preferably 0.4 μm or less.

Further, 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 [mu] m, there is a possibility that sufficient adhesive strength is obtained.

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

  That is, when the thickness of the adhesive layer is too small, a problem that minute bubbles are mixed in the adhesive layer at the time of bonding the protective film and the polarizer tends to occur. Although such bubbles cannot be seen 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 scattering occurs due to dense bubbles and black display is caused. Light leaks (bubbles become bright spots), causing display problems.

Light leakage due to such bubbles easily becomes a problem in the second adhesive layer 25 interposed between the second protective film 20 and the polarizer 5 disposed on the display cell 50 side, and is disposed outside. The first adhesive layer 15 interposed between the first protective film 10 and the polarizer 5 hardly causes a problem. FIG. 3 shows a liquid crystal display device including a display cell (liquid crystal cell) 50 and a polarizing plate 1 disposed on the front side (viewing side) and the rear side (backlight side). This is because the two adhesive layers 25 are arranged in crossed Nicols formed between the front-side polarizer 5 and the rear-side polarizer 5. When light scattering occurs in crossed Nicols, black display collapses and light leakage occurs. Therefore, the thickness T ₂ of the second adhesive layer 25 that does not easily affect the appearance when the polarizing plate 1 is disposed on the display cell 50 may be larger than the thickness T ₁ of the first adhesive layer 15. It is important that light leakage in a black display state can be suppressed.

In contrast, the first adhesive layer 15, because it is located outside of crossed Nicols, the thickness T ₁ is relatively small, thereby less likely to occur even if caused bubbles of light leakage problem.

The thickness T ₂ of the second adhesive layer 25 is specifically 2.0 μm or less, and preferably 1.8 μm or less from the viewpoint of reducing the thickness of the polarizing plate 1. When the thickness T ₂ exceeds 2.0 μm, it is disadvantageous for making the polarizing plate 1 thinner. The lower limit of the thickness T ₂ are not particularly limited thickness T ₁ greater than the best of the first adhesive layer 15, from the viewpoint of adhesiveness, the thickness T ₂ are, is generally 0.01μm or more, preferably 0. It is not less than 05 μm.

In order to effectively suppress irregularities 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 thickness of the first adhesive layer 15 are reduced. The difference from the thickness T ₁ is preferably at least 0.3 μm, more preferably at least 0.5 μm, and even more preferably at least 0.9 μm.

(2) Adhesive for Forming Adhesive Layer As the adhesive for forming the first and second adhesive layers 15 and 25, a photocurable adhesive or a water-based adhesive can be used. As described above, the cause of unevenness on the surface of the first protective film 10 includes a contraction 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) when using a photocurable adhesive for bonding by bonding is generally relatively long due to drying of the solvent (water) by heating and subsequent curing as required. Therefore, the present invention can be suitably applied particularly when the first adhesive layer 15 is formed from a photocurable adhesive, and the obtained effect of suppressing unevenness is high.

  The adhesive forming the first adhesive layer 15 and the adhesive forming the second adhesive layer 25 may be of the same type or different types, but for the reasons described above, the first adhesive layer The adhesive forming 15 is preferably a photo-curable adhesive. The adhesive forming the second adhesive layer 25 is also preferably a photocurable adhesive. The photo-curable adhesive can be used 1) because it can be prepared as a non-solvent type adhesive, so that a drying step can be omitted. 2) It can be used for bonding a protective film having low moisture permeability. There is also an advantage that there are many types of protective films that can be bonded as compared with water-based adhesives.

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

  The photocurable adhesive refers to an adhesive that is cured by irradiating active energy rays such as ultraviolet rays, for example, those containing a polymerizable compound and a photopolymerization initiator, those containing a photoreactive resin, binders Examples thereof include those containing a resin and a photoreactive cross-linking 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 cationic photopolymerization 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 an aqueous solution of a polyvinyl alcohol-based resin, and a water-based two-pack urethane-based emulsion adhesive. Among them, a water-based adhesive composed of an aqueous solution of a polyvinyl alcohol-based resin is preferably used.

  Examples of the polyvinyl alcohol resin include a vinyl alcohol homopolymer obtained by saponifying polyvinyl acetate, which is a homopolymer of vinyl acetate, and a copolymer of vinyl acetate with another monomer copolymerizable therewith. A polyvinyl alcohol-based copolymer obtained by saponifying a polymer, a modified polyvinyl alcohol-based polymer in which a hydroxyl group thereof is partially modified, or the like can be used. The water-based adhesive can include additives such as a polyhydric aldehyde, a water-soluble epoxy compound, a melamine-based compound, a zirconia compound, and a zinc compound.

(3) Polarizer The polarizer 5 may be one obtained by adsorbing and orienting a dichroic dye on a uniaxially stretched polyvinyl alcohol-based resin layer. The thickness of the polarizer 5 is preferably 10 μm or less, and more preferably 7 μm or less. Making the thickness of the polarizer 5 10 μm or less is advantageous for reducing the thickness of the polarizing plate 1, but according to the present invention, even if such a thin polarizer 5 is used, the first protective film is used. 10 Irregularities on the surface can be effectively suppressed.

  As the polyvinyl alcohol-based resin constituting the polyvinyl alcohol-based resin layer, a saponified polyvinyl acetate-based resin can be used. Examples of the polyvinyl acetate resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and 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.

  A film formed of such a polyvinyl alcohol-based resin constitutes the polarizer 5. The method of forming the polyvinyl alcohol-based resin is not particularly limited, and the film can be formed by a known method. However, since it is easy to obtain the polarizer 5 having a thickness of 10 μm or less, the polyvinyl alcohol-based resin It is preferable to apply the solution on a base film 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 17 times or less.

  The degree of saponification of the polyvinyl alcohol-based resin can 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 94.0. ９９99.0% by mole. When the saponification degree is less than 80.0 mol%, the water resistance and the moist heat resistance of the obtained polarizing plate 1 decrease. When a polyvinyl alcohol-based resin having a degree of saponification of more than 99.5 mol% is used, the dyeing speed is reduced, the productivity is reduced, and the polarizer 5 having sufficient polarization performance may not be obtained.

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

  The polyvinyl alcohol-based resin may be a partially modified polyvinyl alcohol. For example, those obtained by modifying a polyvinyl alcohol-based resin with an olefin such as ethylene or propylene; an unsaturated carboxylic acid such as acrylic acid, methacrylic acid, or crotonic acid; an alkyl ester of an unsaturated carboxylic acid, acrylamide, or the like. The percentage of modification is preferably less than 30 mol%, more preferably less than 10%. If the modification exceeds 30 mol%, the dichroic dye becomes difficult to adsorb, and the polarizer 5 having sufficient polarization performance cannot be obtained.

  The average degree of polymerization of the polyvinyl alcohol-based resin is preferably from 100 to 10,000, more preferably from 1500 to 8,000, and still more preferably from 2,000 to 5,000. 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 suitably used in the present invention are trade names such as "PVA124" manufactured by Kuraray Co., Ltd. (degree of saponification: 98.0 to 99.0 mol%), " "PVA117" (degree of saponification: 98.0 to 99.0 mol%), "PVA624" (degree of saponification: 95.0 to 96.0 mol%), "PVA617" (degree of saponification: 94.5 to 95) "AH-26" manufactured by Nippon Synthetic Chemical Industry Co., Ltd. (degree of saponification: 97.0 to 98.8 mol%), "AH-22" (degree of saponification: 97.5 to 57.5%). 98.5 mol%), "NH-18" (degree of saponification: 98.0 to 99.0 mol%), "N-300" (degree of saponification: 98.0 to 99.0 mol%); Japan "JC-33" (degree of saponification: 99.0 mol% or more) and "JM-33" (ken Degree: 93.5-95.5 mol%), "JM-26" (degree of saponification: 95.5-97.5 mol%), "JP-45" (degree of saponification: 86.5-89. 5 mol%), "JF-17" (degree of saponification: 98.0 to 99.0 mol%), "JF-17L" (degree of saponification: 98.0 to 99.0 mol%), "JF- 20 "(degree of saponification: 98.0 to 99.0 mol%).

  The dichroic dye contained (adsorption orientation) in the polarizer 5 can 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, Supra Blue G, Supra Blue GL, Supra Orange GL, Direct Including Sky Blue, Direct First Orange S, and First Black. One type of dichroic dye may be used alone, or two or more types may be used in combination.

(4) First and Second Protective Films The first and second protective films 10 and 20 are each made of a thermoplastic resin, for example, a chain polyolefin resin (eg, a polypropylene resin), and a cyclic polyolefin resin (eg, a norbornene resin). ); Cellulose ester resins such as cellulose triacetate and cellulose diacetate; polyester resins such as polyethylene terephthalate, polyethylene naphthalate and polybutylene terephthalate; polycarbonate resins; (meth) acrylic resins; Alternatively, it may be a transparent resin film composed of a mixture, a copolymer or the like thereof. The first protective film 10 and the second protective film 20 may be the same type of protective film or different types of protective films.

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

  Various products are commercially available as cyclic polyolefin-based resins. Examples of commercially available cyclic polyolefin-based resins are trade names such as “Topas” (manufactured by Topas Advanced Polymers GmbH, available from Polyplastics Co., Ltd.), “ARTON” (manufactured by JSR Corporation), "ZEONOR" (manufactured by ZEON CORPORATION), "ZEONEX" (manufactured by ZEON Corporation), and "APEL" (manufactured by Mitsui Chemicals, Inc.) are included.

  All are trade names such as "ESCINA" (manufactured by Sekisui Chemical Co., Ltd.), "SCA40" (manufactured by Sekisui Chemical Co., Ltd.), and "ZEONOR FILM" (manufactured by Nippon Zeon Co., Ltd.). A commercially available product of the formed cyclic polyolefin resin film may be used as the protective film.

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

  The first protective film 10 and / or the second protective film 20 may be a protective film having an optical function such as a retardation film and a brightness enhancement film. For example, a retardation film provided with an arbitrary retardation value by stretching (eg, 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. It can be.

  On the surface of the first protective film 10 and / or the second protective film 20 opposite to the polarizer 5, a surface treatment such as a hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer, and an antifouling layer is performed. 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 thicknesses of the first and second protective films 10 and 20 are preferably thin from the viewpoint of reducing the thickness of the polarizing plate 1, but if too thin, the strength is reduced and workability is poor. 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 still more preferably 5 to 50 μm. According to the present invention, unevenness 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) Pressure-Sensitive Adhesive Layer As shown in FIG. 2, the polarizing plate 1 is attached to another member (for example, a display device) on the outer surface (the surface opposite to the polarizer 5) of the second protective film 20 in the polarizing plate 1. An adhesive layer 60 for pasting to the display cell 50) may be laminated. The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer 60 is usually made of a (meth) acrylic resin, a styrene resin, a silicone resin, or the like as a base polymer, and a crosslinking agent such as an isocyanate compound, an epoxy compound, or an aziridine compound is added thereto. Made of a pressure-sensitive adhesive composition. The pressure-sensitive adhesive layer may further contain light-scattering properties by containing fine particles.

  The thickness of the pressure-sensitive adhesive layer 60 can be 1 to 40 μm, but it is preferable that the pressure-sensitive adhesive layer 60 be formed as thin as possible without impairing the workability and durability characteristics, and specifically, it is preferable that the thickness be 3 to 25 μm. A thickness of 3 to 25 μm is preferable in that it has good workability and suppresses a dimensional change of the polarizer 5. When the pressure-sensitive adhesive layer 60 is less than 1 μm, the adhesiveness is reduced, and when the pressure-sensitive adhesive layer 60 is more than 40 μm, problems such as the sticking out of the pressure-sensitive adhesive easily occur.

  The method for forming the pressure-sensitive adhesive layer 60 is not particularly limited, and a pressure-sensitive adhesive composition (pressure-sensitive adhesive solution) containing the above-described base polymer and other components is applied to the surface of the second protective film 20. Then, the pressure-sensitive adhesive layer 60 may be formed by drying, or the pressure-sensitive adhesive layer 60 may be transferred to the second protective film 20 after forming the pressure-sensitive adhesive layer 60 on the separator (release film) in the same manner. When forming the pressure-sensitive adhesive layer 60 on the surface of the second protective film 20, a surface treatment, for example, a corona treatment or the like may be performed on the surface of the second protective film 20 or the surface of the pressure-sensitive adhesive layer 60 as 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 polarized light having the opposite property; a film with an antiglare function having an uneven surface; a film with a surface antireflection function A reflective film having a reflective function on its surface; a transflective reflective film having both a reflective function and a transmissive function; a viewing angle compensation film, and the like.

  Examples of a commercially available product corresponding to a reflective polarizing film that transmits a certain kind of polarized light and reflects polarized light having the opposite property include, for example, “DBEF” (manufactured by 3M Co., Ltd., and Sumitomo 3M Co., Ltd. in Japan). Available) and "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 a base material surface and is oriented 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 an optical compensation film in which a liquid crystal compound is coated on a substrate surface and is oriented and fixed include “WV film” (manufactured by FUJIFILM Corporation) and “NH film” (JX Nippon Oil & Gas) Energy Co., Ltd.) and "NR film" (JX Nippon Oil & Energy).

  Commercially available products corresponding to a retardation film made of a cyclic polyolefin-based resin include "ARTON FILM" (manufactured by JSR Corporation), "ESCINA" (manufactured by Sekisui Chemical Co., Ltd.), and "ZEONOR FILM" (Nippon Zeon (Japan)). Co., Ltd.).

<Manufacturing method of polarizing plate>
The polarizing plate of the present invention can be suitably manufactured by, for example, the method shown in FIG. The method for manufacturing the polarizing plate shown in FIG.
(1) A resin layer forming step S10 of forming a polyvinyl alcohol-based resin layer by applying a coating solution containing a polyvinyl alcohol-based resin on at least one surface of a base film and then drying the same to obtain a laminated film. ,
(2) a stretching step S20 of stretching the laminated film to obtain a stretched film,
(3) a dyeing step S30 in which a polyvinyl alcohol-based resin layer of the stretched film is dyed with a dichroic dye to form a polarizer, thereby obtaining a polarizing laminated film;
(4) a first laminating step S40 of laminating one of the first and second protective films on the polarizer of the polarizing laminated film via an adhesive layer to obtain a laminated film;
(5) a peeling step S50 of 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 a single-sided protective film via an adhesive layer;
Are included in this order. Hereinafter, each step will be described with reference to FIGS.

(1) Resin layer forming step S10
Referring to FIG. 5, this step is a step of forming polyvinyl alcohol-based resin layer 6 on at least one surface of base film 30 to obtain laminated film 100. This polyvinyl alcohol-based 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 solution containing a polyvinyl alcohol-based resin to one or both surfaces of the base film 30 and drying the coating layer. The method of forming a polyvinyl alcohol-based resin layer by such coating is advantageous in that a thin-film polarizer 5 is easily obtained.

(Base film)
The base film 30 can be made of a thermoplastic resin, and is preferably made 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 resins such as chain polyolefin resins and cyclic polyolefin resins (norbornene resins); polyester resins; (meth) acrylic resins; cellulose triacetate; Cellulose ester resins such as cellulose diacetate; polycarbonate resins; polyvinyl alcohol resins; polyvinyl acetate resins; polyarylate resins; polystyrene resins; polyether sulfone resins; polysulfone resins; polyamide resins; polyimides. -Based 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 more thermoplastic resins, or a plurality of resin layers composed of one 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 stretching the laminated film 100 in a stretching step S20 described below.

  Examples of the chain polyolefin resin include a homopolymer of a chain olefin such as a polyethylene resin and a polypropylene resin, and a copolymer composed of two or more chain olefins. The base film 30 made of a chain polyolefin-based resin is preferable because it is easily stretched stably at a high magnification. Among them, the base film 30 is made of a polypropylene resin (a polypropylene resin which is a homopolymer of propylene or a copolymer mainly composed of propylene), a polyethylene resin (a polyethylene resin which is a homopolymer of ethylene, or mainly composed of ethylene). Is more preferable.

  The 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.

  Other monomers copolymerizable with propylene include, for example, ethylene and α-olefin. As the α-olefin, an α-olefin having 4 or more carbon atoms is preferably used, and more preferably an α-olefin having 4 to 10 carbon atoms. Specific examples of the α-olefin having 4 to 10 carbon atoms include, for example, linear monoolefins such as 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene and 1-decene; Branched monoolefins such as -methyl-1-butene, 3-methyl-1-pentene and 4-methyl-1-pentene; and 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, and preferably 0.5 to 10% by weight. The content of other monomers in the copolymer can be determined by measuring the infrared (IR) spectrum according to the method described on page 616 of "Polymer Analysis Handbook" (1995, published by Kinokuniya Bookstore). You can ask.

  Among them, 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 generally comprises a polycondensate of a polyhydric carboxylic acid or a derivative thereof and a polyhydric alcohol. As the polyvalent carboxylic acid or a derivative thereof, a divalent dicarboxylic acid or a derivative thereof can be used, and examples thereof include terephthalic acid, isophthalic acid, dimethyl terephthalate, and dimethyl naphthalenedicarboxylate. As the polyhydric alcohol, a dihydric diol can be used, 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 state before the crystallization treatment is easier to apply such as stretching. If necessary, a crystallization treatment can be carried out at the time of stretching or by heat treatment after stretching. Further, a copolymerized polyester having reduced crystallinity (or made amorphous) by further copolymerizing another type of monomer with the skeleton of polyethylene terephthalate is also preferably used. Examples of such resins include, for example, those obtained by copolymerizing cyclohexanedimethanol or isophthalic acid. Since these resins are also excellent in stretchability, they can be suitably used.

  Specific examples of polyester resins other than polyethylene terephthalate and its copolymer 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 having a compound having a (meth) acryloyl group as a main constituent monomer. Specific examples of the (meth) acrylic resin include, for example, poly (meth) acrylates such as polymethyl methacrylate; methyl methacrylate- (meth) acrylic acid copolymer; methyl methacrylate- (meth) acrylic acid Ester copolymer; methyl methacrylate-acrylate- (meth) acrylic acid copolymer; methyl (meth) acrylate-styrene copolymer (MS resin, etc.); methyl methacrylate and alicyclic hydrocarbon group And a copolymer having the compound (e.g., methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate-norbornyl (meth) acrylate copolymer). Preferably, a polymer having a poly (meth) acrylate C _1-6 alkyl ester as a main component such as poly (methyl meth) acrylate is used, and more preferably, a methyl methacrylate as a main component (50 to 100). % By weight, preferably 70 to 100% by weight).

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

  Various products are commercially available as polycarbonate-based resins. Examples of commercially available polycarbonate resins are “Panlite” (manufactured by Teijin Chemicals Ltd.), “Iupilon” (manufactured by Mitsubishi Engineering-Plastics Co., Ltd.), “SD POLICA” (manufactured by Sumitomo Dow). (Manufactured by Dow Chemical Co., Ltd.).

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

  With respect to the cyclic polyolefin-based resin and the cellulose ester-based resin that can be used for the base film 30, those described for the protective film are cited. The chain polyolefin-based resin, polyester-based resin, (meth) acryl-based resin, and polycarbonate-based resin described above in relation to the base film 30 can also be used as a constituent material of the protective film.

  Any appropriate additive may be added to the base film 30 in addition to the thermoplastic resin described above. Examples of such additives include an ultraviolet absorber, an antioxidant, a lubricant, a plasticizer, a release agent, a coloring inhibitor, a flame retardant, a nucleating agent, an antistatic agent, a pigment, and a 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 film 30 is less than 50% by weight, the high transparency or the like inherent to the thermoplastic resin may not be sufficiently exhibited.

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

(Coating liquid containing polyvinyl alcohol-based 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, and polyethylene glycol. It is preferable that the compounding amount of the additive is not more than 20% by weight of the polyvinyl alcohol-based resin.

(Coating of coating liquid and drying of coating layer)
The method of applying the above coating liquid to the base film 30 includes wire bar coating; roll coating such as reverse coating and gravure coating; die coating; comma coating; lip coating; spin coating; Method; fountain coating method; dipping method; spray method and the like.

  When the coating liquid is applied to both sides of the base film 30, the coating can be performed one by one using the above-described method, or can be performed using a dipping method, a spray coating method, or another special device. Coating can be performed on both sides of the film 30 at the same time.

  The drying temperature and drying time of the coating layer (the polyvinyl alcohol-based resin layer before drying) are set according to the type of the solvent contained in the coating liquid. The drying temperature is, for example, 50 to 200C, and preferably 60 to 150C. 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-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 surfaces, curling of the film that may occur during the production 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, and more preferably 5 to 20 μm. If the polyvinyl alcohol-based resin layer 6 has a thickness in this range, it passes through a stretching step S20 and a dyeing step S30 described below, and has good dyeing properties of the dichroic dye, excellent polarization performance, and a thickness of 10 μm or less. The child 5 can be obtained. When the thickness of the polyvinyl alcohol-based 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, the film tends to be too thin after stretching, and the dyeing properties tend to deteriorate.

  Prior to the application of the coating solution, at least the surface of the base film 30 on which the polyvinyl alcohol-based resin layer 6 is formed, in order to improve the adhesion between the base film 30 and the polyvinyl alcohol-based resin layer 6. , Corona treatment, plasma treatment, flame (flame) treatment and the like.

  In addition, prior to the application of the coating liquid, a polyvinyl alcohol-based resin is interposed on the base film 30 via a primer layer or an adhesive layer in order to improve the adhesion between the base film 30 and the polyvinyl alcohol-based resin layer 6. The resin layer 6 may be formed.

(Primer layer)
The primer layer can be formed by applying a coating liquid for forming a primer layer on the surface of the base material film 30 and then drying it. The coating liquid for forming a primer layer contains a component that exhibits a certain degree of strong adhesion to both the base film 30 and the polyvinyl alcohol-based resin layer 6. The coating liquid for forming a primer layer usually contains a resin component and a solvent that provide 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 resins and polyvinyl alcohol resins. Above all, a polyvinyl alcohol-based resin that gives good adhesion is preferably used.

  Examples of the polyvinyl alcohol-based resin include a polyvinyl alcohol resin and a derivative thereof. Derivatives of the polyvinyl alcohol resin include, in addition to polyvinyl formal and polyvinyl acetal, those obtained by modifying a polyvinyl alcohol resin with olefins such as ethylene and propylene; and unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid. Modified products; those modified with alkyl esters of unsaturated carboxylic acids; those modified with acrylamide. Among the above-mentioned polyvinyl alcohol-based resins, it is preferable to use a polyvinyl alcohol resin.

  As the solvent, a general organic solvent or an aqueous solvent that can dissolve the resin component is usually used. Examples of the solvent include, for example, 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 trichloroethylene and chloroform; alcohols such as ethanol, 1-propanol, 2-propanol and 1-butanol. However, if a primer layer is formed using a coating liquid for forming a primer layer containing an organic solvent, the base film 30 may be dissolved. Therefore, a solvent is selected in consideration of the solubility of the base film 30. Is preferred. In consideration of the influence on the environment, it is preferable to form the primer layer from a coating solution using 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 a primer layer. The cross-linking agent is appropriately selected from known ones such as organic and inorganic ones according to the type of the thermoplastic resin to be 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-part curing type or two-part 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, diglycidylaniline, and diglycidylamine.

  Examples of the isocyanate-based crosslinking agent include tolylene diisocyanate, hydrogenated tolylene diisocyanate, trimethylolpropane-tolylene diisocyanate adduct, triphenylmethane triisocyanate, methylenebis (4-phenylmethane) triisocyanate, isophorone diisocyanate, and ketoximes thereof. A block product or a phenol block product is exemplified.

  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 organometallic compounds. Metal salts, metal oxides, metal hydroxides, for example, magnesium, calcium, aluminum, iron, nickel, zirconium, titanium, silicon, boron, zinc, copper, vanadium, chromium, tin or more divalent Salts, oxides and hydroxides of metals having a valence are mentioned.

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

  Preferred examples of the organometallic compound include an organotitanium compound, an organozirconium compound, an organoaluminum compound, and an organosilicon compound. As the organometallic compound, only one kind may be used alone, or two or more kinds may be used in combination.

  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 And titanium chelates such as polytitanium acetylacetonate, titanium octylene glycolate, titanium lactate, titanium triethanol aminate, and titanium ethyl acetoacetate; and 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, zirconium acetylacetonate bisethylacetoacetate, and the like.

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

  In addition to the above low molecular crosslinking agents, high molecular crosslinking agents such as methylolated melamine resins and polyamide epoxy resins can also be used. Examples of commercially available polyamide epoxy resins include “SUMIREZ Resin 650 (30)” and “SUMIREZ Resin 675” (all trade names) sold by Taoka Chemical Industry Co., Ltd.

  When a polyvinyl alcohol-based resin is used as the resin component for 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 suitably used as the crosslinking agent.

  The ratio of the resin component and the cross-linking agent in the primer layer-forming coating liquid ranges from about 0.1 to 100 parts by weight of the cross-linking agent to 100 parts by weight of the resin component. It may be appropriately determined according to the conditions and the like, and it is particularly preferable to select from a range of about 0.1 to 50 parts by weight. Further, the coating liquid for forming a primer layer 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, and more preferably 0.1 to 0.4 μm. When the thickness is less 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. When the thickness is more than 1 μm, it is disadvantageous for thinning the polarizing plate.

  The method for applying the coating liquid for forming a primer layer to the base film 30 can be the same as the method for applying the coating liquid for forming a polyvinyl alcohol-based resin layer. The primer layer is applied to the surface (one or both surfaces of the base film 30) to 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 composed of the coating liquid for forming a primer layer are set according to the type of the solvent contained in the coating liquid. The drying temperature is, for example, 50 to 200C, and preferably 60 to 150C. 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 application to the base film 30 is not particularly limited. For example, when the polyvinyl alcohol-based resin layer 6 is formed on both surfaces of the base film 30, After forming the primer layer on both sides of the base film 30, the polyvinyl alcohol-based resin layer 6 may be formed on both sides, or after forming the primer layer and the polyvinyl alcohol-based resin layer 6 on one side of the base film 30 in order, A primer layer and a 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, a laminated film 100 composed of a base film 30 and a polyvinyl alcohol-based resin layer 6 is stretched, and is formed of a stretched base film 30 ′ and a polyvinyl alcohol-based resin layer 6 ′. In this step, the stretched film 200 is obtained. The stretching treatment is usually uniaxial stretching.

  The stretching magnification of the laminated film 100 can be appropriately selected according to the desired polarization characteristics, but is preferably more than 5 times and 17 times or less, more preferably more than 5 times, with respect to the original length of the laminated film 100. 8 times or less. If the stretching ratio is 5 or less, the degree of polarization of the polarizer 5 may not be sufficiently high because the polyvinyl alcohol-based resin layer 6 is not sufficiently oriented. On the other hand, if the stretching ratio exceeds 17 times, the film is likely to break during stretching, and the thickness of the stretched film 200 becomes unnecessarily thin, so that workability and handleability in the subsequent steps may be reduced.

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

  The stretching treatment may be longitudinal stretching in the film longitudinal direction (film transport direction), or may be transverse stretching or oblique stretching in the film width direction. Examples of the longitudinal stretching method include roll-to-roll stretching using a roll, compression stretching, and stretching using a chuck (clip). The lateral stretching method includes a tenter method and the like. As the stretching treatment, any of a wet stretching method and a dry stretching method can be employed, but the use of the dry stretching method is preferred in that 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 entire base film 30 exhibit fluidity to the extent that they can be stretched, and preferably the phase transition temperature (melting point or glass transition temperature) of the base 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 even more 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.

  If the stretching temperature is lower than the phase transition temperature of −30 ° C., it is difficult to achieve a high-magnification stretching of more than 5 times, or the flowability of the base film 30 tends to be too low to make the stretching process difficult. If the stretching temperature exceeds the phase transition temperature of + 30 ° C., the fluidity of the base film 30 tends to be too large, making stretching difficult. The stretching temperature is within the above range, more preferably 120 ° C. or higher, since a high stretching ratio of more than 5 times can be more easily achieved. This is because, when the stretching temperature is 120 ° C. or more, even if the stretching ratio is more than 5 times, there is no difficulty in the stretching process.

  As a heating method of the laminated film 100 in the stretching treatment, a zone heating method (for example, a method of blowing in hot air and heating in a stretching zone such as a heating furnace adjusted to a predetermined temperature); And a method for heating the roll itself; a heater heating method (a method in which an infrared heater, a halogen heater, a panel heater, etc. are installed above and below the laminated film 100 and heated by radiant heat). In the inter-roll stretching method, a zone heating method is preferred from the viewpoint of uniformity of the stretching temperature. In this case, the two nip roll pairs may be installed in the stretch zone where the temperature is adjusted, or may be installed outside the stretch zone. However, the two nip roll pairs are installed outside the stretch zone to prevent adhesion between the laminated film 100 and the nip roll. Is preferred.

  In the case of the zone heating method, the stretching temperature refers to the atmosphere temperature in the zone (for example, in a heating furnace), and also in the heater heating method, when heating is performed in the furnace, the atmosphere temperature in the furnace. 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 pre-heat treatment step of pre-heating 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 method is the inter-roll stretching, the preheating may be performed at any timing before, during, or after passing through the upstream nip roll. When the stretching 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 the 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, after the stretching process in the stretching process S20, a heat setting process may be provided. The heat setting process is a process of performing heat treatment at a crystallization temperature or higher while maintaining the stretched film 200 in a tensioned state while holding the end portion of the stretched film 200 with a clip. This heat setting promotes crystallization of the polyvinyl alcohol-based resin layer 6 '. 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 step S30
Referring to FIG. 7, this step is a step of dyeing polyvinyl alcohol-based resin layer 6 ′ of stretched film 200 with a dichroic dye and adsorbing and orienting the same to obtain polarizer 5. Through this step, a polarizing laminated film 300 in which the polarizer 5 is laminated on one 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 containing a dichroic dye (dyeing solution). As the staining solution, a solution in which the dichroic dye is dissolved in a solvent can be used. Water is generally used as a 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 a dyeing solution containing iodine, since the dyeing efficiency can be further improved. Examples of iodides 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 from 0.01 to 20% by weight. Among iodides, it is preferable to add potassium iodide. When potassium iodide is added, the ratio of iodine to potassium iodide is preferably in the range of 1: 5 to 1: 100 by weight, more preferably in the range of 1: 6 to 1:80. More preferably, 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 a range of 15 seconds to 15 minutes, and preferably 30 seconds to 3 minutes. The temperature of the dyeing solution is preferably in the range of 10 to 60C, more preferably in the range of 20 to 40C.

  Although the dyeing step S30 can be performed before the stretching step S20 or these steps can be performed simultaneously, the dichroic dye adsorbed on the polyvinyl alcohol-based resin layer can be favorably oriented. As described above, it is preferable to perform the dyeing step S30 after performing at least some stretching treatment on the laminated film 100. That is, the stretched film 200 obtained by performing the stretching treatment to the target magnification in the stretching step S20 can be subjected to the dyeing step S30, and after performing the stretching treatment at a lower magnification than the target in the stretching step S20. During the dyeing step S30, a stretching treatment can be performed until the total stretching magnification reaches a target magnification. As the latter embodiment, 1) after performing the stretching treatment at a lower magnification than the target in the stretching step S20, and then performing the stretching treatment during the dyeing processing in the dyeing step S30 such that the total stretching magnification becomes the target magnification. As described later, when the crosslinking treatment is performed after the dyeing treatment, 2) after performing the stretching treatment at a lower magnification than the target in the stretching step S20, the total stretching magnification is set to the target during the dyeing treatment in the staining step S30. And the like, and then the stretching treatment is performed during the crosslinking treatment so that the final total stretching magnification becomes the target magnification.

  The dyeing step S30 may include a cross-linking step performed subsequent to the dyeing processing. The crosslinking treatment can be performed by immersing the dyed film in a solution containing a crosslinking agent (crosslinking solution). As the cross-linking agent, conventionally known substances can be used, and examples thereof include boron compounds such as boric acid and borax, glyoxal, and glutaraldehyde. One type of the crosslinking agent may be used alone, or two or more types may be used in combination.

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

  The crosslinking solution may include iodide. By adding iodide, the in-plane polarization performance of the polarizer 5 can be made more uniform. Examples of iodides 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 concentration of iodide in the crosslinking solution is preferably from 0.05 to 15% by weight, more preferably from 0.5 to 8% by weight.

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

  The crosslinking treatment can be performed simultaneously with the dyeing treatment by blending a crosslinking agent into the dyeing solution. Further, a stretching treatment may be performed during the crosslinking treatment. The specific mode of performing the stretching treatment during the crosslinking treatment is as described above. Further, using two or more kinds of crosslinking solutions having different compositions, the treatment of dipping in the crosslinking solution may be performed twice or more.

  After the dyeing step S30, it is preferable to perform a washing step and a drying step before a first bonding step S40 described later. The washing step usually includes a water washing step. The water washing treatment can be performed 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, 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 in addition to water.

  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
Referring to FIG. 8, in this step, a first adhesive layer is provided 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 via an adhesive layer. In this step, one of the protective film 10 and the second protective film 20 is bonded to obtain a bonded film 400. FIG. 8 shows an example in which the first protective film 10 is bonded via the first adhesive layer 15, but the second protective film 20 is bonded via the second adhesive layer 25. Is also good. When the polarizing laminated film 300 has the polarizers 5 on both sides of the base film 30 ′, usually, protective films are bonded on the polarizers 5 on both sides. 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 bonded to polarizer 5 via an adhesive layer (first adhesive layer 15 or second adhesive layer 25).

  The bonding of the protective film via the adhesive layer is performed, for example, by applying an adhesive to the protective film and / or the bonding surface of the polarizer 5 using a known means, and applying the adhesive via the adhesive coating layer. Then, the protective film and the polarizer 5 are superimposed on each other, and bonded using a bonding roll or the like.

  In order to reduce the thickness of the adhesive layer like the first adhesive layer 15, it is preferable to apply an adhesive using a small-diameter gravure or the like, and particularly, a gravure rotation draw (gravure rotation speed with respect to line speed). The thickness of the adhesive layer can be reduced by a method such as increasing the rotation speed of the gravure and increasing the number of lines of the gravure mesh. In particular, to make the thickness of the adhesive layer 1 μm or less, it is preferable to use a gravure having a mesh carved by laser engraving, and it is particularly preferable to use a gravure roll having a honeycomb shape. For example, a honeycomb shape having a number of honeycombs per inch exceeding 400 rows is suitably used.

  When a photocurable adhesive is used as the adhesive, a curing step of curing the photocurable adhesive by irradiating active energy rays after performing the above-described bonding is performed. Although the light source of the active energy ray is not particularly limited, an active energy ray (ultraviolet ray) having a light emission distribution at a wavelength of 400 nm or less is preferable. A black light lamp, a microwave excitation 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 a wavelength region effective for activating the polymerization initiator is 0.1 to 6000 mW / cm ² . It is preferable to be 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 the irradiation intensity is 6000 mW / cm ² or less, the light radiated from the light source and the light due to the heat generated during 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 according to the composition of the photocurable adhesive, and the integrated light amount expressed as the product of the irradiation intensity and the irradiation time is 10 to 10,000 mJ / cm ² . It is preferable to be set so that If the integrated light quantity is 10 mJ / cm ² or more to generate a sufficient amount of the active species derived from the polymerization initiator can proceed more reliably the curing reaction, if it is 10000 mJ / cm ² or less, longer irradiation time Good productivity can be maintained without becoming too much.

  When using a water-based adhesive, a drying step is usually performed after lamination to dry the water-based adhesive to remove water contained in the water-based adhesive. Drying can be performed, for example, by introducing the laminated film into a drying oven. The drying temperature (temperature of the drying furnace) is preferably 30 to 90 ° C. When the temperature is lower than 30 ° C., the protective film tends to be easily separated 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 slightly higher temperature, for example, 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.

  In pasting the protective film on the polarizer 5, the surface of the protective film on the polarizer 5 side may be subjected to plasma treatment, corona treatment, ultraviolet irradiation treatment, and flame (flame) in order to improve the adhesion to the polarizer 5. A) Surface treatment such as treatment and saponification treatment (easy adhesion treatment) can be performed, and among them, it is preferable to perform plasma treatment, corona treatment or saponification treatment. For example, when the protective film is made of a cyclic polyolefin resin, a plasma treatment or a corona treatment is usually performed. In the case of a cellulose ester resin, a saponification treatment is usually performed. As the saponification treatment, a method of dipping in an aqueous alkali solution such as sodium hydroxide or potassium hydroxide may be mentioned.

(5) Peeling step S50
Referring to FIG. 9, this step is a step of peeling and removing base film 30 ′ from laminating film 400 obtained by laminating a protective film. Through this step, a polarizing plate 500 with a single-sided protective film in which a protective film (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 stuck to both of the polarizers 5, one strip of the polarizing laminate is formed by the peeling step S 50. From the film 300, two polarizing plates with a single-sided protective film 500 are obtained.

  The method of peeling and removing the base film 30 ′ is not particularly limited, and the substrate film 30 ′ can be peeled by the same method as the peeling step of a separator (release film) performed by a usual polarizing plate with an adhesive. The base film 30 'may be peeled off immediately after the first laminating step S40, or may be rolled up once after the first laminating step S40, and then peeled off while unwinding in a subsequent step. You may.

(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 pasted in the first pasting step S40 via the adhesive layer. This is a step of bonding the other one 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. As for the bonding method of the protective film and the surface treatment (easy adhesion treatment) in the bonding, the contents described for the first bonding step S40 are cited.

<Display device>
Referring to FIG. 2, the display device of the present invention includes a display cell 50 and the above-described polarizing plate 1 of the present invention disposed on at least one surface thereof. The polarizing plate 1 can be arranged and pasted on the display cell 50 using the pressure-sensitive 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. Therefore, the appearance of the display device is excellent. Also, light leakage in the black display state can be effectively suppressed.

  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 may be another display device such as an organic EL device. In the display device, the polarizing plate may be disposed on at least one surface of the display cell 50, but may be disposed on both surfaces.

  When the display device is a liquid crystal display device, usually, polarizing plates are arranged on both surfaces of the liquid crystal cell. In this case, the polarizing plates on both sides may be the polarizing plates 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 (viewing side) polarizing plate or a rear (backlight side) polarizing plate with respect to the liquid crystal cell. A conventionally known liquid crystal cell can be used.

  Hereinafter, the present invention will be described more specifically with reference to 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 3% by weight aqueous solution of polyvinyl alcohol was prepared. A cross-linking agent (“SUMIREZ Resin 650” manufactured by Taoka Chemical Industry Co., Ltd.) was mixed with the aqueous solution at a ratio of 5 parts by weight to 6 parts by weight of the polyvinyl alcohol powder, and a coating solution for forming a primer layer was formed. I got

  Next, an unstretched polypropylene (PP) film (melting point: 163 ° C.) having a thickness of 90 μm was prepared as a base film, and one surface thereof was subjected to corona treatment. The coating liquid for forming a primer layer 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 polymerization degree 2400, saponification degree 98.0 to 99.0 mol%) is dissolved in hot water at 95 ° C., and a polyvinyl alcohol aqueous solution having a concentration of 8% by weight is dissolved. Was prepared and used as a coating liquid for forming a polyvinyl alcohol-based resin layer.

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

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

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

  Next, 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. (2) Cross-linking treatment was performed 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. Thereafter, the substrate 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 / a primer layer / a polarizer.

(5) Production of polarizing plate (first bonding step, peeling step, second bonding step)
A cyclic polyolefin-based resin film (“ZF14” manufactured by Zeon Corporation, thickness: 23 μm) was prepared as the first protective film disposed on the outside (viewing side) when the polarizing plate was disposed on the display cell. . After applying a corona treatment to the bonding surface of the first protective film, a photocurable adhesive (“KR-70T” manufactured by ADEKA Corporation) is applied to the corona treated surface using a small-diameter gravure coater. Then, after disposing the first protective film on the polarizer of the polarizing laminated film produced in the above (4) via the adhesive coating layer, the first protective film was laminated using a laminating roll. Next, 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 base film was peeled off from the obtained laminated film (peeling step). The substrate film was easily peeled off to obtain a polarizing plate with a single-sided protective film having a layer structure of first protective film / first adhesive layer / polarizer / primer layer.

As the second protective film disposed on the display cell side when the polarizing plate was disposed on the display cell, a cyclic polyolefin-based resin film (“ZF14” manufactured by Zeon Corporation, 23 μm in thickness) was prepared. After applying a corona treatment to the bonding surface of the second protective film, a photocurable adhesive (“KR-70T” manufactured by ADEKA Corporation) is applied to the corona treated surface using a small-diameter gravure coater. Then, after arranging the second protective film on the surface of the obtained one-sided protective film-attached polarizing plate opposite to the first protective film via the adhesive coating layer, the second protective film is attached using a bonding roll. I combined. Next, the adhesive is cured by ultraviolet irradiation 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 Was obtained. 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 application of the photocurable adhesive and the “first or second protective film” after application of the photocurable adhesive (before bonding with the polarizer). And the total thickness of the coated adhesive layer ”is measured using a non-contact optical interference type film thickness meter (“ F-20 ”manufactured by Filmetrics Co., Ltd.), and the difference between the first and second adhesive layers is measured. 2 The thicknesses of the adhesive layers were T ₁ and T ₂ . The thickness of the adhesive layer before bonding and curing with the polarizer obtained in this way is maintained almost as it is after bonding with the polarizer and curing, and the adhesion after curing in the obtained polarizing plate. That the thickness is substantially the same as the thickness of the adhesive layer is confirmed 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 to 5, Comparative Examples 1 and 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 as shown in Table 1.

[Evaluation of reflection image distortion and light leakage]
(1) Evaluation of distortion of reflected image The polarizing plates obtained in Examples and Comparative Examples were cut out to a size of 4 ", which were adhered on one side of a liquid crystal cell via an adhesive layer on the second protective film side and evaluated. The fluorescent lamp was projected on the surface of the first protective film of the evaluation sample by specular reflection, 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: There is almost no distortion, and the reflected image is clear.
C: Although relatively distorted, a relatively clear reflected image is obtained.
D: Large distortion.

(2) Light Leakage Evaluation A 4 ″ -size polarizing plate was similarly bonded to the other surface of the liquid crystal cell in the evaluation sample used in the above (1). The polarizers were bonded so that crossed Nicols were formed (the absorption axes of the polarizers were orthogonal to each other), and light was irradiated from the first protective film surface side of one of the polarizers in the obtained evaluation sample. In the black display state, the presence or absence (light leakage) of light transmitted to the first protective film side of the other polarizing plate was visually evaluated according to the following evaluation criteria.

A: No light leakage,
B: Light leakage is observed (a bright spot exists).

  REFERENCE SIGNS LIST 1 polarizing plate, 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 cell, 60 adhesive layer, 100 laminated film, 200 stretched film, 300 polarizing laminated film, 400 laminated film, 500 with single-sided protective film Polarizer.

Claims (12)

A polarizer,
A first protective film laminated on one surface of the polarizer via a first adhesive layer having a thickness of 1.0 μm or less ;
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 comprising:
The second protective film is a protective film that is disposed closer to the display cell than the first protective film when the polarizing plate is disposed on the display cell,
The thickness of the polarizer is 10 μm or less,
The first and second protective films have a thickness of 5 to 50 μm,
A polarizing plate wherein 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 layers of a photo-curable adhesive.   The polarizing plate according to claim 1, wherein the thickness of the first adhesive layer is 0.7 μm or less. The polarizing plate according to claim 1, wherein the thickness of the first adhesive layer is 0.5 μm or less. The polarizing plate according to claim 1, wherein a thickness of the second adhesive layer is 1.3 μm or more. The polarizing plate according to any one of claims 1 to 5 , wherein a difference between a thickness of the second adhesive layer and a thickness of the first adhesive layer is 0.3 µm or more. The polarizing plate according to claim 6 , wherein the difference is 0.8 µm or more. The polarizing plate according to claim 7 , wherein the difference is 0.9 µm or more. The polarizing plate according to any one of claims 1 to 8 , further comprising a pressure-sensitive adhesive layer laminated on an outer surface of the second protective film and bonded to the display cell. A display cell, the display device comprising a polarizing plate according to any one of claims 1 to 9 disposed on at least one surface. A display device comprising: a display cell; and the polarizing plate according to claim 9 disposed on at least one surface thereof, wherein the polarizing plate is bonded to the display cell via the adhesive layer. A method for using the polarizing plate according to any one of claims 1 to 9 ,
A method of using a polarizing plate, wherein when arranging the polarizing plate on a display cell, the second protective film is arranged closer to the display cell than the first protective film.

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