JP5886575B2 - Manufacturing method of laminate - Google Patents

Description

  The present invention is a laminate comprising a polarizing plate, a surface protective film bonded to one surface of the polarizing plate, and a separate film bonded to the other surface of the polarizing plate via an adhesive layer. And a manufacturing method thereof.

  A polarizing film is widely used as a film obtained by adsorbing and orienting a dichroic dye on a polyvinyl alcohol resin film. An iodine polarizing film using iodine as a dichroic dye, a dye polarizing film using a dichroic direct dye as a dichroic dye, and the like are known. These polarizing films are usually bonded on one or both sides with a protective film formed from triacetyl cellulose or cycloolefin via an adhesive made of an aqueous solution of a polyvinyl alcohol resin, etc. A polarizing plate is constructed.

  The polarizing plate has a surface protective film on one side and a pressure-sensitive adhesive layer on the other side, and a separate film is laminated on this pressure-sensitive adhesive layer until it is bonded to the liquid crystal cell for a certain period of time. It is common to be done.

  However, there is a problem that the polarizing plate easily curls depending on the amount of water, and when curling occurs in a state where the pressure-sensitive adhesive layer and the separate film are laminated, the pressure-sensitive adhesive layer and the separate film are displaced, and the pressure-sensitive adhesive layer There is a risk of streaking. Since the streaks remain after the separation film is peeled off from the polarizing plate and bonded to the liquid crystal cell, the display quality of the liquid crystal display device is affected. Further, the curling of the polarizing plate also affects the display quality of the liquid crystal display device.

  As means for solving such a problem, Japanese Patent Application Laid-Open No. 2008-122790 (Patent Document 1) and Japanese Patent Application Laid-Open No. 2005-326531 (Patent Document 2) disclose that the water content of the polarizing film is relatively high and the polarization is changed. A method for adjusting the moisture content of a protective film to be bonded to a film is disclosed.

JP 2008-122790 A JP 2005-326531 A

  However, the configuration of the conventional polarizing plate or the manufacturing method thereof is complicated, and a polarizing plate having a simpler configuration and a simpler manufacturing method of the polarizing plate have been desired. Therefore, an object of the present invention is a laminate in which a surface protective film is bonded to one surface of a polarizing plate and a separate film is bonded to the other surface through an adhesive layer, It is an object of the present invention to provide a laminate having a simple structure that suppresses the occurrence of streaks in the pressure-sensitive adhesive layer and a method for producing the same.

The present invention includes a polarizing plate, a surface protective film bonded to one surface of the polarizing plate, and a separate film bonded to the other surface of the polarizing plate via an adhesive layer. A laminate,
When the water content R ₁ (%) of the polarizing plate is 23 ° C. and the relative water content of the polarizing plate is R ₀ (%) in an atmosphere having a relative humidity of 55%, the following formula (1):
−0.85 (%) ≦ R ₁ (%) − R ₀ (%) ≦ −0.2 (%) Formula (1)
It is a laminated body that satisfies the relationship.

The polarizing plate includes a polarizing film made of a polyvinyl alcohol-based resin, and an optical compensation film bonded to one surface of the polarizing film,
The optical compensation film includes a transparent support made of a cellulose-based resin, an alignment film formed on one side of the transparent support, and a liquid crystal compound formed on the surface of the alignment film opposite to the transparent support A coating layer containing, and is bonded to the one surface of the polarizing film on the transparent support side,
It is preferable that the laminated structure on the one surface of the polarizing film is different from the laminated structure on the other surface of the polarizing film.

  It is preferable that the polarizing plate further includes a transparent protective film bonded to the other surface of the polarizing film.

  It is preferable that the transparent protective film and the surface protective film are bonded to each other, and the coating layer containing the liquid crystal compound and the separate film are bonded to each other.

  The transparent protective film is preferably surface-treated on the surface opposite to the polarizing film.

The alignment film is preferably made of a polyvinyl alcohol resin.
The coating layer containing the liquid crystal compound is preferably an optical compensation layer containing a discotic liquid crystal.

The optical compensation layer is a layer having a negative birefringence composed of a liquid crystal compound having a discotic structural unit,
The disc surface of the discotic structural unit is inclined with respect to the transparent support surface,
It is preferable that an angle formed by the disc surface of the discotic structural unit and the surface of the transparent support is changed in the thickness direction of the optical compensation layer.

  The angle formed by the disc surface of the discotic structural unit with respect to the transparent support surface increases with an increase in the distance from the transparent support side of the optical compensation layer in the thickness direction of the optical compensation layer. preferable.

The present invention also includes a polarizing plate, a surface protective film bonded to one surface of the polarizing plate, and a separate film bonded to the other surface of the polarizing plate via an adhesive layer. A method for producing a laminate comprising:
Equilibrium water content of the polarizing plate in an atmosphere where the moisture content R ₁ (%) immediately before bonding the surface protective film and the separate film to the polarizing plate is 23 ° C. and a relative humidity of 55%. When the rate is R ₀ (%), a polarizing plate manufacturing process for manufacturing so as to satisfy the relationship of the above formula (1),
A laminate bonding step of bonding the surface protective film to one surface of the polarizing plate and bonding the separate film via the pressure-sensitive adhesive layer to the other surface of the polarizing plate; The present invention also relates to a method for manufacturing the laminate.

The polarizing plate includes a polarizing film made of a polyvinyl alcohol-based resin, an optical compensation film bonded to one surface of the polarizing film, and a transparent protective film bonded to the other surface of the polarizing film,
The optical compensation film includes a transparent support made of a cellulose-based resin, an alignment film formed on one side of the transparent support, and a liquid crystal compound formed on the surface of the alignment film opposite to the transparent support A coating layer containing, and is bonded to the one surface of the polarizing film on the transparent support side,
The polarizing plate manufacturing step is a polarizing plate laminating step in which the optical compensation film, the polarizing film, and the transparent protective film are laminated together in this order, and are bonded to each other by passing between two rolls. It is preferable to contain.

  The polarizing plate manufacturing step preferably includes a drying step for retaining the polarizing plate in an atmosphere of 60 ° C. or higher and 90 ° C. or lower for 210 seconds or longer.

  The laminate of the present invention is a polarizing body having a simple structure in which a surface protective film is bonded to one surface of a polarizing plate and a separate film is bonded to the other surface through an adhesive layer. Curling is unlikely to occur, and the streaks of the pressure-sensitive adhesive layer associated therewith are also unlikely to occur. Further, according to the method for producing a laminate of the present invention, a laminate capable of suppressing the occurrence of curling and the accompanying generation of streaks in the pressure-sensitive adhesive layer, that is, a surface protective film, a polarizing plate, and a pressure-sensitive adhesive layer And the laminated body of the simple structure by which the separate film was laminated | stacked in this order can be manufactured.

It is a schematic sectional drawing which shows a preferable example of the laminated constitution of the laminated body which concerns on this invention. It is the schematic which shows an example of the apparatus for manufacturing the laminated body which concerns on this invention.

Hereinafter, the laminate of the present invention and the manufacturing method thereof will be described in detail with reference to the drawings.
<Configuration of laminate>
FIG. 1 is a schematic cross-sectional view showing a preferred example of the layer configuration of a laminate according to the present invention. The laminate 1 is a polarizing plate 20, a surface protective film 30 that is bonded to one surface of the polarizing plate 20, and a separate that is bonded to the other surface of the polarizing plate 20 via an adhesive layer 50. A film 40. The surface protective film 30 is provided to protect the surface of the polarizing plate 20. The pressure-sensitive adhesive layer 50 is used for bonding the polarizing plate 20 with the surface protective film 30 to another member, for example, a liquid crystal cell, and the separate film 40 temporarily protects the surface of the pressure-sensitive adhesive layer 50. The polarizing plate 20 has a polarizing film 21. In addition, when the laminated structure on one surface of the polarizing film is different from the laminated structure on the other surface of the polarizing film, a problem of curling of the laminated body is likely to occur. Such a configuration is more effective in that curling can be suppressed.

  The polarizing plate 20 includes a polarizing film 21, a transparent protective film 22 that is bonded to one surface of the polarizing film 21, and an optical compensation film 23 that is bonded to the other surface of the polarizing film 21. The optical compensation film 23 was formed on the surface of the transparent support 231 made of cellulose resin, the alignment film 232 formed on one side of the transparent support 231, and the surface of the alignment film 232 opposite to the transparent support 231. A coating layer 233 containing a liquid crystal compound, and is bonded to one surface of the polarizing film 21 on the transparent support 231 side. And the transparent protective film 22 of the polarizing plate 20 and the surface protective film 30 are bonded together, and the coating layer 233 of the optical compensation film 23 of the polarizing plate 20 and the separate film 40 are bonded through the adhesive layer 50. ing.

When the polarizing plate 20 has a water content R ₁ (%) of R ₀ (%) as an equilibrium water content of the polarizing plate 20 in an atmosphere having a temperature of 23 ° C. and a relative humidity of 55%, the following formula (1):
−0.85 (%) ≦ R ₁ (%) − R ₀ (%) ≦ −0.2 (%) Formula (1)
Satisfy the relationship.

When the polarizing plate 20 satisfies the above relationship, the laminate 1 formed by laminating the surface protective film 30 and the separate film 40 on the polarizing plate 20 is less likely to curl, resulting in the occurrence of streaks in the pressure-sensitive adhesive layer 50. Is also suppressed. On the other hand, when “R ₁ (%)-R ₀ (%)” is less than −0.85 (%), curling is likely to occur in the laminate 1, and the occurrence of streaks in the pressure-sensitive adhesive layer 50 associated therewith. Is likely to occur.

  The curl as described above can occur mainly before the laminate is applied to the liquid crystal display device. Regarding the curl that occurs before the laminate is applied to the liquid crystal display device, the curl with the convex surface on the surface protective film side, that is, the concave surface on the separate film side, is less than the curl with the concave surface on the surface protective film side, that is, the convex side on the separate film side. Is even more inconvenient. This is because in the former case, the bonding surface with the liquid crystal cell becomes a concave surface, and it becomes difficult to bond with higher accuracy than when it is a convex surface.

When the polarizing plate 20 satisfies the above relationship with respect to the moisture content R ₁ (%), curling of the laminated body 1 is suppressed, and the occurrence of streaks in the pressure-sensitive adhesive layer is also suppressed. Incidentally, a polarizing plate, for the moisture content R ₁ (%), more preferably the following formula (2):
−0.5 (%) ≦ R ₁ (%) − R ₀ (%) ≦ −0.2 (%) Formula (2)
Satisfy the relationship.

[Measurement method of moisture content of polarizing plate]
The moisture content of the polarizing plate referred to in this specification is a conversion value calculated based on a moisture measurement value (value measured using an infrared moisture meter) measured by a light transmission method. In the present specification, the moisture content of the polarizing plate is calculated as follows. First, the moisture measurement value of the polarizing plate is measured by a light transmission method, and then the moisture content of the polarizing plate is determined by a dry weight method (dried at 105 ° C. for 1 hour to obtain a moisture content by a weight difference before and after drying). That is, when the weight of the polarizing plate in the state to be measured and the atmosphere is W ₁ , and the weight of the polarizing plate after drying the same polarizing plate at 105 ° C. for 1 hour is W ₂ , the following formula (3 ):
Moisture content (%) of polarizing plate = {(W ₁ −W ₂ ) / W ₁ } × 100 Formula (3)
The value calculated in step 4 is defined as the moisture content of the polarizing plate.

  When the same operation for obtaining the moisture content based on the dry weight method is performed on a polarizing plate having various moisture measurement values (values measured using an infrared moisture meter), a conversion formula for obtaining the moisture content from the moisture measurement value is obtained. Can do. By using the obtained conversion formula, the moisture content based on the dry weight method can be estimated based on the moisture measurement value measured using an infrared moisture meter.

  What is necessary is just to measure the moisture content in an infrared moisture content meter according to the instruction manual of the apparatus manufacturer. Examples of the infrared moisture meter include Kurabo Industries RX-300 and Fuji Work IM-3SCV.

  The equilibrium moisture content means the moisture content in a state where the polarizing plate has reached equilibrium in an atmosphere at a temperature of 23 ° C. and a relative humidity of 55%. When the polarizing plate is placed in a constant atmosphere at a temperature of 23 ° C. and a relative humidity of 55%, the moisture content fluctuates and the moisture content gradually becomes an equilibrium state. The equilibrium moisture content means the moisture content in this equilibrium state. In this specification, the equilibrium moisture content is specifically the moisture content when the polarizing plate is held in a clean room at a temperature of 23 ° C. and a relative humidity of 55% for 7 days. The equilibrium moisture content is a value based on a dry weight method calculated from a conversion formula based on a moisture measurement value measured by a light transmission method (a value measured using an in-line moisture content meter) in the same manner as the above moisture content. is there. In the present invention, the moisture content of the polarizing plate does not mean the moisture content of the individual members constituting the polarizing plate, but the moisture content of the entire polarizing plate formed by combining the individual constituent members. The moisture content of the polarizing plate in the laminate is obtained by, for example, obtaining the polarizing plate by detaching the surface protective film and the separate film from the laminated body and then wiping off the adhesive using an organic solvent such as ethanol. It can obtain | require by measuring the moisture content of.

[Separate film]
The separate film 40 is not particularly limited as long as it is a release-treated plastic film, and a known separate film can be used. As the separate film 40, for example, a film made of a transparent resin such as polyethylene terephthalate and subjected to a release treatment with a silicone resin or the like can be used.

[Adhesive layer]
The pressure-sensitive adhesive that forms the pressure-sensitive adhesive layer 50 includes various pressure-sensitive adhesives that have been used for pasting liquid crystal cells and polarizing plates, such as acrylic, rubber-based, urethane-based, silicone-based, and polyvinyl ether. What was formed using the adhesive can be used. In addition, energy ray curable adhesives and thermosetting adhesives may be used, and among these, acrylic adhesives based on acrylic resins having excellent transparency, weather resistance, heat resistance, etc. are preferred. .

  Acrylic adhesive is not particularly limited, but (meth) acrylic such as butyl (meth) acrylate, ethyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate. An acid ester base polymer or a copolymer base polymer using two or more of these (meth) acrylic acid esters is preferably used. Furthermore, polar monomers are copolymerized in these base polymers. Examples of polar monomers include (meth) acrylic acid, 2-hydroxypropyl (meth) acrylate, hydroxyethyl (meth) acrylate, (meth) acrylamide, N, N-dimethylaminoethyl (meth) acrylate, glycidyl (meth) ) A monomer having a functional group such as a carboxy group, a hydroxyl group, an amide group, an amine group, and an epoxy group, such as acrylate.

  These acrylic pressure-sensitive adhesives can of course be used alone, but usually a crosslinking agent is used in combination. Crosslinking agents include divalent or polyvalent metal salts that form carboxylic acid metal salts with carboxyl groups, polyamine compounds that form amide bonds with carboxyl groups Examples thereof include polyepoxy compounds and polyol compounds that form an ester bond with a carboxyl group, and polyisocyanate compounds that form an amide bond with a carboxyl group. Of these, polyisocyanate compounds are widely used as organic crosslinking agents.

  The energy ray curable adhesive has the property of being cured by irradiation with energy rays such as ultraviolet rays and electron beams, and has adhesiveness even before irradiation with energy rays to adhere to an adherend such as a film. It is a pressure-sensitive adhesive that has the property of being adhered and cured by irradiation with energy rays to adjust the adhesion. As the energy ray curable adhesive, it is particularly preferable to use an ultraviolet curable adhesive. The energy beam curable pressure-sensitive adhesive generally comprises an acrylic pressure-sensitive adhesive and an energy beam polymerizable compound as main components. Usually, a crosslinking agent is further blended, and if necessary, a photopolymerization initiator and a photosensitizer can be blended.

  In addition to the base polymer and the cross-linking agent described above, the pressure-sensitive adhesive composition includes, for example, natural products and the like in order to adjust the pressure-sensitive adhesive force, cohesive force, viscosity, elastic modulus, glass transition temperature, etc. Appropriate additives such as synthetic resins, tackifier resins, antioxidants, ultraviolet absorbers, dyes, pigments, antifoaming agents, corrosion inhibitors, and photopolymerization initiators can also be blended. Further, a pressure-sensitive adhesive layer exhibiting light scattering properties can be formed by containing fine particles.

  The thickness of the pressure-sensitive adhesive layer 50 is preferably 1 to 40 μm, but it is desirable to apply it thinly within a range that does not impair the workability and durability characteristics of the laminate 1, and good workability is maintained, and a polarizing plate More preferably, it is 3-25 micrometers from the point which suppresses the dimensional change of 20. If the pressure-sensitive adhesive layer 50 is too thin, the tackiness is lowered, and if it is too thick, problems such as stickiness sticking out easily occur.

[Surface protection film]
The surface protective film 30 is preferably formed from a polyethylene-based resin, a polypropylene-based resin, a polystyrene-based resin, a polyethylene terephthalate-based resin, which is easy to handle and ensures a certain degree of transparency. A film formed by molding two or more kinds into a single layer or a multilayer can be used.

  Specifically, the surface protective film 30 includes sanitect (sold by Sanei Kaken Co., Ltd.) in which an adhesive layer is formed on the surface of the polyethylene resin film, and an adhesive layer on the surface of the polyethylene terephthalate resin film. Commercially available products such as the formed E-mask (manufactured by Nitto Denko Corporation) and MASTACK (manufactured by Fujimori Kogyo Co., Ltd.) in which an adhesive layer is formed on the surface of the polyethylene terephthalate resin film.

  Among these, the self-adhesive surface protective film having adhesiveness to the polarizing plate 20 alone is simple because it does not need to protect the pressure-sensitive adhesive layer on the surface protective film surface, and can be used more suitably. As a commercial item of the self-adhesive resin film (surface protective film) which shows suitable peeling force with respect to the polarizing plate 20, Toraytec (manufactured by Toray Industries, Inc.) made of a polyethylene resin can be exemplified.

  The peeling force between the surface protective film 30 and the polarizing plate 20 is preferably 0.01 to 5 N / 25 mm, more preferably 0.01 to 2 N / 25 mm, and still more preferably 0.01 to 0.5 N / 25 mm. When the peeling force is less than 0.01 N / 25 mm, the adhesive force between the polarizing plate 20 and the surface protective film 30 is small, and thus the surface protective film 30 may be partially peeled off. Moreover, since it will become difficult to peel the surface protection film 30 from the polarizing plate 20 when peeling force exceeds 5 N / 25mm, it is unpreferable.

[Polarizer]
(Polarizing film)
As the polarizing film 21, for example, a film made of polyvinyl alcohol resin, polyvinyl acetate resin, ethylene / vinyl acetate (EVA) resin, polyamide resin, polyester resin, etc., adsorbed and oriented with a dichroic dye, A polyvinyl alcohol / polyvinylene copolymer containing an oriented molecular chain of a dichroic dehydrated product of polyvinyl alcohol (polyvinylene) in a partially oriented polyvinyl alcohol film. In particular, a polyvinyl alcohol resin layer having a dichroic dye adsorbed and oriented is preferably used.

  The polyvinyl alcohol-based resin constituting the polarizing film 21 is usually obtained by saponifying a polyvinyl acetate-based resin. The saponification degree of the polyvinyl alcohol-based resin is usually 85 mol% or more, preferably 90 mol% or more, and more preferably 99 to 100 mol%. Polyvinyl acetate resins include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith, such as ethylene-vinyl acetate copolymers. Etc. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, and unsaturated sulfonic acids. The degree of polymerization of the polyvinyl alcohol-based resin is usually in the range of 1000 to 10000, preferably in the range of 1500 to 5000.

  These polyvinyl alcohol resins may be modified. For example, polyvinyl formal, polyvinyl acetal, polyvinyl butyral and the like modified with aldehydes may be used. Usually, as a starting material for producing a polarizing film, an unstretched film of a polyvinyl alcohol-based resin film having a thickness of 20 to 100 μm, preferably 30 to 80 μm is used. Industrially, the practical width of the film is 1500 to 4000 mm. This unstretched film is processed in the order of, for example, a swelling process, a dyeing process, a crosslinking process, and a water washing process, subjected to uniaxial stretching in the process up to the crosslinking process, and finally dried to obtain a polarizing film. The thickness of the obtained polarizing film is, for example, 5 to 50 μm.

  Examples of the dichroic dye used in the dyeing process include iodine and organic dyes. Examples of 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, Spura Blue G, Spura Blue GL, Spura Orange GL, Direct Sky Blue, Direct First Orange S, First Black, etc. can be used. One type of these dichroic dyes may be used, or two or more types may be used in combination.

  A conventionally known substance can be used as the crosslinking agent used in the crosslinking step. Examples thereof include boron compounds such as boric acid and borax, glyoxal, and glutaraldehyde. One kind of these may be used, or two or more kinds may be used in combination.

(Optical compensation film)
The optical compensation film 23 includes a transparent support made of a cellulose-based resin, an alignment film formed on one side of the transparent support, and a liquid crystal compound formed on the opposite side of the alignment film from the transparent support And a coating layer containing. The optical compensation film 23 is bonded to the one surface of the polarizing film 21 on the transparent support side.

  The transparent support 231 constituting the optical compensation film 23 is preferably made of a cellulose resin. Specific examples of the cellulose resin include acetyl cellulose resins such as diacetyl cellulose and triacetyl cellulose. Among them, triacetyl cellulose is generally used.

  The alignment film 232 formed on one surface of the transparent support 231 is often composed of a hydrophilic resin, and is generally composed of a polyvinyl alcohol resin. The polyvinyl alcohol resin may be, for example, modified polyvinyl alcohol into which an alkyl group is introduced. Usually, a coating layer made of such a hydrophilic resin is formed on one surface of the transparent support 231 and the surface thereof is rubbed to form the alignment film 232.

  The coating layer 233 containing a liquid crystal compound is generally an optical compensation layer obtained by coating and aligning a coating liquid containing a discotic liquid crystal. For example, a film in which nematic liquid crystal is tilted and aligned (Shin Nihon) It is also possible to use “NH film” sold by Petroleum Corporation. This coating layer 233 is preferably an optical compensation layer having a negative birefringence made of a liquid crystalline compound having a discotic structural unit. The disc surface of the discotic structural unit is preferably inclined with respect to the transparent support surface, and the angle formed by the disc surface of the discotic structural unit and the transparent support surface varies in the thickness direction of the optical compensation layer. More preferably. In this embodiment, the angle formed by the disc surface of the discotic structural unit with respect to the transparent support surface increases as the distance from the transparent support side of the optical compensation layer increases in the thickness direction of the optical compensation layer. Oriented ones are also effective. The angle formed by the disc surface of the discotic structural unit with respect to the transparent support surface can be, for example, a structure that increases sequentially from the transparent support side in the range of about 5 to 50 degrees. As a specific example of an optical compensation film in which an alignment film and a discotic liquid crystal coating layer are formed on a transparent support, a “wide view” film (“WV film”) sold by Fuji Photo Film Co., Ltd. "May be expressed as").

(Transparent protective film)
Examples of the transparent protective film 22 include a cellulose resin film, a cycloolefin resin film, a polyester resin film such as polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate, a polycarbonate resin film, an acrylic resin film, and a polypropylene resin. Examples thereof include films that have been widely used in the art, such as resin films.

  The transparent protective film 22 is preferably transparent and has high chemical resistance. For example, a cellulose resin film is preferable.

  The cellulose resin that can be used for the transparent protective film is preferably a cellulose acetate resin. The cellulose acetate-based resin is a part of cellulose or a complete acetate ester, and examples thereof include triacetyl cellulose, diacetyl cellulose, and cellulose acetate propionate.

  Examples of such a cellulose acetate resin film include commercially available products such as Fujitac (registered trademark) TD80 (manufactured by Fuji Film Co., Ltd.), Fujitac (registered trademark) TD80UF (manufactured by Fuji Film Co., Ltd.), Fujitac ( Registered trademark TD80UZ (manufactured by Fuji Film Co., Ltd.), KC8UX2M (manufactured by Konica Minolta Opto Co., Ltd.), KC4UY (manufactured by Konica Minolta Opto Co., Ltd.) and the like can be suitably used.

  In addition, a cellulose acetate-based resin film imparted with retardation characteristics is also preferably used. As a commercially available cellulose acetate-based resin film imparted with such retardation characteristics, WV BZ 438 (manufactured by Fuji Film Co., Ltd.), KC4FR-1 (manufactured by Konica Minolta Opto, Inc.) and the like can be mentioned. Cellulose acetate is also called acetyl cellulose or cellulose acetate.

  The cellulose acetate-based resin film is subjected to saponification treatment in order to enhance the adhesion to the polarizing film 21, particularly when the cellulose acetate-based resin film is laminated with the polarizing film 21 using an aqueous adhesive. As the saponification treatment, a method of immersing in an alkaline aqueous solution such as sodium hydroxide or potassium hydroxide can be employed.

  When the transparent protective film as described above is in a roll state, the films tend to adhere to each other and easily cause blocking. Therefore, the roll end portion is usually subjected to uneven processing, or a ribbon is inserted into the end portion. In addition, a roll wound by pasting a protective film is used.

  The transparent protective film is preferably thin, but if it is too thin, the strength is lowered and the processability is poor. On the other hand, when it is too thick, problems such as a decrease in transparency and a longer curing time after lamination occur. Therefore, the suitable thickness of a transparent protective film is 5-100 micrometers, for example, Preferably it is 10-80 micrometers, More preferably, it is 20-40 micrometers.

(Adhesive layer)
In the polarizing plate 20, the polarizing film 21 and the transparent protective film 22 or the optical compensation film 23 are bonded via an adhesive layer made of an aqueous adhesive, for example. Examples of the adhesive that bonds the polarizing film 21 to the transparent protective film 22 or the optical compensation film 23 include a water solvent adhesive, an organic solvent adhesive, a hot melt adhesive, and a solventless adhesive. Can be used. Examples of aqueous solvent adhesives include polyvinyl alcohol resin aqueous solutions and aqueous two-component urethane emulsion adhesives, and examples of organic solvent adhesives include two-component urethane adhesives, and solventless adhesives. Examples of the agent include a one-pack type urethane adhesive and an epoxy adhesive.

  When an aqueous polyvinyl alcohol resin solution is used, the polyvinyl alcohol resin used as an adhesive includes a vinyl alcohol homopolymer obtained by saponifying polyvinyl acetate, which is a homopolymer of vinyl acetate, as well as vinyl acetate and this. And vinyl alcohol copolymers obtained by saponifying a copolymer with another copolymerizable monomer, and modified polyvinyl alcohol polymers obtained by partially modifying the hydroxyl groups. A polyhydric aldehyde, a water-soluble epoxy compound, a melamine compound, a zirconia compound, a zinc compound, or the like may be added to the adhesive as an additive. When such a water-based adhesive is used, the adhesive layer obtained therefrom is usually 1 μm or less.

  Moreover, a photocurable adhesive agent can also be used as an adhesive agent when the polarizing film 21 and the transparent protective film 22 or the optical compensation film 23 are bonded. Examples of the photocurable adhesive include a mixture of a photocurable epoxy resin and a photocationic polymerization initiator.

(Adhesive layer)
In the polarizing plate 20, the polarizing film 21 and the transparent protective film 22 or the optical compensation film 23 are, for example, through an adhesive layer similar to the adhesive layer 50 used for bonding the polarizing plate 20 and the separate film 40. It can also be pasted.

(Other optical layers)
The polarizing plate 20 may be laminated with other optical layers not shown in practical use. Or the transparent protective film 22 or the optical compensation film 23 may have the function of these optical layers. Examples of other optical layers include a reflective polarizing film that transmits certain types of polarized light and reflects polarized light that exhibits the opposite properties, a film with an antiglare function having an uneven shape on the surface, and a surface antireflection function. Examples thereof include an attached film, a reflective film having a reflective function on the surface, a transflective film having both a reflective function and a transmissive function, a viewing angle compensation film, and a light diffusion film that diffuses light.

  Commercially available products corresponding to reflective polarizing films that transmit certain types of polarized light and reflect polarized light that exhibits the opposite properties include DBEF (available from 3M, Sumitomo 3M Co., Ltd.), APF (Available from 3M, available from Sumitomo 3M Limited). Examples of the viewing angle compensation film include an optical compensation film coated with a liquid crystal compound on the surface of the substrate and oriented, a retardation film made of a polycarbonate resin, and a retardation film made of a cyclic polyolefin resin. Commercially available products corresponding to an optical compensation film coated with a liquid crystal compound on the substrate surface and oriented are WV film (Fuji Film Co., Ltd.), NH film (Shin Nippon Oil Co., Ltd.), NR Examples include films (manufactured by Nippon Oil Corporation). Commercial products corresponding to retardation films made of cyclic polyolefin resins include Arton (registered trademark) film (manufactured by JSR Corporation), Essina (registered trademark) (manufactured by Sekisui Chemical Co., Ltd.), Zeonor ( Registered trademark) film (manufactured by Optes Co., Ltd.).

  When the polarizing plate 20 is used as a viewing side polarizing plate of a liquid crystal display device, these optical layers are preferably laminated on the surface of the transparent protective film 22 opposite to the surface bonded to the polarizing film 21. Is done. The transparent protective film 22 and these optical layers are bonded via the same adhesive layer or pressure-sensitive adhesive layer as described in the bonding of the transparent protective film 22 or the optical compensation film 23 and the polarizing film 11 described above. be able to.

<Production method of polarizing film>
Although the manufacturing method of the polarizing film 21 is not limited, Hereinafter, two typical methods are illustrated. The first method is a method in which a polyvinyl alcohol-based resin film is uniaxially stretched in air or an inert gas, followed by solution treatment in the order of a swelling step, a dyeing step, a boric acid treatment step, and a water washing step, followed by drying. is there. In the second method, an unstretched polyvinyl alcohol-based resin film is solution-treated with an aqueous solution in the order of a swelling step, a dyeing step, a boric acid treatment step, and a water washing step, and wetted in the boric acid treatment step and / or the previous step This is a method of performing uniaxial stretching and finally drying.

  In any method, uniaxial stretching may be performed in one step or in two or more steps. As a stretching method, a known method can be adopted. For example, stretching between rolls in which stretching is performed with a peripheral speed difference between two nip rolls that transport a film, for example, heat described in Japanese Patent No. 2731813. Examples thereof include a roll stretching method and a tenter stretching method. The order of the steps is basically as described above, but there are no restrictions on the number of treatment baths, treatment conditions, and the like. Moreover, you may add the process which is not described in the said 1st and 2nd method for another objective. Examples of such processes include boric acid treatment in a solution containing boric acid, followed by immersion treatment (iodide treatment) with an aqueous iodide solution not containing boric acid or zinc chloride containing no boric acid. The process etc. which perform the immersion process (zinc process) by the aqueous solution to perform are mentioned.

  The swelling step is performed for the purpose of removing foreign matter from the film surface, removing the plasticizer in the film, imparting easy dyeability in the next step, and plasticizing the film. The processing conditions are determined within a range in which these objects can be achieved, and in a range in which problems such as extreme dissolution and devitrification of the base film do not occur. When the film previously stretched in the gas is swollen, for example, the film is immersed in an aqueous solution at 20 to 70 ° C, preferably 30 to 60 ° C. The immersion time of the film is 30 to 300 seconds, preferably 60 to 240 seconds. In order to swell the unstretched raw film from the beginning, the film is immersed in an aqueous solution of 10 to 50 ° C., preferably 20 to 40 ° C., for example. The immersion time of the film is 30 to 300 seconds, preferably 60 to 240 seconds.

  In the swelling process, problems such as swelling of the film in the width direction and wrinkling of the film are likely to occur, so known widening of widening roll (expander roll), spiral roll, crown roll, cross guider, bend bar, tenter clip, etc. It is preferable to transport the film while removing wrinkles of the film with an apparatus. In order to stabilize the film transport in the bath, the water flow in the swelling bath is controlled by an underwater shower, EPC (Edge Position Control device: a device that detects the edge of the film and prevents the film from meandering), etc. It is also useful to use together. In this step, since the film swells and expands in the film transport direction, it is preferable to take measures such as controlling the speed of the transport roll before and after the treatment tank in order to eliminate the sag of the film in the transport direction. In addition to pure water, the swelling treatment bath used is boric acid (described in JP-A-10-153709), chloride (described in JP-A-06-281816), inorganic acid, inorganic salt, water-soluble An aqueous solution to which an organic solvent, alcohol or the like is added in an amount of 0.01 to 0.1% by weight can also be used.

  The dyeing step with the dichroic dye is performed for the purpose of adsorbing and orienting the dichroic dye on the film. The processing conditions are determined within a range in which these objects can be achieved, and in a range in which problems such as extreme dissolution and devitrification of the base film do not occur. When iodine is used as the dichroic dye, for example, iodine / potassium iodide / water = 0.003 to 0.2 / 0.1 in a weight ratio of 10 to 45 ° C., preferably 20 to 35 ° C. An immersion treatment is performed for 30 to 600 seconds, preferably 60 to 300 seconds, using an aqueous solution having a concentration of 10/100. Instead of potassium iodide, other iodides such as zinc iodide may be used. Other iodides may be used in combination with potassium iodide. Furthermore, compounds other than iodide, such as boric acid, zinc chloride, cobalt chloride, etc. may coexist. When boric acid is added, it is distinguished from the following crosslinking step in that it contains iodine. Any dye containing 0.003 parts by weight or more of iodine with respect to 100 parts by weight of water can be regarded as a dyeing tank.

  When a water-soluble dichroic dye is used as the dichroic dye, for example, dichroic dye / water = 0.001 to 0.1 / by weight ratio under a temperature condition of 20 to 80 ° C., preferably 30 to 70 ° C. A 100-concentration aqueous solution is used for 30 to 600 seconds, preferably 60 to 300 seconds. The aqueous solution of the dichroic dye to be used may contain a dyeing assistant or the like, and may contain, for example, an inorganic salt such as sodium sulfate, a surfactant or the like. The dichroic dye may be used alone, or two or more dichroic dyes may be used in combination.

  As described above, the film may be stretched in a dyeing tank. Stretching is performed by a method of giving a peripheral speed difference between the nip rolls before and after the dyeing tank. Similarly to the swelling step, a widening roll (expander roll), a spiral roll, a crown roll, a cross guider, a bend bar, and the like can be installed in the dyeing bath and / or at the bath entrance / exit.

  The boric acid treatment step is performed by immersing a polyvinyl alcohol resin film dyed with a dichroic dye in an aqueous solution containing 1 to 10 parts by weight of boric acid with respect to 100 parts by weight of water. When the dichroic dye is iodine, it is preferable to contain 1 to 30 parts by weight of iodide. Examples of iodide include potassium iodide and zinc iodide. Further, compounds other than iodide, such as zinc chloride, cobalt chloride, zirconium chloride, sodium thiosulfate, potassium sulfite, sodium sulfate, etc. may coexist.

  The boric acid treatment step is carried out for water resistance by crosslinking or hue adjustment (for example, to prevent bluish tint). When a boric acid treatment step is performed for water resistance, a cross-linking agent such as glyoxal or glutaraldehyde can be used in addition to or together with boric acid, if necessary. In addition, the boric acid treatment for water resistance may be referred to by names such as water resistance treatment, crosslinking treatment, and immobilization treatment. In addition, boric acid treatment for hue adjustment may be referred to by a name such as complementary color treatment or re-dyeing treatment.

  This boric acid treatment step is performed by appropriately changing the concentrations of boric acid and iodide and the temperature of the treatment bath according to the purpose. The boric acid treatment step for water resistance and the boric acid treatment step for hue adjustment are not particularly distinguished, but can be carried out under the following conditions. When the raw film is subjected to a swelling step, a dyeing step, and a boric acid treatment step, and the boric acid treatment step is aimed at water resistance by cross-linking, boric acid is added to 3 parts by weight of 100 parts by weight of water. A boric acid treatment bath containing 10 parts by weight and 1 to 20 parts by weight of iodide is used, and is usually performed at a temperature of 50 to 70 ° C, preferably 55 to 65 ° C. The immersion time is 90 to 300 seconds. In addition, when performing a dyeing process and a boric-acid treatment process to the film extended | stretched previously, the temperature of a boric-acid treatment bath is 50-85 degreeC normally, Preferably it is 55-80 degreeC.

  You may make it perform the boric-acid treatment process for a hue adjustment after the boric-acid treatment process for water resistance. For example, when the dichroic dye is iodine, a boric acid treatment bath containing 1 to 5 parts by weight of boric acid and 3 to 30 parts by weight of iodide for 100 parts by weight of water is used for this purpose. Usually, it is carried out at a temperature of 10 to 45 ° C. The immersion time is usually 3 to 300 seconds, preferably 10 to 240 seconds. The subsequent boric acid treatment step for adjusting the hue is usually performed at a lower boric acid concentration, a higher iodide concentration, and a lower temperature than the boric acid treatment step for water resistance.

  These boric acid treatment steps may consist of a plurality of steps and are usually carried out in 2 to 5 steps. In this case, the aqueous solution composition and temperature of each boric acid treatment tank to be used may be the same or different within the above-described range. The boric acid treatment step for water resistance and the boric acid treatment step for hue adjustment may be performed in a plurality of steps, respectively.

  In the boric acid treatment step, the film may be stretched as in the dyeing step. The final cumulative draw ratio is 4 to 7 times, preferably 4.5 to 6.5 times. The cumulative stretching ratio here means how long the reference length in the length direction of the original film is in all the films after the completion of the stretching process. For example, it is 1 m in the original film. If the portion is 5 m in all the films after the stretching treatment, the cumulative stretching ratio at that time is 5 times.

  After the boric acid treatment step, a water washing step is performed. The water washing step is performed by immersing the polyvinyl alcohol resin film subjected to the boric acid treatment step for water resistance and / or hue adjustment in water, spraying water as a shower, or combining immersion and spraying. The temperature of the water in the washing step is usually 2 to 40 ° C., and the immersion time is 2 to 120 seconds.

  Here, in each step after the stretching treatment, tension control may be performed so that the tension of the film becomes substantially constant. Specifically, when stretching is completed in the dyeing process, tension control is performed in the subsequent boric acid treatment process and the water washing process. When stretching is completed in the previous step of the dyeing step, tension control is performed in subsequent steps including the dyeing step and the boric acid treatment step. When the boric acid treatment step comprises a plurality of boric acid treatment steps, the film is stretched in the boric acid treatment step from the beginning or the first to the second step, and the next boric acid treatment step after the boric acid treatment step in which the stretching treatment has been performed. Tension control is performed in each step from the acid treatment step to the water washing step, or the above-described film is stretched in the boric acid treatment step from the first to the third step, and the boric acid next to the boric acid treatment step in which the stretching treatment is performed. It is preferable to perform tension control in each step from the treatment step to the water washing step. Industrially, in each step from the boric acid treatment step to the water washing step following the boric acid treatment step in which the film was stretched in the boric acid treatment step from the first or first to the second stage, and the stretching step was performed. More preferably, tension control is performed. In addition, when performing the above-described iodide treatment or zinc treatment after the boric acid treatment, tension control can also be performed for these steps.

  As the nip roll for controlling the tension and the guide roll for controlling the film conveyance direction, a rubber roll, a stainless steel polishing roll, a sponge rubber roll, and the like can be used.

  The tension in each step from the swelling step to the water washing step may be the same or different. The tension to the film in the tension control is not particularly limited, and is appropriately set within a range of 150 to 2000 N / m, preferably 600 to 1500 N / m per unit width. When the tension is less than 150 N / m, the film is likely to be wrinkled. On the other hand, when the tension exceeds 2000 N / m, problems such as film breakage and life reduction due to bearing wear occur. The tension per unit width is calculated from the film width near the entrance of the process and the tension value of the tension detector. In addition, when tension control is performed, there are cases where the film is inevitably slightly stretched or shrunk, but in the present invention, this is not included in the stretching process.

  A drying process is performed at the end of the manufacturing process of a polarizing film. The drying treatment is preferably carried out in a large number of stages by changing the tension little by little, but is usually carried out in 2 to 3 stages due to restrictions on equipment. When performed in two stages, the tension in the front stage is preferably set in the range of 600 to 1500 N / m, and the tension in the rear stage is preferably set in the range of 250 to 1200 N / m. When the tension becomes too large, the film breaks more, and when it becomes too small, the generation of wrinkles increases, which is not preferable. Moreover, it is preferable to set the drying temperature of the former stage from the range of 30-90 degreeC, and the drying temperature of the latter stage from the range of 40-100 degreeC. If the temperature is too high, the film will be ruptured and the optical properties will be deteriorated. If the temperature is too low, streaks will increase, which is not preferable. The drying treatment temperature can be 60 to 600 seconds, for example, and the drying time in each stage may be the same or different. If the time is too long, it is not preferable in terms of productivity, and if the time is too short, drying is insufficient, which is not preferable.

  As described above, the polyvinyl alcohol-based resin film is subjected to uniaxial stretching, dyeing with a dichroic dye, and boric acid treatment to obtain a polarizing film. The thickness of this polarizing film is usually 5 to 50 μm.

<Method for producing laminate>
The method for producing a laminate of the present invention comprises a polarizing plate, a surface protective film bonded to one surface of the polarizing plate, and a separate bonded to the other surface of the polarizing plate via an adhesive layer. It is a manufacturing method of a laminated body provided with a film, Comprising: It has the following (i) polarizing plate manufacturing process and (ii) laminated body bonding process.

In the polarizing plate production process, the polarizing plate is a polarizing plate in an atmosphere where the moisture content R ₁ (%) immediately before bonding the surface protective film and the separate film to the polarizing plate is 23 ° C. and 55% relative humidity. When the equilibrium moisture content is R ₀ (%), the following formula (1):
−0.85 (%) ≦ R ₁ (%) − R ₀ (%) ≦ −0.2 (%) Formula (1)
It is the process of manufacturing so that this relationship may be satisfy | filled.

  The laminate bonding step is a step of bonding a surface protective film to one surface of the polarizing plate and bonding a separate film via an adhesive layer to the other surface of the polarizing plate.

  FIG. 2 is a schematic view showing an example of an apparatus for producing a laminate according to the present invention. The case where the laminated body 1 shown in FIG. 1 is manufactured using the apparatus 60 shown in FIG. 2 is demonstrated. First, the transparent protective film 22, the polarizing film 21, and the optical compensation film 23 are laminated in this order via an adhesive layer made of, for example, a water-based adhesive, and are passed between the two nip rolls 61 and 62 to pass each other. A polarizing plate laminating step for laminating is performed. Next, a drying process is performed by passing the inside of the drying furnace 63. The polarizing plate 20 is manufactured through the above steps. That is, a polarizing plate manufacturing process has a polarizing plate bonding process and a drying process.

  Next, using the backup roll 64, the surface protective film 30 is bonded to the surface of the transparent protective film 22 of the polarizing plate 20, and further, the optical compensation film 23 of the polarizing plate 20 using the constituent member (not shown). The laminated body bonding process which bonds the separate film 40 to the surface via the adhesive layer 50 is performed.

  Below, the detail of (i) polarizing plate manufacturing process and (ii) laminated body bonding process is demonstrated.

(I) Polarizing plate manufacturing process (polarizing plate bonding process)
As the two nip rolls used in the polarizing plate bonding step, a rubber roll, a stainless steel polishing roll, a sponge rubber roll, or the like can be used. Among them, the rubber roll is preferably made of NBR or the like, and the stainless steel polishing roll is preferably made of SUS304, SUS316 or the like. Moreover, a cylindrical roll may be used as a nip roll, and a crown roll may be used.

  The moisture content of the polarizing plate 20 can be adjusted by adjusting the push-in amount of the nip rolls 61 and 62. When the amount of pushing is small, the amount of adhesive between the polarizing film 21 and the transparent protective films 22 and 23 tends to increase, and the moisture content of the polarizing plate 20 tends to increase. Defects may occur, which is not preferable. Moreover, when the pushing amount between the nip rolls 61 and 62 is too large, the moisture content tends to be small, which is not preferable. The temperature in the polarizing plate bonding step is usually in the range of about 15 to 30 ° C. In addition, an adhesive agent is apply | coated at the temperature of 15-40 degreeC after the preparation, for example.

  In the above description, the method of simultaneously bonding the transparent protective film 22 and the optical compensation film 23 to the polarizing film 21 has been described. However, in the polarizing film 21, it is possible to sequentially bond one surface at a time using a nip roll. . In addition, it is preferable to bond both surfaces simultaneously from the viewpoint of production efficiency.

(Drying process)
A drying process is performed in order to remove the water contained in an aqueous adhesive, when an aqueous adhesive is used. Drying is performed by continuously passing through a drying furnace maintained at an appropriate temperature. For example, the drying can be performed while continuously passing through the drying furnace, but is not limited thereto.

  In the drying process in the drying furnace 63, it is preferable that the polarizing plate is controlled to stay in an atmosphere of 60 ° C. or higher and 90 ° C. or lower for a predetermined time or longer. When the drying time is less than the predetermined time, the drying becomes insufficient, and the manufactured polarizing plate may have a large curl. The predetermined time at this time is preferably 210 seconds or more, and preferably 600 seconds or less from the viewpoint of productivity.

(Moisture content measurement)
Polarizing plate used in the method for producing a laminate according to the present invention, moisture content R ₁ immediately before laminating the surface protection film and the separate film (%) satisfies the relation of the equation (1). In the apparatus 60 shown in FIG. 2, the moisture content R ₁ (%) of the polarizing plate 20 just before the surface protective film and the separate film are bonded is measured using an infrared moisture meter at a point P1 indicated by an arrow. After measuring the value, the moisture content R ₁ (%) can be obtained using the conversion formula as described above. Point P1 is a point immediately before the surface protective film and the separate film are bonded to the polarizing plate.

(Ii) Laminate Bonding Step The laminate of the present invention has a surface protective film bonded to one surface of the polarizing plate prepared as described above, and a separate film via an adhesive layer on the other surface. Is pasted. The method for forming the pressure-sensitive adhesive layer used for laminating the separate film on the polarizing plate is not particularly limited, and includes the above-mentioned base polymer on a surface different from the surface on which the protective film is laminated. After applying a solution containing each component and drying to form a pressure-sensitive adhesive layer, it may be obtained by laminating a separate film that has been subjected to a release treatment such as a silicone-based adhesive, or a pressure-sensitive adhesive on the separate film After forming the layer, it may be transferred to a polarizing plate and laminated. Moreover, when forming an adhesive layer on a polarizing plate, you may perform an adhesion | attachment process, for example, a corona treatment, etc. to at least one of a polarizing plate and an adhesive layer as needed. The surface of the pressure-sensitive adhesive layer on the side opposite to the polarizing plate is protected by the separation film that has been subjected to the release treatment as described above, and the separation film is applied to the liquid crystal cell or other optical film. It is peeled off before the board is bonded.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

<Examples and Comparative Examples>
(Preparation of polarizing film)
A polyvinyl alcohol film having an average polymerization degree of about 2,400 and a saponification degree of 99.9 mol% or more and a thickness of 75 μm is stretched while being immersed and swollen in pure water at 30 ° C. while maintaining a tension state. The film was stretched in the longitudinal direction up to a magnification of 1.3. The polyvinyl alcohol film was dyed with an aqueous solution having a mass ratio of iodine / potassium iodide / water at 30 ° C. of 0.05 / 2/100 while maintaining the above draw ratio. While performing a crosslinking treatment with an aqueous solution having a potassium fluoride / boric acid / water mass ratio of 12/5/100, the film was stretched to a total magnification of 5.6 times and then washed with pure water at 12 ° C. The polyvinyl alcohol film after washing was dried at 65 ° C. to obtain a polarizing film in which iodine was adsorbed and oriented on polyvinyl alcohol.

(Preparation of adhesive)
Separately, in 100 parts by weight of water, 1.8 parts by weight of carboxyl group-modified polyvinyl alcohol (“Kuraray Poval KL318” manufactured by Kuraray Co., Ltd.) and a water-soluble polyamide epoxy resin (“Sumi” manufactured by Sumika Chemtex Co., Ltd.) 0.9 parts by weight of Resin Resin 650 "(aqueous solution having a solid content concentration of 30% by weight)) was dissolved to prepare a polyvinyl alcohol-based resin adhesive.

(Preparation of polarizing plate)
An optical compensation film (“WV FILM Wide View EA80” (trade name), manufactured by Fuji Film Co., Ltd.) having a thickness of 83 μm is provided on one side of the polarizing film obtained previously, and triacetyl cellulose is provided on the other side. A transparent protective film made of resin having a thickness of 83 μm (“Matte Hard Coat TAC Film DTAC AG6 UV80H-25W (H)” (trade name), manufactured by Dai Nippon Printing Co., Ltd.) is used for each of the above two adhesives. Bonding was performed by passing between two nip rolls to obtain a laminated film. For the examples and comparative examples, the push amounts of the two nip rolls were set to 700 and 1000 μm as shown in Table 1.

  The laminated film was sequentially passed through a drying furnace (three stages in total) maintained at a predetermined temperature and dried to obtain a polarizing plate. The temperature of the first stage drying furnace was about 50 ° C., and the temperature of the second stage drying furnace was about 80 ° C. The temperature of the third stage drying furnace was about 45 ° C. The residence time of the second stage drying furnace was 222 seconds.

(Measurement of moisture content of polarizing plate)
For the polarizing plate, at the time immediately before laminating the surface protection film and the separate film, by measuring the water content measurements was calculated moisture content R ₁ a (%) by the method described above. The equilibrium water content R ₀ (%) of this polarizing plate was also measured and calculated by the method described above. Table 1 shows the values of water content R ₁ (%), equilibrium water content R ₀ (%), and water content R ₁ (%) − equilibrium water content R ₀ (%) calculated for each polarizing plate.

(Production of laminate)
A surface protective film with a pressure-sensitive adhesive layer (NBO-0424, manufactured by Fujimori Kogyo Co., Ltd.) having a thickness of 60 μm is provided on the triacetylcellulose side of the polarizing plate obtained above, and then an acrylic pressure-sensitive adhesive is provided on the optical compensation film side. Each laminated film of each example and each comparative example shown in Table 1 (surface protective film and surface protective film) was obtained by laminating a separate film (MRV-38, manufactured by Mitsubishi Plastics Co., Ltd.) having a thickness of 25 μm and a pressure-sensitive adhesive layer of A polarizing plate on which a separate film with an adhesive was laminated was obtained. In addition, the moisture content of the polarizing plate in the obtained laminated body is the same value as the moisture content just before bonding.

<Evaluation>
The following evaluation was performed about each laminated body produced above.

(Evaluation of stripes on the adhesive layer)
A 3 inch size measurement sample was cut out from each of the above laminates, and stored for one week in an atmosphere controlled at a temperature of 23 ° C. and a relative humidity of 55%. The measurement sample after storage was placed on a flat table, and the streaks of the pressure-sensitive adhesive layer (the pressure-sensitive adhesive layer between the polarizing plate and the separate film) of the measurement sample were visually evaluated based on the following level judgment criteria.

Level 1: When the depth of the deepest streaks generated in the pressure-sensitive adhesive layer is less than 3 mm Level 2: When the depth of the deepest streaks generated in the pressure-sensitive adhesive layer is about 5 mm ± 2 mm Level 3: Generated in the pressure-sensitive adhesive layer When the depth of the deepest stripe is about 8 to 15 mm Level 4: When the depth of the deepest stripe generated in the pressure-sensitive adhesive layer is deeper than Level 3 The results are shown in Table 1.

As shown in Table 1, level 3 was added to the pressure-sensitive adhesive layer of the comparative laminate having “moisture content R ₁ (%) − equilibrium water content R ₀ (%)” of the polarizing plate of less than −0.85. This streak was observed. On the other hand, in the example in which “moisture content R ₁ (%) − equilibrium water content R ₀ (%)” of the polarizing plate is −0.85 (%) or more, the curl amount of the laminate is small, and the pressure-sensitive adhesive layer No level 3 streaking was observed. Therefore, when the “moisture content R ₁ (%) − equilibrium water content R ₀ (%)” of the polarizing plate satisfies the relationship of the above formula (1), the generation of streaks in the pressure-sensitive adhesive layer can be suppressed. Conceivable.

  DESCRIPTION OF SYMBOLS 1 Laminated body, 20 Polarizing plate, 21 Polarizing film, 22 Transparent protective film, 23 Optical compensation film, 231 Transparent support body, 232 Orientation film, 233 Coating layer, 30 Surface protective film, 40 Separate film, 50 Adhesive layer, 61 , 62 Nip roll, 63 Drying furnace, 64 Backup roll.

Claims (4)

Manufacture of a laminate comprising a polarizing plate, a surface protective film bonded to one surface of the polarizing plate, and a separate film bonded to the other surface of the polarizing plate via an adhesive layer A method,
A polarizing plate manufacturing process for manufacturing the polarizing plate;
A laminate laminating step of laminating the surface protective film on one surface of the polarizing plate and laminating the separate film via the pressure-sensitive adhesive layer on the other surface of the polarizing plate; Prepared,
The polarizing plate includes a polarizing film made of a polyvinyl alcohol-based resin, and a transparent protective film bonded to one surface of the polarizing film with a water-based adhesive ,
The polarizing plate manufacturing process, and the polarizing film even without low, together by passing between the two rolls in the state in which the said transparent protective film are laminated in this order via an adhesive layer comprising a water-based adhesive viewing including the bonding to a polarizing plate bonding step,
The water content of the polarizing plate immediately before bonding of the surface protective film and the separate film to the polarizing plate is R ₁ (%), and the equilibrium water content of the polarizing plate in an atmosphere having a temperature of 23 ° C. and a relative humidity of 55%. The manufacturing method of a laminated body which adjusts the pushing amount of said two rolls so that the relationship of following formula (1) may be satisfy | filled in the said polarizing plate bonding process when a rate is set to _R0 (%) .
−0.85 (%) ≦ R ₁ (%) − R ₀ (%) ≦ −0.2 (%) Formula (1) The polarizing plate further includes an optical compensation film bonded to the surface of the polarizing film opposite to the transparent protective film with a water-based adhesive ,
In the polarizing plate bonding step, the optical compensation film, an adhesive layer made of the aqueous adhesive , the polarizing film, an adhesive layer made of the aqueous adhesive, and the transparent protective film in this order. passing between the two rolls in a stacked state, method for producing a laminate according to claim 1. The optical compensation film includes a transparent support made of a cellulose-based resin, an alignment film formed on one surface of the transparent support, and a liquid crystal compound formed on the surface of the alignment film opposite to the transparent support. The manufacturing method of the laminated body of Claim 2 which has a coating layer containing this, and is bonded together by said one surface of the said polarizing film at the transparent support side. The said polarizing plate manufacturing process is a manufacturing method of the laminated body of any one of Claims 1-3 including the drying process which makes the said polarizing plate retain for 210 second or more in 60 degreeC or more and 90 degrees C or less atmosphere.

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