JP2009244486A - Phase difference integrated type composite polarizing plate, and image display device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image display device which has excellent display quality and is flat and free of peeling even under a humidification or heating condition, and a phase difference integrated type composite polarizing plate which is disposed on both sides of a liquid crystal panel of a liquid crystal display device to reduce curvature and distortion. <P>SOLUTION: The phase difference integrated type composite polarizing plate has a protection film laminated on at least one surface of a polarizer formed of a polyvinyl alcohol-based resin film, and has (n) layers of phase difference films with (n) layers of an adhesive interposed on the other surface when the protection film is laminated on one surface of the polarizer or outside one protection film when protection films are laminated on both the surfaces of the polarizer, and the adhesive is disposed even outside the phase difference film farthest from the polarizer to form (n+1) layers of the adhesive in total, the storage modulus G' of the fist adhesive counted from the polarizer side at an angular frequency of 0.1 (1/sec.) at 85°C being smaller than those of the second and above adhesives, where (n) is an integer of not less than 1. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a retardation-integrated composite polarizing plate used for a liquid crystal panel or an organic electroluminescent panel. The present invention also relates to an image display device using the retardation-integrated composite polarizing plate.

  In recent years, due to various advantages such as low power consumption, low voltage operation, light weight, and thin shape, liquid crystal display devices (LCD), organic electroluminescence display devices and touch panel type display devices are mobile phones, personal digital assistants (Personal Digital Assistants): Applications as information display devices such as PDAs), personal computers and televisions are rapidly increasing.

  Plastic display panels have come to be used for further weight reduction, thickness reduction, and flexibility, but there is a problem that warpage and distortion are larger than conventional glass panels. There is a need for a solution.

  In the case of a liquid crystal display device, the cause of warping is due to expansion and contraction due to heating and moisture absorption of a liquid crystal panel having a pair of transparent substrates that sandwich the liquid crystal and various optical films laminated on both sides of the panel. This occurs due to a difference in distortion balance between the image viewing side (front side) and the backlight side (rear side). Various techniques have been tried to reduce such warpage.

  For example, it is known that the distortion of the film can be suppressed by softening the adhesive for laminating each optical film. For example, the adhesive used for laminating the liquid crystal panel and the optical film has a certain low elastic modulus adhesion. A method is known in which distortion of a film is suppressed by using an agent to reduce frame loss (Patent Document 1). In addition, there is also known a method for suppressing the occurrence of warpage under wet heat conditions by using a pressure-sensitive adhesive that causes displacement when the polarizing plate and the liquid crystal panel are bonded (Patent Document 2). However, when a low modulus adhesive is used for pasting, reliability is impaired and peeling may occur or foam may occur under heating conditions.

  Moreover, the method of making the interlayer thickness of a panel and a polarizer into 90 micrometers or less (patent document 3), and the method of making the absorption axis angle difference of the polarizing plate of the visual recognition side of a liquid crystal panel and a back side into 50 degrees or less (patent document 4). However, in certain liquid crystal modes, sufficient optical compensation cannot be obtained and the display quality may deteriorate.

JP 2001-335767 A (Claims) JP 2003-50313 A (Claims) JP 2006-292939 A (Claims) JP 2002-221724 A (Claims)

  The inventor of the present invention has achieved the present invention as a result of intensive studies on further warpage and distortion reduction while maintaining good display quality in an image display device using a plastic substrate. That is, an object of the present invention is to provide an image display device that has good display quality and is flat and does not peel off even under humidification or heating conditions. Another object of the present invention is to provide a retardation-integrated composite polarizing plate which is effective in reducing warpage and distortion by being disposed on both sides of a liquid crystal panel of such a liquid crystal display device.

  In order to achieve the above object, according to the present invention, when a protective film is laminated on at least one side of a polarizer made of a polyvinyl alcohol-based resin film via an adhesive and a protective film is laminated on one side of the polarizer, the other When a protective film is laminated on both sides of the polarizer and on both sides of the polarizer, the retardation film is the farthest from the polarizer, having n retardation films on the outer side of one protective film via an n-layer adhesive. In the retardation-integrated composite polarizing plate in which an adhesive is also arranged outside the adhesive layer, and the adhesive layers are a total of n + 1 layers, the angular frequency at 85 ° C. of the first adhesive counted from the polarizer is 0.1. (1 / sec) storage elastic modulus G ′ (hereinafter simply referred to as storage elastic modulus) is smaller than that of the second and subsequent pressure-sensitive adhesives. With composite polarizing plate U) is provided. Here, n is an integer of 1 or more.

As n representing the number of retardation films, 1 or 2 is preferable.
The storage modulus of the first pressure-sensitive adhesive is preferably 1.0 × 10 ^{4 to} 6.0 × 10 ⁴ Pa.
The pressure-sensitive adhesive is preferably a (meth) acrylic pressure-sensitive adhesive having a thickness of 1 to 30 μm.

Although the composite polarizing plate of this invention can be used for various uses, it can be preferably used as an image display apparatus by bonding an image display panel.
In this case, the present invention can be suitably applied to an image display device in which the substrate constituting the image display panel is a plastic resin substrate.
The image display device can be preferably applied to a liquid crystal display device, an organic electroluminescence display device, and a touch panel display device.

  Since the retardation integrated composite polarizing plate according to the present invention can reduce the warpage and distortion of the liquid crystal panel as compared with the retardation integrated composite polarizing plate of the conventional configuration, it can be applied to plastic panels and thin glass panels. It becomes possible.

Hereinafter, the present invention will be described in detail.
1. Composite polarizer invention, the protective film over at least one surface adhesive polarizer comprising a polyvinyl alcohol-based resin film is laminated on the other surface if obtained by laminating a protective film on one surface of the polarizer, and polarization When protective films are laminated on both sides of the polarizer, there are n layers of retardation films on the outside of one protective film via n layers of adhesive, and the adhesive is also on the outside of the retardation film farthest from the polarizer. And the storage elastic modulus of the first pressure-sensitive adhesive (hereinafter referred to as the first pressure-sensitive adhesive) counted from the polarizer side is the second and subsequent layers. The present invention relates to a retardation-integrated composite polarizing plate characterized by being smaller than that of the above adhesive.
The layer number n of the retardation film laminated | stacked on a polarizer is an integer greater than or equal to 1, 1-3 are preferable, More preferably, it is 1-2.

An example of the basic layer configuration of the composite polarizing plate of the present invention, where n = 1, in which one retardation film is laminated, is shown in cross-sectional schematic views in FIGS.
1A has a transparent protective layer 12 on one surface of a polarizer 11 made of a polyvinyl alcohol-based resin, and a first retardation film (hereinafter referred to as “first adhesive film”) on the other surface with a first adhesive 21 interposed therebetween. , A first retardation film) 31 and a second pressure-sensitive adhesive (hereinafter referred to as a second pressure-sensitive adhesive) 22.
FIG. 1B is different from FIG. 1A only in that a laminated structure in which both surfaces of a polarizer 11 made of polyvinyl alcohol resin are sandwiched between transparent protective films 12 and 13 is used. It is.
In any case, the actual product preferably has a structure in which a release sheet is attached to the second pressure-sensitive adhesive 22, and the release sheet is removed prior to use and attached to the substrate.

  By combining the retardation plate and the polarizing plate in this way, it can be used as a linear polarizing plate having a viewing angle compensation function or a circular polarizing plate. When used as a linear polarizing plate, the slow axis of the first retardation film is preferably orthogonal to the absorption axis of the polarizing plate. When used as a circular polarizing plate, the slow axis of the first retardation film and the polarization The absorption axes of the plates are crossed at a predetermined angle.

Next, another example of n = 2 in which two retardation films are laminated, which is an example of a basic layer configuration of the composite polarizing plate of the present invention, is schematically shown in cross section in FIGS. 2 (a) and 2 (b). Shown in the figure.
In FIG. 2A, a polarizer 11 made of polyvinyl alcohol resin has a transparent protective layer 12 on one side, and a first retardation film 31 is laminated on the other side with a first adhesive 21 interposed therebetween. Furthermore, a second retardation film (hereinafter referred to as a second retardation film) 32 is laminated via a second adhesive 22 and has a third adhesive (hereinafter referred to as a third adhesive) 23. Structure.
FIG. 2B is different from FIG. 2A only in that a laminated structure in which both surfaces of a polarizer 11 made of polyvinyl alcohol resin are sandwiched between transparent protective films 12 and 13 is used. It is.
In either case, the actual product preferably has a structure in which a release sheet is attached to the third pressure-sensitive adhesive 23. The release sheet is removed prior to use and attached to the substrate.

In order to obtain a circular polarization state with good display quality when used as a circularly polarizing plate, the first retardation film 31 in FIG. 1 has a phase difference value of ¼ wavelength for each wavelength. It is necessary to be a phase difference film (hereinafter abbreviated as λ / 4 plate).
However, in general, a retardation film produced by stretching a polymer film cannot obtain a reverse wavelength dispersion characteristic having a retardation value of ¼ with respect to all measurement wavelengths. In many cases, a completely circular polarization state is obtained only in the wavelength range. Therefore, in order to obtain a complete circular polarization state over a wide band, at least one retardation film (hereinafter abbreviated as λ / 2 plate) having a retardation value of ½ wavelength for each wavelength, It is preferable to use a so-called broadband λ / 4 plate in which at least one λ / 4 plate is laminated.

When the present invention effectively functions as a broadband circularly polarizing plate for the above reasons, as shown in FIG. 2, the first retardation film 31 corresponding to the λ / 2 plate is interposed through the second adhesive 22. The second retardation film 32 corresponding to the λ / 4 plate is used in a laminated form.
Here, the angle setting of each slow axis when laminating the λ / 2 plate and the λ / 4 plate is not particularly limited as long as it functions as a circularly polarizing plate at a broadband wavelength. Preferably, the angle formed by the slow axes of the λ / 2 plate and the λ / 4 plate is set to approximately 60 °.

  When the composite polarizing plate of the present invention is used in an image display device, the adhesive 22 is bonded to the image display panel in FIG. 1, and the adhesive 23 is bonded to the image display panel in FIG. .

Next, each member constituting the present invention will be described in detail.
1-1. The linear polarizing plate constituting the polarizer composite polarizing plate refers to a polarizer having a protective layer laminated thereon or a single polarizer.
A polarizer has a function of selectively transmitting linearly polarized light in one direction from natural light.
For example, an iodine polarizing film in which iodine is adsorbed and oriented on a polyvinyl alcohol film, a dye polarizing film in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol film, and a dichroic dye is coated. Examples include a fixed coating type polarizer. These iodine-based polarizing films, dye-based polarizing films, and coating-type polarizers have a function of selectively transmitting linearly polarized light in one direction from natural light and absorbing linearly polarized light in the other direction. It is called a polarizer. Among these polarizers, it is preferable to use an absorption polarizer excellent in visibility, and among them, it is most preferable to use an iodine-based polarizing film excellent in polarization degree and transmittance as the polarizer. The thickness of the absorptive polarizer is about 5 to 40 μm.

When the above-described absorption polarizer is used as a material constituting an elliptically polarizing plate, it is used as a linear polarizing plate having a transparent protective layer laminated on at least one side because it is used in various environments.
The protective film used for the transparent protective layer is typified by cellulose acetate-based resin, and at least a part of cellulose is esterified, and examples thereof include triacetyl cellulose, diacetyl cellulose, and cellulose acetate propionate. It is done. Examples of commercially available triacetyl cellulose films include “Fujitack Film” (available in various grades) sold by Fuji Film Co., Ltd., “KC8UX2M”, “KC8UY” sold by Konica Minolta Opto Co., Ltd. "And" KC4UY "(both are trade names).

The polarizer and the protective film are bonded with an adhesive. As the adhesive used for bonding the polarizer and the transparent protective layer, any adhesive can be used in consideration of the respective adhesiveness.
Specific examples of the adhesive include a water solvent adhesive, an organic solvent adhesive, a hot melt adhesive, and a solventless adhesive.
Specific examples of adhesives are listed by material. Monomer / oligomer adhesives such as (meth) acrylate and oxetane; urea resin, melamine resin, phenol resin, resorcinol resin, epoxy, urethane resin Resin adhesives such as vinyl acetate resin, polyvinyl alcohol resin, acrylic resin and cellulose resin; chloroprene, nitrile rubber, styrene butadiene rubber, styrene block copolymer thermoplastic elastomer, butyl rubber, natural Examples thereof include rubber-based adhesives such as rubber-based, recycled rubber-based, chlorinated rubber-based, and silicone rubber-based; and natural adhesives such as glue and starch-based.
More specifically, as an aqueous solvent adhesive, for example, an aqueous solution of a polyvinyl alcohol resin, an aqueous two-component urethane emulsion adhesive using a urethane resin, etc., an organic solvent adhesive, for example, urethane Examples of the two-component urethane adhesive using a resin and the solventless adhesive include a one-component urethane adhesive using a urethane resin.

  The cellulose acetate-based resin film is usually subjected to saponification treatment in order to improve the adhesion with the polarizer. As the saponification treatment, a method of immersing in an alkaline aqueous solution such as sodium hydroxide or potassium hydroxide can be employed. The surface may be subjected to a surface treatment such as an antiglare treatment, a hard coat treatment, an antistatic treatment, or an antireflection treatment, depending on the application.

  After laminating the polarizer and the protective film, a drying process is performed. The drying process is performed, for example, by blowing hot air, and the temperature at that time is appropriately selected from the range of about 40 to 100 ° C., preferably 60 to 100 ° C. The drying time is about 20 to 1,200 seconds.

1-2. The retardation film is obtained by stretching a film made of a thermoplastic resin. The thermoplastic resin is not particularly limited as long as it has good transparency, and is an olefin polymer, a polyolefin polymer, a polycarbonate polymer, a polyester polymer, a polystyrene polymer, a polysulfone polymer. , Polyethersulfone polymers, polyvinyl alcohol polymers, and the like. In the case of using a cyclic olefin resin as a suitable example from the viewpoint of hygroscopicity and optical properties, for example, a thermoplastic resin having a monomer unit made of a cyclic olefin, such as norbornene or a polycyclic norbornene monomer, It can be a hydrogenated product of a cyclic olefin ring-opening polymer or a ring-opening copolymer using two or more cyclic olefins, and addition of a cyclic olefin with a chain olefin or an aromatic compound having a vinyl group A copolymer may also be used. In addition, a polar group may be introduced.

  In the case of a copolymer of a cyclic olefin and a chain olefin or an aromatic compound having a vinyl group, examples of the chain olefin include ethylene and propylene, and examples of the aromatic compound having a vinyl group Examples thereof include styrene, α-methylstyrene, and nuclear alkyl-substituted styrene. In such a copolymer, the unit of the monomer comprising the cyclic olefin may be 50 mol% or less, for example, about 15 to 50 mol%. In particular, when a terpolymer of a cyclic olefin, a chain olefin, and an aromatic compound having a vinyl group is used, the monomer unit composed of the cyclic olefin can have a relatively small amount. In such a terpolymer, the unit of monomer composed of a chain olefin is usually about 5 to 80 mol%, and the unit of monomer composed of an aromatic compound having a vinyl group is usually about 5 to 80 mol%.

Commercially available thermoplastic cyclic olefin-based resins include “Topas” sold by Ticona, Germany, “Arton” sold by JSR, and “Zeonor” sold by Nippon Zeon. ZEONOR ”and“ ZEONEX ”,“ Appel ”sold by Mitsui Chemicals, Inc. (both are trade names).
Such a cyclic olefin-based resin is formed into a film, and a known film forming method such as a solvent casting method or a melt extrusion method is appropriately used for forming the film.
Formed cyclic olefin-based resin films are also commercially available, for example, “Essina” and “SCA40” sold by Sekisui Chemical Co., Ltd., “Zeonor film” sold by Optes, There are “Arton Film” and the like (all are trade names) sold by JSR Corporation.

  The cyclic olefin-based resin film can be given an arbitrary retardation value by performing an orientation treatment by a known stretching method. Usually, stretching is performed continuously while unwinding the film from the roll, and in a heating furnace, a uniaxial or biaxial thermal stretching method can be employed in the roll traveling direction or in a direction perpendicular to the traveling direction. . As the temperature of the heating furnace, a range from the vicinity of the glass transition temperature of the cyclic olefin resin to the glass transition temperature + 100 ° C. is usually employed. The draw ratio is usually about 1.1 to 6 times, preferably 1.1 to 3.5 times. At this time, it is also possible to perform stretching such that the conveying direction and tension in the heating furnace are adjusted to incline at an arbitrary angle with respect to the width direction.

  The thickness of the cyclic olefin-based resin film and the cellulose acetate-based resin film is preferably thin. However, if it is too thin, the strength is lowered and the processability is inferior. On the other hand, if it is too thick, the transparency is lowered or the weight is large. Problems occur. Therefore, an appropriate thickness of these films is, for example, about 5 to 200 μm, and preferably 20 to 100 μm.

1-3. The pressure-sensitive adhesive for forming the pressure- sensitive adhesive layer is, for example, a polymer such as (meth) acrylic polymer, silicone polymer, polyester, polyurethane, polyamide, polyether, fluorine polymer, and rubber polymer as a base polymer. Can be appropriately selected and used.
The pressure-sensitive adhesive layer prevents foaming and peeling due to moisture absorption, reduces optical properties due to differences in thermal expansion, prevents warping of the image display panel, and, in turn, forms a high-quality and highly durable image display device. Those having low hygroscopicity and excellent heat resistance are preferred.
Among these, a (meth) acrylic polymer that is excellent in optical transparency and exhibits appropriate wettability, cohesiveness, and adhesive pressure-sensitive adhesive properties is preferable.

The (meth) acrylic polymer refers to a polymer containing alkyl (meth) acrylate as a main monomer unit. In the present specification, acrylate or / and methacrylate is represented as (meth) acrylate.
As for carbon number of the alkyl group in alkyl (meth) acrylate, the thing of 1-12 is preferable, More preferably, it is C4-C12 alkyl (meth) acrylate of an alkyl group. Specific examples of the alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, and isononyl (meth) acrylate. And lauryl (meth) acrylate and the like.
Alkyl (meth) acrylates can be used alone or in combination.

The (meth) acrylic polymer may be a copolymer of an alkyl (meth) acrylate and a monomer copolymerizable therewith (hereinafter referred to as a copolymerization monomer).
The copolymerization ratio of the copolymerization monomer is not particularly limited, but is preferably about 0.1 to 50% by weight with respect to all monomer units of the (meth) acrylic polymer.

  Examples of the copolymerization monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, (meth Hydroxyl group-containing monomers such as 8-hydroxyoctyl acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate and (4-hydroxymethylcyclohexyl) -methyl acrylate; (meth) acrylic acid And carboxyl group-containing monomers such as carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid. In addition, acid anhydride group-containing monomers such as maleic anhydride and itaconic anhydride; caprolactone adducts of acrylic acid; styrene sulfonic acid and allyl sulfonic acid, 2- (meth) acrylamide-2-methylpropane sulfonic acid, (meth) Examples thereof include sulfonic acid group-containing monomers such as acrylamide propanesulfonic acid, sulfopropyl (meth) acrylate, (meth) acryloyloxynaphthalene sulfonic acid; and phosphoric acid group-containing monomers such as 2-hydroxyethylacryloyl phosphate.

  Moreover, a nitrogen-containing vinyl monomer is mention | raise | lifted. For example, maleimide, N-cyclohexylmaleimide, N-phenylmaleimide; N-acryloylmorpholine; (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N-hexyl ( (N-substituted) such as (meth) acrylamide, N-methyl (meth) acrylamide, N-butyl (meth) acrylamide, N-butyl (meth) acrylamide, N-methylol (meth) acrylamide, N-methylolpropane (meth) acrylamide, etc. ) Amide monomer; aminoethyl (meth) acrylate, aminopropyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, t-butylaminoethyl (meth) acrylate, 3- (3- Pyridinyl) propyl (meth) acrylate (Meth) acrylic acid alkylaminoalkyl monomers; (meth) acrylic acid methoxyethyl, (meth) acrylic acid alkoxyalkyl monomers such as ethoxyethyl; N- (meth) acryloyloxymethylene succinimide and N Succinimide monomers such as-(meth) acryloyl-6-oxyhexamethylene succinimide, N- (meth) acryloyl-8-oxyoctamethylene succinimide, N-acryloylmorpholine, and the like are also examples of monomers for modification.

  Furthermore, vinyl acetate, vinyl propionate, N-vinyl pyrrolidone, methyl vinyl pyrrolidone, vinyl pyridine, vinyl piperidone, vinyl pyrimidine, vinyl piperazine, vinyl pyrazine, vinyl pyrrole, vinyl imidazole, vinyl oxazole, vinyl morpholine, N-vinyl carboxylic acid amide , Vinyl monomers such as styrene, α-methylstyrene, N-vinylcaprolactam; cyanoacrylate monomers such as acrylonitrile and methacrylonitrile; epoxy group-containing acrylic monomers such as glycidyl (meth) acrylate; (meth) acrylic Polyethylene glycol acid, polypropylene glycol (meth) acrylate, methoxyethylene glycol (meth) acrylate, methoxypolypropylene glycol (meth) acrylate Glycol acrylic ester monomers such as Le; (meth) acrylic acid tetrahydrofurfuryl, fluorine (meth) acrylate, silicone (meth) acrylate and 2-acrylic acid ester-based monomers such as methoxyethyl acrylate and the like can also be used.

The average molecular weight of the (meth) acrylic polymer is not particularly limited, but is preferably 300,000 to 2,500,000 as the weight average molecular weight.
The (meth) acrylic polymer may be produced by various known methods. For example, a radical polymerization method such as a bulk polymerization method, a solution polymerization method, or a suspension polymerization method can be appropriately selected. As the radical polymerization initiator, various known azo and peroxide initiators can be used. The reaction temperature is usually about 50 to 80 ° C., and the reaction time is 1 to 8 hours. Among the above production methods, the solution polymerization method is preferable, and ethyl acetate, toluene and the like are generally used as the solvent for the acrylic polymer. The solution concentration is usually about 10 to 40% by weight. The (meth) acrylic polymer can be obtained as an aqueous emulsion.

  Examples of rubber-based adhesive base polymers include natural rubber, isoprene-based rubber, styrene-butadiene-based rubber, recycled rubber, polyisobutylene-based rubber, styrene-isoprene-styrene-based rubber, and styrene-butadiene-styrene-based rubber. Etc. Examples of the base polymer of the silicone pressure-sensitive adhesive include dimethylpolysiloxane and diphenylpolysiloxane.

  The pressure-sensitive adhesive can contain a crosslinking agent. Adhesion and durability can be improved by the crosslinking agent, and reliability at high temperatures and the shape of the adhesive itself can be maintained. As the crosslinking agent, isocyanate-based, peroxide-based, epoxy-based, metal chelate-based, oxazoline-based, and the like can be used as appropriate.

  The blending ratio of the base polymer such as the (meth) acrylic polymer and the crosslinking agent is not particularly limited, but is usually 10 parts by weight or less of the crosslinking agent (solid content) with respect to 100 parts by weight of the base polymer (solid content). 0.01 to 10 parts by weight, more preferably 0.1 to 5 parts by weight.

In addition to the above-mentioned base polymer, the pressure-sensitive adhesive may be blended with various additives as necessary without departing from the object of the present invention.
Examples of the additive include tackifiers, plasticizers, glass fibers, glass beads, metal powders, other inorganic powders, fillers, pigments, colorants, fillers, antioxidants, ultraviolet absorbers, and the like. .
Moreover, it is good also as an adhesive layer etc. which contain microparticles | fine-particles and show light diffusibility.

  The pressure-sensitive adhesive layer is formed by laminating the pressure-sensitive adhesive layer on the optical film such as the polarizer, polarizing plate or retardation plate. The forming method is not particularly limited, and examples thereof include a method of applying a pressure-sensitive adhesive solution to the optical film and drying, a method of transferring with a release sheet provided with a pressure-sensitive adhesive layer, and the like.

  As a constituent material of the release sheet, paper, polyethylene, polypropylene, polyethylene terephthalate and other synthetic resin films, rubber sheets, paper, cloth, non-woven fabric, nets, foam sheets and metal foils, and appropriate thin leaf bodies such as laminates thereof Etc. In order to improve the peelability from the pressure-sensitive adhesive layer, the surface of the release sheet may be subjected to a low-adhesive release treatment such as silicone treatment, long-chain alkyl treatment, and fluorine treatment as necessary.

  The thickness of the pressure-sensitive adhesive layer is generally 1 to 30 μm, preferably 5 to 25 μm, and more preferably 5 to 15 μm.

1-4. Storage Elastic Modulus of Adhesive In the present invention, the storage adhesive G ′ at the angular frequency of 0.1 (1 / sec) at 85 ° C. of the first adhesive as counted from the polarizer side is the second and subsequent adhesives. Less than that.
The storage elastic modulus of the first adhesive may be appropriately set depending on the substrate or the purpose of use, in particular preferably ^{1.0 × 10 4 ~6.0 × 10 4} Pa.
In the present invention, the storage elastic modulus of the first pressure-sensitive adhesive is smaller than the storage elastic modulus of the second and subsequent pressure-sensitive adhesives. The storage elastic modulus of the second and subsequent pressure-sensitive adhesives may be appropriately set according to the substrate used and the purpose, and is specifically preferably 2.0 × 10 ^{4 to} 1.0 × 10 ⁵ Pa.
The storage elastic modulus of the first pressure-sensitive adhesive is preferably 1.0 × 10 ^{4 to} 9.0 × 10 ⁴ Pa smaller than the storage elastic modulus of the second and subsequent pressure-sensitive adhesives.

  As a method of adjusting the storage elastic modulus of the pressure-sensitive adhesive, the storage elastic modulus of an arbitrary pressure-sensitive adhesive may be measured and selected as appropriate based on the result.

In the case of a pressure-sensitive adhesive containing a (meth) acrylic polymer which is preferable as the pressure-sensitive adhesive, the ratio of the polymer and the crosslinking agent can be adjusted to obtain the desired storage elastic modulus.
In this case, the proportion of the crosslinking agent may be appropriately set according to the type and molecular weight of the polymer to be used and the type of the crosslinking agent to be used. Use in a smaller proportion than the pressure-sensitive adhesive used.
Specifically, with respect to 100 parts by weight of the base polymer (solid content), the crosslinking agent (solid content) is 10 parts by weight or less, further 0.01 to 10 parts by weight, and further 0.1 to 5 parts by weight. What is necessary is just to adjust suitably in the range.

2. Image Display Device The composite polarizing plate of the present invention can be used for various applications, but can be preferably used as an image display device by being bonded to an image display panel.
In the image display device using the composite polarizing plate optical plate of the present invention, an example of a basic layer configuration is shown in a schematic cross-sectional view in FIG. FIG. 3 shows an example in which a retardation film is further laminated on (a) of FIG. 2 as a composite polarizing plate.
In the image display panel, electrodes, pixels, and the like are formed between a pair of glass substrates and plastic substrates.
Examples of the image display panel include a liquid crystal panel and an organic electroluminescence panel.

The substrate constituting the image display panel is generally made of glass from the viewpoint of optical properties such as mechanical strength and transparency. However, in the present invention, since warping and distortion due to the film can be reduced, plastic cells and thin glass cells can be used. It can be used suitably.
Examples of plastic substrates include films made of cellulose resins such as triacetyl cellulose and diacetyl cellulose, acrylic resin films, epoxy resin films, polyester resin films, polyarylate resin films, polyethersulfone resin films, norbornene, etc. Examples thereof include a film made of a cyclic polyolefin resin containing a cyclic olefin as a monomer. Moreover, in order to adjust the flexibility of the plastic substrate, a glass fiber, a filler, or the like may be added to the substrate. At this time, it is preferable to match the refractive index of the additive with the refractive index of the surrounding plastic because the translucency increases.

Preferable specific examples of the image display device include a liquid crystal display device, an organic electroluminescence (organic EL) display device, a touch panel type display device, and the like.
Hereinafter, each display device will be described.

2-1. Liquid crystal display device A liquid crystal display device is mainly composed of a liquid crystal panel in which liquid crystal is sealed between two substrates having electrodes, and performs display depending on whether or not a voltage is applied thereto or the magnitude of the applied voltage. is there.

When the composite polarizing plate of the present invention is applied to a liquid crystal display device, it is disposed only on the front side when the liquid crystal panel is a reflection type, and on both the front side and the rear side when the liquid crystal panel is a transflective type or a transmission type. FIG. 3 corresponds to an example in which composite polarizing plates are arranged on both sides.
Here, the retardation film as described above is selected in an optimum combination from the viewpoint of the design and cost of the liquid crystal panel, and is added or removed. The first polarizing plate is disposed on one side of the liquid crystal panel and the second polarizing plate is disposed on the other side. The absorption axis of the first polarizing plate and the absorption axis of the second polarizing plate are In general, they are arranged in a substantially orthogonal relationship, but they can also be arranged so that their absorption axes are substantially parallel.

  The liquid crystal panel at this time is a device in which liquid crystal is sealed between two transparent substrates in order to switch the amount of transmitted light, and has a function of changing the alignment state of the liquid crystal by applying a voltage. It may be widely used in display devices. The liquid crystal panel typically has a structure including at least a pair of transparent substrates arranged opposite to each other, transparent electrodes provided on the surfaces facing each other, and a liquid crystal layer sealed between the electrodes. Have. Depending on the alignment state of the liquid crystal layer enclosed in the liquid crystal panel and the alignment state of the liquid crystal layer when a voltage is applied between the electrodes, for example, twisted nematic (TN) mode or vertical alignment (VA) There are various types of modes.

2-2. Organic electroluminescent (organic EL) display device An organic electroluminescent (organic EL) display device is an organic electroluminescent means in which a substance containing an organic compound is excited by receiving energy from an electric field and re-emits energy in the form of light. This is the display device used.
As a specific example, it consists of a substrate / transparent electrode (anode) / hole transport layer / light emitting layer / electron transport layer / transparent electrode (cathode) / substrate, and holes injected from the anode and electrons injected from the cathode are Each arrives at the light-emitting layer through the hole transport layer and the electron transport layer and recombines there, whereby organic molecules emit light through an excited state. At this time, as the composite polarizing plate, an elliptical polarizing plate is disposed on the viewing side substrate from the viewpoint of preventing reflection of external light.

2-3. Touch Panel Type Display Device As a touch panel type display device, a touch panel is arranged with a certain gap on the surface side of a liquid crystal display device.
As a configuration of the touch panel of the touch panel type display device, the upper electrode and the lower electrode are arranged with a certain gap formed of an air layer. Then, the upper electrode is brought into contact with the lower electrode by pressing with a touch pen or the like, and the position information is detected as a signal.
The liquid crystal display device of the touch panel display device has a structure in which a liquid crystal layer is sandwiched between a glass panel and a glass panel, and a front polarizing plate and a back polarizing plate are attached to the outside thereof.

  EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated further more concretely, this invention is not limited by these examples. In the examples, “%” and “part” representing the content or amount used are based on weight unless otherwise specified.

(1) Production of polarizing plate 1) Polarizing plate W
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 uniaxially stretched at a draw ratio of 5 times in a dry method, and while maintaining tension, iodine / potassium iodide / Water weight ratio was immersed in an aqueous solution of 0.05 / 5/100 at 28 ° C. for 60 seconds. Next, it was immersed in an aqueous solution of potassium iodide / boric acid / water at a weight ratio of 10 / 9.5 / 100 at 74 ° C. for 300 seconds. After washing with pure water at 26 ° C. for 20 seconds, it was dried at 30 to 65 ° C. to obtain a linear polarizer in which iodine was adsorbed and oriented on polyvinyl alcohol. Its thickness was about 25 μm.
After applying a polyvinyl alcohol adhesive on both sides of the polarizer thus obtained, a saponification treatment was applied to a 40 μm-thick triacetylcellulose film (“KC4UY”, manufactured by Konica Minolta Opto). The thing was bonded and the polarizing plate W (thickness 105 micrometers) was obtained.
2) Polarizing plate S
After applying a polyvinyl alcohol adhesive on one side of the polarizer obtained in 1), a 40 μm thick triacetyl cellulose film (“KC4UY”, manufactured by Konica Minolta Opto) was subjected to saponification treatment. Was bonded to obtain a polarizing plate S (thickness: 65 μm).

(2) Manufacture of adhesive 1) Adhesive sheet A
As the base polymer, a solution (solid content 15%) containing an acrylic polymer having a weight average molecular weight of 1,000,000 consisting of a copolymer of butyl acrylate: acrylic acid = 95: 5 (weight ratio) was used. To the acrylic polymer solution, 0.2 part of Coronate L (manufactured by Nippon Polyurethane) was added to 100 parts of the polymer solid content to prepare a solution of adhesive A.
The adhesive solution A was applied to a separator made of a polyester film provided with a surface coating of a silicone-based heavy release agent, heat-treated at 100 ° C. for 5 minutes to provide an adhesive layer having a thickness of 25 μm, and a silicone-based light release A separator made of a polyester film provided with a surface coat of the adhesive was laminated and then cured at 23 ° C. for 1 week to produce an adhesive sheet A made of adhesive A.
2) Adhesive sheet B
As the base polymer, a solution (solid content 15%) containing an acrylic polymer having a weight average molecular weight of 1,000,000 consisting of a copolymer of butyl acrylate: acrylic acid = 95: 5 (weight ratio) was used. 0.4 parts of Coronate L (manufactured by Nippon Polyurethane) was added to the acrylic polymer solution with respect to 100 parts of the polymer solid content to prepare a solution of the adhesive B.
A pressure-sensitive adhesive sheet B made of the pressure-sensitive adhesive B was produced in the same manner as in 1) except that the pressure-sensitive adhesive solution B was used.
2) Adhesive sheet C
As the base polymer, a solution (solid content 15%) containing an acrylic polymer having a weight average molecular weight of 1,000,000 consisting of a copolymer of butyl acrylate: acrylic acid = 95: 5 (weight ratio) was used. To the acrylic polymer solution, 1.5 parts of Coronate L (manufactured by Nippon Polyurethane) was added to 100 parts of the polymer solid content to prepare a solution of the adhesive B.
A pressure-sensitive adhesive sheet C made of the pressure-sensitive adhesive C was produced by the same method as in 1) except that the pressure-sensitive adhesive solution C was used.

3) Measurement of storage modulus of pressure-sensitive adhesive Using pressure-sensitive adhesive sheets A, B, and C, a plurality of layers of each pressure-sensitive adhesive were laminated to prepare a laminated sample having a thickness of about 1 mm for storage modulus measurement.
Using the obtained sample, the storage elastic modulus G ′ in the sliding mode at 85 ° C. and the angular frequency of 0.1 (1 / sec) was measured using a dynamic viscoelasticity measuring device Physica MCR101 manufactured by Anton Paar. did.
The results are as shown in Table 1 below. The storage elastic modulus G ′ of the pressure-sensitive adhesive A is smaller than the pressure-sensitive adhesive B, and the storage elastic modulus G ′ of the pressure-sensitive adhesive B is smaller than the pressure-sensitive adhesive C.

(3) Production of composite polarizing plate 1) Composite polarizing plate W
The constituent materials shown below were used.
Polarizing plate: Polarizing plate W obtained in (1) (absorption axis 0 °)
-Adhesive: Adhesive A or C obtained in (2) above
First retardation film: λ / 2 plate (slow axis 15 °) [Cycloolefin resin film (trade name: Arton, manufactured by JSR Corporation, thickness 29 μm) uniaxially stretched product]
Second retardation film: λ / 4 plate (slow axis 75 °) [cycloolefin resin film (trade name: Arton, JSR Co., Ltd., uniaxially stretched product with a thickness of 26 μm)
The retardation film used was subjected to corona discharge treatment on both sides.

A composite polarizing plate having the structure shown in FIG.
The polarizing plate W and the first retardation film 31 are pasted via the first adhesive 21, and then the opposite side of the retardation film 31 and the second retardation film 32 are pasted via the second adhesive 22. A broadband circularly polarizing plate was obtained.
Furthermore, the 3rd adhesive 23 was stuck on the other surface of the phase difference film 32, and the composite polarizing plate W was obtained.
The thickness of the composite polarizing plate W with the pressure-sensitive adhesive thus obtained is
Polarizing plate W (105 μm) + first adhesive (25 μm) + first retardation film (29 μm) + second adhesive (25 μm) + second retardation film (26 μm) + third adhesive (25 μm) = 235 μm Met.

2) Composite polarizing plate S
A composite polarizing plate S having the configuration shown in FIG. 4B was manufactured in the same manner as in 1) except that the polarizing plate and the pressure-sensitive adhesive were changed as follows.
Polarizing plate: Polarizing plate S obtained in (1) (absorption axis 0 °)
-Adhesive: Adhesive B or C obtained in (2) above

The thickness of the composite polarizing plate S with pressure-sensitive adhesive thus obtained is
Polarizing plate S (65 μm) + first adhesive (25 μm) + first retardation film (29 μm) + second adhesive (25 μm) + second retardation film (26 μm) + third adhesive (25 μm) =
It was 195 μm.

○ Example 1
In 1) of the above (3), a composite polarizing plate W was produced using the pressure-sensitive adhesive A as the first pressure-sensitive adhesive and the pressure-sensitive adhesive C as the second and third pressure-sensitive adhesives.
The outline of the configuration of the composite polarizing plate W is as follows. In the following description, the first retardation film and the second retardation film are abbreviated as the first retardation and the second retardation, respectively. The same applies hereinafter.
Polarizing plate W / adhesive A / first retardation / adhesive C / second retardation / adhesive C

○ Comparative Example 1
In 1) of the above (3), a composite polarizing plate W was produced using the adhesive A as the first to third adhesives.
The outline of the configuration of the composite polarizing plate W is as follows.
Polarizing plate W / adhesive A / first retardation / adhesive A / second retardation / adhesive A

○ Comparative Example 2
In 1) of the above (3), a composite polarizing plate W was produced using the adhesive C as the first to third adhesives.
The outline of the configuration of the composite polarizing plate W is as follows.
Polarizing plate W / adhesive C / first retardation / adhesive C / second retardation / adhesive C

○ Comparative Example 3
In 1) of the above (3), a composite polarizing plate W was produced using the pressure-sensitive adhesive A as the second pressure-sensitive adhesive and the pressure-sensitive adhesive sheet C as the first and third pressure-sensitive adhesives.
The outline of the configuration of the composite polarizing plate W is as follows.
Polarizing plate W / adhesive C / first retardation / adhesive A / second retardation / adhesive C

○ Comparative Example 4
In 1) of the above (3), a composite polarizing plate W was produced using the pressure-sensitive adhesive A as the third pressure-sensitive adhesive and the pressure-sensitive adhesive C as the first and second pressure-sensitive adhesives.
The outline of the configuration of the composite polarizing plate W is as follows.
Polarizing plate W / adhesive C / first retardation / adhesive C / second retardation / adhesive A

Example 2
In 2) of the above (3), a composite polarizing plate S was produced using the adhesive B as the first adhesive and the adhesive C as the second and third adhesives.
The outline of the configuration of the composite polarizing plate S is as follows.
Polarizing plate S / adhesive B / first retardation / adhesive C / second retardation / adhesive C

○ Comparative Example 5
In 2) of the above (3), a composite polarizing plate S was produced using the adhesive B as the first to third adhesives.
The outline of the configuration of the composite polarizing plate S is as follows.
Polarizing plate S / adhesive B / first retardation / adhesive B / second retardation / adhesive B

○ Comparative Example 6
In 2) of the above (3), a composite polarizing plate S was produced using the adhesive C as the first to third adhesives.
The outline of the configuration of the composite polarizing plate S is as follows.
Polarizing plate S / adhesive C / first retardation / adhesive C / second retardation / adhesive C

○ Comparative Example 7
In 2) of the above (3), a composite polarizing plate S was produced using the adhesive B as the second adhesive and the adhesive sheet C as the first and third adhesives.
The outline of the configuration of the composite polarizing plate S is as follows.
Polarizing plate S / adhesive C / first retardation / adhesive B / second retardation / adhesive C

○ Comparative Example 8
In 2) of the above (3), a composite polarizing plate S was manufactured using the adhesive B as the third adhesive and the adhesive C as the first and second adhesives.
The outline of the configuration of the composite polarizing plate S is as follows.
Polarizing plate S / adhesive C / first retardation / adhesive C / second retardation / adhesive B

(Warpage test method and method for measuring warpage)
Using the composite polarizing plates W and S obtained in the examples and comparative examples, the composite polarizing plates W and S were cut into a 4-inch size (60 × 80 mm polarizing plate absorption axis 0 °) and shown in FIGS. 5 (a) and 5 (b). In this way, this was bonded to one side of a 4-inch size PET film (thickness 190 μm) or one side of a PES film (thickness 200 μm) to obtain a sample for warpage measurement.
Further, as shown in FIG. 5 (c), a warp measurement sample was prepared by bonding a composite polarizing plate W having an absorption axis of 0 ° and a composite polarizing plate W having an absorption axis of 90 ° to both sides of the PES film. It was.
This sample was allowed to stand for 120 hours under heating at 85 ° C., and left at room temperature (23 ° C. 60% RH) for 1 hour. After that, the sample is placed on a smooth surface so that the convex surface is in contact with the desk surface, and the distance from the desk surface to the corner of the sample is measured with a metal ruler. mm).
Tables 2 and 3 show the results of the warpage test using the composite polarizing plate W and the composite polarizing plate S obtained in the examples and comparative examples, respectively. Further, the appearance of the sample after the test was visually evaluated. The results are also shown in Table 2 and Table 3.

As apparent from Tables 2 and 3, when the low elastic modulus adhesive A or B was used as the first adhesive as in Examples 1 and 2, the amount of warpage was greatly reduced.
On the other hand, when the low elastic modulus adhesive A or B was used as the second adhesive or the third adhesive as in Comparative Examples 3, 4, 7, and 8, almost no warpage suppression effect was seen. .
Thus, the composite polarizing plate of the present invention can effectively suppress warping by using the low elastic modulus adhesive in place. In particular, since it can be applied to a liquid crystal display device using a plastic substrate, an organic electroluminescence display device, and a touch panel display device, its industrial value is great.

  The composite polarizing plate of the present invention can effectively suppress warping by using a low elastic modulus adhesive in place, and can also be applied to liquid crystal display devices, organic electroluminescence display devices and touch panel type display devices. Can do.

FIG. 1 is a schematic cross-sectional view of an example of n = 1 in which one retardation film is laminated, which is an example of a basic layer configuration of the composite polarizing plate of the present invention. (A) of FIG. 1 is an example which has a protective film only on the single side | surface of a polarizer, (b) is an example which has a protective film on both surfaces of a polarizer. FIG. 2 is a schematic cross-sectional view of an example of n = 2 in which two retardation films are laminated, which is an example of a basic layer configuration of the composite polarizing plate of the present invention. (A) of FIG. 2 is an example which has a protective film only on the single side | surface of a polarizer, (b) is an example which has a protective film on both surfaces of a polarizer. FIG. 3 is a diagram showing a layer configuration showing an example of an image display device 1 manufactured using the composite polarizing plate of the present invention. FIG. 4 is a diagram illustrating a layer configuration of the composite polarizing plate manufactured in the example. FIG. 5 is a diagram illustrating a layer configuration of a sample used when a warpage test is performed using the composite polarizing plate manufactured in the example.

Explanation of symbols

11 Polarizer
12 Protective film
21 First adhesive
22 Second adhesive
2n nth adhesive
31 First retardation film
32 Second retardation film
40 Image display panel
50 PET or PES
60 PES

Claims (9)

When a protective film is laminated on at least one side of a polarizer made of a polyvinyl alcohol resin film via an adhesive, and a protective film is laminated on one side of the polarizer, a protective film is placed on the other side and on both sides of the polarizer. In the case of lamination, an adhesive layer has n layers of retardation films on the outer side of one protective film with n layers of adhesives, and an adhesive is also arranged on the outer side of the retardation film farthest from the polarizer. In the retardation integrated composite polarizing plate having a total of n + 1 layers, the storage modulus G ′ of the first pressure-sensitive adhesive at an angular frequency of 0.1 (1 / sec) at 85 ° C. counted from the polarizer side. A retardation-integrated composite polarizing plate characterized in that is smaller than that of the second and subsequent pressure-sensitive adhesives. Here, n is an integer of 1 or more. 2. The retardation-integrated composite polarizing plate according to claim 1, wherein n is 1 or 2. The storage elastic modulus G ′ at an angular frequency of 0.1 (1 / sec) at 85 ° C. of the first pressure-sensitive adhesive is 1.0 × 10 ^{4 to} 6.0 × 10 ⁴ Pa. 2. A retardation-integrated composite polarizing plate according to 2. The retardation integrated composite polarizing plate according to claim 1, wherein the pressure-sensitive adhesive is a (meth) acrylic pressure-sensitive adhesive having a thickness of 1 to 30 μm. An image display device obtained by bonding the retardation-integrated composite polarizing plate according to claim 1 and an image display panel. 6. The image display device according to claim 5, wherein the substrate constituting the image display panel is made of a plastic resin substrate. The image display device according to claim 5, which is a liquid crystal display device. The image display device according to claim 5, which is an organic electroluminescence display device. The image display device according to claim 5, wherein the image display device is a touch panel type display device.

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