JP6136093B2 - Composite polarizing plate and liquid crystal display device - Google Patents

Description

  The present invention relates to a composite polarizing plate and a liquid crystal display device using the same.

  As a composite polarizing plate for the purpose of thinning, a first pressure-sensitive adhesive layer, a polarizer (polarizing film), a second pressure-sensitive adhesive layer, and a transparent plastic substrate are laminated in this order. A composite polarizing plate has been proposed. In this composite polarizing plate, a polarizer and a transparent plastic substrate are directly laminated via a second pressure-sensitive adhesive layer, and the second pressure-sensitive adhesive layer is in a temperature range of 23 to 80 ° C. A pressure-sensitive adhesive layer showing a storage elastic modulus of 0.15 to 1 MPa is employed (Patent Document 1).

JP 2010-39458 A

  In general, a polarizing film easily shrinks under high temperature and high humidity. In the composite polarizing plate, a pressure sensitive adhesive having a high storage elastic modulus is used as a second pressure sensitive adhesive layer for bonding a polarizer and a transparent plastic substrate. By adopting the agent layer, the shrinkage of the polarizing film and the transparent plastic substrate is suppressed even under high temperature and high humidity. However, in the case of a composite polarizing plate in which a polarizing film and a transparent protective film are laminated and the transparent protective film and a transparent plastic substrate are bonded via a pressure-sensitive adhesive layer, the storage elastic modulus as described above is obtained. When a high pressure-sensitive adhesive layer was used, there was a problem that the transparent plastic substrate also contracted following the contraction of the polarizing film that occurred at high temperature and high humidity.

  In a liquid crystal panel in which a liquid crystal cell is sandwiched between a pair of glass substrates, the orientation is controlled by an electric field applied to the liquid crystal cell, and thus generally an antistatic function is imparted to the glass substrate. It is desired to provide an antistatic function on the composite polarizing plate side. Here, when the antistatic function is imparted to the composite polarizing plate, for example, an antistatic layer is provided on the transparent plastic substrate, and the antistatic layer and the circuit board of the liquid crystal panel are connected to a conductive paste or conductive tape. In the composite polarizing plate that shrinks under high temperature and high humidity as described above, the conductive paste or conductive tape that connects the antistatic layer and the circuit board is cut. There was a case.

  In addition, the glass substrate constituting the liquid crystal panel is also required to be thin. Here, in the case of the composite polarizing plate as described above, it is bonded to the glass substrate through the first pressure-sensitive adhesive layer, but the composite polarizing plate contracts under high temperature and high humidity. And there exists a possibility that curvature may arise in the thinned glass substrate.

  Accordingly, an object of the present invention is to provide a composite polarizing plate in which shrinkage is suppressed under high temperature and high humidity. In particular, an antistatic layer is provided on a transparent plastic substrate, and the antistatic layer is used as a conductive paste. Or providing a composite polarizing plate in which the conductive paste or conductive tape is not cut even under high temperature and high humidity when connected to a circuit board of a liquid crystal panel via a conductive tape, and in addition, a thin glass An object of the present invention is to provide a composite polarizing plate capable of suppressing the warpage of a glass substrate even under high temperature and high humidity when bonded to a substrate.

The present invention has the following configuration.
[1] A composite polarizing plate in which a first pressure-sensitive adhesive layer, a polarizing plate, a second pressure-sensitive adhesive layer, and a transparent plastic substrate are laminated in this order,
The polarizing plate has a polarizing film and a transparent protective film in contact with the second pressure-sensitive adhesive layer,
The storage elastic modulus at 80 ° C. of the first pressure-sensitive adhesive layer is 10 to 100 KPa, and the storage elastic modulus at 80 ° C. of the second pressure-sensitive adhesive layer is 0.1 to 60 KPa. .
[2] The composite polarizing plate according to [1], wherein the polarizing plate has a transparent protective film in contact with the first pressure-sensitive adhesive layer.
[3] The composite polarizing plate according to [1] or [2], wherein the transparent elastic substrate has a tensile elastic modulus of 2000 to 4500 MPa.
[4] The composite polarizing plate according to any one of [1] to [3], wherein the transparent plastic substrate has a thickness of 10 to 100 μm.
[5] The composite polarizing plate according to any one of [1] to [4] above, wherein an antistatic layer is laminated on the side opposite to the surface in contact with the second pressure-sensitive adhesive layer in the transparent plastic substrate. .
[6] The composite polarizing plate according to [5] above, a liquid crystal panel having a circuit board, an antistatic layer of the composite polarizing plate, and a conductive paste or conductive tape connecting the circuit board of the liquid crystal panel. A liquid crystal display device provided.

  ADVANTAGE OF THE INVENTION According to this invention, the composite polarizing plate by which shrinkage | contraction was suppressed under high temperature and high humidity can be provided. In particular, when an antistatic layer is provided on a transparent plastic substrate, and the antistatic layer is connected to the circuit board of the liquid crystal panel through a conductive paste or conductive tape, the conductive paste or conductive material can be used even at high temperatures and high humidity. In addition, a composite polarizing plate that can suppress warping of the glass substrate even at high temperatures and high humidity when bonded to a thin glass substrate can be provided. can do.

It is a cross-sectional schematic diagram which shows an example of the layer structure in the composite polarizing plate of this invention. It is a cross-sectional schematic diagram which shows an example of the layer structure in the composite polarizing plate of this invention. It is a cross-sectional schematic diagram which shows an example of the layer structure in the composite polarizing plate of this invention. It is a cross-sectional schematic diagram which shows an example of the layer structure in the composite polarizing plate of this invention. It is a cross-sectional schematic diagram which shows an example of the layer structure in the composite polarizing plate of this invention.

  Examples of the layer structure of the composite polarizing plate of the present invention are schematically shown in FIGS. As shown in FIG. 1, the composite polarizing plate 10 of the present invention includes a first pressure-sensitive adhesive layer 1, a polarizing film 3, a transparent protective film 2a, a second pressure-sensitive adhesive layer 4, and a transparent plastic substrate 5. Is a composite polarizing plate in which the second pressure-sensitive adhesive layer 4 and the transparent plastic substrate 5 are in contact with each other. Further, as shown in FIG. 2, a transparent protective film 2b may be provided between the first pressure-sensitive adhesive layer 1 and the polarizing film 3, and as shown in FIG. An antistatic layer 6 may be laminated on the side opposite to the surface in contact with the second pressure sensitive adhesive layer 4. Further, as shown in FIG. 4, a retardation plate 7 (also serving as a transparent protective film) may be provided between the first pressure-sensitive adhesive layer 1 and the polarizing film 3, as shown in FIG. A retardation plate 7 and a third pressure-sensitive adhesive layer 8 may be provided between the first pressure-sensitive adhesive layer 1 and the polarizing film 3. In addition, the separator (not shown) is normally bonded to the opposite side to the polarizing film 3 of the 1st pressure sensitive adhesive layer 1 until it bonds to another member, and a composite polarizing plate is protected. Keep it.

  Hereinafter, each layer will be described with reference to the drawings.

<Polarizing plate>
The polarizing plate in this invention is one of the structural members of a composite polarizing plate, and has a polarizing film and the transparent protective film laminated | stacked on the 2nd pressure sensitive adhesive layer side. Such a polarizing plate may have a two-layer structure of polarizing film 3 / transparent protective film 2a as shown in FIG. 1, and transparent protective film 2b / polarizing film 3 / transparent protective film 2a as shown in FIG. The three-layer structure may be used. From the viewpoint of versatility, the three-layer polarizing plate is preferable.

<Polarizing film>
The polarizing film is a film having a function of extracting linearly polarized light from incident natural light. For example, a polarizing film in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin film can be used. The polyvinyl alcohol resin constituting the polarizing film can be obtained by saponifying a polyvinyl acetate resin. Examples of the polyvinyl acetate resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith. Examples of other monomers copolymerized with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, acrylamides, and the like. The saponification degree of the polyvinyl alcohol resin is usually about 85 to 100 mol%, preferably 98 mol% or more. This polyvinyl alcohol-based resin may be further modified, and for example, polyvinyl formal and polyvinyl acetal modified with aldehydes may be used. Moreover, the polymerization degree of polyvinyl alcohol-type resin is about 1000-10000 normally, Preferably it is about 1500-5000.

  A film obtained by forming such a polyvinyl alcohol resin is used as a raw film of a polarizing film. The method for forming a polyvinyl alcohol-based resin is not particularly limited, and can be formed by a known method. Although the film thickness of the raw film which consists of polyvinyl alcohol-type resin is not specifically limited, For example, it is about 1-150 micrometers. Considering easiness of stretching, the film thickness is preferably 10 μm or more.

  The polarizing film is a step of uniaxially stretching such a polyvinyl alcohol resin film, a step of dyeing a polyvinyl alcohol resin film with a dichroic dye and adsorbing the dichroic dye, and a dichroic dye adsorbed. The polyvinyl alcohol resin film is manufactured through a step of treating with a boric acid aqueous solution and a step of washing with water after the treatment with the boric acid aqueous solution. As the dichroic dye, iodine or a dichroic organic dye is used.

<Transparent protective film>
A transparent protective film is laminated on at least one surface of the polarizing film. Both are bonded by an appropriate adhesive such as an aqueous solution, an organic solvent solution, or a solventless type. As the transparent protective film, various resin films conventionally known as transparent protective films for polarizing plates can be used. In general, a cellulose acetate resin film, particularly a triacetyl cellulose film is preferably used. Similarly, when a transparent protective film is laminated on both surfaces of the polarizing film, a known transparent resin film can be used.

<Transparent plastic substrate>
The transparent plastic substrate is not particularly limited as long as it does not impair transparency. Examples thereof include acrylic resins, polyester resins such as polyethylene terephthalate, cyclic olefin resins such as polycarbonate and norbornene resins, and cellulose esters such as triacetyl cellulose. And various resin films made of polyethylene resin, polyethylene, polypropylene, polystyrene, polyvinyl chloride and the like. Among these, a polyethylene terephthalate film and a cellulose ester resin film are preferably used from the viewpoints of hardness, transparency, productivity, cost, and the like.

  Polyethylene terephthalate is a so-called direct polymerization method in which terephthalic acid and ethylene glycol (and other dicarboxylic acids and / or other diols if necessary) are directly reacted, dimethyl ester of terephthalic acid and ethylene glycol (and other if necessary) The dimethyl ester of dicarboxylic acid and / or other diol) can be obtained by any production method such as a so-called transesterification reaction method. Moreover, the polyethylene terephthalate may contain a well-known additive as needed. Known additives include, for example, lubricants, antiblocking agents, heat stabilizers, antioxidants, antistatic agents, light resistance agents, impact resistance improvers and the like. However, since transparency is required for the transparent plastic substrate laminated on the polarizing plate, it is preferable to keep the additive amount to a minimum.

  A stretched polyethylene terephthalate film can be produced by forming the above-described polyethylene terephthalate into a film and subjecting it to a stretching treatment. Stretching is uniaxial stretching in the MD direction (flow direction) or TD direction (direction perpendicular to the flow direction), biaxial stretching in both the MD direction and the TD direction, stretching in a direction that is neither the MD direction nor the TD direction. It may be performed by any method such as oblique stretching. By performing such stretching operation, a polyethylene terephthalate film having high mechanical strength can be obtained. Above all, the film whose PET orientation axis is approximately 45 ° with respect to the MD direction due to the biaxial stretching Boeing phenomenon or oblique stretching is used as a transparent plastic substrate and bonded with a polarizing plate and roll-to-roll. By doing this, it is preferable because it is possible to obtain a composite polarizing plate that can eliminate the poor visibility caused when the polarizing axis of the polarizing sunglasses and the polarizing axis of the polarizing plate are orthogonal when the screen of the liquid crystal panel is viewed with polarized sunglasses.

  In the case of biaxial stretching, for example, a method of longitudinally stretching (stretching in the MD direction) a non-oriented film extruded into a sheet shape at a temperature equal to or higher than the glass transition temperature and then laterally stretching (stretching in the TD direction) The method of extending | stretching longitudinally and laterally simultaneously etc. is mentioned.

  The cellulose ester-based resin film is a film made of a partially esterified product or a completely esterified product of cellulose, and examples thereof include a film made of cellulose acetate ester, propionate ester, butyrate ester, and mixed ester thereof. More specifically, a triacetyl cellulose film, a diacetyl cellulose film, a cellulose acetate propionate film, a cellulose acetate butyrate film, and the like can be given. As such a cellulose ester resin film, an appropriate commercially available product, for example, Fujitac TD80 (Fuji Film Co., Ltd.), Fujitac TD80UF (Fuji Film Co., Ltd.), Fujitac T40UZ (Fuji Film Co., Ltd.) Fujitac TD80UZ (Fuji Film Co., Ltd.), KC8UX2M (Konica Minolta Opto Co., Ltd.), KC8UY (Konica Minolta Opto Co., Ltd.), KC4UY (Konica Minolta Opto Co., Ltd.), etc. can be used. .

  In the present invention, a retardation film having a retardation can be used as the transparent plastic substrate. In this case, the retardation film is preferably disposed so that the slow axis of the retardation film intersects with the absorption axis of the polarizing film at an angle of about 45 °. As retardation films, polyvinyl alcohol, polycarbonate, polyester, polyarylate, polyimide, polyolefin, cyclic polyolefin, polystyrene, polysulfone, polyethersulfone, polyvinylidene fluoride / polymethyl methacrylate, liquid crystal polyester, acetylcellulose, ethylene-acetic acid Examples thereof include an optical film in which refractive index anisotropy is expressed by stretching a polymer film made of a saponified vinyl copolymer, polyvinyl chloride, or the like. In addition, a film that exhibits refractive index anisotropy by applying and aligning a liquid crystalline compound on an optically isotropic substrate having no phase difference, or an anisotropic refractive index by applying an inorganic layered compound A film exhibiting properties can also be used as a retardation film. When the retardation film is used as a transparent plastic substrate, it preferably exhibits a quarter wavelength retardation with respect to the wavelength of incident light, and the in-plane retardation value in that case is generally about 90 to 200 μm, Preferably it is 120-160 micrometers. The quarter wavelength plate has a function of changing linearly polarized light emitted from the polarizing film into elliptically polarized light or circularly polarized light. If a polarizing plate using a retardation film is placed on the front side of the liquid crystal cell as a transparent plastic substrate, the polarization axis of the polarizing sunglasses and the polarizing axis of the polarizing plate are orthogonal when the screen of the liquid crystal panel is viewed with polarized sunglasses. This makes it possible to eliminate the poor visual recognition that occurs. Here, the polarized sunglasses are glasses in which a polarizing plate is incorporated, and transmit only linearly polarized light that vibrates in one direction (for example, the horizontal direction or the vertical direction).

  From the viewpoint of resisting the shrinkage of the polarizing plate under high temperature and high humidity, the tensile elastic modulus of the transparent plastic substrate is preferably in the range of 2000 to 4500 MPa.

  The thickness of the transparent plastic substrate is appropriately selected depending on the material to be applied, but is preferably 10 to 100 μm, more preferably 20 to 60 μm, and further preferably 25 to 40 μm.

<Pressure sensitive adhesive layer>
The composite polarizing plate 10 of the present invention includes a first pressure-sensitive adhesive layer 1 and a second pressure-sensitive adhesive layer 4 (FIGS. 1 to 4), and further includes the first pressure-sensitive adhesive layer 1 and the polarization. Between the film 3, a retardation plate 7 and a third pressure-sensitive adhesive layer 8 may be provided.

  The first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer only have to have a predetermined storage elastic modulus, which will be described later. In order to form these pressure-sensitive adhesive layers, for example, acrylic A pressure-sensitive adhesive mainly composed of a resin such as rubber, urethane, ester, silicone, or polyvinyl ether is used. Among these, a pressure-sensitive adhesive using an acrylic resin having excellent transparency, weather resistance, heat resistance, and the like as a base polymer is preferable. In particular, select and use one that retains moderate wettability and cohesion, has excellent adhesion to transparent protective films and polarizing films, and does not cause peeling problems such as lifting and peeling under heating and humidification conditions. It is preferable. Further, a pressure-sensitive adhesive called an energy ray curable type or a thermosetting type may be used. Moreover, the adhesive agent similar to what was mentioned above can be used also about the adhesive agent which forms a 3rd pressure sensitive adhesive layer.

  The acrylic resin used for forming the pressure-sensitive adhesive layer is not particularly limited. For example, butyl (meth) acrylate, ethyl (meth) acrylate, isooctyl (meth) acrylate, (meth) acrylic acid A (meth) acrylic acid ester base polymer such as 2-ethylhexyl and a copolymer base polymer using two or more of these (meth) acrylic acid esters are preferably used. Furthermore, polar monomers are copolymerized with 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 ( Mention may be made of monomers having a carboxy group, a hydroxyl group, an amide group, an amino group, an epoxy group and the like, such as (meth) acrylate.

  These acrylic resins can be used alone as a pressure-sensitive adhesive, but usually a crosslinking agent is blended. As the crosslinking agent, a divalent or polyvalent metal ion that forms a carboxylic acid metal salt with a carboxyl group, a polyamine compound that forms an amide bond with a carboxyl group, Examples include polyepoxy compounds and polyols that form ester bonds with carboxyl groups, and polyisocyanate compounds that form amide bonds with carboxyl groups. Of these, polyisocyanate compounds are widely used as organic crosslinking agents.

  The energy ray curable pressure sensitive adhesive has the property of being cured by irradiation of energy rays such as ultraviolet rays and electron beams, and has adhesiveness before the irradiation of energy rays and adheres to films and the like. It is a pressure-sensitive adhesive that has the property of adhering to the body and being cured by irradiation with energy rays to adjust the adhesion. As the energy ray curable pressure sensitive adhesive, it is particularly preferable to use an ultraviolet curable pressure sensitive adhesive. The energy beam curable pressure sensitive adhesive generally comprises an acrylic resin as described above and an energy beam polymerizable compound as main components. Usually, a crosslinking agent is further blended, and a photopolymerization initiator and a photosensitizer may be blended as necessary.

  The pressure-sensitive adhesive composition used for forming the pressure-sensitive adhesive layer includes, in addition to the above base polymer and crosslinking agent, pressure-sensitive adhesive pressure-sensitive adhesive, cohesive force, viscosity, elastic modulus, glass Appropriate additives such as natural or synthetic resins, tackifying resins, antioxidants, dyes, pigments, antifoaming agents, corrosives, photoinitiators, etc., for adjusting the transition temperature, etc. Can also be used. Furthermore, it can also be set as the pressure sensitive adhesive layer which contains microparticles | fine-particles and shows light-scattering property.

  The pressure-sensitive adhesive layer is prepared by dissolving or dispersing each component as described above in an organic solvent such as toluene or ethyl acetate to form a pressure-sensitive adhesive composition having a solid content concentration of about 10 to 40% by weight on the substrate. It can be formed by applying to and drying to remove the organic solvent. In the case of an energy ray curable pressure-sensitive adhesive, a desired cured product can be obtained by irradiating the thus formed coating film with energy rays such as ultraviolet rays and electron beams.

  As a method for forming the pressure-sensitive adhesive layer, a conventionally known method can be adopted. For example, (1) the pressure-sensitive adhesive composition described above is applied to the surface to be attached to a polarizing film or a transparent protective film, A method of drying and curing by irradiating with energy rays as necessary, or (2) from a laminate in which a pressure-sensitive adhesive layer has been previously formed on the surface of a separator, to the surface to which a polarizing film or a transparent protective film is applied Examples thereof include a method of transferring the pressure adhesive layer. Further, from the viewpoint of enhancing the adhesion between the adherend surface and the pressure-sensitive adhesive layer, the adherend surface is preferably subjected to corona treatment. In addition, when a pressure sensitive adhesive layer is formed by the method of said (1), it is preferable to bond a separator in order to protect the same layer.

  The thickness of the pressure-sensitive adhesive layer is usually about 1 to 40 μm, but in order to reduce the thickness of the composite polarizing plate without impairing workability and durability, it is preferably 3 to 25 μm. Furthermore, the thickness of the second pressure-sensitive adhesive layer is more preferably 5 to 15 μm.

  If necessary, the pressure-sensitive adhesive layer may contain fine particles for exhibiting light scattering properties, or a filler made of glass fiber, glass beads, resin beads, metal powder, or other inorganic powders. In addition, pigments, colorants, antioxidants, ultraviolet absorbers and the like may be blended. Examples of ultraviolet absorbers include salicylic acid ester compounds, benzophenone compounds, benzotriazole compounds, cyanoacrylate compounds, and nickel complex compounds.

<First pressure sensitive adhesive layer>
The first pressure-sensitive adhesive layer has a storage elastic modulus at 80 ° C. of 10 to 100 KPa. When the first pressure-sensitive adhesive layer has the predetermined storage elastic modulus, for example, the composite polarizing plate of the present invention is bonded to the thinned glass substrate via the first pressure-sensitive adhesive layer. When it does, the curvature of a glass substrate can be suppressed also under high temperature and high humidity. Moreover, from the viewpoint of suppressing warpage of the glass substrate, the storage elastic modulus at 80 ° C. of the first pressure-sensitive adhesive layer is preferably 10 to 60 KPa, and more preferably 20 to 50 KPa.

<Second pressure-sensitive adhesive layer>
The second pressure-sensitive adhesive layer has a storage elastic modulus at 80 ° C. of 0.1 to 60 KPa. Since the second pressure-sensitive adhesive layer has the predetermined storage elastic modulus, the composite polarizing plate of the present invention can be satisfactorily suppressed from contracting the polarizing plate and the transparent plastic substrate even under high temperature and high humidity. It becomes possible. In particular, when an antistatic layer is provided on a transparent plastic substrate and the antistatic layer is connected to the circuit board of the liquid crystal panel via a conductive paste or conductive tape, it is conductive even under high temperature and high humidity. It becomes possible to prevent cutting of the paste or the conductive tape. Moreover, from the viewpoint of the shrinkage suppression described above, the storage elastic modulus at 80 ° C. of the second pressure-sensitive adhesive layer is preferably 0.1 to 40 KPa, and more preferably 0.1 to 30 KPa.

  In order to control the second pressure-sensitive adhesive layer to the predetermined storage elastic modulus, an acrylic resin (1) and an acrylic resin (2), which will be described later, are used as the adhesive for forming the second pressure-sensitive adhesive layer. A pressure-sensitive adhesive containing a silicone oligomer (3) and a crosslinking agent (4) is preferred.

<Acrylic resin (1)>
Acrylic resin (1): an acrylic resin containing the structural unit (a) derived from the monomer (A) and the structural unit (b) derived from the monomer (B), and having a weight average molecular weight Acrylic resin that is 100000 to 2000000

（式（Ａ）中、Ｒ^１は水素原子またはメチル基を表し、Ｒ^２は炭素数１〜１４のアルキル基またはアラルキル基を表す。Ｒ^２の水素原子は炭素数１〜１０のアルコキシ基によって置換されていてもよい。） Monomer (A): (meth) acrylic acid ester represented by formula (A)

(In Formula (A), R ¹ represents a hydrogen atom or a methyl group, R ² represents an alkyl group having 1 to 14 carbon atoms or an aralkyl group. The hydrogen atom of R ² is represented by an alkoxy group having 1 to 10 carbon atoms. May be substituted.)

Monomer (B): Monomer (B-1) represented by (B-1) and / or (B-2) below: at least one carboxyl group and one olefinic double bond Containing monomer (B-2): at least one polar functional group selected from the group consisting of a hydroxyl group, an amide group, an amino group, an epoxy group, an oxetanyl group, an aldehyde group and an isocyanate group, an olefinic double bond, Monomers containing

<Acrylic resin (2)>
Acrylic resin (2): acrylic resin containing structural unit (a) and structural unit (b) and having a weight average molecular weight of 50,000 to 500,000

<Silicone oligomer>
Silicone oligomer (3): An oligomer containing 2 to 100 structural units (s) derived from a compound represented by the following formula (S). (However, the silicone oligomer (3) may contain two or more different structural units (s).)

（式（Ｓ）中、Ｒ^３、Ｒ^４はアルキル基又はフェニル基を表し、Ｘ及びＹは、水素原子、置換されていてもよいアルキル基、置換されていてもよいフェニル基、置換されていてもよいアルコキシ基、置換されていてもよいフェノキシ基、置換されていてもよいアラルキル基、置換されていてもよいアラルキルオキシ基、ビニル基、ビニルオキシ基、１，２−エポキシシクロヘキシル基、１，２−エポキシシクロヘキシルオキシ基、スチリル基、スチリルオキシ基、メタクリロイルオキシ基、アミノ基、ウレイド基、メルカプト基又はイソシアネート基を表す。）

(In the formula (S), R ³ and R ⁴ represent an alkyl group or a phenyl group, and X and Y are a hydrogen atom, an optionally substituted alkyl group, an optionally substituted phenyl group, or a substituted group. An optionally substituted alkoxy group, an optionally substituted phenoxy group, an optionally substituted aralkyl group, an optionally substituted aralkyloxy group, a vinyl group, a vinyloxy group, a 1,2-epoxycyclohexyl group, 1, 2-epoxycyclohexyloxy group, styryl group, styryloxy group, methacryloyloxy group, amino group, ureido group, mercapto group or isocyanate group are represented.)

The second pressure-sensitive adhesive layer has a creep amount of 200 to 600 μm measured by a predetermined test method described in Examples described later from the viewpoint of suppressing shrinkage of the composite polarizing plate at high temperature and high humidity. It is preferable that it exists in the range, and it is more preferable that it exists in the range of 300-400 micrometers.
<Third pressure-sensitive adhesive layer>
When a retardation plate is provided between the first pressure-sensitive adhesive layer and the polarizing film, the polarizing film and the retardation plate can be bonded via the third pressure-sensitive adhesive layer. The third pressure-sensitive adhesive layer preferably exhibits a storage elastic modulus of 0.15 to 1 MPa in a temperature range of 23 to 80 ° C. In order to obtain such a storage elastic modulus, for example, it is effective to add a urethane acrylate oligomer to the above-mentioned pressure-sensitive adhesive composition. It is more preferable that such urethane acrylate oligomer is blended and then cured by irradiation with energy rays.

<Phase difference plate>
As shown in FIGS. 4 and 5, the composite polarizing plate of the present invention may include a retardation plate 7 between the first pressure-sensitive adhesive 1 and the polarizing film 3 instead of the transparent protective film 2 b. it can. Thereby, the composite polarizing plate which provided the viewing angle compensation function of the liquid crystal cell can be formed, or an elliptical or circular polarization mode composite polarizing plate can be formed. Such a retardation plate can be obtained, for example, by stretching a thermoplastic resin film. The type of the thermoplastic resin constituting the retardation plate is not particularly limited, and examples thereof include the above-mentioned cellulose acetate-based resins, cyclic olefin-based resins such as polycarbonate and norbornene-based resins.

  An optical compensation film can also be used as the retardation plate. The optical compensation film is for compensating the optical retardation when the polarizing plate is mounted on a liquid crystal display. For example, the optical compensation film is formed by forming a coating layer of an inorganic layered compound to express the retardation in the thickness direction. Examples thereof include a film and an optical compensation film on which a coating layer of a liquid crystal compound is formed. Commercially available optical compensation films with a liquid crystal compound coating layer include “Wide View” (sometimes referred to as “WV film”) sold by FUJIFILM Corporation, and JX Nippon Mining & Metals. There are “NH film”, “NV film”, etc. sold by Seki Energy Co., Ltd.

  The angle formed between the slow axis of the retardation plate or the optical compensation film and the absorption axis of the polarizing film is not particularly limited, and is appropriately set according to the specifications of the applied liquid crystal cell. When a retardation plate or an optical compensation film is bonded to form a composite polarizing plate with a viewing angle compensation function, color loss is more likely to occur than when a polarizing plate and a retardation plate are simply laminated. Since it can suppress effectively, it is preferable.

<Antistatic layer>
As shown in FIG. 3, an antistatic layer 6 can be laminated on the side of the transparent plastic substrate 5 opposite to the surface in contact with the second pressure-sensitive adhesive layer 4. The antistatic layer 6 is made of a transparent resin containing an antistatic agent that becomes transparent after the resin is cured in a known ultraviolet curable resin, a fluorine-based or silicone-based leveling agent, and a solvent-drying resin on a transparent plastic substrate 5. The transparent resin can be formed by coating with UV and curing the transparent resin. In general, in order to obtain a function as an antistatic layer, the surface resistance value is preferably 10 ¹⁴ Ω / □ or less, and more preferably 10 ¹² Ω / □ or less.

  Antistatic agents that become transparent after resin curing include organic antistatic agents and inorganic antistatic agents. Examples of the organic antistatic agent include various cationic antistatic agents having a cationic group such as quaternary ammonium salt, pyridinium salt, and primary to tertiary amino groups, sulfonate group, sulfate ester base, phosphorus Anionic antistatic agents having anionic groups such as acid ester bases, phosphonic acid bases, amphoteric antistatic agents such as amino acids and aminosulfate esters, nonionic charges such as amino alcohols, glycerols, and polyethylene glycols And various surfactant type antistatic agents such as an antistatic agent, and polymer antistatic agents obtained by increasing the molecular weight of the antistatic agent as described above, and tertiary amino groups and quaternary ammonium groups. Monomers and oligomers that are polymerizable by ionizing radiation, such as N, N-dialkylaminoalkyl (meth) acrylate monomers, Polymerizable antistatic agents such as quaternary compounds of may also be used.

As the inorganic antistatic agent, fine particles such as ATO, SnO ₂ , ITO, etc. are used. In particular, in order to give transparency to the coating film after curing the resin, the particle size is not more than the wavelength of visible light, that is, 700 nm or less. Is desirable. The addition amount of the inorganic antistatic agent is desirably 10 to 80% by weight with respect to the resin. Transparent and antistatic ability by coating an organic antistatic agent or an inorganic antistatic agent having a particle size smaller than or equal to the wavelength of visible light in a transparent resin on a transparent plastic substrate A flexible plastic substrate is obtained.

  As a method for applying a paint containing an antistatic agent, known methods such as a roll coating method, a gravure coating method, a screen coating method, and a fountain coating method can be used.

<Other layers>
In addition, by constructing a transparent plastic substrate surface with a surface treatment layer such as a hard coat layer, an antiglare layer, and an antireflection layer together with an antistatic layer, visibility and hardness and scratch resistance are increased. It is also possible. However, in order to maintain the function of the antistatic layer, the surface resistance value is preferably 10 ¹⁴ Ω / □ or less, and more preferably 10 ¹² Ω / □ or less even when the surface treatment layer is provided.

  The hard coat layer can have a smooth surface or a surface with irregularities. For example, a resin material such as silicone, acrylic or urethane acrylate can be used alone, or a filler can be mixed with the resin. The layer formed by application | coating of what was made to illustrate can be illustrated. The hard coat layer can be provided by applying and curing the above hard coat resin by a known method such as a spin coat method or a micro gravure coat method. The thickness of the hard coat layer is about 1 to 30 μm, preferably 3 μm or more, and preferably 20 μm or less. The refractive index is usually 1.65 or less, preferably 1.45 to 1.65.

  The anti-glare layer is formed to prevent disturbance of visibility caused by external light reflected on the surface of the polarizing plate, for example, a roughening method such as a sand blast method or an embossing method, or an ultraviolet ray. In general, it is formed to have a concavo-convex structure on the surface of a transparent plastic substrate by a method of applying and curing a coating liquid in which transparent fine particles are mixed with a curable resin. If the above-described hard coat layer is formed in a state in which surface irregularities are provided, it becomes an antiglare layer.

  The antireflection layer is formed for the purpose of preventing reflection of external light on the surface of the polarizing plate, and can be provided by a known method. For example, it can be formed by providing a layer of an organic substance, a metal, a metal compound, or the like using a coating method such as microgravure coating or a physical vapor deposition method such as vapor deposition or sputtering.

  Examples of the organic substance used for forming the antireflection layer include a polymer into which a fluorine atom is introduced. As the metal, aluminum, silver or the like can be preferably used. Metal compounds are generally inorganic, and inorganic oxides, inorganic sulfides, inorganic fluorides, and the like can be used. Examples of the inorganic oxide include silicon oxide, zinc oxide, titanium oxide, niobium oxide, cerium oxide, indium-tin oxide, tungsten oxide, molybdenum oxide, antimony oxide, aluminum oxide, and zirconium oxide. Examples of inorganic sulfides include zinc sulfide and antimony sulfide. Examples of inorganic fluorides include aluminum fluoride, lithium fluoride, sodium fluoride, magnesium fluoride, calcium fluoride, strontium fluoride, barium fluoride, yttrium fluoride, lanthanum fluoride, cerium fluoride, fluoride Examples include samarium, niobium fluoride, and lead fluoride. In the case of providing an antireflection layer, it is sufficient that there is at least one layer composed of these organic substances, metals, metal compounds, etc., but a multilayer may be used as necessary.

<Method for producing composite polarizing plate>
An example of a method for producing the composite polarizing plate of the present invention will be described below. A transparent protective film is bonded to one or both sides of the polarizing film with a known adhesive to obtain a polarizing plate. Next, a first pressure-sensitive adhesive layer is laminated on the surface of the polarizing plate. In addition, a separator is usually bonded to the outside of the first pressure-sensitive adhesive layer.

  On the other hand, a second pressure sensitive adhesive layer is laminated on one surface of a transparent plastic substrate. Here, it is usual to provide a separator that temporarily protects the surface of the second pressure-sensitive adhesive layer on the outside. When an antistatic layer or other layers (hard coat layer, antiglare layer, antireflection layer, etc.) are provided on the other surface of the transparent plastic substrate, the transparent plastic substrate on which these layers are provided in advance Two pressure-sensitive adhesive layers may be laminated, or after forming a three-layer structure of a transparent plastic substrate / second pressure-sensitive adhesive layer / separator, an antistatic layer or the like is provided on the transparent plastic substrate. Also good.

  Subsequently, a composite polarizing plate can be obtained by bonding the transparent protective film of the polarizing plate obtained previously and the 2nd pressure sensitive adhesive layer which peeled the separator.

  If the layer constitution of the composite polarizing plate of the present invention is taken, it is not limited to the above-mentioned order of formation. For example, after forming the first and second pressure-sensitive adhesive layers on both surfaces of the polarizing plate, a transparent plastic substrate is pasted. May be combined.

  As a method for bonding the polarizing plate and the transparent plastic substrate, a single wafer bonding method or a sheet / roll composite bonding method can be employed. Further, when a transparent plastic substrate can be produced in a long length and the required quantity is large, a roll-to-roll bonding method is particularly useful.

<Liquid crystal display device>
The composite polarizing plate of the present invention can be a liquid crystal display device by bonding the first pressure-sensitive adhesive layer to a glass substrate of a liquid crystal panel. Here, when the composite polarizing plate is protected by a separator, the composite polarizing plate is peeled off and then bonded to the liquid crystal panel. From the viewpoint of antistatic properties, the composite polarizing plate of the present invention preferably has an antistatic layer laminated on the side opposite to the surface in contact with the second pressure-sensitive adhesive layer in the transparent plastic substrate. In this case, the composite polarizing plate of the present invention is preferably disposed on the viewing side of the liquid crystal display device with the antistatic layer as the outside.

  In addition, the composite polarizing plate of this invention can also be bonded to image display elements, such as organic EL, and can be set as an image display apparatus.

<Conductive paste or conductive tape>
The conductive paste or conductive tape is generally commercially available, has sufficient conductivity, and has good adhesion to the antistatic layer provided on the transparent plastic substrate and the circuit board of the liquid crystal panel Is appropriately selected. Examples include conductive rubber members, rubber with metal foil laminated on the surface, plastic members wound with metal foil, Au, Ag, Cu, Co, Ni, Sn, Pb containing at least any one element or alloy, so-called Examples thereof include resin, metal wiring, or metal foil tape containing at least one of metal solder, Au, Ag, Cu, Co, Ni, Sn, and Pb or an alloy.

  Hereinafter, the present invention will be further described with reference to examples, but the present invention is not limited to the following examples.

<Measurement of storage modulus>
Two 25 ± 1 mg spherical samples are prepared from the pressure-sensitive adhesive, and each sample is placed between three plate jigs one by one to prepare a sample piece. Using a dynamic viscoelasticity measuring device “DVA-200” manufactured by IT Measurement Control Co., Ltd. for the sample piece, the storage elastic modulus (G ′) at 80 ° C. is obtained by a non-resonant forced vibration method with a frequency of 10 Hz. taking measurement. By measuring the storage elastic modulus (G ′) of the pressure-sensitive adhesive at 80 ° C. in this way, the storage elastic modulus of the pressure-sensitive adhesive layer at 80 ° C. formed from the pressure-sensitive adhesive can be measured. .

<Creep amount>
The pressure sensitive adhesive is bonded to a polarizing plate SRW062A manufactured by Sumitomo Chemical Co., Ltd. At this time, corona discharge treatment was performed on the pressure-sensitive adhesive layer side and the polarizing plate side under the conditions of 280 W and 10 m / min. Next, after cutting into a size of 25 mm × 100 mm, this is bonded to an alkali-free glass (Corning Co., Ltd., Eagle-XG), then autoclaved at 5 MPa, 50 ° C., 20 min, A test piece for measuring the creep amount is prepared. The sample piece thus prepared is allowed to stand for 24 hours in an environment of 23 ° C. × 55% and then cured, and then a load of 1 kg is applied so as to be parallel to the long side of the test piece. The amount of displacement of the pressure-sensitive adhesive layer from the beginning to 3000 seconds is measured with a laser displacement meter (LK-G15 manufactured by KEYENCE Corp.) to obtain the creep amount.

<Corona discharge device>
In this example, the following corona discharge device was used.
Corona surface treatment frame STR-1764, high frequency power supply CT-0212, high voltage transformer CT-T02W (all manufactured by Kasuga Denki Co., Ltd.).

<Transparent plastic substrate with antistatic layer>
As a transparent plastic substrate with an antistatic layer, “Transparent optical protective film manufactured by Toppan Printing Co., Ltd .; 40KSPLR” was used. The tensile elastic modulus of the substrate is 3431 to 4412 MPa in the MD direction, 2941 to 3431 MPa in the TD direction, and the thickness is 45 μm. The surface resistance value of the antistatic layer is 5 × 10 ¹¹ Ω / □.

<Pressure sensitive adhesive layer>
The following pressure sensitive adhesives were used as pressure sensitive adhesives for forming the pressure sensitive adhesive layer.
(1) Pressure sensitive adhesive A
Storage elastic modulus (G ′) at 80 ° C .; 34 KPa
・ Creep amount: 343 μm
・ Film thickness: 10μm
(2) Pressure sensitive adhesive B (manufactured by Sumitomo Chemical Co., Ltd., optical pressure sensitive adhesive L2)
Storage modulus at 80 ° C. (G ′); 227 KPa
・ Creep amount: 193μm
・ Film thickness: 5μm
(3) Pressure sensitive adhesive C
-Storage elastic modulus (G ') at 80 ° C; 36 KPa
・ Creep amount: 254 μm
・ Film thickness: 25μm
(4) Pressure sensitive adhesive D
Storage modulus at 80 ° C. (G ′); 53 KPa
・ Creep amount: 236 μm
・ Film thickness: 10μm

<Example 1>
(Preparation of pressure sensitive adhesive C)
69:20 butyl acrylate (BA), methyl acrylate (MA), 2-phenoxyethyl acrylate (PEA), 2-hydroxyethyl acrylate (HEA) and acrylic acid (AA) based on solids content Was polymerized at a weight ratio of 9: 1: 1 to obtain an acrylic resin having a weight average molecular weight of 1,500,000. Subsequently, 100 parts by weight of the acrylic resin was added to 0.5 part by weight of an adduct of tolylene diisocyanate (trade name: Coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.), 2 parts by weight of an antistatic agent, and a silane compound. (Product name: KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd.) 0.3 parts by weight was mixed. Next, this mixture was diluted with methyl ethyl ketone (MEK) so as to have a concentration of 15% to obtain a pressure-sensitive adhesive composition (pressure-sensitive adhesive C).

(Preparation of pressure sensitive adhesive A)
"Preparation of acrylic resin (1)"
Based on the solid content, butyl acrylate (BA) and acrylic acid (AA) were polymerized at a weight ratio of 99: 1 to obtain an acrylic resin (1) having a weight average molecular weight of 1.3 million.
"Preparation of acrylic resin (2)"
Polymerization of butyl acrylate (BA), butyl methacrylate (BMA), methyl acrylate (MA) and 2-hydroxyethyl acrylate (HEA) in a weight ratio of 35: 44: 20: 1, based on solids content An acrylic resin (2) having a weight average molecular weight of 100,000 was obtained.
"Preparation of pressure sensitive adhesive A"
The adduct body of the tolylene diisocyanate which is a crosslinking agent (trade name: Coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.) with 100 parts by weight (weight ratio 70:30) of the acrylic resin (1) and acrylic resin (2) described above. 3 parts by weight and a silane compound (trade name: KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd.) 0.3 parts by weight, and diluted with methyl ethyl ketone (MEK) to a concentration of 15%, pressure-sensitive adhesive composition A product (pressure-sensitive adhesive A) was obtained.

(Preparation of a laminate of a transparent plastic substrate and a second pressure-sensitive adhesive layer)
In the transparent plastic substrate with the antistatic layer described above, a pressure sensitive adhesive layer formed from the pressure sensitive adhesive A is bonded as a second pressure sensitive adhesive layer to the surface without the antistatic layer. Thus, a laminate in which both were laminated was produced. In addition, when bonding both, the corona discharge process was implemented on each bonding surface on the conditions of 280 W and 10 m / min, and it was made to improve the adhesiveness of a pressure sensitive adhesive layer and a plastic substrate.

(Preparation of polarizing plate)
A polyvinyl alcohol film having a thickness of 75 μm made of polyvinyl alcohol having an average degree of polymerization of about 2400 and a saponification degree of 99.9 mol% or more is uniaxially stretched about 5 times in a dry manner and further kept at 60 ° C. while maintaining a tension state. And then immersed in an aqueous solution having a weight ratio of iodine / potassium iodide / water of 0.05 / 5/100 at 28 ° C. for 60 seconds. Then, it was immersed in an aqueous solution having a weight ratio of potassium iodide / boric acid / water of 8.5 / 8.5 / 100 at 72 ° C. for 300 seconds. Subsequently, it was washed with pure water at 26 ° C. for 20 seconds and then dried at 65 ° C. to obtain a polarizing film in which iodine was adsorbed and oriented on polyvinyl alcohol.
On both surfaces of this polarizing film, a 40 μm thick triacetyl cellulose film having a saponified surface was bonded as a transparent protective film. For bonding, a water-based adhesive is used, and after the bonding, the transparent protective film is adhered to the polarizing film by drying at 80 ° C. for 5 minutes, and consists of three layers of transparent protective film / polarizing film / transparent protective film. A polarizing plate was produced.

(Formation of first pressure-sensitive adhesive layer)
By laminating a pressure-sensitive adhesive layer formed from pressure-sensitive adhesive C as a first pressure-sensitive adhesive layer on one side of the polarizing plate, the first pressure-sensitive adhesive layer and the polarizing plate are laminated. The body was made. In addition, when bonding both together, the corona discharge process was implemented on each point joining surface on the conditions of 280 W and 10 m / min, and it was made to improve the adhesiveness of a 1st pressure sensitive adhesive layer and a polarizing plate.

(Production of composite polarizing plate)
The side opposite to the first pressure-sensitive adhesive layer in the polarizing plate to which the first pressure-sensitive adhesive layer is bonded, and the second in the transparent plastic substrate on which the second pressure-sensitive adhesive layer is formed. A pressure sensitive adhesive layer was bonded to prepare a composite polarizing plate. In addition, when bonding both, like the above, each bonding surface was subjected to corona discharge treatment so as to enhance the adhesion between them.

(Heat resistance test)
The composite polarizing plate was cut into a size of 92 mm × 53 mm so that the polarizing plate absorption axis was 83 ° with respect to the long side to obtain a sample for evaluation. Subsequently, this sample for evaluation was bonded to alkali-free glass (Corning Co., Ltd., Eagle-XG), and then autoclaved under conditions of 5 MPa, 50 ° C., 20 min, and the adhesion between the glass and the evaluation sample. Was enough.
Next, after the sample for evaluation bonded to the glass was heat-treated in a high-temperature bath (85 ° C.) for 100 hours, the dimensions of the transparent plastic substrate were measured using a two-dimensional measuring instrument “NEXIV VMR-12072” manufactured by Nikon Corporation. The amount of change (shrinkage) was measured. As a result, the dimensional change (shrinkage) on the long side was 131 μm, and the dimensional change (shrinkage) on the short side was 190 μm.

<Example 2>
(Preparation of pressure sensitive adhesive D)
100 parts by weight of the acrylic resin (1) used in Example 1 was added 3 parts by weight of a tolylene diisocyanate adduct (trade name: Coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.) as a crosslinking agent and a silane compound (trade name). : KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd.) 0.3 parts by weight, and diluted with methyl ethyl ketone so as to have a concentration of 15% to obtain a pressure-sensitive adhesive composition (pressure-sensitive adhesive D).

  A composite polarizing plate was produced in the same manner as in Example 1 except that pressure sensitive adhesive D was used instead of pressure sensitive adhesive A used in Example 1. Next, as a result of measuring the dimensional change (shrinkage) of the transparent plastic substrate by the same test method as in Example 1 for the composite polarizing plate, the dimensional change (shrinkage) on the long side is: The dimensional change amount (shrinkage amount) on the short side was 227 μm.

<Comparative Example 1>
A composite polarizing plate was produced in the same manner as in Example 1 except that pressure-sensitive adhesive B was used instead of pressure-sensitive adhesive A used in Example 1. Next, as a result of measuring the dimensional change (shrinkage) of the transparent plastic substrate by the same test method as in Example 1 for the composite polarizing plate, the dimensional change (shrinkage) on the long side is: The dimensional change amount (shrinkage amount) on the short side was 335 μm.

  Comparing the results of Example 1, Example 2 and Comparative Example 1, as shown in Example 1 and Example 2, the second pressure-sensitive adhesive layer (formed from pressure-sensitive adhesives A and D) was 80. In the case where the storage elastic modulus (G ′) at 34 ° C. is 34 KPa and 53 KPa, the shrinkage of the transparent plastic substrate can be satisfactorily suppressed, while the second pressure-sensitive adhesive as shown in Comparative Example 1 When the storage elastic modulus (G ′) at 80 ° C. of the agent layer (formed from the pressure sensitive adhesive B) was 227 KPa, the shrinkage of the transparent plastic substrate could not be sufficiently suppressed. In addition, when the results of Example 1 and Example 2 are compared, the storage modulus (G ′) at 80 ° C. of the second pressure-sensitive adhesive layer of Example 1 (formed from pressure-sensitive adhesive A) is lower. It was found that the amount of shrinkage of the transparent plastic substrate was lower.

DESCRIPTION OF SYMBOLS 1 1st pressure sensitive adhesive layer 2a, 2b Transparent protective film 3 Polarizing film 4 Second pressure sensitive adhesive layer 5 Transparent plastic substrate 6 Antistatic layer 7 Phase difference plate 8 Third pressure sensitive adhesive layer 10 Composite polarizing plate

Claims (4)

A liquid crystal display device comprising a composite polarizing plate, a liquid crystal panel having a circuit board, an antistatic layer of the composite polarizing plate and a conductive paste or conductive tape connecting the circuit board of the liquid crystal panel,
It said composite polarizing plate, the first pressure-sensitive adhesive layer, a polarizing plate, the second pressure-sensitive adhesive layer, transparent plastic substrates are laminated in this order,
The antistatic layer is laminated on the side opposite to the surface in contact with the second pressure-sensitive adhesive layer in the transparent plastic substrate,
The polarizing plate has a polarizing film and a transparent protective film in contact with the second pressure-sensitive adhesive layer,
Storage modulus at 80 ° C. of the first pressure-sensitive adhesive layer is 20 ~ 50 KPa, a storage elastic modulus at 80 ° C. of the second pressure sensitive adhesive layer, a liquid crystal display is 0.1~34KPa Equipment . The liquid crystal display device according to claim 1, wherein the polarizing plate has a transparent protective film in contact with the first pressure-sensitive adhesive layer. The liquid crystal display device according to claim 1, wherein the transparent plastic substrate has a tensile elastic modulus of 2000 to 4500 MPa. The liquid crystal display device according to claim 1, wherein the transparent plastic substrate has a thickness of 10 to 100 μm.

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