JP4485188B2 - Laminated sheet and image display device - Google Patents

Description

  The present invention relates to a laminated sheet suitable for an input side of a touch panel and an image display device in which the laminated sheet is arranged.

  In the liquid crystal display device of the pen input type, the liquid crystal display cell and the protection panel are prevented in order to prevent the display from being distorted due to the liquid crystal display cell being bent by a pressing force when inputting through the protection panel arranged on the viewing side of the liquid crystal display cell. A method of providing a gap between the two was adopted. However, in this method, there is a problem that visibility is lowered due to reflection of light at the interface between the liquid crystal display cell and the protective panel.

  For the reflection loss, a method of filling the gap with a gel substance or a method of bonding a protective panel with an adhesive layer has been proposed. However, the method of filling the gel-like substance has a problem in that the manufacturing work such as the peripheral sealing process is complicated, and the visibility is easily lowered due to foaming or the like. Further, the adhesive method using the adhesive layer has a problem that the pressing force at the time of input is easily transmitted to the liquid crystal display cell, and it is difficult to prevent display disturbance due to bending.

In view of the above, the group to which the present inventors have previously proposed a technique in which a liquid crystal display cell and a protective panel are brought into close contact with each other via a buffer sheet provided with adhesive layers on both sides (Patent Document 4). However, it has been found that there is a problem that the liquid crystal display is not sufficiently disturbed by pressing during input, and foaming or peeling occurs at the adhesive interface. Such foaming or peeling is particularly likely to occur at the bonding interface with the plastic material under heating or humidification.
JP-A-6-337411 Japanese Patent Laid-Open No. 7-36621 JP-A-7-1114010 JP-A-9-318932

  The present invention is less likely to cause a drop in visibility due to interface reflected light, can suppress display disturbance due to bending of the liquid crystal display cell during input via a pen or the like, and can be bonded to a plastic material even under heating or humidification. The development of a member that is less prone to foaming and peeling and that is easy to manufacture.

The present invention has a relaxation layer made of a transparent viscoelastic body through a transparent adhesive layer under the rigid layer made of a transparent polymer, and optically passes through the transparent adhesion layer under the relaxation layer. a laminated sheet ing a part,
The relaxation layer was formed of an acrylic polymer obtained by photopolymerizing a monomer containing a (meth) acrylic acid alkyl ester and a polyfunctional (meth) acrylate having 2 to 8 (meth) acryloyl groups. (However, the relaxation layer does not contain a plasticizer)
The two adhesive layers are acrylic adhesives containing an acrylic polymer obtained by polymerizing a monomer containing an alkyl (meth) acrylate, an isocyanate crosslinking agent and a silane coupling agent, It is formed with an acrylic pressure-sensitive adhesive containing 0.5 to 15 parts by weight of an isocyanate-based crosslinking agent per 100 parts by weight of the polymer, and both the pressure-sensitive adhesive layers are 5 N / 25 mm above the triacetyl cellulose film. der shows the 180 ° peel value of is,
The optical component is intended to provide an image display device of a touch input type having a polymer film Der Ru laminated sheet, and the laminated sheet.

  According to the laminated sheet of the present invention, it is possible to prevent a gap from being interposed between the liquid crystal display cell and the protective panel, and it is difficult to cause a decrease in visibility due to interface reflected light. Display distortion due to bending of the liquid crystal display cell during touch input with a pen, etc. is less likely to occur, and it has excellent adhesion and adhesion, and it is difficult to cause foaming or peeling at the adhesive interface with plastic materials even under heating or humidification. Excellent durability.

  In addition, the laminated sheet is excellent in workability and workability, and can be easily applied to a liquid crystal display cell or the like. The manufacturing operation of the touch input type image display device is simple, and the mass productivity is excellent. Incidentally, foaming or peeling occurs between the layers in the contact treatment by the adhesive force of the relaxation layer without providing the adhesive layer.

  The laminated sheet according to the present invention has a relaxing layer made of a transparent viscoelastic body via a transparent adhesive layer on the lower side of the rigid layer made of a transparent polymer, and a transparent adhesive layer on the lower side of the relaxing layer. The two adhesive layers have a 180 degree peel value of 5 N / 25 mm or more with respect to the triacetyl cellulose film.

  An example of a laminated sheet is shown in FIG. 1 is a rigid layer, 2 is an adhesive layer, 3 is a relaxation layer, and 5 is an optical component. The figure shows a touch input type image display device in which a laminated sheet is arranged on the viewing side of the liquid crystal display cell 8.

The rigid layer functions as a protective panel, and is formed of a transparent polymer for the purpose of suppressing deformation due to pressing force at the time of touch input via a pen or the like with its strength or rigidity. If the rigid layer sinks and deforms excessively at the time of touch input, display disturbance is likely to occur. The rigid layer has a dynamic storage elastic modulus G ′ (1 Hz, shear) at 20 ° C. of 2 × 10 ⁸ Pa or more, especially 5 × 10 ⁸ to 1 × from the viewpoint of preventing display disturbance due to the subduction deformation. It is preferably 10 ²⁰ Pa, particularly 1 × 10 ⁹ to 1 × 10 ¹⁵ Pa.

  Polymers that can be preferably used for forming the rigid layer are those having a light transmittance of 70% or more, in particular 80% or more, in particular 85% or more. Those having excellent mechanical strength and good heat resistance are more preferred. Incidentally, examples of polymers for forming a rigid layer include polyester resins such as polyethylene naphthalate resin and polyethylene terephthalate resin (PET), (meth) acrylic resins and polycarbonate resins, triacetyl cellulose resins and norbornene resins. And epoxy resins, polyimide resins, polyetherimide resins, polyamide resins, polysulfone resins, polyphenylene sulfide resins, polyethersulfone resins, polystyrene resins, and the like. The (meth) acrylic means acryl or methacryl (hereinafter the same).

  The rigid layer can be formed as a film, sheet, plate, or the like made of one or more transparent polymers, and may be formed by an appropriate method such as a casting method or an extrusion method. The thickness is generally 100 μm to 2 mm, in particular 120 μm to 1.5 mm, in particular 150 μm to 1 mm. The rigid layer may be composed of a single layer or may be composed of two or more composite layers.

  The rigid layer may be provided with the surface treatment layer 6 on the upper side thereof as shown in the figure, that is, on the side that becomes the viewing side of the image display device. The surface treatment layer is, for example, an antireflection layer, an antireflection layer, an antireflection layer, a hard coat layer, an antistatic layer, or a contamination prevention layer that exhibits both functions. Can be formed to exhibit various known functions, and one or more of these functional layers can be provided.

Incidentally wherein the antireflection layer is for the purpose of antireflection of outdoor daylight on the laminated sheet surface, for example, SiO ₂ or ZrO _2, Al ₂ O ₃ and _{Y 2 O 3, TiO 2,} MgF 2 and BaF _2, CaF ₂ and LaF _2, LiF and NaF, such as inorganic oxides and inorganic halides SrF _2, or monolayers or superposition of their interference thin film comprising a composite, etc., etc., an anti-reflection in accordance with conventional It can be formed as a film.

  The anti-reflection layer is intended to prevent the external light from being regularly reflected on the surface of the laminated sheet and obstructing the visibility of the light transmitted through the laminated sheet, such as display light. For example, a sandblasting method, an embossing method, etc. It can be formed as an anti-glare layer according to the prior art, such as a method of forming a coating film with transparent fine particles, or a method of forming a coating film containing transparent fine particles, or the like, in which a fine concavo-convex structure is provided on the surface of the laminated sheet. The reflection preventing layer may also serve as a diffusion layer that diffuses the light transmitted through the laminated sheet and expands the viewing angle.

  Examples of the transparent fine particles for forming fine irregularities include inorganic fine particles composed of silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide, and the like having an average particle diameter of 0.5 to 50 μm. , Organic fine particles composed of crosslinked or non-crosslinked polymer particles, and the like, and one kind or two or more kinds can be used. In the case of forming a surface fine concavo-convex structure, the amount of transparent fine particles used is 2 to 50 parts by weight, especially 3 to 35 parts by weight, per 100 parts by weight of a binder resin such as an ultraviolet curable silicone resin that forms a coating film. 5 to 25 parts by weight is particularly preferable.

  The antireflection antireflection layer exhibits an antireflection function and an antireflection function. For example, the antireflection layer is superimposed on the antireflection layer, or the above-described coating containing transparent fine particles is antireflection. It can be formed by a method of manufacturing as a coherent interference thin film.

  The hard coat layer is intended to prevent scratches on the surface of the laminated sheet. For example, an unsaturated polyester resin, an unsaturated (meth) acrylic resin, an unsaturated polyurethane resin, a polyamide resin, or a silicone resin. It can be formed as a cured film of an appropriate curable resin such as ultraviolet ray, electron beam curable type, or thermosetting type such as epoxy resin.

  A hard hard coat layer excellent in slipperiness is preferable, and a layer having a surface hardness of 2H or more, especially 3 to 8H, particularly 4 to 6H is preferable from the point of touch input, particularly pen input. If the surface hardness is less than 2H, the scratch resistance at the time of pen input may be insufficient. Further, in terms of slipperiness with respect to pen input, the dynamic friction coefficient at the time of pen input is preferably 0.02 to 0.30, especially 0.05 to 0.25, and particularly preferably 0.07 to 0.20. If the coefficient is less than 0.02, the pen may slide too much, and if it exceeds 0.30, the sliding may be poor and the pen movement may become too heavy, resulting in poor writing.

  The hard coat layer is preferably located on the upper side (surface side) of the antireflection layer or the antireflection layer, and the thickness is 30 μm or less, especially 0.1 to 25 μm, especially 0, in view of hardness and durability. .2 to 20 μm is common. The hard coat layer can also be formed to contain a transparent fine particle or the like to serve as a reflection preventing layer.

  The antistatic layer is intended to prevent dust adhering due to electrification, and can be formed, for example, as a transparent conductive film. Moreover, it can also form as an antistatic layer which doubles as a reflection preventing layer by using a conductive material for transparent fine particles.

  The contamination prevention layer is intended to prevent contamination due to adhesion of fingerprints and the like, and can be formed as a coating film made of, for example, a polyfluorinated alkyl ether compound.

  The transparent conductive film is, for example, gold, silver, copper, aluminum, nickel, tin, titanium, iron, alloys thereof, indium oxide, tin oxide, titanium oxide, cadmium oxide, a mixture or a composite thereof, etc. It can be formed as a thin film made of a metal oxide made of, another metal compound made of copper iodide or the like. The thin film can be formed by, for example, vacuum deposition, sputtering, ion plating, spray pyrolysis, chemical plating, electroplating, or a combination thereof.

  When the antireflection layer is located on the surface of the laminated sheet, particularly, the antistatic layer and / or antifouling layer is preferably provided on the upper side (surface side). When providing both an antistatic layer and a pollution prevention layer, the system which provides a pollution prevention layer above an antistatic layer is common.

  The surface treatment layer can be directly attached to the surface of the rigid layer by a coating method or the thin film forming method, or is attached to a separate support substrate such as a transparent film as shown in the figure, and the support substrate. Can be adhered to the surface of the rigid layer 1 through an appropriate transparent adhesive layer 7 such as an adhesive layer.

The relaxation layer is transparent for the purpose of preventing display disturbance due to relaxation of the pressing force during touch input via a pen, etc., improving the writing quality of the pen by appropriate elastic deformation during input, and mitigating external impact. It is formed of a viscoelastic body. A preferable relaxation layer has a light transmittance of 60% or more, especially 70% or more, particularly 75% or more, and a storage elastic modulus G (shear) by dynamic viscoelasticity of 10 ⁷ Pa or less, especially 7 × 10 ^5. 10 ² Pa, especially 5 × 10 ^{5 to} 5 × 10 ² Pa.

When the G is more than 10 ⁷ Pa, there are cases where the writing quality at the time of pen input and the prevention of cracking of the glass cell substrate against impact are poor. Also, if it is less than 10 ³ Pa, it may be too soft and display may be disturbed at the time of pen input, and the edge part may protrude during cutting processing such as punching of a laminated sheet, which may cause poor workability or handling. . The storage elastic modulus G is a value at 25 ° C. obtained from a temperature dispersion profile of G at −50 to 100 ° C. at a frequency of 1 Hz. The temperature dispersion profile can be known with a dynamic viscoelasticity measuring apparatus (for example, ARES manufactured by Rheometric Co., Ltd.).

  The relaxation layer can be formed as a film-like material or a sheet-like material composed of one or two or more viscoelastic materials, and has a thickness of 0.1 to 3 mm, especially 0.2 to 2 mm, especially 0. 4-1.5 mm is preferable. If the thickness is less than 0.1 mm, the display may be disturbed when inputting, the writing quality of pen input may be deteriorated, and the glass cell substrate may be cracked due to impact, and if it exceeds 3 mm, image degradation due to parallax may occur.

Examples of viscoelastic bodies that form the relaxation layer include ionomer resins in which the molecules of ethylene / methacrylic acid copolymer are cross-linked with metal ions such as Na ⁺ and Zn2 ⁺ , ethylene / vinyl acetate copolymer (EVA), polyvinyl chloride, polyethylene ( Examples thereof include polyolefins such as PE) and polypropylene (PP), ethylene / ethyl acrylate copolymers, polyamide resins, polybutyral resins, and thermoplastic resins such as polystyrene resins.

  Also, polystyrene, polyolefin, polydiene, polyvinyl chloride, polyurethane, polyester, polyamide, fluorine, chlorinated polyethylene, polynorbornene, polystyrene / polyolefin copolymer, (hydrogenated) polystyrene / butadiene. Thermoplastic elastomers that exhibit rubber elasticity, such as copolymer systems and polystyrene / vinyl polyisoprene copolymer systems, and also viscoelastic bodies for forming relaxation layers that are blended with one or more of these thermoplastic elastomers. It is given as.

  Further, for example, an adhesive layer made of various adhesives such as acrylic, rubber, polyester, and silicone can be cited as a viscoelastic body for forming a relaxation layer.

  The pressure-sensitive adhesive forming the relaxation layer may be of a type that crosslinks with light such as ultraviolet rays or electron beams, or heat. The pressure-sensitive adhesive layer forming the relaxation layer may be, for example, an appropriate blend of various additives such as an antioxidant, an ultraviolet absorber, a tackifier, a plasticizer, a light diffusing material, and an inorganic filler. .

  The acrylic polymer used to form the acrylic pressure-sensitive adhesive can be obtained by vinyl polymerization of a (meth) acrylic acid alkyl ester by a conventional method. In the polymerization, a modifying monomer may be copolymerized for the purpose of improving physical properties such as optical properties and heat resistance. The pressure-sensitive adhesive layer can be obtained, for example, by applying a coating treatment of such a polymer solution, or by subjecting the dry film to a cross-linking treatment for the purpose of adjusting pressure-sensitive adhesive properties such as removability and heat resistance, if necessary.

  Examples of the (meth) acrylic acid alkyl ester used for the formation of the acrylic polymer include those having a linear or branched alkyl group having 1 to 18 carbon atoms, especially 4 to 12 carbon atoms. Specifically, for example, butyl (meth) acrylate, isobutyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, ( Examples include (meth) acrylic acid alkyl esters such as allyl (meth) acrylate, lauryl (meth) acrylate, and stearyl (meth) acrylate, and one or more (meth) acrylic acid alkyl esters are used. it can.

  Examples of the modifying monomer include monoethylenic monomers copolymerizable with (meth) acrylic acid alkyl ester. Specific examples thereof include (meth) acrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, itaconic acid, maleic acid, fumaric acid, carboxyl group-containing monomers such as crotonic acid, maleic anhydride and itaconic anhydride. And an acid anhydride monomer such as, and a caprolactone adduct of (meth) acrylic acid.

  Furthermore, it has a hydroxyalkyl group such as 2-hydroxyethyl group, 2-hydroxypropyl group, 4-hydroxybutyl group, 6-hydroxyhexyl group, 8-hydroxyoctyl group, 10-hydroxydecyl group, 12-hydroxylauryl group ( Hydroxyl group-containing monomers such as (meth) acrylic acid esters and (4-hydroxymethylcyclohexyl) -methyl acrylate, styrenesulfonic acid and allylsulfonic acid, 2- (meth) acrylamide-2-methylpropanesulfonic acid and (meth) acrylamidepropane Modification of sulfonic acid group-containing monomers such as sulfonic acid, sulfopropyl (meth) acrylate and (meth) acryloyloxynaphthalene sulfonic acid, and phosphoric acid group-containing monomers such as 2-hydroxyethylacryloyl phosphate It is mentioned as an example of Nomar.

  Furthermore, (N-substituted) amides such as (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N-butyl (meth) acrylamide, N-methylol (meth) acrylamide, and N-methylolpropane (meth) acrylamide. Monomers, alkylaminoalkyl (meth) acrylate monomers such as aminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, and t-butylaminoethyl (meth) acrylate are also modifying monomers. As an example.

  In addition, (meth) acrylic acid alkoxyalkyl monomers such as methoxyethyl (meth) acrylate and ethoxyethyl (meth) acrylate, N- (meth) acryloyloxymethylene succinimide and N- (meth) acryloyl-6-oxyhexa Succinimide monomers such as methylene succinimide and N- (meth) acryloyl-8-oxyoctamethylene succinimide are also examples of the modifying monomer.

  Also 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 amides Examples of the modifying monomer include vinyl monomers such as styrene, α-methylstyrene and N-vinylcaprolactam, and cyano (meth) acrylate monomers such as (meth) acrylonitrile.

  Furthermore, epoxy group-containing acrylic monomers such as glycidyl (meth) acrylate, polyethylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate, methoxyethylene glycol (meth) acrylate and methoxypolypropylene glycol (meth) acrylate Such as glycol acrylic ester monomers such as tetrahydrofurfuryl (meth) acrylate, fluorine (meth) acrylate, silicone (meth) acrylate and (meth) acrylate ester monomers such as 2-methoxyethyl (meth) acrylate, etc. An example of a quality monomer is given.

  One or more modifying monomers can be used. The proportion of the (meth) acrylic acid alkyl ester or the monomer used for modifying it is preferably 60 to 100% by weight, more preferably 70 to 99% by weight, especially 85 to 95% by weight. Accordingly, the proportion of the modifying monomer used is 40% by weight or less, especially 1 to 30% by weight, particularly 5 to 15% by weight.

  As described above, the acrylic polymer is prepared by using a known monomer such as a solution polymerization method, an emulsion polymerization method, a bulk polymerization method, a suspension polymerization method, a photopolymerization method, or the like on one monomer or a mixture of two or more monomers. An appropriate method can be applied. In the preparation, one or more kinds of polymerization initiators can be used as necessary. As the polymerization initiator, appropriate ones such as a photopolymerization initiator and a thermal polymerization initiator are used according to the polymerization method. Can be used.

  Examples of the photopolymerization initiator include 4- (2-hydroxyethoxy) phenyl (2-hydroxy-2-propyl) ketone, α-hydroxy-α, α′-dimethylacetophenone, methoxyacetophenone, and 2,2- Acetophenone compounds such as dimethoxy-2-phenylacetophenone, 2,2-diethoxyacetophenone, 1-hydroxycyclohexyl phenyl ketone, and 2-methyl-1- [4- (methylthio) -phenyl] -2-morpholinopropane-1 can give.

  Also, benzoin ether compounds such as benzoin ethyl ether, benzoin isopropyl ether and anisoin methyl ether, α-ketol compounds such as 2-methyl-2-hydroxypropiophenone, ketal compounds such as benzyldimethyl ketal, 2- Aromatic sulfonyl chloride compounds such as naphthalenesulfonyl chloride, photoactive oxime compounds such as 1-phenone-1,1-propanedione-2- (o-ethoxycarbonyl) oxime, benzophenone and benzoylbenzoic acid, 3,3 ′ Examples of photopolymerization initiators include benzophenone compounds such as -dimethyl-4-methoxybenzophenone.

  Examples of thermal polymerization initiators include benzoyl peroxide, t-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate and di (2-ethoxyethyl) peroxy. Organic peroxides such as dicarbonate, t-butylperoxyneodecanoate, t-butylperoxybivalate, (3,5,5-trimethylhexanoyl) peroxide, dipropionyl peroxide, diacetyl peroxide It is done.

  Also, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), 1,1′-azobis (cyclohexane 1-carbonitrile), 2,2′-azobis (2 , 4-dimethylvaleronitrile), 2,2′-azobis (2,4-dimethyl-4-methoxyvaleronitrile), dimethyl-2,2′-azobis (2-methylpropionate), 4,4′- Azo series such as azobis (4-cyanovaleric acid), 2,2′-azobis (2-hydroxymethylpropionitrile), 2,2′-azobis [2- (2-imidazolin-2-yl) propane] Compounds and the like are also examples of thermal polymerization initiators.

  The usage-amount of a polymerization initiator can be suitably determined according to the kind, and generally is 0.005-5 weight part per 100 weight part of monomers. In particular, photopolymerization per 100 parts by weight of the monomer from the viewpoint of reducing the remaining amount of unreacted monomer that is likely to cause bubbles at the adhesive interface in the laminated sheet and reducing the remaining amount of polymerization initiator that is likely to cause yellowing. It is preferable that the initiator is 0.005 to 1 part by weight, especially 0.05 to 0.5 part by weight, and the thermal polymerization initiator is 0.01 to 5 parts by weight, especially 0.05 to 3 parts by weight. .

  In preparing the acrylic polymer, one or two or more kinds of cross-linking agents (internal cross-linking agents) are used as necessary for the purpose of increasing the shear strength when the cohesive force is improved by cross-linking treatment to obtain a relaxation layer. Agent) can also be copolymerized. As the cross-linking agent, a polyfunctional (meth) acrylate having a plurality of, especially 2 to 8, (meth) acryloyl groups in the molecule can be preferably used.

  Incidentally, specific examples of the polyfunctional (meth) acrylate include hexanediol di (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate and neopentyl glycol di (meta). ) Acrylate, pentaerythritol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, epoxy acrylate, polyester acrylate, urethane acrylate, and the like.

  The amount of the cross-linking agent used is 0.01 to 10 parts by weight per 100 parts by weight of (meth) acrylic acid alkyl ester, especially from the viewpoint of preventing the generation of bubbles and the prevention of swelling at the adhesive interface in the laminated sheet. 0.03 to 7 parts by weight, particularly 0.05 to 5 parts by weight is preferred. A relaxed layer with a small amount of use and a low degree of cross-linking tends to generate bubbles at the adhesion interface, and a relaxed layer with a large amount of use and a high degree of cross-linking has a low adhesive force and tends to swell.

  The pressure-sensitive adhesive forming the relaxation layer is preferably a pressure-sensitive adhesive layer formed by photopolymerization with ultraviolet rays or the like from the viewpoint of processability to a pressure-sensitive adhesive sheet or the like and adhesive properties. The preparation can be carried out with a pressure-sensitive adhesive composition containing the above-mentioned photopolymerization initiator, and the formation of the relaxation layer thereby is achieved by oxygen substituted for the pressure-sensitive adhesive coating layer with an inert gas such as nitrogen gas. A method in which photopolymerization is performed in a dilute atmosphere or a method in which the coating layer is covered with a light-transmitting film and photopolymerization is performed while being shielded from air is preferable.

The light irradiated by the photopolymerization is preferably ultraviolet rays having a wavelength of about 180 to 460 nm, or electromagnetic radiation having longer or shorter wavelengths, and ultraviolet rays are particularly preferred. As the ultraviolet ray source, for example, one or two or more appropriate ones such as mercury arc, carbon arc, low pressure, medium pressure, high pressure mercury lamp, metal halide lamp, chemical lamp, black light lamp, etc. can be used. An irradiation treatment with an integrated light amount of 0.5 to 10 J / cm ² is preferable from the viewpoint of production efficiency of the relaxation layer. In some cases, the formation of a relaxation layer having a thickness of 0.1 mm or more causes undulation by polymerization heat, but the undulation can be suppressed by applying a cooling treatment during photopolymerization.

  For the purpose of adjusting physical properties such as viscoelasticity, one or more transparent plasticizers can be blended in the relaxation layer as necessary. The blending amount is generally 5 to 300 parts by weight, especially 10 to 150 parts by weight, especially 15 to 200 parts by weight per 100 parts by weight of the viscoelastic body.

  Examples of plasticizers include dimethyl phthalate, diethyl phthalate, dibutyl phthalate, diheptyl phthalate, di-2-ethylhexyl phthalate, diisononyl phthalate, diisodecyl phthalate, dibutylbenzyl phthalate, dioctyl phthalate, and butyl phthalate. Examples thereof include phthalic acid compounds such as rubutyl glycolate, and adipic acid compounds such as diisobutyl adipate and diisononyl adipate, diisodecyl adipate and dibutoxyethyl adipate.

  Also, sebacic acid compounds such as dibutyl sebacate and di-2-ethylhexyl sebacate, phosphoric acid compounds such as triethylene phosphate, triphenyl phosphate, tricresyl phosphate, trixylenyl phosphate, cresyl phenyl phosphate, dioctyl Examples of plasticizers include fatty acid compounds such as sebacate and methylacetylricinoleate and epoxy compounds such as diisodecyl-4,5-epoxytetrahydrophthalate.

  Furthermore, trimellitic trimellitic acid compounds such as tributyl trimellitic acid, tri-2-ethylhexyl trimellitic acid, tri-n-octyl trimellitic acid and triisodecyl trimellitic acid, other polyoxyalkylene glycols such as polypropylene glycol and polytetramethylene glycol, olein Examples of plasticizers include butyl acid, chlorinated paraffin, polybutene, and polyisobutylene.

  In addition, in the relaxation layer, a color purity improver exhibiting neon light (570 to 590 nm) absorption characteristics, pigments such as pigments and dyes for the purpose of liquid crystal color correction, and adhesives, as long as transparency is not impaired. Add appropriate additives such as imparting agents, antioxidants, anti-aging agents, UV absorbers, silane coupling agents, natural and synthetic resins and rubbers, acrylic oligomers, glass fibers and glass beads You can also The relaxation layer can also contain transparent fine particles to exhibit light diffusibility.

Furthermore, an organic layered clay mineral can be dispersed and blended in the relaxation layer. In that case, as a viscoelastic body, dynamic storage elastic modulus at 20 ° C. (1 Hz) from the viewpoint of preventing disturbance of display by relaxing input pressure with a pen or the like and relaxing external impact and preventing cracking of the glass cell substrate. There ¹⁰ 3 ^~6 × ¹⁰ 6 Pa, the polymer of inter alia 2 × ¹⁰ 3 ~10 5 Pa can be preferably used.

  Specific examples of the polymer include resins such as polyurethane, polyester, acrylic, natural rubber, and butyl rubber, and rubbers. In particular, acrylic resins can be preferably used from the viewpoints of heat resistance, moisture resistance reliability, transparency, processability to sheets and the like, and affinity with organic layered clay minerals.

  For example, a sheet-like material that forms a relaxation layer may be prepared by, for example, applying a viscoelastic body, which is made fluid using a solvent or the like, onto a supporting substrate, such as a roll coating method, a casting method, a curtain coating method, or a casting method. This method can be carried out by a method of developing and heating (curing) drying the development layer, or a method of photopolymerizing the development layer. In forming the spreading layer, particularly when photopolymerization is performed, the viscosity of the spreading liquid can be adjusted by preliminarily polymerizing by irradiation with light for the purpose of controlling fluidity, if necessary.

  The relaxation layer can be formed as a single layer or a multilayer formed of a laminate. Incidentally, a laminate comprising a polyolefin layer / a thermoplastic resin layer such as EVA / polyolefin layer, a laminate comprising a polyolefin layer / polyolefin + thermoplastic elastomer layer / polyolefin layer, a laminate comprising a PP layer / PE layer / PP layer, a polyolefin A laminate comprising a plurality of layers having different blend ratios of thermoplastic elastomer and thermoplastic elastomer can be preferably used as the relaxation layer.

  The optical component used for forming the laminated sheet is an appropriate component that may be used in a touch-input image display device, particularly an appropriate component that may be disposed on the upper side (viewing side) of the cell substrate of the display cell. You may be 1 type, or 2 or more types. Incidentally, examples thereof include a polarizing plate and a retardation plate (optical compensation plate). In the present invention, an optical component made of a polymer film such as a film-type polarizing plate or a retardation film is advantageously used from the viewpoint of light weight.

  Optical components include, for example, an elliptical polarizing plate and a circular polarizing plate made of a laminate of a polarizing plate and a retardation plate, or a wide viewing angle polarizing plate made of a laminated body of a viewing angle compensation plate and a polarizing plate as an optical compensation plate. One or more optical components may be laminated.

  Incidentally, the above-mentioned elliptically polarizing plate or circularly polarizing plate can be used when converting linearly polarized light into elliptically polarized light or circularly polarized light, or converting elliptically polarized light or circularly polarized light into linearly polarized light. Further, the wide viewing angle polarizing plate can be used when the viewing angle is enhanced by compensating for the phase difference caused by the liquid crystal layer.

  In the above, as the polarizing plate, for example, a hydrophilic polymer film such as a polyvinyl alcohol film, a partially formalized polyvinyl alcohol film, or an ethylene / vinyl acetate copolymer partially saponified film is used in two colors such as iodine or a dichroic dye. Examples thereof include a polarizing film made of a polyene-oriented film such as a film stretched by adsorbing an active substance, a polyvinyl alcohol dehydrated product or a polyvinyl chloride dehydrochlorinated product. The thickness of the polarizing film is generally 5 to 80 μm, but is not particularly limited thereto.

  The polarizing plate may be one having a transparent protective layer on one side or both sides of the polarizing film. For the formation of the transparent protective layer, a polymer having excellent transparency, mechanical strength, thermal stability, moisture shielding property, isotropy and the like is preferably used. For example, polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such as diacetyl cellulose and triacetyl cellulose, acrylic polymers such as polymethyl (meth) acrylate, polystyrene, acrylonitrile / styrene copolymers, etc. Examples thereof include styrene-based polymers and polycarbonate-based polymers.

  In addition, polyethylene, polypropylene, ethylene / propylene copolymers, olefin polymers such as cyclo polyolefin and norbornene polyolefin, vinyl chloride polymers, nylon and aromatic amide polymers, imide polymers and sulfone polymers, poly Transparent protection of ether sulfone polymers, polyether ether ketone polymers, vinylidene chloride polymers, vinyl alcohol polymers, vinyl butyral polymers, arylate polymers, polyoxymethylene polymers, epoxy polymers, and blends of these polymers Examples of the polymer for layer formation are listed. Among them, a transparent protective layer made of a cellulose polymer is preferable.

  The transparent protective layer can be formed by a coating method of a polymer solution, but generally, a bonding method using a film is adopted. For the bonding treatment, for example, an appropriate adhesive such as an isocyanate-based adhesive, a polyvinyl alcohol-based adhesive, a gelatin-based adhesive, a vinyl latex-based adhesive, or a water-based proester-based adhesive can be used. The thickness of the transparent protective layer can be appropriately determined, but is generally 500 μm or less, in particular 1 to 300 μm, particularly 5 to 200 μm.

  On the other hand, as the retardation film, a birefringent film or a liquid crystal polymer obtained by stretching a film made of the polymer exemplified in the above-described rigid layer, relaxation layer, and transparent protective layer by an appropriate method such as uniaxial or biaxial. And a film in which an alignment layer of a liquid crystal polymer is supported by a film. The thickness of the retardation plate is not particularly limited, and can be appropriately determined according to the retardation or the like, but is generally 10 to 300 μm, especially 20 to 150 μm.

  For the purpose of use, for example, various wave plates such as a quarter wave plate and a half wave plate, and for the purpose of compensating for coloration and viewing angle by birefringence of a liquid crystal layer (optical compensator plate). It may have an appropriate phase difference. Accordingly, the retardation plate may be a tilted orientation film in which the refractive index in the thickness direction is controlled, or a laminate in which two or more retardation plates are laminated to control optical characteristics such as retardation. Also good.

  The quarter-wave plate can be used for conversion of linearly polarized light into circularly polarized light or conversion of circularly polarized light into linearly polarized light, and thus can be used for forming a circularly polarizing plate. The circularly polarizing plate is effectively used, for example, when adjusting the color tone of an image of a reflective liquid crystal display device in which the image is displayed in color, and also has an antireflection function. The half-wave plate can be used for conversion of the polarization plane of linearly polarized light.

  As the optical compensation plate, a retardation plate made of a uniaxially stretched film or other retardation plates can be used. The elliptically polarizing plate can be effectively used to achieve high-quality black-and-white display by compensating for coloring caused by birefringence due to STN type liquid crystal. A retardation plate having a controlled three-dimensional refractive index (elliptical refractive index) such as a tilted orientation film is preferable because it can compensate for coloring that occurs when a liquid crystal display is viewed from an oblique direction.

  The viewing angle compensator, which is one of the optical compensators, is designed to compensate the perspective image and widen the viewing angle for good viewing so that the liquid crystal display screen is clear when viewed from the front and oblique directions. It is a phase difference plate. As the viewing angle compensation plate, a biaxially stretched film, a uniaxially stretched film with a controlled refractive index in the thickness direction, a tilted alignment film, or the like is used.

  In particular, a viewing angle compensator in which an alignment layer of a liquid crystal polymer, particularly an optically anisotropic layer composed of a tilted alignment layer of a discotic liquid crystal polymer, is supported by a triacetyl cellulose film from the viewpoint of a viewing angle expansion effect, etc. Can be used.

  The viewing angle compensation plate can be used to form a wide viewing angle polarizing plate. In addition, the tilted orientation film is a method in which a heat-shrinkable film is bonded to a polymer film and the polymer film is stretched or / and contracted to act on the shrinkage force by heating, or on one or both of the front and back surfaces of the polymer film. It can be obtained by a method of applying a shearing force, a method of obliquely aligning a liquid crystal polymer, or the like.

  The optical compensation plate is preferably positioned between a display main body such as a liquid crystal display cell and a polarizing plate from the viewpoint of improving the compensation effect. Therefore, a laminated sheet provided with an optical compensation plate is usually provided with a polarizing plate, and the polarizing plate is disposed between the relaxation layer and the optical compensation plate.

  In the laminated sheet, a relaxation layer 3 is bonded to the lower side (back side) of the rigid layer 1 via a transparent adhesive layer 2 as shown in the figure, and the transparent layer 4 is interposed below the relaxation layer 3. The optical component 5 is adhered, and both the adhesive layers 2 and 4 are those having a 180 degree peel value (adhesive force) of 5 N / 25 mm or more with respect to a triacetyl cellulose (TAC) film. . The peeling speed is 300 mm / min.

  When the adhesive force is less than 5 N / 25 mm, heat resistance and moisture resistance are poor, and foaming and peeling are likely to occur at the adhesive interface in a heating atmosphere and a humidified atmosphere, resulting in poor durability of the laminated sheet. From the viewpoint of durability, the adhesive strength of the pressure-sensitive adhesive layer is preferably 7 to 50 N / 25 mm, especially 10 to 40 N / 25 mm, particularly 12 to 30 N / 25 mm.

  The adhesive layer for adhesion can be formed according to the adhesive layer exemplified in the relaxation layer. Therefore, the relaxation layer can also serve as the adhesive layer for adhesion, but generally the relaxation layer is soft and lacks cohesive force and does not exhibit the adhesive force.

  The pressure-sensitive adhesive layer for adhesion showing the adhesive force can be formed of, for example, an acrylic pressure-sensitive adhesive mainly composed of (meth) acrylic acid alkyl ester and an isocyanate-based crosslinking agent.

  The adhesive strength (adhesive strength) of the pressure-sensitive adhesive layer comprising the acrylic pressure-sensitive adhesive can be controlled by the degree of crosslinking of the polymer component or the like via the isocyanate-based crosslinking agent, and the degree of crosslinking depends on the type of isocyanate-based crosslinking agent used. The amount used can be appropriately selected and adjusted.

  Therefore, the amount of the isocyanate-based crosslinking agent used can be appropriately determined according to the adhesive force and the like, but generally 0.5 to 15 parts by weight, especially 1 to 10 parts by weight per 100 parts by weight of the acrylic polymer, In particular, the amount is 2 to 5 parts by weight.

  As the isocyanate-based crosslinking agent, one or two or more suitable compounds having an isocyanate group can be used, and generally those having two or three or more isocyanate groups are used.

  Incidentally, as specific examples of the isocyanate-based crosslinking agent, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, diphenylmethane-4,4-diisocyanate, commercially available coronate L, Millionate MR, Coronate EH, Coronate HL (the four points are trade names, all manufactured by Nippon Polyurethane Industry Co., Ltd.), obtained by reaction of various polyether polyols, polyester polyols, polyamides, and the like with isocyanate compounds, Examples thereof include compounds having an isocyanate group at the end of the molecule.

  When the acrylic polymer is obtained by copolymerizing the above cross-linking agent, it is preferable to use one or two or more appropriate silane coupling agents in the acrylic pressure-sensitive adhesive. The blending amount of the silane coupling agent can be appropriately determined according to the adhesive force and the like, but generally 0.05 to 10 parts by weight, especially 0.1 to 5 parts by weight, per 100 parts by weight of the acrylic polymer, In particular, it is 0.2 to 3 parts by weight.

  Incidentally, specific examples of the silane coupling agent include polymerizable unsaturated group-containing silicon compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, and methacryloxypropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, and 3 -Glycidoxypropylmethyldimethoxysilane, silicon compounds having an epoxy structure such as 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-aminopropyltrimethoxysilane and N- (2-aminoethyl) 3- Examples thereof include amino group-containing silicon compounds such as aminopropyltrimethoxysilane, N- (2-aminoethyl) 3-aminopropylmethyldimethoxysilane, and 3-chloropropyltrimethoxysilane.

  The thickness of the adhesive layer for adhesion can be determined as appropriate, but is generally 500 μm or less, in particular 1 to 200 μm, particularly 5 to 100 μm. The peel value can be adjusted even by controlling the thickness, and a thickness of 10 to 50 μm is particularly preferable from the point of achieving the peel value.

  The pressure-sensitive adhesive layer provided in the laminated sheet, for example, the pressure-sensitive adhesive layer (7) of the film-like surface treatment layer, the pressure-sensitive adhesive layer in the case of forming an optical component composed of a laminate, etc., also exhibit the above peel value. This is preferable from the viewpoint of durability of the laminated sheet.

  In addition, if necessary, the adhesive layer provided on the lower side of the optical component of the laminated sheet also exhibits the peel value as described above, in order to adhere the laminated sheet to a display main body such as a liquid crystal display cell. This is preferable from the standpoint of maintaining the close contact state of the laminated sheet with respect to the display main body due to prevention of the above. When the pressure-sensitive adhesive layer is exposed on the surface, it is preferable to temporarily cover the cover with a release film for the purpose of preventing adhesion of foreign matter and the like until it is put to practical use.

  The laminated sheet, particularly one or more layers, particularly the rigid layer, located on the upper side (viewing side) of the relaxation layer, exhibits ultraviolet absorbing ability for the purpose of improving the weather resistance of the relaxation layer. May be. The ultraviolet absorbing ability can be imparted by an appropriate method such as a method of blending an ultraviolet absorber in the layer. As the ultraviolet absorber, for example, one or more appropriate compounds such as a salicylic acid ester compound, a benzophenone compound, a benzotriazole compound, a cyanoacrylate compound, and a nickel complex compound can be used.

  The laminated sheet can be preferably used in a touch input type, particularly a pen input type image display device composed of a liquid crystal display device or the like. In this case, the laminated sheet is arranged on the viewing side of the display main body composed of the liquid crystal display cell or the like with the optical component 5 side as the liquid crystal display cell 8 side and the rigid layer 1 as the upper side as shown in the figure. At the time of application, it is preferable to adhere to the display main body through an adhesive layer from the viewpoint of reducing the reflection loss of light. In the figure, 9 is a polarizing plate provided on the back side of the liquid crystal display cell.

  A surface treated film (N5SPB, manufactured by Kimoto Co., Ltd.) with an anti-glare hard coat treatment applied to the surface of a 188 μm thick PET film, and a 250 μm thick PET film (Mitsubishi Chemical Polyester Co., Ltd.) subjected to an easy adhesion treatment After pressing the upper side of the rigid layer comprising a pressure-sensitive adhesive layer via a pressure-sensitive adhesive layer, the pressure-bonded body and the sheet-like relaxation layer are pressure-bonded to each other via a pressure-sensitive adhesive layer, and then the pressure-sensitive pressure-relaxed relaxation layer and the polarizing layer are polarized. A plate (Nitto Denko Corp., SEG5425DU) was roll-bonded via an adhesive layer to obtain a laminated sheet.

The relaxation layer was prepared by adding 90 parts of butyl acrylate (parts by weight, the same applies hereinafter), 10 parts of hydroxybutyl acrylate, 2, 2 to a reaction vessel equipped with a cooling pipe, a nitrogen introduction pipe, a thermometer, an ultraviolet irradiation device, and a stirring device. -To 100 parts of a syrup-like acrylic polymer / monomer mixture having a polymerization rate of 8% obtained by adding 0.1 part of dimethoxy-2-phenylacetophenone and preliminarily polymerizing by ultraviolet irradiation, 0. 4 parts, 0.1 part of 1-hydroxy-cyclohexyl-phenylketone was blended and applied onto a 100 μm thick polyester separator, and irradiated with 2000 mJ / cm ² of UV light with a UV lamp in a nitrogen atmosphere. It was photopolymerized to obtain a transparent sheet having a thickness of 1 mm.

  The adhesive layer was obtained by reacting 100 parts of butyl acrylate, 5 parts of acrylic acid, and 0.2 part of azobisisobutyronitrile in an ethyl acetate solvent at 60 ° C. for 7 hours. For 100 parts of the copolymer solution, 0.8 part of a polyisocyanate compound (manufactured by Nippon Polyurethane, Coronet L) and a silane coupling agent [3-glycidoxypropyltrimethoxysilane] (manufactured by Shin-Etsu Chemical Co., Ltd., KBM-403) 0.1 part was added to obtain a pressure-sensitive adhesive composition, which was coated on a polyester separator and dried at 90 ° C. for 5 minutes to obtain a transparent layer having a thickness of 25 μm.

Comparative Example 1
A laminated sheet was obtained in the same manner as in Example 1 except that the rigid layer and the relaxation layer, and the relaxation layer and the polarizing plate were roll-bonded without using the adhesive layer.

  A laminated sheet was obtained in the same manner as in Example 1 except that the rigid layer and the relaxation layer were roll-bonded without using an adhesive layer.

Hiei example 3
A laminated sheet was obtained in the same manner as in Example 1 except that the relaxing layer and the polarizing plate were roll-bonded without using an adhesive layer.

Hiei example 4
A laminated sheet was obtained according to Example 1 except that all the adhesive layers were replaced with the following.
Replacement adhesive layer: 100 parts of butyl acrylate, 5 parts of acrylic acid, and 0.2 part of azobisisobutyronitrile were reacted in an ethyl acetate solvent at 60 ° C. for 7 hours. To 100 parts of the polymer solution, 0.4 parts of coronate L, 0.04 part of polyhydroxyalkylamine compound (Asahi Denka Co., Ltd., EDP-300) and KBM-403: 0.1 part are added to form an adhesive composition. A transparent adhesive layer having a thickness of 25 μm obtained by applying the product on a polyester separator and drying it at 90 ° C. for 5 minutes.

Evaluation Test Adhesive Force The adhesive layer used in the examples and comparative examples is provided on a PET film having a thickness of 50 μm to form an adhesive tape having a width of 25 mm, and a 2 kg rubber roller is reciprocated once against a TAC film having a thickness of 80 μm. Then, a 180 degree peel value (peeling) at room temperature (25 ° C.) was measured with a tensile tester (manufactured by Shimadzu Corporation, Autograph) under the condition of a tensile speed of 300 mm / min.

Adhesive strength The integrated sheets obtained in Examples and Comparative Examples were cut to a width of 25 mm, and between a rigid layer and a relaxation layer (rigid / loose) or a relaxation layer at room temperature under a tensile speed of 300 mm / min with a tensile tester. The 90 degree peel value between the film and the polarizing plate (slow / biased) was measured.

Durability The integrated sheets obtained in Examples and Comparative Examples were cut into 12 mm sizes, and the polarizing plate side was adhered to a glass plate through the same kind of adhesive layer as that sheet, and then autoclaved (50 ° C. × 0.5 Mpa). × 15 minutes), a heating test in which it is put in an atmosphere at 80 ° C. for 500 hours, or 60 ° C. × 90% R.D. A humidification test was performed in an H atmosphere for 500 hours, and changes in appearance were visually observed and evaluated according to the following criteria.
○: When failure such as foaming or peeling is not observed ×: When failure such as foaming or peeling occurs

The results are shown in the following table.
To TAC adhesive force Adhesive strength (N / 25mm) Durability
(N / 25 mm) Tsuyoshi / slow slow / polarized heated humidified
Example 15 18 15 ○ ○
Comparative Example 1 15 3 2 × ×
Comparative Example 2 15 3 15 × ○
Comparative Example 3 15 18 2 × ×
Comparative Example 4 4 6 4 × ×

Cross-sectional side view of laminated sheet and its application example

Explanation of symbols

1: Rigid layer 2, 4: Adhesive layer
3: Relaxation layer
5: Optical parts
6: Surface treatment layer
7: Adhesive layer
8: Liquid crystal display cell (display main)
9: Polarizing plate


Patent applicant Nitto Denko Corporation
Agent Tsutomu Fujimoto

Claims (6)

It has a relaxation layer made of a transparent viscoelastic body through a transparent adhesive layer on the lower side of the rigid layer made of a transparent polymer, and has an optical component through the transparent adhesive layer on the lower side of the relaxation layer. A laminated sheet comprising:
The relaxation layer was formed of an acrylic polymer obtained by photopolymerizing a monomer containing a (meth) acrylic acid alkyl ester and a polyfunctional (meth) acrylate having 2 to 8 (meth) acryloyl groups. (However, the relaxation layer does not contain a plasticizer)
The two adhesive layers are acrylic adhesives containing an acrylic polymer obtained by polymerizing a monomer containing an alkyl (meth) acrylate, an isocyanate crosslinking agent and a silane coupling agent, It is formed with an acrylic pressure-sensitive adhesive containing 0.5 to 15 parts by weight of an isocyanate-based crosslinking agent per 100 parts by weight of the polymer, and both the pressure-sensitive adhesive layers are 5 N / 25 mm above the triacetyl cellulose film. The 180 degree peel value of
A laminated sheet in which the optical component is a polymer film.   The monomer related to the acrylic polymer used for forming the relaxing layer further contains a modifying monomer, and the proportion of the modifying monomer used is 100 (meth) acrylic acid alkyl ester and the total amount of the modifying monomer. The laminated sheet according to claim 1, which is 40% by weight or less with respect to weight%.   The monomer related to the acrylic polymer used for forming the relaxation layer is a polyfunctional (meth) acrylate having from 10 to 10 (meth) acryloyl groups per 100 parts by weight of the (meth) acrylic acid alkyl ester. The laminated sheet according to claim 1 or 2, comprising parts by weight. The laminated sheet according to any one of claims 1 to 3 , wherein the laminated sheet has at least one of an antireflection layer, an antireflection layer, a hard coat layer, an antistatic layer, and a contamination prevention layer on the rigid layer. . Touch input-type image display device having a laminated sheet according to any one of claims 1-4. The image display device of the pen-having a laminated sheet according to any one of claims 1-4 on the viewer side of the liquid crystal display cell.

Images