JP2013087225A - Adhesive for optical film, adhesive sheet for optical film, adhesion method of optical film, optical film with adhesive layer, and display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive for optical films, which can suppress the deterioration of adhesive force, rise of haze and change in hue even in the case such that the adhesive is placed under high-temperature and high-humidity conditions for a long time after it is used for the adhesion of an optical film and which is excellent in deformation followability of an optical film.SOLUTION: An adhesive including 0.1-3 pts.mass of a crosslinking agent to 100 pts.mass of an urethane urea resin having a mass average molecular weight of 50,000-200,000 is used for the adhesion of optical films.

Description

  The present invention relates to an adhesive and an adhesive sheet used to adhere an optical film. Moreover, this invention relates also to the adhesion method of the optical film using the said adhesive. Furthermore, the present invention relates to an optical film having the pressure-sensitive adhesive and a display device in which the optical film is adhered with the pressure-sensitive adhesive.

  Optical films are widely used in display devices and the like as transparent films having specific optical functions. For example, an optical compensation film, a polarizer protective film, an antireflection film and the like used for a liquid crystal display device can be given as specific examples of the optical film. These films are required to be laminated at a predetermined position in the liquid crystal display device and stably held in the usage environment of the liquid crystal display device. For this reason, at the time of manufacturing a liquid crystal display device, it is generally performed to adhere and fix an optical film using an adhesive.

  Conventionally, various pressure-sensitive adhesives have been proposed as pressure-sensitive adhesives for optical films. A typical optical film pressure-sensitive adhesive is an acrylic pressure-sensitive adhesive mainly containing an acrylic resin, and is described in, for example, Patent Documents 1 and 2. Some urethane-based pressure-sensitive adhesives mainly containing a urethane resin have also been proposed, and are described in Patent Documents 3 to 5, for example. Further, a urethane urea pressure-sensitive adhesive mainly containing a urethane urea resin is also described in Patent Documents 6 and 7.

  On the other hand, as a pressure-sensitive adhesive for application to transparent conductive films such as ITO and conductive members such as metal circuits, a pressure-sensitive adhesive in which a crosslinking agent is added to a urethane urea resin obtained by reacting a polyamino compound with a urethane prepolymer has been proposed. (See Patent Document 8). It is described that this adhesive does not cause corrosion, does not cause foaming or peeling under high temperature and high humidity conditions, exhibits good plasticizer resistance and processability, and has high adhesiveness. However, this patent document does not describe application of the pressure-sensitive adhesive to an optical film.

JP 2006-77235 A Special table 2008-507617 JP 2003-292928 A JP 2007-119599 A JP 2009-91522 A JP 2010-180290 A JP 2011-26418 A JP 2011-148965 A

  In a display device such as a liquid crystal display device, the temperature of the light emitting element gradually increases when it is continuously used because it emits heat during display. In recent years, it has been studied to install and use a display device outdoors exposed to sunlight, and a device having excellent durability even under high temperature and high humidity is required. For this reason, the adhesive which sticks the optical film incorporated in the display apparatus is also required to exhibit a stable function without adversely affecting the display apparatus under high temperature and high humidity. Specifically, it exhibits sufficient adhesiveness even under high temperature and high humidity, and of course has excellent deformation followability of the optical film. In addition, whitening and yellowing are prevented, and display performance is not deteriorated. It is required to be a thing.

From such a viewpoint, when various adhesives that have been proposed in the past are applied to an optical film and evaluated for a long time under high temperature and high humidity, the haze increases or the color changes. It turns out that there are many cases. Further, it has been found that even if the increase in haze and the change in color can be suppressed, it is not possible to follow the dimensional change of the film under high temperature and high humidity, thereby reducing the display performance of the display device.
Therefore, the present inventors have attempted to develop a pressure-sensitive adhesive for an optical film that solves such problems of the prior art. That is, the present inventors follow a decrease in adhesive force, an increase in haze, a change in color, and a deformation of the film even when the optical film is used for adhesion of an optical film and then placed under high temperature and high humidity for a long time. In order to provide a pressure-sensitive adhesive for optical films, the present inventors have intensively studied.

  As a result of repeated trials and errors, the present inventors have found that the adhesive obtained by mixing a specific resin with a cross-linking agent exhibits excellent performance particularly for optical films and solves the problems of the prior art. I found out. The present invention has been provided based on such knowledge, and includes the following configurations.

[1] An optical film pressure-sensitive adhesive containing 0.1 to 3 parts by mass of a crosslinking agent with respect to 100 parts by mass of a urethane urea resin having a mass average molecular weight of 50,000 to 200,000.
[2] The adhesive for optical films according to [1], wherein the urethane urea resin is obtained by reacting a polyamino compound with a urethane prepolymer obtained by reacting a polyol and a polyisocyanate.
[3] The pressure-sensitive adhesive for optical films according to [2], wherein the polyisocyanate is isophorone diisocyanate.
[4] The optical film pressure-sensitive adhesive according to [2] or [3], further comprising a silane coupling agent.
[5] The optical film pressure-sensitive adhesive according to any one of [1] to [4], which is used to adhere a retardation film.
[6] The optical film pressure-sensitive adhesive according to [5], wherein the retardation film is composed of a cycloolefin resin.
[7] The pressure-sensitive adhesive for optical films according to [5] or [6], which is used between the retardation film and glass and used to adhere both.
[8] The pressure-sensitive adhesive for optical films according to [5] or [6], which is used between the retardation film and the polarizing plate and used to adhere both.
[9] A pressure-sensitive adhesive sheet for an optical film comprising the pressure-sensitive adhesive according to any one of [1] to [8].

[10] A method for adhering an optical film, comprising a step of sequentially laminating and pressing the optical film, the adhesive sheet according to [9], and an adhesive object.
[11] The method for adhering an optical film according to [10], wherein the optical film is a retardation film.
[12] The method for adhering an optical film according to [10] or [11], wherein the adhesion object is glass or a polarizing plate.
[13] An optical film with a pressure-sensitive adhesive layer having a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive according to any one of [1] to [8] on the surface of the optical film.
[14] The optical film with an adhesive layer according to [13], wherein a release film is further formed on the adhesive layer formed on the optical film.
[15] A display device in which an optical film is adhered by the adhesive according to any one of [1] to [8].
[16] The display device according to [15], which is a liquid crystal display device.

  The pressure-sensitive adhesive of the present invention can be effectively used for sticking an optical film. Even when the optical film is adhered using the pressure-sensitive adhesive of the present invention and then placed under a high temperature and high humidity for a long time, the decrease in adhesive force, increase in haze, and change in color are effectively suppressed, and the film It can follow the deformation. For this reason, the display apparatus which adhere | attached the optical film using the adhesive of this invention can maintain a stable display function over a long period of time.

It is sectional drawing which shows one Embodiment of the adhesive sheet which has a peeling film on both surfaces. It is sectional drawing which shows one embodiment of the optical film with an adhesive layer. It is sectional drawing which shows one embodiment of the optical film with the adhesion layer made to adhere to the adhesion target object. It is sectional drawing which shows one embodiment of the optical film with an adhesive layer which has an adhesive layer and a peeling film. It is sectional drawing which shows one embodiment of the optical film with an adhesive layer which has an adhesive layer and a peeling film on both surfaces. It is a graph which shows the viscoelasticity measurement result of the adhesive of this invention. It is a graph which shows the viscoelasticity measurement result of the acrylic adhesive used in Comparative Examples 1-2.

  Below, the adhesive for optical films of this invention is demonstrated in detail. The description of the constituent elements described below may be made based on typical embodiments and specific examples of the present invention, but the present invention is not limited to such embodiments and specific examples. In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

[Features of pressure-sensitive adhesive of the present invention]
The pressure-sensitive adhesive for optical films of the present invention is characterized by containing 0.1 to 3 parts by mass of a crosslinking agent with respect to 100 parts by mass of a urethane urea resin having a mass average molecular weight of 50,000 to 200,000. The pressure-sensitive adhesive of the present invention may contain components other than the urethane urea resin and the crosslinking agent.

[Urethane urea resin]
The urethane urea resin used for the pressure-sensitive adhesive of the present invention is a resin having a urethane bond and a urea bond in the polymer chain. The urethane urea resin used for the pressure-sensitive adhesive of the present invention preferably has an ester bond and / or an ether bond in the polymer chain. The urethane urea resin used for the pressure-sensitive adhesive of the present invention is more preferably a resin obtained by reacting a polyamino compound with a urethane prepolymer obtained by reacting a polyol and a polyisocyanate. At this time, a reaction terminator may be used as necessary, or a catalyst such as a tertiary amine compound or an organometallic compound may be used.

The mass average molecular weight of the urethane urea resin used for the pressure-sensitive adhesive of the present invention is 50,000 to 200,000, and preferably 80,000 to 150,000. The mass average molecular weight here is a mass average molecular weight in terms of standard polystyrene by gel permeation chromatography (GPC). It is preferable that the solution viscosity (25 degreeC) of 50 mass% solid content of the urethane urea resin used for the adhesive of this invention is 3000-25000 mPa * s.
The glass transition temperature (Tg) of the urethane urea resin used for the pressure-sensitive adhesive of the present invention is preferably in the range of −80 ° C. to 0 ° C. in order to impart sufficient pressure-sensitive adhesiveness to the pressure-sensitive adhesive.
Below, the polyol, polyisocyanate, and polyamino compound which can be used for the synthesis | combination of a preferable urethane urea resin are demonstrated.

[Polyol]
Examples of the polyol that can be used for the synthesis of the urethane urea resin include polyether polyols, polyester polyols, polycarbonate polyols, copolymers thereof, and other glycols. Moreover, polyols other than these can also be used.

  As the polyether polyols, compounds having two or more hydroxyl groups and ether bonds can be used. For example, polymers, copolymers, and grafts of alkylene oxides such as propylene oxide, tetrahydrofuran, ethylene oxide, and butylene oxide. Copolymers; polyether polyols by condensation of hexanediol, methylhexanediol, heptanediol, octanediol or mixtures thereof; glycols in which alkylene oxides such as ethylene oxide are added to bisphenols such as bisphenol A and bisphenol F Can be used.

  As the polyester polyols, compounds having two or more hydroxyl groups and ester bonds can be used. For example, a polyester polyol obtained by condensation reaction of a polyfunctional alcohol component and a dibasic acid component can be used. Examples of the polyfunctional alcohol component include ethylene glycol, propylene glycol, dipropylene glycol, diethylene glycol, triethylene glycol, butylene glycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, and 3,3 ′. -Dimethylol heptane, polyoxyethylene glycol, polyoxypropylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, octanediol, butylethylpentanediol, 2-ethyl-1,3-hexane Examples include compounds having two hydroxyl groups such as diol, cyclohexanediol, bisphenol A, and bisphenol F, and three or more hydroxyl acids such as glycerin, trimethylolpropane, and pentaerythritol. Compounds having the like. Examples of the dibasic acid component include aliphatic or aromatic dibasic acids such as terephthalic acid, adipic acid, azelaic acid, sebacic acid, phthalic anhydride, isophthalic acid, and trimellitic acid. Other polyester polyols include β-butyrolactone, β-propiolactone, γ-butyrolactone, γ-valerolactone, δ-valerolactone, ε-caprolactone, γ-caprolactone, γ-heptanolactone, α-methyl- Polyester polyols obtained by ring-opening polymerization of cyclic ester compounds such as lactones such as β-propiolactone can also be used.

  Polycarbonate polyols have a structural unit represented by — [— O—R—O—CO —] — (R represents a divalent organic group). Polycarbonate polyols can be obtained, for example, by a reaction between glycol or bisphenol and a carbonate ester, or a reaction in which phosgene is allowed to act on glycol or bisphenol in the presence of an alkali. Examples of the carbonic acid ester used in the above reaction include dimethyl carbonate, diethyl carbonate, diphenyl carbonate, ethylene carbonate, propylene carbonate, and the like. Examples of the glycol or bisphenol used in the above reaction include ethylene glycol, propylene glycol, dipropylene glycol, diethylene glycol, triethylene glycol, butylene glycol, 3-methyl-1,5-pentanediol, and 2-methyl-1. , 8-octanediol, 3,3′-dimethylolheptane, polyoxyethylene glycol, polyoxypropylene glycol, propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1 , 6-hexanediol, 1,9-nonanediol, neopentyl glycol, octanediol, butylethylpentanediol, 2-ethyl-1,3-hexanediol, cyclohexanediol, or bisphenol Bisphenols such Lumpur A, bisphenol F, ethylene oxide bisphenol, mention may be made of bisphenols obtained by adding alkylene oxide such as propylene oxide.

  Examples of glycols other than the above include, for example, compounds having two hydroxyl groups such as ethylene glycol, diethylene glycol, triethylene glycol, butanediol, propanediol, 1,6-hexanediol, neopentyl glycol, and cyclohexanedimethanol; glycerin A compound having three or more hydroxyl groups such as trimethylolpropane, trimethylolethane, pentaerythritol, sorbitol, methylglucoside; at least one ionic functional group (for example, carboxyl group, phosphate group, sulfonate group, first group A polyol containing ˜tertiary amino group, quaternary ammonium group, phosphonium group, and quaternary sulfonium group) can be used.

Among the polyols, it is preferable to use a polyol having a polypropylene glycol skeleton. Among the polyols used in the present invention, the amount of the polyol having a polypropylene glycol skeleton is preferably 50 to 100% by mass.
The number average molecular weight of the polyol used in the present invention is preferably 800 to 4,000, and more preferably 1,000 to 3,000.

[Polyisocyanate]
Examples of the polyisocyanate that can be used for the synthesis of the urethane urea resin include aromatic polyisocyanate, aliphatic polyisocyanate, araliphatic polyisocyanate, and alicyclic polyisocyanate.

  Examples of the aromatic polyisocyanate include 1,3-phenylene diisocyanate, 4,4′-diphenyl diisocyanate, 1,4-phenylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6 -Tolylene diisocyanate, 4,4'-toluidine diisocyanate, 2,4,6-triisocyanate toluene, 1,3,5-triisocyanate benzene, dianisidine diisocyanate, 4,4'-diphenyl ether diisocyanate, 4,4 ', 4 "-triphenylmethane triisocyanate and the like can be used.

  Examples of the aliphatic polyisocyanate include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate and the like can be used.

  Examples of the araliphatic polyisocyanate include ω, ω′-diisocyanate-1,3-dimethylbenzene, ω, ω′-diisocyanate-1,4-dimethylbenzene, ω, ω′-diisocyanate-1,4-diethylbenzene. 1,4-tetramethylxylylene diisocyanate, 1,3-tetramethylxylylene diisocyanate, and the like can be used.

  Examples of the alicyclic polyisocyanate include isophorone diisocyanate (also known as IPDI), 1,3-cyclopentane diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, methyl-2,4-cyclohexane diisocyanate, and methyl. -2,6-cyclohexane diisocyanate, 4,4'-methylenebis (cyclohexyl isocyanate), 1,4-bis (isocyanatomethyl) cyclohexane, and the like can be used.

  In addition to the above, a trimethylolpropane adduct of the above polyisocyanate, a trimer having an isocyanurate ring, and the like can be used in combination. Polyphenylmethane polyisocyanate, naphthylene diisocyanate, modified polyisocyanate thereof, and the like can be used. As the polyisocyanate-modified product, a carbodiimide group, a uretdione group, a uretoimine group, a burette group reacted with water, a group of isocyanurate groups, or a modified product having two or more of these groups can be used. A reaction product of a polyol and a diisocyanate can also be used as a polyisocyanate.

[Polyamino compound]
The polyamino compound that can be used for the synthesis of the urethane urea resin is a compound having two or more amino groups. Examples of polyamino compounds include ethylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, triethylenetetramine, diethylenetriamine, triaminopropane, 2,2,4-trimethylhexamethylenediamine, and 2-hydroxyethylethylenediamine. N- (2-hydroxyethyl) propylenediamine, (2-hydroxyethylpropylene) diamine, (di-2-hydroxyethylethylene) diamine, (di-2-hydroxyethylpropylene) diamine, (2-hydroxypropylethylene) Aliphatic polyamines such as diamine, (di-2-hydroxypropylethylene) diamine, and piperazine; isophorone diamine, dicyclohexylmethane-4,4′-diamine, etc. An alicyclic polyamine: phenylenediamine, xylylenediamine, 2,4-tolylenediamine, 2,6-tolylenediamine, diethyltoluenediamine, 3,3′-dichloro-4,4′-diaminodiphenylmethane, 4, An aromatic diamine such as 4′-bis- (sec-butyl) diphenylmethane; and a dimer amine obtained by converting a carboxyl group of a dimer acid into an amino group, a dendrimer having a primary or secondary amino group at a terminal, and a propoxy amine at both terminals. The polyoxyalkylene glycol diamine etc. which have can be used.
As the polyamino compound used in the present invention, it is preferable to use a compound obtained by Michael addition reaction of an ethylenically unsaturated compound with a compound having two or more primary amino groups, and further, an ethylenic compound having a hydroxyl group as the ethylenically unsaturated compound. It is preferred to use unsaturated compounds.

[Crosslinking agent]
The crosslinking agent used for the pressure-sensitive adhesive of the present invention is used in an amount of 0.1 to 3 parts by mass with respect to 100 parts by mass of the urethane urea resin. By making the usage-amount of a crosslinking agent 3 mass parts or less, when the adhesive is applied to an optical film, the outstanding effect of this invention can be enjoyed. More preferably, the crosslinking agent is used in an amount of 0.2 to 1.5 parts by mass.

  The crosslinking agent used for the pressure-sensitive adhesive of the present invention preferably has a functional group such as an isocyanate group, an epoxy group, an alkoxysilyl group, a methylol group, an aziridine group, or a carbodiimide group. As the crosslinking agent, for example, polyisocyanate compounds, polyfunctional epoxy compounds, high molecular weight polycarbodiimides, N-methylol group-containing compounds, polyfunctional aziridine compounds, metal chelates and the like can be used.

  As the crosslinking agent used in the pressure-sensitive adhesive of the present invention, it is particularly preferable to use a polyisocyanate compound. The polyisocyanate compound is a compound having a plurality of isocyanate groups in the molecule, and specifically, tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate. Polyisocyanate compounds such as tetramethylxylylene diisocyanate, naphthalene diisocyanate, triphenylmethane triisocyanate, polymethylene polyphenyl isocyanate, and adducts of these polyisocyanate compounds with polyol compounds such as trimethylolpropane, Burettes, isocyanurates, and these polyisocyanates Sulfonate compound and a known polyether polyols, polyester polyols, acrylic polyols, polybutadiene polyols, adducts, etc. and polyisoprene polyol and the like.

  Examples of the crosslinking agent other than the polyisocyanate compound include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, bisphenol A / epichlorohydrin type epoxy resin, N, N, N ′. , N′-tetraglycidyl-m-xylenediamine, 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, N, N-diglycidylaniline, N, N-diglycidyltoluidine, etc. A polyfunctional aziridine compound such as 2,2′-bishydroxymethylbutanol tris [3- (1-aziridinyl) propionate], 4,4′-bis (ethyleneiminocarbonylamino) diphenylmethane; for example, aluminum, iron, Copper, sub- , Tin, titanium, nickel, antimony, magnesium, vanadium, and polyvalent metals such as chromium and zirconium, and metal chelates, such as coordination compounds with acetylacetone or ethyl acetoacetate.

[Other components of adhesive]
The pressure-sensitive adhesive of the present invention may contain components other than the urethane urea resin and the crosslinking agent. For example, an acrylic resin, a polyester resin, an amino resin, an epoxy resin, or a polyurethane resin may be used in combination as a resin other than the urethane urea resin.
Further, the pressure-sensitive adhesive of the present invention includes an antioxidant, a metal corrosion inhibitor, a tackifier, a silane coupling agent, an ultraviolet absorber, a light stabilizer such as a hindered amine compound, a filler, an ionic property as necessary. Additives such as liquids may be included. Examples of the antioxidant include phenolic antioxidants, amine-based antioxidants, lactone-based antioxidants, phosphorus-based antioxidants, sulfur-based antioxidants, and the like. These antioxidants may be used alone or in combination of two or more. As the metal corrosion inhibitor, a benzotriazole-based resin is preferable because of the compatibility and high effect of the pressure-sensitive adhesive. Examples of the tackifier include rosin resin, terpene resin, terpene phenol resin, coumarone indene resin, styrene resin, xylene resin, phenol resin, and petroleum resin. Examples of the silane coupling agent include mercaptoalkoxysilane compounds (for example, mercapto group-substituted alkoxy oligomers). Examples of the ultraviolet absorber include benzotriazole compounds and benzophenone compounds. Examples of the ionic liquid include ionic liquids such as a nitrogen-containing onium salt, a sulfur-containing onium salt, or a phosphorus-containing onium salt, and are preferably described in paragraph numbers 0018 to 0028 of JP2011-89138A. Ionic liquids to be used. The description of paragraph numbers 0018 to 0028 in Japanese Patent Application Laid-Open No. 2011-89138 is incorporated herein as part of this specification.
The compounding amount of these additives is usually preferably 0.01 to 10 parts by mass, more preferably 0.05 to 5 parts by mass, and particularly preferably 0.1 to 3 parts by mass with respect to 100 parts by mass of the adhesive layer. preferable.
In addition, the material and aspect described in Paragraph Nos. 0021 to 0105 of JP 2011-148965 A can also be adopted in the present invention, and these descriptions are cited here as a part of this specification.

[Application of adhesive]
The pressure-sensitive adhesive of the present invention can be directly applied to a material to be adhered. The applicable law is not particularly limited. For example, it may be dissolved in a solvent and applied as a solution and then dried (solution method), or may be formed into a sheet and stacked (sheet method). When applied as a solution, it may be applied to a release film and then contacted with an optical film (transfer method), or after being laminated with a release film having a different release performance and finished into a sheet having a release film on both sides The adhesive layer from which the release film has been peeled may be brought into contact with an optical film or an adhesive object to be bonded to the optical film (adhesive sheet method).
When the adhesive is applied in the form of a solution, examples of the solvent include methyl ethyl ketone, ethyl acetate, toluene, xylene, acetone, benzene, dioxane, acetonitrile, tetrahydrofuran, diglyme, dimethyl sulfoxide, N-methylpyrrolidone, dimethylformamide and the like. Can be used. After applying the solution, the pressure-sensitive adhesive layer can be formed by removing the solvent at high temperature or under reduced pressure.

[Viscoelastic modulus of adhesive layer]
The pressure-sensitive adhesive layer of the present invention has a low storage elastic modulus (hereinafter referred to as G ′) and a loss sine (hereinafter referred to as tan δ) obtained as a ratio (G ″ / G ′) of the storage elastic modulus (hereinafter referred to as G ″). By using a high pressure-sensitive adhesive, the deformation followability is improved. G ′ of the pressure-sensitive adhesive layer of the present invention is preferably 5 × 10 ⁷ or less, preferably 1 × 10 ⁷ or less, within a range of −50 ° C. to 120 ° C., and 5 × 10 ⁶ or less. Is more preferable. The tan δ of the pressure-sensitive adhesive layer of the present invention is preferably 0.1 or more, more preferably 0.15 or more, and further preferably 0.2 or more within the range of −50 ° C. to 120 ° C. . The glass transition temperature obtained from tan δ is preferably lower than −20 ° C., more preferably lower than −35 ° C.
The values of G ′, G ″, and tan δ can be adjusted by the mass average molecular weight of the urethane urea resin, the composition of the monomer, the blending amount (crosslinking degree) of the crosslinking agent, and the like.

[Thickness of adhesive layer]
The thickness of the pressure-sensitive adhesive layer formed using the pressure-sensitive adhesive of the present invention is preferably 5 to 50 μm, and more preferably 10 to 30 μm. If the thickness of the pressure-sensitive adhesive layer is less than or equal to the above upper limit value, it is difficult for deformation to occur during the punching process of the pressure-sensitive adhesive, and it is difficult for bubbles to be generated and optical unevenness after bonding, and the total thickness of the module does not become too thick. . On the other hand, if the thickness of the pressure-sensitive adhesive layer is not less than the above lower limit value, practical adhesive strength to the optical film is easily obtained, and in the durability test, defects such as peeling and air bubbles are caused, or the optical film is deformed. However, sufficient followability cannot be obtained, and problems such as optical defects such as white spots are unlikely to occur.
When using a pressure-sensitive adhesive having a large mass average molecular weight, the viscosity of the coating liquid for forming the pressure-sensitive adhesive layer tends to be high, and the concentration of the coating liquid may be decreased, but the thickness is the upper limit. The following pressure-sensitive adhesive layer can be easily formed even if the coating solution concentration is reduced.

[Adhesive sheet]
The pressure-sensitive adhesive of the present invention can be formed into a sheet to form a pressure-sensitive adhesive sheet. The pressure-sensitive adhesive sheet can be produced, for example, by dissolving a pressure-sensitive adhesive in a solvent and removing the solvent after coating. The coating method can be appropriately selected from knife coaters, micro bar coaters, air knife coaters, reverse roll coaters, reverse gravure coaters, bario gravure coaters, die coaters, curtain coaters and the like.
The pressure-sensitive adhesive sheet of the present invention is prepared, for example, by preparing a release film provided with a release agent layer on a substrate such as a polymer film, and applying and drying the pressure-sensitive adhesive coating liquid of the present invention on the release agent layer. Can be obtained. As shown in FIG. 1, the release sheet preferably has a structure in which the upper and lower sides of the pressure-sensitive adhesive layer 112 are sandwiched between two release films 114 each having a release agent layer 115 provided on a base material 116. The pressure-sensitive adhesive sheet of the present invention having such a structure is obtained by applying and drying the pressure-sensitive adhesive coating liquid on the release layer surface of the first release film in which the release agent layer is provided on the polymer film, and then the first release film and Can be obtained by bonding and pressure-bonding the release layer surface of the second release film composed of release agent layers having different release forces to the pressure-sensitive adhesive layer surface.
When the release force of the first release film and the second release film is close, when the release film on the light release force side is peeled off, there is a tearing phenomenon in which the adhesive floats from the release film on the heavy release force side. Occur. Therefore, the peel force of the release film on the heavy peel force side is preferably 0.15N to 0.05N, and the peel force of the peel film on the light peel force side is preferably 0.04N to 0.01N. Further, the value of heavy peeling force / light peeling force is preferably 1.5 or more, and more preferably 2.0 or more.
Moreover, at this time, when the difference of the peeling force of two peeling films can be maintained, after apply | coating an adhesive coating liquid previously to a 2nd peeling film, a 1st peeling film may be bonded and pressure-bonded. .
The shape of the pressure-sensitive adhesive sheet may be a sheet shape or may be wound up in a roll shape.

  If the pressure-sensitive adhesive sheet is used, there is no need for the application of the pressure-sensitive adhesive at the bonding stage and the drying step, and the pressure-sensitive adhesive sheet can be laminated and pressed between the optical film and the pressure-sensitive adhesive object. is there. That is, an optical film, an adhesive sheet, and an adhesion target object are laminated | stacked in this order, and an optical film and an adhesion target object can be easily adhere | attached by pressurizing the obtained laminated body.

[Optical film with adhesive layer]
As shown in FIG. 2, the optical film 110 with an adhesive layer can be manufactured by laminating | stacking the adhesive of this invention on the surface of the optical film 111 as the adhesive layer 112. As shown in FIG. As a method of applying the pressure-sensitive adhesive to the surface of the optical film, the above-described solution method, sheet method and the like can be used. As shown in FIG. 3, the optical film with the pressure-sensitive adhesive layer is easily applied to the pressure-sensitive adhesive object by applying pressure so that the pressure-sensitive adhesive layer 112 is in contact with the pressure-sensitive adhesive object 113 to which the optical film 111 is to be attached. Can be attached.
Moreover, after peeling off the release film 114 on one side of the pressure-sensitive adhesive sheet using the pressure-sensitive adhesive of the present invention shown in FIG. 1, the pressure-sensitive adhesive layer is bonded to the pressure-sensitive adhesive layer 112 as shown in FIG. An attached optical film can be manufactured. At this time, in order to prevent the adhesive from sticking to an unintended object or being deteriorated by being exposed to air, the release film should be peeled off just before trying to bond as much as possible. .
Furthermore, when the above-mentioned pressure-sensitive adhesive of the present invention is formed into a sheet to form a pressure-sensitive adhesive sheet, an optical film with a pressure-sensitive adhesive layer can also be produced by directly pressing the optical film after applying it to the release film, and its production The method can be selected for convenience.
By performing a known surface treatment such as corona treatment or plasma treatment on the bonding surface of the optical film to be bonded, the adhesiveness between the pressure-sensitive adhesive layer and the optical film can be further improved.
The shape of such an optical film with an adhesive may be a sheet or may be rolled up.

As shown in FIG. 3, the optical film with the pressure-sensitive adhesive layer is easily attached to the pressure-sensitive adhesive object by overlapping and pressing the pressure-sensitive adhesive object to be bonded to the pressure-sensitive adhesive layer from which the release film has been peeled off. can do. At this time, in order to prevent the adhesive from sticking to an unintended object or being deteriorated by being exposed to air, the release film should be peeled off just before trying to bond as much as possible. .
Moreover, as a means for suppressing such a case, a mode in which a release film 114 is further formed on the pressure-sensitive adhesive layer 112 as shown in FIG. 4 can be cited as a preferred example. The release film 114 preferably includes a base material 116 and a release agent layer 115. At this time, lamination is performed such that the release film 115 side of the release film contacts the surface of the pressure-sensitive adhesive layer 112. When making especially roll shape, it is preferable to roll up by applying such a peeling film, peeling a peeling film at the time of use, and sticking an optical film with an adhesive layer to an adhesion target object.
The pressure-sensitive adhesive layer may be formed on both sides of the optical film. Moreover, you may form said peeling film further on the adhesive layer formed in both surfaces. As a specific example of such an embodiment, the embodiment shown in FIG. 5 can be cited. At the time of use, for example, the adhesive layer exposed by peeling off one release film is superimposed on the adhesive object, and the other adhesive layer exposed by peeling the other release film is used as another adhesive object. It is possible to adhere by pressurizing the whole.

As the release film substrate, for example, various polymer films can be used, and polyethylene terephthalate is particularly preferable from the viewpoint of surface smoothness and processability. As the release agent constituting the release agent layer, for example, a general-purpose addition type or condensation type silicone release agent or a long-chain alkyl group-containing compound is used. In particular, an addition type silicone release agent having high reactivity is preferably used. Specific examples of silicone release agents include BY24-4527 and SD-7220 manufactured by Toray Dow Corning Silicone, KS-3600, KS-774, and X62-2600 manufactured by Shin-Etsu Chemical Co., Ltd. Is mentioned. Further, the silicone release agent may contain a silicone resin which is an organosilicon compound having a SiO ₂ unit and a (CH ₃ ) ₃ SiO _1/2 unit or CH ₂ ═CH (CH ₃ ) SiO _1/2 unit. preferable. Specific examples of the silicone resin include BY24-843, SD-7292, SHR-1404, etc. manufactured by Toray Dow Corning Silicone, KS-3800, X92-183, manufactured by Shin-Etsu Chemical Co., Ltd., and the like.

[Adhesive optical films, etc.]
The optical film that adheres using the pressure-sensitive adhesive of the present invention is a transparent film having a specific optical function. For example, a retardation film (optical compensation film) having optical anisotropy and having a retardation in a specific in-plane direction and a retardation in a specific thickness direction can be exemplified as a particularly preferable optical film. Examples of the material constituting such a retardation film include cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate propionate butyrate, cellulose propionate butyrate and the like. Of cellulose acylates; and cycloolefin resins. As a commercially available resin material that can be used as a retardation film, Arton (manufactured by JSR), Zeonore (manufactured by Nippon Zeon), and the like can be given.

  As an adhesive using the pressure-sensitive adhesive of the present invention, a polarizer protective film (sometimes referred to as a polarizing plate protective film) formed to protect the polarizer functions as a support for the polarizer in the polarizing plate. Examples thereof include a polarizing plate substrate and an antireflection film that suppresses reflection of light incident from the outside. Examples of the material constituting these include exemplary materials constituting the retardation film.

  Furthermore, what adheres using the adhesive of this invention is a cycloolefin phase difference film and a polarizing plate especially from a polyethylene terephthalate (PET) or a polycarbonate (PC) from the outstanding adhesiveness and deformation | transformation followability. preferable.

[Display device]
Various display devices can be manufactured by adhering an optical film using the adhesive of the present invention. Examples of typical display devices include a liquid crystal display device (liquid crystal display panel), a plasma display device (plasma display panel), and an organic electroluminescence display device (organic EL panel). The pressure-sensitive adhesive of the present invention is particularly preferably applied to a liquid crystal display device, and is preferably applied to bonding of a retardation film and a polarizing plate of a liquid crystal display device or bonding of a retardation film and a display panel.
The display device in which the optical film is adhered using the pressure-sensitive adhesive of the present invention can be used for a long time or when used outdoors in a high-temperature or high-humidity environment. Even when the panel is placed under high humidity, a stable display function can be maintained. That is, even when left under a high temperature and high humidity for a long time, the adhesive of the present invention may change the color of the display, promote whitening, or cause distortion or uneven display due to dimensional changes. Can be prevented.

  The features of the present invention will be described more specifically with reference to examples and comparative examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below. In the examples, “parts” and “%” represent “parts by weight” and “% by weight” unless otherwise specified.

(Example 1) Manufacture of a laminate 1 using a urethane urea pressure-sensitive adhesive 1
(1) Production of pressure-sensitive adhesive and pressure-sensitive adhesive sheet [synthesis of amino compound]
After adding 19 parts of 4-hydroxybutyl acrylate and 19 parts of butyl acrylate to 25.0 parts of isophorone diamine (IPDA) and 25.0 parts of toluene, the mixture was reacted at 80 ° C. for 2 hours, and then 63 parts of toluene was added to form a solid. What adjusted the content to 50% was used as the amino compound solution.
[Synthesis of urethane urea resin]
589 parts of bifunctional polypropylene glycol, 161 parts of isophorone diisocyanate, 2188 parts of toluene and 0.06 part of dibutyltin dilaurate as a catalyst were reacted at 100 ° C. for 2 hours, then cooled to 40 ° C., 804 parts of ethyl acetate, After adding 3.12 parts of acetylacetone, 78.3 parts of the amino compound solution described above was added and aged for 1 hour.
Furthermore, 3.5 parts of 2-amino-2-methyl-propanol and 200 parts of ethyl acetate were added to obtain a urethane urea resin. The urethane urea resin had a weight average molecular weight Mw of 100,000.
[Preparation of Urethane Urea Adhesive]
0.7 parts of a diisocyanate crosslinking agent and 0.5 parts of a silane coupling agent were blended with 100 parts of the solid content of the urethane urea resin to prepare a urethane urea pressure-sensitive adhesive.
[Creation of urethane urea adhesive sheet]
The above urethane urea pressure-sensitive adhesive is applied on a 38 μm thick heavy release PET film (A71 manufactured by Teijin DuPont Films) with an applicator to a dry film thickness of 25 μm, dried at 100 ° C. for 3 minutes, and then coated. A urethane-urea pressure-sensitive adhesive sheet was prepared by laminating a 38 μm-thick lightly peeled PET film (RL-07 made by Oji Specialty Paper) on the film surface.

(2) Creation of laminate [laminate A]
Peel off the light release PET film of the aforementioned urethane urea-based adhesive film on a 30 μm thick cycloolefin phase difference film (ARTON manufactured by JSR) and paste it with a roll, and then peel off the heavy release PET film side. A laminate of A retardation film / adhesive layer (25 μm thickness) / glass is prepared by bonding to 1.1 mm glass with a roll and then holding it in an autoclave at 50 ° C. and 0.5 MPa for 20 minutes. did.
[Laminate B]
A polarizing plate with an adhesive (F1205DU manufactured by Nitto Denko Corporation) is further bonded onto the cycloolefin phase difference film of the laminate A, and the polarizing plate / adhesive layer / retardation film / adhesive layer (25 μm thickness) / A glass laminate B was prepared.

(Example 2) Manufacture of a laminate using a urethane urea pressure-sensitive adhesive 2
By changing the thickness of the urethane urea-based pressure-sensitive adhesive layer from 25 μm to 100 μm, and otherwise performing the same manufacturing process as in Example 1, the retardation film / pressure-sensitive adhesive layer (100 μm thickness) / glass laminate A and polarized light A laminate B of plate / adhesive layer / retardation film / adhesive layer (100 μm thickness) / glass was produced.

(Comparative Examples 1-2) Manufacture of laminated body using acrylic adhesive 1-2
Comparative Example 1-2 was made in the same manner as in Examples 1-2 except that an acrylic adhesive (SK Dyne 2094 manufactured by Soken Chemical Co., Ltd.) was used instead of the urethane urea-based adhesive used in the Examples. Laminates A and B were produced.

(Test Example 1) High temperature and high humidity durability evaluation test The haze (Hz) and total light transmittance (Tt) of the laminate A produced in Examples 1-2 and Comparative Examples 1-2 were measured using a turbidimeter (Nippon Denshoku). “Haze Meter NDH2000” manufactured by Kogyo Co., Ltd.), and the lightness (L *) and chromaticity (a *, b *) were measured using a color difference meter (“Spectro Color Meter SE” manufactured by Nippon Denshoku Industries Co., Ltd.). It was measured. Thereafter, each laminate was placed in an oven set at 85 ° C. and a relative humidity of 90% and taken out after 100 hours. After 30 minutes, haze (Hz), total light transmittance (Tt), brightness (L *), The amount of change was calculated by measuring the chromaticity (a *, b *). The results are shown in Table 1 below.

  As is clear from the results in Table 1, the amount of change in the laminates of Examples 1-2 was smaller than that of the corresponding laminates of Comparative Examples 1-2. This means that when the optical film is adhered using the adhesive of the present invention, haze increase and color change are effectively suppressed even when the film is placed under high temperature and high humidity for a long time after adhesion. It shows that Moreover, since the laminated body A of Examples 1-2 showed sufficient adhesive force even after the high-temperature and high-humidity test, it was also confirmed that the fall of adhesive force can also be suppressed.

  Performed when the same test was performed by changing the conditions of 85 ° C and 90% relative humidity to 70 ° C and 80% relative humidity, or when the same test was performed by changing to 65 ° C and 90% relative humidity. The amount of change in haze (Hz), total light transmittance (Tt), lightness (L *), and chromaticity (a *, b *) of the laminates of Examples 1 and 2 was small.

(Test Example 2) White spot test Two laminates B in Examples 1 and 2 and Comparative Examples 1 and 2 were facilitated for 500 hours in an atmosphere of 80 ° C./20% relative humidity and 60 ° C./90% relative humidity. After leaving it in place, place it on the top and bottom surfaces of the liquid crystal panel (Binitt Co., Ltd.) so that it is in a crossed nicols position, illuminate the backlight from below, and visually observe the white spots from the top. . Table 2 shows the results of evaluation based on the following criteria.
Evaluation criteria ○: No white spots were observed on the polarizing plate.
Δ: Slight white spots were observed on the polarizing plate.
X: White spots were observed on the polarizing plate.

  As is clear from the results in Table 2, the laminate B of Examples 1 and 2 had fewer white spots than the corresponding laminate B of Comparative Examples 1 and 2. This means that even when the optical film is adhered using the adhesive of the present invention and then placed under a high temperature and high humidity for a long time, the adhesive follows the stress change for the dimensional change of the film, This indicates that the film is not distorted and the influence on the optical properties can be suppressed.

(Test Example 3) Viscoelasticity measurement The same urethane urea pressure-sensitive adhesive as that used in Example 1 was laminated to form a pressure-sensitive adhesive layer having a thickness of 2 mm. The storage elastic modulus (G ′) and the loss elastic modulus (G ″) were measured with a rheometer (manufactured by Relogica: Model DYNALYSERDAR-2000) under the conditions of a frequency of 1 Hz and a heating rate of 3 ° C./min. The sine (tan δ) was determined as the ratio of G ′ to G ″ (G ″ / G ′). The results are shown in FIG.
Further, using the acrylic adhesive used in Comparative Examples 1 and 2 instead of the urethane urea adhesive used in Example 1, the storage elastic modulus (G ′) and the loss elastic modulus (G ″) were similarly obtained. FIG. 7 shows the result of measuring the loss sine (tan δ).
As is clear from FIG. 6, the urethane urea pressure-sensitive adhesive satisfying the conditions of the present invention exhibits a low storage elastic modulus (G ′) and a high loss sine (tan δ), which are preferable for deformation followability, and over a wide temperature range. The glass transition temperature obtained from tan δ is lower than −35 ° C., indicating excellent deformation followability.

  The adhesive of the present invention can suppress a decrease in adhesive strength, an increase in haze, and a change in color even when it is used for adhesion of an optical film and then placed under high temperature and high humidity for a long time. Therefore, the pressure-sensitive adhesive of the present invention can be effectively used for the production of a display device that requires adhesion of an optical film. Therefore, the present invention has high industrial applicability.

DESCRIPTION OF SYMBOLS 110 Optical film with an adhesive layer 111 Optical film 112 Adhesive layer 113 Adhesive target object 114 Release film 115 Release agent layer 116 Base material

Claims (16)

  The adhesive for optical films which contains 0.1-3 mass parts of crosslinking agents with respect to 100 mass parts of urethane urea resins whose mass mean molecular weight is 50,000-200,000.   The pressure-sensitive adhesive for an optical film according to claim 1, wherein the urethane urea resin is obtained by reacting a polyamino compound with a urethane prepolymer obtained by reacting a polyol and a polyisocyanate.   The pressure-sensitive adhesive for optical films according to claim 2, wherein the polyisocyanate is isophorone diisocyanate.   Furthermore, the adhesive for optical films of Claim 2 or 3 containing a silane coupling agent.   The pressure-sensitive adhesive for optical films according to any one of claims 1 to 4, which is used for sticking a retardation film.   The pressure-sensitive adhesive for optical films according to claim 5, wherein the retardation film is composed of a cycloolefin resin.   The pressure-sensitive adhesive for an optical film according to claim 5 or 6, wherein the pressure-sensitive adhesive is applied between the retardation film and glass and is used to adhere both.   The pressure-sensitive adhesive for an optical film according to claim 5 or 6, wherein the pressure-sensitive adhesive is applied between the retardation film and the polarizing plate and is used to adhere both.   The adhesive sheet for optical films containing the adhesive of any one of Claims 1-8.   A pressure-sensitive adhesive method for an optical film, comprising a step of sequentially laminating and pressing an optical film, the pressure-sensitive adhesive sheet according to claim 9 and a pressure-sensitive adhesive object.   The method for adhering an optical film according to claim 10, wherein the optical film is a retardation film.   The method for adhering an optical film according to claim 10 or 11, wherein the adhesion object is glass or a polarizing plate.   The optical film with an adhesive layer which has an adhesive layer which consists of an adhesive of any one of Claims 1-8 on the surface of an optical film.   The optical film with an adhesive layer according to claim 13, wherein a release film is further formed on the adhesive layer formed on the optical film.   The display apparatus with which the optical film is adhere | attached with the adhesive of any one of Claims 1-8.   The display device according to claim 15, which is a liquid crystal display device.