Adhesive sheet and optical laminate

Abstract

To provide an adhesive sheet that is formed from a photocurable composition and is suitable for adjusting the anchoring force with an optical film to a large value.SOLUTION: An adhesive sheet 1 of the present invention is formed from a photocurable composition which contains a monomer group and / or a partial polymerization product of the monomer group. In the photocurable composition, the amount of an isocyanate-based crosslinking agent is less than 0.05 pt.wt. relative to the total of 100 pts.wt. of the monomer group and the partial polymerization product. In the adhesive sheet 1, the monomer group contains an ether group-containing monomer, and the amount of the ether group-containing monomer is 25 pts.wt. or more relative to 100 pts.wt. of the monomer group. When a polymer is synthesized from the monomer group, the glass transition temperature of the polymer, as calculated from the Fox equation, is higher than -60°C.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a pressure-sensitive adhesive sheet and an optical laminate. [Background technology]

[0002] Various image display devices, such as liquid crystal display devices and electroluminescence (EL) display devices, generally include an optical laminate including an optical film such as a polarizing film and an adhesive sheet. Adhesive sheets are typically used to bond the optical films included in the optical laminate and to bond the optical laminate to an image display panel. Typical adhesive sheets are sheets obtained by polymerizing and crosslinking monomers including acrylic monomers, silicone monomers, and the like to harden them.

[0003] An example of a pressure-sensitive adhesive sheet is disclosed in Patent Document 1. In Patent Document 1, the pressure-sensitive adhesive sheet is produced by irradiating a pressure-sensitive adhesive composition with light. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 3052972 Summary of the Invention [Problem to be solved by the invention]

[0005] Typical PSA sheets are manufactured, for example, by the following thermal curing method. First, a polymer is produced by polymerizing a polymerizable monomer in an organic solvent, and a crosslinking agent or the like is blended with the resulting polymer to prepare a PSA composition. This PSA composition is then coated on a substrate such as a release liner, and the organic solvent is removed by heating to form a sheet. If necessary, thermal aging is performed to complete the crosslinking, thereby producing a PSA sheet. This manufacturing process requires the combustion of large amounts of fuel, such as LNG, to generate the thermal energy required for the thermal removal of the solvent and for thermal aging. Furthermore, releasing the thermally removed organic solvent directly into the atmosphere can have a significant adverse effect on the surrounding environment. For this reason, the organic solvent is often burned in a deodorizing furnace or the like before being released. This not only requires additional fuel for combustion in the deodorizing furnace, but also converts the organic solvent itself into CO2 upon combustion, which is then released into the atmosphere, resulting in a manufacturing process with extremely high CO2 emissions.

[0006] In recent years, climate change caused by greenhouse gases has become an urgent issue, and governments around the world have set numerical targets to reduce CO2 emissions. Therefore, there is a demand to select manufacturing processes that emit less CO2.

[0007] The method of producing an adhesive sheet using light (photo-curing method) can reduce the amount of energy required to form the adhesive sheet and CO2 emissions compared to the above-mentioned heat-curing method. In the curing method, an isocyanate-based crosslinking agent is usually blended into the pressure-sensitive adhesive composition, and the isocyanate-based crosslinking agent tends to improve the anchoring strength between the pressure-sensitive adhesive sheet and the optical film. On the other hand, when an optical laminate is produced using a pressure-sensitive adhesive sheet formed by the photocuring method, the anchoring strength between the pressure-sensitive adhesive sheet and the optical film is small, and peeling tends to occur easily between the pressure-sensitive adhesive sheet and the optical film.

[0008] Therefore, the present invention provides a pressure-sensitive adhesive sheet that is formed from a photocurable composition and is suitable for adjusting the anchoring force with an optical film to a large value. [Means for solving the problem]

[0009] As described above, according to the studies of the present inventors, when a pressure-sensitive adhesive sheet formed by a photocuring method is used, peeling tends to occur more easily between the pressure-sensitive adhesive sheet and the optical film than when a pressure-sensitive adhesive sheet formed by a thermosetting method is used. This tendency is presumably due to the fact that when a pressure-sensitive adhesive sheet formed by a thermosetting method is bonded to an optical film, the curing of the pressure-sensitive adhesive sheet proceeds further on the surface of the optical film, whereas when a pressure-sensitive adhesive sheet formed by a photocuring method is bonded to the optical film, curing hardly proceeds at all. This problem can occur particularly significantly when the optical film contains a uniaxially stretched film such as a polarizer, or when the thickness of the pressure-sensitive adhesive sheet is 30 μm or less.

[0010] Based on the above findings, the inventors further investigated and discovered that even in a photocurable composition that contains almost no isocyanate-based crosslinking agent, the anchoring strength between an adhesive sheet formed from the photocurable composition and an optical film can be adjusted to a large value by appropriately adjusting the amount of ether group-containing monomer and the glass transition temperature calculated using the FOX equation, and thus completed the present invention.

[0011] The present invention provides A pressure-sensitive adhesive sheet formed from a photocurable composition containing a monomer group and / or a partial polymer of the monomer group, the amount of the isocyanate-based crosslinking agent in the photocurable composition is less than 0.05 parts by weight per 100 parts by weight of the total of the monomer group and the partial polymer, the monomer group includes an ether group-containing monomer, the amount of the ether group-containing monomer blended is 25 parts by weight or more per 100 parts by weight of the monomer group, The adhesive sheet is provided such that, when a polymer is synthesized from the monomer group, the glass transition temperature of the polymer calculated from the FOX formula is higher than -60°C.

[0012] Furthermore, the present invention provides The above adhesive sheet, an optical film including at least one selected from the group consisting of a polarizing film and a retardation film; An optical laminate comprising: [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a pressure-sensitive adhesive sheet that is formed from a photocurable composition and is suitable for adjusting the anchoring strength with an optical film to a large value. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a cross-sectional view schematically illustrating an example of the pressure-sensitive adhesive sheet of the present invention. [Figure 2A] FIG. 2 is a schematic diagram illustrating a method for measuring the amount of creep of a pressure-sensitive adhesive sheet. [Figure 2B] FIG. 2 is a schematic diagram illustrating a method for measuring the amount of creep of a pressure-sensitive adhesive sheet. [Figure 3A] 1A to 1C are schematic diagrams illustrating an example of a method for producing a pressure-sensitive adhesive sheet according to the present invention. [Figure 3B] 1A to 1C are schematic diagrams illustrating an example of a method for producing a pressure-sensitive adhesive sheet according to the present invention. [Figure 3C] 1A to 1C are schematic diagrams illustrating an example of a method for producing a pressure-sensitive adhesive sheet according to the present invention. [Figure 4] 1 is a cross-sectional view schematically showing an example of an optical laminate of the present invention. [Figure 5] 1 is a cross-sectional view schematically showing an example of an optical laminate of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] The pressure-sensitive adhesive sheet according to the first aspect of the present invention comprises: A pressure-sensitive adhesive sheet formed from a photocurable composition containing a monomer group and / or a partial polymer of the monomer group, the amount of the isocyanate-based crosslinking agent in the photocurable composition is less than 0.05 parts by weight per 100 parts by weight of the total of the monomer group and the partial polymer, the monomer group includes an ether group-containing monomer, the amount of the ether group-containing monomer blended is 25 parts by weight or more per 100 parts by weight of the monomer group, When a polymer is synthesized from the monomer group, the glass transition temperature of the polymer calculated from the FOX formula is higher than -60°C.

[0016] In a second aspect of the present invention, for example, in the pressure-sensitive adhesive sheet according to the first aspect, the partial polymer has a relative dielectric constant of 3.8 or more at a frequency of 100 Hz.

[0017] In a third aspect of the present invention, for example, in the pressure-sensitive adhesive sheet according to the first or second aspect, the ether group-containing monomer includes an alkoxy group-containing monomer.

[0018] In a fourth aspect of the present invention, for example, in the pressure-sensitive adhesive sheet according to the third aspect, the alkoxy group-containing monomer is represented by the following formula (1). [ka] In the formula (1), R 1 is a hydrogen atom or a methyl group, and R 2 is an alkyl group, and n is an integer of 1 to 30.

[0019] In a fifth aspect of the present invention, for example, in the pressure-sensitive adhesive sheet according to the third or fourth aspect, the alkoxy group-containing monomer includes 2-methoxyethyl acrylate.

[0020] In a sixth aspect of the present invention, for example, in the pressure-sensitive adhesive sheet according to the first or second aspect, the ether group-containing monomer has a ring structure.

[0021] In a seventh aspect of the present invention, for example, in the pressure-sensitive adhesive sheet according to any one of the first to sixth aspects, the glass transition temperature is 0°C or lower.

[0022] In an eighth aspect of the present invention, for example, in the pressure-sensitive adhesive sheet according to any one of the first to seventh aspects, the photocurable composition does not contain an isocyanate-based crosslinking agent.

[0023] In a ninth aspect of the present invention, for example, in the pressure-sensitive adhesive sheet according to any one of the first to eighth aspects, the content of solvent in the photocurable composition is 5 wt % or less.

[0024] In a tenth aspect of the present invention, for example, the pressure-sensitive adhesive sheet according to any one of the first to ninth aspects has a surface that has been subjected to a surface modification treatment.

[0025] The optical laminate according to the eleventh aspect of the present invention is A pressure-sensitive adhesive sheet according to any one of the first to tenth aspects; An optical film including at least one selected from the group consisting of a polarizing film and a retardation film. Film and Equipped with.

[0026] In a twelfth aspect of the present invention, for example, in the optical laminate according to the eleventh aspect, the anchoring force between the pressure-sensitive adhesive sheet and the optical film is 10.0 N / 25 mm or more.

[0027] The present invention will be described in detail below, but the present invention is not limited to the following embodiments and can be implemented in any modified form without departing from the gist of the present invention.

[0028] [Embodiment of adhesive sheet] An example of a pressure-sensitive adhesive sheet according to this embodiment is shown in FIG. 1. The pressure-sensitive adhesive sheet 1 in FIG. 1 is formed from a photocurable composition containing a group of monomers and / or a partial polymer of the monomers. The amount of the isocyanate-based crosslinking agent in the photocurable composition is less than 0.05 parts by weight per 100 parts by weight of the total of the monomers and the partial polymer. In other words, the photocurable composition does not contain more than 0.05 parts by weight of the isocyanate-based crosslinking agent per 100 parts by weight of the total of the monomers and the partial polymer. The monomer group includes an ether group-containing monomer, and the amount of the ether group-containing monomer per 100 parts by weight of the monomer group is 25 parts by weight or more.

[0029] In this embodiment, when polymer A is synthesized from the above monomer group, the glass transition temperature Tg of polymer A calculated from the FOX formula is greater than -60°C. The glass transition temperature Tg of polymer A tends to correlate with the glass transition temperature of pressure-sensitive adhesive sheet 1. The glass transition temperature Tg is, for example, -55°C or higher, and may be -50°C or higher. There are no particular limitations on the upper limit of the glass transition temperature Tg, and it is, for example, 0°C or lower, or may be -20°C or lower, or may be -40°C or lower. The FOX formula is represented by the following formula (I): 1 / Tg=w1 / Tg1+w2 / Tg2+···+w m / Tg m (I)

[0030] In the above formula (I), Tg is the glass transition temperature (K) of polymer A. w1, w2, ... w m are the weight fractions of each monomer in the monomer group. , ···Tg m are the glass transition temperatures (K) of the individual polymers of each monomer. For example, w1 is the weight fraction of a first monomer in a group of monomers, and Tg1 is the glass transition temperature (K) of a single polymer of the first monomer. The glass transition temperature (K) of polymer A can be calculated from formula (I) and converted into units to determine the glass transition temperature Tg (°C) of polymer A.

[0031] As shown in FIG. 1, the pressure-sensitive adhesive sheet 1 has surfaces 1a and 1b facing each other. As an example, the pressure-sensitive adhesive sheet 1 is attached to an optical film via surface 1a, and the pressure-sensitive adhesive sheet 1 is attached to an image display panel via surface 1b. Surface 1a of the pressure-sensitive adhesive sheet 1, which comes into contact with the optical film, may or may not have been subjected to a surface modification treatment. Surface 1a that has been subjected to a surface modification treatment tends to improve the anchoring force between the pressure-sensitive adhesive sheet 1 and the optical film. On the other hand, surface 1b of the pressure-sensitive adhesive sheet 1 is preferably not subjected to a surface modification treatment. Examples of surface modification treatments include corona treatment, plasma treatment, excimer treatment, and flame treatment. Surface 1a is preferably subjected to corona treatment as a surface modification treatment.

[0032] The surface modification treatment may be carried out in an inert gas atmosphere. By carrying out the surface modification treatment in a state where the oxygen concentration is reduced by the inert gas, the risk of ignition of the remaining monomers can be reduced. Specifically, the surface modification treatment is preferably carried out at an oxygen concentration of 8% by volume or less, more preferably 6% by volume or less, and even more preferably 3% by volume or less. If the oxygen concentration is too low, the introduction of functional groups into the pressure-sensitive adhesive sheet surface by the surface modification treatment may be insufficient, so the oxygen concentration is preferably 0.01% by volume or more, more preferably 0.1% by volume or more, and more preferably 0.5% by volume or more. % or more by volume is particularly preferred. Specific examples of the inert gas include nitrogen and argon. The surface modification treatment may be carried out under normal pressure (1 atmosphere).

[0033] The conditions for the surface modification treatment, which is a corona treatment, are expressed in terms of the discharge amount, for example, 0.6 to 100 kJ / m 2 The lower limit of the discharge amount is 1 kJ / m 2 More than 2kJ / m 2 More than 5kJ / m 2 More than 7kJ / m 2 More than 10kJ / m 2 More than 13kJ / m 2 More than 15kJ / m 2 More than 20kJ / m 2 More than 25kJ / m 2 More than 30kJ / m2 or more, and 35kJ / m 2 The upper limit of the discharge amount is 70 kJ / m 2 Below, 60kJ / m 2 Below, 50kJ / m 2 Below, 45kJ / m 2 Below, 40kJ / m 2 Below, 30kJ / m 2 Below, 20kJ / m 2 Below 18kJ / m 2 When the corona treatment is carried out in an atmosphere with an oxygen concentration of 10% by volume or more and 20.9% by volume or less, the discharge amount is 1 to 18 kJ / m 2 And When the corona treatment is carried out in an atmosphere with an oxygen concentration of 0.01% by volume or more and less than 10% by volume, the discharge amount is 1 to 60 kJ / m 2 The discharge amount of the corona treatment may be appropriately adjusted. This tends to further improve the anchoring force between the pressure-sensitive adhesive sheet 1 and the optical film.

[0034] (Photocurable composition) As described above, the pressure-sensitive adhesive sheet 1 is formed from a photocurable composition. The photocurable composition is a pressure-sensitive adhesive composition that forms the pressure-sensitive adhesive sheet 1 when irradiated with light. In the photocurable composition, the monomer group includes, for example, a (meth)acrylic monomer. The content of the (meth)acrylic component in the photocurable composition, i.e., the (meth)acrylic monomer and its partial polymerized product, may be 50% by weight or more, 60% by weight or more, 70% by weight or more, or even 80% by weight or more. In this case, an acrylic pressure-sensitive adhesive sheet 1 containing a (meth)acrylic polymer and its crosslinked product as the main component can be formed. However, the photocurable composition is not limited to the above examples. In this specification, (meth)acrylic means acrylic and methacrylic. (Meth)acrylate means acrylate and methacrylate.

[0035] An example of the (meth)acrylic monomer is a (meth)acrylic acid alkyl ester having an alkyl group of 1 to 20 carbon atoms on the side chain. The number of carbon atoms in the alkyl group may be 7 or less, 6 or less, 5 or less, or even 4 or less. The alkyl group may be linear or branched. Examples of the (meth)acrylic acid alkyl ester include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, isobutyl (meth)acrylate, n-pentyl (meth)acrylate, isopentyl (meth)acrylate, n-hexyl (meth)acrylate, isohexyl (meth)acrylate, isoheptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and the like. acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, n-dodecyl (meth)acrylate (lauryl (meth)acrylate), n-tridecyl (meth)acrylate, n-tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, and octadecyl (meth)acrylate. The (meth)acrylic acid alkyl ester may be n-butyl (meth)acrylate.

[0036] The amount of the (meth)acrylic acid alkyl ester blended per 100 parts by weight of the monomer group is, for example, 75 parts by weight or less, and may be 60 parts by weight or less, 50 parts by weight or less, 40 parts by weight or less, or even 30 parts by weight or less. The lower limit of the blended amount is, for example, 10 parts by weight or more. The monomer group may not contain the (meth)acrylic acid alkyl ester. In calculating the blended amount of a specific monomer, the weight of the partially polymerized product is converted into the weight of each monomer before polymerization.

[0037] The monomer group may contain a carboxyl group-containing monomer. The carboxyl group-containing monomer may be a (meth)acrylic monomer; in other words, the (meth)acrylic monomer may contain a carboxyl group-containing monomer. Examples of carboxyl group-containing monomers include (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid. The amount of the carboxyl group-containing monomer per 100 parts by weight of the monomer group may be, for example, 10 parts by weight or less, 9 parts by weight or less, 8 parts by weight or less, 7 parts by weight or less, 6 parts by weight or less, 5 parts by weight or less, 4.8 parts by weight or less, 4 parts by weight or less, 3 parts by weight or less, 2 parts by weight or less, 1 part by weight or less, or even 0.5 parts by weight or less. The lower limit of the amount is, for example, 0.1 parts by weight or more, and in some cases, may be 0.5 parts by weight or more. The monomer group may not contain a carboxyl group-containing monomer.

[0038] The monomer group may contain a hydroxy group-containing monomer. The hydroxy group-containing monomer may be a (meth)acrylic monomer, in other words, the (meth)acrylic monomer may contain a hydroxy group-containing monomer. The hydroxy group-containing monomer may contribute to improving the cohesive strength of the PSA sheet. Examples of hydroxy group-containing monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)-methyl acrylate. The hydroxy group-containing monomer is preferably 2-hydroxyethyl (meth)acrylate or 4-hydroxybutyl (meth)acrylate. The amount of the hydroxy group-containing monomer blended per 100 parts by weight of the monomer group may be, for example, 20 parts by weight or less, 15 parts by weight or less, 10 parts by weight or less, 7.5 parts by weight or less, 5 parts by weight or less, 4 parts by weight or less, 3 parts by weight or less, 2 parts by weight or less, 1 part by weight or less, or even 0.5 parts by weight or less. The lower limit of the blended amount may be, for example, 0.01 parts by weight or more, 0.03 parts by weight or more, or even 0.05 parts by weight or more. The monomer group may not contain a hydroxy group-containing monomer.

[0039] As described above, the monomer group includes an ether group-containing monomer. The ether group-containing monomer may be a (meth)acrylic monomer, in other words, the (meth)acrylic monomer may contain an ether group-containing monomer. The ether group-containing monomer can contribute to improving the anchoring strength between the pressure-sensitive adhesive sheet 1 and the optical film.

[0040] The ether group-containing monomer preferably includes an alkoxy group-containing monomer. The alkoxy group-containing monomer is, for example, an alkylene oxide adduct represented by the following formula (1): R in formula (1) 1 is a hydrogen atom or a methyl group. 2 is an alkyl group. The alkyl group may be linear or branched. R 2is preferably a linear is an alkyl group. 2 Examples of n are methyl and ethyl groups. It is an integer of 0, preferably an integer of 1 to 12, and may be an integer of 1 to 5. [ka]

[0041] Examples of the alkylene oxide adduct shown in formula (1) include 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-(2-ethoxyethoxy)ethyl (meth)acrylate, The alkoxy group-containing monomer preferably includes 2-methoxyethyl acrylate (MEA).

[0042] The ether group-containing monomer is not limited to the alkylene oxide adducts. The ether group-containing monomer may have a ring structure, and the ring structure may have an ether group. The ring structure may not contain any functional groups other than the ether group. Examples of ring structures having an ether group include a tetrahydrofuran ring and a dioxane ring. Examples of ether group-containing monomers having a ring structure include cyclic trimethylolpropane formal (meth)acrylate and tetrahydrofurfuryl (meth)acrylate.

[0043] As described above, the amount of the ether group-containing monomer blended per 100 parts by weight of the monomer group is 25 parts by weight or more, preferably 30 parts by weight or more, and may be 40 parts by weight or more, 50 parts by weight or more, 60 parts by weight or more, 70 parts by weight or more, 80 parts by weight or more, or even 90 parts by weight or more. The upper limit of the blended amount is, for example, 99 parts by weight or less. However, if the blended amount of the ether group-containing monomer is too high, the water absorbency of the pressure-sensitive adhesive sheet 1 may increase. When a highly water-absorbent pressure-sensitive adhesive sheet 1 is used in an image display device, metal components included in the image display device tend to corrode easily. From this perspective, the upper limit of the blended amount of the ether group-containing monomer may be 80 parts by weight or less, or even 70 parts by weight or less. It is particularly preferable that the blended amount of the ether group-containing monomer be 50 to 70 parts by weight per 100 parts by weight of the monomer group.

[0044] The monomer group may contain, but preferably does not contain, other monomers than the (meth)acrylic acid alkyl ester, carboxyl group-containing monomer, hydroxy group-containing monomer, and ether group-containing monomer, such as aromatic ring-containing monomers such as benzyl (meth)acrylate.

[0045] In the photocurable composition, each of the above-mentioned monomers may be contained as a partial polymer. The partial polymer may be either a homopolymer or a copolymer. The partial polymer can appropriately increase the viscosity of the photocurable composition, thereby contributing to the stable formation of a coating layer, which will be described later.

[0046] The dielectric constant P of the partial polymer at a frequency of 100 Hz is preferably 3.8 or more. When the dielectric constant P is this high, even when the pressure-sensitive adhesive sheet 1 is used in combination with an optical film having a low dielectric constant, particularly a polarizing film, there is a tendency that a decrease in sensitivity of the touch sensor provided in the image display device can be suppressed.

[0047] The dielectric constant P can be measured by the following method. First, a test piece having a thickness of 30 μm and consisting only of a partially polymerized product is prepared. The dielectric constant of this test piece is measured at a frequency of 100 Hz in accordance with JIS K6911:1995. The obtained measured value can be regarded as the dielectric constant P. The detailed conditions for measuring the dielectric constant are as follows: Measurement conditions Measurement method: capacitance method (apparatus: Agilent Technologies 4294A Precision Impedance Analyzer) Electrode configuration: 12.1 mm diameter, 0.5 mm thick aluminum plate Counter electrode: 3oz copper plate Measurement environment: 23±1℃, 52±1%RH

[0048] The relative dielectric constant P is preferably 3.8 or more, and may be 4.0 or more, 5.0 or more, 6.0 or more, 7.0 or more, or even 8.0 or more. The upper limit of the relative dielectric constant P is not particularly limited. , for example, 10.0 or less.

[0049] The photocurable composition usually contains a photopolymerization initiator. Examples of the photopolymerization initiator are photoradical generators that generate radicals when exposed to visible light and / or ultraviolet light with a wavelength shorter than 450 nm.

[0050] Examples of photopolymerization initiators include benzoin ethers such as benzoin methyl ether, benzoin isopropyl ether, and benzil dimethyl ketal; substituted benzoin ethers such as anisole methyl ether; substituted acetophenones such as 2,2-diethoxyacetophenone and 2,2-dimethoxy-2-phenylacetophenone; α-hydroxyalkylphenones such as 1-hydroxycyclohexyl-phenyl ketone; substituted alpha-ketols such as 2-methyl-2-hydroxypropiophenone; aromatic sulfonyl chlorides such as 2-naphthalenesulfonyl chloride; photoactive oximes such as 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime; and benzophenone compounds such as benzophenone, benzoylbenzoic acid, methyl benzoylbenzoate, 4-phenylbenzophenone, hydroxybenzophenone, acrylated benzophenone, 4-benzoyl-4'-methyldiphenyl sulfide, and 3,3',4,4'-tetra(t-butylperoxycarbonyl)benzophenone. Thioxanthone compounds such as thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, and 2,4-diethylthioxanthone; 2,4,6-trichloro-s-triazine, 2-phenyl-4,6-bis(trichloromethyl)-s-triazine, 2-(p-methoxyphenyl)-4,6-bis(trichloromethyl)-s-triazine, and 2-(p-tolyl)-4,6-bis(trichloromethyl)-s-triazine triazine-based compounds such as 2-piperonyl-4,6-bis(trichloromethyl)-s-triazine, 2,4-bis(trichloromethyl)-6-styryl-s-triazine, 2-(naphth-1-yl)-4,6-bis(trichloromethyl)-s-triazine, 2-(4-methoxy-naphth-1-yl)-4,6-bis(trichloromethyl)-s-triazine, 2,4-trichloromethyl-(piperonyl)-6-triazine, and 2,4-trichloromethyl-(4'-methoxystyryl)-6-triazine;Examples of suitable photocurable compositions include oxime ester compounds such as 1,2-octanedione, 1-[4-(phenylthio)-, 2-(O-benzoyloxime)], and O-(acetyl)-N-(1-phenyl-2-oxo-2-(4'-methoxy-naphthyl)ethylidene)hydroxylamine; phosphine compounds such as bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide and 2,4,6-trimethylbenzoyldiphenylphosphine oxide; quinone compounds such as 9,10-phenanthrenequinone, camphorquinone, and ethylanthraquinone; borate compounds; carbazole compounds; imidazole compounds; and titanocene compounds. The photocurable composition may contain one or more photopolymerization initiators.

[0051] The amount of the photopolymerization initiator in the photocurable composition is, for example, 0.02 to 10 parts by weight, and may be 0.05 to 5 parts by weight, relative to 100 parts by weight of the total of the monomer group and its partial polymer.

[0052] The photocurable composition may contain a crosslinking agent. An example of the crosslinking agent is a polyfunctional monomer having two or more polymerizable functional groups in one molecule. The polyfunctional monomer may be a (meth)acrylic monomer. Examples of the polyfunctional monomer are a monomer having two or more C=C bonds in one molecule, and a monomer having one or more C=C bonds and one or more polymerizable functional groups such as epoxy groups, aziridine groups, oxazoline groups, hydrazine groups, methylol groups, etc. in one molecule. The polyfunctional monomer is preferably a monomer having two or more C=C bonds in one molecule.

[0053] Examples of polyfunctional monomers include (poly)ethylene glycol di(meth)acrylate, (poly) Polyfunctional acrylates (such as ester compounds of polyhydric alcohols and (meth)acrylic acid) such as propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,2-ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol diacrylate (NDDA), 1,12-dodecanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, and tetramethylolmethane tri(meth)acrylate; allyl (meth)acrylate, vinyl (meth)acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylate, butyl di(meth)acrylate, and hexyl di(meth)acrylate. The polyfunctional monomer is preferably a polyfunctional acrylate, and more preferably trimethylolpropane tri(meth)acrylate, hexanediol di(meth)acrylate, or dipentaerythritol hexa(meth)acrylate.

[0054] The crosslinking agent may contain a crosslinking agent other than the above-mentioned polyfunctional monomer. Examples of other crosslinking agents include isocyanate-based crosslinking agents. The photocurable composition may contain an isocyanate-based crosslinking agent as the crosslinking agent, or may contain both the above-mentioned polyfunctional monomer and an isocyanate-based crosslinking agent. The isocyanate-based crosslinking agent may contribute to improving the anchoring strength between the pressure-sensitive adhesive sheet 1 and the optical film.

[0055] As the isocyanate-based crosslinking agent, a compound having at least two isocyanate groups (isocyanate compound) can be used. The number of isocyanate groups contained in the isocyanate compound is preferably 3 or more. The upper limit of the number of isocyanate groups is not particularly limited, and is, for example, 5. Examples of the isocyanate compound include aromatic isocyanate compounds, alicyclic isocyanate compounds, and aliphatic isocyanate compounds.

[0056] Examples of aromatic isocyanate compounds include phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-toluidine diisocyanate, 4,4'-diphenyl ether diisocyanate, 4,4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, and xylylene diisocyanate.

[0057] Examples of alicyclic isocyanate compounds include 1,3-cyclopentene diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, and hydrogenated tetramethylxylylene diisocyanate.

[0058] Examples of the aliphatic isocyanate compound include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), pentamethylene diisocyanate (PDI), 1,2-propylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate, and 2,4,4-trimethylhexamethylene diisocyanate.

[0059] Examples of the isocyanate crosslinking agent include polymers (dimers, trimers, pentamers, etc.) of the above-mentioned isocyanate compounds, adducts obtained by adding them to polyhydric alcohols such as trimethylolpropane, urea-modified products, biuret-modified products, allophanate-modified products, isocyanurate-modified products, carbodiimide-modified products, polyether polyols, polyester polyols, acrylic and urethane prepolymers obtained by addition of olefin polyols, polybutadiene polyols, polyisoprene polyols, etc.

[0060] The isocyanate-based crosslinking agent preferably includes an aliphatic isocyanate compound and / or a derivative of an aliphatic isocyanate compound. It is particularly preferred that the isocyanate-based crosslinking agent is at least one selected from the group consisting of pentamethylene diisocyanate (PDI)-based crosslinking agents (PDI and its derivatives) and hexamethylene diisocyanate (HDI)-based crosslinking agents (HDI and its derivatives). Specific examples of PDI-based crosslinking agents include isocyanurate-modified PDI. Specific examples of HDI-based crosslinking agents include isocyanurate-modified and biuret-modified HDI.

[0061] The amount of crosslinking agent in the photocurable composition varies depending on the molecular weight, the number of functional groups, etc., but may be, for example, 5 parts by weight or less, 3 parts by weight or less, 2 parts by weight or less, 1 part by weight or less, or even 0.5 parts by weight or less, relative to 100 parts by weight of the total of the monomer group and its partial polymer. The lower limit of the amount may be, for example, 0.01 part by weight or more, or even 0.05 part by weight or more.

[0062] However, as described above, the photocurable composition does not contain more than 0.05 parts by weight of an isocyanate-based crosslinking agent per 100 parts by weight of the total of the monomer group and the partial polymer. The amount of the isocyanate-based crosslinking agent may be less than 0.05 parts by weight, less than 0.03 parts by weight, or even less than 0.01 parts by weight per 100 parts by weight of the total of the monomer group and the partial polymer. The photocurable composition may not contain an isocyanate-based crosslinking agent. In this embodiment, even though the photocurable composition contains almost no isocyanate-based crosslinking agent, the anchoring strength between the pressure-sensitive adhesive sheet 1 formed from the photocurable composition and the optical film tends to be adjusted to a large value.

[0063] The photocurable composition may contain additives other than those described above, such as a chain transfer agent, a rework improver, a corrosion inhibitor, a silane coupling agent, a viscosity modifier, a tackifier, a plasticizer, a softener, an antioxidant, a filler, a colorant, an antioxidant, a surfactant, an antistatic agent, and an ultraviolet absorber.

[0064] The solvent content in the photocurable composition is, for example, 5% by weight or less, and may be 4% by weight or less, 3% by weight or less, 2% by weight or less, 1% by weight or less, or even 0.5% by weight or less. The photocurable composition may be substantially free of solvent. "Substantially free of solvent" means that solvents derived from additives and the like are allowed in a content of, for example, 0.1% by weight or less, preferably 0.05% by weight or less, and more preferably 0.01% by weight or less.

[0065] The viscosity of the photocurable composition is preferably 5 to 150 poise. A photocurable composition having a viscosity in the above range is particularly suitable for forming a coating layer, which will be described later.

[0066] (Physical properties and characteristics of adhesive sheets) The polymerization rate of the monomer group in the pressure-sensitive adhesive sheet 1 is preferably 90% or more, and may be 95% or more, 98% or more, or even 99% or more.

[0067] The gel fraction of the pressure-sensitive adhesive sheet 1 is, for example, 50% or more, and may be 70% or more, 75% or more, 80% or more, or even 85% or more. The upper limit of the gel fraction of the pressure-sensitive adhesive sheet 1 is, for example, 95% or less, and in some cases may be 80% or less, or 75% or less. When the gel fraction of the pressure-sensitive adhesive sheet 1 is 75% or less, the pressure-sensitive adhesive sheet 1 tends to adhere more easily to the optical film, and the anchoring force with the optical film tends to be further improved.

[0068] The creep amount of the pressure-sensitive adhesive sheet 1 is, for example, 500 μm or less, and may be 300 μm or less, 180 μm or less, 160 μm or less, 150 μm or less, 100 μm or less, or even 50 μm or less. The lower limit of the creep amount is, for example, 5 μm or more, 10 μm or more, or even 20 μm or more.

[0069] The creep amount of the pressure-sensitive adhesive sheet 1 can be evaluated as follows (see FIGS. 2A and 2B). First, a laminate of the pressure-sensitive adhesive sheet 1 to be evaluated and a support film 51 is cut into a 10 mm x 50 mm strip to form a test piece 52. The support film 51 is positioned to suppress deformation of the pressure-sensitive adhesive sheet 1 at the portion to which the load is applied during testing, thereby enabling more accurate measurement of the creep amount. The support film 51 may be, for example, a resin film such as a polyethylene terephthalate (PET) film. The support film 51 may also be an optical film or a laminate containing an optical film. The support film 51 may have any thickness that does not deform under the load, and may be, for example, 20 to 200 μm. Next, as shown in FIGS. 2A and 2B, the test piece 52 is attached to the surface of a stainless steel test plate 53 at a joining surface measuring 10 mm long x 10 mm wide using the pressure-sensitive adhesive sheet 1. Note that FIG. 2B is a cross section BB of FIG. 2A. The test piece 52 is attached to the test plate 53 so that no air bubbles are trapped between the test plate 53 and the pressure-sensitive adhesive sheet 1. After attachment, the test plate 53 is placed in an autoclave at 50°C and 5 atmospheres (absolute pressure) for 15 minutes to homogenize the bond between the test plate 53 and the pressure-sensitive adhesive sheet 1. Next, the test plate 53 and the test piece 52 are held vertically with the test plate 53 facing upward and left in a 25°C atmosphere for at least 5 minutes. Then, with the test plate 53 still fixed, a 500g weight is fixed to the center of the lower end of the test piece 52, and a 500gf load 54 is applied vertically downward. The amount of creep (displacement) of the pressure-sensitive adhesive sheet 1 relative to the test plate 53 3600 seconds after the load 54 began to be applied is measured as the weight drop distance. A laser displacement meter can be used to measure the weight drop distance.

[0070] The thickness of the pressure-sensitive adhesive sheet 1 is, for example, 500 μm or less, and may be 250 μm or less, 150 μm or less, 100 μm or less, 50 μm or less, 30 μm or less, 25 μm or less, or even 20 μm or less. The lower limit of the thickness of the pressure-sensitive adhesive sheet 1 is, for example, 2 μm or more, and may be 5 μm or more.

[0071] (Method of manufacturing pressure-sensitive adhesive sheet) The pressure-sensitive adhesive sheet 1 can be produced, for example, by the following method. First, as shown in Figures 3A and 3B, a first laminate 15 is produced, which includes, in this order, a base sheet 21, a coating layer 22 containing a photocurable composition, and a release liner 23. The pressure-sensitive adhesive sheet 1 can be formed from the coating layer 22 by irradiating the first laminate 15 with light 14 (Figure 3C).

[0072] Irradiation of light 14 onto first laminate 15 is typically carried out from the side of base sheet 21 (FIG. 3A). At this time, light 14 passes through base sheet 21 to reach coating layer 22 and cure coating layer 22. However, irradiation with light 14 may also be carried out from the side of release liner 23, or from both the sides of release liner 23 and base sheet 21 (FIG. 3B). PSA sheet 1 formed from coating layer 22 is sandwiched between base sheet 21 and release liner 23 until release liner 23 is peeled off, and constitutes part of second laminate 16.

[0073] An example of the substrate of the release liner 23 (hereinafter referred to as "liner substrate") is a resin film. Examples of resins that can be contained in the liner substrate include polyesters such as polyethylene terephthalate and polyethylene naphthalate, acetate resins, polyethersulfone, polycarbonate, polyamide, polyimide, polyolefin, (meth)acrylic resins, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyvinyl alcohol, polyarylate, and polyphenylene sulfide. The resin is preferably polyethylene terephthalate. and the like polyesters.

[0074] The release liner 23 may have light 14 transparency, or may have light 14 transparency of the same order as that of the base sheet 21 .

[0075] The thickness of the release liner 23 is, for example, 10 to 200 μm, and may be 25 to 150 μm.

[0076] The release liner 23 may include a layer other than the liner substrate. The release liner 23 may include a release layer. For example, the release liner 23 includes a liner substrate and a release layer formed on one surface of the liner substrate. This release liner 23 can be used with the release layer facing the coating layer 22.

[0077] The release layer is typically a cured layer of a release agent composition containing a release agent. A variety of release agents can be used, including silicone-based release agents, fluorine-based release agents, long-chain alkyl-based release agents, fatty acid amide-based release agents, and silica powder. The release liner 23 may be provided with a cured layer of a release agent composition containing a silicone-based release agent as the main component (hereinafter referred to as "silicone release layer"). Silicone release layers are particularly suitable for achieving both good adhesion to the pressure-sensitive adhesive sheet 1 and good releasability. In this specification, "main component" refers to the component with the highest content.

[0078] Silicone-based release agents are various curable silicone materials, such as addition reaction type, condensation reaction type, ultraviolet curable type, electron beam curable type, and solventless type, with addition reaction curable silicone materials being preferred. Addition reaction curable silicone materials are particularly suitable for forming a release layer that has both good adhesion and releasability to the pressure-sensitive adhesive sheet 1. The curable silicone material may be a silicone-modified resin in which reactive silicone is introduced into an organic resin such as a urethane, epoxy, or alkyd resin by graft polymerization or the like.

[0079] An example of an addition reaction curable silicone material is a polyorganosiloxane having a vinyl group or an alkenyl group in the molecule. The addition reaction curable silicone material may not have a hydrosilyl group. Examples of alkenyl groups include 3-butenyl, 4-pentenyl, 5-hexenyl, 6-heptenyl, 7-octenyl, 8-nonenyl, 9-decenyl, 10-undecenyl, and 11-dodecenyl groups. Examples of polyorganosiloxanes include polyalkylalkylsiloxanes such as polydimethylsiloxane, polydiethylsiloxane, and polymethylethylsiloxane, polyalkylarylsiloxanes, and copolymers of multiple Si atom-containing monomers such as poly(dimethylsiloxane-diethylsiloxane). The polyorganosiloxane is preferably polydimethylsiloxane.

[0080] A release agent composition containing a silicone-based release agent as a main component (hereinafter referred to as "silicone release agent composition") usually contains a crosslinking agent. An example of the crosslinking agent is a polyorganosiloxane having a hydrosilyl group. The crosslinking agent may have two or more hydrosilyl groups in one molecule.

[0081] The silicone release agent composition may contain a curing catalyst. Examples of the curing catalyst include platinum-based catalysts. Examples of the platinum-based catalyst include chloroplatinic acid, platinum olefin complexes, and chloroplatinic acid olefin complexes. The amount of the platinum-based catalyst used is, for example, 10 to 1000 ppm (by weight, platinum equivalent) based on the total solid content of the composition.

[0082] The silicone release agent composition may contain additives. Examples of additives are release control agents and adhesion promoters. Examples of release control agents are unreactive silicone resins, and more specific examples are organosiloxanes such as octamethylcyclotetrasiloxane, and MQ resins. The amounts of release control agents and adhesion promoters used are determined based on the total amount of the composition. The total amount of the additives is, for example, 1 to 30% by weight based on the solid content. Further examples of the additives include fillers, antistatic agents, antioxidants, UV absorbers, plasticizers, and colorants. The total amount of the additives used is, for example, 10% by weight or less based on the total solid content of the composition.

[0083] The silicone release agent composition may contain an organic solvent. Examples of organic solvents include hydrocarbon solvents such as cyclohexane, n-hexane, and n-heptane; aromatic solvents such as toluene and xylene; ester solvents such as ethyl acetate and methyl acetate; ketone solvents such as acetone and methyl ethyl ketone; and alcohol solvents such as methanol, ethanol, and butanol. Two or more organic solvents may be contained. The amount of organic solvent used is preferably 80 to 99.9% by weight of the silicone release agent composition.

[0084] The release layer can be formed, for example, by heating and drying a coating film containing the release agent composition formed on a liner substrate. The release agent composition can be applied by various coating methods, such as roll coating, kiss roll coating, gravure coating, reverse coating, roll brushing, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, lip coating, and die coating. Heating and drying can be performed by, for example, hot air drying. The heating temperature and time vary depending on the heat resistance of the liner substrate, but are typically 80 to 150°C and 10 seconds to 10 minutes. If necessary, irradiation with active energy rays such as ultraviolet rays may be used in combination.

[0085] The thickness of the release layer is, for example, 10 to 300 nm. The upper limit of the thickness may be 200 nm or less, 150 nm or less, 120 nm or less, 110 nm or less, 100 nm or less, less than 100 nm, 90 nm or less, 80 nm or less, 70 nm or less, less than 70 nm, or even 65 nm or less. The lower limit of the thickness may be 15 nm or more, 20 nm or more, 25 nm or more, 30 nm or more, 35 nm or more, 40 nm or more, 45 nm or more, or even 50 nm or more.

[0086] The release liner 23 may be in the form of a sheet or a continuous piece.

[0087] An example of the base sheet 21 is a resin film. Examples of the resin contained in the base sheet 21 are the same as the examples of the resin that can be contained in the liner base material.

[0088] The base sheet 21 preferably has excellent light 14 transmittance.

[0089] The thickness of the base sheet 21 is, for example, 10 to 200 μm, and may be 25 to 150 μm.

[0090] The base sheet 21 may have a release layer on the surface on the side of the coating layer 22. Examples of the release layer that the base sheet 21 may have and the manufacturing method thereof are the same as the examples of the release layer that the release liner 23 may have and the manufacturing method thereof. Both the release liner 23 and the base sheet 21 may have a release layer. In this case, both release layers may be formed from a release agent composition containing the same release agent as a main component. Furthermore, the thicknesses of both release layers may be different; for example, the release layer provided on the base sheet 21 may be thicker.

[0091] For base sheet 21, a sheet having a greater peel strength from adhesive sheet 1 than release liner 23 can usually be selected.

[0092] The base sheet 21 may be in the form of a sheet or a continuous sheet.

[0093] The first laminate 15 is formed, for example, by forming a coating layer 22 on a base sheet 21 (or a release liner 23), and then forming a release liner 23 (or the base sheet 21) on the formed coating layer 22. Alternatively, the first laminate 15 may be formed by applying the photocurable composition in a poured manner into the space between the base sheet 21 and the release liner 23, which are held at a predetermined distance so that their main surfaces face each other.

[0094] The coating layer 22 can be formed by various coating methods such as roll coating, kiss roll coating, gravure coating, reverse coating, roll brush, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, lip coating, and die coating.

[0095] The thickness of the coating layer 22 can be adjusted depending on the desired thickness of the pressure-sensitive adhesive sheet 1, and may be, for example, 5 to 500 μm, 5 to 250 μm, 5 to 150 μm, 5 to 100 μm, 5 to 50 μm, 5 to 30 μm, 5 to 25 μm, or even 5 to 20 μm.

[0096] The light 14 irradiated onto the first laminate 15 is, for example, visible light or ultraviolet light having a wavelength shorter than 450 nm. The light 14 may include light with a wavelength in the same range as the absorption wavelength of the photopolymerization initiator contained in the photocurable composition. Light 14 from which short-wavelength light of 300 nm or less has been filtered out using a filter or the like may be irradiated. Cutting out short-wavelength light is suitable for suppressing deterioration of the base sheet 21 due to the light 14. The light source for the light 14 is, for example, a light irradiation device equipped with an ultraviolet irradiation lamp. Examples of ultraviolet irradiation lamps include ultraviolet LEDs, low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, xenon lamps, microwave-excited mercury lamps, black light lamps, chemical lamps, germicidal lamps, low-pressure discharge mercury lamps, and excimer lasers. Two or more ultraviolet irradiation lamps may be combined.

[0097] The illumination with light 14 may be continuous or intermittent.

[0098] The illuminance of the light 14 is, for example, 1 to 20 mW / cm 2 The irradiation time of the light 14 is, for example, 5 The cumulative amount of light 14 applied to the first laminate 15 is, for example, 100 to 5000 mJ / cm 2 2 is.

[0099] If necessary, release liner 23 may be peeled off from second laminate 16 to expose the surface of pressure-sensitive adhesive sheet 1 (for example, surface 1a), which may then be subjected to a surface modification treatment.

[0100] [Embodiment of Optical Laminate] An example of the optical laminate of this embodiment is shown in Figure 4. The optical laminate 10 of Figure 4 includes the above-mentioned pressure-sensitive adhesive sheet 1 and at least one optical film 2 selected from the group consisting of polarizing films and retardation films. The pressure-sensitive adhesive sheet 1 is preferably in direct contact with the optical film 2. In the example of Figure 4, the surface 1a of the pressure-sensitive adhesive sheet 1 is in contact with the optical film 2. The optical laminate 10 may have a structure in which the base sheet used in producing the pressure-sensitive adhesive sheet 1 is laminated on the pressure-sensitive adhesive sheet 1. The optical laminate 10 can be used as an optical film with a pressure-sensitive adhesive sheet.

[0101] (Optical film) The optical film 2 has a surface 2a facing the pressure-sensitive adhesive sheet 1. For example, the surface 2a is in contact with the surface 1a of the pressure-sensitive adhesive sheet 1. The surface 2a of the optical film 2 may have been subjected to a surface modification treatment. The surface 2a that has been subjected to the surface modification treatment tends to improve the anchoring force between the pressure-sensitive adhesive sheet 1 and the optical film 2. Examples of surface modification treatments include those described above for the pressure-sensitive adhesive sheet 1.

[0102] The surface 2a is preferably subjected to a corona treatment as a surface modification treatment. When the surface 2a is subjected to a corona treatment, the conditions such as the discharge amount may be, for example, the same as those described above for the pressure-sensitive adhesive sheet 1. The amount can be adjusted appropriately within the range.

[0103] As described above, the optical film 2 includes at least one selected from the group consisting of a polarizing film and a retardation film. The optical film 2 may be a laminated film including a polarizing film and / or a retardation film. The optical film 2 may include a glass film. However, the optical film 2 is not limited to the above examples.

[0104] The polarizing film includes a polarizer. The polarizing film typically includes a polarizer and a protective film (transparent protective film). The protective film is disposed, for example, in contact with the main surface (the surface having the largest area) of the polarizer. The polarizer may be disposed between two protective films. The protective film may be disposed on at least one surface of the polarizer.

[0105] The polarizer is not particularly limited, and examples include hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and partially saponified ethylene-vinyl acetate copolymer films, which are uniaxially stretched after adsorbing a dichroic substance such as iodine or a dichroic dye; and oriented polyene films such as dehydrated polyvinyl alcohol and dehydrochlorinated polyvinyl chloride. Polarizers typically consist of a polyvinyl alcohol film (including partially saponified ethylene-vinyl acetate copolymer films) and a dichroic substance such as iodine.

[0106] The thickness of the polarizer is not particularly limited and may be, for example, 80 μm or less, 50 μm or less, 30 μm or less, 25 μm or less, or even 20 μm or less. The lower limit of the polarizer thickness is not particularly limited and may be, for example, 1 μm or more, 5 μm or more, 10 μm or more, or even 15 μm or more. A thin polarizer (for example, a thickness of 20 μm or less) is suppressed in dimensional change and can contribute to improving the durability of the optical laminate, particularly durability at high temperatures.

[0107] The material for the protective film may be, for example, a thermoplastic resin that is excellent in transparency, mechanical strength, thermal stability, moisture barrier properties, isotropy, etc. Specific examples of such thermoplastic resins include cellulose resins such as triacetyl cellulose, polyester resins, polyethersulfone resins, polysulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, (meth)acrylic resins, cyclic polyolefin resins (norbornene-based resins), polyarylate resins, polystyrene resins, polyvinyl alcohol resins, and mixtures thereof. The material for the protective film may be a thermosetting resin or an ultraviolet-curable resin such as a (meth)acrylic, urethane, acrylic urethane, epoxy, or silicone-based resin. When the polarizing film has two protective films, the materials of the two protective films may be the same or different. For example, a protective film made of a thermoplastic resin may be bonded to one main surface of a polarizer via an adhesive, and a protective film made of a thermosetting resin or an ultraviolet-curable resin may be bonded to the other main surface of the polarizer. The protective film may contain one or more optional additives, such as ultraviolet absorbers, antioxidants, lubricants, plasticizers, release agents, color inhibitors, flame retardants, nucleating agents, antistatic agents, pigments, and colorants.

[0108] Films containing (meth)acrylic resins tend to have low adhesive strength with pressure-sensitive adhesive sheets. However, with the pressure-sensitive adhesive sheet 1 of the present embodiment, even when in contact with the surface of a protective film containing a (meth)acrylic resin, the anchoring strength with the optical film 2 can be adjusted to a sufficiently high value.

[0109] The thickness of the protective film can be determined as appropriate, but is generally about 10 to 200 μm in terms of strength, workability such as handling, thinness, and the like.

[0110] The polarizer and the protective film are usually adhered to each other via an aqueous adhesive or the like. Examples of aqueous adhesives include isocyanate-based adhesives, polyvinyl alcohol-based adhesives, gelatin-based adhesives, vinyl latex, aqueous polyurethane, and aqueous polyester. Examples of adhesives other than the above-mentioned adhesives include ultraviolet-curable adhesives and electron beam-curable adhesives. Electron beam-curable polarizing plate adhesives exhibit suitable adhesive properties for various protective films. The adhesive may contain a metal compound filler.

[0111] In the polarizing film, a retardation film or the like can be formed on the polarizer instead of the protective film. Another protective film or a retardation film or the like can be further provided on the protective film.

[0112] The protective film may have a hard coat layer on the surface opposite to the surface bonded to the polarizer, and may also be subjected to treatments for purposes such as anti-reflection, anti-sticking, diffusion, and anti-glare.

[0113] The polarizing film may be a circular polarizing film.

[0114] The retardation film may be a film obtained by stretching a polymer film or a film obtained by aligning and fixing a liquid crystal material. The retardation film has birefringence, for example, in the in-plane and / or thickness direction.

[0115] Retardation films include anti-reflection retardation films (see JP 2012-133303 A,

[0221] ,

[0222] ,

[0228] ), viewing angle compensation retardation films (see JP 2012-133303 A,

[0225] ,

[0226] ), and tilted orientation retardation films for viewing angle compensation (see JP 2012-133303 A,

[0227] ).

[0116] The specific configuration of the retardation film, for example, the retardation value, the arrangement angle, the three-dimensional birefringence, whether it is a single layer or a multilayer, etc., is not particularly limited, and any known retardation film can be used.

[0117] The thickness of the retardation film is preferably 20 μm or less, more preferably 10 μm or less, further preferably 1 to 9 μm, and particularly preferably 3 to 8 μm.

[0118] The retardation film may include, for example, a quarter-wave plate and / or a half-wave plate in which a liquid crystal material is aligned and fixed.

[0119] (Properties of optical laminate) In this embodiment, the anchoring force F between the pressure-sensitive adhesive sheet 1 and the optical film 2 tends to be large. The anchoring force F is, for example, 7.0 N / 25 mm or more, and may be 8.0 N / 25 mm or more, 9.0 N / 25 mm or more, 10.0 N / 25 mm or more, 11.0 N / 25 mm or more, 12.0 N / 25 mm or more, 15.0 N / 25 mm or more, 20.0 N / 25 mm or more, 22.0 N / 25 mm or more, 23.0 N / 25 mm or more, 24.0 N / 25 mm or more, or even 25.0 N / 25 mm or more. The larger the anchoring force F, the more effectively peeling between the pressure-sensitive adhesive sheet 1 and the optical film 2 can be suppressed. The upper limit of the anchoring force F is not particularly limited, and may be, for example, 50 N / 25 mm or less, or 30 N / 25 mm or less.

[0120] The anchoring force F between the pressure-sensitive adhesive sheet 1 and the optical film 2 can be measured by the following method. First, the optical laminate 10 to be evaluated is cut into a size of 25 mm wide x 150 mm long to prepare a test piece. Next, the entire surface of the optical film 2 provided on the test piece is placed on a stainless steel test plate via double-sided tape, and a 2 kg roller is moved back and forth once to press them together. Next, the adhesive sheet 1 provided on the test piece is placed on the evaluation sheet, and a 2 kg roller is moved back and forth once to press them together. The evaluation sheet is not particularly limited as long as it has a size of 30 mm wide x 150 mm long and does not peel off from the adhesive sheet 1 during the test. For example, an ITO film (such as 125 Tetolite OES (manufactured by Oike Kogyo Co., Ltd.)) can be used as the evaluation sheet. Next, using a commercially available tensile tester, while holding the evaluation sheet, the adhesive sheet 1 is peeled off from the optical film 2 at a peel angle of 180° and a pulling rate of 300 mm / min, and the average value of the peel force is determined as the anchoring force F between the adhesive sheet 1 and the optical film 2. The above test is performed in an atmosphere of 23°C.

[0121] Another example of the optical laminate of the present embodiment is shown in Fig. 5. The optical laminate 11 in Fig. 5 has a laminated structure in which an adhesive sheet 1A, an optical film 2A, an adhesive sheet 1B, and an optical film 2B are laminated in this order. The optical laminate 11 may have a structure in which the base sheet used in producing the adhesive sheet 1A is laminated on the adhesive sheet 1A.

[0122] In the optical laminate 11, typically, the optical film 2A is a retardation film and the optical film 2B is a polarizing film. The pressure-sensitive adhesive sheet 1B functions as an interlayer pressure-sensitive adhesive between the optical films 2A and 2B. A known pressure-sensitive adhesive may be used for the pressure-sensitive adhesive sheet 1B.

[0123] The optical laminate of this embodiment can be distributed and stored, for example, as a rolled body obtained by rolling up a strip-shaped optical laminate, or as a sheet-shaped optical laminate.

[0124] The optical laminate of this embodiment is typically used in an image display device. The image display device can be formed, for example, by bonding the optical laminate 10 or 11 to an image display panel. The bonding is performed, for example, using an adhesive sheet 1. The image display device may be an organic EL display or a liquid crystal display. However, the image display device is not limited to the above examples. The image display device may be an electroluminescence (EL) display, a plasma display (PD), a field emission display (FED), or the like. The image display device can be used for home appliance applications, in-vehicle applications, public information displays (PID), and the like. [Example]

[0125] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the examples shown below.

[0126] [Polarizing film] First, an 80 μm-thick polyvinyl alcohol film was stretched 3 times between rolls with different speed ratios while dyeing for 1 minute in a 0.3% iodine solution at 30°C. Next, it was immersed in an aqueous solution containing 4% boric acid and 10% potassium iodide at 60°C for 0.5 minutes, and stretched until the total stretch ratio reached 6 times. Next, it was immersed in an aqueous solution containing 1.5% potassium iodide at 30°C for 10 seconds to wash, and then dried at 50°C for 4 minutes to obtain a 28 μm-thick polarizer. A 30 μm-thick transparent protective film made of a modified acrylic polymer having a lactone ring structure was attached to one side of the polarizer using a polyvinyl alcohol-based adhesive. Furthermore, a 47 μm-thick transparent protective film made of a triacetyl cellulose film (Konica Minolta, product name "KC4UY") with a hard coat layer (HC) was attached to the other surface of the polarizer using a polyvinyl alcohol adhesive. The polarizing film was fabricated by heating and drying for 5 minutes in an oven set at 70°C. Furthermore, a discharge of 63 W / m was applied to the surface of the polarizing film on the transparent protective film side made of modified acrylic polymer.2 ·min Rona treatment was performed.

[0127] [Release Liner A] A silicone-based release agent composition was obtained by mixing 30 parts by weight of an addition reaction curable silicone (LTC761 containing a hexenyl group-containing polyorganosiloxane, a 30 wt% toluene solution, manufactured by Dow Corning Toray Co., Ltd.), 0.9 parts by weight of a release control agent (BY24-850 containing an unreactive silicone resin, manufactured by Dow Corning Toray Co., Ltd.), 2 parts by weight of a curing catalyst (SRX212 containing a platinum catalyst, manufactured by Dow Corning Toray Co., Ltd.), and a toluene / hexane mixed solvent (volume ratio 1:1) as a diluent. The silicone solids concentration in the release agent composition was 1.0 wt%. Next, the release agent composition was applied with a wire bar to one side of a liner substrate (Lumirror XD500P polyester film, 75 μm thick) and heated at 130°C for 1 minute to prepare release liner A, which had a release layer (60 nm thick) on one side.

[0128] [Release Liner B] Release liner B having a release layer (thickness 120 nm) on one side was prepared in the same manner as release liner A, except that the thickness of the release agent composition applied to the liner substrate was changed.

[0129] [Monomer Syrup A1] The mixture contained 49 parts by weight of n-butyl acrylate (BA), 1 part by weight of 4-hydroxybutyl acrylate (HBA), and 50 parts by weight of 2-methoxyethyl acrylate (MEA), and 0.05 parts by weight of 1-hydroxycyclohexyl-phenyl ketone (Omnirad184, manufactured by IGM Resins BV) as a photopolymerization initiator and 2,2-dimethoxy-1,2-diphenyl acrylate. 0.05 parts by weight of luetan-1-one (Omnirad 651, manufactured by IGM Resins BV) The mixture was placed in a four-neck flask and irradiated with ultraviolet light under a nitrogen atmosphere to obtain a partially photopolymerized monomer syrup A1. UV irradiation was continued until the viscosity of the liquid in the flask reached approximately 20 Pa s (measurement conditions: BH viscometer No. 5 rotor, 10 rpm, measurement temperature 30°C).

[0130] [Monomer Syrup A2~A6] Monomer syrups A2 to A6 were prepared in the same manner as for the monomer syrup A1, except that the monomers used were changed as shown in Table 1.

[0131] [Table 1]

[0132] The abbreviations in Table 1 are as follows: BA: n-butyl acrylate 2EHA: 2-ethylhexyl acrylate HBA: 4-hydroxybutyl acrylate MEA: 2-Methoxyethyl acrylate Omnirad184: 1-hydroxycyclohexyl-phenyl ketone (Omnirad184, manufactured by IGM Resins BV) Omnirad651: 2,2-dimethoxy-1,2-diphenylethan-1-one (Omnirad651, manufactured by IGM Resins BV)

[0133] [Photocurable composition C1~C8] Next, the monomer syrup and additives were mixed so as to obtain the compositions shown in Table 2 below, thereby obtaining photocurable compositions C1 to C8.

[0134] [Table 2]

[0135] The abbreviations in Table 2 are as follows: NDDA: 1,9-nonanediol diacrylate A-100: Acetoacetyl group-containing silane coupling agent (A-100, manufactured by Soken Chemical & Engineering Co., Ltd.)

[0136] Example 1 Photocurable composition C1 was applied to the release layer surface of release liner A with an applicator to form a coating layer (thickness: 20 μm). Next, the above-mentioned release liner B was placed on the formed coating layer to obtain a first laminate. Release liner B was placed so that the release layer was in contact with the coating layer. Next, a light with an illuminance of 2.5 mW / cm was applied from the side of release liner A in the first laminate. 2 The sample was irradiated with ultraviolet light (black light source) for 640 seconds. The coating layer was photocured to form a second laminate composed of release liner A, a pressure sensitive adhesive sheet (thickness: 20 μm), and release liner B.

[0137] Next, release liner B was peeled off from the second laminate, and the above-mentioned polarizing film was placed on the exposed surface of the pressure-sensitive adhesive sheet, thereby obtaining the optical laminate of Example 1. The polarizing film was placed so that the surface on the side of the transparent protective film made of a modified acrylic polymer was in contact with the pressure-sensitive adhesive sheet.

[0138] (Examples 2-3, 5, 7-8 and Comparative Examples 1-2) Optical laminates of Examples 2 to 3, 5, 7 to 8 and Comparative Examples 1 to 2 were obtained in the same manner as in Example 1, except that the photocurable compositions used were changed as shown in Table 3.

[0139] Example 4 Except for using photocurable composition C3, a second laminate was formed in the same manner as in Example 1. Next, release liner B was peeled off from the second laminate, and a discharge amount of 63 W / m was applied to the exposed surface of the PSA sheet. 2 The exposed surface was then subjected to corona treatment for 10 min. By disposing the film, an optical laminate of Example 4 was obtained. The polarizing film was disposed so that the surface on the transparent protective film side made of a modified acrylic polymer was in contact with the pressure-sensitive adhesive sheet.

[0140] Example 6 Except for using photocurable composition C4, a second laminate was formed in the same manner as in Example 1. Next, release liner B was peeled off from the second laminate, and a discharge of 63 W / m 2 was applied to the exposed surface of the PSA sheet. 2 The exposed surface was then subjected to corona treatment for 10 min. By disposing the film, an optical laminate of Example 6 was obtained. The polarizing film was disposed so that the surface on the transparent protective film side made of a modified acrylic polymer was in contact with the pressure-sensitive adhesive sheet.

[0141] (Reference example 1) [Preparation of (meth)acrylic polymer] A four-neck flask equipped with a stirring blade, thermometer, nitrogen gas inlet tube, and condenser was charged with 99.0 parts by weight of BA and 1 part by weight of HBA. Next, 0.1 parts by weight of AIBN as a polymerization initiator was added to 100 parts by weight of the BA and HBA mixture. Nitrogen gas was introduced with gentle stirring to replace the atmosphere in the flask with nitrogen. The liquid temperature in the flask was maintained at around 55°C, and the polymerization reaction was allowed to proceed for 7 hours. Ethyl acetate was then added to the resulting reaction solution to adjust the solids concentration to 12% by weight, yielding a (meth)acrylic polymer solution. The weight-average molecular weight (Mw) of the (meth)acrylic polymer was 1.65 million.

[0142] [Preparation of optical laminate] 100 parts by weight of the solid content of the (meth)acrylic polymer was mixed with 0.3 parts by weight of a peroxide-based crosslinking agent (dibenzoyl peroxide, manufactured by NOF Corporation, trade name "Niper BMT"), 0.1 parts by weight of an isocyanate-based crosslinking agent (trimethylolpropane xylene diisocyanate, manufactured by Mitsui Takeda Chemicals, Inc., trade name "Takenate D110N"), and 0.2 parts by weight of an acetoacetyl group-containing silane coupling agent (manufactured by Soken Chemical & Engineering Co., Ltd., trade name "A-100") to obtain a thermosetting (solvent-based) pressure-sensitive adhesive composition.

[0143] Next, the above-mentioned pressure-sensitive adhesive composition was applied to the release surface of a 38 μm thick PET film (Mitsubishi Chemical Polyester Film, MRF38), a release film whose release surface was silicone-treated, to form a coating film, which was then left in an environment of 23°C until preheating, and then preheating and main heating were carried out continuously in an air-circulating constant-temperature oven while the base film and coating film were transported to form a pressure-sensitive adhesive sheet with a thickness of 20 μm. The above-mentioned polarizing film was placed on the exposed surface of the pressure-sensitive adhesive sheet to obtain the optical laminate of Reference Example 1. The polarizing film was placed so that the surface on the transparent protective film side made of modified acrylic polymer was in contact with the pressure-sensitive adhesive sheet.

[0144] [Glass transition temperature] When a polymer was synthesized from the monomer syrup or the monomer group used in producing the (meth)acrylic polymer of Reference Example 1, the glass transition temperature Tg of the polymer was calculated using the FOX formula.

[0145] [Gel fraction] The gel fraction of the prepared pressure-sensitive adhesive sheet was measured by the following method. First, a portion of the pressure-sensitive adhesive sheet was scraped off to obtain a small piece weighing approximately 0.2 g. Next, the obtained small piece was wrapped in a stretched porous polytetrafluoroethylene membrane (NTF1122 (average pore size 0.2 μm) manufactured by Nitto Denko) and tied with kite string to obtain a test piece. Next, the total weight (weight A) of the pressure-sensitive adhesive sheet piece, stretched porous membrane, and kite string was measured. The total weight of the stretched porous membrane and kite string used was defined as weight B. Next, the test piece was immersed in a container filled with ethyl acetate and allowed to stand at 23°C for one week. After standing, the test piece was removed from the container and dried in a dryer set at 130°C for two hours, and then the weight C of the test piece was measured. The gel fraction of the pressure-sensitive adhesive sheet was calculated from weight A, weight B, and weight C according to the following formula: Gel fraction (wt%) = (CB) / (AB) × 100

[0146] [Anchoring power] The anchoring force F between the pressure-sensitive adhesive sheet and the polarizing film was measured for the prepared optical laminate by the method described above. The double-sided tape used was "No. 531" manufactured by Nitto Denko Corporation. The stainless steel test plate used was a SUS304 plate (width 40 mm x length 120 mm). The evaluation sheet used was an ITO film (125 Tetolite OES, manufactured by Oike Kogyo). The tensile tester used was an autograph SHIMAZU AG-I 10KN ( A microscope (manufactured by Shimadzu Corporation) was used.

[0147] [Dielectric constant] The dielectric constant P at a frequency of 100 Hz was measured for the partially polymerized product contained in the monomer syrup and the (meth)acrylic polymer of Reference Example 1 by the method described above.

[0148] [Table 3]

[0149] As can be seen from Table 3, the optical laminates of the examples, which used pressure-sensitive adhesive sheets formed from photocurable compositions in which the blending amount of ether group-containing monomer and the glass transition temperature Tg calculated using the FOX formula were adjusted to fall within the above-mentioned ranges, had larger anchoring strengths F between the pressure-sensitive adhesive sheet and the optical film (polarizing film) than the comparative examples. In particular, in Examples 1, 2, 4, and 6 to 8, the anchoring strength F values ​​were comparable to or greater than that of the optical laminate of Reference Example 1, which used a pressure-sensitive adhesive sheet made from a thermosetting pressure-sensitive adhesive composition containing an isocyanate-based crosslinking agent.

[0150] In Examples 1 and 7, the anchoring force F was significantly high. This result is presumably due to the fact that the gel fraction of the pressure-sensitive adhesive sheet in Examples 1 and 7 was relatively low, and the pressure-sensitive adhesive sheet easily adhered to the optical film. From the results of Examples 3 to 6, it can be seen that the pressure-sensitive adhesive sheet was subjected to surface modification. It can be seen that the anchoring force F increases by performing quality treatment.

[0151] Furthermore, as can be seen from Table 3, the dielectric constant P at a frequency of 100 Hz of the partial polymer contained in the monomer syrup used in the examples was 3.8 or more. From these results, it is presumed that the pressure-sensitive adhesive sheet used in the examples can suppress a decrease in sensitivity of the touch sensor provided in the image display device, even when used in combination with an optical film having a low dielectric constant. [Industrial Applicability]

[0152] The pressure-sensitive adhesive sheet of the present invention can be used, for example, in optical laminates and image display devices. [Explanation of symbols]

[0153] 1 adhesive sheet 2 Optical Film 10,11 Optical laminate

Claims

1. A pressure-sensitive adhesive sheet formed from a photocurable composition containing a monomer group and / or a partial polymer of the monomer group, the amount of the isocyanate-based crosslinking agent in the photocurable composition is less than 0.05 parts by weight per 100 parts by weight of the total of the monomer group and the partial polymer, the monomer group includes an ether group-containing monomer, the amount of the ether group-containing monomer blended is 25 parts by weight or more per 100 parts by weight of the monomer group, When a polymer is synthesized from the monomer group, the glass transition temperature of the polymer calculated from the FOX formula is higher than -60°C.

2. The pressure-sensitive adhesive sheet according to claim 1 , wherein the partial polymer has a relative dielectric constant of 3.8 or more at a frequency of 100 Hz.

3. The pressure-sensitive adhesive sheet according to claim 1 , wherein the ether group-containing monomer comprises an alkoxy group-containing monomer.

4. The pressure-sensitive adhesive sheet according to claim 3 , wherein the alkoxy group-containing monomer is represented by the following formula (1): 【Chemical 1】 In the formula (1), R 1 is a hydrogen atom or a methyl group, and R 2 is an alkyl group, and n is an integer from 1 to 30.

5. The pressure-sensitive adhesive sheet according to claim 3, wherein the alkoxy group-containing monomer includes 2-methoxyethyl acrylate.

6. The pressure-sensitive adhesive sheet according to claim 1 , wherein the ether group-containing monomer has a ring structure.

7. The pressure-sensitive adhesive sheet according to claim 1 , wherein the glass transition temperature is 0° C. or lower.

8. The pressure-sensitive adhesive sheet according to claim 1 , wherein the photocurable composition does not contain an isocyanate-based crosslinking agent.

9. The pressure-sensitive adhesive sheet according to claim 1 , wherein the photocurable composition contains a solvent in an amount of 5% by weight or less.

10. The pressure-sensitive adhesive sheet according to claim 1 , which has a surface that has been subjected to a surface modification treatment.

11. The pressure-sensitive adhesive sheet according to any one of claims 1 to 10, an optical film including at least one selected from the group consisting of a polarizing film and a retardation film; An optical laminate comprising:

12. The optical laminate according to claim 11, wherein the anchoring force between the pressure-sensitive adhesive sheet and the optical film is 10.0 N / 25 mm or more.

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