Optical film with adhesive, optical element, and method for manufacturing the same

Abstract

To provide an optical film with an adhesive that is unlikely to cause peeling or wrinkling when bonded to a rigid substrate having a curved surface, and that also has excellent processability.SOLUTION: An optical film with adhesive (30) includes an adhesive layer (21) provided on one main surface of an optical film (11). A ratio d / D of a thickness d of the adhesive layer to a total thickness D of the optical film and the adhesive layer is preferably 0.4-0.7. A storage elastic modulus G'25°C of the adhesive layer at a temperature of 25°C is preferably 25kPa or more, and a storage elastic modulus G'120°C at a temperature of 120°C is preferably 30kPa or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical film with a pressure-sensitive adhesive that is attached to a substrate having a curved surface, an optical element, and a method for producing the same. [Background technology]

[0002] Optical films such as polarizing plates and anti-reflection films are disposed on the surfaces of optical elements such as displays and eyeglass lenses, and the films are generally attached via an adhesive. Patent Documents 1 and 2 disclose attaching optical films via an adhesive to the surfaces of optical elements having curved shapes, such as curved displays and concave / convex lenses. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-157101 [Patent Document 2] International Publication No. 2024 / 024409 Summary of the Invention [Problem to be solved by the invention]

[0004] When a pressure-sensitive adhesive film having a pressure-sensitive adhesive layer on the surface of an optical film is bonded to a curved optical element, the film may wrinkle at the curved portion or peel off from the optical element. This tendency is particularly pronounced when the film is bonded by pressing while heated. Furthermore, a pressure-sensitive adhesive film having a pressure-sensitive adhesive layer on the surface of an optical film has processability issues, such as reduced adhesion due to the pressure-sensitive adhesive layer receding inward from the edge of the optical film during cutting.

[0005] In view of the above, an object of the present invention is to provide an optical film with a pressure-sensitive adhesive that is less likely to peel or wrinkle when attached to a substrate having a curved surface and has excellent processability. [Means for solving the problem]

[0006] One embodiment of the present invention is an optical film with a pressure-sensitive adhesive, which has a pressure-sensitive adhesive layer on one main surface of the optical film. Examples of the optical film include optically isotropic films and optically anisotropic films. The optical film may include a polarizer. The optical film may be a circular polarizer including a polarizer and at least one retardation layer, and the retardation layer may be an aligned liquid crystal layer.

[0007] The ratio d / D of the thickness d of the pressure-sensitive adhesive layer to the thickness D of the pressure-sensitive adhesive optical film (total thickness of the optical film and the pressure-sensitive adhesive layer) is preferably 0.4 to 0.7. The thickness D of the pressure-sensitive adhesive optical film may be 50 to 150 μm. The thickness d of the pressure-sensitive adhesive layer may be 20 to 80 μm. The thickness of the optical film may be 25 to 70 μm.

[0008] Storage modulus G' of adhesive layer at 25°C 25℃ The storage modulus G' of the pressure-sensitive adhesive layer at a temperature of 120°C is preferably 25 kPa or more. 120℃ G' is preferably 30 kPa or less. 120℃ / G' 25℃ G' may be 0.35 to 0.65. 25℃ / d may be 0.50 kPa / μm or more. 120℃ / d may be 1.00 kPa / μm or less.

[0009] An optical element is formed by laminating the above-mentioned pressure-sensitive adhesive optical film to a rigid substrate having a curved surface. Examples of optical elements include displays and lenses. The pressure-sensitive adhesive optical film may be laminated to the substrate by heat pressing. [Effects of the Invention]

[0010] The pressure-sensitive adhesive optical film of the present invention is resistant to peeling and wrinkling when attached to a rigid substrate having a curved surface, and has excellent processability. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view of an optical film with a pressure-sensitive adhesive according to an embodiment. [Figure 2] FIG. 1 is a cross-sectional view of an optical element in which an optical film with a pressure-sensitive adhesive is bonded to a substrate having a curved surface. DETAILED DESCRIPTION OF THE INVENTION

[0012] Fig. 1 is a cross-sectional view schematically showing an optical film with a pressure-sensitive adhesive according to one embodiment of the present invention. The optical film with a pressure-sensitive adhesive 30 comprises an optical film 11 and a pressure-sensitive adhesive layer 21 provided on one main surface of the optical film. In Fig. 1, a release liner 41 is releasably attached to the pressure-sensitive adhesive layer 21 of the optical film with a pressure-sensitive adhesive 30.

[0013] 2 is a cross-sectional view schematically showing an optical element 80 in which an optical film with adhesive is bonded to a rigid substrate 50 having a curved surface. Examples of optical elements 80 having a curved surface include lenses for eyeglasses or sunglasses, displays, etc. Materials for the substrate 50 include glass and plastic, and examples of plastic materials include acrylic, polycarbonate, polyimide, and cyclic polyolefin. The radius of curvature of the curved surface of the substrate 50 is, for example, about 10 to 500 mm, and may be 30 to 300 mm or 50 to 200 mm.

[0014] 2 shows a configuration in which the entire substrate 50 has a spherically curved surface, but the substrate may have a curved surface in part and a flat surface in other parts. In the optical element 80 shown in FIG. 2, the pressure-sensitive adhesive layer 21 of the pressure-sensitive adhesive-backed optical film 30 is bonded to the convex curved surface of the substrate 50. The pressure-sensitive adhesive-backed optical film 30 may also be bonded to the concave curved surface of the substrate 50.

[0015] [Configuration of adhesive-backed optical film] <Optical film> Examples of the optical film 11 include an optically isotropic film and an optically anisotropic film. As the optically isotropic film, a transparent film is preferable. As the optically anisotropic film, a retardation plate, a polarizer, etc. can be mentioned. The optical film may be a laminate of multiple films or an optically functional film having a coating layer on the surface of the film.

[0016] An example of a laminate of a plurality of optical films is a polarizing plate, which includes a polarizer and, if necessary, has a transparent film laminated on one or both sides as a polarizer protective film.

[0017] Examples of polarizers 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 dichroic substances such as iodine or dichroic dyes, and polyene-based oriented films such as dehydrated polyvinyl alcohol and dehydrochlorinated polyvinyl chloride.

[0018] A thin polarizer having a thickness of 10 μm or less can also be used as the polarizer. Examples of thin polarizers include those described in JP-A-51-069644, JP-A-2000-338329, WO2010 / 100917, Japanese Patent No. 4691205, and Japanese Patent No. 4751481.

[0019] As the polarizer protective film, a transparent resin film such as a cellulose-based resin, a cyclic polyolefin-based resin, an acrylic-based resin, a phenylmaleimide-based resin, a polycarbonate-based resin, etc. When polarizer protective films are provided on both sides of a polarizer, the polarizer protective films on both sides may be films made of the same resin material or films made of different resin materials.

[0020] Examples of optically functional films include retardation plates, viewing angle widening films, viewing angle limiting (peeping prevention) films, brightness enhancing films, and anti-reflection films. The optical film 11 may include an optically functional film on one or both surfaces of a polarizer. The optical film 11 may include a touch panel sensor as an optically functional film.

[0021] The optical film 11 may be a circular polarizing plate having a retardation plate on one side of a polarizer. The circular polarizing plate may be a transparent film disposed adjacent to the polarizer. When the retardation plate has a retardation of λ / 4 and the angle between the slow axis direction of the retardation plate and the absorption axis direction of the polarizer is 45°, the laminate of the polarizer and the retardation plate functions as a circular polarizing plate that emits light incident from the surface on the polarizer side as circularly polarized light from the surface on the retardation layer side.

[0022] Examples of the retardation layer constituting a circular polarizer include a stretched resin film and an oriented liquid crystal layer. When the retardation layer is an oriented liquid crystal layer, the circular polarizer may include an alignment film for aligning liquid crystal molecules in a predetermined direction. The retardation layer may have a laminated structure of two or more layers. For example, by laminating a polarizer, a λ / 2 plate, and a λ / 4 plate so that their optical axes form a predetermined angle, a wideband circular polarizer that functions as a circular polarizer over a wide band of visible light can be obtained. Furthermore, by laminating a retardation layer that functions as a λ / 4 plate with a positive C plate such as a homeotropically oriented liquid crystal layer, a circular polarizer with small changes in polarization state depending on the viewing angle can be obtained.

[0023] The thickness of the optical film 11 is not particularly limited and may be, for example, about 5 to 150 μm, or may be 10 to 100 μm, 20 to 75 μm, 25 to 70 μm, or 30 to 60 μm. If the optical film is too thin, the processability and handleability of the film may be reduced. Furthermore, if the optical film is too thin, wrinkles may occur when the optical film is attached to an adherend. Therefore, the optical film thickness is preferably 25 μm or more. If the optical film is too thick, lifting or peeling may occur when the pressure-sensitive adhesive-attached optical film is attached to the curved surface of the substrate 50. Therefore, the optical film thickness is preferably 70 μm or less.

[0024] <Adhesive layer> The adhesive layer 21 for bonding the optical film 11 to the substrate 50 is preferably made of an optically transparent adhesive. The adhesive layer 21 may be a laminate of a plurality of adhesive layers.

[0025] The adhesive constituting the adhesive layer 21 can be appropriately selected from those having a base polymer such as an acrylic polymer, a silicone polymer, a polyester, a polyurethane, a polyamide, a polyvinyl ether, a vinyl acetate / vinyl chloride copolymer, a modified polyolefin, an epoxy-based, a fluorine-based, or a rubber-based polymer. In particular, an acrylic adhesive is preferably used because it has excellent optical transparency, exhibits adhesive properties such as appropriate wettability, cohesiveness, and adhesiveness, and is also excellent in weather resistance and heat resistance.

[0026] The acrylic pressure-sensitive adhesive preferably contains an acrylic base polymer in an amount of 50% by weight or more, more preferably 70% by weight or more, and even more preferably 80% by weight or more, based on the total solid content of the pressure-sensitive adhesive composition. As the acrylic base polymer, one having a (meth)acrylic acid alkyl ester monomer unit as the main skeleton is preferably used. In this specification, "(meth)acrylic" means acrylic and / or methacrylic.

[0027] As the (meth)acrylic acid alkyl ester, a (meth)acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms is preferably used. The (meth)acrylic acid alkyl ester may have a branched alkyl group. The content of the (meth)acrylic acid alkyl ester is preferably 40% by weight or more, more preferably 50% by weight or more, and even more preferably 60% by weight or more, based on the total amount of monomer components constituting the base polymer. The acrylic base polymer may be a copolymer of a plurality of (meth)acrylic acid alkyl esters. The arrangement of the constituent monomer units may be random or block.

[0028] The acrylic base polymer may contain an acrylic monomer having a crosslinkable functional group as a copolymerization component. When the base polymer has a crosslinkable functional group, the gel fraction of the pressure-sensitive adhesive can be easily increased by thermal crosslinking or photocuring of the base polymer. Examples of the acrylic monomer having a crosslinkable functional group include a hydroxyl group-containing monomer and a carboxyl group-containing monomer.

[0029] 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-hydroxymethyl)cyclohexylmethyl (meth)acrylate.

[0030] The acrylic base polymer may contain a nitrogen-containing monomer as a monomer component. Examples of the nitrogen-containing monomer include vinyl monomers such as N-vinylpyrrolidone, methylvinylpyrrolidone, vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyloxazole, vinylmorpholine, (meth)acryloylmorpholine, N-vinylcarboxylic acid amides, and N-vinylcaprolactam, and cyanoacrylate monomers such as acrylonitrile and methacrylonitrile. Among these, N-vinylpyrrolidone and (meth)acryloylmorpholine are preferably used.

[0031] The monomer components forming the acrylic polymer may contain a polyfunctional polymerizable compound (polyfunctional monomer). Examples of polyfunctional polymerizable compounds include compounds having two or more ethylenically unsaturated groups in one molecule, and compounds having one C=C bond and a polymerizable functional group such as epoxy, aziridine, oxazoline, hydrazine, or methylol. Among these, compounds having two or more ethylenically unsaturated groups in one molecule, such as polyfunctional (meth)acrylates, are preferred. Specific examples of the polyfunctional polymerizable compound include polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, polytetramethylene glycol di(meth)acrylate, bisphenol A ethylene oxide modified di(meth)acrylate, bisphenol A propylene oxide modified di(meth)acrylate, alkanediol di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, ethoxylated isocyanuric acid triacrylate, pentaerythritol tri(meth)acrylate, and pentaerythritol di(meth)acrylate. acrylate, trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, ethoxylated pentaerythritol tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol poly(meth)acrylate, dipentaerythritol hexa(meth)acrylate, neopentyl glycol di(meth)acrylate, glycerin di(meth)acrylate, urethane (meth)acrylate, epoxy (meth)acrylate, butadiene (meth)acrylate, isoprene (meth)acrylate, etc. The polyfunctional polymerizable compound may be an oligomer.

[0032] The base polymer can be prepared by a known polymerization method such as solution polymerization, UV polymerization, bulk polymerization, or emulsion polymerization. When preparing the base polymer, a polymerization initiator such as a photopolymerization initiator or a thermal polymerization initiator may be used depending on the type of polymerization reaction. A chain transfer agent may be used to adjust the molecular weight of the base polymer.

[0033] From the viewpoint of providing the pressure-sensitive adhesive with appropriate adhesive holding strength and flexibility, the weight-average molecular weight of the base polymer is preferably 200,000 to 1,000,000, and more preferably 250,000 to 800,000. The molecular weight of the base polymer refers to the molecular weight of the polymer before the introduction of a crosslinked structure.

[0034] When a polyfunctional monomer is used in addition to a monofunctional monomer as a monomer component forming the base polymer, the monofunctional monomer may be polymerized first to form a prepolymer composition with a low degree of polymerization (prepolymerization), and then the polyfunctional monomer may be added to the syrup of the prepolymer composition to polymerize the prepolymer and the polyfunctional monomer (postpolymerization). By prepolymerizing the prepolymer in this manner, a crosslinked structure due to the polyfunctional monomer can be uniformly introduced into the base polymer. Alternatively, a pressure-sensitive adhesive layer may be formed by applying a mixture of the prepolymer composition and unpolymerized monomer components (a pressure-sensitive adhesive composition) to a substrate, followed by postpolymerization on the substrate. Because the prepolymer composition has low viscosity and excellent coatability, applying a pressure-sensitive adhesive composition, which is a mixture of the prepolymer composition and unpolymerized monomers, to a substrate and then postpolymerizing the composition can increase the productivity of the pressure-sensitive adhesive layer and achieve a uniform thickness.

[0035] The prepolymer composition can be prepared, for example, by partially polymerizing (preliminarily polymerizing) a composition (referred to as a "prepolymer-forming composition") obtained by mixing the monomer components constituting the acrylic base polymer with a polymerization initiator. The monomer in the prepolymer-forming composition is preferably a monofunctional monomer, such as a (meth)acrylic acid alkyl ester or a polar group-containing monomer, among the monomer components constituting the acrylic polymer. The prepolymer-forming composition may also contain a polyfunctional monomer. For example, a portion of the polyfunctional monomer components that serve as raw materials for the base polymer may be incorporated into the prepolymer-forming composition, and after polymerization of the prepolymer, the remainder of the polyfunctional monomer components may be added and subjected to post-polymerization.

[0036] The prepolymer-forming composition may contain, in addition to the monomer and polymerization initiator, a chain transfer agent, etc., as necessary. The polymerization method for the prepolymer is not particularly limited, but polymerization by irradiation with actinic rays such as UV light is preferred from the viewpoint of adjusting the reaction time to achieve a desired range of molecular weight (polymerization rate) of the prepolymer. The polymerization initiator and chain transfer agent used in the prepolymerization are not particularly limited.

[0037] The polymerization rate of the prepolymer is not particularly limited, but is preferably 3 to 50% by weight, more preferably 5 to 40% by weight, from the viewpoint of achieving a viscosity suitable for application to a substrate. The polymerization rate of the prepolymer can be adjusted to a desired range by adjusting the type and amount of photopolymerization initiator used, the irradiation intensity and irradiation time of actinic rays such as UV light, etc.

[0038] The prepolymer composition is mixed with the remaining monomer components (post-polymerization monomers) constituting the acrylic base polymer, and optionally with a polymerization initiator, a chain transfer agent, a silane coupling agent, a crosslinking agent, etc. to form a pressure-sensitive adhesive composition. The post-polymerization monomer preferably contains a polyfunctional monomer. In addition to the polyfunctional monomer, a monofunctional monomer may also be added as the post-polymerization monomer.

[0039] The base polymer of the pressure-sensitive adhesive preferably has a crosslinked structure. For example, as described above, a base polymer having a crosslinked structure can be obtained by using a polyfunctional polymerizable compound as a monomer component forming the base polymer. A crosslinked structure can also be formed by adding a crosslinking agent after polymerizing the base polymer. Commonly used crosslinking agents include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, carbodiimide-based crosslinking agents, and metal chelate-based crosslinking agents. The content of the crosslinking agent is typically in the range of 0.01 to 5 parts by weight, preferably 0.05 to 3 parts by weight, and more preferably 0.07 to 2.5 parts by weight, per 100 parts by weight of the base polymer. The base polymer may contain both a crosslinked structure formed by a polyfunctional polymerizable compound and a crosslinked structure formed by a crosslinking agent such as polyisocyanate.

[0040] In addition to the components exemplified above, the adhesive may contain additives such as various oligomers, silane coupling agents, tackifiers, plasticizers, softeners, UV absorbers, antidegradants, fillers, colorants, antioxidants, surfactants, and antistatic agents.

[0041] The adhesive layer is formed by applying a layer of the adhesive composition to a substrate, and then drying the solvent and crosslinking and curing the base polymer as needed. The crosslinking and curing reaction may be carried out by heating or irradiation with active energy rays.

[0042] The thickness of the pressure-sensitive adhesive layer 21 is not particularly limited, but from the viewpoint of suppressing peeling or wrinkling at curved surfaces when the pressure-sensitive adhesive-attached optical film 30 is attached to the substrate 50, the thickness of the pressure-sensitive adhesive layer 21 is preferably 20 μm or more, more preferably 25 μm or more, and may be 30 μm or more, 35 μm or more, or 40 μm or more. From the viewpoint of processability of the pressure-sensitive adhesive-attached optical film 30, the thickness of the pressure-sensitive adhesive layer 21 is preferably 80 μm or less, more preferably 75 μm or less, and may be 70 μm or less, 65 μm or less, or 60 μm or less.

[0043] Storage modulus G' of pressure-sensitive adhesive layer 21 at a temperature of 25°C 25℃ is preferably 25 kPa or more. If the storage modulus of the pressure-sensitive adhesive layer 21 at room temperature is excessively low, when the pressure-sensitive adhesive-attached optical film is cut into chips that match the size and shape of the substrate to be adhered, the pressure-sensitive adhesive is likely to be damaged on the cut surface (edge ​​surface), and processability tends to be poor. 25℃ is more preferably 30 kPa or more, and even more preferably 35 kPa or more. 25℃ There is no particular upper limit to G'. 25℃ is preferably 200 kPa or less, and may be 150 kPa or less, 100 kPa or less, 80 kPa or less, 60 kPa or less, or 50 kPa or less.

[0044] The thickness d of the pressure-sensitive adhesive layer 21 is small, and the storage modulus G' at room temperature is 25℃From the viewpoint of the processability of the pressure-sensitive adhesive optical film, the storage modulus G' of the pressure-sensitive adhesive layer at room temperature is 25℃ Dividing this by the thickness d gives G' 25℃ / d (unit: kPa / μm) is preferably 0.50 or more, and may be 0.55 or more, 0.60 or more, 0.65 or more, or 0.70 or more. From the viewpoint of suppressing peeling or wrinkles at the curved surface portion when the pressure-sensitive adhesive-attached optical film is attached to the substrate 50, G' 25℃ / d is preferably 2.0 or less, more preferably 1.70 or less, even more preferably 1.60 or less, and may be 1.50 or less, 1.40 or less, 1.30 or less, 1.20 or less, 1.10 or less, or 1.00 or less.

[0045] Storage modulus G' of adhesive layer 21 at a temperature of 120°C 120℃ is preferably 30 kPa or less. Since the pressure-sensitive adhesive layer 21 has a small storage modulus at high temperatures, the occurrence of wrinkles in the film tends to be suppressed when the pressure-sensitive adhesive-attached optical film is attached to a substrate 50 having a curved surface by heat pressing. 120℃ G' is more preferably 25 kPa or less, and may be 20 kPa or less or 18 kPa or less. 120℃ There is no particular limitation on the lower limit of G'. 120℃ is preferably 5 kPa or more, and may be 10 kPa or more or 15 kPa or more.

[0046] The thickness d of the pressure-sensitive adhesive layer 21 is large, and the storage modulus G' at high temperature is 120℃ The smaller the storage modulus G' of the pressure-sensitive adhesive layer at high temperatures, the greater the stress relaxation effect of the pressure-sensitive adhesive layer during bonding by hot pressing, and the occurrence of wrinkles and cracks in the film, and peeling of the film from the substrate, etc., tend to be suppressed. From the viewpoint of the bonding properties of the pressure-sensitive adhesive-attached optical film by hot pressing, the storage modulus G' of the pressure-sensitive adhesive layer at high temperatures 120℃ Dividing this by the thickness d gives G' 120℃ / d (unit: kPa / μm) is preferably 1.00 or less, more preferably 0.80 or less, even more preferably 0.70 or less, and may be 0.60 or less, 0.55 or less, 0.50 or less, 0.45 or less, or 0.40 or less. 120℃ / d is preferably 0.10 or more, and may be 0.15 or more, 0.20 or more, or 0.25 or more.

[0047] As described above, the pressure-sensitive adhesive layer 21 has a storage modulus G' at room temperature from the viewpoint of processability. 25℃ It is preferable that the storage modulus G' at high temperatures is large from the viewpoint of bonding properties by hot pressing. 120℃ It is preferable that G' of the pressure-sensitive adhesive layer 21 is small. 25℃ and G' 120℃ The ratio G' 120℃ / G' 25℃ is preferably 0.35 to 0.65, more preferably 0.40 to 0.60.

[0048] <Optical film with adhesive> A pressure-sensitive adhesive layer 21 is bonded to one main surface of the optical film 11 to obtain a pressure-sensitive adhesive-attached optical film 30. The pressure-sensitive adhesive composition may be applied to the optical film 11, followed by drying the solvent, crosslinking, curing, etc. to form the pressure-sensitive adhesive layer 21 on the optical film 11. The application of the pressure-sensitive adhesive and the bonding of the pressure-sensitive adhesive layer are preferably carried out by a roll-to-roll method.

[0049] Until the pressure-sensitive adhesive-attached optical film is bonded to a substrate as an adherend, it is preferable to temporarily attach a release liner 41 to the exposed surface of the pressure-sensitive adhesive layer 21, as shown in Fig. 1. The release liner 41 preferably has a release layer on the surface of the film substrate. Examples of materials for the release layer include silicone-based release agents, fluorine-based release agents, long-chain alkyl-based release agents, and fatty acid amide-based release agents. The thickness of the release liner is approximately 10 to 200 µm, and preferably 20 to 80 µm.

[0050] An adhesive layer 21 is provided on one main surface of the optical film 11, and if necessary, a release liner 41 is temporarily attached to the surface of the adhesive layer 21. The adhesive-backed optical film is then cut into chips that match the size and shape of the substrate to be adhered.

[0051] In the adhesive-backed optical film processed into chips, a release liner 41 is temporarily attached to the surface of the adhesive layer 21, but the side of the adhesive layer 21 is exposed to the outside, and during transportation and handling, the adhesive may protrude from the side, causing problems such as contamination and blocking.

[0052] From the viewpoint of preventing glue chipping and glue stains caused by the adhesive squeezing out from the side surface (edge ​​surface) of the adhesive-backed optical film, it is preferable that the edge surface of the adhesive layer 21 of the adhesive-backed optical film be located more inward than the edge surface of the optical film 11 and the edge surface of the release liner 41. As a method for obtaining a chip in which the edge surface of the adhesive layer 21 is located more inward, as shown in JP 2014-115468 A, there is a method in which pressure is applied from above and below the adhesive-backed optical film to cause the adhesive to squeeze out from the edge surface of the optical film, and in a state in which the adhesive is squeezing out, the adhesive layer is cut together with the optical film and the release liner.

[0053] Specifically, the pressure-sensitive adhesive optical film is cut into sheets of a predetermined size by punching with a Thomson blade, cutting with a cutting machine such as a super cutter, cutting with a round blade or a countersunk blade, laser processing, or the like, and the stack of multiple sheets of pressure-sensitive adhesive optical film is used as the workpiece to be processed. This workpiece is clamped and fixed from above and below with a fixing means such as a clamp, and pressure is applied from above and below to cause the pressure to protrude from the edges. In this state, cutting is performed using a rotary blade or the like, and by releasing the pressure after cutting, the end face 21 of the pressure-sensitive adhesive layer recedes inward, resulting in a chip of pressure-sensitive adhesive optical film in which the end face of the pressure-sensitive adhesive layer 21 is located more inward than the end face of the optical film 11 (and the end face of the release liner 41).

[0054] In the chip obtained in this manner, the edge surface of the adhesive layer 21 is located more inward than the edge surface of the optical film 11 (and the edge surface of the release liner 41), thereby suppressing contamination and blocking due to the adhesive spilling out from the edge surface. The distance between the edge surface of the optical film 11 and the edge surface of the adhesive layer 21 (the inward recession of the adhesive layer 21) is preferably 5 μm or more, more preferably 10 μm or more, and may be 20 μm or more, 30 μm or more, or 40 μm or more. If the inward recession of the adhesive layer 21 is excessively large, adhesion problems such as peeling from the edge of the optical film after being attached to the adherend may occur. Therefore, the inward recession of the adhesive layer 21 is preferably 200 μm or less, more preferably 180 μm or less, and may be 160 μm or less, 150 μm or less, or 140 μm or less.

[0055] The thickness D of the pressure-sensitive adhesive optical film 30 (total thickness of the optical film and the pressure-sensitive adhesive layer) is preferably 50 to 150 μm, and may be 55 to 130 μm, 60 to 120 μm, 65 to 110 μm, or 70 to 100 μm. The ratio d / D of the thickness d of the pressure-sensitive adhesive layer 21 to the thickness D of the pressure-sensitive adhesive optical film 30 is preferably 0.35 to 0.70, and may be 0.40 to 0.65 or 0.45 to 0.60.

[0056] The thicker the optical film 11, the greater the mechanical strain at the bonding interface, making the optical film more susceptible to wrinkling, cracking, peeling, etc. When d / D is 0.35 or more, the thickness ratio of the pressure-sensitive adhesive layer 21 is large, and the storage modulus G' of the pressure-sensitive adhesive layer 21 at high temperatures is 120℃ When the pressure is 30 kPa or less, the effect of relaxing the strain occurring at the bonding interface is high, and the bonding characteristics tend to be good.

[0057] The larger the thickness d of the adhesive layer 21 and the larger the thickness ratio of the adhesive layer 21 in the adhesive-attached optical film 30, the larger the amount of adhesive that protrudes from the edge surface due to pressure from above and below during the cutting process described above, and the larger the amount of retraction of the adhesive layer inward when the pressure is released after processing.25℃ When the compressive strength is 25 kPa or more, the pressure-sensitive adhesive optical film has excellent processability, and loss of the pressure-sensitive adhesive at the edge surface due to recession of the pressure-sensitive adhesive layer during processing tends to be suppressed.

[0058] [Optical elements] The optical element 80 is obtained by laminating the above-mentioned pressure-sensitive adhesive optical film 30 to a rigid substrate 50 having a curved surface. Examples of the optical element include a display and a lens. When the optical element is a display, the substrate 50 may be a cover window disposed on the viewing side surface of the display.

[0059] The lamination method is not particularly limited, but heat pressing is preferred from the viewpoint of making the shape of the pressure-sensitive adhesive-attached optical film conform to the curved surface shape of the rigid substrate 50. The heating temperature during heat pressing is, for example, about 100 to 150°C.

[0060] In the curved portion, the curvature of the inner surface (the side closest to the center of curvature) is smaller than that of the outer surface, causing mechanical strain at the bonding interface. Because the substrate 50 is rigid, its shape changes little even when strain occurs, whereas the optical film 11 is flexible, and mechanical strain can cause cracks in the film or deformation and wrinkles. Furthermore, if the shape of the film cannot follow the curved shape of the substrate 50, the film may peel off from the substrate.

[0061] As described above, in the present invention, the optical film 11 and the adhesive layer 21 have a predetermined thickness, and the adhesive layer has a predetermined viscoelasticity, which acts to relieve strain in the adhesive layer 21, resulting in good bonding properties and suppressing the occurrence of peeling, wrinkles, cracks, etc. Furthermore, there is little loss of adhesive at the edge surfaces of the adhesive-attached optical film processed into chips, which tends to suppress problems such as peeling from the edge surfaces. [Example]

[0062] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0063] [Adhesive sheet manufacturing example] <Adhesive sheet A> (Preparation of Pressure-Sensitive Adhesive Composition) Monomers were added to a reaction vessel: 60 parts by weight of n-octyl acrylate (NOAA), 30 parts by weight of butyl acrylate (BA), 8 parts by weight of 4-hydroxybutyl acrylate (4HBA), and 2 parts by weight of N-vinyl-2-pyrrolidone (NVP). As photopolymerization initiators, 0.05 parts by weight of "Omnirad651" (manufactured by IGM Resins) and 0.05 parts by mass of "Omnirad184" (manufactured by IGM Resins) were then added. The mixture was then irradiated with ultraviolet light under a nitrogen atmosphere, thereby polymerizing a portion of the monomer components and obtaining a prepolymer composition with a polymerization rate of approximately 10%.

[0064] To 100 parts by weight of the prepolymer composition, 0.08 parts by weight of dipentaerythritol hexaacrylate (DPHA) as a polyfunctional monomer, 0.05 parts by mass of "Omnirad651" as a photopolymerization initiator, and 0.3 parts by mass of "KBM-403" (manufactured by Shin-Etsu Chemical Co., Ltd.) as a silane coupling agent were added to obtain a pressure-sensitive adhesive composition.

[0065] <Formation of adhesive sheet> The above-mentioned pressure-sensitive adhesive composition was applied to the release-treated surface of a release liner having a release-treated surface on one side to form a coating layer, and another release liner was laminated onto this coating layer. The pressure-sensitive adhesive composition was then cured by irradiation with ultraviolet light to obtain PSA sheet A1, which had a 15 μm-thick pressure-sensitive adhesive layer with release liners laminated to both sides. By changing the coating thickness of the pressure-sensitive adhesive composition, PSA sheet A2, PSA sheet A3, PSA sheet A4, PSA sheet A5, and PSA sheet A6 were prepared.

[0066] <Adhesive sheet B> The monomer composition during prepolymer preparation was changed to 59 parts by weight of lauryl acrylate (LA), 40 parts by weight of 2-ethylhexyl acrylate (2EHA), and 1 part by weight of 4HBA, and the polyfunctional monomer was changed to 0.15 parts by weight of 1,6-hexanediol diacrylate (HDDA). Apart from these changes, a 50 μm thick adhesive sheet B1 was obtained in the same manner as adhesive sheet A.

[0067] <Adhesive sheet C> (Preparation of Base Polymer) 99 parts by weight of BA and 1 part by weight of 4HBA as monomers, and 0.1 parts by weight of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator were charged into a reaction vessel together with ethyl acetate, and the mixture was reacted at 55°C for 8 hours under a nitrogen gas stream to obtain a solution of acrylic polymer C having a weight-average molecular weight of approximately 1.6 million.

[0068] (Preparation of Pressure-Sensitive Adhesive Composition) A pressure-sensitive adhesive composition was obtained by blending 0.3 parts by weight of dibenzoyl peroxide (Niper BMT manufactured by Nippon Oil & Fats Co., Ltd.) and 0.1 parts by weight of trimethylolpropane xylylene diisocyanate (Takenate D110N manufactured by Mitsui Chemicals Co., Ltd.) as crosslinking agents with 100 parts by weight of the polymer into a solution of acrylic polymer C, as well as 0.2 parts by weight of a silane coupling agent (KBM-403).

[0069] <Formation of adhesive sheet> The above pressure-sensitive adhesive composition was applied to the release-treated surface of the release liner, and then dried and crosslinked by heating at 155° C. for 2 minutes, to obtain a 50 μm-thick pressure-sensitive adhesive sheet C.

[0070] <Adhesive sheet D> (Preparation of Acrylic Oligomer) Monomers, namely, 95 parts by weight of BA, 3 parts by weight of methyl acrylate (MA), 2 parts by weight of acrylic acid (AA), and 0.1 parts by weight of a polymerization initiator (AIBN), together with 140 parts by weight of toluene, were charged into a reaction vessel, and the mixture was reacted at 70°C for 8 hours under a nitrogen gas stream to obtain a solution of acrylic oligomer D having a weight-average molecular weight of approximately 45,000.

[0071] (Preparation of Pressure-Sensitive Adhesive Composition and Formation of Pressure-Sensitive Adhesive Sheet) A pressure-sensitive adhesive composition was obtained by blending 30 parts by weight (solids equivalent) of acrylic oligomer D, 1 part by weight of "Niper BMT" and 0.01 part by weight of "Takenate D110N" as crosslinking agents per 100 parts by weight of the polymer, into a solution of acrylic polymer C. Using this pressure-sensitive adhesive composition, a 50 μm thick pressure-sensitive adhesive sheet D was obtained in the same manner as pressure-sensitive adhesive sheet C.

[0072] <Adhesive sheet E> (Preparation of Base Polymer) A solution of acrylic polymer E having a weight average molecular weight of approximately 2,000,000 was obtained in the same manner as in the preparation of polymer C, except that the monomer composition was changed to 94.9 parts by weight of BA, 5 parts by weight of AA, and 0.1 parts by weight of 2-hydroxyethyl acrylate (2HEA).

[0073] (Preparation of Pressure-Sensitive Adhesive Composition and Formation of Pressure-Sensitive Adhesive Sheet) A pressure-sensitive adhesive composition was obtained by blending 0.6 parts by weight of trimethylolpropane tolylene diisocyanate ("Coronate L" manufactured by Tosoh Corporation) as a crosslinking agent per 100 parts by weight of the acrylic polymer C solution. Using this pressure-sensitive adhesive composition, a 50 μm thick pressure-sensitive adhesive sheet E was obtained in the same manner as pressure-sensitive adhesive sheet C.

[0074] <Adhesive sheet F> A pressure-sensitive adhesive composition was obtained by blending 0.1 parts by weight of "Niper BMT" and 0.45 parts by weight of "Coronate L" as crosslinking agents, and 0.2 parts by weight of a silane coupling agent ("KBM-403"), relative to 100 parts by weight of the polymer, into a solution of acrylic polymer C. Using this pressure-sensitive adhesive composition, a 50 μm thick pressure-sensitive adhesive sheet E was obtained in the same manner as pressure-sensitive adhesive sheet C.

[0075] <Measurement of storage modulus> The release liner was peeled off from the pressure-sensitive adhesive sheet, and multiple pressure-sensitive adhesive layers were laminated to a thickness of approximately 1.0 mm to prepare a measurement sample. Dynamic viscoelasticity measurements were performed under the following conditions using a rotational rheometer (Rheometric Scientific's "Advanced Rheometric Expansion System (ARES)") equipped with 8.0 mmφ parallel plates, and the storage modulus was read at temperatures of 25°C and 120°C. (Measurement conditions) Deformation mode: Torsion Measurement frequency: 1Hz Heating rate: 5°C / min Measurement temperature: -40~150℃

[0076] [Example of optical film production] <Film A: Circular polarizer> A 20 μm thick acrylic film was bonded to one side of a 5 μm thick polyvinyl alcohol polarizer via a UV-curable adhesive (1 μm thick), and a 7 μm thick retardation layer was bonded to the other side of the polarizer via a UV-curable adhesive (1 μm thick) to obtain Film A (circular polarizer). The retardation layer was a 3 μm thick homogeneously aligned liquid crystal (positive A plate) and a 4 μm thick homeotropically aligned liquid crystal layer (positive C plate) bonded together via a UV-curable adhesive (1 μm thick), and the surface on the homogeneously aligned liquid crystal layer side was bonded to the polarizer. The angle between the absorption axis direction of the polarizer and the alignment direction (slow axis direction) of the homogeneously aligned liquid crystal layer was 45°.

[0077] <Film B: Circular polarizer> A 20 μm thick acrylic film was attached to one side of a 5 μm thick polyvinyl alcohol polarizer via a UV-curable adhesive (1 μm thick), and a 47 μm thick polycarbonate retardation film was attached to the other side of the polarizer via an acrylic pressure-sensitive adhesive layer (5 μm thick) to obtain Film B (circular polarizing plate). The angle between the absorption axis direction of the polarizer and the slow axis direction of the retardation film was 45°.

[0078] <Films C and D: PET film> As films C and D, biaxially stretched polyester films with thicknesses of 50 μm and 100 μm were prepared.

[0079] [Preparation of adhesive film] Using a roll laminator, an adhesive sheet was laminated to one side of the optical film, and an adhesive layer was laminated to one side of the optical film, with a release liner (38 μm thick) temporarily attached to the surface of the adhesive layer to produce an adhesive-backed film. The optical film and adhesive sheet were combined as shown in Table 1. For optical films A and B (circular polarizers), an adhesive sheet was laminated to the surface on the retardation layer side.

[0080] [evaluation] <Laminating> The adhesive film was cut into a circle with a diameter of 50 mm and bonded to the convex surface of a spherical acrylic plate (2 mm thick) with a diameter of 50 mm and a curvature radius of 100 mm. The bonding was performed using a heat press machine. The acrylic plate was placed on a flat lower mold with the convex side facing up, and then the adhesive optical film was placed on top of it. A concave upper mold with a curvature radius of 100 mm was pressed against the plate. The temperature was 120°C, the pressing pressure was 1 kN, and the pressing time was 3 seconds.

[0081] The samples after lamination were visually inspected to check the state of lamination (presence or absence of lifting) and the presence or absence of cracks in the optical film, and for those without these defects, the number of wrinkles was counted.

[0082] <Workability> Using a super cutter (continuous automatic cutting machine), the adhesive-backed film was cut into rectangles measuring 50 mm x 50 mm. Several cut rectangular adhesive-backed optical films were stacked to a thickness of 140 mm to form the workpiece. The workpiece was clamped at a clamping pressure of 0.1 MPa and the outer surface of the workpiece was machined using a side mill. The blade rotation speed during machining was 4500 rpm, and the feed rate (the relative movement speed of the workpiece to the blade) was 600 mm / min.

[0083] The edge of the chip of the adhesive-coated film after cutting was observed using an optical microscope, and the distance between the edge of the adhesive layer and the edge of the film (how far the edge of the adhesive layer was recessed inward from the edge of the film) was measured, and this was taken as the "recession amount."

[0084] [Evaluation results] Table 1 shows the configuration of the pressure-sensitive adhesive optical films in the examples and comparative examples, as well as the evaluation results of lamination and processability.

[0085] [Table 1]

[0086] In Example 1, in which a 35 μm-thick film A (circular polarizer) and a 50 μm-thick adhesive layer A3 were laminated, no peeling or cracking occurred when the film was attached to a curved substrate, and the number of wrinkles was less than 10, indicating good attachment properties. Furthermore, the adhesive-attached optical film of Example 1 had good cutting processability, with the amount of retraction of the adhesive layer during cutting being less than 200 μm.

[0087] Example 2, in which the thickness of the adhesive layer was changed to 25 μm, Example 3, in which the thickness of the adhesive layer was changed to 75 μm, and Example 6, in which adhesive layer D was used, also had good bonding properties and processability, similar to Example 1. Examples 4 and 5, in which film A in Examples 2 and 3 was replaced with film C (PET film) having a thickness of 50 μm, also had good bonding properties and processability.

[0088] In Comparative Example 1, in which Film A was laminated with a 15 μm-thick adhesive layer A1, cracks occurred in the film when it was bonded to a curved substrate. In Comparative Example 2, in which Film A was laminated with a 100 μm-thick adhesive layer A5, the bonding properties were good, but the amount of recession of the adhesive layer during cutting exceeded 200 μm, and processability was poor.

[0089] Comparative Example 9, in which film A and pressure-sensitive adhesive layer B having a thickness of 50 μm were laminated, had poor processability, similar to Comparative Example 2. In Comparative Example 9, the storage modulus G' of the pressure-sensitive adhesive at room temperature (25° C.) 25℃ It is believed that the small size of the wire is the cause of the deterioration of cutting workability.

[0090] In Comparative Examples 6 to 8, in which Film A was laminated with 50 μm-thick adhesive layers C, E, and F, 10 or more wrinkles were generated when the film was attached to the curved substrate. From the results of Examples 4 and 5 and Comparative Examples 6 to 9, from the viewpoint of cutting processability, the storage modulus G' of the adhesive layer at room temperature (25°C) 25℃ From the viewpoint of suppressing the occurrence of wrinkles when bonding by hot pressing, it is preferable that the storage modulus G' at high temperature (120°C) is large. 120℃ It can be seen that it is preferable that is small.

[0091] In Comparative Example 3, in which a 70 μm-thick film B (circular polarizer) was laminated with a 25 μm-thick adhesive layer A2, 10 or more wrinkles occurred when the film was attached to a curved substrate, similar to Comparative Examples 6 to 8. The same was true for Comparative Example 4, in which a 50 μm-thick film C (PET film) was laminated with an adhesive layer A2. In Comparative Example 5, in which a 100 μm-thick film D (PET film) was laminated with an adhesive layer A2, peeling occurred over the entire surface when the adhesive-attached film was attached to a curved substrate.

[0092] A comparison of Examples 4 and 5 with Comparative Example 4 shows that the thicker the pressure-sensitive adhesive layer, the better the bonding properties tend to be. A comparison of Example 2 with Comparative Examples 3 to 5 shows that the thinner the film, the better the bonding properties tend to be. These results suggest that excellent bonding properties tend to be obtained when the thickness of the pressure-sensitive adhesive layer is large, the thickness of the film substrate is small, and the ratio d / D of the thickness d of the pressure-sensitive adhesive layer to the total thickness D of the pressure-sensitive adhesive-backed film is large. On the other hand, when the thickness d of the pressure-sensitive adhesive layer is large and d / D is excessively large, as in Comparative Example 2 described above, processability tends to decrease.

[0093] Comparing the above examples and comparative examples, it can be seen that by adjusting the thickness of the film and adhesive layer that make up the adhesive film, as well as the storage modulus of the adhesive layer at room temperature (25°C) and high temperature (120°C), the adhesive film can achieve both excellent adhesion properties to curved substrates and excellent cutting processability. [Explanation of symbols]

[0094] 11 Optical film 21 adhesive layer 30 Optical film with adhesive 41 Release liner 50 Substrate 80 Optical Elements

Claims

1. An optical film with a pressure-sensitive adhesive, comprising an optical film having a pressure-sensitive adhesive layer on one main surface thereof, a ratio d / D of a thickness d of the pressure-sensitive adhesive layer to a total thickness D of the optical film and the pressure-sensitive adhesive layer is 0.4 to 0.7; The pressure-sensitive adhesive layer has a storage modulus G' at a temperature of 25°C. ２５℃ is 25 kPa or more, and the storage modulus G' at a temperature of 120°C １２０℃ is 30 kPa or less, Optical film with adhesive.

2. 2. The optical film with adhesive according to claim 1, wherein the thickness d of the adhesive layer is 20 to 80 μm.

3. 3. The pressure-sensitive adhesive optical film according to claim 1, wherein a total thickness D of the optical film and the pressure-sensitive adhesive layer is 50 to 150 μm.

4. 3. The pressure-sensitive adhesive optical film according to claim 1, wherein the optical film has a thickness of 25 to 70 μm.

5. The pressure-sensitive adhesive layer is G' １２０℃ / G' ２５℃ 3. The pressure-sensitive adhesive optical film according to claim 1, wherein the σ is 0.35 to 0.

65.

6. The pressure-sensitive adhesive layer has a storage modulus G' at a temperature of 25°C. ２５℃ G' is the value obtained by dividing by the thickness d. ２５℃ The pressure-sensitive adhesive optical film according to claim 1 or 2, wherein / d is 0.50 kPa / μm or more.

7. The pressure-sensitive adhesive layer has a storage modulus G' at a temperature of 120°C. １２０℃ G' is the value obtained by dividing by the thickness d. １２０℃ The pressure-sensitive adhesive optical film according to claim 1 or 2, wherein / d is 1.00 kPa / μm or less.

8. The pressure-sensitive adhesive optical film according to claim 1 , wherein the optical film comprises a polarizer.

9. The pressure-sensitive adhesive optical film according to claim 1 or 2, wherein the optical film is a circular polarizing plate comprising a polarizer and at least one retardation layer.

10. The pressure-sensitive adhesive optical film according to claim 9 , wherein the retardation layer is an aligned liquid crystal layer.

11. An optical element comprising a rigid substrate having a curved surface and the pressure-sensitive adhesive optical film according to claim 1 attached thereto.

12. 12. The method for manufacturing an optical element according to claim 11, wherein the pressure-sensitive adhesive-attached optical film is bonded to the substrate by heat pressing.

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