Optical laminates, image display devices and adhesive compositions

Abstract

The optical laminate provided by this invention comprises an optical substrate and an adhesive layer disposed on the surface of the optical substrate. The adhesive layer comprises an adhesive composition containing a silane coupling agent. The silane coupling agent contains isocyanate rings and does not contain isocyanate groups. The surface on which the adhesive layer is disposed is a modified surface that has been modified by irradiation energy. The optical laminate exhibits excellent peel resistance at high temperatures.

Description

Technical Field

[0001] This invention relates to optical laminates, image display devices, and adhesive compositions. Prior Technology

[0002] Various thin-film image display devices, such as liquid crystal displays (LCDs) and organic EL displays, typically include an optical stack, which comprises an optical substrate and an adhesive layer disposed on the surface of the optical substrate. Examples of optical substrates include image forming layers such as liquid crystal layers and organic EL light-emitting layers, optical thin films such as polarizing plates and retardation films, and cover windows. The adhesive layer is used to bond the various layers contained in the optical stack. Furthermore, in optical substrates composed of multiple layers, such as polarizing plates composed of polarizing elements and polarizing element protective films, there are also cases where the multiple layers are bonded by an adhesive layer.

[0003] Patent Document 1 discloses an optical laminate comprising a transparent adhesive, an adhesive layer containing a specific silane coupling agent, and a polarizing plate, wherein the specific silane coupling agent has an epoxy group at one end. Patent Document 1 describes how the adhesion of the adhesive layer to the glass plate can be improved by containing the aforementioned silane coupling agent. Previous technical documents Patent documents

[0004] Patent Document 1: Japanese Patent Application Publication No. 7-20314 Summary of the Invention

[0005] The problem the invention aims to solve Image display devices may be exposed to high temperatures. Therefore, optical laminates are required to be resistant to peeling between layers bonded by adhesive layers even at high temperatures; in other words, they must have excellent peel resistance at high temperatures. Furthermore, for the sake of lightweighting and high functionality, image display devices often use optical substrates other than glass substrates, thus requiring that peeling between optical substrates other than glass substrates also be resistant. However, according to the present inventors' research, the optical laminate of Patent Document 1 does not adequately meet these requirements.

[0006] The purpose of this invention is to provide an optical laminate with excellent resistance to peeling at high temperatures.

[0007] The means to solve the problem The present invention provides an optical laminate comprising an optical substrate and an adhesive layer disposed on the surface of the optical substrate; The aforementioned adhesive layer comprises an adhesive composition containing a silane coupling agent; The aforementioned silane coupling agent contains an isocyanate ring but does not contain an isocyanate group; The aforementioned surface, which has been modified by irradiation energy, is the surface modified surface with the aforementioned adhesive layer.

[0008] In another aspect, the present invention provides an image display device comprising the optical stack and image forming layer of the present invention described above.

[0009] In another aspect, the present invention provides an adhesive composition disposed on the surface of an optical substrate for use by the user; The adhesive composition contains a silane coupling agent; The aforementioned silane coupling agent contains an isocyanate ring but does not contain an isocyanate group; The aforementioned surface, which is a modified surface that has been modified by irradiation energy, can be used to configure the aforementioned adhesive composition.

[0010] Invention Effects According to the present invention, an optical laminate with excellent resistance to peeling at high temperatures can be provided. Simple Explanation of the Diagram

[0011] Figure 1 is a schematic cross-sectional view showing an example of the optical laminate of the present invention. Figure 2 is a schematic cross-sectional view showing another example of the optical laminate of the present invention. Figure 3 is a schematic cross-sectional view showing another example of the optical laminate of the present invention. Figure 4 is a schematic cross-sectional view showing an example of the image display device of the present invention. Figure 5A shows the distribution of silane coupling agent in the adhesive layer of the optical laminate prepared in Example 3. Figure 5B shows the distribution of silane coupling agent in the adhesive layer of the optical laminate prepared in Comparative Example 1. Implementation

[0012] The embodiments of the present invention will be described below with reference to the drawings. The present invention is not limited to the following embodiments.

[0013] [Optical stack] Figure 1 shows the optical laminate of this embodiment. The optical laminate 100 of Figure 1 includes an optical substrate 1 and an adhesive layer 2. The adhesive layer 2 is disposed on the surface 11 of the optical substrate 1. The adhesive layer 2 and the optical substrate 1 are in contact with each other. The surface 11 on which the adhesive layer 2 is disposed is a modified surface 12 that has been modified by irradiation energy. The adhesive layer 2 contains an adhesive composition containing a silane coupling agent (hereinafter referred to as "Si agent (X)"), which contains an isocyanate ring but does not contain an isocyanate group. The isocyanate ring has the structure shown in the following formula (1). At least one * (bonding site) in formula (1) is bonded with a molecular structure (Y) containing Si atoms and hydrolyzable groups. The molecular structure (Y) may be bonded to two * or all three *. There are no particular restrictions on the unbonded molecular structure (Y), which can be bonded with hydrogen atoms, halogen atoms or organic residues.

[0014] [Chemical Formula 1]

[0015] We believe that the presence of Si (X) helps maintain the cohesive strength of the adhesive layer 2 at high temperatures (e.g., 50-100°C, typically 80°C) and improves its adhesion to the modified surface 12 of the optical substrate 1 at high temperatures. Maintaining cohesive strength, in other words, inhibiting the aggregation and destruction of the adhesive layer 2 and improving adhesion will lead to improved peel resistance at high temperatures. We hypothesize that the above contributions will have the following effects: (I) Especially when the multiple * bonds of the isocyanate ring have molecular structures (Y), the distribution of molecular structures (Y) that can form covalent bonds with the modified surface 12 in the adhesive layer 2 can become more uniform; (II) The NCO structure that can form hydrogen bonds with the modified surface 12 extends equally in three directions in the isocyanate ring; and (III) The NCO structure of the isocyanate ring is different from the isocyanate group and is not easy to form bonds with other materials, such as polymers or crosslinking agents, that may be contained in the adhesive layer 2, thereby improving the uniformity of the crosslinking structure of the adhesive layer 2. In addition, according to the research of the inventors of this case, the cohesive force of the adhesive layer 2 can be evaluated using the 800% modulus.

[0016] Furthermore, Si agent (X) can be relatively abundant in region 21 near the interface 3 between the adhesive layer 2 and the optical substrate 1. Predisposition in region 21 can further enhance adhesion to the modified surface 12 at high temperatures. From the above perspective, Si agent (X) can also be predisposed in region 21 near the interface 3 between the adhesive layer 2 and the optical substrate 1. Region 21 near interface 3 refers to, for example, a region extending from interface 3 towards the thickness of the adhesive layer 2, occupying approximately 20% of the thickness of the layer 2. The distribution of Si agent (X) in the adhesive layer 2 can be confirmed, for example, by using an evaluation method that allows elemental analysis along the thickness direction of the layer, such as time-of-flight secondary ion mass spectrometry (TOF-SIMS). Predisposition can be confirmed, for example, by using a plot obtained from TOF-SIMS, where the horizontal axis represents the etching time (corresponding to the thickness direction of the adhesive layer 2) and the vertical axis represents the intensity of SiOH+ (m / z=45). In the adhesive layer 2 containing Si agent (X), the sum of the areas of the SiOH+ peaks in region 21 can be more than 50%, 60%, 70%, 80%, or even more than 90% of the sum of the areas of the measurable SiOH+ peaks in the adhesive layer 2. Furthermore, the intensity of SiOH+ can also be the normalized value (normalized intensity) obtained during TOF-SIMS evaluation based on the intensity of ions that are abundantly generated from the adhesive layer 2 and whose m / z does not overlap with SiOH+. When the adhesive layer 2 contains an acrylic adhesive composition, this ion is, for example, C2H3+.

[0017] In the example of Figure 1, an adhesive layer 2 is disposed entirely on the surface 11 of the optical substrate 1. When viewed perpendicularly to the surface 11, the optical substrate 1 and the adhesive layer 2 have the same shape. However, the adhesive layer 12 may be disposed on at least a portion of the surface 11. Furthermore, the surface 11 in Figure 1 is entirely a modified surface 12. However, at least a portion of the surface 11 may be a modified surface 12.

[0018] [Si agent(X)] The Si agent (X) contains isocyanuric acid rings. The number of isocyanuric acid rings contained in the Si agent (X) can be 1 or more, or even 1. In the Si agent (X), the number of Si atoms in each isocyanuric acid ring can be 1, or more than 1, 2 or more, or even 3 or more. The number of Si atoms contained in a single molecular structure (Y) is not limited, but is typically 1.

[0019] The Si atom of the Si agent (X) can also be bonded with a molecular structure containing a hydrolyzable group. The hydrolyzable group can be, for example, an alkoxy group with 1 to 4 carbon atoms, which can be methoxy or ethoxy, or even just methoxy. The hydrolyzable group can also be directly bonded to the Si atom.

[0020] The Si agent (X) does not contain isocyanate groups. The Si agent (X) may be free of reactive functional groups other than isocyanate groups, and particularly may not contain reactive functional groups other than isocyanate groups at the ends. However, the reactive functional groups do not include hydrolyzable groups bonded to Si atoms or isocyanate rings. Examples of reactive functional groups are epoxy, amino, vinyl, styrene, (meth)acryl, urea, and mercapto, especially epoxy and amino groups, and specifically epoxy groups. Compared to isocyanate groups, these groups have lower reactivity with other materials that may be contained in the adhesive layer 2. However, the absence of reactive functional groups helps to improve the uniformity of the crosslinking structure of the adhesive layer 2. Furthermore, amino groups readily react with materials other than polymers, such as crosslinking agents.

[0021] An example of Si agent (X) is shown in the following formula (2). The Si agent (X) in formula (2) is tris(trialkoxysilylalkyl)triisocyanate. R1, R2 and R3 in formula (2) are each independently an alkyl group having 1 to 6 carbon atoms, and may be an alkyl group having 2 to 4 carbon atoms, or propyl. R11, R12, R13, R21, R22, R23, R31, R32 and R33 are each independently an alkoxy group having 1 to 4 carbon atoms, and may be methoxy or ethoxy, or may be methoxy.

[0022] [Chemical Formula 2]

[0023] [Adhesive composition] The content of Si agent (X) in the adhesive composition of adhesive layer 2 is, for example, 0.01% by weight or more and 5.0% by weight or less, or 0.01% by weight or more and 3.0% by weight or less, 0.05% by weight or more and 1.0% by weight or less, 0.1% by weight or more and 0.5% by weight or less, or even 0.15% by weight or more and 0.4% by weight or less. Appropriate control of the content helps to more reliably improve the peeling resistance at high temperatures.

[0024] The adhesive composition may include, for example, a (meth)acrylic polymer. The (meth)acrylic polymer can be the main component of the adhesive composition; in other words, the adhesive composition may also be acrylic. Acrylic adhesive compositions exhibit excellent properties such as transparency, processability, durability, and adhesion. However, the adhesive composition is not limited to being acrylic. In this specification, (meth)acrylic acid means acrylic acid and / or methacrylic acid. Furthermore, the main component refers to the component with the highest content in the composition. The content of the main component may be, for example, 50% by weight or more, and may be 70% by weight or more, 80% by weight or more, 90% by weight or more, 95% by weight or more, 97% by weight or more, 98% by weight or more, and even 99% by weight or more.

[0025] The adhesive composition may also contain one or more (meth)acrylic polymers.

[0026] <(meth)acrylic polymers> (Meth)acrylic polymers may have units (a2) derived from (meth)acrylic monomers (a1) with alkyl groups having 1 to 30 carbon atoms in their side chains, or may have units (a2) as the main unit. The alkyl groups may be linear or branched. (Meth)acrylic polymers may also have one or more types of units (a2).

[0027] Examples of monomers (a1) are: methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, butyl methacrylate, tert-butyl methacrylate, isobutyl methacrylate, n-pentyl methacrylate, isopentyl methacrylate, n-hexyl methacrylate, isohexyl methacrylate, isoheptyl methacrylate, 2-ethylhexyl methacrylate, n-octyl methacrylate, isooctyl methacrylate, n-nonyl methacrylate, isononyl methacrylate, n-decyl methacrylate, isodecyl methacrylate, n-dodecyl methacrylate (laurate methacrylate), n-tetrazolium methacrylate, and n-tetradecyl methacrylate. In this specification, "major unit" means a unit that accounts for, for example, 50% or more by weight of the total constituent units of the polymer, preferably 80% or more by weight, more preferably 90% or more by weight, and even more preferably 94% or more by weight. The upper limit of the percentage of major units is, for example, 99.9% or less, or 99.5% or less.

[0028] (Meth)acrylic polymers may also have units (a2) derived from monomers (a1) with long-chain alkyl groups on their side chains. For example, the monomer (a1) is dodecyl (meth)acrylate. In this specification, long-chain alkyl means alkyl groups having 6 to 30 carbon atoms.

[0029] When (meth)acrylic polymers are homopolymers, they may also have units (a2) derived from monomers (a1) with a Tg range of -70°C to -20°C. For example, the monomer (a1) is 2-ethylhexyl acrylate.

[0030] (Meth)acrylic polymers may also have units other than unit (a2). Such units may be, for example, derived from units (b2) of monomers (b1) that can copolymerize with monomers (a1). (Meth)acrylic polymers may also have one or more types of units (b2).

[0031] Examples of monomers (b1) include (meth)acrylate monomers (c1) containing hydroxyl groups. Monomer (b1) can also be (meth)acrylate monomers containing hydroxyl groups. Examples of monomers (c1) include hydroxyalkyl methacrylates such as 2-hydroxyethyl methacrylate, 3-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, 6-hydroxyhexyl methacrylate, 8-hydroxyoctyl methacrylate, 10-hydroxydecyl methacrylate, and 12-hydroxylauryl methacrylate, as well as (4-hydroxymethylcyclohexyl)-methacrylate. From the perspective of improving the durability of adhesive components, monomer (c1) can also be 2-hydroxyethyl methacrylate or 4-hydroxybutyl methacrylate.

[0032] Monomer (b1) can also be an amino-containing monomer or a amide-containing monomer. Examples of amino-containing monomers include N,N-dimethylaminoethyl (meth)acrylate and N,N-dimethylaminopropyl (meth)acrylate. Examples of amide-containing monomers include: (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, N-isopropylacrylamide, N-methyl (meth)acrylamide, N-butyl (meth)acrylamide, N-hexyl (meth)acrylamide, N-hydroxymethyl (meth)acrylamide, N-hydroxymethyl-N-propane (meth)acrylamide, aminomethyl (meth)acrylamide, etc. Acrylamide monomers such as acrylamide, aminoethyl (meth)acrylamide, mercaptomethyl (meth)acrylamide, and mercaptoethyl (meth)acrylamide; N-acrylyl heterocyclic monomers such as N-(meth)acrylylmorpholin, N-(meth)acrylylpiperidine, and N-(meth)acrylylpyrrolidine; and N-vinylpyrrolidone and N-vinyl-ε-caprolactam monomers containing N-vinyl lactam.

[0033] Monomer (b1) can also be a carboxyl-containing monomer. Examples of carboxyl-containing monomers include (meth)acrylic acid, carboxyethyl (meth)acrylic acid, carboxypentyl (meth)acrylic acid, itaconic acid, maleic acid, fumaric acid, and crotonic acid. However, units derived from carboxyl-containing monomers have a stronger effect on increasing the elastic modulus of adhesive layer 2, and tend to reduce the freedom of design in terms of the physical properties of adhesive layer 2 containing (meth)acrylic polymers with such units. Furthermore, (meth)acrylic polymers containing such units can provide corrosion resistance to optical substrates through the materials contained in the optical substrates. From this perspective, the content of units derived from carboxyl-containing monomers in (meth)acrylic polymers should preferably be 5% by weight or less, and can be 3% by weight or less, 1.5% by weight or less, 1% by weight or less, 0.5% by weight or less, or even 0% by weight (excluding such units).

[0034] Monomer (b1) can also be a multifunctional monomer. By using multifunctional monomers, the gel fraction of the adhesive composition can be adjusted. Examples of multifunctional monomers include: hexanediol di(meth)acrylate (1,6-hexanediol di(meth)acrylate), butanediol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, neopentyl tetraethylene di(meth)acrylate, neopentyl tetraethylene tri(meth)acrylate, dinepentyl tetraethylene hexa(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate, allyl methacrylate, vinyl methacrylate, epoxy acrylate, polyester acrylate and carbamate acrylate, and other multifunctional acrylates; as well as divinylbenzene. The polyfunctional acrylates are preferably 1,6-hexanediol diacrylate or dinepentylenetetrol hexa(meth)acrylate.

[0035] Examples of other monomers (b1) besides those mentioned above include: 2-methoxyethyl methacrylate, 2-ethoxyethyl methacrylate, methoxytriethylene glycol methacrylate, 3-methoxypropyl methacrylate, 3-ethoxypropyl methacrylate, 4-methoxybutyl methacrylate, and 4-ethoxybutyl methacrylate, etc., alkoxyalkyl esters of methacrylate; epoxypropyl methacrylate and methyl epoxypropyl methacrylate, etc., monomers containing epoxy groups; sodium vinyl sulfonate, etc., monomers containing sulfonic acid groups; and monomers containing phosphate groups. The following are included: cyclopentyl methacrylate, cyclohexyl methacrylate, and isoborneol methacrylate, which are methacrylates with alicyclic hydrocarbon groups; phenyl methacrylate, phenoxyethyl methacrylate, and benzyl methacrylate, which are methacrylates with aromatic hydrocarbon groups; vinyl esters such as vinyl acetate and vinyl propionate; aromatic vinyl compounds such as styrene and vinyltoluene; olefins or dienes such as ethylene, propylene, butadiene, isoprene, and isobutylene; vinyl ethers such as vinyl alkyl ethers; and vinyl chloride.

[0036] In (meth)acrylic polymers, the total content of units derived from (meth)acrylic monomers (C1) having hydroxyl groups, amino monomers, amide monomers, and polyfunctional monomers is, for example, 20% by weight or less, and may be 10% by weight or less, 8% by weight or less, or even 5% by weight or less. When the (meth)acrylic polymer contains this unit, the total content of this unit is, for example, 0.01% by weight or more, and may also be 0.05% by weight or more.

[0037] The total content of units (b2) derived from monomer (b1) in (meth)acrylic polymers is, for example, 30% by weight or less, 10% by weight or less, or 0% by weight (excluding the unit).

[0038] (Meth)acrylic acid polymers can be formed by polymerizing monomer groups containing the aforementioned monomers using known methods. Monomers can also be polymerized with portions of the monomers. Polymerization can be carried out, for example, by solution polymerization, emulsion polymerization, bulk polymerization, thermal polymerization, and active energy line polymerization. Considering the potential to form adhesive compositions with excellent optical transparency, solution polymerization and active energy line polymerization are preferable. Polymerization should avoid contact between the monomers and / or portions of the polymer and oxygen; therefore, polymerization can be carried out, for example, in an inert gas environment such as nitrogen, or under oxygen-barrier conditions such as resin films. The resulting (meth)acrylic acid polymer can be any form of random copolymer, block copolymer, graft copolymer, etc., or it can be a random copolymer.

[0039] The polymerization system that forms (meth)acrylic acid polymers may also contain one or more polymerization initiators. The type of polymerization initiator can be selected according to the polymerization reaction, for example, it can be a photopolymerization initiator or a thermal polymerization initiator.

[0040] Solvents used in solution polymerization include, for example, esters such as ethyl acetate and n-butyl acetate; aromatic hydrocarbons such as toluene and benzene; aliphatic hydrocarbons such as n-hexane and n-heptane; alicyclic hydrocarbons such as cyclohexane and methylcyclohexane; and ketones such as methyl ethyl ketone and methyl isobutyl ketone. However, the solvent is not limited to the above examples. The solvent may also be a mixture of two or more solvents.

[0041] The polymerization initiators used in solution polymerization are, for example, azo-based polymerization initiators, peroxide-based polymerization initiators, and redox-based polymerization initiators. Examples of peroxide-based polymerization initiators include dibenzoyl peroxide and tributyl maleate peroxide. Among these, the azo-based polymerization initiator disclosed in Japanese Patent Application Publication No. 2002-69411 is preferred. Examples of such azo-based polymerization initiators include 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis-2-methylbutyronitrile, dimethyl 2,2'-azobis(2-methylpropionic acid) ester, and 4,4'-azobis-4-cyanovaleric acid. However, the polymerization initiator is not limited to the examples above. The amount of azo-based polymerization initiator used is, for example, 0.05 to 0.5 parts by weight, or 0.1 to 0.3 parts by weight, relative to 100 parts by weight of the total monomer.

[0042] The active energy rays used in active energy line polymerization include, for example, ionizing radiation such as alpha rays, beta rays, gamma rays, neutron rays, and electron beams, as well as ultraviolet light. Ultraviolet light is preferred. Polymerization using ultraviolet irradiation is also called photopolymerization. The polymerization system of active energy line polymerization typically includes a photoinitiator. The polymerization conditions for active energy polymerization are not limited as long as they can form (meth)acrylic acid polymers.

[0043] Examples of photopolymerization initiators include: benzoin ether-based photopolymerization initiators, acetophenone-based photopolymerization initiators, α-keto alcohol-based photopolymerization initiators, aromatic sulfonyl chloride-based photopolymerization initiators, photoactive oxime-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzyl-based photopolymerization initiators, diphenyl ketone-based photopolymerization initiators, ketal-based photopolymerization initiators, and 9-oxosulfuron-methyl-2-ethylhexylene ... It is a photopolymerization initiator. However, photopolymerization initiators are not limited to the above examples.

[0044] Examples of benzoin ether-based photopolymerization initiators include: benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-dimethoxy-1,2-diphenylethyl-1-one, and anisole methyl ether. Examples of acetophenone-based photopolymerization initiators include: 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenyl ketone, 4-phenoxydichloroacetophenone, and 4-(tributyl)dichloroacetophenone. Examples of α-ketool-based photopolymerization initiators include: 2-methyl-2-hydroxyphenylacetone and 1-[4-(2-hydroxyethyl)phenyl]-2-methylprop-1-one. Examples of aromatic sulfonyl chloride-based photopolymerization initiators include 2-naphthalenesulfonyl chloride. Photoactive oxime photopolymerization initiators include, for example, 1-benzyl-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime. Benzoin-based photopolymerization initiators include, for example, benzoin. Benzyl-based photopolymerization initiators include, for example, benzyl. Diphenyl ketone-based photopolymerization initiators include, for example, diphenyl ketone, benzoic acid, 3,3'-dimethyl-4-methoxydiphenyl ketone, polyvinyl diphenyl ketone, and α-hydroxycyclohexylphenyl ketone. Ketal-based photopolymerization initiators include, for example, benzyl dimethyl ketal. 9-Oxysulfuron Photopolymerization initiators, for example, include: 9-oxosulfuron. 2-Chloro-9-oxysulfur 2-Methyl-9-oxosulfur 2,4-Dimethyl-9-oxosulfur Isopropyl 9-Oxysulfur 2,4-Diisopropyl-9-oxosulfur Dodecyl 9-oxosulfur .

[0045] The amount of photopolymerization initiator used is, for example, 0.01 to 1 part by weight relative to 100 parts by weight of the total monomer, or 0.05 to 0.5 parts by weight.

[0046] Furthermore, multifunctional monomers (such as multifunctional acrylates) of monomer (b1) can also be used in either solvent-based or photopolymerization-initiator type adhesive compositions. When using both multifunctional monomers and photopolymerization initiators in solvent-based adhesive compositions, the adhesive composition can be cured by irradiation with a photopolymerization-initiator, for example, after removing the solvent by heat drying.

[0047] The weight average molecular weight (Mw) of (meth)acrylic polymers is, for example, 1 million or more, and can be 1.2 million or more, 1.5 million or more, 1.8 million or more, or even 2 million or more. The upper limit of Mw is, for example, below 3 million.

[0048] The molecular weight distribution (Mw / number average molecular weight (Mn)) of (meth)acrylic acid polymers is, for example, 2 to 20, or 4 to 15. Furthermore, the Mw and Mn values ​​of the polymers and oligomers in this specification are values ​​determined by GPC (Gel Permeation Chromatography) (converted to polystyrene).

[0049] The content of (meth)acrylic polymer in the adhesive composition, in terms of solid content, is, for example, 50% by weight or more, 60% by weight or more, or even 70% by weight or more.

[0050] <(meth)acrylic acid oligomers> The adhesive composition may also contain (meth)acrylic oligomers.

[0051] Except for the difference in Mw, the (meth)acrylic acid oligomers can have the same composition as the aforementioned (meth)acrylic acid polymers. The Mw of the (meth)acrylic acid oligomers is, for example, 1000 or more, or 2000 or more, 3000 or more, or even 4000 or more. The upper limit of the Mw of the (meth)acrylic acid oligomers is, for example, 30000 or less, or 15000 or less, 10000 or less, or even 7000 or less.

[0052] (Meth)acrylate oligomers, for example, have one or more constituent units derived from the following monomers: methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate, isobutyl methacrylate, dibutyl methacrylate, terbutyl methacrylate, amyl methacrylate, isoamyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, heptyl methacrylate, octyl methacrylate, etc. Alkyl methacrylates such as isooctyl acrylate, nonyl methacrylate, isononyl methacrylate, decyl methacrylate, isodecyl methacrylate, undecyl methacrylate, and dodecyl methacrylate; esters of methacrylic acid and alicyclic alcohols such as cyclohexyl methacrylate, isocamphenyl methacrylate, and dicyclopentyl methacrylate; aryl methacrylates such as phenyl methacrylate and benzyl methacrylate; and methacrylates derived from terpene derivative alcohols.

[0053] (Meth)acrylate oligomers can also have building blocks derived from acrylic monomers with larger bulk structures. Examples of such acrylic monomers include: alkyl methacrylates with branched alkyl groups, such as isobutyl methacrylate and tributyl methacrylate; esters of (meth)acrylate and alicyclic alcohols, such as cyclohexyl methacrylate, isocamphene methacrylate, and dicyclopentyl methacrylate; and aryl methacrylates, such as phenyl methacrylate and benzyl methacrylate. These acrylic monomers preferably have cyclic structures, and more preferably two or more cyclic structures. Furthermore, if ultraviolet irradiation is to be applied during the polymerization of (meth)acrylate oligomers and / or during the formation of adhesive compositions, the acrylic monomers should preferably not have unsaturated bonds to avoid hindering polymerization and / or formation. For example, alkyl methacrylates with branched alkyl groups, or esters of (meth)acrylate and alicyclic alcohols, can be used.

[0054] Specific examples of (meth)acrylic acid oligomers include: copolymers of butyl acrylate, methyl acrylate, and acrylic acid; copolymers of cyclohexyl methacrylate and isobutyl methacrylate; copolymers of cyclohexyl methacrylate and isocamphene methacrylate; copolymers of cyclohexyl methacrylate and acrylamide; copolymers of 1-adamantyl acrylate and methyl methacrylate; copolymers of dicyclopentyl methacrylate and isocamphene methacrylate; copolymers of at least one of dicyclopentyl methacrylate, cyclohexyl methacrylate, isocamphene methacrylate, isocamphene methacrylate, and cyclopentyl methacrylate with methyl methacrylate; homopolymers of dicyclopentyl acrylate; homopolymers of 1-adamantyl methacrylate; and homopolymers of 1-adamantyl acrylate.

[0055] The polymerization method for (meth)acrylic acid oligomers can be the same as the polymerization method for (meth)acrylic acid polymers described above.

[0056] When the adhesive composition contains (meth)acrylic oligomers, the amount of these oligomers, relative to 100 parts by weight of the (meth)acrylic polymer, is, for example, 70 parts by weight or less, 50 parts by weight or less, and more specifically, 40 parts by weight or less. The lower limit of the amount of these oligomers, relative to 100 parts by weight of the (meth)acrylic polymer, is, for example, 0.05 parts by weight or more, 0.1 parts by weight or more, and more specifically, 0.2 parts by weight or more. The adhesive composition may also not contain (meth)acrylic oligomers.

[0057] (Meth)acrylic acid oligomers can also be used in either solvent-based or active energy line curing adhesive compositions. However, when used in active energy line curing adhesive compositions and the (meth)acrylic acid oligomers are already dissolved in the solvent, the mixture containing the (meth)acrylic acid oligomers can be cured by irradiating the active energy line, for example, after removing the solvent by heat drying.

[0058] Crosslinking agent The adhesive composition may also contain cross-linking agents. By using cross-linking agents, the cohesive strength of the adhesive composition can be improved.

[0059] Examples of crosslinking agents include organic crosslinking agents and multifunctional metal chelates. Examples of organic crosslinking agents include isocyanate-based, peroxide-based, epoxy-based, and imine-based crosslinking agents. Multifunctional metal chelates have a structure in which a multivalent metal and an organic compound are covalently or coordinately bonded. Examples of multivalent metals include Al, Cr, Zr, Co, Cu, Fe, Ni, V, Zn, In, Ca, Mg, Mn, Y, Ce, Sr, Ba, Mo, La, Sn, and Ti. The atoms in the organic compounds in which the multivalent metal can be covalently or coordinately bonded are typically oxygen atoms. Examples of organic compounds include alkyl esters, alcohols, carboxylic acids, ethers, and ketones. Furthermore, organic crosslinking agents and multifunctional metal chelates can also be used with any type of adhesive composition, including solvent-based and active energy line-curing adhesives.

[0060] When the adhesive composition is solvent-based, the crosslinking agent should preferably be an isocyanate-based or peroxide-based crosslinking agent. Isocyanate-based crosslinking agents can be difunctional or trifunctional. However, to maintain cohesive strength at high temperatures, trifunctional crosslinking agents are preferable. Trifunctional crosslinking agents will form a three-dimensional crosslinked structure. Furthermore, isocyanate-based and peroxide-based crosslinking agents can be used together. By using them together, cohesive strength at high temperatures can be maintained while simultaneously improving adhesion. The isocyanate-based crosslinking agent used should preferably be trifunctional.

[0061] When the adhesive composition contains a crosslinking agent, its blending amount relative to 100 parts by weight of the (meth)acrylic polymer is, for example, 0.01 to 10 parts by weight, 0.1 to 5 parts by weight, or even 0.1 to 3 parts by weight.

[0062] When isocyanate-based crosslinking agents are used alone, their blending amount relative to 100 parts by weight of (meth)acrylic polymer is, for example, 0.01 to 3 parts by weight, 0.01 to 1 part by weight, 0.01 to 0.5 parts by weight, or even 0.01 to 0.3 parts by weight.

[0063] When using both isocyanate-based and peroxide-based crosslinking agents, the weight ratio of the peroxide-based crosslinking agent to the isocyanate-based crosslinking agent is, for example, 1.0 or more, 1.2 or more, 1.5 or more, or even 2 or more. Furthermore, the upper limit of the weight ratio is, for example, 500 or less, 300 or less, or even 200 or less.

[0064] <Additives> The adhesive composition may also contain other additives. Examples of additives include: silane coupling agents other than Si agent (X), polysiloxane compounds such as polysiloxane oils (excluding silane coupling agents), polyether compounds (such as polyalkylene glycols, primarily polypropylene glycol), colorants such as pigments and dyes, surfactants, plasticizers, tackifiers, surface lubricants, leveling agents, softeners, antioxidants, anti-aging agents, light stabilizers, ultraviolet absorbers, polymerization inhibitors, antistatic agents (alkali metal salts, ionic liquids, ionic solids, etc. of ionic compounds), inorganic fillers, organic fillers, metal powders, and powders, particles, or foils. When silane coupling agents other than Si agent (X) are included, the content of such silane coupling agents may be less than 0.5% by weight, less than 0.1% by weight, less than 0.05% by weight, and may be less than 0.01% by weight. The adhesive composition may also exclude silane coupling agents other than Si agent (X). When polysiloxane is included, the content of polysiloxane may be less than 0.5% by weight, less than 0.1% by weight, less than 0.05% by weight, and even less than 0.01% by weight. The adhesive composition may also exclude polysiloxane.

[0065] [Adhesive layer] The thickness of adhesive layer 2 is, for example, 1~200µm, 5~150µm, or even 10~100µm. Adhesive layer 2 can be a single layer or a laminate containing two or more layers. All of the two or more layers may contain the above-mentioned adhesive composition.

[0066] The 800% modulus of adhesive layer 2 at 80°C is, for example, 0.18~0.5 N / mm², possibly 0.2~0.4 N / mm², or even 0.2~0.3 N / mm². The 800% modulus refers to a characteristic expressed as a value obtained by applying a tensile force in one direction to adhesive layer 2, imparting an elongation of 800%, and dividing the stress (tensile stress) generated in adhesive layer 2 at this point by the initial cross-sectional area of ​​adhesive layer 2. The 800% modulus of adhesive layer 2 can be evaluated as follows.

[0067] The adhesive layer 2 of the evaluation object was cut into a long sheet of 30mm × 100mm. Then, without introducing air bubbles, the cut adhesive layer 2 was wound along its long side to obtain a cylindrical test piece with a height of 30mm corresponding to the short side length. Next, the obtained test piece was mounted on a tensile testing machine such as TENSILON, and a uniaxial tensile test was performed on its height direction to obtain the elongation-stress curve of the adhesive layer 2. Furthermore, the test piece preparation and uniaxial tensile test were performed at 23°C, with the initial jig distance set to 10mm and the tensile speed set to 300mm / min. The stress at 800% elongation (when the jig distance is 90mm) was calculated from the obtained elongation-stress curve, and divided by the initial cross-sectional area of ​​the test piece to obtain the 800% modulus of the adhesive layer 2.

[0068] The adhesion of the adhesive layer 2 to the polyethylene terephthalate (PET) film at 80°C is, for example, 1.8 N / 25 mm or more, and may be 2.0 N / 25 mm or more, 2.5 N / 25 mm or more, 2.7 N / 25 mm or more, 3.0 N / 25 mm or more, 3.2 N / 25 mm or more, and more preferably 3.5 N / 25 mm or more. The upper limit of the adhesion is, for example, 10.0 N / 25 mm or less. However, the above-mentioned adhesion is evaluated with the adhesive layer 2 disposed on the modified surface of the PET film. In other words, the above-mentioned adhesion is the adhesion to the modified surface of the PET film.

[0069] The total transmittance of the adhesive layer 2 in the visible light wavelength region (according to JIS K7136) should preferably be 85% or more, and more preferably 90% or more.

[0070] The aforementioned adhesive composition is an adhesive composition disposed on the modified surface 12 of the optical substrate 1 in the optical laminate 100. From this perspective, the present invention provides an adhesive composition disposed on the surface 11 of the optical substrate 1; the adhesive composition includes a silane coupling agent; the aforementioned silane coupling agent contains isocyanate rings and does not contain isocyanate groups; the aforementioned surface on which the aforementioned adhesive composition is disposed is a modified surface that has been modified by irradiation energy.

[0071] [Formation of the adhesive layer] The adhesive layer 2 can be formed, for example, by the following methods. A solvent-based adhesive composition is coated onto a substrate film (release film) or similar material, and the polymerization solvent is removed by drying. The adhesive layer 2 formed on the substrate film can be transferred to the surface 11 of the optical substrate 1. The active energy line curing adhesive composition is coated onto a substrate film or similar material and then cured by irradiation with active energy lines. In addition to irradiation with active energy lines, drying by heating can also be performed. Furthermore, when coating the adhesive composition, one or more solvents other than the polymerization solvent can be added to the composition.

[0072] The coating surface of the adhesive composition in the substrate film can also be subjected to a peeling process. An example of a peeling process is a polysiloxane treatment using polysiloxane compounds.

[0073] The drying temperature can be, for example, 40~200℃, 50~180℃, or even 70~170℃. However, it can be adjusted by adjusting the composition of the adhesive components.

[0074] The drying time can be, for example, 5 seconds to 20 minutes, 5 seconds to 10 minutes, or even 10 seconds to 5 minutes. However, it can be adjusted by adjusting the composition of the adhesive.

[0075] Adhesive components can be coated using methods such as roller coating, contact roller coating, gravure coating, reverse coating, roller brush coating, spray coating, dip roller coating, bar coating, knife coating, air knife coating, curtain coating, lip coating, and extrusion coating using a die coating machine.

[0076] [Optical substrate] The optical substrate 1 has a modified surface 12. The modified surface 12 is a surface modified by irradiation energy. During surface modification, functional groups are generated on the surface of the substrate. The surface modification using irradiation energy is selected from at least one of corona treatment, plasma treatment, and ultraviolet treatment (such as excimer laser irradiation).

[0077] Energy irradiation can be carried out in a gaseous environment containing inert gases such as nitrogen, or in air. The irradiation energy can be, for example, 0.05~20 J / cm², or 0.1~5 J / cm². Known methods can be used for the energy irradiation of each treatment.

[0078] The optical substrate 1 can be made of resin; in other words, it can be a resin substrate. Furthermore, the Si agent (X) can also be located in the region 21 near the interface 3 between the adhesive layer 2 and the optical substrate 1. However, the optical substrate 1 is not limited to being a resin substrate. Examples of resins constituting the optical substrate 1 include polyesters such as PET, acrylic resins, polyolefins, polycyclic olefins, polyimides, polyurethanes, and modified cellulose such as triacetate (TAC). Acrylic resins can also have cyclic structures such as amide rings, amide rings, anhydride rings, and lactone rings. However, the resin is not limited to the examples described above.

[0079] Examples of optical substrate 1 include optical compensation films such as polarizing films, polarizer protection films, phase difference films, and viewing angle compensation films; anti-reflection films; antistatic films; conductive films; buffer films; decorative films; cover windows; liquid crystal layers; and organic EL light-emitting layers; as well as laminates thereof. However, optical substrate 1 is not limited to the above examples and may be any optical substrate used in image display devices.

[0080] The polarizing film includes a polarizing element. A protective film for the polarizing element may also be bonded to at least one side of the polarizing element through an adhesive layer. The polarizing element is typically a polyvinyl alcohol (PVA) film in which iodine is oriented by various methods such as air stretching (dry stretching) or boric acid water stretching, and coating.

[0081] A retardation film is a thin film that exhibits birefringence in the in-plane direction and / or in the thickness direction. Examples of retardation films include stretched resin films and films in which liquid crystal materials have been oriented and immobilized.

[0082] Examples of phase retardation films include: λ / 4 plates, λ / 2 plates, anti-reflection phase retardation films (see, for example, paragraphs 0221, 0222, and 0228 of Japanese Patent Application Publication No. 2012-133303), viewing angle compensation phase retardation films (see, for example, paragraphs 0225 and 0226 of Japanese Patent Application Publication No. 2012-133303), and tilt-oriented phase retardation films for viewing angle compensation (see, for example, paragraph 0227 of Japanese Patent Application Publication No. 2012-13303). However, the phase retardation film is not limited to the above examples as long as it has birefringence in the in-plane direction and / or in the thickness direction. There are no limitations on the phase difference value, arrangement angle, 3D birefringence, single layer or multiple layers of the phase retardation film. The phase retardation film can be a known type of film.

[0083] The thickness of the phase retardation film can be, for example, less than 50µm, less than 20µm, less than 10µm, or even 1~9µm.

[0084] The thickness of the optical substrate 1 is, for example, 1µm or more, 5µm or more, and even 25µm or more. The upper limit of the thickness of the optical substrate 1 is, for example, 200µm or less.

[0085] The total transmittance of the optical substrate 1 in the visible light wavelength region (according to JIS K7136) should preferably be 85% or more, and more preferably 90% or more.

[0086] The total transmittance of the optical laminate 100 in the visible light wavelength region (according to JIS K7136) should preferably be 85% or more, and more preferably 90% or more.

[0087] The optical laminate 100 in Figure 1 includes one optical substrate 1 and one adhesive layer 2. The optical laminate of the present invention may also include two or more optical substrates 1 and / or two or more adhesive layers 2. In other words, the optical laminate of the present invention includes at least one optical substrate 1 and at least one adhesive layer 2.

[0088] The optical laminate 110 in Figure 2 includes a phase retardation film 4, polarizer protective films 5A and 5B, a polarizer 6, and adhesive layers 7A, 7B, and 7C. The optical laminate 110 sequentially laminates the phase retardation film 4, adhesive layer 7A, polarizer protective film 5A, adhesive layer 7B, polarizer 6, adhesive layer 7C, and polarizer protective film 5B. At least one adhesive layer selected from the three adhesive layers 7A, 7B, and 7C is the aforementioned adhesive layer 2. All adhesive layers 7A, 7B, and 7C may also be adhesive layers 2. Furthermore, at least one optical substrate in contact with adhesive layer 2 is the aforementioned optical substrate 1. The two optical substrates in contact with adhesive layer 2 may also be the aforementioned optical substrate 1.

[0089] When the optical laminate 110 has two or more adhesive layers 2, the composition of the adhesive components contained in each adhesive layer 2 may be the same or different.

[0090] The optical laminate of the present invention can also be an optical substrate for use as an adhesive layer attached to other components.

[0091] Figure 3 shows an example of an optical substrate with an adhesive layer. The optical substrate 120 with an adhesive layer in Figure 3 includes an optical substrate 1, an adhesive layer 2, and a release liner 8. The release liner 8 is disposed on the side of the adhesive layer 2 opposite to the bonding surface with the optical substrate 1. The release liner 8 has the function of protecting the adhesive layer 2 during the circulation and storage of the optical substrate 120 with the adhesive layer, and it is peeled off when the optical substrate 120 with the adhesive layer is used.

[0092] The release liner 8 is typically a resin film. Examples of resins constituting the release liner 8 include polyesters such as PET, polyolefins such as polyethylene and polypropylene, polycarbonate, acrylic resin, polystyrene, polyamide, and polyimide. The surface of the release liner 8 in contact with the adhesive layer 2 may also undergo a release treatment. The release treatment may be, for example, a polysiloxane treatment using a polysiloxane compound. However, the release liner 8 is not limited to the above examples.

[0093] The thickness of the peeling liner 8 is, for example, 20µm to 100µm.

[0094] The optical substrate 120 with adhesive may also have two or more optical substrates 1 and / or two or more adhesive layers 2. Furthermore, in the optical substrate 120 with adhesive having two or more adhesive layers, at least one adhesive layer may be the aforementioned adhesive layer 2.

[0095] The optical stack of the present invention may also have any layers other than those described above.

[0096] The optical laminate of the present invention can be distributed and stored, for example, in the form of a single sheet or in the form of a wound body formed by winding a strip laminate.

[0097] The optical laminate of the present invention can also be used in image display devices.

[0098] [Image display device] Figure 4 shows an example of an image display device. The image display device 200 in Figure 4 has a laminated structure in which a substrate 51, an adhesive layer 10A, an image forming layer (organic EL layer) 52, an adhesive layer 10B, an optical substrate 1, an adhesive layer 2, and a cover film 53 are sequentially stacked. The image display device 200 includes an optical laminate 100. The substrate 51, the image forming layer 52, and the cover film 53 may have the same configuration as those of a known organic EL display.

[0099] At least one of the adhesive layers 10A and 10B can also be the aforementioned adhesive layer 2. In this case, at least one component that is in contact with the adhesive layers 10A and 10B that are adhesive layers 2 is an optical substrate 1.

[0100] The image display device 200 in Figure 4 is an organic EL display. However, the image display device 200 of the present invention is not limited to the above example.

[0101] The image display device 200 can have any configuration as long as it has the optical laminate of the present invention.

[0102] The image display device 200 may also be a flexible image display device.

[0103] Example The present invention will now be described in more detail with reference to the embodiments shown below. The present invention is not limited to the embodiments shown below.

[0104] The abbreviations or names shown below correspond to the compounds as follows. BA: Butyl acrylate HBA: Hydroxybutyl acrylate 2EHA: 2-Ethylhexyl acrylate NVP: N-vinylpyrrolidone D110N: Trimethylolpropane / diisocyanate adduct (Mitsui Chemicals manufactures TAKENATE D110N, an isocyanate-based crosslinking agent). BPO: Benzoyl peroxide (peroxide-based crosslinking agent) KBM9659: Tri-(trimethoxysilylpropyl)triisocyanate (Shin-Etsu Chemical, Si agent (X)) KBM403: 3-Epoxypropoxypropyltrimethoxysilane (Shin-Etsu Chemical Co., Ltd., a silane coupling agent with an epoxy group at the end). KBM573: N-Phenyl-3-aminopropyltrimethoxysilane (Shin-Etsu Chemical Co., Ltd., a silane coupling agent with an amino group).

[0105] [Preparation of (meth)acrylic acid polymers] (Synthesis example 1) In a four-necked flask equipped with a stirring blade, thermometer, nitrogen inlet tube, and cooler, 99 parts by weight of BA and 1 part by weight of HBA were added, and the mixture was diluted with ethyl acetate and toluene to a concentration of 50% by weight. The toluene content in the diluent was set at 5% by weight. Next, 0.1 parts by weight of AIBN was added as a polymerization initiator relative to 100 parts by weight of the BA and HBA mixture. Nitrogen was introduced into the flask while stirring slowly to purify the nitrogen, and the liquid temperature in the flask was maintained at approximately 55°C for 7 hours for polymerization. Then, ethyl acetate was added to the resulting reaction solution to adjust the solids concentration to 20% by weight, thereby obtaining a solution of (meth)acrylic acid polymer A1. The Mw of (meth)acrylic acid polymer A1 was 1.8 million. Furthermore, the Mw of the (meth)acrylic acid polymers prepared in each synthesis example was determined by GPC under the following conditions. • Analytical apparatus: Waters, Acquity APC • Tubing: Tosoh, G7000HXL+GMHXL+GMHXL • Column temperature: 40℃ • Solution: Tetrahydrofuran (with added acid) • Flow rate: 0.8 mL / min Injection volume: 100µL • Detector: Differential refractometer (RI) • Standard sample: Agilent, polystyrene (PS)

[0106] (Synthesis example 2) 96 parts by weight of 2EHA, 1 part by weight of HBA, and 3 parts by weight of NVP were fed into a flask, and the proportion of toluene in the solvent used for dilution was set to 30% by weight. Otherwise, a solution of (meth)acrylic polymer A2 was obtained in the same manner as in Synthesis Example 1. The Mw of (meth)acrylic polymer A2 was 1.2 million.

[0107] (Synthesis example 3) Except that the proportion of toluene in the solvent used for dilution was set to 5% by weight, a solution of (meth)acrylic polymer A3 was obtained in the same manner as in Synthesis Example 2. The Mw of (meth)acrylic polymer A3 was 2 million.

[0108] (Synthesis Example 4) The toluene content in the solvent used for dilution was set to 0% by weight, the amount of polymerization initiator was set to 0.05 parts by weight of AIBN, and the polymerization reaction time was set to 2 hours. Otherwise, a solution of (meth)acrylic polymer A4 was obtained in the same manner as in Synthesis Example 2. The Mw of (meth)acrylic polymer A4 was 2.8 million.

[0109] The (meth)acrylic polymers prepared in each synthesis example are summarized in Table 1 below.

[0110] [Table 1]

[0111] [Preparation of adhesive composition] Solvent-based adhesive compositions P1 to P11 were obtained by mixing (meth)acrylic acid polymer solutions, crosslinking agents, and silane coupling agents in the manner shown in Table 2 below. Furthermore, the contents of the polymer, crosslinking agent, and silane coupling agent are values ​​converted from solid content.

[0112] [Table 2]

[0113] [Fabrication of Optical Laminates] (Example 1) The prepared adhesive composition P1 was applied to the release-treated surface of a release film (Mitsubishi resin, MRF#38) using a fountain coater, and then dried in an air-circulating constant-temperature oven set to 155°C for 2 minutes to form an adhesive composition layer (20µm thick). Separately, a modified PET film (75µm thick) with an air-treated surface (irradiation energy: 0.3J / cm²) was prepared as an optical substrate. The adhesive composition layer formed above was bonded to the modified surface of the prepared PET film to create an optical laminate comprising an adhesive layer and an optical substrate. Furthermore, the bonding was performed such that the portion not in contact with the adhesive layer was formed with a width of at least 50mm from one side of the PET film.

[0114] (Examples 2-9) Except that adhesive compositions P2 to P9 were used to replace adhesive composition P1, the optical laminates of Examples 2 to 9 were obtained in the same manner as in Example 1.

[0115] (Comparative Example 1) The adhesive composition P3 was used to replace the adhesive composition P1, and a PET film without the modified surface (of the same thickness) was used as the optical substrate. Otherwise, the optical laminate of Comparative Example 1 was obtained in the same manner as in Example 1.

[0116] (Comparative Example 2) The adhesive composition P10 was used to replace the adhesive composition P1, and a PET film without the modified surface (of the same thickness) was used as the optical substrate. Otherwise, the optical laminate of Comparative Example 2 was obtained in the same manner as in Example 1.

[0117] (Comparative Example 3) Except that adhesive composition P10 was used to replace adhesive composition P1, the optical laminate of Comparative Example 3 was obtained in the same manner as in Example 1.

[0118] (Comparative Example 4) Except that adhesive composition P1 was used instead of adhesive composition P1, the optical laminate of Comparative Example 4 was obtained in the same manner as in Example 1.

[0119] [Evaluate] [Is there any bias in Si agent (X)?] For the optical stacks of Example 3 and Comparative Example 1, the presence of Si agent (X) in the adhesive layer was evaluated using TOF-SIMS with etched ions. In this evaluation method, elemental analysis was performed along the thickness direction of the adhesive layer. The TOF-SIMS evaluation conditions are as follows. • Device: ULVAC-PHI manufactured, TRIFT-V • Evaluation object: The m / z of the corresponding SiOH + ion is 45. • Etching ions: Ar gas cluster ions • Etching ion acceleration voltage: 10kV • Primary ions irradiated: Bi³⁺ • Primary ion acceleration voltage: 30kV • Etching from the exposed surface of the adhesive layer toward the optical substrate

[0120] The evaluation results of each optical laminate of Example 3 and Comparative Example 1 are shown in Figures 5A and 5B, respectively. In Figures 5A and 5B, the horizontal axis represents etching time (in seconds), and the vertical axis represents the normalized intensity of SiOH+ ions after normalization based on the intensity of C2H3+ ions. As shown in Figure 5A, in the optical laminate of Example 3, Si agent (X) bias was confirmed in region 21 near the interface between the adhesive layer and the PET film (slanted area). In the graph of Figure 5A, the sum of the areas of the SiOH+ peaks in region 21 (accounting for 20% of the thickness of the adhesive layer) is more than 90% of the sum of the areas of the measurable SiOH+ peaks in the adhesive layer. On the other hand, as shown in Figure 5B, no Si agent (X) bias was observed in the optical laminate of Comparative Example 1. The bias of Si agent (X) was confirmed by the combination of Si agent (X) and the modified surface of the optical substrate. Furthermore, in the plots of each figure, a higher intensity of SiOH+ ions was observed in the region within the PET film. We believe this is because the intensity of C2H3+ ions, which serves as the standard, becomes very small in the PET film compared to the adhesive layer containing (meth)acrylic polymers.

[0121] [800% Modulus] The 800% modulus of the adhesive layer was evaluated as follows. The adhesive layer formed on the release film was cut into a rectangular shape with a width of 30 mm and a length of 100 mm, and rolled into a cylindrical shape to prevent air bubbles from entering, serving as the test specimen. Using a tensile testing machine, the stress at 800% elongation was determined from the elongation-stress curve of the test specimen measured under conditions of an initial fixture distance of 10 mm and a tensile speed of 300 mm / min, and the 800% modulus (N / mm²) was calculated from the obtained stress. Furthermore, 800% elongation refers to a fixture distance of 90 mm. The tensile testing machine used was an Autograph AG-IS manufactured by Shimadzu Corporation. The evaluation was conducted at room temperature (23°C).

[0122] [High-Temperature Adhesion] The high-temperature (80°C) adhesion of the adhesive layer to the optical substrate was evaluated as follows. Optical laminates prepared in each embodiment and comparative example were laminated with another PET film (75µm thick) that had undergone the same corona treatment as described above. Next, the laminated laminate was cut into long sheets with a width of 25mm and a length of 150mm to obtain test samples. The lamination was performed by bringing the adhesive layer of the optical laminate to the modified surface of the other PET film, and when cutting into long sheets, ensuring that the other PET film had a first free end (50mm long) at one end along the long side of the laminate, not in contact with the adhesive layer. Furthermore, during lamination, a 2kg pressing roller, as specified in Japanese Industrial Standard (formerly JIS) Z0237:2009, was passed back and forth once at a temperature of 25°C. The cutting was performed so that the portion of the optical substrate not in contact with the adhesive layer, which was set during the fabrication of the optical laminate, was positioned as the second free end (50 mm in length) at the other end along the aforementioned long side. Subsequently, the test specimen, after being allowed to stand for 30 minutes, was mounted on a tensile testing machine equipped with a constant temperature bath. The mounting was performed by having one fixture of the testing machine hold the first free end and the other fixture hold the second free end. Next, the ambient temperature of the testing machine and the test specimen was controlled to the evaluation temperature (80°C). After the ambient temperature reached the evaluation temperature and the specimen was allowed to stand for 5 minutes, a peeling test was performed by stretching both free ends in opposite directions at a test speed of 300 mm / min. After the test began, the initial measured value (stress value) measured from the initial tensile distance (expansion distance between fixtures) up to 10 mm was ignored, and the average value of the stress values ​​measured from the initial tensile distance up to 80 mm was taken as the high-temperature adhesion.

[0123] The evaluation results of each optical laminate of the embodiments and comparative examples are listed in Table 3 below.

[0124] [Table 3]

[0125] As shown in Table 3, the optical laminates of the embodiments can maintain the cohesive force of the adhesive layer while improving the high-temperature adhesion. In addition, when the adhesive composition contains a silane coupling agent with epoxy groups at the end, the degree of improvement in high-temperature adhesion brought about by the surface modification of the PET film is small (Comparative Examples 2 and 3).

[0126] Industrial availability The optical laminate of the present invention can be used, for example, in an image display device.

[0127] 1: Optical substrate 10A, 10B, 2, 7A, 7B, 7C: Adhesive layer 11: Surface 12: Modified surface 21: Area 3: Interface 4: Phase retardation thin film 51:Substrate 52: Image-forming layer (organic EL layer) 53: Covering film 5A, 5B: Polarizing component protective film 6:Polarizer 8: Peeling the liner 100, 110, 120: Optical laminates 200: Image display device

Claims

1. An optical laminate comprising an optical substrate and an adhesive layer disposed on the surface of the optical substrate; the adhesive layer comprising an adhesive composition comprising a (meth)acrylic polymer, a silane coupling agent, and a crosslinking agent; the silane coupling agent comprising isocyanate rings and not isocyanate groups; the surface on which the adhesive layer is disposed is a modified surface modified by irradiation energy; the content of the silane coupling agent in the adhesive composition being 0.05% by weight or more and 5.0% by weight or less.

2. The optical laminate of claim 1, wherein the aforementioned silane coupling agent is located in the region near the interface between the aforementioned adhesive layer and the aforementioned optical substrate.

3. The optical laminate of claim 1 or 2, wherein the content of the aforementioned silane coupling agent in the aforementioned adhesive composition is 0.05% by weight or more and 1.0% by weight or less.

4. The optical laminate as claimed in claim 1 or 2, wherein the aforementioned optical substrate is made of resin.

5. The optical laminate of claim 1 or 2, wherein the weight average molecular weight of the aforementioned (meth)acrylic polymer is 1.8 million or more.

6. The optical laminate as claimed in claim 1 or 2, wherein the aforementioned surface modification using irradiation energy is selected from at least one of corona treatment, plasma treatment and ultraviolet treatment.

7. An image display device comprising: an optical stack as described in any one of claims 1 to 6; and an image forming layer.

8. An adhesive composition for application to the surface of an optical substrate; the adhesive composition comprises a (meth)acrylic polymer, a silane coupling agent, and a crosslinking agent; the aforementioned silane coupling agent contains isocyanate rings and does not contain isocyanate groups; the surface to which the aforementioned adhesive composition is applied is a modified surface that has been surface-modified by irradiation energy; the aforementioned silane coupling agent is present in an amount of 0.05% by weight or more and 5.0% by weight or less.

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