Optical resin composition and optical resin sheet

Abstract

To provide an optical resin composition which is excellent in adhesive force, holding power, and bending resistance while maintaining good transparency in the form of an optical resin sheet.SOLUTION: An optical resin composition contains an acrylic polymer (A) and a crosslinking agent component (B). The acrylic polymer (A) is obtained by copolymerizing a crosslinkable functional group-containing monomer and a (meth)acrylate ester monomer in which the number of carbon atoms at an ester group terminal is 1 or more and 18 or less. The acrylic polymer (A) has a glass transition temperature Tg of -10.0°C or lower. The crosslinking agent component (B) contains an aliphatic or alicyclic polyisocyanate having a weight average molecular weight of 2,100 or more and 200,000 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an optical resin composition and an optical resin sheet. [Background technology]

[0002] In recent years, optical components such as pressure-sensitive adhesives, adhesives, and films for displays have become increasingly demanding due to the trend toward higher image definition, touch panels, flexible displays, and a wider variety of usage locations. These demands not only require transparency and a certain level of adhesive strength, but also various other properties, such as high weather resistance, high transparency, strong adhesive strength, high humidity and heat resistance, flex resistance, reworkability, and control of electrical properties. In particular, the trend toward more flexible and foldable displays has led to increasingly sophisticated performance requirements for pressure-sensitive adhesives and adhesives used to bond optical components together. Specifically, performance requirements include strong adhesive strength, high cohesive strength (high holding power), and flex resistance while maintaining transparency.

[0003] For example, Patent Document 1 discloses a pressure-sensitive adhesive composition containing an acrylic polymer having a specific structure and an organic polyisocyanate-based crosslinking agent or an epoxy-based crosslinking agent, and discloses that the pressure-sensitive adhesive composition can provide a film with excellent stress dispersion properties. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2017-132872 Summary of the Invention [Problem to be solved by the invention]

[0005] However, there is a demand for a technology that maintains transparency while providing superior adhesive strength, holding power, and flex resistance compared to the technology described in Patent Document 1, etc. In particular, foldable displays have been marketed in recent years, and flex resistance has become an important performance.

[0006] The present invention has been made in view of the above circumstances, and provides an optical resin composition that has excellent adhesive strength, holding power, and flex resistance while maintaining good transparency when made into an optical resin sheet, and an optical resin sheet using the optical resin composition. [Means for solving the problem]

[0007] That is, the present invention includes the following aspects. (1) An optical resin composition comprising an acrylic polymer (A) and a crosslinking agent component (B), the acrylic polymer (A) is obtained by copolymerizing a crosslinkable functional group-containing monomer and a (meth)acrylic acid ester monomer having an ester group terminal with 1 or more and 18 or less carbon atoms; the glass transition temperature Tg of the acrylic polymer (A) is −10.0° C. or lower, The crosslinking agent component (B) comprises an aliphatic or alicyclic polyisocyanate having a weight average molecular weight of 2,100 or more and 200,000 or less. (2) The optical resin composition according to (1), wherein the average number of isocyanate groups in the crosslinking agent component (B) is 2.0 or more and 6.5 or less. (3) The optical resin composition according to (1) or (2), wherein the content of the crosslinking agent component (B) is 0.01 parts by mass or more and 5.0 parts by mass or less relative to 100 parts by mass of the acrylic polymer (A). (4) The weight average molecular weight of the acrylic polymer (A) is 5.0 × 10 5 Over 5.0 x 10 6 The optical resin composition according to any one of (1) to (3), which is: (5) The optical resin composition according to any one of (1) to (4), wherein the crosslinkable functional group is at least one selected from the group consisting of a hydroxyl group, an epoxy group, a carboxyl group, and a vinyl group. (6) The optical resin composition according to any one of (1) to (5), wherein the content of the structural units derived from the (meth)acrylic acid ester monomer is 0.01% by mass or more and 99.99% by mass or less, based on the total mass of the acrylic polymer (A). (7) The aliphatic or alicyclic polyisocyanate is a polyisocyanate derived from at least one diisocyanate (b1) selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates, a bifunctional polyol (b2) having a number average molecular weight of 1,500 or more, and a trifunctional or higher polyol (b3) having a number average molecular weight of 500 or more, The optical resin composition according to any one of (1) to (6), wherein the ratio NCO / OH of the molar amount of isocyanate groups in the diisocyanate (b1) to the total molar amount of hydroxyl groups in the polyol (b2) and the polyol (b3) is 3 or more and 30 or less. (8) The mass ratio (b3) / (b2) of the polyol (b3) to the polyol (b2) is 0.1 / 99.9 or more and 99.9 / 0.1 or less, and With respect to 100 parts by mass of the diisocyanate (b1), the content of the polyol (b2) is 0.1 parts by mass or more and 250 parts by mass or less, The optical resin composition according to (7), wherein the content of the polyol (b3) is 0.1 parts by mass or more and 190 parts by mass or less. (9) The optical resin composition according to (7) or (8), wherein the polyol (b2) and the polyol (b3) are one or more polyols selected from the group consisting of polyester polyols, polyether polyols, epoxy polyols, polyolefin polyols, and polycarbonate polyols. (10) The optical resin composition according to any one of (1) to (9), wherein the crosslinking agent component (B) has an isocyanate group content of 1% by mass or more and 10% by mass or less. (11) The optical resin composition according to any one of (1) to (10), further comprising 0.01 parts by mass or more and 0.5 parts by mass or less of a silane coupling agent (C) relative to 100 parts by mass of the acrylic polymer (A). (12) The optical resin composition according to any one of (1) to (11), wherein the crosslinking agent component (B) comprises at least one member selected from the group consisting of an isocyanate compound other than the aliphatic or alicyclic polyisocyanate, a carbodiimide compound, an oxazoline compound, a polyfunctional acrylic acid ester monomer, a peroxide, a titanium coupling agent, a zirconium compound, a metal aluminum chelate, a hydrazide compound, an epoxy crosslinking agent, a thermal acid generator, and a photoacid generator. (13) The optical resin composition according to any one of (1) to (12), wherein the crosslinking agent component (B) is applied to a glass surface, and the cured film formed thereon has a thickness of 40 μm and a Konig hardness of 60 or less at 23°C after storage for 168 hours at 23°C and 65% humidity. (14) An optical resin sheet obtained by curing the optical resin composition according to any one of (1) to (13) with heat or light. (15) The optical resin sheet according to (14), wherein the thickness of the optical resin sheet is 1 μm or more and 1000 μm or less. (16) The optical resin sheet according to (14) or (15), wherein the optical resin composition is applied onto a polyethylene terephthalate film having a thickness of 25 μm, dried at 125° C. for 3 minutes to cure the composition, and then stored in an environment of 23° C. and 50% RH for 7 days. The optical resin sheet has a thickness of 70 μm, a width of 20 mm, and a length of 100 mm, and the polyethylene terephthalate film is provided on one side of the optical resin sheet. The optical resin sheet is then pressed against a SUS304BA plate as an adherend by one reciprocal stroke with a 2 kg roller, and aged at 23° C. for 30 minutes. After this, the 180-degree peel adhesive strength measured at 23° C. and a speed of 300 mm / min is 2.0 N / 20 mm or more and 65 N / 20 mm or less. (17) The optical resin sheet according to any one of (14) to (16), wherein the optical resin composition is applied onto a polyethylene terephthalate film having a thickness of 25 μm, dried at 125° C. for 3 minutes to cure the composition, and then stored in an environment of 23° C. and 50% RH for 7 days, and the optical resin sheet has a thickness of 70 μm, a width of 25 mm, and a length of 130 mm and is provided with the polyethylene terephthalate film on one side thereof, and is attached to an SUS304BA plate as an adherend so that an overlapping area of ​​25 mm in width and 25 mm in length is formed. The optical resin sheet is then pressed back and forth once with a 2 kg roller, aged at 23° C. for 1 hour, aged at 40° C. for a further 30 minutes, and then a 500 g weight is hung from the lower end of the optical resin sheet in an environment of 40° C. for 1 hour. When the optical resin sheet is then returned to an environment of 23° C., the amount of displacement of the optical resin sheet is 2 mm / hour or less. (18) The optical resin sheet according to any one of (14) to (17), wherein the optical resin composition is applied onto a release-treated polyethylene terephthalate film having a thickness of 38 μm, dried at 125° C. for 3 minutes to cure, and then stored in an environment of 23° C. and 50% RH for 7 days. The optical resin sheet is peeled off from the release-treated polyethylene terephthalate film to obtain an optical resin sheet having a thickness of 70 μm. The optical resin sheet is attached to a glass having a haze value of 0.1%, and the haze value measured with a haze meter is 2.0% or less. (19) The optical resin sheet according to any one of (14) to (18), wherein the optical resin composition is applied onto a release-treated polyethylene terephthalate film having a thickness of 38 μm, dried at 125° C. for 3 minutes to cure the composition, and then stored in an environment of 23° C. and 50% RH for 7 days. The optical resin sheet obtained by peeling the composition from the release-treated polyethylene terephthalate film has a thickness of 70 μm. The optical resin sheet is then stored in an environment of 23° C. and 50% RH for 7 days, wrapped in a mesh sheet, immersed in ethyl acetate at 23° C. for 1 week, removed, and dried at 120° C. for 2 hours. The gel fraction calculated by the above-described method is 40.0 mass % or more and 99.9 mass % or less. (20) The optical resin composition was coated on a 38 μm thick release-treated polyethylene terephthalate film, dried at 125°C for 3 minutes to cure, and then stored in a 23°C, 50% RH environment for 7 days. The resulting optical resin sheet was peeled off from the release-treated polyethylene terephthalate film to obtain a 70 μm thick optical resin sheet. The resulting laminate was then cut to a width of 10 mm and a length of 40 mm. The laminate was then set in a tensile tester with a chuck distance of 10 mm, and a Young's modulus of 0.40 N / mm was measured in a tensile test carried out at a speed of 300 mm / min in a 23°C environment. 2 The optical resin sheet according to any one of (14) to (19) below: [Effects of the Invention]

[0008] According to the optical resin composition of the above aspect, it is possible to provide an optical resin composition that has excellent adhesive strength, holding strength, and flex resistance while maintaining good transparency when made into an optical resin sheet. The optical resin sheet of the above embodiment is obtained by curing the optical resin composition, and has good transparency, and is excellent in adhesive strength, holding power, and flex resistance. DETAILED DESCRIPTION OF THE INVENTION

[0009] In this specification, the term "polyol" refers to a compound having two or more hydroxy groups (-OH) in one molecule. In addition, in this specification, the term "polyisocyanate" refers to a reaction product in which a plurality of monomer compounds having two or more isocyanate groups (-NCO) are bonded together. In addition, in this specification, unless otherwise specified, "(meth)acrylic" includes methacrylic and acrylic, and "(meth)acrylate" includes methacrylate and acrylate.

[0010] ≪Optical resin composition≫ The optical resin composition of this embodiment contains an acrylic polymer (A) and a crosslinking agent component (B).

[0011] The acrylic polymer (A) is a polymer obtained by copolymerizing a crosslinkable functional group-containing monomer and a (meth)acrylic acid ester monomer having 1 or more and 18 or less carbon atoms at the ester group terminal.

[0012] The glass transition temperature Tg of the acrylic polymer (A) is −75.0° C. or higher and −10.0° C. or lower, preferably −74.0° C. or higher and −20.0° C. or lower, more preferably −73.0° C. or higher and −30.0° C. or lower, even more preferably −72.0° C. or higher and −40.0° C. or lower, particularly preferably −71.0° C. or higher and −50.0° C. or lower, and most preferably −71.0° C. or higher and −50.0° C. When the glass transition temperature Tg of the acrylic polymer (A) is within the above range, the adhesive strength and flex resistance when formed into an optical resin sheet tend to be excellent. The glass transition temperature of the acrylic polymer (A) can be determined by, for example, evaporating the organic solvent and water from a solution in which the acrylic polymer (A) is dissolved or dispersed under reduced pressure, vacuum-drying the resulting solution, and measuring the value at a temperature rise rate of 5°C / min using a differential scanning calorimetry (DSC) analyzer.

[0013] The crosslinking agent component (B) contains an aliphatic or alicyclic polyisocyanate having a weight average molecular weight of 2,100 or more and 200,000 or less.

[0014] The optical resin composition of this embodiment has the above-mentioned structure, and thus an optical resin sheet can be obtained that has excellent adhesive strength, holding power, and flex resistance while maintaining good transparency. The flex resistance here is evaluated in terms of the modulus of elasticity, maximum stress, and elongation percentage for the sake of simplicity, as shown in the examples described below. The flex resistance can be achieved by a layer obtained by curing the optical resin composition that has a low modulus of elasticity (Young's modulus), a high elongation percentage, and a high maximum stress. That is, a layer that easily conforms to deformation due to bending, easily relaxes stress, and is resistant to fracture (has a high maximum stress) is considered to have excellent flex resistance. The preferred range of Young's modulus will be described later.

[0015] <Acrylic polymer (A)> The acrylic polymer (A) is a polymer obtained by copolymerizing a crosslinkable functional group-containing monomer (a1) and a (meth)acrylic acid ester monomer (a2) having 1 to 18 carbon atoms at the ester group terminal.

[0016] The crosslinkable functional group-containing monomer (a1) has a polymerizable functional group and a crosslinkable functional group capable of forming a crosslinked structure with the crosslinker component (B). Examples of the polymerizable functional group include a vinyl group. Examples of the crosslinkable functional group include a hydroxyl group, a thiol group, an amino group, an amide group, an epoxy group, a carboxyl group, and a vinyl group. Among these, a hydroxyl group, an epoxy group, or a carboxyl group is preferred, and a hydroxyl group is more preferred. The crosslinkable functional group can also be imparted by modification after polymerizing an acrylic ester.

[0017] The acrylic polymer (A) may contain only one type of structural unit derived from the crosslinkable functional group-containing monomer (a1) and one type of structural unit derived from the (meth)acrylic acid ester monomer (a2), or may contain two or more types in combination. That is, the acrylic polymer (A) may be obtained by copolymerizing one type of each of the crosslinkable functional group-containing monomer (a1) and the (meth)acrylic acid ester monomer (a2), or may be obtained by copolymerizing two or more types of each of the crosslinkable functional group-containing monomer (a1) and the (meth)acrylic acid ester monomer (a2). The (meth)acrylic acid ester monomer (a2) may or may not have a crosslinkable functional group, but preferably does not have one.

[0018] The acrylic polymer (A) may further contain, in addition to the structural units derived from the crosslinkable functional group-containing monomer (a1) and the structural units derived from the (meth)acrylic acid ester monomer (a2), structural units derived from other polymerizable monomers (a3) ​​(hereinafter, simply referred to as "other polymerizable monomers (a3)"). That is, the acrylic polymer (A) may be obtained by copolymerizing one or more crosslinkable functional group-containing monomers (a1), one or more (meth)acrylic acid ester monomers (a2), and one or more other polymerizable monomers (a3). The other polymerizable monomers (a3) ​​may or may not have a crosslinkable functional group.

[0019] The crosslinkable functional group-containing monomer (a1) is preferably a polymerizable (meth)acrylic monomer having a crosslinkable functional group.

[0020] Examples of polymerizable (meth)acrylic monomers having a crosslinkable functional group include the following (i) to (viii), which may be used singly or in combination of two or more. (i) Acrylic esters having a hydroxyl group, such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxybutyl acrylate, 4-hydroxybutyl acrylate, 6-hydroxyhexyl acrylate, and 8-hydroxyoctyl acrylate. (ii) Methacrylates having a hydroxyl group, such as 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 4-hydroxybutyl methacrylate, 6-hydroxyhexyl methacrylate, and 8-hydroxyoctyl methacrylate. (iii) (meth)acrylic acid esters having a polyvalent hydroxy group, such as acrylic acid monoester or methacrylic acid monoester of glycerin, and acrylic acid monoester or methacrylic acid monoester of trimethylolpropane. (iv) Unsaturated carboxylic acids such as acrylic acid and methacrylic acid. (v) Unsaturated amides such as (meth)acrylamide. (vi) (meth)acrylic acid esters having an amino group, such as dimethylaminoethyl (meth)acrylate and diethylaminoethyl (meth)acrylate. (vii) (meth)acrylic acid esters having an epoxy group, such as glycidyl methacrylate. (viii) (Meth)acrylic acid esters having a carboxyl group, such as 2-carboxyethyl acrylate and 2-carboxyethyl methacrylate.

[0021] When the polymerizable (meth)acrylic monomer having a crosslinkable functional group is a (meth)acrylic acid ester monomer having a crosslinkable functional group, the number of carbon atoms in the ester moiety is preferably 1 or more and 18 or less, more preferably 1 or more and 12 or less, even more preferably 1 or more and 10 or less, particularly preferably 1 or more and 8 or less, and most preferably 2 or more and 8 or less.

[0022] The (meth)acrylic acid ester monomer (a2) has 1 or more and 18 or less carbon atoms at the ester group terminal.

[0023] Examples of the (meth)acrylic acid ester monomer (a2) include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, (Meth)acrylate esters such as isononyl acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate (lauryl (meth)acrylate), tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, nonadecyl (meth)acrylate, eicosyl (meth)acrylate, benzyl (meth)acrylate, and cyclohexyl (meth)acrylate may be mentioned. These may be used alone or in combination of two or more.

[0024] Examples of other polymerizable monomers (a3) ​​include the following (i) to (iv): These may be used alone or in combination of two or more. (i) Unsaturated carboxylic acids such as maleic acid and itaconic acid. (ii) Monomers having an epoxy group, such as 1,2-epoxy-4-vinylcyclohexane, allyl glycidyl ether, and 4-hydroxybutyl acrylate glycidyl ether. (iii) Unsaturated amides such as N-methylolacrylamide, diacetoneacrylamide, and dimethylaminopropylacrylamide. (iv) Vinyl acetate, (meth)acrylonitrile, styrene, vinyltoluene, N-vinylpyrrolidone, N-vinylcaprolactam, acryloylmorpholine.

[0025] Furthermore, as other monomers copolymerizable with the crosslinkable functional group-containing monomer (a1) and the (meth)acrylic acid ester monomer (a2), polymerizable ultraviolet-stable monomers disclosed in JP-A-1-261409 (Reference 1) and JP-A-3-006273 (Reference 2), etc., may be used.

[0026] Specific examples of the polymerizable ultraviolet-stable monomer include 4-(meth)acryloyloxy-2,2,6,6-tetramethylpiperidine, 4-(meth)acryloylamino-2,2,6,6-tetramethylpiperidine, 1-crotonoyl-4-crotonoyloxy-2,2,6,6-tetramethylpiperidine, and 2-hydroxy-4-(3-methacryloxy-2-hydroxypropoxy)benzophenone.

[0027] For example, the acrylic polymer (A) can be obtained by solution polymerizing the above-mentioned monomer components in the presence of a known radical polymerization initiator such as a peroxide or an azo compound, and diluting the solution with an organic solvent, etc., as necessary.

[0028] The aqueous-based acrylic polymer (A) can be produced by a known method such as solution polymerization of an olefinically unsaturated compound followed by conversion into an aqueous phase, or emulsion polymerization. In this case, water solubility or water dispersibility can be imparted by neutralizing the acidic moiety of a carboxylic acid-containing monomer such as acrylic acid or methacrylic acid, or a sulfonic acid-containing monomer, with an amine or ammonia.

[0029] The content of the structural unit derived from the crosslinkable functional group-containing monomer (a1) is preferably from 0.01 to 25% by mass, more preferably from 0.02 to 23% by mass, even more preferably from 0.03 to 21% by mass, and particularly preferably from 0.04 to 20% by mass, relative to the total mass of the acrylic polymer (A). When the content of the structural unit derived from the crosslinkable functional group-containing monomer (a1) is within the above range, the resulting optical resin sheet tends to have better adhesive strength and cohesive strength (holding power).

[0030] The content of the structural units derived from the (meth)acrylic acid ester monomer (a2) is preferably from 0.01% to 99.99% by mass, more preferably from 10% to 99.99% by mass, even more preferably from 50% to 99.99% by mass, and particularly preferably from 80% to 99.99% by mass, relative to the total mass of the acrylic polymer (A). When the content of the structural units derived from the (meth)acrylic acid ester monomer (a2) is within the above range, the resulting optical resin sheet tends to have better adhesive strength and cohesive strength (holding power).

[0031] The content of the structural unit derived from the crosslinkable functional group-containing monomer (a1) and the content of the structural unit derived from the (meth)acrylic acid ester monomer (a1) can be calculated, for example, from the blending amounts of the crosslinkable functional group-containing monomer (a1) and the (meth)acrylic acid ester monomer (a2) used in the production of the acrylic polymer (A). 1 H-NMR spectrum, 12 It can also be calculated from the composition ratio calculated by combining C-NMR spectrum, IR spectrum, and mass spectrum analysis.

[0032] The weight average molecular weight Mw(A) of the acrylic polymer (A) is 5.0 × 10 5 Over 5.0 x 10 6 Preferably, it is 6.0 x 10 or less. 5 Over 2.5 x 106 More preferably, it is 6.5×10 or less. 5 Over 2.0 x 10 6 More preferably, it is 7.0×10 or less. 5 Over 1.9 x 10 6 It is particularly preferable that the weight average molecular weight Mw(A) of the acrylic polymer (A) is within the above range. When the weight average molecular weight Mw(A) of the acrylic polymer (A) is within the above range, the resulting optical resin sheet tends to have better adhesive strength, cohesive strength (holding strength), and moist heat resistance. The weight average molecular weight Mw(A) of the acrylic polymer (A) can be measured, for example, using the method described in the examples below.

[0033] <Crosslinking agent component (B)> The crosslinking agent component (B) contains an aliphatic or alicyclic polyisocyanate having a weight average molecular weight of 2,100 or more and 200,000 or less.

[0034] The weight average molecular weight Mw(b) of the aliphatic or alicyclic polyisocyanate is from 2100 to 200,000, preferably from 2500 to 150,000, more preferably from 2800 to 100,000, even more preferably from 3000 to 80,000, and particularly preferably from 3200 to 70,000. When the weight average molecular weight Mw(b) of the aliphatic or alicyclic polyisocyanate is within the above range, the resulting optical resin sheet can have a lower elastic modulus (Young's modulus), a higher elongation, and a higher breaking strength. The Mw(b) of an aliphatic or alicyclic polyisocyanate is the weight average molecular weight measured by GPC using polystyrene as a standard.

[0035] The average number of isocyanate groups in the aliphatic or alicyclic polyisocyanate is preferably from 2.0 to 6.5, more preferably from 2.3 to 6.3, even more preferably from 2.4 to 6.1, and particularly preferably from 2.5 to 6.0. When the average number of isocyanate groups in the aliphatic or alicyclic polyisocyanate is within the above range, the acrylic polymer (A) and the crosslinking agent component (B) more effectively form a crosslinked network, and the resulting optical resin sheet can have a larger elongation percentage and a higher breaking strength.

[0036] The average number of isocyanate groups (fn) of an aliphatic or alicyclic polyisocyanate can be calculated using the following formula. In the formula, "Mn" represents the number average molecular weight of the aliphatic or alicyclic polyisocyanate, and "NCO%" represents the isocyanate group content of the aliphatic or alicyclic polyisocyanate. The number average molecular weight Mn of the aliphatic or alicyclic polyisocyanate is the weight average molecular weight based on polystyrene measured by GPC. The method for measuring NCO% will be described later.

[0037] [fn] = [Mn] × [NCO%] / 4200

[0038] The aliphatic or alicyclic polyisocyanate (b) is preferably a polyisocyanate derived from at least one diisocyanate (b1) selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates, a bifunctional polyol (b2) having a number average molecular weight of 1500 or more, and a trifunctional or higher polyol (b3) having a number average molecular weight of 500 or more.

[0039] The ratio NCO / OH of the molar amount of isocyanate groups in the diisocyanate (b1) to the total molar amount of hydroxyl groups in the polyol (b2) and the polyol (b3) is preferably from 3 to 30, more preferably from 4 to 25, even more preferably from 5 to 22, and particularly preferably from 6 to 20. When the NCO / OH is within the above range, the crosslinking agent component (B) can be synthesized without gelling, and the resulting optical resin sheet can have a lower elastic modulus, a higher elongation, and a higher breaking strength.

[0040] The aliphatic or alicyclic polyisocyanate (b) may be a polyisocyanate having, in one molecule, all of the structural units derived from a diisocyanate, a polyol (b2), and a polyol (b3), or may be a mixture of polyisocyanates having, in one molecule, a structural unit derived from at least one selected from the group consisting of a diisocyanate, a polyol (b2), and a polyol (b3).

[0041] The aliphatic or alicyclic polyisocyanate (b) may have at least one structure selected from the group consisting of an allophanate structure, a uretdione structure, an iminooxadiazinedione structure, an isocyanurate structure, a urea structure, a urethane structure, and a biuret structure. Among these, it is preferable that the aliphatic or alicyclic polyisocyanate (b) has at least one structure selected from the group consisting of a urethane structure, an allophanate structure, a biuret structure, a urea structure, and an isocyanurate group, and more preferably contains a urethane structure.

[0042] [Diisocyanate (b1)] The diisocyanate (b1) is at least one selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates.

[0043] Examples of aliphatic diisocyanates include, but are not limited to, 1,4-diisocyanatobutane, 1,5-diisocyanatopentane, ethyl (2,6-diisocyanato)hexanoate, 1,6-diisocyanatohexane (hereinafter sometimes abbreviated as "HDI"), 1,9-diisocyanatononane, 1,12-diisocyanatododecane, 2,2,4- or 2,4,4-trimethyl-1,6-diisocyanatohexane, etc. These aliphatic diisocyanates may be used alone or in combination of two or more.

[0044] Examples of alicyclic diisocyanates include, but are not limited to, 1,3- or 1,4-bis(isocyanatomethyl)cyclohexane (hereinafter sometimes abbreviated as "hydrogenated XDI"), 1,3- or 1,4-diisocyanatocyclohexane, 3,5,5-trimethyl-1-isocyanato-3-(isocyanatomethyl)cyclohexane (hereinafter sometimes abbreviated as "IPDI"), 4-4'-diisocyanato-dicyclohexylmethane (hereinafter sometimes abbreviated as "hydrogenated MDI"), 2,5- or 2,6-diisocyanatomethylnorbornane, etc. These alicyclic diisocyanates may be used alone or in combination of two or more.

[0045] These aliphatic diisocyanates and alicyclic diisocyanates may be used alone, or two or more of them may be used in combination. From the viewpoint of flexibility, the mass ratio of the alicyclic polyisocyanate to the aliphatic diisocyanate is preferably 0 / 100 or more and 30 / 70 or less, and more preferably 0 / 100 or more and 20 / 80 or less.

[0046] Among these, the diisocyanate is preferably HDI, IPDI, hydrogenated XDI, or hydrogenated MDI, more preferably HDI or IPDI, and even more preferably HDI.

[0047] In addition to the diisocyanates described above, the following isocyanate monomers may also be used to produce the polyisocyanate. (1) Aromatic diisocyanates such as diphenylmethane-4,4'-diisocyanate (MDI), 1,5-naphthalene diisocyanate, tolylene diisocyanate (TDI), xylylene diisocyanate, and m-tetramethylxylylene diisocyanate (TMXDI). (2) Triisocyanates such as 4-isocyanatomethyl-1,8-octamethylene diisocyanate (hereinafter sometimes referred to as "NTI"), 1,3,6-hexamethylene triisocyanate (hereinafter sometimes referred to as "HTI"), bis(2-isocyanatoethyl) 2-isocyanatoglutarate (hereinafter sometimes referred to as "GTI"), and lysine triisocyanate (hereinafter sometimes referred to as "LTI").

[0048] [Polyol (b2) and Polyol (b3)] The polyol (b2) has a number average molecular weight of 1500 or more and is a bifunctional polyol (diol). The polyol (b3) has a number average molecular weight of 500 or more and is a polyol having three or more functional groups.

[0049] The number average molecular weight of the polyol (b2) is at least 1500, and preferably at least 1800. When the number average molecular weight of the polyol (b2) is at least the above-mentioned lower limit, the hardness of the cured film obtained by curing only the polyisocyanate is low and the flexibility is good. On the other hand, the upper limit of the number average molecular weight of the polyol (b2) is not particularly limited, but can be, for example, 12,000, preferably 11,000, more preferably 10,000, even more preferably 8,000, still more preferably 6,000, particularly preferably 5,000, and most preferably 4,200. The number average molecular weight Mn of the polyol (b2) is, for example, the number average molecular weight measured by GPC using polystyrene as a standard. When two or more polyols (b2) are used in combination, the number average molecular weight of the mixture is calculated.

[0050] The number average molecular weight of the polyol (b3) is at least 500, and preferably at least 800. When the number average molecular weight of the polyol (b3) is at least the above lower limit, the hardness of the cured film obtained by curing only the polyisocyanate is low and the flexibility is good. On the other hand, the upper limit of the number average molecular weight of the polyol (b3) is not particularly limited, but can be, for example, 3,000, and is preferably 2,200. The number average molecular weight Mn of the polyol (b3) is, for example, the number average molecular weight measured by GPC using polystyrene as a standard. When two or more types of polyol (b3) are used in combination, the number average molecular weight of the mixture is calculated.

[0051] The polyol (b2) is preferably at least one bifunctional polyol (diol) selected from the group consisting of polyester polyols, polyether polyols, epoxy polyols, polyolefin polyols, and polycarbonate polyols, and more preferably a bifunctional polyester polyol.

[0052] Examples of bifunctional polyester polyols include the following polyester polyols (1) and (2). (1) Polyester polyols obtained by the condensation reaction of a dibasic acid, either alone or in a mixture of two or more kinds, with a dihydric alcohol, either alone or in a mixture of two or more kinds. (2) Polycaprolactone polyol obtained by ring-opening polymerization of ε-caprolactone with a dihydric alcohol. Examples of the dibasic acid include succinic acid, adipic acid, dimer acid, maleic anhydride, phthalic anhydride, isophthalic acid, terephthalic acid, 1,4-cyclohexanedicarboxylic acid, and other carboxylic acids. Examples of the dihydric alcohol include ethylene glycol, propylene glycol, diethylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, trimethylpentanediol, and cyclohexanediol.

[0053] Among these, the bifunctional polyester polyol is preferably a bifunctional polycaprolactone polyol.

[0054] Commercially available bifunctional polycaprolactone polyols include, for example, trade names "PLACCEL 210" (number average molecular weight 1000), "PLACCEL 220" (number average molecular weight 2000), "PLACCEL 230" (number average molecular weight 3000), and "PLACCEL 240" (number average molecular weight 4000), all of which are manufactured by Daicel Corporation.

[0055] The polyol (b3) may be any polyol having three or more functionalities, preferably a polyol having three to ten functionalities, more preferably a polyol having three to seven functionalities, even more preferably a polyol having three to five functionalities, particularly preferably a polyol having three to four functionalities, and most preferably a trifunctional polyol (triol). The trifunctional polyol (triol) is preferably at least one trifunctional polyol (triol) selected from the group consisting of polyester polyol, polyether polyol, epoxy polyol, polyolefin polyol, and polycarbonate polyol, and more preferably a trifunctional polyester polyol.

[0056] Examples of trifunctional polyester polyols include polyester polyols of either (1) or (2) below. (1) Polyester polyols obtained by the condensation reaction of a dibasic acid, either alone or in a mixture of two or more kinds, with a trihydric alcohol, either alone or in a mixture of two or more kinds. (2) Polycaprolactone polyol obtained by ring-opening polymerization of ε-caprolactone with a trihydric alcohol. Examples of the dibasic acid include succinic acid, adipic acid, dimer acid, maleic anhydride, phthalic anhydride, isophthalic acid, terephthalic acid, 1,4-cyclohexanedicarboxylic acid, and other carboxylic acids. Examples of the trihydric alcohol include trimethylolpropane, glycerin, pentaerythritol, 2-methylolpropanediol, and ethoxylated trimethylolpropane.

[0057] Among them, trifunctional polyester polyols are preferably trifunctional polycaprolactone polyols.

[0058] Commercially available trifunctional polycaprolactone polyols include, for example, trade names "PLACCEL 305" (number average molecular weight 550), "PLACCEL 308" (number average molecular weight 850), "PLACCEL 309" (number average molecular weight 900), "PLACCEL 312" (number average molecular weight 1250), and "PLACCEL 320" (number average molecular weight 2000), all of which are manufactured by Daicel Corporation.

[0059] In the aliphatic or alicyclic polyisocyanate (b), the mass ratio of the polyol (b2) to the polyol (b3) (mass ratio of (b2) / (b3)) is preferably from 0.1 / 99.9 to 99.9 / 0.1, more preferably from 1 / 99 to 99 / 1, even more preferably from 3 / 97 to 90 / 10, particularly preferably from 3 / 97 to 85 / 15, and most preferably from 5 / 95 to 80 / 20. When the mass ratio of (b2) / (b3) is equal to or greater than the lower limit, the hardness of the cured film obtained by curing the polyisocyanate alone is low and the flexibility is better. Furthermore, an optical resin sheet having superior adhesive strength and flexibility can be obtained. On the other hand, when the mass ratio of (b2) / (b3) is equal to or less than the upper limit, the optical resin sheet having superior adhesive strength, flexibility, and cohesion can be obtained. The mass ratio of (b2) / (b3) can be calculated, for example, from the blending amounts of each polyol when producing the polyisocyanate.

[0060] In the aliphatic or alicyclic polyisocyanate (b), the content (charge amount) of the polyol (b2) relative to 100 parts by mass of the diisocyanate is usually 0.1 part by mass or more and 250 parts by mass or less, preferably 0.1 part by mass or more and 210 parts by mass or less, more preferably 0.1 part by mass or more and 170 parts by mass or less, even more preferably 0.5 part by mass or more and 100 parts by mass or less, even more preferably 1 part by mass or more and 50 parts by mass or less, still more preferably 1.5 parts by mass or more and 45 parts by mass or less, and particularly preferably 1.7 parts by mass or more and 42 parts by mass or less. When the content of polyol (b2) is equal to or greater than the lower limit, the hardness of the cured film obtained by curing the polyisocyanate alone is low and the flexibility is better. Furthermore, an optical resin sheet having superior adhesive strength, curability, and flex resistance can be obtained. On the other hand, when the content of polyol (b2) is equal to or less than the upper limit, the polyisocyanate can be maintained in a liquid state without gelation during production, and the flexibility of the optical resin sheet obtained can be better. The content of polyol (b2) can be calculated, for example, from the amounts of diisocyanate and polyol (b2) blended when producing the polyisocyanate.

[0061] In the aliphatic or alicyclic polyisocyanate (b), the content (charge amount) of the polyol (b3) relative to 100 parts by mass of the diisocyanate is usually 0.1 parts by mass or more and 190 parts by mass or less, preferably 1 part by mass or more and 140 parts by mass or less, more preferably 1 part by mass or more and 90 parts by mass or less, even more preferably 2 parts by mass or more and 80 parts by mass or less, even more preferably 5 parts by mass or more and 70 parts by mass or less, still more preferably 7 parts by mass or more and 65 parts by mass or less, and particularly preferably 10 parts by mass or more and 60 parts by mass or less. When the content of polyol (b3) is equal to or less than the upper limit, the polyisocyanate can be maintained in a liquid state without gelling during production, and the curability and flexibility of the resulting optical resin sheet are improved. On the other hand, when the content of polyol (b3) is equal to or more than the lower limit, the hardness of the cured film obtained by curing the polyisocyanate alone is low and the flexibility is improved. Furthermore, an optical resin sheet having better adhesive strength and curability can be obtained. The content of polyol (b3) can be calculated, for example, from the amounts of diisocyanate and polyol (b3) blended when producing the polyisocyanate.

[0062] [Other crosslinking agent components] The crosslinking agent component (B) may contain, in addition to the aliphatic or alicyclic polyisocyanate (b), one or more other crosslinking agent components (b') selected from the group consisting of an isocyanate compound other than the aliphatic or alicyclic polyisocyanate (b), a carbodiimide compound, an oxazoline compound, a polyfunctional acrylic acid ester monomer, a peroxide, a titanium coupling agent, a zirconium compound, a metal aluminum chelate, a hydrazide compound, an epoxy-based crosslinking agent, a thermal acid generator, and a photoacid generator.

[0063] The content of the aliphatic or alicyclic polyisocyanate (b) in the crosslinker component (B) is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, and particularly preferably 100% by mass, based on the total mass of the crosslinker component (B). When the content of the aliphatic or alicyclic polyisocyanate (b) in the crosslinker component (B) is equal to or more than the above lower limit, the effects achieved by the optical resin composition of this embodiment can be more fully exhibited.

[0064] Examples of isocyanate compounds other than the aliphatic or alicyclic polyisocyanate (b) include the aliphatic or alicyclic diisocyanate monomers exemplified in the diisocyanate (b1) above, as well as the aromatic diisocyanates and triisocyanates exemplified in the diisocyanate (b1) above, and polyisocyanates derived therefrom.

[0065] Carbodiimide compounds can be obtained, for example, by reacting isocyanate groups of polyisocyanate compounds with each other to remove carbon dioxide. Commercially available carbodiimide compounds include Carbodilite V-02, Carbodilite V-02-L2, Carbodilite V-04, Carbodilite E-01, and Carbodilite E-02 (all of which are product names manufactured by Nisshinbo).

[0066] Examples of the oxazoline compound include a polymeric compound having at least two oxazoline groups in the side chain, and a monomeric compound having at least two oxazoline groups in one molecule.

[0067] Examples of polyfunctional acrylic acid ester monomers include tripentaerythritol acrylate, trimethylolpropane triacrylate, a condensate of pentaerythritol and acrylic acid, 1,6-hexanediol diacrylate, etc. The polyfunctional acrylic acid ester monomers referred to here contain two or more vinyl groups and are distinguished from the above-mentioned crosslinkable functional group-containing monomers.

[0068] Examples of peroxides include benzoyl peroxide, cumene hydroperoxide, 2,5-dimethylhexane-2,5-dihydroperoxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3, di-tert-butyl peroxide, tert-butylcumyl peroxide, di(2-tert-butylperoxyisopropyl)benzene, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, dicumyl peroxide, di-tert-butylperoxyisophthalate, tert-butylperoxybenzoate, 2,2-bis(tert-butylperoxy)butane, 2,2-bis(tert-butylperoxy)octane, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, di(trimethylsilyl)peroxide, and trimethylsilyltriphenylsilyl peroxide.

[0069] Examples of titanium coupling agents include isopropyl triisostearoyl titanate, isopropyl tris(dioctyl pyrophosphate) titanate, isopropyl tri(N-aminoethyl-aminoethyl) titanate, tetraoctyl bis(di-tridecyl phosphite) titanate, tetra(2,2-diallyloxymethyl-1-butyl)bis(di-tridecyl) phosphite titanate, and bis(octyl pyrophosphate)oxyacetate titanate. , bis(dioctyl pyrophosphate)ethylene titanate, isopropyl trioctanoyl titanate, isopropyl dimethacryl isostearoyl titanate, isopropyl tridodecylbenzenesulfonyl titanate, isopropyl isostearoyl diacryl titanate, isopropyl tri(dioctyl sulfate) titanate, isopropyl tricumylphenyl titanate, tetraisopropyl bis(dioctyl phosphite) titanate, and the like.

[0070] Examples of the zirconium compound include zirconium tetraacetylacetonate, zirconyl 2-ethylhexanoate, and zirconyl naphthenate.

[0071] Examples of metal aluminum chelates include aluminum triacetylacetone.

[0072] Examples of the hydrazide compound include aliphatic carboxylic acid hydrazides, alicyclic carboxylic acid hydrazides, and aromatic carboxylic acid hydrazides. Examples of aliphatic carboxylic acid hydrazides and alicyclic carboxylic acid hydrazides include saturated or unsaturated fatty acid hydrazides such as lauric acid hydrazide, palmitic acid hydrazide, stearic acid hydrazide, adipic acid dihydrazide, sebacic acid dihydrazide, dodecanedioic acid dihydrazide, eicosanedioic acid dihydrazide, and sorbic acid hydrazide; oxyfatty acid hydrazides such as α-oxybutyric acid hydrazide and glyceric acid hydrazide; 7,11-octadecadiene-1,18-dicarbohydrazide, 1,3-bis(hydrazinocarbonoethyl)-5-isopropylhydantoin, and tris(hydrazinocarbonylethyl)isocyanurate. Examples of aromatic carboxylic acid hydrazides include 1-naphthoic acid hydrazide, 2-naphthoic acid hydrazide, phthalic acid dihydrazide, isophthalic acid dihydrazide, terephthalic acid dihydrazide, and 2,6-naphthoic acid dihydrazide.

[0073] Examples of epoxy crosslinking agents include polyfunctional epoxy resins manufactured by Mitsubishi Gas Chemical Company, Inc., trade names of "TETRAD-C" and "TETRAD-X".

[0074] Examples of the thermal acid generator include salts formed from a strong acid and a base, such as onium salts, which have the function of generating an acid by heat, and imidosulfonates. Examples of onium salts include aryl diazonium salts, diaryliodonium salts such as diphenyliodonium salts; di(alkylaryl)iodonium salts such as di(tert-butylphenyl)iodonium salts; trialkylsulfonium salts such as trimethylsulfonium salts; dialkylmonoarylsulfonium salts such as dimethylphenylsulfonium salts; diarylmonoalkyliodonium salts such as diphenylmethylsulfonium salts; and triarylsulfonium salts. Furthermore, as the salt formed from a strong acid and a base, in addition to the above-mentioned onium salts, salts formed from the following strong acids and bases, for example, pyridinium salts, can also be used. Examples of strong acids include arylsulfonic acids such as p-toluenesulfonic acid and benzenesulfonic acid; perfluoroalkylsulfonic acids such as camphorsulfonic acid, trifluoromethanesulfonic acid, and nonafluorobutanesulfonic acid; and alkylsulfonic acids such as methanesulfonic acid, ethanesulfonic acid, and butanesulfonic acid. Examples of bases include pyridine; alkylpyridines such as 2,4,6-trimethylpyridine; N-alkylpyridines such as 2-chloro-N-methylpyridine; and halogenated N-alkylpyridines. Examples of imidosulfonates include naphthoyl imidosulfonate and phthalimidosulfonate, but are not limited thereto as long as they are compounds that generate acid when heated.

[0075] The photoacid generator used is one that generates a cationic polymerizable acid upon irradiation with ultraviolet light, and the reaction proceeds more rapidly when heat is applied. Examples of such photoacid generators include onium salts (diazonium salts, sulfonium salts, iodonium salts, selenium salts, pyridinium salts, ferrocenium salts, phosphonium salts, etc.) consisting of an anion component such as SbF6-, PF6-, BF4-, AsF6-, (CF5)4-, or PF4(CF2CF3)2-, and a cation component. These may be used alone or in combination of two or more. Specific examples include aromatic sulfonium salts, aromatic iodonium salts, aromatic phosphonium salts, and aromatic sulfoxonium salts.

[0076] [Method for producing crosslinking agent component (B)] When the crosslinking agent component (B) is an aliphatic or alicyclic polyisocyanate (b), it is obtained by reacting the above-mentioned diisocyanate (b1), polyol (b2), and polyol (b3). Hereinafter, polyol (b2) and polyol (b3) may be collectively referred to simply as polyol.

[0077] The polyol (b2) and the polyol (b3) can be used alone or as a mixture. When used as a mixture, they may be mixed before being reacted with the diisocyanate, or each polyol may be reacted alone with the diisocyanate to form a polyisocyanate, and then mixed. That is, examples of methods for producing polyisocyanate include a method of simultaneously reacting a diisocyanate with a polyol (b2) and a polyol (b3) to obtain a polyisocyanate; a method of mixing a reaction product of a diisocyanate with a polyol (b2) and a reaction product of a diisocyanate with a polyol (b3) to obtain a polyisocyanate; and a method of reacting a diisocyanate with a polyol (b2) or a polyol (b3) and then further reacting with the remaining polyol to obtain a polyisocyanate.

[0078] The amounts of polyol (b2) and polyol (b3) to be blended are preferably such that the mass ratio of polyol (b2) to polyol (b3) falls within the above range.

[0079] During the reaction, the molar ratio of isocyanate groups of the diisocyanate to hydroxyl groups of the polyol (b2) and polyol (b3) (molar ratio of isocyanate groups / hydroxyl groups) is preferably from 3 to 30, more preferably from 4 to 25, even more preferably from 5 to 22, and particularly preferably from 6 to 20. When the NCO / OH ratio is within the above range, the crosslinking agent component (B) can be synthesized without gelling, and the resulting optical resin sheet can have a lower elastic modulus, a higher elongation, and a higher breaking strength.

[0080] The reaction between polyol and diisocyanate is carried out as follows: The reaction temperature is usually from room temperature (about 23°C) to 200°C, and preferably from 60°C to 130°C. If the reaction temperature is above the lower limit, the reaction time is shorter, while if the reaction temperature is below the upper limit, an increase in the viscosity of the polyisocyanate due to undesirable side reactions can be more effectively avoided, and coloration of the resulting polyisocyanate can also be more effectively avoided.

[0081] The reaction may be carried out without a solvent or in any solvent inert to isocyanate groups. If necessary, a known catalyst may be used to promote the reaction between the isocyanate groups and the hydroxyl groups.

[0082] [Physical properties of crosslinker component (B)] The isocyanate group content (NCO group content) of the crosslinking agent component (B), in a state substantially free of solvents and diisocyanates, is preferably from 1 to 10% by mass, more preferably from 2 to 9% by mass, even more preferably from 2.5 to 8.5% by mass, and particularly preferably from 2.7 to 8.2% by mass, relative to the total mass of the crosslinking agent component (B). The NCO group content can be determined, for example, by reacting the isocyanate groups in the crosslinking agent component (B) with an excess of amine (dibutylamine, etc.) and back-titrating the remaining amine with an acid such as hydrochloric acid.

[0083] Only the above-mentioned crosslinking agent component (B) is applied to glass and stored for 168 hours in an environment of 23°C and 65% humidity. After that, the moisture in the film reacts with the polyisocyanate composition to form a cured film having a thickness of 40 μm, and the Konig hardness in an environment of 23°C is 60 or less, preferably 57 or less, more preferably 55 or less, and even more preferably 54 or less. Having a Konig hardness of not more than the above upper limit results in low hardness and excellent flexibility.

[0084] [Content of crosslinking agent component (B)] The content of the crosslinking agent component (B) is preferably 0.01 to 5.00 parts by mass, more preferably 0.03 to 4.00 parts by mass, even more preferably 0.05 to 3.50 parts by mass, and particularly preferably 0.07 to 3.00 parts by mass, relative to 100 parts by mass of the acrylic polymer (A). When the content of the crosslinking agent component (B) is within the above range, the optical resin sheet tends to have excellent curing properties, as well as excellent flex resistance, adhesive strength, and holding power. The content of the crosslinking agent component (B) can be calculated, for example, from the amount of the crosslinking agent component (B) used when producing the optical resin composition.

[0085] [Isocyanate group / Crosslinkable functional group] The molar ratio of the isocyanate groups of the crosslinking agent component (B) to the crosslinkable functional groups (particularly, hydroxyl groups) of the acrylic polymer (A) contained in the optical resin composition of this embodiment (the molar ratio of isocyanate groups / crosslinkable functional groups) is determined depending on the required physical properties of the optical resin sheet, but is usually 0.01 or more and 50 or less.

[0086] <Other ingredients> The optical resin composition of this embodiment may further contain 0.01 to 0.5 parts by mass of a silane coupling agent (C) relative to 100 parts by mass of the acrylic polymer (A). By containing the silane coupling agent (C) in an amount within the above numerical range, the optical resin composition of this embodiment can further improve the adhesive strength of the resulting optical resin sheet and further suppress lifting and peeling at the interface with the adherend upon heating and humidification.

[0087] Examples of the silane coupling agent (C) include, but are not limited to, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, ureidopropyltriethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidyloxypropyltrimethoxysilane, 3-glycidyloxypropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-isocyanatepropyltriethoxysilane, methyltriethoxysilane, and methyltrimethoxysilane.

[0088] The content of the silane coupling agent (C) is preferably 0.01 to 0.5 parts by mass, more preferably 0.05 to 0.4 parts by mass, per 100 parts by mass of the acrylic polymer (A).

[0089] The optical resin composition of this embodiment may further contain other additives. Other additives include, for example, curing catalysts, solvents, pigments (extender pigments, colored pigments, metallic pigments, etc.), tackifying resins, photopolymerization initiators, ultraviolet absorbers, light stabilizers, radical stabilizers, anti-yellowing agents that suppress discoloration during the baking process, coating surface conditioners, flow conditioners, pigment dispersants, antifoaming agents, thickeners, film-forming aids, etc.

[0090] The curing catalyst may be a basic compound or a Lewis acid compound. Examples of the basic compound include metal hydroxides, metal alkoxides, metal carboxylates, metal acetylacetinates, hydroxides of onium salts, onium carboxylates, halides of onium salts, metal salts of active methylene compounds, onium salts of active methylene compounds, aminosilanes, amines, phosphines, etc. The onium salt is preferably an ammonium salt, a phosphonium salt, or a sulfonium salt. Examples of the Lewis acid compound include organotin compounds, organozinc compounds, organotitanium compounds, and organozirconium compounds.

[0091] Examples of the solvent include 1-methylpyrrolidone, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, dipropylene glycol monomethyl ether, propylene glycol monomethyl ether, 3-methoxy-3-methyl-1-butanol, ethylene glycol diethyl ether, diethylene glycol diethyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dipropylene glycol dimethyl ether (DPDM), propylene glycol dimethyl ether, methyl ethyl ketone, and acetone. Examples of suitable solvents include methyl isobutyl ketone, propylene glycol monomethyl ether acetate, ethanol, methanol, isopropanol, 1-propanol, isobutanol, 1-butanol, tert-butanol, 2-ethylhexanol, cyclohexanol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, 1,4-butanediol, 1,3-butanediol, ethyl acetate, isopropyl acetate, butyl acetate, toluene, xylene, pentane, isopentane, hexane, isohexane, cyclohexane, solvent naphtha, and mineral spirits. These solvents may be used alone or in combination of two or more.

[0092] In addition, known pigments (extender pigments, colored pigments, metallic pigments, etc.), ultraviolet absorbers, light stabilizers, radical stabilizers, anti-yellowing agents that suppress coloring during the baking process, coating surface conditioners, flow conditioners, pigment dispersants, antifoaming agents, thickeners, and film-forming aids can be appropriately selected and used.

[0093] <Method of manufacturing optical resin composition> The optical resin composition can be produced by a conventionally known method, such as a melt-kneading method using a general mixer such as a Banbury mixer, a single-screw extruder, a twin-screw extruder, a co-kneader, or a multi-screw extruder, or a method in which the components are dissolved or dispersed and mixed, then coated onto a substrate film using a coater or the like, and the solvent is then removed by heating.

[0094] <Optical resin sheet> The optical resin sheet of this embodiment is obtained by curing the above-described optical resin composition with heat or light.

[0095] The optical resin sheet of this embodiment has good transparency, and is excellent in adhesive strength, holding power, and flex resistance.

[0096] The thickness of the optical resin sheet of the present embodiment can be appropriately determined depending on the application, but is preferably 1 μm or more and 1000 μm or less, more preferably 3 μm or more and 900 μm or less, even more preferably 5 μm or more and 800 μm or less, and particularly preferably 7 μm or more and 700 μm or less.

[0097] The optical resin sheet of this embodiment can be produced, for example, by applying the above-described optical resin composition to a substrate, drying it as necessary, and then curing it.

[0098] The substrate is not particularly limited, but examples thereof include paper such as fine paper, coated paper, cast-coated paper, thermal paper, and inkjet paper; fabrics such as woven fabric and nonwoven fabric; resin films such as polyvinyl chloride, synthetic paper, polyethylene terephthalate (PET), polypropylene, polyethylene, cellulose triacetate, cellulose diacetate, polystyrene, polycarbonate, nylon, polyvinyl alcohol, ethylene-vinyl acetate copolymer, and polyimide; porous resin films such as porous polypropylene film; vapor-deposited films in which aluminum or the like is vapor-deposited on PET, polyolefin, or the like; and metal foil. The substrate may have a release-treated surface.

[0099] Examples of methods for applying the optical resin composition to a substrate include methods using an applicator, a roll coater, a knife coater, a gravure coater, etc. When drying is performed after the application, examples include a heat drying method in which the obtained laminate is placed in a dryer or the like and dried at a temperature of 50°C to 150°C for 1 minute to 30 minutes. Other drying methods include natural drying, hot air drying, infrared drying, etc.

[0100] The heating temperature during curing can be 70°C or higher and 150°C or lower, 75°C or higher and 145°C or lower, or 80°C or higher and 140°C or lower.

[0101] The optical resin sheet of this embodiment is prepared by coating the optical resin composition on a polyethylene terephthalate film having a thickness of 25 μm, drying and curing the film at 125° C. for 3 minutes, and then storing the film in an environment of 23° C. and 50% RH for 7 days. This optical resin sheet has a thickness of 70 μm, a width of 20 mm, and a length of 100 mm and is provided with the polyethylene terephthalate film on one side. The sheet is then pressed back and forth with a 2 kg roller once, and cured at 23° C. for 30 minutes. After this, the 180-degree peel adhesive strength measured at 23° C. and a speed of 300 mm / min is preferably 2.0 N / 20 mm or more and 65 N / 20 mm or less, more preferably 4.0 N / 20 mm or more and 63 N / 20 mm or less, even more preferably 5.0 N / 20 mm or more and 61 N / 20 mm or less, and particularly preferably 6.0 N / 20 mm or more and 58 N / 20 mm or less. When the 180-degree peel adhesive strength is equal to or greater than the above lower limit, the adhesive strength is superior.

[0102] The optical resin sheet of this embodiment is prepared by coating the optical resin composition on a polyethylene terephthalate film having a thickness of 25 μm, drying the film at 125° C. for 3 minutes to cure the composition, and then storing the film in an environment of 23° C. and 50% RH for 7 days. The optical resin sheet has a thickness of 70 μm, a width of 25 mm, and a length of 130 mm and is provided with the polyethylene terephthalate film on one side. The optical resin sheet is then attached to an SUS304BA plate as an adherend so that the sheet overlaps within an area of ​​25 mm in the width direction and 25 mm in the length direction. The sheet is then pressed back and forth with a 2 kg roller, cured at 23° C. for 1 hour, and further cured at 40° C. for 30 minutes. After that, a 500 g weight is hung from the lower end of the optical resin sheet in an environment of 40° C. for 1 hour. When the sheet is then returned to an environment of 23° C., the amount of displacement of the optical resin sheet is preferably 2 (mm / hour) or less, more preferably 1 (mm / hour) or less, even more preferably 0.5 (mm / hour) or less, and particularly preferably 0.3 (mm / hour) or less. When the amount of displacement is equal to or less than the upper limit, the holding power (cohesion power) is superior. Furthermore, the lower limit of the amount of deviation is preferably as small as possible, and can be set to, for example, 0.0 (mm / hour).

[0103] The optical resin sheet of this embodiment is prepared by applying the optical resin composition to a 38 μm-thick release-treated polyethylene terephthalate film, drying and curing the film at 125° C. for 3 minutes, storing the film at 23° C. and 50% RH for 7 days, and peeling the resulting 70 μm-thick optical resin sheet from the release-treated polyethylene terephthalate film. The resulting sheet is attached to a glass plate with a haze value of 0.1% and measured with a haze meter to have a haze value of preferably 2.0% or less, more preferably 1.0% or less, even more preferably 0.9% or less, and particularly preferably 0.8% or less. Having a haze value equal to or less than the upper limit of the above range results in superior transparency. Furthermore, the lower limit of the haze value is preferably as small as possible, and can be set to, for example, 0.1%.

[0104] The optical resin sheet of this embodiment is prepared by coating the optical resin composition onto a 38 μm-thick release-treated polyethylene terephthalate film, drying it at 125°C for 3 minutes to cure it, and then storing it at 23°C and 50% RH for 7 days. The resulting 70 μm-thick optical resin sheet is then stored at 23°C and 50% RH for 7 days, wrapped in a mesh sheet, immersed in ethyl acetate at 23°C for 1 week, removed, and dried at 120°C for 2 hours. The gel fraction calculated by the method is preferably 40.0% to 99.9% by mass, more preferably 55.0% to 99.9% by mass, more preferably 58.0% to 99.9% by mass, and particularly preferably 62.0% to 99.9% by mass. Having a gel fraction equal to or greater than the lower limit above provides excellent curability, cohesion, and durability against humidity and heat. The gel fraction referred to here is the percentage of the mass of the optical resin sheet that has been immersed in ethyl acetate and then dried relative to the mass of the optical resin sheet before immersion in ethyl acetate.

[0105] The optical resin sheet of this embodiment is prepared by coating the optical resin composition onto a 38 μm-thick release-treated polyethylene terephthalate film, drying and curing for 3 minutes at 125° C., storing the film in an environment of 23° C. and 50% RH for 7 days, and peeling the film from the release-treated polyethylene terephthalate film to obtain an optical resin sheet with a thickness of 70 μm. The resulting film is laminated to a thickness of 210 μm, cut into a width of 10 mm and a length of 40 mm, and then set in a tensile tester with a chuck distance of 10 mm. A tensile test was carried out at a speed of 300 mm / min in an environment of 23° C., and the Young's modulus was 0.40 N / mm. 2 Preferably, it is 0.30 N / mm or less. 2 More preferably, it is 0.25 N / mm 2 More preferably, it is 0.20 N / mm or less. 2 When the Young's modulus is equal to or less than the upper limit, the flexibility, adhesive strength, and flex resistance are excellent. The lower limit of the Young's modulus is preferably as small as possible. 2 It can be 0.02N / mm 2 It can be said that:

[0106] As described above, the optical resin sheet of this embodiment has good transparency and excellent adhesive strength, holding power, and flex resistance, and is therefore suitable for use as, for example, an optical transparent adhesive sheet (OCA). [Example]

[0107] The present invention will be described below with reference to examples, but the present invention is not limited to the following examples.

[0108] [Physical Properties 1] (glass transition temperature Tg) The glass transition temperature of the acrylic polymer (A) was determined by evaporating the organic solvent and water from the acrylic polymer (A) solution under reduced pressure, vacuum-drying the resulting solution, and measuring the temperature using a differential scanning calorimetry (DSC) analyzer at a heating rate of 5°C / min.

[0109] [Physical Properties 2] (Number average molecular weight and weight average molecular weight) The number average molecular weight and weight average molecular weight are those measured by gel permeation chromatography (GPC) using the following equipment, using polystyrene standards.

[0110] (Measurement conditions) Equipment: Tosoh Corporation, HLC-802A Column: Tosoh Corporation, G1000HXL x 1 G2000HXL x 1 G3000HXL x 1 Carrier: Tetrahydrofuran Detection method: differential refractometer

[0111] [Physical Properties 3] (Isocyanate group content) First, 2 g to 3 g of the measurement sample was weighed out into a flask (Wg). Next, 20 mL of toluene was added to dissolve the measurement sample. Next, 20 mL of a 2 N toluene solution of di-n-butylamine was added, mixed, and left at room temperature for 15 minutes. Next, 70 mL of isopropyl alcohol was added and mixed. Next, this liquid was titrated with a 1 N hydrochloric acid solution (factor F) as an indicator. The obtained titration value was V2 mL. Next, the titration value obtained without the sample was V1 mL. Next, the isocyanate group content (NCO%) (mass%) of the crosslinker component (B) was calculated using the following formula.

[0112] "Isocyanate group content (mass%)" = (V1-V2) x F x 42 / (W x 1000) x 100

[0113] [Physical Properties 4] (average number of isocyanate functional groups) The average number of isocyanate functional groups (average NCO number) of the crosslinker component (B) was calculated by the following formula. In the formula, "Mn" means number average molecular weight, and the value measured in "Physical Properties 2" above was used. For "NCO %", the value calculated in "Physical Properties 3" above was used.

[0114] "Average number of isocyanate functional groups" = (Mn × NCO% × 0.01) / 42

[0115] [Preparation of cured film of crosslinker component (B)] Each crosslinking agent component (B) was applied onto a glass plate using an applicator, and after storing in an environment of 23°C and 65% humidity for 168 hours, a cured film having a thickness of 40 µm was obtained.

[0116] [Physical Properties 5] (Konig hardness) The Konig hardness (times) of each cured film was measured in an environment of 23°C using a Konig hardness tester (Pendulum hardness tester manufactured by BYK Gardner).

[0117] <Evaluation method> [Preparation of Optical Resin Sheet 1] Each optical resin composition was applied to a 25 μm thick polyethylene terephthalate (PET) film using an applicator so that the thickness after drying would be 70 μm, and then dried for 3 minutes at 125° C. Thereafter, the film was stored in an environment of 23° C. and 50% RH for 7 days to obtain an optical resin sheet 1 having a PET film on one side for measuring 180-degree peel adhesive strength and holding power.

[0118] [Preparation of optical resin sheet 2] Each optical resin composition was applied using an applicator to a 38 μm-thick release-treated PET film so that the thickness after drying would be 70 μm, and then dried at 125° C. for 3 minutes. The sheet was then stored in an environment of 23° C. and 50% RH for 7 days to obtain an optical resin sheet 2 having a release-treated PET film on one side for gel fraction measurement, haze measurement, and tensile testing. The release-treated PET film was peeled off and used for each evaluation.

[0119] [Rating 1] (180 degree peel adhesive strength) The optical resin sheet 1 obtained in the above "Preparation of optical resin sheet 1" was cut to a width of 20 mm and a length of 100 mm to obtain a test piece. Next, the test piece was attached to a SUS304BA plate as an adherend, and the test piece was pressed against the SUS304BA plate by rolling a 2 kg roller back and forth once. After curing for 30 minutes at 23°C, the 180-degree peel adhesive strength was measured using a tensile tester at a speed of 300 mm / min. Adhesion strength of 2.0 N / 20 mm or more was evaluated as good.

[0120] [Rating 2] (holding force) The optical resin sheet 1 obtained in the above "Preparation of Optical Resin Sheet 1" was cut to a width of 25 mm and a length of 130 mm to obtain a test piece. Next, the test piece was attached to a SUS304BA plate (adherend) so that the 25 mm wide and 25 mm long areas overlapped, and the test piece was pressed back and forth with a 2 kg roller once, cured at 23°C for 30 minutes, and then cured at 40°C for an additional hour. Thereafter, a 500 g weight was hung from the bottom end of the test piece in a 40°C environment for 1 hour, and the amount of displacement (mm / hour) of the test piece when returned to a 23°C environment was measured. The smaller the amount of displacement, the better the holding power (cohesion), and a displacement of 0.5 (mm / hour) or less was evaluated as having good holding power (cohesion).

[0121] [Rating 3] (Hayes) The optical resin sheet 2 obtained in the above "Preparation of optical resin sheet 2" was attached to a glass having a haze value of 0.1%, and the release-treated polyethylene terephthalate film was peeled off to prepare a test piece. Next, the haze of the test piece was measured using a haze meter (HMG-2DP) manufactured by Suga Test Instruments, with the side of the test piece from which the release-treated polyethylene terephthalate film had been peeled placed under a light source. A haze value of 1.0% or less was evaluated as having good transparency.

[0122] [Rating 4] (gel fraction) Approximately 0.1 g to 0.2 g of the optical resin sheet 2 obtained in the above "Preparation of optical resin sheet 2" from which the release-treated PET film had been peeled off was sampled, wrapped in a mesh sheet, immersed in ethyl acetate for one week, and then dried for two hours at 120° C. Next, the gel fraction (% by mass) was calculated using the following formula. Those with a gel fraction of 60% by mass or more were evaluated as having good curability.

[0123] (gel fraction) = (Sample mass after adding to ethyl acetate and drying) / (Sample mass before adding to ethyl acetate) × 100

[0124] [Rating 5] (Tensile test: Young's modulus, elongation, maximum stress, and strain energy index) The optical resin sheet 1 obtained in the above "Preparation of Optical Resin Sheet 1" from which the release-treated PET film had been peeled was laminated to a thickness of 210 μm and cut to a width of 10 mm and a length of 40 mm. The sheet was then set in a tensile tester with a chuck distance of 10 mm, and the Young's modulus, elongation, and maximum stress were measured at a speed of 300 mm / min using the tensile tester in an environment of 23°C. The strain energy index was then calculated from the obtained elongation and maximum stress using the following formula. Young's modulus: 0.25N / mm 2 Those having a strain energy index of 2.00 or more were evaluated as having good flex resistance.

[0125] (Strain energy index) = {(elongation rate (%)) / 100) × (maximum stress)} × 1 / 2

[0126] <Synthesis of acrylic polymer (A)> [Synthesis Example 1-1] (Synthesis of acrylic polymer A-1) A four-neck flask equipped with a stirrer, thermometer, nitrogen gas inlet tube, and condenser was charged with 97 parts by mass of 2-ethylhexyl acrylate (2EHA) and 3 parts by mass of 4-hydroxybutyl acrylate (4HBA), and 140 parts by mass of ethyl acetate as a solvent. Next, while stirring under a nitrogen gas atmosphere, 0.15 parts by mass of 2,2'-azobisisobutyronitrile (AIBN) was charged as a polymerization initiator, and the reaction was carried out at 63°C for 8 hours. After the reaction, the mixture was cooled to obtain acrylic polymer A-1 with a solids concentration of 42.0% by mass.

[0127] [Synthesis Examples 1-2 to 1-14] (Synthesis of Acrylic Polymers A-1 to A-14) Each acrylic polymer was synthesized in the same manner as in Synthesis Example 1-1, except that the blending ratio of each monomer was as shown in Tables 1 and 2.

[0128] The compositions and physical properties of the synthesized acrylic polymers are shown in the following Tables 1 and 2. In Tables 1 and 2, the abbreviations for the monomers represent the following compounds.

[0129] (Crosslinkable Functional Group-Containing Monomer (a1)) 4HBA: 4-hydroxybutyl acrylate HEA: Hydroxyethyl acrylate AA: acrylic acid

[0130] ((Meth)acrylic acid ester monomer (a2)) 2EHA: 2-ethylhexyl acrylate MEA: methoxyethyl acrylate iOA: isooctyl acrylate iNA: Isononyl acrylate EA: Ethyl acrylate MA: methyl acrylate BezA: Benzyl acrylate BA: butyl acrylate PEA: Phenoxyethyl acrylate

[0131] (Other polymerizable monomers (a3)) NVP: N-vinyl-2-pyrrolidone

[0132] [Table 1]

[0133] [Table 2]

[0134] <Synthesis of Crosslinker Component (B)> [Synthesis Example 2-1] (Synthesis of Polyisocyanate Component B-1) A four-neck flask equipped with a thermometer, a stirring blade, and a reflux condenser was charged with 100 parts by mass of HDI under a nitrogen stream, and 4.7 parts by mass of a bifunctional polycaprolactone polyol (manufactured by Daicel Corporation, trade name "PLACCEL 220", number average molecular weight 2000) (hereinafter, sometimes referred to as "polyol b2-1" or simply "b2-1") and 33 parts by mass of a trifunctional polycaprolactone polyol (manufactured by Daicel Corporation, trade name "PLACCEL 308", number average molecular weight 850) (hereinafter, sometimes referred to as "polyol b3-1" or simply "b3-1") (an amount such that the molar ratio of the isocyanate groups of HDI to the hydroxyl groups of polyol b2-1 and polyol b3-1 was 10.0) was added. The temperature inside the reactor was maintained at 90°C for 110 minutes or more while stirring, and the reaction was terminated when the yield reached 40% by mass. The reaction liquid was filtered, and then unreacted HDI was removed using a thin-film distillation apparatus to obtain polyisocyanate component B-1.

[0135] [Synthesis Examples 2-2 to 2-6] (Synthesis of Polyisocyanate Components B-2 to B-6) Each polyisocyanate component was synthesized in the same manner as in Synthesis Example 2-1, except that the types and blending ratios of raw materials were as shown in Table 3.

[0136] [Synthesis Example 2-7] (Synthesis of Polyisocyanate Component B-7) A four-neck flask equipped with a thermometer, a stirring blade, and a reflux condenser was charged with 100 parts by mass of HDI and 8.9 parts by mass of trimethylolpropane (hereinafter sometimes referred to as "polyol b3-3" or simply "b3-3") under a nitrogen stream, and the temperature inside the reactor was maintained at 75°C for 5 hours with stirring to carry out a urethanization reaction. The reaction liquid was filtered, and then unreacted HDI was removed using a thin-film evaporator to obtain an isocyanurate-type polyisocyanate (hereinafter sometimes referred to as "polyisocyanate component B-7").

[0137] [Synthesis Example 2-8] (Synthesis of Polyisocyanate Component B-8) A four-neck flask equipped with a thermometer, stirring blade, and reflux condenser was charged with 100 parts by mass of HDI under a nitrogen stream. The temperature inside the reactor was maintained at 62°C with stirring, and 0.095 parts by mass of trimethylbenzylammonium hydroxide was added and reacted for 4 hours. When the conversion rate reached 38% by mass, 0.02 parts by mass of phosphoric acid was added to terminate the reaction. The reaction solution was filtered, and unreacted HDI was removed using a thin-film evaporator to obtain an isocyanurate-type polyisocyanate (hereinafter sometimes referred to as "polyisocyanate component B-8").

[0138] [Synthesis Example 2-9] (Synthesis of Polyisocyanate Component B-9) A four-neck flask equipped with a thermometer, stirring blade, and reflux condenser was charged with 100 parts by mass of HDI under a nitrogen stream, and 30 parts by mass of polyol b3-1 (an amount such that the molar ratio of isocyanate groups in HDI to hydroxyl groups in polyol b3-1 was 11.4) was added. While stirring, the temperature inside the reactor was maintained at 95°C for 80 minutes. The reaction was stopped when the yield reached 39% by mass. After filtering the reaction solution, unreacted HDI was removed using a thin-film distillation apparatus to obtain polyisocyanate component B-9.

[0139] [Synthesis Example 2-10] (Synthesis of Polyisocyanate Component B-10) A four-neck flask equipped with a thermometer, stirring blade, and reflux condenser was charged with 100 parts by mass of HDI under a nitrogen stream. 22.0 parts by mass of a trifunctional polycaprolactone polyol (hereinafter sometimes referred to as "polyester polyol b3-3") (manufactured by Daicel Corporation, trade name "Placcel 305", number average molecular weight 550) (an amount sufficient to achieve a molar ratio of HDI isocyanate groups to polyol hydroxyl groups of 9.9) were added. The temperature inside the reactor was maintained at 90°C for 75 minutes while stirring. The reaction was terminated when the yield reached 33% by mass. The reaction solution was filtered, and unreacted HDI was removed using a thin-film distillation apparatus to obtain polyisocyanate component B-10.

[0140] The composition and physical properties of each synthesized polyisocyanate component are shown in Table 3. In Table 3, the polyols are the following compounds.

[0141] (Polyol (b2)) b2-1: Difunctional polycaprolactone polyol, manufactured by Daicel Corporation, trade name "Placcel 220", number average molecular weight 2000

[0142] (Polyol (b2')) b2'-1: Polyether polyol, manufactured by Asahi Glass Co., Ltd., trade name "Excenol 2020", number average molecular weight 2000

[0143] (Polyol (b3)) b3-1: Trifunctional polycaprolactone polyol, manufactured by Daicel Corporation, trade name "Placcel 308", number average molecular weight 850 b3-2: Trifunctional polycaprolactone polyol, manufactured by Daicel Corporation, trade name "Placcel 312", number average molecular weight 1250 b3-3: Trifunctional polycaprolactone polyol, manufactured by Daicel Corporation, trade name "Placcel 305", number average molecular weight 550

[0144] (Polyol (b3')) b3'-1: Trimethylolpropane (TMP)

[0145] [Table 3]

[0146] <Production of Optical Resin Composition> [Example 1] (Production of Optical Resin Composition O-a1) To 100 parts by mass of acrylic polymer A-1, 0.5 parts by mass of polyisocyanate component B-1, 0.1 parts by mass of silane coupling agent (3-glycidoxypropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBM-403"), and ethyl acetate were added to obtain optical resin composition O-a1 with a solid content of 30% by mass.

[0147] [Examples 2 to 14 and Comparative Examples 1 to 5] (Production of Optical Resin Compositions O-a2 to O-a14 and O-b1 to O-b5) Each optical resin composition was produced in the same manner as in Example 1, except that the types and blending ratios of the acrylic polymer (A) and the crosslinking agent component (B) were as shown in Tables 4 to 6.

[0148] Tables 4 to 6 show the composition and evaluation results of each optical resin composition.

[0149] [Table 4]

[0150] [Table 5]

[0151] [Table 6]

[0152] As can be seen from Tables 4 to 6, the optical resin sheets prepared using the optical resin compositions O-a1 to O-a14 (Examples 1 to 14) each containing an acrylic polymer (A) having a glass transition temperature Tg of -69.7°C or higher and -58.0°C or lower, which is obtained by copolymerizing a crosslinkable functional group-containing monomer with a (meth)acrylic acid ester monomer having a carbon number at the ester group terminal within a specific numerical range, and an aliphatic polyisocyanate having a weight average molecular weight of 4,180 or higher and 32,700 or lower and an average number of isocyanate groups of 3.8 or higher and 5.0 or lower, as the crosslinker component (B), had good transparency and were excellent in adhesive strength, holding power, and flex resistance.

[0153] On the other hand, optical resin sheets using optical resin compositions O-b1, O-b3, O-b4 and O-b5 (Comparative Examples 1, 3, 4 and 5), which contain 0.5 parts by mass each of polyisocyanate components B-7 to B-9 having a weight-average molecular weight of less than 1,400 as crosslinker components (B) per 100 parts by mass of acrylic polymer (A), had good transparency, holding power and adhesive strength, but poor flex resistance. In addition, an optical resin sheet using an optical resin composition O-b2 (Comparative Example 2) containing 0.05 parts by mass of a polyisocyanate component B-7 having a weight-average molecular weight of less than 1,400 as a crosslinking agent component (B) per 100 parts by mass of an acrylic polymer (A) had good transparency and adhesive strength, but poor holding power and bending resistance. [Industrial Applicability]

[0154] According to the optical resin composition of this embodiment, it is possible to provide an optical resin composition that has excellent adhesive strength, holding power, and flex resistance while maintaining good transparency when made into an optical resin sheet. The optical resin sheet of the above aspect is obtained by curing the optical resin composition, and has good transparency and excellent adhesive strength, holding power, and flex resistance.

Claims

1. An optical resin composition comprising an acrylic polymer (A) and a crosslinking agent component (B), the acrylic polymer (A) is obtained by copolymerizing a crosslinkable functional group-containing monomer and a (meth)acrylic acid ester monomer having an ester group terminal with 1 to 18 carbon atoms, the glass transition temperature Tg of the acrylic polymer (A) is −10.0° C. or lower, the crosslinking agent component (B) contains an aliphatic or alicyclic polyisocyanate having a weight average molecular weight of 2,100 or more and 200,000 or less, the aliphatic or alicyclic polyisocyanate is a polyisocyanate derived from at least one diisocyanate (b1) selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates, a bifunctional polyol (b2) having a number average molecular weight of 1,500 or more, and a tri- or higher functional polyol (b3) having a number average molecular weight of 500 or more; a molar ratio NCO / OH of the isocyanate groups of the diisocyanate (b1) to the total molar amount of hydroxyl groups of the polyol (b2) and the polyol (b3) is 3 or more and 30 or less; Optical resin composition.

2. 2. The optical resin composition according to claim 1, wherein the average number of isocyanate groups in the crosslinking agent component (B) is 2.0 or more and 6.5 or less.

3. 3. The optical resin composition according to claim 1, wherein the content of the crosslinking agent component (B) is 0.01 parts by mass or more and 5.0 parts by mass or less relative to 100 parts by mass of the acrylic polymer (A).

4. The weight average molecular weight of the acrylic polymer (A) is 5.0 × 10 ５ Above 5.0 x 10 ６ The optical resin composition according to any one of claims 1 to 3, wherein:

5. 5. The optical resin composition according to claim 1, wherein the crosslinkable functional group is at least one selected from the group consisting of a hydroxyl group, an epoxy group, a carboxyl group, and a vinyl group.

6. 6. The optical resin composition according to claim 1, wherein the content of the structural units derived from the (meth)acrylic acid ester monomer is 0.01% by mass or more and 99.99% by mass or less, based on the total mass of the acrylic polymer (A).

7. a mass ratio (b3) / (b2) of the polyol (b3) to the polyol (b2) is 0.1 / 99.9 or more and 99.9 / 0.1 or less, and With respect to 100 parts by mass of the diisocyanate (b1), the content of the polyol (b2) is 0.1 parts by mass or more and 250 parts by mass or less, The optical resin composition according to any one of claims 1 to 6, wherein the content of the polyol (b3) is 0.1 parts by mass or more and 190 parts by mass or less.

8. The optical resin composition according to any one of claims 1 to 7, wherein the polyol (b2) and the polyol (b3) are one or more polyols selected from the group consisting of polyester polyols, polyether polyols, epoxy polyols, polyolefin polyols, and polycarbonate polyols.

9. 9. The optical resin composition according to claim 1, wherein the crosslinking agent component (B) has an isocyanate group content of 1% by mass or more and 10% by mass or less.

10. The optical resin composition according to any one of claims 1 to 9, further comprising 0.01 parts by mass or more and 0.5 parts by mass or less of a silane coupling agent (C) relative to 100 parts by mass of the acrylic polymer (A).

11. The optical resin composition according to any one of claims 1 to 10, wherein the crosslinking agent component (B) comprises at least one selected from the group consisting of an isocyanate compound other than the aliphatic or alicyclic polyisocyanate, a carbodiimide compound, an oxazoline compound, a polyfunctional acrylic acid ester monomer, a peroxide, a titanium coupling agent, a zirconium compound, a metal aluminum chelate, a hydrazide compound, an epoxy-based crosslinking agent, a thermal acid generator, and a photoacid generator.

12. The optical resin composition according to any one of claims 1 to 11, wherein the crosslinking agent component (B) is applied to a glass surface, and the cured film formed has a thickness of 40 µm and a Konig hardness of 60 times or less in a 23°C environment after storage for 168 hours in a 23°C and 65% humidity environment.

13. An optical resin sheet obtained by curing the optical resin composition according to any one of claims 1 to 12 with heat or light.

14. The optical resin sheet according to claim 13, wherein the optical resin sheet has a thickness of 1 μm or more and 1000 μm or less.

15. 15. The optical resin sheet according to claim 13 or 14, wherein the optical resin composition is applied to a polyethylene terephthalate film having a thickness of 25 μm, dried at 125° C. for 3 minutes to cure the composition, and then stored in an environment of 23° C. and 50% RH for 7 days. The optical resin sheet has a thickness of 70 μm, a width of 20 mm, and a length of 100 mm, and the polyethylene terephthalate film is provided on one side of the optical resin sheet. The optical resin sheet is then pressed back and forth once with a 2 kg roller, and aged at 23° C. for 30 minutes. After this, the 180-degree peel adhesive strength measured at 23° C. and a speed of 300 mm / min is 2.0 N / 20 mm or more and 65 N / 20 mm or less.

16. The optical resin sheet according to any one of claims 13 to 15, wherein the optical resin composition is applied onto a polyethylene terephthalate film having a thickness of 25 μm, dried at 125°C for 3 minutes to be cured, and then stored in an environment of 23°C and 50% RH for 7 days, and the optical resin sheet has a thickness of 70 μm, a width of 25 mm, and a length of 130 mm and is provided with the polyethylene terephthalate film on one side thereof, and is attached to an SUS304BA plate as an adherend so that an overlapping range of 25 mm in width and 25 mm in length is achieved. The optical resin sheet is then pressed back and forth once with a 2 kg roller, aged at 23°C for 1 hour, and aged at 40°C for a further 30 minutes. After that, a 500 g weight is hung from the lower end of the optical resin sheet in an environment of 40°C for 1 hour, and then returned to an environment of 23°C, and the amount of displacement of the optical resin sheet is 2 mm / hour or less.

17. The optical resin sheet according to any one of claims 13 to 16, wherein the optical resin composition is applied to a release-treated polyethylene terephthalate film having a thickness of 38 µm, dried at 125°C for 3 minutes to cure, and then stored in an environment of 23°C and 50% RH for 7 days. The optical resin sheet is peeled off from the release-treated polyethylene terephthalate film to obtain a 70 µm-thick optical resin sheet. The optical resin sheet is attached to glass having a haze value of 0.1%, and the haze value measured with a haze meter is 2.0% or less.

18. The optical resin sheet according to any one of claims 13 to 17, wherein the optical resin composition is applied to a release-treated polyethylene terephthalate film having a thickness of 38 µm, dried at 125°C for 3 minutes to cure, and then stored in an environment of 23°C and 50% RH for 7 days. The optical resin sheet is peeled from the release-treated polyethylene terephthalate film to obtain an optical resin sheet having a thickness of 70 µm. The optical resin sheet is then stored in an environment of 23°C and 50% RH for 7 days, wrapped in a mesh sheet, immersed in ethyl acetate at 23°C for 1 week, removed, and dried at 120°C for 2 hours. The gel fraction calculated by the above calculation is 40.0 mass% or more and 99.9 mass% or less.

19. The optical resin composition was coated on a 38 μm thick release-treated polyethylene terephthalate film, dried at 125° C. for 3 minutes to cure, and then stored in a 23° C., 50% RH environment for 7 days. The optical resin sheet obtained by peeling it from the release-treated polyethylene terephthalate film to a thickness of 70 μm was laminated to a thickness of 210 μm, cut to a width of 10 mm and a length of 40 mm, and then set in a tensile tester so that the chuck distance was 10 mm. A tensile test was carried out in a 23° C. environment at a speed of 300 mm / min, and the Young's modulus was 0.40 N / mm. ２ The optical resin sheet according to any one of claims 13 to 18, wherein:

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