Optical pressure-sensitive adhesive composition

Abstract

To provide an optical adhesive composition that achieves heating reworkability to enable an adhesive layer to be easily removed from a component such as cover glass at a temperature higher than the service temperature of an image display device.SOLUTION: An optical adhesive composition gives a release force X of 4.0 N / 20 mm or less, where the release force X is a release force determined by puling a film at a temperature of 100°C, a release angle of 180 degrees, and a tensile rate of 50 mm / min, the film bonded to a glass plate through an adhesive layer formed from the optical adhesive composition.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an optical pressure-sensitive adhesive composition. [Background technology]

[0002] Conventionally, in image display panels, in order to prevent a decrease in visibility due to refraction or reflection of light and a lack of strength due to fixation only to a housing, a pressure-sensitive adhesive layer has been filled between the image display panel and a cover glass, a film sensor, etc. As a technical document relating to such pressure-sensitive adhesives, for example, Patent Document 1 discloses an optical pressure-sensitive adhesive.

[0003] For image display devices that have been judged to be defective due to the presence of foreign matter (microgel, etc.) in the adhesive layer, the cover glass, etc. is separated, and the defect-free image display panel is recovered and reused. As a method for separating the cover glass, for example, a method is used in which a metal wire is slid into the adhesive layer to separate the image display panel from the adhesive layer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2020-023679 Summary of the Invention [Problem to be solved by the invention]

[0005] Recently, there has been an increasing demand for image display devices (such as car navigation systems and rearview monitors) that use organic EL display panels and are larger, curved, multi-display, or irregularly shaped, and as a result, cover glass and other parts are becoming larger, more complex, and more expensive. Therefore, when an image display device is judged to be defective, it is strongly desired that the cover glass and other parts can also be recovered and reused.

[0006] However, with the method of sliding a metal wire to separate the adhesive layer as described above, it is difficult to separate large and complex cover glass from an organic EL display panel without damaging it.

[0007] On the other hand, organic EL display panels formed on polyimide substrates are flexible, unlike liquid crystal display panels formed on glass substrates. Therefore, it is possible to peel off the cover glass, etc. from the adhesive layer by heating the panel to a temperature higher than the operating temperature to reduce the adhesive strength of the adhesive layer to the cover glass, etc., and then bending the adhesive layer together with the organic EL display panel, without cutting off the adhesive layer.

[0008] However, to prevent damage or deformation to the image display panel or cover glass during separation and recovery, the adhesive force (peel force) must be kept low. However, it is not easy to achieve such a low peel force while still maintaining high adhesive reliability when the image display device is in use.

[0009] The present invention was conceived under these circumstances, and an object of the present invention is to provide an optical pressure-sensitive adhesive composition that achieves heat reworkability, allowing the pressure-sensitive adhesive layer to be easily peeled from a cover glass or the like at temperatures higher than those during use of an image display device. [Means for solving the problem]

[0010] As a result of intensive research to achieve the above object, the present inventors have found that the use of an optical pressure-sensitive adhesive composition having a specific peel strength can improve thermal reworkability. The present invention has been completed based on these findings.

[0011] That is, the present invention provides an optical pressure-sensitive adhesive composition having a peel strength X of 4.0 N / 20 mm or less. Peel strength X: Peel strength when a film attached to a glass plate via an adhesive layer formed from the adhesive composition is pulled at 100°C, a peel angle of 180°, and a pulling rate of 50 mm / min.

[0012] In the optical pressure-sensitive adhesive composition, the ratio (Y / X) of the peel strength Y to the peel strength X is preferably 15.0 or less. Peel strength Y: Peel strength when a film attached to a glass plate via an adhesive layer formed from the adhesive composition is pulled at 25°C at a peel angle of 180° and a pulling rate of 50 mm / min

[0013] The optical pressure-sensitive adhesive composition has a storage modulus of 0.1×10 at 100°C. 5 It is preferable that the viscosity is 1 Pa or more.

[0014] The optical pressure-sensitive adhesive composition preferably has a moisture content of 0.6 to 5.0 wt % when stored at 23° C. and 50% RH for 24 hours.

[0015] For the above optical pressure-sensitive adhesive composition, the pressure-sensitive adhesive layer was laminated on both sides with glass plates, and the chromaticity b * It is preferable that the change in is 1.0 or less.

[0016] The present invention also provides a pressure-sensitive adhesive layer formed from the optical pressure-sensitive adhesive composition.

[0017] The pressure-sensitive adhesive layer is preferably used when the adherend is a film substrate and / or an organic EL display panel. [Effects of the Invention]

[0018] The optical pressure-sensitive adhesive composition of the present invention has the above-mentioned configuration and therefore has excellent heat reworkability, allowing the pressure-sensitive adhesive layer to be easily peeled off from a cover glass, etc. at high temperatures. Therefore, by using the optical pressure-sensitive adhesive composition of the present invention, it is possible to separate large and complex cover glasses, etc. and organic EL display panels without damaging or deforming them. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an image display device. [Figure 2]FIG. 2 is a schematic cross-sectional view showing the image display device during separation and recovery. DETAILED DESCRIPTION OF THE INVENTION

[0020] 1 is a schematic cross-sectional view showing an image display device 10. The image display device 10 has a pressure-sensitive adhesive layer 2 formed from the optical pressure-sensitive adhesive composition of the present invention. The pressure-sensitive adhesive layer 2 is disposed between a cover glass 1 and an organic EL display panel 3, and these are bonded together.

[0021] 2 is a schematic cross-sectional view showing the image display device 11 during separation and recovery. The organic EL display panel 3 is flexible and can bend together with the adhesive layer 2. Therefore, the adhesive layer 2 loses its adhesive strength at a temperature higher than that during use of the image display device, and is easily peeled off from the cover glass 1 as it bends.

[0022] [Optical pressure-sensitive adhesive composition] The optical pressure-sensitive adhesive composition of the present invention has a peel force X of 4.0 N / 20 mm or less when a film attached to a glass plate via the pressure-sensitive adhesive layer is pulled at 100°C at a peel angle of 180° and a pulling rate of 50 mm / min.

[0023] The configuration in which the peel force X is 4.0 N / 20 mm or less is preferable in that the pressure-sensitive adhesive layer formed from the optical pressure-sensitive adhesive composition of the present invention can achieve excellent thermal reworkability, allowing the pressure-sensitive adhesive layer to be easily peeled from glass during separation and recovery.

[0024] The peel force X is not particularly limited, but is preferably 3.6 N / 20 mm or less, more preferably 3.3 N / 20 mm or less. The lower limit of the peel force X is not particularly limited, but is usually 0.5 N / 20 mm, 1.0 N / 20 mm, or 1.5 N / 20 mm. If the lower limit of the peel force X is 0.5 N / 20 mm, reworkability at high temperatures is improved.

[0025] The temperature at which separation from the cover glass etc. is performed is not particularly limited, but considering that in-vehicle displays etc. may be exposed to high temperatures of around 80°C in the summer and the adhesive layer is required to have durability exceeding 80°C, and that exposure to excessively high temperatures during separation and recovery is likely to cause deterioration of the organic EL display panel, a temperature of around 100°C is preferable. The temperature condition of 100°C for the peel force X above was determined to reflect this.

[0026] In the optical pressure-sensitive adhesive composition of the present invention, the ratio (Y / X) of the peel force Y to the peel force X is preferably 15.0 or less, where X is the peel force when a film attached to a glass plate via the pressure-sensitive adhesive layer is pulled at 25°C at a peel angle of 180° and a pulling rate of 50 mm / min.

[0027] The ratio (Y / X) of 15.0 or less is preferable in that the pressure-sensitive adhesive layer formed from the optical pressure-sensitive adhesive composition of the present invention can achieve both heat reworkability and durability.

[0028] The ratio (Y / X) is not particularly limited, but is more preferably 13.0 or less, and even more preferably 11.0 or less. The lower limit of the ratio (Y / X) is not particularly limited, and may be, for example, 1.0, 1.5, or 2.0. When the lower limit of the ratio (Y / X) is 0.5 N / 20 mm, sufficient durability can be maintained under reliability conditions while ensuring thermal reworkability.

[0029] The peel force Y is not particularly limited, but is preferably 20.0 N / 20 mm or less, more preferably 18.0 N / 20 mm or less, and even more preferably 16.0 N / 20 mm or less. The lower limit of the peel force Y is not particularly limited, and may be, for example, 2.0 N / 20 mm, 3.0 N / 20 mm, or 4.0 N / 20 mm. A peel force Y of 20.0 N / 20 mm or less is effective in improving reworkability, and a lower limit of 2.0 N / 20 mm can reliably suppress peeling.

[0030] The peel force (peel force X, ratio (Y / X), peel force Y) can be adjusted to a value within a preferred range by, for example, appropriately adjusting the content of units derived from the following polar group-containing monomers (hydroxyl group-containing monomers, nitrogen-containing group-containing monomers, etc.) in the following acrylic polymer of the following acrylic pressure-sensitive adhesive composition, thereby adjusting the adhesive force and the degree of water release during separation and recovery.

[0031] The optical pressure-sensitive adhesive composition of the present invention has a storage modulus at 100°C (G'100) of 0.3 × 10 5 It is preferable that the tensile strength is 1 Pa or more.

[0032] The storage modulus (G'100) is 0.1 x 10 5 The constitution of having a surface tension of 100 Pa or more is preferable in that the pressure-sensitive adhesive layer formed from the optical pressure-sensitive adhesive composition of the present invention is less likely to leave adhesive residue on glass when separated and recovered.

[0033] The storage modulus (G'100) is not particularly limited, but is preferably 0.2 x 10 5 Pa or more, more preferably 0.3 × 10 5 The upper limit of the storage modulus (G'100) is, for example, 2.5 × 10 5 Pa, and may be 2.0 x 10 5 Pa or 1.5 x 10 5 The upper limit of the storage modulus (G'100) may be 2.5 × 10 5 If the temperature is 0.1 Pa, the material becomes flexible and easy to handle during rework at high temperatures.

[0034] The storage modulus (G'25) of the optical pressure-sensitive adhesive composition at 25°C is not particularly limited, but is preferably 1.0 x 10 5 Pa or more, preferably 1.3 × 10 5 Pa or more, more preferably 1.5 × 10 5 The upper limit of the storage modulus (G'25) is, for example, 4.0 × 10 5 Pa, 3.5 x 10 5 Pa or 3.0 x 10 5The storage modulus (G'25) may be 1.0×10 Pa. 5 When the viscosity is 4.0×10 Pa or more, the handling property is improved. 5 When the thickness is 0.05 Pa, the level difference absorbency during use tends to be improved.

[0035] The storage modulus can be determined by dynamic viscoelasticity measurement using, for example, a dynamic viscoelasticity measurement device (Advanced Rheometric Expansion System (ARES), manufactured by Rheometric Scientific).

[0036] The storage modulus can be adjusted to a value within a preferred range by, for example, appropriately adjusting the contents of units derived from the following (meth)acrylic acid alkyl ester and the following alicyclic monomer, the weight average molecular weight, and the content of the crosslinking agent and / or the polyfunctional monomer in the following acrylic polymer of the following acrylic pressure-sensitive adhesive composition.

[0037] The optical pressure-sensitive adhesive composition of the present application preferably has a moisture content of 0.6 to 5.0 wt %, more preferably 0.7 to 3.5 wt %, and even more preferably 0.8 to 2.0 wt % when stored for 24 hours at 23°C and 50% RH. If the moisture content is 0.6 wt % or more, moisture is released at the interface with the glass when heated to a high temperature during separation and recovery, making the peel strength more likely to decrease, while if the moisture content is 5.0 wt % or less, condensation is less likely to occur.

[0038] The moisture content can be determined by a coulometric titration moisture measurement method using, for example, a coulometric titration moisture measuring device "CA-06" manufactured by Mitsubishi Chemical Corporation and a thermal vaporization device "VA-06" manufactured by Mitsubishi Chemical Corporation, or by measuring the weight before and after storage and subtracting the weight before storage from the weight after storage.

[0039] The moisture content can be adjusted to a value within a preferred range, for example, by appropriately adjusting the content of units derived from the following polar group-containing monomers (hydroxyl group-containing monomers, nitrogen atom-containing group-containing monomers, etc.) in the following acrylic polymer of the following acrylic pressure-sensitive adhesive composition.

[0040] The optical pressure-sensitive adhesive composition of the present invention has a chromaticity of 0.01g when an adhesive layer having glass plates attached to both sides is stored at 100°C for 1000 hours. * The change in chromaticity b is preferably 1.0 or less, more preferably 0.8 or less, and even more preferably 0.7 or less. * When the change in chromaticity b is 0.7 or less, the change in hue is small even when exposed to high temperatures during separation and recovery, which is preferable in that it indicates excellent durability of the adhesive layer. * The lower limit of the change in is usually 0.

[0041] In addition, the above chromaticity b * The amount of change in chromaticity b of the pressure-sensitive adhesive layer before and after storage was measured using, for example, a spectrophotometer "U-4100" manufactured by Hitachi High-Tech Corporation. * Measure the chromaticity b after storage. * From the value of chromaticity b before saving * It can be obtained by subtracting the value of

[0042] As described above, the peel strength, storage modulus and moisture content can be adjusted by adjusting the type of resin constituting the optical pressure-sensitive adhesive composition, the monomer composition, the degree of crosslinking and the like.

[0043] The term "optical" in the optical pressure-sensitive adhesive composition means that the composition is used for optical applications. More specifically, the term means that the composition is used for the manufacture of products (optical products) that use optical members. Examples of optical products include image display devices, input devices such as touch panels, and the like. Among these, self-luminous display devices such as organic electroluminescence (EL) display devices are preferred.

[0044] Examples of the optical pressure-sensitive adhesive composition include an acrylic pressure-sensitive adhesive composition, a rubber pressure-sensitive adhesive composition, a silicone pressure-sensitive adhesive composition, a polyester pressure-sensitive adhesive composition, a polyurethane pressure-sensitive adhesive composition, a polyamide pressure-sensitive adhesive composition, an epoxy pressure-sensitive adhesive composition, a vinyl alkyl ether pressure-sensitive adhesive composition, a fluorine-based pressure-sensitive adhesive composition, etc. The pressure-sensitive adhesive composition may be used alone or in combination of two or more types.

[0045] Among these, it is preferable to include an acrylic pressure-sensitive adhesive composition, since this has excellent adhesion and tends to reduce the peeling force during separation and recovery.

[0046] The acrylic pressure-sensitive adhesive composition preferably contains an acrylic polymer as a polymer component. The term "(meth)acrylic" refers to "acrylic" and / or "methacrylic" (either one or both of "acrylic" and "methacrylic"), and the same applies hereinafter. The term "(meth)acryloyl group" refers to "acryloyl group" and / or "methacryloyl group" (either one or both of "acryloyl group" and "methacryloyl group"). When the acrylic polymer is a copolymer, it may be a random copolymer or a block copolymer.

[0047] The acrylic polymer preferably contains, for example, 40% by weight or more of units derived from (meth)acrylic acid alkyl esters having a linear or branched alkyl group having 1 to 20 carbon atoms at the ester terminal, relative to 100% by weight of all monomer units. Hereinafter, a (meth)acrylic acid alkyl ester having an alkyl group having m to 1 carbon atoms at the ester terminal will be referred to as "(meth)acrylic acid C m-l It is sometimes referred to as "alkyl ester."

[0048] (Meth)acrylic acid C 1-20Specific examples of alkyl esters include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, s-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and isopropyl (meth)acrylate. Examples of suitable acrylates include octyl acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, isostearyl (meth)acrylate, nonadecyl (meth)acrylate, and eicosyl (meth)acrylate. Among these, n-butyl acrylate, 2-ethylhexyl acrylate, and isostearyl acrylate are preferred.

[0049] (Meth)acrylic acid C in the acrylic polymer 1-20 The content of the alkyl ester-derived units is preferably more than 30% by weight, more preferably 35% by weight or more, even more preferably 40% by weight or more, and particularly preferably 45% by weight or more, based on 100% by weight of all monomer units. The upper limit may be, for example, 98% by weight, 90% by weight, 70% by weight, or 55% by weight. 1-20 When the content of the alkyl ester-derived unit is within the above range, it becomes easier to achieve a balance between adhesive strength and cohesive strength.

[0050] (Meth)acrylic acid C 1-20 The alkyl esters may be used alone or in combination of two or more.

[0051] The acrylic polymer may contain a unit derived from another monomer (copolymerizable monomer) having a (meth)acryloyl group or an alkenyl group that can be polymerized with the (meth)acrylic acid alkyl ester. Examples of the copolymerizable monomer include polar group-containing monomers having a polar group (such as a carboxy group, an acid anhydride group, a hydroxyl group, a sulfonic acid group or a phosphate group, an epoxy group, or a nitrogen atom-containing group), and alicyclic monomers. The copolymerizable monomers may be used alone or in combination of two or more.

[0052] Examples of the carboxy group-containing monomer include acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid.

[0053] Examples of the acid anhydride group-containing monomer include maleic anhydride and itaconic anhydride.

[0054] The total content of units derived from carboxyl group-containing monomers and acid anhydride group-containing monomers in the acrylic polymer may be 1% by weight or less, or 0.5% by weight or less, based on 100% by weight of all monomer units, from the viewpoint of preventing metal corrosion. The lower limit is usually 0% by weight, since it is preferable not to use them, at least intentionally.

[0055] Examples of hydroxyl group-containing monomers include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)methyl (meth)acrylate. Among these, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, and 4-hydroxybutyl methacrylate are preferred.

[0056] The content of units derived from hydroxyl group-containing monomers in the acrylic polymer is preferably 1.0 wt% or more, more preferably 2.0 wt% or more, even more preferably 5 wt% or more, particularly preferably 10 wt% or more, and most preferably 15 wt% or more, based on 100 wt% of all monomer units. The upper limit may be, for example, 50 wt%, or may be 45 wt%, 40 wt%, or 35 wt%. When the content of units derived from hydroxyl group-containing monomers is 1.0 wt% or more, it becomes easier to suitably adjust the adhesiveness of the pressure-sensitive adhesive and the degree of crosslinking by reaction with a crosslinking agent, and when the upper limit is 50 wt%, it becomes easier to adjust the water absorption of the pressure-sensitive adhesive layer.

[0057] Examples of sulfonic acid group or phosphate group-containing monomers include styrenesulfonic acid, allylsulfonic acid, sodium vinylsulfonate, 2-(meth)acrylamido-2-methylpropanesulfonic acid, (meth)acrylamidopropanesulfonic acid, sulfopropyl (meth)acrylate, (meth)acryloyloxynaphthalenesulfonic acid, and 2-hydroxyethyl acryloylphosphate.

[0058] Examples of epoxy group-containing monomers include epoxy group-containing acrylates such as glycidyl (meth)acrylate and 2-ethyl glycidyl ether (meth)acrylate, allyl glycidyl ether, and glycidyl ether (meth)acrylate.

[0059] Examples of the nitrogen atom-containing group-containing monomer include a cyano group-containing monomer, an isocyanate group-containing monomer, an amide group-containing monomer, an amino group-containing monomer, a nitrogen atom-containing ring-containing monomer, etc. When the acrylic polymer contains a nitrogen atom-containing group-containing monomer, good adhesion reliability is likely to be obtained in the optical pressure-sensitive adhesive composition.

[0060] Examples of the cyano group-containing monomer include acrylonitrile and methacrylonitrile.

[0061] An example of the isocyanate group-containing monomer is 2-isocyanatoethyl (meth)acrylate.

[0062] Examples of the amide group-containing monomer include (meth)acrylamide; N,N-dialkyl(meth)acrylamides such as N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dipropyl(meth)acrylamide, N,N-diisopropyl(meth)acrylamide, N,N-di(n-butyl)(meth)acrylamide, and N,N-di(t-butyl)(meth)acrylamide; N-alkyl(meth)acrylamides such as N-ethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N-butyl(meth)acrylamide, and Nn-butyl(meth)acrylamide; N-vinylcarboxylic acid amides such as N-vinylacetamide; and monomers having a hydroxyl group and an amide group, such as N-(2-hydroxyethyl)(meth)acrylamide. N-hydroxyalkyl(meth)acrylamides such as N-(2-hydroxypropyl)(meth)acrylamide, N-(1-hydroxypropyl)(meth)acrylamide, N-(3-hydroxypropyl)(meth)acrylamide, N-(2-hydroxybutyl)(meth)acrylamide, N-(3-hydroxybutyl)(meth)acrylamide, and N-(4-hydroxybutyl)(meth)acrylamide; monomers having an alkoxy group and an amide group, for example, N-alkoxyalkyl(meth)acrylamides such as N-methoxymethyl(meth)acrylamide, N-methoxyethyl(meth)acrylamide, and N-butoxymethyl(meth)acrylamide; and others such as N,N-dimethylaminopropyl(meth)acrylamide and N-(meth)acryloylmorpholine. Among these, (meth)acrylamide is preferred.

[0063] Examples of amino group-containing monomers include aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, and t-butylaminoethyl (meth)acrylate.

[0064] Examples of the nitrogen atom-containing ring-containing monomer include N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-(meth)acryloyl-2-pyrrolidone, N-(meth)acryloylpiperidine, N-(meth)acryloylpyrrolidine, N-vinylmorpholine, N-vinyl-3-morpholinone, N-vinyl-2-caprolactam, N-vinyl-1,3-oxazin-2-one, N-vinyl-3,5-morpholinedione, and N-vinylpyrazine. azole, N-vinylisoxazole, N-vinylthiazole, N-vinylisothiazole, monomers having a succinimide skeleton (e.g., N-(meth)acryloyloxymethylene succinimide, N-(meth)acryloyl-6-oxyhexamethylene succinimide, N-(meth)acryloyl-8-oxyhexamethylene succinimide, etc.), itaconimides (e.g., N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide, N-laurylitaconimide, etc.), etc. Among these, N-vinyl-2-pyrrolidone is preferred.

[0065] In order to improve adhesive strength, the content of units derived from monomers having a nitrogen atom in the acrylic polymer is preferably 40% by weight or less, more preferably 35% by weight or less, even more preferably 25% by weight or less, and particularly preferably 20% by weight or less, relative to 100% by weight of all monomer units. The lower limit may be 0% by weight, 1% by weight, 3% by weight, 10% by weight, or 15% by weight.

[0066] The polar group-containing monomers may be used alone or in combination of two or more.

[0067] When the acrylic polymer contains the alicyclic monomer, the optical pressure-sensitive adhesive composition can be easily peeled while maintaining high cohesive strength. Examples of the alicyclic monomer include (meth)acrylic acid cycloalkyl esters having a cycloalkyl group with 4 to 10 carbon atoms, (meth)acrylic acid esters having a bicyclic hydrocarbon ring, and (meth)acrylic acid esters having a tricyclic or higher hydrocarbon ring. The cycloalkyl group, the bicyclic hydrocarbon ring, and the tricyclic or higher hydrocarbon ring may have a substituent. Examples of the substituent include halogen atoms (e.g., fluorine atoms, chlorine atoms, bromine atoms, iodine atoms), and linear or branched alkyl groups having 1 to 6 carbon atoms (e.g., methyl groups, ethyl groups, n-propyl groups, isopropyl groups, etc.). The number of the substituents is, for example, 1 to 6. Two or more substituents may be the same or different.

[0068] Examples of the (meth)acrylic acid cycloalkyl ester include cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, 3,3,5-trimethylcyclohexyl (meth)acrylate, cycloheptyl (meth)acrylate, cyclooctyl (meth)acrylate, etc. Among these, cyclohexyl acrylate and 3,3,5-trimethylcyclohexyl methacrylate are preferred.

[0069] Examples of the (meth)acrylic acid ester having a bicyclic hydrocarbon ring include bornyl (meth)acrylate and isobornyl (meth)acrylate.

[0070] Examples of the (meth)acrylic acid ester having three or more hydrocarbon rings include dicyclopentanyl (meth)acrylate, dicyclopentanyloxyethyl (meth)acrylate, tricyclopentanyl (meth)acrylate, 1-adamantyl (meth)acrylate, 2-methyl-2-adamantyl (meth)acrylate, and 2-ethyl-2-adamantyl (meth)acrylate.

[0071] The above alicyclic monomers may be used alone or in combination of two or more.

[0072] The content of the alicyclic monomer-derived units in the acrylic polymer is preferably 40% by weight or less, more preferably 30% by weight or less, and even more preferably 25% by weight or less, based on 100% by weight of all monomer units. The lower limit may be 0% by weight, 10% by weight, or 15% by weight. When the content of the alicyclic monomer-derived units is within the above range, the cohesive strength of the pressure-sensitive adhesive is increased while the peel strength is easily reduced.

[0073] The copolymerizable monomer may contain a monomer (other monomer) other than the polar group-containing monomer and the alicyclic monomer, such as an alkoxy group-containing monomer, an alkoxysilyl group-containing monomer, a vinyl ester, a vinyl alkyl ether, an aromatic hydrocarbon group-containing monomer, an olefin, or a diene.

[0074] Examples of the alkoxy group-containing monomer include alkoxyalkyl(meth)acrylates, alkoxypolyalkylene glycol(meth)acrylates, and the like.

[0075] Examples of the alkoxyalkyl (meth)acrylates include 2-methoxyethyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, propoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, and ethoxypropyl (meth)acrylate.

[0076] Examples of the alkoxypolyalkylene glycol (meth)acrylates include methoxyethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, and methoxypolypropylene glycol (meth)acrylate.

[0077] Examples of the alkoxysilyl group-containing monomer include alkoxysilyl group-containing (meth)acrylates and alkoxysilyl group-containing vinyl compounds.

[0078] Examples of the alkoxysilyl group-containing vinyl compound include 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, and 3-(meth)acryloxypropylmethyldiethoxysilane.

[0079] Examples of the alkoxysilyl group-containing vinyl compound include vinyltrimethoxysilane and vinyltriethoxysilane.

[0080] The copolymerizable monomer may contain the alkoxy group-containing monomer, but preferably does not contain it. The content of the unit derived from the alkoxy group-containing monomer in the acrylic polymer may be less than 20 wt%, less than 10 wt%, less than 3 wt%, less than 1 wt%, or less than 0.3 wt%, relative to 100 wt% of all monomer units, in order to facilitate sheet formation of the pressure-sensitive adhesive layer without problems such as gelation. The lower limit is usually 0 wt%.

[0081] Examples of the vinyl esters include vinyl acetate and vinyl propionate.

[0082] Examples of the vinyl alkyl ethers include methyl vinyl ether and ethyl vinyl ether.

[0083] Examples of the aromatic hydrocarbon group-containing monomer include aromatic vinyl compounds and (meth)acrylic acid esters having an aromatic hydrocarbon group.

[0084] Examples of the aromatic vinyl compound include styrene, α-methylstyrene, and vinyltoluene.

[0085] Examples of the (meth)acrylic acid ester having an aromatic hydrocarbon group include phenyl (meth)acrylate, phenoxyethyl (meth)acrylate, and benzyl (meth)acrylate.

[0086] Examples of the olefins or dienes include ethylene, butadiene, isoprene, and isobutylene.

[0087] In addition to these, the other monomers may also include heterocycle-containing (meth)acrylates such as tetrahydrofurfuryl (meth)acrylate, halogen atom-containing (meth)acrylates such as vinyl chloride and fluorine atom-containing (meth)acrylates, and (meth)acrylic acid esters obtained from terpene compound derivative alcohols.

[0088] The other monomers may each be used alone or in combination of two or more.

[0089] The content of the copolymerizable monomer-derived units in the acrylic polymer is preferably 1% by weight or more, more preferably 10% by weight or more, and even more preferably 15% by weight or more, based on 100% by weight of all monomer units. The upper limit of the content of the copolymerizable monomer-derived units may be, for example, 55% by weight, 45% by weight, or 38% by weight. When the content of the copolymerizable monomer-derived units is 0.01% by weight or more, the effect of use is easily obtained, and when the upper limit is 50% by weight, the balance between adhesive strength and cohesive strength is easily achieved.

[0090] In addition, the total content of the units derived from the carboxyl group-containing monomer, acid anhydride group-containing monomer, hydroxyl group-containing monomer, nitrogen atom-containing group-containing monomer, and alkoxy group-containing monomer in the acrylic polymer is preferably 55% by weight or less, more preferably 50% by weight or less, even more preferably 45% by weight or less, particularly preferably 40% by weight or less, and most preferably 38% by weight or less, based on 100% by weight of all monomer units. The lower limit may be, for example, 1% by weight, 10% by weight, or 15% by weight. When the total content is 55% by weight or less, metal corrosion is easily prevented, and when the lower limit is 1% by weight, the peeling force during separation and recovery is easily reduced.

[0091] The acrylic polymer may contain unpolymerized monomers (such as the (meth)acrylic acid alkyl esters and the copolymerizable monomers) or oligomers thereof.

[0092] The weight average molecular weight (Mw) of the acrylic polymer is 10 × 10 4 More preferably, 20×10 4 More preferably, 30×10 4 More preferably, 40×10 4 or more, most preferably 50 x 10 4 More preferably, 55×10 4 The upper limit is usually 500 x 10 4 and 150×10 4 Or 75 x 10 4 The weight average molecular weight (Mw) may be 10×10 4 When the adhesive strength, cohesive strength, and storage modulus are balanced, the upper limit is 500×10 4 If so, good adhesive reliability is likely to be obtained even in a high-temperature environment. The Mw can be measured as a value converted into standard polystyrene by gel permeation chromatography (GPC).

[0093] In addition to the acrylic polymer, the optical pressure-sensitive adhesive composition may contain, within the scope of the effects of the present invention, for example, a polymerization initiator, a crosslinking agent, a polyfunctional monomer, a silane coupling agent, a solvent, a tackifying resin (such as a rosin derivative, a polyterpene resin, a petroleum resin, or an oil-soluble phenol), an antioxidant, a filler, an ultraviolet absorber, an antioxidant, a chain transfer agent, a plasticizer, a softener, a surfactant, an antistatic agent, or a rust inhibitor. These additives may be used alone or in combination of two or more.

[0094] The total content of the additives in the optical pressure-sensitive adhesive composition is preferably 10% by weight or less, more preferably 5% by weight or less, even more preferably 3% by weight or less, and particularly preferably 1% by weight or less, in order to ensure sufficient transparency after the pressure-sensitive adhesive layer is formed.

[0095] Examples of the polymerization initiator include a photopolymerization initiator (photoinitiator) and a thermal polymerization initiator. One or more types of the polymerization initiators may be used. The pressure-sensitive adhesive layer formed from the optical pressure-sensitive adhesive composition has sufficient shape stability, and therefore does not necessarily need to contain a polymerization initiator.

[0096] Examples of the photopolymerization initiator include benzoin ether-based photopolymerization initiators, acetophenone-based photopolymerization initiators, α-ketol-based photopolymerization initiators, aromatic sulfonyl chloride-based photopolymerization initiators, photoactive oxime-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzyl-based photopolymerization initiators, benzophenone-based photopolymerization initiators, ketal-based photopolymerization initiators, and thioxanthone-based photopolymerization initiators.

[0097] Examples of the benzoin ether photopolymerization initiator include benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-dimethoxy-1,2-diphenylethan-1-one, and anisole methyl ether.

[0098] Examples of the acetophenone-based photopolymerization initiator include 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexyl phenyl ketone, 4-phenoxydichloroacetophenone, and 4-(t-butyl)dichloroacetophenone.

[0099] Examples of the α-ketol photopolymerization initiator include 2-methyl-2-hydroxypropiophenone, 1-[4-(2-hydroxyethyl)phenyl]-2-methylpropan-1-one, and the like.

[0100] Examples of the aromatic sulfonyl chloride photopolymerization initiator include 2-naphthalenesulfonyl chloride.

[0101] Examples of the photoactive oxime-based photopolymerization initiator include 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime.

[0102] The benzoin-based photopolymerization initiator includes, for example, benzoin.

[0103] Examples of the benzyl photopolymerization initiator include benzyl.

[0104] Examples of the benzophenone-based photopolymerization initiator include benzophenone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, and α-hydroxycyclohexylphenyl ketone.

[0105] Examples of the ketal-based photopolymerization initiator include benzyl dimethyl ketal.

[0106] Examples of the thioxanthone-based photopolymerization initiator include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, and dodecylthioxanthone.

[0107] When the photopolymerization initiator is used, the amount used is not particularly limited, but is preferably 0.01 to 1 part by weight, more preferably 0.05 to 0.5 parts by weight, per 100 parts by weight of the acrylic polymer.

[0108] Examples of the thermal polymerization initiator include azo-based polymerization initiators, peroxide-based polymerization initiators (dibenzoyl peroxide, tert-butyl permaleate, etc.), redox-based polymerization initiators, etc. Among these, azo-based polymerization initiators are preferred.

[0109] Examples of the azo-based polymerization initiator include 2,2'-azobisisobutyronitrile, 2,2'-azobis-2-methylbutyronitrile, 2,2'-azobis(2-methylpropionate)dimethyl, and 4,4'-azobis-4-cyanovaleric acid.

[0110] When the azo-based polymerization initiator is used, the amount used is not particularly limited, but is preferably 0.05 to 0.5 parts by weight, more preferably 0.1 to 0.3 parts by weight, per 100 parts by weight of the acrylic polymer.

[0111] The crosslinking agent can be contained for the purpose of crosslinking within the pressure-sensitive adhesive layer or crosslinking between the pressure-sensitive adhesive layer and an adjacent surface. Specific examples include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, carbodiimide-based crosslinking agents, melamine-based crosslinking agents, urea-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, hydrazine-based crosslinking agents, and amine-based crosslinking agents. These may be used alone or in combination of two or more.

[0112] The isocyanate crosslinking agent is preferably a compound having two or more isocyanate groups in one molecule, and specific examples include aromatic isocyanates (tolylene diisocyanate, xylene diisocyanate, polymethylene polyphenyl diisocyanate, tris(p-isocyanatophenyl)thiophosphate, diphenylmethane diisocyanate, etc.), alicyclic isocyanates (isophorone diisocyanate, etc.), and aliphatic isocyanates (hexamethylene diisocyanate, etc.).

[0113] The epoxy crosslinking agent is preferably a compound having two or more (preferably 3 to 5) epoxy groups in one molecule, and specific examples include N,N,N',N'-tetraglycidyl-m-xylylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, 1,6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, and polyglycerol polyglycidyl ether.

[0114] The oxazoline-based crosslinking agent is preferably a compound having one or more oxazoline groups in one molecule.

[0115] Examples of the aziridine crosslinking agent include trimethylolpropane tris[3-(1-aziridinyl)propionate], trimethylolpropane tris[3-(1-(2-methyl)aziridinylpropionate)], and the like.

[0116] The carbodiimide crosslinking agent is preferably a low molecular weight compound or a high molecular weight compound having two or more carbodiimide groups.

[0117] The content of the crosslinking agent is preferably 5 parts by weight or less, more preferably 0.001 to 5 parts by weight, even more preferably 0.005 to 3 parts by weight, and particularly preferably 0.01 to 1 part by weight, relative to 100 parts by weight of the acrylic polymer, in order to easily achieve a good balance between adhesive strength, cohesive strength, and storage modulus.

[0118] The polyfunctional monomer can be contained in place of the crosslinking agent or in combination with the crosslinking agent for the purpose of adjusting the cohesive strength. Specific examples include ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and the like. (meth)acrylate, ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,12-dodecanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate, allyl (meth)acrylate, vinyl (meth)acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylate, butyldiol (meth)acrylate, hexyldiol di(meth)acrylate, etc. These may be used alone or in combination of two or more.

[0119] The content of the polyfunctional monomer is preferably 5 parts by weight or less, more preferably 3 parts by weight or less, and even more preferably 1 part by weight or less, relative to 100 parts by weight of the acrylic polymer. The lower limit may be 0 part by weight, or may be 0.001 part by weight, 0.005 part by weight, 0.007 part by weight, or 0.01 part by weight. When the content of the polyfunctional monomer is within the above range, it is easy to avoid a decrease in the adhesive strength between the pressure-sensitive adhesive layer and the adjacent layer due to excessive cohesive force.

[0120] Examples of the silane coupling agent include γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-aminopropyltrimethoxysilane, and N-phenylaminopropyltrimethoxysilane. Among these, γ-glycidoxypropyltrimethoxysilane is preferred. The silane coupling agents may be used alone or in combination of two or more.

[0121] The content of the silane coupling agent in the optical pressure-sensitive adhesive composition is preferably 1.0 part by weight or less, more preferably 0.5 part by weight or less, relative to 100 parts by weight of the acrylic polymer, in order to maintain the adhesive reliability to glass when an image display device is used and reduce adhesive residue when separated and recovered. The lower limit may be 0 part by weight, 0.01 part by weight, or 0.03 part by weight.

[0122] Examples of the solvent include organic solvents such as esters (ethyl acetate, n-butyl acetate, etc.), aromatic hydrocarbons (toluene, benzene, etc.), aliphatic hydrocarbons (n-hexane, n-heptane, etc.), alicyclic hydrocarbons (cyclohexane, methylcyclohexane, etc.), ketones (methyl ethyl ketone, methyl isobutyl ketone, etc.), etc. One or more of the solvents may be used.

[0123] The optical pressure-sensitive adhesive composition may be in any form (type), such as an emulsion type, a solvent type (solution type), a hot melt type, etc. Among these, the solvent type is preferred.

[0124] The optical pressure-sensitive adhesive composition can be prepared, for example, by mixing and polymerizing the monomers constituting the acrylic polymer, any additives, any solvent, etc., using a known or conventional method for a solvent-based pressure-sensitive adhesive composition.

[0125] [Adhesive layer] The pressure-sensitive adhesive layer of the present invention is formed from the optical pressure-sensitive adhesive composition and is used to bond an adherend such as an organic EL display panel to a transparent member (such as a cover glass) arranged on the viewing side of the image display panel.

[0126] The pressure-sensitive adhesive layer maintains good adhesive strength when the image display device is in use, and by having the peel strength X as described above, exhibits excellent thermal reworkability, in that the pressure-sensitive adhesive layer can be easily peeled off from the cover glass or the like by utilizing the flexibility of the flexible organic EL display panel when the cover glass or the like is separated and recovered.

[0127] The pressure-sensitive adhesive layer is formed by applying (coating) the optical pressure-sensitive adhesive composition to an organic EL display panel, and, if necessary, drying by heating and / or curing. The formed pressure-sensitive adhesive surface may be protected by a release film before being attached to a cover glass or the like. The release film is peeled off when the panel is attached to an adherend.

[0128] The application (coating) of the above-mentioned organic EL display panel can be carried out by a known or conventional coating method using, for example, a coater (gravure roll coater, reverse roll coater, kiss roll coater, dip roll coater, bar coater, knife coater, spray coater, comma coater, direct coater, etc.).

[0129] The pressure-sensitive adhesive layer may be formed by attaching a pressure-sensitive adhesive sheet to the organic EL display panel. The pressure-sensitive adhesive sheet is formed by applying (coating) the optical pressure-sensitive adhesive composition to a release film by the same coating method as above, and, if necessary, drying by heating and / or curing.

[0130] The pressure-sensitive adhesive sheet may be one in which the adhesive surface of the pressure-sensitive adhesive layer formed on the release film is protected by another release film, and the adhesive surface is protected by two film substrates. The pressure-sensitive adhesive sheet may also be one in which both sides of the release film on which the pressure-sensitive adhesive layer is formed are release surfaces, and the adhesive surface is protected by being wound into a roll.

[0131] Examples of the release film include substrates having a release treatment layer, low-adhesion substrates made of fluoropolymers, and low-adhesion substrates made of non-polar polymers. Substrates having a release treatment layer include, for example, plastic films and paper surface-treated with release treatment agents such as silicone-based, long-chain alkyl-based, fluorine-based, and molybdenum sulfide. Examples of the fluorine-based polymer in the low-adhesion substrate made of fluoropolymer include polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, and chlorofluoroethylene-vinylidene fluoride copolymer. Examples of the non-polar polymer include olefin-based resins (e.g., polyethylene, polypropylene, etc.). The release film can be formed by a known or conventional method. The thickness of the release film is not particularly limited. →Have you added the melting point item? It may not be very relevant this time.

[0132] The thickness of the pressure-sensitive adhesive layer is preferably, for example, 10 to 1000 μm. The lower limit may be 20 μm, or may be 30 μm, 40 μm, or 50 μm. The upper limit may be 900 μm, or may be 800 μm, 700 μm, or 500 μm. When the thickness is 10 μm or more, step absorbability is improved, and damage to the pressure-sensitive adhesive layer during separation and recovery is less likely to occur, making it easier to improve heat reworkability. When the upper limit is 1000 μm, the pressure-sensitive adhesive layer bends together with the organic EL display panel during separation and recovery, making it easier to peel, making it easier to improve heat reworkability.

[0133] The pressure-sensitive adhesive layer has excellent adhesive strength during use, and may therefore be used to bond an image display panel other than an organic EL display panel (such as a liquid crystal display panel or a plasma display panel) to a transparent member (such as a cover glass).

[0134] The pressure-sensitive adhesive layer may also be used to bond a film substrate (optical film (anti-reflection film, polarizing plate, retardation plate, etc.), film sensor, etc.) provided on the viewing side of the image display panel to a transparent member (cover glass, etc.) as an adherend.

[0135] The pressure-sensitive adhesive layer may also be used to form a surface protection film on a film substrate (plastic film) as an adherend. Because the pressure-sensitive adhesive layer has good conformability, the surface protection film is useful for protecting the surface of optical members (e.g., image display panels).

[0136] Examples of plastic materials for the plastic film include polyester resins (polyethylene terephthalate, etc.), acrylic resins (polymethyl methacrylate, etc.), polycarbonate, triacetyl cellulose (TAC), polysulfone, polyarylate, polyimide, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, ethylene-propylene copolymer, cyclic olefin polymer, etc. Only one type of the above plastic materials may be used, or two or more types may be used. [Example]

[0137] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0138] <Preparation of Pressure-Sensitive Adhesive Composition>

[0139] (Adhesive composition A) A monomer mixture consisting of 10 parts by weight of 2-ethylhexyl acrylate (2EHA), 35 parts by weight of n-butyl acrylate (BA), 20 parts by weight of cyclohexyl acrylate (CHA), and 35 parts by weight of 4-hydroxybutyl acrylate (4HBA) was added to a four-neck flask along with 0.09 parts by weight of 2,2-dimethoxy-1,2-diphenyl-1-one (trade name "Irgacure 651", BASF Japan Ltd.) and 0.09 parts by weight of 1-hydroxy-cyclohexyl-phenyl-ketone (trade name "Irgacure 184", BASF Japan Ltd.). The mixture was exposed to ultraviolet light in a nitrogen atmosphere to partially photopolymerize, yielding a partially polymerized product with a polymerization rate of approximately 10%. To 100 parts by weight of this partial polymer, 0.14 parts by weight of a polyfunctional monomer (dipentaerythritol hexaacrylate, trade name "KAYARAD DPHA", manufactured by Nippon Kayaku Co., Ltd.) and 0.3 parts by weight of a silane coupling agent (3-glycidoxypropyltrimethoxysilane, trade name "KBM-403", manufactured by Shin-Etsu Chemical Co., Ltd.) were added and mixed uniformly to prepare adhesive composition A.

[0140] (Adhesive composition B) A monomer mixture consisting of 60 parts by weight of n-butyl acrylate (BA), 20 parts by weight of 4-hydroxybutyl acrylate (4HBA), and 20 parts by weight of N-vinyl-2-pyrrolidone (NVP) was added to a four-neck flask along with 0.09 parts by weight of 2,2-dimethoxy-1,2-diphenyl-1-one (trade name "Irgacure 651", manufactured by BASF Japan Ltd.) and 0.09 parts by weight of 1-hydroxycyclohexylphenyl ketone (trade name "Irgacure 184", manufactured by BASF Japan Ltd.). The mixture was exposed to ultraviolet light in a nitrogen atmosphere to partially photopolymerize, yielding a partially polymerized product with a polymerization rate of approximately 10%. To 100 parts by weight of this partial polymer, 0.2 parts by weight of a polyfunctional monomer (dipentaerythritol hexaacrylate, trade name "KAYARAD DPHA", manufactured by Nippon Kayaku Co., Ltd.) and 0.3 parts by weight of a silane coupling agent (3-glycidoxypropyltrimethoxysilane, trade name "KBM-403", manufactured by Shin-Etsu Chemical Co., Ltd.) were added and mixed uniformly to prepare adhesive composition B.

[0141] (Adhesive composition C) A monomer mixture consisting of 50 parts by weight of n-butyl acrylate (BA), 40 parts by weight of isostearyl acrylate (ISA), and 10 parts by weight of N-vinyl-2-pyrrolidone (NVP) was added to a four-neck flask with 0.09 parts by weight of 2,2-dimethoxy-1,2-diphenyl-1-one (trade name "Irgacure 651" from BASF Japan Co., Ltd.) and 0.09 parts by weight of 1-hydroxycyclohexylphenyl ketone (trade name "Irgacure 184" from BASF Japan Co., Ltd.). The mixture was partially photopolymerized by exposure to ultraviolet light under a nitrogen atmosphere to obtain a partially polymerized product with a polymerization rate of approximately 10%. 0.02 parts by weight of a multifunctional monomer (dipentaerythritol hexaacrylate, trade name "KAYARAD DPHA" from Nippon Kayaku Co., Ltd.) was added to 100 parts by weight of this partially polymerized product and mixed uniformly to prepare Pressure-Sensitive Adhesive Composition B.

[0142] (Adhesive composition D) Adhesive composition D was prepared in the same manner as adhesive composition B, except that the amount of polyfunctional monomer (dipentaerythritol hexaacrylate, trade name "KAYARAD DPHA", manufactured by Nippon Kayaku Co., Ltd.) was 0.01 parts by weight and the polymerization rate was approximately 10%.

[0143] (Adhesive composition E) A monomer mixture consisting of 47 parts by weight of 2-ethylhexyl acrylate (2EHA), 45 parts by weight of isostearyl acrylate (ISA), 3 parts by weight of 4-hydroxybutyl acrylate (4HBA), and 5 parts by weight of N-vinyl-2-pyrrolidone (NVP) was added to a four-neck flask along with 0.09 parts by weight of 2,2-dimethoxy-1,2-diphenyl-1-one (trade name "Irgacure 651", BASF Japan Ltd.) and 0.09 parts by weight of 1-hydroxy-cyclohexyl-phenyl-ketone (trade name "Irgacure 184", BASF Japan Ltd.). The mixture was exposed to ultraviolet light in a nitrogen atmosphere to partially photopolymerize, yielding a partially polymerized product with a polymerization rate of approximately 10%. To 100 parts by weight of this partial polymer, 0.02 parts by weight of a polyfunctional monomer (dipentaerythritol hexaacrylate, trade name "KAYARAD DPHA", manufactured by Nippon Kayaku Co., Ltd.) and 0.3 parts by weight of a silane coupling agent (3-glycidoxypropyltrimethoxysilane, trade name "KBM-403", manufactured by Shin-Etsu Chemical Co., Ltd.) were added and mixed uniformly to prepare adhesive composition E.

[0144] (Adhesive composition F) Adhesive composition F was prepared in the same manner as adhesive composition E, except that the amount of polyfunctional monomer (dipentaerythritol hexaacrylate, trade name "KAYARAD DPHA", manufactured by Nippon Kayaku Co., Ltd.) was 0.10 parts by weight and the polymerization rate was approximately 10%.

[0145] [Table 1]

[0146] <Examples 1 to 8, Comparative Example 1>

[0147] Each of the pressure-sensitive adhesive compositions A to F was applied to the release-treated surface of a release film (a polyethylene terephthalate film with one side treated for release, 38 μm thick, product name "MRF38", manufactured by Mitsubishi Plastics, Inc.) to form a coating layer, and then a similar release film was placed on the coating layer. Subsequently, the composition was illuminated with a black light at an intensity of 6.5 mW / cm 2of ultraviolet rays, with an integrated light intensity of 1500mJ / cm 2 Polymerization was continued until irradiation was achieved, and a pressure-sensitive adhesive sheet was prepared in which release films were provided on both sides of the pressure-sensitive adhesive layer. The thickness of the pressure-sensitive adhesive layer is shown in Table 2.

[0148] Various properties were evaluated and measured by the following methods.

[0149] (Measurement of peeling force X) The pressure-sensitive adhesive sheet obtained above was cut to a width of 50 mm and a length of 100 mm, and the pressure-sensitive adhesive sheet was applied to a glass substrate (blue-edged polished glass, "OF1", manufactured by Matsunami Glass Industry Co., Ltd.) using a 2 kg roller to prepare an evaluation sample. The evaluation sample was then stored in an environment of 23°C and 50% RH for 30 minutes, after which the tensile strength was measured using a tensile tester ("Autograph", manufactured by Shimadzu Corporation) at a peel angle of 180° and a pulling rate of 50 mm / min in an environment of 100°C, and the peel force (N / 20 mm) was calculated from the obtained tensile strength. The results are shown in Table 2.

[0150] (Measurement of peel force Y) The peel force was measured in the same manner as for the peel force X, except that the measurement was carried out in an environment of 25°C and 50% RH. The results are shown in Table 2.

[0151] (Measurement of storage modulus) The release film was peeled off from the pressure-sensitive adhesive sheet obtained above, leaving only the pressure-sensitive adhesive layer to prepare a pressure-sensitive adhesive layer sample with a thickness of approximately 1.5 mm. The storage modulus of the sample was measured at 25°C and 100°C using a dynamic viscoelasticity measuring device (Advanced Rheometric Expansion System (ARES), manufactured by Rheometric Scientific) under conditions of parallel plates (8.0 mmφ), torsion mode, and a frequency range of 1 Hz. The results are shown in Table 2.

[0152] (Moisture content measurement) The pressure-sensitive adhesive sheet obtained above was cut into 1cm x 1cm pieces, the release film removed, and the pieces were attached to aluminum foil to prepare evaluation samples. These samples were left in an environment of 95°C and 0% RH until there was no weight change, and the weight (W1) of the sample after complete removal of moisture was measured. The weight (W2) of the sample after 24 hours in an environment of 23°C and 50% RH was then measured, and the moisture content was calculated using the following formula. The results are shown in Table 2.

[0153] Moisture percentage (weight %) = ((W1-W2) / W1)×100

[0154] (chromaticity b * (measurement of change in The adhesive sheet obtained above was cut into a 5cm x 5cm piece, and the release film was peeled off. Glass plates were attached to both sides of the adhesive layer to form an evaluation sample. The adhesive layer was measured for chromaticity b using a spectrophotometer (U-4100, Hitachi High-Tech Corporation) at a light source of D65 and an irradiation angle of 2° before and after storage at 100°C. * Measure the color b before and after storage. * Measure the chromaticity b before storage. * From the value of b after saving * By subtracting the value of b * The change in the amount of oxidative stress was calculated, and the results are shown in Table 2.

[0155] (Evaluation of heat reworkability) The pressure-sensitive adhesive sheet obtained above was cut into a width of 50 mm and a length of 100 mm, and the pressure-sensitive adhesive sheet was applied to a glass substrate (blue-edged polished glass, "OF1", manufactured by Matsunami Glass Industry Co., Ltd.) using a 2 kg roller to prepare an evaluation sample. The evaluation sample was then stored in an environment of 23°C and 50% RH for 30 minutes, after which it was peeled at a peel angle of 180° and a pulling rate of 50 mm / min in an environment of 100°C using a tensile tester ("Autograph", manufactured by Shimadzu Corporation), and the peeled surface was visually inspected for adhesive residue on the glass side. Evaluation was performed according to the following criteria. The results are shown in Table 2.

[0156] ○ (Good): No adhesive residue △ (Acceptable): Some glue residue was found (Poor): There was adhesive residue on the entire surface

[0157] [Table 2]

[0158] The pressure-sensitive adhesive layers of Examples 1 to 8 had peel strengths X in the range of 1.0 to 3.2 N / 20 mm, which was 4.0 / 20 mm or less, and showed good results of ◯ or Δ in terms of heat reworkability.

[0159] On the other hand, the adhesive layer of Comparative Example 1 exhibited a peel strength X of 5.6 N / 20 mm and a poor result of x for heat reworkability. [Explanation of symbols]

[0160] 10 Image display device 1 cover slip 2. Adhesive layer 3. Organic EL display panel 11 Image display device during separation and recovery

Claims

1. Contains an acrylic polymer, The peel force X is 4.0 N / 20 mm or less. Storage modulus at 100°C is 0.1 x 10 ５ Pa or more, The following (i), (ii) or (iii) is satisfied: Optical pressure-sensitive adhesive composition. Peel strength X: Peel strength when a film attached to a glass plate via a 50 to 500 μm thick adhesive layer formed from the adhesive composition is pulled at 100° C. at a peel angle of 180° and a pulling rate of 50 mm / min. (i) The content of units derived from hydroxyl group-containing monomers in the acrylic polymer is 1.0 to 50% by weight, and the content of units derived from alicyclic monomers is 15 to 40% by weight. (ii) The content of units derived from hydroxyl group-containing monomers in the acrylic polymer is 2.0 to 50% by weight, and the content of units derived from monomers having nitrogen atoms is 10 to 40% by weight. (iii) The content of units derived from hydroxyl group-containing monomers in the acrylic polymer is 1.0 to 50% by weight, and the content of isostearyl (meth)acrylate is more than 30% by weight.

2. The optical pressure-sensitive adhesive composition according to claim 1 , wherein the ratio (Y / X) of the following peel strength Y to the peel strength X is 15.0 or less. Peel strength Y: The peel strength when a film attached to a glass plate via a 50 to 500 μm thick adhesive layer formed from the adhesive composition is pulled at 25° C. at a peel angle of 180° and a pulling rate of 50 mm / min.

3. 3. The optical pressure-sensitive adhesive composition according to claim 1, which has a moisture regain of 0.6 to 5.0 wt % after storage at 23° C. and 50% RH for 24 hours.

4. The optical pressure-sensitive adhesive composition according to any one of claims 1 to 3, wherein a change in chromaticity b* of a pressure-sensitive adhesive layer having glass plates attached to both sides thereof when stored at 100°C for 1000 hours is 1.0 or less.

5. A pressure-sensitive adhesive layer formed from the optical pressure-sensitive adhesive composition according to any one of claims 1 to 4.

6. The adhesive according to claim 5, wherein the adherend is a film substrate and / or an organic EL display panel. agent layer.

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