Optical adhesive sheet

Abstract

The present application relates to the technical field of optical adhesive, in particular to an optical adhesive sheet. The optical adhesive sheet comprises an acrylic copolymer, which contains 10-20 wt% of hydrophilic monomers, based on 100 wt% of the total weight of monomer components in the acrylic copolymer; wherein the structure of the hydrophilic monomers is as shown in the following formula: wherein n is a natural number between 1 and 15. The optical adhesive sheet of the present application is suitable for bonding of plastic touch display modules, and has good blister resistance, bonding performance and weather resistance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical adhesive, in particular to an optical adhesive sheet. BACKGROUND

[0002] Optical clear adhesive (OCA) has excellent optical and adhesive properties, and becomes an important adhesive material for touch display components, and has been widely used in products with touch display screens such as mobile phones, tablets, and vehicle displays. Due to the diversification of the application environment of touch display modules, the optical adhesive needs to have good weather resistance, such as heat resistance and humidity resistance, under the premise of maintaining its optical transparency and adhesive stability.

[0003] With the rapid development of high molecular materials, such as polymethyl methacrylate (PMMA), polycarbonate (PC), cyclic olefin copolymer (COC), and cyclic olefin polymer (COP), lightweight, high safety, and low cost plastic panels are gradually replacing traditional glass substrates, and are widely used in vehicle displays. However, due to the long-term exposure of vehicle displays to outdoor high-temperature and high-humidity environments, the high molecular materials in the plastic panel will be affected by the humid environment and produce gas. If these gases are not discharged in time, it will affect the adhesion of the optical adhesive to the plastic panel.

[0004] Therefore, the present application is proposed. SUMMARY

[0005] The present application provides an optical adhesive sheet, which has good blister resistance and humidity resistance, can avoid the generation of bubbles between the optical adhesive sheet and the plastic panel, and improves the bonding reliability.

[0006] In order to achieve the above-mentioned purpose of the present application, the present application provides an optical adhesive sheet, which comprises an acrylic copolymer, and the acrylic copolymer contains 10-20 wt% of a hydrophilic monomer, based on 100 wt% of the total weight of the monomer components in the acrylic copolymer.

[0007] The structure of the hydrophilic monomer is as follows:

[0008] wherein n is a natural number between 1 and 15.

[0009] Further, the weight average molecular weight Mw of the acrylic copolymer is 1,000,000-5,000,000 g / mol.

[0010] Further, the optical adhesive sheet further comprises an acrylic oligomer, and the content of the acrylic oligomer is 5-15 parts by weight relative to 100 parts by weight of the acrylic copolymer.

[0011] Further, the weight average molecular weight Mw of the acrylic oligomer is 20,000-100,000 g / mol.

[0012] Further, the high Tg monomer accounts for 85-95 wt% based on the total weight of the monomer component in the acrylic oligomer.

[0013] Further, the high Tg monomer includes at least one of linear and / or branched alkyl (meth)acrylate, alicyclic (meth)acrylate and aromatic (meth)acrylate.

[0014] Further, the high Tg monomer is selected from alicyclic (meth)acrylate.

[0015] Further, the optical adhesive sheet further includes a crosslinking monomer, and the content of the crosslinking monomer is 0.1-0.5 parts by weight relative to 100 parts by weight of the acrylic copolymer.

[0016] Further, the crosslinking monomer is a (meth)acrylate monomer with a functionality of 2-6.

[0017] Further, the optical adhesive sheet further includes a silane coupling agent, and the content of the silane coupling agent is 0.1-1 parts by weight relative to 100 parts by weight of the acrylic copolymer.

[0018] Compared with the prior art, the present application has the following advantages:

[0019] (1) The optical adhesive sheet of the present application introduces a certain amount of hydrophilic monomer into the acrylic copolymer. On the one hand, it utilizes the affinity of the hydrophilic segment to the gas to promote the dissolution of the bubbles and prevent the bubbles from escaping. On the other hand, the hydrophilic segment in the structure of the hydrophilic monomer has good wettability, which can effectively improve the initial adhesion of the optical adhesive sheet and improve the bonding performance. In addition, the hydrophilic monomer with this structure has good flexibility, which can improve the deformation ability of the adhesive sheet.

[0020] (2) The optical adhesive sheet of the present application is suitable for bonding of touch display components, especially for bonding of plastic materials. It not only has good blister resistance, but also has good wettability and weather resistance. DETAILED DESCRIPTION

[0021] The technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments. However, those skilled in the art will understand that the embodiments described below are part of the embodiments of the present invention, not all of them, and are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0022] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or those recommended by the manufacturer. All reagents or instruments used, if the manufacturer is not specified, are commercially available conventional products.

[0023] In the description of the present invention, the term "(meth)acrylate" refers to any of methacrylate, acrylate, and a combination of methacrylate and acrylate, and other terms containing such definitions have the same meaning.

[0024] In the description of the present invention, the term "Tg" refers to "glass transition temperature".

[0025] Due to the different expansion coefficients between the plastic panel and the optical adhesive, and the plastic material's tendency to generate gas under high temperature and humidity, these factors affect the adhesion of the optical adhesive to the plastic panel, making it prone to bubbles, peeling, and delamination. Prior art (CN103242748A) attempts to prevent gas escape by increasing the rigidity of the optical adhesive. However, the inventors of this invention have discovered that increasing the rigidity of the optical adhesive reduces its wettability, thereby deteriorating the bonding performance. Furthermore, increased rigidity reduces deformation. When the expansion coefficients of the optical adhesive and the adhered object differ significantly, a certain gap inevitably forms, leading to delamination and peeling of the adhesive sheet.

[0026] Based on this, the present invention provides an optical adhesive sheet, comprising an acrylic copolymer, wherein the acrylic copolymer contains 10 to 20 wt% of a hydrophilic monomer, based on 100 wt% of the total weight of monomer components in the acrylic copolymer. The structure of the hydrophilic monomer is as follows:

[0027]

[0028] Wherein, n is a natural number between 1 and 15, and can be 1, 5, 7, 8, 12, 15, or any natural number between the two values.

[0029] The inventors of the present invention have discovered that the hydrophilic segments in the hydrophilic monomer having the above molecular structure have good affinity with gas, which can promote the dissolution of bubbles and prevent the escape of bubbles. On the other hand, the hydrophilic monomer has good flexibility, which can improve the initial adhesion of the adhesive sheet and enhance the deformation ability of the adhesive to avoid peeling and delamination.

[0030] As the hydrophilic monomer of the above structure, a substance having the above structure can be synthesized by oneself, or a commercial product can be used. The commercial product substance is called methoxy polyethylene glycol acrylate, and examples thereof include MPE400A and MPE550A produced by Osaka Organic Chemical Industry Co., Ltd. of Japan.

[0031] In one specific embodiment, the acrylic copolymer comprises 10 to 20 wt% of a hydrophilic monomer, based on 100 wt% of the total weight of the monomer components. Specifically, the hydrophilic monomer content may be 10 wt%, 15 wt%, 20 wt%, or any value in between. Excessive hydrophilic monomer content is not recommended, as it can lead to polymerization failure and the inability to produce the desired polymer. However, too low a content can result in poor bubble reduction.

[0032] In a specific embodiment, the acrylic copolymer further contains a soft monomer, which is an alkyl (meth)acrylate having an alkyl group with 4 to 14 carbon atoms, including but not limited to at least one of 2-ethylhexyl acrylate (2-EHA), n-butyl acrylate (BA), dodecyl acrylate (LA) and isodecyl acrylate (IDA).

[0033] In one embodiment, the soft monomer content is not less than 50 wt % and not more than 60 wt % based on 100 wt % of the total weight of the monomer components in the acrylic copolymer. Limiting the soft monomer content to this range can improve the adhesive strength of the adhesive sheet.

[0034] In one embodiment, the acrylic copolymer further comprises a polar monomer, which effectively enhances the adhesive strength of the adhesive sheet. Polar monomers are monomers containing polar groups, such as carboxyl, hydroxyl, vinyl, or nitrogen-containing amide and amino groups. In the present invention, a combination of a polar monomer containing a hydroxyl group and a polar monomer containing a nitrogen atom is preferred.

[0035] The polar monomer containing a hydroxyl group is preferably a (meth)acrylate monomer containing a hydroxyl group, such as 2-hydroxyethyl acrylate (HEA), 2-hydroxyethyl methacrylate, hydroxypropyl acrylate (HPA), and 4-hydroxybutyl acrylate (4-HBA). The hydroxyl-containing monomer may be selected alone or in combination of two or more.

[0036] In a specific embodiment, based on 100 wt % of the total weight of the monomer components in the acrylic copolymer, the content of the polar monomer containing a hydroxyl group is not less than 15 wt % and not more than 20 wt %.

[0037] In a specific embodiment, the polar monomer containing nitrogen atoms includes at least one of N-vinyl-2-pyrrolidone (NVP), N-vinylcaprolactam (NVC) and N,N-dimethylacrylamide.

[0038] In a specific embodiment, based on 100 wt % of the total weight of the monomer components in the acrylic copolymer, the content of the polar monomer containing nitrogen atoms is not less than 10 wt % and not more than 15 wt %.

[0039] In one embodiment, the weight average molecular weight of the copolymer obtained by polymerizing the monomers constituting the acrylic copolymer can be any suitable value, and in the present invention, it is preferably 1,000,000 to 5,000,000 g / mol, and more preferably 1,500,000 to 3,000,000 g / mol.

[0040] The acrylic copolymer can be prepared by conventional polymerization methods, such as free radical polymerization. In one embodiment, the preparation of the acrylic copolymer comprises: mixing the monomer components, adding a certain amount of photoinitiator, and initiating polymerization under ultraviolet light in a protective atmosphere. The acrylic copolymer can be obtained after the reaction is completed.

[0041] Furthermore, based on 100 parts by weight of the total amount of monomer components of the acrylic copolymer, the amount of the photoinitiator is 0.01 to 0.1 parts by weight.

[0042] Furthermore, the photoinitiator is not particularly limited, and conventional initiators can be selected as long as they can initiate polymerization, such as at least one of fluoroboryl acrylate (photoinitiator 184), benzoin diethyl ether (photoinitiator 651) and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (photoinitiator TPO).

[0043] Furthermore, the protective gas may be at least one of nitrogen and argon.

[0044] In a specific embodiment, the optical adhesive sheet further includes an acrylic oligomer, and the content of the acrylic oligomer is 5 to 15 parts by weight relative to 100 parts by weight of the acrylic copolymer, specifically 5 parts by weight, 8 parts by weight, 10 parts by weight, 12 parts by weight, 14 parts by weight, 15 parts by weight or any value between any two ends thereof; regulating the amount of acrylic oligomer in the adhesive within the above range is beneficial to maintaining a good balance between the initial adhesion, high temperature resistance and weather resistance of the adhesive.

[0045] In one specific embodiment, the acrylic oligomer contains 85-95 wt% of a high-Tg monomer, based on 100 wt% of the total weight of the monomer components in the acrylic oligomer. For example, the content can be 85 wt%, 88 wt%, 90 wt%, 92 wt%, 95 wt%, or any value between these two values. The present invention stipulates that the acrylic oligomer contains a relatively high content of high-Tg monomer to ensure that the acrylic oligomer has a higher Tg, impart a certain degree of rigidity to the adhesive, improve the storage modulus at high temperatures, and enhance weather resistance in hot and humid environments. The high-Tg monomer described in the present invention refers to a monomer having a Tg value greater than 10°C, preferably greater than 50°C, and more preferably greater than 100°C.

[0046] In a specific embodiment, the high Tg monomer includes at least one of linear and / or branched alkyl (meth)acrylate, alicyclic (meth)acrylate and aromatic (meth)acrylate, preferably alicyclic (meth)acrylate.

[0047] In one specific embodiment, the alicyclic (meth)acrylates include isobornyl methacrylate (IBOMA), biscyclopentenyl methacrylate (DCPMA), biscyclopentenylethoxy methacrylate, dicyclopentyl methacrylate, 1-adamantyl methacrylate (ADMA), 2-methyl-2-adamantyl methacrylate, and 2-ethyl-2-adamantyl methacrylate. The high Tg monomer may be at least one of the above monomers.

[0048] In a specific embodiment, the aromatic (meth)acrylate includes at least one of aryl (meth)acrylate, phenoxyalkyl (meth)acrylate, and aryl alkyl (meth)acrylate.

[0049] Furthermore, the aryl (meth)acrylate may include phenyl (meth)acrylate; the phenoxyalkyl (meth)acrylate includes 2-phenoxyethyl (meth)acrylate; and the aryl alkyl (meth)acrylate includes benzyl (meth)acrylate.

[0050] In one embodiment, the acrylic oligomer further contains a polar monomer, which can be any of the polar monomers listed above for the acrylic copolymer. The polar monomer in the acrylic oligomer can be the same as or different from the polar monomer selected for the acrylic copolymer.

[0051] In a specific embodiment of the present invention, based on 100 wt% of the total weight of the monomer components in the acrylic oligomer, the polar monomer is contained in an amount of 5 to 15 wt%, for example, 5 wt%, 8 wt%, 10 wt%, 12 wt%, 15 wt% or any value in between.

[0052] In one specific embodiment, the weight-average molecular weight (Mw) of the acrylic oligomer is 20,000 to 100,000 g / mol, for example, 20,000 g / mol, 40,000 g / mol, 50,000 g / mol, 60,000 g / mol, 80,000 g / mol, 100,000 g / mol, or any value therebetween. Limiting the weight-average molecular weight of the acrylic oligomer to this range can yield an adhesive with well-balanced tack, toughness, and weather resistance.

[0053] In one specific embodiment, a chain transfer agent may be added to the acrylic oligomer during polymerization to control the weight-average molecular weight of the oligomer. Conventional chain transfer agents can be selected, such as thiols, such as n-dodecyl mercaptan, 2-mercaptoethanol, pentaerythritol tetrakis(3-mercaptobutyrate) (PE1), or the commercially available 2,4-diphenyl-4-methyl-1-pentene (TPMS). The amount of the chain transfer agent used is 0.3 to 3 parts by weight, based on 100 parts by weight of the total monomer components in the acrylic oligomer.

[0054] In a specific embodiment of the present invention, the acrylic oligomer can be polymerized in a conventional manner. For example, its preparation includes: weighing the monomer components, chain transfer agent and solvent in proportion, mixing them evenly under a protective atmosphere, then adding a certain amount of thermal initiator, heating to a certain temperature to carry out polymerization reaction, and removing the solvent after the reaction is completed to obtain the acrylic oligomer.

[0055] Furthermore, the protective atmosphere is a nitrogen atmosphere or an argon atmosphere.

[0056] Furthermore, the polymerization reaction temperature is 70-80°C, and the reaction time is 2-6 hours. The specific reaction temperature and time can be adjusted according to the type of initiator, so as to be able to initiate polymerization.

[0057] Further, the thermal initiator can be selected from conventional azo initiators including, but not limited to, azobisisobutyronitrile (AIBN), azobisisoheptyl nitrile, and organic peroxide initiators including, but not limited to, dibenzoyl peroxide (BPO), lauroyl peroxide. The thermal initiator can be selected from at least one of the above-listed substances. The amount of the thermal initiator is 0.1 to 2 parts by weight based on 100 parts by weight of the total weight of the monomer components in the acrylic oligomer.

[0058] Further, the solvent can be selected from conventional organic solvents including, but not limited to, at least one of ethyl acetate (EA), toluene (Tol), and methyl ethyl ketone (MEK). The amount of the solvent is 50 to 200 parts by weight based on 100 parts by weight of the total weight of the monomer components in the acrylic oligomer.

[0059] In an embodiment, the optical adhesive sheet further includes a crosslinking monomer. The crosslinking monomer can crosslink the acrylic copolymer. The crosslinking monomer can be selected from multifunctional (meth)acrylate monomers, preferably (meth)acrylate monomers having a functionality of 2 to 6, such as 1,6-hexanediol diacrylate (HDDA) having a functionality of 2, ethoxylated trimethylolpropane triacrylate having a functionality of 3, and trimethylolpropane triacrylate (TMPTA) having a functionality of 3. The crosslinking monomer can be selected from at least one of the above-listed substances.

[0060] The amount of the crosslinking monomer is 0.1 to 0.5 parts by weight based on 100 parts by weight of the acrylic copolymer. Specifically, the amount of the crosslinking monomer can be 0.1 parts by weight, 0.2 parts by weight, 0.3 parts by weight, 0.4 parts by weight, 0.5 parts by weight, or any value between any two of the above values. The introduction of the crosslinking monomer in an appropriate amount can increase the crosslinking density of the system after curing, thereby increasing the rigidity and maintaining a high modulus at high temperatures and inhibiting the escape of bubbles.

[0061] In an embodiment, the optical adhesive sheet further includes a silane coupling agent. The amount of the silane coupling agent is 0.1 to 1 parts by weight based on 100 parts by weight of the acrylic copolymer. Specifically, the amount of the silane coupling agent can be 0.1 parts by weight, 0.3 parts by weight, 0.5 parts by weight, 0.8 parts by weight, 1 parts by weight, or any value between any two of the above values. The introduction of the silane coupling agent in an appropriate amount can improve the adhesive strength and moisture and heat aging resistance of the adhesive and increase the affinity of the adhesive sheet to the glass substrate.

[0062] In the detailed description of the present application, the silane coupling agent includes at least one of 3-(2,3-epoxypropoxy)propyltrimethoxysilane, 3-(2,3-epoxypropoxy)propyltriethoxysilane, 3-aminopropyltrimethoxysilane and N-phenyl-3-aminopropyltrimethoxysilane. The silane coupling agent in the present application can also use commercially available products, such as KBM-403 produced by Japan Shin-Etsu Chemical Industry Co., Ltd.

[0063] In the present application, the preparation method of the adhesive has no particular limitation and the commonly used preparation method of the adhesive can be used. The present application provides a preparation method of an adhesive, which comprises the following steps: mixing the components in proportion, stirring uniformly, standing to defoam, and then obtaining the adhesive to be coated.

[0064] It can be understood that, in order to facilitate production, transportation and sales, the optical transparent adhesive of the present application only limits the component composition and does not limit the existing form of the components, i.e. the components can be mixed with each other or can be stored independently. The mixing or independent storage mode can be selected according to the actual use occasion.

[0065] In the detailed description of the present application, the thickness of the adhesive sheet can be set to different thicknesses according to specific needs, for example, can be 100-200 μm, specifically 100 μm, 120 μm, 150 μm, 180 μm, 200 μm or a value between any two end values.

[0066] The present application also provides an optional preparation method of the above-mentioned adhesive sheet, which comprises the following steps: coating the adhesive on the surface of the release film, UV curing and drying treatment to obtain an adhesive sheet product. In order to facilitate winding and packaging and transportation, a layer of release film can also be coated on the surface of the adhesive sheet.

[0067] The coating method is not limited and conventional coating methods such as roll coating, blade coating or dip coating can be used. The thickness of the release film can be freely selected according to actual needs and is not particularly limited, for example, can be 25-100 μm, specifically 25 μm, 30 μm, 40 μm, 50 μm, 80 μm, 100 μm or a value between any two end values.

[0068] In the detailed description of the present application, the UV curing intensity is 3-10 mW / cm 2 , and the irradiation time is 1-5 min.

[0069] In the detailed description of the present application, the drying temperature is 90-110℃ and the time is 2-5 min.

[0070] In actual use, the release film of the adhesive sheet product of the present application is removed and the adhesive sheet is pasted between two components to be pasted.

[0071] The objects and advantages of the present application will be further illustrated by the following specific examples, but these examples should not be construed as limiting the present application. In the following examples, 1 g represents 1 part by weight.

[0072] Preparation Example A group

[0073] Preparation of acrylic copolymer

[0074] In an open reactor, a certain mass fraction of soft monomer, hydrophilic monomer, polar monomer and photoinitiator were put in, stirred and purged with nitrogen, and then polymerization was carried out under ultraviolet light irradiation until the viscosity of the reactants reached the limited range, thus obtaining acrylic copolymer A.

[0075] The preparation methods of different acrylic copolymers of preparation example A group are the same, and the difference lies in the different amounts or types of components, as shown in the following table 1.

[0076] Table 1 Raw material composition of acrylic copolymer

[0077]

[0078] Note: In the above copolymer A6, due to the too high content of hydrophilic monomer, the copolymerization fails and no effective copolymer can be formed.

[0079] The weight average molecular weight was tested by gel permeation chromatography (GPC) under the following conditions:

[0080] 1) Chromatographic column: PLgel 10 μm MIXED-B (Part No: PL1110-6100), Pore Type: MIXED-B, Length / I.D: 300x7.5 mm.

[0081] 2) Mobile phase: tetrahydrofuran (THF) solution containing 2,6-di-tert-butyl-4-methyl phenol stabilizer, flow rate 0.5 mL / min.

[0082] 3) Injection concentration: 5.0 mg / mL, injection volume: 20 μL, column temperature: 40℃, detector temperature: 40℃.

[0083] 4) Standard sample: polystyrene (Easivial).

[0084] 5) Sample preparation: dissolve the sample in THF to prepare a solution of 5-10 mg / mL, shake for 2 h, and stand overnight. Use a 2 mL disposable syringe to take the upper clear liquid, and then filter the lower filtrate into a special sample bottle using a 0.45 μm filter screen. In addition, prepare a THF blank sample to ensure that the bottle cap is tightly sealed.

[0085] The GPC device used in the present application is Agilent 1260 infinity II, and the test operation of weight average molecular weight is performed according to the device instruction.

[0086] Preparation Example B group

[0087] Preparation of acrylic oligomer

[0088] A certain mass fraction of high Tg monomer, polar monomer, chain transfer agent and solvent were put into a four-necked flask and stirred at 70°C under nitrogen atmosphere. Then a certain mass fraction of thermal initiator was put in, and reacted at 70°C for 2 h and at 80°C for 2 h. After the reaction was completed, the solvent, chain transfer agent and unreacted monomer were dried and removed at 130°C, thereby obtaining a solid acrylic oligomer B.

[0089] The preparation methods of different acrylic oligomers of the preparation example B group are the same, and the difference lies in the different use amount or type of each component, which is shown in the following table 2.

[0090] Table 2 Raw material composition of acrylic oligomer

[0091]

[0092] Example 1

[0093] The present embodiment provides an optical adhesive sheet, which comprises the following components:

[0094] 100 g of acrylic copolymer A1, 10 g of acrylic oligomer B1, 0.25 g of 1,6-hexanediol diacrylate (HDDA) and 0.5 g of silane coupling agent KBM-403.

[0095] The preparation method is as follows: the above materials are uniformly mixed to obtain an adhesive, the adhesive is coated on the surface of a 50 μm thick PET release film by a double roller, and irradiated with ultraviolet light at an intensity of 5 mW / cm 2 for 5 min, and then baked at 100°C for 3 min to obtain an adhesive sheet with a thickness of 150 μm.

[0096] Example 2

[0097] The present embodiment is carried out by referring to example 1, and the only difference is that the use amount of some components of the adhesive sheet is different, and the rest is the same as example 1, and the specific difference is shown as follows:

[0098] 5 g of acrylic oligomer B1, 0.5 g of HDDA and 0.1 g of silane coupling agent KBM-403.

[0099] Example 3

[0100] This example was carried out with reference to Example 1, with the only difference being the amounts and types of some components of the adhesive sheet. The rest were the same as Example 1. The specific differences are as follows:

[0101] 15 g of acrylic oligomer B1, 0.1 g of trimethylolpropane triacrylate (TMPTA), and 1 g of silane coupling agent KBM-403.

[0102] Example 4 Group

[0103] This example group was prepared with reference to Example 1, with the only difference being that the same amount of different acrylic copolymers prepared in Preparation Example A were used. The rest were the same as in Example 1. The specific differences are as follows:

[0104] Example 4a: The acrylic copolymer is A2 prepared in Preparation Example A;

[0105] Example 4b: The acrylic copolymer is A3 prepared in Preparation Example A;

[0106] Example 4c: The acrylic copolymer is A4 prepared in Preparation Example A;

[0107] Example 4d: The acrylic copolymer is A5 prepared in Preparation Example A.

[0108] Example 5 Group

[0109] This example group was prepared with reference to Example 1, with the only difference being that the same amount of different acrylic oligomers prepared in Preparation Example B were used. The rest were the same as in Example 1. The specific differences are as follows:

[0110] Example 5a: The acrylic oligomer is B2 prepared in Preparation Example Group B;

[0111] Example 5b: The acrylic oligomer is B3 prepared in Preparation Example B;

[0112] Example 5c: The acrylic oligomer is B4 prepared in Preparation Example Group B;

[0113] Example 5d: The acrylic oligomer is B5 prepared in Preparation Example B.

[0114] Comparative Example 1

[0115] This comparative example group was carried out with reference to Example 1, except that the amount of acrylic acid oligomer was different. The rest was the same as Example 1. The specific differences are as follows:

[0116] Comparative Example 1a: 2.5 g of acrylic oligomer B1;

[0117] Comparative Example 1b: 20 g of acrylic oligomer B1.

[0118] Test Example

[0119] The optical adhesive sheet prepared in each of the above examples and comparative examples was subjected to the following tests, and the test results are shown in Table 3.

[0120] (1) 180° peeling force test: The test was performed in accordance with the international standard ASTM D3330 "Standard Test Methods for Peel Resistance of Pressure-Sensitive Tape", and the test panel was a PC plate, and the test sample size was 300 mm x 24 mm.

[0121] Normal temperature peeling force test: After the sample was attached to the PC plate, the average adhesion required to tear the sample from the panel was tested at 23 ± 1°C, 50 ± 5% RH after 20 min, expressed in gf / 24 mm.

[0122] 85°C peeling force test: After the sample was attached to the PC plate, the average adhesion required to tear the sample from the panel was tested after 20 min at 23 ± 1°C, 50 ± 5% RH, 30 min in an 85°C oven.

[0123] (2) Initial adhesion test: The test was performed in accordance with the international standard ASTM D3121-17 "Standard Test Methods for Pressure-Sensitive Adhesives Using a Rolling Ball", and the corresponding ball number (#) was recorded. The larger the ball number, the higher the initial adhesion.

[0124] (3) Attachment effect test: The adhesive sheet attached to the PC plate was cut into a whole of 5 cm x 10 cm, and the adhesive sheet and the PC plate were attached to the surface of a plain glass using a vacuum attachment machine at 0.5 MPa, 30°C for 30 min. After 24 h of standing after removal, the appearance of the adhesive sheet was observed visually, and if there were no bubbles, whitening, delamination, or other appearance defects, it was recorded as OK, otherwise the corresponding appearance defects were recorded.

[0125] (4) High temperature and humidity resistance test: The sample in (3) that had been placed at 0.5 MPa, 30°C for 30 min and stood for 24 h after removal was placed at 85°C / 85% RH for 1,000 h, and the surface of the adhesive sheet was observed visually for bubbles, whitening, delamination, or other appearance defects. If there were none, the high temperature and humidity resistance was recorded as OK, otherwise the corresponding appearance defects were recorded.

[0126] Table 3 Performance test results of different examples and comparative examples

[0127]

[0128] The above test results show that the use of the hydrophilic monomer with the structure defined in the present invention as a comonomer of the acrylic copolymer can effectively improve the blister resistance of the adhesive sheet, and can also balance the initial tack, adhesion performance and peel strength of the adhesive sheet, which is conducive to avoiding delamination; and adding a certain amount of acrylic oligomer prepared with a high Tg monomer to the adhesive sheet helps to increase the rigidity and thus enhance the high temperature resistance of the adhesive sheet.

[0129] The test results of Example 4 indicate that the adhesive sheet prepared using the acrylic copolymer with the defined component composition and molecular weight range of the present invention can effectively improve the blister resistance of the adhesive sheet while also balancing the initial tack, adhesion performance, and peel strength of the adhesive sheet. However, if the hydrophilic monomer content is below the defined range, the improvement in blister resistance is poor. This is because the adhesive sheet is not hydrophilic enough and has insufficient affinity for bubbles released by PC, which prevents effective gas dissolution and leads to gas escape. When the hydrophilic monomer content is too high, its steric hindrance is relatively large, the copolymerization reaction activity is very low, and an effective polymer cannot be formed.

[0130] The test results of Example 5 show that by adding an acrylic oligomer within the molecular weight and content range specified in the present invention to an adhesive sheet, an adhesive sheet with balanced initial adhesion, high temperature resistance, and peel strength can be obtained. When the molecular weight of the acrylic oligomer is too high, the compatibility between the acrylic oligomer and the acrylic copolymer deteriorates, resulting in a white appearance. When the molecular weight of the acrylic oligomer is too low, it is difficult to ensure the modulus of the adhesive at high temperature, resulting in a decrease in high temperature and high humidity resistance.

[0131] The test results of Comparative Example 1 show that when the amount of acrylic oligomer used is too low, the high-temperature adhesion of the adhesive cannot be guaranteed, and the high-temperature and high-humidity resistance decreases; when the amount of acrylic oligomer used is too high, the initial adhesion of the adhesive sheet is poor, the bonding performance deteriorates, and delamination is prone to occur under high temperature and high humidity.

[0132] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An optical adhesive sheet, characterized in that The optical adhesive sheet is composed of 100 parts by weight of an acrylic copolymer, 5 to 15 parts by weight of an acrylic oligomer, 0.1 to 0.5 parts by weight of a cross-linking monomer, and 0.1 to 1 part by weight of a silane coupling agent. The acrylic copolymer has a weight-average molecular weight Mw of 1,500,000 to 3,000,000 g / mol and, based on 100 wt% of the total weight of monomer components in the acrylic copolymer, comprises 10 to 20 wt% of a hydrophilic monomer, 50 to 60 wt% of a soft monomer, 15 to 20 wt% of a polar monomer containing a hydroxyl group, and 10 to 15 wt% of a polar monomer containing a nitrogen atom; wherein the hydrophilic monomer is methoxy polyethylene glycol acrylate, and the soft monomer is an alkyl (meth)acrylate having an alkyl group with 4 to 14 carbon atoms; The acrylic oligomer has a weight-average molecular weight Mw of 20,000-100,000 g / mol and, based on 100 wt% of the total weight of monomer components in the acrylic oligomer, is composed of 85-95 wt% of alicyclic (meth)acrylate and 5-15 wt% of polar monomer.

2. The optical adhesive sheet according to claim 1, characterized in that The cross-linking monomer is a (meth)acrylate monomer with a functionality of 2 to 6.

3. The optical adhesive sheet according to claim 2, wherein The crosslinking monomer includes at least one of 1,6-hexanediol diacrylate, ethoxylated trimethylolpropane triacrylate, and trimethylolpropane triacrylate.

4. The optical adhesive sheet according to claim 1, wherein The soft monomer includes at least one of 2-ethylhexyl acrylate, n-butyl acrylate, dodecyl acrylate and isodecyl acrylate.

5. The optical adhesive sheet according to claim 1, wherein The polar monomer containing a hydroxyl group includes at least one of 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl acrylate and 4-hydroxybutyl acrylate.

6. The optical adhesive sheet according to claim 1, wherein The polar monomer containing nitrogen atoms includes at least one of N-vinyl-2-pyrrolidone, N-vinylcaprolactam and N,N-dimethylacrylamide.

7. The optical adhesive sheet according to claim 1, wherein The alicyclic (meth)acrylate includes at least one of isobornyl methacrylate, biscyclopentenyl methacrylate, biscyclopentenyl ethoxy methacrylate, dicyclopentyl methacrylate, 1-adamantyl methacrylate, 2-methyl-2-adamantyl methacrylate, and 2-ethyl-2-adamantyl methacrylate.

8. The optical adhesive sheet according to claim 1, wherein The silane coupling agent includes at least one of 3-(2,3-epoxypropoxy)propyltrimethoxysilane, 3-(2,3-epoxypropoxy)propyltriethoxysilane, 3-aminopropyltrimethoxysilane and N-phenyl-3-aminopropyltrimethoxysilane.

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