Bending-resistant optical adhesive

Abstract

A bending-resistant optical adhesive prepared by means of an UV bulk polymerization method. The optical adhesive prepared by means of this method meets a relatively high viscosity and high creep recovery at different temperatures while meeting a low modulus at low temperature, and has good comprehensive performance. Furthermore, both a thermal polymerization method and a photopolymerization method can be used to synthesize bending-resistant optical adhesives.

Description

Bending-resistant optical adhesive TECHNICAL FIELD

[0001] The present application relates to the field of adhesives, in particular to a bending-resistant optical adhesive. BACKGROUND

[0002] In recent years, foldable devices have been increasingly favored by the market due to their excellent portability. With the popularity of foldable devices, adhesives suitable for the use characteristics of foldable devices are also in demand by the market. In foldable devices, the display has a laminated structure containing elements such as pixel panels, polarizing sheets, touch panels, and cover films. In the manufacturing process of such display panels, for the bonding of elements contained in the laminated structure to each other, for example, an optically transparent optical adhesive sheet with bending resistance is used.

[0003] In some cases, as the temperature decreases, the adhesive layer of the bendable device becomes hard. For example, when folding the bendable device in a low-temperature environment, it is easy to cause whitening or cracking at the folding layer. In addition, if the optical adhesive used cannot maintain good adhesion in a specific environment, there is a risk of bubbles or even peeling between the adhesive film and the backing material substrate (such as PI, PET, Glass, etc.).

[0004] So far, the optical adhesive products used under the foldable screen on the market cannot meet the low modulus at low temperature while meeting the high adhesion and high creep recovery at different temperatures. The comprehensive performance cannot meet the needs of consumers. Therefore, it is of great market value and scientific research significance to develop an optical adhesive for foldable screens with excellent comprehensive performance. SUMMARY

[0005] The present application aims to provide a bending-resistant optical adhesive, which solves the problem that the adhesive layer of the bendable device becomes hard as the temperature decreases. For example, when folding the bendable device in a low-temperature environment, it is easy to cause whitening or cracking at the folding layer. At the same time, the optical adhesive can maintain good adhesion in a specific environment, avoiding the risk of bubbles or even peeling between the adhesive film and the backing material substrate (such as PI, PET, Glass, etc.).

[0006] To solve the above technical problems, the present application provides an optical adhesive in a first aspect:

[0007] A bend-resistant optical adhesive contains an acrylic polymer as a base polymer, the acrylic polymer being a polymer composed of (meth)acrylic alkyl ester and an aromatic compound having the following Chemical Formula 1 as monomer components, wherein the sum of the proportions of the compounds having "Chemical Formula 1" among all the monomer components constituting the acrylic polymer is 0.1-20 wt%, and the glass transition temperature is -40℃ or lower.

[0008]

[0009] Chemical Formula 1

[0010] In the above Chemical Formula 1, X is a single bond, an alkyl group having a carbon number of 1-5, or an oxygen atom; Y is a hydrogen atom or a methyl group, R1 is an alkyl group having a carbon number of 1-10, a halogen atom, or an aryl group having a carbon number of 6-20, n is an integer of 0-5, and R2 is an alkyl group having a carbon number of 1-10 or a (poly)alkyloxy group having a carbon number of 1-30.

[0011] The (meth)acrylic alkyl ester includes one or more of phenylbenzyl ester acrylate, phenoxabenzyl (meth)acrylate, monoethoxylphenylphenoxy (meth)acrylate, and poly(ethoxyl)phenylphenoxy (meth)acrylate.

[0012] The (meth)acrylic alkyl ester has a content of 0.1-20 wt%, and the (meth)acrylic alkyl ester contains one or more of lauryl (meth)acrylate, isododecyl (meth)acrylate, tridecyl (meth)acrylate, isododecyl (meth)acrylate, pentadecyl (meth)acrylate, isopentadecyl (meth)acrylate, hexadecyl (meth)acrylate, isohexadecyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, urethane (meth)acrylate, and urethane (meth)acrylate.

[0013] In addition, the optical adhesive of the present application also includes a certain amount of small molecular weight polyacrylic acid resin (oligomer). The small molecular weight polyacrylic acid resin (oligomer) is obtained by bulk polymerization of functional acrylic monomers and non-functional acrylic monomers through a thermal initiator, and the synthesized small molecular weight polyacrylic acid resin has a molecular weight of 3905 g / mol measured by GPC.

[0014] In the present application, UV bulk polymerization is used to prepare the base polymer. In the polymerization, a corresponding photoinitiator can be selected according to actual needs, and a chain transfer agent can also be added to the reaction system if it is necessary to adjust the molecular weight. The conversion rate, viscosity, and molecular weight of the base polymer are not particularly limited and can be adjusted according to actual needs.

[0015] The second aspect of the present application provides a preparation method of the optical adhesive with bending resistance, comprising the following steps:

[0016] S1: Put the raw materials into a transparent glass reaction kettle, and polymerize into a prepolymer by irradiation;

[0017] The transparent glass reaction kettle in S1 is provided with a nitrogen environment, and the irradiation environment is an ultraviolet environment, and the polymerization product is an acrylic prepolymer. The conversion rate, viscosity and molecular weight of the prepolymer are not particularly limited and can be adjusted according to actual needs.

[0018] S2: According to actual needs, corresponding monomers, oligomers, crosslinking agents, silane coupling agents, initiators and other materials are selected and added to the prepolymer obtained in S1, and if it is necessary to adjust the molecular weight, a chain transfer agent can also be added to the reaction system. Then stir and mix uniformly, and stand or vacuum degassing.

[0019] S3: Preparation of the adhesive tape: R701T-C and R703T-C produced by the Crown are arranged in an opposite manner of release surface, and the above-mentioned adhesive is poured between the two layers of films, and the thickness is controlled at about 50 um by roller extrusion, and then placed under the UV lamp for irradiation and curing, thereby obtaining the OCA adhesive tape.

[0020] The third aspect of the present application provides an optical double-sided adhesive sheet having an adhesive layer on one side or both sides of a substrate. The thickness of the substrate is 50 μm or more.

[0021] The optical double-sided adhesive sheet provided by the present application can be used for the adhesive layer of a bendable organic EL display.

[0022] Compared with the prior art, the present application has the following advantages:

[0023] The present application provides an optical adhesive with bending resistance prepared by UV bulk polymerization. The optical adhesive prepared by this method meets the low modulus at low temperature, while meeting the high adhesion and high creep recovery at different temperatures, and has good comprehensive performance. Further, the thermal polymerization and photopolymerization methods can also be used to synthesize the optical adhesive with bending resistance according to the technical scheme of the present application. DETAILED DESCRIPTION

[0024] In order to make the technical problems, technical solutions and beneficial effects of the present application more clear and explicit, the present application will be further described in detail in combination with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application.

[0025] Table 1: List of adhesive ingredients

[0026]

[0027] Table 2 Optical adhesive implementation

[0028]

[0029] The above-mentioned prepolymer composition shown in Table 1 was added as a post-adding component with the oligomer, the multifunctional monomer (HDDA), LD-301, the silane coupling agent (manufactured by MOMENTIVE, "Silquest A-187") and IrgBDK in the amount shown in Table 1, and then uniformly mixed to obtain an adhesive composition.

[0030] Performance test

[0031] The optical glue prepared in the above-mentioned Examples 1-3 and Comparative Examples 1-3 was made into an OCA adhesive tape, and the related performance was measured, and the test method was as follows, and the results were shown in Table 3.

[0032] 180 degree peel strength test: GB / T 2792-2014;

[0033] Optical test: Konica Minolta colorimetric system, CM-3600A, test standard ASTM

[0034] Storage modulus: TA hybrid rheometer DHR-2, ASTM D4440-15;

[0035] Dynamic bending experiment: radius 3mm, 40 times / min, 500,000 times.

[0036] Table 3 Test results of optical adhesive tape

[0037]

[0038] From the above test results, it can be seen that the present application discloses an optical glue prepared by UV bulk polymerization, which has good bending resistance. The optical glue has low modulus and good adhesion at low temperature, and has good flexibility.

[0039] The above examples are only for illustrating the technical concept and characteristics of the present application, the purpose is to enable those skilled in the art to understand the content of the present application and to implement it, and it cannot limit the protection scope of the present application. Any equivalent changes or modifications made according to the spirit and essence of the present application shall be covered within the protection scope of the present application.

Claims

1. A bend-resistant optical adhesive, comprising an acrylic adhesive layer having an acrylic polymer as a base polymer, characterized in that, The acrylic polymer is a polymer composed of (meth)acrylic alkyl ester and an aromatic compound having the following Chemical Formula 1 as a monomer component, wherein the sum of the proportions of the aromatic compound having "Chemical Formula 1" in all monomer components constituting the acrylic polymer is 0.1-20 wt%, the glass transition temperature is -40°C or lower, and Chemical Formula 1 is In the above Chemical Formula 1, X is a single bond, an alkyl group having a carbon number of 1-5, or an oxygen atom; Y is a hydrogen atom or a methyl group, R1 is an alkyl group having a carbon number of 1-10, a halogen atom, or an aryl group having a carbon number of 6-20, n is an integer of 0-5, and R2 is an alkyl group having a carbon number of 1-10 or a (poly)alkyloxy group having a carbon number of 1-30.

2. The bend-resistant optical adhesive of claim 1, wherein The aromatic compound is one or more of phenylbenzyl ester acrylate, phenoxybenzyl (meth)acrylate, monoethoxyphenylphenoxy (meth)acrylate, and poly(ethoxy)phenylphenoxy (meth)acrylate.

3. The bend-resistant optical adhesive of claim 1, wherein the adhesive is a UV-curable adhesive. The content of the (meth)acrylic alkyl ester is 0.1-20 wt%, and the (meth)acrylic alkyl ester contains an alkyl (meth)acrylate having 12 or more carbons.

4. The bend-insensitive optical adhesive as claimed in claim 3, wherein, The alkyl (meth)acrylate having 12 or more carbons includes one or more of lauryl (meth)acrylate, isododecyl (meth)acrylate, tridecyl (meth)acrylate, isododecyl (meth)acrylate, pentadecyl (meth)acrylate, isopentadecyl (meth)acrylate, hexadecyl (meth)acrylate, isohexadecyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, urethane (meth)acrylate, and urethane (meth)acrylate.

5. An optical double-coated adhesive sheet containing the flexible optical adhesive of any one of claims 1-4.

6. The optical double-coated adhesive sheet according to claim 5, wherein The adhesive sheet has a storage modulus at -20°C of less than 100 KPa.

7. The optical double-coated adhesive sheet according to claim 5, wherein The substrate has a thickness of at least 50 μm.

8. Use of the optical double-coated adhesive sheet of any one of claims 5-7 as an adhesive layer for a flexible organic EL display.

9. An organic EL display having the flexible optical adhesive of any one of claims 1-4 and / or the optical double-coated adhesive sheet of any one of claims 5-7.

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