High-temperature-resistant flexible optical adhesive sheet

Abstract

According to the high-temperature-resistant flexible optical adhesive sheet provided by the invention, through innovative monomer combination and molecular structure design, the optical adhesive sheet with low modulus, high adhesive strength and excellent high-temperature stability is successfully developed. By controlling the ratio of the C6-9 short-chain ester (A) to the C10-20 long-chain ester (B) and the addition amount of the functional monomer and balancing cohesive strength and molecular chain segment activity, the problem of interface failure of a flexible display device in an extreme environment is solved, and the prepared optical adhesive sheet has good adhesive force and low energy storage modulus under a low-temperature condition and also has a good application prospect. The high-temperature-resistant creep-resistant steel has good creep recovery performance under a traditional high-temperature condition of 65 DEG C, and also has good creep recovery performance at a higher temperature of 120 DEG C.

Description

Technical Field

[0001] The present invention relates to the technical field of adhesive sheets, and particularly to a flexible optical adhesive sheet with high temperature resistance. Background Art

[0002] In recent years, due to their excellent portability, foldable devices have become increasingly popular and are more and more widely used in fields such as foldable screen mobile phones, smart wearables, vehicles, and electronic devices. With the popularization of foldable devices, adhesives suitable for the usage characteristics of foldable devices are also in demand in the market. Generally, the OCA adhesives used in foldable devices need to have durability in use against environmental changes, and should also have effective bonding performance, excellent high and low temperature modulus stability and creep performance, and good bonding performance, so as to improve the service life of foldable devices.

[0003] Generally speaking, flexible optical adhesives have a low modulus, the colloid is soft, and the creep performance in a high temperature environment is poor. The generally described high temperature creep performance is the high temperature creep performance at 65°C. The recovery rate of most flexible optical adhesives under this condition is low, and there is still no optical adhesive with good creep performance at 120°C on the market. Developing a flexible optical adhesive with good creep performance at high temperatures from 65°C to even 120°C is of milestone significance for the research and development of foldable devices operating in extreme environments.

[0004] In the existing technologies, it is difficult for flexible optical adhesives to have good creep recovery performance under high temperature (65°C and above) conditions while maintaining a low modulus and good adhesion. To solve the above problems, the present invention proposes a solution for a high temperature resistant flexible optical adhesive sheet for a protective film that can be prepared to simultaneously have good adhesion performance, a low modulus, and excellent high temperature creep performance. Summary of the Invention

[0005] To improve the above situation, the present invention provides a high temperature resistant flexible optical adhesive sheet. The optical adhesive sheet has a pressure sensitive adhesive layer. Among them, the pressure sensitive adhesive layer is composed of a photocurable composition. The photocurable composition includes an acrylic polymer, a photocuring agent having two or more photopolymerizable functional groups, and a photopolymerization initiator. The acrylic polymer uses (meth)acrylic acid alkyl ester A having 6 - 9 carbon atoms, (meth)acrylic acid alkyl ester B having 10 - 20 carbon atoms, an alkoxy group-containing monomer C, a hydroxyl group-containing monomer D, and an N atom-containing monomer E as monomer components.

[0006] Furthermore, the content of the alkoxy group-containing monomer C accounts for 1 - 40 wt% of the total weight of the monomer components.

[0007] Furthermore, the dosage ratio of the (meth)acrylic acid alkyl ester A having 6-9 carbon atoms to the (meth)acrylic acid alkyl ester B having 10-20 carbon atoms is 0.125 < B / A < 0.8.

[0008] Furthermore, based on 100 parts by weight of the acrylic polymer, the total dosage of the hydroxyl group-containing monomer D and the nitrogen atom-containing monomer E does not exceed 10 parts by weight.

[0009] Furthermore, the molecular weight of the acrylic polymer is greater than 1,000,000 g / mol.

[0010] Furthermore, the (meth)acrylic acid alkyl ester A having 6-9 carbon atoms can be one or more of n-hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, and isononyl (meth)acrylate.

[0011] Furthermore, the (meth)acrylic acid alkyl ester B having 10-20 carbon atoms can be one or more of decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate (i.e., lauryl (meth)acrylate), isotridecyl (meth)acrylate, tetradecyl (meth)acrylate, tetrapropenyl (meth)acrylate, pentadecyl (meth)acrylate, cetyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, isooctadecyl (meth)acrylate, and nonadecyl (meth)acrylate.

[0012] Furthermore, the alkoxy group-containing monomer C can be one or more of methoxymethyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, ethoxyethoxyethyl acrylate, 3-methoxypropyl (meth)acrylate, 3-ethoxypropyl (meth)acrylate, 4-methoxybutyl (meth)acrylate, and 4-ethoxybutyl (meth)acrylate.

[0013] Furthermore, the hydroxyl group-containing monomer D can be one or more of 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.

[0014] Further, the N-atom-containing monomer E may be one or more of N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N,N-dimethylacrylamide, N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-(meth)acryloyl-2-pyrrolidone, N-(meth)acryloylpiperidine, N-(meth)acryloylpyrrolidine, N-vinylmorpholine, N-vinyl-3-morpholinone, N-vinyl-2-caprolactam, N-vinyl-3,5-morpholinedione, and N-vinylpyrazole.

[0015] Further, the photocurable composition further includes an acrylate oligomer, and the weight-average molecular weight of the acrylate oligomer is not less than 2000 g / mol and not higher than 9000 g / mol. By using an acrylate oligomer with a molecular weight in the range of 2000 - 9000, preferably 3000 - 8000, and a molecular weight distribution below 2.7, the adhesion of the optical adhesive sheet can be improved while also enabling it to have good optical properties.

[0016] Manufacture of Acrylic Oligomer (Oligomer A)

[0017] Mix 40 parts by weight of isobornyl acrylate, 55 parts by weight of methyl methacrylate, 5 parts by weight of 2-hydroxyethyl acrylate as monomer components, 4 parts by weight of α-thioglycerol as a chain transfer agent, 0.2 parts by weight of AIBN, and 100 parts by weight of toluene as a polymerization solvent. React for 1 h under a nitrogen atmosphere, and then carry out the reaction with stirring at 80°C for 6 h. Subsequently, remove the solvent by high-temperature drying to obtain the acrylic oligomer (Oligomer A). The weight-average molecular weight Mw of the acrylic oligomer (A) is 4700, and the molecular weight distribution is 2.32.

[0018] Compared with the prior art, the prepared optical adhesive sheet of the present invention has good adhesion and a low storage modulus under low-temperature conditions, and has good creep recovery performance under the traditional high-temperature condition of 65°C, and can also have good creep recovery at a higher temperature of 120°C. Therefore, the protective film prepared using this flexible optical adhesive can be applied to folding devices operating in extreme environments. Detailed Embodiments

[0019] In order to make the technical problems, technical solutions, and beneficial effects solved by the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0020] Table 1 Composition List of the Adhesive

[0021] Abbreviation Name Manufacturer NOAA n-Octyl acrylate Osaka Organic LA Acrylic acid + Dialkyl ester BASF 4-HBA Hydroxybutyl acrylate BASF DMAA N,N-Dimethylacrylamide Maclean's reagent EOEOEA Ethoxyethoxyethyl acrylate Shanghai Merck Chemical Technology Co., Ltd. IrgBDK Benzoin dimethyl ether BASF Oligomer A Oligomer Guangdong Crown HDDA 1,6-Hexanediol diacrylate BASF Silquest A-187 MOMENTIVE

[0022] Table 2 - Formulation Compositions of Examples 1 - 3 and Comparative Examples 1 - 3

[0023]

[0024] Examples 1 - 3

[0025] As shown in Table 2, accurately weigh the corresponding amounts of n - octyl acrylate, dodecyl acrylate, hydroxybutyl acrylate, N,N - dimethylacrylamide, ethoxyethoxyethyl acrylate, and benzoin dimethyl ether and place them in a four - necked flask equipped with a stirrer, thermometer, and nitrogen tube. While stirring, introduce nitrogen gas. After stirring for at least 30 minutes, prepare the prepolymer by means of photo - initiated polymerization. The finally obtained prepolymer has a weight - average molecular weight of approximately 2.5 million.

[0026] Comparative Example 1

[0027] As shown in Table 2, accurately weigh the corresponding amounts of n - octyl acrylate, dodecyl acrylate, hydroxybutyl acrylate, N,N - dimethylacrylamide, and benzoin dimethyl ether and place them in a four - necked flask equipped with a stirrer, thermometer, and nitrogen tube. While stirring, introduce nitrogen gas. After stirring for at least 30 minutes, prepare the prepolymer by means of photo - initiated polymerization. The finally obtained prepolymer has a weight - average molecular weight of approximately 2.5 million.

[0028] Comparative Example 2

[0029] As shown in Table 2, accurately weigh the corresponding amounts of n - octyl acrylate, dodecyl acrylate, hydroxybutyl acrylate, N,N - dimethylacrylamide, ethoxyethoxyethyl acrylate, and benzoin dimethyl ether and place them in a four - necked flask equipped with a stirrer, thermometer, and nitrogen tube. While stirring, introduce nitrogen gas. After stirring for at least 30 minutes, prepare the prepolymer by means of photo - initiated polymerization. The finally obtained prepolymer has a weight - average molecular weight of approximately 2.5 million.

[0030] Comparative Example 3

[0031] As shown in Table 2, accurately weigh the corresponding amounts of n - octyl acrylate, dodecyl acrylate, hydroxybutyl acrylate, N,N - dimethylacrylamide, ethoxyethoxyethyl acrylate, and benzoin dimethyl ether and place them in a four - necked flask equipped with a stirrer, thermometer, and nitrogen tube. While stirring, introduce nitrogen gas. After stirring for at least 30 minutes, prepare the prepolymer by means of photo - initiated polymerization. The finally obtained prepolymer has a weight - average molecular weight of approximately 2.5 million.

[0032] Accurately weigh 100 parts of the corresponding prepolymers in Examples 1-3 and Comparative Examples 1-3 above. Add the corresponding amounts of Oligomer A, 1,6-hexanediol diacrylate, and Silquest A-187 to the prepolymer as described in Table 2. After stirring evenly, let it stand for defoaming to obtain the glue.

[0033] Use the light release film R701T-C and the heavy release film R703T-C produced by Guangdong Crown New Materials Technology Co., Ltd. Place them one above the other with their release surfaces facing each other. Pour the above glue between the two films. Control its thickness by rolling extrusion and cure it by irradiating with the UVA band under a UV lamp to prepare an optical adhesive sheet with a thickness of 50 μm.

[0034] Performance testing

[0035] Respectively, make OCA tapes from the optical adhesives prepared in Examples 1-3 and Comparative Examples 1-3 and measure their relevant properties. The test methods are as follows, and the results are shown in Table 3.

[0036] 180-degree peel strength test: GB / T 2792-2014;

[0037] Optical test: Konica Minolta color measurement system, CM-3600A, test standard ASTM D1003;

[0038] Storage modulus: TA hybrid rheometer DHR-2, ASTM D4440-15;

[0039] Creep recovery test: Apply a shear stress of 10 kPa with a TA rheometer and a recovery time of 600 s;

[0040] Dynamic bending experiment: radius 3 mm, 40 times / min, 50,000 times.

[0041] Table 3 - Properties of the high-temperature resistant flexible optical adhesive sheets prepared in the examples and comparative examples

[0042]

[0043] From the above test results, it can be seen that using the scheme disclosed in the examples of the present invention to prepare the flexible optical adhesive sheet can make the prepared optical adhesive sheet have good creep recovery performance at 25 °C, 65 °C, and 120 °C. Moreover, the optical adhesive sheet prepared according to the method provided by this patent has good adhesion performance and bending resistance while having a low modulus.

[0044] The above embodiments are only used to illustrate the technical concept and features of the present invention, and the purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. It is not intended to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.

Claims

1. A high temperature resistant flexible optical adhesive sheet having a pressure sensitive adhesive layer, characterized in that: The pressure-sensitive adhesive layer is composed of a photocurable composition, the photocurable composition includes an acrylic polymer, a photocuring agent having two or more photopolymerizable functional groups, and a photopolymerization initiator, the acrylic polymer having (meth)acrylic acid alkyl ester A having 6 to 9 carbon atoms, (meth)acrylic acid alkyl ester B having 10 to 20 carbon atoms, an alkyloxy-containing monomer C, a hydroxyl-containing monomer D, and a N-atom-containing monomer E as monomer components; The content of the alkyloxy-containing monomer C is 1-40 wt % relative to the total weight of the monomer components.

2. The high temperature resistant flexible optical adhesive sheet according to claim 1, characterized in that: The usage ratio of the (meth)acrylic acid alkyl ester A having 6 to 9 carbon atoms to the (meth)acrylic acid alkyl ester B having 10 to 20 carbon atoms is 0.125<B / A<0.

8.

3. The high temperature resistant flexible optical adhesive sheet according to claim 1, characterized in that: Based on 100 parts by weight of the acrylic acid-based polymer, the total amount of the hydroxyl-containing monomer D and the N-atom-containing monomer E does not exceed 10 parts by weight.

4. A high temperature resistant flexible optical adhesive sheet according to any one of claims 2 to 3, characterized in that: The molecular weight of the acrylic acid-based polymer is greater than 1,000,000 g / mol.

5. The high temperature resistant flexible optical adhesive sheet according to claim 1, characterized in that: The (meth)acrylic acid alkyl ester A having 6 to 9 carbon atoms may be one or more of n-hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, and isononyl (meth)acrylate; The (meth)acrylic acid alkyl ester B having 10 to 20 carbon atoms may be one or more of decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate (i.e., lauryl (meth)acrylate), isotridecyl (meth)acrylate, tetradecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, cetyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, isooctadecyl (meth)acrylate, and nonadecyl (meth)acrylate; The alkyloxy-containing monomer C may be one or more of methoxymethyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, ethoxyethoxyethyl acrylate, 3-methoxypropyl (meth)acrylate, 3-ethoxypropyl (meth)acrylate, 4-methoxybutyl (meth)acrylate, and 4-ethoxybutyl (meth)acrylate; The hydroxyl-containing monomer D may be one or more of 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; The N-atom-containing monomer E may be one or more of N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N,N-dimethylacrylamide, N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-(methyl)acryloyl-2-pyrrolidone, N-(methyl)acryloylpiperidine, N-(methyl)acryloylpyrrolidine, N-vinylmorpholine, N-vinyl-3-morpholinone, N-vinyl-2-caprolactam, N-vinyl-3,5-morpholinedione, and N-vinylpyrazole.

6. The high temperature resistant flexible optical adhesive sheet according to claim 1, characterized in that: The photocurable composition further comprises an acrylate oligomer, and the weight average molecular weight of the acrylate oligomer is not less than 2000 g / mol and not more than 9000 g / mol.

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