Bending-resistant optical adhesive sheet

Abstract

The bending-resistant optical adhesive sheet provided by the invention realizes significant breakthrough in a plurality of key properties. By means of the well-designed adhesive layer formula, it is guaranteed that the optical adhesive sheet can achieve low modulus under the low-temperature condition, and the good adhesive performance and creep performance are achieved at the same time. The optical adhesive sheet has extremely low modulus in a low-temperature environment, so that equipment can still keep excellent flexibility and reliability in an extreme environment, and the excellent adhesive property and creep property of the optical adhesive sheet powerfully guarantee the firm combination between the equipment and a protective film. The bending-resistant optical adhesive sheet disclosed by the invention also shows good optical performance, excellent bending resistance and long-term stability. A more reliable and efficient solution is provided for manufacturing of foldable equipment and other electronic equipment, and development and progress of related industries are promoted.

Description

Technical Field

[0001] The invention relates to the technical field of adhesives, in particular to a bending-resistant optical adhesive sheet. Background Art

[0002] In recent years, with the continuous advancement of science and technology, foldable devices have become increasingly popular and widely used in many fields such as foldable screen mobile phones, smart wearables, vehicles and electronic devices due to their excellent portability. With the gradual popularization of foldable devices, adhesives adapted to their usage characteristics have also become an urgent need of the market. In general, the OCA adhesives used in foldable devices need to have durability in environmental changes, and should also have effective bonding properties, excellent high and low temperature modulus stability and good bonding properties, so as to increase the service life of the foldable device.

[0003] Optical adhesive sheets for protective films of foldable devices require low low-temperature modulus to ensure normal use at low temperatures, and also require the optical adhesive sheets to have good bonding and creep properties. However, existing optical adhesive sheets on the market often have difficulty in achieving low modulus performance at low temperatures while also having good bonding and creep properties.

[0004] In summary, existing optical adhesive sheets for protective films have deficiencies in multiple key performance aspects, which seriously hinders their application and development in the fields of folding screen mobile phones, smart wearables, vehicles, electronic equipment, etc. It can be seen that developing a bending-resistant optical adhesive sheet for protective films that has low modulus, good bonding performance and creep performance has become a technical problem that needs to be solved urgently in the current industry. Summary of the invention

[0005] In view of the problems existing in the above background technology, the main purpose of the present invention is to provide a bending-resistant optical adhesive sheet, which has a low modulus at low temperature and also exhibits excellent bonding performance and creep performance. To achieve this goal, the present invention provides a bending-resistant optical adhesive sheet, the adhesive sheet having an adhesive layer, wherein the adhesive layer comprises an acrylate polymer, an acrylate oligomer and a cross-linking agent.

[0006] The cross-linking agent is a bifunctional oligomer with a specific random copolymer structure, the molecular weight of the bifunctional oligomer is 500-15000 g / mol, and its structure is shown in FIG1 : Figure 1 Wherein R is a (meth)acrylate group, a carboxyl group, a hydroxyl group or an epoxy group, i is 3 to 93, m is 3 to 93, and n is 3 to 93.

[0007] The acrylic ester polymer is a polymer containing acrylic ester monomers as main components, and the acrylic ester monomers include acrylic ester monomers having reactive functional groups.

[0008] Furthermore, the acrylate monomer having a reactive functional group is a hydroxyl-containing acrylate monomer. Preferably, the hydroxyl-containing acrylate monomer includes at least one of hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and hydroxybutyl (meth)acrylate.

[0009] Furthermore, the weight average molecular weight of the acrylic polymer is in the range of 300,000 to 3,000,000.

[0010] Furthermore, the glass transition temperature of the acrylic ester oligomer is greater than or equal to 20° C. and less than or equal to 200° C.

[0011] Furthermore, the weight average molecular weight of the acrylic ester oligomer is not less than 2000 g / mol and not more than 9000 g / mol.

[0012] Furthermore, relative to 100 parts by weight of the acrylic polymer, the amount of the crosslinking agent added in the adhesive layer is 0.1-5 parts by weight, and the content of the acrylic oligomer is less than 30 parts by weight.

[0013] Furthermore, the bending-resistant optical adhesive sheet is used for fixing components in electronic devices.

[0014] Compared with the prior art, the bending-resistant optical adhesive sheet prepared by the present invention has significant advantages. First, under low temperature conditions, it can achieve low modulus while having good bonding and creep properties. This not only ensures that the optical adhesive sheet has an extremely low modulus in a low temperature environment, so that the equipment can still maintain excellent flexibility and reliability in extreme environments, but also its excellent bonding and creep properties effectively guarantee the firm bond between the equipment and the protective film. Second, the bending-resistant optical adhesive sheet of the present invention also exhibits good optical properties, excellent bending resistance and long-term stability. This provides a more reliable and efficient solution for the manufacture of foldable devices and other electronic devices, and helps promote the development and progress of related industries. DETAILED DESCRIPTION

[0015] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the 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.

[0016] Table 1 List of adhesive ingredients Wherein, Oligomer A is 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. In this embodiment, by using an acrylate oligomer with a molecular weight of 2000-9000 g / mol, preferably 3000-8000 g / mol, and a molecular weight distribution of less than 2.7, the addition of the acrylate oligomer improves the adhesion of the optical adhesive sheet and also makes it have good optical properties.

[0017] Table 2 - Formula composition of Examples 1-3 and Comparative Examples 1-2 As shown in Table 2, corresponding proportions of 2-ethylhexyl acrylate, N-vinyl pyrrolidone, hydroxybutyl acrylate, 2-dodecyl acrylate, and dimethyl benzoate were accurately weighed and placed in a four-necked flask equipped with a stirrer, a thermometer, and a nitrogen tube. Nitrogen was introduced while stirring. After stirring for at least 30 minutes, a prepolymer was prepared by photoinitiated polymerization.

[0018] Example 1-3 and Comparative Example 1-2: According to Table 1, corresponding proportions of Oligomer A, Bac-45, PEGDA and Silquest A-187 were added to the prepolymer, and the mixture was stirred evenly and allowed to stand for degassing to obtain glue.

[0019] The light release film R701T-C and the heavy release film R703T-C produced by Guangdong Crown New Material Technology Co., Ltd. are used, and the release surfaces of the two are placed up and down with each other facing each other. The above-mentioned glue is poured between the two layers of film, and its thickness is controlled by roller extrusion and cured by UVA band irradiation under UV lamp to prepare a 50μm thick optical adhesive sheet.

[0020] Performance Testing The optical adhesives prepared in the above Examples 1-3 and Comparative Examples 1-2 were respectively made into OCA tapes and the relevant properties were measured. The test method is as follows and the results are shown in Table 3.

[0021] 180 degree peel force test: GB / T 2792-2014; Optical test: Konica Minolta colorimetric system, CM-3600A, test standard ASTM D1003; Storage modulus: TA hybrid rheometer DHR-2, ASTM D4440-15; Creep recovery test: TA rheometer applies 10kPa shear stress, and the recovery time is 600s; Dynamic bending test: radius 3mm, 40 times / min, 50,000 times.

[0022] Table 3 - Performance test of examples and comparative examples The above test results show that the various test performances of Examples 1-3 are relatively excellent, and while achieving low modulus, they can also have good adhesion and creep performance. Compared with the data of Examples 1-3, the creep performance of Comparative Example 1 is worse than that of Examples 1-3; Comparative Example 2 does not add Oligomer A, and its adhesion is not ideal. .

[0023] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used 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 included in the protection scope of the present invention.

Claims

1. A bending-resistant optical adhesive sheet, the adhesive sheet comprising an adhesive layer, It is characterized in that The adhesive layer comprises an acrylate polymer, an acrylate oligomer and a crosslinking agent, The cross-linking agent is a bifunctional oligomer with a specific random copolymer structure, the molecular weight of the bifunctional oligomer is 500-15000 g / mol, and its structure is shown in FIG1 : Figure 1 Wherein R is (meth)acrylate, carboxyl, hydroxyl or epoxy, i is 3 to 93, m is 3 to 93, and n is 3 to 93; The acrylic polymer is a polymer containing an acrylic ester monomer as a main component, and the acrylic ester monomer includes an acrylic ester monomer having a reactive functional group.

2. The bending-resistant optical adhesive sheet according to claim 1, It is characterized in that The acrylic acid ester monomer having a reactive functional group is an acrylic acid ester monomer containing a hydroxyl group.

3. The bending-resistant optical adhesive sheet according to claim 2, It is characterized in that The hydroxyl-containing acrylate monomer includes at least one of hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and hydroxybutyl (meth)acrylate.

4. The bending-resistant optical adhesive sheet according to claim 1, It is characterized in that The weight average molecular weight of the acrylic polymer is in the range of 300,000 to 3,000,000.

5. The bending-resistant optical adhesive sheet according to claim 1, It is characterized in that The acrylic oligomer has a glass transition temperature of 20° C. or higher and 200° C. or lower.

6. The bending-resistant optical adhesive sheet according to claim 1, It is characterized in that The weight average molecular weight of the acrylic ester oligomer is not less than 2000 g / mol and not more than 9000 g / mol.

7. The bending-resistant optical adhesive sheet according to claim 1, It is characterized in that The amount of the crosslinking agent added to the adhesive layer is 0.1-5 parts by weight relative to 100 parts by weight of the acrylic polymer, and the content of the acrylic oligomer is less than 30 parts by weight.

8. The bending-resistant optical adhesive sheet according to any one of claims 1 to 7 is used for fixing components in electronic devices.

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