Optical adhesive sheet for protective film

Abstract

The invention provides the optical adhesive sheet for the protective film, and a remarkable breakthrough is realized in a plurality of key performances. By means of the well-designed adhesive layer formula, it is guaranteed that the optical adhesive sheet has extremely low modulus at the low temperature (-20 DEG C), equipment can still keep good flexibility and reliability in the extreme environment, the adhesive performance of the optical adhesive sheet is also excellent, and firm combination between the equipment and a protective film is guaranteed. In addition, the optical adhesive sheet further has good optical performance, bending resistance and long-term stability, and a more reliable and efficient solution is provided for manufacturing of foldable equipment and other electronic equipment.

Description

Technical Field

[0001] The present invention relates to the technical field of adhesives, and in particular to an optical adhesive sheet for a protective film. Background Art

[0002] In recent years, foldable devices have become more and more popular due to their excellent portability, and are increasingly widely used in the fields of foldable screen mobile phones, smart wearables, vehicles, electronic equipment, etc. With the popularization of foldable devices, adhesives suitable for the use characteristics of foldable devices are also in demand in the market. In general, OCA adhesives used in foldable devices need to have durability against 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 foldable devices.

[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 good bonding properties. However, it is difficult for the optical adhesive sheets currently available on the market to achieve both low modulus properties at low temperatures and good bonding properties.

[0004] In summary, the shortcomings of existing optical adhesive sheets for protective films in multiple key performances have seriously restricted their application and development in the fields of folding screen mobile phones, smart wearables, vehicles, electronic equipment, etc. Therefore, developing an optical adhesive sheet for protective films that has both low modulus at low temperatures (-20°C) and good bonding performance has become a technical problem that the industry needs to solve urgently. Summary of the invention

[0005] In view of the problems existing in the above-mentioned background technology, the main purpose of the present invention is to provide an optical adhesive sheet for a protective film, which has a low modulus at low temperature (-20°C) and also exhibits excellent bonding performance. To achieve this goal, the present invention provides an adhesive sheet, the adhesive sheet having an adhesive layer, wherein the adhesive layer comprises an acrylic polymer and an acrylic oligomer, the acrylic polymer is a polymer of a monomer component, the monomer component comprises a monomer having a carbon number of 9 or more and a functional monomer, the monomer component comprises more than 90wt% of the (meth) acrylic ester monomer having a carbon number of 9 or more, and the functional monomer is a hydroxyl-containing acrylic ester monomer.

[0006] Furthermore, the monomer component has an alkyl (meth)acrylate with a carbon number of 9 or more, including at least one of nonyl (meth)acrylate, decanyl (meth)acrylate, propylheptyl (meth)acrylate, isodecyl (meth)acrylate, heptadecanyl (meth)acrylate, and lauryl (meth)acrylate.

[0007] Furthermore, the hydroxyl-containing acrylate monomer includes at least one of hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and hydroxybutyl (meth)acrylate.

[0008] Furthermore, the weight average molecular weight of the acrylic polymer is in the range of 300,000 to 3,000,000.

[0009] Furthermore, the glass transition temperature of the acrylic oligomer is 20° C. or higher and 200° C. or lower.

[0010] Furthermore, the weight average molecular weight of the acrylic oligomer is not less than 2000 g / mol and not more than 9000 g / mol.

[0011] Furthermore, the content of the acrylic oligomer in the adhesive layer is less than 30 parts by weight relative to 100 parts by weight of the acrylic polymer.

[0012] Furthermore, the adhesive sheet is used for fixing components in electronic devices.

[0013] Compared with the prior art, the optical adhesive sheet prepared by the present invention has low modulus and good bonding performance under low temperature conditions. It not only ensures that the optical adhesive sheet has an extremely low modulus at low temperature (-20°C), so that the device can still maintain good flexibility and reliability under extreme environments, but also has excellent bonding performance, ensuring a firm bond between the device and the protective film. In addition, the optical adhesive sheet of the present invention also has good optical properties, bending resistance and long-term stability, providing a more reliable and efficient solution for the manufacture of foldable devices and other electronic devices. DETAILED DESCRIPTION

[0014] 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.

[0015] Table 1 List of ingredients of adhesive

[0016]

[0017] 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.

[0018] Table 2 - Formula composition of Examples 1-3 and Comparative Examples 1-2

[0019]

[0020] As shown in Table 2, accurately weigh corresponding amounts of 2-propylheptyl acrylate, isodecyl acrylate, heptadecanyl acrylate, 2-ethylhexyl acrylate, N-vinyl pyrrolidone, hydroxybutyl acrylate, and benzoin dimethyl ether, and place them in a four-necked flask equipped with a stirrer, a thermometer, and a nitrogen tube. Stir and introduce nitrogen. After stirring for at least 30 minutes, prepare a prepolymer by photoinitiated polymerization.

[0021] Example 1-3: Accurately weigh 100 parts of the corresponding prepolymer, add 3 parts of Oligomer A, 0.2 parts of 1,6-hexanediol diacrylate and 0.3 parts of Silquest A-187 purchased from MOMENTIVE to the prepolymer, stir it evenly and let it stand for degassing to obtain glue.

[0022] Comparative Example 1: Accurately weigh 100 parts of the corresponding prepolymer, add 0.2 parts of 1,6-hexanediol diacrylate and 0.3 parts of Silquest A-187 purchased from MOMENTIVE to the prepolymer, stir it evenly and let it stand for degassing to obtain glue.

[0023] Comparative Example 2: Accurately weigh 100 parts of the corresponding prepolymer, add 3 parts of Oligomer A, 0.2 parts of 1,6-hexanediol diacrylate and 0.3 parts of Silquest A-187 purchased from MOMENTIVE to the prepolymer, stir it evenly and let it stand for degassing to obtain glue.

[0024] The light release film R701T-C and heavy release film R703T-C produced by Guangdong Crown New Material Technology Co., Ltd. were placed up and down with their release surfaces facing each other, and the above glue was poured between the two layers of film. The thickness was controlled by roller extrusion and cured by UVA band irradiation under UV lamp to prepare a 50μm thick optical adhesive sheet.

[0025] Performance Testing

[0026] 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.

[0027] 180 degree peel force test: GB / T 2792-2014;

[0028] Optical test: Konica Minolta colorimetry system, CM-3600A, test standard ASTM D1003 Storage modulus: TA hybrid rheometer DHR-2, ASTM D4440-15;

[0029] Dynamic bending test: radius 3mm, 40 times / min, 50,000 times.

[0030] Table 3 - Performance test of examples and comparative examples

[0031]

[0032] The above test results show that the optical adhesive sheet prepared by the scheme disclosed in the embodiment of the present invention can have a low modulus at low temperature and good adhesion, and also have good optical properties and bending resistance.

[0033] 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. An adhesive sheet comprising an adhesive layer, characterized in that: The adhesive layer comprises an acrylic polymer and an acrylic oligomer, wherein: The acrylic polymer is a polymer of monomer components. The monomer component includes a monomer having 9 or more carbon atoms and a functional monomer, The monomer component contains 90 wt % or more of the (meth)acrylic acid ester monomer having 9 or more carbon atoms, The functional monomer is a hydroxyl-containing acrylate monomer.

2. An adhesive sheet according to claim 1, characterized in that: The monomer component has an alkyl (meth)acrylate with a carbon number of 9 or more, including at least one of nonyl (meth)acrylate, decanyl (meth)acrylate, propylheptyl (meth)acrylate, isodecyl (meth)acrylate, heptadecanyl (meth)acrylate, and lauryl (meth)acrylate.

3. The adhesive sheet according to claim 1, characterized in that: The hydroxyl-containing acrylate monomer includes at least one of hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and hydroxybutyl (meth)acrylate.

4. An adhesive sheet according to any one of claims 2 to 3, characterized in that: The weight average molecular weight of the acrylic polymer is within a range of 300,000 to 3,000,000.

5. The adhesive sheet according to claim 1, characterized in that: The weight average molecular weight of the acrylic oligomer is not less than 2000 g / mol and not more than 9000 g / mol.

6. The adhesive sheet according to claim 1, characterized in that: The content of the acrylic oligomer in the adhesive layer is less than 30 parts by weight relative to 100 parts by weight of the acrylic polymer.

7. The adhesive sheet according to any one of claims 1 to 6 is used for fixing components in electronic devices.

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