Radiation-curable optical adhesive composition and adhesive film thereof

Abstract

The invention relates to the technical field of optical cement, in particular to a radiation curing optical cement composition and a cement film thereof. The optical adhesive composition is prepared from the following components in parts by mass: 100 parts of acrylate copolymer, 3 to 15 parts of acrylic acid modified polyol, 5 to 10 parts of cross-linking agent, 0.5 to 1.5 parts of photoinitiator and 0.5 to 1.2 parts of curing agent. After UV radiation curing, an adhesive film prepared from the optical adhesive composition has excellent optical performance and high filling performance, is easy to rework, and is suitable for bonding of electronic product display modules.

Description

Technical Field

[0001] This invention relates to the field of optical adhesive technology, and more specifically, to a radiation-cured optical adhesive composition and its film. Background Technology

[0002] Optical adhesives are widely used for bonding display panels in electronic products such as mobile phones and tablets due to their colorless transparency, high light transmittance, strong adhesion, and low curing shrinkage. To prevent external light from entering the display panel and affecting the display effect, the perimeter of the display panel is usually shielded by printed black masking frames (such as photoresist or ink). These black masking frames form a stepped height difference structure on the surface of the display panel. Therefore, optical adhesives are required to have good height filling properties to fully bond the black masking frames and the display panel.

[0003] Traditional optical adhesives have poor leveling properties, making it difficult to effectively fill height differences during curing or bonding, resulting in gaps remaining at the edges of the display panel, affecting sealing and optical uniformity. Secondly, in the bonding process between the display panel and the display module, if the adhesive film is peeled off after the display module is bonded, it is prone to breakage, affecting rework efficiency.

[0004] Therefore, it is of great significance to provide an optical adhesive that combines excellent optical properties with high filling capacity and easy rework. Summary of the Invention

[0005] In view of this, the present invention is proposed to solve the above-mentioned technical problems. To this end, the present invention provides a radiation-curable optical adhesive composition. The adhesive film prepared from this optical adhesive composition exhibits excellent optical properties and high filling capacity after UV radiation curing, and is easy to rework, making it suitable for bonding display modules in electronic products.

[0006] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution: The first aspect of the present invention provides a radiation-curable optical adhesive composition comprising the following components: 100 parts by weight of acrylate copolymer, 3-15 parts by weight of acrylic acid modified polyol, 5-10 parts by weight of crosslinking agent, 0.5-1.5 parts by weight of photoinitiator and 0.5-1.2 parts by weight of curing agent.

[0007] Furthermore, the preparation method of the acrylic acid modified polyol is as follows: the isocyanate compound and the polyol compound are placed in a reaction vessel for reaction, and after the reaction is completed, a hydroxyl-containing acrylate monomer is added for end capping to obtain the acrylic acid modified polyol.

[0008] Furthermore, the molar ratio of the isocyanate group of the isocyanate compound to the hydroxyl group of the polyol compound and the hydroxyl group of the acrylate monomer is 2:1:1.

[0009] Furthermore, the molecular weight of the polyol compound is 500~5,000 g / mol.

[0010] Furthermore, the acrylate copolymer is copolymerized from a main monomer and a functional monomer, the functional monomer including a hydroxyl-containing monomer, and the hydroxyl-containing monomer accounts for 10-20 wt% of the weight of the comonomer of the acrylate copolymer.

[0011] Furthermore, the crosslinking agent is a polyfunctional (meth)acrylate monomer.

[0012] Furthermore, the curing agent includes isocyanate-based curing agents.

[0013] A second aspect of the present invention provides an adhesive film comprising the optical adhesive composition described in the first aspect of the present invention.

[0014] Furthermore, the thickness of the adhesive film is 100~200 μm.

[0015] Furthermore, the adhesive film, after UV curing, shall meet at least one of the following characteristics: (1) the haze after aging at 85°C and 85% relative humidity for 7 days shall not be higher than 0.3%; (2) the tensile strength shall not be lower than 2 MPa; and (3) the elongation at break shall not exceed 550%.

[0016] Compared with the prior art, the technical solution of the present invention has at least the following beneficial effects: The optical adhesive composition provided by this invention, by introducing acrylic-modified polyol, can effectively reduce the cohesive density of the adhesive film and improve its fluidity before UV curing, thereby promoting high filling capacity and achieving better adhesion. Furthermore, it exhibits superior compatibility with acrylate copolymers, resulting in excellent optical properties. After UV curing, the hydroxyl groups of the acrylic-modified polyol crosslink with the crosslinking agent, forming an interpenetrating crosslinked network structure with the acrylate copolymer, which improves the tensile properties of the adhesive film and facilitates rework. Detailed Implementation

[0017] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

[0018] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0019] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges or individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0020] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0021] Unless otherwise specified, all technical features and optional technical features of this invention can be combined to form new technical solutions.

[0022] It should be noted that (meth)acrylic acid in this invention refers to at least one of acrylic acid and methacrylic acid.

[0023] The first aspect of the present invention provides a radiation-curable optical adhesive comprising the following components: 90-110 parts by weight of acrylate copolymer, 3-15 parts by weight of acrylic acid modified polyol, 5-10 parts by weight of crosslinking agent, 0.5-1.5 parts by weight of photoinitiator and 0.5-1.2 parts by weight of curing agent.

[0024] In one specific embodiment, the radiation curing includes ultraviolet (UV) curing.

[0025] In this invention, by introducing acrylic-modified polyols into the optical adhesive, the acrylic-modified polyols can reduce the cohesive density of the adhesive film and improve its fluidity before UV irradiation. This helps the adhesive film fill the height difference of the display panel's shielding layer, achieving better adhesion and sealing. Moreover, the acrylic-modified polyols have good compatibility with acrylate copolymers, avoiding whitening problems caused by phase separation and allowing the adhesive film to maintain high optical properties. Furthermore, after UV radiation curing, the hydroxyl groups of the acrylic-modified polyols crosslink with the crosslinking agent, forming an interpenetrating crosslinked network structure with the acrylate copolymer, which can improve the tensile properties of the adhesive film and facilitate rework.

[0026] In one specific embodiment, the acrylate copolymer is copolymerized from a main monomer and a functional monomer, wherein the functional monomer includes a hydroxyl-containing monomer. The hydroxyl-containing monomer has strong polarity and can impart good adhesive properties to the optical adhesive.

[0027] In one specific embodiment, the functional monomer includes at least one selected from acrylamide, N-(hydroxymethyl)acrylamide, diacetone acrylamide, acetoacetoxyethyl methacrylate, glycidyl (meth)acrylate, dimethylaminoethyl methacrylate, allyl acetate, hydroxyethyl (meth)acrylate, and hydroxypropyl (meth)acrylate. In one specific embodiment, the hydroxyl-containing monomer is preferably hydroxyethyl acrylate. In one specific embodiment, the functional monomer is a combination of allyl acetate and hydroxyethyl acrylate.

[0028] In one specific embodiment, the functional monomer in the comonomer of the acrylate copolymer has a weight ratio of 20~30 wt%, specifically 20 wt%, 25 wt%, 30 wt%, or any value between the two extremes.

[0029] In one specific embodiment, the hydroxyl-containing monomer in the comonomer of the acrylate copolymer accounts for 10-20 wt% by weight, specifically 10 wt%, 15 wt%, 20 wt%, or any value between these two extremes. Limiting the proportion of hydroxyl-containing monomer within this range ensures that the film has good transparency and adhesion.

[0030] In one specific embodiment, the main monomer is an alkyl methacrylate, including at least one of methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, n-octyl acrylate, isooctyl acrylate, nonyl methacrylate, isononyl methacrylate, and lauryl methacrylate, preferably isooctyl acrylate.

[0031] In one specific embodiment, the main monomer in the comonomer of the acrylate copolymer accounts for 70~80 wt% by weight, specifically 70 wt%, 75 wt%, 80 wt% or any value between the two extremes.

[0032] The acrylate copolymer of the present invention can be prepared by conventional polymerization methods. One preparation method is listed below, which includes: mixing the main monomer, functional monomer and solvent, stirring at 60~90℃ for 20~40 min under an inert atmosphere, adding an initiator, and reacting for 4~6 h to obtain the acrylate copolymer.

[0033] In one specific embodiment, the solvent is used to dissolve the raw materials and adjust the solid content, and can be a conventional organic solvent, such as ethyl acetate, toluene, acetone, diethyl ether, etc. The amount of solvent used is not specifically limited and can be adjusted according to the actual required solid content. In one specific embodiment, the solid content of the acrylate copolymer can be 30-60%.

[0034] In one specific embodiment, the amount of the initiator is 0.1 to 1 part by mass relative to 100 parts by mass of the total comonomer. The initiator may be an azo initiator, such as azobisisobutyronitrile (AIBN).

[0035] In one specific embodiment, the weight-average molecular weight of the acrylate copolymer is between 200,000 and 1,200,000. As an example, the molecular weight of the acrylate copolymer can be 200,000, 400,000, 800,000, 1,200,000, or any value between these two extremes. Maintaining the molecular weight of the acrylate copolymer within this range helps prevent problems such as die-cutting overflow in the optical film and avoids deterioration of the film's filling performance due to excessively high molecular weight.

[0036] In one specific embodiment, the preparation method of the acrylic-modified polyol is as follows: An isocyanate compound and a polyol compound are placed in a reaction vessel and reacted. After the reaction is complete, a hydroxyl-containing acrylate monomer is added for end-capping, thus obtaining the acrylic-modified polyol. The isocyanate group of the isocyanate compound undergoes a nucleophilic addition reaction with the hydroxyl group of the polyol compound to generate a urethane functional group connecting the two parts. The urethane functional group has a large spatial volume and exhibits hard segment characteristics in the polymer, providing high tensile strength after UV curing, which helps improve the reworkability of the film. After the reaction is complete, the ends of the isocyanate compound are end-capped with a hydroxyl-containing acrylate monomer. Since acrylate contains double bonds, the film can be cross-linked with a crosslinking agent through the double bonds of the acrylate monomer after UV curing.

[0037] In one specific embodiment, the preparation method of the acrylic acid modified polyol includes: mixing an isocyanate compound and a polyol compound, heating to 60-80°C under an inert atmosphere, stirring for 3-5 h, and after the reaction is complete, adding hydroxyethyl acrylate and stirring for 1-3 h to end-cap, thereby obtaining the acrylic acid modified polyol.

[0038] In one specific embodiment, the complete reaction of the isocyanate compound and the polyol compound can be determined by performing infrared analysis on a small amount of the reaction intermediate, and the hydroxyl groups of the polyol can be determined to have reacted completely based on the results.

[0039] In one specific embodiment, the molar ratio of the isocyanate group of the isocyanate compound, the hydroxyl group of the polyol compound, and the hydroxyl group of the acrylate monomer is 2:1:1. Limiting the molar ratio of these groups within this range ensures that the polyol compound reacts completely with the isocyanate compound, and that the hydroxyl-containing acrylate monomer is completely capped.

[0040] In one specific embodiment, the weight-average molecular weight of the polyol compound is 500-5,000 g / mol. As an example, the weight-average molecular weight of the polyol can be 500 g / mol, 1,000 g / mol, 2,000 g / mol, 3,000 g / mol, 4,000 g / mol, 5,000 g / mol, or any value between these two extremes. If the weight-average molecular weight of the polyol compound is below 500 g / mol, the higher the mass content of the hard segment (urethane) in the acrylic-modified polyol, the worse the compatibility with the acrylate copolymer, leading to an increase in the haze value of the film. If the weight-average molecular weight of the polyol compound is above 5,000 g / mol, the lower its hard segment mass content, the lower the tensile strength of the film after UV curing, resulting in a decrease in the reworkability of the film.

[0041] In one specific embodiment, the polyol compound includes at least one selected from polyether polyols, polyester polyols, polycarbonate polyols, polycaprolactone polyols, and castor oil-based polyols, preferably polyether polyols. The polyether polyol may be at least one selected from polypropylene glycol and polyethylene glycol.

[0042] In one specific embodiment, the isocyanate compound includes at least one selected from 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, terephthalic diisocyanate, 1,5-naphthalene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), dicyclohexylmethane diisocyanate (HMDI), and hydrogenated diphenylmethylene diisocyanate.

[0043] In one specific embodiment, the hydroxyl-containing acrylate monomer may be hydroxyethyl acrylate.

[0044] In one specific embodiment, the crosslinking agent is a polyfunctional (meth)acrylate monomer.

[0045] In one specific embodiment, the acrylic acid-modified polyol in the composition is 3 to 15 parts by weight relative to 100 parts by weight of the acrylate copolymer, specifically 3 parts by weight, 5 parts by weight, 7 parts by weight, 10 parts by weight, 12 parts by weight, 13.5 parts by weight, 15 parts by weight, or any value between the two extremes.

[0046] In one specific embodiment, the crosslinking agent has a functionality of not less than 2, and is, for example, at least one of trimethylolpropane trimethacrylate, pentaerythritol triacrylate, tripropylene glycol diacrylate, 1,6-hexanediol diacrylate, bisphenol A dimethacrylate, polyethylene glycol diacrylate, dipentaerythritol hexaacrylate, pentaerythritol tetraacrylate, and trimethylolpropane triacrylate (TMPTA).

[0047] In this invention, the crosslinking agent and the acrylic-modified polyol undergo double bond crosslinking after UV irradiation to form a second crosslinking network structure, which in turn forms an interpenetrating crosslinking network with the acrylate copolymer, giving the film excellent optical properties.

[0048] In one specific embodiment, the crosslinking agent in the composition is 5 to 10 parts by weight relative to 100 parts by weight of the acrylate copolymer, specifically 5 parts by weight, 7 parts by weight, 10 parts by weight, 12 parts by weight, 13.5 parts by weight, 15 parts by weight, or any value between the two extremes. If the amount of crosslinking agent is too low, the degree of crosslinking of the film after UV curing is low, and the tensile strength of the film is low; if the amount of crosslinking agent is too high, the density of crosslinking between the acrylic modified polyol and the crosslinking agent in the film increases, the compatibility with the acrylate copolymer deteriorates, resulting in whitening of the film and a decrease in optical properties.

[0049] In one specific embodiment, the curing agent includes an isocyanate curing agent, and the isocyanate curing agent may include at least one of hexamethylene diisocyanate (HDI), isophorone diisocyanate, and diphenylmethane diisocyanate.

[0050] In one specific embodiment, the curing agent in the composition is 0.5 to 1.2 parts by weight relative to 100 parts by weight of the acrylate copolymer, specifically 0.5 parts by weight, 0.7 parts by weight, 1 part by weight, 1.1 parts by weight, 1.2 parts by weight, or any value between the two extremes.

[0051] In one specific embodiment, the photoinitiator may be a conventional free radical photoinitiator, including at least one of 1-hydroxycyclohexylphenyl ketone (photoinitiator 184) and 2-hydroxy-2-methyl-1-phenylacetone.

[0052] In one specific embodiment, the photoinitiator in the composition is 0.5 to 1.5 parts by weight relative to 100 parts by weight of the acrylate copolymer, specifically 0.5 parts by weight, 0.7 parts by weight, 1 part by weight, 1.1 parts by weight, 1.2 parts by weight, 1.5 parts by weight, or any value between the two extremes.

[0053] A second aspect of the present invention provides an adhesive film comprising the optical adhesive composition described in the first aspect of the present invention.

[0054] In one specific embodiment, the thickness of the adhesive film is 100~200 μm, specifically it can be 100 μm, 150 μm, 200 μm or any value between the two extremes.

[0055] In one specific embodiment, the adhesive film, after UV curing, shall meet at least one of the following characteristics: (1) the haze after aging at 85°C and 85% relative humidity (RH) for 7 days shall not be higher than 0.3%; (2) the tensile strength shall not be lower than 2 MPa; and (3) the elongation at break shall not exceed 550%.

[0056] This invention also provides a method for preparing an adhesive film, comprising the following steps: The acrylate copolymer, acrylic modified polyol, crosslinking agent, photoinitiator and curing agent are mixed evenly in a solvent, allowed to stand to defoam, and then coated onto the surface of the release film. After drying and curing, an adhesive film is formed.

[0057] In one specific embodiment, the solvent may be one of the organic solvents listed above. The amount of solvent can be adjusted according to the coating solids content, which can be 15% to 30% for the optical adhesive. For example, the coating solids content of the optical adhesive can be 15%, 20%, 30%, or any value between these two extremes.

[0058] In one specific embodiment, the drying temperature is 40~100℃ and the time is 4~6 min.

[0059] In one specific embodiment, the surface of the adhesive film may be further covered with a release film, which serves to protect the surface of the adhesive film and facilitate winding and transportation.

[0060] In one specific embodiment, the film also needs to be cured by placing it at 50-70°C for 40-60 hours.

[0061] In one specific implementation, the film needs to be stored in a black bag to protect it from light before use.

[0062] In one specific embodiment, the release film is a fluorinated release film.

[0063] In one specific embodiment, the thickness of the release film is 40~120 μm, specifically 40 μm, 50 μm, 60 μm, 80 μm, 100 μm, 120 μm, etc., or any value within the above range, without being specifically limited here.

[0064] The following describes embodiments of the present invention. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in the art or according to the product instructions. Reagents, materials, or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0065] In the following examples or comparative examples, 1 g represents 1 part by mass.

[0066] Example 1 (1) Preparation of acrylate copolymers: 75 g of isooctyl acrylate, 10 g of allyl acetate, 15 g of hydroxyethyl acrylate and 100 g of ethyl acetate were added to a reaction vessel and stirred at 65 °C for 30 min under a nitrogen atmosphere. Then, 0.1 g of azobisisobutyronitrile was added and reacted for 90 min. The temperature was raised to 80 °C and another 0.1 g of azobisisobutyronitrile was added and reacted for 4 h. Finally, a certain amount of ethyl acetate was added to obtain an acrylate copolymer with a solid content of 50% and a weight average molecular weight of 800,000.

[0067] (2) Preparation of acrylic acid modified polyols: 1 mol of polypropylene glycol PPG-2000 (manufacturer: Shandong Wanhua Chemical Group Co., Ltd., molecular weight 2,000 g / mol) and 2 mol of 4,4'-diisocyanate dicyclohexylmethane (HMDI) were added to a reaction vessel. The mixture was slowly heated to 70°C under nitrogen atmosphere and stirred for 4 h. A small amount of the reaction intermediate was taken for infrared analysis. After the hydroxyl groups of the polyol had reacted completely, 2 mol of hydroxyethyl acrylate was added for end-capping. The mixture was stirred for 2 h. The -NCO peak and -OH peak disappeared by infrared analysis, indicating the end of the reaction. Acrylic acid modified polyol was obtained.

[0068] (3) Preparation of the adhesive film: More than 100 g of the prepared acrylate copolymer, more than 8 g of the prepared acrylic modified polyol, 7 g of TMPTA, 0.8 g of HDI and 1 g of photoinitiator 184 were mixed with a certain amount of ethyl acetate to make the optical solid content 20%. The mixture was then allowed to stand to defoam and coated onto the surface of a 100 µm thick fluorine release film. The film was dried at 40 °C for 3 min and then dried at 100 °C for 3 min to form a 150 µm thick film. The surface of the film was then coated with a 50 µm thick fluorine release film and cured at 60 °C for 48 h to obtain the finished film. The film was then stored in a black bag away from light.

[0069] Example 2 This embodiment is based on Example 1, with the only differences being the type of isocyanate compound in the acrylic-modified polyol and the amount of some components in the optical adhesive. The preparation method and solid content of the adhesive film are the same as in Example 1. The specific differences are as follows: The isocyanate compound of the acrylic acid modified polyol was replaced by an equal amount of IPDI. The optical adhesive contained 3 g of acrylic acid modified polyol, 5 g of TMPTA, 0.5 g of HDI and 0.5 g of photoinitiator 184.

[0070] Example 3 This embodiment is based on Example 1, with the only differences being the type of isocyanate compound in the acrylic-modified polyol and the amount of some components in the optical adhesive. The preparation method and solid content of the adhesive film are the same as in Example 1. The specific differences are as follows: The isocyanate compound of the acrylic acid modified polyol was replaced by an equal amount of HDI. The optical adhesive contained 15 g of acrylic acid modified polyol, 10 g of TMPTA, 1.2 g of HDI and 1.5 g of photoinitiator 184.

[0071] Example 4 group This example group is based on Example 1, with the only difference being the type of polyol compound used in the acrylic acid-modified polyol. The preparation method and solid content of the film are the same as in Example 1, and the specific differences are as follows: Example 4a: The polyol compound used was an equal amount of polypropylene glycol PPG-500 (manufacturer: Shandong Wanhua Chemical Group Co., Ltd., molecular weight 500 g / mol). Example 4b: The polyol compound used was an equal amount of polypropylene glycol PPG-5000 (manufacturer: Shandong Wanhua Chemical Group Co., Ltd., molecular weight 5,000 g / mol). Example 4c: The polyol compound used was an equal amount of polypropylene glycol PPG-400 (manufacturer: Shandong Wanhua Chemical Group Co., Ltd., molecular weight 400 g / mol). Example 4d: The polyol compound used was an equal amount of polypropylene glycol PPG-6000 (manufacturer: Shandong Wanhua Chemical Group Co., Ltd., molecular weight 6,000 g / mol).

[0072] Example 5 group This example group is based on Example 1, with the only difference being the amount of monomer used in the acrylate copolymer. The preparation method and solid content of the film are the same as in Example 1, and the specific differences are as follows: Example 5a: 80 g of isooctyl acrylate, 10 g of allyl acetate, and 10 g of hydroxyethyl acrylate were used to obtain an acrylate copolymer with a weight-average molecular weight of 500,000. Example 5b: 70 g of isooctyl acrylate, 10 g of allyl acetate, and 20 g of hydroxyethyl acrylate were used to obtain an acrylate copolymer with a weight-average molecular weight of 1.2 million. Example 5c: 85 g of isooctyl acrylate, 10 g of allyl acetate, and 5 g of hydroxyethyl acrylate were used to obtain an acrylate copolymer with a weight-average molecular weight of 100,000. Example 5d: 65 g isooctyl acrylate, 10 g allyl acetate, 25 g hydroxyethyl acrylate, the resulting acrylate copolymer gelled.

[0073] Comparative Example 1 This comparative example group was conducted in accordance with Example 1, with the only differences being the amount of acrylic acid-modified polyol or the optical adhesive component. The preparation method and solid content of the adhesive film were the same as in Example 1, and the specific differences are as follows: Comparative Example 1a: 2g of acrylic acid-modified polyol; Comparative Example 1b: 17g of acrylic acid-modified polyol; Comparative Example 1c: Contains no acrylic modified polyols, crosslinking agents, or photoinitiators.

[0074] Comparative Example 2 This comparative example group was conducted in accordance with Example 1, except that the amount of crosslinking agent was different. The preparation method and solid content of the film were the same as in Example 1. The specific differences are as follows: Comparative Example 2a: 4 g of TMPTA; Comparative Example 2b: 11 g of TMPTA.

[0075] Performance testing The films prepared in the above embodiments and comparative examples were subjected to the following performance tests, and the test results are recorded in Table 1.

[0076] (1) Haze test: The test was conducted according to the national standard GB / T 2410-2008 "Determination of transmittance and haze of transparent plastics". A 40 mm × 60 mm sample of the film was taken, the release film on both sides was removed, and the film was attached between two pieces of plain glass. A mercury lamp (power density 160 W / cm, wavelength 365 nm, radiation energy 2,000 mJ / cm) was used. 2 Irradiation; the haze values ​​of the cured film and the film after double 85 aging were tested with a haze meter, where double 85 aging means that the cured film was placed in an environment of 85℃ and 85%RH humidity for 7 days.

[0077] (2) Tensile strength and elongation at break test: The test was conducted in accordance with the national standard GB / T 30776-2014 "Test method for tensile strength and elongation at break of adhesive tape". A 10 mm × 30 mm adhesive film sample was taken, the release film was removed, and the tensile strength and elongation at break of the adhesive film before and after UV testing were tested using a tensile testing machine. The UV test was conducted using a mercury lamp (power density 160 W / cm, wavelength 365 nm, radiation energy 2,000 mJ / cm). 2 It is prepared by curing the adhesive film after irradiation.

[0078] Table 1 Performance Test Results As can be seen from the test results of Examples 1-3 in Table 1, the haze values ​​of the optical adhesive film after UV curing and after 7 days of double 85 aging are both 0.3% or less, indicating that the short-chain acrylic modified polyol and acrylic copolymer have good compatibility, and the optical adhesive has good optical properties and aging resistance. The tensile strength of the obtained optical adhesive before UV curing is low, not exceeding 1 MPa, indicating that the acrylic modified polyol can reduce the cohesive strength of the film, which is beneficial for the film to cope with the adhesion of height differences. After UV curing, the tensile strength of the film is greatly improved, not less than 2 MPa. The main reason is that the polyol polymerizes with the acrylic polyfunctional crosslinking agent in the film, crosslinking into a network structure, which increases the cohesive strength of the film and reduces the elongation at break, thus giving the film good reworkability.

[0079] The test results of Example 4 show that for acrylic modified polyols prepared using polyol compounds of different molecular weights, a decrease in the molecular weight of the polyol compound leads to an increase in the haze value of the film and an increase in the tensile strength after UV curing. This is because the smaller the molecular weight of the polyol compound, the higher its hard segment content, which leads to poorer compatibility with the acrylic polymer and thus an increase in haze value. Conversely, the soft segment content will be larger, resulting in low tensile strength of the film after UV curing, which is not conducive to achieving the reworkability of the film.

[0080] The test results of Example 5 show that when the amount of hydroxyl monomer in the acrylate copolymer is lower than the limit, the molecular weight of the acrylate copolymer is lower, and the haze value of the film increases significantly after aging with double 85. This is because the film forms a multiphase structure with water molecules in the test environment, resulting in decreased aging resistance. When the content of hydroxyl monomer is too high, the acrylate copolymer gels.

[0081] The test results of Comparative Example 1 show that when the amount of acrylic modified polyol is too low, the tensile strength of the film after UV treatment is low and the elongation at break is high, which is not conducive to rework; conversely, it will lead to a decrease in the optical properties of the film. If acrylic modified polyol, acrylic polyfunctional crosslinking agent and photoinitiator are not added, the tensile strength of the film before and after UV treatment is low because the optical adhesive composition does not undergo UV reaction.

[0082] The test results of the two comparison groups show that when the amount of crosslinking agent is too low, the haze value after 7 days of aging with double 85 will increase. The main reason is that the degree of crosslinking after UV curing of the film is low, and water molecules can easily enter the film, thus leading to an increase in the haze value of the film. When the amount of crosslinking agent is too high, the crosslinking density between the acrylic modified polyol and the crosslinking agent in the film increases, and the compatibility with the acrylate copolymer becomes worse, which will also cause the film to turn white, its haze value to increase, and its optical performance to decrease.

[0083] The parts of this invention not described in detail are techniques known to those skilled in the art.

[0084] The basic principles of the present invention have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in the present invention are merely examples and not limitations, and should not be considered as essential features of each embodiment of the present invention. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the present invention to the necessity of employing the aforementioned specific details.

[0085] In the detailed description and claims, a list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B.

[0086] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A radiation-cured optical adhesive composition, characterized in that, The optical adhesive composition comprises the following components: 100 parts by weight of acrylate copolymer, 3-15 parts by weight of acrylic acid modified polyol, 5-10 parts by weight of crosslinking agent, 0.5-1.5 parts by weight of photoinitiator, and 0.5-1.2 parts by weight of curing agent.

2. The optical adhesive composition according to claim 1, characterized in that, The preparation method of the acrylic acid modified polyol is as follows: the isocyanate compound and the polyol compound are placed in a reaction vessel to react. After the reaction is complete, a hydroxyl-containing acrylate monomer is added for end capping to obtain the acrylic acid modified polyol.

3. The optical adhesive composition according to claim 2, characterized in that, The molar ratio of the isocyanate group of the isocyanate compound to the hydroxyl group of the polyol compound and the hydroxyl group of the acrylate monomer is 2:1:

1.

4. The optical adhesive composition according to claim 2 or 3, characterized in that, The molecular weight of the polyol compound is 500~5,000 g / mol.

5. The optical adhesive composition according to claim 1, characterized in that, The acrylate copolymer is composed of a main monomer and a functional monomer copolymerized together. The functional monomer includes a hydroxyl-containing monomer. The weight percentage of the hydroxyl-containing monomer in the comonomer of the acrylate copolymer is 10-20 wt%.

6. The optical adhesive composition according to claim 1, characterized in that, The crosslinking agent is a polyfunctional (meth)acrylate monomer.

7. The optical adhesive composition according to claim 1, characterized in that, The curing agent includes isocyanate-based curing agents.

8. A film, characterized in that, Includes the optical adhesive composition according to any one of claims 1 to 7.

9. The adhesive film according to claim 8, characterized in that, The thickness of the adhesive film is 100~200 μm.

10. The adhesive film according to claim 9, characterized in that, The adhesive film, after UV curing, must meet at least one of the following characteristics: (1) the haze after aging at 85°C and 85% relative humidity for 7 days is not higher than 0.3%; (2) the tensile strength is not lower than 2 MPa; and (3) the elongation at break is not higher than 550%.

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