Acid-free water-blocking OCA (Optical Clear Adhesive), preparation method thereof and application of acid-free water-blocking OCA in electronic products

Abstract

The invention belongs to the technical field of optical cement, and particularly relates to an acid-free water-blocking OCA optical cement, a preparation method thereof and application of the acid-free water-blocking OCA optical cement in electronic products. The acid-free water-blocking OCA optical adhesive comprises a heavy release film, an OCA optical adhesive layer and a light release film, and the OCA optical adhesive layer comprises the following components in parts by mass: 40-60 parts of an acrylic ester prepolymer containing cardanol, 40-60 parts of an acrylic ester prepolymer containing an acylhydrazone bond and 1-3 parts of a photoinitiator. The acid-free water-blocking OCA optical adhesive prepared by the preparation method provided by the invention has relatively high light transmittance, excellent high-temperature and high-humidity resistance and normal-temperature and low-temperature bending resistance.

Description

Technical Field

[0001] This invention belongs to the field of optical adhesive technology, specifically relating to an acid-free, water-blocking OCA optical adhesive, its preparation method, and its application in electronic products. Background Technology

[0002] OCA optical adhesive is an optically transparent adhesive used for bonding transparent optical devices and display devices. It has a substrate-free double-sided bonding tape structure and achieves lamination through a release film. It has excellent optical transparency, clarity, and good adhesion performance, and is widely used in optical components such as electronic product display screens to play a role in bonding and encapsulation, reducing interface reflection, and improving screen brightness and contrast.

[0003] Although the amount of OCA optical adhesive used is small, it directly determines the performance of electronic devices. To improve adhesion, some OCA optical adhesives often contain acidic substances. However, these acidic substances can cause corrosion of ITO glass and optical components in high-humidity environments. Therefore, developing acid-free, water-resistant OCA optical adhesives is of great significance.

[0004] Furthermore, with the advancement of technology, electronic product displays are evolving towards curved screens, foldable screens, and rollable screens, thus placing higher demands on the repeated bending resistance of OCA optical adhesives. The applicant has previously developed an optical adhesive film with high light transmittance, strong adhesion, and good weather resistance, and has applied for a related patent (publication number CN120005529A). However, this technical solution uses nanoparticle silicon dioxide, and although it has undergone modification treatment, the applicant found that its flexibility at low temperatures is poor, affecting the low-temperature bending performance of curved screens, foldable screens, and rollable screens.

[0005] Chinese patent CN118126656A discloses a flexible OCA optical adhesive, a foldable mobile phone screen, and its preparation method. The optical adhesive comprises the following raw material components by weight: 100 parts of a bendable OCA optical adhesive, 0.01-0.1 parts of a crosslinking agent, 0.01-0.1 parts of an adhesion modifier, 2-5 parts of a small-molecule tackifying resin, and 8-15 parts of a solvent. The foldable mobile phone screen of this technology exhibits excellent optical properties, including high light transmittance and low haze. It shows no abnormalities during static bending at high temperatures and humidity, and exhibits no abnormalities during dynamic bending at room temperature after 100,000 cycles. It also shows no abnormalities during dynamic bending at low temperatures, demonstrating excellent optical and bending resistance. However, the high-temperature and high-humidity test time for this technology is relatively short, and its high-temperature and high-humidity resistance needs improvement, as does its bending performance. Summary of the Invention

[0006] To address the aforementioned problems, the present invention aims to provide an acid-free, water-blocking OCA optical adhesive, its preparation method, and its application in electronic products. This addresses one or more technical problems existing in the prior art, and at least provides a beneficial alternative or creates favorable conditions. The acid-free, water-blocking OCA optical adhesive provided by this invention exhibits high light transmittance, excellent resistance to high temperature and humidity, and good bending performance at normal and low temperatures.

[0007] The technical solution adopted in this invention is as follows: In a first aspect, the present invention provides an acid-free water-blocking OCA optical adhesive, comprising a heavy release film, an OCA optical adhesive layer and a light release film, wherein the OCA optical adhesive layer comprises the following components in parts by weight: 40-60 parts of acrylate prepolymer containing cashew phenol, 40-60 parts of acrylate prepolymer containing acylhydrazone bonds, and 1-3 parts of photoinitiator.

[0008] This invention employs a blend of cashew phenol-containing acrylate prepolymers and acrylate prepolymers containing hydrazone bonds. The cashew phenol-containing acrylate prepolymer provides low-temperature flexibility, high-temperature and high-humidity resistance, and adhesion. The hydrazone bonds in the acrylate prepolymer exhibit dynamic reversibility, enabling the OCA optical adhesive to self-heal upon bending. Furthermore, the acrylate prepolymer containing hydrazone bonds possesses high polarity. The resulting acid-free, water-resistant OCA optical adhesive not only exhibits high light transmittance but also prevents blistering, whitening, or delamination caused by high-temperature moisture penetration under high-temperature and high-humidity conditions, maintaining high peel strength. It also demonstrates good bending performance at both room and low temperatures, making it suitable for foldable electronic products.

[0009] In a specific embodiment of the present invention, the thickness of the OCA optical adhesive layer is 25-300 μm.

[0010] In a specific embodiment of the present invention, the thicknesses of the heavy release film and the light release film are each independently selected from 50-100 μm.

[0011] In a specific embodiment of the present invention, the acrylate prepolymer containing cashew nut shells is obtained by polymerizing butyl acrylate, o-phenylphenoxyethyl acrylate, isobornyl methacrylate, and alkenylated cashew nut shells.

[0012] In a specific embodiment of the present invention, the mass ratio of butyl acrylate, o-phenylphenoxyethyl acrylate, isobornyl methacrylate and alkenylated cashew phenol is 55-78:2-5:10-15:10-25.

[0013] The cashew phenol-containing acrylate prepolymer provided by this invention is polymerized using specific butyl acrylate, o-phenylphenoxyethyl acrylate, isobornyl methacrylate, and alkenyl cashew phenol. In particular, this invention introduces o-phenylphenoxyethyl acrylate and alkenyl cashew phenol, utilizing the high refractive index of o-phenylphenoxyethyl acrylate and the biphenyl groups and flexible oxygen chains contained in its molecular structure to improve the light transmittance and high temperature and humidity resistance of OCA optical adhesive. The long-chain aliphatic side chains of cashew phenol also have excellent flexibility at low temperatures, which can improve the room temperature foldability and low temperature foldability of OCA optical adhesive. The inventors found that in the preparation process of the cashew phenol-containing acrylate prepolymer, it is also necessary to control the mass ratio of butyl acrylate, o-phenylphenoxyethyl acrylate, isobornyl methacrylate, and alkenyl cashew phenol to be 55-78:2-5:10-15:10-25, otherwise the high temperature and humidity resistance, room temperature bending, and low temperature bending of OCA optical adhesive will decrease.

[0014] In a specific embodiment of the present invention, the method for preparing the cashew phenol-containing acrylate prepolymer includes the following steps: Butyl acrylate, o-phenylphenoxyethyl acrylate, isobornyl methacrylate, alkenylated cashew nut shell powder, and a first thermal initiator were mixed and reacted under nitrogen protection to obtain a cashew nut shell powder-containing acrylate prepolymer.

[0015] In a specific embodiment of the present invention, the first thermal initiator is selected from at least one of dicumyl peroxide, benzoyl peroxide, and azobisisobutyronitrile.

[0016] In a specific embodiment of the present invention, the amount of the first thermal initiator used is 0.8-1.2% of the total mass of butyl acrylate, o-phenylphenoxyethyl acrylate, isobornyl methacrylate and alkenyl cashew phenol.

[0017] In a specific embodiment of the present invention, the method for preparing the cashew phenol-containing acrylate prepolymer includes the following steps: Butyl acrylate, o-phenylphenoxyethyl acrylate, isobornyl methacrylate, alkenylated cashew nut shell powder, and a first thermal initiator are mixed and reacted at 60-70℃ for 2-4 hours under nitrogen protection to obtain a cashew nut shell powder-containing acrylate prepolymer.

[0018] In a specific embodiment of the present invention, the preparation method of the alkenylated cashew phenol includes the following steps: Cashew nut phenol, alkaline catalyst, acid-binding agent, polymerization inhibitor and solvent are mixed, and diallyl carbamoyl chloride is added to react. After the reaction is completed, the solvent is removed, the mixture is washed, and the alkenylated cashew nut phenol is obtained by rotary evaporation.

[0019] In particular, the alkenylated cashew phenol prepared by the present invention using specific diallyl carbamoyl chloride and cashew phenol can improve the high temperature and high humidity resistance, room temperature folding resistance and low temperature bending resistance of OCA optical adhesive.

[0020] In a specific embodiment of the present invention, the alkaline catalyst is selected from at least one of sodium hydroxide, sodium bicarbonate, and sodium carbonate.

[0021] In a specific embodiment of the present invention, the acid-binding agent is selected from at least one of triethylamine and sodium bicarbonate.

[0022] In a specific embodiment of the present invention, the polymerization inhibitor is selected from at least one of p-hydroxyanisole, hydroquinone, and diethylhydroxylamine.

[0023] In a specific embodiment of the present invention, the solvent is selected from at least one of tetrahydrofuran, toluene, tetramethylbenzene, n-hexane, and n-octane.

[0024] In a specific embodiment of the present invention, the molar ratio of cashew phenol and diallyl carbamoyl chloride is 1:1.1-1.2.

[0025] In a specific embodiment of the present invention, the molar ratio of cashew phenol and acid-binding agent is 1:1-3.

[0026] In a specific embodiment of the present invention, the mass ratio of cashew phenol, alkaline catalyst, polymerization inhibitor and solvent is 10:0.1-0.3:0.03-0.13:0.05-0.1:60-80.

[0027] In a specific embodiment of the present invention, the preparation method of the alkenylated cashew phenol includes the following steps: Cashew nut phenol, alkaline catalyst, acid-binding agent, polymerization inhibitor and solvent are mixed, and diallyl carbamoyl chloride is added and reacted at 60-80℃ for 1-3 hours. After the reaction is completed, the solvent is removed, the mixture is washed, and the alkenylated cashew nut phenol is obtained by rotary evaporation.

[0028] In a specific embodiment of the present invention, the acrylate prepolymer containing hydrazone bonds is obtained by polymerization of isooctyl acrylate, dihydrazide and terpene aldehyde.

[0029] In a specific embodiment of the present invention, the method for preparing the acrylate prepolymer containing acylhydrazone bonds includes the following steps: Diazid and anhydrous acetic acid were mixed, and terpene aldehyde was added dropwise to react. After the reaction was completed, the mixture was filtered under reduced pressure, washed, and dried to obtain an intermediate containing acylhydrazone bonds and double bonds. The intermediate containing acylhydrazone bonds and double bonds, isooctyl acrylate, and a second thermal initiator were mixed and reacted under nitrogen protection to obtain an acrylate prepolymer containing acylhydrazone bonds.

[0030] In a specific embodiment of the present invention, the terpene aldehyde is 10-undecenal.

[0031] In particular, the acrylate prepolymer containing acylhydrazone bonds prepared by the present invention using a specific terpene aldehyde undecenal with dihydrazide and isooctyl acrylate can effectively improve the high temperature and high humidity resistance, room temperature folding resistance and low temperature bending resistance of OCA optical adhesive.

[0032] In a specific embodiment of the present invention, the dihydrazide is selected from at least one of oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, adipic acid dihydrazide, azelaic acid dihydrazide, and sebacate dihydrazide.

[0033] In a specific embodiment of the present invention, the molar ratio of the dihydrazide and the terpene aldehyde is 1:1.8-2.2.

[0034] In a specific embodiment of the present invention, the mass ratio of the dihydrazide and anhydrous acetic acid is 1:5-10.

[0035] In a specific embodiment of the present invention, the mass ratio of the intermediate containing acylhydrazone bonds and double bonds to isooctyl acrylate is 70-80:20-30.

[0036] In a specific embodiment of the present invention, the second thermal initiator is selected from at least one of dicumyl peroxide, benzoyl peroxide, and azobisisobutyronitrile.

[0037] In a specific embodiment of the present invention, the amount of the second thermal initiator used is 0.8-1.2% of the total mass of the intermediate product containing acylhydrazone bonds and double bonds and isooctyl acrylate.

[0038] In a specific embodiment of the present invention, the method for preparing the acrylate prepolymer containing acylhydrazone bonds includes the following steps: Diazidamide and anhydrous acetic acid were mixed, and terpene aldehyde was added dropwise to carry out the reaction. The reaction temperature was 50-70℃ and the reaction time was 30-60 min. After the reaction was completed, the mixture was filtered under reduced pressure, washed, and dried to obtain an intermediate product containing acylhydrazone bonds and double bonds. The intermediate product containing acylhydrazone bonds and double bonds, isooctyl acrylate, and a second thermal initiator were mixed and reacted at 60-70℃ for 2-4 h under nitrogen protection to obtain an acrylate prepolymer containing acylhydrazone bonds.

[0039] In a specific embodiment of the present invention, the photoinitiator is selected from at least one of benzophenone, 2-hydroxy-2-methyl-1-phenyl-1-propanone and 1-hydroxycyclohexylphenyl ketone.

[0040] Secondly, the present invention provides a method for preparing an acid-free, water-blocking OCA optical adhesive, comprising the following steps: An acrylate prepolymer containing cashew phenol, an acrylate prepolymer containing acylhydrazone bonds, and a photoinitiator are mixed evenly to obtain OCA optical adhesive. The OCA optical adhesive is then uniformly coated between a heavy release film and a light release film. In a specific embodiment of the present invention, the conditions for ultraviolet curing are: the wavelength of the ultraviolet light is 280-420 nm, and the energy of the ultraviolet light is 2000-3000 mJ / cm². 2 .

[0041] Compared with the prior art, the present invention has the following beneficial effects: The acid-free, water-blocking OCA optical adhesive provided by this invention has high light transmittance (>95%), excellent high temperature and high humidity resistance (no bubble rebound, no whitening, no yellowing, no peeling or delamination after 1000 hours at 85℃ and 85% humidity), and resistance to room temperature bending (>200,000 times) and low temperature (-20℃) bending performance (>100,000 times). Detailed Implementation

[0042] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0043] Preparation Examples 1-6: Preparation of Acrylate Prepolymers Containing Cashew Phenolic Acid Preparation Example 1: Acrylate Prepolymer Containing Cashew Phenol 60g of butyl acrylate, 3g of o-phenylphenoxyethyl acrylate, 12g of isobornyl methacrylate, 25g of alkenylated cashew nut shell powder and 1g of benzoyl peroxide were mixed and reacted at 65°C for 3 hours under nitrogen protection to obtain a cashew nut shell powder-containing acrylate prepolymer.

[0044] Among them, alkenylated cashew phenol: 100g of cashew nut phenol, 2g of sodium hydroxide, 67g of triethylamine, 0.6g of hydroquinone and 600g of toluene were mixed, and 58.5g of diallyl carbamoyl chloride was added. The mixture was reacted at 70℃ for 3h. After the reaction was completed, the toluene was removed, the mixture was washed, and the alkenylated cashew nut phenol was obtained by rotary evaporation.

[0045] Preparation Example 2: Acrylate Prepolymer Containing Cashew Phenol 60g of butyl acrylate, 15g of isobornyl methacrylate, 25g of alkenylated cashew nut shell powder and 1g of benzoyl peroxide were mixed and reacted at 65°C for 3 hours under nitrogen protection to obtain a cashew nut shell powder-containing acrylate prepolymer.

[0046] Alkenylated cashew phenol is prepared as in Example 1.

[0047] Preparation Example 3: Acrylate Prepolymer Containing Cashew Phenol 50g of butyl acrylate, 3g of o-phenylphenoxyethyl acrylate, 12g of isobornyl methacrylate, 35g of alkenylated cashew nut shell powder and 1g of benzoyl peroxide were mixed and reacted at 65°C for 3 hours under nitrogen protection to obtain a cashew nut shell powder-containing acrylate prepolymer.

[0048] Alkenylated cashew phenol is prepared as in Example 1.

[0049] Preparation Example 4: Acrylate Prepolymer 85g of butyl acrylate, 3g of o-phenylphenoxyethyl acrylate, 12g of isobornyl methacrylate and 1g of benzoyl peroxide were mixed and reacted at 65°C for 3 hours under nitrogen protection to obtain acrylate prepolymer.

[0050] Preparation Example 5: Acrylate Prepolymer Containing Cashew Phenol 60g of butyl acrylate, 3g of o-phenylphenoxyethyl acrylate, 12g of isobornyl methacrylate, 25g of alkenylated cashew nut shell powder and 1g of benzoyl peroxide were mixed and reacted at 65°C for 3 hours under nitrogen protection to obtain a cashew nut shell powder-containing acrylate prepolymer.

[0051] Among them, alkenylated cashew phenol: 100g of cashew nut alcohol, 2g of sodium hydroxide, 67g of triethylamine, 0.6g of hydroquinone and 600g of toluene were mixed, and 28g of acryloyl chloride was added. The mixture was reacted at 70℃ for 3h. After the reaction was completed, the toluene was removed, the mixture was washed, and the alkenylated cashew nut alcohol was obtained by rotary evaporation.

[0052] Preparation Example 6: Acrylate Prepolymer Containing Cashew Phenol 60g of butyl acrylate, 3g of o-phenylphenoxyethyl acrylate, 12g of isobornyl methacrylate, 25g of alkenylated cashew nut shell powder and 1g of benzoyl peroxide were mixed and reacted at 65°C for 3 hours under nitrogen protection to obtain a cashew nut shell powder-containing acrylate prepolymer.

[0053] Among them, alkenylated cashew phenol: 100g of cashew nut powder, 2g of sodium hydroxide, 67g of triethylamine, 0.6g of hydroquinone and 600g of toluene were mixed, and 59g of vinyltrichlorosilane was added. The mixture was reacted at 70°C for 3 hours. After the reaction was completed, the toluene was removed, the mixture was washed, and the alkenylated cashew nut powder was obtained by rotary evaporation.

[0054] Preparation Examples 7-8: Preparation of Acrylate Prepolymers Containing Acrylate Bonds Preparation Example 7: Acrylate Prepolymer Containing Acylhydrazone Bonds 100g of oxalic acid dihydrazide and 600g of anhydrous acetic acid were mixed, and 285g of 10-undecenal was added dropwise to carry out the reaction. The reaction temperature was 60℃ and the reaction time was 60min. After the reaction was completed, the mixture was filtered under reduced pressure, washed, and dried to obtain an intermediate product containing acylhydrazone bonds and double bonds. 20g of the intermediate product containing acylhydrazone bonds and double bonds, 80g of isooctyl acrylate, and 1g of benzoyl peroxide were mixed and reacted at 70℃ for 3h under nitrogen protection to obtain an acrylate prepolymer containing acylhydrazone bonds.

[0055] Preparation Example 8: Acrylate Prepolymer Containing Acrylate-Hydroxy Bonds 100g of oxalic acid dihydrazide and 600g of anhydrous acetic acid were mixed, and 191g of 7-octenal was added dropwise to react. The reaction temperature was 60℃ and the reaction time was 60min. After the reaction was completed, the mixture was filtered under reduced pressure, washed, and dried to obtain an intermediate product containing acylhydrazone bonds and double bonds. 20g of the intermediate product containing acylhydrazone bonds and double bonds, 80g of isooctyl acrylate, and 1g of benzoyl peroxide were mixed and reacted at 70℃ for 3h under nitrogen protection to obtain an acrylate prepolymer containing acylhydrazone bonds.

[0056] Examples 1-3 and Comparative Examples 1-8: Preparation of Acid-Free Water-Blocking OCA Optical Adhesives Example 1 The acid-free, water-resistant OCA optical adhesive comprises, from top to bottom, a heavy release film, an OCA optical adhesive layer, and a light release film. The OCA optical adhesive layer comprises the following components in parts by weight: 40 parts of the cashew phenol-containing acrylate prepolymer of Preparation Example 1, 60 parts of the acylhydrazone-containing acrylate prepolymer of Preparation Example 7, and 0.3 parts of 1-hydroxycyclohexylphenyl ketone.

[0057] The thickness of the OCA optical adhesive layer is 50µm.

[0058] The thickness of the re-release film is 75µm. The thickness of the light release film is 50 μm.

[0059] The preparation method of the acid-free water-blocking OCA optical adhesive includes the following steps: An acrylate prepolymer containing cashew phenol, an acrylate prepolymer containing acylhydrazone bonds, and 1-hydroxycyclohexylphenyl ketone were mixed evenly to obtain an OCA optical adhesive. The OCA optical adhesive was then uniformly coated between a heavy release film and a light release film, and ultraviolet light was applied at a wavelength of 365 nm and a wavelength of 2500 mJ / cm². 2 After curing with energy light for 3 minutes, an acid-free and water-resistant OCA optical adhesive is obtained.

[0060] Example 2 The acid-free, water-resistant OCA optical adhesive comprises, from top to bottom, a heavy release film, an OCA optical adhesive layer, and a light release film. The OCA optical adhesive layer comprises the following components in parts by weight: 45 parts of the cashew phenol-containing acrylate prepolymer of Preparation Example 1, 55 parts of the acylhydrazone-containing acrylate prepolymer of Preparation Example 7, and 0.3 parts of 1-hydroxycyclohexylphenyl ketone.

[0061] The thickness of the OCA optical adhesive layer is 50µm.

[0062] The thickness of the re-release film is 75µm. The thickness of the light release film is 50 μm.

[0063] The preparation method of the acid-free water-blocking OCA optical adhesive includes the following steps: An acrylate prepolymer containing cashew phenol, an acrylate prepolymer containing acylhydrazone bonds, and 1-hydroxycyclohexylphenyl ketone were mixed evenly to obtain an OCA optical adhesive. The OCA optical adhesive was then uniformly coated between a heavy release film and a light release film, and ultraviolet light was applied at a wavelength of 365 nm and a wavelength of 2500 mJ / cm². 2 After curing with energy light for 3 minutes, an acid-free and water-resistant OCA optical adhesive is obtained.

[0064] Example 3 The acid-free, water-resistant OCA optical adhesive comprises, from top to bottom, a heavy release film, an OCA optical adhesive layer, and a light release film. The OCA optical adhesive layer comprises the following components in parts by weight: 50 parts of the cashew phenol-containing acrylate prepolymer of Preparation Example 1, 50 parts of the acylhydrazone-containing acrylate prepolymer of Preparation Example 7, and 0.3 parts of 1-hydroxycyclohexylphenyl ketone.

[0065] The thickness of the OCA optical adhesive layer is 50µm.

[0066] The thickness of the re-release film is 75µm. The thickness of the light release film is 50 μm.

[0067] The preparation method of the acid-free water-blocking OCA optical adhesive includes the following steps: An acrylate prepolymer containing cashew phenol, an acrylate prepolymer containing acylhydrazone bonds, and 1-hydroxycyclohexylphenyl ketone were mixed evenly to obtain an OCA optical adhesive. The OCA optical adhesive was then uniformly coated between a heavy release film and a light release film, and ultraviolet light was applied at a wavelength of 365 nm and a wavelength of 2500 mJ / cm². 2 After curing with energy light for 3 minutes, an acid-free and water-resistant OCA optical adhesive is obtained.

[0068] Comparative Example 1 The acid-free, water-blocking OCA optical adhesive comprises, from top to bottom, a heavy release film, an OCA optical adhesive layer, and a light release film. The OCA optical adhesive layer comprises the following components in parts by weight: 40 parts of the cashew phenol-containing acrylate prepolymer of Preparation Example 2, 60 parts of the acylhydrazone-containing acrylate prepolymer of Preparation Example 7, and 0.3 parts of 1-hydroxycyclohexylphenyl ketone.

[0069] The thickness of the OCA optical adhesive layer is 50µm.

[0070] The thickness of the release film is 75µm.

[0071] The thickness of the light release film is 50 μm.

[0072] The preparation method of the acid-free water-blocking OCA optical adhesive includes the following steps: An acrylate prepolymer containing cashew phenol, an acrylate prepolymer containing acylhydrazone bonds, and 1-hydroxycyclohexylphenyl ketone were mixed evenly to obtain an OCA optical adhesive. The OCA optical adhesive was then uniformly coated between a heavy release film and a light release film, and ultraviolet light was applied at a wavelength of 365 nm and a wavelength of 2500 mJ / cm². 2 After curing with energy light for 3 minutes, an acid-free and water-resistant OCA optical adhesive is obtained.

[0073] Comparative Example 2 The acid-free, water-resistant OCA optical adhesive comprises, from top to bottom, a heavy release film, an OCA optical adhesive layer, and a light release film. The OCA optical adhesive layer comprises the following components in parts by weight: 40 parts of the cashew phenol-containing acrylate prepolymer of Preparation Example 3, 60 parts of the acylhydrazone-containing acrylate prepolymer of Preparation Example 7, and 0.3 parts of 1-hydroxycyclohexylphenyl ketone.

[0074] The thickness of the OCA optical adhesive layer is 50µm.

[0075] The thickness of the release film is 75µm.

[0076] The thickness of the light release film is 50 μm.

[0077] The preparation method of the acid-free water-blocking OCA optical adhesive includes the following steps: An acrylate prepolymer containing cashew phenol, an acrylate prepolymer containing acylhydrazone bonds, and 1-hydroxycyclohexylphenyl ketone were mixed evenly to obtain an OCA optical adhesive. The OCA optical adhesive was then uniformly coated between a heavy release film and a light release film, and ultraviolet light was applied at a wavelength of 365 nm and a wavelength of 2500 mJ / cm². 2 After curing with energy light for 3 minutes, an acid-free and water-resistant OCA optical adhesive is obtained.

[0078] Comparative Example 3 The acid-free, water-blocking OCA optical adhesive comprises, from top to bottom, a heavy release film, an OCA optical adhesive layer, and a light release film. The OCA optical adhesive layer comprises the following components in parts by weight: 40 parts of the acrylate prepolymer of Preparation Example 4, 60 parts of the acrylate prepolymer containing acylhydrazone bonds of Preparation Example 7, and 0.3 parts of 1-hydroxycyclohexylphenyl ketone.

[0079] The thickness of the OCA optical adhesive layer is 50µm.

[0080] The thickness of the release film is 75µm.

[0081] The thickness of the light release film is 50 μm.

[0082] The preparation method of the acid-free water-blocking OCA optical adhesive includes the following steps: An acrylate prepolymer, an acrylate prepolymer containing acylhydrazone bonds, and 1-hydroxycyclohexylphenyl ketone were mixed evenly to obtain an OCA optical adhesive. The OCA optical adhesive was then uniformly coated between a heavy release film and a light release film. Ultraviolet light was applied at a wavelength of 365 nm and a wavelength of 2500 mJ / cm². 2 After curing with energy light for 3 minutes, an acid-free and water-resistant OCA optical adhesive is obtained.

[0083] Comparative Example 4 The acid-free, water-resistant OCA optical adhesive comprises, from top to bottom, a heavy release film, an OCA optical adhesive layer, and a light release film. The OCA optical adhesive layer comprises the following components in parts by weight: 40 parts of the cashew phenol-containing acrylate prepolymer of Preparation Example 5, 60 parts of the acylhydrazone-containing acrylate prepolymer of Preparation Example 7, and 0.3 parts of 1-hydroxycyclohexylphenyl ketone.

[0084] The thickness of the OCA optical adhesive layer is 50µm.

[0085] The thickness of the release film is 75µm.

[0086] The thickness of the light release film is 50 μm.

[0087] The preparation method of the acid-free water-blocking OCA optical adhesive includes the following steps: An acrylate prepolymer containing cashew phenol, an acrylate prepolymer containing acylhydrazone bonds, and 1-hydroxycyclohexylphenyl ketone were mixed evenly to obtain an OCA optical adhesive. The OCA optical adhesive was then uniformly coated between a heavy release film and a light release film, and ultraviolet light was applied at a wavelength of 365 nm and a wavelength of 2500 mJ / cm². 2 After curing with energy light for 3 minutes, an acid-free and water-resistant OCA optical adhesive is obtained.

[0088] Comparative Example 5 The acid-free, water-resistant OCA optical adhesive comprises, from top to bottom, a heavy release film, an OCA optical adhesive layer, and a light release film. The OCA optical adhesive layer comprises the following components in parts by weight: 40 parts of the cashew phenol-containing acrylate prepolymer of Preparation Example 6, 60 parts of the acylhydrazone-containing acrylate prepolymer of Preparation Example 7, and 0.3 parts of 1-hydroxycyclohexylphenyl ketone.

[0089] The thickness of the OCA optical adhesive layer is 50µm.

[0090] The thickness of the release film is 75µm.

[0091] The thickness of the light release film is 50 μm.

[0092] The preparation method of the acid-free water-blocking OCA optical adhesive includes the following steps: An acrylate prepolymer containing cashew phenol, an acrylate prepolymer containing acylhydrazone bonds, and 1-hydroxycyclohexylphenyl ketone were mixed evenly to obtain an OCA optical adhesive. The OCA optical adhesive was then uniformly coated between a heavy release film and a light release film, and ultraviolet light was applied at a wavelength of 365 nm and a wavelength of 2500 mJ / cm². 2 After curing with energy light for 3 minutes, an acid-free and water-resistant OCA optical adhesive is obtained.

[0093] Comparative Example 6 The acid-free, water-resistant OCA optical adhesive comprises, from top to bottom, a heavy release film, an OCA optical adhesive layer, and a light release film. The OCA optical adhesive layer comprises the following components in parts by weight: 40 parts of the cashew phenol-containing acrylate prepolymer of Preparation Example 1, 60 parts of the acylhydrazone-containing acrylate prepolymer of Preparation Example 8, and 0.3 parts of 1-hydroxycyclohexylphenyl ketone.

[0094] The thickness of the OCA optical adhesive layer is 50µm.

[0095] The thickness of the release film is 75µm.

[0096] The thickness of the light release film is 50 μm.

[0097] The preparation method of the acid-free water-blocking OCA optical adhesive includes the following steps: An acrylate prepolymer containing cashew phenol, an acrylate prepolymer containing acylhydrazone bonds, and 1-hydroxycyclohexylphenyl ketone were mixed evenly to obtain an OCA optical adhesive. The OCA optical adhesive was then uniformly coated between a heavy release film and a light release film, and ultraviolet light was applied at a wavelength of 365 nm and a wavelength of 2500 mJ / cm². 2 After curing with energy light for 3 minutes, an acid-free and water-resistant OCA optical adhesive is obtained.

[0098] Comparative Example 7 The acid-free, water-resistant OCA optical adhesive comprises, from top to bottom, a heavy release film, an OCA optical adhesive layer, and a light release film. The OCA optical adhesive layer comprises the following components in parts by weight: 100 parts of the cashew phenol-containing acrylate prepolymer of Preparation Example 1 and 0.3 parts of 1-hydroxycyclohexylphenyl ketone.

[0099] The thickness of the OCA optical adhesive layer is 50µm.

[0100] The thickness of the release film is 75µm.

[0101] The thickness of the light release film is 50 μm.

[0102] The preparation method of the acid-free water-blocking OCA optical adhesive includes the following steps: An acrylate prepolymer containing cashew phenol and 1-hydroxycyclohexylphenyl ketone were mixed evenly to obtain OCA optical adhesive. The OCA optical adhesive was then uniformly coated between a heavy release film and a light release film. Ultraviolet light was applied at a wavelength of 365 nm and a wavelength of 2500 mJ / cm². 2 After curing with energy light for 3 minutes, an acid-free and water-resistant OCA optical adhesive is obtained.

[0103] Comparative Example 8 The acid-free, water-blocking OCA optical adhesive comprises, from top to bottom, a heavy release film, an OCA optical adhesive layer, and a light release film. The OCA optical adhesive layer comprises the following components in parts by weight: 100 parts of the acrylate prepolymer containing acylhydrazone bonds from Preparation Example 7, and 0.3 parts of 1-hydroxycyclohexylphenyl ketone.

[0104] The thickness of the OCA optical adhesive layer is 50µm.

[0105] The thickness of the release film is 75µm.

[0106] The thickness of the light release film is 50 μm.

[0107] The preparation method of the acid-free water-blocking OCA optical adhesive includes the following steps: An acrylate prepolymer containing acylhydrazone bonds and 1-hydroxycyclohexylphenyl ketone were mixed evenly to obtain OCA optical adhesive. The OCA optical adhesive was then uniformly coated between a heavy release film and a light release film. Ultraviolet light was applied at a wavelength of 365 nm and a wavelength of 2500 mJ / cm². 2 After curing with energy light for 3 minutes, an acid-free and water-resistant OCA optical adhesive is obtained.

[0108] The acid-free, water-blocking OCA optical adhesives prepared in Examples 1-3 and Comparative Examples 1-8 were subjected to the following performance tests: 1. Light transmittance: The glass cover plate / OCA optical adhesive / ITO sheet are bonded together and tested according to GB / T 2410-2008 "Determination of light transmittance and haze of transparent plastics".

[0109] 2. High temperature and humidity resistance: Each OCA optical adhesive is bonded to the glass cover plate and placed at 85℃ and 85% humidity for 1000 hours. The adhesion is observed. If there is no bubble rebound, no whitening, no yellowing, and no peeling or delamination, it is OK. If any piece has the above defects, it is NG. For OK samples, the peel strength is calculated. The peel strength test method is as follows: refer to GB / T 2792-2014 "Test Method for Peel Strength of Adhesive Tapes" for 180° peel strength test.

[0110] 3. Room Temperature Bending Resistance: Each OCA optical adhesive is adhered to a 0.1mm flexible tempered glass film, which is then fixed to a folding screen testing fixture. The test temperature is 25℃, and the bending radius R = 1.0mm. Bending is performed from 0° to 180°, with 100,000, 150,000, and 200,000 bending tests conducted. At 100,000 cycles, the experiment is stopped, and the protective film is observed for blistering, cracking, peeling, or creases. If these occur, the number of cycles is recorded as <100,000. If no such phenomena occur, the test continues. At 150,000 cycles, the experiment is stopped, and the protective film is observed for blistering, cracking, peeling, or creases. If these phenomena occur, the number of cycles is recorded as <150,000. If no such phenomena occur, the test continues. At 200,000 cycles, the experiment is stopped, and the OCA optical adhesive is observed for blistering, cracking, or peeling. If these phenomena occur, the number of cycles is recorded as <200,000. If no such phenomena occur, the number of cycles is recorded as >200,000.

[0111] 4. Low-temperature bending resistance: Each OCA optical adhesive is adhered to a 0.1mm flexible tempered glass film, and then fixed to a folding screen testing fixture. The test temperature is -20℃, the bending radius R = 1.0mm, and bending is performed from 0° to 180°. Bending tests are conducted for 50,000 and 100,000 cycles respectively. When the test reaches 50,000 cycles, the experiment is stopped, and the protective film is observed for bubbling, cracking, peeling, creases, etc. If these occur, the number of cycles is recorded as <50,000. If no such phenomena occur, the test continues. When the test reaches 100,000 cycles, the experiment is stopped, and the OCA optical adhesive is observed for bubbling, cracking, peeling, etc. If these phenomena occur, the number of cycles is recorded as <100,000. If no such phenomena occur, the number of cycles is recorded as >100,000.

[0112] The results of the above performance tests are shown in Table 1 below.

[0113] Table 1 As shown in Table 1, the acid-free water-blocking OCA optical adhesive provided by the present invention is formulated by compounding an acrylate prepolymer containing cashew phenol and an acrylate prepolymer containing acylhydrazone bonds. The resulting OCA optical adhesive has high light transmittance, high temperature and high humidity resistance, room temperature bending resistance and low temperature bending resistance.

[0114] As can be seen from Example 1 and Comparative Examples 1-3, only the OCA optical adhesive prepared by using o-phenylphenoxyethyl acrylate and a specific amount of cashew phenol prepolymer in this invention can achieve high temperature and high humidity resistance of 1000h, room temperature folding resistance >200,000 times, and -20℃ folding resistance >100,000 times.

[0115] As can be seen from Example 1 and Comparative Examples 4-5, only the OCA optical adhesive prepared by the specific alkenylated cashew phenol in this invention can achieve high temperature and high humidity resistance of 1000h, room temperature folding resistance of >200,000 times, and -20℃ folding resistance of >100,000 times. This may be because the flexible cross-linking network formed by alkenylated cashew phenol prepared by acryloyl chloride is not as good as that of diallyl carbamoyl chloride, while the Si-O-Si bond in the alkenylated cashew phenol prepared by vinyltrichlorosilane is too rigid, reducing flexibility.

[0116] As can be seen from Example 1 and Comparative Example 6, only the OCA optical adhesive prepared by using the specific terpene aldehyde 10-undecenal in this invention can achieve high temperature and high humidity resistance of 1000h, room temperature folding resistance >200,000 times, and -20℃ folding resistance >100,000 times. This may be because the rigid terpene ring and flexible long aliphatic chain structure of 10-undecenal improve the high temperature and high humidity resistance and bending resistance of the OCA optical adhesive.

[0117] As can be seen from Example 1 and Comparative Examples 7-8, the OCA optical adhesive prepared by the combined action of acrylate prepolymer containing cashew phenol and acrylate prepolymer containing hydrazone bonds in this invention can achieve high temperature and high humidity resistance of 1000h, room temperature folding resistance of >200,000 times, and folding resistance of >100,000 times at -20℃.

[0118] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. An acid-free water-blocking OCA optical adhesive, characterized in that, From top to bottom, it comprises a heavy release film, an OCA optical adhesive layer and a light release film, wherein the OCA optical adhesive layer comprises the following components by mass fraction: a cashew phenol-containing acrylate prepolymer 40-60 parts, an acylhydrazone bond-containing acrylate prepolymer 40-60 parts, and a photoinitiator 0.1-1 part; The cashew phenol-containing acrylate prepolymer is obtained by polymerization of butyl acrylate, o-phenylphenoxyethyl acrylate, isobornyl methacrylate and alkenyl cashew phenol; The acylhydrazone bond-containing acrylate prepolymer is obtained by polymerization of isooctyl acrylate, dihydrazide and terpene aldehyde.

2. The acid-free water-resistant OCA optical glue according to claim 1, wherein, The thickness of the OCA optical adhesive layer is 25-300 μm. 3.The acid-free moisture-resistant OCA optical glue of claim 2, characterized in that, The mass ratio of the butyl acrylate, o-phenylphenoxyethyl acrylate, isobornyl methacrylate and alkenyl cashew phenol is 55-78:2-5:10-15:10-25. 4.The acid-free water-blocking OCA optical glue according to any one of claims 1-3, characterized in that, The preparation method of the cashew phenol-containing acrylate prepolymer comprises the following steps: The butyl acrylate, o-phenylphenoxyethyl acrylate, isobornyl methacrylate, alkenyl cashew phenol and first thermal initiator are mixed, and then the mixture is reacted under nitrogen protection and temperature rising to obtain the cashew phenol-containing acrylate prepolymer. 5.The acid-free water-blocking OCA optical glue of claim 4, wherein, The preparation method of the alkenyl cashew phenol comprises the following steps: The cashew phenol, alkaline catalyst, acid binding agent, polymerization inhibitor and solvent are mixed, and then the mixture is reacted by adding diallylaminocarbonyl chloride, and then the solvent is removed, the mixture is washed and rotary evaporated to obtain the alkenyl cashew phenol. 6.The acid-free water-blocking OCA optical glue according to any one of claims 1-3, characterized in that, The preparation method of the acylhydrazone bond-containing acrylate prepolymer comprises the following steps: The dihydrazide and anhydrous acetic acid are mixed, and then the mixture is reacted by dropwise adding terpene aldehyde, and then the mixture is filtered under reduced pressure, washed and dried to obtain an intermediate product containing acylhydrazone bond and double bond, the intermediate product containing acylhydrazone bond and double bond, isooctyl acrylate and second thermal initiator are mixed, and then the mixture is reacted under nitrogen protection and temperature rising to obtain the acylhydrazone bond-containing acrylate prepolymer.

7. The acid-free water-resistant OCA optical glue according to claim 6, characterized in that, The terpene aldehyde is 10-undecenal. 8.The acid-free moisture-resistant OCA optical glue according to claim 7, characterized in that, The mass ratio of the intermediate product containing acylhydrazone bond and double bond and isooctyl acrylate is 70-80:20-30.

9. The method of making an acid-free, water-resistant OCA optical adhesive according to any one of claims 1-8, characterized in that, The method comprises the following steps: The cashew phenol-containing acrylate prepolymer, acylhydrazone bond-containing acrylate prepolymer and photoinitiator are uniformly mixed to obtain an OCA optical adhesive, the OCA optical adhesive is uniformly coated between the heavy release film and the light release film, and then the OCA optical adhesive is cured by ultraviolet light to obtain the acid-free and water-resistant OCA optical adhesive.

10. The acid-free and water-resistant OCA optical adhesive according to any one of claims 1-8 is applied to electronic products.

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