OCA Optical Adhesive for Bonding In-Vehicle Displays and Its Preparation Method

Abstract

The present invention discloses an OCA optical adhesive for bonding vehicle-mounted displays and a preparation method thereof. The raw materials for preparing the optical adhesive include, by weight: 15-25 parts of a hydroxyl-containing acrylic functional monomer, 0.5-2 parts of a methyl- and nitrogen atom-containing acrylic functional monomer, 10-30 parts of an acrylic hard monomer with a glass transition temperature higher than 130°C, 45-75 parts of an acrylic soft monomer with a glass transition temperature lower than -30°C, 0.02-0.2 parts of a photoinitiator, 0.1-0.5 parts of a multi-functional copolymer monomer, 0.1-0.5 parts of a silane coupling agent, and 0.1-0.5 parts of a light stabilizer. The OCA optical adhesive provided by the present invention has excellent optical properties, heat resistance, high-temperature and high-humidity resistance, ultraviolet resistance, and bonding properties, can ensure perfect bonding with special materials of vehicle-mounted displays, and can maintain excellent properties in a very harsh high-temperature and high-humidity environment, having good application prospects.

Description

Technical Field

[0001] The present invention relates to the field of optical adhesives, and particularly to an OCA optical adhesive for bonding vehicle-mounted displays and a preparation method thereof. Background Art

[0002] With the development of the Internet of Vehicles, sharing, autonomous driving, and new forces in the automotive industry, as well as the rapid rise of new energy vehicles, not only has there been a bold attempt in the appearance of automobiles, but also great efforts have been made in the automotive interior, especially in the central control screen of automobiles. Automotive intelligent screens such as extra-large central control screens, triple screens, and through-type central control screens have emerged in an endless stream. Large size, suspension, multi-functional interaction, and intelligent matching have made it a trend to add a sense of technology to the central control screen. Making the automotive intelligent cockpit understand your needs and anticipate your thoughts, the market demand growth space for vehicle-mounted displays is huge.

[0003] Behind the vehicle-mounted display, the bonding of OCA optical transparent adhesive is indispensable. Conventional OCA optical adhesives are mainly used to bond various material devices after touching the touch screen, achieving the effect of capacitive touch sensing. High-quality OCA optical adhesives should possess characteristics such as high light transmittance, high transparency, and high adhesion.

[0004] However, in recent years, polymer plastic panels such as polymethyl methacrylate (PMMA), polycarbonate (PC), and cycloolefin polymer (COP) have been used as the mainstream panels for vehicle-mounted displays due to their advantages such as light weight, flexibility, low cost, and safety. The OCA optical adhesives used in automotive vehicle-mounted displays not only require characteristics such as high light transmittance, high transparency, and high adhesion, but also need to ensure no problems such as bubbling, peeling, turbidity, or white opacity during the bonding process of materials such as PMMA and PC. Moreover, due to the long service life of automobiles and their long-term exposure to outdoor environments, higher stability is required, and excellent heat resistance, high-temperature and high-humidity resistance, and ultraviolet resistance should be possessed.

[0005] With the rapid rise of the automotive industry, automotive intelligent screens such as large in-vehicle central control screens, triple screens, and integrated central control screens have emerged in an endless stream. Polymer plastic panels such as polymethyl methacrylate (PMMA), polycarbonate (PC), and cycloolefin polymer (COP) have been used as the mainstream panels for in-vehicle displays due to their advantages such as light weight, flexibility, low cost, and safety. However, due to the special nature of their materials, exhaust gas phenomena will occur under high-temperature conditions, resulting in bubbling or peeling between the OCA optical adhesive and the display panel module. At the same time, under high-temperature and high-humidity conditions, moisture from the outside can penetrate from the edge of the display panel, causing turbidity or white opacity inside the display panel. As its bonding material, conventional OCA optical adhesives are difficult to solve problems such as bubbling, peeling, turbidity, or white opacity in the touch panel. In addition, due to the long service life of automobiles and their long-term exposure to outdoor environments, they require more excellent heat resistance, high-temperature and high-humidity resistance, and UV resistance compared to conventional touch panels.

[0006] Japanese Patent JP2017160416A provides an optical adhesive sheet suitable for filling the gap between a polarizing film and a resin cover in a liquid crystal display device, as well as a polarizing film and a liquid crystal display device having the adhesive sheet. The optical adhesive sheet X has a laminated structure of an adhesive layer (11, 12) and a substrate (13). The thickness of the adhesive layer 11 is 30 μm or more, and the storage modulus at 95 °C is 1.0×104 Pa or higher. The loss tangent of the adhesive layer 12 at 95 °C is 0.08 or more. The thickness of the substrate 13 is 15 - 150 μm. The polarizing film Y with an adhesive layer has a laminated structure of an adhesive sheet X and a polarizing film 21. The liquid crystal display device includes a resin cover, a liquid crystal panel, and a laminated structure of the adhesive sheet X between them. In the liquid crystal display device, the adhesive sheet X is attached to the resin cover on the side of the adhesive layer 11 and to the polarizing film of the liquid crystal panel on the side of the adhesive layer 12. Patent CN105793305A discloses a copolymer of a monomer mixture, the monomer mixture containing about 25 parts by mass to about 80 parts by mass of an alkyl (meth)acrylate, about 15 parts by mass to about 50 parts by mass of a hydroxyl-containing monomer, and about 5 parts by mass to about 25 parts by mass of a macromonomer having a glass transition temperature (Tg) of about 50 °C or higher. The copolymer substantially does not contain acidic groups.

[0007] The products prepared by the above solutions naturally have excellent weather resistance. However, since their macromolecular structure is formed by post-adding and mixing, it will reduce the optical performance, and both the light transmittance and haze performance will decline. Moreover, their production process is too complex. It not only requires the combination of two adhesives, but also the synthesis method of the adhesives needs to be completed in multiple steps, making it difficult to ensure stability and the yield rate.

[0008] Therefore, it is necessary to improve the current technology to provide a more reliable solution. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to provide an OCA optical adhesive for bonding vehicle-mounted displays and a preparation method thereof in view of the deficiencies in the above-mentioned prior art.

[0010] To solve the above technical problem, the technical solution adopted by the present invention is: an OCA optical adhesive for bonding vehicle-mounted displays, and its raw materials for preparation include, by weight: 15-25 parts of hydroxyl-containing acrylic functional monomers, 0.5-2 parts of acrylic functional monomers containing methyl and nitrogen atoms, 10-30 parts of acrylic hard monomers with a glass transition temperature higher than 130°C, 45-75 parts of acrylic soft monomers with a glass transition temperature lower than -30°C, 0.02-0.2 parts of photoinitiator, 0.1-0.5 parts of multi-functional copolymer monomers, 0.1-0.5 parts of silane coupling agent, and 0.1-0.5 parts of light stabilizer.

[0011] Preferably, the hydroxyl-containing acrylic functional monomer is one or a mixture of more than one of 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, hydroxybutyl methacrylate, and 4-hydroxybutyl acrylate.

[0012] Preferably, the acrylic functional monomer containing methyl and nitrogen atoms is one or a mixture of more than one of methacrylamide, N-hydroxymethyl methacrylamide, and dimethylaminoethyl methacrylate).

[0013] Preferably, the acrylic hard monomer with a glass transition temperature higher than 130°C is one or a mixture of more than one of acrylamide, isobornyl methacrylate, N-vinylpyrrolidone, and 4-acryloylmorpholine.

[0014] Preferably, the acrylic soft monomer with a glass transition temperature lower than -30°C is one or a mixture of more than one of 2-ethylhexyl acrylate, butyl acrylate, and ethyl acrylate.

[0015] Preferably, the photoinitiator is one or a mixture of more than one of 1-hydroxycyclohexyl phenyl ketone, 2,2-dimethoxy-2-phenylacetophenone, and 2-methyl-2-hydroxypropyl phenyl ketone.

[0016] Preferably, the multi-functional copolymer monomer is one or a mixture of more than one of 1,6-hexanediol diacrylate, ethoxylated trimethylolpropane triacrylate, and trimethylolpropane triacrylate.

[0017] Preferably, the silane coupling agent is one or a mixture of more than one of γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, and γ-aminopropyltrimethoxysilane.

[0018] Preferably, the light stabilizer is one or a mixture of more than one of 2,6 - di - tert - butyl - 4 - methylphenol, 4 - hydroxymethyl - 2,6 - di - tert - butylphenol, and tris(nonylphenyl) phosphite.

[0019] Preferably, the preparation method of the OCA optical adhesive for bonding vehicle-mounted displays includes the following steps:

[0020] S1. Add 15 - 25 parts of hydroxyl - containing acrylic functional monomers, 0.5 - 2 parts of acrylic functional monomers containing methyl and nitrogen atoms, 10 - 30 parts of acrylic hard monomers with a glass transition temperature higher than 130°C, 45 - 75 parts of acrylic soft monomers with a glass transition temperature lower than - 30°C, and 0.01 - 0.1 part of photoinitiator into a reaction kettle. Under stirring conditions, pass nitrogen for 10 - 30 minutes;

[0021] S2. Irradiate the obtained mixture with a UVLED ultraviolet lamp for 2 - 10 minutes to obtain a prepolymer;

[0022] S3. Then add 0.01 - 0.1 part of photoinitiator, 0.1 - 0.5 part of multi - functional copolymer monomer, 0.1 - 0.5 part of silane coupling agent, and 0.1 - 0.5 part of light stabilizer, and mix evenly to obtain the OCA optical adhesive for bonding vehicle-mounted displays.

[0023] The beneficial effects of the present invention are as follows:

[0024] The OCA optical adhesive for bonding vehicle-mounted displays provided by the present invention is prepared from raw materials such as hydroxyl - containing acrylic functional monomers, acrylic functional monomers containing methyl and nitrogen atoms, hard monomers, soft monomers, and multi - functional copolymer monomers by an ultraviolet synthesis process. By selecting special monomers and reasonably matching the proportions of various monomers, the obtained product has excellent optical properties, heat resistance, high temperature and high humidity resistance, ultraviolet resistance, and bonding properties, can ensure perfect bonding with the special materials of vehicle-mounted displays, and can maintain excellent performance in very harsh high - temperature and high - humidity environments, having good application prospects;

[0025] The hydroxyl - containing acrylic functional monomers in the present invention have excellent hydrophilic groups: hydroxyl groups (-OH), which undergo hydrophilic reactions with water molecules in a high - humidity environment to maintain the optical transparency of the OCA optical adhesive and are not easily peeled off due to water molecule penetration;

[0026] The acrylic functional monomers containing methyl and nitrogen atoms in the present invention not only have excellent cohesion of single - methyl monomers and excellent exhaust gas properties of nitrogen - atom monomers, but also have excellent adhesion to PMMA and PC after combination, and have excellent compatibility with the deformation and aging of PMMA and PC caused by harsh environments;

[0027] The acrylic hard monomer with a glass transition temperature higher than 130°C in the present invention has the properties of high temperature and humidity resistance without whitening, and can synergistically enhance the effect with the acrylic functional monomer containing methyl and nitrogen atoms; the acrylic soft monomer with a glass transition temperature lower than -30°C can provide high adhesion. Detailed Description of the Invention

[0028] The following examples are used to further elaborate the present invention in detail, so that those skilled in the art can implement it according to the description in the specification.

[0029] It should be understood that the terms such as "having", "comprising", and "including" used herein do not exclude the presence or addition of one or more other elements or their combinations.

[0030] Unless otherwise specified, the test methods used in the following examples are all conventional methods. The materials, reagents, etc. used in the following examples can be obtained from commercial channels unless otherwise specified. For those not specifying specific conditions in the following examples, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. For reagents or instruments without indicating the manufacturer, they are all conventional products that can be purchased commercially.

[0031] The present invention provides an OCA optical adhesive for bonding vehicle-mounted displays, and its preparation raw materials include, by weight: 15-25 parts of hydroxyl-containing acrylic functional monomer, 0.5-2 parts of acrylic functional monomer containing methyl and nitrogen atoms, 10-30 parts of acrylic hard monomer with a glass transition temperature higher than 130°C, 45-75 parts of acrylic soft monomer with a glass transition temperature lower than -30°C, 0.02-0.2 parts of photoinitiator, 0.1-0.5 parts of multi-functional copolymer monomer, 0.1-0.5 parts of silane coupling agent, and 0.1-0.5 parts of light stabilizer.

[0032] Its preparation method includes the following steps:

[0033] S1. Add 15-25 parts of hydroxyl-containing acrylic functional monomer, 0.5-2 parts of acrylic functional monomer containing methyl and nitrogen atoms, 10-30 parts of acrylic hard monomer with a glass transition temperature higher than 130°C, 45-75 parts of acrylic soft monomer with a glass transition temperature lower than -30°C, and 0.01-0.1 parts of photoinitiator into the reaction kettle. Under stirring conditions, introduce nitrogen for 10-30 minutes;

[0034] S2. Irradiate the obtained mixture with a UVLED ultraviolet lamp for 2-10 minutes to obtain a prepolymer;

[0035] S3. Then add 0.01-0.1 parts of photoinitiator, 0.1-0.5 parts of multi-functional copolymer monomer, 0.1-0.5 parts of silane coupling agent, and 0.1-0.5 parts of light stabilizer, and mix evenly to obtain the OCA optical adhesive for bonding vehicle-mounted displays.

[0036] The present invention is obtained by using raw materials such as hydroxyl-containing acrylic functional monomers, methyl- and nitrogen atom-containing acrylic functional monomers, hard monomers, soft monomers, photoinitiators, multi-functional copolymer monomers, silane coupling agents, and light stabilizers through an ultraviolet synthesis process. It is mainly obtained through the copolymerization and synergistic reaction of two functional monomers, namely hydroxyl-containing acrylic functional monomers and methyl- and nitrogen atom-containing acrylic functional monomers.

[0037] Among them, in the ultraviolet synthesis process, a UVLED ultraviolet lamp is used to irradiate the monomer mixture with ultraviolet rays for a prepolymerization reaction to obtain a prepolymer with a target viscosity and molecular weight. After adding different additives to the prepolymer, it is cured to obtain a finished OCA optical adhesive. The conventional solvent method synthesis process consumes a large amount of organic solvents, harms the environment, has a poor uniformity of molecular weight distribution, cannot obtain finished products with ultra-high molecular weights, and the obtained finished OCA optical adhesive has poor compatibility with PMMA and PC and insufficient weather resistance. The ultraviolet synthesis process adopted by the present invention has the advantages of being solvent-free and 100% conversion of monomers. By adjusting the viscosity and molecular weight of the glue through prepolymerization, the obtained finished OCA optical adhesive has excellent bonding with PMMA and PC and has high resistance to weathering yellowing and the like.

[0038] Among them, the hydroxyl-containing acrylic functional monomer is one or a mixture of more of 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, hydroxybutyl methacrylate, and 4-hydroxybutyl acrylate. The hydroxyl (-OH) is an excellent hydrophilic group, which undergoes a hydrophilic reaction with water molecules in a high-humidity environment to maintain the optical transparency of the OCA optical adhesive and is not easily peeled off due to water molecule penetration. Considering the reaction characteristics, molecular structure, and molecular weight, the hydroxyl-containing acrylic functional monomer is preferably 2-hydroxyethyl acrylate in the present invention.

[0039] Among them, the methyl- and nitrogen atom-containing acrylic functional monomer is one or a mixture of more of methacrylamide, N-hydroxymethyl methacrylamide, and dimethylaminoethyl methacrylate. The acrylic functional monomer in which methyl and nitrogen atoms are combined not only has excellent cohesion of a single methyl monomer and excellent air exhaust of a nitrogen atom monomer, but also has excellent adhesion to PMMA and PC after combination, and has excellent compatibility with the deformation and aging of PMMA and PC caused by harsh environments. Considering the distribution mode of methyl and nitrogen atoms and the polymerization effect, the methyl- and nitrogen atom-containing acrylic functional monomer is preferably dimethylaminoethyl methacrylate in the present invention.

[0040] Among them, the acrylic hard monomer with a glass transition temperature higher than 130°C is one or a mixture of acrylamide, isobornyl methacrylate, N-vinylpyrrolidone, 4-acryloylmorpholine. Considering the synergistic enhancement effect with the above-mentioned acrylic functional monomers containing methyl and nitrogen atoms, the acrylic hard monomer N-vinylpyrrolidone with a nitrogen atom and a glass transition temperature as high as 175°C is preferably selected in the present invention.

[0041] Among them, the acrylic soft monomer with a glass transition temperature lower than -30°C is one or a mixture of 2-ethylhexyl acrylate, butyl acrylate, ethyl acrylate.

[0042] Among them, the photoinitiator is one or a mixture of 1-hydroxycyclohexyl phenyl ketone, 2,2-dimethoxy-2-phenylacetophenone, 2-methyl-2-hydroxypropyl phenyl ketone.

[0043] Among them, the multi-functional copolymer monomer is one or a mixture of 1,6-hexanediol diacrylate, ethoxylated trimethylolpropane triacrylate, trimethylolpropane triacrylate.

[0044] Among them, the silane coupling agent is one or a mixture of γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-aminopropyltrimethoxysilane.

[0045] Among them, the light stabilizer is one or a mixture of 2,6-di-tert-butyl-4-methylphenol, 4-hydroxymethyl-2,6-di-tert-butylphenol, tris(nonylphenyl) phosphite.

[0046] The above is the general concept of the present invention. The following provides detailed examples and comparative examples on this basis to further illustrate the present invention.

[0047] Example 1

[0048] Into a reaction kettle, 20% 2-hydroxyethyl acrylate containing hydroxyl groups (calculated based on the raw materials of the prepolymer as 100% by mass fraction, the same hereinafter), 0.5% dimethylaminoethyl methacrylate containing methyl groups, 20% N-vinylpyrrolidone hard monomer, 59.45% butyl acrylate soft monomer, and 0.05% 1-hydroxycyclohexyl phenyl ketone were added. Under stirring conditions, nitrogen was passed for 20 minutes, and the mixture was irradiated with ultraviolet rays using a UVLED ultraviolet lamp for 5 minutes to effectively locally polymerize and obtain a prepolymer with a viscosity of about 5000 mPa·s; then, based on this prepolymer, 0.05% of 2,2-dimethoxy-2-phenylacetophenone (i.e., 0.05% of the mass of the prepolymer, similar hereinafter), 0.25% of 1,6-hexanediol diacrylate, 0.25% of γ-glycidoxypropyltrimethoxysilane, and 0.25% of 2,6-di-tert-butyl-4-methylphenol were added. After mixing evenly, the OCA optical adhesive for bonding vehicle-mounted displays was obtained.

[0049] Example 2

[0050] Into a reaction kettle, 20% 2-hydroxyethyl acrylate, 1.0% dimethylaminoethyl methacrylate, 20% N-vinylpyrrolidone, 58.95% butyl acrylate, and 0.05% 1-hydroxycyclohexyl phenyl ketone were added in terms of mass fraction. Under stirring conditions, nitrogen was passed for 20 minutes, and the mixture was irradiated with ultraviolet rays using a UVLED ultraviolet lamp for several minutes to effectively locally polymerize and obtain a prepolymer with a viscosity of about 5000 mPa·s; then, based on this prepolymer, 0.05% of 2,2-dimethoxy-2-phenylacetophenone, 0.25% of 1,6-hexanediol diacrylate, 0.25% of γ-glycidoxypropyltrimethoxysilane, and 0.25% of 2,6-di-tert-butyl-4-methylphenol were added. After mixing evenly, the OCA optical adhesive for bonding vehicle-mounted displays was obtained.

[0051] Example 3

[0052] Into a reaction kettle, 20% 2-hydroxyethyl acrylate, 2.0% dimethylaminoethyl methacrylate, 20% N-vinylpyrrolidone, 57.95% butyl acrylate, and 0.05% 1-hydroxycyclohexyl phenyl ketone were added in terms of mass fraction. Under stirring conditions, nitrogen was passed for 20 minutes, and the mixture was irradiated with ultraviolet rays using a UVLED ultraviolet lamp for several minutes to effectively locally polymerize and obtain a prepolymer with a viscosity of about 5000 mPa·s; then, based on this prepolymer, 0.05% of 2,2-dimethoxy-2-phenylacetophenone, 0.25% of 1,6-hexanediol diacrylate, 0.25% of γ-glycidoxypropyltrimethoxysilane, and 0.25% of 2,6-di-tert-butyl-4-methylphenol were added. After mixing evenly, the OCA optical adhesive for bonding vehicle-mounted displays was obtained.

[0053] Example 4

[0054] Charge 20% 2-hydroxyethyl acrylate, 1.0% dimethylaminoethyl methacrylate, 10% N-vinylpyrrolidone, 68.95% butyl acrylate, and 0.05% 1-hydroxycyclohexyl phenyl ketone by mass fraction into a reaction kettle. Under stirring conditions, purge with nitrogen for 20 minutes, and irradiate the mixture with ultraviolet rays from a UVLED ultraviolet lamp for several minutes to effectively locally polymerize and obtain a prepolymer with a viscosity of about 5000 mPa·s. Then, based on this prepolymer, add 0.05% 2,2-dimethoxy-2-phenylacetophenone, 0.25% 1,6-hexanediol diacrylate, 0.25% γ-glycidoxypropyltrimethoxysilane, and 0.25% 2,6-di-tert-butyl-4-methylphenol. After mixing evenly, the OCA optical adhesive for bonding vehicle-mounted displays is obtained.

[0055] Comparative Example 1

[0056] Charge 20% 2-hydroxyethyl acrylate, 20% N-vinylpyrrolidone, 59.95% butyl acrylate, and 0.05% 1-hydroxycyclohexyl phenyl ketone by mass fraction into a reaction kettle. Under stirring conditions, purge with nitrogen for 20 minutes, and irradiate the mixture with ultraviolet rays from a UVLED ultraviolet lamp for several minutes to effectively locally polymerize and obtain a prepolymer with a viscosity of about 5000 mPa·s. Then, based on this prepolymer, add 0.05% 2,2-dimethoxy-2-phenylacetophenone, 0.25% 1,6-hexanediol diacrylate, 0.25% γ-glycidoxypropyltrimethoxysilane, and 0.25% 2,6-di-tert-butyl-4-methylphenol. After mixing evenly, the OCA optical adhesive for bonding vehicle-mounted displays is obtained.

[0057] Comparative Example 2

[0058] Charge 20% 2-hydroxyethyl acrylate, 3.0% dimethylaminoethyl methacrylate, 20% N-vinylpyrrolidone, 56.95% butyl acrylate, and 0.05% 1-hydroxycyclohexyl phenyl ketone by mass fraction into a reaction kettle. Under stirring conditions, purge with nitrogen for 20 minutes, and irradiate the mixture with ultraviolet rays from a UVLED ultraviolet lamp for several minutes to effectively locally polymerize and obtain a prepolymer with a viscosity of about 5000 mPa·s. Then, based on this prepolymer, add 0.05% 2,2-dimethoxy-2-phenylacetophenone, 0.25% 1,6-hexanediol diacrylate, 0.25% γ-glycidoxypropyltrimethoxysilane, and 0.25% 2,6-di-tert-butyl-4-methylphenol. After mixing evenly, the OCA optical adhesive for bonding vehicle-mounted displays is obtained.

[0059] Comparative Example 3

[0060] Into a reaction kettle, 10% 2-hydroxyethyl acrylate, 1.0% dimethylaminoethyl methacrylate, 20% N-vinylpyrrolidone, 68.95% butyl acrylate, and 0.05% 1-hydroxycyclohexyl phenyl ketone were added by mass fraction. Under stirring conditions, nitrogen was passed for 20 minutes, and the mixture was irradiated with ultraviolet rays using a UV LED ultraviolet lamp for several minutes to effectively locally polymerize and obtain a prepolymer with a viscosity of about 5000 mPa·s; then, based on this prepolymer, 0.05% 2,2-dimethoxy-2-phenylacetophenone, 0.25% 1,6-hexanediol diacrylate, 0.25% γ-glycidoxypropyltrimethoxysilane, and 0.25% 2,6-di-tert-butyl-4-methylphenol were added. After mixing evenly, the OCA optical adhesive for bonding vehicle-mounted displays was obtained.

[0061] Comparative Example 4

[0062] Into a reaction kettle, 30% 2-hydroxyethyl acrylate, 1.0% dimethylaminoethyl methacrylate, 20% N-vinylpyrrolidone, 48.95% butyl acrylate, and 0.05% 1-hydroxycyclohexyl phenyl ketone were added by mass fraction. Under stirring conditions, nitrogen was passed for 20 minutes, and the mixture was irradiated with ultraviolet rays using a UV LED ultraviolet lamp for several minutes to effectively locally polymerize and obtain a prepolymer with a viscosity of about 5000 mPa·s; then, based on this prepolymer, 0.05% 2,2-dimethoxy-2-phenylacetophenone, 0.25% 1,6-hexanediol diacrylate, 0.25% γ-glycidoxypropyltrimethoxysilane, and 0.25% 2,6-di-tert-butyl-4-methylphenol were added. After mixing evenly, the OCA optical adhesive for bonding vehicle-mounted displays was obtained.

[0063] Comparative Example 5

[0064] Into a reaction kettle, 20% 2-hydroxyethyl acrylate, 1.0% dimethylaminoethyl methacrylate, 5% N-vinylpyrrolidone, 73.95% butyl acrylate, and 0.05% 1-hydroxycyclohexyl phenyl ketone were added by mass fraction. Under stirring conditions, nitrogen was passed for 20 minutes, and the mixture was irradiated with ultraviolet rays using a UV LED ultraviolet lamp for several minutes to effectively locally polymerize and obtain a prepolymer with a viscosity of about 5000 mPa·s; then, based on this prepolymer, 0.05% 2,2-dimethoxy-2-phenylacetophenone, 0.25% 1,6-hexanediol diacrylate, 0.25% γ-glycidoxypropyltrimethoxysilane, and 0.25% 2,6-di-tert-butyl-4-methylphenol were added. After mixing evenly, the OCA optical adhesive for bonding vehicle-mounted displays was obtained.

[0065] Comparative Example 6

[0066] Into a reaction kettle, put 20% 2-hydroxyethyl acrylate, 1.0% dimethylaminoethyl methacrylate, 30% N-vinylpyrrolidone, 48.95% butyl acrylate, and 0.05% 1-hydroxycyclohexyl phenyl ketone by mass fraction. Under stirring conditions, pass nitrogen for 20 minutes, and irradiate the mixture with UV LED ultraviolet light for several minutes to effectively polymerize locally and obtain a prepolymer with a viscosity of about 5000 mPa·s; then, based on this prepolymer, add 0.05% 2,2-dimethoxy-2-phenylacetophenone, 0.25% 1,6-hexanediol diacrylate, 0.25% γ-glycidoxypropyltrimethoxysilane, and 0.25% 2,6-di-tert-butyl-4-methylphenol. After mixing evenly, the OCA optical adhesive for bonding vehicle-mounted displays is obtained.

[0067] Performance Test and Analysis

[0068] The OCA optical adhesives obtained in Examples 1-4 and Comparative Examples 1-6 of the present invention were respectively coated on a 100 μm polyester film (release film) using a doctor blade coater to form a coating with a thickness of 250 μm, and then covered with a 50 μm polyester film (release film) to remove oxygen. The polyester film with the coating was irradiated with UV LED ultraviolet light (3 mW / cm) for 300 seconds to obtain an OCA sheet for bonding vehicle-mounted displays, and the following tests were carried out. Test method:

[0069] Adhesion Test

[0070] Uncover one side of the polyester film (release film) of the OCA sheets in Examples 1-4 and Comparative Examples 1-6, stick it on a 0.05 MM transparent PET film, cut it into samples with a width of 25.4 mm and a length of 300 mm, uncover the other side of the polyester film (release film), and roll and stick it on a SUS 304 steel plate at a speed of 600 MM / MIN with a 2KG roller, and let it stand for 20 min. Use a tensile testing machine to test its 180° peel adhesion, and the specific test method refers to the ASMTD3330 international standard.

[0071] Bubble and Peel Test

[0072] An OCA sheet of Examples 1-4 and Comparative Examples 1-6 was bonded between a polycarbonate (PC) film and ITO respectively to form a lamination module, which was placed in a high-pressure defoaming machine (50 °C, 0.5 MPa) for 15 minutes, and then all were put into a high-temperature oven set at 105 °C or a environmental test chamber set at 85 °C and 85% relative humidity (RH) for accelerated aging test. After 1000 hours, the lamination module was taken out and cooled to room temperature, and visually observed whether there was any bubbling or peeling in the lamination module. Among them, no bubbling was observed and evaluated as A, slight bubbling was observed and evaluated as B, obvious bubbling was observed and evaluated as C, and peeling phenomenon was observed and evaluated as D;

[0073] UV aging test

[0074] An OCA sheet of Examples 1-4 and Comparative Examples 1-6 was bonded between a polycarbonate (PC) film and ITO respectively to form a lamination module, which was placed in a high-pressure defoaming machine (50 °C, 0.5 MPa) for 15 minutes, and then all were put into a UV environmental test chamber set at QUV: 340 nm, 0.55 w / m2, temperature: 60 °C, relative humidity (RH) < 35% for UV aging test. After 1000 hours, the lamination module was taken out and cooled to room temperature, and visually observed whether there was any bubbling or peeling in the lamination module. Among them, no bubbling was observed and evaluated as A, slight bubbling was observed and evaluated as B, obvious bubbling was observed and evaluated as C, and peeling phenomenon was observed and evaluated as D;

[0075] Transmittance test

[0076] The OCA sheets of Examples 1-4 and Comparative Examples 1-6 were put into a environmental test chamber set at 85 °C and 85% relative humidity (RH) for accelerated aging test. After 1000 hours, the OCA sheets were cooled to room temperature within 5 minutes, and the transmittance and haze were tested using a transmittance tester. The transmittance and haze values of the OCA sheets were measured before and after the aging test respectively. After the accelerated aging test, the OCA of the present invention has a transmittance greater than 90% and a haze value less than 1%.

[0077] Viscoelastic properties

[0078] The viscoelastic properties of the OCA sheets of Examples 1-4 and Comparative Examples 1-6 were tested using an ARES dynamic viscoelastic measurement device (rheometer). Samples with a diameter of 8 mm were punched out by preparing OCA sheets with a thickness of 1 mm. Using the measurement conditions of 1 Hz, a temperature range of -40 °C to 120 °C, and a temperature increase rate of 3 °C / min, the storage modulus (G') of the samples was recorded at 80 °C.

[0079] The test results are shown in Table 1 below:

[0080] Table 1

[0081]

[0082]

[0083] Through the performance data analysis of Examples 1-4 and Comparative Examples 1-6, the OCA optical adhesive obtained by the co-reaction of two functional monomers, 2-hydroxyethyl acrylate (hydroxyl-containing acrylic functional monomer) and dimethylaminoethyl methacrylate (methyl- and nitrogen atom-containing acrylic functional monomer), has more excellent data indicators and weather resistance. The simultaneous participation of N-vinylpyrrolidone (nitrogen atom-containing, Tg: 175 °C acrylic hard monomer) in the polymerization reaction has a synergistic enhancement effect, which can further enhance the performance of the OCA optical adhesive.

[0084] When the mass ratios of other materials are constant:

[0085] The applicable amount of 2-hydroxyethyl acrylate (hydroxyl-containing acrylic functional monomer) is 15-25%. When the amount is 10%, although the OCA optical adhesive obtained has good performance in adhesion test and transmittance test, its viscoelastic properties such as storage modulus (G') at 80 °C, bubble and peel tests, and UV aging test do not meet the standards, and the weather resistance is poor. When the amount is 30%, the OCA optical adhesive obtained fails to meet the standards in all test performances, and the weather resistance is poor.

[0086] The applicable amount of dimethylaminoethyl methacrylate (methyl- and nitrogen atom-containing acrylic functional monomer) is 15-25%. When the amount is 0, the viscoelastic properties such as storage modulus (G') at 80 °C, bubble and peel tests, and UV aging test of the OCA optical adhesive obtained do not meet the standards, and the weather resistance is poor. When the amount is 3%, although the viscoelastic properties such as storage modulus (G') at 80 °C, adhesion test, bubble and peel tests, and UV aging test of the OCA optical adhesive obtained are all good, its optical performance is extremely poor, and the transmittance test fails to meet the standards.

[0087] The applicable amount of N-vinylpyrrolidone (nitrogen atom-containing, Tg: 175 °C acrylic hard monomer) is 10-25%. When the amount is 5, although the OCA optical adhesive obtained has good performance in transmittance test, its adhesion test, viscoelastic properties such as storage modulus (G') at 80 °C, bubble and peel tests, and UV aging test do not meet the standards, and the weather resistance is poor. When the amount is 30%, although the OCA optical adhesive obtained has good performance in transmittance test and viscoelastic properties such as storage modulus (G') at 80 °C, its bubble and peel tests and UV aging test performances do not meet the standards.

[0088] Through the above comparative analysis of data, when the preferred amounts of 2-hydroxyethyl acrylate is 20%, dimethylaminoethyl methacrylate is 1%, and N-vinylpyrrolidone is 20%, its viscoelastic properties such as storage modulus (G') at 80 °C, adhesion test, blistering and peeling test, UV aging test, and optical properties all reach relatively good levels, making it a preferred formulation. The OCA optical adhesive obtained in the present invention, as an OCA optical adhesive for bonding vehicle-mounted displays, can fully meet its performance requirements and ensure the use effect in an environment of ultraviolet rays, temperature, and humidity for a long time.

[0089] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and embodiments. It can be fully applied to various fields suitable for the present invention. For those familiar with the field, additional modifications can be easily made. Therefore, without departing from the general concept defined by the claims and the equivalent scope, the present invention is not limited to specific details.

Claims

1. An OCA optical adhesive for bonding a vehicle-mounted display screen, characterized in that It is prepared by any one of the following methods: Method 1: Based on 100% of the raw materials of the prepolymer, 20% 2-hydroxyethyl acrylate, 0.5% dimethylaminoethyl methacrylate, 20% N-vinylpyrrolidone hard monomer, 59.45% butyl acrylate soft monomer, and 0.05% 1-hydroxycyclohexyl phenyl ketone are added to the reaction kettle by mass fraction. Under stirring conditions, nitrogen is passed for 20 minutes, and the mixture is irradiated with ultraviolet rays using a UVLED ultraviolet lamp for 5 minutes to effectively locally polymerize and obtain a prepolymer with a viscosity of 5000 mPa·s; Then, based on this prepolymer, 0.05% 2,2-dimethoxy-2-phenylacetophenone, 0.25% 1,6-hexanediol diacrylate, 0.25% γ-glycidoxypropyltrimethoxysilane, and 0.25% 2,6-di-tert-butyl-4-methylphenol are added by mass fraction. After mixing evenly, the OCA optical adhesive for bonding vehicle-mounted displays is obtained; Method 2: Based on 100% of the raw materials of the prepolymer, 20% 2-hydroxyethyl acrylate, 1.0% dimethylaminoethyl methacrylate, 20% N-vinylpyrrolidone, 58.95% butyl acrylate, and 0.05% 1-hydroxycyclohexyl phenyl ketone are added to the reaction kettle by mass fraction. Under stirring conditions, nitrogen is passed for 20 minutes, and the mixture is irradiated with ultraviolet rays using a UVLED ultraviolet lamp for several minutes to effectively locally polymerize and obtain a prepolymer with a viscosity of 5000 mPa·s; Then, based on this prepolymer, 0.05% 2,2-dimethoxy-2-phenylacetophenone, 0.25% 1,6-hexanediol diacrylate, 0.25% γ-glycidoxypropyltrimethoxysilane, and 0.25% 2,6-di-tert-butyl-4-methylphenol are added by mass fraction. After mixing evenly, the OCA optical adhesive for bonding vehicle-mounted displays is obtained; Method 3: Based on 100% of the raw materials of the prepolymer, 20% 2-hydroxyethyl acrylate, 2.0% dimethylaminoethyl methacrylate, 20% N-vinylpyrrolidone, 57.95% butyl acrylate, and 0.05% 1-hydroxycyclohexyl phenyl ketone are added to the reaction kettle by mass fraction. Under stirring conditions, nitrogen is passed for 20 minutes, and the mixture is irradiated with ultraviolet rays using a UVLED ultraviolet lamp for several minutes to effectively locally polymerize and obtain a prepolymer with a viscosity of 5000 mPa·s; Then, based on this prepolymer, 0.05% 2,2-dimethoxy-2-phenylacetophenone, 0.25% 1,6-hexanediol diacrylate, 0.25% γ-glycidoxypropyltrimethoxysilane, and 0.25% 2,6-di-tert-butyl-4-methylphenol are added by mass fraction. After mixing evenly, the OCA optical adhesive for bonding vehicle-mounted displays is obtained.

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