Reworkable folding screen protective film and preparation method thereof

Abstract

The invention discloses a foldable screen protective film capable of being reworked and a preparation method thereof, the protective film comprises an HC layer, a silica gel layer, an optical adhesive layer and an isolation layer, and the optical adhesive layer is obtained by coating optical adhesive and then curing. The optical adhesive comprises the following raw material components in parts by weight: 60-90 parts of alkyl (meth) acrylate, 5-25 parts of a polar monomer A, 1-10 parts of tackifying resin, 0.02-2 parts of a photoinitiator and 0.01-1 part of a curing agent. The prepared protective film has reliable bending resistance and good reworkability, the peel strength of the protective film is improved through the (methyl) acrylate tackifying resin added into the optical adhesive layer, and the reliable bending resistance of the protective film is guaranteed. The polar monomer A containing ether bonds can increase intermolecular acting force, improve creep recovery performance and reduce sacrifice of chemical crosslinking to peel strength, meanwhile, a plurality of hydrophilic groups enable the protective film to be easily peeled off when ethanol is wiped, and the protective film is endowed with good reworkability.

Description

Technical Field

[0001] The present invention relates to the field of adhesive materials, and in particular to a reworkable folding screen protective film and a preparation method thereof. Background Art

[0002] Foldable phone screens are more susceptible to damage when bent and used, leading to high repair costs. Therefore, foldable screen protective films play a crucial role in this new form factor of electronic products. Foldable screen protective films must not only offer reliable bending resistance but also be easily peeled off and replaced when damaged, requiring excellent reworkability. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a reworkable folding screen protective film and a preparation method thereof in view of the deficiencies in the above-mentioned prior art.

[0004] To solve the above technical problems, the technical solution adopted by the present invention is: a reworkable folding screen protective film, characterized in that it includes an HC layer, a silicone layer, an optical adhesive layer, and an isolation layer stacked in sequence, the optical adhesive layer being obtained by coating an optical adhesive and then curing it, and the optical adhesive includes the following raw material components in parts by weight: 60-90 parts of (meth)acrylate alkyl ester, 5-25 parts of polar monomer A, 1-10 parts of tackifying resin, 0.02-2 parts of photoinitiator and 0.01-1 part of curing agent.

[0005] Preferably, the alkyl (meth)acrylate is one or more of methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, heptyl (meth)acrylate, isobornyl (meth)acrylate, isooctyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate or octadecyl (meth)acrylate.

[0006] Preferably, the polar monomer A is one or more of a hydroxyl-containing monomer and an ether bond-containing monomer.

[0007] Preferably, the hydroxyl-containing monomer is hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate or triethylene glycol monoacrylate;

[0008] The monomer containing an ether bond is methoxyethyl acrylate, glycidyl methacrylate, ethoxyethoxyethyl acrylate, triethylene glycol monoacrylate, methoxydiethylene glycol acrylate or methoxytriethylene glycol acrylate.

[0009] Preferably, the tackifying resin is one or more of (meth)acrylate tackifying resin, epoxy resin, polyurethane resin, and rosin resin.

[0010] Preferably, the raw materials for preparing the (meth)acrylate tackifying resin include, by weight, 70-90 parts of alkyl (meth)acrylate, 5-15 parts of polar monomer B, 0.5-5 parts of chain transfer agent, and 0.1-1 part of photoinitiator.

[0011] Preferably, the polar monomer B is one or more of a carboxyl group-containing monomer and a nitrogen atom-containing monomer.

[0012] The carboxyl-containing monomer is acrylic acid or carboxyethyl acrylate;

[0013] The monomer containing nitrogen atoms is (meth)acrylamide, diethylaminoethyl (meth)acrylate, N-vinylpyridine, N-vinylimidazole, N-vinylmorpholine or N-vinylpyrrolidone.

[0014] Preferably, the chain transfer agent is trimethylolpropane tris(3-mercaptopropionate).

[0015] Preferably, the photoinitiator is 2,4,6 (trimethylbenzoyl) diphenylphosphine oxide, 2,4,6 (trimethylbenzoyl) ethyl phosphonate, 1-hydroxy-cyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone or 2,2-dimethoxy-2-phenylethanone.

[0016] Preferably, the curing agent is 1,6-hexanediol diacrylate, polyethylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate or dipentaerythritol hexaacrylate.

[0017] The present invention also provides a method for preparing the reworkable folding screen protective film as described above, characterized in that it comprises the following steps:

[0018] S1. Preparation of (meth)acrylate prepolymer:

[0019] First, according to parts by weight, 60-90 parts of alkyl (meth)acrylate, 5-25 parts of polar monomer A, and 0.01-1 parts of photoinitiator are mixed in a reaction kettle, and then stirring is started and nitrogen is introduced for 15-60 minutes, and then irradiated with ultraviolet light to react to obtain a (meth)acrylate prepolymer;

[0020] S2, preparation of (meth)acrylate tackifying resin:

[0021] According to parts by weight, 70-90 parts of alkyl (meth)acrylate, 5-15 parts of polar monomer B, 0.5-5 parts of chain transfer agent, and 0.1-1 parts of photoinitiator are first mixed in a reaction kettle, and then stirring is started and nitrogen is introduced for 15-60 minutes, and then irradiated with ultraviolet light to react to obtain a (meth)acrylate tackifying resin;

[0022] S3. Preparation of optical adhesive layer:

[0023] To 100 parts of a (meth)acrylate prepolymer, 1-10 parts of a (meth)acrylate tackifying resin, 0.01-1 parts of a photoinitiator, and 0.01-1 parts of a curing agent were added, in parts by weight, and the mixture was stirred evenly to obtain an optical adhesive. The optical adhesive was then coated on a release film, and the release film was laminated to the adhesive surface, and the mixture was cured under 365 nm ultraviolet light to obtain an optical adhesive layer.

[0024] S4. Preparation of protective film:

[0025] The release film on one side of the optical adhesive layer is torn off, the adhesive surface is plasma-treated and then laminated with the silicone layer. The release film retained on the other side of the optical adhesive layer forms an isolation layer. Then, the other side of the silicone layer is laminated with the plasma-treated HC layer to obtain a reworkable folding screen protective film that includes, in sequence, an HC layer, a silicone layer, an optical adhesive layer, and an isolation layer.

[0026] The beneficial effects of the present invention are:

[0027] The present invention provides a reworkable folding screen protective film and a preparation method thereof. The protective film prepared by the present invention has reliable bending resistance and good reworkability, and can be widely used in screen protection of folding screen mobile phones;

[0028] In some preferred embodiments, the (meth)acrylate tackifying resin added to the optical adhesive layer of the present invention enhances its peel strength and ensures reliable flexural resistance. The polar monomer A containing ether bonds not only increases intermolecular forces, improves creep recovery, and reduces the sacrifice in peel strength caused by chemical crosslinking, but also has multiple hydrophilic groups that facilitate peeling of the protective film when wiped with ethanol, imparting good reworkability. DETAILED DESCRIPTION

[0029] The present invention is further described in detail below with reference to the embodiments so that those skilled in the art can implement the invention with reference to the description.

[0030] It should be understood that terms such as “having”, “including” and “comprising” used herein do not preclude the existence or addition of one or more other elements or combinations thereof.

[0031] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Materials and reagents used in the following examples are commercially available unless otherwise specified. In the following examples, where specific conditions are not specified, the experiments were conducted under conventional conditions or those recommended by the manufacturer. Reagents and instruments used, where the manufacturer is not specified, are commercially available conventional products.

[0032] The present invention provides a reworkable folding screen protective film, comprising an HC layer, a silicone layer, an optical adhesive layer, and an isolation layer stacked in sequence. The optical adhesive layer is obtained by coating an optical adhesive and then curing the optical adhesive. The optical adhesive comprises the following raw material components in parts by weight: 60-90 parts of (meth)acrylate, 5-25 parts of polar monomer A, 1-10 parts of tackifying resin, 0.02-2 parts of photoinitiator, and 0.01-1 parts of curing agent.

[0033] In a preferred embodiment, the alkyl (meth)acrylate is one or more of methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, heptyl (meth)acrylate, isobornyl (meth)acrylate, isooctyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate or octadecyl (meth)acrylate.

[0034] In a preferred embodiment, the polar monomer A is one or more of a hydroxyl-containing monomer and an ether-containing monomer. Choosing hydroxyl-containing and ether-containing monomers can result in a lower low-temperature modulus (<150 kPa at -20°C) for the optical adhesive, reducing the risk of fracture of the HC layer of the protective film and extending the life of the protective film.

[0035] In a preferred embodiment, the hydroxyl-containing monomer is hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate or triethylene glycol monoacrylate.

[0036] In a preferred embodiment, the ether bond-containing monomer is methoxyethyl acrylate, glycidyl methacrylate, ethoxyethoxyethyl acrylate, triethylene glycol monoacrylate, methoxydiethylene glycol acrylate or methoxytriethylene glycol acrylate.

[0037] In a preferred embodiment, the tackifying resin is one or more of (meth)acrylate tackifying resin, epoxy resin, polyurethane resin, and rosin resin.

[0038] In a preferred embodiment, the raw materials for preparing the (meth)acrylate tackifying resin include, by weight, 70-90 parts of alkyl (meth)acrylate, 5-15 parts of polar monomer B, 0.5-5 parts of chain transfer agent, and 0.1-1 part of photoinitiator.

[0039] In a preferred embodiment, polar monomer B is one or more of a carboxyl-containing monomer and a nitrogen-containing monomer. Polar monomer B contains polar groups such as carboxyl and nitrogen atoms, which form strong intermolecular hydrogen bonds with the hydroxyl groups and ether bonds in polar monomer A. This allows the tackifying resin to be evenly dispersed in the prepolymer, providing good compatibility and preventing phase separation during use of the optical adhesive, thereby improving the wettability and bonding performance of the optical adhesive.

[0040] In a preferred embodiment, the carboxyl group-containing monomer is acrylic acid or carboxyethyl acrylate.

[0041] In a preferred embodiment, the monomer containing a nitrogen atom is (meth)acrylamide, diethylaminoethyl (meth)acrylate, N-vinylpyridine, N-vinylimidazole, N-vinylmorpholine or N-vinylpyrrolidone.

[0042] In a preferred embodiment, the chain transfer agent is trimethylolpropane tris(3-mercaptopropionate).

[0043] In a preferred embodiment, the photoinitiator is 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2,4,6-trimethylbenzoyl)ethylphosphonate, 1-hydroxy-cyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone or 2,2-dimethoxy-2-phenylethanone.

[0044] In a preferred embodiment, the curing agent is 1,6-hexanediol diacrylate, polyethylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate or dipentaerythritol hexaacrylate.

[0045] The present invention also provides a method for preparing the above reworkable folding screen protective film, comprising the following steps:

[0046] S1. Preparation of (meth)acrylate prepolymer:

[0047] First, 60-90 parts by weight of alkyl (meth)acrylate, 5-25 parts of polar monomer A, and 0.01-1 part of photoinitiator are mixed in a reaction kettle, and then stirring is started and nitrogen is introduced for 15-60 minutes, and then irradiated with ultraviolet light to react to obtain a (meth)acrylate prepolymer;

[0048] S2, preparation of (meth)acrylate tackifying resin:

[0049] According to parts by weight, 70-90 parts of alkyl (meth)acrylate, 5-15 parts of polar monomer B, 0.5-5 parts of chain transfer agent, and 0.1-1 parts of photoinitiator are first mixed in a reaction kettle, and then stirring is started and nitrogen is introduced for 15-60 minutes, and then irradiated with ultraviolet light to react to obtain a (meth)acrylate tackifying resin;

[0050] S3. Preparation of optical adhesive layer:

[0051] To 100 parts of a (meth)acrylate prepolymer, 1-10 parts of a (meth)acrylate tackifying resin, 0.01-1 parts of a photoinitiator, and 0.01-1 parts of a curing agent were added, in parts by weight, and the mixture was stirred evenly to obtain an optical adhesive. The optical adhesive was then coated on a release film, and the release film was laminated to the adhesive surface, and the mixture was cured under 365 nm ultraviolet light to obtain an optical adhesive layer.

[0052] S4. Preparation of protective film:

[0053] The release film on one side of the optical adhesive layer is torn off, the adhesive surface is plasma-treated and then laminated with the silicone layer. The release film retained on the other side of the optical adhesive layer forms an isolation layer. Then, the other side of the silicone layer is laminated with the plasma-treated HC layer to obtain a reworkable folding screen protective film that includes, in sequence, an HC layer, a silicone layer, an optical adhesive layer, and an isolation layer.

[0054] In a preferred embodiment, the thickness of the optical adhesive layer is 15-70 μm, more preferably 35 μm.

[0055] In a preferred embodiment, the thickness of the silica gel layer is 10-50 μm, more preferably 25 μm.

[0056] In a preferred embodiment, the thickness of the HC layer is 25-100 μm, more preferably 50 μm.

[0057] In the optical adhesive layer of the present invention, the (meth)acrylate tackifying resin ensures its reliable bending resistance, and the multiple hydrophilic groups of the polar monomer A containing ether bonds make it easy to peel off the protective film when wiping with ethanol, thus giving it good reworkability.

[0058] The above is the overall concept of the present invention. Detailed embodiments and comparative examples are provided below to further illustrate the present invention.

[0059] Example 1

[0060] S1. Preparation of (meth)acrylate prepolymer:

[0061] According to weight parts, 80 parts of 2-ethylhexyl acrylate, 15 parts of methoxytriethylene glycol acrylate, 5 parts of hydroxybutyl acrylate, and 0.05 parts of 1-hydroxy-cyclohexylphenyl ketone were mixed in a reactor, and then stirred and nitrogen was introduced for 30 minutes. Then, ultraviolet light was used to irradiate the reaction, and the total irradiation energy was controlled to 3000mJ / cm 2 , obtaining a (meth)acrylate prepolymer;

[0062] S2, preparation of (meth)acrylate tackifying resin:

[0063] According to weight parts, 49 parts of 2-ethylhexyl acrylate, 40 parts of butyl methacrylate, 10 parts of N-vinyl pyrrolidone, 1 part of trimethylolpropane tris(3-mercaptopropionate), and 0.5 parts of 1-hydroxy-cyclohexylphenyl ketone were mixed in a reactor, and then stirred and nitrogen was introduced for 30 minutes. Then, the reaction was irradiated with an ultraviolet lamp, and the total irradiation energy was controlled to 5000mJ / cm 2 , to obtain a (meth)acrylate tackifying resin;

[0064] S3. Preparation of optical adhesive layer:

[0065] According to parts by weight, 5 parts of (meth)acrylate tackifying resin, 0.1 parts of 2,2-dimethoxy-2-phenyl acetone, and 0.05 parts of 1,6-hexanediol diacrylate were added to 100 parts of (meth)acrylate prepolymer, and the mixture was stirred thoroughly to obtain an optical adhesive. The optical adhesive was then coated on a release film, and the release film was attached to the adhesive surface. The adhesive was cured under 365nm ultraviolet light, and the total irradiation energy was controlled to be 10000mJ / cm 2 , obtaining an optical adhesive layer with a thickness of 35 μm;

[0066] S4. Preparation of protective film:

[0067] The isolation film on one side of the 35μm optical adhesive layer and the 25μm silicone layer was torn off, and the adhesive surface was plasma treated before the optical adhesive layer and the silicone layer were laminated. The release film retained on the other side of the optical adhesive layer formed an isolation layer. Then, the isolation film on the other side of the silicone layer was torn off, and the silicone layer and the back substrate of the 50μm HC layer were plasma treated and then laminated to obtain a protective film including the HC layer, the silicone layer, the optical adhesive layer, and the isolation layer in sequence.

[0068] Among them, the release film, the silicone layer and the HC layer are all conventional products, and those skilled in the art will know that they are not limited in the present invention, and the same shall apply hereinafter.

[0069] Example 2

[0070] S1. Preparation of (meth)acrylate prepolymer:

[0071] According to weight parts, 75 parts of 2-ethylhexyl acrylate, 20 parts of ethoxyethoxyethyl acrylate, 5 parts of hydroxybutyl acrylate, and 0.05 parts of 1-hydroxy-cyclohexylphenyl ketone were mixed in a reactor, and then stirred and nitrogen was introduced for 30 minutes. Then, ultraviolet light was used to irradiate the reaction, and the total irradiation energy was controlled to 3000mJ / cm 2 , obtaining a (meth)acrylate prepolymer;

[0072] S2, preparation of (meth)acrylate tackifying resin:

[0073] According to weight parts, 49 parts of 2-ethylhexyl acrylate, 40 parts of butyl methacrylate, 10 parts of N-vinyl pyrrolidone, 1 part of trimethylolpropane tris(3-mercaptopropionate), and 0.5 parts of 1-hydroxy-cyclohexylphenyl ketone were mixed in a reactor, and then stirred and nitrogen was introduced for 30 minutes. Then, the reaction was irradiated with an ultraviolet lamp, and the total irradiation energy was controlled to 5000mJ / cm 2 , obtaining a (meth)acrylate tackifying resin;

[0074] S3. Preparation of optical adhesive layer

[0075] According to parts by weight, 5 parts of (meth)acrylate tackifying resin, 0.1 parts of 2,2-dimethoxy-2-phenyl acetone, and 0.05 parts of 1,6-hexanediol diacrylate were added to 100 parts of (meth)acrylate prepolymer, and the mixture was stirred thoroughly to obtain an optical adhesive. The optical adhesive was then coated on a release film, and the release film was attached to the adhesive surface. The adhesive was cured under 365nm ultraviolet light, and the total irradiation energy was controlled to be 10000mJ / cm 2 , obtaining an optical adhesive layer with a thickness of 35 μm;

[0076] S4. Preparation of protective film:

[0077] The isolation film on one side of the 35μm optical adhesive layer and the 25μm silicone layer was torn off, and the adhesive surface was plasma treated before the optical adhesive layer and the silicone layer were laminated. The release film retained on the other side of the optical adhesive layer formed an isolation layer. Then, the isolation film on the other side of the silicone layer was torn off, and the silicone layer and the back substrate of the 50μm HC layer were plasma treated and then laminated to obtain a protective film including the HC layer, the silicone layer, the optical adhesive layer, and the isolation layer in sequence.

[0078] Example 3

[0079] S1. Preparation of (meth)acrylate prepolymer:

[0080] According to weight parts, 60 parts of 2-ethylhexyl acrylate, 15 parts of lauryl acrylate, 15 parts of ethoxyethoxyethyl acrylate, 10 parts of hydroxybutyl acrylate, and 0.05 parts of 1-hydroxy-cyclohexylphenyl ketone were mixed in a reactor, and then stirred and nitrogen was introduced for 30 minutes. Then, ultraviolet light was used to irradiate the reaction, and the total irradiation energy was controlled to 3000mJ / cm 2 , obtaining a (meth)acrylate prepolymer;

[0081] S2, preparation of (meth)acrylate tackifying resin:

[0082] According to weight parts, 49 parts of 2-ethylhexyl acrylate, 40 parts of butyl methacrylate, 10 parts of N-vinyl pyrrolidone, 1 part of trimethylolpropane tris(3-mercaptopropionate), and 0.5 parts of 1-hydroxy-cyclohexylphenyl ketone were mixed in a reactor, and then stirred and nitrogen was introduced for 30 minutes. Then, the reaction was irradiated with an ultraviolet lamp, and the total irradiation energy was controlled to 5000mJ / cm 2 , to obtain a (meth)acrylate tackifying resin;

[0083] S3. Preparation of optical adhesive layer

[0084] According to parts by weight, 5 parts of (meth)acrylate tackifying resin, 0.1 parts of 2,2-dimethoxy-2-phenyl acetone, and 0.05 parts of 1,6-hexanediol diacrylate were added to 100 parts of (meth)acrylate prepolymer, and the mixture was stirred thoroughly to obtain an optical adhesive. The optical adhesive was then coated on a release film, and the release film was attached to the adhesive surface. The adhesive was cured under 365nm ultraviolet light, and the total irradiation energy was controlled to be 10000mJ / cm 2 , obtaining an optical adhesive layer with a thickness of 35 μm;

[0085] S4. Preparation of protective film:

[0086] The isolation film on one side of the 35μm optical adhesive layer and the 25μm silicone layer was torn off, and the adhesive surface was plasma treated before the optical adhesive layer and the silicone layer were laminated. The release film retained on the other side of the optical adhesive layer formed an isolation layer. Then, the isolation film on the other side of the silicone layer was torn off, and the silicone layer and the back substrate of the 50μm HC layer were plasma treated and then laminated to obtain a protective film including the HC layer, the silicone layer, the optical adhesive layer, and the isolation layer in sequence.

[0087] Example 4

[0088] S1. Preparation of (meth)acrylate prepolymer:

[0089] According to weight parts, 75 parts of 2-ethylhexyl acrylate, 20 parts of ethoxyethoxyethyl acrylate, 5 parts of hydroxybutyl acrylate, and 0.05 parts of 1-hydroxy-cyclohexylphenyl ketone were mixed in a reactor, and then stirred and nitrogen was introduced for 30 minutes. Then, ultraviolet light was used to irradiate the reaction, and the total irradiation energy was controlled to 3000mJ / cm 2 , obtaining a (meth)acrylate prepolymer;

[0090] S2, preparation of (meth)acrylate tackifying resin:

[0091] According to weight parts, 49 parts of 2-ethylhexyl acrylate, 40 parts of butyl methacrylate, 10 parts of acrylic acid, 1 part of trimethylolpropane tris(3-mercaptopropionate), and 0.5 parts of 1-hydroxy-cyclohexylphenyl ketone were mixed in a reactor, and then stirred and nitrogen was introduced for 30 minutes. Then, ultraviolet light was used to irradiate the reaction, and the total irradiation energy was controlled to 5000mJ / cm 2 , to obtain a (meth)acrylate tackifying resin;

[0092] S3. Preparation of optical adhesive layer

[0093] According to parts by weight, 5 parts of (meth)acrylate tackifying resin, 0.1 parts of 2,2-dimethoxy-2-phenyl acetone, and 0.05 parts of 1,6-hexanediol diacrylate were added to 100 parts of (meth)acrylate prepolymer, and the mixture was stirred thoroughly to obtain an optical adhesive. The optical adhesive was then coated on a release film, and the release film was attached to the adhesive surface. The adhesive was cured under 365nm ultraviolet light, and the total irradiation energy was controlled to be 10000mJ / cm 2 , obtaining an optical adhesive layer with a thickness of 35 μm;

[0094] S4. Preparation of protective film:

[0095] The isolation film on one side of the 35μm optical adhesive layer and the 25μm silicone layer was torn off, and the adhesive surface was plasma treated before the optical adhesive layer and the silicone layer were laminated. The release film retained on the other side of the optical adhesive layer formed an isolation layer. Then, the isolation film on the other side of the silicone layer was torn off, and the silicone layer and the back substrate of the 50μm HC layer were plasma treated and then laminated to obtain a protective film including the HC layer, the silicone layer, the optical adhesive layer, and the isolation layer in sequence.

[0096] Example 5

[0097] S1. Preparation of (meth)acrylate prepolymer:

[0098] According to weight parts, 70 parts of 2-ethylhexyl acrylate, 15 parts of lauryl acrylate, 15 parts of triethylene glycol monoacrylate, and 0.05 parts of 1-hydroxy-cyclohexyl phenyl ketone were mixed in a reactor, and then stirred and nitrogen was introduced for 30 minutes. Then, ultraviolet light was used to irradiate the reaction, and the total irradiation energy was controlled to 3000mJ / cm 2 , obtaining a (meth)acrylate prepolymer;

[0099] S2, preparation of (meth)acrylate tackifying resin:

[0100] According to weight parts, 49 parts of 2-ethylhexyl acrylate, 40 parts of butyl methacrylate, 10 parts of N-vinyl pyrrolidone, 1 part of trimethylolpropane tris(3-mercaptopropionate), and 0.5 parts of 1-hydroxy-cyclohexylphenyl ketone were mixed in a reactor, and then stirred and nitrogen was introduced for 30 minutes. Then, the reaction was irradiated with an ultraviolet lamp, and the total irradiation energy was controlled to 5000mJ / cm 2 , obtaining a (meth)acrylate tackifying resin;

[0101] S3. Preparation of optical adhesive layer

[0102] According to parts by weight, 5 parts of (meth)acrylate tackifying resin, 0.1 parts of 2,2-dimethoxy-2-phenyl acetone, and 0.05 parts of 1,6-hexanediol diacrylate were added to 100 parts of (meth)acrylate prepolymer, and the mixture was stirred thoroughly to obtain an optical adhesive. The optical adhesive was then coated on a release film, and the release film was attached to the adhesive surface. The adhesive was cured under 365nm ultraviolet light, and the total irradiation energy was controlled to be 10000mJ / cm 2 , obtaining an optical adhesive layer with a thickness of 35 μm;

[0103] S4. Preparation of protective film:

[0104] The isolation film on one side of the 35μm optical adhesive layer and the 25μm silicone layer was torn off, and the adhesive surface was plasma treated before the optical adhesive layer and the silicone layer were laminated. The release film retained on the other side of the optical adhesive layer formed an isolation layer. Then, the isolation film on the other side of the silicone layer was torn off, and the silicone layer and the back substrate of the 50μm HC layer were plasma treated and then laminated to obtain a protective film including the HC layer, the silicone layer, the optical adhesive layer, and the isolation layer in sequence.

[0105] Comparative Example 1

[0106] S1. Preparation of (meth)acrylate prepolymer:

[0107] According to weight parts, 60 parts of 2-ethylhexyl acrylate, 30 parts of lauryl acrylate, 10 parts of hydroxybutyl acrylate, and 0.05 parts of 1-hydroxy-cyclohexylphenyl ketone were mixed in a reactor, and then stirred and nitrogen was introduced for 30 minutes. Then, ultraviolet light was used to irradiate the reaction, and the total irradiation energy was controlled to 3000mJ / cm 2 , obtaining a (meth)acrylate prepolymer;

[0108] S2, preparation of (meth)acrylate tackifying resin:

[0109] According to weight parts, 49 parts of 2-ethylhexyl acrylate, 40 parts of butyl methacrylate, 10 parts of N-vinyl pyrrolidone, 1 part of trimethylolpropane tris(3-mercaptopropionate), and 0.5 parts of 1-hydroxy-cyclohexylphenyl ketone were mixed in a reactor, and then stirred and nitrogen was introduced for 30 minutes. Then, the reaction was irradiated with an ultraviolet lamp, and the total irradiation energy was controlled to 5000mJ / cm 2 , to obtain a (meth)acrylate tackifying resin;

[0110] S3. Preparation of optical adhesive layer

[0111] According to parts by weight, 5 parts of (meth)acrylate tackifying resin, 0.1 parts of 2,2-dimethoxy-2-phenyl acetone, and 0.1 parts of 1,6-hexanediol diacrylate were added to 100 parts of (meth)acrylate prepolymer, and the mixture was stirred thoroughly to obtain an optical adhesive. The optical adhesive was then coated on a release film, and the release film was attached to the adhesive surface. The adhesive was cured under 365nm ultraviolet light, and the total irradiation energy was controlled to be 10000mJ / cm 2 , obtaining an optical adhesive layer with a thickness of 35 μm;

[0112] S4. Preparation of protective film:

[0113] The isolation film on one side of the 35μm optical adhesive layer and the 25μm silicone layer was torn off, and the adhesive surface was plasma treated before the optical adhesive layer and the silicone layer were laminated. The release film retained on the other side of the optical adhesive layer formed an isolation layer. Then, the isolation film on the other side of the silicone layer was torn off, and the silicone layer and the back substrate of the 50μm HC layer were plasma treated and then laminated to obtain a protective film including the HC layer, the silicone layer, the optical adhesive layer, and the isolation layer in sequence.

[0114] Comparative Example 2

[0115] S1. Preparation of (meth)acrylate prepolymer:

[0116] According to weight parts, 60 parts of 2-ethylhexyl acrylate, 15 parts of lauryl acrylate, 15 parts of ethoxyethoxyethyl acrylate, 10 parts of hydroxybutyl acrylate, and 0.05 parts of 1-hydroxy-cyclohexylphenyl ketone were mixed in a reactor, and then stirred and nitrogen was introduced for 30 minutes. Then, ultraviolet light was used to irradiate the reaction, and the total irradiation energy was controlled to 3000mJ / cm 2 , obtaining a (meth)acrylate prepolymer;

[0117] S2. Preparation of optical adhesive layer

[0118] According to parts by weight, 0.1 parts of 2,2-dimethoxy-2-phenylethanone and 0.05 parts of 1,6-hexanediol diacrylate were added to 100 parts of (meth)acrylate prepolymer, and the mixture was stirred thoroughly to obtain an optical adhesive. The optical adhesive was then coated on a release film, and the release film was attached to the adhesive surface. The adhesive was cured under 365nm ultraviolet light, and the total irradiation energy was controlled to be 10000mJ / cm 2 , obtaining an optical adhesive layer with a thickness of 35 μm;

[0119] S3. Preparation of protective film:

[0120] The isolation film on one side of the 35μm optical adhesive layer and the 25μm silicone layer was torn off, and the adhesive surface was plasma treated before the optical adhesive layer and the silicone layer were laminated. The release film retained on the other side of the optical adhesive layer formed an isolation layer. Then, the isolation film on the other side of the silicone layer was torn off, and the silicone layer and the back substrate of the 50μm HC layer were plasma treated and then laminated to obtain a protective film including the HC layer, the silicone layer, the optical adhesive layer, and the isolation layer in sequence.

[0121] Performance Testing

[0122] The protective films prepared in the examples and comparative examples were subjected to the following performance tests:

[0123] (1) Rheological test: A circular optical adhesive layer sample with a thickness of 0.8 mm and a diameter of 8 mm was placed between the probes of an ARES-G2 rheometer. The temperature was scanned from -50 to 100 °C at a heating rate of 3 °C / min. The Tg, storage modulus, and loss modulus of the sample were tested.

[0124] (2) Creep test: A circular optical adhesive sample with a thickness of 0.8 mm and a diameter of 8 mm was placed between the probes of an ARES-G2 rheometer. A shear stress of 10 kPa was applied and maintained for 600 s. The applied stress was then removed and allowed to recover for 600 s. The creep properties of the sample were tested. The maximum deformation of the sample and the recovery ratio after 600 s were recorded.

[0125] (3) 180° peel strength test: The protective films of Examples 1-5 and Comparative Examples 1-2 were cut into samples with a length of 30 mm and a width of 25.4 mm. The isolation film was then torn off and the protective film was pressed onto the HC surface of the folding screen mobile phone module using a 2 kg rubber roller. After standing for 24 hours in an environment of 23°C and 50% RH, the peel strength was tested using a tensile testing machine.

[0126] (4) Reworkability test: Tear off the isolation film of the protective film and adhere it to the HC surface of the folding screen mobile phone module. Let it stand in an environment of 23°C and 50% RH for 7 days. Then wipe ethanol at the beginning to peel off the protective film and observe whether there is any residual glue. If there is no residual glue, it indicates that the reworkability is acceptable. If there is residual glue, the reworkability is unacceptable.

[0127] (5) Dynamic bending test: Remove the isolation film from the protective film and attach it to the HC surface of the folding screen mobile phone module. Leave it in an environment of 23°C and 50% RH for 24 hours. Then fix it on the fixture of the dynamic bending machine and perform a dynamic bending test at a speed of 20 times / min from 0° to 180°. If there are no bubbles, delamination or other defects between the layers after bending 200,000 times, the dynamic bending test passes. If there are defects, the test fails.

[0128] The test results of each embodiment and comparative example are shown in Table 1:

[0129] Table 1

[0130]

[0131]

[0132] From the above results we can see that:

[0133] The protective films of Examples 1-5 have excellent comprehensive properties;

[0134] Compared with Example 3, the (meth)acrylate prepolymer of Comparative Example 1 did not contain a polar monomer containing an ether bond (ethoxyethoxyethyl acrylate), but the content of lauryl acrylate was increased accordingly. Its creep recovery performance and peel strength were significantly worse than those of Example 3.

[0135] Compared with Example 3, the optical adhesive layer of Comparative Example 2 did not contain (meth)acrylate tackifying resin, and its peel strength and bending resistance were significantly worse than those of Example 3.

[0136] Performance analysis of Examples 1-5 and Comparative Examples 1-2 demonstrates that the addition of a (meth)acrylate tackifying resin improves peel strength and ensures reliable flex resistance. The ether-bonded polar monomer A not only increases intermolecular forces, improving creep recovery and reducing the impact of chemical crosslinking on peel strength, but also possesses multiple hydrophilic groups that facilitate peeling of the protective film when rubbed with ethanol, imparting improved reworkability.

[0137] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the description and implementation methods. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to specific details.

Claims

1. A reworkable folding screen protective film, characterized in that: The optical adhesive comprises an HC layer, a silicone layer, an optical adhesive layer, and an isolation layer stacked in sequence. The optical adhesive layer is obtained by coating an optical adhesive and then curing the optical adhesive. The optical adhesive comprises the following raw material components in parts by weight: 60-90 parts of alkyl (meth)acrylate, 5-25 parts of polar monomer A, 1-10 parts of tackifying resin, 0.02-2 parts of photoinitiator, and 0.01-1 part of curing agent.

2. The reworkable folding screen protective film according to claim 1, characterized in that: The alkyl (meth)acrylate is one or more of methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, heptyl (meth)acrylate, isobornyl (meth)acrylate, isooctyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate or octadecyl (meth)acrylate.

3. The reworkable folding screen protective film according to claim 1, characterized in that: The polar monomer A is one or more of a hydroxyl-containing monomer and an ether bond-containing monomer.

4. The reworkable folding screen protective film according to claim 3, characterized in that: The hydroxyl-containing monomer is hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate or triethylene glycol monoacrylate; The monomer containing an ether bond is methoxyethyl acrylate, glycidyl methacrylate, ethoxyethoxyethyl acrylate, triethylene glycol monoacrylate, methoxydiethylene glycol acrylate or methoxytriethylene glycol acrylate.

5. The reworkable folding screen protective film according to claim 1, characterized in that: The tackifying resin is one or more of (meth)acrylate tackifying resin, epoxy resin, polyurethane resin, and rosin resin.

6. The reworkable folding screen protective film according to claim 5, characterized in that: The raw materials for preparing the (meth)acrylate tackifying resin include, by weight, 70-90 parts of (meth)acrylate alkyl ester, 5-15 parts of polar monomer B, 0.5-5 parts of chain transfer agent and 0.1-1 part of photoinitiator.

7. The reworkable folding screen protective film according to claim 6, characterized in that: The polar monomer B is one or more of a carboxyl group-containing monomer and a nitrogen atom-containing monomer.

8. The reworkable folding screen protective film according to claim 7, characterized in that: The carboxyl-containing monomer is acrylic acid or carboxyethyl acrylate; The monomer containing nitrogen atoms is (meth)acrylamide, diethylaminoethyl (meth)acrylate, N-vinylpyridine, N-vinylimidazole, N-vinylmorpholine or N-vinylpyrrolidone.

9. The reworkable foldable screen protective film according to claim 4, characterized in that: The chain transfer agent is trimethylolpropane tris(3-mercaptopropionate).

10. The reworkable foldable screen protective film according to claim 6, characterized in that: The photoinitiator is 2,4,6 (trimethylbenzoyl) diphenylphosphine oxide, 2,4,6 (trimethylbenzoyl) ethyl phosphonate, 1-hydroxy-cyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone or 2,2-dimethoxy-2-phenylethanone.

11. The reworkable foldable screen protective film according to claim 1, characterized in that: The curing agent is 1,6-hexanediol diacrylate, polyethylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate or dipentaerythritol hexaacrylate.

12. A method for preparing a reworkable foldable screen protective film according to any one of claims 1 to 11, characterized in that: The following steps are involved: S1. Preparation of (meth)acrylate prepolymer: First, according to parts by weight, 60-90 parts of alkyl (meth)acrylate, 5-25 parts of polar monomer A, and 0.01-1 parts of photoinitiator are mixed in a reaction kettle, and then stirring is started and nitrogen is introduced for 15-60 minutes, and then irradiated with ultraviolet light to react to obtain a (meth)acrylate prepolymer; S2, preparation of (meth)acrylate tackifying resin: According to parts by weight, 70-90 parts of alkyl (meth)acrylate, 5-15 parts of polar monomer B, 0.5-5 parts of chain transfer agent, and 0.1-1 parts of photoinitiator are first mixed in a reaction kettle, and then stirring is started and nitrogen is introduced for 15-60 minutes, and then irradiated with ultraviolet light to react to obtain a (meth)acrylate tackifying resin; S3. Preparation of optical adhesive layer: To 100 parts of a (meth)acrylate prepolymer, 1-10 parts of a (meth)acrylate tackifying resin, 0.01-1 parts of a photoinitiator, and 0.01-1 parts of a curing agent were added, in parts by weight, and the mixture was stirred evenly to obtain an optical adhesive. The optical adhesive was then coated on a release film, and the release film was laminated to the adhesive surface, and the mixture was cured under 365 nm ultraviolet light to obtain an optical adhesive layer. S4. Preparation of protective film: The release film on one side of the optical adhesive layer is torn off, the adhesive surface is plasma-treated and then laminated with the silicone layer. The release film retained on the other side of the optical adhesive layer forms an isolation layer. Then, the other side of the silicone layer is laminated with the plasma-treated HC layer to obtain a reworkable folding screen protective film that includes, in sequence, an HC layer, a silicone layer, an optical adhesive layer, and an isolation layer.

Images