Ultraviolet curing pressure-sensitive adhesive and preparation method thereof

Abstract

The invention provides an ultraviolet curing pressure-sensitive adhesive and a preparation method thereof, and belongs to the technical field of novel polymer materials. The ultraviolet curing pressure-sensitive adhesive is prepared from the following raw materials in parts by weight: 60-80 parts of (methyl) acrylate polymer with carboxyl functional groups; 5-15 parts of epoxy resin; 50 to 70 parts of a multifunctional reactive diluent; and 0.5 to 10 parts of a photoinitiator. The pressure-sensitive adhesive is high in peel strength and good in durability, does not contain a solvent and can be quickly crosslinked and cured under ultraviolet light, a large amount of energy waste is reduced compared with traditional thermocuring, and the preparation method is simple and suitable for large-scale industrial production.

Description

Technical Field

[0001] The invention relates to the technical field of new polymer materials, and in particular to an ultraviolet light-cured pressure-sensitive adhesive and a preparation method thereof. Background Art

[0002] Polarizer is one of the main components of liquid crystal display panels, accounting for about 11% of the panel cost. In order to adapt to the use in liquid crystal displays, a layer of pressure-sensitive adhesive must be attached to the polarizer, and a release film must be laminated to protect the pressure-sensitive adhesive to form a projection polarizer. When in use, the release film can be torn off and the polarizer can be easily attached to the glass substrate of the liquid crystal display.

[0003] The pressure-sensitive adhesives used in existing polarizers are mainly acrylic solvent-based pressure-sensitive adhesives. However, due to the inherent characteristics of acrylic pressure-sensitive adhesives, their products are prone to poor bonding or display in high temperature and high humidity environments, resulting in poor product durability. In addition, this type of pressure-sensitive adhesive has high fluidity and is easy to flow out of the polarizer and cause pollution. Moreover, it is difficult for existing pressure-sensitive adhesives to achieve high durability. In high temperature and high humidity environments, the polarizer and the substrate will separate and warp or water ripples will appear. If this type of polarizer is used in practice, there will be great safety hazards.

[0004] Therefore, how to obtain a UV-curable pressure-sensitive adhesive for polarizers with high durability and high peeling force and a preparation method thereof are technical problems that need to be solved at present. Summary of the invention

[0005] The object of the present invention is to provide a UV-curable pressure-sensitive adhesive and a preparation method thereof, so as to solve the technical problems of poor durability and insufficient peel strength of the existing pressure-sensitive adhesive for polarizers.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a UV-curable pressure-sensitive adhesive, which is prepared from the following raw materials in parts by weight:

[0008]

[0009] Furthermore, the (meth)acrylate polymer having a carboxyl functional group is copolymerized from at least two polymerizable monomers, and at least one of the at least two polymerizable monomers is a monomer having a carboxyl functional group.

[0010] Furthermore, the monomer having a carboxyl functional group is selected from methacrylic acid, crotonic acid, maleic acid, itaconic acid and citraconic acid.

[0011] Further, the other monomer of the at least two polymerizable monomers is selected from ethyl acrylate, butyl acrylate, methyl methacrylate, isobutyl acrylate, isobutyl methacrylate, 2-ethylhexyl acrylate, tert-butyl methacrylate, acryloylmorpholine, isooctyl acrylate, isooctyl methacrylate, tetrahydrofuran acrylate, tetrahydrofuran methacrylate, isobornyl acrylate, isobornyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, vinyl acetate, cyclohexyl acrylate, 2-phenoxyethyl acrylate, 2-phenoxyethyl methacrylate, glycidyl acrylate and glycidyl methacrylate.

[0012] Furthermore, the multifunctional reactive diluent comprises one or more of ethylene glycol dimethacrylate, tripropylene glycol diacrylate, pentaerythritol triacrylate and trimethylolpropane triacrylate.

[0013] Furthermore, the photoinitiator comprises one or more of benzoin dimethyl ether, benzoin ethyl ether, α,α'-dimethoxy-α-phenylacetophenone, α,α-diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxy-cyclohexyl benzophenone, benzophenone and ethyl 4-dimethylaminobenzoate.

[0014] Furthermore, the amount of carboxyl functional groups in the (meth)acrylate polymer having carboxyl functional groups is 50 mmol / 100 g to 90 mol / 100 g.

[0015] The present invention also provides a method for preparing a UV-curable pressure-sensitive adhesive, comprising the following steps:

[0016] The (meth)acrylate polymer having a carboxyl functional group, epoxy resin, multifunctional active diluent and photoinitiator are mixed and then cured under ultraviolet light.

[0017] Furthermore, the wavelength of the ultraviolet light is 180 to 450 nm, and the curing time is 5 to 10 seconds.

[0018] Beneficial effects of the present invention:

[0019] The multifunctional active diluent used in the present invention can be used as a diluent or an active monomer, and is copolymerized and cross-linked with a (meth)acrylate polymer having a carboxyl functional group under a photoinitiator, thereby improving the durability and anti-aging performance of the pressure-sensitive adhesive; the addition of epoxy resin makes the pressure-sensitive adhesive have excellent peeling force and anti-bounce performance. The three components cooperate with each other to solve the problem that the current pressure-sensitive adhesive for polarizers is prone to poor bonding or display under high temperature and high humidity environments, thereby resulting in poor durability of the polarizer.

[0020] The pressure-sensitive adhesive of the present invention does not contain solvent, can be rapidly cross-linked and cured under ultraviolet light, and reduces a large amount of energy waste compared to traditional thermal curing. The preparation method of the present invention is simple and suitable for large-scale industrial production. DETAILED DESCRIPTION

[0021] The present invention provides a UV-curable pressure-sensitive adhesive, which is prepared from the following raw materials in parts by weight:

[0022]

[0023] In the present invention, the content of the (meth)acrylate polymer having a carboxyl functional group is preferably 62 to 75 parts by weight, and more preferably 65 to 70 parts. In the present invention, when the content of the (meth)acrylate polymer having a carboxyl functional group is too little, the initial adhesion of the pressure-sensitive adhesive will be reduced and the durability will be reduced; when the content is too much, the anti-bounce performance of the pressure-sensitive adhesive will be reduced. Therefore, in the ultraviolet light-cured pressure-sensitive adhesive of the present invention, the content of the (meth)acrylate polymer having a carboxyl functional group is preferably 60 to 80 parts.

[0024] In the present invention, the content of the epoxy resin is preferably 8 to 12 parts by weight, and more preferably 10 parts. In the present invention, the content of the epoxy resin has an impact on the performance of the pressure-sensitive adhesive. When the amount of the epoxy resin is too high, the anti-bounce performance of the pressure-sensitive adhesive will be reduced; and when the amount of the epoxy resin is too small, the anti-bounce performance will also be affected. Therefore, in the ultraviolet light-cured pressure-sensitive adhesive of the present invention, the amount of the epoxy resin is preferably 5 to 15 parts.

[0025] In the present invention, the content of the multifunctional reactive diluent is preferably 55 to 65 parts by weight, and more preferably 58 to 62 parts. In the present invention, the content of the multifunctional reactive diluent has an impact on the performance of the pressure-sensitive adhesive. When the content is too little, the viscosity of the pressure-sensitive adhesive is too high, the fluidity is poor, and it cannot effectively adhere to the substrate; when the content is too much, the pressure-sensitive adhesive has high fluidity, and it is easy to flow out when used as a polarizer, and the durability is reduced. Therefore, in the ultraviolet light-curable pressure-sensitive adhesive of the present invention, the amount of the multifunctional reactive diluent is preferably 50 to 70 parts.

[0026] In the present invention, the content of the photoinitiator is preferably 1 to 8 parts by weight, and more preferably 2 to 7 parts. In the present invention, the content of the photoinitiator increases, and the curing speed of the pressure-sensitive adhesive is accelerated. If the amount of the photoinitiator is too small, the UV radiation energy required during curing is high, and the curing speed is slow; conversely, if the amount of the photoinitiator is too large, the UV radiation energy required during curing is very low, and the curing speed is too fast, and it can even be cured under sunlight or fluorescent light (containing a small amount of UV light), which affects the room temperature storage stability.

[0027] In the present invention, the (meth)acrylate polymer having a carboxyl functional group is copolymerized from at least two polymerizable monomers, and at least one of the at least two polymerizable monomers is a monomer having a carboxyl functional group.

[0028] In the present invention, the monomer having a carboxyl functional group is preferably methacrylic acid, crotonic acid, maleic acid, itaconic acid or citraconic acid.

[0029] In the present invention, the other monomer of the at least two polymerizable monomers is preferably ethyl acrylate, butyl acrylate, methyl methacrylate, isobutyl acrylate, isobutyl methacrylate, 2-ethylhexyl acrylate, tert-butyl methacrylate, acryloylmorpholine, isooctyl acrylate, isooctyl methacrylate, tetrahydrofuran acrylate, tetrahydrofuran methacrylate, isobornyl acrylate, isobornyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, vinyl acetate, cyclohexyl acrylate, 2-phenoxyethyl acrylate, 2-phenoxyethyl methacrylate, glycidyl acrylate or glycidyl methacrylate.

[0030] In the present invention, the multifunctional reactive diluent is preferably one or more of ethylene glycol dimethacrylate, tripropylene glycol diacrylate, pentaerythritol triacrylate and trimethylolpropane triacrylate, and more preferably pentaerythritol triacrylate and / or trimethylolpropane triacrylate.

[0031] In the present invention, the photoinitiator is preferably one or more of benzoin dimethyl ether, benzoin ethyl ether, α,α'-dimethoxy-α-phenylacetophenone, α,α-diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxy-cyclohexyl benzophenone, benzophenone and ethyl 4-dimethylaminobenzoate, and is further preferably one or more of benzoin dimethyl ether, benzoin ethyl ether and α,α'-dimethoxy-α-phenylacetophenone.

[0032] In the present invention, the amount of the carboxyl functional group in the (meth)acrylate polymer having a carboxyl functional group is 50 mmol / 100 g to 90 mol / 100 g, preferably 60 mol / 100 g to 80 mol / 100 g.

[0033] The present invention also provides a method for preparing a UV-curable pressure-sensitive adhesive, comprising the following steps:

[0034] The (meth)acrylate polymer having a carboxyl functional group, epoxy resin, multifunctional active diluent and photoinitiator are mixed and then cured under ultraviolet light.

[0035] In the present invention, the wavelength of the ultraviolet light is 180 to 450 nm, preferably 230 to 370 nm; the curing time is 5 to 10 s, preferably 6 to 9 s.

[0036] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0037] Example 1

[0038] Preparation of (meth)acrylate polymers with carboxyl functional groups:

[0039] 49 parts of methyl methacrylate, 45 parts of butyl acrylate, 6 parts of crotonic acid, 0.2 parts of initiator VAZO 67, and 150 parts of n-butanol were mixed in a glass bottle, nitrogen was introduced for two minutes to remove oxygen, and the reaction bottle was sealed, and the reaction bottle was placed in a polymerization device at 60° C. for 24 hours to prepare a (meth) acrylic acid ester polymer with a carboxyl functional group, with a solid content of 35%. The content of carboxyl groups in the synthesized polymer per 100 g of the polymer was 79 mmol.

[0040] 80 parts of (meth)acrylate polymer having carboxyl functional group, 10 parts of epoxy resin EPON828, 66 parts of ethylene glycol dimethacrylate and 5 parts of benzoin ethyl ether are mixed and coated on the substrate, and then irradiated under 350nm UV light for 5s for curing.

[0041] Example 2

[0042] Preparation of (meth)acrylate polymers with carboxyl functional groups:

[0043] 49 parts of isobutyl methacrylate, 44.5 parts of 2-ethylhexyl acrylate, 6 parts of methacrylic acid, 0.5 parts of initiator VAZO 67, and 150 parts of n-butanol were mixed in a glass bottle, nitrogen was introduced for two minutes to remove oxygen, and the reaction bottle was sealed, and the reaction bottle was placed in a polymerization device at 60° C. for 24 hours to prepare a (meth) acrylic acid ester polymer with a carboxyl functional group, with a solid content of 40%. The content of carboxyl groups in the synthesized polymer per 100 g of the polymer was 85 mmol.

[0044] 75 parts of (meth)acrylate polymer having carboxyl functional group, 5 parts of epoxy resin EPON828, 70 parts of tripropylene glycol diacrylate and 6 parts of benzoin dimethyl ether are mixed and coated on the substrate, and then irradiated under 350nm UV light for 10s for curing.

[0045] Example 3

[0046] Preparation of (meth)acrylate polymers with carboxyl functional groups:

[0047] 55 parts of butyl acrylate, 42 parts of isooctyl acrylate, 3 parts of maleic acid, 0.5 parts of initiator VAZO 67, and 150 parts of acetone were mixed in a glass bottle, nitrogen was introduced for two minutes to remove oxygen, and the reaction bottle was sealed, and the reaction bottle was placed in a polymerization device at 60° C. for 24 hours to prepare a (meth) acrylic acid ester polymer with a carboxyl functional group, with a solid content of 38%. The content of carboxyl groups in the synthesized polymer per 100 g of the polymer was 75 mmol.

[0048] 60 parts of (meth)acrylate polymer having carboxyl functional group, 15 parts of epoxy resin EPON828, 60 parts of trimethylolpropane triacrylate and 3 parts of 1-hydroxy-cyclohexyl benzophenone are mixed and coated on the substrate, and then irradiated under 350nm UV light for 10s for curing.

[0049] Example 4

[0050] 65 parts of (meth) acrylic acid ester polymer with carboxyl functional group, 12 parts of epoxy resin EPON828, 65 parts of ethylene glycol dimethacrylate and 5 parts of 1-hydroxy-cyclohexyl benzophenone were mixed and coated on the substrate, and irradiated under 350nm UV light for 5s for curing;

[0051] The preparation of the (meth)acrylate polymer having a carboxyl functional group is the same as in Example 1.

[0052] Example 5

[0053] 80 parts of (meth) acrylate polymer with carboxyl functional group, 15 parts of epoxy resin EPON828, 60 parts of pentaerythritol triacrylate and 10 parts of α,α'-dimethoxy-α-phenylacetophenone were mixed and coated on the substrate, and irradiated under 350nm UV light for 8s for curing;

[0054] The preparation of the (meth)acrylate polymer having a carboxyl functional group is the same as in Example 2.

[0055] Example 6

[0056] 70 parts of (meth) acrylate polymer with carboxyl functional group, 10 parts of epoxy resin EPON828, 70 parts of trimethylolpropane triacrylate and 3 parts of 1-hydroxy-cyclohexyl benzophenone were mixed and coated on the substrate, and irradiated under 350nm UV light for 9s for curing;

[0057] The preparation of the (meth)acrylate polymer having a carboxyl functional group is the same as in Example 3.

[0058] The performance of the polarizing films made from the pressure-sensitive adhesives prepared in Examples 1 to 6 was tested.

[0059] Peel strength: GBT 2792-2014 Test method for peel strength of adhesive tape;

[0060] Aging test: GBT 17875-1999 Accelerated aging test method for pressure-sensitive adhesive tapes;

[0061] Adhesion: GBT 4851-2014 Test method for adhesive tape adhesion;

[0062] Initial tack: GB / T 4852-2002 Test method for initial tack of pressure-sensitive adhesive tapes (rolling ball method).

[0063] Table 1 Test results

[0064]

[0065] As can be seen from the above embodiments, the present invention provides a UV-curable pressure-sensitive adhesive and a preparation method thereof. It can be seen from the test results of the present invention that the UV-curable pressure-sensitive adhesive of the present invention has high peel strength and holding force, and the aging test shows that the pressure-sensitive adhesive of the present invention has good durability and is not easy to precipitate residual adhesive when used as a polarizer. In addition, the pressure-sensitive adhesive of the present invention does not contain solvents and can be rapidly cross-linked and cured under ultraviolet light, which reduces a large amount of energy waste compared to traditional thermal curing, and the preparation method of the present invention is simple and suitable for large-scale industrial production.

[0066] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A UV-curable pressure-sensitive adhesive, characterized in that: Prepared from the following raw materials in parts by weight:

2. The UV-curable pressure-sensitive adhesive according to claim 1, characterized in that: The (meth)acrylate polymer having a carboxyl functional group is copolymerized by at least two polymerizable monomers, and at least one of the at least two polymerizable monomers is a monomer having a carboxyl functional group.

3. The UV-curable pressure-sensitive adhesive according to claim 2, characterized in that: The monomer having a carboxyl functional group is selected from methacrylic acid, crotonic acid, maleic acid, itaconic acid and citraconic acid.

4. The UV-curable pressure-sensitive adhesive according to claim 2 or 3, characterized in that: The other monomer of the at least two polymerizable monomers is selected from ethyl acrylate, butyl acrylate, methyl methacrylate, isobutyl acrylate, isobutyl methacrylate, 2-ethylhexyl acrylate, tert-butyl methacrylate, acryloylmorpholine, isooctyl acrylate, isooctyl methacrylate, tetrahydrofuranyl acrylate, tetrahydrofuranyl methacrylate, isobornyl acrylate, isobornyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, vinyl acetate, cyclohexyl acrylate, 2-phenoxyethyl acrylate, 2-phenoxyethyl methacrylate, glycidyl acrylate and glycidyl methacrylate.

5. The UV-curable pressure-sensitive adhesive according to any one of claims 1 to 3, characterized in that: The multifunctional reactive diluent comprises one or more of ethylene glycol dimethacrylate, tripropylene glycol diacrylate, pentaerythritol triacrylate and trimethylolpropane triacrylate.

6. The UV-curable pressure-sensitive adhesive according to claim 5, characterized in that: The photoinitiator comprises one or more of benzoin dimethyl ether, benzoin ethyl ether, α,α'-dimethoxy-α-phenylacetophenone, α,α-diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxy-cyclohexyl benzophenone, benzophenone and ethyl 4-dimethylaminobenzoate.

7. The UV-curable pressure-sensitive adhesive according to claim 1 or 2, characterized in that: The amount of the carboxyl functional group in the (meth)acrylate polymer having a carboxyl functional group is 50 mmol / 100 g to 90 mol / 100 g.

8. The method for preparing the UV-curable pressure-sensitive adhesive according to any one of claims 1 to 7, characterized in that: The following steps are involved: The (meth)acrylate polymer having a carboxyl functional group, epoxy resin, multifunctional active diluent and photoinitiator are mixed and then cured under ultraviolet light.

9. The method for preparing the UV-curable pressure-sensitive adhesive according to claim 8, characterized in that: The wavelength of the ultraviolet light is 180-450 nm, and the curing time is 5-10 seconds.

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