High-reliability UV adhesive for polaroid and preparation method of high-reliability UV adhesive

Abstract

The high-reliability UV adhesive for the polaroid is prepared from the following raw materials in percentage by weight: 25 to 55 percent of alicyclic epoxy resin, 3 to 15 percent of dicyclopentadiene acrylate monomer, 10 to 30 percent of acrylic acid modified castor oil epoxy resin, 10 to 30 percent of glycidyl ether type epoxy compound, 1 to 10 percent of adhesion promoter, 0.3 to 3 percent of sensitizer and 0.5 to 8 percent of photoacid generator. The UV adhesive disclosed by the invention has relatively high bonding strength to a COP film, the adhesion is not attenuated over time, the UV adhesive has the advantage of yellowing resistance, and the defects that the conventional UV adhesive is low in adhesion and is reduced over time are overcome.

Description

Technical Field

[0001] The present invention belongs to the field of photocurable materials, and relates to a highly reliable UV adhesive for polarizers and a preparation method thereof. Background Art

[0002] Currently, a TAC film (triacetyl cellulose film) is usually used as a protective film for protecting a PVA (polyvinyl alcohol) polarizer in an image display device. However, the TAC film has poor moisture resistance and heat resistance, and there is a problem of yellowing of the PVA when used at high temperature and high humidity. Therefore, a method of using a COP film with excellent moisture resistance and heat resistance to replace the TAC film as a material for the polarizer protective film is required.

[0003] However, when using a COP film to replace the TAC as the protective film, conventional adhesives have weak bonding strength, resulting in poor reliability. The UV adhesive of the present invention has a high bonding strength to the COP film, the adhesion over time does not decay, and has the advantage of yellowing resistance, solving the disadvantages of low adhesion and decreasing over time of conventional UV adhesives. Summary of the Invention

[0004] In order to solve the disadvantages of poor adhesion of conventional UV adhesives to the COP film and decreasing over time in the prior art, the present invention provides a highly reliable UV adhesive for polarizers and a preparation method thereof, which can be applied to the bonding application of polarizers.

[0005] The technical solution of the present invention to solve the above technical problems is as follows:

[0006] A highly reliable UV adhesive for polarizers is composed of the following raw materials in weight percentages: alicyclic epoxy resin 25 - 55%, dicyclopentadiene acrylate monomer 3 - 15%, acrylic acid modified castor oil epoxy resin 10 - 30%, glycidyl ether type epoxy compound 10 - 30%, adhesion promoter 1 - 10%, sensitizer 0.3 - 3%, photoacid generator 0.5 - 8%.

[0007] On the basis of the above technical solution, the present invention can also be improved as follows.

[0008] Further, the alicyclic epoxy resin refers to a compound having at least an alicyclic structure and an epoxy group in the molecule, such as commercially available products with the trade names "CELLOXIDE 2021P", "CELLOXIDE 2081" of Nippon Shokubai, and S-60 of Nantong New Naxi.

[0009] Further, the dicyclopentadiene acrylate monomer refers to 512AS (CAS No.: 65983-31-5) and 512M (CAS No.: 68586-19-6) of Hitachi Chemical Co., Ltd. of Japan, and the molecular chain contains a molecular structure of cyclopentadiene.

[0010] Furthermore, the acrylic acid-modified castor oil epoxy resin is a reaction product of castor oil epoxy resin and acrylic acid. The molecular structure of the resin contains both epoxy functional groups and acrylate functional groups. The molecular formula is as follows:

[0011]

[0012] The castor oil epoxy resin is a bio-based resin material. It is synthesized from castor oil through specific chemical reactions and has excellent mechanical properties and chemical resistance, as well as good flexibility and adhesion. The structural formula of the castor oil epoxy resin is as follows:

[0013]

[0014] Synthesis route of the acrylic acid-modified castor oil epoxy resin: Add castor oil epoxy resin, acrylic acid, and triphenylphosphine into a three-necked flask, heat to 110 - 130 °C, and react for 3 - 4 hours. Then, test the acid value. When the acid value is less than 0.2, the reaction ends, and the acrylic acid-modified castor oil epoxy resin can be obtained. The reaction formula is as follows:

[0015]

[0016] Furthermore, the glycidyl ether type epoxy compound is prepared by reacting a polyhydric phenol or polyhydric alcohol with epichlorohydrin. It can include aliphatic glycidyl ethers (12 to 14 carbon atoms), 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, o-tolyl glycidyl ether, nonylphenyl glycidyl ether, ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, 1,4-cyclohexanedimethanol diglycidyl ether, trimethylolpropane triglycidyl ether, etc.

[0017] Furthermore, the adhesion promoter refers to 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, CAS No.: 10217-34-2.

[0018] Furthermore, the sensitizer includes anthracene derivatives, benzoin derivatives, benzophenone, 2,4-benzophenone derivatives, etc. Such as 9,10-dibutoxyanthracene, benzoin methyl ether, benzoin isopropyl ether, α,α-dimethoxy-α-phenylacetophenone, dichlorobenzophenone, methyl o-benzoylbenzoate, 4,4'-bis(dimethylamino)benzophenone, 4,4'-bis(diethylamino)benzophenone, etc.

[0019] Furthermore, the photoacid generator includes sulfonium salts and iodonium salt-based cationic photoinitiators, which can generate super-strong protonic acids under UV light irradiation. For example: IRGACURE 250 from BASF, WPI-113, WPI-116, and WPI-124 from Fujifilm of Japan.

[0020] The preparation method of a highly reliable UV adhesive for polarizing films according to the present invention includes: weighing 25-55% of alicyclic epoxy resin, 3-15% of dicyclopentadiene acrylate monomer, 10-30% of acrylic acid-modified castor oil epoxy resin, 10-30% of glycidyl ether-type epoxy compound, 1-10% of adhesion promoter, 0.3-3% of sensitizer, and 0.5-8% of photoacid generator. Add them into a blender in sequence, evacuate to a vacuum degree of -0.08 to -0.05 MPa, stir at 500-1000 revolutions per minute for 0.5-2 hours, stir evenly, let it stand naturally to room temperature, and then seal and package.

[0021] The beneficial effects of the present invention are as follows: For the highly reliable UV adhesive for polarizing films prepared by the present invention, acrylic acid-modified castor oil epoxy resin is synthesized. There are both epoxy functional groups and acrylate functional groups in the molecular chain, making the modified resin a bridging agent that crosslinks acrylate and epoxy resin in the formulation into a large molecule, having better mechanical properties and optical properties. And preferably using castor oil as the main chain, the modified resin has excellent flexibility and elongation. The castor oil-modified epoxy resin contains castor oil components, so it has better water resistance. In addition, the castor oil structure can adsorb oily substances such as mold release agents in the polarizing film material, making the UV adhesive have better adhesion to the polarizing film material and smaller attenuation of adhesion over time. The dicyclopentadiene acrylate monomer is preferably used, which has excellent optical stability, and the cyclopentadiene structure in the monomer has better compatibility and adhesion with the COP film of the polarizing film. 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane is a silane coupling agent containing an oxetane structure, and the oxetane functional group can participate in cationic reactions, which can improve the problem of attenuation of adhesion over time of the UV adhesive to the polarizing film material. Specific Embodiments

[0022] The principles and features of the present invention are described below. The examples given are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0023] Example 1

[0024] Accurately weigh the following raw materials: 40 g of 2021P, 10 g of dicyclopentadiene acrylate 512AS, 19 g of acrylic acid modified castor oil epoxy resin, 20 g of 1,4-butanediol diglycidyl ether, 5 g of 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, 1.5 g of 9,10-dibutoxyanthracene, and 4 g of IRGACURE 250; Add the above components into a double planetary power mixer in sequence, evacuate to a vacuum degree of -0.08 MPa, stir at 500 revolutions per minute for 2 hours, stir evenly, let it stand naturally to room temperature, and then seal and package it.

[0025] Example 2

[0026] Accurately weigh the following raw materials: 40 g of 2021P, 10 g of dicyclopentadiene acrylate 512AS, 19 g of acrylic acid modified castor oil epoxy resin, 21 g of 1,4-cyclohexanedimethanol diglycidyl ether, 2-

[0027] (3,4-epoxycyclohexyl)ethyltriethoxysilane 5 g, 9,10-dibutoxyanthracene 1.5 g, IRGACURE 250 4 g; Add the above components into a double planetary power mixer in sequence, evacuate to a vacuum degree of -0.05 MPa, stir at 750 revolutions per minute for 1 hour, stir evenly, let it stand naturally to room temperature, and then seal and package it.

[0028] Example 3

[0029] Accurately weigh the following raw materials: 30 g of 2081P, 3 g of dicyclopentadiene acrylate 512M, 30 g of acrylic acid modified castor oil epoxy resin, 30 g of 1,4-cyclohexanedimethanol diglycidyl ether, 10 g of 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, 1 g of 4,4'-bis(diethylamino)benzophenone, and 7 g of WPI-12; Add the above components into a double planetary power mixer in sequence, evacuate to a vacuum degree of -0.06 MPa, stir at 700 revolutions per minute for 1.5 hours, stir evenly, let it stand naturally to room temperature, and then seal and package it.

[0030] Example 4

[0031] Accurately weigh the following raw materials: 50 g of 2021P, 10 g of dicyclopentadiene acrylate 512AS, 10 g of acrylic acid modified castor oil epoxy resin, 21 g of 1,4-cyclohexanedimethanol diglycidyl ether, 10 g of 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, 1.5 g of 9,10-dibutoxyanthracene, and 8 g of IRGACURE 2508; Add the above components into a double planetary power mixer in sequence, evacuate to a vacuum degree of -0.07 MPa, stir at 800 revolutions per minute for 1 hour, stir evenly, let it stand naturally to room temperature, and then seal and package it.

[0032] Example 5

[0033] Accurately weigh the following raw materials: 40 g of 2021P, 15 g of dicyclopentadiene acrylate 512M, 19 g of acrylic acid modified castor oil epoxy resin, 10 g of 1,6 - hexanediol diglycidyl ether, 10 g of 2 - (3,4 - epoxycyclohexyl) ethyltriethoxysilane, 3 g of benzoin methyl ether, 1 g of WPI - 116; Add the above components into a double - planetary power mixer in sequence, evacuate to a vacuum degree of - 0.08 MPa, stir at 1000 revolutions per minute for 0.5 hour, stir evenly, let it stand naturally to room temperature, and then seal and package it.

[0034] Comparative Example 1

[0035] Accurately weigh the following raw materials: 50 g of 2021P, 10 g of 1,6 - hexanediol diacrylate, 10 g of bisphenol A epoxy resin, 21 g of 1,4 - cyclohexanedimethanol diglycidyl ether, 1.5 g of 9,10 - dibutoxyanthracene, 8 g of IRGACURE 250; Add the above components into a double - planetary power mixer in sequence, evacuate to a vacuum degree of - 0.08 MPa, stir at 500 revolutions per minute for 2 hours, stir evenly, let it stand naturally to room temperature, and then seal and package it.

[0036] Comparative Example 2

[0037] Accurately weigh the following raw materials: 40 g of 2021P, 10 g of 1,6 - hexanediol diacrylate, 19 g of hydrogenated bisphenol A epoxy resin, 20 g of 1,4 - butanediol diglycidyl ether, 5 g of 3 - ethyl - 3 - [(2 - ethylhexyloxy) methyl] epoxybutane (CAS: 298695 - 60 - 0), 1.5 g of 9,10 - dibutoxyanthracene, 4 g of IRGACURE 250; Add the above components into a double - planetary power mixer in sequence, evacuate to a vacuum degree of - 0.08 MPa, stir at 500 revolutions per minute for 2 hours, stir evenly, let it stand naturally to room temperature, and then seal and package it.

[0038] The performance of a highly reliable UV adhesive for polarizing films of the present invention was tested through the following experiments.

[0039] Performance Test of Test Examples

[0040] Curing light source 1: 385 nm LED lamp, light intensity 500 mW / cm 2 , irradiate for 2 s

[0041] Refractive index: Abbe refractometer

[0042] Peeling strength: universal testing machine, COP film + PVA film

[0043] b value: spectrophotometer

[0044] The test results are shown in Table 1 as follows:

[0045] Table 1 Comparative test results of the performance of the samples prepared in Examples 1-5 and ordinary UV adhesives

[0046]

[0047]

[0048] It can be seen from the above results that compared with the existing ordinary UV adhesives, a highly reliable UV adhesive for polarizers of the present invention has a higher bonding strength to the COP film, the adhesion over time does not decay, and has the advantage of good optical yellowing.

[0049] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A high reliability UV adhesive for polarizer, composed of the following raw materials in percentage by weight: Alicyclic epoxy resin 25-55%, dicyclopentadiene acrylate monomer 3-15%, acrylic acid modified castor oil epoxy resin 10-30%, glycidyl ether type epoxy compound 10-30%, adhesion promoter 1-10%, sensitizer 0.3-3%, photoacid generator 0.5-8%.

2. The high reliability UV adhesive for polarizer according to claim 1, characterized in that: The alicyclic epoxy resin refers to a compound having at least an alicyclic structure and an epoxy group in the molecule.

3. The high reliability UV adhesive for polarizer according to claim 1, characterized in that: The molecular chain of the dicyclopentadiene acrylate monomer contains the molecular structure of cyclopentadiene.

4. The high reliability UV adhesive for polarizer according to claim 1, characterized in that: The molecular formula of the acrylic acid-modified castor oil epoxy resin is as follows: 。 5. The high reliability UV adhesive for polarizer according to claim 4, characterized in that: The acrylic acid-modified castor oil epoxy resin is synthesized by reacting castor oil epoxy resin with acrylic acid.

6. The high reliability UV adhesive for polarizer according to claim 5, characterized in that: The synthetic route of the acrylic acid modified castor oil epoxy resin is as follows: castor oil epoxy resin, acrylic acid and triphenylphosphine are added into a three-necked flask, heated to 110-130° C., reacted for 3-4 hours, and then the acid value is tested. When the acid value is less than 0.2, the reaction is completed to obtain the acrylic acid modified castor oil epoxy resin. The reaction formula is as follows: 。 7. The high reliability UV adhesive for polarizer according to claim 1, characterized in that: The glycidyl ether type epoxy compound is prepared by reacting polyphenol or polyol with epichlorohydrin.

8. The high reliability UV adhesive for polarizer according to claim 1, characterized in that: The adhesion promoter is 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, CAS number: 10217-34-2; the sensitizer includes one of anthracene derivatives, benzoin derivatives, benzophenone, and 2,4-benzophenone derivatives; the photoacid generator is a sulfonium salt or iodonium salt cationic photoinitiator.

9. The high-reliability UV adhesive for polarizer according to claim 1, wherein the preparation method comprises: Weigh 25-55% of alicyclic epoxy resin, 3-15% of dicyclopentadiene acrylate monomer, 10-30% of acrylic acid-modified castor oil epoxy resin, 10-30% of glycidyl ether epoxy compound, 1-10% of adhesion promoter, 0.3-3% of sensitizer, and 0.5-8% of photoacid generator; add them into a blender in sequence, evacuate to a vacuum degree of -0.08 to -0.05 MPa, stir at 500 to 1000 rpm for 0.5 to 2 hours, stir evenly, let it dry naturally to room temperature, and seal and package.

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