A high-reliability UV adhesive for polarizers and its preparation method

Abstract

This invention provides a high-reliability UV adhesive for polarizing films, composed of the following raw materials by weight percentage: 25-55% alicyclic epoxy resin, 3-15% dicyclopentadiene acrylate monomer, 10-30% acrylic acid-modified castor oil epoxy resin, 10-30% glycidyl ether type epoxy compound, 1-10% adhesion promoter, 0.3-3% sensitizer, and 0.5-8% photoacid generator. The UV adhesive of this invention exhibits high adhesion strength to COP films, maintains adhesion over time, and is resistant to yellowing, overcoming the shortcomings of conventional UV adhesives, such as low adhesion and degradation over time.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of light-cured materials, and relates to a high-reliability UV adhesive for a polarizing sheet and a preparation method thereof. BACKGROUND

[0002] At present, the polarizing sheet used in an image display device usually uses a TAC film (triacetyl cellulose film) as a protective film for protecting a PVA polyvinyl alcohol polarizer. However, the TAC film has poor moisture resistance and heat resistance, and when used at high temperature and high humidity, there is a problem of yellowing of the PVA. Therefore, a method of using a COP film having excellent moisture resistance and heat resistance instead of the TAC film as a material for the polarizer protective film is needed.

[0003] However, when the COP film is used instead of the TAC as the protective film, the conventional adhesive has weak adhesion strength, resulting in poor reliability. The UV adhesive of the present application has high adhesion strength to the COP film, and the adhesion force does not decrease over time, and has the advantage of yellowing resistance, solving the shortcomings of the conventional UV adhesive that the adhesion force is low and decreases over time. SUMMARY

[0004] In order to solve the shortcomings of the conventional UV adhesive that the adhesion force to the COP film is not good and decreases over time in the prior art, the present application provides a high-reliability UV adhesive for a polarizing sheet and a preparation method thereof, which can be applied to the adhesion application of the polarizing sheet.

[0005] The technical scheme for solving the above technical problems of the present application is as follows:

[0006] A high-reliability UV adhesive for a polarizing sheet is composed of the following raw materials in percentage by weight: alicyclic epoxy resin 25-55%, dicyclopentadiene acrylate monomer 3-15%, acrylate modified castor oil epoxy resin 10-30%, glycidyl ether type epoxy compound 10-30%, adhesion promoter 1-10%, sensitizer 0.3-3%, and photo-acid generator 0.5-8%.

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

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

[0009] Further, the dicyclopentadiene acrylate monomer refers to 512AS (CAS No. 65983-31-5) and 512M (CAS No. 68586-19-6) of Japan Hitachi Kasai, which have a molecular structure containing cyclopentadiene in the molecular chain.

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

[0011]

[0012] The castor oil epoxy resin is a bio-based resin material synthesized from castor oil as raw material 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] The synthesis route of the acrylic modified castor oil epoxy resin is as follows: castor oil epoxy resin, acrylic acid, and triphenylphosphine are added to a three-necked flask, heated to 110-130°C, and reacted for 3-4 hours. When the acid value is less than 0.2, the reaction is complete, and the acrylic modified castor oil epoxy resin is obtained. The reaction formula is as follows:

[0015]

[0016] Further, the glycidyl ether type epoxy compound is prepared by reacting a polyhydric phenol or a 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, nonyl phenyl 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] Further, the adhesion promoter refers to 2-(3,4-epoxycyclohexyl)ethyl triethoxysilane, CAS No.: 10217-34-2.

[0018] Further, 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, o-benzoylbenzoic acid methyl ester, 4,4'-bis(dimethylamino)benzophenone, 4,4'-bis(diethylamino)benzophenone, etc.

[0019] Further, the photoacid generator, including sulfonium salt and iodonium salt cationic photoinitiator, such cationic photoinitiator can produce super strong protonic acid under UV light. For example: IRGACURE 250 of BASF company, WPI-113, WPI-116 and WPI-124 of Fujifilm company in Japan.

[0020] The preparation method of the high-reliability UV glue for polarizing plate includes: weighing 25-55% of alicyclic epoxy resin, 3-15% of dicyclopentadiene acrylate monomer, 10-30% of acrylic 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. The above components are sequentially added into a stirring machine, vacuumized to a vacuum degree of-0.08 to-0.05 MPa, stirred at 500-1000 revolutions per minute for 0.5-2 hours, uniformly stirred, naturally air-dried to room temperature, and sealed and packaged.

[0021] The high-reliability UV glue for polarizing plate prepared by the method has the following advantages: the acrylic modified castor oil epoxy resin is synthesized, the molecular chain has both epoxy functional groups and acrylate functional groups, the modified resin becomes a bridging agent, the acrylate and the epoxy resin in the formula are crosslinked into a macromolecule, and the modified resin has better mechanical properties and optical properties; the castor oil is used as the main chain, the modified resin has excellent flexibility and elongation; the castor oil modified epoxy resin contains castor oil components, has better water resistance, and the castor oil structure can absorb oily substances such as release agents in the polarizing plate film material, so that the UV glue has better adhesion to the polarizing plate film material and smaller adhesion decay over time; the dicyclopentadiene acrylate monomer has excellent optical stability, the cyclopentadiene structure in the monomer has better compatibility and adhesion to the COP film of the polarizing plate; and the 2-(3,4-epoxycyclohexyl) ethyl triethoxysilane is a silane coupling agent containing an oxetane structure, the oxetane functional group can participate in cationic reaction, and the UV glue can improve the adhesion decay problem of the UV glue to the polarizing plate film material over time. DETAILED DESCRIPTION

[0022] The principles and characteristics of the present application are described below, and the examples are only used to explain the present application, and are not used to limit the scope of the present application.

[0023] Example 1

[0024] Accurately weigh the following raw materials, 2021P 40g, dicyclopentadiene acrylate 512AS 10g, acrylic modified castor oil epoxy resin 19g, 1,4-butanediol diglycidyl ether 20g, 2-(3,4-epoxycyclohexyl)ethyl triethoxysilane 5g, 9,10-dibutoxyanthracene 1.5g, IRGACURE 250 4g; sequentially add the above components into a double planetary dynamic mixing stirrer, vacuum to a vacuum degree of -0.08 MPa, stir at 500 rpm for 2 hours, stir uniformly, naturally air for room temperature, seal and package.

[0025] Example 2

[0026] Accurately weigh the following raw materials, 2021P 40g, dicyclopentadiene acrylate 512AS 10g, acrylic modified castor oil epoxy resin 19g, 1,4-butanediol diglycidyl ether 20g, 2-(3,4-epoxycyclohexyl)ethyl triethoxysilane 5g, 9,10-dibutoxyanthracene 1.5g, IRGACURE 250 4g; sequentially add the above components into a double planetary dynamic mixing stirrer, vacuum to a vacuum degree of -0.08 MPa, stir at 500 rpm for 2 hours, stir uniformly, naturally air for room temperature, seal and package.

[0027] Example 3

[0028] Accurately weigh the following raw materials, 2021P 40g, dicyclopentadiene acrylate 512AS 10g, acrylic modified castor oil epoxy resin 19g, 1,4-butanediol diglycidyl ether 20g, 2-(3,4-epoxycyclohexyl)ethyl triethoxysilane 5g, 9,10-dibutoxyanthracene 1.5g, IRGACURE 250 4g; sequentially add the above components into a double planetary dynamic mixing stirrer, vacuum to a vacuum degree of -0.08 MPa, stir at 500 rpm for 2 hours, stir uniformly, naturally air for room temperature, seal and package.

[0029] Example 3

[0030] Accurately weigh the following raw materials, 2021P 40g, dicyclopentadiene acrylate 512AS 10g, acrylic modified castor oil epoxy resin 19g, 1,4-butanediol diglycidyl ether 20g, 2-(3,4-epoxycyclohexyl)ethyl triethoxysilane 5g, 9,10-dibutoxyanthracene 1.5g, IRGACURE 250 4g; sequentially add the above components into a double planetary dynamic mixing stirrer, vacuum to a vacuum degree of -0.08 MPa, stir at 500 rpm for 2 hours, stir uniformly, naturally air for room temperature, seal and package.

[0031] Example 4

[0032] Example 5

[0033] The following raw materials were accurately weighed: 2021P 40 g, dicyclopentadiene acrylate 512M 15 g, acrylic modified castor oil epoxy resin 19 g, 1,6-hexanediol diglycidyl ether 10 g, 2-(3,4-epoxycyclohexyl)ethyl triethoxysilane 10 g, benzoin methyl ether 3 g, and WPI-1 61 g. The above components were sequentially added to a double planetary dynamic mixing stirrer, vacuumed to a vacuum degree of -0.08 MPa, stirred at 1000 rpm for 0.5 hours, uniformly stirred, naturally air-dried to room temperature, and sealed and packaged.

[0034] Comparative Example 1

[0035] The following raw materials were accurately weighed: 2021P 50 g, 1,6-hexanediol diacrylate 10 g, bisphenol A epoxy resin 10 g, 1,4-cyclohexanedimethanol diglycidyl ether 21 g, 9,10-dibutoxyanthracene 1.5 g, and IRGACURE 250 8 g. The above components were sequentially added to a double planetary dynamic mixing stirrer, vacuumed to a vacuum degree of -0.08 MPa, stirred at 500 rpm for 2 hours, uniformly stirred, naturally air-dried to room temperature, and sealed and packaged.

[0036] Comparative Example 2

[0037] The following raw materials were accurately weighed: 2021P 40 g, 1,6-hexanediol diacrylate 10 g, hydrogenated bisphenol A epoxy resin 19 g, 1,4-butanediol diglycidyl ether 20 g, 3-ethyl-3-[(2-ethylhexyloxy)methyl]epoxybutane (CAS: 298695-60-0) 5 g, 9,10-dibutoxyanthracene 1.5 g, and IRGACURE 250 4 g. The above components were sequentially added to a double planetary dynamic mixing stirrer, vacuumed to a vacuum degree of -0.08 MPa, stirred at 500 rpm for 2 hours, uniformly stirred, naturally air-dried to room temperature, and sealed and packaged.

[0038] The performance of the high-reliability UV adhesive for a polarizing sheet of the present application was tested by the following test.

[0039] Test Example Performance Test

[0040] Curing light source 1: 385 nm LED lamp, light intensity 500 mW / cm 2 , irradiation time 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:

[0045] Table 1 Test results of the samples prepared by Examples 1-5 and common UV glue

[0046]

[0047]

[0048] From the above results, it can be seen that the high-reliability UV glue for polarizing plate of the present application has higher adhesive strength to COP film, non-decay of adhesion over time, and good optical yellowing advantage compared with the existing common UV glue.

[0049] The above description is merely preferred embodiments of the present application, and not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A high-reliability UV adhesive for polarizing plates, consisting of the following raw materials in weight percentage: Cycloaliphatic epoxy resin 25-55%, dicyclopentadiene acrylate monomer 3-15%, acrylic 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%; the acrylic modified castor oil epoxy resin molecular formula as follows: 。 2. The high-reliability UV adhesive for a polarizing plate according to claim 1, characterized by comprising: The synthesis route of the acrylic modified castor oil epoxy resin: castor oil epoxy resin, acrylic acid, triphenylphosphine are added to a three-necked flask, heated to 110-130℃, after 3-4 hours of reaction, test the acid value, when the acid value is less than 0.2, the reaction is completed, and the acrylic modified castor oil epoxy resin is obtained; the reaction formula is shown as follows: 。 3. The high-reliability UV adhesive for a polarizing plate according to claim 1, characterized by comprising: The glycidyl ether type epoxy compound is prepared by reacting a polyhydric phenol or a polyhydric alcohol with an epichlorohydrin.

4. The high-reliability UV adhesive for a polarizing plate according to claim 1, characterized by comprising: The adhesion promoter is 2-(3,4-epoxy cyclohexyl) ethyl triethoxysilane, CAS number: 10217-34-2; the sensitizer includes one of anthracene derivatives, benzoin derivatives, and benzophenone; the photoacid generator is a sulfonium salt or iodonium salt cationic photoinitiator.

5. The method for preparing high-reliability UV glue for polarizing plates according to claim 1, characterized in that, Comprise: Take cycloaliphatic epoxy resin 25-55%, dicyclopentadiene acrylate monomer 3-15%, acrylic 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%; sequentially added into a blender, vacuum to a vacuum degree of -0.08 to -0.05 MPa, stirred at 500-1000 rpm for 0.5-2 hours, uniformly stirred, naturally air dried to room temperature, sealed packaging.

Images