Anti-whitening optically clear adhesive

Abstract

The present invention relates to an anti-whitening optical clear adhesive. The raw materials for producing the optically clear adhesive comprise a base material and two kinds of monomers, the monomers are an ethoxylated polyol acrylate monomer and another polyol acrylate monomer, and the weight average molecular weight of the ethoxylated polyol acrylate monomer is from 500 to 3000 g / mol. The present invention also relates to a double-sided optical clear adhesive tape, comprising the optical clear adhesive. The anti-whitening property of the optically clear adhesive of the present invention is significantly improved.

Description

Anti- Whitening Optically Clear AdhesiveTECHNICAL FIELD

[0001] The present invention relates to the technical field of optically clear adhesive and optically clear adhesive tape, in particular to an anti-whitening optically clear adhesive.BACKGROUND

[0002] With the development of electronic devices, the use of display devices such as liquid crystal displays and input devices such as touch screens is becoming increasingly widespread. In these display and input devices, in order to ensure the proper use and performance of optical components therein, high transmittance optically clear adhesive (OCA optical adhesive) is required.

[0003] At present, the application fields and scenarios of electronic devices are continuously expanding, and the requirements for the OCA optical adhesive used therein are gradually increasing. It is necessary to maintain the high transparency and good adhesion of the OCA optical adhesive under various environments (high temperature and / or high humidity, sunlight irradiation, etc.). The transparency characteristic of the OCA optical adhesive can generally be evaluated by its light transmittance or whitening degree.

[0004] Therefore, it is necessary to develop an OCA optical adhesive with improved anti-whitening properties to meet the application requirements of the developing electronic devices.SUMMARY

[0005] An objective of the present invention is to provide an OCA optical adhesive, comprising two different polyol acrylate monomers, namely an ethoxylated polyol acrylate monomer with a weight average molecular weight (Mw) from 500 to 3000 g / mol and another polyol acrylate monomer. The combined use of the above twomonomers significantly improves the anti-whitening property of the OCA optical adhesive of the present invention.

[0006] Another objective of the present invention is to provide an OCA optical adhesive, comprising the above two different polyol acrylate monomers and a plasticizer, which can further improve the anti-whitening property of the OCA optical adhesive of the present invention.

[0007] A further objective of the present invention is to provide an OCA optical tape using the OCA optical adhesive with improved anti-whitening property.

[0008] The above-mentioned objectives of the present invention are achieved by the following technical solutions.

[0009] In one aspect, the present invention provides an OCA optical adhesive, the raw materials for producing the OCA optical adhesive comprise a base material and two kinds of monomers, the monomers are ethoxylated polyol acrylate monomers and another polyol acrylate monomer,

[0010] wherein the weight average molecular weight of the ethoxylated polyol acrylate monomer is from 500 to 3000 g / mol.

[0011] Optionally, the weight average molecular weight of the ethoxylated polyol acrylate monomer is from 600 to 2000 g / mol, preferably from 650 to 1600 g / mol, and more preferably 690 to 1500 g / mol.

[0012] Optionally, relative to the total weight of the base material in the OCA optical adhesive, the content of the ethoxylated polyol acrylate monomer is 2% to 20% by weight, preferably 5% to 15% by weight, and the content of the other polyol acrylate monomer is 2% to 5% by weight, preferably 2% to 4% by weight.

[0013] Optionally, the ethoxylated polyol acrylate monomer is a polyol acrylate monomer containing 5 to 40 ethoxy groups, preferably a polyol acrylate monomer containing 6 to 30 ethoxy groups, more preferably one or more of 6(ethoxy)trimethylolpropane triacrylate, 9(ethoxy)trimethylolpropane triacrylate, 15(ethoxy)trimethylolpropane triacrylate, 24(ethoxy)dipentaerythritol hexaacrylate; and / or, the other polyol acrylate monomer is one or more of pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate or dipentaerythritol hexaacrylate.

[0014] Optionally, the raw materials for producing the OCA optical adhesive further comprise a photo initiator, a thermal crosslinker or a coupling agent, and / or the base material is an acrylic adhesive.

[0015] Optionally, the raw materials for producing the OCA optical adhesive further comprise a plasticizer, preferably a sucrose resin.

[0016] Optionally, relative to the total weight of the base material of the OCA optical adhesive, the content of the plasticizer is 5% to 40% by weight, preferably 10% to 30% by weight.

[0017] Optionally, the plasticizer is a low- substituted sucrose benzoate.

[0018] Optionally, after being stored for 500 hours at 85°C and 85RH, the haze value at the center of the OCA optical adhesive is 0.1 or below, and the haze value at the edge is 2.0 or below; preferably, the haze value at the center of the OCA optical adhesive is 0.08 or below, and the haze value at the edge is 1.6 or below; after being stored for 800 hours at 85°C and 85RH, the haze value at the center of the OCA optical adhesive is 1.1 or below, and the haze value at the edge is 4.5 or below; preferably, the haze value at the center of the OCA optical adhesive is 0.15 or below, and the haze value at the edge is 2 or below.

[0019] In another aspect, the present invention provides a double-sided optical clear adhesive tape comprising the above-mentioned OCA optical adhesive.

[0020] The OCA optical adhesive according to the embodiment of the present disclosure can produce the following beneficial technical effects:

[0021] By replacing the common used OCA optical adhesive with the OCA optical adhesive provided by the present disclosure, the OCA optical adhesive can significantly improve its anti-whitening property without affecting the peeling force.DETAILED DESCRIPTION

[0022] To further clarify the objectives, technical solutions, and advantages of the embodiments of the present invention, the technical solutions of the present invention will be described clearly and completely below in conjunction with the following specific implementation methods. Obviously, the described specificembodiments are part of the embodiments of the present invention. Based on the described embodiments of the present invention, all other embodiments obtained by those skilled in the art without inventive effort fall within the protection scope of the present invention.

[0023] According to one aspect of the present disclosure, an OCA optical adhesive is provided, the raw materials for which comprise a base material and two kinds of monomers, the monomers are ethoxylated polyol acrylate monomers and another polyol acrylate monomer, wherein the weight average molecular weight of the ethoxylated polyol acrylate monomer is from 500 to 3000 g / mol.

[0024] Optionally, the weight average molecular weight of the ethoxylated polyol acrylate monomer can be from 550 to 2000 g / mol, preferably from 600 to 2000 g / mol, preferably from 650 to 1600 g / mol, more preferably from 690 to 1500 g / mol, more preferably from 690 to 1590 g / mol.

[0025] Optionally, relative to the total weight of the base material in the OCA optical adhesive, the content of the ethoxylated polyol acrylate monomer is 2% to 20% by weight, preferably 5% to 15% by weight, more preferably 7.5% to 10% by weight, and the content of the other polyol acrylate monomer is 2% to 5% by weight, preferably 2% to 4% by weight, more preferably 2% to 3% by weight.

[0026] Optionally, the ethoxylated polyol acrylate monomer may be a polyol acrylate monomer containing 5 to 40 ethoxy (EO) groups, preferably a polyol acrylate monomer containing 6 to 30 ethoxy groups, more preferably a polyol acrylate monomer containing 10 to 25 ethoxy groups. The ethoxylated polyol acrylate monomer according to the present invention includes, but is not limited to, one or more of 6(ethoxy)trimethylolpropane triacrylate (M3160), 9(ethoxy)trimethylol propane triacrylate (M3190), 15(ethoxy)trimethylolpropane triacrylate (M3150), 24(ethoxy)dipentaerythritol hexaacrylate (M6240) and the like. Specifically, the chemical formula of 9(ethoxy)trimethylolpropane triacrylate (M3190) is shown in formula I below:

[0027] formula I.

[0028] The chemical formula of 24(ethoxy)dipentaerythritol hexaacrylate(M6240) is shown in formula II below:

[0030] Optionally, the other polyol acrylate monomer includes, but is not limited to, one or more of pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate (DPHA), etc., preferably one of them.

[0031] Optionally, the base material may be an adhesive commonly used in OCA optical adhesive, for example, acrylic adhesives, epoxy adhesives, or silicone adhesives. Preferably, the adhesive is an acrylic water-based adhesive.

[0032] Optionally, the raw material for producing the OCA optical adhesive according to the present invention may comprise a photo initiator, which is a cleavagetype initiator. Preferably, the photo initiator comprises, but is not limited to, a low- yellowing cleavage-type photo initiator, such as one or more of phenyl bis(2,4,6- trimethylbenzoyl)phosphine oxide, diphenyl (2,4,6-trimethylbenzoyl)phosphine oxide, ethyl (2,4,6-trimethylbenzoyl) phenylphosphinate and 1-hydroxy-cyclohexyl- phenylketone.

[0033] Optionally, the raw materials for producing the OCA optical adhesive according to the present invention may further comprise a thermal crosslinking agent or a coupling agent. Specifically, the thermal crosslinking agent comprises, but is not limited to, isophorone diisocyanate (IPDI) and derivatives thereof, dicyclohexylmethane diisocyanate (HMDI) and derivatives thereof, hexamethylenediisocyanate (HDI) and derivatives thereof. The coupling agent comprises, but is not limited to, silane coupling agents, such as VTMO.

[0034] Optionally, raw materials for producing the OCA optical adhesive according to the present invention further include a plasticizer, preferably sucrose resin.

[0035] Optionally, relative to the total weight of the base material in the OCA optical adhesive, the content of the plasticizer is 5% to 40% by weight, preferably 10% to 30% by weight, preferably 15% to 30% by weight, and more preferably 20% to 30% by weight.

[0036] Optionally, the sucrose resin is a low- substituted sucrose benzoate having a molecular formula of Ci2Hi4O3(OH)8-n(C7H5O2)n. The degree of substitution of the low- substituted sucrose benzoate may be 5.5 or more, preferably 5.5-7.4, more preferably 6.0-6.9. Specifically, the resin according to the present invention includes, but is not limited to, sucrose benzoate and its derivatives. The above-mentioned degree of substitution refers to the average number of hydrogen atoms on the hydroxyl groups of the sucrose molecule being substituted during the synthesis of the sucrose resin. For example, in the synthesis of sucrose benzoate (see the formula III below for molecular structural), the average number of hydrogen atoms of 8 hydroxyl groups on the sucrose molecule being substituted by benzoic acid, if the degree of substitution is 7, it means that 7 out of the 8 hydroxyl groups on each sucrose molecule have hydrogen atoms substituted by benzoic acid on average. The degree of substitution can be calculated by measuring the content of hydroxyl groups in the sucrose benzoate compound obtained by the synthesis reaction by the phenolphthalein titration method, and then calculating the degree of substitution using the following formula:

[0037] Degree of substitution of sucrose benzoate =8-n(residual hydroxyl content)8

[0038] Formula III.

[0039] In one aspect, the present invention further provides an OCA optical adhesive tape using the OCA optical adhesive described above.

[0040] The OCA optical adhesive according to the embodiments of the present disclosure can produce the following beneficial technical effects: by using the OCA optical adhesive provided by the present invention, the OCA optical adhesive can have a significantly improved anti-whitening property while having a comparable bonding property.

[0041] Examples

[0042] The examples of the present invention are merely illustrative descriptions of the technical solutions of the present invention, but do not mean that the technical solutions of the present invention are limited to these specific examples.

[0043] The examples of the present invention use the following test method to test the anti-whitening property and peel adhesion of the OCA optical adhesive.

[0044] 1 , Test Methods

[0045] 1.1 Test Method for Anti-Whitening Property

[0046] The OCA optical adhesive sample is assembled in a “glass - OCA optical adhesive - glass” structure. UV curing is performed from either side of the glass using a Honle CUBE400 curing device with a curing dose of 3000 mJ / cm2UVA, to obtain a cured OCA optical adhesive sample. The cured OCA optical adhesive sample was placed in a high-temperature and high-humidity chamber (85°C±1 °C temperature and 85%±5% relative humidity) for 500 hours and 800 hours of aging.

[0047] Subsequently, the haze values at the center and edges of the OCA optical adhesive sample are measured after aging for 500 hours and 800 hours, and the haze values were determined according to ASTMD1003.

[0048] 1.2 Test Method for Peel Adhesion

[0049] The OCA optical tape samples are cut into 20cmx20mm (length*width) strip samples. The spacer on one side of the strip sample is removed, and the adhesive surface is rolled onto transparent PET (50pm thick) of 30cmx25mm (lengthx width). The spacer on the other side of the strip sample is then removed, and the corresponding OCA adhesive surface is rolled onto the acetone-cleaned test glass. A 4kg steel roller is used to roll back and forth on the PET for 5 times, at a rolling speed of lOm / min, to obtain the test sample. Subsequently, the test sample is placed in a UV curing device, and UV curing is performed from the transparent PET side, at a curing dose of 3000 mJ / cm2UVA.

[0050] After standing at 23°C±1°C and 50%±5% relative humidity for 20 minutes, the test sample is inserted into a Zwick Roell tensile tester to allow the test sample to peel at an angle of 180°. The peel adhesion is measured using this tester (sensor: 100 N) at a speed of 300 mm / min. The test results for each sample are represented by the average of three measurements (N / cm).

[0051] 1.3 Test Method for weight average molecular weight

[0052] The weight-average molecular weight (Mw) is measured by Gel Permeation Chromatography (GPC). Mw is determined using an Agilent GPC 1260 Infinity II system. The column used is a MIX column, PLgel MIXED-B LS. Tetrahydrofuran (THF) is used as the mobile phase, and the test is conducted at 30 °C. The Mw of the test sample is calculated based on polystyrene standards with known Mw.

[0053] Z Raw Materials and Preparation Process

[0054] 2.1 Raw Materials Used

[0055] The raw materials used in the examples and comparative examples of the present invention and their abbreviations, and details are shown in Table 1 below.

[0056] Table 1. Raw materials used in the examples and comparative examples of the present invention

[0057] 2,2 Preparation Process

[0058] (1) Preparation Process of OCA Optical Adhesive

[0059] An ethoxylated polyol acrylate monomer (monomer 1), a polyol acrylate monomer (monomer 2), a photoinitiator and a coupling agent are added to the acrylic copolymer, and the mixture is stirred at a stirring speed of 600 rpm for 30-45 minutes to ensure thorough mixing of all components, obtaining the OCA optical adhesive.

[0060] (2) Preparation Process of OCA Optical Tape

[0061] The above-mentioned OCA optical adhesive is coated on the spacer to form an OCA optical adhesive layer with a thickness of 100pm, resulting in a singlesided adhesive spacer. The single-sided adhesive spacer is then placed in an oven and dried at 120°C for 4 minutes to volatilize the solvent. After the drying process, anotherspacer is covered on the other side of the adhesive layer, to obtain a double-sided OCA optical tape with a thickness of 100pm.

[0062] 3, Examples and Comparative Examples

[0063] Example 1

[0064] Relative to the total weight of the acrylic copolymer (JR21), 5wt% of 9(ethoxy)trimethylolpropane triacrylate (M3190), 2.5wt% of dipentaerythritol hexaacrylate (DPHA), 2wt% of vinyltrimethoxysilane (VTMO) and 0.5wt% of ethyl (2,4,6-trimethylbenzoyl) phenylphosphinate (TPO-L) were added. The mixture is stirred at a stirring speed of 600 rpm for 30-45 minutes to ensure thorough mixing, to obtain an OCA optical adhesive.

[0065] The OCA optical adhesive was coated onto a polyethylene terephthalate spacer (RF12N D75) to form an OCA optical adhesive layer with a thickness of 100pm, resulting in a single-sided adhesive spacer. The single-sided adhesive spacer is placed in an oven and dried at 120°C for 4 minutes to volatilize the solvent. After the drying process was completed, a polyethylene terephthalate spacer (RF02N D50) is covered on the other side of the adhesive layer, to obtain a double-sided OCA optical tape with a thickness of 100pm.

[0066] Example 2

[0067] Except for the addition amount of 9(ethoxy)trimethylolpropane triacrylate (M3190) was 7.5wt%, the preparation steps were the same as those in Example 1.

[0068] Example 3

[0069] Except for the addition amount of 9(ethoxy)trimethylolpropane triacrylate (M3190) was 10wt%, the preparation steps were the same as those in Example 1.

[0070] Example 4

[0071] Relative to the total weight of the acrylic acid copolymer (JR21), 5wt% of 24(ethoxy)dipentaerythritol hexaacrylate (M6240), 2.5wt% of dipentaerythritol hexaacrylate (DPHA), 2wt% of vinyltrimethoxysilane (VTMO) and 0.5wt% of ethyl (2,4,6-trimethylbenzoyl) phenylphosphinate (TPO-L) were added to the acrylic acid- io -copolymer (JR21). The mixture is stirred at a stirring speed of 600 rpm for 30-45 minutes to obtain an OCA optical adhesive.

[0072] The preparation steps for the double-sided OCA optical tape were the same as those in Example 1.

[0073] Example 5

[0074] Relative to the total weight of the acrylic acid copolymer (JR21), 5wt% of 9(ethoxy)trimethylolpropane triacrylate (M3190), 2.5wt% of dipentaerythritol hexaacrylate (DPHA), 2wt% of vinyltrimethoxysilane (VTMO) and 0.5wt% of ethyl (2,4,6-trimethylbenzoyl) phenylphosphinate (TPO-L) were added to the acrylic acid copolymer (JR21). The mixture is stirred at a stirring speed of 600 rpm for 30-45 minutes to ensure thorough mixing, to obtain an adhesive composition. Subsequently, after 10wt% of plasticizer SB-III was dissolved in ethyl acetate solvent at a ratio of 1 : 1, SB-III ethyl acetate solvent was added to the mixed adhesive composition, and further stirred and mixed to obtain OCA optical adhesive.

[0075] The preparation steps for the double-sided OCA optical tape were the same as those in Example 1.

[0076] Example 6

[0077] Except for the addition amount of the tackifying resin SB-III was 30wt%, the preparation steps were the same as those in Example 5.

[0078] Example 7

[0079] Except for replacing 9(ethoxy)trimethylolpropane triacrylate (M3190) with 24(ethoxy)dipentaerythritol hexaacrylate (M6240), the preparation steps were the same as those in Example 5.

[0080] Comparative Example 1

[0081] Except for replacing 9(ethoxy)trimethylolpropane triacrylate (M3190) with 3 (ethoxy )trimethylolpropane triacrylate (M3130), the preparation steps were the same as those in Example 1.

[0082] Comparative Example 2

[0083] Except for replacing 9(ethoxy)trimethylol propane triacrylate (M3190) with 24(ethoxy)dipentaerythritol hexaacrylate (M6240) and plasticizer SB-III wasreplaced with terpene phenol resin (TSR-1007), the preparation steps were the same as those in Example 5.

[0084] Comparative Example 3

[0085] Except for replacing 9(ethoxy)trimethylol propane triacrylate (M3190) with 24(ethoxy)dipentaerythritol hexaacrylate (M6240) and plasticizer SB-III was replaced with terpene phenol resin (TSR-1007), the preparation steps were the same as those in Example 6.

[0086] Table 2. Content of each component in the examples and comparative examples

[0087] T Influence of Different Component Contents on Peeling Adhesion and Anti-aging Properties of OCA Optical Adhesive

[0088] Table 3. Test Results of Adhesive Tape Properties in Examples and Comparative Examples

[0089] Based on the test results of Examples and Comparative Examples in Table 3, it can be seen that after aging for 500 hours and 800 hours, the haze values at the side of the OCA optical adhesives in Examples 1-4 of the present invention are significantly reduced compared with thoes of Comparative Example 1. It is evident that when the weight average molecular weight of the ethoxylated polyol acrylate monomer is lower than 500(Comparative Example 1), the haze values at the center and sides of the obtained OCA optical adhesive are excessively high after aging; while as the increase of the weight average molecular weight of the ethoxylated polyol acrylate monomer (Examples 1 and 4), the peeling adhesion and the haze values at the center and sides of the obtained OCA optical adhesive are further improved after aging.

[0090] Meanwhile, after further introducing sucrose resin (SB-III), the antiwhitening properties of the OCA optical adhesives of Examples 5-6 of the present disclosure after aging for 500 hours and 800 hours are further improved compared with those of Examples 1-4 (the haze values at the center and sides are further reduced). Furthermore, when the weight average molecular weight of the ethoxylated polyol acrylate monomer in Example 7 of the present invention is further increased, the antiwhitening property of the OCA optical adhesive containing plasticizer of the present invention can be further improved. In addition, compared with other resins used in Comparative Examples 2-3, the OCA optical adhesive with added sucrose resin in Examples 5-7 of the present invention exhibit better anti-whitening properties.

Claims

What is claimed is:

1. An optically clear adhesive, is characterized in that, the raw materials for producing the optically clear adhesive comprise a base material and two kinds of monomers, the monomers are ethoxylated polyol acrylate monomers and another polyol acrylate monomer, wherein the weight average molecular weight of the ethoxylated polyol acrylate monomer is from 500 to 3000 g / mol.

2. The optically clear adhesive according to claim 1, is characterized in that, the weight average molecular weight of the ethoxylated polyol acrylate monomer is from 600 to 2000 g / mol, preferably from 650 to 1600 g / mol, and more preferably from 690 to 1500 g / mol.

3. The optically clear adhesive according to claims 1 or 2, is characterized in that, relative to the total weight of the base material in the optically clear adhesive, the content of the ethoxylated polyol acrylate monomer is 2% to 20% by weight, preferably 5% to 15% by weight, and the content of the other polyol acrylate monomer is 2% to 5% by weight, preferably 2% to 4% by weight.

4. The optically clear adhesive according to any one of claims 1 to 3, is characterized in that, the ethoxylated polyol acrylate monomer is a polyol acrylate monomer containing 5 to 40 ethoxy groups, preferably a polyol acrylate monomer containing 6 to 30 ethoxy groups, more preferably one or more of 6(ethoxy) trimethylolpropane triacrylate, 9(ethoxy) trimethylolpropane triacrylate, 15(ethoxy) trimethylolpropane triacrylate, 24(ethoxy) dipentaerythritol hexaacrylate; and / or, the other polyol acrylate monomer is one or more of pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate or dipentaerythritol hexaacrylate.

5. The optically clear adhesive according to any one of claims 1 to 4, is characterized in that, the raw materials for producing the optically clear adhesive further comprise a photo initiator, a thermal crosslinker or a coupling agent, and / or the base material is an acrylic adhesive.

6. The optically clear adhesive according to any one of claims 1 to 5, is characterized in that, the raw materials for producing the optically clear adhesive further comprise a plasticizer, preferably a sucrose resin.

7. The optically clear adhesive according to claim 6, is characterized in that, relative to the total weight of the base material of the optically transparent adhesive, the content of the plasticizer is 5% to 40% by weight, preferably 10% to 30% by weight.

8. The optically clear adhesive according to claim 6 or 7, is characterized in that, the plasticizer is a low- substituted sucrose benzoate.

9. The optically clear adhesive according to any one of claims 1 to 8, is characterized in that, after being stored for 500 hours at 85°C and 85RH, the haze value at the center of the optically clear adhesive is 0.1 or below, and the haze value at the edge is 2.0 or below; preferably, the haze value at the center of the optically clear adhesive is 0.08 or below, and the haze value at the edge is 1.6 or below; after being stored for 800 hours at 85°C and 85RH, the haze value at the center of the optically clear adhesive is 1.1 or below, and the haze value at the edge is 4.5 or below; preferably, the haze value at the center of the optically clear adhesive is 0.15 or below, and the haze value at the edge is 2 or below.

10. A double-sided optically clear adhesive tape, is characterized in that, it comprises the optical clear adhesive according to claims 1 to 9.

Images