Liquid optical cement as well as preparation method and application thereof

Abstract

The invention provides a liquid optical adhesive as well as a preparation method and application thereof. The liquid optical adhesive is prepared from the following raw materials in parts by weight: 20-50 parts of active oligomer, 50-80 parts of functional monomer and 0.5-3 parts of photoinitiator, wherein the active oligomer comprises urethane acrylate; and the viscosity of the polyurethane acrylate at the temperature of 25 DEG C is 25000 to 35000 mPa. S. Through selection and compounding of all the components, the prepared liquid optical cement has relatively low viscosity, high curing speed and good bending resistance, and can meet the use requirements of OLED module bending protection and mobile phone bending areas.

Description

Technical Field

[0001] This invention belongs to the field of adhesive technology, and particularly relates to a liquid optical adhesive, its preparation method and application. Background Technology

[0002] With the rapid development of consumer electronics, automotive displays, and smart wearables, the requirements for thinner and lighter displays, higher reliability, and superior optical performance are increasing. In the lamination assembly of these devices, especially in the bending area of ​​OLED modules in foldable / rollable devices (such as foldable phones and tablets), optical adhesives with high light transmittance, low haze, excellent weather resistance, and reliable adhesion are required.

[0003] Traditionally, solid optical adhesive tape (OCA) has been primarily used. OCA is a pre-made dry film of specific thickness and size, which is then bonded using hot pressing and roll forming processes. While OCA exhibits stable optical performance, it has significant limitations: OCA bonding requires pre-cutting into sheets corresponding to the screen size, and the process involves hot roll forming. To prevent air bubbles during bonding, vacuum degassing is necessary, making the process complex. Defective products are difficult to rework, resulting in low yield and significantly increased production costs. Secondly, OCA has stringent requirements for the flatness of the bonding surface, and air bubbles are easily generated when bonding to curved or irregularly shaped structures. Furthermore, once bonding fails, it is difficult to peel off and rework, leading to material waste, reduced production yield, and high overall production costs.

[0004] To overcome the shortcomings of OCA (Optical Cordless Acrylic Acid), UV-curable liquid optical adhesive (LOCA) was developed. Also known as optical UV adhesive or ultraviolet light curable adhesive, LOCA is a single-component, low-viscosity UV-curable adhesive. Compared to traditional OCA optical adhesives, LOCA's advantages lie primarily in its curing method and process control. Firstly, LOCA cures quickly and is inexpensive, eliminating the need for hot pressing, vacuum degassing, and roller flattening required for optical tape bonding, thus saving significant space and energy. Secondly, the process control is superior. As a liquid optical adhesive at room temperature, it is fluid and suitable for bonding surfaces of various sizes and shapes. After bonding, it automatically forms a film between the two surfaces. Furthermore, LOCA cures into a gel-like state, allowing for easy separation of the bonding surfaces. After removing the gel, it can still be used in production, meeting rework requirements and increasing the bonding yield to over 95%, even reaching 98%. The main bonding process of LOCA involves dispensing, bonding, leveling, curing, testing, and packaging. It requires less equipment, is simple to operate, and is easier to mass-produce.

[0005] However, existing LOCA still faces the following technical bottlenecks in application: (1) To ensure that the cured adhesive layer has sufficient mechanical strength and heat resistance, it is often necessary to use prepolymers with higher molecular weight or add reinforcing fillers, which results in a high initial viscosity of the adhesive. The high viscosity adhesive has a slow leveling and filling speed after dispensing, making it difficult to quickly and perfectly fill micron-level slits or the bending area of ​​the mobile phone; (2) In the bending area of ​​the folding screen, LOCA is required to have a sufficiently high modulus to support the screen structure after curing, and it must also have excellent flexibility and bending resistance. Existing LOCA sacrifices flexibility while increasing crosslinking density and modulus, resulting in brittle fracture during bending; while excessive pursuit of flexibility will reduce the modulus and fail to provide effective support; (3) There is an inherent contradiction between the need for fast curing and sufficient curing. If the curing speed is too fast, the surface may be cured while the bottom layer is not dry. If the light exposure time is extended or post-curing is relied upon to ensure deep curing, it will seriously restrict production efficiency.

[0006] Therefore, developing a liquid optical adhesive with low viscosity, fast curing speed, and flexural strength is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a liquid optical adhesive, its preparation method, and its application. By selecting and compounding each component in specific amounts, the present invention enables the prepared liquid optical adhesive to have low viscosity, fast curing speed, suitable modulus, low glass transition temperature, and good bending resistance, thus meeting the requirements for bending protection of OLED modules and use in the bending areas of mobile phones.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a liquid optical adhesive, wherein the raw materials for preparing the liquid optical adhesive comprise the following components by weight:

[0010] 20-50 parts of active oligomer

[0011] 50-80 parts of functional monomer

[0012] Photoinitiator 0.5-3 parts;

[0013] The active oligomers include polyurethane acrylates;

[0014] The viscosity of the polyurethane acrylate at 25°C is 25000-35000 mPa·s.

[0015] In this invention, polyurethane acrylate is selected as the active oligomer, which has high elongation at break and flexibility, giving LOCA excellent bending resistance. Simultaneously, polyurethane acrylate can form physical crosslinking points through hydrogen bonding, improving the strength and modulus of LOCA, enabling it to possess sufficient strength while maintaining good flexibility, providing reliable support. The polar bonds in its molecules can form strong van der Waals forces or hydrogen bonds with the substrate surface, further improving the adhesion performance of LOCA. Blending with suitable functional monomers can reduce the viscosity of the LOCA system, ensuring that LOCA can fill the small gaps in the display module, eliminating air bubbles and forming a defect-free, uniform adhesive layer. By selecting and blending the components in specific amounts, this invention produces LOCA with low viscosity, fast curing speed, suitable modulus, low glass transition temperature, and good bending resistance, meeting the requirements for bending protection in OLED modules and use in the bending areas of mobile phones.

[0016] The amount of the active oligomer can be 20 parts, 22 parts, 24 parts, 26 parts, 28 parts, 30 parts, 32 parts, 34 parts, 36 parts, 38 parts, 40 parts, 42 parts, 44 parts, 46 parts, 48 ​​parts, or 50 parts, etc.

[0017] The amount of the functional unit can be 50, 52, 54, 56, 58, 60, 62, 64, 66, 68, 70, 72, 74, 76, 78 or 80 parts, etc.

[0018] The amount of the photoinitiator can be 0.5 parts, 1 part, 1.5 parts, 2 parts, 2.5 parts, or 3 parts, etc.

[0019] The viscosity of the polyurethane acrylate at 25°C can be 25000 mPa·s, 26000 mPa·s, 27000 mPa·s, 28000 mPa·s, 29000 mPa·s, 30000 mPa·s, 31000 mPa·s, 32000 mPa·s, 33000 mPa·s, 34000 mPa·s, or 35000 mPa·s, etc.

[0020] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The purpose and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0021] Preferably, the Young's modulus of the polyurethane acrylate is 0.8-1.2 MPa, such as 0.8 MPa, 0.9 MPa, 1 MPa, 1.1 MPa or 1.2 MPa.

[0022] Preferably, the weight-average molecular weight of the polyurethane acrylate is 25,000-30,000, such as 25,000, 26,000, 27,000, 28,000, 29,000 or 30,000.

[0023] Preferably, the glass transition temperature of the polyurethane acrylate is -25 to -15°C, such as -25°C, -23°C, -21°C, -19°C, -17°C, or -15°C.

[0024] Preferably, the polyurethane acrylate includes sartoma CN9021.

[0025] Preferably, the viscosity of the liquid optical adhesive at 25°C is ≤100 mPa·s, such as 50 mPa·s, 55 mPa·s, 60 mPa·s, 65 mPa·s, 70 mPa·s, 75 mPa·s, 80 mPa·s, 85 mPa·s, 90 mPa·s, 95 mPa·s, or 100 mPa·s.

[0026] Preferably, the functional monomer includes a monofunctional reactive diluent and / or a polyfunctional reactive diluent.

[0027] Preferably, the monofunctional reactive diluent comprises 2-phenoxyethyl acrylate and / or monofunctional polyurethane acrylate.

[0028] Preferably, the multifunctional reactive diluent comprises any one or a combination of at least two of 1,6-hexanediol diacrylate, propane trimethylol triacrylate, or polyether polyurethane acrylate.

[0029] Preferably, the photoinitiator comprises any one or a combination of at least two of the following: 2,2-dimethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, (2,4,6-trimethylbenzoyl)diphenylphosphine oxide, hydroxycyclohexylphenyl ketone, diphenyl-(2,4,6-trimethylbenzoyl)phosphine oxide, ethyl 2,4,6-trimethylbenzoylphenylphosphonate, 2,4,6-trimethylbenzoyl-di(p-tolyl)phosphine oxide, methyl diethanolamine, 2-isopropylthioxanthone, or methyl acetophenone.

[0030] In a second aspect, the present invention provides a method for preparing the liquid optical adhesive as described in the first aspect, the method comprising the following steps:

[0031] The active oligomer, functional monomer and photoinitiator are mixed and cured to obtain the liquid optical adhesive.

[0032] Preferably, the mixing is carried out under light-protected conditions.

[0033] Preferably, the mixing is carried out at room temperature.

[0034] Preferably, the mixing method includes stirring.

[0035] Preferably, the stirring time is 2-3 hours, such as 2 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours, or 3 hours.

[0036] Preferably, the curing is carried out under ultraviolet light.

[0037] Preferably, the curing time is 20-30s, such as 20s, 21s, 22s, 23s, 24s, 25s, 26s, 27s, 28s, 29s or 30s.

[0038] In a second aspect, the present invention provides an application of liquid optical adhesive as described in the first aspect in OLED modules.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] The liquid optical adhesive prepared by this invention has a low viscosity (between 80-100 mPa·s), a fast curing speed (≤30 s), a modulus of 0.5-0.7 MPa at room temperature, and a low Tg. g With good flexibility, it can effectively absorb and buffer the stress generated when the OLED module is bent, thus protecting the OLED module. The modulus at low temperature is 150-160MPa, which ensures that the adhesive layer has sufficient cohesive strength and support at low temperature, fully meeting the needs of OLED bending area protection and mobile phone bending area use. Detailed Implementation

[0041] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0042] The source information of some raw materials in this embodiment of the invention is as follows:

[0043] Polyurethane acrylate: Sartoma, CN9021;

[0044] Monofunctional polyurethane acrylate: Nanjing Beiyue, BY-120;

[0045] Polyether polyurethane acrylate A: Nanjing Beiyue, BY-119;

[0046] Polyether polyurethane acrylate B: Nanjing Beiyue, BY-268;

[0047] Trimethylbenzoyl-diphenylphosphine oxide (TPO): Shanghai Maclean;

[0048] 1-Hydroxycyclohexylphenyl ketone (184): Shanghai Maclean;

[0049] Methyldiethanolamine (GC-407): Guangchuan Electronic Materials Co., Ltd.;

[0050] 2-Isopropylthioxanthone (GC-406): Guangchuan Electronic Materials Co., Ltd.;

[0051] Phenylenol bis(2,4,6-trimethylbenzoyl)phosphine oxide (BAPO): Guangchuan Electronic Materials Co., Ltd.

[0052] Example 1

[0053] This embodiment provides a liquid optical adhesive and its preparation method. The raw materials for preparing the liquid optical adhesive include the following components by weight:

[0054] Polyurethane acrylate: 25 parts;

[0055] Monofunctional polyurethane acrylate: 50 parts;

[0056] Polyether polyurethane acrylate A: 12 parts;

[0057] Polyether polyurethane acrylate B: 4 parts;

[0058] 1-Hydroxycyclohexylphenyl ketone: 0.5 parts;

[0059] Trimethylbenzoyl-diphenylphosphine oxide: 1 part;

[0060] GC-460: 0.2 copies;

[0061] GC-407: 0.2 copies;

[0062] Phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide: 1 part;

[0063] The preparation method of the liquid optical adhesive includes the following steps:

[0064] Following the above formulation, polyurethane acrylate, monofunctional polyurethane acrylate, polyether polyurethane acrylate A, polyether polyurethane acrylate B, 1-hydroxycyclohexylphenyl ketone, trimethylbenzoyl-diphenylphosphine oxide, GC-460, GC-407, and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide were mixed and stirred at room temperature in the dark for 2 hours to obtain a polymer solution with a viscosity of 80 mPa·s. 9 mL of the polymer solution was then poured into a 10×10×0.5 cm... 3 After the polytetrafluoroethylene (PTFE) material has flowed and filled the mold, a high-pressure UV lamp (with a light energy of 3000 mJ / cm²) is placed inside. 2After being exposed to light for 30 seconds, a fully cured liquid optical adhesive was obtained.

[0065] Example 2

[0066] This embodiment provides a liquid optical adhesive and its preparation method. The raw materials for preparing the liquid optical adhesive include the following components by weight:

[0067] Polyurethane acrylate: 48 parts;

[0068] Monofunctional polyurethane acrylate: 60 parts;

[0069] Polyether polyurethane acrylate A: 8 parts;

[0070] Polyether polyurethane acrylate B: 11 parts;

[0071] 1-Hydroxycyclohexylphenyl ketone: 0.5 parts;

[0072] Trimethylbenzoyl-diphenylphosphine oxide: 0.8 parts;

[0073] GC-460: 0.7 copies;

[0074] GC-407: 0.2 copies;

[0075] Phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide: 0.6 parts;

[0076] The preparation method of the liquid optical adhesive includes the following steps:

[0077] Following the above formulation, polyurethane acrylate, monofunctional polyurethane acrylate, polyether polyurethane acrylate A, polyether polyurethane acrylate B, 1-hydroxycyclohexylphenyl ketone, trimethylbenzoyl-diphenylphosphine oxide, GC-460, GC-407, and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide were mixed and stirred at room temperature in the dark for 2.5 h to obtain a polymer solution with a viscosity of 91 mPa·s. 9 mL of the polymer solution was then poured into a 10×10×0.5 cm... 3 After the polytetrafluoroethylene (PTFE) material has flowed and filled the mold, a high-pressure UV lamp (with a light energy of 3000 mJ / cm²) is placed inside. 2 After being exposed to light for 28 seconds, a fully cured liquid optical adhesive was obtained.

[0078] Example 3

[0079] This embodiment provides a liquid optical adhesive and its preparation method. The raw materials for preparing the liquid optical adhesive include the following components by weight:

[0080] Polyurethane acrylate: 30 parts;

[0081] Monofunctional polyurethane acrylate: 50 parts;

[0082] Polyether polyurethane acrylate A: 4 parts;

[0083] Polyether polyurethane acrylate B: 7 parts;

[0084] 1-Hydroxycyclohexylphenyl ketone: 0.3 parts;

[0085] Trimethylbenzoyl-diphenylphosphine oxide: 0.4 parts;

[0086] GC-460: 0.6 copies;

[0087] GC-407: 0.5 copies;

[0088] Phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide: 0.8 parts;

[0089] The preparation method of the liquid optical adhesive includes the following steps:

[0090] Following the above formulation, polyurethane acrylate, monofunctional polyurethane acrylate, polyether polyurethane acrylate A, polyether polyurethane acrylate B, 1-hydroxycyclohexylphenyl ketone, trimethylbenzoyl-diphenylphosphine oxide, GC-460, GC-407, and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide were mixed and stirred at room temperature in the dark for 3 hours to obtain a polymer solution with a viscosity of 92 mPa·s. 9 mL of the polymer solution was then poured into a 10×10×0.5 cm... 3 After the polytetrafluoroethylene (PTFE) material has flowed and filled the mold, a high-pressure UV lamp (with a light energy of 3000 mJ / cm²) is placed inside. 2 After being exposed to light for 30 seconds, a fully cured liquid optical adhesive was obtained.

[0091] Example 4

[0092] The only difference from Example 1 is that polyether polyurethane acrylate B is replaced with an equal amount of trimethylolpropane triacrylate, while the amounts of other components and the preparation methods are the same as in Example 1.

[0093] Comparative Example 1

[0094] The only difference from Example 1 is that polyurethane acrylate CN9021 is replaced with an equal amount of polyester acrylate (Sartoma, CN2282), while the amounts of other components and the preparation methods are the same as in Example 1.

[0095] Comparative Example 2

[0096] The only difference from Example 1 is that polyurethane acrylate CN9021 is replaced with an equal amount of polysiloxane acrylic resin (Dearson, CERANATE series), while the amounts of other components and the preparation methods are the same as in Example 1.

[0097] Comparative Example 3

[0098] The only difference from Example 1 is that the amount of polyurethane acrylate used is 80 parts, while the amount of other components and the preparation method are the same as in Example 1.

[0099] Comparative Example 4

[0100] The only difference from Example 1 is that the amount of polyurethane acrylate used is 15 parts, while the amounts of the other components and the preparation methods are the same as in Example 1.

[0101] Performance test (1) Viscosity: Select the rotor of the No. 0 rotational viscometer, immerse the rotor vertically into the sample to the immersion mark on the rotor rod, start the instrument at a speed of 60 rpm, and record the data after the reading on the display screen stabilizes.

[0102] (2) Curing time: Touch the surface with your finger or polyethylene film at intervals until there are no adhesive marks, and record the time.

[0103] (3) Glass transition temperature (T) g Tested according to GB / T 19466.2-204.

[0104] (4) Modulus at room temperature / low temperature (-25℃): Tested in accordance with GB / T 45159.4-2025.

[0105] The liquid optical adhesives provided in the examples and comparative examples were tested according to the above performance testing methods, and the results are shown in Table 1:

[0106] Table 1

[0107]

[0108] As shown in Table 1, the liquid optical adhesives prepared in Examples 1-3 of this invention have low viscosity (between 80-100 mPa·s), fast curing speed (≤30 s), and a modulus of 0.5-0.7 MPa at room temperature, exhibiting low Tg. g With good flexibility, it can effectively absorb and buffer the stress generated when the OLED module is bent, thus protecting the OLED module. The modulus at low temperature is 150-160MPa, which ensures that the adhesive layer has sufficient cohesive strength and support at low temperature, fully meeting the needs of OLED bending area protection and mobile phone bending area use.

[0109] A comparison of Examples 1 and 4 shows that Example 4 uses a trifunctional reactive diluent. As the number of functional groups increases, the crosslinking density gradually increases, as does the viscosity and T. g Significantly increased, but flexibility and bending resistance decreased.

[0110] As can be seen from the comparison between Example 1 and Comparative Examples 1-2, after replacing polyurethane acrylate CN9021 with polyester acrylate or polysiloxane acrylic resin, the viscosity of Comparative Example 1 increased to 175 mPa·s and the curing time was extended to 42s, resulting in decreased coating processability and production efficiency. The viscosity of Comparative Example 2 decreased to 68 mPa·s and the curing time was delayed to 48s, with a low temperature modulus of only 128 MPa and insufficient cohesive strength. Neither of these results in a suitable application for the bending areas of OLEDs and mobile phones.

[0111] As can be seen from the comparison between Example 1 and Comparative Examples 3-4, if the amount of polyurethane acrylate used is too large (Comparative Example 3), the viscosity increases to 145 mPa·s, and the T0... g When the temperature is increased to 8.5℃, the room temperature modulus increases to 0.9MPa, but the flexibility and bending cushioning ability decrease. If the amount of polyurethane acrylate is too small (Comparative Example 4), the low temperature modulus drops to 122MPa, the curing time is extended to 36s, the cohesive strength and curing efficiency decrease, and neither can meet the usage requirements.

[0112] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A liquid optical adhesive, characterized in that, The raw materials for preparing the liquid optical adhesive include the following components by weight: 20-50 parts of active oligomer 50-80 parts of functional monomer Photoinitiator 0.5-3 parts; The active oligomers include polyurethane acrylates; The viscosity of the polyurethane acrylate at 25°C is 25000-35000 mPa·s.

2. The liquid optical adhesive according to claim 1, characterized in that, The Young's modulus of the polyurethane acrylate is 0.8-1.2 MPa; Preferably, the weight-average molecular weight of the polyurethane acrylate is 25,000-30,000; Preferably, the glass transition temperature of the polyurethane acrylate is -25 to -15°C; Preferably, the viscosity of the liquid optical adhesive at 25°C is ≤100 mPa·s.

3. The liquid optical adhesive according to claim 1 or 2, characterized in that, The functional monomers include monofunctional reactive diluents and / or polyfunctional reactive diluents.

4. The liquid optical adhesive according to claim 3, characterized in that, The monofunctional reactive diluent includes 2-phenoxyethyl acrylate and / or monofunctional polyurethane acrylate; Preferably, the multifunctional reactive diluent comprises any one or a combination of at least two of 1,6-hexanediol diacrylate, propane trimethylol triacrylate, or polyether polyurethane acrylate.

5. The liquid optical adhesive according to any one of claims 1-4, characterized in that, The photoinitiator comprises any one or a combination of at least two of the following: 2,2-dimethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, (2,4,6-trimethylbenzoyl)diphenylphosphine oxide, hydroxycyclohexylphenyl ketone, diphenyl-(2,4,6-trimethylbenzoyl)phosphine oxide, ethyl 2,4,6-trimethylbenzoylphenylphosphonate, 2,4,6-trimethylbenzoyl-di(p-tolyl)phosphine oxide, methyl diethanolamine, 2-isopropylthioxanthone, or methyl acetophenone.

6. A method for preparing a liquid optical adhesive as described in any one of claims 1-5, characterized in that, The preparation method includes the following steps: The active oligomer, functional monomer and photoinitiator are mixed and cured to obtain the liquid optical adhesive.

7. The preparation method according to claim 6, characterized in that, The mixing was carried out under light-protected conditions; Preferably, the mixing is carried out at room temperature.

8. The preparation method according to claim 6 or 7, characterized in that, The mixing method includes stirring; Preferably, the stirring time is 2-3 hours.

9. The preparation method according to any one of claims 6-8, characterized in that, The curing is carried out under ultraviolet light; Preferably, the curing time is 20-30 seconds.

10. The application of a liquid optical adhesive as described in any one of claims 1-5 in an OLED module.

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