A multi-curing liquid crystal frame sealant and preparation method thereof

Abstract

The present invention relates to a multi-curing liquid crystal sealant. The multi-curing liquid crystal sealant comprises the following raw material components, calculated by mass percentage: 25-50% of a modified methacrylic resin, 25-50% of a siloxane-modified resin, 1-10% of hydrophobic silica, 1-5% of a silane coupling agent, 10-30% of an organic filler, 0.1-1% of a photoinitiator, 1-10% of a thermal curing agent, and 1-5% of a reactive diluent. The modified methacrylic resin is obtained by modifying a bisphenol A epoxy acrylate resin with caprolactone and has a molecular weight of 400-700 Da. The present invention uses the siloxane-modified resin as a main resin. On the basis of UV curing and thermal curing, the sealant is endowed with moisture curing capability. Simultaneously, Si-O-Si has excellent hydrophobicity, greatly improving the moisture resistance of the sealant. In addition, due to the introduction of long-chain siloxane, the flexibility of the resin is improved, thereby strengthening the adhesive strength of the sealant.

Description

Technical Field

[0001] The present invention relates to the technical field of adhesives, and in particular to a multi-curing liquid crystal frame sealing adhesive and a preparation method thereof. Background Art

[0002] As a core material in the ODF process, sealant securely bonds the TFT and CF substrate through UV or thermal curing, ensuring uniform thickness of the LCD layer and a stable panel structure. Its dense resin network, synergistically working with fillers, effectively blocks the infiltration of moisture, dust, and other external factors, preventing contamination and degradation of the LCD, and guaranteeing the long-term reliability of the display device. Its material properties, such as low shrinkage and resistance to high temperatures and humidity, directly determine panel yield and display quality. Especially in flexible displays and narrow-bezel designs, sealant requires both flexibility and ultra-thin sealing capabilities, driving display technology towards thinner, lighter, and more environmentally adaptable displays. It is a key enabler for efficient manufacturing and breakthrough performance of modern LCD panels.

[0003] In the prior art, the typical curing methods for liquid crystal display frame glue are UV curing, thermal curing, and UV+thermosetting dual curing. The advantage of simple UV curing frame glue is that it can quickly complete curing and reduce contamination of the liquid crystal, but its fatal disadvantage is insufficient adhesion. Simple thermosetting frame glue has excellent adhesion after curing because the main resin is epoxy resin. However, since the thermal curing reaction time is usually about 1 hour, the uncured frame glue is in contact with the liquid crystal for a long time, which will inevitably cause liquid crystal contamination and liquid crystal puncture, seriously affecting the process manufacturing. In this context, UV+thermosetting has become the mainstream curing method for liquid crystal frame glue, which can effectively balance the balance between liquid crystal contamination and adhesion. However, since the UV curing rate is usually less than 95% and the thermal curing rate is usually less than 85%, it is difficult to maintain performance for a long time under high temperature and high humidity conditions. This becomes a hidden danger for long-term use of the product, especially in areas with extreme weather, and cannot meet the needs of long-term use. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a multi-curing liquid crystal frame sealant.

[0005] To achieve the above-mentioned object, the technical solution adopted by the present invention is: a multi-curing liquid crystal frame sealant, which comprises the following raw material components, calculated by weight percentage: 25-50% modified methacrylic resin, 25-50% siloxane-modified resin, 1-10% hydrophobic silica, 1-5% silane coupling agent, 10-30% organic filler, 0.1-1% photoinitiator, 1-10% thermal curing agent and 1-5% reactive diluent, wherein the modified methacrylic resin is obtained by caprolactone-modified bisphenol A epoxy acrylate resin and has a molecular weight between 400-700 Da. The structural formula of the siloxane-modified resin is as follows:

[0006] ,

[0007] Wherein, R1 is -OCH3 or -OC2H5; R2 is -CH2(CH2) n CH3, n is 6-16.

[0008] As a specific embodiment, the structural formula of the active diluent is as follows:

[0009] ,

[0010] Where n is 3-5, R is 、 or .

[0011] As a specific embodiment, the organic filler is any one of polyester particles, polystyrene particles, and polyacrylic acid particles.

[0012] As a specific embodiment, the photoinitiator is at least one of benzophenone compounds, acetophenone compounds, acylphosphine oxide compounds, titanocene compounds, and oxime ester compounds.

[0013] As a specific implementation, the thermal curing agent is a hydrazide curing agent.

[0014] As a specific embodiment, the hydrophobic silica is selected from any one of the brands R8200 and R972 produced by Evonik of Germany.

[0015] As a specific embodiment, the mass ratio of the modified methacrylic resin to the silicone modified resin is 1:0.25-1:3. Preferably, the mass ratio of the modified methacrylic resin to the silicone modified resin is 1:1-1:2.5.

[0016] Another object of the present invention is to provide a method for preparing the above-mentioned multi-curing liquid crystal frame sealant, comprising the following steps:

[0017] Add the raw materials of each component into a mixing tank according to the above weight ratio, place it in a planetary mixer and stir for 30-40 minutes to mix the components evenly, and control the temperature below 28°C. Then use a three-roll grinder for grinding, with the gap between the three-roller feed port rollers being 10μm and the gap between the three-roller discharge port rollers being less than 5µm. Grind thoroughly to obtain the required frame sealing glue.

[0018] Due to the application of the above technical solution, the present invention has the following advantages over the prior art: the frame sealant of the present invention uses a siloxane-modified resin as the main resin, which, on the basis of UV curing and thermal curing, gives the frame sealant the ability to cure in moisture. At the same time, Si-O-Si has good hydrophobicity, which greatly improves the moisture resistance of the frame sealant. Moreover, due to the introduction of long-chain siloxane, the flexibility of the resin is improved, which strengthens the adhesion of the frame sealant. At the same time, the active diluent used in the present invention will also participate in the reaction, which can further increase the cross-linking density of the frame sealant as a whole, thereby improving the moisture resistance and adhesion of the frame sealant. In addition, the modified methacrylic resin used in the present invention is a caprolactone-modified bisphenol A epoxy acrylate resin with a molecular weight of 400-700 Da. By introducing the polyester chain segment of caprolactone, the free rotation ability of the CC bond is increased, breaking the rigid benzene ring structure of the bisphenol A epoxy acrylate. At the same time, the hydrophobic ester bond structure of caprolactone can effectively block the penetration of water molecules, which is beneficial to improving the overall adhesion and moisture permeability of the frame sealant.

[0019] The active diluent used in the present invention can not only react with the resin to form a tighter network structure during the reaction, but also introduce a hydrophobic Si-O-Si structure, which is beneficial to improving the overall performance of the sealant. DETAILED DESCRIPTION

[0020] The technical solution of the present invention is further described below with reference to specific embodiments.

[0021] The present invention provides a multi-curing liquid crystal frame sealant, which comprises the following raw material components, calculated by mass percentage: 25-50% modified methacrylic resin, 25-50% siloxane-modified resin, 1-10% hydrophobic silica, 1-5% silane coupling agent, 10-30% organic filler, 0.1-1% photoinitiator, 1-10% thermal curing agent, and 1-5% reactive diluent. The modified methacrylic resin is obtained by caprolactone-modified bisphenol A epoxy acrylate resin and has a molecular weight between 400 and 700 Da. The structural formula of the siloxane-modified resin is as follows:

[0022] ,

[0023] Wherein R1 is -OCH3; R2 is -CH2(CH2) 10 CH3.

[0024] The reactive diluents used in the following examples have the following structural formula:

[0025] ,

[0026] Where n is 3-5, R is 、 or . Example 1

[0027] This example provides a multi-curing liquid crystal frame sealant. Taking the total mass of the frame sealant as 100%, the frame sealant includes the following raw material components: 30% modified methacrylic resin, 45% siloxane modified resin, 3% reactive diluent, 1.5% silane coupling agent, 2% hydrophobic silica, 15% organic filler, 0.5% photoinitiator, and 3% thermal curing agent.

[0028] In this embodiment, the purchase information of each raw material is as follows:

[0029] Modified methacrylic resin: purchased from Allnex Resins (China) Co., Ltd., brand EBECRYL 3605;

[0030] Active diluent: purchased from DESINGER MOLECULES INC, brand CS783;

[0031] Silane coupling agent: purchased from Momentive, brand A-186;

[0032] Hydrophobic silica: purchased from Evonik, brand: R8200;

[0033] Organic filler: purchased from Suzhou Nanovitamin Life Science Technology Co., Ltd., brand LXDNP-200;

[0034] Thermal curing agent: adipic acid dihydrazide, purchased from Ajinomoto Co., Ltd., brand ADH;

[0035] Photoinitiator: 2-hydroxy-2-methyl-1-phenylpropanone, purchased from Valley Technology, brand 1173.

[0036] The preparation method of the liquid crystal frame sealant comprises the following steps:

[0037] The raw materials of each component are added to a mixing tank according to the above-mentioned weight ratio, placed in a planetary mixer and stirred for 30 minutes to mix the components evenly, and the temperature is controlled below 28°C. Then, a three-roll grinder is used for grinding, and the gap between the rollers at the feed port of the three rollers is 10 μm, and the gap between the rollers at the discharge port is less than 5 μm. The frame sealing glue is obtained by sufficient grinding. Example 2

[0038] Compared with Example 1, the difference between this example is that the mass ratio of the modified methacrylic resin to the silicone modified resin is 1:1, and the contents of the other components are also the same. Example 3

[0039] Compared with Example 1, the difference between this example is that the mass ratio of the modified methacrylic resin to the silicone modified resin is 1:2, and the contents of the other components are also the same. Example 4

[0040] Compared with Example 1, the difference between this example is that the mass ratio of the modified methacrylic resin to the silicone modified resin is 1:2.5, and the contents of the other components are also the same. Example 5

[0041] Compared with Example 1, the difference between this example is that the mass ratio of the modified methacrylic resin to the silicone modified resin is 1:0.5, and the contents of the other components are also the same. Example 6

[0042] Compared with Example 1, the difference between this example is that the mass ratio of the modified methacrylic resin to the silicone modified resin is 1:0.25, and the contents of the other components are also the same. Example 7

[0043] Compared with Example 1, the difference between this example is that the mass ratio of the modified methacrylic resin to the silicone modified resin is 1:3, and the contents of the other components are also the same. Example 8

[0044] The difference between this example and Example 1 is that the types of hydrophobic silica used in the two examples are different. The hydrophobic silica used in this example was purchased from Evonik and has the brand name R972.

[0045] Comparative Example 1

[0046] Compared with Example 1, the difference between this example is that the siloxane modified resin in the liquid crystal frame sealant is completely replaced by modified methacrylic resin, accounting for 75%, and the rest is the same as Example 1.

[0047] Comparative Example 2

[0048] Compared with Example 1, the difference between this example is that 30% of the modified acrylate and 45% of the silicone modified resin in the liquid crystal frame sealant are all replaced by epoxy resin, accounting for 75%. The rest is the same as Example 1.

[0049] In this comparative example, the purchasing information of each raw material is as follows:

[0050] Epoxy resin: Bisphenol A epoxy resin was used, purchased from Nan Ya Resins, brand 128E;

[0051] Comparative Example 3

[0052] Compared with Example 1, this example differs in that 45% of the siloxane-modified resin in the liquid crystal frame sealant is replaced with the bisphenol A epoxy resin used in Comparative Example 2, and the rest is the same as Example 1.

[0053] Comparative Example 4

[0054] The difference between this example and Example 1 is the choice of active diluent. In this example, the active diluent used is , purchased from Hunan Servi New Material Technology Co., Ltd., brand JRD-130P (different from Example 1 in structure).

[0055] Comparative Example 5

[0056] This example differs from Example 1 in the choice of silica. In this example, hydrophilic silica was used, purchased from Evonik, brand R106. The preparation method for the liquid crystal frame sealant in this example was the same as in Example 1.

[0057] All the embodiments and comparative examples have the same preparation method of the liquid crystal frame sealant.

[0058] Performance Testing

[0059] The liquid crystal frame sealants described in Examples 1-8 and Comparative Examples 1-5 were subjected to the following tests:

[0060] 1) Room temperature adhesion: Place a tiny drop of the liquid crystal sealant on one of two 30×40 mm glass sheets with polyimide (PI) films, and place the other glass test piece on top of the other piece in a cross-shaped pattern, pressing to ensure complete adhesion. 2 Irradiate with a metal halide UV lamp and heat at 120°C for 60 minutes to obtain an adhesive test piece. The adhesive test piece is subjected to a tensile test (2 mm / sec) using the clamps provided above and below. Divide the measured value (N) by the cross-sectional area of ​​the seal coating (mm 2 ) The value obtained is the bonding strength of the adhesive;

[0061] 2) Post-PCT adhesion: Following the sample preparation method for room temperature bonding, the prepared sample was placed in a PCT test chamber and placed at 121°C, 100% humidity and 2 atm pressure for 24 hours to test the sample adhesion.

[0062] 3) Long-term moisture permeability: Use a coating machine to apply the liquid crystal sealant to a thickness of 200-300 μm into a smooth release film, and irradiate it with a metal halide lamp at 100 mW / cm for 30 seconds. 2After irradiation with ultraviolet light (wavelength 365nm), the film was heated at 120°C to obtain a cured film for moisture permeability measurement. A moisture permeability test cup was prepared using the method based on JIS Z 0208, "Test method for moisture-proof packaging materials (cup method)." The cured film was then placed in a constant temperature and humidity oven at 60°C and 90% humidity, and the moisture permeability was measured for 480 hours.

[0063] 4) Liquid crystal contamination test: Take 0.1g of the liquid crystal sealant in a 5ml glass bottle, add 0.9g of liquid crystal, and then use 3000mJ / cm 2 The samples were irradiated with a metal halide UV lamp and then heated at 120°C for 60 minutes to simulate the contact conditions between the LCD and the LCD frame adhesive in actual production. A few drops of LCD were taken from a glass bottle and dropped into a dedicated LCD contamination test cell. The VHR was measured using the TOYO 6254 test instrument.

[0064] The test results are summarized in Table 1.

[0065] Table 1 Comparison of LCD frame sealant performance test

[0066]

[0067] It can be seen from Examples 1 to 8 that the liquid crystal frame sealant using the technical solution of the present invention has a room temperature bonding strength to the PI glass of more than 4 MPa, a PCT bonding strength attenuation of less than 25% after 24 hours, and a moisture permeability of the cured film formed in the liquid crystal display element of 480 (g / m 2 ) The following illustrates that the liquid crystal frame sealant of this solution has excellent resistance to high temperature and high humidity. In addition, the VHR in the liquid crystal contamination test is greater than 95%, indicating good resistance to liquid crystal contamination.

[0068] Compared to Example 1, Examples 6 and 7 primarily differ in the dosages of the modified methacrylic resin and the siloxane-modified resin. This demonstrates that the modified methacrylic resin exhibits reduced liquid crystal contamination, while the epoxy-modified resin exhibits superior adhesion and high-temperature and high-humidity resistance. Conversely, when the modified methacrylic resin to siloxane-modified resin dosage ratio is 1:1.5, all performance characteristics reach an optimal state. When the modified methacrylic resin to siloxane-modified resin dosage ratio is 1:3, as in Example 7, the adhesive strength is better than in Example 1, but the liquid crystal contamination VHR is relatively poor, falling below 96%. When the modified methacrylic resin to siloxane-modified resin dosage ratio is 1:0.25, as in Example 6, the adhesive strength is relatively poor compared to Example 1, with a relatively large attenuation of the adhesive strength. Overall, the overall performance of the liquid crystal sealant is superior when the modified methacrylic resin to siloxane-modified resin dosage ratio is between 1:1 and 1:2.5.

[0069] Comparing Comparative Example 1 with Example 1, it can be seen that Comparative Example 1 has excellent liquid crystal pollution performance due to containing only UV-cured acrylate, but the adhesion strength is greatly reduced, far lower than that of Example 1. At the same time, the high temperature and high humidity resistance is also poor, which proves that the comprehensive performance of the system with UV curing alone is poor, and multi-curing liquid crystal frame sealing glue has more advantages.

[0070] From the comparison between Comparative Example 2 and Example 1, it can be seen that although the room temperature adhesion of Comparative Example 2 is similar to that of Example 1, the post-PCT adhesion is significantly weaker than that of Example 1, and the high temperature and high humidity resistance and liquid crystal contamination performance are also significantly weaker than those of Example 1. In particular, the liquid crystal contamination performance is very poor, which can easily cause defects in liquid crystal display products. This shows that compared with the multi-cured liquid crystal frame sealant provided in Example 1, the single heat-cured frame sealant in Comparative Example 2 has poor overall performance and will have a greater risk of use.

[0071] Analysis of Comparative Example 3 and Example 1 shows that all performances of Example 1 are superior to those of Comparative Example 3, proving that compared with the common UV+heat dual-curing system, the present invention provides a multi-curing liquid crystal frame sealant. By virtue of the siloxane modification of the main resin, the frame sealant is endowed with moisture-curing capability, and due to the hydrophobicity of the siloxane group, the overall water resistance is further improved. Therefore, in the use of liquid crystal display products, the multi-curing liquid crystal frame sealant provided by the present invention has more advantages.

[0072] Analysis of Comparative Examples 4 and 5 with Example 1 shows that conventional epoxy diluent is used in Comparative Example 4, and hydrophilic silica is used in Comparative Example 5. The anti-liquid crystal contamination performance of both is comparable to that of Example 1, but their adhesion and high temperature and high humidity resistance are significantly worse than those of Example 1. Therefore, the comprehensive performance is not as good as that of Example 1, indicating that the multi-curing liquid crystal frame sealant prepared by combining the hydrophobic silica with the siloxane active diluent in the present invention has the best effect.

[0073] The above embodiments are intended only to illustrate the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made in accordance with the spirit of the present invention are intended to be covered by the scope of protection of the present invention.

Claims

1. A multi-curing liquid crystal frame sealant, characterized in that: The raw material components are as follows: 25-50% modified methacrylic resin, 25-50% siloxane modified resin, 1-10% hydrophobic silica, 1-5% silane coupling agent, 10-30% organic filler, 0.1-1% photoinitiator, 1-10% thermal curing agent and 1-5% reactive diluent, wherein the modified methacrylic resin is obtained by caprolactone-modified bisphenol A epoxy acrylate resin, and its molecular weight is between 400-700 Da. The structural formula of the siloxane modified resin is as follows: ， Wherein, R1 is -OCH3 or -OC2H5; R2 is -CH2(CH2) n CH3, n is 6-16; The structural formula of the active diluent is as follows: ， Where n is 3-5, R is 、 or .

2. The multi-curing liquid crystal frame sealant according to claim 1, characterized in that: The organic filler is any one of polyester microparticles, polystyrene microparticles, and polyacrylic acid microparticles.

3. The multi-curing liquid crystal frame sealant according to claim 1, characterized in that: The photoinitiator is at least one of benzophenone compounds, acetophenone compounds, acylphosphine oxide compounds, titanocene compounds and oxime ester compounds.

4. The multi-curing liquid crystal frame sealant according to claim 1, characterized in that: The heat curing agent used is a hydrazide curing agent.

5. The multi-curing liquid crystal frame sealant according to claim 1, characterized in that: The hydrophobic silica is selected from any one of the brands R8200 and R972 produced by Evonik of Germany.

6. The multi-curing liquid crystal frame sealant according to claim 1, characterized in that: In the raw material components, the mass ratio of the modified methacrylic resin to the silicone modified resin is 1:1-1:2.

5.

7. A method for preparing the multi-curing liquid crystal frame sealant according to any one of claims 1 to 6, comprising the following steps: Add the raw materials of each component into a mixing tank according to the above weight ratio, place it in a planetary mixer and stir for 30-40 minutes to mix the components evenly, and control the temperature below 28°C. Then use a three-roll grinder for grinding, with the gap between the three-roller feed port rollers being 10μm and the gap between the three-roller discharge port rollers being less than 5µm. Grind thoroughly to obtain the required frame sealing glue.

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