UV (ultraviolet) and hot dual-curing edge sealing adhesive for liquid crystal display without frames on four sides

Abstract

The invention belongs to the technical field of UV adhesives, and discloses a UV and thermal dual-curing edge sealing adhesive for a liquid crystal display without a frame on four sides, which comprises the following components in parts by weight: 0.5-2 parts of a photoinitiator, 15-30 parts of a reactive diluent, 10-20 parts of dual-curing resin, 0.5-1.5 parts of a silane coupling agent, 50-70 parts of a filler, 0.3-0.8 part of an auxiliary agent and 1-5 parts of an epoxy curing agent. The UV and hot dual-curing edge sealing adhesive has the characteristics of low volume shrinkage, high and low temperature impact resistance, high temperature and high humidity resistance, high adhesion, rapid forming and the like, and is suitable for a frameless liquid crystal display.

Description

Technical Field

[0001] This invention belongs to the field of UV adhesives, and particularly relates to a UV and heat-curing dual-curing edge sealant that can be used in four-sided frameless liquid crystal displays. Background Technology

[0002] In the manufacturing process of liquid crystal displays (LCDs), edge-sealing adhesives are used on the non-display areas of the display to seal the area where the display panel connects to the polarizer, preventing the intrusion of external moisture and contaminants, while maintaining the stability of the liquid crystal layer. Traditional edge-sealing adhesives mainly rely on a single curing system, such as UV curing, thermosetting, or moisture curing. Although UV curing systems have a fast curing speed (seconds) and are suitable for high-efficiency production, acrylic UV adhesives typically experience a volume shrinkage rate of 8-10% during polymerization due to the high molecular crosslinking density, leading to stress concentration within the adhesive layer. Thermosetting epoxy resin systems have excellent adhesive strength and resistance to moisture and heat, but require high temperatures (70-120℃) for curing, and the volume shrinkage rate of epoxy resin is approximately 2%-6%. Moisture-curing polyurethane systems have good flexibility, but the curing speed is slow (several hours), and byproducts are released during curing, which may form bubbles or pores. The volume shrinkage rate fluctuates significantly (5%-8%), making it difficult to meet the requirements of high-precision edge sealing. Therefore, existing edge sealing adhesive systems all have inherent defects, especially in terms of poor performance in terms of volume shrinkage rate. The substrates encapsulated by edge sealing adhesive mainly include polarizers, PI films and TFT glass backplates. Polarizers are flexible substrates. If the edge sealing adhesive shrinks too much during curing, it will cause polarizer deformation, resulting in damage to the appearance of the display and a decrease in sealing performance after long-term use, which directly affects the reliability and yield of the display.

[0003] In the design of four-sided frameless LCD displays, shrinkage stress can also cause interface delamination between the glass substrate and the polarizer, affecting display uniformity. Therefore, the edge sealing adhesive suitable for four-sided frameless LCD displays needs to be studied. Summary of the Invention

[0004] In view of this, the present invention provides a UV and heat-curing dual-curing edge sealant that can be used in the edge sealing manufacturing process of a four-sided frameless liquid crystal display, in order to solve the problem that existing adhesives cannot simultaneously guarantee rapid curing and low volume shrinkage.

[0005] The present invention solves the technical problem by adopting the following technical solution: This invention first provides a UV and heat-curing dual-curing edge sealant for use in four-sided borderless liquid crystal displays, comprising the following components by weight: Photoinitiator 0.5 to 2 parts; 15 to 30 parts of reactive diluent; 10 to 20 parts of dual-curing resin; 0.5-1.5 parts of silane coupling agent; 50-70 parts of filler; Additives: 0.3-0.8 parts; 1-5 parts of epoxy curing agent.

[0006] Furthermore, the dual-curing resin of the present invention is prepared by reacting bisphenol A epoxy resin with methacrylate. The two ends of the molecular chain of the dual-curing resin are different reactive groups. One end of the long chain is a UV-curable methacrylate bond, and the other end of the long chain is a heat-curable epoxy bond. Therefore, the dual-curing resin has both the rapid curing characteristics of UV resin and the aging resistance of epoxy resin.

[0007] Preferably, the dual-cured resin is prepared by the following method: 50-60 parts by weight of bisphenol A epoxy resin are added to a reactor, the temperature is raised to 75℃-85℃ under nitrogen protection and stirred, 0.7-0.9 parts by weight of the catalyst triethylbenzylammonium chloride and 20-30 parts by weight of methacrylic acid are added dropwise at a constant temperature, the temperature is raised to 115℃-125℃ after the addition is completed and the reaction is maintained at this temperature, the reaction is stopped when the acid value is less than 1 mg KOH / g, and the material is discharged hot to obtain the dual-cured resin.

[0008] Preferably, the silane coupling agent includes at least one of 3-aminopropyltriethoxysilane (KH-550), 3-epoxypropoxytrimethoxysilane (KH-560), anilinemethyltriethoxysilane, anilinemethyltrimethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane (KH-570).

[0009] Preferably, the photoinitiator includes at least one of diphenyl-(2,4,6-trimethylbenzoyl)phosphine oxide (photoinitiator TMO), isopropylthioxanthone (photoinitiator ITX), and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (photoinitiator 819).

[0010] Preferably, the reactive diluent is a monofunctional reactive monomer. A functional group refers to a reactive group; the more reactive groups, the faster the reaction and the greater the volume shrinkage. Therefore, this invention selects a monofunctional reactive monomer, that is, a monomer containing only one reactive group. More preferably, the monofunctional reactive monomer includes at least one of isobornyl methacrylate (IBOMA), laurate acrylate (LA), isobornyl acrylate (IBOA), stearate acrylate (SA), and ethoxyethoxyethyl acrylate (EOEOEA).

[0011] Preferably, the filler includes at least one selected from calcium carbonate, barium sulfate, spherical silica powder, spherical alumina, and talc. Adding fillers can adjust the hardness of the UV adhesive and reduce its volume shrinkage after curing.

[0012] Preferably, the epoxy curing agent is epoxy curing agent D230.

[0013] Preferably, the additive is a polysiloxane defoamer, including a polysiloxane solution or an organically modified polysiloxane.

[0014] The present invention also provides a method for preparing the above-mentioned UV and heat-curing dual-curing edge sealant, comprising the following steps: The photoinitiator and reactive diluent are mixed and stirred at 70-75℃ until clear and transparent. The dual-curing resin is added and stirred at 40-50℃ for 40-60 minutes. The silane coupling agent is added and stirred for 10-20 minutes. The additives are added and stirred for 10-20 minutes. Then, the filler is added in batches, and each batch is stirred for 30-40 minutes. The system temperature is then cooled to 10-15℃. The epoxy curing agent is added and stirred for 5-10 minutes. The mixture is filtered through a 300-mesh filter to finally obtain the UV and heat dual-curing edge sealant.

[0015] The above preparation method was carried out in a high-speed mixer. During the mixing process, except for the batch mixing at 1800 r / min after adding the filler, the speed was 800 r / min for all other batches.

[0016] The method of using the edge sealing adhesive obtained by the present invention is as follows: spray the edge sealing adhesive onto the area that needs to be sealed with a glue gun, then first UV cure and shape it, and then place it at room temperature (20-25℃) for 18-24 hours to allow the epoxy component to fully cure.

[0017] The beneficial effects of this invention are reflected in: 1. The UV and heat-curing dual-curing edge sealant provided by this invention has the characteristics of low volume shrinkage, resistance to high and low temperature impact, resistance to high temperature and high humidity, high adhesion, rapid molding, and low water vapor transmission rate, and is suitable for four-sided frameless liquid crystal displays.

[0018] 2. The dual-curing resin molecular chain of this invention has different reactive groups at both ends. Therefore, the edge-sealing adhesive adopts a two-stage curing process: First, UV curing is performed. After being exposed to light, the photoinitiator triggers a cross-linking reaction between the reactive diluent and the dual-curing resin. Only the double bond groups at one end of the straight chain of the dual-curing resin participate in the reaction, forming a flexible and highly elastic colloid. Therefore, the volume shrinkage of the colloid is small, the shrinkage stress is slowly released, and it plays a role in preliminary shaping. Then, room temperature heat curing is performed. The epoxy groups at the other end of the straight chain of the dual-curing resin cure slowly, resulting in low shrinkage stress and low volume shrinkage rate. Therefore, the volume shrinkage rate of the edge-sealing adhesive system of this invention is lower than that of the UV system, while the process efficiency is consistent with that of the UV system. In addition, the epoxy component in the edge-sealing adhesive system of this invention also plays a role in improving the water vapor barrier performance, aging resistance, and high and low temperature impact resistance of the edge-sealing adhesive. At the same time, the addition of spherical fillers in the system can further reduce the volume shrinkage coefficient and improve the physical properties of the UV adhesive, reducing water vapor transmission rate and improving wear resistance and damp heat resistance. Attached Figure Description

[0019] Figure 1 This is a diagram illustrating the reaction process for preparing the dual-curing resin in the examples; Figure 2 The image shows the 1H NMR spectrum of the dual-cured resin prepared in the examples. Detailed Implementation

[0020] The embodiments of the present invention are described in detail below. These embodiments are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operation processes. However, the scope of protection of the present invention is not limited to the following embodiments.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which embodiments of this application belong. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the embodiments of this application.

[0022] The dual-curing resin used in the following examples was prepared as follows: 55 parts by weight of bisphenol A epoxy resin E-44 were added to a reactor, and the temperature was raised to 80°C under nitrogen protection and stirred. 0.75 parts by weight of the catalyst triethylbenzylammonium chloride and 23 parts by weight of methacrylic acid were added dropwise at a constant temperature. After the addition was complete, the temperature was raised to 120°C and maintained for reaction. The reaction was stopped when the acid value was less than 1 mg KOH / g, and the product was discharged hot to obtain the dual-curing resin. The reaction process is as follows: Figure 1 As shown, the proton NMR spectrum of the obtained product is as follows: Figure 2As shown, in the synthesized dual-curing resin, the hydrogen atoms on the carbon-carbon double bonds are at 6.081 PPM and 5.59 PPM, respectively, with peak areas of approximately 2.2, indicating a 1:1 ratio. Meanwhile, the two hydrogen atoms on the epoxy bonds are at 2.84 PPM and 2.70 PPM, with peak areas also approximately 1:1. This demonstrates that the dual-curing resin contains two types of reactive groups.

[0023] Example 1 This embodiment prepares the UV and heat-curing dual-curing edge sealant according to the following steps: Add 1 part of photoinitiator TMO, 0.5 parts of photoinitiator 819, and 18 parts of lauric acrylate to a mixing tank. Stir in a 70°C water bath until clear and transparent. Then add 12.5 parts of dual-curing resin to the mixing tank, set the stirring temperature to 40°C, and stir for 60 minutes. Add 1.2 parts of silane coupling agent KH-550 and stir for 20 minutes. Add 0.5 parts of defoamer QM-2068 and stir for 20 minutes. Add a total of 62.5 parts of spherical silica powder in 3 batches, stirring for 30 minutes after each batch. Then cool the system temperature to 10°C, add 3 parts of epoxy curing agent D230, stir at low speed for 5 minutes, filter, and package to finally obtain UV and heat-curing dual-curing edge sealant.

[0024] Example 2 This embodiment prepares UV and heat-curing edge sealant under the same conditions as in Example 1, except that 18 parts of lauric acid acrylate are replaced with 18 parts of ethoxyethoxyethyl acrylate (EOEOEA).

[0025] Example 3 This embodiment prepares UV and heat-curing edge sealant under the same conditions as in Example 1, except that 18 parts of laurate acrylate are replaced with 18 parts of isobornyl methacrylate (IBOMA).

[0026] Comparative Example 1 This comparative example was prepared under the same conditions as Example 1, with the only difference being that the dual-curing resin was replaced with UV resin 2-functional polyurethane acrylate (double bond 5400); and the amount of epoxy curing agent D230 added was 0.

[0027] Comparative Example 2 This comparative example was prepared under the same conditions as in Example 1, using UV and thermal double-curing edge sealant for a four-sided frameless liquid crystal display, with the only difference being that the amount of spherical silica powder filler added was 0.

[0028] Comparative Example 3 This comparative example was prepared under the same conditions as Example 1, using UV and heat-curing dual-curing edge sealant for a four-sided frameless liquid crystal display. The only difference was that 18 parts of monofunctional reactive diluent laurate acrylate were replaced with 18 parts of difunctional reactive diluent HDDA; and the amount of epoxy curing agent D230 added was 0.

[0029] Comparative Example 4 Commercially available pure epoxy edge sealing adhesive uses a large amount of aliphatic epoxy resin 3150 as the main resin and 622P as the diluent.

[0030] The comprehensive performance comparison parameters of the edge sealing adhesives obtained in the above embodiments and comparative examples are shown in Table 1.

[0031] Table 1 In Table 1: 1. The test method for water permeability (i.e. water vapor transmission rate) is as follows: After the sealing adhesive is made into a thin film with a thickness of 0.25 micrometers and cured, it is measured by a water vapor transmission rate tester (Saicheng WPT-201) at 50℃ and 100%RH.

[0032] 2. The test method for resistance to damp heat is as follows: Seal the frameless LCD display with edge sealing adhesive. After curing, place the sample in a constant temperature and humidity circulating chamber (Hongjin Instruments HTK-TH-100DH) and test it under the conditions of 85℃ and 85% humidity. Observe whether the edge sealing adhesive peels off or cracks.

[0033] 3. The test method for high and low temperature cyclic impact resistance is as follows: Seal the frameless LCD display with edge sealing adhesive. After curing, place the sample in a high and low temperature impact chamber (Huitai Machinery HT-LC60-502) and test it under the condition of -40℃ (0.5h) to 70℃ (0.5h) for 800 cycles. Observe whether the edge sealing adhesive peels off or cracks.

[0034] 4. The test method for volume shrinkage rate is as follows: The volume shrinkage rate of the edge banding adhesive is determined according to the density method in the relevant provisions of the international standard ISO3521.

[0035] 5. The curing methods for the edge sealing adhesives obtained in each embodiment and comparative example are as follows: the edge sealing adhesives of Examples 1 to 3 and Comparative Examples 1 to 3 are first UV cured to set, and then placed at room temperature (25°C) for 24 hours; the edge sealing adhesive of Example 4 is cured at 70°C for 12 hours.

[0036] Comparative analysis revealed that: Examples 1, 2, and 3, after employing monofunctional reactive monomers, dual-curing resins, and spherical silica powder fillers, exhibited low volume shrinkage, good water vapor permeability, and good aging performance of the edge sealant; Comparative Examples 1, 2, and 3, after eliminating their core materials, showed reduced volume shrinkage, water vapor permeability, and aging performance; Although commercially available epoxy edge sealants have good performance in all aspects, their curing time and temperature are not acceptable to the manufacturing process of LCD panels.

[0037] The UV and heat-curing dual-curing edge sealant provided by this invention has a low volume shrinkage rate and excellent adhesion, meeting various process conditions in the manufacturing of liquid crystal displays, such as high-temperature and high-humidity aging, high- and low-temperature shock, and low moisture permeability. Furthermore, the edge sealant of this invention is simple to apply, cures instantly, and is suitable for large-scale production.

[0038] The above description describes some specific embodiments of this application, but in actual applications, the application should not be limited to these embodiments. For those skilled in the art, other modifications and alterations made based on the technical concept of this application should fall within the protection scope of this application.

Claims

1. A UV and heat-curing dual-curing edge sealant for use in four-sided frameless liquid crystal displays, characterized in that, Includes the following components by weight: Photoinitiator 0.5 to 2 parts; 15 to 30 parts of reactive diluent; 10 to 20 parts of dual-curing resin; 0.5-1.5 parts of silane coupling agent; 50-70 parts of filler; Additives: 0.3-0.8 parts; 1-5 parts of epoxy curing agent.

2. The UV and heat-curing dual-curing edge sealant as described in claim 1, characterized in that, The dual-curing resin is prepared by reacting bisphenol A epoxy resin with methacrylate. One end of the long chain of the dual-curing resin is a UV-curable methacrylate bond, and the other end of the long chain is a heat-curable epoxy bond.

3. The UV and heat-curing dual-curing edge sealant as described in claim 1 or 2, characterized in that, The dual-cured resin is prepared by the following method: 50-60 parts by weight of bisphenol A epoxy resin are added to a reactor, the temperature is raised to 75℃-85℃ under nitrogen protection and stirred, 0.7-0.9 parts by weight of the catalyst triethylbenzylammonium chloride and 20-30 parts by weight of methacrylic acid are added dropwise at a constant temperature, the temperature is raised to 115℃-125℃ after the addition is completed and the reaction is maintained at this temperature, the reaction is stopped when the acid value is less than 1 mg KOH / g, and the material is discharged hot to obtain the dual-cured resin.

4. The UV and heat-curing dual-curing edge sealant as described in claim 1, characterized in that: The silane coupling agent includes at least one of 3-aminopropyltriethoxysilane, 3-epoxypropoxytrimethoxysilane, anilinemethyltriethoxysilane, anilinemethyltrimethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane.

5. The UV and heat-curing dual-curing edge sealant as described in claim 1, characterized in that: The photoinitiator includes at least one of diphenyl-(2,4,6-trimethylbenzoyl)phosphine oxide, isopropylthioxanthone, and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

6. The UV and heat-curing dual-curing edge sealant as described in claim 1, characterized in that: The reactive diluent is a monofunctional reactive monomer.

7. The UV and heat-curing dual-curing edge sealant as described in claim 6, characterized in that: The monofunctional reactive monomer includes at least one of isoborneol methacrylate, isoborneol acrylate, laurate acrylate, stearate acrylate, and ethoxyethoxyethyl acrylate.

8. The UV and heat-curing dual-curing edge sealant as described in claim 1, characterized in that: The filler includes at least one of calcium carbonate, barium sulfate, spherical silica powder, spherical alumina, and talc.

9. The UV and heat-curing dual-curing edge sealant as described in claim 1, characterized in that: The additive is a polysiloxane defoamer.

10. A method for preparing a UV and heat-curing dual-curing edge sealant as described in any one of claims 1 to 9, characterized in that, Includes the following steps: The photoinitiator and reactive diluent are mixed and stirred at 70℃-75℃ until clear and transparent. The dual-curing resin is added and stirred at 40℃-50℃ for 40-60 minutes. The silane coupling agent is added and stirred for 10-20 minutes. The additives are added and stirred for 10-20 minutes. Then, the filler is added in batches, and each batch is stirred for 30-40 minutes. The system temperature is then cooled to 10℃-15℃. The epoxy curing agent is added and stirred for 5-10 minutes. The mixture is filtered through a 300-mesh filter to obtain the UV and heat dual-curing edge sealant.

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