UV and moisture dual-curing packaging adhesive suitable for flexible electronic paper and preparation method of UV and moisture dual-curing packaging adhesive

Abstract

The invention discloses a UV and moisture dual-curing packaging adhesive suitable for flexible electronic paper and a preparation method of the UV and moisture dual-curing packaging adhesive. The invention discloses a photocurable coating which is prepared from the following raw materials in parts by weight: 20-40 parts of modified dual-cured polyurethane acrylate, 8-15 parts of polyurethane acrylate, 10-30 parts of a methacrylate diluent, 1-3 parts of a photoinitiator, 0.2-0.5 part of a dispersing agent, 0.2-0.5 part of a defoaming agent, 2-5 parts of a silane coupling agent, 0.5-1 part of an anti-settling agent and 5-10 parts of spherical filler. The packaging adhesive provided by the invention has the characteristics of fast shaping, bending resistance, low volume shrinkage, strong adhesive strength, high and low temperature circulation resistance and low permeable rate.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electronic paper packaging, in particular to a protective packaging material for a flexible display device and a curing process thereof, and more particularly to a UV-moisture dual-curing packaging adhesive for flexible electronic paper and an application method thereof. BACKGROUND

[0002] Flexible electronic paper is an important direction of next-generation display technology, and its core advantage lies in its bendable and rollable characteristics. However, the internal electronic components, especially the flexible electrodes and TFT backplanes based on organic materials or metal nanowires, are extremely sensitive to water vapor and oxygen in the environment. These invasive gases can cause electrode corrosion, organic material degradation, TFT performance drift, and other problems, ultimately leading to display failure and shortened lifespan. Therefore, high-performance flexible packaging technology is a key guarantee for the commercialization of flexible electronic paper. Substrate packaging, which uses flexible glue to bond and seal the flexible substrate with good barrier properties and the completed electronic paper panel, is an important solution. This solution requires the packaging adhesive to not only have excellent bonding performance and flexibility, but also its curing process must be compatible with the temperature-sensitive flexible electronic paper manufacturing process.

[0003] Currently, the packaging adhesives and their curing methods used in this field can be mainly divided into three categories, but all have significant limitations: Thermosetting packaging adhesives (such as epoxy resin, silicone): This type of adhesive requires high temperatures (usually > 100°C). However, flexible plastic substrates (such as PET, PEN) and functional layers often cannot withstand high-temperature baking, and their high-temperature process requirements are fundamentally incompatible with the low heat resistance of flexible electronic components.

[0004] Pure UV-curing packaging adhesives: This type of packaging adhesive can be quickly cured at room temperature by ultraviolet irradiation, with high efficiency and low thermal impact. However, the curing mechanism has a natural defect - it can only act on areas that can be directly irradiated by ultraviolet light. For shadowed areas in the packaging structure that are blocked by lines and electrodes, or for gaps in three-dimensional complex configurations, ultraviolet light cannot effectively reach, resulting in incomplete curing and forming weak points in the packaging. In addition, most acrylate-based UV-curing systems have a high modulus after curing, and their flexibility and bending fatigue resistance are insufficient, making it difficult to adapt to repeated bending applications.

[0005] Pure moisture curing type encapsulation glue: this kind of encapsulation glue relies on the reaction with moisture in the air to realize curing, can effectively fill the shadow area, there is no curing blind spot, and usually has good flexibility after curing. But its curing speed is extremely dependent on the environmental humidity and the thickness of the glue layer, in dry environment or thick glue layer, the curing time is long (may need several hours to several days), which seriously slows down the production rhythm and affects the manufacturing efficiency. At the same time, the small molecules that do not completely react during the curing process may be slowly released, which may cause potential pollution and corrosion risk to sensitive electronic components.

[0006] In summary, the existing encapsulation glue with single curing mode is difficult to fully meet the harsh requirements of low processing temperature, no curing blind spot, high curing efficiency, excellent flexibility and high reliability of flexible electronic paper. Therefore, the UV / moisture dual curing mechanism provides a very potential solution to the above technical problems through a step-by-step and synergistic curing method. SUMMARY

[0007] In order to solve the problems of high water permeability, poor moisture resistance and poor bending fatigue resistance of the existing flexible electronic paper encapsulation glue, the present application provides a UV and moisture dual curing encapsulation glue suitable for flexible electronic paper, which aims to modify the polyurethane acrylate to have both isocyanate groups and methacrylate groups, so that the resin has both UV curing responsiveness and moisture curing activity. With the synergistic effect of this dual curing group, the glue can realize the step-by-step reaction of "UV rapid shaping + moisture deep curing", and finally form a dense organic whole, which not only significantly reduces the water permeability, improves the aging resistance and barrier properties, but also enhances the bonding strength and bending resistance through the flexible nature of the polyurethane segment, fully meeting the packaging needs of flexible electronic paper.

[0008] In order to achieve the purpose, the present application adopts the following technical solutions: The present application first provides a UV and moisture dual curing encapsulation glue suitable for flexible electronic paper, which comprises the following raw materials by weight: modified dual curing polyurethane acrylate 20-40 parts, methacrylate diluent 10-30 parts, polyurethane acrylate 8-15 parts, photoinitiator 1-3 parts, dispersant 0.2-0.5 parts, defoamer 0.2-0.5 parts, silane coupling agent 2-5 parts, anti-settling agent 0.5-1 part, and spherical filler 5-10 parts.

[0009] Further, the modified dual-curing polyurethane acrylate is prepared by the following method: polypropylene glycol is added into a reaction kettle, and dehydrated at -0.1 MPa to -0.2 MPa and 100-120°C for 1-2 hours until no bubbles are generated; the temperature is lowered to 60-70°C, and isophorone diisocyanate (IPDI) and catalyst dibutyltin dilaurate (DBTL) are added under the protection of dry nitrogen; the temperature is raised to 75-85°C, and the reaction is kept for 2-4 hours. Then the obtained prepolymer is cooled to 50-60°C, and hydroxyethyl acrylate (HEA) is added dropwise, and the temperature of the system is strictly controlled to be no higher than 60°C to prevent local overheating and gelation. After the addition is completed, the reaction is continued at 50-60°C for 2-4 hours, and then the temperature is lowered to 40-50°C, and γ-isocyanate propyl triethoxysilane (IPTS) is added dropwise, and the reaction is kept at 40-50°C for 2-3 hours to obtain the modified dual-curing polyurethane acrylate. The mass ratio of polypropylene glycol, IPDI, HEA and IPTS is 1:2.2:1:0.9.

[0010] The synthesis path and molecular formula of the modified dual-curing polyurethane acrylate are shown in Figures 1 to 3 Figure 1 First, as shown in Figure 2 Then, as shown in Figure 3 Finally, as shown in

[0011] Further, the methacrylate diluent is one or more of dicyclopentane methyl methacrylate (HDCPMA), isobornyl methacrylate (IBOMA) and tricyclokevane dimethylol dimethacrylate (TCDMA).

[0012] Further, the functionality of the polyurethane acrylate agent is two, the elongation at break is 160-200%, and the adhesion to the corona-treated PI film is no higher than 10 g.mil / 100.in 2 .24h, and the adhesion to the corona-treated PI film is 5B, such as Qiaoyuhua 3166, Sartomer CN8888NS and Double Bond 5400.

[0013] Further, the photoinitiator is one or more of photoinitiator ITX, photoinitiator TPO, photoinitiator 819 and photoinitiator 369.

[0014] Further, the dispersant is BYK-111.

[0015] Further, the defoaming agent is Ziming QM-2068.

[0016] Further, the silane coupling agent can be KH-560. ​

[0017] Further, the anti-settling agent can be selected from fumed silica (such as fumed silica TS-610).

[0018] Further, the spherical filler is silicon powder (such as Jiangsu Lianrui NQ5040H).

[0019] The application also provides a preparation method of the UV and moisture dual-curing encapsulating glue, comprising the following steps: Step 1: Take the formula amount of methacrylate diluent, add a predetermined proportion of photoinitiator to it, and place it in a 70-75°C water bath environment for heating and stirring until the photoinitiator is completely dissolved and the system is clear and transparent, then transfer it to a stirring kettle, add modified dual-curing polyurethane acrylate, polyurethane acrylate, dispersant, defoaming agent and silane coupling agent; replace the air in the stirring kettle with nitrogen, stir at a speed of 800-1000 r / min for 30-50 min to ensure that the components are fully dispersed and uniform, then add an anti-settling agent and a spherical filler, vacuum the stirring kettle to a negative pressure (-0.1 Mpa to -0.2 Mpa), adjust the speed to 1000-1500 r / min, continue to stir and disperse for 50-60 min, maintain the negative pressure (-0.1 Mpa to -0.2 Mpa), and finally restore it to normal pressure by introducing nitrogen; Step 2: Filter the material obtained in step 1 through a 200-mesh filter cloth, and introduce the filtrate into a filling machine; Step 3: Perform a canning operation on the material in the filling machine under nitrogen protection, and simultaneously vacuum degas during the canning process, to finally obtain a UV and moisture dual-curing encapsulating glue suitable for flexible electronic paper.

[0020] Compared with the prior art, the application has the following beneficial effects: 1. The encapsulating glue of the application significantly improves its barrier performance and weather resistance by using modified dual-curing polyurethane acrylate. Specifically, the molecular structure of the modified dual-curing polyurethane acrylate has both isocyanate groups (moisture curing activity) and methacrylate groups (UV curing activity), which can link the moisture curing components and UV curing components in the system, allowing them to be both UV and moisture cured. This dual-curing synergistic effect allows the glue to form a structurally dense organic whole, and because the moisture curing resin properties are retained, its aging resistance and water vapor barrier performance are significantly better than those of traditional pure light-cured resins. At the same time, the dual-reactive groups can promote the crosslinking of the system at the molecular level to form a three-dimensional network structure, further strengthening the integrity of the barrier surface, and ultimately significantly reducing the water permeability of the encapsulating glue and improving its moisture resistance.

[0021] 2、The encapsulation glue of the present application can realize rapid setting through UV curing, and the workpiece can enter the next process after setting, effectively shortening the production cycle; and the glue solution has good storage stability and is not easy to deteriorate under conventional storage conditions, and the operation process is simple, which can adapt to the large-scale production needs of flexible electronic paper.

[0022] 3、Through encapsulation simulation test verification, the encapsulation glue of the present application has excellent moisture resistance and can maintain stable performance for a long time under high temperature and high humidity conditions, effectively resisting water vapor intrusion, and can still maintain reliable encapsulation effect in repeated bending, temperature fluctuation and other scenes, adapting to the complex application environment of flexible electronic paper.

[0023] 4、The encapsulation glue of the present application has excellent adhesion performance to flexible substrates, electronic paper panels and other substrates, which can ensure no risk of delamination during long-term use; and the glue solution is 100% solid content and does not contain volatile components, and no toxic and harmful substances are generated during curing process, which is green and environmentally friendly. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figures 1 to 3 Synthesis path diagram of modified double-cured polyurethane acrylate: Figure 1 Prepolymer prepared by reacting polypropylene glycol and isophorone diisocyanate; Figure 2 Prepolymer reacted with hydroxyethyl acrylate to introduce acrylate double bond; Figure 3 Prepolymer after introducing acrylate double bond is reacted with gamma-isocyanate propyl triethoxy silicon. DETAILED DESCRIPTION

[0025] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application are described in detail. The following content is only an example and description of the concept of the present application, and those skilled in the art can make various modifications or supplements or use similar ways instead, as long as they do not deviate from the concept of the present application, which shall belong to the protection scope of the present application.

[0026] Unless otherwise specified, each raw material used in the following examples is commercially available.

[0027] Example 1 The modified dual-curing polyurethane acrylate used in this example was prepared as follows: 50 g of polypropylene glycol was added to a reaction kettle, dehydrated at -0.1 MPa and 110°C for 1-2 hours until no bubbles were generated; cooled to 65°C, and 110 g of IPDI and 5 g of catalyst DBTL were added under dry nitrogen protection, heated to 80°C, and reacted for 2 hours. The obtained prepolymer was then cooled to 55°C, and 50 g of HEA was added at a rate of 30 drops per minute. The system temperature was strictly controlled not to exceed 60°C during the addition to prevent local overheating and gelation. After the addition was completed, the reaction was continued at 50-60°C for 3 hours, and then cooled to 45°C. 45 g of γ-isocyanate propyl triethoxysilane was added at a rate of 40 drops per minute, and the reaction was continued at 45°C for 3 hours to obtain the modified dual-curing polyurethane acrylate.

[0028] The encapsulation adhesive was prepared according to the following steps in this example: Step 1: 25 g of isobornyl methacrylate IBOMA was taken, and 1.55 g of photoinitiator TPO and 0.25 g of photoinitiator 819 were added. The mixture was heated and stirred in a 70°C water bath environment until the photoinitiators were completely dissolved and the system was clear and transparent. Then it was transferred to a stirred tank, and 25 g of modified dual-curing polyurethane acrylate, 10 g of polyurethane acrylate (Qiaoyou Chemicals 3166), 0.25 g of dispersant BYK-111, 0.2 g of defoamer QM-2068, and 3 g of silane coupling agent KH-560 were added. Nitrogen was introduced to replace the air in the stirred tank, and the mixture was stirred at a speed of 1000 r / min for 30 min to ensure that the components were fully dispersed and uniform. Then 1 g of gas silicon TS-610 and 8 g of silicon powder NQ5040H were added. The stirred tank was vacuumed to a negative pressure of -0.2 MPa, the stirring speed was adjusted to 1200 r / min, and the stirring and dispersion were continued for 60 min. The negative pressure was maintained at -0.2 MPa, and the material was naturally cooled to 20°C. Finally, nitrogen was introduced to restore the normal pressure.

[0029] Step 2: The material obtained in Step 1 was filtered through a 200-mesh filter cloth, and the filtrate was introduced into a filling machine. Step 3: The material in the filling machine was subjected to a nitrogen-protected canning operation, and vacuum degassing was performed simultaneously during the canning process. Finally, a UV and moisture dual-curing encapsulation adhesive suitable for flexible electronic paper was obtained.

[0030] Example 2 The encapsulation adhesive was prepared according to the same method as in Example 1, except that the content of modified dual-curing polyurethane acrylate was 30 g when preparing the encapsulation adhesive.

[0031] Comparative Example 1 The encapsulation adhesive was prepared according to the same method as in Example 1, except that the modified dual-cure urethane acrylate was replaced by an equal amount of polyurethane acrylate (Sartomer CN9014NS) when preparing the encapsulation adhesive.

[0032] Comparative Example 2 The encapsulation adhesive was prepared according to the same method as in Example 1, except that the modified dual-cure urethane acrylate was replaced by an equal amount of moisture-curing resin (Sartomer CN1073NS) when preparing the encapsulation adhesive.

[0033] Comparative Example 3 The comparative example used a commercially available UV moisture two-component encapsulation adhesive as a comparison, and the main resin components thereof were: UV resin and moisture-curing resin.

[0034] The curing method of the edge sealing adhesive obtained in each example and comparative example was as follows: Example 1, 2 and Comparative Example 3: first irradiated by LED lamp (wavelength 395 nm, energy 6000 mj / cm 2 ), and then cured at 25°C, 30-40% humidity environment for 48 hours.

[0035] Comparative Example 1: irradiated by LED lamp (wavelength 395 nm, energy 6000 mj / cm 2 ).

[0036] Comparative Example 2: cured at 25°C, 30-40% humidity environment for 48 hours.

[0037] The encapsulation adhesive of each example and comparative example was tested for the following properties: 1. Water vapor transmission rate (i.e. water vapor transmission rate): the edge sealing adhesive was made into a sheet with a thickness of 0.25 microns, and after curing, a water vapor transmission rate tester (Sai Cheng WPT-201) was used to measure at 50°C, 100% RH.

[0038] 2. Moisture resistance: the moisture-sensitive color-changing silicone was placed between two pieces of glass, and the edges were sealed with the encapsulation adhesive. After curing, the sample was placed in a constant temperature and humidity cycle box (Hongjin Instrument HTK-TH-100DH), and tested according to the conditions of 50°C, 100% humidity, and the color change time of the silicone was observed.

[0039] 3. High and low temperature cycle impact resistance: the moisture-sensitive color-changing silicone was placed between two pieces of glass, and the edges were sealed with the encapsulation adhesive. After curing, the sample was placed in a high and low temperature impact box (Huitai Machinery HT-LC60-502), and tested according to the conditions of "-25°C constant temperature for 0.5h ~ 70°C constant temperature for 0.5h" as 1 cycle, continuously for 200 cycles. During the test, the color change of the color-changing silicone was observed periodically, and the time of the first obvious color change was recorded (judged as the starting point of encapsulation failure).

[0040] 4. Shear force: encapsulation adhesive was used to bond glass and PS film, bonding area 0.5 cm 2 , adhesive film thickness 0.25 microns. Shear force test was performed using ZQ-990LA-2 universal testing machine from Zwick, and the maximum shear force value (unit: kgf) at the time of sample fracture was recorded.

[0041] 5. Bending times comparison: encapsulation adhesive was made into a thickness of 0.25 microns of sheet, after complete curing, using a flexible material bending tester from Hill, the bending diameter was set to 1 cm (i.e. the curvature radius corresponding diameter when the sample was bent), 180° reciprocating bending test was performed, and the cumulative bending times at which the sample first appeared cracking, delamination or fracture was recorded.

[0042] The test results are shown in Table 1.

[0043] Table 1. Performance test results of each example and comparative example The test results of Example 1-2 and Comparative Example 1-2 show that the modified dual-cure polyurethane acrylate has lower water permeability and better weather resistance than pure UV-cured and moisture-cured resins, and the modified dual-cure polyurethane acrylate makes the encapsulation adhesive have more excellent barrier properties and excellent bending resistance. Compared with the two-component UV and moisture encapsulation adhesives on the market, the performance advantages are obvious.

[0044] The above only describes the preferred embodiments of the present application, and it should be noted that for ordinary skilled in the art, without departing from the principles of the present application, corresponding adjustments and improvements can also be made, and these adjustments and improvements should also be considered as the protection scope of the present application.

Claims

1. A UV and moisture dual-cured encapsulation adhesive suitable for flexible electronic paper, characterized in that, The encapsulating glue comprises the following raw materials by weight: Modified dual-curing polyurethane acrylate 20-40 parts, Methacrylate diluent 10-30 parts, Polyurethane acrylate 8-15 parts, Photoinitiator 1-3 parts, Dispersant 0.2-0.5 parts, Defoaming agent 0.2-0.5 parts, Silane coupling agent 2-5 parts, Anti-settling agent 0.5-1 part, Spherical filler 5-10 parts.

2. A UV and moisture dual-curing encapsulation adhesive suitable for flexible electronic paper according to claim 1, wherein, The modified dual-curing polyurethane acrylate is prepared by the following method: polypropylene glycol is added to a reaction kettle, dehydrated at-0.1 MPa to-0.2 MPa and 100-120℃ for 1-2 hours until no bubbles are generated; cooled to 60-70℃, and then isophorone diisocyanate IPDI and catalyst dibutyltin dilaurate DBTL are added under dry nitrogen protection; warmed to 75-85℃, and then incubated for 2-4 hours; the obtained prepolymer is then cooled to 50-60℃, and hydroxyethyl acrylate HEA is added dropwise, with the temperature controlled to be no higher than 60℃ during the dropwise addition; after the dropwise addition is completed, the reaction is continued at 50-60℃ for 2-4 hours, and then cooled to 40-50℃, and then γ-isocyanate propyl triethoxysilane IPTS is added dropwise, and incubated at 40-50℃ for 2-3 hours to obtain the modified dual-curing polyurethane acrylate.

3. A UV and moisture dual-curing encapsulation adhesive suitable for flexible electronic paper according to claim 2, characterized in that: The mass ratio of polypropylene glycol, IPDI, HEA, and IPTS is 1:2.2:1:0.

9.

4. The UV and moisture dual-curable encapsulation adhesive for flexible electronic paper according to claim 1, wherein: The methacrylate diluent is one or more of dicyclopentane methyl acrylate HDCPMA, isobornyl methacrylate IBOMA, and tricyclokevane dimethylol dimethacrylate TCDMA.

5. The UV and moisture dual-curable encapsulation adhesive for flexible electronic paper according to claim 1, wherein: The polyurethane acrylate has a functionality of two, an elongation at break of 160-200%, and a water permeability of not more than 10 g.mil / 100.in 2 .24h, the adhesion to the corona-treated PI film is 5B.

6. A UV and moisture dual-curable encapsulation adhesive for flexible electronic paper according to claim 1, wherein: The photoinitiator is one or more of photoinitiator ITX, photoinitiator TPO, photoinitiator 819, and photoinitiator 369.

7. A UV and moisture dual-curable encapsulation adhesive for flexible electronic paper according to claim 1, wherein: The dispersant is BYK-111, the defoaming agent is QM-2068, and the silane coupling agent is KH-560.

8. A UV and moisture dual-cured encapsulation adhesive suitable for flexible electronic paper according to claim 1, wherein: The anti-settling agent is fumed silica.

9. The UV and moisture dual-curing encapsulating adhesive for flexible electronic paper as described in claim 1, characterized in that: The spherical filler is silicon powder.

10. A method for preparing the UV and moisture dual-curing encapsulation adhesive for flexible electronic paper according to any one of claims 1 to 9, characterized in that, The method comprises the following steps: Step 1: a formula amount of methacrylate diluent is taken, a predetermined proportion of photoinitiator is added thereto, and then placed in a 70-75℃ water bath environment for heating and stirring until the photoinitiator is completely dissolved and the system is clear and transparent, and then transferred to a stirring kettle, and then modified dual-curing polyurethane acrylate, polyurethane acrylate, dispersant, defoaming agent, and silane coupling agent are added; nitrogen is introduced to replace the air in the stirring kettle, and then stirred at a speed of 800-1000 r / min for 30-50 min, and then anti-settling agent and spherical filler are added, and then the stirring kettle is vacuumed to a negative pressure of-0.1 MPa to-0.2 MPa, the speed is adjusted to 1000-1500 r / min, and then continues to be stirred and dispersed for 50-60 min, and then the negative pressure is maintained at-0.1 MPa to-0.2 MPa, and then the material is naturally cooled to 20-25℃, and finally nitrogen is introduced to restore to normal pressure; Step 2: the material obtained in step 1 is filtered through 200-mesh filter cloth, and the filtrate is introduced into a filling machine. Step 3, nitrogen protection of the material in the filling machine under the operation of canning, simultaneous vacuum degassing during the canning process, finally obtain the UV and moisture dual-curing encapsulation glue suitable for flexible electronic paper.

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