Impact-resistant OCA (Optically Clear Adhesive) for replacing foam rubber and preparation method of impact-resistant OCA

Abstract

The invention discloses an impact-resistant OCA (optical clear adhesive) for replacing foam rubber and a preparation method of the impact-resistant OCA, and belongs to the technical field of OCA, the impact-resistant OCA for replacing the foam rubber comprises an optical light release film, an impact-resistant layer and an optical heavy release film which are sequentially arranged from top to bottom; the anti-impact layer is prepared from the following components in parts by weight: 80 to 110 parts of an adhesive, 30 to 60 parts of a UV monomer, 0.5 to 1.5 parts of a microsphere foaming agent, 0.3 to 0.6 part of a curing agent, 0.1 to 0.5 part of a cross-linking agent and 0.5 to 1 part of a silane coupling agent. The microsphere foaming agent is added into the adhesive, and due to the characteristic of thermal expansion, a porous hollow structure is formed in the material, so that the density of the material is reduced, and the buffering capacity and the compression resistance effect are improved; the test result shows that compared with a competitive product, the rubber has better buffering capacity and anti-pressure capacity, can replace foam rubber to be used under more conditions and occasions, and has higher competitiveness.

Description

Technical Field

[0001] The invention belongs to the technical field of OCA optical adhesives, and in particular relates to an impact-resistant OCA replacing foam adhesive and a preparation method thereof. Background Art

[0002] Rubber elastomer foam glue is widely used in OLED. It has good elasticity and cushioning properties, can effectively absorb impact and protect OLED panels. For example, rubber elastomer foam glue treated by special processes such as grafting reaction not only maintains the high elasticity of rubber, but also improves aging resistance and solvent resistance. Some special foaming materials use chemical foaming methods to form porous foam glue. The internal pore structure of this foam glue can absorb energy through pore compression and deformation when subjected to external force, thereby playing a buffering role. However, foam glue has the following disadvantages: 1. It is relatively thick and has limited buffering capacity. The general production thickness of foam glue is between 100μm-1000μm, and the falling ball buffering absorption rate is between 50%-60%, which is not conducive to the thickness reduction of OLED equipment finished products; 2. Uneven thickness. The uneven thickness of foam glue will lead to inconsistent buffering performance of foam glue in different parts, affecting the overall protection effect of OLED panel; 3. The production process is complicated and the cost is relatively high; 4. Release of harmful substances: Some foam glues may contain harmful substances, such as volatile organic compounds (VOCs).

[0003] The patent application with publication number CN114836152A discloses a foaming resin glue, a photocurable cross-linked rubber elastomer foam and a preparation method thereof. The foaming resin glue is obtained by grafting reaction of the following raw materials: 100 parts of rubber elastomer; 10-35 parts of grafting monomer I; 1-10 parts of grafting monomer II; 0.1-0.6 parts of free radical initiator; 0.5-1.5 parts of antioxidant; 300-600 parts of organic solvent; the present invention produces gas by a chemical foaming method to form a porous structure to manufacture rubber elastomer foam, and cross-links it by UV light curing; the elastomer foam prepared by the application has certain advantages such as impact resistance, compression resilience and shear resistance, but inevitably has the defects of uneven thickness and limited buffering capacity. Therefore, it is urgent to study and prepare an OCA optical glue with good thickness uniformity, good buffering effect and strong compressive resistance while reducing the thickness. Summary of the invention

[0004] The object of the present invention is to provide an impact-resistant OCA replacing foam adhesive and a preparation method thereof, so as to improve the impact resistance of OCA optical adhesive.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] An impact-resistant OCA replacing foam adhesive comprises: an optical light release film, an impact-resistant layer and an optical heavy release film arranged in sequence from top to bottom;

[0007] The impact-resistant layer comprises, by weight, 80-110 parts of adhesive, 30-60 parts of UV monomer, 0.5-1.5 parts of microsphere foaming agent, 0.3-0.6 parts of curing agent, 0.1-0.5 parts of cross-linking agent and 0.5-1 parts of silane coupling agent.

[0008] Furthermore, the adhesive is one or more combinations of acrylic pressure-sensitive adhesive, silicone adhesive, PU adhesive and EP adhesive.

[0009] Among them, acrylic pressure-sensitive adhesive is a kind of adhesive, which is copolymerized by main monomer, second monomer and functional group monomer. The main monomer makes the pressure-sensitive adhesive pressure-sensitive, which is acrylic acid with a low glass transition temperature (Tg) of the polymer. The second monomer gives the pressure-sensitive adhesive cohesion. The homopolymers of these monomers often have a higher Tg. The functional group monomer can make the pressure-sensitive adhesive produce a certain degree of cross-linking, improving its bonding performance.

[0010] The main components of acrylic pressure-sensitive adhesive include 2-ethyl acrylate, N,N-diethyl-2-acrylamide and acrylate.

[0011] Further, the UV monomer is one or more combinations of isooctyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate (2-EHA), isobornyl acrylate (IBOA) and acrylic acid.

[0012] Furthermore, the model of the microsphere foaming agent is one or more combinations of JH25D, F-35D and LT-I.

[0013] Among them, the microsphere foaming agent is a heat-expandable microsphere, which contains a low-boiling-point liquid or gas. When subjected to external stimulation (such as heating), the substance in the microsphere vaporizes or expands, causing the volume of the microsphere to increase rapidly, thereby forming a porous structure in the material. These porous structures can change the physical properties of the material, such as density, hardness, and cushioning performance. The microsphere foaming agent has the following characteristics: ① Improve the cushioning performance, absorb and disperse energy by compressing the gas in the microsphere and the elastic deformation of the microsphere itself, thereby improving the cushioning energy of the material; ② Wide range of particle sizes and uniform dispersion. The particle size of the microsphere foaming agent usually ranges from a few microns to tens of microns. The uniform particle size ensures that the cushioning effect is stable and reliable throughout the material; ③ Good controllability. The expanded microspheres will not undergo secondary expansion, which will affect the thickness uniformity of the product; ④ Reduce the material density. Since the density of the expanded microsphere foaming agent is low, the material will become lighter, which is very important for some products that require weight (such as portable electronic devices). At the same time, the lower density does not affect the cushioning performance of the material, which is conducive to maintaining good protection while reducing weight. Select one or more of them and add them into the special buffered OCA.

[0014] Furthermore, the curing agent is 184 and triphenyl phosphite (TPO).

[0015] The basic function of UV curing photoinitiator is to initiate polymerization, cross-linking and grafting reactions after absorbing ultraviolet light, so that the liquid forms a solid film in a very short time.

[0016] Furthermore, the cross-linking agent is one or more combinations of EM2217, EM235, and SR238NS.

[0017] Furthermore, the silane coupling agent is one or more combinations of KH-570, U03 and KBM550.

[0018] A method for preparing an impact-resistant OCA replacing foam glue comprises the following steps:

[0019] S1, mixing the adhesive, UV monomer, microsphere foaming agent, curing agent, cross-linking agent and silane coupling agent uniformly under an inert gas atmosphere, filtering, and degassing to obtain an impact-resistant layer coating liquid;

[0020] S2. Apply the impact-resistant layer coating liquid on the heavy release protective film, and attach the other side of the impact-resistant layer coating liquid to the light release protective film to obtain a semi-finished product; evenly apply the semi-finished product with a scraper, solidify, heat and foam, and obtain an impact-resistant OCA with a light release protective film, an impact-resistant layer and a heavy release protective film structure from top to bottom.

[0021] Furthermore, the scraper-coated semi-finished product is a product that uses a scraper coating method to evenly distribute the impact-resistant layer coating liquid between the light release protective film and the heavy release protective film.

[0022] Furthermore, the curing is UV light cross-linking curing for 4-10 minutes.

[0023] Furthermore, the heating and foaming is performed at 90-110° C. for 0.5-2 min.

[0024] Furthermore, the thickness of the impact-resistant layer is 100-220 μm; the thickness of the light release protective film is 50-150 μm; and the thickness of the heavy release protective film is 100-200 μm.

[0025] Beneficial effects of the present invention:

[0026] (1) The impact-resistant OCA provided by the present invention that replaces foam adhesive not only meets the requirements of OLED for buffering performance and compressive resistance, but also has a thin and uniform thickness, a simple preparation method and a relatively low cost, and no harmful substances are released by adding one or more microsphere foaming agents into the adhesive layer and coating it once.

[0027] (2) The microsphere foaming agent used in the present invention is added to the adhesive. Due to its thermal expansion characteristics, a porous hollow structure is formed in the material, which reduces the material density and improves the buffering capacity and pressure resistance. At the same time, due to the uniformity of its particle size and good compatibility, the prepared material has good stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention will be further described below in conjunction with the accompanying drawings.

[0029] Figure 1 It is a schematic structural diagram of an impact-resistant OCA replacing foam glue prepared by the preparation method provided by the present invention. DETAILED DESCRIPTION

[0030] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] Example 1

[0032] S1. Mix 100 parts of acrylic pressure-sensitive adhesive, 40 parts of isooctyl acrylate, 0.9 parts of microsphere foaming agent (F-35D), 0.5 parts of curing agent (184), 0.2 parts of cross-linking agent (EM2217) and 0.7 parts of KH-570 in an inert gas atmosphere, filter and degas to obtain an impact-resistant layer coating solution;

[0033] S2. Apply the impact-resistant layer coating liquid on the heavy release protective film, and attach the other side of the impact-resistant layer coating liquid to the light release protective film to obtain a semi-finished product; use a scraper to evenly coat the semi-finished product (use a scraper to coat the impact-resistant layer coating liquid so that it is evenly distributed between the light release protective film and the heavy release protective film), cross-link and cure with UV light for 6 minutes, and foam at 100°C for 1 minute to obtain an impact-resistant OCA with a light release protective film of 100 μm, an impact-resistant layer of 130 μm and a heavy release protective film structure of 150 μm from top to bottom.

[0034] The structure of the above-mentioned impact-resistant OCA is as follows Figure 1 shown.

[0035] Example 2

[0036] S1. Mix 110 parts of acrylic pressure-sensitive adhesive, 30 parts of isooctyl acrylate, 1.5 parts of microsphere foaming agent (F-35D), 0.3 parts of curing agent (184), 0.5 parts of cross-linking agent (EM2217) and 0.5 parts of KH-570 in an inert gas atmosphere, filter and degas to obtain an impact-resistant layer coating solution;

[0037] S2. Apply the impact-resistant layer coating liquid on the heavy release protective film, and attach the other side of the impact-resistant layer coating liquid to the light release protective film to obtain a semi-finished product; use a scraper to evenly coat the semi-finished product (use a scraper to coat the impact-resistant layer coating liquid so that it is evenly distributed between the light release protective film and the heavy release protective film), cross-link and cure with UV light for 6 minutes, and foam at 100°C for 1 minute to obtain an impact-resistant OCA with a light release protective film of 100 μm, an impact-resistant layer of 130 μm and a heavy release protective film structure of 150 μm from top to bottom.

[0038] The structure of the above-mentioned impact-resistant OCA is as follows Figure 1 shown.

[0039] Example 3

[0040] S1. Mix 80 parts of acrylic pressure-sensitive adhesive, 60 parts of isooctyl acrylate, 0.5 parts of microsphere foaming agent (F-35D), 0.6 parts of curing agent (184), 0.2 parts of cross-linking agent (EM2217) and 1 part of KH-570 in an inert gas atmosphere, filter and degas to obtain an impact-resistant layer coating solution;

[0041] S2. Apply the impact-resistant layer coating liquid on the heavy release protective film, and attach the other side of the impact-resistant layer coating liquid to the light release protective film to obtain a semi-finished product; use a scraper to evenly coat the semi-finished product (use a scraper to coat the impact-resistant layer coating liquid so that it is evenly distributed between the light release protective film and the heavy release protective film), cross-link and cure with UV light for 6 minutes, and foam at 100°C for 1 minute to obtain an impact-resistant OCA with a light release protective film of 100 μm, an impact-resistant layer of 130 μm and a heavy release protective film structure of 150 μm from top to bottom.

[0042] The structure of the above-mentioned impact-resistant OCA is as follows Figure 1 shown.

[0043] Example 4

[0044] Compared with Example 1, the difference between this example is that the model of the microsphere foaming agent in S1 is replaced with JH25D. The specific implementation steps of S1 are as follows:

[0045] S1. Mix 100 parts of acrylic pressure-sensitive adhesive, 40 parts of isooctyl acrylate, 0.9 parts of microsphere foaming agent (JH25D), 0.5 parts of curing agent (184), 0.2 parts of cross-linking agent (EM2217) and 0.7 parts of KH-570 in an inert gas atmosphere, filter and degas to obtain an impact-resistant layer coating solution;

[0046] The remaining raw materials and preparation process remain the same as in Example 1.

[0047] The structure of the above-mentioned impact-resistant OCA is as follows Figure 1 shown.

[0048] Example 5

[0049] Compared with Example 1, the difference between this example is that the model of the microsphere foaming agent in S1 is replaced with LT-I. The specific implementation steps of S1 are as follows:

[0050] S1. Mix 100 parts of acrylic pressure-sensitive adhesive, 40 parts of isooctyl acrylate, 0.9 parts of microsphere foaming agent (LT-I), 0.5 parts of curing agent (184), 0.2 parts of cross-linking agent (EM2217) and 0.7 parts of KH-570 in an inert gas atmosphere, filter and degas to obtain an impact-resistant layer coating solution;

[0051] The remaining raw materials and preparation process remain the same as in Example 1.

[0052] The structure of the above-mentioned impact-resistant OCA is as follows Figure 1 shown.

[0053] Example 6

[0054] S1. Mix 100 parts of acrylic pressure-sensitive adhesive, 40 parts of isooctyl acrylate, 0.9 parts of microsphere foaming agent (F-35D), 0.5 parts of triphenyl phosphite, 0.2 parts of cross-linking agent (SR238NS) and 0.7 parts of KBM550 in an inert gas atmosphere, filter and degas to obtain an impact-resistant layer coating solution;

[0055] S2. Apply the impact-resistant layer coating liquid on the heavy release protective film, and attach the other side of the impact-resistant layer coating liquid to the light release protective film to obtain a semi-finished product; use a scraper to evenly coat the semi-finished product (use a scraper to coat the impact-resistant layer coating liquid so that it is evenly distributed between the light release protective film and the heavy release protective film), cross-link and cure with UV light for 6 minutes, and foam at 100°C for 1 minute to obtain an impact-resistant OCA with a light release protective film of 100 μm, an impact-resistant layer of 130 μm and a heavy release protective film structure of 150 μm from top to bottom.

[0056] The structure of the above-mentioned impact-resistant OCA is as follows Figure 1 shown.

[0057] Example 7

[0058] Compared with Example 1, the difference between this embodiment is that the thickness of the impact-resistant layer in S2 is changed to 220 μm. The specific implementation steps are as follows:

[0059] S2. Apply the impact-resistant layer coating liquid on the heavy release protective film, and attach the other side of the impact-resistant layer coating liquid to the light release protective film to obtain a semi-finished product; use a scraper to evenly coat the semi-finished product (use a scraper to coat the impact-resistant layer coating liquid so that it is evenly distributed between the light release protective film and the heavy release protective film), cross-link and cure with UV light for 6 minutes, and foam at 100°C for 1 minute to obtain an impact-resistant OCA with a light release protective film of 100 μm, an impact-resistant layer of 220 μm, and a heavy release protective film structure of 150 μm from top to bottom.

[0060] The remaining raw materials and preparation process remain the same as in Example 1.

[0061] The structure of the above-mentioned impact-resistant OCA is as follows Figure 1 shown.

[0062] Comparative Example 1

[0063] Compared with Example 1, the difference between this comparative example is that no microsphere foaming agent is added in S1. The specific implementation steps of S1 are as follows:

[0064] S1, 101 parts of acrylic pressure-sensitive adhesive, 40 parts of isooctyl acrylate, 0.5 parts of curing agent (184), 0.2 parts of cross-linking agent (EM2217) and 0.7 parts of KH-570 are mixed uniformly under an inert gas atmosphere, filtered, and degassed to obtain an impact-resistant layer coating solution;

[0065] The remaining raw materials and preparation process remain the same as in Example 1.

[0066] The structure of the above-mentioned impact-resistant OCA is as follows Figure 1 shown.

[0067] Comparative Example 2

[0068] This comparative example is a commercially available conventional foam adhesive (Iwatani foam).

[0069] Comparative Example 3

[0070] This comparison is for HG's competitor OCA.

[0071] The performance of the impact-resistant OCA (hereinafter referred to as OCA) prepared in Examples 1 to 7 and Comparative Examples 1 to 3 was tested;

[0072] Adhesion: stick the test sample on the adhesive steel plate and let it stand for 20 minutes; tear off 10mm of the sample strip from the bottom to the top on the steel plate, then insert the bottom of the steel plate completely into the bottom of the card slot of the tensile machine, and then move the steel plate to align the sample strip with the adhesive strip, and tighten the screws to fix the steel plate; stick the torn 10mm strip completely overlapping the adhesive strip together, and select a 180° peel force test speed of 300mm / min to test its adhesion.

[0073] Drop ball cushioning test:

[0074] 1. Preparation: First, cut the copper foil into 1cm*4cm size, then cut the OCA into 1.5cm*4.5cm size, tear off the OCA light release protective film, laminate the adhesive surface of the OCA with the copper foil, and use scissors to cut the laminated sample into 1cm*1cm size;

[0075] 2. Test: Wipe the sensor platform clean with a dust-free cloth, take the cut sample (1cm*1cm), tear off the heavy release protective film, fit the adhesive surface to the sensor with the copper foil facing up, take a steel ball (12g), turn on the magnetic adsorption, adsorb the steel ball above the hanger (the height of the ball is 55mm from the sensor), and test the buffering force.

[0076] Backpressure test:

[0077] 1. Preparation: prepare a piece of white glass, attach OCA to the white glass, attach the polarizer to the other side of OCA, attach the polarizer with another piece of OCA, attach PET to OCA, attach the support film (film + glue) to PET, attach the back pressure test sample to the copper foil, and attach the copper foil + back pressure test sample to the support film surface;

[0078] 2. Test: ① The sensor descends at a speed of 4mm / min; ② The initial extrusion force is set to 1N; ③ After reaching 1N, maintain the pressure for 500s, then pick up the screen and observe the cover surface; ④ After the 1N force test is OK, repeat the test at the original extrusion position with an extrusion force increase of 0.5N each time, until the back pressure is just not visible from the cover surface (not lit) after the test (observe the reflection under the incandescent lamp). At this time, the maximum force that the tested screen can withstand is the back pressure test result;

[0079] The results are shown in Table 1:

[0080] Table 1

[0081]

[0082] According to the embodiments, comparative examples and Table 1, it can be seen that the difference between embodiments 2-3 and embodiment 1 is the reasonable change of the raw material ratio without affecting the performance. From the results in Table 1, the performance is not much different; the difference between embodiments 4-6 and embodiment 1 is the reasonable replacement of raw materials. After testing, the prepared OCA has greater viscosity and strong buffering capacity and compressive resistance; based on the results of embodiments 1-7, it can be found that the special buffer OCA provided by the present invention has compression resistance and buffering as the main functional layers. After being cured by a precise coating method, while ensuring that the adhesive layer is completely cured, the obtained special buffer OCA has good thickness uniformity and anti-buffering effect.

[0083] Compared with Example 1, Comparative Example 1 differs in whether a microsphere foaming agent is added. From the results, it can be seen that the cushioning performance and compressive resistance are greatly reduced. This is because the microsphere foaming agent has the characteristic of thermal expansion, which can form a porous hollow structure in the material, reduce the material density, and improve the cushioning capacity and compressive resistance of OCA; Compared with Comparative Example 2, Example 7 shows that OCA of the same thickness has not only better cushioning capacity and compressive rebound ability than foam glue, but also good viscosity, which means that it can replace foam glue in more situations and occasions; Compared with Comparative Example 3, Examples 1-6 show that the impact-resistant OCA prepared by the preparation method provided by the present invention has better cushioning capacity and compressive resistance than competing products, has strong competitiveness, and is suitable for large-scale production and application.

[0084] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0085] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An impact-resistant OCA replacing foam adhesive, characterized in that: It includes: an optical light release film, an impact-resistant layer and an optical heavy release film arranged in sequence from top to bottom; The impact-resistant layer comprises, by weight, 80-110 parts of adhesive, 30-60 parts of UV monomer, 0.5-1.5 parts of microsphere foaming agent, 0.3-0.6 parts of curing agent, 0.1-0.5 parts of cross-linking agent and 0.5-1 parts of silane coupling agent.

2. The impact-resistant OCA replacing foam adhesive according to claim 1, characterized in that: The adhesive is one or more combinations of acrylic pressure-sensitive adhesive, silicone adhesive, PU adhesive and EP adhesive.

3. The impact-resistant OCA replacing foam adhesive according to claim 1, characterized in that: The UV monomer is one or more combinations of isooctyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, isobornyl acrylate and acrylic acid.

4. The impact-resistant OCA replacing foam adhesive according to claim 1, characterized in that: The model of the microsphere foaming agent is one or more combinations of JH25D, F-35D and LT-I.

5. The impact-resistant OCA replacing foam adhesive according to claim 1, characterized in that: The curing agent is 184 and triphenyl phosphite.

6. The impact-resistant OCA replacing foam adhesive according to claim 1, characterized in that: The cross-linking agent is one or more combinations of EM2217, EM235, and SR238NS.

7. The impact-resistant OCA replacing foam adhesive according to claim 1, characterized in that: The silane coupling agent is one or more combinations of KH-570, U03 and KBM550.

8. A method for preparing an impact-resistant OCA replacing foam glue as claimed in any one of claims 1 to 7, characterized in that: The steps include: S1, mixing the adhesive, UV monomer, microsphere foaming agent, curing agent, cross-linking agent and silane coupling agent uniformly under an inert gas atmosphere, filtering, and degassing to obtain an impact-resistant layer coating liquid; S2, coating the impact-resistant layer coating liquid on the heavy release protective film, and laminating the other side of the impact-resistant layer coating liquid on the light release protective film to obtain a semi-finished product; The semi-finished product is evenly coated with a scraper, cured, and heated for foaming to obtain an impact-resistant OCA having a structure of a light release protective film, an impact-resistant layer, and a heavy release protective film from top to bottom.

9. The method for preparing an impact-resistant OCA replacing foam glue according to claim 8, characterized in that: The scraper-coated semi-finished product is a product that uses a scraper coating method to evenly distribute the impact-resistant layer coating liquid between the light release protective film and the heavy release protective film; the curing is UV light cross-linking curing for 4-10 minutes; the heating foaming is foaming at 90-110°C for 0.5-2 minutes.

10. The method for preparing an impact-resistant OCA replacing foam glue according to claim 8, characterized in that: The thickness of the impact-resistant layer is 100-220 μm; the thickness of the light release protective film is 50-150 μm; and the thickness of the heavy release protective film is 100-200 μm.

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