Edge warping prevention dual-curing coating for curved surface and composite film

Abstract

The invention discloses an anti-edge-warping dual-curing coating for a curved surface and a composite film. The dual-curing coating is prepared from the following raw materials in parts by weight: 30-70 parts of hydroxyl-containing modified acrylate, 20-50 parts of an acrylic monomer with the functionality greater than or equal to 3, 0.1-1 part of a flatting agent, 20-40 parts of a solvent, 0.01-0.5 part of a catalyst, 2-15 parts of a curing agent and 3-7 parts of a photoinitiator. The composite film comprises a shaping layer, and the shaping layer is formed by curing the anti-edge-warping dual-curing coating for the curved surface. Compared with the prior art, the double-curing coating has ultrahigh hardness and low shrinkage rate after curing, and after UV curing, the whole structure of the composite film can be driven to be matched with the curved surface direction of the curved screen to be bent inwards and shaped, so that the high-molecular base material layer is effectively prevented from bouncing back and warping.

Description

Technical Field

[0001] The invention belongs to the field of shapeable coatings, and in particular relates to an anti-warping dual-curing coating and a composite film for curved surfaces. Background Art

[0002] Nowadays, 3D curved screen mobile phones are loved and recognized by people, but the current conventional mobile phone screen protective films are not very compatible with curved screens. First, tempered films are difficult to form, and it is difficult to fit 100% which will affect touch and under-screen fingerprint unlocking; second, ordinary polyethylene terephthalate (PET) protective film can be made into curved screen protective film by hot pressing and other methods, but the disadvantage of this method is that it is easy to warp after fitting, it is easy to produce white edges, and the yield rate is extremely low; third, thermoplastic polyurethane elastomer (TPU) flexible protective film, TPU flexible protective film is excellent in fitting, but it has low hardness and is easy to be scratched, excessive fitting is easy to produce bubbles, and nail scratches and heavy marks are caused.

[0003] Patent publication number CN110105896A proposes a curved screen protective film and its preparation method, which includes an anti-scratch layer, a PET substrate, an elastomer layer, a silicone layer and a fluorine release film. The invention provides an elastomer layer and a reasonable thickness of each layer, so that the protective film has the basic performance of a PET screen protective film, and further improves its softness, drop resistance, and edge warping resistance, and describes the preparation method of the elastomer layer. In this invention, the elastomer layer is mainly set to improve the softness and certain drop resistance of the protective film, and cooperate with the silicone layer to fit the curved screen to achieve edge warping resistance. However, the elastomer layer in this invention is a flexible soft substrate with TG < 20°C, and the temperature has a greater impact on its hardness. When the temperature is low, its hardness increases, which affects the softness and edge warping resistance of the entire protective film. Although the setting of the elastomer layer makes the entire protective film softer, the properties of the PET film itself will not change, so the preparation yield of the protective film is low.

[0004] Patent publication number CN107033799A proposes a curved protective film with a multifunctional layer and a preparation method thereof. The invention is composed of a protective film layer, a hardening layer, a first substrate layer, a high-viscosity layer, a second substrate layer, a silicone layer, and a fluorine release layer from top to bottom. The first substrate layer and the second substrate layer are PET substrates with a thickness of 50 to 100 μm, and the main function of the high-viscosity layer is to increase the thickness and buffering capacity. The invention has anti-fouling and anti-fingerprint effects, high cleanliness, and anti-blue light effects, protecting the eyes. In the invention, the first substrate layer and the second substrate layer are both PET substrates, and the shaping force of the invention depends only on the adhesion of the silicone layer to the curved screen. At present, the screens of most curved screen products on the market have been treated with anti-fingerprint coating (AF) hydrophobic and oleophobic treatment, resulting in that the vast majority of pressure-sensitive adhesives have low adhesion to their screens. And because of the high hardness and difficulty in shaping of the PET substrate film, the invention only relies on the adhesion of the silicone layer and uses 2 layers of PET substrate film on the curved screen, which is easy to warp and produce white edges, which has been verified in the market. Summary of the invention

[0005] The purpose of the present invention is to provide a dual-curing coating and composite film for anti-warping of curved surfaces, which can solve the problem of high hardness and difficulty in shaping of PET substrate films in the existing curved surface protective films, which leads to easy warping and white edge problems on curved screens.

[0006] The technical solution of the present invention is:

[0007] A double-curing coating for preventing warping of curved surfaces, the double-curing coating comprising the following raw materials in parts by weight: 30-70 parts of hydroxyl-modified acrylate, 20-50 parts of acrylic monomer with a functionality of ≥3, 0.1-1 parts of leveling agent, 10-40 parts of solvent, 0.01-0.5 parts of catalyst, 2-15 parts of curing agent, and 3-7 parts of photoinitiator;

[0008] The hydroxyl-modified acrylate is a hydroxyl-containing polyurethane acrylate, which is prepared by polymerizing 100 to 200 parts of polyhydric alcohol, 150 to 300 parts of polyisocyanate, 100 to 200 parts of hydroxyl-containing acrylate and 0.2 to 0.5 parts of a polymerization catalyst by weight.

[0009] As a preferred embodiment, in the above-mentioned dual-curing coating for anti-warping of curved surfaces, the polyhydric alcohol is one or more of neopentyl glycol hydroxypivalate, neopentyl glycol, trimethylolpropane, pentaerythritol, 2,2,4-trimethyl-1,3-pentanediol, and 1,4-cyclohexanedimethanol.

[0010] As a preferred embodiment, in the above-mentioned dual-curing coating for anti-warping of curved surfaces, the polyisocyanate is one or more of 2,4-toluene diisocyanate, diphenylmethane diisocyanate, xylene diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, isophorone diisocyanate, and lysine diisocyanate trimer.

[0011] As a preferred embodiment, the anti-warping dual-curing coating for curved surfaces described above, the hydroxyl acrylate is one or more of hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, pentaerythritol triacrylate, and dipentaerythritol pentaacrylate.

[0012] As a preferred embodiment, in the above-mentioned dual-curing coating for preventing warping of curved surfaces, the polymerization catalyst is dibutyltin dilaurate.

[0013] The method for preparing the anti-warping dual-curing coating for curved surfaces and the hydroxyl-containing polyurethane acrylate of the present invention comprises the following steps:

[0014] Step 1. Add the weighed polyisocyanate and hydroxyl-containing acrylate into the reactor and stir well;

[0015] Step 2. Add a polymerization catalyst, heat to 30-100°C and stir for 3-6 hours;

[0016] Step 3. Add polyhydric alcohol, heat to 30-100° C. and stir for 3-6 hours to obtain hydroxyl-containing polyurethane acrylate.

[0017] As a preferred embodiment, in the above-mentioned dual-curing coating for anti-warping of curved surfaces, the acrylic monomer with a functionality ≥ 3 is one or more of trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, and ethoxylated trimethylolpropane triacrylate;

[0018] The leveling agent is an organic silicone leveling agent;

[0019] The solvent is one or more of lipid solvents, ether solvents and benzene solvents;

[0020] The catalyst is one or more of an organic bismuth catalyst, an organic tin catalyst, and an organic zinc catalyst;

[0021] The curing agent is one or more of an aromatic polyisocyanate curing agent, an aliphatic polyisocyanate curing agent or an alicyclic polyisocyanate curing agent.

[0022] A composite film for curved surfaces comprises a shaping layer, wherein the shaping layer is formed by curing the anti-warping edge dual-curing coating for curved surfaces of the present invention.

[0023] A composite film for curved surfaces is formed by laminating a hardening protective layer, a hardening layer, a polymer substrate layer, a shaping layer, a bubble-removing pressure-sensitive adhesive layer, and a pressure-sensitive adhesive protective film in sequence.

[0024] As a preferred embodiment, the hardened film protective layer is a low-viscosity heat-curing polyurethane (PU) protective film, the hardened layer is an acrylic hardened coating, the polymer substrate layer is a polyethylene terephthalate (PET) layer, the bubble-removing pressure-sensitive adhesive layer is a silicone bubble-removing pressure-sensitive adhesive layer specially made for AF screens or an OCA optical adhesive (Optically Clear Adhesive) layer specially made for AF screens, and the pressure-sensitive adhesive protective film is a fluorine release film or a silicone release film.

[0025] The thickness of the hardened protective layer is 45-55 μm, the thickness of the hardened layer is 2-4 μm, the thickness of the PET substrate layer is 20-40 μm, the thickness of the shaping layer is 50-70 μm, the thickness of the bubble-removing pressure-sensitive adhesive layer is 20-40 μm, and the thickness of the pressure-sensitive adhesive protective film is 45-55 μm.

[0026] The steps for preparing the composite membrane of the present invention are as follows:

[0027] 1. Weigh the components of the setting layer by weight and stir them evenly to obtain a setting layer coating;

[0028] 2. Coat the setting layer coating on the other side of the PET substrate coated with the hardening layer, attach the release film after thermal curing, and place it in a 50°C environment under light shielding for curing to obtain a protective film prefabricated layer;

[0029] 3. Tear off the release film under the shaping layer in the protective film prefabricated layer, apply a bubble-removing pressure-sensitive adhesive layer on the shaping layer, attach a pressure-sensitive adhesive protective film, and obtain a protective film prefabricated product;

[0030] 4. After die-cutting according to the curved screen to be protected, tear off the pressure-sensitive adhesive protective layer in the protective film and stick it on the curved screen, and then UV cure it to complete the preparation.

[0031] The design idea of ​​the present invention is:

[0032] First, the hydroxyl-containing polyurethane acrylate and isocyanate-containing acrylate contained in the shaping layer of the present invention can be well thermally cured at a certain temperature through the nucleophilic addition reaction of hydroxyl and isocyanate groups. After film pasting, the two different polyurethane acrylates further crosslink with themselves and each other through double bonds on the molecules, and can crosslink with monomers with high functionality (functionality ≥ 3) contained in the shaping layer. In this way, through the dual curing of thermal curing and light curing, the shaping layer has a high hardness and a very low shrinkage rate after curing, forcing the PET substrate film attached thereto to fit tightly to the coating and the curved screen, helping the high-hardness PET substrate film to be completely shaped, preventing it from deforming and warping, and producing white edges; secondly, the adhesion of the bubble-removing pressure-sensitive adhesive to the curved screen increases the difficulty of warping; finally, the present invention only uses a single-layer PET film, which has a better shaping effect and has achieved a good technical progress compared to the prior art.

[0033] The advantages and beneficial effects of the present invention are:

[0034] Compared with the prior art, the dual-curing coating of the present invention has ultra-high hardness and low shrinkage after curing. After ultraviolet (UV) curing, it can drive the entire structure of the composite film to bend inward and shape in the direction of the curved surface of the curved screen, effectively preventing the polymer substrate layer from rebounding and warping. DETAILED DESCRIPTION

[0035] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only embodiments of a part of the present invention, rather than all embodiments.

[0036] The polyurethane acrylates in the embodiment of the present invention include two types: hydroxyl-containing polyurethane acrylate A and isocyanate-containing polyurethane acrylate B. The specific preparation method is as follows:

[0037] Synthesis of Hydroxyl-containing Polyurethane Acrylate A:

[0038] Weigh 175g of 2,4-toluene diisocyanate and 117g of hydroxyethyl acrylate, put them into a reactor and stir for 30 minutes, then add 0.3g of dibutyltin dilaurate, stir and heat to 60°C, and keep warm for 5 hours. Then add 147g of 2,2,4-trimethyl-1,3-pentanediol, and keep warm at 70°C for 5 hours. After discharging, hydroxyl-containing polyurethane acrylate A can be obtained.

[0039] Synthesis of isocyanate-containing polyurethane acrylate B:

[0040] Weigh 223g of isophorone diisocyanate, 66g of hydroxyethyl methacrylate and 72g of hydroxypropyl methacrylate, put them into a reactor and stir for 30 minutes, then add 0.35g of dibutyltin dilaurate, stir and heat to 70°C, and keep warm for 6 hours. Then add 145g of 1,4-cyclohexanedimethanol and keep warm at 80°C for 5 hours. After discharging, isocyanate-containing polyurethane acrylate B is obtained.

[0041] The hardened film protective layer described in the following embodiments is a low-viscosity heat-curing polyurethane (PU) protective film, the hardened layer is an acrylic hardened coating, the polymer substrate layer is a polyethylene terephthalate (PET) layer, the bubble-removing pressure-sensitive adhesive layer is a silicone bubble-removing pressure-sensitive adhesive layer specially used for AF screens, and the pressure-sensitive adhesive protective film is a fluorine release film.

[0042] Below, the present invention is further described in detail by examples.

[0043] Embodiment 1:

[0044] The thickness of each layer of the composite film in this embodiment is as follows:

[0045] Hardened protective layer 50μm, hardened layer 3μm, PET base material layer 30μm, shaping layer 60μm, bubble-removing pressure-sensitive adhesive layer 30μm, pressure-sensitive adhesive protective layer 50μm.

[0046] The shaping layer is prepared by mixing the following ingredients in parts by weight:

[0047] 40 parts of hydroxyl-containing polyurethane acrylate A, 37 parts of dipentaerythritol hexaacrylate, 8 parts of pentaerythritol triacrylate, 0.2 parts of silicone leveling agent (BYK306 from BYK Chemical Company, Germany), 14.75 parts of ethyl acetate, 0.05 parts of organic tin catalyst (dibutyltin dilaurate), 8 parts of hexamethylene diisocyanate, and 5 parts of 184 photoinitiator (hydroxycyclohexane phenone).

[0048] The steps for preparing the composite membrane in this embodiment are as follows:

[0049] 1. Weigh the components of the setting layer by weight and stir them evenly to obtain a setting layer coating;

[0050] 2. Coat the setting layer coating on the other side of the PET substrate coated with the hardening layer, attach the release film after thermal curing, and place it in a 50°C environment under light shielding for curing to obtain a protective film prefabricated layer;

[0051] 3. Tear off the release film under the shaping layer in the protective film prefabricated layer, apply a bubble-removing pressure-sensitive adhesive layer on the shaping layer, attach a pressure-sensitive adhesive protective film, and obtain a protective film prefabricated product;

[0052] 4. After die-cutting according to the curved screen to be protected, tear off the pressure-sensitive adhesive protective layer in the protective film and stick it on the curved screen, and then UV cure it to complete the preparation.

[0053] Example 2

[0054] The thickness of each layer of the composite film in this embodiment is as follows:

[0055] Hardened protective layer 50μm, hardened layer 3μm, PET base material layer 30μm, shaping layer 60μm, bubble-removing pressure-sensitive adhesive layer 30μm, pressure-sensitive adhesive protective layer 50μm.

[0056] Wherein, the shaping layer is composed of the following components by weight:

[0057] 40 parts of isocyanate-containing polyurethane acrylate B, 37 parts of dipentaerythritol hexaacrylate, 8 parts of pentaerythritol triacrylate, 0.2 parts of organosilicon leveling agent (BYK-310 from BYK Chemical Company, Germany), 14.75 parts of ethyl acetate, 0.05 parts of organotin catalyst (dibutyltin dilaurate), 6 parts of hexamethylene diisocyanate, 4 parts of isophorone diisocyanate, 1173 photoinitiator (2-hydroxy-2-methyl-1-phenyl-1-propanone) 5 parts. The steps for making the composite film of this embodiment are the same as those of the above embodiment 1.

[0058] Example 3

[0059] The thickness of each layer of the composite film in this embodiment is as follows:

[0060] Hardened protective layer 50μm, hardened layer 3μm, PET base material layer 30μm, shaping layer 60μm, bubble-removing pressure-sensitive adhesive layer 30μm, pressure-sensitive adhesive protective layer 50μm.

[0061] Wherein, the shaping layer is composed of the following components by weight:

[0062] 60 parts of hydroxyl-containing polyurethane acrylate A, 15 parts of trimethylolpropane trimethacrylate, 5 parts of pentaerythritol tetraacrylate, 0.2 parts of silicone leveling agent (Tego-1484 from German Digo Chemical Company), 9.75 parts of ethyl acetate, 10 parts of butyl acetate, 0.2 parts of organic bismuth catalyst (bismuth laurate), 12 parts of hexamethylene diisocyanate, and 7 parts of 184 photoinitiator (hydroxycyclohexane phenone).

[0063] The steps for preparing the composite membrane in this embodiment are the same as those in the above embodiment 1.

[0064] Example 4

[0065] The thickness of each layer of the composite film in this embodiment is as follows:

[0066] Hardened protective layer 50μm, hardened layer 3μm, PET base material layer 30μm, shaping layer 60μm, bubble-removing pressure-sensitive adhesive layer 30μm, pressure-sensitive adhesive protective layer 50μm.

[0067] Wherein, the shaping layer is composed of the following components by weight:

[0068] 60 parts of isocyanate-containing polyurethane acrylate B, 15 parts of trimethylolpropane trimethacrylate, 5 parts of pentaerythritol tetraacrylate, 0.2 parts of silicone leveling agent (Tego-415 from German Digo Chemical Company), 9.75 parts of ethyl acetate, 10 parts of butyl acetate, 0.2 parts of organic bismuth catalyst (bismuth cyclohexane acid), 12 parts of isophorone diisocyanate, 3 parts of 1,5-pentamethylene diisocyanate, and 7 parts of 1173 photoinitiator (2-hydroxy-2-methyl-1-phenyl-1-propanone).

[0069] The steps for preparing the composite membrane in this embodiment are the same as those in the above embodiment 1.

[0070] Example 5

[0071] Physical tests were performed on the composite films prepared in Examples 1 to 4 of the present invention, and the test results are shown in the following table:

[0072]

[0073] Embodiments 1 to 4 of the present invention use PET film as the substrate, which can be rolled up after thermal curing. After die-cutting, the ultra-high hardness and high shrinkage rate of the shaping layer are mainly utilized to drive the entire structure to bend inward, that is, to bend in the direction of the curved surface of the curved screen. It has great resistance to PET rebound and warping, which is the main reason why PET is used as the substrate while still ensuring that the composite film has the advantage of being shaped without rebound, warping, and white edges.

[0074] Embodiments 1 to 4 of the present invention have the excellent surface treatment properties of the PET protective film, such as anti-fingerprint and anti-scratch coating and self-repairing coating, easy bubble removal, and excellent mechanical adhesion, and can overcome the edge warping of the PET protective film when used for a curved screen. Compared with the currently conventional PET curved protective film, it has good shaping, no warping, no rebound, no white edges, and a high yield of more than 95%.

[0075] At the same time, compared with the conventional tempered protective film, the embodiments 1 to 4 of the present invention can be rolled up after heat curing, are convenient for transportation and storage, are easy to shape, and can be 100% laminated without affecting the sensitivity of the touch screen. In addition, compared with the conventional TPU curved surface protective film, the embodiments of the present invention have high hardness, good scratch resistance, fast finger pressure rebound, and can be quickly and automatically laminated by a robot. After heat curing, the shaping layer and the silicone layer of the embodiments 1 to 4 of the present invention are both soft coatings, making the entire protective film softer than a single-layer PET film. After the robot is laminated and withdrawn, the edge will not rebound and warp immediately, which is more conducive to mechanical automation construction.

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that after reading the specification of this application, the technicians can still modify or replace the specific implementation mode of the present invention with equivalents, but these modifications or changes do not deviate from the scope of protection of the pending claims of the present application.

Claims

1. A dual-curing coating for anti-warping of curved surfaces, characterized in that: The dual-curing coating is composed of the following raw materials in parts by weight: 30-70 parts of hydroxyl-modified acrylate, 20-50 parts of acrylic monomer with a functionality of ≥3, 0.1-1 parts of leveling agent, 10-40 parts of solvent, 0.01-0.5 parts of catalyst, 2-15 parts of curing agent, and 3-7 parts of photoinitiator; The hydroxyl-modified acrylate is a hydroxyl-containing polyurethane acrylate, which is prepared by polymerizing 100 to 200 parts of polyhydric alcohol, 150 to 300 parts of polyisocyanate, 100 to 200 parts of hydroxyl-containing acrylate and 0.2 to 0.5 parts of a polymerization catalyst by weight.

2. The anti-warping dual-curing coating for curved surfaces according to claim 1, characterized in that: The polyhydric alcohol is one or more of neopentyl glycol hydroxypivalate, neopentyl glycol, trimethylolpropane, pentaerythritol, 2,2,4-trimethyl-1,3-pentanediol and 1,4-cyclohexanedimethanol.

3. The anti-warping dual-curing coating for curved surfaces according to claim 1, characterized in that: The polyisocyanate is one or more of toluene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, isophorone diisocyanate, and lysine diisocyanate trimer.

4. The anti-warping dual-curing coating for curved surfaces according to claim 1, characterized in that: The hydroxyl-containing acrylate is one or more of hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, pentaerythritol triacrylate, and dipentaerythritol pentaacrylate.

5. The anti-warping dual-curing coating for curved surfaces according to claim 1, characterized in that: The polymerization catalyst is dibutyltin dilaurate.

6. The anti-warping dual-curing coating for curved surfaces according to claim 1, characterized in that: The preparation method of hydroxyl-containing polyurethane acrylate comprises the following steps: Step 1. Add the weighed polyisocyanate and hydroxyl-containing acrylate into the reactor and stir well; Step 2. Add a polymerization catalyst, heat to 30-100°C and stir for 3-6 hours; Step 3. Add polyhydric alcohol, heat to 30-100° C. and stir for 3-6 hours to obtain hydroxyl-containing polyurethane acrylate.

7. The anti-warping dual-curing coating for curved surfaces according to claim 1, characterized in that: The acrylic monomer with functionality ≥3 is one or more of trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, and ethoxylated trimethylolpropane triacrylate; The leveling agent is an organic silicone leveling agent; The solvent is one or more of lipid solvents, ether solvents and benzene solvents; The catalyst is one or more of an organic bismuth catalyst, an organic tin catalyst, and an organic zinc catalyst; The curing agent is one or more of an aromatic polyisocyanate curing agent, an aliphatic polyisocyanate curing agent or an alicyclic polyisocyanate curing agent.

8. A composite film for a curved surface, characterized in that: The composite film comprises a shaping layer, and the shaping layer is formed by curing the anti-warping dual-curing coating for curved surfaces according to any one of claims 1 to 7.

9. The composite film for curved surfaces according to claim 8, characterized in that: The composite film is formed by laminating a hardening protective layer, a hardening layer, a polymer base material layer, a shaping layer, a bubble-removing pressure-sensitive adhesive layer and a pressure-sensitive adhesive protective film in sequence.

10. The composite film applicable to curved surfaces according to claim 9, characterized in that: The hardened film protective layer is a low-viscosity heat-curing polyurethane protective film, the hardened layer is an acrylic hardened coating, the polymer substrate layer is a polyethylene terephthalate layer, the bubble-removing pressure-sensitive adhesive layer is a silicone bubble-removing pressure-sensitive adhesive layer dedicated to AF screens or an OCA optical adhesive layer dedicated to AF screens, and the pressure-sensitive adhesive protective film is a fluorine release film or a silicone release film; The steps of preparing the composite membrane are as follows: (1) Weighing the components of the setting layer by weight and stirring them evenly to obtain a setting layer coating; (2) coating a setting layer coating on the other side of the PET substrate coated with the hardening layer, attaching a release film after thermal curing, and then shielding and ripening to obtain a protective film prefabricated layer; (3) tearing off the release film under the shaping layer in the protective film prefabricated layer, coating the bubble-removing pressure-sensitive adhesive layer on the shaping layer, and attaching the pressure-sensitive adhesive protective film to obtain a protective film prefabricated product; (4) After die-cutting according to the curved screen to be protected, the pressure-sensitive adhesive protective layer in the protective film is torn off and attached to the curved screen, and then UV-cured to obtain the product.

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