Composite binder, preparation method and application thereof, and display device

Abstract

The invention relates to a composite binder, a preparation method and application thereof and a display device. The composite binder comprises a first adhesive film and a second adhesive film which are arranged in a stacked mode, preparation raw materials of the first adhesive film comprise a first prepolymer, and preparation raw materials of the second adhesive film comprise a second prepolymer; the preparation monomers of the first prepolymer comprise first alkyl acrylate, second alkyl acrylate and acrylamide, and the preparation monomers of the second prepolymer comprise third alkyl acrylate, fourth alkyl acrylate and a functional monomer; the first acrylic acid alkyl ester and the third acrylic acid alkyl ester do not contain hydroxyl groups or hydroxyl-like groups, and the second acrylic acid alkyl ester and the fourth acrylic acid alkyl ester contain at least one of hydroxyl groups and hydroxyl-like groups. The composite binder is good in humidity and heat resistance.

Description

Technical Field

[0001] The present application relates to the field of material technology, and in particular to a composite adhesive and a preparation method and application thereof, and a display device. Background Art

[0002] Optically transparent pressure-sensitive adhesives (OCA) are widely used in optical electronic displays. For example, they are used to bond display modules, touch screens or cover lenses on LCD, OLED and other display devices. Among them, pressure-sensitive adhesives bonding display modules, touch screens or cover lenses in display devices are called optical laminates. However, traditional OCAs have poor moisture and heat resistance when bonding display modules, touch screens and cover lenses.

[0003] Therefore, it is necessary to improve the traditional technology. Summary of the invention

[0004] Based on this, the present application provides a composite adhesive with good moisture and heat resistance, a preparation method and application thereof, and a display device.

[0005] The technical solution of this application to solve the above technical problems is as follows.

[0006] On the one hand, the present application provides a composite adhesive, including a first adhesive film and a second adhesive film stacked together, wherein the raw materials for preparing the first adhesive film include a first prepolymer, and the raw materials for preparing the second adhesive film include a second prepolymer; monomers for preparing the first prepolymer include a first alkyl acrylate, a second alkyl acrylate and acrylamide, and monomers for preparing the second prepolymer include a third alkyl acrylate, a fourth alkyl acrylate and a functional monomer; the first alkyl acrylate and the third alkyl acrylate do not contain hydroxyl groups or hydroxyl-like groups, and the second alkyl acrylate and the fourth alkyl acrylate contain at least one of hydroxyl groups and hydroxyl-like groups.

[0007] In some of the embodiments, in the composite adhesive, the first prepolymer includes the following monomers, calculated by mass percentage: 60% to 85% of a first alkyl acrylate, 10% to 30% of a second alkyl acrylate, and 4% to 25% of acrylamide.

[0008] In some embodiments, in the composite adhesive, the first prepolymer satisfies at least one of the following characteristics:

[0009] (1) The first alkyl acrylate includes acrylic acid C4~C 18 Alkyl ester; Optionally, the acrylic acid C4~C 18 The alkyl ester includes at least one of n-butyl acrylate, n-butyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, isooctyl acrylate, isooctyl methacrylate, lauryl acrylate and isostearyl acrylate;

[0010] (2) the second alkyl acrylate comprises at least one of hydroxyethyl acrylate, hydroxybutyl acrylate and 2 (2-ethoxyethoxy) ethyl acrylate;

[0011] (3) The acrylamide monomer includes at least one of acrylamide, methacrylamide, N-methylacrylamide, N-methylmethacrylamide, N,N-dimethylacrylamide, N,N-dimethylacrylamide, N,N-dimethylmethacrylamide, N-octylacrylamide and N-octylmethacrylamide.

[0012] In some of the embodiments, in the composite adhesive, the raw materials for preparing the first adhesive film further include at least one of a first alkyl methacrylate, a first cross-linking agent, a first photoinitiator, a first chain transfer agent and a first silane coupling agent.

[0013] In some embodiments, in the composite adhesive, the raw material for preparing the first adhesive film satisfies at least one of the following characteristics:

[0014] (1) The mass of the first alkyl methacrylate is 2% to 5% of the mass of the first prepolymer;

[0015] (2) The mass of the first cross-linking agent is 0.5% to 5% of the mass of the first prepolymer;

[0016] (3) The mass of the first photoinitiator is 0.1% to 1.5% of the mass of the first prepolymer;

[0017] (4) The mass of the first chain transfer agent is 0.01% to 0.5% of the mass of the first prepolymer;

[0018] (5) The mass of the first silane coupling agent is 0.01% to 0.5% of the mass of the first prepolymer.

[0019] In some embodiments, in the composite adhesive, the raw materials for preparing the first adhesive film meet at least one of the following characteristics:

[0020] (1) the first alkyl methacrylate comprises at least one of methyl methacrylate, ethyl methacrylate and isooctyl methacrylate;

[0021] (2) the first cross-linking agent comprises at least one of polyurethane acrylate and polyether urethane methacrylate;

[0022] (3) the first photoinitiator includes at least one of hydroxycyclohexane phenone, 4-acryloxybenzophenone and 2,2-dimethoxy-2-phenylacetophenone;

[0023] (4) the first chain transfer agent includes dodecanethiol;

[0024] (5) The first silane coupling agent includes KH560.

[0025] In some of the embodiments, in the composite adhesive, the second prepolymer includes the following monomers: 60% to 80% of the third alkyl acrylate, 10% to 30% of the fourth alkyl acrylate and 3% to 12% of the functional monomer.

[0026] In some embodiments, in the composite adhesive, the second prepolymer satisfies at least one of the following characteristics:

[0027] (1) The third alkyl acrylate includes C4-C8 alkyl acrylate; optionally, the C4-C8 alkyl acrylate includes at least one of n-butyl acrylate, n-butyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, isooctyl acrylate and isooctyl methacrylate;

[0028] (2) the fourth alkyl acrylate comprises at least one of hydroxyethyl acrylate, hydroxybutyl acrylate and 2 (2-ethoxyethoxy) ethyl acrylate;

[0029] (3) The functional monomer includes at least one of an acrylic monomer, an amide monomer and a vinyl monomer; optionally, the acrylic monomer includes at least one of acrylic acid and methacrylic acid; optionally, the amide monomer includes at least one of acrylamide and methacrylamide; optionally, the vinyl monomer contains a nitrogen-containing heterocycle; optionally, the vinyl monomer includes at least one of N-vinyl caprolactam and N-vinyl pyrrolidone.

[0030] In some of the embodiments, in the composite adhesive, the raw materials for preparing the second adhesive film further include at least one of a second alkyl methacrylate, a second cross-linking agent, a second photoinitiator, a second chain transfer agent, a second silane coupling agent and an antioxidant.

[0031] In some embodiments, in the composite adhesive, the raw material for preparing the second adhesive film satisfies at least one of the following characteristics:

[0032] (1) The mass of the second alkyl methacrylate is 2% to 5% of the mass of the second prepolymer;

[0033] (2) The mass of the second cross-linking agent is 1% to 5% of the mass of the second prepolymer;

[0034] (3) The mass of the second photoinitiator is 0.05% to 1.5% of the mass of the second prepolymer;

[0035] (4) The mass of the second chain transfer agent is 0.15% to 0.5% of the mass of the second prepolymer;

[0036] (5) The mass of the second silane coupling agent is 0.15% to 0.5% of the mass of the second prepolymer;

[0037] (6) The mass of the antioxidant is 0.05% to 0.5% of the mass of the second prepolymer.

[0038] In some embodiments, in the composite adhesive, the raw material for preparing the second adhesive film satisfies at least one of the following characteristics:

[0039] (1) the second alkyl methacrylate comprises at least one of n-butyl methacrylate, tert-butyl methacrylate and isooctyl methacrylate;

[0040] (2) the second cross-linking agent comprises at least one of hexamethylene diisocyanate, polyurethane acrylate and polyether urethane methacrylate;

[0041] (3) the second photoinitiator comprises at least one of diphenyl-(2,4,6-trimethylbenzoyl)-phosphine oxide and phenyl-bis(2,4,6-trimethylbenzoyl)-phosphine oxide;

[0042] (4) the second chain transfer agent includes dodecanethiol;

[0043] (5) The second silane coupling agent includes KH560;

[0044] (6) The antioxidant includes pentaerythritol 4[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate.

[0045] In some embodiments, in the composite adhesive, the composite adhesive satisfies at least one of the following characteristics:

[0046] (1) The thickness ratio of the first adhesive film to the second adhesive film is 1:3-10;

[0047] (2) The thickness of the first adhesive film is 25 μm to 100 μm;

[0048] (3) The thickness of the second adhesive film is 125 μm~500 μm.

[0049] On the one hand, the present application provides a method for preparing a composite adhesive, comprising the following steps:

[0050] A first adhesive film and a second adhesive film are formed in a stacked arrangement, wherein the raw materials for preparing the first adhesive film include a first prepolymer, and the raw materials for preparing the second adhesive film include a second prepolymer; monomers for preparing the first prepolymer include a first alkyl acrylate, a second alkyl acrylate and acrylamide, and monomers for preparing the second prepolymer include a third alkyl acrylate, a fourth alkyl acrylate and a functional monomer; the first alkyl acrylate and the third alkyl acrylate do not contain hydroxyl groups or hydroxyl-like esters, and the second alkyl acrylate and the fourth alkyl acrylate contain at least one of hydroxyl groups and hydroxyl-like esters.

[0051] In some embodiments, in the method for preparing the composite adhesive, the step of forming the first adhesive film and the second adhesive film stacked together comprises:

[0052] Mixing the raw materials for preparing the first adhesive film to obtain a first adhesive material;

[0053] Forming the first rubber material into a coating film, and curing the coating film to obtain a first film layer;

[0054] Mixing the raw materials for preparing the second adhesive film to obtain a second adhesive material;

[0055] Forming the second rubber material into a coating film, and curing the coating film to obtain a second film layer;

[0056] The first film layer and the second film layer are compounded to form the first adhesive film and the second adhesive film which are stacked.

[0057] On one hand, the present application provides the use of the above-mentioned composite adhesive or the composite adhesive prepared by the above-mentioned preparation method in the preparation of a display device.

[0058] On the one hand, the present application provides a display device, comprising the composite adhesive or the composite adhesive prepared by the above preparation method

[0059] In some embodiments, in a display device, the display device includes a first substrate and a second substrate, the first substrate and the second substrate are connected via the composite adhesive, the first adhesive film in the composite adhesive is connected to the first substrate, and the second adhesive film in the composite adhesive is connected to the second substrate.

[0060] Compared with the prior art, the composite adhesive of the present application has the following beneficial effects:

[0061] The composite adhesive of the present application includes a first adhesive film and a second adhesive film which are stacked. The first adhesive film includes a first prepolymer prepared from a specific monomer, and the second adhesive film includes a second prepolymer prepared from a specific monomer. This ensures that the composite adhesive has good moisture and heat resistance and maintains a high light transmittance and a low haze under high temperature and high humidity environmental conditions.

[0062] The composite adhesive of the present application is used to bond display modules, touch screens or cover lenses in display devices, especially for bonding display modules, touch screens or cover lenses with high-step-difference inks on the surface. The second adhesive film in the composite adhesive can fully fill the high-step-difference ink, so that it maintains a high light transmittance and a low haze under high temperature and high humidity environmental conditions, without bubbles, cracks, yellowing and the like, and meets the appearance requirements of optical electronic display devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] In order to more clearly illustrate the technical solutions in the embodiments of the present application and to more completely understand the present application and its beneficial effects, the following is a brief introduction to the drawings required for the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application, and those skilled in the art can obtain other drawings based on these drawings without creative work.

[0064] Figure 1 A schematic diagram of the structure of a composite adhesive provided in one embodiment;

[0065] Figure 2 The structure of a display device provided in one embodiment is schematically shown.

[0066] Description of reference numerals:

[0067] 110: composite adhesive; 1101: first adhesive film; 1102: second adhesive film; 100: display device; 120: first substrate; 130: second substrate; 140: high step-difference ink layer. DETAILED DESCRIPTION

[0068] The present application will be further described in detail below in conjunction with the embodiments and examples. It should be understood that these embodiments and examples are only used to illustrate the present application and are not used to limit the scope of the present application. The purpose of providing these embodiments and examples is to make the understanding of the disclosure of the present application more thorough and comprehensive.

[0069] It should also be understood that the present application can be implemented in many different forms and is not limited to the embodiments and examples described herein. Those skilled in the art can make various changes or modifications without violating the connotation of the present application, and the equivalent forms obtained also fall within the scope of protection of the present application. For example, the features illustrated or described as part of one embodiment can be combined in another embodiment in a suitable manner to produce a new embodiment. In addition, in the description below, a large number of specific details are given in order to provide a more comprehensive understanding of the present application. It should be understood that the present application can be implemented without one or more of these details.

[0070] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing implementation modes and embodiments and are not intended to limit this application.

[0071] Unless otherwise specified or incompatible herewith, the terms and phrases used herein shall have the following meanings:

[0072] In the present application, "plurality", "multiple", "multiple times", etc., unless otherwise specified, refer to a number greater than 2 or equal to 2. For example, "one or more" means one or greater than or equal to two.

[0073] As used herein, "combination thereof", "any combination thereof", "any combination thereof" etc. include all suitable combinations of any two or more of the listed items.

[0074] Herein, the “suitable” mentioned in “suitable combination”, “suitable method”, “any suitable method”, etc., shall be based on the ability to implement the technical solution of this application, solve the technical problems of this application, and achieve the expected technical effects of this application.

[0075] Herein, "preferred", "better", "more preferred", and "suitable" are only used to describe implementation methods or examples with better effects, and it should be understood that they do not constitute a limitation on the scope of protection of this application. If multiple "preferred" items appear in a technical solution, unless otherwise specified and there is no contradiction or mutual restriction, each "preferred" item is independent.

[0076] In the present application, "further", "further", "particularly" and the like are used for descriptive purposes to indicate differences in content, but should not be construed as limiting the scope of protection of the present application.

[0077] In this application, "optionally", "optional", and "optional" mean optional or dispensable, that is, any one of the two parallel schemes of "yes" or "no". If multiple "options" appear in a technical solution, unless otherwise specified and there is no contradiction or mutual restriction, each "optional" is independent.

[0078] In the present application, the terms "first", "second", "third", "fourth", etc. in "the first aspect", "the second aspect", "the third aspect", "the fourth aspect", etc. are used only for descriptive purposes and cannot be understood as indicating or implying relative importance or quantity, nor can they be understood as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first", "second", "third", "fourth", etc. only serve the purpose of non-exhaustive enumeration and description, and it should be understood that they do not constitute a closed limitation on quantity.

[0079] In the present application, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0080] In the present application, when it comes to a numerical interval (i.e., a numerical range), unless otherwise specified, the distribution of the optional numerical values ​​in the numerical interval is considered to be continuous, and includes the two numerical endpoints (i.e., the minimum value and the maximum value) of the numerical interval, and each numerical value between the two numerical endpoints. Unless otherwise specified, when the numerical interval only refers to the integers in the numerical interval, it includes the two endpoint integers of the numerical range, and each integer between the two endpoints, which is equivalent to directly listing each integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be combined. In other words, unless otherwise specified, the numerical range disclosed herein should be understood to include any and all sub-ranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, a percentage, a ratio, etc. "Numerical interval" allows broadly including numerical interval types such as percentage intervals, ratio intervals, and ratio intervals.

[0081] The temperature parameters in this application, unless otherwise specified, are allowed to be either constant temperature treatment or to vary within a certain temperature range. It should be understood that the constant temperature treatment allows the temperature to fluctuate within the accuracy range controlled by the instrument. Fluctuations within the range of ±5°C, ±4°C, ±3°C, ±2°C, and ±1°C are allowed.

[0082] In this application, the term "room temperature" or "normal temperature" generally refers to 4°C to 35°C, for example, 20°C ± 5°C. In some embodiments of this application, "room temperature" or "normal temperature" refers to 10°C to 30°C. In some embodiments of this application, "room temperature" or "normal temperature" refers to 20°C to 30°C.

[0083] In this application, when referring to the unit of a data range, if there is a unit only after the right endpoint, it means that the units of the left and right endpoints are the same. For example, 3~5 h means that the units of the left endpoint "3" and the right endpoint "5" are both h (hours).

[0084] All documents mentioned in this application are cited as references in this application, just as each document is cited as reference separately. Unless they conflict with the invention purpose and / or technical solution of this application, the cited documents involved in this application are cited with all contents and all purposes. When the cited documents are involved in this application, the definitions of relevant technical features, terms, nouns, phrases, etc. in the cited documents are also cited. When the cited documents are involved in this application, the examples and preferred methods of the cited relevant technical features can also be incorporated into this application as references, but are limited to the implementation of this application. It should be understood that when the cited content conflicts with the description in this application, the present application shall prevail or be modified adaptively according to the description of this application.

[0085] The mass or weight of the relevant components mentioned in the specification of the embodiments of the present application may not only refer to the specific content of each component, but also indicate the proportional relationship of the mass or weight between the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the specification of the embodiments of the present application, it is within the scope disclosed in the specification of the embodiments of the present application. Specifically, the mass or weight described in the specification of the embodiments of the present application may be units known in the chemical industry such as μg, mg, g, and kg.

[0086] It is known that a considerable portion of laminates contain high-step-difference inks. When using OCA to achieve bonding of the display module to the touch screen and cover lens, it is necessary to ensure that the OCA is fully filled with the high-step-difference ink so that the entire optical laminate still maintains an appearance that meets the requirements of optical electronic displays under a variety of environmental conditions.

[0087] See also Figure 1 In one embodiment of the present application, a composite adhesive 110 is provided, comprising a first adhesive film 1101 and a second adhesive film 1102 which are stacked, wherein the raw material for preparing the first adhesive film 1101 comprises a first prepolymer, and the raw material for preparing the second adhesive film 1102 comprises a second prepolymer; monomers for preparing the first prepolymer comprise a first alkyl acrylate, a second alkyl acrylate and acrylamide, and monomers for preparing the second prepolymer comprise a third alkyl acrylate, a fourth alkyl acrylate and a functional monomer; the first alkyl acrylate and the third alkyl acrylate do not contain hydroxyl groups or hydroxyl-like groups, and the second alkyl acrylate and the fourth alkyl acrylate contain at least one of hydroxyl groups and hydroxyl-like groups.

[0088] The composite adhesive of the present application includes a first adhesive film and a second adhesive film which are stacked. The first adhesive film includes a first prepolymer prepared from a specific monomer, and the second adhesive film includes a second prepolymer prepared from a specific monomer. This ensures that the composite adhesive has good moisture and heat resistance and maintains a high light transmittance and a low haze under high temperature and high humidity environmental conditions.

[0089] The composite adhesive of the present application is used to bond display modules, touch screens or cover lenses in display devices, especially for bonding display modules, touch screens or cover lenses with high-step-difference inks on the surface. The second adhesive film in the composite adhesive can fully fill the high-step-difference ink, so that it maintains a high light transmittance and a low haze under high temperature and high humidity environmental conditions, without bubbles, cracks, yellowing and the like, and meets the appearance requirements of optical electronic display devices.

[0090] In some of the examples, in the composite adhesive, the first prepolymer includes the following monomers, by mass percentage: 60% to 85% of a first alkyl acrylate, 10% to 30% of a second alkyl acrylate, and 4% to 20% of acrylamide.

[0091] It can be understood that in the preparation monomers of the first prepolymer, the first alkyl acrylate includes but is not limited to 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85% by mass percentage; the second alkyl acrylate includes but is not limited to 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%; acrylamide includes but is not limited to 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%; in some examples, it can be within the range consisting of any two of these point values ​​as end values, the same below.

[0092] In some of the examples, in the composite adhesive, the first prepolymer includes the following monomers, by mass percentage: 65% to 80% of a first alkyl acrylate, 15% to 30% of a second alkyl acrylate, and 10% to 20% of acrylamide.

[0093] It can be understood that the first alkyl acrylate and the second alkyl acrylate are monofunctional monomers; the hydroxy-like group refers to a group with properties similar to the hydroxyl group (-OH) and can undergo a reaction similar to the hydroxyl group in the polymerization reaction; further, the alkyl acrylate containing the hydroxy-like group includes but is not limited to 2 (2-ethoxyethoxy) ethyl acrylate.

[0094] In some of the examples, in the composite binder, the first alkyl acrylate comprises C4-C 18 Alkyl ester; optionally, acrylic acid C4~C 18The alkyl ester includes at least one of n-butyl acrylate, n-butyl methacrylate, t-butyl acrylate, t-butyl methacrylate, isooctyl acrylate, isooctyl methacrylate, lauryl acrylate, and isostearyl acrylate.

[0095] In some examples, in the composite binder, the second alkyl acrylate includes at least one of hydroxyethyl acrylate, hydroxybutyl acrylate, and 2(2-ethoxyethoxy)ethyl acrylate.

[0096] In some of the examples, in the composite adhesive, the acrylamide monomer includes at least one of acrylamide, methacrylamide, N-methylacrylamide (CAS No. 1187-58-2), N-methylmethacrylamide (CAS No. 3887-02-3), N,N-dimethylacrylamide, N-,N-dimethylacrylamide, N,N-dimethylmethacrylamide, N-octylacrylamide and N-octylmethacrylamide.

[0097] In some of the examples, in the composite adhesive, the raw materials for preparing the first adhesive film further include at least one of a first alkyl methacrylate, a first cross-linking agent, a first photoinitiator, a first chain transfer agent, and a first silane coupling agent.

[0098] In some of the examples, in the composite binder, the mass of the first alkyl methacrylate is 2% to 5% of the mass of the first prepolymer.

[0099] It can be understood that the percentage of the mass of the first alkyl methacrylate to the mass of the first prepolymer includes but is not limited to 2%, 3%, 4%, and 5%.

[0100] In some of the examples, in the composite adhesive, the mass of the first cross-linking agent is 0.5% to 5% of the mass of the first prepolymer.

[0101] It can be understood that the percentage of the mass of the first cross-linking agent to the mass of the first prepolymer includes but is not limited to 0.5%, 1%, 2%, 3%, 4%, and 5%.

[0102] In some of the examples, in the composite adhesive, the mass of the first photoinitiator is 0.1% to 1.5% of the mass of the first prepolymer.

[0103] It will be appreciated that the percentage of the mass of the first photoinitiator to the mass of the first prepolymer includes but is not limited to 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, and 1.5%.

[0104] In some of the examples, in the composite adhesive, the mass of the first chain transfer agent is 0.01% to 0.5% of the mass of the first prepolymer.

[0105] It can be understood that the percentage of the mass of the first chain transfer agent to the mass of the first prepolymer includes but is not limited to 0.01%, 0.1%, 0.2%, 0.3%, 0.4%, and 0.5%.

[0106] In some of the examples, in the composite adhesive, the mass of the first silane coupling agent is 0.01% to 0.5% of the mass of the first prepolymer.

[0107] It can be understood that the percentage of the mass of the first silane coupling agent to the mass of the first prepolymer includes but is not limited to 0.01%, 0.1%, 0.2%, 0.3%, 0.4%, and 0.5%.

[0108] In some examples, in the composite binder, the first alkyl methacrylate includes at least one of methyl methacrylate, ethyl methacrylate, and isooctyl methacrylate.

[0109] The first alkyl methacrylate is used to control the reaction rate to maintain the product morphology.

[0110] In some examples, in the composite adhesive, the first cross-linking agent includes at least one of polyurethane acrylate and polyether urethane methacrylate.

[0111] Furthermore, the polyurethane acrylate includes but is not limited to at least one of CN 8888 NS and CN 8888 SFN of SARTOMER; the polyether urethane methacrylate includes but is not limited to at least one of BR-5541MD and BR-5541M of BOMAR.

[0112] The first cross-linking agent is used to assist the first prepolymer in cross-linking the components during UV polymerization.

[0113] In some examples, in the composite adhesive, the first photoinitiator includes an aldehyde or ketone compound.

[0114] In some examples, in the composite adhesive, the first photoinitiator includes at least one of hydroxycyclohexane phenone, 4-acryloxybenzophenone, and 2,2-dimethoxy-2-phenylacetophenone.

[0115] Hydroxycyclohexane phenone, 4-acryloxybenzophenone and 2,2-dimethoxy-2-phenylacetophenone are all surface curing agents / photoinitiators.

[0116] In some examples, in the composite binder, the first chain transfer agent includes dodecanethiol.

[0117] The first chain transfer agent controls the molecular weight distribution.

[0118] In some of the examples, in the composite adhesive, the first silane coupling agent includes KH560.

[0119] The first silane coupling agent maintains stability in a high humidity environment.

[0120] In some of the examples, in the composite adhesive, the second prepolymer includes the following monomers: 60% to 80% of the third alkyl acrylate, 10% to 30% of the fourth alkyl acrylate, and 3% to 12% of the functional monomer.

[0121] It can be understood that in the preparation monomers of the second prepolymer, the third alkyl acrylate includes but is not limited to 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, and 80% by mass percentage; the fourth alkyl acrylate includes but is not limited to 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, and 30%; and the functional monomers include but are not limited to 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, and 12%.

[0122] It is understood that the third alkyl acrylate and the fourth alkyl acrylate are monofunctional monomers.

[0123] In some of the examples, in the composite adhesive, the third alkyl acrylate includes a C4~C8 alkyl acrylate; optionally, the C4~C8 alkyl acrylate includes at least one of n-butyl acrylate, n-butyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, isooctyl acrylate and isooctyl methacrylate.

[0124] In some examples, in the composite binder, the fourth alkyl acrylate includes at least one of hydroxyethyl acrylate, hydroxybutyl acrylate, and 2(2-ethoxyethoxy)ethyl acrylate.

[0125] In some of the examples, in the composite adhesive, the functional monomer includes at least one of an acrylic monomer, an amide monomer and a vinyl monomer; optionally, the acrylic monomer includes at least one of acrylic acid and methacrylic acid; optionally, the amide monomer includes at least one of acrylamide and methacrylamide; optionally, the vinyl monomer contains a nitrogen heterocycle; optionally, the vinyl monomer includes at least one of N-vinyl caprolactam and N-vinyl pyrrolidone.

[0126] In some of the examples, in the composite adhesive, the raw materials for preparing the second adhesive film further include at least one of a second alkyl methacrylate, a second cross-linking agent, a second photoinitiator, a second chain transfer agent, a second silane coupling agent, and an antioxidant.

[0127] In some of the examples, in the composite binder, the mass of the second alkyl methacrylate is 2% to 5% of the mass of the second prepolymer.

[0128] It can be understood that the percentage of the mass of the second alkyl methacrylate to the mass of the second prepolymer includes but is not limited to 2%, 3%, 4%, and 5%.

[0129] In some of the examples, in the composite adhesive, the mass of the second cross-linking agent is 1% to 5% of the mass of the second prepolymer.

[0130] It can be understood that the percentage of the mass of the second cross-linking agent to the mass of the second prepolymer includes but is not limited to 1%, 2%, 3%, 4%, and 5%.

[0131] In some of the examples, in the composite adhesive, the mass of the second photoinitiator is 0.05% to 1.5% of the mass of the second prepolymer.

[0132] It will be appreciated that the percentage of the mass of the second photoinitiator to the mass of the second prepolymer includes but is not limited to 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, and 1.5%.

[0133] In some of the examples, in the composite adhesive, the mass of the second chain transfer agent is 0.15% to 0.5% of the mass of the second prepolymer.

[0134] It can be understood that the percentage of the mass of the second chain transfer agent to the mass of the second prepolymer includes but is not limited to 0.15%, 0.2%, 0.3%, 0.4%, and 0.5%.

[0135] In some of the examples, in the composite adhesive, the mass of the second silane coupling agent is 0.15% to 0.5% of the mass of the second prepolymer.

[0136] It can be understood that the percentage of the mass of the second silane coupling agent to the mass of the second prepolymer includes but is not limited to 0.15%, 0.2%, 0.3%, 0.4%, and 0.5%.

[0137] In some of the examples, in the composite adhesive, the weight of the antioxidant is 0.05% to 0.5% of the weight of the second prepolymer.

[0138] It can be understood that the percentage of the mass of the antioxidant to the mass of the second prepolymer includes but is not limited to 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, and 0.5%.

[0139] In some examples, in the composite binder, the second alkyl methacrylate includes at least one of n-butyl methacrylate, tert-butyl methacrylate, and isooctyl methacrylate.

[0140] The second alkyl methacrylate is used to control the reaction rate to maintain the product morphology.

[0141] In some examples, in the composite adhesive, the second cross-linking agent includes at least one of hexamethylene diisocyanate, polyurethane acrylate, and polyether urethane methacrylate.

[0142] Furthermore, hexamethylene diisocyanate includes but is not limited to Aquolin® 268; polyurethane acrylate includes but is not limited to CN 8881 NS of SARTOMER; polyether urethane methacrylate includes but is not limited to BR-5541M series of BOMAR.

[0143] The second crosslinking agent is used to assist the second prepolymer in crosslinking the components during UV polymerization.

[0144] In some examples, in the composite adhesive, the second photoinitiator includes a peroxide.

[0145] In some examples, in the composite binder, the second photoinitiator includes at least one of diphenyl-(2,4,6-trimethylbenzoyl)-phosphine oxide and phenyl-bis(2,4,6-trimethylbenzoyl)-phosphine oxide.

[0146] Diphenyl-(2,4,6-trimethylbenzoyl)-phosphine oxide and phenyl-bis(2,4,6-trimethylbenzoyl)-phosphine oxide are both deep-layer curing agents / photoinitiators.

[0147] In some examples, in the composite binder, the second chain transfer agent includes dodecanethiol.

[0148] The second chain transfer agent controls the molecular weight distribution.

[0149] In some of the examples, in the composite adhesive, the second silane coupling agent includes KH560.

[0150] In some of the examples, in the composite binder, the antioxidant includes pentaerythritol 4[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate.

[0151] In some of the examples, in the composite adhesive, a thickness ratio of the first adhesive film to the second adhesive film is 1:3-10.

[0152] In some of the examples, in the composite adhesive, the thickness of the first adhesive film is 25 μm-100 μm.

[0153] It can be understood that the thickness of the first adhesive film includes but is not limited to 25μm, 30μm, 35μm, 40μm, 45μm, 50μm, 55μm, 60μm, 65μm, 70μm, 75μm, 80μm, 85μm, 90μm, 95μm, and 100μm.

[0154] In some of the examples, in the composite adhesive, the thickness of the second adhesive film is 125 μm~500 μm.

[0155] It can be understood that the thickness of the second adhesive film includes but is not limited to 125μm, 150μm, 175μm, 200μm, 225μm, 250μm, 275μm, 300μm, 325μm, 350μm, 375μm, 400μm, 425μm, 450μm, 475μm, and 500μm.

[0156] In some of the examples, in the composite adhesive, the total thickness of the first adhesive film and the second adhesive film is ≥200 μm.

[0157] An embodiment of the present application provides a method for preparing a composite adhesive, comprising the following steps:

[0158] A first adhesive film and a second adhesive film are formed in a stacked arrangement. The raw materials for preparing the first adhesive film include a first prepolymer, and the raw materials for preparing the second adhesive film include a second prepolymer; monomers for preparing the first prepolymer include a first alkyl acrylate, a second alkyl acrylate and acrylamide, and monomers for preparing the second prepolymer include a third alkyl acrylate, a fourth alkyl acrylate and a functional monomer; the first alkyl acrylate and the third alkyl acrylate do not contain hydroxyl groups or hydroxyl-like groups, and the second alkyl acrylate and the fourth alkyl acrylate contain at least one of hydroxyl groups and hydroxyl-like groups.

[0159] In some of the examples, in the method for preparing the composite adhesive, the step of forming a first adhesive film and a second adhesive film stacked together includes:

[0160] Step S10: mixing the raw materials for preparing the first adhesive film to obtain a first adhesive material;

[0161] Step S20: forming the first adhesive into a coating film, and curing the coating film to obtain a first film layer;

[0162] Step S30: mixing the raw materials for preparing the second adhesive film to obtain a second adhesive material;

[0163] Step S40: Forming the second rubber material into a coating film, and curing it to obtain a second film layer;

[0164] Step S50: Compounding the first film layer and the second film layer to form a first adhesive film and a second adhesive film that are stacked.

[0165] It can be understood that there is no order between step S10 to step S20 and step S30 to step S40.

[0166] In some examples, step S10 includes the following steps:

[0167] A first prepolymer, a first alkyl methacrylate, a first cross-linking agent, a first photoinitiator, a first chain transfer agent, and a first silane coupling agent are mixed.

[0168] In some examples, in step S10, the preparation of the first prepolymer includes the following steps:

[0169] The first alkyl acrylate, the second alkyl acrylate and acrylamide are mixed, and a first polymerization reaction is carried out under the action of a third photoinitiator to obtain a first prepolymer.

[0170] Further, the third photoinitiator includes hydroxycyclohexane phenone.

[0171] Furthermore, the first polymerization reaction is carried out under the action of ultraviolet light.

[0172] In some examples, step S30 includes the following steps:

[0173] The second prepolymer, the second alkyl methacrylate, the second cross-linking agent, the second photoinitiator, the second chain transfer agent, the second silane coupling agent and the antioxidant are mixed.

[0174] In some examples, in step S30, the preparation of the second prepolymer includes the following steps:

[0175] The third alkyl acrylate, the fourth alkyl acrylate and the functional monomer are mixed, and a second polymerization reaction is carried out under the action of a fourth photoinitiator to obtain a first prepolymer.

[0176] Further, the fourth photoinitiator includes hydroxycyclohexane phenone.

[0177] Furthermore, the second polymerization reaction is carried out under the action of ultraviolet light.

[0178] In some examples, in step S20 and step S40, curing is performed under a UV lamp; further, the UV lamp has a UV wavelength of 300 nm to 400 nm and an irradiation intensity of 3 mw / cm 2 The total energy of the UV light is 2000mj / cm 2 .

[0179] In some examples, in step S50, the first film layer and the second film layer are stacked and then degassed to form a first adhesive film and a second adhesive film that are stacked. Further, a high-pressure degassing machine is used for degassing.

[0180] One embodiment of the present application provides the use of the above-mentioned composite adhesive or the composite adhesive prepared by the above-mentioned preparation method in the preparation of a display device.

[0181] An embodiment of the present application provides a display device, comprising the composite adhesive or the composite adhesive prepared by the above preparation method.

[0182] See also Figure 2 In some examples, a display device 100 is provided, which includes a first substrate 120 and a second substrate 130, wherein the first substrate 120 and the second substrate 130 are connected via a composite adhesive 110, a first adhesive film 1101 in the composite adhesive 110 is connected to the first substrate 120, and a second adhesive film 1102 in the composite adhesive is connected to the second substrate 130.

[0183] It can be understood that the composite adhesive 110 is a film layer.

[0184] In some examples, in the display device 100 , the surface where the second substrate 130 is connected to the second adhesive film 1102 has a high-step ink layer 140 .

[0185] Furthermore, a high-step ink layer 140 is formed around the surface where the second substrate 130 is connected to the second adhesive film 1102 .

[0186] It can be understood that the first adhesive film is in contact with at least one surface of the first substrate, and the second adhesive film is in contact with at least one surface of the second substrate and fills the high-step ink on the surface.

[0187] The composite adhesive of the present application can fully fill the high-step-difference ink in the laminate (the combined layer of the first substrate and the second substrate), so that the display device maintains a high light transmittance and a low haze under high temperature and high humidity environmental conditions, without bubbles, cracks, yellowing, etc., and meets the appearance requirements of optical electronic display devices.

[0188] In some of the examples, in the display device, the first substrate and the second substrate each independently include one of a display module, a touch screen, and a cover lens.

[0189] Further, the display module includes one or more of a liquid crystal display (LCD), a plasma display, an OLED display, and a Micro LED display.

[0190] Further, the touch screen includes one or more of soda silicate glass, aluminosilicate glass, PC (polycarbonate) plastic, and PMMA (polymethyl methacrylate) plastic.

[0191] Further, the cover lens includes one or more of anti-reflection anti-reflection (AR) glass, anti-glare (AG) glass, PC (polycarbonate) plastic, PMMA (polymethyl methacrylate) plastic.

[0192] The present application is further described in detail below in conjunction with specific implementation methods, but the implementation methods of the present application are not limited thereto.

[0193] Example 1

[0194] Preparation of the first film

[0195] (1) 69 parts of isooctyl acrylate (2-EHA), 15 parts of hydroxyethyl acrylate (HEA), 16 parts of N,N-2-methyl acrylamide (DMAA) and 0.08 parts of photoinitiator hydroxycyclohexane phenone were added into a reactor, nitrogen was introduced, and after the oxygen in the reactor was completely replaced, the ultraviolet lamp was turned on to carry out polymerization reaction. When the temperature rose by 13°C, the reaction was stopped to obtain a prepolymer (the viscosity of the prepolymer was about 200 cps~300 cps, and the polymerization rate was about 10%~13%);

[0196] (2) Add 3 parts of BR5541 as a crosslinking agent, 3 parts of isooctyl methacrylate (EHMA) as a monomer for controlling the reaction rate, 0.1 parts of hydroxycyclohexane phenone as a photoinitiator, 0.04 parts of chain transfer agent dodecanethiol and 0.3 parts of silane coupling agent KH560 to the prepolymer prepared in step (1), mix well, and obtain a first rubber compound;

[0197] (3) The first adhesive is coated on a silicone-treated polyethylene terephthalate (PET) release film, and then covered with another layer of polyethylene terephthalate (PET) release film. Then, an ultraviolet lamp (ultraviolet wavelength is 300 nm to 400 nm) is turned on at an irradiation intensity of 3 mw / cm 2 The total energy of the UV light is 2000mj / cm 2 , and a first adhesive film with a thickness of 25 μm was obtained.

[0198] Preparation of the second film

[0199] (4) 63 parts of n-butyl acrylate (BA), 30 parts of 4-hydroxybutyl acrylate (4-HBA), 7 parts of N-vinyl pyrrolidone (NVP) and 0.08 parts of photoinitiator hydroxycyclohexane phenone were added into the reactor, nitrogen was introduced, and after the oxygen in the reactor was completely replaced, the ultraviolet lamp was turned on to carry out polymerization reaction. When the temperature rose by 13°C, the reaction was stopped to obtain a prepolymer (the viscosity of the prepolymer was about 200 cps~300 cps, and the polymerization rate was about 8%~10%);

[0200] (5) Add 1.5 parts of Aquolin® 268 as a crosslinking agent, 4 parts of butyl methacrylate (BMA) as a monomer for controlling the reaction rate, 0.05 parts of diphenyl-(2,4,6-trimethylbenzoyl)-phosphine oxide as a photoinitiator, 0.17 parts of dodecanethiol as a chain transfer agent, 0.1 parts of 4-[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid] pentaerythritol ester as an antioxidant, and 0.3 parts of KH560 as a silane coupling agent to the prepolymer prepared in step (4), mix well, and obtain a second rubber compound;

[0201] (6) The second adhesive is coated on the silicone-treated polyethylene terephthalate (PET) release film, and then covered with another layer of polyethylene terephthalate (PET) release film. Then, an ultraviolet lamp (ultraviolet wavelength is 300 nm to 400 nm) is turned on at an irradiation intensity of 3 mw / cm 2 The total energy of the UV light is 2000mj / cm 2 , a second adhesive film with a thickness of 125 μm was obtained.

[0202] Preparation of composite adhesive

[0203] (7) The first adhesive film prepared in step (3) and the second adhesive film prepared in step (6) are laminated and degassed using a high-pressure degassing machine (25° C., 2.5 kg, 20 min). After degassing, the adhesive is allowed to stand for 2 hours to obtain an optically transparent composite adhesive with a thickness of 200 μm.

[0204] Example 2

[0205] The method is basically the same as Example 1, except that in step (1), the weight proportions of isooctyl acrylate, hydroxyethyl acrylate and N,N-2-methyl acrylamide are different, wherein isooctyl acrylate (2-EHA) is 60 parts, hydroxyethyl acrylate (HEA) is 10 parts, and N,N-2-methyl acrylamide (DMAA) is 25 parts.

[0206] Example 3

[0207] The method is basically the same as Example 1, except that in step (4), 7 parts of N-vinyl pyrrolidone (NVP) are replaced by an equal amount of acrylamide.

[0208] Comparative Example 1

[0209] The first adhesive film prepared in step (3) of Example 1.

[0210] Comparative Example 2

[0211] The second adhesive film prepared in step (6) of Example 1.

[0212] Comparative Example 3

[0213] The method is basically the same as Example 1, except that in step (1), N,N-2-methyl acrylamide (DMAA) is not added. The specific method is as follows:

[0214] (1) Add 77 parts of isooctyl acrylate (2-EHA), 23 parts of hydroxyethyl acrylate (HEA) and 0.08 parts of photoinitiator hydroxycyclohexane phenone into a reactor, introduce nitrogen, and after the oxygen in the reactor is completely replaced, turn on the ultraviolet lamp to carry out polymerization reaction. When the temperature rises by 13°C, stop the reaction to obtain a prepolymer (the viscosity of the prepolymer is about 200 cps~300 cps, and the polymerization rate is about 10%~13%).

[0215] Film Optical Test

[0216] The quartz glass sheet was wiped with alcohol three times, and then the composite adhesive was attached to the quartz glass sheet. According to the ASTM D1009 standard, the transmittance and haze of the adhesive layer were measured using a color haze meter. Three parallel tests were conducted, and the results are shown in Table 1.

[0217] Table 1

[0218]

[0219] The composite adhesive was placed in an environment of 85°C and 85% RCH for 1000 h, and then optical testing was performed again. The results are shown in Table 2.

[0220] Table 2

[0221]

[0222] It can be seen from Table 1 and Table 2 that compared with the use of acrylamide as the functional monomer in the prepolymer of the second adhesive film in Example 3, the use of nitrogen-containing heterocyclic vinyl monomer N-vinyl pyrrolidone as the functional monomer in the prepolymer of the second adhesive film in Example 1 and Example 2 has a higher transmittance and lower haze to obtain the adhesive layer.

[0223] The composite adhesive prepared in each embodiment and comparative example was cut into a size of 273.5 mm*176.7 mm, and pasted between a glass of 286.5 mm*184.7 mm*0.6 mm and a PC of 286.5 mm*184.7 mm*2 mm with high-step ink on the edges (upper / lower edges 13 mm, left / right edges 8 mm), and degassed in a high-pressure degassing machine (45°C, 5 kg, 30 min). After degassed, the laminate was allowed to stand for 2 hours to obtain a laminate.

[0224] Laminate Weathering Test

[0225] The laminates containing the composite adhesives of each embodiment and comparative example were placed in an oven at 105°C (temperature 85°C, humidity 85%), -45°C, and hot and cold shock (-45°C to 95°C), and the appearance of the laminated samples was observed after 1000 hours to record whether there were bubbles, cracks, yellowing, and whether the high-break ink was fully filled. Two parallel tests were conducted. The results of the laminate containing the composite adhesive of Example 1 are shown in Table 3; the results of the laminate containing the composite adhesive of Comparative Example 1 are shown in Table 4; the results of the laminate containing the composite adhesive of Comparative Example 2 are shown in Table 5; the results of the laminate containing the composite adhesive of Comparative Example 3 are shown in Table 6.

[0226] Table 3

[0227]

[0228] Table 4

[0229]

[0230] Table 5

[0231]

[0232] Table 6

[0233]

[0234] As can be seen from Tables 3 to 6, the laminate containing the composite adhesive of the embodiment has no bubbles, cracks, yellowing and other phenomena in the weathering test, which meets the appearance requirements of the optical electronic display device; that is, the composite adhesive provided by the embodiment has good moisture and heat resistance. However, in Comparative Example 1, a single-layer first adhesive film is used as an adhesive, and its filling effect on the high-step ink on the second substrate (PC) is not good, and bubbles appear at the edge. In Comparative Example 2, a single-layer second adhesive film is used as an adhesive, and the adhesion to the first substrate (glass) is poor, and cracks (linear) appear at the edge; in Comparative Example 3, the first adhesive film does not add DMAA, which causes a significant decrease in the adhesion of the adhesive layer to the first substrate (glass), and severe cracks (blocks) appear at the edge.

[0235] The tensile strength, elongation at break and stretching distance of the composite adhesives provided in Example 1 and Example 2 were tested:

[0236] Sample preparation: Take a 45mm*25mm test piece, remove the film, cover the upper and lower sides with tape to facilitate connection with the fixture, leaving a 25mm*25mm square in the center of the sample for testing.

[0237] Testing machine: tensile testing machine;

[0238] Test standard: GB / T 30776-2014 "Test method for tensile strength and elongation at break of adhesive tape";

[0239] The test results are shown in Table 7.

[0240] Table 7

[0241]

[0242] It can be seen from Table 7 that compared with Example 2, Example 1 has better tensile strength, elongation at break and tensile distance, and the toughness of the composite adhesive prepared in Example 1 is better than that in Example 2.

[0243] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0244] The above-described embodiments only express several implementation methods of the present application, which is convenient for understanding the technical solution of the present application in detail, but it cannot be understood as limiting the scope of protection of the invention patent. It should be pointed out that for ordinary technicians in this field, without departing from the concept of the present application, several modifications and improvements can be made, which all belong to the scope of protection of the present application. It should be understood that the technical solutions obtained by those skilled in the art through logical analysis, reasoning or limited experiments on the basis of the technical solutions provided in the present application are all within the scope of protection of the claims attached to the present application. Therefore, the scope of protection of the patent of this application shall be based on the content of the attached claims, and the description can be used to interpret the content of the claims.

Claims

1. A composite adhesive, characterized in that: The invention comprises a first adhesive film and a second adhesive film which are stacked, wherein the raw materials for preparing the first adhesive film comprise a first prepolymer, and the raw materials for preparing the second adhesive film comprise a second prepolymer; monomers for preparing the first prepolymer comprise a first alkyl acrylate, a second alkyl acrylate and acrylamide, and monomers for preparing the second prepolymer comprise a third alkyl acrylate, a fourth alkyl acrylate and a functional monomer; the first alkyl acrylate and the third alkyl acrylate do not contain hydroxyl groups or hydroxyl-like groups, and the second alkyl acrylate and the fourth alkyl acrylate contain at least one of hydroxyl groups and hydroxyl-like groups.

2. The composite adhesive according to claim 1, characterized in that Calculated by mass percentage, the first prepolymer includes the following preparation monomers: 60% to 85% of a first alkyl acrylate, 10% to 30% of a second alkyl acrylate and 4% to 25% of acrylamide.

3. The composite adhesive according to claim 2, characterized in that: The first prepolymer satisfies at least one of the following characteristics: (1) The first alkyl acrylate includes acrylic acid C4~C 18 Alkyl ester; Optionally, the acrylic acid C4~C 18 The alkyl ester includes at least one of n-butyl acrylate, n-butyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, isooctyl acrylate, isooctyl methacrylate, lauryl acrylate and isostearyl acrylate; (2) the second alkyl acrylate comprises at least one of hydroxyethyl acrylate, hydroxybutyl acrylate and 2 (2-ethoxyethoxy) ethyl acrylate; (3) The acrylamide monomer includes at least one of acrylamide, methacrylamide, N-methylacrylamide, N-methylmethacrylamide, N,N-dimethylacrylamide, N,N-dimethylacrylamide, N,N-dimethylmethacrylamide, N-octylacrylamide and N-octylmethacrylamide.

4. The composite adhesive according to any one of claims 1 to 3, characterized in that The raw materials for preparing the first adhesive film further include at least one of a first alkyl methacrylate, a first cross-linking agent, a first photoinitiator, a first chain transfer agent and a first silane coupling agent.

5. The composite adhesive according to claim 4, characterized in that: The raw materials for preparing the first adhesive film meet at least one of the following characteristics: (1) The mass of the first alkyl methacrylate is 2% to 5% of the mass of the first prepolymer; (2) The mass of the first cross-linking agent is 0.5% to 5% of the mass of the first prepolymer; (3) The mass of the first photoinitiator is 0.1% to 1.5% of the mass of the first prepolymer; (4) The mass of the first chain transfer agent is 0.01% to 0.5% of the mass of the first prepolymer; (5) The mass of the first silane coupling agent is 0.01% to 0.5% of the mass of the first prepolymer.

6. The composite adhesive according to claim 4, characterized in that: The raw materials for preparing the first adhesive film meet at least one of the following characteristics: (1) the first alkyl methacrylate comprises at least one of methyl methacrylate, ethyl methacrylate and isooctyl methacrylate; (2) the first cross-linking agent comprises at least one of polyurethane acrylate and polyether urethane methacrylate; (3) the first photoinitiator includes at least one of hydroxycyclohexane phenone, 4-acryloxybenzophenone and 2,2-dimethoxy-2-phenylacetophenone; (4) the first chain transfer agent includes dodecanethiol; (5) The first silane coupling agent includes KH560.

7. The composite adhesive according to any one of claims 1 to 3, 5 to 6, characterized in that: The second prepolymer comprises the following preparation monomers: 60% to 80% of the third alkyl acrylate, 10% to 30% of the fourth alkyl acrylate and 3% to 12% of the functional monomer.

8. The composite adhesive according to claim 7, characterized in that The second prepolymer satisfies at least one of the following characteristics: (1) The third alkyl acrylate includes C4-C8 alkyl acrylate; optionally, the C4-C8 alkyl acrylate includes at least one of n-butyl acrylate, n-butyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, isooctyl acrylate and isooctyl methacrylate; (2) the fourth alkyl acrylate comprises at least one of hydroxyethyl acrylate, hydroxybutyl acrylate and 2 (2-ethoxyethoxy) ethyl acrylate; (3) The functional monomer includes at least one of an acrylic monomer, an amide monomer and a vinyl monomer; optionally, the acrylic monomer includes at least one of acrylic acid and methacrylic acid; optionally, the amide monomer includes at least one of acrylamide and methacrylamide; optionally, the vinyl monomer contains a nitrogen-containing heterocycle; optionally, the vinyl monomer includes at least one of N-vinyl caprolactam and N-vinyl pyrrolidone.

9. The composite adhesive according to claim 7, characterized in that: The raw materials for preparing the second adhesive film further include at least one of a second alkyl methacrylate, a second cross-linking agent, a second photoinitiator, a second chain transfer agent, a second silane coupling agent and an antioxidant.

10. The composite adhesive according to claim 9, characterized in that The raw materials for preparing the second adhesive film meet at least one of the following characteristics: (1) The mass of the second alkyl methacrylate is 2% to 5% of the mass of the second prepolymer; (2) The mass of the second cross-linking agent is 1% to 5% of the mass of the second prepolymer; (3) The mass of the second photoinitiator is 0.05% to 1.5% of the mass of the second prepolymer; (4) The mass of the second chain transfer agent is 0.15% to 0.5% of the mass of the second prepolymer; (5) The mass of the second silane coupling agent is 0.15% to 0.5% of the mass of the second prepolymer; (6) The mass of the antioxidant is 0.05% to 0.5% of the mass of the second prepolymer.

11. The composite adhesive according to claim 9, characterized in that: The raw materials for preparing the second adhesive film meet at least one of the following characteristics: (1) the second alkyl methacrylate comprises at least one of n-butyl methacrylate, tert-butyl methacrylate and isooctyl methacrylate; (2) the second cross-linking agent comprises at least one of hexamethylene diisocyanate, polyurethane acrylate and polyether urethane methacrylate; (3) the second photoinitiator comprises at least one of diphenyl-(2,4,6-trimethylbenzoyl)-phosphine oxide and phenyl-bis(2,4,6-trimethylbenzoyl)-phosphine oxide; (4) the second chain transfer agent includes dodecanethiol; (5) The second silane coupling agent includes KH560; (6) The antioxidant includes pentaerythritol 4[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate.

12. The composite adhesive according to any one of claims 1 to 3, 5 to 6, and 8 to 11, characterized in that: The composite adhesive meets at least one of the following characteristics: (1) The thickness ratio of the first adhesive film to the second adhesive film is 1:3-10; (2) The thickness of the first adhesive film is 25 μm to 100 μm; (3) The thickness of the second adhesive film is 125 μm~500 μm.

13. A method for preparing a composite adhesive, characterized in that: The following steps are involved: A first adhesive film and a second adhesive film are formed in a stacked arrangement, wherein the raw materials for preparing the first adhesive film include a first prepolymer, and the raw materials for preparing the second adhesive film include a second prepolymer; monomers for preparing the first prepolymer include a first alkyl acrylate, a second alkyl acrylate and acrylamide, and monomers for preparing the second prepolymer include a third alkyl acrylate, a fourth alkyl acrylate and a functional monomer; the first alkyl acrylate and the third alkyl acrylate do not contain hydroxyl groups or hydroxyl-like esters, and the second alkyl acrylate and the fourth alkyl acrylate contain at least one of hydroxyl groups and hydroxyl-like esters.

14. The preparation method according to claim 13, characterized in that: The steps of forming the first adhesive film and the second adhesive film stacked in layers include: Mixing the raw materials for preparing the first adhesive film to obtain a first adhesive material; Forming the first rubber material into a coating film, and curing the coating film to obtain a first film layer; Mixing the raw materials for preparing the second adhesive film to obtain a second adhesive material; Forming the second rubber material into a coating film, and curing the coating film to obtain a second film layer; The first film layer and the second film layer are compounded to form the first adhesive film and the second adhesive film which are stacked.

15. Use of the composite adhesive according to any one of claims 1 to 12 or the composite adhesive prepared by the preparation method according to any one of claims 13 to 14 in preparing a display device.

16. A display device, characterized in that: It includes the composite adhesive as described in any one of claims 1 to 12 or the composite adhesive prepared by the preparation method as described in any one of claims 13 to 14.

17. The display device according to claim 16, characterized in that The display device comprises a first substrate and a second substrate, wherein the first substrate and the second substrate are connected via the composite adhesive, a first adhesive film in the composite adhesive is connected to the first substrate, and a second adhesive film in the composite adhesive is connected to the second substrate.

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