Adhesive composition, optical glue solution, flexible display module and flexible display device

Abstract

The invention discloses an adhesive composition, an optical glue solution, a flexible display module and a flexible display device. The adhesive composition comprises acrylic matrix resin and a modified acrylate monomer, wherein the modified acrylate monomer contains an amido bond. The optical adhesive layer prepared from the adhesive composition is applied to the flexible display module and the flexible display device, so that the flexible display module and the flexible display device can be bent in a high-temperature and high-humidity dynamic bending process; the risk of cohesion failure caused by the optical adhesive layer can be effectively reduced, and the problem that the flexible screen is too large in crease after the display device is repeatedly bent is solved.

Description

Technical Field

[0001] The present invention relates to the field of display technology, and more specifically to an adhesive composition, an optical adhesive, a flexible display module, and a flexible display device. Background Art

[0002] With the rapid development of display technology, the demand for different types of displays is increasing. Flexible display devices have foldable characteristics, which require high performance of module materials. Among them, optical adhesive materials are used as stress adjustment layers and adhesive layers. After the display device is folded repeatedly, the optical adhesive layer is prone to creases, affecting the display effect.

[0003] In addition, when the display device is folded under high temperature and high humidity conditions, the optical adhesive has poor heat resistance and there is a risk of cohesive failure. Therefore, how to prevent creases from forming on the optical adhesive layer in the flexible display device and enhance the cohesive force of the optical adhesive layer has become a technical problem that needs to be solved in this field. Summary of the invention

[0004] In view of this, the object of the present invention is to provide an adhesive composition, an optical adhesive, a flexible display module, and a flexible display device, so as to at least solve the problem of cohesive failure of the optical adhesive layer and excessive creases after bending during the high temperature and high humidity bending process of the flexible display device.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] In one aspect, the present invention provides an adhesive composition, comprising an acrylic base resin and a modified acrylate monomer; wherein the modified acrylate monomer contains an amide bond.

[0007] Optionally, the amount of the modified acrylate monomer is 1 wt%-10 wt% of the amount of the acrylic base resin.

[0008] Optionally, the modified acrylate monomer is obtained by modifying an acrylate monomer with a compound containing an amide bond.

[0009] Optionally, the acrylic ester monomer structure does not contain a branched chain and contains 4-18 carbon atoms.

[0010] Optionally, the acrylate monomer is selected from butyl acrylate.

[0011] Optionally, the compound containing an amide bond is selected from butyl acrylamide.

[0012] Optionally, the acrylic matrix resin is selected from one or more of 2-ethylhexyl acrylate (2-EHA), lauryl acrylate (LA), n-hexyl acrylate (HA) and hydroxyethyl acrylate.

[0013] Optionally, the acrylic ester matrix resin contains 2-ethylhexyl acrylate, lauryl acrylate, n-hexyl acrylate and hydroxyethyl acrylate in a mass ratio of (40-60):(15-25):(15-25):(5-15).

[0014] Optionally, the adhesive composition further comprises a solvent and an initiator.

[0015] Optionally, the solvent is selected from one or more of ethyl acetate, methacrylate and sec-butyl acetate.

[0016] Optionally, the initiator is selected from one or more of azobisisobutyronitrile (AIBN), dimethyl diisobutyrate (AIBME) and azobisisoheptanenitrile (ABVN).

[0017] In another aspect, the present invention provides an optical adhesive prepared from the adhesive composition as described above.

[0018] In another aspect, the present invention provides a method for preparing the optical adhesive as described above, comprising the following steps:

[0019] The acrylic base resin and the modified acrylic ester monomer are dissolved in a solvent, reacted in a nitrogen atmosphere in the presence of an initiator, and the reaction product is dried to obtain an acrylic ester polymer;

[0020] The acrylate polymer is mixed with a solvent to obtain the optical adhesive.

[0021] Optionally, the reaction conditions are: constant temperature reaction at 50-70°C for 3-6 hours, and then heating to 70-90°C for constant temperature reaction for 2-4 hours.

[0022] In another aspect, the present invention provides an optical adhesive layer obtained by curing the optical adhesive as described above.

[0023] In yet another aspect, the present invention provides an optical adhesive, wherein the optical adhesive comprises the optical adhesive layer as described above.

[0024] Optionally, the optical adhesive further includes a first release film and a second release film, and the first release film and the second release film are respectively attached to two opposite surfaces of the optical adhesive layer.

[0025] In another aspect, the present invention provides a flexible display module, comprising:

[0026] Flexible display panels;

[0027] A first stacked structure disposed on the flexible display panel near the light-emitting side, the first stacked structure comprising a first optical adhesive layer, a functional film layer, a second optical adhesive layer and a cover layer sequentially disposed on the flexible display panel;

[0028] A second stacked structure disposed on the flexible display panel away from the light emitting side, the second stacked structure comprising a support layer and a first adhesive layer disposed on a side of the support layer close to the flexible display panel;

[0029] in

[0030] The first optical adhesive layer and / or the second optical adhesive layer comprises the optical adhesive layer as described above.

[0031] Optionally, the cover layer includes a first transparent polymer layer, a second adhesive layer, a thin glass layer, a third adhesive layer and a second transparent polymer layer which are arranged in sequence.

[0032] Optionally, the second adhesive layer and / or the third adhesive layer comprises the optical adhesive layer as described above.

[0033] Optionally, the second stacked structure further comprises a protective layer disposed between the flexible display panel and the first adhesive layer; and

[0034] A fourth adhesive layer is disposed between the protective layer and the flexible display panel.

[0035] Optionally, the third adhesive layer and / or the fourth adhesive layer comprises the optical adhesive layer as described above.

[0036] In another aspect, the present invention provides a flexible display device, comprising the flexible display module as described above.

[0037] The beneficial effects of the present invention are as follows:

[0038] The adhesive composition provided by the present invention, by adding a specific modified acrylic ester monomer to an acrylic matrix resin, the amide bond in the modified acrylic ester monomer forms a hydrogen bond with the carbonyl group in the ester group, thereby enhancing the cohesion of the optical adhesive or optical adhesive layer prepared by the adhesive composition, and further improving its high temperature and high humidity bending performance. Preferably, a long-chain amide bond-modified acrylic ester monomer without branches is introduced to reduce the mutual attraction between macromolecular chains, increase the flexibility of the polymer material, and increase the elastic stage strain. In addition, the introduction of short straight-chain acrylic ester monomers such as n-hexyl acrylate has the ability to quickly disentangle molecules, which helps to improve the creep recovery performance of the optical adhesive. The optical adhesive layer prepared by the adhesive composition is used in a flexible display module and a flexible display device, so that the flexible display module and the flexible display device can effectively reduce the risk of cohesive failure of the optical adhesive layer during the high temperature and high humidity dynamic bending process and improve the problem of excessive creases of the flexible screen after repeated bending of the display device. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The specific implementation modes of the present invention will be further described in detail below in conjunction with the accompanying drawings.

[0040] Figure 1 A schematic diagram showing cohesive failure of the optical adhesive layer when the flexible display device is dynamically bent at high temperature and high humidity.

[0041] Figure 2 A schematic diagram of the structure of optical adhesive in some embodiments is shown.

[0042] Figure 3 A schematic diagram of the structure of a flexible display module in some implementation modes is shown. DETAILED DESCRIPTION

[0043] In order to more clearly illustrate the present invention, the present invention is further described below in conjunction with preferred embodiments and accompanying drawings. Similar components in the accompanying drawings are represented by the same reference numerals. It should be understood by those skilled in the art that the content specifically described below is illustrative rather than restrictive, and should not be used to limit the scope of protection of the present invention.

[0044] When the flexible display device is dynamically bent at high temperature and high humidity, the optical adhesive layer is prone to cohesive failure risk, such as Figure 1 In view of the problems that the optical adhesive layer may suffer from cohesive failure and excessive crease after bending when the flexible display device is bent at high temperature and high humidity, a specific embodiment of the present invention provides an adhesive composition, which comprises an acrylic matrix resin and a modified acrylate monomer; wherein the modified acrylate monomer contains an amide bond.

[0045] In the adhesive composition provided in this embodiment, an acrylate monomer modified by an amide bond is introduced, and the amide bond (-NHCO-) ​​forms a hydrogen bond with the carbonyl group (C=O) in the ester group in the system, thereby enhancing the cohesion of the optical adhesive and further improving the high-temperature bending resistance, so that the bending of the module can effectively reduce the risk of cohesive failure of the optical adhesive layer.

[0046] The carbonyl group in the ester group in the system here may come from the raw material system before polymerization and / or the acrylate polymer formed by polymerization when the adhesive composition is used to prepare the optical adhesive.

[0047] In some examples, the modified acrylate monomer is obtained by modifying an acrylate monomer with a compound containing an amide bond. In some examples, the acrylate monomer structure does not contain a branched chain and contains 4-18 carbon atoms. For example, the acrylate monomer includes but is not limited to butyl acrylate and the like. The aforementioned amide bond-modified long-chain acrylate monomer without a branched chain reduces the mutual attraction between macromolecular chains, increases the flexibility of the polymer material, and increases the elastic stage strain. The optical adhesive or optical adhesive layer obtained by the adhesive composition as a whole has good cohesion and creep recovery properties. The flexible display module and the flexible display device containing the optical adhesive layer can effectively reduce the risk of cohesion failure of the optical adhesive layer and improve the problem of excessive creases in the flexible screen after repeated bending of the display device during high temperature and high humidity dynamic bending, while ensuring that the interface adhesion does not fail.

[0048] In some examples, the compound containing an amide bond includes but is not limited to acrylamide butyl. The aforementioned compound containing an amide bond can not only provide an amide bond in the system to form a hydrogen bond with the carbonyl (C=O) in the ester group in the system to enhance the cohesive force of the optical adhesive, but also does not affect the long-chain non-linear structure of the acrylate monomer, thereby giving the polymer material good flexibility.

[0049] In some examples, the amount of the modified acrylate monomer is 1wt%-10wt% of the amount of the acrylic matrix resin. If the amount of the modified acrylate monomer is too little, the cohesive force of the obtained optical adhesive layer is too low; if the amount of the modified acrylate monomer is too much, the adhesion between the optical adhesive layer and the interface becomes poor. For example, the amount of the modified acrylate monomer includes but is not limited to 3wt%-9wt%, 3wt%-6wt%, 3wt%, 6wt%, 9wt% and the like of the amount of the acrylic matrix resin. In some further specific examples, the preparation of the modified acrylate monomer comprises the following steps:

[0050] The amide bond-containing compound and the acrylate monomer are reacted in a closed environment in the presence of a catalyst to obtain the modified acrylate monomer.

[0051] Furthermore, in the preparation of the modified acrylate monomer, the catalyst is preferably an amino alcohol catalyst. The reaction temperature is preferably 25° C. and the reaction time is 4-8 hours.

[0052] In this embodiment, the acrylate monomer is a copolymerizable monomer. Exemplary acrylate matrix resins include, but are not limited to, one or more selected from 2-ethylhexyl acrylate, lauryl acrylate, n-hexyl acrylate, and hydroxyethyl acrylate.

[0053] In this embodiment, the Tg of 2-ethylhexyl acrylate is less than -60°C, and after polymerization, it provides a lower Tg for the pressure-sensitive adhesive, so that it has good fluidity and obtains better initial adhesion and peel strength.

[0054] Lauryl acrylate can reduce the mutual attraction between macromolecular chains, increase the flexibility of polymer materials, and increase the strain in the elastic stage.

[0055] n-Hexyl acrylate can introduce short straight-chain acrylate monomers, which have the ability of rapid molecular disentanglement and help improve the creep recovery performance of optical adhesives.

[0056] The monomer containing -OH functional group in the structure of hydroxyethyl acrylate participates in the copolymerization reaction, which can cause slight cross-linking of the copolymer and form a certain degree of three-dimensional network structure, which helps to improve the cohesion of the pressure-sensitive adhesive.

[0057] Exemplarily, the acrylic ester matrix resin contains 2-ethylhexyl acrylate, lauryl acrylate, n-hexyl acrylate and hydroxyethyl acrylate.

[0058] In some examples, in the acrylic ester matrix resin, the content of 2-ethylhexyl acrylate is 40wt%-60wt%, 40wt%-55wt%, 40wt%-50wt%, 45wt%-50wt%, 50wt%-60wt%, 50wt%-65wt%, 50wt%, by mass percentage.

[0059] In some examples, in the acrylic ester matrix resin, the content of lauryl acrylate is 15wt%-25wt%, 15wt%-20wt%, 20wt%-25wt%, 15wt%, 20wt%, 25wt%, etc., calculated by mass percentage.

[0060] In some examples, in the acrylic ester matrix resin, the content of n-hexyl acrylate is 15wt%-25wt%, 15wt%-20wt%, 20wt%-25wt%, 15wt%, 20wt%, 25wt%, etc., calculated by mass percentage.

[0061] In some examples, in the acrylic ester matrix resin, the content of hydroxyethyl acrylate is 5wt%-15wt%, 5wt%-10wt%, 10wt%-15wt%, 5wt%, 10wt%, 15wt%, etc., calculated by mass percentage.

[0062] In some examples, the acrylic ester matrix resin contains 2-ethylhexyl acrylate, lauryl acrylate, n-hexyl acrylate and hydroxyethyl acrylate in a mass ratio of (40-60):(15-25):(15-25):(5-15). Preferably, the mass ratio of 2-ethylhexyl acrylate, lauryl acrylate, n-hexyl acrylate and hydroxyethyl acrylate in the acrylic ester matrix resin is 50:20:20:10. At this time, the optical adhesive layer prepared from the obtained adhesive composition has high cohesion and good adhesion.

[0063] In some examples, the adhesive composition further includes a solvent and an initiator.

[0064] When the comonomers are copolymerized to form acrylate polymers to obtain optical adhesive, each comonomer needs to be polymerized under the action of an initiator. The role of the solvent includes but is not limited to giving the optical adhesive a desired viscosity and providing a suitable polymerization reaction environment.

[0065] Exemplary solvents include, but are not limited to, one or more selected from ethyl acetate, methacrylate, and sec-butyl acetate.

[0066] In the adhesive composition, the preferred total mass ratio of the solvent to the acrylic base resin and the modified acrylate monomer includes but is not limited to 1:3-1:10, 1:5-1:10, etc.

[0067] Exemplary initiators include, but are not limited to, one or more selected from azobisisobutyronitrile, dimethyl diisobutyrate, and azobisisoheptanenitrile.

[0068] In the adhesive composition, the preferred amount of the initiator added is 1 wt% to 3 wt% of the total mass of the acrylic base resin and the modified acrylate monomer.

[0069] According to another specific embodiment of the present invention, an optical adhesive is provided. The optical adhesive is prepared from the adhesive composition as described above.

[0070] In the optical adhesive, the amide bond introduced into the modified acrylate monomer forms a hydrogen bond with the carbonyl group in the ester group in the system, which gives the optical adhesive layer formed after the optical adhesive is applied good cohesion; in addition, the introduction of the modified acrylate monomer reduces the mutual attraction between the macromolecular chains in the obtained optical adhesive, increases the flexibility of the polymer material, and increases the elastic stage strain, thereby making the flexible display module or flexible display device containing the optical adhesive layer formed by curing the optical adhesive have a stable structure, high cohesion and elastic stage strain.

[0071] The optical adhesive in this embodiment includes, but is not limited to, being used for bonding a laminated structure in a flexible display module or a flexible display device.

[0072] Exemplarily, the optical adhesive liquid can be directly coated on a substrate and cured to obtain an optical adhesive layer.

[0073] Exemplary coating methods include, but are not limited to, coating using a flat plate coater.

[0074] Exemplary curing conditions include, but are not limited to, curing temperature: 60-100° C., curing time: 12-24 h.

[0075] According to another specific embodiment of the present invention, a method for preparing an optical glue is provided, the method comprising the following steps:

[0076] The acrylic base resin and the modified acrylic ester monomer are dissolved in a solvent, reacted in a nitrogen atmosphere in the presence of an initiator, and the reaction product is dried to obtain an acrylic ester polymer;

[0077] The acrylate polymer is mixed with a solvent to obtain the optical adhesive.

[0078] For example, in a nitrogen atmosphere, the temperature is preferably raised uniformly to the reaction temperature within 30-60 minutes.

[0079] For example, the reaction conditions are: constant temperature reaction at 50-70° C. for 3-6 hours, and then temperature rise to 70-90° C. for 2-4 hours. If the temperature and time are not within these conditions, the reaction rate may be difficult to control and the reaction may be incomplete.

[0080] The preferred reaction conditions are: react at 65°C for 4 hours, then heat to 75°C for 3 hours. In this case, the above effects are better.

[0081] Exemplarily, the mass ratio of the acrylic ester polymer to the solvent is 1:1.

[0082] In some specific examples, the preparation of the optical glue includes the following steps:

[0083] Add acrylate monomer, amide bond-modified acrylate monomer and ethyl acetate in a certain proportion into a four-necked flask, stir mechanically, and introduce N 2 Then the temperature was raised to 65°C, the initiator was dissolved in ethyl acetate solution, and it was added dropwise to the flask using a constant pressure funnel, and the reaction was carried out at a constant temperature for 4 hours. The reaction temperature was raised to 75°C and the temperature was kept constant for 3 hours. After the reaction was completed, the product was cooled to room temperature and poured out. It was placed in a vacuum oven for 12 hours to obtain an acrylate polymer; the acrylate polymer and ethyl acetate were fully mixed in a mass ratio of 1:1 to obtain an optical adhesive.

[0084] According to another specific embodiment of the present invention, an optical adhesive layer is provided. The optical adhesive layer is obtained by curing the optical adhesive liquid as described above.

[0085] The optical adhesive layer in this embodiment is transparent and has all the advantages brought by the above-mentioned optical adhesive, which will not be described in detail here. For example, the optical adhesive layer has high cohesion and elastic phase strain, which can reduce the risk of cohesion failure of the optical adhesive layer when the module is bent and improve the problem of excessive creases on the flexible screen after repeated bending of the display device.

[0086] Exemplary curing conditions include, but are not limited to, curing temperature: 60-100° C., curing time: 12-24 h.

[0087] In this embodiment, the optical adhesive layer can be used in the required scene according to actual needs, and its thickness can also be determined according to actual needs, and there is no requirement for the thickness of the optical adhesive layer. And the thickness of the optical adhesive layer can be controlled by the thickness of the wet film coated with the optical adhesive liquid. Exemplarily, the thickness of the optical adhesive layer includes but is not limited to about 30-100 μm, 30-70 μm, 40-60 μm, 50 μm, etc.

[0088] According to another specific embodiment of the present invention, an optical adhesive is provided, wherein the optical adhesive comprises the optical adhesive layer as described above.

[0089] like Figure 2 As shown, in some examples, the optical adhesive further includes a first release film 1 and a second release film 3, and the first release film 1 and the second release film 3 are respectively attached to two opposite surfaces of the optical adhesive layer 2. The first release film 1 and the second release film 3 can protect the optical adhesive layer.

[0090] Exemplarily, the material of the first release film 1 and the second release film 3 includes but is not limited to polyethylene terephthalate.

[0091] According to another specific embodiment of the present invention, a flexible display module is provided, such as Figure 3 As shown, the flexible display module includes:

[0092] Flexible display panel 300;

[0093] A first stacked structure disposed on the flexible display panel 300 near the light-emitting side, wherein the first stacked structure comprises a first optical adhesive layer 400, a functional film layer 500, a second optical adhesive layer 600 and a cover layer 700 sequentially disposed on the flexible display panel 300;

[0094] A second stacked structure disposed on the flexible display panel 300 away from the light emitting side, the second stacked structure comprising a support layer 100 and a first adhesive layer 200 disposed on a side of the support layer 100 close to the flexible display panel 300;

[0095] in,

[0096] The first optical adhesive layer 400 and / or the second optical adhesive layer 600 include the optical adhesive layer as described above.

[0097] It can be understood that the optical adhesive layer is obtained by curing the optical adhesive provided in the above specific embodiments.

[0098] In the flexible display module, the first optical adhesive layer 400 bonds the flexible display panel 300 and the functional film layer 500, and has good bonding, optical transmittance and bending resistance.

[0099] In some examples, the first optical adhesive layer 400 including the optical adhesive layer as described above has strong cohesive force and high elastic modulus, which can effectively reduce the problems of the flexible display module affecting the structural stability due to the failure of the cohesive force of the optical adhesive layer and the excessive crease of the flexible display panel after repeated bending during the high temperature and high humidity dynamic bending process, so that the flexible display module has good characteristics such as prevention of bad falling off, recovery force and peeling force. Considering that the first optical adhesive layer 400 preferably has adhesion, anti-bending properties, etc., the thickness of the suitable first optical adhesive layer 400 includes but is not limited to 35-70um, preferably 50um.

[0100] In the flexible display module, the second optical adhesive layer 600 bonds the cover plate layer 700 and the functional film layer 500, and has good bonding properties, optical transmittance, and bending resistance.

[0101] In some examples, the second optical adhesive layer 600 including the optical adhesive layer as described above has strong cohesive force and high elastic modulus, which can effectively reduce the problems of the flexible display module affecting the structural stability due to the failure of the cohesive force of the optical adhesive layer and the excessive crease of the flexible display panel after repeated bending during the high temperature and high humidity dynamic bending process, so that the flexible display module has good characteristics such as prevention of bad falling off, recovery force and peeling force. Considering that the second optical adhesive layer 600 preferably has adhesion, anti-bending properties, etc., the thickness of the suitable second optical adhesive layer 600 includes but is not limited to 35-70um, preferably 50um.

[0102] When the first optical adhesive layer 400 and the second optical adhesive layer 600 are both the aforementioned optical adhesive layers, the flexible display module including them has better structural stability and anti-bending properties.

[0103] In this embodiment, the flexible display panel 300 may display an image through a screen defined on the front surface of the flexible display panel 300 .

[0104] In some examples, the functional film layer 500 includes, but is not limited to, for example, an anti-reflection layer. The material of the anti-reflection layer may include a polarization component, which can polarize the light passing through it to reduce the reflection of external light. In some specific examples, the polarization component may be a polarizing film. The polarizing film may include a polarizing layer and a plurality of protective substrates, wherein the polarizing layer is interposed between the plurality of protective substrates. The polarizing layer may include a polyvinyl alcohol film. The polarizing layer may be stretched in a predetermined direction. The stretching direction of the polarizing layer may be an absorption axis, and the direction perpendicular thereto may be a transmission axis. A plurality of protective substrates may be respectively disposed on one surface and another surface of the polarizing layer. The protective substrate may include a cellulose resin (such as triacetyl cellulose, polyester resin, etc.) or be formed by the cellulose resin, but is not limited thereto.

[0105] The material of the functional film layer 500 includes, but is not limited to, ultra-thin glass (UTG), polyurethane film (TPU), etc. It can be the same as or different from the material of the cover layer. The appropriate thickness of the functional film layer 500 can be 30-100um. At this time, the function of the functional film layer 500 can be better exerted, while ensuring good flexibility and stability of the structure.

[0106] The cover layer 700 may be a protective layer disposed on the outermost side in the light emitting direction of the flexible display panel 300. The cover layer 700 may be a single-layer structure or a multi-layer structure.

[0107] When the cover layer 700 is a multi-layer structure, in some examples, it may include a first transparent polymer layer, a second adhesive layer, a thin glass layer, a third adhesive layer, and a second transparent polymer layer arranged in sequence.

[0108] In some examples, the second adhesive layer and / or the third adhesive layer comprises an optical adhesive layer as described in the previous embodiment.

[0109] The second adhesive layer is used to bond the first transparent polymer layer and the thin glass layer, and the third adhesive layer is used to bond the second transparent polymer layer and the thin glass layer. The second adhesive layer and the third adhesive layer need to have good adhesion and bending resistance. In some examples, the second adhesive layer and / or the third adhesive layer include an optical adhesive layer as described in the previous embodiment. At this time, the second adhesive layer and / or the third adhesive layer have strong cohesion and high elastic modulus, which can effectively reduce the problems of the flexible display module in the high temperature and high humidity dynamic bending process due to the failure of the cohesion of the optical adhesive layer, thereby affecting the structural stability and the excessive crease of the flexible display panel after repeated bending, so that the flexible display module has good characteristics such as prevention of bad shedding, recovery force and peeling force.

[0110] When the cover layer 700 is a single layer, or when the cover layer 700 is a multilayer, its material or the material of the first transparent polymer and the second transparent polymer can be polyethylene terephthalate (PET), polyimide (CPI), polymethyl methacrylate (PMMA), etc. with flexible properties, so as to increase the surface hardness, scratch resistance, fingerprint resistance, and dirt resistance. The thickness of the exemplary cover layer can be 30-100um. If the cover layer is too thick, the bendability of the flexible display module will be affected, and if it is too thin, the impact resistance of the flexible display module will be affected.

[0111] In some other examples, the second stacked structure further includes a protective layer disposed between the flexible display panel 300 and the first adhesive layer 200 ; and a fourth adhesive layer disposed between the protective layer and the flexible display panel 300 .

[0112] The protective layer arranged between the flexible display panel 300 and the first adhesive layer 200 may be a back film. Among them, the back film may be made of polyethylene glycol (PEG) or polyetherimide (PEI). The back film is adhered to the side opposite to the light emitting direction of the flexible display panel 300 through the fourth adhesive layer to protect the flexible display panel 300. Among them, the fourth adhesive layer may be made of pressure-sensitive adhesive (PSA), optically clear adhesive (OCA), optically clear resin (OCR), etc. When the fourth adhesive layer is an optically clear adhesive, it may include the aforementioned optical adhesive layer. At this time, the bending resistance, anti-bad shedding, recovery force and peeling force characteristics of the flexible display module during high temperature and high humidity dynamic bending can be further improved. The thickness of the fourth adhesive layer includes but is not limited to 10-50um.

[0113] Further, when the second stacked structure includes a protective layer disposed between the flexible display panel 300 and the first adhesive layer 200, the first adhesive layer can be used to bond the protective layer and the support layer 100. Among them, the first adhesive layer 200 can be a pressure-sensitive adhesive (PSA), an optically clear adhesive (OCA), an optically clear resin (OCR), etc. When the first adhesive layer 200 is an optically clear adhesive, it can include the aforementioned optical adhesive layer, at this time, the bending resistance, anti-bad falling, recovery force and peeling force characteristics of the flexible display module during high temperature and high humidity dynamic bending can be further improved. The thickness of the fourth adhesive layer includes but is not limited to 10-50um.

[0114] The support layer 100 is used to ensure that the entire flexible display module has sufficient support capability. The material of the support layer 100 may be stainless steel, carbon fiber board, etc. The thickness may include but is not limited to 100-250um.

[0115] In this embodiment, the flexible display module may be a foldable display module. In the foldable display module, the flexible display panel is foldable and includes a display surface for displaying an image (i.e., a surface on the light-emitting side) and a rear surface opposite to the display surface (i.e., a surface away from the light-emitting side). The first stacked structure can be folded together with the flexible display panel; the second stacked structure can also be folded together with the flexible display panel.

[0116] According to another specific embodiment of the present invention, a flexible display device is provided, wherein the flexible display device comprises the flexible display module as described above.

[0117] Since the flexible display device includes the flexible display module, it has all the advantages of the flexible display module, which will not be described in detail here.

[0118] Likewise, when the flexible display module is foldable, the flexible display device is also a foldable display device.

[0119] Below in conjunction with specific embodiment, technical scheme of the present invention is described.It should be understood that these embodiments are only used to illustrate the present application and are not used to limit the scope of the present application.The experimental method of not indicating specific conditions in the following examples is usually measured according to national standards.If there is no corresponding national standard, then according to general international standards, normal conditions, or according to the conditions recommended by the manufacturer, carry out.

[0120] In the following specific embodiments, the preparation of the optical adhesive and the optical adhesive layer is as follows:

[0121] In this experiment, 2-ethylhexyl acrylate (2-EHA), lauryl acrylate (LA), n-hexyl acrylate (HA), and hydroxyethyl acrylate (HBA) were selected as copolymer monomers, and a modified long-chain acrylate monomer containing an amide bond was introduced. Ethyl acetate was selected as the solvent, and azobisisobutyronitrile (AIBN) was used as the initiator. The solvent method was used to synthesize acrylate polymers, and the detailed process is as follows:

[0122] The above-mentioned copolymer monomers, modified long-chain acrylate monomers containing amide bonds and ethyl acetate were added into a four-necked flask according to the proportion, mechanically stirred, and N 2 Then the temperature was raised to 65°C, the initiator was dissolved in ethyl acetate (the amount of the initiator was 1wt%-3wt% of the total mass of the modified long-chain acrylate monomer containing an amide bond of each comonomer), and it was added dropwise into the flask using a constant pressure funnel, and the reaction was carried out at a constant temperature for 4 hours. The reaction temperature was raised to 75°C and kept at a constant temperature for 3 hours. After the reaction was completed, the product was cooled to room temperature and poured out; it was placed in a vacuum oven for 12 hours to obtain an acrylate polymer;

[0123] The acrylic acid ester polymer and ethyl acetate are fully mixed in a mass ratio of 1:1 to obtain an optical adhesive solution;

[0124] Take an appropriate amount of the optical adhesive liquid, apply it on the polyethylene terephthalate film, apply it with a flat coater, and cure and dry it in an oven at a curing temperature of 60-100°C for 12-24 hours to obtain an optical adhesive layer with a thickness of about 50um. Take it out after 3 minutes, stick a release film on it, and cut it into standard sample sizes for testing as required.

[0125] Wherein, the preparation method of the modified long-chain acrylate monomer containing an amide bond is as follows:

[0126] In a dry reactor, add appropriate amounts of butyl acrylate, butyl acrylamide (for example, the mass ratio of butyl acrylate to butyl acrylamide can be 1:1) and amino alcohol catalyst. Seal the reactor and react at room temperature 25°C. After 4-8 hours of reaction, it can be observed that the product (modified long-chain acrylate monomer containing amide bonds) begins to form. By analyzing the product with an infrared spectrometer, it can be found that the characteristic peak of amide appears in the product. This indicates that the ester group is successfully converted into an amide bond.

[0127] Example 1

[0128] The optical adhesive layer was prepared according to the above method, except that the modified long-chain acrylate monomer containing an amide bond was not added; wherein the addition ratio (mass ratio) of each copolymer monomer was EHA:LA:HA:HBA=50:20:20:10.

[0129] Example 2

[0130] The optical adhesive layer was prepared according to the above method, wherein the addition ratio (mass ratio) of each copolymer monomer was EHA:LA:HA:HBA=50:20:20:10. The modified long-chain acrylate monomer containing amide bond accounted for 3wt% of the total mass of the above acrylic matrix resins.

[0131] Example 3

[0132] The optical adhesive layer was prepared according to the above method, wherein the addition ratio (mass ratio) of each comonomer was EHA:LA:HA:HBA=50:20:20:10. The amide bond modified long chain acrylate monomer was added to account for 6wt% of the total mass of the above comonomers.

[0133] Example 4

[0134] The optical adhesive layer was prepared according to the above method, wherein the addition ratio (mass ratio) of each comonomer was EHA:LA:HA:HBA=50:20:20:10. The amide bond modified long chain acrylate monomer added accounted for 9wt% of the total mass of the above comonomers.

[0135] Comparative Example 1

[0136] The optical adhesive layer was prepared according to the above method, except that the amide bond modified long chain acrylate monomer was replaced by butyl acrylate, wherein the addition ratio (mass ratio) of each comonomer was EHA:LA:HA:HBA=50:20:20:10. The added butyl acrylate accounted for 6wt% of the total mass of the above comonomers.

[0137] Table 1 shows the creep recovery performance of the optical adhesive layer of each embodiment above. From the data, it can be concluded that the optical adhesive with amide bond-modified long-chain acrylate monomer has an increased recovery capacity when the fixed strain is 200%. The method for the above performance test is:

[0138] Sample preparation: 8mm diameter circular film, 0.7mm thickness of laminated film.

[0139] Testing equipment: Rheometer.

[0140] At 25℃, rheometer equipment test, when the strain of the rubber material reaches 200%, the external force is maintained unchanged for 10 minutes, and then the external force is removed and recovered for 10 minutes.

[0141] Table 1

[0142]

[0143] Table 2 shows the optical adhesive layers of various embodiments used in flexible display devices to obtain optical adhesive modules (such as Figure 3(As shown in the table) Bending test results. As can be seen from Table 2, after 5w times of dynamic bending at 60°C / 90% under high temperature and high humidity, the optical adhesive module using Example 1 fails to bend, and the failure phenomenon is the destruction of the cohesive force of the optical adhesive. There is no problem with bending the optical adhesive modules using Examples 2 and 3, but the optical adhesive module using Example 4 fails to bend, and the failure phenomenon is the peeling of the optical adhesive from the upper and lower interfaces, and the failure of the adhesion to the interface. It can be seen that adding amide bond modification groups after the optical adhesive liquid can enhance the cohesive force of the optical adhesive. When the added amount reaches a certain level, the problem of failure of the adhesion to the cover plate interface will occur. The performance is best when the amount of amide bond modification groups added is 6wt%, and the crease is the smallest after bending.

[0144] Table 2

[0145]

[0146] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the protection scope of the present invention.

Claims

1. An adhesive composition, characterized in that The adhesive composition comprises an acrylic base resin and a modified acrylate monomer, wherein the modified acrylate monomer contains an amide bond.

2. The adhesive composition according to claim 1, characterized in that The amount of the modified acrylate monomer used is 1 wt%-10 wt% of the amount of the acrylic base resin used.

3. The adhesive composition according to claim 1, characterized in that The modified acrylate monomer is obtained by modifying an acrylate monomer with a compound containing an amide bond.

4. The adhesive composition according to claim 3, characterized in that The acrylic acid ester monomer structure does not contain side chains and contains 4 to 18 carbon atoms; and / or The acrylate monomer is selected from butyl acrylate.

5. The adhesive composition according to claim 3, characterized in that The compound containing an amide bond is selected from butyl acrylamide.

6. The adhesive composition according to claim 3, characterized in that The acrylic matrix resin is selected from one or more of 2-ethylhexyl acrylate, lauryl acrylate, n-hexyl acrylate and hydroxyethyl acrylate; and / or The acrylic ester matrix resin contains 2-ethylhexyl acrylate, lauryl acrylate, n-hexyl acrylate and hydroxyethyl acrylate in a mass ratio of (40-60):(15-25):(15-25):(5-15).

7. The adhesive composition according to claim 3, characterized in that: The adhesive composition further comprises a solvent and an initiator; and / or The solvent is selected from one or more of ethyl acetate, methacrylate and sec-butyl acetate; and / or The initiator is selected from one or more of azobisisobutyronitrile, dimethyl diisobutyrate and azobisisoheptanenitrile.

8. An optical glue, characterized in that: The adhesive composition is prepared from the adhesive composition according to any one of claims 1 to 7.

9. The method for preparing an optical adhesive according to claim 8, characterized in that: The steps include: The acrylic base resin and the modified acrylic ester monomer are dissolved in a solvent, reacted in a nitrogen atmosphere in the presence of an initiator, and the reaction product is dried to obtain an acrylic ester polymer; The acrylate polymer is mixed with a solvent to obtain the optical adhesive.

10. The preparation method according to claim 9, characterized in that: The reaction conditions are: react at a constant temperature of 50-70°C for 3-6 hours, then heat to 70-90°C for a constant temperature reaction for 2-4 hours.

11. An optical adhesive layer, characterized in that: The optical adhesive is obtained by curing the optical adhesive as described in claim 8.

12. An optical adhesive, characterized in that: The optical adhesive comprises the optical adhesive layer as claimed in claim 11.

13. The optical adhesive according to claim 12, characterized in that: The optical adhesive further comprises a first release film and a second release film, wherein the first release film and the second release film are respectively attached to two opposite surfaces of the optical adhesive layer.

14. A flexible display module, characterized in that: Include: Flexible display panels; A first stacked structure disposed on the flexible display panel near the light-emitting side, the first stacked structure comprising a first optical adhesive layer, a functional film layer, a second optical adhesive layer and a cover layer sequentially disposed on the flexible display panel; A second stacked structure disposed on the flexible display panel away from the light emitting side, the second stacked structure comprising a support layer and a first adhesive layer disposed on a side of the support layer close to the flexible display panel; in, The first optical adhesive layer and / or the second optical adhesive layer comprises the optical adhesive layer as claimed in claim 11.

15. The flexible display module according to claim 14, characterized in that: The cover layer comprises a first transparent polymer layer, a second adhesive layer, a thin glass layer, a third adhesive layer and a second transparent polymer layer which are arranged in sequence.

16. The flexible display module according to claim 15, characterized in that: The second adhesive layer and / or the third adhesive layer comprises the optical adhesive layer as claimed in claim 11.

17. The flexible display module according to claim 14, characterized in that: The second stacked structure further includes a protective layer disposed between the flexible display panel and the first adhesive layer; and A fourth adhesive layer is disposed between the protective layer and the flexible display panel.

18. The flexible display module according to claim 17, characterized in that: The third adhesive layer and / or the fourth adhesive layer comprises the optical adhesive layer as claimed in claim 11.

19. A flexible display device, characterized in that: It comprises a flexible display module as described in any one of claims 14 to 18.

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