OCA glue, OCA adhesive, adhesive film and preparation method

Abstract

The invention discloses an OCA glue, an OCA adhesive and a preparation method. The OCA glue comprises the following components by weight: 40 to 90 parts of a soft monomer, 4 to 6 parts of a hard monomer, 5 to 8 parts of a functional monomer, 70 to 150 parts of a first solvent, an initiator and a silane coupling agent; the initiator is 0.3 to 0.6% of the total weight of the soft monomer, the hard monomer and the functional monomer; the silane coupling agent is 0.1 to 0.5% of the total weight of the soft monomer, the hard monomer and the functional monomer. The OCA adhesive comprises 100 parts of OCA glue, 30 to 50 parts of a second solvent and a crosslinking agent; the crosslinking agent is 0.04 to 0.2% of the weight of the OCA glue. The OCA adhesive of the invention still has good adhesion and cohesion at a relatively thin thickness of 13 to 15 μm, and can effectively solve the phenomenon of warping and delamination caused by slippage between layers due to insufficient adhesion of the folding display module.

Description

Technical Field

[0001] The invention belongs to the technical field of OCA glue, and in particular relates to an OCA glue, an OCA adhesive and a preparation method. Background Art

[0002] With the development of the mobile phone industry, people have gradually eliminated large candy-bar phones and turned to pay more attention to foldable phones. Foldable phones have gradually gained favor from mobile phone manufacturers and end users due to their advantages such as multi-screen display and easy portability. However, there are also many problems that need to be solved. For foldable screens, the key to achieving folding is to reduce the thickness of the screen or module. It is imperative to thin the OCA glue layer (a special adhesive layer used to bond optical components), but the peeling force of the OCA glue is also reduced after thinning. Therefore, it is necessary to improve the OCA glue to provide a more reliable solution.

[0003] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention and should not be regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the invention

[0004] The object of the present invention is to provide an OCA glue, an OCA adhesive and a preparation method thereof, wherein the OCA adhesive has excellent adhesion and cohesion at a relatively thin thickness.

[0005] In order to achieve the above object, a technical solution provided by a specific embodiment of the present invention is as follows:

[0006] An OCA glue comprises the following components in parts by weight: 40 to 90 parts of a soft monomer, 4 to 6 parts of a hard monomer, 5 to 8 parts of a functional monomer, 70 to 150 parts of a first solvent, an initiator and a silane coupling agent;

[0007] The initiator is 0.3-0.6% of the total weight of the soft monomer, the hard monomer and the functional monomer;

[0008] The silane coupling agent accounts for 0.1-0.5% of the total weight of the soft monomer, the hard monomer and the functional monomer.

[0009] In one or more embodiments of the present invention, the soft monomer is selected from 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, hexyl (meth)acrylate, n-nonyl (meth)acrylate, isopentyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, dodecyl (meth)acrylate, isooctyl acrylate and 2-methylbutyl (meth)acrylate.

[0010] In one or more embodiments of the present invention, the hard monomer is selected from methyl methacrylate, methyl acrylate, acrylamide, dimethylacrylamide, isobornyl (meth)acrylate and N-vinyl pyrrolidone.

[0011] In one or more embodiments of the present invention, the functional monomer is selected from 2-hydroxyethyl acrylate, 2-hydroxy-propyl acrylate, 4-hydroxybutyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, acrylamide, N-hydroxymethyl acrylamide, maleic anhydride, and glycidyl methacrylate.

[0012] In one or more embodiments of the present invention, the initiator is selected from azobisisobutyronitrile and azobisisoheptanenitrile.

[0013] Another specific embodiment of the present invention provides a technical solution as follows:

[0014] A method for preparing OCA glue comprises the following steps:

[0015] Mix the soft monomer, hard monomer, functional monomer and part of the first solvent, raise the temperature to 62-64° C., add part of the initiator, and react for 2.5-3.5 hours;

[0016] Add some initiator and react for 1.2 to 2 hours;

[0017] Add some initiator, react for 25-35 minutes, and then heat to 73-77°C;

[0018] Add the remaining initiator and react for 1.8 to 2.2 hours;

[0019] Cool, add silane coupling agent and the remaining first solvent, mix well, and obtain OCA glue.

[0020] Another specific embodiment of the present invention provides a technical solution as follows:

[0021] An OCA adhesive comprises the following components in parts by weight: 100 parts of the above-mentioned OCA glue, 30 to 50 parts of a second solvent and a cross-linking agent;

[0022] The cross-linking agent accounts for 0.04-0.2% of the weight of the OCA glue.

[0023] Another specific embodiment of the present invention provides a technical solution as follows:

[0024] A method for preparing an OCA adhesive comprises mixing OCA glue, a cross-linking agent and a second solvent, stirring and mixing at 20-25° C., evacuating, and standing to degas, so as to obtain the OCA adhesive.

[0025] Another specific embodiment of the present invention provides a technical solution as follows:

[0026] A film comprises a light release film, an adhesive layer and a heavy release film which are stacked in sequence, wherein the adhesive layer is formed by the above-mentioned OCA adhesive.

[0027] Compared with the prior art, the OCA adhesive in the present invention can have higher bonding performance to various materials at a thickness of 13 to 15 μm, and can effectively solve the problems of warping and delamination caused by slippage between layers due to insufficient bonding force in the folding display module.

[0028] The OCA adhesive prepared by the present invention contains a silane coupling agent and has a large number of polar groups, which can further improve the bonding ability and water whitening resistance of the OCA adhesive to various substrates, and can effectively improve the aging resistance of the OCA adhesive in the folding display module. DETAILED DESCRIPTION

[0029] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention are clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0030] A specific embodiment of the present invention provides an OCA glue, comprising the following components in parts by weight: 40 to 90 parts of a soft monomer, 4 to 6 parts of a hard monomer, 5 to 8 parts of a functional monomer, 70 to 150 parts of a first solvent, an initiator and a silane coupling agent; the initiator is 0.3 to 0.6% of the total weight of the soft monomer, the hard monomer and the functional monomer; the silane coupling agent is 0.1 to 0.5% of the total weight of the soft monomer, the hard monomer and the functional monomer.

[0031] Specifically, by combining the above components and limiting the amount of each component, the obtained OCA glue has high bonding performance. When used in folding mobile phones, it can effectively solve the problems of warping and delamination caused by slippage between layers of the folding display module due to insufficient bonding force.

[0032] Further, the soft monomer is selected from 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, hexyl (meth)acrylate, n-nonyl (meth)acrylate, isopentyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, dodecyl (meth)acrylate, isooctyl acrylate and 2-methylbutyl (meth)acrylate.

[0033] Furthermore, the hard monomer is selected from methyl methacrylate, methyl acrylate, acrylamide, dimethylacrylamide, isobornyl (meth)acrylate and N-vinyl pyrrolidone.

[0034] Further, the functional monomer is selected from 2-hydroxyethyl acrylate, 2-hydroxy-propyl acrylate, 4-hydroxybutyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, acrylamide, N-hydroxymethyl acrylamide, maleic anhydride, and glycidyl methacrylate.

[0035] Specifically, the functional monomer contains more polar groups. By adding the functional monomer and controlling the amount of the functional monomer, the peeling force of the OCA glue can be effectively improved and have a suitable TG (glass transition temperature).

[0036] Further, the initiator is selected from azobisisobutyronitrile and azobisisoheptanenitrile, the silane coupling agent is propyltrimethoxysilane, and the first solvent is ethyl acetate.

[0037] Another specific embodiment of the present invention provides a method for preparing OCA glue, comprising steps 1-5.

[0038] Step 1, mix the soft monomer, the hard monomer, the functional monomer and part of the first solvent, raise the temperature to 62-64° C., add part of the initiator, and react for 2.5-3.5 hours.

[0039] Specifically, in this step, the reaction concentration, i.e., the total weight of the soft monomer, the hard monomer, the functional monomer and the initiator in the first solvent, is 44.3%. By controlling the reaction concentration, the reaction speed can be increased to ensure that the reaction proceeds fully. The amount of the initiator added is 0.06% of the total weight of the soft monomer, the hard monomer and the functional monomer.

[0040] Step 2, add some initiator and react for 1.2 to 2 hours.

[0041] Specifically, the amount of the initiator added is 0.13% of the total weight of the soft monomer, the hard monomer and the functional monomer.

[0042] Step 3, add some initiator, react for 25 to 35 minutes and then heat to 73 to 77°C.

[0043] Specifically, the amount of the initiator added is 0.2% of the total weight of the soft monomer, the hard monomer and the functional monomer.

[0044] Step 4, add the remaining initiator and react for 1.8 to 2.2 hours.

[0045] Step 5, cooling, adding silane coupling agent and the remaining first solvent, mixing, and obtaining OCA glue.

[0046] Specifically, by adding the initiator in multiple steps, the monomers are helped to fully participate in the reaction, ensuring complete polymerization to form acrylic prepolymers. The prepared acrylic prepolymer, namely OCA glue, has a weight average molecular weight of 1 million to 1.4 million, preferably 1.1 million to 1.2 million.

[0047] Another specific embodiment of the present invention provides an OCA adhesive, comprising the following components in parts by weight: 100 parts of the above-mentioned OCA glue, 30-50 parts of a second solvent, and a cross-linking agent; the cross-linking agent is 0.04-0.2% by weight of the OCA glue.

[0048] Specifically, the crosslinking agent can use an organic crosslinking agent or a multifunctional metal chelate. As the organic crosslinking agent, an isocyanate crosslinking agent, a peroxide crosslinking agent, or an epoxy crosslinking agent can be selected. An isocyanate crosslinking agent is preferred, and an isocyanate crosslinking agent and a peroxide crosslinking agent can also be used in combination. The second solvent is ethyl acetate.

[0049] Another specific embodiment of the present invention provides a method for preparing an OCA adhesive, comprising mixing OCA glue, a cross-linking agent and a second solvent, stirring and mixing at 20 to 25° C., evacuating the mixture, and standing the mixture for degassing to obtain the OCA adhesive.

[0050] Another specific embodiment of the present invention provides an adhesive film, comprising a light release film, an adhesive layer and a heavy release film stacked in sequence, wherein the adhesive layer is formed by the above-mentioned OCA adhesive.

[0051] Specifically, the light release film and the heavy release film may be PET release films, and the thickness of the adhesive layer is 13 to 15 μm.

[0052] The present invention is further described in detail below in conjunction with specific embodiments.

[0053] Example 1

[0054] OCA glue, by weight, includes 88 parts of soft monomer, 5.5 parts of hard monomer, 6.5 parts of functional monomer, 123 parts of ethyl acetate, initiator azobisisobutyronitrile and silane coupling agent propyltrimethoxysilane, the amount of azobisisobutyronitrile is 0.59% of the total weight of the soft monomer, hard monomer and functional monomer, and the amount of propyltrimethoxysilane is 0.3% of the total weight of the soft monomer, hard monomer and functional monomer. Among them, the soft monomer includes 73 parts of isooctyl acrylate and 15 parts of butyl acrylate, the functional monomer is hydroxybutyl acrylate, and the hard monomer is dimethylacrylamide.

[0055] Isooctyl acrylate, butyl acrylate, hydroxybutyl acrylate, dimethylacrylamide and part of ethyl acetate are mixed, nitrogen is introduced and the temperature is raised to 62°C, and then 0.06% of azobisisobutyronitrile based on the total weight of soft monomer, hard monomer and functional monomer is added, and the reaction concentration is 44.3%. The temperature is maintained and stirred for 3 hours.

[0056] Then, 0.13% of azobisisobutyronitrile based on the total weight of the soft monomer, the hard monomer and the functional monomer was added, and the reaction was carried out for 1.5 hours.

[0057] Then, 0.2% of azobisisobutyronitrile based on the total weight of the soft monomer, the hard monomer and the functional monomer was added, and the reaction was carried out for 30 minutes, and then the temperature was raised to 73°C.

[0058] Then, 0.2% of azobisisobutyronitrile based on the total weight of the soft monomer, the hard monomer and the functional monomer was added and the reaction was carried out for 2 hours.

[0059] The mixture was cooled to room temperature, propyltrimethoxysilane and the remaining ethyl acetate were added, and stirred evenly to obtain OCA glue with a TG of -60°C.

[0060] In parts by weight, take 100 parts of OCA glue, 40 parts of ethyl acetate and cross-linking agent hexamethylene diisocyanate, the amount of hexamethylene diisocyanate is 0.09% of the weight of OCA glue, mix, stir for 10 minutes at 20°C, evacuate, and let stand until there are no bubbles, to obtain an OCA adhesive with a solid content of 25%.

[0061] Examples 2-5, Comparative Examples 1-5

[0062] The operations of Examples 2-5 and Comparative Examples 1-5 are the same as those of Example 1, except that the types and amounts of raw materials of the OCA glue are different, as shown in Table 1.

[0063] Table 1 Raw material dosage of OCA glue in Examples 1-5 and Comparative Examples 1-5

[0064]

[0065] Take the OCA adhesive in each implementation and each comparative example respectively, coat the adhesive on a PET heavy release film with a coating thickness of 15 μm, put it into a 100° C. oven and bake it for 3 min to form an adhesive layer, and finally cover the adhesive layer with a PET light release film and mature it at 40° C. for 3 days to obtain a film.

[0066] The light release film in the film was peeled off and a 50μm thick PET film was attached. The resulting sample was placed in a constant temperature and humidity environment (temperature 23°C, humidity 50%) for 2 hours and then tested for 24H peeling force, creep recovery performance, and dynamic / static bending of glass and SUS. Before the test, the 50μm PET, glass, and SUS steel plates were all treated with Plasma surface treatment. The working conditions of Plasma were: back vacuum degree 50Pa, discharge power 350W, and working time 90s.

[0067] Peel strength test: Peel strength is tested in accordance with GB / T 2792-2014 "Test method for peel strength of adhesive tapes".

[0068] Creep recovery test: TA rheometer applies 20kPa shear stress, recovery time is 600s, creep recovery rate at room temperature exceeds 90%, and maximum strain exceeds 300%; creep recovery rate at -20℃ exceeds 85%, and maximum strain exceeds 90%, which is qualified.

[0069] Dynamic bending test: Lay 50μm thick PET film on both sides of the film, bind it to the bending plate with a fixed tape, control the flexible material bending life tester, adjust the bending radius by adjusting the height difference between the two plates, and automatically bend from 0°-180° 20W times (30 times / min). The sample is qualified if there is no crease, the OCA film layer and other layers do not delaminate or warp, and the bonding is firm.

[0070] Static bending test: stick 50μm thick PET on both sides of the film, and then cut it into 160mm*40mm strips, and then fix a 1N weight (100g) at the tail of the sample with high-temperature insulating tape, hang it on a fixture with a radius of R=1.5mm, put it into a 65℃ / 95% humidity test box for 24h, take it out after cooling, and test the crease width at the tail. The measured width is qualified if it reaches 35mm.

[0071] Table 2 Test results

[0072]

[0073]

[0074] Referring to Table 2, the test performance of the samples in Examples 1-5 is excellent compared with the comparative examples. In the examples, appropriate amounts of raw materials are matched, especially the amount of functional monomers is appropriate, so that the samples contain an appropriate amount of hydroxyl groups and TG is also low, and the rebound effect in the creep recovery test is better.

[0075] In Comparative Examples 1 and 2, the amount of functional monomers used exceeds the range specified in the present invention, and the hydroxyl content increases. Although the peeling force is significantly improved, it is NG in the bending test, the creep recovery does not reach 90%, and it is easy to gel during the test, so the reaction concentration needs to be reduced. However, after the reaction concentration is reduced, the number of small molecules increases, and the retention effect at high temperature is poor, which cannot meet the requirements.

[0076] In Comparative Examples 3-5, the amount of hard monomer used exceeded the range specified in the present invention, the peeling force was reduced to varying degrees, and the creep recovery and bending tests were unqualified, failing to meet the requirements.

[0077] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention.

[0078] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. An OCA glue, characterized in that: The invention comprises the following components by weight: 40 to 90 parts of soft monomer, 4 to 6 parts of hard monomer, 5 to 8 parts of functional monomer, 70 to 150 parts of first solvent, initiator and silane coupling agent; The initiator is 0.3-0.6% of the total weight of the soft monomer, the hard monomer and the functional monomer; The silane coupling agent accounts for 0.1-0.5% of the total weight of the soft monomer, the hard monomer and the functional monomer.

2. The OCA glue according to claim 1, characterized in that: The soft monomer is selected from 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, hexyl (meth)acrylate, n-nonyl (meth)acrylate, isopentyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, dodecyl (meth)acrylate, isostearyl acrylate and 2-methylbutyl (meth)acrylate.

3. The OCA glue according to claim 1, characterized in that: The hard monomer is selected from methyl methacrylate, methyl acrylate, acrylamide, dimethylacrylamide, isobornyl (meth)acrylate and N-vinyl pyrrolidone.

4. The OCA glue according to claim 1, characterized in that: The functional monomer is selected from 2-hydroxyethyl acrylate, 2-hydroxy-propyl acrylate, 4-hydroxybutyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, acrylamide, N-hydroxymethyl acrylamide, maleic anhydride, and glycidyl methacrylate.

5. The OCA glue according to claim 1, characterized in that: The initiator is selected from azobisisobutyronitrile and azobisisoheptanenitrile.

6. A method for preparing the OCA glue according to any one of claims 1 to 5, characterized in that: The steps include: Mix the soft monomer, hard monomer, functional monomer and part of the first solvent, raise the temperature to 62-64° C., add part of the initiator, and react for 2.5-3.5 hours; Add some initiator and react for 1.2 to 2 hours; Add some initiator, react for 25-35 minutes, and then heat to 73-77°C; Add the remaining initiator and react for 1.8 to 2.2 hours; Cool, add silane coupling agent and the remaining first solvent, mix well, and obtain OCA glue.

7. An OCA adhesive, characterized in that: The method comprises the following components in parts by weight: 100 parts of the OCA glue according to any one of claims 1 to 5, 30 to 50 parts of a second solvent and a cross-linking agent; The cross-linking agent accounts for 0.04-0.2% of the weight of the OCA glue.

8. A method for preparing the OCA adhesive according to claim 7, characterized in that: The OCA glue, the cross-linking agent and the second solvent are mixed, stirred and mixed at 20-25° C., vacuumed, and allowed to stand for degassing to obtain the OCA adhesive.

9. An adhesive film, characterized in that: The invention comprises a light release film, an adhesive layer and a heavy release film which are stacked in sequence, wherein the adhesive layer is formed by the OCA adhesive according to claim 7.

10. The adhesive film according to claim 9, characterized in that: The adhesive layer has a thickness of 13 to 15 μm.

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